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61.
Similar NH4+ and NO3?.uptake kinetic patterns were observed in Neoagardhiella baileyi (Harvey ex Kiitzing) Wyinne & Taylor and Gracilaria foliifera (Forssk?l) Borgesen. NO3? was taken up in a rate-sturating fashion described by the Michaelis-Menten equation. NH4+ uptake was multicomponent: a saturable component was accompanied by a diffusive or a high K component showing no evidence of saturation (at ≤50 μM [NH4+]). Nitrogen starved plantsi(C/N atom ratios > ca. 10) showed higher transient rates of NH4+ uptake at a given concentration than plants not N-Iimited. Only plants with high N content exhibited diel changes inNH4+ uptake rates, and showed transient rates of NH4+ accumulation which did not greatly exceed the capacity to incorporate N in steady-state growth. NH4+ was preferred over NO3?even in plants preconditioned on NO3?as the sole N. source, NO3? uptake was suppressed at 5μM [NH4+], but simultaneous uptake occurred at unsurpressed rates at lower concentrations. Potential for N accumulation was greater via NH4+uptake than via NO3?uptake. Changing capacity for NH4+ uptake with N content appears to be a mechanism whereby excessive accumulation of N was avoided by N-.satiated plants but a large accumulation was possible for N-depleted plants. 相似文献
62.
Foster MC Hwang SJ Massaro JM Hoffmann U DeBoer IH Robins SJ Vasan RS Fox CS 《Obesity (Silver Spring, Md.)》2011,19(6):1284-1289
Microalbuminuria is a common condition associated with increased incidence of cardiovascular events and mortality. Abdominal obesity is associated with microalbuminuria, but studies linking visceral adipose tissue (VAT) and microalbuminuria are limited. Our objective was to determine the associations of albuminuria with VAT and subcutaneous adipose tissue (SAT). We performed a cross-sectional study in the Framingham Multi-Detector Computed Tomography (MDCT) cohort (n = 3099, 48.2% women, mean age 53 years). VAT and SAT volumes were measured using computed tomography. Urinary albumin-to-creatinine ratio (UACR) was calculated from spot urine samples. Microalbuminuria was defined as a UACR >25 mg/g in women or >17 mg/g in men. Overall, 7.9% (n = 244) of the sample had microalbuminuria. Among men, VAT (odds ratio (OR) 1.48 per s.d., P < 0.0001) and SAT (OR 1.37 per s.d., P = 0.0002) were associated with microalbuminuria in minimally adjusted models, which remained significant after multivariable adjustment (VAT OR 1.34 per s.d., P = 0.001; SAT OR 1.28 per s.d., P = 0.005). Additionally, when considered jointly, VAT (P = 0.002) but not SAT (P = 0.2) was associated with microalbuminuria. In women, VAT was associated with microalbuminuria after minimal adjustment (OR 1.28, P = 0.01), but not after multivariable adjustment (OR 1.03, P = 0.8). In multivariable models in women, SAT was associated with a decreased odds of having microalbuminuria (OR 0.75 per s.d., P = 0.03). In conclusion, VAT is associated with microalbuminuria in men but not women. Albuminuria may be a manifestation of visceral adiposity. 相似文献
63.
Duangporn Jamsai Anne E. O’Connor Kathleen D. DeBoer Brett J. Clark Stephanie J. Smith Catherine M. Browne Jonathan G. Bensley Julie A. Merriman Wai Shan Yuen Peter Koopman Keith T. Jones Moira K. O’Bryan 《PloS one》2013,8(2)
The integrity of male germ cell genome is critical for the correct progression of spermatogenesis, successful fertilization, and proper development of the offspring. Several DNA repair pathways exist in male germ cells. However, unlike somatic cells, key components of such pathways remain largely unidentified. Gametogenetin (GGN) is a testis-enriched protein that has been shown to bind to the DNA repair protein FANCL via yeast-two-hybrid assays. This finding and its testis-enriched expression pattern raise the possibility that GGN plays a role in DNA repair during spermatogenesis. Herein we demonstrated that the largest isoform GGN1 interacted with components of DNA repair machinery in the mouse testis. In addition to FANCL, GGN1 interacted with the critical component of the Fanconi Anemia (FA) pathway FANCD2 and a downstream component of the BRCA pathway, BRCC36. To define the physiological function of GGN, we generated a Ggn null mouse line. A complete loss of GGN resulted in embryonic lethality at the very earliest period of pre-implantation development, with no viable blastocysts observed. This finding was consistent with the observation that Ggn mRNA was also expressed in lower levels in the oocyte and pre-implantation embryos. Moreover, pachytene spermatocytes of the Ggn heterozygous knockout mice showed an increased incidence of unrepaired DNA double strand breaks (DSBs). Together, our results suggest that GGN plays a role in male meiotic DSB repair and is absolutely required for the survival of pre-implantation embryos. 相似文献
64.
