Biomedical subjects

N A Kefalides

Publications and source records attributed to N A Kefalides.

At least 19 recordsLinked to original sources

PubMed1991

The effects of interleukin-1 on the expression of thrombospondin and fibronectin by rabbit articular chondrocytes.

Studies to evaluate the effects of recombinant interleukin-1 beta (IL-1) on the expression of matrix proteins by rabbit articular chondrocytes were conducted. Chondrocytes expressed high levels of message for thrombospondin (Tsp) and fibronectin (Fn). RNA slot-blot analysis demonstrated that treatment of the cultures with IL-1 (100 ng/ml) for 24 h caused a 70% suppression of their steady-state Tsp mRNA levels whereas those of Fn were not affected. Steady-state mRNA levels for the intracellular protein, actin, were not modulated by treatment with IL-1. The suppression of Tsp mRNA levels by IL-1 (100 ng/ml) was maximal by 4 h and was concentration dependent; half-maximal suppression was estimated to require 0.12 ng/ml IL-1. Cycloheximide treatment enhanced Tsp mRNA levels, but did not modulate IL-1 suppression of Tsp mRNA. Using pulse-labeling and immunoprecipitation techniques, we found that IL-1 suppression of Tsp mRNA levels was reflected in a coordinate inhibition of Tsp protein synthesis. Chondrocyte synthesis of Fn was not affected by IL-1. These data suggest that IL-1 specifically regulates chondrocyte expression of Tsp at least in part by decreasing the amount of Tsp mRNA available for translation.

Actins↗

PubMed1991

The biosynthesis of proteoglycans and interstitial collagens by bovine pericardial fibroblasts.

The biosynthesis of interstitial collagens (types I and III) and proteoglycans was studied in fibroblasts isolated from the parietal layer of bovine pericardium. Confluent cultures were labeled with Na2 35SO4 for proteoglycans or 14C-proline for collagens. The proteoglycans synthesized by pericardial fibroblasts were purified by DEAE-Sephacel chromatography and further fractionated into three components by gelfilitration. Two minor high molecular weight proteoglycans were shown by SDS-PAGE to be resistant to chondroitinase ABC and AC, and partially degraded by nitrous acid. The major, low molecular weight proteoglycan had a core protein of 45 kDa and is considered to be a dermatan sulfate/chondroitin sulfate proteoglycan since it was resistant to nitrous acid, but digested partially by chondroitinase AC and completely by ABC. The pericardial fibroblasts synthesized predominantly type I collagen and low amounts (about 10%) of type III collagen which was detected by delayed reduction on SDS-PAGE. The data show that pericardial fibroblasts synthesize the same macromolecules that can be extracted from the intact tissue and suggest that the proteoglycan may play a structural as well as physiological role.

Animals↗

PubMed1991

Differential suppression of host cell protein synthesis and mRNA levels in herpes simplex virus-infected endothelial cells.

Earlier studies from this laboratory have shown that infection of vascular cells with herpes simplex virus 1 or 2 (HSV-1, HSV-2) results in the differential suppression of extracellular matrix proteins including fibronectin (FN), type IV collagen, thrombospondin (TSP) and Factor VIII von Willebrand protein. The present study was designed to determine whether a correlation exists between suppression of synthesis of specific proteins and their mRNA levels. We have measured the steady-state levels of mRNAs for several extracellular matrix proteins (type IV collagen, FN and TSP) and two intracellular proteins (actin and tubulin) in human endothelial cells (EC) following HSV-1 infection. The results show that during the first 5 h post-infection, when there is a rapid decrease in the synthesis of extracellular matrix proteins, the steady-state levels of the corresponding mRNAs remain relatively high, but progressively decline to levels of less than 20% by 13 h post-infection. These findings suggest that in the early hours post-infection there is an alteration in the translatability of the hybridizable message followed by degradation in the later hours.

Cells, Cultured↗

PubMed1991

Studies on human laminin and laminin-collagen complexes.

