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Biomedical subjects

D G Bristol

Publications and source records attributed to D G Bristol.

At least 19 recordsLinked to original sources
PubMed1999

Glutamine and transforming growth factor-alpha stimulate extracellular regulated kinases and enhance recovery of villous surface area in porcine ischemic-injured intestine.

BACKGROUND: Epidermal growth factor (EGF) signals enterocyte proliferation via extracellular regulated kinases (ERKs). Because glutamine is required for EGF-stimulated proliferation and stimulates ERKs in intestinal cell culture, we hypothesized that glutamine and the EGF-related peptide transforming growth factor-alpha (TGF-alpha) would synergistically enhance repair associated with stimulation of ERKs. METHODS: Thiry-Vella loops were created in juvenile pigs. One half of the loop was subjected to 2 hours of ischemia, and the other half served as control. Loops were infused daily with Ringer's solution containing 140 mmol/L glucose, 140 mmol/L glutamine, 140 mmol/L glucose plus 60 micrograms/L TGF-alpha, or 140 mmol/L glutamine plus 60 micrograms/L TGF-alpha. RESULTS: After 2 hours of ischemia, complete villous epithelial sloughing was present. By 18 hours, villous epithelium had fully restituted, but villi remained stunted until 144 hours after injury. Glutamine + TGF-alpha triggered sustained increases in ERK activity compared with glucose-treated tissues (maximal at 18 hours), whereas glutamine alone or glucose + TGF-alpha caused only transient elevations in ERK activity. By 72 hours, villous surface area had increased to normal values with glutamine plus TGF-alpha treatment, whereas villi remained stunted with glucose alone, glutamine alone, or glucose plus TGF-alpha. CONCLUSIONS: Glutamine plus TGF-alpha treatment restored mucosal architecture within 72 hours of severe ischemic injury associated with sustained elevations in ERK activity.

Animals↗
PubMed1998

Change in insulin sensitivity or responsiveness is not a major component of the mechanism of action of ractopamine in beef steers.

Our objective was to determine whether the beta-adrenergic agonist ractopamine altered sensitivity or responsiveness to insulin. We used the hyperinsulinemic, euglycemic clamp approach in five multicatheterized beef steers to evaluate insulin sensitivity (ED50) and responsiveness (Rmax or Rmin) during control or ractopamine feeding (80 mg/kg feed). Steers had blood vessel catheters and ultrasound flow probes that allowed measurement of net uptake and release of glucose and insulin by portal-drained viscera (PDV), liver and hindlimb. Steers ate meals of equal size every 2 h. Steers were fed at 1.8 times calculated maintenance energy. The design was a single reversal. Two rates of insulin infusion followed a base-line period on each of three sample days. Insulin was infused into a mesenteric vein at 10, 20, 40, 80, 160 and 320 mU/(h.kg body weight). During the base-line period, arterial concentrations of glucose, oxygen, nonesterified fatty acids and insulin were not different between control and ractopamine feeding. Arterial urea was lower during ractopamine than during control feeding (5.02 vs. 6.20 mmol/L, respectively, P < 0.01). Net release of glucose by liver and net uptake of glucose by the hindlimb were not affected by treatment. Similarly, net release of insulin by PDV and net uptake of insulin by liver were not affected by treatment. The Rmax and ED50 for steady-state glucose infusion rate, total glucose entry, hepatic glucose production and hindlimb glucose uptake did not differ between treatments. There was a trend for a lower ED50 in hindlimb with ractopamine treatment (P < 0.13). These data do not support a change in sensitivity or responsiveness of tissues to insulin as a major component of the mechanism of action of ractopamine.

Adrenergic beta-Agonists↗
PubMed1996

Jejunocolostomy or ileocolostomy for treatment of cecal impaction in horses: nine cases (1985-1995).

