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Biomedical subjects

G Koch

Publications and source records attributed to G Koch.

At least 415 records · Page 23Linked to original sources
PubMed1978

Efficacy of oral mexiletine in the prevention of exercise-induced ventricular ectopic activity.

The anti-arrhythmic effect of oral mexiletine on exercise-induced ventricular arrhythmia was studied in a double blind trial of 10 patients suffering from ventricular ectopic beats of different origins. There was a good reproducibility of the amount of ectopic ventricular activity between consecutive exercise tests when no active drug was given. Treatment for 1 week with mexiletine 600 mg daily resulted in a statistically significant reduction in ventricular ectopic beats, particularly during and after exercise; there were virtually no side-effects. The results suggest that mexiletine has considerable potential in the treatment of ventricular arrhythmias.

Adult↗
PubMed1978

Type-C oncovirus isolate from human leukemic bone marrow: further in vitro and in vivo characterization.

Rabbit corneal cells transformed by a putative human type-C helper virus pseudotype of the mouse sarcoma virus produce large amounts of transforming and non-transforming viruses. The virions are antigenically related to the woolly monkey (simian) sarcoma-leukemia type-C oncovirus. Typical sarcoma virus lesions developed in newborn rats injected with virus-producing rabbit cells. Cells producing only the putative type-C helper viruses as a result of exposure to a high dilution of transforming virus stock induce lymphosarcomas after inoculation into newborn rats.

Animals↗
PubMed1978

Statistical analysis of measurement errors of binding data in the Farr technique.

A detailed statistical analysis of measurement errors in the Farr technique is performed, and approximated formulas for the error covariances are given. These formulas are then checked by means of experimental data. In particular, the analysis shows that the usually adopted linear extrapolation for the estimate of total antibody sites concentration may lead to relevant errors in the affinity distribution determination due to the low accuracy of data at high values of free hapten concentration. Conversely, this analysis may constitute the basis for implementing an optimal estimate procedure.

Animals↗
PubMed1978

A gene on human chromosome 6 functions in assembly of tissue-specific adenosine deaminase isozymes.

In human tissues, adenosine deaminase (ADA) (adenosine aminohydrolase; EC 3.5.4.4) activity can be separated by gel electrophoresis into several isozymes. A structural gene (ADA) on chromosome 20 codes for the "erythrocyte" isozyme, ADA-1, which is also expressed in some nonerythroid tissues. Nonerythroid cells also differentially express five ADA "tissue isozymes" of a greater molecular weight than ADA-1. Each ADA tissue isozyme has a characteristic electrophoretic mobility and tissue distribution. It has been suggested that these ADA tissue isozymes are composed of ADA-1 and other components. We report that the expression of one of these tissue isozymes, ADA-d, is dependent upon ADA on chromosome 20 and another gene on chromosome 6 which functions in the assembly of the ADA tissue isozymes. In human-mouse hybrids segregating human chromosomes, chromosome 6(+),20(+) hybrids express both ADA-1 and ADA-d; chromosome 6(-),20(+) hybrids express only ADA-1; while 6(+),20(-) hybrids have no human ADA activity. ADA-d formation also occurs in vitro by self-assembly when an extract of human erythrocytes or chromosome 6(-),20(+) hybrids is mixed with a homogenate of chromosome 6(+),20(-) hybrids. The gene on chromosome 6, designated ADCP, codes for an adenosine deaminase complexing protein. The product of ADCP presumably combines with ADA-1 to form the ADA tissue isozymes. The data are consistent with the hypothesis that the distribution of enzymatic activity between ADA-1 and the tissue isozymes depends on the expression of the gene for ADA complexing protein, while the differences in the electrophoretic mobilities of the ADA isozymes, except ADA-1, are generated, as suggested by others, by the degree of glycosylation of the complexing protein.

Adenosine Deaminase↗
PubMed1978

[The immunohistochemical demonstration of the Thiol: proteindisulfid oxidoreductase (TPO) in pancreas and isolated Langerhans'islets. A light-, fluorescent- and electron microscopic study (author's transl)].

Thiole: Protein disulfide Oxidoreductase (E. C. 1.8.4.2) is capable of catalyzing thiole-disulfid exchange reactions and might have an important function in both protein biosynthesis and degradation. By using histochemical methods we were able to demonstrate the localization of this enzyme in the Langerhans'islets and in the acinus cells of rat pancreas. The reaction of the acinus cells, however, was much weaker than that of the islets. Electron microscopic experiments revealed the enzyme to be located in the outer membrane of the nucleus, in the membranes of the endoplasmic reticulum and B-cell granules, and in the plasmalemma also. All these structures are known to be involved in the insulin biosynthesis and secretion. There is a good correlation between morphological and biochemical findings. In acinus cells there are a few reaction in the outer nucleus membrane, the membranes of the endoplasmatic reticulum, and the plasmalemm.

Animals↗
PubMed1978

[The immunhistochemical investigation of trypsin and trypsin-like-activity in the small intestine, pancreas and isolated Langerhans islets. A light-, fluorescent- and electron microscopic study (author's transl)].

By means of the indirect immunofluorescence and immunenzyme technique trypsin and trypsin-like activity in fixed cryostate sections of pancreas and gut and pellets of isolated pancreatic islets respectively were investigated using specific antiserum against trypsin. The enzyme was demonstrated in the cytoplasma of the acinus cells, the epithel cell of the intercalated ducts and the excretory (interlobular) ducts of the exocrine pancreas. By light and fluorescence microscopy we could also localize a high activity in pancreatic islets. Results taken from electron microscope show the enzyme in the region of the peripheral endoplasmatic reticulum, the surface of the mitochondria, the zymogen granules of the acinus cells and in the region of the membranes of the endoplasmatic reticulum and in the granules of the B-cells of the pancreatic islets. These results are discussed in correlation with biochemical data concerning the importance of trypsin/trypsin-like activity in the specific conversion of prohormones into hormones.

