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Biomedical subjects

D L Davis

Publications and source records attributed to D L Davis.

At least 181 records · Page 10Linked to original sources
PubMed1985

Mating behavior, boar-to-boar behavior during rearing and soundness of boars penned individually or in groups from 6 to 27 weeks of age.

Individual and group-reared boars were compared in two experiments, for treatment effects on mating behavior, growth rate, feed consumption and feed/gain. Soundness also was evaluated in one experiment. Boar-to-boar behaviors were studied in group-penned boars. In Exp. 1, boars were either reared in a group of five or individually from 12 to 27 wk of age, or group-penned from 12 to 19 wk and individually from 1-9 wk. In Exp. 2, boars were either penned individually from 6 to 27 wk, group-penned (eight/pen) from 6 to 27 wk, grouped from 6 to 12 wk and then penned individually, or individually penned from 6 to 12 wk and then group-penned. Beginning at 29 wk of age, boars were tested every 2 wk for mating behavior in the presence of an estrous gilt. Four mating tests were conducted in Exp. 1 and five tests in Exp. 2. Individually penned boars grew faster from 6 to 12 wk old in Exp. 2, but no other treatment effects on growth rate were observed. Treatment had very little effect on mating test behaviors, but individual penning markedly reduced leg soundness. Sheath sniffing first appeared at 16 to 18 wk of age in group-penned boars and was followed closely by anal sniffing. Side nosing increased between 20 and 23 wk. Mounting activity from 12 to 27 wk old was correlated with mating test score in Exp. 1 (.76; P less than .01) and Exp. 2 (.55; P less than .05).

Animals↗
PubMed1985

Altrenogest and fat for summer breeding of primiparous sows.

Delaying the onset of estrus after weaning and adding fat to the postweaning diet were studied for their effects on estrus and fertility in 232 crossbred primiparous sows on a commercial swine farm. Sows were assigned randomly to the following treatments after weaning in June, July, August, or September, 1983: 1) altrenogest (20 mg/d) was fed for 7 d after weaning (n = 76), 2) altrenogest was fed for 7 d plus .53 kg dried animal and vegetable fat product (.45 kg actual fat/d) for 14 d after weaning (n = 78), or 3) no treatment (controls, n = 78). While a similar proportion of sows came into heat after weaning (lactation length = 4 wk), sows fed altrenogest (14.4 +/- .2 d) returned to estrus about 9 d later (P less than .01) than controls (5.6 +/- .2 d). Serum progesterone concentration was assayed in blood samples collected from a subgroup (74%) of the cows not observed in estrus by 3 wk after weaning to determine possible causes of anestrus. If serum progesterone (greater than 5 ng/ml) was elevated, we assumed that sows had ovulated without expressing estrus (behavioral anestrus) or ovulated with undetected estrus (less overt estrus or error in estrous detection), whereas low progesterone (less than or equal to 5 ng/ml) indicated that sows were anovulatory. About 53% of the sows not observed in estrus across all treatments had luteal function, probably resulting from post-weaning ovulation. Incidence of anovulation without estrus was 47%. Farrowing rate was higher (P less than .05) for sows fed only altrenogest (64%) compared with controls (46%), but similar to fat supplemented, altrenogest-treated sows (52%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Body growth and testicular characteristics of boars fed a synthetic progestogen, altrenogest.

