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Notes: Summary This paper describes the morphological events which take place in the hamster Leydig cell during its process of prenatal and postnatal differentiation. The most strinking feature of the prenatal differentiation is the high development of the vesicular form of the smooth endoplasmic reticulum (S.E.R.). At around the end of the first month of postnatal life the vesicular form of the S.E.R. is replaced by a truly reticular S.E.R. formed by numerous interconnected cisternae. From fetal to adult life the amount of ribosomes decreases whereas the number of mitochondria and Golgi cisternae increases. It is concluded that the differentiation mechanism of the hamster Leydig cell differs from that observed in the Leydig cell of other species, even of those closely related to the hamster, such as the mouse.

Notes: Summary The ultrastructure of the rat uterine luminal epithelium has been examined during normal pregnancy, pseudopregnancy, lactation and lactation-pregnancy, all being conditions when a blastocyst is known to be able to implant. In all four groups of animals the epithelium passes through three characteristic and structurally similar states, namely a pre-attachment state, an attachment state and a postattachment state. The attachment state is characterized by a close contact between apposing luminal surfaces of the epithelium. It is concluded that implantation in an undamaged uterus claims a sequence of certain changes in the uterine luminal epithelium, and that the blastocyst attachment occurs within the early part of that period when the luminal epithelium is in the attachment state.

Notes: Summary Fertilized rabbit ova were studied in the period from 25 to 144 hr after insemination. Eggs were recovered by flushing the uterine horns and oviducts with Hank's solution. The cells were morphologically alike in the 24 and 48 hr ova. At 661/2 hr blastomeres were differentiated into an inner mass of cells with dense cytoplasm and an outer trophoblastic layer with less dense cytoplasm. Otherwise no morphological differences were seen. Whether the 661/2 hr ova were morulas or blastocysts is discussed. The 96 hr ova were clearly blastocysts. Inner cells and trophoblastic cells at this stage bad the same cytoplasmic density. Mitochondria were increased in number and crystal-like figures were present for the first time. In the 120 and 144 hr ova the cytoplasm of the trophoblastic cells was denser than that of the inner cells. Trophoblastic cells were characterized by their density, crystal-like figures, elongated mitochondria with transverse cristae and many single ribosomes and they were interconnected with well developed junctional complexes. In a few cases a continuity seemed to exist between trophoblastic cells and inner cells. The latter were characterized by cytoplasm of less density than that of the trophoblastic cells, rounded mitochondria and fewer ribosomes. The fine structure of the crystal-like figures, their possible origin and differentiation of the mitochondria are discussed.

Notes: Summary A histochemical and ultrastructural investigation of the early development of the adenohypophysis was carried out on a human material. Special attention was paid to an accumulation of hyaluronic acid and chondroitin-4-and/or-6-sulfate in the mesenchyma; its role in morphogenesis of the Rathke's pouch is discussed. The role of the vessels as a “critical factor” in the budding of the parenchyma and in the differentiation of secretory cells is discussed. Canalicular extensions from the original lumen of the pouch into the core of parenchymal buds, which migrate into the mesenchyma, is a new observation. The participation of canaliculi in formation of follicular structures of pars distalis is described and discussed. The primitive cell type lining the pouch is also found in the wall of canaliculi and follicular structures. The cell type is described and its role as the real progenitor cell of the adenohypophysis is discussed. Three types of colloid are noticed in pars distalis: 1. In the follicular structures, 2. in the slits or clefts caused by partial occlusion of the lumen of the pouch, and 3. mesenchymal extravasal colloid presumably representing material squeezed out from the aforementioned clefts or slits. It is concluded that the colloid contains material secreted from different types of granulated cells as well as material from the surface coat of the luminal cells.

Notes: Summary Small quantities of ferritin or Thorotrast were injected into the visual cortex of the cat in order to determine which cells in the cerebrum exhibited endocytic activity when exposed to foreign material. Blocks of tissue from the cortex and adjacent white matter were examined by electron microscopy 5 h and 20 h after injection. Some neurons and oligodendrocytes and all the astrocytes examined showed pinocytotic activity. Increasing the time of exposure of the tissue to the tracer did not appear to result in greatly increased uptake by individual cells, except in the case of astrocytes. Neutrophils, which invaded the tissue after 5 h, and in increased numbers after 20 h, exhibited minimal endocytic activity when they invaded the grey matter. They were more active in the white matter. Up to 20 h after injection, the three most important endocytic elements in the cerebrum were astrocytes (collectively), pale perivascular cells within the basement membrane of the blood vessels and phagocytes, which appeared to be reactive endogenous cells.

Notes: Summary Examinations of 10 muscle biopsies in Duchenne type of progressive muscular dystrophy were performed. The different particular myopathic changes are analysed and their specificity is discussed. Two groups of changes are observed, one concerning total fiber involvement, the other the focal degenerations. In the first group muscle fiber necrosis, associated regenerations, fiber degeneration with initial disturbance of the filamentous arrangement and atrophia simplex are described. Focal myopathic changes appeared predominantly in type I fibers and consisted of Z-streaming and lipid storage in central fiber parts. None of the particular fiber changes are specific, only the distribution of their frequency shows a characteristic pattern. Pathogenic factors of the different particular fiber changes are discussed, especially of the lipid accumulation in the type I fibers.

Notes: Summary Skeletal muscles from a patient with type IV glycogenosis were studied by light and electron microscopy. The distinctive polysaccharide deposits were more abundant in the tongue and diaphragm than other skeletal muscles. The involved myofibers contained fusiform areas filled with polyhedral or rounded granules of basophilic material that was further characterized by staining with periodic acid-Schiff, Grocott methenamine silver and alcian blue. Ultrastructurally the deposits were composed of branched filaments, osmophilic granules and electron-dense amorphous material. There are sufficient ultrastructural, histochemical and chemical similarities among the deposits in type IV glycogenosis, Lafora bodies and visceral deposits in myoclonus epilepsy, corpora amylacea and basophilic degeneration of the myocardium to suggest a common composition and mechanism of synthesis possibly through reversal of the debranching enzyme system. However, sharing a biochemical pathway does not necessarily imply a common etiological factor.

Notes: Summary The object of the present study was to analyse the ultrastructure of Opalski cells, obtained in tissue culture according to the method described by Mossakowskiet al. (1970). The electron microscopic picture of the Opalski cells was characterized by scanty endoplasmic reticulum and Golgi apparatus and a greatly reduced number of mitochondria, as compared with glial cells cultured in vitro. Their cytoplasm contained two types of spherical bodies, one of which corresponded to lysosome-like bodies; the second one, in the authors' opinion, represented an accumulation of mucopolysaccharide substances. The ultrastructural picture of Opalski cells corresponded well with their previously described histochemical properties.

Notes: Abstract Although experimental and clinical experience indicates that large doses of testosterone lead to premature cessation of growth, the exact mechanism and precise site of action of this hormone on the growth apparatus of long bones remain unknown. In this study, plateaued male rats were injected with supraphysiologic doses of testosterone to observe the submicroscopic effects on the various zones of the epiphyseal cartilage. In the zone of cell division there were increased numbers of dividing cells. The maturing cells accumulated larger amounts of secretory products at earlier stages of their life cycle, and appeared to undergo a more abrupt hypertrophy. In the zone of prehypertrophy, the interterritorial matrix contained foci of early and premature calcification and thicker and longer collagen fibers than at comparable levels in controls. It is concluded that in intact animals, even large doses of testosterone initially cause a stimulation of chondrocyte proliferation, prior to promoting maturation processes.

Notes: Abstract The initiation of prisms occurs in the proximal region of the outer surface of the outer mantle fold in the pallial space bounded externally by the periostracum. The first step in the formation of a prism is similar to that observed in the formation of nacre, namely, the elaboration of an electron-dense lamella that serves as the internal boundary of the future prism. Fragments of the lamella become detached and migrate to a chamber bounded externally by the periostracum. These lamellar fragments form envelopes within which crystal initiation and growth oocur. At the same time stout interprismatic walls appear. They are also derived from the lamellae. Growth consisting of the formation of additional crystals and the organic components finally give rise to the mature elongated prism. Growth of the shell occurs at the margin chiefly by formation of new prisms in this area. In addition a modified environment consisting of duplicature of the periostracum on the distal surface results in the formation of thin spurs containing prisms that occur within the confines of the space created by the periostracal loop.

Notes: Abstract Ten male weanling Holtzman rats, injected intraperitoneally with aqueous estradiol (Progynon, Schering), in daily doses of 1 μg. per g body weight, were sacrificed, simultaneously with controls receiving an equivalent amount of diluent, at intervals ranging from one hour to six days. Upper tibial epiphyseal cartilage plates (ECP), procesed for electron microscopy, revealed, as early as three hours after injection, appreciable enhancement of secretory activity, evidenced, in the zone of matrix secretion, by the abundance in Golgi cisternae of stippled material representing proteinpolysaccharide complexes. Disintegration of the lining membrane of individual Golgi vesicles was advanced after twenty-four hours; following three days of treatment, few vesicles remained intact, and pools of initially intravacuolar material were observable in the gound plasm. Long filaments, suggestive of primary or precursor collagen fibrils were apparent in this secretion. After six days, virtual lakes of this substance filled cells in the zone of prehypertophy, with consequent displacement of the rough endoplasmic reticulum against the cell periphery. Cytoplasmic vacuoles, containing mateerial similar to that found in the lacunar moat, and displaying finely beaded, radially arrayed filaments on the lining membrane were frequently encountered. Our observations suggest an initial acclleration of chondrocytic secretory activity, with subsequent retardation of transport. The resultant retention and intracellular polymerization of precollagenous products accelerates hypertrophy, thereby promoting early degeneration of chondrocytes. These ultrastructural alterations are apparently estrogen-specific.

Notes: Abstract A small patch of cells in the epithelium of the anterior surface of the collar of the serpulidPomatoceros caeruleus contains membrane-bound vacuoles filled with crystalline material. The crystals have rhomboidal or rectangular profiles and have been shown by electron diffraction analysis to be composed of hydroxyapatite and calcium magnesium phosphate. The apices of the cells are bordered by microvilli. Some cells also have apical cilia. The cells contain Golgi complexes in the apical cytoplasm. Large numbers of mitochondria are distributed thoughout the cytoplasm. The possible function of these mineral-containing cells as sites for storage of calcium and/or phosphorus is discussed.

Notes: Abstract The organic phase (or crystallite ghost) associated with each crystallite, together with the background material associated with each crystallite cluster, was demonstrated in calcified cartilage using basic chromium sulphate as a combined fixative, stain, and demineralizing agent. Subsequent treatment of the tissue with papain, or with hyaluronidase, suggests that the crystallite ghosts represented a protein-polysaccharide complex and that the background material was principally protein together with some acid polysaccharide. The relationship between inorganic and organic phases is discussed.

Notes: Summary Fractions with 95–98% glomeruli have been obtained from rat kidneys with a sieve method described in detail. 10 different rinsing solutions have been used during isolation and their influence on the ultrastructure of the glomeruli has been controlled electron microscopically. The podocytes exhibit a strong edema of cytoplasm and nucleus, reaching up to cytolysis, after Krebs-Henseleit-bicarbonate-, Krebs-Ringer-phosphate- and Robinson-solution. After a Krebs-Henseleit-bicarbonate solution with pH 7.9 instead of pH 7.4 most podocytes have been damaged irreversibly. A satisfying ultrastructure resulted after solutions with a higher colloid osmotic pressure or osmotic pressure. The best results have been obtained with Krebs-Henseleit-bicarbonate solution pH 7.4+3% dextran (mol wt 40000), after which about 60% of the podocytes have been calculated to be intact. 40% of the podocytes in this fraction mainly were mechanically damaged. While endothelium and mesangium show only minor structural aberrations after the different rinsings, thus most podocytes are damaged irreversibly after Krebs-Henseleit-bicarbonate pH 7.9, and on the other hand about 60% may be intact after Krebs-Henseleit-bicarbonate pH 7.4+3% dextran.

