PubMed Health⌕ Search

Biomedical subjects

K Gorgas

Publications and source records attributed to K Gorgas.

At least 37 records · Page 2Linked to original sources
PubMed1989

Biochemical effects and zonal heterogeneity of peroxisome proliferation induced by perfluorocarboxylic acids in rat liver.

Rats were treated for 5 to 14 days with perfluoroacetate, perfluorobutyrate and perfluorooctanoate. Alterations in hepatic morphology with special reference to the peroxisomal compartment were investigated by light and electron microscopy following cytochemical staining of catalase activity with the alkaline 3,3'-diaminobenzidine medium. All three compounds induced hepatomegaly and peroxisome proliferation. Perfluorobutyrate and perfluorooctanoate were found to be more active than perfluoroacetate. Perfluorooctanoate-induced peroxisome proliferation was more prevalent in centrilobular than in periportal hepatocytes. Peroxisomes in centrilobular liver cells frequently were of round shape, exhibited diameters of up to 1.5 microns and were predominantly located within smooth endoplasmic reticulum-glycogen areas. In periportal cells, however, clusters of polymorphous peroxisomes ranging from 250 to 1,100 nm in diameter were observed at the periphery of smooth endoplasmic reticulum-glycogen regions. Peroxisome proliferation was accompanied by a change of peroxisomal and mitochondrial enzyme activities, in particular an increase in peroxisomal palmitoyl-CoA oxidation. Significant alterations in the concentration of peroxisomal matrix and membrane polypeptides were also noted. Within the first 2 days, perfluorooctanoate treatment exerted a strong hypolipidemic activity and both compounds perfluorooctanoate and perfluorobutyrate raised the level of hepatic free acid-soluble CoA nearly 10-fold as compared with control livers. The results suggest perfluorinated carboxylic acids to be model substances suitable to correlate biochemical and morphological parameters with the zonal heterogeneity of the peroxisomal compartment in rat liver. Due to the manifold hepatic effects, contact of humans with perfluorinated carboxylic acids or their metabolic precursors may represent a severe health risk.

Animals↗
PubMed1989

Zonal heterogeneity of peroxisome proliferation and morphology in rat liver after gemfibrozil treatment.

The effect of gemfibrozil on the fine structure of peroxisomes across the rat liver lobule was investigated by light and electron microscopy using the alkaline diaminobenzidine (DAB) medium for the visualization of catalase peroxidatic activity. The oral administration of gemfibrozil for 2 weeks induces a striking heterogeneity in the lobular distribution of peroxisomes. The size and shape of peroxisomes, variety of matrix modifications, catalase content, and position within the cell, are functions of the zonal localization of the hepatocytes. The largest and most numerous peroxisomes were found in the centrilobular region indicating that these cells are most sensitive to peroxisome proliferation. On the other hand, the greatest variety of peroxisome shapes and matrix alterations (tubules and plates) was seen more peripherally in the mid-zonal and periportal regions. The larger, round centrilobular peroxisomes stained less intensely than the elongated peroxisomes found more peripherally, indicating a discrepancy between peroxisome size and catalase content. A distinct population of small irregularly shaped peroxisomes, lacking matrix specializations and containing variable catalase content, was found in the mid-zonal region. Peroxisomes in the centrilobular region were located within areas of the cell containing SER and glycogen while those in the more peripheral region were relegated to areas of the cytoplasm separate from RER and SER. In addition to modifications of peroxisomes, gemfibrozil treatment resulted in a proliferation and formation of whorled configurations of SER. This was particularly evident in the mid-zonal region, where single peroxisomal profiles could be seen surrounded by whorls of SER membranes. The results suggest that rat liver hepatocytes of the centrilobular region are the most sensitive to peroxisome proliferation and those of the periportal area are most susceptible to peroxisome matrix alterations after gemfibrozil treatment.

Animals↗
PubMed1988

Ultrastructure of the kidney of a South American caecilian, Typhlonectes compressicaudus (Amphibia, Gymnophiona). I. Renal corpuscle, neck segment, proximal tubule and intermediate segment.

