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Biomedical subjects

L Pechet

Publications and source records attributed to L Pechet.

At least 19 recordsLinked to original sources
PubMed1995

Continuous improvement, quality control, and cost containment in clinical laboratory testing. Effects of establishing and implementing guidelines for preoperative tests.

OBJECTIVE: To develop guidelines for laboratory tests ordered before admission for elective surgery. DESIGN: A seven-step continuous quality improvement process. SETTING: The Departments of Laboratory Medicine, Surgery, and Anesthesia of the University of Massachusetts Medical Center, a 384-bed, teaching, tertiary-care facility. PARTICIPANTS: Core group of the Department of Laboratory Medicine and the Laboratory Medical Advisory Committee. INTERVENTION: Guidelines were developed for laboratory tests ordered before elective surgery. They were divided into four major groups as well as by age and gender. After an intense educational effort, consent was obtained from the majority of surgeons, who agreed to delegate the ordering of tests to the nurses and anesthesiologists who examine patients before surgery. MAIN OUTCOME MEASURE: Charts chosen at random by the medical records department for the period prior to implementation of guidelines were reviewed and compared with records 1 and 2 years later. RESULTS: Reductions of 50% and 60% in the first and second years, respectively, in the overall number of tests ordered per patient were demonstrated. An improvement in the appropriateness of tests was also documented: 81% in the first year and 86% in the second year, compared with 65% appropriateness prior to implementation of guidelines. A 1-year savings of $66,981 and an overall 2-year savings of $75,995 were documented. CONCLUSIONS: We have described an approach that involves a sustained educational effort and collaboration of nurses and physicians and have presented specific guidelines for preoperative testing. A major decrease in the number of tests ordered, an increase in their appropriateness, and marked fiscal savings were documented.

Child, Preschool↗
PubMed1995

A laboratory rotation for medical house officers. Bridging the gap.

In an attempt to improve physicians' laboratory practice behavior, the Department of Hospital Laboratories at the University of Massachusetts Medical Center developed a rotation for first year housestaff. Medical interns were chosen for this pilot program because they are the most frequent users of our laboratory facilities. Rotations provide an overview of the laboratory organization, quality control and assurance, appropriate use of laboratory testing, cost containment, and an introduction to different laboratory disciplines. As assessed by discussions during an interview following completion of the program, the participants have shown an increased understanding of how a modern hospital laboratory functions and of the complexity of services provided. The respect for the laboratory staff and confidence in test results issued have increased, and house officers are more likely to use laboratory services in a more cost-efficient manner.

Blood Banks↗
PubMed1992

Characterization of a factor VIII immunogenic site using factor VIII synthetic peptide 1687-1695 and rabbit anti-peptide antibodies.

A 9 amino acid peptide, Ser-Pro-Arg-Ser-Phe-Gln-Lys-Lys-Thr, corresponding to the clotting factor VIII (FVIII) sequence Ser1687-Thr1695, was synthesized in order to analyze a site on FVIII to which antibody inhibitors of FVIII may be directed. This sequence contained a thrombin cleavage site. It was predicted to be immunogenic because a Hopp-Woods hydrophilicity analysis of the amino acid sequence of FVIII showed it to be very hydrophilic, and it contained a proline. The HPLC-purified peptide was cleaved by thrombin at Arg1689-Ser1690, as determined by amino acid sequencing of the cleavage product. Thrombin which had been treated with a specific chloromethyl ketone inhibitor, did not cleave the peptide. Two rabbits immunized with the peptide/keyhole limpet hemocyanin conjugate generated FVIII inhibitory sera with titers of 5.4 and 4.8 Bethesda units. These rabbit anti-peptide antibodies reacted with a peptide/-BSA conjugate on immunodot blot analyses and with native, affinity-purified FVIII in Western blots. In competitive immunoradiometric assays, cryosupernatants of 38/82 patients with FVIII inhibitors reacted with the synthetic peptide. We conclude that FVIII peptide Ser1687-Thr1695 is cleaved by thrombin at the same peptide bond which is cleaved in FVIII, and the peptide contains a site to which patients' inhibitory antibodies can be directed.

