Immunogenicity and acceptance of influenza A (H1N1) vaccine in a cohort of chronic hepatitis C patients receiving pegylated-interferon treatment

Background & Aims

Individuals at risk of (H1N1) influenza A infection are recommended to receive vaccination. Chronic hepatitis C (CHC) patients receiving treatment might be at a higher risk of respiratory bacterial infections after influenza infection. However, there are no observational studies evaluating the immunogenicity, tolerance and acceptance of 2009 influenza A vaccine in CHC patients.

Methods

We evaluated the immunogenicity of influenza A vaccine (Pandemrix®) by using the hemagglutination inhibition (HI) titers method in a well defined cohort of CHC patients receiving or not receiving pegylated-interferon and ribavirin, and compared it with healthy subjects (controls). A group of patients with inflammatory bowel disease (IBD) under immunosuppression, thought to have a lower immune response to seasonal influenza vaccine, were also included as a negative control group. In addition, tolerance to injection site reactions and acceptance was assessed by a validated questionnaire (Vaccinees' perception of injection-VAPI-questionnaire).

Results

Of 114 subjects invited to participate, 68% accepted and, after exclusions, 72 were included. Post-vaccination geometric mean titers and seroprotection/seroconversion rates were optimal in CHC patients with ongoing treatment (n = 15; 232, CI95% 46–1166; 93%; 93%), without treatment (n = 10; 226, CI95% 69–743: 100%; 100%) and controls (n = 15;168, CI95% 42–680; 93%; 86%) with no differences between groups (P = 0.8). In contrast, IBD patients had a significantly lower immunogenic response (n = 27; 60, CI95% 42–680;66%;66%; P = 0.006). All the groups showed a satisfactory tolerance although CHC patients with ongoing treatment showed more local discomfort after vaccine injection.

Conclusion

There appeared to be no differences between CHC patients and healthy controls in serological response and acceptance of (H1N1) influenza vaccination.

Alzheimer's disease therapeutic trials: EU/US Task Force report on recruitment, retention, and methodology

While we may not be able to find a cure for Alzheimer's disease (AD) in the near future, several drugs presently in trials have shown promise as possible modifiers of disease progression. However, we may not be able to demonstrate efficacy due to issues of recruitment, retention, site-to-site variability, and other methodological issues. It is thus incumbent on the scientific community to find solutions to these problems, particularly as the field moves toward preventing illness or treating the disease in its prodromal stages, where these methodological issues will become even more critical. We need to better understand why participants agree or refuse to enter drug trials, and why both primary care physicians and Alzheimer's specialists agree or refuse to involve their patients. We also need to quantify the impact of requiring imaging studies, extensive questionnaires, cognitive testing, and lumbar punctures on recruitment and retention. With these concerns in mind, an international task force meeting of experts from academia and industry in the United States, European Union, and Japan in San Diego, California on November 2, 2011 to focus on recruitment, retention and other methodological issues related to clinical trials for AD. Based on the recommendations of this Task force meeting, this Perspectives article critically reflects on the most critical and timely methodological issues related to recruitment and retention in prevention and therapeutic trials in AD, which are paralleled by a paradigm shift in the diagnostic conceptualization of this disease, as reflected by recently new proposed diagnostic criteria involving preclinical stages of the disease.

Clinical validation of the European Panel on the Appropriateness of Gastrointestinal Endoscopy (EPAGE) II criteria in an open-access unit: a prospective study

BACKGROUND AND STUDY AIMS

The European Panel on the Appropriateness of Gastrointestinal Endoscopy (EPAGE I) criteria were recently updated (EPAGE II), but no prospective studies have used these criteria in clinical practice. The aim of the current study was to validate the EPAGE II criteria in an open-access endoscopy unit.

