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71.
Intravenous bolus injection of prostaglandin I2 in the Inactin-anaesthetised rat produces a slow dose-dependant vasodepression which reaches maximum approximately 15 s. after injection. Administration of 9 beta-[3H1]-prostaglandin I2 by the same route followed by serial arterial sampling and TLC analysis revealed a slow conversion into one less polar metabolite starting after 20 s and reaching 40% by two minutes in the circulation. These experiments indicate that prostaglandin I2 survives pulmonary transit for a sufficiently long time to elicit a biological action. Thus its continuous systemic vascular synthesis could play an important role in the control of hypertension. 相似文献
72.
The Prophage of SPβc2DcitK1, a Defective Specialized Transducing Phage of BACILLUS SUBTILIS 总被引:4,自引:0,他引:4
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The defective specialized transducing phage SP beta c2dcitK1 carries two known bacterial genes, kauA and citK, as well as SP beta hage markers including the heat-sensitive repressor allele, c2. Some phage genes (including essential ones) are missing. When SP beta c2dcitK1 transduces SP beta-sensitive cells of Bacillus subtilis, the defective prophage is inserted into sites in the homologous bacterial DNA of the attSP beta-kauA-citK region of the recipient chromosome. During the growth of these transductants, occasional excisions occur that result in the loss of the phage genes and of the heterogenotic state. These excisions increase greatly in frequency during growth at repressor-inactivating temperatures. The kinds of insertions and excisions seen suggest that a Campbell-type (CAMPBELL 1962) circular phage genome may occur transiently. If the transductants are superinfected by SP beta c2 or by the clear-plaque mutant SP beta c1, the resulting double lysogen can be heat induced to release high-frequency-of-transduction (HFT) lysates for kauA and citK. 相似文献
73.
Light Effects in Yeast: Evidence for Participation of Cytochromes in Photoinhibition of Growth and Transport in Saccharomyces cerevisiae Cultured at Low Temperatures
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Stanislaw Uaszewski Theofanis Mamouneas Win-Kuang Shen Philip J. Rosenthal John R. Woodward Vincent P. Cirillo Leland N. Edmunds Jr 《Journal of bacteriology》1979,138(2):523-529
Visible light of moderate intensity inhibits growth, respiration, protein synthesis, and membrane transport in bakers' yeast and has a deleterious effect on membrane integrity. The results of this study indicate that these effects require the presence of cytochromes b and a/a(3). The light sensitivities of growth rate and [(14)C]histidine uptake in wild-type rho(+) Y185 and D225-5A strains of Saccharomyces cerevisiae were compared with those in a variety of mutants lacking cytochrome b or a/a(3) or both; a close correlation was found between the presence of these respiratory pigments and photosensitivity. Thus, strain TL5-3C, a nuclear petite lacking cytochromes b, a, and a(3), was resistant to light; strain GL5-6A, another nuclear petite having reduced amounts of cytochromes a and a(3), was partially resistant; strains MB127-20C and MB1-6C, nuclear petites lacking only cytochrome b, were also only partially resistant to light; whereas mutants containing all three cytochromes but having their respiratory chain either nonfunctional (strain ZK3-6B) or uncoupled (strain 18-27/t12) were fully sensitive to light. Finally, an equal-energy, broad-band action spectrum for the light inhibition of growth and transport indicated that blue light (408 nm) was most effective; these wavelengths correspond to the Soret region of the cytochrome absorption spectrum. The results suggest, therefore, that the yeast cytochromes b, a, and a(3) are the primary photoreceptors for the inhibitory effects of light and, perhaps, for other processes, such as the entrainment of biological rhythms in this species. 相似文献
74.
In an enzyme-specific drug screening system nalidixic acid and 3'-FTdR, inhibitors of DNA synthesis, both reduce the growth of wild type and temperature-sensitive point mutants of phage T3 with different efficiencies. The wild type shows the strongest sensitivity against the drugs, while an exonuclease mutant is the most insensitive variant. The DNA polymerase mutants exhibit an intermediate degree of inhibition. The anthracycline antibiotics violamycin BI and adriblastin which preferentially inhibit RNA synthesis show the same degree of inhibition for all mutants. This is true also for the RNA synthesis inhibitor lambdamycin, which is identical with chartreusin. The protein synthesis inhibitors chloramphenicol and o-phenanthroline, a chelating agent, impair all mutants to the same extent. Our data confirm the hypothesis that structural variants of essential viral enzymes, when compared with the wild type should reveal different sensitivities against specific inhibitors and show that this T3 system could be used for the indication of specific inhibitors of DNA synthesis. 相似文献
75.
