The hypertensive response to soman and its relation to brain acetylcholinesterase inhibition

Intravenous injection of soman in the rat produced a rapid and dose related increase in blood pressure. The dose response curve was very steep, threshold responses occurring after intravenous injection of 10 micrograms/kg, and maximum increases of about 50 mmHg occurring after 40 micrograms/kg. Heart rate also generally increased. An increase in blood pressure also followed injection of soman subcutaneously, intramuscularly, intraperitoneally and into the cerebral ventricles, although the onset was slower and higher doses were required. The magnitude of the pressor response was correlated with the degree of AChE activity in the cortex, hypothalamus and brain stem, but not in the striatum. The pressor response was aborted or prevented by atropine, but not by methylatropine. It also was prevented by phenoxybenzamine. Atropine increased survival following an LD50 dose of soman; phenoxybenzamine prevented the pressor response but did not alter the survival rate.

Metabolism of leukotriene A4 by human erythrocytes. A novel cellular source of leukotriene B4

Human erythrocytes transformed leukotriene A4 into leukotriene B4. Metabolism was proportional to the erythrocyte concentration, even at subphysiological levels (0.08-4 X 10(9) erythrocytes/ml). Comparative metabolic studies excluded the possibility that leukotriene B4 originated from trace amounts of polymorphonuclear leukocytes or platelets present in the purified erythrocyte suspensions. For example, suspensions of isolated platelets (100-500 X 10(6) cells/ml) failed to convert leukotriene A4 into leukotriene B4; and conversion by suspensions of isolated polymorphonuclear neutrophils was insufficient to account for the amounts of leukotriene B4 formed by erythrocytes. Leukotriene B4 formation was maximal within 2 min and substrate concentration dependent. Enzymatic activity originated from a 56 degrees C labile nondialyzable (Mr greater than 30,000) soluble component in the 100,000 X g supernatant obtained from lysed erythrocytes. In contrast to the contemporary view, our results indicate that human erythrocytes are not metabolically inert in terms of eicosanoid biosynthesis. The role of human erythrocytes during inflammatory or pulmonary disorders deserves re-examination in this context.

Deference and dominance in old age: an exploration in social theory

Nonverbal expressions of power and control in the daily lives of old people are examined from a life span perspective that combines social exchange theory, Goffman's classic work on deference and demeanor, and Henley's power theory of nonverbal communication and paralinguistics. Because of societal devaluation of the aged and the typical later life declines in power resources, old people are likely to experience a loss of status and social control during everyday nonverbal rituals of dominance nd deference. Supporting evidence is drawn from studies of the social impact of the physical setting and interactions between institutional old people and staff members. Discussion emphasizes the generally subtle nature of nonverbal expressions of dominance and deference, the impact of normal sensory declines in typical later life role transitions, and the potential for ageist interpretations of nonverbal cues.

Suppression of auditory nerve responses. II. Suppression threshold and growth, iso-suppression contours

Two-tone "synchrony suppression" was studied in responses of single auditory nerve fibers recorded from anesthetized cats. Suppression thresholds for suppressor tones set to a fiber's characteristic frequency (CF) were approximately equal to discharge rate thresholds for CF tones. Suppression thresholds above and below CF were usually lower than the corresponding discharge rate thresholds. However, at all frequencies studied (including CF), suppression thresholds were higher than the corresponding thresholds for discharge synchronization. Across fibers, rates of suppression growth for suppressors at CF were greatest in low-CF fibers and least in high-CF fibers, and there was a systematic decrease in suppression growth rate at CF as CF increased. Within fibers, rates of suppression growth above CF were typically less than at CF, and slopes were monotonically decreasing functions of frequency. Within-fiber rates of suppression growth below CF were variable, but they usually were greater than rates of growth at CF. Iso-suppression contours (frequencies and intensities producing criterion amounts of suppression) indicated that tones near CF are the most potent suppressors at near-threshold intensities, and that the frequency producing the most suppression usually shifts downward as the amount of suppression increases. These data support the notion that synchrony suppression arises primarily as a passive consequence of hair cell activation.

