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Biomedical subjects

T Li

Publications and source records attributed to T Li.

At least 505 records · Page 28Linked to original sources
PubMed1993

[Role of oxygen-derived free radicals in stress-induced gastric ulceration].

In the present work, the role of oxygen-derived free radicals in the pathogenesis of the gastric mucosal injury induced by cold-restraint stress was studied in rats. The results were as follows. (1) In rats pretreated with superoxide dismutase (SOD), a scavenger of superoxide anions, or with dimethyl sulfoxide and mannitol, scavengers of hydroxyl radicals, the gastric lesions induced by stress became much less extensive. (2) The mucosal content of malondialdehyde, a metabolic product of lipid peroxides, was significantly increased during stress. (3) Histochemical study revealed that the gastric mucosa abounded in xanthine oxidase (XO), the enzymic activity of which was increased during stress. In the rats pretreated with allopurinol, to inhibit XO activity, the extent of gastric mucosal lesions was decreased significantly. These suggested that oxygen free radicals might be one of the important factors in inducing gastric mucosal injury during stress and the increase of XO activity might be responsible for the production of the radicals.

Animals↗
PubMed1993

[Viscoelastic property alterations in patients with rheumatic heart disease and congestive heart failure].

Few papers on alteration of whole blood viscoelastic properties in patients with congestive heart failure (CHF) have been reported. In this study viscoelastic property parameters were measured in 63 consecutive patients with rheumatic heart disease and CHF. All subjects were divided into four groups according to NYHA classification of heart function. There were 14 class I, 16 class II 20 class III and 13 class IV. Contraves low-shear-30 rheometer was used for measuring the viscoelastic parameters. The results demonstrated that there was no significant difference of these parameters between class I and class II, that the apparent viscosity, AI and eta' in class III were higher than those in class I, and that eta 0.512, eta 5.96 AI, eta', eta" and G' in class III were higher than those in class II. All viscoelastic parameters but eta p in class IV were markedly higher than those in other groups. However, there were no statistically significant difference of eta p among all subjects and nor significant difference of these parameters between male and female were noted. There was a negative correlation between viscoelastic parameters and heart function parameters by pulse Doppler echocardiography (peak flow velocity, stroke volume and cardiac output). The results also showed a significant direct correlation between eta 0.512 AI, and eta" and the heart function parameters mentioned above.

Adolescent↗
PubMed1993

[Analysis on postoperative prognosis in relation to blood ketone body ratios in surgical patients with liver disease].

Eighty-one patients with liver disease were studied for the postoperative changes in the arterial blood ketone body ratio (KBR) and routine liver function tests. The postoperative patients were classified into three groups-according to the postoperative changes in KBR. In the 54 patients of group A, KBR did not decrease to below 0.7, only 2 cases with complications (3.7%); in the 25 patients of group B, KBR decreased transiently to 0.4-0.7 and then increased to over 0.7, 9 cases with complications (36.0%), but they were ameliorated concomitantly with the restoration of KBR; in the 2 cases of group C, KBR decreased irreversibly to below 0.4, and a variety of complications occurred, so the patients finally died of multiple organ failure (MOF). It was found that routine liver function tests were less reliable direct indicators for the onset of postoperative hepatic insufficiency than KBR, which reflected the oxidoreduction state of liver mitochondria.

Adult↗
PubMed1993

[Study on hydrolytic kinetics of metronidazole-phosphate in rabbit plasma by HPLC].

A HPLC method for the simultaneous determination of metronidazole and metronidazole-phosphate in rabbit plasma has been established. This method is simple, sensitive, reproducible and has a good linearity. It has been used to study the hydrolytic kinetics of metronidazole-phosphate in rabbit plasma. The results show that hydrolytic process of metronidazole-phosphate in vitro at 37 degrees C follows a first order kinetics with the rate constant 0.016 min-1 and half-life 43 min.

Animals↗
PubMed1992

Conformations, interactions, and thermostabilities of RNA and proteins in bean pod mottle virus: investigation of solution and crystal structures by laser Raman spectroscopy.

