Effects of recombinant bovine somatotrophin, insulin-like growth factor-I and insulin on the proliferation of bovine granulosa cells in vitro

Treatment of heifers with recombinant bovine somatotrophin (BST) significantly increases the population of small ovarian follicles and peripheral concentrations of somatotrophin, insulin-like growth factor-I (IGF-I) and insulin. To investigate the possible mechanism(s) involved in the action of BST on ovarian follicles, the effects of BST, IGF-I and insulin, given alone or in combination with either FSH or LH, on the proliferation of bovine granulosa cells in vitro were examined using a serum-free culture system. Bovine granulosa cells were obtained from antral follicles classified into three size categories according to diameter: small < 5 mm; medium-sized 5-10 mm and large > 10 mm. The proliferation of granulosa cells was assessed by the incorporation of [3H]thymidine into the cultured cells. Both FSH and LH (1-1000 ng/ml) inhibited the proliferation of bovine granulosa cells obtained from all three size classes of follicles in a dose-dependent manner. BST, at doses ranging from 1 to 1000 ng/ml, had no effect on the proliferation of granulosa cells from small and medium-sized follicles, but inhibited the division of granulosa cells from large follicles in a dose-dependent manner. Treatment with either IGF-I (10-3000 ng/ml) or insulin (0.5-1000 ng/ml) stimulated, in a dose-dependent manner, the proliferation of granulosa cells obtained from all three size categories of follicles. No synergistic interaction between BST (30 ng/ml) and either FSH (50 ng/ml) or LH (5 ng/ml) was observed in granulosa cells from all three size classes of follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of recombinant bovine somatotropin on the superovulatory response to pregnant mare serum gonadotropin in heifers

Treatment of mature heifers with recombinant bovine somatotropin (BST) increases the number of ovarian follicles of 2-5 mm in diameter. This study was carried out to investigate whether the increase in the number of small follicles induced by BST treatment can enhance the superovulatory response. In the first experiment, 24 heifers were assigned, in a randomized block design, to four treatment groups: 1) control; 2) BST; 3) pregnant mare serum gonadotropin (PMSG); 4) BST+PMSG. On Day 7 of the estrous cycle, animals in groups 2 and 4 received injections of 320 mg BST (in a sustained release formulation), while heifers in groups 1 and 3 received 10 ml saline. Five days later heifers in groups 3 and 4 were treated with a single dose of 2000 IU PMSG to induce superovulation. Embryos were recovered nonsurgically on Days 6-8 of the following cycle, and all heifers underwent laparoscopy on Day 9 to assess ovulation rate. In a second experiment, 24 heifers were assigned randomly to four treatment groups: 1) PMSG (1000 IU); 2) BST (320 mg) + PMSG (1000 IU); 3) PMSG (2000 IU); 4) BST (320 mg) + PMSG (2000 IU), and then treated as for experiment I. In both experiments, all heifers were scanned daily using real-time ultrasound from the day before BST injection until the day of ovulation to monitor dynamics of ovarian follicular growth and development, and blood samples were collected daily throughout the experimental period for measurement of peripheral progesterone, estradiol-17 beta, growth hormone (GH), and insulin-like growth factor-I (IGF-I).(ABSTRACT TRUNCATED AT 250 WORDS)

The milk-alkali syndrome. A reversible form of acute renal failure

The milk-alkali syndrome became rare with the advent of modern ulcer therapy with nonabsorbable antacids, histamine2 blockers, and sucralfate. An increased frequency of this syndrome seems likely with the growing popularity of the use of calcium carbonate as an antacid or as calcium supplementation to prevent osteoporosis. We treated five patients who had six episodes of the milk-alkali syndrome; four of these cases were diagnosed between 1990 and 1992. All patients were ingesting massive quantities of calcium and absorbable alkali and were unaware of the toxic effects of these compounds. All patients presented with the triad of hypercalcemia, metabolic alkalosis, and renal failure. All metabolic abnormalities were corrected, and renal function improved with appropriate supportive measures and cessation of calcium and alkali ingestion. In two patients, the renal failure was so severe that dialysis was necessary. In four patients, either the serum amino-terminal parathyroid hormone or 1,25-dihydroxycholecalciferol levels were appropriately decreased in response to hypercalcemia. The serum carboxy-terminal parathyroid hormone levels were increased because of renal failure. Since both physicians and patients are often unaware of the calcium and alkali content of many nonprescription medicines, the diagnosis of the milk-alkali syndrome, a reversible cause of renal failure, can be missed if a detailed history of such intake is not elicited. Measurement of the serum amino-terminal parathyroid hormone and 1,25-dihydroxycholecalciferol levels may help differentiate milk-alkali syndrome from primary hyperparathyroidism.

