The origin of yolk in the oocytes of Nereis virens (Annelida,Polychaeta)

Summary Comparative studies have been made of development of the adenohypophysis using the Rathke's pouch (RP)-derived model system. Rathke's pouch with associated mesenchyme and ventral hypothalamus, was microsurgically isolated from 15-day fetal rats and placed in mild trypsin solution. Three variations of donor tissue were isolated and transplanted beneath the kidney capsule of adult hosts: A) pure pouch epithelium; B) pouch epithelium plus mesenchyme; and C) pouch epithelium with mesenchyme and ventral hypothalamus. After 30 days the grafts were isolated and processed for light and electron microscopy. Cell types were characterized by immunostaining as well as by morphological criteria. In group A well differentiated mammotrophs dominated the grafts, many of which were hypertrophied with widely dilated endoplasmic reticulum and Golgi saccules. Mammotrophs, frequently with mitotic figures, were distributed evenly throughout the grafts. Somatotrophs and gonadotrophs were neither abundant nor well differentiated in group A, but were both abundant and more extensively differentiated in groups B and C. Both somatotrophs and gonadotrophs were typically localized at margins of the graft adjacent to connective tissue spaces. Well differentiated mammotrophs were present in groups B and C although there were fewer hypertrophied mammotrophs than in group A; and immunoreaction to prolactin was weaker than in group A.Tumor-like features found in all three groups included some loss of tissue integrity and large, vascular lakes unlined by endothelium.These findings suggest that differentiation of mammotrophs may be inhibited in part by mesenchyme associated with Rathke's pouch, since in the absence thereof these cells become hyperplastic. Conversely, differentiation of somatotrophs and gonadotrophs appears more dependent on these mesenchymal elements for normal development.     

Regulation of biosynthesis and release of pars intermedia peptides in Rana ridibunda: dopamine affects both acetylation and release of alpha-MSH

Dopamine is likely an important physiological melanotropin release-inhibiting factor in amphibians. This study concerns the effects of dopamine on the biosynthesis and release of peptides from the pars intermedia of the frog Rana ridibunda. Our results show that this secretagogue has no immediate effects on either the rate of biosynthesis of pro-opiomelanocortin nor on the direction of processing of this prohormone. Pulse-chase experiments revealed that dopamine inhibited the release of all newly synthesized POMC-related peptides in a dose-dependent manner. For each dopamine concentration tested, the degree of inhibition exerted on the release of the various newly synthesized peptides by a given concentration of secretagogue was approximately the same, with the exception of that found for the alpha-MSH related peptides. Analysis of the release of these melanotropins was complex because dopamine not only inhibited their release but also, either directly or indirectly, inhibited the acetylation reaction which converts des-N alpha-acetyl alpha-MSH to alpha-MSH. Dopamine was shown to be less potent in inhibiting the release of des-N alpha-acetyl alpha-MSH than inhibiting release of the acetylated form of the peptide. In amphibians a preferential release of the less-bioactive non-acetylated form of MSH under inhibitory conditions induced by dopamine may be of physiological importance.     

Axonal projections within the brain-retrocerebral complex of the cricket,Teleogryllus commodus

Summary The cerebral origins and axonal trajectories of neurons projecting to the retrocerebral complex of the cricket, Teleogryllus commodus, were examined in silver-intensified nickel preparations. Spatially separate groups of somata in the pars intercerebralis (PI) and in the pars lateralis (PL), commonly accepted as neurosecretory loci, were found to give rise to axons which terminate in the nervus corporis allati 2, the corpus allatum, or the corpus cardiacum. Additional findings demonstrated a distinct group of somata from the PI whose axons run in the esophageal nerve (stomatogastric nervous system), nine somata in the subesophageal ganglion with axons projecting into the nervus corporis allati 2, and also a small cluster of tritocerebral perikarya with axons terminating in the corpus cardiacum. Somata residing in the PI and PL were found to be compartmentally organized based upon the retrocerebral destinations of their axons. Possible functional consequences of these results with respect to the insect neurosecretory system are discussed.     

Cell types in the fetal pars tuberalis of the human adenohypophysis at mid-gestation

Summary The pars tuberalis of the adenohypophysis was investigated in three human fetuses at mid-gestation by electron microscopy or immunohistochemistry. In addition to gonadotrophs and thyrotrophs, identified by immunohistochemistry and ultrastructural morphology, electron microscopy revealed the existence of an additional differentiated cell type closely resembling pars tuberalis-specific cells known from other species. The role of this cell type in the human endocrine regulation remains to be elucidated.     