The ultrastructure of the renal corpuscle, the neck segment, the proximal tubule and the intermediate segment of the kidney of a South American caecilian, Typhlonectes compressicaudus (Amphibia, Gymnophiona) was examined by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and freeze-fracture technique. The glomerular filter apparatus consists of the podocyte epithelium, a distinct basement membrane, a subendothelial space and the capillary endothelium. Emanating from the podocyte cell body, several long primary processes encircle neighboring capillaries. The short slender foot processes originating from the primary processes interdigitate with those from other primary processes, thereby forming the meandering filtration slit. Thick bundles of microfilaments are found in the primary processes, but absent in the foot processes. The basement membrane consists of a lamina rara externa and a rather thin lamina densa (50 nm thickness). The wide subendothelial space contains abundant microfibrils, a few collagen fibrils and many thin processes of mesangial cells. The endothelium is flat and fenestrated (compared to mammals displaying relatively few fenestrations); some of the fenestrations are bridged by a diaphragm. The glomerular mesangium is made up of the mesangial cells and a prominent mesangial matrix containing microfibrils and collagen fibrils. The cells of the neck and intermediate segments display numerous cilia with their microtubules arranged in the typical 9 + 2 pattern. The basal bodies of the cilia are attached to thick filaments with a clear crossbanding pattern of 65 nm periodicity. The proximal tubule is composed of cells typical for this segment (PT cells) and light cells lacking a brush border (bald-headed cells). The PT cells measure 10-25 micron in height and 15-30 micron in width and do not interdigitate at their lateral borders with each other. Their basolateral cell membrane is amplified by many folds projecting into lateral intercellular spaces and into basal recesses. The brush border is scarce and composed of loosely arranged short microvilli.

Amphibians↗
PubMed1988

Modification of surfactant metabolizing cells in rat lung by clofibrate, a hypolipidemic peroxisome proliferating agent. Evidence to suggest that clofibrate influences pulmonary surfactant metabolism.

The influence of clofibrate (ethyl-alpha-p-chlorophenoxy-isobutyrate), a hypolipidemic peroxisome proliferating agent, has been tested on the lungs of adult male rats. Drug administration for 7 days caused structural changes in two types of lung cells, both of which are involved in the metabolism of the pulmonary surfactant. By light microscopy the prominent features were the presence of enlarged type II alveolar epithelial cells and foamy intraalveolar macrophages. Compared with controls, type II cells in treated rats apparently contained more numerous surfactant-containing lamellar bodies, as visualized in semi-thin sections of Epon-embedded tissue. This difference was quantified morphometrically by light microscopy: the number of lamellar bodies was estimated as the profile number per individual type II alveolar cell, transsected at its nucleus. Clofibrate administration for 7 days resulted in a significant increase in the number of the lamellar inclusions. In contrast the number of type II alveolar cells per area of lung remained unchanged. There was no evidence of atelectasis or inflammatory infiltration in the drug-treated lungs, a finding confirmed in sections of perfusion-fixed, paraffin-embedded whole lung-lobes. By electron microscopy the lamellar inclusion bodies in the type II alveolar cells in treated rats, apart from being more numerous and sometimes smaller, were morphologically identical to those in controls. The vacuolated alveolar macrophages seen in treated rats also contained various lamellar phospholipid inclusions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Clofibrate increases the number of peroxisomes and of lamellar bodies in alveolar cells type II of the rat lung.

