Structural and ultrastructural features of boar seminal vesicles

The morphological features of boar seminal vesicles were examined by light and transmission microscopy. Boar seminal vesicles consist of glandular tissue arranged in multiple lobules containing a system of ramified secretory tubules. The secretory tubules are composed of a mucosa formed by an epithelium and an underlying lamina propria and, are surrounded by a muscular layer. The epithelium is made up of columnar cells and occasional basal cells. Mast cells are frequently found among epithelial cells. Three types of columnar cells, considered different stages of the secretory cell cycle, are present: principal cells, clear cells and dense cells. Principal cells are functionally differentiated cells characterised by abundant mitochondria, great development of the rough endoplasmic reticulum and presence of secretory granules in their cytoplasm. The apical surface of many principal cells shows apical blebs filled with PAS-positive material. No acid mucosubstances are detected. Microvilli cover the apical surface except in the apical blebs. Dense cells, arranged between principal cells, are also functional differentiated cells but with signs of cellular degeneration. Clear cells are an initial differentiated stage of columnar cells and are characterised by the presence of a poorly developed rough endoplasmic reticulum and by the absence of secretory granules. Proliferating cells are present among columnar cells. Basal cells contain scarce cytoplasm, few organelles and no secretory granules. The lack of mitotic activity in these cells suggests that they do not act as precursors of columnar cells.     

Structure of the parathyroid glands,as revealed by different methods of fixation

Summary Stereology and semi-automatic image analysis were used with the aim of comparing the structure of parathyroid glands from untreated adult Mongolian gerbils fixed by immersion with those fixed by perfusion. Subclassification of the chief cells based upon the staining affinity or electron density of the cytoplasm was readily performed only in glands fixed by immersion, and so-called atrophic cells were observed only in these glands. The atrophic cells were often surrounded by light chief cells. In glands fixed by perfusion, light chief cells were only rarely encountered. A significant difference between glands fixed by immersion and those fixed by perfusion was found only with regard to the form of cells and nuclei, those fixed by perfusion being more spherical. When comparing individual cells within glands fixed by immersion, light chief cells were more spherical and had a significantly larger nuclear and cellular size, and a lower mitochondrial volume density than the intermediate/dark chief cells. Otherwise there were no significant differences in any of the parameters investigated. These data indicate that occurrence of socalled light chief cells and atrophic cells is a result of improper fixation. The results of this study do not favour the concept of a functional cycle with a simultaneous occurrence of active and inactive cells within parathyroid glands.     

Lectin histochemistry of the boar bulbourethral glands

The present study describes, for the first time, the glycosidic content of boar bulbourethral glands using lectin histochemistry. Fourteen horseradish peroxidase- or digoxigenin-labelled lectins with different carbohydrate specificities were used in samples obtained from 3 healthy Landrace boars. The results obtained indicate that endpiece and duct cells synthesize and secrete mainly O-glycoproteins with alpha- and beta-D-N-acetylgalactosamine, beta-D-galactose-beta(1-->3)-D-N-acetylgalactosamine, D-N-acetylglucosamine and neuraminic acid residues. Glycoproteins secreted by bulbourethral glands have a role in the protection and lubrication of the urethra. In addition, they may be also involved in the regulation of the sperm metabolic activity and in the maintenance of the structural integrity of acrosomal and plasma membranes.     

Disintegration of spermatozoa in the infundibular sperm-host glands of the fowl

Summary The disintegration of spermatozoa in the infundibular sperm-host glands of the fowl was investigated by electron microscopy. After the 15th day following artificial insemination, secretory granules in the epithelial cells of the sperm-host glands increase in number and size, and subsequently the contents of the granules are released into the glandular lumen, so that the electron density of the lumen increases. At this stage, spermatozoa stored in the glands begin to undergo degenerative changes starting from the head. The heads become distended and chromatin of the nucleus begins to disperse as small masses, simultaneously with the destruction of the acrosome. As the dispersion of chromatin progresses, mitochondria of the middle piece become distended and irregular in shape, and then disintegrate. At the last stage, most of the organelles have disappeared, but the fibrous sheath and axial-filament complex are still identified.The authors are greatly indebted to Assoc. Prof. Osamu Koga for his invaluable advice. The authors also wish to thank Mr. Takayuki Möri for his helpful suggestions and technical advice. This investigation was supported by a grant from the Ministry of Education of Japan (156185)     

