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Biomedical subjects

S Gay

Publications and source records attributed to S Gay.

At least 127 records · Page 7Linked to original sources
PubMed1998

Molecular biology of cartilage and bone destruction.

Molecular biology has provided various new insights into the mechanisms operative in the pathogenesis of rheumatoid arthritis. Reflecting the unique character of rheumatoid synovium, advances have been achieved addressing the molecular changes taking place at the area of interaction between the aggressively growing synovium and the articular cartilage and bone. Key issues in the review period addressing this interaction were hyperplasia of rheumatoid arthritis synovium, mechanisms of activation and cell cycle regulation of synovial fibroblasts, pathways of synovial attachment to cartilage and bone, and the regulation of matrix-degrading enzymes.

Apoptosis↗
PubMed1998

Retrovirus-associated rheumatic syndromes.

The influence of environmental factors in the initiation of autoimmune rheumatic diseases is still under debate. Infections with viruses (e.g., retroviruses) or expression of gene products encoded by endogenous retroviruses are believed to contribute to both loss of tolerance for autoantigens and immunosuppression. In various rheumatic disorders the detection of retroviral antibodies provides evidence for retroviral gene expression and suggests a role in the etiopathogenesis. Molecular mimicry, defects in apoptosis, altered autoantigens, and alterations of monocyte or macrophage as well as dendritic cell functions may contribute to the molecular mechanisms causing the loss of tolerance. On the other hand, destruction of lymphocytes during lytic retrovirus infections as well as envelope gene-env derived immunosuppressive retroviral gene products may prevent chronic inflammatory diseases and tissue destruction. Furthermore, retrovirus encoded super-antigens with the potency to skew the T-cell repertoire may seriously modify the host's immune system.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Do antivirals have any utility in the treatment of arthritis?

Viruses have been linked to arthritides by several pathways. Apart from the ability of different viral pathogens to cause arthritic symptoms directly, only some circumstantial evidence for the involvement of (retro)viruses in the pathogenesis of rheumatoid arthritis has been presented in recent years. Therefore, the question of whether antiviral agents can be used to treat arthritis has become of interest. However, the mechanisms by which exogenous retroviral infection as well as activation of endogenous retroviral sequences may potentially lead to the induction of rheumatoid arthritis is just beginning to emerge. Moreover, the hypothesis that persistent viral infection may account for some hitherto unclassified, chronic arthritides, still needs to be confirmed. Therefore, the use of antiviral agents in the treatment of arthritides has been limited to viral complications of anti-arthritic therapy and to some experimental approaches. In this review, we will focus on current concepts of viral involvement in arthritis and point to future directions in the use of antiviral agents for arthritis.

Journal Article↗
PubMed1998

Retroviral sequences in rheumatoid arthritis synovium.

There are several relationships between retroviruses and cellular transformation, as well as retroviruses being involved in the development of autoimmune diseases. Retroviruses have been discussed as etiologic agents modulating or triggering certain pathways in the pathogenesis of rheumatoid arthritis (RA). However, none of the currently known retroviruses has been identified as specific for RA. Due to the unique properties of retroviruses, distinct experimental approaches can be used to detect retroviral activity in cells and tissues. Current research in RA using state-of-the-art molecular biology techniques includes both the search for exogenous and endogenous retroviral gene sequences in synovium of patients with RA.

Animals↗
PubMed1998

Mechanism of joint destruction in rheumatoid arthritis.

The synovium in rheumatoid arthritis (RA) is characterized by an increase in lining layer thickness and infiltration of inflammatory cells into the sublining area. Fibroblasts in the lining layer develop the appearance of "transformed cells", under the influence of proto-oncogenes involved in the regulation of the cell cycle. Fibroblast and macrophage-derived cytokines such as IL-1 and TNF-alpha are present abundantly in the rheumatoid synovium and stimulate these cells to produce destructive enzymes. Other cytokines such as IL-4 and IL-10 represent a physiological attempt to reverse the inflammatory process. Adhesion molecules facilitate both the migration of cells to the joint as well as the attachment of synovium to bone and cartilage. Joint destruction is mediated by enzymes such as serine proteases, matrix metalloproteinases (MMPs) and the cathepsins. Treatments directed against various components of the inflammatory cascade have shown promise. Inhibition of MMPs or adhesion molecules, blockade of IL-1 or TNF-alpha and the use of anti-Fas antibodies to induce apoptosis offer new possibilities for the treatment of RA. More recently, the employment of genes with antiarthritic properties has shown therapeutic potential.

