Effect of estradiol-17 beta on peripheral plasma concentration of 15-keto-13,14-dihydro PGF2 alpha and luteolysis in cyclic cattle

Friesian heifers (n = 10) were assigned randomly to receive an intravenous injection of estradiol-17 beta (E2; 3 mg) or saline:ethanol vehicle solution (6 ml; 1:1) on day 13 of the estrous cycle. Blood was collected from the jugular vein by venipuncture into heparinized vacutainer tubes at 30 minute intervals for 2 hours (h) preinjection, 10.5 h postinjection and then at 3 h intervals until estrus. Repeated hormone measurements of 15-keto-13,14-dihydro-PGF2 alpha (PGFM) and progesterone (P4) were evaluated by split-plot analysis of variance. Mean concentration of PGFM for the 12.5 h acute sampling phase was 164.1 +/- .14 pg/ml. A treatment by time interaction was detected (P less than .01). After treatment with E2, PGFM concentrations began to increase at approximately 3.5 h, reached a mean peak of 330.4 +/- 44.5 pg/ml (n = 5) at 5.5 +/- .3 h, and returned to basal concentration by 9.0 +/- .6 h. Vehicle treatment did not alter concentrations of PGFM. Injection of E2 on day 13 of the estrous cycle caused luteolysis (P4 concentration less than 1 ng/ml) to occur earlier following injection (96.9 +/- 10.6 h less than 153.6 +/- 17.7 h; P less than 0.05) than did the vehicle control treatment. During the chronic sampling phase of 3 h intervals, 39 of 606 samples (6.4%) were classified as PGFM spikes (323.0 +/- 50.0 pg/ml); 21 (53%) of the spikes occurred at a mean interval of 18.9 +/- 3.86 h before the time of completed luteolysis. Exogenous E2 induced an acute increase in PGFM that may be indicative of uterine PGF2 alpha production. Peaks of PGFM in plasma were temporally associated with luteolysis on a within cow basis.     

Prostaglandins F in uterine and ovarian venous plasma from nonpregnant and pregnant ewes collected by cannulation

Periodic collections of uterine venous blood were obtained from three nonmated, three pregnant and two mated but nonpregnant ewes in which uterine veins were cannulated with polyvinyl tubing on day 11 postestrus. Frequent sampling was achieved in three of these ewes with additional cannulae in the ovarian veins. Blood samples were collected at 3-hr intervals from 0600 on day 12 to 1800 on day 13 and then at 6-hr intervals through day 15. On day 13, three additional samples at 30-min intervals were collected between 1400 and 1530. Prostaglandins F (PGF) in plasma were quantified by radioimmunoassay.     

Circadian rhythms in hot flashes in natural and surgically-induced menopause

The aim of this study was to investigate circadian and ultradian variations in menopausal hot flash. The number of hot flashes per 2-hr period was collected from 25 diurnally-active, perimenopausal women for 1 week in January or February of each year for 3 consecutive years. Fourteen women were experiencing natural menopause (NM) (mean age 51.9 years) and 11 were experiencing surgically-induced menopause (SIM) (mean age 52.0 years). The difference in the number of hot flashes between the two types of menopause at each clock time was not statistically significant; neither was the mean number of hot flashes per 24 hr different between the two groups (Student's t-test). Data when normalized for each woman and placed end-to-end revealed by cosinor analysis circadian rhythmicity in the SIM group (P = 0.02) but not in the NM group. A 12-hr periodicity was detected in both groups (P less than 0.001 for both). An 8-hr rhythm was detected only for the NM group (P = 0.04). Both groups combined exhibited statistically significant rhythmicities with periods of 24 hr (P = 0.003), 12 hr (P less than 0.001) and 8 hr (P = 0.005). Regardless of the type of menopause, the women could be separated into two groups based on the temporal pattern of hot flashes during the day. One group was defined by the occurrence of peak frequency of flashes during the morning (0400-0959), while the second group was defined by the occurrence of the peak in the evening (1600-2159).(ABSTRACT TRUNCATED AT 250 WORDS)     

