Analysis of nitrogen saturation potential in Rocky Mountain tundra and forest: implications for aquatic systems

We employed grass and forest versions of the CENTURY model under a range of N deposition values (0.02–1.60 g N m^–2 y^–1) to explore the possibility that high observed lake and stream N was due to terrestrial N saturation of alpine tundra and subalpine forest in Loch Vale Watershed, Rocky Mountain National Park, Colorado. Model results suggest that N is limiting to subalpine forest productivity, but that excess leachate from alpine tundra is sufficient to account for the current observed stream N. Tundra leachate, combined with N leached from exposed rock surfaces, produce high N loads in aquatic ecosystems above treeline in the Colorado Front Range. A combination of terrestrial leaching, large N inputs from snowmelt, high watershed gradients, rapid hydrologic flushing and lake turnover times, and possibly other nutrient limitations of aquatic organisms constrain high elevation lakes and streams from assimilating even small increases in atmospheric N. CENTURY model simulations further suggest that, while increased N deposition will worsen the situation, nitrogen saturation is an ongoing phenomenon.     

The effects of early experience on adult copulatory behavior in zoo-born chimpanzees (Pan troglodytes)

This paper examines the relationship between the early rearing experience of zoo-born, zoo-reared chimpanzees (Pan troglodytes) and the subsequent occurrence of successful copulation as adults. Developmental histories were acquired for 71 subjects via questionnaires and phone interviews. The following variables related to aspects of chimpanzees' early rearing experience were examined: (1) Rearing conditions, that is, hand reared alone, reared with siblings or peers, or reared by at least one adult conspecific. (2) Age removed from mother. (3) Sex of subject, and/or (4) participation in shows. Each of these variables was then compared to the subjects' sexual competence, defined here as having been observed to exhibit functional copulatory behavior as adults. Seventy-five percent of the subjects were observed to exhibit functional copulatory behavior on at least one occasion. No single component of rearing was successful in producing sexually competent adults 100% of the time; no rearing condition, as defined in this study, resulted in reproductive failure for all subjects experiencing those conditions. Chimpanzees that were hand reared alone, that is, in the total absence of conspecifics, were least likely to copulate as adults; about half of those chimpanzees that were reared with siblings or peers (and in the absence of adult conspecifics) copulated as adults. Almost 90% of those chimpanzees that were reared with at least one adult conspecific copulated as adults. Chimpanzees removed from their mothers at an early age (less than one year of age) were less likely to reproduce as adults. Male and female chimpanzees were equally likely to reproduce as adults. Participation in shows or demonstrations appeared to have no effect on chimpanzees' ability to copulate as adults. © 1994 Wiley-Liss, Inc.     

Gestation length in rhesus macaques (Macaca mulatta)

We describe some of the sources of variation in gestation length among rhesus macaques. the data were obtained from the timed-mating breeding program at the California Regional Primate Research Center (CRPRC). Information about approximately 700 pregnancies that resulted in spontaneous vaginal deliveries of liveborn young is presented. The average length of these pregnancies was 166.5 days. In this population, older females with higher parities had significantly longer pregnancies and significantly heavier infants than other females did. Other factors, including infant sex, month of conception, maternal reproductive history, and paternal identity, had no consistent effect upon gestation length.     

Aurintricarboxylic Acid Protects Hippocampal Neurons from NMDA-and Ischemia-Induced Toxicity In Vivo

Abstract: The polymeric dye aurintricarboxylic acid (ATA) has been shown to protect various cell types from apoptotic cell death, reportedly through inhibition of a calcium-dependent endonuclease activity. Recent studies have indicated that there may be some commonalities among apoptosis, programmed cell death, and certain other forms of neuronal death. To begin to explore the possibility of common biochemical mechanisms underlying ischemia-or excitotoxin-induced neuronal death and apoptosis in vivo, gerbils or rats subjected to transient global ischemia or NMDA microinjection, respectively, received a simultaneous intracerebral infusion of ATA or vehicle. As a biochemical marker of neuronal death, spectrin proteolysis, which is mediated by activation of calpain I, was measured in hippocampus after 24 h. ATA treatment resulted in a profound reduction of both NMDA-and ischemia-induced spectrin proteolysis, consistent with the possibility of some common mechanism in apoptosis and other forms of neuronal death in vivo.     

