Androgen receptors in the rat epididymis and their hormonal control.

The concentrations of cytoplasmic receptor sites for androgens in the caput, corpus and cauda epididymidis, and the effect of ligation of the efferent ducts and testosterone treatment after bilateral castration on the concentration of receptors in the caput have been measured. Androgen receptors in the ventral prostate have been measured in the same animals for comparison. The caput has the highest concentration of receptor sites, the corpus the lowest. The ligation of the efferent ducts has no effect on this concentration which is dependent on testicular androgens. The present data do not yet allow explanation of the differential response of the different regions of the epididymis and of the other accessory glands to the administration of androgens.     

Periovulatory changes in serum concentration and ovarian content of 5 alpha-androstane-3 alpha, 17 beta-diol in the adult rat

The high amounts of 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) present in immature female rats decline towards first ovulation, but on the day of first proestrus a peak is seen. This raises the possibility that during adulthood similar proestrous peaks may occur. Therefore, serum concentrations and ovarian content of 3 alpha-diol were estimated every two hours between 0900 and 2100 h in adult cyclic rats on the day of proestrus. In the same rats, serum concentrations of estradiol (E2), progesterone (P) and luteinizing hormone (LH) were measured, as were ovarian contents of E2 and P. A significant elevation in ovarian 3 alpha-diol was found between 0900 and 1700 h proestrus, whereas serum concentrations of 3 alpha-diol were elevated from 1300 to 2100 h. The high morning values of ovarian 3 alpha-diol correlated with those for ovarian E2 (p less than 0.005); the elevated serum concentrations of 3 alpha-diol during the afternoon correlated with serum P (p less than 0.005) and with serum LH concentrations (p less than 0.005). Serum and ovarian values were positively correlated for P and E2, but not for 3 alpha-diol. The rise in serum 3 alpha-diol could be prevented by blocking the LH surge with sodium pentobarbitone (Nembutal; 35 mg/kg b.w.) administered at 1300 h. In Nembutal-treated rats, the concentration of 3 alpha-diol at 1700 h (886 pg/ml) was significantly lower than in saline-treated control rats (1135 pg/ml; p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute hormonal control of pyruvate kinase and lactate formation in the isolated rat hepatocyte.

The activity of pyruvate kinase from the isolated rat hepatocyte was studied under conditions which allow investigation into the hormonal regulation of the enzyme. Incubating hepatocytes from fed or fasted rats with 1 μm glucagon gives approximately 60% inhibition of the enzyme activity determined at 1.6 mm P-enolpyruvate. A good correlation between the regulation of pyruvate kinase and lactate formation from 10 mm dihydroxyacetone is observed in hepatocytes from fasted rats. When hepatocytes are incubated in a Krebs-Ringer phosphate buffer, the inhibition of the pyruvate kinase activity by 1 μm glucagon is not accompanied by a marked inhibition of lactate production from fructose. Half-maximal regulation is observed at 0.26 ± 0.02 nm glucagon and 0.37 ± 0.05 nm glucagon for the enzyme and lactate formation from dihydroxyacetone respectively. Incubating hepatocytes with 10 mm l-alanine enhances inhibition of pyruvate kinase by physiological concentrations of glucagon, lowering the half-maximally effective concentration of glucagon from 0.3 nm to approximately 0.1 nm. A small but consistent inhibition of pyruvate kinase by 10 μm epinephrine is also observed and this inhibition is enhanced by 0.5 mm theophylline and by 10 mm l-alanine. The inhibition of pyruvate kinase by epinephrine both in the absence and presence of theophylline is blocked by the α-adrenergic antagonist phenoxybenzamine. The β-adrenergic blocker propranolol has no influence on the inhibition of the enzyme by epinephrine. Adenosine 3′:5′-monophosphate, N⁶O²-dibutyryl adenosine 3′:5′-monophosphate, and guanosine 3′:5′-monophosphate also inhibit glycolysis from dihydroxyacetone and modulate pyruvate kinase activity in hepatocytes from fasted rats. Oleate, ethanol, and 3-hydroxybutyrate inhibit dihydroxyacetone glycolysis, but they do not influence the activity of pyruvate kinase. The divalent metal ionophore A23187 slightly stimulates lactate synthesis from dihydroxyacetone, but it has no influence on pyruvate kinase activity.     

