Natural Reproductive Cycle Research Articles

2 In vitro fertilization in the natural cycle

In vitro fertilization in the natural or spontaneous reproductive cycle was first described by Edwards and his colleagues in 1980 following the birth of their first natural cycle IVF baby 2 years earlier. Many groups attempted to follow their lead but it was almost ten years later that the next publication of success appeared (Foulot et al, 1989). The concept of IVF in the natural cycle is particularly attractive and so in 1987 our group also started evaluating the technique. Initial success in the patients with tubal lesions was not translated to patients with other infertility indications. Unfortunately the technique as initially developed was relatively inefficient with significant procedural losses at each stage. Over the succeeding four years a number of changes have been introduced and the efficiency considerably improved. Although these changes have improved take-home baby rates, overall pregnancy rates per embryo have not altered and are still lower than spontaneous in vivo pregnancy rates. It is likely that in the future, with current developments in culture techniques and greater understanding of gamete biology, this situation will change significantly.

Oviductal morphology and egg shelling in the oviparous lizards Crotaphytus collaris and Eumeces obsoletus.

Morphological changes occurring in the oviduct and epithelial cells of the lizards Crotaphytus collaris and Eumeces obsoletus during the natural reproductive cycle were examined and quantified. Additionally, development of the eggshell at different stages of gravidity was described. The anterior uterus of each species has a distinct glandular type which differs between species: in E. obsoletus, the glands are tubular and in C. collaris, branched saccular. The branched saccular glands in the anterior uterus of C. collaris produce collagen-like material that forms the fibers of the shell membranes. However, fibers from the eggshell of E. obsoletus did not stain for collagen. The shell of both species is composed of a multilayered inner boundary covered externally by fibers of varying thickness. Initial layers are composed of thick fibers all lying along the same general axis. Outer layers of fibers are progressively thinner and an external surface layer composed of glycosaminoglycans (GAGs) is also present. In C. collaris, calcium, which is deposited in relatively small amounts on the shell surface, appears to be secreted by the epithelium of the anterior uterus. The nonciliated secretory epithelial cells covering the villi-like folds of the posterior infundibulum secrete GAGs. Epithelial cell height of the infundibular villi is greatest during early gravidity. A functional relationship may exist between luteal activity and oviductal secretory activity because the activity of the glandular epithelium varied as gravidity progressed.

Environmental Control of Seasonal Reproduction in a Parthenogenetic Lizard Cnemidophorus uniparens

Previous studies of the parthenogenetic whiptail lizard Cnemidophorus uniparens have provided the best evidence for an endogenous circannual rhythm of reproduction in a reptile. However, these studies were restricted to captive animals on constant photothermal conditions. We report the results of field and laboratory studies indicating that timing of reproduction is dramatically affected by seasonal temperature change. Our field data show that between-year variations in timing of breeding in natural populations are correlated with between-year variations in spring temperatures. Our laboratory data demonstrate that reproduction is delayed and synchronized by exposure to winter-like photothermal conditions. Thus, temperature appears to be the most important environmental cue regulating timing of reproduction in this species. However, the conclusion of previous studies that the natural reproductive cycle is controlled by a circannual rhythm is equivocal and requires further study.

Photoperiodic control of seasonal reproduction in tropical weaver bird

AbstractExperiments were performed in order to provide information on the extent of involvement of daylength, if any, in the control of seasonal breeding in the tropical weaver bird. The reproductive cycle was completely abolished in both short and long photoperiods. The cycle was suppressed in short photoperiods, and in long photoperiods gonads were maintained in a stimulated state indefinitely. These results indicated a definite photoperiodic requirement for gonadal development in the weaver bird. the photoperiodic response threshold was found to be 11 hours daily. Gonads in a period of 12L/12D exhibited cyclicity, though at a low level, indicating that a light period of 12 hours daily allows gonadal regression which is abolished in longer photoperiods. On correlating these laboratory observations with the natural reproductive cycle, it seems that the annual timing of reproduction in the weaver bird may coincide with the time in the spring when the increasing day length reaches the photoperiodic response threshold.

