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Biomedical subjects

P Hess

Publications and source records attributed to P Hess.

At least 127 records · Page 7Linked to original sources
PubMed1982

Extracellular versus intracellular digoxin action on bovine myocardium, using a digoxin antibody and intracellular glycoside application.

1. The actions of externally and internally applied digoxin in heart ventricular muscle have been compared. 2. External application of digoxin (5 x 10(-8)--10(-7) M) had an inotropic effect, a steady level of twitch tension being reached at the end of about 3 hr. 3. Addition of an anti-digoxin antibody to the bathing solution prevented or reversed the digoxin effect, depending on the time of application. 4. The efflux of the antibody-[3H]digoxin-complex could be fitted by a single exponential with a half-time of 18 min. 5. In the absence of antibody, [3H]digoxin washout was two-compartmental with half-times of 4 and 72 min respectively. It is thought that the fast process signifies efflux from the extracellular space while the slow process reflects the washout of initially membrane bound glycoside. 6. When digoxin was applied by a cut end method, there was no effect on contractile strength. 7. The profile of radioactivity several hours following exposure to [3H]digoxin clearly indicated movement from cell to cell, the concentration of [3H]digoxin being above 10(-7) M in half the preparation at the end of 6 hr. Longitudinal diffusivity averaged 8.6 x 10(-8) cm-2 sec-1. 8. We conclude that digoxin has an inotropic effect when reaching the surface membrane of cardiac cells from the outside but is ineffective when applied from the inside.

Action Potentials↗
PubMed1982

Free magnesium in sheep, ferret and frog striated muscle at rest measured with ion-selective micro-electrodes.

1. Neutral carrier-based liquid membrane micro-electrodes were constructed which are suitable for continuous measurements of [Mg(2+)](i) in cardiac and skeletal muscle preparations.2. The electrodes show a Nernstian behaviour in pure MgCl(2) solutions. In the presence of a constant ionic background chosen to simulate the cytoplasmic composition, the calibration function flattens progressively with lower [Mg(2+)], due to the interference of K(+) and Na(+). The response to changes in [Mg(2+)] is less than 0.5 sec.3. In quiescent preparations at room temperature (23 degrees C), the following basal [Mg(2+)](i) were determined: 3.5 mM (sheep Purkinje fibres), 3.1 mM (sheep ventricular muscle), 3.0 mM (ferret ventricular muscle) and 3.3 mM (frog skeletal muscle).4. In cardiac tissue, electrical stimulation does not measurably affect the basal [Mg(2+)](i).5. In the presence of 0.5 mM-Mg(2+) (o), the calculated Mg(2+) equilibrium potentials, E(Mg), are in the range of -23 to -25 mV, suggesting that Mg(2+) is not passively distributed across the sarcolemma in striated muscle.6. Further studies were performed on sheep Purkinje fibres to investigate the effect of various experimental interventions on [Mg(2+)](i).7. Elevating [Mg(2+)](o) from 0.5 to 10 mM resulted in a reversible increase of [Mg(2+)](i). The initial rate of increase corresponds to a Mg(2+) influx of 0.42 p-mole/cm(2).sec, or a magnesium permeability, P(Mg), of 1.6 x 10(-8)cm/sec.8. Increasing P(CO) (2) from nominally 0 to 100 mmHg (Tris-buffered vs. bicarbonate-buffered Tyrode solution) produced a reversible decrease in [Mg(2+)](i) by roughly 0.45 mM, probably due to Mg(2+) binding the newly formed intracellular HCO(3) (-).9. The effect of metabolic poisoning on [Mg(2+)](i) was assessed by exposure to cyanide, iodoacetic acid and 2-4-dinitrophenol. No significant increase in [Mg(2+)](i) indicative of a liberation of Mg(2+) from ATP was observed.

Animals↗
PubMed1975

Feline oncornavirus-associated cell membrane antigen. II. Antibody titers in healthy cats from household and laboratory colony environments.

Antibody titers to the feline oncornavirusassociated cell membrane antigen (FOCMA) were determined for 447 healthy cats from laboratory colony and household environments. Only 2.7 percent of 221 cats from colony environments were antibody positive as compared to 50.4 percent of 256 cats from household environments. Incidence of FOCMA antibody and geometric mean antibody titer for pet cats from New York City representing single cat apartment habitats were substantially lower than values for unscreened cats from the Boston, Glasgow, and Detroit suburban environments. Geometric mean antibody titer for young adults in the Boston population was significantly higher than titers for kittens or aged cats. This may be due to greater mobility resulting in increased exposure to other cats. In contrast to the high frequency of FOCMA antibody positivity in pet-cat populations, less than 2 percent of the same groups were positive for virus group-specific antigen in peripheral blood leukocytes and platelets. This was interpreted as an indication that many more cats became infected with feline leukemia virus under natural conditions that the number developing persistent virus infection and/or clinical leukemia.

Animals↗
PubMed1975

Feline oncornavirus-associated cell membrane antigen. III. Antibody titers in cats from leukemia cluster households.

Serum samples from 182 healthy cats residing in environments known to have a natural exposure to feline leukemia virus (FeLV) were examined for the presence of antibody to the feline oncornavirus-associated cell membrane antigen. The number included 138 cats from leukemia-"cluster" households. Such cats previously showed greatly increased frequencies of FeLV infection, as determined by the virus group-specific antigen (gasa) in peripheral blood leukocytes and platelets. The geometric mean antibody titer for all 182 cats with known exposure to FeLV was 4.69, more than four times higher than the mean titer for healthy pet cats from the same geographic areas but with no known FeLV exposure. About 92 percent of the cats in exposure environments were positive for FeLV gsa or feline oncornavirus-associated cell membrane antigen (FOCMA) antibody, and gsa-positive cats had lower FOCMA antibody geometric mean titers than gsa-negative cats. In the exposure environments, no differences were seen for cats of different sexes, but a higher geometric mean antibody titer was observed for cats 5 years and over when compared to younger groups. These results prove that previous reports of increased incidences of leukemia in cluster households were not due to chance alone, but rather to increased infection rates of cats in the FeLV environment. Also, they suggest that horizontal transmission of FeLV is highly efficient under crowded conditions, and that most cats naturally exposed to virus elicit an active immune response.

Age Factors↗
PubMed1975

Feline oncornavirus-associated cell membrane antigen. IV. Antibody titers in cats with naturally occurring leukemia, lymphoma, and other diseases.

Cats with naturally occurring leukemia and lymphoma had low or negative humoral antibody titers to the feline oncornavirus-associated cell membrane antigen (FOCMA). Geographic differences were seen in the relative frequencies of various forms of lymphoproliferative neoplasms. Lymphatic leukemia and thymic lymphoma were most common in Boston, whereas alimentary lymphoma was most frequent in Glasgow. No significant differences were found in geometric mean FOCMA antibody titers for the various forms of leukemia-lymphoma or for feline leukemia virus (FeLV)-positive as compared to FeLV-negative cats. Approximately 70% of 76 Boston cats with nonregenerative anemias were FeLV gs antigen (gsa) positive; this was similar to the percentage with leukemia-lymphoma from the same population that was positive. Fifty-five to 62% of the Boston cats with other infectious diseases, such as peritonitis and septicemia, were gsa positive. We postulate that this is due to a predisposition to infectious diseases by the immunosuppressive action of FeLV. Young cats from the Boston population that developed lymphoma, infectious peritonitis, and certain other diseases were more likely to be FeLV gsa positive than older cats with the same diseases.

Age Factors↗