PubMed Health⌕ Search

Biomedical subjects

R D Boyd

Publications and source records attributed to R D Boyd.

At least 19 recordsLinked to original sources
PubMed1992

Gestational changes in Ca2+ transport across rat placenta and mRNA for calbindin9K and Ca(2+)-ATPase.

The unidirectional maternofetal clearance (Kmf) of 45Ca was measured across the rat placenta over the last one-third of gestation. Kmf for 45Ca normalized to its diffusion coefficient in water (Kmf/Dw) increased 72-fold between days 15 and 22 of gestation from 3.5 +/- 0.3 to 253.1 +/- 22.0 cm/g placenta, respectively. At 15 and 18 days of gestation, Kmf/Dw for 45Ca was similar to Kmf/Dw for the paracellular marker [14C]mannitol, but at 21 and 22 days of gestation, Kmf/Dw for 45Ca was significantly higher than Kmf/Dw for [14C]mannitol, indicating that an additional route of transfer, other than diffusion, becomes available to calcium during this period. Northern hybridization analysis demonstrated that rat placental calbindin9K-to-beta-actin mRNA ratio increased 135-fold between 15 and 22 days of gestation and was temporally associated with the gestational increase in Kmf/Dw for 45Ca. In contrast, rat placental Ca(2+)-ATPase-to-beta-actin mRNA ratio increased only two- to threefold over the same gestational period and did not mirror the gestational changes in calcium clearance. These trends suggest that the expression of placental calbindin9K, but not Ca(2+)-ATPase, may be rate limiting to placental calcium transport in the rat.

Actins↗
PubMed1992

Influence of genotype and sex on the response of growing pigs to recombinant porcine somatotropin.

The dose-dependent effects of porcine somatotropin (pST) on growth performance and composition of carcass gain were investigated in 150 growing pigs. The experiment involved two genotypes (barrows from the Pig Improvement Company [PIC] and a University of Nebraska [NEB] gene pool line) and two sexes (PIC barrows and boars). At 30 kg, pigs were randomly assigned within each genotype and sex subclass to receive daily i.m. injections of 50, 100, 150, or 200 micrograms of pST/kg BW or an equivalent volume of an excipient. A diet (3.5 Mcal of DE/kg) supplemented with crystalline amino acids and containing 22.5% CP was available on an ad libitum basis until pigs were slaughtered at approximately 90 kg live weight. Excipient-treated PIC barrows exhibited faster and more efficient growth (P less than .001) and a higher capacity for carcass protein accretion (P less than .001) but similar rates of lipid deposition compared to excipient-treated NEB barrows. Within the PIC genotype, control boars grew at a rate similar to that of barrows, but they were more efficient (P less than .05) and deposited more carcass protein (P less than .05) and less lipid (P less than .001). Carcass protein accretion rate increased (P less than .001) up to approximately 150 micrograms of pST.kg BW-1.d-1, whereas lipid deposition decreased (P less than .001) with each incremental dose of pST. Although differences between PIC boars and barrows for all criteria were negated with increasing pST dose, they were maintained between the two genotypes. Polynomial regressions suggested that a slightly higher pST dose was required to optimize the feed:gain ratio compared with rate of gain and that the dose (micrograms per kilogram BW per day) was a function of the genotype and sex (feed:gain: 185, 170, and 155; rate of gain: 155, 155, and 125 for NEB barrows, PIC barrows, and PIC boars, respectively).

Adipose Tissue↗
PubMed1992

Temporal response of circulating metabolites and hormones during somatotropin treatment of growing pigs.

