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Biomedical subjects

M R Murphy

Publications and source records attributed to M R Murphy.

At least 91 records · Page 5Linked to original sources
PubMed1986

Passage of inert particles varying in length and specific gravity through the postruminal digestive tract of steers.

Postruminal passage of inert particles varying in specific gravity, length, and time of administration in relation to feeding, as well as interactions among these factors, were studied in four ruminally cannulated steers. Animals were allowed access to a 40% grain mix, 60% long alfalfa hay diet for 6 h daily. Eleven combinations of particle specific gravity (.9, 1.17, 1.41, or 1.77) and length (1, 5, or 10 mm) were used. Two hundred particles of each combination were placed in the abomasum at the beginning of the meal, the end of the meal, or 6 or 12 h after the end of the meal. Recovery of particles in feces within 24 or 48 h of administration and times of first appearance and maximal concentration were examined. Particle recovery 24 h after dosing as a percentage of 48-h recovery and time of maximal concentration in feces best described postruminal passage of inert particles. Passage was affected by specific gravity, but not length, of particles. Those having a specific gravity of 1.17 passed most quickly. Time at which particles were placed in the abomasum in relation to feeding affected the passage of particles varying in specific gravity. This interaction may be important in studies of ruminal passage that depend on marker appearance in feces.

Animals↗
PubMed1986

Malt sprouts as a source of supplemental protein for ruminants.

Nitrogen solubility, ruminal degradation, and amino acid composition of pelleted malt sprouts, pelleted corn gluten feed, and soybean meal were studied. Four rumen-cannulated steers were fed diets containing 45% pelleted malt sprouts or 45% pelleted corn gluten feed in a 2 X 2 crossover design with 15-d periods. Ruminal degradation of dry matter and nitrogen from malt sprouts or corn gluten feed was estimated by disappearance of these components from polyester bags after 1, 2, 3, 4, 6, 8, 10, 12, 16, or 24 h of in situ fermentation. For comparison, degradation of soybean meal after 2, 4, 8, or 24 h was measured. Malt sprouts had less soluble nitrogen than corn gluten feed, but available crude protein contents were similar. Malt sprouts dry matter was degraded more slowly than was corn gluten feed dry matter. Nitrogen degradation rates of the two feeds, after correction for unavailable nitrogen, did not differ. Malt sprouts had higher concentrations of arginine, lysine, and aspartate than corn gluten feed; however, corn gluten feed had higher concentrations of the other amino acids measured. Malt sprouts would be expected to provide more amino acids of feed origin to the lower gut of ruminants, provided passage rates of the supplements are similar.

Animal Feed↗
PubMed1985

Factors stimulating migration of holotrich protozoa into the rumen.

The effects of feeding and various reticular infusions on ruminal holotrich concentrations were studied in an attempt to identify possible factors stimulating their migration into the rumen. It was concluded that glucose entering the reticulo-rumen shortly after feeding could stimulate migration of holotrich protozoa.

Animals↗
PubMed1984

Effect of ruminal ammonia-nitrogen concentration on protein degradation in situ.

Two experiments were conducted to determine the effect of ruminal ammonia-nitrogen concentration on rate of ruminal protein degradation. In Experiment 1, four Holstein steers were fed a basal diet of corn grain and corn silage at hourly intervals. Continuous intraruminal infusions of solutions containing sodium bicarbonate and either sodium chloride or ammonium chloride resulted in ruminal ammonia-nitrogen concentrations that averaged 4.8 and 17.3 mg/dl. Ruminal fluid pH, fluid volume, and turnover rate of fluid and molar percentage of acetate, propionate, and butyrate were similar across treatments, reflecting steady state conditions. Rates of nitrogen and dry matter disappearance from polyester bags containing soybean protein supplements with 10.2 or 50.1% soluble nitrogen were not affected by increase of ruminal ammonia-nitrogen concentrations from 4.8 to 17.3 mg/dl. In Experiment 2, Holstein steers were fed twice daily a basal diet of urea-supplemented corn grain and corn silage. Polyester bags containing soybean protein supplements were placed in the rumen at -4, 0, or 4 h with reference to feeding and incubated from 1 to 12 h. Peak ruminal ammonia-nitrogen concentrations occurred during different periods of incubation for each treatment. Ruminal ammonia-nitrogen concentrations ranged from 3 mg/dl at 6 h postfeeding to 46 mg/dl at 1 h postfeeding. Nitrogen and dry matter disappearance rates during 0 to 1 and 1 to 12 h of incubation did not differ among treatments.

