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Biomedical subjects

U Welsch

Publications and source records attributed to U Welsch.

At least 109 records · Page 6Linked to original sources
PubMed1983

Ultrastructural changes in lactating tissue related to the suppression of milk secretion by concanavalin A.

The plant lectin, concanavalin A (Con A) suppresses milk secretion when infused into the mammary gland or when incubated with lactating tissue in vitro. Toward defining its mode of action, we infused Con A into rat and goat mammary glands via the teats and observed effects on lactating cells. Lectin dosages were 2 and 25 mg per gland for rats and goat, respectively. Tissue samples were taken 1 and 3 h post infusion for rats and at 24 h for the goat. Control and Con A-treated tissues were observed by light microscopy and by both thin section and freeze fracture electron microscopy. In comparison to controls, Con A-treated tissues of both species exhibited alveoli with enlarged cells and relatively empty lumina; cells were distended with secretory vesicles and fat droplets. Apical plasma membranes of lectin-affected cells of the rat displayed a marked reduction in the number of microvilli, and exhibited an atypical branching and folded structure. Morphometry was employed to quantitate changes in cell and secretory product parameters in both rat and goat tissue. Microtubule numbers and distribution did not appear to be altered by Con A but considerable changes were noted in the arrangement of microfilaments associated with the secretory surface of lectin-treated epithelial cells. Various related ultrastructural changes and the role of Con A in perturbing the microfilament system are discussed.

Animals↗
PubMed1983

Septate junctions with paired septa in the cephalochordate Branchiostoma lanceolatum.

The cells of the atrial epithelium of Branchiostoma lanceolatum are interconnected by an apical zonula adhaerens and a septate junction extending between the apical zonula adhaerens and a level corresponding to the middle of the nucleus. The spacing of the septa, which are relatively few in number (about 10), varies considerably. Within the junction paired and unpaired septa occur. The thickness of the paired septa measures 16-25 nm, the distance between the individual septa of the paired structure 6-12 nm, and the intercellular space at the site traversed by the septa 17-20 nm. At the intersection between three cells the septa (paired or unpaired) delineate a central triangular space.

Animals↗
PubMed1983

In vivo binding and effects of concanavalin A (Con A) on rat and mouse pulmonary alveolar epithelial cells and macrophages.

The binding and effects of inhaled or infused concanavalin A (Con A) preparations on rat and mouse pulmonary alveolar epithelium and macrophages were studied by a number of light- and electron-microscopical techniques. In comparison with BSA, inhaled Con A persisted considerably longer in the lung indicating the presence of Con A-receptors and mechanisms which prevent its rapid removal. In the lung periphery ferritin-labeled Con A was bound to type I and II pneumonocytes and macrophages. The density of binding sites was greater on type II than type I pneumonocytes. Within the time studied (up to 2 h) comparatively small amounts of the lectin were incorporated by endocytosis into the alveolar epithelium. The pulmonary macrophages bound and incorporated massive amounts of the lectin by endocytosis within 15 min. High doses of Con A lead to morphological deformation of the apical cytoplasmic zone of type II pneumonocytes and to a partial or complete collapse of the alveolar lumen. The possibility that the lectin may suppress surfactant secretion is discussed.

Animals↗
PubMed1983

Phagocytosis in the amphibian lung.

The experimental administration of carbon particles into the lung of 2 amphibian species (Bufo fowleri, Kaloula pulchra) induces the appearance of macrophages in the alveoli, which evidently are derived from blood monocytes. These cells are characterized by high activities of acid phosphatase and alpha-naphthyl acetate esterase. They take up the carbon particles into membrane bound vacuoles of variable sizes. In addition carbon was found in lysosomal bodies and free in the cytoplasm. Large accumulations of intraalveolar carbon are surrounded by 2 to 3 layers of flattened macrophages. These cells can multiply by mitosis. Laden with carbon they can disintegrate or return into the connective tissue underneath the alveolar epithelium. This epithelium exhibits a marked activation in areas of intraalveolar carbon deposits: increase in volume, formation of a well developed brush border, generation of a large nucleolus and numerous cisterns of the rough ER. The epithelial cells ingest carbon particles which can be found within clear vacuoles or lamellated bodies. Activated epithelial cells can undergo mitosis.

