Deficiency of immunoreactive somatostatin in the median eminence of Snell dwarf mice

Snell dwarf mice (dw/dw) are characterized by a genetically determined, congenital lack of pituitary GH, TSH and prolactin. Given that hypothalamic somatostatin is involved in the regulation of pituitary GH and TSH release, it was decided to investigate the content of immunoreactive somatostatin (IRS) in the median eminence of dw/dw and phenotypically normal mice of the same strain. The content of IRS in the pyloric antrum and pineal gland of these animals was also examined. The effects of ovariectomy and of hyperprolactinemia (induced by a pituitary graft under the kidney capsule) on the median eminence content of IRS were also studied in both normal and dwarf mice. Median eminence IRS content was significantly lower in the dw/dw (23.6 +/- 1.8 ng) than in normal mice (57.4 +/- 7.1 ng); no difference was found in the pyloric IRS content of dw/dw (16.9 +/- 1.6 ng/mg of protein) and normal animals (13.8 +/- 1.9 ng/mg of protein), nor in the pineal content of IRS (639.4 +/- 64.4 pg/gland in the dw/dw; 732 +/- 265 pg/gland in normals). Neither ovariectomy nor hyperprolactinemia were found to affect the IRS content in the tissues studied in normal or dwarf mice. Treatment of an additional group of 9 dwarf mice with L-thyroxine (L-T4 2 micrograms/48 h. s.c. for 2 weeks) significantly increased the animals weight (10.2 +/- 0.4 g versus 7.4 +/- 0.3 g) and produced maturation of facial features; however, it did not change the IRS content in any of the tissues studied. It is concluded that the content of IRS in the median eminence of mice with a congenital lack of GH, TSH and prolactin is significantly reduced and that this is unlikely to be related to the deficiency of thyroid hormones in these animals.     

Hypothalamic catecholamine histofluorescence in dwarf mice

Summary Brains of growth hormone (GH)-and prolactin (PRL)-deficient Ames (df/df) and Snell (dw/dw) dwarf mice and normal mice of the same strains were examined for catecholamine (CA) histofluorescence, with particular emphasis upon the hypothalamic tuberoinfundibular (A12) (arcuate nucleus/median eminence) region, which plays a role in the regulation of both GH and PRL. Dwarfs and normal animals of both types also were treated with a drug regimen to deplete sequentially neuronal CA stores (reserpine), inhibit CA oxidation (nialamide) and load dopaminergic A12 cells with exogenous transmitter (norepinephrine), in order to test viability and axonal transport capacity of A12 neurons. In both types of dwarfs, compared with normals, fluorescence was markedly reduced in the zona externa of the median eminence, which is normally rich in terminals from A12 neurons. Fluorescence in the median eminence was particularly weak in Ames dwarfs, and A12 perikarya were difficult to discern in this group. Snell dwarfs showed reduced fluorescence of A12 perikarya when compared with the brightly fluorescent perikarya seen in normal mice. In supraoptic and paraventricular nuclei, and in the zona interna of the median eminence, CA fluorescence attributable to NE was comparable among dwarfs and normals; fluorescence of dopaminergic perikarya in substantia nigra was also unaffected in dwarfs. Exogenously administered NE effected enhanced fluorescence of A12 Perikarya in normal mice and in Snell dwarfs; NE treatment in the Ames dwarf, however, failed to increase significantly the faint fluorescence of A12 cell bodies. The results indicate that dopaminergic A12 neurons in Snell dwarf mice are present and viable. Reduction in DA in the median eminence in both genetic dwarfs and failure of CA uptake in Ames dwarfs may indicate altered axon morphology or transport capacity, and/or abnormal DA biosynthesis, which may be more severe in Ames than in Snell dwarfs. Thus, genetic alteration in differentiation of pituitary cells may play a significant role in development of the CA systems in the hypothalamus.Supported by PHS Grants HD 18243 (CP), NS15816 and AG00847 (JRS) and HS12671 (AB).     