Ammonia↗
PubMed1984

Water dynamics of dairy cattle as affected by initiation of lactation and feed intake.

Effects of lactation and feed intake on sizes and half-lives of body water pools were investigated in four Holstein cows in a thermoneutral environment. Various markers were administered, on average, 24 days prepartum (Period 1, feed intake fixed to average of consumption after offered at a rate ensuring 10% refusal), 24 days postpartum (Period 2, restricted to intake in Period 1), and 42 days postpartum (Period 3, feed again offered at a rate ensuring 10% refusal). Total body water decreased from period 1 to 2; however, it did not change as a percent of body weight. Estimated body water half-lives and fluxes for the three periods were 7.5, 3.7, and 2.9 days; and 42, 66, and 87 liters/day. Increased water intake during lactation closely matched water secreted in milk. Empty body water, estimated by a two-compartment, four-parameter model, as a percent of body weight did not change across periods. Lactation and increased feed intake decreased half-life of body water. Plasma volume increased as a percent of body weight because of loss of body weight in early lactation; however, extracellular volume tended to decrease with body weight. Initiation of lactation and feed intake during lactation affect water dynamics of the dairy cow.

Animals↗
PubMed1984

Ruminal bypass of drinking water in lactating cows.

Drinking water that does not equilibrate with ruminal fluid, i.e., bypasses the rumen, was studied qualitatively and quantitatively in eight rumen-fistulated lactating Holstein cows. Decreased temperatures in the sulcus omasi and abomasum shortly after initiation of drinking indicated that water had bypassed the rumen. Recovery of a water-soluble marker, included in drinking water offered after water was withheld for 4.5 or 9 h following feeding, was used to estimate ruminal bypass. For respective treatments, 18 and 5% of drinking water was calculated to have bypassed the rumen. Ruminal bypass in lactating cows drinking relatively large amounts of water could affect comparisons of water intake with total ruminal fluid outflow as measured by dilution of a water-soluble marker. Drinking water should not be assumed to equilibrate with ruminal fluid.

Abomasum↗
PubMed1983

Dose-independent pharmacokinetics of fentanyl.

Fentanyl is used as an analgesic in small doses (1-2 micrograms X kg-1) and as an anesthetic in very large doses (greater than 150 micrograms X kg-1). It has been demonstrated that the effects of fentanyl correlate with its concentrations in plasma. It is important, therefore, to know whether or not the pharmacokinetics of fentanyl vary with dose size in order to predict the plasma concentrations and effects produced by various dosage regiments. The authors studied the pharmacokinetics of fentanyl in dogs. 3H-fentanyl (2.5-640 micrograms X kg-1) was injected intravenously in dogs anesthetized at a stable level with enflurane-O2. Arterial plasma and urine were analyzed for unchanged 3H-fentanyl. Kinetic indices were derived by nonlinear least-squares analysis of log concentration of fentanyl in plasma (ng X ml-1) versus time after a bolus injection. The terminal elimination half-time (t 1/2 beta = 211 min), the apparent volume of distribution (9.5 l X kg-1), the volume of the central compartment (1.14 l X kg-1), and the clearance (37 ml X kg-1 X min-1) of fentanyl were independent of dose over the 6.4-640 micrograms X kg-1 dose range. The distribution volume and distribution half-times were lower for the 2.5 micrograms X kg-1 than for some of the larger doses; this was attributed to differences in experimental conditions. The authors conclude that the pharmacokinetics of fentanyl are dose independent certainly over the 6.4-640 micrograms X kg-1 dose range. There is no evidence of saturation of biotransformation or tissue uptake mechanisms for doses in the range of 2.5 to 640 micrograms X kg-1.

Animals↗
PubMed1983

Effects of varying particle size of forage on digestion and chewing behavior of dairy heifers.

