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Biomedical subjects

G Koch

Publications and source records attributed to G Koch.

At least 379 records · Page 21Linked to original sources
PubMed1980

Synchronization of HeLa cell cultures by inhibition of DNA polymerase alpha with aphidicolin.

Both the inhibitory effect of aphidicolin on the replicative alpha-polymerase and the reversibility of its action in vivo (Pedrali-Noy & Spadari, 1979, Biochem. Biophys. Res. Commun. 88, 1194-2002) allow the synchronization of cells in culture. Aphidicolin prevents G1 cells from entering the DNA synthetic period, blocks cells in "S" phase, allows G2, M and G1 cells to continue the cell cycle and to accumulate at the G1/S border. Aphidicolin is a more useful reagent than hydroxyurea and thymidine because it does not affect cell viability or "S" phase duration and does not interfere with the synthesis of dNTPs or DNA polymerases. In fact cells exposed to the drug continue to synthesize all three DNA polymerases alpha, beta and gamma as well as all dNTPs which, when the block is removed, are present at levels optimal for DNA initiation and replication. The technique is simple and can be applied to cells growing in suspension or monolayers and allows one to harvest large quantities of synchronized cells.

Aphidicolin↗
PubMed1980

Somatic cell genetics of adenosine deaminase expression and severe combined immunodeficiency disease in humans.

The somatic cell hybrid method has been used to study the number and different types of human genes involved in the expression of adenosine deaminase (ADA; adenosine aminohydrolase, EC 3.5.4.4) in normal cells and cells from a patient with ADA-deficient severe combined immunodeficiency disease (SCID). Genetic and biochemical characterization of ADA in SCID and the ADA tissue-specific isozymes in normal human cells indicates that additional genes, besides the ADA structural gene on chromosome 20, are involved in ADA expression. Human chromosome 6 encodes a gene, ADCP-1, whose presence is necessary for the expression of an ADA-complexing protein in human-mouse somatic cell hybrids [Koch, G. & Shows, T. B. (1978) Proc. Natl. Acad. Sci. USA 75, 3876-3880]. We report the identification of a second gene, ADCP-2, on human chromosome 2, that is also involved in the expression of the ADA-complexing protein. The data indicate that these two ADCP genes must be present in the same cell for that cell to express the complexing protein. Human-mouse somatic cell hybrids, in which the human parental cells were fibroblastss from an individual with ADA-deficient SCID, also required human chromosomes 2 and 6 to express the ADA-complexing protein, indicating that neither ADCP-1 nor ADCP-2 is involved in the ADA deficiency in SCID. The SCID-mouse hybrid cells expressed no human ADA even when human chromosome 20 had been retained. The deficiency of human ADA in these hybrids maps to human chromosome 20, and therefore is not due to the repression or inhibiton of ADA or its product by unlinked genes or gene products. We propose that the expression of the polymeric ADA tissue isozymes in human cells requires at least three genes: ADA on chromosome 20, ADCP-1 on chromosome 6, and ADCP-2 on chromosome 2. A genetic scheme is presented and the different genes involved in ADA expression and their possible functions are discussed.

Adenosine Deaminase↗
PubMed1980

Amplification of translational control by membrane-mediated events: a pleiotropic effect on cellular and viral gene expression.

This review deals with the events which are triggered in tissue culture cells upon exposure to medium hyperosmolarity, to virus infection and to inducers of terminal differentiation. Increased medium osmolarity mimics, in several ways, events which follow infection of cells by cytopathogenic viruses. These are: inhibition of uptake of amino acids, glucose and uridine, the release or activation of a low molecular weight substance which mediates an immediate and specific inhibition of polypeptide chain initiation, and alteration in the phosphorylation state of ribosomal proteins. All these effects appear to be related to or be a consequence of membrane alterations. Similar alterations in transport and protein synthesis are initiated in Friend erythroleukemic cells upon induction of terminal differentiation.

Amino Acids↗
PubMed1980

[Lung function, gas exchange and regulation of ventilation in patients with portocaval encephalopathy (author's transl)].

In 17 patients, breathing room air and pure oxygen, with histologically proven cirrhosis of the liver and portocaval encephalopathy grade I, static and dynamic lung volumes, closing capacity and arterial blood gases were determined. Furthermore, CO2, response curves were provided and mouth occlusion pressure measurements were carried out. The residual volume was found to be increased (130 +/- 8% of predicted) which resulted in decreased vital capacity (79 +/- 2% of predicted) with total lung capacity being normal (94 +/- 2% of predicted). Closing capacity was increased to 134 +/- 5% of the predicted value. Gas exchange for oxygen was impaired (AaDO2 = 262 +/- 30% of predicted). Arterial PO2, however, was within normal range PaO2 = 84 +/- 3.6 mm Hg) due to hyperventilation (PaCO2 = 28.1 +/- 0.8 mm Hg). Hypoxic ventilatory stimulation could be excluded because inspiration of pure oxygen caused no change of PaCO2 (PaCO2 = 27.3 + 0.7 mm Hg and PaO2 = 465 + 16.9 mm Hg with FIO2 = 1.0). The slope of the CO2 response curves was normal, the mouth occlusion pressures, however, were higher than the predicted value: up to PaCO2 of 55 mm Hg. The slope of these curves being smaller than predicted. The results show that in patients with portocaval encephalopathy the lung function is disturbed due to premature airway closure with consequently decreased regional ventilation: perfusion ratios and that regulation of ventilation is impaired by a loss of sensitivity for CO2 with high basal output of the respiratory centers not related to CO2.

