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Biomedical subjects

A M Merritt

Publications and source records attributed to A M Merritt.

At least 55 records · Page 3Linked to original sources
PubMed1986

Nosocomial infections and bacterial antibiotic resistance in a university equine hospital.

A base-line study of bacteria isolated from horses admitted to the Veterinary Medical Teaching Hospital during a 6-month period was performed to determine the extent of multiresistant nosocomial infections caused by gram-negative aerobic bacteria other than Salmonella spp. Results of this study indicated that 21.9% of the 105 horses from which cultures and sensitivities were available had developed nosocomial gram-negative aerobic infections, with high rates of resistance to gentamicin, kanamycin, and trimethoprim sulfadiazine, three of the most often prescribed antibiotics in this hospital. In addition, a prospective study of antibiotic-resistant bacteria of fecal origin was performed to determine whether there was a change in the degree of antibiotic resistance of a horse's intestinal flora while the horse was hospitalized. Bacterial culturing for gram-negative lactose fermenting bacteria was done on fecal specimens collected directly from the rectum on day 1 and day 7 of a horse's hospitalization. Susceptibility testing was done on each isolant. Of the 24 paired fecal specimens obtained, Escherichia coli and Klebsiella sp isolated on day 7 were resistant to a significantly higher number of antibiotics than day 1 isolants (P = 0.003, P = 0.043, respectively).

Animals↗
PubMed1986

Gastroenterostomy for treatment of gastroduodenal ulcer disease in 14 foals.

Gastroenterostomy was performed in 14 foals to treat gastric outflow obstruction caused by advanced gastroduodenal ulcer disease. The onset of excessive salivation and teeth grinding, without response to medical treatment, combined with endoscopic and radiographic evidence of gastric outflow obstruction, were indications for surgical intervention. Successful outcome in 5 foals was attributed to early diagnosis, patient stabilization, early surgical correction, and postoperative management including antibiotics and antiulcer medication.

Animals↗
PubMed1986

D-xylose absorption in the growing foal.

Seven healthy foals (five ponies and two horses) were maintained on grass pasture with their dams. All foals had normal faeces at the time of testing. An oral xylose absorption test was performed on each foal at one, two and three months of age. Following an 8 h fast, 0.5 g/kg D-xylose as a 10 per cent solution was given via a nasogastric tube. Control and 30 min interval plasma samples were collected for 3 h and the plasma was analysed for xylose using the phloroglucinol microassay technique. Maximum xylose concentration levels were reached between 30 and 60 mins for each of the foals. The mean (+/- sem) peak xylose concentration at one, two and three months of age was 3.14 +/- 0.29, 2.19 +/- 0.30 and 1.25 +/- 0.22 mmol/litre respectively, which were all significantly different from each other. Xylose absorption capacity decreased, therefore, with age, becoming similar to the adult horse by three months of age. The oral xylose absorption test can be used to evaluate small intestinal absorptive capacity in the foal provided that the results are compared with foals of the same age group.

Administration, Oral↗
PubMed1986

Faecal composition in foal heat diarrhoea.

Developmental changes of the gastrointestinal tract were probably responsible for the changes in faecal composition during the first week of the foals' life, which resembled small intestinal ingesta of adult horses, suggesting a minimal colonic modification. Faecal composition at the time of foal heat diarrhoea was suggestive of a secretory-type diarrhoea, in that the electrolyte concentration accounted for most of faecal osmolality and the faecal pH was alkaline. After foal heat diarrhoea faecal composition slowly approached that of adult horses. These data suggest that foal heat diarrhoea is most likely caused by hypersecretion in the small intestinal mucosa, which may overwhelm an immature colon that is unable to compensate by increased fluid and electrolyte absorption.

Animals↗
PubMed1986

Jejunal myoelectrical activity in the conscious neonatal pig.

