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71.
The use of Triton X-100 to solubilize membrane fragments from Anabaena flos-aquae in conjunction with DEAE cellulose chromatography allows the separation of three green fractions. Fraction 1 is detergent-solubilized chlorophyll, and Fraction 2 contains one polypeptide in the 15 kdalton area. Fraction 3, which contains most of the chlorophyll and shows P-700 and photosystem I activity, shows by SDS gel electrophoresis varying polypeptide profiles which reflect the presence of four fundamental bands as well as varying amounts of other polypeptides which appear to be aggregates containing the 15 kdalton polypeptide. The four fundamental bands are designated Band I at 120, Band II at 52, Band III at 46, and Band IV at 15 kdaltons. Band I obtained using 0.1% SDS contains chlorophyll and P-700 associated with it. When this band is cut out and rerun, the 120 kdalton band is lost, but significant increases occur in the intensities of Bands II, III, and IV as well as other polypeptides in the 20–30 kdalton range.The use of 1% Triton X-100 coupled with sucrose density gradient centrifugation allows the separation of three green bands at 10, 25 and 40% sucrose. The 10% layer contains a major polypeptide which appears to be Band IV. The 25 and 40% layers show essentially similar polypeptide profiles, resembling Fraction 3 in this regard, except that the 40% layer shows a marked decrease in Band III. Treatment of the material layering at the 40% sucrose level with a higher (4%) concentration of Triton X-100 causes a loss (disaggregation) of the polypeptides occurring in the 60–80 kdalton region and an increase in the lower molecular weight polypeptides. Thus, aggregation of the lower molecular weight polypeptides accounts for the variability seen in the electrophoresis patterns. Possible relations of the principal polypeptides to the known photochemical functions in the original membrane are discussed. 相似文献
72.
Triethyltin (TET) stimulated the basal respiration of Escherichia coli K-12 membrane vesicles in chloride (Cl-) medium but it had little effect on respiration in sulphate (SO4(2-)) medium. Since this uncoupling activity was Cl- dependent it was attributed to the Cl-/hydroxide (OH-) exchange reaction known to be mediated by TET [1,2]. TET inhibited the oxidation of succinate by intact E. coli in both Cl- and SO4(2-) medium, but at the same concentration of TET, inhibition was always more extensive in Cl- than SO4(2-) medium. In Cl- medium uncoupling in membrane vesicles and inhibition of succinate oxidation in intact bacteria occurred over the same concentration range and it appeared that the same mechanism, i.e. Cl-/OH- exchange, was responsible for both effects. Inhibition of succinate oxidation in SO4(2-) medium was not substantial until the concentration of TET was greater than 10(-5) M. Although the nature of this inhibition could not be determined by experiments with membrane vesicles indirect evidence from growth experiments indicated that it was due to impairment of oxidative phosphorylation. The relationship between these biochemical findings and the bacteriocidal action of TET was examined by using various concentrations of anion and substrate in the growth medium. Growth was inhibited in media containing either Cl- or SO4(2-) as the main anion but at a particular concentration of TET, inhibition was greater in Cl- medium. Growth was also inhibited to a greater extent in succinate than glucose medium. Furthermore in either Cl- or SO4(2-) glucose medium, lactic acid production increased as the concentration of TET was increased. These findings imply that the bacteriocidal action of TET is related to its effect(s) on oxidative phosphorylation. 相似文献
73.
Summary Cells of embryos carrying a lethal nucleolar mutation have been maintained in vitro for extended periods of time. Normally
these mutants live only 9 to 12 days after fertilization but their cells in culture will survive for more than 3 months. The
extent of ribosomal RNA (rRNA) synthesis was determined in primary cultures prepared from normal embryos and nucleolar mutants
having different numbers of ribosomal RNA genes. We found that the accumulation of radioactivity into rRNA for normal and
mutant embryos was similar in vivo and in vitro. In primary cultures of normal embryos which have two nucleoli per cell and
mutant embryos which have only one nucleolus per cell, the incorporation of radio-activity into rRNA was similar even though
the normal cells have twice as many rRNA genes. Thus the mechanism which regulates dosage compensation of the rRNA genes operates
both in vivo and in vitro.
This work was supported by Grant GB38651 from the National Science Foundation. 相似文献
74.
