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Biomedical subjects

C J Wilcox

Publications and source records attributed to C J Wilcox.

At least 127 records · Page 7Linked to original sources
PubMed1978

Induction of lactation: lactational, physiological, and hormonal responses in the bovine.

Milk yields, physiological responses, and concentrations of plasma hormones were evaluated in 24 attempts to induce lactation in nonlactating dairy cows. Subcutaneous injections of estradiol-17beta and progesterone (.10 and .25 mg/kg body weight per day) for 7 consecutive days were used. Dexamethasone injections (.028 mg/kg body weight per day) on days 18 to 20 were given during 12 attempts at induction. Milking was initiated on day 21. All cows showed proestrus activity within 2 days after the first steroid injection; this subsided, then reappeared in many animals between days 16 to 20. In 14 of 24 attempts mean daily milk production was greater than 5 kg. Actual or projected 305-day lactation milk yields were between 1859 and 5354 kg. However, milk yields of seven induced cows averaged only 73% (32% to 136% range) of their previous natural lactations. Dexamethasone injections increased the number of cows that produced more than 5 kg/day; however, milk yields were not improved. Concentrations of estradiol, estrone, and progesterone in plasma were unaffected by dexamethasone, but concentrations of glucocorticoids in plasma were depressed on days 19 to 22. Concentrations of prolactin (peak and mean) in plasma for six cows each that produced greater or less than 5 kg/day did not differ. However, concentrations of prolactin increased in the week following steroid injections (days 8 to 15) only in those cows that produced greater than 5 kg/day but were elevated in all cows during the 3rd wk.

Animals↗
PubMed1978

Adrenal responsiveness in pre- and postpartum dairy cows.

Adrenal responsiveness was evaluated by injecting 10 multiparous dairy cows with 200 IU adrenocorticotropin between -13 and -2 days prepartum (I) and postpartum between 24 and 40 h (II) and 21 and 24 days (III). Concentrations of glucocorticoids following injection were influenced by day of injection, temperature, and minimum percent relative humidity but not by breed, breed X injection day interaction, or age of cow. Likewise differences in regressions for adrenal response and mean response (ng/ml) for the three injections were nil. Mean concentrations at peak (45, 60, and 120 min postinjection samples) adjusted for preinjection concentrations also did not differ for the three periods of injection. Mean concentrations of glucocorticoids in plasma for daily samples between -13 and -2 days prepartum were 5.3 +/- .4 (n = 61), reached a peak of 14.8 +/- .3 ng/ml the day of calving, and remained high for 2 days postpartum. Estradiol increased through prepartum sampling from 23.3 to 339.6 +/- 94.1 pg/ml the day of calving, then declined abruptly. Progestins began to decline about -5 days prepartum from mean concentration of 4.09 +/- .62 (n = 25) and attained low concentrations (.30 +/- .06 ng/ml) 2 days postpartum. Although there was a surge of glucocorticoids at parturition, this was not associated with a modification in adrenal responsiveness or with prepartum concentrations of other steroid hormones of plasma. Adrenal potential in prepartum and postpartum dairy cows appears well maintained.

Adrenal Glands↗
PubMed1977

Cold pressor test in women: effect on vaginal blood flow.

Vaginal blood flow changes in women were evaluated qualitatively by heat-flow discs mounted on cooled vaginal probe. Statistically significant increases in vaginal blood flow, systolic blood pressure, and pulse rate were found in seven normal subjects during a 4 minute immersion of one hand in ice water.

Adult↗
PubMed1977

A study of prostaglandin F2alpha as the luteolysin in swine: II Characterization and comparison of prostaglandin F, estrogens and progestin concentrations in utero-ovarian vein plasma of nonpregnant and pregnant gilts.

Polyvinyl catheters were inserted into the right and left utero-ovarian veins (UOV) and saphenous vein (SV) and artery (SA) of six non-pregnant (O) and five pregnant (P) gilts on day 11 after onset estrus. Beginning on day 12, UOV blood samples were collected at 15-min intervals from 0800 to 1100 hr and 2000 to 2300 hr, and single samples were taken at 1200 and 2400 hrs. Peripheral blood (SA or SV) was sampled at 0800, 1200, 2000 and 2400 hr until gilts returned to estrus (X = 20.6 days) or day 24 of pregnancy. UOV plasma PGF concentrations (ng/ml; n = 1929) were measured by RIA. Status (P vs O) by day interactions were detected (P less than .01) but variances among treatments were heterogenous (P less than .01). Curvilinear day trends were detected for PGF in 0 gilts (P less than .01) but not P gilts. PGF peaks, defined as concentrations greater than two SD above the mean concentration for each gilt, occurred with greater frequency (chi2 = 16.4; P less than .01) in O than P gilts; and mean peak levels (X +/- SE) were 5.04 +/- .27 and 3.84 +/- .13 ng/ml, respectively. Progesterone concentrations were maintained in pregnant pigs and were indicative of luteal maintenance. Systematic differences in day trends of utero-ovarian venous plasma estradiol were detected between O and P pigs. These differences may be of paramount physiological importance and are discussed.

