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B F Becker

Publications and source records attributed to B F Becker.

10 recordsLinked to original sources
PubMed1979

Studies on lithium transport across the red cell membrane. V. On the nature of the Na+-dependent Li+ countertransport system of mammalian erythrocytes.

Ouabain-resistant Na+-Li+ countertransport was studied on erythrocytes of man, sheep, rabbit, and beef. A transport system, exchanging Li+ for Na+ in a ratio of 1:1, was present in all four species. Li+ uptake by the exchange system increased 30-fold in the order man less than HK-sheep less than LK-sheep less than rabbit less than LK-beef. This order is identical to that of ouabain-resistant Na+-Na+ exchange in these species, but bears no relation to the Na+-K+ pump activity. The activity of the Na+-Li+ exchange system varied up to 7 and 16-fold among individual red cell specimens from man and beef, the variability being much smaller in sheep and rabbit erythrocytes. The affinities of the system for Li+ and Na+ were similar among the species and individuals (half saturation of the external site at about 1 mM Li+ and 50 mM Na+, respectively). 50-60% of Na+-Li+ exchange was blocked by N-ethylmaleimide in all species. p-Chloromercuribenzene sulfonate inhibited the exchange only in beef and sheep erythrocytes (60-80%). The two SH-reagents act by decreasing the maximum activity of the system, whilst leaving its affinity for Li+ unaltered. Phloretin was a potent inhibitor in all species. 1 mM each of furosemide, ethacrynic acid, and quinidine induced only a slight inhibition. The Na+-Li+ exchange of human and beef erythrocytes increased 3.5-fold upon elevation of the extracellular pH from 6 to 8.5, the pH-dependence arising from a change in affinity of the system for the cations and being similar to that reported for ouabain-resistant Na+-Na+ exchange in beef erythrocytes. It is concluded that a transport system exists in the red cell membranes of the four species which can mediate ouabain-resistant exchange of either Na+ for Na+, Na+ for Li+, or Li+ for Li+. The exchange system exhibits essentially identical transport characteristics in the four species, but shows a marked inter- and intra-species variability in maximum transport capacity and some differences in susceptibility towards inhibitors. A similar transport system is probably present also in other tissues. The exchange system seems to be distinct from the conventional Na+-K+ pump and shows no clear relation to one of the furosemide-sensitive, ouabain-resistant Na+ transport systems described in the literature.

4-Chloromercuribenzenesulfonate↗
PubMed1979

Studies on lithium transport across the red cell membrane. VI. Properties of a sulfhydryl group involved in ouabain-resistant Na+-Li+ (and Na+-Na+) exchange in human and bovine erythrocytes.

The reactivity of the SH-group essential for ouabain-resistant Na+-Li+ (and Na+-Na+) exchange and its location within the membrane are studied on human and beef erythrocytes and beef red cell ghosts. N-ethylmaleimide (NEM), 1,6-hexane dimaleimide, and iodoacetamide can induce an irreversible, partial inhibition of Na+-Li+ exchange in erythrocytes of the two species. The development of the inhibition due to the alkylating agents is greatly accelerated by external Na+ and Li+. The inhibition takes 3 min (NEM) and 60 min (iodoacetamide) to come to completion in isotonic Na+ media, but is hardly detectable in choline+, K+ or Mg2+ media. The transport site of the exchange system and the site promoting NEM binding exhibit similar affinities for external Na+. The impermeable, monofunctional glutathione derivative of 1,6-hexane dimaleimide does not inhibit Na+-Li+ exchange. The mercurials PCMBS, PCMB, and Hg2+ inhibit Na+-Li+ exchange in beef, but not in human erythrocytes. The inhibitory action of PCMBS, being slightly accelerated by external Na+, is fully reversed by penetrating thiols such as 2-mercaptoethanol, whilst glutathione, an impermeable thiol, is ineffective. Pretreatment with PCMBS affords partial protection from the irreversible inhibition caused by NEM. Oxidation with copper orthophenanthroline inhibits Na+-Li+ exchange only when performed in the presence of penetrating thiols such as 2-mercaptoethanol. It is concluded that the SH-reagents studied inhibit Na+-Li+ exchange by modifying an essential SH-group of a membrane protein in such a way that the turnover number of the exchange system is reduced. This SH-group is separated from both the red cell exterior and interior by a penetration barrier and seems to be distinct from the cation binding site. The action of external Na+ and Li+ in promoting the reaction of alkylating inhibitors is interpreted to result from a conformational change of the transport protein induced by the binding of external Na+ or Li+.

4-Chloromercuribenzenesulfonate↗
PubMed1979

Benefits of self-insured hospitalization programs.

As part of hospitals' continuing efforts to control costs, many have begun to consider implementing self-insured hospitalization programs for their employees. Not only can self-insurance provide cash flow savings and actual cost savings but it can also promote prevention among hospital employees.

Accounts Payable and Receivable↗
PubMed1978

Evidence for anionic cation transport of lithium, sodium and potassium across the human erythrocyte membrane induced by divalent anions.

