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Biomedical subjects

L M Ryan

Publications and source records attributed to L M Ryan.

At least 19 recordsLinked to original sources
PubMed1992

Articular cartilage vesicles generate calcium pyrophosphate dihydrate-like crystals in vitro.

OBJECTIVE: To identify the morphology of a mineral-forming of adult porcine hyaline articular cartilage digest and characterize the mineral it forms. METHODS: Electron microscopy, Fourier transform infrared (FTIR) spectroscopy, x-ray microanalysis, compensated polarized light microscopy, and biochemical studies including 14C-labeled UDPG pyrophosphohydrolase radiometric assay. RESULTS: This fraction of articular cartilage digest contained membrane-limited vesicles resembling growth plate cartilage matrix vesicles and formed mineral after only 24 hours in physiologic salt solution containing 1 mM ATP: The mineral contained inorganic pyrophosphate, 95% of which derived from ATP, and phosphate, 93% of which derived from inorganic phosphate in the medium. The FTIR spectrum of this mineral closely resembled the spectrum of standard calcium pyrophosphate dihydrate (CPPD) crystals. Compensated polarized light microscopy showed positively birefringent, rod-shaped crystals morphologically identical to CPPD. Ca:P ratios, defined by energy-dispersive microanalysis, were also consistent with CPPD. CONCLUSION: The articular cartilage vesicle fraction of porcine hyaline cartilage is capable of generating mineral that strongly resembles CPPD.

Adenosine Triphosphate↗
PubMed1992

ATP-induced chondrocalcinosis.

OBJECTIVE: To determine whether adult articular cartilage mineralizes in the presence of ATP. METHODS: Intact adult porcine articular cartilage and monolayers of chondrocytes were cultured in physiologic media containing ATP, and mineralization was measured as retention of 45Ca. Cartilage was analyzed by electron microscopy. RESULTS: Articular cartilage sequestered 45Ca when incubated with 100 microM ATP: Use of the ATP analog alpha, beta-methylene ATP did not promote mineralization and addition of pyrophosphatase inhibited mineralization, indicating that hydrolysis of ATP to AMP and inorganic pyrophosphate is necessary for the process to occur. Mineral was concentrated in articular cartilage vesicles in the perichondral area. CONCLUSION: Adult articular cartilage mineralizes in the presence of ATP, in a manner similar to that found with isolated matrix or articular cartilage vesicles. This supports the notion that these structures have a role in chondrocalcinosis.

Adenosine Triphosphate↗
PubMed1992

Phase II trial for the evaluation of trimetrexate in patients with inoperable squamous carcinoma of the esophagus.

EST 2287 was a Phase II clinical trial conducted by the Eastern Cooperative Oncology Group (ECOG) designed to evaluate trimetrexate in patients with advanced, measurable, inoperable squamous cell carcinoma of the esophagus. The drug was given at a dose of 12 mg/m2 daily for 5 days every 21 days to patients with carcinoma of the esophagus. The purpose of this study was to evaluate treatment efficacy in terms of tumor response and to assess the toxicity. According to a two-stage stopping rule, the study closed after 15 patients had entered. There were no responses to treatment, and median survival from study entry was 4.3 months. There was one treatment-related death caused by infection. One patient experienced life-threatening hematologic toxicity. Overall severe or worse toxicity occurred in more than half of the patients. It is concluded that additional trials of trimetrexate at this dose and schedule in patients with carcinoma of the esophagus are not warranted.

Aged↗
PubMed1991

Transforming growth factor beta 1 stimulates inorganic pyrophosphate elaboration by porcine cartilage.

The overproduction of inorganic pyrophosphate (PPi) by cartilage is thought to be a key element in the formation of calcium pyrophosphate dihydrate (CPPD) crystals in joints, and the subsequent development of pseudogout or chondrocalcinosis. We report herein that transforming growth factor beta 1 (TGF beta 1), alone and in synergy with epidermal growth factor (EGF) or TGF alpha, markedly stimulates PPi elaboration by porcine articular cartilage in organ culture and monolayer culture. This effect is not seen with platelet-derived growth factor, basic fibroblast growth factor, or insulin-like growth factor types 1 and 2, substances which also affect chondrocyte metabolism or are mitogenic. TGF beta 1 produces only a modest increase in nucleoside triphosphate pyrophosphohydrolase (NTPPPH), a chondrocyte ectoenzyme that produces PPi; this implies the existence of other pathways for PPi elaboration. TGF beta 1 is present in joint fluid and cartilage. TGF beta 1, TGF alpha, and EGF are the first known physiologic modifiers of cartilage PPi production. They provide a novel model for the study of CPPD crystal formation in cartilage, as well as new insights into the pathogenesis of this common affliction of aging.

Animals↗
PubMed1991

Relationship between fetal weight and malformation in developmental toxicity studies.