The purpose of this study was to define and quantify patterns of normal jejunal myoelectrical activity in the conscious neonatal pig. Twelve 3-day-old piglets were obtained from a local herd. At 7 days of age four bipolar Ag-AgCl electrodes were surgically implanted at 5 cm intervals on the jejunum. Piglets were divided into fed (n = 7) and fasted (n = 5) groups and a minimum of four daily recordings were made from each pig between 7 and 14 days of age. Slow wave and spike activity were seen in all animals. Slow waves occurred at a frequency of 17.0 +/- 0.3 cycles/min (c.p.m.) in fed and 16.8 +/- 0.2 c.p.m. in fasted piglets. Spike activity predominated, occurring in characteristic migrating myoelectrical complexes (m.m.c.s.) and occupying 79% of the recording time in fed and 73% in fasted piglets (P less than 0.05). The activity front (phase 3) of the m.m.c. recurred every 47.7 +/- 2.4 min in fed, and 50.9 +/- 2.3 min in fasted piglets. The m.m.c. periodicity in both groups was irregular, with a range of 4-145 min in fed, and 8-104 min in fasted piglets. Activity fronts lasted 4.8 +/- 0.1 min in fed and 4.4 +/- 0.1 min in fasted piglets. All piglets demonstrated intense, short (2.5-5.0 s), distinct bursts of intense spike activity (migrating action potential complexes, m.a.p.c.s.). These were rapidly conducted in an aboral direction at a velocity of 1.8 cm/s in fed, and 0.8 cm/s in fasted piglets (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1986

Body fluid concentrations and pharmacokinetics of chloramphenicol given to mares intravenously or by repeated gavage.

Serum concentrations and the pharmacokinetics of chloramphenicol were determined in 6 healthy mares after a single IV administration (50 mg/kg of body weight) or after the 1st and 5th sequential intragastric (IG) administration (50 mg/kg/6 hours) of chloramphenicol. Synovial fluid, peritoneal fluid, CSF, and urinary concentrations of chloramphenicol after the IG administrations also were determined. Mean (+/- SEM) overall elimination rate constant (K) values for the IV, 1st IG, and 5th IG dosages were 0.42 +/- 0.064/hr, 0.42 +/- 0.049/hr, and 0.29 +/- 0.074/hr, respectively, and were not significantly different from one another (P greater than 0.05). Bioavailability was 40 +/- 8.6% after the 1st IG administration and was 21 +/- 5.2% after the 5th IG administration. Values for the area under the curve (AUC) for the 1st and 5th IG dosages were significantly different from the AUC value for the IV dosage, and the AUC value for the 5th IG dosage was significantly different from that for the 1st IG dosage. Chloramphenicol was administered to 2 mares in 6 consecutive doses; the first and last doses were given IV and the others were given IG. Mean K values after the 2 IV doses were 0.38 +/- 0.112/hr and 0.56 +/- 0.078/hr, which were not significantly different from each other or from the mean value for the IV dosage given to all 6 mares. Absorption of chloramphenicol decreased with repeated IG administrations, resulting in lower concentrations of chloramphenicol with subsequent administrations. Five consecutive IG doses of chloramphenicol were administered to 4 of the mares in a separate experiment and did not alter intestinal xylose absorption.

Animals↗
PubMed1986

Evaluation of the myoelectrical activity of the equine ileum infected with Strongylus vulgaris larvae.

Five weanling ponies were subjected to an intensive 6-week deworming program after which 4 Ag-AgCl bipolar electrodes were implanted surgically on the distal ileum. For 3 hours each day for 5 consecutive days, ileal myoelectrical activity was recorded from fed ponies under 3 sequential conditions: preinoculation, after oral administration of 1,000 killed Strongylus vulgaris infective larvae (3 ponies), and after oral administration of 1,000 live S vulgaris infective larvae. Recordings were analyzed for slow wave frequency, percentage duration of phases I, II, and III of the migrating myoelectrical complex (MMC), and the frequency of distinct, rapidly migrating action-potential complexes within phase 2 of the MMC. After administration of live and killed infected 3rd-stage larvae, there was a marked increase in the number of disrupted phase III complexes, and a significant (P less than 0.001) increase in the number of migrating action-potential complexes. In addition, after inoculation of live 3rd-stage larvae, there was a significant increase (P less than 0.001) in the percentage of time that the MMC was occupied by prolonged periods devoid of spike activity (phase I). The results indicate that S vulgaris larval mucosal penetration and submucosal migration can cause changes in ileal myoelectrical activity that could cause colic, and that larval antigen alone within the lumen may disrupt ileal motility.

Animals↗
PubMed1985

Effect of lidamidine-HCl on Escherichia coli heat-stable enterotoxin-induced jejunal water and electrolyte secretion in neonatal piglets.

