Background and Aims

Specific leaf area (SLA), a key element of the ‘worldwide leaf economics spectrum’, is the preferred ‘soft’ plant trait for assessing soil fertility. SLA is a function of leaf dry matter content (LDMC) and leaf thickness (LT). The first, LDMC, defines leaf construction costs and can be used instead of SLA. However, LT identifies shade at its lowest extreme and succulence at its highest, and is not related to soil fertility. Why then is SLA more frequently used as a predictor of soil fertility than LDMC?

Methods

SLA, LDMC and LT were measured and leaf density (LD) estimated for almost 2000 species, and the capacity of LD to predict LDMC was examined, as was the relative contribution of LDMC and LT to the expression of SLA. Subsequently, the relationships between SLA, LDMC and LT with respect to soil fertility and shade were described.

Key Results

Although LD is strongly related to LDMC, and LDMC and LT each contribute equally to the expression of SLA, the exact relationships differ between ecological groupings. LDMC predicts leaf nitrogen content and soil fertility but, because LT primarily varies with light intensity, SLA increases in response to both increased shade and increased fertility.

Conclusions

Gradients of soil fertility are frequently also gradients of biomass accumulation with reduced irradiance lower in the canopy. Therefore, SLA, which includes both fertility and shade components, may often discriminate better between communities or treatments than LDMC. However, LDMC should always be the preferred trait for assessing gradients of soil fertility uncoupled from shade. Nevertheless, because leaves multitask, individual leaf traits do not necessarily exhibit exact functional equivalence between species. In consequence, rather than using a single stand-alone predictor, multivariate analyses using several leaf traits is recommended.

Inspired by the localization, on 15q21.2 of the CYP19A1 gene in the linkage region of speech and language disorders, and a rare translocation in a dyslexic individual that was brought to our attention, we conducted a series of studies on the properties of CYP19A1 as a candidate gene for dyslexia and related conditions. The aromatase enzyme is a member of the cytochrome P450 super family, and it serves several key functions: it catalyzes the conversion of androgens into estrogens; during early mammalian development it controls the differentiation of specific brain areas (e.g. local estrogen synthesis in the hippocampus regulates synaptic plasticity and axonal growth); it is involved in sexual differentiation of the brain; and in songbirds and teleost fishes, it regulates vocalization. Our results suggest that variations in CYP19A1 are associated with dyslexia as a categorical trait and with quantitative measures of language and speech, such as reading, vocabulary, phonological processing and oral motor skills. Variations near the vicinity of its brain promoter region altered transcription factor binding, suggesting a regulatory role in CYP19A1 expression. CYP19A1 expression in human brain correlated with the expression of dyslexia susceptibility genes such as DYX1C1 and ROBO1. Aromatase-deficient mice displayed increased cortical neuronal density and occasional cortical heterotopias, also observed in Robo1−/− mice and human dyslexic brains, respectively. An aromatase inhibitor reduced dendritic growth in cultured rat neurons. From this broad set of evidence, we propose CYP19A1 as a candidate gene for human cognitive functions implicated in reading, speech and language.

Electronic supplementary material

The online version of this article (doi:10.1007/s10519-012-9532-3) contains supplementary material, which is available to authorized users.

Background and Aims

Genome size is a function, and the product, of cell volume. As such it is contingent on ecological circumstance. The nature of ‘this ecological circumstance’ is, however, hotly debated. Here, we investigate for angiosperms whether stomatal size may be this ‘missing link’: the primary determinant of genome size. Stomata are crucial for photosynthesis and their size affects functional efficiency.

Methods

Stomatal and leaf characteristics were measured for 1442 species from Argentina, Iran, Spain and the UK and, using PCA, some emergent ecological and taxonomic patterns identified. Subsequently, an assessment of the relationship between genome-size values obtained from the Plant DNA C-values database and measurements of stomatal size was carried out.

Key Results

Stomatal size is an ecologically important attribute. It varies with life-history (woody species < herbaceous species < vernal geophytes) and contributes to ecologically and physiologically important axes of leaf specialization. Moreover, it is positively correlated with genome size across a wide range of major taxa.

Conclusions

Stomatal size predicts genome size within angiosperms. Correlation is not, however, proof of causality and here our interpretation is hampered by unexpected deficiencies in the scientific literature. Firstly, there are discrepancies between our own observations and established ideas about the ecological significance of stomatal size; very large stomata, theoretically facilitating photosynthesis in deep shade, were, in this study (and in other studies), primarily associated with vernal geophytes of unshaded habitats. Secondly, the lower size limit at which stomata can function efficiently, and the ecological circumstances under which these minute stomata might occur, have not been satisfactorally resolved. Thus, our hypothesis, that the optimization of stomatal size for functional efficiency is a major ecological determinant of genome size, remains unproven.