Apoptosis↗
PubMed1998

Clonally-related immunoglobulin VH domains and nonrandom use of DH gene segments in rheumatoid arthritis synovium.

BACKGROUND: Synovia of patients with long-standing rheumatoid arthritis (RA) are typically infiltrated with B lymphocytes and plasma cells that secrete large amounts of immunoglobulin. The CDR3 of an immunoglobulin heavy chain is composed of the VH-DH-JH join, with interposed N region addition, and thus defines clonal relatedness. Furthermore, the CDR3 lies at the center of the antigen binding site, so its length and composition influence antigen binding. We sought definitive evidence of an antigen-driven B cell response (i.e., clones derived from the same VH, DH, and JH gene segments with shared somatic mutations) in RA synovial mRNA transcripts, and to characterize CDR3 intervals at the target of inflammation in this autoimmune disease. MATERIALS AND METHODS: We screened a cDNA library generated from unselected cells from the knee joint of a 62-year-old white female with long-standing RA. This technique does not have the potential bias of selecting for antibodies that express a particular reactivity such as rheumatoid factor. C gamma recombinants were sequenced and progenitor VH, DH, and JH gene segments were assigned and somatic mutations determined by comparison to germline sequences. Analyses of DH reading frame utilization and hydropathy characteristics of CDR3s were performed. RESULTS: Two of 67 recombinants were derived from the same VH (V3-11) and JH gene segments, demonstrated shared mutations, and contained nearly identical VH-DH-JH joins, including N region addition. Three other recombinants contained identical sequence throughout the variable domain. We also found preferential utilization of a limited number of VH and DH gene segments and marked preference for a DH reading frame encoding predominantly hydrophilic residues. CONCLUSIONS: Analysis of expressed heavy chain variable domains strongly supports the hypothesis that the B cell response in RA synovium is at least in part antigen driven and oligoclonal.

Amino Acid Sequence↗
PubMed1998

[In vivo verification of in vitro release specifications of a theophylline sustained-release preparation].

Especially in drugs with a narrow therapeutic range, "within product bioequivalence" i.e. "batch-to-batch bioequivalence" should be scrutinized. Therefore, pharmacokinetics and bioavailability of to batches at the upper and lower in vitro specification range as well as a batch representing the middle of the specification range was evaluated in an in vivo bioequivalence study. An open, randomized, 3-way crossover, multiple dose study in 18 healthy, male volunteers was selected for this purpose. Bioequivalence regarding rate (Cmax ss; t75%Cmax) and extent (AUCss) of absorption could be established for both extreme batches at the lower and upper in vitro specification range. Additionally both batches proved to be bioequivalent compared to the batch in the middle of the in vitro specification range. As a result, reproducible concentration-time profiles can be guaranteed for all batches of this sustained release theophylline (CAS 58-55-9) preparation. Furthermore, pharmacokinetic characteristics of all three batches meet the quality criteria defined for sustained release theophylline preparations, guaranteeing optimal concentration/time profiles for the therapy of asthma.

Adult↗
PubMed1998

[Pharmacokinetics of a theophylline sustained-release formulation after single and twice daily dosage].

Sustained release theophylline (CAS 58-55-9) preparations may be dosed once or alternatively twice-a-day, depending on the intention of a theophylline therapy. A once-a-day dosage regimen is considered appropriate in patients with nocturnal asthma attacks, whereas a twice-a-day regimen is advantageous for guaranteeing bronchodilatation and to control the underlying inflammatory disease. Therefore, pharmacokinetic characteristics of both modes of administration were evaluated in a randomised, two-way crossover study in 18 female and male elderly volunteers under multiple-dose conditions. The shape of the pharmacokinetic profiles showed the expected and pronounced differences, while the extent of absorption was bioequivalent. Twice daily administration decreased the nocturnal maximum concentration and at the same time increased the minimum concentration. At the expense of the nocturnal excess, the peak-trough fluctuations (PTF) were reduced from 92.1% to 39.5%. Plateau times of 11.4 h and 20.2 h were achieved with both modes of administration. As for theophylline with its narrow therapeutic range, high quality sustained release preparations distinguish themselves by long plateau times and small peak-trough fluctuations such as those observed with the preparation under investigation. When using this preparation, therapeutic concentrations necessary for safety and efficacy are assured under either a once- or a twice-daily dosing regimen.

