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Biomedical subjects

R F Seamark

Publications and source records attributed to R F Seamark.

At least 109 records · Page 6Linked to original sources
PubMed1983

Blood flow in the ovary and adjacent structures of the non-pregnant sheep.

Blood flow of the ovary, vascular pedicle and oviduct was measured in anaesthetized non-cycling and cycling ewes by timed collection of ovarian venous blood. The degree of arterio-venous shunting across the ovary and pedicle was estimated both in vivo and in vitro by perfusing the tissues with 15 +/- 5 micrometers radioactive microspheres. The mean ovarian blood flow in non-cycling animals was 1.9 ml/min, which was 51% of blood flow in the ovarian vein. In cycling animals ovarian blood flow at midcycle was 2.9 ml/min (66% of ovarian venous flow) in non-luteal ovaries and 4.3 ml/min (79% of venous flow) in luteal ovaries. The degree of arterio-venous shunting was low in all stages of the cycle (1.0-2.6% across ovary + pedicle). The degree of shunting was also found to be very small in vitro (0.007-1.38%) in both non-luteal and luteal ovaries. A considerable number of microspheres was entrapped in the vascular pedicle of the ovary indicating the presence of an extensive capillary bed. There was an inverse relationship between blood flow in the ovary and flow in the vascular pedicle. Alterations in distribution of blood flow between the ovary and adjacent structures supplied by the ovarian artery may be of functional significance in allowing rapid changes in ovarian blood flow. The results of the present study indicate that changes in ovarian blood flow during the oestrus cycle are not caused by an action on arterio-venous shunt vessels.

Animals↗
PubMed1983

Endocrine responses of goats after induction of superovulation with PMSG and FSH.

Goats in Group A were pretreated for 9 days with a synthetic progestagen, administered via intravaginal sponge, and 1000 i.u. PMSG s.c. on Day 12 of the oestrous cycle. Goats in Group B had the same PMSG treatment, but not the progestagen pretreatment. Group C goats received a s.c. twice daily injection of a porcine FSH preparation (8 mg on Day 12, 4 mg Day 13, 2 mg Day 14 and 1 mg Day 15). Oestrus was synchronized in all animals by 50 micrograms cloprostenol, 2 days after the start of gonadotrophin treatment. The vaginal progestagen sponges were removed from Group A at the same time. Mean ovulation rate was slightly higher in FSH-treated than in the PMSG-treated animals, whereas the incidence of large follicles that failed to ovulate was significantly elevated in PMSG-treated animals in Group B. More goats in Groups A and B than in Group C exhibited premature luteal failure. Progestagen pretreatment appeared to suppress both follicular and luteal activity, as indicated by numbers of large non-ovulating follicles and by the magnitude and duration of elevated plasma oestradiol levels following PMSG stimulation, and by decreased plasma progesterone levels before and after PMSG treatment. Oestrogenic response to FSH was considerably less than that to PMSG, as indicated both by a considerably shorter duration of elevation of circulating oestradiol levels during the peri-ovulatory period, and by lower maximal oestradiol levels. Differences in the ovarian responses to PMSG and FSH may be attributed primarily to differences in the biological half-life of each preparation.

Animals↗
PubMed1983

Superovulation treatments and embryo transfer in Angora goats.

A high incidence of early luteal regression after PMSG superovulation was associated with low recovery of embryos from reproductive tracts of Angora goats flushed later than Day 5 after onset of oestrus. Embryos were successfully recovered (mean 7.9/female) by flushing on Days 2-5. Mean ovulation rate after an FSH regimen (16.1 +/- 0.8) was significantly higher than that after a single injection of PMSG (10.8 +/- 1.2). Fertilization rate and survival of embryos following transfer to naturally synchronized recipient feral goats did not differ between the two gonadotrophin regimens: the mean number of kids born to 47 donors treated with FSH (7.5 +/- 0.6) was significantly greater than that to 28 donors treated with PMSG (4.8 +/- 0.6). Irrespective of hormonal treatment, the numbers of embryos recovered and of kids born were correlated with ovulation rate (r = 0.82, P less than 0.001 for both). Embryo survival was influenced by ovulation rate in recipients, with 52%, 63% and 75% of transferred embryos being carried to term by recipients with 1,2 and 3 CL, respectively (P less than 0.01). More embryos survived (65%) when 2 embryos were transferred to each recipient than when 1 (51%) or 3 (48%) were transferred. In recipients receiving 2 embryos, survival was significantly improved by transfer of both embryos to the same oviduct (70%) than when one was transferred to each oviduct (62%). The percentage survival of embryos was optimal when oestrus of recipients was synchronized within +/- 1 day of oestrus in donors.