Exposure to developmental toxicants may cause fetal malformations, increase prenatal death rates and reduce fetal weight at term. However, there has been little formal study of the relationship among these effects. Certainly, no statistical methods are currently available to jointly analyze these effects of exposure. As a preliminary step in developing such methods, simple exploratory analyses were conducted using a series of ten studies conducted for the National Toxicology Program. Because fetal weight and malformation status were both reported for all live fetuses, the data permitted an exploration of the correlation between these two outcomes. The data show a clear pattern wherein malformed fetuses tended to be lighter at term than nonmalformed fetuses. While these patterns cannot be used to draw inferences regarding the biological relationship between fetal weight and malformation, they do suggest the potential value in developing statistical models for the joint effect of exposure on fetal weight and malformations.

Animals↗
PubMed1991

Stimulation of cartilage inorganic pyrophosphate elaboration by ascorbate.

Ascorbate (0-500 microM) stimulates synthesis and secretion of collagen by cartilage explants in a dose-dependent fashion as estimated by [3H]proline incorporation. Concurrent elaboration of inorganic pyrophosphate (PPi) parallels [3H]proline incorporation (less than 0.001, Wilcoxon rank sum). The effect on proline and PPi is abolished by ascorbate oxidase. Another reducing agent, Vitamin E, did not promote PPi accumulation about cartilage. Inhibitors of collagen synthesis, including monensin, tumor necrosis factor alpha, and 2',2'dipyridyl also inhibited PPi elaboration. Cycloheximide (1 micrograms/ml) inhibited the ascorbate stimulated PPi elaboration 54% but did not attenuate the secretion of PPi by unstimulated cartilage. Cosecretion of collagen and PPi by chondrocytes may explain these results. Moreover, at least two pathways exist for PPi elaboration, a cycloheximide sensitive path and another independent of new protein synthesis.

2,2'-Dipyridyl↗
PubMed1991

Phase II study of aminothiadiazole in advanced squamous cell carcinoma of the esophagus.

Twenty-three patients with advanced inoperable squamous cell carcinoma of the esophagus were treated with aminothiadiazole (A-TD) 125 mg/m2 weekly plus allopurinol daily in a phase II cooperative group trial. No patients responded to treatment; 17 patients progressed, three showed stable disease, and three were unevaluable. There were no life-threatening hematologic or metabolic toxicities. The median survival from study entry was 5 months. A-TD is not active in advanced squamous cell carcinoma of the esophagus.

Adult↗
PubMed1991

Synovial fluid ATP: a potential substrate for the production of inorganic pyrophosphate.

The enzyme nucleoside triphosphate pyrophosphohydrolase (NTPPPH) is present in all joint fluids and on intraarticular cells. It generates inorganic pyrophosphate (PPi) from nucleoside triphosphate substrate, thus serving as a potential source of the PPi which forms in the cartilages of patients with calcium pyrophosphate dihydrate (CPPD) crystal deposition. NTPPPH is also important in matrix vesicle induced calcification with basic calcium phosphate (BCP) crystals. An articular substrate for this enzyme was sought. ATP was measured in the joint fluids from 107 patients with various forms of arthritis. Synovial fluid ATP levels were higher in patients with CPPD deposits than in osteoarthritis (p less than 0.02) or rheumatoid arthritis (p less than 0.002). ATP also correlated with PPi concentration (p less than 0.05) and with the presence of BCP crystals (p less than 0.05), but not with cellularity of the fluid, NTPPPH activity, or age of the donor. This substrate for NTPPPH may contribute to CPPD crystal deposition by generating PPi and may stimulate matrix vesicle induced formation of BCP crystals in several forms of arthritis.

Adenosine Triphosphate↗
PubMed1990

Cartilage inorganic pyrophosphate elaboration is independent of sulfated glycosaminoglycan synthesis.

Inorganic pyrophosphate (PPi), a product of glycosaminoglycan synthesis, may be cosecreted with matrix proteoglycan to reach the extracellular site where calcium pyrophosphate dihydrate crystals form. To test this hypothesis, sulfated glycosaminoglycan synthesis by articular cartilage in culture was stimulated or inhibited while the effect on extracellular PPi was measured. When stimulated by 0.8 mM xyloside to increase 35SO4 incorporation (mean +/- SEM % of control 183 +/- 16, n = 5), PPi accumulation changed little (from 54 +/- 6 pmoles/mg to 63 +/- 8 pmoles/mg of cartilage wet weight). Inhibition of sulfation with monensin or diethylcarbamazine disproportionately lowered 35SO4 incorporation compared with PPi elaboration. Using 60 mM diethylcarbamazine, PPi production was preserved (105 +/- 8% mean +/- SEM) compared with control cultures, while sulfation was markedly inhibited (7 +/- 1%). This dissociation of sulfate incorporation and PPi secretion indicates that it is not likely that glycosaminoglycan sulfation is the source of the PPi that escapes from chondrocytes to participate in the formation of extracellular crystals.

Animals↗
PubMed1990

Stimulation of pyrophosphate production in articular cartilage by a platelet-derived factor is independent of mitogenesis.

