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排序方式: 共有111条查询结果,搜索用时 15 毫秒
41.
Barbora de Courten Michaela Jakubova Maximilian PJ de Courten Ivica Just Kukurova Silvia Vallova Patrik Krumpolec Ladislav Valkovic Timea Kurdiova Davide Garzon Silvia Barbaresi Helena J. Teede Wim Derave Martin Krssak Giancarlo Aldini Jozef Ukropec Barbara Ukropcova 《Obesity (Silver Spring, Md.)》2016,24(5):1027-1034
42.
Studies on the ovulation rate, prenatal survival and litter size of Chinese Meishan pigs have given widely divergent results depending on the extent of inbreeding of the animals, their original genetic diversity, the age and parity, and the conditions of management. To obtain meaningful results, it is necessary to characterize the population under study. The following report characterizes populations of Meishan and Yorkshire of a widely diverse background. First farrowing data were collected on 21 Meishan and 20 Yorkshire gilts. Meishan gilts had 12.4 fully formed piglets and Yorkshire gilts had 7.4 fully formed piglets (P < 0.01). Meishan gilts averaged 1.86 mummified fetuses per litter vs 0.05 per Yorkshire litter (P < 0.01). Yorkshire piglets averaged 1.3 kg body weight at birth vs 0.9 kg for Meishan piglets (P < 0.01). At 47 days of second gestation, 19 Meishan and 12 Yorkshire sows averaged 22.7 and 16.3 corpora lutea (CL), respectively (P < 0.01). Uterine length and number of fetuses were not different (P > 0.40) in the two breeds. Daily estrous detection of 50 Meishan and 34 Yorkshire gilts began at 60 and 120 days of age, respectively. Meishan gilts reached sexual maturity at 95 days of age, which was 105 days earlier than Yorkshire gilts (P < 0.01). Meishan gilts were in estrus nearly 1 day longer than Yorkshire gilts at first, second and third estrus (P < 0.05). No differences in cycle length between breeds were detected for the first or second estrous cycle (P > 0.60). Nineteen Meishan gilts were slaughtered at 51 days of gestation and their reproductive tracts were recovered. The mean number of dissected CL (17.0), number of fetuses (13.1), total uterine length (396 cm), spacing per fetus (29.9 cm), allantoic (124.9 ml) and amniotic (32.2 ml) volumes, crown-rump length (82.8 mm), weight (35.4 g), sex, and direction of each fetus were determined. Chinese Meishan gilts reached puberty much earlier and were in estrus longer than Yorkshire gilts and Meishan sows had more CL than Yorkshire sows. 相似文献
43.
Michelle S Teng Martijn PJ Dekkers Ling Bee Ng Suzanne Rademakers Gert Jansen Andrew G Fraser John McCafferty 《BMC biology》2006,4(1):22-9
Background
G-protein-coupled receptors (GPCRs) play a crucial role in many biological processes and represent a major class of drug targets. However, purification of GPCRs for biochemical study is difficult and current methods of studying receptor-ligand interactions involve in vitro systems. Caenorhabditis elegans is a soil-dwelling, bacteria-feeding nematode that uses GPCRs expressed in chemosensory neurons to detect bacteria and environmental compounds, making this an ideal system for studying in vivo GPCR-ligand interactions. We sought to test this by functionally expressing two medically important mammalian GPCRs, somatostatin receptor 2 (Sstr2) and chemokine receptor 5 (CCR5) in the gustatory neurons of C. elegans. 相似文献44.
45.
Improved analyses of human mtDNA sequences support a recent African origin for Homo sapiens 总被引:3,自引:1,他引:2
New quantitative methods are applied to the 135 human mitochondrial
sequences from the Vigilant et al. data set. General problems in analyzing
large numbers of short sequences are discussed, and an improved strategy is
suggested. A key feature is to focus not on individual trees but on the
general "landscape" of trees. Over 1,000 searches were made from random
starting trees with only one tree (a local optimum) being retained each
time, thereby ensuring optima were found independently. A new tree
comparison metric was developed that is unaffected by rearrangements of
trees around many very short internal edges. Use of this metric showed that
downweighting hypervariable sites revealed more evolutionary structure than
studies that weighted all sites equally. Our results are consistent with
convergence toward a global optimum. Crucial features are that the best
optima show very strong regional differentiation, a common group of 49
African sequences is found in all the best optima, and the best optima
contain the 16 !Kung sequences in a separate group of San people. The other
86 sequences form a heterogeneous mixture of Africans, Europeans,
Australopapuans, and Asians. Thus all major human lineages occur in Africa,
but only a subset occurs in the rest of the world. The existence of these
African-only groups strongly contradicts multiregional theories for the
origin of Homo sapiens that require widespread migration and interbreeding
over the entire range of H. erectus. Only when the multiregional model is
rejected is it appropriate to consider the root, based on a single locus,
to be the center of origin of a population (otherwise different loci could
give alternative geographic positions for the root). For this data, several
methods locate the root within the group of 49 African sequences and are
thus consistent with the recent African origin of H. sapiens. We
demonstrate that the time of the last common ancestor cannot be the time of
major expansion in human numbers, and our results are thus also consistent
with recent models that differentiate between the last common ancestor,
expansion out of Africa, and the major expansion in human populations. Such
a two-phase model is consistent with a wide range of molecular and
archeological evidence.