A synthetic progestogen (altrenogest) was fed to 24 Yorkshire X Duroc boars to determine effects on body growth, serum testosterone, and testicular characteristics. Boars from six litters (blocks) were allotted randomly to one of four treatment groups at 12 wk of age. Treatment groups were: controls, altrenogest fed for 3 wk, altrenogest fed for 6 wk and altrenogest fed for 9 wk. Treatment began at 15 wk of age at a daily dose of 20 mg X boar-1. Although there were no differences among treatment groups for gain and feed intake, boars fed altrenogest for 6 and 9 wk tended to consume more feed and were less (P less than .05) efficient than boars fed altrenogest for 3 wk or controls. Boars fed altrenogest for 3, 6 and 9 wk maintained lower (P less than .05) peripheral serum testosterone concentrations than controls from 15 to 24 wk of age. However, serum testosterone increased after altrenogest withdrawal in the 3- and 6-wk treatment groups but did not reach control concentrations by 24 wk. Boars fed altrenogest for 9 wk maintained serum testosterone below 1 ng/ml during the treatment period. Despite lower concentrations of serum testosterone in altrenogest-treated boars, backfat thickness was similar to controls, perhaps suggesting a slight anabolic effect of altrenogest on nutrient partitioning. Testicular weights and volumes at 24 wk decreased (P less than .001) linearly with increased duration of altrenogest feeding. Serum testosterone and estradiol in testicular venous effluent at castration were lower (P less than .01) in altrenogest-treated boars than in controls. These data demonstrate that feeding altrenogest inhibits both testicular growth and steroidogenesis of boars without altering body growth or backfat thickness.

Animals↗
PubMed1985

A case of homosexual erotomania.

Erotomania has previously been described exclusively in terms of delusional heterosexual relationships, and almost all of the patients reported to manifest this syndrome are women. We report the case of a schizophrenic man with a chronic, fixed delusion involving a homosexual lover. Theoretical implications regarding the psychodynamics of this syndrome are discussed.

Adult↗
PubMed1985

Culture and storage of pig embryos.

Studies have consistently demonstrated that 4-cell pig embryos can be cultured to the blastocyst stage in a simple salt solution containing bovine serum albumin (BSA). Pig embryos appear to be detrimentally affected by lower levels of lactate and pyruvate than are mouse embryos, but in general their in-vitro requirements are similar. Results from embryos cultured between the 4-cell and blastocyst stages are consistent enough to allow the use of culture for the storage and shipment of pig embryos. However, results obtained after culture and transfer indicate a reduction in viability similar to that observed for cultured cattle and mice embryos. Embryos collected earlier than the 4-cell stage have been difficult to support in vitro beyond one or two cleavage divisions. Pig blastocysts may benefit from serum in their in-vitro environment: lamb, fetal calf and human serum supported continued development but pig serum was detrimental. There are conflicting reports on the efficacy of a more complete medium (Minimum Essential Medium) on the growth of pig embryos. Embryo culture will almost certainly contribute to the application of biotechnology to embryos by providing more appropriate environments for in-vitro manipulations and also, possibly, by providing a system for the early selection of desirable embryonic genotypes.

Animals↗
PubMed1984

Medical misinformation: communication between outport Newfoundland women and their physicians.

A middle-aged woman in a Newfoundland outport fishing village visits the doctor at a local medical clinic and complains of a case of bad nerves. Because he neither adequately understands the subtleties of the village concept of nerves nor the local etiquette of disease disclosure, the physician misinterprets the women's complaint and treats her for an ailment she does not have. The incident discourages the woman and other villagers from seeking medical care in the future. Any outport doctor should be familiar with the character of nerves as effectors of temperament, as conversation capital, and as female status enhancers and also with the role that 'women the worrier' plays in the local fishery. Features of village life which the physician, in this case study, fails to understand include: the complex patterns of social interaction behind the woman's decision to seek medical aid, the outporter's reluctance to ask for help or become obligated to others, and the local fear of persons in positions of authority. Most importantly the doctor is ignorant of the local view of the physician as a kind of moral adjudicator with the power to undermine the patient's reputation as a good woman in the community.

Communication↗
PubMed1984

Influence of reduced litter size and daily litter separation on fertility of sows at 2 to 5 weeks postpartum.

