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Biomedical subjects

J Peltonen

Publications and source records attributed to J Peltonen.

At least 127 records · Page 7Linked to original sources
PubMed1989

Collagen gene expression by cultured human skin fibroblasts. Abundant steady-state levels of type VI procollagen messenger RNAs.

Previous studies have suggested that procollagen types I and III are the major collagenous gene products of cultured human skin fibroblasts. In this study the expression of 10 different genes, encoding the subunit polypeptides for collagen types I-VI, by human skin fibroblasts in culture was analyzed by molecular hybridizations. Northern transfer analysis demonstrated the presence of specific mRNA transcripts for collagen types I, III, IV, V, and VI, but not for type II collagen. Quantitation of the abundance of these mRNAs by slot blot hybridizations revealed that type I, III, and VI procollagens were the major collagenous gene products of skin fibroblasts in culture. The mRNAs for type IV and V collagens represented only a small percentage of the total collagenous mRNA transcripts. Further analysis by in situ hybridization demonstrated that the majority of the cultured cells coexpressed the genes for type I, III, and VI procollagen pro-alpha chains. Further in situ hybridization analyses revealed the expression of type VI collagen genes in normal human skin. These data demonstrate that human skin fibroblast cultures can be used to study the transcriptional regulation of at least nine genetically distinct procollagen genes. The data further suggest that type VI collagen, in addition to types I and III, may be a major collagenous component of human skin.

Cells, Cultured↗
PubMed1989

Type 1 neurofibromatosis: selective expression of extracellular matrix genes by Schwann cells, perineurial cells, and fibroblasts in mixed cultures.

Cutaneous neurofibromas, characteristic lesions of neurofibromatosis 1, are composed of an abundant extracellular matrix and nerve connective tissue-derived cell types: Schwann cells, perineurial cells, and fibroblasts. In this study, the extracellular matrix gene expression by these cells was examined under culture conditions that allowed them to be metabolically active and readily identifiable by morphologic and immunocytochemical criteria. Northern hybridizations demonstrated expression of genes for type I, III, IV, and VI collagens, as well as for fibronectin, laminin, and elastin. In situ hybridizations revealed that all three cell types expressed pro alpha 1 (I), pro alpha 2 (VI), and laminin B1 chain genes. However, fibroblasts did not contain [35S]cDNA-mRNA hybrids specific for type IV collagen, whereas both Schwann cells and perineurial cells expressed these genes. Perineurial cells and fibroblasts readily expressed the fibronectin gene whereas Schwann cells were essentially devoid of the corresponding mRNA. Perineurial cells also expressed the gene for laminin A chain. The results indicate that the extracellular matrix gene expression profiles of Schwann cells, perineurial cells, and fibroblasts are distinct: all three cell types are capable of expressing some of the genes for extracellular matrix components, such as type I and VI collagens, whereas Schwann cells and perineurial cells may have the primary role in synthesizing basement membrane zone components, type IV collagen and laminin. These observations potentially relate to the mechanisms of growth and development of human neurofibromas. The results attest to the applicability of the methodology utilized here to study other human tumors with mixed cell populations.

Blotting, Northern↗
PubMed1989

Localization of integrin receptors for fibronectin, collagen, and laminin in human skin. Variable expression in basal and squamous cell carcinomas.

VLA integrins in human skin were examined by indirect immunofluorescence utilizing antibodies recognizing the beta 1, alpha 2, alpha 3, or alpha 5 subunits. Staining of fetal, newborn, or adult skin with antibodies to beta 1, alpha 2, or alpha 3 subunits gave essentially similar staining patterns: intense staining was associated with the basal layer of the epidermis, hair follicles, and blood vessel walls. The alpha 5 subunit could be detected only in epidermis and the inner root sheath of hair follicles in fetal skin. In epidermis, the staining reaction for the beta 1 subunit was not only found in sites interfacing with the basement membrane zone, but also around the entire periphery of these cells. We speculate that these receptors might have previously unrecognized functions in cell-cell interactions or that these findings may suggest the presence of previously unrecognized ligands in the intercellular spaces of keratinocytes. Examination of nine nodular basal cell carcinomas revealed a prominent staining reaction with anti-beta 1 and anti-alpha 3 antibodies at the periphery of the tumor islands. In contrast, staining of five squamous cell carcinomas revealed either the absence of integrins or altered and variable expression. Thus, matrix components and their receptors may participate in modulation of growth, development, and organization of human skin.