J Schubert P Uciechowski M Zielinska-Skowronek C Tietjen R Leo R E Schmidt 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(12):3814-3819
In these studies, the role of glycosylphosphatidylinositol (GPI)-anchored surface molecules during T cell activation was investigated in fresh T cells and T cell lines obtained from patients with paroxysmal nocturnal hemoglobinuria. For control, GPI-expressing T cells of the same patients were used. Unstimulated GPI- T cells exhibited significantly reduced surface expression of the activation Ag CD45R0, compared with GPI+ T cells. In addition, in measurements of proliferation, IFN-gamma production, and induction of second messengers such as cytoplasmic Ca2+, CD48- lymphocytes showed a similar response to TCR-specific stimulation, compared with CD48+ lymphocytes. In contrast, stimulation with the lectin PHA produced a decreased response of CD48- lymphocytes in these functions. In addition, stimulation with cross-linked CD59 mAb increased the proliferation of GPI-molecule expressing CD48+ T cell lines only. From these data, it can be concluded that GPI-anchored surface molecules play an important role in T lymphocyte activation. 相似文献
75.
Eduard Kühn Rudi Van Cauwenbergh Leo Huybrechts Hendrik Deelstra 《Biological trace element research》1992,32(1-3):289-292
Plasma concentrations of cGH, T3, and T4 were not different between dwarf and normal broiler breeders. Normal hens had a liver selenium content of 710±35 ng/g, and
dwarf hens 656 ±nine ng/g (n=8). Following injections into a wing vein of different doses (1.5, 3, 6, 12, and 24 μg/kg) of the hypothalamic hormone TRH,
GH was increased after 15 min. This effect seemed to last longer in dwarf chickens. Plasma concentrations of T3 increased significantly 1 h after TRH in normal hens, but TRH was ineffective in raising T3 levels in dwarf animals. The selenium content of livers obtained following decapitation after 2 h was also increased in normal
hens up to 902±42 ng/g using the highest dose of TRH (24 μg/kg). This seemed not to be the case for dwarf animals. A much
smaller. number of hepatic cGH receptors was also found in dwarf hens, whereas the affinity of the hepatic GH receptor was
not influenced by the genotype. It is concluded that the sex-linked dwarf hens are unable to increase their hepatic T4 into T3 conversion following a TRH challenge probably because of a deficiency in hepatic GH receptors. The lower content of selenium
in dwarfs and their inability to increase its uptake after TRH seem therefore to support the hypothesis that selenium has
a direct role in the activity of the 5′-deiodinase complex. 相似文献
76.
Sean P. Forestell Nicolas Kalogerakis Leo A. Behie 《Applied microbiology and biotechnology》1992,38(2):165-172
A new medium supplement mixture, PPRF92, has been developed to enable the serial subculture of human diploid fibroblasts (MRC-5 cells) on microcarriers. Furthermore, the PPRF92 supplements enable cell growth at serum levels as low as 1%. Through an optimization programme, the PPRF92 supplements have evolved into a simple mixture with the concentrations of key components at a level that makes the overall cost very competitive with medium containing 10% foetal bovine serum (FBS). Furthermore, the PPRF92 supplement mixture is most efficacious when FBS is replaced with the cheaper, and more widely available, adult bovine serum (ABS). Although medium exchange with serum is necessary in order to achieve confluence on microcarriers, the PPRF92 mixture is only necessary at the initiation of each passage. Using the medium replinishment protocol that has been developed in our laboratory, MRC-5 cells were successfully serially passaged through 13 bead-to-bead transfers on microcarriers in DMEM/F12 medium enriched with the PPRF92 supplement mixture reported here, and 1% ABS.Correspondence to: L. A. Behie 相似文献
77.
