The rumen fermentation rates in individual lactating cows were measured in four different experiments. The results disclosed that the amounts and proportions of volatile acids formed could vary widely. In one case, a marked difference in the proportions of the acids produced arose within the experiment and correlated with a difference in the proportion of methane formed.
The average rate of production per day was 10.5 moles butyric acid, 12.8 moles propionic acid, and 40 moles acetic acid. Manometric estimations of rate gave lower results than those obtained by the zero-time method, due to delay after sampling and to failure of the acids to liberate stoichiometric quantities of carbon dioxide.
For those experiments in which zero-time rates were estimated, the average specific absorption rates, i.e., the amount absorbed per hour per micromole of acid in the rumen, were 0.37 for butyric acid, 0.38 for propionic acid, and 0.26 for acetic acid.
The carbon dioxide, acids, and microbial cells produced in the rumen fermentation are estimated to account for about 90% of the carbon found in the milk and respiratory CO2 of the cows. The carbon dioxide from the fermentation was about 27% of the carbon dioxide exhaled.
Compared to the catastrophic impacts of various environmental disturbances and the subsequent recovery of scleractinian coral communities from these events, little is known about the early successional dynamics of coral communities following major volcanic eruptions. The 1988 volcanic eruption of Gunung Api, Banda Islands, Indonesia, provided a unique opportunity to study the rate at which a reef-building coral community develops on an andesitic lava flow. Coral colonization was studied at three locations varying in substrate characteristics. Five years after the eruption, the sheltered lava flow supported a diverse coral community (124 species) with high coral cover
. Tabulate acroporids were a dominant component of the lava flow coral community, with some colonies measuring over 90 cm in diameter. Higher average coral diversity, coral abundance and cover were recorded on the andesitic lava flow than on an adjacent carbonate reef not covered by the lava, and on a substrate of unstable pyroclastic deposits located on the southwestern coast of the volcano. In some areas of high coral diversity and environmental stability, andesitic lava flows may create local hot-spots of coral diversity by providing a structurally complex, predator-free and stable substrate for the recruitment of coral species from the adjacent and regional species pools. 相似文献
A methanogenic acetate enrichment was initiated by inoculation of an acetate-mineral salts medium with domestic anaerobic digestor sludge and maintained by weekly transfer for 2 years. The enrichment culture contained a Methanosarcina and several obligately anaerobic nonmethanogenic bacteria. These latter organisms formed varying degrees of association with the Methanosarcina, ranging from the nutritionally fastidious gram-negative rod called the satellite bacterium to the nutritionally nonfastidious Eubacterium limosum. The satellite bacterium had growth requirements for amino acids, a peptide, a purine base, vitamin B12, and other B vitamins. Glucose, mannitol, starch, pyruvate, cysteine, lysine, leucine, isoleucine, arginine, and asparagine stimulated growth and hydrogen production. Acetate was neither incorporated nor metabolized by the satellite organism. Since acetate was the sole organic carbon source in the enrichment culture, organism(s) which metabolize acetate (such as the Methanosarcina) must produce substrates and growth factors for associated organisms which do not metabolize acetate. 相似文献
Ulcerative colitis is distinguished by abundant prostaglandin E2 (PGE2) in the stools and by severe diarrhea. To determine whether luminal PGE2 alters normal colonic absorption, Na+ and Cl−transport across isolated rat proximal colon were studied before and after 16, 16 dimethyl PGE2 (dmPGE2) addition to flux chambers. Luminal administration of dmPGE2 significantly reduced the net mucosal to serosal fluxes of Na+ and Cl−. These antiabsorptive tive effects of dmPGE2 on Na+ and Cl− active transport were reflected by a reduced metabolic rate of colonic tissue slices incubated with dmPGE2. Addition of dmPGE2 significantly reduced oxidation of glucose by the colon. Structurally, dmPGE2 reduced the length of colonic mucosal microvilli, thereby decreasing absorptive surface area. These results suggest that PGE2 released into the colonic lumen of patients with ulcerative colitis exerts antiabsorptive effects on the colon and in this way contributes to the associated diarrhea. 相似文献
