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Biomedical subjects

R C Cochran

Publications and source records attributed to R C Cochran.

At least 73 records · Page 4Linked to original sources
PubMed1989

Serving capacity of crossbred yearling beef bulls. II. Summer grazing activity and body temperature patterns during average and heavy mating loads at pasture.

Ten low (LSC) and 10 high (HSC) serving capacity yearling bulls were exposed individually to 25 naturally cyclic (N) cows for 3 d (average mating load) and subsequently to 9 estrus-synchronized (S) cows for 1 d (heavy mating load) in a randomized complete block design consisting of 10, 4-d blocks. Bulls were fitted with vibracorders and temperature acquisition modules to record grazing activity and body temperature (BT), respectively. During the N cow treatment, LSC bulls had fewer (P less than .05) services per cow and a higher mount to service ratio than HSC bulls, and LSC bulls tended (P = .12) to graze less total time than HSC bulls (7.8 vs 9.0 h/d, respectively). However, both groups of bulls exhibited similar diurnal grazing patterns with two major daily grazing periods; the first (0400 to 1300) peaked early in the morning (0600) and the second (1700 to 2200) occurred in late afternoon and evening. During the S cow treatment, LSC and HSC bulls did not differ (P = .60) in grazing time or pattern, but similar mating activity was exhibited by both SC groups while exposed to S cows. Bulls grazed little during the hottest part of the day (1300 to 1700), and LSC and HSC bulls spent only 2.2 and 2.4 h, respectively, grazing during dark, cooler periods near midnight. Body temperature did not differ between SC groups and averaged 39.3 degrees C during N cow treatment and 39.4 degrees C during S cow treatment. Body temperature had a distinct, monophasic diurnal pattern in bulls exposed to an average mating load.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Serum hormone levels associated with spawning activity in the mummichog, Fundulus heteroclitus.

Daily collections of the mummichog, Fundulus heteroclitus, from field populations during the first 45 days of the breeding season revealed a semilunar cycle in the sperm index. Peaks in the sperm index were preceded by 6 days with peaks in the serum testosterone concentration. Bihourly sampling of field populations during a 72-hr period at the new moon showed both diel cycling and an upward trend in serum progesterone levels in female mummichogs. Male mummichogs had 12-hr cycles in serum 17 beta-hydroxy-4-androstene-3,11-dione levels, the peaks of which preceded high tide by 4 hr. The physiological significance of these cycles are discussed.

Androgens↗
PubMed1988

Comparisons of ruminal fermentation characteristics and microbial populations in bison and cattle.

Ruminal microbial populations, fermentation characteristics, digestibility, and liquid flow rates in two ruminally cannulated bison and two ruminally cannulated Hereford steers fed a prairie hay diet were compared. No significant differences in anaerobic bacterial counts, volatile fatty acid concentrations, or ruminal pHs were evident between bison and cattle. Also, no significant differences in neutral detergent fiber digestibility, indigestible fiber retention time, or intake were detected between bison and cattle, although cattle had higher levels (P less than 0.08) of ruminal dry matter and indigestible fiber than bison. Bison had a smaller (P = .02) ruminoreticular volume, faster liquid dilution rates, and faster liquid turnover times than cattle. The average ruminal ammonia nitrogen concentration was higher (P = 0.02) in bison (1.17 mg/dl) than in cattle (0.79 mg/dl). Total ciliate protozoal counts and cell volume were greater (P = 0.07) in bison (32.8 x 10(4)/g and 407.1 x 10(-4) ml/g, respectively) than in cattle (15.7 x 10(4)/g and 162.2 x 10(-4) ml/g, respectively). Bison harbored higher (P less than 0.02) numbers of Dasytricha spp., Eudiplodinium maggii, Eudiplodinium bursa, and Epidinium spp. than cattle and possessed a type B protozoan population. The cattle possessed a mixed type A-type B population that was characterized by Ophryoscolex spp. and Polyplastron spp. in association with low concentrations of Epidinium spp. and Eudiplodinium maggii.

Animal Feed↗
PubMed1988

Evaluation of internal markers isolated by alkaline hydrogen peroxide incubation and acid detergent lignin extraction.

