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Biomedical subjects

G E Mitchell

Publications and source records attributed to G E Mitchell.

At least 19 recordsLinked to original sources
PubMed1995

Effects of cysteamine on pulsatile growth hormone release and plasma insulin concentrations in sheep.

The effects of cysteamine (CSH; 0, 50, or 100 mg/kg BW), a somatostatin depleting agent, on growth hormone (GH) and insulin (INS) secretion were studied in sheep (Ovis aries). Cysteamine was administered as a single intragastric bolus on day 0 (0900). Jugular blood samples were collected at 15-min (GH) and 2-hr (INS) intervals over an 8-hr period (1100-1900) on day 0, 3, and 7. Intragastric administration of CSH at 50 mg/kg BW augmented (quadratic, P = .04) mean plasma GH concentration, with the greatest response occurring on day 3. Baseline GH concentrations were elevated in wethers dosed with 50 mg/kg BW CSH on day 3, whereas wethers dosed with 100 mg/kg BW CSH had lower baseline GH concentrations on day 0 (CSH x day interaction, P = .02). Cysteamine administration increased GH pulse amplitude (quadratic, P = .15), with the greatest magnigtude of change occurring with 50 mg/kg BW CSH on day 0 and 3. Frequency of GH pulses was increased (quadratic, P = .10) following CSH treatment. Administration of 100 mg/kg BW CSH augmented plasma INS on day 0 (CSH x day interaction, P = .09). These findings indicate that CSH alters GH and INS secretion in a dose-dependent and temporal manner. The observed changes in mean and baseline plasma GH concentrations associated with 50 mg/kg BW CSH are consistent with somatostatin depletion; however, higher doses of CSH appear to disrupt GH secretion by an alternative mechanism.

Animals↗
PubMed1995

Cysteamine-induced depletion of somatostatin in sheep: time course of depletion and changes in plasma metabolites, insulin, and growth hormone.

Eight crossbred wethers (51 +/- 2 kg BW), surgically fitted with abomasal cannulas, were used to determine the extent and time course of cysteamine (CSH)-induced depletion of somatostatin (SRIF) in abomasal tissue and associated changes in plasma metabolites, insulin, and growth hormone (GH). Cysteamine was administered as a single i.v. bolus (50 mg.kg BW-1 x 10 min-1) on d 0. Abomasal biopsies were obtained on d -7, -3, 0, 1, 3, and 10. On d 0, additional biopsies were taken at 2, 4, and 8 h after CSH administration. Jugular blood samples were collected over 8 h at 15-min intervals on d -2, 0, and 1. Cysteamine administration decreased (P < .05) tissue SRIF on d 0 (2, 4, and 8 h), 1, and 3; maximal depletion (42 to 55% of Pre-treatment; Pre-trt) occurred during the initial 24 h, returning to Pre-trt by d 10. Gel chromatography of pooled -7 d abomasal tissue extracts showed five peaks of SRIF immunoreactivity; the predominate peak eluted in the same position as synthetic SRIF-14. Plasma glucose, lactate, and NEFA concentrations increased (P = .001) after CSH administration and reached peak at 2 h after treatment and declined to Pre-trt concentrations by 24 h. Insulin increased (P = .001) to a maximum at h 4 and returned to Pre-trt by 24 h. Mean and baseline GH were higher (P < .07) on day of CSH administration, and pulse amplitude was lower (P < .10) on d 0 and 1. These data show that CSH rapidly reduces SRIF in abomasal tissue in a reversible manner; suggesting that CSH-treated sheep may provide a SRIF-deficient model for studying the physiological role of SRIF in ruminants.

Animals↗
PubMed1993

In vitro and in vivo ruminal and physiological responses to endophyte-infected tall fescue.

