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J Nachman

Publications and source records attributed to J Nachman.

52 records · Page 3Linked to original sources
PubMed1990

The three-dimensional structure of recombinant bovine chymosin at 2.3 A resolution.

The crystal structure of recombinant bovine chymosin (EC 3.4.23.4; renin), which was cloned and expressed in Escherichia coli, has been determined using X-ray data extending to 2.3 A resolution. The crystals of the enzyme used in this study belong to the space group I222 with unit cell dimensions alpha = 72.7 A, b = 80.3 A, and c = 114.8 A. The structure was solved by the molecular replacement method and was refined by a restrained least-squares procedure. The crystallographic R factor is 0.165 and the deviation of bond distances from ideality is 0.020 A. The resulting model includes all 323 amino acid residues, as well as 297 water molecules. The enzyme has an irregular shape with approximate maximum dimensions of 40 x 50 x 65 A. The secondary structure consists primarily of parallel and antiparallel beta-strands with a few short alpha-helices. The enzyme can be subdivided into N- and C-terminal domains which are separated by a deep cleft containing the active aspartate residues Asp-34 and Asp-216. The amino acid residues and waters at the active site form an extensive hydrogen-bonded network which maintains the pseudo 2-fold symmetry of the entire structure. A comparison of recombinant chymosin with other acid proteinases reveals the high degree of structural similarity with other members of this family of proteins as well as the subtle differences which make chymosin unique. In particular, Tyr-77 of the flap region of chymosin does not hydrogen bond to Trp-42 but protrudes out in the P1 pocket forming hydrophobic interactions with Phe-119 and Leu-32. This may have important implications concerning the mechanism of substrate binding and substrate specificity.

Amino Acid Sequence↗
PubMed1990

Radiobiological characterization of head and neck and sarcoma cells derived from patients prior to radiotherapy.

The radiobiological parameters of 33 tumor cell lines were studied in biopsy samples obtained from patients prior to radiotherapy. Epithelial tumor cells derived from head and neck cancer patients were more radioresistant than tumor cell lines derived from patients with sarcoma regardless of method of analysis. The presence of radioresistant tumor cell lines was associated with local failure in some patients. However, the presence of radiosensitive tumor cells did not necessarily predict local control. Our data suggest radiocurability is complex and inherent radiobiological parameters of tumor cells may be only one factor in radiotherapy outcome.

Carcinoma, Squamous Cell↗
PubMed1990

Efficacy and toxicity of 12 courses of ABVD chemotherapy followed by low-dose regional radiation in advanced Hodgkin's disease in children: a report from the Children's Cancer Study Group.

Sixty-four patients aged 2 to 18 years with advanced-stage Hodgkin's disease (HD) were treated on a Children's Cancer Study Group (CCSG) pilot toxicity study (521-P). Therapy consisted of 12 courses of Adriamycin (doxorubicin; Adria Laboratories, Columbus, OH), bleomycin, vinblastine, and dacarbazine (ABVD), followed by low-dose (2,100 cGy in 12 fractions) regional irradiation (RT). All patients were monitored for toxicity with particular attention to the pulmonary system. Six patients (9%) developed grade 3 or 4 pulmonary toxicity. Three had grade 3 toxicity based solely on changes in carbon monoxide diffusing capacity (DLCO) and remained well for more than 3 years after diagnosis. There was one fatality among the three symptomatic cases. In five cases, toxicity occurred prior to RT. One occurred after seven courses of ABVD, one after nine courses, and three after 10 courses. In one of these five cases, ABVD was stopped. The patient was given nitrogen mustard (mechlorethamine), vincristine, prednisone, and procarbazine (MOPP). This patient subsequently developed recurrence of HD and died of overwhelming sepsis. The other four continued on study and completed their chemotherapy. Three patients had no further bleomycin, and one continued bleomycin at 50% of the assigned dose. They all received mantle RT following chemotherapy, one with a boost dose to the mediastinum to 3,800 cGy and one with added RT to both lungs (1,050 cGy). In the sixth case of pulmonary toxicity, symptoms were first noticed 2 weeks after mantle RT to 3,500 cGy. This patient died of progressive respiratory failure. The event-free survival (EFS) and overall survival is 87% at 3 years. These early results indicate that this therapy is effective in advanced HD in children but has a 9% incidence of acute pulmonary toxicity.

Adolescent↗
PubMed1990

Therapy for childhood non-Hodgkin's lymphomas, nonlymphoblastic type. Review of recent studies and current recommendations.