The hypolipidemic drug clofibrate, which causes a striking proliferation of hepatic peroxisomes, and the induction of peroxisomal lipid metabolizing enzymes, was tested for its influence on rat lung. Alveolar cells type II of the lung are the major source of the surface-active phospholipid-apoprotein complex. Their surfactant-containing lamellar bodies are part of the pulmonary surfactant system. To test the possible relationship between lung peroxisomes and the phospholipid-rich lamellar bodies in alveolar cells type II, clofibrate was administered to male rats. Drug treatment for 7 days resulted in a 30% (p less than 0.001) increase in the number of lamellar bodies within the type II cells, as estimated by morphometry on semithin sections of the lung. In contrast, the average number of type II cells per area of lung remained unchanged which indicates that type II cell proliferation did not occur. Intraalveolar macrophages were consistently vacuolated and markedly increased in size in the lungs of the treated rats. Peroxisomes (microperoxisomes) were identified cytochemically using the alkaline diaminobenzidine (DAB) method for catalase, a marker enzyme of these organelles. Ultrastructural-morphometric analysis of the lungs showed that clofibrate treatment resulted in a 60% increase in the profile number of DAB-positive peroxisomes (p less than 0.005) in alveolar cells type II which are known to be actively involved in the synthesis of the pulmonary surfactant. The number of mitochondria remained unchanged. A great variation in shape and size of the proliferated peroxisomes was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Ultrastructure of hepatocytes in golden ide (Leuciscus idus melanotus L.; Cyprinidae: Teleostei) during thermal adaptation.

The morphological alterations of hepatocytes of golden ide, Leuciscus idus melanotus, following adaptation to low and high temperatures (14 and 28 degrees C) were investigated by means of light and electron microscopy. The temperature-dependent behaviour of peroxisomes was visualized cytochemically with the alkaline diaminobenzidine medium; the morphological studies were supplemented by the biochemical determination of catalase activity. Cold adaptation of ide hepatocytes is manifested by proliferation and stacking of endoplasmic reticulum, an enhanced secretory activity of Golgi fields and a higher number of peroxisomes as compared with the warm-adapted animals. The latter organelles are characterized by a marked heterogeneity in size, shape and catalase activity, and by a more intimate association with mitochondria and endoplasmic reticulum. The occurrence of small peroxisomal profiles is restricted to lower temperature. Catalase activity can be shown both cytochemically and biochemically to increase during cold adaptation. Whereas the number of mitochondria seems to be unaffected by thermal adaptation, stacking of mitochondria as well as the formation of intramitochondrial membrane piles indicate cold-adaptive processes. A feature typical of warm-adaptation is the formation of membrane-glycogen complexes, which may represent the morphological expression of enhanced carbohydrate metabolism documented in a decreased storage of glycogen at 28 degrees C. At 28 degrees C lipid is the predominant storage product. These findings indicate that fish liver is well-suited to serve as a model for the analysis of the interaction of environmental temperature conditions and hepatic morphology.

Adaptation, Physiological↗
PubMed1985

Morphology and innervation of a testicular 'rete mirabile' in the guinea-pig.

The morphology and innervation of the testicular artery and pampiniform plexus of the guinea-pig was investigated using light immunohistochemistry as well as transmission and scanning electron microscopy. The tortuous, spiraled testicular artery embedded within the epididymal fat pad is totally encompassed by a thin-walled sinus-like labyrinthine structure comprising the pampiniform plexus. Characteristic features of this lacunar system are: 1. Endothelial bridges, strands or trabeculae of various length, width and thickness which project into the lumen, occasionally branch, and attach to the opposite or adjacent area of the venous wall. 2. A frequent discontinuous smooth muscular layer. Nerve fibers were localized by use of antibodies against dopamine-beta-hydroxylase (DBH-IR), neuropeptide Y (NPY-IR), and substance P (SP-IR). A great abundance of NPY-IR and DBH-IR axon bundles are seen surrounding the testicular artery. Fibers emanating from this dense plexus travel into the interstitium to finally innervate the walls of the sinus-like system, including the cross-luminal trabeculae. In contrast, larger varicosities are distinctive for SP-IR fibers which are also located at the media-adventitia border of the arterial and venous walls but to a far lesser extent than that seen with DBH-IR or NPY-IR. The axon varicosities supplying the arterial and venous walls contain a heterogeneous population of various types of vesicles, mostly including small agranular and granular ones as well as large granular vesicles of various size and density. The most conspicuous feature concerning the innervation pattern of the venous wall is the occurrence of numerous neuroendothelial contact zones. The findings of the investigated 'rete mirabile' are discussed with respect to rheology and temperature control for the maintenance of normal spermatogenesis.

