HIV infection results in a highly prevalent syndrome of cognitive and motor disorders designated as HIV-associated dementia (HAD). Neurologic dysfunction resembling HAD has been documented in cats infected with strain PPR of the feline immunodeficiency virus (FIV), whereas another highly pathogenic strain (C36) has not been known to cause neurologic signs. Animals experimentally infected with equivalent doses of FIV-C36 or FIV-PPR, and uninfected controls were evaluated by magnetic resonance diffusion-weighted imaging (DW-MRI) and spectroscopy (MRS) at 17.5 – 18 weeks post-infection, as part of a study of viral clade pathogenesis in FIV infected cats. Goals of the MR imaging portion of the project were to determine whether this methodology was capable of detecting early neuropathophysiology in the absence of outward manifestation of neurological signs, and to compare MR imaging results for the two viral strains expected to have differing degrees of neurologic effects. We hypothesized that there would be increased diffusion, evidenced by the apparent diffusion coefficient as measured by DW-MRI, and altered metabolite ratios measured by MRS, in the brains of FIV-PPR infected cats relative to C36-infected cats and uninfected controls. Increased apparent diffusion coefficients were seen in the white matter, gray matter, and basal ganglia of both the PPR and C36 infected (asymptomatic) cats. Thalamic MRS metabolite ratios did not differ between groups. The equivalently increased diffusion by DW-MRI suggests similar indirect neurotoxicity mechanisms for the two viral genotypes. DW-MRI is a sensitive tool to detect neuropathophysiological changes in vivo that could be useful during longitudinal studies of FIV.
Lentiviral neuropathology; HIV-associated dementia (HAD); Magnetic Resonance Spectroscopy (MRS); Diffusion-Weighted Imaging (DW-MRI); Apparent Diffusion Coefficient (ADC); FIV-PPR; FIV-C36
CD8 T cells protect the host from disease caused by intracellular pathogens, such as the Toxoplasma gondii (T. gondii) protozoan parasite. Despite the complexity of the T. gondii proteome, CD8 T cell responses are restricted to only a small number of peptide epitopes derived from a limited set of antigenic precursors. This phenomenon is known as immunodominance and is key to effective vaccine design. However, the mechanisms that determine the immunogenicity and immunodominance hierarchy of parasite antigens are not well understood.
Here, using genetically modified parasites, we show that parasite burden is controlled by the immunodominant GRA6-specific CD8 T cell response but not by responses to the subdominant GRA4- and ROP7-derived epitopes. Remarkably, optimal processing and immunodominance were determined by the location of the peptide epitope at the C-terminus of the GRA6 antigenic precursor. In contrast, immunodominance could not be explained by the peptide affinity for the MHC I molecule or the frequency of T cell precursors in the naive animals. Our results reveal the molecular requirements for optimal presentation of an intracellular parasite antigen and for eliciting protective CD8 T cells.
Toxoplasma gondii is a widespread intracellular parasite that can cause severe disease in immunocompromised individuals and lead to fetal abnormalities if contracted during pregnancy. Establishment of protective immunity relies on CD8 T cells, which recognize antigenic peptides presented by MHC class I molecules on the surface of T. gondii-infected cells. Intriguingly, while the proteome of T. gondii is large, CD8 T cell responses target a very limited set of peptides. These peptides can be ranked according to the magnitude of the associated CD8 response (from immunodominant down to subdominant). Yet, little is known about the rules that define their immunogenicity and the hierarchy of the associated T cell responses. Using a panel of genetically modified T. gondii where the GRA6 dominant antigen was mutated, we show that the C-terminal location of the epitope within the source antigen is the critical parameter for immunodominance. Interestingly, when placed at the C-terminus of GRA6, the subdominant status of an epitope can be overturned. Our results unravel the mechanisms that make parasite antigens accessible for the MHC I presentation pathway. They may help to ameliorate natural immune responses and improve vaccine design against intravacuolar pathogens.
