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At least 811 records · Page 45Linked to original sources
PubMed1979

Induction of lysosomal enzyme secretion by alveolar macrophages in response to the purified complement fragments C5a and C5a des-arg.

Purified C5a and its "inactive" form, C5a des-arg, were shown to induce secretion of acid hydrolases from rabbit alveolar macrophages (AM) in a concentration-dependent manner. Secretion increased with time to 5 times above controls by 72 hr. Concentrations of these enzymes in the cell lysates did not decrease during the incubation, suggesting that synthesis of new enzyme was occurring. The lysosomal enzyme secretion was accompanied by increased pinocytosis and release of proteolytic enzymes from the macrophages. At no time was significant lactic dehydrogenase liberated, indicating that secretion was selective and not due to cell death. Data presented also suggest that C5a des-arg induced secretion from the macrophages of a chemotactic factor for neutrophils. It was concluded that C5a and C5a des-arg may play a role in lung injury by interactions with AM, inducing the secretion of acid hydrolases and proteolytic enzymes that can cause tissue damage, and by regulating the influx of other inflammatory cells into the interstitium and air spaces.

Anaphylatoxins↗
PubMed1977

[Effect of triton WR 1339 on the ultrastructure of liver parenchymal and stromal cells in rats with chronic toxic hepatitis].

A preliminary injection of triton WR 1339 protectively influenced the chronic toxic CCl4-hepatitis. The ultrastructural peculiarities were close to the normal ones in hepatocytes, in addition to the increased triglyceride rejection from cells by means of autophagy. The revealed stimulation signs of pinocytosis in hepatocytes and the Kupfer cells are accompanied by the activation of the Golgi complex and, probably, by the increased protein catabolism in lysosomes. The signs of phagocytosis increase in the Kupfer cells were determined. It is supposed that the marked ultrastructural peculiarities of liver cells reflect a more effective restoration or a lesser injury under the influence of triton WR 1339.

Animals↗
PubMed1984

Stimulation of macrophage activity by 12-O-tetradecanoylphorbol-13-acetate.

Treatment of resident murine peritoneal macrophages with 12-O-tetradecanoyl phorbol-13-acetate (TPA) rapidly converted the cells to tumour cytostatic and cytolytic effector cells, as determined by growth inhibition or lysis of T-lymphoma cells (Eb, EL4) in vitro. The effective TPA concentrations were 10(-8) to 10(-7)M. Macrophages became cytotoxic as early as one to two hours after exposure to TPA, and tumour cytotoxicity persisted up to 48 hours. TPA did not interfere with the action of the lymphokine macrophage activating factor (MAF) but acted in synergy with it. Generation of antitumour-active macrophages by TPA was accompanied by other metabolic and functional changes, such as an enhancement of the hexose monophosphate shunt, glucosamine incorporation, RNA and protein synthesis, release of prostaglandin E2, thromboxane and prostacyclin, as well as pinocytosis. These data show that TPA may be a valuable model substance to complement studies of MAF; furthermore, use of TPA may help to clarify the role of activated macrophages during tumour promotion and tumour defense.

Animals↗
PubMed1981

On the mechanism of the uptake of horseradish peroxidase into the retrograde transport system of ligated postganglionic sympathetic nerves in vitro.

The mechanism of the uptake of horseradish peroxidase (HRP) by damaged post-ganglionic sympathetic axons was studied in vitro. HRP was applied to the damaged axons at the time of nerve injury or after a 3 hours or 17 hours delay. An interval of 3 hours or 17 hours between nerve injury and exposure to HRP had no effect on the localisation of the HRP in the damaged axons or on its retrograde transport to their perikarya. Evidence was found for the pinocytotic uptake of the enzyme by the damaged axons and its accumulation within those axons in elongated cisternae and larger rounded vesicles. In further experiments the damaged axons were treated with HRP at 0 degrees C and then washed in HRP-free medium. The tracer entered the axons in a diffuse form under these conditions but no pinocytotic uptake was observed. However, following 24 hours further incubation at 37 degrees C, HRP could not be found in the perikarya. Treatment at 0 degrees C did not produce any lasting damage to the retrograde transport mechanism. The results of these experiments are compatible with the involvement of pinocytosis in the uptake of HRP in a form suitable for retrograde transport.

