The neurohypophysis of the crested newt

Summary In the median eminence of the newt a medial region and two lateral regions are described.In cross section, the medial region appears to be made up of 1) an outer or glandular zone (Zone I) containing aldehyde-thionine-positive and negative nerve fibres and blood capillaries. Nerve fibres appear aligned in palisade array along the capillaries. 2) An inner zone (Zone II) made up of a) a layer of aldehyde-thionine-positive nerve fibres (fibrous layer) belonging to the preoptic hypophyseal tract and b) a layer of ependymal cells lining the infundibular lumen and reaching the blood vessels with their long processes.The lateral regions display a less pronounced stratification and aldehyde-thionine positive nerve fibres are nearly absent.A slender lamina (ependymal border) containing mainly aldehyde-thionine-positive nerve fibres and ependymal cells connects the median eminence to the pars nervosa.At the ultrastructural level, in the outer zone of the medial region at least 4 types of nerve fibres and nerve endings are identified:Type I nerve fibres containing granular vesicles of 700–1000 Å and clear vesicles (250–400 Å).Type II nerve fibres containing granular vesicles and polymorphous granules of 900–1300 Å and clear vesicles (250–400 Å).Type III nerve fibres containing dense granules of 1200–2000 Å and clear vesicles of 250–400 Å.Type IV nerve fibres containing only clear vesicles of 250–400 Å. In the inner zone too, all these nerve fiber types are found among ependymal cells, while the fibrous layer consists of nerve fibres containing granules of 1200–2000 Å in diameter.In the lateral regions Type I, Type II and Type IV nerve fibres and their respective perivascular terminals are found; axons containing dense granules (1200–2000 Å) are scanty. In these regions typical synapses between Type I nerve fibres and processes rich in microtubules are visible.The classification and functional significance of nerve fibres in the median eminence are still unsolved, but it may be assumed that nerve fibres of the medial region belong to both the preoptic hypophyseal and tubero hypophyseal tract, while the lateral regions are characterized by nerve fibres of the tubero hypophyseal tract. Peculiar specializations of the ependymal cells in the median eminence of the newt are also discussed.Work supported by a grant from the Consiglio Nazionale delle Ricerche.The authors are indebted to Mr. G. Gendusa and P. Balbi for technical assistance.     

Ultrastructural immunocytochemical localization of neurophysin and vasopressin in the median eminence and posterior pituitary of the guinea pig

Summary With the use of tissue prepared by freeze-substitution and the unlabelled antibody enzyme technique, neurophysin and vasopressin were localized at the ultrastructural level in the posterior pituitary and median eminence of the guinea pig. In the posterior pituitary neurophysin was found in the large neurosecretory granules (1300–1500 Å) of axons, Herring bodies, and nerve terminals. In some of these axons immunoreactive neurophysin was found outside of granules in the axoplasm. By light microscopy neurophysin was found in both the zona interna and zona externa of the median eminence; this was confirmed by electron microscopy. In the zona interna as in the posterior pituitary, neurophysin was localized both inside and outside the large neurosecretory granules. In the zona externa, immunoreactive deposit was primarily located in granules with a diameter of 900–1100 Å in nerve terminals abutting on the primary portal plexus. The distribution of vasopressin paralleled that of neurophysin except that the hormone was rarely extragranular. These results demonstrate for the first time that both neurophysin and vasopressin are present in granules of axons that are in contact with the hypophysial portal vasculature.The authors wish to thank Dr. Alan Robinson for the gifts of antiserum to bovine neurophysin I and for purified bovine neurophysin I; Dr. Ludwig Sternberger for the peroxidase-anti-peroxidase complex; and Dr. Robert Utiger for antiserum to lysine vasopressinSupported in part by U.S. Public Health Service grant RR-00167 to the Wisconsin Regional Primate Research Center from the National Institutes of Health. Primate Center publication No. 14-017.Recipient of NIH, NINDS Teacher-Investigator Award NS-1108.     