Localization of luteinizing hormone β-mRNA by in situ hybridization in the sheep pars tuberalis

Summary The localization of luteinizing hormone beta (LH)-mRNA was studied by in situ hybridization in the pars tuberalis of sheep using a homologous sheep double-stranded ³²P-or ³⁵S-cDNA. The labelled cDNA probe detected one mRNA sequence in the pars tuberalis by Northern blot analysis; this sequence was similar to that detected in the pituitary. In situ, the labelling of LH-mRNA in the horizontal and sagittal tissue sections was found throughout the pars tuberalis. This labelling was prevented by adding an excess of cold probe or treating the sections by ribonuclease before in situ hybridization. Controls showed a labelling in the pars distalis, but not in the median eminence, hypothalamus, cerebral cortex and liver sections. Double labelling by using a specific LH-antiserum indicated that the labelling of LH-mRNA appeared more intense in LH-containing cells that were found only in the ventral part of the pars tuberalis. These results suggest that the entire pars tuberalis is able to produce the LH subunit, but that the level of translation greatly varies according to the location of the cells.     

Phagocytic activity of the stellate cells in the anuran pars intermedia

Summary In an attempt to study further the stellate cell and its functions, the ultrastructure of this cell type in the neurointermediate lobe of the bullfrog, Rana catesbeiana, was examined in both organ and dissociated-cell culture. The cytoplasmic activity of stellate cells from neurointermediate lobes incubated 3 1/2 or 5 1/2 h was greater than that of those in vivo. Mitochondria and bundles of cytoplasmic filaments were numerous, in addition to prominent, well-developed Golgi complexes with associated vesicles. The most striking ultrastructural feature was the presence of phagocytic vacuoles that contain cellular debris. The stellate cells were seen to form cytoplasmic processes that phagocytosed this extracellular debris identifiable as belonging to the secretory cells of the pars intermedia. The stellate cells from the dissociated-cell preparations were also seen to contain debris within phagocytic vacuoles. In those neurointermediate lobes transplanted for 3 1/2 to 4 days into the anterior chamber of the eye, the stellate cells demonstrated similar phagocytic ability, but the phagocytic vacuoles contained material that seemed to be at a later stage of degradation. In all three of these conditions, the stellate cells were not seen to release this cellular debris nor were they seen to undergo cell division. These glial-like stellate cells of the pars intermedia acted as macrophages in all three of these experiments. There is now, therefore, a need to determine under what conditions, if any, these stellate cells function in vivo as macrophages.Supported by NSF Program for Small College Faculty Engaged in Research at Larger Institutions and Department of Energy — Associated Western Universities Faculty Participation Program. The authors thank Dr. W. Ferris and Dr. J. Berliner for the use of the electron microscopy facilities at the University of Arizona and Nuclear Medicine Laboratory, UCLA, respectively. Warm thanks are due to Ms. Ruth Cole for technical assistance     

PAS-positive cells of the pars intermedia are calcium-sensitive in the goldfish maintained in a hyposmotic milieu

Summary Cytological changes in the pars intermedia of the goldfish were investigated after adding calcium to deionized water (DW). In fish maintained in DW, the PAS-positive cells are highly stimulated in comparison to cells of fish kept in fresh water (FW). In DW supplemented with calcium at the same concentration as in FW (2 mM/l), the hyperactivity of the PAS-positive cells is prevented. When calcium ions are added 60 h before the animals are sacrificed, the PAS positive cells start to show signs of regression and their granules are stored: the release of the granular material appears to be suppressed by calcium. In the goldfish, the PAS-positive cells, homologous to a similar cell type in the eel, react only very weakly with the PAS technique. The name calcium-sensitive cells appears to be more appropriate in the goldfish for this particular cell type, secreting an unknown factor. This factor, different from the prolactin produced in the rostral pars distalis of the hypophysis, might be an equivalent of a hypercalcin.     

