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151.
Apparent Differential Selection at an Isozyme Locus between Queens and Workers of the Ant APHAENOGASTER RUDIS 总被引:1,自引:0,他引:1 下载免费PDF全文
R. H. Crozier 《Genetics》1973,73(2):313-318
The frequencies of two alleles at a cathodal malate dehydrogenase locus in populations of A. rudis were studied in 47 colonies from three localities in Georgia and one in New Jersey. The male gene frequencies of the New Jersey and one Georgia locality differ significantly. All the queens at one Georgia locality were heterozygotes. This genotypic distribution differs strongly from that of the workers, in which approximately equal numbers of heterozygotes and homozygotes were found. The heterozygote excess among queens but not their worker progeny suggests differential selection between these castes. This study also shows that rudis colonies consist of a single, once-mated queen and her worker progeny. 相似文献
152.
Kimball SR O'Malley JP Anthony JC Crozier SJ Jefferson LS 《American journal of physiology. Endocrinology and metabolism》2004,287(4):E772-E780
Loss of muscle strength is a principal factor in the development of physical frailty, a condition clinically associated with increased risk of bone fractures, impairments in the activities of daily living, and loss of independence in older humans. A primary determinant in the decline in muscle strength that occurs during aging is a loss of muscle mass, which could occur through a reduction in the rate of protein synthesis, an elevation in protein degradation, or a combination of both. In the present study, rates of protein synthesis and the relative expression and function of various biomarkers involved in the initiation of mRNA translation in skeletal muscle were examined at different times throughout the life span of the rat. It was found that between 1 and 6 mo of age, body weight increased fourfold. However, by 6 mo, gastrocnemius protein synthesis and RNA content per gram of muscle were lower than values observed in 1-mo-old rats. Moreover, the relative expression of two proteins involved in the binding of initiator methionyl-tRNA to the 40S ribosomal subunit, eukaryotic initiation factors (eIF)2 and eIF2B, as well as the 70-kDa ribosomal protein S6 kinase, S6K1, was lower at 6 mo compared with 1 mo of age. Muscle mass, protein synthesis, and the aforementioned biomarkers remained unchanged until approximately 21 mo. Between 21 and 24 mo of age, muscle mass decreased precipitously. Surprisingly, during this period protein synthesis, relative RNA content, eIF2B activity, relative eIF2 expression, and S6K1 phosphorylation all increased. The results are consistent with a model wherein protein synthesis is enhanced during aging in a futile attempt to maintain muscle mass. 相似文献
153.
Twelve of 30 species examined in the ant genus Polyrhachis carry single nucleotide insertions at one or two positions within the mitochondrial cytochrome b (cytb) gene. Two of the sites are present in more than one species. Nucleotide substitutions in taxa carrying insertions show the strong codon position bias expected of functional protein coding genes, with substitutions concentrated in the third positions of the original reading frame. This pattern of evolution of the sequences strongly suggests that they are functional cytb sequences. This result is not the first report of +1 frameshift insertions in animal mitochondrial genes. A similar site was discovered in vertebrates, where single nucleotide frameshift insertions in many birds and a turtle were reported by Mindell et al. (Mol Biol Evol 15:1568, 1998). They hypothesized that the genes are correctly decoded by a programmed frameshift during translation. The discovery of four additional sites gives us the opportunity to look for common features that may explain how programmed frameshifts can arise. The common feature appears to be the presence of two consecutive rare codons at the insertion site. We hypothesize that the second of these codons is not efficiently translated, causing a pause in the translation process. During the stall the weak wobble pairing of the tRNA bound in the peptidyl site of the ribosome, together with an exact Watson–Crick codon–anticodon pairing in the +1 position, allows translation to continue in the +1 reading frame. The result of these events is an adequate level of translation of a full-length and fully functional protein. A model is presented for decoding of these mitochondrial genes, consistent with known features of programmed translational frameshifting in the yeast TY1 and TY3 retrotransposons.Reviewing Editor: Dr. W. Ford Doolittle 相似文献
154.
The inheritance of elements of geotropic performance in lines of rats (A and B) has been investigated by examining the orientation of young offspring produced in matings of F1(AxB) with A: Previous studies had shown that the three recognizable groups of receptor elements concerned in geotropic orientation in each of these lines appeared to be inherited in such a way that B groups were dominant with respect to A groups, although this was to a minor extent complicated by influences affecting the variation of orientation as well as the exact form of the curve relating orientation angle (θ) to slope of surface. In the backcross F1 x A, therefore, at least eight different types of curves were to be expected. These are in fact identifiable among the forty-one individuals carefully studied. Their classification is concordant with the behavior of the respective indices of variation of θ, for which an interpretation has been provided. The basic result is, therefore, that the three receptor groups of excitation units are inherited independently, and alternatively as regards the members of a homologous pair, and that rather simple dominance relations obtain between homologous groups from the two races, namely that a B effect is dominant over the homologous A effect. This interpretation has been tested in various ways, and is in principle completely consistent with the results of a similar experiment involving races A and K. 相似文献
155.
156.
