Ultrastructural and histochemical investigations of Call-Exner bodies in rabbit Graafian follicles

In a histological survey of 19 mammalian species, Call-Exner bodies of conventional size and appearance were found in only 5, namely, human, rhesus monkey, rabbit, guinea-pig and sheep. Rabbit ovaries were used for characterizing these bodies using quantitative histochemistry, lectin binding and electron microscopy. Call-Exner bodies were topographically distinct lacunae of the extracellular space probably containing hyaluronic acid with proteoglycan complexes. The staining characteristics of the antrum and Call-Exner bodies were generally similar. However, in contrast to the antrum, the smaller lacunae contained suspended filaments with a distinctive peripheral membrane upon which a rosette of granulosa cells was resting. The membrane and narrow intercellular clefts probably prevent much exchange of large glycosaminoglycan complexes with the antrum. The origin and significance of Call-Exner bodies require further study, but it is clear that they are associated with secretion rather than with necrosis as sometimes suggested.     

Ultrastructural and histochemical studies on guard cells

Serial thick sections of guard cells from Vicia faba L., Nicotiana tabacum L., Allium cepa L., Zea mays L. and Beta vulgaris L. were obtained systematically (600–800 nm) and viewed with the transmission electron microscope in an effort to demonstrate the presence or absence of a symplastic transport pathway within the stomatal complex. Eight to ten stomata from each species were examined, and no continuous plasmodesmata were found connecting guard cells to sister guard cells or to adjacent epidermal or subsidiary cells. Continuous plasmodesmata were observed in immature guard cells, but were sealed (truncated) during the development of the mature cell wall. Histochemical stains, phosphotungstic acid and silver methenamine, were used to demonstrate differentiation within the mature guard-cell wall. The structural differentiation of the stomatal apoplastic region is discussed in relation to fanctional specialization. Plasma-membrane elaborations or plasmalemmasomes were identified in the guard cells of Zea, and it is suggested that these structures may function in ion transport.Abbreviations PTA-HCl phosphotungstic acid and hydrochloric acid - SM silver methenamine - UA-LC uranyl acetate and lead citrate     

Ultrastructural and histochemical comparison in two haplotaxids

Pelodrilus leruthi Hrabe, 1958 and Haplotaxis gordioides Hartman, 1821 have been investigated from a histochemical point of view. A different distribution and number of fast and slow fibres has been detected in the two species. Pelodrilus leruthi specimens living in different caves, show some differences in the body wall muscle thickness and in the structure of the ventral nerve cord. A correlation with their different life styles is proposed.     

Ultrastructural investigations on sporogenesis inEquisetum fluviatile

Summary The spore mother cells ofEquisetum fluviatile undergo meiotic division, each forming a tetrad of spores. The spore protoplasts are separated from each other by an accumulation of mitochondria (organellar plate) at first and later on by plasma membranes, no cell wall is formed. The first layer of the sporoderm, the exine, originates from the plasmodial tapetum and is deposited at the outer side of the plasmalemma of the young spore. The exine reaches a thickness of about 330 nm. In the phase of spore greening the so-called perine, originating from the tapetum, is placed onto the exine and the inner layer of the sporoderm, the intine, is formed from the spore protoplast. The mature spore, about 40 m in diameter, does not enter dormancy and remains viable only for a few days.Member of the Study group on electron microscopy at the TierÄrztliche Hochschule Hannover.     

Ultrastructural and histochemical aspects of zinc accumulation by fish scales

The effect of zinc exposure on the ultrastructure of the scales and scale associated cells of the estuarine teleost, Fundulus heteroclitus was investigated in laboratory experiments. The Timm sulfide silver stain indicated that in the calcified region of the scales, Zn was colocalized with the calcium phosphate mineral crystals. X-ray diffraction analysis showed that Zn did not have an effect on crystal structure. The scale osteoblasts of Zn-exposed fish showed an increase in the number of lysosome-like structures contained by the cytoplasm. In Zn-exposed animals, X-ray microanalysis revealed that these structures contain greatly increased levels of zinc and sulfur relative to controls. In all specimens, the lysosomes contained higher levels of Zn than either the surrounding cytoplasm or adjacent scales. The findings suggest that osteoblast lysosomes may be involved in the accumulation of Zn and other metals by fish scales by the enzymatic degradation of metallothioneins or other metal-binding proteins. This could represent an important mechanism for the detoxification of excess heavy metal ions taken up from the environment and the metabolism of essential metals by calcified tissues.     