Periovulatory changes in female sexual behavior and patterns of ovarian steroid secretion in group-living rhesus monkeys

The behavior of nine intact group-living adult female rhesus was observed for 30 min daily with each of four adult male rhesus across a verified ovulatory menstrual cycle. Blood samples collected from females daily or on alternate days were analyzed for estradiol, testosterone, and progesterone. Female patterns of approach, follow, and initiate proximity increased several days prior to the estradiol peak, peaked on the day of the estradiol peak, then declined completely or to very low frequencies. Mounts, intromissions, and ejaculations increased significantly on the day of the estradiol peak, remained elevated for 2 more days, then declined completely by the fifth day after peak estradiol. Ejaculations never occurred outside of a 10-day period starting 4 days before the estradiol peak and ending 5 days after the estradiol peak. During this period females initiated over 90% of all approaches. Female hand slap, threaten away, and stand up increased significantly on the first day of increased copulation, remained elevated while copulation was significantly elevated, then decreased along with the decline in copulation. Ten of eleven patterns of female behavior correlated significantly with estradiol level prior to the estradiol peak. All were significantly inversely correlated with progesterone level after the estradiol peak. No pattern of female behavior correlated significantly with testosterone either before or after the estradiol peak. Similarly, male patterns of behavior correlated with female levels of estradiol and progesterone, but not testosterone. These results demonstrate a relationship between increased serum estradiol and increased female initiation of sexual behavior. The finding that some patterns of female behavior increase several days prior to copulation, whereas other behaviors increase coincident with increased copulation suggests that the behavior of group-living rhesus females serves two functions. The first is to communicate sexual interest and the second is to maintain the consort pair and increase the probability that ejaculation will occur. In addition, the strong correlation between preovulatory female behavior and estradiol level suggests that the female's behavior provides precise information about her reproductive state and could thus coordinate copulation with maximal fertility.     

Intratesticular steroid levels and their hormonal control

Litter-mate adult male rats were treated with daily intramuscular injections of ACTH (10.5 micrograms), dexamethasone (2.0 mg), ethynyl estradiol (1.7 micrograms) and hCG (5 IU) for three consecutive days. The animals were sacrificed on the fourth day and the intratesticular and peripheral plasma steroid levels were analyzed. The steroids measured by radioimmunoassay included pregnenolone, 17-hydroxypregnenolone, dehydroepiandrosterone, progesterone, 17-hydroxyprogesterone, androstenedione, testosterone and dihydrotestosterone. In addition, the sulphoconjugated forms of pregnenolone, dehydroepiandrosterone, testosterone and dihydrotestosterone were estimated in the peripheral blood. The administration of ACTH diminished the intratesticular levels of all steroids studied. Also dexamethasone and ethynyl estradiol treatment suppressed all intratesticular steroid levels, except that of pregnenolone (the former) and of 17-hydroxyprogesterone (the latter). The suppressive effect of ethynyl estradiol was strongest on the levels of the delta 5-steroids and that of dexamethasone on the delta 4-steroids; the latter was significantly stronger than the effect of ACTH. The stimulatory effect of hCG was limited to the metabolism of progesterone and was restricted to the sequence: 17-hydroxyprogesterone----androstenedione----testosterone---- dihydrotestosterone. Dexamethasone-suppression, and hCG-stimulation of the intratesticular levels of delta 4-steroids, was mirrored by corresponding changes in the peripheral plasma levels, with the exception of the plasma levels of androstenedione which were not influenced by any of the treatments studied. Also the suppression of intratesticular testosterone and dihydrotestosterone levels by ACTH, dexamethasone, or ethynyl estradiol was closely reflected by their plasma levels both in the unconjugated and sulphoconjugated forms. On the hand, the administration of ACTH diminished the intratesticular levels of pregnenolone and progesterone but significantly increased those in the plasma. Moreover, both ACTH and ethynyl estradiol reduced the levels of all delta 5-steroids in testicular tissue, but not in the peripheral plasma, although they decreased the circulating levels of pregnenolone sulphate and dehydroepiandrosterone sulphate. The data are interpreted as suggesting that the hormonal agents studied interfere with testicular steroidogenesis through different mechanisms.     

