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Biomedical subjects

E Fischer

Publications and source records attributed to E Fischer.

At least 235 records · Page 13Linked to original sources
PubMed1981

Relationship between Energy-dependent Phosphate Uptake and the Electrical Membrane Potential in Lemna gibba G1.

High rates of phosphate uptake into phosphate-starved Lemna gibba L. G1 were correlated with a high membrane potential (pd = -220 millivolts). In plants maintaining a low pd (-110 millivolts), the uptake rate was only 20% of that of high-pd plants. At the onset of phosphate transport, the membrane of high-pd plants was transiently depolarized. This effect was much smaller in low-pd plants. Light stimulated phosphate uptake and the repolarization upon phosphate-induced depolarization, especially in plants grown without sucrose. The phosphate uptake rate was optimal at pH 6 and decreased with increasing pH, corresponding to the phosphate-induced pd changes. Phosphate starvation stimulated the uptake and increased the phosphate-induced depolarization, thus indicating that phosphate uptake depends on the intracellular phosphate level. It is suggested that uptake of monovalent phosphate in Lemna gibba proceeds by an H(+) cotransport dependent on the proton electrochemical potential difference and, hence, on the activity of an H(+) -extrusion pump.

Journal Article↗
PubMed1981

Intestinal sugar transport in experimental diabetes.

The increased sugar transport was examined in the isolated small intestine of streptozotocin-diabetic rats. In the small intestine of these animals, the rate of glucose absorption in vivo is slightly increased, but not that of galactose of 3-O-MG (3-O-Methylglucose); however, in the isolated small intestine, the mucosal-to-serosal but not the serosal-to-mucosal flux of glucose, galactose, and 3-O-MG is increased. The enhanced sugar transport is due neither to the direct toxic effect of streptozotocin nor to a lack of circulating insulin. It is not the result of an increased intraepithelial sugar metabolism. Hyperglycemia, produced gy i.v. glucose infusion, generates the same increase of the intestinal sugar transport as experimental diabetes but the high blood sugar has to be maintained for 4 h before the intestinal effect appears. Hyperglycemia and hypergalactosemia enhance the intestinal transport of glucose, galactose, and 3-O-MG, but not that of fructose; the transport of the latter is increased by hyperfructosemia. The enhanced intestinal sugar transport produced by high blood sugar inhibited by phloretin but not by phlorizin and is completely estimated in cycloheximide-treated animals. It is proposed that sustained high blood sugar induces the synthesis of new carrier sites which are most likely located in the basolateral membrane.

3-O-Methylglucose↗
PubMed1981

Schistosoma mansoni: autoantibodies and polyclonal B cell activation in infected mice.

The appearance of autoantibodies was investigated during the course of Schistosoma mansoni infection in C57Bl/6 mice. Anti-liver autoantibodies or lymphocyte-reactive alloantibodies were detected respectively without cell-mediated immunity against liver antigen or lymphocytotoxic activity. Anti-liver, anti-DNA, anti-Ig and anti-lymphocyte antibodies were shown 6-7 weeks after the beginning of the infection concomitantly with the increase of immunoglobulin levels and circulating immune complexes. At this period, the antibody response to polyvinylpyrrolidone (PVP) was increased and the injection of spleen cells from day-45-infected mice to uninfected recipients increased the anti-PVP antibody response. Conversely, the injection of spleen cells from uninfected to infected mice did not modify the anti-PVP Ab response. After 6 weeks of infection, the basal thymidine incorporation of spleen cells was increased contrasting with the marked inhibition of spleen cell response to PHA. The present data are consistent with the induction of a polyclonal non-specific B cell activation by S. mansoni.

Animals↗
PubMed1981

[Permeability barrier of bacterial cell envelopes as cause of resistance to antibiotics (author's transl)].