Neonatal piglets were anesthetized, and two jejunal loops, 20 cm in length, were prepared. Then, either water or 0.12, 0.25, 0.5 or 1.0 mg/kg of lidamidine-HCl was injected intraduodenally on a randomized basis, one treatment per pig. Following this, a crude heat-stable enterotoxin (ST) preparation produced from E. coli no. 1261 was injected into the proximal jejunal loop, and trypticase soy broth (TSB) (with osmolality adjusted to equal the enterotoxin preparation) was injected into the distal jejunal loop. Piglets remained anesthetized for 3 h and were then killed. Fluid was collected from the loops for measurement of volume and Na, K and Cl concentration. Empty loop lengths were measured. There was a significant dose-related reduction of volume and Cl content, and a dose-related, but not significant, reduction in Na content in St-treated loops. A comparison of the mean differences in responses between toxin- and TSB-treated loops indicated that the major 'counter-toxic' effect of the lidamidine was a dose-related increase in water and electrolyte absorption.

Animals↗
PubMed1984

Influence of coronavirus (transmissible gastroenteritis) infection on jejunal myoelectrical activity of the neonatal pig.

Four silver-silver chloride electrodes were surgically implanted at 5-cm intervals on the jejunal serosa of 7 neonatal pigs. Daily recordings, 7 h in duration, were made from each piglet beginning 3 days after surgery. Characteristic migrating motility complexes and short, distinct (2.5-5.0 s), rapidly aboral migrating bursts of intense spike activity ("migrating action potential complexes") were seen in all preinfection recordings. Piglets were inoculated with a 1-ml oral dose of a 0.1% gut suspension from coronavirus (transmissible gastroenteritis) infected pigs. This resulted in inappetence, vomiting, and diarrhea, most marked on the second day postinfection, but which had abated by the third day. When compared to recordings from both fed and fasted noninfected (control) animals, infection significantly altered jejunal myoelectrical activity by (a) shortening the duration of the migrating motility complex on day 1 postinfection and prolonging it on day 2, (b) increasing the number of abnormal activity fronts, and (c) decreasing the number of migrating action potential complexes. Slow wave frequency and the duration of phase 3 of the migrating motility complex were unaffected. When compared to fed control animals, infected piglets also showed a slight shortening of phase 1 of the migrating motility complex on day 1 postinfection and a prolongation on days 2 and 3, as well as a shortening of phase 2 on the second and third days postinfection. Changes in myoelectrical activity were not solely due to decreases in food intake, as abnormalities persisted when food intake returned to normal on postinfection day 3, and disruption of the activity front and migrating motility complex duration were purely transmissible-gastroenteritis-virus-induced phenomena. These findings suggest that infection with transmissible gastroenteritis virus disrupts organized propulsive activity in the jejunum of the neonatal pig.

Animals↗
PubMed1983

Simultaneous pancreatic, gastric and hormonal responses to 2-deoxyglucose in the conscious pig.

The effect of vagal stimulation induced by 2-deoxy-D-glucose (2DG) on gastric acid and pancreatic bicarbonate output, and portal gastrin and secretin concentrations, was assessed in conscious miniature pigs. Electrical vagal stimulation has previously been shown to induce profuse pancreatic water and bicarbonate secretion in anaesthetized pigs. Pigs in this study were surgically prepared with gastric and pancreatic fistulas and indwelling jugular and portal catheters. An intravenous bolus of 2DG (100 mg/kg body weight) caused a significant increase in both gastric acid and pancreatic bicarbonate output although the latter was about 50% of the reported response to electrical vagal stimulation. Portal gastrin concentration rose significantly after 2DG, but the portal secretin concentration did not change. The presence of secretin in the small intestine was confirmed by intrajejunal HCl infusion. Failure of portal secretin concentration to rise after 2DG infusion rules against a role for this hormone in the pancreatic response.

Animals↗
PubMed1983

Influence of alpha-cellulose on myoelectric activity of proximal canine colon.

