Thiamine and Cholinergic Transmission in the Electric Organ of Torpedo

The electric organ of Torpedo marmorata was found to contain as much as 120 +/- 24 nmol of thiamine per g of fresh tissue. The vitamin was distributed as nonesterified thiamine (32%), thiamine monophosphate (22%), thiamine diphosphate (8%), and an important proportion of thiamine triphosphate (38%). A high level of thiamine triphosphate was found in synaptosomes isolated from the electric organ. In contrast, the synaptic vesicles did not show any enrichment in thiamine, whereas they contained a marked peak of acetylcholine (ACh) and ATP. Thus thiamine seems to be very abundant in cholinergic nerve terminals; its localization is apparently extravesicular, either in the axoplasm or in association with plasma membrane. When calcium was reduced and magnesium increased in the external medium, the efficiency of transmission was diminished, owing to inhibition of ACh release; in a parallel manner the degree of thiamine phosphorylation was found to increase--this condition is known to modify the repartition of ACh between vesicular and extravesicular compartments. Electrical stimulation, which causes periodic variations of the level of ACh and ATP, also caused significant changes in thiamine esters. In addition, related changes of the vitamin and the transmitter were observed under other conditions, suggesting a functional link between the metabolism of thiamine and that of ACh in cholinergic nerve terminals.     

The ultrastructural basis of steroid production in the Y-organ and the mandibular organ of the crabs Hemigrapsus nudus (Dana) and Carcinus maenas L.

Summary The ultrastructure of the steroid producing Y-organ and the mandibular organ of the crustaceans Hemigrapsus nudus and Carcinus maenas has been studied with reference to the well investigated steroid secreting cells (SSC) of mammals. In accordance with the most important characteristic of mammalian SSC, abundant SER could be shown in the Y-organ, where it is unevenly distributed. The amount of SER seems to vary in correlation with the secretion of moulting hormone during the moult cycle. Most Y-organ cells contain a great number of mitochondria of the tubular type, another important characteristic of mammalian SSC. The ultrastructure of the mandibular organ of C. maenas differs considerably from that of the Y-organ. Some SER was found, mitochondria of unusual shape and size were conspicuous. No definite conclusion as to the function of the mandibular organ is yet to be drawn.Dedicated to Prof. Dr. Peter Karlson on the occasion of his 60th birthdaySupported by the Deutsche Forschungsgemeinschaft, grant Ad 24/4We wish to thank Dr. A. Owczarzak, Oregon State University, Corvallis, Oregon, for providing the facilities for our work with H. nudus and Thomas Gallenstein for many helpful discussions of technical problems     

Ultrastructural observations on synaptic ribbons in the pineal organ of the goldfish

Summary Synaptic ribbons in the pineal organ of the goldfish were examined electron microscopically with particular attention to their topography. These structures were formed of parallel membranes, which were poorly preserved with OsO₄ fixation and could be extracted from thin sections with pronase indicating their proteinaceous nature. Synaptic ribbons were closely apposed to the plasma membrane bordering dendrites of ganglion cells, but were also related to processes of both photoreceptor and supportive cells. Their close proximity to invaginations of the plasma membrane and portions of the endoplasmic reticulum suggest that they are involved in the turnover of cytoplasmic membranes. Tubular and spherical organelles of unknown function are also described.     

Evidence for a nervous connection between the brain and the pineal organ in the guinea pig

Summary Following the injection of horseradish peroxidase into the pineal organ of the guinea pig, approximately 30 nerve fibers were demonstrated in the pineal stalk due to the retrograde transport of the tracer enzyme in these elements. Finely branched extensions of these nerve fibers are directed toward the distal portion of the pineal organ. This projection of central nervous elements enters the pineal organ via the habenular or posterior commissures. Neuronal perikarya projecting into the pineal organ are found in the region of the paraventricular nucleus near the border of the third ventricle.In partial fulfillment of the requirements for the degree of Dr. med., Faculty of Medicine, Justus Liebig University of Giessen     

Regulation by testosterone of the glucosamine-6-phosphate synthase activity in the male reproductive organs of rat

Accessory reproductive organs of male rat were found to contain high activities of glucosamine-6-phosphate synthase (glucosaminephosphate isomerase (glutamine-forming), EC 5.3.1.19). Castration caused drastic reduction (75%) in the enzyme activity of ventral prostate. Testosterone propionate administration restored the enzyme activity while cortisol and estradiol-17β did not cause any effect. Cycloheximide blocked the stimulation caused by testosterone.     