Intact human laminin and laminin type IV collagen complexes were extracted from term placental membranes and their structures were examined by electroimmunoblot and by rotary shadowing electron microscopy. Rotary shadowing electron microscopy revealed a structure of human laminin which is essentially similar to the cruciform structure of the mouse tumor (EHS) laminin, but with some notable differences. The observed lengths of the short arms in the human laminin are different. One short arm has an average length of 34 nm and another short arm a length of 42 nm. In the mouse laminin all three short arms are of equal length. The average length of the long arm is 97 nm, which is longer than that of mouse tumor laminin (77 nm). The distal portion of the long arm has two clearly separated globular domains instead of the single one observed with tumor laminin. Human laminin was found in various states of aggregation including dimers, trimers and higher aggregates. Laminin molecules appeared to attach to a point in type IV collagen located 87 nm from C-terminus, or at 174 nm from C-terminus and one with less frequency, at 251 nm from C-terminus. A small number of molecules appeared to bind at the N-terminus of the collagen. These laminin-collagen interactions occurred via the distal globular domains of both the short and long arms of laminin. The data suggest that human laminin extracted from placenta is structurally different from that isolated from the mouse EHS tumor.

Chromatography, Gel↗

PubMed1991

Changes in the subunit composition of laminin during the increased tumorigenesis of mouse A9 cells.

We compared the structure and subunit composition of laminin in less tumorigenic mouse A9 and highly tumorigenic mouse A9HT cells by pulse-chase studies. During a 15' pulse, the ratio of laminin B1 to B2 subunits in cell lysates is 1:1 in both the A9 and A9HT cells; however, after a 3 hr chase, this ratio changes to 6:1 and 2:1 in the A9 and A9HT cells, respectively. Analysis of mature laminin subunits in culture media after a 3 hr chase also showed a similar higher ratio of B1 to B2 in the A9 cells as compared to the A9HT cells. The higher ratio of B1 to B2 subunits in A9 cells was evident as early as after a 30' pulse. A comparative analysis of steady-state levels of mRNAs for the laminin subunits B1 and B2 between A9 and A9HT cells showed a ratio of 1:1 for B1 and a ratio of 1:1.65 for B2. The ratio of B1 to B2 mRNAs in A9 cells was 1:1.3 whereas in A9HT cells it was 1:2.5, suggesting changes in the processing of mRNA in the highly tumorigenic A9HT cells. These observations suggest that the processing of laminin B subunits is altered during the process of increased tumorigenicity, thus resulting in the synthesis and secretion of structurally different laminin in tumorigenic A9HT cells as compared to the parent and less tumorigenic A9 cells.

Animals↗

PubMed1990

Laminin "A" chain fragment of Mr 43 kilodalton contains PC12 cell attachment promoting site.

In the present study, the ability of a 43 K fragment, originating from the long arm of the 400 K laminin "A" chain (Rao and Kefalides, manuscript in press), to promote the attachment and de novo neurite outgrowth by the pheochromocytoma cell line, (PC12) was studied. Unprimed PC12 cells (not treated with nerve growth factor, NGF), just as the primed cells (treated with NGF), rapidly and efficiently attach to the laminin fragment but less efficiently to the intact laminin coated bacteriological plastic surfaces. The neurite outgrowth was continuous from primed cells attached to both laminin and laminin fragment substrates, when cultured for four days in the presence of NGF. On the other hand, no significant neurite outgrowth was observed from unprimed PC12 cells attached to the laminin fragment coated bacteriological dishes, in the absence of NGF. These data suggest that the 43 K laminin "A" chain fragment contains the PC12 cell attachment promoting site.

Adrenal Gland Neoplasms↗

PubMed1990

Identification and characterization of a 43-kilodalton laminin fragment from the "A" chain (long arm) with high-affinity heparin binding and mammary epithelial cell adhesion-spreading activities.