PATIENTS AND METHODS

A prospective observational study was conducted in an open-access endoscopy unit at a tertiary care referral center. Consecutive outpatients (n = 1004; mean age 58.9 ± 13.1 years; 45 % men) were referred for diagnostic colonoscopy between September 2009 and February 2010. The appropriateness of colonoscopy was assessed based on EPAGE II criteria, and the relationship between appropriateness and both referral doctor and detection of significant lesions was examined. The effectiveness of EPAGE II criteria in assessing appropriateness was measured by means of sensitivity, specificity, and positive and negative predictive values for detecting significant lesions.

RESULTS

Colonoscopic cecal intubation was achieved in 956 patients (95.2 %). Most referral doctors were gastroenterologists (58.0 %) and the most common indication was colorectal cancer (CRC) screening (35.2 %). EPAGE II criteria were applicable in 968 patients (96.4 %); of these patients, the indication was appropriate in 778 (80.4 %), inappropriate in 102 (10.5 %), and uncertain in 88 (9.1 %). Patients with appropriate or uncertain indications based on EPAGE II criteria had more relevant endoscopic findings than those with inappropriate indications (38.8 % vs. 24.5 %; OR 1.95, 95 %CI 1.22 - 3.13; P < 0.005). Sensitivity and negative predictive value of EPAGE II criteria for detecting significant lesions were 93.1 % (95 %CI 90 % - 96 %) and 75.5 % (95 %CI 67 % - 84 %), respectively, whereas for advanced neoplastic lesions these values were 98.0 % (95 %CI 95 % - 100 %) and 98.0 % (95 % CI 95 % - 100 %), respectively. Adherence to EPAGE II recommendations was an independent predictor of finding a significant lesion (OR 1.93, 95 %CI 1.20 - 3.11; P = 0.007).

CONCLUSIONS

EPAGE II is a simple, valid score for detecting inappropriate colonoscopies in clinical practice.

Glutamate-vasopressin interactions and the neurobiology of anabolic steroid-induced offensive aggression

In the latero-anterior hypothalamus (LAH) increased glutamate and vasopressin (AVP) activity facilitate anabolic androgenic steroid (AAS)-induced offensive aggression. In addition, adolescent AAS treatment increases the strength of glutamate-mediated connections between the LAH and the brain nucleus of stria terminalis (BNST). The current set of studies used male Syrian hamsters exposed to AAS during adolescence to examine whether increased glutamate-mediated stimulation of the BNST is dependent on LAH-AVP signaling and whether this neural pathway modulates adolescent AAS-induced offensive aggression. In the first set of AAS-treated animals offensive aggression was measured following blockade of glutamate activity within the BNST using NBQX. Then, in a second group of AAS-treated animals aggression levels were examined following simultaneous blockade of LAH-AVP activity using Manning compound and stimulation of BNST glutamate using AMPA. Lastly, the number of AVP fibers in apposition to glutamate cells was examined in AAS and control animals, using double-label immunofluorescence. The results showed that administration of NBQX into the BNST dose-dependently reduced aggressive behavior in AAS-treated animals. Further, the current results replicated previous findings showing that blockade of LAH-AVP significantly reduces aggressive behavior in AAS-treated animals. In these animals stimulation of BNST-AMPA receptors had a linear effect on aggression, where the smallest dose exacerbated the inhibitory effect of the V1a antagonist, the medium dose had no effect and the highest dose recuperated aggression to control levels. Finally when compared with control animals, AAS treatment produced a significant increase in the number of AVP fibers in apposition to LAH-glutamate cells. Overall, these results identify the BNST as a key brain region involved in aggression control and provide strong evidence suggesting that AVPergic-mediated stimulation of BNST-glutamate is a possible mechanism that facilitates aggression expression in adolescent AAS-treated animals.

Clinical Pharmacogenetics Implementation Consortium guidelines for thiopurine methyltransferase genotype and thiopurine dosing

Thiopurine methyltransferase (TPMT) activity exhibits monogenic co-dominant inheritance, with ethnic differences in the frequency of occurrence of variant alleles. With conventional thiopurine doses, homozygous TPMT-deficient patients (~1 in 178 to 1 in 3,736 individuals with two nonfunctional TPMT alleles) experience severe myelosuppression, 30-60% of individuals who are heterozygotes (~3-14% of the population) show moderate toxicity, and homozygous wild-type individuals (~86-97% of the population) show lower active thioguanine nucleolides and less myelosuppression. We provide dosing recommendations (updates at http://www.pharmgkb.org) for azathioprine, mercaptopurine (MP), and thioguanine based on TPMT genotype.

