Adverse effects of dietary and furosemide-induced sodium depletion on thermoregulation

In this study, the diuretic furosemide was used in combination with dietary sodium (Na) restriction to quantify the effects of moderate to severe Na depletion on heat tolerance in a validated model of heat stress in rats. Rats were subjected to an Na depletion regimen as follows: a control group (I, n = 17) had free access to a normal diet and tap water; group II (n = 20) consumed the same normal diet and tap water, but was treated with the diuretic furosemide at a dose of 10 mg.kg-1.d-1, ip; group III (n = 18) had free access to an Na-free diet and deionized drinking water; group IV (n = 21) consumed the same Na-free diet and electrolyte-free water, but was also treated with furosemide. Both the dietary and drug manipulations affected significant (p less than 0.05) negative electrolyte and water balances. Group IV consistently exhibited the greatest decrements. Following the 4-d depletion all four groups were acutely exposed to a 42 degrees C, 25-30% rh environmental heat stress during which time core body temperature increased. The time required for rectal temperature to reach 42.6 degrees C was significantly (p less than 0.05) decreased from a time of 242 +/- 8 min in the control group to 176 +/- 14, 181 +/- 8, and 111 +/- 11 min in groups II, III and IV, respectively. We concluded that Na deprivation and diuretic treatment can elicit a 25-50% reduction in heat tolerance due to electrolyte depletion and dehydration. These data confirm that during environmental heat stress uncompensated negative Na balance may predispose an individual to heat illnesses.

Viral isolation and systemic immune responses after intracameral inoculation of herpes simplex virus type 1 in Igh-1-disparate congenic murine strains

Igh-1-disparate congenic murine strains differ in their susceptibility to develop contralateral chorioretinitis after intracameral (AC) inoculation with Herpes simplex virus type 1 (HSV-1): 75% of BALB/cByJ (Igh-1a) and 5% of C.B-17 (Igh-1b) develop necrotizing chorioretinitis. To determine the mechanism of influence of host genetics on development of contralateral chorioretinitis, the authors did viral isolation studies in contralateral eyes, determined in vivo and in vitro T-cell responses, and HSV-antibody levels at various times after AC inoculation of BALB/cByJ and C.B-17 mice with HSV-1. Viral isolation was similar in both mouse strains (P less than 0.2). Similarities in systemic immune responses included suppressed delayed-type hypersensitivity responses 5 days, cytotoxic T-lymphocyte and lymphocyte proliferation responses 8 days, and viral neutralizing antibody titers 5 days postinoculation (PI). Differences in systemic immune responses included: (1) delayed-type hypersensitivity responses were not suppressed in C.B-17 mice (P greater than 0.1) and were hyperactive in BALB/cByJ mice (P less than 0.025) 10 days PI and (2) HSV-neutralizing antibody production was higher in C.B-17 mice 10 days PI. These data suggest that the mere presence of HSV-1 in the uninoculated eye is insufficient for the development of chorioretinitis. Virus-specific delayed-type hypersensitivity reactions might be involved in the pathogenesis of retinitis in BALB/cByJ mice; and virus-neutralizing antibodies and suppressed HSV-specific delayed-type hypersensitivity reactions might be instrumental in the protection enjoyed by C.B-17 mice.

Effects of blood transfusion and cyclosporin on rabbit corneal graft survival

Blood transfusion prolongs renal, cardiac, and skin allograft survival, but promotes rejection of bone marrow allografts. At present, it is unclear whether transfusion induces allograft tolerance or sensitization in corneal transplants. We performed eccentric penetrating keratoplasty on New Zealand albino rabbits, using Dutch rabbits as donors. Twenty-four recipient rabbits were randomly allocated into four groups. The control group received no pretreatment. The other three groups received a donor-specific whole-blood transfusion and/or cyclosporin seven days before the corneal transplants. A single blood transfusion accelerated allograft rejection by an average of 8.8 days (p = 0.0005). In contrast, a single cyclosporin pretreatment prolonged graft survival by an average of 5.3 days (p = 0.02). There was no evidence of interaction effects between transfusion and cyclosporin (p = NS). Therefore, unlike renal, cardiac, and skin allografts and similar to bone marrow allografts, prior blood transfusion accelerates corneal allograft rejection in our rabbit model. Although our data can not be extrapolated to human corneal transplants, our results raise the question whether blood transfusion can sensitize humans to corneal allografts.