共查询到20条相似文献,搜索用时 15 毫秒
1.
Zinc has been implicated to play a role in the pathogenesis and management of diabetes. Since the intestinal transport of several minerals as calcium, magnesium and strontium was found to be altered in the diabetic rats, we postulated that intestinal zinc transport may be also altered in the diabetic rat. Therefore, using single pass perfusion technique we determined lumen to mucosa flux, net absorption and the mucosa to lumen flux of zinc in the small and large intestinal segments of diabetic rats, diabetic rats treated with insulin and in control rats. Tissue distribution of transported 65Zn into various organs and tissue concentrations of native zinc in the groups of rats studied were determined. Our results indicate that lumen to mucosa flux (μmole/h/g wet weight) was decreased in all intestinal segments of the diabetic rats compared to controls. However, the total capacity (mμmole/h/cm length) was similar. The specific activity and total capacity of net absorption of zinc was similar in all intestinal segments of the rats studied. The reverse mucosa to lumen flux was significantly decreased in all segments of diabetic rats compared to corresponding values in control rats. Tissue distribution of 65Zn following the perfusion study showed increased retention of 65Zn in the liver, kidney and femurs of the diabetic rats compared to controls. Serum and tissue concentration of native zinc in various organs were similar in all groups of rats studied. The mechanism(s) responsible for these findings are discussed. 相似文献
2.
The effect of the nephrotoxic aminoglycoside antibiotic, gentamicin, on calcium uptake by renal cortical mitochondria was assessed in vitro. Gentamicin was found to be a competitive inhibitor of mitochondrial Ca++ uptake. This effect displayed a dose response with a Ki of 233 μM and occurred at gentamicin concentrations below those that inhibit mitochondrial electron transport. These results further demonstrate the potential for gentamicin to alter membrane function and thereby contribute to toxic cell injury via its interactions with divalent cations. 相似文献
3.
Plasma 24,25-(OH)2D3 exhibits diurnal rhythmic variations in the adult rat. The decrease in 24,25-(OH)2D3 occurring at the onset of feeding during light-dark transition coincides with a decrease in plasma calcium but is inversely related to plasma phosphate and to increased intestinal calcium transport activity. 相似文献
4.
L Krupp A V Chobanian P I Brecher 《Biochemical and biophysical research communications》1976,72(4):1251-1258
The tumor-specific transplantation antigen (TSTA) in crude three molar potassium chloride (3M KCl) extracts of a chemically-induced, murine fibrosarcoma was purified by ammonium sulfate salt fraction at 20% saturation (S20S) and by polyacrylamide gel electrophoresis (PAGE). Mice, which had been pretreated with the S20S precipitate, displayed retarded outgrowth of a 100-fold supralethal dose of the corresponding, but not of a non-cross-reactive syngeneic tumor. Analysis of PAGE gels by Coomassie Blue staining revealed at least 30 bands in the crude 3M KCl extract, and only two components (Rf 0.34 and 0.43) in the ammonium sulfate fraction. That these two components bore TSTA activity was demonstrated by the observation that the immunoprotective activity of crude 3M KCl extracts was localized to the Rf 0.25–0.50 region. The two components present in the S20S fraction had isoelectric points of 5.05 and 6.9, and estimated molecular weights of 40,000 and 75,000, thus demonstrating the soluble nature of the active principle. These findings offer the prospect of a chemical dissection of the polymorphic TSTA surface markers on MCA-induced murine tumors. 相似文献
5.