OBJECTIVE: To determine whether complete cecal bypass, by jejunocolostomy or ileocolostomy, is an effective treatment for horses with cecal impaction. DESIGN: Retrospective analysis of medical records. ANIMALS: 9 horses with cecal impaction managed by jejunocolostomy (3) or ileocolostomy (6) performed with or without typhlotomy for evacuation of cecal contents. PROCEDURE: Information on age, breed, gender, duration of medical treatment, preoperative abnormalities, surgical procedure, and postoperative complications was retrieved from the medical records. Follow-up data were obtained via telephone interview with owners. RESULTS: 6 males and 3 females between 9 and 24 years old (median, 14 years) were included. Five of 9 horses had signs of mild pain associated with reintroduction of food after surgery. All 7 horses for which follow-up information was available were still alive between 7 and 54 months (median, 1.5 years) after surgery. CLINICAL IMPLICATIONS: Jejunocolostomy or ileocolostomy resulted in apparently permanent resolution of cecal impaction in these horses and acceptable long-term outcomes. Mild signs of abdominal pain associated with the onset of feeding can be expected in the early postoperative period.

Anastomosis, Surgical↗
PubMed1995

Loop colostomy for treatment of grade-3 rectal tears in horses: seven cases (1983-1994)

OBJECTIVE: To determine the feasibility of performing a single-incision loop colostomy for treatment of grade-3 rectal tears in horses. DESIGN: Retrospective case series. ANIMALS: Seven adult horses with grade-3 rectal tears. PROCEDURE: A single-incision loop colostomy was performed with horses under general anesthesia (n = 6) or while restrained in standing stocks (n = 1). The rectal tear was lavaged via an endoscope. The colostomy was resected after the rectal tear healed. RESULTS: Rectal tears ranged from 4 to 10 cm in diameter and were > 25 cm proximal to the anus. All horses survived colostomy surgery. One horse was euthanatized at the request of the owner 1 day after surgery. Six horses underwent colostomy resection 13 to 30 days after colostomy. All horses had evidence of atrophy of the distal portion of the small colon, predisposing to impaction at the small colon anastomosis in 2 horses. One horse was euthanatized while hospitalized because of severe recurrent colic. Five horses were discharged from the hospital 31 to 45 days after admission. One horse was euthanatized 60 months after discharge from the hospital because of severe colic, and 4 horses were alive at the time of follow-up evaluation (3 to 12 months after discharge). CLINICAL IMPLICATIONS: The prognosis for horses with grade-3 rectal tears treated by colostomy appears to be favorable.

Animals↗
PubMed1995

Repeat laparotomy for gastrointestinal disorders in cattle: 57 cases (1968-1992).

A study was conducted to investigate indications for, typical findings during, and outcome of repeat laparotomies in 57 cattle with gastrointestinal disorders. Cattle were grouped according to the reason the initial laparotomy had been performed. Group-1 cattle (n = 46) had had left or right displacement of the abomasum (LDA or RDA) or right volvulus of the abomasum. Group-2 cattle (n = 10) had had ruminal, reticular, or abomasal obstruction or perforation. Group-3 cattle (n = 7) had had obstruction, volvulus, distention, or perforation of the small or large intestine. Median interval between laparotomies was 1 month (range, 1 day to 38 months). Intraoperative findings during repeat laparotomy in group-1 cattle included LDA (n = 18), RDA (9), right volvulus of the abdomen (5), pneumoperitoneum (1), diffuse abdominal adhesions (1), cecal adhesions (1), adhesions of the rumen to the body wall (1), abscess in the cranial portion of the abdomen (1), reticular adhesions (1), localized necrosis (1), and idiopathic rumen distention (1). Intraoperative findings during repeat laparotomy in group-2 cattle included abscess in the cranial portion of the abdomen (4), no abnormalities (1), distended rumen (1), ruptured abomasum (1), recurrent abomasal impaction (1), diffuse abdominal adhesions (1), and pyloric fat necrosis (1). Intraoperative findings during repeat laparotomy in group-3 cattle included LDA (3), RDA (1), cecal volvulus (1), anastomotic rupture (1), and impacted colocolostomy (1). Seven cows and 1 calf underwent additional repeat laparotomies. Forty-four (77%) of the 57 cattle were discharged following final laparotomy. Fourteen of the 20 group-1 cattle, 1 of the 6 group-2 cattle, and 2 of the 3 group-3 cattle for which follow-up information was available were productive after repeat laparotomy.

