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PubMed2001

Testing the taxonomic integrity of Paranthropus boisei sensu stricto.

The craniodental hypodigm of Paranthropus boisei sensu stricto is morphologically distinctive, but it has been suggested that the substantial variation in mandibular and dental size in that hypodigm may exceed that which is reasonable to subsume within a single hominin species. In this study, Fligner and Killeen, coefficient of variation (CV)-based and average taxonomic distance (ATD)-based bootstrap tests, were used to compare variation in size and shape of the mandibular corpus remains attributed to P. boisei s.s. with the variation observed in samples of great apes and modern humans. The degree of size variation in the P. boisei s.s. mandibular hypodigm is never observed in human and chimpanzee samples, is rare in gorillas, but is not uncommon in orangutans. However, the shape variation in the fossil group is comparable to the variation in the extant reference groups. Although the size variation in P. boisei s.s. is substantial, it is exaggerated by the effects of taphonomy. The small mandibles are more often abraded, whereas the large mandibles are more likely to have been infiltrated with matrix. On the basis of the results of this investigation of the mandibular corpus, there are no grounds for rejecting the "single-species" hypothesis for P. boisei s.s. When Sokal and Braumann's adjusted CV values were used to predict the index of sexual dimorphism (ISD) for the P. boisei s.s., despite the substantial geological time embraced by the mandibular corpus hypodigm, the predicted value of lnISD, when corrected for taphonomic factors, is comparable to the sexual dimorphism observed within Gorilla.

Animals↗

PubMed2005

QTL analysis and QTL-based prediction of flowering phenology in recombinant inbred lines of barley.

Combining ecophysiological modelling and genetic mapping has increasingly received attention from researchers who wish to predict complex plant or crop traits under diverse environmental conditions. The potential for using this combined approach to predict flowering time of individual genotypes in a recombinant inbred line (RIL) population of spring barley (Hordeum vulgare L.) was examined. An ecophysiological phenology model predicts preflowering duration as affected by temperature and photoperiod, based on the following four input traits: f(o) (the minimum number of days to flowering at the optimum temperature and photoperiod), theta1 and theta2 (the development stages for the start and the end of the photoperiod-sensitive phase, respectively), and delta (the photoperiod sensitivity). The model-input trait values were obtained from a photoperiod-controlled greenhouse experiment. Assuming additivity of QTL effects, a multiple QTL model was fitted for the model-input traits using composite interval mapping. Four to seven QTL were identified for each trait. Each trait had at least one QTL specific to that trait alone. Other QTL were shared by two or all traits. Values of the model-input traits predicted for the RILs from the QTL model were fed back into the ecophysiological model. This QTL-based ecophysiological model was subsequently used to predict preflowering duration (d) for eight field trial environments. The model accounted for 72% of the observed variation among 94 RILs and 94% of the variation among the two parents across the eight environments, when observations in different environments were pooled. However, due to the low percentage (34-41%) of phenotypic variation accounted for by the identified QTL for three model-input traits (theta1, theta2 and delta), the QTL-based model accounted for somewhat less variation among the RILs than the model using original phenotypic input trait values. Nevertheless, days to flowering as predicted from the QTL-based ecophysiological model were highly correlated with days to flowering as predicted from QTL-models per environment for days to flowering per se. The ecophysiological phenology model was thus capable of extrapolating (QTL) information from one environment to another.

Chromosome Mapping↗

PubMed1976

The regulation of carbamoyl phosphate synthase activity in rat liver mitochondria.

The rate at which isolated rat liver mitochondria synthesized citrulline with NH4C1 as nitrogen source was markedly dependent on the protein content of the diet. 2. Citrulline synthesis was not rate-limited by substrate concentration, substrate transport or ornithine transcarbamoylase activity under the conditions used. 3. The intramitochondrial content of an activator of carbamoyl phosphate synthase, assumed to be N-acetyl-glutamate, varied markedly with dietary protein content. The variation in the concentration of this activator was sufficient to account for the observed variation in the rates of citrulline synthesis if this synthesis were rate-limited by the activity of carbamoyl phosphate synthase. 4. The rates of urea formation from NH4Cl as nitrogen source in isolated liver cells showed variations in response to diet that closely paralleled the variations in the rates of citrulline synthesis observed in isolated mitochondria. 5. These results are consistent with the postulate that when NH4Cl plus ornithine are present in an excess, the rate of urea synthesis is regulated at the level of carbamoyl phosphate synthase activity.

