Pulses of growth hormone (GH) release in acromegaly may arise from hypothalamic regulation or from random events intrinsic to adenomatous tissue. To distinguish between these possibilities, serum GH concentrations were measured at 5-min intervals for 24 h in acromegalic men and women with active (n = 19) and inactive (n = 9) disease and in normal young adults in the fed (n = 20) and fasted (n = 16) states. Daily GH secretion rates, calculated by deconvolution analysis, were greater in patients with active acromegaly than in fed (P < 0.05) but not fasted normal subjects. Significant basal (nonpulsatile) GH secretion was present in virtually all active acromegalics but not those in remission or in fed and fasted normal subjects. A recently introduced scale- and model-independent statistic, approximate entropy (ApEn), was used to test for regularity (orderliness) in the GH data. All but one acromegalic had ApEn values greater than the absolute range in normal subjects, indicating reduced orderliness of GH release; ApEn distinguished acromegalic from normal GH secretion (fed, P < 10(-12); fasted, P < 10(-7)) with high sensitivity (95%) and specificity (100%). Acromegalics in remission had ApEn scores larger than those of normal subjects (P < 0.0001) but smaller than those of active acromegalics (P < 0.001). The coefficient of variation of successive incremental changes in GH concentrations was significantly lower in acromegalics than in normal subjects (P < 0.001). Fourier analysis in acromegalics revealed reduced fractional amplitudes compared to normal subjects (P < 0.05). We conclude that GH secretion in acromegaly is highly irregular with disorderly release accompanying significant basal secretion.
The objective of this research was to examine the potential for intercalation of trichloroethene (TCE) by clay minerals associated with aquifer sediments. Sediment samples were collected from a field site in Tucson, AZ. Two widely used Montmorillonite specimen clays were employed as controls. X-ray diffraction, conducted with a controlled-environment chamber, was used to characterize smectite interlayer d-spacing for three treatments (bulk air-dry sample, sample mixed with synthetic groundwater, sample mixed with TCE-saturated synthetic groundwater). The results show that the d-spacing measured for the samples treated with TCE-saturated synthetic groundwater are larger (~26%) than those of the untreated samples for all field samples as well as the specimen clays. These results indicate that TCE was intercalated by the clay minerals, which may have contributed to the extensive elution tailing observed in prior miscible-displacement experiments conducted with this sediment.
Smectite; montmorillonite; clay; sorption; X-ray diffraction
Modifications to the gene encoding human alpha-synuclein have been linked to development of Parkinson’s disease. The highly conserved structure of alpha-synuclein suggests a functional interaction with membranes, and several lines of evidence point to a role in vesicle-related processes within nerve terminals. Using recombinant fusions of human alpha-synuclein including new genetic tags developed for correlated LM and EM (the tetracysteine-biarsenical labeling system or the new fluorescent protein for EM, MiniSOG), we determined the distribution of alpha-synuclein when over-expressed in primary neurons at supramolecular and cellular scales, in three dimensions (3D). We observed specific association of alpha-synuclein with a large and otherwise poorly characterized membranous organelle system of the presynaptic terminal, as well as with smaller vesicular structures within these boutons. Furthermore, alpha-synuclein was localized to multiple elements of the protein degradation pathway, including multivesicular bodies in the axons and lysosomes within neuronal cell bodies. Examination of synapses in brains of transgenic mice over-expressing human alpha-synuclein revealed alterations of the presynaptic endomembrane systems similar to our findings in cell culture. 3D electron tomographic analysis of enlarged presynaptic terminals in several brain areas revealed that these terminals were filled with membrane-bounded organelles, including tubulo-vesicular structures similar to what observed in vitro. We propose that alpha-synuclein over-expression is associated with hypertrophy of membrane systems of the presynaptic terminal previously shown to have a role in vesicle recycling. Our data support the conclusion that alpha- synuclein is involved in processes associated with the sorting, channeling, packaging and transport of synaptic material destined for degradation.