Environmental and hormonal control of turion formation in Myriophyllum verticillatum

The turions of Myriophyllum verticillatum, an aquatic vascularplant, develop in the fall and function in propagation and dispersalas well as in over-wintering. Experiments with controlled evnironmentsindicate that both temperature and photoperiod regulate turionformation. Turions can be induced at 15°C or lower, butnot at 20°C. At 15°C, turions form in both 8- and 12-hrdays, but not in 16-hr days. Plants collected in early springdo not form turions readily in response to short days unlesspreviously exposed to long days; thus, turion formation is along-day-short-day response. This combination of photoperiodand temperature requirements probably prevents turion developmentin early spring when the temperature and photoperiod are similarto those in the fall. Treatment of plants with ABA (10^–5M) enhances turion development under marginally inductive conditions(12-hr days at 15°C) but cannot induce it under long days.On the other hand, the cytokinin benzyladenine (10^–5 M)blocks turion formation. GA3 (10^–5 M) and AMO-1618 (10^–5M) exert only small qualitative effects on turion development,while IAA (10^–5 M) retards it. During turion development,the level of ABAlike activity and of one or two unidentifiedinhibitors increases. Cytokinin activity decreases at the startof turion formation, increases during development, then decreasesat abscission. Thus two lines of evidence suggest that a decreasein cytokinin activity and an increase in acidic inhibitor activityplay important roles in turion induction. ¹Present address: Biological Station, University of Michigan,Ann Arbor, Michigan 48109, U. S. A. (Received December 1, 1975; )     

Cellular localization of ovarian prostaglandin endoperoxide synthase during pseudopregnancy in the rat

The specific cellular localization of prostaglandin endoperoxide (PGH) synthase, the enzyme responsible for initiating the conversion of arachidonic acid to prostaglandins, was studied throughout pseudopregnancy in the rat. Pseudopregnancy was induced by administration of eCG (20 IU) to immature, 27-day-old rats followed by hCG injection (10 IU) on Day 29. Animals were necropsied on Days 1 (Day 1 = 1 day post hCG), 5, 9, and 13 of pseudopregnancy. Ovaries were removed and processed for cellular identification of PGH synthase by immunohistochemistry. Immunoreactive PGH synthase was distributed throughout the CL at each of the 4 different days of pseudopregnancy, with the majority of the luteal cells exhibiting varying degrees of staining. The connective tissue centrum of the CL, however, lacked PGH synthase immunoreactivity. Quantitative assessment of the immunostaining distribution was accomplished with a computer-based image analysis program (Kontron IBAS). Results are expressed as the percentage of a digitized luteal area that contained intense immunoreactivity between Day 1 (0.6 +/- 0.2% immunoreactive area) and Day 5 (16.8 +/- 2.7%) of pseudopregnancy. The area of luteal immunostaining was similar on Day 5 and Day 9 (16.8 +/- 2.7% and 14.7 +/- 2.0%, respectively) followed by a decrease (p less than 0.05) in immunoreactivity on Day 13 (9.1 +/- 2.2%). The region of the CL adjacent to the germinal epithelium had an increase (p less than 0.01) in PG synthase staining distribution compared to the region of the CL adjacent to the ovarian medulla on all days of pseudopregnancy except Day 1. These findings demonstrate that PGH synthase is present in the rat CL throughout pseudopregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Release of prostaglandin from rat epididymal fat pad on nervous and hormonal stimulation

