A method is presented for the detection in crude lysates of subnanogram amounts of proteins covalently bound to a specific nucleic acid sequence. The sensitivity of this method enabled us to study proteins cross-linked to specific DNA and mRNA sequences by irradiation of intact Escherichia coli cells with ultraviolet light. Among the proteins cross-linked to pBR322 DNA, the single strand binding protein, the HU-proteins, and the RNA polymerase beta and sigma subunits were present. Some, but not all proteins were cross-linked to 5-bromodeoxyuridine-substituted DNA more efficiently than to normal DNA. Ribosomal protein S1 is by far the most prominent protein cross-linked to mRNAs. Among the proteins cross-linked in smaller amounts to mRNAs are translation initiation factor IF 1, and at least six proteins of the 30 S ribosomal subunit, among which is S21. No 50 S proteins, nor IF-2, IF-3 or any of the elongation factors could be detected. Some UV-induced nucleic acid-protein cross-links were found to be heat-labile. It is concluded that the method employed may be used to compare the proteins interacting with different mRNAs, as well as single-copy DNA sequences from bacteria and eucaryotes with low complexity genomes. 相似文献
Intrinsic processes are assumed to underlie life history expression and trade‐offs, but extrinsic inputs are theorised to shift trait expression and mask trade‐offs within species. Here, we explore application of this theory across species. We do this based on parentally induced embryo temperature as an extrinsic input, and mass‐specific embryo metabolism as an intrinsic process, underlying embryonic development rate. We found that embryonic metabolism followed intrinsic allometry rules among 49 songbird species from temperate and tropical sites. Extrinsic inputs via parentally induced temperatures explained the majority of variation in development rates and masked a relationship with metabolism; metabolism explained a minor proportion of the variation in development rates among species, and only after accounting for temperature effects. We discuss evidence that temperature further obscures the expected interspecific trade‐off between development rate and offspring quality. These results demonstrate the importance of considering extrinsic inputs to trait expression and trade‐offs across species. 相似文献
In a case-control study of 84 myocardial infarction patients and 84 population controls we investigated the association between iron status parameters and myocardial infarction during the acute phase and after six weeks. Immediately after the infarction mean ferritin levels were significantly higher, whereas iron levels and iron saturation of transferrin were significantly lower in cases than in controls. Six weeks after the infarction, serum iron levels were still significantly lower in cases than in controls. Neither serum ferritin levels nor serum iron levels did show a clear association with the size of the ischemic tissue damage as estimated by creatine phosphokinase levels. Our results indicate that serum ferritin and iron levels are influenced by the traumatic effects of the myocardial infarction. Possibly, these transient changes are an acute effect, as seen in infections. An increased uptake of iron in the reticulo-endothelial system for synthesis of ferritin, may account for the lowered serum iron level and the iron saturation of transferrin. 相似文献
The mating behaviour of 28 gilts was studied. The gilts were reared under two different social conditions known to affect both their puberty attainment and reproductive parameters during early pregnancy. The different social conditions were applied from an average age of 137 days onwards. Ten gilts were housed individually, having neither tactile nor visual contact with other pigs. The remaining gilts (n=18) were housed pairwise, having additional contact with gilts in adjacent pens and daily boar contact from 180 days of age onwards. At third oestrus, the gilts were artificially inseminated and subsequently introduced to one of three vasectomized boars for a period of 20 min. The gilts were slaughtered 10±1 days after insemination.
The mating behaviour varied considerably between individual gilts, partly because of differences in mating behaviour between the two groups of gilts. More (P<0.05) individually housed gilts showed a standing response latency upon introduction of the boar. During this latency period, the individually housed gilts initiated contact with the boar. Once the standing response was elicited, mating behaviour was similar in gilts of both social groups. One individually housed gilt did not show a standing response and consequently was not mated. The mating behaviour of the boars did not differ for the gilts of the two social conditions.
