Vascular anatomy of the descending colon of the horse.

The blood supply to the descending colon of the horse was studied by gross dissection and methyl methacrylate corrosion casts. The arterial supply is derived from the left colic artery and cranial rectal artery with the left colic artery supplying approximately the proximal three fourths. Each artery gives off four to eight arcuate arteries that form a series of anastomosing arcades. The arcade pattern continues to form a marginal artery that parallels the long axis of the colon. Small branches from the marginal artery anastomose with adjacent branches to form a secondary arcade. The secondary arcade lies approximately 1 cm proximal to the mesenteric teniae and sends off long arteries at regular intervals that course circumferentially around the bowel. The long arteries begin under the serosal mesothelium and perforate the muscular layers to course in the submucosal layer. The long arteries branch off supplying the wall of the colon and arborize over the antimesenteric surface, anastomosing with the vessels from the opposite side. The result is the formation of a series of vascular rings surrounding the colon. Venous return, in general, parallels the arterial supply.

Dihydrocapsaicin (DC) protects against serum hyperlipidemia in guinea pigs fed a cholesterol-enriched diet.

Juvenile guinea pigs were maintained either on a standard diet (cholesterol-free) or a 0.5% cholesterol-enriched vitamin C deficient diet for six weeks. Half of the animals of each dietary group were treated with dihydrocapsaicin (DC) at the rate of 8 mg per animal per day. DC administration significantly altered food consumption, body weight, and dry weight of feces of animals maintained on the standard diet. In addition, the mean serum triglyceride concentration of these animals was significantly decreased with DC treatment. Food consumption, body weight and (wet) fecal weight of animals maintained on the 0.5% cholesterol-enriched diet were significantly lower than the corresponding values in control animals even though the liver was much larger in proportion to the total body weight. The mean serum cholesterol concentration of the animals fed a cholesterol-enriched diet was significantly elevated. However, in animals also receiving DC, the cholesterol and triglyceride levels were comparable to controls fed a regular diet. The gross and microscopic fatty infiltration of the liver observed in the cholesterol-fed animal were minimized in those animals fed cholesterol and DC.

Application of isolated hepatocytes to studies of drug metabolism in large food animals.

A definitive hazard assessment of xenobiotics translocated through food animals into edible products such as meat or milk requires a complete analysis of metabolism in food animals. However, large animal metabolism studies present many experimental difficulties. None of several in vitro alternatives such as subcellular fractions has been established as an acceptable predictor of in vivo metabolism. The feasibility of using isolated hepatocytes to predict the metabolism of xenobiotics, both quantitatively and qualitatively, in large ruminant animals (e.g. cattle) is being studied in our laboratory. A procedure was developed for isolating hepatocytes aseptically from the caudate process of the liver which was obtained surgically from 100-125 kg calves. A modified two-step vascular perfusion procedure provides hepatocyte suspensions that are typically greater than or equal to 85% viable and greater than or equal to 1 X 10(7) viable hepatocytes/g of liver (wet wt). Xenobiotic metabolism has been evaluated in suspensions and primary cultures using aldrin epoxidation, ethoxycoumarin O-deethylation, and 7-hydroxycoumarin glucuronidation and sulfation. Metabolic activities are relatively short-lived in suspensions less than or equal to 4 h, but quite stable up to 10 h when cultured on collagen-coated plates in chemically defined medium. Bovine hepatocytes behave similarly in culture to rodent hepatocytes. Although primary culturing of hepatocytes is more difficult than suspensions, primarily due to the asepsis requirements, it is the method of choice for xenobiotic metabolism determinations in isolated hepatocytes of cattle.

Biliary motility: postnatal changes in guinea pigs.

Intravital microscopy, a new in vivo technique, documented age-dependent changes in choledochoduodenal junction motility in male guinea pigs. In the guinea pig, the choledochoduodenal junction served as a pump that actively emptied its luminal contents into the duodenum. In the neonates (less than or equal to 1 wk old), this choledochoduodenal junction pump was not fully developed. Unlike the older guinea pigs, some neonates had an incompetent sphincter ductus choledochi (SDC) allowing retrograde flow of bile during ampullary contractions. While fasting, neonates had decreased frequency of SDC (1.2 +/- 0.4 contractions/min) and ampullary (0.1 +/- 0.1 contractions/min) contractions as compared to juveniles (4-6 wk old) (SDC = 6.4 +/- 1.0; ampulla = 1.2 +/- 0.2 contractions/min) and adults (greater than 1 yr old) (SDC = 6.7 +/- 1.6; 0.8 +/- 0.2 contractions/min). Following a meal (Ensure), unlike older guinea pigs, the neonate did not have a significant increased duration and decreased frequency of SDC contractions. Altered neonatal SDC motility correlated with an incompletely developed SDC including decreased muscle mass and mucosal thickness. By 4 wk of age, choledochoduodenal junction motility was similar to that of the adult. These developmental alterations in junctional motility and structure may affect the flow of bile into the duodenum contributing to physiologic cholestasis and decreased intraduodenal bile acids seen in neonates.

