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Biomedical subjects

D L Snyder

Publications and source records attributed to D L Snyder.

At least 55 records · Page 3Linked to original sources
PubMed1988

Serum lipids in spontaneously hypertensive rats and Sprague-Dawley rats fed menhaden oil.

Dietary n-3 fatty acids, abundant in fish oil, exert a variety of effects that attenuate cardiovascular disease. In this study, we assessed the effect of fish oil (menhaden oil) on the serum lipid profile in hypertensive and normotensive rats. Spontaneously hypertensive rats (SHR) or Sprague-Dawley rats (SD) were fed either standard powdered diet (L-485), or L-485 + 5% menhaden oil (MO) or L-485 + 5% corn oil (CO) from weaning through eight months of age. Systolic blood pressure (BP) was periodically determined on SHR. Serum lipid profiles were performed at eight months on samples taken from the exposed hearts of anesthetized, fasted rats. SHR, compared with SD (diets combined) had significantly lower triacylglycerols (TG), higher cholesterol (CHOL), higher high density lipoprotein cholesterol (HDL CHOL), higher low density lipoprotein cholesterol (LDL CHOL), and a higher LDL:HDL ratio. Comparisons among diets (strains combined) revealed that rats fed MO had the lowest values for TG, CHOL, LDL and LDL:HDL; HDL did not vary with diet. SHR were less responsive to diet-induced changes than were SD; no decrease in TG, LDL or LDL:HDL was observed in SHR, nor was degree of hypertension altered in SHR by the MO or CO diet. In summary, MO is more effective than CO in shifting the lipid profile of rats toward one that is less atherogenic. However, the SD rat is more susceptible to diet-induced lipid modification than is the SHR.

Animals↗
PubMed1988

Serum hormones in diet-restricted gnotobiotic and conventional Lobund-Wistar rats.

In order to clarify the reasons for life extension due to the germ-free state and mild dietary restriction, serum levels of thyroid stimulating hormone, thyroxine, triiodothyronine, prolactin, and testosterone were determined in conventional and gnotobiotic (single microbe contaminations) Lobund-Wistar rats fed either ad libitum or restricted to 12 grams (70% of ad libitum) of diet per day from weaning. Thyroid hormone levels were slightly higher in gnotobiotic rats, declined between 7 and 30 months of age in all rats, and were not affected by dietary restriction. Prolactin showed a significant rise with age within the ad libitum rats only. Testosterone levels declined significantly with age in all rats, but were significantly higher in restricted rats at all ages. These results indicate that mild dietary restriction extends life span without reducing circulating levels of thyroid stimulating hormone, thyroxine, triiodothyronine, or testosterone in mature Lobund-Wistar rats, and prevents the age-associated rise in serum prolactin. Life extension in germ-free rats is not related to differences in endocrine function.

Aging↗
PubMed1988

Field experience trials comparing narasin and monensin.

Narasin is effective against all species of chicken coccidia when tested in battery cage and floor pen studies. To confirm the efficacy of narasin under practical broiler production conditions, the drug was fed at concentrations of 60 ppm or 80 ppm to broiler chickens being raised by six different commercial broiler producers in five different geographic areas. Monensin was fed in each trial at a concentration of 100 ppm or 121 ppm as a reference control. The usual management practices of each of the integrated broiler companies were followed throughout the respective trials. Nine trials were conducted and approximately 100,000 broilers were tested for each treatment. No adverse reactions attributable to treatments were observed in any of the trials, and performance results obtained with narasin-medicated birds were generally comparable with those obtained with monensin-medicated birds in the same trial. These findings support the conclusion that narasin at final feed concentrations in the range of 60 to 80 ppm can be safely and effectively used as an anticoccidial agent in commercial broiler production facilities.

Animals↗
PubMed1988

B6 vitamer content of rat tissues measured by isotope tracer and chromatographic methods.

