The role of alpha and beta adrenergic receptors in cortisol-induced hyperglycaemia in the common African toad (Bufo regularis)

The role of adrenergic receptors in cortisol-induced hyperglycaemia is not well known. The present study investigates the effects of adrenergic receptor blockers in cortisol-induced hyperglycaemia in the common African toad (Bufo regularis). Each toad was fasted and anesthetized with sodium pentobarbitone (3 mg/100 g i.p). The animals (control) received intravenous (i.v) injection of 0.7% amphibian saline while animals (untreated) were given cortisol (20 μg/kg). In pre-treatment groups, animals received prazosin (0.2 mg/kg i.v), propranolol 0.5 mg/kg or combination of prazosin (0.2 mg/kg i.v) and propranolol (0.5 mg/kg i.v) before i.v injection of cortisol (20 μg/kg). Thereafter, blood samples were collected for estimation of blood glucose level using the modified glucose oxidase method. Cortisol caused significant increase in blood glucose level from 44.4±3.8 to 71.7±9.7 mg/dl. Pretreatment of the toads with propranolol (0.5 mg/kg i.v) caused significant reduction (p≤ 0.01) in cortisolinduced hyperglycaemia while pre-treatment with prazosin (0.2 mg/kg i.v) produced no significant effect on hyperglycaemia induced by cortisol. The combination of both prazosin and propranolol completely abolished the effects of cortisol on blood glucose level. The results suggest that cortisol-induced hyperglycaemia in the toad (B. regularis) is mediated probably by both the α- and β-adrenergic receptors with the beta adrenergic receptors playing dominant role.Keywords: Cortisol, hyperglycaemia, prazosin, propranolol, amphibian saline, common African toad.African Journal of Biotechnology Vol. 12(36), pp. 5554-555

The role of adrenergic receptors in nicotine-induced hyperglycemia in the common African toad (Bufo regularis)

The role of adrenergic receptors in nicotine-induced hyperglycaemia has not been well studied in amphibians. Thus, this study investigates the effects of alpha and beta adrenergic receptor blockers in nicotine-induced hyperglycaemia in the common African toad Bufo regularis. Toads fasted for 24 h were anaesthetized with sodium pentobarbitone (3 mg/100 g body weight) intraperitoneally (i.p) and given intravenous (i.v) injection of 0.7% amphibian saline, or nicotine (50 µg/kg), nicotine(50 µg/kg i.v) 30 min after pretreatment with prazosin (0.2 mg/kg i.v), propranolol (0.5 mg/kg i.v) or combination of both prazosin (0.2 mg/kg i.v) and propranolol (0.5 mg/kg, i.v). Thereafter, blood samples were also collected from truncus arteriosus for estimation of blood glucose level using the modified glucose oxidase method. Nicotine caused significant increase (P<0.01) in the levels of blood glucose in the common African toad. Pre-treatment of the toads with prazosin (0.2 mg/kg i.v) or propranolol (0.5 mg/kg, i.v) significantly (p < 0.01) reduced the hyperglycaemia induced by nicotine (50 µg/kg i.v). However, the combination of prazosin (0.2 mg/kg i.v) and propranolol (0.5 mg/kg, i.v) abolished the hyperglycaemic effect of nicotine (50 µg/kg i.v). The above results on glucose metabolism suggests involvement of both alpha and beta adrenoceptors in nicotine-induced hyperglycaemia in common African toad B. regularis.Keywords: Nicotine, hyperglycaemia, prazosin, propranolol, common African toad Bufo regularis.African Journal of Biotechnology, Vol 13(30) 3101-310

Some thermo-physical properties of yam cuts of two geometries

The effects of variation of temperature (-18 to 33°C) and geometries (slab and cylinder) on some thermo-physical properties of white yam were investigated. The measured parameters were density, specific heat, and thermal diffusivity at constant moisture level of 72.7% ± 0.69 (wet basis) using transient heat transfer method. Both the density and specific heat of the sample increased with increase in temperature to maximum levels after which further increase led to a reduction of the values of these parameters; however, they were independent of sample’s geometry. The rate of heat diffusion per second for the yam as measured was between 2.365 to 11.86 x 10-8 m2 and 2.676 to 8.062 x 10-8 m2 for slab and cylinder respectively. The thermal diffusivity and computed thermal conductivity were found to increase with increase in temperature. Conclusively, these thermo-physical properties were correlated with temperature using polynomials of the third order empirical model