Amino Acid Sequence↗
PubMed1992

Hypothesis for the control of clotting factor VIII inhibitory antibodies by decreasing potency of helper T-cell-recognized epitopes in factor VIII.

The study of the immunobiology of FVIII inhibitors may lead to new therapies for this potentially severe complication of haemophilia A and to new principles for the use of therapeutic proteins. In order to characterize the idiotype-anti-idiotype networks regulating FVIII inhibitors, we developed rabbit anti-idiotypic sera to 7 murine inhibitors and found at least 12 independent FVIII loci to which inhibitors could be raised. Rabbit antisera to the FVIII peptide, Ser1687-Thr1695, characterized one functional site to which about 46% of patients' inhibitor sera reacted. The multiplicity of inhibitor-recognized epitopes in FVIII makes it impractical, at the present time, to develop clinically useful specific anti-idiotypic therapies for FVIII inhibitors. Alternatively, one might induce genomic mutations in recombinant FVIII molecules to decrease immunogenicity of epitopes recognized by T helper cells. Methods to design such altered therapeutic proteins are presented, based on changing the longitudinal hydrophobic strip-of-helix which is in or near many T-cell-presented epitopes.

Animals↗
PubMed1990

Factor VIII epitopes recognized with inhibitory monoclonal antibodies.

To test whether anti-idiotypic immunoregulation of factor VIII(FVIII)-inhibiting antibodies could be feasible in hemophiliacs, we assayed the minimal number and range of immunogenic, functional FVIII epitopes to which a series of murine anti-FVIII monoclonal antibodies (MAb) were directed. Rabbit anti-idiotypic sera to 7 MAb were prepared and used in competitive immunoradiometric assays to test Id similarities among 36 murine MAb. At least 12 immunogenic and functional epitopes were found on the FVIII molecule. The large range of target loci for FVIII inhibitors will make their immunoregulation by anti-idiotypic methods difficult.

Animals↗
PubMed1989

Development of anti-idiotypic antibodies in a patient with a factor VIII autoantibody.

Antibodies against coagulation factor VIII were detected in a 33-year-old who developed severe bleeding 2 months postpartum. After treatment with plasmapheresis and immunosuppressive agents, the inhibitor was no longer detectable, but anti-idiotypic antibodies were detected, as demonstrated by binding in immunoradiometric assays, and by in vitro neutralization of the initial factor VIII autoantibodies. The anti-idiotypic titer subsequently declined but was still detectable 1 year later. Three commercial immunoglobulin preparations and pooled multiparous IgG also bound to (but did not neutralize) the patient's factor VIII antibody. These studies suggest that anti-idiotypic antibodies, arising in the face of immunosuppressive therapy, might suppress autoimmunity to factor VIII and confirm the presence of anti-idiotypic antibodies in pooled normal immunoglobulins.

Adult↗
PubMed1987

Identification of six functional clotting factor VIII:C epitopes by analysis of cross-reactive public idiotypes in murine monoclonal VIII:C inhibitors.

Six factor VIII:C epitopes which can elicit clotting factor inhibitory antibodies were demonstrated by analysis of public idiotypes of murine monoclonal anti-VIII:C inhibitors. Anti-idiotypic immunoradiometric assays were developed with rabbit antibodies to murine VIII:C inhibitors: Synbiotics, Hybritech, C7F7 and RFF-VIIIC/8. Crossreactions among 10 murine monoclonal antibodies (MoAbs) to VIII:C were tested, showing 6 functional and immunospecific VIII:C epitopes. One epitope on the C-terminal, 80,000 dalton fragment of VIII:C was identified with cross-reaction among 3 MoAbs (Synbiotics, Chemicon, and IB3). Another unique site on this same fragment was recognized with C7F7. Two MoAbs (RFF-VIIIC/6 and RFF-VIIIC/8) defined another site with cross-reactive idiotypes on the N-terminal, 90,000 dalton fragment. Hybritech MoAb identified a fourth functionally distinct site to which no other cross-reacting MoAbs bound. A fifth functional locus was defined with RFF-VIIIC/2 which reacted with an N-terminal site (distinct from the RFF-VIIIC/6 X RFF-VIIIC/8-defined site). A sixth functional locus was recognized with RFF-VIIIC/5 which reacted with a C-terminal site (distinct from the Synbiotics/Chemicon/IB3-defined site but possibly near the C7F7-defined site). RFF-VIIIC/10 identified a non-functional locus on the middle region of VIII:C. These MoAb-based assays resolve six sites to which high-titered inhibitors are directed and offer a path to further study the immunoregulation of human anti-VIII:C inhibitors.