Tegument and apical end organ fine structure in the metacestode and adult Proteocephalus ambloplitis

The tegument of plerocercoid and adult P. ambloplitis was examined. Differences in tegument structure existed between these two stages. Plerocercoids of P. ambloplitis lacked extensive vacuolization and unicellular gland cells characteristic of adult tegument. Plerocercoid microtriches were short and conoid; adult microtriches were lenticular with an extended, whip-like shaft. An inclusion, not previously reported from proteocephalid cestodes, is described. Adult tegument had ducts, originating from underlying unicellular glands, extending through the distal cytoplasm and opening to the exterior between microtriches.

The apical end organ cavity of P. ambloplitis contained numerous labyrinth-like spherical bodies. These structures appeared to be synthesized and secreted into the end organ by a thin cellular lining of the end organ. This lining was composed of discrete, filamentous cells believed to be modified subtegumental cell bodies. Spherical structures identical to those observed within the end organ cavity occurred within this cellular lining. The spherical bodies may be associated with enzymes necessary for tissue migration by the metacestode.     

Ultrastructural development of the neurohemal organ joined to the ecdysial gland after imaginal moulting in the male isopod Sphaeroma serratum fab. (Crustacea Flabellifera)

Summary The present ultrastructural study deals with the lateral cephalic nerve plexus of Sphaeroma serratum, a neurohemal organ joined to the Y organ (ecdysial gland). This plexus acts as a storage centre for neurosecretory products from two sources: the two autochtonous cells (plexus cells) within the plexus itself, and the neurosecretory cells in various parts of the central nervous system, particulary the mandibular ganglion (A-cells).In prepuberal animals, plexus cells and subesophageal A-cells produce neurosecretory granules of two types measuring 1550±50Å and 1570±40Å respectively. Five categories of axon terminals were distinguished in the plexus. The granules found in two of these terminal types are believed to come from the plexus cells and from the mandibular ganglion A-cells.Cessation of production of neurosecretory granules in these A cells and plexus cells was observed in puberal animals, in the plexus with concomitant depletion and disappearance of different granule categories. The first axon terminals affected by this process are the two categories containing granules originating in the plexus and mandibular ganglion A-cells. Degeneration of the ecdysial gland in male Sphaeroma serratum might be connected with the cessation of granule formation in these two types of cell.

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Résumé Chez Sphaeroma serratum, la mue de puberté est suivie d'une dégénérescence de l'organe Y (glands de mue). Le plexus nerveux céphalique latéral, organe neurohémal accolé à cette glande a été l'objet de la présente étude ultrastructurale. Cet organe représente un centre de stockage de neurosécrétions qui proviennent d'une part, de deux cellules autochtones (cellules plexales) situées au sein même de ce plexus, d'autre part, de cellules neurosécrétrices situées dans le ganglion mandibulaire (cellules de type A).Chez les individus pubères, les cellules plexales et les cellules A du ganglion sous-oesophagien synthétisent des granules de neurosécrétion dont la taille est respectivement 1550±50Å et 1570±40Å. Il a été reconnu au sein du plexus 5 catégories de terminaisons dont les granules proviendraient pour deux d'entre elles des cellules plexales et des cellules A du ganglion mandibulaire. Chez les animaux pubères on observe un arrêt de la synthèse des granules de neurosécrétion au sein des cellules plexales et des cellules A du ganglion mandibulaire. Simultanément on enregistre dans le plexus la raréfaction puis la disparition des divers types de granules. Ce processus atteint en premier les terminaisons correspondant aux cellules plexales et aux cellules A du ganglion mandibulaire. La dégénérescence de la glande de mue chez les mâles pourrait être en relation avec l'arrêt de synthèse de ces cellules.

