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Mediobasal Hypothalamus (mediobasal + hypothalamus)
Selected AbstractsEvidence for Increased Neuropeptide Y Synthesis in Mediobasal Hypothalamus in Relation to Parental Hyperphagia and Gonadal Activation in Breeding Ring DovesJOURNAL OF NEUROENDOCRINOLOGY, Issue 3 2007S. Ramakrishnan Like lactating mammals, male and female ring dove parents increase their food consumption to meet the energetic challenges of provisioning their young. To clarify the neurochemical mechanisms involved, the present study investigated the relationship between parental hyperphagia and changes in activity of the potent orexigen neuropeptide Y (NPY) in the hypothalamus of breeding doves. Changes in NPY-immunoreactive (NPY-ir) cell numbers in the tuberal hypothalamus of male and female doves were examined by immunocytochemistry at six stages of the breeding cycle. Parallel NPY mRNA measurements were recorded in mediobasal hypothalamus (which includes the tuberal hypothalamus) by semiquantitative reverse transcription-polymerase chain reaction using 18S rRNA as the internal standard. NPY mRNA changes were also measured in the mediobasal hypothalamus of nonbreeding doves following intracranial administration of prolactin, an orexigenic hormone that is elevated in the plasma of parent doves, and in response to food deprivation, which mimics the negative energy state that develops in parents as they provision their growing young. NPY-ir cell numbers in the tuberal hypothalamus and NPY mRNA levels in the mediobasal hypothalamus were significantly higher in breeding males and females during the period of parental hyperphagia after hatching than during the late incubation period when food intake remains unchanged. In nonbreeding doves, food deprivation and prolactin treatment increased NPY mRNA in this region by two- to three-fold, which suggests that NPY expression is sensitive to hormonal and metabolic signals associated with parenting. We conclude that NPY synthesis is increased in the mediobasal hypothalamus during the posthatching period, which presumably supports increased NPY release and resulting parental hyperphagia. NPY-ir and mRNA were also high in the mediobasal hypothalamus prior to egg laying when food intake remained unchanged. Several lines of evidence suggest that this elevation in NPY supports the increased gonadal activity that accompanies intense courtship and nest building interactions in breeding doves. [source] Loss of steroidogenic factor 1 alters cellular topography in the mouse ventromedial nucleus of the hypothalamusDEVELOPMENTAL NEUROBIOLOGY, Issue 4 2004Aline M. Davis Abstract Knockout (KO) mice lacking the orphan nuclear receptor steroidogenic factor 1 (SF-1) exhibit marked structural abnormalities of the ventromedial nucleus of the hypothalamus (VMH). In this study, we sought to determine the molecular mechanisms underlying the VMH abnormalities. To trace SF-1-expressing neurons, we used a SF-1/enhanced green fluorescent protein (eGFP) transgene. Although the total numbers of eGFP-positive cells in wild-type (WT) and SF-1 KO mice were indistinguishable, cells that normally localize precisely within the VMH were scattered more diffusely in adjacent regions in SF-1 KO mice. This abnormal distribution is likely due to the loss of SF-1 expression in VMH neurons rather than secondary effects of deficient steroidogenesis, as redistribution also was seen in mice with a CNS-specific KO of SF-1. Thus, the absence of SF-1 alters the distribution of cells that normally form the VMH within the mediobasal hypothalamus. Consistent with this model, the hypothalamic expression patterns of the transcription factors islet-1 and nkx2.1 also were displaced in SF-1 KO mice. Independent of gene expression, birthdate analyses further suggested that cells with earlier birthdates were affected more severely by the loss of SF-1 than were later born cells. We conclude that the absence of SF-1 causes major changes in cellular arrangement within and around the developing VMH that result from altered cell migration. