Circadian nature of the photoperiodic clock in Japanese quail

Summary The photoperiodic clock in quail (Coturnix colurnix japonica) is based upon a rhythm of photoinducibility (Øi) but the extent to which this rhythm is circadian remains unclear. Two types of experiment investigated this situation. In the first, gonadectomized quail were adapted to live in periods of darkness by training them on a schedule containing one short day and 3 days of darkness (SD/DD/DD/DD). They were then exposed to a single pulse of 6 or 10 h of light at different times across 3 days of darkness. The photoperiodic response, measured by the increase in LH secretion, showed clear rhythmicity, demonstrating unequivocally the circadian nature of Øi. The second set of experiments employed Nanda-Hamner cycles and varied the length of the photoperiod from 6 to 11 h. Responsiveness in a 36 h or a 60 h cycle was highly dependent upon the length of the photoperiod, something not predicted from theory. For instance, LD 6:30 was not photoperiodically inductive but LD 10:26 was clearly inductive. Close analysis of patterns of LH secretion indicated an unexpected delay before induction occurred and then a rapid rise to a stable level of induction. When LH was measured in every pulse under LD 10:26 there was no evidence that LH levels alternately increased and decreased. This is not consistent with the simplest interpretation of Nanda-Hamner experiments where alternate pulses of light are thought to entrain the rhythm or induce a photoperiodic response by coinciding with Øi. It is concluded that the quail's photoinducible rhythm is indeed based on a circadian rhythm but one that is only weakly self-sustaining. Possibly as a consequence of this, the rhythm's behaviour under abnormal photoperiodic cycles may be rather different from that found in other species and from other circadian rhythms in quail.Abbreviations Øi photoinducible phase - LH luteinizing hormone     

Parenchymal fine structure of the subfornical organ in the Japanese quail,Coturnix coturnix japonica

Summary The parenchyma of the subfornical organ (SFO) of the Japanese quail was studied by light and electron microscopy. The SFO consists of ependymal, intermediate, and basal (perimeningeal) layers. In the intermediate layer, neurons, glial cells, and their processes are found. Axons containing dense core granules approximately 80 nm in diameter are numerous, some of which make synaptic contact with the neuronal perikarya or dendrites. Synaptic vesicles in some axons contain a dense dot in the interior after treatment with 5-hydroxydopamine. The activity of the SFO, which is probably concerned with elicitation of drinking by angiotensin II, may be regulated at least partly by afferent monoaminergic axons. Capillaries with a non-fenestrated endothelium are occasionally found in the parenchyma. The basal layer is occupied by glial processes abutting on the digitating layer of perivascular connective tissue of meningeal vessels. The endothelium of these vessels is occasionally fenestrated. Trypan blue injected systemically accumulated in the SFO, but not in the deeper areas of the brain. The absence of a blood-brain barrier is suggested in the SFO.     

Surface fine structure of the subfornical organ in the Japanese quail,Coturnix coturnix japonica

The surface ultrastructure of the subfornical organ (SFO) was investigated in the Japanese quail. The SFO consists of a body and a stalk. The body of the SFO can be divided into rostral and caudal parts. On the rostral part, each ependymal cell possesses a short central solitary cilium; clustered cilia are also occasionally seen. Microvilli are abundant. On the caudal part, cells with a solitary cilium are fewer in number, and clustered cilia are rarely found. Microvilli are not as abundant as on the rostral part. In addition, large bulbous protrusions, tufts of small protrusions, deep funnel-shaped hollows, small pinocytotic invaginations and possible cerebrospinal fluid-contacting axons are sporadically observed on the surface of various regions of the body. Each ependymal cell of the stalk has a wide apical surface. A central solitary cilium, microvilli and other structures are observed more rarely on the stalk than on the body, while clustered cilia are not seen on the stalk. These structures are compared with those of the mammalian SFO and further discussed in relation to the possible dipsogenic receptor function for angiotensin II.     

