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PubMed1981

Histamine in brain capillaries.

A high amount of histamine was found in capillaries isolated by subcellular fractionation from the brain. In view of the important effects of histamine on vascular permeability in peripheral vessels, it was thought that histamine had a similar function in the cerebral vasculature. Intracarotic histamine infusion resulted in an enhanced pinocytosis of endothelial cells and te oedematous swelling of the astrocytic end-feet system. [3H]-Histamine, injected in the cerebral ventricles, accumulated in the capillary wall. Histamine and cimetidine activated hydroxyfatty acid and prostaglandin D2 synthesis in isolated brain capillaries. The possible function of the capillary histamine in the regulation of permeability of microvessels is discussed.

Animals↗
PubMed1982

Adult cystinosis: electron microscopy of the conjunctiva.

An ultrastructural study was made on the conjunctiva of a 38-year-old man with adult cystinosis. Intracellular cystine crystals were found not only in fibroblasts but also in numerous macrophages. Both fibroblasts and macrophages showed increased pinocytosis. Occasionally there were macrophage degenerations with extracellular cystine crystals present. Whether this increased macrophage reaction indicates a specific difference to childhood cystinosis remains a matter of speculation.

Adult↗
PubMed1975

Calcium excretion and deposition during sporogenesis in Physarella oblonga.

Calcium excretion and deposition were studied during sporogenesis in the myxomycete, Physarella oblonga. Prior to fruiting, the migrating vegetative plasmodium contains numerous, large channels connected to the external environment. During early sporangial development, these channels become smaller and are isolated as channel remnants. Plasmodial microfilament bundles also disappear at this time. Internally, two types of spheres, each about 0.5-1.5 mum in diameter, are formed in the channel remnants. A dense sphere appears to originate from small particles initially secreted from the mitochondria. These particles then enter the channels and channel remnants by reverse pinocytosis and fuse to form the dense spheres. A second, less dense sphere has no detectable cytoplasmic origin but also appears to form in the channels and channel remnants. Both types of spheres are concentrated by the fusion of channel remnants to form enlarged regions (knots and spikes) of the developing capillitium. Some of the channel remnants also fuse with the outer surface of the sporangium, depositing both spheres to the outside. Both spheres have been studied by various light and electron microscopic techniques and with specific histochemical and analytical procedures. The less dense spheres appear to contain a major portion of calcium in the form of calcium carbonate. These results are compared to other recent studies on calcium deposition in the Myxomycetes and a different mechanism for calcium deposition is proposed.

Calcification, Physiologic↗
PubMed1980

Scanning electron microscopy on the rat liver with alpha-naphthylisothiocyanate- induced cholestasis.

Intrahepatic cholestatic rat livers were studied with the scanning electron microscopy at 3, 24, 48 and 96 hours after a single dose administration of alpha-naphthylisothiocyanate (ANIT, 100 mg/kg body weight). Cholestasis reached the peak at 48 hours and decreased thereafter. On intercellular surfaces of hepatocytes, round indentations appeared at 3 hours and became larger and more numerous at 24 hours. On sinusoidal surfaces, small pits were observed at 3 and 24 hours. Bile canaliculi were dilated and their microvilli became shorter and sparse in all specimens. They became tortuous at 3 hours and after 48 hours tortuous canaliculi were greatly increased. Side branches of the bile canaliculi showed increase at 24 hours and were numerous at 48 hours. At the same time when changes in bile canaliculi were most remarkable, some of side branches communicated directly with the Disse space. At 96 hours canalicular changes became less observable and the communications disappeared. In conclusion, in the liver with ANIT-induced cholestasis, bile components possibly regurgitate 1) from the hepatocytes by reversed pinocytosis through intercellular surface indentations and sinusoidal surface pits in the early phase of cholestasis, and 2) from the bile canaliculus through the bile canaliculus-the Disse space communications at the peak of cholestasis.

1-Naphthylisothiocyanate↗
PubMed1997

Human fetal endothelial cells acquire zinc(II) from both the protein bound and nonprotein bound pools in serum.

