Neuropeptides and the control of food intake in fish

The brain, particularly the hypothalamus, integrates input from factors that stimulate (orexigenic) and inhibit (anorexigenic) food intake. In fish, the identification of appetite regulators has been achieved by the use of both peptide injections followed by measurements of food intake, and by molecular cloning combined with gene expression studies. Neuropeptide Y (NPY) is the most potent orexigenic factor in fish. Other orexigenic peptides, orexin A and B and galanin, have been found to interact with NPY in the control of food intake in an interdependent and coordinated manner. On the other hand cholecystokinin (CCK), cocaine and amphetamine-regulated transcript (CART), and corticotropin-releasing factor (CRF) are potent anorexigenic factors in fish, the latter being involved in stress-related anorexia. CCK and CART have synergistic effects on food intake and modulate the actions of NPY and orexins. Although leptin has not yet been identified in fish, administration of mammalian leptin inhibits food intake in goldfish. Moreover, leptin induces CCK gene expression in the hypothalamus and its actions are mediated at least in part by CCK. Other orexigenic factors have been identified in teleost fish, including the agouti-related protein (AgRP) and ghrelin. Additional anorexigenic factors include bombesin (or gastrin-releasing peptide), alpha-melanocyte-stimulating hormone (alpha-MSH), tachykinins, and urotensin I. In goldfish, nutritional status can modify the expression of mRNAs encoding a number of these peptides, which provides further evidence for their roles as appetite regulators: (1) brain mRNA expression of CCK, CART, tachykinins, galanin, ghrelin, and NPY undergo peri-prandial variations; and (2) fasting increases the brain mRNA expression of NPY, AgRP, and ghrelin as well as serum ghrelin levels, and decreases the brain mRNA expression of tachykinins, CART, and CCK. This review will provide an overview of recent findings in this field.

Characterization of two forms of cocaine- and amphetamine-regulated transcript (CART) peptide precursors in goldfish: molecular cloning and distribution, modulation of expression by nutritional status, and interactions with leptin

Complementary DNAs encoding two forms of cocaine- and amphetamine-regulated transcript (CART) peptide precursors were identified from goldfish brain and named CART I and CART II. Each cDNA contains a signal peptide sequence, the putative CART-like peptide, and a carboxy-terminal extension peptide. Form I encodes a 117-amino acid pro-CART, whereas form II encodes a 120-amino acid pro-CART. Both forms resemble mammalian CART peptides. Each goldfish CART precursor is encoded by three exons interrupted by two introns within genomic DNA. RT-PCR, slot blot, and Northern blot analysis showed that the mRNAs for form I and II precursors have a widespread distribution. Form I and II are present in the brain, pituitary, eye, gonads, and kidney. Form I is also present in the gill. In the brain, form I is predominant in the olfactory bulb and hypothalamus, and form II is predominant in the optic tectum. Food deprivation for 96 h induced a decrease in form I mRNA levels in the telencephalon-preoptic region, hypothalamus, and olfactory bulb and in form II mRNA expression in the olfactory bulb. An increase in mRNA levels was observed 2 h following a meal in the olfactory bulbs and hypothalamus for form I whereas no postprandial changes in form II mRNA levels were observed. Intracerebroventricular injections of human CART alone induced a significant decrease in food intake. Injections of leptin reinforced the inhibition of feeding behavior and food intake seen in CART-treated fish. Central injection of leptin induced an increase in CART I mRNA in the optic tectum, hypothalamus, and olfactory bulbs but had no effect on CART II mRNA expression in the brain. These results suggest that CART peptides act as leptin-regulated satiety factors in goldfish and that they might have other physiological roles besides feeding, possibly in sensory information processing.

Interactions between orexin A, NPY and galanin in the control of food intake of the goldfish, Carassius auratus

The neuropeptides orexin A (OXA), neuropeptide Y (NPY) and galanin (GAL) have been shown to play a role in the regulation of food intake in mammals. They also significantly stimulate feeding in goldfish. In order to assess the interactions between these peptides in the control of feeding in goldfish, we investigated the effects of central injection of specific receptor antagonists for NPY (BIBP 3226) and GAL (M40) on OXA-induced feeding and the effects of desensitization of orexin receptors on NPY- and GAL-induced feeding. We investigated the effects of BIBP 3226 on GAL-induced feeding and the effects of M40 on NPY-induced feeding. We also examined the effects of coinjection of each pair of neuropeptides on feeding behavior. Injections of 10 ng/g OXA, 5 ng/g NPY and 10 ng/g GAL each induced an increase in feeding. Fish treated with 5 ng/g BIBP or 20 ng/g M40 had food consumption similar to saline controls. BIBP at 5 ng/g significantly reduced NPY- and OXA-induced feeding. Injections of 20 ng/g M40 significantly decreased GAL-induced feeding, but had no effect on OXA-induced feeding. Blocking of orexin receptors by treatment with high doses of OXA (100 ng/g) resulted in a decrease in both NPY- and GAL-induced feeding. Coinjection with 0.5 ng/g OXA and either 0.5 ng/g NPY or 0.5 ng/g GAL resulted in a food intake higher than that observed in saline control fish and in fish treated with NPY or GAL alone at 0.5 ng/g. NPY mRNA expression was increased in the telencephalon and in the hypothalamus compared to saline-treated fish, following injection of OXA. These results indicate that both NPY and GAL are at least, in part, dependent on coaction with OXA for the stimulation of food intake and feeding behavior in goldfish. In addition, the effects of OXA are mediated, in part, by the NPY pathway. This suggests a functional interdependence between these three peptidergic systems in the control of energy balance in goldfish.

Neuropeptide Y stimulates food consumption through multiple receptors in goldfish

In this study, the acute effects of brain intracerebroventricular (icv) injections of mammalian neuropeptide Y (NPY) Y1 ([31Leu,34Pro]NPY), Y2 (NPY2-36) and Y5 ([D-32Trp]NPY) receptor subtype agonists on food intake in goldfish were examined. Icv injection of Y1 and Y5 receptor agonists in dosages of 1 and 5 ng/g exhibited dose-dependent effects on food intake; however, higher dosages of both receptor subtypes had desensitising effects on food intake, and caused a decrease in food intake in comparison to the lower dosages. At 10 and 20 ng/g, Y1 receptor agonist-treated fish exhibited feeding significantly lower than intact and saline-injected fish; fish treated with the same dosages of Y5 agonist exhibited food intake similar to intact and saline-injected fish. Y2 agonist had no effects on food intake. Co-icv administration of Y1 and Y5 agonists in dosages of 1 and 5 ng/g caused enhanced food intake that was additive of the individual doses alone. However, desensitising one receptor did not influence the responsiveness of the other. Co-icv injection of Y1 receptor agonist in desensitizing high dosages (10 and 15 ng/g) with Y5 receptor agonist in lower doses (1 and 5 ng/g, respectively) or vice versa, resulted in a food intake similar to the dosages of Y1 and Y5 receptor agonists at 1 and 5 ng/g given alone. Overall, this study demonstrates that NPY acts centrally through Y1 and Y5 receptors to stimulate food intake in goldfish. The Y1 and Y5 receptors appear to act independently in the stimulation of food intake in goldfish.