Localization of neuropeptide Y-immunoreactive cells and fibres in the brain of the Japanese quail

Summary In the present study, we have demonstrated, by means of the biotin-avidin method, the widespread distribution of neuropeptide Y (NPY)-immunoreactive structures throughout the whole brain of the Japanese quail (Coturnix coturnix japonica). The prosencephalic region contained the highest concentration of both NPY-containing fibres and perikarya. Immunoreactive fibres were observed throughout, particularly within the paraolfactory lobe, the lateral septum, the nucleus taeniae, the preoptic area, the periventricular hypothalamic regions, the tuberal complex, and the ventrolateral thalamus. NPY-immunoreactive cells were represented by: a) small scattered perikarya in the telencephalic portion (i.e. archistriatal, neostriatal and hyperstriatal regions, hippocampus, piriform cortex); b) medium-sized cell bodies located around the nucleus rotundus, ventrolateral, and lateral anterior thalamic nuclei; c) small clustered cells within the periventricular and medial preoptic nuclei. The brainstem showed a less diffuse innervation, although a dense network of immunopositive fibres was observed within the optic tectum, the periaqueductal region, and the Edinger-Westphal, linearis caudalis and raphes nuclei. Two populations of large NPY-containing perikarya were detected: one located in the isthmic region, the other at the boundaries of the pons with the medulla. The wide distribution of NPY-immunoreactive structures within regions that have been demonstrated to play a role in the control of vegetative, endocrine and sensory activities suggests that, in birds, this neuropeptide is involved in the regulation of several aspects of cerebral functions.Abbreviations AA archistriatum anterius - AC nucleus accumbens - AM nucleus anterior medialis - APP avian pancreatic polypeptide - CNS centrai nervous system - CO chiasma opticum - CP commissura posterior - CPi cortex piriformis - DIC differential interferential contrast - DLAl nucleus dorsolateralis anterior thalami, pars lateralis - DLAm nucleus dorsolateralis anterior thalami, pars medialis - E ectostriatum - EW nucleus of Edinger-Westphal - FLM fasciculus longitudinalis medialis - GCt substantia grisea centralis - GLv nucleus geniculatus lateralis, pars ventralis - HA hyperstriatum accessorium - Hp hippocampus - HPLC high performance liquid chromatography - HV hyperstriatum ventrale - IF nucleus infundibularis - IO nucleus isthmo-opticus - IP nucleus interpeduncularis - IR immunoreactive - LA nucleus lateralis anterior thalami - LC nucleus linearis caudalis - LFS lamina frontalis superior - LH lamina hyperstriatica - LHRH luteinizing hormone-releasing hormone - LoC locus coeruleus - LPO lobus paraolfactorius - ME eminentia mediana - N neostriatum - NC neostriatum caudale - NPY neuropeptide Y - NIII nervus oculomotorius - NV nervus trigeminus - NVI nervus facialis - NVIIIc nervus octavus, pars cochlearis - nIV nucleus nervi oculomotorii - nIX nucleus nervi glossopharyngei - nBOR nucleus opticus basalis (ectomamilaris) - nCPa nucleus commissurae pallii - nST nucleus striae terminalis - OM tractus occipitomesencephalicus - OS nucleus olivaris superior - PA palaeostriatum augmentatum - PBS phosphate-buffered saline - POA nucleus praeopticus anterior - POM nucleus praeopticus medialis - POP nucleus praeopticus periventricularis - PP pancreatic polypeptide - PYY polypeptide YY - PVN nucleus paraventricularis magnocellularis - PVO organum paraventriculare - R nucleus raphes - ROT nucleus rotundus - RP nucleus reticularis pontis caudalis - Rpc nucleus reticularis parvocellularis - RPgc nucleus reticularis pontis caudalis, pars gigantocellularis - RPO nucleus reticularis pontis oralis - SCd nucleus subcoeruleus dorsalis - SCv nucleus subcoeruleus ventralis - SCNm nucleus suprachiasmaticus, pars medialis - SCNl nucleus suprachiasmaticus, pars lateralis - SL nucleus septalis lateralis - SM nucleus septalis medialis - Ta nucleus tangentialis - TeO tectum opticum - Tn nucleus taeniae - TPc nucleus tegmenti pedunculo-pontinus, pars compacta - TSM tractus septo-mesencephalicus - TV nueleus tegmenti ventralis - VeL nucleus vestibularis lateralis - VLT nucleus ventrolateralis thalami - VMN nucleus ventromedialis hypothalami A preliminary report of this study was presented at the 15th Conference of European Comparative Endocrinologists, Leuven, Belgium, September 1990     

