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Biomedical subjects

J P Peters

Publications and source records attributed to J P Peters.

At least 19 recordsLinked to original sources
PubMed1992

Disappearance of acetic acid from the bovine reticulorumen at basal and elevated concentrations of acetic acid.

Disappearance of acetic acid was quantified to determine whether removal of this acid from the reticulorumen is altered when ruminal acetic acid concentrations are elevated. Ruminally fistulated beef steers (n = 3 per experiment; BW = 320 +/- 9 kg) were fed eight times daily a 46% corn-based concentrate:54% mixed hay diet to meet maintenance energy requirements (3.5 kg of DM/d). In situ production of acetic acid, determined by pulsed-continuous infusion of [1-14C]acetic acid, was 530 mmol/h (CV = 12%). Disappearance from the reticulorumen (i.e., presumed absorption) was 460 mmol/h (CV = 2%) or 87% (CV = 2%) of ruminal production. Variation is described within an operational steady state. Acetic acid concentrations were increased by continuous infusion of unlabeled acetic acid into the reticulorumen. Ruminal disappearance (mmol/h) increased when this simulated production was elevated up to and exceeding in situ rates reported previously (530 to 2,700 mmol/h). These data suggest that two-thirds to three-fourths of ruminal acetate production disappeared across the reticuloruminal wall when concentration was elevated; the complement exited from the rumen with the liquid phase. The reticulorumen has an additional capacity to remove acetic acid; however, it does so with an apparent reduced efficiency at higher production rates. Liquid out-flow may affect the efficiency of reticuloruminal disappearance. Sites distal to the rumen become quantitatively important when ruminal acetic acid concentrations are increased.

Absorption↗
PubMed1992

Effect of recombinant porcine somatotropin and dietary protein on pancreatic digestive enzymes in the pig.

This study was conducted to determine the effect of daily recombinant porcine somatotropin (rpST) injection (0 or 120 micrograms/kg BW) and dietary CP level of the feed (14 or 26% CP) on pancreatic characteristics of growing pigs. Daily injection of rpST did not affect pancreatic weight (P = .885) but did decrease pancreatic amylase content (P = .005). The ratios of amylase:protein and amylase:trypsin were also lowered by daily rpST injection (P = .002 and P = .0002, respectively). There were protein x rpST and protein x rpST x sex interactions for the ratio of amylase:chymotrypsin. The CP content of the diet had a greater effect than the injection of rpST on pancreatic characteristics. Pigs consuming the 26% CP diet had significantly higher pancreatic weight (P = .003) and greater total pancreatic chymotrypsin (P = .006) than pigs consuming the 14% CP diet. The ratios of trypsin and chymotrypsin to DNA were also higher in pigs fed the 26% CP diet (P = .007 and P = .005, respectively). These responses were not influenced by sex. Recombinant porcine somatotropin seemed to have a slight effect on porcine pancreatic characteristics; however, dietary protein had a greater effect on pancreatic characteristics in market-weight hogs.

Adipose Tissue↗
PubMed1992

Collection of pancreatic exocrine secretions by formation of a duodenal pouch in cattle.

Collection of exocrine pancreatic secretions from cattle by use of a single-unit cannula was performed. The major advantage of the cannula was simple technical management. A small pouch of the duodenum into which the major pancreatic duct drains was formed. Continuity of the duodenum was reestablished by end-to-end anastomosis. A side arm of the cannula was inserted into the pouch to collect exocrine secretions, and the main portion of the cannula was placed cranial to the anastomosis to return pancreatic secretions to the small intestine between collection periods. The accessory pancreatic duct was ligated in 2 of 4 cattle to evaluate possible secretory contribution from this source. All cattle remained healthy after cannulation, and cattle gained approximately 100 kg of body weight in the 5 months after surgery. The mean secretory rate for exocrine pancreatic secretion in cattle was 106 +/- 6.8 ml/h. There was no effect of feeding on the pattern of secretion nor were there significant differences between cattle. A fistula formed between the pouch and duodenum approximately 120 days after surgery in the first 2 cattle used. Development of fistulas was prevented for 300 days in subsequently prepared cattle by use of surgical mesh around the cannulas, leading to functional cannulation sites. Preparation of a duodenal pouch appeared useful for long-term studies of pancreatic exocrine secretion in cattle.

Animals↗
PubMed1991

Pilocarpine and digestive efficiency in beef cattle fed a high-concentrate diet.

