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Biomedical subjects

J Risteli

Publications and source records attributed to J Risteli.

At least 253 records · Page 14Linked to original sources
PubMed1984

Basement membrane laminin and type IV collagen in various benign and malignant adnexal tumors of the skin: an immunohistochemical study.

Thirty benign and seven malignant adnexal tumors of the skin and one lymph node metastasis were stained for laminin and type IV collagen with rabbit antibodies against the human basement membrane (BM) proteins using the immunoperoxidase technique. Fifteen of the benign sweat gland, sebaceous gland, and hair follicle tumors showed a continuous and distinct BM around the tumor aggregates. The cylindromas and eccrine spiradenomas seemed to produce excessive amounts of BM material, part of which was seen as amorphic patches within the tumor cell clusters, whereas the trichofolliculomas, trichoepitheliomas, and pilomatrixomas showed an absence of BM from many areas. In syringomas, in addition to the tubular structures surrounded by a continuous BM, undifferentiated cell nests containing granular BM material were present. They probably represent primitive structures obtaining during early development into tubules. The seven malignant tumors and the only metastasis studied here all contained small, narrow strips of BM material extracellularly between the infiltrating tumor clusters. Only in two cases was faint staining for laminin found within the cells. The pepsin pretreatment of the formalin-fixed, paraffin-embedded samples had most probably degraded the intracytoplasmic BM material in most cases. The BM defects were found to be associated with malignancy and low differentiation of the adnexal skin tumors, as reported previously for other tumor types, but a partial loss of BM was also associated with high differentiation in some benign adnexal tumors.

Adenoma↗
PubMed1984

Immunohistochemical localization of epidermal basement membrane laminin and type IV collagen in bullous lesions of dermatitis herpetiformis.

Antibodies against the human basement membrane proteins, laminin and the 7-S domain of type IV collagen, were used to study the epidermal basement membrane in lesional skin from four patients with dermatitis herpetiformis. The staining pattern of both antigens was mostly fragmented and sometimes absent on papillary microabscesses, but when present it was attached to the epidermal basal cells. On papillary microblisters and larger blisters the staining of both antigens showed discontinuities and was located in the floor of the blister, except for two cases where tiny fragments of laminin staining were also seen in the roof of larger blisters. These results suggest that blister formation in dermatitis herpetiformis takes place between the epidermal basal cells and the basement membrane.

Adolescent↗
PubMed1983

Structural diversity and domain composition of a unique collagenous fragment (intima collagen) obtained from human placenta.

Intima collagen was obtained from pepsin digests of human placenta in two forms, which differ to some extent in the size of their constituent polypeptide chains (Mr 50 000-70 000). These chains are connected by disulphide bonds to large aggregates. The aggregates are arranged in a triple-helical conformation with a remarkably high thermal stability (Tm 41-62 degrees C) and are resistant to further proteolytic digestion. Reduction of as little as 5% of the disulphide bonds produces mainly monomeric triple helices (Mr about 160 000) with Tm 32 degrees C. Partially reduced material can be separated into triple-helical and non-collagenous domains by proteolysis. Pepsin releases a collagenous component with chains of Mr 38 000. Bacterial collagenase liberates two non-collagenous segments (Mr 15 000-30 000) rich in cystine. Treatment with collagenase before reduction separates intima collagen into a large fragment composed of collagenous (Tm 41 degrees C) and non-collagenous structures and a single non-collagenous segment. The data support the electron-microscopical model of intima collagen [Furthmayr, Wiedemann, Timpl, Odermatt & Engel (1983) Biochem. J. 211, 303-311], indicating that the basic unit of the fragment consists of a continuous triple helix joining two globular domains.

Amino Acids↗
PubMed1983

Effect of the structural components of basement membranes on the attachment of teratocarcinoma-derived endodermal cells.

The effect of biochemically purified basement membrane components as mediators of cell attachment is studied in vitro using an endodermal PYS-2 cell line known to produce a basement membrane-like insoluble matrix. Fibronectin is shown to be as effective as laminin as an attachment-promoting protein, although the latter is a major product of these cells and the former is not produced by them in any detectable amount. Fibronectin also increases the attachment of the cells to type IV collagen-coated plates, but laminin lacks this effect. Protein synthesis-blocking agents such as cycloheximide totally abolish the attachment-promoting effect of extracellularly supplied laminin, but not that of extracellular fibronectin. Type IV collagen alone is no better a substratum for these cells than type I collagen or the plastic surface of the dish itself. The importance of an intact tertiary structure for the attachment is obvious in the case of both fibronectin and laminin. Denatured molecules or smaller fragments of these molecules do not promote cell attachment.