Analysis of Indole-3-Acetic Acid and Related Indoles in Culture Medium from Azospirillum lipoferum and Azospirillum brasilense 总被引:2,自引:1,他引:1 下载免费PDF全文
Alan Crozier Paulo Arruda Janie M. Jasmim Ana Maria Monteiro Gran Sandberg 《Applied microbiology》1988,54(11):2833-2837
Analysis of neutral and acidic ethyl acetate extracts from culture medium of Azospirillum brasilense 703Ebc by high-performance liquid chromatography (HPLC) and combined gas chromatography-mass spectrometry demonstrated the presence of indole-3-acetic acid (IAA), indole-3-ethanol, indole-3-methanol, and indole-3-lactic acid. IAA in media of 20 strains of A. brasilense and Azospirillum lipoferum was analyzed quantitatively by both the colorimetric Salkowski assay and HPLC-based isotopic dilution procedures. There was little correlation between the estimates obtained with the two procedures. For instance, the Salkowski assay suggested that the culture medium from A. brasilense 703Ebc contained 26.1 μg of IAA ml−1, whereas HPLC revealed the presence of only 0.5 μg of IAA ml−1. Equivalent estimates with A. brasilense 204Ed were 10.5 and 0.01 μg of IAA ml−1, respectively. The data demonstrate that the Salkowski assay is not a reliable method for measuring the IAA content of Azospirillum culture medium and that estimates in excess of 10 μg of IAA ml−1 should be viewed with particular caution. Metabolism of [2′-14C]IAA by A. brasilense 703Ebc yielded radiolabeled indole-3-methanol, whereas roots of maize (Zea mays L.) seedlings gave rise to [14C]oxindole-3-acetic acid and an array of polar metabolites. Metabolism of [2′-14C]IAA by maize roots inoculated with A. brasilense 703Ebc produced a metabolic profile characteristic of maize rather than Azospirillum species. 相似文献
157.
Emma M. Brown Gordon J. McDougall Derek Stewart Gema Pereira-Caro Rocio González-Barrio Philip Allsopp Pamela Magee Alan Crozier Ian Rowland Chris I. R. Gill 《PloS one》2012,7(11)
Fruit and vegetable consumption is associated at the population level with a protective effect against colorectal cancer. Phenolic compounds, especially abundant in berries, are of interest due to their putative anticancer activity. After consumption, however, phenolic compounds are subject to digestive conditions within the gastrointestinal tract that alter their structures and potentially their function. However, the majority of phenolic compounds are not efficiently absorbed in the small intestine and a substantial portion pass into the colon. We characterized berry extracts (raspberries, strawberries, blackcurrants) produced by in vitro-simulated upper intestinal tract digestion and subsequent fecal fermentation. These extracts and selected individual colonic metabolites were then evaluated for their putative anticancer activities using in vitro models of colorectal cancer, representing the key stages of initiation, promotion and invasion. Over a physiologically-relevant dose range (0–50 µg/ml gallic acid equivalents), the digested and fermented extracts demonstrated significant anti-genotoxic, anti-mutagenic and anti-invasive activity on colonocytes. This work indicates that phenolic compounds from berries undergo considerable structural modifications during their passage through the gastrointestinal tract but their breakdown products and metabolites retain biological activity and can modulate cellular processes associated with colon cancer. 相似文献
158.
From the relations between critical illumination in a flash (Im) and the flash frequency (F) for response of the sunfish to visual flicker when the proportion of light time to dark time (tL/tD) in a flicker cycle is varied at one temperature (21.5°) the following results are obtained: At values of tL/tD between 1/9 and 9/1 the F - log Im curves are progressively shifted toward higher intensities and lower Fmax.. Fmax. is a declining rectilinear function of the percentage of the flash cycle time occupied by light. The rod and the cone portions of the flicker curve are not shifted to the same extent. The cone portion and the rod region of the curve are each well described by a probability integral. In terms of F as 100 F/Fmax. the standard deviation of the underlying frequency distribution of elemental contributions, summed to produce the effect proportional to F, is independent of tL/tD. The magnitude of log Im at the inflection point (r''), however, increases rectilinearly with the percentage light time in the cycle. The proportionality between Im and σII1 is independent of tL/tD. These effects are interpreted as consequences of the fact that the number of elements of excitation available for discrimination of flicker is increased by increasing the dark interval in a flash cycle. Decreasing the dark interval has therefore the same kind of effect as reducing the visual area, and not that produced by decreasing the temperature. 相似文献
159.
A.B. Zhang L.J. He R.H. Crozier C. Muster C.-D. Zhu 《Molecular phylogenetics and evolution》2010,54(3):1035-1039
Sample size has long been one of the basic issues since the start of the DNA barcoding initiative and the global biodiversity investigation. As a contribution to resolving this problem, we propose a simple resampling approach to estimate several key sampling sizes for a DNA barcoding project. We illustrate our approach using both structured populations simulated under coalescent and real species of skipper butterflies. We found that sample sizes widely used in DNA barcoding are insufficient to assess the genetic diversity of a species, population structure impacts the estimation of the sample sizes, and hence will bias the species identification potentially. 相似文献
160.