Thomas A. Gasiewicz John C. Smith 《Biochimica et Biophysica Acta (BBA)/General Subjects》1976,428(1):113-122
75Se and 109Cd tracers were used to study the binding of Se and Cd to plasma proteins at various SeO32? doses and times up to 24 h after the simultaneous subcutaneous administration of SeO32? and CdCl2 to adult male rats. The simultaneous injection of CdCl2 and SeO32? markedly increased both Se and Cd plasma levels over that in control animals. Gel permeation chromatography of plasma indicated that at all times up to 24 h Cd and Se were bound in an atomic ratio of approx. 1 : 1 in 330 000 and 130 000 dalton fractions. From 4 to 24 h, Cd and Se appeared in the 420 000 dalton fraction, also with an atomic ratio of approx. 1 : 1. The 330 000 dalton molecules appeared to have a maximal binding capacity for the Cd-Se complex at a concentration of approx. 30 μmol/ml of plasma, while the 130 000 and 420 000 dalton molecules show a higher binding capacity. Studies in vitro revealed that SeO32? does not interact directly with Cd and plasma proteins. It is metabolized by erythrocytes to a form that interacts in an atomic ratio of 1 : 1 with Cd to form a protein-bound complex of 130 000 daltons. 相似文献
6.
Large quantities of NaCl and CaCl2 but not KCl given intrapertoneally decreased the antinociceptive activity of morphine. NaCl also antagonized the effect of morphine on the stereo-specific binding of opiates. This high dose of NaCl doubled the level of sodium in the brain but did not alter the specific gravity of brain tissue. These effects of NaCl confirm the antagonistic effects of NaCl that have been reported. 相似文献
7.
Bradford O. Fanger Dace Viceps-Madore John A. Cidlowski 《Archives of biochemistry and biophysics》1984,235(1):141-149
It is reported that receptors for epidermal growth factor (EGF) in HeLa S3 cells exist in two forms, which differ in both affinity and capacity. Both the number of receptors and their distribution into low- and high-affinity forms are modulated by glucocorticoids. Scatchard analysis of saturation binding assays performed at 0 °C indicates that there is a low-affinity class of receptors (), which contains approximately 6 × 104 binding sites per cell, and a second, high-affinity class of receptors () containing approximately 5 × 103 binding sites per cell. Exposure of HeLa S3 cells to 10?7m dexamethasone for 24 h increased EGF binding to whole cells by increasing the numbers of low- and high-affinity receptors by 20 and 114%, respectively. The increase in EGF binding depends upon the dose of dexamethasone, being raised from 10?11 to 10?6m. EGF binding is half-maximal near 2–4 × 10?9m, a concentration equal to the Kd of dexamethasone for the glucocorticoid receptor in these cells. The increase in EGF binding is specific for glucocorticoids, occurring when the HeLa S3 cells are exposed to 10?7m cortisol or dexamethasone for 24 h, but not when the cells are similarly treated with testosterone, 5α-dihydroxytestosterone, 17β-estradiol, or progesterone. The effect on EGF binding appears to be biphasic; the initial rapid increase occurs between 8 and 12 h, is blocked by both 10?6m cyclohexamide and 0.1 μg/ml actinomycin D, and is followed by a more gradual increase thereafter. These data indicate that glucocorticoids are able to regulate both the number of EGF receptors and their distribution into high- and low-affinity components. Press, Inc. 相似文献
8.
Using Electron Paramagnetic Resonance Spectroscopy, Al3+ was shown to produce a dramatic decrease of membrane lipid fluidity on the microorganism at a pH > 2. The ability of Al3+ to alter lipid fluidity was enhanced with increasing pH (from 3 to 5). At pH 4, 10?2 M Al3+ increased the lower lipid phase transition by 39°C, and a detectable change was observed with AlCl3 concentrations as low as 10?5 M. The ability of Al3+ to increase the lower lipid phase transition temperature of is the largest of any cation/lipid interaction yet reported. 相似文献
9.
When a single dose of urethan was injected into the peritoneal cavity of rats immediately after partial hepatectomy, DNA synthesis was delayed by 12 h. The induction of ornithine decarboxylase which was induced biphasically following partial hepatectomy was also reduced and delayed by 14–15 h by the administration of urethan. S-Adenosylmethionine decarboxylase activity in urethan-treated rat liver at 20 h and 29 h after operation was significantly lower than that of untreated animals. This enzyme activity was shown to increase thereafter, reaching a higher level than in untreated rats at 37–42 h. Hepatic spermidine content changed biphasically in a manner similar to DNA synthesis. These results suggest that the activities of ornithine decarboxylase and S-adenosylmethionine decarboxylase may correlate with DNA synthesis and that an increase of spermidine concentration is necessary to DNA synthesis. 相似文献
10.