Abomasum↗
PubMed1994

Evaluation of factors associated with postoperative ileus in horses: 31 cases (1990-1992)

Medical records of horses that underwent surgical treatment for colic between 1990 and 1992 were reviewed. Horses with a pulse rate of > or = 60 beats/min or signs of abdominal pain, which were also accompanied by a volume of > 2 L of material that refluxed from the stomach during the postoperative period (excluding horses with anterior enteritis), comprised the postoperative ileus (POI) group. Horses that had < 2 L of material reflux during the postoperative period and survived > 3 days after surgery comprised the reference population. The association of preoperative and intraoperative clinical variables with development of POI was evaluated by use of logistic regression analysis. Of 148 horses, 117 were assigned to the reference population, and 31 (21%) developed POI. Multiple logistic regression analysis was used to determine that PCV, pulse rate, type and location of lesion detected during surgery, and serum glucose concentration were the most important variables associated with development of POI. Time of recovery from anesthesia to development of POI was 0.5 to 120 hours (median, 13 hours). Duration of POI was 1 to 7 days (median, 1 day). Four of 31 (13%) horses with POI died. Of 148 horses, only 10 (7%) died; however, 4 of the 10 (40%) deaths in the short-term postoperative period were attributable to POI.

Animals↗
PubMed1994

Avulsion of the origin of the peroneus tertius tendon in a foal.

A 3-month-old foal was examined because of lameness and fracture of the left lateral trochlear ridge of the femur. Arthroscopy of the left femoropatellar joint was elected. After induction of general anesthesia and placement of the foal in dorsal recumbency, it was noticed that the left hind limb was extended at the tibiotarsal joint and flexed at the femorotibial joint. Avulsion fracture at the origin of the peroneus tertius tendon was diagnosed. Fracture fragments were excised. The horse had mild left hind limb lameness at the time of follow-up evaluation 1 year after discharge.

Animals↗
PubMed1992

Pedunculated lipomas as a cause of intestinal obstruction in horses: 17 cases (1983-1990).

The medical records of 17 horses that were evaluated and treated because of colic caused by pedunculated lipomas between 1983 and 1990 were reviewed. The mean age of the horses was 16.6 +/- 3.9 years (range, 10 to 26 years), which was significantly greater than that of the population of horses evaluated because of colic (control population) during the same period. There were significantly more geldings (76.5%), compared with the control population. Nasogastric reflux ranged from 1 to 16 L in 8 horses and was not obtained in 9 horses. Abdominal palpation per rectum revealed small intestinal distention in 13 horses, displaced large colon in 7 horses, and large colon impaction in 2 horses. Peritoneal fluid was abnormal in 11 of 12 horses from which it was obtained successfully. One horse was euthanatized after unsuccessful medical treatment. Surgery was performed in 16 horses. Lipomas were blindly resected in 5 horses or exteriorized and resected in 6 horses. The method used to resect the lipoma was not recorded in 5 horses. The ileum and/or jejunum was strangulated in 15 horses, the small colon was strangulated in 1 horse, and the jejunum was obstructed in 1 horse. The length of intestine resected ranged from 0.15 to 7.2 m. Fourteen horses survived surgery, of which 11 were discharged from the hospital (short-term survival rate of 78.6%). Excluding 2 horses lost to follow-up evaluation, 6 of 12 horses that survived surgery were alive 2 to 56 months following surgery (long-term survival rate of 50%), and 9 of 15 horses died or were euthanatized (fatality rate of 60%).

Animals↗
PubMed1992

Effects of antibiotic prophylaxis on postoperative complications after rumenotomy in cattle.