A recently described procedure of reduction and carboxymethylation followed by heparin-Sepharose chromatography [Arumugham et al. (1988) Connect. Tissue Res. 18, 135-147] was used to characterize high-affinity heparin binding fragments of the laminin "A" chain. Two laminin fragments of Mr 53K and 43K selectively bound to the heparin-Sepharose column from the chymotrypsin digest of laminin, indicating that these fragments originate from the "A" chain. Without reduction and carboxymethylation but in the presence of 2.0 M urea, the heparin-Sepharose-bound material from the chymotrypsin laminin digest contains all the attachment-promoting activity for normal mouse mammary epithelial cells. The reduced 200-kDa intact three short arm fragment, fragments of Mr 70K-160K obtained either from laminin or from the reduced 200-kDa three short arm fragment, and the 53-kDa heparin binding fragment were all inactive in promoting the adhesion of mouse mammary epithelial cells. The mammary epithelial cell adhesion and spreading properties of laminin are associated with the high-affinity heparin binding 43-kDa fragment. The mammary epithelial cells attach to the 43-kDa fragment substrate and synthesize laminin, collagen type IV, and desmoplankins I and II as are the cells attached to laminin substrate and to the cells grown on tissue culture dishes. The biologically active 43-kDa fragment is generated from laminin, but not from the three short arm fragment. These results suggest that normal mouse mammary epithelial cells interact with laminin through a single site which is present in the 43-kDa heparin binding fragment located on the long arm of the "A" chain.

Animals↗

PubMed1990

The effect of heparin on fibronectin and thrombospondin synthesis and mRNA levels in cultured human endothelial cells.

Studies to eludicate the effect of heparin on the synthesis of extracellular matrix components by cultured human umbilical vein endothelial cells (EC) were conducted. Using pulse-labeling and ELISA techniques, we found that EC grown in the presence of heparin (90 micrograms/ml) and endothelial cell growth factor (ECGF) synthesized 50% less fibronectin (FN) than did ECGF-treated control cultures. No change in the synthesis of thrombospondin (TSP) was induced by heparin. The effect of heparin on EC FN synthesis was independent of whether the cells were cultivated on plastic or gelatin substrates. However, ECGF modulates the effect of heparin on EC synthesis of FN. RNA slot-blot analysis demonstrated that heparin treatment specifically decreased the steady-state mRNA levels for both FN and TSP in the cells. Steady-state levels of mRNA for two intracellular proteins, actin and tubulin, were unchanged. These data suggest that heparin decreases EC expression of FN at least in part by decreasing the amount of FN mRNA available for translation. The failure of heparin to inhibit TSP expression, although it reduces TSP mRNA levels, points to the possibility that the rate of EC synthesis of TSP is translationally or post-translationally regulated.

Cells, Cultured↗

PubMed1990

Inhibition of proteoglycan synthesis in human endothelial cells after infection with herpes simplex virus type 1 in vitro.

The effects of herpes simplex virus type 1 (HSV-1) infection on proteoglycan synthesis by human endothelial cells were studied as a model of endothelial cell injury. Confluent cultures of early passage endothelial cells from human umbilical vein were infected with HSV-1 at multiplicities of infection from 0.001 to 1.0. HSV-1 infection produced a dose-dependent inhibition of total proteoglycan synthesis of up to 85%. Although there was a 2- to 3-fold increase in the quantity of virus necessary to cause 50% inhibition of heparan sulfate compared to chondroitin/dermatan sulfate proteoglycan, the inhibition was relatively parallel, even up to high virus doses. There was no inhibition of an undersulfated heparan sulfate proteoglycan that contained glycosaminoglycan chains shorter than the predominant species. The results indicate that HSV-1 infection of human endothelial cells produces complex effects on host-cell metabolism. The viral-induced changes in proteoglycan metabolism may influence cell-matrix interactions and lead to altered vessel wall function.

Cell Membrane↗

PubMed1990

Suppression of host mRNA in human smooth muscle cells by a virion competent factor in herpes simplex virus type 1.

