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Biomedical subjects

G Koch

Publications and source records attributed to G Koch.

At least 343 records · Page 19Linked to original sources
PubMed1983

Kinetics of fluorine in deciduous enamel after application of fluoride-containing varnish (Duraphat). II. A statistical approach to the design and evaluation of a clinical experiment.

The aim of this report is to discuss the design and technique for evaluation of an in vivo experiment on the kinetics of fluorine in deciduous enamel after application of fluorine-containing varnish (Duraphat). The analysis of variance technique used in the analysis of the results of the experiments is described in more detail than in the preceding report. The figure technique used in this report series is described. The method error study performed before carrying out the main experiment is analysed. A brief discussion follows about the consequences that different method errors have on the design of the experiment. The conclusion is that analysis of variance is a more reliable tool than multiple t-test, when evaluation of experiments is to be carried out.

Analysis of Variance↗
PubMed1982

The proliferative activity of antibody forming cells in the mouse bone marrow.

The proliferative activity of antibody-forming cells was studied in the bone marrow of mice immunized with either sheep erythrocytes (SRBC), TNP-LPS or DNP-Ficoll. Peak proliferative activity was found during the first few days of the response. Elimination of the proliferating cells in this period caused a profound and longlasting suppression of the antibody formation in the marrow.

Animals↗
PubMed1982

Alterations in plasma-membrane functions after poliovirus infection.

After exposure of HeLa cells to poliovirus there is a rapid decline (within minutes) in fluorescence polarization of DPH (1,6-diphenyl-1,3,5-hexatriene). Within one hour after infection the (Na+/K+)ATPase activity of an isolated plasma-membrane-rich fraction is enhanced, the cell volume decreases, and the intracellular concentration of a potent low-molecular-weight inhibitor of host protein synthesis increases.

Cell Membrane↗
PubMed1982

Influence of serum and poliovirus infection on the transport and accumulation of AIB in HeLa cells.

The kinetics of active transport of the model amino acid AIB (aminoisobutyric acid) into HeLa cells were analysed. Serum withdrawal from cell-culture medium prior to transport assay strongly lowers the influx and steady-state distribution of AIB. Readdition of serum restores the rate of influx within 30 min, while the capacity to concentrate AIB is only partially reestablished. These changes are due to alterations in the activity of system A. In the time-course of poliovirus infection the initial rate of AIB transport shows two distinct changes. Early in the infection there is an increase in influx, followed by a strong decrease later in infection. These alterations are also attributed to transport system A.

Aminoisobutyric Acids↗
PubMed1982

Antibody formation in mouse bone marrow during secondary type responses to various thymus-independent antigens.

The data presented in this paper show that different thymus-independent (TI) antigens have a differential capacity of inducing antibody formation in mouse bone marrow, both after primary and secondary intravenous immunization. Primary immunization with certain TI antigens (e.g., lipopolysaccharide [LPS], TNP-LPS, DNP-Ficoll) induces the appearance of antibody-forming cells not only in the spleen, but also in the bone marrow. A single injection of certain other TI antigens (e.g., pneumococci [Pn], TNP-conjugated detoxified LPS [TNP-dLPS], TNP-conjugated Brucella abortus bacteria [TNP-BA] ), on the other hand, induces antibody formation in the spleen only. After secondary immunization with these TI antigens only TNP-BA induces a PFC response in the bone marrow. Pn, TNP-dLPS and TNP-BA, but also DNP-Ficoll, are unable to induce bone marrow antibody formation after secondary injection of the antigen, in spite of the clear-cut secondary type character of the splenic response. Thus, the absence of a bone marrow PFC response after secondary immunization with these antigens is not due to a failure to induce memory B cells. This data implies that either two subpopulations of memory B cells exist, one giving rise to antibody formation in the spleen and the other accounting for the bone marrow response, or that antibody can selectively inhibit the secondary bone marrow antibody response to certain TI antigens.

Animals↗
PubMed1982

Differential incorporation of thymidylate analogues into DNA by DNA polymerase alpha and by DNA polymerases specified by two herpes simplex viruses.