The salivary glands of the cockroach Nauphoeta cinerea (Olivier)

The innervation of the salivary gland of the cockroach Nauphoeta cinerea (Olivier) has been investigated with the use of light and scanning electron microscopy. Light microscopy of methylene blue stained glands reveals the presence of a dual innervation arising from the ventral nerve cord and the stomodeal nervous system; the principal innervation is that from the ventral nerve cord which passes to the gland via the reservoir ducts. Branches of these nerves form a plexus on the acinar surface, the axons of which exhibit swelling at irregular intervals. The presence of this surface plexus and the axonal swellings was confirmed by scanning electron microscopy both in normal glands and in those in which the basal lamina had been removed by means of an HCl-collagenase digestion method. No acinar plexus was seen to be formed by branches of the stomatogastric nerve that were associated with the gland. However, other branches of this nerve were clearly connected with a complex network of multipolar neurones on the surfaces of the anterior regions of both salivary reservoirs.     

Morphological evidence for a direct innervation of the mouse vomeronasal glands

Summary The morphological evidence for a direct autonomic innervation of the mouse vomeronasal glands is presented. Axonal varicosities containing a few densecore vesicles and numerous clear vesicles (36–60 nm in diameter) make synaptic contacts with the secretory cells at the base of the glandular acini. The axonal presynaptic membrane is associated with a distinct dense material and it is separated from the secretory cell by a synaptic cleft of about 12–14 nm. At the postsynaptical level, coated vesicles can be found. Additional postsynaptical specializations have not been observed.     

Histological and ultrastructural alterations of rat thyroid gland after short-term treatment with high doses of thyroid hormones

The aim of the present study was to investigate histological alterations of rat thyroid gland after short-term treatment with supraphysiological doses of thyroid hormones. Rats from experimental groups were treated with triiodothyronine (T3) or thyroxine (T4) during five days. In both treated groups, thyrocyte height was reduced and follicular lumens were distended. Progressive involutive changes of the thyroid parenchyma were apparent, including follicular remodeling (fusion) and death of thyrocytes. Morphological changes confirmed by quantitative analysis were more pronounced in the T4-treated group. Our results demonstrate that thyrotoxicosis, whether induced by T3 or T4, leads to different grades of thyroid tissue injury, including some irreversible damages. These changes might be explained at least in part by lack of trophic and cytoprotective effects of the thyroid stimulating hormone. Since the period required for morphophysiological recovery may be unpredictable, findings presented here should be taken into consideration in cases where the thyroid hormones are used as a treatment for thyroid and non-thyroid related conditions.     

Crystalloid structures within giant mitochondria of the prothoracic glands of Spodoptera littoralis (Bois) (Lepidoptera)

The fine structure of the prothoracic glands of Spodoptera littoralis was investigated during the first half of the last larval instar. The secretory cells have two types of mitochondria, micromitochondria and macromitochondria. The micromitochondria have rounded to elongated profiles and sometimes branch. They contain lamellar, tubular and also tubulo-vesicular cristae. The macromitochondria appear generally rounded or oval and possess tubular cristae. Many regular parallel membranes appear within macromitochondria. Favorable sections show tubular structures packed in honeycomb fashion. The mitochondrial cristae are in connection with the tubular structures. Honeycomb and parallel membranes increase in number as the size of the macromitochondria increases.     

