C3HeB/FeJ Research Articles

A brief-access test for bitter taste in mice.

Inbred mouse strains vary in their response to bitter-tasting compounds as assessed by 48 h preference tests. These differences are generally assumed to result from altered gustatory function, although such long-term tests could easily reflect additional factors. We developed a brief-access taste test and tested the responses of two inbred strains, as well as C3. SW congenic mice, to the bitter stimulus sucrose octaacetate (SOA). Water-deprived trained mice were tested with five concentrations of SOA (0.00018-0.18 mM) and distilled water in a Davis MS- 160 apparatus. Trials were 5 s in duration and stimuli were presented randomly within blocks; each stimulus trial was preceded by a water rinse trial. Each concentration was presented twice in a session and mice were repeatedly tested across consecutive days. SOA-taster mice, including the SWR/J (SW) inbred and C3. SW congenic taster (T) mice, avoided licking SOA at concentrations >0.003 mM. In comparison, C3HeB/FeJ (C3) and C3. SW demitaster mice (D) licked all concentrations at the same rate as water. Concentration-response functions were similar across strains for both the brief-access test and a parallel 48 h preference test run on separate groups of mice. Furthermore, concentration-response functions were similar whether or not the brief-access test was preceded by a 4 day, single concentration pretest with SOA. The brief-access test is a suitable assay for bitter taste function in mice because it minimizes possible post-ingestive influences on taste.

Endotoxin induction of hepatic metallothionein is mediated through cytokines

Metallothionein (MT), a low molecular-weight, cysteine-rich, metal-binding protein, is induced by many environmental factors and a variety of stimuli. Bacterial endotoxin (lipopolysaccharide, LPS) injection is experimentally used to produce acute stress and is an effective inducer of hepatic MT. However, the mechanism of LPS induction of MT is not known. In the present studies, we used two substrains of mice, differing in their production of cytokines after LPS administration, to test the hypothesis that MT induction by LPS is mediated through cytokines. Normal ( C3Heb FeJ ) and low cytokine-producing ( C3H HeJ ) mice were given various doses of LPS, interleukin-1 (IL-1), interleukin-6 (IL-6), or tumor necrosis factor (TNF), and hepatic MT was determined 24 hr later by the Cd/hemoglobin assay. The low-cytokine-producing mice were much less responsive to the induction of MT by LPS (50 vs 150 μg MT/g liver after 1.0 mg LPS/kg, ip) than the normal mice, but were equally responsive to the induction of MT by IL-1 (0.03–1.0 μg/mouse), IL-6 (0.5–5.0 μg/mouse), and TNF (0.005–0.5 μg/mouse). All the cytokines produced a dose-dependent increase of hepatic MT levels in these two murine substrains (up to five- to sevenfold over controls). In conclusion, these data suggest that LPS induction of MT may be mediated through cytokines.

Relationship of Route of Infection to Susceptibility and Immune Response of Inbred Mice to Y Strain Trypanosoma Cruzi

C3HeB/FeJ (C3H) mice infected ip with 10(6), 5 x 10(5), and 10(5) blood-form trypomastigotes (BFTs) of the Y strain of Trypanosoma cruzi were more resistant than C57B1/6 (B6) mice infected in the same manner. This pattern of susceptibility is opposite that reported for other stocks of this parasite. In a second experiment, C3H and B6 mice were infected ip or sc with 2 x 10(6), 10(6), 5 x 10(5), 10(5), or 10(3) Y strain BFTs. C3H mice infected ip with the 3 highest doses were again more resistant than the B6 mice, while mice infected ip with the 2 lowest doses were essentially equivalent in resistance. Thus, the difference in susceptibility was detectable, in terms of parasitemia levels and survival, primarily at the higher infection doses. For the groups infected sc, the pattern of susceptibility reversed. B6 mice infected with the 3 highest doses had lower parasitemia levels than the corresponding C3H mice, while C3H and B6 mice infected with 10(5) or 10(3) BFTs were similar in resistance. Blastogenic responses of lymphoid cells to phytohemagglutinin (PHA) and a soluble trypanosome extract (STE) were compared for C3H mice infected ip or sc to determine if the susceptibility to infection obtained with the 2 routes would be associated with differences in immune responses. Mesenteric lymph node cells (MLNCs) of mice infected ip were responsive to the STE early in infection, while superficial lymph node cells (SLNCs) of these mice were not. C3H mice infected sc had SLNCs which yielded strong responses to STE, while their MLNCs were relatively unresponsive. PHA stimulated responses by lymphoid cells from mice infected ip or sc were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

The relative importance of Ah versus H-2 genetype on Trichinella resistance following exposure to 3-methylcholanthrene

The relative influence of Ah vs H-2 genotype on the outcome of Trichinella spiralis (Tsp) infections of mice was examined following methylcholanthrene (MC) treatment. Female mice of four inbred strains were treated with MC and infected 24 h later with Tsp muscle larvae. The strains, with their respective major histocompatibility complex (MHC) haplotype, aryl hydrocarbon hydroxylase responsiveness ( Ah phenotype) and level of susceptibility to Tsp infection, were: C3HeB/FeJ (C3), H-2 k, Ah b, Tsp susceptible; C57BL/10.BR (B10.BR), H-2 k, Ah b , Tsp susceptible; C57BL/10.Q (B10.Q), H-2 k, Ah b, Tsp resistant; and AKR/J (AK), H-2 k , Ah d , Tsp resistant. The proliferative response of splenic lymphocytes to crude Tsp L 1 stage antigen was significantly depressed in all MC-treated groups, with the exception of the B10.BR strain. MC administered at 40 mg/kg impaired the ability of C3 and B10.Q mice to eliminate adult worms. At 80 mg/kg, C3 strain mice were also impaired, as well as AK strain mice. The fecundity of female worms recovered from B10 or AK strain mice was not significantly altered by MC treatment, although female worms from treated C3 mice exhibited increased fecundity on day 9 post infection. Muscle larvae burdens of MC-treated B10 and C3 mice were elevated, while those of AK strain mice were unaffected. These data suggest that with acute exposures to MC, the immunogenetic resistance or susceptibility of a given mouse strain may have a more pronounced effect on immune depression and the severity of Tsp infection than does the Ah phenotype.