Notes: Summary The cecum of germfree rats, as studied by light microscopy and scanning and transmission electron microscopy, differs in many respects from the cecum of conventional rats. Epithelial cells in germfree rats are taller and have larger nuclei and longer microvilli than similar cells in conventional rats. The cecal mucosa of germfree rats shows a larger variability in the arrangement of the crypts of Lieberkühn than does the mucosa of conventional rats. Some crypts are funnel-shaped and connected close to the mucosal surface with adjacent similar crypts to form long valleys. Less wide crypts open on elevated regions of the mucosal surface. The lamina propria of germfree animals is devoid of plasma cells but rich in mast cells. Germfree animals show hypertrophy of the tunica muscularis externa. In conventional rats the cecal lumen contains a large variety of morphologically different bacteria. However, the lumen of the crypts of Lieberkühn contains only one type of elongated bacteria, which are present in large amounts. This finding suggests that symbiotic relations may be of particular importance in the crypts of Lieberkühn in the cecum.

Notes: Summary The temporal organ of Scutigerella immaculata is situated in a pit just behind of the antenna. The pit represents an epidermal invagination. It is coated by cuticle and corresponds to the outside by a circular opening. More than half of the pit is filled up with a complicated network of branching and anastomosing cuticular protuberances. The cuticle of the protuberances is very thin and perforated by tiny pores. There are about ten sense cells situated under the pit, each of which forms a distal as well as a proximal process. Each distal process shows two ciliary structures. After branching they enter the cuticular protuberances and branch inside of it, as well. The sense cells are surrounded by glandular sheath cells, in which trichogen and tormogen cells can be distinguished. The secretion product of the sheath cells surrounds the distal parts of the sense cells inside of the cuticular protuberances. By comparison to sense organs of insects it must be presumed that the temporal organ represents an olfactory organ which may also function as hygroreceptor.

Notes: Summary The steps of triparanol (MER-29) action on the ultrastructural organization of the mature Leydig cell and possible antagonistic effects of HCG were investigated. The administration of this compound produces marked ultrastructural effects in the adult Leydig cell. The main action is on membranous structures such as the smooth endoplasmic reticulum, which hypertrophies markedly. It becomes arranged in numerous concentric layers (whorls). These are of different size and shape; a whole series of gradual changes from whorl to dense body with a crystalline pattern can be followed. Other cellular structures which undergo changes after MER-29 are the Golgi complex, the mitochondria and the plasma membrane. Dense bodies appear in large numbers. When HCG is given together with MER-29, it counteracts partially the effect of the latter. When injected in two doses, after four doses of MER-29, the effect of HCG is even more conspicuous.

Notes: Summary The identification and distribution of endocrine cells in embryonic adenohypophysis of Seyllium canicula, and chronology of cellular differentiation and histogenesis of this gland have been investigated in this work. More clearly than in the adult, the presence of four populations of endocrine cells, each one located in a different lobe, is demonstrated. Secretion granules of rostral lobe cells are glycoprotidic, their modal diameter is 170 nm; median lobe ones, of same dimensions, are protidic or polypeptidic. The nemo-intermediate lobe big granules (modal diameter: 260 nm) are glycoprotidic, the ventral lobe small granules (modal diameter: 120 nm), protidic or polypeptidic. At stage 10 mm, Rathke's pouch cells are recognized from stomodeal epithelium by enigmatic inclusions, the “odd bodies” of Schechter. At stage 35 mm, preoptic and tuberal nucleus cells include neurosecretory granules of same diameter varying about 100 nm. At this same stage, granules appear simultaneously in the four hypophyseal lobes, including the neuro-intermediate lobe where no neurosecretory fiber is present. Direct innervation of endocrine cells of this lobe is accomplished at stage 45 mm and is accompanied by changes of granules dimensions. The end of embryonic development is characterized by increasing granular load of endocrine cells.

Notes: Summary The taste buds of the barbels of Corydoras paleatus have been studied with the electron microscope. Each taste bud is composed of two cell types: receptor cells and supporting cells. The supporting cells extend from the base of the taste bud to the surface where they bear microvilli. The apex of the uniform, spindle shaped receptor cells has a free, cone-shaped appendage. The receptor cells, unlike the supporting cells, contain numerous mitochondria, peripherally-located vesicles, and two types of tubuli. Single axons project from a nerve plexus close to the base of the taste bud and run to perikarya of the receptor cells. Frequently bundles of tubuli lie close to the area of contact between axon and receptor cell membranes. Most of the taste buds contain individual degenerating cells. A special type of secretory cell is present in the epithelium of the barbels.

Notes: Summary The ultrastructure of spermatogonia and spermatocytes of Lithobius was studied. The spermatogonia show a nucleus with dispersed chromatin and a compact nucleolus. Their cytoplasm contains free ribosomes and polysomes; mitochondria and dictyosomes are not abundant. During spermatocyte growth, nucleus and cytoplasm increase markedly in volume. The dispersion of the chromatin is more pronounced; the nucleolus shows frequent budding. Ribosomes, mitochondria, dictyosomes and endoplasmic reticulum are very numerous. New structures are (1) accumulations of concentric reticular saccules with a cytoplasmic center, (2) piles of narrow cisternae originating from the regular endoplasmic reticulum or from concentric saccules. The synthetic activity during spermatocyte growth manifests itself by (1) numerous signs of nucleo-cytoplasmic exchanges, (2) an increase in the number of mitochondria and ribosomes, (3) a high activity of the Golgi apparatus. This is probably related to the gigantism of spermatocytes in Chilopoda.

Notes: Summary The cavity receptor organ (previously X-organ or organ of Bellonci) of Artemia salina consists of ciliated neurons whose cilia protrude into a cavity beneath the cuticle. The neuronal dendrites penetrate a giant accompanying cell and epidermal cells before entering the cavity. The cavity beneath the cuticle, the ciliated neurons and the connexion with the medulla terminalis justifies a homologization with the frontal filament organ of cirripeds and the third unit of copepods. The term cavity receptor is suggested for this organ. It is hardly homologous with the second unit of copepods and the organs described for many malacostracans under the names of sensory pore X-organ or organ of Bellonci. The latter organs are very similar to the cavity receptor but have an internal cavity formed by glial cells. The cavity receptor organ was previously considered neurosecretory but in the light of the present knowledge it is rather sensory although a double function cannot be denied.

Notes: Summary A tubular network was found in the terminal endings of the visual receptor cells in the human, the monkey (Macaca mulatta), the cat and the dog. These tubules are arranged in close groups in the vicinity of the synaptic lamellae and the invaginated dendrites. According to the form, diameter, density of the tubules and to the consistence of the network formed by them one can distinguish at these places an initial type (type I), a transitory (type II) and a vesicular one (type III). In the the type III branching, bizarre forms are frequent. The diameter of all the tubules reaches 500–600 Å, their density and walls being the same as in the synaptic vesicles. Similar networks also occur in the axons of the visual receptor cells of the monkey.

Notes: Summary “Buffy coats” of normal human peripheral blood were fixed in 2.5% glutaraldehyde (buffered with 0.1 M Na-cacodylate, pH 7.3) and incubated with a mixture of osmium tetroxide and zinc iodide (pH 5.2) after the method of Maillet (1959). Utilizing an electron probe microanalyser (Siemens), the authors demonstrated the presence of osmium and zinc in the specimen, whereas the presence of iodide could not be proved with certainty. The ratio of osmium and zinc in the precipitates ranges from 3/2 to 4/1. Electron microscopic studies of the leukocytes have lead to the following results: the Golgi apparatus, the perinuclear cleft and the endoplasmic reticulum (ER) of all types of leukocytes are strongly impregnated with osmium/zinc, whereas the matrices of the mitochondria are less impregnated. Osmium/zinc precipitates have also been detected in the lysosomes of monocytes and plasma cells. No reaction was evident in the leukocytic granules or centrioles. The presence of lipid droplets in eosinophils has been demonstrated. These droplets show a dense homogeneous osmium/zinc impregnation which reaches its maximum after 40 minutes of incubation, compared with much longer incubation times (5–6 hours) for other cellular components. Setting the pH of the osmium tetroxide-zinc iodide solution to 6.2 resulted in a dense impregnation of the “externum” of the eosinophilic granules. At this same pH, the perinuclear cleft, Golgi apparatus and mitochondrial matrix did not show a definite reaction. The extent of impregnation of the lipid droplets of the eosinophils showed no dependency on pH. Care must be taken when a stain containing uranyl acetate is used since this substance dissolves the Os/Zn precipitates. Exposure of the precipitates to the uranyl acetate for longer than 2 minutes results in gradual dissolution within complete dissolution in 10 minutes.

Notes: Summary Sections of undemineralized tooth germs ofAmbystoma andTriturus were examined. The ultrastructure of early germs, both larval and adult, and of dentinogenesis, resembled that of mammals. In adult bicuspid teeth, once the dentine of the cusps was mineralized, mineral crystals of a similar size to early mammalian enamel crystals, appeared between the dentine and the inner dental epithelium (i.d.e). Concomitantly, the i.d.e showed features of mammalian secreting ameloblasts. This new layer, regarded as true enamel, lacked collagen, possessed an ordered arrangement of crystals and reached a maximum thickness of 6 μm. In larval monocuspid teeth, once dentine mineralization had reached the plasma membranes of the i.d.e at the tip of the cusp, the i.d.e developed a ruffled border. At this stage the dentine of the tip, regarded as enameloid, was very hard and difficult to section. The ruffled border, characteristic of other cells which transport materials, was regarded as indicating that the i.d.e was removing organic matter from the enameloid. The differences in development between larval and adult teeth support the concept that there is a change in cellular activity of the i.d.e which occurs during metamorphosis from the larval to the adult urodele.

Notes: Summary The fine structure of the upper tibial epiphyseal plate of the normal guinea pig has been investigated. On morphological and functional grounds this cartilage can be divided into four zones. In all zones the chondrocytes are distributed in an electronlucent organic matrix composed of thin collagenous fibrils and small non-membrane-bounded granules representing proteoglycans. 1. The reserve cell zone consists of a primitive type of hyaline cartilage. The cells have a very high nucleo-cytoplasmic ratio. The endoplasmic reticulum is the most developed cellular organelle. 2. In the proliferative zone the flattened cells are arranged in distinct columns. The endoplasmic reticulum and the Golgi complex are prominent. Mitochondria and lysosomes are more numerous than in the reserve cells. Extracellularly, the collagen fibrils are brought together in longitudinal and transversal septa. 3. In the hypertrophying zone the cells are more rounded and the pericellular zones wider than in the preceding zones. The endoplasmic reticulum contains dilated cisternae. The Golgi complex includes many large vacuoles. Mitochondria and lysosomes are more abundant than previously. 4. There is a progressive mineralization of the longitudinal septa in the calcifying zone. Within the cells the amount of endoplasmic reticulum is decreased. Its cisternae mostly are short, rounded, and non-continuous. The Golgi apparatus is poorly developed, and the mitochondria few.

Notes: Summary The rostral zone of the intermediate lobe of the mouse hypophysis can clearly be distinguished from the other lobes of the adenohypophysis, especially from the pars tuberalis and the remainder of the intermediate lobe. It consists almost exclusively of corticotrophic cells which show reactive changes after adrenalectomy. The hypophysial stalk is entirely surrounded by this zone; laterally it forms large cell aggregations which extend dorsally as thin cell strands. The corticotrophs are also found within the hypophysial stalk which they invade along the blood vessels; frequently they are dispersed among the typical cells of the intermediate lobe, especially along the neural lobe and the hypophysial cleft.

Notes: Summary The development of the external zone of the median eminence of the mouse was studied in the electron microscope. The examination follows the development of the embryo from the 15th day of the gestation period and the juvenile growth until 24 days of age. Single terminals of the tubero-infundibular neurons of the external zone were found to extend to the outer basement membrane of the perivascular space of the portal primary capillary plexus in the 16 day-old embryo. In the 18 day-old embryo a narrow external zone has developed. Organization of the external zone into the adult pattern is accomplished at the age of three to four weeks. Small agranular as well as large granular vesicles are present in the tubero-infundibular nerve terminals even in the 16 day-old embryo. Changes in the organization of the nerve endings along the outer perivascular basement membrane in relation to the ependymal vascular feet were considered.

