Immunohistochemical evidence of seasonal changes of gonadotropes in male ruin lizard (Podarcis sicula campestris De Betta)

The pars distalis from the pituitary gland of adult male ruin lizards (Podarcis sicula campestris De Betta), captured during the five periods of the annual sexual cycle (emergence from hibernation, reproductive period, summer regression, autumnal recrudescence, winter arrest), was studied immunohistochemically using specific antibodies against hFSHbeta, hLHbeta, oFSHbeta, and oLHbeta with the avidin-biotin complex (ABC) procedure to monitor the seasonal changes in shape, size and percentage area taken up from gonadotropes. FSH containing cells were specifically identified with anti-hFSHbeta and anti-oFSHbeta sera, whereas the LH cells were localized by anti-hLHbeta. The anti-oLHbeta serum showed cross-reactivity with the cells immunostained by the three above antisera (anti-hFSHbeta, anti-oFSHbeta, and anti-hLHbeta). None of the cells contained both gonadotropic hormones as shown by the double-immunostaining procedure. Generally, FSH cells were larger and more numerous than LH cells. FSH cells were elongated or pyriform in shape from spring to autumn, whereas they were round or oval during the winter stasis and until the emergence from hibernation. The size and the percentage area occupied by FSH cells showed an annual pattern with two distinct peaks in the reproductive and in the autumnal recrudescence periods. LH cells did not show seasonal changes in shape, being round or oval throughout the reproductive cycle, whereas their size and the area they occupied underwent seasonal variations. The LH cells reached the largest size during the reproductive period and the smallest size during the summer regression. The percentage area occupied by LH cells in the pars distalis peaked at the emergence from hibernation and during the summer refractory period, when FSH cells displayed their lowest values.     

Sequence analysis and expressional regulation of messenger RNAs encoding beta subunits of follicle-stimulating hormone and luteinizing hormone in the red-bellied newt, Cynops pyrrhogaster

Two distinct cDNAs encoding beta subunits of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were cloned from the cDNA library constructed for the pituitary of the red-bellied newt, Cynops pyrrhogaster, and sequenced. The newt FSHbeta and LHbeta cDNAs encode polypeptides of 129 and 131 amino acids, including signal peptides of 20 and 19 amino acids, respectively. The number and position of cysteine and N-glycosylation in each of the beta subunits of FSH and LH, which are considered essential for assembly of the alpha subunit, are well conserved between the newt and other tetrapods. The high homology (41.6%) between the beta subunits of newt FSH and LH imply less specificity of FSH and LH in gonadal function. One cDNA encoding the common polypeptide chain alpha subunit of FSH and LH was also isolated from the newt pituitary gland. The mRNAs of FSHbeta, LHbeta, and the alpha subunit were expressed only in the pituitary gland among various newt tissues. Double-staining with in situ hybridization and immunohistochemistry revealed coexpression of FSHbeta and LHbeta in the same newt pituitary cells. Ovariectomy induced a significant increase in FSHbeta mRNA levels, but there was no significant change in LHbeta or alpha subunit mRNA levels compared with those in control animals. Taken together, these data suggest that two kinds of gonadotropins, namely FSH and LH, are expressed in the same gonadotropin-producing cells in the pars distalis of the newt as well as in other tetrapods and that the expression of FSHbeta is negatively regulated by the ovaries.     

Gonadotroph-lactotroph associations and expression of prolactin receptors in the equine pituitary gland throughout the seasonal reproductive cycle