Limited research has been conducted on the structure of the pars triangularis (PT) in dyslexia despite functional neuroimaging research finding it may play a role in phonological processing. Furthermore, research to date has not examined PT size in ADHD even though the right inferior frontal region has been implicated in the disorder. Hence, one of the purposes of this study was to examine the structure of the PT in dyslexia and ADHD. The other purposes included examining the PT in relation to overall expressive language ability and in relation to several specific linguistic functions given language functioning often is affected in both dyslexia and ADHD. Participants included 50 children: 10 with dyslexia, 15 with comorbid dyslexia/ADHD, 15 with ADHD, and 10 controls. Using a 2 (dyslexia or not) X 2 (ADHD or not) MANCOVA, findings revealed PT length and shape were comparable between those with and without dyslexia. However, children with ADHD had smaller right PT lengths than those without ADHD, and right anterior ascending ramus length was related to attention problems in the total sample. In terms of linguistic functioning, presence of an extra sulcus in the left PT was related to poor expressive language ability. In those with adequate expressive language functioning, left PT length was related to phonological awareness, phonological short-term memory and rapid automatic naming (RAN). Right PT length was related to RAN and semantic processing. Further work on PT morphology in relation to ADHD and linguistic functioning is warranted.

Because poor comprehension has been associated with small cerebral volume and there is a high comorbidity between developmental dyslexia, ADHD, and specific language impairment, the goal of this study was to determine if cerebral volume is reduced in dyslexia and ADHD in general, as some suggest, or if reduction in volume corresponds with poor receptive language functioning regardless of diagnosis. Participants included 46 children with and without dyslexia and ADHD, ages 8-12 years. Results indicated that cerebral volume was comparable between those with and without dyslexia and ADHD overall. However, when groups were further divided into those with and without receptive language difficulties, children with poor receptive language had smaller volumes bilaterally as hypothesized. Nonetheless, the relationship between cerebral volume and receptive language was not linear; rather, our results suggest small volume is associated with poor receptive language only in those with the smallest volumes in both dyslexia and ADHD.

Synaptic activity recorded from low-density networks of cultured rat hippocampal neurons was monitored using microelectrode arrays (MEAs). Neuronal networks were patterned with poly-L-lysine (PLL) using microcontact printing (µCP). Polydimethysiloxane (PDMS) stamps were fabricated with relief structures resulting in patterns of 2 µm-wide lines for directing process growth and 20 µm-diameter circles for cell soma attachment. These circles were aligned to electrode sites. Different densities of neurons were plated in order to assess the minimal neuron density required for development of an active network. Spontaneous activity was observed at 10–14 days in networks using neuron densities as low as 200 cells/mm2. Immunocytochemistry demonstrated the distribution of dendrites along the lines and the location of foci of the presynaptic protein, synaptophysin, on neuron somas and dendrites. Scanning electron microscopy demonstrated that single fluorescent tracks contained multiple processes. Evoked responses of selected portions of the networks were produced by stimulation of specific electrode sites. In addition, the neuronal excitability of the network was increased by the bath application of high K+ (10–12 mM). Application of DNQX, an AMPA antagonist, blocked all spontaneous activity, suggesting that the activity is excitatory and mediated through glutamate receptors.

Polyacrylamide and poly(ethylene glycol) diacrylate hydrogels were synthesized and characterized for use as drug-release and substrates for neuron cell culture. Protein release kinetics was determined by incorporating bovine serum albumin (BSA) into hydrogels during polymerization. To determine if hydrogel incorporation and release affects bioactivity, alkaline phosphatase was incorporated into hydrogels and released enzyme activity determined using the fluorescence-based ELF-97 assay. Hydrogels were then used to deliver brain derived neurotrophic factor (BDNF) from hydrogels polymerized over planar microelectrode arrays (MEA). Primary hippocampal neurons were cultured on both control and neurotrophin-containing hydrogel-coated MEAs. The effect of released BDNF on neurite length and process arborization was investigated using automated image analysis. Increased spontaneous activity as a response to released BDNF was recorded from the neurons cultured on top of hydrogel layers. These results demonstrate that proteins of biological interest can be incorporated into hydrogels to modulate development and function of cultured neural networks. These results also set the stage for development of hydrogel-coated neural prosthetic devices for local delivery of various biologically active molecules.

Biochemical surface modification has been used to direct cell attachment and growth on a biocompatible gel surface. Acrylamide-based hydrogels were photo-polymerized in the presence of an acroyl-streptavidin monomer to create planar, functionalized surfaces capable of binding biotin-labelled proteins. Soft protein lithography (microcontact printing) of proteins was used to transfer the biotinylated extracellular matrix proteins, fibronectin and laminin, and the laminin peptide biotin-IKVAV, onto modified surfaces. As a biological assay, we plated LRM55 astroglioma and primary rat hippocampal neurons on patterned hydrogels. We found both cell types to selectively adhere to areas patterned with biotin-conjugated proteins. Fluorescence and bright-field modes of microscopy were used to assess cell attachment and cell morphology on modified surfaces. LRM55 cells were found to attach to protein-stamped regions of the hydrogel only. Neurons exhibited significant neurite extension after 72 hr in vitro, and remained viable on protein stamped areas for more than 4 weeks. Patterned neurons developed functionally active synapses, as measured by uptake of the dye FM 1-43FX. Results from this study suggest that hydrogel surfaces can be patterned with multiple proteins to direct cell growth and attachment.

