2 – Molting and Regeneration

A high-liter antiserum has been obtained from two rabbits immunized with a glutaraldehyde conjugate of synthetic pigment-dispersing hormone (PDH) from Uca pugilator and bovine thyroglobulin. The antiserum blocked melanophore-dispersing activity of the peptide in vivo. In sinus glands (SG) of Carcinus maenas, Cancer pagurus, Uca pugilator and Orconectes limosus, electron-microscopic immunocytochemistry revealed sparsely distributed axon endings containing a distinct PDH-immunoreactive type of neurosecretory granules (diameter 90–130 nm). Exocytotic figures indicating release of the content of these granules into hemolymph lacunae were occasionally observed. Preservation of fine structure and antigenicity of the PDH granules were markedly dependent on the fixation procedure used. A preliminary experiment with C. maenas showed that preterminal axon dilatations near the basal lamina seemed to accumulate PDH-granules when animals were kept in complete darkness for three days. Immunodot blotting of fractions after high pressure liquid chromatography (HPLC) of extracts from SGs of C. maenas and O. limosus revealed a strongly immunoreactive substance at a retention time very similar to those of synthetic PDHs of Uca pugilator and Pandalus borealis. It is also coincident with a zone of biological activity. Thus, the antigen demonstrated by immunocytochemistry is identical or very similar to one of the known PDHs.

The ultrastructure of nerve endings containing pigment-dispersing hormone (PDH) in crustacean sinus glands: Identification by an antiserum against a synthetic PDH

The granules of neurosecretory cells in the supraesophageal ganglion of the earthworm, Lumbricus terrestris L., are formed by the Golgi apparatus. The process of neurosecretion is discussed in relation to this observation.

Neurosecretion. XII. The formation of neurosecretory granules in the earthworm, Lumbricus terrestris L.

1. The pericardial organs and anterior ramifications (both neurohaemal structures) of six species of crabs have been examined as whole mounts by the histochemical method for monoamines based on formaldehyde-induced fluorescence. 2. A small number of specifically fluorescing axons (not more than six green and six yellow) innervate the pericardial organ; one of the green-fluorescent and one yellow-fluorescent axon branches and also innervates the anterior ramification. 3. All of the fluorescing axons enter via segmental nerves 1, 2 and 3 from the ventral ganglion. 4. One large, brilliant green-fluorescing axon, and the small green-fluorescing axon which branches to the AR, have been traced in Carcinus to cell bodies in the circumoesophageal connective ganglion. These cells may give rise to the entire population of green-fluorescing axons and terminals in the neurohaemal organs. 5. Each axon, throughout its course in the pericardial organ, supplies a dense array of varicosities (blebs) at surfaces which are directly exposed to the haemolymph. The anterior ramifications are also supplied with blebs. 6. Lack of fluorescence in controls not exposed to paraformaldehyde, reversible quenching of fluorescence by treatment with sodium borohydride, and depletion of the fluorescence by reserpinization of the crabs, all confirm that the fluorescence is specific and represents the intracellular localization of monoamines. 7. With the aid of data available elsewhere we conclude that there are distributed, in parallel with peptide-secreting axons and terminals in the pericardial organs and anterior ramifications, a group of dopamine-containing and a group of 5-hydroxytryptamine-containing axons and terminals.

Fluorescence localization of monoamines in crab neurosecretory structures.

A. Introduction Neurosec re to ry cells have t r ad i t i ona l l y been defined main ly on the basis of the i r cy to logy a t the l ight-microscope level. According to this def in i t ion (ScHARRER and SCHARRER 1954) neurosecre tory cells possess all the a t t r i bu te s of neurons axons and dendr i tes , Nissl subs tance and neurofibri ls and in add i t ion show conspicuous signs of secre tory ac t iv i ty , often possessing a wel l -developed Golgi zone ( S T ~ L and SEITE 1954) and showing in the i r cy top lasm accumula t ions of secre tory mate r ia l , which appea r genera l ly to pass down the axon. KNOWLES and CARLISLE (1956) have incorpora ted into the morphologic defini t ion the fea ture t h a t in mos t cases the axons of neurosecre tory cells end b l indly on or near the vascu la r sys tem, forming charac ter i s t ic s torage-release s t ruc tures called neurohemal organs. Imp l i c i t in the t heo ry of nem'osecret ion is the behef t h a t these special ized cells p roduce and discharge into the circulat ion physiological ly ac t ive subs tances ( \"neurohormones\" ) . However , physiologic cr i ter ia are not genera l ly inc luded in the def ini t ion of neurosecret ion and in m a n y groups of animals \"neurosec re to ry\" neurons are found for which no physiologic significance is known. Since neuromelan in and o ther p r e sumab ly iner t neurop igments can mimic neurosecret ion bo th morpholog ica l ly and in s ta in ing proper t ies (cf. BERN and HAGADORN 1963, for references), there are considerable po ten t i a l difficulties in a pure ly cytologic def ini t ion, a t least a t the level of the l ight microscope. The app l i ca t ion of the e lect ron microscope to the s tudy of neurosccre tory sys tems has been of impor t ance for several reasons. F i r s t , i t has been used to e luc ida te fu r the r the s t ruc ture of neurosecre tory cells. Second, i t has enabled one to s t u d y in finer de ta i l the character is t ics of the secre tory p roduc ts of those neurosecre to ry cells whose physiologic significance is known, in the hope of f inding s t ruc tu ra l differences be tween neuroseere tory mate r ia l s and the var ious subs tances which m a y mimic t hem a t the l ight-microscope level. Las t ly , the

The fine structure of the supraesophageal ganglion of the rhynchobdellid leech, Theromyzon rude, with special reference to neurosecretion

1. Homogenates of sinus glands in isotonic sucrose cause little dispersion of black chromatophores when injected into legs or whole Uca. A liberation of hormone occurs when homogenates of sinus glands in isotonic sucrose are diluted in distilled water. A fraction, sedimentable by high speed centrifugation, when resuspended in distilled water and injected into the test animals, induces a dispersion of the chromatophores. These results support the view that the black chromatophore-dispersing hormone is contained within granules in sinus glands.2. The release of the hormone from the granules, obtainable by lowering the tonicity of the medium or by dilution in isotonic saline solutions, suggests that the granules possess a semipermeable membrane.3. The release of the hormone from the granules is increased by heating, by freezing and thawing, and by the action of detergents and digitonin.4. The black chromatophore-dispersing hormone may be a polypeptide, since it is inactivated by extracts of hepatopancreas an...

Maria Dolores Pérez-González

Papers

Evidence for hormone-containing granules in sinus glands of the fiddler crab uca pugilator