相似文献
46.
47.
T M Widowski S E Curtis P J Dziuk W C Wagner O D Sherwood 《Biology of reproduction》1990,43(2):290-297
Behavioral and endocrine changes in the sow following injection with prostaglandin F2 alpha (PGF2 alpha) or its analogue, cloprostenol (CLO), were monitored to identify endocrine correlates of prepartum activity (nest-building). On Day 112 postcoitum, within 15 min after injection with 10 mg PGF2 alpha, sows offered straw in pens engaged in intense prepartum activity, but few behavioral changes occurred during the first 2 h following administration of 175 micrograms CLO. The temporal pattern of prepartum activity, however, was affected by both prostaglandins. In control sows, most prepartum activity came during Hours 16-0 before delivery of first piglet (delivery). After CLO, sows engaged in nest-building more during Hours 32-17 and less during Hours 16-0. In another experiment, sows in farrowing crates were injected with saline, 175 micrograms CLO, or 10 mg PGF2 alpha on Day 112 and blood was collected 0, 15, 30, 60, and 90 min later. Another sample was collected when spontaneous prepartum activity was first observed. For approximately 90 min after PGF2 alpha treatment, sows rooted, pawed, and bit and rubbed faces on crate bars; after saline and CLO, this behavior was rarely observed. After prostaglandin treatment, plasma progesterone tended to decline, a 10-fold rise in relaxin came within 15 min, but estrone did not change. Plasma prolactin rose 10-fold within 30 min after PGF2 alpha treatment, and rose more gradually after CLO treatment. When sows exhibited spontaneous prepartum activity (approximately 7 h before delivery), endocrine status was characterized by low progesterone, high estrone:progesterone ratio, and high prolactin.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
48.
N Lübcker J Dabrowski TA Zengeya PJ Oberholster G Hall S Woodborne 《African Journal of Aquatic Science》2016,41(4):399-411
The alien invasive silver carp Hypophthalmichthys molitrix established a self-sustaining feral population in an oligotrophic impoundment, Flag Boshielo Dam, in South Africa. The ability of this population to persist in a dam with low algal biomass (median annual suspended chlorophyll a = 0.08 µg l?1), and limited access to rivers considered large enough for successful spawning, has implications for their invasive potential in other systems. Stomach content and stable isotope analysis were used to assess the trophic ecology of H. molitrix, which was then compared with indigenous Mozambique tilapia Oreochromis mossambicus, on a seasonal basis during 2011. Hypophthalmichthys molitrix are generalist filter feeders, with a diet consisting primarily of sediment, vegetative detritus, dinoflagellates and diatoms. The dominance of sediments in their stomachs suggests occasional benthic scavenging. However, H. molitrix occupied a higher trophic level (TL = 2.8) than expected, suggesting that this population subsidised their diet with an unidentified dietary constituent, characterised by enriched nitrogen values. Although the stomach contents indicated dietary overlap between H. molitrix and O. mossambicus, stable isotopes revealed fine-scale resource partitioning, despite both species occupying the same trophic level. Nonetheless, the persistence of this feral H. molitrix population in an oligotrophic impoundment highlights their phenotypic plasticity. 相似文献
49.
Recently, a group of diplomonads has been found to use a genetic code in
which TAA and TAG encode glutamine rather than termination. To survey the
distribution of this characteristic in diplomonads, we sought to identify
TAA and TAG codons at positions where glutamine is expected in genes for
alpha-tubulin, elongation factor-1 alpha, and the gamma subunit of
eukaryotic translation initiation factor-2. These sequences show that the
variant genetic code is utilized by almost all diplomonads, with the genus
Giardia alone using the universal genetic code. Comparative phylogenetic
analysis reveals that the switch to this genetic code took place very early
in the evolution of diplomonads and was likely a single event. Termination
signals and downstream untranslated regions were also cloned from three
Hexamita genes. In all three of these genes, the predicted TGA termination
codon was found at the expected position. Interestingly, the untranslated
regions of these genes are high in AT. This is incongruent with the coding
regions, which are comparatively GC-rich.
相似文献
50.
Apoptosis is characterized by DNA strand breaks with a 3'-OH terminus, which are analyzed by terminal deoxy(d)-UTP nick end labeling (TUNEL). Proteinase K digestion is thought to be an essential step in the TUNEL procedure. The effects of decalcifying reagents on general staining and the TUNEL assay for cartilage sections are largely unknown. The effects of these reagents on retention and integrity of DNA in chondrocytes have not been described until now. We evaluated the effects of various decalcifying solutions, including 10% EDTA, 10% citric acid, 5% trichloroacetic acid, 5% acetic acid and a commercial hydrochloric acid-based reagent, on general cartilage staining and the TUNEL assay for cartilage. The effects of proteinase K on nucleus preservation were also examined. Decalcification with 10% EDTA gave the best result for general cartilage staining. Chondrocyte DNA was retained and intact after using this reagent. Decalcification with 10% EDTA is also the safest method of decalcification if the TUNEL assay is applied to cartilage. Proteinase K digestion may have adverse effects on nucleus preservation in cartilage. Awareness of these effects is important whenever the TUNEL assay is applied. 相似文献