Expression and regulation of neuropeptide Y messenger ribonucleic acid in cultured immature rat Leydig and Sertoli cells

Morphological and transcriptomic alterations in neonatal lamb testes following developmental exposure to low-level environmental chemical mixture

Exposure to anthropogenic environmental chemical mixtures could be contributing to the decline in male reproductive health. This study used the biosolid treated pasture (BTP) sheep model to assess the effects of exposure to low-dose chemical mixtures. Maternal BTP exposure was associated with lower plasma testosterone concentrations, a greater proportion of Sertoli cell-only seminiferous tubules, and fewer gonocytes in the testes of neonatal offspring. Transcriptome analysis highlighted changes in testicular mTOR signalling, including lower expression of two mTOR complex components. Transcriptomic hierarchical analysis relative to the phenotypic severity demonstrated distinct differential responses to maternal BTP exposure during pregnancy. Transcriptome analysis between phenotypically normal and abnormal BTP lambs demonstrated separate responses within the cAMP and PI3K signalling pathways towards CREB. Together, the results provide a potential mechanistic explanation for adverse effects. Exposure could lower gonocyte numbers through mTOR mediated autophagy, but CREB mediated survival factors may act to increase germ cell survival.

Neuropeptide Y regulates proliferation and apoptosis in granulosa cells in a follicular stage-dependent manner

Background

The complex regulatory mechanism involved in ovarian follicular development is not completely understood. Neuronal neuropeptide Y (NPY) is involved in the regulation of feeding behavior, energy homeostasis, and reproduction behavior, while its function in ovarian follicular development is not clear. The objective of this study was to investigate if and how NPY regulates follicle development in the ovary.

Methods

All experiments were performed using Sprague Dawley rats. To understand NPY expression pattern at different stages of follicular development, NPY content was assessed using immunohistochemistry in individual follicles. NPY and its receptors expression pattern were evaluated in granulosa cells isolated from preantral (PA), early antral (EA) and late antral follicles (LAF). The influence of NPY on granulosa cell proliferation and apoptosis were further assessed in vitro, using Ki67- and TUNEL-positivity assays. To investigate whether NPY induced-proliferation in EA granulosa cells is mediated through the activation of NPY receptor Y5 (NPY5R) and Mitogen-activated protein kinase (MEK) signal pathway, EA granulosa cells were treated with NPY5R antagonist (CGP71683) and MEK inhibitors (PD98059 and U0126), and Ki67-positive cells were assessed.

Results

NPY protein expression was follicular stage-dependent and cell type-specific. NPY signal intensity in EA was higher than those in PA and LAF. Antral granulosa cells showed the highest signal intensity compared to mural granulosa cells, cumulus cells and theca cells. Granulosa cells NPY protein content and mRNA abundance were higher in EA than in LAF. NPY receptor contents in granulosa cells were follicular stage-dependent. While NPY reduced apoptosis of EA granulosa cells, it increased the proliferation through NPY5R and MEK pathway. In contrast, in LAF granulosa cells, NPY reduced proliferation and increased the number of apoptotic cells, with no significant effects on PA granulosa cells.

Conclusion

This study is the first to evaluate the intraovarian role of NPY in granulosa cells at various stage of follicular development. These results indicate that NPY regulates granulosa cells proliferation and apoptosis in a follicular stage-dependent and autocrine manner. NPY may play a role in pathogenesis of ovarian follicular disorders.

Seasonal variations in cellular expression of neuropeptide Y (NPY) in testis of the catfish, Clarias batrachus and its potential role in regulation of steroidogenesis