Cerebroside and Sulfatide Biosynthesis in the Brain of Snell Dwarf Mouse: Effects of Thyroxine and Growth Hormone in the Early Postnatal Period

Snell dwarf mice (dw/dw) and normal mice (+/?) were injected with thyroxine (T₄) (1 μg/animal, four injections) and growth hormone (GH) (20 μg/animal, four injections) from the 5th to the 15th day of life. In the untreated dw/dw mouse brain, the specific activities of UDP-galactose:ceramide galactosyltransferase (CGalT), PAPS:cerebroside sulfotransferase (CST), and 2′,3′-cyclic nucleotide 3′-phosphohydrolase (CNP) were decreased by 28, 25, and 37%, respectively, compared with the control untreated +/? mice. The major effect of T₄ was an increase of the brain CNP in the +/? mice (+40%) and dw/dw mice (+111%). The treatment with T₄ also brought to normal the level of CGalT in dw/dw brain; a somewhat less marked effect on CST was observed. The treatment with GH had a great stimulatory effect on CNP: the specific activity of this enzyme increased by 40 and 69% in +/? and dw/dw mouse brain, respectively. On the contrary, no effect of GH on the CGalT activity was observe in this study. Our results suggest that T₄ and GH may have both independent and complementary actions on the myelin-associated enzymes during the early postnatal period of brain development.     

Factors Contributing to the Poor Myelination in the Brain of the Snell Dwarf Mouse

Abstract: Conventional histological examination of the pituitary does not distinguish Snell dwarf mutants (dw/dw) from their normal littermates (+/?) in the neonatal stage. However, immunohistochemical examination of pituitaries of litters born to heterozygous Snell parents revealed that in approximately 25% of the glands examined, the number of positive cells was very low in the neonatal stage. We attempted to delineate the events resulting in the poor myelination in the brain of the Snell dwarf mouse, and to devise an immunohistochemical method for identifying the mutant neonate. Differences in the brain weights of the dw/dw and +/? mice first became apparent on the 10th day of age, and from this time on no further increase in the weight of the dwarf mouse brain was recorded. Increase in CNPase activity was found to be suppressed in the cerebrum and brain stem throughout the developmental stage, but not in the other parts of the brain. The yield of isolated myelin decreased by 58% in the mutant mouse, but CNPase activity was equivalent to that of control myelin. Differences in DNA content per cerebrum from the dw/dw and +/? mice first became apparent on the 10th day of age. Henceforth, the dw/dw mice showed no further increase, although the +/? mice continued to increase. [³H]Thymidine incorporation into the DNA fraction in vivo on the 7th day of age, when glial cell proliferation in the cerebrum is most active, was suppressed to about 50% of the control level in all parts of the dwarf brain. These findings indicate that the poor myelination found in the mutant cerebrum is a hypomyelination due to reduced oligodendroglial proliferation caused by lack of circulating growth hormone.     

Growth hormone modulates hypothalamic inflammation in long‐lived pituitary dwarf mice

Mice in which the genes for growth hormone (GH) or GH receptor (GHR^?/?) are disrupted from conception are dwarfs, possess low levels of IGF‐1 and insulin, have low rates of cancer and diabetes, and are extremely long‐lived. Median longevity is also increased in mice with deletion of hypothalamic GH‐releasing hormone (GHRH), which leads to isolated GH deficiency. The remarkable extension of longevity in hypopituitary Ames dwarf mice can be reversed by a 6‐week course of GH injections started at the age of 2 weeks. Here, we demonstrate that mutations that interfere with GH production or response, in the Snell dwarf, Ames dwarf, or GHR^?/? mice lead to reduced formation of both orexigenic agouti‐related peptide (AgRP) and anorexigenic proopiomelanocortin (POMC) projections to the main hypothalamic projection areas: the arcuate nucleus (ARH), paraventricular nucleus (PVH), and dorsomedial nucleus (DMH). These mutations also reduce hypothalamic inflammation in 18‐month‐old mice. GH injections, between 2 and 8 weeks of age, reversed both effects in Ames dwarf mice. Disruption of GHR specifically in liver (LiGHRKO), a mutation that reduces circulating IGF‐1 but does not lead to lifespan extension, had no effect on hypothalamic projections or inflammation, suggesting an effect of GH, rather than peripheral IGF‐1, on hypothalamic development. Hypothalamic leptin signaling, as monitored by induction of pStat3, is not impaired by GHR deficiency. Together, these results suggest that early‐life disruption of GH signaling produces long‐term hypothalamic changes that may contribute to the longevity of GH‐deficient and GH‐resistant mice.     

