The effect of stocking densities on reproductive performance in laboratory zebrafish (Danio rerio).

Despite the growing popularity of the zebrafish model system, the optimal husbandry conditions for this animal are not well defined. The aim of this study was to examine the effect of stocking density on reproductive performance in zebrafish. In this study, undertaken by eight different zebrafish facilities, clutches of at least 200 wild-type zebrafish embryos from a single pairwise mating were produced at each participating institution and subsequently reared according to "in-house protocols" until they were 14 weeks old. Fish were then randomly assigned into treatment groups with balanced sex ratios and densities of 3, 6, or 12 fish/L. After a 1-month acclimation period, fish were spawned in pair crosses every 2 weeks for 3 months, for a total of six spawning dates. The number of viable and nonviable embryos produced in each clutch were counted at 1 day postfertilization. Although there was a great deal of variability in clutch size and percent spawning success among laboratories, there were no significant differences in average clutch size, spawning success, or percent viable among the treatment densities. These data suggest that using stocking densities as high as 12 fish/L does not have a negative impact on performance, when measured by reproductive performance.

The impact of cirrhosis on CD4+ T cell counts in HIV-seronegative patients.

BACKGROUND: Studies of the progression liver fibrosis in human immunodeficiency virus (HIV) and hepatitis C virus-coinfected patients suggest that cirrhosis is associated with immunosuppression, as measured by low absolute CD4(+) T cell counts. However, we hypothesized that, in patients with advanced liver disease, low CD4(+) T cell counts may occur secondary to portal hypertension and splenic sequestration, regardless of the presence or absence of HIV infection. METHODS: Sixty HIV-seronegative outpatients with cirrhosis were enrolled during the period 2001-2003 in a prospective, cross-sectional study of the association between liver disease and CD4(+) T cell counts and percentages. Demographic characteristics, liver disease-related characteristics, and laboratory results--including CD4(+) T cell parameters--were collected. RESULTS: A total of 39 patients (65%) had a low CD4(+) T cell count; 26 patients (43%) and 4 patients (7%) had CD4(+) T cell counts <350 and <200 cells/mm(3), respectively. Abnormal CD4(+) T cell counts were associated with splenomegaly (P=.03), thrombocytopenia (P=.002), and leukopenia (P<.001). The percentage of CD4(+) T cells was normal in 95% of patients who had a low absolute CD4(+) T cell count. CD4(+) T cell counts were significantly lower among cirrhotic patients than among 7638 HIV-seronegative historic control subjects without liver disease. CONCLUSIONS: Cirrhosis is associated with low CD4(+) T cell counts in the absence of HIV infection. Discordance between low absolute CD4(+) T cell counts and normal CD4(+) T cell percentages may be attributable to portal hypertension and splenic sequestration. Our findings have significant implications for the use and interpretation of absolute CD4(+) T cell counts in HIV-infected patients with advanced liver disease.