To help determine physiologically important routes by which zinc (Zn) is acquired by human fetal vascular endothelium, the authors incubated cultured umbilical vein endothelial cells with 65Zn(II)-tracer labeled human fetal whole serum, ultrafiltrate (containing low molecular mass serum zinc complexes), and dialyzed serum (containing protein-bound zinc). Zinc from whole serum and from both serum fractions entered a rapidly labeled cellular compartment, removable by edetic acid (EDTA), representing Zn bound to the outside cell surface, and accumulatively, an EDTA-resistant compartment-probably largely internalized Zn. Entry of Zn into the EDTA-resistant pool from both serum fractions was strongly temperature-dependent, and was not via the EDTA-sensitive pool. Entry from the ultrafiltrate was resolvable into high affinity saturable, and non- (or hardly-) saturable components. Transfer from the dialyzed serum fraction was not significantly saturable, but only partially accounted for by nonspecific pinocytosis. Thus, Zn is obtained by fetal vascular endothelium partly from low molecular mass serum species, probably through at least one carrier-mediated membrane transport system; but also from Zn complexed with serum protein, via at least one metabolism-related route.

Dialysis↗
PubMed1988

Effects of bile acids and endotoxin on the function and morphology of cultured hamster Kupffer cells.

The mechanisms of hepatic reticuloendothelial cell dysfunction in obstructive jaundice were investigated using cultured hamster Kupffer cells. The introduction of free bile acids, cholic acid (CA) at concentrations over 2 mM and chenodeoxycholic acid (CDCA) over 1 mM inhibited colloidal carbon pinocytosis. CA and CDCA at concentrations over 0.5 mM inhibited IgG-coated sheep red blood cell phagocytosis. With the application of conjugated bile acid and endotoxin at concentrations over 50 micrograms/ml, endocytic function was inhibited. With bile acids, a dose-dependent increase in the concentration of beta-glucuronidase occurred in the culture medium, and with endotoxin a time-dependent increase in beta-glucuronidase was noted. Bile acids produced alterations in cell organelles before destruction of the cell membrane. The presence of endotoxin led to the appearance of large vacuoles in the cytoplasm. These observations suggest that bile acids and endotoxin inhibit Kupffer cells by different mechanisms. We tentatively conclude that bile acids rather than endotoxin influence Kupffer cells in vivo.

Animals↗
PubMedDate not supplied

On the mechanism of cellular cadmium uptake.

Review of the available evidence on the mechanism of cellular Cd uptake in the rat jejunum supports the concept that this process consists of nonspecific binding to anionic sites on the membrane, followed by a temperature-dependent and rate-limiting internalization step. Because temperature-sensitive transmembrane movement of Cd can be demonstrated also in isolated brush-border vesicles and in erythrocyte ghosts, it is not likely to result from pinocytosis but may be related directly to membrane fluidity. There is no need to assume the existence of saturable Cd carriers, or competition of Cd with essential polyvalent cations for their specific transport systems. Uptake of Cd by tubular epithelium in the kidney of the intact rabbit appears to resemble that described for the jejunum, with the internalization step limiting the rate of uptake.

Animals↗
PubMed1983

Effects of trypan blue on thyroid secretion: localization of trypan blue within the colloid space and phagolysosomes of thyroid follicles.

Trypan blue was previously shown to directly inhibit thyroid secretion following TSH stimulation. Inhibition of both colloid droplet formation and thyroglobulin proteolysis was demonstrated. By observing the characteristic bright red fluorescence of the dye-protein complex, we have demonstrated that trypan blue rapidly enters the colloid space and combines with thyroglobulin. In addition, the dye in association with thyroglobulin has been demonstrated within phagosomes and phagolysosomes by centrifugation of the lysosomal (P15) fraction on both sucrose and Percoll density gradients. Lability or latency of the dye with the phagolysosomal contents was demonstrated and the dye was found in association with thyroglobulin by column chromatography. It is proposed that the complexing of trypan blue to thyroglobulin alters its attachment to specific follicular cell receptors, inhibits pinocytosis, and, thus, thyroid hormone secretion.