Fasting differentially regulates expression of agouti-related peptide,pro-opiomelanocortin,prepro-orexin,and vasoactive intestinal polypeptide mRNAs in the hypothalamus of Japanese quail

Research in mammals has established the existence of a neuronal network that lies within the hypothalamus and that regulates energy homeostasis. However, it is unknown whether this system has been evolutionarily conserved. The objective of the present study was therefore to examine the influence of the agouti-related peptide (AGRP), pro-opiomelanocortin (POMC), prepro-orexin, and vasoactive intestinal polypeptide (VIP) genes on energy balance in birds by quantifying the effect of a 24-h fast on their expression in the hypothalamus of the Japanese quail. In situ hybridization revealed strong signals for AGRP and POMC mRNAs in the infundibular nucleus (IN), for prepro-orexin in the lateral hypothalamic area (LHy) and periventricular hypothalamic nucleus, and for VIP in the LHy. POMC mRNA was co-localized with -melanocyte-stimulating hormone-like immunoreactivity in individual IN neurons. Compared with the ad-libitum-fed state, a 24-h fast resulted in a 2.2-fold increased expression of AGRP mRNA in the IN. However, fasting did not induce changes in POMC, prepro-orexin, or VIP mRNAs. The results suggest an involvement of the central melanocortin system in the regulation of energy balance in birds, as in mammals. In contrast, orexins in birds may be primarily involved in the control of physiological functions other than energy homeostasis.This research was supported by a Commonwealth Fellowship to D.P.-S. and a BBSRC Fellowship to T.B.     

Day-night rhythms in opiate modulation of body temperature in male Japanese quail

Summary Male Japanese quail,Coturnix coturnix japonica, displayed day-night rhythms in their body temperature, with significantly higher temperatures during the day than at night. There were individual variations in both the temperatures attained and amplitude of the day-night rhythm of body temperature in the group-housed birds. Accompanying these diurnal patterns in body temperature there were day-night rhythms in the effects of intraperitoneal administrations of the opiate agonist, morphine (1.0 and 10 mg·kg^-1) and prototypic opiate antagonist, naloxone (10 mg·kg^-1) on colonic body temperature. In the daytime, the body temperature response profiles of quail treated with morphine were dependent on the initial body temperature of the bird. In those birds with the lower daytime body temperatures, morphine caused an initial hyperthermic response that was followed by a hypothermia and then a weak hyperthermia; whereas, in birds with the higher initial body temperatures there was a pronounced hypothermia followed by a marked hyperthermia. At night, morphine induced a hyperthermic response in all quail that was followed by a hypothermia. These effects of morphine were blocked by naloxone, with naloxone by itself significantly decreasing the daytime temperature of those quail with the higher initial body temperature. Naloxone had no significant effects on the nighttime body temperatures of any of the quail. These results show that there are day-night rhythms and individual differences in opiate sensitivity and modulation of body temperature in male quail. These findings also suggest that endogenous opioid systems are involved in either the generation and/or expression of the day-night rhythm of body temperature in quail.Abbreviations LD light-dark - T _L low initial body temperatures - T _H high initial body temperatures     

Monoamine fluorescence in the median eminence of the Japanese quail,Coturnix coturnix japonica,following medial basal hypothalamic deafferentation