Report of the task force on designing clinical trials in early (predementia) AD

BACKGROUND

A large number of promising candidate disease-modifying treatments for Alzheimer disease (AD) continue to advance into phase II and phase III testing. However, most completed trials have failed to demonstrate efficacy, and there is growing concern that methodologic difficulties may contribute to these clinical trial failures. The optimal time to intervene with such treatments is probably in the years prior to the onset of dementia, before the neuropathology has progressed to the advanced stage corresponding to clinical dementia.

METHOD

An international task force of individuals from academia, industry, nonprofit foundations, and regulatory agencies was convened to discuss optimal trial design in early (predementia) AD.

RESULTS

General consensus was reached on key principles involving the scope of the AD diagnosis, the selection of subjects for trials, outcome measures, and analytical methods.

CONCLUSION

A consensus has been achieved in support of the testing of candidate treatments in the early (predementia) AD population.

Continuous light and melatonin: daily and seasonal variations of brain binding sites and plasma concentration during the first reproductive cycle of sea bass

The present study reports on the daily and seasonal variations in plasma melatonin concentration, and also in optic tectum and hypothalamus melatonin binding sites, in male European sea bass maintained under natural photoperiod (NP) or continuous light (LL) from early stages of development. Samples were collected on a 24-h cycle, at four physiological phases of their first annual reproductive cycle, i.e., pre-spermatogenesis, spermatogenesis, spermiation and post-spermiation. Under NP, (1) plasma melatonin levels were higher at night than during the day regardless of the year period, and the duration of the signal matched the duration of the dark phase; (2) daily variations in Kd and Bmax were found in the optic tectum, but only during spermiation, with the acrophase being 180° out of phase with the plasma melatonin variations; and (3) significant seasonal Kd and Bmax changes were seen in the hypothalamus. Under LL, (1) plasma melatonin showed no elevation during the subjective night; and (2) Kd and Bmax exhibited seasonal variations in the hypothalamus. These results led to the conclusion that long-term exposure to LL affected both plasma melatonin and receptor oscillations; particularly, LL disrupted the receptor density circadian oscillation found in the optic tectum during spermiation under NP. This oscillation appears to be important for sea bass to pursue gametogenesis until full spermiation. The persistence of both daily and seasonal variation of receptor affinity and density in the hypothalamus under LL indicates that these variations are controlled by internal circadian and circannual clocks that do not involve melatonin.

Current knowledge on the melatonin system in teleost fish

Melatonin is a much conserved feature in vertebrates that plays a central role in the entrainment of daily and annual physiological rhythms. Investigations aiming at understanding how melatonin mediates the effects of photoperiod on crucial functions and behaviors have been very active in the last decades, particularly in mammals. In fish a clear-cut picture is still missing. Here we review the available data on (i) the sites of melatonin production in fish, (ii) the mechanisms that control its daily and annual rhythms of production and (iii) the characterization of its different receptor subtypes, their location and regulation. The in vivo and in vitro data on melatonin effects on crucial neuroendocrine regulations, including reproduction, growth, feeding and behavioral responses, are also reviewed. Finally we discuss how manipulation of the photic cues impact on fish circannual clock and annual cycle of reproduction, and how this can be used for aquaculture purposes.

