The effect of metabolic and hypercapnic acidosis on myocardial blood flow was studied during intravenous infusions of hydrochloric acid solutions (n = 12) and during passive ventilation with 5% CO2 (n = 5) in anaesthetized, closed chest dogs. Below a pH of 7.2 metabolic acidosis at normal arterial CO2-tensions caused an increase of coronary blood flow and a decrease of coronary vascular resistance associated with a narrowed myocardial arteriovenous O2-difference, indicating vasodilation at unchanged myocardial oxygen consumption. In propranolol-pretreated dogs myocardial blood flow and coronary oxygen AV difference remained unaffected, suggesting that the coronary dilatory effect of metabolic acidemia involves beta adrenergic stimulation. Coronary vasodilation induced by increasing arterial pCO2 was found to the significantly greater as compared with the dilatory effect of metabolic acidosis at the same blood pH level. Blocking of beta receptors did not reduce the coronary response to increased arterial CO2-tensions. It is concluded that the coronary vasodilation observed during hypercapnic acidosis is neither mediated by a beta adrenergic stimulation nor dependent of the concomitant change in blood pH. The possible sites of the coronary dilatory actions of increased arterial CO2-tensions are discussed.

Acidosis↗

PubMedDate not supplied

Open-air-nesting honey bees Apis dorsata and Apis laboriosa differ from the cavity-nesting Apis mellifera and Apis cerana in brood hygiene behaviour.

The cavity-nesting Apis mellifera and Apis cerana bees detect, uncap, and remove diseased brood. The hygiene behaviour of open-air-nesting bees Apis dorsata and Apis laboriosa was investigated in India and Nepal. Sealed A. dorsata pupae were pin-killed or deep-frozen. The workers removed 73 or 37% of damaged pin-killed pupae depending on the diameter of the pins, and only 7% of the frozen undamaged pupae. Migrating A. dorsata and A. laboriosa left unopened the sealed brood in deserted combs. Thus, A. dorsata and A. laboriosa do not open undamaged cells with dead brood. This behaviour is a more efficient mechanism in preventing the spread of diseases and parasitic mites than uncapping and removing dead pupae by A. mellifera and A. cerana. It may be beneficial for migrating A. dorsata and A. laboriosa to temporarily disuse part of the comb cells in exchange for arresting the mites there and thus reducing the increase of their population.

Animals↗

PubMedDate not supplied

Molecular epidemiology of Haemophilus influenzae type B: failure of rifampin prophylaxis in a day care center.

Two of 16 children (14 to 24 months old) in a day care center developed Haemophilus influenzae type B (HIB) meningitis within a 3-week period. One day after the first child was diagnosed 13 children and 5 personnel received rifampin. Two children received no rifampin because they had received the HIB vaccine. After the second child was diagnosed HIB carriage was detected in 3 of the 15 children and 2 of 43 family members but in none of the caretakers. All seven isolates were biotype 1 but outer membrane protein analysis revealed two strains. One child, who had received rifampin for only 2 days initially, and a sibling of another child carried a common strain. A second strain was recovered from: the first meningitic child; the second meningitic child and another child, both of whom had initially received rifampin (20 mg/kg for 4 days); and one HIB-vaccinated child and his father. After the second rifampin administration all carriers were free of HIB. One child who was not treated with rifampin (because he had been vaccinated for HIB) was the apparent source of reinfection for the day care group. These data emphasize that when rifampin prophylaxis is initiated it should be administered to all classroom contacts.

Adult↗

PubMedDate not supplied