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Biomedical subjects

P Nuhn

Publications and source records attributed to P Nuhn.

At least 19 recordsLinked to original sources
PubMed1992

Phospholipase A2 inhibition by alkylbenzoylacrylic acids.

3-(4-Alkylbenzoyl)acrylic acids (ABAAs) were synthesized by acylation of alkylbenzenes with maleic anhydride and then screened in vitro for inhibition of phospholipase A2 (PLA2) from snake venom and from porcine pancreas. The inhibitory potency of ABAAs increased with the length of the alkyl residues resulting in IC50 values of between 10(-7) and 10(-4) mol/L. The most potent inhibitors of the snake venom PLA2 were the 4-(n)-hexadecyl and octadecyl (OBAA) derivatives. Kinetic experiments referred to a time-dependent inhibitory reaction. Irreversibility was examined by dilution and dialysis. A molar ratio of inactivation of OBAA of nearly 20 was estimated. Double reciprocal replots of the apparent inactivation constants to the concentration of OBAA gave a (pseudo) first order rate constant of inactivation of 2.3 min-1. For the dissociation constant of the enzyme-inhibitor intermediate, a value of 6 x 10(-6) mol/L was obtained. On the other hand, the PLA2 from porcine pancreas seemed hardly to be inhibited by ABAAs. The present data are discussed in relation to the proposed model for PLA2 inactivation by manoalide. In human PMNs leukotriene B4 and 5-HETE production was essentially reduced. In human platelets the thrombin-induced TxA2 production was reduced. Since these effects disappeared after addition of arachidonic acid, these findings refer to a PLA2 inhibition. The immunologically induced bronchospasm in guinea pigs was significantly and dose-dependently inhibited by OBAA. This indicates that ABAAs might be useful in treating allergic diseases, such as asthma, eczema, allergic shock and others.

Acrylates↗
PubMed1991

[Diagnostics].

Explore the source record for details and available documents.

Animals↗
PubMed1990

Studies on sucrose-palmitate-stearate-containing vesicles encapsulating the cytostatic drug methylglyoxal-bis-guanyl-hydrazone.

Vesicles prepared from sucrose-palmitate-stearate and cholesterol encapsulating the anticancer drug methylglyoxal-bis-guanylhydrazone, were investigated. Treatment with drug-loaded vesicles of this composition in a q.d. 1-4 schedule resulted for murine leukemias P388 in nearly the same increase in life span as the corresponding dose of the free drug. Even very high dosages of sucrose-palmitase-stearate (up to 480 mg.kg-1.d-1) were tolerated by mice.

Animals↗
PubMed1990

[Statistical analysis of the in-vitro action of combination antiviral agents].

Similar to the chemotherapy of bacterial infections, with the advanced development of virostatics a combination of antiviral agents is supposed to be introduced into the causal treatment of viral illness. The present studies explain a method for in vitro testing of virostatic combinations in cell cultures. The principle of the method is based on the checkerboard-technique used to test antibiotic combinations. As example the combination of trisodium phosphonoformate with bromovinyl-2'-deoxyuridine, acyclovir or 2-hexadecylglycero-3-phosphocholine was tested against herpes simplex virus, type 1. For evaluation of the test results the so-called reduction dose 50 (RD50) was introduced. The RD50 corresponds to this substance concentration, which reduces alone or in combination with a second virostatic the virus concentration used in the test system to its TCID50. With analogy to the calculation of infectious doses the computation of the RD50 was performed by using the method of Spearman and Kaerber. The calculated values allow the comparability of the antiviral activity of substances and their combinations. Corresponding to testing of antibiotics the further analysis of combinations was carried out by calculation of fractional inhibitory concentration (FIC), synergy factors (SF), and the construction of isobolograms. In this way, indifferent, synergistic and antagonistic effects of substance combination should be determined.

Anti-Bacterial Agents↗
PubMed1979

[Studies on the control of IgM-antibody synthesis V. Affinity of anti-DNP antibodies in carps immunized with DNP-ficoll (author's transl)].

