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Biomedical subjects

J Fareed

Publications and source records attributed to J Fareed.

At least 325 records · Page 18Linked to original sources
PubMed1984

Platelet activation by human pancreatic fluid.

The effects of human pancreatic fluid (HPF) on platelet aggregation and activation were studied. HPF, obtained at operation from nine patients with chronic pancreatitis and two with pancreas cancer, was pooled, lyophilized, and adjusted to a concentration of 1 mg protein/cc of 0.9% saline after dialysis. Platelet aggregation was evaluated by measuring platelet count after iv administration of HPF to five rabbits in concentrations ranging from 0.2 to 2.0 mg/kg. Platelet activation was evaluated by adding 0.1-ml aliquots of pooled HPF in various concentrations to 0.9 ml of human platelet-rich plasma. After a 15-min incubation at 37 degrees C, the platelets were removed by centrifugation and the supernatant examined for platelet-release products. Serotonin was measured by high-performance liquid chromatography (HPLC) and platelet factor 4 and thromboxane B2 were measured by radioimmunoassay. A significant decrease in rabbit platelet count signifying platelet aggregation was seen after iv administration of 1.0 mg/kg (P less than 0.05) and 2.0 mg/kg (P less than 0.001) HPF. Platelet activation was confirmed by a significant increase (P less than 0.05) in serotonin, platelet factor 4, and thromboxane B2 at almost all concentrations of HPF. This study indicates that HPF induces platelet aggregation and activation and suggests that platelet contact with pancreatic exocrine fluid may have both local and systemic effects that are important in the pathophysiology of acute pancreatitis.

Adult↗
PubMed1984

Performance characteristics of a simple radioimmunoassay for fibrinopeptide A.

FPA, although identified 15 years ago, is now becoming an increasingly important diagnostic tool in the evaluation of the hemostatic process. Since this peptide is generated in very small amounts, only very sensitive methods, such as RIA, are useful for its quantitation. Measurement of this peptide allows for a most precise and reliable monitor of any ongoing thrombotic event in which thrombin is generated. Commercial kits have become available for fast and simple clinical evaluations of FPA. The Mallinckrodt RIA Quanti FPA kit has proved its reliability in precision, accuracy, fast turnaround time, and applicability to a routine laboratory setting. This assay kit was evaluated in our laboratory in various aspects. The following points summarize our finding: FPA is a useful diagnostic parameter to evaluate the activation of coagulation pathways in various pathologic states. A study of 170 normal plasma samples resulted in 1.7 +/- 0.5 ng/ml. No significant difference between males and females was noted. FPA levels are evaluated in patients with hypercoagulable states, DIC, and related thrombotic states. Our studies have shown that FPA levels are also elevated in certain cancers, postsurgical states, and certain other conditions in which the coagulation process is activated. During therapeutic heparinization, FPA levels are reduced; thus this form of therapy can be monitored using FPA levels. High-risk population (thrombotic) can be easily screened using FPA measurement. We propose that a multicenter study on FPA levels be conducted to prove its clinical relevance to other diseases.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation Tests↗
PubMed1984

Development and performance characteristics of a competitive enzyme immunoassay for fibrinopeptide A.

A simple nonisotopic method for the quantitation of FPA in biologic samples has been developed utilizing a competitive enzyme immunoassay technique. The performance characteristics of these assays have been investigated in both the experimental and clinical settings and were found to be satisfactory for the routine clinical application. This method is comparable to a commercially available RIA kit (Mallinckrodt, St. Louis, MO) in both the clinical and normal samples. This assay can be used in the diagnosis of hypercoagulable states associated with various diseases. Subclinical activation of coagulation can be readily assessed when the global tests, such as the prothrombin time, partial thromboplastin time, and thrombin time, have no value. This test is of value in the monitoring of the newer antithrombotic agents, such as the low molecular weight heparin fractions that do not effect the global assays, such as the partial thromboplastin time. Similarly, the risk of thrombosis associated with the use of procoagulant therapy, such as the activated prothrombin complex concentrates, can be readily assessed using this assay. It is proposed that the FPA measurement may also provide useful information on the quality control of various plasma-based therapeutic products, such as plasma concentrates or activated prothrombin complex concentrates. FPA generation tests are currently proposed for the screening of antithrombotic and prohemostatic agents.

