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Biomedical subjects

G Z Ma

Publications and source records attributed to G Z Ma.

5 recordsLinked to original sources
PubMed2001

[Progress in knowledge-based X-ray fluorescence spectrometry].

The review focuses on the expert systems and knowledge engineering in X-ray fluorescence spectrometry. It includes mainly a knowledge-controlled strategy combining the scan-based method with the fixed channel measurements, a XRF interpretation system of spectra with fuzzy logic and pattern recognition, and an expert system for qualitative interpretation of XRF spectra using a certainty factor. In the review, a series of the studies of exploring the knowledge engineering system in XRF are also included, which consists of four parts, i.e. spectra identification, pattern recognition with decision-making, quantitative determination combined with the theoretical alpha coefficients and neural networks, and XRF analysis without standards.

Algorithms↗
PubMed1996

Inhibition of Bcr serine kinase by tyrosine phosphorylation.

The first exon of the BCR gene encodes a new serine/threonine protein kinase. Abnormal fusion of the BCR and ABL genes, resulting from the formation of the Philadelphia chromosome (Ph), is the hallmark of Ph-positive leukemia. We have previously demonstrated that the Bcr protein is tyrosine phosphorylated within first-exon sequences by the Bcr-Abl oncoprotein. Here we report that in addition to tyrose 177 (Y-177), Y-360 and Y283 are phosphorylated in Bcr-Abl proteins in vitro. Moreover, Bcr tyrosine 360 is phosphorylated in vivo within both Bcr-Abl and Bcr. Bcr mutant Y177F had a greatly reduced ability to transphosphorylate casein and histone H1, whereas Bcr mutants Y177F and Y283F had wild-type activities. In contrast, the Y360F mutation had little effect on Bcr's autophosphorylation activity. Tyrosine-phosphorylated Bcr, phosphorylated in vitro by Bcr-Abl, was greatly inhibited in its serine/threonine kinase activity, impairing both auto- and transkinase activities of Bcr. Similarly, the isolation of Bcr from cells expressing Bcr-Abl under conditions that preserve phosphotyrosine residues also reduced Bcr's kinase activity. These results indicate that tyrosine 360 of Bcr is critical for the transphosphorylation activity of Bcr and that in Ph-positive leukemia, Bcr serine/threonine kinase activity is seriously impaired.

Animals↗
PubMed1991

Rotavirus infection of the oropharynx and respiratory tract in young children.

Oropharyngeal aspirates were obtained from 89 infants hospitalized with respiratory illnesses accompanied or not by diarrhea and 33 control patients without the diseases. Rotavirus was detected from 25 of these patients by immunocytology, isolation of the virus in cultures of MA104 cells, or both. None of the control patients gave a positive result. The infection involves squamous cells and globlet cells probably originating from the oropharynx, and ciliated columnar epithelial cells from the respiratory tract. The virus from 2 specimens was propagated by repeatedly passaging in the cultures and found to have characteristic morphology of rotavirus. The electrophoretic patterns of the viral RNA extracted from them are closely similar to those obtained with the rotavirus genome extracted from the stool of the same patients. Repeated stool specimens were also obtained, and sera were paired from some of these subjects. All but one of the patients who gave a positive virology for their aspirates also showed a significant rise in the titres of common group A rotavirus antibody, neutralizing antibody against one or more of serotypes of rotavirus, or both. Patients who excreted rotavirus in their stools were younger and had significantly lower titres of rotavirus antibodies in their acute sera, than those who shedded the virus in the oropharynx but did not excrete the virus in repeated stool specimens. The prevalence of rotavirus in the oropharyngeal aspirates from these patients surpassed that of adenovirus, respiratory syncytial virus, influenza virus, and herpes simplex virus combined.

Antibodies, Viral↗
PubMed1988

Development of neutralizing antibodies and group A common antibodies against natural infections with human rotavirus.

We determined the levels of group A common and neutralizing antibodies against human rotavirus in paired serum specimens obtained from 38 infants within 12 days of the onset of diarrhea. Thirty of the infants excreted rotavirus in stools, and eight did not. Nine patients (30%) with rotavirus diarrhea and seven patients (88%) with diarrhea due to other causes had detectable levels (greater than or equal to 1: 80) of immunoglobulin (IgG) common antibodies in acute-phase sera. All the patients with rotavirus diarrhea showed at least fourfold rises in titers of IgG or IgM common antibodies or both, while only two control patients showed significant rises in either IgG or IgM common antibodies in their convalescent-phase sera. Of the 19 patients excreting "short" electropherotypes of rotavirus, 18 showed at least fourfold rises in titers of neutralizing antibodies against serotype 2 human rotavirus but not against serotype 1, 3, or 4. Nine of the ten patients excreting "long" electropherotypes showed significant rises in neutralizing antibodies against serotype 3, and the other patient showed a significant rise in neutralizing antibodies against serotype 1. One patient excreted long and short electropherotypes simultaneously, and he also showed a significant rise in neutralizing antibodies against serotype 2 and 3 viruses. The control patients with diarrhea did not show significant changes in titers of antibodies against any of the serotypes. These results demonstrated that the neutralizing antibody response within 2 weeks after clinical onset is specific for the infecting serotype of rotavirus.

Antibodies, Viral↗