The absence of peroxisomes in patients with the cerebro-hepato-renal (Zellweger) syndrome is accompanied by a number of biochemical abnormalities, including an accumulation of very long-chain fatty acids. We show by immunoblotting that there is a marked deficiency in livers from patients with the Zellweger syndrome of the peroxisomal beta-oxidation enzyme proteins acyl-CoA oxidase, the bifunctional protein with enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase activities and 3-oxoacyl-CoA thiolase. Using anti-(acyl-CoA oxidase), increased amounts of cross-reactive material of low Mr were seen in the patients. With anti-(oxoacyl-CoA thiolase), high Mr cross-reactive material, presumably representing precursor forms of 3-oxoacyl-CoA thiolase, was detected in the patients. Catalase protein was not deficient, in accordance with the finding that catalase activity is not diminished in the patients. Thus in contrast to the situation with catalase functional peroxisomes are required for the stability and normal activity of peroxisomal beta-oxidation enzymes. 相似文献
Effects of glucagon and forskolin on the phosphorylation and changes of activity of carnitine palmitoyltransferase (CPT) have been studied in isolated rat hepatocytes using anti-CPT immunoglobulin. When the activity was determined in lysed hepatocytes after glucagon or forskolin treatment, it was found to be stimulated 30-80% mainly through increased affinity for palmitoyl-CoA. By SDS electrophoresis of the immunoprecipitates, CPT subunit (Mr 69000) was noted to be phosphorylated 4-5-fold with glucagon (1.2 X 10(-7) M) and forskolin (0.1 mM) over control. These results indicate that hepatic ketogenesis is regulated with glucagon by phosphorylation of CPT through cAMP-dependent protein kinase. 相似文献
Stimulated T cell-derived inhibitory factor for cellular DNA synthesis (STIF), a lymphokine produced from concanavalin A (Con A)-stimulated rat suppressor T cells, was examined for its inhibitory effect on various cultured cells and on in vitro immune reactions. STIF could inhibit the DNA synthesis of a variety of normal and neoplastic cells from rats, mice, and humans in a dose-dependent fashion. Kinetics studies revealed that STIF selectively inhibited cellular DNA synthesis after incubation for 12 hr, but after 36 hr, it also inhibited RNA and protein syntheses. The inhibited cellular DNA synthesis by 12-hr incubation with STIF was recovered after culturing the cells in STIF-free medium. The inhibitory effect of STIF on the DNA synthesis was not blocked by addition of a sugar (alpha-methyl-D-mannoside, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, L-fucose, or L-rhamnose) in culture, as determined by using rat bone marrow cells. STIF inhibited proliferative responses of rat lymphocytes to T cell mitogens, Con A and phytohemagglutinin, and a B cell mitogen, lipopolysaccharide, as well as IL 2-dependent growth of cloned T572 cells. It could also inhibit both blastogenesis and cytotoxic T cell generation in allogeneic mixed lymphocyte reaction. The release of IL 2 from Con A-stimulated T cells was also inhibited by the added STIF in culture, as demonstrated from the finding that IL 2 activity was not detected in the supernatants even after an anion-exchange column chromatography. These results indicate that STIF could inhibit cellular DNA synthesis in a species-unrestricted manner and thus inhibits the proliferation of various normal and neoplastic cells, and that it could also inhibit lectin- or IL 2-dependent T cell proliferation as well as IL 2 production from T cells in in vitro immune reactions. 相似文献
The brain CRF concentration of spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) was examined by rat CRF radioimmunoassay. Anti-CRF serum was developed by immunizing rabbits with synthetic rat CRF. Synthetic rat CRF was also used as tracer and standard. The displacement of 125I-rat CRF by serially diluted extracts of male Wistar rats hypothalamus, thalamus, midbrain, pons, medulla oblongata, cerebral cortex, cerebellum and neurointermediate lobe was parallel to the displacement of synthetic rat CRF. In both WKY and SHR the highest levels of CRF immunoreactivity were shown by the hypothalamus and neuro-intermediate lobe, and considerable CRF immunoreactivity was also detected in other brain regions. The CRF immunoreactivity in the hypothalamus, neurointermediate lobe, midbrain, medulla oblongata and cerebral cortex was significantly reduced in SHR and it may suggest that CRF abnormality may be implicated in the reported abnormalities in the pituitary-adrenal axis, autonomic response and behavior of SHR. 相似文献
The effects of SO2 on stomatal aperture of attached sunflower leaves were observed with a remote-control light microscope system that permitted continuous observation of stomatal responses over periods of several hours. The relationship between actual stomatal aperture and stomatal conductance, measured with a porometer, also was examined on leaves before and after exposure to SO2.
A distinction between uninjured and injured regions was clearly visible on leaves after exposure to 1.5 microliters per liter SO2 for less than an hour. During the exposure, the mean value of apertures for many stomata, which indicates stomatal conductance and transpiration rate, tended to decrease simultaneously in the uninjured and injured regions. However, the rate of decrease in the injured region was slower than that in the uninjured region because of a transient opening induced by water-soaking in the injured region. The transient opening was less common in stomata near veins and veinlets.
