Immunocytologic detection of peptides immunologically related to LRH and to SRIF in the garden dormouse under various conditions]

Immunocytologic technics have allowed us to detect appreciable and progressively increasing amounts of LRH and of SRIF in the median eminence of the dormouse during hibernation at 6 degrees C. In animals conditioned to darkness at 22 degrees C with the ovarian involution that is very important, there exists a nearly total disappearance of LRH while the amount of SRIF remains high. On the contrary permanent lighting at 22 degrees C responsible of an important reactivation of the genital sphere provoques a massive accumulation of LHR in the median eminence; SRIF is present in large amounts during the first weeks but diminishes of the experience is prolonged.     

Morphological equivalent of the bifunctional role of somatostatin

Summary Using the immunoenzyme bridge-technique at the light and electron microscopic levels, somatostatin can be demonstrated in the perikarya of the anterior periventricular nucleus, in the median eminence and in the parvocellular hypothalamic nuclei of the rat. In the latter regions the perikarya are negative, whereas a positive reaction for somatostatin is found in a delicate network of fibers and middle-sized granules of very small axons. In light of these results, the double function of somatostatin — as release inhibiting hormone and as transmitter — is discussed. The positive staining reaction in the organum vasculosum laminae terminalis of male and female rats as well as in the subfornical organ, the nucleus dorsalis thalami and the nucleus medialis habenulae in female controls and pregnant rats is not due to somatostatin-containing structures, but partly to substance P and partly to a substance which could not be defined.Supported by the Deutsche Forschungsgemeinschaft (Grant Nr. Kr. 569/1) and Stiftung Volkswagenwerk     

Immunocytochemical localization of somatostatin and vasotocin in the brain of the Pacific hagfish,Eptatretus stouti

Summary The brain of the Pacific hagfish, Eptatretus stouti, was studied immunocytochemically using antisera against somatostatin (SRIH), arginine vasopressin (AVP), and adrenocorticotropic hormone (ACTH). SRIH-immunoreactive perikarya were distributed bilaterally in the postoptic nucleus and in the hypothalamic nucleus. Although several short, stained fibers were observed in the vicinity of the perikarya, SRIH-immunoreactivity was not found in the neurohypophysis, nor in other parts of the brain. On the other hand, presumed arginine vasotocin (AVT) perikarya were distributed in an arc-shaped region extending from the posterior part of the preoptic nucleus to the anterior-most end of the hypothalamic nucleus and projected their fibers to the neurohypophysis. Most presumptive AVT perikarya were located close to the paired prehypophysial arteries near the anterior end of the postoptic nucleus. In the neurohypophysis, abundant presumptive AVT-fibers terminated in the posterior dorsal wall, although some fibers terminated in the anterior dorsal wall and only a few fiber endings were found in the ventral wall. No ACTH-positive cells were detected in the hagfish brain or in the pituitary gland.Supported from a grant from the National Science Foundation PCM 8141393     

Differing immunoreactivities of somatostatin in the cortex and the hypothalamus of the rat

Summary Using an antibody against somatostatin (antiserum F), two somatostatin-immunoreactive systems, (i) a hypothalamic and (ii) an extrahypothalamic cortical system, are demonstrated in the rat. Another antiserum raised against somatostatin (antiserum BS 102) stains only the axons but not the perikarya of the hypothalamic system; the cortical somatostatin system does not react with this antiserum. The electron microscopic findings do not allow decision whether the above-mentioned hypothalamic and cortical neurons possess a common prohormonal form of somatostatin, immunoreactive only with antiserum F. They show, however, that the granules in both neuronal systems differ considerably; in the cortical neurons they measure approximately 65 nm in diameter, in the hypothalamic neurons 90–120 nm in diameter. Thus, both somatostatin systems are different and independent from one another.Supported by the Deutsche Forschungsgemeinschaft (Grant Nr. Kr 569/3) and the Stiftung Volkswagenwerk     

Further demonstration of the ambient temperature dependence of the annual biological cycles in the edible dormouse,Glis glis