Eighteen Holstein heifers were fed long and chopped coarse and fine alfalfa hay ad libitum to evaluate effects of physical form on digestion and chemical composition of feed and fecal particles and to examine the applicability of a sinusoidal model to chewing behavior. Recordings of jaw movement were divided into 1-h segments for analysis. Least square mean size of fecal particles from coarse and finely chopped diets were 290 and 297 micrometers as compared to 227 micrometers on long hay. Intakes of dry matter were greater an digestibilities lower for chopped as compared to long hay. Crude protein content of separated feed and fecal particles increased as particle size decreased. Neural and acid detergent fiber concentrations decreased in feed and feces with decreasing particle size. Lignin content of feed particles decreased as particle size decreased, whereas for fecal particles lignin as a percent of cell wall followed a "U" shaped pattern of declining then increasing as size decreased. Patterns were sinusoidal for eating and ruminating long and chopped hays and total chewing (eating and ruminating) of long hay. Our results suggest a gradual effect on chemical degradation and physical detrition of digesta particles and chewing behavior as forage particle size decreased.

Animal Feed↗
PubMed1983

Effect of source and particle size of supplemental phosphate on rumen function of steers fed high concentrate diets.

We examined effects of source and particle size of supplemental defluorinated rock phosphate, to meet phosphorus requirements, on rumen function of 195-kg Holstein steers fed high concentrate. Two sources and two particle sizes of each source were evaluated in a 5 X 5 Latin square with 14-day periods. There was no effect of source on ruminal mH [- log (mean (H+)]; however, ruminal mH was higher in animals fed supplements of larger particle size. This effect was also evident when rumen pH versus time curves were integrated below pH 6. Animals fed supplements of larger particle size had less area below pH 6 than those fed supplements of smaller size. Ruminal buffering capacity at pH 7 was affected by diet; however, orthogonal comparisons between treatment means were not significant. Neither source nor particle size of the supplement affected ruminal fluid osmolality, total volatile fatty acid concentration, or fecal starch. Water intake and ruminal dry matter on HyCal supplemented diets; however, there was also a trend toward increasing rumen fluid volume. The net effect was little change of dilution rate of ruminal fluid. This may explain why rumen fermentation was not affected greatly. Conventional phosphate supplements may have potential as rumen buffering agents, but higher levels of feeding should be studied.

Animals↗
PubMed1982

The anesthetic potency of fentanyl in terms of its reduction of enflurane MAC.

Infusion rates for fentanyl were calculated to produce stable plasma concentrations at which the ability of fentanyl to reduce enflurane MAC could be studied utilizing the tail clamp method and measurement of end-tidal enflurane. Following the determination of control enflurane MAC in each animal, an infusion of fentanyl was begun. Group 1 received continuous successive infusion rates of 0.05, 0.1, and 0.2 micrograms . kg-1 . min-1 with respective loading doses (given over 20 min) of 15, 15, and 30 micrograms/kg; Group 2 received infusions of 0.2, 0.8, and 3.2 micrograms . kg-1 . min-1 with loading doses of 30, 90, and 270 micrograms/kg, respectively. Group 3 was studied in the same manner except that fentanyl was omitted from the infusion solution. Enflurane MAC was determined at each infusion level and blood samples were analyzed for the concentration of fentanyl. Fentanyl concentrations in plasma were proportional to the infusion rate. Enflurane MAC was decreased significantly in proportion to fentanyl plasma concentrations up to 30 ng/ml where a reduction of MAC by 65% was evident. A threefold higher concentration produced a minimal further reduction. In Group 3 dogs, no change in enflurane MAC was seen. It was concluded that predictable, stable levels of fentanyl in plasma can be achieved, that there is a close relationship between the concentration of fentanyl in plasma and its enflurane sparing effect, and that there is a ceiling to this concentration-response relationship.

Anesthesia, General↗
PubMed1982

The enflurane sparing effect of morphine, butorphanol, and nalbuphine.