Herpes simplex virus type 1 produces an early decrease in protein synthesis in cultured smooth muscle cells isolated from human umbilical artery. To confirm that suppression of host protein synthesis occurs before virus protein expression, cultures were treated with actinomycin D (5 micrograms/ml) continuously from the beginning of infection. In the presence of actinomycin D, by 3.5 hours postinfection, virus-infected cultures showed much less incorporation of [35S]methionine into sodium dodecyl sulfate-polyacrylamide electrophoresis-separated products than did identically treated mock-infected cultures. In the absence of actinomycin D, there was incorporation of radiolabel into viral proteins as early as 4.5 hours postinfection. Hybridization of slot-blotted total RNA demonstrated that virus-infected cultures treated with and without actinomycin D showed a marked decrease in hybridizable RNA by 2 hours PI when compared with mock-infected controls. This decrease was seen with cDNA probes for the mRNA for secreted extracellular matrix macromolecules (fibronectin, thrombospondin and collagen chains alpha 2(I), alpha 1(III] as well as with cDNA probes for RNA of intracellular macromolecules actin and beta-tubulin. In vitro translation of total RNA isolated from infected human smooth muscle cells at 2 and 5 hours postinfection resulted in far less [35S]methionine incorporation into sodium dodecyl sulfate-polyacrylamide electrophoresis-separated products than would be predicted from the amount of hybridizable RNA available. The results suggest that host message is rapidly rendered nonfunctional as well as degraded by means of a virion-competent mechanism(s).

Dactinomycin↗

PubMed1989

Heparin increases mRNA levels of thrombospondin but not fibronectin in human vascular smooth muscle cells.

The effects of heparin (180 micrograms/ml) on steady state mRNA levels for fibronectin, thrombospondin, actin and collagen types I and III were investigated in human umbilical artery smooth muscle cells. Heparin caused a 120% increase in thrombospondin mRNA levels and a 60% and 180% increase in the mRNA levels of procollagen chains alpha 2(I) and alpha 1(III), respectively. No change in fibronectin or actin mRNA levels resulted from heparin treatment. We reported earlier (Biochem. Biophys. Res. Comm. 148:1264, 1987) that heparin increases smooth muscle cell synthesis of both fibronectin and thrombospondin. These data show that heparin coordinately regulates thrombospondin mRNA and protein levels. The heparin induced increase in fibronectin biosynthesis apparently reflects control at the translational or post-translational level.

Actins↗

PubMed1989

Lithium chloride restores host protein synthesis in herpes simplex virus-infected endothelial cells.

In previous studies we have shown that herpes simplex virus type 1 (HSV-1) infection suppresses host-cell protein synthesis in human endothelial cells (EC). It has been demonstrated that lithium salts prevent viral replication in HSV-1 infected cells. In the present study, we have measured host-cell protein synthesis in HSV-1 infected EC in the presence or absence of 20 and 30 mM LiCl. Although LiCl restored synthesis of almost all host-cell proteins, [35S]methionine incorporation was most pronounced in thrombospondin and plasminogen activator inhibitor 1 and least in fibronectin and type IV collagen. LiCl was more effective at the higher concentration (30 mM) and when the compound was added to the EC culture at the time of infection rather than after adsorption of HSV-1. Synthesis of virus proteins continued in LiCl-treated EC but at a reduced rate. The data suggest that LiCl not only interferes with virus replication, but may also, to some extent, interfere with the virion-associated inhibition of host protein synthesis.

Chlorides↗

PubMed1989

Bovine pericardial proteoglycan: biochemical, immunochemical and ultrastructural studies.