The present study demonstrates seasonal variation in the cellular expression of neuropeptide Y (NPY), a known orexigenic neuropeptide, in the testis of the catfish, Clarias batrachus and its relation with testicular steroids. In vitro effects of NPY on androgen production and activities of steroidogenic enzymes were also analyzed to reaffirm the relation between NPY and steroids. NPY-immunoprecipitation was observed in Sertoli cells, interstitial cells and germ cells in recrudescing testis. Intensity of NPY-immunoreaction in the interstitial cells increased steadily with initiation of spermatogenesis and reached maximal in fully grown testes, and then decreased suddenly in the spermiating/spent testis. NPY was also expressed considerably in Sertoli cells in recrudescing testis, but disappeared in the fully grown testis. A moderate NPY-immunoreactivity was also seen in spermatogonial cells in recrudescing testis, but intense NPY-immunoprecipitation was detected in advanced germ cells (spermatids/spermatozoa) in fully mature testis. NPY-immunoreation intensity in interstitial cells showed positive correlation with increasing levels of testicular testosterone and 11-ketotestosterone, and with activities of 3β-HSD & 17β-HSD coinciding with advancing testicular activities. NPY treatment of testicular fragments in vitro stimulated the activities of 3β-HSD & 17β-HSD and increased testosterone & 11-ketotestosterone levels. This study for the first time demonstrates the existence of NPY peptide at cellular levels in fish testis, which stimulates androgen production by acting directly at testicular level.

Seasonal ovarian immunolocalization of neuropeptide Y and its role in steriodogenesis in Asian catfish, Clarias batrachus

The present study was undertaken to examine the cellular localization and potential steroidogenic role of neuropeptide Y (NPY) in the ovary of the freshwater catfish, Clarias batrachus. NPY-immunoreaction was observed in the follicular cells (granulosa and thecal cells) in the growing ovarian follicles, and the intensity of staining increased steadily from the initiation of follicular development until follicles were fully grown. Thereafter as follicles matured the stain intensity decreased. Positive correlations were found between NPY expression and the ovarian levels of 17β-estradiol, testosterone, and activities of 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β-HSD) in the ovary. In vitro NPY treatment stimulated the production of the two steroids and the activities of two enzymes. This is the first report of NPY immunoreactivity at the cellular level in the fish ovary and implicates this orexigenic peptide in the modulation of ovarian steroidogenesis.

The germline stem cell niche unit in mammalian testes

This review addresses current understanding of the germline stem cell niche unit in mammalian testes. Spermatogenesis is a classic model of tissue-specific stem cell function relying on self-renewal and differentiation of spermatogonial stem cells (SSCs). These fate decisions are influenced by a niche microenvironment composed of a growth factor milieu that is provided by several testis somatic support cell populations. Investigations over the last two decades have identified key determinants of the SSC niche including cytokines that regulate SSC functions and support cells providing these factors, adhesion molecules that influence SSC homing, and developmental heterogeneity of the niche during postnatal aging. Emerging evidence suggests that Sertoli cells are a key support cell population influencing the formation and function of niches by secreting soluble factors and possibly orchestrating contributions of other support cells. Investigations with mice have shown that niche influence on SSC proliferation differs during early postnatal development and adulthood. Moreover, there is mounting evidence of an age-related decline in niche function, which is likely influenced by systemic factors. Defining the attributes of stem cell niches is key to developing methods to utilize these cells for regenerative medicine. The SSC population and associated niche comprise a valuable model system for study that provides fundamental knowledge about the biology of tissue-specific stem cells and their capacity to sustain homeostasis of regenerating tissue lineages. While the stem cell is essential for maintenance of all self-renewing tissues and has received considerable attention, the role of niche cells is at least as important and may prove to be more receptive to modification in regenerative medicine.

Neuropeptide Y acts within the rat testis to inhibit testosterone secretion

The factors that influence Leydig cell activity currently include peptides such as neuropeptide Y (NPY). In this work we investigated the ability of this compound, injected directly into the testes of adult male rats, to alter testosterone (T) release into the general circulation. At a 5μg/kg dose administered 1h prior to challenge with human chorionic gonadotropin (hCG, 1.0 U/kg, iv), NPY significantly (P<0.01) blunted the T response to this gonadotropin. The inhibitory effect of NPY was observed in animals pretreated with an antagonist to gonadotropin-releasing hormone or not, indicating that the decrease in plasma T found was most likely independent of pituitary luteinizing hormone. However, testicular levels of steroidogenic acute regulatory (STAR) protein or translocator protein (TSPO) in the Leydig cells did not exhibit consistent changes, which suggested that other mechanisms mediated the blunted T response to hCG. We therefore used autoradiography and immunohistochemistry methodologies to identify NPY receptors in the testes, and found them primarily located on blood vessels. Competition studies further identified these receptors as being Y(1), a subtype previously reported to modulate the vasoconstrictor effect of NPY. The absence of significant changes in STAR and TSPO levels, as well as the absence of Y(1) receptors on Leydig cells, suggest that NPY-induced decreases in T release is unlikely to represent a direct effect of NPY on these cells. Rather, the very high expression levels of Y(1) found in testicular vessels supports the concept that NPY may alter gonadal activity, at least in part, through local vascular impairment of gonadotropin delivery to, and/or blunted T secretion from, Leydig cells.