Ultrastructure of the peptidergic and monoaminergic neurons in the hypothalamic neurosecretory system of Anuran Batracians

Summary In the toad Bufo arenarum Hensel the following regions of the hypothalamic — neurohypophyseal system were studied under the electronmicroscope: preoptic and paraventricular nuclei, median eminence and infundibular process of the neurohypophysis.Neuronal perikarya of the preoptic nucleus are loaded with typical neurosecretory granules of peptidergic nature having a mean diameter of 1660 Å. While most neurons of the winter toad are in a storage stage a few show signs of a more active synthetic activity. A distinctive feature of preoptic neurons is the presence of large lipid droplets. The paraventricular nucleus contains small neurons containing granulated vesicles with a mean diameter of 800-1000 Å. In the region extending between these two nuclei and the median eminence axons containing either neurosecretory elementary granules or granulated vesicles are observed.The inner zone of the median eminence is occupied by axons of the preoptic neurohypophyseal tract; two types of axons, according to the size and density of the neurosecretory granules, may be recognized. The outer zone of the median eminence contains mainly axons and nerve terminals containing granulated vesicles of probable monoaminergic nature and only a few with granules of peptidergic type.The neurohypophysis contains two kinds of axons: one with more dense granules of 1800 Å and the other with granules of lesser electron density and 2100 Å. At the ending proper small clear vesicles of synaptic type are found.A progressive increase in volume of the peptidergic granules along the axon is demonstrated. This is of the order of 218% from the preoptic perikarya down to the infundibular process. The physiological significance of the two neurosecretory systems — i.e. the monoaminergic and the peptidergic — and the probable nature of the two types of peptidergic axons is discussed.Supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas and by the Air Force Office of Scientific Research (AF-AFOSR 963-67).The authors want to express their gratitude to Mrs. Defilippi-Novoa and Mr. Alberto Sáenz for their skillful assistance.     

On different types of nerve endings in the frog median eminence after fixation with permanganate and glutaraldehyde-osmium

Summary In the frog median eminence, fixed with glutaraldehyde and osmium tetroxide, four types of nerve endings can be generally distinguished. These endings are in contact with the pericapillary spaces of primary portal vessels and can be identified by the internal structure and the size of their granules and vesicles. Type 1 contains large granules (1500–2400 Å in diameter) and small clear vesicles (300–500 Å in diameter), type 2 intermediate granules (about 1100–1700 Å in diameter) and small clear vesicles, type 3 small granules (about 600–1000 Å in diameter) and small clear vesicles, type 4 only numerous small clear vesicles. The mixed types containing the large, intermediate and small dense granules in the same ending are infrequently found.After KMnO₄ or LiMnO₄ fixation the granules and vesicles mentioned above are observed as follows. The large granules in the type 1 nerve ending appear mostly pale or less-dense. The intermediate granules in the type 2 also appear mostly pale or less-dense, but some frequently show granules of high density. The small granules in the type 3 consistently contain the dense substance and these endings can be subdivided into two different types according to the populations of different sizes of dense granules [type 3a (900–1000 Å) and type 3b (500–800 Å)]. Dense-cored and cleared-synaptic vesicles are frequently present with together in the type 3 endings. The small vesicles (300–400 Å), in the type 4, appear generally pale (type 4a), but some nerve endings contain small dense cored-vesicles (type 4b).The author wishes to thank Prof. H. Fujita for his advice and criticism.     

Ultrastructural immunocytochemical localization of luteinizing hormone-releasing hormone (LH-RH) in the median eminence of the guinea pig

Summary LH-RH was localized at the ultrastructural level in axons and nerve terminals of the median eminence of the male guinea pig. LH-RH positive neuronal profiles were most concentrated in the medial-dorsal aspect of the infundibular stalk and in the post-infundibular median eminence at the level immediately following separation of the stalk from the base of the brain. LH-RH containing axon profiles were most abundant in the palisade zone; nerve terminals in contact with the hypophysial portal vasculature were relatively rare. The hormone was present within granules that measured 900–1,200 Å in axons of the palisade zone and 400–800 Å in nerve terminals abutting on the portal plexus. The differently sized granules represent heterogeneous populations.Supported in part by U.S. Public Health Service grant HD-09636 from the National Institutes of Health and RR-00167 to the Wisconsin Regional Primate Research Center from the National Institutes of Health. Primate Center Publication No. 15-031The authors wish to thank Dr. Sandy Sorrentino, Jr. for the gift of antiserum to LH-RH and Dr. Ludwig Sternberger for the peroxidase.antiperoxidase complex     

