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At least 595 records · Page 33Linked to original sources
PubMed1996

Ultrastructural changes in the blood-brain barrier in rats after treatment with nimodipine and flunarizine. A comparison.

The idea of using induced hypertension to treat the symptomatic ischaemia resulting from vasospasm after subarachnoidal hemorrhage, and the effect of this therapy on the blood-brain barrier, is checked in animal experiments. This therapy is combined with the application of nimodipine, which is recognised as the standard medication for prophylaxis of vasospasm. The effects of the induced hypertension combination with Nimodipine and in combination with another calcium antagonist, Flunarizine are compared. Seventy-four narcotised rats, one group with 22 animals treated with Nimodipine and 22 with placebo, and a second group 20 animals treated with Flunarizine and 10 with placebo, are evaluated. The blood pressure is raised to 150-180 mmHg by i.v. application of norfenephrine and measured continuously. The standard tracer, horseradish peroxidase, is applied as indicator for the blood-brain barrier function. 15 minutes later the experimental animals are exsanguinated by perfusion with saline, then perfused with Karnovsky's solution. After removal, the brains are stained for peroxidase to visualise extravasation of the horseradish peroxidase, and after evaluation of the results each brain is assigned to its experimental group. In the Nimodipine group, a significant accumulation (p < 0.001) of perivascular deposits of peroxidase reaction product were found, these were not found in the placebo group. The Flunarizine group does not differ from its placebo group in the number of extravasates, and thus, with respect to protein extravasation, appears better than the Nimodipine group. In electron micrographs of the extravasates one sees intact tight junctions and a neuroendothelial transport, and also vesicles, filled with horseradish peroxidase in the endothelium, the muscle cells, and the brain parenchyma, which arise from pinocytosis. The vesicles, which transport the high-molecular-weight protein, horseradish peroxidase, also transport other proteins and can, therefore, cause a brain edema. It follows from these morphological results that Nimodipine can disrupt the blood brain barrier function and can, therefore, also interfere with cerebral autoregulation, which depends on the resistance of vessels.

Animals↗
PubMed1975

Structure and mode of function of the organelles associated with nutrition of the macrogametes of Eimeria acervulina.

The macrogamete of Eimeria acervulina, lay and developed within the host cell in a parasitophorous vacuole. The cytoplasmic membrane of the host cell bordering the vacuole was not smooth, but it had numerous folds extending into the vacuole. These "intravacuolar folds" varied in depth and number in different sections. In some, the majority of the folds were disconnected from the host cell. Once disconnected, they evidently disintegrated forming the amorphous, particulate material present in the parasitophorous vacuole. The pellicle of the young macrogamete consisted of a single unit membrane with an osmiophilic material representing the second membrane. Two unit membranes were apparent at a later stage of development when the wall-forming bodies had been formed and amylopectin granules deposited. Two kinds of organelles were present on the surface of the macrogamete, typical micropores and invaginations of the pellicle. The micropores arose from an invagination of the outer membrane, which continued through the invagination without interruption. Irrespective of whether an inner membrane was present in the pellicle or not, a thickened cylindrical wall around the inner portion of the invagination was always present. Micropores appeared in large numbers in both micro- and macrogametocytes. As many as three micropores were seen in a surface area of 2 mu2. Invaginations arose in a similar manner by infolding of the pellicle. They differed from micropores in that the thickened cylindrical wall present around the inner portion of the micropore was absent, and also in that invaginations had no uniform appearance. They were of varying shapes, and lengths, varying from very short V-shaped to long and narrow. Micropores and invaginations take in nutrients in the form of particulate matter present in the parasitophorous vacuole, this material having been derived from the host-cell membranous "intravacuolar folds". The micropores function as cytostomes and the invaginations take in material by means of pinocytosis. Large numbers of intravacuolar tubules were seen at the surface of the macrogamete. They were present only at certain areas of the macrogamete and in groups and were connecting the parasite with the host cell. They were about 80-110 nm in diameter, and were seen to attain a length of up to 6 mu. Evidence was obtained indicating that the tubules transport free ribosomes from the host cell to the parasite. The ribosomes were seen to accumulate in "pockets" within the cytoplasm of the host cell, at the area where the tubules were connected.

