Preovulatory Females Research Articles

Reproductive Conditions of the Atlantic Sturgeon (Acipenser oxyrinchus) in the Hudson River

Ninety-four prespawning adult Atlantic sturgeon (Acipenser oxyrinchus) were sampled in the Hudson River for age, sex, body size, gonad weight, fecundity, mature oocyte size, and plasma concentrations of gonadotropins, sex steroids, and vitellogenin during the spring spawning migrations in 1992 and 1993. In males, the age and total length ranged from 12 yr to 19 yr and from 133 cm to 204 cm and in females from 14 yr to 36 yr and from 197 cm to 254 cm. The majority of males were 13–16 yr old, and females were 16–20 yr old. Some females had residual atretic ovarian bodies, presumably remaining from a previous spawning and indicating iteroparity. Pre-ovulatory condition was recognized by migration of the germinal vesicle or by germinal vesicle breakdown and by significantly elevated plasma gonadotropins, progesterone, and vitellogenin. All pre-ovulatory females were captured upriver from Hudson River kilometer 136. Individual fecundity ranged from 0.4 million to 2.0 million eggs and oocyte diameter from 2.4 mm to 2.9 mm, and both characters exhibited a significant (p<0.05) positive relationship with female body size. Iteroparous females, tentatively identified by the presence of atretic bodies remaining in the ovary from a previous spawning, had significantly (p<0.05) higher fecundity and produced larger eggs, compared with females spawning presumably for the first time.

Overripening as the cause of low survival to hatch in Lake Erie coho salmon (Oncorhynchus kisutch) embryos

We investigated the cause of the low survival to hatch of embryos of coho salmon (Oncorhynchus kisutch) from the Fairview, Pennsylvania, stock in Lake Erie. In 1988, survival to hatch of this stock was only 42%, whereas another Great Lakes coho salmon stock of similar genetic origin had an 84% survival to hatch. Laboratory cross-fertilization studies between the Fairview stock and a reference Lake Erie stock from Simcoe, Ontario, showed that eggs from the Fairview stock were the probable source of the low fertility. The presence of overripe eggs in Fairview females was associated with poor fertilization and low survival to hatch. Plasma gonadotropin II levels were similar in preovulatory females taken from the Fairview and Simcoe stocks, but testosterone and 17α, 20β-dihydroxy-4-pregnen-3-one levels were significantly lower in the Fairview females. Increasing the triiodo-L-thyronine (T3) content of the eggs by the administration of T3 to the preovulatory females did not enhance egg fertility. We propose that the low survival to hatch of the Fairview embryos is due to delayed oocyte maturation and ovulation and vent maturation, which may have been caused by exposure of the Fairview salmon to warmer water during the period of late ovarian maturation and migration.

Physiological evidence for two sturgeon gonadotrophins in Acipenser transmontanus

Physiological evidence in white sturgeon Acipenser transmontanus suggests that two gonadotrophins, termed sturgeon gonadotropin I (stGTH I) and sturgeon gonadotropin II (stGTH II), are involved in regulating reproduction. Pituitary and plasma concentrations of stGTH I were found to be higher than concentrations of stGTH II during vitellogenesis and the early stages of spermatogenesis. Conversely, pituitary and plasma concentrations of stGTH II were greater compared with stGTH I during ovulation and spermiation. The gonadotropin releasing hormone analog D-Ala 6-des-Gly 10-GnRH ethylamide (GnRHa) was effective in stimulating the release of both gonadotrophins in mature males and preovulatory females, with a maximal response occurring in the spring. Collectively, the data supports our view that sturgeon possess a dual gonadotropin system controlling reproduction.