Adult↗
PubMed1989

Human laminin: cloning and sequence analysis of cDNAs encoding A, B1 and B2 chains, and expression of the corresponding genes in human skin and cultured cells.

A human placental lambdagt11 expression cDNA library was probed for laminin cDNAs by a combination of immunoscreening using polyclonal anti-human laminin antibody, and plaque hybridizations using a mouse laminin A chain cDNA. A total of 36 recombinant clones were isolated and characterized. Northern blot hybridizations with poly(A)+RNA, isolated from cultured human skin fibroblasts, revealed hybridization either to (a) a single 10 kb transcript consistent with A chain; (b) a single 5.7 kb transcript consistent with B1 chain; or (c) polymorphic 5.6 and 8.2 kb transcripts consistent with B2 chain of human laminin. Nucleotide sequencing of representative cDNA clones (approximately 2.5 kb in size) confirmed that these three groups of cDNAs encoded C-terminal sequences of laminin A, B1 and B2 chains, respectively. Deduced amino acid sequences for both B1 and B2 chains contained epidermal growth factor-like sequences and alpha-helical heptad repeats, as found previously for mouse laminin. Partial laminin A chain cDNA encoded 680 amino acid residues characterized by several internal repeats. This portion of the peptide accounted for a large part of the globular domain (fragment 3), the whole length of a second (T2) and portions of a third (T1) globular domain. The human A chain also contained an Arg-Gly-Asp sequence, a potential cell-binding site, which is not found in the same segment of mouse laminin. The newly isolated cDNAs were also utilized to analyze expression of laminin mRNAs by cultured human cells and tissues. The results demonstrated that the laminin A, B1, and B2 chain genes were expressed in an uncoordinate manner in both cultured cells and tissues, with a particularly low level of the A chain mRNA being present.

Amino Acid Sequence↗
PubMed1988

Quantitation of Schwann cells and endoneurial fibroblast-like cells after experimental nerve trauma.

Schwann cells and endoneurial fibroblast-like cells were quantitated for 30 weeks in both nonregenerating and freely regenerating, transected rat sciatic nerve. Immunocytochemical recognition of S-100 protein was used as a marker for Schwann cells and other immunocytochemical and histological methods in the differentiation of S-100 protein-negative endoneurial cells in cross sections of the distal stump 10 mm distal to the site of transection. A marked increase in the total number of cells was observed during the first 4 weeks after the injury in both operative groups. The quantitative relationships between cell populations remained essentially the same as in normal nerves, although the proliferation of the S-100 protein-negative cell population was proportionately slightly stronger when compared to the number of these cells in normal nerves. After the initial proliferation, a gradual decrease occurred in the total number of cells per cross section. This was most marked in the non-regenerating nerves, whereas in the regenerating nerves the decrease in cell number ceased at 16 weeks. The number of Schwann cells was 3.5 times as high as in the control nerves in this phase. The method used in the present study is less laborious than morphometry employing electron microscopy. Furthermore, electron microscopic characteristics of endoneurial cells are not always reliable after nerve trauma, because normal anatomical relationships have become disturbed. This study demonstrates that S-100 protein immunocytochemistry is useful in the study of traumatic lesions of peripheral nerve.

Animals↗
PubMed1988

Schwann cells and collagen synthesis in taxol-treated nerve crush. An electron microscopic study.