L.R. DeBoer D.M. Slaughter R.D. Applegate R.J. Sobieski & S.S. Crupper 《Letters in applied microbiology》2001,33(5):382-386
AIMS: The purpose of this study was to investigate the staphylococcal flora associated with wild turkey populations. METHODS AND RESULTS: Faecal samples obtained from 26 wild turkeys over a 16-month period were inoculated onto mannitol salt agar plates to select for staphylococci. Fifty-seven randomly chosen isolates were identified as Staphylococcus lentus and their susceptibility determined against clindamycin, chloramphenicol, ciprofloxacin, erythromycin, oxacillin, penicillin G, rifampin, tetracycline, trimethoprim-sulfamethoxazole, and vancomycin. Resistance was minimal as only 3 isolates showed resistance to clindamycin, 3 isolates were resistant to oxacillin, 3 isolates were resistant to penicillin G, and 1 isolate was resistant to erythromycin. Multiple antibiotic resistance was also minimal. CONCLUSIONS: S. lentus is the predominant staphylococcal species associated with wild turkey faeces and antibiotic resistance in these organisms is not problematic. SIGNIFICANCE AND IMPACT OF THE STUDY: S. lentus has been shown as a potential causative agent of inflammatory reactions in the respiratory tract. Due to increased numbers of wild turkeys and more frequent human exposure, surveys to monitor microbial populations are warranted. 相似文献
65.
66.
Augustine-Rauch KA Zhang QJ Posobiec L Mirabile R DeBoer LS Solomon HM Wier PJ 《Birth defects research. Part A, Clinical and molecular teratology》2004,70(10):773-788
BACKGROUND: SB-236057 is a potent skeletal teratogen in rodents and rabbits. The study objective was to identify the critical developmental window of compound sensitivity and to characterize the early onset of SB-236057 embryopathy. METHODS: SB-236057 was orally administered to Sprague Dawley dams at 100 mg/kg/day on days 6-7, 8-11, 12-14, or 15-17 postcoitus (pc). The critical window of sensitivity was identified to occur between days 8-11 pc. Dams were then dosed on days 8-11 pc and embryos were evaluated by histochemical procedures on days 11, 13, or 15 pc. RESULTS: Axial malformations were evident by day 11 pc. Analysis of the cartilaginous skeleton revealed missing posterior axial skeletal elements. However, only about one-third of the malformed fetuses exhibited obvious rib and vertebrae abnormalities, and none of the affected fetuses exhibited abnormal appendicular skeletal elements. Expression pattern of sonic hedgehog in the notochord and floor plate was not affected, suggesting ventral midline signaling was not disrupted. Histological analysis demonstrated hypoplastic and/or missing musculature in proximity to the ribs and vertebrae. Caspase 3 analysis revealed no increases in apoptotic cells in the musculature. Confocal analysis of the limbs demonstrated truncated peripheral nerve formation and shortening of the appendicular musculature. CONCLUSIONS: SB-236057 is speculated to alter paraxial mesoderm programming. Many of the skeletal malformations may be caused secondarily from musculature abnormalities, suggesting that the myotome may be particularly sensitive to the compound. Furthermore, the finding that peripheral nerve trajectories were altered along the axis and in the limb suggests that SB-236057 may alter early embryonic signaling pathways necessary for neuronal differentiation/axonal guidance that occur subsequently in embryo-fetal development. 相似文献
67.
Tallury SP Hilu KW Milla SR Friend SA Alsaghir M Stalker HT Quandt D 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2005,111(7):1229-1237
Section Arachis is the largest of nine sections in the genus Arachis and includes domesticated peanut, A. hypogaea L. Most species are diploids (x=10) with two tetraploids and a few aneuploids. Three genome types have been recognized in this section (A, B and D), but
the genomes are not well characterized and relationships of several newly described species are uncertain. To clarify genomic
relationships in section Arachis, cytogenetic information and molecular data from amplified fragment length polymorphism (AFLP) and the trnT-F plastid region were used to provide an additional insight into genome composition and species relationships. Cytogenetic
information supports earlier observations on genome types of A. cruziana, A. herzogii, A. kempff-mercadoi and A. kuhlmannii but was inconclusive about the genome composition of A. benensis, A. hoehnei, A. ipaensis, A. palustris, A. praecox and A. williamsii. An AFLP dendrogram resolved species into four major clusters and showed A. hypogaea grouping closely with A. ipaensis and A. williamsii. Sequence data of the trnT-F region provided genome-specific information and showed for the first time that the B and D genomes are more closely related
to each other than to the A genome. Integration of information from cytogenetics and biparentally and maternally inherited
genomic regions show promise in understanding genome types and relationships in Arachis. 相似文献
68.