An interaction between gonadotroph and lactotroph cells of the pituitary gland has long been recognized in several species. The current study was conducted to investigate whether an association between gonadotrophs and lactotrophs occurs in mares and whether prolactin receptors are expressed within the pituitary gland of this species. The effects of both reproductive state and season on these variables were examined in pituitary glands obtained from sexually active mares in July (breeding season), sexually active mares in November (non-breeding season) and anoestrous mares in November. Pituitaries were dissected out immediately after death and immunofluorescent staining was carried out on 6 micrometer sections using specific antibodies to the LHbeta subunit, FSHbeta subunit, prolactin and prolactin receptor. Gonadotrophs were observed in both the pars distalis and pars tuberalis; although they appeared mostly as isolated cells, small groups of gonadotrophs were also identified in the pars distalis. In contrast, lactotrophs were observed only as clusters of cells exclusively in the pars distalis of sexually active and anoestrous mares in November and in most of the sexually active mares in July. A specific gonadotroph-lactotroph association was identified only between large isolated gonadotrophs and lactotroph clusters. Double immunofluorescent staining for FSHbeta and prolactin revealed a similar gonadotroph-lactotroph association to the one detected for LH gonadotrophs. No statistical difference in the gonadotroph:lactotroph ratio was observed as a result of changes in reproductive status or season. However, a tendency for a simultaneous decrease in the number of gonadotrophs and an increase in the number of lactotrophs was detected in anoestrous animals. Prolactin receptor immunoreactivity was found in the pars distalis, but not in the pars tuberalis, of sexually active (July and November) and anoestrous animals for both long and short forms of the receptor. No prolactin receptor co-localization for either form of the receptor was observed in LH or FSH gonadotrophs in either of the reproductive states examined during both summer and winter seasons. Furthermore, no significant difference was apparent in the proportion of cells expressing prolactin receptors between mares of different reproductive state or season. The specific anatomical association between gonadotroph and lactotroph cells and the expression of prolactin receptors in the equine pituitary gland indicate a potential role of prolactin in the regulation of gonadotrophin secretion. However, the absence of evidence for co-localization of prolactin receptors in LH or FSH cells does not support the hypothesis of a direct effect of prolactin on the gonadotroph as reported in a short day breeder. The results raise the possibility that, in horses, an intermediate regulatory cell may mediate the action of prolactin on gonadotroph function.     

Seasonal variations in the histology of the pituitary gland of Cirrhinus mrigala (Ham.) an Indian freshwater major carp, in relation to gonadal activity.

1. Seasonal variations in the histology of the pituitary gland of Cirrhinus mrigala (Ham.), an Indian freshwater major carp, in relation to gonadal activity has been studied during a one year period commencing, January, 1971. 2. The proximal pars distalis undergoes a great deal of seasonal variation in size, weight and nature of pituicytes. 3. The percentage composition of acidophils and cyanophils in the proximal pars distalis show a reciprocal relationship during the year. The acidophils predominate during the restitution phase of the gonads while the cyanophils preponderate among the different cell types during the breeding season. 4. The chromophobes do not show any significant fluctuation in numerical abundance in relation to gonadal activity. 5. Cyanophils of the proximal pars distalis undergo changes with change in gonadal activity Concentration of glycoproteinaceous material is extremely low during the restitution phase but high during the maturation phase. The cyanophils also undergo hypertrophy and hyperplasia during the spawning period. The latter discharge their contents and become vacuolated during the post spawning period. 6. The number and size of the globules in the cyanophils are related to gonadal activity. 7. Acidophils present in the rostral pars distalis and pars intermedia do not appear to be related to gonadal activity in C. mrigala. 8. The average weight of the gland is directly related to the state of maturation of the gonads, an observation being recorded here for the first time.     

Seasonal changes of the Leydig cells of viscacha (Lagostomus maximus maximus). A light and electron microscopy study

The Leydig cells of viscacha (seasonal rodent) show cytoplasmic hypertrophy and regional distribution during the breeding period (summer-autumn). The dominant organelles are smooth endoplasmic reticulum (SER) and mitochondria. A moderately well-developed Golgi, abundant lipid inclusions, dense bodies like lysosomes in different stages, and centrioles are observed. Extensive or focal desmosome and gap-like junctions between neighbouring Leydig cells are present. These cells exhibit an evident hypotrophy and an increase in the number of dense bodies during the gonadal regression in winter (July and August). Cells in different stages of involution are observed in this period. Their nuclei are irregular and heterochromatic. The cytoplasm contains few mitochondria. The vesicular SER is scarse. Irregular and large intercellular spaces with microvilli and amorphous material are present. The junctional complexes are absent. The nuclear and cytoplasmic volume and development of SER and mitochondria increase during the recovery period (spring). The lipid inclusions decrease. Dilatations of the intercellular space with microvilli and limited by focal desmosome-like junctions are observed. In conclusion, the Leydig cells of Lagostomus maximus maximus show deep changes alongside the reproductive cycle. The photoperiod variations, through pineal hypothalamus pituitary axis and the hormone melatonin, are probably responsible for them. Moreover, the fall of serum and tubular testosterone would be one of the factors responsible for gonadal regression.     