Summary In the male edible dormouse, it has been proposed that the annual temperature cycle is the major external factor triggering annual biological rhythms in this hibernating species. The present study was designed to explore (i) the effects of suppression of the annual thermoperiodic cycle under natural photoperiodic conditions, and (ii) the effects of acute exposure to a warm environment on basal plasma T4 levels observed during hibernation. The results of the first experiment demonstrate an absence of circannual cycles of hibernation, body weight, and endocrine thyroid and gonadal functions in the absence of annual fluctuations of temperature (constant warm environment at 24°C) despite the maintenance of a normal photoperiodic cycle. On the other hand, acute exposure to 24°C during the late stage of hibernation stimulated thyroid function as expressed by a consistent transitory rise in plasma T4 concentrations, which was maximal within 7 days and restored to basal levels after 14 days. These findings are in close agreement with the concept that in the edible dormouse, the annual thyroid cycle is synchronized with the annual temperature cycle. Moreover, the present study, combined with prior data indicating that the thyroid cycle induces the testis cycle, suggests that the ambient temperature cycle may be intricately involved in the control of neuroendocrine cycles in dormice, although the mechanism is still unknown.     

Isolation, characterization and PCR multiplexing of polymorphic microsatellite markers in the edible dormouse, Glis glis

We isolated and characterized 10 dinucleotide microsatellite loci in the edible dormouse, Glis glis (Linnaeus). Four multiplex panels were developed. Loci were amplified in samples from two geographically distant populations (Torgny in Belgium and Montseny in Spain). All loci were polymorphic in Spain but four were monomorphic in Belgium. Individuals from Belgium and Spain exhibited an average allelic diversity of 1.9 and 3.3 and an observed heterozygosity ranging from 0.08 to 0.47 and from 0.04 to 0.72, respectively.     

Immunohistochemical evidence for a magnocellular somatostatin cell group in the anterior paraventricular thalamus of the rat

Summary By use of the indirect immunofluorescence technique a small group of large somatostatin-positive neurons is described in the subependymal area of the anterior paraventricular thalamus of the male rat. Retrograde-tracing experiments suggest that they project to areas outside the blood-brain barrier.     

Ultrastructural immunohistochemical localization of vasopressin in the hypothalamic-neurohypophysial system of three murids

Vasopressin was immunohistochemically localized at the electron microscopic (EM) level in the hypothalamic-neurohypophysial system (HNS) of three murids. Antiserum to vasopressin was produced in rabbits injected with lysine vasopressin (LVP) conjugated to egg albumin (EA), anti-EA being precipitated prior to staining. Sternberger's unlabeled antibody peroxidase technique was employed, immunoreactivity being designated by peroxidase anti-peroxidase (PAP) molecules and electron opacity. Immunoreactive neurosecretory granules (NSG) were found in the perikarya of the supraoptic nucleus (SON) in all three murids investigated, although far more profusely in the two wild strains. Immunoreactive axonal NSG were observed in the inner and outer zones of the median eminence (ME), and within most of the axons and terminals in the neurohypophysis. The concentration of primary serum effective for staining the SON (110–150) was far higher than that required for the ME and the neurohypophysis (1:500–1:1,200). AntiLVP also induced electron opacity of granules in cells of the pars intermedia (PI). Discussion centers on the significance of immunoreactive NSG in the neurosecretory (NS) perikarya, on the possibility of an extragranular pool of hormone, and on speculation about the electron opacity of the PI granules.     

Seasonal changes in thyroid-gonadal interactions in the edible dormouse,Glis glis