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 424,436, 2004 [source] Hypothalamic sensing of circulating lactate regulates glucose productionJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 11-12 2009Andrea Kokorovic Abstract Emerging studies indicate that hypothalamic hormonal signalling pathways and nutrient metabolism regulate glucose homeostasis in rodents. Although hypothalamic lactate-sensing mechanisms have been described to lower glucose production (GP), it is currently unknown whether the hypothalamus senses lactate in the blood circulation to regulate GP and maintain glucose homeostasis in vivo. To examine whether hypothalamic sensing of circulating lactate is required to regulate GP, we infused intravenous (i.v.) lactate in the absence or presence of inhibition of central/hypothalamic lactate-sensing mechanisms in normal rodents. Inhibition of central/hypothalamic lactate-sensing mechanisms was achieved by three independent approaches. Tracer-dilution methodology in combination with the pancreatic clamp technique was used to assess the effect of i.v. and central/hypothalamic administrations on glucose metabolism in vivo. In the presence of physiologically relevant increases in the levels of plasma lactate, inhibition of central lactate-sensing mechanisms by lactate dehydrogenase inhibitor oxamate (OXA) or ATP-sensitive potassium channels blocker glibenclamide increased GP. Furthermore, direct administration of OXA into the mediobasal hypothalamus increased GP in the presence of similar elevation of circulating lactate. Together, these data indicate that hypothalamic sensing of circulating lactate regulates GP and is required to maintain glucose homeostasis. [source] Gene Expression Profiles of Intracellular and Membrane Progesterone Receptor Isoforms in the Mediobasal Hypothalamus During Pro-OestrusJOURNAL OF NEUROENDOCRINOLOGY, Issue 12 2009B. Liu Progesterone action is mediated by its binding to specific receptors. Two progesterone receptor (PR) isoforms (PRA and PRB), three membrane progesterone receptor (mPR) subtypes (mPR,, mPR, and mPR,) and at least one progesterone membrane-binding protein [PR membrane component 1 (PRmc1)] have been identified in reproductive tissues and brain of various species. In the present study, we examined gene expression patterns for PR isoforms, mPR subtypes and PRmc1 in the rat mediobasal hypothalamus (MBH) during pro-oestrus. The mRNA level for each receptor subtype was quantified by a real-time reverse transcriptase-polymerase chain reaction (RT-PCR) at the time points: 13.00 h on dioestrous day 2; 09.00, 13.00, 17.00 and 22.00 h on pro-oestrus; and 13.00 h on oestrus. For PR, one primer set amplified PRA+PRB, whereas a second primer set amplified PRB. As expected, PRA+PRB mRNA expression was greater than PRB in MBH tissue. PRB mRNA levels increased throughout the day on pro-oestrus, with the highest levels being observed at 17.00 h. PRB mRNA levels in the MBH were increased by 2.4- and 3.0-fold at 13.00 and 17.00 h, respectively, on pro-oestrus compared to 13.00 h on dioestrous day 2. There were differential mRNA expression levels for mPRs and PRmc1 in the MBH, with the highest expression for PRmc1 and the lowest for mPR,. The mPR, mRNA contents at 13.00 and 17.00 h on pro-oestrus were increased by 1.5-fold compared to that at 13.00 h on dioestrous day 2. The mPR, mRNA levels at 13.00 and 17.00 h on pro-oestrus were 2.5- and 2.4-fold higher compared to that at 13.00 h on dioestrous day 2, respectively. PRA+PRB, mPR, and PRmc1 mRNA levels did not vary on pro-oestrus. These findings suggest that the higher expression of PRB, mPR, and mPR, in the MBH on pro-oestrous afternoon may influence both genomic and nongenomic mechanisms of progesterone action during the critical pre-ovulatory period. [source] Gonadotrophin-Releasing Hormone Pulse Generator Activity in the Hypothalamus of the GoatJOURNAL OF NEUROENDOCRINOLOGY, Issue 10 2009S. Ohkura Pulsatile release of gonadotrophin-releasing hormone (GnRH) is indispensable to maintain normal gonadotrophin secretion. The pulsatile secretion of GnRH is associated with synchronised electrical activity in the mediobasal hypothalamus (i.e. multiple unit activity; MUA), which is considered to reflect the rhythmic oscillations in the activity of the neuronal network that drives pulsatile GnRH secretion. However, the cellular source of this ultradian rhythm in GnRH activity is unknown. Direct input from kisspeptin neurones in the arcuate nucleus (ARC) to GnRH cell bodies in the medial preoptic area or their terminals in the median eminence could be the intrinsic source for driving the GnRH pulse generator. To determine whether kisspeptin signalling could be