Temporal responses in the circulating concentrations of a number of intermediary metabolites and metabolic hormones were studied in chronically catheterized barrows (n = 4 per treatment) after either daily i.m. injection of porcine somatotropin (pST, 120 micrograms/kg of BW) or excipient. Blood sampling (every 1 or 2 h) began 24 h before the first injection (d 0) and continued until the end of d 2. Sampling was repeated on d 7 of treatment. Feed intake declined by d 3 in the pST-treated pigs and was 31% lower by d 7 of treatment (P less than .05). Blood glucose and plasma insulin concentrations began to increase about 3 h after the first pST injection, almost returning to preinjection levels before the next injection. By the end of d 2, circulating levels of glucose and insulin were higher in pST-treated pigs than in the controls. A temporal pattern of hyperglycemia and hyperinsulinemia was observed postinjection on each day of treatment. Although pST treatment did not chronically increase basal plasma concentrations of nonesterified fatty acids and glycerol, both metabolites exhibited transient postinjection elevations, the magnitudes of which were augmented by duration of treatment. Plasma urea nitrogen concentrations began to decrease within a few hours after the first pST injection and by d 7 were 70% (P less than .01) lower in the pST-treated pigs. A model is presented implicating pST-induced decreases in peripheral tissue insulin sensitivity and(or) responsiveness in the observed temporal responses in lipid and carbohydrate metabolism.

Animals↗
PubMed1992

Effect of somatotropin on nonesterified fatty acid and glycerol metabolism in growing pigs.

Eight crossbred barrows (71 kg initial BW) were allocated to two treatments involving daily i.m. injections of either excipient (control) or recombinantly derived porcine somatotropin (120 micrograms/kg of BW). On d 8 of treatment, beginning 15 h after injection, glycerol and nonesterified fatty acid (NEFA) kinetics were determined using a primed, continuous infusion of [2-3H]glycerol and [9,10(n)-3H]oleic acid. Kinetics were examined under both basal conditions and during a hyperinsulinemic/euglycemic clamp. Plasma concentrations of NEFA and glycerol and their respective entry rates were highly correlated. Insulin had no effect on plasma glycerol or glycerol entry rate, probably due to the very low rates that were observed in both the control and somatotropin-treated pigs. However, both plasma NEFA and oleic acid entry rate were reduced during hyperinsulinemia. Although indices of fat mobilization tended to be higher in pigs treated with somatotropin, the magnitude of the increases were small and would be sufficient to account for only a minor fraction of the decreased lipid accretion observed in somatotropin-treated pigs.

Animals↗
PubMed1992

Effect of porcine somatotropin on in vivo glucose kinetics and lipogenesis in growing pigs.

Crossbred barrows were used for in vivo studies investigating hormonal regulation of lipogenesis. The first experiment examined an in vivo method for determining rates of lipogenesis. Three barrows were infused with [U-14C]glucose and incorporation of radioactivity into triglycerides was determined in up to five biopsies of subcutaneous adipose tissue obtained over 7 h. Incorporation was linear after blood glucose specific radioactivity had reached a plateau and was constant over the entire infusion. For the second experiment, eight pigs (71 +/- 2.5 kg) were allocated to one of two treatments involving daily injections of excipient (control) or porcine somatotropin (pST; 120 micrograms/kg of BW). On d 10, beginning 15 h after injection, glucose incorporation into adipose tissue lipid was determined under both basal and hyperinsulinemic/euglycemic conditions. Basal glucose incorporation into lipid, particularly fatty acids, was markedly reduced (greater than 90%) during pST treatment. Although glucose incorporation was increased to a similar extent in both groups by hyperinsulinemia, the pST-treated pigs still exhibited markedly lower rates. Based on kinetic data, the decrease in lipid accretion of pST-treated pigs was primarily the result of a decrease in the rate of de novo synthesis. Furthermore, the reductions in glucose incorporation into fatty acids, glucose irreversible loss rate, and feed intake that occur with pST treatment were quantitatively similar.

Adipose Tissue↗
PubMed1992

Recurrence of neuroleptic malignant syndrome via an inadvertent rechallenge in a woman with mental retardation.

A case was described in which neuroleptic malignant syndrome reoccurred as the result of an inadvertent rechallenge in a woman with mild mental retardation. This potentially lethal disorder has an incidence of approximately 1% and a mortality rate of about 15%. Individuals with mental retardation are thought to be at greater risk, and some recommendations were offered to prevent recurrence.

Adult↗
PubMed1991

Morphologic and morphometric changes in synovial membrane associated with mechanically induced osteoarthrosis.

