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Biomedical subjects

G Tian

Publications and source records attributed to G Tian.

At least 55 records · Page 3Linked to original sources
PubMed1997

[A study on the effects of three kinds of treatment in chronic hepatitis B].

To study the effects of three kinds of treatment: Zhuling polysaccharides combined with hepatitis B vaccine (group I), LAK cells, induced by interleukin-2 (IL-2) in vitro, transfusion therapy, (group II), bacille Calmette-Guerin (BCG) combined with persatin (group III) in chronic hepatitis B and the mechanism of their effects, we observed 286 patients with chronic hepatitis B, diagnosed according to the criteria made by The 6th National Meeting for Viral Hepatitis and Substantiated by the results of liver biopsy. The patients were divided into 3 treatment groups randomly, with interferon 3 MIU, thrice a week and 10% glucose 500 ml (i.v.) dripping everyday as two different control groups. The ALT recovery rates in group I, II, III were 64%, 35% and 57%, respectively. At the end of the treatment, the HBeAg and HBV DNA clearence rates in group I, II, III were 43% and 44%, 34% and 30%, 57% and 61%, respectively. After one year of follow up, the HBeAg and HBV DNA clearence rates in group I, II, III were 59%, 58%, 61% and 55%, 70%, 60%, respectively. The effects of these kinds of treatment were similar to these of interferon. We also injected Zhuling polysaccharides combined with hepatitis B vaccine, Zhuling polysaccharides alone and normal saline as control to DHBV vertical transmission duck. It was shown that serum DHBV DNA was cleared and the results were also proved by liver histologic change in the two treatment groups. According to these data, it is suggested that the three kinds of treatment for hepatitis B could restore the ALT level, suppress the replication of HBV and improve the liver histologic change. Their effects were similar to those of interferon.

Adult↗
PubMed1997

[Observation on acupoint electric potential in pilots under vestibular stimulation].

To study the possibility of using acupoint electric potential as an index for evaluation of pilot's reaction to vestibular stimulation, electric potential was measured on both sides of left and right Neiguan points and Zusanli points in 80 pilots. Rotation chair was used as the method of stimulation. The results showed that changes of acupoint electric potentials were not significant (P >0.05) during 5 min uniform rotation. While the changes under head motion stimulation were significant (P<0.05 or 0.01) as compared with the pretest values. Relationship between symptoms and the corresponding acupoint potential changes remain to be studied further.

Acupuncture Points↗
PubMed1997

[Analysis of frequency domain correlative cardiogram (FCG) in 151 healthy pilots].

Frequency domain correlative cardiogram (FCG) is a relatively new noninvasive method for diagnosis of coronary heart disease. However there has been little information about the application of FCG in pilots. To explore whether the FCG diagostic standards of normal people, can be applied to healthy pilots, 151 male pilots aged 22-47 (mean = 30 +/- 6 years) were examined with the HBD-II A instrument manufactured by Hong Kong WEX company. The results showed that the characteristics of FCG graph of the pilots were similar to that of the common healthy men. It indicates that the diagnostic standard of FCG for normal people can be used to pilots, so it might be useful in selection and real-time medical monitoring during ground training.

Adult↗
PubMed1997

[Changes of electrogastrogram in pilots under vestibular stimulus].

The active electrogastrogram (EGG) of 81 pilots under vestibular stimulus was recorded and analysed by the method of running spectrum analysis. The subjects were randomly divided into group A and B. The results showed: that changes in dominant frequency instability coefficient (DFIC), dominant power instability coefficient(DPIC), tachygastria, bradygastria and normal slow wave components (NSW) of EGG occured under vestibular stimulus. These parameters of EGG may be used as indices to reflect the function of autonomic nervous system under vestibular stimulus. No difference of those parameters had been found between group A and B during the period of per-rotating, and the period of rotation.

Aerospace Medicine↗
PubMed1997

[EGG and nausea under vestibular stimulus].