The effect of nerve crush on collagen synthesis in rat sciatic nerve was studied by electron microscope. The crushed nerves were treated with taxol which is known to increase the amount of cytoplasmic microtubules at the expense of other cell organelles such as rough endoplasmic reticulum and Golgi complexes. The results were compared to those seen in crushed nerves without taxol treatment. After the injury the amount of collagen fibrils increased at the site of the trauma in both groups when compared to intact controls. Thin (30 mn in diameter) collagen fibrils were often arranged closely to the Schwann cell surface and were connected to deep invaginations in areas where the basal lamina had lost its typical integrity. This was concluded to indicate a probable site of collagen secretion and it provides further evidence that an adult injured nerve Schwann cell is capable of synthesizing fibrous collagen. In taxol-treated nerves additional, abnormally close connection between thin microfibrils of about 10 nm and thin 20-30 nm collagen fibrils appeared in an end-to-end fashion. The microfibrils showed occasional collagenous transverse band like structures. The rough endoplasmic reticulum and Golgi complex play an important role in the posttranslational modifications of the procollagen molecule. Taxol-induced degeneration of cell organelles such as the Golgi complex, which is also essential in the secretion of proteins may thus lead to defective maturation of collagen and may explain partly the altered collagen fibril formation.

Alkaloids↗
PubMed1988

Fibronectin gene expression by epithelial tumor cells in basal cell carcinoma: an immunocytochemical and in situ hybridization study.

Previous observations have demonstrated that fibronectin is deposited in high abundance in basal cell carcinoma stroma. In this study, the nature of fibronectin and the site of its synthesis were explored in 10 basal cell carcinomas of the nodulo-ulcerative type by immunocytochemistry and in situ hybridization. First, simultaneous localization of epithelial tumor cell islands and fibronectin epitopes was carried out by double immunofluorescence staining with monoclonal anti-cytokeratin antibodies and polyclonal fibronectin antibodies, the latter recognizing both the cellular and plasma types of the protein. Large amounts of fibronectin were deposited in the basal cell carcinoma stroma, with the highest concentration present in the immediate proximity of the epithelial cell islands. Immunofluorescence with a monoclonal anti-fibronectin antibody, which is directed against the ED-domain of cellular fibronectin and does not recognize the plasma type of fibronectin, revealed essentially the same staining pattern as that obtained with the polyclonal anti-fibronectin antibody. This observation suggested that fibronectin in BCC was predominantly of the cellular type. Second, in situ hybridizations, utilizing a human fibronectin specific cDNA, demonstrated that the highest concentration of fibronectin mRNA was found in the most peripheral cell layer of the epithelial tumor islands. The presence of fibronectin mRNAs in the tumor cells of the central regions of the islands, as well as within occasional stromal cells, was also noted. Thus, two lines of evidence suggest that the epithelial tumor cells are predominantly responsible for the synthesis and deposition of fibronectin in basal cell carcinoma. The presence of fibronectin may explain the characteristic biologic behavior of basal cell carcinomas, including low degree of metastatic potential and local destructive nature of the tumors.

Autoradiography↗
PubMed1988

Three-year results of bracing in scoliosis.

We treated 107 patients with idiopathic scoliosis with the Boston brace. The primary correction was good in all the curve patterns. The follow-up time after weaning averaged 3 years. The best final result was achieved in thoracic and lumbar curves (mean 2 degrees). The final correction was worse in patients with an initial curve less than 30 degrees when compared with the patients with larger curves. Except the double major curves, there was a positive correlation between the primary correction, duration of the treatment, and the final result. The results in 14 patients with bracing for 12 hours daily did not differ from the remainder. Progression of the initial curve more than 5 degrees after the treatment was noted in 24 patients. Three patients were operated on later because of progression. We conclude that bracing can prevent progress of scoliosis.

Adolescent↗
PubMed1988

Regeneration after physeal distraction of the radius in sheep.