Blood Coagulation Tests↗
PubMed1984

Diagnostic efficacy of a simple radioimmunoassay test for fibrinogen/fibrin fragments containing the B beta 15-42 sequence.

A simple RIA method for B beta 15-42 RPs has been evaluated in our laboratory to investigate experimental and clinical fibrinolytic states. The assay utilizes bentonite precipitation to remove cross-reacting fibrinogen. Due to the heterogeneity in molecular weights of the B beta RPs, the results are expressed as nanograms per milliliter. The linear range of the assay is 2 to 40 ng/ml, with a capability of detecting up to 200 ng/ml. A special anticoagulant mixture (heparin or EDTA/aprotinin) is required for sample collection. Certain precautions in the care and handling of specimens are also necessary. Increased levels of B beta RPs were observed in the following conditions: malignancy (associated with increased release of tissue plasminogen activators), pancreatitis, liver diseases, pregnancy, and postexercise testing (associated with increased release of tissue plasminogen activators). Increased levels of B beta RPs were also found during thrombolytic therapy, anabolic steroid treatment, prothrombin complex concentrate therapy, blood component therapy, and low molecular weight heparin subcutaneous therapy (associated with an increase in tissue plasminogen activator release). Our studies suggest that B beta RPs are sensitive molecular markers of the endogenous activation of fibrinolytic system and may provide useful diagnostic information on a pathologic process that often remains undetectable by routine laboratory methods.

Evaluation Studies as Topic↗
PubMed1984

Molecular markers of contrast media-induced adverse reactions.

Currently used routine laboratory screening methods are not reliable in the prediction of contrast media-related adverse reactions. Cost-effective laboratory methods for various molecular markers of pathophysiologic activation have now become available. In vitro activation tests in high-risk patients may prove to be useful in the prediction of contrast-induced activation of various adverse reactions. If prior clinical evaluation of a patient suggests an ongoing pathologic process, profiling of the following molecular markers may prove to be useful and helpful in avoiding contrast-induced adverse reactions: Fibrinopeptide A, platelet factor 4, thromboxane B2, 5-HETE, physiologic inhibitors of proteases, B beta 15-42 related peptides, bradykinin/kininogen, and anaphylactozins. In patients suspected of reacting to contrast agents, a small dose of 1 to 5 ml can be injected as a bolus and molecular marker profiling on blood drawn after the infusion may prove to be useful screening tests. Additional clinical studies are needed to prove this. However, this screening test should be performed with extreme caution, since some of the patients are known to react to as little as 1 ml dose. The safety of newly developed nonionic contrast agents can be readily assessed by profiling various molecular markers of adverse reactions, which provide a more reliable and quantitative assessment of contrast-induced adverse reactions. Based on molecular marker profiling, various prophylactic agents can be given to high-risk patients to avoid contrast-induced adverse reactions.

Angiocardiography↗
PubMed1984

Effects of protease inhibitors on coagulation abnormalities in acute canine pancreatitis.

Coagulation abnormalities associated with severe pancreatitis were studied in 24 dogs. Group I consists of six control subjects who had duodenotomy alone. Group II consists of six dogs with pancreatitis induced by bile injection ( lcm3 /kg) into the pancreatic duct. The six dogs in Group III and the six in Group IV were given aprotinin (trasylol) 1.0 mg/kg and S-2441 (10mg/kg), a new synthetic protease inhibitor, respectively. These were given over 10 minutes by intravenous infusion, 20 minutes after bile induced pancreatitis. Blood was drawn for amylase, prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, and platelets, in addition to markers for hypercoagulation, fibrinopeptide A, antithrombin III, and markers for fibrinolysis, B beta 15-42 immunoreactive peptides and alpha 2 antiplasmin at baseline, 30 minutes, 1 hour, 3 hours, 6 hours, and daily for 3 days after injection of bile or duodenotomy. There was no significant difference in PT, platelets, antithrombin III, and fibrinopeptide A among the four groups. Fibrinogen levels and PTT were minimally elevated in animals with bile induced pancreatitis, but these changes reached significance only at 24 hours and 48 hours, respectively (P less than 0.05). Immunoreactive B beta 15-42 became elevated at 30 minutes indicating fibrinolysis in animals with pancreatitis, and these changes were significant compared with Group I control subjects (P less than 0.05) throughout the study. Levels of alpha 2 antiplasmin were decreased in Group II animals with pancreatitis, which also suggests fibrinolysis. Amylase was elevated in Group II animals with pancreatitis (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1984

Antithrombotic actions and pharmacokinetics of heparin fractions and fragments.