Relationships between alkaloid compounds in endophyte-infected tall fescue and ruminal metabolism were studied in two experiments. In the first experiment, different combinations of the pyrrolizidine alkaloids, N-formyl and N-acetyl loline, were incubated with ruminal fluid for 0, 24, or 48 h. Rate of disappearance of N-formyl and N-acetyl loline increased over time. After 48 h, disappearance of N-formyl loline and combinations of N-formyl and N-acetyl loline was greater than N-acetyl loline. Significant amounts of N-formyl and N-acetyl loline were metabolized and converted to loline. In the second experiment, abomasally cannulated sheep were fed increasing amounts of endophyte-infected feed to compare diet digestibility, alkaloid metabolism, and physiological responses. Total tract DM digestibility was greatest for the endophyte-free diet, as were ruminal and total tract ADF, ruminal NDF, and total tract CP digestibilities. N-Formyl and N-acetyl loline recoveries averaged 5% from abomasal contents and 0% in feces. Sixty-eight percent of the pyrrolizidine alkaloids recovered in abomasal contents had been metabolizable to loline. Ergot alkaloids administered in the diet were recovered (50 to 60%) in the abomasal contents, but recovery was only 5% in fecal collections. No significant differences occurred in the physiological parameters measured. Results indicate that response to endophyte-infected tall fescue may be influenced by ruminal metabolism.

Acremonium↗
PubMed1993

Bovine plasma vitamin A responses to selected nutrients, monensin, and endophytic fescue.

Previous research at this station adapted a maximal dose response (MDR) method of evaluating vitamin A status and utilization for use in beef cattle. This method was used in two experiments. In this first experiment, forty-eight crossbred steers (average weight, 284 kg) were fed diets supplemented with salt, monensin or both, and injected with vitamin E, zinc or selenium. Steers receiving monensin had higher (38.5 micrograms/dl, monensin; 31.0 micrograms/dl, controls) initial plasma concentrations of vitamin A (P = .14). However, monensin did not affect post-dosing (MDR) vitamin A concentrations. None of the other dietary treatments or injections affected either pre- or post-dosing concentrations of vitamin A in the plasma. In a second experiment 23 lactating multiparous beef cows (average weight, 500 kg) grazing either fungal endophyte-infected or endophyte-free tall fescue were used to assess possible influences of infected fescue upon vitamin A metabolism. Fungal endophyte infection did not affect either pre- (44.9 micrograms/dl, end-noninf.; 47.7 micrograms/dl, end-inf.) or post-dosing (57.2 micrograms/dl, end-noninf.; 59.3 micrograms/dl, end-inf.) vitamin A concentrations.

Acremonium↗
PubMed1992

Voluntary intake and ingestive behavior of steers grazing Johnstone or endophyte-infected Kentucky-31 tall fescue.

Effects of grazing low-endophyte (Acremonium coenophialum Morgan-Jones and Gams, less than 1% infection) Johnstone (J) or high-endophyte (60% infection) Kentucky-31 (K) tall fescue (Festuca arundinacea Schreb.) on grazing behavior and voluntary intake were studied. Six Angus steers (average initial BW = 326 kg) grazed 1.21-ha plots of each forage cultivar (three steers per cultivar) in four 28-d periods beginning May 27. Daytime observations (0630 until 2130) revealed that J steers spent more (P less than .10) time grazing and lying down and took more (P less than .05) prehensile bites than K steers did; conversely, steers grazing K spent more (P less than .10) time standing and idling than J steers did. Idling time showed a forage x period interaction (P less than .10). Mean OM bite size (grams per bite) was not affected (P greater than .10) by forage but differed (P less than .10) among periods. Limited nighttime observations (2130 until 0630) revealed no effects (P greater than .10) of forage on grazing time or number of prehensile bites taken. Voluntary intakes of OM and NDF did not differ (P greater than .10) between steers grazing J and K; however, a forage x period interaction (P less than .10) existed such that, during Period 1, steers grazing J had greater (P less than .01) OM and NDF intakes than did steers grazing K. These data suggest that cattle grazing endophyte-infected tall fescue display altered daytime grazing behavior and that reduction of voluntary intake attributable to endophyte infection may be less severe under free-grazing than has been reported for controlled environmental conditions.

Acremonium↗
PubMed1992

Influence of rumen fermentation on response to endophyte-infected tall fescue seed measured by a rat bioassay.