The effect of pilocarpine HCl, a parasympathetic muscarinic agonist, on digestive characteristics was evaluated in growing beef steers fed a high-grain diet. Oral doses of 0, 2 or 4 mg/kg BW were administered daily to each of eight steers immediately prior to offering an 88% concentrate: 12% hay diet in this three-period crossover design (19 d/period). Treatments did not improve digestibilities of dry matter, organic matter and nitrogen, ruminal liquid volume and fractional dilution rate, body weight gain or feed efficiency. Although daily voluntary feed intake was not altered by treatment (P = .25), there was a dose-dependent slowing of the rate at which feed was consumed (P less than .01). Also, ruminal fluid pH was increased with increasing dose (5.36, 5.55 and 6.11 respectively; P = .10). These observations indicate that the digestive improvements due to pilocarpine reported to occur in mature, nongrowing cattle consuming a high-forage diet are not observed in growing steers fed a production-type diet.

Administration, Oral↗
PubMed1990

Disappearance and passage of propionic acid from the rumen of the beef steer.

Studies were conducted to define steady state pH, propionic acid concentrations and fluid turnover in the rumen of steers fed every 3 h and to determine whether rates of ruminal propionic acid disappearance were linearly related to their in situ production rates. Ruminally fistulated beef steers (326 +/- 11 kg; n = 3) were fed eight times daily a 54% mixed hay: 46% corn-based concentrate diet to meet maintenance energy requirements. Maximal acceptable variations from the mean at steady state conditions of pH, propionic acid concentrations and specific activity, and liquid flow (Cr marker concentrations) were defined as 4%, 20%, 30% and 10%, respectively, across 4 h of observation. In situ production of propionic acid, determined by pulse-continuous infusion of 1-14C-propionic acid, was 142 mmol/h (CV = 8.4%). The ruminal half-life of propionic acid was estimated to be 1.5 h and the liquid flow rate was 3.8 liters/h. Propionic acid production rates subsequently were elevated by continuous intraruminal infusion of buffered propionic acid. Irrespective of production (basal and infusion) rate, approximately 66% disappeared (i.e., presumed absorption) and 34% passed from the rumen to the lower tract in the liquid phase. Ruminal disappearance of propionate was linearly related with its production rate, and propionate concentrations and production rates also were linearly related. Liquid passage was linearly related to production rate, but there was insufficient evidence to conclude that fractional dilution rate or ruminal volume were similarly related. When ruminal production of propionic acid is elevated, the rumen has additional absolute capacity to remove propionate, but the fractional removal appears to be constant. The digestive tract distal to the rumen is likely an important site of propionate absorption in cattle when propionate production is high.

Absorption↗
PubMed1990

Propionic acid disappearance from the foregut and small intestine of the beef steer.

Studies were conducted to determine the disappearance of propionic acid from the rumen and across the small intestine. Four crossbred beef steers, fitted with ruminal, duodenal and ileal cannulas, were given pulsed-continuous infusions of a nonabsorbable liquid phase marker (CrEDTA) and buffered propionic acid to achieve ruminal propionate productions (RPP) of 142 (basal), 567 and 997 mmol/h. Liquid flows from the rumen, and at the duodenum and ileum (2.75, 3.57 and .92 liters/h, respectively) were not affected by RPP (P greater than .23), although significant differences existed between sites (P = .001), reflecting a net addition of liquid between the rumen and duodenum and a net removal of liquid within the small intestine. Propionate disappearance from the rumen was 40 to 57% irrespective of RPP, with the complement passing from the rumen. Of the propionate that exited the rumen, 93 to 97% disappeared prior to entering the duodenum. Overall removal of RPP prior to the duodenum was 97 to 99% irrespective of RPP. Passage of propionic acid at the duodenum and at the ileum did not differ (P greater than .76) across all RPP, and the overall mean passages did not differ from zero (P greater than .34); similar results were observed for other VFA. These observations indicate that essentially all RPP is removed prior to entering the small intestine. Additionally, net propionate disappearance across the small intestine was undetectable and likely biologically irrelevant. Therefore, VFA absorption does not appear to be a limiting biological process in the beef steer.

Animals↗
PubMed1990

The effects of diet on water flux and volatile fatty acid concentrations in the rumen of growing beef steers fed once daily.