Peptidergic not monoaminergic fibers profusely innervate the young adult human testis

Numerous studies have reported that intratesticular nerves exert important regulatory effects on the functions of the male gonad; however, as yet little is known about their distribution in the young adult human testis. The purpose of this study was to explore whether peptidergic and adrenergic nerves occur in the male gonad of this age, and, if present, to depict their distribution further. Thirty testes were collected from 15 reproductively healthy donors aged 21-32 years. Antibodies against protein gene product 9.5 (PGP 9.5), neuropeptide Y (NPY), C-terminal flanking peptide of NPY (CPON) and vasoactive intestinal peptide (VIP) were employed for immunohistochemical detection of intratesticular peptidergic nerves, and those against dopamine-beta-hydroxylase (DBH) and 5-hydroxytryptamine (5-HT) for monoaminergic ones. The testicular parenchyma exhibited a rich innervation by PGP 9.5-positive fibers, mainly associated with Leydig cell nests, blood vessels, and seminiferous tubules. Numerous NPY- and CPON-immunoreactive (IR) nerves also appeared in the gonads, but the vast majority were confined to blood vessels. A small number of VIP-IR fibers were detected in some arterioles. By contrast, however, no fibers displaying DBH or 5-HT immunoreactivity were observed within the testis. Additionally, expression of PGP-9.5, NPY, CPON, VIP, DBH and 5-HT was found in Leydig cells, PGP 9.5 in spermatogonia, and NPY and CPON in peritubular myoid cells. Our results suggest that the young adult human testis is devoid of monoaminergic nerves but profusely innervated by peptidergic fibers, which may serve as major neuronal regulators for testicular functions at this age.

RFamide-related peptide and messenger ribonucleic acid expression in mammalian testis: association with the spermatogenic cycle

RFamide-related peptide (RFRP), the mammalian homolog of avian gonadotropin-inhibitory hormone, has a pronounced suppressive action on the reproductive axis across species. In mammals, RFRP acts directly on GnRH neurons, and likely at the level of the pituitary, to inhibit gonadotropin secretion. In the present study, we examined whether RFRP might act outside of mammalian brain on reproductive tissues directly. Using RT-PCR and in situ hybridization, we found that both RFRP and its receptors [G protein-coupled receptor (GPR) 147 and GPR74] are expressed in the testis of Syrian hamster. These results were confirmed and extended using double- and triple-label immunohistochemistry. RFRP expression was observed in spermatocytes and in round to early elongated spermatids. Significant expression of RFRP was not seen in Leydig cells. GPR147 protein was observed in myoid cells in all stages of spermatogenesis, pachytene spermatocytes, maturation division spermatocytes, and in round and late elongated spermatids. GPR74 proteins only appeared in late elongated spermatids. Additionally, we found that RFRP and its receptor mRNA are markedly altered by day length and reproductive condition. These findings highlight a possible novel autocrine and/or paracrine role for RFRP in Syrian hamster testis, potentially contributing to the differentiation of spermatids during spermiogenesis.