Possible alteration of toxicity of endophyte-infected tall fescue by ruminal fermentation was studied using 28 Harlan Sprague-Dawley rats (avg. initial wt., 141 g). These were assigned randomly to one of four treatments in a 2*2 factorial consisting of a 14-day growth period with weights and feed consumption data determined on days 0, 5, 10 and 14. Treatments were: endophyte-infected Kentucky-31 tall fescue seed (E+) or endophyte free Johnstone tall fescue seed (E-) that was incubated for 0 (NON) or 24 hours (INC) with rumen fluid collected from a 290-kg cannulated steer fed a diet containing 37% endophyte-infected tall fescue hay. Diets consisted of 50% lab chow, 39% fescue seed and 11% rumen contents (air-dry basis). Alkaloid content (N-acetyl plus N-formyl loline) for the four diets were 2540, 2680, 0, and 0 micrograms/g for E+NON, E+INC, E-NON, and E-INC diets, respectively. E- treatments gained faster, consumed more feed and converted feed more efficiently (P < .05) than did E+ fed groups. No difference in feed intake was observed within E+ treatments, however, the E+INC diet gained faster (P < .05) and converted feed more efficiently (P < .05) than did E+NON fed rats (2.56 vs 1.96 g/d and 5.94 vs 7.51 g of feed/g of gain for gain and feed conversion, respectively). Including endophyte-infected seed in rat diets depressed performance (ie. intake, gain and feed efficiency). This depression was partially alleviated by a 24-hour incubation with rumen fluid contents suggesting that toxicity of endophyte-infected tall fescue is lessened due to rumen microbial action.

Acremonium↗
PubMed1991

The effect of microwave and conventional cooking on the temperature profiles and microbial flora of minced beef.

Beef mince samples were cooked to the rare, medium and well done states by microwave and conventional oven methods. The raw samples all contained large numbers of contaminating organisms and low numbers of Listeria monocytogenes were detected in the majority of samples. A substantial proportion of the contaminating flora survived in mince cooked by microwaves to the rare, medium and well done states, prior to a 30-min standing period. Listeria monocytogenes survived in all samples cooked by microwaves to the rare state, prior to the standing period and was still present in one of three after the standing period. It was also detected in one of three samples cooked to medium prior to a standing period. This organism was not detected in mince cooked by conventional oven methods. In all the samples cooked by microwaves with a standing period and samples cooked to rare and medium by conventional oven, survival of some of the microflora occurred. The survival rate decreased with the severity of the cooking treatment.

Animals↗
PubMed1991

Effect of irradiation on microorganisms in strawberries.

Seventeen samples of strawberries from seven different growers were analysed for total counts, Enterobacteriaceae, fluorescent pseudomonads and yeast and mould counts before and after irradiation at 1.2 or 2 kGy. Enterobacteriaceae were absent (less than 5 cfu/g) from all irradiated strawberries but were always detected at counts of greater than 30 cfu/g in untreated samples. This criterion was true for both fresh and stored (5 days at 8 degrees C) strawberries. Assuming no other sanitizing treatment, the Enterobacteriaceae count appears to be suitable for differentiating between irradiated and non-irradiated strawberries. The other counts used in this study were not suitable for this purpose. Isolates from irradiated strawberries could be classified into four types based on colony morphology. Three types consisted of aerobic spore-forming bacteria whilst the fourth group consisted of yeasts.

Bacteria↗
PubMed1991

Metabolism of narasin in chickens and Japanese quail.

Thirty mature chicken hens and 60 mature Japanese quail hens were used to compare pathways of narasin excretion. Carbon-14-labeled narasin was injected into chickens (.7 microCi) and quail (.113 microCi) via cardiac puncture. Blood, sampled at varying times thereafter, and eggs and excreta collected daily for 28 days, were analyzed for 14C. Groups of six chickens and 12 quail were killed prior to [14C]narasin injection and on Days 1, 7, 14, and 28 postinjection to obtain tissue samples for 14C analysis. Blood rapidly cleared the label in both species. Less than 1% of the dose of [14C]narasin remained in blood plasma after 3 h postinjection in both chickens and quail. Label excretion peaked on Day 1 in both species, and most of the 14C was cleared via the excreta (76.7 and 93.6% of the dose for quail and chickens, respectively). Label appeared in the excreta more rapidly and cleared more quickly in quail than in chickens. After 24 h, 68 and 49% of the dose of [14C]narasin appeared in the excreta of quail and chickens, respectively. More label was recovered in the eggs of quail (4.18% of the dose) than in the eggs of chickens (1.32% of the dose). Liver, heart, fat, and ovarian tissues contained traces of radioactivity 1 day postinjection in both species. Muscle and kidney did not contain detectable amounts of label. By Day 7, all tissue had cleared 14C beyond detectable limits. The results indicate that chickens and quail metabolize [14C]narasin via similar pathways and that excretion in quail may be more rapid than in chickens.