Immunoreactivity to gonadotropin-releasing hormone and gonadotropic hormone in the brain and pituitary of the rainbow trout Salmo gairdneri

Summary Immunoreactivity to gonadotropin-releasing hormone (GnRH) and gonadotropic hormone (GTH) was studied at the light-microscopical level in the brain and pituitary of rainbow trout at different stages of the first reproductive cycle using antisera against synthetic mammalian GnRH and salmon GTH. GnRH perikarya were localized exclusively in the preoptic nucleus, both in the pars parvicellularis and the pars magnocellularis. A few somata contacted the cerebrospinal fluid. Not all neurosecretory cells were GnRH-positive, indicating at least a bifunctionality of the preoptic nucleus. We recorded no differences between sexes or stages of gonadal development in the location of GnRH perikarya, whereas gradual changes were found in staining intensity during the reproductive cycle. GnRH fibres ran from the partes parvicellularis and magnocellularis through the hypothalamus and merged into a common tract at the transverse commissure before entering the pituitary. In the pituitary, GnRH was localized in the neural tissue of the neurointermediate lobe and, to a lesser extent, in the neural protrusions penetrating the proximal pars distalis. The bulk of GTH-positive cells was situated in the proximal pars distalis. Some cells were found more rostrally amidst prolactin cells or in the neurointermediate lobe. Only a limited number of GTH cells appeared to be in close contact with GnRH-positive material.     

Regulation of gonadotropin subunit genes in tilapia

A steroidogenic tilapia gonadotropin (taGtH=LH) was purified from pituitaries of hybrid tilapia (Oreochromis niloticus x O. aureus) and a homologous RIA was established. This RIA enabled the study of the endocrine regulation of GtH release, the transduction pathways involved in its secretion and its profile during the spawning cycle. Discrepancies between steroid and taGtH peaks during the cycle led to the conclusion that an additional gonadotropin similar to salmonid FSH operates early in the cycle. In order to identify this hormone and to study the endocrine control of synthesis of all gonadotropin (GtH) subunits, a molecular approach was taken. The cDNA sequences and the entire gene sequences encoding the FSHbeta and LHbeta subunits, as well as an incomplete sequence of the glycoprotein hormone alpha subunit (GPalpha), were cloned. Salmon gonadotropin-releasing hormone (sGnRH) elevated mRNA steady-state levels of all three GtH subunits in cultured pituitary cells. Pituitary adenylate cyclase-activating polypeptide (PACAP) and neuropeptide Y (NPY) also stimulated the expression of these subunits and potentiated the effect of GnRH, except that NPY did not affect FSHbeta. The GnRH and NPY effects were found to be mediated mainly through protein kinase C (PKC), while protein kinase A (PKA) cascade was involved to a lesser extent. Mitogen-activated protein kinase (MAPK) cascade takes part in mediating GnRH effects, possibly via PKC. Testosterone (T) and estradiol (E2), but not 11-ketotestosterone (KT), are able to elevate GPalpha and LHbeta mRNAs in pituitary cells of early maturing or regressing males. Low levels of T exposure are associated with elevated FSHbeta mRNA in cells of mature fish, while higher levels suppress it, but elevate LHbeta mRNA. In vivo observations also showed the association of low T levels with increased FSHbeta mRNA and high T levels with elevated LHbeta mRNA. In accordance with these findings, analysis of LHbeta and FSHbeta 5' gene-flanking regions revealed on both gene promoters a GtH-specific element (GSE), half site estrogen response elements (ERE), cAMP response element (CRE) and AP1. In vitro experiments showed that recombinant human activin-A leads to higher levels of GPalpha, FSHbeta and LHbeta mRNAs in pituitary cell culture. Porcine inhibin marginally decreased the mRNA levels of GPalpha and FSHbeta, but at a low level (1 ng/ml) it stimulated that of LHbeta. These results shed some light on certain hypothalamic and gonadal hormones regulating the expression of GtH subunit genes in tilapia. In addition, they provide evidence for their differential regulation, and insight into their mode of action.     

