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Biomedical subjects

J R Hunt

Publications and source records attributed to J R Hunt.

At least 55 records · Page 3Linked to original sources
PubMed1989

Effects of pH on cell fusion induced by electric fields.

Electrofusion has recently become an important area of cell biology research. We studied the effects of pH of the cell medium on the electrofusion of human red blood cells. Cell fusion was monitored by observing the movement of a lipophylic dye between neighboring fused cells using a fluorescence microscope. The cells were first brought into close contact by dielectrophoresis. Fusion was then induced by three pulses of high-intensity electric field. Within minutes following the pulse application, many cells were observed to fuse together to form fusion chains of different lengths. We found that the optimal pH for cell fusion is around pH 7.5. At this pH, the fusion yield was highest (ranging from 57 to 81%) and the average number of cells within a fusion chain was also the largest. The dependence of cell fusion on pH is more sensitive at low than at high pH. The fusion yield was decreased by 40% when the pH was changed from 7.5 to 6.0, but there was only a 20% decrease in yield between pH 7.5 and 10.0. We suspect that the observed pH effects may be caused by a redistribution of fixed charges at the cell surface, or changes in amphipathicity of the surface proteins.

Cell Fusion↗
PubMed1988

Bioavailability in humans of zinc from beef: intrinsic vs extrinsic labels.

Beef is a concentrated source of zinc. However, the bioavailability of Zn from beef has not been clearly established. It is also unclear whether there is a difference in absorption between intrinsic and extrinsic Zn. To address these questions, a calf was labeled with 65ZnCl2 and the meat was used as a source of intrinsically labeled beef. Twelve subjects were given a meal containing 100 g beef labeled either intrinsically or extrinsically with 65ZnCl2. Gamma-ray emissions, as determined by whole-body counting, were used to calculate Zn absorption. Absorption values were 20.9 +/- 5.5% from the extrinsic meal and 26.4 +/- 10.6% from the intrinsic meal, a difference that was not statistically significant (p greater than 0.05). Zn absorption was thus much less than the 40% assumed in establishing the 1980 Recommended Dietary Allowance for Zn. These results also indicate that extrinsic labels of Zn are valid markers of zinc absorption in beef.

Adult↗
PubMed1988

The effect of past and current dietary Zn intake on Zn absorption and endogenous excretion in the rat.

Effects of previous dietary Zn (or body Zn stores) and current dietary Zn intake on absorption and endogenous excretion of Zn were studied by using radioisotope dilution. Rats were fed diets containing 1.5, 12.6 or 50.3 mg Zn/kg for 19 d (dietary period I). Total body Zn in the three groups was 1870 +/- 340, 3953 +/- 698 and 4126 +/- 844 micrograms Zn/rat. Each group was divided into four subgroups fed 3.6, 12.6, 20.5 or 50.3 mg Zn/kg diet for 3 wk (dietary period II). Rats were injected intramuscularly with 65Zn after 7 d of dietary period II. True absorption and endogenous excretion were calculated by isotope dilution. Zinc intake, urinary and fecal excretion, balance and percent Zn absorption were significantly affected only by dietary Zn in dietary period II (P less than 0.01). Endogenous excretion was affected by both past dietary Zn deficiency (body Zn stores) and by dietary Zn in dietary period II (P = 0.0001). Total body Zn at the end of the experiment was significantly affected by both periods of dietary treatment (P less than 0.001), but total body Zn concentration was affected only by the final dietary treatment (P less than 0.05). These results show that Zn absorption is affected by the current diet, but that turnover of Zn (endogenous excretion) is regulated by both current Zn intake and past Zn intake, probably through an effect on body Zn stores.

Animals↗
PubMed1988

65Copper absorption by women fed intrinsically and extrinsically labeled goose meat, goose liver, peanut butter and sunflower butter.