76.
Eggs of Baltic herring were incubated (10°C; 16S) in sea water containing mixtures of Cd, Cu and Pb at concentrations of 0.56–5.0, 0.0167–0.15, 0.56–5.0 mg metal/l; embryonic survival until hatching, viable hatch and uptake of metals by embryos and early larvae were measured. Negative effects of metals on embryonic survival and viable hatch were additive in the case of Cu and Cd. Pb did not exer detrimental effects. Uptake of metals with exposure time was non-linear in eggs and linear in larvae. Total uptake of Cu and Cd by eggs was subjected to antagonistic or synergistic action of the other two metals present. Accumulation of Pb by eggs was enhanced when Cu was also present. 相似文献
77.
78.
Summary The mortality rate from leukemia and other neoplastic diseases for the years 1957–1969 was compared in 85,356 BCG-vaccinated newborns at Cook County Hospital, Chicago, and 534,870 nonvaccinated population in Chicago (all black). All cases of cancer deaths under 20 years of age in the black population of Chicago were obtained from death certificates at the Chicago Board of Health. The total black population 20 years of age and under was determined by demographic means from the Chicago Board of Health birth records, adjusted for deaths under the period of study. There were 13 deaths among the vaccinated for a rate of 1.17/100,000/year and 306 deaths among the nonvaccinated for a rate of 4.39/100,000/year. The difference was statistically highly significant (p<0.001). This was a reduction of 74% in the vaccinated group as compared to the nonvaccinated. There were no deaths from malignancies in the under 1 year of age group in the vaccinated, but a drop in the rates to 50% or less in the later age groups (except 10–14 years) in the vaccinated as compared to the nonvaccinated. Thus revaccination at given intervals (1–2 years) is recommended. The National Cancer Institute checked death reports due to cancer elsewhere in the country in our vaccinated population. To reduce the possibility of error, deaths due to trauma in the two groups were determined. No differences in the rates were found. The major categories of neoplasms for this age group were (1) leukemia, (2) central nervous system, (3) lymphoma, and (4) bone and connective tissue. This was a retrospective study. Statistically designed, controlled studies may provide definite conclusions. 相似文献
79.
I Silberberg R L Baer S A Rosenthal G J Thorbecke V Berezowsky 《Cellular immunology》1975,18(2):435-453
In order to further define the role of Langerhans cells in contact allergic reactions, passive transfer studies were done in guinea pigs using 2,4-dinitro-1-chlorobenzene (DNCB)-sensitive donor cells. Langerhans cells were found in the lumen of dermal vessels resembling lymphatics at 2, 3, 15, and 48 hr after DNCB challenge. In contrast to the previously reported findings in actively sensitized guinea pigs, the changes involving Langerhans cells in passively sensitized guinea pigs were mainly noted in the dermis. These consisted of increased numbers of Langerhans cells and of mononuclear cells apposed to Langerhans cells 3 or more hours after challenge with DNCB. The increased Langerhans cell population in the dermis and the presence of Langerhans cells in dermal vessels in specifically challenged sites in adoptive immune reactions furnishes further support for a significant role of Langerhans cells in the interaction between antigen and sensitized cells. 相似文献
80.
Evidence for the synthesis of soluble peptidoglycan fragments by protoplasts of Streptococcus faecalis. 总被引:13,自引:8,他引:5
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Growing protoplasts of Streptococcus faecalis 9790 were found to synthesize and excrete soluble peptidoglycan fragments. The presence of soluble peptidoglycan derivatives in culture supernatants was determined by (i) incorporation of three different radioactively labeled precursors (L-lysine, D-alanine, and acetate) into products which, after hen egg-white lysozyme hydrolysis, had the same KD values on gel filtration as muramidase hydrolysis products of isolated walls; (ii) inhibition of net synthesis of these products by cycloserine and vancomycin; and (iii) identification of disaccharide-peptide monomer using the beta-elimination reaction, gel filtration, and high-voltage paper electrophoresis. Under the conditions of these experiments the presence of newly synthesized, acid-precipitable (macromolecular) peptidoglycan was not detected. The predominance of monomer (70 to 80%) in lysozyme digests of peptidoglycan synthesized by protoplasts was in sharp contrast to digest of walls from intact streptococci which contain mostly peptide cross-linked products. Biosynthesis and release of relatively uncross-linked, soluble peptidoglycan fragments by protoplasts was related to the absence of suitable, preexisting acceptor wall. 相似文献