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41.
The respective effects of cholera and Bordetella pertussis toxins were studied in time and concentration dependent experiments, following glycerol and fatty acid release, GTP and cAMP levels. Cholera toxin, after a lag time of 30 min, stimulated linearly GTP and cAMP accumulation and lipolysis (maximal effect: 2-fold increase at 5 micrograms/ml). Pertussis toxin presented a biphasic effect both in time and concentration dependent studies. Up to a maximum reached after 2 h with 1.4 units LPF/ml the stimulation affected GTP (3 fold) and cAMP (7 fold) levels, glycerol and fatty acid release (15 fold). Beyond this, an inhibition occurred, yielding a decrease towards basal values of GTP and cAMP content whereas the glycerol and fatty acid release was stopped. These results, which are the first reporting the fluctuation of the GTP content of intact cells challenged with bacterial toxins, show a close relationship between GTP and cyclic AMP levels and lipolytic activity. 相似文献
42.
D H Lambert D A Bryant V L Stirewalt J M Dubbs S E Stevens Jr R D Porter 《Journal of bacteriology》1985,164(2):659-664
The genes for the following proteins were localized by hybridization analysis on the cyanelle genome of Cyanophora paradoxa: the alpha and beta subunits of phycocyanin (cpcA and cpcB); the alpha and beta subunits of allophycocyanin (apcA and apcB); the large and small subunits of ribulose-1,5-bisphosphate carboxylase (rbcL and rbcS); the two putative chlorophyll alpha-binding apoproteins of the photosystem I-P700 complex (psaA and psaB); four apoproteins believed to be components of the photosystem II core complex (psbA, psbB, psbC, and psbD); the two apoprotein subunits of cytochrome b-559 which is also found in the core complex of photosystem II (psbE and psbF); three subunits of the ATP synthase complex (atpA and atpBE); and the cytochrome f apoprotein (petA). Eighty-five percent of the genome was cloned as BamHI, BglII, or PstI fragments. These cloned fragments were used to construct a physical map of the cyanelle genome and to localize more precisely some of the genes listed above. The genes for phycocyanin and allophycocyanin were not clustered and were separated by about 25 kilobases. Although the rbcL gene was adjacent to the atpBE genes and the psbC and psbD genes were adjacent, the arrangement of other genes encoding various polypeptide subunits of protein complexes involved in photosynthetic functions was dissimilar to that observed for known chloroplast genomes. These results are consistent with the independent development of this cyanelle from a cyanobacterial endosymbiont. 相似文献
43.
Dr. Michel Jangoux Philippe Dubois Anne Lambert Catherine Yourassowsky 《Cell and tissue research》1985,242(3):657-660
Summary A microcanalicular network is demonstrated within the ossicle stroma and the dermal tissue of two asteroid species. Microcanaliculi are presumed to be mesodermal structures. They consist of convoluted tubular ducts lined by epithelial cells associated with scattered basiepithelial nervous processes. Such a microcanalicular system has not been reported previously from any echinoderm species. Its discovery in asteroids entails some conceptual changes, especially considering the physiology of the body wall.Research assistants of the National Fund for Scientific Research (NFSR, Belgium) 相似文献
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45.
The effects of whooping cough were studied in 21 children admitted to hospital with the disease and in their families. The illness caused considerable distress to both child and family. Parents suffered especially from fears for the life and health of their child and from serious loss of sleep. Two months after admission the child''s behaviour was still disturbed, but in most cases the rest of the family had returned to normal. There was much misunderstanding and misinformation about whooping cough among both parents and doctors. 相似文献
46.