Anatomy and ultrastructure of the salivary (prosomal) glands in unfed water mite larvae Piona carnea (C.L. Koch, 1836) (Acariformes: Pionidae)

Anatomy and ultrastructure of prosomal salivary glands in the unfed water mite larvae Piona carnea (C.L. Koch, 1836) were examined using serial semi-thin sections and transmission electron microscopy. Three pairs of alveolar salivary glands shown are termed lateral, ventro-lateral and medial in accordance with their spatial position. These glands belong to the podocephalic system and are situated on the common salivary duct from back to forth in the above mentioned sequence. The arrangement of the medial glands is unusual because they are situated one after another on the medial (axial) body line, therefore they are termed anterior and posterior medial glands. The secretory duct of the anterior medial gland mostly turns right, and the duct of the posterior gland turns left. The salivary glands are located in the body cavity partly inside the gnathosoma and in the idiosoma in front of the brain (synganglion). Each gland is represented by a single acinus (alveolus) and is composed of several cone shaped secretory cells arranged around the large central (intra-acinar) cavity with the secretory duct base. The cells of all glands are filled with secretory vesicles of different electron density. The remaining cell volume is occupied by elements of rough endoplasmic reticulum, and the membrane enveloping vesicles may have ribosomes on its external surface. Large nuclei provided with large nucleoli occupy the basal cell zones. The pronounced development of the prosomal salivary glands indicates their important role in extra-oral digestion of water mite larvae.     

Effects of metopirone on the structure of endocrine glands in the male lizard,Cnemidophorus l. lemniscatus (L.)

Summary Adrenals, pituitary glands, thyroids, testes and kidneys of metopirone-treated and control male lizards were studied by light microscopy. Pituitary-interrenal axis: A great hypertrophy and hyperplasia of the interrenal cells and the pituitary corticotrophs were found in the experimental group. Pituitary-thyroid axis: Metopirone-treated animals showed a moderate hypertrophy and degranulation of pituitary thyrotrophs, and signs of uneven hyperactivity of the thyroid. Pituitary-testicular axis: By effect of metopirone, a marked regression of pituitary interstitiotrophs and a virtual disappearance of the testicular interstitial gland took place. The second portion of the kidney sexual segments appeared degranulated as in castrated animals. The pituitary folliculotrophs and the seminiferous epithelium of the testis did not show alterations.     

Substrate-histochemical investigations and ultrahistochemical demonstrations of acid phosphatase in larval and prepupal salivary glands of Drosophila melanogaster

Summary A major function of the larval salivary glands of Drosophila melanogaster is known to be the production of a mucopolysaccharide that serves as an adhesive during puparium formation. In order to localize the mucosubstances during development substrate histochemical methods were used, and the site of acid phosphatase was demonstrated by the ultrahistochemical lead-salt method. It could be shown that the glue-granules in the corpus cells of larval salivary glands as well as the large secretion vacuoles in the prepupal corpus cells give a positive -amylase-resistent PAS-reaction, which indicates neutral mucosubstances. Granular PAS-positive deposits in the larval and prepupal collum cells were reduced after preincubation with -amylase and may represent glycogen, which has also been seen in electron micrographs of these cells. The Hale-reaction gave a weak indication that acid mucosubstances are present in the larval glue granules and in the large prepupal secretory vacuoles. After digestion of sialic acid with -neuraminidase the weak indication was absent showing that the acid mucosubstances had been sialomucines. Ultrahistochemical demonstration of acid phosphatase indicated the presence of this enzyme in Golgi fields and lysosomal structures. Acid phosphatase seems to be missing in the large secretion vacuoles of the prepupal salivary gland.It is concluded, that the large vacuoles in the corpus cells of prepupal salivary glands represent a secretion product, obviously a mucosubstance. The lysosomal structures, containing acid phosphatase, may be accumulated in preparation for the autolysis of the gland which begins about two hours after the pupal moult, i.e. 15 hours after puparium formation.This investigation was supported by grants from the Deutsche Forschungsgemeinschaft (Ga 97/6).     

Structural,ultrastructural and immunohistochemical evidence of testosterone effects and its ablation on the bulbourethal gland of the Artibeus planirostris bat (Chiroptera,Mammalia)

This study evaluated the effects of testosterone in the bulbourethral glands (BG) of the bat, Artibeus planirostris, by performing castration and posterior hormonal supplementation of the animals. The results showed a decrease in testosterone levels in animals 15 days after castration, which induced a small reduction in epithelium height, percentage of AR+ cells, and an increase in the amount of basal cells. This reduction became more severe in groups castrated for longer periods (19 and 22 days), where there was also an increase in apoptotic cells. Moreover, the hormonal supplementation increased testosterone levels (after 3 and 7 days of supplementation), causing a glandular reactivation that increased the epithelium height and AR expression. In conclusion, BG took longer to respond to ablation of testosterone than other reproductive glands, since it showed evident aspects of regression only in animals 22 days after castrated.     

