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Biomedical subjects

G Koch

Publications and source records attributed to G Koch.

At least 217 records · Page 12Linked to original sources
PubMed1990

Receptors for atrial natriuretic peptide (ANP) and cyclic GMP responses in HeLa cells.

Cultured HeLa cells display specific binding sites for atrial natriuretic peptide (ANP). Studies with [125I]-(1-28)-rat ANP revealed the presence of a single class of high affinity binding sites on HeLa cells: The apparent dissociation constant (Kd) was 5 nM and the maximal number was 29,000 sites/cell as derived from Scatchard analysis. Furthermore, ANP elevates levels of cGMP in a dose dependent manner with an EC50 close to the Kd for [125I]ANP binding. ANP-mediated elevation of cellular cGMP leads to a significant reduction of bumetanide-sensitive Na+, K+, 2Cl(-)-cotransport in HeLa cells, studied by 22Na+ and 86Rb+ influx measurements. These data indicate (1) that distinct functionally active receptors for ANP are present on HeLa cells and (2) ANP influences the activity of Na+,K+,2Cl(-)-cotransport in these cells.

Atrial Natriuretic Factor↗
PubMed1990

The Na+,K+,2Cl-cotransport system in HeLa cells: aspects of its physiological regulation.

We have previously reported on the biochemical properties of a Na+,K+,2Cl-cotransport system in HeLa cells and here we deal with aspects of its physiological regulation. Na+,K+,2Cl-cotransport in HeLa cells was studied by 86Rb+ influx and 86Rb+/22Na+ efflux measurements. The effects of rat atrial natriuretic peptide (ANP), isoproterenol, and amino acids on 86Rb+ flux, mediated by the bumetanide-sensitive Na+,K+,2Cl-cotransport system and the ouabain-sensitive Na+/K(+)-pump, were investigated. ANP reduced bumetanide-sensitive 86Rb+ influx under isotonic as well as under hypertonic conditions. Similar decrease of bumetanide-sensitive 86Rb+ influx was observed in the presence of 8-bromo-cGMP, while neither isoproterenol as a beta-receptor agonist nor 8-bromo-cAMP-could alter bumetanide-sensitive 86Rb+ influx. Furthermore, efflux of 86Rb+ and 22Na+ was greatly reduced in the presence of bumetanide and ANP. Together with our recent findings, showing functionally active, high affinity receptors for ANP on HeLa cells (Kort and Koch, Biochim. Biophys. Res. Commun. 168: 148-154, 1990), this study indicates that ANP participates in the regulation of the Na+,K+,2Cl-cotransport system in HeLa cells. Further measurements revealed that amino acids as present in the growth medium (Joklik's minimal essential medium) and the amino acid derivative alpha-methyl-aminoisobutyric acid (metAIB, 1 and 5 mM, respectively) also reduced Na+,K+,2Cl-cotransport-mediated 86Rb+ uptake and diminished the stimulatory effect of hypertonicity on the contransporter. In addition, the Na+/K(+)-pump was markedly stimulated in the presence of amino acids, while neither ANP and 8-Br-GMP nor isoproterenol and 8-Br-cAMP had a significant effect on the activity of the Na+/K(+)-pump.

Amino Acids↗
PubMed1990

Poliovirus type 1 enters the human host through intestinal M cells.

It was demonstrated by electron microscopy that after in vitro incubation of human Peyer's patches with poliovirus type 1, either Sabin or Mahoney strain, poliovirus particles adhere specifically to and are endocytosed by intestinal epithelial M cells. These findings suggest that M cells in humans are the site of poliovirus penetration of the intestinal epithelial barrier.

Adult↗
PubMed1990

The use of monoclonal antibodies in an enzyme immunospot assay to detect isotype-specific antibody-secreting cells in pigs and chickens.