The uptake of antibiotics into bacterial cells depends on the structures and mechanisms involved in general transport of substrates. Because of their different molecular architecture, the distinct layers of the cell envelope differ in permeability. The cell-wall of gram-positive bacteria, which is simply structured, is therefore more permeable to a series of antibiotics than is the gram-negative cell-wall which is built like other biological membranes. The energy dependent uptake of many antimetabolic antibiotics in managed by the selective transport systems of the cytoplasmic membrane. In the case of antibiotics, which are not analogous in structure with metabolites, the dependence of the drug on active transport is less obvious. The uptake of antibiotics may even be influenced by the target-site of the drug in the cytoplasm. An example is the accumulation of aminoglycoside antibiotics which is initiated by binding of the drugs to the ribosome. The autoinduction of aminoglycoside uptake is associated with an increased transport of polyamines. The broad variety of modes of resistance, based on permeability, results from the large number of components involved in the uptake of antibiotics. Resistance of bacteria can depend on alterations of every layer of the cell envelope. The existence of a capsule can cause resistance, as well as the specific loss of protein components of the outer membrane, which are involved in the uptake of special substrates. The exclusion of antimetabolites by the loss of the cognate transport system yields well defined resistance. By contrast, resistance towards a wide variety of unrelated antibiotics results from the uncoupling of energization and transport phenomena. Resistance based on reduced uptake becomes even more complex when the modification of the target site alters the accumulation of antibiotics. Far beyond common mechanisms is the ability of cells to actively excrete antibiotics. Far beyond common mechanisms is the ability of cells to actively excrete antibiotics that have already penetrated. The induction of selective export systems for tetracyclines is not dependent on activities of cell-borne transport systems but is a consequence of the acquisition of resistance plasmids.

Anti-Bacterial Agents↗
PubMed1981

[Changes in plasma zinc under anesthesia and surgery (author's transl)].

Postoperative hypozincemia is a common finding and may be interpreted as ACTH-induced dissociation of zinc from the albumin fraction in plasma. Due to the high protein-bound fraction of zinc in plasma rapidly developing hypozincemia may be caused by dilution of plasma proteins. This may be roughly checked by dividing plasma zinc concentration by plasma protein concentration. By this means we observed that in middle ear surgery and in laparotomies under NLA during anesthesia and surgery there is no evidence for dissociation of zinc from plasma proteins. This probably stress-induced phenomenon was, however, already seen in the first postoperative hour after laparotomies. During anesthesia and surgery we observed a profound increase in renal zinc excretion, the cause of which in unknown.

Anesthesia↗
PubMed1981

[Electrolyte balance in major abdominal surgery. IV. Water diuresis under anesthesia and surgery (author's transl)].

12 patients with major laparotomies were studied during anesthesia alone, during three hours of surgery and during the first two hours of recovery. We demonstrated a decrease in plasma potassium and plasma sodium concentration starting with anesthesia and development of a moderate metabolic acidosis. Plasma osmolality was stable during anesthesia and surgery, but slightly decreased in the early postoperative period. Urine formation and osmolar clearance as well as renal sodium and potassium excretion showed a rising tendency during operation, reaching their maximal values in the recovery room. Sodium balance was positive during and after surgery, and sodium retention amounted to about 75% of sodium infused. Urine-to-plasma-osmolality-ratio was 2,0 under anesthesia alone, decreased during surgery and reached control values in the recovery room. In 5 out of 12 patient studied we demonstrated a temporary water diuresis at different points of anesthesia and laparotomy and occasionally even in the postoperative period. This could be due to low plasma levels of ADH caused by relative hypervolemia in the absence of other stimuli of ADH-secretion.

Acidosis↗
PubMed1980

[Increased success rate of renal transplantation by HLA-DR-typing: a retrospective analysis of the South-German co-operative study group for renal transplantation (author's transl)].

Retrospective HLA-DR-typing and the influence of HLA-DR antigen on transplantation prognosis was studied in 90 kidney donor-recipient pairs. It was clearly demonstrated that HLA-DR compatible donor kidney provides a significantly better transplant prognosis than if there is HLA-DR incompatibility. Donor kidneys with only one identical HLA-DR antigen gave a six-month survival rate of 80%. Only HLA-AB identical cadaver kidneys ("full house identity") give similar survival times. Because of relatively lower polymorphism of the HLA-DR alloantigen system, HLA-DR identical donor organs are discovered more frequently than when HLA-AB antigens are taken into consideration. HLA-DR identical donor kidneys (identical for both HLA-DR antigens) have an even better transplant prognosis than "full house identical" kidneys, since the survival rate in the former is 87% after six months.

HLA Antigens↗
PubMed1980

Effect of insulin on the biliary excretion of some organic anions in rats.

In rats insulin enhanced the biliary excretion of rose bengal (50 mg/kg) and bromcresol green (25 mg/kg), and raised the depressed bile flow caused by these organic anions. There was, however, no parallelism between the choleretic effect of insulin and the increase in biliary transport of the two dyes.

Animals↗
PubMed1980

[Tritium- and carbon-14-contents of wines of different vintage from the northern and southern hemisphere (author's transl)].

The carbon-14 and tritium radioactivity contents of up to 19 vintages of German and South African wines were compared. A similar large dependence of the 14C- and of the 3H-activity in the German wine on the nuclear weapon tests of the years 1962/63 was found out. The radioactivity level is also 1977/78 still essential higher than before 1950. The South African wines have been influenced considerably smaller by nuclear explosions. The highest 3H-values were found in the vintage 1963 of the German wine with 5910 pCi/litre and in the vintage 1964 of the South African wine with 510 pCi/litre.