Absorption of stable 65Cu incorporated intrinsically or extrinsically into foods was studied in women fed a diet marginal in Cu content. Isotopic enrichment was 73.1 +/- 1.0 atom percent 65Cu in goose breast meat, 74.9 +/- 0.5 atom percent in goose liver, and 55-69.5 atom percent in two crops of peanuts. Seven women were fed a basal diet containing 1.25 mg Cu/d. At 4-wk intervals, they were fed test meals over a 3-d period; each set of meals contained one of the labeled test foods in amounts with similar copper content. Absorption of 65Cu from intrinsically labeled liver was (mean +/- SD) 65 +/- 4%; extrinsic liver, 65 +/- 10%; E/I = 1.00 +/- 0.16. 65Cu absorption from intrinsically labeled goose breast meat was 54 +/- 6%; extrinsic meat, 52 +/- 10%; E/I = 0.97 +/- 0.18. 65Cu absorption from intrinsically labeled peanut butter was 58 +/- 15%; extrinsic peanut butter, 54 +/- 10%; E/I = 0.93 +/- 0.11. 65Cu absorption from extrinsically labeled sunflower butter was 50 +/- 2%. There were no differences in absorption of intrinsic and extrinsic Cu from these foods. Absorption of Cu was significantly higher from goose liver than from goose meat or sunflower butter (P less than 0.05). With a dietary intake of 1.25 +/- 0.20 mg Cu/d, Cu balance, exclusive of surface losses, was essentially zero (0.01 +/- 0.13 mg/d) in the seven subjects.

Animals↗
PubMed1988

Effect of estradiol-17 beta-monopalmitate on the incidence of sudden death syndrome in male broiler chickens.

One-thousand male broiler crossbred chickens were implanted subcutaneously with 15 mg of estradiol-17 beta-monopalmitate at 2 wk of age; another 1,000 chickens served as untreated controls. Each of the treatments consisted of 8 pens of 125 chickens each. All chickens that died during the 9-wk experiment were necropsied and the incidence of sudden death syndrome (SDS), determined. There was no significant difference between treated and control groups in total mortality or in mortality attributed to SDS. Treated birds had higher feed-to-gain ratios and drank more water than controls.

Animals↗
PubMed1988

Influence of light intensity on behavior and performance of broiler chickens.

The influence of two light intensity treatments, 180 and 6 lx, on behavior and performance of broiler chickens was examined in two experiments. The first experiment tested male chickens reared to 9 wk of age and the second experiment tested both sexes reared separately to 6 wk. Behavioral data were collected by scan sampling of behavior recorded on video tape. Standing, walking, and total activity were higher under the 180 lx than the 6-lx treatment (P less than .01), whereas feeding and drinking were not significantly affected by light intensity. Body weight, feed and water consumption, and feed conversion were unaffected by light intensity. Incidence of leg disorders at 6 wk and the percentage of bruised carcasses at 64 days were significantly lower under the higher light intensity treatment in the first experiment, as was mortality to 3 and 6 wk in the second experiment. No significant light intensity X sex interactions were detected. Results did not support the hypothesis that brighter lighting reduces performance due to increased chicken activity. Use of brighter lighting had no adverse effects on performance and there was some evidence that it may have a beneficial effect on welfare by reducing bruising.

Animals↗
PubMed1988

Relationships between age, body weight, and season of the year and the incidence of sudden death syndrome in male broiler chickens.

The aim of this study was to examine relationships between the incidence of sudden death syndrome (SDS) in male broiler chickens and age, body weight, and season of the year. The data used were from 23 experiments conducted from July 1982 to June 1987 involving a total of 89,988 chickens aged 1-day to a maximum of 70 days. All chickens that died during the experiments were necropsied and the incidence of SDS noted. Incidence of death from SDS as a percentage of mortality ranged from 1.31 to 9.62% among experiments. Death rate from SDS showed a significant increase with body weight. The SDS mortality rate reached a maximum when birds were between 21 and 27 days of age. Death rate from SDS increased up to about 21 days and remained between 80 and 86/100,000 chickens per day to 39 days, with a gradual decline to the end of the observation period (63 days), when it was 54/100,000 per day. Death rate from SDS may be related to the month in which the experiment started, with the highest mortality occurring in January and the lowest in July. Correlations between death rates from SDS and other causes were not significant.