Feeding [14C]pyridoxine to growing rats for 146 days produced uniform labelling of the total vitamin B6 pool, thus permitting the radioactivity to be used as an absolute standard for evaluating the accuracy of vitamin B6 analyses. The results demonstrated that trichloroacetic acid extraction followed by cation exchange chromatography accurately measures the B6 vitamers. It is essential to homogenize tissues in a protein-denaturing agent in order to avoid shifts in the vitamer content, particularly in liver. In rats approximately 80% of the radioactivity was found in carcass and 8-9% each in liver and skin. Pyridoxamine phosphate equalled or exceeded the concentration of pyridoxal phosphate in heart, brain and kidney. The total vitamin B6 pool in weanling and adult rats averaged about 16 nmol/g body wt. Meta-phosphoric acid extraction followed by reverse phase chromatography gave good agreement with the cation exchange method in rat liver but with cat plasma yielded pyridoxal phosphate values below those of the cation exchange or enzymatic methods. The discrepancies encountered between different homogenization techniques and chromatographic methods emphasize the need for constant vigilance and continual verification of results by independent methods.

Animals↗
PubMed1987

Dihydrotestosterone does not induce prostate adenocarcinoma in L-W rats.

It has been postulated that dihydrotestosterone (DHT) is the active trophic androgen in initiating pathogenic changes in the prostate gland. Groups of prostate cancer-susceptible male L-W rats (age 3 months) were treated with subcutaneous depots of testosterone or of DHT. After 14 months, prostate adenocarcinomas had developed in 24% of the testosterone-treated rats but not in the DHT-treated rats. In the latter rats, the testes were significantly reduced in weight, there was no evidence of spermatogenesis, and serum testosterone levels were not detectable. It appears that DHT as administered to L-W rats had an antiandrogenic effect.

Adenocarcinoma↗
PubMed1987

Growth rate of male germfree Wistar rats fed ad libitum or restricted natural ingredient diet.

Germfree life and feed restriction initiated at an early age are known to extend life span. We have examined growth rate and life expectancy in germfree (GF) and conventional (CV) male Lobund Wistar rats, fullfed (F) or restricted (R) to 12 grams/day of natural ingredient diet L-485. GF-F and CV-F rats show comparable growth rates during the first 6 months of life. Thereafter, the GF-F rat falls behind, with its body weight stabilizing at 85% of the CV rat's weight at 2 years of age (510 g vs 435 g). In contrast, GF-R rats become slightly, but significantly, heavier than CV-R rats after an initial 6 months of comparable growth. At 2 years of age GF-R rats weigh 12% more than the CV-R rats (340 g vs 300 g). Physiological parameters were examined in each treatment group in animals that had to be sacrificed because of contamination. These gnotobiotic (GN) rats (see text) and their CV counterparts were grouped as adult (7 to 11 months) and old (18 to 28 months) rats. The most significant findings were: GN-F rats have smaller hearts than CV-F rats, both on an absolute and relative basis; restriction did not affect absolute testes size but elevated serum testosterone levels; serum T4 was reduced by restriction only in CV rats, and declined with age in all groups; and serum T3 was higher in adult GN-F and GN-R rats, but fell to CV levels in old age.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Abnormal vaginal bleeding in adolescents.

The evaluation and management of abnormal vaginal bleeding should be tailored to the individual case. Pediatricians caring for adolescents need to be skilled in the evaluation and management of this common adolescent problem. Physicians who do not feel comfortable with their skills in the performance of a pelvic exam should obtain consultation from an adolescent specialist or a gynecologist who has experience with adolescents.

Blood Coagulation Disorders↗
PubMed1983

Effect of pinealectomy on seasonal changes in antler growth and concentrations of testosterone and prolactin in white-tailed deer.