Circadian rhythm of tryptophan hydroxylase activity in chicken retina

1. Retinal tryptophan hydroxylase activity in chickens (1-4 weeks old and embryos) was estimated by determination of levels of 5-hydroxytryptophan (5HTP) in retinas at defined intervals after inhibition of aromatic L-amino acid decarboxylase with m-hydroxybenzylhydrazine (NSD1015). 2. The relationship of tryptophan hydroxylase activity to photoperiod was explored. In chickens maintained on a 12-hr light: 12-hr dark cycle, a diurnal cycle in tryptophan hydroxylase activity was observed. Activity during middark phase was 4.4 times that seen in midlight phase. Cyclic changes in tryptophan hydroxylase activity persisted in constant darkness with a period of approximately 1 day, indicating regulation of the enzyme by a circadian oscillator. The phase of the tryptophan hydroxylase rhythm was found to be determined by the phase of the light/dark cycle. The relationship of the tryptophan hydroxylase rhythm to the light/dark cycle mirrors previously described rhythms of melatonin synthesis and serotonin N-acetyltransferase (NAT) activity in the retina. 3. Light exposure for 1 hr during dark phase suppressed NAT activity by 82%, while tryptophan hydroxylase activity was suppressed by only 30%. 4. Based on the differential responses of retinal NAT activity and tryptophan hydroxylase activity to acute light exposure during dark phase, it was predicted that exposure to light during dark phase would divert serotonin in the retina from melatonin biosynthesis to oxidation by MAO. In support of this, levels of 5-hydroxyindole acetic acid (5HIAA) in retina were found to be elevated approximately two-fold in chickens exposed to 30 min of light during dark phase. In pargyline-treated chickens, 2 hr of light exposure during dark phase was found to increase retinal serotonin levels by 64% over pargyline-treated controls. 5. Cyclic changes in tryptophan hydroxylase activity and NAT activity persisted for 2-3 days in constant light. Tryptophan hydroxylase activity at mid-night gradually decreased on successive days in constant light; on the first day of constant light, tryptophan hydroxylase activity at mid-night was 70% of activity seen during middark phase of the normal light/dark cycle and decreased further on subsequent days. In contrast, on each of 3 days of constant light, NAT activity at mid-night was approximately 15% of normal middark phase activity. 6. Cycloheximide completely inhibited the nocturnal increase in tryptophan hydroxylase activity when given immediately before light offset. The nocturnal increase in NAT activity was inhibited in a similar fashion. 7. Like the development of the NAT rhythm, cyclic changes of tryptophan hydroxylase activity in the retinas of chickens began on or immediately before the day of hatching. hatching.(ABSTRACT TRUNCATED AT 400 WORDS)     

Radioimmunoassay of cortisol in peripheral blood plasma of buffaloes peripartum

Changes in the concentration of cortisol were observed in the jugular venous plasma of pregnant buffaloes on days 30, 15, 5, 2 and 1 prepartum, at partum, at regular 6-hr intervals up to 72 hr postpartum and on days 4, 6, 10, 18, 34 and 50 postpartum. A radioimmunoassay (RIA) procedure for cortisol standardized in the laboratory was used. Mean plasma cortisol levels showed little fluctuation (P<0.05) between days 30 and 2 prepartum with the values ranging from 1.28 +/- 0.23 to 1.46 +/- 0.13ng/ml. A small (but nonsignificant) rise in the hormone level was observed one day prepartum followed by a sharp increase to a high mean value of 3.78+/-0.36 ng/ml (P<0.05) at parturition. A sharp decline (P<0.05) to a low mean value was recorded within 6 hr postpartum followed by marked fluctuations in the hormone level up to 72 hr postpartum. The hormone levels subsequently varied narrowly between 1.74+/-0.39 and 2.01+/-0.27 ng/ml up to 50 days postpartum.     

