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Biomedical subjects

W Kaplan

Publications and source records attributed to W Kaplan.

At least 19 recordsLinked to original sources
PubMed2000

Equilibrium folding of dimeric class mu glutathione transferases involves a stable monomeric intermediate.

The conformational stabilities of two homodimeric class mu glutathione transferases (GSTM1-1 and GSTM2-2) were studied by urea- and guanidinium chloride-induced denaturation. Unfolding is reversible and structural changes were followed with far-ultraviolet circular dichroism, tryptophan fluorescence, enzyme activity, chemical cross-linking, and size-exclusion chromatography. Disruption of secondary structure occurs as a monophasic transition and is independent of protein concentration. Changes in tertiary structure occur as two transitions; the first is protein concentration dependent, while the second is weakly dependent (GSTM1-1) or independent (GSTM2-2). The second transition corresponds with the secondary structure transition. Loss in catalytic activity occurs as two transitions for GSTM1-1 and as one transition for GSTM2-2. These transitions are dependent upon protein concentration. The first deactivation transition coincides with the first tertiary structure transition. Dimer dissociation occurs prior to disruption of secondary structure. The data suggest that the equilibrium unfolding/refolding of the class mu glutathione transferases M1-1 and M2-2 proceed via a three-state process: N(2) <--> 2I <--> 2U. Although GSTM1-1 and GSTM2-2 are homologous (78% identity/94% homology), their N(2) tertiary structures are not identical. Dissociation of the GSTM1-1 dimer to structured monomers (I) occurs at lower denaturant concentrations than for GSTM2-2. The monomeric intermediate for GSTM1-1 is, however, more stable than the intermediate for GSTM2-2. The intermediates are catalytically inactive and display nativelike secondary structure. Guanidinium chloride-induced denaturation yields monomeric intermediates, which have a more loosely packed tertiary structure displaying enhanced solvent exposure of its tryptophans and enhanced ANS binding. The three-state model for the class mu enzymes is in contrast to the equilibrium two-state models previously proposed for representatives of classes alpha/pi/Sj26 GSTs. Class mu subunits appear to be intrinsically more stable than those of the other GST classes.

Anilino Naphthalenesulfonates↗
PubMed1997

Conformational stability of pGEX-expressed Schistosoma japonicum glutathione S-transferase: a detoxification enzyme and fusion-protein affinity tag.

A glutathione S-transferase (Sj26GST) from Schistosoma japonicum, which functions in the parasite's Phase II detoxification pathway, is expressed by the Pharmacia pGEX-2T plasmid and is used widely as a fusion-protein affinity tag. It contains all 217 residues of Sj26GST and an additional 9-residue peptide linker with a thrombin cleavage site at its C-terminus. Size-exclusion HPLC (SEC-HPLC) and SDS-PAGE studies indicate that purification of the homodimeric protein under nonreducing conditions results in the reversible formation of significant amounts of 160-kDa and larger aggregates without a loss in catalytic activity. The basis for oxidative aggregation can be ascribed to the high degree of exposure of the four cysteine residues per subunit. The conformational stability of the dimeric protein was studied by urea- and temperature-induced unfolding techniques. Fluorescence-spectroscopy, SEC-HPLC, urea- and temperature-gradient gel electrophoresis, differential scanning microcalorimetry, and enzyme activity were employed to monitor structural and functional changes. The unfolding data indicate the absence of thermodynamically stable intermediates and that the unfolding/refolding transition is a two-state process involving folded native dimer and unfolded monomer. The stability of the protein was found to be dependent on its concentration, with a delta G degree (H2O) = 26.0 +/- 1.7 kcal/mol. The strong relationship observed between the m-value and the size of the protein indicates that the amount of protein surface area exposed to solvent upon unfolding is the major structural determinant for the dependence of the protein's free energy of unfolding on urea concentration. Thermograms obtained by differential scanning microcalorimetry also fitted a two-state unfolding transition model with values of delta Cp = 7,440 J/mol per K, delta H = 950.4 kJ/mol, and delta S = 1,484 J/mol.

Affinity Labels↗
PubMed1997

The effect of anticipatory discharge orders on length of hospital stay in staff pediatric patients.

Effective discharge planning should serve to reduce length of stay (LOS) and lower readmission rates. A combined prospective/retrospective study was undertaken to assess the effectiveness of anticipated discharge order forms in decreasing LOS for staff pediatric patients. Resident physicians provided advance notice of the planned discharge date to nursing staff and patient family members. Patient selection was random, and the data were collected prospectively. These subjects were matched with patients for whom the order form was not used, and the data was collected retrospectively. Matching variables included: diagnosis, age, gender, race, and method of payment. There were 103 matched pairs. LOS was collapsed into low and high categories. There was a significant difference when comparing subject groups (chi 2 = 8.5; P = 0.005). Whereas only 14% of experimental patients were categorized as high LOS, 32% of control patients were classified as such. Physician prediction of discharge date helped decrease patient LOS.