There was a good correlation between pore width and stomatal conductance measured with a porometer before exposure to SO2. This correlation continued in leaves exposed to SO2 until visible, irreversible injury occurred, but then it disappeared.
The results of these experiments indicate the necessity of continuous observation of individual stomata under the microscope to understand the effects of air pollutants such as SO2 on stomatal behavior.
Arginine-vasopressin and oxytocin in various portions of rat brain were determined by radioimmunoassays. The hormones were extracted from tissue samples into 0.1 N HCl and then purified partially with acetone-petroleum ether extraction. The non-equilibration method was used for the assays. In this method recovery rates of arginine-vasopressin and oxytocin were 73.0 +/- 4.4% and 75.0 +/- 3.8%, respectively. Sensitivities of the assays were 1 pg of arginine-vasopressin and 0.75 pg (0.3 microU) of oxytocin per assay tube. The higher concentrations of arginine-vasopressin and oxytocin were confirmed in the hypothalamo-neurohypophyseal system, where these hormones are synthesized, transported and stored. Relatively high concentrations of these hormones, especially oxytocin, were detected in spinal cord. Amygdala, hippocampus, limbic forebrain and pineal body contained a certain amount of arginine-vasopressin (2-20 pg/mg protein). Oxytocin (1-7 pg/mg protein) was also detected in amygdala, pons and medulla oblongata, pineal body and midbrain. The low concentrations of these hormones were also found in cerebral cortex and cerebellum. 相似文献
Rat hepatocytes were cultured for 72 h with or without the addition of 0.5 mM clofibric acid. The activities of individual enzymes of the peroxisomal beta-oxidation pathway (acyl-CoA oxidase, enoyl-CoA hydratase-3-hydroxyacyl-CoA dehydrogenase bifunctional protein, and 3-ketoacyl-CoA thiolase) decreased in the control culture, but markedly increased synchronously in the clofibric acid-treated culture. The levels of mRNAs coding for these enzymes and the rates of synthesis of the enzymes were also elevated in the clofibric acid-treated culture, although no proportional relationship was observed between the time-dependent changes of these parameters. The increase in mRNAs was much higher than the increase in the rate of synthesis of the enzymes. The activity of catalase, its mRNA level and the rate of its synthesis were slightly affected. The effects of clofibric acid on the peroxisomal beta-oxidation enzymes and catalase in primary cultured hepatocytes were very similar to those observed in vivo. These results, therefore, suggest that primary culture of hepatocytes should provide a useful means for investigating the mechanism of induction of peroxisomal enzymes and the mechanism of action of peroxisome proliferators. 相似文献
When pig liver phosphorylase kinase was assayed at various concentrations of Mg2+, about 2-fold stimulation was observed around 2-3 mM Mg2+ (Mg2+/ATP ratio, 20-30) compared with the activity at 0.3 mM Mg2+ (Mg2+/ATP ratio, 3). This stimulation was specific for Mg2+ among the divalent cations tested and the process was reversible. Km values for ATP and phosphorylase b were decreased 3.6- and 9.5-fold, respectively, at 3 mM Mg2+ compared with those obtained at 0.3 mM Mg2+. These results indicate that the activity of liver phosphorylase kinase is influenced by free Mg2+. 相似文献
Poly(A+) RNA was prepared from hepatic free polysomes of rats which had been fed di(2-ethylhexyl) phthalate for the induction of peroxisomal beta-oxidation enzymes. This preparation was enriched for the mRNAs of these enzymes by sucrose density gradient centrifugation, and used for the synthesis of double-stranded cDNA. Recombinant plasmids were constructed from the cDNA and pBR322 by dG X dC-tailing method and used for the transformation of an Escherichia coli strain, chi 1776. By differential colony hybridization using [32P]cDNA of partially purified liver poly(A+) RNA from induced and noninduced rats as probes, and then by hybridization-selected translation, we obtained two clones with cDNA inserts which specifically selected acyl-CoA oxidase mRNA. On Northern blotting, both cDNA inserts hybridized to 3.8-kilobase RNA which was increased about 10-fold by di(2-ethylhexyl) phthalate treatment of the rats. The cleavage maps of the cDNA inserts showed they overlap with each other. We conclude that the above two recombinant plasmid clones contain cDNA sequences for rat acyl-CoA oxidase. 相似文献
A kinetic model was devised for the hydrolysis and synthesis of maltose and isomaltose by two glucoamylases from Rhizopus niveus and Aspergillus niger, and the validity of the model was verified experimentally at 313 K and pH 5.0. For both enzymes, the formations of maltose and isomaltose from glucose were parallel reversible reactions, and glucosyl transfer between maltose and isomaltose was not observed. The enzymes catalyzed rapid hydrolysis and synthesis of maltose. Isomaltose was hydrolyzed and synthesized more slowly, but the level produced from glucose was much higher than that of maltose. These hydrolysis and condensation reactions were expressed well by the model. 相似文献