Addressing the overlap problem in the quantitative analysis of two dimensional NMR spectra: Application to <Superscript>15</Superscript>N relaxation measurements

A quantitative analysis of 2D ¹H-¹⁵N spectra is often complicated by resonance overlap. Here a simple method is presented for resolving overlapped correlations by recording 2D projection planes from HNCO data sets. Applications are presented involving the measurement of ¹⁵N T₁ relaxation rates in a high molecular weight protein, malate synthase G, and in a system that exchanges between folded and unfolded states, the drkN SH3 domain. By supplementing relaxation data recorded in the conventional way as a series of 2D ¹H-¹⁵N data sets with a series of a pair of projection planes the number of dynamics probes is increased significantly for both systems studied.     

Long-term effects of prenatal stress on dopamine and glutamate receptors in adult rat brain

Prenatal stress greatly influences the ability of an individual to manage stressful events in adulthood. Such vulnerability may result from abnormalities in the development and integration of forebrain dopaminergic and glutamatergic projections during the prenatal period. In this study, we assessed the effects of prenatal stress on the expression of selective dopamine and glutamate receptor subtypes in the adult offsprings of rats subjected to repeated restraint stress during the last week of pregnancy. Dopamine D₂-like receptors increased in dorsal frontal cortex (DFC), medial prefrontal cortex (MPC), hippocampal CA₁ region and core region of nucleus accumbens (NAc) of prenatally stressed rats compared to control subjects. Glutamate NMDA receptors increased in MPC, DFC, hippocampal CA₁, medial caudate-putamen, as well as in shell and core regions of NAc. Group III metabotropic glutamate receptors increased in MPC and DFC of prenatally stressed rats, but remained unchanged in all other regions examined. These results indicate that stress suffered during the gestational period has long lasting effects that extend into the adulthood of prenatally stressed offsprings. Changes in dopamine and glutamate receptor subtype levels in different forebrain regions of adult rats suggest that the development and formation of the corticostriatal and corticolimbic pathways may be permanently altered as a result of stress suffered prenatally. Maldevelopment of these pathways may provide a neurobiological substrate for the development of schizophrenia and other idiopathic psychotic disorders.     

Development of "normal" dermatomes and somatotopic maps by "abnormal" populations of cutaneous neurons

During development, motor and sensory axons grow to peripheral targets with remarkable precision. Whereas much has been learned about the development of motoneuron connectivity, less is known about the regulation of cutaneous innervation. In adults, dorsal root ganglia (DRG) innervate characteristic skin regions, termed dermatomes, and their axons project somatotopically in the dorsal horn. Here, we have investigated whether cutaneous neurons are selectively matched with specific skin regions, and whether peripheral target skin influences the central connections of cutaneous neurons. To address these questions, we shifted limb buds rostrally in chick embryos prior to axon outgrowth, causing DRGs to innervate novel skin regions, and mapped the resulting dermatomes and central projections. Following limb shifts, cutaneous innervation arose from more rostral and from fewer DRGs than normal, but the overall dermatome pattern was preserved. Thus, DRGs parcel out innervation of skin in a consistent manner, with no indication of matching between skin and DRGs. Similarly, cutaneous nerves established a "normal" somatotopic map in the dorsal horn, but in more rostral segments than usual. Thus, the peripheral target skin may influence the pattern of CNS projections, but does not direct cutaneous axons to specific populations of neurons in the dorsal horn.     

Habitat Degradation of Rhinopithecus bieti in Yunnan, China

Black-and-white snub-nosed monkeys (Rhinopithecus bieti) are endemic to the Trans-Himalayas in Northwest Yunnan and Southeast Tibet between the upper Yangtze and Mekong Rivers. Based on field surveys and previous reports, we identified the dark-coniferous forest, the mixed coniferous and broadleaf forest, and oak patches as suitable habitats (SH) for the monkeys. Summer grazing lands (SGL), which were made by local people cutting and burning the dark-coniferous forest at the high altitude belt, replaced SH. To have a general view of the status of the SH in Yunnan, we estimated the areas of SH and SGL from satellite images in 1997, and compared with areas estimated from aerial photo-based maps (ca. 1958). The work resulted in: 1) the area of SH was 4,169 km² in 1997; 2) SGL was 1,923 km²; 3) during the past 40 years, the area of SH decreased by 31% (1,887 km²), and SGL increased by 204% (1,291 km²); and 4) the mean size of forest patches decreased from 15.6 to 5.4 km². In addition, the area of SGL is positively correlated to local human population (R² 0.53), implying that the reduction and fragmentation of habitat for Rhinopithecus bieti is a result of population growth of humans, who mostly employ traditional modes of production. Only 11 monkey groups remained in the changing habitat. Considering that forests at lower elevation were also encroached upon by farmlands in a similar way, the forest ecosystem is highly threatened. The destruction will continue unless there is a change in the mode of production in the region.     