Older triploid fish retain impaired reproductive endocrinology in the European sea bass Dicentrarchus labrax

This paper reports on an evaluation of growth, gonadal development and reproductive endocrinology of older triploid (3n) European sea bass Dicentrarchus labrax in comparison with their diploid (2n) counterparts throughout their fifth and seventh annual cycle of life. While older triploids retained impaired reproductive endocrinology, a sexually related dimorphic growth was observed with 3n females attaining the largest sizes. Comparisons of some body indexes showed that 3n females had a significantly lower hepato-somatic index (I(H)) than 2n females but a significantly higher viscero-somatic index (I(F)). In contrast, both male and female triploids showed significantly lower gonado-somatic index (I(G)) than diploids. Accordingly, diploids produced mature gametes but triploids did not, demonstrating that despite the longer time given to triploids for gonadal development, they could not reproduce. Furthermore, older triploids had lower levels of plasma sex steroids (testosterone, T; 11-ketotestosterone, 11-KT and oestradiol-17beta, E(2)) and luteinizing hormone (LH) than their 2n counterparts with 3n females showing drastic effects of triploidization on their reproductive endocrinology. Vitellogenin (VTG) was undetectable in 3n females. Gonadal content of steroid hormones and Sparus aurata-type gonadotropin-releasing hormone (sbGnRH) in the brain and pituitary were also lower in triploids compared with diploids. These results suggest that older 3n D. labrax retain functional sterility in both sexes, and 3n females might reach larger sizes than 3n males and their 2n counterparts in this species.

Zebrafish: from hematology to hydrology

Hemostasis is a defense mechanism that protects an organism from bleeding. Abnormal hemostasis results in bleeding disorders and thrombosis. Several factors are known to control hemostasis in mammals. Despite this progress, more factors remain to be identified. Classical genetic approaches have resolved physiological pathways. However, classical genetics could not be applied completely to hemostasis pathways a decade ago. We introduced zebrafish as a model system to study hemostasis and thrombosis using classical genetic methods. First, we established that zebrafish hemostasis is essentially similar to mammalian hemostasis. Secondly, we developed screening tools for isolating hemostatic mutants. These tools enabled us to identify hemostatic mutants, as well as providing a means to study hemostasis by knockdown methods. Continued characterization of the physiology of thrombus formation led to the novel finding of thrombocyte clustering. Recently, we have discovered that fish secrete proteases, which participate in hemostasis and may have direct relevance in humans. Future work to identify most of the players in thrombus formation is underway.

Temporal profile of brain and pituitary GnRHs, GnRH-R and gonadotropin mRNA expression and content during early development in European sea bass (Dicentrarchus labrax L.)

A likely endocrine control mechanism for sexual differentiation in size-graded populations of European sea bass (Dicentrarchus labrax) is proposed by evaluating the brain expression and pituitary content of two forms of gonadotropin-releasing hormone (GnRH), namely sea bream (sbGnRH) and salmon (sGnRH), the pituitary expression of one subtype of GnRH receptor (dlGnRH-R-2A) and the three gonadotropin (GtH) subunits, namely glycoprotein alpha (GPalpha), follicle-stimulating hormone beta (FSHbeta) and luteinizing hormone beta (LHbeta), as well as the pituitary and plasma LH levels between 50 and 300 days post-hatching (dph). Four gradings were conducted between 2 and 8 months after hatching, resulting in a population of large and small individuals, having 96.5% females (female-dominant population) and 69.2% males (male-dominant population), respectively, after the last grading. The onset of gonadal differentiation was different in the two sexes, and coincided with a peak of expression of sbGnRH or sGnRH. Furthermore, the expression of these GnRHs was correlated with the expression of dlGnRH-R-2A. Sex-related differences in the brain and pituitary content of sbGnRH were also found at the time of sexual differentiation. Moreover, the observed sexual dimorphism at the transcriptional or synthesis level of these GnRH forms suggests that a different neuro-hormonal regulation is operating according to sex. At the onset of sex differentiation, FSHbeta transcriptional activity reached maximal values, which were maintained until the completion of the process. The present study suggests a role for sbGnRH, sGnRH and the dlGnRH-R-2A during gonadal differentiation, possibly through enhancement of FSHbeta gene expression. In males, a different endocrine regulation seems to exist also during spermiogenesis and spermiation, when gene transcription, peptide synthesis and release of LH are of greater importance.