Ultrastructure of the median eminence of the rat

Summary The ependymal cells bordering the median eminence to the third ventricle are characterised by many microvillus-like projections and bulbous cell processes of the luminal plasma membrane. The latter contain many vesicles 500–1,000 Å in diameter. Cilia with 9+2 fibrillar pattern are seen occasionally. Adhesive devices in the from of zonula adhaerens and zonula occludens are found in the apical part of the intercellular junction. Unmyelinated nerve fibres with a mean diameter of 1 and containing many electron dense granules of 830–1,330 Å are often seen between the ependymal cells.Two types of glial cells are found in the median eminence. One is characterised by a nucleus with dense blods of chromatin and dense cytoplasm, and it is associated chiefly with the nerve fibres in the region of the hypothalamo-hypophysial tract. The other type of glial cell is characterised by fine, uniformly distributed chromatin in the nucleus and a relatively pale cytoplasm and branched processes which terminate perivascularly in the base of the median eminence.Myelinated nerve fibres are seen only in the region of the hypothalamo-hypophysial tract. Only a part of them contain electron dense granules 1,330–2,330 Å in diameter.Three types of unmyelinated nerve fibres can be distinguished in the median eminence according to the size of the electron dense granules they contain: 1. Nerve fibres containing granules 1,330–2,330 Å in diameter. They are seen primarily in the hypothalamo-hypophysial tract, but also in the zona externa; 2. those containing granules with a mean diameter of 1,330 Å; and 3. those containing granules with a mean diameter of 1,000 Å. The last two types are both encountered in the hypothalamo-hypophysial tract, the zona externa and the perivascular region of the base of the median eminence. Under high magnification, the membrane of the granules show evidence of a trilaminar structure and the content of the granules with a low electron density appeares to consist of small microvesicles or globular components. Besides granules, these nerve fibres contain vesicles mostly 420 Å in diameter whose relative number increases towards the perivascular nerve endings. 53 per cent of the inclusions in the hypothalamo-hypophysial tract are granules and 47 per cent vesicles, while the corresponding percentages for the zona externa are 40 and 60 and for the perivascular nerve endings 20 and 80.The mean width of the pericapillary space is 1 , but it varies greatly. It containes many collagen fibrils and fibroblasts. The capillary endothelium is frequently fenestrated and contains many vesicles of various sizes.Two types of granules-containing cells are found in the pars tuberalis depending on the size of the electron dense granules: 1. cells containing granules with a mean diameter of 1,330 Å: and 2. cells containing granules with a mean diameter of 2,000 Å. In addition, there are occasional follicular cavities filled with amorphous material, microvilli and cilia of 9+2 fibrillar pattern.Aided by a grant from the Sigrid Jusélius Stifteise.     

Effects of thyroidectomy, propylthiouracil, and thyroxine on pituitary content and immunocytochemical staining of thyrotropin (TSH) and thyrotropin releasing hormone (TRH)