Effects of food deprivation and refeeding on neuropeptide Y (NPY) mRNA levels in goldfish

In mammals, NPY is a key factor in the regulation of feeding behavior. In the present study, the effects of refeeding for 1-3 h in 72-75-h food deprived (FD) goldfish on the levels of NPY mRNA in telencephalon-preoptic (TEL-POA), hypothalamus (HYP) and optic tectum-thalamus (OT-THAL) were examined, using Northern blot analysis. Goldfish FD for 72 h exhibited a significant increase in NPY mRNA levels in all brain regions. At 1 h after 72-h FD (73-h FD), NPY mRNA was significantly increased in TEL-POA and OT-THAL, but remained the same as 72-h FD fish in HYP. At 3 h after 72-h FD (75 h), all brain regions exhibited a significant increase in NPY mRNA levels. However, subsequent refeeding for 1-3 h rapidly and completely reversed the effects of FD in all brain regions, reaching fed levels within 1-3 h of refeeding. Serum GH levels were highest in 72-h FD fish, but decreased significantly over 1-3 h after 72-h FD; whereas, refeeding reversed the increase in serum GH levels only at 3 h after refeeding. Taken together, these results further support that NPY is a physiological brain transducer involved in the regulation of daily appetite and feeding in goldfish.

Somatostatins and their receptors in fish

Somatostatin (SRIF) is a multigene family of peptides. SRIF-14 is conserved with identical primary structure in species across the vertebrates. The presence of multiple SRIF genes has been demonstrated in a number of fish species. Notably, three distinct SRIF genes have been identified in goldfish. One of these genes, which encodes [Pro(2)]SRIF-14, has also been identified in sturgeon and African lungfish, and is closely associated with the amphibian [Pro(2),Met(13)]SRIF-14 gene and mammalian cortistatin gene. The main neuroendocrine role of SRIF-14 peptide that has been determined in fish is the inhibition of pituitary growth hormone secretion. The functions of SRIF-14 variant or larger forms of SRIF peptide and the regulation of SRIF gene expression remain to be explored. Type one and two SRIF receptors have been identified from goldfish and type three SRIF receptor from an electric fish. Fish SRIF receptors display considerable homology to mammalian counterparts in terms of primary structure and negative coupling to adenylate cyclase. The identification of the multiple gene family of SRIF peptides and multiple types of SRIF receptors in fish opens a new avenue for the study of physiological roles of SRIF, and the molecular and cellular mechanisms of SRIF actions in fish.

The hypothalamic-pituitary-interrenal axis and the control of food intake in teleost fish

Although environmental, social and physical stressors have been shown to inhibit food intake and feeding behavior in fish, little is known about the mechanisms that mediate the appetite-suppressing effects of stress. Since the hypothalamic-pituitary-interrenal (HPI) axis is activated in response to most forms of stress in fish, components of this axis may be involved in mediating the food intake reductions elicited by stress. Recent investigations into the brain regulation of food intake in fish have identified several signals with orexigenic and anorexigenic properties. Among these appetite-regulating signals are related neuropeptides that can activate the HPI axis, namely corticotropin-releasing factor (CRF) and urotensin I (UI). Central injections of CRF or UI, or treatments that result in an increase in hypothalamic CRF and UI gene expression, can elicit dose-dependent decreases in food intake that can be reversed by pre-treatment with a CRF-receptor antagonist. Evidence also suggests that cortisol, the end product of HPI activation in most fishes (i.e. Osteichthyes), may be involved in the regulation of food intake. Overall, while elements of the HPI axis may mediate some of the appetite-suppressing effects of stress, it is undetermined how either CRF-related peptides, cortisol, or other elements of the stress response interact with the complex circuitry of the hypothalamic feeding center.

Appetite-suppressing effects of urotensin I and corticotropin-releasing hormone in goldfish (Carassius auratus)

Fish urotensin I (UI), a member of the corticotropin-releasing hormone (CRH) family of peptides, is a potent inhibitor of food intake in mammals, yet the role of UI in the control of food intake in fish is not known. Therefore, to determine the acute effects of UI on appetite relative to those of CRH, goldfish were given intracerebroventricular (i.c.v.) injections of carp/goldfish UI and rat/human CRH (0.2-200 ng/g) and food intake was assessed for a 2-hour period after the injection. UI and CRH both suppressed food intake in a dose-related manner and UI (ED50 = 3.8 ng/g) was significantly more potent than CRH (ED50 = 43.1 ng/g). Pretreatment with the CRH receptor antagonist, alpha-helical CRH(9-41), reversed the reduction in food intake induced by i.c.v. UI and CRH. To assess whether endogenous UI and CRH modulate fish appetite, goldfish were given intraperitoneal implants of the glucocorticoid receptor antagonist, RU-486 (50 and 100 microg/g), or the cortisol synthesis inhibitor, metyrapone (100 and 200 microg/g), and food intake was monitored over the following 72 h. Fish treated with either RU-486 or metyrapone were characterized by a sustained and dose-dependent reduction in food intake. Pretreatment with i.c.v. implants of alpha-helical CRH(9-41) partially reversed the appetite-suppressing effects of RU-486 and metyrapone. In a parallel experiment, the effects of RU-486 (100 microg/g) and metyrapone (200 microg/g) intraperitoneal implants on brain UI and CRH gene expression were assessed. Relative to sham-implanted controls, fish treated with RU-486 or metyrapone had elevated UI mRNA levels in the hypothalamus and CRH mRNA levels in the telencephalon-preoptic brain region. Together, these results suggest that UI is a potent anorectic peptide in the brain of goldfish and that endogenous CRH-related peptides can play a physiological role in the control of fish appetite.

Effects of CART peptides on food consumption, feeding and associated behaviors in the goldfish, Carassius auratus: actions on neuropeptide Y- and orexin A-induced feeding

CART (cocaine- and amphetamine-regulated transcript) peptides are novel brain neuropeptides that have been shown to have a role in the control of feeding behavior in mammals. The effects of intracereboventricular (i.c.v.) administration of two CART fragments, CART (62-76) and CART (55-102) on feeding and behavioral activity of goldfish (Carassius auratus) were examined. Both CART peptide fragments inhibited food intake in goldfish. Co-injection of CART peptide and neuropeptide Y (NPY) reduced the increase in feeding caused by injection of NPY alone. CART (55-102) was more potent than CART (62-76). Co-treatment with CART (55-102) and orexin A inhibited the feeding response induced by orexin A alone. Feeding behavior was stimulated relative to saline controls following injection of CART (62-76) alone and co-injection of NPY and CART (62-76), but was not affected by treatment with CART (55-102) alone, NPY and CART (55-102) or orexin A and CART (55-102). Total behavioral activity was increased with NPY, orexin A, and both CART fragments alone as compared to saline controls, as well as in fish co-treated with NPY and CART (62-76) or NPY and CART (55-102) as compared to saline controls and NPY-treated fish. Tremors were seen in fish treated with CART (55-102) alone, and in fish co-treated with NPY and CART (55-102) and orexin A and CART (55-102). Co-treatment of the fish with NPY but not with orexin A significantly lowered the frequency of fish showing tremors as compared to fish treated with CART alone. These results indicate that CART peptides are involved in the regulatory pathways of feeding and behavioral activity in goldfish.

Somatostatin family of peptides and its receptors in fish

Somatostatin (SRIF or SS) is a phylogenetically ancient, multigene family of peptides. SRIF-14 is conserved with identical primary structure in species of all classes of vertebrates. The presence of multiple SRIF genes has been demonstrated in a number of fish species and could extend to tetrapods. Three distinct SRIF genes have been identified in goldfish. One of these genes, which encodes [Pro2]SRIF-14, is also present in sturgeon and African lungfish, and is closely associated with amphibian [Pro2,Met13]SRIF-14 gene and mammalian cortistatin gene. The post-translational processing of SRIF precursors could result in multiple forms of mature SRIF peptides, with differential abundance and tissue- or cell type-specific patterns. The main neuroendocrine role of SRIF-14 peptide that has been determined in fish is the inhibition of pituitary growth hormone secretion. The functions of SRIF-14 variant or larger forms of SRIF peptide and the regulation of SRIF gene expression remain to be explored. Type 1 and type 2 SRIF receptors have been identified from goldfish and a type 3 SRIF receptor has been identified from an electric fish. Fish SRIF receptors display considerable homology with mammalian counterparts in terms of primary structure and negative coupling to adenylate cyclase. Although additional types of receptors remain to be determined, identification of the multiple gene family of SRIF peptides and multiple types of SRIF receptors opens a new avenue for the study of physiological roles of SRIF, and the molecular and cellular mechanisms of SRIF action in fish.