Animals↗
PubMed1977

A study of prostaglandin F2alpha as the luteolysin in swine: III effects of estradiol valerate on prostaglandin F, progestins, estrone and estradiol concentrations in the utero-ovarian vein of nonpregnant gilts.

Polyvinyl catheters were placed into the right and left utero-ovarian veins and saphenous vein and artery of three control (C) and four estradiol valerate (EV) treated gilts on Day 9 after onset of estrus. The EV treated gilts received 5mg EV/day on Days 11 through 15 after onset of estrus. On Days 12 through 17 utero-ovarian vein blood samples were collected at 15 min intervals from 0700 to 1000 hr and 1900 to 2200 hr and single samples were taken at 1100 and 2300 hr. Peripheral blood samples (saphenous vein or artery) were taken at 0700, 1100, 1900 and 2300 hr from Day 12 until the control gilts returned to estrus or until Day 25 for EV treated gilts and used to measure plasma steroid hormone concentrations. Utero-ovarian vein prostaglandin F (gf) concentrations (ng/ml, n-1,177) were measured by RIA. Status (control vs EV treated gilts) by day interactions were detected (P=.10). Curvilinear day trends were detected for plasma PGF concentrations in control (P less than .01) but not EV treated gilts. PGF concentrations (X +/- S.D.) for control and EV treated gilts were 1.20 +/- 2.08 and .26 +/- .84 ng/ml, respectively. PGF peaks (concentrations greater than X + 2 S.D.) occurred with greater frequency in control gilts (X2 =4.87; P less than .05). The interestrus interval (X +/- S.E.) for control and treated gilts was 19.0 +/- .6 and 146.5 +/- 74.8 days, respectively. Data indicate tht t estradiol valerate may exert its luteotrophic effect by preventing PGF release from the uterus.

Animals↗
PubMed1976

Detection and characterization of differences in plasma corticoid response to treatments.

Ten experiments involving 3013 observations and 103 animals were studied to characterize variation associated with bovine plasma corticoid concentrations (ng/ml). Total corticoids, corticosterone, or cortisol were measured by competitve protein binding assay. Animals were noncystic or cystic, and measurements were made to establish basal concentrations or to estimate response to stimulation by adrenocorticotrophic hormone injection. Data were analyzed by least squares with the nested model: treatment regimen, animal in treatment, sample in animal in treatment, and sampling time to the highest order of regression (up to seventh) which was statistically significant (P less than .05). Estimates of error variances ranged from .31 for basal cortisol in cystic animals to 233.27 for total corticoids in noncystic, stimulated animals. Coefficients of variation among experiments ranged from 33 to 87% with mean 61%. In most analyses, estimates of experimental error were large indicating need for careful attention to experimental design to insure efficient least-cost experimentation. Use of the power function for nested analysis of variance to accomplish this is demonstrated.

Adrenal Cortex Hormones↗
PubMed1976

Effect of a synthetic corticoid on milk yield and composition and on blood metabolites and hormones in dairy cows.

Twenty-five dairy cows were assigned randomly by breed to flumethasone treatment (10 mug/day, 13 cows) or placebo control (12 cows) from 4 to 44 wk of lactation. Lactation means and trends with stage of lactation were treatment responses. Mean milk yields of cows supplemented with flumethasone were not significantly different from controls. Mean metabolite (glucose, nonesterified fatty acids, and total esterified fatty acids) and hormone concentrations (corticoids, insulin, and prolactin) of blood plasma and their trends throughout lactation were unaffected by supplementation. Data were pooled to determine effects of stage of lactation, temperature, pregnancy, and month on these variables. Changes during lactation were systematic for feed intake, body weight, milk yield, milk components except somatic cells, blood metabolites, and prolactin. At environmental temperatures above 18 C, effects were consistently negative for milk yield and composition, but only above 26 C for feed intake. Prolactin of plasma increased with increasing temperature to 18.2 C and then decreased. No other plasma metabolite or hormone was affected by days pregnant, age, or temperature. Months affected feed intake, milk yield, milk fat percentages, all blood metabolites, and prolactin. Prolactin concentrations increased as daylight hours increased. Our inability to augment established lactation by feeding a supplement of synthetic glucocorticoid to lactating cows is consistent with the view that a lack of avialable corticoids does not limit persistency of lactation in the cow.

Animals↗
PubMed1976

Plasma progestins, estradiol, and luteinizing hormone following prostaglandin F2 alpha injection.