Notes: Summary Investigations of the fine structure of blood eosinophils of seven clinically healthy “Toulouse”-geese (Anser anser dom.) reveal striking differences between these cells and the heterophils. The eosinophils are characterized by an oval or nearly round profile. The nucleus contains chromatin mainly concentrated in dense chromocentres. Mitochondria turning into osmiophilic granules, vacuoles, multivesicular bodies, and microfilaments are prominent cytoplasmatic elements. Typical cytoplasmic organelles are numerous elliptic, oval, or round osmiophilic granules, frequently containing a nearly bacilliform internum. The internum possesses a substructure of parallel arranged dense bands, until now observed only in mammalian eosinophils. The ultrastructural and biochemical characteristics imply that the internum-containing granules of the eosinophils represent a state of an ionotropic, microheterogeneous gel and not that of a cristalloid body. The appearence of membraneous, vesicular, and tubular structures in the internum of several granules may be an equivalent of a certain phase of development.

Notes: Summary Following a previous light microscopic morphological and histochemical investigation the rectal gland of rabbits was studied by electron microscopy. The results are as follows: 1. The rectal gland of the rabbit consists of tubuli. Its secretory cells are cuboidal and columnar elements with prominent apical cytoplasmic caps and protrusions extending into the glandular lumen. 2. Swollen cellular apices and protuberances apparently being pinched off—equivalents of an apocrine extrusion—are described. These structures do not represent artefacts caused by fixation. 3. Examination by electron microscopy indicated that there is a marked number of light and dark secretory granules in the apical parts of the cells. 4. Mitochondria, arrays of granular endoplasmic reticulum and Golgi complexes are fewer than in other skin glands of rabbits. 5. An interesting observation is the presence of numerous lamellated bodies and big cytolysosomes.

Notes: Summary The ultrastructure of unfertilized and fertilized egg investments ofPomatoceros triqueter is described. A characteristic feature is the presence of a hitherto unrecorded additional investment layer, inserted between the chorion and the “outer border layer”, which is referred to as the intermediate layer. The fertilization reaction consists of the release of cortical granule material into the perivitelline “space”, and the severing of the microvillous cytosome to “outer border layer” connections, thus allowing an increase in the width of the perivitelline “space”. More ridged corrugations are found on the outer surface of the investments in the fertilized as compared with the unfertilized condition.

Notes: Summary In Drosophila melanogaster, different electron-dense substances injected into larval hemolymph are transported to the lumen of renal tubules by all four segments of the renal tubules. In the initial segment, responsible for primary urine formation, 3-hydroxykynurenine, gold chloride, colloidal silver, and hemoglobin are transported by “cytopempsis”: here all substances penetrate the basal membrane, are concentrated in large basal folds of the cell membrane, and are further transported by vesicles. During transcellular passage, the vesicle contents are concentrated enough to crystallize. Iron polysaccharide, however, is first taken up by the cytoplasm, where it is concentrated and transported to the tubule lumen by newly-formed endoplasmic reticulum. In the other segments, the above substances are similarly transported to the lumen of renal tubules, but in these cases larger complexes of accumulations are formed from basal infoldings of the cell membrane. These complexes are mostly surrounded by a secondary membrane and, probably due to water uptake, may enlarge enormously during passage to the tubule lumen. A secondary membrane is not formed in the case of hemoglobin or gold chloride. During transcellular passage, the osmolality of vesicle contents approaches that of the fluid within tubule lumen. In the lumen of the initial segment the primary urine is mainly crystalline; the concentration is lower in the lumen of other segments. Substances can be detected within the lumen of the main tubule segment as soon as 1 minute after injection.

Notes: Summary The fine structure of receptor and epithelial cells in the retina of the pacific hagfish, Polistotrema stouti, has been investigated and compared with previous observations made in the atlantic hagfish, Myxine glutinosa. The receptor cells in Polistotrema have cylindrical outer segments which consist of numerous discs arranged perpendicularly to the long axis of the cell. Characteristic synaptic bodies (synaptic lamellae) occur at the receptor base. Membranous inclusions in the epithelial cells suggest phagocytosis of outer segments. In Myxine, the outer segments are whorl-like, and synaptic bodies are absent at the receptor base. There are no signs of phagocytosis in the epithelial cells. The results are discussed from a functional and phylogenetical point of view.

Notes: Summary The hemolymph ofAstacus astacus (L.) contains only one cell type, the so-called amoebocyte. It appears, however, in three functional forms which are dependent upon age: The clotting cell, the phagocyte and the granular amoebocyte. The young clotting cells are characterized by large numbers of granules containing a tubular internal structure. It is suggested that these granules are the storage site of a hemagglutinin. Small vesicles are situated in the perinuclear cisterna and the periphery of the clotting cells contains cytoplasmic microtubules. The clotting cells are very fragile and their cytolysis accelerates the clotting process of the hemolymph. In the phagocytes initial stages of the formation of membrane bounded inclusion bodies are to be found, which later in the granular amoebocytes, take up most of the cytoplasmic space. It is supposed that these inclusions are involved in the synthesis of hemocyanin.

Notes: Summary The postnatal development of the rat prostate has been studied with the electron microscope. Major developmental changes begin during the second week after birth and involve organelles associated with the formation of secretions. The amount of granular endoplasmic reticulum and the size of the Golgi complex increase greatly. Large vacuoles that probably contain secretory material are formed, and the lumen of the prostatic acini appears to contain secreted material. Large lysosomes with polymorphic interiors are present as early as 10 days after birth, and they become numerous by the end of the third week. Differences in fine structure between the different lobes of the prostate are detectable in 10–14 day old rats. The subsequent differentiation of the granular endoplasmic reticulum into the forms characteristic of the different prostatic lobes is described. The initial changes in the prostate occur in advance of sexual maturity of the animal, and the adult appearance of the gland is attained by 4–5 weeks after birth.

Notes: Summary The organ of Bellonci in Sphaeroma serratum comprises principal cells which consists of a cell body and an outer segment connected by a ciliary piece. The outer segment is prolonged by bundles of very long microvilli which are free in the central lumen, whereas the cell body is bounded by flat bordering cells. In the cell body there are large electron-dense spheres and a lot of granules, the latter appearing to be glycogen according to results obtained with light and electron microscopical cytochemical methods. These substances are released in the central lumen. The principal cells have not the fine structure of neurosecretory but of sensory cells. They may be photosensitive or chemosensitive elements. These results set the problem of the homology of the organs named “of Bellonci” seen in various groups of Crustacea.

Notes: Summary The neurons of the infundibular nucleus of the chicken are multipolar, partly bipolar. Part of the ventricular processes of the nerve cells passes by between the ependymal cells into the cerebrospinal fluid where they form globular, intraventricular nerve endings (diameter about 3,5 to 5,5 μ). The liquor contacting nerve endings (LCNE) contain numerous mitochondria, endoplasmic reticulum, polyribosomes, granulated vesicles (diameter about 1300 Å) and scattered microtubules. The intraventricular terminal bears a cilium (type 9+0), its basal body gives rise to slim rootlet fibres. Sometimes, free liquor cells occur on the LCNE. The ventricular nerve processes that build up the LCNE are dendrites. In the hypendymal synaptic zone, axons containing granulated vesicles (1000 Å, 1300 Å) form synapses with the ventricular dendrites. The perikarya of the nerve cells are characterized by an abundant endoplasmic reticulum, polyribosomes, Golgi areas, mitochondria, granulated vesicles (diameter about 1300 Å) and numerous axo-somatic synapses. In the region of the infundibular nucleus, two types of ependymal cells can be distinguished: light and dark cells. The apical part of the latter forms several smaller and larger cytoplasmic processes. The light cells bear numerous cilia (type 9+2). On the basis of the new morphological data, the possible function of the liquor contacting neurons of the infundibular nucleus is discussed.

Notes: Summary The antennae of Scolytus multistriatus were examined with light and scanning and transmitting-electron microscopy to determine the distributions, types and structures of sense organs. Four types of sensilla were found: (1) sensilla chaetica, a singly-innervated receptor; (2) sensilla basiconica, Type A, a short, thin-walled, multiple-innervated receptor; (3) sensilla basiconica, Type B, a long, thin-walled multiple-innervated receptor; and (4) sensilla trichodea, short, thick-walled, multiple-innervated receptors. The positioning of dendrite(s) with regard to pore tubules is elaborated. Evidence for lack of sensory axon fusion is presented.

Notes: Summary The paired maxillary nephridia of Polyxenus lagurus were studied by light and electron microscopy. 1. Each maxillary nephridium is subdivided into three segments, viz. lateral sacculus, tubule and duct. 2. The sacculus has the shape of a flattened pyramid. Tendons, mostly of collagenic fibers, are attached to its edges. The sacculus is stretched at the sides of the head capsule between occiput and gena by muscles inserting at the tendons. 3. The cells of the sacculus are flattened and enclose a wide lumen. They represent typical podocytes with basal pedicelli, and contain numerous pinocytotic vesicles and other vacuoles. 4. The cells of the coiled tubule bear at their luminal surface a fringe of microvilli. Their bases are characterized by many infoldings. Numerous mitochondria and transparent vacuoles are situated between the folds. Due to the infoldings the nuclei are located in the apical portions of the cells. Here also many lysosomes and lipid droplets occur. Septate desmosomes are frequently differentiated between adjacent tubule cells. 5. At the distal part of the gnathochilarium the tubule transforms into the outleading duct. Both ducts terminate separately close to the median body plane in front of the sense bolsters of the gnathochilarium. No cuticular intima of the lumen can be found. This finding corresponds to the theory of the mesodermal origin of the duct as well as of the whole nephridium.—The results are compared with published data on the structure of nephridial organs in the head of other arthropods.

Notes: Summary The Excretory organ (H-system) of Ascaris lumbricoides has been investigated electronmicroscopically. In adult animals this single-cell-organ embedded in the lateral lines extends from the nerve ring to approximately the middle of the body. In the second quarter of the body it lacks a continuous canal lumen, and it seems to be degenerated. In all of the other regions (except the stem leading to the excretory pore) it consists of two zones. The inner zone lining the canal lumen contains several extraplasmatic spaces; at least those placed the farthest inside communicate with the canal lumen. The outer cell membrane shows many infoldings, some of which extend deeply into the cytoplasm. The tissue of the lateral line adjacent to the canal system contains very many intercellular spaces which build a coherent intracellular “rainage”-system. Experiments have been performed in order to localize the ATPase activity histochemically. Possible mechanisms for the forming of the excretory fluid are discussed under consideration of physiological results already published.

Notes: Summary Selected tarsal bristles of the tick Amblyomma americanum (L.) (Acarina: Ixodidae; nymphal stage) were studied by means of scanning and transmission electron microscopy. All sensilla are multi-innervated and have thick cuticular walls containing either an elaborate pore canal system or a single slit opening at the tip. These sensilla, often equipped with two mechanoreceptive dendrites attached to the bristle base, apparently serve a dual function: mechano- and chemoreception. The fine structure of each sensillum is similar to that of other arthropod setae except for the ciliary region of the dendrite. Instead of the common 9 double-tubules, the tick sensilla usually have 11 (“11+0”). Compared to insect or spider tarsal bristles, tick setae are less abundant but more complex in structure and of greater variety.

