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Biomedical subjects

R Webb

Publications and source records attributed to R Webb.

At least 199 records · Page 11Linked to original sources
PubMed1981

A chemical approach to solving bridging phenomena in steroid radioimmunoassays.

Steroid radioimmunoassays (RIA) employ antibodies raised against a carrier protein-steroid conjugate. Individual antibodies may recognize the steroid, the protein or the chemical bridge used to join them together. Use of the same bridge in the tracer results in higher affinity binding of the tracer than the native ligand which in turn results in a loss of sensitivity and precision. We have greatly reduced bridge-binding in a RIA for androstenedione. Conjugates and radioiodinated labels were prepared with either an ester or either chemical bridge. By using an antibody and the corresponding label with the heterologous bridge very sensitive assays were obtained.

Androstenedione↗
PubMed1981

Temporal relationships between peripheral plasma concentrations of oxytocin, progesterone and 13,14-dihydro-15-keto-prostaglandin F2 alpha during the oestrous cycle and early pregnancy in the ewe.

Peripheral plasma concentrations of oxytocin, 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM), progesterone and LH were determined at 3 hourly intervals during the oestrous cycle (n = 3) and in early pregnancy (n = 4) in sheep. The progesterone and LH concentrations showed that the cycling ewes were sampled during the periods of luteal regression (decreasing progesterone concentrations), the preovulatory gonadotrophin surge and the beginning of the next luteal phase (increasing progesterone concentrations). The pregnant ewes had basal LH concentrations and luteal phase concentrations of progesterone (greater than 1ng/ml after day 5 following mating) throughout the whole of the sampling period. Oxytocin concentrations in the non-pregnant ewes decreased around the time of luteal regression to reach low concentrations (mean concentrations of approximately 18pg/ml) during the preovulatory period and then increased after the preovulatory surge. PGFM concentrations exhibited a pulsatile pattern with increasing concentrations as progesterone levels fell. In the pregnant ewes oxytocin concentrations gradually fell until approximately 16 days post-mating (approximately 7-8pg/ml). The magnitude of the pulses in PGFM concentrations were also lower than in the cycling ewes. These results demonstrate that the increased concentrations of PGFM which are found during the period of luteal regression are not caused by increased peripheral concentrations of oxytocin.

Animals↗
PubMed1981

Management of the papillae during intrarenal surgery.

The intersegmental nature of renal incisions is axiomatic. Deviation from the intersegmental plane is hazardous. If divided along intra-arterial planes papillae appear to heal with little structural or functional impairment.

Adult↗
PubMed1981

Control of the preovulatory gonadotropin surge in the ewe.

The aims of this study were to determine the effect of ovariectomy on the release of LH and FSH during the preovulatory gonadotropin surge and to ascertain, by the use of sodium pentobarbitone (NaPb), if the secretion of these pituitary hormones requires continuous stimulation from the hypothalamus. Sheep were treated with NaPb for 2 h beginning 1) immediately before the gonadotropin surge, 2) during the ascending limb of the gonadotropin surge, and 3) during the descending limb of the gonadotropin surge. Ewes were ovariectomized (ovx) at each of the time periods listed above, and intact ewes included were at times 2 and 3. A group of intact ewes was given 100 microgram gonadotropin-releasing hormone (GnRH) in addition to NaPb at time 2, NaPb given during the ascending limb of the gonadotropin surge caused a transient fall in peripheral LH and FSH; however, the release of gonadotropins was reinitiated and the surge continued when the ewes recovered from anesthesia. Treatment with NaPb after the apex of the gonadotropin surge did not affect circulating levels of LH and FSH. Ewes given NaPb and ovx before the initiation of the gonadotropin surge released significantly less LH and FSH during the surge than the other treatment groups. The total amounts of LH and FSH released in intact and ovx ewes treated with NaPb after the surge was initiated were not different than those levels in the saline-treated controls. Intact ewes treated with 100 micrograms GnRH also released an amount of LH similar to that in the control group. We conclude that gonadotropin release from the pituitary gland requires the continual presence of GnRH during the ascending limb of the preovulatory gonadotropin surge, and that once the surge has been triggered, the ovaries do not appear to be required for further hypothalamic stimulation.

Animals↗
PubMed1981

Follicular steroidogenesis and gonadotropin binding to ovine follicles during the estrous cycle.