Monoclonal antibodies directed against porcine immunoglobulin isotypes G, G1, G2, M, and A and against chicken immunoglobulin isotopes G, M, and A were tested in an antigen-specific spot-forming cell (SFC) assay based on the principle of the enzyme immunoassay. The SFC assay was used to quantitate ovalbumin (OA)-specific antibody-secreting cells (ASC) in pigs that had been primed and boosted with OA. The SFC assay was also used to quantitate trinitrophenyl (TNP)-specific ASC in chickens that had been primed with TNP-conjugated keyhole lympet haemocyanin (TNP-KLH). Although, the classical plaque-forming cell (PFC) assay cannot reliably detect isotope-specific ASC in pigs and chickens, it can detect these cells in mice. Therefore, we compared the OA- and TNP-specific SFC assays with PFC assays that were specific for these antigens in mice. The study demonstrated that the SFC assay is superior to the PFC assay in detecting both OA-specific ASC and TNP-specific ASC. The frequencies of OA-specific and TNP-specific SFC detected in mice were of the same order of magnitude as those detected in pigs and chickens. We concluded that the SFC assay is the better method for quantitating ASC in pigs, chickens, and probably all domestic animals for which isotype-specific monoclonal antibodies are available.

Animals↗
PubMed1990

Chemosensitisation by verapamil and cyclosporin A in mouse tumour cells expressing different levels of P-glycoprotein and CP22 (sorcin).

The relationships between resistance to adriamycin, vincristine, colchicine and etopside, expression of P-glycoprotein and CP22 (sorcin), and resistance modification by verapamil and cyclosporin A have been studied in a panel of multidrug-resistant (MDR) mouse tumour cell lines. Whereas there was a generally good correlation between the degree of resistance and the amount of P-glycoprotein, no relationship between resistance and CP22 expression was seen. At 3.3 microM verapamil, the sensitisation of the MDR cell lines was no greater than that of the parent line. At 6.6 microM verapamil, however, sensitisation of the MDR lines generally exceeded that of the parent line, although the line CR 2.0, expressing very high levels of P-glycoprotein was an exception. Little sensitisation to etoposide was seen in any of the lines. When cyclosporin A was used as the sensitiser at either 2.1 or 4.2 microM, there was a greater effect in lines expressing moderate to high levels of P-glycoprotein than in the parent line, although this tendency was less for adriamycin than for the other cytotoxics. Sensitisation to etoposide was much greater with cyclosporin A than with verapamil. At low levels (less than 1 microM) of CsA, however, sensitisation to colchicine was greater in the parent line than in cell line CR 2.0. These studies indicate that chemosensitisation by verapamil and cyclosporin A is extremely complex, depending upon sensitiser dose, the particular cytotoxic and the cell line. At low doses of the sensitisers, the sensitisation may be greater in lines expressing low levels of P-glycoprotein than in lines showing high levels.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Expression of avian leukaemia virus env-gp85 in Spodoptera frugiperda cells by use of a baculovirus expression vector.

We studied the genetic expression of gp85 of avian leukaemia virus (ALV) subgroup A in a baculovirus/insect cell system. 5'terminal sequences of the gag gene were added to precede the ALV gp85 sequence and a stop codon was introduced at the boundary of gp85 and gp37. The resulting construct was then cloned into the baculovirus transfer vector pAcYM1, which contains the polyhedrin promoter of Autographa californica nuclear polyhedrosis virus (AcNPV). Cells of the insect Spodoptera frugiperda (Sf9) were cotransfected with the resulting recombinant transfer vector pAc85 and infectious AcNPV/E2 DNA. After cotransfection, recombinant baculovirus that lacked the polyhedrin gene and expressed gp85 was selected from the supernatant and used to infect Sf9 cells. The expression of the gp85 gene peaked 3 days after infection, but expression products were not released into the culture medium even though the signal peptide had been cleaved. Owing to incomplete N-glycosylation in the insect cells the largest gp85 product had an Mr of only 65,000. In immunofluorescence tests and immunoblots the recombinant gp85 products reacted with polyclonal and monoclonal antibodies directed against ALV gp85 of subgroup A. Chickens inoculated with crude lysates of Sf9 cells infected with gp85-expressing recombinant baculovirus developed antibodies directed against ALV gp85. These antibodies were not capable of neutralizing ALV.

Animals↗
PubMed1990

Antigenic domains on the peplomer protein of avian infectious bronchitis virus: correlation with biological functions.