Two experiments were conducted to determine the influence of various lactational treatments on the incidence of estrus and subsequent fertility of sows. Experiment 1 consisted of 60 crossbred (Yorkshire X Duroc) sows assigned to one of four treatment groups. Litter size was reduced (RLS) to two to four nursing pigs/sow at 2 (n = 16), 3 (n = 15) or 4 (n = 15) wk of lactation for 5 d before final weaning or litters were weaned from control sows (n = 14) at 5 wk of age. Reduced litter size resulted in 19 of 43 (44%) sows detected in estrus on the day of weaning. More (P less than .05) RLS sows were in estrus 0 to 3 d after weaning than control sows. Fertility traits (number of corpora lutea, eggs recovered, egg recovery rate, eggs fertilized, fertilization rate, cleaved eggs and cleavage rate) were similar among treatment groups at 4 to 6 d postestrus. Experiment 2 consisted of 59 crossbred (Yorkshire X Duroc) sows assigned to one of four treatment groups. Litters were separated from their dams for 6 (n = 20) or 12 (n = 10) h/d between 2 and 4 wk or litters were weaned at 2 (n = 13) and 4 (n = 15) wk of age. Lactational estrus was detected in 13 of 20 (65%) sows and 5 of 10 (50%) sows that were separated from their litters for 6 or 12 h/d, respectively. Lactational estrus (LE, n = 18) in sows was observed 4 to 8 d after initial separation, while sows remaining anestrus during lactation (LA, n = 12) were in estrus 2 to 7 d postweaning. Average intervals from separation or weaning to estrus for LE and LA sows and for sows whose litters were weaned at 2 or 4 wk were 5.9, 4.4, 4.4 and 4.2 d, respectively, and were longer (P less than .05) for LE sows. Fertility traits were similar among treatment groups. These studies demonstrate that lactations of 2 to 5 wk and lactational treatments of sows, including either litter reduction before weaning or daily separation of sows from their litters, resulted in similar postweaning or post-treatment intervals to estrus and similar fecundity regardless of treatment or lactation length. While 50% of the sows responded to treatments, reasons for the lack of response in the remaining sows is not explained, but it appears that body weight and backfat of sows at weaning, and feed intake during lactation were unrelated to the success of the treatments imposed.

Animals↗
PubMed1984

Embryo transfer in swine.

Embryo transfer is used to propagate genetically superior swine while minimizing disease risks. Embryos are harvested through a ventral midline incision in the anesthetized sow 4-6 days after estrus, using a glass tube or Foley catheter. Embryos are transferred to similarly prepared sows by injection directly into the uterus through a tomcat catheter or glass pipette. Embryos typically are transferred within a few hours of collection but may be stored in culture medium at 37 C for up to 30 hours.

Animals↗
PubMed1983

Embryo transfer for conserving valuable genetic material from swine herds with pseudorabies.

Embryo transfer was used to conserve genetic material from 2 swine herds seropositive for pseudorabies virus (PRV). Embryos (n = 805) were recovered from 38 PRV-seropositive Duroc sows in Iowa and, after 4 to 10 hours' culture and shipment to Illinois, were transferred to 34 recipients from a herd seronegative for PRV. All recipients remained seronegative for PRV, and 22 of the recipients farrowed 208 pigs (189 alive) that also were seronegative for PRV. There was no evidence of PRV in the embryo recovery medium or in the uterine and oviductal cells recovered with the embryos. Transfer of morulae resulted in higher (P less than 0.02) farrowing rates than did transfer of 4- to 8-cell embryos, but litter size was not affected.

Animals↗
PubMed1983

The effects of maternal diabetes on fetal maturation and neonatal health.

This investigation focused on the relation between metabolic control of maternal diabetes in pregnancy and the health status of the fetus and newborn in the spontaneously diabetic BB rat. The basic hypothesis tested was that "tight" control of maternal diabetes before conception and during pregnancy should result in diminished fetal and neonatal morbidity and mortality. Behavioral teratologic tests were employed to evaluate the possible long-term effects of diabetes in pregnancy on postnatal development. The results demonstrated that approximation to glucose homeostasis in diabetic BB dams was associated with increased litter and fetal size, decreased perinatal mortality, and a significant reduction in the incidence of congenital malformation. Postnatal growth and neurologic function were also enhanced. These findings are supportive of efforts to initiate diabetic control prior to conception and especially during the critical period of fetal organogenesis during the first 8 weeks of human pregnancy.