Animals↗
PubMed1983

Use of imported cryopreserved hamster oocytes in the diagnosis of male infertility.

Frozen hamster oocytes have been imported from England to Australia to establish a test for human sperm fertilizing capacity based on penetration of zona-free hamster oocytes. When examined under similar conditions used for human in vitro fertilization (IVF), high and consistent rates of penetration by human spermatozoa were obtained which were similar whether the spermatozoa had been stored frozen or freshly collected. The availability of a validated test of the capacity of human spermatozoa to fuse with a receptive vitelline membrane should prove useful in combination with other clinical parameters in the evaluation of male infertility.

Animals↗
PubMed1982

Urinary 6-sulphatoxy melatonin excretion during the human menstural cycle.

The excretion of 6-sulphatoxy melatonin in urine has been shown to provide a reliable index of melatonin production in man. Daily measurements made in two healthy ovulating women showed that both the total amount excreted/day and the proportion excreted during the sleep period remained relatively constant for each subject throughout the menstrual cycle. These data do not support the view that there are changes in melatonin production which correlate with cyclical reproductive endocrine function in the human.

Adult↗
PubMed1982

Effects of melatonin implants on the circadian rhythm of plasma melatonin and prolactin in sheep.

The effects of implanting Silastic capsules containing melatonin on plasma melatonin and prolactin levels were investigated in pinealectomized (Px) and sham-operated sheep (SPx). Prior to implantation, melatonin was found in plasma samples obtained during the night period from SPx sheep (mean value 150 pg/ml), but could not be (less than 25 pg/ml) detected in plasma samples obtained during the day in SPx sheep or in any sample obtained during the night or day period in Px sheep. Following implantation, a constant basal plasma melatonin level of about 165 pg/ml was established in all sheep with a superimposed nighttime rise in SPx animals suggesting no diminution of endogenous melatonin production during the dark period. Following melatonin treatment, there was a marked depression in plasma prolactin levels in both SPx and Px sheep. These results are interpreted to indicate that 1) there is no negative feedback of melatonin upon its own synthesis and release, 2) that there is no circadian change in the rate of metabolism of melatonin and 3) that constant melatonin availability in sheep caused a depression in plasma prolactin levels similar to that found following exposure of animals to a short day.

Animals↗
PubMed1981

Neonatal body water turnover: a putative index of perinatal morbidity.

The water metabolism of 46 newborn babies was determined during a 10 day period by means of an isotope dilution technique, and correlations were sought with the clinical assessment of the babies by multiple obstetric and pediatric clinical criteria. The babies, 48 to 72 hours of age, were given a single oral dose (2 ml/kg) of deuterated water (D2O), a nonradioactive tracer, and the urinary excretion rate was followed by means of infrared spectrophotometry. After a period of equilibration of the D2O with body water (20 hours), the rate of D2O clearance was found to be a single exponential decay process, thus allowing the fraction of total body water lost each hour (the rate constant) to be calculated for each baby. The median values of the rate constants X 10(4)(h-1) for 14 growth-retarded babies ws 104 (98% confidence limits, 97.8 to 122) compared with 76.3 (67.0 to 80.2) for 16 normal mature babies and 82.1 (73.4 to 90.6) for 16 normal premature babies. These data indicate that, compared with normal mature or normal premature babies, growth-retarded infants have a significantly (P less than 0.05) faster turnover of water during the first 10 days of postnatal life. Since there was little overlap in results between the normally grown and the retarded infants, the measurement of water turnover may provide a useful index of perinatal morbidity.

Body Water↗
PubMed1981

Endocrine profiles and fertility status of human menstrual cycles of varying follicular phase length.

Assessment of the relationship between ovarian endocrine function and follicular phase length was made in 48 patients (51 cycles) with spontaneous ovular cycles of varying length. On the basis of follicular phase length when measured from the first day of menstruation to, and including, the day of the luteinizing hormone (LH) peak, cycles were grouped into short (less than 21 days), medium (12 to 16 days), and long (more than 6 days). Daily serum LH, androstenedione, 17 beta-estradiol, progesterone, and 17 alpha-hydroxyprogesterone concentrations were determined in the periovular period. The overall pattern of serum steroid concentrations in medium and long cycles was similar to that previously described for normal women. However, cycles with a short follicular phase had lower mean concentrations of androstenedione and estradiol. In order to assess the fertility potential of cycles with follicular phases of varying length, the prior 265 cycles of 92 consecutive patients who conceived with artificial insemination by donor (AID) were studied. In all cases, insemination occurred on day 0 and day + 1 with respect to the LH peak, and all cycles were assumed to have equal fertility potential. Statistical analysis revealed no significant difference in fertility potential among cycles with follicular phases of differing length.