There is a growing body of literature examining the utility of behavioral treatment in primary progressive aphasia (PPA). There are, however, no studies exploring treatment approaches to improve speech production in individuals with apraxia of speech (AOS) associated with the nonfluent variant of PPA. The purpose of this study was to examine a novel approach to treatment of AOS in nonfluent PPA. We implemented a treatment method using structured oral reading as a tool for improving production of multisyllabic words in an individual with mild AOS and nonfluent variant PPA. Our participant showed a reduction in speech errors during reading of novel text that was maintained at one year post-treatment. Generalization of improved speech production was observed on repetition of words and sentences and the participant showed stability of speech production over time in connected speech. Results suggest that oral reading treatment may offer an efficient and effective means of addressing multisyllabic word production in AOS associated with nonfluent PPA, with lasting and generalized treatment effects.
apraxia of speech; treatment; speech therapy; nonfluent PPA; primary progressive aphasia
Pulmonary damage caused by chronic colonization of the cystic fibrosis (CF) lung by microbial communities is the proximal cause of respiratory failure. While there has been an effort to document the microbiome of the CF lung in pediatric and adult patients, little is known regarding the developing microflora in infants. We examined the respiratory and intestinal microbiota development in infants with CF from birth to 21 months. Distinct genera dominated in the gut compared to those in the respiratory tract, yet some bacteria overlapped, demonstrating a core microbiota dominated by Veillonella and Streptococcus. Bacterial diversity increased significantly over time, with evidence of more rapidly acquired diversity in the respiratory tract. There was a high degree of concordance between the bacteria that were increasing or decreasing over time in both compartments; in particular, a significant proportion (14/16 genera) increasing in the gut were also increasing in the respiratory tract. For 7 genera, gut colonization presages their appearance in the respiratory tract. Clustering analysis of respiratory samples indicated profiles of bacteria associated with breast-feeding, and for gut samples, introduction of solid foods even after adjustment for the time at which the sample was collected. Furthermore, changes in diet also result in altered respiratory microflora, suggesting a link between nutrition and development of microbial communities in the respiratory tract. Our findings suggest that nutritional factors and gut colonization patterns are determinants of the microbial development of respiratory tract microbiota in infants with CF and present opportunities for early intervention in CF with altered dietary or probiotic strategies.
While efforts have been focused on assessing the microbiome of pediatric and adult cystic fibrosis (CF) patients to understand how chronic colonization by these microbes contributes to pulmonary damage, little is known regarding the earliest development of respiratory and gut microflora in infants with CF. Our findings suggest that colonization of the respiratory tract by microbes is presaged by colonization of the gut and demonstrated a role of nutrition in development of the respiratory microflora. Thus, targeted dietary or probiotic strategies may be an effective means to change the course of the colonization of the CF lung and thereby improve patient outcomes.
Edwardsiella ictaluri is the cause of extensive mortalities and economic losses to the channel catfish industry of the southeast United States. Here we report the complete genome of Edwardsiella ictaluri 93-146. Whole-genome sequence analysis of E. ictaluri provides a tool for understanding the genomic regions specific to the species and the Edwardsiella genus.
Over the past century, the Brazilian Atlantic forest has been reduced to small, isolated fragments of forest. Reproductive isolation theories predict a loss of genetic diversity and increases in inbreeding and spatial genetic structure (SGS) in such populations. We analysed eight microsatellite loci to investigate the pollen and seed dispersal patterns, genetic diversity, inbreeding and SGS of the tropical tree Copaifera langsdorffii in a small (4.8 ha), isolated population. All 112 adult trees and 128 seedlings found in the stand were sampled, mapped and genotyped. Seedlings had significantly lower levels of genetic diversity (A=16.5±0.45, mean±95% s.e.; He=0.838±0.006) than did adult trees (A=23.2±0.81; He=0.893±0.030). Parentage analysis did not indicate any seed immigration (mseeds=0) and the pollen immigration rate was very low (mpollen=0.047). The average distance of realized pollen dispersal within the stand was 94 m, with 81% of the pollen travelling <150 m. A significant negative correlation was found between the frequency and distance of pollen dispersal (r=−0.79, P<0.01), indicating that short-distance pollinations were more frequent. A significant SGS for both adults (∼50 m) and seedlings (∼20 m) was also found, indicating that most of the seeds were dispersed over short distances. The results suggested that the spatial isolation of populations by habitat fragmentation can restrict seed and pollen gene flow, increase SGS and affect the genetic diversity of future generations.