Ultrastructure and cytochemistry of the gastric mucosa of a reptile,Tiliqua scincoides

Summary The gastric mucosa of a reptile, the lizard Tiliqua scincoides, has been examined by light and electron microscopy. The gastric pits lead into glands that are extensively coiled in the proximal stomach but become progressively shorter and straighter in the distal stomach. The following epithelial cell types have been identified: (i) Surface mucous cells (SMC) line the entire lumenal surface as well as the pits. They contain mucus granules that stain with periodic acid-Schiff and, like the granules of mammalian SMC, commonly contain an electron dense core that appears not to be mucus (periodic acid-chromic acid-silver methenamine nonreactive). (ii) Glandular mucous cells are present in glands throughout the mucosa. They are probably homologous with the mucous neck and antral gland cells of mammals; like SMC their mucus granules contain nonglycoprotein cores. (iii) Oxynticopeptic cells (OPC) are the predominant cell type in the proximal glands but become infrequent distally. Their fine structure resembles that of OPC in other nonmammalian vertebrates, with features like those of both parietal cells and zymogen cells of mammals, (iv) Endocrine cells of three different types have been identified. Two of these show close similarities to the EC and ECL cells of mammals.The authors thank Mrs. D. Flavell for technical assistance. This study was supported by a grant from the Clive and Vera Ramaciotti Foundations     

Dynamics of heparin-binding proteins on boar sperm

The presence, topology and dynamics of heparin-binding proteins (HBP) on boar sperm were evaluated. HBP distribution was analyzed by subcellular parting, using biotinylated heparin followed by colorimetric detection. HBP were detected as peripherical and integral periacrosomal membrane proteins. Indirect fluorescence microscopy of sperm incubated with biotinylated heparin was used to evidence heparin binding on sperm at different physiological stages. Two different fluorescent patterns (A and B) were found, which probably correspond to non-capacitated and capacitated sperm as assessed by the ability to undergo acrosome reaction with calcium ionophore A23187 and by the increase of p32 phosphorylated protein. In A pattern, corresponding to untreated sperm, fluorescence located mostly on the post-acrosomal region; in B pattern, corresponding to incubated sperm, on the acrosomal region. Upon incubation under capacitating conditions (TALP), sperm having the B pattern was augmented compared with non-incubated sperm (p < 0.001). Differences in the HBP patterns (p < 0.0001) were observed in sperm incubated under non-capacitating conditions in relation to sperm incubated in TALP, indicating that the modification of HBP patterns is probably related to capacitation. No difference was observed when untreated sperm were permeabilized prior to staining, suggesting that HBP are present on the sperm surface. The effect of heparin on capacitation dependent protein tyrosine phosphorylation was also analyzed, finding a decrease in p32 phosphorylation in the presence of heparin. This suggests that the capacitation enhancement mediated by this glycosaminoglycan involves an alternative intracellular pathway. The finding that heparin binds to sperm differently according to its physiological state, is a new evidence of the remodelling of sperm membrane surface upon capacitation and may provide a useful and relatively simple method to evaluate in vitro modification of boar sperm physiological state.     