Animals↗
PubMed1978

The use of cytochalasins in studies on the molecular biology of virus--host cell interactions.

In conclusion, one can say that the cytochalasins--in their brief history of application in virology--have proven to be valuable tools in studies on the molecular biology of virus--host cell interactions. On the other hand, viral systems can be useful in defining the primary sites of action of cytochalasins in certain cells. In interpreting the effects of cytochalasins on virus replication, however, one must take into consideration that the cytochalasins exert a wide variety of alterations in cellular functions. Infections by viruses interfere primarily with the synthesis of host DNA, RNA, and proteins. The experiments reviewed here were carried out with different viruses, different cell lines, and--more important--under very different experimental conditions. Nevertheless, a number of informative observations emerge which provide insight into specific aspects of the interaction of viruses with their host cells, and help us to understand the mode of action of cytochalasins on specific cellular functions: Cytochalasins may decrease or increase the competence of cells for infection by viruses. For the DNA viruses, vaccinia virus and adenovirus, cytochalasin treatment of host cells resulted in a reduced virus yield; whereas for the RNA viruses, poliovirus, parainfluenza virus, and VSV, cytochalasin treatment results in an increased virus yield. The precise mechanism by which cytochalasins exert these effects remain unclear. It is proposed that the cytochalasin-mediated enhancement of cell infectibility for poliovirus--the only system for which this effect has been studied in more detail--is primarily due to a reduction of polypeptide chain initiation. This reduction dramatically amplifies the inherent translational advantage of virus mRNAs over host cell mRNAs, resulting in a relative stimulation of viral mRNA translation. The cytochalasin-mediated sensitization of cells for infection by isolated poliovirus RNA is explainable by a comparable effect on protein synthesis. In this case, cytochalasin may act in part by substituting for the function of a viral protein(s). When cytochalasin B is added to cells which have previously been infected by intact HSV, formation of infectious virus particles is severely inhibited...

Cell Line↗
PubMed1978

[Results of islet transplantation in diabetic dogs].

The influence of histocompatibility on islet transplantation in dogs was studied. Donors and hosts were chosen by help of the macrophage-electrophoresis-mobility test. By subtotal pancreatectomy and twice applying streptocotocin diabetes was successfully induced in recipient animals. Isolation of pancreating islets from the donor was done by means of the collagenase method combined with the Ficoll-gradient-separating technique. The grafting occurred via portal vein into the liver. Significant decrease of blood sugar during 10 weeks was observed in animals with good compatibility. This effect lasted only 14 days in cases of bad compatibility. Concentrations of insulin in the portal vein and superior caval vein 4 weeks after grafting was lower in cases with high-grade histoincompatibility. The duration of functioning of transplanted islets depends on the histocompatibility.

Animals↗
PubMed1978

Distribution of tritium in the different organs of calves and pigs after ingestion of various tritiated feeds.

A research programme on the transfer of tritium in the food chain has been in progress for several years on the experimental farm of the Nuclear Energy Research Center at Mol. The studies reported here are related to the distribution of tritium in the organs of farm animals contaminated in various ways. Two young male calves ingested tritiated milk; the daily intake of 3H-organic form was about 15 muCi for each calf and the total activity ingested until the sacrifice was 482 muCi. Three male pigs from the same litter and about 7 weeks old were used for each experiment on the administration of tritium under different forms: (a) single intraperitoneal injection of 39.3 mCi HTO (P2, P3, P4). (b) daily ingestion of 28.4 muCi HTO. The total activity ingested was respectively 569 muCi (P5) and 766.8 muCi (P6). (c) ingestion of tritiated potatoes. The total activity ingested was respectively 21 muCi (P8), 40.3 muCi (P9) and 48.1 muCi (P10). (d) ingestion of tritiated milk powder. The total activity ingested was respectively 60.6 muCi (P13), 110.4 muCi (P11) and 154.5 muCi (P12). After slaughtering of each animal various organs were removed and analyzed for the 3H content in the tissue water and in the organic matter. We could verify that the chemical form of 3H present in the food is of great importance for the incorporation of 3H in the organic matter of the animal organs. The total incorporation increases by a factor 5.6 when 3H is ingested as tritiated milkpowder by pigs as compared to HTO and with a factor 15 for calves. When tritiated potatoes were ingested by pigs a factor 15.6 was found. The transfer of 3H from HTO and milk feed ingested in the organic fraction of organs is lower for pig than for calf. When we consider the 3H in the tissue water of organs the specific activity (SA) is a little lower than the SA of ingested HTO and after ingestion of tritiated milk feed the activity is very low and no difference due to the species is found. After fractionation of liver and spleen tissue following the technique of Schmidt--Thannhauser radioactivity was found in all liver and spleen constituent lipids--RNA--DNA and proteins, but after isolation and purification of DNA following the original methods, we have not been able to demonstrate that tritium is really incorporated into DNA molecules of a non-dividing organ such as the liver nor of an actively dividing organ such as the spleen.

Animal Feed↗
PubMed1978

[Treatment of meconium ileus equivalent].

A 12-year old boy with mucoviscidosis developed a mechanical obstruction of the small intestine. The diagnosis of a meconium ileus equivalent was made and a conservative treatment was started. After this treatment failed, a laparotomy was performed which verified the diagnosis of a meconium ileus equivalent. It was possible to move the inspissated feces inside the terminal ileum into the ascending colon. The postoperative course was uneventful. The etiology, differential diagnosis, and both conservative and operative treatment of this complication of the mucoviscidosis are discussed.

Acetylcysteine↗