The simple repeat poly(dT-dG).poly(dC-dA) common to eukaryotes is absent from eubacteria and archaebacteria and rare in protozoans 总被引:5,自引:0,他引:5
Genomic DNA from a wide variety of prokaryotic and eukaryotic organisms has
been assayed for the simple repeat sequence poly(dT-dG).poly(dC-dA) by
Southern blotting and DNA slot blot hybridizations. Consistent with
findings of others, we have found the simple alternating sequence to be
present in multiple copies in all organisms in the animal kingdom (e.g.,
mammals, reptiles, amphibians, fish, crustaceans, insects, jellyfish,
nematodes). The TG element was also found in lower eukaryotes
(Saccharomyces cerevisiae, Neurospora crassa, and Dictyostelium discoideum)
and at a much lower frequency in protozoans (Oxytricha fallux and
Tetrahymena thermophila). The sequence was also repeated in high copy
number in a higher plant (Zea mays) as well as at very high levels in a
unicellular green alga (Chlamydomonas reinhardi). Although the copy number
of the repeat per haploid genome was generally proportional to genome size,
there was a greater-than-1,000-fold variation in the number of
(TG)25/100-kb genomic DNA. By contrast, no eu-or archaebacterium--including
Myxococcus xanthus, whose life cycle is very similar to that of the slime
mold Dictyostelium discoideum, and Halobacter volcanii, whose genome
contains other repeated sequences-- was found whose genomic DNA contained
this sequence in detectable amounts. A computer search also failed to find
the TG element in human mitochondrial DNA.
相似文献
69.
Protein evolution in different cellular environments: cytochrome b in sharks and mammals 总被引:4,自引:0,他引:4
DNA sequences for the mitochondrial cytochrome b gene were determined for
13 species of sharks. Rates and patterns of amino acid replacement are
compared for sharks and mammals. Absolute rates of cytochrome b evolution
are six times slower in sharks than in mammals. Bivariate plots of the
number of nonsynonymous and silent transversions are indistinguishable in
the two groups, however, suggesting that the differences in amino acid
replacement rates are due primarily to differences in DNA substitution
rates. Patterns of amino acid replacement are also similar in the two
groups. Conserved and variable regions occur in the same parts of the
cytochrome b gene, and there is little evidence that the types of amino
acid changes are significantly different between the groups. Similarity in
the relative rates and patterns of protein change between the two groups
prevails despite dramatic differences in the cellular environments of
sharks and mammals. Poor penetrance of physiological differences through to
rates of protein evolution provides support for the neutral theory and
suggests that, for cytochrome b, patterns of evolution have been relatively
constant throughout much of vertebrate history.
相似文献
70.
Studies were conducted with one-year-old plants of the perennial legume, lucerne ( Medicago sativa L.), to determine the effects of various levels of S (0.3, 1.5, and 7.5 m M ) on N2 -fixation, photosynthesis, herbage free amino acid pools and protein amino acids, levels of protein, and activities of key enzymes of leaf nitrogen and carbon metabolism. Sulphur deficiencies in the 0.3 m M S treatment, as determined by N:S ratios, did not appear until the second growth cycle. This treatment was severely S-deficient by the end of the third growth cycle. Sulphur deficiencies did not occur in the other two treatments over three cycles of growth. By the middle of the second growth cycle acetylene reduction rates of plants grown with 0.3 m M S were lower than those of other treatments. At the end of the third growth cycle acetylene reduction rates of the 0.3 m M S treatment were ca . 30–35% that of the other treatments. There was no effect of S-deficiency on photosynthesis, levels of leaf NADP-isocitrate dehydrogenase and glutamine synthetase activity, or concentrations of leaf protein over the course of the experiments. Levels of NAD-glutamate dehydrogenase, NAD-malate dehydrogenase, and glutamate oxaloacetate trans-aminase activity and concentrations of free methionine, arginine, urea, and ammonia increased, with S-deficiency. Boron concentrations were very high (ca. 300 μg/g dry wt.) in S-deficient plants. The mole percent methiomne in leaf protein decreased slightly and chlorophyll concentration decreased markedly with S-deficiency. This study suggests that N2 -fixation is affected early during S-deprivation of lucerne and that subsequent effects of S-deficiency may be due to loss of fixed nitrogen. 相似文献