The effect of recombinant bovine somatotrophin on ovarian follicular growth and development in heifers

The effects of recombinant bovine somatotrophin (BST) on the dynamics of ovarian follicular growth and development and peripheral insulin concentrations were investigated. Initially, studies were carried out in a population of Hereford x Friesian heifers to validate the ultrasound technique. In the first experiment, 12 heifers were injected daily with either 25 mg BST or vehicle for two oestrous cycles, and the effects on follicular dynamics and peripheral insulin were determined. In a second experiment, 12 heifers were given a single injection of 10 ml saline or 320 mg BST in a sustained-release formulation to examine the temporal relationships between growth hormone (GH), insulin-like growth factor-1 (IGF-1), insulin and the number of follicles. The validation studies demonstrated that small follicles (< 5 mm in diameter) could be clearly detected by real-time ultrasound, and that 75% (9 of 12) of heifers showed three waves of dominant follicle development during the oestrous cycle, whereas the remainder had only two waves. The changes in the numbers of follicles of the three size categories (< 5 mm, small; 5-10 mm, medium-sized and > 10 mm, large) also displayed a wave pattern similar to that of the dominant follicle, with a marked reduction in the number of subordinate follicles as the dominant follicle grew and reached its maximum size. In Expt 1, BST treatment increased the number of small follicles and caused a rise in peripheral insulin concentrations (P < 0.01) throughout the treatment period.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between selection for pituitary responsiveness to gonadotrophin releasing hormone in sheep and differences in gonadotrophin subunit mRNAs

Selection of the luteinizing hormone (LH) response to exogenous gonadotrophin-releasing hormone (GnRH) in sheep has resulted in the establishment of two lines (High and Low) with a fivefold difference in pituitary sensitivity to GnRH. The effect of selection on gonadotrophin gene expression in the presence or absence of an exogenous gonadotrophin-releasing hormone (GnRH) challenge in twenty-week-old ram lambs from both lines was examined. Before treatment with either GnRH or saline, LH and follicle-stimulating hormone (FSH) concentrations were significantly higher in the High line than in the Low line animals (LH and FSH: P < 0.01). One hour after either GnRH or saline, all animals were slaughtered. In the absence of a GnRH challenge, there were significantly higher concentrations of all three gonadotrophin subunit mRNAs in the High line compared with the Low line, corresponding to the higher basal concentrations of LH and FSH. When comparing treatments between the lines, following a GnRH challenge, LH beta subunit mRNA was significantly (P < 0.001) higher in both lines than before the GnRH, whereas there was no significant change in either alpha or FSH beta subunit mRNA. These results indicate that the differences in basal gonadotrophin secretion are related to differences in gonadotrophin subunit mRNAs with the High line animals having an inherently greater amount of all three gonadotrophin subunit mRNAs. Selection has not altered the differential amounts of gonadotrophin subunit mRNAs, since there is an overall increase in all three gonadotrophin subunits. GnRH appears to preferentially control LH beta mRNA in both High and Low line animals.

Stress fractures in the athlete. Diagnosis and management

Stress fractures can be a troublesome injury for the sports medicine clinician. The first description was in military personnel, but recently there is an increasing awareness and diagnosis of stress fractures in the athletic population. Stress fractures have been described in all extremities. Some fractures appear to have a degree of sports specificity. Bone is a dynamic tissue which strengthens and remodels in response to stress. Maladaptation to stress causes osteoclastic activity to supersede osteoblastic activity, thereby allowing weakening of the bone. These areas of weakening may fracture and create prodromal symptoms and clinical findings. Localised pains of insidious onset which are activity related are the hallmarks in the clinical history. The physical examination can exhibit localised tenderness, redness and swelling. Radiographs can be negative for up to 4 months. The gold standard for diagnosis is the triple phase 99mtechnetium bone scan. The treatment of a stress fracture is usually conservative. Very few cases require surgical management. The algorithm of conservative management includes: rest, appropriate education for treatment and preventive care, analgesics, serial radiographs, icing and physical therapy modalities, appropriate exercise to prevent detraining, rehabilitation and a regimented return to participation and competition.