Animals↗
PubMed1997

Computer analysis of living cells: movements of the chromatoid body in early spermatids compared with its ultrastructure in snap-frozen preparations.

Quantitative analyses of cytoplasmic and nuclear organelle movements in living interphase cells at defined stages of differentiation are few. By phase contrast videomicroscopy and digital imaging techniques, we have traced the path of the chromatoid body (CB) and analysed its rapidly changing positions in relation to the nuclear envelope, Golgi complex and nuclear pale chromatin areas in living early spermatids of the rat. The CB had intimate interactions with the nuclear envelope and moved both in parallel and perpendicular fashion in relation to it. It had successive short contacts with the Golgi complex and nuclear pale chromatin areas. It was also seen to scan between two pale chromatin areas and it had pinocytosis-like transient engulfments during interactions with the pale chromatin. In ultrastructural analysis of snap-frozen preparations, the CB had a large contact area with the nuclear envelope with several intermediate organelles that may be involved in nucleocytoplasmic material transport. It is evident that quantitative image analysis of living cells is a powerful guide for ultrastructural analyses. The snap-freezing technique gives new possibilities for studies of structures that are sensitive to conventional fixation procedures.

Animals↗
PubMed2001

Ultrastructure of the enteromonad flagellate Caviomonas mobilis.

Caviomonas mobilis was collected from the caecum of mice harbouring a controlled fauna. Phase contrast and immunofluorescence microscopy using an anti-tubulin antibody and electron microscopy demonstrated the presence of one basal body bearing a flagellum and a second barren basal body, both inserted in the face of two cup-like depressions in the nuclear surface, as in other enteromonad/diplomonad genera. Three microtubular fibres arise close to the main basal body: the first, composed of three microtubules cross-linked with a dense structure, lies within a groove above the nuclear surface; the second is oriented antero-dorsally and corresponds to the peristyle as observed by light microscopy; and the third is situated ventrally, below the proximal part of the recurrent flagellum, and corresponds to the funis. There is no mitochondrion, no Golgi body, the endoplasmic reticulum is reduced, there is no cytostome, the cell feeds by pinocytosis and phagocytosis and the division spindle is intranuclear. The cytological characters of Caviomonas are homologous to those of genera which comprise the enteromonad/diplomonad evolutionary lineage, as previously presumed.

Animals↗
PubMed2003

Cellular responses to increasing Cd concentrations in the freshwater crab, Potamonautes warreni, harbouring microbial gill infestations.

We investigated the uptake, transport, storage and defence mechanisms in the freshwater crab, Potamonautes warreni, harbouring microbial gill infestations and exposed to increasing chronic (0.2, 0.5, 1.0 mg l(-1)) and acute (2.0 mg l(-1)) cadmium (Cd) concentrations under controlled laboratory conditions over a period of 21 days. Transmission electron microscopy and X-ray microanalysis revealed that the microbial gill fauna was eliminated on exposure to 0.2 mg Cd(2+) l(-1) and that Cd became increasingly adsorbed and incorporated into lamellar crystal deposits and permeated the cuticle of the gills of P. warreni. Degeneration of the apical membrane infoldings and vacuolation of epithelial cells occurred concurrently with pinocytosis, endocytosis and pronounced phagocytotic activity in the epithelia and haemal canal of the gills. Elevated Cd exposures (0.5 or 1.0 mg l(-1)) resulted in the swelling and dissociation of mitochondrial outer membranes together with an increase in transport of Cu, Cl and S by haemocytes in the haemal canal to epithelial tissues depleted in these elements. Cd also accumulated in tightly coiled concentric membrane whorls in the haemal canal, whereas the highest concentrations of Cd were found within aggregates of lysosome-like bodies in cuticulin-secreting cells of the gill stem. Chronic exposure to Cd induced increased fatigue and mild uncoordinated motor activity. In contrast, at an acute exposure of 2.0 mg l(-1) over 48 h, P. warreni showed a time-specific rapid loss of motor function, although only mild cellular lesions occurred in the gill tissues. The significance of cellular changes in the gill epithelia and altered motor activity of P. warreni with increased waterborne Cd are discussed as potential biomarker responses in monitoring aquatic pollution.