Summary This study was conducted to determine changes in thyroid-gonadal interaction in the edible dormouse during the phase of the annual cycle that corresponds to the end of the breeding season (from June to September). We evaluated intra-hypothalamic luteinizing hormone-releasing hormone (LHRH) content, and plasma concentrations of luteinizing hormone (LH), testosterone, thyroid-stimulating hormone (TSH) and thyroxine (T4) in three groups of dormice: (1) controls; (2) dormice receiving sufficient T4 supplementation to maintain June levels in control animals until September, thus counteracting the seasonal reduction of T4 that normally begins in July; and (3) thyroidectomized dormice. The effect of thyroidectomy was only detectable in June, when plasma T4 concentration in the control group was maximal, and consisted of a significant decrease in plasma testosterone levels. This provides strong support for the hypothesis that thyroid function positively influences gonadal function during the breeding season. The T4 supplementation resulted in a decrease in hypothalamic LHRH concentration, suggesting that an increased LHRH release led to the observed stimulated hypophyseal secretion of LH in June and September and the increased circulating testosterone levels in September. There was no detectable effect in July and August. These results show that thyroid axis activation of the hypothalamic-pituitary-gonadal system is only possible during certain phases of the annual cycle, particularly evidenced here during the breeding season. They also reinforce our conclusions drawn from the thyroidectomy results. Conversely, the summer testicular regression which normally occurs after the breeding season is no longer controlled by plasma T4 levels. Even though the sensitivity of the gonadal axis to the thyroid axis appears to reappear at the end of the summer, results of previous studies indicate that this resumption is only temporary.Abbreviations LH luteinizing hormone - LHRH luteinizing hormone-releasing hormone - RIA radioimmunoassay - T4 thyroxine - TSH thyroid-stimulating hormone     

Neuropeptides and thermoregulation: the interactions of bombesin, neurotensin, TRH, somatostatin, naloxone and prostaglandins

In this study we have examined the interactions of bombesin (1 microgram ICV), neurotensin (1 microgram ICV), TRH (10 micrograms ICV), somatostatin (10 micrograms ICV), PGE2 (10 micrograms ICV) and naloxone (10 mg/kg SC) on thermoregulation in the rat at room temperature (20 +/- 1 degree C). Given alone, bombesin, neurotensin, somatostatin and naloxone all produced hypothermia (bombesin greater than neurotensin greater than somatostatin congruent to naloxone). PGE2 was hyperthermic, and TRH had no effect. Bombesin and PGE2 neutralized one another's effects. Neurotensin had no effect on PGE2-induced hyperthermia. Naloxone enhanced the hypothermic effect of bombesin and somatostatin enhanced the rate of onset of hypothermia after bombesin. TRH had no effect on bombesin-induced hypothermia. TRH, somatostatin and naloxone had no effect on neurotensin-induced hypothermia. TRH antagonized the hypothermia due to naloxone and somatostatin.     

Immunohistochemical localization of somatostatin in the human hypothalamus

Summary In order to identify clearly the nervous structures containing somatostatin in the human hypothalamus, an immunohistochemical localization of this neurohormone was performed at light-microscopic level. Using a antiserum specific to somatostatin and the unlabeled antibody peroxidase-antiperoxidase technique, we have found somatostatin in neurons with cell bodies in an area in the anterior hypothalamus corresponding to the infundibular nucleus. Somatostatin-containing fibers were also detected in the neurovascular zone of the pituitary stalk, suggesting that somatostatin is released in that region to reach the capillaries in the pituitary portal plexus. A large bundle of somatostatin fibers extending from the anterior part of the paraventricular nucleus up to the posterior portion of the mammillary bodies has also been detected. The role of these fibers still remains to be clarified.     

Topography of somatostatin cells in the stomach of the rat: Possible functional significance

Summary Somatostatin cells in the stomach of the rat have a characteristic shape and distribution. In the antral mucosa they occur together with gastrin cells and enterochromaffin cells at the base of the glands. In the oxyntic mucosa they are scattered along the entire glands with some predominance in the zone of parietal cells. Throughout the gastric mucosa the somatostatin cells possess long and slender processes that emerge from the base of the cell and end in clublike swellings. Such processes appear to contact a certain proportion of neighbouring gastrin cells in the antral mucosa and parietal cells in the oxyntic mucosa.Exogenous somatostatin given by intravenous infusion to conscious rats counteracted the release of gastrin stimulated by feeding, elevated antral pH or vagal excitation. Gastrin causes parietal cells to secrete HCl and endocrine cells in the oxyntic mucosa to mobilise and synthesise histamine. Somatostatin is known to block the response of the parietal cells to gastrin. In contrast, somatostatin did not block the response of the histamine-storing endocrine cells to gastrin, perhaps because these endocrine cells lack receptors to somatostatin. Conceivably, somatostatin in the gastric mucosa has a paracrine mode of action. The observations of the present study suggest that somatostatin may affect some, but not all of the various cell types in the stomach. Under physiological conditions this selectivity may be achieved in the following ways: 1) Communication may be based on direct cell-to-cell contact. 2) Only certain cell types are supplied with somatostatin receptors.     

