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Biomedical subjects

M Citron

Publications and source records attributed to M Citron.

64 records · Page 4Linked to original sources
PubMed1991

O6-methylguanine-DNA methyltransferase in human normal and tumor tissue from brain, lung, and ovary.

The resistance of human tumor strains in culture to cell killing by alkylating nitrosoureas is correlated with their levels of the DNA repair activity O6-methylguanine-DNA methyltransferase. Strains with the Mer- phenotype have no activity and are extremely sensitive. However, the relationship between the sensitivity of human tumors in vivo and transferase levels is not known, and even the existence of Mer- human tumors in vivo has been questioned. In this study 73 human tumor and normal tissue samples from brain, lung, and ovary were assayed for transferase levels and methylpurine glycosylase activity. For each organ, transferase levels varied over 100-fold, and Mer- tumors were detected in each group. There was no correlation between transferase and glycosylase levels, indicating that the absence of transferase in some tumor samples was not an artifact due to necrosis or inactivation of enzymes in the extract.

Bacterial Proteins↗
PubMed1991

Non-Hodgkin's lymphoma during pregnancy.

A rare case of non-Hodgkin's lymphoma stage IE complicating pregnancy is presented. The diagnosis was made by biopsy at 28 weeks gestation and treated with 2635 rad of external radiotherapy with abdominal and pelvic shielding beginning at 30 weeks gestation. Following delivery, the patient received combination chemotherapy and is disease-free 6 years later. The baby, weighing 2015 g, was delivered by cesarean section at term. The effects of radiotherapy on a fetus are reviewed and the factors that were considered in the treatment of this patient are discussed. Radiotherapy with protective shielding can be an effective initial modality of treatment in this setting.

Adult↗
PubMed1991

Greenfield filter as primary therapy for deep venous thrombosis and/or pulmonary embolism in patients with cancer.

In 1985, as a result of the high complication rate associated with anticoagulants in patients who have cancer and deep venous thrombosis (DVT) and/or pulmonary embolism (PE), we established a policy of placing Greenfield filters (GFs) as primary therapy instead of anticoagulation. Since 1985 we have been asked to consult in the treatment of 18 patients with cancer and with DVT and/or PE, and we have placed a GF in each of these patients. This represented 34% (18/53) of the filters placed during that same period. Over the same 4-year period, 11 patients with cancer and DVT and/or PE underwent anticoagulation therapy. The purpose of this study was to compare the results of anticoagulation versus GF insertion in these two groups of patients. A significantly higher number of major complications (n = 4) occurred in the anticoagulation group (p less than 0.05, Fisher's exact test) than in the GF group (n = 0). The four complications that occurred in the anticoagulation group included three bleeding episodes (tumor bleeding, gastrointestinal bleeding, and hip hematoma) and one PE, despite adequate anticoagulation. Two patients died as a direct result of these complications (PE and gastrointestinal bleeding). The three patients with bleeding complications each required a transfusion of more than 3 units of blood. All four of the patients with complications had metastatic disease (pancreatic carcinoma, chronic lymphocytic leukemia, prostate carcinoma, and uterine carcinoma). Although this is a small, nonrandomized, nonprospective study, the data seem to indicate that GF placement is safer than anticoagulation for DVT or PE in patients with cancer and particularly in patients with metastatic disease. We conclude that GF insertions may be a better primary treatment than anticoagulation.

Adult↗
PubMed1990

The c4 repressors of bacteriophages P1 and P7 are antisense RNAs.

The c4 repressors of P1 and P7 inhibit antirepressor synthesis and are solely responsible for heteroimmunity of the phages. We show that c4 is a new type of antisense RNA acting on a target, ant mRNA, that is transcribed from the same promoter. Interaction depends on complementarity of two pairs of short sequences encompassing the ribosome binding site involved in ant expression. We demonstrate that heteroimmunity of P1 and P7 is due to just two substitutions in each of the complementary sequences of c4 and ant mRNA. Based on P1-P7 sequence comparison and a mutant analysis, we propose a secondary structure model for c4 RNA, with the complementary regions in loops as important sites for antisense control.

Base Sequence↗
PubMed1989

Three additional operators, Op21, Op68, and Op88, of bacteriophage P1. Evidence for control of the P1 dam methylase by Op68.

The repressor of bacteriophage P1, encoded by the c1 gene, is responsible for maintaining the P1 prophage in the lysogenic state. Previously, 11 c1 repressor binding sites or operators scattered over the whole genome of P1 have been found. From sequence analysis an asymmetric, 17-base pair consensus sequence, ATTGCTCTAATAAATTT, was derived. Using a synthetic 15-base-long oligodeoxyribonucleotide as operator probe, we have identified three additional operators. We have mapped the operators at the positions 21,68, and 88 of the P1 genome and determined their sequence. These operators are controlled by c1 because corresponding P1 DNA fragments (i) require c1 repressor in vivo in order to be clonable in multicopy plasmids, (ii) exhibit a c1-repressible promoter activity, (iii) are retarded by c1 repressor protein during electrophoresis, and (iv) contain the 17-base pair consensus sequence with one mismatch base each. Furthermore, we suggest that expression of the DNA adenine methylase (dam) encoded by P1 is controlled via Op68.

Bacteriophages↗
PubMed1983

Microcomputer produced anaglyphs for evaluation and therapy of binocular anomalies.

An Atari 800 microprocessor with a color television monitor was used to produce red-green anaglyphs. These computer produced anaglyphs allow for rapid manipulation of vergence stimuli which allow the doctor greater control in diagnosis and therapy of binocular anomalies. Additionally, computer controlled stimuli allow for animation, and delivery of reinforcing aspects. The present paper describes a system in use.

Computers↗
PubMedDate not supplied

Production of amyloid-beta-peptide by cultured cells: no evidence for internal initiation of translation at Met596.

It has been suggested that the A beta fragment of the amyloid precursor protein in Alzheimer's disease arises from internal translation initiation at Met596 (1). Here we use the recently described in vitro model of A beta production and secretion (2) to examine this hypothesis. We show that A beta is no longer detectable when the beta APP reading frame is destroyed by introduction of frame shift mutations that leave the A beta coding region intact. This result strongly suggests that internal initiation at Met596 does not contribute significantly to the amount of A beta observed.

Amino Acid Sequence↗