Effects of day length and endogenous control on the annual reproductive cycle of the antelope ground squirrel,Ammospermophilus leucurus

1. Male antelope ground squirrels were removed from the field in fall, winter, spring, and summer and separate groups exposed for 50 days each to photoperiods of 16 h (LD 16∶8) and 8 h (LD 8∶16) and ambient temperature of 23 ‡C. Control samples from the field were obtained at the beginning and end of each of these experiments. A single experiment was conducted with females in winter. 2. At no time of year was there a significant difference (P>0.05) in the mass or condition of reproductive tissues of animals exposed to LD 16∶8 and those exposed to LD 8∶16. The changes in both long-day and short-day groups during each experiment paralleled the natural seasonal reproductive cycle, with a peak in late winter and early spring. 3. In association with an annual cycle of body mass,A. leucurus showed significant seasonal differences in the tendency to increase body mass and gonadal fat when held in captivity; however these responses were also unaffected by differences in experimental photoperiod. 4. Because the 50-day manipulations of photoperiod did not affect testicular activity at any season, we conclude that the annual gonadal cycle ofA. leucurus is under endogenous control. Factors that may have been involved in the evolutionary history of this adaptation are discussed.

Effects of pinealectomy on gonadal activity in the cyprinid teleost, Notemigonus crysoleucas

Investigations were initiated to examine the effects of pinealectomy on gonadal activity in the cyprinid teleost, Notemigonus crysoleucas, during different phases of the reproductive cycle and maintained under different photoperiod-temperature regimes. The effects of pinealectomy varied depending on the phase of the natural reproductive cycle when the organ was removed, as well as, with the photoperiod-temperature regime under which the experimental animals were maintained. Pinealectomy causes testicular regression during the gonadal preparatory and prespawning season and retards final testicular maturation during the spawning season in fish maintained on a long photoperiod-warm temperature regime. Under these conditions epiphysectomy retarded ovarian development or caused ovarian involution during all phases of the gonadal maturation cycle. In Notemigonus maintained on a long photoperiod-low temperature regime, pinealectomy had no apparent effects on gonadal development during the preparatory and spawning seasons. During the prespawning season pinealectomy repressed ovarian development and caused testicular regression in fish exposed to a long photoperiod-low temperature regime. During the prespawning and spawning seasons pinealectomy stimulated gonadal activity in fish maintained on a short photoperiod-warm temperature regime. Under these same conditions epiphysectomy failed to alter gonadal activity during the gonadal preparatory season. No obvious changes could be detected in gonadal activity in pinealectomized fish exposed to short photoperiodlow temperature regimes during any phase of the gonadal maturation cycle. These data suggest that the pineal in Notemigonus may be either stimulatory or inhibitory to gonadal development depending on the photoperiod-temperature regime to which the fish are exposed.

The reproductive cycle of the viviparous seaperch, Cymatogaster aggregata Gibbons

The natural reproductive cycle of male and female Cymatogaster aggregata is described with reference to gametogenesis, development of secondary sex structures, reproductive behavior, and gestation. Spermatocytogenesis starts in early spring and by June or July clusters of spermatozoa fill the seminiferous tubules. Concurrently the Sertoli cells and interstitial cells of Leydig increase in size and secondary sex structures develop on the male anal fin. When the sexes mingle in summer, the males perform very elaborate reproductive behavior. Fertilization occurs about mid-December—5 months after mating—and the ovary is then modified to maintain the young embryos until parturition in mid-summer. Oocyte formation is highest in July and August, just after parturition, while vitellogenesis and oocyte maturation occur mainiy from October to December. These seasonal changes are discussed in relation to changes in environmental temperature and photoperiod.

Seasonal variations in the hormone content of the pituitary gland of the perch, Perca fluviatilis L

Lyophilized pituitary brei of Perca fluviatilis, taken from Windermere at seasonal intervals, was administered to hypophysectomized male Fundulus heteroclitus by intraperitoneal injection, thrice weekly for 6 weeks, at 100 μg in 0.01 ml of 0.6% NaCl per gram weight of fish. Two control groups received 0.6% NaCl and standard beef growth hormone (NIH-GH-Bi, 20 μg/gm), respectively. Stimulation of growth in length, supplemented by parallel data on weight and scale-width increments, was equivalent to 20–50 μg GH-B6 during the autumn and winter months. A significant increase in growth-promoting potency in April was followed by a maximum in June, equivalent to 250 μg of GH-B1. A decline in July was followed by near total exhaustion of the growth-promoting potency of the perch pituitary in August. The maximum accumulation of growth hormone in the hypophysis preceded the estimated natural growth peak of the perch by 4–6 weeks. No such lag was observed in respect to the gonads: maximal gonadotrophin content of the hypophysis, reflected in stimulation of regressed testes and onset of nuptial coloration in the assay fish, coincided with the peak of the natural reproductive cycle in April. In August the pituitary was depleted of gonadotrophin. The thyrotrophic activity of the perch pituitary followed a similar cycle, of lesser magnitude. Perch pituitary preparations maintained adrenal cortical histology at near normal, except in July; and stimulated the restoration of melanin pigment, proliferation of new melanocytes, and the spawning reflex response.