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Biomedical subjects

R E Erb

Publications and source records attributed to R E Erb.

At least 37 records · Page 2Linked to original sources
PubMed1979

Variables associated with peripartum traits in dairy cows. IV. Seasonal relationships among temperature, photoperiod, and blood plasma prolactin.

Concentrations of prolactin in plasma were measured in 176 dairy cows and heifers from 13 days before calving to 2.5 days after calving over 21 mo. Prolactin averaged 35.1, 115.0, and 34.4 ng/ml prepartum (days -13 to -2), peripartum (days -1.0 to +.5), and postpartum (days +1.5 and +2.5). Season of the year affected prolactin in all periods. The linear covariate of daily photoperiod (hours of daylight per 24 h) accounted for as much variation in prolactin prepartum and postpartum as did linear covariates of both photoperiod and average daily temperature. However, it was possible to account for additional seasonal variation in prolactin peripartum by addition of the temperature covariate to the photoperiod covariate. Although photoperiod was related either directly or indirectly more than temperature to factors affecting prolactin seasonally, these statistical inferences cannot prove that prolactin is more dependent on photoperiod than on temperature because the two metereorological measures were correlated (r = .84). When the data were grouped for correlation analysis by months, correlations between temperature and prolactin among prepartum samples collected in the spring and in the fall were positive, small but significant.

Animals↗
PubMed1979

Effect of sexual experience, location, malnutrition, and repeated sampling on concentrations of testosterone in blood plasma of Gallus domesticus roosters.

Five studies were conducted with mature White Leghorn roosters to study variables associated with concentrations of testosterone in blood sampled from a wing vein. Testosterone in blood plasma was unchanged 15, 30, or 45 min after collection of semen artificially whether or not roosters were trained for collection of semen. Likewise, cohabitation with hens for 7 to 8 hr was without effect. However, trained roosters had higher (P less than .05) plasma testosterone concentrations after 7 to 8 hr in a new location than untrained roosters. Furthermore, both groups in the new location had higher testosterone concentrations than the controls not translocated. Plasma testosterone was decreased (P less than .01) about 50% within 2 weeks by feeding a diet low in crude protein (2%) which decreased feed intake 33% and caused weight loss; those fed 12% crude proteins were unchanged. Variations in concentrations of testosterone among sequential samples of blood collected at 45 min intervals for 3 hr indicated random pulsatile releases of testosterone as reported for mammals. Sequential sampling at 15 min intervals for 1 to 2 hr revealed that the testosterone increases (up to 10 ng/ml) lasted for about 1 hr and that the returns to basal concentrations required about 1 to 1.5 hr. The interval between pulsatile releases may be as long as 3 hr in some roosters. These results indicate that roosters have spontaneous and pulsatile releases of testosterone as expected, because roosters release luteinizing hormone episodically during both light and dark cycles of the day.

Animals↗
PubMed1977

Hormonal control of mammogenesis and onset of lactation in cows--a review.

Estrogen stimulates development of mammary ducts, and progesterone and estrogen stimulate proliferation of secretory tissues. In vivo, sequential addition of insulin (step 1), glucocorticoid (step 2), and prolcatin (step 3) leads to biosynthesis of casein and lactose. In cows, mammogenesis continues until termination of pregnancy and overlaps onset of lactation. Progesterone probably inhibits differentiation of secretory cells at step 2 or step 3. Sensitivity of individual cells to progestational inhibition may decrease variably which may be interdependent upon relative increases in estrogen, prolactin, corticoids, and growth hormone to cause asynchronies among them at calving. Since prolactin in plasma is not correlated with progesterone or the estrogens, factors other than feed-back effects of ovarian steroids may be responsible for its sustained increase periparturiently. Also, elevated prolactin periparturiently may be unrelated to subsequent rates of lactation because its "basal" concentrations may meet requirements when inhibiting effects of progesterone are removed. This concept is attractive because mammary cells neither are synchronized highly for biosynthesis nor secrete normal milk for several days after calving. At the latter time, concentrations in plasma are low for progesterone and estrogen, similar to 3 days before calving for glucocoiticoids and prolactin, and increasing for insulin. Evidence of lactation under unusual circumstances was discussed.

Animals↗
PubMed1977

Blood plasma and milk prolactin, and effects of sampling technique on composition of milk from suckled ewes.

Relations of techniques of sampling milk to its composition and concentrations of prolactin in blood plasma and milk from 59 suckled ewes were compared; Prolactin in milk and blood samples 0 to 2 h (hour 0) after removal of lambs did not differ significantly within autumn or summer, but both were doubled in summer. After the hour 0 sampling (summer only), one side of the udder of each of 12 ewes (group 1) was milked hourly for 4 h, and the opposite side was milked only at 0 and 4 h. Group 2 ewes were milked only at 0 and 4 h and blood was collected from both groups at 0 h and 4 h. Concentrations of prolactin were correlated in pairs of milk or blood samples from the same ewe and in plasma and milk of ewes in group 2 but not in group 1. Prolactin in milk increased between 0 h and 4 h in groups 1 and 2. Although milk lactose and prolactin concentrations differed among hourly samples, their average was similar to that of milk accumulated in the contralateral side for 4 h (group 1). Variations among ewes in progesterone of plasma indicated luteal activity during autumn and none during summer. Prolactin was unchanged in milk stored at -23 C for 30 days. The hour-0 milk-sampling technique was satisfactory to compare among individuals the concentrations of prolactin, total protein, or somatic cells in milk but not percentage fat and lactose, or milk yield due to variable time from last suckling to milking at hour 0.

Animals↗
PubMed1977

Assay of prolactin after freezing cow's milk.

Concentrations of prolactin were similar in aliquots of the same milk sample stored for 2 days at 4 C or --23 C but averaged lower if prepared for assay at 30 C than if prepared at 40 or 50 C. Average deviations in prolactin between duplicate measurements relative to respective treatment averages were lowest generally when technique of mixing included vortexing for 5 s immediately prior to pipetting volumes of milk for assay. The average deviation of differences in prolactin among duplicate measurements relative to average concentrations of prolactin were about the same for colostrum, milk, and blood plasma (11, 17, and 14%) stored frozen. Prolactin can be measured reliably in frozen cow's milk provided samples are warmed to 40 C to 50 C and mixed thoroughly when prepared for assay.

Animals↗
PubMed1977

Urinary creatinine as an index of urinary excretion of estrogen in cows prepartum and postpartum.

Urine was collected from 55 cows via indwelling urinary catheters for periods of 12 h on different days (28 days prepartum to 60 days postpartum). Excretion of urinary creatinine (mg/h per kg bodyweight) among Holsteins increased from .94 on day 28 prepartum to 1.14 on day .5 postpartum and then decreased to .82 on days 30 to 45 of lactation. Excretion of creatinine among 12-h collections of urine on different days did not differ for groups of cows within periods prepartum and postpartum, and coefficients of variation within cows were 12 to 13%. Ratio of urinary estradiol (-17 alpha) to urinary creatinine was correlated (.93) more highly with its excretion based on volume of urine excreted than was its urinary concentration (.79) within periods prepartum and postpartum. Ratios of urinary metabolites to urinary creatinine rather than their concentrations should be used to express rates of excretion in cows' urine when urine excreted per hour is unknown. Moreover, daily rates of excretion of estradiol in urine can be estimated [ng estradiol/day = A X ng/mg urinary creatinine x kg bodyweight x 24 h, where A is average excretion of urinary creatinine (mg/h per kg bodyweight)] for respective days prepartum and postpartum.

Animals↗