Childhood non-Hodgkin's lymphomas can be divided into two broad groups based on histologic findings: lymphoblastic and nonlymphoblastic. Lymphoblastic lymphomas often appear with a mediastinal mass and have a propensity for relapse in the bone marrow and CNS. Nonlymphoblastic lymphomas occur primarily in the abdomen and head-neck region. Relapses tend to occur within the first year and may be either local or systemic. Marrow and/or CNS involvement at diagnosis, bulk disease (reflected as elevated serum lactic dehydrogenase levels), and mediastinal occurrences are adverse prognostic features for nonlymphoblastic lymphomas. Chemotherapy is the treatment of choice for both types of childhood non-Hodgkin's lymphomas. In general, radiation therapy is not necessary for optimal treatment of these tumors. Localized non-Hodgkin's lymphomas of either histologic type are highly curable with short-course chemotherapy. Disseminated non-Hodgkin's lymphomas, particularly those with marrow and/or CNS involvement, remain a major treatment challenge.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1988

In vitro radiobiological parameters of human sarcoma cell lines.

In vitro radiobiologic survival parameters have been determined for 7 human osteosarcoma, 5 human soft tissue and bone sarcomas, and 4 Ewing's sarcoma cell lines. The mean D0 values were 99.5 +/- 11.6 cGy, 90.5 +/- 7.7 cGy and 95.8 +/- 7.9 cGy for osteosarcomas, soft tissue and bone sarcomas and Ewing's sarcomas, respectively. These in vitro survival data do not predict the clinical radiation resistance generally attributed to osteosarcomas and soft tissue and bone sarcomas, and do not differ substantially from the results obtained with the clinically radioresponsive Ewing's sarcomas.

Bone Neoplasms↗
PubMed1987

Structure of form III crystals of bovine pancreatic trypsin inhibitor.

The structure of bovine pancreatic trypsin inhibitor has been solved in a new crystal form III. The crystals belong to space group P2(1)2(1)2 with a = 55.2 A, b = 38.2 A, c = 24.05 A. The structure was solved on the basis of co-ordinates of forms I and II of the inhibitor by molecular replacement, and the X-ray data extending to 1.7 A were used in a restrained least-squares refinement. The final R factor was 0.16, and the deviation of bonded distances from ideality was 0.020 A. Root-mean-square discrepancy between C alpha co-ordinates of forms III and I are 0.47 A, whilst between forms II and III the discrepancy is 0.39 A. These deviations are about a factor of 3 larger than the expected experimental errors, showing that true differences exist between the three crystal forms. Two residues (Arg39 and Asp50) were modeled with two positions for their side-chains. The final model includes 73 water molecules and one phosphate group bound to the protein. Sixteen water molecules occupy approximately the same positions in all three crystal forms studied to date, indicating their close association with the protein molecule. Temperature factors also show a high degree of correlation between the three crystal forms.

Amino Acid Sequence↗
PubMed1987

Nonlymphoblastic T-cell lymphoma in children.

Three children with nonlymphoblastic, non-Hodgkin's lymphomas, showed morphologic features that suggested nonlymphoblastic T-cell origin. Tissue for immunologic study was available from two of the three patients; both showed immunophenotypes of T-cells. Although nearly all T-cell lymphomas in children are lymphoblastic based on morphology, nonlymphoblastic T-cell lymphomas do occur in pediatric patients.

Antibodies, Monoclonal↗
PubMed1987

Disparate histologic responses in simultaneously resected primary and metastatic osteosarcoma following intravenous neoadjuvant chemotherapy.

Seven patients with newly diagnosed metastatic osteosarcoma underwent simultaneous resection of the primary tumor and metastases following intravenous (IV) neoadjuvant chemotherapy. Histologic response was assessed in all tumor specimens. Disparate responses were noted between primary tumor and metastases and, in some cases, between two or more metastatic tumor deposits. The diverse histologic response to neoadjuvant chemotherapy suggests tumor cell heterogeneity. Changing postoperative therapy on the basis of the histologic response induced in the primary tumor may not be appropriate.

Adolescent↗
PubMed1986

Ordered water structure in an A-DNA octamer at 1.7 A resolution.