Several triphosphates (TP) of 5-substituted deoxyuridine (dU), like 5-ethyl (Et), 5-n-propyl (n-Pr), 5-iso-propyl (iso-Pr), 5-n-hexyl (n-Hx), and 5-trifluorothymidine (F3-dT) were used as substrates for HeLa DNA polymerase alpha and for two herpes simplex virus (HSV)-coded DNA polymerases isolated from HeLa cells infected with HSV-1, strain C42 (wild-type), or its mutant resistant to phosphonoformate (PFAr). All polymerases were purified up to the DNA-cellulose column step and they showed comparable specific activities. The incorporation into DNA studied with all the alkyl analogues of dUTP is several times higher with the virus enzymes than with DNA polymerase alpha. The DNA polymerase of the mutant virus incorporates dUTP analogues to a lower extent than the wild-type polymerase. The two virus enzymes also differ in the Km and Vmax values for different substrates, indicating that the mutation to PFAr has affected the structure of the virus DNA polymerase. Surprisingly, all three enzymes use F3-dTTP as substrate for DNA synthesis to an equal but limited extent.

DNA↗
PubMed1982

Rationale for combined alpha-beta-adrenoceptor blockade: haemodynamic considerations.

Increased peripheral vascular resistance is the cause of elevated blood pressure in most forms of systemic hypertension. Both structural changes in response to increased wall stress and functional alterations in vascular smooth muscle itself appear to contribute to the elevated resistance. As mediators of the vasoconstrictor responses, alpha-adrenoceptors apparently play an important if not predominant role in the initiation and/or maintenance of high resistance and pressure. In contrast to beta-receptor blockade alone, combined alpha-beta-receptor blockade lowers blood pressure predominantly by alpha-receptor-mediated reduction of the systemic vascular resistance, both when induced acutely and, in particular, during long-term administration. Cardiac output is maintained at pretreatment level, as is left ventricular filling pressure. Since a well-balanced blockade of both alpha- and beta-receptors counteracts the pathophysiological changes causing and/or maintaining hypertension and tends to restore cardiovascular dynamics towards normal, combined alpha-beta-receptor blockade appears at present to be one of the most logical and rational therapeutic approaches to hypertension.

Adrenergic alpha-Antagonists↗
PubMed1982

Traumatic ulcerative gingival lesion.

Gingival ulcers caused by tooth brushing in 13 patients with an average age of 29.9 years are presented. The lesions show characteristic clinical features not compatible with simple traumatic ulcers, e.g. running a more chronical course, the duration averaging 6.5 months. Repeated trauma and, in some cases, infection might explain the chronicity. The lesion is suggested to be designated traumatic ulcerative gingival lesion. As treatment, cessation of tooth brushing for 2 weeks and concomitant mouthrinses with chlorhexidine are recommended.

Adolescent↗
PubMed1982

Poliovirus-induced alterations in HeLa cell membrane functions.

Protein synthesis, amino acid uptake, membrane potential, cell volume, Na+ and K+ levels, and ATPase (Na+,K+ activated; EC 3.6.1.3) activity were investigated in control and poliovirus-infected HeLa cells. Inhibition of protein synthesis was first observed 60 min postinfection and reached a maximum at 120 min. The onset of protein synthesis inhibition coincided with a decrease in cell volume and with an elevation of ATPase activity in isolated HeLa cell membranes. Some 3 h after virus adsorption, ATPase activity was inhibited, the Na+-K+ gradient of the cell collapsed, both membrane potential-dependent tetraphenylphosphonium ion uptake and amino acid uptake were reduced, and the cell volume increased. These results provide further experimental support for the hypothesis that modification of the cell membrane plays an important role in the strategy of cytopathogenic viruses in the shutoff of host metabolism and cell death.

Adenosine Triphosphatases↗
PubMed1982

Induction and inhibition of Friend erythroleukemia cell differentiation by pyrimidine analogs: analysis of the requirement for intracellular accumulation and incorporation into DNA.

