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Biomedical subjects

G D Potter

Publications and source records attributed to G D Potter.

At least 19 recordsLinked to original sources
PubMed2006

Meal size and feeding frequency influence serum leptin concentration in yearling horses.

Energy is an essential nutrient for all horses, and it is especially important in performance horses, pregnant and lactating mares, and young growing horses. A negative energy balance in horses such as these may result in unsatisfactory performance, decreased fertility, or slow growth. Therefore, ensuring adequate energy intake is an important aspect of the nutritional management of the equine. This study was undertaken to investigate the effects of feeding large, carbohydrate-rich, concentrate meals on the satiety-inducing hormone, leptin. Three groups of yearling horses were rotated through 3 feeding schedules in a replicated 3x3 Latin square design. Horses were fed 2, 3, or 4 times per day (2x, 3x, and 4xfeeding schedules, respectively), each for a period of 11 d, with the total amount of daily feed held constant. Horses were weighed and BCS was determined on the first day of each period. Blood samples were collected before the morning meal on d 1, 4, and 7 of each period. Additionally, blood was sampled for the last 24 h of the 2xand 4xdietary periods. Neither weight nor BCS changed during the study (P = 0.99 and P = 0.28, respectively). Both mean and peak plasma glucose were greatest in 2xhorses (P < 0.05), as were mean areas under the curve. Serum leptin concentration increased in 2xhorses (P < 0.05), but not in horses fed 3 or 4 times daily. Leptin was elevated in horses with greater BCS (P < 0.05) and increased steadily throughout the study (P < 0.05). Data from the 24-h collection indicated that 2xhorses had fluctuations in leptin production throughout the day (P < 0.05), whereas horses fed 4 times daily did not. Overall, this study indicates that feeding horses 2 large concentrate meals daily can increase mean serum leptin concentrations and may cause fluctuations in leptin production over a 24-h period. This departure from baseline leptin concentration has the potential to affect appetite, along with numerous other physiological processes.

Animal Feed↗
PubMed2001

Infliximab for refractory ulcerative colitis.

Eight patients with active ulcerative colitis (UC), refractory to usual combination medical therapy, were treated with a single i.v. dose of chimeric monoclonal antibody to recombinant human tumor necrosis factor alpha; many of these patients were scheduled for surgical colectomy because of their active disease. All patients responded extremely well to a single 5 mg/kg infusion of infliximab, with marked improvement after the infusion clinically, colonoscopically, and histologically on colonic biopsy. There were no significant complications or side effects; mean duration of remission has not been determined because none of the patients have relapsed. Infliximab appears to be a potent agent for inducing remission in refractory patients with ulcerative colitis.

Adult↗
PubMed1998

Prevalence of Helicobacter pylori in peptic ulcer patients in greater Rochester, NY: is empirical triple therapy justified?

OBJECTIVES: Among patients with peptic ulcer disease, the prevalence of Helicobacter pylori has been reported to range from 80% to 90%. Thus empirical cost-effective therapy has been suggested. We surveyed patients with peptic ulcer disease in Rochester, NY. METHODS: From two teaching hospitals all patients who had duodenal ulcers (DU) and/or gastric ulcers (GU) on esophagogastroduodenoscopy (EGD) with antral biopsy for histology for H. pylori and for rapid urease (CLO) test were included in the study. We examined a total of 160 patients with DU and 145 patients with GU, age range 18-92 yr, obtaining clinical data, race, medication profile, and history of use of nonsteroidal antiinflammatory drugs (NSAIDs). An ulcer was defined if the lesion with loss of mucosal integrity was > or = 0.5 cm, with apparent depth. H. pylori was considered present if CLO test and/or histology were positive for H. pylori. To confirm the reliability of nonuse of NSAIDs, we randomly checked blood samples of 90 such patients from the ambulatory clinic for the presence of salicylates. To identify the sensitivity of the CLO test, we performed a serology test for H. pylori antibody in 100 subjects to compare the CLO test results. Also, 500 CLO test results were compared to the histology results for H. pylori. RESULTS: Among 160 DU patients, 16 were NSAID users with negative H. pylori and excluded from the prevalence study. Of the remaining 144 patients with DU, H. pylori was present in 88 patients (61%). When these data were analyzed according to race, H. pylori was present in 54 (52%) of 104 whites compared to 34 of 40 (85%) nonwhites (blacks, Hispanics, Asians) (p < 0.01). Among 145 GU patients 18 were NSAID users with negative H. pylori and excluded from the prevalence analysis. Of the remaining 127 patients with GU, H. pylori was present in 87 patients (61%). Among them, H. pylori was present in 46 of 87 (53%) whites, whereas 31 of 40 nonwhites (78%) were H. pylori-positive (p < 0.01). Antral histology and CLO test for H. pylori were in agreement in 92% of cases. Serology and CLO test for H. pylori were in agreement in 87% of cases. None of the randomly screened patients, including 16 ulcer patients with negative H. pylori, showed presence of salicylate in blood. CONCLUSION: In greater Rochester, NY, where the majority of our patients with EGD were whites, the prevalence of H. pylori among ulcer patients was lower compared to other regions, particularly among whites. This suggests that an additional causative factor or factors for peptic ulcers may be present. Hence, empirical antibiotic therapy of ulcer patients without confirming the presence of H. pylori may not be justified.