The major proteoglycan in bovine parietal pericardium is a low molecular weight dermatan-sulfate proteoglycan. It possesses structural and immunologic characteristics similar to those of the small proteoglycan found in tendon. We demonstrate that digestion of purified pericardial proteoglycan with low levels of V8 protease results in the liberation of the glycosaminoglycan chain and of a 40 kDa resistant fragment. A similar 40 kDa fragment can be obtained by V8 protease digestion of the proteoglycan deglycosylated by chondroitinase ABC. Although the protein core size of the pericardial proteoglycan is similar to that of tendon PG II, the size of the glycosaminoglycan chain liberated from the former is smaller. The pericardial proteoglycan and its V8 protease products reacted with an anti-PG II antiserum by immunoblotting. The anti-PG-II antibody localized in the pericardial tissue by the immunoperoxidase technique. The presence of intrachain disulfide bonds in the structure of pericardial proteoglycan core protein and V8 resistant fragment was demonstrated by their decreased electrophoretic mobility after disulfide reduction. Digestion of pericardial proteoglycan with Cathepsin C resulted in a rapid liberation of the glycosaminoglycan chain from the core protein, indicating that its attachment site was very close to the amino terminus. Ultrastructural examination of pericardial tissue utilizing Cuprolinic Blue revealed a periodic association of the proteoglycan with the d/e band on the collagen fibrils. Electron microscopic immunohistochemical studies confirmed the perifibrillar association of pericardial proteoglycan. The present data demonstrate that, although the pericardial proteoglycan possesses some unique structural features, it shares structural and immunological characteristics to place it in the category of the small PG II family.

Aggrecans↗

PubMed1989

Collagen metabolism in ultraviolet irradiated hairless mouse skin and its correlation to histochemical observations.

Early biochemical studies of ultraviolet (UV) irradiated human skin reported a loss of insoluble collagen with a concomitant increase in the soluble fraction. Recent work has described an early increase in type III collagen during chronic irradiation of hairless mice as determined by cyanogen bromide digests of whole skin. In order to understand the correlation of these events and those seen with histochemistry, in the present study we irradiated hairless mice for up to 24 weeks with approximately 4 minimal erythema doses (MEDs) of UVB thrice weekly with Westinghouse FS-40 bulbs. Skin samples were taken at 4-week intervals from irradiated and age-matched control mice. Collagen was isolated from other skin proteins by acid extraction, pepsin digestion, and salt precipitation. Estimates of types I and III collagen were made by interrupted polyacrylamide gel electrophoresis and densitometric scanning. Compared with unirradiated controls, there was a small increase in the ratio of type III to total collagen after 8 weeks of UV. There were no significant increases at later time points until after 24 weeks of radiation. Total collagen in normal mouse skin, determined by hydroxyproline content, remained constant over the 24 weeks, while UV radiation produced significant increases at 4, 8, 12, and 16 weeks, returning to control levels at week 20. There was no change in the degree of hydroxylation at any time point in either group. Thus, chronic UV exposure resulted in increased collagen synthesis until late in the course of irradiation. Because there is a lack of consistent change in the ratio of type III to total collagen, the early increases in collagen content may represent both types I and III, synthesized in relatively unchanging proportions.

Animals↗

PubMed1988

Partial characterization of a low molecular weight proteoglycan isolated from bovine parietal pericardium.

Knowledge of the nature of pericardial connective tissue components is incomplete. To gain a better understanding of the composition of this tissue, bovine parietal pericardium was extracted with 4 M guanidine hydrochloride yielding a proteoglycan-containing protein mixture. This was fractionated by a three-step chromatographic procedure with the resultant purification of a 75-110 Kd proteoglycan. The purified proteoglycan was susceptible to chondroitinase ABC digestion but resistant to chondroitinase AC and nitrous acid degradation suggesting the presence of dermatan sulfate glycosaminoglycan(s). This is the first reported isolation of a proteoglycan from parietal pericardium.

Animals↗

PubMed1988

Comparative ultrastructural localization of collagen types III, IV, VI and laminin in rat uterus and kidney.

Antibodies against collagen types III and VI have been localized by electron immunohistochemistry with two different techniques in normal rat uterus and kidney. Antibodies directed against two components of the extracellular matrix with known localization, laminin and type IV collagen, were used as controls for the specificity of the localization. The results demonstrate that types III and VI are found in the interstitium as fine (10- to 15-nm), beaded fibrils and filaments (6- to 10-nm), respectively. Both are often found associated with thick, crossbanded type I collagen fibers (30- to 35-nm) and occasionally associated with some basement membranes adjacent to the interstitium. Further, the findings suggest that collagens III and VI may connect the various components of the extracellular matrix, such as type I fibers with basement membranes and other structures, thus forming an integrated functional unit.

