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Biomedical subjects

D N Marple

Publications and source records attributed to D N Marple.

At least 37 records · Page 2Linked to original sources
PubMed1987

Effects of parachlorophenylalanine, quipazine and cyproheptadine on growth hormone and adrenocorticotropin secretion in steers.

Adrenergic and perhaps dopaminergic neurons provide inhibitory regulation of growth hormone (GH) secretion in ruminants. This suggests that either serotonergic or other neurons regulate the stimulatory release of GH. The nature of neurotransmitter control of adrenocorticotropin (ACTH) secretion in ruminants has not been determined. Parachlorophenylalanine (PCPA; serotonin synthesis inhibitor), quipazine (serotonin receptor agonist) and cyproheptadine (serotonin receptor antagonist) were utilized in Holstein steers to determine whether serotonin receptors mediate stimulatory actions on GH and ACTH secretion. PCPA (100 mg/kg BW) administered each day at 1900 hr for three successive days did not alter mean GH concentrations, amplitude of GH peaks, nor the number of GH peaks. Likewise, PCPA altered none of these parameters for ACTH. Quipazine injected iv at .1 or .5 mg/kg BW increased plasma GH (P less than .05) and ACTH (P less than .001) concentrations. There was a dose effect of quipazine on both GH (P less than .05) and ACTH (P less than .0001) secretion. Pretreatment of steers with cyproheptadine (.06 and .6 mg/kg BW) reduced the stimulation of GH by quipazine (P less than .0001) and decreased basal GH concentrations (P less than .0004). Cyproheptadine at .06 mg/kg BW did not alter quipazine effects on ACTH, however, the higher dose decreased the peak ACTH response (P less than .02) to quipazine. Studies with quipazine and cyproheptadine indicated that serotonergic mechanisms are likely involved in the regulation of GH and ACTH secretion in steers.

Adrenocorticotropic Hormone↗
PubMed1987

Effect of photoperiod and temperature on prolactin secretion in ovariectomized gilts.

Five ovariectomized (OVX) gilts were placed in each of two chambers at 20 C with a photoperiod of 12 h light and 12 h dark for 8 d (12L:12D). On d 1, blood samples were collected via jugular cannula every 30 min from 0830 to 1630. At 1630, 200 micrograms of thyrotropin releasing hormone (TRH) were injected iv and blood samples taken every 10 min for 1 h and every 30 min for the next 2 h. On d 2, samples were taken every 30 min from 0830 to 0930 and from 1530 to 1630. Temperature was changed to 10 C or 30 C on d 3. Samples were taken from 0830 to 1630 on d 3, 4 and 9. At 1630 on d 9, the TRH challenge was repeated. Mean basal serum concentrations of prolactin (PRL) were similar for all gilts and for all periods. However, serum PRL response (ng PRL X ml-1 X 150 min-1) to TRH increased (P less than .0001) after exposure to 30 C, while exposure to 10 C failed to alter PRL response. In Exp. 2, six ovariectomized gilts were assigned to each chamber. The protocol of Exp. 1 was followed through d 3, except temperature and photoperiod were changed to 10 C and 8L:16D or 30 C and 16L:8D. On d 34 the TRH challenge was repeated. Mean basal serum concentration of PRL was similar for all gilts and all periods. However, simultaneous increases in temperature and photoperiod increased (P less than .005) serum PRL response to TRH, whereas simultaneous decreases in temperature and photoperiod failed to alter PRL response to TRH.

Animals↗
PubMed1987

Effect of animal density on endocrine development in gilts.