A comparative ex vivo and in vivo study of day and night perception in teleosts species using the melatonin rhythm

The purpose of this study was to determine and compare the light sensitivity of two commercially important, phylogenetically different teleost species in terms of melatonin production. Three series of experiments were performed on both Atlantic salmon and European sea bass. First, a range of light intensities were tested ex vivo on pineal melatonin production in culture during the dark phase. Then, light transmission through the skull was investigated, and finally short-term in vivo light sensitivity trials were performed. Results showed that sea bass pineal gland ex vivo are at least 10 times more sensitive to light than that of the salmon. Light intensity threshold in sea bass appeared to be between 3.8 x 10(-5) and 3.8 x 10(-6) W/m2 in contrast to 3.8 x 10(-4) and 3.8 x 10(-5) W/m2 in salmon. These highlighted species-specific light sensitivities of pineal melatonin production that are likely to be the result of adaptation to particular photic niches. Light transmission results showed that a significantly higher percentage of light penetrates the sea bass pineal window relative to salmon, and confirmed that penetration is directly related to wavelength with higher penetration towards the red end of the visible spectrum. Although results obtained in vivo were comparable, large differences between ex vivo and in vivo were observed in both species. The pineal gland in isolation thus appeared to have different sensitivities as the whole animal, suggesting that retinal and/or deep brain photoreception may contribute, in vivo, to the control of melatonin production.

Organochlorine compounds in liver and concentrations of vitellogenin and 17beta-estradiol in plasma of sea bass fed with a commercial or with a natural diet

Results from previous experiments directed to determine the effect of different nutritional factors or the effect of xenobiotics on hormonal control of reproduction, lead to the hypothesis that hormonal perturbations repeatedly observed in sea bass (Dicentrarchus labrax) broodstock feeding commercial diets could have been caused by the presence of aryl hydrocarbon receptor (AhR) ligands, such as dioxins, furans and polychlorinated biphenyls (PCBs) in the diet. To evaluate this hypothesis, dioxins and related compounds were analysed in liver of female sea bass fed with a commercial or with a natural diet consisting of trash fish (bogue, Boops boops), and concentrations of vitellogenin (VTG) and 17beta-estradiol (E2) were determined in plasma obtained previously in monthly samplings of these animals. As observed in other experiments, females fed with a commercial diet exhibited lower VTG and higher E2 plasma levels than females fed with the natural diet. In liver, sea bass fed with the commercial diet exhibited a profile clearly dominated by high-chlorinated dioxins while in fish fed with the natural diet this profile was dominated by low chlorinated furans. However, typical AhR ligands, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin showed no differences between groups or, as is the case of planar PCBs, showed higher concentrations in the liver of fish fed with the natural diet. These results do not permit to explain the observed hormonal alterations by a possible antiestrogenic effect caused by dioxins and related compounds.

Cloning, characterisation, and expression of three oestrogen receptors (ERalpha, ERbeta1 and ERbeta2) in the European sea bass, Dicentrarchus labrax

Three oestrogen receptor [ER] subtypes have been described in teleost fish, namely ERalpha, and two ERbeta subtypes, called ERbeta1 and ERbeta2 (or ERbeta and ERgamma in Atlantic croaker). Their expression during embryonic development and gonadal growth has evoked interest in their potential role in sexual differentiation and gonadal development in fish. We cloned three oestrogen receptors from adult liver (sb-ERalpha cDNA) and ovary (partial sb-ERbeta1 and sb-ERbeta2 cDNAs) of the European sea bass, and according to their phylogenetic relatedness to other ERs in teleosts, named them sea bass [sb-] ERalpha, ERbeta1 and ERbeta2. Deduced amino acid numbers for sb-ERalpha, sb-ERbeta1 and sb-ERbeta2 were 639, 517 and 608, respectively, representing in the case of sb-ERbeta1 and sb-ERbeta2 about 90% of the open reading frame. Highest amino acid identities were found for sb-ERalpha with eelpout ERalpha (88.7%), for sb-ERbeta1 with Atlantic croaker ERgamma (85.8%), and for sb-ERbeta2 with Atlantic croaker ERbeta (90.1%). Southern analysis confirmed that all three sea bass oestrogen receptors (sb-ERs) are the products of three distinct genes. In adult sea bass, ERalpha was predominantly expressed in liver and pituitary, while sb-ERbeta1 and sb-ERbeta2 were more ubiquitously expressed, with highest expression levels in pituitary. In a mixed-sex population of juvenile sea bass, sb-ERalpha expression was significantly elevated in gonads at 200 days posthatch (dph), while for sb-ERbeta1 and sb-ERbeta2 highest expression levels were observed in gonads at 250 dph. For sb-ERbeta2, expression was also significantly higher in the brain at 250 dph. The cloning of these three ER subtypes in the European sea bass together with the results obtained on expression levels in adult and juvenile animals has given us the foundation to investigate their possible role in sexual differentiation and development in this species in future studies.