Animals↗
PubMed1983

Biochemical characterization of variants of the Ehlers-Danlos syndrome type VI.

Three variants of the Ehlers-Danlos syndrome type VI are described: a severe form with skeletal, dermal and ocular manifestations associated with a lack of hydroxylysine in skin and little lysyl hydroxylase activity in cultured fibroblasts; a similarly affected form with a nearly normal hydroxylsine content in skin, but with only little enzyme activity in cultured fibroblasts; and a predominantly ocular form with no biochemical abnormality in skin or cultured skin fibroblasts. The activities of prolyl 4-hydroxylase and the two hydroxylysyl glycosyltransferases were normal in all cases, and the failure to find lysyl hydroxylase activity was not due to altered solubility characteristics of the enzyme or to the presence of an enzyme inhibitor. The collagen produced in cell culture, however, was hydroxylated to a markedly higher extent than that found in skin. In both the mutant and control cells hydroxylation of lysyl residues was less sensitive to ascorbate deficiency than that of prolyl residues.

Adolescent↗
PubMed1983

Aminoterminal propeptide of type III procollagen in serum in alcoholic liver disease.

An assay of serum antigens related to the aminoterminal propeptide of type III procollagen has been suggested for monitoring fibrotic processes in the liver. These antigens were measured here in 61 alcoholics who were divided into four groups on the basis of liver histology: normal light microscopy, fatty liver, alcoholic cirrhosis with hepatitis, and inactive cirrhosis. All the subjects having alcoholic hepatitis with cirrhosis had elevated values in the assay, whereas some of those with either fatty liver or inactive cirrhosis still had normal values. It was, therefore, not possible on the basis of this method alone to distinguish fatty liver from cirrhosis or alcoholic hepatitis, although very high values were suggestive of alcoholic hepatitis. In a follow-up study, the aminopropeptide value decreased slowly during recovery from alcoholic hepatitis and increased rapidly after a new drinking bout. The antigens detected by the assay are heterogeneous in human serum. The proportions of the three main peptide forms varied during recovery from alcoholic hepatitis, the authentic propeptide being the main one at the acute stage, but almost disappearing later. The usefulness of the assay could probably be improved if distinct assays were available for the different antigen forms.

Adult↗
PubMed1982

Heterogeneity of the antigens related to the aminoterminal propeptide of type III procollagen in human serum.

Inhibition curves that are considerably less steep than the reference peptide curve are a constant finding when human serum samples are studied with the radioimmunoassay for the aminoterminal propeptide Col 1-3 of type III procollagen. This is due to the presence in the serum of three main peptide forms which differ in their antigenic properties and can be separated by gel filtration. Their molecular sizes are, respectively, larger than, equal to and smaller than the peptide Col 1-3. The proportions of these forms were different in a number of serum samples tested. An elevated value in the Col 1-3 radioimmunoassay need not reflect increased deposition of type III collagen in the liver, but could also be due to increased degradation of a newly-synthesized type III procollagen or degradation of a tissue form still containing the aminoterminal propeptide. This should be considered when interpreting elevated serum values.

Amino Acid Sequence↗
PubMed1982

Increase in circulating basement membrane antigens in diabetic rats and effects of insulin treatment.

The serum concentrations of two recently discovered antigens derived from basement membranes (7-S collagen and laminin P2) were assayed in streptozotocin-diabetic rats as possible indicators of basement membrane metabolism. The concentrations of both increased significantly after 8 weeks of diabetes, and that of 7-S collagen at least remained elevated up to 24 weeks. Treatment with insulin, which did not correct the metabolic disturbances, inhibited the increase in the concentration of 7-S collagen in serum, but did not completely normalize that of laminin P2.

Animals↗
PubMed1981

Immunological characterization of the 7-S domain of type IV collagens.

