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K S Koch

Publications and source records attributed to K S Koch.

18 recordsLinked to original sources
PubMed1992

Differential expression of the transfected liver-specific alpha 1-inhibitor III gene in normal hepatocytes and hepatoma cells in culture.

Normal and malignant hepatocytes were transfected during log phase culture with a nested series of DNA plasmids containing 5'-flanking regions of the rat liver-specific acute phase plasma proteinase alpha 1-inhibitor III (alpha 1 I3) gene. Under these conditions, luciferase reporter gene expression in primary adult rat and mouse hepatocytes was 10-fold higher than luciferase expression in hepatoma lines (human HepG2 and Hep3B; rat FAZA). Optimal expression in primary rat hepatocytes required regions stretching 2214 bp 5'-upstream of the transcription start site. Shorter 5'-flanking sequences were optimal for expression in hepatoma cells (-1025 and -186 bp for rat and human lines, respectively) and primary mouse hepatocytes (-225 bp). In contrast, regions from -186 to -225 bp drove luciferase expression in primary rat hepatocytes, but only 20-75% of optimal levels. Qualitative differences were unaccounted for by non-equivalent uptake of plasmid DNA, suggesting that tissue specific gene expression is regulated differently in normal and malignant cells, and with apparent species specificity.

Acute-Phase Proteins↗
PubMed1992

Induction of cyclin mRNA and cyclin-associated histone H1 kinase during liver regeneration.

Cyclins and cyclin-associated cdc kinases are key regulators of oocyte maturation (Maller, J. L. (1990) in The Biology and Medicine of Signal Transduction (Nishizuka, Y., Endo, M., and Tanaka, C., eds) pp. 323-328, Raven Press, New York), yeast cell cycles (Nurse, P. (1990) Nature 344, 503-508), DNA replication in cell-free systems (D'Urso, F., Marraccino, R. L., Marshak, R. R., and Roberts, J. M. (1990) Science 250, 786-791), and amphibian cell proliferative transitions (Hunt, T. (1991) Nature 350, 462-463). The extent to which these regulatory molecules participate in the growth control of differentiated epithelial cells like hepatocytes is unknown. Therefore, we investigated the expression of "G1" (E, C, and D) and "G2/M" (A, B1, and B2) cyclin mRNAs, the relative levels of cyclin A- and B1-associated histone H1-kinase activity, and the appearance of cyclin-associated kinases (p32/p33cdk2 and p33/p34cdc2) in regenerating rat liver and in control tissues from sham hepatectomized rats. To do this, we exploited a battery of human cyclin cDNAs and cyclin antisera that recognize rat molecules. The results suggest an apparent sequence of regeneration-specific changes: 1) elevated and induced expression of cyclins E (2.1 kilobases (kb)) and C (4 kb), and D mRNAs (4 kb), within 12 h, respectively; 2) induction of cyclins A (3.4 and 1.8 kb), B1 (2.5 and 1.8 kb), and B2 (1.9 kb) mRNAs at 24 h; 3) induction of cyclin A- and B1-associated nuclear histone H1 kinase at 24 h; and 4) enhanced levels of PSTAIRE-containing proteins of Mr approximately 32-33 and 33-34 kDa in nuclear extracts from 24-h regenerating liver that co-immunoprecipitate with cyclin A and B1 antisera, respectively. These observations provide an intellectual framework that unifies the biology of hepatocyte mitogenesis, proto-oncogene expression, and the machinery of the cell cycle.

Animals↗
PubMed1991

Retroviral vector infection and transplantation in rats of primary fetal rat hepatocytes.

Retroviral vectors were used to transduce recombinant DNA encoding firefly luciferase, Escherichia coli beta-galactosidase or human factor IX into fetal rat hepatocytes in primary culture. Hepatocytes were transduced optimally during a restricted time interval, 2-4 days post-plating. Although efficient and stable expression of reporter gene products was observed in vitro, it was affected differentially by culture conditions (plating density, media constituents) and chemical modulators of hepatocyte growth and differentiation (gelatin, hydrocortisone, isobutylmethylxanthine). Cultured cells, mock-infected or infected with a luciferase-expressing vector, were harvested non-enzymatically and injected subcutaneously into the dorsal neck fascia of neonatal syngeneic rats. Tissue isolated from injection sites one week later contained hepatocyte foci. In animals transplanted with infected cells, the preliminary results suggest that luciferase activity was present at these sites in proportion to the numbers of injected cells. These findings and previous observations made with hepatocytes from neonatal and adult primary cultures, indicate that from day 19 in utero through maturity the transient temporal 'period of susceptibility' to infection in vitro is independent of the developmental state of starting tissue. Transplantability of cultured fetal hepatocytes infected with retroviral vectors and stably expressing reporter gene products suggests that such cells might provide promising models for liver gene therapy.

