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191.
192.
Effects of fasting on hepatic catecholamine receptors 总被引:1,自引:0,他引:1
193.
James C. Fuscoe J.Patrick ONeill Richard Machanoff Abraham W. Hsie 《Mutation research》1982,96(1):15-30
We describe an assay for the quantification of reverse mutations at the hypoxanthine-guanine phosphoribosyltransferase (hgprt) locus in Chinese hamster ovary cells utilizing the selective agent L-azaserine (AS). Conditions are defined in terms of optimal AS concentration, cell density, and phenotypic expression time. After treatment, replicate cultures of 106 cells are allowed a 48-h phenotypic expression time in 100-mm plates. AS (10 μM) is then added directly to the growing culture and AS-resistant (ASr) cells form visible colonies. This assay is used to quantify ICR-191-, ICR-170-, and N-ethyl-N-nitrosourea-induced reversion of independently isolated HGPRT? clones. The ASr phenotype is characterized both physiologically and biochemically. All ASr clones isolated are stably resistant to AS and aminopterin but sensitive to 6-thioguanine. They also have re-expressed HGPRT enzyme. In addition, several revertants are shown to contain altered HGPRT. The data provide further evidence that ICR-191 and ICR-170 cause structural gene mutations in mammalian cells and also suggest that ICR-191, ICR-170, and N-ethyl-N-nitrosourea induce similar types of mutations in Chinese hamster ovary cells. 相似文献
194.
The cytotoxic and mutagenic effect of (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti BPDE) in normally excision diploid human cells treated just prior to onset of S was compared with that of cells allowed ~ 16 h for excision repair before onset of S and with that observed in excision-deficient serodema pigmentosum (SP12BE) cells. The cells were synchronized by release from density inhibition of cell replication. DNA synthesis began ~ 22 h after the cells were plated at lower density (i.e., 1.4 × 104 cells/cm2). The frequency of thioguanine-resistant mutants induced in normal cells treated just prior to onset of S was ~ 12- to 16-fold higher than that observed in cells treated in early G1 or treated in G0 (confluence) and then plated at lower density. The frequency approximated that expected for XP12BE cells from extrapolation of data obtained at lower doses. The frequency of mutants measured in normal cells treated in exponential growth was also much higher than that in the cells treated in early G1 or in G0, No such difference could be seen in XP12BE cells treated in exponential growth or in G0. In contrast to the mutagenicity data in the normal cells, there was no significant difference in the slope of the survival curve of normal cells treated at various times prior to S phase at low densities. However, normal cells treated even at the onset of S exhibited survival equal to XP12BE cells give a 4- to 5-fold lower dose. The data support the hypothesis that DNA synthesis is the cellular event which converts unexcised DNA lesions into mutations. However, they indicate that S is not the event primarily responsible for translating DNA damage into cell death. Accompanying studies on the rate of excision of anti BPDE adducts from the normal cells during the period priot to S support the conclusions. 相似文献
195.
Hideki Shinno Chiseko Noda Keiji Tanaka Akira Ichihara 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,633(3)
L-Lysine-2-oxoglutarate reductase (EC 1.5.1.8, NADP+) in the liver of adult rats increased 4–5-times when the animals were treated with alloxan. In diabetic rats injection of insulin or adrenalectomy prevented the increase in enzyme activity. The activity of the similar enzyme in kidney was not changed by these treatments. The enzyme activity in primary cultured adult rat hepatocytes was also induced by addition of dexamethasone and glucagon together, and glucagon could be replaced by dibutyryl cyclic AMP. Insulin inhibited the induction. The hormonal induction was also inhibited by actinomycin D and by cycloheximide. During development of rats, fetal liver showed very low activity, but the activity appeared on day 1 after birth and then increased rapidly, reaching the adult level by day 5. The activity of the kidney enzyme increased more slowly and reached the adult level 1 month after birth. Intra-uterine injection of glucagon caused precocious induction of the liver enzyme in fetuses. These results indicate that the activity of L-lysine-2-oxoglutarate reductase in the adult liver and in part in neonatal liver also, is controlled by both glucagon and glucocorticoid. 相似文献
196.
197.