81 pilots were exposed to vestibular stimulus with Coriolis acceleration. They were divided into two groups, the first group consisted of 38 pilots with nausea symptoms, the second group 43 pilots without nausea symptom. Dominant frequency instability coefficient (DFIC), dominant power instability coefficient (DPIC), Tachygastria, Bradygastria and normal slow wave components (NSW) of the electrogastrogram (EGG) were analyzed. The results showed that Bradygastria and NSW of EGG were related to nausea symptom of pilots under Coriolis stimulation.

Aerospace Medicine↗
PubMed1997

[Sphygmographic parameters in fighter and transport pilots].

To evaluate and discover hidden cardiovascular trouble in pilots, the cardiovascular function of 129 active male pilots was examined with a new sphygmographic method. 13 pilots (10.3%) were found to have abnormal cardiovascular function. The average arterial blood pressure and medium artery modulus of the fighter pilots aged from 30 to 34 years are inferior to those aged from 25 to 29 obviously, however, that is not the case in transport pilots. This indicates that frequent examination of cardiovascular function with convenient special method is necessary for the improvement of the quality of medical monitor on pilots.

Adult↗
PubMed1997

[Study of spectrometer calibration experiment research].

Spectrometer calibration is very important for quantitative research of imaging spectral remote sensing. After spectral calibtation and radiometric calibration, it was known that the average shift of wavelength of SE590 channels was 8nm, and the linear response was depended on the change of energy recieved by SE590, and spectral response resolution was unreasonable beyond 950nm range. At last, the calibration results were proved by the field experiment measurement data.

English Abstract↗
PubMed1997

Evaluation of hydroxyethyl-starch-ferrioxamine as an intravascular MR contrast agent for assessment of myocardial perfusion.

PURPOSE: The present study was carried out to evaluate a new intravascular contrast agent hydroxyethyl-starch-ferrioxamine (HES-FO) for assessment of myocardial perfusion. MATERIAL AND METHODS: Isolated pig hearts were perfused with a crystalloid cardioplegic solution in a Langendorff apparatus. MR images were acquired along the short cardiac axis using T1- and T2*-weighted methods. Gd-DTPA and HES-FO were used as the standard extracellular and test contrast agents, respectively. RESULTS: We found that T1-weighted signal intensity was not significantly affected by HES-FO, but increased significantly in presence of Gd-DTPA. On the other hand, HES-FO resulted in a rapid, transient but significant decrease in T2*-weighted signal intensity. Although Gd-DTPA also decreased T2*-weighted signal intensity considerably, it took much longer for the T2*-weighted signal intensity to return to its initial steady-state with Gd-DTPA than with HES-FO. Moreover, increasing the dose of HES-FO (from 0.0023-0.0138 mmol/kg b.w.) had no effect on the time at which the T2* effect reached its maximum or on the duration of the T2* effect. However, these times and durations were affected significantly by increasing the dose of Gd-DTPA (0.0023-0.027 mmol/kg b.w.). CONCLUSION: The results suggest that HES-FO provides information regarding myocardial vascular flow which cannot be obtained using Gd-DTPA. It is expected that the combined use of intravascular and extracellular type contrast agents will allow more complete assessment of tissue perfusion.

Animals↗
PubMed1996

Pathway leading to correctly folded beta-tubulin.

We describe the complete beta-tubulin folding pathway. Folding intermediates produced via ATP-dependent interaction with cytosolic chaperonin undergo a sequence of interactions with four proteins (cofactors A, D, E, and C). The postchaperonin steps in the reaction cascade do not depend on ATP or GTP hydrolysis, although GTP plays a structural role in tubulin folding. Cofactors A and D function by capturing and stabilizing beta-tubulin in a quasi-native conformation. Cofactor E binds to the cofactor D-beta-tubulin complex; interaction with cofactor C then causes the release of beta-tubulin polypeptides that are committed to the native state. Sequence analysis identifies yeast homologs of cofactors D (cin1) and E (pac2), characterized by mutations that affect microtubule function.

