Gonadal development and associated changes in liver size and sexual steroids during the reproductive cycle of captive male and female Atlantic cod (Gadus morhua L.)

Gametogenesis in female and male Atlantic cod (Gadus morhua L.) was investigated by sampling blood plasma and gonadal tissue from 19 to 33-month-old fish. The reproductive cycles of both female and male Atlantic cod are characterized by distinct annual variations in gonadal size and developmental stage and these are associated with changes in sex steroids and liver size. I(H) did not change during early gonadal development, but both spent females and males had lower I(H) than late maturing females and spermiating males, respectively. In females I(G) was correlated to plasma E2 levels and they were highest in spawning females. The lowest levels during the reproductive cycle were observed in spent females. Plasma T levels were low throughout ovarian development, and were at a minimum in spent females. 11-ketotestosterone in plasma of males increased rapidly during spermiation, while T increased at earlier testicular stages and reached maximum during spermiation. High plasma levels of steroids in male and female cod during spawning serve to promote further development and growth of less advanced stages of germ cells.     

Hormonal oscillations during the estrous cycle influence the morphophysiology of the gerbil (Meriones unguiculatus) female prostate (skene paraurethral glands)

The hormonal oscillations that occur during the female reproductive cycle influence the morphophysiology of several organs of the reproductive system. The female prostate is a functional organ sensitive to the action of steroidal hormones, but it is not known whether the hormonal oscillations that occur during the reproductive cycle can alter the biology of this gland. Thus, the present work aims to evaluate the morphofunctional aspects of the female prostate during the gerbil estrous cycle. For this purpose, morphological, morphometric-stereological, serological, and immunocytochemical analyses were carried out. The results of the present study show that the hormonal oscillations that occurred during the estrous cycle altered both the structure and functionality of the gerbil female prostate. These alterations include increased prostatic growth and augmented secretory activity during the proestrus and estrus phases and a gradual decrease of the secretory activity and glandular development in the diestrus I and II phases. These cyclical oscillations appear to be determined by the hormonal peaks of estrogen in diestrus II and by the high levels of progesterone during estrus, since the androgen levels remained constant throughout the estrous cycle.     

Maintenance of lung myeloperoxidase activity in proestrus females after trauma-hemorrhage: upregulation of heme oxygenase-1

Previous studies showed that females in the proestrus stage of the reproductive cycle maintain organ functions after trauma-hemorrhage. However, it remains unknown whether the female reproductive cycle is an important variable in the regulation of lung injury after trauma-hemorrhage and, if so, whether the effect is mediated via upregulation of heme oxygenase (HO)-1. To examine this, female Sprague-Dawley rats during diestrus, proestrus, estrus, and metestrus phases of the reproductive cycle or 14 days after ovariectomy underwent soft tissue trauma and then hemorrhage (mean blood pressure 40 mmHg for 90 min followed by fluid resuscitation). At 2 h after trauma-hemorrhage or sham operation, lung myeloperoxidase (MPO) activity and intercellular adhesion molecule (ICAM)-1, cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-3, and HO-1 protein levels were measured. Plasma 17beta-estradiol concentration was also determined. The results indicated that trauma-hemorrhage increased lung MPO activity and ICAM-1, CINC-1, and CINC-3 levels in ovariectomized females. These parameters were found to be similar to sham-operated animals in proestrus female rats subjected to trauma-hemorrhage. Lung HO-1 protein level in proestrus females was increased significantly compared with female rats subjected to trauma-hemorrhage during diestrus, estrus, and metestrus phases of the reproductive cycle and ovariectomized rats. Furthermore, plasma 17beta-estradiol level was highest in proestrus females. Administration of the HO inhibitor chromium mesoporphyrin prevented the attenuation of shock-induced lung damage in proestrus females. Thus these findings suggest that the female reproductive cycle is an important variable in the regulation of lung injury following trauma-hemorrhage and that the protective effect in proestrus females is likely mediated via upregulation of HO-1.     

Effect of salmon calcitonin on renal excretion of adenosine 3', 5' monophosphate in man.