Evidence for the action of bovine follicular fluid factor(s) other than inhibin in suppressing follicular development and delaying oestrus in heifers

The aim of this study was to investigate the importance of inhibin in the delay in return to oestrus in heifers induced by steroid-stripped bovine follicular fluid (bFF). Oestrous activity was synchronized in 18 Hereford x Friesian heifers with two injections of prostaglandin (PG) 12 days apart. At the time of the second PG injection (time 0), the animals were assigned at random to one of three experimental groups and received i.v. injections of 20 ml saline (controls, n = 6), whole bFF (FF group, n = 6) or bFF in which the bioactive inhibin content had been reduced by > 95% by immunoaffinity chromatography (-INH group, n = 6; inhibin content approximately 0.8 ml whole bFF) every 8 h for 2 days. In a dose-response study, 2.5 ml whole bFF was insufficient to delay oestrus consistently following a similar synchronization regimen. Blood samples were taken every 8 h, initially before each injection and then subsequently for a further 9 days for hormone analysis. Animals were observed every 8 h throughout the experiment for signs of behavioural oestrus. The ovaries of all animals were examined using real-time ultrasonography about 30 h after the second PG injection. Treatment failed to suppress peripheral follicle-stimulating hormone (FSH) concentrations, although a significant increase was observed in both treatment groups after cessation of injections. Progesterone concentrations fell immediately after the second PG injection in all animals and remained below minimum detectable concentrations in all treated animals for the remainder of the experiment. In control animals, progesterone rose above minimum detectable concentrations by day 6 and continued to rise until the end of the experiment. Analysis of samples taken from treated animals several days after observed oestrus revealed that all had apparently ovulated. Mean daily luteinizing hormone (LH) concentrations did not differ between treatment groups before ovulation, but after ovulation, mean daily LH was significantly reduced in control animals as progesterone concentrations rose. Follicular development, as assessed by the mean antral diameter of the largest follicle on a pair of ovaries at ultrasound examination, was significantly suppressed in treated animals compared with controls (P < 0.01) and there was no significant difference (P = 0.397) between the two treatment groups. Control animals displayed oestrus 68 h (+/- 8 SEM) after the second PG injection, but oestrus was delayed in treated animals to 186h +/- 5 (FF group) and 191 h +/- 6 (-INH group).

Apparent alpha-inhibin subunit immunoactivity in porcine and ovine luteal extracts is due to interference by cytosolic proteases in the assay

Immunoreactive alpha-inhibin (ir-inhibin) was measured in luteal homogenates and subcellular fractions of ovine and porcine corpora lutea (CL) and in pig granulosa cells (GCs), using a sensitive radioimmunoassay specific for the 1-26 amino acid sequence of the N-terminus of the alpha chain of porcine inhibin (p1-26 alpha-inhibin). Inclusion of N-ethylmaleimide (N-EM) and/or EDTA in the immunoassay had no effect on the measurement of p1-26 alpha-inhibin peptide standards, on ir-inhibin levels in ovine follicular fluid and serum, or on ir-inhibin in subcellular fractions of pig GC. Fractionation of porcine GC homogenates on sucrose gradients demonstrated a major particular peak of ir-inhibin (buoyant density, 1.15-1.21 g/cm3) with variable activity in the cytosol. The particulate ir-inhibin peak was released into the cytosol by pretreatment of GC homogenates with the saponin, digitonin, prior to fractionation. Porcine GC extracts contained a protein (M(r) 45,000) which immunoblotted against p1-26 alpha-inhibin antibody. In the absence of inhibitors of proteolysis, apparent ir-inhibin activity was very high in extracts of sheep and pig CL. However, inclusion of N-EM or EDTA in the radioimmunoassay significantly reduced ir-inhibin levels in porcine and ovine CL extracts in a dose-dependent manner. Measurements of peptide tracer integrity indicated that porcine luteal cytosol degraded 125I-labelled p1-26 alpha-inhibin peptide. Subcellular fractionation studies demonstrated high levels of apparent ir-inhibin in luteal cytosol fractions, with only minor activity peaks associated with particulate fractions; however, this material was not releasable by digitonin. Immunoblotting of detergent extracts of porcine luteal particulate fractions failed to demonstrate alpha-inhibin material, and immunocytochemical localization studies of alpha-inhibin in porcine and ovine luteal sections were negative. Our results are consistent with the intracellular packaging/storage of a form of alpha-inhibin (M(r) similar to that of alpha-inhibin subunit precursor) in the porcine granulosa cell. However, luteinization of the porcine follicle was associated with a dramatic fall in ir-inhibin content, and the loss of immunostaining for alpha-inhibin peptides. We conclude that porcine and ovine CL contain little, if any, authentic inhibin. These studies emphasize the importance of excluding proteolytic artefacts when measuring biological peptides in luteal tissue extracts by radioimmunoassay.

