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Biomedical subjects

A Geerts

Publications and source records attributed to A Geerts.

At least 73 records · Page 4Linked to original sources
PubMed1990

Collagen type I and III occur together in hybrid fibrils in the space of Disse of normal rat liver.

Collagen type I and procollagen type III were localized at the ultrastructural level on ultrathin frozen sections of rat liver by the protein A-gold technique using affinity-purified primary antibodies. Both collagen type I and procollagen type III were localized on nearly all solitary and bundled fibrils in the space of Disse. Simultaneous localization of collagen type I and procollagen type III by a double-labeling procedure using protein A-gold probes of different sizes unequivocally demonstrated the presence of both collagens in the same fibrils. Measurement of the diameter of large numbers of collagen fibrils in the space of Disse of the rat liver showed a unimodal distribution of the fibril diameters around an average value of 62.4 nm (S.D. = 12.8 nm), and 91% of the collagen bundles contained less than 30 fibrils. Additional measurements on epoxy resin-embedded material of five biopsy specimens of normal human liver showed a comparable unimodal distribution of the fibril diameters around an average value of 57.2 nm (S.D. = 9.6 nm), and 74% of the bundles contained less than 60 fibrils. The latter observation demonstrates that human liver contains broader interstitial collagen bundles than rat liver. From these results, we conclude that the space of Disse of normal rat and human liver contains a uniform population of striated interstitial collagen fibrils. In the rat liver, these fibrils contain both collagen type I and procollagen type III. Therefore the concept that procollagen type III is predominantly localized in small diameter fibrils or bundles, whereas collagen type I is preferentially localized in thick ones, does not hold.

Animals↗
PubMed1990

Ultrastructure and function of hepatic fat-storing and pit cells.

The present paper reviews the literature on the ultrastructure and function of sinusoidal fat-storing cells and pit cells in the mammalian liver. Ultrastructurally, fat-storing cells are characterized by the presence of cytoplasmic fat droplets, well developed rough endoplasmic reticulum; a Golgi complex; multivesicular bodies; one or two centrioles; and few, rather small, lysosomes. These lysosomes are sometimes associated with fat droplets. Fat-storing cells may bear a cilium and project characteristic cytoplasmic processes into the space of Disse. These processes contain microtubules and filaments. Fat-storing cells are the main storage site of retinol esters in the mammalian body. Moreover, these cells have the potential of synthesizing several connective tissue components including the collagens type I, III, and IV; fibronectin; laminin; heparan sulfate; chondroitin sulfate; and dermatan sulfate. Pit cells are polarized cells, with most organelles localized at one site of the nucleus near the cytocentre. They are characterized electron microscopically by the presence of dense cytoplasmic granules with a specific ultrastructure, by rod-cored vesicles, and by multivesicular bodies. It has recently been shown that pit cells have natural killer activity to certain tumor cells and have many features in common with large granular lymphocytes. They therefore may act in the liver as a first line of defense against neoplasia, metastasis, and viral infections.

Animals↗
PubMed1989

In vitro differentiation of fat-storing cells parallels marked increase of collagen synthesis and secretion.

Fat-storing cells were isolated and purified from livers of normal adult rats and maintained in primary culture. By light and electron microscopy it was established that they underwent phenotypic changes into cells with the ultrastructural characteristics of myofibroblasts, between the third and sixth day in culture. These morphological changes were accompanied by a 2-fold increase of L-[3H]proline incorporation into secretory proteins and an 11-fold increase into secreted collagenase-sensitive proteins. In contrast, incorporation into cell layer-associated proteins and into cell layer-associated collagenase-sensitive proteins was not significantly elevated. Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in combination with fluorography, demonstrated that the main collagen type secreted by the myofibroblast-like cells was collagen type I. Collagen types III and IV, and fibronectin were present in lesser amounts. The similarity between the well known in vivo alterations of fat-storing cells under pathological conditions and the spontaneous in vitro differentiation described in this study, makes primary cultures of fat-storing cells a valuable tool for studying their role in chronic liver disease.

Adipose Tissue↗
PubMed1988

Localization of four phosphatases in rat liver sinusoidal cells. An enzyme cytochemical study.

In the present study we have localized neutral phosphatase, acid phosphatase, alkaline phosphatase and 5' nucleotidase in the sinusoidal cells of rat liver using enzyme cytochemistry at light and electron microscopical level. Neutral phosphatase was present in the endoplasmic reticulum and nuclear envelope of parenchymal cells and of sinusoidal endothelial, Kupffer and fat-storing cells. The intensity of the neutral phosphatase reaction was stronger in sinusoidal than in parenchymal cells. Sinusoidal cells were devoid of cytochemically demonstrable alkaline phosphatase. Abundant acid phosphatase was present in the many lysosomes of endothelial and Kupffer cells. Substantially less acid phosphatase-positive lysosomes were found in fat-storing cells. 5' nucleotidase was present on the cell membrane of fat-storing cells, on 90% of all Kupffer cells and on the microvilli of parenchymal cells. We have further shown that combined staining for 5' nucleotidase and for endogenous peroxidase, offers a histochemical tool to discriminate between the three main sinusoidal cell types in normal rat liver.