Regulation of food intake by neuropeptide Y in goldfish

In mammals, neuropeptide Y (NPY) is a potent orexigenic factor. In the present study, third brain ventricle (intracerebroventricular) injection of goldfish NPY (gNPY) caused a dose-dependent increase in food intake in goldfish, and intracerebroventricular administration of NPY Y1-receptor antagonist BIBP-3226 decreased food intake; the actions of gNPY were blocked by simultaneous injection of BIBP-3226. Goldfish maintained on a daily scheduled feeding regimen display an increase in NPY mRNA levels in the telencephalon-preoptic area and hypothalamus shortly before feeding; however, a decrease occured in optic tectum-thalamus. In both fed and unfed fish, brain NPY mRNA levels decreased after scheduled feeding. Restriction in daily food ration intake for 1 wk or food deprivation for 72 h resulted in increased brain NPY mRNA levels. Results from these studies demonstrate that NPY is a physiological brain signal involved in feeding behavior in goldfish, mediating its effects, at least in part, through Y1-like receptors in the brain.

Molecular cloning and expression of a type-two somatostatin receptor in goldfish brain and pituitary

Somatostatin (SRIF or SS) exerts diverse inhibitory actions through binding to specific receptors. In this study, a SRIF receptor cDNA was cloned and sequenced from goldfish brain using PCR and cDNA library screening. The cDNA encodes a 380-amino acid goldfish type-two SRIF receptor (designated as sst(2)), with seven putative transmembrane domains (TMD) and YANSCANP motif in the seventh TMD, a signature sequence for the mammalian SRIF receptor (sst) family. In addition, the amino acid sequence of the receptor has 61-62% homology to mammalian sst(2), 41-47% homology to other mammalian sst subtypes and 41-43% homology to recently identified fish sst(1) and sst(3) receptors. Both SRIF-14 and [Pro(2)]SRIF-14, two of the native goldfish SRIF forms, but not a putative goldfish SRIF-28, significantly inhibited forskolin-stimulated adenosine 3':5'-cyclic monophosphate (cAMP) release in COS-7 cells transiently expressing goldfish sst(2), suggesting functional coupling of the receptor to adenylate cyclase. None of the three peptides affected inositol phosphate production in the same receptor expression system. Northern blot showed that mRNA for the sst(2) receptor is widely distributed in goldfish brain, and highly expressed in the pituitary. The decrease in pituitary sst(2) mRNA levels following estradiol implantation suggests the presence of a negative feedback mechanism on sst(2) gene expression.

Brain regulation of feeding behavior and food intake in fish

In mammals, the orexigenic and anorexigenic neuronal systems are morphologically and functionally connected, forming an interconnected network in the hypothalamus to govern food intake and body weight. However, there are relatively few studies on the brain control of feeding behavior in fish. Recent studies using mammalian neuropeptides or fish homologs of mammalian neuropeptides indicate that brain orexigenic signal molecules include neuropeptide Y, orexins, galanin and beta-endorphin, whereas brain anorexigenic signal molecules include cholecystokinin, bombesin, corticotropin-releasing factor, cocaine- and amphetamine-regulated transcript, and serotonin. Tachykinins may also have an anorectic action in fish. The brain hypothalamic area is associated with regulation of food intake, while sites outside the hypothalamus are also involved in this function. There is correlation between short-term changes in serum growth hormone levels and feeding behavior, although possible mechanisms integrating these functions remain to be defined.

Osteosynthesis of metastatic lesions of the proximal femur with a solid femoral nail and interlocking spiral blade inserted without reaming

OBJECTIVES

To evaluate the efficiency of a solid femoral nail and interlocking spiral-blade, inserted without reaming (UFN/ spiral blade, Synthes-Stratec, Oberdorf, Switzerland), for the fixation of pathologic and impending pathologic fractures of the proximal femur, particularly those involving the subtrochanteric area.

DESIGN

Retrospective, consecutive series.

SETTING AND PATIENTS

All patients treated for pathologic and impending pathologic fractures of the trochanteric or subtrochanteric area, stabilized using a UFN/spiral blade, inserted without reaming, from June 1994 to June 1997.

INTERVENTION

Femoral intramedullary nailing was performed without reaming on a radiolucent operating room table. The nail was inserted through a five-centimeter supratrochanteric approach, and the interlocking spiral-blade device was introduced percutaneously.

METHODS

The following parameters were assessed: pathology reports, location of bone lesions, patient survival, pain relief, ambulation, hardware failure on successive radiographs, and intraoperative complications.

RESULTS

Twelve pathologic and impending pathologic fractures were stabilized in ten patients. Two patients required bilateral nailing that was staged with intervals of two and three weeks, respectively. The average postsurgical survival was six and one-half months. No implant failure was noted, and no surgical revision was performed. One intraoperative death occurred during surgery and was documented on autopsy as massive pulmonary fat embolization. Neither patient with bilateral nailing suffered from fat embolism syndrome.

CONCLUSIONS

Femoral nail insertion without reaming using an interlocking spiral blade provides appropriate stabilization of the proximal femur in case of metastatic lesions, even with extensive subtrochanteric involvement. Although the nails were inserted without reaming, this did not avoid the risk of fat embolization syndrome. This study only addressed results in patients with short-term survival.

The inhibitory effects of (gamma)-aminobutyric acid (GABA) on growth hormone secretion in the goldfish are modulated by sex steroids

Double-labelling studies at the electron microscopic level demonstrated that gamma-aminobutyric acid (GABA)-immunoreactive nerve endings are associated with growth-hormone-secreting cells in the proximal pars distalis of the goldfish pituitary gland, suggesting that GABA may be important for the control of growth hormone release in this species. An in vitro assay for GABA-transaminase activity demonstrated that the pituitary is a site for the metabolism of GABA to succinic acid. In vitro, GABA or the GABA antagonists bicuculline and saclofen did not affect the rate of growth hormone release from dispersed pituitary cells in static incubation. In contrast, intracerebroventricular injection of GABA reduced serum growth hormone levels within 30 min. During the seasonal gonadal cycle, intraperitoneal injection of GABA was without effect in sexually regressed goldfish, but caused a significant decrease in serum growth hormone levels in sexually recrudescent animals. Intraperitoneal implantation of solid silastic pellets containing oestradiol increased serum GH levels fivefold in sexually regressed and recrudescent goldfish; in both groups, GABA suppressed the oestradiol-stimulated increase in circulating growth hormone levels. The effect of oestradiol on basal serum growth hormone levels was specific since progesterone and testosterone were without effect. However, in recrudescent animals treated with progesterone and testosterone, the inhibitory effects of GABA on serum growth hormone levels were absent, indicating a differential role for these steroids in growth hormone release. Taken together, these results demonstrate that GABA has an inhibitory effect on growth hormone release in goldfish.

Molecular cloning and expression of cDNA encoding a brain bombesin/gastrin-releasing peptide-like peptide in goldfish

A complementary DNA (cDNA) of 928 bp encoding a bombesin (BBS)/gastrin-releasing peptide (GRP) precursor was identified from goldfish brain. Goldfish BBS/GRP messenger RNA (mRNA) encodes a 157 amino acid precursor, which contains a signal peptide sequence, the 22 amino acid putative BBS/GRP-like peptide, and a carboxy-terminal extension peptide. Reverse transcription-polymerase chain reaction (PCR) (RT-PCR) demonstrated that the mRNA for this precursor has a widespread distribution in goldfish brain, and is also present in skin, gastrointestinal tract, gonad, and gill. Phylogenetic analysis of BBS/GRP-like peptide precursors in vertebrates shows that goldfish BBS/GRP is more closely related to the known GRP precursors than to BBS precursors.