Animals↗
PubMed1985

Serial section analysis of mouse hepatic peroxisomes.

The ultrastructure and organization of mouse hepatic peroxisomes were investigated using serial thin sections and the alkaline diaminobenzidine technique for visualization of the peroxidatic activity of catalase. Mouse periportal hepatocytes exhibit three classes of peroxisomes which display morphological and cytochemical heterogeneity: 1) large, circular to ovoid organelles containing a crystalline nucleoid, 2) small, circular to elongate, anucleoid particles, and 3) tail-like extensions which are devoid of both catalase activity (only traces of reaction deposits) and a crystalline core. Serial section analysis reveals that these profiles correspond to three diverse interconnecting peroxisomal segments which constitute a highly complex organelle. In particular, the large nucleoid-containing peroxisomal segment exhibits an intimate relationship to the endoplasmic reticulum. However, direct membrane continuities between the two compartments are never observed. With respect to the complex structure of the organelle the following conclusions can be drawn concerning biochemical studies on liver peroxisomes: 1) During homogenization and subcellular fractionation procedures, fragmentation of peroxisomes into particles of different size classes should be expected. 2) These peroxisomal fragments are inhomogeneous with respect to their matrix contents and possess at least one rupture site on their membrane surface. 3) Soluble matrix and, to a lesser degree, membrane components of peroxisomes contribute to the soluble fraction. 4) Crude microsomal fractions are regularly contaminated by peroxisomal membrane fragments.

Animals↗
PubMed1984

Marginal plates in hepatic peroxisomes of Ichthyophis glutinosus (Amphibia: Gymnophiona). A cytochemical study.

The ultrastructure of hepatic peroxisomes was investigated in Ichthyophis glutinosus (Amphibia: Gymnophiona), employing perfusion fixation and the diaminobenzidine (DAB) technique for the visualization of catalase. The majority of peroxisomes is circular or rod-shaped, although elongated particles occasionally occur. They contain a finely granular matrix, lightly stained after the DAB procedure. Their mean diameter is approximately 0.25 micron. Serial sections reveal that the circular and rod-shaped peroxisomal profiles are cross and oblique sections of highly tortuous, tubular organelles exceeding 2 micron in length. In addition to tubular profiles, elongated, rectangular particles, as well as straight dumbbell-shaped organelles with distinct marginal plates are observed. They range from 900 to 1650 nm in length (mean = 1200 nm). In the flattened, thin central portion of the dumbbell-shaped particle, the peroxisomal membranes form a cisterna enclosing one or two uniformly thick marginal plates, which display a definite substructure with a periodicity of 10 nm. These findings indicate that peroxisomes in the liver of Ichthyophis exhibit a complex organization. It is suggested that the organelles undergo a specific differentiation process, morphologically characterized by the formation of enlarged segments of unusual shape.

3,3'-Diaminobenzidine↗
PubMed1984

Peroxisomes in sebaceous glands. III. Morphological similarities of peroxisomes with smooth endoplasmic reticulum and Golgi stacks in the circumanal gland of the dog.