Adipose Tissue↗
PubMed1990

High-performance liquid chromatographic determination of 4-methylimidazole in sheep plasma and in ammoniated tall fescue hay.

A method for 4-methylimidazole (4MI) extraction and quantitation in body fluids and forage samples was developed. The procedures involve ion-pair extraction of the compound with the quantitation done by ion-pair liquid chromatography. The results indicate that this high-performance liquid chromatographic method is sensitive, reproducible and more rapid than others that have been previously used. The mean recovery of 4MI from plasma and tall fescue (Festuca arundinacea) hay samples were above 95 and 85%, respectively. The versatility of the procedure makes it suitable for the determination of 4MI in body fluids and in forage samples.

Ammonia↗
PubMed1990

Pharmacokinetics of 4-methylimidazole in sheep.

The pharmacokinetics of 4-methylimidazole (4MI), a toxin found in ammoniated forage, was studied after i.v. infusion or oral administration of a single dose of 20 mg 4MI/kg BW to sheep. A two-compartment open model was used to describe i.v. infusion data. Oral data were described by a one-compartment open model. A rapid distribution phase (t1/2 alpha = 28 min) was observed after i.v. infusion. The biological half-lives obtained after i.v. infusion (t1/2 beta = 9.72 h) and oral dosing (t1/2 beta = 9.37 h) were similar. The bioavailability of oral 4MI was .69, with a relatively rapid absorption phase (t1/2abs = 1.52 h). The relatively large volume of distribution (61.6 and 65.8 liters for i.v. infusion and oral dosage, respectively) indicates that 4MI is distributed in the extravascular compartment. A dose of 20 mg/kg BW did not cause any apparent ill effects to the animals.

Absorption↗
PubMed1990

Plasma vitamin A levels in cattle in response to large doses of vitamin A.

A dose response procedure was developed for evaluating vitamin A status and utilization in cattle. This could be useful for evaluating diets, vitamin A stores and homeostatic control of vitamin A. Three experiments were designed to determine: 1) size of vitamin A dose required to increase plasma vitamin A concentrations; 2) time after dosing when plasma vitamin A concentrations peak, and 3) if changes in plasma vitamin A concentrations are useful in assessing dietary vitamin A utilization. Using twenty-four steers and heifers, the first two experiments showed that 30X or 40X daily vitamin A requirement (daily requirement calculated as X = body weight in kilograms times 55 International Units of vitamin A) given orally was sufficient to cause plasma vitamin A concentrations to rise 20 hours after dosing. Plasma vitamin A concentrations increased (P less than .01) from 57 to 81 micrograms/dl and 64 to 84 micrograms/dl after a 30X or 40X treatment, respectively. Twenty-X daily requirement resulted in a slight increase after 20 hours (P greater than .05). Seventy-two feedlot steers were used in experiment three to determine if diet affects vitamin A dose response. Variations in feed intake, monensin in the diet or a single dose of vitamin E did not cause significant changes in plasma vitamin A response to vitamin A dosage. Steers receiving monensin had higher initial plasma vitamin A concentrations, but no differences were observed after dosing. Results indicate that dose responses may be useful in assessing dietary vitamin A utilization.

Administration, Oral↗
PubMed1989

Porcine immunoglobulin transfer after prepartum treatment with selenium or vitamin E.