Observations on the reproductive effects of once or twice weekly injections for 6 weeks of the GnRH agonist deslorelin in the cow

This study investigated the reproductive effects in Holstein-Friesian cows of once or twice weekly intramuscular injection for 6 weeks of 100 microg of the GnRH agonist deslorelin at intervals. Oestrus was synchronized in non-lactating Holstein-Friesian cows before they were allocated randomly to receive either 100 microg deslorelin once weekly (D1; N=10) or twice weekly (D2; N=8) or acted as untreated controls (CON; N=8). The first injection was given on day 6 post-oestrus and the last injection on day 48 post-oestrus. Blood samples were collected twice weekly from each cow until day 76 after the synchronized oestrus to profile plasma P4. A single injection of prostaglandin was administered to all cows on day 20 post-oestrus to ensure luteolysis occurred. Ovaries were examined twice weekly by transrectal ultrasonography and then subsequently at weekly intervals to monitor ovarian structures. Progesterone profiles observed over two complete cycles for CON cows were typical of those expected for cows displaying regular oestrous cycles. Injection of deslorelin on day 6 post-oestrus induced ovulation in 100% (18/18; D1 and D2) of deslorelin-treated cows. Three categories of responses based on plasma P4 profiles were defined amongst the deslorelin-treated cows. Complete anoestrus was observed in 20% (2/10) of D1 and 63% (5/8) of D2 cows. A partial response characterised by intermittently low concentrations of P4 was observed in 50% (5/10) of D1 and 25% (2/8) of D2. A complete lack of response to deslorelin, with P4 profiles indistinguishable from CON cows, was seen in 30% (3/10) of D1 and 13% (1/8) of D2 cows. When results from D1 and D2 were pooled, a greater proportion of deslorelin-treated cows had abnormal ovarian cycles during the treatment period (56% versus 0%; D1 and D2 versus CON, P <0.001). In conclusion, the repeated injection of deslorelin either once or twice weekly for 6 weeks significantly altered the ovarian cycles of some cows; individual cow responses observed varied widely and ranged from complete anoestrus to a cycle indistinguishable from normal.     

Atypical 24-hour rhythms of serotonin N-acetyltransferase activity in the rat pineal gland

Previous long-term studies have shown that in the pineal gland of rats melatonin synthesis is subject to infradian rhythms with periods between 4 and 7 days. Since in these studies melatonin-related parameters were measured at one timepoint of a 24-hr cycle only, the aim of the present investigation was to extend these experiments by more frequent sampling, to characterize the infradian rhythmicity in more detail. Male Sprague-Dawley rats kept under a light schedule of LD 12:12 (lights on at 0700) were killed at 6-hr intervals on 8 consecutive days. After decapitation the pineal gland was rapidly dissected out, followed by measurements of one of the melatonin-forming enzymes, serotonin N-acetyltransferase (NAT) activity. It was found that pineal NAT activity exhibited the well known day/night rhythm, i.e. low activity during daytime and strikingly enhanced activity at night, during the first 4 days of the experiment. On the fifth night (from Saturday to Sunday) an unusually high NAT peak occurred at 2400 hr, followed by two atypical 24-hr cycles. In the first cycle the midnight and 0600 hr values were equal and in the second cycle the 0600 hr value was significantly higher than the midnight value. To investigate whether the unusually high NAT peak was a single event or not, four additional short-term experiments were carried out at 2400 hr on 4 consecutive weekends, from Friday to Monday. In each of the four 4-day experiments a distinctly higher peak of NAT activity was found on Saturday, but with time the peaks became less prominent.(ABSTRACT TRUNCATED AT 250 WORDS)     

Arachidonic acid metabolites and their circadian rhythm in patients with allergic bronchial asthma

The aim of this study was to investigate circadian variation in concentrations of arachidonic acid (AA) metabolites in relation to the circadian pattern in bronchial patency. Blood samples were obtained at 4-hr intervals from 2000 of 1 day until 1400 of the next from 12 diurnally active asthmatic and six diurnally active non-asthmatic patients. Bloods were analyzed for the prostanoids thromboxane A2 (measured as stable metabolite 6-keto-PGF1a), PGE2 and PGF2a. Airways patency was assessed by self-measurement of peak expiratory flow (PEF). In asthmatics, circadian variation was detected in PEF as well as PGE2 and TXB2. The circadian trough of the PEF rhythm closely coincided with the circadian peak of the PGE2 and TXB2 rhythms. In the controls, the PEF was not circadian rhythmic. Of the AA metabolites only 6-keto-PGF1a exhibited 24-hr bioperiodicity in the controls. The controls exhibited a significantly higher circadian mean of PEF (P less than 0.001), while the asthmatics had a lower 24-hr average PGE2 but greater mean TXB2/PGE2 ratio. The obstructive effect caused by the overall 24-hr deficiency of PGE2 in asthmatics is possibly amplified by the increased of TXB2 during the early morning hours. This dissociation of the temporal patterns in TXB2 and PGE2 levels over the 24 hr is discussed as a characteristic finding for asthmatics.     