During the last few years many reports on the antithrombotic actions of low molecular weight fractions (LMF) have become available and are being tested in the experimental and clinical settings. Although derived from commercial heparins, the mode of antithrombotic actions, pharmacokinetics and physiologic disposition of these agents is distinct from the parent materials. The antithrombotic potency of these fractions is generally assigned in terms of their ability to inhibit serine proteases such as factor Xa and thrombin in the presence of antithrombin III (AT III). However, these agents are also reported to exert their antithrombotic actions via non AT III mediated inhibition of serine proteases (XIIa, IXa), activation of fibrinolysis via the release of plasminogen activators and charge transition on vascular surfaces. In order to evaluate the relative pharmacologic actions of heparin and its derivatives, we utilized defined animal models to obtain data in terms of pharmacologic parameters. Significant differences between heparin and its derivatives were evident. Human studies on the pharmacokinetics and the endogenous actions of these agents confirmed our preclinical findings. These studies suggest that well-defined preclinical studies are an essential element in the development of newer antithrombotic agents.

Animals↗
PubMed1983

A serotonin and beta HCG-producing islet cell carcinoma associated with focal nodular hyperplasia of the liver.

A 48-year-old woman is described with a pancreatic islet cell carcinoma that had no clinical evidence of hormone production. This neoplasm was removed by radical distal pancreatectomy. Immunohistochemical and extraction studies performed on the tumor tissue revealed that it was producing serotonin and beta HCG. Circulating levels of these hormones were elevated in preoperative serum samples that had been frozen. Beta HCG, a known tumor marker, has remained normal following operation, and this mirrors her clinical course since she has no evidence of disease 1.5 yr after operation. This patient also had focal nodular hyperplasia of the liver. It is possible that the trophoblastic hormone, beta HCG, which was being produced in excess by the islet tumor, may have directly or indirectly caused or facilitated the development of focal nodular hyperplasia.

Adenoma, Islet Cell↗
PubMed1983

Synthetic peptide substrates in hemostatic testing.

Since the introduction of synthetic chromogenic and fluorogenic peptide substrates from serine proteases, the testing of coagulation has undergone a dramatic conceptual and methodological change. The concept of coagulation profiling has emerged and automated methodologies are being introduced. Synthetic substrate methods for the evaluation of antithrombin-III; progressive antithrombin; plasminogen; antiplasmin; prekallikrein; antikallikrein ; alpha 1-antitrypsin; prothrombin; heparin; platelet factor IV; urokinase; tissue activator of plasminogen; factor assays; amidolytic equivalents of prothrombin time; and partial thromboplastin time have been developed. Studies on antithrombin-III indicate that immunological methods evaluate the total immunoreactive-antithrombin-III (antigenic) level and do not discriminate between functionally active forms and the AT-III serine protease complex. The clinical significance of AT-III measured by immunological methods is highly questionable. The coagulant assays for the measurement of AT-III require purified alpha-thrombin preparations. The noncoagulant forms of thrombin (beta- and gamma-) result in falsely low antithrombin-III quantitation. The molecular heterogeneity in a given thrombin preparation if standardized in terms of its amidolytic activity does not produce any errors in the quantitation of AT-III levels with synthetic peptide methods. None of the immunological methods provide clinically relevant information except in normal plasma where the immunological and functional activities are identical. Analysis of pathologic plasma samples using laser nephelometry, radial immunodiffusion and radioimmunoassay methods revealed that the functional activity of various serine protease inhibitors is greatly reduced but the reduction in the immunological quantities is minimal. Since coagulation proteins are functional, a ratio between their functional activity and absolute protein levels may be a useful parameter. Employing human and bovine thrombin; bovine and human Xa with their respective substrates, the absolute quantitation of heparin is satisfactorily carried out, however, these assays only measure heparin concentrations and do not reflect the overall anticoagulant effect of heparin. Using the synthetic substrates, the value of measuring absolute concentrations of heparin in a patient on heparin therapy is questionable. With the introduction of fluorogenic substrates, the presence of activated coagulation factors may be demonstrated in patients with thrombotic disorders.(ABSTRACT TRUNCATED AT 400 WORDS)

Anticoagulants↗
PubMed1983

Impact of automation on the quantitation of low molecular weight markers of hemostatic defects.

