Biomedical subjects
Publications and source records attributed to M Engelhard.
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In a multicenter prospective randomized therapeutic trial in advanced (stage II-IV disease, Ann Arbor classification) high-grade malignant non-Hodgkin's lymphomas (NHL, Kiel classification) a sequential combination of the COP-BLAM (5 cycles) and the IMVP-16 (2 cycles) protocols was employed. Response was first determined after 2-3 cycles. In a response-adapted manner the therapy was immediately switched to IMVP-16 if only a partial remission or no response was obtained as evidenced by the first restaging. The aim of the study is the investigation of the efficiency of this concept to induce stable remissions. In an additional randomized trial, involving all patients reaching complete remissions after chemotherapy (second restaging), the prognostic relevance of adjuvant radiotherapy as compared to therapy-free follow-up is evaluated. Eighty percent of the 191 recruited qualified patients have so far become evaluable. Complete clinical remissions were achieved in 76/148 (51%) of the patients up to the first, in 52/85 (61%) of the patients up to the second restaging. Only in a few cases did the expected toxicity of intensive polychemotherapy reach WHO grade 3-4, including nausea and diarrhea, infections, septic complications, myelotoxicity, and stomatitis. Four of the 29 deaths recorded so far occurred in complete remission due to treatment-related complications, whereas 22/29 (76%) died in progression and 3 of unrelated causes.
Clinical manifestations including rheumatoid changes, lymph node swelling, fever, butterfly rash, anaemia and leukopenia had developed gradually over a period of years in a 46-year-old female patient. Due to these findings systemic lupus erythematosus (SLE) was suspected. Further diagnostic procedures revealed concomitant pulmonary tuberculosis. In the course of the tuberculostatic therapy, there occurred six episodes of marked exacerbation of drug-induced SLE signs and symptoms including fever, myalgia, swelling of joints, butterfly rash and high titers of antinuclear antibodies. These exacerbations were induced by single-agent or combination therapy with ethambutol, pyrazinamide, streptomycin and/or prothionamide and resolved readily after discontinuation of the drug(s). With concomitant use of hydroxychloroquine sulfate, a combination therapy with rifampicin and cycloserine did not give rise to further complications although the autoantibodies persisted. This treatment regimen was given until clinical cure was achieved.
The Kiel classification provides a new subdivision of non-Hodgkin lymphomas into distinct entities showing different clinical and prognostic properties. In comparison with earlier classifications this system defines additional types of lymphoma (e.g. CC lymphoma, LP immunocytoma) (for abbreviations see text) which are to be considered separate entities also from a clinical point of view. By data derived from a multicenter prospective observation study (1,127 patients recruited from 1975 to 1980, follow-up until 1985) a precise definition of the clinical features of each lymphoma entity (e.g. frequency, age and sex distribution, patterns of initial involvement and spread of disease) was possible. In addition, the effect of radio- and/or chemotherapeutic measures was evaluated. Strictly localized disease (stage I/IE according to the Ann Arbor classification) occurred in 1.5 to 8% of patients with NHL of low-grade malignancy (comprising 69.4% of cases studied) and in 8 to 17% of patients with high-grade malignant NHL (comprising 30.2% of cases studied). Loco-regional irradiation alone was able to induce complete remission in 86 to 89% (CB and IB lymphomas) and in 100% (LP immunocytoma, CB-CC and CC lymphomas), respectively, of stage I/IE patients. Only CC and IB lymphomas showed a relevant risk of relapse (40% and 50%, respectively). Total lymphoid irradiation as able to induce stable complete remissions in about 50% of patients with stage III of CB-CC lymphoma. Probabilities of survival of patients with initial stages III and IV treated by several types of chemotherapy reflect different prognostic features of individual lymphoma entities.(ABSTRACT TRUNCATED AT 250 WORDS)
A 27-year-old male patient with ataxia telangiectasia (AT) developed atypical chronic lymphocytic leukemia with increasing bone marrow infiltration in the absence of organomegaly. One-third of the leukemia cells expressed a mature suppressor/cytotoxic T cell phenotype (T3+ T4- T6- T8+ T10-), two-thirds demonstrated additional helper/inducer T cell-associated antigens (T3+ T4+ T6- T8+ T10-), and a small fraction reacted with a natural killer (NK) cell-specific monoclonal antibody (Leu 11+). The proliferative response to stimulation in vitro with lectins and various monoclonal antibodies resembled the proliferation pattern of mature thymocytes: The cells responded to phytohemagglutinin (PHA), concanavalin A (ConA), stimulation of the T3-Ti receptor complex with Sepharose-bound anti-T3, and stimulation of the sheep erythrocyte receptor protein with anti-T11(2) and anti-T11(3) in conjunction with exogenous interleukin-2 (IL 2); they failed, however, to proliferate after stimulation with anti-T11(2) and anti-T11(3) alone. There was no response in the mixed lymphocyte reaction (MLR) and no suppression of the MLR between two healthy donors. Antibody-dependent cell-mediated cytotoxicity and NK activity could not be demonstrated. Cytogenetic analysis revealed complex clonal aberrations, including an interstitial deletion of the long arm of chromosome 14 concerning bands q21-31, loss of chromosome 20, and loss of the Y chromosome. Cytostatic chemotherapy was of little use and caused serious side effects, whereas leukapheresis proved effective in reducing the tumor load. The clinical data and laboratory findings in this case correspond to three previously described patients with AT who developed chronic T cell leukemia. Thus, in adult patients with AT, malignant proliferation of cytogenetically marked and phenotypically heterogeneous mature T cells seems to be a frequent complication.