Aromatase immunoreactivity in the rat brain: Gonadectomy-sensitive hypothalamic neurons and an unresponsive “limbic ring” of the lateral septum-bed nucleus-amygdala complex

The aromatase (estrogen synthetase) enzyme catalyzes the conversion of androgens to estrogens in peripheral tissues, as well as in the brain. Our study aimed at comparing the brain distribution of aromatase-immunoreactive neurons in male and female, normal and gonadectomized rats. Light microscopic immunostaining was employed using a purified polyclonal antiserum raised against human placental aromatase. Two anatomically separate aromatase-immunoreactive neuronal systems were detected in the rat brain: A “limbic telencephalic” aromatase system was composed by a large population of labeled neurons in the lateral septal area, and by a continuous “ring” of neurons of the laterodorsal division of the bed nucleus of stria terminalis, central amygdaloid nucleus, stria terminalis, and the substantia inominata-ventral pallidum-fundus striati region. The other, “hypothalamic” aromatase system consisted of neurons scattered in a dorsolateral hypothalamic area including the paraventricular, lateral and dorsomedial hypothalamic nuclei, the subincertal nucleus as well as the zona incerta. In addition, a few axon-like processes (unresponsive to gonadectomy) were present in the preoptic-anterior hypothalamic complex, the ventral striatum, and midline thalamic regions. No sexual dimorphism was observed in the distribution or intensity of aromatase-immunostaining. However, 3 days, 2, 3, 8, 16, or 32 weeks after gonadectomy, aromatase-immunoreactive neurons disappeared from the hypothalamus, whereas they were still present in the limbic areas of both sexes. The results indicate the existence of two distinct estrogen-producing neuron systems in the rat brain: (1) a “limbic ring” of aromatase-labeled neurons of the lateral septum-bed nucleus-amygdala complex unresponsive to gonadectomy; and (2) a sex hormone-sensitive “hypothalamic” aromatase neuron system.     

Postnatal Action of Growth and Thyroid Hormones on the Retarded Cerebral Myelinogenesis of Snell Dwarf Mice (dw)

Abstract: Snell dwarf mice (dw) showed a lower CNPase activity (59% of the normal controls) only in the cerebrum among different parts of the CNS, and a strikingly reduced level of spontaneous locomotion activity with an indistinct diurnal periodicity in a 24-h record at 40 days of age. Daily administration of bGH and T₄ to the dwarfs during the first 40 days of postnatal life restored CNPase activity to the level of the normal controls, and was accompanied by normalization of the pattern of spontaneous locomotion activity. Daily administration of bGH alone also restored CNPase activity and spontaneous locomotion, but to a lesser extent. The daily administration of thyroid stimulating hormone (TSH) alone, however, failed to restore CNPase activity, in spite of the fact that the thyroid glands of the TSH-treated dwarfs were indistinguishable from the normal controls in organization and appearance. These results indicate that the restoration of both the retarded myelinogenesis and abnormal behavior of the Snell dwarf mice might essentially depend upon GH levels and the synergistic effects of T₄.     

The influence of ovarian factors on the somatostatin-growth hormone system during the postnatal growth and sexual development in lambs

The aim of the study was to elucidate the effects of ovarian hormones on somatostatin in the hypothalamic neurons and growth hormone (GH) secretion during the postnatal growth and development of sheep. The study was performed on 9-week-old (infantile) lambs that were ovary-intact (OVI) or ovariectomized (OVX) at 39 days of age, and on 16-week-old (juvenile) lambs that were OVI or OVX at 88 days of age. Hormones in neurons and somatotropic cells were assayed with immunohistochemistry and radioimmunoassay. Following ovariectomy, immunoreactive somatostatin was more abundant (p<0.05) in the hypothalamus of infantile lambs, whereas in juvenile lambs it was more abundant (p<0.05) in the periventricular nucleus but reduced (p<0.01) in the median eminence. In contrast to somatostatin in the hypothalamus, the content of immunoreactive GH in the hypophysis was less in OVX infantile lambs, but greater in OVX juvenile lambs (p<0.05). Basal blood serum concentrations of GH were greater (p<0.05) in OVX infantile lambs, whereas in OVX juvenile lambs, mean and basal concentrations of GH and amplitude of GH pulses were less than in OVI lambs (p<0.05). The postnatal increase in body weight was greatest in middle-late infancy (p<0.01). The body weight did not differ (p>0.05) between OVI and OVX lambs. In conclusion, ovarian factors may inhibit the GH secretion in infantile lambs but enhance the GH secretion in juvenile lambs. Transition to puberty, as related to the growth rate, appears to be due mainly to change in gonadal influence on the somatostatin neurosecretion. A stimulation of somatostatin output in the median eminence by gonadal factors in infancy is followed by a stimulation of somatostatin accumulation after infancy. Thus, ovarian factors modulate mechanisms within the somatotropic system of lambs to synchronize the somatic growth with sexual development.     