5'-Nucleotidase↗
PubMed1988

Cell population kinetics of Kupffer cells during the onset of fibrosis in rat liver by chronic carbon tetrachloride administration.

The cell population kinetics of Kupffer cells (KCs) were investigated during the induction of fibrosis in rat liver by carbon tetrachloride. KCs, characterized microscopically by their specific peroxidase pattern, increased in number during the first 24 h after CCl4 injection. After repeated injections of the toxin the number of KCs increased logarithmically. After 9 weeks of CCl4 treatment, the KC population reached a new steady state with a 2.6-times-higher cell number than in control animals. Local KC proliferation was demonstrated by the metaphase arrest technique using vinblastine. It was calculated that at 24 h and at 72 h after one injection of CCl4, local proliferation did not account for the entire growth of the population. This means that, in addition to local proliferation of KCs, an influx of mononuclear phagocytes into the liver sinusoids occurred.

Animals↗
PubMed1987

Modulation of collagen synthesis by fat-storing cells, isolated from CCl4- or vitamin A-treated rats.

In an attempt to elucidate the role of fat-storing cells (FSCs) in liver fibrosis, we investigated the collagen synthesis by FSCs freshly isolated from rats treated with CCl4, with vitamin A, and from untreated rats. FSCs from CCl4-treated rats contained a small number of lipid droplets and an abundant rough endoplasmic reticulum (RER), while those from vitamin A-treated rats showed numerous large lipid droplets and scanty RER. The population doubling times of FSCs isolated from normal, CCl4-treated, and vitamin A-treated rats were 38 +/- 4.3, 24 +/- 2.5, and 48 +/- 6.3 hr, respectively. The rate of collagen synthesis by FSCs from CCl4-treated rats was four- to sixfold enhanced, while collagen synthesis by FSCs from vitamin A-treated rats was suppressed. The ratio of collagen type I to type III produced by FSCs from CCl4 rats was enhanced as compared with control rats (94.7:5.3 vs 87.6:12.4). Therefore, FSCs can be considered to play an important role in the pathogenesis of liver fibrosis.

Animals↗
PubMed1986

Immunogold localization of procollagen III, fibronectin and heparan sulfate proteoglycan on ultrathin frozen sections of the normal rat liver.

In the present study, we have localized by immunocytochemistry at the LM and EM level, procollagen type III (PIIIP), fibronectin (FN) and heparan sulfate proteoglycan (HSPG). Intracellularly, PIIIP was observed in both parenchymal and endothelial cells. In parenchymal cells, PIIIP was found in Golgi derived vesicles. This observation suggests that PIIIP synthesis is a normal function of liver parenchymal cells. In endothelial cells, vesicles, which could not be identified, were seen to contain PIIIP. This result does not allow to conclude, whether sinusoidal endothelial cells secrete or take up PIIIP. Extracellularly, PIIIP was present around portal and central veins, in the space of Disse and between adjacent parenchymal cells. In the space of Disse, almost all interstitial collagen fibrils reacted with the anti PIIIP antibodies. This observation leads to the conclusion that most fibrils of the space of Disse contain type III in addition to type I collagen molecules. By immunofluorescence, FN was seen mainly along the sinusoids in discrete dots. By EM, FN was found to be present in diffuse material closely associated with the sinusoidal membrane of the parenchymal cells and in strands connecting adjacent parenchymal cells, parenchymal and endothelial cells or parenchymal cells and collagen fibrils. FN was also present in vascular and ductular basal laminae. Strong HSPG reaction was observed around bile ducts. Moderate reaction was seen around blood vessels and in the space of Disse. In the latter location, the ultrastructural distribution of HSPG resembles that of FN, i.e. HSPG is present in diffuse material and in strands.

Animals↗
PubMed1986

Kupffer cells from CCl4-induced fibrotic livers stimulate proliferation of fat-storing cells.

The interaction between fat-storing cells (FSCs) and Kupffer cells (KCs) in vitro has been studied in an attempt to clarify certain aspects of the pathogenesis of fibrotic process in the liver. FSCs and KCs were isolated from the livers of rats either treated with CCl4 for 6 weeks, or with vitamin A for 6 weeks or from untreated rats by the pronase-collagenase digestion method. FSCs were further purified by centrifugation over a double layered metrizamide gradient, and KCs were separated from other sinusoidal cells by the dish adherence technique. FSCs from CCl4-treated rats divided rapidly, while those from vitamin A-treated rats divided slowly, as compared with untreated rats. Furthermore, the proliferation of FSCs was enhanced in the presence of KCs from CCl4-treated rats, but was slightly suppressed by KCs from normal and vitamin A-treated rats. This enhancement was mediated by a non-dialyzable, soluble factor present in the conditioned medium of KCs from CCl4-treated rats, but was not detected in the conditioned medium of KCs from normal or vitamin A-treated rats. From the present study, a growth factor secreted by KCs from CCl4-treated rats may play an important role in controlling the proliferation of FSCs during the pathogenesis of liver fibrosis.

