The erythrocyte membrane was investigated in weanling male rats pair fed with magnesium-deficient and control diets for 8 days. Fluorescence polarization studies revealed a 15% increase in the fluidity of membranes from deficient rats. A similar increase in the fluidity of liposomes indicated that protein was not involved. The change was associated with decreased osmotic fragility of intact erythrocytes; the cells lost their biconcavity and had a flattened appearance with surface irregularities. Analysis of the membranes showed decreased amounts of magnesium, cholesterol, and sphingomyelin in the deficient group. The reduced ratios of cholesterol to phospholipid and sphingomyelin to phosphatidylcholine were consistent with the increased fluidity. Addition of physiological amounts of magnesium to the medium rigidified membranes incubated in tris(hydroxymethyl)-aminomethane buffer, and this was prevented by the presence of EDTA. Cross-incubation experiments with erythrocyte ghosts and plasma from the two groups of rats showed that magnesium-deficient plasma increased the fluidity of control ghosts and control plasma rigidified ghosts from magnesium-deficient rats. Addition of sufficient magnesium chloride to raise the magnesium content of deficient plasma to normal had no significant effect. These results show that the increased fluidity of the erythrocyte membrane in magnesium deficiency is due to physicochemical exchange with the plasma. Although magnesium can directly influence membrane fluidity, the change during its deficiency in vivo is mainly mediated indirectly via disturbances in lipid metabolism.

The effect of capsaicin, a pungent ingredient in capsicum fruit, upon gastric acid secretion and mucosal blood flow was assessed in the anesthetized rat. At each 15 minute interval, 0.3 ml saline solution, with or without various doses of pure synthetic capsaicin (the doses varied from 50 to 2,000 microgram/kg rat) was delivered into the gastric lumen via a gastric fistula. The gastric contents were withdrawn after 15 minutes for acid assay and replaced with a new saline solution. Capsaicin of increasing doses (up to 1,000 microgram/kg) progressively increased the acid output. Gastric inhibitors hexamethonium and atropine, completely abolished the acid secretion induced by capsaicin whereas secretin only partially reduced such a response. The systemic blood pressure was not affected by the capsaicin or the method employed. However, the aminopyrine clearance which was the indicator of the gastric mucosal blood flow increased in accordance with the increase in the acid output. It is suggested that the effect of capsaicin on the acid secretion and mucosal blood flow is by the release of endogenous gastric secretagogues which increase both tissue perfusion and the secretory activity.

Heat stress is a life-threatening factor in commercial broilers raised in the tropics (e.g., Thailand) without temperature-controlled housing facilities. However, these temperature-controlled facilities are hardly affordable by small-scale farmers. To avoid such limitations, a Thai indigenous crossbred line (C line), selected as a candidate meat-type chicken to survive in the tropical environment, was examined for its capacity to tolerate the tropical climate and for its immune functions. Comparisons, in terms of the stress and innate and humoral immune responses using the heterophil-to-lymphocyte ratio, abdominal exudative cell phagocytic activities, and serum anti-SRBC titer, were made between C-line chicks and the corresponding cohorts from their low-meat-yielding Thai indigenous (T line) parents and from high-meat-yielding commercial broiler (B line) chickens. The responses were evaluated in the 3 different seasons of Thailand (monsoon, summer, and winter). Significantly higher stress levels (P < 0.001), based on the heterophil-to-lymphocyte ratios, were detected in the B line chicks compared with those in the T and C lines at all ages regardless of the season, suggesting that the B line chicks were vulnerable to tropical heat stress whereas the T and C lines were well adapted, with no significant differences detected between the latter two. The innate and humoral immunities of B-line chicks were significantly lower (P < 0.001) than those of T-and C-line chicks. The differences were immense in the summer, when the immunity of the C-and T-line chicks outperformed that of the B-line chicks, with mean opsonized-SRBC phagocytic activities of 7.90, 8.31, and 4.74 and mean IgG titers of 8.00, 8.40, and 5.10, respectively. This could be a consequence of the heat stress causing immunosuppression in B-line chicks, and could represent a noteworthy adaptation to the tropical conditions of the C-and T-line chicks. The apparent climate-tolerant capacity conserved in the C-line chickens, with approximately 50% T genetics, could serve as a guideline for further genetic improvement toward a high-meat-yielding chicken that retains a suitable heat tolerance.

No abstract