Preprotachykinin gene expression in goldfish brain: sexual, seasonal, and postprandial variations

Recently, we described the complete nucleotide sequence of gamma-preprotachykinin (gamma-PPT) mRNA and the deduced amino acid sequence of the precursor on the basis of molecular cloning and sequence analysis of cDNA from goldfish brain. In the present study, gamma-PPT gene expression in the brain of goldfish was examined using quantitative Northern blot analysis. The results showed that the gamma-PPT gene is highly but differentially expressed in the olfactory bulbs, hypothalamus, and posterior brain regions. There are sexual dimorphism and seasonal variations in gamma-PPT gene expression. In addition, the postprandial changes in gamma-PPT gene expression in the olfactory bulbs and hypothalamus suggest that tachykinin peptides are involved in regulation of feeding behavior in goldfish.

Characterization and distribution of somatostatin binding sites in goldfish brain

Somatostatin (SRIF) binding sites were characterized in goldfish brain. Binding of (125)I-[Tyr(11)]-SRIF-14 to a brain membrane preparation was found to be saturable, reversible, and time-, temperature-, and pH-dependent. Binding was also displaceable by different forms of SRIF. Under optimal conditions (22 degrees C, pH 7.2), the equilibrium binding of (125)I-[Tyr(11)]-SRIF-14 to goldfish brain membranes was achieved after 60 min incubation. Analysis of saturable equilibrium binding revealed a one-site model fit with K(a) of 1.3 nM. SRIF-14, mammalian SRIF-28, and salmon SRIF-25 displaced (125)I-[Tyr(11)]-SRIF-14 binding with similar affinity, whereas other neuropeptides, e.g., substance P, were unable to displace (125)I-[Tyr(11)]-SRIF-14. Autoradiography studies demonstrated that (125)I-[Tyr(11)]-SRIF-14 binding sites are found throughout the goldfish brain. A high density of (125)I-[Tyr(11)]-SRIF-14 binding sites was found in the forebrain, including the nucleus preopticus, nucleus preopticus periventricularis, nucleus anterioris periventricularis, nucleus lateralis tuberis, nucleus dorsomedialis thalami, nucleus dorsolateralis thalami, nucleus ventromedialis thalami, and nucleus diffusus lobi inferioris. In midbrain, (125)I-[Tyr(11)]-SRIF-14 binding sites were found in the optic tectum. The facial and vagal lobes and the mesencephalic-cerebellar tract were found to have a high density of binding sites. This study provides the first characterization and distribution of specific binding sites for SRIF in a fish brain.

Postprandial, seasonal and sexual variations in cholecystokinin gene expression in goldfish brain

Recently, we described the complete nucleotide sequence of cholecystokinin (CCK) mRNA and the deduced amino acid sequence of the precursor on the basis of molecular cloning and sequence analysis of cDNA from goldfish brain. In this study, we investigated the hypothesis that CCK has a role in feeding behavior by examining CCK gene expression in the brain of goldfish using Northern blot. We showed that CCK gene is widely but differentially expressed in broad areas of the goldfish brain, including the olfactory bulbs, telencephalon and preoptic region, hypothalamus, optic tectum-thalamus and posterior brain regions, with highest levels in hypothalamus. We found that CCK mRNA levels in goldfish olfactory bulbs, telencephalon-preoptic region, optic tectum-thalamus, and posterior brain were influenced by sex at least sometime of the seasonal gonadal cycle, with female fish having higher levels than males during at least one of the four seasonal sampling times. We also observed a transient and acute increase in the CCK mRNA levels in the olfactory bulbs, telencephalon-preoptic region, hypothalamus, and posterior brain at 120 min after a meal. These widespread postprandial changes in CCK gene expression in goldfish brain indicate that CCK peptides have multiple roles in regulation of feeding behavior in goldfish. This supports the idea that CCK plays a role as a satiety factor in goldfish.

Actions of two forms of gonadotropin releasing hormone and a GnRH antagonist on spawning behavior of the goldfish Carassius auratus

The central effects of two native forms of gonadotropin-releasing hormone (GnRH), salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II), and a GnRH antagonist, ¿Ac-delta 3-Pro(1), 4FD-Phe(2), D-Trp(3, 6)mGnRH (analog E), on the spawning behavior of sexually recrudescent female goldfish were investigated. The effects of analog E were also observed in mature males. Female spawning behavior was induced by intramuscular injection of females with prostaglandin F(2alpha) and placing them in the presence of mature males. Behavioral responses were quantified by recording the numbers of spawning acts performed by each pair of fish for 2 h following brain intracerebroventricular (icv) injection of different dosages of peptide or saline as control. For males, the time spent courting the female was recorded. Each pair of fish was pretested to determine their level of spawning behavior, for comparison to spawning behavior following icv treatment. Icv injection of analog E caused a significant decrease in the number of spawning acts performed by females, suggesting a role of endogenous GnRH in modulating female spawning behavior. icv injection of 0.5 ng/g of sGnRH or cGnRH-II significantly stimulated female spawning behavior, whereas doses of 1 ng/g and higher resulted in an almost complete inhibition of spawning, reflecting a down-regulation as a result of the excessive dosages. Analog E suppressed the actions of exogenous sGnRH and cGnRH-II on spawning behavior, as both the sGnRH- and cGnRH-II-induced increases in the number of spawning acts were inhibited by concomitant treatment with analog E. Analog E-injected males showed no alteration in courtship behavior. These results indicate that GnRH peptides play a major role in the control of female reproductive behavior in goldfish, but have little or no role in the control of male behavior.

Differential expression of corticotropin-releasing factor (CRF) and urotensin I precursor genes, and evidence of CRF gene expression regulated by cortisol in goldfish brain

Corticotropin-releasing factor (CRF) and urotensin I (UI) precursor cDNAs were cloned and sequenced from a goldfish brain cDNA library in order to investigate the distribution of CRF and UI mRNAs in goldfish brain and the regulation of CRF and UI gene expression. The CRF (966-bp) and UI (769-bp) cDNAs encode 163- and 146-amino acid precursors, respectively, and consist of a signal peptide sequence, a cryptic region, and a 41-amino acid mature peptide at the carboxy terminal. The deduced amino acid sequences of the CRF and UI peptides exhibit a sequence identity of 54%. Northern blot analysis revealed a single size of CRF (1.3 kb) and UI (2.0 kb) mRNAs, which are expressed in the telencephalon-preoptic, hypothalamic, optic tectum-thalamus, and posterior brain regions, but not in the pituitary. In addition, while the CRF gene is strongly expressed in the olfactory bulbs, the UI gene is not. In brain regions in which both genes are expressed, the mRNA levels of CRF were three- to sevenfold higher that those of UI. While the low expression levels of the UI gene prevented further analysis of its regulation, the regulation of CRF gene expression by cortisol was examined. In response to intraperitoneal implants of cortisol (300 microg/g BW) the level of CRF mRNA in the telencephalon-preoptic region decreased to 69% of control values at 6 and 24 h posttreatment. In sham-treated fish, in parallel with a transient injection stress-elicited increase in plasma cortisol, CRF mRNA levels declined to 72% of control value at 6 h postinjection and recovered after 24 h. Injection of the glucocorticoid antagonist, RU-486 (100 microg/g BW), prevented the reduction in CRF gene expression associated with the injection stress at 6 h and increased CRF mRNA levels to 145% of control value after 24 h. In contrast, the various implants had no effect on CRF mRNA levels in either the hypothalamus or the optic tectum-thalamus region. These results provide evidence of differential expression of the CRF and UI genes in hypothalamic and extrahypothalamic regions of goldfish brain. Furthermore, they demonstrate that stress levels of plasma cortisol can lead to a decrease in CRF gene expression that is mediated by glucocorticoid receptors in the telencephalon-preoptic region and give an indication of the regional specificity of the regulation of CRF gene expression by cortisol.