Gonadotropin-inhibitory hormone and its receptor in the avian reproductive system

Many hormones that are classified as neuropeptides are synthesized in vertebrate gonads in addition to the brain. Receptors for these hormones are also expressed in gonadal tissue; thus there is potential for a highly localized autocrine or paracrine effect of these hormones on a variety of gonadal functions. In the present study we focused on gonadotropin-inhibitory hormone (GnIH), a neuropeptide that was first discovered in the hypothalamus of birds. We present different lines of evidence for the synthesis of GnIH and its receptor in the avian reproductive system including gonads and accessory reproductive organs by studies on two orders of birds: Passeriformes and Galliformes. Binding sites for GnIH were initially identified via in vivo and in vitro receptor fluorography, and were localized in ovarian granulosa cells along with the interstitial layer and seminiferous tubules of the testis. Furthermore, species-specific primers produced clear PCR products of GnIH and GnIH receptor (GnIH-R) in songbird and quail gonadal and other reproductive tissues, such as oviduct, epididymis and vas deferens. Sequencing of the PCR products confirmed their identities. Immunocytochemistry detected GnIH peptide in ovarian thecal and granulosa cells, testicular interstitial cells and germ cells and pseudostratified columnar epithelial cells in the epididymis. In situ hybridization of GnIH-R mRNA in testes produced a strong reaction product which was localized to the germ cells and interstitium. In the epididymis, the product was also localized in the pseudostratified columnar epithelial cells. In sum, these results indicate that the avian reproductive system has the capability to synthesize and bind GnIH in several tissues. The distribution of GnIH and its receptor suggest a potential for autocrine/paracrine regulation of gonadal steroid production and germ cell differentiation and maturation.

Sterility and gene expression in hybrid males of Xenopus laevis and X. muelleri

BACKGROUND

Reproductive isolation is a defining characteristic of populations that represent unique biological species, yet we know very little about the gene expression basis for reproductive isolation. The advent of powerful molecular biology tools provides the ability to identify genes involved in reproductive isolation and focuses attention on the molecular mechanisms that separate biological species. Herein we quantify the sterility pattern of hybrid males in African Clawed Frogs (Xenopus) and apply microarray analysis of the expression pattern found in testes to identify genes that are misexpressed in hybrid males relative to their two parental species (Xenopus laevis and X. muelleri).

METHODOLOGY/PRINCIPAL FINDINGS

Phenotypic characteristics of spermatogenesis in sterile male hybrids (X. laevis x X. muelleri) were examined using a novel sperm assay that allowed quantification of live, dead, and undifferentiated sperm cells, the number of motile vs. immotile sperm, and sperm morphology. Hybrids exhibited a dramatically lower abundance of mature sperm relative to the parental species. Hybrid spermatozoa were larger in size and accompanied by numerous undifferentiated sperm cells. Microarray analysis of gene expression in testes was combined with a correction for sequence divergence derived from genomic hybridizations to identify candidate genes involved in the sterility phenotype. Analysis of the transcriptome revealed a striking asymmetric pattern of misexpression. There were only about 140 genes misexpressed in hybrids compared to X. laevis but nearly 4,000 genes misexpressed in hybrids compared to X. muelleri.

CONCLUSIONS/SIGNIFICANCE

Our results provide an important correlation between phenotypic characteristics of sperm and gene expression in sterile hybrid males. The broad pattern of gene misexpression suggests intriguing mechanisms creating the dominance pattern of the X. laevis genome in hybrids. These findings significantly contribute to growing evidence for allelic dominance in hybrids and have implications for the mechanism of species differentiation at the transcriptome level.

Evolutionary conservation of neuropeptide expression in the thymus of different species

Evidence suggests that the immune and neuroendocrine systems cross talk by sharing ligands and receptors. Hormones and neuropeptides produced by the neuroendocrine system often modulate the function of lymphoid organs and immune cells. We have previously reported the intrathymic expression of somatostatin (SOM) in the mouse and that several neuropeptides, most notably calcitonin-gene-related peptide (CGRP), neuropeptide Y (NPY), SOM and substance P (SP), can modulate thymocyte development. However, little is known about the intrathymic expression of these neuropeptides either in the mouse or in other species. Moreover, a comparative analysis of the expression of these molecules would highlight the evolutionary importance of intrathymic neuroendocrine interactions in T-cell development. We have studied the expression of different neuropeptides in the thymus of zebrafish, Xenopus, avians, rodent, porcine, equine and human by immunohistochemistry and reverse transcription-polymerase chain reaction. We found that CGRP, NPY, SOM, SP and vasointestinal polypeptide (VIP) are expressed in the thymus of all species investigated. The thymic location of many of these neuropeptides was conserved and appears to be within the stromal compartments. Interestingly, in the avian thymus the expression of CGRP, SOM and SP appears to change depending on the age of the tissue. These findings suggest that neuropeptides may play an important role in T-cell development and provide further evidence of cross talk between the immune and neuroendocrine systems.