responsible for producing pulsatile GnRH secretion, we studied goats, measured plasma levels of luteinising hormone (LH) and recorded MUA in the posterior ARC, where the majority of kisspeptin neuronal cell bodies are located. Rhythmic volleys of MUA were found to be accompanied by LH pulses with regular intervals in the ARC, where kisspeptin neuronal cell bodies were found. Exogenous administration of kisspeptin stimulated a sustained increase in LH secretion, without influencing MUA, suggesting that the GnRH pulse generator, as reflected by MUA, originated from outside of the network of GnRH neurones, and could plausibly reflect the pacemaker activity of kisspeptin neurones, whose projections reach the median eminence where GnRH fibres project. These observations suggest that the kisspeptin neurones in the ARC may be the intrinsic source of the GnRH pulse generator. [source] GPR30 Differentially Regulates Short Latency Responses of Luteinising Hormone and Prolactin Secretion to OestradiolJOURNAL OF NEUROENDOCRINOLOGY, Issue 9 2009D. Lebesgue Rapid, nongenomic actions of 17,-oestradiol (E2) on hypothalamic neurones that may be relevant to reproductive function were described decades ago. The orphan G protein-coupled receptor, GPR30, was recently shown to bind oestrogens and to trigger rapid signalling in vitro, and is expressed in several rat and human brain regions, including the hypothalamus. We used two complementary approaches to investigate the role of GPR30 in hypothalamic responses to E2 that are relevant to reproductive physiology. Serial blood sampling after the acute administration of the selective GPR30 agonist G1 was used to assess the role of GPR30 in short latency negative-feedback inhibition of luteinising hormone (LH) secretion and facilitation of prolactin secretion in ovariohysterectomised female rats. In vivo RNA interference (RNAi), mediated by adeno-associated virus-expressing small hairpin RNA (shRNA) infused into the mediobasal hypothalamus, was used to study the effects of GPR30 knockdown on these rapid responses to E2. Longer-term actions of E2 on female sexual behaviour (lordosis) were also examined in female rats subjected to in vivo RNAi. Administration of E2 or G1 triggered a short latency surge of prolactin secretion, and animals subjected to GPR30 RNAi showed significantly less E2 -dependent prolactin release than animals receiving control virus. G1 did not mimic E2 negative-feedback inhibition of LH secretion, and GPR30 RNAi did not interfere with E2 suppression of LH or facilitation of lordosis behaviour. These findings suggest that activation of GPR30 promotes short latency prolactin secretion but does not mediate E2 negative-feedback inhibition of LH secretion or E2 facilitation of female reproductive behaviour. [source] Evidence for Increased Neuropeptide Y Synthesis in Mediobasal Hypothalamus in Relation to Parental Hyperphagia and Gonadal Activation in Breeding Ring DovesJOURNAL OF NEUROENDOCRINOLOGY, Issue 3 2007S. Ramakrishnan Like lactating mammals, male and female ring dove parents increase their food consumption to meet the energetic challenges of provisioning their young. To clarify the neurochemical mechanisms involved, the present study investigated the relationship between parental hyperphagia and changes in activity of the potent orexigen neuropeptide Y (NPY) in the hypothalamus of breeding doves. Changes in NPY-immunoreactive (NPY-ir) cell numbers in the tuberal hypothalamus of male and female doves were examined by immunocytochemistry at six stages of the breeding cycle. Parallel NPY mRNA measurements were recorded in mediobasal hypothalamus (which includes the tuberal hypothalamus) by semiquantitative reverse transcription-polymerase chain reaction using 18S rRNA as the internal standard. NPY mRNA changes were also measured in the mediobasal hypothalamus of nonbreeding doves following intracranial administration of prolactin, an orexigenic hormone that is elevated in the plasma of parent doves, and in response to food deprivation, which mimics the negative energy state that develops in parents as they provision their growing young. NPY-ir cell numbers in the tuberal hypothalamus and NPY mRNA levels in the mediobasal hypothalamus were significantly higher in breeding males and females during the period of parental hyperphagia after hatching than during the late incubation period when food intake