Liver and brown fat mitochondrial response to cold in the garden dormouse (Eliomys quercinus)

The involvement of two organs, i.e. the liver and the brown adipose tissue (BAT) in response to cold in a hibernating species such as the garden dormouse has been studied. 2. In animals living in the cold, mitochondrial respiratory rates significantly increased (with respect to those living at 28 degrees C) in both organs with a larger increase in the BAT (+152% in the BAT and 67% in the liver). 3. The increase in BAT activity was obtained by a concomitant increase in: (a) the BAT mass (+30%), (b) the total mitochondrial mass (+20%), and (c) the mitochondrial respiratory rate (+64%). In the liver the increase was due only to an augmentation in mitochondrial mass and activity. 4. These results indicate that: (a) the BAT exerts a pre-eminent role in the physiological response to cold of garden dormouse, (b) a certain non-shivering thermogenesis (NST) is present in the liver of such species. In addition we suggest that a local thermoregulatory response would take place in a metabolically important organ such as the liver.     

The effect of selective sst1, sst2, sst5 somatostatin receptors agonists, a somatostatin/dopamine (SST/DA) chimera and bromocriptine on the "clinically non-functioning" pituitary adenomas in vitro

The aim of the work was to investigate the effects of somatostatin analogs acting selectively on sst1 (BIM-23926), sst2 (BIM-23120) and sst5 (BIM-23206) receptor subtypes on the viability of "clinically non-functioning" pituitary adenomas in vitro. The effects of native SST (SST-14), a SST/DA chimera (BIM-23A387) and a D(2)-dopamine receptor agonist bromocriptine (BC) were also examined. The study was performed on 10 surgically removed pituitary macroadenomas, diagnosed before surgery as "non-functioning". A part of each tumor was mechanically dispersed and digested with collagenase to isolate the tumoral cells. Another part of each tumor was fixed, embedded in paraffin and immunostained to reveal the pituitary hormones and SST receptor subtypes (sst1, sst2A, sst2B, sst3, sst4, sst5). The tumoral cell suspensions were incubated for 24 h with the substances mentioned above. The quantity of viable cells was estimated using the EZ4U system. The results were compared with the immunohistochemical evaluation of the hormonal profile of adenoma and the sst receptor subtype immunoreactivities present. The findings indicate that selective sst1, sst2 and sst5 receptors agonists, SST/DA chimera and D(2)-dopamine receptor agonist bromocriptine affect the viability of some, but not all, "clinically non-functioning" pituitary adenomas in vitro. The most effective was bromocriptine. The investigated somatostatin analogs including SST/DA chimera exerted roughly similar inhibitory effects. Further studies are needed to fully evaluate the potential usefulness of these compounds in the pharmacological treatment of "non-functioning" pituitary tumors.     

Peptides as regulators of the immune system: emphasis on somatostatin

Study of the communication between nervous and immune systems culminated in the understanding that cytokines, formerly considered exclusively as immune system-derived peptides, are endogenous to the brain and display central actions. More recently, immune cells have been recognized as a peripheral source of “brain-specific” peptides with immunomodulatory actions. This article reviews studies concerning reciprocal effects of selected cytokines and neuropeptides in the nervous and immune systems, respectively. The functional equivalence of these two categories of communicators is discussed with reference to the example of the actions of neuropeptide somatostatin in the immune system.     