Aged↗
PubMed1998

[The effect of bile secretion on the pharmacokinetics of a theophylline sustained-release preparation].

Bile excretion changes the physiological milieu of the duodenum, possibly resulting in enhanced absorption of a drug due to increased solubilisation. This possible influence of bile salts following stimulation of gallbladder emptying by the release of cholecystokinin on the pharmacokinetics of a sustained release theophylline (CAS 58-55-9) preparation (Bronchoretard) was evaluated in this study. An open, randomised, 3-way crossover study in 12 healthy, non-smoking volunteers was selected to prove or reject this hypothesis. All subjects received 500 mg of the sustained release theophylline formulation under two different cholagogia stimulating test conditions compared with a fasting reference condition. A standard breakfast and i.m. administration of cholecystokinin enabled a reproducible modulation of bile flow: a moderate and extreme contraction of the gallbladder could be induced after a standard breakfast and after i.m. administration of cholecystokinin, respectively. Following a standard breakfast, gallbladder volumes were approximately halved (50.6%) compared to the baseline volume after 79 min. Injection of 0.3 microgram/kg body weight cholecystokinin resulted in fast and complete gallbladder evacuation (94.6%) 36 min after the application of this cholagogue stimulus. Gallbladder volumes remained more or less constant under fasting conditions. This manipulation of bile flow did not influence concentration/time profiles of the sustained release theophylline preparation compared to the fasting condition. Even almost complete evacuation of the gallbladder after administration of cholecystokinin did not modify the concentration/time profile of theophylline in a relevant way. An unintentional rapid release of theophylline could be excluded for this sustained release formulation for all three treatments, as not a single case of dose dumping was observed. Furthermore, in vitro dissolution investigations using synthetic surfactants can predict neither food effects nor bile influence on the in vivo absorption at least for the sustained release formulation tested.

Adult↗
PubMed1998

[Pharmacokinetics of a new fluid theophylline sustained-release drug form. Microcapsules in a sachet].

A new sustained release theophylline (CAS 58-55-9) formulation was especially designed for the elderly and children. Microcapsules of theophylline, administered as a suspension in water, proved to be a suitable dosage form for a clientele with impaired or difficult deglutition. Pharmacokinetic characteristics of 2 batches at the lower (T1) and upper (T2) in vitro dissolution specification range of this new formulation and a pellet formulation (R) as a comparator were evaluated in an open, randomised, 3-way, multiple dose, crossover study with an asymmetric dosage regimen of 400 mg and 200 mg theophylline. Smooth and safe plasma concentrations with a high and long-lasting plateau were achieved with this new formulation. Plateau times which are independent of the asymmetric dosage regimen ranged from 16.4 h (T1) to 13.8 h (T2) and could therefore cover sufficient time of the dosage interval. Maximum plasma levels of 9.6 micrograms/ml and 10.0 micrograms/ml were attained 6.6 and 6.1 h after dosing of T1 and T2, coinciding perfectly with the time of the critical morning dip at 2-6 a.m. With a nocturnal excess of 15.5% (T1) and 17.9% (T2), this circadian-tailored asymmetric dosage regimen proved to take into account the chronopathology of asthma and the chronopharmacokinetics of theophylline sustained release preparations. Bioequivalence of all 3 formulations compared with each other with regard to rate (Cmax ss) and extent (AUCss) of absorption could be established for the 2 batches at the upper and lower in vitro specification range and for both batches of the new formulation compared to the reference. All in all, the safety and efficacy of this new liquid sustained release theophylline preparation could be established. Furthermore, in vitro specifications were justified according to current EC guidelines.

Aged↗
PubMed1998

Cysteine proteinase cathepsin K mRNA is expressed in synovium of patients with rheumatoid arthritis and is detected at sites of synovial bone destruction.

