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H Mei

Publications and source records attributed to H Mei.

29 records · Page 2Linked to original sources
PubMed1996

Expression and characterization of glutathione peroxidase activity in the human blood fluke Schistosoma mansoni.

Antioxidants may play an important role in immune evasion by schistosome parasites. Previous studies have focused on the roles of superoxide dismutase and glutathione S-transferase. In the present study, glutathione peroxidase (GPX) activity was measured in different fractions of worm extracts from several developmental stages of Schistosoma mansoni. The enzyme activity was shown to be developmentally regulated, with higher specific activities being found in the tegument-enriched Nonidet P-40 extract of adult worms (the stage least susceptible to immune killing) than in the larval stages (which are most susceptible to immune elimination). In all extracts tested, the activity against cumene hydroperoxide, even when glutathione S-transferase activity was removed, was higher than that for hydrogen peroxide. The expression of GPX cDNA in pGEX-2T by bacteria produced a 50-kDa fusion protein and a 32-kDa truncated protein. The latter was due to termination at the internal UGA codon that codes for selenocysteine. GPX activity was detected in the recombinantly produced GPX but not with Sj26-glutathione S-transferase from the vector. Mutating the TGA codon to TGT produced a full-length product, GPXm (19 kDa), that was used to produce 19 monoclonal antibodies. Anti-GPXm monoclonal antibodies recognized a 19-kDa molecule in adult-worm extract which, upon removal by immunoprecipitation, resulted in the loss of over 90% of the GPX activity, suggesting that a single form of GPX exists in the schistosome.

Animals↗
PubMed1995

Schistosoma mansoni: cloning and characterization of a gene encoding cytosolic Cu/Zn superoxide dismutase.

Two forms of Cu/Zn superoxide dismutase (SOD) have been identified in Schistosoma mansoni, signal peptide-containing SOD (SP-SOD, Simurda et al., 1988, Exp. Parasitol. 67, 73-84) and cytosolic SOD (CT-SOD, Hong et al., 1992, Exp. Parasitol. 75, 308-322). The SP-SOD gene has been previously characterized. We report the isolation and characterization of the gene encoding CT-SOD. A cDNA clone of CT-SOD was radiolabeled and used to screen an EMBL3 genomic library. Of 100,000 plaques, 1 hybridizing phage contained an insert of 14.6 kb. The CT-SOD gene spans 8.5 kb of chromosomal DNA and possesses three exons (150, 285, and 234 bp, respectively) and two introns (4.9 and 2.7 kb, respectively) which interrupt the coding region. Separate copies of the gene as determined by restriction fragment patterns on Southern blots are found on two YAC clones. Using YAC clones that contain the CT-SOD gene, fluorescence in situ hybridization on chromosomes identified a copy of the gene located on the middle region of chromosome 1 and another copy localized to the middle region of the long arm of chromosome 3. Primer extension and nuclease protection assay performed on total RNA define the transcription initiation site and allow the identification of potential cis-acting sequences, such as a CAAT box and a hexanucleotide GCCCGG. Comparison of this gene with Cu/Zn SOD genes from Drosophila, humans, and mice identifies conserved exons that represent functional domains in the SOD protein.

Amino Acid Sequence↗
PubMed1994

Macromolecular infarct-specific magnetic resonance contrast agents.

PURPOSE: To identify safe and effective magnetic resonance imaging (MRI) agents for infarction, the authors investigate the possibility of using a small population of infarct-avid phosphonates to target macromolecular MRI agents to infarction. METHODS: Several phosphonylated radiolabeled (gadolinium-153, iron-59) macroaggregates were synthesized. Biodistribution was assessed in a drug-induced rat model of diffuse myocardial infarction (MI). Agents that demonstrated preferential accumulation in infarcted whole hearts were additionally evaluated in occluded and reperfused rabbit hearts. Phosphonylated T2 agents have been thoroughly studied with MRI of MI, and the results are reported. RESULTS AND DISCUSSION: Typically, core size was 11 to 13 nm and particle size was 120 nm. Phosphorus content was < 12% by weight. The relaxivities were R1 of 12 to 20 1/(mM.sec) and R2 of 119 to 270 1/(mM.sec) at 20 MHz in .5% agar. One hour after injection of .03 mmol/kg of the agent into six rabbits (45-minute occlusion with 1-hour reperfusion), the average myocardial tissue agent content was 70 +/- 30 nmol Fe/g (infarct) compared with 9 +/- 2 nmolFe/g (normal); P = .000. Similarly, the infarct zone was clearly discerned by MRI as hypointense on spin echo images, TR/TE = 400/30 msec and 2,000/30 msec with low-dose agent, whereas infarct was barely discernible only on TR/TE = 2,000/90 msec without agent. The magnetic resonance infarcts correlated with histology. CONCLUSION: Simple phosphonylated macromolecules can be used as low-dose, infarct-specific MRI agents.

Animals↗
PubMed1991

Application of Gd-DTPA in diseases of the central nervous system.

Patients whose routine MRI were negative but were clinically highly suspected of having intra-cranial or intra-spinal canal space-occupying lesions, and those whose routine MRI were positive but presented difficulties in defining the contour or the nature of the lesion, or difficulty in distinguishing the lesion from the surrounding edema were selected for Gd-DTPA enhancement. Altogether there were 80 cases, in which 51 had intracranial lesions and 29 intraspinal canal lesions. In each patient, Gd-DTPA 0.06-0.1 mmol/kg was injected intravenously 5 minutes before imaging (pituitary microadenoma images were taken immediately and 10 minutes after injection). No patient had contrast media reaction or complications. In cases with hemorrhage, hematoma, edema, cyst and arteriovenous malformation, no marked enhancement was observed after contrast media injection. When difficulty in differential diagnosis between these lesions and tumors occurs, injection of Gd-DTPA is very helpful. Gd-DTPA enhancement is of great benefit in diagnosis of intracranial or intraspinal canal tumors in four ways. 1) It reveals lesions which can not be demonstrated or can not be demonstrated clearly before enhancement, including iso-intensity lesions and small lesions which comprised 13.7% of our cases. 11 cases with equivocal diagnoses before enhancement obtained unequivocal diagnoses after enhancement. 2) It differentiates the tumor from edema more definitely. 3) It helps to distinguish the nature of lesions. 4) It shortens examination time when the T2 weighted image procedure is omitted.

Adenoma↗
PubMed1989

A study of the renal sinus and its application in stone surgery.

The anatomical structure of the renal sinus was studied in 160 adult cadaver kidneys. Important anatomical features were described in the capsule of the sinus fatty tissue, including capsular septum of the hilus renalis, and the distribution of the posterior pelvic transverse artery. The implications of these findings in stone surgery are discussed.

Humans↗
PubMed1982

Rat bladder isograft model for focal carcinoma.

A model for focal bladder carcinoma in rats was developed with the use of an isograft technique. Bladder tumors developed by carcinogen induction with FANFT or MNU were grafted to bladders of syngeneic rats. Ninety-six per cent (56 our of 58) of the grafts were taken and 83 per cent (34 out of 41) of the grafted tumors remained neoplastic. Most of the grafts from FANFT-induced tumor remained localized at the original site whereas many from the MNU-induced tumor spread beyond the original graft area. The model system may be useful for the evaluation of chemotherapeutic agents as well as for the studies of basic mechanisms of tumor growth and spreading.

Animals↗