Previous studies have demonstrated immunocytochemical staining for beta chains of thyroid stimulating hormone (TSH-beta) in rough endoplasmic reticulum of pituitary cells hypertrophied after thyroidectomy ("thyroidectomy cells") (Moriarty CG(1976): J Histochem Cytochem (24:846; Moriarty GC, Tobin RB (1976): J Histochem Cytochem 24:1140). Here we report the localization of thyrotropin releasing hormone (TRH) in serial sections of the same pituitaries to determine if it could be found at similar sites. No staining for TRH was found in hypertrophied TSH cells formed 42 days after the surgery, or after 14, 34, and 70 days of propylthiouracil (PTU) treatment. The loss in immunostaining in the PTU-treated rats was correlated with radioimmunoassay (RIA) measurements that showed a 65% reduction in anterior pituitary TRH content after 34, 70, and 98 days of PTU treatment (from 22.9--7.8 pg/mg wet wt) and a 50% reduction in TSH content after 34 days of treatment. When thyroxine was administered to hypothyroid rats for 3 days before death, our previous studies had demonstrated intense staining for TSH in granules inside the rough endoplasmic reticulum. In this study, the radioimmunoassay showed that TSH content rose dramatically in the hypothyroid animals treated with PTU for 77 days and thyroxine for 2 days before death (from 8.5--64.1 mU/mg wet wt); however, the rise in TRH content was minimal (5.8--9.8 pg/mg wet wt). The immunocytochemical stain for TRH correlated well with the RIA showing a weak reaction mainly on small granules in the cytoplasm. No reaction for TRH was found in rough endoplasmic reticulum. These results suggest that TRH and TSH storage sites are dissimilar in the hypothyroid rat. The presence of stain for TRH in granules in the cytoplasm suggests that it might play a role in the storage or packaging of TSH. Its absence in profiles of rough endoplasmic reticulum staining intensely for TSH suggests that it is not synthesized at this site. No definite conclusions about its origin can be drawn at this time.     

Photoperiodic and osmotic influences on the ultrastructure of the hypothalamic neurosecretory system of the White-crowned sparrow,Zonotrichia leucophrys gambelii

Summary An attempt was made to correlate functional changes in the neurohypophysis of the White-crowned Sparrow, Zonotrichia leucophrys gambelii, with morphologic features on the light- and electron-microscope levels. The aldehyde-fuchsin-staining anterior median eminence possesses essentially the same ultrastructural features as the non-staining posterior median eminence. The axon terminals are characterized by the presence of a large number of small vesicles (approximately 400 Å in diameter) and occasional electron-dense granules. The more-or-less depleted anterior median eminence occasionally evident in the photosensitive bird showing testicular development is indistinguishable ultrastructurally from the more intensely staining median eminence generally characteristic of the photorefractory bird. In the median eminence, stainability and functional state do not seem to be correlated with changes in the type, size or number of vesicles. A slight increase in the number of granules was noted in the photorefractory bird but this was considered insufficient basis to account for differences in stainability.The pars nervosa, on the other hand, responded to osmotic stimuli (saline drinking water) by loss of stainability and decrease in numbers of elementary neurosecretory granules. Small vesicles are also present in the pars nervosa axon terminals, but are intermingled with neurosecretory granules in normal birds. Acute-osmotic birds, however, had axon terminals almost entirely occupied by small vesicles.It is to be emphasized that the pars nervosa and the median eminence are two structurally very different regions of the neurohypophysis. The basis for aldehyde-fuchsin staining in the median eminence appears to differ from that in the pars nervosa. The implications of these findings are considered in regard to hypothalamic control over gonadotropic activity in the White-crowned Sparrow.Dedicated to Professor Dr. W. Bargmann in honor of his 60th birthday.This investigation was supported by grant GB-2484 from the National Science Foundation to Professor Bern, grant GB-2819 from the National Science Foundation to Professor Mewaldt, and grant NB-01353 from the National Institutes of Health to Professor Farner. The authors wish to express their appreciation of the technical assistance of Mrs. Irene Brown, Mr. John Butchart, Sally S. Kibby, Mrs. Carol Nicoll, and Mr. John Striffler. Mrs. Emily Reid kindly prepared the histograms.     

A case of the syndrome of inappropriate secretion of TSH.

A girl aged 4 years with goiter and accelerated physical and skeletal growth was found to be hyperthyroid on the basis of elevated serum thyroid hormone level, nevertheless both the basal TSH and TSH responsiveness to TRH were maintained within the normal range. Serum TSH was suppressed by exogenous T3 and dexamethasone administration, but not significantly changed after propylthiouracil (PTU) treatment. The diurnal rhythmicity of anterior pituitary hormones was preserved with the high nocturnal peak of TSH and prolactin. Clinically, neither thyrotoxic signs nor evidences of pituitary tumor were observed. Her accelerated growth and elevated thyroid hormone level appeared to be induced by inappropriate secretion of TSH. In view of the literature, this is the first case of the syndrome of inappropriate secretion of TSH excluding the neoplastic origin in Japan.     