Dairy animals, ranging from days 8 to 13 of the estrous cycle, were fitted with indwelling jugular catheters 1 day prior to either intramuscular injection of prostaglandin F2alpha free acid (30 mg, n=4) or intrauterine deposition of prostaglandin F2alpha free acid (10 mg, n = 3). Blood samples were collected at 6, 4, 2, and 0 h prior to administration of prostaglandin F2alpha and at 1, 3, and every 2 h thereafter until ovulation. Progestins, estradiol, and luteinizing hormone in plasma were measured by radioimmunoassay. Hormonal changes and interrelationships within animals were evaluated by least squares analyses. Decreases in progestins of plasma within 24 h indicated prostaglandin F2alpha induced luteolysis in six of the seven animals. Estradiol increased linearly from time of injection to 52 h postinjection. Intervals from administration of prostaglandin to onset of estrus, peak of luteinizing hormone, and ovulation were 74.9 +/- 21, 78.8 +/- 21, and 99.5 +/- 19 h.

Animals↗
PubMed1976

Factors that influence milk cholesterol and lipid phosphorus: content and distribution.

Average cholesterol content of 356 raw milk samples was 152.2 mug/ml and upon centrifugation (3000 X g for 8 min), 16.9% was distributed in the skim milk phase. Lipid phosphorus averaged 19.0 mug/ml and was partitioned 50:50 between cream and skim milk phases. Weight ratios of cholesterol to lipid phosphorus for milk and skim milk were 8.30:1 and 2.94:1. When variation due to milk yield, fat percent, and somatic cell numbers (deoxyribonucleic acid percent reflectance) was accounted for by least squares, cholesterol content and distribution did not differ among breeds (Holstein, Jersey, and Guernsey). Breed differences in lipid phosphorus content of whole milk could not be detected. However, Holsteins had a significantly lower content of lipid phosphorus and a higher weight ratio for skim milk. Milk yield, fat content, and somatic cells affected responses of cholesterol and lipid phosphorus. This supports a multiple origin concept for membrane material in skim milk.

Animals↗
PubMed1976

Sensitive colorimetric determination of cholesterol in dairy products.

Cholesterol can be determined colorimetrically in dairy products at levels of larger than or equal to 10 mug (coefficient of variation = 5.3%) with an o-phthalaldehyde reagent when non-cholesterol lipids are eliminated prior to color development. Absorbance for 2 mg tripalmitin was found to be equivalent to about 20 mug cholesterol. Saponification followed by hexane extraction removed interfering lipids. Using the described procedure, 238 individual raw milk samples were found to contain 144.4+/-37.9 mug cholesterol/ml, while their skim milk portions had 26.5+/-6.4 mug cholesterol/ml (mean +/- standard deviation). The o-phthalaldehyde cholesterol estimates agreed with those obtained by a gas-liquid chromatographic procedure when cheese and ice cream were analyzed by the colorimetric procedure with and without prior fat extraction.

Animals↗
PubMed1975

The circulating plasma volume of the foetal lamb as an index of its weight and rate of weight gain (g/day) in the last third of gestation.

In a series of foetal lambs weighing between 1,100 and 5,228 g, the circulating plasma volume was estimated by the dye dilution method, using Evans Blue, to test the possibility that the plasma volume could be used as an index of foetal weight in chronic studies. The data, analysed by the method of least squares regression, indicate that plasma volume and foetal weight are closely correlated (R-2 equals 0.922) and linearly so in the range of data studied. There was no evidence that the relation differed for singlets and twins. A single equation, Y equals 71.8 plus 10.11 X--where Y is the estimated weight and X the plasma volume, can be used to predict the weight from plasma volume in both. Some results of the application of the method in chronic studies are presented.

Animals↗
PubMed1975

Portable device for vaginal thermal conductance studies.

Design and development of a portable and self-contained vaginal probe, consisting of an acetone-filled silver cylinder attached to a pressure gauge, is described. Qualitative changes in vaginal thermal conductance were inferred from rates of thermal expansion of precooled acetone measured as a pressure rise. Administration of 10 mg estradiol-17 beta i.v. to ovariectomized heifers resulted in significant increases in rate of thermal expansion.

Acetone↗
PubMed1975

Environmental and managemental factors affecting conception rate in a subtropical climate.

Data representing 5,062 services during 1960 to 1971 in the Florida Agricultural Experiment Station dairy herd were analyzed by least squares to delineate factors affecting conception rates. Overall conception rate was 37.9%. From a set of 21 climatological measurements, the five selected as most important ranked (1) maximum temperature day after insemination, (2) rainfall day of insemination, (3) minimum temperature day of insemination, (4) solar radiation day of insemination, and (5) minimum temperature day after insemination. Warm months were more closely associated with lower conception rates than were cool months (33.7 compared to 40.1%); month effects appeared to be accounted for by the climatological measurements. Conception rates declined with age: heifers, 47.6%; young cows, 42.7%; older cows, 31.9%. No decline with advancing service number (1 to 5) occurred. Service sire and inseminator effects were detected as expected. Although breeds differed (Aryshires, 33.8; Brown Swiss, 34.6; and Guernseys, 37.0; Holsteins, 35.5; and Jerseys, 48.4%), there was no evidence of breed (Jerseys and Holsteins) by month or breed by season interactions nor was it possible to detect age by season interactions.