Monoclonal antibodies (MAbs) directed against structural proteins of infectious bronchitis virus (IBV) were produced to analyse the antigenic structure of this virus. Competitive binding of enzyme-labelled and unlabelled MAbs to IBV peplomer protein was analysed in an antibody binding assay to test the relatedness of the epitopes defined by the MAbs. Based on the competition groups, eight epitope clusters were defined (S-A to S-H); six of these clusters (S1-A to S1-F) were located on the S1 subunit and two (S2-G and S2-H) on the S2 subunit of the peplomer protein. Epitope clusters S1-A and S1-B overlapped extensively. The biological activities of the MAbs were determined and correlated to the epitope clusters. Monoclonal antibodies directed against epitope clusters S1-A to S1-E and one MAb directed against cluster S2-G moderately to strongly neutralized IBV at titres higher than 2 log10, whereas the remaining MAbs, directed against S1 and S2, neutralized at titres lower than 2 log10. One MAb, directed against cluster S1-D, inhibited the agglutination of chicken erythrocytes.

Animals↗
PubMed1990

Absorption of beta-casomorphins from autoperfused lamb and piglet small intestine.

beta-Casomorphins (beta-CMs) derived from milk beta-casein may exert various opiate activities in milk-fed infants. To assess the physiological significance of beta-CMs as a source of circulating opioids in infants, we measured absorption rates of several beta-CMs under near-physiological conditions using in situ autoperfused lamb intestine. The naturally occurring beta-CMs, beta-CM-7 and beta-CM-4-amide, were absorbed readily into blood with no transfer into lymph. Uptake peaked within several minutes of the luminal infusion of peptide but then declined sharply and stopped within a further 10-15 min. The recovery in blood, intestinal contents, and tissue at the end of the 30-min experiment was less than 1% of the infused dose. The low recovery was due to rapid proteolysis based on in vitro studies that demonstrated half-lives of less than 5 min in lamb blood, luminal contents, and lymph. The synthetic dipeptidyl peptidase IV-resistant analogue beta-[D-Ala2]CM- 4-amide was stable during incubation in blood, lymph, or luminal contents and was absorbed into blood at rates that were maximal within several minutes and remained steady for the 30-min period. We conclude that although natural beta-CMs are transferred across the lamb small intestine, rapid degradation within the intestinal lumen, gut epithelium, and blood would prevent entry into the circulation under normal conditions. Val-beta-CM-7, a putative stable precursor, had similar stability and kinetics of absorption to beta-CM-7, results that exclude Val-beta-CM-7 as a stable precursor for delivery of beta-CMs to the circulation. Essentially identical results to those in lambs were obtained in 7-day-old piglets.

Amino Acid Sequence↗
PubMed1990

Caries-preventive effect of fluoride dentifrices with and without anticalculus agents: a 3-year controlled clinical trial.

A 3-year, double-blind, randomized caries trial was conducted to evaluate the relative anticaries efficacy of four sodium fluoride dentifrices containing 250 ppm fluoride, 1,000 ppm fluoride in combination with 1% disodium 1-hydroxyethylidene-1.1-bisphosphonate (HEBP), and 1,000 ppm fluoride in combination with 1% disodium azacycloheptylidene-2.2-bisphosphonate (AHBP). As a positive control, a monofluorophosphate dentifrice (1,000 ppm fluoride) was used. At outset 1,161 Icelandic children, 11 and 12 years of age, were randomly assigned to one of the five treatment groups and 1,035 subjects completed the trial. After 3 years of unsupervised brushing, the dentifrice containing 250 ppm fluoride was significantly less effective in controlling the caries increment. The combination of sodium fluoride and AHBP was significantly more effective than the positive control.

Analysis of Variance↗
PubMed1990

Glass ionomer cements as a fluoride release system in vivo.

Fluoride release to saliva from three glass ionomer cements, Vitrabond, Ketac-Fil, and ChemFil II, was followed for six weeks in vivo. Colony forming units (CFU) of S. mutans present in saliva before and after placement of glass ionomer restorations were analysed. Thirty-six children received 1-6 glass ionomer cement restorations of one of the three materials. Unstimulated saliva was collected and analysed before insertion of restorations (baseline measurement), immediately after treatment, after 3 weeks and after 6 weeks. The fluoride concentration was measured according to a method slightly modified from Ekstrand (1977) and Duckworth et al. (1987). Baseline concentration of fluoride was between 0.038 and 0.050 ppm. Immediately after placement of GIC restorations, fluoride concentrations increased to 0.8 for ChemFil II and 1.2 ppm for Ketac-Fil and Vitrabond. After 3 weeks, concentrations of released fluoride decreased about 35% for all three materials, and after 6 weeks, concentrations decreased another 30%. However, still after 6 weeks, the fluoride concentrations of unstimulated saliva was 10 times higher than the baseline values. The more restored teeth surfaces the higher was the saliva fluoride concentration found. The prevalence of S. mutants in saliva decreased after placement of the GIC restorations.