Toxoplasma gondii is a globally ubiquitous pathogen that can cause severe disease in immunocompromised humans and the developing fetus. Given the proven role of Toxoplasma-secreted kinases in the interaction of Toxoplasma with its host cell, identification of novel kinase inhibitors could precipitate the development of new anti-Toxoplasma drugs and define new pathways important for parasite survival. We selected a small (n = 527) but diverse set of putative kinase inhibitors and screened them for effects on the growth of Toxoplasma
in vitro. We identified and validated 14 noncytotoxic compounds, all of which had 50% effective concentrations in the nanomolar to micromolar range. We further characterized eight of these compounds, four inhibitors and four enhancers, by determining their effects on parasite motility, invasion, and the likely cellular target (parasite or host cell). Only two compounds had an effect on parasite motility and invasion. All the inhibitors appeared to target the parasite, and interestingly, two of the enhancers appeared to rather target the host cell, suggesting modulation of host cell pathways beneficial for parasite growth. For the four inhibitors, we also tested their efficacy in a mouse model, where one compound proved potent. Overall, these 14 compounds represent a new and diverse set of small molecules that are likely targeting distinct parasite and host cell pathways. Future work will aim to characterize their molecular targets in both the host and parasite.
Report of case series
To report a problem with bioabsorbable poly-l-lactide-co-d, l-lactide, PLDLLA, posterior lumbar instrumented fusion (PLIF) cage implants.
Summary of background data
Synthetic bioabsorbable implants have recently been introduced to spinal surgery and their indications and applications are still being explored. There is evidence that the use of bioabsorbable cages may be of benefit in interbody spinal fusion.
We present a case series of nine patients who have undergone PLIF with bioabsorbable cages in the lumbar spine.
At follow-up over at least 1 year, four of these patients were found to have osteolysis around the implant on CT scanning. One of these patients underwent an operation to remove the cage and histology sent during surgery suggested that the implant had caused the bone loss and there was no evidence of infection. Another patient had ongoing pain in relation to the lysis, while the other two patients with lysis remained asymptomatic.
PLDLLA cage, which has high osteolytic nature, is considered not suitable as a fusion cage.
Bioabsorbable cage; PLIF; Osteolysis
The avascular intervertebral disc (IVD) receives nutrition via transport from surrounding vasculature; poor nutrition is believed to be a main cause of disc degeneration. In this study, we investigated the effects of mechanical deformation and anisotropy on the transport of two important nutrients – oxygen and glucose – in human annulus fibrosus (AF). The diffusivities of oxygen and glucose were measured under three levels of uniaxial confined compression – 0%, 10%, and 20% – and in three directions – axial, circumferential, and radial. The glucose partition coefficient was also measured at three compression levels. Results for glucose and oxygen diffusivity in AF ranged from 4.46×10−7 to 9.77×10−6 cm2/s and were comparable to previous studies; the glucose partition coefficient ranged from 0.71 to 0.82 and was also similar to previous results. Transport properties were found to decrease with increasing deformation, likely caused by fluid exudation during tissue compression and reduction in pore size. Furthermore, diffusivity in the radial direction was lower than in the axial or circumferential directions, indicating that nutrient transport in human AF is anisotropic. This behavior is likely a consequence of the layered structure and unique collagen architecture of AF tissue. These findings are important for better understanding nutritional supply in IVD and related disc degeneration.
glucose; oxygen; nutrition; diffusion; partitioning; solubility; intervertebral disc
Insulin-like peptides (ILPs) regulate a multitude of biological processes, including metabolism and immunity to infection, and share similar structural motifs across widely divergent taxa. Insulin/insulin-like growth factor signaling (IIS) pathway elements are similarly conserved. We have shown that IIS regulates reproduction, innate immunity, and lifespan in female Anopheles stephensi, a major mosquito vector of human malaria. To further explore IIS regulation of these processes, we identified genes encoding five ILPs in this species and characterized their expression in tissues. Antisera to ILP homologs in Anopheles gambiae were used to identify cellular sources in An. stephensi females by immunocytochemistry. We analyzed tissue-specific ILP transcript expression in young and older females, in response to different feeding regimens, and in response to infection with Plasmodium falciparum with quantitative reverse transcriptase-PCR assays. While some ILP transcript changes were evident in older females and in response to blood feeding, significant changes were particularly notable in response to hormonal concentrations of ingested human insulin and to P. falciparum infection. These changes suggest that ILP secretion and action may be similarly responsive in Plasmodium-infected females and potentially alter metabolism and innate immunity.
insect; mosquito; insulin signaling; malaria; Anopheles; Plasmodium
The intervertebral disc (IVD) receives important nutrients, such as glucose, from surrounding blood vessels. Poor nutritional supply is believed to play a key role in disc degeneration. Several investigators have presented finite element models of the IVD to investigate disc nutrition; however, none has predicted nutrient levels and cell viability in the disc with a realistic 3D geometry and tissue properties coupled to mechanical deformation. Understanding how degeneration and loading affect nutrition and cell viability is necessary for elucidating the mechanisms of disc degeneration and low back pain. The objective of this study was to analyze the effects of disc degeneration and static deformation on glucose distributions and cell viability in the IVD using finite element analysis.