3 beta-hydroxysteroid dehydrogenase inhibitor reduces ovarian steroid production but increases ovulation rate in the ewe: interactions with gonadotrophins and inhibin

Two experiments were carried out during the breeding season in ewes, first to investigate the effects of oral administration of a 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) inhibitor (epostane) on the number of corpora lutea, and secondly to investigate the mechanism through which epostane acts. In the first experiment Dorset Horn ewes were treated orally with 25, 50, 100 or 200 mg epostane twice daily between days 10 and 15 of the oestrous cycle. All doses of epostane resulted in an increase in the number of corpora lutea per ewe, although the response was curvilinear, with the 25 mg dose showing the largest response and the 200 mg group the smallest response. Although there was no difference between groups in the number of ewes showing oestrus, the higher doses of epostane had a detrimental effect on fertility. In the second experiment Welsh Mountain ewes were treated twice daily with 25 mg epostane from day 10 of the oestrous cycle and the ovaries were removed for analysis during either the luteal or the follicular phases. Treatment significantly increased the number of follicles greater than 6 mm in diameter, but significantly reduced in-vitro follicular oestradiol and testosterone production. Despite a marked increase in peripheral inhibin concentrations there was no effect on in-vitro inhibin production. Epostane treatment also caused a significant reduction in peripheral FSH concentrations and an increase in mean LH concentration. The latter was due to an increase in LH pulse frequency during the luteal phase and LH pulse amplitude during the follicular phase. These results confirm that treatment of ewes with epostane orally has a significant effect on follicular steroidogenesis and causes a significant increase in the number of corpora lutea per ewe. This effect on ovulation rate is not via an increase in peripheral FSH concentration, but may be caused by a reduction in follicular steroid activity either directly on the ovary or via an alteration in the pattern of LH secretion.

Migration of green (Chelonia mydas) and loggerhead (caretta caretta) turtles to and from eastern Australian rookeries

Feeding-ground captures of green (Chelonia mydas) and loggerhead (Caretta caretta) turtles tagged while nesting at eastern Australian rookeries over a 21-year period are summarised. These turtles which nest in the Great Barrier Reef region range widely throughout the Arafura and Coral seas. The tag recoveries include many from turtles that live in neighbouring countries and migrate to breed in Australia. The breeding female shows a high fidelity to her home feeding ground as well as to her nesting beach. Most recaptures of the green turtles occurred during hunting for food by indigenous people while most recaptures of loggerhead turtles were incidental captures in commercial fishing activities. Migratory behaviour, imprinting and navigation are discussed.

Mechanism controlling ovulation rate in ewes in relation to seasonal anoestrus

Three experiments were carried out during seasonal anoestrus in Finnish Landrace and Scottish Blackface ewes, to establish whether the differences between the breeds in ovulation rate are functional during the non-breeding season and are therefore independent of the mechanism controlling ovulation. In Expt 1, follicles greater than or equal to 2 mm in diameter were dissected from the ovaries of both breeds and incubated individually for 2 h to assess their ability to secrete oestradiol and testosterone. In both breeds, follicles producing greater than or equal to 500 pg oestrogen/ml/h (oestrogen-active) were readily identifiable from a population producing less (oestrogen-inactive). The number of oestrogen-active follicles in each breed was similar to the number of ovulations near the end of the breeding season. Oestrogen-active follicles also had more luteinizing hormone (LH) receptors and larger diameters than oestrogen-inactive follicles. There were, however, no significant differences between the two follicle types in follicular fluid or in-vitro testosterone concentrations. In Expt 2, seasonally anoestrous Scottish Blackface ewes were unilaterally ovariectomized; the second ovary was removed 7 days later. Follicles from both ovaries were processed as described for Expt 1; oestrogen-active follicles were categorized according to their ability to produce greater than 500 pg/ml/h. There were twice as many oestrogen-active follicles in the second ovary as in the first ovary; the number of oestrogen-active follicles in the second ovary was also similar to the total number of oestrogen-active follicles in both ovaries of the Scottish Blackface ewes in Expt 1.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of recombinant bovine somatotropin on ovarian function in heifers: follicular populations and peripheral hormones