Animals↗
PubMed1996

Inhibition of human steroid 5alpha reductases type I and II by 6-aza-steroids: structural determinants of one-step vs two-step mechanism.

We have discovered that 17beta-[N,N-(diethyl)carbamoyl]-6-azaandrost-4-en-3-one is a time-dependent inhibitor of type II 5alpha-reductase, as is the drug finasteride. Unlike finasteride, the 6-aza-steroid is not a time-dependent inhibitor of type I 5 alpha-reductase. Finasteride inhibition of type II enzyme proceeds in a two-step mechanism. At pH 6 and 37 degrees C, an initial finasteride-reductase complex is formed with a K(i)(app) of 11.9 +/- 4.1 nM. In a second step, an irreversible complex is formed with a rate constant of inactivation of 0.09 +/- 0.01 s(-1). In contrast, the 6-aza-steroid is a reversible inhibitor. From the results of a simplified mathematical analysis, based on the rapid equilibrium approximation, the inhibitor and the enzyme form an initial complex with a K(i) of 6.8 +/- 0.2 nM. The reversible formation of a final complex, with an overall K(i) of 0.07 +/- 0.02 nM, is characterized by a first-order isomerization rate constant 0.0035 +/- 0.0001 s(-1) for the forward step and 0.00025 +/- 0.00006 s(-1) for the backward step. All rate constants for the two-step mechanism were obtained by using a general numerical integration method. The best fit values for the association and dissociation rate constants were 5.0 microM(-1) s(-1) and 0.033 +/- 0.008 s(-1), respectively, and the isomerization rate constants were 0.0035 +/- 0.007 s(-1) and 0.000076 +/- 0.000019 s(-1). These values correspond to an initial K(i) of 6.5 nM and an overall dissociation constant of 0.14 nM. The data presented here show that both finasteride and the 6-aza-steroid analogs are potent against type II 5alpha-reductase, although their mechanisms of inhibition are different.

5-alpha Reductase Inhibitors↗
PubMed1996

In vivo time-dependent inhibition of human steroid 5 alpha-reductase by finasteride.

Finasteride (17 beta-(N-t-butylcarbamoyl)-4-aza-5 alpha-androstan-1-en-3- one), a time-dependent, irreversible inhibitor of human steroid 5 alpha-reductase (5AR), may only reduce dihydrotestosterone levels in humans by approximately 60% at the doses used clinically. A theoretical model was developed to aid in understanding the in vivo efficacy data of finasteride. According to the theory, whether an enzyme can be inhibited in vivo by an irreversible inhibitor is dependent on the value of a ratio of the observed rate of enzyme inhibition over the rate constant for inhibitor elimination. As shown, this ratio should be in excess of 3 for > 95% inhibition of the target in vivo. Subsequent application of the theory to evaluate the in vivo efficacy data of finasteride indicates low effective concentration of finasteride at the inhibition sites and suggests complete inhibition of 5AR 2, but insufficient suppression of 5AR 1 at the clinical doses.

5-alpha Reductase Inhibitors↗
PubMed1996

[Clinical significance of changes of urinary enzymes in pregnancy induced hypertension].

OBJECTIVE: To study the clinical significance of changes of N-acetyl-beta-D-glucosaminidase (NAG) and lysozyme in random urine sample in pregnancy induced hypertension (PIH). METHODS: The concentration of NAG was measured by oronitrophenol spectrophotometric methods, and the concentration of lysozyme by agar plate diffusion method. Random urine samples from 266 pregnant women were examined, 110 cases were normal pregnant women, 156 cases were PIH patients. RESULTS: (1) The level of NAG and lysozyme in moderate and severe PIH patients were significantly higher than that in mild PIH patients and normal pregnant women (P < 0.01) and it increased with the severity of disease. (2) There was a positive correlation between NAG and protein/creatinine (Pr/Cr) ratio in random urine. (3) There was a positive correlation between urinary lysozyme and serum beta 2-microglobulin (r = 0.874, P < 0.05). CONCLUSION: Determination of urinary NAG and lysozyme levels will differentiate various states of PIH.