The relations between dietary fiber intake and myoelectric activity of the proximal canine colon were examined in four normal beagles fed four diets of varying fiber content in a randomized block design. The basal diet was a canned, meat-based product to which 3, 6, and 9% by weight of alpha-cellulose was added. Colonic motility was monitored using four bipolar Ag-AgCl electrodes. Two slow-wave frequencies were observed: 1) 18.4 +/- 0.1 cycles/min (cpm) and 2) 5.6 +/- 0.03 cpm. Fiber had no effect on either frequency. Spike activity showed three distinct patterns: 1) short bursts phase locked to slow waves of the 18.4 cpm frequency, 2) short bursts phase locked to slow waves of the 5.6 cpm frequency, and 3) prolonged sequences unrelated to slow waves, lasting from 5 to greater than 60 s and grouped in distinct aborally conducted bursts that occurred at a frequency of 2.9 +/- 0.1/h (SE). Fiber had no effect on the frequency of these bursts, but as fiber intake increased there was a linear decrease in burst duration from 11.4 +/- 0.6 min for the basal diet to 8.2 +/- 0.4 min for the high-fiber diet (P less than 0.001). We conclude that luminal factors influence spike burst activity in the proximal colon, because increments of undigestible fiber reduce burst duration on a dose-related basis.

Animals↗
PubMed1983

Phloroglucinol microassay for plasma xylose in dogs and horses.

The phloroglucinol microassay technique for measuring plasma concentrations of xylose was compared with the more tedious orcinolferric chloride technique. Sequential blood samples were collected from 5 dogs and 6 horses every 30 minutes after oral administration of 0.5 g of D-xylose/kg of body weight. Comparison of the results by regression analysis shows a highly significant (P less than 0.01) positive linear correlation for both dogs (r = 0.95) and horses (r = 0.77). These results indicate that xylose in canine and equine plasma can be accurately measured by the phloroglucinol technique.

Animals↗
PubMed1983

Reliability of single-sample phosphorus fractional excretion determination as a measure of daily phosphorus renal clearance in equids.

In 4 healthy horses and 1 Welsh pony, fractional renal excretions of phosphorus (FEp) determined from 9 hourly time collections taken over a 24-hour period were compared to assess whether a single-sample collection would be an accurate indicator of the daily FEp. The mean FEp for each animal varied from 0.115% to 0.302%; the 2 animals with the highest values were significantly different (P less than 0.05) from the 3 with the lowest values. Individual variation within animals was not great, however, because it was calculated that the 24-hour FEp value could be found within +/- 0.087% of the single sample value 95% of the time in a given animal.

Animals↗
PubMed1982

Effects of fiber on digestibility and transit time in dogs.

This study examines effects of variations in fiber content on nutrient assimilation, fecal output, and gastrointestinal transit time in the dog. Four normal Beagles were fed four diets in a randomized block design. The basal diet was a canned, balanced, meat-based dog food (Alpo Trio) to which added 3, 6, and 9% by weight of alpha cellulose (Solka Flok). Food intake and fecal outputs were recorded for 5-day periods. Samples of diets and fecal collections were analyzed for dry matter, nitrogen, fat, carbohydrate and ash; digestibilities were calculated. Transit times were measured by a radiographic marker technique. Fecal weight and water increased linearly; digestibility of dry matter decreased from 90 to 70% and ash from 43 to 32% with added fiber. Responses of protein, carbohydrate and fat were less pronounced but were regular; regressions of their digestibilities on added fiber were significant. Regression estimate of true digestibility for alpha-cellulose was 6%. Intestinal transit time decreased from a mean of 37.4 to 28.7 hours with added fiber. Decreased intestinal time would contribute to depression of fry matter digestibility. Increased fecal water output probably also reflected retention by fiber.

Animals↗
PubMed1981

Exuberant granulation tissue in the stomach of a horse.

A 4-year-old stallion was examined because of a 2-month history of inappetance and weight loss. Diarrhoea had also developed a month before presentation. Abnormal clinical findings were emaciation, diarrhoea, ventral oedema, palpable mesenteric lymph node enlargement and a large mass in the left cranial portion of the abdomen. Significant laboratory findings were anaemia (packed cell volume 0.21 litres/litre), hypoalbuminaemia (16 g/litre) and xylose malabsorption. The horse was euthanased and at necropsy a 10.5 kg pendunculated mass composed of granulation tissue was found within and attached to the stomach. There was villous atrophy diffusely throughout the small intestine. The inciting cause of the gastric mass was not determined.

Animals↗