Ultrastructural and histochemical study of the gallbladder epithelia of rainbow trout and tench

The simple, high columnar gallbladder epithclia of the rainbow trout (Salmo gairdneri, Rich.) and the tench (Tinca linca, L.) are composed of light and dark cells. Within the dark cells two types must be distinguished: less hydrated, but normal epithelial cells and degenerating cells. The latter seem to be eliminated from the epithelium through phagocytosis by monocytes and macrophages, which possibly correspond with the ‘basal regenerative cells’ of earlier investigations. Since they are mainly found near the basement membrane, an hypothesis is put forth that they do not enter the gallbladder lumen, but migrate back into the subepithelial connective tissue after phagocytosis. Light and less hydrated dark cells are specialized for absorption of water and dissolved bile salts and for secretion of mucus, which mainly consists of acid glycoproteins. Interspecific differences are seen with regard to both functions. So, in the tench only single microvilli arc developed apically, whereas a true brush border is seen in the rainbow trout. Thus, a higher absorptive rate can be assumed in the rainbow trout. Or, with respect to mucus secretion, in the rainbow trout the granular endoplasmic reticulum predominates, whereas in the tench the smooth endoplasmic reticulum, often associated with glycogen and even forming ‘glycogen bodies’, is better developed. In the rainbow trout fibrillar granules of highly condensed acid glycoproteins are seen to be secreted. In the tench only vesicles of flocculent content occur. Perhaps, these morphological and subsequent metabolic differences may be related to the various feeding habits of the predatory rainbow trout and the omnivorous tench. Seasonal variations as expected especially in the tench after winter rest could not be established.     

Histological, histochemical, enzyme histochemical and ultrastructural investigations of the testis of Padogobius martensi between annual breeding seasons

From July to March, the testis of the spring‐spawning freshwater goby Padogobius martensi is characterized by spermatogonial proliferation. A close correlation exists among type of proliferating spermatogonia, gonado‐somatic (I_G) profiles and morphological and functional variations of the Leydig cells. The I_G reach their minimal levels by the end of summer and increase progressively but modestly during autumn and winter. Declining I_G levels are associated with proliferation of primary spermatogonia only, whereas increasing I_G levels are associated with predominant proliferation of secondary spermatogonia. Minimal I_G levels are reached when the germinal epithelium is formed by a continuum of primary spermatogonia and associated Sertoli cells. The proliferation of secondary spermatogonia begins only at this time. Spermatogenesis in autumn occurs when spermatogonial cysts contain at the most 16 cells and it rarely results in the maturation of several cysts so that the amount of sperm cells produced is either negligible or scarce. A number of degenerating cells are usually present within the spermatogonial and meiotic cysts. Leydig cells are the unique cells that display features of steroidogenic cells: mitochondria with tubular cristae, extensive smooth endoplasmic reticulum (SER), 3β‐hydroxysteroid dehydrogenase (3β‐HSD) and glucose‐6‐phosphate dehydrogenase (G6PD) activity and sudanophilia. Light and dark Leydig cell varieties are always present. During regression, Leydig cells undergo a marked decrease in SER amount, mitochondrial sizes and number of mitochondrial cristae. In parallel, the 3β‐HSD and G6PD activities and sudanophilia decrease progressively until they become undetectable by the end of regression. In autumn, mitochondria increase in size, reaching sizes similar to those observed at the end of the spawning season in the light cells, but not in the dark cells. The SER, on the contrary, undergoes a modest and irregular increase only in a part of the Leydig cells, mostly of the light type. In parallel, the 3β‐HSD and G6PD activities increase until they become moderately intense by the end of autumn. At the end of winter, the SER is extensive and regularly dilated in both Leydig cell types, whereas mitochondria still have sizes similar to those observed in December. The 3β‐HSD and G6PD activities are strong and sudanophilia is again detectable. Sertoli cells undergo changes in shape and position in relation to the proliferation of primary spermatogonia and the development of cysts. A junction modulation occurs in association with these changes. Sertoli cells also undergo changes indicative of a decrease in activity immediately after spawning (loss of mitochondrial cristae and clarification of the mitochondrial matrix) and of an increase in activity by the end of the regressing phase (darkening of the mitochondrial matrix and increase in mitochondrial cristae, rough endoplasmic reticulum (RER) and free ribosomes). In addition, they are involved in the phagocytosis of degenerating germ cells at all stages of their development. Macrophages are found in the testis interstitium only, where they are usually adjacent to Leydig cells, myoid cells and blood capillaries and do not participate in the phagocytosis of degenerating germ cells. Myoid cells do not undergo ultrastructural changes except for an increase in the amount of heterochromatin by the end of spawning. The meaning of the autumnal spermatogenic wave and the relationships between the development of the germinal epithelium and the changes of the Leydig and Sertoli cells are discussed.     