Amylopectin↗
PubMed1975

An electron microscopic and cytochemical study of the cell coat of Trypanosoma cruzi in tissue cultures.

Using the cytochemical method of Thiery, a polysaccharide surface coat was demonstrated with the electron microscope in the various developmental stages of Trypanosoma cruzi maintained in tissue cultures. The cell coat was observed on the whole surface membrane system of T. cruzi. A positive reaction, similar to that observed in the cell membrane, was also obtained in the membranes of some vacuoles in the cytoplasm of the parasites. No granules were found in the parasites. No granules were found in the parasite which could represent reserve polysaccharides. The possible role of the cell coat in such phenomena as adhesion, agglutination, phago- and pinocytosis and antigenicity is discussed.

Adhesiveness↗
PubMed1979

Fine structural evidence of increased endothelial permeability in chronic lathyrism.

The endothelium of the thoracic aorta of Wistar rats intoxicated with Beta-Aminopropionitrile (BAPN) for 9 weeks was studied. The animals were sacrificed at intervals, from the first to the 9th week of the treatment and 1, 2 and 3 months after the end of the treatment. Changes in the endothelial cells were studied by electron microscopy after staining with uranyl acetate and lead citrate, after impregnation with lanthanum. BAPN increased endothelial permeability, pinocytosis was more active in treated rats than controls, the intercellular junctions widened and cytoplasmic lesions with cell necrosis occurred. These intimal changes were comparable to those observed in man during ageing and in arteriosclerosis.

Animals↗
PubMed1975

A hypothesis for the pathogenesis of Crohn's disease based on an ultrastructural study.

The epitheloid cells forming the granulomata of Crohn's disease show striking vacuolation from the coalescing of pinocytotic vesicles with double membrane-bound bodies and their subsequent fusion with lysosomal dense bodies. The fine detail of the granulomata in each individual is uniform but varies from case to case in such a way as to suggest an episodic stimulation of pinocytosis and vacuole formation. The production of such granulomata with these cyclical appearances is consistent with an intermittent stimulus by exogenous antigen or antigen antibody complexes arriving in the diet.

Adolescent↗
PubMed1977

Studies on the binding characteristics of antimycin A and albumin in relation to the inhibitor activity of the complex on rat proximal tubular sodium transport.

As reported previously [11] Antimycin A is effective in inhibiting sodium transport of the proximal tubule only when applied to the luminal side and in the presence of albumin. Therefore the interaction of Antimycin A with albumin was examined with the technique of equilibrium dialysis. It was found that Antimycin A was bound to albumin at five sites with a dissociation constant of 2.5 X 10(-6) M. This finding suggests that Antimycin A is taken up by the tubular cell as an Antimycin A/albumin complex via pinocytosis. In the pinocytotic vesicle this complex probably dissociates, and free Antimycin A is released into the cytoplasm where it can reach it's sites of action in the mitochondria and at the plasma membrane. This uptake mechanism might provide a general method to incorporate substances into the cell which do not penetrate the plasma membrane.

Antimycin A↗
PubMed1981

Fine structure of a malignant hemangioendothelioma of the esophagus.

The histology and electron-microscopy of a malignant hemangioendothelioma of the esophagus wall appearing in a 42 year old male is presented. By light microscopy the tumor is composed of vessels and capillary-like structures of an anastomosing nature covered by atypical endothelial cells. These cells infiltrate the interstitial spaces growing into the posterior mediastinal area. Electron microscopy confirms the endothelial nature of the neoplastic cells, showing characteristics of the cell type, as is the presence of Weibel-Palade bodies, filaments and active pinocytosis. Hemangioendothelioma should be differentiated from other vascular tumors (angiosarcoma) as are hemangiopericytoma or hemangioblastoma, being composed exclusively of malignantly transformed endothelial cells.

Adult↗
PubMed1982

Vascular and tubular renin in the kidneys of mice.