In vivo temporal changes in ruminal liquid flow, liquid volume and VFA concentrations were determined in growing steers following once-daily feeding. Crossbred beef steers (n = 8; 278 +/- 8 kg), used in a crossover design, were trained to consume 180% of their maintenance energy intake within 2 h of either a high-forage (54% hay: 46% concentrate; HF) or high-concentrate (28% hay: 72% concentrate; HC) diet. For each animal on each diet, ruminal VFA concentrations, liquid volumes and liquid dilution rates were determined during a 2-h period before feeding and during three consecutive 2-h periods following feeding. Water was withheld during these periods to observe physiologically rather than behaviorally induced changes. At equal energy intakes, diet alone had no effect on VFA concentrations (P greater than .10), although changes in total VFA, acetic and isobutyric acids differed during the time periods following feeding due to diet (diet x time period interaction; P less than or equal to .10). Ruminal volume and dilution rate were altered in a reciprocal manner due to diet, with greater volumes and lower dilution rates observed in HC than in HF steers. Differences among time periods were observed for dilution rate and propionic acid concentrations. In general, these differences can be explained by comparison of the prefeeding time period with the postfeeding time periods. A numerical, but not statistically significant, increase in ruminal volume was observed following feeding. The effects of diet on volume and liquid dilution rate of the rumen must be considered when assessing total nutrients available for animal absorption.

Analysis of Variance↗
PubMed1990

Influence of dietary forage and feed intake on carbohydrase activities and small intestinal morphology of calves.

Twenty (12 Holstein, 8 Longhorn cross) calves (198 kg and 7 mo old) were used in a randomized complete block design to evaluate the effects of dietary forage concentration and feed intake on carbohydrase activities and small intestinal (SI) morphology. Calves were individually fed 90% forage (alfalfa) or a 90% concentrate (50% sorghum: 50% wheat) diet at either one or two times NEm for 140 d and slaughtered; tissues and small intestinal digesta were collected. Increased feed intake increased (P less than .05) pancreatic weight, alpha-amylase and glucoamylase activities in the pancreas, SI length and SI digesta weight. Forage-fed calves gained faster (P less than .01) and had greater (P less than .05) pancreatic protein concentrations, alpha-amylase and glucoamylase activities in the pancreas and greater SI digesta alpha-amylase activities than grain-fed calves did. Increased feed intake increased (P less than .01) mucosal weight/cm small intestine only in forage-fed calves and increased (P less than .05) SI surface/volume only in grain-fed calves. Mucosal weight was greatest (P less than .05) at the terminal ileum, surface/volume was greatest (P less than .05) in the duodenum, and mucosal protein concentration was highest (P less than .05) in the SI mid-section. Mucosal lactase was higher (P less than .05) in proximal segments, whereas mucosal isomaltase was higher in middle and distal segments of the small intestine. For mucosal maltase activity, there was a feed intake x SI sampling site interaction (P less than .05) and for trehalase, a diet x feed intake x SI sampling site interaction (P less than .05). The SI distribution patterns of maltase and isomaltase were similar, as were those of trehalase and lactase. The alpha-amylase activity in the pancreas and SI morphology were influenced greatly by diet composition and feed intake by calves.

Amylases↗
PubMed1989

In vitro total-gas, CH4, H2, volatile fatty acid, and lactate kinetics studies on luminal contents from the small intestine, cecum, and colon of the pig.

Two experiments were conducted to assess differences in fermentative activities of digesta obtained from various regions of the pig gastrointestinal tract. In experiment 1, the contents of small intestines, ceca, and colons of 110-kg pigs were collected, diluted twofold, and incubated for 2 h at 37 degrees C. In experiment 2, colonic samples from 16,100-kg pigs were similarly treated, except that the incubation period was 5 h. Total gas (gas pressure), CH4, H2, lactate, formate, acetate, propionate, butyrate, valerate, and isovalerate were measured in experiment 1. Only the gas variables were measured in experiment 2. Statistically significant differences (P greater than 0.05) were not observed among the gas production rate estimates across the small-intestinal, cecal, and colonic regions in experiment 1. Furthermore, all the small-intestinal samples and half the cecal samples assayed in experiment 1 were nonmethanogenic. The mean methanogenic and total-gas production rate estimates for the colonic samples in experiment 1 were 0.052 ml g of wet contents-1 h-1 and 1.7 ml of total gas g of wet contents-1 h-1, respectively. No differences in the methanogenic rate estimates were detected between the proximal, middle, and distal thirds of the pig colons (P greater than 0.05). The volatile fatty acid and lactate molar percentages measured in experiment 1 were consistent with previously published observations. Hydrogen accumulated to the greatest extent (7 microM on average) in the in vitro incubations of small-intestinal contents, whereas the H2 concentrations ranged from 0.5 to 1 microM for the incubated cecal and colonic samples in experiment 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Factors affecting the in vitro production of volatile fatty acids by mixed bacterial populations from the bovine rumen.