Studies on the Development of the Desiccation-sensitive (Recalcitrant) Seeds of Avicennia marina (Forssk.) Vierh.: The Acquisition of Germinability and Response to Storage and Dehydration

Germinability and responses to storage and dehydration werestudied throughout the development of the desiccation-sensitiveseeds of Avicennia marina. Seeds acquired the ability to produceroots at 55 d after fruit set (DAFS) which is shortly afterhistodifferentiation, but the capacity for full germinability(seedling establishment) was not attained until 70 DAFS, whichis midway through the phase of growth and reserve accumulation.Pre-mature seeds showed a germination lag that was equivalentto the period between harvest and full maturity, but, followingshort-term storage, this was reduced to that of mature seeds.At no stage, however, would seeds with an intact pericarp germinate. Once seeds were fully germinated, storage lifespan under non-desiccatingconditions was independent of developmental stage, but was considerablyreduce by the presence of the pericarp, probably because offungal contamination. Prior to the acquisition of full germinationcapacity, the seeds were unable to tolerate any dehydrationbut became tolerant to slight water loss once they became fullygerminable, after which desiccation sensitivity was not influencedby the stage of development. If rapidly dried, excised axesof germinable seeds survived to lower water contents than didaxes removed from seeds following slower drying.Copyright 1993,1999 Academic Press Desiccation-tolerance/sensitivity, germination, mangrove, recalcitrant, seed development, seed storage     

Total chemical synthesis and NMR characterization of the glycopeptide tx5a, a heavily post-translationally modified conotoxin, reveals that the glycan structure is alpha-D-Gal-(1-->3)-alpha-D-GalNAc.

The 13-amino acid glycopeptide tx5a (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp* = 6-bromotryptophan and Thr* = Gal-GalNAc-threonine), isolated from Conus textile, causes hyperactivity and spasticity when injected intracerebral ventricularly into mice. It contains nine post-translationally modified residues: four cysteine residues, two gamma-carboxyglutamic acid residues, and one residue each of 6-bromotryptophan, 4-trans-hydroxyproline and glycosylated threonine. The chemical nature of each of these has been determined with the exception of the glycan linkage pattern on threonine and the stereochemistry of the 6-bromotryptophan residue. Previous investigations have demonstrated that tx5a contains a disaccharide composed of N-acetylgalactosamine (GalNAc) and galactose (Gal), but the interresidue linkage was not characterized. We hypothesized that tx5a contained the T-antigen, beta-D-Gal-(1-->3)-alpha-D-GalNAc, one of the most common O-linked glycan structures, identified previously in another Conus glycopeptide, contalukin-G. We therefore utilized the peracetylated form of this glycan attached to Fmoc-threonine in an attempted synthesis. While the result-ing synthetic peptide (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp* =6-bromotryptophan and Thr* = beta-D-Gal-(1-->3)-alpha-D-GalNAc-threonine) and the native peptide had almost identical mass spectra, a comparison of their RP-HPLC chromatograms suggested that the two forms were not identical. Two-dimensional 1H homonuclear and 13C-1H heteronuclear NMR spectroscopy of native tx5a isolated from Conus textile was then used to determine that the glycan present on tx5a indeed is not the aforementioned T-antigen, but rather alpha-D-Gal-(1-->3)-alpha-D-GalNAc.     

Estimating dataset size requirements for classifying DNA microarray data.

A statistical methodology for estimating dataset size requirements for classifying microarray data using learning curves is introduced. The goal is to use existing classification results to estimate dataset size requirements for future classification experiments and to evaluate the gain in accuracy and significance of classifiers built with additional data. The method is based on fitting inverse power-law models to construct empirical learning curves. It also includes a permutation test procedure to assess the statistical significance of classification performance for a given dataset size. This procedure is applied to several molecular classification problems representing a broad spectrum of levels of complexity.