Biomedical subjects
Publications and source records attributed to S Pan.
Chromosome studies were performed on 13 patients with the Cornelia de Lange syndrome. With the technique of chromosome banding analysis, no chromosomal abnormalities were found.
A direct immunoplaque assay was utilized without agar or other semi-solid matrix for examining antibody secreting cells by scanning electron microscopy. For this purpose a polylysine procedure was used whereby 'charged' coverslips absorbed onto their surface an even monolayer of target sheep erythrocytes. Hemolysin secreting splenocytes derived either from mice immunized in vivo with SRBC or from normal or primed splenocytes immunized in vitro with the same antigen formed large numbers of hemolytic plaques on the RBC-coated polylysine treated coverslips. SEM examination of such plaque-forming cells revealed the presence of cells with the typical surface morphology of lymphocytes present in whole spleen cell suspensions. Many of the lymphocytes were covered with numerous microvilli while a small percentage were relatively free of such villi and exhibited a much smoother surface. Examination of lymphocytes secreting hemolytic antibody on polylysine coated coverslips sensitized with target erythrocytes thus permits the direct examination and analysis of surface morphologic features and also permits a direct comparison with other features revealed by light and fluorescent microscopy.
A patient with Ph1 positive chronic myeloid leukemia (CML) developed blastic transformation which by morphologic criteria appeared to be localized to the lymphatic system. Chromosome analysis at this time, however, revealed new chromosomal abnormalities in addition to the existing Ph1 in all tissues studied (lymph node, blood, and bone marrow) consisting primarily of extra chromosome numbers 19 and 9 and a second Ph1. Therapy resulted in clinical remission with significant decrease in the aneuploid cell lines. However, these reappeared with recurrence of the blast crisis. Colony formation in semisolid culture of blood and marrow cells at the time of initial blast crisis yielded growth patterns characteristic of CML. On recurrence of the blast crisis after therapy, growth patterns were characteristic of CML in blast crisis or acute myeloblastic leukemia even though blood and marrow still showed relatively low levels of myeloblasts and promyelocytes. Possible explanations are discussed for the disparity in distribution between morphologic and chromosomal abnormalities in this patient.
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A fiber-optic enzyme biosensor for the direct measurement of organophosphate nerve agents was developed. The basic element of this biosensor is organophosphorus hydrolase immobilized on a nylon membrane and attached to the common end of a bifurcated optical fiber bundle. The enzyme catalyzes the hydrolysis of organophosphate compounds to form stoichiometric amounts of chromophoric products that absorb light at specific wavelengths. The back-scattered radiation of the specific incident radiation was measured using a photomultiplier detector and correlated to the organophosphate concentration. The effects of buffer pH, temperature, and the units of enzyme immobilized on the steady-state and kinetic response of the biosensor were investigated to optimize the operating conditions for the fiber-optic enzyme biosensor. These conditions were then used to measure parathion, paraoxon, and coumaphos selectively without interference from carbamates and triazines. Concentrations as low as 2 microM can be measured in less than 2 min using the kinetic response. When stored in buffer at 4 degreesC the biosensor shows long-term stability.
The role of superoxide radicals and the protective effects of superoxide dismutase (SOD), allopurinol, 16,16-dimethyl-prostaglandin E2 (dmPGE2), cimetidine and pirenzepine in diethyldithiocarbamate (DDC)-treated rats were evaluated. Pretreatment with Cu,Zn-SOD (superoxide radical scavenger) 60,000 units/kg, allopurinol (competitive inhibitor of xanthine oxidase) 50 mg/kg, dmPGE2 (prostaglandin analogue) 10 micrograms/kg, cimetidine (H2-receptor antagonist) 10 mg/kg or pirenzepine (selective antimuscarinic drug) 10 mg/kg all significantly reduced the DDC-induced (800 mg/kg) gastric antral ulcer formation in rats. DDC treatment substantially decreases the gastric mucosal Cu,Zn-SOD activity. In this study treatment with DDC and SOD, DDC and dmPGE2, DDC and cimetidine, and DDC and pirenzepine were demonstrated significantly to prevent the decrease of gastric mucosal Cu,Zn-SOD activity. However, allopurinol did not have this effect. The results suggest that SOD and/or superoxide radicals may play an important role in the mechanism of DDC-induced gastric antral ulcer. The protective property against ulcer formation of these drugs studied might be due to the action of SOD in the gastric mucosa.