Animals↗
PubMed1982

Correlation of human neutrophil secretion, chemoattractant receptor mobilization, and enhanced functional capacity.

Studies were performed to elucidate further the phenomenon of secretagogue-mediated enhancement in the binding of the chemoattractant f-met-leu-[3H]phe to human neutrophils (PMN). Specific f-met-leu-[3H]phe binding to unstimulated PMN reached maximum levels after 10 to 15 min of incubation at 0 degrees C with a saturating concentration of peptide, and consisted of a readily displaceable and a nondisplaceable component. PMN, preexposed to A23187 (2.5 X 10(-8) M) or PMA (0.5 ng/ml) for 30 min at 37 degrees C to stimulate limited and preferential release of specific (secondary) granules (10 to 20% of total lysozyme, no beta-glucuronidase), demonstrated an approximate doubling in the displaceable component of f-met-leu-["3H]phe binding, accompanied by an increasing nondisplaceable component that could not be explained by bulk pinocytosis of extracellular fluid (assessed by [3H]sucrose uptake). The increase in f-met-leu-[3H]phe binding was not affected by inhibitors of protein synthesis, could not be attributed to the secreted products lysosyme or lactoferrin acting on the cell, and, on the basis of studies with PMN from patients with chronic granulomatous disease, could not be attributed to the effects of reactive oxygen species generated in low concentration during stimulation. Functional studies on PMN indicated that preexposure to secretagogues at concentrations demonstrated to increase receptor availability also enhanced subsequent f-met-leu-phe-mediated superoxide and hydrogen peroxide generation. The present data demonstrate that secretagogues may activate PMN to enhance their subsequent responses in f-met-leu-phe-mediated processes, and, combined with previous reports, support the concept that specific granules provide a source of preformed membrane and receptor material that is translocated to the cell surface during the secretion associated with directed locomotion.

1-Butanol↗
PubMed1983

Separation of bronchoalveolar cells from the guinea pig on continuous gradients of Percoll: functional properties of fractionated lung macrophages.

Lung macrophages from normal guinea pig lungs were separated from bronchoalveolar cells into three fractions according to buoyant density by centrifugation on continuous iso-osmotic gradients of Percoll [3]. A reproducible pattern of functional activity distinguished these three macrophage fractions. With increasing density and decreasing cell size, the respective fractions exhibited increased stimulated migration, superoxide anion release and pinocytosis, and increased protein concentration of the cells. These differences, coupled with previous observations that these fractions also exhibited morphological and cytochemical differences [3], support the notion that these fractions of macrophages may represent different stages of maturation (or differentiation) of alveolar macrophages in the lungs of normal guinea pigs.

Animals↗
PubMed1978

Alterations in rat jejunal permeability to a macromolecular tracer during a hyperosmotic load.

The effects of intraluminal hyperosmolality on the intestinal permeability of a macromolecular tracer, horseradish peroxidase, was assessed in rats by light and electron microscopic cytochemistry. After 60 minutes of an intraluminal hypertonic perfusion of 600 mOsM mannitol, horseradish peroxidase was demonstrable in the intercellular spaces between adjacent absorptive epithelial cells of jejunal villi, along the microvillar brush border, in numerous pinocytotic vesicles, in multivesicular bodies, as well as in large lysosomes. Horseradish peroxidase was frequently found extending from the luminal surface of the cell through the tight junctional region and into more basal portions of the intercellular space. In occasional cells, fragments of the interdigitating plasma membranes of two adjacent absorptive cells appeared to bud off into the cytoplasm of one cell. In contrast, after 60 minutes of isotonic perfusion, horseradish peroxidase was confined to the microvillar brush border, a few pinocytotic vesicles, and occasional multivesicular bodies. These experiments suggest that the passage of macromolecules across the jejunal epithelium of adult rats is enhanced under conditions of luminal hyperosmotic stress. This may be due to an alteration in the functional integrity of the tight junctional macromolecular barrier or to an enhanced rate of pinocytosis.

