Biomedical subjects
Publications and source records attributed to R Horn.
The effects of the protein cross-linking reagents glutaraldehyde, tannic acid, and formaldehyde were examined in voltage-clamped and internally perfused squid axons. All three reagents reduced sodium and potassium currents and reduced or abolished sodium inactivation. Glutaraldehyde and tannic acid produced an alteration of potassium current kinetics.
Interstitial oedema in the alveolar septa is the first morphologically recognisable change to be observed in cases of shock. It is brought about by the altered function of the membranes of the damaged epithelium and endothelium in the alveolar wall. At the same time there is an impairment of gaseous exchange, which is rendered more difficult by the exudative process in the interstitium. Pari passu with these events there is injury to the cells of both the alveolar epithelium and the alveolar capillary endothelium. Both these processes are still reversible. The point of irreversibility appears to be reached - so far as time is concerned - at the end of the 1st week, after which the injurious effects on the cell are established, since the thin alveolar wall, necessary for the exchange of gases, becomes overgrown with bulky alveocytes (Type II) and the fibroblasts in the alveolar interstitium crowd the capillaries away from the surface of the alveolus. In most of the advanced cases of shock this process of thickening of the alveolar wall exceeds the critical value, and respiratory exchange is so impaired that satisfactory functioning of the lungs is no longer possible.
A 27-year-old man, a known heroin addict with previously diagnosed nephrotic syndrome, had a percutaneous renal biopsy for recurrent proteinuria. The biopsy revealed a glomerular lesion compatible with focal sclerosing hephropathy. The renal interstitium also demonstrated numerous active granulomas characterized by the presence of both multilamellated basophilic material and areas of unstained fibrillar material. These findings represent a previously undescribed complication of parenteral heroin abuse--renal granuloma formation.
Lipoprotein-X containing plasma from a patient with familial lecithin:cholesterol acyltransferase (LCAT) deficiency, was used as substrate and incubated with postheparin plasma or partly purified lipases. LP-X could not be demonstrated by agar gel electrophoresis after incubation with postheparin plasma from a healthy subject, from a patient with chronic active hepatitis deficient in hepatic lipase, or with partly purified lipoprotein lipase. After incubation a marked increase in free fatty acids (FFA) was observed. In contrast LP-X was still present after incubation when postheparin plasma deficient in lipoprotein lipase or partly purified hepatic lipase was added to the substrate. Only minor changes in the concentration of FFA occurred. After addition of oleic acid to the substrate LP-X could not be demonstrated by agar gel electrophoresis. However, in the isolated low density lipoproteins, LP-X like particles were still present as viewed by electron microscopy. Our results strongly suggest that the change in electrophoretic mobility of LP-X was induced by the release of FFA. This was achieved by lipoprotein lipase, but not by hepatic lipase.
Explore the source record for details and available documents.
Repetitive stimulation was studied in the axon of the giant neuron, R2, of Aplysia in the presence of TEA. In 25 or 50 mM extracellular TEA, a plateau develops on the axon spike during repetitive stimulation at frequencies greater than 3/sec. The plateau in extracellular TEA is inhibited by 30 mM CoCl2 or 1 mM CdCl2, and is enhanced by raising the Ca concentration. Intracellular TEA induces a plateau on the axon spike at frequencies less than 1/30sec. This plateau increases in duration with repetitive stimulation at higher frequencies and is inhibited by 30 mM CoCl2 or 1 mM CdCl2. The increase in spike duration during repetitive firing in the presence of TEA is indicative of an increased entry of Ca during the spike train.
Explore the source record for details and available documents.
1. Intracellular recordings were obtained from the axon of the giant neurone R2 of Aplysia in order to study the ionic dependency of action potentials. 2. The overshoot potential of the axon spike increases with Na concentration in the manner predicted for a Na electrode. The maximum rate of rise (Vm) is linearly related to Na concentration. The overshoot potential is insensitive to Ca concentration at Na concentrations as low as 250 mM. 3. Tetrodotoxin (TTX) or replacement of Na with Tris abolishes action potentials in the axon but not soma of R2. Addition of 4-aminopyridine to a Na-free solution permits axon spikes to be generated. These action potentials are blocked by 30 mM-Co2+, but not by TTX. The overshoot potential and Vm of these action potentials increase monotonically with Ca concentration. 4. Axonal action potentials can be generated when an equimolar concentration of Sr is substituted for all of the Ca and Mg in Na-free medium. These action potentials are abolished by 30 mM-Ca2+ or mM-Co2+, and increase with Sr concentration. 5. TTX-resistant Ba spikes can similarly be elicited in R2 axon. These action potentials are reduced by Ca, Co, or Cd, and enhanced by raising the Ba concentration. 6. The Vm of Na spikes in the absence of Ca is greater in the axon than in the soma of R2, whereas the Vm of divalent spikes is greater in the soma. 7. During repetitive stimulation the axon spikes incrase in duration. This broadening is inhibited by replacing Ca in the bath with Mn or by the addition of 30 mM-CoCl2, and is enhanced by raising the Ca concentration by 30 mM. 8. The action potention of R2 axon has a mixed Na/Ca dependency. The density of Ca current may be greater in the some than in the axon of this cell.
Explore the source record for details and available documents.
The soma but not the axon of the giant neuron, R2, of Aplysia can generate an all-or none Ca spike in Na-free or TTX-containing medium (Junge and Miller, 1974). Extracellular axonal recordings made at several distances from the soma provide evidence that the transition in ability to fire a spike in Na-free medium occurs within the first 250 micrometer of the axon. Application of 25 mM TEA-Br to the bathing medium causes a more than tenfold increase in the duration of the somatic action potential. The duration of the axonal action potential in TEA decreases with distance from the soma. At distances greater than 3 mm from the soma this concentration of TEA causes little or no increase in the duration of the axon spike. The effect of 25 mM TEA on both the soma and proximal axon is blocked reversibly by 30 mM CoCl2 or 1 mM CdCl2. The duration of the somatic action potential in TEA increases with an increase in Ca concentration of the bath. At a constant concentration of Na, the voltage level of the somatic plateau increases with Ca concentration in the manner predicted for a Ca electrode. In the presence of 11 mM Ca2+ the potential of the plateau is relatively insensitive to Na concentration. The TEA plateau in R2 reveals a prolonged voltage-dependent permeability to Ca. The duration of the plateau may indicate the degree of Ca activation during a spike.
In a study of a different subject, the difference between habitual intercuspidation and retral contact position was determined in 21 fully dentulous patients. Registration of the retral position of the mandible was performed by interocclusal wax records and the graphic method. In none of the probands, habitual intercuspidation and retral contact position coincided. In contrast to other authors, we found that siginificant differences between the two methods of registration are an explanation for the differences found betweeen the two positions of the mandible in the sagittal direction.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.