The interrelationships among [125I]hCG binding in thecal and granulosa cells, antral fluid steroid concentrations, follicular size, and ovarian steroid secretion were examined at three different stages of the estrous cycle. Group 1 ewes were ovariectomized during the luteal phase of the estrous cycle, and the other groups were ovariectomized before (group 2), or after (group 3) the peak of the preovulatory LH surge. Times of luteolysis and the LH surge were assessed by measurement of peripheral concentrations of progesterone and LH. Three patterns of [125I]hCG binding to follicles were noted: 1) binding to both thecal and granulosa cells (activated follicle), 2) binding to the thecal cell layer only, and 3) no observed binding. In general, there was one active follicle per ewe, or one per ovary, and the number of active follicles was not different from the number of corpora lutea in each of the three groups. The active follicles were significantly larger than the other two classes of follicles. Antral fluid estradiol concentrations were significantly greater in the active follicles and were higher in group 2 ewes than in the other two groups. In group 2, antral fluid testosterone concentrations were significantly higher in follicles with LH receptors in the thecal cell layer only. Ovarian secretion of testosterone and estradiol increased during the early follicular phase (group 2), with the major secretion coming from the ovary containing the active follicle. Ovarian progesterone secretion was high in ovaries containing active corpora lutea which prevented the assessment of ovarian follicular secretion of progesterone. The follicle with LH receptors in thecal and granulosa cells was responsible for the increased estradiol secretion observed during the preovulatory period and is presumed to be the ovulatory follicle.

Animals↗
PubMed1981

Patterns of plasma prolactin in post-partum suckled cows.

Blood samples taken on alternate days through indwelling jugular venous catheters from 12 suckled cows between days 14 and 48 post partum contained significantly less prolactin than samples collected on intermediate days by jugular venepuncture. Samples taken through the catheter every 2 h for 72 h periods revealed a repetitive daily biphasic pattern of prolactin secretion with low concentration at 09.00 and 19.00 h and high concentration at 13.00 and 23.00 h. In two groups of cows, one group calving at the beginning of March (increasing photoperiod) and the other calving during June (decreasing photoperiod), there was a significant negative correlation between stage of lactation and plasma prolactin concentrations in samples taken by venepuncture.

Animals↗
PubMed1980

Plasma progesterone and gonadotrophin concentrations and ovarian activity in post-partum dairy cows.

Plasma progesterone concentrations in jugular vein blood samples collected every other day after calving from 13 Friesian dairy cows indicated that ovarian cyclic activity was initiated by 16.6 +/- 1.1 (s.e.m.) days post partum, except for 1 cow which did not resume cyclic activity until Day 98 post partum. Rectal palpation of the ovaries indicated that a developing follicle was recognizable at a mean time of 15.7 +/- 2.0 days after calving. During the first oestrous cycle after parturition there was a significantly shorter period when plasma progesterone levels were elevated than during the next 2 cycles. Concentrations of progesterone, LH, FSH and prolactin were determined for 4 cows, in blood samples taken every 6 h from 2 to 36 days post partum. Tonic LH release was lower during the first 10 days than subsequently, but the lack of change in pattern for FSH suggests dissimilar control mechanisms for these hormones during this time. Three cows showed evidence of a resumption of ovarian cyclicity during the sampling period: in 2 there was an initial LH surge of a magnitude which would normally give rise to ovulation, followed 4 days later by an increase in plasma progesterone lasting only 5 and 9 days. This progesterone was considered to be of follicular origin. A second LH surge was followed by the presence of a corpus luteum.

Animals↗
PubMed1979

Management of the papillae during intrarenal surgery.

The papillae are involved in renal disease and, hence, are an inextricable consideration in intrarenal surgical procedures. Guide lines for their management are newly emergent and, consequently, tentative. If divided along intra-arterial planes they appear to heal with little functional impairment. Resections of papillae, which are limited to the intracaliceal portions, involve no medullary structures and heal without apparent dysfunction.

Animals↗
PubMed1978

Computed tomography in the diagnosis of diseases of the paranasal sinuses.

The authors investigated 31 patients suffering from benign and malignant lesions of the paranasal sinuses. Clinical, conventional radiological methods and computed tomography were used. In benign lesions CT added little significant information to that obtained by conventional radiological methods. In malignant lesions, however, CT provides additional valuable information. It gives a clear picture of the posterior, superior and orbital extent of paranasal tumours. It also shows the extent of the tumour into the infratemporal fossa.

Adult↗
PubMed1977

Response of cyclic and post-partum suckled cows to injections of synthetic LH-RH.

Doses of 125, 250 or 500 micrograms LH-RH were injected i.m. into suckled beef cows on approximately Day 11 of an oestrous cycle synchronized by prostaglandin treatment. There was a positive linear relationship between dose of LH-RH and the area under the measured LH peak. Administration of 500 micrograms LH-RH as a single injection to suckled cows 13-32 days post partum resulted in LH release but failed to induce normal ovarian activity. A small transient rise in plasma progesterone for 6--9 days occurred at the expected time after injection in 50% of animals. Administration of 500 micrograms LH-RH to suckled beef cows approximately 20--30 days post partum and a second injection approximately 10 days later at the time when the resulting transient rise in plasma progesterone had returned to basal values induced normal cyclic activity (as shown by progesterone concentrations and observed oestrus) at 35 days compared with 70 days for untreated controls. Pituitary responsiveness to LH-RH, as assessed by LH levels, was found to increase up to 20 days post partum.

Animals↗