Copaifera langsdorffii; tropical trees; microsatellite loci; seed dispersal; pollen dispersal; spatial genetic structure
The aim of this review is to explore the evolution of the logopenic variant of primary progressive aphasia as a distinct clinical entity and to outline recent advances that have clarified its clinical characteristics, neural underpinnings and potential genetic and pathological bases. This is particularly relevant as researchers attempt to identify clinico-pathological relationships in subtypes of primary progressive aphasia in hopes of utilizing language phenotype as a marker of underlying disease.
Recent work has served to refine and expand upon the clinical phenotype of the logopenic variant. Logopenic patients show a unique pattern of spared and impaired language processes that reliably distinguish this syndrome from other variants of progressive aphasia. Specifically, they exhibit deficits in naming and repetition in the context of spared semantic, syntactic and motor speech abilities. Further, there is a growing body of evidence indicating a possible link between the logopenic variant phenotype and specific pathological and genetic correlates.
Findings indicate that the logopenic variant is a distinct subtype of progressive aphasia that may hold value as a predictor of underlying pathology. Additional research, however, is warranted in order to further clarify the cognitive-linguistic profile and to confirm its relation to certain pathological and genetic processes.
logopenic progressive aphasia; primary progressive aphasia; logopenic variant; Alzheimer’s disease
Giant cell tumour of bone (GCT) is a relatively rare benign bone tumour more frequent in young people (20–40 years). Histologically, two cell types are represented, stromal cells of osteoblastic origin and a distinctive osteoclast-like population probably of monocytic origin. GCTs can be aggressive and they recur locally in up to 50% of cases; up to 5% of GCTs metastasise to the lungs and spontaneous transformation to a high-grade malignancy occurs in 1–3% of patients. The aetiology of GCT is not known, and no risk factors have been recognised, although familial clustering of both Paget’s disease and GCT has been reported.
GCTs account for approximately 3–5% of primary bone tumours. GCT is rarely multicentric and usually occurs at the epiphyses of long bones, but may also affect other bones.
There are few randomised, prospective clinical trials available to guide clinical management of GCT. Recent developments have led to evaluation of newer therapeutic agents, including biphosphonates and denosumab, with encouraging results. We report the case of a 66-year-old woman affected by GCT. In 1985 the patient, then 41 years old, presented a cystic lesion on her left tibia, which was removed surgically. This lesion relapsed two years later. Therefore the patient was hospitalised and received a diagnosis of “multicentric giant cell bone lesions” (limb-girdle, sternum, mandible, ribs), confirmed by histological examination. These lesions showed hyperactivity on bone scintigraphy. Plain radiographs demonstrated destructive lytic lesions. Blood and urinary examinations showed markedly elevated levels of bone alkaline phosphatase and urine pyridinoline and there was persistent bone pain. In 1993 normocalcaemic primary hyperparathyroidism was diagnosed and an adenoma was removed, with no relapse of the disease. Subsequently the patient started clodronate therapy, i.v., followed by alendronate-neridronate per os and clodronate i.m. for about nine years. Biphosphonate therapy caused a modest and transient decrease in bone indexes. Initial bone lesions were unchanged on computed tomography 25 years after diagnosis, but new bone lesions had appeared. MEN1 gene and CasR analyses were negative.
This is a rare case of a patient affected by multicentric giant cell tumours with a 25-year follow up. A slow progression of the lesion is documented, as well as the absence of significant effect of biphosphonate therapy.
We developed and tested three dimensional (3-D) indices for quantifying severity of deformational plagiocephaly (DP).
We evaluated the extent to which infants with and without DP (as determined by clinic referral and two experts’ ratings) could be correctly classified.
Infants ages 4–11 months, including 154 with diagnosed DP and 100 infants without a history of DP or other craniofacial condition. After excluding participants with discrepant expert ratings, data from 90 infants with DP and 50 infants without DP were retained.
Two-dimensional histograms of surface normal vector angles were extracted from 3-D mesh data and used to compute the severity scores below.
Left Posterior Flattening Score (LPFS), Right Posterior Flattening Score (RPFS), Asymmetry Score (AS), Absolute Asymmetry Score (AAS) and an approximation of a previously described 2-D measure, the Oblique Cranial Length Ratio (aOCLR). Two-dimensional histograms localized the posterior flatness for each participant.
We fit receiver operating characteristic curves and calculated the area under the curves (AUC) to evaluate the relative accuracy of DP classification using the above measures.
The AUC statistics were: AAS=91%; LPFS=97%, RPFS=91%; AS=99%, and aOCLR=79%.
