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Biomedical subjects

M Lei

Publications and source records attributed to M Lei.

80 records · Page 5Linked to original sources
PubMed1991

Isolation and molecular evolutionary analysis of a cytochrome c gene from Oryza sativa (rice)

A cytochrome c gene, OsCc-1, from rice (Oryza sativa) has been isolated and analyzed. The OsCc-1 gene encodes a cytochrome c protein that is typical of higher-plant cytochrome c proteins. OsCc-1 consists of three exons separated by two introns that are 817 and 747 bp in length, respectively. From genomic DNA hybridization analysis, OsCc-1 appears to be one of possibly two cytochrome c genes in several Asian, American, and Indian rice species and varieties surveyed. A single, unique cytochrome c gene appears to be present in one African cultivated rice species. We performed comparative molecular evolutionary analyses of OsCc-1 and other cytochrome c genes. We calculated a unit evolutionary period of 19.4 Myr for cytochrome c DNA sequences, which agrees closely with previous estimates based on protein sequence comparisons.

Amino Acid Sequence↗
PubMed1991

[A randomized controlled trail of maprotiline treatment of depressive disorder].

In order to evaluate the clinical effects of maprotiline (home made), the authors made a clinical comparison with Ludimil (Cida-Geigy) 96 cases (66 endogenous depression and 30 neurotic depression) meet the CMA diagnostic criteria (1984) were analysed. The patients' symptoms were assessed with HAMD, side effects with TESS. The study group included 72 patients treated with chinese product, the rest cases as control group treated with Ludimil. No significant differences of efficacy in terms of age, sex and duration of symptoms were found in both groups. After the six-week course of Maprotiline treatment, the authors found the dosage, therapeutic effect and adverse reaction in both groups are very similar. It is concluded that the chinese product is safe and effective.

Depressive Disorder↗
PubMed1990

Inhibition of human tumor growth by intraperitoneal immunotoxins in nude mice.

Intracavitary administration of immunotoxins may play a role in the control of malignant effusions. Selection of immunotoxins for this form of therapy is based on their prior evaluation in preclinical studies. Monoclonal antibodies (mAb) 454A12 (antitransferrin receptor), and 260F9 are directed against antigens which are present on tumor cells in pleural and peritoneal effusions of patients with adenocarcinoma of the breast and ovary. In the present study, immunotoxins derived by conjugating these mAb to recombinant ricin A (rRA) were shown to be cytotoxic to human ovarian adenocarcinoma HEY cells in vitro and in vivo. In the in vitro assay 454A12-rRA and 260F9-rRA were 1000-fold and 10-fold, respectively, more cytotoxic than free rRa against HEY cells, and both immunotoxins were potentiated approximately 1000-fold by monensin. For in vivo studies HEY cells were injected i.p. into nude mice at a challenge dose (3 x 10(5) cells) which produced carcinomatosis with ascites, leading to death 30 days following injection. Administration of 454A12-rRA i.p. following the challenge dose resulted in a complete cure, whereas administration of 260 F9-rRA with monensin significantly prolonged survival. The greater cytotoxicity of 454A12-rRA than 260F9-rRA against HEY cells could be accounted for by the greater number of binding sites and higher internalization rate for 454A12-rRA and mAb 454A12 than 260F9-rRA and mAb 260F9, respectively. These results suggest a potential role for 454A12-rRA and 260F9-rRA plus monensin in the intracavitary therapy of malignant effusions associated with carcinoma of breast and ovary. In the case of 260F9-rRA, this represents the first preliminary indication of the suitability of this immunotoxin for intracavitary therapy of malignancies.

Adenocarcinoma↗
PubMed1981

A monoclonal antiidiotypic antibody to MOPC 315 IgA inhibits the growth of MOPC 315 myeloma cells in vitro.