Method of Approach
A realistic 3D finite element model of the IVD was developed based on mechano-electrochemical mixture theory. In the model, the cellular metabolic activities and viability were related to nutrient concentrations, and transport properties of nutrients were dependent on tissue deformation. The effects of disc degeneration and mechanical compression on glucose concentrations and cell density distributions in the IVD were investigated. To examine effects of disc degeneration, tissue properties were altered to reflect those of degenerated tissue, including reduced water content, fixed charge density, height, and endplate permeability. Two mechanical loading conditions were also investigated: a reference (undeformed) case and a 10% static deformation case.
In general, nutrient levels decreased moving away from the nutritional supply at the disc periphery. Minimum glucose levels were at the interface between the nucleus and annulus regions of the disc. Deformation caused a 6.2% decrease in the minimum glucose concentration in the normal IVD, while degeneration resulted in an 80% decrease. Although cell density was not affected in the undeformed normal disc, there was a decrease in cell viability in the degenerated case, in which averaged cell density fell 11% compared with the normal case. This effect was further exacerbated by deformation of the degenerated IVD.
Both deformation and disc degeneration altered the glucose distribution in the IVD. For the degenerated case, glucose levels fell below levels necessary for maintaining cell viability, and cell density decreased. This study provides important insight into nutrition-related mechanisms of disc degeneration. Moreover, our model may serve as a powerful tool in the development of new treatments for low back pain.
glucose; annulus fibrosus; nucleus pulposus; mechanical loading; cell density
Metagenomic samples from oceans around the globe were used to examine the biogeography of the dominant marine heterotrophic bacterial clade, SAR11. Analysis uncovers evidence of adaptive radiation in response to environmental parameters, particularly temperature.
By generating 37 new Antarctic metagenomes and analysing the internal transcribed spacer (ITS) regions of the SAR11 clade in a total of 128 surface marine metagenomes, we identified phylotype distributions that strongly correlated with temperature and latitude.By assembling SAR11 genomes from Antarctic metagenome data, we identified specific genes, biases in gene functions and signatures of positive selection in the genomes of the polar SAR11—genomic signatures of adaptive radiation.Our data demonstrate the importance of adaptive radiation in an organism's ability to proliferate throughout the world's oceans, and describe genomic traits characteristic of different phylotypes in specific marine biomes.These bacteria are important marine heterotrophs and have a fundamental role in oceanic nutrient cycling. These findings, therefore, have important implications for our ability to predict how changes in ocean temperature may affect bacterial ecology.
The ubiquitous SAR11 bacterial clade is the most abundant type of organism in the world's oceans, but the reasons for its success are not fully elucidated. We analysed 128 surface marine metagenomes, including 37 new Antarctic metagenomes. The large size of the data set enabled internal transcribed spacer (ITS) regions to be obtained from the Southern polar region, enabling the first global characterization of the distribution of SAR11, from waters spanning temperatures −2 to 30°C. Our data show a stable co-occurrence of phylotypes within both ‘tropical' (>20°C) and ‘polar' (<10°C) biomes, highlighting ecological niche differentiation between major SAR11 subgroups. All phylotypes display transitions in abundance that are strongly correlated with temperature and latitude. By assembling SAR11 genomes from Antarctic metagenome data, we identified specific genes, biases in gene functions and signatures of positive selection in the genomes of the polar SAR11—genomic signatures of adaptive radiation. Our data demonstrate the importance of adaptive radiation in the organism's ability to proliferate throughout the world's oceans, and describe genomic traits characteristic of different phylotypes in specific marine biomes.