Adult↗
PubMed1981

Urinary steroid metabolites and the overgrowth of lean and fat tissues in obese girls.

Studies were made of steroid metabolites excreted in the urine of 17 obese girls 11.4 to 16.8 yr and 17 normal girls 11 to 17 yr. Creatinine excretion (muscle mass), total body water (or deuterium space), lean body mass and body fat were determined in the obese girls. Extracellular volume (corrected bromide space) was also measured and by difference with body water, intracellular water or soft tissue cell mass was calculated. In normal girls 24-h creatinine excretion was determined, but body water was predicted from height and weight. It was found, as in previous studies, that the obese girls had excess muscle mass and soft tissue cell mass for height. The excess growth of muscle, lean tissue, and body length in obese girls correlated with increments in oxosteroid (17 ketosteroid) excretion. The overall weight increase correlated with increased excretion of corticosteroid metabolites--a finding of interest since a physiological Cushing's syndrome was postulated for fat girls many years ago. When the normal and obese girls were divided by age at 14 yr and the subgroups compared (normal obese) the younger girls showed differences with respect to height, weight, total body water, fat and percentage fat. Differences in steroid metabolites were not found. In older girls the same findings were made again, but here it was clear that the increments in body size, particularly muscle mass, correlated with augmented oxosteroid excretion. Evidence is cited that these findings are not just related to a larger steroid pool in obese girls.

17-Ketosteroids↗
PubMed1981

Morphological and functional relations of Graafian follicle growth to ovulation in women using ultrasonic, laparoscopic and biochemical measurements.

The daily growth rates of ovarian follicles were recorded ultrasonically for five days until ovulation in 56 spontaneously ovulating women and related to endocrine and clinical parameters. Over the 5-day period, the average diameter of the follicle destined to ovulate increased from 12 to 23 mm, the second largest follicle from 6 to 12 mm, the third largest follicle from 5 to 9 mm and the fourth largest follicle from 4 to 8 mm. Similar but lesser growth rates occurred in the follicles in the contralateral ovary. Ovulation occurred within 24 hours of the luteinizing hormone (LH) peak, and the mean peak diameter of the ovulating follicle was 23.2 +/- 0.3 (SEM) mm, (range 18-29 mm) before ovulation, and subsequent luteal function was judged to be normal. Follicular growth was most closely correlated with increasing peripheral blood oestrogen levels. In 16 women who had a laparoscopy within 12 hours of the last ultrasound and following the LH peak, the mean diameter of the largest follicle as measured by ultrasound (23.6 +/- 0.4 mm) was similar to that measured at laparoscopy (22.8 +/- 0.04 mm) and estimated from the volume of follicular fluid aspirated (average 5.8 +/- 0.2 ml), 22.5 mm. The follicular fluid levels of progesterone were high on the day of the LH peak and blood progesterone levels had risen significantly indicating that luteinization of the dominant Graafian follicles had already occurred prior to ovulation. This study confirms that ultrasonic monitoring provides a reliable measure of follicular growth and allows studies correlating morphological changes with both normal and abnormal endocrine function of the human ovary.

Adult↗
PubMed1981

Human luteal phase function following oocyte aspiration from the immediately preovular graafian follicle of spontaneous ovular cycles.

Human luteal phase function as evaluated by peripheral venous blood steroid levels does not appear to be impaired following the aspiration of follicular fluid together with a cumulus enclosed oocyte and a number of granulosal cells from the immediate preovular follicle in women having otherwise spontaneous ovular cycles. The day to day levels of luteinising hormone, oestradiol-17 beta, 17 alpha-hydroxy-progesterone, progesterone and basal temperatures in 14 women who had their preovular follicle aspirated were compared with a control group of 28 spontaneously ovulating women. It was concluded that a carefully performed single aspiration of the contents of a preovular follicle, for the purpose of extra-corporeal fertilisation of the mature oocyte, did not lead to impaired steroid function of the subsequent corpus luteum, although the prolactin levels were increased due to the effects of the relaxant anaesthetic and/or the laparoscopic procedure. A safe and simple laparoscopic procedure is also described, which is particularly suitable for women with a likelihood of extensive pelvic adhesions.

Adult↗
PubMed1981

Measurement of blood volume in fetal and neonatal sheep using red blood cells labelled with 99m technetium.

