Muscular atrophy due to glue sniffing

Summary A glue sniffer manifested marked muscular atrophy in the four extremities while sensory functions remained more or less intact. Glue analysis revealed n-hexane, toluene, and ethyl acetate as leading solvents. Rat experiments revealed that metabolism of n-hexane was not modified by co-administered toluene and vice versa, indicating that the atypical symptom in the present case was not due to metabolic modification between n-hexane and toluene.This work was supported in part by a research grant from the Fujiwara Memorial Foundation.     

Reverse flow in the human fetal descending aorta as a sign of severe fetal asphyxia preceding intrauterine death

Flow velocity waveforms (FVW) in the descending part of the human fetal aorta were monitored in 35 cases of severe intrauterine growth retardation (IUGR) showing pathological intrauterine circulation (end-diastolic block). In 5 of the 35 fetuses, reversed aortic flow was observable during diastole and the simultaneously recorded CTG findings were pathological. All 5 fetuses having this circulatory sign died in utero within the next day. Controls were 260 healthy fetuses with normal growth curves; no end-diastolic block or reverse flow was found in this group. Diastolic reverse flow in the fetal descending aorta appears to reflect severely altered circulation preceding imminent fetal death.     

The innervated left ventricle: a mathematical model of function

A model of the innervated left ventricle is developed that characterises the left ventricle as a time-varying elastance (P/V) element which is a function of both end-diastolic volume and frequency of stimulation of the left stellate ganglion. This model is an extension of a denervated model developed earlier and accurately simulates the ventricular responses to various preload and afterload conditions at a given ionotropic state.     

Saltatory conduction revealed by unidimensional latency-topography of peripheral nerve impulse

The ventral or dorsal root of the rat was placed on 12 electrodes arranged side by side at 0.4 mm intervals. Impulse conduction along the fiber was displayed using unidimensional latency-topography, which corresponds to the relation between latency and electrode distance. The relation revealed step-like displacement, which implies saltatory conduction of the impulse. Since the distance between the plateaux corresponded to internodal length, the conduction velocity could be calculated from the length and the time differences between plateaux. It was found from 36 observations that: (i) mean internodal length was 0.92 ± 0.13 mm (range 0.70–1.25 mm); (ii) mean conduction velocity was 76.1 ± 20.7 m/s; and (iii) the correlation coefficient of conduction velocity and internodal length was statistically significant at r = 0.38 (P < 0.025), so the longer the internodal length, the higher the conduction velocity.     

First heart sound spectra in relation to anterior mitral-leaflet closing velocity

A mathematical model is presented to relate mitral valve leaflet closing velocity to the subsequent vibrational magnitude following valve closure. This relationship is investigated experimentally by means of phonocardiographic and echocardiographic recordings from 17 human subjects. Fast Fourier transform analysis of digitised first heart sounds from each subject reveals that the sound intensities in different frequency bands are not uniformly related to the valve-leaflet closing velocity, obtained from the anterior mitral leaflet echocardiogram. It is found that, in the frequency range up to 150 Hz, closing velocity correlates best with sound intensity in the 30–45 hz bandwidth.     

Inhibition of ATPase activity in human red cell membranes by tetracaine.

This study describes the inhibition by tetracaine of two transport-related enzymes in human red cell membranes: NaK-ATPase and Ca-ATPase. Tetracaine (2.5 mM) inhibited both enzymes between pH 7.0 and 7.8; the degree of inhibition increased as the pH increased. Inhibition of NaK-ATPase increased sharply between pH 7.4 and 7.8, whereas inhibition of Ca-ATPase increased gradually. Concentration-effect studies were conducted at tetracaine concentrations between 0.25 and 2.5 mM at pH 7.8. NaK-ATPase was significantly inhibited by 1.0 mM tetracaine and inhibition increased sharply with tetracaine concentration. Ca-ATPase was significantly inhibited by 0.5 mM tetracaine. but inhibition was essentially linear with tetracaine concentration. In the presence of 2.5 mM tetracaine the K_0.5 for activation of NaK-ATPase by Na⁺ and K⁺ was increased 3- and 5-fold respectively. The V_max was also decreased. In the case of Ca-ATPase, tetracaine did not alter the k_0.5 for activation by Ca²⁺ but decreased V_max. These results demonstrate that NaK-ATPase is more sensitive than Ca-ATPase to inhibition by tetracaine and suggest that the non-ionized form of the local anesthetic is primarily responsible for the inhibition of both enzymes.     

Effect of unilateral ablation of the vestibular cerebellum on visual-vestibular interaction

Experiments were conducted to evaluate the role of the vestibulocerebellum in the production of visual-vestibular-oculomotor reflexes in rabbits. Oculomotor responses (nystagmus) were compared with optokinetic, vestibular, and combined visual-vestibular stimuli obtained before and after surgical removal of the right flocculus, paraflocculus, and paramedian lobes. Nystagmus responses with slow components directed toward the side of the surgical lesion were stronger than those in the opposite direction for each of the stimuli used. The vestibulocerebellum appears to facilitate the production of visual-vestibular-oculomotor responses in increasing the gain of the contralaterally directed oculomotor reflexes.     

Facilitation and impulse propagation failure at the frog neuromuscular junction

Exposure of frog neuromuscular junctions to solutions which contain a high concentration of calcium ions produces failure of neuromuscular transmission. This failure of transmission is abrupt and usually complete. However, some terminals produce small end-plate potentials even after the exposure to a high concentration of calcium ions.A second stimulus to the nerve can overcome the block of neuromuscular transmission if the interval between the stimuli is less than a critical value. The size of the end-plate potential is almost independent of the interstimulus interval if the latter is less than the critical value but more than the refractory period. The depth of this neuromuscular block is affected by temperature, potassium ions, osmotic pressure, cobalt ions, and prior high frequency stimulation of the nerve.Neuromuscular transmission failure coincides with failure of the nerve action potential (NAP) to invade the terminal. Prior to propagation failure, the second extracellularly recorded NAP is smaller, but is conducted faster than the first NAP.The relevance of these findings to the facilitation of transmitter release seen in solutions of normal divalent ion content is discussed.     

Membrane structure in cultured astrocytes

Astrocytes cultured from the brains of neonatal rat pups acquire at least two specializations of intramembrane particle distribution: 'assemblies' and gap junctions. The number and appearance of assemblies in the cultured astrocytes is not markedly influenced by the presence or absence of a collagen substrate, and the range of concentrations of assemblies in astrocytic membranes is fairly stable from 7 through 28 days in culture. The assemblies are not concentrated in apposition to the substrate, even though the astrocytic membranes containing the highest concentration of assemblies in vivo are apposed to basal lamina. Quantitative analysis shows that assemblies are not uniformly distributed over the plasmalemma of a single cell, raising the possibility that the nature of cells around an astrocytic process may influence its membrane composition in vitro.     

The Effects of Laser Light on Sperm Motility and Velocity in vitro

The effect of Laser light on the motility and the velocity of human spermatozoa were measured by means of multiple exposure photography. Total sperm motility increased after Laser irradiation at 4 J/cm2, 8 J/cm2 and 32 J/cm2 respectively with respect to control. However, no influence on sperm velocity was demonstrated after Laser irradiation. This observation suggests that Laser light stimulates non-motile live spermatozoa.