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Biomedical subjects

K Hedman

Publications and source records attributed to K Hedman.

86 records · Page 5Linked to original sources
PubMed1982

Deposition of an intermediate form of procollagen type III (pN-collagen) into fibrils in the matrix of amniotic epithelial cells.

We have followed the deposition and maturation of the pericellular matrix of amniotic epithelial cell cultures for up to eight weeks using metabolic labeling and immunoelectron microscopy. This matrix contains mainly collagen type III and fibronectin. Cleavage of the carboxypropeptide occurred after secretion of the procollagen molecules into the medium but was not accompanied by a significant release of the aminopropeptide. The early matrix, as isolated from the cultures by a deoxycholate procedure, contained collagenous proteins predominantly composed of pN alpha 1(III) chains, which still possessed the aminopropeptide, and only little material in the form of alpha 1(III) chains. The relative amount of alpha 1(III) chains increased during subsequent days of culture. Electron microscopy showed two types of structures in the matrix: thin fibrils, ranging from 10 to 30 nm in diameter, with no apparent cross-striation, and 50-500 nm thick bundles composed of filamentous and amorphous material. In the fibrils, immunoferritin electron microscopy showed a regular staining for the aminopropeptide of procollagen type III with a periodicity of 71 nm. These collagenous fibrils did not stain for fibronectin which was found in the bundles. Since most of the aminopropeptide in the matrix appeared covalently linked as pN-collagen, we conclude that the deposition of this intermediate form of procollagen is a general mechanism in collagen type III fibrillogenesis.

Amnion↗
PubMed1982

Structure of the pericellular matrix: association of heparan and chondroitin sulfates with fibronectin-procollagen fibers.

Immunofluorescent staining of a pericellular matrix produced by cultured human embryonic skin fibroblasts showed a codistribution among fibronectin, heparan sulfate proteoglycans and part of the chondroitin sulfate in a fibrillar network. Isolated matrix in an "intact" form could be scraped off the dish after detergent solubilization of the cells. On centrifugation in cesium chloride density gradients, most sulfated glycosaminoglycans and matrix proteins remained associated and were recovered at a density of 1.34 g/cm3 (greater or equal to 2 M CsCl). However, when 4 M guanidine hydrochloride was included in the gradient medium, the components dissociated, suggesting that the sulfated glycosaminoglycans are bound to matrix proteins by strong noncovalent linkages. Interactions between sulfated glycosaminoglycans produced by the fibroblasts and fibronectin could also be demonstrated by affinity chromatography on immobilized plasma fibronectin and by immunoprecipitation of fibronectin in conditioned culture medium, which resulted in a coprecipitation of the sulfated glycosaminoglycans. In these two systems, the fibronectin glycosaminoglycan bonds were broken at 0.2 M salt and were apparently weaker than the bonds responsible for the structural integrity of the matrix. These findings implicate heparan and chondroitin sulfate proteoglycans as integral compounds of the pericellular matrix fibers and suggest that the association of the proteoglycans with the fibronectin-procollagen matrix is stabilized by multiple molecular interactions.

Cells, Cultured↗
PubMed1982

Uukuniemi virus maturation: accumulation of virus particles and viral antigens in the Golgi complex.

We studied the maturation of Uukuniemi virus and the localization of the viral surface glycoproteins and nucleocapsid protein in infected cells by electron microscopy, indirect immunofluorescence, and immunoelectron microscopy with specific antisera prepared in rabbits against the two glycoproteins G1 and G2 and the nucleocapsid protein N. Electron microscopy of thin sections from infected cells showed virus particles maturing at smooth-surfaced membranes close to the nucleus. Localization of the G1/G2 and N proteins by indirect immunofluorescence at different stages after infection showed the antigens to be present throughout the cell interior but concentrated in the juxtanuclear region. The G1/G2 antiserum also appeared to stain the nuclear and plasma membranes. Double staining with tetramethylrhodamine isothiocyanate-conjugated wheat germ agglutinin, which preferentially stains the Golgi complex, and fluorescein isothiocyanate-conjugated anti-rabbit immunoglobulin G, which stained the G1/G2 or N proteins, showed that the staining of the juxtanuclear region coincided. Similarly, double staining for thiamine pyrophosphatase, an enzyme activity specific for the Golgi complex, showed the fluorescence and the cytochemical stain to coincide in the juxtanuclear region. Immunoperoxidase electron microscopy of cells permeabilized with saponin revealed that the viral glycoproteins were present in the rough endoplasmic reticulum and the nuclear and Golgi membranes; the latter was heavily stained. With this method, the N protein was localized to the cytoplasm, especially around smooth-surfaced vesicles in the Golgi region. Taken together, the results indicate that Uukuniemi virus and its structural proteins accumulate in the Golgi complex, supporting the idea that this compartment rather than the plasma membrane is the site of virus maturation. This raises the interesting possibility that deficient transport of the glycoproteins to the plasma membrane and hence their accumulation in the Golgi complex determines the site of virus maturation.

Animals↗
PubMed1980

Intracellular localization of fibronectin using immunoperoxidase cytochemistry in light and electron microscopy.