The generation of memory B-cell subpopulations capable of proliferation and expansion of the pool: effect of time and antigen 总被引:1,自引:0,他引:1
The ability of antigen to induce proliferation of memory B lymphocytes, thus perpetuating and expanding the memory cell pool, has been examined using an antibody-forming cell (AFC) assay. This method provided confirmation of previous studies in which serum antibody titer was used as a relative measure of pool size and demonstrated directly that the number of antibody-forming cells is increased. Memory cell subpopulations were prepared by lg velocity sedimentation from recently immunized donors (2 weeks) and tested for their ability to proliferate, thus expanding the memory cell pool. Both large and small immature DNP-specific memory cells displayed antigen-dependent and antigen-independent proliferation while mature cells (8 weeks postpriming) were capable only of antigen-dependent proliferation. Chicken γ-globulin (CGG) specific memory cells were also evaluated in this system and were found to differ from DNP-specific cells in several ways. (A) DNP-specific AFC were found to be concentrated in the spleen while CGG-specific AFC were found predominantly in the bone marrow early after transfer and in the spleen upon delayed challenge. (B) The rate of maturation of CGG-specific memory cells capable of antigen-driven proliferation and pool expansion was delayed in comparison to DNP-specific memory cells. The relationship of these functionally defined subsets to previously described memory cell subpopulations is discussed. 相似文献
11.
The maturation of helper T lymphocytes during an immune response was studied with respect to sequential changes in the functional specificity and affinity toward certain antigens. Protein-carrier (BαA)-reactive helper T cells obtained after a relatively long priming period were effectively stimulated by relatively lower doses of antigen than shortly primed helper T lymphocytes. When hapten (PAB)-reactive helper T lymphocytes were utilized as a model of helper T cells, reactivity also increased progressively to smaller concentrations of PAB-conjugates at successive intervals after primary immunization. Concomitantly, the cross-reactivity of PAB-reactive helper T cells to structurally related MAB- or OAB-determinants also decreased. Moreover, the PAB-reactive helper T cells of the relatively longer priming period were very susceptible to tolerance induction upon treatment with PAB-d-GL, whereas the reactivity of those helper T cells of the relatively shorter priming period was not abolished by this treatment. These results clearly indicate that there are qualitative changes in the helper T lymphocyte population during an immune response, and that this represents the sequential development or selection of helper T lymphocytes of higher specificity and apparent affinity to a corresponding antigenic determinant. 相似文献
12.
A new method for the simple analysis of methylated amino acids based on autoradiography is introduced. With this technique a survey of protein methylation in a prokaryote, Escherichia coli, and a eukaryote, fibroblasts in culture, was carried out in an attempt to identify, quantitate, and determine the subcellular localization of all the methylated amino acids found in the proteins of these organisms.In mammalian cells using an established mouse fibroblast line (3T3), we have found that nuclei-free and mitochondria-free cytoplasm contain readily detectable amounts of four identifiable methylated amino acids: N?,N?-dimethyllysine, N?,N?,N?-trimethyllysine, NG,NG-dimethylarginine (or NG-methylarginine), and NG,N′G-dimethylarginine. The crude nuclear pellet also contains these methylated amino acids, but in addition contains N?-methyllysine and a new as yet unidentified methylated compound. Histones purified from these nuclei contain essentially the same array of methylated compounds.The ribosomal subunits of the mammalian cells contained only small amounts of the methylated amino acids; the 40S subunit contained a substantial amount of just one, NG,NG-dimethylarginine (or NG-methylarginine), and smaller amounts of NG,N′G-dimethylarginine, and an as yet unidentified methylated compound. The 60S subunit contained even smaller amounts of methylated amino acids, 50% of which was N?,N?,N?-trimethyllysine and smaller amounts of N?-methyllysine, N?,N?-dimethyllysine, and NG,NG-dimethylarginine. These subunits also contained an as yet unidentified methylated compoundThese results were in marked contrast to those that we obtained with the prokaryote, Escherichia coli. Only the proteins of the 50S ribosomal subunit of the bacteria contained methylated amino acids. Of those present 50% was N?,N?,N?-trimethyllysine, with the remainder distributed about equally between N?-methyllysine and three unknowns, one of which is apparently the same as that found in the 60S subunit of the mouse fibroblasts. All of the N?-methyllysine was apparently in the small acidic proteins, L7 and L12. 相似文献
13.