Antisera were raised against the long and short form of mouse and human 7-S collagen and against type IV collagens solubilized by acid extraction or limited digestion with pepsin. All the antisera showed strong binding for 7-S collagen in radioimmunoassays demonstrating that the 7-S domain which serves as a cross-linking region of type IV collagen is the most immunogenic portion of the molecule. Cross-reaction studies and analysis of fragments showed a complex antigenic structure including some determinants common to the long and short form of 7-S collagen and others unique for the long form. Purified antibodies against 7-S collagen reacted in indirect immunofluorescence with almost all basement membranes of the body indicating that the 7-S domain is a common structural element of type IV collagens.

Animals↗
PubMed1981

Type IV collagens' isolation and characterization of 7S collagen from human kidney, liver and lung.

7S collagens were isolated after bacterial collagenase treatment of basement membrane material prepared from the pepsin digest of human kidney, liver and lung. The 7S collagens were purified by combination of molecular sieve and ion exchange chromatography. 7S collagen from each of these sources showed similar amino acid composition, electrophoretic patterns of reduced and unreduced samples. Antibodies raised against human placental 7S collagen in rabbits completely cross-reacted with the 7S collagen preparation obtained from kidney, liver and lung in enzyme-immunoassays. Since 7S collagen in known to be a major cross-linked segment of type IV collagens, the data indicate that collagenous proteins of basement membranes are organized in similar networks in a variety of organs.

Amino Acids↗
PubMed1980

Immunochemical distinction between two different chains of type IV collagen.

Antisera against mouse and human basement-membrane type IV collagen showed in radioimmunoassays distinct binding with large pepsin fragments obtained from the C-terminal portions of alpha 1 (IV)- and alpha 2 (IV)-chains. These reactions were specific for each constituent polypeptide chain. The data were confirmed by immunoadsorption, allowing the separation of antibodies with restricted chain specificity. Inhibition assays with CNBr peptides demonstrated the different localizations of antigenic determinants, which were either species-specific or shared by the human and mouse antigens.

Animals↗
PubMed1980

7-S collagen: characterization of an unusual basement membrane structure.

A new type of collageneous structure, tentatively named 7-S collagen, was isolated from a mouse tumor basement membrane, mouse and human placenta, bovine lens capsule and human kidney. The protein was solubilized from the tissues by limited digestion with pepsin or trypsin and could easily be separated from other collageneous protein because of its resistance towards further degradation by bacterial collagenase at 20 degrees C. 7-S collagen showed an amino acid composition typical of basement membrane collagen and contained 22% carbohydrate mainly as glucosyl-galactosyl bound to hydroxylysine but also some mannose and glucosamine. Ultracentrifugal analysis demonstrated that the proteins were homogeneous with a sedimentation coefficient of about 7.2 S and with a molecular weight of about 360,000 both in phosphate buffer pH 7 and 6 M guanidine. The peptide was triple helical as shown by circular dichroism and exhibited a biphasic melting profile indicating two conformationally distinct domains with tm = 48 degrees C and 70 degrees C. The more stable domain could be isolated as an homogeneous fragment (Mr = 225,000) after a second digestion with collagenase at 37 degrees C. This fragment contained all the disulfide bonds (42 Cys/1,000 residues) of the original molecule. Electron microscopy showed a rod-like structure in agreement with the hydrodynamic properties of 7-S collagen. The dimensions of these peptides were 3 X 95 nm (long form) and 2.4 X 40-50 nm (short form). Complete reduction of 7-S collagen under denaturing conditions produced several polypeptide chains in the molecular weight range of 27,000-153,000 which differ from each other by Mr increments 25,000-27,000. Separation of the chains on agarose did not reveal any simple stoichiometric relationship indicating that some chains are either cross-linked or represent fragments produced during proteolytic treatments. Complete reduction of 7-S collagen under non-denaturing conditions lowered the thermal transiton of the triple helix to 48 degrees C but did not change its molecular weight except when exposed to dissociating solvents. 7-S collagens were potent immunogens and could be characterized by radioimmunoassays. Antigenicity was slightly reduced by reduction and denaturation while collagenase at 37 degrees C produced a larger decrease. Proteins obtained from various sources showed distinct immunological relationships although interspecies differences in affinity exist. No or only little cross-reaction was observed with type IV and V collagens and some further fragments of basement membrane collagen. The data indicate that 7-S collagen is a unique component of basement membranes which shows a more compact and stable structure than other collageneous proteins.

Amino Acids↗