Novel 3-D-based plagiocephaly posterior severity scores provided better sensitivity and specificity in the discrimination of plagiocephalic and typical head shapes than the 2-D measurements provided by a close approximation of OCLR. These indices will allow for more precise quantification of the DP phenotype in future studies on the prevalence of this condition, which may lead to improved clinical care.
plagiocephaly; head shape
Emdogain® (enamel matrix derivative, EMD) is well recognized in periodontology, where it is used as a local adjunct to periodontal surgery to stimulate regeneration of periodontal tissues lost to periodontal disease. The biological effect of EMD is through stimulation of local growth factor secretion and cytokine expression in the treated tissues, inducing a regenerative process that mimics odontogenesis. The major (>95%) component of EMD is Amelogenins (Amel). No other active components have so far been isolated from EMD, and several studies have shown that purified amelogenins can induce the same effect as the complete EMD. Amelogenins comprise a family of highly conserved extracellular matrix proteins derived from one gene. Amelogenin structure and function is evolutionary well conserved, suggesting a profound role in biomineralization and hard tissue formation. A special feature of amelogenins is that under physiological conditions the proteins self-assembles into nanospheres that constitute an extracellular matrix. In the body, this matrix is slowly digested by specific extracellular proteolytic enzymes (matrix metalloproteinase) in a controlled process, releasing bioactive peptides to the surrounding tissues for weeks after application. Based on clinical and experimental observations in periodontology indicating that amelogenins can have a significant positive influence on wound healing, bone formation and root resorption, several new applications for amelogenins have been suggested. New experiments now confirm that amelogenins have potential for being used also in the fields of endodontics, bone regeneration, implantology, traumatology, and wound care.
amelogenins; bone formation; endodontics; implantology; wound healing
Between January 2004 and February 2006, 109 patients after intentionally curative surgery for oesophageal or gastric cardia cancer were randomised to standard follow-up of surgeons at the outpatient clinic (standard follow-up; n=55) or by regular home visits of a specialist nurse (nurse-led follow-up; n=54). Longitudinal data on generic (EuroQuol-5D, European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30) and disease-specific quality of life (EORTC QLQ-OES18), patient satisfaction and costs were collected at baseline and at 6 weeks and 4, 7 and 13 months afterwards. We found largely similar quality-of-life scores in the two follow-up groups over time. At 4 and 7 months, slightly more improvement on the EQ-VAS was noted in the nurse-led compared with the standard follow-up group (P=0.13 and 0.12, respectively). Small differences were also found in patient satisfaction between the two groups (P=0.14), with spouses being more satisfied with nurse-led follow-up (P=0.03). No differences were found in most medical outcomes. However, body weight of patients of the standard follow-up group deteriorated slightly (P=0.04), whereas body weight of patients of the nurse-led follow-up group remained stable. Medical costs were lower in the nurse-led follow-up group (€2600 vs €3800), however, due to the large variation between patients, this was not statistically significant (P=0.11). A cost effectiveness acceptability curve showed that the probability of being cost effective for costs per one point gain in general quality-of-life exceeded 90 and 75% after 4 and 13 months of follow-up, respectively. Nurse-led follow-up at home does not adversely affect quality of life or satisfaction of patients compared with standard follow-up by clinicians at the outpatient clinic. This type of care is very likely to be more cost effective than physician-led follow-up.
oesophageal cancer surgery; follow-up; quality of life; patient satisfaction; costs
MUTYH Associated Polyposis (MAP), a Polyposis predisposition caused by biallelic mutations in the Base Excision Repair (BER) gene MUTYH, confers a marked risk of colorectal cancer (CRC). The MAP phenotype is difficult to distinguish from other hereditary CRC syndromes. Especially from Familial Adenomatous Polyposis (FAP) and to a lesser extend Lynch Syndrome, which are caused by germline mutations in the APC and Mismatch Repair (MMR) genes, respectively.
Here we review research findings regarding MUTYH interactions, genotypic and phenotypic characteristics of MAP, as well as surveillance and treatment of the disease. The applied papers, published between 1/1 2002- 1/2 2008, were found through PubMed.