Immunocytochemical localization of somatostatin in cell bodies of the rat hypothalamus.

Cell bodies of small to moderate-sized neurons in the female rat hypothalamus were stained specifically for somatostatin (SRIF) by means of the unlabeled antibody-peroxidase-antiperoxidase immunocytochemical method. SRIF-positive perikarya were scattered throughout the periventricular nucleus in a limited region extending from the middle of the optic chiasm to the rostral margin of the median eminence. The same neurons were revealed with either rabbit (R) or guinea pig (GP) anti-SRIF antisera. Positive cell bodies were more readily assessed with GP antibodies because nonspecific background staining was much less with these than with R anti-SRIF. Positive perikarya were not observed in other hypothalamic nuclei and ependymal elements were also immunocytochemically negative.     

Identification of growth-hormone- and prolactin-containing neurons within the avian brain

Prolactin (PRL)- and growth-hormone (GH)-containing perikarya and fibers independent of the anterior pituitary gland have been reported to exist in the central nervous system of several mammalian species. The specific distributions of PRL- or GH-like neurons in the avian forebrain and midbrain, however, have not been reported. The objective of the study was to identify GH- and PRL-containing neurons in the hypothalamus and a few extrahypothalamic areas of two avian species. Brain and peripheral blood samples were collected from laying and broody turkey hens and ring doves. Broody turkey hens and doves had significantly higher plasma PRL concentrations compared with laying hens. Coronal brain sections were prepared and immunostained using anti-turkey GH and anti-chicken synthetic PRL antibodies. In turkey hens, the most dense GH-immunoreactive (ir) perikarya and fibers were found in hippocampus (Hp), periventricular hypothalamic nucleus, paraventricular nucleus, inferior hypothalamic nucleus, infundibular hypothalamic nucleus, medial and lateral septal area, and external zone of the median eminence (ME). In the ring dove, a similar pattern of distribution of GH-ir neurons was noticed at the brain sites listed above except that GH-ir fibers and granules were found only in the internal zone of ME and not in the external zone. In both turkeys and doves, the most immunoreactive PRL-ir perikarya and fibers were found in the medial and lateral septal area, Hp (turkey only), and bed nucleus of the stria terminalis pars magnocellularis. There were no apparent differences in the staining pattern of GH- or PRL-ir neurons between the laying and broody states in either species. However, the presence of GH-ir- and PRL-ir perikarya and fibers in several hypothalamic nuclei indicates that GH and PRL may influence parental behavior, food intake, autonomic nervous system function, and/or reproduction.     

The origin of somatostatin fibers in the median eminence and neural lobe of Rana temporaria

Summary A light microscopic immunocytochemical study of the brain of frogs with hypothalamic lesions was performed in order to obtain evidence concerning the origin of somatostatin fibers in the median eminence and neural lobe of the hypophysis. The results indicate that the somatostatin fibers of the neural lobe originate from somatostatin perikarya located in the prechiasmatic part of the hypothalamus and possibly also in the telencephalon. The somatostatin neurons of the pars ventralis tuberis cinerei do not send axons to the neural lobe. The frog median eminence contains axon terminals of somatostatin neurons located in the pars ventralis of the tuber cinereum. Many other somatostatin fibers of the frog median eminence originate from somatostatin neurons located outside the tuber cinereum. Most of these neurons probably lie in the preoptic hypothalamic region.This investigation was supported by a grant from the Belgian Nationaal Fonds voor Geneeskundig Wetenschappelijk Onderzoek     

Dominant dwarfism in transgenic rats by targeting human growth hormone (GH) expression to hypothalamic GH-releasing factor neurons.