Notes: Summary According to light microscopical studies glomerula and proximal convoluted tubules of the elasmobranch kidney are characterized by structural peculiarities, which possibly are related to the physiological uremia of this group of animals. In order to obtain morphological fundamentals for cytochemical and physiological studies, the authors have investigated the above mentioned parts of the nephron with the electron microscope. The results are as follows: 1. The remarkable thickness of the glomerular tufts in the elasmobranchs—averaging 7 μ—is due to the presence of a cell-rich layer (diameter about 6 μ) between podocytes and endothelium. 2. The podocytes bear individual cilia protruding into the capsular space. They further contain bundles of fine filaments (diameter approximately 80 Å) which possibly are myofilaments. Between the feet of the podocytes slit membranes occur on the surface of the basement lamina. 3. The medium layer of the vascular wall corresponds to a strongly thickened basement lamina, into which besides collagen fibrils and fuzzy material different cells are embedded. The majority of these intralamellar cells consists of branched elements the processes of which spread inside the membrane. In contrast to earlier statements, which were based on light microscopical observations, these cells are interpreted to represent fibrocytic elements and not smooth muscle cells. A second intralamellar cell type which does not possess any processes, is marked by well developed cisternae of rough endoplasmic reticulum. 4. The relatively thick endothelium of the glomerular vessels possesses a rugged surface, its pseudofenestration beeing less regular than in glomerular capillaries of higher vertebrates. 5. Vesiculated spherical bodies, swollen cellular apices and protuberances apparently being pinched off in the proximal convoluted tubule—possibly equivalents of an apocrine extrusion—are described. The authors are of the opinion that these structures do not represent artifacts caused by fixation. It remains on open question, whether this extrusion contributes to the composition of the tubular urine. 6. The “Basalreifen” of the kidney tubule as have been described by light microscopists, correspond to crests of the inner surface of the basement lamina, the “basale Kittfäden” to the strips of cytoplasm between these “Basalreifen”.

Notes: Summary Light and electron microscopic techniques were employed to study the distribution and intensity of the non-specific alkaline phosphatase activity in the epithelium of the three forestomachs of the goat. The effects on the enzyme reaction of different fixatives, prefixatives, and incubation times were determined. Alkaline phosphatase was found to be present only in the stratum corneum, stratum granulosum, and stratum spinosum superf. of each of the specimens. Different prefixation of the specimens, either by formol calcium (24 h), glutaraldehyde (2, 5, 30, 120 min), or osmium tetroxide (2 or 5 min) had no influence on the distribution of the enzyme and the intensity of its reaction. Maximal intensity of the reaction was obtained after an incubation period of 10 min at room temperature, as seen with the light microscope. To demonstrate the enzyme in sections in the electron microscope, an incubation period of 5 min at 4° C was found to be optimal. The products of the enzyme reaction were located on cell membranes and in cell particles. The “membrane-bound” reaction products in the specimens prefixed with glutaraldehyde were found on the outer surface of the plasma membrane; after a short prefixation with osmium tetroxide (3 min), they appeared on the inner surface of the plasma membrane.

Notes: Summary Ultrastructural changes in the micro- and macronucleus throughout division were followed in synchronized cultures of the suctorian, Tokophrya infusionum. After an initial swelling, the micronucleus elongates enormously; microtubules within the micronucleus proliferate and lengthen as the micronucleus elongates. Changes in the macronucleus become visible only after micronuclear division is well underway. The chromatin bodies fuse into long chromatin strands, and the large bundles of microtubules present in the resting macronucleus break up into small groups which parallel the chromatin strands. Colchicine, which prevents reproduction in Tokophrya, seems to block division at a very early stage. The macronucleus appears the same as the resting nucleus of untreated organisms, with numerous microtubules and distinct chromatin bodies. The chromatin in the micronucleus aggregates into large clumps, however, and proliferation of microtubules does not occur.

Notes: Summary First the granulosa cells establish close contact with the plasma membrane of the oocyte. Then, the zona pellucida separates them. The oocyte acquires numerous microvillosities, and an intensely active micropinocytosis is observed in the ovocytic invaginations. Granules originating in the theca externa pass through the intercellular spaces of the granulosa and invade the zona pellucida and the invaginations of the oocyte. At the level of these invaginations, coated vesicles incorporate granules and form granular vesicles without coating. These granular vesicles are transformed into cortical vitelline spheres. The nutritive function, generally assigned to the pyriform cells, is not confirmed in this study. The great development of the Golgi apparatus in these cells suggests a secretory function. Perhaps the pyriform cells secrete the amorphous component of the periovocytic space.

Notes: Summary In each ommatidium of the meal moth a retinula is formed from a varying number (9–12, mostly 11) of elongated, prismatic sense cells. In addition, a basal retinular cell is situated near the basement membrane in the center of the other (“distal”) retinular cells. The axis of the retinula is occupied by many microvilli forming the axial structure, the distal section of which is the slender “axial thread”. Proximally, the axial structure widens (to 8.5 mμ instead of 1 μm in diameter) and is now called rhabdom. Cross sections of the rhabdom mostly look like a petaloid with four petals; this figure is due to longitudinal infoldings along the length of the rhabdom surface. The rhabdom cross section is subdivided into several brushes of microvilli (“rhabdom sectors”), each one being characterized by an approximately parallel arrangement of its microvilli. One rhabdom sector may be composed of one or two rhabdomeres respectively. The basal retinular cell participates in rhabdom formation through a small brush of microvilli at the proximal end of the rhabdom. Proximally, the distal retinular cells taper into slender neurites which are embedded in grooves at the surface of the basal retinular cell and the tracheal end cell respectively. One tracheole piercing the basement membrane together with the neurites of one retinula branches into about 30 tracheoles surrounding the retinula. The crystalline cone cells touch the cornea; proximally, their cytoplasm forms a point which eventually terminates amongst the distal tips of the retinular cells, immediately at the axial thread.—Our work was restricted to light adapted eyes; in this condition, light transmission in the distal part of the retinula seems to be blocked by retinular cell pigment except inside the axial thread.

Notes: Summary This research was undertaken in order to determine if known biochemical processes involving the conversion of fluoroacetate are reflected morphologically at the electron microscopic level. No changes were observed in the hepatocytes after 2.5 mg/kg of fluoroacetate and sacrifice at 3 hours, but with 5 mg/kg of the drug there was an increase in the amount of agranular endoplasmic reticulum, an aberrant shape of mitochondria, and a disappearance of visible glycogen. One hour after 10, 15, 20, or 30 mg/kg of fluoroacetate the results showed a tremendous increase in the amount of agranular endoplasmic reticulum, an aberration in mitochondrial structure, and a disappearance of the intramitochondrial granules and glycogen. The possible relationship of these changes to fluoroacetate poisoning is discussed.

Notes: Summary In this study the ultrastructural features of tissue from the posterior hypothalamic area were investigated. Ovariectomized cats which were either treated with sesame oil placebo or with estrogen for varying periods of time were used. The following observations were noted. 1. The cat that was treated with placebo one month after ovariectomy showed an increase in the number of dense core (granulated) vesicles within neuronal cytoplasm. This observation was not apparent in the cats which were treated with estrogen one month after ovariectomy. 2. In the cat that had been Ovariectomized for two months before treatment with placebo was initiated, axon terminals contained more dense core vesicles than were observed in axonal endings from estrogen-treated cats in the two month ovariectomy group. 3. The tissue from cats that were continuously treated with estrogen for one month after ovariectomy displayed dense-core vesicles in both somata and neuropil. It is suggested that the ultrastructural changes observed were dependent on both the time of initiation and the length of estrogen treatment. 4. It is concluded that the preliminary observations in this study provide anatomical evidence suggesting that estrogen level in the cat may affect the functional activity of the posterior hypothalamic area.

Notes: Summary Fifteen ring canals or intercellular bridges connect the oocyte and 15 nurse cells in Drosophila. Recently, Koch and King (1969) proposed that these ring canals formed independently of a cell furrow and that cytokinesis during the 4 cell divisions producing the 16 cells occurred through fusion of vesicles aligned along the division plane. Serial sections of germaria, fixed with glutaraldehyde, have been studied with the electron microscope, and no evidence has been found for fusion of vesicles in the cleavage of cells. The probability that the chromate-OsO4 fixation used by Koch and King resulted in an artifact is discussed.

Notes: Summary The cellular organisation of the osphradium of Planorbarius as revealed by the previously described light microscope studies is confirmed in the present study. A third epithelial cell type, the basal cell, is described. Perception is carried out by dendritic processes from osphradial sensory neurones, forming free nerve-endings in the sensory region of the osphradial epithelium. Ciliated cells and secretory cells of the osphradial epithelium are concerned with the transport of material in the osphradial canal. Many of the ultrastructural features of molluscan central ganglia are present in the osphradial ganglion, including inter-axonal chemical synapses. Neuromuscular junctions are present in the sheath surrounding the organ and these may be involved in a behavioural response of the organ. The need for further electrophysiological studies is emphasised.

Notes: Summary The peripheral retina and lamina ganglionaris of Musca domestica have been investigated electronmicroscopically. Peripheral Retina 1. The four Semper cells of each ommatidium form thread-like processes which extend proximally through the retinula and end at a level just distal to the basement membrane. 2. Rhabdomeres No. 1–6 have a conical form, being approximately 2 μ in diameter at the distal ends and 1 μ at the proximal ends. The consequences of this special shape are, a) that the mean number of absorbed quanta per volume unit remains approximately constant throughout the length of the rhabdomeres and, b) that about half the amount of photopigment per rhabdomere compared with a cylindrical rhabdomere of 2 μ diameter is adequate in order to allow the same total absorption. In contrast to the above, rhabdomeres No. 7 and 8 have a diameter of about 1 μ throughout their length. 3. The spatial arrangement of the rhabdomeres in Musca domestica is of a definite rotationally asymmetrical pattern. This pattern is not universal in Dipterans as is witnessed by the rotationally symmetrical pattern found in a more primitive species, Wilhelmia equina (Simuliidae). The microvilli in the distal ends of Musca rhabdomeres are oriented in a specific manner, whereby their long axes are parallel in rhabdomeres No. 1 and 4, 2 and 5, and 3 and 6 respectively. 4. Pigment granules within retinula cells No. 1–6 migrate to the bases of the microtubules upon bright adaptation. No pigment migration is observed in retinula cells No. 7 and 8. Migration of particles has been previously proposed as a protective mechanism for rhabdomeres No. 1–6 during bright illumination. Lamina Ganglionaris 1. Pour monopolar neuron somata have been found distal to each optical cartridge in the lamina. The four fibers of these neurons form a bundle and enter the crown of photoreceptor cell axon terminals. Two large diameter fibers which are derived from two type I somata form the central second order neurons, L1 and L2 in each cartridge. The two small diameter fibers, L3 and L4 withdraw between the photoreceptor axon terminals R5 and R6 to a point on the periphery of the cartridge where they remain throughout the lamina. L4 sends a short collateral back into the base of its parent cartridge. 2. Paired centrifugal fiber endings are located between receptor axon terminals on the periphery of each cartridge. In medial and proximal sections through the cartridges there is one pair of centrifugal endings per receptor axon terminal. The pair of centrifugal endings located between axon terminals No. 5 and 6 bifurcates distally so that L3 and L4 are surrounded by two pairs of centrifugal endings as they withdraw from the center of the cartridge. 3. The following cell contacts, which appear to be synaptic in nature, have been observed between various fibers within the cartridges and are characterized by the presence of a T-shaped synaptic ribbon and synaptic vesicles within the presynaptic fibers and occasionally by a membranous postsynaptic structure (see the Table and Pig. 33). Commonly, two postsynaptic fibers share one presynaptic site. The receptor axon terminals R1–6 provide synaptic inputs to L1 and L2 as well as to the centrifugal endings α, β. L3 receives an input from at least one of the receptor axons and from one centrifugal fiber. L4 receives an input from a centrifugal fiber and is possibly presynaptic to L1 and L2. The centrifugal fibers make synaptic contact with one another and are presynaptic to small unidentified fibers. Neurons L1 and L2 are also presynaptic to small fibers of unknown origin. Furthermore T-shaped ribbons have been observed within the centrifugal fibers as well as within the receptor axon terminals at points of contact with epithelial glial cells. 4. The epithelial glial cells are arranged in a strict and orderly fashion between the optical cartridges. Throughout most of the eye, each glial cell touches upon exactly three cartridges and each cartridge is surrounded by three cells. Exceptions to this rule occur within the equatorial and marginal regions of the eye. The distal surfaces of the epithelial cells are characterized by extensive outfoldings of the limiting membranes. The greater portion of the cytoplasm is filled with numerous mitochondria and infolded membranes. 5. The mirror image pattern inversion of the ommatidia at the equator in the peripheral retina is projected onto the lamina as witnessed by the location of fibers L3, L4 and R7, R8 in relation to the cartridges. This inversion can also be observed in the arrangement of the epithelial glial cells between the cartridges. 6. Whereas six retinula cell axon terminals are usually found in the cartridges a different situation exists in the equator region of the eye. In this region the cartridges contain seven to eight axon terminals of retinula cells No. 1–6. This agrees with the result that in the equator region seven to eight rhabdomeres No. 1–6 view one and the same point in the environment rather than the usual six rhabdomeres (Kirschfeld, 1967).