Neuropeptides of the pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal polypeptide/growth hormone-releasing hormone/secretin family in testis

Mammalian testicular development and the maintenance of spermatogenesis are hormone-dependent processes that are controlled by the pituitary gonadotropins and testosterone. Recent studies have demonstrated the presence of many neuropeptides and their receptors in the testis, suggesting that these peptides operate as local regulators of testicular germ cell development and function. Among these testicular neuropeptides, the peptides that belong to the pituitary adenylate cyclase-activating polypeptide (PACAP) family, particularly growth hormone-releasing hormone and secretin, appear to show some unique common features in terms of intratesticular localization and the time of expression during the spermatogenic cycle. However, their precise physiologic roles and mechanisms of action remain unknown. This review analyzes the available information on the functional interactions among the testicular cells that appear to be mediated by locally produced neuropeptides, with a special emphasis on the peptides of the PACAP family.

Neuropeptide Y and lipid increase apolipoprotein AIV gene expression in rat hypothalamus

Apolipoprotein AIV (apo AIV) is a circulating signal released from intestinal cells in response to lipid feeding and contributes to the anorectic effect of a lipid meal. We have demonstrated that apo AIV is also synthesized in the hypothalamus, and that hypothalamic apo AIV gene expression is regulated physiologically. Neuropeptide Y (NPY) is a hypothalamic neuropeptide with broad regulatory actions in the central nervous system. In the present studies, the effects of intracerebroventricular (i.v.t.) administration of NPY and of intraduodenal lipid infusion on hypothalamic apo AIV gene expression were determined using competitive RT-PCR in fasted rats. I.v.t. injection of NPY alone significantly increased apo AIV mRNA levels in the hypothalamus in a dose-dependent manner. Intraduodenal infusion of lipid also stimulated the gene expression of hypothalamic apo AIV, but no further significant increment occurred when i.v.t. injection of NPY was combined with lipid infusion. These results suggest that NPY and lipid may regulate apo AIV gene expression in the rat hypothalamus.

Neuropeptides of the pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal polypeptide/growth hormone-releasing hormone/secretin family in testis

Mammalian testicular development and the maintenance of spermatogenesis are hormone-dependent processes that are controlled by the pituitary gonadotropins and testosterone. Recent studies have demonstrated the presence of many neuropeptides and their receptors in the testis, suggesting that these peptides operate as local regulators of testicular germ cell development and function. Among these testicular neuropeptides, the peptides that belong to the pituitary adenylate cyclase-activating polypeptide (PACAP) family, particularly growth hormone-releasing hormone and secretin, appear to show some unique common features in terms of intratesticular localization and the time of expression during the spermatogenic cycle. However, their precise physiologic roles and mechanisms of action remain unknown. This review analyzes the available information on the functional interactions among the testicular cells that appear to be mediated by locally produced neuropeptides, with a special emphasis on the peptides of the PACAP family.

