Hemodynamic responses to alfentanil in halothane-anesthetized dogs

Alfentanil is an opioid that has been used both as a sole anesthetic and in conjunction with other inhalation anesthetics. However, its effects on myocardial performance and regional blood flow are not clearly known. Using sonomicrometry and radioactive microsphere techniques, we examined the hemodynamic responses to alfentanil when given as a loading dose (45 micrograms/kg) followed by continuous infusion (3 micrograms X kg-1 X min-1) in dogs anesthetized with halothane. Similar plasma levels of alfentanil were observed after the loading and infusion doses, and both techniques of administration produced a significant reduction in arterial pressure without change in global or regional function of the left ventricle. Although cardiac output and left ventricular end-diastolic pressure remained unchanged, heart rate and systemic vascular resistance decreased significantly after the loading dose and recovered slightly when alfentanil was infused continuously. Despite the systemic hypotension, alfentanil did not alter perfusion to the heart, brain, muscle, and skin; however, blood flow to the renal cortex and the arterial supply to the liver decreased by 25 and 60%, respectively. Reduction in blood flow to the kidneys and the liver suggests that alfentanil should be used with caution when normal function of these organs is in question.     

CHARACTERIZATION OF RAT TESTICULAR ALCOHOL DEHYDROGENASE

A protein from rat testes that catalyzes the oxidation of ethanolin the presence of NAD⁺, but not NADP⁺, has been characterizedenzymatically and compared to that of hepatic alcohol dehydrogenaseobtained from the same animals. The testicular enzyme, likethe hepatic enzyme, has a K_m value for ethanol in the 0.5–1.0-mMrange and can utilize other alcohols such as n-propanol, n-butanol,and isobutanol, although the K_m values for these other alcoholsare considerably lower (0.03–0.08 mM) that that for ethanol.The testicular enzyme is more heat-labile than is the hepaticenzyme. Finally, the testicular enzyme catalyzes the oxidationof retinol and its retinol dehydrogenase activity is inhibitedby ethanol.     

Behavioural, physiological and immunological consequences of social status and aggression in chronically coexisting resident-intruder dyads of male rats

The behavioural and physiological consequences of social status and reciprocal fighting in resident-intruder dyads of Long Evans male rats were evaluated. Before a chronic cohabitation of 10 days, residents and intruders were individually housed for one month to increase their aggressiveness. Control animals included isolates, i.e., animals kept individually housed throughout the experiment and pair-housed rats, i.e., pairs of rats housed together from their rats in the laboratory. In 19 out of 20 dyads, a clear dominance relationship developed with an advantage to the resident in 68% of the cases. Dominants showed more exploratory activity than subordinates in a open-field test at the end of the cohabitation period; subordinates groomed longer than animals from other experimental groups. Dominants had lower pain thresholds than individually and pair-housed animals. Both dominants and subordinates had higher tyrosine hydroxylase enzymatic activities in the left adrenal than isolated and pair-housed rats. Subordinates lost body weight and had higher plasma corticosteroid concentrations than animals from the other experimental groups. In addition, they had smaller thymus glands and reduced spleen lymphocyte responses to mitogenic stimulation in vitro, in comparison to dominant animals. These results show that subordination in the dyadic resident-intruder paradigm leads to a complex syndrome of behavioural and physiological changes, some of which may be modulated by the intensity of aggressive interactions.     

Medicaid families under managed care. Anticipated behavior

This study reports the results of a household survey of 495 Medicaid clients eligible under the Aid to Families with Dependent Children program in Monroe County, New York. The purpose of the study has been to examine the views and to anticipate the health care choices/decisions of Medicaid clients prior to their enrollment in a new, county-wide Medicaid-managed care program. The findings indicate significant ethnic differentials among the Medicaid poor, both in the choice of care source and in the reasons offered for that choice. Forty percent of those interviewed would like to change to a new source of care, but less than 13% can actually be expected to change. Private practice arrangements were the preferred source of care, yet distance to such sources appears to represent a major stumbling block to access. This study suggests that the managed-care approach being offered in Monroe County may offer the Medicaid eligibles a new stigma-free way of affiliating with a health care provider. This is being recognized by those surveyed as an important element. The study demonstrates that the choices made by the Medicaid recipients are perfectly rational given the recipients' knowledge of Medicaid and the health care system, and the general conditions in which they find themselves. These findings have important implications for the move of Medicaid programs from the fee-for-service to the managed-care/HMO system.     

Behavioral state-specific changes in human hippocampal theta activity

Although there has been extensive examination of the behavioral and physiologic correlates of hippocampal theta activity in animals, the human literature consists of a single case study. We investigated the differential effects of four behavioral states on human hippocampal theta activity in 16 epilepsy surgery patients. Behavioral conditions included resting eyes closed (RC), resting eyes open (RO), eyes open with auditory word activation (AW), and eyes open with visuospatial activation (VS). Hippocampal theta activity decreased during both RO and VS compared to both RC and AW. There were reciprocal changes in delta activity. Comparisons of RO to VS and of RC to AW were nonsignificant. The results demonstrate state-specific changes in human hippocampal theta and are consistent with the animal literature that relates hippocampal theta to sensorimotor integration and forebrain volitional mechanisms.     

Short and middle latency vestibular evoked responses to acceleration in man.

We have succeeded in recording short and middle latency vestibular evoked responses in human subjects. The head was held rigidly in a special, patented head holder, constructed individually for each subject, which gripped the teeth of the upper jaw. The stimulus consisted of 2/sec steps of angular acceleration impulses produced by a special motor with intensities of about 10,000 degrees/sec 2 and with a rise time of 1-2 msec. The electrical activity was recorded as the potential difference between special forehead and mastoid electrodes having a large, secure contact area with the skin. The activity was digitally filtered and averaged in 2 separate channels by means of a Microshev 2000 evoked response system. The short latency responses, with peaks at about 3.5 msec (forehead positive), 6.0 msec (forehead negative) and 8.4 msec (forehead positive; bandpass: 200-2000 Hz; average of 1024 trials), had amplitudes of about 0.5 microV. The middle latency responses had peaks at about 8.8 msec (forehead positive), 18.8 msec (forehead negative) and 26.8 msec (forehead positive; 30-300 Hz; N = 128 trials), with larger amplitudes (about 15 microV). These responses were consistently recorded in the same subject at different times and were similar in different normal subjects. Strenuous control experiments were conducted in order to ensure that these responses are not artefacts due to the movement of conducting media (head, electrodes and leads) in the electromagnetic field of the motor and are elicited by activation of normal labyrinths.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructural changes in the blood-brain barrier after nimodipine treatment and induced hypertension

Fourty-four narcotized rats were split into two equal groups, one being treated with nimodipine and the other with a placebo. By use of norfenefrine the blood pressure was raised to values of 150 and 180 mm Hg within the limits of the autoregulation of brain perfusion and under continuous measurement. Fifteen minutes after application of the standard tracer, horseradish peroxidase, the animals were exsanguinated using a saline perfusion and then perfusion-fixed with Karnovsky's solution. After development of the peroxidase staining the brain sections were evaluated and then allocated to their respective groups. In brain tissues from the experimental group significantly more frequent perivascular accumulations of horseradish peroxidase reaction product were found (P less than 0.001). In electron micrographs it could be seen that the tight junctions were intact and that there was a neuroendothelial transport, with horseradish peroxidase-filled vesicles, in the endothelium, muscle cells, and brain parenchyma. These vesicles represent a medium of transport for all proteins of high molecular weight and can therefore result in brain edema. It is concluded that nimodipine damages the blood-brain barrier by disturbance of the autoregulation of the cerebral blood flow.