Variations in immunocytochemical localization of cathepsin B and thyroxine in follicular cells of the rat thyroid gland and plasma TSH concentrations over 24 hours

Summary Immunocytochemical localization of cathepsin B and thyroxine (T4) in follicular cells of the rat thyroid gland and plasma concentrations of thyroid stimulating hormone (TSH) were examined at six evenly spaced times over 24 h. By light- and electron microscopy, immunodeposits for cathepsin B were localized in cytoplasmic granules of various sizes, whereas those for T4 were detected mainly in larger granules of the cells and in the colloid lumen. The size and location of cytoplasmic granules showing immunoreactivity for cathepsin B and T4 in the cells varied over 24 h, corresponding to a change in plasma TSH concentrations. These immunopositive large granules appeared in the apical cytoplasm at 12.00 h, when the level of TSH was highest. At 20.00 h when the level of TSH was lowest, T4-positive granules almost disappeared, and cathepsin B-positive small granules were abundantly seen in the basal region. From 00.00 h to 08.00 h, these positive granules changed in the same manner as those seen from 12.00 h to 20.00 h, associated with an increase in plasma TSH levels. These results suggest that newly formed colloid droplets migrate from the apical to the basal regions. Cathepsin B may play a role not only in the degradation of thyroglobulin but in the maturation of thyroid hormones during the migration of the granules.     

Etude au microscope électronique de la neurohypophyse de Rana esculenta L.

Résumé L'éminence médiane et la pars nervosa de Rana esculenta diffèrent du point de vue de leur structure.L'éminence médiane se compose de 2 zones différentes: la zone externe placée près du lobe distal et la zone interne située sous l'épendyme. Dans la zone externe, on distingue, d'après la taille et la forme des grains de sécrétion, 5 types de terminaisons.1. des terminaisons avec de fins granules sphériques denses de 800 à 1000 Å de diamètre; 2. des terminaisons avec des granules de 1000 à 1200 Å de diamètre; 3. des terminaisons avec des grains de forme irrégulière de diamètre supérieur aux précédents (1200 à 1600 Å); 4. des terminaisons avec de volumineux grains denses sphériques d'environ 1200 à 1800 Å de diamètre; 5. un petit nombre de terminaisons ne contenant que des vésicules. Les terminaisons des catégories 3 et 4 sont probablement du type neurosécrétoire.La zone interne contient de nombreuses fibres neurosécrétrices. Elles sont de 2 types, l'une avec de gros granules (1600–2400 Å), l'autre avec des granules moins volumineux (1300–2000 Å). Des fibres non neurosécrétrices ont également été observées.Dans la pars nervosa, on rencontre deux types principaux de fibres neurosécrétrices, l'une avec des grains denses de 1600 à 2400 Å de diamètre, l'autre avec des grains moins denses d'environ 1300 à 2000 Å de diamètre. Dans la zone externe bordant la pars intermedia des fibres aminergiques avec de fines granulations ont été observées.

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Electron microscopic study of the neurohypophysis of Rana esculenta L.

Summary The median eminence and the pars nervosa of Rana esculenta have a different structure.The median eminence has 2 different zones: the outer zone situated near the pars distalis and the inner zone under the ependyme. In the outer zone there are, according to the size and the shape of the granules, 5 types of nerve terminals.1. Endings containing spherical fine dense granules of 800 to 1000 Å in diameter; 2. Endings with spherical granules from 1000 to 1200 Å in diameter; 3. Endings with granules of irregular shape which are bigger than the former (1200 to 1600 Å); 4. Endings with spherical dense granules of about 1200 to 1800 Å in diameter; 5. A few endings containing only clear vesicles. Type 3 and type 4 endings are probably neurosecretory.The inner zone contains numerous neurosecretory fibres. They are of two types: one with big granules (1600–2400 Å), the second with smaller granules (1300–2000 Å). Non-neurosecretory fibres have also been observed.The pars nervosa contains two principal types of neurosecretory fibres: one with dense granules of 1600 to 2400 Å in diameter, the other with lighter granules of about 1300 to 2000 Å. In the external zone lining the pars intermedia, aminergic fibres with fine granules have been observed.