Cellular associations of pituitary gonadotrophs in a rodent (Lagostomus maximus maximus) with photoperiod-dependent reproduction

The morphological characteristics and percentage of the cellular associations between gonadotrophs (LH- and FSH-secreting cells) and other cellular types were studied in pituitary pars distalis of adult male viscachas (Lagostomus maximus maximus) by double immunohistochemistry using specific antibodies to LH, FSH, PRL, GH, ACTH, TSH and S-100 protein (by folliculostellate cells; FSC), during long and short photoperiods. Bihormonal gonadotrophs were observed in ventro-medial and dorsal regions, interspersed between monohormonal gonadotrophs, and their number increased in short photoperiod. LH- and FSH-gonadotrophs were found around lactotrophs, enclosed by somatotrophs in the dorsal region, and associated with irregular corticotrophs. Gonadotrophs and thyrotrophs were associated along blood vessels and follicular structures. The cytoplasmic prolongations of FSC were in contact with both gonadotrophs. The percentage of LH–FSH, LH–ACTH, LH–FSC, FSH–LH, FSH–PRL, FSH–GH, FSH–ACTH, FSH–TSH and FSH–FSC associations decreased, whereas LH–PRL increased in short as compared to long photoperiod. The most abundant associations were LH–GH and LH–TSH during long photoperiod, but LH–GH and LH–PRL during short photoperiod. FSH–GH and FSH–PRL were the most numerous associations, and LH–FSC and FSH–FSC were the less abundant ones in both photoperiods. These results provide the morphological evidence for specific cellular associations between gonadotrophs and other cellular types of viscacha pituitary.     

Distribution of immunoreactivities for adenohypophysial hormones in the pituitary gland of the polypteriform fish, Polypterus endlicheri

Polypteriform fish constitutes the most primitive living descendent of the ancient bony fish. In polypteriform fish, only proopiomelanocortin (POMC) has been identified so far in the adenohypophysis, which is surprising in view of their evolutionary importance. In the present study, distribution of immunoreactive adenohypophysial hormones was examined in juvenile individuals of Polypterus endlicheri. Antisera to tetrapod and fish adenohypophysial hormones were used as immunostaining probes. Adrenocorticotropin (ACTH)-like cells were detected by antisera to salmon POMC N-terminal peptide, porcine ACTH and mammalian alpha-melanotropin (MSH), and were distributed in the rostral pars distalis in close proximity to the hypophysial duct. MSH-like cells were found in the pars intermedia, and were stained by anti-salmon N-Ac-beta-endorphin II as well as anti-mammalian alpha-MSH and anti-salmon POMC-N terminal peptide. Prolactin (PRL)-like cells were detected only after application of anti-sturgeon PRL, and were distributed in the rostral pars distalis, where PRL-positive material was found in columnar mucinous cells lining the diverticuli of the hypophysial duct. Growth hormone (GH)-like cells were stained with antisera to sturgeon GH, human GH, salmon GH and blue shark GH, and were distributed in the proximal pars distalis. Somatolactin (SL)-like cells were stained with anti-salmon SL, and were distributed in the pars intermedia. Two types of glycoprotein hormone-positive cells were detected in the proximal pars distalis. Although both types of cells were stained with several antisera to glycoprotein hormones, such as sturgeon LHbeta and salmon LHbeta, it was difficult to know which types of cells produce LH, FSH, or TSH. Thus, the present study revealed seven types of adenohypophysial hormone-like cells in the Polypterus pituitary gland, which may provide the morphological basis for better understanding on evolution of the pituitary gland and the adenohypophysial hormones in vertebrates.     