We report and interpret laser Raman spectra of the three virion components of bean pod mottle virus (BPMV). The top component of BPMV is an empty capsid; middle and bottom components package the RNA2 and RNA1 genome segments, respectively. All components were investigated as both single crystals and aqueous solutions, the latter over wide ranges of temperature and ionic strength. The isolated RNA2 molecule of BPMV middle component was also investigated in both H2O and D2O solutions. The results permit assessment of RNA and protein structures, their mutual interactions in the virions, and their conformational thermostabilities and comparison of these structural characteristics for solution and crystal states of the particles. The principal findings of this study are (i) The extent of ordered A-form backbone (74%) and of base pairing (38% AU + 22% GC) in unpackaged (aqueous) RNA2 are significantly altered by packaging. The A-form secondary structure of RNA2 is increased by 12 +/- 4%, and guanine base interactions are also substantially increased with packaging. (ii) The thermostability of Raman-monitored secondary structure of unpackaged RNA2 (Tm approximately 43 degrees C) is greatly increased in the packaged state (Tm approximately 53 degrees C). This increase corresponds to a stabilization of the A-form backbone geometry in 15 +/- 5% of genome nucleotides. (iii) Packaging of RNA2 in the middle component stabilizes subunit-subunit interactions of the capsid, as evidenced by a thermal denaturation temperature Td approximately 65 degrees C for the virion, compared with Td approximately 55 degrees C for the empty capsid. (iv) Raman marker-band shifts implicate the purine 7N sites of RNA2 and aromatic side chains of subunits as the principal targets for RNA-subunit interaction. (v) At the conditions of the present experiments (8 degrees C, pH approximately 7, moderate ionic strength), the subunit secondary structures observed for solutions of the top, middle, and bottom components are indistinguishable by Raman spectroscopy from secondary structures observed for corresponding crystalline samples. (vi) On the other hand, side chains of subunits in the top component (empty capsid) yield significantly different Raman intensities in crystalline and solution states. These differences are interpreted as the result of changes in a small number of side-chain environments between crystal and solution. (vii) Similarly, small differences exist between RNA Raman markers of crystalline and aqueous virions, which are attributed to altered environments of nucleotide residues and to a small increase in the amount of A-form backbone geometry upon going from the crystal to the solution.(ABSTRACT TRUNCATED AT 400 WORDS)

Base Composition↗
PubMed1992

New Middle Pleistocene hominid crania from Yunxian in China.

Two fossil human crania have been found in Middle Pleistocene terrace deposits of the Han River in Yun county (Yunxian), Hubei province, China (Figs 1 and 2). These damaged but relatively complete adult specimens show a mixture of features associated both with Homo erectus and with 'archaic H. sapiens'. The Yunxian crania (Figs 3 and 4), although crushed and distorted to varying degrees, are unusual in having major elements of the basicranium, palate, face and cranial vault preserved together. The specimens reveal many details of facial and basicranial anatomy rarely seen in hominid crania of comparable antiquity. Moreover, they are the most complete crania of such great age discovered on the Asian mainland. They consequently throw new light on Middle Pleistocene hominid diversity and the relationships among regionally disparate Middle Pleistocene hominids.

Animals↗
PubMed1992

Retinal degeneration is rescued in transgenic rd mice by expression of the cGMP phosphodiesterase beta subunit.

The beta subunit of the cGMP phosphodiesterase (PDE) gene has been identified as the candidate gene for retinal degeneration in the rd mouse. To study the molecular mechanisms underlying degeneration and the potential for gene repair, we have expressed a functional bovine cGMP PDE beta subunit in transgenic rd mice. One transgenic mouse line showed complete photoreceptor rescue across the entire span of the retina. A second independently derived line showed partial rescue in which photoreceptors in the superior but not the inferior hemisphere of the retina were rescued. In the latter animals, intermediate stages of degeneration were observed in the transition zone between rescued and diseased photoreceptors. Pathologic changes in the retina ranged from vesiculation of the basalmost outer segment discs in otherwise structurally intact rod cells to photoreceptors with highly disorganized outer segments and intact inner segments. Totally or partially rescued retinas showed a corresponding restoration of cGMP PDE activity, whereas nonrescued retinas had minimal enzyme activity, characteristic of the rd phenotype. These transgenic animals provide models for studying the molecular basis of retinal degenerative disease and conclusively demonstrate that the phenotype of rd mice is produced by a defect in the beta subunit of cGMP PDE.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1992

Crystallization and preliminary X-ray diffraction studies of coxsackievirus B1.

Preparations of coxsackievirus B1 (CVB1) derived from an infectious cDNA clone have been crystallized in multiple crystal forms. Using high intensity synchrotron radiation, an orthorhombic form of the crystals was shown to diffract X-rays to at least 2.9 A resolution. The unit cell has a primitive lattice with dimensions a = 323 A, b = 450 A, and c = 522 A. A crystallographic asymmetric unit of these CVB1 crystals probably contains an entire virus particle, implying the presence of 60-fold non-crystallographic redundancy. This CVB1 crystal form appears to be suitable for high-resolution structure determination by X-ray crystallography.