The objective of this study was to investigate the possible effect of recombinant bovine somatotropin (BST) on ovarian folliculogenesis and ovulation rate. Twelve Hereford x Friesian heifers received daily injections of either 25 mg BST (6 heifers) or vehicle (6 heifers) for a period of two estrous cycles until slaughter. Blood samples were collected three times a week for measurements of peripheral growth hormone (GH), insulin-like growth factor I (IGF-I), FSH, LH, estradiol, and progesterone. Serial blood samples were also taken every 10 min for 8 h on Days 12 and 19 of the second estrous cycle to monitor GH, IGF-I, FSH, and LH profiles. At the end of treatment (Day 7 of the third estrous cycle), the heifers were killed and their ovaries were collected. Ovulation rate was determined by counting the number of fresh corpora lutea (CL). All antral follicles greater than or equal to 2 mm in diameter were dissected to assess antral follicle populations. Granulosa and thecal cells from the three largest follicles and CL from each heifer were collected for FSH and LH binding measurements. All heifers had a single ovulation. The treated heifers had significantly more antral follicles (60.2 +/- 6.7) than did the animals in the control group (33.2 +/- 3.2) (p less than 0.001). When follicles were grouped according to diameter, the mean numbers of follicles greater than 10 mm, 5-10 mm, and 2-5 mm in diameter were 0.8 +/- 0.2, 6.8 +/- 1.4, and 52.5 +/- 6.5 for the treated group, and 0.8 +/- 0.2, 6.5 +/- 1.0, and 25.8 +/- 2.7 for controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of gonadal negative feedback on the gonadotrophin responses to gonadotrophin-releasing hormone (GnRH) in ram lambs from two lines of sheep selected for their luteinizing hormone response to GnRH

Divergent selection has resulted in two lines of lambs (high and low) that have a 5-fold difference in their ability to release luteinizing hormone (LH) in response to 5 micrograms of gonadotrophin-releasing hormone (GnRH). Baseline gonadotrophin concentrations, the gonadotrophin responses to a GnRH challenge and the concentrations of testosterone and oestradiol were compared in lambs which were castrated at birth and intact lambs from both selection lines at 2, 6, 10 and 20 weeks of age. The pattern of LH and follicle-stimulating hormone (FSH) secretion was similar in the two lines, but differed between the intact and the castrated lambs. Basal LH and FSH secretion were significantly higher in the castrates than in the intact lambs from both selection lines. The high-line lambs had significantly higher basal FSH concentrations at all ages tested and significantly higher basal LH concentrations during the early postnatal period. The magnitude of the gonadotrophin responses to GnRH differed significantly between the intact and the castrated lambs within each line, the amount of gonadotrophins secreted by the castrated lambs being significantly greater. The removal of gonadal negative feedback by castration did not alter the between-line difference in either LH or the FSH response to the GnRH challenge. Throughout the experimental period, the concentration of testosterone in the intact lambs was significantly greater than in the castrated lambs in both selection lines, but no significant difference was seen in the concentrations of oestradiol. No significant between-line differences were found in the peripheral concentrations of testosterone or oestradiol in the intact lambs from the two selection lines. Therefore, despite similar amounts of gonadal negative feedback in the selection lines, there were significant between-line differences in basal gonadotrophin concentrations, at 2 and 6 weeks of age, and in the LH and FSH responses to an exogenous GnRH challenge, at all ages tested. Removal of gonadal negative feedback did not affect the magnitude of the between-line difference in the response of the lines to GnRH stimulation. The results indicate that the effects of selection on gonadotrophin secretion are primarily at the level of the hypothalamo-pituitary complex.