Acetylglucosaminidase↗
PubMed1996

[The evaluation of cefmetazole in clinical use. The study group of cefmetazole in clinical use].

To study the clinical effect of cefmetazole (CMZ), we treated with CMZ 1,926 patients with various infections involving the respiratory tract, gastrointestinal tract, liver and biliary tract, skin and soft tissue and others. The marked effect rate was 56.5%, and the effect rate 33.7%. The sensitivity test of CMZ was also performed in vitro. Staphylococcus aureus, streptococcus, staphylococcus epidermis, E. coli, S. typhi, B. salmonella, B. shigella, B. Klebsiella pneumoniae, B. proteus, etc. were sensitive to CMZ. Injecting CMZ can prevent the infection of operation. The study of the adverse reaction of CMZ showed, an adverse reaction rate of 4.2% (the gastrointestinal tract, allergy, kidney and nervous system). These results suggested that CMZ is an antibiotic of broad spectrum, high efficacy and low toxicity. It is effective in treating sensitive bacterial infection, unknown pathogenic infection and mixed bacterial infection, and preventing infection in surgery.

Adolescent↗
PubMed1995

The DNA-binding domain of the hexameric arginine repressor.

The arginine repressor of Escherichia coli is a classical feedback regulator, signalling the availability of L-arginine inside the cell. It differs from most other bacterial repressors in functioning as a hexamer, but structural details have been lacking and its shares no clear sequence homologies with other transcriptional regulators. Analysis of the amino acid residue sequence and proteolytic cleavage pattern of the repressor was used to identify a region predicted to house the DNA-binding function. When this protein fragment is overexpressed from a clone of the corresponding gene fragment, it represses ornithine transcarbamylase levels in vivo, and binds to the operator DNA in vitro, both in an arginine-independent manner. Sedimentation equilibrium and gel filtration indicate that the purified protein fragment is a monomer in solution. The results thus define the domain organization of the repressor at low resolution, suggesting that the N and C-terminal portions of the polypeptide chain are separated by a structural and functional border that decouples hexamerization and arginine binding from DNA binding.

Allosteric Regulation↗
PubMed1995

Mechanism of time-dependent inhibition of 5 alpha-reductases by delta 1-4-azasteroids: toward perfection of rates of time-dependent inhibition by using ligand-binding energies.

Finasteride (17 beta-N-tert-butylcarbamoyl-4-aza-5 alpha-androstan-1-en-3- one) is a time-dependent, apparently irreversible inhibitor of 5 alpha-reductases, but does not fully inhibit the activity of 5 alpha-reductase in vivo. This limited efficacy has been attributed to its slow rate of inhibition against the type-1 isozyme [Tian, G. (1995) J. Pharm. Sci. (in press)]. Here the feasibility of increasing the rate of inhibition of 5 alpha-reductases by providing binding energies with the inhibitor at a site remote from the center of chemical transformation was explored. Substitution of N-(2,5-bis(trifluoromethyl)phenyl) group, which had been shown to benefit 6-azasteroids in the binding to 5 alpha-reductases [Frye, S., Haffner, C. D., Maloney, P. R., Hiner, R. N., Unwalla, R. J., Batchelor, K. W., Bramson, H. N., Stuart, J. D., Schweiker, S. L., Van Arnold, J., Bickett, D. M., Moss, M. L., Tian, G., Lee, F. W., Tippin, T. K., James, M. K., Grizzle, M. K., Long, J. E., & Croom, D. K. (1995) J. Med. Chem. 38, 2621-2627], for the N-tert-butyl substituent at C-17 of finasteride did not perturb the mechanism of inhibition but significantly increased the rate of inhibition of type-1 5 alpha-reductase. The rate of inhibition was too fast to determine accurately when the normal substrate testosterone was used in the progress curve analysis as this inhibition rate is approaching the value of kcat/Km for the enzyme reaction.

5-alpha Reductase Inhibitors↗