Monospecific antisera and the immunocytochemical PAP-method have been used to localize renin in the kidneys of mice. With this procedure, reaction product was not only observed in the epitheloid cells of kidney vessels but also in kidney tubules: in the apical portion of proximal tubule cells and in some cells of the connecting and the cortical collecting tubule. To answer the question, whether the occurrence of renin in kidney tubule cells is the consequence of tubular synthesis or that of glomerular filtration of plasma renin followed by its uptake from the tubular lumen, tracer experiments with radioiodinated renin and with horseradish peroxidase were undertaken. The results of these studies as well as other arguments suggest reabsorptive pinocytosis of the filtered hormone as the source of tubular renin.

Animals↗
PubMed1986

The blood-brain barrier to horseradish peroxidase at the onset of bicuculline-induced seizures in hypothalamus, pallidum, hippocampus, and other selected regions of the rabbit.

Rabbits were subjected to bicuculline-induced generalized seizures of 15-min duration to elucidate the mechanism by which the macromolecule horseradish peroxidase (HRP) traverses the blood-brain barrier (BBB) in specific brain areas. Transendothelial pinocytosis at the level of arterioles was the main route of passage. In addition, in thalamus and hippocampus pinocytotic vesicles were observed in capillaries. In thalamus, hypothalamus and septum vesicles in the endothelium of venules were also present. Repeatedly, pinocytotic vesicles were ejecting their content into the interendothelial clefts, so that the presence of HRP reaction product between adjacent tight junctions cannot be considered a conclusive evidence for their opening. The HRP, which had reached the neuropil due to the seizure-evoked BBB opening, accumulated in the interstitial spaces and penetrated the synaptic cleft. Uptake of the tracer in vesicular form into presynaptic boutons, presumably excitatory ones as diagnosed by their ultrastructural features, was observed in all brain regions. The uptake was rare in septum, periaqueductal gray, hypothalamus, and cerebellar cortex; frequent in pallidum, hippocampus, and medulla oblongata; and very intense in thalamus. Uptake in postsynaptic dendrites was present mostly in the vicinity of boutons. Incorporation into glial processes was rare and confined to perivascular astrocytes. It is suggested, that HRP traverses the BBB by regionally selective, transmitter-controlled pinocytotic transport and that the neuronal uptake of the foreign protein is at least partially dependent on the involvement of synapses of particular brain regions in the paroxysmal activity during the generalized seizures.

Animals↗
PubMed1977

Retrograde axonal transport of horseradish peroxidase. Uptake at mouse neuromuscular junctions following systemic injection.

Eye muscles were examined histochemically for the presence of horseradish peroxidase (HRP) activity after intravenous injections of large doses of this tracer protein. HRP had penetrated through the blood vessels and diffused into the areas of motor end plates, where it outlined axon terminals at the synaptic clefts. HRP was incorporated into pinocytotic vesicles in the axons from where an intraaxonal transport in the retrograde direction to the nerve cell bodies in the brainstem followed. Accumulation of HRP in perikarya of motor neurons can therefore be the result of a physiological process of pinocytosis at the axon terminals. In this way exogenous macromolecules in the blood can by-pass the blood-brain barrier and reach the lower motor neurons in the CNS.

Animals↗
PubMed1975

Ultrastructural studies on cerebrovascular permeability in acute hypertension.

Acute hypertension, experimentally induced by intravenous injection of metaraminol in adult rabbits, rapidly induced a damage of the blood-brain barrier in the cerebral cortex, as visualized by Evans-blue-conjugated albumin and horseradish peroxidase. Extravasation of these two exogenous tracers was demonstrated to occur in arterioles, in capillaries and, rarely, in venules. Peroxidase passed the endothelial cell into the nervous tissue in either or three different ways, i.e. through channels, often sigmoidshaped, in the cytoplasm, and transendothelial pinocytosis. The third pathway could, although rarely, be demonstrated between adjacent endothelial cells after cleavage of junctional complexes. The tracer peroxidase was further spread along the blood vessel within the basement membrane and in the extracellular space of the brain. Damaged endothelial cells with diffuse cytoplasmic peroxidase activity and large vesicles were occasionally observed within the areas with blood-brain barrier injury. There were also signs of increased pinocytotic activity in endothelial cells outside the barrier damaged cortical areas. Nerve cells and neuroglial cells could show either a diffuse cytoplasmic peroxidase activity or a vesicular location of the tracer, or sometimes both. The observations are discussed in relation to previous studies on the mechanism of transendothelial passage of protein tracers at blood-brain barrier damage.