Through in depth studies, the biochemical pathways of hemostasis-related systems have been elucidated in terms of well-defined molecular mechanisms. The interrelationships of coagulation, fibrinolytic, kallikrein-kinin, platelets, prostaglandins, blood vessel, and complement systems are now well understood. Methods are currently developed to quantitate the molecular markers of each of these systems and define the involvement of each in disease and drug-related aberrations. Molecular markers allow for very early detection of disease states well before clinical manifestations are seen or current coagulation methods are affected. Therefore prophylactic or therapeutic treatment can begin before a disease state causes damage. Platelet factor 4 and beta-thromboglobulin are low molecular weight proteins released from the light (alpha) granules of platelets and provide a reliable index of endogenous activation and consumption of platelets. Serotonin and ADP are released during activation from the beta-granules and can be measured by high-performance liquid chromatography. Fibrinopeptide A is a molecular marker of the activation of the coagulation process and provides a useful index of the action of thrombin on fibrinogen. Elevated levels of this peptide are found in patients with hypercoagulable states or a thrombotic tendency. B beta 15-42 peptides are released at the early stages of fibrinolysis and are a useful collective parameter for the measurement of the activation of fibrinolysis. In both the primary and secondary fibrinolytic disorders this peptide is elevated. Circulating kinins provide information on the activation of the kallikrein system and are useful in monitoring coagulation and shock related disorders. Arachidonic acid metabolites, such as thromboxanes and prostacyclins, are products of platelet and vascular endothelium interactions. Their measurement in peripheral blood provides a useful tool to measure the vascular and platelet-related thrombotic defects. Furthermore, antiplatelet therapy can be monitored using these parameters. Numerous other metabolites of arachidonic acid such as the leukotrienes and PAFs also are generated in various immunopathologic disorders associated with hemostatic activation. Unlike the other coagulant tests, the measurement of molecular markers in native blood or plasma samples provides a true picture of the endogenous physiology. Since no activator or additive is added to influence the test, these markers provide the most relevant information on the pathophysiologic condition. Since most of these markers are proteins or low molecular weight products, isotopic and nonisotopic immunoassays, high performance liquid chromatography and fluorometric methods can be used to analyze their levels. Furthermore, multiple panels can be developed to profile various pathologic states.(ABSTRACT TRUNCATED AT 400 WORDS)

Arachidonic Acid↗
PubMed1983

Inhibition of bradykinin-induced contraction of isolated smooth muscle tissue preparations by oligopeptide thiobenzyl ester substrates for serine proteases.

Synthetic peptide substrates containing various chromophores and fluorophores have been utilized in the quantitation of serine protease activities. Recently, amino acid thiobenzyl esters containing arginine and lysine have also been used to evaluate the serine proteases. In an attempt to develop specific peptide thiobenzyl substrates, we have screened D-Pro-Phe-Arg-S-CH2-C6H5, D-Phe-Phe-Arg-S-CH2-C6H5, D-Gly-Pro-Arg-S-CH2-C6H5, and D-Val-Leu-Lys-S-CH2-C6H5 to determine the enzymatic activity of serine proteases. Since we found that D-Pro-Phe-Arg-pNA is a potent inhibitor of the bradykinin induced contractile action of isolated smooth muscle preparations such as the guinea pig ileum and rat uterus, we screened D-Pro-Phe-Arg-S-CH2-C6H5 at a 5 X 10(-5) M and found that it completely blocked the bradykinin (1 ng) induced contraction of the isolated rat uterus preparation. Other peptide thiobenzyl esters produced somewhat weaker effects, however, none of the free peptides not C6H5CH2SH, at concentrations of up to 10 microns, produced any significant contraction or inhibition of the isolated smooth muscle preparation. These observations suggest that peptide thiobenzyl esters are effective blockers of bradykinin induced contraction of the isolated smooth muscle preparations and the amino acid sequence of the peptides plays an important role in the determination of relative potency of each of these peptide derivatives. Moreover, the result of this investigation provides the basis for a new approach to further design specific inhibitors of the pharmacologic actions of biologically active peptides.

Animals↗