Summary Monoamine fluorescence was examined in the ventral hypothalamus of the Japanese quail, Coturnix coturnix japonica after medial basal hypothalamic deafferentation. In sham-operated control birds, numerous yellow-green fluorescent fibers were observed in the median eminence and the nucleus tuberis. In the area of the paraventricular organ, a number of fluorescent fibers and cell bodies were observed. In birds with deafferented hypothalami, fluorescence disappeared both in the median eminence and the nucleus tuberis. In the area of the paraventricular organ, which was within the area of deafferentation, fluorescence of neuronal perikarya did not change, but fluorescent fibers decreased markedly in number. Disappearance of monoamine fluorescence in the median eminence and the nucleus tuberis is discussed in relation to the tanycyte absorptive function and gonadal development.Supported by Grants from the Ministry of Education to Professors T. Bando and H. Kobayashi, and a Grant from the Ford Foundation to Prof. H. Kobayashi.     

Protein polymorphism in two populations of the wild quail Coturnix coturnix japonica

To evaluate genetic variability in two populations of the wild quail Cofurnix coturnix japonica , proteins and enzymes were examined by starch gel electrophoresis.
Rare variants so far not observed in domestic quail were found in the following five enzymes; aspartate aminotransferase, acid phosphatase, pancreatic esterase, isocitrate dehydrogenase and lactate dehydrogenase. The proportion of polymorphic loci ( P _poly) and the expected average heterozygosity ( H ) in one of the two populations were estimated to be 0.484 (15/31) and 0.085, respectively. Those in another population were 0.433 (13/30) and 0.086, respectively. The genetic distance (Nei, 1975) between the two wild quail populations was D = 0.0074. D values of 0.0321 and 0.0189 were estimated between the laboratory quail population previously examined (Kimura et al., 1982) and each of these two wild populations.     

Smooth muscle cells in the walls of ovarian follicles in the Japanese quail

Summary The walls of pre-ovulatory follicles of the Japanese quail were examined at the ultrastructural level for the presence of cells displaying the typical morphological features of smooth muscle cells. These characteristics were found in the cells of the chordae, the tunica albuginea, and the theca externa. Small, elongated cells, containing microfilaments, were observed in the theca of prelampbrush follicles localized in the ovarian cortex. These thecal cells were considered as the putative precursors of the thecal smooth muscle cells of the pre-ovulatory follicle. The difference between the smooth muscle cells of the pre-ovulatory follicle and those in the wall of the most recent post-ovulatory follicle is the contracted state of the latter, which is most evident in the cells of the theca externa. It can be concluded that the cells of the theca externa are smooth muscle cells which are mainly contracted during the ovulatory process. A comparison was made with other vertebrate species.     

Renewal and proliferation of spermatogonia during spermatogenesis in the Japanese quail,Coturnix coturnix japonica

Summary Four different types of spermatogonia were identified in the seminiferous tubules of the Japanese quail: a dark type A (A_d), 2 pale A type (A_p1 and A_p2), and a type B. A model is proposed describing the process of spermatogonial development in the quail. The A_d spermatogonia are considered to be the stem cells. Each divides to produce a new A_d spermatogonium and a A_p1 spermatogonium during Stage IX of the cycle of the seminiferous epithelium. An A_p1 spermatogonium produces two A_p2 spermatogonia during Stage II of the cycle, A_p2 spermatogonia produce four type B spermatogonia during Stage VI of the cycle, and type B spermatogonia produce eight primary spermatocytes during Stage III of the cycle. Consequently, 32 spermatids can result from each division of an A_d spermatogonium. Spermatogonial development in the quail differs from the process described in mammals in that there are fewer mitotic divisions and they are all synchronized with the cycle of the seminiferous epithelium. It is suggested that the fewer mitotic divisions explain why a smaller area of the seminiferous tubule is occupied by a cellular association in the quail than in mammals like the rat, ram and bull. The duration of spermatogenesis from the division of the A_d spermatogonia to sperm release from the seminiferous epithelium was estimated to be 12.77 days.     