Alkyldeoxyuridines which differ from thymidine by a C5 substitution of straight or branched alkyl chains of two to six carbon atoms have been tested for their ability to be taken up, phosphorylated, and incorporated into DNA. Analysis of the uptake of 5-ethyl-2'-deoxyuridine and 5-propyl-2'-deoxyuridine (n-PrdU)--similar to both thymidine and 5-bromo-2'-deoxyuridine--indicates that transport is dependent upon a functional cellular thymidine kinase. All of the aforementioned pyrimidines with the exception of n-PrdU are phosphorylated to the triphosphate and incorporated into DNA. The homologs 5-iso-propyl-2'-deoxyuridine (iso-PrdU) and 5-hexyl-2'-deoxyuridine are neither transported into the cell, phosphorylated, nor incorporated into DNA. These analogs were tested (i) for their ability to induce in the absence of dimethyl sulfoxide and (ii) to determine whether they enhance or inhibit dimethyl sulfoxide-induced differentiation of Friend erythroleukemia cells. Inhibition of erythroid differentiation appears to require the incorporation of thymidine analogs into DNA, and thus only 5-ethyl-2'-deoxyuridine and 5-bromo-2'-deoxyuridine were effective in inhibiting dimethyl sulfoxide-induced differentiation. The observation that iso-PrdU, and to a lesser extent n-PrdU and 5-propyldeoxyuridine monophosphate, induce differentiation under conditions in which they are not detectable intracellularly is strong evidence that this class of inducer acts at the cell membrane.

Animals↗
PubMed1982

Quantitation of antibody production in mouse bone marrow during the secondary response to sheep erythrocytes.

The antibody production per organ was quantitated during the secondary response to sheep erythrocytes (SRBC) by measuring the hemolysin production in short-term cultures of spleen and bone marrow cells. Using this assay it was shown that during the first 5 days of the response the spleen is the major site of antibody production, whereas thereafter the bone marrow is the major source. By comparing the hemolysin production per organ and the total number of hemolysin-producing plaque-forming cells (PFC) per organ it was shown that the mean antibody production per PFC varied both in spleen and bone marrow during the secondary response. The mean antibody production per PFC was minimal when the PFC response was maximal. In the bone marrow the mean production per PFC decreased from day 3 to day 5, probably due to immigration of low producing PFC from the spleen. Beyond day 6 the production per cell increased in both spleen and bone marrow, indicating a further maturation of the PFC.

Animals↗
PubMed1982

The capacity and mechanism of bone marrow antibody formation by thymus-independent antigens.

Primary immunization of mice with certain thymus-independent (TI) antigens (i.e., TNP-LPS and DNP-Ficoll) leads to antibody formation in the bone marrow (BM). TNP-Brucella abortus, Pneumococcus pneumoniae organisms, and alpha-(1,6) dextran, on the other hand, do not induce a BM antibody-producing plaque-forming cell (PFC) response. This paper deals with the mechanism underlying antibody formation in the BM to TNP-LPS and DNP-Ficoll. The majority of the BM-localizing PFC induced by TNP-LPS are formed within the BM from the proliferating lymphocyte pool, because this response was found to be resistant to splenectomy and sensitive to treatment with hydroxyurea (HU) before immunization. This local activation of newly formed B cells requires in addition to the antigenic signal of TNP-LPS the mitogenic signal from the lipid A component of LPS. In contrast, the BM PFC response to DNP-ficoll was reduced in splenectomized mice and resistant to HU treatment before the primary immunization. Thus, antibody formation in the BM to DNP-Ficoll is mainly dependent on long-lived B cells that migrate from the peripheral lymphoid organs into the BM.

Animals↗
PubMed1982

Kinetics of fluorine in deciduous enamel after application of fluoride-containing varnish (Duraphat).

The fluorine concentration in tooth enamel was determined in vivo after one single application of Duraphat fluoride varnish from 24 hours up to six months after treatment. A micro-acid-drop technique was used in 68 clinically intact deciduous upper central incisors in 34 pre-school children 4-5 years of age to determined the fluoride concentration in the enamel. The experimental data from the biopsy procedures were analysed by means of analysis of variance. The application of fluoride varnish results in an increase in fluoride in surface as well as subsurface enamel 24 hours after treatment. Thereafter a releasing process of fluorine from the enamel seems to start. Therefore the results indicate that there might be a caries inhibiting effect of fluoride varnish in primary enamel based more upon the kinetics of fluorine rather than a permanent uptake.

Child, Preschool↗
PubMed1982

Effect of 250 and 1000 ppm fluoride dentifrice on caries. A three-year clinical study.

In a 3-year clinical trial, the caries prophylactic effect of two dentifrices containing 1000 ppm F and one containing 250 ppm F was compared. 541 twelve and thirteen-year-old children took part in the study. The children were randomly divided into three groups. Each group of children and their families used one of the dentifrices daily at home. The children were examined for caries at the start of the study and again after an interval of one year. The caries increment was equal in the three groups during the experimental period. This indicates that a 250 ppm F dentifrice has the same caries preventive effect as a 1000 ppm F dentifrice.

Adolescent↗