Adolescent↗
PubMed1995

Disinfectant colitis. Rinse as well as you wash.

Commercially available endoscope disinfecting solutions readily cause colonic damage if allowed to contact mucosa. The two most common cleaning solutions differ in their initial toxic effect (glutaraldehyde directly injuries crypt epithelium, and hydrogen peroxide compromises mucosal stroma), but both ultimately result in tissue necrosis over time. Within 12-48 h after colonoscopy, patients show signs of bloody diarrhea, cramping, and fever--symptoms that may be confused with an infectious process. Based on a literature review and our own experimental studies, we conclude that hydrogen peroxide alone is responsible for a unique form of colitis commonly referred to as pseudolipomatosis by pathologists. This controversial lesion becomes visible as opaque plaques or pseudomembranes even while colonoscopy is in progress and is almost assuredly due to the effervescent release of molecular oxygen. Diligent rinsing is necessary to minimize patients' exposure to residual disinfecting chemicals in the endoscope. When an automatic disinfecting machine is employed, it may require strict adherence to proper maintenance and volume adjustments in the rinse cycle. Forced air drying and an additional preprocedure rinse of channels and the exterior of the scope should ensure a chemical-free examination.

Animals↗
PubMed1994

Technique for long-term ileal cannulation in ponies.

A T-cannula was fitted permanently into the ileum of ten mature ponies to quantify the role of the prececal and postileal segments of the digestive tract in equine nutrition studies. The ponies were anesthetized, positioned in left lateral recumbency, and the distal small intestine was exteriorized through a right paralumbar incision. A silastic T-cannula was inserted through a 2-cm longitudinal incision into the lumen of the ileum, on the antimesenteric surface, and sutured to the ileum. The stem of the cannula was exteriorized through a 2-cm circular skin incision, 6 cm caudal to the 16th rib. Nine ponies were alive with functional cannulas after six months. Primary complications associated with cannulation of the ileum were clinical signs of depression and dehydration produced by leakage of intestinal contents around the stem of the cannula. These complications were resolved with fluid and electrolyte therapy.

Animals↗
PubMed1991

Nonsurgical recovery of degenerative ova from the uteri of mares.

Degenerated ova were recovered with and without viable embryos 6 days after ovulation in 30 of 210 collections from 24 of 66 mares. All ova were approximately 150 mum in diameter, with an intact zona pellucida and at various stages of cytoplasmic degeneration. Most of the ova were collapsed, although some had an oval appearance. Most of the ova were from maiden 2-year-old mares. Thirty-four of the ova were recovered from the first or second collections. Two ova were recovered from the third collection from two mares. Two degenerative ova per collection were recovered from five collections; three of these collections also contained viable embryos. Degenerated ova were recovered from three mares twice; but not from consecutive collection attempts. Recovered ova were fixed in 2% glutaraldehyde-PBS for scanning electron microscopy. These data indicate that not all unfertilized ova remain permanently in the oviduct; many traverse it and enter the uterus. Furthermore, these data also suggest that when degenerative ova pass into the uterus they either degenerate further and (or) move into the vagina. This is supported by the fact that not all ova can be accounted for when the uterus and (or) the oviducts are washed.

Journal Article↗
PubMed1991

Bile acid stimulation of cyclic AMP and ion transport in developing rabbit colon.