Ammonium Chloride↗

PubMed1979

Quantification of human plasma inorganic pyrophosphate. II. Biologic variables.

Plasma inorganic pyrophosphate (PPi) levels rose predictably (28%) after vigorous systemic exercise and returned to baseline values after 30 minutes of rest. Plasma PPi levels were greater (36%) in femoral venous blood than in femoral arterial blood. Forearm muscular exercise, however, did not result in a detectable rise in plasma PPi levels in antecubital veins. The physiologic reasons for both the systemic exercise effect and the arteriovenous differences remain unknown. Measurement of plasma PPi for 10 consecutive days in a single normal subject under basal conditions, where these and other previously identified biologic variables (fasting and diurnal variation) were controlled, showed a coefficient of variation of 12.7%. Thus biologic variability contributed less to observed variation in plasma PPi than did methodologic errors (coefficient of variation of method = 8%). The striking reproducibility of plasma PPi in this subject suggests that this important metabolite is under rather tight homeostatic control.

Calcium Pyrophosphate↗

PubMed1983

Ultrastructural study of transganglionic degeneration following dental lesions.

Transganglionic degeneration in the trigeminal main sensory nucleus (MSN) and pars interpolaris (PI) was studied in cats following dental lesions. At early survival times, three types of terminal alteration were seen in both MSN and PI: (1) flocculent degeneration, (2) neurofilamentous hyperplasia and, (3) glycogen accumulation. With longer survival times, the magnitude of these terminal alterations increases. Electron dense degeneration was only seen in the ventral half of PI. Phagocytosis of the altered terminals was also observed. The study suggests a plausible explanation for the variations observed in the CNS projection of primary afferents with degeneration and with HRP transport studies.

Animals↗

PubMed1990

cAMP levels and in situ measurement of cAMP related enzymes during yeast-to-hyphae transition in Candida albicans.

Intracellular levels of cAMP and specific activities of adenylate cyclase, cAMP phosphodiesterase and cAMP-dependent protein kinase were measured during filamentation in the dimorphic fungus Candida albicans. Enzymatic assays were performed in permeabilized cells under conditions prevented endogenous proteolysis. The variations observed in cAMP levels were mainly accounted for by variations in the specific activities of adenylate cyclase and cAMP phosphodiesterase at different stages during germ tube formation. cAMP-dependent protein kinase, measured with kemptide as exogenous substrate, was developmental regulated. Some properties of the enzymatic activities from cell-free extracts are described.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2026

First insights into the role of evolutionary history in shaping venom composition of Vipera ammodytes.

Understanding intraspecific venom variation requires distinguishing the contributions of neutral population history from natural selection. This study aims to determine whether venom variation in Vipera ammodytes species complex is structured across eight phylogenetic groups. Despite a complex evolutionary history, venom composition did not differ among phylogenetic groups within the analytical framework used, suggesting that shared ancestry alone does not explain venom variation. Whether local adaptation to environmental conditions explains the observed variation remains an open question for future studies.

Animals↗

PubMed1976

A comparison between gonadotropin radioimmunoassays with the use of 48 hour and six-day incubation methods.

A double-antibody radioimmunoassay for human follicle-stimulating hormone (FSH) and human luteinizing hormone (LH) which can be carried to completion in 48 hours was compared with the conventional six-day double-antibody radioimmunoassay. The bound-over total (B/T) dose response curves for the 48 hour assay were comparable in slope and dose range with the six-day assay and the four per cent average within-assay and the nine per cent between-assay coefficients of variation for the 48 hour assay were comparable with the variation observed in the conventional six-day assay. Maximum variation among identical serum samples assayed in both systems was 15.3 per cent so that quantitative results obtained with either assay system were comparable.

Chorionic Gonadotropin↗

PubMed1976

Variation in a natural population of Schizophyllum commune. Variation within the extreme isolates for growth rate.

