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Biomedical subjects

P Geck

Publications and source records attributed to P Geck.

At least 55 records · Page 3Linked to original sources
PubMed1980

Electrically silent cotransport on Na+, K+ and Cl- in Ehrlich cells.

A cotransport system for Na+, K+ and Cl- in Ehrlich cells is described. It is insensitive towards ouabain but specifically inhibited by furosemide and other 'high ceiling' diuretics at concentrations which do not affect other pathways of the ions concerned. As the furosemide-sensitive fluxes of these ions are no affected by changes in membrane potential, and as their complete inhibition by furosemide does not appreciably alter the membrane potential, they appear to be electrically silent. Application of the pulse-response methods in terms of irreversible thermodynamics reveals tight coupling between the furosemide-sensitive flows of Na+, K+ and Cl- (q close to unity for all three combinations) at a stoichiometry of 1: 1 : 2. The site for each of the ions appears to be rather specific: K+ can be replaced by Rb+ but not by other cations tested whereas Cl- can be poorly replaced by Br- but not by NO(-)3, in contradistinction to the Cl(-)-OH- exchange system. The cotransport system appears to function in cell volume regulatin as it tends to make the cell swell, thus counteracting the shrinking effect of the ouabain-sensitive (Na+, K+) pump. The experiments presented could not clarify whether the cotransport process is a primary or secondary active one; while incongruence between transport and conjugated driving force seems to indicate primary active transport, it is very unlikely that hydrolysis of ATP supplies energy for the transport process, since thre is not stimulation of ATP turnover observable under operation of the cotransport system.

Adenosine Triphosphate↗
PubMed1980

Coupling of ion flows in cell suspension systems.

A valid test for cotransport between solutes is a demonstration that the degree of coupling between all coupled solute flows concerned, q defined in terms of Irreversible Thermodynamics, is sufficiently close to unity. The usual method to determine q kinetically by pulses and responses of flows can not simply be applied to rheogenic ion flows, as electrical potential difference changes due to the pulses can hardly be avoided. If, however, the ion flows are all electrically silent, changes in electrical potential difference (PD.) should not interfere with the determination of q. This holds for the furosemide-sensitive fluxes of Na+, K+, and Cl- in Ehrlich cells, each of which could be shown to be unaffected by a change in electrical PD and vice versa. Hence the q values could be determined for any pair of the three ion flows concerned and none differed significantly from unity. These results appear to indicate a furosemide-sensitive, electrically silent ternary symport mechanism for Na+, K+, Cl- with the stoichiometry 1:1:2, which is active but does not utilize ATP. It is assumed to function as a very efficient regulator of cellular volume and may be identical with other previously described binary symport systems.

Animals↗
PubMed1976

Coupling in secondary transport. Effect of electrical potentials on the kinetics of ion linked co-transport.

In a previous paper kinetic equations of secondary active transport by cotransport have been derived. In the present paper these equations have been expanded by including the effect of an electrical potential difference in order to make them applicable to the more realistic systems of secondary active transport driven by the gradients of Na+ or H+. Thermodynamically an electrical potential difference is as a driving force fully exchangeable with an equivalent chemical potential difference. This is not necessarily so for the kinetics of co-transport. It is not always the same whether a given difference in electrochemical activity of the driver ion is mainly osmotic, i.e. due to difference in concentration, or electric, i.e. due to a difference in the electrochemical activity coefficient. In most cases a difference in concentration is more effective in driving co-transport than is an equivalent difference in electrical potential leading to the same difference in electrical activity. The effectiveness of the latter highly depends on the model, whether it is of the affinity type or of the velocity type, but also on whether the loaded or the unloaded carrier bears an electrical charge. With the same electrical potential difference co-transport is as a rule faster if the ternary complex rather than the empty carrier is charged. Also the "standard parameters", (see Glossary, page 62) Jmax and Km, of the overall transport respond differently to the introduction of an electrical potential difference, depending on the model. So an electrical potential difference will mostly affect Km if the loaded carrier is ionic, and mostly Jmax if the empty carrier is ionic, provided that the mobility of the loaded carrier is greater than that of the empty one. On the other hand, distinctive criteria between affinity type and velocity type models are partly affected by an electrical potential difference. If the translocation steps of loaded and unloaded carrier are no longer rate limiting for the overall transport, electrical effects on the transport rate are bound to vanish as does the activation by co-transport.