Using a ligation method, rat rectal epithelium was exposed to 2% sodium salicylate, and light and electron microscopic methods were used to assay for: 1) permeability of the epithelium to a marker dye, trypan blue, and 2) damage expressed in terms of disruption of the epithelial surface. Rectal mucosa was exposed to salicylate at pH 4.8, 7.0, and 9.0, and the effects of pretreatment with phlorizin were also studied. Results indicated that 2% sodium salicylate does very little damage to rectal epithelial cells at pH 7.0 while enhancing their permiability to trypan blue, an effect that is reversed upon washing out the sodium salicylate. The major cellular change induced by salicylate was a reduction in the length or distribution of glycocalyx filaments on microvilli of epithelial cells. It was also noted that pretreatment with phlorizin counteracted some of the effects of salicylate treatment. 相似文献
14.
This study was carried out to evaluate the behavioral implications of previously reported declines in striatal dopamine receptors sensitive to [3H]-neuroleptic specific binding. Rotational behavior was examined following right intrastriatal dopamine (DA) injections in nialamide pretreated rats that had been previously unilaterally lesioned in the left substantia nigra with 6-hydroxydopamine. Results showed that following DA injections old rats exhibited significant deficits in rotational behavioral response strength when compared to young rats. Results are discussed in terms of relating behavioral alterations in stereotypic behavior that occur with senescence to changes in striatal D2 receptors. 相似文献
15.
Rats were trained in a two-choice discrete trial avoidance paradigm to discriminate between saline and 3.0 mg/kg of morphine administered S.C. The microinjection of 0.3–3.0 μg of morphine into the lateral ventricle produced discriminative effects equivalent to those of the systemic training dose as measured by responding on the morphine-appropriate choice lever. Discriminative effects equivalent to those of the morphine training dose were not consistently produced by administration of morphine into the periaqueductal gray, lateral septum or dorsomedial thalamus in doses as high as 10 μg. However, the discriminative effects of systematically administered morphine were blocked by 10–30 μg of naloxone administered intracerebrally at all of the brain sites tested. Thus, the primary site at which morphine acts to produce discriminative effects in the rat is central, although the specific brain areas mediating these effects remain unidentified. The actions of naloxone could be the result of diffusion of the drug into the ventricular system or into the systemic circulation. 相似文献
16.
D F Callen C R Wolf R M Philpot 《Biochemical and biophysical research communications》1978,83(1):14-20
Cells of , harvested from log phase cultures, contain cytochrome P-450 and are capable of activating promutagens to products that are genetically active in the same cell. The effect of cumene hydroperoxide, a compound known to support cytochrome P-450-mediated reactions, on the activation of a variety of the promutagens was investigated. In all cases the genetic activity of the promutagens was increased. With dimethyl-nitrosamine as the promutagen, the increased rate of gene conversion was linear for at least 1 hr. Yeast cytochrome P-450 was stable in intact cells in the presence of cumene hydroperoxide. However, in microsomal preparations the cytochrome was rapidly destroyed. When cumene hydroperoxide was added to a suspension of intact yeast cells, a spectrum with a Soret maximum at 455 nm — indicative of an interaction with cytochrome P-450 — was observed. 相似文献
17.