D4 Dopamine and Metabotropic Glutamate Receptors in Cerebral Cortex and Striatum in Rat Brain

The characterization of the functional interactions between the metabotropic glutamate receptors (mGluR) and the dopaminergic (DR) receptors in the corticostriatal projections may provide a possible interpretation of synaptic events in the basal ganglia. It has been suggested that presynaptic D2-type receptor located on glutamatergic corticostriatal neurons regulates the release of glutamate. In a first approach we have studied the cellular distribution of the D4R and the mGluRs in cerebral cortex and striatum employing immunocytochemistry. D4R positive neurons were particularly numerous in medial prefrontal cortex mainly occupying layers II and III. An even distribution was found on small round-shaped neurons in the striatum. Group I mGluR1-like immunoreactivity (mGluR1-LI) was found in medial and deep layers of the cerebral cortex while group III mGluR4a labeled more superficial layers; group II mGluR2/3 signal was intense on fine fibers with a punctate appearance. In the striatum, mGluR1 and mGluR2/3 stained mainly fibers while mGluR4a labeled round shaped cell bodies. After lateral ventricular injection of colchicine, an axonal transport and firing activity blocker, D4R labeling significantly increased in cerebral cortex and decreased in the striatum. mGluR1 and mGluR4a signal decreased in cerebral cortex and only mGluR4a signal decreased in the striatum. These results support previous reports indicating a presynaptic localization of D4R in the striatum. In contrast, striatal mGluR1 appears to be a postsynaptic receptor probably synthesized in situ. Our results do not support the hypothesis of a colocalization of D4 receptor and one or more of the metabotropic glutamatergic receptors studied here.     

Specific Neurochemical Derangements of Brain Projecting Neurons in Apolipoprotein E-Deficient Mice

Abstract: Apolipoprotein E (apoE)-deficient mice provide a useful system for studying the role of apoE in neuronal maintenance and repair. Previous studies revealed specific memory impairments in these mice that are associated with presynaptic derangements in projecting forebrain cholinergic neurons. In the present study we examined whether dopaminergic, noradrenergic, and serotonergic projecting pathways of apoE-deficient mice are also affected and investigated the mechanisms that render them susceptible. The densities of nerve terminals of forebrain cholinergic projections were monitored histochemically by measurements of acetylcholinesterase activity, whereas those of the dopaminergic nigrostriatal pathway, the noradrenergic locus coeruleus cortical projection, and the raphe-cortical serotonergic tract were measured autoradiographically using radioligands that bind specifically to the respective presynaptic transporters of these neuronal tracts. The results obtained revealed that synaptic densities of cholinergic, noradrenergic, and serotonergic projections in specific brain regions of apoE-deficient mice are markedly lower than those of controls. Furthermore, the extent of presynaptic derangement within each of these tracts was found to be more pronounced the further away the nerve terminal is from its cell body. In contrast, the nerve terminal density of the dopaminergic neurons that project from the substantia nigra to the striatum was unaffected and was similar to that of the controls. The rank order of these presynaptic derangements at comparable distances from the respective cell bodies was found to be septohippocampal cholinergic > nucleus basalis cholinergic > locus coeruleus adrenergic > raphe serotonergic ? nigrostriatal dopaminergic, which interestingly is similar to that observed in Alzheimer's disease. These results suggest that two complementary factors determine the susceptibility of brain projecting neurons to apoE deficiency: pathway-specific differences and the distance of the nerve terminals from their cell body.     

Topographic controls on the distribution of tree islands in the high Andes of south‐western Ecuador