Amphibians↗
PubMed1983

The fine structure of the parabronchi and the gas exchange area of the Adelie penguin lung.

The parabronchi of the Adelie penguin are endowed with wide atria forming pockets between a loose meshwork of bundles of smooth muscle cells lining the parabronchial lumen. The atrial epithelium is of variable thickness and bears numerous microvilli, which are overlain by/or embedded in sheets or whorls of lamellar material ("trilaminar substance", diameter of one lamella 8 ..10 nm) forming layers of very variable thickness. The cells contain either stacks or whorls of this material or roundish lamellated bodies, and are interconnected by desmosomal contacts as well as what presumably represent tight junctions. Underneath the epithelium and within the bundles of muscle cells regularly nerve fibres have been found. The diameter of the morphological air/blood barrier is about 165...210 nm in thin areas, excluding a 12...20 nm thick layer covering the luminal plasma membrane of the air capillary epithelium. The blood capillary endothelium ordinarily is markedly thicker (40...250 nm) than the air capillary epithelium (17...25 nm). The basal lamina between endo- and epithelium is a uniform structure measuring about 95...105 nm. The endothelial cells are interconnected by desmosomal and probably tight junctions.

Animals↗
PubMed1982

Light- and electron microscopical observations on the caecilian spleen. A contribution to the evolution of lymphatic organs.

Red and white pulp were distinguished in the spleen of the caecilian species Ichthyophis paucisulcus and Afrocaecilia taitana. The red pulp was composed of endothelium-lined sinusoids and reticular connective tissue. Between the processes of the reticulum cells, accompanied by fine collagen fibrils, the following cell types were found: lymphocytes, macrophages (frequency containing fragments of erythrocytes), neutrophils, eosinophils, mast cells and/or basophils (metachromatic granules), thrombocytes, plasma cells, pigment cells as well as cells which presumably represent blast cells. Morphological evidence suggested the formation of thrombocytes in the red pulp. Besides sinusoids, ellipsoids and peculiar arteriolar vessels with a high endothelium and a loose layer of muscle cells were observed. Veins were concentrated in the splenic periphery. White pulp consisted of arterioles which were surrounded by a lymphocyte sheath. Follicles were not identified with certainty. Occasionally mitotic figures were associated with lymphocytes. On the basis of our findings, we suggest the following functions of the caecilian spleen: destruction of aged erythrocytes, formation of thrombo- and lymphocytes as well as of plasma cells and, to a marked lesser degree, of other blood cells.

Amphibians↗
PubMed1981

The telencephalon of Ichthyophis paucisulcus (Amphibia, Gymnophiona (= Caecilia)). A quantitative cytoarchitectonic study.

A parcellation of the telencephalon of Ichthyophis paucisulcus (Amphibia, Gymnophiona (= Caecilia) has been performed with a quantitative cytoarchitectonic method. Ten different regions have been delineated and compared with earlier reports on telencephalic regions in anurans, urodeles and caecilians. The most striking difference between the brain of Ichthyophis and other amphibian brains is the high level of morphological differentiation of the accessory olfactory bulb in Ichthyophis and the large extension of this brain region. This feature may be a correlate of the advanced development and the particular structure of Jacobson's organ in this species.

Amphibians↗
PubMed1980

[Electron microscopic studies of reptilian lung innervation].

The Reptilian lung is richly innervated, in all species investigated bundles of nervefibres and autonomous ganglia have been detected. Several types of nerves and nerve endings of varicosities can be differentiated. The possible cholinergic, adrenergic and purinergic nature of the 3 types of nerve endings or varicosities is discussed on the basis of morphological criteria. The nerve terminals have been observed at intrapulmonary neurons and in the immediate neighbourhood of smooth muscle cells and of pneumocytes II.

Adrenergic Fibers↗
PubMed1980

[Ultrastructural studies of the alveolar epithelium of reptiles living in different habitats].