Bile acids elicit Cl secretion and increases in short circuit current (Isc) in rabbit distal colon in vitro in adult but not newborn animals. In this investigation we found that concentrations of taurodeoxycholic acid (TDC) as low as 50 microM significantly increase cyclic AMP (cAMP) in adult but not newborn colon. Further, blocking the increases of cAMP in adult colon with 3,4,5-trimethoxybenzoate 8-(N,N-dimethylamino) octyl ester (TMB-8), partially inhibited the effect of TDC on Cl secretion. TMB-8 did not block the effect of increases in cAMP seen with vasoactive intestinal peptide (VIP), theophylline, or forskolin. When newborn colon was exposed to 1 mM TDC, limited Cl secretion was elicited. Increased cAMP is not seen in newborn colon where TDC-induced secretion is absent. Thus, increases in cAMP may represent one part of the coupling of TDC stimulation to Cl secretion.

Animals↗
PubMed1990

Intestinal development and regeneration.

This first article of a new series on "cellular" gastroenterology focuses on the embryogenesis and neonatal development of the gut. In this context, the effects of malnutrition, morbidity, and trauma on intestinal histodynamics are discussed, as are compensatory adaptations analogous to those in the circulatory responses to heart failure.

Adult↗
PubMed1990

Atrial natriuretic factor and cyclic guanosine monophosphate: ion transport in rat colon in vitro and in vivo.

The role of atrial natriuretic factor receptors in the colon is uncertain. Accordingly, the effects of atrial natriuretic factor in vivo and in vitro were studied. In vivo perfusion of the colon in Sprague-Dawley rats was used to measure Na+, K+, Cl-, and water transport, while atrial natriuretic factor was infused into the jugular vein at 0.5 or 1.0 micrograms.kg-1.min-1. In vitro experiments in Ussing chambers measured short-circuit current and ion fluxes before and after atrial natriuretic factor administration. Because cyclic guanosine monophosphate is thought to be a second messenger for atrial natriuretic factor, short-circuit current was also determined before and after exposure to 8-Br-cyclic guanosine monophosphate. Plasma atrial natriuretic factor (atriopeptin III) levels were determined by radioimmunoassay. The in vivo transport of water, sodium, and chloride and the secretion of potassium were not altered by atrial natriuretic factor infusion. In vitro studies showed no change in Na+ or Cl- transport or change in short-circuit current. Plasma atrial natriuretic factor concentrations increased from 139 +/- 55 pg/mL to 1385 +/- 396 pg/mL during infusion, and urine output increased from 12.6 +/- 0.5 microL/min to 37.4 +/- 2.9 microL/min (P less than 0.05). In contrast, 8-Br-cyclic guanosine monophosphate in vitro caused a significant (P = 0.0004) increase in short-circuit current from 1.2 +/- 0.2 to 2.9 +/- 0.3 microEq.cm-2.h-1.

Animals↗
PubMed1989

Phenamil inhibits electrogenic sodium absorption in rabbit ileum.

Electrogenic Na absorption, independent of either nutrients or other ions, occurs in the rabbit ileum. However, unlike electrogenic Na absorption in the distal colon and other tight epithelia, this ileal transport system is not inhibited by amiloride. Because of this amiloride insensitivity, ileal electrogenic Na absorption has been poorly characterized. To more clearly delineate the underlying mechanisms of this pathway, we examined the effects of phenamil, an amiloride analogue, on ion fluxes and electrical parameters in rabbit ileum in vitro under short-circuit conditions. Phenamil has been shown to have a high affinity for Na channels, but minimal effect on Na-H exchange. Amiloride (10(-8) through 10(-4) M) had a minimal effect on short-circuit current. In contrast, phenamil induced a significant decrease in short-circuit current; the maximal effect was seen at 10(-4) M phenamil. There was an associated decrease in conductance at 10(-4) M phenamil. Ion flux studies were performed in normal, chloride-free and bicarbonate-free Ringer's solution; under each condition, 10(-4) M phenamil inhibited mucosal-to-serosal Na flux, net Na flux, and short-circuit current without significantly altering other fluxes. Phenamil did not inhibit the electrical response to either 10 mM glucose or 1 mM theophylline, indicating that the drug did not block either nutrient-coupled electrogenic Na absorption or electrogenic Cl secretion, and did not inhibit sodium-potassium-stimulated adenosine triphosphatase. These results demonstrate that electrogenic Na absorption in rabbit ileum may be blocked by the amiloride analogue phenamil, suggesting that, in this epithelium, Na absorption may occur via Na channels in which the amiloride-binding site has been significantly altered.