Detoxications in peripatus. Sulphate, phosphate and histidine conjugations

Phenols were detoxified in the Onycophoran Peripatoides novaezealandiae by conjugation with sulphuric acid and phosphoric acid, but no evidence for a glycoside detoxication could be found. [(14)C]Benzoic acid was metabolized in 24h to N(2)-benzoyl-l-histidine, which was identified by electrophoresis, chromatography and dilution analysis. Similar conjugates were formed with p-aminobenzoic acid and p-nitrobenzoic acid. In longer-duration experiments further unidentified metabolites were formed, two of which appeared to result from the further metabolism of the histidine conjugate.     

Ultrastructural and experimental investigations of sperm-egg interactions in fertilization ofHydra carnea

Summary Fertilization in the freshwater hydrozoanHydra carnea has been examined by light, scanning and transmission electron microscopy. Sperm penetrate the jelly coat which covers the entire egg surface only at the site of the emission of the polar bodies. The egg surface exhibits a small depression, the so called fertilization pit at this site. Sperm-egg fusion takes place only at the bottom of the fertilization pit.Hydra sperm lack a structurally distinct acrosome and in most of the observed cases, fusion was initiated by contact between the membrane of the lateral part of the sperm head and the egg surfacce. Neither microvilli nor a fertilization cone are formed at the site of gamete fusion. The process of membrane fusion takes only a few seconds and within 1 to 2 min sperm head and midpiece are incorporated in the egg.Electron dense material is released by the egg upon insemination but cortical granule exocytosis does not occur and a fertilization envelope is not formed. The possible polyspermy-preventing mechanisms in hydrozoans are discussed. Hydra eggs can be cut into halves whereupon the egg membranes reseal at the cut edges and the fragments assume a spherical shape. Fragments containing the female pronucleus can be inseminated and exhibit normal cleavage and development. The observation that in such isolated parts the jelly coat will not fuse along the cut edges was used to determine its role in site-specific gamete fusion. These experiments indicate that site-specificity of gamete fusion can be attributed to special membrane properties at the fertilization pit.     

Ultrastructural investigations of Arbutus unedo-Laccaria amethystea mycorrhiza synthesized in vitro

Summary Anatomy and ultrastructure of the arbutoid mycorrhiza of Arbutus unedo-Laccaria amethystea from axenic culture are described. In comparison to non-inoculated roots, the rhizodermal cells of mycorrhizas are of greater volume, their nuclei are enlarged and show an irregular shape, plasmalemma and cytoplasm with mitochondria, plastids, endoplasmic reticulum and dictyosomes are increased. Several ontogenetical states are documented. The arbutoid mycorrhiza as a connecting link between ectomycorrhiza and ericoid mycorrhiza is discussed.