Animals↗
PubMed1975

Absorption of intact protein by colonic epithelial cells of the rat.

Colonic absorption of intact protein was examined in adult rats using histological and ultrastructural procedures. Horseradish peroxidase was introduced into ligated colonic loops and retained therein for 5, 10, 20, or 30 minutes prior to excision of the loops, and their processing for microscopy. Morphological evaluation revealed evidence of peroxidase absorption via pinocytosis. Tracer particles were observed adherent to the mucosal border, in apical pinocytotic vesicles, in vesicles adjacent to and fusing with lateral and basal cell membranes, in extracellular spaces throughout the mucosa, in lymphatic channels of the submucosa and occasionally in blood capillaries of mucosal and submucosal regions. The significance of these findings is discussed in light of the frequent presence of dietary and/or microbial macromolecules in the luminal milieu of the large intestine. It is suggested that pinocytotic uptake and subsequent vesicular transport and exocytosis of intact protein may occur in the colon of some species, and that such a phenomenon may be responsible for penetration of the mucosal barrier by macromolecular antigens or toxins.

Animals↗
PubMed1984

Phagocytic uptake of latex beads by rat peritoneal macrophages: comparison of morphological and radiochemical assay methods.

Contrary to previous reports, commercially available 1000-nm latex beads were found to be labelable with 125I, yielding a product that retained its radiolabel on storage at 4 degrees C and when incubated in tissue-culture media. This finding permitted a radiochemical method to measure phagocytic uptake of latex particles by rat peritoneal macrophages cultured in vitro, and a direct comparison with the established method of particle counting by light microscopy. The two methods yielded closely similar data, demonstrating that the (much more convenient) radiochemical method for quantitating phagocytic uptake is both feasible and reliable. The kinetics of phagocytic uptake of the latex particles and the effect of low temperature and metabolic inhibitors (sodium fluoride and 2,4-dinitrophenol) are described. Ongoing phagocytosis did not alter the rate of fluid-phase pinocytosis by macrophages.

Animals↗
PubMed1990

Uptake of tritiated uteroglobin by the endometrium of the rabbit during peri-implantation.

Uteroglobin, labelled with N-succinimidyl-(2-3-3H)-propionate, was applied in vivo for 3 h to pregnant rabbit uteri 7 and 9 days after mating. Light- and electron-microscopic autoradiographs showed that the endometrial epithelium, both ciliated and non-ciliated cells, is able to take up 3H-uteroglobin, however, with differing intensity. Large areas of labelling were found in the luminal epithelium, whereas the glandular epithelium contained fewer silver grains. Moreover, intensively labelled single cells or symplasms occurred in both luminal and glandular epithelium. They were identified as degenerating or dead cells. After internalization by pinocytosis or phagocytosis, the tritiated uteroglobin was observed in multivesicular bodies or in lysosomes with floccular content. Later, radioactivity was either found within residual bodies or distributed throughout the entire epithelium and the subepithelial stroma, i.e., the silver grains could no longer be assigned to specific cell organelles.

Animals↗
PubMed1984

Glycosaminoglycan metabolism of cultured fibroblasts from bovine vitreous.

Glycosaminoglycan metabolism of cultured vitreal cells of bovine origin was investigated with the following results: Cultured vitreal cells distributed the synthesized macromolecules after [35S] sulfate incorporation into the culture medium (extracellular pool), the membrane-bound proteoglycans (pericellular pool), and within the cells (intraocular pool). No extracellular plateau was reached after 3 days; the pericellular and intracellular pools showed a steady state of radioactivity after 48 and 24 h, respectively. Pulse-chase experiments exhibited a rapid turnover of intracellular polysaccharides and a slower metabolism of pericellular polymers. Pinocytosis, adsorption and degradation of vitreal and corneal cell secretion by vitreal cells were observed to a comparable extent. Chondroitin sulfate isomers and heparan sulfate could be detected in minor proportions. The relevance of glycosaminoglycan metabolism in the replacement of cultured vitreal cells into the vitreous cavity is discussed.