Animals↗
PubMed1983

Prostaglandins in swine blastocysts.

The activity of phospholipase A2 (PLA2) and the content of prostaglandins (PGF and PGE-A) in swine blastocysts were determined on Days 7 through 14 of gestation by using radioenzymatic and radioimmunoassay techniques. Both PLA2 activity and PG content increased in the blastocyst with age. PLA2 activity on Day 14 and PG content on Day 12 were significantly higher than those on earlier stages of pregnancy. The content of PGE-A was always greater than that of PGF and the difference became significant on Days 11 and 12 of pregnancy. It is suggested that PGs of embryonic origin may be associated with blastocyts elongation and migration as well as early pregnancy recognition in the pig.

Animals↗
PubMed1983

Temperature effects on dog hindpaw series and parallel vascular circuits.

The effect of environmental temperature (skin surface) on distribution of blood flow between the parallel vascular circuits has been assessed in vascularly and neurally isolated hindpaws perfused at constant pressure. The paw was sealed in a chamber filled with water at 10, 20, 30, or 40 degrees C. Peripheral resistance increased as the temperature decreased in both innervated and denervated paws. Resistance in the denervated paws was less than in the innervated paws at all temperatures. Recovery of 85Sr microspheres was less at 40 degrees C than at 10, 20, or 30 degrees C in the denervated paws but did not change in innervated paws. Capillary availability (diffusion capacity and filtration coefficient) increased with each elevation in temperature in both groups. At 10 degrees C both arteriovenous (AV) shunt and capillary flows were low in innervated paws with low capillary and high shunt flow in denervated paws. At 20 and 30 degrees C capillary flow increased with temperature and arteriovenous anastomosis (AVA) flow was unchanged in denervated paws. In innervated paws AV shunt flow fraction slightly increased, with capillary perfusion markedly increased as temperature was elevated. The increased capillary flow in both groups passed through an enlarged capillary bed, whereas the number and/or diameter of AVAs remained essentially unchanged.

Animals↗
PubMed1983

Length-dependent sensitivity at lengths greater than Lmax in vascular smooth muscle.

Previous work has shown that vascular smooth muscle sensitivity depends on muscle length (arterial circumference) at lengths equal to and less than that for maximum active force (Lmax). In the present study dose-response curves were obtained from dog anterior tibial artery rings at lengths equal to or longer than Lmax. The curves were compared with dose-response curves obtained at lengths less than Lmax. The agonist concentration for half maximal response (ED50) was determined by graphical estimation and by calculation from a best-fit curve. The results show that with norepinephrine (NE) stimulation 1) ED50 decreased significantly at each step when the rings were stretched from Lmax to 1.15 Lmax and then to 1.30 Lmax; 2) ED50 increased significantly when length was decreased from 1.15 to 1.00 Lmax; 3) ED50 decreased significantly at each step when the rings were stretched from 0.70 Lmax to Lmax and then to 1.30 Lmax; and 4) for NE concentration greater than the ED50 at Lmax, active stress was significantly higher at Lmax than at 0.70 Lmax or 1.30 Lmax. For an NE concentration less than the ED50 at Lmax, the active stress at 1.30 Lmax was higher than the active stress at Lmax and at 0.70 Lmax. The results show that sensitivity of vascular smooth muscle continually increases with stretch and does not have a maximum at the length for maximum active force.

Animals↗
PubMed1983

Innervation sites of dog hindpaw series and parallel vascular circuits.