Intravenous infusion of salmon calcitonin in six healthy subjects produced an increase in the plasma levels and urinary excretion of cyclic AMP. Cyclic AMP clearance diminished but remained higher than inulin clearance. Salmon calcitonin was also infused in six hypertensive patients with normal glomerular filtration rate. Arterial and renal venous plasma concentration of cyclic AMP were clearly raised. The difference between both these concentrations was not significant in the control periods but became marked during the treatment and post treatment periods demonstrating a net extraction of cyclic AMP from plasma by the kidneys. Renal extraction of cyclic AMP was lower than its urinary excretion in the control periods whereas it was clearly higher after salmon calcitonin was given. This shows that salmon calcitonin stimulates the production of cyclic AMP in extra-renal tissues and that the excess of cyclic AMP formed is catabolized by the kidneys.     

Plasma calcium and calcitonin in the marine teleost, Gadus morhua

Total, free and ionic plasma levels of calcium as well as total plasma magnesium and inorganic phosphate levels were studied in the Atlantic cod, Gadus morhua, in relation to salmon calcitonin injections. Plasma ion levels and endogenous levels of calcitonin were studied during environmentally induced hypercalcemia. It is concluded that no apparent relationship between calcitonin and calcium levels was found, and it is implied that calcitonin in fish may have a physiological function not related to blood calcium regulation.     

Consequences of acute stress and cortisol manipulation on the physiology, behavior, and reproductive outcome of female Pacific salmon on spawning grounds

Life-history theory predicts that stress responses should be muted to maximize reproductive fitness. Yet, the relationship between stress and reproduction for semelparous salmon is unusual because successfully spawning individuals have elevated plasma cortisol levels. To tease apart the effects of high baseline cortisol levels and stress-induced elevation of cortisol titers, we determined how varying degrees of cortisol elevation (i.e., acute and chronic) affected behavior, reproductive physiology, and reproductive success of adult female pink salmon (Oncorhynchus gorbuscha) relative to different states of ovulation (i.e., ripe and unripe). Exhaustive exercise and air exposure were applied as acute stressors to manipulate plasma cortisol in salmon either confined to a behavioral arena or free-swimming in a spawning channel. Cortisol (eliciting a cortisol elevation to levels similar to those in post-spawn female salmon) and metyrapone (a corticosteroid synthesis inhibitor) implants were also used to chemically manipulate plasma cortisol. Cortisol implants elevated plasma cortisol, and impaired reproductive success; cortisol-treated fish released fewer eggs and died sooner than fish in other treatment groups. In contrast, acute stressors elevated plasma cortisol and the metyrapone implant suppressed plasma cortisol, but neither treatment significantly altered reproductive success, behavior, or physiology. Our results suggest that acute stressors do not influence behavior or reproductive outcome when experienced upon arrival at spawning grounds. Thus, certain critical aspects of salmonid reproduction can become refractory to various stressful conditions on spawning grounds. However, there is a limit to the ability of these fish to tolerate elevated cortisol levels as revealed by experimental elevation of cortisol.     

Dining from the coast to the summit: Salmon and pine nuts determine the summer body condition of female brown bears on the Shiretoko Peninsula

Body condition in mammals fluctuates depending on energy intake and expenditure. For brown bears (Ursus arctos), high‐protein foods facilitate efficient mass gain, while lipids and carbohydrates play important roles in adjusting dietary protein content to optimal levels to maximize energy intake. On the Shiretoko Peninsula, Hokkaido, Japan, brown bears have seasonal access to high‐lipid pine nuts and high‐protein salmon. To assess seasonal and annual fluctuation in the body condition of adult female brown bears in relation to diet and reproductive status, we conducted a longitudinal study in a special wildlife protection area on the Shiretoko Peninsula during 2012–2018. First, analyses of 2,079 bear scats revealed that pine nuts accounted for 39.8% of energy intake in August and salmon accounted for 46.1% in September and that their consumption by bears varied annually. Second, we calculated the ratio of torso height to torso length as an index of body condition from 1,226 photographs of 12 adult females. Results indicated that body condition continued to decline until late August and started to increase in September when salmon consumption increased. In addition, body condition began to recover earlier in years when consumption of both pine nuts and salmon was high. Furthermore, females with offspring had poorer body condition than solitary females, in particular in late August in years with low salmon consumption. Our findings suggest that coastal and subalpine foods, which are unique to the Shiretoko Peninsula, determine the summer body condition of female brown bears, as well as their survival and reproductive success.     