adaptive radiation; Antarctica; metagenome; Pelagibacter; phylotype distribution
In nature, the complexity and structure of microbial communities varies widely, ranging from a few species to thousands of species, and from highly structured to highly unstructured communities. Here, we describe the identity and functional capacity of microbial populations within distinct layers of a pristine, marine-derived, meromictic (stratified) lake (Ace Lake) in Antarctica. Nine million open reading frames were analyzed, representing microbial samples taken from six depths of the lake size fractionated on sequential 3.0, 0.8 and 0.1 μm filters, and including metaproteome data from matching 0.1 μm filters. We determine how the interactions of members of this highly structured and moderately complex community define the biogeochemical fluxes throughout the entire lake. Our view is that the health of this delicate ecosystem is dictated by the effects of the polar light cycle on the dominant role of green sulfur bacteria in primary production and nutrient cycling, and the influence of viruses/phage and phage resistance on the cooperation between members of the microbial community right throughout the lake. To test our assertions, and develop a framework applicable to other microbially driven ecosystems, we developed a mathematical model that describes how cooperation within a microbial system is impacted by periodic fluctuations in environmental parameters on key populations of microorganisms. Our study reveals a mutualistic structure within the microbial community throughout the lake that has arisen as the result of mechanistic interactions between the physico-chemical parameters and the selection of individual members of the community. By exhaustively describing and modelling interactions in Ace Lake, we have developed an approach that may be applicable to learning how environmental perturbations affect the microbial dynamics in more complex aquatic systems.
metagenomics/metaproteomics; Antarctic meromictic lake; green sulfur bacteria; virus/phage; nutrient cycle; Lotka–Volterra predator–prey model
Inbreeding and a consequent loss of genetic diversity threaten small, isolated populations. One mechanism by which genetically impoverished populations may become extinct is through decreased immunocompetence and higher susceptibility to parasites. Here, we investigate the relationship between immunity and inbreeding in bumblebees, using Hebridean island populations of Bombus muscorum. We sampled nine populations and recorded parasite prevalence and measured two aspects of immunity: the encapsulation response and levels of phenoloxidase (PO). We found that prevalence of the gut parasite Crithidia bombi was higher in populations with lower genetic diversity. Neither measure of immune activity was correlated with genetic diversity. However, levels of PO declined with age and were also negatively correlated with parasite abundance. Our results suggest that as insect populations lose heterozygosity, the impact of parasitism will increase, pushing threatened populations closer to extinction.
inbreeding; social insects; heterozygosity; disease; immune defence
Commercial greenhouse growers in both Japan and China are increasingly using reared orange-tailed bumblebees known previously as Bombus hypocrita Pérez as pollinators. Phylogenetic analysis of the DNA (COI) barcodes with Bayesian methods shows that this “species” is a long-standing confusion of two cryptic species. We find that the orange-tailed bumblebees in North China are actually part of the widespread Russian (otherwise white-tailed) B. patagiatus Nylander (as B. patagiatus ganjsuensis Skorikov, n. comb.), whereas the orange-tailed bees in Japan are true B. hypocrita. This situation has been further complicated because two other cryptic species from North China that were previously confused with the Russian B. patagiatus are now recognised as separate: B. lantschouensis Vogt n. stat. and B. minshanensis Bischoff n. stat.. As demand for pollination services by greenhouse growers inevitably increases, these bees are more likely to be transported between countries. In order to conserve genetic resources of pollinator species for their option value for future food security, we advocate preventing trade and movement of B. patagiatus from China into Japan and of B. hypocrita from Japan into China.
It is well known that obesity is a risk factor for sleep-disordered breathing (SDB). However, whether SDB predicts increase in BMI is not well defined. Data from the Sleep Heart Health Study (SHHS) were analyzed to determine whether SDB predicts longitudinal increase in BMI, adjusted for confounding factors.
A full-montage unattended home polysomnogram (PSG) and body anthropometric measurements were obtained approximately five years apart in 3001 participants. Apnea-hypopnea index (AHI) was categorized using clinical thresholds: < 5 (normal), ≥ 5 to <15 (mild sleep apnea), and ≥ 15 (moderate to severe sleep apnea). Linear regression was used to examine the association between the three AHI groups and increased BMI. The model included age, gender, race, baseline BMI, and change in AHI as covariates.
Mean (SD) age was 62.2 years (10.14), 55.2% were female and 76.1% were Caucasian. Five-year increase in BMI was modest with a mean (SD) change of 0.53 (2.62) kg/m2 (p=0.071). A multivariate regression model showed that subjects with a baseline AHI between 5–15 had a mean increase in BMI of 0.22 kg/m2 (p=0.055) and those with baseline AHI ≥ 15 had a BMI increase of 0.51 kg/m2 (p<0.001) compared to those with baseline AHI of <5.