Notes: Summary Ultrastructural evidence is presented for the manufacture, storage, and release of a distinctive cellular product in the corpus allatum of the insect Leucophaea. This product (C body material) originates in the Golgi zone and acquires a characteristic, regularly structured appearance of exceptionally high electron density. The differential distribution of this easily identified product in various sites in the organ permits the reconstruction of a sequence of dynamic events involving transport from the intra- to the extracellular compartment which affords access to the circulation. A small amount of (surplus ?) C body material becomes incorporated in multivesicular bodies. The variability in the occurrence, distribution, and fate of the C body material during various periods of the animal's life cycle, and under experimentally altered conditions, suggests a relationship with the glandular function of the corpus allatum. Conspicuous deposits of C body material, especially in the extracellular stroma, parallel situations in which the hormonal activity of the organ seems to be low or temporarily suspended. Thus the ultrastructural manifestations of intermittent sluggishness in the system, as observed in Leucophaea, provide valuable cues for the existence of a periodically changing production line involving a specific glandular material. The precise relationship with the comparable cyclicity of juvenile hormone activity remains to be ascertained.

Notes: Summary 1. There is a gradual proximo-distal increase in the thickness of the muscle coat of the human ductuli efferentes, duetus epididymidis and ductus deferens. Circularly arranged smooth muscle bundles predominate in the ductuli efferentes and ductus epididymidis of the caput section. Scanty strands of longitudinally and obliquely oriented smooth muscle bundles form an additional, incomplete outer muscle layer around the ductus epididymidis of the corpus. Small smooth muscle-like cells constitute the muscle elements of the upper sections of the excretory ducts (from the ductuli efferentes to the midcauda). At the transition of the corpus and cauda epididymidis ordinary large smooth muscle cells join the small contractile cells to form—in more distal sections of the cauda—a composed, thick subepithelial muscle coat. In most distal portions of the cauda, the two-layered muscle coat of the ductus epididymidis is transformed into a three-layered coat, a pattern of construction which is retained in the vas deferens. 2. Electron microscopically, three types of contractile cells are distinguished in the human ductuli efferentes and ductus epididymidis: a) contractile cells of medium transparency containing exclusively thin myofilaments (60 Å in diameter), b) dark contractile cells containing bundles of thin myofilaments (60 Å in diameter) and single coarse filaments (140 Å in diameter), c) light contractile cells with loosely dispersed, interweaving thin and thick myofilaments. Commutual diameter changes at regular intervals are seen in individual myofilaments, giving the impression of structural periodicity not unlike that of filaments of striated muscle. Ordinary smooth muscle cells of the cauda epididymidis and vas deferens are characterized by uniformly sized, closely packed but evenly distributed thin myofilaments with numerous dense patches. 3. Fluorescence microscopy performed on formaldehyde treated freeze dried tissues reveals that the contractile cells of the ductuli efferentes in man and monkey receive a low number of single adrenergic terminal fibres penetrating the depth of the muscle coat. The adrenergic innervation of the ductus epididymidis is restricted to small peritubular nerve fascicles running contiguous to the most superficially located bundles of smooth muscle-like cells. The adrenergic ground plexus is rather wide-meshed in the proximal cauda, becomes increasingly dense in more distal cauda sections and in initial, funicular portions of the vas deferens, and reaches maximum density in abdominal parts of the ductus. Perivascular and adventitial adrenergic plexuses are well developed at arteries of the caput and corpus epididymidis in man, monkey, rabbit, guinea-pig and rat. 4. Electron microscopically, noradrenergic nerves have been identified by the presence of small granular vesicles in preterminal varicose axon dilatations. Nerve fibre swellings filled with small empty spherical vesicles have been considered to belong to “cholinergic” neurons whereas occasional varicosities equipped with some large membrane bound granules and abundant mitochondria may represent local expansions of sensory axons. 5. Neuromuscular relationships in the upper sections of excretory ducts comprise adrenergic synapses by distance (more than 1000 Å), and a few intimate, ensheated close contacts, whereas the main type of contact of nerves to ordinary smooth muscle cells in the lower duct section is by means of close but not intimate approach (500–2000 Å). 6. Adrenergic synapses in the ductus epididymidis and ductus deferens of the monkey resemble—what concerns their morphology, relationship to effectors and distribution pattern—those of man. 7. In accordance with the total number of vascular and non-vascular adrenergic nerves, visualized by fluorescence microscopy, the amount of noradrenaline varied considerably in different sections of the human male internal genital organs: The lowest amounts were estimated in the testis (0.12±0.03 μg/g). Medium to high concentrations were detected in various sections of the caput and corpus epididymidis (ductuli efferentes 0.60±0.09 μg/g; ductuli efferentes and caput 0.72±0.13 μg/g; corpus epididymidis 1.04±0.25 μg/g; proximal cauda 0.95±0.17 μg/g; distal cauda 0.97±0.19 μg/g). The highest noradrenaline content was found in the human vas deferens (prox. vas deferens 1.11±0.21 μg/g; interm. vas deferens 1.20±0.42 μg/g; distal portion 1.43±0.39 μg/g). 8. For comparison, the noradrenaline content of the testis and epididymis of the rhesus monkey, the epididymis of the rabbit and the vas deferens of the rabbit, mouse, guinea-pig and rat has been determined. 9. Adrenaline of exogenous origin was detected in the vas deferens, cauda epididymidis and plexus pampiniformis of two cases who received this catecholamine as part of the local anaesthetic drug mixture. Due to methodological reasons, the presence of small amounts of adrenaline of endogenous source in adrenergic nerves of the human and monkey internal male genital organs cannot be excluded. 10. The differences in motility behaviour of the ductus epididymidis (spontaneous, rhythmic contractions) and ductus deferens (absence of any spontaneous movements under conditions at rest) in vivo and in vitro have been correlated with the occurrence of specialized contractile cells in the upper segment (ductuli efferentes, ductus epididymidis of the caput, corpus and initial cauda) and ordinary large smooth muscle cells in the lower segment (ductus epididymidis of the distal cauda and the vas deferens) and furthermore correlated with differences in the pattern of the adrenergic innervation; the concept is advanced that progressive cytological differentiation of smooth muscle cells and the development of a dense direct adrenergic innervation suppresses autocontractility and, that the reverse condition may favour spontaneous motility of smooth muscle elements.

Notes: Summary The muscular layer of the fish oesophagus is made up exclusively of striated muscles, which form a circular and a longitudinal layer. The intestinal muscular layer of the tench, which is an exception among the vertebrates in this respect, consists of two layers of striated muscles and a layer of smooth ones. The organization of striated muscle fibres is described from the muscular layer of the alimentary canal in four species: the tench, crucian carp, gudgeon and stone-loach. The fibres of the oesophagus differ from each other in diameter, length of sarcomeres, glycogen content and, in the case of one species, organization of SR. On the basis of the organization of sarcomeres all the fibres examined must be counted among the slow-contracting ones (broad Z line). The sarcoplasmic reticulum is organized according to the Z type except for the fibres of the oesophageal muscles in which the SR represents the A-I type. Two types, “en grappe” and “en plaque”, of nerve endings have been observed. The presence of relatively large dense core vesicles seems to indicate their adrenergic origin.

Notes: Summary Light- and electron microscopical studies were carried out to demonstrate ATPases activated by Mg++, by (Mg++-Na+-K+), and by Ca++. Histological sections showed clear differences of the activity of Mg++- and Ca++-stimulated ATPases in the light microscope in different layers of the epithelium as well as in different areas of the forestomach. The deeper layers reacted more intensely than the superficial ones. The intensity of the reaction (which depends on incubation time) in the omasal epithelium was stronger than in the lamina epithelialis of the reticulum and much stronger than in the lamina epithelialis of the rumen. In the electron microscope, the reaction products of the ATPase appeared on the outer surface of cell membranes (plasmalemmata). No deposits of the reaction products were observed on those areas of the cell membranes, which are involved in the formation of desmosomes and semidesmosomes. The basal parts of the basal cells were also free from reaction products. As for the distribution and ultrastructural localisation of the deposits, no differences were observed among the ATPase stimulated by Mg++, (Mg++-Na+-K+), and Ca++. Using the technique of Coleman et al. (1967), the cell membranes of ruminal epithelium were isolated. Biochemical assays of the enzymes were carried out. The quantity of cell membranes obtained was 0.3% of the whole homogenate, when compared with 5′-nucleotidase, which is the typical enzyme of plasmalemmata. The biochemical enzyme assays showed that, besides Mg++- and Ca++-dependent ATPases, a (Na+-K+)-dependent transport ATPase exists in the cell membranes of ruminal epithelial cells.

Notes: Summary The granulosa thickens by mitotic division of the small follicle cells, without any external contribution. The pyriform cells arise from the transformation of certain small cells and show many morphological and cytological similarities with young oocytes. In spite of this resemblance, there is no proof for the germinal nature of the pyriform cells. The nucleolus of these cells shows certain peculiarities, and a clear separation of fibrillar and granular components. The physiological significance of the pyriform cells remains to be determined, but they have no duct and their large Golgi apparatus has no relationship with the granules incorporated by the oocyte. The degeneration of many pyriform cells is one of the reasons for the reduction of the granulosa. Some ultrastructural features of this degenerative process are described.

Notes: Summary After a specific time of glutaraldehyde-acrolein fixation, microtubule walls appear to be composed of single 6.5–7.5 nm diameter osmiophilic subunits. Variations in the duration of glutaraldehyde-acrolein and also glutaraldehyde-osmium fixation reveal a two layered wall containing osmiophilic subunits, 4.0–4.5 nm in diameter, arranged radially, in tandem. The double-layered wall is demonstrated by microdensitometer traces. These observations are discussed in relation to previously proposed models of microtubule substructure.

Notes: Summary The utilization of actinomycin D during the regeneration of young and adult Planarians shows that the two groups of animals react differently to the antibiotic. Regeneration takes place in the presence of the antibiotic in young Planarians, whereas it is entirely inhibited in adult ones, applying the same concentration (50 μg/cm3). In the young animals it begins immediately after decapitation. Their return into the water, after a treatment with the antibiotic lasting from 1 to 4 days, does not interfere with the morphological differentiation. The ultrastructural investigation exhibits that in the majority of the undifferentiated cells the nucleolus is largely dissociated. The lesions gradually extend to the whole cell which frequently degenerates. The morphologically undifferentiated cells are weakly impaired (depletion of the granular component of the nucleolus), and they recover a normal structure after their return into water. These results lead us to study the RNA synthesis, during these experimentations, on the whole organism as well as the cellular level.

Notes: Summary An electron-microscopic investigation, based on the suggestion that differences seen in progesterone levels under differing hormonal conditions might be reflected in the ultrastructural organisation of the lutein cells of the guinea-pig was undertaken. Comparisons were made between corpora lutea taken from animals during the normal oestrous cycle, pregnancy and lactation, and after hysterectomy or hypophysectomy. The lutein cells from the oestrous cycle corpus luteum appeared to be of two types, “light” and “dark”. The former were more numerous. The main difference between them lay in the arrangement of the endoplasmic reticulum. Lutein cells from corpora lutea (with the exception of the “old” degenerating corpora lutea) all contained well-developed agranular endoplasmic reticulum, little granular endoplasmic reticulum, several electron-dense lipid granules, lysosomal bodies which ranged from small spherical bodies to large autophagic vesicles and mitochondria. The mitochondria were numerous, and in the corpus luteum of pregnancy, they were closely associated with the parallel arrays of granular endoplasmic reticulum. With minor exceptions, the lutein cells of the guinea-pig present a strikingly uniform picture despite their hormonal condition. The manner in which this uniformity of ultrastructure may be related to observed differences in progesterone levels in the corpus luteum of the guinea-pig is discussed.