An immunocytochemical staining method for light and electron microscopy was developed to permit adequate penetration of staining conjugates with high specificity, while preserving acceptable ultrastructure. For this purpose an indirect immunoperoxidase method with Staphylococcal protein A-peroxidase conjugates was used in the presence of saponin on aldehyde-saponin-fixed cells. As the first application, fibronectin was localized intracellularly in human embryonic skin fibroblasts. Fibronectin was detected in large amounts in the cisternae of rough endoplasmic reticulum and in 200 nm (secretory?) vesicles. Little fibronectin was present in the Golgi complex; the stacked Golgi cisternae were conspicuously devoid of this protein. The 200 nm vesicles were mostly distributed on the mature side of the Golgi apparatus. These results indicate that fibronectin is exclusively localized to intracellular structures involved in secretory function and suggest that fibronectin may not be processed in significant amounts within the cisternal stacks of the Golgi complex.

Animals↗
PubMed1979

Isolation of the pericellular matrix of human fibroblast cultures.

The pericellular matrix of human fibroblast cultures was isolated, using sequential extraction with sodium deoxycholate and hypotonic buffer in the presence of protease inhibitor. The matrix attached to the growth substratum had a "sackcloth-like" structure as seen by phase contrast, immunofluorescence, and scanning electron microscopy, and it had a vaguely filamentous ultrastructure similar to that seen in intact cell layers. The matrix consisted of hyaluronic acid and heparan sulfate as the major glycosaminoglycan components and fibronectin and procollagen as major polypeptides as shown by metabolic labeling, gel electrophoresis, immunofluorescence, and collagenase digestion. This pericellular matrix can be regarded as an in vitro equivalent of the loose connective tissue matrix.

Cell Line↗
PubMed1978

Fibronectin and the pericellular matrix of normal and transformed adherent cells.

Fibronectin is a major glycoprotein component of normal fibroblasts in culture. External fibronectin is predominantly present in a pericellular fibrillar matrix that mediates distant cell-cell and cell-substratum contacts. A small proportion of external fibronectin is closely associated with the plasma membrane. In the matrix, fibronectin is partially disulfide bonded into complexes. Plasma transglutaminase, activated by thrombin, also cross-links external fibronectin into high-molecular-weight covalent complexes. In cultures of normal fibroblasts, pericellular matrix fibronectin displays extensive codistribution with (pro)collagens types I and III. Transformed adherent cells show decreased formation of the fibronectin-collagen matrix. The deficient synthesis of fibronectin and other matrix components and abnormal interactions with the matrix may account for several phenotypic characteristics of transformed cells. The pericellular matrix structure has been prepared by use of deoxycholate and hypotonic medium to solubilize the cells. The matrix contains glycosaminoglycans, procollagens, and fibronectin. The fibronectin codistributes with the procollagens. The matrix may be considered to be an in vitro equivalent of the connective tissue matrix and basal laminae found in vivo. Human sarcoma cells spread rapidly on the prepared matrix and assume an elongated morphology characteristic of normal fibroblasts. The prepared matrix may provide a general tool to study the effects of matrix on cellular behavior and differentiation.

Animals↗
PubMed1978

External fibronectin of cultured human fibroblasts is predominantly a matrix protein.

The distribution of a major glycoprotein (fibronectin) of human fibroblast cultures was studied in immunoelectron microscopy with peroxidase- or ferritin-labeled antibodies. External fibronectin was visualized in pericellular structures, in some areas on the growth substratum, and to a lesser degree in close association with the upper and lower surface membranes of the cell. The pericellular fibronectin-containing structures consisted of amorphous or vaguely fibrillar material forming strands or patches, 50-500 nm in diameter; the structures appeared to mediate distant cell-to-cell and cell-to-substrate contacts. When in close association with the plasma membrane, fibronectin markers were seen as discrete patches. The exact relationship between this form of fibronectin and the plasma membrane, however, remained open. Filamentous material was commonly seen in the cortical cytoplasm under patches of membrane-associated fibronectin. The distribution that we observed is consistent with the proposed roles of fibronectin in cell interactions with neighboring structures and with its presence in vivo as an extracellular glycoprotein in connective tissue matrix and basal laminae.

Cell Adhesion↗
PubMedDate not supplied

A pooled-data analysis of three randomized, double-masked, six-month clinical studies comparing the intraocular pressure reducing effect of latanoprost and timolol.

PURPOSE: To compare the intraocular pressure (IOP) reduction by latanoprost and timolol, and to study factors of prognostic value for assessing this reduction. METHODS: We analyzed 829 patients included in three phase 111 studies comparing six months' treatment with 0.005% latanoprost once daily and 0.5% timolol twice daily in patients with open-angle glaucoma or ocular hypertension. Analysis of covariance controlled for differences in baseline IOP and sex was used to assess the IOP reduction. RESULTS: Latanoprost reduced diurnal IOP (average of morning, noon and afternoon assessments) by 7.7 mmHg (31%) and timolol by 6.5 mmHg (26%) after six months of treatment. Thus the diurnal IOP was reduced 1.2 mmHg (18%) more with latanoprost than with timolol (p<0.001). Latanoprost-treated patients showed a further decrease in morning IOP of 0.7 mmHg (9%, p<0.001) from the initial morning IOP reduction obtained at two weeks. No such further decrease in IOP was seen with timolol. Higher baseline diurnal IOP resulted in a larger diurnal reduction during treatment with both drugs (p<0.001). Diurnal IOP in women was reduced 0.7 mmHg (11%) less than males with both drugs (p<0.001). CONCLUSIONS: Latanoprost was more effective than timolol in reducing mean diurnal IOP. The effect after two weeks was maintained for timolol while with latanoprost there was a further, significant IOP reduction from two weeks to six months. Baseline IOP was the only factor of clinical importance found to be of prognostic value for assessing the IOP reduction.

Aged↗