In 18 sheep, gradual physeal distraction of the distal radius was performed by external fixation. Separation of the physis from the metaphysis occurred in all the sheep. Prior to bone formation, collagen fibers were organized according to the direction of the distraction, and lamellar bone was formed if the collagen bundles were lineally organized. In the area where the collagen was disorganized, and also near the periosteum, woven bone was first formed, which was then remodeled into lamellar bone. In some sheep separate groups of chondrocytes were isolated in the metaphyseal area after the distraction. In 2 animals a double physis was formed in the metaphyseal area. This was obviously due to the separation of proliferative chondrocytes in the metaphysis as a result of distraction. After consolidation of the distraction area, this zone of chondrocytes, located in the metaphysis, was still producing new bone 20 weeks postoperatively.

Animals↗
PubMed1988

Cellular differentiation and expression of matrix genes in type 1 neurofibromatosis.

The cellular heterogeneity of cutaneous tumors from nine patients with type 1 (von Recklinghausen's) neurofibromatosis was studied using several antigenic markers with special reference to focal heterotopic differentiation and interindividual variation. Furthermore, cells which actively express the genes for type I and III collagens and fibronectin, the major components of the abundant extracellular matrix of neurofibromas, were localized using in situ hybridizations. In eight of nine cases, the S-100 protein positive cells, i.e. Schwann-like cells, composed 60 to 80% of the total cell population. However, in one case, only about 40% of the cells were S-100 protein positive. The latter tumor was studied with respect to perineurial cell differentiation and stained with a mixture of two antibodies, directed against the S-100 protein and type IV collagen. In Schwann cells, the staining reaction for S-100 protein was observed in the nuclear region, whereas the staining reaction for type IV collagen was located peripherally, corresponding to the basement membrane zone covering the cells. The stromal cells which showed only the peripheral staining profile were considered to be neoplastic perineurial cells. Distinct structures with epithelial, endothelial, or smooth muscle cell differentiation were present within the benign tumors, as detected by immunostaining for cytokeratin, epithelial membrane antigen, factor VIII-related antigen and desmin, respectively. In situ hybridizations revealed a clearly detectable expression of type I procollagen genes in less than 10% and type III procollagen gene in less than 5% of the total cell population. Active synthesis of fibronectin was limited to the vascular walls, when examined by in situ hybridization, and antibodies to cellular fibronectin localized to the same areas. However, antibodies to plasma fibronectin produced a uniform staining reaction throughout the tumors suggesting that most of the fibronectin in neurofibromas is plasma-derived. The latter observation suggests that neurofibroma cells are freely accessible to various plasma proteins, including growth factors, which may influence the growth characteristics of these lesions.

Antibodies, Monoclonal↗
PubMed1988

Cultured neurofibromatosis tumor fibroblasts lack beta-adrenergic receptors.

Beta-adrenergic receptors on cultured neurofibromatosis (NF) skin and tumor fibroblasts were characterized by a radioligand binding assay using (-)-125I-iodocyanopindolol (ICYP), a potent beta-antagonist. NF tumor fibroblasts had a very low density of beta-adrenergic receptors (0-450 binding sites/cell) when compared to fibroblasts obtained from a healthy skin area of NF patients or from healthy controls (average 1,800 binding sites/cell). The apparently low binding of ICYP to the NF tumor fibroblasts can be an expression of an alteration in the structure or function of the plasma membrane.

Fibroblasts↗
PubMed1987

Reversible endoneurial changes after nerve injury.

