Effects of muscarinic receptor antagonists on acetylcholine-induced contractions of jejunal smooth muscle in horses.

This study investigated the effects of a muscarinic type 1 (M(1)), 2 (M(2)), and 3 (M(3)) antagonists (4-DAMP, pirenzepine, and methoctramine, respectively) on acetylcholine (Ach)-induced contractions of longitudinal jejunal muscle strips of horses. Strips were irrigated with Krebs-Henseleit solution gassed with 95% O(2) and 5% CO(2), and the developed tension in response to Ach was recorded before and after incubation with increasing concentrations of 4-DAMP (10(-8)-10(-6) M), pirenzepine (10(-6)-10(-4) M), and methoctramine (10(-5)-10(-3) M). When competitive antagonism was characterized, the affinity constant (pA(2)) was calculated by Schild plots.

In vivo surface strain and stereology of the frontal and maxillary bones of sheep: implications for the structural design of the mammalian skull.

Does the skull of the sheep behave as a tube or as a complex of independent bones linked by sutures? Is the architecture within cranial bones optimized to local strain alignment? We attempted to answer these questions for the sheep by recording from rosette strain gauges on each frontal and maxillary bone and from single-axis gauges on each dentary of five sheep while they fed on hay. Bone structure was assessed at each rosette gauge site by stereological analysis of high-resolution radiographs. Structural and strain orientations were tested for statistical agreement.

Circadian variation of portal, arterial and venous blood levels of melatonin in pigs and its relationship to food intake and sleep.

Circadian levels of melatonin were determined in the hepatic portal vein, cranial vena cava, and the lower aorta of ten juvenile pigs. Blood was sampled every hour for a total of 24 hr via temporary cannulas introduced into blood vessels under anesthesia. No peak levels of melatonin were found in the mid-scotophase, but hepatic portal concentrations peaked at 06.