Amiloride↗
PubMed1989

Postpartum reproductive performance in the multiparous mare fed to obesity.

Twenty multiparous Quarter Horse mares were assigned to one of two treatment groups at 40 to 75 d of pregnancy. Group 1 was the control group and the mares were fed to maintain a moderate degree of body fat (condition score 5.5 to 7). Group 2 was the obese group and the mares were fed to achieve (prepartum) and then maintain (post partum) an extremely high degree of body fat (condition score 9). Estrous intensity was evaluated using subjective teasing scores ranging from 0 (rejection) to 4 (maximum receptivity). Mares were artificially inseminated beginning with the second postpartum ovulatory cycle; the study was terminated after 63 d of pregnancy. Duration of estrus, maximum teasing score and the number of mares exhibiting overt estrus (teasing score > 2) did not differ between treatment groups during the first and second postpartum ovulatory cycles. The intervals from foaling to first cycle ovulation, foaling to second cycle ovulation, and first to second cycle ovulation were also similar between treatment groups. All mares in both treatment groups conceived and maintained pregnancy. The first cycle conception rate and the number of cycles per conception did not differ between treatment groups. A high degree of body fat produced by overfeeding during gestation did not adversely affect postpartum reproductive performance in the multiparous mare.

Journal Article↗
PubMed1989

Electrogenic sodium transport in the developing rabbit cecum.

The adult rabbit cecum absorbs Na by an electrogenic, Cl-independent process that is inhibited by the amiloride analogue phenamil. In the colon, this transport system is unique to the cecum. Because the developing colon exhibits many specialized functions, we have now examined the development of electrogenic Na transport in the newborn rabbit. Cecal tissue from animals between 7 and 38 days old was mounted in modified Ussing chambers for measurement of Na and Cl flux (J) and the short-circuit current (Isc). At 7-10 days, the (Isc) was only 0.8 +/- 0.18 microEq cm-2 h-1, but by 35-38 days it had increased to 4.6 +/- 0.79 microEq cm-2 h-1. The Na transport increased in parallel with Isc; JNanet = -0.49 +/- 0.33 microEq cm-2 h-1 at 7-10 and 4.7 +/- 1.6 microEq cm-2 h-1 at 35-38 days. The Na transport was not inhibited by phenamil (10-4 M) at 7-10 days, but by the 35-38-day period, phenamil reduced the JNanet to 1.6 +/- 0.37 microEq cm-2 h-1. The Cl secretion was not stimulated by theophylline in the 14-16-day-old cecum, nor was Na absorption stimulated by epinephrine. The rabbit cecum does not demonstrate electrogenic Na absorption until after the 4th week of life.

Animals↗
PubMed1989

Potassium secretion in response to taurodeoxycholic acid in the newborn rabbit colon.

The newborn colon fails to secrete Cl in response to concentrations of dihydroxy bile acid that cause Cl secretion in adult colonic tissue in vitro. Bile acids also cause secretion of potassium in adult tissues, but there is no information concerning bile acid effects on potassium transport in newborn colon. We mounted newborn rabbit distal colon in Ussing chambers specially designed for newborn colon and measured potassium transport. Basal potassium transport was secretory. Taurodeoxycholic acid, 100 microM, (TDC) decreased JKnet from -0.76 +/- 0.07 to -0.94 +/- 0.11 microEq cm-2 h-1, p less than 0.05, without increasing Isc. Serosal ouabain, 0.1 mM, abolished the secretory response to TDC. Mucosal Ba2+, a potassium channel blocker in many epithelia, did not inhibit K secretion. Similar serosal exposure to TDC in adult colon tissues decreased JKnet from -0.09 +/- 0.29 to -1.63 microEq cm-2 h-1, p less than 0.01, and increased Isc. We conclude that, although the chloride secretory response to dihydroxy bile acids is absent in the newborn, K secretion is elicited in the newborn, similar to the adult colon.

Animals↗
PubMed1989

Isolated sphenoid sinus disease.

