Search

The nurse practitioner and physician's assistant are new health practitioners providing primary health care. When teamed with family physicians, these new health practitioners can extend patient services. Family physicians should be trained to work with new health practitioners effectively. Presented is a model where a nurse practitioner and family practice residents work as co-practitioners in a family practice unit. A nurse practitioner in this role can improve the continuity of the relationship between patient and provider in a family practice residency.

Actin was localized in the sperm head of the plains mouse, Pseudomys australis, using NBD-phallacidin, a fluorescent-labeled phallotoxin. It was found to be present in the two ventral hooks in sperm from the testis, epididymis, and vas deferens. Faint fluorescence was observed in other regions of the sperm head, whereas autofluorescence occurred in the midpiece of the tail in some preparations. The material in the ventral hooks was also found to be birefringent, which is consistent with it showing preferential orientation.

Mammalian spermatozoa have previously been shown to contain actin, but its subcellular localization and function have not been elucidated. In this study, actin has been localized at the ultrastructural level in human, bull, rabbit, and golden hamster spermatozoa by a monoclonal antiactin antibody and a preembedding immunogold labeling technique. Specific labeling was localized 1) around the connecting piece in the neck region of sperm from all four species, although a species-specific pattern was evident; 2) on the external surface of the fibrous sheath of human sperm; 3) in the perinuclear space underlying the postacrosomal sheath of bull and rabbit sperm; and 4) between the plasma membrane and outer acrosomal membrane along the concave margin of the hamster sperm head. SDS-PAGE and Western blots immunostained with the monoclonal antibody confirmed the presence of actin in SDS extracts of Percoll-purified sperm from each species.

Ultrastructural and histochemical techniques have been utilized to study selected aspects of the fine structure of the three-hooked sperm head of the plains mouse, Pseudomys australis. The peripheral layer of the two ventral hooks was found to consist of a continuation of the postacrosomal dense lamina. Parallel ridges connected the dense lamina and plasma membrane in the postacrosomal region and ventral hooks. Both these regions stained intensely with silver nitrate. The distribution of actin filaments in the hooks was investigated using NBD-phallacidin. Fluorescence was more intense in the apical regions of the ventral hooks, and two bands of fluorescence extended caudally from their base. It was also shown that the equatorial segment of the acrosome extended onto the dorsal hook. The structural features of the three hooks are discussed in relation to their possible functional significance.

Fifteen cats and 6 dogs developed ventricular arrhythmias during halothane anesthesia. Halothane was administered by precision vaporizer, using a semiclosed anesthetic system. Cardiac arrhythmias were diagnosed within 5 to 10 minutes after a surgical plane of anesthesia was achieved. Arrhythmias in 9 of 15 cats and 3 of 6 dogs were converted to sinus rhythm by increasing the inspired halothane concentration. Conversion to sinus rhythm occurred within 4 minutes. Cardiac arrhythmias were reestablished in 8 of 9 cats and 2 of 3 dogs, after decreasing the inspired halothane concentration to its original value. Increasing the inspired halothane concentration can convert anesthetic-associated ventricular arrhythmias to sinus rhythm in dogs and cats.

The distribution of monomeric and polymeric actin in spermatozoa from the bull, boar, rabbit, human, rat, mouse, golden hamster, and guinea pig has been examined by using a monoclonal antiactin antibody and NBD-phallacidin. Actin was present in sperm from each species. When the monoclonal antibody was used, there was a species-specific distribution and intensity of fluorescence, but no generalized pattern. Specific fluorescence was noted in the neck and principal piece of human sperm; in the postacrosomal region, neck, and midpiece of bull and boar sperm; in the postacrosomal region, neck, and principal/equatorial segment border of rabbit sperm; in the neck region of hamster sperm; and in the neck, midpiece, and principal piece of rat, mouse, and guinea pig sperm. Sperm from all eight species displayed no specific fluorescence with NBD-phallacidin, indicating that actin was present in a nonfilamentous form. SDS extracts of sperm were analyzed by SDS-PAGE and Western blotting; in sperm from each species, a 42-kD protein with specific affinity for the monoclonal antibody was present.

The sperm head of many Australian hydromyine rodents has three curved hooks projecting from its anterior margin; the structure of the hooks has been characterized, but their function is unknown. In this study, we have investigated whether the hooks might have evolved to assist sperm penetration through more formidable egg vestments, particularly the zona pellucida. Cumulus-oocyte complexes were obtained from two species that possess a three-hooked sperm head (Pseudomys australis and P. nanus) and one species that does not (Notomys alexis) and examined by light and electron microscopy. After fixation in the presence of ruthenium red, the zona pellucida was found to consist of a fibrillar meshwork, but there were no interspecific structural differences. A corona radiata was absent, and the cumulus extracellular matrix was composed of filaments and electron-dense granules in each species. Measurements of the zona thickness in freshly ovulated, unfixed oocytes revealed that it was thinnest (7.8 microns) in P. australis, which has a three-hooked sperm head, and thickest (11.4 microns) in N. alexis, the species in which the ventral hooks are absent. Hence, no correlation was found between the thickness of the zona pellucida or the structure of the cumulus-oocyte complex, and the presence of three hooks on the sperm head. We conclude, therefore, that it is unlikely that the evolution of the three-hooked sperm head is an adaptation for penetration of increased barriers around the oocyte.

The sperm head of the plains mouse, Pseudomys australis, has three curved hooks projecting from its anterior margin. The two ventral hooks have previously been shown to consist largely of an extension of the subacrosomal material. To characterize further the structure and composition of the ventral hooks, we have examined their formation during spermiogenesis using transmission electron microscopy, silver staining, and actin localization with NBD-phallacidin. The ventral hooks develop as an extension of the perinuclear space and postacrosomal dense lamina on the anteroventral margin of the sperm head. Bundles of 6-nm-thick filaments appear in the core of each hook; these are probably actin filaments based on staining of the hooks with NBD-phallacidin. Just prior to spermiation, electron-dense material condenses in the core of the ventral hooks and concurrently in the perinuclear space in the remainder of the sperm head. The two ventral hooks thus appear to consist of a core of perinuclear material and actin filaments, which is enclosed by a continuation of the postacrosomal dense lamina.