Acidic lipids with smooth muscle-stimulating properties were extracted from rat epididymal fat pads and were shown to co-chromatograph with (PGE1) prostaglandin E1, PGE2, and PGF2alpha. Further chemical identification was not possible with the small amounts of material available. A basal efflux of PGE and PGF compounds was observed following incubation of adipose tissue in vitro. Increased efflux of PG was detected under conditions reported to enhance free fatty acid release, i.e., addition of lipolytic hormones or drugs to the incubating medium, prior fasting of the animal, or stimulation of the epididymal nerve. These results, together with a decreased release of PG-like material in the presence of insulin, suggested that the efflux may be associated with lipolysis resulting from activation of a hormone-sensitive lipase. Since the PGs are known to affect the concentration of cyclic adenosine 3', 5'-monophosphate in adipose tissue, and this nucleotide is an intermediary in hormone-stimulated lipolysis, it is possible that the PGs released may serve to maintain the homeostasis of adipose tissue by way of a physiological feedback control mechanism.     

Periovulatory changes in the local release of vasoactive peptides, prostaglandin f(2alpha), and steroid hormones from bovine mature follicles in vivo

We previously proposed that an endothelin-angiotensin-atrial natriuretic peptide system may contribute to inducing ovulation of mature bovine follicles by modulating follicular secretion of steroids and prostaglandins (PGs). Thus, this study aimed to determine the real-time changes in the local release of angiotensin II (Ang II), endothelin (ET), atrial natriuretic peptide (ANP), PGF(2alpha), and steroid hormones from bovine mature follicles during the periovulatory period in vivo. Seven cows were treated for superovulation using FSH and PGF(2alpha) injections. Two dialysis capillary membranes per follicle were surgically implanted into the theca layer of mature follicles and connected to a microdialysis system (MDS). Fractions of the perfusate were collected from Day -1 (Day 0 = LH surge) to Day 3. Five out of seven treated cows were normally ovulated, and the newly formed corpora lutea were observed at the end of the experiment. In these five ovulated cows, the release of estradiol, androstenedione, and progesterone in the theca layer increased (P < 0.05) synchronously with the LH surge. Acute increases in PGF(2alpha) and Ang II concentrations in the ovarian venous plasma (OVP) were observed at 24-48 h after the peak of the LH surge, when multiple ovulations were expected to occur. The follicular Ang II release was low during the pre-LH surge period and rose (P < 0.05) at the beginning of the increase in the LH surge. On the other hand, ET-1 release dropped (P < 0.05) when plasma LH started to increase. However, no clear changes in ANP concentration in the MDS perfusate and plasma were observed. The above local changes in Ang II, PGF(2alpha), as well as steroid hormones were not observed in cows (n = 2) that did not show an LH surge and ovulation. The present results demonstrate for the first time the local release of Ang II, ET-1, and ANP from the bovine mature follicle in real-time in vivo and show that Ang II and PGF(2alpha) concentrations in the OVP acutely increase around the time of ovulation. The overall results support the concept of a local functional ET-Ang-ANP system in the bovine mature follicle that may be involved in the ovulatory process.     

Angiogenesis and its hormonal control in the corpus luteum of the pregnant rat

Beginning on Day 8 of pregnancy (Day 1 = sperm in vaginal smear), rats were injected i.p. with [3H] thymidine (TDR), killed 3 h later, and corpora lutea (CL) were dissected and saved for determining radioactivity in the acid-insoluble fraction or for autoradiography to determine labeling index (LI) of luteal and endothelial cells. An approximate doubling in DNA content in CL occurred between Days 13 and 14, with a high level maintained through Day 23. This was reflected in an abrupt increase in [3H] TDR incorporation on Day 13, with the peak reached on Day 14 and a subsequent decline to baseline values on Day 18. Autoradiography revealed that the LI of luteal endothelial cells rose from 2.1% on Day 12 to 10.0% on Day 14, and the LI of luteal cells correspondingly increased from 0.3% to 2.3%. Hypophysectomy (H) on Day 12 resulted, by Day 14, in no change in serum progesterone (P4) and TDR incorporation and LI of endothelial cells. However, after H and hysterectomy (HS) on Day 12, by Day 14, animals had low values for LI of endothelial and luteal cells, [3H] TDR incorporation and serum P4. After H + HS at Day 12, animals injected daily with estradiol cyclopentylpropionate (200 micrograms/day) on Days 12-14 had serum P4, [3H] TDR incorporation and LI of endothelial cells comparable to intact controls but not to luteal cells. However, similar treatment with testosterone cypionate (200 micrograms/day) or P4 (10 mg/day) did not maintain [3H] TDR incorporation or LI of either cell type, although serum P4 and estradiol levels were restored to normal values.(ABSTRACT TRUNCATED AT 250 WORDS)     