Animals↗
PubMed1988

Comparative investigations on the uptake of phallotoxins, bile acids, bovine lactoperoxidase and horseradish peroxidase into rat hepatocytes in suspension and in cell cultures.

Two alternative uptake mechanisms for phallotoxins by liver cells are debated: carrier-mediated uptake and receptor-mediated endocytosis. We have compared the properties of hepatocellular uptake of the phallotoxins, phalloidin and demethylphalloin, with the uptake of cholate as a substrate for carrier-mediated uptake and compared with iodinated bovine lactoperoxidase or iodinated horseradish peroxidase, as the latter are known to be taken up by vesicular endocytosis. Uptake of phallotoxins and [14C]cholate uptake into isolated hepatocytes is independent of extracellular calcium but inhibited by A23187 or by monensin. Uptake of bovine lactoperoxidase strictly depends on external Ca2+, was insensitive to A23197 and was not inhibited by monensin. No mutual uptake inhibition between phalloidin or cholate and peroxidases was seen, indicating independent permeation pathways in hepatocytes. However, high concentrations of cytochalasin B inhibited the uptake of either phalloidin, cholate or bovine lactoperoxidase. Horseradish peroxidase uptake, which was taken as an indicator for fluid pinocytosis, was low in isolated hepatocytes and could not account for the amount of phalloidin or cholate taken up. In cultured rat hepatocytes, uptake of phallotoxins decreased within 1 day to 10% of the uptake seen in freshly isolated hepatocytes. The results indicate different mechanisms for hepatocellular phallotoxin/bile-acid uptake and peroxidase internalization. As monolayer cultures of hepatocytes rapidly lost the carrier-mediated uptake of phallotoxins and bile acids, freshly isolated hepatocytes might be a more suitable experimental model than cultured cells for kinetic studies on this transport system.

Amanitins↗
PubMed1983

Ectoglycosyltransferase activities at the surface of cultured neurons.

Glycosyltransferase activities (ectogalactosyl, ectofucosyl and ectosialyl) were studied at the external surface of exclusively neuronal cultures. An appropriate methodology gave the possibility to eliminate sources of errors due to the hydrolysis of nucleotide sugar substrates or due to cellular uptake of free sugars. Ovomucoid and asialofetuin coupled to Sepharose and Ultrogel beads were used as exogenous substrate to circumvent possible substrates pinocytosis. Ectoglycosyltransferase activities were studied as function of protein concentration, incubation time and amount of bead coupled exogenous acceptors. The data show that these enzymes are present at the external surface of the neuronal membrane; their possible role in cell - cell interactions is suggested.

Animals↗
PubMed1984

Uptake of free hemoglobin by rat liver parenchymal cells.

Parenchymal cells isolated from rat liver are capable of taking up free hemoglobin. Uptake was saturable with a concentration for half-maximal velocity of 1.35 mg/ml (1.99 X 10(-5) M) hemoglobin. At a concentration of 0.088 mg/ml, the endocytic index for hemoglobin uptake was 4.5 microliters/h per mg of cell protein. This may be compared with the rate of fluid pinocytosis by these cells of 0.025 microliter/h per mg of cell protein (determined with yeast invertase as the marker). Free beta globin chains were also taken up with an endocytic index of 26.7 microliters/h per mg of cell protein at a beta chain concentration of 0.075 mg/ml. Hemoglobin inhibited the uptake of labeled beta globin. Hemoglobin-haptoglobin complex at a concentration of 0.12 mg/ml (as hemoglobin) was cleared at a rate of 0.89 microliter/h per mg cell protein and its uptake was also inhibited by free hemoglobin. We conclude that haptoglobin serves to conserve the iron of hemoglobin by preventing its renal clearance and not by promoting its hepatic uptake.

Animals↗
PubMed1991

A peptide from the GAP-binding domain of the ras-p21 protein as well as azatyrosine block ras-induced maturation of Xenopus oocytes.