Ultrastructural and biochemical seasonal changes in epididymal corpus and cauda of viscacha (Lagostomus maximus maximus)

The reproductive and adaptative behavior of wild rodents is synchronized primarily by the photoperiod. The viscacha, a South American rodent of nocturnal habits and seasonal reproduction is photoperiod‐dependent and its reproductive behavior is regulated by the retinohypothalamic‐pituitary pineal axis. Adult males exhibit an annual reproductive cycle with periods of maximum gonadal activity (summer‐early autumn) and gonadal regression (winter). The corpus and the cauda, the most sensitive segments of the epididymis to changes induced by the photoperiod, were analyzed using electron microscopy and enzymatic biochemistry. During gonadal regression, principal and clear cells showed signs of involution with respect to the activity period. These were characterized by more irregular nuclei, smaller cytoplasms, large vacuoles, altered mitochondria, and glycogen deposits. All cellular populations of the epididymal epithelium in regression presented abundant lysosome‐like dense bodies during the active period. In addition, we measured the activity of four acid glycosidases in the cauda epididymis along the reproductive cycle. N‐acetyl‐β‐D‐glucosaminidase (NAG), an enzyme that degrades endocytosed substances from the epididymal lumen, increased significantly during gonadal regression relative to the active period. These results demonstrate that the viscacha epididymis exhibits significant ultrastructural and biochemical changes during the reproductive cycle. We demonstrate that during regression, melatonin secretion in viscacha increases. This study shows that the epididymal epithelium is reduced. Thus, we postulate that the changes observed in the epididymis are modulated by pineal melatonin. Despite these changes, the epididymis might maintain a microenvironment suitable for the survival of stored spermatozoa. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Cytology and cytochemistry of the hypophysis of the freshwater teleost Rhamdia hilarii (Val., 1840).

The characterization of cell types in the rostral pars distalis, proximal pars distalis and pars intermedia of the Bagre fish hypophysis during the reproductive cycles, as well as a cytochemical study of mucosubstances were undertaken. The cytophysiological relationship among the different acidophilic, basophilic and chromophobic cells with the several hypophyseal hormones was also considered.     

Life span changes in the presence of alpha-melanocyte-stimulating-hormone-containing cells in the human pituitary.

Since recent circumstantial evidence has suggested possible functions of alpha-MSH in intrauterine growth and labour, the presence of this hormone in the human pituitary was determined by means of the indirect immunofluorescence procedure during development and adulthood. Cross reaction of the antibodies with other peptides was measured after which they were purified by solid phase absorption. Experiments on the rat pituitary showed that staining of alpha-MSH- and ACTH-containing cells could be obtained well until 48 h after death. In the pars distalis the ability of ACTH-containing cells to take up stain increased during the period of post-mortem storage. In the youngest human fetus studied (15 weeks) only alpha-MSH-containing cells were found in the pars intermedia and no ACTH-containing cells were observed. In the other fetal pituitaries a distinct pars intermedia containing more alpha-MSH cells than ACTH cells was found. In the pars distalis of the fetuses more ACTH- than alpha-MSH-containing cells were observed. From birth to 19 years, progressively fewer alpha-MSH containing cells could be detected in the 'zona intermedia' and pars distalis, while in adults only a few such cells were found in either area. Irrespective of age, sex, cause of death or therapy, alpha-MSH-containing cells were found in all pituitaries throughout life. The number of ACTH containing cells gradually increased in the zona intermedia and pars distalis and reached a high adult level in the latter structure. In the pituitaries of seven anencephalics, no alpha-MSH-containing cells were present. The presence of alpha-MSH in the fetal pars intermedia, the change in the ratio of the alpha-MSH/ACTH cells during the course of development, and the absence of alpha-MSH in anencephaly all support the possibility that human fetal pituitary alpha-MSH is involved in both intrauterine growth and fetal adrenal function and thus also in parturition.     

Seasonal variations in the testis and epididymis of vizcacha (Lagostomus maximus maximus).

Seasonal changes in reproductive activity in the adult male vizcacha (Lagostomus maximus maximus), a South American rodent, were investigated. Monthly, for 2 yr, the animals were killed and decapitated during the night near their burrows in the vicinity of San Luis, Argentina. The testes, epididymides, and pineal glands were removed and used for biochemical and structural studies. Significant changes associated with seasonal cycles were found. 1) In July-August (winter in South America), a short hibernal period of sexual quiescence, decline in testicular and epididymal weights, arrest of spermatogenesis, and decrease of serum testosterone were observed. The gonads regressed during this period, with regression most pronounced in August. 2) During September-November (spring), a recovery period--without arrest of spermatogenesis--was observed, with significant expression of gonadal activity during April-May (autumn). In this season, gonadal weight was increased and spermatogenesis was complete. These results indicate an increase in sexual activity as well as in the ability to secrete testosterone. A gradual reduction of testicular activity appeared in June-July (early winter). Conversely, in this period, the pineal hydroxyindole-O-methyl transferase activity decreased in contrast to the highest values observed in winter. Our findings indicate that the male adult vizcacha under natural conditions exhibits an annual reproductive cycle. A possible relationship between increased pineal activity and gonadal regression is also suggested.     