Cortisol production by dispersed guinea-pig adrenal cells; a specific, sensitive and reproducible response to ACTH....and its fragments 总被引:1,自引:0,他引:1
Naturally occurring steroids and peptide hormones, tested at supraphysiological concentrations, were without effect on basal and human (h) 1-39 ACTH (NIBSC code 74/555, 25 ng/l (5.5 X 10(-12) mol/l] stimulated cortisol production. Further, low concentrations of angiotensin II, N-pro-opiocortin (N terminal fragment 1-76) and gamma-MSH all of which have been reported to synergise with ACTH with regard to cortisol production, were without significant effect alone or in combination with ACTH over the range 2.2 X 10(-13) to 5.5 X 10(-12) mol/l. The activity of h 1-39 was compared with that of the ACTH related peptides 1-24, 1-18, 1-17, 1-16, 1-13-NH2 (alpha MSH), 1-10 and 4-10. The dose responses were parallel and the same maximal cortisol output was observed with all the peptides except the 1-10 fragment. Half maximal stimulation occurred at 3.1 X 10(-12) (1-24), 4.4 X 10(-12) (h 1-39), 1.5 X 10(-11) (1-39), 3.3 X 10(-10) (1-18), 5 X 10(-9) (1-13-NH2), 8 X 10(-9) (1-17), 2 X 10(-7) (1-16) and 1 X 10(-5) (4-10) mol/l respectively. Interference by the above ACTH-derived peptides in cortisol secretion by the cells in response to 5.5 X 10(-12) mol/l h 1-39 ACTH was minimal over the range 5.2 X 10(-12)-2.2 X 10(-6) mol/l. The sensitivity of the adrenal cells to h 1-39 ACTH was such that 2 ng/l (4.4 X 10(-13) mol/l) provoked cortisol secretion over the control (P less than 0.05, n = 17). The coefficient of variation within assay for each dose on the full standard curve (2.2 X 10(-13)-1.1 X 10(-10) mol/l) was less than 10% (n = 6). Half maximal stimulation was given by 14.5 ng/l (3.2 X 10(-12) mol/l). Between control and 1.1 X 10(-10) mol/l ACTH there was a 32 +/- 8 (mean +/- SD, n = 9) fold change in cortisol production. 相似文献
47.
48.
Purification and characterization of 3-dehydroquinase from Escherichia coli. 总被引:1,自引:1,他引:0 下载免费PDF全文
A procedure has been developed for the purification of 3-dehydroquinase from Escherichia coli. Homogeneous enzyme with specific activity 163 units/mg of protein was obtained in 19% overall yield. The subunit Mr estimated from polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate was 29,000. The native Mr, estimated by gel permeation chromatography on Sephacryl S-200 (superfine) and on TSK G3000SW, was in the range 52,000-58,000, indicating that the enzyme is dimeric. The catalytic properties of the enzyme have been determined and shown to be very similar to those of the biosynthetic 3-dehydroquinase component of the arom multifunctional enzyme of Neurospora crassa. 相似文献
49.
Levels of ribosomal protein S1 and elongation factor G in the growth cycle of Escherichia coli. 下载免费PDF全文
The relative levels of ribosomes, ribosomal protein S1, and elongation factor G in the growth cycle of Escherichia coli were examined with two-dimensional polyacrylamide gel electrophoresis. Nonequilibrium pH gradient polyacrylamide gel electrophoresis was used in the first dimension, and polyacrylamide gradient-sodium dodecyl sulfate gel electrophoresis was used in the second dimension. The identities of protein spots containing S1 and elongation factor G were confirmed by radioiodination of the proteins and peptide mapping of the radiolabeled peptides. The levels of ribosomes and ribosomal protein S1 were coordinately reduced during transition from exponential phase to stationary phase. There was no accumulation of S1 in the stationary phase. In marked contrast, the level of elongation factor G showed no significant change from exponential phase to stationary phase. The relative level of elongation factor G compared with ribosomes or S1 increased by about 2.5-fold during transition from exponential phase to stationary phase. The results show that there are differences between the regulation of the levels of elongation factor G and of ribosomal proteins, including S1, apparent during the transition from exponential to stationary phase. 相似文献
50.
G. Wynne Griffith A. M. Adelstein P. M. Lambert J. A. C. Weatherall 《BMJ (Clinical research ed.)》1972,3(5826):553-556
Early neonatal mortality in England and Wales in the second quarter of 1970 after a major influenza epidemic was slightly but significantly higher than in the corresponding quarter of the previous year. An increase was also noted in the first quarter of 1970. Analysis of infant mortality and an index of influenza prevalence over the past quarter-century indicates that similar increases occurred in relation to four of the other five major influenza epidemics during the period, the exception being the “Asian ''flu” epidemic of the autumn of 1957. It is suggested that the increased mortality in 1970 was the consequence of an increase in the prematurity rate, but we have no evidence to indicate whether the effect is specifically due to the virus or is nonspecific in nature. 相似文献