Animals↗
PubMed1975

Transitory changes in plasma progestins, estradiol, and luteinizing hormone approaching ovulation in the bovine.

Progestins, estradiol, and luteinizing hormone were measured by radioimmunoassay in bovine plasma samples collected from indwelling jugular catheters daily on days minus 6 to minus 4, every 6 h on days minus 3 and minus 2, and every 2 h from day minus 1 to ovulation. Least squares analyses characterized time trends within animals and interrelationships between these hormones. Plasma progestins decreased from 5.7 ng/ml at day minus 6 to .07 ng at the peak of luteinizing hormone. No preovulatory peripheral increase in plasma progestins was detected. Estradiol increased from 2 pg/ml at day minus 4 to 6 pg at minus 12 h and then increased abruptly to 7.4 pg at the peak of luteinizing hormone. This matter increase in estradiol was synchronous with the acute preovulatory surge of luteinizing hormone. Association was positive between estradiol and luteinizing hormone, but negative between progestins and estradiol. Estradiol decreased 50% by 5 h following the peak of luteinizing hormone with a return to base (2 pg) at 14 h. An increase of .1 ng luteinizing hormone/ml plasma per day was linear from day minus 6 to 8 h prior to the luteinizing hormone peak. Luteinizing hormone increased to a peak of 13.5 ng/ml and remained elevated for 10.5 h. These results are consistent with the hypothesis that an increase at proestrus in estradiol rather than progestins triggers the preovulatory surge of luteinizing hormone in the bovine.

Animals↗
PubMed1975

Adrenal responsiveness in lactating holstein cows.

Ten Holstein cows, in second to fifth lactation, received 200 IU adrenocorticotrophin at approximately 4, 8, 16, 24, 32, and 40 wk of lactation. Blood samples were collected from indwelling jugular catheters at -60 and 0 min pre-injection and at 2, 6, 10, 15, 20, 30, 45, 60, 120, 180, 240, 360, 540, and 720 min postinjection. Post-injection concentrations of glucocorticoids were influenced by milk yield, stage of lactation, age, and mean environmental temperature but not by pre-injection concentration of glucocorticoids or days pregnant. As milk yield, cow age, and daily temperature (range 6.4 to 26.9 C) increased, glucocorticoid response decreased whereas it increased with advancing stage of lactation. Curves of adrenal response for the six injection times during lactation were not parallel, and average response adjusted for significant independent variables increased roughly in linear fashion from 15 to 53 ng/ml between 4 and 40 wk of lactation. Adrenal responsiveness was less in cows injected on days when temperatures were above 21.1 C than in those injected below this temperature. There was no evidence that adrenal function or milk production was altered in high producing cows at higher environmental temperatures differently from in low producing cows. The change in adrenal function during advancing lactation was not associated with pre-treatment peripheral plasma glucocorticoid concentrations which did not change. There appears to be a well mainained adrenal potential and sustained adrenocortical activity throughout lactation.

Adrenal Glands↗
PubMed1975

Bovine vaginal circulation: changes during estrous cycle.

Vaginal thermal conductance was measured in 12 heifers and 7 cows with a gradient layer heat flow probe. Values rose for 4 to 5 days prior to day of behavioral estrus (day 0), with a peak on days --2 and --1, and then declined from day 0 to +5. Curves for heifers were higher than those for cows although there was no evidence that they were not parallel. Changes during the cycle appear to result from estrogen-induced alterations in blood flow rate in vaginal tissues.

Age Factors↗
PubMed1975

Characteristics of White Leghorn chickens selected for heat tolerance.

A series of studies was conducted to identify and delineate factors associated with responses of chickens to high ambient temperatures. Two populations of birds were used which had been selected divergently for tolerance to stress at 40.6 degrees C. and 75% R.H. and at 5 weeks of age. After four generations of selection for survival time the lines had separated by 28 minutes: 58 vs. 86 minutes for the low and high, respectively. Egg production, hatchability, Haugh units and specific gravity did not differ between lines. Egg weight was greater in the low line. The body temperature of chicks at 30 minutes of heat stress was correlated (r = -0.454; P less than 0.05) to survival time. Body weight was correlated (r = -0.325) with resistance to heat stress while loss of body weight during heat stress was correlated (r = +0.478) with resistance. There was no apparent difference between lines in respect to resistance of 16-day old embryos to heat stress.

Animals↗