Calcitonin stimulates plasminogen activator in porcine renal tubular cells: LLC-PK1

Plasminogen activators are highly selective proteases that activate the proenzyme plasminogen to the general protease, plasmin. We studied a porcine kidney cell line, originally isolated as a high producer of plasminogen activator, in which activities of cellular adenylate cyclase and cAMP-dependent protein kinase are increased in response to calcitonin. We found that salmon calcitonin, in the concentration range 0.03-300 nM, increased plasminogen activator production up to approximately 1,000-fold and concurrently inhibited cell multiplication; both of these effects were reversible. Human calcitonin was approximately 0.01 times as potent as salmon calcitonin, corresponding to potency differences observed in other biological systems. Plasminogen activator production was also stimulated by other agents that raise cellular cAMP levels such as cholera toxin, phosphodiesterase inhibitors, and vasopressin, but not to the same extent as by calcitonins. The rapidity and sensitivity of the plasminogen activator determination and other cellular responses may make it possible in the future to use this cell stain in a convenient bioassay for calcitonins and their analogues.     

The reproductive cycle of the asteroid Coscinasterias muricata in Port Phillip Bay, Victoria, Australia

The reproductive cycles of two populations of Coscinasterias muricata from Port Phillip Bay, Victoria, Australia are described in terms of organ indices, oocyte development and progesterone levels. Both Governor's Reef and South Channel Fort populations exhibited clearly defined reproductive cycles with two spawning periods, during summer and during spring. In both populations, the pyloric caecal index and gonadal index showed inverse cycles suggesting nutrient translocation from the pyloric caeca to the gonads for gametogenesis. Physiological changes, such as decreases in pyloric caecal index, and increases in gonadal index and oocyte diameter were observed following the months of increased progesterone concentrations in the female pyloric caeca. These results indicate a role for this steroid in the reproductive cycle. The results from the Governor's Reef population suggest that the influence of progesterone on the reproductive cycle of female C. muricata is regulated by photoperiod. Results also provide evidence of a role for seawater temperature in the reproductive process of this species.     

Reversed-phase high-performance liquid chromatography of salmon calcitonin and its degradation products in biological samples using column switching and flow-through radioisotope detection

For the determination of salmon calcitonin and its degradation products in biological samples, a reversed-phase HPLC method with column switching and flow-through radioisotope detection has been developed using high specific activity [¹²⁵I]salmon calcitonin. Effects of the precolumn packing material and washing solvent were examined in terms of [¹²⁵I]salmon calcitonin recovery. Spiked samples of [¹²⁵I]salmon calcitonin in plasma and kidney homogenate were injected onto a LiChroprep RP-8 precolumn after dilution with 0.1% trifluoroacetic acid. After washing the polar interfering compounds with 0.1% trifluoroacetic acid, the concentrated [¹²⁵I]salmon calcitonin and its degradation products were eluted and separated on a W-Porex C₁₈ column with a gradient of 0.1% trifluoroacetic acid in acetonitrile-water. Detection and calibration of [¹²⁵I]salmon calcitonin were possible down to picogram levels. Reproducible kinetic data for the degradation of intact [¹²⁵I]salmon calcitonin by rat kidney homogenate could be traced.     

Ecdysteroid levels during adult reproductive and embryonic developmental stages of Sarcophaga bullata (Sarcophagidae: Diptera)

Ecdysteroid levels were determined during the period of the adult reproductive cycle in the ovovivparous fleshfly Sarcophaga bullata. Low levels were found in males during the 10 days following eclosion while the entire adult female showed a significant peak of ecdysteroid activity at 190 h post eclosion (i.e. during embryogenesis). When the female reproductive tract was analyzed it was observed that the ovaries became vitellogenic a short time after a protein meal was offered at 96 h post eclosion: at 140 h, ecdysteroid activity was recorded in the developing oöcytes. The major peak of ecdysteroids during the reproductive cycle was found in developing embryos at 190 h. The significance of these releases of ecdysteroids is discussed in relation to major embryonic developmental events.     