The alveolar epithelium of various reptiles living in different habitats has been investigated with the light and electron microscopes. In all species pneumocytes of type I and II can be distinguished. The comparatively uniform pneumocytes I cover the blood capillaries and usually exhibit a smooth surface. Occasionally they bear in their marginal parts, especially when bordering a pneumocyte II, some microvilli. Their main characteristics are: pinocytotic vesicles and apical bundles of microfilaments. In the aquatic Trionyx particularly thin areas resembling precursor structures of a fenestration have been detected. In this species the blood-air barrier is unusually thin (280...350 nm). The thickness of this barrier otherwise varies considerably: in Agama, Chamaeleo, Hemidactylus and Pseudemys it measures normally less than 400 nm. In Tamnophis, Caiman and various turtles it measures from 400 to over 500 nm. The pneumocytes II exhibit a remarkable morphological variability which concerns a) the cellular dimensions, b) the microvilli, c) diameter, number and structure of the lamellar bodies, d) the number of mucous granules, e) the lateral and basal labyrinth. The lamellar bodies are especially numerous in the terrestrial species Hemidactylus and Testudo. Most aquatic turtles contain few pneumocytes II with few lamellar bodies. In the squamata the blood capillaries bulge into the alveolar lumen, in turtles and tortoises they are deeply embedded into the connective tissue.

Animals↗
PubMed1979

[Enzyme histochemical study of the brain of Chthonerpeton indistinctum (Gymnophiona, Amphibia)].

In the brain of the Caecilian species Chthonerpeton indistinctum the following enzymes have been demonstrated by means of histochemical techniques: acid phosphatase, alpha-naphthylacetate esterase, acetylcholin esterase. Acid phosphatase occurs in the cytoplasm of the neurons in 4 different types of localization. Its activity in the ventral parts of the brain is markedly higher than in the dorsal ones. Of particularly high activity are: the motor neurons in the tegmentum, the nucleus mesencephali trigemini, individual large neurons in the marginal zone of the grey matter of the telencephalon, which seems to be a special character of the Caecilians among the Amphibia. The ependyma exhibits local differences in respect of acid phosphatase activity. alpha-Naphthylacetate esterase marks in particular the secretory neurons of the hypothalamus, the large perikarya of the nucleus mesencephali trigemini and the motor neurons of the tegmentum. In the telencephalon the alpha-naphthylacetate esterase activity corresponds to that of acid phosphatase. Acetylcholin esterase marks--with certain restrictions--cholinergic neurons. These predominate in Chthonerpeton in the caudal parts of the brain. In the telencephalon amygdala, septal area striatum and the mitral cells are of comparatively high activity. The neurosecretory neurons of the hypothalamus are particularly rich in this enzyme. As an anurans the cholinergic fasciculus retroflexus as asymmetric. The tectum opticum is of secondary simplicity and does not exhibit a clearly recognizable stratification.

Acetylcholinesterase↗
PubMed1977

Freeze fracture studies on the annelid septate junction.

Freeze-fractured preparations of septate junctions between epidermal cells of annelids (Lumbricus terrestris and Tubifex spec.) have been investigated. In Lumbricus the protoplasmic face (PF) of the plasma membrane is characterized by variously arranged rows of particles. Apically the rows take an undulating course and often are separated by wide distances. In the basal part of the junction the rows run closely together and more or less in parallel. The diameter of the particles measures 80--120 A, the distance between two particles (centre to centre) is 150--250 A. Additionally striking rows of large particles (long diameter 150--200 A). Are to be observed mainly near the basal part of the junction. In Tubifex both faces of the plasma membrane could be studied in detail. The protoplasmic face (PF) contains rows of distinct individual particles (mean diameter 100--150 A, centre to centre distance approx. 250 A) whereas the particles of the extracellular face (EF, mean diameter 200-250 A) usually form continuous strands in which the individual particles seem to fuse. The density of arrangement of the strands varies considerably. Additionally ladder-shaped membrane structures have been observed in plasma membranes of this species.

Animals↗
PubMed1977

Histological, immuno- and enzyme-histochemical investigations on the adenohypophysis of the urodeles, Mertensiella caucasica and Triturus cristatus and the caecilian, Chthonerpeton indistinctum.