In the canine circumanal gland, the morphological alterations of peroxisomes during differentiation and maturation of the glandular cells were studied by electron microscopy, cytochemistry and freeze-etch technique. Each of the following three cell types has its own characteristic peroxisomal population: 1) The basal cell contains only a few small peroxisomes, which appear as spherical and tubular profiles showing strong DAB reaction. In the differentiating basal cells, these are joined by a few dilated, hemispherical organelles with intensely stained small marginal plates. 2) In the intermediate cell, additional to spherical and tubular peroxisomes, numerous elongated organelles with distinct marginal plates are observed, displaying weak catalase activity. 3) In the mature cell, dumbbell-shaped peroxisomes with enlarged marginal plates predominate. Serial section analysis and freeze-etching studies reveal that these dilated particles are of erythrocyte-like shape. They exhibit very weak catalase activity or do not contain any visible DAB reaction product. In their flattened, thin central portions, the membranes enclose the marginal plates and form straight cisternae, which are closely associated with adjacent fenestrated cisternae of ER on both sides, referred to as paramarginal cisternae. Dumbbell-shaped peroxisomes with their corresponding paramarginal cisternae form large peroxisome-ER-complexes. Furthermore, three to five dumbbell-shaped particles are often stacked in parallel. Only at their flat poles are the organelles in close contact with paramarginal cisternae. The observation of continuities, in particular between erythrocyte-like organelles and tubular peroxisomes in mature glandular cells, indicates the existence of a peroxisomal compartment composed of two segments in the mature stage. In freeze-etch replicas of mature glandular cells, only the dilated segments of the peroxisomal compartment can be easily recognized because of their unusual size and erythrocyte-like shape. Additionally, on the E-face of their central portion, a straight, square or rectangular area with a distinct crystalline pattern is seen, which corresponds to the marginal plate. These findings indicate that the circumanal gland of the dog offers a unique possibility to analyze the biological properties of a well-defined peroxisomal compartment.

Animals↗
PubMed1984

Peroxisomes in sebaceous glands. V. Complex peroxisomes in the mouse preputial gland: serial sectioning and three-dimensional reconstruction studies.

The ultrastructure of peroxisomes in partially differentiated cells of the mouse preputial gland was investigated using serial thin sections and three-dimensional reconstruction as well as the alkaline diaminobenzidine technique for visualization of the peroxidatic activity of catalase. An analysis of serial sections indicates that the different types of intensely stained peroxisomal profiles, classified according to their shape, represent random planes through highly complex peroxisomes. These organelles exceed 4 micron in length and exhibit a focal heterogeneity with respect to their size, shape and enzyme distribution. The graphical three-dimensional reconstruction demonstrates that the most intricate peroxisomes are characterized by tortuous, elongate, and branched tubular segments of varying diameter equipped with enlarged terminal hollow-spherical structures which engulf areas of cytoplasm. A close spatial relationship is established between adjacent peroxisomes and peroxisomes and mitochondria, the latter two of which synchronously develop into highly complex structures. A close association is also observed between peroxisomes and the endoplasmic reticulum, whereby membrane continuities between the two compartments cannot be demonstrated. These observations are inconsistent with traditional concepts concerning peroxisomal shape and size, the number per cell, as well as their biogenesis from the endoplasmic reticulum. The functional significance of individual highly complex peroxisomes and their assemblage forming an extensive net-like membraneous system throughout the cell is discussed with respect to intracellular energy transport and transmembrane electron exchange.

Animals↗
PubMed1984

Peroxisomes in sebaceous glands. IV. Aggregates of tubular peroxisomes in the mouse Meibomian gland.

The occurrence of peroxisomes, their morphogenesis during the process of sebaceous transformation and their spatial relationship to the endoplasmic reticulum and lipid droplets were investigated by light and electron microscopy after visualization of the peroxidatic activity of catalase using an alkaline diaminobenzidine medium. The morphological alterations of peroxisomes display a characteristic sequence: During cellular differentiation, a remarkable proliferation of exclusively tubular, diaminobenzidine-reactive peroxisomes occurs. As maturation proceeds, an extensive elongation of tubular peroxisomes is seen. Concomitantly, they are densely packed in a regular, hexagonal arrangement and both the diameter and the catalase content gradually decreases. The most conspicuous feature of mature glandular cells are numerous highly organized aggregates of tubular, almost unstained peroxisomes with a diameter of 50 nm, arranged in a hexagonal pattern. They resemble adjacent tubular profiles of smooth endoplasmic reticulum. However, membrane continuities between these two compartments were never observed. During lethal disintegration peroxisomes subsequently decrease in number, probably by rapid sequestration within autophagolysosomes. The role of tubular peroxisomes in the biosynthesis of wax esters in the mouse Meibomian gland is discussed.