Nestin is an intermediate filament protein (IFP) expressed in undifferentiated cells during CNS development and in CNS tumors. Previous studies have arrived at different conclusions in terms of which types of CNS tumors express nestin. In this report we establish an immunohistochemical protocol using antigen retrieval, which significantly enhances staining with two polyclonal anti-nestin antisera, #130 and #4350. The staining pattern was identical for the two nestin antisera and very similar to that of vimentin, while glial fibrillary acidic protein (GFAP), immunoreactivity was absent from 9.5-week-old forebrain. The current study of 20 primary CNS tumors from pediatric patients included seven ependymomas, seven primitive neuroectodermal tumors (PNETs), five pilocytic astrocytomas, and one glioblastoma multiforme (GBM). All these tumors expressed nestin to various extents, in contrast to five brain metastases tested. Strong nestin immunoreactivity was found in malignant primary CNS tumors, whereas benign pilocytic astrocytomas showed low but consistent nestin expression. In all tumors nestin immunoreactivity was confined to the cytoplasm of tumor cells and was co-expressed with astrocyte markers vimentin, GFAP, and S-100. Vascular endothelial cells of all neoplasms also showed marked immunoreactivity for nestin and vimentin, whereas they were negative for GFAP and S-100. In conclusion, antiserum #4350 detected nestin in formalin-fixed, paraffin-embedded tissue sections by heat-induced antigen retrieval immunohistochemistry. Nestin was expressed in both highly malignant and low malignant gliomas, indicating the potential use of nestin as a diagnostic tumor marker in surgical pathology. 相似文献
Bioinformatics is the use of informatics tools and techniques in the study of molecular biology, genetic, or clinical data. The field of bioinformatics has expanded tremendously to cope with the large expansion of information generated by the mouse and human genome projects, as newer generations of computers that are much more powerful have emerged in the commercial market. It is now possible to employ the computing hardware and software at hand to generate novel methodologies in order to link data across the different databanks generated by these international projects and derive clinical and biological relevance from all of the information gathered. The ultimate goal would be to develop a computer program that can provide information correlating genes, their single nucleotide polymorphisms (SNPs), and the possible structural and functional effects on the encoded proteins with relation to known information on complex diseases with great ease and speed. Here, the recent developments of available software methods to analyze SNPs in relation to complex diseases are reviewed with emphasis on the type of predictions on protein structure and functions that can be made. The need for further development of comprehensive bioinformatics tools that can cope with information generated by the genomics communities is emphasized. 相似文献
The human plutiripotent stem cell registry (hPSCreg) is a global database for human embryonic and induced pluripotent stem cells (hESC, hiPSC). The publicly accessible Registry (https://hpscreg.eu) was set up to provide a transparent resource of quality‐assessed hPSC lines as well as to increase reproducibility of research and interoperability of data.ObjectivesIn this review, we describe the establishment of the Registry and its mission, its development into a knowledgebase for hPSC and the current status of hPSC‐focussed databases. The data categories available in hPSCreg are detailed. In addition, sharing and hurdles to data sharing on a global level are described.ConclusionsAn outlook is provided on the establishment of digital representatives of donors using hybrids of data and hPSC‐based biological models, and how this can also be used to reposition databases as mediators between donors and researchers.hPSCreg as a data hub for pluripotent stem cells: Key utility and function. 相似文献
An acetate-fermenting strain of Methanosarcina was isolated from an acetate enrichment culture inoculated with anaerobic sludge from a waste treatment digestor. In pure culture, this organism fermented acetate in the absence of added hydrogen at rates comparable in magnitude to those found in digestor systems. This rate was significantly higher than previously obtained for pure cultures of this genus. Mineral components of yeast extract were highly stimulatory for cultures growing on methanol. Comparable stimulation was not observed for cultures growing on acetate. Labeling studies indicated that acetate was converted to methane and CO2 as predicted by previous studies on mixed cultures. Total oxidation or reduction of acetate was not the mechanism of conversion of acetate to methane by the pure culture. The ability of this strain to form colonies or to produce methane from acetate was apparently influenced by the choice of substrate and conditions used for growing the inoculum. 相似文献