remains unchanged. In nonbreeding doves, food deprivation and prolactin treatment increased NPY mRNA in this region by two- to three-fold, which suggests that NPY expression is sensitive to hormonal and metabolic signals associated with parenting. We conclude that NPY synthesis is increased in the mediobasal hypothalamus during the posthatching period, which presumably supports increased NPY release and resulting parental hyperphagia. NPY-ir and mRNA were also high in the mediobasal hypothalamus prior to egg laying when food intake remained unchanged. Several lines of evidence suggest that this elevation in NPY supports the increased gonadal activity that accompanies intense courtship and nest building interactions in breeding doves. [source] Distribution of Corticotropin-Releasing Factor Binding Protein-Immunoreactivity in the Rat Hypothalamus: Association With Corticotropin-Releasing Factor-, Urocortin 1- and Vimentin-Immunoreactive FibresJOURNAL OF NEUROENDOCRINOLOGY, Issue 3 2005B. A. Henry Abstract Corticotropin-releasing factor binding protein (CRF-BP) is a 37-kDa protein with high affinity binding sites for both corticotropin-releasing factor (CRF) and urocortin 1. Previous studies have examined the distribution of CRF-BP mRNA and peptide within the central nervous system. Due to the predominant cortical localisation, very little is known about CRF-BP in subcortical structures including the hypothalamus. The present study employed immunohistochemistry to characterise the distribution of CRF-BP-like-immunoreactive (-ir) cells and fibres in the rat hypothalamus. Bipolar and multipolar CRF-BP-ir neurones were scattered throughout the rostro-caudal extent of the hypothalamus. Distinct clusters of CRF-BP-ir neurones were identified in the anterior and posterior parvocellular and dorsal cap subdivisions of the paraventricular nucleus (PVN), as well as in the dorsal hypothalamic area, dorsomedial hypothalamic nucleus (DMN), ventral premammillary nucleus and zona incerta. CRF-BP-ir fibres extending from the third ventricle were found in the mediobasal hypothalamus and within the arcuate nucleus-median eminence region. Double immunostaining together with confocal microscopy demonstrated that the CRF-BP-immunostained fibres within the mediobasal hypothalamus coincided with vimentin immunostaining indicating that CRF-BP-ir is present within tanycytes. To define the relationship between CRF-BP-ir cells and endogenous ligands for CRF-BP, double immunohistochemistry was performed to examine possible sites within the hypothalamus where CRF- or urocortin 1-ir fibres innervate regions that contain CRF-BP-ir cell bodies. CRF-BP-ir cell bodies typically coincided with dense CRF-ir, but not urocortin 1-ir fibre innervation. CRF-ir fibre innervation was moderate to high within the anterior and posterior parvocellular subdivisions of the PVN, the dorsal cap of the PVN, DMN and the zona incerta; all regions that contained CRF-BP-ir cell populations. These studies demonstrate that, within the hypothalamus, CRF-BP-ir cells and fibres are concentrated within a circuitry known to be involved in mediating neuroendocrine and autonomic responses to stress. [source] The Hypothalamic Insulin-Like Growth Factor-1 Receptor and Its Relationship to Gonadotropin-Releasing Hormones Neurones During Postnatal DevelopmentJOURNAL OF NEUROENDOCRINOLOGY, Issue 2 2004S. S. Daftary Abstract Reproduction in vertebrates is controlled by hypophysiotropic gonadotropin-releasing hormone (GnRH) neurones. Pulsatile GnRH release increases during reproductive development, resulting in the onset and progression of puberty and, ultimately, the acquisition and maintenance of adult reproductive function. These changes in GnRH release are largely due to inputs to GnRH cells from other factors, including the neurotrophic factor, insulin-like growth factor-1 (IGF-1). Here, molecular studies were undertaken to quantify expression of IGF-1 receptor (IGF-1R) mRNA in the preoptic area-anterior hypothalamus (POA-AH) and mediobasal hypothalamus (MBH)-median eminence (ME), the sites of GnRH perikarya and neuroterminals, respectively. Immunocytochemical studies were also carried out to study the anatomical relationship between the IGF-1R and GnRH neurones. Experiments were performed in a developmental context using neonatal (P5), peripubertal (,P30) and adult (P60) male and female mice. We found that IGF-1R mRNA