Kelly Dix Leo T. Burka Walter C. Dauterman 《Journal of biochemical and molecular toxicology》1992,7(4):199-204
Propetamphos [(E)-l-methylethyl 3[[(ethylamino)methoxyphosphinothioyl]oxy]-2-bu-tenoate], the active ingredient in Safrotin,® is an organophosphate developed by Sandoz, Ltd.® (Switzerland) as an insecticide (1). Although metabolism of propetamphos has been previously investigated (2,3), there is no pharmacokinetic data available in the literature. The current studies were undertaken to investigate the pharmacokinetics of propetamphos following intravenous administration in male and female Fischer 344 (F344) rats. Rats were dosed via an indwelling jugular cannula at a dose of 12 mg/kg (one-tenth the oral LD-50). Blood samples were withdrawn via the cannula at predetermined timepoints to quantitate plasma concentrations of propetamphos over time. Propetamphos is highly bound to plasma proteins (free fraction = 0.06). Free propetamphos concentration in plasma vs. time data were analyzed by noncompartmental methods. The terminal elimination rate constant, λ, was significantly different for males versus females (0.015 min?1 for males and 0.037 min?1 for females, p = 0.001). Plasma was cleared of unbound propetamphos at rates of 0.559 ± 0.069 and 0.828 ± 0.181 L/min/kg for males and females (mean ± standard error). Mean residence times (MRTs) for propetamphos in the body for males and females were 28.3 ± 5.7 and 14.4 ± 3.5 min, and the volume of distribution at steady state (Vss) was 14.7 ± 2.6 and 12.3 ± 4.5 L/kg. The differences in these parameters, clearance (CI), MRT, and Vss, were not statistically significant at the p < 0.05 level for males versus females, but MRT was nearly significantly different (p = 0.08). Because of the rapid elimination of propetamphos from plasma following intravenous administration, it is unlikely that propetamphos would bioaccumulate in environmentally exposed animals. Although the pharmacokinetic parameters were not statistically different for males and females in these studies, there was a clear clinical difference in their susceptibility to propetamphos toxicity. Female rats presented with overt signs of organophosphate intoxication, whereas males were only slightly effected. The observed gender-related clinical difference in susceptibility to toxicity suggests that there may be a difference in the extent of elimination due to activation versus detoxication of propetamphos in males and females. Another possible explanation for the clinical difference in propetamphos toxicity is that inhibition of acetyl-cholinesterase by the activated, oxygenated form of propetamphos (propetamphos oxon) may be greater in females than in males. 相似文献
78.
Use of synthetic resin cases for the scanning electron microscopic study of the kidney tubule system
L Magaudda G Cutroneo S De Leo A Pisani G Santoro G Anastasi 《Archivio italiano di anatomia e di embriologia》1990,95(2):87-104
Aim of our present work was to investigate a new method to study the three-dimensional arrangement, the length and the diameter of the different parts of the renal tubules. The ureter was cannulated after blocking the urinary flow with a binding of the ureter itself at its intermediate third, and injected in it against flow a synthetic resin (Mercox) normally used for vascular corrosion casts. It was demonstrated that the binding maintained only for 24 hours is adequate for morphological studies of the urinary tracts from papillar ducts until the Henle's loop. On the contrary the binding maintained for 7 days induced marked changes in the tubular architecture similar to the first anatomo-pathological changes of the nephrosclerosis following a chronic obstructive nephropathy. 相似文献
79.
John Leo Abernethy Charles M. Lovett Gary F. Kuzmin John D. Kuhlberg William A. Wilson 《Bioorganic chemistry》1981,10(2):189-199
Restriction of hydrazides of N-blocked amino acids mainly to electrophilic action, in acylating crude papain, has been achieved by means of a large amount of aniline, with formation of insoluble anilides of N-acylamino acids. Similarly, nucleophilic behavior, on the part of a hydrazide, has been promoted by introducing a large proportion of an N-acylamino acid to produce an insoluble N1,N2-diacylhydrazine. Achiral, chiral and racemic hydrazides and their corresponding N-acylamino acids were utilized in the study. Among the more informative combinations of reactants were Z-dl-alanine hydrazide with aniline and then with Z-glycine. A stereospecific response in the former situation produced Z-l-alanine anilide. In the latter case, a stereoselective interaction produced Z-Gly-NHNH-lAla-Z more rapidly than Z-Gly-NHNH-d-Ala-Z. The final incubation period yielded an optically pure D product. Differences in stereochemical control have been delineated in terms of different spatial aspects for interactions at the S and S′ subsites of sulfhydryl proteolytic enzymes. A racemic reactant encountered firm stereospecificity as an electrophile at the S subsite but only modest stereoselectivity as a nucleophile at the S′ subsite. The ready availability of crude papain allows an effective procedure for the synthesis of substantial quantities of diacylhydrazines. 相似文献
80.
We developed two simple methods for extracting specific, cell-free, soluble antigens of the mold form ofParacoccidioides brasiliensis. Detection of these antigens by a microimmunodiffusion test permits the rapid and accurate identification of cultures ofP. brasiliensis. ThirtyP. brasiliensis isolates treated by these techniques produced specific exoantigens detectable by the immunodiffusion test. None of the other
78 fungal pathogens or saprophytes tested produced identical exoantigens. Personnel in any diagnostic laboratory who want
a rapid and specific method for identifying or confirming suspected isolates ofP. brasiliensis can use the simple procedures described. 相似文献