Sex difference in the neurotensin-immunoreactive cell populations of the preoptic area in quail (Coturnix japonica)

The distribution of neurotensin-immunoreactive cells and fibers was analyzed by immunocytochemistry in the forebrain of male and female Japanese quail (Coturnix japonica) by using an antibody directed against the C-terminal part of the molecule. Immunoreactive perikarya were located almost exclusively in the medial preoptic area with small populations also being present in the nucleus paraventricularis and in the tuberal region. Immunoreactive fibers were observed not only throughout the preoptic area-hypothalamus, but also in the septal region, nucleus intercollicularis, substantia grisea centralis and the classical catecholaminergic areas of the mesencephalon, such as the area ventralis of Tsai and the nucleus tegmenti pedunculo-pontinus, pars compacta. The preoptic neurotensin-immunoreactive cells were exclusively located within the boundaries of the sexually dimorphic medial preoptic nucleus. They were significantly more numerous in females than in males. In females, the number of neurotensin cells varied during the ovulatory cycle: fewer cells were observed in birds that were about to lay an egg (they had a calcified egg in the oviduct) than in those that had already laid or were not going to lay on that day. These data indicate major variations in the expression of neurotensin in response to neurochemical or neuroendocrine changes associated with ovulation.     

Cytochalasin D inhibits basal body migration and ciliary elongation in quail oviduct epithelium

Summary The effects of cytochalasin D (CD) were studied by scanning (SEM) and transmission (TEM) electron-microscopic examination at different stages of ciliary differentiation in epithelial cells of quail oviduct. Immature quails were prestimulated by estradiol benzoate injections to induce ciliogenesis in the undifferentiated oviduct. After 24 h of CD culture, SEM study revealed inhibition of ciliogenesis and dilation of the apex of non-ciliated cells. TEM study showed that 2 h of CD treatment produced dilation of lateral intercellular spaces, after 6 h of treatment, this resulted in intracellular macrovacuolation. Vacuoles were surrounded by aggregates of dense felt-like material. CD also induced the disappearance of microvilli, and rounding of the apical surface of undifferentiated cells and those blocked in ciliogenesis. Centriologenesis was not inhibited by CD; basal bodies assembled in generative complexes in the supranuclear region after 24 h of treatment. However, the migration of mature basal bodies towards the apical surface was impaired. Instead, they anchored onto the membrane of intracellular vacuoles; growth of cilia was induced in the vacuole lumen. Cilium elongation was disturbed, giving abnormally short cilia with a dilated tip; microtubules failed to organize correctly.     

Effect of hyaluronic acid on the emergence of neural crest cells from the neural tube of the quail,Coturnix coturnix japonica

Summary Hyaluronic acid (HA) added to the medium of quail neural tubes explanted in vitro influences the number of migratory neural crest cells that emerge, compared with controls. Neural crest cells were counted with an ocular grid after 20 h of migration into 0.1 mm wide areas or bins lying parallel to the neural tube, and the results were analyzed by linear regression. A low concentration of HA (5 g/ml) significantly decreased the total number of neural crest cells in all bins adjacent to the neural tube, whereas several high concentrations of HA (250, 500, and 1000 g/ ml) significantly increased the number of neural crest cells. Intermediate concentrations of HA (50 and 100 g/ml) did not differ from that of controls. Linear regressions of number of cells versus distance from the tube showed no significant differences among the slopes of control, low HA, and high HA treatments, providing evidence that HA does not influence the rate of cell migration. Scanning electron microscopy showed that cells in neuroepithelia exposed to low HA (5 g/ml) appeared in tighter contact, while cells of neuroepithelia in high HA (500 g/ml) appeared more loosely organized, compared with controls. Cells in tight contact could be restrained from leaving the neuroepithelium, whereas cells in loose contact could more readily move out of the neural tube, thus explaining the differences in cell numbers in low HA and high HA, respectively. We conclude that HA can be a factor in the differential adhesivity among neuroepithelial cells and may be important in the initial separation of the neural crest from the neural tube.     