Periovulatory changes in the endoscopic appearance of the reproductive tract and teasing behavior in the bitch

A variety of diagnostic techniques have been applied to address the problem of determining optimal mating time in the bitch, although some have not been objectively investigated. Nine healthy bitches were examined daily using routine clinical methods as part of their normal breeding management with the aim of establishing which method was most useful. Accordingly, measurement of the degree of vulval swelling, endoscopic measurement of the vaginal mucosal color and appearance, and objective evaluation of behavior of the bitch were related to the time of ovulation (calculated when progesterone reached 5 ng/mL; Day 0) and the duration of the fertilization period (Day 2 to Day 5) determined by measurement of plasma progesterone concentration and assessment of vaginal cytology. There was a surprisingly large individual variation in measurements of vulval swelling, such that although trends were apparent this technique was not precise enough to establish the optimal mating time. However, measuring color saturation and vaginal mucosal fold width was successful. A consistent change in the mucosal color saturation was observed that related to the beginning (Day −5) and duration of the fertile period although there was no difference in measurement of color saturation between Day −5 and Day 2 (P = 0.31), and Day 2 and Day 5 (P = 0.43). The vaginal mucosal folds were smaller in width at the beginning of the fertilization period (Day 2) than at the beginning of the fertile period (Day −5) (P = 0.008), and all bitches had a consistent appearance of mucosal contours on Day 3. Assessment of sexual behavior was not considered precise enough to enable determination of the optimal time for mating because of the large amount of individual variation in behavioral scores. There was no difference in female behavior scores between Day −5 and Day 2 (P = 0.29), or between Day 2 and Day 5 (P = 0.06). Using objective techniques this study has quantified changes in the color and fold width of the vaginal mucosa that have previously only been subjectively reported. These changes can be used to identify the fertilization period and it is possible, with future refining of the technique, that endoscopic examination could replace vaginal cytology to be used in conjunction with plasma progesterone concentration when examining bitches to determine the optimal time to breed.     

Morphological changes of the ovary and hormonal changes through the ovarian cycle of the common marmoset (Callithrix jacchus)

Laparoscopic observations of morphological changes of the ovary during the ovarian cycle in conjunction with radioimmunoassay of serum progesterone and estradiol-17β was investigated as a method of monitoring the ovarian cycle in the common marmoset. In the common marmoset, plural follicles first appeared in each ovary five days prior to ovulation. At three to four days prior to ovulation one or two follicles developed into translucent blisters on the surface of the ovary. As the follicles filled with follicular fluid, they became larger and clearer until one to two days prior to ovulation, at which time they formed well defined, transparent bubbles protruding from the surface of the ovary. After ovulation, the ovulation point could be detected at the center of the follicle, sometimes surrounded by a corpus of engorged blood vessels. Ovulations of the plural follicles were not simultaneous, and due to the time lag ovulations took at least 12 to 20 hrs in four out of seven animals examined. After two to five days of ovulation the corpus hemorragicum, a bright red protrusion made of tissue and blood disrupted by ovulation, was found. Subsequently, the color of the formatted corpus luteum changed from dark-red to yellow then to yellow white. While the corpus luteum remained reddish in color serum progesterone was maintained at as high levels as in the luteal phase. There was no mature follicle or corpus luteum in subordinate female ovaries.