The neural control of the distribution of blood flow between the parallel nutritional and nonnutritional vascular circuits in the dog hindpaw has been assessed. The right hindpaw of anesthetized dogs was vascularly and neurally isolated and placed in a volume recorder sealed by the skin flap. The animals were heparinized. The autoperfused preparation was isovolumetric during the control period. The inflow tubing had side arms for measurement of perfusion pressure and for injections of indicators (131I-albumin, 86Rb and 85Sr-microspheres). Vascular volume changes were determined from venous time-concentration curves and by plethysmography. The peripheral cut ends of the superficial and deep fibular nerves and the tibial nerve were individually stimulated at 5 and 11 Hz. The permeability surface area product of 86Rb and the capillary filtration coefficient were determined and A-V shunt patency was assessed by the venous recovery of 85Sr 15 microns microspheres. Each nerve stimulation increased blood flow resistance. Superficial fibular nerve innervation included essentially uniform effects on the arterioles and A-V shunts, the upstream arteries and also the veins. Deep fibular nerve stimulation indicated that its innervation included the arteries and the A-V shunt nonexchange vessels. Tibial nerve stimulations indicated that its innervation included the A-V shunt vessels and veins with minimal influences on the arteries and arterioles.

Animals↗
PubMed1983

Cancer prevention: assessing causes, exposures, and recent trends in mortality for U.S. males, 1968-1978.

This paper addresses some enduring issues concerning prevention of environmental and occupational cancer. The first part reviews methodological problems of estimating cancer risks and outlines some research priorities. The second part documents countervailing trends in chemical production during the past two decades, noting the doubling of some synthetic organic human carcinogens and the leveling off of some heavy metal carcinogens. The final section details recent increases in site-specific causes of cancer mortality for men old enough to have developed workplace cancers (ages 35 to 84), considering those cancers that have been linked with exposures to toxic chemicals and to cigarette smoking. This paper points out that Doll and Peto's (1981) analysis of U.S. cancer trends does not indicate some important increases in older males; they conclude that apart from cigarette smoking, there is no generalized increase in cancer for persons up to age 64. In fact, there has been a sharp reduction in cancer mortality for those under age 45. This reduction more than offsets increases in some cancers for those ages 45 to 65. Men ages 55 to 84 have experienced major increases in mortality for certain cancers plausibly associated with occupational exposures, including cancers of the brain, lung, and multiple myeloma. These older age groups have potentially sustained longer workplace exposures to carcinogens, some of which have 25-year or greater latencies. Changes in infectious diseases, workplace exposures, diagnostic trends, environment, and nutrition require further study.

Adult↗
PubMed1983

Influence of supplemental light on sow performance during and after lactation.

A completely randomized block experiment with two treatments was designed to investigate the effect of supplemental light on sow performance during and after lactation. Crossbred multi- and primiparous sows were exposed to either limited (control, n = 164) or 16 h (n = 163) timer-controlled supplemental light beginning 3 to 9 d before expected farrowing. Overhead illumination (32 to 266 lux) was furnished by seven fixtures (two tubes each) of cool white fluorescent light at twice-daily feedings in control rooms (less than 1 h/d) and for 16 h/d in supplementally lighted rooms (16 h). Litter size was equalized within 48 h postpartum (10 +/- .1 pigs/litter; X +/- SE) in each of five identical rooms that served alternately as control or 16-h treatments during 10 consecutive weekly farrowings (September 24 to November 26, 1981). Litters were heavier (P less than .05) at weaning (26 +/- .1 d) for 16-h than for control sows (57.8 +/- 1 vs 54.3 +/- 1 kg) while pigs weaned (9.2 +/- .1 vs 9.1 +/- .1), piglet survival (90 vs 91%) and days to mating (5.9 +/- .4 vs 5.5 +/- .3) were similar (P greater than .05). However, more (P less than .01) 16-h than control sows (83 vs 68%) were mated by 5 d postweaning. Multiparous sows weaned heavier (P less than .05) litters than primiparous sows (57.9 +/- 1 vs 50.1 +/- 1 kg) while overall litter weight increased (P less than .05) 141 +/- 6 g for each 10 lux increase in light intensity. We concluded that litter weight is increased and return to postweaning estrus more synchronous when sows are exposed to 16 h supplemental ligh/d during a 4-wk lactation.

Animals↗