Stimulation of feeding behavior and food consumption in the goldfish, Carassius auratus, by orexin-A and orexin-B

The neuropeptides, orexin-A and orexin-B, have been demonstrated to have a physiological role in the regulation of food intake in mammals. The effects of human orexin-A and orexin-B intracerebroventricular (i.c.v.) injection on the feeding behavior of goldfish (Carassius auratus) were investigated. I.c.v. injection of orexin-A and orexin-B both caused a significant increase in appetite, as indicated by an increased number of feeding acts. Orexin-A and orexin-B both significantly stimulated food consumption, as indicated by increased total food intake during a 60-min observation period; the actions of orexin-A were dose dependent. Orexin-A was more potent than orexin-B in stimulation of both feeding behavior and food intake. These results indicate that orexin peptides are involved in the hypothalamic regulatory pathways of feeding behavior in goldfish.

Distal femoral fractures after knee arthroplasty

In seven patients who sustained eight distal femoral fractures following knee arthroplasty all fractures were treated operatively. Seven with open reduction internal fixation and one with external fixation. Seven of eight fractures had an unsatisfactory result. This was due not only to bone quality and fracture comminution, but also to technical problems and choice of implant. Revision surgery is often required.

Molecular cloning and expression of two type one somatostatin receptors in goldfish brain

Somatostatin (SRIF or SS) exerts diverse inhibitory actions through binding to specific receptors. In this study, two SRIF receptor complementary DNAs (cDNAs) were cloned and sequenced from goldfish brain using PCR and cDNA library screening. The two cDNAs share 92% similarity in nucleotide sequence and 98% similarity in the deduced amino acid sequences and are presumably derived from duplicate genes, as goldfish are tetraploid. Two cDNAs encode two 367-amino acid goldfish type one SRIF receptors (designated as sst1A and sst1B, respectively), with seven putative transmembrane domains (TMD) and YANSCANP motif in the 7th TMD, a signature sequence for mammalian SRIF receptor (sst) family. In addition, the amino acid sequences of two receptors have 76% and 75% similarity to human or rat sst1, respectively, and 39-55% similarities to other mammalian sst subtypes (sst2-5), suggesting that the two receptors could be the goldfish homologs of mammalian sst1. The difference between goldfish and mammalian sst1 is mainly reflected by the extreme divergence in their extracellular N termini. Both SRIF-14 and [Pro2]SRIF-14, two of the native goldfish SRIF forms, significantly inhibited forskolin-stimulated cAMP release in COS-7 cells transiently expressing goldfish sSt1A or sst1B, suggesting functional coupling of the two receptors to adenylate cyclase. Northern blot and RT-PCR showed that messenger RNAs (mRNAs) for both receptors are widely distributed throughout goldfish brain, whereas only one receptor mRNA is expressed in the pituitary. RT-PCR analysis also detected sst1 receptor mRNAs in several peripheral tissues. These findings provide fundamental information for studying the mechanism of SRIF actions in vertebrates and structural analysis of mammalian sst receptors.

Dopaminergic regulation of three somatostatin mRNAs in goldfish brain

Three distinct somatostatin cDNAs characterized previously from goldfish brain encode three preprosomatostatins (PSS), designated as PSS-I, PSS-II and PSS-III. In this study, dopaminergic regulation of PSS gene expression was examined by Northern blot analysis in the forebrain of goldfish. Intraperitoneal injection of the non-selective dopamine (DA) agonist, apomorphine, significantly decreased the levels of all three PSS mRNAs, indicating an inhibitory regulation of PSS gene expression by DA. The involvement of DA receptor subtypes in the regulation of PSS gene expression was examined using the D1 receptor agonist and antagonist drugs SKF 38393 and SCH 23390, and the D2 agonist and antagonist drugs LY 171555 and pimozide, respectively. The results provide evidence for inhibitory and/or stimulatory regulation of PSS gene expression by DA through both D1 and D2 receptors, which are dependent on the temporal pattern of dopamine input and reproductive stage of the fish. Demonstration of involvement of both DA D1 and D2 receptors in the dopaminergic regulation of goldfish brain PSS gene expression is a novel finding, distinct from the observations in mammalian models.

Expression of three distinct somatostatin messenger ribonucleic acids (mRNAs) in goldfish brain: characterization of the complementary deoxyribonucleic acids, distribution and seasonal variation of the mRNAs, and action of a somatostatin-14 variant

In this study, three somatostatin (SRIF) complementary DNAs (cDNAs) were characterized from goldfish brain. The cDNAs encode three distinct preprosomatostatins (PSS), designated as PSS-I, PSS-II, and PSS-III. The goldfish PSS-I, PSS-II, and PSS-III contain enzymatic cleavage recognition sites, potentially yielding SRIF-14 with sequence identical to mammalian SRIF-14, SRIF-28 with [Glu1, Tyr7, Gly10]SRIF-14 at its C-terminus, and [Pro2]SRIF-14, respectively. The brain distribution of the three SRIF messenger RNAs (mRNAs) were differential but overlapping in the telencephalon, hypothalamus and optic tectum-thalamus regions. Seasonal variations in the levels of the three mRNAs were observed, with differential patterns between the three mRNAs and differences between the sexes. However, only the seasonal alteration in the levels of the mRNA encoding PSS-I showed close association with the seasonal variation in brain contents of immunoreactive SRIF-14 and inversely correlated with the seasonal variation in serum GH levels described in the previous studies, suggesting that SRIF-14 is involved in the control of the seasonal variation in serum GH levels. The putative SRIF-14 variant, [Pro2]SRIF-14, inhibited basal GH secretion from in vitro perifused goldfish pituitary fragments, with similar potency to SRIF-14; [Pro2]SRIF-14 also inhibited stimulated GH release from the pituitary fragments, supporting that [Pro2] SRIF-14 is a biologically active form of SRIF in goldfish.

[Primary surgical care of pelvic fractures associated with perineal laceration]

Unstable fractures of the pelvic ring, associated to perineal lacerations are severe injuries occurring during high-energy trauma. High rates of septic complications and mortality have been reported with these injuries. Current treatment guidelines, while dealing with open pelvic fractures or dislocations are discussed, based on a current review of the literature and on our local experience. At our institution, 55 unstable type B or C fractures of the pelvic ring were treated by osteosynthesis between 1991 and 1997. Of these, 11 patients presented with an associated perineal laceration (20%). Simultaneously to the immediate pelvic ring fixation, a diversion colostomy was performed in all these patients. Repeated wound debridements and wide spectrum antibioprophylaxis were associated. Of these 11 patients presenting an open pelvic fracture, only one died of pelvic sepsis at three weeks. 10 patients survived (91%) and went on to bony union, without any local infectious complications. Aggressive multidisciplinary initial surgical management is a rule when dealing with this type of injuries, immediate colostomy and careful wound debridement must be associated to the initial osteosynthesis.