Our findings suggest that there is a positive association between severity of SDB and subsequent increased BMI over approximately 5 years. This observation may help explain why persons with SDB have difficulty losing weight.
Sleep Apnea; Weight Gain; Obesity
Cryptic diversity within bumblebees (Bombus) has the potential to undermine crucial conservation efforts designed to reverse the observed decline in many bumblebee species worldwide. Central to such efforts is the ability to correctly recognise and diagnose species. The B. lucorum complex (Bombus lucorum, B. cryptarum and B. magnus) comprises one of the most abundant and important group of wild plant and crop pollinators in northern Europe. Although the workers of these species are notoriously difficult to diagnose morphologically, it has been claimed that queens are readily diagnosable from morphological characters. Here we assess the value of colour-pattern characters in species identification of DNA-barcoded queens from the B. lucorum complex. Three distinct molecular operational taxonomic units were identified each representing one species. However, no uniquely diagnostic colour-pattern character state was found for any of these three molecular units and most colour-pattern characters showed continuous variation among the units. All characters previously deemed to be unique and diagnostic for one species were displayed by specimens molecularly identified as a different species. These results presented here raise questions on the reliability of species determinations in previous studies and highlights the benefits of implementing DNA barcoding prior to ecological, taxonomic and conservation studies of these important key pollinators.
Interactions involving several parasite species (multi-parasitized hosts) or several host species (multi-host parasites) are the rule in nature. Only a few studies have investigated these realistic, but complex, situations from an evolutionary perspective. Consequently, their impact on the evolution of parasite virulence and transmission remains poorly understood. The mechanisms by which multiple infections may influence virulence and transmission include the dynamics of intrahost competition, mediation by the host immune system and an increase in parasite genetic recombination. Theoretical investigations have yet to be conducted to determine which of these mechanisms are likely to be key factors in the evolution of virulence and transmission. In contrast, the relationship between multi-host parasites and parasite virulence and transmission has seen some theoretical investigation. The key factors in these models are the trade-off between virulence across different host species, variation in host species quality and patterns of transmission. The empirical studies on multi-host parasites suggest that interspecies transmission plays a central role in the evolution of virulence, but as yet no complete picture of the phenomena involved is available. Ultimately, determining how complex host–parasite interactions impact the evolution of host–parasite relationships will require the development of cross-disciplinary studies linking the ecology of quantitative networks with the evolution of virulence.
multi-parasitized hosts; multi-host parasites; intrahost competition; immune system; interspecies transmission; epidemiology
Understanding polyphenism, the ability of a single genome to express multiple morphologically and behaviourally distinct phenotypes, is an important goal for evolutionary and developmental biology. Polyphenism has been key to the evolution of the Hymenoptera, and particularly the social Hymenoptera where the genome of a single species regulates distinct larval stages, sexual dimorphism and physical castes within the female sex. Transcriptomic analyses of social Hymenoptera will therefore provide unique insights into how changes in gene expression underlie such complexity. Here we describe gene expression in individual specimens of the pre-adult stages, sexes and castes of the key pollinator, the buff-tailed bumblebee Bombus terrestris.
cDNA was prepared from mRNA from five life cycle stages (one larva, one pupa, one male, one gyne and two workers) and a total of 1,610,742 expressed sequence tags (ESTs) were generated using Roche 454 technology, substantially increasing the sequence data available for this important species. Overlapping ESTs were assembled into 36,354 B. terrestris putative transcripts, and functionally annotated. A preliminary assessment of differences in gene expression across non-replicated specimens from the pre-adult stages, castes and sexes was performed using R-STAT analysis. Individual samples from the life cycle stages of the bumblebee differed in the expression of a wide array of genes, including genes involved in amino acid storage, metabolism, immunity and olfaction.
Detailed analyses of immune and olfaction gene expression across phenotypes demonstrated how transcriptomic analyses can inform our understanding of processes central to the biology of B. terrestris and the social Hymenoptera in general. For example, examination of immunity-related genes identified high conservation of important immunity pathway components across individual specimens from the life cycle stages while olfactory-related genes exhibited differential expression with a wider repertoire of gene expression within adults, especially sexuals, in comparison to immature stages. As there is an absence of replication across the samples, the results of this study are preliminary but provide a number of candidate genes which may be related to distinct phenotypic stage expression. This comprehensive transcriptome catalogue will provide an important gene discovery resource for directed programmes in ecology, evolution and conservation of a key pollinator.