A study was conducted to determine the effect of social crowding on the development of endocrine organs involved in the reproductive process in growing and finishing gilts. One hundred four littermate gilts weighing approximately 30 kg were randomly assigned to treatment groups of either 8 or 16 pigs/pen. Gilts raised in pens of eight were allotted 1.06 m2 per pig from 30 to 65 kg and 1.25 m2 from 65 to 100 kg; whereas, one-half the area was provided for gilts raised in pens of 16. Littermate gilts raised in pens of 8 and 16 were slaughtered on the same day when the average weight of pigs reached 100 kg. At slaughter, the brain, adrenals, pituitary, uterus and ovaries were removed and weighted. The brain was lyophilyzed and reweighed to yield dry brain weight. Gilts raised in the low-density groups had heavier adrenal (P less than .01), pituitary (P less than .08), brain (P less than .11), dry-brain (P less than .02), uterine (P less than .09) and ovarian (P less than .07) tissues. Furthermore, significantly more gilts in the low-density, compared with the high-density groups, had ovulated at slaughter. In a second study, eight littermate gilts raised in pens of 8 or 16 and weighing approximately 100 kg were moved to individual pens and fitted with a jugular vein catheter. Following blood sample collection at 15-min intervals for 2 h, 200 IU of adrenocorticotropin (ACTH) were infused into the cannula. Blood samples were collected at 15-min intervals for an additional 2 h. There were no differences between basal or ACTH-stimulated concentrations of plasma cortisol between treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1986

Body composition and other physical parameters as determinants of age at sexual maturity and performance efficiency in dwarf hens divergently selected for body weight.

Hens in this study were produced from random breeding within lines (high, low, and control) of dwarf White Leghorns that had been divergently selected for four generations for 20-week body weight. Birds were weighed at 10 weeks of age and placed in individual cages at 18 weeks of age. Body weights, shank lengths, and egg weights were obtained at sexual maturity (day of first egg) and at 4, 8, 12, and 16 weeks after sexual maturity. Egg production was recorded during 28-day periods. Thirty hens/line were sampled at sexual maturity and at the above times after sexual maturity for body composition (percent fat, protein, moisture, and ash). High line hens showed increased percent body fat and reduced percent protein and moisture compared to low and control hens. Coefficients of determination (R2) for age at sexual maturity and body weight were small (R2 less than or equal to .20) for high and control hens. There were no meaningful relationships between body weight or other physical measurements and sexual maturity in low hens. There were no significant relationships between body composition and age at sexual maturity in high and control hens. There was a strong cubic association (R2 = .73; P less than .001) between percent ash and age at sexual maturity in low hens, although the biological importance of this relationship was uncertain. Coefficients of determination between body weight and performance efficiency (egg mass per body weight) were small to moderate (R2 = .04 to .46) for high and control hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1985

Glucagon, insulin, and growth hormone responses to glucose infusion in lactating dairy cows.

Early lactation in the dairy cow is associated with an increased demand for energy that can only be met by hormone-mediated partitioning of nutrients. The purpose of this study was to determine adaptive responses of basal and glucose-stimulated glucagon (IRG), insulin (IRI), and growth hormone (GH) concentrations to early lactation. Blood was collected via jugular cannulas from nonpregnant nonlactating (NPNL) cows and cows 14 days antepartum (AP) and 5 and 30 days postpartum (PP). Basal concentrations of IRI decreased with lactation, IRG was essentially unchanged, and GH was increased with lactation. The molar IRI/IRG (I/G) ratio was decreased from 4.6 at day 14 AP to 1.3 at day 30 PP. The effects of exogenous glucose (0.56 mM/kg body wt) on IRI were greatest during pregnancy and declined with lactation. IRG responses to glucose were similar except in NPNL cows, which had a minimal but prolonged IRG inhibition, GH responses to glucose infusion were absent in NPNL cows and were most significant at 5 days PP. The decreased I/G and elevated GH concentrations suggests that both IRG and GH play a role in nutrient partitioning during early lactation.

Animals↗
PubMed1985

The effect of pen density during rearing on subsequent reproductive performance in gilts.

A study involving 109 crossbred gilts of Duroc and Landrace breeding that were reared in equal-sized pens with 8 or 16 pigs/pen was initiated to determine the effects of pen density during rearing on subsequent reproductive and maternal performance. Gilts in pens of eight were allowed 1.06 m2/animal from 30 to 65 kg and 1.25 m2/animal from 65 to 100 kg, whereas those in pens of 16 were allowed only one-half as much floor area per animal. Gilts raised in groups of eight farrowed 1.0 more pigs/litter (P less than .05), and .7 more pigs/litter born alive (P = .15), than gilts reared in groups of 16 pigs/pen. There were no pen-density differences in the number of corpora lutea at 30 d of gestation (P = .33) or in litter birth weight (P = .26). After adjusting by covariance for the number of live pigs at the beginning of the lactation period, gilts from the pen density of 16 had more pigs per litter alive (P less than .01) and heavier litter weights (P less than .05) at 21 d postpartum and higher piglet survival rates to 21 d (P less than .02) than gilts that were reared in the low pen-density of eight pigs/pen. Results of this study indicate that pen density during the growing-finishing period may affect subsequent reproductive and maternal performance of gilts.