1. The passive net transport of Li+ and Na+ across the human red cell membrane was accelerated by the divalent anions carbonate, sulphite, oxalate, phosphite and malonate. Phthalate, maleate, sulphate and succinate were found additionally to stimulate downhill transport of K+. Marked differences in anion efficacy and selectivity were observed. 2. The effects of these 'carbonate type' anions were reversible and fully blocked by SITS, dipyridamole and other inhibitors of anion transfer. 3. Cation transport acceleration induced by the monovalent anions salicylate, benzoate, thiocyanate and 2,4-dinitrophenol were inhibited by dipyridamole, but not affected by SITS. A great number of mono- and polyvalent anions were without detectable influence on Li+ transport. 4. Li+ net uptake induced by oxalate exhibited a pH dependence similar to that reported for halide self exchange. 5. Transport acceleration by carbonate type anions displayed a linear, 1:1 dependence on the concentrations of both the anion and the cation and was symmetric with respect to the two sides of the membrane. 6. It is concluded that the divalent carbonate type anions form singly charged, negative 1:1 ion pairs with the respective alkali metal cations, the ion pairs traversing the red cell membrane via the anion exchange pathway. This concept of anionic formation of some of the ion pairs considered. The relative efficacies and cation selectivities of polyvalent anions can largely be explained on the basis of electrostatic interactions governing ion pair formation. However, the chelating properties, structural flexibility, polarizability of the anions and the accessibility of the ion pairs to the anion exchange pathway need also be considered. 7. An exchange of NaCO-3 ion pairs for internal HCO-3 or Cl- is discussed as a possible mode of cellular pH regulation.

Anions↗
PubMed1977

Studies on the lithium transport across the red cell membrane. III. Factors contributing to the intraindividual variability of the in vitro Li+ distribution across the human red cell membrane.

1. Extracellular potassium bicarbonate, ouabain, dipyridamole and the Na+ distribution between red cells and plasma influence Li+ transport across the human red cell membrane. The significance of these parameters for the intraindividual variability of the steady-state ratio of external to internal Li+ was studied in vitro. 2. Elevation of external K+ in the physiological concentration range increases the steady-state distribution ratio Lie+/Lii+ indirectly by increasing the ratio Nae+/Nai+ through activation of the Na+-K+ pump, and directly by inhibiting ouabain-sensitive Li+ uptake. 3. A rise in bicarbonate concentration decreases the Li+ ratio directly by accelerating Li+ uptake through a leak, and indirectly by increasing the Na+ leak, thus reducing the Na+ ratio. 4. Dipyridamole blocks both bicarbonate effects. 5. Ouabain decreases the Na+ ratio and inhibits Li+ uptake by the Na+-K+ pump, thereby exerting two opposite effects on the Li+ distribution ratio. 6. The results confirm the previous observation that the steady-state Li+ distribution depends strongly on the Na+ distribution ratio, i-e., the driving force for Na+-dependent Li+ uphill countertransport. It is concluded that the Na+ distribution between red cells and plasma and the concentrations of K+ and bicarbonate in plasma need to be considered as factors influencing the in vivo Li+ distribution. However, the considerable interindividual differences of Li+ distribution cannot be ascribed to variations in these parameters.

Bicarbonates↗
PubMed1977

Studies on the lithium transport across the red cell membrane. II. Characterization of ouabain-sensitive and ouabain-insensitive Li+ transport. Effects of bicarbonate and dipyridamole.

In studies on Li+ net-transport across the human red cell membrane following results were obtained: 1. In K+- and Na+-free choline chloride media, Li+ is transported into the erythrocytes against an electrochemical gradient. This Li+ uphill transport as well as Li+ downhill transport into the cells is inhibited by ouabain, ATP-depletion, and by external K+ and Na+. The effects of K+ and Na+ are relieved at high Li+ concentrations. 2. Ouabain-sensitive Li+ uptake, determined at 10 mM external Na+, does not obey simple Michaelis-Menten kinetics and exhibits a maximum at about pH 7. 3. Ouabain-resistant Li+ downhill transport into erythrocytes increases with rising pH. It is comprised of a saturating component and a component linearly dependent on external Li+. The linear component is partly inhibited by dipyridamole and accelerated by bicarbonate. The bicarbonate effect can be completely blocked by dipyridamole, phlorizin and phenylbutazone. 4. Li+ release is not inhibited by ouabain, ATP-depletion and external K+. It increases with external Na+ concentration, tending to saturate at 150 mM Na+. Na+-independent Li+ release is stimulated by bicarbonate. It is concluded that ouabain-sensitive Li+ uptake is mediated at the K+-site(s) of the Na+-K+ pump. Li+, K+ and Na+ appear to compete for a common site (or sites). The stimulation of Li+ transfer by bicarbonate and the inhibition by dipyridamole suggest a participation of anionic species in ouabain-resistant Li+ transfer. The Na+-dependent Li+ release and the "saturating component" of Li+ uptake are ascribed to the Na+-dependent Li+ countertransport system.

Adenosine Triphosphate↗
PubMed1976

Studies on the lithium transport across the red cell membrane. I. Li+ uphill transport by the Na+-dependent Li+ counter-transport system of human erythrocytes.

Li+ net-transfer across cell membranes was studied on human erythrocytes and ghosts preloaded with 1-2 mM Li+ and incubated in saline media of varying composition at initial thermodynamic equilibrium for Li+. The following results were obtained: 1. Li+ is extruded from glycolyzing erythrocytes against an electrochemical gradient until a steady-state Li+ distribution is established after 24-28 h. 2. The initial rate of Li+ extrusion is not altered by ouabain or by reduction of ATP levels to less than 25% of the normal value. 3. Replacement of external Na+ by K+ or choline+ abolishes the establishment of an electrochemical Li+ gradient. 4. The Li+ distribution ratio Lie+/Lii+ increases proportional to the ratio Nae+/Nai+ at constant extravellular K+ concentrations. 5. In ghost suspension an uphill Li+ transport is driven by an oppositely directed Na+ gradient. The direction of the Li+ uphill transport can be reversed by reversing the Na+ gradient. From the results it is concluded that the Li+ uphill transport across human red cell membranes is mediated by a Na+-dependent Li+ counter-transport system. This system is not inhibited by ouabain and does not appear to be identical to the Na+-Na+ exchange system described by Garrahan and Glynn.

Adenosine Triphosphate↗