Effects of growth and maturation on biliary structures of guinea pigs.

The biliary system and major duodenal papilla of male guinea pigs were examined in vivo using intravital microscopy. Study of the photomicrographs and videotape recordings indicated that biliary organs changed with age and growth of the guinea pigs. Physiological data including the frequency of sphincteric contractions were recorded and efforts were made to correlate these data with changes in structure thought to be due to maturation. The volume of smooth muscle in the bile duct sphincter (measured using histological sections) increased with age as did surface area of the mucosa. The bile duct was separate from the pancreatic duct in each of 28 guinea pigs. Study of the guinea pig extrahepatic biliary system (EBS) allowed the isolated examination of effects of maturation on bile duct capacity. The anatomical reason for this is that the ampulla of the bile duct emptied into the duodenum (independently of the pancreatic duct) at the major duodenal papilla. The duct of the pancreas entered the duodenum distally (caudally) to the major duodenal papilla on the minor duodenal papilla. The separation of biliary and pancreatic ducts simplified the making of casts of the EBS. It is important to consider this feature in selection of a model for studies of bile duct function in living animals. Three anatomical techniques were selected to focus from differing perspectives on growth-related changes that occurred among the EBS of neonatal, juvenile and adult animals. These techniques were: The capacity (volume) of bile contained within the EBS was determined using plastic casts of the system.(ABSTRACT TRUNCATED AT 250 WORDS)

Xenobiotic metabolism in suspensions and primary cultures of isolated hepatocytes prepared from the caudate process of bovine liver.

Isolated hepatocytes were prepared from 100- to 125-kg Holstein male calves (n = 10) by perfusion of the caudate process of the caudate lobe of the liver. The 11th or 12th rib on the right side was resected to provide exposure of the caudate process. Complete postsurgical recovery of the donor from partial lobectomy was confirmed by growth data and serum chemical and hematologic criteria. Hepatocytes were isolated under aseptic conditions, using a 2-step collagenase vascular perfusion procedure. Hepatocyte preparations averaged 85% viability, and the yield averaged 1.2 X 10(7) viable hepatocytes/g of (wet weight) liver. Morphologic characteristics of hepatocytes examined under light and scanning electron microscopy were considered normal, except for occasional surface blebs. Freshly isolated hepatocytes in suspension rapidly decreased in viability and xenobiotic metabolizing capacity (aldrin epoxidation and ethoxycoumarin 0-deethylation and 7-hydroxycoumarin glucuronidation and sulfation), and hepatocytes surviving the initial 2 to 3 hours appeared to undergo repair. As an alternative, primary monolayer cultures on collagen-coated plates were evaluated. Hepatocytes attached to the collagen surface within 4 hours and appeared flattened by 12 hours. Although metabolic activity decreased about 30% over 8 hours in culture, the pattern of ethoxycoumarin metabolites was relatively constant. It was not determined to what extent the apparent loss of metabolic capacity was caused by hepatocyte detachment from the collagen surface. Although complicated by the requirement for asepsis, primary cultures were superior to suspensions for xenobiotic metabolism studies in cattle.

Relative growth of the anulus fibrosus and nucleus pulposus in human and kitten fetuses.

Growth in volume of the anulus fibrosus (AF) and nucleus pulposus (NP) was quantified using serial histological sections of human and kitten fetuses. Fetal intervertebral discs were studied that had clearly outlined AF and NP. Regression equations were calculated and graphs plotted by microcomputer. An increase in surface areas of these intervertebral structures was also recorded; however, volume was a better indicator of relative growth than was surface area. The AF volume of the fetal human increased more in proportion to the intervertebral disc than it did for the fetal kittens. There was significantly slower growth of the human NP compared to the kitten NP when related to the total intervertebral disc. The analysis for each species was done separately. Comparisons of the growth relationships of humans and kittens for the AF and NP were related to crown-rump length as the independent variable, and were different at the p less than or equal to 0.01 level of significance. The thoracic intervertebral discs were emphasized due to species-specific differential growth of the AF. The intercapital ligament (IC) was separated from mesenchyme over the dorsal surface of the kitten AF, and this affected the relationships of AF and NP volumes when compared to humans. Use of human histological sections is essential in the study of differential growth of the human vertebral column because fetal kittens have an IC that affects relative growth of both AF and NP.