     

Observations of the pineal region of non-eutherian mammals

Summary A survey has been made of the pineal region of the brain of 11 species of marsupials belonging to 5 families and a species from both families of monotremes.The results show that the pineal body of non-eutherian mammals, although well-defined in all species, has a very varied morphology. Three types of pineal recess occur: (i) a pineal recess in sensu stricto, (ii) an intercommissural pineal recess, and (iii) an infrapineal recess. The existence of nerve fibres which pass through the pineal body and form a spatial link between the habenular and posterior commissures, has been demonstrated in marsupials and monotremes. It is also likely that these animals as well as eutherian mammals possess a nervus conarii. Nerve cells are not a constant feature of the non-eutherian pineal body.The subcommissural organ (SCO) is present in all species. It does not exhibit the same degree of morphological variation as the pineal body. Horizontal sections available for 4 species within 3 families of marsupials show it to be composed of a median portion joined to bilateral protuberances. Large nerve cells occur within the SCO in all marsupial species; they are absent from the monotreme SCO. Tentatively, the relationship of these neurons to the SCO is considered to be merely one of association.The importance of an extended comparative study of this region in non- eutherian mammals in order to add insight into its phylogeny and function is emphasized.     

A correlated scanning and transmission electron microscopic study of maturation ameloblasts in developing molar teeth of rats

Summary Maturation ameloblasts of developing molar teeth of the rat were studied by both scanning and transmission electron microscopy. After fixation, teeth were frozen and split. One face of the fractured tooth was used for SEM, the other for TEM.It was found that in some regions proximal junctional complexes separate the interameloblast space from the intercellular space of the papillary layer. Thereby an intercellular ameloblastic compartment is delineated which in some specimens contains a substance interpreted to be colloidal. Elsewhere the proximal junctions of ameloblasts are not present and free communication between the extracellular spaces is evident. The apical pole of ameloblasts varies in structure. Over some areas there is a distinct distal border zone with membranous infoldings which in some regions resembles a striated or ruffled border, but in other regions the membranes show whorl configurations. The distal border zone also contains granules with flocculent material. Elsewhere the ameloblasts display no distal border zone and the cells show a smooth membrane (except for pinocytotic vesicles and hemidesmosomes) facing the enamel surface. The lateral surface of ameloblasts exhibits a variety of surface configurations similar to but not as pronounced as those reported previously in rat incisor maturation ameloblasts.The authors wish to thank Pauletta Sanders and Helen Ruane for technical assistance. This project was supported in part by USPHS NIH Grant DE04059-03 and by the Medical Research Council of Great Britain     

Long-term culture of human aortas

Summary Segments of human thoracic aorta were maintained in long-term explant culture for 18 weeks in serum-supplemented medium. The aortas were grossly normal in appearance, and random samples fixed for light microscopy prior to culture revealed a normal morphology. The intima contained no more than five layers of smooth muscle cells. After 7 days in culture, the intima was noticeably thicker than the uncultured segments. The increased thickness was due to proliferating smooth muscle cells and production of extracellular material. After several months in culture, extracellular material consisting of collagen and flocculent material was present in areas resembling atherosclerotic fibrous plaques. A peripheral growth, which formed around the explant, was composed of fibroblastlike cells and added to the overall thickness of the intima. However, aortic segment maintained for up to 2 months in serum-free culture medium showed no cellular proliferation. This study demonstrates that changes resembling early stages of atherosclerosis occur in human aortas maintained in explant culture using routine culture procedures. Supported in part by the Pangborn Fund and the Graduate School of the University of Maryland. This is publication 443 from the Cellular Pathobiology Laboratory.