The exact role of MUTYH in CRC tumorgenesis is still uncertain, although MAP tumors show distinct molecular features, including somatic G:C>T:A transversions in the APC gene. Furthermore, cooperation between the BER and the MMR systems exists, as MUTYH interacts with MMR gene-products. Possibly, monoallelic defects in both pathways are of significance to CRC development.
Specific MUTYH variants are found to be characteristic in distinct ethnic populations, which could facilitate future genetic screening. Knowledge concerning functional consequences of many MUTYH germline mutations remains sparse. Most thoroughly investigated are the two most common MUTYH variants, Y179C and G396D, both generating dysfunctional gene products.
Phenotypic features of MAP include: development of 10-100 colorectal adenomas, debuting at 46-47 years, often CRC at time of clinical diagnosis, and in some, development of extracolonic manifestations.
Colorectal cancer; MUTYH associated polyposis; The MUTYH gene; base excision repair; (Attenuated) familial adenomatous polyposis; lynch syndrome.
ACE inhibition results in secondary prevention of coronary artery disease (CAD) through different mechanisms including improvement of endothelial dysfunction. The Perindopril-Function of the Endothelium in Coronary artery disease Trial (PERFECT) evaluated whether long-term administration of perindopril improves endothelial dysfunction.
PERFECT is a 3-year double blind randomised placebo controlled trial to determine the effect of perindopril 8 mg once daily on brachial artery endothelial function in patients with stable CAD without clinical heart failure. Endothelial function in response to ischaemia was assessed using ultrasound. Primary endpoint was difference in flow-mediated vasodilatation (FMD) assessed at 36 months.
In 20 centers, 333 patients randomly received perindopril or matching placebo. Ischemia-induced FMD was 2.7% (SD 2.6). In the perindopril group FMD went from 2.6% at baseline to 3.3% at 36 months and in the placebo group from 2.8 to 3.0%. Change in FMD after 36 month treatment was 0.55% (95% confidence interval −0.36, 1.47; p = 0.23) higher in perindopril than in placebo group. The rate of change in FMD per 6 months was 0.14% (SE 0.05, p = 0.02) in perindopril and 0.02% (SE 0.05, p = 0.74) in placebo group (0.12% difference in rate of change p = 0.07).
Perindopril resulted in a modest, albeit not statistically significant, improvement in FMD.
ACE inhibition; brachial reactivity; endothelial function; cardiovascular disease prevention; atherosclerosis; coronary heart disease
Background: Identification of risk factors for the development of hepatocellular carcinoma (HCC) is important for HCC surveillance in chronic hepatitis B virus (HBV) infection. Our aim was to study the independent risk factors and effect of HBV genotypes on HCC development in a prospective longitudinal cohort of chronic hepatitis B patients.
Patients and methods: Chronic hepatitis B patients recruited since 1997 were prospectively followed up for the development of HCC. HCC was diagnosed by a combination of α fetoprotein, imaging, and histology. Liver cirrhosis was defined as ultrasonic features of cirrhosis together with hypersplenism, ascites, varices, and/or encephalopathy.
Results: In total, 426 patients were followed up for 1664 person years; median 225 (range 12–295) weeks. Forty nine (11%) patients had underlying clinical liver cirrhosis. A total of 242 (57%) and 179 (42%) patients had HBV genotypes C and B, respectively. Twenty five patients developed HCC in a median follow up of 121 (range 14–236) weeks. The overall incidence of HCC was 1502 cases per 100 000 person years. On multivariate analysis, clinical liver cirrhosis and HBV genotype C infection were independently associated with HCC development, with an adjusted relative risk of 10.24 (95% confidence interval (CI) 4.39–23.89; p<0.001) and 2.84 (95% CI 1.05–7.72; p = 0.040), respectively. Patient age, sex, hepatitis B e antigen (HBeAg) status, alanine aminotransferase (ALT) levels, and basal core promoter mutations did not predict HCC development. Patients infected with HBV genotype C tended to have persistently positive HBeAg or fluctuating HBeAg status and higher ALT levels during the follow up period.
