Saponification of esters of chiral alpha-amino acids anchored through their amine function on solid support.

Anchoring an alpha-amino acid residue by its amine function onto a solid support is an alternative to develop chemistry on its carboxylic function. This strategy can involve the use of amino-acid esters as precursors of the carboxylic function. A complete study on the Wang-resin was performed to determine the non racemizing saponification conditions of anchored alpha-amino esters. The use of LiOH, NaOH, NaOSi(Me)3, various solvents and temperatures were tested for this reaction. After saponification and cleavage from the support, samples were examined through their Marfey's derivatives by reversed phase HPLC to evaluate the percentage of racemization.     

Karyotype characterization of the lake sturgeon, Acipenser fulvescens (Rafinesque 1817) by chromosome banding and fluorescent in situ hybridization.

A karyotype analysis using several staining techniques was carried out on the North American lake sturgeon, Acipenser fulvescens. The chromosome number was found to be 2n = 262 +/- 6. A representative karyotype of 264 chromosomes was composed of 134 meta- and submetacentrics, 70 telo- and acrocentrics, and 60 microchromosomes. The constitutive heterochromatin, revealed by C banding, was localized in various positions on several chromosomes, including microchromosomes. The signals of fluorescent in situ hybridization (FISH) with a HindIII satellite DNA probe were visible as centromeric heterochromatin blocks on 48 chromosomes. The telomeric repeat (TTAGGG)n detected by FISH was localized at both ends of all chromosomes and two chromosomes were entirely marked. Fluorescent staining with GC-specific chromomycin A3 showed recognizable fluorescent regions, whereas a more uniform base composition was revealed by the AT-specific 4',6-diamidino-2-phenylindole (DAPI). After silver staining, the active nucleolar organizer regions (NORs) were detected on 12 chromosomes. FISH with the 5S probe showed four signals on four small chromosomes. Our data suggest that A. fulvescens is a tetraploid species.     

Habitat and landscape factors associated with neotropical waterbird occurrence and richness in wetland fragments

Habitat destruction alters the structure and spatial arrangement of remnants and creates a novel matrix, affecting the structure of biological communities. This study evaluated the contribution of patch, class and landscape level attributes of 42 wetland fragments and surrounding landscapes on the richness, abundance and presence of waterbird species. Twelve monthly censuses identified 55 species––ranging from 3 to 40 among fragments, and a total of 84,286 birds––ranging from 15 to 19,322. Wetland areas varied from 0.2 ha to 145.2 ha. The presence of 37 out of 42 species could be predicted from the structure of the fragments and the landscapes. The most important predictors were the wetland area (22 models), the rice field matrix permeability (13 models), the microhabitat richness (7 models), the wetland connectivity (5 models), and the wetland isolation (5 models). Discriminant analysis showed that fragments richer in species than expected from their areas, are found in landscapes with greater connectivity and matrix permeability than the species-poor fragments. The total area of rice fields was not related to the richness, abundance or presence of waterbirds in the wetlands fragments. The results suggest that the maintenance of the connectivity among fragments and the matrix permeability through rice-fields could be managed to foster the waterbird conservation at the landscape scale.     

Multiple independent evolutionary solutions to core histone gene regulation

Background  

Core histone genes are periodically expressed along the cell cycle and peak during S phase. Core histone gene expression is deeply evolutionarily conserved from the yeast Saccharomyces cerevisiae to human.     

Dynamics of noninvasively estimated microvascular O2 extraction during ramp exercise.

Utilization of near-infrared spectroscopy (NIRS) in clinical exercise testing to detect microvascular abnormalities requires characterization of the responses in healthy individuals and theoretical foundation for data interpretation. We examined the profile of the deoxygenated hemoglobin signal from NIRS {deoxygenated hemoglobin + myoglobin [deoxy-(Hb+Mb)] approximately O(2) extraction} during ramp exercise to test the hypothesis that the increase in estimated O(2) extraction would be close to hyperbolic, reflecting a linear relationship between muscle blood flow (Q(m)) and muscle oxygen uptake (Vo(2)(m)) with a positive Q(m) intercept. Fifteen subjects (age 24 +/- 5 yr) performed incremental ramp exercise to fatigue (15-35 W/min). The deoxy-(Hb+Mb) response, measured by NIRS, was fitted by a hyperbolic function [f(x) = ax/(b + x), where a is the asymptotic value and b is the x value that yields 50% of the total amplitude] and sigmoidal function {f(x) = f(0) + A/[1 + e(-(-c+dx))], where f(0) is baseline, A is total amplitude, and c is a constant dependent on d, the slope of the sigmoid}, and the goodness of fit was determined by F test. Only one subject demonstrated a hyperbolic increase in deoxy-(Hb+Mb) (a = 170%, b = 193 W), whereas 14 subjects displayed a sigmoidal increase in deoxy-(Hb+Mb) (f(0) = -7 +/- 7%, A = 118 +/- 16%, c = 3.25 +/- 1.14, and d = 0.03 +/- 0.01). Computer simulations revealed that sigmoidal increases in deoxy-(Hb+Mb) reflect a nonlinear relationship between microvascular Q(m) and Vo(2)(m) during incremental ramp exercise. The mechanistic implications of our findings are that, in most healthy subjects, Q(m) increased at a faster rate than Vo(2)(m) early in the exercise test and slowed progressively as maximal work rate was approached.     

Presence of an Endogenous Factor in Avian CNS with Agonistic Action on Benzodiazepine Receptors

In the present paper we describe the presence in avian CNS of an endogenous inhibitor of [³H]flunitrazepam binding. This compound was extracted from a synaptic membrane fraction isolated from chick optic lobe and brain using an exhaustive aqueous washing procedure, then purified by means of solid-phase extraction with C₁₈ cartridges and several HPLC steps until an homogeneous peak was obtained. Its chemical structure was studied by size-exclusion chromatography of the purified material which indicated that it possesses a molecular weight below 1350. Although its inhibitory activity was lost by HCl treatment, its peptidic nature was ruled out by an amino acid and N-terminal sequence analyses. Ultraviolet absorption spectrum showed two main peaks at 230 and 280 nm. The endogenous compound was found to inhibit competitively [³H]flunitrazepam binding to its recognition site without affecting [³H]GABA binding to the same receptor complex. The behavior of the endogenous factor in an in vitro GABA shift test and GABA-dependent chloride flux experiments were similar to that of benzodiazepine receptor agonists. In conclusion, these results demonstrate the existence in avian CNS of a competitive endogenous inhibitor of benzodiazepine binding with agonistic action on benzodiazepine receptors.