Effect of photoperiod manipulation on the daily rhythms of melatonin and reproductive hormones in caged European sea bass (Dicentrarchus labrax)

Reproduction in fish is cyclical and timed to guarantee the survival of the offspring. Seasonal variations in reproductive hormones of fish have been deeply investigated in fish over the last years. However, there are few studies regarding the daily changes in reproductive hormone profiles in teleosts. The aim of the present research was to investigate the effects of photoperiod manipulation on melatonin and reproductive hormones (pituitary sbGnRH, pituitary LH and plasma LH, testosterone [T], and 11-ketotestosterone [11KT]) daily rhythms in male sea bass, kept in net cages under farming conditions in winter (9L:15D). Fish were distributed in two groups, one under constant long photoperiod (18L:6D) and the other under natural photoperiod. The photoperiod strongly influenced the daily melatonin profile, so that the duration of the nocturnal melatonin rise was longer in the control group than in the group exposed to the artificial photoperiod (18L:6D). A daily rhythm was observed in the pituitary sbGnRH profile in both groups, showing the lowest levels during the dark period. A daily rhythm of pituitary LH was detected in the control group, which was suppressed in the group under long photoperiod. Daily variations in plasma LH were observed, the highest levels being found in the dark phase in both groups, although this profile was significantly altered by artificial light, maintaining a fixed relationship between the first nocturnal rise of melatonin and the nocturnal peaks of plasma LH in both groups. Plasma T levels showed significant fluctuations in their daily cycle following a sinusoidal pattern with an acrophase around sunrise in both groups, without any influence of light regime. No significant daily variations in plasma levels of 11-KT were observed in none of the groups. Our results provide the first evidence of the presence of daily variations in pituitary sbGnRH content, pituitary and plasma LH, and plasma T in sea bass. Artificial lights suppressed the circulating melatonin and significantly affected the daily rhythm of LH storage and release.

Copper and zinc retention by an organically amended soil

This paper describes changes in retention of Cu and Zn in laboratory experiments by a sandy soil that had been amended in the field with different composted wastes. The amounts of the metals retained increased as a result of the amendments, especially after two years. Desorption of the sorbed metals was always negligible, regardless of the treatment. The proportion of Cu retained was considerably higher than that of Zn, suggesting a higher affinity of the soil for the former. The greater sorption in the amended soils indicates a build-up of fresh sites for metal retention. The use of 'log(activity) vs. pH' plots showed that the nature of the surfaces retaining metals on the untreated and amended soils is different. At comparable pH values, the amended soils gave higher solution metal concentrations. Some of the possible environmental consequences of the use of these amendments for remediation purposes are discussed.