Mechanism of activation of cyclic GMP-dependent protein kinase from rat liver by multiple modulators
Charles W. Mackenzie III Thomas E. Donnelly Jr. 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,633(3):444-456
A number of polyanionic compounds, including DNA, RNA and polyglutamate, were shown to exhibit protein kinase stimulatory modulator activity as they were required for cyclic GMP to stimulate the phosphorylation of various cationic substrates by rat liver cyclic GMP-dependent protien kinase. Anionic proteins (casein, phosvitin) were phosphorylated poorly by the enzyme and their phosphorylation was not stimulated by the stimulatory modulators. Studies of the mechanism of action suggest that the modulators interact directly with the substrates to form a complex which is a better substrate than free histone. The observed effect of modulator is complex as it depends on the ratio of modulator to histone and the resultant state of the complex formed (better or poorer substrate than free histone). The observed effect is also dependent on the properties of the histone substrate as Michaelis-Menten kinetics are not observed in the phosphorylation of arginine-rich histone in the absence or presence of cyclic GMP. 相似文献
198.
Cell junctions and intercellular communication 总被引:1,自引:0,他引:1
J. -P. Revel S. B. Yancey D. J. Meyer B. Nicholson 《In vitro cellular & developmental biology. Plant》1980,16(12):1010-1017
Summary We have compared intercellular communication in normal and regenerating rat liver. Gap junctions are greatly reduced in size
and numbers 29 to 35 hr after hepatectomy, but we still find some 90% of hepatocytes coupled by electrophysiological criteria.
The spread of dyes such as carboxyfluorescein however is very limited in the regenerating organs as compared to the situation
in the controls. We show how the apparent discrepancies between morphological and physiological data can be reconciled. We
also present a summary of preliminary findings on the biosynthesis of gap junction protein and some of the conclusions one
can draw from the sequence of 58 amino acids at the amino terminal of the protein.
Presented in the symposium on Molecular and Morphological Aspects of Cell-Cell Communication at the 31st Annual Meeting of
the Tissue Culture Association, St. Louis, Missouri, June 1–5, 1980.
The original research described was supported by Grants GM 06965 and RR 07003 from the National Institute of Health, and funds
from the North-west Area Foundation. David Meyer and Barbara Yancey were the recipients of NIH postdoctoral fellowships (NS
06240 and AM05700). This symposium was supported in part by Contract 263-MD-025754 from the National Cancer Institute and
the Fogarty International Center. 相似文献
199.
William H. J. Douglas James A. McAteer Robert T. Dell'orco David Phelps 《In vitro cellular & developmental biology. Plant》1980,16(4):306-312
Summary A one-step vital stain is described for the macroscopic visualization of histotypic cell aggregates in fetal rat lung organotypic
cultures. Organotypic cultures are incubated in 0.05-0.1% 2,3,5′-triphenyl tetrazolium chloride (TTC) in culture medium (37°C).
Living cells reduce the tetrazole to a water-insoluble red colored formazan. Cell aggregates appear as densely stained foci
against the lighter background of the Gelfoam substrate. Stained cultures may be scanned macroscopically to determine the
degree of reaggregation and assess cell viability. Identification of aggregates by TTC staining improves the efficiency of
tissue processing for electron microscopy and does not alter the ultrastructural appearance of the cultured cells.
This work was funded in part by the United Cerebral Palsy Research and Educational Foundation, Inc. and the National Heart,
Lung, and Blood Institute (Grants 1ROHL19513 and 1 R01HL21008). 相似文献
200.
Hans M.G. Princen Gerard C.M. Selten Anne-Marie E. Selten-Versteegen Gera P.B.M. Mol-Backx Willem Nieuwenhuizen Sing Hiem Yap 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,699(2):121-130
To study the effect of regenerative response of the liver following partial hepatectomy on the synthesis of major plasma proteins (secretory proteins), we have determined the sequence contents and the distribution of albumin and fibrinogen polypeptide mRNAs in rat liver at intervals after partial hepatectomy and sham operation. Using a quantitative technique for the isolation of polyribosomes, we demonstrated that the distribution of RNA between free and membrane-bound polyribosomal fraction was unchanged in these experiments. There was no shift in the polyribosomal population to favor free polyribosomes after partial hepatectomy. However, there was a dramatic increase (5–6-fold) of the fibrinogen polypeptide mRNA concentration during the first 24 h after resection. In contrast, the albumin mRNA concentration decreased (2–3-fold). There were no α-fetoprotein mRNA sequences detectable in any liver RNA fraction in these experimental animals. In sham-operated rats with intact livers, similar changes of fibrinogen polypeptide and albumin mRNA concentrations as described in regenerating liver after partial hepatectomy, were observed. These results suggest that albumin and fibrinogen synthesis after partial hepatectomy is reciprocally regulated at the mRNA level and represents a nonspecific acute phase response to surgical trauma. 相似文献