Animals↗
PubMed1984

Muscle protein synthesis and growth of two strains of chicks vaccinated for Newcastle disease and infectious bronchitis.

Rates of in vitro protein synthesis were monitored during an 8-week period in male broilers and Leghorns. The birds received vaccinations during Weeks 2 and 5 posthatching for Newcastle disease and infectious bronchitis by the administration of a standard dose of the mixed vaccine in the drinking water. Both types of birds exhibited a marked decline in the rate of protein synthesis during each week after vaccination. The decline in ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) levels were not as pronounced as those for protein synthesis, but DNA concentrations did tend to reflect the protein pattern between Weeks 5 and 6. Live weight of both types of birds increased at a steady rate throughout the period, but grams of carcass protein accrued per week followed the protein synthesis rate patterns during the 8-week period. The results suggest that Leghorns are more susceptible than broilers to the stress of vaccination.

Animals↗
PubMed1983

Growth and in vitro protein synthesis in two strains of chicks.

An in vitro method was used to estimate rates of skeletal muscle protein synthesis and degradation in fast (broiler) and slow (White Leghorn) growing birds. Four birds/strain were sacrificed at weekly intervals for 8 wk and biweekly thereafter to wk 14. The extensor digitalis communis, a muscle containing both red and white type fibers and the extensor carpi ulnaris, a white fiber-type muscle, were removed from the right wing and incubated in a Krebs-Ringer solution that contained either 14C-tyrosine for determination of rates of protein synthesis or cycloheximide for determination of rates of protein degradation. The contralateral muscles were removed and muscle weight, length and volume recorded. Proximate analysis was conducted on the carcass and inedible portions of the birds to determine protein, fat and moisture content. Nucleic acid concentrations were measured in the wing muscles. Broilers grew more rapidly than Leghorns, with a twofold difference in body weight by wk 3 and a threefold difference by wk 8. The greater total protein deposition, with more of this protein deposited in the carcass portion than the inedible portion. White muscle had a greater growth rate than the mixed fiber type muscle. Concentrations of RNA and DNA were similar between strains.

Animals↗
PubMed1983

Serum progesterone, enzymes, and electrolytes of hens laying a low or high incidence of shell-less eggs.

Three experiments were conducted to determine possible differences in serum progesterone, enzymes, and electrolytes between hens laying a high or low incidence of shell-less (SL) eggs. Blood was taken at time of oviposition and at 6, 12, 18, and 25 hr later, irrespective of the stage of the sequence. The results indicated no significant differences in average serum progesterone between hens laying a high or low incidence of SL eggs. In general, the patterns of serum progesterone in relation to time of oviposition was similar for each type. No significant differences were observed in serum phosphorus, magnesium, glutamate pyruvate transaminase, or alkaline phosphatase between hens laying a high or low incidence of SL eggs. It was concluded that the production of SL eggs is not related to abnormal serum progesterone, alkaline phosphatase, glutamate pyruvate transaminase, magnesium, or phosphorus levels.

Alanine Transaminase↗
PubMed1983

Growth and development of meat animals.

During the past 25 yr, animal scientists have learned much about the effects of environmental factors, nutritional treatments, the use of anabolic agents and genetic selection on growth of animals. Progress has been made in terms of body and carcass composition as well as a more fundamental understanding of growth at the cellular level. Current emphasis is directed towards action of hormones on tissue metabolism, factors regulating hormone secretion, mechanisms of synthesis and degradation of proteins and the energetic efficiency of protein and fat synthesis. The overall objectives are to control growth of animals with respect to rate and composition of gain and to improve the efficiency of growth.

Adipose Tissue↗
PubMed1982

Characterization of [3H] corticosterone binding activity in adrenal incubation media.