A single preoperative dose of antibiotic proved as effective as a preoperative and 7-day postoperative course in reducing complications following rumenotomy in cattle. Exploratory rumenotomy was performed on 29 healthy Angus steers, which were allotted to the following treatment groups: (1) no antibiotic therapy, (2) single-dose, preoperative, antibiotic prophylaxis, using potassium penicillin G, and (3) preoperative potassium penicillin G prophylaxis, followed by a 7-day postoperative course of procaine penicillin G. Steers receiving antibiotics had significantly greater postoperative feed intake, lower rectal temperatures, and fewer abscesses at the surgical site than those receiving no antibiotics. There was no significant difference between animals receiving a single preoperative dose of antibiotic and those treated for an additional 7 days after surgery. In human medicine, it is generally agreed that a single preoperative dose of antibiotic offers effective prophylaxis. There are few published reports on antimicrobial prophylaxis in the veterinary literature, particularly in regard to large animals. Considering USDA requirements for milk withholding times and withdrawal times prior to slaughter for food animals receiving antibiotics, the findings of this study have medical as well as economic value.

Abscess↗
PubMed1991

Cutaneous laser-Doppler velocimetry in nine animal species.

The assessment of cutaneous microcirculation by laser-Doppler velocimetry (LDV) has been primarily limited to human studies. The purpose of this investigation was to establish normal values in various species and anatomic sites for blood flow, velocity, and volume as determined by LDV. Microcirculation was measured with a laser-Doppler velocimeter in 54 animals, 6 healthy animals from each of 9 species. The standard sites used were the buttocks, convex surface of the ear, metacarpal pad, humeroscapular junction, thoracolumbar junction, ventral portion of the abdomen, dorsal metacarpus (hooved animals), and ventral surface of the tail (horse). Significant differences in blood flow, velocity, and volume were measured between species and sites within species. The ventral portion of the abdomen consistently had the highest relative blood flow across all species except the monkey. Measurements in the canine metacarpal pad had a high SD, possibly indicating the stratum corneum and epidermis to be too thick for LDV. Our findings provide baseline data in several species, with application of LDV in comparative dermatologic research.

Animals↗
PubMed1990

Surgery of the neonatal bovine digestive tract.

Many disorders of the calf's gastrointestinal tract require surgical intervention if a successful outcome is to be obtained. The most common abnormalities in this category are abomasal volvulus, abomasal ulcers, small intestinal accidents, and atresia of the spiral colon. These can be differentiated by the age of the animal at presentation and a careful physical examination. Special considerations in neonatal gastrointestinal surgery include: ensuring adequate serum immunoglobulin status, rapid treatment of dehydration and hypoglycemia, and consideration of the inheritability of any corrected defects. Prompt attention to metabolic disturbances and correction of the abnormalities are essential for a successful outcome.

Animals↗
PubMed1990

Interspecies and interregional analysis of the comparative histologic thickness and laser Doppler blood flow measurements at five cutaneous sites in nine species.

Studies in dermatology, cutaneous pharmacology, and toxicology utilize skin from different animal species and body sites. However, regional differences exist in topical chemical percutaneous absorption studies in man and in animal. The objective of this study was to compare epidermal thickness and number of cell layers across species and body sites using both formalin-fixed paraffin and frozen sections. Cutaneous blood flow determined by laser Doppler velocimetry (LDV) was compared to histologic data. Six animals of each of the following species were used: monkeys, pigs, dogs, cats, cows, horses, rabbits, rats, and mice. Cutaneous blood flow was determined and 6-mm skin biopsies were taken directly from the following sites: buttocks, ear, humeroscapular joint, thoracolumbar junction, and abdominal area. When the two histologic methods were compared across all species and body sites, the thickness of the epidermis was significantly greater, and the thickness of the stratum corneum significantly less, in paraffin sections versus frozen sections (p less than 0.05). There were no differences in the number of viable cell layers determined by both methods. The values for LDV-determined blood flow did not significantly correlate (p greater than 0.05) to epidermal or stratum corneum thickness. However, regional and species differences were noted in all these parameters. In conclusion, these data indicate that thickness and LDV blood flow are independent and must be evaluated separately when comparisons are made between species and body sites. This work provides a data base for future comparative studies in which a knowledge of skin thickness or blood flow might be important variables.