Alterations in pituitary gland sensitivity in ram lambs to physiological doses of gonadotrophin-releasing hormone (GnRH), after divergent selection based on the luteinizing hormone response to a pharmacological GnRH challenge

Divergent selection in 10-week-old Finn-Dorset ram lambs was based on the luteinizing hormone (LH) response to a pharmacological dose of GnRH (5 micrograms). After eight generations of selection, the LH responses of the two lines (low and high) to GnRH differed by a factor of five. This study investigates the pituitary sensitivity of the two lines to exogenous GnRH. Initially, two pilot studies were performed: one to determine the range of doses of GnRH which would stimulate LH pulses of similar amplitude to those seen endogenously, and the other to confirm that sodium pentobarbitone prevents pulsatile LH secretion in prepubertal ram lambs. The results indicated that barbiturate anaesthesia suppressed pulsatile LH secretion in castrated and intact ram lambs. A model system was therefore constructed in 18 10-week-old intact ram lambs (high n = 7, low n = 11), whereby endogenous pulsatile LH secretion was prevented by sodium pentobarbitone anaesthesia and the amplitudes of LH pulses produced in response to different doses of exogenous GnRH could be measured. The GnRH dose-response curves demonstrated that there was a five-fold difference in the sensitivity of the pituitary glands of the two lines to stimulation with GnRH. The projected minimum concentration of GnRH required to produce a measurable pulse of LH was 4.75 ng for the high-line animals and 26.6 ng for the low-line animals. The results indicated that the low-line animals required five times more GnRH than the high-line lambs to stimulate LH pulses of similar amplitude (high line 43.67 ng; low line 206.55 ng). These results demonstrate that selection has produced two lines of sheep which differ in the control of LH secretion at the level of the hypothalamus-pituitary gland.

Does follicular dominance occur in ewes?

The process by which a single follicle is selected to ovulate while others regress is unknown in ewes. If the dominant follicle secretes substances that directly inhibit the growth of other follicles, the superovulatory response to the administration of exogenous gonadotrophins may be blunted. Administration of 1250 iu pregnant mares' serum gonadotrophin (PMSG) before or after the emergence of the dominant follicle in the follicular phase, or 1000 iu PMSG in the presence or absence of a large healthy or atretic follicle during the luteal phase did not affect the induced ovulatory response. Comparisons between the ovary with or without the dominant follicle did not reveal any differences in ovulatory response to PMSG. The in-vitro features (i.e. mitotic index, oestradiol and testosterone production) of follicles ipsilateral or contralateral to the dominant follicle during the early and late follicular phases were also similar. If the dominant follicle secretes substances detrimental to the other follicles, this could be mimicked in vitro. Co-culture of small follicles with the largest follicles in a closed system did not reduce their incorporation of 3H thymidine in granulosa cells, compared with small follicles cultured alone. These data suggest that dominance is probably not operative in sheep. The administration of 500 iu of PMSG during the midfollicular phase increased ovulation rate in Merino ewes, indicating that dominance is essentially passive in ewes and can easily be overcome by raising gonadotrophin concentration.

'Benign' familial neonatal convulsions

Nine family members over five generations are described in whom convulsions occurred in the first week of life. Routine studies, including cranial computed tomography and electroencephalography, failed to reveal an etiology in the proband, nor was a specific etiology ever found in other affected family members. All affected individuals developed normally. Three had recurrent seizures outside the first year of life. This condition is of particular importance to those who care for infants with seizures. An appropriate family history should obviate the need for unnecessary diagnostic tests as well as prolonged anticonvulsant therapy, but counseling regarding the increased risk of subsequent seizures should be provided to affected individuals.

Bacterial RNA isolation with one hour centrifugation in a table-top ultracentrifuge

A procedure for the rapid preparation of cesium-chloride purified RNA from E. coli and the cyanobacterium Synechococcus sp. PCC7942 is described. Cells are lysed in modified sucrose, Triton X-100, EDTA, Tris buffer with phenol/chloroform. The cleared lysate is extracted further with phenol/chloroform and RNA is peleted by centrifugation through a 5.7 M CsCl cushion. High quality RNA can be prepared in three hours using this procedure.