Conclusion: Genotype C HBV infection is an independent risk factor for HCC development in addition to liver cirrhosis.
hepatitis B; genotype; hepatocellular carcinoma; liver cirrhosis; basal core promoter mutations
Mucosal, cutaneous and Epidermodysplasia verruciformis (EV)-related human papillomaviruses (HPVs) were searched by broad-spectrum PCR in 86 conjunctival neoplasia biopsies and 63 conjunctival non-neoplastic control tissue from Ugandan subjects. Seven different EV-related HPV types, including a putative new HPV, and two mucosal HPVs were detected in 25% (14 out of 56) of HIV-positive, in 10% (three out of 30) of HIV-negative conjunctival neoplasia samples, and rarely (0–1.6%) in control subjects. The absence of high-risk HPVs and the low detection frequency of EV-related HPV types in more advanced tumour stages (10%) raise doubts about their role in conjunctival carcinomas.
conjunctiva squamous cell carcinoma; conjunctival intraepithelial neoplasia; papillomavirus; human immunodeficiency virus; Uganda
The Bcl-2 family of apoptotic regulators is thought to play an essential role in cancer development and influence the sensitivity of tumour cells to radiotherapy. Bid is an abundantly expressed Bcl-2 family protein playing a central role in various pathways of apoptosis by integrating and converging signals at the mitochondria. The relevance of apoptotic modulation by Bcl-2 and related proteins in tumour development and radiation response for human tumours remains undefined. Therefore, a study was made regarding the expression of Bid in patients with locally advanced cervix carcinoma who received radiotherapy. Bid expression was assessed using immunohistochemistry in pretreatment archival biopsies from 98 patients. The data were correlated with clinicopathologic characteristics and treatment outcome. Pretreatment tumour radiosensitivity data were available for 60 patients. Strong Bid expression was associated with a patient age less than the median of 52 years (P=0.034) and poor metastasis-free survival. In multivariate analysis, after allowing for stage, Bid expression was a significant prognostic factor for both disease-specific and metastasis-free survival (P=0.026). It is concluded that strong tumour Bid expression is associated with poor outcome following radiotherapy regardless of intrinsic tumour cell radiosensitivity, and is adverse prognostic for disease-specific and metastasis-free survival in younger patients.
Bcl-2 family; cervix carcinoma; prognosis; metastasis; radiotherapy
We have recently developed a candidate human immunodeficiency virus type 1 (HIV-1) vaccine model, based on virus-like particles (VLPs) expressing gp120 from a Ugandan HIV-1 isolate of clade A (HIV-VLPAs), which shows the induction of neutralizing antibodies as well as cytotoxic T lymphocytes (CTL) in BALB/c mice by intraperitoneal (i.p.) administration. In the present study, immunization experiments based on a multiple-dose regimen have been performed with BALB/c mice to compare different routes of administration. i.p. and intranasal (i.n.), but not oral, administration induce systemic as well as mucosal (vaginal and intestinal) immunoglobulin G (IgG) and IgA responses. These immune sera exhibit >50% ex vivo neutralizing activity against both autologous and heterologous primary isolates. Furthermore, the administration of HIV-VLPAs by the i.n. immunization route induces a specific CTL activity, although at lower efficiency than the i.p. route. The HIV-VLPAs represent an efficient strategy to stimulate both arms of immunity; furthermore, the induction of specific humoral immunity at mucosal sites, which nowadays represent the main port of entry for HIV-1 infection, is of great interest. All these properties, and the possible cross-clade in vivo protection, could make these HIV-VLPAs a good candidate for a mono- and multicomponent worldwide preventive vaccine approach not restricted to high-priority regions, such as sub-Saharan countries.
Scanning electron and atomic force microscopy was used for the first time to view the maturation of SARS-CoV at the cell surface.
Scanning electron and atomic force microscopy was used for the first time to view the maturation of the severe acute respiratory syndrome–associated coronavirus at the cell surface. The surface form of the cells at advanced infection displayed prolific pseudopodia that, in addition to the rest of the plasma membrane, were also active sites of virus release. High magnification of the maturing virus particles showed a rosette appearance with short knoblike spikes under both the scanning electron and atomic force microscopes. The final expulsion step of the maturing virus particles seemed to result in some disruptions to the plasma membrane. The cytoskeletal network along the edge of the infected cells was enhanced and could be involved in transporting and expelling the progeny virus particles. Thickening of the actin filaments at the cell edge provided the bending force to extrude the virus particles.