We sought to determine whether synovial leukocytic inflammation is a primary event in mechanically induced osteoarthrosis. Repetitive impulse loading (50 ms duration at 60 Hz for 40 minutes each day) was applied to the right hindlimbs of 24 New Zealand white rabbits for 3, 6, or 9 weeks. The synovial membrane from the medial suprapatellar area was examined qualitatively using transmission electron microscopy and quantitatively using light microscopic morphometry. The results indicate that synovial inflammation is not a primary event in this mechanically induced osteoarthrosis, but synovial hyperplasia occurs prior to histologically evident cartilage destruction at 6-9 weeks.

Animals↗
PubMed1991

Mechanical determinants of osteoarthrosis.

The joint is an organ and functions as a mechanical bearing created of biological materials. In the joint, as in all connective tissues, there is a relationship between mechanical factors and tissue behavior. Therefore, it is not surprising that joint health and osteoarthrosis are reflections of both mechanical and biological factors. Osteoarthrosis is not a disease, but organ failure caused initially by mechanical factors. The biological changes follow. There is no habitual pathophysiological cascade. Osteoarthrosis is best thought of not as a common final pathway, but as a common end stage. The hypotheses that in osteoarthrosis substructural disorganization of the matrix proceeds chondrocytic enzyme production, that impulsive loading is an essential factor in the progressive cartilage destruction, and that tidemark advancement and horizontal cartilage splitting are the primary mechanisms in progressive cartilage loss are discussed.

Animals↗
PubMed1991

Metabolic effects of porcine somatotropin: nitrogen and energy balance and characterization of the temporal pattern of blood metabolites and hormones.

Twelve barrows (61 kg) received daily injections of either pituitary-derived porcine somatotropin (pST; 120 micrograms/kg body weight) or an equivalent volume of excipient. Blood samples were taken 1 d before initiation and on d 9 of treatment to characterize the temporal patterns of blood hormones and metabolites. Nitrogen (N) and energy (E) balances were performed on d 14 through 19 of treatment. Pigs treated with pST retained more N than controls (38.4 vs 23.0 g/d, P less than .01) and had a slightly higher apparent digestibility of N and E (88 vs 84% and 88 vs 85%, respectively, P less than .05). However, this improvement in apparent digestibility was probably a consequence of the lower feed intake (23% reduction) rather than a direct effect of pST. Treatment with pST resulted in chronic elevations in circulating concentrations of insulin-like growth factor I (406 vs 171 ng/ml), glucose (114 vs 86 mg/dl), insulin (3.9 vs 1.6 ng/ml), and nonesterified fatty acids (NEFA; 135 vs 59 mu Eq/liter). Diurnal patterns of glucose, insulin, and NEFA were also altered in pST-treated pigs. Plasma urea N levels were decreased with pST treatment (9.6 vs 24.0 mg/dl), but the diurnal pattern was unaltered. Our results indicate that the effect of pST is primarily on postabsorptive use of nutrients. In growing pigs, pST exerts a profound effect on N metabolism and on circulating concentrations of hormones and metabolites.

Animals↗
PubMed1991

Effect of colostrum intake on hepatic gluconeogenesis and fatty acid oxidation in the neonatal pig.

A total of 24 newborn pigs were used to determine 1) the relationship between the quantity of colostrum consumed and the capacity for gluconeogenesis and fatty acid oxidation and 2) whether fatty acid oxidation limits gluconeogenesis in isolated hepatocytes. Neonatal pigs were obtained prior to nursing and allotted to one of three treatment groups; fed (ad libitum), limit-fed (25% of fed group), or fasted. Hepatocytes were isolated when pigs were 24 h old. Colostrum intake altered the metabolic status of neonates such that the capacity for glucose synthesis and oxidation of octanoate increased with intake. Glucose synthesis with lactate as the substrate was greater (P less than .01) for fed pigs (10.79 mumol glucose.h-1.mg DNA-1) than for either limit-fed (6.56) or fasted counterparts (4.78), which were similar (P greater than .10). Colostrum intake failed to stimulate synthesis from alanine. The oxidation rate for octanoate was similar for fed and limit-fed pigs (.62 and .61 nmol CO2.h-1.mg DNA-1, respectively) but greater (P less than .05) than that observed for fasted counterparts (.36). Oxidation of octanoate (2 mM) was approximately 30-fold greater than for oleate (1 mM); oxidation of the latter was not affected by either colostrum intake or the addition of carnitine (1 mM). The increase in octanoate oxidation, however, did not elicit an increase in glucose synthesis by fasting pigs with either lactate or alanine as precursors. Thus, we conclude that gluconeogenesis is a function of colostrum intake and that reducing equivalents and(or) ATP may not be primary factors limiting glucose synthesis in pigs fasted from birth.