Blood volume has been measured in fetal and neonatal sheep using red blood cells labelled with 99mTc. The calculated volumes were highly correlated with simultaneous measurements made using the standard 51Cr labelled red cell method, although in absolute terms the 99m Tc method provided volumes which on average exceeded by a small percentage those determined with the 51Cr method. Measurements using the 99mTc method were also made at different ages in fetal and neonatal sheep and, while no correlation could be demonstrated between blood volume and either fetal or neonatal age, neonatal blood volumes were highly correlated with body weight. The 99mTc method is considered to be a reliable technique for measuring perinatal blood volumes in sheep with the short half-life of the isotope offering additional advantages.

Animals↗
PubMed1981

Hormonal and cellular interactions in follicular steroid biosynthesis by the sheep ovary.

Studies of isolated cell types from sheep follicles revealed several functional changes which occur during follicular maturation. Cyclic AMP production by granulosa cells from the smallest follicles studied (1-3 mm diameter) was stimulated by FSH but not by hCG, suggesting functional FSH receptors at this early stage of differentiation. Medium-sized follicles (4-6 mm) responded to both FSH and hCG. Granulosa cells were unable to synthesize androgens, but readily converted exogenous testosterone to oestradiol-17 beta. This conversion occurred to a limited extent in the cells from the smallest follicles, but was much greater in medium and large (greater than 6 mm) follicles. Oestradiol production by theca preparations from small follicles was barely detectable, but increased markedly with increasing follicle size. Androgen (androstenedione and testosterone) production by theca preparations was stimulated by hCG. This stimulation was short-lived, and levels declined to below control values after 6 h of culture. This decline could not be prevented by addition of cyclic AMP. The presence of granulosa cells with thecal preparations (i.e. follicle wall tissue) enhanced production of androgen by the theca, the effect being more marked for testosterone than for androstenedione. In-vivo studies in which granulosa cells and follicular fluid were removed during the preovulatory period suggested that granulosa cells and/or follicular fluid contributed to the oestradiol secreted into the ovarian vein during this period, but did not exclude a significant contribution by the theca as well.

Androgens↗
PubMed1981

The role of the pineal gland in seasonality.

The life time reproductive performance of 2 flocks of Merino crossbred ewes pinealectomized at 7-60 days of age, and maintained in South Australia did not differ from that of sham-operated control animals kept in the same flocks. The pineal gland is therefore not a major determinant of reproductive success, but a role for the pineal in adjusting breeding activity to season is not excluded. It was confirmed that pineal denervation of adult ewes by cranial sympathectomy could have disruptive effects and evidence of a seasonal change in pineal function was obtained from studies of plasma levels of melatonin, a putative pineal hormone, and a pineal peptide with gonadotrophin releasing activity. That melatonin stems mainly, but not exclusively, from the pineal gland was confirmed by studies of urinary excretion values. Adult Merino ewes produced 39-90 micrograms melatonin/day, mostly (80%) during the dark period, whereas pinealectomized animals produced less than one-fifth this amount. A link was provided between the pineal gland and diet. Melatonin and other 5-methoxyindoles influenced the activity of alpha-chymotrypsin and may regulate the availability of precursor substances required for the synthesis of neurotransmitters important in reproduction.

Animals↗
PubMed1981

Cervical ripening with combinations of vaginal prostaglandin F2-alpha estradiol, and relaxin.

The first of a 2-part trial consisted of a double-blind randomized pilot study in which 4 groups of 10 patients near term received 1 of the following hormonal combinations in a vaginal gel 15 hours before surgical induction of labor: 1) prostaglandin F2 alpha (PGF2 alpha) and relaxin; 2) relaxin and estradiol; 3) estradiol and PGF2 alpha; and 4) relaxin, estradiol, and PGF2 alpha. In each group the mean cervical score improved after treatment; the relaxin/PGF2 alpha combination was associated with the greatest improvement in cervical score (4.8). The highest incidence of subsequent labor was also seen in the relaxin/PGF2 alpha group (40%). However, with the exception of the latter group, the clinical effects of these hormonal combinations were neither greater nor smaller than the previously published effects of these hormones used individually in similar circumstances. The second part of the study further explored the possibility of an additive effect of relaxin and PGF2 alpha in combination as suggested by the pilot study, and an additional 40 patients were given this combination. Analysis of these larger numbers showed no additive effect when these hormones were used in combination compared with when they were used individually. Thus, in the circumstances described, there is no clinical advantage to the concurrent administration of any combination of relaxin, PGF2 alpha and estradiol with regard to cervical ripening and/or the initiation of parturition.

Administration, Topical↗