levels in the POA-AH were significantly different among all age groups, with levels higher at P60 then P5 or ,P30. Levels of IGF-1R mRNA in the MBH-ME were lower at P5 than ,P30 or P60. Qualitative observations suggested that IGF-1R immunoreactivity in POA-AH increased from P5 through P60. Quantitative double-label immunocytochemistry studies showed that GnRH perikarya expressed IGF-1R. Taken together, the results demonstrate expression of, and developmental changes in, IGF-1R gene and protein in brain regions containing GnRH and other neuroendocrine cells. Moreover, the novel finding that the IGF-1R is expressed on GnRH perikarya in vivo suggests a potential direct anatomical locus where IGF-1 can regulate reproductive development and function. [source] The Gonadotropin-Releasing Hormone Neurosecretory System of the Jerboa (Jaculus orientalis) and its Seasonal VariationsJOURNAL OF NEUROENDOCRINOLOGY, Issue 12 2000S. El Ouezzani Abstract The distribution of cells expressing gonadotropin-releasing hormone (GnRH) immunoreactivity was examined in the brain of adult jerboa during two distinct periods of the reproductive cycle. During spring,summer, when the jerboa is sexually active, a high density of cell bodies and fibres immunoreactive (IR) for GnRH was observed at the level of separation of the frontal lobes, in the medial septal nucleus (MS) and in the diagonal band of Broca (DBB), in the preoptic area (POA), in the organum vasculosum laminae terminalis (OVLT), in the retrochiasmatic area and hypothalamus. In autumn, when the jerboa is sexually inactive, GnRH-immunoreactivity was less intense than during spring,summer. In the POA, we noted a 55% decrease in the number of GnRH containing cells with no change in cell numbers in the MS-DBB. Furthermore, a lower density of GnRH immunopositive axon fibres is observed in all the previously mentioned structures and the immunoreaction intensity was very weak particularly within the median eminence and OVLT. Independently of the season, the GnRH immunoreactivity within neurones and fibres was similar in jerboas living in captivity and in jerboas living in their natural biotope. The effects of photoperiod on the density of POA-GnRH and arcuate nucleus ,-endorphin-containing cells were studied in jerboas maintained in long day [(LD) 16-h light, 8-h dark] and short day [(SD) 8-h light, 16-h dark] for 8 weeks. In the POA, the GnRH-IR cell number was not significantly altered by the photoperiod. Similarly, in the mediobasal hypothalamus, the number of ,-endorphin-IR neurones was not affected by such a parameter. Consequently, the GnRH seasonal variations cannot be correlated to changes in the photoperiod alone. [source] Noradrenergic Control of Arginine Vasopressin Release from the Ewe Hypothalamus In Vitro: Sensitivity to OestradiolREPRODUCTION IN DOMESTIC ANIMALS, Issue 2 2008SPS Ghuman Contents The present study aims at ascertaining the influence of ,1 -adrenoreceptors on arginine vasopressin (AVP) release in vitro and determine whether E2 modulates the ,1 -adrenoreceptor and AVP interaction. Ten minutes after ewe killing, sagittal midline hypothalamic slices (from the anterior preoptic area to the mediobasal hypothalamus with the median eminence, 2 mm thick, 2 per sheep) were dissected, placed in oxygenated minimum essential media- , (MEM- ,) at 4°C and within 2 h were singly perifused at 37°C with oxygenated MEM- , (pH 7.4; flow rate 0.15 ml/min), either with or without E2 (24 pg/ml). After 4 h equilibration, 10 min fractions were collected for 4 h interposed with 10 min exposure at 60 min to a specific ,1 -adrenoreceptor agonist or antagonist at various doses (0.1,10 mm). At the end of all perifusions, slices responded to KCl (100 mm) with AVP efflux (p < 0.05). Release of AVP was enhanced (p < 0.05) by the ,1 -adrenoreceptor agonist (methoxamine 10 mm; no E2, n = 7 perifusion chambers: from 14.3 ± 2.7 to 20.9 ± 3.9, with E2, n = 10: from 10.7 ± 1.2 to 18.4 ± 3.4 pg/ml) or the antagonist (thymoxamine 10 mm; no E2, n = 5: from 9.5 ± 3.1 to 30.4 ± 6.0, with E2, n = 10: from 10.8 ± 0.9 to 39.1 ± 6.3 pg/ml). With the agonist, the response occurred only at 80 min (p < 0.05) both in the presence and absence of E2. Whereas, after the antagonist, values were higher (p < 0.05) throughout the post-treatment period (80,170 min) without E2, but declined by 150 min in the presence of E2. Furthermore, the response