The ras-oncogene-encoded p21 protein is known to produce malignant transformation of NIH 3T3 cells as well as maturation of Xenopus oocytes when microinjected into these cells. p21 protein is known to bind a GTPase activating protein (GAP) intracellularly; residues 32-45 have been implicated in interacting with GAP. We demonstrate here that a peptide corresponding to residues 35-47 of p21 as well as the antibiotic azatyrosine inhibit the ras-induced maturation of Xenopus oocytes in a dose-related manner upon microinjection. We have previously shown that this p21 peptide and azatyrosine could inhibit the effects of p21 protein on cell transformation and pinocytosis in NIH 3T3 cells. In the present study, in which we have extended these results to the oocyte system, we also demonstrate that both partially inhibit insulin-induced oocyte maturation, a process which is thought to involve activation of endogenous p21 protein; on the other hand, both agents fail to inhibit oocyte maturation induced by progesterone, which is known not to act through p21 protein activation. Control studies with other peptides and tyrosine analogues support the selective nature of these events. These results suggest that both the p21-related peptide and azatyrosine have potent anti-ras effects intracellularly.

Alanine↗
PubMed1989

Satellite cells as blood-ganglion cell barrier in autonomic ganglia.

In a preliminary study a difference in the uptake and transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) between the trigeminal ganglion and the superior cervical ganglion was observed. After injection of WGA-HRP and HRP into the trigeminal ganglion, peroxidase was found in the space between the satellite cell processes and the ganglion cells. The ganglion cells showed pinocytosis and uptake of WGA-HRP and HRP. In the superior cervical ganglion WGA-HRP and HRP were found alongside the satellite cells but were absent in the space between satellite cells and ganglion cells. Intravenous injection revealed the presence of HRP in the space between sensory ganglion cells and their satellite cells of the trigeminal and nodose ganglion whereas HRP was absent in the space between autonomic ganglion cells and their satellite cells of the superior cervical, medial cervical and pterygopalatine ganglion although HRP lined the satellite cell membranes. By means of electron microscopy, satellite cell processes in the superior cervical ganglion were found to enwrap ganglion cells very tightly with a marginal space between both cell types. Satellite cells and their processes were mutually anchored by numerous tight junctions. In the trigeminal ganglion the extracellular space between ganglion cells and satellite cells was larger and satellite cells were found to be more loosely arranged around the ganglion cells. Satellite cell processes were only occasionally linked by tight junctions. It is concluded that satellite cells in autonomic ganglia comprise an effective barrier for WGA-HRP and HRP and probably large molecules in general. This barrier is absent in sensory ganglia.

Animals↗
PubMed1984

A cytotoxic mononuclear phagocytic cell line.

A human mononuclear phagocytic cell line (M22) was established from lymph node cells of a cancer patient. Little or no multiplication occurred in the absence of target cells such as primary or continuous cultures of human, monkey, or mouse. In response to a target stimulus, M22 altered from the resting thick-walled stage and in time, target cells were destroyed. M22 resembled a monocyte, possessing Fc and complement receptors, strong nonspecific esterase activity, pinocytosis, and lacking B- and T-cell markers but differed by lacking lysozyme. It possessed acid and alkaline phosphatases but lacked myeloperoxidase. Unlike other described monocyte lines, M22 was unique in its nonspecific cytotoxic activity.

Adult↗
PubMed1983

A study of intestinal copper-binding proteins in mottled mice.

The substantial retention of Cu2+ and to a lesser extent Zn2+, in the gut mucosa of neonatal MO mutant mice is largely associated with a low molecular weight protein tentatively identified as metallothionein. [35S]Cysteine incorporation into this protein in mutant mice is elevated, indicating that Cu2+ retention in the gut is associated with an increase in the synthesis of metallothionein. The high Cu2+ levels of mutant gut tissue decline rapidly with age to reach an approximately normal level by 24 days of age; this decline cannot be prevented by dietary supplementation and it is suggested that gut 'closure' and consequent reduced uptake by pinocytosis are important factors in this decline.

Aging↗