Cell culture models can provide information pertaining to the effective dose, toxiciology, and kinetics, for a variety of neuroactive compounds. However, many in vitro models fail to adequately predict how such compounds will perform in a living organism. At the systems level, interactions between organs can dramatically affect the properties of a compound by alteration of its biological activity or by elimination of it from the body. At the tissue level, interaction between cell types can alter the transport properties of a particular compound, or can buffer its effects on target cells by uptake, processing, or changes in chemical signaling between cells. In any given tissue, cells exist in a three-dimensional environment bounded on all sides by other cells and components of the extracellular matrix, providing kinetics that are dramatically different from the kinetics in traditional two-dimensional cell culture systems. Cell culture analogs are currently being developed to better model the complex transport and processing that occur prior to drug uptake in the CNS, and to predict blood-brain barrier permeability. These approaches utilize microfluidics, hydrogel matrices, and a variety of cell types (including lung epithelial cells, hepatocytes, adipocytes, glial cells, and neurons) to more accurately model drug transport and biological activity. Similar strategies are also being used to control both the spatial and temporal release of therapeutic compounds for targeted treatment of CNS disease.

OBJECTIVE--To determine the influence of insulin dependent diabetes on the prevalence of myocardial ischaemia and on global left ventricular systolic performance. DESIGN--Stress treadmill electrocardiograms and simultaneous Doppler measurement of aortic maximum acceleration were obtained during exercise on symptom free subjects. The electrocardiograms were scored blindly according to the Minnesota code. PARTICIPANTS--39 identical twin pairs (22 male) discordant for insulin dependent diabetes and 39 non-diabetic controls of similar age and sex were examined. The twins and controls had a mean age of 37 (range 25-69) with a mean (SD) duration of diabetes in the diabetic twin of 17 (7) years. Those selected were normotensive and had no renal impairment. RESULTS--Systolic blood pressure was significantly higher in the diabetic twins than in their non-diabetic cotwins both at rest (p < 0.05) and at peak exercise (p < 0.01). Electrocardiographic evidence of ischaemia was not correlated within twin pairs and was found in similar numbers of diabetic twins, their non-diabetic cotwins, and control subjects. Abnormal electrocardiograms were found in a similar number of diabetic twins (23%), non-diabetic cotwins (18%), and controls (15%). There was a significant correlation in Doppler measurements of global left ventricular systolic function within the identical twins; no significant difference was found for these Doppler measurements in the diabetic twins, non-diabetic cotwins, or controls. CONCLUSION--Exercise characteristics and cardiac function seem to be subject to shared genetic or shared environmental influences or both, whereas electrocardiographic features of ischaemia seem to be environmentally determined. In a selected cohort of diabetic identical twins without evidence of nephropathy there was no evidence that diabetes influenced the prevalence of myocardial ischaemia or global left ventricular systolic function.

Gemfibrozil is a potent lipid regulating drug whose major effects are to increase plasma high density lipoproteins (HDL) and to decrease plasma triglycerides (TG) in a wide variety of primary and secondary dyslipoproteinemias. Its mechanism of action is not clear. Six patients with primary familial endogenous hypertriglyceridemia with fasting chylomicronemia (type V lipoprotein phenotype) with concurrent subnormal HDL cholesterol levels (HDL deficiency) were treated initially by diet and once stabilized, were given gemfibrozil (1,200 mg/d). Each patient was admitted to the Clinical Research Center with metabolic kitchen facilities, for investigation of HDL and TG metabolism immediately before and after 8 wk of gemfibrozil treatment. Gemfibrozil significantly increased plasma HDL cholesterol, apolipoprotein (apo) AI, and apo AII by 36%, 29%, and 38% from base line, respectively. Plasma TG decreased by 54%. Kinetics of apo AI and apo AII metabolism were assessed by analysis of the specific radioactivity decay curves after injection of autologous HDL labeled with 125I. Gemfibrozil increased synthetic rates of apo AI and apo AII by 27% and 34%, respectively, without changing the fractional catabolic rates. Stimulation of apo AI and apo AII synthesis by gemfibrozil was associated with the appearance in plasma of smaller (and heavier) HDL particles as assessed by gradient gel electrophoresis and HDL composition. Postheparin extra-hepatic lipoprotein lipase activity increased significantly by 25% after gemfibrozil, and was associated with the appearance in plasma of smaller very low density lipoprotein particles whose apo CIII:CII ratio was decreased. These data suggest that gemfibrozil increases plasma HDL levels by stimulating their synthesis. Increased transport (turnover) of HDL induced by gemfibrozil may be significant in increasing tissue cholesterol removal in these patients.