Notes: Summary Cytodifferentiation during early spermatogenesis in the calyptoblastic hydroid, Campanularia flexuosa, was studied at the fine structural level. Clusters of spermatogonia-like cells are found in gonangial sporosacs near the mesoglea. Early events in spermiogenesis include: a gradual elongation of the sperm head and nucleus; close apposition of nuclear envelope to chromatin; positioning of four mitochondria at the posterior portion of the nucleus; formation of a single, simple flagellum from a basal body located in the center of the mitochondrial quadrangle; a high degree of Golgi activity, possibly involved in the production of a multiple acrosome complex.

Notes: Summary The ultrastructure of the ocelli of Lithobius forficatus L. was investigated by means of conventional electron microscopy. The dioptric apparatus consists of an unequal biconvex corneal lens which has a lamella-like fine structure. Crystalline cones and special pigment cells are lacking. The eye cup is composed of 35 to 110 sense cells of two different morphological types. The large visual cells of the distal region are characterized by unilaterally inserted rhabdomeres which form in a radial symmetrical arrangement the extended closed rhabdome. The proximal part of the eye cup is occupied by somewhat smaller basal cells of conical shape, showing an indistinct retinula. These cells have numerous microvilli either in the apex region or laterally which interdigitate to form stiltlike double or “multiple” rhabdomeres in close communication to the central rhabdome. In both types of sense cells particular zones appear because of the characteristic distribution of certain cell elements. They are arranged perpendicularly to the optical axis in the large receptors and vertical in the main axis of the basal cells. Elements of ER and other vesicles constitute a “Schaltzone” which borders the microvilli of the rhabdomer. This Schaltzone probably is a functional structure correlated to the adaptional state of the eye. The cytoplasmatic zone contains numerous different multivesicular and few large multilamellar bodies. The functional meaning of the organization of the Lithobius ocellus is discussed.

Notes: Summary Herring bodies in the neurohypophysis of sexually mature Acipenseridae (Acipenser güldenstädti Brand, Acipenser stellatus Pallas) were studied light- and electronmicroscopically. The fishes were taken in nature at different periods of their life cycle. Some of them were kept in 17‰, 22‰, and 32‰ NaCl solution for 1–48 hours before fixation. Herring bodies are large (up to 50 μ) swellings in neurosecretory axons originating in the preoptic nucleus. Most of them are in the terminal portion and are located between the ependymal cells lining the recessus hypophyseus where they protrude into the lumen. Rarely such Herring bodies are situated in the pericapillary space. Two zones, a central and a peripheral, can be distinguished in the neuroplasm of Herring bodies. Mitochondria, neurotubules, and neurofilaments are concentrated in the inner zone; neurosecretory granules, vacuoles, and various osmiophilic inclusions occupy the peripheral zone. Neurotubules may be thin and cylindrical, or swollen and beaded. Neurosecretory granules are either electron dense elementary granules or swollen with a finely granulated content. Some granules show broken membranes. These different types seem to reflect a process of extrusion of neurohormones into the neuroplasm of the ending. Other types of osmiophilic inclusions include dense bodies, comb-like bodies, and lamellar bodies. Vacuoles vary as to their origin, the structure of their membranes, and their size. Synaptic vesicles and residual neurosecretory granules are never observed in these Herring bodies. Seven types of Herring bodies can be distinguished ultrastructurally in the Acipenseridae studied. They differ with respect to the presence and relative frequency of the different structural components mentioned. Transitional forms between these types of Herring bodies are found. The plasmalemma of some Herring bodies protruding into the recessus hypophyseus is destroyed. It is suggested that at these sites neurohormones are released by the macroapocrine type of secretion. The functional significance of different inclusions in the Herring bodies of Acipenseridae are discussed.

Notes: Summary The midgut cells of workers, queens and males of the ant Formica polyctena show cytological characteristics which were studied in the course of postembryonic development and annual cycle. The microvilli of the regenerating cells appear before the elimination of the regressing larval and pupal cells. At the time of pupation, an active phase of apocrine secretion begins in the dorsal part of the midgut epithelium, while the absorptive function is carried out by all cells of the organ. Two types of cytoplasmic inclusions coexist: polysaccharides and mineral concretions. The polysaccharides are particulary abundant in larvae and pupae. Glycogen is metabolized during histogenesis; acid mucopolysaccharides, elaborated in the Golgi apparatus, represent a mucous secretion. The spherites are composed of concentric strata of calcium phosphate and chloride and a matrix of mucopolysaccharides. These minerals form in the ergastoplasmic cisternae of pupal cells only. Their accumulation could be related to the insect's diet, or it could reflect a process of excretion.

Notes: Summary The ultrastructure of Limulus cardiac muscle was examined. The hearts were fixed in situ by perfusion with isotonic glutaraldehyde solution while in relaxed, contracted, or stretched states. The sarcomeres are relatively long, varying in length from about 2.5 to 6.6 μ. The average A-band length is 2.46 μ. M lines are absent, and H zones are poorly distinguished. Thick and thin filament diameters average about 200 Å and 50 Å, respectively; each thick filament is surrounded by 8–12 thin ones. Superficial invaginations of the sarcolemma occur, making contact with the Z lines of the outermost myofibrils. There is an extensive sarcoplasmic reticulum and transverse (T) tubules. Some T tubules run longitudinally and some open into deep sarcolemmal invaginations which extend into the fiber interior. The T tubules swell markedly in hypertonic solution. Single neurons and small bundles of neurons are observed in close apposition with myocardial cells. Intercalated disks are found in Limulus heart at regions of contact between contiguous myocardial cells lying end to end; semitight or gap junctions are essentially absent. Prominent differences in sarcomere lengths sometimes occur across the disk, thus indicating that the disks demarcate cells functionally. Hence, in addition to direct motoneuron activation, there may be some transfer of excitation across the intercalated disks in accord with our previous finding that propagating, overshooting action potentials can be induced in this heart.

Notes: Summary The purpose of this study has been to elucidate the structure of the rectal complex of the meal worm, in particular of the perinephric membrane and the leptophragmata. Most of Grimstone's (1968) findings have been confirmed, but in some respects a different interpretation is suggested. 1. The perinephric membrane is limited towards the hemocoele by a basement membrane secreted by a layer of elongated cells. Over the leptophragmata, these cells are lacking, whereas the basement membrane is enormously thickened, constituting the so-called blister. 2. The tracheole cells form a network in all of the perinephric membrane. 3. The perinephric membrane may be divided into an outer and an inner sheath. The main part of the outer sheath is an acellular matrix, probably a basement membrane secreted by the tracheole cells. This matrix is extremely thin over the leptophragmata. 4. The inner sheath is mostly made up of tracheole cells. In the inner part of this sheath, multiple extremely thin cell layers are observed; it is suggested that cells in these layers have nuclei located in the innermost layer of the sheath. The inner sheath is absent over the leptophragma. 5. The leptophragma is a thin plate-like protrusion from a modified tubule cell, the leptophragma cell. Together the cell body and the cytoplasmic rim of the leptophragma cell make up a short funnel communicating with the tubule lumen; the short funnel is filled with thin microvilli without mitochondria.

Notes: Summary In the peculiar slime glands of the Onychophora, the secretory tubes consist of a glandular epithelium surrounded by a layer of connective and muscular tissue. The connective layer, bounded by basal membranes of neutral mucopolysaccharides and mucoproteins, contains two kinds of fibrils: collagenous fibrils and an especial type of elastic fibrils. The muscle fibers, which are scattered and circularly oriented, are more simply organized than those of the somatic muscles. The glandular epithelium is constituted by prismatic cells of the same type, with a large polyploid basally situated nucleus, containing a very large nucleolus. The cytoplasm of these cells is filled with ribonucleins in form of ergastoplasm and in numerous free ribosomes. Concentric lamellar structures of ergastoplasm, which originate basally close to the nucleus, are well developed in the central region of the cell and become disorganized at the apex, where they liberate great quantities of ribosomes. The secretion of these cells consists essentially of proteins, which accumulate in the apical region without passing through the poorly developed Golgi apparatus. These proteins, therefore, are not concentrated in secretory granules, rather they are released in a diffuse form, into the glandular cavity. They are discharged in cytoplasmic expansions detached from the apical region, together with a large quantity of free ribosomes. Polyploidy, large nucleolus, well developed granular ergastoplasm, abundance of free ribosomes, non-participation of the Golgi apparatus and lack of concentration in secretory granules are correlated with rapid and continuous synthesis of proteins which are the principal component of the slime.

Notes: Summary By light and electron microscopy investigation of the human gastric mucosa five types of ultrastructurally different endocrine cells have been detected: 5-hydroxytryptamine storing enterochromaffin (EC) cells, gastrin storing G cells, and functionally undefined ECL, D and D1 cells. By direct application of Masson's argentaffin reaction as well as of Sevier-Munger's and Grimelius' argyrophil method to electron microscopy specimens, selective deposition of silver grains upon the endocrine granules of such cells was obtained. In particular, only EC cell granules reacted to the argentaffin method, granules of both EC and ECL cells heavily reacted to Sevier-Munger's technique, granules of EC, ECL, G and D1 cells reacted to Grimelius' technique, while D cell granules failed to react either to argentaffin or argyrophil methods. By the application of the same silver methods to paraffin sections as well as by other selective staining methods for endocrine granules (5-hydroxytryptamine techniques, lead-haematoxylin, HCl-basic dye method), at least four of the above cell types were also identified under light microscope. This opens the way for extensive studies of such cells in conventional histologie specimens.

Notes: Summary Male chick embryos of a sex-linked cross were injected with 0.1 mg of estradiol benzoate on the fourth day of incubation. Their left gonads, together with ovaries from uninjected control females, were dissected at various intervals after hatching and processed for electron microscopic study. At the time of hatching no differences were found between the intersexual gonads of treated chicks and control ovaries with the exception of the presence, in the former, of great number of germ cells in interphase. Cortical degeneration in intersexual gonads began on the third day and was almost completed by the tenth. During this period germ cells underwent cytolysis while accompanying pre-follicular cells showed cytological characteristics which were undistinguishable from those found in control ovaries. This fact tends to suggest that the primary incompetency responsible for cortical degeneration lies in the germ cells and not in the pre-follicular cells.

Notes: Summary The granulosa cells of the ovarian follicle of the rat and the domestic fowl have been studied with the light and electron microscope. The nuclei of the granulosa cells were irregular with indentations and large in proportion to the cytoplasm of the cell. The mitochondria had a dense, dark matrix with only few cristac. The Golgi apparatus was moderately developed, located towards the oocyte in a juxtanuclear position. The endoplasmic reticulum was rather sparse. Lipid droplets were only occasionally encountered. Microtubules were regularly observed. The functions of the granulosa cells are discussed. Compared with the steroid-producing cells of the theca interna of the same follicles, the granulosa cells primarily are the nursing cells for the growing oocyte and mainly have the characteristics of protein forming cells.

Notes: Summary The fine structure of granulosa cells of the domestic fowl as seen after administration of steroids is described. Diaethylstilboestrol, estradiol and hydroxy-progesterone were given as intramuscular injections for a 28-days period. The main cytoplasmic changes of the granulosa cells were an increase in the number of mitochondria and dense bodies. The Golgi apparatus became enlarged, and occupied a large portion of the cell. The nucleus was found located adjacent to the oocyte, and there was an increase in number of the annular desmosomes. The investigation has demonstrated that even if steroids in high dosages induce atrophic alterations of the ovary, they stimulated proliferation of the granulosa cells of the small follicles. Apparently the small follicles with the granulosa cells retain the ability to regain development, which may be to some importance when steroids are used therapeutically (gynecologic disorders, contra-ception).