Concentrations of steroids and expression of messenger RNA for steroidogenic enzymes and gonadotropin receptors in bovine ovarian follicles of first and second waves and changes in second wave follicles after pulsatile LH infusion

The objectives were to compare expression of mRNA for cytochrome P450 cholesterol side-chain cleavage (P450scc), cytochrome P450 17alpha-hydroxylase (P450c17), cytochrome P450 aromatase (P450arom), 3beta-hydroxysteroid dehydrogenase Delta(4), Delta(5) isomerase (3beta-HSD), FSH receptor (FSHr) and LH receptor (LHr) in bovine ovarian follicles of the first and second waves of the bovine oestrous cycle and to determine if LH infusion changes growth, steroidogenesis and gene expression in second wave follicles. Transrectal ultrasonography was used to examine follicular size changes during the oestrous cycle in non-lactating Holstein cows (n=31). Saline or purified bovine LH was infused intravenously into cows at emergence of follicular waves for 2 or 4 days using a computer-controlled syringe pump (n=5-6 per treatment). Treatments were: wave 1, saline (W1S); wave 2, saline (W2S) or LH (25 microg/h; W2LH). During infusion, blood samples were collected at 12min intervals for 8h via i.v. catheters for measurement of serum LH concentrations. Ovaries were removed from cows on days 2 or 4 after emergence of follicular waves. Follicles were frozen and stored at -80 degrees C. Follicular fluid (FF, 50 microl) was collected for determination of progesterone (P4), oestradiol-17beta (E2) and androstenedione (A4) concentrations. Frozen sections (14 microm) were used for in situ hybridization to measure expression of mRNA (% pixel intensity) for P450scc, P450c17, P450arom, 3beta-HSD, FSHr, and LHr. LH infusion resulted in a serum LH pattern (high frequency) similar to the early luteal phase. There were no significant differences in size of follicles among the three treatment groups. Follicular fluid concentrations of E2 and A4 in W2S were lower than those of W1S on day 2 of a follicular wave. LH infusion into cows during the midluteal phase increased follicular fluid E2 and A4 concentrations in second wave follicles on day 2 of a follicular wave (W2LH) compared to those of W2S. The increase in follicular fluid E2 on day 2 in wave 2 follicles after LH infusion occurred possibly through an increase in mRNA expression of P450c17 and 3beta-HSD. In conclusion, follicular fluid concentrations of E2 and A4 were lower in W2S than in W1S and E2 and A4 concentrations were restored by infusion of LH in W2LH with an increase in mRNA expression of P450c17 and 3beta-HSD.     

Intraluteal administration of a nitric oxide synthase blocker stimulates progesterone and oxytocin secretion and prolongs the life span of the bovine corpus luteum