The dynamics of affinity of anti-DNP antibodies of carps immunized with T cell independent DNP-Ficoll was studied during the immune response. The intrinsic affinity (KO) of antibodies to monovalent epsilon-DNP-lysine is 10(5)--10(6)M-1 and does not change significantly in course of the immunisation. The affinity of tetrameric IgM antibodies to multivalent DNP-T4 conjugate is only 10(2)--10(3)-fold greater than to monovalent hapten, contrary to about 10(6)-fold higher values following immunisation with T cell-dependent antigens. The functional affinity (KF) increases during immune response slightly. KO and KF or antibodies are dependent on antigen dose. High antigen doses elicite antibodies with higher affinity.

Animals↗
PubMed1979

[On the suitability of migration inhibition techniques in the in-vitro-diagnostics of chromium allergy (author's transl)].

1. Under the conditions of cell culture potassium dichromate is reduced to trivalent chromium (diphenylcarbacid/fotometry). Trivalent chromium reacts with proteins more strongly than the hexavalent chromium (gelchromatography/atom absorption spectrophotometry) and presumably represents the actual hapten. 2. Because of this in-vitro-conjugation chromium salts are suitable in their unconjugated form for applying in migration inhibition tests (capillary/Clausen technique). 3. In migration inhibition tests potassium dichromate showed a better antigenicity than chromium chloride. The capillary method was more sensitive than the Clausen technique when using the same test concentration. 4. Correlations between the degree of the patch test and the value of the migration inhibition did not exist.

Allergens↗
PubMed1978

Calorimetric, 13C NMR, and 31P NMR studies on the interaction of some phenothiazine derivatives with dipalmitoyl phosphatidylcholine model membranes.

1. The dipalmitoyl phosphatidylcholine/water system was employed to study the interaction of phenothiazines with model membranes. In particular the effects of the drugs upon the lipid phase transition were examined using differential scanning calorimetry and NMR spectroscopy. The studied phenothiazines have peripheral (diethazine) or central (chlorpromazine) properties. 2. Both drugs were observed to lower the phase transition temperature of dipalmitoyl phosphatidylcholine. The molar activity of chlorpromazine is somewhat higher than of diethazine. At low concentrations the drugs affect the dipalmitoyl phosphatidylcholine pretransition endotherm. 3. In the 13C NMR spectra of the drug-containing samples the signal of the trimethylammonium group of dipalmitoyl phosphatidylcholine is broadened, whereas a narrowing of the signal of the fatty-acid chain methylene groups is observed. Further, addition of the phenothiazines causes higher values of the effective chemical shift anisotropy of the 31P in the phosphate group, in comparison to the pure dipalmitoyl phosphatidylcholine sample. 4. The results obtained by three different techniques indicate a higher fluidity in the fatty-acid chain region and a mobility reduction of the polar headgroup of the dipalmitoyl phosphatidylcholine molecules in the presence of the phenothiazines. These phenomena can be well accounted for by a model for the incorporation of the phenothiazines in the dipalmitoyl phosphatidyl-choline bilayer, in which the dialkylaminoalkyl chains are located near the polar headgroups and the ring system does not penetrate far beyond the glycerol backbone into the hydrocarbon phase.

Calorimetry, Differential Scanning↗
PubMed1978

[6-(2,4-Dinitrophenyl)-mercaptopurine, a stronger immunosuppressive drug than 6-mercaptopurine to primary humoral T-cell dependent immune response in mice].

The suppressive effect of 6-(2,4-Dinitrophenyl)-mercatopurine (DNP-MP) and 6-mercaptopurine (MP) was investigated on the early primary immune response of mice against the T-cell dependent antigens DNP49-bovine gamma globuline (BGG), sheep red blood cells (SRBC) or FITC8-BCG and the T-cell independent DNP22-Ficoll. The number of IgM antibody forming cells (AbFC) to the hapten determinants and to the SRBCs per 10(6) spleen cells was determined. DNP-MP reduced the number of AbFCs after the immunisation with the T cell dependent antigens always stronger than the MP, independently of the antigen type by which the mice had been immunised. The Anti-DNP22-Ficoll immune response was suppressed equally by both immunosuppressive drugs. DNP-MP is not a specific immunosuppressive drug for the anti-DNP-B-lymphocytes. Helper T-cells and macrophages are discussed as target cells for the stronger unspecific action of DNP-MP.

Animals↗