Localization of serotonin in the hypothalamus and the mesencephalon of the guinea-pig

Summary The distribution of serotonin in the hypothalamus and the mesencephalon of guinea-pigs pretreated with both pargyline and L-tryptophan was investigated immunohistochemically using monoclonal antibodies to 5-HT. 5-HT-positive fibers and varicosities appeared distributed throughout the hypothalamus. Some areas showed a greater density of immunoreactivity: the suprachiasmatic nucleus, the region of the supraoptic crest, the area of the medial forebrain bundle, the ventral part of the nucleus ventromedialis, the median eminence and the ventral part of the mammillary bodies. 5-HT nerve fibers were also scattered in the posterior lobe of the pituitary. An extensive supraependymal plexus of immunoreactive axons was observed in most ventricular regions. No 5-HT positive cell bodies were present in the hypothalamus of the guinea-pig under our experimental conditions, whereas an intense serotonin immunoreactivity was detected in perikarya of the brain stem. 5-HT cell bodies were found predominantly in the raphe region including the nucleus raphe dorsalis and raphe medianus, nucleus interpeduncularis, reticular formation and dorsal area of the medial lemniscus.     

Development of immunoreactive somatostatin in C-cell complexes in the thyroid gland of the dog

Summary In connection with our previous finding that an intense immunoreaction to somatostatin transiently appears in thyroid C cells of the dog during early fetal periods, the present study investigated C-cell complexes in thyroid glands from early fetuses to adults in an attempt to clarify whether the transient appearance of immunoreactivity to somatostatin is dependent on the degree of differentiation of C cells. C-cell complexes retain their fetal characteristics; even in the complexes of postnatal dogs, there are numerous undifferentiated cells, immature C cells and primitive follicular cells, which are not yet organized into follicles. Neither the degree of differentiation of C cells nor that of other constituent elements of the complexes affected the developmental pattern of somatostatin immunoreactivity in C cells. The C cells located in complexes displayed the same pattern of developmental changes in immunoreactivity to somatostatin as the cells in thyroid parenchyma. In the C-cell complexes of early fetal dogs a very intense immunoreactivity for somatostatin was observed; almost all calcitonin-positive cells were also somatostatin positive. The immunoreactivity to somatostatin progressively decreased with age. In the postnatal complexes the number of somatostatin-positive cells was very small compared with that of calcitoninpositive cells.     

An intermittent somatostatin-immunoreactivity in the cortex and basal ganglia of the rat

Summary Using light microscopic immunohistochemistry, somatostatinpositive structures were observed in the cortex of the rat. These structures, including cells and fibers, are widely distributed in all cortical laminae and are also found in the basal ganglia. The positive results were obtained exclusively in two groups of animals sacrificed during two different months of two subsequent years. The reason for this variability in the immunocytochemical stainability of cortical structures remains enigmatic.Supported by the Deutsche Forschungsgemeinschaft (Grant Nr. Kr 569/3) and Stiftung Volkswagenwerk     

Immunocytochemical investigation of forebrain control by somatostatin of the pituitary in the teleost Poecilia latipinna

Summary An extensive system of somatostatin-immunoreactive neurons has been localized in the forebrain and pituitary of the molly (Poecilia latipinna), using the unlabelled antibody immunocytochemical method.In the hypothalamus, reactive perikarya were scattered throughout the parvocellular divisions of the preoptic nucleus. These cells were smaller in size and more ventral in position than those which stained with antisera to the neurohypophysial hormones, vasotocin and isotocin. A few very small somatostatin-immunoreactive cells were observed in the tuberal region and in the nuclei of the lateral and posterior recesses — areas which were rich in somatostatin-immunoreactive fibres.Somatostatin cells were also found in a small area of the ventral thalamus, mainly in the dorsolateral nucleus. Some of these neurons were large and multipolar, and appeared to form tracts of fibres into the posterior hypothalamus. In the telencephalon there were a few stained cells in the ventral area, with a complex pattern of fibres occurring in parts of the dorsal area.Somatostatin-immunoreactivity was intense in the central and posterior neurohypophysis, and particularly in its finger-like projections into the proximal pars distalis, around groups of growth hormone cells. Examination of material from fishes under various experimental conditions provided evidence for the somatostatin fibres originating from the preoptic neurons being involved in the control of growth hormone secretion.