Biomedical subjects
Publications and source records attributed to M Klein.
A Latex test has been developed for the detection of virus specific IgG and IgM antibodies. Virus was incubated with serum and the resulting virus-antibody complex harvested. Latex particles sensitized with anti IgG and anti IgM were added and the quantity and type of bound antibody determined.
In an interview study of 480 aged persons, questions on satisfaction with several aspects of life were included. A factor analysis allows to distinguish a factor relating to "depressivity" from a factor "satisfaction with social contacts" and a health-related dimension.
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Behavioral sensitization of the gill-withdrawal reflex of Aplysia is caused by presynaptic facilitation at the synapses of the mechanoreceptor sensory neurons of the reflex onto the motor neurons and interneurons. The presynaptic facilitation has been shown to be simulated by serotonin (the putative presynaptic facilitatory transmitter) and by cyclic AMP and to be accompanied by an increase in the Ca2+ current of sensory neuron cell bodies exposed to tetraethylammonium. This increase in the Ca2+ current could result from either a direct action on the Ca2+ channel or an action on an opposing K+ current. Here we report voltage clamp experiments which indicate that the increase in Ca2+ current associated with presynaptic facilitation results from a decrease in a K+ current. Stimulation of the connective (the pathway that mediates sensitization) or application of serotonin causes a decrease in a voltage-sensitive, steady-state outward current measured under voltage clamp as well as an increase in the transient net inward and a decrease in the transient outward currents elicited by brief depolarizing command steps. The reversal potential of the steady-state synaptic current is sensitive to extracellular K+ concentration, and both the steady-state synaptic current and the changes in the transient currents are blocked by K+ current blocking agents and by washout of K+. These results suggest that serotonin and the natural transmitter released by connective stimulation act to decrease a voltage-sensitive K+ current. The decrease in K+ current prolongs the action potential, and this in turn increases the duration of the inward Ca2+ current and thereby enhances transmitter release.
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Various inhibitors were used to study further the mechanism of natural killing and to compare it to lympholysis by cytotoxic T lymphocytes (CTL). The respiratory inhibitors DNP and NaN3 or low temperatures (0 degrees) blocked the cell contact phase of target-effector interaction in the CTL system but not the NK system. The lytic stage was also inhibited by the glycolytic inhibitors, iodoacetate and NaF, in the NK system as previously shown in the CTL system. Dimethylsulphoxide, a dipolar solvent, and cytochalasin B, a microtubule disruptor, inhibited NK target binding. Pre-treatment of Nk cells with glutaraldehyde, a protein cross-linking agent, completely prevented lysis, but not the formation of target-effector conjugates. The lytic phase of NK lysis was inhibited by chloroquine which also inhibited lysosomal enzyme function. Lysosome defective, beige mutant mice were also totally deficient in NK lytic function and this defect could not be restored with cGMP. T-cell and macrophage mediated cytolysis was previously shown to be relatively normal in beige mice. These results suggest that (i) the mechanism of NK cytolysis is a complex, multistep process, and (ii) this process is fundamentally different from that occurring in CTL. A 'stimulus-secretion' model of NK cytolysis is presented in which it is postulated that lysosomal enzymes may be the lytic molecules.
The author describes a gaseous caloric test using Freon to cool the tympanic membrane. The experiment was used to study the temperature of the tympanic membrane and its variation in relation to the temperature of the material containing the Freon. It was found that the tympanic response was stereotyped if the temperature of such material was between 22 and 30 degrees. Comparison with the aqueous caloric test showed twice as long a recovery time for the latter. Study of nystagmographic tracings in 36 patients tested successively with Freon in Bruning's positions I and IV and with water at 30 and 44 degrees showed constant relations and a great similarity in responses. Clinical study of a number of cases also showed identical responses. Statistical calculation revealed satisfactory correlation coefficients between the two methods. The single test using Freon thus represents a rapid and quantitative method for the investigation of vestibular function. It is a useful test in everyday practise.
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Chicks fed raw soybean meal (RSBM) as a sole protein source developed a significantly enlarged pancreas as compared to chicks fed heated soybean meal. No difference in DNA, RNA and protein content was observed, but the number of acinar cells was significantly higher in pancreases of chicks fed RSBM, after 14 and 28 days of feeding. Histological and ultrastructural analyses revealed that the enlargement of the pancreas resulted both from the hyperplasmic increase in the number of acinar cells and from the dilution of the acini by intercellular connective tissue and the appearance of cytopathogenetic areas.
We studied 25 anesthetized and thoracotamized dogs before and during 5 hours of acute regional myocardial ischemia. Krypton-81m (81mKr) was infused constantly into the aortic sinuses. The myocardial equilibrium of this tracer was used to image and assess the distribution of regional myocardial perfusion using a gamma camera and digital computer. The epicardial ECG was recorded, S-T segment elevation and the loss of R and appearance of Q waves were measured, and the plasma activity of creatine kinase (CK) was determined in aortic and coronary venous blood throughout these experiments. Ten dogs underwent left anterior descending coronary artery (LAD) narrowing for 5 hours and received no drugs. Five dogs received nifedipine 13 microgram/kg, and another five received 1.0 microgram/kg intravenously 30 minutes after LAD narrowing. Those dogs receiving nifedipine, 13 microgram/kg, showed a 30% fall in aortic pressure, a 12% rise in heart rate, and an extension of regional ischemia. The ECG showed an extension of infarct size, and CK release into the coronary vein appeared earlier than in the controls. Dogs receiving nifedipine, 1 microgram/kg, showed a 12% fall in blood pressure, no rise in heart rate, an improvement in regional perfusion, and ECG signs that suggested limitation of infarct size. There also was delayed release of coronary venous CK. The effects of nifedipine on the natural history of regional myocardial perfusion, the electrocardiogram, and enzyme release from the heart were dose related and cannot be generalized. These observations warrant further clinical investigation to improve the use of this agent in man.
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