Je tiens à exprimer mes vifs remerciements, à Monsieur le Professeur E. Follenius pour l'intérêt constant qu'il prend à ce travail. Je remercie également Madame R. O. Clauss, collaboratrice technique et Madame Schwoerer, photographe, pour leur aide précieuse.     

Effect of transection at different levels of hypothalamus on the hypothalamo-hypophysial system of the toad,Bufo bufo,with particular reference to the ultrastructure of the zona externa of the median eminence

Summary The ultrastructural changes taking place in the median eminence of Bufo bufo 3 hours to 4 months after transection of the brain at different levels, are described.5 types of neurons in the zona externa of the median eminence of normal toads are described. All types of neurons degenerate, and profound changes of the ultrastructure of the capillaries are observed after transection just behind, or immediately in front of the optic chiasma. A few neurons containing dense granules with a diameter of about 1,000–1,300 Å remain intact, however. The degeneration following denervation in front of the optic chiasma was considerably delayed compared to degeneration after denervation behind the optic chiasma.After transection more rostral to the optic chiasma, no significant degeneration of the median eminence was observed.The results are discussed with regard to degenerative dynamics and origin of the different nerve types. It is concluded, that all types of neurons terminating in the median eminence, originate at a level between the caudal and rostral parts of the preoptic nucleus, some fibres, however, containing dense, 1,000–1,300 Å granules, originate caudally to the optic chiasma, in the posterior hypothalamus.Part of this study was presented at the Vth International Symposium on Neurosecretion, Kiel, Germany, August 1969.     

The effect of propylthiouracil and temperature on avian thyroid activity.

High ambient temperatures cause a reduction in thyroid gland size of chickens but propylthiouracil (PTU) treatment produces an increase in gland size regardless of temperature. This increase in size after PTU treatment during high temperature is evident after 7 days of PTU treatment but not after 14 days of treatment. Cyclic AMP-dependent protein kinase is activated in the thyroid gland with PTU treatment during high temperatures with no alteration in activity in the pituitary. These results suggest that the pituitary is not activated by TRH during periods of high ambient temperature and the thyrotrophs may release TSH in direct response to lowered serum thyroid levels produced by PTU treatment.     

Hypothalamic neurosecretion and metamorphosis inXenopus laevis

Summary The frontal brain was removed from premetamorphic larvae ofXenopus laevis. Part of the animals was kept in a 0.01% propylthiouracil (PTU) solution for 21, 30 or 90 days, together with unoperated controls. Others were reared in tap water for the same length of time. The hypothalamus, the pituitary and the thyroids were studied in sagittal sections stained with aldehyde fuchsin or pseudoisocyanine (PIC).Operated tadpoles lacking the telencephalon only, could not be distinguished from unoperated controls. Extirpation of the preoptic region of the hypothalamus lowered the activity of the thyrotropic (TSH) cells and of the thyroids, and blocked metamorphosis. In animals with intact PIC-positive cells in the dorsal preoptic region, PTU induced a degranulation of these cells, stimulated the TSH cells and caused a strong hypertrophy of the thyroids. It is concluded that these neurosecretory cells in the dorsal preoptic region produce a thyrotropin-releasing factor (TRF), indispensable for the endocrine regulation of metamorphosis, and that the thyroid hormones have a negative feed-back influence upon the TRF cells.In part of the animals lacking the rostral hypothalamus, new PIC-positive cells were observed to develop immediately behind the preoptic region. In these animals PTU was somewhat less effective than in the animals with an intact dorsal preoptic region. This means either that the newly differentiated PIC-positive cells have a TRF function or that the thyroids can exert a direct negative feed-back upon the TSH cells. The latter possibility is supported by the fact that even in the absence of any neurosecretory cell PTU stimulated the thyroids.Blocking of thyroid hormone production by PTU inhibited the differentiation of the hypothalamus, of the median eminence and of the portal vessels. It may be deducted that during metamorphosis the general morphogenetic effect of the thyroid hormones stimulates the differentiation of the structures necessary for the augmentation of the TSH activity.The author thanks Prof. Dr.P.G.W.J. van Oordt for his active interest and helpful advices, MissTineke Aafjes for technical assistance and Mr.H. van Kooten for making the diagrams and photographs.     

