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Biomedical subjects

B C Pressman

Publications and source records attributed to B C Pressman.

64 records · Page 4Linked to original sources
PubMed1966

Induced and spontaneous movements of potassium ions into mitochondria.

1. Net movements of K(+) into metabolizing liver mitochondria before and after the addition of valinomycin have been measured by using selective glass electrodes. The advantage of using an automatic titrator to hold the K(+) concentration constant is demonstrated. 2. According to the energy source provided the induced movement after the addition of valinomycin can be either in or out. 3. Uptakes and rates of movement are higher in media containing acetate (20mm) than in media containing chloride (20mm). In each mixture comparisons were made at three pH values; at pH6.36 the induced rates are less than at pH7.0 or 7.8 but the final uptakes attained are increased. 4. The rate of uptake is increased by inorganic phosphate. 5. The presence of Mg(2+) slightly decreases the induced uptake and rate of movement; Ca(2+) can cause the induced movement of K(+) to be outward. 6. The rate of induced K(+) movement is related to the rate of extra oxygen consumption but with different factors in acetate (24 K(+) ions/oxygen molecule) and chloride media (10 K(+) ions/oxygen molecule). 7. The amount of K(+) gained is proportional to the loss of fluorescence of the suspension. 8. When K(+) moves there is a contrary movement of H(+) but the ratio depends on the conditions. At pH6.36 in chloride media the K(+)/H(+) ratio exceeded 10:1 and in no case did it fall to unity. 9. When K(+) is taken up there is a proportional diminution of light-scattering; it is inferred that swelling takes place along with K(+) accumulation. 10. It is shown by the use of tracer (42)K(+) that turnover of the ion in mitochondria is increased by valinomycin. 11. It is concluded that valinomycin both increases the permeability to K(+) and also, given an adequate energy supply, stimulates the K(+)-accumulating mechanism.

Adenosine Triphosphatases↗
PubMedDate not supplied

Characterization of the coronary vasodilator and hemodynamic actions of monensin, a carboxylic ionophore.

The effects of monensin on coronary blood flow (CBF) and other hemodynamic parameters were studied in anesthetized dogs. A dose-response relationship was established, and it was found that the lowest doses of monensin (5-25 micrograms/kg) produced a dose-dependent increase (3-5x) in CBF with a concomitant decrease in total peripheral resistance (TPR). Pretreatment with diphenhydramine, atropine, indomethacin, or propranolol resulted in no reduction in peak increase in CBF or in the duration of response to monensin. However, the response was partially blocked by aminophylline. Large doses (100 and 200 micrograms/kg) produced a dose-dependent increase in cardiac output, aortic pressure, and LV dP/dt max. The duration of these effects was dose-dependent, ranging from 60 to 120 min or longer. Heart rate remained unchanged with all doses of monensin. Pretreatment with propranolol, H87/07 (a cardioselective beta-blocker), and D-600 given alone or in combination significantly reduced, but did not completely abolish, the monensin-induced increase in LV dP/dt max and aortic pressure responses. The increase in CBF in the left anterior descending coronary artery was not significantly affected by these drug pretreatments. Thus, our studies indicate that monensin has two distinct pharmacological effects--in the lower dose range (less than 25 micrograms/kg) it produces a direct relaxation of the blood vessels resulting in an increase in CBF and a decrease in TPR; at high doses (greater than 25 micrograms/kg) it increases myocardial contractility and aortic blood pressure.

Animals↗
PubMedDate not supplied

Diets high in polyunsaturated oils decrease lymphocyte membrane anisotropy and B-cell mitogenesis.

Balb/c mice were fed semipurified diets containing 40% of total calories as lipids: olive, safflower, or fish oil. After 2 weeks of feeding, splenic mononuclear cells were isolated and assayed for steady-state fluorescence anisotropy by means of the probe diphenylhexatriene. Splenocytes were also incubated with the mitogens concanavalin A, phytohemagglutinin, or lipopolysaccharide; subsequent uptake of tritiated thymidine was measured as an index of proliferation. No differences were observed in the membrane anisotropy and mitogenesis of mice fed the olive oil diet (high in monounsaturated fatty acids) and the control group. However, membrane anisotropy was significantly lowered in mice fed the safflower or fish oil diets (high in polyunsaturated fatty acids), and the mitogenic response to lipopolysaccharide was suppressed. Mitogenic responses to concanavalin A and phytohemagglutinin were not significantly affected by the type of lipid in the diet.

Animals↗