Manabu Murakami Yasutoshi Muto Hisataka Moriwaki Toshiharu Ohgo 《Biochemical and biophysical research communications》1981,103(2):706-712
The effect of the acyclic polyisoprenoid (C20); geranylgeranyl-acetone (GGA) and its derivatives on mannolipid formation from GDP-mannose in rat liver microsomes was studied. Remarkable increases in mannolipid biosynthesis (Rf 0.24 and/or Rf 0.50) were observed by additions of GGA, its hydroxylated compound (GGA-OH) and phosphorylated material (GGA-OP). These results strongly suggest that GGA-OP is involved in mannolipid formation (Rf 0.24) as an acceptor, in analogy to retinylphosphate. On the other hand, the mechanism for increased formation of an endogenous mannolipid (Rf 0.50) by GGA and GGA-OH is attributable to the enhancement of mannosyltransferase activity. 相似文献
18.
Cytochrome P-450 revealed: the effect of the respiratory cytochromes on the spectrum of bacterial cytochrome P-450 总被引:1,自引:0,他引:1
P M Stevenson R T Ruettinger A J Fulco 《Biochemical and biophysical research communications》1983,112(3):927-934
Soluble extracts of Bacillus megaterium ATCC 14581 prepared by centrifuging a sonicated cell suspension at 40,000 xg for 30 min apparently contained no cytochrome P-450 unless the culture had been grown in the presence of an inducer: a reduced+CO minus reduced spectrum was used to measure cytochrome P-450 concentration. When the 40,000 xg supernatants from the uninduced cultures were recentrifuged at 105,000 xg the respiratory cytochromes, including one like cytochrome a1, were sedimented, and cytochrome P-450 was observed to be 100 nM or 30 +/- 9 p mol cytochrome P-450/mg protein (n=9). Measurements of cytochrome P-450 in cultures induced with phenobarbital were always higher after ultracentrifugation. There was soluble cytochrome o in all extracts. When cytochrome a1 was present a deep trough at 441 nm developed in the reduced +CO minus reduced difference spectrum of the 40,000 xg supernatant of both the uninduced and the induced cultures. The 40,000 xg supernatant obtained after lysing protoplasts of B. megaterium did not contain cytochrome a1 and always gave a good measure of cytochrome P-450. 相似文献
19.
L.E. Roel P. Levine D. Rubin D. Markovitz H.N. Munro R.J. Wurtman 《Life sciences》1978,22(21):1887-1891
A single dose of L-dihydroxyphenylalanine (L-DOPA, 500 mg/kg, i.p.) that caused massive disaggregation of brain polysomes also suppressed the incorporation of [3H] lysine into trichloracetic acid (TCA)-precipitable proteins of cortex, cerebellum, hypothalamus, brainstem and striatum. The magnitude of this inhibition of [3H] protein synthesis was similar in all brain regions studied, and was not related to changes in the specific activity of the precursor amino acid. 相似文献
20.
Protochlorophyllide-binding proteins were investigated and possible changes in the pigment-protein association during light-induced chlorophyll synthesis were analyzed. Three major results were obtained. (1) Four protochlorophyllide-binding polypeptides were separated electrophoretically on polyacrylamide gels and visualized by their fluorescence. The number and size of these protochlorophyllide-binding proteins isolated from darkgrown and illuminated plants were not affected by light. (2) The association of pigment with these proteins was studied using exogenous [3H]protochlorophyllide as substrate in an NADPH-dependent in vitro chlorophyll synthesis assay. It was found that a constant exchange of protein-bound and free pigment occurs and that freshly synthesized chlorophyllide does not accumulate on any of the four pigment-binding proteins in vitro. (3) NADPH does not affect the amount of pigment bound to protein in vitro, even during chlorophyll synthesis which occurred only in the presence of NADPH. 相似文献