Comparative development of thoracic intervertebral discs and intra-articular ligaments in the human, monkey, mouse, and cat.

Developmental features of thoracic intervertrebral discs and their association in the adult with other vertebral structures were investigated in four species. The human anulus fibrosus, nucleus pulposus, and intra-articular ligaments were compared to those of the fetal rhesus monkey, mouse, and kitten. Photomicrographs of transverse sections of intervertebral discs document the presence of intra-articular ligaments in fetuses of these four species. Both transverse and sagittal sections of kittens were used to identify the intercapital ligament as it differentiated from the dorsal part of the intra-articular ligament. Relatively frequent dorsal herniation of the thoracic nucleus pulposus in humans may be due to the vestigial nature of the human intra-articular ligament. Quadrupeds have well-developed intra-articular ligaments, which explains anatomically the paucity of dorsal protrusions of the nucleus pulposus into the vertebral canal in the thoracic region of the cat and mouse when compared to the human. The intra-articular ligament was closely associated with the developing prenatal mammalian intervertebral disc in the four species studied, and this relationship and its surgical importance are described.

Anatomy and therapeutic resection of the peroneus tertius muscle in a foal.

A foal with a congenital flexure deformity of the right hock was unable to walk because of an abnormally short peroneus tertius (PT) muscle. Tension on the muscle origin and insertions limited the dorsal angle of hock extension to a 70-degrees arc. The intrauterine position of the fetus probably caused the defect. All the PT attachments were dissected in several other limbs, and illustrations made from these dissections were used to study the anatomy and surgical approach. Immediately after resection of the PT muscle, the foal's right hock extended an additional 30 degrees. Two months later, the foal had normal gaits, with normal extension and flexion of the hock and stifle.

Branching patterns of the hepatic artery in the dog: arteriographic and anatomic study.

Eleven arteriograms, 7 corrosion casts, and 40 dissection studies of 51 clinically normal dogs were examined for the branching patterns of the hepatic artery. An injection of radiopaque medium for selective arteriography was made initially to radiograph the celiac artery, after which a technique defined as superselective arteriography was done, advancing a catheter tip into the hepatic artery. Superselective arteriograms for study of the hepatic artery are described, and the anatomic variants of its branching are discussed. Three major types of hepatic artery branching patterns were identified. The first consists of a single hepatic artery trunk, and this pattern was found in four dogs. The second type with two separate branches of the hepatic artery was found in 27 dogs. The third type was seen in 20 dogs and consisted of 3, 4, or 5 branches that originated directly from the hepatic artery. The origin of the right gastric artery varied, as did the branching of the celiac artery. The most common termination of the celiac artery was as two branches in 31 dogs, and these branches were the hepatic artery and a gastrosplenic trunk. The gastrosplenic trunk subsequently divided to form the left gastric artery and the splenic artery. The usual description of the celiac artery is that it ends by trifurcating. A scheme was developed in which the three major types of hepatic artery branching patterns were outlined. This scheme encompases the hepatic lobar artery variants and can serve as a basis for interpretation of detailed hepatic arteriograms.

Electrophysiologic studies of cutaneous nerves of the thoracic limb of the dog.

The cutaneous innervation of the thoracic limb was investigated in 36 barbiturate-anesthetized dogs, using electrophysiologic techniques. The cutaneous area (CA) innervated by each cutaneous nerve was delineated in at least five dogs by stroking the hair in the area with a small watercolor brush while recording from the nerve. Mapping of adjacent CA revealed areas of considerable overlapping. The part of the CA of a given nerve supplied by only that nerve is referred to as its autonomous zone. Of all nerves arising from the brachial plexus, only the suprascapular, subscapular, lateral thoracic, thoracodorsal, and cranial and caudal pectoral nerves lacked cutaneous afferents. The dorsal cutaneous branch of C6 had a CA, but no grossly demonstrable dorsal cutaneous branches for C7 C8, or T1 were found. The cervical nerves had ventral cutaneous branches, but no lateral cutaneous branches. Thoracic nerves T2-T4 had dorsal, ventral, and lateral cutaneous branches. The cutaneous branches of the brachiocephalic, axillary, musculocutaneous, radial, median, and ulnar nerves all had CA which were overlapped by adjacent CA, thus their autonomous zones were much smaller than the cutaneous areas usually depicted for these nerves in anatomy and neurology textbooks.

Physiologic properties of contraction of the canine cremaster and cranial preputial muscles.