Binding Sites↗
PubMed1975

Driving forces of amino acid transport in animal cells.

Our observations on the response of TPP+ uptake into K+-depleted cells on the extracellular K+ concentration and on the addition of ouabain and amino acid appear to provide suggestive evidence of, or are at least consistent with, the operation of a powerful, K+-activated electrogenic pump. They are also consistent with the assumption that in these K+-depleted cells the active uptake of amino acid energized by the electric PD presumably generated by this electrogenic pump. It follows that an energy source other than the electrochemical potential gradient of Na+ ions need not be invoked to explain active amino acid transport with inverted Na+ and K+ distribution. In the presence of an electrogenic cation pump one should expect that owing to the activity of this pump the electrical PD is raised under these conditions to a value outweighing the opposed chemical potential gradient of Na+. The experimental evidence so far available is clearly consistent with such an assumption.

Adenosine Triphosphate↗
PubMed1975

Interaction of steroids with the transport system of glucose in human erythrocytes.

Steroids inhibit the exchange transport of glucose in human erythrocytes. The extent of inhibition is roughly correlated to the affinity of the steroids to the membrane lipids. All C-21-steroids tested show a competitive inhibition while the C-19-steriods show different types of inhibition. 5Beta-androstane-3,17-dione acts as a competitive inhibitor. The inhibition by testosterone is of mixed type, while with androst-4-ene-3,17-dione and 5alpha-androstane-3,17-dione a non-competitive inhibition is observed. In this case two inhibitor molecules can be bound per transport molecule. The "non-competitive" inhibitors compete also to some extent with the glucose binding. This effect, however, is at high inhibitor concentrations masked by the more powerful non-competitive inhibition. Competitive and non-competitive inhibitors compete with each other. The structural requirements for the different types of inhibition are discussed.

17-Ketosteroids↗
PubMed1975

Virological studies on gynaecological patients.

Endometrial epithelial cells and blood samples taken simultaneously with the curettage (first serum) of 138 patients suffering from menstrual bleeding disorders as well as materials obtained from 16 induced abortions, were studied for the presence of virus. Fourteen adenovirus 2 strains were isolated from samples of the patients. Endometrial epithelial cells of 35 patients were examined with immunofluorescence method and 23 of them displayed specific fluorescence referring to the presence of viral antigens, with adenovirus and herpesvirus antisera. Studying withserological reactions the first and second (convalescent) sera of patients, high titers were found against type 2 herpesvirus in both sera, and titer rise against the latent adenovirus types in the second sera. Neither infective virus nor the presence of viral antigens were demonstrable in materials obtained from induced abortions.

Abortion, Induced↗
PubMed1975

[Etiology and prevention of recurring aphthous stomatitis].

New results concerning the etiology of recurrent aphthae are reported. According to own experiments of the authors, adenoviruses persisting in the epithelial cells of the oral mucosa may sensitize the aphthous patient. Adenovirus antigen was demonstrable in the oral mucosa cells in more than 50% of the patients and in the lymphocytes in approx. 1% of the patients. Lymphoblast transformation in the circulating lymphocytes could be demonstrated in vitro with heat-inactivated type 1 adenovirus, in 75% of the patients. This virus type has been isolated from 2 patients. Köbner's isomorphous phenomenon could be demonstrated in aphthous patients. The use of a disinfectant for mouth rinsing, the removal of foci as well as vitamin treatment are recommended for preventing recurrent aphthae.

Adenoviridae Infections↗