Two extreme dikaryotic idolates chosen from a large sample of a localised population of Schizophyllum commune exhibited a considerable amount of genetical variation for growth rate at the near ambient temperature of 20 degrees C and at the higher temperature of 30 degrees C. The potential variation within these extreme isolates were greater than the variation observed in the whole sample. Regression analysis of the variation in growth rate of the dikaryotic progeny of the extreme isolates on that of their component monokaryons showed that the nature of gene action was not the same in these two stages of the life cycle. The simple additive-dominance model of gene action was adequate to explain the variation in growth rate in both of the extreme isolates at both of the temperatures. The small deviations from this model could be accounted for by unequal gene frequencies due to small sample size although a low incidence of non-allelic interactions could not be rule out. Directional dominance for growth rate was detected in both isolates at the more normal temperature and it was opposing in direction in the two isolates. In the slow growing isolate the dominance was for faster growth and in the fast growing isolate it was for slower growth. This is expected for a character which displays overall ambi-directional dominance if isolates with more extreme growth rates than those recovered in the population sample are eliminated by stabilising selection. The dominance is temperature dependent being ambi-directional in both isolates at the higher temperature. Environmental heterogeneity, the buffering effects of directional dominance and genotype-environment interactions and opposing selective forces operating on the monokaryotic and dikaryotic stages of the life cycle are possible contributory factors to the considerable free and potential variability displayed in this small, localised population.

Agaricales↗

PubMed2005

Local adaptation in the rock pocket mouse (Chaetodipus intermedius): natural selection and phylogenetic history of populations.

Elucidating the causes of population divergence is a central goal of evolutionary biology. Rock pocket mice, Chaeotdipus intermedius, are an ideal system in which to study intraspecific phenotypic divergence because of the extensive color variation observed within this species. Here, we investigate whether phenotypic variation in color is correlated with local environmental conditions or with phylogenetic history. First, we quantified variation in pelage color (n=107 mice) and habitat color (n=51 rocks) using a spectrophotometer, and showed that there was a correlation between pelage color and habitat color across 14 sampled populations (R2=0.43). Analyses of mtDNA sequences from these same individuals revealed strong population structure in this species across its range, where most variation (63%) was partitioned between five geographic regions. Using Mantel tests, we show that there is no correlation between color variation and mtDNA phylogeny, suggesting that pelage coloration has evolved rapidly. At a finer geographical scale, high levels of gene flow between neighboring melanic and light populations suggest the selection acting on color must be quite strong to maintain habitat-specific phenotypic distributions. Finally, we raise the possibility that, in some cases, migration between populations of pocket mice inhabiting different lava flows may be responsible for similar melanic phenotypes in different populations. Together, the results suggest that color variation can evolve very rapidly over small geographic scales and that gene flow can both hinder and promote local adaptation.

Adaptation, Physiological↗

PubMed2005

Remediation of soil from lead-contaminated kindergartens reduces the amount of lead adhering to children's hands.

Risk related to contaminated soil is based on the oral intake of soil and dust among children. This exposure is a consequence of mouthing behaviour, which exposes children to whatever adheres to their hands or toys. This project compared hand exposure of children to lead following outdoor playground activities before and after an intervention. The intervention consisted of replacement of contaminated top soil from the most intensively used playground areas and coverage of bare soil with wood chips or grass. We included children from three kindergartens: one with very low levels of lead in soil and two kindergartens with an average lead concentrations in soil of 100-200 mg/kg. Measurements of lead in soil 5-7 weeks after interventions in two kindergartens verified that the interventions had effectively reduced the potential exposure to lead from the most intensively used areas of the playgrounds. The average lead concentration in soil after intervention was below 10 mg/kg. We found a good agreement between the average concentration of lead in soil and the amount of lead on the hands of the children. Thus, the exposure marker worked and had the advantage compared to a blood sample, that we could evaluate the effect of the interventions shortly after they were accomplished using a noninvasive method. The amount of lead on the hands measured in one of the two kindergartens after the remediation (0.73 microg) was not significantly different from the control kindergarten (0.58 microg). Children from the second kindergarten still had higher median exposures to lead (1.29 microg), but a large overlap existed with several children having lower amounts of lead on their hands than some children from the control kindergarten. Large variations in the amount of lead on hands were observed. Variations may reflect true differences in concentrations of lead in soil, but may also reflect different behavior and playing patterns. Our study demonstrated, that it was possible in a cost-effective way to reduce exposure significantly and to verify the effect with a sensitive, noninvasive method shortly after the interventions had been implemented..

Child↗

PubMedDate not supplied

Variation in exposure levels for high hazard frequently monitored agents.