Animals↗
PubMed1984

[Electron microscopy study of deoxyribonuclease penetration into chick embryo fibroblasts and the effect of the enzyme on the cells].

Peroxidase labeled DNase (0.25 g/ml) penetrated into the chick fibroblast culture cells by means of pinocytosis to be localized in pinocytotic vacuoles. Within a 24 hour-incubation of the cell culture with DNase a relative volume of vacuoles in cells increased from 4.6 to 19.5 per cent, the majority of pinocytic vacuoles being filled with labeled DNase. The incubation of cells with non-labeled DNase (24 hours) did not damage DNA-containing cell structures. The data obtained permit to explain the selective effect of the enzyme on the viral DNA and the inhibition of reproduction of DNA-containing viruses by the interaction of the viral DNA and DNase inside pinocytic vacuoles which protect the cells from the enzyme damaging effect.

Animals↗
PubMed1984

In vitro effects of 4-hydroperoxycyclophosphamide on the morphology and function of human peripheral blood mononuclear phagocytic cells (macrophages).

Human peripheral blood mononuclear cells were incubated for 1 hr in 4-hydroperoxycyclophosphamide (0.5 to 10.0 micrograms/ml), and the adherent, esterase-positive cells (macrophages) were studied. At 2 hr, a reduction was noted in both latex particle ingestion and Fc gamma receptor binding and phagocytosis. At 24 hr, spreading and pinocytosis were reduced, and cytoplasmic vacuoles developed. This vacuolization represented dilatation of the rough endoplasmic reticulum. These morphological and functional changes occurred with 4-hydroperoxycyclophosphamide concentrations which did not reduce viability or produce detectable DNA alkylation. This effect on macrophages may offer a mechanism whereby low-dosage cyclophosphamide could modify the immune response.

Cell Adhesion↗
PubMed1983

Macromolecular absorption by histologically normal and abnormal small intestinal mucosa in childhood: an in vitro study using organ culture.

Knowledge of the mechanism of macromolecular absorption in the small intestine is based largely on animal studies. We have attempted to assess qualitatively and quantitatively the amount and the mechanism of uptake of horseradish peroxidase (HRP), a model macromolecule, in human small intestine, employing biopsy material from children undergoing gastrointestinal investigations. The biopsy material was incubated in culture medium containing HRP, and a comparison was made between histologically normal and histologically abnormal biopsies. In the normal specimens HRP was detected in pinocytotic vesicles along the villous epithelium. It was also seen in multivesicular bodies and in the interepithelial cell spaces at the base and tip of the villus. These latter areas corresponded to regions where damaged and extruding enterocytes, diffusely penetrated by HRP, were seen. This demonstrates that intact macromolecules can be taken up by normal small intestine in vitro in childhood and indicates two possible routes of antigen entry: (a) by active absorption through intact enterocytes and (b) through damaged or extruding cells. In the abnormal specimens the distribution of HRP was more varied. Most specimens showed an increased presence of HRP in the interepithelial cell spaces and an increased number of enterocytes diffusely penetrated by HRP, but a decrease in pinocytosis in the most severely abnormal enterocytes. An increase in HRP was also observed in the basement membrane and, in one instance, within capillaries of the lamina propria. It was concluded that when an enteropathy is present, an increase in mucosal permeability to macromolecules may result. This is most likely due to an increase in the passive diffusion of macromolecules into the mucosa.

Adolescent↗
PubMed1978

[Metabolic unit in the microcirculatory system of the exocrine part of the pancreas].