Reproductive Cycle of the American Alligator

The reproductive cycle of the American alligator, Alligator mississippiensis , was studied using blood and tissue samples from wild alligators, and blood samples drawn from a captive breeding stock at the Rockefeller Wildlife Refuge in Louisiana. Generally the cycle commences in March as air and water temperatures increase. By early April the seminiferous tubules are full of actively dividing spermatocytes and maturing spermatids. Testis mass is greatest at this time and plasma testosterone is at a peak (>50 ng/ml), but mature spermatozoa do not appear until late April and mid May when mating takes place. Plasma testosterone levels decline rapidly in June after spermiation, and are low to nondetectable in July and August when the testes are fully regressed. A second small peak in testosterone occurs in September without any obvious changes in testicular histology. In the female a similar temperature dependent initiation of the ovarian cycle occurs in late March. Plasma estradiol levels reach a peak (>600 pg/ml) in mid April, and ovarian follicles increase from 5 mm to 45 mm in diameter at ovulation in May. Plasma testosterone is also high in preovulatory females (ca. 1.5 ng/ml). Plasma progesterone shows a periovulatory surge to levels as high as 16 ng/ml, but declines rapidly during the 3½ wk between ovulation and oviposition. During egg incubation (66 days) when the female remains close to the nest, ovarian steroids remain undetectable.

The stimulatory and inhibitory role of the hypothalamus in the regulation of ovulation in grass frog, Rana temporaria L

In our previous experiments it was found that lesions placed in the infundibular hypothalamus induced an advanced ovulation in hibernating frogs, Rana temporaria. It was suggested that this premature ovulation was the effect of gonadotropin-releasing hormone (GnRH) due to the injury of some hypothalamic area inhibiting its release or its action on the pituitary gonadotrophs. To investigate this hypothesis, the following experiments were undertaken: (1) an attempt to induce ovulation with exogenous GnRH in hibernating frogs; (2) an attempt to inhibit ovulation with anti-GnRH serum in preovulatory hibernating animals nonlesioned and with lesions of the infundibular hypothalamus; and (3) administration of bromocriptine in hibernating animals to assess whether this substance, as an agonist of dopamine, possesses an inhibitory action on the ovulation. The following results were obtained: (1) lesions of the infundibular hypothalamus in hibernating preovulatory females caused an advanced ovulation during hibernation; (2) the exogenous GnRH administered to p preovulatory females induced ovulation during hibernation; (3) the anti-GnRH serum injected into hibernating preovulatory lesioned females inhibited preterm ovulation during, but not after, hibernation; (4) the immunoneutralization of endogenous GnRH in nonlesioned females resulted in an inhibition of the posthibernatory ovulation; (5) bromocriptine inhibited posthibernatory ovulation in nonlesioned hibernating animals. Thus, the results of these experiments support the suggestion that induction of accelerated ovulation in lesioned hibernating animals involved the releasing action of GnRH. This action of GnRH seemed to be facilitated by the ablation of inhibitory dopaminergic function of hypothalamus in lesioned animals.

Female Color Change in the Keeled Earless Lizard, Holbrookia propinqua: Relationship to the Reproductive Cycle

The orange and yellow coloration of female Holbrookia propinqua appears to be closely associated with ovarian events, intensifying rapidly during the final stages of vitellogenesis and reaching maximum brightness prior to ovulation. All females having recent corpora lutea or bearing oviducal eggs retained bright colors. Females with the dullest colors lacked orange and yellow pigmen- tation, had relatively small follicles, and were at early stages of the reproductive cycle. Further studies are needed to determine the course of chromatic variation between successive reproductive cycles and to evaluate the turn-on and turn-off hypotheses of the adaptive value of the female reproductive colora- tion. Distinctive changes in color pattern associated with reproduction occur in female iguanid lizards of several genera, including Crotaphytus (Cooper and Ferguson, 1972a, 1972b, 1973),Holbrookia (Clarke, 1965; Judd, 1973), Gambelia (Medica et al., 1975) and Sceloporus (Dixon, 1957). Female reproductive colora- tion may be induced by progesterone or testosterone injections and its onset may be hastened by estrogen injection in Crotaphytus collaris (Cooper and Ferguson, 1972a, 1972b, 1973) and Gambelia wislizeni (Medica et al., 1973). Although a hormonal basis for pigment depositions is well established, possible roles of the colors in reproductive behavior remain speculative and little is known regarding the relationships of the colors to reproductive cycling. Gravid females often show the most intense pigmentation (Judd, 1976; Fitch, 1956; Medica et al., 1973), usually orange to red, but the timing of pigment deposition with respect to courtship, copulation, follicular development, oviposition, and luteal activity remain largely unknown in most species. Only in Crotaphytus and Gambelia have some of these relationships been studied. Female C. collaris develop orange lateral spots, changing from a dull, non-breeding pattern to maximum birght- ness in a single day. This rapid color change occurs in preovulatory females approximately 10-13 days before oviposition (Ferguson, 1976; Fitch, 1956). Max- imal color intensity in G. wislizeni is also established during vitellogenesis, prior to ovulation (Medica et al., 1973). In this paper, intensity of orange and yellow pigmentation is correlated with reproductive state in the keeled earless lizard, Holbrookia propinqua, and impli- cations of this relationship for hypotheses about the adaptive significance of the coloration are discussed.