Splenic lymphocyte production of an endorphin during endotoxic shock

Endogenous opioids have been reported to elicit some of the pathophysiologic responses to endotoxic shock by binding to the δ-opiate receptor. We have previously reported the production of immunoreactive (ir)-endorphin by B lymphocytes treated with bacterial lipopolysaccharide (LPS). We postulated that this lymphocyte-derived ir-endorphin may be an extrapituitary source of the endogenous opioid component associated with the pathophysiology of endotoxic shock. To test this hypothesis, we chose to study the LPS-sensitive ( C3HeB FeJ ) and -resistant ( C3H HeJ ) inbred mouse model. We treated these mice with intraperitoneal injections of LPS or B-lymphocyte-derived ir-endorphin. The LPS-sensitive mice presented with a severe hypothermic and pathophysiologic response pattern when treated with LPS or with ir-endorphin. The LPS-resistant mice, which were unresponsive to the LPS, however, presented with the typical hypothermic and pathophysiologic responses to the ir-endorphin. Immunofluorescence on the splenic leukocytes in the LPS-treated mice showed significant ir-endorphin present only in the LPS-sensitive mice at a time point preceding onset of the pathophysiologic response pattern. Taken together, this evidence strongly suggests a role for B-lymphocyte-derived ir-endorphin in the pathophysiology of endotoxic shock. The implications of immune system regulation of neuroendocrine function are discussed.

Visceral leishmaniasis in congenic mice of susceptible and resistant phenotypes: immunosuppression by adherent spleen cells.

Visceral leishmaniasis is one of several parasitic diseases of humans characterized by immune suppression. A murine model of disseminated leishmaniasis utilizing inbred strains of specific genetic constitution was used to study the mechanisms of immunosuppression elicited during the course of infection. Resistant (Lshr) and susceptible (Lshs) strains of mice were challenged with amastigotes of Leishmania donovani and evaluated as to immune status at intervals between 2 and 40 weeks after challenge. The proliferative responses of splenic lymphocytes to T-cell mitogens, a B-cell mitogen, and parasite antigens were measured to evaluate the relative immune status of parasitized mice and noninfected control mice. Lymphocytes from resistant C3Heb/FeJ (C3H) mice responded normally to concanavalin A and phytohemagglutinin throughout the course of infection. Parasite antigen responses appeared 2 weeks after challenge of C3H mice and remained vigorous for periods up to 6 months. In contrast, immune suppression during infection was profound in both the curing (C57B1/10) and noncuring (B10.D2) phenotypes of Lshs congenic mice. Both Lshs strains developed severe infection as evidenced by high parasite burdens in the liver and spleen 4 to 5 weeks after challenge; splenic lymphocytes taken from these mice between 2 and 8 weeks became increasingly unresponsive to the T-cell mitogens as well as to parasite antigens. The noncuring B10.D2 mice which suffered chronic infection continued to be suppressed for as long as 40 weeks. C57B1/10 (curing) mice, in contrast, cleared infection between 12 and 16 weeks. After spontaneous recovery or elimination of parasites by antimonial drug therapy, the response of spleen cells to T-cell mitogens or parasite antigens were restored to normal. The spleen cells from the Lshs strains of mice obtained during the height of infection suppressed the proliferative responses of spleen cells from their uninfected counterparts upon cocultivation in vitro. Removal of adherent cells from the suppressive spleen cell populations restored normal mitogen responses. On the basis of adherence characteristics, phagocytosis, and morphology, the suppressor was identified as a macrophage population which appears to be responsible for a nonspecific immunosuppression of Lshs mice with significant parasite burdens of L. donovani.

Selective association of lipid-rich R-like lipopolysaccharide subunits with murine spleen cells

SDS-PAGE was used to analyze the subunit composition of 125I-lipopolysaccharide (LPS) in the cell-associated and supernatant fractions of murine spleen cells after culture with radiolabeled LPS from the smooth strain of E. coli 055:B5. Quantitative estimates from densitometric scans of autoradiographs indicated that certain R-like subunits were selectively enriched in cell-associated fractions by a factor of 2.8 as compared to native 055 LPS. Coincident with this selective enrichment was a 57% decrease in these subunits in supernatant fractions. In contrast, the level of polysaccharide-containing subunits in cell-associated fractions was equivalent to or less than the corresponding subunit in native LPS. LPS bound at 37°C was capable of eliciting a significant B-lymphocyte proliferative response in responder spleen cells. However, this selective binding of lipid-rich R-like subunits to splenocytes is insufficient, by itself, to initiate a triggering event since it is both quantitatively and qualititatively indistinguishable in lymphoid cells from the LPS responder ( C3HeB FeJ ) mouse and the LPS non-responder ( C3H HeJ ) mouse.