The potencies of morphine and of the narcotic analgesic agonist-antagonists butorphanol and nalbuphine in terms of their ability to decrease enflurane MAC were studied. Following the determination of control MAC for enflurane in each dog, an intravenous bolus dose of either butorphanol tartrate, nalbuphine hydrochloride, morphine, or placebo was administered and enflurane MAC was redetermined. A higher dose of the same drug was then administered and enflurane MAC was redetermined up to a total of four doses in each animal. The successive doses for morphine and nalbuphine were 0.5, 1.5, 5.0, and 20.0 mg/kg; for butorphanol, 0.1, 0.3, 1.0, and 4.0 mg/kg; lactated Ringer's solution was used as a placebo. Both butorphanol and nalbuphine produced significant reductions of enflurane MAC (11 and 8%, respectively) at their lowest doses. No further reductions were produced by three- to forty-fold larger doses of either agonist-antagonist. Morphine produced a 17% reduction of enflurane MAC at the lowest dose with progressive decreases of enflurane MAC up to 63% at a dose of 5 mg/kg morphine. A fourfold increase in the morphine dose did not further decrease MAC. No change in enflurane MAC occurred in the animals given placebo. It was concluded that there is a "ceiling" to the potency of butorphanol and nalbuphine as anesthetic supplements. There is also a limit to the anesthetic sparing effect of morphine, but it is considerably greater than that of the agonist-antagonist narcotic analgesics.

Anesthetics↗
PubMed1981

Species-typical behavior of hamsters deprived from birth of the neocortex.

Hamsters deprived from birth of the neocortex developed normally and displayed the usual hamster-typical behavioral patterns. With the additional concurrent destruction of midline limbic convolutions (cingulate and underlying dorsal hippocampal), there were deficits in maternal behavior and a lack of development of play behavior. These findings demonstrate in a rodent (i) that the striatal complex and limbic system, along with the remaining neuraxis, are sufficient for giving expression to a wide range of unlearned forms of species-typical behavior and (ii) that midline limbic structures are required for the expression of play behavior and the integrated performance of maternal behavior.

Animals↗
PubMed1981

Methadone reduces sexual performances and sexual motivation in the male Syrian golden hamster.

The debilitating effect of opiate drugs on sexual function has been known clinically for hundreds of years but has become a topic of experimental investigation only recently. The purpose of the current study was to examine the effects of the opiate drugs methadone and the opiate blocking drug naltrexone on the sexual behavior of male hamsters. Methadone, administered at dosages of 1, 2, 4, 8, and 16 mg/kg, was found to cause a dose related decline in measures of both sexual performance and sexual motivation, with measures of sexual performance being the more sensitive to the drug. The debilitating effect of methadone was judged to be highly selective for sexual behavior since, for example, at 16 mg/kg of methadone, sexual behavior was eliminated but ambulatory activity was unaffected. Pretreatment with naltrexone blocked the effects of methadone and posttreatment reversed the effects, thereby indicating that the methadone was inhibiting sexual behavior by acting on specific opiate receptors. The results demonstrate that the male hamster is an excellent small animal model for use in studying the mechanisms of opiate induced sexual dysfunction and further support the hypothesis that the endogenous opiates may be involved in the regulation of sexual behavior.

Animals↗
PubMed1981

Pharmacokinetics of intravenous morphine in patients anesthetized with enflurane-nitrous oxide.

Morphine is used as an anesthetic supplement. Its disposition in surgical patients under enflurane-nitrous oxide anesthesia has not been determined. Available data on morphine concentrations in plasma after equivalent intravenous doses are conflicting, possibly as a result of varying degrees of specificity of the analytical methods for the unchanged, pharmacologically active form of the drug. This study determined the pharmacokinetics of morphine (0.05, 0.1, 0.14, or 0.2 mg/kg) injected intravenously in 10 surgical patients anesthetized with enflurane-N2O-O2. Arterial plasma was analyzed for unchanged morphine and conjugated morphine. Specificity of the analytical procedure for unchanged morphine was achieved by the combination of solvent extraction and radioimmunoassay techniques. Kinetic indices were derived by nonlinear least-squares analysis of log concentration (ng/ml) vs. time relationships. Morphine disposition was independent of dose in this fourfold range and was best described by a three-compartment model with a mean elimination half-time (t1/2 beta) of 104 +/- 5 min. The apparent volumes of distribution (Vd) and of the central compartment (V1) were 3.4 +/- 0.2 and 0.13 +/- 0.02 l/kg, respectively, while the clearance (ClB) was 23 +/- 1 ml x min-1 x kg-1. Extraction of morphine by the liver appeared to be complete. Conjugated morphine was eliminated from plasma with a t1/2 beta of 169 +/- 15 min. The ultimate elimination of morphine from the body was dependent upon its uptake from slowly perfused peripheral tissues, K10 greater than k31(P less than .001).

Adolescent↗