Animals↗
PubMed1976

Uptake of horseradish peroxidase (HRP) by the endothelium of the short-term stored rabbit cornea.

In vitro study of the uptake of horseradish peroxidase (HRP) by the corneal endothelium was carried out on rabbit corneae which were stored in a preserving medium for various periods. The stored corneae were incubated in HRP solution with or without adenosine triphosphate (ATP). The number of pinocytotic vesicles decreased as the storage time was prolonged. Addition of ATP to the HRP solution led to an increase in the pinocytotic vesicles in all storage periods. The pinocytosis in the 12-day stored corneal endothelium was only observed when the tissue was incubated in an HRP solution containing ATP. From these results, it was concluded that the viability of the stored corneae can be evaluated with uptake of HRP by the endothelial cell, and that the addition of ATP leads to an enhancement of pinocytotic activity in the endothelial cell.

Adenosine Triphosphate↗
PubMed1977

Cytostatic efficacy of DNA-complexes of adriamycin, daunomycin and actinomycin D. I. Comparative studies in Novikoff hepatoma, human mammary carcinoma cells and human leukemic leukocytes.

Inhibitory effects of adriamycin, daunomycin, actinomycin D and of the related DNA-complexes on DNA and RNA synthesis were compared by precursor uptake studies in Novikoff hepatoma cells, human mammary carcinoma cells and human leukemia cells. In addition, nuclear RNA labelling profiles were analyzed in human acute leukemia blast cells and nucleolar RNA synthesis was studied in Novikoff hepatoma cells in vitro after incubations of the tumor cells with adriamycin and DNA-adriamycin. The studies revealed that compared to the free drugs a) the DNA complexes were generally less active with respect to inhibition of overall DNA and RNA synthesis in these divergent tumor cell types, b) characteristic differences between adriamycin and daunomycin which are related to a more rapid cellular uptake of daunomycin were still present after complexing of both drugs to calf thymus DNA, and c) the intracellular mode of action of the free antibiotics was not changed by complex formation with DNA. These results indicate that a preferential incorporation of the macromolecular complexes into the tumor cells by pinocytosis--as originally postulated by Trouet et al. (1972)--is not likely for Novikoff hepatoma cells, human mammary carcinoma cells and human acute leukemia blast cells. In contrast, it may be concluded from this study that the DNA complexes dissociate already at the outer cell membrane resulting in a generally decreased but kinetically drug-specific cellular uptake. In a second communication it will be demonstrated that these in-vitro effects do not correlate with the therapeutic efficacy efficacy of the complexed drugs in vivo.

Acute Disease↗
PubMed1983

Electron microscopic studies on multinucleate foreign body giant cells derived from Kupffer cells in mice given Indian ink intravenously.

Changes in Kupffer cells in mice given intravenous Indian ink were studied with the electron microscope. Kupffer cells as well as hepatic sinusoidal endothelial cells take up Indian ink particles by pinocytosis. In addition, a few Ito cells and hepatocytes ingest a small number of particles. The carbon particles are stored in cytoplasmic vacuoles in all these cell types. Aggregates of Kupffer cells containing many vacuoles stuffed with carbon particles are seen in the sinusoidal lumen, Disse space and interlobular connective tissue space 3 and 4 days after injection with Indian ink. One month after the injection, large clumps of aggregated Kupffer cells containing numerous carbon-filled vacuoles are distributed in the Disse space and other connective tissue spaces. The Kupffer cells in these clumps are in close contact and are partly fused with one another. After 3, 4 and 6 months, large multinucleate foreign body giant cells with numerous large vacuoles containing densely-packed ink particles are seen throughout the liver tissue. They are considered to be formed by fusion of Kupffer cells. Some endothelial cells also store ink particles in cytoplasmic vacuoles for as long as 6 months after injection.

Animals↗