Acute toxicity and adverse effects of aqueous and ethanol extracts of Parkia biglobosa pods on biochemical parameters of Clarias gariepinus

The acute toxicity of the aqueous and ethanol extracts of Parkia biglobosa pods against Clarias gariepinus was investigated under laboratory conditions. Agitated behaviours and respiratory distress were also observed during the exposure period. The adverse effects on biochemical parameters were assessed using semi-static bioassays for 28 days. The ethanol extract of P. biglobosa pods was found to be more acutely toxic with a 96 h LC₅₀ value of 13.96 mg l^?1 than the aqueous extracts, with a 96 h LC₅₀ value of 19.95 mg l^?1 against C. gariepinus. Both extracts induced agitated behaviours and respiratory distress in exposed organisms. The activities of superoxide dismutase (SOD), catalase (CAT) and the concentration of malondialdehyde (MDA) were significantly lower (p < 0.05) in groups of organisms exposed to extracts of P. biglobosa when compared with the control group after 14 days. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) were also significantly (p < 0.05) lower compared with activities of the enzymes in the control group after 28 days. The current study has shown that the introduction of P. biglobosa pods into aquatic ecosystems is acutely toxic to fish and would possibly be to other non-target aquatic organisms especially invertebrates.     

STUDY ON THE PROLIFERATIVE STATE OF HAEMOPOIETIC STEM CELLS (CFU)

Hydroxyurea was used to study the proliferation rate of haemopoietic stem cells (CFUJ in normal mice, after irradiation or transplantation into irradiated recipients. It was demonstrated that the proliferation rate of endogenous CFU_S (endo-CFU,) and exogenous CFU_S (exo-CFU_s) are identical. After irradiation (650 R) the surviving endo-CFU_s begin to proliferate immediately. By contrast exo-CFU, transplanted into the irradiated recipient mouse (850 R), begin to proliferate only after about 30 hr. However, injection of isoproterenol (which stimulates adenyl cyclase) or dibutyryl cyclic adenosine 3′,5′-monophosphate shortly after marrow cell graft, triggers the transplanted CFU_S into cell cycle as shown by an almost immediately increased sensitivity to hydroxyurea. Isoproterenol is capable of inducing DNA synthesis also in stem cells of normal mice but it takes about 20 hr before CFU, become to be increasingly sensitive to hydroxyurea.     

Uptake and leaching of nitrogen from artificial urine applied to grassland on different dates during the growing season

Artificial urine, equivalent to 30 g N m^-2, was applied to replicated plots in a perennial ryegrass (Lolium perenne L.) sward, each plot receiving a single application on one of six dates between July and November 1990. Recoveries of urine-N in herbage up to the end of the growing season in November decreased linearly for consecutive application dates, ranging from 40% of the urine-N applied in July to a negligible proportion of the final application. In contrast, contents of urine-derived N remaining in the soil (to 1-m depth) in November increased from 3% of the N applied in July to 66% for the final application. Almost all of this was present as nitrate + nitrite-N. Only soils that had received urine in September or later contained significantly greater quatities of mineral-N than the control plots. The mineral-N content of soils collected the following April indicated that most of this urine-derived N had been lost from the soil over the winter. Estimates of the quantities of N leached ranged from 0.7 g N m^-2 from untreated plots to 18.6 g N m^-2 from plots treated with urine in November. Although grass yields and N uptakes in March and April provided evidence of a residual effect from the previous year's urine applications, contents of mineral-N and of potentially mineralisable N in urine-treated soils in April were not significantly different from those in untreated soils.