Measurement of 17α,20β-dihydroxy-4-pregnen-3-one in plasma of trout ( Salmo gairdneri Richardson): Seasonal changes and response to salmon pituitary extract

A simple direct radioimmunoassay for 17α,20β-dihydroxy-4-pregnen-3-one in plasma of female rainbow trout was developed. Two antisera were evaluated and both were found to be highly specific. High levels of the steroid (ca. 400 ng ml −1) were found during ovulation. 17αOH-Progesterone levels were also high, but testosterone and 17β-oestradiol levels were lower than in preovulatory fish. Injections of salmon pituitary extracts into preovulatory females (to induce premature ovulation) raised plasma levels of 17α,20β-dihydroxy-4-pregnen-3-one from <10 to 250–780 ng ml −1.

Female sex pheromone of the Ayu, Plecoglossus altivelis, involved in courtship behaviour.

This report deals with the courtship behaviour and the presence of a female sex pheromone of the Ayu, Plecoglossus altivelis. Increased ventilatory frequencies and fin display reactions in the male Ayu were elicited by the water sample inclusive of post-ovulatory females. It was noticed that the males were able to discriminate post-ovulatory females from pre-ovulatory females without actually sighting the female. Some highlighted aspects derived from these experiments are listed as follows; 1. Post-owlatory females released a female sex pheromone, which males detect by olfaction. 2. The female sex pheromone, produced in the ovaries of post-ovulatory females, is secreted through the urogenital papilla. 3. The female sex pheromone was found to be a water-ether soluble basic substance, having an Rf value of 0.43 on the thin layer chromatogram (silica gel) with a chyclohexane-ethyl alcohol (4:1) solvent. 4. The female sex pheromone from post-owlatory females played the role of first trigger, inducing a series of courtship behaviour of the Ayu.

Surface morphology in the ofactory epithelium of normal male and female rhesus monkeys.

Olfactory epithelium of male and female rhesus monkeys has been studied by transmission electron microscopy. It is shown that the epithelial surface differs greatly between male and female monkeys. Differences are most prominent between male and preovulatory females. During the ovulatory phase of the ovarian cycle remarkable histological alterations occur especially in the sustentacular cells. These alterations are correlated with physiological and behavioral phenomena demonstrating a possible structural basis for the changes in olfactory threshold in relation to sex hormones.

A specific radioimmunoassay of plasma progesterone.

ABSTRACT A specific progesterone antibody was obtained by immunizing a ewe with 11α-hydroxy-progesterone-hemisuccinate conjugated to bovine serum albumin. This antibody was used for the assay of progesterone in crude plasma extracts. The sensitivity of the assay was 0.05 ng. The accuracy was confirmed by the recovery of known amounts of progesterone added to plasma. The inter- and intra-assay coefficient of variation was 8%. Specificity was confirmed by a) checking cross reactivity of various steroids; b) failure of other steroids added to plasma to influence the accurate measurement of progesterone, and c) finding comparable progesterone levels in plasma extracts with and without chromatography. Mean values of progesterone (ng/ml) were 0.26 ± 0.08 (sd) in males and postmenopausal females; 0.50 ± 0.44 in preovulatory females; and 12.1 ± 4.81 in postovulatory females.