Insects encode multiple ILPs but only one homolog of the vertebrate IR that activates the insulin signaling pathway. However, it remains unclear whether all insect ILPs are high affinity ligands for the IR or have similar biological functions. The yellow fever mosquito, Aedes aegypti, encodes eight ILPs with prior studies strongly implicating ILPs from the brain in regulating metabolism and the maturation of eggs following blood feeding. Here we addressed whether two ILP family members expressed in the brain, ILP4 and ILP3, have overlapping functional and receptor binding activities. Our results indicated that ILP3 exhibits strong insulin-like activity by elevating carbohydrate and lipid storage in sugar-fed adult females, whereas ILP4 does not. In contrast, both ILPs exhibited dose-dependent gonadotropic activity in blood-fed females as measured by the stimulation of ovaries to produce ecdysteroids and the uptake of yolk by primary oocytes. Binding studies using ovary membranes indicated that ILP4 and ILP3 do not cross compete; a finding further corroborated by cross-linking and immunoblotting experiments showing that ILP3 binds the MIR while ILP4 binds an unknown 55 kDa membrane protein. In contrast, each ILP activated the insulin signaling pathway in ovaries as measured by enhanced phosphorylation of Akt. RNAi and inhibitor studies further indicated that the gonadotropic activity of ILP4 and ILP3 requires the MIR and a functional insulin signaling pathway. Taken together, our results indicate that two members of the Ae. aegypti ILP family exhibit partially overlapping biological activity and different binding interactions with the MIR.
insect; insulin; metabolism; reproduction; mosquito
canSAR is a fully integrated cancer research and drug discovery resource developed to utilize the growing publicly available biological annotation, chemical screening, RNA interference screening, expression, amplification and 3D structural data. Scientists can, in a single place, rapidly identify biological annotation of a target, its structural characterization, expression levels and protein interaction data, as well as suitable cell lines for experiments, potential tool compounds and similarity to known drug targets. canSAR has, from the outset, been completely use-case driven which has dramatically influenced the design of the back-end and the functionality provided through the interfaces. The Web interface at http://cansar.icr.ac.uk provides flexible, multipoint entry into canSAR. This allows easy access to the multidisciplinary data within, including target and compound synopses, bioactivity views and expert tools for chemogenomic, expression and protein interaction network data.
Previous research with deafferented subjects suggests that efference copy can be used to update limb position. However, the contributions of efference copy to limb localization are currently unclear. We examined the performance of JDY, a woman with severe, longstanding proprioceptive deficits from a sensory peripheral neuropathy, on a reaching task to explore the contribution of efference copy to trajectory control. JDY and eight healthy controls reached without visual feedback to a target that either remained stationary or jumped to a second location after movement initiation. JDY consistently made hypermetric movements to the final target, exhibiting significant problems with amplitude control. Despite this amplitude control deficit, JDY’s performance on jump trials showed that the angle of movement correction (angle between pre- and post-correction movement segments) was significantly correlated with the distance (but not time) of movement from start to turn point. These data suggest that despite an absence of proprioceptive and visual information regarding hand location, JDY derived information about movement distance that informed her movement correction on jump trials. The same type of information that permitted her to correct movement direction on-line, however, was not available for control of final arm position. We propose that efference copy can provide a consistent estimate of limb position that becomes less informative over the course of the movement. We discuss the implications of these data for current models of motor control.
deafferentation; efference copy; motor control; proprioception; reaching
All vector mosquito species must feed on the blood of a vertebrate host to produce eggs. Multiple cycles of blood feeding also promote frequent contacts with hosts, which enhance the risk of exposure to infectious agents and disease transmission. Blood feeding triggers the release of insulin-like peptides (ILPs) from the brain of the mosquito Aedes aegypti, which regulate blood meal digestion and egg formation. In turn, hemocytes serve as the most important constitutive defense in mosquitoes against pathogens that enter the hemocoel. Prior studies indicated that blood feeding stimulates hemocytes to increase in abundance, but how this increase in abundance is regulated is unknown. Here, we determined that phagocytic granulocytes and oenocytoids express the A. aegypti insulin receptor (AaMIR). We then showed that: 1) decapitation of mosquitoes after blood feeding inhibited hemocyte proliferation, 2) a single dose of insulin-like peptide 3 (ILP3) sufficient to stimulate egg production rescued proliferation, and 3) knockdown of the AaMIR inhibited ILP3 rescue activity. Infection studies indicated that increased hemocyte abundance enhanced clearance of the bacterium Escherichia coli at lower levels of infection. Surprisingly, however, non-blood fed females better survived intermediate and high levels of E. coli infection than blood fed females. Taken together, our results reveal a previously unrecognized role for the insulin signaling pathway in regulating hemocyte proliferation. Our results also indicate that blood feeding enhances resistance to E. coli at lower levels of infection but reduces tolerance at higher levels of infection.