Immunohistochemical localization of corticotropin-releasing factor (CRF)-containing neurons in the hypothalamus of the Japanese quail,Coturnix coturnix

Immunohistochemical localization of corticotropin-releasing factor (CRF)-like immunoreactivity in the brain of the Japanese quail was studied by means of the peroxidase anti-peroxidase (PAP) method. CRF-immunopositive perikarya of parvocellular neurons were observed mainly in the nucleus praeopticus medialis and nucleus paraventricularis. Additional perikarya were also detected in the nucleus hypothalamicus posterior medialis in the hypothalamus and in the non-hypothalamic nucleus accumbens, nucleus septalis lateralis and nucleus dorsomedialis and dorsolateralis thalami. No CRF immunoreaction was found to coexist with the vasotocin (Vt)-containing system in comparative examination of consecutive sections treated with anti-vasopressin (Vp) serum. The CRF-immunoreactive fibers were detected mainly in the external layer of the anterior median eminence but not in its posterior division. Unilateral adrenalectomy induced the marked reduction in number of the CRF immunopositive fibers in the anterior median eminence.     

Immunohistochemical localization of laminin,neural cell adhesion molecule,collagen type IV and T-61 antigen in the embryonic retina of the Japanese quail by in vivo injection of antibodies

Summary Antibodies against laminin (LN), fibronectin (FN), collagen type IV (Col IV), neural cell adhesion molecule (N-CAM), T-61 antigen, actin, tubulin and neurofilament protein were injected into the eyes of quail embryos (Coturnix coturnix japonica) of different ages. Twenty h after injection, the heads of the embryos were fixed and the antibodies visualized in sections with the use of fluorescein-isothiocyanate (FITC) or peroxidase-labeled second antibodies by light- and electron microscopy. Antibodies against cell surface molecules, such as N-CAM, LN, Col IV and T 61, labeled matrix and membrane components of the retinal cells in different antigen-specific patterns. Antibodies against intracellular antigens, such as actin, tubulin and neurofilament protein labeled nonspecifically the vitreous body and the inner basal lamina of the retina, but resulted in only a very weak and diffuse labeling of retinal cells. N-CAM was detected in high concentration in the optic fiber layer on the surface of axons and on the membranes of all retinal cells. Col IV, LN and T 61 antigen were found predominantly in the optic fiber layer. LN and Col IV were located on the surface of axons and the endfeet of ventricular (neuroepithelial) cells in a patchy distribution. The T-61 antigen was found in early stages in the cell-free space of the optic fiber layer, on the surface of ventricular cells and axons, and at later stages also in high-density patches between nerve fibers. The distribution of LN and T-61 antigen together with data from in vitro experiments suggests a crucial role of these proteins in axon extension in the avian retina during early development of the optic fiber layer.     

T3 implantation mimics photoperiodically reduced encasement of nerve terminals by glial processes in the median eminence of Japanese quail

Photoperiodically generated triiodothyronin (T₃) in the mediobasal hypothalamus (MBH) has critical roles in the photoperiodic response of the gonads in Japanese quail. In a previous study, we demonstrated seasonal morphological changes in the neuro-glial interaction between gonadotrophin-releasing hormone (GnRH) nerve terminals and glial endfeet in the median eminence (ME). However, a direct relationship between photoperiodically generated T₃ and seasonal neuro-glial plasticity in the ME remained unclear. In the present study, we examined the effect of T₃ implantation into the MBH on the neuro-glial interaction in the ME. T₃ implantation caused testicular growth and reduced encasement of nerve terminals in the external zone of the ME. In contrast, no morphological changes were observed in birds given an excessive dose of T₃, which did not cause testicular growth. These results support the hypothesis that thyroid hormone regulates photoperiodic GnRH secretion via neuro-glial plasticity in the ME. T. Yoshimura was supported by the Program for Promotion of Basic Research Activities for Innovative Biosciences (PROBRAIN) and a Grant-in-Aid for Encouragement of Young Scientists from the Ministry of Education, Science, Sports, and Culture, Japan.