Changes in Northwest Atlantic Arctic and Subarctic conditions and the growth response of Atlantic salmon

There has been a systematic change in the weight at age of Atlantic salmon (Salmo salar L.) in the Northwest Atlantic that is related to climate variability. This relationship emerged from analyses of broad-scale measures of ocean surface thermal habitat, which show that expansion of the area bounding 4–8°C is associated with greater growth. To further elucidate the effect of the environment on salmon growth, time series of sea surface temperature (SST), sea ice coverage, chlorophyll concentration, net primary production and zooplankton abundance were examined temporally and spatially in relation to changes in the weight of salmon. SST and zooplankton data were extracted from in situ analyses, whereas sea ice and chlorophyll-based measures of productivity were collected with satellite sensors. Salmon growth was found to be unrelated to productivity at the base of the food chain but highly associated with thermal regime during winter and spring. Warming conditions during specific segments of the salmon life cycle have been associated with poor adult recruitment; yet, warming during others is beneficial to salmon growth and is assumed to increase reproductive output of spawning fish. Despite these positive influences, climate change will continue to erode the viability of salmon populations while the negative effects of warming on survivorship outweigh the benefits of any increase in reproductive output related to growth.     

Reproductive priming in mature male Atlantic salmon parr exposed to the sound of redd cutting

The sounds of a wild female Atlantic salmon cutting a redd were associated with significant increases in the levels of plasma 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) and of expressible milt in mature male parr, comparable with levels of the steroid and milt produced in parr exposed to the priming pheromone, prostaglandin F_2a. Hence auditory cues may have a significant role in synchronising reproductive physiology in Atlantic salmon.     

Aggression in the female golden hamster: effects of reproductive state and social isolation

To gain information on possible hormonal correlates, the aggressive behavior of intact female hamsters towards males was observed at various times during the estrous cycle, pseudopregnancy, pregnancy, and lactation. For methodological information, estrous cycle females also were tested after varying periods of social isolation. It was found that pregnant and especially lactating hamsters were more aggressive than pseudopregnant or estrous cycling females. Comparisons of days within each reproductive condition showed that aggression tended to be higher on certain days: the day preceding behavioral estrus of the estrous cycle, Day 10 of pregnancy, and the first 5 days of lactation. Except for pseudopregnancy, sexual behavior unaccompanied by aggression occurred at some time during all reproductive conditions, and both sexual behavior and aggression were found to occur together on Day 10 of pregnancy and Day 1 of lactation. The changes in aggressive behavior associated with reproductive states were attributed to increased male interest, inhibition by ovarian hormones, and facilitation by prolactin. Increasing periods of social isolation also were found to be associated with increased aggression. It was suggested that this effect, too. might have been due to increased prolactin levels.     

Potential applications of electrical impedance techniques in female mammalian reproduction

The measurement of electrical impedance is one of many methods that can be used for monitoring various reproductive events in female mammals. This paper summarizes the key findings in this research area that have been achieved during the past four decades. The electrical impedance in the vagina, vaginal vestibule and vulva during the estrous/menstrual cycle shows significant changes that vary among these reproductive organs, different locations in these organs and mammalian species. The changes of vaginal and vulvar impedance during periestrus are temporarily associated with the preovulatory luteinizing hormone (LH) peak and are significantly correlated with systemic levels of estradiol and progesterone. In humans, significant impedance changes during the menstrual cycle and their close association with the LH peak and ovulation have been found not only in the vagina, but also in the tongue. Findings of a number of studies suggest the possibility of using vaginal, vestibular and vulvar impedance to predict and confirm the fertile period of the estrous/menstrual cycle. There is some evidence that vulvar and cervical impedance may be a reliable indicator of impending parturition. Results in several studies also indicate the possibility of using electrical impedance methods to confirm the existence of ovarian follicular cysts, endometriosis and cervical neoplasia. However, physical and biological factors that may affect the impedance variation in the female reproductive system and tongue are still poorly understood. Their detection allows us to improve our ability to predict more precisely various reproductive processes by impedance techniques. This review also provides some considerations about the origin of impedance changes in the female reproductive system and tongue that may be useful for the systematic development of impedance methods in the field of female mammalian reproduction.     