SARS coronavirus replication; atomic force microscopy; scanning electron microscopy; research
Alkaline phosphatase activity and phosphate transport rates in Rhizobium meliloti increased significantly when medium phosphate levels decreased to approximately 10 (mu)M. Both responses were abolished in a Tn5:: phoB mutant, but the mutant could be complemented by a plasmid that contained cloned R. meliloti phoB. The PhoB(sup-) mutant had a normal symbiosis phenotype under growth conditions that supplied either limiting or nonlimiting levels of phosphate to the host plant Medicago sativa, suggesting that induction of genes by PhoB was not required for normal symbiotic function.
The erbAalpha gene encodes two alpha-thyroid hormone receptor isoforms, TRalpha1 and TRalpha2, which arise from alternatively processed mRNAs, erbAalpha1 (alpha1) and erb alpha2 (alpha2). The splicing and alternative polyadenylation patterns of these mRNAs resemble that of mRNAs encoding different forms of immunoglobulin heavy chains, which are regulated at the level of alternative processing during B cell differentiation. This study examines the levels of erbAalpha mRNA in eight B cell lines representing four stages of differentiation in order to determine whether regulation of the alternatively processed alpha1 and alpha2 mRNAs parallels the processing of immunoglobulin heavy chain mRNAs. Results show that the pattern of alpha1 and alpha2 mRNA expression is clearly different from that observed for immunoglobulin heavy chain mRNAs. B cell lines display characteristic ratios of alpha1/alpha2 mRNA at distinct stages of differentiation. Furthermore, expression of an overlapping gene, Rev-ErbAalpha (RevErb), was found to correlate strongly with an increase in the ratio of alpha1/alpha2 mRNA. These results suggest that alternative processing of erbAalpha mRNAs is regulated by a mechanism which is distinct from that regulating immunoglobulin mRNA. The correlation between RevErb and erbAalpha mRNA is consistent with negative regulation of alpha2 via antisense interactions with the complementary RevErb mRNA.
The activities of fumarase- and manganese-cofactored superoxide dismutase (SOD), encoded by the fumC and sodA genes in Pseudomonas aeruginosa, are elevated in mucoid, alginate-producing bacteria and in response to iron deprivation (D. J. Hassett, M. L. Howell, P. A. Sokol, M. L. Vasil, and G. E. Dean, J. Bacteriol. 179:1442-1451, 1997). In this study, a 393-bp open reading frame, fagA (Fur-associated gene), was identified immediately upstream of fumC, in an operon with orfX and sodA. Two iron boxes or Fur (ferric uptake regulatory protein) binding sites were discovered just upstream of fagA. Purified P. aeruginosa Fur caused a gel mobility shift of a PCR product containing these iron box regions. DNA footprinting analysis revealed a 37-bp region that included the Fur binding sites and was protected by Fur. Primer extension analysis and RNase protection assays revealed that the operon is composed of at least three major iron-regulated transcripts. Four mucoid fur mutants produced 1.7- to 2.6-fold-greater fumarase activity and 1.7- to 2.3-greater amounts of alginate than wild-type organisms. A strain devoid of the alternative sigma factor AlgT(U) produced elevated levels of one major transcript and fumarase C and manganase-cofactored SOD activity, suggesting that AlgT(U) may either play a role in regulating this transcript or function in some facet of iron metabolism. These data suggest that the P. aeruginosa fagA, fumC, orfX, and sodA genes reside together on a small operon that is regulated by Fur and is transcribed in response to iron limitation in mucoid, alginate-producing bacteria.
The hydroxyethylurea human immunodeficiency virus type 1 (HIV-1) protease inhibitors SC-55389A and SC-52151 were used to select drug-resistant variants in vitro. One clinical HIV-1 strain (89-959) and one laboratory HIV-1 strain (LAI) were passaged in peripheral blood mononuclear cells or CEMT4 cells in the presence of SC-55389A. Resistant isolates from both strains consistently had a mutation to serine for asparagine at amino acid 88 (N88S) in the protease gene either alone or in combination with a change to phenylalanine at position 10. The N88S mutation, recreated by oligonucleotide-mediated site-directed mutagenesis in HXB2, was sufficient to confer resistance to SC-55389A. In contrast, SC-52151-resistant variants selected from the monocytotropic strain SF162 had multiple substitutions in the protease gene (I11V, M461, F53L, A71V, and N88D), and the N88D mutation, re-created by oligonucleotide-mediated site-directed mutagenesis in HXB2, did not confer resistance to SC-52151. The potencies of L735,524 and Ro31-8959 were not reduced when these compounds were assayed against variants with either the N88S or N88D substitution. Position 88 is in a helix that lies behind the substrate binding pocket and may indirectly influence inhibitor binding through interactions with the amino acid at position 31. The selected mutations were persistent in the viral populations after more than 20 passages in the absence of drugs. Passaging of virus first in SC-55389A alone and then in combination with SC-52151 resulted in the accumulation of more mutations in the protease gene (L10F, D35E, D37M, I47V, 154L, A71V, V82I, and S88D) and in the selection of a variant that was cross-resistant to multiple protease inhibitors. These results indicate that a mutation in the HIV-1 protease at a position that is located outside of the substrate binding pocket confers resistance to a protease inhibitor and that mutations in the protease gene accumulate with increasing selection pressure and can persist in the absence of selection pressure.