Animals↗
PubMed1989

Transforming growth factor-alpha stimulates proto-oncogene c-jun expression and a mitogenic program in primary cultures of adult rat hepatocytes.

Human transforming growth factor-alpha (TGF-alpha, MW 5547) initiates a mitogenic program in "quiescent" 11-to 13-day-old primary cultures of adult rat hepatocytes. Using validated growth reinitiation assays and chemically defined conditions (Koch and Leffert, 1979a) that simulate proto-oncogene expression in regenerating liver (Kruijer et al., 1986), we find that 5.4 nM TGF-alpha stimulates: (i) increases in rates of amiloride-sensitive 22Na+ uptake; (ii) a transient induction in steady-state mRNA levels of proto-oncogene c-jun; (iii) specific increases in hepatocyte nuclear [3H]dT labeling indices, augmented synergistically by insulin and glucagon; and (iv) increases in rates of S-phase entry. Comparative studies indicate that TGF-alpha is a more effective hepatocyte growth promoter than mouse epidermal growth factor. These observations, and published reports linking normal and cancerous liver as biosynthetic sources of TGF-alpha, suggest an autocrine or paracrine role for TGF-alpha in the control of hepatic growth, regeneration, and gene expression.

Animals↗
PubMed1979

Increased sodium ion influx is necessary to initiate rat hepatocyte proliferation.

Serum-free media containing 10-50 ng insulin, glucagon and epidermal growth factor (EGF) ml-1 stimulate adult rat hepatocyte proliferation in 10-15 day old primary liver cell cultures. The kinetics of this response simulate hepatocellular transitions that accompnay liver regeneration after 67% hepatectomy. Amiloride, a Na+ influx inhibitor, reversibly blocks these transitions in vitro (ID50 approximately 0.02 mM) and in vivo (ID50 approximately 25 mg kg-1). Inhibition is observed with other cation flux modulators, including ouabain (ID50 approximately 0.2 mM), 0.2 microM monensin and 0.2 microM nigericin, but not with 0.3 mM furosemide or tetrodotoxin. The prereplicative interval in culture (0-12 hr) is characterized by preferential cellular responsiveness to EGF (0-3 hr) followed by insulin plus glucagon (3-12 hr). Parallel culture and animal studies show that the amiloride-sensitive and prereplicative intervals coincide. In culture, a "burst" of 22Na+ influx, stimulated by peptide-supplemented media within 1 min but decreased later at 12 hr, is retarded by amiloride. This drug also blocks delayed prereplicative events involving increased amino acid "A" transport system function at 4-8 hr, and 3H-uridine and 3H-leucine incorporation into RNA and protein, respectively, at 8-12 hr. These findings suggest that at least two time-ordered processes are necessary to initiate hepatic growth fully: first, activation of Na+ flux systems by peptides similar or identical to EGF; and second, potentiation of these and subsequent cellular events by the combined action of insulin plus glucagon. [Amiloride: N-amidino-3,5-diamino-6-chloropyrazinecarboxamide; furosemide: 4-chloro-N-furfuryl-5-sulfamoylanthranilic acid; AIB: alpha-aminoisobutyric acid; ID50: administered dose giving 50% inhibition of a maximal response; dFBS: dialyzed fetal bovine serum; L.I.: 3H-dT nuclear labeling index.]

Amiloride↗
PubMed1979

Liver cells.

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Animals↗
PubMed1978

Hepatocyte growth control: in vitro approach to problems of liver regeneration and function.

Primary monolayer fetal and adult rat hepatocyte culture systems, which are being used to help analyze in vivo mechanisms controlling liver regeneration, proliferation, and differentiation are described. With results from animal studies of normal or genetically altered rats subjected to partial hepatectomy, to chemical infusions, or to specific dietary deficiency regimens, an apparently complex growth regulatory pattern has emerged. The data suggest a working hypothesis postulating interactions among hormone, nutritional, lipoprotein, and novel nucleotide factors at multiple regulatory sites. These findings may provide some conceptual and experimental basis for future research regarding the development of hepatic cancer, as it may arise spontaneously or from exposure to environmental carcinogens.

Animals↗
PubMed1977

Proliferation of hepatocytes.

Hepatocyte proliferation may be controlled by reversible patterns of endocrine changes, monitored by the liver, involving known hormones and their receptors. A two-programme model of related interactions among nutrients, specific lipoproteins, and highly phosphorylated nucleotides is postulated. This hypothesis stems from in vitro studies of rat hepatocyte proliferation under chemically defined conditions and from in vivo studies using partially hepatectomized, hormone-infused, developing and lipotrope-deficient rats. Certain findings are discussed with regard to receptor systems which show negatively cooperative properties; to problems of proliferative specificity; and to novel approaches for defined studies of chemical hepatocarcinogenesis.

2-Acetylaminofluorene↗