Adrenergic control of hypothalamic function during osmotic stress in the mallard duck (Anas platyrhynchos)

Summary The role of the paraventricular nucleus (PVN) and biogenic amines (BA) in regulating the level of corticoids in the serum of osmotically stressed mallard ducks (Anas platyrhynchos) was analyzed employing three experimental approaches: 1) pharmacologic alteration of central BA levels, 2) microscopic evaluation of BA distribution, and 3) placement of electrolytic lesions into the PVN. Reserpine and -methyl-p-tyrosine (mpt), agents that decrease the amount of BA's in the central nervous system, produced a fivefold increase in the concentration of serum corticoids. Conversely, pargyline and amphetamine, agents that increase the functional pool of BA's, prevented the rise in serum corticoid concentration normally observed in birds challenged with an intraperitoneal injection of hypertonic saline. When the topographic distribution of BA's was analyzed in the brains of osmotically stressed and nonstressed ducks distinct changes in the intensity of catecholamine (CA) fluorescence were observed in only one location, the PVN of the hypothalamus. Additionally, electrolytic lesions stereotaxically placed in the PVN blocked the osmotic stress-induced rise in serum corticoid concentration. These data therefore indicate that the PVN in the mallard duck plays some role in regulating the observed stress-induced rise in serum corticoid concentration, and that this regulatory function is probably inhibited by catecholamines.This research was supported by research grant No. GB 33321 from the National Science Foundation. We wish to express our sincere thanks to Mr. Howard Funk, research director, Colorado Division of Wildlife, for the use of the State's animal facilitiesThis research was submitted as partial fulfillment for the degree of Doctor of Philosophy, Department of Physiology and Biophysics, Colorado State University, Ft. Collins, CO 80521     

Innervation of the cultured fetal rat pancreas

Summary The fetal rat pancreas, explanted at 18 days of gestation and cultured up to ten days, contains numerous acetylcholinesterase-positive neurons. These nerves usually appear in small ganglia although single nerve cells are encountered. The axons of these intrapancreatic nerves appear to terminate only in the islet tissue and not on any exocrine components of the expiant. It is concluded that the fetal rat pancreas contains an islet-specific group of cholinergic neurons.We gratefully acknowledge the skilled technical assistance of Dan Whitehead and the secretarial assistance of Mary Pat Brady     

Septate junctions in the cephalic epidermis of turbellarians (Bipalium)

Summary In the epidermis of turbellarians septate junctions of the pleated sheet type have been demonstrated in conventional thin sections and freeze fractured preparations. The structure of these junctions entirely agrees with that found in molluscs and arthropods.Financially supported by DFG (Sto 75/3,4; We 380/5)     

The coxal glands of geophilomorpha (chilopoda): Organs of osmoregulation

Summary The organs terminating at the coxal pores of the tug-legs of Geophilomorpha are not repugnatorial glands, but possess typical transport epithelia with deep apical and basal infoldings of the cell membranes, between which numerous large mitochondria are located. Many transport vesicles are found in the basal region but fewer in the apical cytoplasm. The apex is characterized by bundles of longitudinally oriented microtubules, sparse endoplasmic reticulum and free ribosomes. Single neurosecretory axons with synaptoid areas are scattered among the cells. It is suggested that the coxal organs have a diuretic function in moist habitats and an antidiuretic effect in arid environments. The switch-over is evidently controlled by a neuroendocrine mechanism.     

Relationship between collagen fibril diameters and body size

Summary Suspensions of collagen fibrils obtained from derma of Elasmobranchia and Actinopterygia of different body sizes and developmental stages were examined by transmission electron microscopy. Fibril diameters were measured and classified into groups comprising a 20 nm diameter interval. Diagrams showing fibril populations of each fish were made. The measurements were averaged and their confidence intervals and standard errors determined. For each species other diagrams were plotted in which the mean diameters were correlated to the body length of each sample. The results show that: 1) a correlation exists between an increase in diameter of collagen fibrils and somatic growth until sexual maturity is reached; 2) fibril populations are subsequently spread over a wider range due to the presence in the derma of classes of newly formed and therefore thinner fibrils. The deposition of new fibrils is possibly influenced by individual factors; 3) no relationship exists between mean fibril diameter and body size; 4) no relationship exists between phylogenetic position and pattern of diameter distribution.Research supported by a grant from C.N.R. Roma (69.02087.0115.1150)     

The effect of age on the ultrastructure of the mid-gut cells of the hymenopteran Nasonia vitripennis (Walk.) (Hymenoptera,Pteromalidae)