Long-Term Treatment of Rats with Morphine Reduces the Activity of Messenger Ribonucleic Acid Coding for the β-Endorphin/ACTH Precursor in the Intermediate Pituitary

Abstract: Chronic administration of morphine to rats for a period of 4 weeks resulted in a 50-60% decrease in the tissue concentrations of β-endorphin and in the in vitro release from the neurointermediate pituitary. Incorporation of [³H]phenylalanine into isolated intermediate/posterior pituitaries in vitro revealed a reduction in the amount of label incorporated into the β-endorphin/ ACTH precursor to a similar extent (about 45%), but essentially no effect on the conversion of the precursor into β-lipotropin and β-endorphin. Extraction of mRNA from intermediate/posterior pituitaries followed by cell-free translation in a reticulocyte system showed no significant decrease in the total level of translatable mRNA. In contrast, the content of translatable mRNA coding for the β-endorphin/ACTH precursor was significantly reduced by 50-60%. Thus, long-term treatment with morphine appears to depress β-endorphin formation in the rat intermediate pituitary at the pretranslational level by markedly decreasing the activity of mRNA coding for the β-endorphin/ACTH precursor without any alteration in the processing of this precursor.     

Morphology and immunocytochemistry of the turtle pituitary gland with special reference to the pars tuberalis

Summary Examination of pituitaries from young and adult turtles representing four families, reveals that in addition to the abundant juxtaneural pars tuberalis (JuxPT) found in this class of reptiles, there is generally a substantial amount of pars tuberalis (PT) tissue closely associated with the pars distalis (PD). The PT forms a cortical layer especially conspicuous around the anterior tip of the PD in some species (Trionyx, Kinosternon, Sternotherus), or it forms a thick dorsal layer of tissue irregularly extending onto the sides of the PD in others (Pseudemys, Chrysemys, Lepidochelys, Chelonia).Immunocytochemical studies using unlabelled second antibody and peroxidase-antiperoxidase reveal that in turtles of all ages, the PT tissue allied with the PD (the PTinterna) is composed primarily of cells containing glycoprotein hormones (FSH, LH and TSH), especially the gonadotropins. The juxPT, however, consists mainly of secretory cells unstained by the antisera tested and includes only a small number of gonadotropes and thyrotropes. Although usually widely distributed in the testudinate adenohypophysis, the great majority of gonadotropes and thyrotropes present in the hatchling are in the PTinterna. It is probable that a concentration of these cells in the PTinterna is widespread among vertebrates.In all turtles examined, lactotropes occur principally in the anterior and ventral part of the PD proper; somatotropes are posterior and dorsal. Corticotropes are concentrated as the lactotropes in the anterior PD, but some are also scattered throughout the posterior half of the gland. Lactotropes, corticotropes, and with a few exceptions, somatotropes, do not occur in PT tissue in the turtle.We are grateful to Drs. Harold Papkoff and J.C. Ramachandran of the Hormone Research Laboratory of the University of California in San Francisco for their generous gifts of several antisera and to Dr. Ludwig Sternberger for the peroxidase-antiperoxidase used in this study. Thanks are also given to Phyllis Thompson for assistance with the illustrations and to William Rainey, David Owen and John Cadle for specimens that they made available. Use of the facilities of the Electron Microscope Laboratory of the University of California at Berkeley is gratefully acknowledged, including use of the JEOL-JEM 100CX transmission electron microscope purchased under National Science Foundation Grant Number PCM-7821561. This work was supported by NSF grant PCM-7812470 to PL     

A whole range of fine structural criteria for immunohistochemically identified LH cells in rats

Summary Pituitaries from normal, young and adult male rats were fixed either in sublimate-formalin or in glutaraldehyde-osmium. In adjacent Paraplast sections, almost all the gonadotrophs were immunostained with both LH and FSH antisera. The rat LH and FSH antisera used were shown to be highly specific by the absorption test and by double antibody radioimmunoassay. Thin and thick adjacent Epon sections were prepared for EM and immunohistochemical examination. Cells stained with the rat LH antiserum were identified by LM, and then observed in detail by EM. On the basis of these observations we suggest that the LH cells are arranged in a sequence of basophils, i.e., Types II/III, III, III/IV and IV: Type II/III basophils are elongate with a cytoplasmic process and less vesiculated. They have morphological features of Type II (classical thyrotrophs) and also of Type III basophils. Type III basophils are oval in shape and moderately vesiculated. Both Types II/III and III basophils can be divided into two classes of cell characterized mainly by the existence of only small secretory granules (150–220 nm in diameter) (Type A) or by the coexistence of small and large (350–500 nm) (Type B). Type III/IV basophils are cells intermediate between types III and IV basophils, and moderately vesiculated with an abundance of secretory granules (150–300 nm in diameter). Type IV basophils are large, spherical or oval cells whose RER cisternae are conspicuously dilated; they contain less numerous secretory granules (150–300 nm in diameter). It is concluded that LH cells are not a single cell type, but include a wide range of subtypes.