An ultrastructural study of oogenesis in a marine triclad

The ultrastructural features of oocyte differentiation were studied in the marine triclad Cercyra hastata. Oocytes at several stages of maturation, each surrounded by follicle cell projections, are present within each of the two ovaries. A pre-vitellogenic and a vitellogenic stage have been detected in the oogenesis of C. hastata. The pre-vitellogenic stage is mainly characterized by an increase in the nuclear and nucleolar volume and activity, and the appearance and development of cortical granule precursors which are elaborated by the Golgi complex. In early phases of the vitellogenic stage, intense delamination and blebbing of the nuclear envelope occurs which probably contributes to an increase in number of cytoplasmic membranes and to transfer of nuclear material to the cytoplasm. The rough endoplasmic reticulum is extensively developed and often assumes a ‘whorl’ array. Several areas of yolk precursor formation appear in the whorls. Numerous 2–5 μm protein yolk globules are subsequently formed which appear surrounded by a double membrane (cisternae of the smooth endoplasmic reticulum) and become randomly distributed throughout the cytoplasm of mature oocytes. The peripheral ooplasm is occupied by a monolayer of electron-dense cortical granules. Finally, the evolutionary significance of the autosynthetic mechanism of yolk production is discussed.     

Comparison of the early chromatin reaction of the mouse thymocytes incubated with phytohemagglutinin and Concanavalin A

Summary The proventriculus, gizzard and pyloric antrum (region between the gizzard and the duodenum) of 18-day Black Australorp chick embryos and of chicks within 30 h of hatching have been studied by electron microscopy. D and EC cells, and putative G, D₁ and A-like cells were identified (terminology of Solcia et al., 1973) but no ECL cells. No endocrine cells of any kind were revealed in the gizzard.Supported by grants from the Senyte Research Comittee of the University of the Witwaterstrand, Johannesburg     

An ultrastructural study of macrophage-mediated resorption of calcified tissue

Summary Ultrastructural observations on macrophage-mediated resorption of calcified tissue of killed fetal long bones are described and correlated with increased ⁴⁵Ca release into the medium. Macrophages disrupt calcified tissue extracellularly and appear to engulf large fragments of mineralized matrix. Ruffled borders, which are common features of osteoclasts at sites of resorption of bone, do not develop in macrophages. However, clear zones are seen in macrophages as well as osteoclasts. These findings provide additional evidence for non-osteoclast-mediated resorption of calcified tissue.This study was supported by Grant DE-04443 from USPHS     

Centrin in Giardia lamblia - ultrastructural localization

Giardia lamblia is a multiflagellar parasite and one of the earliest diverging eukaryotic cells. It possesses a complex cytoskeleton based on different groups of microtubular structures - a ventral adhesive disc, four pairs of flagella, a median body and funis. Centrin is an important member of the EF-hand family of calcium-binding proteins, and it is known to show calcium-sensitive contractile behaviour. In the present study, we performed an ultrastructural localization of centrin in G. lamblia using several monoclonal antibodies to centrin. Microtubular structures such as the basal bodies, all the flagella axonemes, the adhesive disc, funis, and the median bodies presented positive labelling to centrin. In addition, the dense rods also demonstrated positive labelling. These results show that centrin is located in key positions related to microtubules. The role of centrin in these dynamic regions is discussed.     

Ultrastructural changes of Drosophila larval and prepupal salivary glands cultured in vitro with ecdysone

Summary Alterations in the ultrastructure of in vitro cultured larval salivary glands of Drosophila melanogaster in response to the steroid hormone ecdysone were studied in relation to complex changes in puffing patterns. We found that the changes in the fine structure of cultured glands reflected progression of the puffing pattern, and they paralleled those seen in vivo. We observed that glue secretion by exocytosis, the main function of salivary glands, took place between puff stage 5 (PS5) and PS7. Glue could not be expectorated under culture conditions but was slowly released from the lumen through a duct into the medium. After the cultured glands reached PS13/PS14, further progress of puffing and fine structural alterations required that the ecdysteroid titer be transiently extremely low or absent. Under in vitro conditions we did not observe the putative new secretory program(s) described for glands in vivo after PS12. However, ultrastructural changes which unambiguously indicated that an autohistolytic process had begun in vitro started to appear after PS17. Many salivary gland cells developed numerous features of progressive self-degradation between PS18 and PS21. Actual degradation of salivary glands in vivo seemed to be rapid, but in vitro degradation was never completed, probably due to a lack of exogenous factors from the hemolymph. Manipulations of ecdysone titer in vitro in the culture medium, known during the larval puffing cycle to cause premature induction of developmentally specific puffing patterns, did not affect the normal development of ultrastructural features of the cytoplasm and nucleus.