Exposure to proinflammatory cytokines (e.g., IL-1beta) or lipopolysaccharide (LPS) produces an acute activation of the immune response and results in a repertoire of behavioral patterns collectively termed sickness behaviors. Although nonspecific responses to pathogenic infection have traditionally been viewed as maladaptive effects of infection, sickness behaviors may have significant, adaptive value for the host. One set of adaptive behaviors affected by infection among mammals and birds is mate choice. In Experiment 1, female prairie voles exhibited the expected increase in blood corticosterone concentrations in response to a 0.1 cc i.p. LPS injection (50 microg), indicating activation of the endocrine system. A separate cohort of females was injected with LPS or saline and paired for 6 h with a novel, previously unpaired male. Following the cohabitation period, LPS-injected females spent significantly more time (p < 0.05) with the familiar partner when given a choice between familiar and unfamiliar males in a three-chamber apparatus designed to test partner preferences. Saline-injected females spent significantly more time with the unfamiliar male. In Experiment 2, males injected with LPS or saline spent equal amounts of time with familiar and unfamiliar females following a 6 h cohabitation with a naive female, and therefore, did not exhibit preferences. From a proximate perspective, this study provides evidence that sickness behaviors influence female, but not male, partner preference in prairie voles.

Animals↗

PubMedDate not supplied

Melatonin mediates seasonal adjustments in immune function.

In addition to seasonal changes in reproductive function, seasonal changes in immune function are mediated by the pineal hormone, melatonin. Melatonin affects immune function both indirectly, acting through other hormones, and directly by acting on components of the immune system. Melatonin also affects tumorigenesis and tumor development. We hypothesize that many of the indirect effects of melatonin on immune function are mediated through glucocorticoids, and appear to be part of an integrated series of adaptations to manage energy. Direct effects of melatonin on immune function appear to be mediated by melatonin receptors on lymphatic tissue or on immune cells in circulation. Winter is energetically demanding and stressful; thermoregulatory demands typically increase when food availability decreases. Individuals would enjoy a survival advantage if seasonally recurring stressors could be anticipated and countered by bolstering immune function. To summarize, melatonin may be part of an integrative system to coordinate reproductive, immunologic and other physiological processes to cope successfully with energetic stressors during winter.

Adaptation, Physiological↗

PubMedDate not supplied

Cost analysis of the Novacor Left Ventricular Assist System as an outpatient bridge to heart transplantation.

Three patients were bridged to heart transplantation with the wearable Novacor Left Ventricular Assist System (Baxter Healthcare Corp., Oakland, CA) (LVAS). Two have been transplanted and discharged. The third patient remains at home. Hospitalization costs, which include the unit room charge, admission profile to the unit, and daily supply charge, were determined for all patients and compared. The patients were transferred from the surgical intensive care unit to a telemetry unit once they were hemodynamically stable. The projected hospitalization costs, if the patients had remained in the hospital, were calculated to determine probable savings for the third party payer. The average period from admission to placement of the Novacor LVAS was 15 days (range, 7-21 days). The average hospitalization cost from admission to time of Novacor left ventricular assist device implant was $2,240/day, and the average hospitalization cost after implant to discharge was $1,570/day. Hospitalization cost savings were $2,632 for the first patient, $5,922 for the second patient, and $132,124 for the third patient, who has not been transplanted. Although the number of patients is small, the daily hospitalization cost was higher before the Novacor LVAS was implanted. This is related to the severity of the disease and the length of stay in a surgical intensive care unit. There also is a significant cost savings for the third party payer, especially if the patient has to wait a significant amount of time before heart transplantation. These are important considerations in this time of managed care.

Ambulatory Care↗

PubMedDate not supplied

Learned immunosuppression is associated with an increased risk of chemically-induced tumors.

Based on the hypothesis that certain aspects of the CNS and immune system interact and that altered immune function affects carcinogenesis, an animal model was developed to examine the effects of learned immunosuppression on the development of a chemically induced tumor. In two experiments, we evaluated whether mice, for which immunosuppression was associated with a neutral (conditioned) stimulus, would exhibit an increased susceptibility to tumor development upon reexposure to the conditioned stimulus, as compared to nonconditioned and control animals. A taste aversion conditioning paradigm, based on classical conditioning techniques, was employed to suppress immune function using the cytotoxic and immunosuppressive drug cyclophosphamide (CY) as the unconditioned stimulus and consequently increase the risk of chemically induced tumorigenesis. CY (100 mg/kg, intraperitoneal) was paired with saccharin in the drinking water (0.1%) of adult female mice (CF-1). Conditioned mice were exposed to saccharin twice in the absence of CY, on days 4 and 7 after the first exposure (day 1). All mice were injected with the chemical carcinogen 9,10-dimethylbenzanthracene (DMBA, 50 mg/kg, subcutaneous) on day 4 of conditioning. Two subsequent exposures to saccharin alone substantially increased the risk of developing DMBA-induced tumors (ranging from 83-91%), as compared to control animals (36%) that had not received this pairing. Mice that received all agents (i.e., CY, DMBA, and saccharin) in a slightly different order did not display elevated tumor incidence. Three separate exposures to CY also significantly increased the number of animals developing tumors in response to the carcinogen (75%). Mice were observed for at least 8 weeks after conditioning.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