Factors affecting in vitro ruminal bacterial VFA production were examined. Treatments consisted of high and low initial pH (6.7, 5.7), osmolality (600, 400 mOsm) and concentrations of acetic (40, 0 mM) and propionic acids (20, 0 mM). Response variables measured included the production of acetic, propionic and total VFA, total gas and methane. Initial pH affected (P less than .05) most variables either independently or in combination with one or more of the other factors. Acetic acid production was reduced 40% (P = .03) when initial acetic acid concentrations were 40 mM compared with 0 mM. Also, acetic acid production was less (P less than .01) at low initial pH (5.7) than at high initial pH (6.7). Propionic acid production was greater (P = .05) at high vs low initial acetic acid concentrations. Propionic acid production was greater in response to low vs high initial osmolality, although the magnitude of this difference depended on initial pH (interaction P = .02). Total production of VFA was greater (P less than .01) at high than at low initial pH; however, at low initial pH, no difference (P greater than .05) was observed due to initial osmolality, whereas at high pH, production was greater (interaction P = .04) for low than for high initial osmolality. The diminished production of total VFA at pH 5.7 occurred primarily due to reduced acetic acid production, although increased production of propionic and butyric acids was noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1987

Cellular composition of follicles of follicle centre cell lymphomas in relation to germinal centres of reactive lymph nodes. A morphometrical electromicroscopical study.

The cell spectrum of neoplastic and benign reactive germinal centres was determined ultrastructurally. The degree in which the cell composition found in reactive germinal centres is maintained in analogous structures of follicular lymphomas was investigated by pattern recognition methods and discriminant analysis based on the frequencies of the various lymphoid and non-lymphoid cell types. The follicular lymphomas included lymphomas with predominantly centrocytes (FCCL, Cb-cc) and lymphomas with predominantly centroblasts (FCCL, Cb). Pattern analysis of FCCL Cb, FCCL Cb-cc and reactive germinal centres indicates that FCCL Cb follicles resemble reactive germinal centres in more aspects than follicles of FCCL Cb-cc. Clear statistical differences were encountered between the frequencies of the lymphoid cell types and of the follicular dendritic and histiocytic reticulum cells in follicles of FCCL Cb-cc and FCCL Cb and reactive germinal centres. Application of a discriminant analysis using a combination of the frequency of centrocytes and follicular dendritic cells demonstrated that both types of neoplastic follicles and reactive germinal centres were correctly classified on the basis of their cell spectrum. For the three groups the most potent discriminator was the centrocyte, whereas the small and large centroblast were of less value. For discrimination between Cb-cc follicles and reactive germinal centres again the centrocyte was the most potent discriminator. Discrimination between FCCL Cb follicles and reactive germinal centres of FCCL Cb-cc follicles can be easily achieved using the frequencies of small centroblasts or centrocytes on their own. These findings indicate that (1) follicles of both FCCL Cb and FCCl Cb-cc differ greatly in the cellular composition and not only with respect to their content of centroblasts but also in their content of follicular dendritic cells and (2) they may be considered as neoplasms representing different developmental phases of germinal centres.

Castleman Disease↗
PubMed1986

Consequences of accelerated gain and growth hormone administration for lipid metabolism in growing beef steers.

Lipid accretion and metabolism during accelerated gain and growth hormone administration were examined in a 29-d trial with 24 beef steers. Treatments in this 2 X 2 factorial design consisted of level of feeding (restricted or ad libitum) and exogenous hormone [pituitary-derived bovine growth hormone (GH) at 38 IU/d or excipient]. Live weight gain was not affected by hormone treatment. Protein content of the 9-10-11th rib section was greatest in steers receiving GH irrespective of feeding level, whereas a reduction of lipid content due to GH was seen only with ad libitum feeding. Restricted-fed steers had the highest plasma concentrations of free fatty acids (FFA), and only at this feeding level did GH treatment result in further elevation of FFA concentrations. In vitro rates of adipose lipogenesis, esterification and lipolysis were greatest in tissue from ad libitum-fed steers. The only effect of GH on in vitro metabolism was a tendency for lower lipolytic rates with ad libitum feeding. GH did not affect adipocyte size. The mechanism for the effect of GH on lipid deposition could not be determined from incubations of adipose slices from chronically treated steers, although enhanced responsiveness to an in vivo lipolytic challenge was observed. By inference, substrate availability appears to determine the productive responses to GH.

Adipose Tissue↗
PubMed1984

Distribution of dendritic reticulum cells in follicular lymphoma and reactive hyperplasia. Light microscopic identification and general morphology.