Animals↗
PubMed1983

Comparative behaviour of the components of the factor VIII complex in acute myocardial infarction.

The three components of the factor VIII complex: VIII coagulant (VIII:C), VIII related antigen (VIII R:Ag) and the VIII related von Willebrand factor (VIII R:WF) were studied in patients with acute myocardial infarction (AMI). Using a carefully standardized technique for the determination of VIII R:WF, a significantly higher R:WF level was found in 32 patients compared to 19 control subjects, confirming our previous results. However VIII R:AG was increased to an even greater extent, resulting in a VIII R:Ag/VIII R:WF ratio of 1.58 +/- 0.084 in patients, compared to 1.21 +/- 0.045 in controls. A similar increase of the VIII R:AG/VIII:C ratio was noted in the 13 patients in whom VIII:C was investigated. In 7 patients with severe AMI who could be investigated twice the plasma levels of both VIII R:Ag and VIII R:WF were found to be lower a week after the acute event than during the first 48 hours. However the VIII R:Ag/VIII R:WF ratio was not significantly reduced after 7 days. Acute phase reaction and endothelial injury resulting in release of multimers which are less polymerised are probably involved in the above changes.

Adult↗
PubMed1980

Leukemia cutis in blastic transformation of chronic myelocytic leukemia: TdT positive blasts and response to vincristine and prednisone.

A patient with chronic myelocytic leukemia (CML) in blast transformation with extensive involvement of the skin is reported. The leukemic infiltrates consisted of blasts with lymphoblastoid morphology which were positive for terminal deoxynucleotidyl transferase (TdT) by fluorescent assay. The infiltrates rapidly resolved with vincristine and prednisone therapy. Similar recurrence 4 and 8 months later responded as dramatically to the same therapy and to cytosine arabinoside. This unusual case of extensive leukemia cutis supports the evidence that patients in blast crisis with TdT positive cells are responsive to vincristine and prednisone. The implications of this case in terms of the origin of these cells based upon morphology and TdT content, as well as the diagnosis and therapy, are discussed.

Aged↗
PubMed1980

B-lineage prolymphocytic leukemia as a distinct clinicopathologic entity.

Prolymphocytic leukemia (PLL) was described originally by Galton and his colleagues as a special variant of chronic lymphocytic leukemia (CLL) with distinct clinical and hematologic features. Subsequent authors have described considerable heterogeneity in the clinical and immunologic features of PLL but have not dealt in detail with pathologic descriptions of their cases. Consequently, one might question whether PLL represents one disorder or a heterogeneous group of disorders. Three patients who satisfied Galton's original diagnostic criteria for PLL were examined by pathologic and immunologic methods. The spleens of these patients showed distinctive pseudonodular pathologic features. The malignant prolymphocytes were characterized as B-lineage by the presence of surface IgM and IgD, the expression of HLA-DR antigen, the absence of E-rosette formation, and the absence of natural killer cell activity. The existence of B-lineage prolymphocytic leukemia is affirmed as a distinct entity with unique pathologic, clinical, and immunobiologic characteristics.

Aged↗
PubMed1979

Characterization and experimental use of a monospecific antiserum to factor IX.

Purified human factor IX was used to develop xenogeneic neutralizing and precipitating antibodies. The final antiserum (R2) neutralized only factor IX and was equivalent to 220 Bethesda-inhibitory units. It showed two precipitating lines, one of which disappeared after absorption with human albumin. On immunodiffusion and Laurell immunoelectrophoresis, the albumin-absorbed R2 antiserum showed one precipitin line of identity, or one rocket respectively, with normal plasma, a Red Cross factor IX preparation (rich in factors IX, II and X), the original antigen, and Hemophilia-B antigen-positive plasmas. No line or rocket developed with normal plasma absorbed with aluminum hydroxide or with antigen-negative contained only factor IX neutralizing and precipitating antibodies. Experiments with various factor IX concentrates revealed that the majority contained excess factor IX antigen compared to their coagulant activity. In addition, crossed antigen-antibody electrophoresis uncovered differences in the migration of the factor IX of Konyne preparations, when done in the presence of EDTA or calcium. This monospecific antiserum to human factor IX was subsequently used to investigate a large population of hemophilia B patients and carriers.