To test the role of nitric oxide (NO) in secretory functions of bovine corpora lutea (CL), two groups of four Holstein heifers each were treated as follows: Group 1, Nomega-Nitro-L-Arginine Methyl Ester (L-NAME), an inhibitor of nitric oxide synthase (NOS), on Day 11 or 12 of the cycle and Group 2, L-NAME on Days 17 and 18 of the cycle. All treatments were administered by an intraluteal microdialysis system (MDS). Drugs were infused for 4-hr periods on the designated days, and the treatment periods were preceded and followed by 4-hr control periods. Perfusate and jugular blood samples were collected at half-hour intervals. Perfusate samples were analyzed for progesterone (P4), oxytocin (OT), prostaglandin F2alpha (PGF2alpha), and leukotriene C4 (LTC4); jugular plasma samples were analyzed for P4, OT, and LH. Perfusion of L-NAME on Day 11 or 12 consistently increased P4 concentration in the perfusate, but had no effect on the life span of the CL. Perfusion of L-NAME on Days 17-18 also elevated P4 levels in the perfusate, and in addition, maintained P4 levels in the plasma of three of the four treated animals through Day 25 of the cycle. L-NAME perfusion also increased OT release concomitant with P4 into the perfusate at both the mid- and late-luteal phase treatments. For the most part, concentrations of LH, OT, and P4 in the jugular plasma samples collected during the perfusions were unaffected by treatments. L-NAME perfusion caused small, but significant (P < 0.05) increases in perfusate PGF2alpha and LTC4 at Days 17 and 18 and in LTC4 on Day 11 or 12. These data indicate that NO plays a direct luteolytic role in regression of the bovine CL.     

Plasma adrenocorticotropic hormone and cortisol in pigs: effects of time of day on basal and stressor-altered concentrations

An initial study was conducted to establish the presence in plasma of diurnal rhythms of immunoreactive porcine adrenocorticotropic hormone (pACTH) and cortisol in castrated male pigs (barrows). Fourteen barrows with jugular catheters were bled at 6-hr intervals for 24 hr. Significant changes in plasma pACTH were evident with peak levels (61 +/- 6 pg/ml) at 0100-0700 hr and a trough (38 +/- 4 pg/ml) at 1900 hr. Changes (P less than 0.05) in plasma cortisol were also present in barrows with a peak (44 +/- 6 ng/ml) at 0700 hr and a trough (21 +/- 5 ng/ml) at 1900 hr. Plasma norepinephrine and epinephrine were measured at the same time intervals and did not differ among hours. In these unstressed pigs the ratio cortisol/log10pACTH at 0700 hr (25.3 +/- 3.0) was greater than the ratio at 1900 hr (12.9 +/- 2.7). Sequential blood samples were subsequently taken on four of the barrows 12 and 26 days later. Plasma pACTH was variable among pigs and did not differ among hours. Plasma cortisol on both dates was greater (P less than 0.05) in the morning (0100 or 0700 hr) than at 1900 hr. The ratio cortisol/log10pACTH at 0700 hr was repeatedly greater than at 1900 hr. A second study was conducted to determine whether plasma pACTH and cortisol responses to mild (32 degrees C for 2 hr) or strong (20-min restraint) stressors were dependent on the time of day of stressor application (0800 hr, AM; 1600 hr, PM). Response-associated parameters (maximum concentration, maximum incremental concentration, and integrated response) for pACTH and cortisol did not differ between AM and PM. However, a qualitative difference existed between the AM and PM plasma pACTH responses to restraint +32 degrees C wherein the AM response consisted of a single prolonged surge, and the PM response of an initial major peak followed by a second significant minor peak. A suggested explanation is that the initial 20-min restraint stressor potentiated the hypothalamic-hypophyseal response to 32 degrees C. These studies are the first direct measurements which suggest the presence of diurnal changes in plasma ACTH and cortisol in barrows. The studies also indicate for barrows an absence of diurnal changes in plasma epinephrine and norepinephrine. The responsiveness of the pituitary-adrenocortical axis to stressors did not exhibit quantitative diurnal changes at the time periods measured. However, it is hypothesized that the repeatable AM-PM difference in the ratio cortisol/log10ACTH reflects a diurnal change in adrenal responsiveness to ACTH in unstressed pigs.     