Animals↗
PubMed1990

Bone and cartilage changes following experimental varus or valgus tibial angulation.

The purpose of this work was to determine whether subchondral bone changes are an integral part of the development of osteoarthrosis of the knee following experimentally created tibial angulation. Thirty degree varus or valgus proximal tibial osteotomies were created in female New Zealand white rabbits. Bone and cartilage changes were assessed grossly, radiologically, and histologically. Thirty-four weeks following osteotomy, severe cartilage changes, including osteophytes, fibrillation, derangement of cell columns, and cloning, were evident on the overloaded condyle, accompanied by increased subchondral bone density. The pattern of cartilage deterioration was different from that found in other experimental, mechanically induced arthroses. We conclude that osteoarthrosis is a final common pathway for mechanically induced joint failure, and that progressive cartilage change is associated with increased subchondral bone density.

Animals↗
PubMed1990

Regional patterns of bone loss and altered bone remodeling in response to calcium deprivation in laboratory rabbits.

This study explores the effects of a calcium-deficient diet on patterns of bone remodeling, and examines regional differences in the amount of bone lost. Skeletally mature female rabbits (n = 6) were fed a calcium-deficient diet (0.10% Ca2+ and 0.50% P) for 14 weeks. A separate group of rabbits (n = 4) were fed a maintenance diet (1.2% Ca2+ and 0.45% P). Bone mineral content, serum calcium, and serum phosphorus were measured each week during the experimental period. Following sacrifice, the L3 vertebra, femoral head, proximal tibial metaphysis, and tibial midshaft were analyzed histomorphometrically. Rabbits had 20% less vertebral bone after only 14 weeks of a calcium-deficient diet. As in human postmenopausal osteoporosis, bone loss in calcium-deficient rabbits occurs in the trabecular bone of the lumbar spine before that in the trabecular bone of the lower extremity. Calcium-deficient diets alone do not lead to increased osteoid volume or thickness. Because bone loss is relatively rapid and because the pattern of loss is similar in some respects to that found in humans, adult rabbits may provide an attractive model of calcium deficiency osteoporosis in a skeletally mature mammal in which remodeling is predominant over modeling.

Animals↗
PubMed1990

Filtration of water from mother to conceptus via paths independent of fetal placental circulation in sheep.

1. Four pregnant ewes were operated on at 121-126 days of gestation. An electromagnetic flow sensor and an inflatable occluder were placed on the maternal common internal iliac artery. The ovarian arteries and veins were ligated. Indwelling catheters were placed in a maternal femoral artery and uterine vein and in the amniotic and allantoic fluids. An inflatable occluder was placed around the umbilical cord, close to the fetal abdomen. 2. Eight to nine days after surgery, the cord was occluded, the fetus killed and uterine blood flow reduced to one-quarter of its control value. The rate of water loss from the uterine circulation was calculated from blood flow and the venoarterial difference in blood osmolality. The amniotic and allantoic fluids were made hypertonic by infusion of 2 l into each sac of a solution of 1.5 mol of mannitol per litre of saline. The rate of water loss from the maternal uterine circulation was then measured five times over the next 4.5 h. 3. The combined filtration coefficient surface area product of the interfaces between maternal blood and the amniotic and allantoic sacs, normalized per kilogram fetal body weight, was (2.8 +/- 0.5) x 10(-6) cm3 s-1 kPa-1 kg-1 (mean +/- S.E.M).

Allantois↗
PubMed1990

Absent maternofetal potassium gradient at term.

