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Biomedical subjects

E Heinz

Publications and source records attributed to E Heinz.

At least 91 records · Page 5Linked to original sources
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↗
PubMed1979

Characterization of lipids from chloroplast envelopes.

The major neutral, glycolipids and phospholipids from envelopes of spinach chloroplasts were analyzed with respect to proportions, positional distribution and pairing of fatty acids. All specificities in the diacylglycerol portions of lipids known from previous analyses of lipids from whole leaves were also found in envelope lipids. Diacylglycerols and galactolipids share a common diacylglycerol portion. The only exception is digalactosyl diacylglycerol, which contains 18:3/16:0 but lacks 18:3/16:3 species reverting the distribution in other galactolipids. Phosphatidylcholine, phosphatidylglycerol and sulfoquinovosyl diacylglycerol are distinct from the galactolipids, because each one has a unique diacylglycerol profile. The diacylglycerol species present in phosphatidylcholine and galactolipids or free diacylglycerols do not provide evidence for a biogenetic relation between phosphatidylcholine and galactolipids at the level of envelopes.

Chloroplasts↗
PubMed1977

Galactosylation of different monogalactosyldiacylglycerols by cell-free preparations from pea leaves.

The formation of digalactosyldiglycerol (DGD) from monogalactosyldiglycerol (MDG) was studied in cell-free preparations from pea leaves. Under optimized conditions UDP-[U-14C]galactose was incorporated into a single lipid which was shown to be DGD by cochromatography before and after deacylation and by cocrystallization of the acetyl derivative. Seven MGD species were prepared which had different fatty acids and from zero to eight double bonds. These substrates were dispersed at identical overall concentrations by sonication in Triton X-100 solution and galactosylation rates were measured under optimized conditions. Galactosylation rates increased with the number of double bonds up to a total of six, beyond which the rate decreased again. These galactosylation rates cannot be related to difference in the diglyceride moieties of natural MGD and DGD.

Cell-Free System↗
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↗