Aim To evaluate the hypothesis that geomorphometric parameters of upper montane Andean environments have an important influence on the regional fire ecology and consequently play a role in the spatial distribution of ‘remnant’ tree islands dominated by Polylepis. Location A glacial landscape located between 3600 and 4400 m elevation in Cajas National Park, south‐western Ecuador. Methods The eigenvalue ratio method was used to evaluate the regional geomorphometric parameters of a 30‐m digital elevation model for Cajas National Park. The landscape character was evaluated by quantifying the topographic roughness, organization, and gradient. This information was used to determine the spatial correlations between terrain characteristics and the distribution of tree islands in the region. Results We demonstrate a strong spatial correlation between areas of high topographic roughness and gradient, and the locations of the major tree islands. We find that there is a distinctive relationship between the topographic roughness and organization in the vicinity of the tree islands (e.g. increased upslope roughness and decreased topographic grain strength) that substantiates the notion that the tree islands are located in relatively inaccessible topography. Main conclusions In the northern and central Andes, the location of Polylepis‐dominated ‘forest islands’ has been shown to be a function of climate, terrain characteristics, and anthropogenic disturbances. Although the relative importance of various ecological factors has been debated, it remains clear that fires have exerted a strong influence on these ecosystems. Other authors have noted that tree islands are more likely to occur at the base of cliffs, above moist areas, and in other areas where fires do not burn frequently. Our results corroborate these observations, and demonstrate that the occurrence of Polylepis patches is strongly correlated with specific combinations of terrain features. Although we do not discount the importance of other factors in determining the spatial position and areal extent of these forests, we demonstrate strong support for fire‐related hypotheses.     

Predicting fine‐scale distributions of peripheral aquatic species in headwater streams

Headwater species and peripheral populations that occupy habitat at the edge of a species range may hold an increased conservation value to managers due to their potential to maximize intraspecies diversity and species' adaptive capabilities in the context of rapid environmental change. The southern Appalachian Mountains are the southern extent of the geographic range of native Salvelinus fontinalis and naturalized Oncorhynchus mykiss and Salmo trutta in eastern North America. We predicted distributions of these peripheral, headwater wild trout populations at a fine scale to serve as a planning and management tool for resource managers to maximize resistance and resilience of these populations in the face of anthropogenic stressors. We developed correlative logistic regression models to predict occurrence of brook trout, rainbow trout, and brown trout for every interconfluence stream reach in the study area. A stream network was generated to capture a more consistent representation of headwater streams. Each of the final models had four significant metrics in common: stream order, fragmentation, precipitation, and land cover. Strahler stream order was found to be the most influential variable in two of the three final models and the second most influential variable in the other model. Greater than 70% presence accuracy was achieved for all three models. The underrepresentation of headwater streams in commonly used hydrography datasets is an important consideration that warrants close examination when forecasting headwater species distributions and range estimates. Additionally, it appears that a relative watershed position metric (e.g., stream order) is an important surrogate variable (even when elevation is included) for biotic interactions across the landscape in areas where headwater species distributions are influenced by topographical gradients.     

Regeneration of the visual system in gastropods (Mollusca)

Abstract. The topic of tissue and organ regeneration has been of interest to life scientists ever since the phenomenon was noticed. The reason for this is obvious: if one can learn what drives and controls regeneration, i.e., how lost or damaged structures can be replaced, one not only has a better chance to understand an animal's embryogenesis and evolutionary relationship with other taxa, but one would also be in a better position to treat organ loss or tissue damage in humans. In this context, the possible restitution of individual sensory neurons or nerve projections has been of special interest to us. We identified central visual projections in several gastropod species and found that: (1) projections are very extensive across the brain and (2) they have connections with other systems and organs (including, most likely, non-ocular skin photoreceptors) that may be involved in the integration of signals from different sensors. Investigations of afferent and efferent visual elements at a morphological level should help reveal the neuronal basis of a gastropod's behavioral reactions.     

A plasma global metabolic profiling approach applied to an exercise study monitoring the effects of glucose, galactose and fructose drinks during post-exercise recovery

A global metabolic profiling methodology based on gas chromatography coupled to time-of-flight mass spectrometry (GC-TOFMS) for human plasma was applied to a human exercise study focused on the effects of beverages containing glucose, galactose, or fructose taken after exercise and throughout a recovery period of 6 h and 45 min. One group of 10 well trained male cyclists performed 3 experimental sessions on separate days (randomized, single center). After performing a standardized depletion protocol on a bicycle, subjects consumed one of three different beverages: maltodextrin (MD)+glucose (2:1 ratio), MD+galactose (2:1), and MD+fructose (2:1), consumed at an average of ～1.25 g of carbohydrate (CHO) ingested per minute. Blood was taken straight after exercise and every 45 min within the recovery phase. With the resulting blood plasma, insulin, free fatty acid (FFA) profile, glucose, and GC-TOFMS global metabolic profiling measurements were performed. The resulting profiling data was able to match the results obtained from the other clinical measurements with the addition of being able to follow many different metabolites throughout the recovery period. The data quality was assessed, with all the labelled internal standards yielding values of <15% CV for all samples (n=335), apart from the labelled sucrose which gave a value of 15.19%. Differences between recovery treatments including the appearance of galactonic acid from the galactose based beverage were also highlighted.