Biomedical subjects
Publications and source records attributed to A H Zhang.
The adsorption of CO on the oxygen precovered Rh(111) and the oxidation of CO are investigated with density functional theory. The preferred adsorption site and the possible reaction channel are determined. The experimentally observed inertness of the (2 x 2)-O-CO structure is explained by the reaction barrier and the stability of the reactants.
Quantitative convergent beam electronic diffraction (QCBED) method is a powerful tool for the investigation of the atomic and electronic structure of crystals. In this work, a global optimization algorithm has been adopted and a new fitting manner has been suggested in our recently developed QCBED program. A study of the charge density distribution in intermetallics is demonstrated as an example. Using the QCBED method, an investigation of lattice distortion in oxides is attempted.
A new method for helicase-catalyzed DNA unwinding is described. This assay takes advantage of the substantial change in fluorescence polarization (FP) upon helicase binding and DNA unwinding. The low anisotropy value, due to the fast tumbling of the free oligonucleotide in solution, increases abruptly upon binding of helicase to the fluorescein-labeled oligonucleotide. The high anisotropy of the helicase- DNA complex decreases as the fluorescein-labeled oligonucleotide is released from the complex through helicase-catalyzed DNA unwinding. This FP signal can be measured in real time by fluorescent spectroscopy. This assay can simultaneously monitor DNA binding and helicase-catalyzed DNA unwinding. It can also be used to determine the polarity in DNA unwinding mediated by helicase. This FP assay should facilitate the study of the mechanism by which helicase unwinds duplex DNA, and also aid in screening for helicase inhibitors, which are of growing interest as potential anticancer agents.
Cinnamomin, a type II ribosome-inactivating protein (RIP) isolated from the seeds of Camphora tree (Cinnamomum camphora), could not inactivate its own (autologous) ribosome. Among five RIPs (Cinnamomin A-chain, ricin A-chain, trichosanthin, gelonin, and soporin-S6) tested, only saporin-S6 could cleave the N-glycosidic bond of RNA in C. camphora ribosome to release a specific RNA fragment (R-fragment) after treatment with aniline, which was shorter than that from rat liver ribosome. The amount of saporin-S6 to inactivate C. camphora ribosome was about 1000 times higher than that required for rat liver ribosome. Extra-ribosomal factors (S-100) in the post-ribosomal supernatant could not promote RNA N-glycosidase activity of cinnamomin and gelonin to C. camphora ribosome. These results indicated that there were some changes in the microenvironments of Sarcin/Ricin domain of C. camphora ribosome that abolished the recognition and catalysis of many RIPs. In addition, the length of C. camphora 5.8S ribosomal RNA was found to be longer than that of rat 5.8S ribosomal RNA.
Two adult patients with post-traumatic complete brachial plexus injury were treated with cross-C7 nerve-root transfer from the contralateral side. A detailed documentation of the motor and sensory functional status of the donor upper limb was carried out before and after division of the C7 nerve root. Gross motor deficits were observed immediately after surgery in shoulder extension and adduction, elbow extension, forearm pronation, wrist flexion, and hand movement. Sensory deficit involving the hand was maximal immediately after division of the C7 root. Functional recovery was rapid starting within 10 days following the root division. In both patients, the motor and sensory deficits were temporary. Full functional recovery was documented at 6 months. However, objective qualitative and quantitative differences in the motor and sensory deficits in the donor limbs were still present by 1.5 to 2 years, although these did not affect the functional status of the donor limbs. The presence of multiple segmental root innervation of the muscles and skin, other than the C7 root in the upper limb, provides for a compensatory mechanism that allows for this rapid and full functional recovery following the single nerve-root loss. The absence of any long-term functional deficit makes cross C7 transfer a viable option in the surgical management of complete unilateral brachial-plexus injury.
Six surveillance spots were set up in Jiaozhou Bay to examine the contamination of Ruditapes Philippinarum (R. P) by HAV. Specimens were collected regularly every month. Seventy-five specimens were collected in July 1991-Aug 1992. The precursor RNA of HAV was detected by methods of PCR, RNA dot-blot hybridization and HAV isolation. It showed that R. P. had been contaminated by HAV in some areas of the bay at times, but the virus was in a state of inactivity. Epidemiologic investigation in the same period proved that R. P. was not the direct cause of HA epidemic in Qingdao. However, the domestic sewage is directly drained into the Jiao zhou Bay so the control of the city sewage drainage system must be enforced and health education serve for people in taking sea food and drink should be strengthened.
Hyperlipidemia is one of the main features of nephrotic syndrome (NS), which has been reported to be important in the pathogenesis of mesangial cell proliferation. In an attempt to understand if LDL of the NS patients is more nephrotoxic on the development of mesangial cell proliferation, serum lipoprotein composition of normal controls, patients of NS untreated and treated with steroid drugs were measured, moreover, the influence of LDL from each group of patients on the proliferation of human mesangial cell (HMC) were observed. Lipoprotein composition was measured by enzymic methods. LDL was prepared by ultracentrifugation and used within three weeks. HMC was cultured and identified by classical methods, mesangial cell proliferation was observed by 3H-TdR incorporation according to the dose of LDL from 20-1000 micrograms/ml and time from 24 hours to 72 hours. Our results indicated that: 1. Both the NS patients untreated and treated with steroid drugs showed hypercholesterolemia and hypertriglyceride, serum low-density lipoprotein cholesterol (LDL-ch) concentration were higher in these patients than in the normal control group but there was no significant difference between NS untreated and treated groups. 2. LDL from normal controls or NS patients had biphasic effect on HMC proliferation. Low concentration stimulated HMC proliferation in concentration dependent and time-dependent manner, where as high concentration inhibited HMC proliferation. There was no significant difference on the effect of HMC proliferation between NS untreated and treated groups.(ABSTRACT TRUNCATED AT 250 WORDS)
To investigate the effect of initiating labor by oxytocin infusion on the outcome of delivery in cephalic presentation, the dystocia rate and final modes of delivery were analyzed in 3,090 cases of head presentation using oxytocin infusion and 2,982 cases with spontaneous onset of labor as control group. The results showed that 562 of the cases using oxytocin developed cephalic dystocia, a rate of 18.2%, while 371(12.4%) of the control group had dystocia. Besides, cephalic dystocia, rates of episiotomy, vacuum extraction and cesarean section were all significantly higher in the oxytocin group than those in the control (P < 0.005). Data also showed that the higher dosage, the more frequency and the longer time of pitocin infusion the higher the rate of dystocia.
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