Morphological and functional characterization of large antral follicles in three breeds of sheep with different ovulation rates

Morphological and functional features of large ovarian follicles from three breeds of sheep, with different ovulation rates (Finnish Landrace N = 12, Finnish Landrace X Scottish Blackface N = 16, Merino X Scottish Blackface N = 16) were compared by integrating three techniques; ink labelling, in-vitro oestradiol production and morphological classification. The follicles were removed at two stages of the follicular phase, 1 (PG + 1) or 2 (PG + 2) days after PGF-2 alpha treatment and compared after monitoring their rates of growth with the use of ink labelling. After ovariectomy all follicles greater than or equal to 1 mm in diameter were dissected, and the 8 largest were incubated individually for 2 h to assess their ability to secrete oestradiol and testosterone. After incubation the follicles were processed for histological examination and checked for atresia. An analysis of the follicle population was based on in-vitro oestradiol secretion rates in all three breeds; an oestrogen-active population producing 500-8100 pg oestradiol/ml/h and an oestrogen-inactive population producing 0-499 pg oestradiol/ml/h. A comparison of the 3 approaches demonstrated agreement on 94.3 +/- 1.2% of occasions. Ink-labelling demonstrated that all follicles identified as oestrogen-active were increasing in size. Within oestrogen-active follicles significant correlations were detected between oestradiol production and testosterone production (r = 0.42), oestradiol production and granulosa cell number (r = 0.45) and between oestradiol production and mitotic index (r = -0.38). A regression model fitting breed, stage of atresia, granulosa cell number, in-vitro testosterone production and mitotic index demonstrated that granulosa cell number is a characteristic which contributes significantly to the variation of in-vitro oestradiol production in oestrogen-active and oestrogen-inactive follicles. There was no significant difference between breeds in the mean number of ink-labelled follicles growing from Day PG - 1 to Day PG + 1. There was a significant difference between the breeds in the number of ink-labelled follicles growing between Days PG + 1 and PG + 2 (Days 1 and 2 of the follicular phase), the number being similar to the ovulation rate for the breed. The majority of the oestrogen-active follicles had been recruited by Day PG - 1, although in the Finnish Landrace genotypes more than 30% were recruited on or after Day PG + 1 compared to less than 10% in Merino x Scottish Blackface ewes.(ABSTRACT TRUNCATED AT 400 WORDS)

Neurosecretory-like material in 3rd- and 4th-stage Dirofilaria immitis larvae (Nematoda: Filarioidea)

Phase-interference microscopic examination of the infective, post-infective 3rd-stage and 4th-stage larvae of Dirofilaria immitis has identified a single cell body in each of the paired lateral amphidial nerves which undergoes characteristic morphological change during the development from 3rd- to 4th-stage larvae. Acetaldehyde-fuchsin staining of worm sections revealed fuchsinophilic material in the precise location of the amphidial nerve-cell bodies observed by phase-interference microscopy. This material was found in 70% of infective larvae recovered from mosquitoes and in 100% of larvae recovered from micropore chambers 24 h after implantation into BALB/C mice. In pre-moult larvae recovered at 42 h (Experiment 1) and at 48 h (Experiment 2) fuchsinophilic material was demonstrable, but no staining was observed in those larvae in which separation of the 3rd- and 4th-stage cuticles had occurred. No such material was observed in 4th-stage larvae recovered from chambers after 74 h, and in these larvae the amphidial nerve-cell bodies were not discernible. These cytological observations are consistent with a cycle of elaboration and release of neurosecretion associated with moulting in D. immitis.

Ovarian response to hCG treatment during the oestrous cycle in heifers

The aims of this study were to investigate whether treatment with a single ovulatory dose of hCG, between the day of oestrus and the end of the luteal phase, could induce extra ovulations in heifers and whether the presence of an existing corpus luteum (CL) affected the response. Heifers (N = 32) were injected with 1500 i.u. hCG or saline on a given day of the oestrous cycle. Treatments were repeated during subsequent cycles to provide a total of 71 observations, 57 of which followed an injection of hCG, given between Day 0 (oestrus) and Day 16, and 14 of which followed saline injections as controls. Ovulatory responses were noted by laparoscopy 2 days after hCG treatment. No heifers injected with saline produced additional CL. Of the hCG-treated cycles, 23 resulted in the formation of an additional CL, and this was significantly affected by the stage of the oestrous cycle when hCG was given; a greater response was observed during the early (Days 4-7) and late (Days 14-16) stages of the luteal phase than at the mid-luteal phase of the oestrous cycle. Two heifers were also treated with hCG on Days 17 or 18 of the oestrous cycle, but before oestrus; both had induced CL. There were no significant differences between the left-right orientation of the existing CL or the hCG-induced CL. These results demonstrate that the large, luteal-phase follicle of the cow is capable of ovulating in response to hCG and that the induced CL is not affected by the presence of an existing CL.