The pituitary glands of two urodelan species (Mertensiella caucasica, Triturus cristatus) and one one caecilian species (Chthonerpeton indistinctum) were examined with histological (Alcian blue, Brookes' trichrome stain), enzyme histochemical (acid phosphatase, alpha-naphthylacetate-esterase, acetylcholinesterase) and immunofluorescence techniques (anti-carp GTH, anti-ovine prolactin, anti-synthetic alpha-MSH). In the pituitary gland of Mertensiella and Triturus six chromophilic cell types could be distinguished. A strong fluorescence was observed in the MSH-, GTH- and TSH-cells. In the pituitary gland of Chthonerpeton only five chromophilic cell types could be distinguished: in the rostral part of the pituitary gland the B3-cell; in the basal region of the central area the B2-cell; dorsocaudally the B1-cell. The acidophilic cells were found in the central and caudal part of the pars distalis. The basophils of the pars intermedia could be observed in the dorsocaudal part of the pituitary gland surrounding the neurohypophysis. All acidophilic cells showed a strong immunofluorescence with anti-ovine prolactin (LTH).

Acetylcholinesterase↗
PubMed1977

Freeze-etching of unglycerinated tissue dispersions by application of the oil emulsion technique.

The oil emulsion technique has been applied to rat brain and liver tissue for freeze-etching preparation without antifreeze pretreatment. It has been demonstrated that the dispersed tissue exhibits a high degree of vitrification throughout the mostly globular fragments up to at least 30 micrometer in diameter. Signs of insignificant ice crystal formation of 50 nm and less could only rarely be detected. Although the dispersion process seriously affects the tissue organization as a whole, most cellular organelles and the plasma membrane show satisfactory preservation of structure. In larger tissue drops, a local overall structural preservation of the original cellular organization is recognizable. The results obtained demonstrate the applicability of this method to various biological objects for realizing sufficient cryofixation in the absence of cryoprotectants.

Animals↗
PubMed1976

Histological and histochemical observations on the neurosecretory cells in the diencephalon of Chthonerpeton indistinctum and Ichthyophis paucisulcus (Gymnophiona, Amphibia).

In the diencephalon of two species of Gymnophiona (Amphibia) two neurosecretory nuclei were examined with histological (Alcian Blue, Aldehyde Fuchsin, Brookes Trichrome stain) and enzyme histochemical techniques (acid phosphatase, alpha-naphthyl acetate esterase, acetylcholinesterase (AChE)). In the preoptic nucleus two categories of secretory neurons were distinguished: large and medium sized neurons. The perikarya of both cell types contain very little neurosecretory material. The Alcian Blue method stained the medium sized neurons faintly but selectively. The tractus praeopticohypophyseus is marked by the presence of Herring bodies, which, however, are relatively scarce. The neurohypophysis, in contrast, contains large amounts of neurosecretory material. Both cell types of the preoptic nucleus are characterized by their very strong AChE and alpha-naphthylacetate esterase activity. The AChE also marks the tractus praeoptico-hypophyseus. In the large neurons acid phosphatase is present around the nucleus; in the medium sized neurons this enzyme is concentrated close to the origin of the axon. In the dorso-caudal hypothalamus a small group of neurons is stained with Alcian-Blue. These neurons, which also contain AChE, are located immediately under the ependyma which seems to be specialized in this region.

Acetylcholinesterase↗
PubMed1976

The influence of temperature on the thyroid gland of Chthonerpeton indistinctum (Gymnophiona, Amphibia).

The thyroid gland of the tropical amphibian Chthonerpeton is markedly stimulated when the animal is exposed for two days to relatively high temperatures (36 degrees C). Control animals were kept at 20 degrees C. The stimulated gland exhibits collapsed follicles and a very tall follicular epithelium. At the ultrastructural level the activated epithelial cells were characterized by an increased number of apical microvilli, increased amounts of rough endoplasmic reticulum, an extended Golgi apparatus and a high number of various granular and vesicular inclusions. These differences in histology and fine structure were not paralleled by quantitative results, which were approximately the same in both groups of animals. The values of these determinations were relatively high.

Amphibians↗