Diurnal migration of Echinostoma caproni (Digenea: Echinostomatidae) in ICR mice

Twenty-four female ICR mice, 12 acclimated to a 12 ∶ 12 light-dark cycle and 12 to a 12 ∶ 12 dark-light cycle for 7 days, were each infected with 10 metacercariae of Echinostoma caproni. Infected mice were maintained on their respective lighting regimes for 28 days. Six mice (3 from each group) were necropsied at 4-hr intervals beginning at 0700 hr. The small intestine was removed, opened, and the position of individual worms and worm clusters was measured to the nearest 0.1 cm. Each intestine was subsequently divided into 20 equal segments and individual worms and worm clusters were assigned to the appropriate segment based on the original measurements. All worms were found in the posterior 55% of the intestine (ileum). All posterior segments (10-20), with the exception of segment 18, harbored at least 1 worm at some time. A Monte Carlo simulation of worm abundance in segments 10-17 over all time periods indicated a random distribution, while the same analysis of segments 10-20 indicated a non-random distribution due to large numbers of worms in segment 20 and to the absence of worms in segment 18. To analyze temporal changes in worm distribution, mice were grouped by time of necropsy as follows: night (1900 and 2300 hr), morning (0300 and 0700 hr), and day (1100 and 1500 hr). During the night and morning, E. caproni was heavily concentrated in segments 10-17 and, during the day, worms were located more posteriorly, with a heavy concentration in the last segment (20).     

Circulating concentrations of inhibin-related proteins during the ovulatory cycle of the domestic fowl (Gallus domesticus) and after induced cessation of egg laying

Circulating inhibin A, inhibin B, activin A, total immunoreactive inhibin alpha-subunit (ir-alpha inhibin), LH, FSH and progesterone concentrations were measured throughout the normal ovulatory cycle and after cessation of egg laying induced by feed restriction to investigate the potential involvement of inhibins and activins in the ovulatory cycle of the domestic hen. Plasma inhibin A varied significantly (P < 0.05) during the ovulatory cycle; the concentration was highest at the preovulatory LH surge and reached a nadir 10 h later, at about the time the F(2) follicle makes the transition to become the new F(1) follicle. Plasma FSH concentrations did not change significantly throughout the cycle and showed no correlation with inhibin A. Total ir-alpha inhibin concentrations were much higher than those of inhibin A at all stages of the ovulatory cycle and showed no correlation with inhibin A or FSH. Plasma concentrations of inhibin B and of activin A were below the detection limit of the assays in all plasma samples analysed. In the feed restriction study, plasma inhibin A and total ir-alpha inhibin showed little change until the last day of oviposition (day 0) after which they fell significantly (P < 0.05) and remained low to the end of the experiment (approximately 70-78% decrease relative to day -4). Conversely, plasma FSH increased after cessation of laying and was significantly higher (P < 0.05) from day 3 to the end of the study (approximately 50% increase on day 6 relative to day -4). Plasma FSH values were negatively correlated with inhibin A (r = -0.39; P < 0.005) and total ir-alpha inhibin (r = -0.36; P < 0.005). Plasma LH and progesterone also decreased (P < 0.05) during feed restriction. The decrease in LH preceded the terminal oviposition and the associated fall in inhibin A by 2 days; there was a positive correlation between LH and inhibin A (r = 0.35; P < 0.005). Taken together these findings support (i) a role for LH in promoting inhibin A secretion by preovulatory follicles and (ii) an endocrine role for inhibin A secreted by preovulatory follicles in the maintenance of tonic FSH secretion in laying hens.     