Adolescent↗
PubMed1997

Early restaging gallium scans predict outcome in poor-prognosis patients with aggressive non-Hodgkin's lymphoma treated with high-dose CHOP chemotherapy.

PURPOSE: This prospective study assessed the predictive value of early restaging gallium (Ga) and computed tomographic (CT) scans in poor-prognosis patients with aggressive non-Hodgkin's lymphoma (NHL) who were treated with high-dose cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy. PATIENTS AND METHODS: Thirty newly diagnosed patients with bulky (> or = 10 cm) advanced-stage aggressive NHL were treated with a four-cycle high-dose CHOP regimen (22 patients at maximum-tolerated dose [MTD]: cyclophosphamide 4 g/m2, doxorubicin 70 mg/m2, vincristine 2 mg, and prednisone 100 mg orally for 5 days). All patients had chest/abdominal/pelvic CT scans and 10-mCi Ga scans at baseline and following two and four cycles of therapy. Scans were reviewed in a blinded manner for CT-documented rates of response and sizes of residual masses and Ga avidity of residual masses. The results of early (post-cycle 2) and final (post-cycle 4) restaging were subsequently associated with clinical outcome. RESULTS: CT-documented rates of response and residual mass sizes were indistinguishable in complete responders who remained continuously disease-free (CR-Cont), complete responders who subsequently relapsed (CR-Rel), and partial responders who then progressed (PR/Prog). In marked contrast, early restaging (post-cycle 2) Ga scans accurately delineated these three categories of patients: CR-Cont 90% Ga-negative (18 of 20 patients) versus CR-Rel 25% Ga-negative (one of four patients) versus PR/Prog 0% Ga-negative (zero of six patients) (P = .000014). At a median follow-up duration of 31 months (range, 21 to 46), 94% of patients who had negative early restaging Ga scans remain free from progression (FFP), whereas only 18% of patients who had positive early restaging Ga scans remain FFP (P = .000007). Early restaging Ga scans were more predictive for FFP than final restaging Ga scans because patients who required four full cycles of therapy to become Ga-negative were more likely to develop recurrent disease. CONCLUSION: Early restaging Ga scans delineate patients who are likely to have prolonged disease-free survival from those who fail to respond to intensive induction therapy. Patients whose tumors remain Ga-positive midway through high-dose CHOP therapy have a poor outcome and may be candidates for alternative treatment.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Primary mediastinal large-B-cell lymphoma: radiologic findings at presentation.

OBJECTIVE: Primary mediastinal large-B-cell lymphoma was recently reclassified as a distinct clinical entity. We wished to review the imaging findings for this disease and to compare the findings with those for other disorders with a similar appearance. MATERIALS AND METHODS: We retrospectively reviewed plain films, gallium scintigrams, MR images, and CT scans for 43 patients with primary mediastinal large-B-cell lymphoma. RESULTS: All but one lesion arose in the anterior mediastinum. Areas of fluid attenuation within the masses were evident on CT scans in 50% of cases. Pleural effusions were seen by chest radiography in 33% of patients. Pericardial effusions were present in 32% of patients who underwent CT scans. Of the 21 patients who underwent gallium scintigraphy, all were reported to have positive findings. Also, MR imaging showed evidence of superior vena cava syndrome in one patient. CONCLUSION: Primary mediastinal large-B-cell lymphoma typically is seen as a bulky anterior mediastinal mass that often contains areas of necrosis.

Adult↗
PubMed1995

Porcine class pi glutathione S-transferase: anionic ligand binding and conformational analysis.

The equilibrium binding of the non-substrate ligands 8-anilino-1-naphthalene sulfonate and bromosulfophthalein to porcine class pi glutathione S-transferase (pGSTP1-1) was studied using a variety of techniques (size-exclusion HPLC, steady-state fluorescence, second-derivative spectroscopy, and chemical modification of cysteines). Both ligands share the same binding site which has a highly hydrophobic surface. Occupation of the site inhibits catalytic function with glutathione and 1-chloro-2,4-dinitrobenzene in a non-competitive manner. Data obtained from different structural probes either located at strategic regions of pGSTP1-1 (Trp-28, Trp-38 and Cys-45) or distributed throughout the protein molecule (tyrosine residues) suggest that binding induces a microstructural change that impacts on the functional conformation of the active site.

Anilino Naphthalenesulfonates↗
PubMed1995

Selective sacral rhizotomy for the management of neurogenic bladders in spina bifida patients: long-term followup.

