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991.
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Experiments on the grazing of the ciliate Colpoda steinii on the blue–green alga Anacystis nidulans showed, among other things, that declines of the algal population initiated by grazing often continued for several days after grazing pressure had been released. In addition, long lags were observed when this alga was inoculated into sterile culture medium. Evidence presented in this study indicates that both phenomena were due to cellular damage caused by exposure of algal cells to a sudden increase of light intensity (“light shock”). The occurrence of light shock appeared to exert a destabilizing influence on the grazing relation between Colpoda and Anacystis. 相似文献
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Chromogranin A (CgA) in the gastro-entero-pancreatic (GEP) endocrine system. II. CgA in mammalian entero-endocrine cells 总被引:2,自引:0,他引:2
Chromogranin A (CgA) and related acidic proteins are widely distributed in the organism. They are also present in entero-endocrine cells and in other members of the paraneuron family. Therefore, CgA has been claimed as an universal marker of this cellular community. To yield precise data about the distribution of CgA in entero-endocrine cells, all segments of the gastro-intestinal tract of five mammalian species (man, cattle, pig, cat, guinea-pig) were investigated immunohistochemically for CgA. In serial semithin plastic sections, all CgA-immunoreactive endocrine cells were identified for resident amines or peptides. CgA could be found in ten hormonally identified endocrine cell types and in two or three other endocrine cell types. Entero-endocrine cells containing amines (histamine, serotonin) regularly exhibited CgA-immunoreactivities. In contrast, peptide-containing endocrine cells were largely heterogeneous: Their CgA-immunoreactivities varies among the species, among the gastro-intestinal segments, and even among the members of the same cell population. Hence, seen histochemically, CgA is no universal marker for entero-endocrine cells. Seen biochemically, the observed heterogeneities of CgA-immunoreactivities theoretically can be attributed to various factors (species-specificities of CgA, subclasses of chromogranins, processing of CgA or its pro-protein). Most probably, these heterogeneities are caused by species- or cell-specific differences in the extent of processing of CgA. In addition, some findings point to certain interrelations between the processing or storage of CgA and resident peptides in the secretion granules of enteroendocrine cells. 相似文献
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999.
Modern bryomol-sediments in a cool-water, high-energy setting: the inner shelf off Northern Brittany
Beate Bader 《Facies》2001,44(1):81-103
Summary The inner shelf off Roscoff/North Brittany, France situated in the Western English Channel, provides a unique facility for
studying modern cold water BRYOMOL-carbonate deposits in the North Atlantic. High tidal gauge with extreme strong tidal currents,
which effect the well-mixed water column throughout the year, and strong, seasonal storms characterize the conditions of the
area. The shelf is seperated in two carbonate production zones: Boulder fields and sand fields. The main production areas
are the sand fields with an intensive epifaunal and infaunal colonization by bivalves and the bryozoan thickets ofCellaria spp. and their associated epifauna. The most beneficial and dominant strategies of the sessile benthos are erect flexible
and encrusting growth habits.
The study area is partitioned in two zones: (1) the coarse sediment blanket typified by active sediment generation and little
accumulation, and (2) the shell dune Trezen ar Skoden, characterized by accumulated sediments. Sediment transport and distribution
of facies areas are controlled by the strong semidiurnal tidal current regime and episodically severe storms. As a result
of these high energy processes of redeposition the autochthonous sediment particles are physically reworked and redeposited
while in calmer periods deposition and biological destruction of the components occur.
The Holocene development of the sea level has been of crucial influence to the costal morphology and the establishment of
different carbonate production centers. The benthic communities produce with their carbonate skeletons the first biogenic
sediment and provide substrates for colonization of epi- and endofauna. Changes in the current patterns and the morphology
of the sea bottom resulted in the origin of the shell dune Trezen ar Skoden. 相似文献
1000.
Mikhlid H. Almutairi Nouf S. Al-Numair Narasimha Reddy Parine Bader O. Almutairi Abdulwahed F. Alrefaei Mahmoud Rouabhia Abdelhabib Semlali 《Saudi Journal of Biological Sciences》2021,28(7):3972-3980
Methylenetetrahydrofolate reductase (MTHFR) polymorphism plays a fundamental role in susceptibility to various diseases, including cancers and autoimmune diseases. In the current study, we aimed to compare genotype and allele frequency variations of rs1801131, one of the most common variants found in the MTHFR gene, among Saudi smokers and non-smokers. We hypothesized that genetic variations of this gene are responsible for many diseases, particularly those caused by cigarette smoking (CS) such as pulmonary diseases, oral cancer and lung cancer. We performed a case-control study on a sample of 235 healthy smokers and 239 healthy non-smokers in Saudi Arabia. The rs1801131 SNP genotypes were determined using a genotyping assay and multiple in silico algorithmic software programs were used to identify the effects and structural functions of the rs1801131 (Glu429Ala) mutation. Using chi-squared tests, we found that, among smokers, TG and GG genotype carriers had 0.209-fold (OR = 0.209, P < 0.005) and 0.427-fold (OR = 0.427, P = 0.003) lower risks of CS-related disease compared to TT reference genotypes. In addition, this protective effect was observed in Saudi smokers independent of age, gender, types of smoking, duration, and average daily smoking consumption. Filling a research gap by exploring this topic in the Saudi population, the current findings indicate that genotype and allele distributions of MTHFR rs1801131 polymorphism present fundamental protective effects against the risk of CS-related disease. These findings should be verified in future studies with larger sample sizes, different ethnicities, and patients suffering from CS-related diseases, such as oral cancer and lung cancer. 相似文献