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The molecular events during the photocycle of bacteriorhodopsin have been studied by the method of time-resolved and static infrared difference spectroscopy. Characteristic spectral changes involving the C=O stretching vibration of protonated carboxylic groups were detected. To identify the corresponding groups with either glutamic or aspartic acid, BR was selectively labeled with [4-13C]aspartic acid. An incorporation of ca. 70% was obtained. The comparison of the difference spectra in the region of the CO2- stretching vibrations of labeled and unlabeled BR indicates that ionized aspartic acids are influenced during the photocycle, the earliest effect being observed already at the K610 intermediate. Taken together, the results provide evidence that four internal aspartic acids undergo protonation changes and that one glutamic acid, remaining protonated, is disturbed. The results are discussed in relation to the various aspects of the proton pumping mechanism, such as retinal isomerization, charge separation, pK changes, and proton pathway.
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Clinical data of 48 patients with centrocytic, 83 patients with centroblastic/centrocytic and 64 patients with centroblastic lymphoma who had entered a prospective multicenter study of the Kiel Lymphoma Study Group since October 1975 were compared. Advanced (stage IV) disease at time of diagnosis, predominantly due to bone marrow infiltration, was most frequent in centrocytic (69% of patients) and in centroblastic/centrocytic (51% of patients) lymphomas as compared to only 28% of patients with centroblastic lymphoma. High survival probability of patients with localized centrocytic and centroblastic/centrocytic lymphomas after radiotherapy, contrasting with a worse prognosis of corresponding patients with centroblastic lymphoma, is compatible with the classification of these lymphoma entities as neoplasias of low-grade malignancy. However, as shown by this prospective and previous retrospective trials overall survival probability of patients with advanced centrocytic lymphoma was inferior to that observed in corresponding patients with centroblastic/centrocytic lymphoma. These findings suggest the possibility that patients with advanced centrocytic lymphoma occupy an intermediate position between typical low-grade and typical high-grade malignant non-Hodgkin lymphomas.
A novel mechanism for trifluoroacetylation in solid-phase peptide synthesis, independent of the coupling step, has been elucidated. It involves the presence of trifluoroacetoxymethyl groups on the resin support, which react with resin-bound amines by an intersite nucleophilic reaction. The trifluoroacetoxymethyl groups are generated from preexisting hydroxymethyl sites during treatment with trifluoroacetic acid in dichloromethane or by acidolysis of the benzyl ester bond between the peptide and the resin. The transfer of trifluoroacetyl from hydroxyl to amine occurs during the subsequent neutralization with tertiary amine. The mechanism was first elucidated by model studies with aminomethyl-resins. Then the expected transfer of trifluoroacetyl groups from trifluoroacetoxymethyl-resin to the alpha-amino group of N(epsilon)-benzyloxycarbonyllysine benzyl ester in solution was demonstrated; k(2), 6 x 10(-4) M(-1). Lysine-resins were used to examine the extent of trifluoroacetylation under the conditions of solid-phase peptide synthesis. After a series of acid/base cycles simulating synthetic conditions but without coupling, the poorly nucleophilic alpha-amino group was approximately 1-2% trifluoroacetylated per cycle when attached to resins already containing hydroxymethyl groups. Standard benzyl ester resins without preexisting hydroxymethyl groups gave comparable levels of trifluoroacetylation after the first few synthetic cycles because of gradual acid cleavage of the ester and accumulation of trifluoroacetoxymethyl sites. Peptide chain termination resulting from trifluoroacetylation by this mechanism could be prevented (<0.02% per cycle) by the use of the aminoacyl-4-(oxymethyl)-phenylacetamidomethyl-resin support, which can be synthesized free from extraneous functionalities and which is stable to trifluoroacetic acid under the conditions of solid-phase peptide synthesis.
The best system for the study of cell differentiation is a cell which in its differentiated state differs only by one product. This is the case in the immune system. The undifferentiated, but omnipotent stem cell differentiates into a committed B cell which produces only one type of specific antibody out of a million different, genetically fixed possibilities. Gene translocation and fusion is the basis of this differentiation process.