Follicular dynamics during the ovulatory season in goats

Growth and regression of ovarian follicles>or=3 mm were studied by transrectal ultrasonography for 4 interovulatory intervals in each of 5 Saanen goats. The observed number of growing identified 4-mm follicles per day differed (P<0.05) from randomness, indicating that follicles, on the average, emerged in groups (waves). Averaged over all interovulatory intervals, the number of 3-mm follicles on each day that later reached >or=6 mm followed a pattern of significant peaks on Days 0 (ovulation), 4,8 and 14. A follicular wave was defined by consecutive days of entry of follicles>or=6 mm into the wave, and the day of emergence was defined as the first day that the >or=6 mm follicles were 3 mm. In 15 of 20 (75%) interovulatory intervals, 1 wave emerged during each of Day -2 to Day 1 (Wave 1); Days 2 to 5 (Wave 2); Days 6 to 9 (Wave 3); and Days 10 to 15 (Wave 4). Ovulation occurred during Wave 4. The mean days of emergence of Waves 1 to 4 were Days -1, 4, 8 and 13, respectively. However, in 5 of these 15 interovulatory intervals, 50% of the apparent waves merged or were continuous so that a distinction could not be made between 2 waves. The largest follicle grew to a larger (P<0.05) maximum diameter for Waves 1 (8.7+/-0.3 mm) and 4 (9.7+/-0.3 mm) than for Waves 2 (7.2+/-0.2 mm) and 3 (7.3+/-0.2 mm). The following observations suggested that the phenomenon of follicular dominance was more common during Waves 1 and 4 than during Waves 2 and 3: 1) the interwave intervals (days) were longer (P<0.05) for Waves 1 (3.4+/-0.2) and 4 (4.3+/-0.6) than for Waves 2 and 3 (2.5+/-0.2 for each wave) and 2) the correlation between maximum diameter of largest follicle and the subsequent interwave interval was significant for Waves 1 and 4 but not for Waves 2 and 3. The 5 remaining interovulatory intervals were irregular and involved more than 4 waves, including 2 interovulatory intervals with prolonged follicular phases (14 and 21) and failures of ovulation. In conclusion, the predominant follicular-wave pattern was 4 waves with ovulation from Wave 4, and apparent follicular dominance was expressed during some follicular waves, especially during Waves 1 and 4.     

Growth and DNA replication in rabbit blastocysts.

DNA content and DNA polymerase activity were measured on rabbit blastocysts removed from the uterus at 24-hr intervals over the period of days 4-7 postcoitum (pc). Median DNA content increased 53 times over the 72-hr period, from 25.3 ng on day 4 to 1,360 ng on day 7. Median DNA polymerase activity (fmole of radiolabeled nucleotide incorporated in 30 min at 37 degrees C) increased 393-fold from day 4 to day 7: 32.8 to 12,900. These embryos also increased in surface area and volume by 334-fold and 6,078-fold, respectively. Litters containing individuals with high DNA content also tended to have similar individuals with high DNA polymerase activity. Therefore, DNA polymerase activity may be a useful measure of the potential for the next cell division. A large amount of variation existed between blastocysts in all parameters measured. An analysis of variance, conducted to partition variation between litters and within litters, determined that within-litter variation was actually greater than that between litters, resulting in intraclass correlation coefficients less than 0.5. There was also a positive regression of DNA content and DNA polymerase activity on surface area in 6- and 7-day-old blastocysts after eliminating variation attributable to litters. The developmental pattern of DNA polymerase activity in the rabbit may be quantitatively different from that described in the mouse. The pattern in mammals is very different from that described in several nonmammalian species.     

The effect of constant light and phase shifts on a learned time-place association in garden warblers (Sylvia borin): hourglass or circadian clock?

Garden warblers are able to learn an association between time of day and feeding place. In constant dim light and constant food availability, the learned feeding pattern (successive visits to four feeding rooms for approximately 3 hr each) persisted for at least 1 day in three birds and for at least 6 days in one bird. The free-running feeding rhythm had a period of slightly greater than 23 hr. In response to a 6-hr phase advance of the light-dark cycle, the birds advanced their learned feeding pattern by 2.6 hr on the first day, whereas a 6-hr phase delay had no significant effect. These results are consistent with the hypothesis that the birds use a circadian clock rather than an hourglass mechanism of timing. This conclusion is further supported by the response of birds to forced interruptions of the daily feeding pattern (Krebs and Biebach, 1989).     

Associations between emergence of follicular waves and fluctuations in FSH concentrations during the estrous cycle in ewes