OBJECTIVE: Cysteine proteinases B and L have been shown to be involved in matrix degradation of joints in patients with rheumatoid arthritis (RA). Since the cysteine proteinase cathepsin K is assumed to play a pivotal role in osteoclast mediated bone resorption, we investigated the expression of cathepsin K in RA joints. METHODS: We studied 10 RA and 4 normal synovial specimens and 5 articular heads with RA lesions by in situ hybridization, applying specific riboprobes for cathepsin K, human collagen type I, and cathepsin B. Antibodies against monocyte/macrophage associated CD68 antigen were applied in immunohistochemistry. Reverse transcription-polymerase chain reaction (RT-PCR) and ribonuclease protection assay (RPA) were performed on 4 RA, 1 normal, and 1 immortalized normal fibroblast cultures. RESULTS: Cathepsin K mRNA expression was upregulated in RA synovium compared to normal synovium. Cathepsin K mRNA was expressed mainly by synovial fibroblasts. These data were confirmed by RT-PCR and RPA. In RA articular heads, cathepsin K mRNA was detected at sites where synovium attached and invaded underlying bone. The cells at these sites represented collagen type I and cathepsin B mRNA expressing fibroblasts as well as CD68+ macrophages and giant cells. In addition, a distinct expression of cathepsin K mRNA was also detected around lymphocytic infiltrates in RA synovium. CONCLUSION: The data indicate that cathepsin K is not only expressed by osteoclasts but also by synovial fibroblasts, and suggest that cathepsin K contributes to bone destruction mediated by RA synovial cells. The expression of cathepsin K around lymphocytic infiltrates suggests further to facilitate the movement of mononuclear cells through the perivascular interstitial matrix and thereby contribute to interstitial matrix turnover.

Adult↗
PubMed1997

Human IL-1Ra gene transfer into human synovial fibroblasts is chondroprotective.

Rheumatoid arthritis (RA) is characterized by progressive destruction of synovial cartilage. In vitro, degradation of cartilage is stimulated by IL-1, a proinflammatory cytokine, which is released from RA synovial fibroblasts (RA-SF). To determine whether gene therapy using the gene encoding the naturally occurring inhibitor of IL-1, IL-1 receptor antagonist (IL-1Ra) is feasible, IL-1 Ra-transduced RA-SF were coimplanted with normal human cartilage in SCID mice. The IL-1 Ra-transduced RA-SF continued to secrete IL-1Ra over a 60-day period. Cartilage that was coimplanted with RA-SF transduced with a marker gene exhibited progressive, chondrocyte-mediated cartilage degradation, whereas no such degradation was observed in cartilage that was coimplanted with RA-SF transduced with IL-1 Ra. Thus, gene therapy using a retrovirus-based gene delivery system appears to be a feasible approach to effectively modifying the local synovial environment.

Animals↗
PubMed1997

Tenosynovial nodulosis in a patient infected with human T cell lymphotropic virus I.

We describe a 45-year-old man who presented with multiple nodules along the tendons of the scapular region, the elbows, wrists, forearms, thighs, and ankles. The patient was a carrier of human T cell lymphotropic virus I (HTLV-I), which was probably transmitted from his mother; his mother also had polyarthritis. Histopathologically, the nodules consisted of numerous, small, fibrinoid masses. The synovium adjacent to the tendon sheath was hyperplastic, with fibrinoid necrosis mimicking rheumatoid synovium. However, synovitis was not present inside the adjacent joint. HTLV-I proviral DNA was detected in the cells of the nodule, in tenosynovial cells, and in peripheral blood lymphocytes, but not in skin fibroblasts. In situ reverse transcription assay showed a high quantity of tax/rex messenger RNA in the proliferating lining cells. Based on these features, we classified this case as an atypical manifestation of HTLV-I-associated arthropathy associated with fibrinoid nodules resulting from chronic tenosynovitis.

Carrier State↗
PubMed1997

Kinetics of Fas-induced apoptosis in thymic organ culture.

Although most thymocytes express high levels of Fas antigen (CD95), the role of Fas in apoptosis signaling during thymocyte maturation has not been defined. Fas apoptosis occurs primarily in the CD4+CD8+ subpopulations of thymocytes. Fas expression and apoptosis function were investigated in the CD4-8-, CD4+8+, and CD4+ and CD8 single positive thymocyte subpopulations by in vivo injection of anti-Fas and in vitro incubation of Fas with thymic organ cultures. Fas was first expressed on CD4-8- thymocytes coincident with expression of IL-2R and CD44. In Fas mutant lpr/lpr mice, defective Fas expression correlated with overproduction of late-stage CD4-8(-)-thymocytes. Fas was highly expressed on CD3dull and CD3bright thymocytes. CD4+8+CD3dull thymocytes were sensitive to Fas apoptosis, whereas more mature CD4+8+CD3bright thymocytes were resistant to Fas apoptosis. Anti-Fas incubation with established thymic organ culture for 24 hr resulted in apoptosis of approximately 25% of thymocytes. Continued incubation of thymic organ culture with anti-Fas resulted in an apoptosis rate of 25% of CD4+CD8+ thymocytes per day for the first 3 days of culture. Continued culture for further time points up to 6 days did not result in further apoptosis of the CD4+CD8+ thymocytes. These results suggest that CD4-CD8-CD44+ IL-2R+ thymocytes express Fas and there is overpopulation of the subsequent developmental stage of thymocytes in Fas mutant lpr mice. Also, early-stage CD4+8+ thymocytes are susceptible to Fas apoptosis, whereas Fas apoptosis resistance is required after 3 days of thymic organ culture. We conclude that these two populations of thymocytes are susceptible to Fas ligand-mediated apoptosis during T cell development in the thymus.