Animals↗
PubMed1989

Treatment of teat obstruction in a cow by transfer of oral mucosa and temporary implantation of an intraluminal tube.

A dairy cow was examined because of extensive obstruction of a teat cistern. The teat was treated by surgical resection of scar tissue, transplantation of an oral-mucosal autograft, and temporary implantation of a silastic tube. The silastic tube became dislodged from the teat, and was surgically removed 30 days after the initial surgery. The cow subsequently had 2 normal lactations. Prior to the third postoperative lactation, the cow developed severe udder edema. During lactation, the surgically treated teat became hard and was difficult to milk. The cow was then culled.

Animals↗
PubMed1989

Measuring bovine mammary gland blood flow using a transit time ultrasonic flow probe.

Lactating cattle were used to validate a transit time ultrasonic blood flow metering system for measuring mammary gland arterial blood flow. Blood flow probes were surgically placed around the right external pudic artery. An electromagnetic flow probe was implanted in tandem with the ultrasonic probe in two cows for comparative measurements. The absolute accuracy of the implanted flow probes was assessed in vivo by mechanical means on anesthetized cows after 2 to 3 wk of implantation. The zero offset of the ultrasonic probes ranged from -12 to 8 ml/min. When the ultrasonic probe was properly implanted, the slopes of the calibration curves were linear and ranged from .92 to .95, tracking absolute flow to within 8%. The transit time instrument's performance was examined under a variety of physiological conditions. These included milking and hormone injections. The transit time ultrasonic flow meter accurately measured physiological changes in mammary arterial blood flow in chronically prepared conscious cattle. Blood flow increased 29% during milking. Epinephrine decreased mammary blood flow by 90 to 95%. Oxytocin doses increased mammary blood flow by 15 to 24%.

Animals↗
PubMed1989

Use of a linear stapling device to construct an inverted, triangulated, end-to-end anastomosis of the equine jejunum.

An inverting, triangulated, stapled, end-to-end anastomosis technique was evaluated in the jejunum of four horses. None of the horses showed evidence of gastrointestinal disturbance after surgery; however, stricture and adhesion formation were pronounced in three animals examined 10 days, one month, and two months after surgery. The animal examined four months after surgery had no adhesions present at the anastomosis, and only mild narrowing of the intestinal lumen. Histologic examination of the anastomoses showed lack of a normal mucosal lining in some examined sections up to two months postsurgery. While mucosal and serosal continuity were eventually reestablished, this was not true of the muscularis, the ends of which were joined by fibrous tissue. Gaps in the staple line and malalignment of staples were present in the animal examined four months after surgery, indicating migration and/or loss of the staples from the anastomosis. The inverting, triangulated staple technique had little or no apparent advantages over previously reported results with similar everting techniques. The severity of adhesions observed with the inverting technique suggests that the adhesions observed with the similar everting technique may not be due solely to the everted nature of the anastomosis.

Anastomosis, Surgical↗
PubMed1988

A comparison of three methods of end-to-end anastomosis in the equine small colon.

Six animals were used to compare simple interrupted, simple continuous, and stapled techniques for end-to-end rotated small colon anastomoses. Three ponies were evaluated three days after surgery for adhesion formation and luminal diameter at each anastomosis site. Two ponies and one horse were evaluated 14 days after surgery for adhesion formation. All anastomosis sites were examined histologically for alignment of tissue planes, and evidence of inflammation. No single technique was superior in all areas examined. While only three of the nine anastomoses had mild fibrinous adhesions at three days after surgery, all anastomoses had varying degrees of well-organized adhesions by 14 days after surgery. Three days after surgery luminal diameter was most comprised by the simple continuous technique. Although the simple interrupted technique was most consistent in its alignment of tissue planes, it was only slightly better than the simple continuous pattern. Stapled anastomoses were inverted or everted at all sites examined. Adhesion formation was less extensive, and histologic evidence of inflammation was less severe, in stapled anastomoses. The average times required to complete the simple interrupted, simple continuous, and stapled anastomoses were 22, 14, and 8 minutes, respectively.

Anastomosis, Surgical↗