Responses to prepartum injection of sows with Se and vitamin E (E) were evaluated by determining immunoglobulin (IgA, IgM, IgG) levels in the colostrum and serum of the sows and the serum of their offspring. Fifty-four sows (40 multiparous, 14 primiparous) receiving diets adequate in E and Se according to current NRC (1988) standards were randomly allotted to four treatment groups in which a single i.m. injection of saline (controls), 5 mg of Se, 1,000 IU of E, or both Se and E were given on d 100 of gestation. Sows were bled prior to and 7 d after injection, at farrowing and on d 14 and 28 of lactation. Colostral samples were collected at the initiation of farrowing. Pigs were bled 20 h postpartum and at 14 and 28 d of age. Major immunoglobulin changes in the serum of the sows due to treatment were not seen prior to parturition. Injections of Se and(or) E resulted in higher colostral IgM levels (8.4, 10.7, 9.8 and 9.6 mg/ml, respectively), but only the response from Se was significant (P less than .05). Concentrations of colostral IgA or IgG were not affected by treatment (P greater than .30). Compared with controls, all three treatments increased (P less than .10) IgM concentrations in serum from pigs at birth (28.3, 33.3, 36.0 and 33.5 mg/ml, respectively), whereas IgA and IgG concentrations were not affected (P greater than .30).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Metabolism of decoquinate in chickens and Japanese quail.

Thirty mature chicken hens and 40 mature Japanese quail hens were used in an experiment to compare pathways of decoquinate (DQ) excretion. Labelled DQ was injected into chickens (.5 microCi via wing vein puncture) and quail (.25 microCi via cardiac puncture) on Day 0. Blood was sampled at 0, 1.5, 3, 6, 9, 12, 24, and 48 h postinjection. Eggs and excreta of chickens and quail were collected for 28 and 14 days, respectively, and analyzed for 14C. Six chickens and eight quail were sacrificed prior to 14C-DQ injection and also on Days 1, 7, 14, and 34 or 32 postinjection. Samples of liver, heart, kidney, bile, skin, fat, and muscle were analyzed for 14C. Blood rapidly cleared 14C in both species, and the half-time of 14C excretion via excreta was more rapid in quail (.37 day) than in chickens (.92 day). Little 14C was found in the eggs of quail (.32% of dose) and chickens (.17% of dose). Quail appeared to excrete peak amounts of detectable 14C 1 day earlier (Day 4) than chickens (Day 5). Liver contained the greatest concentration of 14C on Day 1 in both species. By the end of the experiment, less than 1% of the dose remained in liver or other organs. Results indicate that chickens and quail metabolize 14C-DQ at comparable rates and by similar pathways.

Animal Feed↗
PubMed1988

Comparative drug depletion in domestic animals and birds.

Decoquinate (Rhone-Poulenc Inc) and Narasin (Eli Lilly and Co) were selected as model drugs for a comparison of metabolism between major (cattle and chickens) and minor (sheep and quail) species. Decoquinate has been studied in all four species. Narasin studies are in progress in chickens and quail. More than 96% of injected 14C-decoquinate (DQ) was eliminated from blood of all species within 1 hr. Disappearance of the remaining 1 to 4% from blood was rapid for all species. Half-times for DQ appearance in excreta were all less than one day. Cumulative excretion of DQ in eggs of chickens and quail was about 1% for both species. Disappearance of DQ from tissues was essentially complete in 14 days. More than 80% of injected 14C-narasin was eliminated from blood within 1/2 hr. Disappearance of the remainder was rapid for both chickens and quail.

Animals↗
PubMed1986

Physicochemical properties of proteinases from selected psychrotrophic bacteria.

The physicochemical properties of eight extracellular proteinases secreted by psychrotrophic bacteria of dairy origin have been studied. Seven of these proteinases were able to withstand ultra heat treatment (UHT) with D values at 140 degrees C ranging from 2 to 300 s. The six Pseudomonas fluorescens proteinases were glycoproteins of mol. wt 47000-49500. The two Serratia marcescens proteinases, of mol. wt of 51000, did not contain carbohydrate but in other respects were similar to the Pseudomonas proteinases. The proteinases were inhibited by various metal chelators and all contained Ca and Zn in similar proportions. Their amino acid compositions were similar, with alanine as the N-terminal group, cysteine completely absent and very low levels of methionine. Isoelectric points ranged from 5.10 to 8.25. Their physical and chemical properties enabled them to be classified as alkaline metalloendopeptidases. A similarity index (S delta n) was used to predict sequence homology between ten proteinases of known amino acid composition. Comparisons of S delta n of these proteinases showed only minor sequence differences except for those of Ps. fluorescens MC60. Heat resistance could not be related wholly to similarities in protein sequence, but could be related both to the strength of stabilizing Ca2+-protein interactions and to the randomness inherent within the folding of the peptide chain.

Amino Acid Sequence↗