Assumptions about the underlying distribution of occupational exposures are important to the practice of industrial hygiene. They affect decisions on exposure monitoring strategies, the interpretation of monitoring results, and the degree of protection provided by occupational exposure limits and action levels. However, there is little published data validating these assumptions. Strict exposure limits for three highly hazardous agents, asbestos, beryllium, and ionizing radiation, led to frequent monitoring of occupational exposure levels. Consequently, sets of hundreds to thousands of exposure measurements are available for analysis. Statistical analysis of these data sets indicates that within-worker variation, as measured by geometric standard deviation (GSD), tend to be higher than is generally assumed for occupational exposures. The success of health protection programs in identifying and controlling predictable sources of exposure through frequent monitoring is offered as a possible explanation for the relatively high variation observed in these data sets. Despite the high exposure variation, arithmetic mean levels and the percentage of measurements exceeding exposure limits were low, indicating that a large GSD does not imply that working conditions are unacceptable. However, more frequent monitoring is required to assure exposures are acceptable. This article also presents an adaptation of graphical methods, using probability plotting and linear regression, to estimate the distribution parameters of a data set that contains a high percentage of nondetected results.

Air Pollutants↗

PubMed1995

Determination of pesticide metabolites in human urine using an isotope dilution technique and tandem mass spectrometry.

A method that measures 12 analytes in urine and reflects possible exposure to pesticides was developed. The sample preparation involves enzyme hydrolysis and solvent extraction through the use of laboratory robotics, followed by phase-transfer catalysis derivatization and silica cleanup. Samples are analyzed by capillary gas chromatography and tandem mass spectrometry using an isotope dilution technique with 13C-labeled internal standards. The limit of detection is 1 microgram/L (1 part per billion) for most analytes, and most analytes have a linear response up to 100 micrograms/L. The precision of the method is reflected in the variation observed in quality control materials over 33 months; the variation averaged 17% for these analytes. On the basis of the detectable analyte levels of unspiked urine samples collected from unexposed volunteers, this method can be used to measure the low levels necessary for establishing reference range values of the selected pesticides or metabolites.

Calibration↗

PubMed2006

Effects of intraleaf variations in carbonic anhydrase activity and gas exchange on leaf C18OO isoflux in Zea mays.

Variation in the C18OO content of atmospheric CO2 (delta18Oa) can be used to distinguish photosynthesis from soil respiration, which is based on carbonic anhydrase (CA)-catalyzed 18O exchange between CO2 and 18O-enriched leaf water (delta18Ow). Here we tested the hypothesis that mean leaf delta18Ow and assimilation rates can be used to estimate whole-leaf C18OO flux (isoflux), ignoring intraleaf variations in CA activity and gas exchange parameters. We observed variations in CA activity along the leaf (> 30% decline from the leaf center toward the leaf ends), which were only partially correlated to those in delta18Ow (7 to 21 per thousand), delta18O and delta13C of leaf organic matter (25 to 30 per thousand and -12.8 to -13.2 per thousand, respectively), and substomatal CO2 concentrations (intercellular CO2 concentrations, c(i), at the leaf center were approximately 40% of those at the leaf tip). The combined effect of these variations produced a leaf-integrated isoflux that was different from that predicted based on bulk leaf values. However, because of canceling effects among the influencing parameters, isoflux overestimations were only approximately 10%. Conversely, use of measured parameters from a leaf segment could produce large errors in predicting leaf-integrated C18OO fluxes.

Carbon↗

PubMed2005

Response to selection for photoperiod responsiveness on the density and location of mature GnRH-releasing neurons.

