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Biomedical subjects

A Schubert

Publications and source records attributed to A Schubert.

At least 109 records · Page 6Linked to original sources
PubMed1982

[Is diabetes mellitus on the way to an epidemiological state of equilibrium?].

As the result of the investigations about the movement of diabetes mellitus in the district of Neubrandenburg is stated that the increase of the existence essentially is to be traced back to diagnostics, treatment and care. Concomitant with this a structural change of the age of diabetics took place. With great probability in the population of the district of Neubrandenburg on account of the in comparison to the rates of access more quickly increasing rates of loss the diabetes mellitus is already on the way to the equilibrium, in which cases the criteria of classification concerning the diagnostic classification as well as the intensity of the serial examinations will influence the final rate of existence.

Adolescent↗
PubMed1979

Cyanide reactivity of cytochrome c derivatives.

The kinetic rates and equilibrium association constants for cyanide binding have been measured for a series of cytochrome c derivatives as a probe of heme accessibility. The series included horse and yeast cytochromes iodinated at Tyr 67 and 74, horse cytochrome formylated at Trp 59 in both a low and high redox potential form, the Met 80 sulfoxide derivative of horse cytochrome and the N-acylisourea heme propionate derivative of tuna cytochrome. Native cytochromes c are well known to bind cyanide slowly in a reaction simply first order both in cytochrome and cyanide up to at least 100 mM in cyanide. The derivative demonstrate markedly different kinetics which indicate the following conclusions. (1) In spite of chemical modification at different loci, all the derivatives have highly similar reactivity, suggesting common ligation structures and mechanisms for reaction. (2) Compared to native cytochromes, reaction rates are 10-20 fold greater. This is in accord with a more accessible heme crevice, but not a completely opened crevice. For the completely opened case, rate increases are expected to be between three and five orders of magnitude. (3) Reaction rates are either independent of cyanide concentration (zero order) or show only slight variation. A mechanism which accounts for the data over four orders of magnitude in concentration postulates a protein conformation step, opening of the heme crevice, as the rate determining step. This conformation change has a limiting rate of 6 . 10(-2) s-1.

Animals↗
PubMed1979

Effects of calcium-EGTA buffers on active calcium transport in inside-out red cell membrane vesicles.

In inside-out red cell membrane vesicles, the free calcium concentration half-maximally stimulating active calcium uptake is about 2 orders of magnitude smaller in a calcium-EGTA buffer than in media containing unbuffered calcium. In calcium-EGTA buffer, the maximum rate of calcium uptake is determined by the total calcium concentration present. A possible model for explaining these findings is presented.

Biological Transport, Active↗
PubMed1979

Changes in the activity and distribution of the ribosomal dissociation factor of rat liver during growth.

In order to assess the relationships between the rate of growth and the activity of the initiation factors of protein synthesis, the activity and intracellular distribution of partially purified preparations of the ribosomal dissociation factor, obtained from the 0.5 M KCl wash of the ribosomes and from the high-speed supernatant (cytosol) of rat liver, were investigated in animals aged 1, 30, 60, 90 and 180 days. During the early phases of growth the activity of the dissociation factor was found mostly in the KCl wash of ribosomes. With advancing age, this activity decreased whereas that of the supernatant was found to increase. The activity of the supernatant was similar to that of ribosomes at 60, 90 and 180 days of age. The older rats showed, however, a decline in the activity of the dissociation factor. These observations suggest an increased rate of protein synthesis initiation in the early phases of growth in rat liver. With advancing age, a progressive reduction of ribosome recycling into subunits might take place, due to the increased accumulation of the dissociation factor in the cytosol. This might suggest a lowering of the initiation reactions of protein synthesis in such conditions.

Aging↗
PubMed1978

Effects of lanthanum on calcium-dependent phenomena in human red cells.

Lanthanum (0.25 mM) does not penetrate into fresh or Mg2+-depleted cells, whereas it does into ATP-depleted or ATP + 2,3-diphosphoglycerate-depleted cells, into cells containing more than 3 mM calcium, or cells stored for more than 4 weeks in acid/citrate/dextrose solution. In fresh cells loaded with calcium, extracellular lanthanum blocks the active Ca2+-efflux completely and inhibits (Ca2+ + Mg2+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity to about 50%. In Mg2+-depleted cells Ca2+-Ca2+ exchange is inhibited by lanthanum. Ca2+-leak is unaffected by lanthanum up to 0.25 mM concentration; higher lanthanum concentrations reduce leak rate. In NaCl medium Ca2+-leak +/ S.D. amounts to 0.28 +/ 0.08 mumol/1 of cells per min, whereas in KC1 medium to 0.15 +/ 0.04 mumol/1 of cells per min at 2.5 mM [Ca2+]e and 0.25 mM [La3+]e pH 7.1. Lanthanum inhibits Ca2+-dependent rapid K+ transport in ATP-depleted and propranolol-treated red cells, i.e. whenever intracellular calcium is below a critical level. The inhibition of the rapid K+ transport can be attributed to protein-lanthanum interactions on the cell surface, since lanthanum is effectively detached from the membrane lipids by propranolol. Lanthanum at 0.2--0.25 mM concentration has no direct effect on the morphology of red cells. The shape regeneration of Ca2+-loaded cells, however, is blocked by lanthanum owing to Ca2+-pump inhibition. Using lanthanum the transition in cell shape can be quantitatively correlated to intracellular Ca2+ concentrations.

Biological Transport, Active↗
PubMed1977

[Incidence of diabetes mellitus in the Neubrandenburg district].

As result of the examination of the movement of diabetes mellitus in the Neubrandenburg district in 1958 to 1975 it is stated that the increase of the number of patients is to be traced back to diagnosis and treatment. In this connection there is not only a structural change of the age of the diabetics, but the relation between unrecognized and recognized patients is displaced, too. The total number of the carriers of a pathogenic hereditary disposition within the population is increasing. Very probably the portion of the diabetics within the population will settle down on a higher balance value. The most important prophylactic measure to avoid complications above all is the early recognition of the sick persons.

Adolescent↗
PubMed1977

Kinetic studies on the calcium-dependent potassium transport in human red blood cells.

The kinetics of the Ca-dependent K transport across the human red cell membrane were studied under experimental conditions allowing the separation of this step from the previous membrane events. Net potassium and tracer potassium fluxes were measured and a self-consistent model was constructed for calculating the ionic permeability values. All the experimental results could be interpreted by means of a nonsaturable neutral K selective channel. In net K efflux measurements the accompanying C1 movement was found to be rate-limiting, and the charge-carrying C1 permeability of the red cell membrane could be calculated.

Biological Transport↗