Carbon Radioisotopes↗
PubMed1980

Blood transfusion-induced suppression of cellular immunity in man.

The effect of planned blood transfusions on cell-mediated immunity was studied in previously nontransfused prospective kidney graft recipients. Following transfusion of washed erythrocytes a marked suppression of cellular immunity was found, indicated by reduced response to mitogenic (PHA, Con A, PWM) and antigenic stimulation (Ag-C containing PPD, tetanus toxoid, streptolysin, mumps, vaccinia antigen). A second transfusion led to a more pronounced and prolonged immunosuppression. No suppression was found when autologous blood was applied to volunteers. Preliminary results show autologous and allogeneic MLR suppression when mitomycin-C treated patient cells taken after transfusion are added. Our findings indicate that blood transfusion-induced suppression of cell-mediated immunity might be caused by an unspecific suppressor cell.

Blood Transfusion↗
PubMed1980

X-ray microprobe analysis of chloragosomes of untreated and of EDTA-treated Lumbricus terrestris by using fresh air-dried smears.

The chloragosomes of Lumbricus terrestris were analysed by an electron microscope X-ray microphobe, using both air-dried smear preparations and conventional electron microscopic sections. In untreated worms the air-dried chloragosomes showed prominent peaks for Ca and P, distinct peaks for S and Zn, while Na, K, and Cl peaks were barely detectable. In air-dried smears the S peak was constantly more prominent than in EM sections, indicating that chloragosomes contain easily soluble S-compounds. By long-term CaNa2EDTA treatment of the worms, the Ca and P content of the chloragosomes could be significantly decreased, empirically proving, that the storage and mobilisation of chloragosomal Ca and P are closely related.

Animals↗
PubMed1980

[Familial partial pyruvic dehydrogenase deficiency (author's transl)].

Pyruvic dehydrogenase deficiency was found in two living children of a Turkish family, whereas lactate acidosis was found in a dead child. Two further children died with a pattern of a therapy-refractory metabolic acidosis without any recognisable cause. The prerequisites for the creation of lactate acidosis are demonstrated by the example of pyruvic dehydrogenase deficiency. The extent of remaining activity in case of peruvic dehydrogenase deficiency determines the pattern of clinical signs and the course of the disease which can be influenced to a varying degree by additional complications and different attempts at treatment.

Acidosis↗
PubMed1980

Membrane Potential Changes Related to Active Transport of Glycine in Lemna gibba G1.

Accumulation of (14)C-labeled glycine and microelectrode techniques were employed to study glycine transport and the effect of glycine on the membrane potential (Deltapsi) in Lemna gibba G1. Evidence is presented that two processes, a passive uptake by diffusion and a carrier-mediated uptake, are involved in glycine transport into Lemna cells. At the onset of active glycine uptake the component of Deltapsi which depended on metabolism was decreased. The depolarized membrane repolarized in the presence of glycine. This glycine-induced depolarization followed a saturation curve with increasing glycine concentration which corresponded to carrier-mediated glycine influx kinetics. The transport of glycine was correlated with the metabolically dependent component of Deltapsi. It is suggested (a) that the transient change in Deltapsi reflects the operation of an H(+)-glycine cotransport system driven by an electrochemical H(+) gradient; and (b) that this system is energized by an active H(+) extrusion. Therefore the maximum depolarization of the membrane consequently depended on both the rate of glycine uptake and the activity of the proton extrusion pump.

Journal Article↗
PubMed1980

Effects of barbiturates on the hepatic cytochrome P-450 dependent enzyme system and biliary excretion of exogenous organic anions in rats.

Effect of pretreatment (150 mumol/kg i.p. twice daily for 5 days) wtih six barbiturates (barbital, butobarbital, pentobarbital, amobarbital, phenobarbital and thiopental) on the hepatic microsomal drug methabolizing enzyme system and biliary excretion of bromcresol green and bromsulphthalein-glutathione conjugate has been investigated in rats. All six barburates produced microsomal induction. Phenobarbital, thiopental, barbital and butobarbital increased liver weight, biliary flow and biliary excretion of bromcresol green and bromsulphthalein-glutathione conjugate, however, pentobarbital and amobarbital were ineffective in these parameters. Our results seem to indicate that the enhanced biliary excretion of exogenous anions produced by barbiturates is independent of microsomal enzyme induction.

Animals↗