Folliculogenesis was studied daily in 16 interovulatory intervals in 5 Polypay ewes from mid February through April using transrectal ultrasonic imaging. The 3-mm follicles attaining > or = 5 mm on Days--1 (ovulation=Day 0) to 11 showed significant peak numbers on Days 0, 5 and 10. The number of 3- and 4-mm follicles that did not reach > 4 mm was not significant, indicating that these follicles did not manifest a wave pattern. A follicular wave was defined as one or more follicles growing to > or = 5 mm; the day the follicles were 3 mm was the day of wave emergence, and the first wave after ovulation was Wave 1. Waves 1, 2 and 3 emerged on Days -1 to 2,4 to 7 and 8 to 10, respectively. Four interovulatory intervals in April were short (9 to 14 d), indicating the end of the ovulatory season. In the remaining 12 intervals, the ovulatory wave was Wave 3 in one interval, Wave 4 in 8 intervals, and Wave 5 or 6 in 3 intervals. The ovulatory wave followed the rhythmic pattern of Waves 1 to 3 by emerging on Days 11 to 14 in 50% of the intervals. In the remaining intervals, either the ovulatory wave was Wave 4 but did not emerge until Day 16 or other waves intervened between Wave 3 and the ovulatory wave. The longest intervals (22, 24 and 24 d) had >4 waves. Based on a cycle-detection program, peak values of FSH fluctuations were temporally associated with the emergence of waves as indicated by the following: 1) tendency (P < 0.08) for an increase in FSH concentrations between 3 and 2 days before emergence of a wave; 2) close agreement between mean number of waves per interval (mean +/- SEM, 4.1 +/- 0.3) and mean number of identified FSH fluctuations (4.5 +/- 0.3); 3) close agreement in length of interwave intervals (4.0 +/- 0.3) and interpeak (FSH) intervals (3.6 +/- 0.2); 4) positive correlation (r(2)=0.8) for number of the 2 events (follicular waves and FSH fluctuations) within intervals; and 5) a closer (P < 0.01) temporal relationship between the 2 events than would have been expected if the events were independent. The results support a relationship between transient increases in FSH concentrations and emergence of follicular waves throughout the interovulatory interval in Polypay ewes, with the 2 events occurring approximately every 4 d.     

Concentrations of steroids in the utero-ovarian vein blood,serially collected from the two sides of individual baboons,during the follicullar phase

The purpose of this study was to determine and compare the follicular phase steroid hormone secretion into the utero-ovarian vein by the ovary with a dominant follicle and the contralateral ovary in the same baboon. Serial utero-ovarian vein blood from both sides was collected in 25 baboons by the use of a laparoscope on alternate days, starting on day 1 or 3 of the cycle and continuing through 2 to 3 days post-ovulation. Approximately 3–4 days before the day of expected ovulation, samples were collected at 8-hr intervals. Steroids estradiol (E₂) and progesterone (P) were measured in all utero-ovarian vein plasma by radioimmunoassay. In the peripheral plasma, E₂, P, LH, and FSH measurements were carried out. Concentrations of steroids were significantly higher on the side of the ovulating ovary by day 5 before ovulation. Individual plots however, indicated that some baboons may establish the dominant side as early as day 11 before ovulation. The preovulatory gonadotropins had a differential effect on the two ovaries. For example, E₂ values on the ovulatory side ovary declined after increases in LH/FSH, whereas on the contralateral side these values had increased. Both sides showed increases in the level of P with the increases in LH. The mean interval from E₂ peak to LH peak was 24 hrs and LH peak to ovulation was 24 hrs.     

24-hour profiles of blood pressure and heart rate in Cushing's syndrome: relationship between cortisol and cardiovascular rhythmicities

We monitored the circadian profiles of cortisol, systolic and diastolic blood pressure (SBP and DBP) and heart rate (HR) in 33 matched normotensive subjects, 32 patients with essential hypertension and 16 patients with Cushing's Syndrome (8 pituitary adenomas, 6 adrenal adenomas and 2 adrenal carcinomas). Each subject underwent serial blood drawings at 4-hr intervals along the 24-hr cycle. BP and HR were automatically recorded every 30 min. Data were analyzed by conventional statistics and by chronobiological procedures (cosinor rhythmometry). Both the control subjects and essential hypertensives showed a circadian profile of BP and HR characterized by a peak in the early afternoon and a clear nocturnal fall (rhythm detection: P less than 0.001). The rhythmicity of BP was disrupted in patients affected by Cushing's Syndrome, whereas the 24-hr oscillation of HR was preserved (P less than 0.001). Our data are compatible with the view that glucocorticoids are involved in the control of BP circadian rhythm, whereas HR is not under their control.