Natural variation in neuroendocrine traits is poorly understood, despite the importance of variation in brain function and evolution. Most rodents in the temperate zones inhibit reproduction and other nonessential functions in short winter photoperiods, but some have little or no reproductive response. We tested whether genetic variability in reproductive seasonality is related to individual differences in the neuronal function of the gonadotropin-releasing hormone network, as assessed by the number and location of mature gonadotropin-releasing hormone-secreting neurons under inhibitory and excitatory photoperiods. The experiments used lines of Peromyscus leucopus previously developed by selection from a wild population. One line contained individuals reproductively inhibited by short photoperiod, and the other line contained individuals nonresponsive to short photoperiod. Expression of mature gonadotropin-releasing hormone (GnRH) immunoreactivity in the brain was detected using SMI-41 antibody in the single-labeled avidin-biotin-peroxidase-complex method. Nonresponsive mice had 50% more immunoreactive GnRH neurons than reproductively inhibited mice in both short- and long-day photoperiods. The greatest differences were in the anterior hypothalamus and preoptic areas. In contrast, we detected no significant within-lines differences in the number or location of immunoreactive GnRH neurons between photoperiod treatments. Our data indicate that high levels of genetic variation in a single wild population for a specific neuronal trait are related to phenotypic variation in a life history trait, i.e., winter reproduction. Variation in GnRH neuronal activity may underlie some of the natural reproductive and life history variation observed in wild populations of P. leucopus. Similar genetic variation in neuronal traits may be present in humans and other species.

Animals↗

PubMed2007

On the depth and scale of metabolic rate variation: scaling of oxygen consumption rates and enzymatic activity in the Class Cephalopoda (Mollusca).

Recent ecological theory depends, for predictive power, on the apparent similarity of metabolic rates within broad taxonomic or functional groups of organisms (e.g. invertebrates or ectotherms). Such metabolic commonality is challenged here, as I demonstrate more than 200-fold variation in metabolic rates independent of body mass and temperature in a single class of animals, the Cephalopoda, over seven orders of magnitude size range. I further demonstrate wide variation in the slopes of metabolic scaling curves. The observed variation in metabolism reflects differential selection among species for locomotory capacity rather than mass or temperature constraints. Such selection is highest among epipelagic squids (Lolignidae and Ommastrephidae) that, as adults, have temperature-corrected metabolic rates higher than mammals of similar size.

Animals↗

PubMed2006

Combined effects of temperature acclimation and cadmium exposure on mitochondrial function in eastern oysters Crassostrea virginica gmelin (Bivalvia: Ostreidae).

Cadmium and temperature have strong impacts on the metabolic physiology of aquatic organisms. To analyze the combined impact of these two stressors on aerobic capacity, effects of Cd exposure (50 microg/L) on mitochondrial function were studied in oysters (Crassostrea virginica) acclimated to 12 and 20 degrees C in winter and to 20 and 28 degrees C in fall. Cadmium exposure had different effects on mitochondrial bioenergetics of oysters depending on the acclimation temperature. In oysters acclimated to 12 degrees C, Cd exposure resulted in elevated intrinsic rates of mitochondrial oxidation, whereas at 28 degrees C, a rapid and pronounced decrease of mitochondrial oxidative capacity was found in Cd-exposed oysters. At the intermediate acclimation temperature (20 degrees C), effects of Cd exposure on intrinsic rates of mitochondrial oxidation were negligible. Degree of coupling significantly decreased in mitochondria from 28 degrees C-acclimated oysters but not in that from 12 degrees C- or 20 degrees C-acclimated oysters. Acclimation at elevated temperatures also increased sensitivity of oyster mitochondria to extramitochondrial Cd. Variation in mitochondrial membrane potential explained 41% of the observed variation in mitochondrial adenosine triphosphate synthesis and proton leak between different acclimation groups of oysters. Temperature-dependent sensitivity of metabolic physiology to Cd has significant implications for toxicity testing and for extrapolation of laboratory studies to field populations of aquatic poikilotherms, indicating the importance of taking into account the thermal regime of the environment.

Acclimatization↗

PubMedDate not supplied

Augmentation of CD8 and CD4 lymphocytes subsets in AIDS infected children after treatment with a non-toxic chelating agents compound--Rodilemid.

Twelve children were included into the protocol, 5 in March 1989 and 7 in April 1993. All of them were HIV 1 positive and had diarrhoea, important adenopathy and opportunistic infections. Seven out of 12 patients had an immunological monitoring. One out of 12 children with B hepatitis died with liver cirrhosis. Eleven children had a clear improvement in their clinical course, during the treatment. Five out of 7 patients had a significant increase of the CD4 lymphocytes at 4 and 7 months follow-up. Four patients had an important and significant increase of the CD8 count at 4 months and 6 out of 7 patients at 7 months. Interestingly, in 4 out of 7 patients after 7 months treatment we observed higher than normal value of the CD8 count. Variations observed for CD8 population compared to CD4 were more important.

AIDS-Related Opportunistic Infections↗