Two gonadotropin-releasing hormone receptor subtypes with distinct ligand selectivity and differential distribution in brain and pituitary in the goldfish (Carassius auratus)

In the goldfish (Carassius auratus) the two endogenous forms of gonadotropin-releasing hormone (GnRH), namely chicken GnRH II ([His5, Trp7,Tyr8]GnRH) and salmon GnRH ([Trp7,Leu8]GnRH), stimulate the release of both gonadotropins and growth hormone from the pituitary. This control is thought to occur by means of the stimulation of distinct GnRH receptors. These receptors can be distinguished on the basis of differential gonadotropin and growth hormone releasing activities of naturally occurring GnRHs and GnRHs with variant amino acids in position 8. We have cloned the cDNAs of two GnRH receptors, GfA and GfB, from goldfish brain and pituitary. Although the receptors share 71% identity, there are marked differences in their ligand selectivity. Both receptors are expressed in the pituitary but are differentially expressed in the brain, ovary, and liver. Thus we have found and cloned two full-length cDNAs that appear to correspond to different forms of GnRH receptor, with distinct pharmacological characteristics and tissue distribution, in a single species.

mRNA expression of gonadotropin-releasing hormones (GnRHs) and GnRH receptor in goldfish

In goldfish (Carassius auratus), two distinct forms of gonadotropin-releasing hormone (GnRH), namely, salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II), have been identified in the brain using chromatographic, immunological, and molecular cloning approaches. These two native GnRHs act on specific receptors in the anterior pituitary to stimulate the synthesis and release of gonadotropins and growth hormone in goldfish. To evaluate the potential roles of sGnRH and cGnRH-II in both neural and reproductive tissues in goldfish, we studied the mRNA expression of sGnRH, cGnRH-II, and GnRH receptor (GnRH-R) in discrete brain areas, pituitary, ovary, and testis by a combined reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot analysis. Total RNA was extracted from various tissues of sexually recrudescent male and female goldfish and RT-PCR was performed with primers specific for GnRH-R complementary DNA (cDNA), sGnRH cDNA, cGnRH-II cDNA-1, and cDNA-2. Results showed that GnRHs and GnRH-R mRNAs are differentially distributed in the brain. In the goldfish brain, sGnRH mRNA was predominantly expressed in the forebrain areas (olfactory bulb, telencephalon, and hypothalamus) whereas cGnRH-II mRNA-1 were expressed in all brain areas including olfactory bulbs and optic tectum-thalamus. The expression level of cGnRH-II mRNA-2 was much lower than that of cGnRH-II mRNA-1 in the brain. On the other hand, GnRH-R mRNA was expressed in all brain regions and pituitary. In the ovary and testis, GnRH-R mRNA, sGnRH mRNA, and cGnRH-II mRNA-1, but not cGnRH-II mRNA-2, are expressed. Sequence analysis of the PCR products showed that nucleotide sequences of GnRH-R in gonads are identical with that in the brain and pituitary. The coexistence of GnRHs and GnRH-R mRNAs in both neural and gonadal tissues supports the notion that sGnRH and cGnRH-II may act as neurotransmitters and/or neuromodulators in the brain and as autocrine and/or paracrine hormones in gonadal tissues in addition to their established neuroendocrine roles at the pituitary of goldfish.

Evolution of neuroendocrine peptide systems: gonadotropin-releasing hormone and somatostatin

Nine vertebrate and two protochordate gonadotropin-releasing hormone (GnRH) decapeptides have been identified and sequenced. Multiple molecular forms of GnRH peptide were present in the brain of most species examined, and cGnRH-II generally coexists with one or more GnRH forms in all the major vertebrate groups. The presence of multiple GnRH forms has been further confirmed by the deduced GnRH peptide structure from cDNA and/or gene sequences in several teleost species and tree shrew. High conservation of the primary structure of GnRH decapeptides and the overall structure of GnRH genes and precursors suggests that they are derived from a common ancestor. Somatostatin (SRIF) is a phylogenetically ancient, multigene family of peptides. A tetradecapeptide, SRIF (SRIF14) has been conserved, with the same amino acid sequence, in representative species of all classes of vertebrate. Four molecular variants of SRIF14 have been identified. SRIF14 is processed from preprosomatostatin-I, which contains SRIF14 at its C-terminus; preprosomatostatin-I is also processed to SRIF28 in mammals and SRIF26 in bowfin. Teleost fish possess a second somatostatin precursor, preprosomatostatin-II, containing [Tyr7, Gly10]-SRIF14 at the C-terminus, that is mainly processed into large forms of SRIF.

Molecular cloning and expression of cDNA encoding brain preprocholecystokinin in goldfish

A cholecystokinin (CCK) precursor cDNA of 782 bp was identified from goldfish brain. The open reading frame (369 bp) encodes the 123 amino acid precursor which contains mono- and di-basic amino acid endoproteolytic cleavage, C-terminal alpha-amidation and tyrosyl sulfation sites. Expression studies revealed the presence of preproCCK mRNA in the gastrointestinal tract, pituitary and a wide range of brain areas from the olfactory bulbs to the posterior brain region. We have also confirmed the presence of CCK mRNA in the posterior ventrolateral hypothalamus by in situ hybridization, supporting a role of CCK in feeding behavior and regulation of pituitary hormone secretion.

Limb revascularization to stimulate bone fracture healing

A case of nonunion of a tibial fracture and traumatic occlusion of the superficial femoral artery is presented. Bone healing and consolidation occurred dramatically after revascularization was performed.

Cloning of cDNA for goldfish activin beta B subunit, and the expression of its mRNA in gonadal and non-gonadal tissues

We have cloned a full length cDNA coding for activin beta B subunit from the goldfish ovary. Sequence analysis of the goldfish activin beta B shows that this peptide is extremely conserved across vertebrates. The mature region of goldfish activin beta B has 93 and 98% amino acid identity with that of human and zebrafish beta B subunit respectively. The identity of the cloned goldfish activin beta B was further confirmed by expressing the protein in the Chinese hamster ovary (CHO) cells followed by detection of the specific activity of activin in the culture medium using F5-5 cell assay. mRNA of goldfish activin beta B is expressed in a variety of goldfish tissues including ovary, testis, brain, pituitary, kidney and liver, suggesting a wide range of physiological roles for activin in the goldfish.

Cloning and expression pattern of a second [His5Trp7Tyr8]gonadotropin-releasing hormone (chicken GnRH-H-II) mRNA in goldfish: evidence for two distinct genes

Complementary DNAs (cDNAs) encoding [Trp7Leu8]GnRH (sGnRH) and [His5Trp7Tyr8]GnRH (cGnRH-II) peptides have been isolated from the brain of goldfish (X. W. Lin and R. E. Peter, 1996, Gen. Comp. Endocrinol. 101, 282-296). In the present study we report the isolation of a second cDNA encoding cGnRH-II peptide in the brain of goldfish using reverse transcription (RT) and rapid amplification of cDNA ends. There is an overall 79.7% nucleotide sequence similarity between the two cGnRH-II cDNAs, with 65.3, 91.2, and 76.3% similarity between the 5'-untranslated regions, coding regions, and 3'-untranslated regions, respectively, of the two cGnRH-II cDNAs. Comparison of the two cGnRH-II precursors shows 87.2% amino acid similarity. The presence of two cGnRH-II genes was confirmed by the sequence analysis of the introns between exon II and exon III of the two cGnRH-II genes. Results indicate that the intron of the two cGnRH-II genes shows a high divergence in size and sequence, but contains the same splice junction. Expression of the two cGnRH-II mRNAs was detected by RT-polymerase chain reaction assay and Southern blot analysis in all five grossly dissected brain areas, olfactory bulbs and tracts, telencephalon, hypothalamus, optic tectum-thalamus, and posterior brain. However, there was a difference in apparent intensity of hybridization signal for the two cGnRH-II mRNAs in all brain areas, suggesting a difference of expression levels. sGnRH mRNA was detected in the olfactory bulbs, telencephalon, and hypothalamus, but not in midbrain and posterior brain areas. The present finding of duplicate cDNAs and genes for cGnRH-II in goldfish is in agreement with the recent tetraploidization in this species.

