Biomedical subjects
Publications and source records attributed to N R Perkins.
Cesarean section has become a common surgical procedure and there is a tendency for both veterinarians and their clients to regard it as routine. It is important to remember, however, that a cesarean section entails major abdominal surgery, with inherent risks, irrespective of the prevailing conditions or personnel involved.
This article briefly reviews the clinical management of emergency conditions likely to be encountered by veterinarians responsible for the reproductive health of mares. The article discusses rectal tears, breeding injuries, uterine torsion, placental hydrops, and prepubic tendon rupture. A major component discusses a recommended approach to dystocias, and the management of such complications as uterine rupture and prolapse and postpartum hemorrhage. Management of retained fetal membranes and septic metritis is addressed.
Topics addressed in this article include complications of castration, scrotal and inguinal hernias, torsion of the spermatic cord, traumatic injuries to the external genitalia, and posthumous collection of spermatozoa. A concise overview of the clinical management of emergency cases is provided.
Existence of ultradian variation in serum progesterone concentration and the relation between progesterone and luteinizing hormone (LH) secretory patterns were investigated in nonpregnant and pregnant mares. Blood samples were taken every 15 minutes for a 24-hour period on day 8 of the estrous cycle and day 18 of pregnancy, respectively. Progesterone and LH concentrations were determined by radioimmunoassay. Progesterone was secreted in pulsatile manner in nonpregnant and pregnant mares. Luteinizing hormone also was secreted in a pulsatile manner in both groups of mares. There was little temporal relation between LH and progesterone pulses in either pregnant or nonpregnant mares.
A 15-year-old Standard-bred mare was examined because of signs of abdominal discomfort in late gestation. Palpation per rectum revealed tight broad ligaments above and below the uterus, with the right broad ligament running across the top of the uterine body down toward the left, ventral side of the abdomen. A diagnosis of counterclockwise uterine torsion was made and surgical correction was approached via a left, flank laparotomy with the horse standing. The uterus was repositioned and a uterine tear encompassing 180 degrees of the uterine surface was found in the lateral, uterine body just cranial to the cervix. A live colt was delivered vaginally after uterine repositioning and the laparotomy incision was closed. The uterine tear was then repaired via a blind, vaginal approach. The mare was discharged 10 days after surgery. Repair per vaginum of a uterine tear is presented as an alternative treatment in cases for which the tear is recent, abdominal contamination is minimal, and the tear is easily accessible from the vaginal approach.
Pathways of peripheral lymph flow from the legs in horses were studied with casts, and with light and electron microscopic techniques. Although lymph nodes in horses occur in large groups, each lymph vessel draining from the periphery appeared to terminate on a single node within a group. The larger branches of each vessel divided either on the node surface or after penetrating into the node, and 25 to 60 terminal afferent vessels entered either the subcapsular, medullary or trabecular sinuses. Numerous initial efferent lymphatics arose either within the medulla, or at its surface, and they often coalesced to form an anastomosing network on the node surface. Almost all of the one to four efferent lymphatics that left the vicinity of the node terminated on other nodes, usually within more centrally placed groups. This arrangement may aid in the amplification and propagation of immune responses initiated in primary nodes.
The pathways through which lymph flows from terminal afferent lymphatics to the lymph sinuses, and from the sinuses to initial efferent lymphatics, were studied in horse lymph nodes by using Microfil casts and electron microscopy. Terminal afferent lymphatics are continuous with the subcapsular sinus through oval holes, about 3 microns wide, along their length, and through larger openings near their end. Other terminal afferents penetrate into the node within trabeculae and are supported by processes across the lumen. They connect with trabecular and medullary sinuses through oval or round holes, generally 20-30 microns across. Some of these have processes, similar to the luminal strands of the adjacent sinuses, extending across them, apparently providing reinforcement. Initial efferent lymphatics receive lymph from medullary sinuses through holes which are similar to those in afferent lymphatics, though more common, especially near the origin of the vessel. Initial efferents within the medulla appear to be supported by the luminal strands of the surrounding medullary sinuses. It seems likely that these strands, like the trabeculae which surround the penetrating afferent lymphatics, may help to keep the lymphatic vessels open as the node swells while draining an area of infection.
The two main tributaries of the ovine portal vein are the splenic vein, which carries blood mainly from the spleen and forestomachs, and the cranial mesenteric vein. In newborn lambs, these veins are of similar size and they converge at an angle of about 120 degrees. Blood which is carried from the intestines in the cranial mesenteric vein is not completely mixed with that from the splenic vein and it is preferentially distributed to the right side of the liver. As the fore-stomachs develop, the splenic vein becomes relatively larger than the cranial mesenteric and its direction of flow becomes oriented more caudally. Thus in the portal vein of sheep, blood in the cranial mesenteric vein meets a larger volume of blood flowing in almost the opposite direction from the splenic vein. As a result, the extent of mixing of blood in the portal vein of adult sheep is much greater than in young lambs.