ABR measurements in the cat using a forward-masking paradigm

Probe-elicited wave V amplitudes of the auditory brainstem response (ABR) were measured using a forward-masking paradigm. Subjects were anesthetized cats. For individual experiments, probe frequency and intensity were fixed and masker frequencies and intensities were varied. For each masker frequency, the extent to which the probe-elicited wave V amplitude was reduced by the preceding masker was plotted as a function of masker intensity. The rising segments of the masking functions were fitted with straight lines, using a least-squares procedure, to obtain estimates of their slopes. Masking grew most rapidly for masker frequencies below probe frequency, becoming progressively less steep as masker frequency increased. ABR tuning curves were constructed by using the linear fits to define the masker intensity that caused a 50% reduction in probe-elicited wave V amplitude. The shapes of these tuning curves were comparable to whole-nerve action potential (AP) tuning curves obtained under similar stimulus conditions. These results indicate that ABR amplitude measurements in a forward-masking paradigm can be used to estimate the growth of response to masking stimuli and frequency selectivity in a manner similar to AP amplitude measurements.

Auditory brainstem responses during systemic infusion of lidocaine

Auditory brainstem-evoked responses (ABR) to clicks were recorded in unanesthetized restrained cats before, during, and after systemic intravenous infusion of lidocaine hydrochloride. The drug was infused continuously at varying rates. Lidocaine's major effect on ABR was to lengthen latent periods to all wave-form peaks in proportion with the infusion rate. The effect on latent periods was cumulative throughout the auditory brainstem, ie, all interpeak time intervals increased. Increases in ABR latencies were not due to reductions in effective stimulus intensity because lidocaine did not reduce ABR component amplitudes or increase thresholds. The effects of the drug were reversible. The data are consistent with the notion that lidocaine, directly or indirectly, works throughout the auditory brainstem to increase axonal and synaptic conduction times.

The mystery of the frozen M-K medium

Donor corneal material stored or transported in M-K medium can freeze easily if placed in an insulated environment, such as a styrofoam container, with ice that is colder than 0 degrees C. To assure proper maintenance of the recommended temperature of M-K medium of + 4 degrees C, the ice used should be allowed to stand at room temperature until it has a glistening, wet look to its surfaces. M-K medium already cooled to + 4 degrees C can be safely stored and maintained at + 4 degrees C in a well-insulated styrofoam container for approximately 24 hours if this type of glistening-wet, melting ice is used.

Cellular electrophysiological marker of irreversible ischemic myocardial injury

Glass microelectrode studies on posterior papillary muscle (PPM) slice preparations from 20 pentobarbital-anesthetized dogs (15 subjected to prior circumflex coronary artery ligation, 5 to sham ligation) have resulted in the definition of an electrophysiological marker of irreversible ischemic injury, namely, findings of areas composed of cells unable to generate a significant resting potential (less than -25) mV), designated "electrically inactive areas." Electrically inactive areas were essentially confined to PPM from dogs with circumflex coronary ligation; the incidence and distribution of the areas was related to duration of ischemia. Correlative phase- and light-microscopic studies demonstrated close correspondence between such areas and morphological evidence of irreversible ischemic injury. Analysis of frequency and distribution of electrically inactive areas permits quantitative assessment of the extent and spatial distribution of irreversible injury. This method has been used to quantitate injury in PPM from dogs that had been subjected to ligation for varying time periods. The potential utility of this method for evaluation of interventions designed to protect against ischemic injury and to assess electrical properties of surviving cells is considered.

A case of veno-occlusive disease of the liver in Britain associated with herbal tea consumption

Veno-occlusive disease of the liver with clinical and pathological features similar to those of the condition occurring in the Caribbean is described in a young woman resident in Britain. The diagnosis was made from liver biopsies and hepatic venography and was confirmed at necropsy. Small amounts of pyrroliziding alkaloids were recovered from a sample of mate (Paraguay) tea, owned by the patient, to which she was addicted. It seems probable that the consumption of large amounts of this tea over a period of years was the cause of the hepatic disease.

Congenital hepatic fibrosis

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