Jack M. Risdahl

Opiates and infection

This review on the effects of opiate use on infectious diseases discusses the complete spectrum of infections in the opiate user, including those of the lung, the GI tract, the skin, the skeletal system, and the CNS. There is both increased prevalence and increased severity of bacterial and viral infections in injection drug users with the outcome of increased morbidity and mortality. The experimental administration of opiates has lead to a greater understanding of the effects on susceptibility to and progression of infectious diseases. Animal models of opiate dependence and infection are reviewed with specific attention to cases in which the opiate-mediated effects are harmful and in which cases they are beneficial.

Infection of Swine with Mycobacterium bovis as a Model of Human Tuberculosis

Swine were infected with Mycobacterium bovis to develop a model for pulmonary and disseminated tuberculosis in humans. Pigs were inoculated with various doses of M. bovis by intravenous (i.v.), intratracheal (int), or tonsillar routes. Animals were euthanized between 17 and 60 days after inoculation, and tissues were collected for culture and histopathologic examination. Lesions of disseminated tuberculosis were found in pigs given 10(4) or 10(8) cfu of M. bovis i.v. or int; localized pulmonary disease was found in pigs given 10(2) or 10(3) cfu of M. bovis int. Lesions ranged from well-organized tubercles with coagulative necrosis, epithelioid macrophages, and fibrosis to large expansive tubercles with liquefactive necrosis and extracellular growth of M. bovis. Tuberculous meningitis was observed in animals given M. bovis i.v. Swine infected with M. bovis are a useful animal model for elucidating the mechanisms of pathogenesis and host defense to tuberculosis in humans.

Reactivation of Porcine Cytomegalovirus through Allogeneic Stimulation

ABSTRACT Reactivation of latent porcine cytomegalovirus after coculture of peripheral blood mononuclear cells (PBMCs) from pigs with different genetic backgrounds was investigated. Nine of 10 allogeneic coculture pairs were PCR (DNA) positive, whereas 7 coculture pairs had porcine cytomegalovirus (PCMV) RNA, an indication of virus replication. The cell subpopulations harboring PCMV were monocytes and CD8+ T cells.

Acute and chronic morphine administration in swine

Functional responses to acute and chronic morphine administration in domestic swine were examined and correlated with pharmacokinetic profiles. Acute effects of morphine sulfate were monitored in pigs for 24 h and the chronic actions of morphine alkaloid were monitored for 21 days. Serum morphine levels, nociception, locomotor activity, respiratory rate, body temperature, and body weight were monitored during all studies. To assess nociception in a large laboratory animal, a portable thermal stimulating device was constructed. Morphine sulfate administered IV and SC had a half-life of approximately 1 h whereas delayed-release morphine alkaloid delivered SC had a half-life of 28 h. The degree of antinociception paralleled decline in blood morphine levels for both SC- and IV-administered animals. Tolerance occurred to both antinociception as well as weight gain despite morphine levels remaining constant over the 21-day period. Morphine dependence was demonstrated by precipitation of an abstinence syndrome using naloxone. Animals in withdrawal displayed consistent signs, including wet-dog shakes, posture changes, vocalization, and salivation. Collectively, these results indicate that swine may be reliably employed as a model to study the actions of morphine and opiate-like compounds.

Morphine Alteration of Histamine Release in vivo

Studies were performed to evaluate the effects of either acute or chronic morphine exposure on histamine release in vivo and supporting studies in vitro. In order to effectively assess histamine release in swine, studies were undertaken to evaluate the effectiveness of compound 48/80 as an intradermal skin test and determine its ability to release histamine in swine cells. Compound 48/80 skin testing was found to be a useful measure of histamine release in swine as evidenced by dose dependent wheal and flare reaction in vivo and histamine release from swine cells in vitro. Acute effects of morphine were determined on swine administered a single injection of morphine alkaloid. Skin tests using intradermal compound 48/80 and histamine, were performed using compound 48/80 both prior to, and 24 h following initiation of morphine treatment. Morphine tolerant swine were subjected to in vivo skin tests and the resulting wheal and flare responses measured. In select swine skin samples from the test sites were measured for mast cell numbers. Swine dermal mast cells were found to release histamine in a dose dependent manner upon compound 48/80 exposure. Both acute and chronic morphine-treated swine had significantly depressed responses to compound 48/80, however this difference was not due alteration in mast cell number or morphology, and skin responsiveness to histamine remained intact.

Effect of chronic morphine treatment on immune responses to keyhole limpet hemocyanin in swine.

In the U.S., an estimated 2 million individuals have used heroin, including 600,000 on a daily basis [1]. Other opiate drugs are used medically in the treatment of pain. The use of opiate drugs is associated with an increased incidence and/or severity of infectious disease [2, 3, 4], respiratory infections [5] and impairment of cell-mediated immunity [6, 7, 8, 9]. Efforts to determine the effect of opiate drugs on immune response in humans is confounded by polydrug abuse and the effects of poor nutrition and poor hygiene. Therefore, we established a swine model of chronic morphine treatment that demonstrates tolerance and dependence in order to test the effect of opiate drugs on primary and recall immune responses [10]. Swine are suitable for chronic, longitudinal studies requiring repeated sample collection and can be trained to minimize handling stress.