It was concluded that the social conditions of gilts during rearing affected their introductory sexual behaviour. The relationship with reproductive performance during early pregnancy is discussed. 相似文献
We have studied ileum morphology in pigs 3.5 months after partial ileal bypass (PIB) surgery. PIB caused a reduction in the length of the bypassed ileum by 60%, while the circumference was decreased by about 70%. We did not find evidence for dilatation of the functional, neo-terminal ileum. These results in pigs are contrary to those found earlier in rabbits. This may be of importance concerning the choice of animal model to study the effects of PIB. 相似文献
It has previously been reported that pre-exposure to a psychoactive drug can block the conditioned taste aversion associated with that drug. This study was an attempt to investigate alcohol-morphine interactions using this pre-exposure paradigm. After two weeks of adaptation to a schedule of daily 30-minute access to water, rats were pre-exposed to morphine, ethanol, or the respective vehicle control every second day for three days before (Days 1, 3, 5) and after the first conditioning day (Days 8, 10, 12). On conditioning days (Days 7, 14), animals were first presented with a saccharin solution for 30 minutes following which animals that were pre-exposed to morphine were injected with ethanol while those pre-exposed to ethanol were administered with morphine. Saccharin was again presented on three more occasions (Days 21, 28, 35) without drug injection. Using the percent change in saccharin consumed from the first presentation as a measure of aversion, it was found that pre-exposure to morphine blocked ethanol conditioned taste aversion. Similarly, animals pre-exposed to ethanol showed less aversion to the saccharin paired with morphine. This is the first demonstration of a symmetrical relationship between alcohol and the opiates. 相似文献
In order to assess the presence of specific recognition sites for high density lipoprotein (HDL) in vivo, HDL was nitrosylated with tetranitromethane and the decay and liver uptake were compared with that of native HDL. The association of intravenously injected nitrosylated HDL (TNM-HDL) with liver was greatly increased as compared to native HDL. Using a cold cell isolation method, it became evident that the liver endothelial cells were responsible for the increased uptake of the modified HDL. The involvement of the endothelial cells in the uptake of TNM-HDL from the circulation could also be demonstrated morphologically by using the fluorescent dye dioctadecyl-tetramethyl-indocarbocyanine perchlorate (Dil) to label HDL. In vitro competition studies with isolated liver endothelial cells indicated that unlabeled modified HDL and acetylated LDL displaced iodine-labeled TNM-HDL, while no competition was seen with LDL and a slight displacement was seen with unlabeled native HDL. Nonlipoprotein competitors of the scavenger receptor such as fucoidin and polyinosinic acid blocked the interaction of TNM-HDL with the liver endothelial cells. Also the degradation of TNM-HDL was blocked by low concentrations of chloroquine. It can be concluded that a scavenger receptor on liver endothelial cells is involved in the clearance of tetranitromethane-modified HDL, which excludes the possibility of using TNM-HDL in vivo to assess the non-receptor-dependent uptake of HDL. The use of nitrosylated HDL in vitro as a low affinity control is limited to cell types that do not possess scavenger receptors, because cell types with scavenger receptors will recognize and internalize TNM-HDL by a high affinity scavenger pathway. 相似文献
Bacterial flora, activities of 10 potential mucus- and dietary polysaccharide-degrading enzymes, blood group antigenicity of the intestinal glycoproteins, and proteolytic activity in the output from experimentally colectomized dogs with conventional ileostomies and dogs with valveless ileal reservoirs (pouches) were determined. The ileostomies of dogs with conventional surgery (group II) and with pouches (group III) were occluded intermittently during a 6-week period. The duration of occlusion was progressively increased. Group I, five dogs with conventional ileostomies, served as a control group. After occlusion of the ileal pouch for 7 h, total numbers of bacteria increased threefold, glycosidase activity increased fivefold, and blood group antigenicity of the intestinal glycoproteins, which was high in the output from the nonoccluded pouch, was no longer detectable. Proteolytic activity was not influenced by occlusion of the pouch. Significantly lower numbers of bacteria, only minor glycosidase activity, high blood group antigenicities of the intestinal glycoproteins, and higher proteolytic activity were found in ileostomy effluents from groups I and II. Histopathological examination showed chronic inflammation and changes in crypt-villus ratio in all dogs with ileal reservoirs; the ileal mucosa from the dogs with conventional ileostomies did not show any abnormalities. Consequences of the flora-related enzyme activities for the ileal mucosa are discussed. 相似文献
As part of our study of isoenzyme forms of human cytochrome c oxidase, we purified subunit IV from human heart and skeletal muscle with reversed-phase HPLC and determined the N-terminal amino acid sequences and the electrophoretic mobility. The N-terminus of human heart subunit IV proved to be ragged with 30% of the protein lacking the first three residues. Also a Tyr/Phe polymorphism was observed at residue 16. No differences in N-terminal sequence and electrophoretic mobility were observed between subunit IV of cytochrome c oxidase from human heart and skeletal muscle. Therefore, our results suggest that identical subunits IV are present in cytochrome c oxidase from human heart and skeletal muscle. A putative isoform of subunit IV with a blocked N-terminus was purified from human heart cytochrome c oxidase, which proved to have a different retention time on a reversed-phase column and also a slightly higher electrophoretic mobility on an SDS-polyacrylamide gel compared to the native subunit IV. We could not demonstrate the existence of isoforms of subunit IV in human skeletal muscle. 相似文献