Estradiol stimulates growth hormone production in female goldfish

The effects of estradiol (E2) on growth hormone (GH) production was investigated in gonad-intact female goldfish. It was first necessary to generate a specific antibody for use in immunocytochemistry, Western, and dot-blot analyses of GH production. To accomplish this, grass carp GH (gcGH) cDNA was cloned by the reverse transcription polymerase chain reaction (RT-PCR) and expressed in Echerichia coli and a specific polyclonal antibody to recombinant gcGH was generated in the rabbit. In Western blot, the anti-gcGH antibody specifically immunoreacted with recombinant gcGH, purified natural common carp GH, and with a single 21.5-kDa GH form from pituitary extracts of grass carp, common carp, goldfish, and zebrafish but not salmon, trout, or tilapia. Intraperitoneal injection of the recombinant gcGH enhanced the growth rates of juvenile common carp demonstrating biological activity of this GH preparation. Electron microscopic studies showed that the anti-gcGH-I antibody specifically reacted with GH localized in the secretory granules of the goldfish somatotroph. Using anti-gcGH-I in a dot-blot assay, it was found that in vivo implantation of solid silastic pellets containing E2, (100 micrograms/g body weight for 5 days) increased pituitary GH content by 150% in female goldfish. In a second, independent study employing a previously characterized anticommon carp GH antibody for radioimmunoassay, it was found that E2 increased pituitary GH content by 170% and serum GH levels by approximately 350%. The E2-induced hypersecretion of GH and increase in pituitary GH levels was not associated with changes in steady-state pituitary GH mRNA levels, suggesting that this sex steroid may enhance GH synthesis at the posttranscriptional or translational level. Previous observations indicate that GH can stimulate ovarian E2 production. The present results show that E2 can in turn stimulate GH production, indicating the existence of a novel pituitary GH-ovarian feedback system in goldfish.

Fat embolism and death during prophylactic osteosynthesis of a metastatic femur using an unreamed femoral nail

We report a case of cardiovascular collapse and death occurring intraoperatively during the prophylactic nailing of a metastatic femur using an unreamed femoral nail. The cause of death, as documented by the autopsy, was a massive fat embolism. The risk of fat embolism while performing intramedullary nailing is well known and has been linked to the process of medullary reaming. Unreamed femoral interlocking nails recently have become available. Although recent reports in the literature have concluded that the risk of fat embolism appears less likely while using unreamed implants, the surgeon should carefully consider the indications for any type of intramedullary fixation, particularly when dealing with unbroken femurs exhibiting impending pathologic fracture, or when preexisting pulmonary disease such as metastasis is present.

Goldfish gamma-preprotachykinin mRNA encodes the neuropeptides substance P, carassin, and neurokinin A

Two cDNAs, size 969 bp and 1146 bp respectively, encoding goldfish gamma-preprotachykinin (gamma-PPT) were identified. Both cDNAs contain the same 345 bp open reading frame. The deduced 114-amino acid gamma-PPT contains the sequence of substance P, carassin and neurokinin A. sequence analysis of the two cDNA 5'-untranslated regions shows that the two cDNAs may represent different PPT-A gene transcripts resulting from the alternative transcriptional start sites. Expression of gamma-PPT mRNA was detected in a wide range of brain areas from the olfactory bulbs to the posterior brain region, as well as in the intestine, testis and pituitary.

Regulation of growth hormone secretion by amino acid neurotransmitters in the goldfish (I): Inhibition by N-methyl-D, L-aspartic acid

High levels of the amino acid neurotransmitter glutamate were found in the goldfish hypothalamus and pituitary using high performance liquid chromatography with fluorometric detection. A specific polyclonal antibody to glutamate was generated in the rabbit for immunocytochemistry. Localization studies demonstrated that glutamatergic neurons of undetermined origin innervate the particular part of the goldfish adenohypophysis where somatotrophs and gonadotrophs are located. Intraperitoneal and brain third ventricle injection of the glutamate agonist N-methyl-D,L-aspartic acid (NMA) inhibited GH release in vivo. The gonadal steroid estradiol plays an important role in regulating GH secretion by stimulating basal serum GH levels and enhancing the inhibitory effects of NMA on GH secretion. Taken together, these results demonstrate that glutamate is an important regulator of GH secretion in goldfish.

Characterization of cholecystokinin binding sites in goldfish brain and pituitary

The characterization and distribution of cholecystokinin (CCK)/gastrin binding sites were determined in the goldfish central nervous system (CNS). Binding of 125I-sulfated CCK octapeptide (125I-CCK-8s) in tissue sections was found to be saturable, reversible, time dependent, and displaceable by CCK/gastrin-like peptides. Analysis of saturable equilibrium binding revealed a high-affinity binding site (dissociation constant of 0.706 +/- 0.188 nM), which also displayed high affinity for gastrin-17s and caerulein. Lower affinities were observed for the nonsulfated forms of CCK-8 and gastrin-17. These findings suggest that a single primitive CCK/gastrin receptor exists in the goldfish CNS. The distribution of CCK/gastrin binding sites in the goldfish brain and pituitary revealed high densities within the telencephalon and preoptic hypothalamus, as well as within hypothalamic nuclei associated with the brain feeding center. High densities of binding sites were also localized within the midbrain tegmentum and optic tectum of the midbrain, the facial lobe and vagal lobe of the hindbrain, and within the pituitary pars distalis. Overall, these findings support previous studies that indicate that CCK/gastrin-like peptides play a role in the central regulation of feeding behavior and pituitary hormone secretion in fish.

Growth hormone-releasing hormone immunoreactivity in the brain, pituitary, and pineal of the goldfish, Carassius auratus

Using antisera directed against carp growth hormone-releasing hormone (cGHRH), the distribution of immunoreactive (ir) structures in the brain, pituitary, and pineal of the goldfish, Carassius auratus, was investigated. The antisera were produced in rabbits by administration of cGHRH(1-44)-NH(2) followed by cGHRH(1-45)-OH for different periods of time, both coupled to human alpha-globulins via bisdiazotized benzidine as immunogen. Immunoreactive perikarya were visualized in the nucleus preopticus periventricularis (NPP), nucleus lateralis tuberis (NLT), nucleus of the lateral lemniscus (NLL), and the pineal. The preoptic area and area ventralis telencephali seemed to receive innervation from the NPP cells. The fibers of the NLT cell bodies extended caudally along the infundibular floor and innervated the hypophysis. The processes of the NLL perikarya extended rostrally along the lateral lemniscus, curved ventrally along the outer margin of the glomerular nuclear complex, and extended to the dorsal area of the lateral recess, while issuing fascicles that branched off and fanned out to innervate extensively the nucleus diffusus of the hypothalamic inferior lobes and the nucleus lateralis tori; several fiber bundles branched off and extended toward the lateral areas of the paraventricular organ area and even into the rostral region of the hypothalamic inferior lobes. A small percentage of the corticotrophs of the rostral pars distalis, a few cells in the central area of the pars intermedia (PI), and neurohypophysial fibers in the peripheral area of the PI of the pituitary gland had colocalization of GHRH-ir; GHRH-ir fibers in the rostral and proximal pars distalis were sparse. It is suggested that the GHRH-ir perikarya of the diencephalon may stimulate growth hormone release either by modulating the activity of somatotrophs or of other hypothalamic neurosecretory neurons. The innervation of the hypothalamic inferior lobe by GHRH-ir perikarya of the NLL suggests some influence on feeding processes. Presence of GHRH in the pineal implies involvement in some daily cyclic activity.