Synthesis of biologically active tritiated amylin and salmon calcitonin analogues

Amylin is a hormone belonging to the calcitonin protein family of peptides. To facilitate receptor screening studies, alternatively radiolabeled and biologically active amylin and salmon calcitonin analogues were synthesized by reductive methylation. Free amino groups of amylin and salmon calcitonin were methylated by reaction of peptides with formaldehyde and sodium [(3)H]borohydride. Radioactively labeled peptides were purified by size exclusion chromatography followed by HPLC. Analysis by MALDI-TOF mass spectrometry of purified amylin and salmon calcitonin peptides revealed incorporation of both two and four tritiated methyl groups per peptide molecule. Specific activities of 22.6 and 23.2 GBq/mmol were measured for amylin and salmon calcitonin, respectively. Methylation of rat amylin and salmon calcitonin did not affect their biological activities as both retained their potency to inhibit insulin-stimulated glycogen synthesis in isolated rat soleus muscle. The synthesis of these tritiated analogues provides an alternative chemically stable radiolabeled ligand which may be useful in exploring receptor interactions within the calcitonin peptide family.     

Covalent cross-linking of a photoactive derivative of calcitonin to human breast cancer cell receptors

A photoaffinity derivative of salmon calcitonin has been produced by transglutaminase-mediated incorporation of N-(beta-aminoethyl)-4-azido-2-nitroaniline into the hormone. The derivative, purified by high pressure liquid chromatography, retained the abilities to bind to cultured T47D breast cancer cells and to stimulate adenylate cyclase in these cells. In both these respects it was equipotent with synthetic salmon calcitonin. Photolysis of the 125I-labeled photoactive salmon calcitonin derivative bound to T47D cells was accompanied by specific labeling of only one component (Mr approximately 85,000) as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Labeling was observed only upon photolysis and was inhibited by unlabeled synthetic salmon calcitonin but not by the inactive calcitonin analogue, 8-glycine human calcitonin. Reduction did not alter the apparent molecular weight of the calcitonin receptor complex. No macromolecular forms of calcitonin were produced by photolysis in the absence of T47D cells.     

Seasonal gonad progesterone pattern in the soft-shell clam Mya arenaria

Steroidogenesis, which plays a major role in the reproductive cycle of vertebrates, is still for the most part, unknown in invertebrates. The aim of this study was to examine the link between progesterone and the reproductive cycle in Mya arenaria. The soft-shell clams, Mya arenaria were collected in Anse à l'Orignal (Parc Provincial du Bic, Québec, Canada) from July to November 1998. Histological data have shown that female gonads of M. arenaria were in the spawning stage in August and September, while the male gonads were in the ripe stage. This period of active gametogenesis was associated with a depletion of lipid reserves. These lipids could be used as a source of energy and as a substrate for steroidogenesis. Liquid Chromatography coupled to Mass Spectroscopy (LC-MS) and quantified by Enzyme Linked ImmunoSorbent Assay (ELISA) determined progesterone. Progesterone levels in the gonad were increased during the ripe stage in the male and during the spawning stage in the female. These results indicate, for the first time, that progesterone, as in vertebrates, may play a role in the reproductive cycle of M. arenaria.     

Gonadotropin-releasing hormone content in the brain and pituitary of male and female grass rockfish (Sebastes rastrelliger) in relation to seasonal changes in reproductive status.

The involvement of individual molecular forms of GnRH in the regulation of reproductive cyclicity in a viviparous marine teleost, the grass rockfish (Sebastes rastrelliger), was evaluated by relating the brain and pituitary content of the neuropeptide to reproductive status. The presence of sea bream (sb) GnRH, chicken GnRH-II, and salmon GnRH in the brain was confirmed by their elution pattern on HPLC and RIA. In addition, HPLC elution profiles suggest that there may be a fourth form of GnRH. All forms of GnRH were found in male and female brains in all reproductive conditions. However, only sbGnRH could be detected in appreciable amounts in the pituitary. Of the four forms of GnRH found in the rockfish, only sbGnRH fluctuated during the reproductive cycle and large accumulations were detected in the brains and pituitaries of postspawn females and regressed males. The accumulation of sbGnRH at the end of the reproductive cycle is suggested to reflect a decline in GnRH secretion relative to synthesis. The dominance of sbGnRH in the pituitary and its individual fluctuation in relation to seasonal changes in reproductive status suggests that sbGnRH is an important regulator of gonadotropin-mediated reproductive activity in rockfish.