Therapeutic Potential of Date Palm Pollen for Testicular Dysfunction Induced by Thyroid Disorders in Male Rats

Hyper- or hypothyroidism can impair testicular function leading to infertility. The present study was designed to examine the protective effect of date palm pollen (DPP) extract on thyroid disorder-induced testicular dysfunction. Rats were divided into six groups. Group I was normal control. Group II received oral DPP extract (150 mg kg^-1), group III (hyperthyroid group) received intraperitoneal injection of L-thyroxine (L-T4, 300μg kg^-1; i.p.), group IV received L-T4 plus DPP extract, group V (hypothyroid group) received propylthiouracil (PTU, 10 mg kg^-1; i.p.) and group VI received PTU plus DPP extract. All treatments were given every day for 56 days. L-T4 or PTU lowered genital sex organs weight, sperm count and motility, serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone (T), testicular function markers and activities of testicular 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β-HSD). Moreover, L-T4 or PTU increased estradiol (E2) serum level, testicular oxidative stress, DNA damage and apoptotic markers. Morphometric and histopathologic studies backed these observations. Treatment with DPP extract prevented LT4- or PTU induced changes. In addition, supplementation of DPP extract to normal rats augmented sperm count and motility, serum levels of LH, T and E2 paralleled with increased activities of 3β-HSD and 17β-HSD as well as testicular antioxidant status. These results provide evidence that DPP extract may have potential protective effects on testicular dysfunction induced by altered thyroid hormones.     

On the identity of the thyrotropic cell in the red-spotted newt

Summary Although the pars distalis of the red-spotted newt has previously undergone extensive cytological examination, the identity of its thyrotropic cells has remained uncertain. From the present ultrastructural study, cells of type 3 (Masur, 1969) containing granules 150–180 nm in diameter are concluded to be the thyrotropes. Such cells were found to be present in the regions of the pars distalis where thyroidectomy cells arise after ablation of the thyroid gland. Cells of type 3 are probably identical with a population of cells containing granules which stain with silver methenamine indicating the presence of a glycoprotein such as thyroid stimulating hormone (TSH). Thyroidectomy cells containing a few residual granules 150–180 nm in diameter were occasionally found in partes distales from newts killed 3 or 7 days after ablation of the thyroid gland, and were abundant in pituitaries 21 days after thyroidectomy. Only cells of type 3 responded (by vacuolation of granules) when animals were immersed in water containing 10 g/l of thyroxine. No cells of the pars distalis showed cytological change after administration of synthetic thyrotropic releasing hormone (TRH) giving additional support to the view that this hormone has no stimulatory role in amphibians.Work supported in part by research grant 1 R01 AM 16731-01 from the Institute of Arthritis, Metabolism and Metabolic Diseases and in part by grant PCM 75-17637 from the National Science Foundation     

Electron microscopic autoradiography on the localization of serotonin in the frog median eminence

Summary For the identification of the nerve fiber containing serotonin (5-hydroxytryptamine) in the frog median eminence, an electron microscopic autoradiography was performed with 5-hydroxytryptophane-³H which is the precursor of serotonin. At 1 and 24 hours after the intraperitoneal injection, most silver grains were located over the nerve fibers and endings, and a few were also found over the glia cell and the perivascular space. A large number of silver grains were located over the type 3 nerve endings (Nakai, 1971) containing small dense granules about 600–1000 Å in diameter 1 and 24 hours after the injection. Some silver grains were localized over the nerve endings containing intermediate-size dense granules 1100–1700 Å in diameter. Silver grains were also frequently observed over the nerve fibers in the inner layer of frog median eminence. There is no significant difference in the pattern of distribution of silver grains between tissues of 1 hour and 24 hours after the injection.The authors wish to thank Prof. H. Fujita for his advice and criticism.     

Effect of active and passive immunization with TRH on plasma TSH response to propylthiouracil.