Endoneurial changes in the rat sciatic nerve were studied during Wallerian degeneration and subsequent regeneration. After total axotomy two different experimental models were used. In the first the cut ends of the sciatic nerves were left free to allow reinnervation. In the second model the distal end of the transected nerve was sutured to the adjoining muscle to prevent regeneration. Within 2 weeks after the axomoty, a Wallerian type of degeneration was seen with axonal destruction and phagocytosis of myelin sheaths. After 4 weeks endoneurial fibroblastic cells formed circular structures around the Schwann cell columns, i.e., the bands of Buengner in both groups. These fascicle-like structures became more pronounced in the non-regenerating nerves up to 8 weeks, while during reinnervation the cellular reaction in the endoneurium nearly disappeared within this time. Ultrastructurally, the endoneurial fibroblast-like cells showed marked phagocytotic activity and also fragments of basement membrane on their surface. The appearance of thin (25-30 nm in diameter) collagen fibrils closely related to the basement membrane was noted around the bands of Buengner, as well as the appearance of an amorphous extracellular gap between the newly synthetized thin collagen fibrils and normal endoneurial collagen (50-60 nm). The reversible endoneurial compartmentation seems to be important for maintaining the nerve structure, serving as a support for axonal regeneration in addition to the bands of Buengner.

Animals↗
PubMed1987

The effects of nerve transection on the endoneurial collagen fibril sheaths.

The connective tissue changes during Wallerian degeneration and subsequent regeneration were studied in the distal stump of transected sciatic nerves of Wistar rats. In half of the animals regeneration was prevented by suturing the distal stump to muscle and in the rest spontaneous regeneration was allowed. Intact contralateral nerves served as controls. By 4 weeks after transection the Schwann cell columns became surrounded by a layer of thin collagen fibrils that were, on average, 25-30 nm in diameter. This was only half of the fibril diameter observed elsewhere in the endoneurium or in control nerves. The layer of thin fibrils diminished in thickness when axonal regeneration reached the distal stump, especially as the axons became myelinated. At all stages of the experiment the fibril diameter distribution in the surrounding normal endoneurial stroma was comparable with that observed in control nerves. Segments of Schwann cell basement membrane were observed to be closely associated with collagen fibrils both in freely regenerating, as well as in non-regenerating, nerves. The diameter of these fibrils corresponded to that observed in the zone of thin fibrils surrounding the Schwann cell columns. Such areas were not found in control nerves. The data obtained show that deposition of thin collagen fibrils occurs around the Schwann cell columns as a reaction to transection. Our observations on the regenerating nerves indicate that this connective tissue reaction does not prevent regeneration in the early phases following injury and that its progression is limited concomitantly with axonal regeneration.

Animals↗
PubMed1987

Laminin in traumatized peripheral nerve: basement membrane changes during degeneration and regeneration.

The changes in Schwann cell basement membrane associated with degeneration and regeneration during 50 weeks after transection of rat sciatic nerve were studied immunohistochemically with antibodies to laminin. In half of the animals, regeneration was prevented by suturing the nerve stumps aside, whereas in the rest spontaneous regeneration was allowed. Axonal regeneration was monitored with anti-neurofilament protein antibodies. In control nerves, basement membranes surrounding Schwann cells were visualized as circular, laminin-positive structures within the endoneurium. By 8 weeks after transection, Schwann cells had formed columns which were laminin-positive throughout their cross-sectional area and indistinguishable from basement membrane zones in both non-regenerating and regenerating nerves. As axons repopulated the distal stump, the normal shape of Schwann cell basement membrane tubes was slowly restored in freely regenerating nerves. In non-regenerating nerves, however, a striking atrophy of Schwann cell columns was observed. Regenerating axons were only seen inside laminin-positive tubular structures in all phases after 8 weeks in regenerating nerves. On the other hand, restoration of normal shape in laminin-positive basement membrane zones was coincident with appearance of axons in the distal stump, but it did not take place in chronically degenerating nerves. The results show that chronic degeneration leads to an atrophy of Schwann cell columns and results in a decrease in laminin immunoreactivity associated with them.

Animals↗
PubMed1987

Adherent cells from rheumatoid synovia: identity of HLA-DR positive stellate cells.