The disordered production of extracellular inorganic pyrophosphate (PPi) by cartilage contributes to calcium pyrophosphate dihydrate crystal formation and associated diseases. We have previously shown that a factor(s) derived from human platelets markedly stimulates the accumulation of PPi in the media of porcine articular cartilage in organ culture. This is the first known physiologic modifier of PPi production by cartilage. We report herein that platelet derived growth factor (PDGF) is not the platelet factor responsible for PPi stimulation and that the active factor is not mitogenic for chondrocytes. PDGF added to the media of articular cartilage explants in the presence of 0.5% (platelet-poor) plasma (PPP) produces 3.92 +/- 1.6 mumol/L PPi compared with 2.85 +/- 0.7 mumol/L PPi in cartilage exposed to PPP alone. The platelet extract (PE) and PDGF are mitogenic for adult articular chondrocytes in high-density monolayer cultures. Anti-PDGF antibodies block the mitogenic effects of PDGF and PE. The uptake of thymidine labeled with tritium is 157% of control in cells exposed to PE, PPP, and polyclonal goat immunoglobulin G (IgG); 114% of control in cells exposed to PE, PPP, and anti-PDGF antibody; 148% of control in cells treated with PDGF, PPP, and goat IgG; and 98% of control in cells treated with PDGF, PPP, and anti-PDGF antibody. However, anti-PDGF antibody has no effect on PPi accumulation. PPi levels are 17.22 +/- 1.6 mumol/L in media from cartilage treated with PPP, goat IgG, and PE and 17.62 +/- 2.2 mumol/L in cartilage exposed to PE, PPP, and anti-PDGF antibody. We have further characterized the platelet factor responsible for the stimulation of PPi by cartilage. It is not mitogenic for chondrocytes, and it is not PDGF.

Animals↗
PubMed1979

Quantification of human plasma inorganic pyrophosphate. I. Normal values in osteoarthritis and calcium pyrophosphate dihydrate crystal deposition disease.

The methodologic variables of the UDPG pyrophosphorylase method for analysis of inorganic pyrophosphate (PPi) levels in biologic fluids are described. Use of a tourniquet in collection of blood specimens elevated plasma PPi levels from 35% to 55% above control values and may explain the differences in published normal values. The sodium pyrophosphate decahydrate used to prepare the standard solution lost 8 waters of hydration after dessication, which could result in the calculation of spuriously elevated PPi levels. Normal plasma PPi concentration was 2.18 muM with a range (95% confidence limits) of 0.58-3.78 muM. Comparison of plasma PPi in normal subjects, patients with primary osteoarthritis, and patients with calcium pyrophosphate dihydrate deposition disease revealed no significant intergroup differences.

Blood Specimen Collection↗
PubMed1979

Quantification of human plasma inorganic pyrophosphate. II. Biologic variables.

Plasma inorganic pyrophosphate (PPi) levels rose predictably (28%) after vigorous systemic exercise and returned to baseline values after 30 minutes of rest. Plasma PPi levels were greater (36%) in femoral venous blood than in femoral arterial blood. Forearm muscular exercise, however, did not result in a detectable rise in plasma PPi levels in antecubital veins. The physiologic reasons for both the systemic exercise effect and the arteriovenous differences remain unknown. Measurement of plasma PPi for 10 consecutive days in a single normal subject under basal conditions, where these and other previously identified biologic variables (fasting and diurnal variation) were controlled, showed a coefficient of variation of 12.7%. Thus biologic variability contributed less to observed variation in plasma PPi than did methodologic errors (coefficient of variation of method = 8%). The striking reproducibility of plasma PPi in this subject suggests that this important metabolite is under rather tight homeostatic control.

Calcium Pyrophosphate↗
PubMed1979

Concurrent linear scleroderma and systemic lupus erythematosus: a report of two cases.

Two patients with linear scleroderma (en coup de sabre) developed systemic lupus erythematosus (SLE). This association has been well documented in only one previous case. The presence of high titer antibodies to ribonucleoprotein (RNP) initially led to the diagnosis of the mixed connective tissue disease. Development of more serious clinical involvement and antibodies to Sm (case 1) or native deoxyribonucleic acid (nDNA) (case 2) helped establish a diagnosis of SLE. Use of these studies in the differential diagnosis of systemic rheumatic diseases is disucssed briefly. The presence of anti-RNAP antibodies in patients with localized scleroderma may herald a more serious rheumatic disease.

Adult↗
PubMed1977

Renal proximal tubular dysfunction and paroxysmal nocturnal hemoglobinuria.

A patient with paroxysmal nocturnal hemoglobinuria, who required many blood transfusions for hemolytic episodes, had a persistent hyperchloremic metabolic acidosis. Bicarbonate infusion demonstrated a large fractional excretion of bicarbonate (28.6 per cent at a plasma bicarbonate level of 23 meq/liter) which was consistent with proximal renal tubular acidosis. Generalized aminoaciduria and decreased tubular reabsorption of phosphate were also present. Marked deposition of iron in renal proximal tubules was associated with these functional abnormalities. We believe that, as systemic acidosis can promote hemolysis in patients with paroxysmal nocturnal hemoglobinuria, hemolysis can lead, by way of iron deposition in renal tubules, to further acidosis. This cycle should be interrupted with appropriate doses of bicarbonate.

Acidosis, Renal Tubular↗