Dynamic changes in gene expression along the rat epididymis

In the epididymis a series of complex, sequential events transform immature, spermatozoa into mature, motile sperm with fertilizing ability. These events are not intrinsic to germ cells but rather are a direct result of exposure to, and interaction with, the environment created by the epididymal epithelium. Regional differences along the epididymis are essential in the establishment of the environment required for sperm maturation. Although parts of this process have been identified, the molecular basis for the segment-specific differences and how they contribute to the process of sperm maturation, are not yet resolved. The identification of genes expressed in a region-specific manner will provide valuable insight into the functional differences between the regions. To characterize gene expression in the different regions of the epididymis, microarrays containing 1176 rat cDNAs were used to examine gene expression in the initial segment, caput, corpus, and cauda epididymidis of the adult Brown Norway rat. Overall, the cauda epididymidis expressed the most genes and the corpus epididymidis the fewest. A small percentage of genes (3%) were expressed highly (greater than fivefold the average expression on the array) along the tissue. Segment-specific gene expression for genes expressed at high levels was observed in all epididymal segments except the corpus epididymidis. Of the genes on the array, 36% were expressed in all four epididymal segments; expression changes that were a minimum of twofold in either direction between adjacent segments are discussed. The expression of cathepsins and oxidative stress-related genes was investigated. Six of the eight cathepsins on the array (B, C, E, H, L, and K) were expressed above twofold background and showed different levels of expression along the duct with cathepsin K showing the most dramatic change (i.e., a decrease of 87% between the initial segment and the corpus epididymidis). There was also differential expression along the epididymis of many genes associated with oxidative stress defenses. Using the power of expression array technology, we have identified novel transcripts expressed in a segment-specific manner and been able to assess how the expression of several selected gene families is modulated along the epididymis.

Sertoli cells inhibited apoptosis of pachytene spermatocytes and round spermatids

Apoptosis in the testis represents an important physiological mechanism that regulates the number of germ cells in the seminiferous epithelium. This apoptosis is believed to be regulated by many factors, including growth factors and cytokines, which appear to suppress apoptosis of the germ cells. In this study, we examined the roles of Sertoli cells on the regulation of pachytene spermatocyte (PS) and round spermatid (RSd) apoptosis with either a co-culture trans-well system or a direct contact system. Apoptosis was detected by low molecular weight DNA fragmentation assay, in situ end labeling, and an LDH assay. In addition, the level of Bcl-2, Bax, and ICE mRNAs in PS and RSd by Northern blot analysis. When PS and RSd were cultured with Sertoli cells in either a trans-well system or direct contact system, the extent of apoptotic DNA fragmentation and LDH level were both significantly lower than those control values. TUNEL staining also revealed the inhibition of apoptosis of PS and RSd when they were cultured with Sertoli cells compared with controls (p <0.05). Moreover, the extent of apoptotic DNA fragmentation and LDH level were significantly lower in the direct contact system than in the trans-well system. TUNEL staining also demonstrated a more decrease in apoptosis of PS and RSd in the direct contact system compared with the trans-well system (p < 0.05). PS and RSd cultured with Sertoli cells exhibited an increase in Bcl-2 mRNA, whereas those cultured with serum-free medium did not show any change. The levels of Bax and ICE mRNAs decreased in PS and RSd cultured with Sertoli cells in comparison with control values. These results suggest that Sertoli cells can prevent apoptosis of germ cells, and that the effect of Sertoli cells on germ cells is mediated by cell to cell interaction or, remote effects of inhibitory factors on apoptosis.

Immunohistochemical localization of protein gene product 9.5, ubiquitin, and neuropeptide Y immunoreactivities in epithelial and neuroendocrine cells from normal and hyperplastic human prostate

This study was designed to investigate (a) the presence of protein gene product 9.5 (PGP 9.5), ubiquitin, and neuropeptide Y (NPY) in the neuroendocrine and secretory epithelium of the human normal prostate and its secretions, and (b) the changes in immunoreactivity to these proteins in men with benign prostatic hyperplasia. Western blotting and light microscopic immunohistochemistry techniques were used and the numerical density of immunoreactive neuroendocrine cells, and the volume fractions of immunostained secretory epithelium were evaluated. Western blotting revealed the presence of the three antigens in both tissue homogenates and prostate secretion. Some neuroendocrine cells immunoreacted to PGP 9.5 and NPY in all the prostate regions of control specimens. Ubiquitin immunoreactivity was detected in the nuclei from both basal cells and secretory epithelial cells. The cytoplasm of the secretory cells and the glandular lumen also showed immunostaining for the three proteins. The numerical densities of both PGP 9.5 and NPY neuroendocrine cells were lower in hyperplasia than in controls. No differences in the volume fraction occupied by epithelial immunostaining to both proteins was found between hyperplastic and control prostates. We concluded that (a) PGP 9.5 and NPY, but not ubiquitin, are common antigens in both neuroendocrine and secretory prostate cells, (b) the three immunoreactive proteins contribute to the prostate secretions, and (c) the secretion of ubiquitin is markedly diminished in the hyperplastic epithelium.(J Histochem Cytochem 48:1121-1130, 2000)

cNeuropeptide Y family of peptides: Structure, anatomical expression, function, and molecular evolution