Age Factors↗
PubMed1987

Ethanol metabolism in postmenopausal women fed a diet marginal in zinc.

Five postmenopausal women aged 50-63 y were fed a diet of mixed Western foods that supplied an average of 2.6 mg zinc/d for 6 mo. Plasma zinc did not change significantly during Zn depletion but increased slightly when Zn was fed. Zn content of blood cellular components and activities of Zn-containing enzymes were not affected by Zn intake. Ethanol tolerance tests performed at the end of control, middle of depletion, end of depletion, and end of repletion showed a change in ethanol metabolism at the end of the low-Zn intake period that was corrected within 1 mo with Zn supplementation. These data suggest that there are homeostatic mechanisms that maintain circulating levels of Zn. Zn and activity of Zn enzymes in tissues may be decreased before changes in circulating Zn levels are seen. Functional indices of Zn biochemistry, such as ethanol metabolism, may be more sensitive indicators of Zn stores and nutriture than circulating Zn.

Aged↗
PubMed1987

Dietary conditions influencing relative zinc availability from foods to the rat and correlations with in vitro measurements.

Zinc availability from a series of foods was determined using 65Zn-labeled test meals fed to rats. Zinc availability relative to zinc chloride depended on the amount of the zinc source in the test meal. Zinc availability from several foods was similar to that from zinc chloride when tested in smaller amounts, but enhanced when fed in larger amounts. The range of zinc availability was similar for foods of plant and animal origin. Rats retained significantly more zinc from pork, chicken, peanut butter, egg or milk than from rice, beef, soybean flour or navy beans. Foods with intermediate zinc availability were sweet corn, whole wheat bread, cheese and oysters. Several food characteristics were examined for possible relationships with zinc availability, including the solubility or molecular size of zinc compounds after an in vitro enzymatic digestion and the contents of phytic acid, minerals, amino acids, carbohydrate and fatty acids relative to the zinc content of the food. Protein and several amino acids predicted about half of the variance in zinc availability. Following in vitro enzymatic digestion, neither zinc solubility nor the partitioning of zinc between low and high molecular weight substances was a strong predictor of zinc availability.

Amino Acids↗
PubMed1987

Influence of usual zinc intake and zinc in a meal on 65Zn retention and turnover in the rat.

The influences of zinc in a meal and usual zinc intake on zinc retention and turnover were investigated in 7-wk-old male rats fed diets containing 12-151 mg Zn/kg for 3 wk before and after consuming a 65Zn-labeled meal containing ZnCl2. Retention corrected to zero time and turnover rate were determined by whole-body counting. Percent zinc retention was inversely proportional to the natural logarithm of the meal zinc, between 0.09 and 26 mumol. In comparison to lower doses, higher doses resulted in lower percent retention but greater amounts of zinc retained. Although the latter relationship was slightly curvilinear, there was no indication of a limited capacity for zinc retention with high doses. However, doses above 4 mumol resulted in higher turnover rates in rats accustomed to lower zinc intakes. Percent retention and the reciprocal of the turnover rate were proportional to the reciprocal of the dietary zinc concentration. The greatest differences in retention and turnover occurred between 12 and 26 mg Zn/kg diet. The zinc dose in a meal and the usual dietary zinc separately influenced percent zinc retention. These factors also interacted, such that greater dose effects were observed at lower zinc intakes and greater dietary zinc effects were observed at lower doses.

Animals↗
PubMed1987

Behavior of chickens prior to death from sudden death syndrome.