A 2-year study was conducted to determine under controlled conditions the role of the pineal gland in regulating the seasonal changes in antler growth and reproduction of male white-tailed deer. Blood samples were drawn from 6 pinealectomized (PX) and 18 control (C) deer at intervals of 2 weeks and analyzed for testosterone (T) and prolactin (Prl). Relative scrotal circumference and main beam antler length were recorded. Relative scrotal circumference was similar in PX and C groups, but the normal pattern was delayed 1 to 3 months in the PX deer relative to the C deer. The mean dates of beginning antler growth, velvet shedding, antler casting and pelage changes were significantly later in both years for PX deer than in C deer. Testosterone concentrations peaked 1 month later in the PX deer than in the C deer for both yearling and 2-year-old deer. Prl concentrations in C deer, but not in PX deer, were correlated highly with day length, and the PX deer were delayed relative to the C deer in showing the normal Prl pattern. Increasing levels of Prl in both groups coincided with beginning antler growth in both years. These results indicate that the pineal gland does not originate the seasonal cycles of male white-tailed deer but may synchronize cycles among individual deer, and regulate the circannual rhythm of Prl concentrations which may in turn influence other hormonal cycles.

Animals↗
PubMed1982

Effects of monensin fed to replacement dairy heifers during the growing and gestation period upon growth, reproduction, and subsequent lactation.

Sixty Holstein heifers initially weighing 196 kg were assigned by weight to treatments of 0, 200, and 600 mg of monensin. These treatments were fed daily until calving to determine effects of monensin on growth rate, feed consumption, feed efficiency, reproductive performance, and subsequent lactation. Throughout the feeding period the control (0 mg) heifers received sufficient feed to allow a calculated growth rate of .68 kg/day. Monensin treatment groups were fed the same amount of the identical ration over the 448-day experiment. Daily gain, feed intake, and feed efficiency for the 0, 200, and 600 mg treatments were .60, .69, .69 kg, 7.47, 7.46, 7.43 kg, and 12.41, 10.81, 10.81. Although days on trial to first estrus were not different among treatment groups, heifers fed monensin at 200 and 600 mg/day conceived 38 and 34 days sooner than 0 mg heifers. Percent conception, number of calves born, calf birth weight, and calving difficulty were not affected by treatment. Milk production was measured for 120 days subsequent to the experimental feeding of monensin. During this period heifers were fed a common ration ad libitum. Milk production of 17.1, 16.9, and 17.0 kg/day for 0, 200, and 600 mg was not affected by prior treatment.

Animals↗
PubMed1981

Photon time-of-flight-assisted positron emission tomography.

In positron emission tomography (PET), the annihilation radiation is usually detected as a coincidence occurrence that localizes the position of the annihilation event to a straight line joining the detectors. The measure of the difference between the time of flight (TOF) of the annihilation photons between their inception and their detection permits the localization of the position of the annihilation event along the coincidence line. The incorporation of TOF information into the PET reconstruction process improves the signal-to-noise ratio in the image obtained. The utilization of scintillation detectors utilizing cesium fluoride scintillators, fast photomultiplier tubes, and fast timing circuits allows sub-nanosecond coincidence timing resolution needed for the effective use of TOF in PET. Mathematical considerations and pilot experiments show that with state-of-the-art electronic components and through the application of proper reconstruction algorithms, the combination of TOF and PET positional data improves severalfold the signal-to-noise ratio with respect to conventional PET image reconstruction at the cost of increasing the amount of data to be processed. The construction of a TOF-assisted PET device is within the capability of state-of-the-art technology.

Electronics, Medical↗
PubMed1976

Scalp abscess: a complication of the spiral fetal electrode.

During the period from September, 1974, to January, 1975, we performed 276 deliveries, of which 54% were internally monitored with a spiral type of fetal electrode. Eight of the infants monitored (incidence, 5.4%) developed scalp abscesses. We had had no previous complications associated with the electrodes. An intensive investigation was conducted to detect the causative factor(s) of the fetal scalp infections. Case histories of the mothers and infants were scrutinized, instruments were examined, the environment and techniques were analyzed. A survey of maternal and infant complications during the period from September, 1973, to August, 1974, served as control. The findings indicated that a different type of coil electrode had been substituted for the brand we had used previously. The new coil electrode had a barb at the tip, presumably to prevent its falling out of the scalp. We discontinued the use of the coil which had become suspect and returned to the type we had used previously. We have not had another incidence of fetal scalp infection associated with intrapartum monitoring.

Abscess↗