Immunocytochemical studies on the pituitary pars distalis of the Japanese long-fingered bat,Miniopterus schreibersii fuliginosus

Summary Immunocytochemical studies were performed to describe the characteristics of cell types and their distribution in the pars distalis of Japanese long-fingered bat, Miniopterus schreibersii fuliginosus, collected at various stages of the reproductive cycle. Six distinct cell types have been identified in the pars distalis by the unlabeled immunoperoxidase technique and by the ABC method. Growth hormone (GH) and prolactin (PRL) cells were immunostained with antisera against chicken GH and ovine PRL. The GH-immunoreactive cells were round or oval orangeophilic cells distributed throughout the pars distalis with prominent aggregation in the posterolateral region. The PRL cells were pleomorphic carminophilic cells that occurred in small groups within the central and dorsocaudal regions of the pars distalis. They were sparsely distributed in the central region of the pars distalis in the hibernating bats, but increased significantly in the pregnant and lactating bats. The adrenocorticotropic (ACTH) cells were large round or polygonal amphophilic cells in the rostroventral and ventrolateral regions of the pars distalis. The thyrotropic (TSH) cells were small rounded or polygonal and distributed mainly in the ventrolateral region of the pars distalis. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) cells were identified immunocytochemically with antisera against the specific beta subunits of ovine LH and rat FSH. There were two populations of LH and FSH cells, one aggregated in the zona tuberalis and the other scattered singly throughout the rest of the pars distalis. The aggregated cells were immunoreactive with both antisera directed to LH and FSH, while scattered cells were reactive solely with antiserum to either LH or FSH and exhibited seasonal variations. In females, the proportional volume of the pars distalis occupied by LH cells was significantly reduced during pregnancy and lactation. No evidence of involution was observed in pars distalis cells except for PRL cells in males or females during hibernation.     

Seasonal changes in the pituitary gland of the feral hawaiian mongoose (Herpestes auropunctatus)

The Hawaiian mongoose (Herpestes auropunctatus) is a seasonally breeding mammal whose pituitary gland resembles that of other Viverridae. Certain features, such as a prominent pars tuberalis interna and a double-layered pars intermedia forming a cup for the neurohypophysis, are unique. With the light microscope, five different cell types can be recognized in the pars distalis after staining with periodic acid-Schiff (PAS)-orange G. Two types of acidophils are seen, a small yellow-staining cell and a large angular orange cell. Two basophilic cells are also seen, one with fine PAS-positive cytoplasmic granules and the other with coarse PAS-positive granules in the cytoplasm. The last cell type seen is the chromophobe. Differential cell counts indicated an altered distribution of chromophils in the ventral pars distalis of the female mongoose with changing season and reproductive status, but the most striking change was a decreased percentage of basophils in the pars distalis during the nonbreeding season.     

Functional morphology of thyrotropic and corticotropic cells during reproductive cycle in ewe

A histological examination has been carried on the pars distalis of the pituitaries of twelve, healthy sexually mature balady ewes which were classified into three groups Resting, follicular and luteal phases according to the different phases of reproduction. The histological features of the TSH- ACTH-cells during resting phase has been used to establish a standard with which the subsequent changes during the follicular and luteal phases were compared. Using PAS/OG, AB/OG and PFA/AB/PAS/OG stains the TSH- and ACTH-cells were differentiated and identified from the other forms of the pars distalis cells. The topographical study of the TSH- and ACTH-cells in various regions and levels in the pars distalis of balady ewe as well as their frequencies during the different phase of reproductive cycle were discussed. Statistical analysis of the different cell count during the different phases of reproductive cycle was conducted. TSH- and ACTH-cells exhibited signs of increased cellular activities and significantly increased in number during follicular phase and in the other phases of the reproductive cycle.     