Notes: Summary Nerve fibres containing granular vesicles first appear in the median eminence of the rat on the 16th foetal day while secretory granules in the cells of the adenohypophysis are not present till the 17th foetal day. These observations suggest that the differentiation and early activity of pars distalis cells may depend on substances elaborated at nerve terminals in the median eminence. Although the loops of the primary plexus of portal vessels do not develop until the 4th postnatal day, substances released by nerve fibres in the neurohypophysis could reach the pars distalis through vessels already present at the 15th foetal day in the mesenchyme between the diencephalon and the adenohypophysis. This view is supported by the fact that the earliest cells to exhibit ultrastructural evidence of secretory activity are in the rostral pole of the pars distalis, the first region of the gland to become vascularized. The earliest granules to appear in the cells of the pars distalis correspond to those which are considered to contain mucoprotein hormones; somatotrophin type granules were seen only in postnatal tissues. The finding that, in the median eminence, the development of granular vesicles precedes that of agranular vesicles is discussed with reference to the times at which neurosecretory materials and monoamines become detectable in the region.

Notes: Summary Electron microscope study of symbiotes hereditarily transmitted through the eggs of in Homoptera, shows very different types: yeasts, more or less degenerated bacteria and enigmatical forms looking in some way like drops of secretion. Yet the numerous distinct species of symbiotes described in some cases by light microscopists are not always found again. It is not possible to distinguish a genus by its symbiotes.

Notes: Summary The macula densa (MD) site of the kidney, at which the distal tubule is attached to the vascular pole of the glomerulus, was examined with the light microscope in domestic fowl and Japanese quail; and in the fowl also with the electron microscope. The characteristics of mammalian MD cells, as reported in the literature, are compared with those of the cells in the avian MD site. The avian cells possess some of the characteristics of mammalian MD cells and they are distinguishable from the cells in adjacent portions of the distal tubule. The Golgi system in the avian cells is apical to the nucleus, unlike in mammals where its location is basal. The cells in the avian MD sites can be considered as structurally transitional between the typical MD cells in mammals and the ordinary cells of the distal tubule. These findings are discussed in relation to the function of the avian kidney and to its control by the renin mechanism.

Notes: Summary The cells comprising the neural gland in the ascidians Ciona, Styela, and Botryllus have been examined for their fine structural features and enzyme cytochemistry. The gland cells are either cuboidal or irregular in outline. They are full of small vesicles, of which some are pinocytotic, as well as larger vacuoles; they become increasingly vacuolated as their shape decreases in regularity. At the same time, glycogen deposits accumulate and the cisternae of the endoplasmic reticulum become distended. Some of the vacuoles contain an electron dense material or a fibrillar substance, but the cells contain no obvious electron opaque secretory granules associated with an extensive Golgi complex such as occur in the vertebrate adenohypophysis. Acid phosphatase is localized in some of the vesicles and vacuoles, indicating that they are a kind of lysosome, the latter possibly representing autophagic vacuoles. Thiamine pyrophosphatase is also found in many vacuoles as well as in the saccules of the Golgi apparatus which in these cells is in the form of dictyosomes. The results suggest a developmental cycle of increasing cytoplasmic vacuolation, ultimately leading to a breakdown and release of the vacuolar products. The significance of these observations is considered, particularly with respect to the hypothesis that the gland represents the ascidian equivalent of the vertebrate pituitary.

Notes: Summary The weakly electric fish of the family Mormyridae have a three layered epidermis, with a medium layer consisting of hexagonal cells of only 0.22 μm in thickness and about 60 μm in diameter. The lens-shaped nuclei are about 2 μm thick and 7.6 μm in diameter and are situated near the border of the cells. The cells are piled up to hexagonal columns. Their margin is serrate and where it reaches the boundary of the column, it has a thickness of about 0.34 μm. Close to the boundaries of the columns, the cells are linked to their neighbours within the column and of the adjoining column by desmosomes. This layer of the epidermis is confined to those regions of the body surface which also contain electroreceptors. The other layers of the epidermis have a structure as usual in fish, except for the lack of goblet cells.

Notes: Summary Normal thyroid follicular epithelial cells in the rat show three functional phases: (1) synthesis of protein and secretion into the follicular lumen; (2) relative inactivity; (3) resorption of the colloid. The resorption of the colloid is stimulated by the thyrotropic hormone, whereas colloid protein synthesis appears to be independent of pituitary stimulus. Ultrastructural alterations, present in some cellular components during alimentary tocopherolubiquinone deficiency, reflect disturbances in the normal functional phases. The deficiency possibly influences the function of the thyroid gland in two ways: in affecting the metabolism of thyroid hormones which seems to depend on the antioxidant properties of tocopherols, and/or, in affecting the participation of the quinoid forms in the mitochondrial enzyme system. Substitution with either d,1-α-tocopherol or α-tocopherolquinone reverses the alterations and disturbances produced by the dietary deficiency.

Notes: Summary Oocyte development in Asplanchna brightwelli was studied by observation through the transparent body wall of living females and by electron microscopy. During oogenesis, which requires four to six hours, the oocyte increases in volume approximately 1000-fold. Most of its cytoplasm appears to be derived from the vitellarium by direct flow through the cytoplasmic bridge. This flow is rapid enough to be easily observed in the living female at low magnifications. Ribosomes, mitochondria, cortical granules, and lipid droplets were observed in the bridge area in electron micrographs. RNA synthesis during oogenesis was studied by means of autoradiography. Very little synthesis could be demonstrated in oocyte nuclei at any period of oogenesis, whereas the vitellarium nuclei show active incorporation of 3H-uridine throughout the reproductive life of the adult female. Most of this RNA is subsequently transferred to developing oocytes.

Notes: Summary Intraocular injection of colchicine in doses which do not affect the protein synthesis in the retina has profound effects on the axonal transport of protein in the retinal ganglion cells of the rabbit. Rapid axonal transport in these cells is completely inhibited after treatment with relatively low amounts of colchicine. In contrast to this, a certain fraction of the slow axonal transport is resistant to colchicine treatment. Colchicine in doses which completely inhibits fast axonal transport caused discrete morphological changes in the perikaryon and in the axon of the retinal ganglion cell. No disappearance of microtubules and no general proliferation of neurofilaments was observed in the perikaryon of the retinal ganglion cells. There was a slight or moderate increase in the number of filaments in the intra-retinal part of the axons of the retinal ganglion cells.

Notes: Summary The ultrastructure of axonal and dendritic growth cones has been examined in the cerebellar cortex of 7 days old rats and 12 days old cats. The unique feature is a bulge of the perikaryon surface or a varicosity of the growing tip of nerve processes. These cone-like areas contain large amounts of tubular smooth surfaced endoplasmic reticulum (SR) and large vacuoles. They are further characterized by filopodia (Tennyson, 1970) with a fibrillary matrix. Early cell contacts with synaptic membrane specializations are described between filopodia of mossy fiber endings and dendritic growth cones of granular cells. Synaptic vesicles appear early in synaptogenesis. While both vesicles and SR tubules are confined to separate areas of the axonal growth cone it was found that a common affinity to the ZIO staining agent exists. In contrast, the neurofilaments and microtubular components as well as the growth cone vacuoles remain consistently ZIO negative.

Notes: Summary The dorsal organs of the cephalic lobes of the house fly larva, Musca domestica L. were studied by light, scanning and transmission electron microscopy. Five types of receptors were found in the distal part of the dorsal organ: (1) The dome, whose ultrastructure is similar to that of thin-walled pegs, is assumed to be an olfactory receptor. (2) A lateral pore receptor, with the distal tips of two dendrites exposed to the exterior through a pore, is presumed to be a contact chemoreceptor. (3) A scolopidium-like receptor, with an ultrastructure characteristic of a scolopidium receptor except that the dendrite might be exposed to the exterior through an opening, is assumed to be both a mechanoreceptor and contact chemoreceptor. (4) Two receptors, each with one of its two dendrites exposed to the exterior, are probably contact chemoreceptors. (5) Two unclassified receptors, each with one dendritic tip exposed to the exterior and the other dendrite with a tubular body ending near the pore, may serve as both contact chemoreceptors and mechanoreceptors. The last four types are located in the invagination between the dome and the cylindrical portion of the dorsal organ. The seven basal pores of the dome are apparently points of origin of the scolopales and have no sensory function. The dorsal organ is supplied by 35–41 bipolar neurons, indicating the possibility of additional undescribed receptors.

Notes: Summary Ultrastructure of the granulosa lutein cells of the raccoon from throughout pregnancy has been described. The lutein cells often from epithelial cords which are separated by the connective tissues, capillaries and lymphatics. Based on the arrangements and modifications of the cytoplasmic organelles and inclusions, three types of lutein cells have been recognized. The type I lutein cells predominantly contain tubular, agranular endoplasmic reticulum, juxtanuclear Golgi complexes, a few round to rod-shaped mitochondria, some free ribosomes, and occasional lipid droplets. Occasionally the tubular cristae of mitochondria and tubular smooth endoplasmic reticulum appear contiguous. The type II cells contain abundant lace-like and/or stacked fenestrated endoplasmic reticulum cisternae that frequently form membranous whorls, some tubular, agranular endoplasmic reticulum, mitochondria, and lipid droplets. Mitochondria are usually small, but unusual large ones also occur. The small, rod-to round-shaped mitochondria usually have tubular cristae; but the large, oval, elongate, and cup shaped mitochondria possess tubular, lamellar, plate like, and whorl-like cristae. The plasma membranes of the cells are complexly elaborated and folded, especially when apposing each other. In favorable sections, strands of fenestrated cisternae appose the folds of the plasma membranes. In general, the amount of cytoplasmic organelles and inclusions vary greatly in the cells. The type III cells predominantly contain lipid droplets and sparse cytoplasmic organelles. The type I and II cells are found throughout pregnancy, but the type III cells are observed from mid gestation to term. The cytological features of type I and II cells suggest that they probably secrete most of the steroids, whereas the type III cells primarily store lipids.

Notes: Summary Ultrastructural features of the dioptric apparatus of photoreceptors of adult Collembola described by the author has enabled the author to compare the structure of ocular formations with aggregated ommatidia. Four different types of corneulae have been determined, the most remarkable of which are those showing ‘corneal nipples’. The four crystalline cells have alternately different functions during each molting cycle. On their distal surfaces, the cells elaborate cuticular material of the corneula; proximally, they secrete a crystalline cone. The Semper cells thus have both corneogenous and crystallogenous functions. The typically concentric spatial distribution of intracellular organelles in these cells is a characteristic feature for Collembola. Each crystalline cell sends towards the basal membrane a tubular process containing granules, numerous microtubules, and a small amount of glycogen. The shape, the structure, and the chemical composition of the crystalline cones are highly variable. In Collembola, the crystalline formation can either be intracellular or extracellular, and it can be simple or quadripartite. No explanation has yet been advanced for the existence of small crystalline satellites which appear to be associated with the single large crystalline cones; this association is characteristic for the troglobian species Tomocerus problematicus. The dioptric apparatus of Collembolan ommatidia is completed by the presence of two corneogenous cells, the cytoplasm of which contains few organelles and in some cases pigments.

