The purpose of this study was to determine if epileptogenic activity is associated with changes in autonomic cardiac neural discharge and the development of arrhythmias. Nine cats, anesthetized with alpha-chloralose, received pentylenetetrazol (PTZ), 10, 20, 50, 100, 200, and 2,000 mg/kg, intravenously at 10 min intervals. The following were monitored: neural discharge from 1 to 3 postganglionic cardiac sympathetic branches (8 cats, 17 nerves) and the vagus (7 cats, 8 nerves); the electrocorticogram; blood pressure; heart rate; and lead II electrocardiogram. Autonomic dysfunction was manifested by: the observation that autonomic cardiac nerves did not always respond in a predictable manner to changes in blood pressure; the development of a marked increase in variability in mean autonomic cardiac sympathetic and parasympathetic neural discharge; and the fact that the very large increase in the variability of the discharge rate of parasympathetic nerves was seen after PTZ, 50 mg/kg, but did not develop until 100 mg/kg in sympathetic neural discharge. This autonomic imbalance was associated with both interictal and ictal epileptogenic activity. Almost invariably, interictal discharge occurred after PTZ, 10 mg/kg; with higher doses, the duration of ictal activity increased although interictal discharges were present. The altered cardiac autonomic neural discharge was associated with minimal epileptogenic activity in the form of interictal discharges and cardiac arrhythmias which may contribute to sudden unexplained death of the epileptic.
As NASA designs space flights requiring prolonged periods of weightlessness for a broader segment of the population, it will be important to know the acute and sustained effects of weightlessness on the cardiovascular system since this information will contribute to understanding of the clinical pharmacology of drugs administered in space. Due to operational constraints on space flights, earliest effects of weightlessness have not been documented. We examined hemodynamic responses of humans to transitions from acceleration to weightlessness during parabolic flight on NASA's KC-135 aircraft. Impedance cardiography data were collected over four sets of 8-10 parabolas, with a brief rest period between sets. Each parabola included a period of 1.8 Gz, then approximately 20 seconds of weightlessness, and finally a period of 1.6 Gz; the cycle repeated almost immediately for the remainder of the set. Subjects were semi-supine (Shuttle launch posture) for the first set, then randomly supine, sitting and standing for each subsequent set. Transition to weightlessness while standing produced decreased heart rate, increased thoracic fluid content, and increased stroke index. Surprisingly, the onset of weightlessness in the semi-supine posture produced little evidence of a headward fluid shift. Heart rate, stroke index, and cardiac index are virtually unchanged after 20 seconds of weightlessness, and thoracic fluid content is slightly decreased. Semi-supine responses run counter to Shuttle crewmember reports of noticeable fluid shift after minutes to hours in orbit. Apparently, the headward fluid shift commences in the semi-supine posture before launch. is augmented by launch acceleration, but briefly interrupted immediately in orbit, then resumes and is completed over the next hours.
Veterinary public health is another frontier in the fight against human disease. The veterinary public health scope includes the control and eradication of zoonoses, diseases that are naturally transmitted between vertebrate animals and man. These diseases pose a continuous hazard to the health and welfare of the public. More than 100 diseases are categorized as zoonoses, including salmonellosis. It is important to understand how antibiotics are used in humans and in food animals and how these uses affect the evolution of antibacterial resistance. Appropriate use of antibiotics for food animals will preserve the long-term efficacy of existing antibiotics, support animal health and welfare, and limit the risk of transfer of antibiotic resistance to humans. An understanding of the epidemiology of antimicrobial resistance allows development of preventive strategies to limit existing resistance and to avoid emergence of new strains of resistant bacteria. Risk assessments are being used by the Center for Veterinary Medicine at the U.S. Food and Drug Administration as regulatory tools to assess potential risk to humans resulting from antibiotic use in food-producing animals and to then develop microbial safety policies to protect the public health. The veterinary public health scope, in addition to the control and eradication of zoonoses, also includes the development and supervision of food hygiene practices, laboratory and research activities, and education of the public. Thus, it may be seen that there are many ways in which veterinary medicine plays a very important role in public health.
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