Mosquitoes are vectors of several important diseases of humans and other mammals including Dengue fever, malaria and filariasis. These diseases adversely affect worldwide health by killing or debilitating millions of individuals. The key feature of mosquito biology that makes them such important disease vectors is that adult females must feed on the blood of their vertebrate host(s) to produce eggs. In turn, repeated bouts of blood feeding and egg development elevate the risk of mosquitoes feeding on an infected host and transmitting a given pathogen from one individual to another. A key regulator of egg development following blood feeding is the release of insulin-like peptides from the mosquito brain. We have found that insulin-like peptides enhance production of immune cells (hemocytes) that serve as the first line of defense against infection. Conversely, the molecular pathways that regulate egg development and hemocyte proliferation reduce the ability of mosquitoes to tolerate a persistent systemic infection. Taken together, our results indicate that trade-offs exist between reproduction and immune defense in mosquitoes, which is a subject of fundamental interest to evolutionary biologists and of applied importance in understanding disease transmission.
Approximately 14-54% of patients with systemic lupus erythematosus without a history of major neuropsychiatric syndromes (nonNPSLE) have cognitive deficits. Elevated N-methyl-D-aspartate (NMDA) receptor antibodies (anti-NR2) have been reported in 35% of patients with SLE, but few studies have utilized controls or a composite memory index. We hypothesized that serum anti-NR2 would be elevated in nonNPSLE compared to healthy controls, and that elevated anti-NR2 would be associated with memory dysfunction and depression.
Subjects included 43 nonNPSLE patients with a mean age of 36.5 (SD=9.0) and mean education level of 14.7 years (SD=2.5). Twenty-seven healthy control subjects with similar demographic characteristics were also enrolled in this study. A global cognitive impairment index (CII) and a memory impairment index (MII) were calculated using impaired test scores from the ACR-SLE neuropsychological battery. Serum samples were analyzed using a standard ELISA for anti-NR2.
Elevations of serum anti-NR2 were found in 14.0% of the nonNPSLE and 7.4% of the controls (p=0.47). There was no relationship between elevated anti-NR2 status and higher CII or performance on the MII. No relationship between levels of depressive symptoms and anti-NR2 was found.
The frequency of elevated anti-NR2 was low (14.0%) in this sample of SLE patients and not significantly different from controls. A relationship was not found between the presence of anti-NR2 in serum and global cognitive or memory indices, or with depression. Results suggest that serum anti-NR2 is not likely related to mild cognitive dysfunction in SLE patients without a prior history of NPSLE.
SLE; neuropsychology; autoantibodies; NMDA
The SET and MYND Domain (SMYD) proteins comprise a unique family of multi-domain SET histone methyltransferases that are implicated in human cancer progression. Here we report an analysis of the crystal structure of the full length human SMYD3 in a complex with an analog of the S-adenosyl methionine (SAM) methyl donor cofactor. The structure revealed an overall compact architecture in which the “split-SET” domain adopts a canonical SET domain fold and closely assembles with a Zn-binding MYND domain and a C-terminal superhelical 9 α-helical bundle similar to that observed for the mouse SMYD1 structure. Together, these structurally interlocked domains impose a highly confined binding pocket for histone substrates, suggesting a regulated mechanism for its enzymatic activity. Our mutational and biochemical analyses confirm regulatory roles of the unique structural elements both inside and outside the core SET domain and establish a previously undetected preference for trimethylation of H4K20.