Sexual dimorphism of galanin-like immunoreactivity in the brain and pituitary of goldfish, Carassius auratus

A sexually dimorphic distribution of galanin (GAL)-like immunoreactive (ir) neurons and fibers was found in the brain and pituitary of goldfish. The rostralmost GAL-ir perikarya were found in the area ventralis telencephali pars supracommissuralis dorsal to the anterior commissure. In the diencephalon, there was several GAL-ir perikarya in the nucleus preopticus periventricularis (NPP). Males had many GAL-ir perikarya in the nucleus preopticus pars parvocellularis (NPOpp) and isolated GAL-ir perikarya in the NPO pars magnocellularis, and lateral to the NPO; in females GAL-ir perikarya were not found in these sites. A large GAL-ir neuronal aggregation was observed in the nucleus lateralis tuberis pars posterioris (NLTp). Several ir perikarya were present in the nucleus posterioris tuberis; however, unlike in other regions the males revealed fewer neurons than females. Besides the established innervation of the pituitary gland by the NPP, NPO and NLT, the present study revealed GAL-ir perikarya of these nuclei apparently also innervating the telencephalon, thalamus, optic tectum, tegmentum and even some areas of the rhombencephalon. Isolated perikarya were found in the nucleus posterioris periventricularis, the dorsal vicinities of the nucleus recessus lateralis (NRL), nucleus recessus posterioris, and nucleus saccus vasculosus, and in the medulla oblongata ventral to the vagal lobes. In the pituitary gland, GAL-ir fibers ramify and terminate among the pars distalis cells. A small percentage of growth hormone-secreting cells colocalize GAL. In males, most GAL-ir cells of the proximal pars distalis (PPD) showed granular ir product in the entire cell, and some had one or two large granules; in females the ir PPD cells showed clusters of a few fine ir granules of uniform size in each. Sexual dimorphism was also found in the olfactory bulb, telencephalon, infundibulum, mesencephalic tegmentum, optic tectum and medulla oblongata, the males having a more extensive GAL-ir fiber system than the females. Galanin may play a role in both hypophysiotropic and motor functions.

Expression of salmon gonadotropin-releasing hormone (GnRH) and chicken GnRH-II precursor messenger ribonucleic acids in the brain and ovary of goldfish

The complementary DNAs (cDNA) encoding the [Trp7Leu8]gonadotropin-releasing hormone (salmon GnRH; sGnRH) precursor and the [His5Trp7Tyr8]GnRH (chicken GnRH-II; cGnRH-II) precursor of the goldfish brain were isolated and sequenced using reverse transcription and rapid amplification of cDNA ends (RACE). The sGnRH precursor cDNA consists of 540 bp, including an open reading frame of 282 bp, and the cGnRH-II precursor cDNA consists of 682 bp, including an open reading frame of 258 bp. The 94 amino acid-long goldfish sGnRH precursor and 86 amino acid-long goldfish cGnRH-II precursor have the same molecular architecture as GnRH precursors identified to date in other vertebrate species. Using two sets of primers designed to be sense and antisense to the goldfish brain sGnRH precursor cDNA sequence, reverse transcription-polymerase chain reaction (RT-PCR) amplification of total RNA from brain and ovary at gonadal recrudescent, mature ( = prespawning), and postovulatory stages resulted in two predicted sizes of PCR products. The intensities of staining signals of ethidium bromide were similar between brain and ovary samples. The same RT-PCRs were carried out with two sets of primers for cGnRH-II precursor cDNA, resulting in two PCR products of predicted size; however, the ethidium bromide staining signals are much weaker for products amplified from ovarian cDNA than that from brain cDNA. Restriction enzyme analysis verified the expected RT-PCR products. Sequence analysis of ovarian sGnRH precursor cDNA generated by RACE of total RNA from recrudescent ovarian tissue revealed the identical sequence to that of the brain sGnRH cDNA. Northern blot analysis detected a single mRNA transcript of approximately 650 bases for the sGnRH precursor in both the brain and ovary, and 750 bases for the cGnRH-II precursor in the brain. These results demonstrate that two forms of GnRH precursor (sGnRH and cGnRH-II) mRNA are expressed in goldfish brain tissue and that the sGnRH transcript and a low level of cGnRH-II transcript are also expressed in the goldfish ovary.

Structural modifications of non-mammalian gonadotropin-releasing hormone (GnRH) isoforms: design of novel GnRH analogues

Three natural forms of vertebrate gonadotropin-releasing hormone (GnRH) provided the structural basis upon which to design new GnRH agonists: [His5,Trp7,Leu8]-GnRH, dogfish (df) GnRH; [His5,Asn8]-GnRH, catfish (cf) GnRH; and [His5,Trp7,Tyr8]-GnRH, chicken (c) GnRH-II. The synthetic peptides incorporated the position 6 dextro (D)-isomers D-arginine (D-Arg) or D-naphthylalanine (D-Nal) in combination with an ethylamide substitution of position 10. The in vitro potencies for LH and FSH release of these analogues were assessed using static cultures of rat anterior pituitary cells. Efficacious peptides were examined for their gonadotropin-II and growth hormone releasing abilities from perifused goldfish pituitary fragments. Rat LH and FSH release was measured using homologous radioimmunoassays, whereas goldfish growth hormone and gonadotropin-II release were determined using heterologous carp hormone radioimmunoassays. The receptor binding of the most potent analogues was determined in bovine pituitary membrane preparations. Substitution of D-Nal6 into [His5,Asn8]-GnRH increased the potency over 2200-fold compared with the native ligand (cfGnRH) in cultured rat pituitary cells. This was equivalent to a 55-fold greater potency than that of the native mammal (m) GnRH peptide. Substitution of D-Nal6 or D-Arg6 into dfGnRH or cGnRH-II resulted in potencies that were related to the overall hydrophobicity of the analogues. The [D-Nal6,Pro9NEt]-cfGnRH bound to the bovine membrane preparation with an affinity statistically similar to that of [D-Nal6,Pro9NEt]-mGnRH (kd = 0.40 +/- 0.04 and 0.55 +/- 0.10 nM, respectively) in cultured rat pituitary cells. All analogues tested released the same ratio of FSH to LH. In goldfish, the analogues did not possess superagonistic activity but instead desensitized the pituitary fragments at lower analogue doses than that of the sGnRH standard suggesting differences in receptor affinity or signal transduction.

Characterization and distribution of bombesin binding sites in the goldfish hypothalamic feeding center and pituitary

Bombesin (BBS)/gastrin-releasing peptide (GRP) binding sites were characterized and their distribution examined in the goldfish brain and pituitary by radioligand binding and autoradiography. Binding of 125I-[Tyr4]-BBS-14 to tissue sections was found to be saturable, reversible, time-dependent and displaceable by BBS/GRP-like peptides. Analysis of saturable equilibrium binding revealed a one-site model fit with a Kd of 0.665 +/- 0.267 nM. This binding site displayed high affinity for members of the BBS subfamily of peptides, including GRP10 (Ki; 0.292 +/- 0.038 nM) and GRP27 (Ki; 2.034 +/- 1.597 nM), but showed no affinity for the BBS8-14 fragment. While an approximate 100-fold lower binding affinity was displayed by the binding site for neuromedin B (Ki; 6.15 +/- 28.2 nM), litorin was highly effective in displacing radiolabeled BBS binding (Ki; 1.469 +/- 0.427 nM). The localization of saturable and high affinity BBS/GRP binding sites in specific areas of the goldfish brain and pituitary generally revealed a similar anatomical distribution to BBS/GRP-like immunoreactive material reported previously by our laboratory. Quantitative densitometric analysis of radiolabeled BBS binding to brain nuclei and the pituitary revealed a moderate concentration of BBS/GRP binding sites in the hypothalamic feeding area, including the nucleus diffusus libi inferioris, nucleus recessus lateralis, nucleus lateral tuberis, and nucleus anterior tuberis. Other brain nuclei known to influence the brain feeding center which contained a high density of BBS/GRP binding sites included nuclei of the dorsal and ventro-medial telencephalon, the preoptic hypothalamus, and the optic tectum. High densities of BBS/GRP binding sites were also localized in the dorsal cerebellum, and nucleus habenularis. In the pituitary, BBS/GRP binding sites were present in high concentration in the neurointermediate lobe, with a relatively lower density localized in the pars distalis. The present study further supports a role for BBS/GRP-like peptides in the regulation of feeding behavior and anterior pituitary hormone secretion in teleosts.