We report the discovery of fumC, encoding a fumarase, upstream of the sodA gene, encoding manganese superoxide dismutase, in Pseudomonas aeruginosa. The fumC open reading frame, which terminates 485 bp upstream of sodA, contains 1,374 bp that encode 458 amino acids. A second 444-bp open reading frame located between fumC and sodA, called orfX, showed no homology with any genes or proteins in database searches. A fumarase activity stain revealed that P. aeruginosa possesses at least two and possibly three fumarases. Total fumarase activity was at least approximately 1.6-fold greater in mucoid, alginate-producing bacteria than in nonmucoid bacteria and decreased 84 to 95% during the first 5 h of aerobic growth, followed by a rapid rise to maximum activity in stationary phase. Bacteria exposed to the iron chelator 2,2'-dipyridyl, but not ferric chloride, demonstrated an increase in fumarase activity. Mucoid bacteria produced approximately twofold-higher levels of the siderophores pyoverdin and pyochelin than nonmucoid bacteria. Northern blot analysis revealed a transcript that included fumC, orfX, and sodA, the amount of which was increased in response to iron deprivation. A P. aeruginosa fumC mutant produced only approximately 40% the alginate of wild-type bacteria. Interestingly, a sodA mutant possessed an alginate-stable phenotype, a trait that is typically unstable in vitro. These data suggest that mucoid bacteria either are in an iron-starved state relative to nonmucoid bacteria or simply require more iron for the process of alginate biosynthesis. In addition, the iron-regulated, tricarboxylic acid cycle enzyme fumarase C is essential for optimal alginate production by P. aeruginosa.
Pseudomonas aeruginosa is considered a strict aerobe that possesses several enzymes important in the disposal of toxic oxygen reduction products including iron- and manganese-cofactored superoxide dismutase and catalase. At present, the nature of the regulation of these enzymes in P. aeruginosa Is not understood. To address these issues, we used two mutants called A4 and C6 which express altered Fur (named for ferric uptake regulation) proteins and constitutively produce the siderophores pyochelin and pyoverdin. Both mutants required a significant lag phase prior to log-phase aerobic growth, but this lag was not as apparent when the organisms were grown under microaerobic conditions. The addition of iron salts to mutant A4 and, to a greater extent, C6 cultures allowed for an increased growth rate under both conditions relative to that of bacteria without added iron. Increased manganese superoxide dismutase (Mn-SOD) and decreased catalase activities were also apparent in the mutants, although the second catalase, KatB, was detected in cell extracts of each fur mutant. Iron deprivation by the addition of the iron chelator 2,2'-dipyridyl to wild-type bacteria produced an increase in Mn-SOD activity and a decrease in total catalase activity, similar to the fur mutant phenotype. Purified wild-type Fur bound more avidly than mutant Fur to a PCR product containing two palindromic 19-bp "iron box" regions controlling expression of an operon containing the sodA gene that encodes Mn-SOD. All mutants were defective in both ferripyochelin- and ferripyoverdin-mediated iron uptake. Two mutants of strain PAO1, defective in pyoverdin but not pyochelin biosynthesis, produced increased Mn-SOD activity. Sensitivity to both the redox-cycling agent paraquat and hydrogen peroxide was greater in each mutant than in the wild-type strain. In summary, the results indicate that mutations in the P. aeruginosa fur locus affect aerobic growth and SOD and catalase activities in P. aeruginosa. We postulate that reduced siderophore-mediated iron uptake, especially that by pyoverdin, may be one possible mechanism contributing to such effect.