A study was made to determine if chickens dying from sudden death syndrome (SDS) showed any unusual behavioral characteristics during the final 12 h preceding death. Continuous video recordings were made of floor pens of 50 to 120 individually marked male broiler chickens between 3 and 10 wk of age. Behavioral data were obtained from video tapes played back following death of chickens from SDS. Analysis of the video tapes revealed no significant differences between 10 SDS chickens and their matched controls in the frequencies or proportions of time spent in each of 19 different behavioral activities. All SDS chickens exhibited a sudden attack prior to death lasting an average of 53 s and characterized by loss of balance, violent flapping, and strong muscular contractions. There was no evidence that death was preceded by a particular environmental or behavioral event. It was concluded that there were no consistent behavioral symptoms which could be used to identify SDS chickens prior to death.

Animals↗
PubMed1987

Fatty acid composition of hepatic and cardiac tissue from chickens dying of sudden death syndrome.

Gas chromatographic analysis of tissue lipids from broiler chickens dying from sudden death syndrome (SDS) were carried out to determine if anomalies in fatty acid composition could be linked to the disease. Crude extracts of lipids from hearts and livers of chickens dying from SDS and their matched controls (matched for pen number, sex and time of death) were fractionated by thin layer chromatography and the phospholipid, triacylglycerol (TG) and nonesterified aliphatic carboxylic acid [C14-C22] (FA) fractions were transmethylated and analysed by capillary gas chromatography. A number of significant (P less than .05) differences in fatty acid composition were found to exist between males dying of SDS and their controls, the most notable being elevated levels of arachidonic acid in the hepatic TG and cardiac FA fractions of SDS males. Few significant differences were found between SDS females and their controls. There was a trend toward increased desaturation of cardiac and hepatic tissue lipids of male SDS chickens, although this was significant only for the hepatic TG fraction. The results did not support the hypothesis that a lack of arachidonic acid as a precursor of prostaglandin synthesis was a causative factor in the disease.

Animals↗
PubMed1987

Effect of dietary boron on mineral, estrogen, and testosterone metabolism in postmenopausal women.

A study was done to examine the effects of aluminum, magnesium, and boron on major mineral metabolism in postmenopausal women. This communication describes some of the effects of dietary boron on 12 women between the ages of 48 and 82 housed in a metabolic unit. A boron supplement of 3 mg/day markedly affected several indices of mineral metabolism of seven women consuming a low-magnesium diet and five women consuming a diet adequate in magnesium; the women had consumed a conventional diet supplying about 0.25 mg boron/day for 119 days. Boron supplementation markedly reduced the urinary excretion of calcium and magnesium; the depression seemed more marked when dietary magnesium was low. Boron supplementation depressed the urinary excretion of phosphorus by the low-magnesium, but not by the adequate-magnesium, women. Boron supplementation markedly elevated the serum concentrations of 17 beta-estradiol and testosterone; the elevation seemed more marked when dietary magnesium was low. Neither high dietary aluminum (1000 mg/day) nor an interaction between boron and aluminum affected the variables presented. The findings suggest that supplementation of a low-boron diet with an amount of boron commonly found in diets high in fruits and vegetables induces changes in postmenopausal women consistent with the prevention of calcium loss and bone demineralization.

Aged↗
PubMed1986

Myocardial ischemia: platelet and thromboxane concentrations in cardiac lymph and the effects of ibuprofen and prostacyclin.

Blood platelets have been implicated in several mechanisms leading to and/or modifying myocardial ischemia. Cardiac lymph examination allows insight into the extracellular fluid that is in equilibrium with the capillary blood. In order to obtain an index of platelet activation during coronary artery events in the awake chronic animal, we wished to ascertain whether evaluation of cardiac lymph would detect changes in platelet activation resulting from a vascular occlusion. The study used conscious dogs in which cardiac lymph vessels had been previously cannulated by open-chest surgical protocol. The concentrations of immunoreactive thromboxane B2 and platelet counts were assessed in the cardiac lymph during the control period, the 10-60 minute occlusions, and the reperfusion periods. The same protocols were effected on another series of dogs after infusion of ibuprofen or prostacyclin. Initially, immunoreactive thromboxane B2 concentrations in the systemic blood and cardiac lymph were identical. A three-fold increase in immunoreactive thromboxane B2 concentrations occurred in untreated animals and was accompanied by a fall in platelet count in the lymph. The infusion of ibuprofen or prostacyclin, which inhibit platelet aggregation by different mechanisms, prevented both the decrease in platelets and the increase in immunoreactive thromboxane B2. In this study, intravascular events resulting from coronary occlusion invoke a rapid rise of immunoreactive thromboxane B2 in the extravascular fluid. A decrease in platelet escape into the extravascular compartment is interpreted as a result of intravascular aggregation promoting decreased platelet numbers. Thus, examination of continuously flowing cardiac lymph allows rapid detection of intravascular activation of platelets in the awake animal in the absence of surgical trauma.