Mean (SE) umbilical venous plasma potassium concentrations at 5.5, 10, 20, and 30 minutes after the start of laparotomy at term were 4.75 (0.15), 5.95 (0.26), 6.81 (0.23), and 7.59 (0.81) mmol/kg plasma water. Maternal peripheral venous plasma concentrations were 4.30 (0.13) before and 4.26 (0.23) mmol/kg plasma water after laparotomy. Plasma calcium concentration in maternal and cord blood did not change significantly.

Cesarean Section↗
PubMed1990

Experimental stress fractures of the tibia. Biological and mechanical aetiology in rabbits.

We have shown that stress fractures can be induced in the tibial diaphysis of an animal model by the repeated application of non-traumatic impulsive loads. The right hind limbs of 31 rabbits were loaded for three to nine weeks and changes in the bone were monitored by radiography and bone scintigraphy. The presence of stress fractures was confirmed histologically in some cases. Most animals sustained a stress fracture within six weeks and there was a positive correspondence between scintigraphic change and radiological evidence. Microscopic damage was evident at the sites of positive bone scans. The progression, location, and time of onset of stress fractures in this animal model were similar to those in clinical reports, making the model a useful one for the study of the aetiology of stress fractures.

Animals↗
PubMed1990

Dose-response relationships between porcine somatotropin, muscle composition, muscle fiber characteristics and pork quality.

The dose-dependent effects of porcine somatotropin (pST) on cellular aspects of skeletal muscle growth, muscle composition and measures of pork quality were investigated in growing barrows and gilts. Eighty crossbred pigs weighing 46 kg were assigned randomly to receive daily subcutaneous injections of 0, 30, 60, 120 or 200 micrograms pST/kg BW until they weighed 100 kg. Semitendinosus muscle weights were increased with pST dose (linear, P less than .001) by 21%. Percentage of type I and type II muscle fibers was not changed with pST, but cross-sectional area of type I and type II fibers was increased in parallel with muscle weight. Percentage of moisture increased (P less than .01) and percentage of lipid decreased (P less than .01) as pST dose increased. The pH of the longissimus 24 h postmortem increased (P less than .01) .1 to .2 units with increasing pST dose, but subjective evaluation for color, firmness and wateriness of the longissimus indicated no discernible treatment effect. Gardner color difference meter "Rd" and "A" values decreased (P less than .01) with a pST dose of 60 micrograms/kg or more, signifying a slightly darker and less red color, respectively, of the longissimus muscle. Weight loss of loin chops 2.54 cm thick cooked to 71 degrees C (20.3% to 23.7%) and shear force of cores 1.27 cm in diameter (2.89 to 3.76 kg) were not related to pST treatment or dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effect of colostrum intake on plasma glucose, non-esterified fatty acid and glucoregulatory hormone patterns in the neonatal pig.

The effect of colostrum on endocrine and metabolic factors affecting glucose homeostasis was evaluated in 60 neonatal pigs that were fasted, fed (nursed ad libitum) or limit-fed colostrum (25% ad libitum, 4-hr interval feeding). Plasma acquired at birth (t0), and after 10, 20 and 30 hr (t10, t20 and t30, respectively) was analyzed for glucose, non-esterified fatty acids (NEFA), and the glucoregulatory hormones--insulin, glucagon, cortisol, growth hormone and catecholamines. The concentration of glucose and NEFA was similar among treatment groups at birth and increased in proportion to the quantity of colostrum consumed. Pigs fed ad libitum achieved and maintained a higher (greater than or equal to 40%; P less than .01) glucose concentration when compared to fasted neonates. Limit-fed counterparts also achieved and maintained higher levels, with glucose concentration being approximately 20% higher throughout (P less than .05). Fed pigs maintained NEFA concentrations which were approximately 2.5-fold to 4-fold greater than that of fasted pigs (P less than .05). Likewise, limit-fed pigs tended (P = .19) to have elevated NEFA concentrations and a lower (P less than .05) insulin:glucagon molar ratio. An inverse relationship was observed between colostrum intake and plasma concentrations of cortisol and growth hormone. Concentrations of epinephrine and norepinephrine tended (P greater than .10) to be elevated in fed pigs, relative to those of fasted counterparts. Provision of even limited quantities of colostrum is therefore beneficial to the glucoregulatory response in newborn pigs.

Aging↗