Metabolism between exocrine pancreocytes and blood is mediated with the participation of the metabolic section of the microcirculatory system. It includes: blood capillaries, pericapillary space, intracellular gaps and metabolite distributional complex (basal-lateral folds of pancreocytic plasmolemma). As demonstrated morphological and histochemical changes developed in exocrine pancreocytes and in the metabolic section of the pancreatic gland at different stages of the secretory cycle, interconnections between them are complex and dynamical. All the elements of the metabolic section undergo a certain reconstruction adequate to functional state of pancreocytes. Metabolism between glandular cells and the vascular bed is regulated by structural reconstruction of pancreocytic plasmolemma. A certain functional specialization in plasmolemmic folds is noted: basal-lateral folds regulate transport between pericapillary space and intracellular gaps, while the main function of the lateral folds is to transport substances by means of pinocytosis.

Animals↗
PubMed1982

Macrophages and resistance of tumors 6. The effects of supernatants from cultures of normal and tumor cells on phagocytosis.

Mouse resident peritoneal macrophages were cultured with supernatants from cultures of tumor cells and normal cells, then tested for their capacity to phagocytose opsonized sheep erythrocytes (SRBC). Most tumor cells produced inhibitory material but some did not (HeLa, EL-4). Conversely, nonmalignant cells generally did not produce active material though some (Chang B cells) did. Inhibition was not noticeable until after 13 hr contact with tumor supernatant and then became progressively more pronounced at 24 and 48 hr. Phagocytic capacity recovered only partially on reincubation with fresh medium. Inhibition was caused by material of approximate M.W. less than 1,000 (by membrane filtration), which also inhibited macrophage migration in vitro but had no effect on delayed-type hypersensitivity reactions or tumor growth in vivo. There was no species specificity and normal macrophages from various sources were susceptible, although activated or stimulated macrophages were wholly or partly resistant. Tumor carriage was associated with an initial decrease in phagocytic capacity of resident peritoneal macrophages, followed by an increase then a second decrease, although the cells remained susceptible to the inhibitory effect of tumor supernatant in vitro. Depression of phagocytosis was more marked in the presence of normal mouse serum and less marked in the presence of human serum than in the presence of fetal calf serum. Phagocytosis of zymosan and pinocytosis of colloidal gold by mouse macrophages were also depressed by tumor cell products.

Animals↗
PubMed1982

Changes in some properties and functions of plasma membranes of macrophages from young, adult and aged mice.

We studied age-dependent changes in distribution of receptor-ligand complexes in the lateral plain of plasma membrane after binding of six different lectins and anti H-2a and anti Ias antisera to the surface of mouse peritoneal macrophages. Additionally we examined formation of spontaneous rosettes with sheep red blood cells and the phagocytic and pinocytic activities of these macrophages. Macrophages of young and aged mice exhibited a lower mobility of the studied antigens and lectin receptors (determined as a function of patch and cap formation) and a higher rate of formation of spontaneous rosettes. The percentage of Ia antigens bearing macrophages was very low during early ontogenesis; it increased during adulthood and decreased during ageing. The highest percentage of phagocytizing macrophages was found in adult mice, even thought the phagocytic index (i.e., the average quantity of phagocytized particles in a phagocytizing cell) kept increasing during postnatal life. However, the level of pinocytosis was the same in all three groups.

Aging↗
PubMed1981

[Characterization of the convoluted seminiferous tubule wall. I. Ultrastructural aspects after the ligation of the vas deferens and the efferent tubules].

The structure of the wall of the rat seminiferous tubules has been studied by electron microscopy. No significant modifications have been revealed after the ligature of the vas deferens while on the contrary the ligature of the efferent ductules produces a reduction of the contractile filaments and of the pinocytosis vesicles, as well as an increase of the amount of collagen fibers in the basal membrane.

Animals↗
PubMed1981

[Action of x-rays and neuraminidase on pinocytotic activity and microtubule-microfilament system of Ehrlich ascites tumor cells in monolayer culture (author's transl)].