The role of thyrotropin-releasing hormone (TRH) in the secretion of TSH from the anterior pituitary was investigated in rats by active and passive immunization with TRH. The plasma TSH response to propylthiouracil (PTU) in TRH-bovine serum albumin (BSA)-immunized rats was significantly lower than that of BSA-immunized or non-immunized rats. Similarly, the increased plasma TSH level following PTU treatment was significantly suppressed after iv injection of antiserum to TRH. However, the decline in plasma TSH levels was not complete. The results of the present study indicate, at least in part, the physiological significance of endogenous TRH in the regulation of pituitary TSH secretion.     

Ultrastructure of the neurohaemal region of the toad median eminence

Summary According to the internal structure and size of the granules, six types of nerve endings can be distinguished in the toad median eminence: 1. Endings containing mostly dense granules of 600 Å in diameter; 2. Endings containing dense granules of about 800 Å in diameter; 3. Endings which contain dense granules 1,000–2,000 Å in diameter, with the peak at 1,200–1,400 Å; 4. Endings containing granules with a characteristic structure, which differentiate them from the other three types; 5. Scarce endings containing granules 2,000 to 3,800 Å in diameter; and 6. Endings containing only vesicles 400–500 Å in diameter. Types 3 and 4 endings are mainly found in the outer pericapillary zone, and are probably responsible for the strong Gomori-positive reaction observed in this zone. The other four types of endings occur mainly in the inner pericapillary zone, and appear to be Gomori-negative.The probable origins of the different types of endings, and their possible relations with the different releasing factors is discussed.The subendothelial basement membrane has numerous long processes which form a complicated network in contact with all the nerve endings, some nerve fibres and glial cells.Two types of glial cells are described. Pinocytotic vesicles are frequently seen at the points where these cells contact the basement membrane. All the ultrastructural features suggest that these cells are carrying out transport functions.Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina.The author is very grateful to Professor H. Heller for his continued encouragement and criticism and to Mr. J. Lane and Mr. P. Heap for their valuable help.     

Electron microscopic studies on the pars intermedia in normal and in mice with hereditary nephrogenic diabetes insipidus

Summary The ultrastructure of the pars intermedia (PI) of the normal VII +/+ and hereditary nephrogenic diabetes inspidus DI Os/+ mice has been studied with particular reference to the morphology of the glandular cells and their innervation. Four types of cells were observed in both the genotypes of mice, 1) the light glandular cell, 2) the dark cell, 3) a type of cell similar to ependymal cells and 4) a small percentage of typical ACTH cells, observed mostly on the PI border of the cleft and rarely in the centre of PI. The predominant light glandular cells contain mainly two types of membrane bound granules: 1) electron dense core granules, which measure 1500–2500 Å and 2) electron lucent vesicles, which measure 3000–4000 Å in diameter. Granules of intermediate size with various density are also present in both types of mice. The electron dense core granules are predominant in DI Os/+ mice, whereas, electron lucent vesicles are predominant in the normal VII +/+ mice. Similar uniform size membrane bound electron dense granules have been observed in ACTH cells of PI and pars distalis. From earlier experimental evidences and the present observations, it is concluded that the dense core granules in PI may be synthesizing ACTH or ACTH-like substance. It is also discussed that these dense core granules may further mature and give rise to MSH in the form of electron lucent vesicles. If it is so, PI light glandular cells may have dual functions, of producing MSH and ACTH. One of the functions of ependymal-like cells, may be the transport of PI secretion.Three types of nerve endings are observed throughout the PI, making synaptic contact with the predominant cell type. The innervation is more in DI Os/+ mice than in normal mice. The classification of these nerves is according to Bargmann and co-workers 1) peptidergic neurosecretory fibers, contain mainly membrane bound dense core granules, measuring 1200 to 1800 Å, and are the classic neurosecretory granules; 2) adrenergic fibers, measuring 700–900 Å; 3) cholinergic fibers, measuring 300–400 Å. Adrenergic and cholinergic fibers are more towards the hypophysial cleft. The increased innervation, the synaptic contact, the extremely hypertrophied PI and the greater activity of its light glandular cells in the DI Os/+ mice show the PI is under the influence of the nervous system.This study was supported by MRC of Canada Grant No. MA-3759.