Samples from two experiments were used to evaluate the potential of ADL and alkaline peroxide lignin (APL; isolated by sequential, alkaline hydrogen peroxide [AHP] incubation and ADL extraction) for predicting digestibility of warm-season grass diets. Experiment 1 evaluated the influence of level of sorghum grain supplementation on utilization of immature bluestem-range grasses, and Exp. 2 evaluated the influence of supplemental protein x energy level interaction on the utilization of dormant bluestem-range grasses. Internal markers isolated in feed, orts and feces were 1) ADL and 2) APL with AHP incubation either before (APL-PRE) or after (APL-POST) the acid detergent extraction step in the ADL procedure. Organic matter digestibility (OMD) was calculated from the ratio of marker consumed to marker excreted for each internal marker and was compared with OMD from total collection. For Exp. 1 a treatment x marker interaction was observed (P less than .01). The APL-PRE procedure yielded OMD coefficients similar (P greater than .10) to total collection values within most treatments, but OMD coefficients from APL-POST and ADL differed (P less than .05) from total collection within all treatments except at the highest level of supplementation. For Exp. 2, predicted OMD values from ALP-PRE were similar (P greater than .10) to total collection values, whereas OMD predictions from APL-POST and ADL were different (P less than .01) from total collection. In conclusion, APL appears promising as an internal marker for bluestem-range grasses if AHP incubation is incorporated before the acid detergent extraction in the ADL procedure.

Animal Feed↗
PubMed1987

Serum androgens during the annual reproductive cycle of the male mummichog, Fundulus heteroclitus.

A technique for the simultaneous detection of serum concentrations of testosterone (T), 17 beta-hydroxy-4-androstene-3,11-dione (11-KT), and 11 beta, 17 beta-dihydroxy-4-androsten-3-one (11 beta-HT) was established using a combination of high performance liquid chromatography separation and radioimmunoassay. In the mummichog, Fundulus heteroclitus, serum concentrations of T, 11-KT, and 11 beta-HT varied from 11.3, 10.1, and 27.9 ng/ml, respectively, during the breeding season to 0.2, 0.3, and 0.9 ng/ml, respectively, during the nonbreeding season. The changes in serum androgen levels, determined weekly, did not coincide with changes in the gonosomatic index or measurement of sperm/gram testes. Increases in serum androgen levels did coincide with the rise in sperm index, but the decreases in serum concentrations of androgens preceded the fall in sperm index by more than a month. A model is proposed to explain the reproductive cycle of male mummichogs.

Androgens↗
PubMed1987

Influence of lasalocid level on forage intake, digestibility, ruminal fermentation, liquid flow and performance of beef cattle grazing winter range.

Three experiments were conducted to study the effects of lasalocid level on performance, intake, digestibility, ruminal fermentation and fluid flow of beef cattle grazing dormant, tallgrass prairie. In Exp. 1, 120 pregnant, mature beef cows of primarily Hereford breeding (avg wt = 471 kg) were randomly assigned to received 0, 100, 200 or 300 mg lasalocid X head-1 X d-1 in 1.82 kg supplement. Weight changes at 30, 60 or 90 d, condition score change and calf birth weight were not affected (P greater than .10) by lasalocid level. In Exp. 2, estimates of intake and digestibility were obtained with 40 pregnant, mature Hereford cows (avg wt = 474 kg) and 12 esophageal-cannulated, Hereford X Angus steers (avg wt = 225 kg), using Yb and indigestible acid detergent fiber as markers for fecal output and digestibility, respectively. Levels of lasalocid provided to cows and steers were similar, on a body weight (BW) basis, to those in Exp. 1 and corresponded to approximately 0, .22, .44 or .66 mg lasalocid/kg BW. Total diet and forage organic matter digestibility for beef cows decreased (P less than .01) at the .22 mg/kg BW level, but increased at the .44 and .66 mg/kg BW levels. Organic matter intake was not influenced (P greater than .10) by lasalocid addition. In Exp. 3, 16 ruminal-cannulated, Hereford X Angus steers (avg wt = 227 kg) were given the same lasalocid dosages per kg BW as in Exp. 2, and were used to study the effects of lasalocid on ruminal fermentation and fluid flow characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1985

Prefreezing and post-thaw semen characteristics of five ram breeds collected by electroejaculation.

Rams representing five breeds were electroejaculated twice weekly, during a three-week collection period. Ejaculates were evaluated for volume and concentration before freezing and for rate of motility and percentages of motile and abnormal cells both before and after freezing. Interactions between breed and collection period were evident (P<0.05) for semen volume and post-thaw values for rate of motility and percentage motile cells. Breeds differed (P<0.05) in these traits during some periods. In contrast, pre-freezing observations of rate of motility, percentage motile and abnormal cells and post-thaw percentage abnormal cells did not differ (P>0.15) among breeds. Sperm concentration per ejaculate tended to vary (P=0.11) among breeds. Semen characteristics frequently varied across collection periods. Rams within a breed differed (P<0.01) in all semen traits except post-thaw rate of motility and percentage motile cells. Semen was negatively affected by the freezing and thawing procedure. Ram within a breed and ejaculate within ram should be considered when selecting electroejaculated semen for freezing and subsequent use in artificial insemination.