Monolayer cultures of Ehrlich ascites tumor cells in exponential growth phase were treated with X-rays and neuraminidase alone or in combination. A radiation dose of 2 Gy (200 rd) and higher effected a significant inhibition of DNA synthesis and cell proliferation. Neuraminidase treatment in addition to irradiation did not modify the growth-inhibitory irradiation effect. Cells pretreated for 0.5 to 1.0 hours with neuraminidase (in Earle's salt solution) and cultured thereafter (4h) in serum-containing growth medium exhibited an enhanced development of the microtubule-microfilament-system. Morphometric analysis of microtubules on electronmicroscopic sections revealed a nearly 4-fold increased number in neuraminidase treated cells while the average length of microtubules was similar to controls. Pinocytosis as measured by the ultrastructural uptake of ferritin appeared to be increased following neuraminidase treatment. A connection between neuraminic acid containing components (glycoproteins or glycolipids?) of the cell membrane or cell surface, on the one hand, and the cytoskeleton and the endocytotic process of these tumor cells, on the other hand, is suggested.

Animals↗
PubMed1978

[Capillary ultrastructure and permeability in the posterior lobe of the rat pituitary].

The ultrastructure of capillaries and their permeability to horseradish peroxidase and ferritin in rat posterior pituitary has been studied. The capillary wall is formed mainly by flat endothelium penetrated by regularly situated fenestras. The majority of organelles is concentrated in the perikaryon. Caveoles and pinocytotic vesicles are not numerous except for some perikaryons where they are concentrated along the basal surface. Intracellular clefts are interrupted in the regions of fusion of the outer osmiophilic layers of membranes of neighbouring endothelial cells. Horseradish peroxidase and ferritin penetrate partly from the capillary lumen into the pericapillary space: the majority of markers penetrate across the fenestras and the minority--within pinocytosis vesicles. The former way is more rapid than the latter. Ferritin penetrated into the cytoplasm is captured by lysosomes.

Animals↗
PubMed1980

Dynamics of maternal-fetal nutrient transfer.

Several mechanisms account for transfer of substances across the placenta, including passive diffusion, facilitated diffusion, active transport, solute drag, and pinocytosis. The rates at which these processes occur and the rates of equilibration of various substances between maternal and fetal circulation vary widely. In general, gases and some ions equilibrate rapidly while large molecules such as proteins exchange slowly. Some nutrients such as amino acids, calcium, iron, and possibly some vitamins are transported against a concentration gradient. This report compares equilibration rates for various nutrients and discusses the use of mathematical modeling to quantitate certain aspects of the processes, and to gain a better understanding of factors determining placental exchange.

Animals↗
PubMed1978

Regulation by antibody of lectin-induced lymphocyte proliferation: antibody inhibition of mitogenesis and release of lectin from cell surfaces.

Studies were conducted to determine the ways in which antibody regulates proliferation of lymphocytes stimulated by phytohemagglutinin (PHA) and concanavalin A (ConA). Equine lymphocytes were reacted with PHA or ConA for 1 to 10 hours, washed free of excess lectin, then cultured for 3 days and examined for proliferation and incorporation of [3H]thymidine. Both PHA and ConA induced lymphocytes to proliferate after short incubation periods. This response could be interrupted by the addition of antibody to the respective lectin. Total suppression of the proliferative response occurred if antibody was added within the first 2 hours after initial contact with PHA or ConA. Addition at times up to 48 hours produced either total or partial suppression. The removal of excess antibody 4 hours after addition to the culture did not reverse the suppression. Using radiolabeled ConA and PHA, it was observed that suppressive antibody inhibited the release of lectin from metabolically active lymphocytes and from surfaces where pinocytosis was not possible or was minimized. Antibody did not affect the rate of degradation of lectin by the cells. These results indicate that antibody attached to lectins, already bound to the lymphocyte surface, can terminate the lymphocyte response and retard the rate of release of lectin from the cell membrane.

Antibodies↗