Animals↗
PubMed1979

Laboratory prediction of the carrier state in hemophilia B: role of replication of assays.

The authors studied the effect of averaging replicated assays of Factor IX coagulation activity and Factor IX antigen on each plasma specimen in improving the ability to detect carriers of hemophilia B. The improvement resulting from this procedure is particularly marked in tests depending on the linear regression of one characteristic on another to diagnose the carrier state. The effects of averaging assays on the ratio of Factor IX coagulation activity to Factor IX antigen were also explored. The benefits of averaging replications were not greatly increased by use of more than four replications.

Blood Coagulation Tests↗
PubMed1979

Internal synthesis of p23,30 by several lymphoid malignancies.

The aim of this study was to prove the internal synthesis of p23,30 antigen (HLA-D related determinant) on human leukemias and lymphomas on which it has been detected with complement-dependent cytotoxic assays. Murine Ia antigens similar to p23,30 antigen are found on many subsets of cells in the mouse (B lymphocytes, macrophages, allogeneically activated T lymphocytes) and on intercellularly transferred immunoregulatory molecules, which may be adsorbed to other cells. The question exists whether the p23,30 antigen, which occurs on a wide range of human leukemias, is internally synthesized by these tumors or, in some instances, is synthesized by normal lymphocytes and is adsorbed to the leukemic cells. The expression of p23,30 antigen on a limited series of human leukemias and lymphomas was detected by a complement dependent, cytotoxicity assay. The internal synthesis of p23,30 antigen and p44,12 (HLA-A and -B antigens and beta2-microglobulin) was confirmed by immunoprecipitation and these antigens from [35S]methionine labeled, detergent solubilized membranes of tumor cells. In each instance, the synthesis of p23,30 antigen by the malignant cells was confirmed. The distribution of p23,30 antigen (and 1a antigen) on subsets of normal cells and in immunoregulatory molecules was reviewed. In view of these findings, the role of p23,30 antigen in the diagnosis of subsets of human hematologic malignancies was reconsidered.

Antigens, Surface↗
PubMed1978

Some observations on the in vivo effect of propranolol on platelet aggregation and release.

Platelet function was investigated in four normal volunteers, one patient with a mild form of von Willebrand disease, and one with a thrombocytopathy, all taking propranolol. No effect on platelet function attributable to this drug could be demonstrated in any of these subjects. It is suggested that propranolol administered in conventional doses does not impair platelet hemostatic function.

Adult↗
PubMed1978

The effect of trypsin and storage on aggregation and release of human gel-filtered platelets.

Trypsin was studied as an aggregating and release-inducing agent with gel-filtered platelets (GFP) and was compared with ADP, epinephrine and collagen. GFP aggregated irreversibly with final concentrations of 0.5-4 microgram/ml trypsin, 1.6-3.2 micrometer ADP, 2.5-5 micrometer epinephrine and 40 microlite 1/ml soluble collagen. Addition of human fibrinogen to the Tyrode-suspending buffer was required for ADP and epinephrine, but was not necessary for trypsin or collagen. Release of (14C)5HT was obtained with trypsin and collagen using the same concentrations as used in aggregation. GFP stored at room temperature for 48 h were still responsive to trypsin and collagen, whereas aggregability and (14C)5HT release induced by ADP and epinephrine were already impaired 5 h after collection of blood. CP-CPK, an ADP-removing reagent, blocked aggregation and release induced by low trypsin concentrations, suggesting that ADP plays an intermediate role in the mechanism by which trypsin activates platelets. Trypsin appears to be a valuable reagent for studying platelet physiology, particulary following storage.

Blood Coagulation↗