Journal Article↗
PubMed1984

Chlordecone lacks estrogenic properties in the male rat.

The reproductive toxicity of chlordecone has been hypothesized to derive from estrogen mimicry. To test this hypothesis, the effects of estradiol-17 beta, testosterone, and chlordecone on the male reproductive tract of 60-day-old male rats were compared after 72 days of exposure. Estradiol-17 beta (25 micrograms/week) and testosterone (945 micrograms/week), administered by polydimethylsiloxane capsules implanted subdermally, caused significant reductions in spermatogenesis, sperm motility, testicular capacity for secreting testosterone, and the weights of testes and epididymides. Estradiol-17 beta also caused significant declines in serum testosterone concentrations, and the weight of the prostate and seminal vesicles. Chlordecone, administered either by polydimethylsiloxane capsule or by ip injection, had no effect on any of these parameters, except to reduce significantly seminal vesicle weight at the highest dose of injected chlordecone, 7.5 mg/week. Therefore, chlordecone does not mimic estrogen in its effects on the reproductive system of the male rat.

Animals↗
PubMed1984

Testicular androgen and estrogen secretion and benign prostatic hyperplasia in the beagle.

The natural history of benign prostatic hyperplasia (BPH) in the dog is characterized by a slow progression through two phases. The early phase of the disease process is characterized by glandular hyperplasia and occurs as early as 2.5 yr of age. The late phase of the disease is characterized by cystic hyperplasia and occurs after 4 yr. The results of the present study are the first to compare Leydig cell structure and steroidogenic function in dogs with BPH with those in age-matched controls. It was discovered that glandular BPH can occur in young dogs (2.5 yr) in which Leydig cell mass and ultrastructure and maximally stimulated androgen secretion are indistinguishable from those in age-matched controls. These results support the concept that the early phase of BPH (glandular hyperplasia) is not related temporally to some defect in the Leydig cell. In contrast, the late phase of BPH (cystic hyperplasia) in beagles 6 yr of age is associated with diminished smooth endoplasmic reticulum in the Leydig cell and with diminished production of androgens by perfused testes in vitro. During the course of these studies, we discovered that the testes of young beagles with BPH, but not age-matched controls or old beagles with BPH, secrete an unidentified molecule (putative estrogen). This molecule was characterized partially in that it is extractable from testicular venous effluent with diethyl ether, elutes in a discrete fraction in several different high performance liquid chromatographic systems, reacts with an antibody that recognizes 17 beta-estradiol, estrone, and estriol, and competes with 17 beta-[3H]estradiol for the rat uterine estrogen receptor. Based on the elution volume from high performance liquid chromatography, the unknown molecule (putative estrogen) is not estriol, estradiol, or estrone.

Androgens↗
PubMed1983

Subtotal colectomy for obstructing carcinoma of the left colon.

This retrospective review of seven patients with completely obstructing cancers of the left half of the colon, in addition to other reports in the literature, suggests that subtotal colectomy with primary ileal proctostomy may be the treatment of choice for those lesions that are technically resectable and located high enough to permit an intraperitoneal ileal proctostomy. The morbidity and mortality is less than that seen with the staged approach and the length of hospitalization is shorter. By eliminating a second or third hospitalization and a temporary colostomy, palliation is better in those patients who ultimately die from recurrent cancer. Furthermore, those patients resected for cure may have increased rates of long-term survival.

Aged↗
PubMed1983

Testis function in rhesus monkeys treated with a contraceptive steroid formulation.

Rhesus monkeys (Macaca mulatta) were treated with testosterone (100 micrograms/kg/day) plus estradiol (0.5 micrograms/kg/day) via subcutaneous polydimethylsiloxane (PDS;Silastic) implants for thirteen months. This steroid regimen inhibited LH but not FSH secretion by the anterior pituitary, inhibited testicular testosterone and estradiol production and drastically reduced the numbers of vigorously motile spermatozoa in the ejacula. Importantly, these effects on testis function were achieved at dosages of testosterone and estradiol which approximate the amount of these two steroids produced daily in normal rhesus males.

Animals↗
PubMed1983

Somatic tissue responses of male rhesus monkeys treated with a contraceptive steroid formulation.