to the ,1 -adrenoreceptor antagonist was greater (p < 0.05; 90,140 min) than the agonist only in the presence of E2. In conclusion, these results reveal direct ,1 -adrenoreceptor-mediated control of the hypothalamic AVP neuronal system which is modulated by E2. [source] , -Amino Butyric Acid Control of Arginine Vasopressin Release from the Ewe Hypothalamus In Vitro: Sensitivity to OestradiolREPRODUCTION IN DOMESTIC ANIMALS, Issue 5 2007SPS Ghuman Contents The present study aims to ascertain the influence of , -amino butyric acid (GABA)A or B receptors on arginine vasopressin (AVP) release in vitro and determine whether E2 modulates GABA,AVP interaction. Within 10 min of ewe killing, saggital midline hypothalamic slices (from the anterior preoptic area to the mediobasal hypothalamus along with the median eminence, 2-mm thick, two per ewe) were dissected, placed in oxygenated minimum essential media (MEM)- , at 4°C and within 2 h were singly perifused at 37°C with oxygenated MEM- , (pH 7.4; flow rate 0.15 ml/min), either with or without E2 (24 pg/ml). After 4-h equilibration, 10-min fractions were collected for 4 h interposed with a 10-min exposure at 60 min to a specific GABAA or B receptor agonist or antagonist at various doses (0.1,10 mm). GABAA (muscimol; no E2, n = 7 perifusion chambers, with E2, n = 11) or GABAB (baclofen; no E2, n = 8, with E2, n = 15) agonists (10 mm) did not influence AVP concentrations. However, AVP release increased (p < 0.05) 20,30 min after exposure to 10 mm GABAA or B antagonists (bicuculline, no E2, n = 7: from 4.6 ± 0.7 to 33.0 ± 0.4, with E2, n = 17: from 11.9 ± 1.4 to 32.8 ± 6.0; CGP52432, with E2, n = 14: from 14.0 ± 2.6 to 28.8 ± 3.9 pg/ml). At the end of the collection period, hypothalamic slices responded to KCl (100 mm) with AVP efflux (p < 0.05). GABAB but not GABAA antagonist-stimulated AVP release was enhanced in the presence of E2. In summary, AVP release is under the inhibitory influence of GABA input with further potentiation by E2 through GABAB receptors in vitro. [source] Neuroendocrine mechanism of seasonal reproduction in birds and mammalsANIMAL SCIENCE JOURNAL, Issue 4 2010Takashi YOSHIMURA ABSTRACT In temperate zones, animals use changes in day length as a calendar to time their breeding season. However, the photoreceptive and neuroendocrine mechanisms of seasonal reproduction are considered to differ markedly between birds and mammals. This can be understood from the fact that the eye is the only photoreceptive organ, and melatonin mediates the photoperiodic information in mammals, whereas in birds, photoperiodic information is directly received by the deep brain photoreceptors and melatonin is not involved in seasonal reproduction. Recent molecular and functional genomics analysis uncovered the gene cascade regulating seasonal reproduction in birds and mammals. Long day-induced thyroid stimulating hormone in the pars tuberalis of the pituitary gland regulates thyroid hormone catabolism within the mediobasal hypothalamus. Further, this local thyroid hormone catabolism appears to regulate seasonal gonadotropin-releasing hormone secretion. These findings suggest that although the light input pathway is different between birds and mammals (i.e. light or melatonin), the core mechanisms are conserved in these vertebrates. [source] Oral thyroxine administration mimics photoperiodically induced gonadal growth in Japanese quailANIMAL SCIENCE JOURNAL, Issue 5 2004Shinobu YASUO ABSTRACT Most temperate-zone animals are seasonal breeders. In a previous study, it was found that light-induced hormone conversion of thyroxine (T4) prohormone to active 3,5,3,-triiodothyronine (T3) in the mediobasal hypothalamus regulates photoperiodic response of gonads in Japanese quail. Here the effect of T4 or T3, administered in drinking water, on testicular growth in the Japanese quail kept under short days is shown. Testicular length was significantly increased in birds given T4 at doses of 4, 8 and 10 mg/L, while any dose of T3 had little effect on testicular growth. High doses (8 and 10 mg/L) of T4 and T3 resulted in high mortality and/or reduction of bodyweight. Among all of the treatment, 4 mg/L of T4 was the most effective on photoperiodic testicular growth, which caused little reduction in bodyweight. These data provide a new conventional method for promoting gonadal growth under short days. [source] | |||||||||||||