Aluminum Silicates↗
PubMed1990

Occult radiopaque jaw lesions in familial adenomatous polyposis.

Osteomatous jaw lesions have been reported to occur in connection with familial adenomatous polyposis (FAP) of the intestines. The disease is fatal if not treated. The aim of this investigation was to study the occurrence of bone jaw lesions in Swedish families, where some family members have developed FAP, in order to evaluate if these bone changes may be regarded as clinical markers of the disease. 132 individuals from ten families with FAP and a matched control group of 250 individuals were examined. Osteomatous lesions were diagnosed in 24 per cent in the FAP families and in 2 per cent in the controls. Individuals with verified FAP showed an increased occurrens of jaw lesions. Also in family members without verified FAP, first-degree relatives and other relatives, showed a significant higher incidence of osteomatous jaw lesions compared to the controls. Our results suggest that osteomatous jaw lesions in families with FAP are of predictive significance.

Adenomatous Polyposis Coli↗
PubMed1990

Class II composite resin restorations: a three-year clinical study of six different posterior composites.

Class II restorations of five light-cured posterior composite materials (Occlusion, P 30, Fulfil, Profile and Heliomolar) were followed for three years, and restorations of another material (Distalite) were followed for two years. Twenty-four dentists from The Public Dental Health Service in the county of Bohuslän placed 242 Class II restorations in 213 patients. The restorations were evaluated after three years using the USPHS criteria. Stone casts were used to categorize quantitatively the amount of occlusal wear according to the Leinfelder method. No differences could be found between the different materials regarding clinical properties. The failure rate (USPHS ratings Charlie) was low, 6.5 per cent. The average occlusal wear after three years for most of the materials was about 100 micrometers. Heliomolar showed a better resistance to wear compared with the other materials.

Acid Etching, Dental↗
PubMed1990

[Detection of antibodies against Toxoplasma gondii in human sera in immunoblot procedures].

Proteins of Toxoplasma lysate were separated by SDS-polyacrylamide gel electrophoresis with subsequent transfer to a nitrocellulose sheet by electrophoretic blotting. Patient human sera reacted predominant with protein fractions of Toxoplasma antigen of 94 kD and 35 kD. Human sera were tested by Toxoplasma-IgG ELISA and Immunofluorescence assay (IgG-IFAT, IgM-IFAT).

Animals↗
PubMed1990

Variability and reproducibility of arterial and venous circulation parameters in the forearm and calf measured at one-week intervals.

In 12 healthy men aged 22 to 29 years the variability of basal arterial blood flow, maximal arterial blood flow as induced by a 5-min arterial occlusion, vascular resistances, total venous capacity and venous emptying rate and the reproducibility of the measurements were studied in both the upper and lower limbs 3 times at one week's interval under strictly standardised conditions using an automatic venous occlusion plethysmograph. Means, medians, standard errors, and standard deviations were virtually identical or very similar without any statistically significant difference between the 3 study occasions; this implies that valid comparisons can be made when measurements are repeated at several days' interval provided measuring conditions are rigorously standardised. Basal and maximal arterial blood flows and venous emptying rates per 100 ml of tissue were significantly higher (p less than 0.05-p less than 0.001) in the forearm than in the calf. Variability of basal blood flow in terms of standard deviations and in terms of coefficients of variation computed from duplicate determinations were significantly higher than for the other parameters and significantly more elevated in the forearm than in the calf. Variability of maximal arterial blood flow and venous emptying rate also tended to be higher in the forearm than in the leg. The high variability and low reproducibility of basal arterial flow measurements are apparently due to a high degree of random biological variability in particular concerning the forearm vascular bed which makes the forearm basal blood flow poorly suitable for studying effects of interventions in cardiovascular control.

Adult↗