Animals↗
PubMed1986

Serum and synovial fluid antibodies to collagen in rheumatic diseases: a review.

The literature on the occurrence and significance of antibodies to native or denatured collagen in rheumatic diseases is reviewed. Mainly type I and type II collagen have been investigated, both in serum and synovial fluid, with special reference to their possible role in rheumatoid arthritis. Brief results of the analysis of 40 synovial fluid samples, using an ELISA technique are included.

Arthritis, Rheumatoid↗
PubMed1984

On the topology of the catalase biosynthesis and -degradation in the guinea pig liver. A cytochemical study.

The biosynthesis, transport and degradation of catalase have been studied in the guinea pig liver parenchymal cell using 2-allyl-2-isopropylacetamide (AIA) as an inhibitor of de novo formation of catalase. Total catalase activity was assayed biochemically; cytoplasmic catalase was measured microspectrophotometrically after quantitative diaminobenzidine staining of the liver. By morphometry, number and size of peroxisomes in catalase stained sections were determined. From our data we conclude that (1) the final step in the catalase formation takes place inside peroxisomes, (2) catalase is transported from the peroxisomes into the cytoplasm, (3) in the cytoplasm catalase is degraded. These conclusions in part confirm the topological model on the intracellular catalase biosynthesis pathway of Lazarow and de Duve (1973) except for the presence of cytoplasmic catalase which is released from the peroxisomes as proposed earlier by Jones and Masters (1975).

Allylisopropylacetamide↗
PubMed1981

Quantitation of catalase activity by microspectrophotometry after diaminobenzidine staining.

The absorbance of the reaction product of catalase staining with diaminobenzidine is linearly proportional to enzyme activity. This is shown in semithin Epon sections of model systems containing serum albumin and catalase from bovine or guinea pig liver. Absorbance measurements were also performed on semithin sections of guinea pig liver, and from these, the activity of cytoplasmic (extraperoxisomal) catalase has been derived.

3,3'-Diaminobenzidine↗
PubMedDate not supplied

Purified rat liver fat-storing cells in culture divide and contain collagen.

Primary cultures and cell lines were established from suspensions of purified fat-storing cells isolated from the rat liver. When seeded at a suitable density, fat-storing cells in primary culture reached confluency in 3 to 4 days and could be transferred and established as cell lines for at least two passages. The typical morphological characteristics of fat-storing cells in vivo were retained in the cells during primary culture. Vitamin A fluorescence was still associated with lipid droplets of cells in culture up to and including the second passage. Investigation of the cytoskeletal structure by indirect immunofluorescence showed the presence of vimentin, actin and tubulin in the cells; no alpha-prekeratin was present. The presence of vimentin suggested a fibroblastic or possible myogenic origin for fat-storing cells. The presence of connective tissue components in fat-storing cells in culture was demonstrated by indirect immunofluorescence. Collagen Types I and IV and laminin were present intracellularly in small granules in fat-storing cells in primary culture and in the first passage. Cells in the fourth passage contained only collagen Type 1. Fibronectin was only aligned extracellularly along the cell membrane, which did not exclude an extracellular source. Rat liver fat-storing cells in culture show a high proliferating capacity. Cell multiplication during prolonged culture was associated with phenotypic transition to a more fibroblastic appearance and gradual disappearance of vitamin A. These results indicate that fat-storing cells may be among the cell types involved in pathological changes observed during development of liver fibrosis.

Actins↗
PubMedDate not supplied

Antioxidant enzyme gene expression in rats with remnant kidney induced chronic renal failure.

Reactive oxygen intermediates play a role in chronic renal injury and glomerulosclerosis. We investigate changes in renal cortex antioxidant enzyme gene expression in the rat remnant-kidney model of chronic renal failure and compare the new data to enzyme activities published earlier. Antioxidant enzyme gene expression is evaluated by Northern blot analysis of cortex mRNA, using cDNA probes for catalase, copper/zinc-containing superoxide dismutase, and glutathione peroxidase. Catalase gene expression decreases during development of renal failure; this decrease is accompanied by decreased catalase activity during the glomerulosclerosis phase of the remnant-kidney model. Copper/zinc superoxide dismutase and glutathione peroxidase gene expression remain at a normal level during progression of the model, whereas their activities show a temporary decrease in the early remnant kidney. In the remnant-kidney model, catalase seems to be more vulnerable to reactive oxygen intermediates than superoxide dismutase and glutathione peroxidase. Our results show that antioxidant enzyme activity and gene expression do not change in the same direction at all times during disease development and that all antioxidant enzymes do not respond in the same way.

Actins↗