Mosquitoes are insects that vector many serious pathogens to humans and other vertebrates. Most mosquitoes must feed on the blood of a vertebrate host to produce eggs. In turn, multiple cycles of blood feeding promote frequent contacts with hosts and make mosquitoes ideal disease vectors. Both hormonal and nutritional factors are involved in regulating egg development in the mosquito, Aedes aegypti. However, the processes that regulate digestion of the blood meal remain unclear.
Here we report that insulin peptide 3 (ILP3) directly stimulated late phase trypsin-like gene expression in blood fed females. In vivo knockdown of the mosquito insulin receptor (MIR) by RNA interference (RNAi) delayed but did not fully inhibit trypsin-like gene expression in the midgut, ecdysteroid (ECD) production by ovaries, and vitellogenin (Vg) expression by the fat body. In contrast, in vivo treatment with double-stranded MIR RNA and rapamycin completely blocked egg production. In vitro experiments showed that amino acids did not simulate late phase trypsin-like gene expression in the midgut or ECD production by the ovaries. However, amino acids did enhance ILP3-mediated stimulation of trypsin-like gene expression and ECD production.
Overall, our results indicate that ILPs from the brain synchronize blood meal digestion and amino acid availability with ovarian ECD production to maximize Vg expression by the fat body. The activation of digestion by ILPs may also underlie the growth promoting effects of insulin and TOR signaling in other species.
Purpose of review
Dietary saturated fatty acids (SFAs) have been implicated in promoting the metabolic syndrome and atherosclerotic cardiovascular disease. Recent evidence suggests that SFAs promote the metabolic syndrome by activating Toll-like receptor 4 (TLR4). Here we examine emerging molecular evidence that SFAs directly engage pathways of innate immunity, thereby promoting inflammatory aspects of the metabolic syndrome.
Accumulation of SFA in the body is tightly regulated by stearoyl-CoA desaturase 1, an enzyme that converts endogenous SFA to monounsaturated fatty acids. Recent studies have demonstrated that the accumulation of SFA seen with genetic deletion or inhibition stearoyl-CoA desaturase 1 promotes inflammation, TLR4 hypersensitivity, and accelerated atherosclerosis. Therefore, stearoyl-CoA desaturase 1 may play an unexpected role in suppressing inflammation by preventing excessive accumulation of endogenous SFA-derived TLR4 agonists. In parallel, several independent laboratories have demonstrated that TLR4 is necessary for dietary SFAs to induce obesity, insulin resistance, and vascular inflammation in rodent models.
The metabolic syndrome and atherosclerotic cardiovascular disease have long been linked to dietary SFA intake and inflammation. Recent mechanistic insights into how SFAs and downstream metabolites can potentiate inflammation-driven metabolic disease are discussed here.
atherosclerosis; insulin resistance; obesity; polyunsaturated fatty acids; saturated fatty acids; Toll-like receptor 4
Legalising production for medical usage is neither feasible nor desirable
Cerebral atrophy is a well described, but poorly understood complication of HIV infection. Despite reduced prevalence of HIV-associated dementia in the HAART era, HIV continues to affect the brains of patients with chronic infection. In this study we examine patterns of brain volume loss in HIV infected patients on HAART, and demographic and clinical factors contributing to it. We hypothesized that nadir CD4+ lymphocyte count, duration of HIV infection and age would be associated with reduced cortical volumes.
Volumes of cortical and subcortical regions in 69 HIV-infected neuroasymptomatic (NA) individuals and 13 with at least mild AIDS dementia complex (ADC) were measured using voxel-based morphometry. Demographic and clinical factors (age, plasma HIV RNA level, current and nadir CD4 count, duration of infection, CNS penetration of antiretroviral regimen) along with their interactions were entered into a regression model selection algorithm to determine the final models that best described regional brain volumes.
Relative to NA, individuals with ADC exhibited decreased total gray matter and parietal cortex volumes and increased total ventricular volumes. Final regression models showed overall cerebral volume, including gray and white matter volume and volumes of the parietal, temporal, and frontal lobes and the hippocampus, were most strongly associated with disease history factors (nadir CD4 and duration of infection). In contrast, basal ganglia volumes were related most strongly to current disease factors, most notably plasma HIV RNA.
These findings indicate that individuals with a history of chronic HIV infection with previous episodes of severely impaired immune function, as reflected by reduced nadir CD4 + lymphocyte count, may be at greatest risk for cerebral atrophy. The pattern of HIV-associated brain loss may be changing from a subcortical to a cortical disease among patients who are largely asymptomatic on HAART.