Contraction properties of the cremaster and the cranial preputial muscles of 11 mature intact male dogs were investigated. Isometric recordings of muscle contractile tension were performed in situ. Muscle contractions were elicited by stimulating the severed motor nerves. Contraction times of 73.8 ms and 103.2 ms were obtained for the cremaster and the cranial preputial muslces, respectively. Application of repetitive stiumuli produced summation of contractions at low stimulus frequencies. Apparent tetanic fusion and maximum tetanic tension were also observed at relatively low stimulus frequencies, 30 Hz for the cremaster muscle and 28 Hz for the cranial preputial muscle. Optimum length for the cremaster muscle was coincident with its observed in situ resting length (+/- 5 mm), but the optimum length for the cranial preputial muslce deviated by some 20 to 25 mm above the resting length. Possible artifactual errors regarding the cranial preputial muslce's length-tension relationship are discussed.

Thermistor use to monitor urine flow rates in dogs.

The small size of a new thermistor flowmeter facilitated implantation in ureters in anesthetized dogs. It consisted of a self-heating thermistor bead which was suspended centrally within an open catheter and dissipated heat as a function of fluid velocity. A continuous record of instantaneous flow rate was obtained, since the flowmeter catheter maintained a constant cross-sectional area around the thermistor bead. A continuous record of volume output was obtained simultaneously with an additional measurement technique. Spurt volumes of urine delivered in concert with ureter peristalsis were directly correlated to peak flow rates delineated by the flowmeter.

Functional closure of the ductus venosus during early postnatal life in the dog.

Radiographic contrast studies of the ductus venosus performed in 12 pups between the 60th day of intrauterine life and the 5th day after birth indicated that blood flow through the ductus venosus had ceased between the 2nd and 3rd days of extrauterine life. The time of functional closure was not identical with the time of morphologic closure. The functional closure of the ductus venosus was a gradual process and was related to an increase in liver perfusion through the portal vein branches. Both in specimens injected with a radiopaque gum acacia mass and in a corrosion cast of umbilical vein and portal system of the liver, persistence of the lumen of the ductus venosus up to the time of its functional closure was confirmed. The rate of closure in the dog was discussed in relation to that in man and the horse, pig, goat, and sheep.

Anatomy and cannulation of the parotid duct in the dog.

The course of the dog's parotid duct is more complex than previously reported. The newly described features are that the duct has 2 right-angle curves in its terminal part and that it perforates the fascia and mucosa of the cheek between the orbicularis oris and buccinator muscles. The duct does not perforate the buccinator muscle. Based on these findings, a rapid and reliable technique for intubation of the duct was developed.

The dog as an instruction model for surgical correction of mandibular prognathism.

Intraoral sagittal splitting of the mandible in dogs is an instructional exercise for correction of prognathism. The dog was selected as a surgical model for several reasons including the ability of this species to open the mouth widely. Comparative anatomical features of the mandibles of man and dog suggest that a sagittal splitting technique practiced in dogs may give expertise that would avoid complications, such as cutting vessels and nerves in humans. In addition, the dog should be carefully considered as a model for long-term study of surgical complications and of the effects of surgery on mandibular growth in young patients.

Hepatoencephalopathy associated with situs inversus of abdominal organs and vascular anomalies in a dog.

Throughout its life, a 1-year-old Doberman Pinscher dog had had gastrointestinal disorders and episodes of circling. It was less active than its littermates, and it usually seemed lethargic. When 3 months old, the pup had been anesthetized for ear cropping and it had remained anesthetized for 32 hours. Behavioral problems were apparent when the dog was 11 months old. Two weeks later the behavioral problems accentuated to the point that the dog developed "temper tantrums" and became aggressive toward its owner. On the basis of clinicopathologic and contrast radiographic findings, hepatoencephalopathy due to persistent patent ductus venosus was diagnosed and the dog was euthanatized. Situs inversus abdominalis and multiple vascular anomalies were found at necropsy. Gross and microscopic studies of the viscera were correlated with corrosion casts of the vasculature. In addition to changes in organ position, 3 spleens and malformation of the pancreas were observed. Vascular anomalies were: (1) The portal vein was contiguous with the common hepatic vein by way of a patent ductus venosus; branches of the portal vein were not given off to the liver; (2) the caudal vena cava was continued by the azygos vein, and a cranial segment of the caudal vena cava was absent; (3) the hepatic artery was larger than normal; (4) the left gastric artery arose anomalously from the cranial mesenteric artery; and (5) histologic and radiographic study of the liver did not reveal any interlobular branches of the portal vein; however, hypoplastic branches of the gastroduodenal vein did enter the liver and were demonstrated on a corrosion cast.