Animals↗
PubMed1986

Light intensity effects on performance, activity, leg disorders, and sudden death syndrome of roaster chickens.

The effects of light intensity on performance, activity, leg disorders and sudden death syndrome (SDS) of male chickens were examined in two experiments. In each experiment 5,600 1-day-old chicks were divided evenly between 8 light-proof floor pens and reared to 9 weeks of age on one of four light intensity treatments: .5, 10, 20, and 30 1x in Experiment 1 and .1, 1, 10, and 100 1x in Experiment 2. Light intensities less than 10 1x were phased in gradually by 3 weeks of age. Light intensity had no effect on 3, 6, or 9-week body weight, incidence of leg disorders, total mortality, or mortality due to SDS in either experiment (P greater than .05). Effects of light intensity on feed conversion and carcass quality were inconsistent across the two experiments. In both experiments chicken activity, as measured by the proportion of birds standing up of those present in a 2.25-m2 floor grid in each pen, decreased with age (P less than .01) and was influenced by a light intensity by age interaction (P less than .05). It was concluded that bright lighting (greater than or equal to 10 1x) was not effective in reducing the incidence of leg disorders or in altering the SDS mortality rate.

Animals↗
PubMed1985

Creatine kinase and phosphorylase in cardiac lymph: coronary occlusion and reperfusion.

Cardiac lymph, collected from conscious dogs, was monitored for glycogen phosphorylase and creatine kinase (CK) enzymatic activity during control state, circumflex coronary artery (CFX) occlusion, and reperfusion. CFX occlusions, lasting for intervals as short as 10 min, initiated a release of phosphorylase and CK into the cardiac lymph, which was immediately observed during reperfusion of the ischemic tissue. Blood plasma levels did not appear for several hours. In the absence of reperfusion, the appearance of enzymes in cardiac lymph was delayed and peaked later. Glycogen phosphorylase and CK entered the lymph in greater quantities with reperfusion as the length of occlusion was increased. Histological examination of multiple sections of the reperfused hearts showed infarcts in hearts where CFX occlusions lasted 20 min or longer; occlusions of 10-15 min showed evidence of cell injury and death in two hearts and no definable infarct in the majority. Ischemic intervals of short duration release functionally active glycogen phosphorylase and CK, which reflect changes in myocardial cell egress of macromolecules and/or cell death.

Animals↗
PubMed1985

Effect of alternating lights and strain on behavior and leg disorders of roaster chickens.

The effects of light treatment and strain on movement, spacial distribution, activity, and incidence of leg disorders of 4 to 10-week-old male chickens were examined in two experiments. In both, an alternating light treatment, in which high-intensity light alternated from one side of the barn to the other against a background of low intensity light, was compared with a control light treatment of continuous low intensity light supplied to both sides of the barn. Two strains were tested in each experiment. In Experiment 1, chickens responded to the alternating light between 4 and 7 weeks of age, although not between 7 and 10 weeks of age, by moving into areas of relatively high intensity light. In Experiment 2, chickens responded during both periods by moving into areas of relatively low intensity light. Bird distribution was also affected by a geographical side preference. In both experiments, activity was higher in areas of high vs. low light intensity, higher under alternating than control light, and higher for younger than older birds (P less than .05). Activity was also influenced by strain (P less than .01). Incidence of leg disorders was influenced by strain (P less than .01) but not light treatment.

Aging↗