Blood Gas Analysis↗
PubMed1980

Radioenzymatic determination of epinephrine, norepinephrine and dopamine in 0.1 ml plasma samples: plasma catecholamine response to submaximal and near maximal exercise.

A sensitive enzymatic isotope derivative method for simultaneous determination of epinephrine, norepinephrine, and dopamine in 0.1 ml plasma samples is described. The assay consists basically of 1. conversion of epinephrine, norepinephrine, and dopamine into their respective methyl-derivates in the presence of catechol-O-methyltransferase and S-adenosylmethionine-[3H]methyl, 2. extraction of the methylated 3H labelled amines with diethyl ether, 3. separation by thin-layer chromatography, 4. measurement in a beta radiation scintillation counter. The effect of standing upright and of submaximal and near-maximal steady state exercise on plasma epinephrine, norepinephrine, dopamine and plasma renin was studied in 16 young adults aged 22 to 34 years and 9 physically well trained boys 16-17 years old. Standing upright for 2 min did not results in significant changes in either epinephrine, norepinephrine, dopamine or plasma renin activity compared with supine (basal) values. During exercise, epinephrine, norepinephrine, dopamine and plasma renin activity increased exponentially with the work load, peak values being attained at the highest load or immediately after cessation of exercise. The respective maximal values for plasma renin activity and epinephrine and norepinephrine levels were approximately 3, 6 and 10 fold higher than basal values in the adults, and rose as high as 4, 10 and 20 fold in the boys. Peak dopamine values were only 2-3 times higher than the basal values in both adults and boys. It is concluded that the method described provides a suitable tool for a quantitative assessment of adreno-sympathetic tone during physiological and pathophysiological conditions.

Adolescent↗
PubMed1980

Effect of mouthrinsing with a sodium fluoride solution in children with different caries experience.

The present study was designed to investigate the pattern of the caries inhibiting effect of school fluoride mouthrinse programs in children of different baseline caries experience. In Phase I, 170 children 10 and 11 years of age were randomly assigned to a test group who rinsed with a 0.5% NaF solution once every 2 weeks for 3 years or to a control group who rinsed with distilled water. In Phase II, the dental records of 345 children were used. Here, the test group had rinsed weekly with a 0.2% NaF solution, while the control group consisted of children 3 years older who were not included in the program during the ages under study (10-11 to 13-14). The statistical analysis of the data was performed as linear regression of caries increments on baseline scores. The analyses included all tooth surfaces, as well as separate studies of proximal and free smooth surfaces, respectively. It was shown that caries increments increased as the baseline scores increased. The slope of the regression lines indicated that the fluoride mouthrinses were more effective in high caries groups than in low caries groups. The results are in agreement with earlier findings concerning the interaction between factors in the caries process.

Cariostatic Agents↗
PubMed1980

[Diagnostic value of selective parathormone determination in primary hyperparathyroidism].

The preoperative localisation of parathyroid adenomas is difficult even for an experienced surgeon. The rate of unsuccessful exploration of the neck lies between 2 and 18%. This is mainly due to to anomalies and extremely small adenomas. In vivo staining with toulidine blue, isotopic labelled selenmethionin or angiographic localisation are uncertain procedures. More accurate results can be achieved through fractionized measurement of parathyroid hormone with selective venous catheterization. This method was applied in 47 out of 71 patients with a correct localisation being achieved in 77%. In connection with subtle laboratory diagnosis and repeated assessment of serum calcium and phosphorus, this procedure is the method of choice. In cases with normocalcaemia surgical indication should be considered with due reservation despite positive localisation.

Adenoma↗
PubMed1979

Alterations in translational control mechanisms in Friend erythroleukemic cells during DMSO induced differentiation.

Induction of erythroid differentiation in Friend erythroleukemia cells causes a reduction in the rate of protein synthesis and a prolonged growth cycle of the cells. A study of the relative translational efficiencies (RTE) of viral mRNAs and selected host cell mRNAs revealed unexpected low RTEs of the mRNA coding for the gp70 protein and RTE of the mRNA coding for the p30 protein. The RTEs of viral and of some host mRNAs show significant changes during differentiation. The rate of synthesis of corresponding proteins are altered non-coordinately, indicating transcriptional and/or posttranscriptional regulation of mRNA, as well as amplified regulation at the level of translation of mRNA.

Cell Differentiation↗