Rhesus monkeys (Macaca mulatta) were treated with testosterone (100 micrograms/kg/day) plus estradiol (0.5 micrograms/kg/day) via subcutaneous polydimethylsiloxane (PDS; Silastic) implants for thirteen months. This steroid regimen inhibited dramatically spermatogenesis. Gross and histopathological examination of the musculoskeletal, circulatory, endocrine (excluding the testis), central nervous, gastrointestinal and respiratory systems failed to uncover any untoward effects of the long-term exposure due to the contraceptive formulation. Similarly, no remarkable effects were observed in the ionic, chemical and formed elements of blood or secondary sex structures. Failure to detect secondary complications attributed to the steroid treatment offers further justification for evaluating a contraceptive strategy based on administering naturally occurring steroids at sustained rates approximating those at which they are produced endogenously in the human male.

Animals↗
PubMed1983

Spontaneous benign prostatic hyperplasia in the beagle. Age-associated changes in serum hormone levels, and the morphology and secretory function of the canine prostate.

This paper is a cross-sectional study of spontaneous benign prostatic hyperplasia (BPH) in a single canine species. The effects of aging and hormonal changes on the growth, histology, and glandular secretory function of the canine prostate were studied in 42 male beagles ranging in age from 8 mo to 9 yr. The beagle prostate enlarges for at least 6 yr, whether normal or hyperplastic. In contrast, prostatic secretory function, determined by ejaculate volume and total ejaculate protein, declines markedly after 4 yr of age. These reciprocal growth and functional changes in the prostate are closely associated with a progressive increase in the incidence of BPH, which is already apparent in some dogs by age two. With age there is a modest decrease in serum androgen levels with no apparent change in serum 17 beta-estradiol levels. This suggests that the growth and functional changes that are associated with the development of BPH and are initiated very early in life reflect an altered sensitivity of the prostate to serum androgens or a response to the relative decrease in the serum androgen to estrogen ratio.

Aging↗
PubMed1983

Effect of luteinizing hormone on Leydig cell structure and testosterone secretion.

Hypophysectomy or sc implantation of testosterone-estradiol 17 beta (T-E) filled polydimethylsiloxane capsules for 5 days caused a dramatic reduction in testosterone secretion when testes subsequently were perfused in vitro. The diminution in testosterone-secreting capacity of testes from T-E treated rats was coupled closely with reductions in the membrane surface areas of Leydig cell cytoplasmic organelles, particularly those of the smooth endoplasmic reticulum. Simultaneous treatment of T-E implanted rats with LH (12 micrograms/day), but not with FSH, PRL, TSH, or GH, maintained both the Leydig-cell cytoplasmic membranes and the capacity of testes to secrete testosterone in vitro. Testosterone secretion by testes from hypophysectomized rats treated simultaneously with T-E plus LH was identical to that in control rats. Therefore, T-E did not inhibit directly the Leydig cell steroidogenic apparatus. Taken together these results suggest that one of the trophic effects of LH in the Leydig cell is to maintained the integrity of smooth endoplasmic reticulum and enzymes responsible for the conversion of pregnenolone to testosterone.

Animals↗
PubMed1982

Cholecystectomy with and without drainage. A randomized, prospective study of 300 patients.

A randomized, prospective study of 300 cholecystectomies was undertaken to evaluate the merits of drainage through a standard Penrose or Chaffin-Pratt sump tube matched against no drainage at all. There was no difference in mortality or length of hospital stay. There was, however, a significantly higher incidence of postoperative pyrexia due to atelectasis and wound infection in the drainage groups. Neither drain fulfilled its objective of providing outflow for a subhepatic collection, thus avoiding bile peritonitis. This study suggests that surgical drainage after every uncomplicated cholecystectomy is unnecessary and unwise.

Adolescent↗
PubMed1982

Testicular atrophy associated with agenesis of the epididymis in the ACI rat.

The male ACI rat has a congenital Wolffian duct defect manifested by unilateral agenesis of the kidney, ureter, seminal vesicle, ductus deferens, and most of the epididymis. In the adult the testis on the affected side is markedly smaller than the contralateral testis and spermatogenesis is absent. In addition, in vitro perfusion of the affected testis revealed significantly less testosterone secretion than did the contralateral testis. Moreover, electron microscopy revealed that the smooth endoplasmic reticulum of the Leydig cell was significantly decreased. Thus, the affected testes clearly showed deranged spermatogenesis and Leydig cell structure and function. The ACI rat model may provide insight into the potential effects of congenital epididymal abnormalities on the testis of the human.

Animals↗