Forty-three cases of isolated sphenoid sinus disease were reviewed. In 33 cases, headache was a presenting symptom. Seven of 29 cases of inflammatory disease and nine of 13 patients with tumors of the sinus presented with cranial nerve findings. When nonspecific visual disturbances were eliminated, two of 29 cases of inflammation and eight of 13 cases of tumors of the sphenoid sinus had cranial nerve deficits. Ten of 12 CT scans performed on patients with tumors of the sinus demonstrated bony erosion or perisinus extensions. This was not found in any of the 27 scans of patients with inflammatory disease. A thorough cranial nerve examination and a CT scan should be performed early in patients who present with vague and unusual headaches.

Adolescent↗
PubMed1989

Growth performance of yearling horses grazing bermudagrass pastures at different grazing pressures.

Body weight gains and height at the withers were measured in yearling geldings grazing bermudagrass (Cynodon dactylon [L.] Pers.) pastures with neither energy nor protein feed supplementation at stocking rates of 6.7, 8.0, 9.5 and 12.4 yearlings per hectare. Weekly forage samples were taken to estimate the quantity and quality of available forage. These samples were clipped and separated into three equal lengths to characterize upper, middle and lower thirds of the canopy and to determine relationships between available forage and yearling growth rate. Average daily gain was influenced by stocking rate, but gain in height was not affected by stocking rate. Average daily gain ranged from -.31 to .37 kg/d and was negatively related to stocking rate. A quadratic relationship between available forage and ADG was detected. However, a linear relationship between ADG and available forage in top layers of the canopy indicated that animal performance might have been limited by availability of top layer forage in pastures subjected to light grazing pressure.

Analysis of Variance↗
PubMed1988

Methods for collecting follicular oocytes from mares.

A series of experiments was conducted to develop a procedure for consistent, repeatable collection of oocytes from the preovulatory follicle of the mare. In one experiment, in situ follicular aspiration with a needle and syringe was performed on 19 mares. From 37 aspirations, four oocytes were recovered (10% recovery rate). In a second experiment, ovaries were visualized via standing flank laparotomy during which two different aspiration techniques were used. Use of a needle and syringe as in the first experiment resulted in successful oocyte recovery in one of seven (14%) attempts. Aspiration via a continuous irrigation vacuum system (CIV), developed for use during laparotomy, resulted in collection of oocytes from six of 10 (60%) attempts. In the third experiment, oocytes were recovered from seven of 18 (38%) attempts at in situ follicular aspiration using a double-lumen needle attached to the CIV. In each experiment, some mares were subjected to stimulation of follicular maturation by exogenous hormones. Oocyte recovery was significantly increased in treated mares as compared with nontreated mares. Results indicate that collection of equine follicular oocytes by in situ aspiration is possible with moderate success. Oocytes apparently are not physically damaged by the procedure, as most retained either the corona radiata or the entire cumulus cell mass.

Journal Article↗
PubMed1988

Digestion of hay protein in different segments of the equine digestive tract.

Mature ponies fitted with permanent ileal cannulas were used in a 3 X 3 Latin square experiment to quantify prececal, postileal and total tract digestion of hay protein. Coastal Bermuda grass (CB), containing 11.7% crude protein, and two qualities of alfalfa, containing 15.0% (low-protein alfalfa; LA) and 18.1% (high-protein alfalfa; HA) crude protein, were fed in coarsely chopped form at 2% of body weight daily. Total tract apparent digestibility of the N in HA (73.8%) was higher than that in CB (57.0%; P less than .05) and was slightly higher than that in LA (66.1%; P less than .10). Nitrogen in LA was apparently more digestible than that in CB (P less than .05). Apparent prececal digestibilities of N in LA and CB were 1.3% and 9.6%, respectively, and were lower (P less than .05), or tended to be lower (P less than .10), than the 21.0% observed for HA. In relative terms, an average of 9.4% of the total N digestion occurred in the upper tract when CB and LA were fed, whereas 28.5% of total N digestion occurred in the foregut when HA was fed. There was a slightly higher concentration of total plasma free amino acids (P less than .10) at 1 h postfeeding when horses were fed alfalfa. Also, N retention was higher when ponies were fed HA (P less than .05) than when LA or CB were fed. Apparent postileal N digestibility was 52.5% for CB, 65.7% for LA and 66.9% for HA. Differences were not significant, and the large intestine appeared to compensate for the inefficiency of N digestion in the upper tract.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