Glucocorticoid-binding activity in adrenal incubation media was investigated with regard to characterization of a protein-like ligand. Scatchard analysis of corticosterone binding activity indicated the presence of a single non-interacting protein with a dissociation constant (Kd) of 8.81 X 10(-10) M (0 degrees C), a value which is different from that of plasma and cytoplasmic glucocorticoid binding proteins. In addition, an observed lack of affinity of the protein for dexamethasone distinguishes the protein from Type II cytoplasmic receptor proteins. Thus our data suggest a glucocorticoid-binding protein which is distinct from the two known groups of glucocorticoid-binding proteins, corticosteroid-binding globulin (CBG) and cytoplasmic receptors.

Adrenal Glands↗
PubMed1981

The relationship of thyroxine secretion rate to growth of swine.

The thyroxine secretion rate of five barrows and five gilts (Yorkshire x Landrace) was monitored at 4-week intervals from 10 to 26 weeks of age. Thyroxine secretion rate was determined by injecting 131I-thyroxine (20 MUCi) and monitoring both thyroxine concentration in plasma and the decline of labeled thyroxine in plasma over the next 48 to 60 hours. The thyroxine secretion rate increased from 10 to 14 and 14 to 18 weeks of age but remained unchanged thereafter. The metabolic clearance rate of thyroxine increased significantly through 22 weeks of age 11.83, 2.98, 4.65, 6.32 and 6.90 leter/hr), as did the thyroxine distribution space (2.32, 4.32, 7.10, 90.72 and 10.36 liters. Body size (/.75) was correlated with thyroxine distribution space (r = .49) and thyroxine secretion rate (r = .44).

Animals↗
PubMed1981

The effects of floor temperature, supplemental heat and drying at birth on neonatal swine.

The objective was to determine the effects of floor temperature (20 or 30 C), supplemental heat (heat lamp or light bulb) and drying at birth on piglet survival to day 5. Rectal and infrared skin temperatures were taken on 326 piglets for the first 8 hr postpartum. Blood samples were obtained at birth, day 2 and day 5 and analyzed for thyroxine (T4), triiodothyronine (T3) and cortisol by radioimmunoassay. Weight of each pig was recorded at birth and on days 1, 2, and 5. Survival rates were monitored daily. It was postulated that piglets not dried at birth might have increased heat conservation because of vasoconstriction, which may increase the thermostability and survival of the neonate. Supplemental heat was the only treatment that increased rectal temperature after 3 hr postpartum. Skin temperature at 1/2 and 1 hr was increased by drying, and supplemental heat resulted in elevated skin temperatures from 5 to 8 hr postpartum. Plasma cortisol concentrations were elevated at 2 days of age among pigs not given supplemental heat, but no differences were detected at 5 days of age. Plasma T4 concentrations at 5 days of age were lower among male pigs, pigs on the 30 C floor and pigs given supplemental heat. No significant treatment effects were noted in T3 values at day 5. Pig weights and survival rate at 5 days of age were influenced by the interaction of floor temperature and drying pigs at birth. Pigs dried at birth and kept on the 20 C floor were heavier than those on the 30 C floor, whereas those not dried and kept on the 20 C floor weighed less than those on the 30 C floor. The rate of survival was significantly lower among pigs dried at birth and kept on the 20 C floor than among those not dried and on the 30 C floor (80.9 vs 97.2%), while drying had no effect on survival rate among pigs on the 30 C floor (94.5 vs 93.1%).

Animals↗
PubMed1979

Interaction of aging with in vitro adrenocortical responsiveness to ACTH and cyclic AMP.

In vitro adrenal accumulation of cyclic 3'5'-adenosine monophosphate (cyclic AMP) and release of corticosterone in response to adrenocorticotropic hormone (ACTH), cyclic AMP or theophylline was assessed in 60- and 340-day-old male rats. Adrenal tissue from mature animals secreted significantly smaller quantities of corticosterone in response to ACTH, theophylline or cyclic AMP. Additionally, mature tissue accumulated significantly less cyclic AMP after treatment with ACTH or a combination of ACTH and theophylline. The data suggest an age-related refractoriness of adrenal cortical tissue to ACTH which may in part be related to decreased availability of and/or sensitivity to cyclic AMP.

Adrenal Cortex↗