Crystallography↗
PubMed1992

Seating and retention of complete crowns with a new adhesive resin cement.

The retentive property of cast gold complete crowns cemented with an adhesive resin cement (Panavia Ex) was compared with retention of crowns cemented with zinc phosphate cement (Flecks) and the conventional resin cement (Comspan). The effect of these agents on seating of crowns also was evaluated. Panavia cement exhibited the highest retentive strength, with values almost twice those obtained with zinc phosphate cement. However, the difference in mean retention values of crowns cemented with Comspan cement or with zinc phosphate cement was not statistically significant. Both resin cements used in this study provided better seating of crowns than did zinc phosphate cement.

Adhesives↗
PubMed1992

A comparison of metronidazole distribution following intravenous metronidazole and metronidazole phosphate disodium in mice.

The distribution of metronidazole following intravenous metronidazole (MTZ) and metronidazole phosphate disodium (MNP) in mice was investigated by HPLC. The results showed no significant differences in the metronidazole concentrations of liver, kidney, heart, spleen, fat, brain, lung, stomach, jejunum, skeletal muscle, ovary, testis and epididymis (P greater than 0.05). It can be concluded that using MNP as a water-soluble substitute for MTZ should not influence the distribution of metronidazole in mice.

Animals↗
PubMed1992

Detection and analyses by gel electrophoresis of cisplatin-mediated DNA damage.

DNA damage induced by cis-diamminedichloroplatinum (II) (cisplatin: cis-DDP), an anticancer drug, was studied in vitro by monitoring the drug-induced conformational change of pUC18 plasmid DNA, the sensitivity to some restriction enzymes of the damaged DNA and the sequence-dependent termination of DNA synthesis caused by cisplatin. Closed circular, superhelical pUC18 DNA was treated at 37 degrees C for 16 h with various concentrations of cisplatin. Cisplatin-dose-dependent conformational change due to unwinding of the treated DNA was detected by agarose gel electrophoresis. To analyze the base-specificity of the cisplatin damage, the measurement for sensitivity of cisplatin-treated DNA to various types of restriction enzyme and sequence gel analysis of the treated DNA were conducted. The results suggested that cisplatin attacked preferentially the sequence of GG > AG > GNG in the order. In the present assay condition, the cisplatin/DNA nucleotide ratios required for the DNA damage detection were roughly 0.025 for the conformational analysis, 0.001 or more for the restriction enzyme analysis, and less than 0.001 for the sequence gel analysis. By using the present method, it was demonstrated that the cisplatin-mediated DNA damage was inhibited by NaCl, KCl, CaCl2 or MgCl2 at their nearly physiological concentrations, and by reducing agents such as thiourea and 2-mercaptoethanol in the reaction mixture.

Base Sequence↗
PubMed1992

[A randomized control trial of isovolemic hemodilution therapy in cor pulmonale].

The hemorheologic properties are obviously abnormal in patients with cor pulmonale (CP), presenting as high hematocrit (HCT), hyperviscosity and hyper-viscoelasticity. Twenty patients suffering from CP with polycythemia were randomized into either an isovolemic hemodilution (IHD) group or control group. In the IHD group, 10 patients were treated by routine therapy combined with IHD. The other 10 patients in the control group were treated by routine therapy only. The results demonstrated that after treatment in IHD group, all viscoelasticity property parameters except eta p were decreased significantly. Oxygen delivery, oxygen transport capacity, and stroke volume and cardiac output were increased. Mean pulmonary artery pressure and total pulmonary resistance were decreased. However, in the control group only HCT and eta 0.512 were decreased after treatment. The viscosity and eta' of the whole blood in IHD group were decreased more markedly than those in the control group. IHD was well tolerated in most of the patients. There were no complications or side effects. Thus, IHD is a safe, effective and acceptable therapy, and it may play a role in the treatment of cor pulmonale.

Adult↗
PubMed1992

[Determination of naphthoquinone in zicao].

A TLC-spectrophotometric method for the separation and determination of the naphthoquinones in Zicao is described. The sample solution was applied at a point 1 cm from the bottom edge of a silica gel G plate. A mixture of n-hexane-acetone-chloroform-glacial acetic acid was used as the developing solvent. The plate was saturated for 30 min and developed. The spots were scraped and extracted with chloroform for spectrophotometric determination at 523nm. The method has been applied to the analysis of different samples.

Chromatography, Thin Layer↗