Notes: Summary 1. The paired cerebral gland of Polyxenus lagurus is an endocrine organ. It lies directly lateral to the tritocerebral ganglia and is innervated by the nervus glandulae oerebralis. The organ is not ensheathed by connective tissue and extends freely into the hemocoele. It consists of two structurally different regions, viz. a basophilic part adjacent to the brain and a lateral acidophilic region. 2. The basophilic portion traversed by the nervus glandulae cerebralis is composed of gland cells with large, round nuclei, few and small mitochondria and numerous Golgi complexes. Small secretory granules are pinched off from Golgi cisternae and unite to form huge irregular vacuoles whose content is heterogenous and of low electron density. 3. The acidophilic region contains gland cells without processes and few glialike cells. Between these the terminal branches of the nervus glandulae cerebralis are found, and a system of lacunae which communicate with the surrounding hemolymph. The cell surfaces are often vesiculated near the lacunae. Microvilli of gland cells are not rarely extending into hemolymph spaces. The nuclei are lobated. Mitochondria are more numerous and larger than in the other region of the gland. Golgi complexes are both large and abundant; the maximal diameter of the secretory vacuoles formed by their cisternae is 1.7–1.8 μm. The content of the secretory vacuoles is granular and electron dense. In animals not close to molting it shows a regular pattern of light spots and frequently parallel stacks of lamellae. The bounding membrane of the larger vacuoles may appear fragmented in places. Large vacuoles of low density are relatively rare. 4. Changes in the axons of the nervus glandulae cerebralis are noticeable as early as 24 hours after experimental induction of molting. They are then filled with large presumably neurosecretory granules of 1200–1800 Å diameter which had been absent before. Pine structural changes are also recognizable in the acidophilic gland cells. Just before molt the cisternae of the granular endoplasmic reticulum bear regular, blisterlike expansions. Cisternae are no longer recognizable between the secretory vacuoles. Free ribosomes increase in number in these spaces. Golgi cisternae are shortened but show beaded expansions. The flaky content of the inner cisternae resembles that of the secretory vacuoles. The content of all secretory vacuoles is of uniformly high electron density and without light spots or parallel striations. 5. The results are discussed and compared with those of other studies of comparable organs in related animals.

Notes: Summary The fine structure of vascular channels and amebocytes associated with the sheath of the infraesophageal ganglion of Helix aspersa, is described. The extracellular stroma of the sheath, together with the hemocoel and blood vessels, forms an interconnected system of pathways which appears to be involved in the transport of metabolites, amebocytes, hemocyanin and experimentally introduced opaque tracers. The hemocoel, blood capillaries and precapillaries are lined by a discontinuous layer of single muscle cells whose luminal aspect is covered by a lamina of extracellular material named the vascular coat. This coat consists of a ground substance that forms a basement membrane and filamentous elements some of which are collagenous. Gaps in the blood vessel wall seem to provide the main routes for the movement of cells and large molecules to the hemocoel. Tracer experiments have given support to the idea that a diffusion barrier may be absent at the sheath-ganglion junction. Amebocytes have phagocytic properties; they appear associated in groups or scattered singly within the extracellular space of the sheath and the lumen of blood vessels. Single amebocytes have features of mobile cells and may function in the transport of hemocyanin as well as other proteins.

Notes: Summary The present paper describes for the first time the fine structure of ovarian granulosa cells as seen after administration of clomiphene to the domestic fowl for a 28 days period. The main cytoplasmic changes of the granulosa cells seemed to be an increase in the number of mitochondria, dense bodies and complex bodies. The Golgi apparatus became enlarged, and there was an increase in the endoplasmic reticulum, annular desmosomes and cytoplasmic processes. All the observations made are similar to those made after administration of steroids and gonadotropins. In conclusion, therefore, the present study has demonstrated that administration of clomiphene exerts a stimulating effect on the granulosa cells. The mechanism of this effect is discussed.

Notes: Summary The synganglion is bounded by an extracellular sheath and is divided into the cortex and the neuropile. The cortex contains two glial layers, each of which is composed of a distinctive type of glial cell, and three types of neurons. Type I is the least common and most electron dense, type II is most common, and type III represents neurosecretory cells with a larger volume of cytoplasm than in types I and II. Substantial areas of the neuron cell bodies are unsheathed. A third type of glial cell is found in the neuropile. The first glial layer of the cortex, the perineurium, lies beneath the extracellular sheath and overlies the neuron cell bodies contributing to their ensheathment. In areas lacking neuron cells bodies, the perineurium overlies a second glial layer, the subpermeurium, which is inflected inwards where a group of neuron cell bodies is encountered. The subperineurium contributes to the ensheathment of both the cell bodies of neurons and the nerve fibers. It is confluent with glial cells which arise within the neuropile. The neuropile contains nerve fibers and glial cells and is perforated by the esophageal canal, which is lined by the perineurium and subperineurium. Unsheathed nerve fibers contact each other in three ways: end-knob, longitudinal, and cross contacts.

Notes: Summary The fine structure of oyster leucocytes resembles to a great extent, that of typical eucaryotic cells. Organelles which have been described for the first time in this report are light granules, dense granules, protocentriole and X structure. Light microscopy reveals two morphological types of oyster leucocytes: agranular and granular. Based upon nuclear morphology and cytoplasmic compositions revealed in electron microscopy, at least three types of agranular and one type of granular cells are recognized. In the Giemsa-stained preparations, granular leucocytes exhibit three distinct types of cytoplasmic granules: refractile, dark blue, and pink, which presumably correspond to light granules Type A, B, and C seen in the electron micrographs. A granular leucocyte may contain one or more types of granules. Cytochemical investigations show that oyster leucocytes contain at least three hydrolytic enzymes: non-specific esterases, acid, and alkaline phosphatase. The latter two enzymes constitute 63% of the enzyme activity detected. These intracellular enzymes may be associated with the light granules and/or lysosome-like bodies. It is also demonstrated that the granular leucocyte population is significantly higher (P〈0.001) in the oysters experimentally infected with Bacillus mycoides (72.19±4.71%) as contrasted with that of the controls (37.18±4.48%). Leucocytes in progressive stages of degeneration are also described.

Notes: Summary The ciliary epithelium of the olfactory folds in Calamoichthys calabaricus is composed of ciliary cells, supporting cells, and basal cells. All ciliary cells contain numerous mitochondria and bear up to 160 kinocilia. Some rootlets of the basal bodies of the kinocilia, project towards the nucleus, while others run parallel to the epithelial surface and connect with neighbouring basal bodies. Ciliary and olfactory epithelia are separated from each other. — The olfactory epithelium contains olfactory receptor cells, supporting cells, and basal cells. The club shaped olfactory receptor cells have a uniform ultrastructure. The terminal portions of the olfactory dendrites form small olfactory vesicles which are seen above the olfactory surface. 12 sensory cilia project constantly to the more basal portion of the olfactory vesicles, each cilium forming a 25–27° angle with the vertical cell axis. Basally, an axon originates from each olfactory receptor cell. Axons from a number of olfactory receptor cells may combine to form bundles within the epithelium. The supporting cells of the olfactory epithelia are strongly osmiophilic. Supporting cells occur in all parts of the olfactory epithelium and bear few cilia. Numerous mucous vesicles, located within the apical region of the supporting cells, probably have a secretory function.

Notes: Summary Yolk-platelet formation in the South African clawed toad, Xenopus laevis, was studied with the electron microscope. A dual mode of formation was found. One being associated with mitochondria, the other with the Golgi complex. These two ways of yolk formation are named yolk formation I and yolk formation II respectively. Yolk formation I involves an extensive uptake of pinocytotic vesicles, whilst yolk formation II takes place within large Golgi vesicles surrounded by a coat of lipid droplets entirely without participation of pinocytotic activities. Thus it is concluded that yolk platelet I formation represents an extraoocytic synthesis as opposed to the intraoocytic synthesis of yolk platelet II formation.

Notes: Summary The chordotonal organs located in the various head appendages of the Speophyes larva, can be divided into two classes. The scolopidial receptors of the antenna, the labium and the palpus maxillae belong to the first class. They can be compared to the scolopidium of the locust tympanic organ described by Gray.—The second class contains the scolopidial receptors of the mandible and the lacinia: their type is amphinematic. The scolopidial sensilla of the galea represents an intermediate type. We demonstrate many supporting and fixation structures which probably allow a good transmission of all the deformations and strains affecting the tegument. The function of the gap junction which connects the two dendrites in the scolopidia of the second class is discussed. Finally we try to formulate hypothesis of the functioning of scolopidia.

Notes: Summary The notochord of Ichthyophis glutinosus and I. kohtaoensis consists of peripheral flattened cells characterized by a well-developed system of rough endoplasmic reticulum, bundles of tonofilaments, and abundant glycogen particles. These cells contain furthermore fairly high activities of α-naphtyl-acetate esterase and 4-chloro-5-bromoindoxyl acetate esterase as well as acid phosphatase which was found in lysosomal localization. The huge intracellular vacuoles of the centrally situated cells possibly originate from electron translucent spaces within the glycogen fields of the peripheral cells. The notochord sheath consists of variously differentiated layers of collagen fibers and of an elastica externa. The diameters of the collagen fibers increase from the inner towards the outer region of the sheath. A peculiar feature of the Ichthyophis notochord sheath is a ring of mineralized collagen. The notochord of the caecilians investigated is compared with that of anurans, urodeles, and several groups of fish.

Notes: Summary The tarsal taste hairs of the blowfly contain five receptor cells: four contact chemoreceptors and one mechanoreceptor. These cells are surrounded concentrically by two sheath cells with fluid-filled spaces (“vacuoles”) between them. The receptor cell parts are the axon, the cell body, and the dendrite. The latter has an inner segment, a transitional region, and an outer segment. The transitional region shows the 9+0 configuration of a modified cilium with two basal bodies. In the outer segment only microtubules are found. The outer segments of contact chemoreceptors pass through the tube-like dendrite sheath, then through “canal I” of the hair shaft, to reach the pore at the tip of the hair. The outer segment of the mechanoreceptor contains a “tubular body” and terminates at the hair base. The “sheath cell II” (tormogene cell) forms a folded membrane system toward the main liquor space. The fine structure of the tarsal taste hairs is discussed in relation to their function.

Notes: Summary In the haemolymph of Eisenia foetida L. (Sav.) two types of blood cells occur: The eleocytes which are released from the chloragogue tissue and the amoebocytes which are derived from the peritoneal endothelium. Chloragosomes are present in the early stage of the eleocytes, later they are replaced by protein vacuoles containing hemoglobin and ferritin. These products are released into the haemolymph. Therefore the chloragogue tissue may be considered as a temporary liquid tissue represented by the eleocytes. The amoebocytes have the form of either cells with pseudopodia having a transport function, or of petal-shaped phagocytes. Both types contain glycogen deposits, lysosomes and bundles of cytoplasmic filaments which grow out of electron-opaque granules. These granules appear to contain trichohyalin which is gradually transformed into filamentous scleroproteins.

Notes: Summary Radioactive lanthanum nitrate, an electron opaque tracer, was injected into the common bile duct of rats. Two minutes following the end of injection, samples of blood for radioactivity counts, and of liver and kidney for electron microscopic studies were taken. High levels of radioactivity found in the blood, and demonstration of lanthanum in the kidney by electron microscopy, indicated that this tracer entered the blood stream in vivo. No lanthanum was seen in the cytoplasm of liver cells, and there was no evidence of rupture in bile ducts, junctional ducts, or liver cells. Tight junctions connecting parenchymal cells and cholangiolar cells appeared well preserved. Lanthanum was seen in bile canaliculi, interspaces between liver cells, portions of the extracellular space of the liver, lumina of cholangioles and lumina of portal venules and sinusoids. It is postulated that lanthanum passed from the biliary tract, the site of injection, through the tight junction between liver cells and cholangiolar cells. It is suggested that such passage may represent a physiologic pathway, but the possibility of a chemical action of lanthanum on the tight junction can not be ruled out.

Notes: Summary The retina of the worker honeybee is studied by means of electron and light-microscopy. The results are as follows: 1. Generally the single ommatidium is composed of the cornea facette, crystalline cone, 8 retinula cells and the principal, secondary and basal pigment cells. Ommatidia with more than 8 retinula cells occur very rarely. 2. The arrangement of the fourfold crystalline cones with quadrants differently stainable, is found to be constant within the eye-rows. 3. The orientation of the four-divided rhabdoms shows a variable rotation of approximately zero to 90° within the eye-rows. The morphology of the retina of the worker honeybee is discussed with regard to the orientation according to the pattern of polarization of light reflected from the blue sky.