Evolutionary relationships between neuroendocrine peptides are often difficult to resolve across divergent phyla due to independent duplication events in different lineages. Thanks to peptide purification and molecular cloning in many different species, the situation is beginning to clear for the neuropeptide Y (NPY) family, which also includes peptide YY (PYY), the tetrapod pancreatic polypeptide (PP) and the fish pancreatic peptide Y (PY). It has long been assumed that the first duplication to occur in vertebrate evolution generated NPY and PYY, as both of these are found in all gnathostomes as well as lamprey. Evidence from other gene families show that this duplication was probably a chromosome duplication event. The origin of a second PYY peptide found in lamprey remains to be explained. Our recent cloning of NPY, PYY and PY in the sea bass proves that fish PY is a separate gene product. We favour the hypothesis that PY is a duplicate of the PYY gene and that it may have occurred late in fish evolution, as PY has so far only been found in acanthomorph fishes. Thus, this duplication seems to be independent of the one that generate PP from PYY in tetrapods, although both tetrapod PP and fish PY are expressed in the pancreas. Studies in the sea bass and other fish show that PY, in contrast to PP, is expressed in the nervous system. We review the literature on the distribution and functional aspects of the various NPY-family peptides in vertebrates.

Key words: neuropeptide Y, pancreatic polypeptide, fish pancreatic peptide, gene duplication.

Inhibition of apoptosis in cultured immature rat Leydig cells by human chorionic gonadotropin associated with Bcl-2 mRNA expression

Bcl-2 is the first identified negative regulator of apoptotic cell death. When the level of Bcl-2 mRNA in rat whole testes was examined in the present study, it gradually decreased in rats from 2.5 to 9 weeks old. We also examined the effect of human chorionic gonadotropin (hCG) on apoptosis and the level of Bcl-2 mRNA expression in immature Leydig cells in vitro. When the cells were cultured with serum free media (SFM), Bcl-2 mRNA levels gradually decreased. On the other hand, the level of Bcl-2 mRNA in cells treated with 50 ng/ml of hCG decreased at 6 h, but increased after 12 h. At 24 h, the level of Bcl-2 mRNA in the treated cells was almost the same as that of control cells (time = 0). At 12 h after the addition of various concentrations (from 0.1-1000 ng/ml) of hCG, Bcl-2 mRNA levels increased in a dose-dependent manner. An analysis of DNA fragmentation showed that treatment with hCG prevents the apoptosis of immature Leydig cells. Our findings suggest that Bcl-2 mRNA may be related to the programmed cell death of immature rat Leydig cells in vitro, which are inhibited by hCG.

NPY messenger RNA is increased in medial hypothalamus of anorectic tumor-bearing rats

Previous investigations suggest that neuropeptide Y (NPY) feeding mechanisms and corticotropin releasing factor (CRF) are altered in anorectic tumor-bearing (TB) rats. To better determine the relationship of NPY and CRF synthesis to cancer anorexia we measured mRNA for these peptides in medial and lateral hypothalamus of TB and control rats. NPY and CRF mRNA were reliably detected by Northern blot analysis only in medial hypothalamus, where NPY message was elevated significantly in TB rats. CRF mRNA tended to be reduced in both pair-fed (PF) and TB rats, but did not reach statistical significance. Concentrations of NPY or CRF were not altered significantly in either the lateral or medial hypothalamus of TB or PF rats. These results suggest that the transcription of NPY is elevated in PF rats and is increased further in anorectic TB rats. The lack of significant increases in levels of peptides may be related to dilution, due to measuring a relatively large block of hypothalamic tissue. Alternatively, translation of the signal for NPY production may be inhibited, or degradation of peptide levels may be increased.