Summary The ultrastructure of the mid-gut cells of aged female Nasonia vitripennis is described. The mid-gut is a shrunken and distorted organ in the aged animal. The individual cells are highly disorganised and the organelle components are altered. The small lipid droplets formed in the apical cell region do not coalesce to form the large central lipid inclusions characteristic of the young animal. The rough endoplasmic reticulum is reduced and some of the mitochondria enlarge. The mid- and apical cell regions also contain large numbers of cytolysosomes. The basal cell region is essentially unchanged, but the channels formed by the infolded basal plasma membranes are dilated. The changes observed are discussed in relation to previous observations on other insect species.We are indebted to Professor E.W. Knight-Jones in whose Department this work was carried out, and to the Science Research Council for financial support to one of us (I.D.)     

Fine structure of the gap junction in the tunicate heart

Summary The plasma membranes of the tunicate heart exhibit an abundance of macular gap junctions distributed widely over the membrane surface. A study of these junctions by the freeze-etch technique was undertaken in an effort to elucidate the fine structure of this important membrane modification in a primitive heart. In cross or near-cross fractured junctions the junctional particles in contiguous membranes appear to be paired in register and to meet in the midline. In favorable face views, the junctional particles are seen to be disposed in hexagonal array. The individual particles display a distinct rosette-like substructure consistent with a six-membered ring of globular protein molecules clustered around a central channel. Similar junctional-type particles can be found in nonjunctional areas of membrane suggesting that the transport mechanism which they may represent is not restricted to the gap junction.Career Investigator of the American Heart AssociationWe wish to thank Dr. J.B. Jillett for use of the facilities of the Portobello Marine Biological Station; Mr. W.S. Bertaud, Physics and Engineering Laboratory, D.S.I.R., Lower Hutt, who kindly supervised the preparation of some of the freeze-etch replicas; Dr. R.H. Millar of the Dunstaffnage Marine Research Laboratory, Oban, Argyll, Scotland, who identified the tunicate used in the present (and previous) study; Prof. W.D. Trotter who made facilities in the Department of Anatomy, University of Otago Medical School, Dunedin, available to one of us (V.L.); and Mrs. S.M. O'Kane for excellent technical assistance. Generous support from the American Heart Association (to V.L.) and from the Medical Research Council of New Zealand (to D.G.R.) is gratefully acknowledged     

Structural features and quantitative age-dependent changes in the intervascular barrier of the guinea-pig haemochorial placenta

Summary The haemomonochorial placenta of the guinea-pig undergoes several quantitative changes between the 49th and 64th days of gestation, all of which are in such a direction as to increase the efficiency of transplacental transport. The fetal vessels become larger, the maternal vessels increase in surface area by proliferation of microvilli, and the effective mean distance between the two vessel sets decreases. The magnitude of these changes suggests that the efficiency of transport of hydrophilic solutes across the maternal-fetal interface could double, although changes in the number of permeation sites per unit area may modify this relationship. The presence of open intercellular spaces and fenestrations in the fetal endothelium suggests that this layer may not be a major permeability barrier in the guinea-pig, but may create an unstirred layer of extracellular fluid between endothelium and syncytiotrophoblast.     

Sertoli cells of adult rats “in vitro”

Summary A cell line obtained from isolated seminiferous tubules of adult rat testis has been studied in vitro over a period of 35 days.Light and electron microscopic studies performed from hour 2 to the end of culture have shown the presence of a monomorphic cell population. After 5–6 days of culture the cells formed a monolayer. The cytoplasm of the cells contained numerous lipid bodies and produced numerous projections. The nucleus showed several indentations and one or more nucleoli. From the 9th to the 15th day of culture the cells developed a large amount of endoplasmic reticulum, Golgi apparatus and aggregates of electron dense granules. From the 20th to 40th day the cell cultures progressively degenerated.Immunochemical analysis of the culture medium revealed the presence of estradiol-17, which reached its maximum production rate from the 8th day to the 18th day of culture. Corresponding to cell involution estradiol concentration underwent a rapid decrease.On the basis of morphological and biochemical data the cells could be considered Sertoli cells.This work was supported by Grants n. 74.00155.04 and n. 75.01224.04 from the Consiglio Nazionale delle Ricerche (C.N.R.), Rome, Italy, and by Istituto di Ricerca F. Angelini, Rome, ItalyPart of this work was presented at the 10th Italian Congress of Electron Microscopy. Ostuni 1–4 October 1975The excellent technical assistance of Miss Laura Vassallo, Daniela Venturini and Mr. Massimo Rosati and Mario Termine is deeply appreciated