Expression of human growth hormone (hGH) was targeted to growth hormone-releasing (GRF) neurons in the hypothalamus of transgenic rats. This induced dominant dwarfism by local feedback inhibition of GRF. One line, bearing a single copy of a GRF-hGH transgene, has been characterized in detail, and has been termed Tgr (for Transgenic growth-retarded). hGH was detected by immunocytochemistry in the brain, restricted to the median eminence of the hypothalamus. Low levels were also detected in the anterior pituitary gland by radioimmunoassay. Transgene expression in these sites was confirmed by RT-PCR. Tgr rats had reduced hypothalamic GRF and mRNA, in contrast to the increased GRF expression which accompanies GH deficiency in other dwarf rats. Endogenous GH mRNA, GH content, pituitary size and somatotroph cell number were also reduced significantly in Tgr rats. Pituitary adrenocorticotrophic hormone (ACTH) and thyroid-stimulating hormone (TSH) levels were normal, but prolactin content, mRNA levels and lactotroph cell numbers were also slightly reduced, probably due to feedback inhibition of prolactin by the lactogenic properties of the hGH transgene. This is the first dominant dwarf rat strain to be reported and will provide a valuable model for evaluating the effects of transgene expression on endogenous GH secretion, as well as the use of GH secretagogues for the treatment of dwarfism.     

Altered oxidative stress response of the long-lived Snell dwarf mouse

Several single gene mutations in mice that increase the murine life span have been identified, including the Pit-1 mutation which results in the Snell dwarf (Pit1(dw/dw)), however, the biological mechanism of this life-span extension is still unclear. Based on studies that show oxidative stress plays an important role in the aging process, we hypothesized that the increased longevity seen in Snell dwarf mice may result from a resistance to oxidative stress. We report that Snell dwarf mice respond to oxidative stress induced by 3-NPA differently than their wild type littermates. This altered response results in diminished activation of the MEK-ERK kinase cascade and virtually no phosphorylation of c-Jun at Ser63 in dwarf mice after 3-NPA treatment, despite a robust phosphorylation of Ser63 in wild type mice. We propose that this altered management of oxidative stress in dwarf mice is partially responsible for the increased longevity in Snell dwarf mice.     

Meiotic nondisjunction and translocation segregation in dwarf (dw/dw) and control T(1;13)70H heterozygous mice

The meiotic behavior of translocation heterozygous T70 (1;13)H/+ male mice with a Snell dwarf (dw/dw) genotype was compared with that of nondwarf T70H/+ controls. A four-fold increase in the nondisjunction frequency of the normal bivalents occurred as a consequence of the dwarf genotype. This increase is identical to that seen in karyologically normal dwarf males. No effect of the dwarf condition on the segregation of the translocation multivalent could be noted. Thus, translocation heterozygosity does not enhance the meiotic instability caused by the hypopituitary dwarf condition. From a small sample of oocytes from T70H/+ and chromosomally normal dwarf females it is concluded that nondisjunction in females is not increased by the dwarf condition. In general we conclude that animals with higher spontaneous nondisjunction levels are not necessarily more sensitive to factors increasing nondisjunction.     

VCAM‐1 upregulation accompanies muscle remodeling following resistance‐type exercise in Snell dwarf (Pit1dw/dw) mice

Snell dwarf mice (Pit1^dw/dw) exhibit deficiencies in growth hormone, prolactin, and thyroid stimulating hormone. Besides being an experimental model of hypopituitarism, these mice are long‐lived (>40% lifespan extension) and utilized as a model of slowed/delayed aging. Whether this longevity is accompanied by a compromised quality of life in terms of muscular performance has not yet been characterized. In this study, we investigated nontrained and trained muscles 1 month following a general validated resistance‐type exercise protocol in 3‐month‐old Snell dwarf mice and control littermates. Nontrained Snell dwarf gastrocnemius muscles exhibited a 1.3‐fold greater muscle mass to body weight ratio than control values although muscle quality, maximum isometric torque normalized to muscle mass, and fatigue recovery were compromised. For control mice, training increased isometric torque (17%) without altering muscle mass. For Snell dwarf mice, isometric torque was unaltered by training despite decreased muscle mass that rendered muscle mass to body weight ratio comparable to control values. Muscle quality and fatigue recovery improved twofold and threefold, respectively, for Snell dwarf mice. This accompanied a fourfold increase in levels of vascular cell adhesion molecule‐1 (VCAM‐1), a mediator of progenitor cell recruitment, and muscle remodeling in the form of increased number of central nuclei, additional muscle fibers per unit area, and altered fiber type distribution. These results reveal a trade‐off between muscle quality and longevity in the context of anterior pituitary hormone deficiency and that resistance‐type training can diminish this trade‐off by improving muscle quality concomitant with VCAM‐1 upregulation and muscle remodeling.     