Reactive and neoplastic follicles in lymph nodes showing changes of (1) follicular hyperplasia and (2) follicular lymphoma were examined for the presence of dendritic reticulum cells (DRC). These cells could be identified under the light microscope after comparing electron microscopical sections with subsequent 1 micro sections of reactive germinal centres. Quantitative light microscopical evaluation showed that DRC, both mononuclear and binuclear forms, were less numerous in neoplastic follicular structures than in reactive follicles. Before determining the frequency of binucleated DRC in follicular tissue their morphology was studied first in cell suspensions. DRC isolated by enzymatic treatment of tonsils and reactive lymph nodes were morphologically identical and contained one, or at most two, nuclei arranged in a typical doublet formation. Stereological calculations - made on three dimensional models of nuclear complexes prepared from serial tissue sections - indicated that 51 to 68% of DRC in reactive germinal centres were binucleated, whereas in neoplastic follicles this figure is 18 to 23%. The multinucleated giant cell forms of DRC described by others result from complex formation with other DRC or lymphoid cells. The smaller number of DRC and the lower frequency of binucleated DRC in follicular lymphomas suggest that differentiation of DRC from stromal cells is less complete in these neoplasms. The ability to identify DRC reliably by light microscopy offers a new means to define the difference in frequency of DRC. This may be of practical value in distinguishing reactive germinal centres from neoplastic follicles.

Cell Count↗
PubMed1984

Effects of cobalt or hydroxycobalamin supplementation on vitamin B-12 content and (S)-methylmalonyl-CoA mutase activity of tissue from cobalt-depleted sheep.

Lambs (3 months of age) and ewes were fed ad libitum a depletion diet low in cobalt (0.06 ppm) for 7 months. Five sheep were then assigned to each of the following treatments: 330 micrograms hydroxocobalamin (OH-B-12) intramuscularly, 2.7 mg cobalt (Co) orally, and no supplementation (no suppl). Treatments were given on alternate days for 9 weeks. Both forms of resupplementation increased the animal's body weight at slaughter compared to nonsupplementation, while absolute weights and protein concentrations of brain, liver, heart, rumen and kidney were not affected. Supplementation increased concentrations of vitamin B-12 in all tissues; Co and OH-B-12 being equally effective in brain and ruminal mucosa, whereas OH-B-12 had a greater effect in heart, liver and kidney. The greatest concentrations of vitamin B-12 were observed in liver (2630 +/- 160, 1500 +/- 230 and 60 +/- 20 ng/g wet liver for OH-B-12, Co and no suppl groups, respectively) and kidney, although liver contained the greatest absolute amount of vitamin B-12. Activity of (S)-methylmalonyl-CoA mutase, assayed in the presence of added coenzyme B-12, was not increased with resupplementation except in kidney. The activity of mutase without coenzyme added in vitro was correlated with tissue content of vitamin B-12. Through this study we demonstrate that in sheep tissue the activity of (S)-methylmalonyl-CoA mutase is limited by coenzyme rather than enzyme per se. Liver possesses the greatest quantitative activity of mutase and is most responsive to alterations of vitamin B-12 status.

Administration, Oral↗
PubMed1984

Urinary excretion of acetate and propionate by the Holstein cow as affected by physiological state and propionate infusion.

Daily urinary excretion of acetate and propionate was determined for 13 Holstein cows fed for ad libitum consumption a 40% soy-corn concentrate: 60% corn silage diet prepartum and 60% concentrate: 40% silage diet postpartum. Daily excretion of acetate did not differ between periods corresponding to -3, 7, and 11 wk postpartum. Cows excreted more propionic acid at 7 and 11 wk postpartum than at 3 wk prepartum. However, propionic acid excretion did not differ between the two postpartum periods. Propionic acid excretion was not associated with intake of feed during lactation. Rapid intrajugular infusion of propionate (2.5 mmol/kg) increased propionate excretion at -3 and 7 wk postpartum and acetate excretion at 7 wk postpartum. Under physiological conditions urinary excretion of acetate and propionate does not represent a meaningful energy loss.

Acetates↗
PubMed1984

Endocrine changes with infusion of propionate in the dairy cow.

Sodium propionate (2.5 mmol/kg) was infused rapidly via a jugular vein into each of 13 multiparous Holstein cows at 7 wk postpartum for observation of clearance of propionate. Associated concentration changes of acetate and glucose in blood plasma and glucagon and insulin in blood serum were quantified. This dose elevated concentrations of propionate, which declined subsequently at an exponential rate (.108 min-1). Concentrations of glucagon and insulin were increased in the sampling immediately following infusion, yet subsequent decline of insulin concentrations acted to decrease the molar ratio of insulin:glucagon as propionate returned to preinfusion concentrations. Analysis of sample means disclosed a negative correlation -.82 between glucose and molar ratio of insulin:glucagon. These experimental observations suggest that a supraphysiological dose of propionate has an immediate effect on the pancreas to alter endocrine secretion in the lactating cow.

Animals↗