Animals↗
PubMed1997

Cellular pathways of joint destruction.

In the past year, evaluation of cellular pathways of rheumatoid synovial fibroblasts has been the focus of several laboratories investigating the molecular and cellular mechanisms operating in the pathogenesis of rheumatoid arthritis. Major topics that have been reported on include the adhesion and interaction of synovial fibroblasts with cartilaginous matrix and other synovial cells, intracellular signaling, and activation of gene transcription. Novel approaches to inhibiting cartilage destruction have also been described. In the latter case, thorough multicenter characterization of the interleukin-1/interleukin-1 receptor antagonist pathways resulted in the first gene therapy trials in animals and humans.

Arthritis, Rheumatoid↗
PubMed1997

In situ expression of protooncogenes and Fas/Fas ligand in rheumatoid arthritis synovium.

OBJECTIVE: To examine the relationship among the expression of protooncogenes such as c-fos and c-myc, Fas antigen, Fas ligand, and apoptosis in the synovial tissue of patients with rheumatoid arthritis (RA). METHODS: The expression of c-fos, c-myc, Fas antigen, and Fas ligand was examined in synovial tissues of 6 patients with RA and 4 with osteoarthritis (OA) using in situ reverse transcriptase (RT) assay and immunohistochemical staining. Apoptosis was detected by TUNEL method in situ. RESULTS: Expression of protooncogenes, c-fos, and c-myc was detected in all samples from patients with RA, but in only a few cells of OA synovium. 30 to 90% of cells in RA synovium positive for these protooncogenes also coexpressed Fas antigen. Fas positive cells in RA synovium underwent apoptosis to a significant degree. Fas ligand mRNA was detected only in mononuclear cells in RA synovium. CONCLUSION: The expression of protooncogenes is closely related to Fas mediated apoptosis in RA synoviocytes.

Aged↗
PubMed1997

Alternatively spliced CS-1 fibronectin isoform and its receptor VLA-4 in rheumatoid arthritis synovium.

OBJECTIVE: Extracellular matrix components and cell adhesion molecules play a role in the pathogenesis of rheumatoid arthritis (RA). Interaction between the integrin very late antigen-4 (VLA-4) and the connecting segment-1 (CS-1) fibronectin (FN) isoform may contribute to lymphocyte interaction in RA synovium. We examined both mRNA and protein expression of CS-1 FN in inflamed synovium, and VLA-4 expression in synovial tissue and on cultured fibroblast-like synoviocytes from patients with RA. METHODS: Snap frozen synovial tissue specimens of 10 patients with RA and 4 patients with osteoarthritis were examined for expression of CS-1 FN mRNA and protein by in situ hybridization and immunohistochemistry. VLA-4 expression of synovial fibroblasts and in synovial tissue was evaluated by flow cytometry and immunohistochemistry. RESULTS: CS-1 FN mRNA was detected in RA lining layer synoviocytes, around terminal vessels, and in endothelial cells. Double labeling revealed that most lining synoviocytes expressing CS-1 FN mRNA were CD68 negative. VLA-4 was found in RA synovial fibroblasts, sublining mononuclear cells, and lymphoid aggregates. CONCLUSION: Our findings suggest that expression of CS-1 FN may partially correlate with cell proliferation in the RA lining layer. VLA-4 was found in RA synovial lining, as well as on cultured synovial fibroblasts. Thus, VLA-4/CS-1 FN interaction may facilitate lymphocyte interaction and synovial proliferation in RA.

Anti-Allergic Agents↗