Influence of testicular hormones on the somatostatin-GH system during the growth promoted transition to puberty in sheep

The aim of the present study was to investigate whether the growth promoted transition to puberty in lambs involved changes in the effects of testicular hormones on somatostatin in hypothalamic neurons and GH secretion. The study was performed in infants (9-week-old) testis-intact (TEI) and orchidectomized (ORCHX) at the sixth week of age, and pubertal lambs (16-week-old) TEI and ORCHX at the 12th week of age (n = 20). In TEI lambs, the changes included a pubertal increase in immunoreactive somatostatin in the periventricular nucleus and median eminence with simultaneous neuropeptide depletion in the median eminence, and a decrease in the percentage of the hypophyseal area (PA) occupied by GH-immunoreactive cells (P < 0.05). The mean concentration of GH in the peripheral blood plasma was greater (P < 0.001) in early infancy (5 wk), because of the greater (P < 0.0001) pulse amplitude, and then uniformly low until puberty. The postnatal increase in the body weight (BW) was prominent (P < 0.01) in middle-late infancy (9-12 wk) because of the large daily live-weight gain. After orchidectomy somatostatin was abundant. This effect on nerve terminals in the median eminence was greater (P < 0.01) in infancy and lesser (P < 0.05) in puberty. Conversely, the PA occupied by GH cells was lower in the ORCHX pubertal lambs compared to TEI lambs (P < 0.05). The GH concentration and pulse characteristics were less (P < 0.05) in the infantile and pubertal ORCHX lambs compared to the TEI lambs. However, this effect was weak (P < 0.05) until middle infancy because of no influence on the GH basal concentration, and strong (P < 0.001) after late infancy. The BW did not differ (P > 0.05) between TEI and ORCHX lambs. Findings suggest activation of GH negative autofeedback loop in middle infancy. Testicular factors may play an inhibitory role in regulating somatostatin accumulation and a stimulatory role in GH secretion until puberty. The start of puberty is related to an attenuation in the stimulatory role of gonadal factors in regulating somatostatin depletion in nerve terminals associated with an intensification of the stimulatory role of gonadal factors in regulating GH secretion. From a somatic perspective of growth rate, these mechanisms do not seem to be important. Thus, testicular factors modulate mechanisms within the somatostatin-GH system to integrate somatotropic and gonadotropic functions at the time of growth-promoted sexual maturation in sheep.     

Immunocytochemical localization of somatostatin-containing neurons in the rat hypothalamus

Summary The rat hypothalamus was studied at the light microscopic level with the use of single and double immunocytochemical staining methods. It was shown that the rat supraoptic and paraventricular hypothalamic nuclei, and their accessory neurosecretory nuclei, do not contain magnocellular somatostatin neurons. The distribution of the hypothalamic parvocellular somatostatin cells is described. The parvocellular component of the rat hypothalamic paraventricular nucleus is, at least partly, composed of somatostatin cells: they form a fairly well circumscribed periventricular cell mass. The rat suprachiasmatic nuclei contain separate somatostatin neurons and vasopressin neurons. Scattered somatostatin cells are present in the entire arcuate nucleus. In addition to the periventricular somatostatin cells located in the preopticanterior hypothalamic area and in the arcuate nucleus, the rat hypothalamus also contains numerous scattered somatostatin cells located distant from the third ventricle.This investigation was supported by a grant from the Belgian Nationaal Fonds voor Geneeskundig Wetenschappelijk Onderzoek     

Fibroblasts from long-lived mutant mice exhibit increased autophagy and lower TOR activity after nutrient deprivation or oxidative stress

Previous work has shown that primary skin-derived fibroblasts from long-lived pituitary dwarf mutants resist the lethal effects of many forms of oxidative and nonoxidative stress. We hypothesized that increased autophagy may protect fibroblasts of Pit-1(dw/dw) (Snell dwarf) mice from multiple forms of stress. We found that dwarf-derived fibroblasts had higher levels of autophagy, using LC3 and p62 as markers, in response to amino acid deprivation, hydrogen peroxide, and paraquat. Fibroblasts from dwarf mice also showed diminished phosphorylation of mTOR, S6K, and 4EBP1, consistent with the higher levels of autophagy in these cells after stress. Similar results were also observed in fibroblasts from mutant mice lacking growth hormone receptor (GHRKO mice) after amino acid withdrawal. Our results suggested that increased autophagy, regulated by TOR-dependent processes, may contribute to stress resistance in fibroblasts from long-lived mutant mice.     

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