Animals↗

PubMed1988

Characterization of a renal tubular epithelial cell line which secretes the autologous target antigen of autoimmune experimental interstitial nephritis.

Proximal tubular epithelial cells from mice which develop autoimmune interstitial nephritis were found to express the nephritogenic target antigen, 3M-1. Anti-3M-1 mAbs (alpha 3M-1-Ab) were used to positively select for 3M-1-secreting tubular epithelium and, after stabilization in culture, this new cell line (MCT) was examined for the production of several moieties important to either immune interactions or to the development of extracellular matrix. Alkaline phosphatase-staining MCT cells also express epithelial growth factor receptors with a Kd of 0.87 nM and an epithelial growth factor receptor constant (Ro) of 2.1 X 10(4) receptors/cell. MCT culture supernatants contain greater amounts of laminin, and types IV and V procollagens compared to types I and III procollagens, and growing MCT cells on type I collagen matrix causes them to preferentially secrete even more type IV and V procollagen. The 30,000-Mr 3M-1 antigen could be immunoprecipitated from biosynthetically labeled MCT cell supernatants with alpha 3M-1-Ab. An identical-sized moiety was isolated by immunoaffinity chromatography from collagenase-solubilized mouse kidney tubular basement membranes. The 3M-1 antigen can be found on the MCT cell surface by radioimmunoassay, or deposited in a linear array in the extracellular matrix surrounding the MCT cells in culture by immunofluorescence. Mature messenger RNA species for both class I and class II major histocompatibility complex (MHC) molecules were detected by Northern hybridization, and their corresponding cell surface gene products were detected by cytofluorography of MCT cells stained with haplotype-specific antibodies. Both the cell surface 3M-1 and the small amounts of detected class II MHC molecules appear to be biologically functional, as MCT cells can support the proliferation of 3M-1-specific, class II MHC-restricted helper T cells in culture. These findings suggest that MCT cells provide all the necessary biological parameters for interfacing both as the target of a nephritogenic immune response, and as a potential source for new extracellular matrix which develops as a fibrogenic response to interstitial nephritis.

Animals↗

PubMed1988

Monoclonal antibodies to heparan sulfate proteoglycan: development and application to the study of normal tissue and pathologic human kidney biopsies.

Monoclonal antibodies (mAbs) (4F2 and 7E12) were prepared against heparan sulfate proteoglycan (HSPG) isolated from bovine glomeruli. Enzyme linked immunosorbent assays (ELISA) and immunoblotting demonstrated that the mABs reacted with HSPG. Indirect immunofluorescence (IF) showed that the mAbs stained renal basement membranes (BMs) and BMs in other organs of normal bovine and human tissues in patterns typical of HSPG. Immunoinhibition studies, and immunoblotting of heparan lyase digested HSPG, indicated that the mAbs recognize HSPG core protein. In kidney biopsies from patients with acute poststreptococcal GN, intact linear glomerular BM (GBM) staining for HSPG was noted despite markedly widened capillary loops. In membranous and in diffuse proliferative lupus GN, loss of HSPG staining was demonstrated at sites of immunodeposition of IgG or C3, while increased staining for HSPG was noted in areas of newly formed GBM. Extensive loss of HSPG was seen in areas of glomerular sclerosis and necrosis. In biopsies from patients with minimal change glomerulonephritis (GN) and mesangioproliferative lupus GN, a normal linear GBM distribution of HSPG was noted. The findings are discussed in the context of current knowledge regarding the pathogenesis of glomerular injury. MAbs to BM HSPG should prove useful for future immunochemical studies, and for the study of diseases of the basement membrane.

Animals↗