Selective sacral rhizotomy was introduced for the management of high pressure neurogenic bladders commonly encountered in myelodysplastic patients. In 1992, 2 of us (I.F. and W.K.) first reported results with selective sacral rhizotomy and cord untethering in 8 spina bifida patients. We report long-term followup of our original 8 patients and 3 additional patients. This followup demonstrates remarkable success in maintaining bladder volume and low pressures after rhizotomy and cord untethering. Uninhibited contractions resolved in all patients postoperatively. A more favorable response occurred in the patients younger than 9 years, supporting early intervention with selective sacral rhizotomy.

Adolescent↗
PubMed1990

An experimental model for chronic lymphedema.

Although a multitude of operations exist for the treatment of lymphedema, none is highly successful. An experimental model that reliably and easily produces chronic lymphedema in an extremity would be useful to study treatments in a controlled and comparative manner and would enhance our understanding of the physiology and treatment of lymphedema. Many models that simulate clinical lymphedema have been described, but they suffer from cumbersome protocols, high laboratory costs, and an inconsistent yield of permanent lymphedema. We describe an experimental model for chronic lymphedema in the lower extremity of the rat that creates a lymphatic block in the groin induced by radiation treatment and one operation--surgical division of the superficial and deep lymphatics. All animals develop stable chronic lymphedema of the lower extremity within days of operation, with swelling that persists for at least 9 months. A mortality rate of 8 percent was associated with this technique. Methods for quantification of limb swelling are described, as is analysis of the lymphatic block by lymphoscintigraphic imaging of lymph channels and nodes. This model has the advantages of simplicity of technique, cost-effective use of rodent subjects, reproducibility of lymphedema, and quantification of results.

Animals↗
PubMed1986

Pharmacokinetics of radiolabeled monoclonal antibody B6.2 in patients with metastatic breast cancer.

Thirteen patients with metastatic breast carcinoma were given injections of 50-1593 micrograms of 131I-monoclonal antibody (MAb) B6.2 immunoglobulin G and F(ab')2 for pharmacokinetic evaluation and radioimmunoimaging. Blood clearance of the 131I-MAb-B6.2 was biphasic. The mean half-times (t 1/2 alpha, t 1/2 beta) for the immunoglobulin G were 3.5 +/- 1.7 and 20.9 +/- 11.0 h, respectively. The t 1/2 alpha for the F(ab')2 was 1.7 +/- 1.3 h, and the t 1/2 beta was 31.0 +/- 5.7 h. The percentage of protein bound 131I for the immunoglobulin G and for the F(ab')2 at 72 h was 73.7 +/- 11.4% and 58.2 +/- 14.5%, respectively. In vitro reactivity of MAb B6.2 with granulocytes isolated from normal subjects and patients was demonstrated by cytofluorometric and radioimmunoassays. MAb B6.2 was shown to bind with normal cross-reacting antigen, a cell surface antigen known to be expressed on normal human granulocytes. Reactivity with normal cross-reacting antigen on granulocytes is consistent with the skeletal images obtained during immunoscintigraphy of all 13 patients. A specific tumor image was observed in one patient. No toxicity was encountered. In spite of extensive preclinical data suggesting that 131I-MAb B6.2 would be a useful agent for radioimmunoimaging, the clinical utility of this reagent is probably limited because of the reactivity with granulocytes.

Adult↗
PubMed1985

Disseminated bilateral chorioretinitis due to Histoplasma capsulatum in a patient with the acquired immunodeficiency syndrome.

A 31-year-old white male homosexual was healthy until March 1984, when he developed Pneumocystis carinii pneumonia, which resolved with treatment. In April 1984 he developed fever, followed by hepatosplenomegaly, headaches, blurred vision, pancytopenia and pulmonary infiltrates. On June 11, intracytoplasmic yeast were noted within leukocytes on a peripheral blood smear, and amphotericin B was started. The patient developed progressive respiratory and renal insufficiency and died on June 13, 1984. Autopsy histopathology demonstrated disseminated histoplasmosis and Histoplasma capsulatum was cultured from numerous tissues. Ocular histopathologic examination using special fungal stains and electron microscopy revealed numerous budding yeasts characteristic of Histoplasma capsulatum in the choroid, retina and central retinal vein. Their identification as H. capsulatum was confirmed by immunofluorescent staining.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Zygomycosis. Report of four cases with formation of chlamydoconidia in tissue.

The authors describe spheric to ovoid chlamydoconidia and mucoraceous hyphae in tissues from four patients, two with cutaneous and two with pulmonary zygomycosis. The diagnosis in each case was confirmed by immunofluorescence staining and the presence of characteristic hyphae in tissue. It is important that these conidia be recognized, because they can easily be mistaken for other fungi, nematode ova, or other microorganisms in tissue sections, thereby resulting in the potential for misdiagnosis.

Adult↗