Evaluation of hydroxylapatite root implants in baboons.

To determine if there is a need for close conformation of a hydroxylapatite implant to the root socket for successful prevention of alveolar ridge resorption after tooth extraction, second premolars and lateral incisors of six mature baboons were extracted bilaterally, and custom-fitted root replicas or half-length, plug-shaped forms of hydroxylapatite were implanted in the fresh sockets. Results showed that precise fit, as achieved by a custom-fitted implant, was not necessary for success. All implants were completely accepted, with evidence of new bone formation continuing for up to six months, the duration of the study. No resorption of the alveolar ridge was observed by gross or microscopic examination.

Dimethyl sulfide in milk of lactating dairy cows fed various sulfur compounds.

Mature dairy cows in late lactation were given capsules containing 26, 40, 60, or 80 g of D,L-methionine; 32, 49, 69, or 90 g of methionine hydroxy analog; or 1, 2, or 4 ml of dimethyl sulfide. Animals used as controls received capsules containing water. Milk was collected at hourly intervals for 5 h and analyzed for dimethyl sulfide content by gas chromatography. All experimental cows were managed and fed (mainly corn silage plus concentrate with some hay and pasture) with the rest of the herd but were limited to water and clover hay during the 5-h experimental periods. Administration of 60 or 80 g of D,L-methionine or 1, 2, or 4 ml of dimethyl sulfide resulted in the appearance of dimethyl sulfide in the milk. The concentration of dimethyl sulfide in milk from cows receiving orally administered dimethyl sulfide (2 or 4 ml) was greatest at 1 h. When D,L-methionine (60 or 80 g) was given, dimethyl sulfide concentrations were lower and peaked later in the sampling period. The maximum concentration of dimethyl sulfide in the milk was 4.5 ppb when 4 ml of dimethyl sulfide were administered orally. No dimethyl sulfide was in the milk for any amount of methionine hydroxy analog, for 26 or 40 g of D,L-methionine, or for control capsules.

Fluoride uptake and dissolution behavior of a synthetic dental enamel-like substrate.

A new ceramic form of hydroxylapatite and enamel were found to behave similarly in regard to their acid dissolution behavior in the presence and absence of topically applied fluoride. Discrepancies between the two materials can be explained by morphological differences between the rough enamel and smooth ceramic particles.

Synthesis and narcotic agonist-antagonist evaluation of some 2,6-methano-3-benzazocine-11 propanols. Analogues of the ring C bridged oripavine-7-mehtanols.

A general synthesis of variously substituted 2,6-methano-3-benzazocine-11-propanols is described. Nine N-CH3 derivatives and their corresponding N-cyclopropylmethyl counterparts were prepared and studied in the mouse acetylcholine induced writhing and rat phenazocine antagonism tests. The results are compared with literature information on the bridged oripavine methanols. It is concluded that the synthetic analogues have a different structure-activity profile, in general being weak agonists but potent antagonists.

Utilization of proteins by the equine species.

Protein digestion, nitrogen retention, plasma protein, plasma urea, and plasma-free amino acids were determined for ponies fed 3 different protein supplements. Substitution of casein, corn gluten meal, or corn gluten meal plus lysine for a portion of the cornstarch in a low-protein basal ration increased apparent digestion of protein. Substitution with either casein or corn gluten meal plus lysine produced a significant increase (P less than 0.05) in nitrogen retention, whereas the corn gluten meal substitution did not. Nitrogen retention, expressed as percentage of nitrogen absorbed, was increased significantly (P less than 0.05) by the addition of casein to the basal ration. Significant change in plasma protein concentration did not occur when different sources of protein were added to the basal ration, but plasma urea nitrogen increased significantly (P less than 0.05) in the ponies given the casein variation of the ration. Lysine supplementation resulted in a marked increase in plasma lysine concentration. Seemingly the equine species responds to differences in the quality of dietary protein.

Involvement of vitamin B6 in the dethiomethylation of methionine by rumen microorganisms.

The dethiomethylation of methionine by a dialyzed extract obtained from the protozoa-rich fraction of rumen fluid is stimulated 2.5-fold by pyridoxal phosphate and strongly inhibited by deoxypyridoxine, a pyridoxal phosphate antagonist. These effects are not seen with undialyzed extracts or with whole rumen fluid. It is suggested that the anaerobic dethiomethylation of methionine by rumen microorganisms requires pyridoxal phosphate as a cofactor.