Induction of triploidy and gynogenesis in teleost fish with emphasis on marine species

The induction of triploidy and gynogenesis by chromosome set manipulation has traditionally been studied more intensively in freshwater than in marine fish. In the last years, however, several studies have applied these manipulations in about a dozen marine species, including mainly sparids, moronids and flatfishes. This paper focuses on the methodologies used to induce, verify, and assess performance of both triploids and gynogenetics of these marine species. Since many of them are batch spawners and have small and fragile eggs and larvae, peculiarities relating to broodstock management, gamete quality and mortality assessment during early larval stages are also taken into account. However, data show that if handling is correct and the treatments are optimized, triploid and gynogenetic rates of 100% can be easily achieved. Survival of triploids with respect to the controls is about 70-80%, whereas in gynogenetics it is generally low and more variable, depending on the species considered. In the marine fish investigated so far, triploidy has not resulted in significantly higher growth rates. On the other hand, the induction of gynogenesis has resulted in the production of both all-female and mix-sex stocks. Throughout the paper, special reference is made to the European sea bass (Dicentrarchus labrax L.), a species of both basic and applied interest, for which a comprehensive study has been carried out on the induction, verification and performance of triploids and gynogenetics.

Action of leptin on in vitro luteinizing hormone release in the European sea bass (Dicentrarchus labrax)

The discovery of leptin has sparked a rapidly growing number of publications concerning the role of leptin in the regulation of body adiposity, feeding, and reproductive system in mammals. To date, there have been no reports on the presence of leptin-related peptide, and functional studies on the role of leptin remain limited in fishes. We investigated the effect of mouse recombinant leptin on basal and sea bream (sb) GnRH-induced LH release from dispersed pituitary cells obtained from male European sea bass (Dicentrarchus labrax) at different stages of sexual development. The potential interaction of leptin with the porcine neuropeptide Y (pNPY), known to play a dual role in feeding and reproduction in vertebrates, was also investigated. High doses of leptin (10(-8)-10(-6) M) and/or pNPY (0.1 and 1 nM) had different effects on LH release at various stages of sexual development. Porcine NPY alone was weakly effective on basal LH release, but it enhanced LH release induced by leptin (10(-6) M) in late prepuberty but not in early postpuberty. Additive or inhibitory effects of leptin were observed on sbGnRH-induced LH release depending on sbGnRH dose and stage of sexual development. The direct action of leptin on LH release at the pituitary level in sea bass suggests that leptin is a regulator of the reproductive system in fishes.

Comparison of the gonadal development and plasma levels of sex steroid hormones in diploid and triploid sea bass, Dicentrarchus labrax L

The goal of this study was to compare the reproductive physiology of triploid and diploid European sea bass (Dicentrarchus labrax L.). Gonads of diploid and triploid fish (males and females) were examined both microscopically and macroscopically, together with the plasma levels of the major sex steroids produced (testosterone and estradiol-17beta) when fish were adults. Prior to sexual maturation, the gonadosomatic index (GSI) of triploid males was similar to that of diploids. However, the GSI in 4-year-old adult triploid males was 1.8 times lower than that of diploids (P < 0.05). All diploid males exhibited normal gonadal development. In contrast, in triploid males spermatogenesis was impaired during late meiosis, affecting severely spermiogenesis. This was achieved by an increasing imbalance in the amount of DNA present in daughter cells of the same type as spermatogenesis progressed, as demonstrated by abnormal cell sizes, culminating in inviable spermatids. Thus, no spermiating triploid fish were observed during 4 years, which included three full consecutive maturation cycles. Furthermore, the germ cells from triploids were significantly larger than those from diploids (P < 0.001). Seasonal profiles of plasma levels of testosterone in 4-year-old males were essentially similar in both ploidies. On the other hand, triploid females had rudimentary ovaries containing oogonia and primary oocytes that were arrested during meiotic prophase I, while diploid females exhibited all stages of ovarian development. Diploid females showed levels of testosterone and estradiol-17beta significantly higher than those of triploids (P < 0.05), in which no endocrine signs of maturation were observed at all. Regarding sex ratios, triploids had 10% more females than diploids (P < 0.05) but in both ploidies males predominated, as is usually found in this species under culture conditions. These results show that triploidy blocked the initial phases of meiosis in females and the latter ones in males, resulting in the absence of or reduced gonadal development, respectively. In conclusion, we provide an explanation for the lack of gonadal development in triploid male fish, and, to the best of our knowledge, we report for the first time a case in which induced triploidy completely blocks meiosis in both sexes, thus conferring functional sterility in the sea bass.