The crystal structure of the deoxyoctamer d(G-G-Br U-A-BrU-A-C-C) was refined to a resolution of 1.7 A using combined diffractometer and synchrotron data. The analysis was carried out independently in two laboratories using different procedures. Although the final results are identical the comparison of the two approaches highlights potential problems in the refinement of oligonucleotides when only limited data are available. As part of the analysis the positions of 84 solvent molecules in the asymmetric unit were established. The DNA molecule is highly solvated, particularly the phosphate-sugar back-bone and the functional groups of the bases. The major groove contains, in the central BrU-A-BrU-A region, a ribbon of water molecules forming closed pentagons with shared edges. These water molecules are linked to the base O and N atoms and to the solvent chains connecting the O-1 phosphate oxygen atoms on each strand. The minor groove is also extensively hydrated with a continuous network in the central region and other networks at each end. The pattern of hydration is briefly compared with that observed in the structure of a B-dodecamer.

Amino Acid Sequence↗
PubMed1985

Sequential high-dose cytosine arabinoside-asparaginase treatment in advanced childhood leukemia.

Sequential high-dose cytosine arabinoside (ara-C) and asparaginase were given to 41 children age six months to 21 years of age with advanced leukemia. Ten of 22 patients with acute lymphocytic leukemia (ALL) and eight of 19 patients with acute nonlymphocytic leukemia (ANLL) obtained complete remissions. The most significant toxicity seen was infection in 22 patients. In addition, patients given intrathecal chemotherapy within 24 hours of ara-C developed neurologic toxicity. The high response rate seen in these patients with advanced leukemia indicates that a trial of this regimen is warranted in children with less advanced ALL and ANLL.

Acute Disease↗
PubMed1983

Prolonged second remissions in childhood acute lymphocytic leukemia: a report from the Childrens Cancer Study Group.

To date, median duration of second and subsequent remissions in childhood acute lymphocytic leukemia (ALL) has been short, with most studies reporting median remission duration less than 6 months. In May 1979, the Childrens Cancer Study Group (CCSG) undertook a pilot study to assess the efficacy of a vincristine, methotrexate, and L-asparaginase regimen (modified Capizzi) for maintenance in children with ALL in second or subsequent remission. Thirty patients were treated with this maintenance regimen. By life table analysis, predicted median duration of hematologic remission was 57 weeks. Ten patients (33%) were in continuous hematologic remission at 1 year and three (10%) continue in remission greater than 2 years from maintenance onset. Major toxicity included leukoencephalopathy in four patients, three of whom had experienced at least one central nervous system relapse prior to study entry. Allergic reactions to Escherichia coli L-asparaginase were common. Nine of 30 patients experienced at least one CNS relapse during therapy. We conclude that a modified Capizzi regimen is the most effective regimen reported to date for maintaining second and subsequent remission in childhood ALL. CCSG is currently utilizing this regimen in an ongoing open study.

Asparaginase↗
PubMed1982

Primary pulmonary Hodgin's disease: a case report.

A case of Hodgkin's disease occurred with pulmonary involvement as the initial feature. The disease was initially seen clinically and roentgenographically as a diffuse pulmonary infiltrate. To our knowledge, the pattern of diffuse pneumonic involvement without intrathoracic lymphadenopathy at presentation has been reported only in one other case. Differentiation of this diffuse pneumonic pattern of primary pulmonary Hodgkin's disease from the more common pattern of a focal mass or infiltrate is important in considering appropriate therapy.

Adolescent↗
PubMed1979

Relapse rates following cessation of chemotherapy during complete remission of acute lymphocytic leukemia.

The therapeutic benefit of maintenance chemotherapy beyond three years for children with acute lymphocytic leukemia (ALL) in continuous complete remission was evaluated by the investigators of Childrens Cancer Study Group (CCSG). Two hundred and twenty leukemic children in first remission for three years or longer and who had received at least three years of continuous chemotherapy were eligible. One hundred and one patients were randomized to either continue chemotherapy for an additional three years or to discontinue therapy, and 119 patients nonrandomly continued or discontinued therapy. The patients had received a variety of chemotherapy regimens. The study period extended from April 1970 until December 1977, with a median follow-up time of 25 months. Relapses occurred in 15 randomized patients (15%). Randomized patients remaining on chemotherapy experienced a statistically significant lower relapse rate than patients randomized to discontinue therapy. Also among randomized patients, bone marrow relapse was significantly more frequent in males than in females. Considering the total patient group, age and white blood count at diagnosis had no significance in predicting relapse. Of relapse events in males, 21% were isolated testicular relapses, identifying the testicles as a major risk site in males completing three years of continuous complete remission. This study demonstrates that continuing chemotherapy beyond three years results in a significant prolongation of remission in males, although the eventual survival outcome for later discontinuance of therapy will require longer follow-up.

Bone Neoplasms↗