Rheumatoid synovia were enzymatically digested and the in vitro morphology of different types of plastic adherent cells was observed. Four main types of cells were found after 24 hours in culture: stellate cells which had nuclei resembling those of classical cultured fibroblasts, but which stained positively with I2 antibody (anti-HLA-DR antibody); fibroblastic cells; cells which resembled morphologically in vitro macrophages and which were I2 and OKM-1 positive; round monocytes. The stellate cells did not stain with anti-S-100 or OKT-6 antibodies, which are used to detect classical antigen presenting dendritic cells. Furthermore, in the presence of indomethacin the stellate shaped cells were replaced by new I2 positive cells with a typical fibroblast shape. These results support the view that the stellate cells in synovial cell cultures represent HLA-DR positive fibroblasts, probably B cells of synovial lining.

Arthritis, Rheumatoid↗
PubMed1987

Perineurial cells in culture. An immunocytochemical and electron microscopic study.

Perineurium is a cellular ensheathment protecting the nerve fascicles, i.e., groups of Schwann cell-axon units, in the peripheral nerves. To date, culturing of perineurial (PN) cells has not been reported. Pieces of nerve fascicles from sciatic nerves of adult Wistar rats were used as a source of PN cell cultures. Outgrowth of very large squamous cells was observed from about 90% of the explants. The cells divided slowly and their very large, flattened phenotype and their sheetlike growth patterns were distinct from those of the other connective tissue cells of peripheral nerves, such as Schwann cells or endoneurial fibroblasts. Selected pieces were re-explanted 1 to 10 times and about 1 to 5% of all explants gave rise to cultures which were apparently free from other cell types. They were concluded to be originated from the perineurium according to their light microscopic and ultrastructural properties and their ability to express specific antigens; the cells produced laminin and formed patches of basement membrane material on their surface. These characteristics are not associated with fibroblastic cells and the lack of S-100 protein differentiated the PN cells from the Schwann cells. Furthermore, cultured PN cells expressed fibronectin which is not produced by Schwann cells. PN cells showed characteristically prominent cytoplasmic actin containing stress fibers and staining with antibodies to vimentin showed arrays of intermediate filaments. The cells were negative for cytokeratin, glial fibrillary acidic protein, desmin, and factor VIII-related antigen indicating that they were not related to epithelial, glial, muscle-derived, or endothelial cells, respectively. PN cell cultures maintained their viability up to 5 to 8 passages and did not become overgrown by other cell types. Samples from normal human sciatic nerve and from neurofibromas from patients with von Recklinghausen's neurofibromatosis were cultured as described for rat sciatic nerve. The resulting cultures contained cells which had characteristics resembling those of cultured rat PN cells when studied at the light microscopic level. The present novel method to grow PN cells in cultures provides a possibility to study the specific functions of these cells under conditions not influenced by stimuli from e.g., the axons or the Schwann cells. The present data also provides evidence that PN cells, in addition to Schwann cells and fibroblasts, take part in the formation of neurofibromas.

Animals↗
PubMed1986

Collagen in human aorta. Changes in the type III/I ratio and concentration of the reducible crosslink, dehydrohydroxylysinonorleucine in ascending aorta from healthy subjects of different age and patients with annulo-aortic ectasia.

The type III/I + III collagen ratio was studied in intima-medial samples of ascending aortas obtained from patients with the Marfan syndrome or other annulo-aortic ectasia (dilatation of the ascending aorta) and from control subjects, using electrophoretic analysis of cyanogen bromide peptides. The [3H]borohydride-reduced crosslinks of collagens were analysed by ion-exchange chromatography. Type III/I + III collagen ratios were twice as high in adult aortas as those found in skin samples of the same age. This ratio was lower in fetal and very young aortic samples and in 6-8 out of 12 pathological aortas (including one sample from a Marfan patient) when compared with adult controls. In contrast, the type III/I + III collagen ratio was high in fetal or very young skin and the values obtained from several patients did not differ from those of the control skin samples. In one pathological aorta out of six studied, the concentration of the reducible crosslink, dehydrohydroxylysinonorleucine, was higher than in controls, suggesting increased collagen synthesis or impaired maturation of collagen. These changes point to altered collagen metabolism in aortas of patients with annulo-aortic ectasia.

Adolescent↗