Animals↗
PubMed1983

Neurotensin and substance P immunoreactive nerve endings in the guinea pig carotid sinus and their ultrastructural counterparts.

The carotid sinus of the guinea pig was analysed immunohistochemically for the occurrence of neuropeptides. Immunoreactivity (IR) for neurotensin (NT) and substance P (SP) is distributed in two different populations of nerve endings and varicosities. NT-IR fibers penetrate deeply into the tunica media of the elastic segment of the carotid sinus and form the large, branched lanceolate nerve terminals. Electron-microscopic investigations have revealed that the NT-IR varicosities correspond to the large afferent baroreceptor endings containing abundant mitochondria. SP-IR fibers are located mainly at the media-adventitial border. They seem to be correlated to dense-core, vesicle-containing varicosities identified in the electron microscope. Therefore, these fibers may constitute afferent and efferent perivascular plexus regulating the vascular tone of the carotid sinus wall.

Animals↗
PubMed1979

[The fine structure of myotendinous and myo-epithelial junctions in the guinea pig tongue (author's transl)].

The insertion of muscle fibers in the subepithelial connective tissue layer of the guinea pig tongue was studied light and electron microscopically. Fibers of the tractus verticalis approach the epithelium penetrating the lamina propria, both the reticular and papillar layer. Terminating muscle fibers split up and form branching finger-like cytoplasmic processes. The myotendinous junctions of such terminal processes fine structurally correspond to myotendinous junctions generally observed in skeletal or smooth muscles. The entire brush-like formation, however, is more far-reaching and highly differentiated. Filament bundles (spine-like profiles) originate from the plasmalemma and extend to the lamina densa of the basal lamina, especially in those regions where actin filaments are attached to the plasmalemma. Microfibrils (10 to 12 nm diameter) reach the lamina densa of the basal lamina. They form bundles which are continuous with fibrotubular strands of elaunin fibers and elastic fiber microfibrils. Furthermore, microfibrils are interwoven with collagen fibrils.

Animals↗
PubMed1977

The fine structure of human digital arterio-venous anastomoses (Hoyer-Grosser's organs).

Hoyer-Grosser's organs were studied in human digital biopsies. The fine structure of both the supplying arteries and collecting veins was found to be inconspicuous. Endothelial cells in the AV canals form a continuous layer. They are characterized by their rich content of specific organelles (Weibel-Palade bodies), especially in the venous segments. The epitheloid zone is composed of a variety of ramified smooth muscle cells (RSM). These appear either dense, when well provided with bundles of myofilaments, or clear, when including only a few myofilaments. The nuclei of dense RSM show condensed chromatin, while those of clear RSM are larger with loose chromatin texture. In addition, all transitional forms occur. Cell organelles are rarely seen within all types of RSM. The cytoplasmic processes reach other as well as endothelial cells. The preservation of our material did not allow observation of specialized membrane contacts in these zones. All RSM are invested with a regular basal lamina and well provided with surface vesicles. Profiles of free basal lamina material and faint collagen (argyrophil) fibers are seen in the wide intercellular spaces. RSM poor in myofilaments are interpreted to represent "epitheloid cells" of light microscopy. Their number constantly decreases from the arterial segment of the AV canal to the venous segment. Here the cytoplasmic processes of RSM become less pronounced and the wall of the anastomotic segment continuously changes to that of the collecting vein. Dense RSM rich in myofilaments are compared with pacemaker cells found inthe ureter. Both internal and external elastic membranes are absent in AV canals. A dense network of unmyelinated nerve fibers is found in the adventitial layer of the AV canal, especially in its arterial segment. The axons branch out from small dermal nerves which also contain two or three myelinated axons. The myelin sheaths terminate where the axons reach the adventitia of the AV canals. Axon varicosities filled with mitochondria are thought to be terminals of myelinated axons and are interpreted as receptory. Axon varicosities with synaptic-type vesicles are assumed to be terminals of sympathetic and para sympathetic fibers. All axon profiles are confined to the adventitial layer of the anastomotic segment.

Arteriovenous Anastomosis↗