Spleen cells from BALB/c mice immunized with MOPC 315 IgA were fused with P3X63/Ag8 myeloma cells. Hybrid clones were screened for antibody production by a plate-binding radioimmunoassay in which MOPC 315 IgA was reacted with culture supernatants and 125I-protein A. One antibody-producing hybridoma clone (D10) was selected and injected i.p. into BALB/c mice. Ascitic fluid of tum or-bearing animals reacted specifically with MOPC 315 IgA and the reaction was inhibited by DNP- aminocaproic acid, indicating that the monoclonal antibody was directed against the hapten-binding site of MOPC 315 IgA. The monoclonal antiidiotypic antibody was of the complement (C)-binding IgG2a subclass and inhibited IgA production and growth of MOPC 315 cells in vitro in the presence of guinea pig C, as assessed by inhibition of formation of plaques and colonies by MOPC 315 cells in agar.

Animals↗
PubMed1979

Limited proteolysis of glutamine synthetase is inhibited by glutamate and by feedback inhibitors.

Limited proteolysis of glutamine synthetase from Escherichia coli has been studied under nondenaturing conditions (pH 7.6, 20 degrees C). Trypsin cleaves the polypeptide chain of glutamine synthetase into two principal fragments, Mr = about 32,000 and 18,000. The covalently bound AMP group is attached to the larger fragment and its presence does not affect cleavage. Although the cleaved polypeptide chain does not dissociate under nondenaturing conditions, catalytic activity is lost. Chymotrypsin and Staphylococcus aureus protease produce similar cleavages in glutamine synthetase. The substrate L-glutamate retards tryptic as well as chymotryptic digestion. Tryptic digestion is also retarded by some of the feedback inhibitors of glutamine synthetase including CTP, L-alanine, L-serine, L-histidine, and glucosamine 6-phosphate. An implication of these findings is that there is a region of the glutamine synthetase polypeptide chain that is particularly susceptible to proteolysis. Either the glutamate and inhibitor sites are formed partly by this suceptible peptide or the binding of glutamate and some inhibitors induces conformational changes within the E. coli glutamine synthetase molecule in the region of the susceptible peptide.

Chymotrypsin↗
PubMedDate not supplied

Convolution and correlation: a case study of scanning imaging and analysis systems.

The relationship between convolution/correlation operation and the data acquisition process of the scanning microscope and spectrometer families is analyzed. It is shown that a coordinate or event sensitive detector, and the intrinsic or extrinsic property of the specimen response, are two important factors in distinguishing the data acquisition mode of such systems. Four types of convolution- and correlation-based modes are extracted to illuminate the physical characteristics of scanning imaging and analysis systems by focusing on the probe, specimen, detector, and their relationships. Criteria for identifying these modes are explored. In addition, the physical meanings of general existing coefficients between the independent variables of convolution and correlation are investigated.

Journal Article↗
PubMedDate not supplied

Inhibition of protein synthesis by monoclonal anti-idiotypic antibody-ricin A chain conjugates in MOPC 315 myeloma cells.

Three monoclonal antiidiotypic antibodies (AIA) to MOPC 315 IgA, G3 (IgG2b), A2 (IgG1) and D10 (a hybrid molecule consisting of gamma 1 and gamma 2a heavy chains), were characterized with respect to their binding constants (Ka) to MOPC 315 mouse myeloma cells. The Ka of G3 and A2 was 10(8)/mole; and that of D10 was 3 X 10(7)/mole. The AIA did not bind to a non-immunoglobulin (Ig) producing subclone of MOPC 315 cells (MOPC 315.36). Immunotoxins derived by conjugating ricin A chain (RTA) to G3 and A2 but not to D10 preferentially inhibited protein synthesis in MOPC 315 over MOPC 315.36 cells. These results suggest that the effectiveness of these immunotoxins assessed on the basis of their targeted cytotoxicity against MOPC 315 cells was dependent on the Ka but not on the Ig subclass of the AIA component of the immunotoxin.

Animals↗