Several K immunoglobulin antisera out of a large number studied showed the unique property of reacting with a membrane structure present on all T and B lymphocytes examined. This antigen was detected on lymphocytes by indirect fluorescence, direct fluorescence, and by cytotoxic analysis. Absorption of the antiserum by all K myeloma proteins, K Bence-Jones proteins, and kappa light chains removed the activity; L proteins had no effect. The possibility that the cross-reacting membrane antigen is part of the HL-A system was discussed.
Certain antisera to immunoglobulins containing kappa-chains show the presence of antibodies that cross-react with beta2-microglobulin. This was most apparent with an antiserum made to highly purified F(ab) fragments of Fr II gamma-globulin. These cross-reactive antibodies caused positive fluorescence and cytotoxicity reactions with a variety of cell types including T cells. These reactions were completely removed by absorption with highly purified kappa-chains but not with lambda-chains or lambda immunoglobulins. beta2-microglobulin preparations also absorbed or inhibited the special cellular reactivities. Evidence was obtained that HLA-bound beta2-microglobulin was more efficient in this respect. The possibility is discussed that similar cross-reactive antibodies may have been involved in some previous studies of inhibition of T cell function by immunoglobulin antisera.
Dissociation, denaturation, and deactivation of aldolase from rabbit muscle in the acid pH range have been investigated using sedimentation analysis, fluorescence, circular dichroism, and activity tests. Under comparable experimental conditions the pH-dependent profiles of deactivation and denaturation parallel the dissociation of the enzyme. In the range of dissociation at pH4-5tetramers and monomers are in equilibrium. Intrinsic chromophores and far-ultraviolet circular dichroism suggest the transition to be a complex multistep process. At pH approximately 2.3 the enzyme is split into its fully inactive monomers which still contain some residual secondary structure. After reassociation under optimum conditions (0.2 M phosphate buffer pH 7.6, 1 mM EDTA, 0.1 mM dithiothreitol, 0 degrees C, enzyme concentration 0.4-59 mug/ml) up to 95% enzymic activity is recovered which belongs to a renatured tetrameric species indistinguishable from the native enzyme by all available biochemical and physicochemical criteria.
Tetrameric rabbit muscle aldolase has been dissociated to the monomer at pH 2.3 and fully reassociated and reactivated at pH 7.6 Kinetics of reactivation and refolding were followed by slow and fast kinetic techniques after neutralization of the acidic enzyme solutions by dilution or rapid mixing. Rate constants (k), reaction orders (n), and activation evergies (E) were calculated from measurements on the time, concentration, and temperature dependence of the reactions. The experimental results prove reactivation at high enzyme concentration (c greater than 4mug/ml) to obey first-order kinetics; at lower concentrations a transition to a higher reaction order is observed. Because of concentration-dependent deactivation at low enzyme concentrations reactivation measurements could not be extended below c approximately o.5 mug/ml. In the accessible concentration range incomplete separation of reassociation and transconformation processes as well as intrinsic residual activity of the isolated subunits lead to an average value of n = 1.40 +/- 0.18. Renaturation as monitored by protein fluorescnce is a multi-step process composed of a fast increase in flurescence emission (first-order rate constant k approximately 15 s-1) and a slow concentration-dependent decrease which parallels the recovery of enzyme activity (n = 1.46 +/- 0.12). The activation energy of both processes is of the order of E = 12-16 Kcal/mol (50-67 kJ/mol). Reassociation is a prerequisite of full catalytic function and native fluorescence.
The cross-reaction of phenylalanyl-transfer ribonucleic acid (tRNA) ligases from different microorganisms with antibodies raised against the purified enzyme from Escherichia coli has been investigated. The results of immunotitration and immunodiffusion experiments and of the sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of immunoprecipitates revealed: (i) a high degree of immunochemical identity of this enzyme only within the family Enterobacteriaceae; (ii) intermediate-to-weak cross-reaction with the phenylalanyl-tRNA ligases from Pseudomonadaceae, Rhodopseudomonas spheroides, and Bacillus stearothermophilus; (iii) no detectable cross-reaction (with the methods employed) with the enzymes from several gram-positive organisms, Euglena gracilis, and several fungi. As revealed by immunochemical analysis, a merodiploid strain of E. coli carrying an episome (F148) that covers the aroD region of the E. coli chromosome possesses at least twice the amount of phenylalanyl-tRNA ligase in comparison with its haploid parent strain. This suggests that the cistrons for both the alpha and beta polypeptides of this enzyme are mapping in this area.
The experiments leading to the determination of the primary strucutre of Bence-Jones-Protein Vor. are reported. The variable part of this immunoglobulin polypeptide chain can easily be identified as a typical representative of subgroup I of the lambde-chains. The constant part is characterized by the Kern- and OZ+ markers. The sequence data of this protein are in complete agreement with the demands of the germ line theroy of antibody formation. To demonstrate the evolutionary origin of the V-henes, a phylohenetic tree of all completely sequenced Vk-, Vlambde-, and VH-chains is constructed. Teh evolutionary rate of immunoglobulins is calculated and compared to that of other protein families.
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