Bilateral enucleation and captivity influence the reproductive cycle of male Viscacha (Lagostomus maximus maximus)

The viscacha (Lagostomus maximus maximus) is a seasonal rodent living in the Southern Hemisphere. The adult males exhibit an annual reproductive cycle characterized by a gonadal regression period during winter. In this study, we investigated the effects of bilateral enucleation and captivity on their annual reproductive cycle. Testicular volume relative to body weight was recorded monthly in intact and bilaterally enucleated animals placed under natural photoperiod, water, and food ad lib. and constant temperature. Testes and accessory organs were evaluated by qualitative and quantitative light microscopic studies. The intact animals showed an annual reproductive cycle with complete gonadal atrophy in the first year. In the second year, testicular regression was observed but attenuated in regard to that recorded in the first winter period, indicating that adaptive changes might be involved. Bilateral enucleation in the viscacha dampened and extended the period of its annual reproductive cycle. The results suggest that both conditions, constant captivity and enucleation, produced stimulatory effects on the reproductive system of this rodent. Furthermore, local control mechanisms might be responsible for the morphological differences observed in testes, epididymis, and seminal vesicles from both groups, which exhibited similar levels of serum testosterone. Finally, an intact retinohypothalamic-pineal axis and/or photoperiodic input would be necessary to maintain the reproductive cycle amplitude and timing in viscacha.     

Cyclical mitotic activity in the adeno-hypophysis of Rana temporaria

Summary In the pars distalis, the pars intermedia and the pars tuberalis of the hypophysis of Rana temporaria, an annual mitotic cycle is described.In the pars distalis there exists a gradient of mitotic activity, corresponding to a gradient of distribution of the PAS positive cells.In the pars distalis, the rate of cell degeneration and of cell renewal of the PAS positive cells seems to be faster than of the orange G positive cells.The replacement of degenerated PAS positive cells of the pars distalis seems to occur mainly during the months immediately following on the period of maximal activity of the PAS positive cells.     

Distribution of 7B2 (secretogranin V)-like immunoreactivity in the Japanese red-bellied newt (Cynops pyrrhogaster) pituitary

In this study, we examined 7B2 (secretogranin V)-like immunoreactivity (IR) in the Japanese red-bellied newt (Cynops pyrrhogaster) pituitary. Results showed that the pars nervosa was filled with immunoreactive granules. In the pars intermedia, all melanotrophs showed 7B2-IR. In the pars distalis, immunoreactive cells were dispersed, and the 7B2-immunoreactive cells were also immunopositive for the β-subunit of bullfrog luteinizing hormone (fLHβ). 7B2-IR co-localized with fLHβ-IR in the same secretory granules. Our results suggest that 7B2 may participate in the secretion processes of gonadotropins in the pars distalis.     

Regulation of gonadotropin beta subunit gene expression by testosterone and gonadotropin-releasing hormones in the goldfish, Carassius auratus

Sex steroids differentially regulate gonadotropin (GTH) beta subunits (FSHbeta and LHbeta) gene expression in the pituitary of goldfish: a strong in vivo inhibitory effect on FSHbeta mRNA production, but a weak stimulatory effect on LHbeta in sexually immature and recrudescent fish. In the present study, to examine a direct effect of testosterone (T) and gonadotropin-releasing hormone (GnRH) on the mRNA levels of FSHbeta and LHbeta subunits in the pituitary, in vitro experiments were performed using dispersed pituitary cells of sexually immature, recrudescent, mature and regressed goldfish. T treatment in vitro did not significantly decrease FSHbeta mRNA levels, but increased that of LHbeta only in the cells of immature fish. Salmon-type GnRH increased FSHbeta mRNA levels in cells of mature fish, but decreased the levels in cells of sexually regressed fish. From these results, it was suggested that: (1) in vivo effect of sex steroids on gene expression of GTH beta subunits is not always exerted on the pituitary; and (2) the different responses of GTH beta subunits by sex steroids between in vivo and in vitro are partly due to a complex pathway through hypothalamic factors, such as GnRH, in the case of in vivo.