Search PubMed⌕ Search

Biomedical subjects

H Yuan

Publications and source records attributed to H Yuan.

At least 91 records · Page 5Linked to original sources
PubMed1999

Type 2 Cu2+ in pMMO from Methylomicrobium album BG8.

EPR spectra were obtained for the type 2 Cu2+ site in particulate methane monooxygenase (pMMO) from Methylomicrobium album BG8 grown on K15NO3 and 63Cu(NO3)2. The concentration of the type 2 Cu2+ signal was approximately 200 microM per 25 mg/ml protein in packed cells and membrane fractions, a concentration that is consistent with its attribution to pMMO, and the EPR parameters were consistent with electron paramagnetic resonance (EPR) parameters previously assigned to pMMO. The superhyperfine structure due to nitrogen is better resolved because I = 1/2 for 15N whereas I = 1 for 14N and A(15N)/A(14N) = 1.4. Under these conditions, superhyperfine structure is resolved in the g region of the X-band spectrum. At low microwave frequency (S-band) the resolution of the nitrogen superhyperfine structure improves. Signals are attributed to type 2 Cu2+ in which cupric ion is bound to four (less likely three) nitrogen donor atoms.

Amino Acid Sequence↗
PubMed1999

A preliminary study on osteoinduction of two kinds of calcium phosphate ceramics.

With respect to the effect of material factors on calcium phosphate biomaterial-induced osteogenesis, the osteoinductive property of two kinds of porous hydroxyapatite ceramics, which were made by different producers, was investigated in dorsal muscles of dogs. One hydroxyapatite ceramic (S-HA), macroporous implants with rough pore walls containing abundant micropores, was made by Sichuan Union University (Chengdu, China); the other hydroxyapatite ceramic (J-HA), porous implants with smooth macropore walls composed of regularly aligned crystal grains, was provided by Mitsubishi Ceramic Int. (Japan). Different tissue response was detected histologically and microradiographically after the ceramic samples had been implanted in dorsal muscles of dogs for 3 and 6 months. Bone formation was found in S-HA at 3 months, which increased at 6 months. In contrast, no bone formation was detected in J-HA at both 3 and 6 months. These results indicate that with the special architecture, calcium phosphate ceramic can induce bone formation in soft tissue. As both materials were very similar in their chemical and crystallographic structures, but varied in their microstructures, the latter seem to be an important factor affecting the osteoinductive capacity of calcium phosphate ceramics. These data suggest that, by controlling the preparation of calcium phosphate ceramic, bone substitutes with intrinsic osteoinductive property can be developed from calcium phosphates.

Animals↗
PubMed1999

HLA-DR-DQ alleles and HLA-DP alleles are independently associated with susceptibility to different stages of post-schistosomal hepatic fibrosis in the Chinese population.

Abstract: Evaluation of human leukocyte antigen (HLA) class I and class II genes was performed on patients from China with Schistosomiasis japonica. Patients were categorized as grade 0 (n=44), grade I (n=81), grade II (n=99), or grade III (n=6) based on increasing severity of hepatic fibrosis due to repeated Schistosoma japonicum infections. These results show that the HLA-DRB1*1101-DQA1*0501-DQB1*0301 (Pc<0.02) and HLA-DRB1*1501-DRB5*0101 (Pc<0.02) haplotypes are associated with protection and susceptibility to grade I fibrosis, respectively, and that the HLA-DPA1*0103 -DPB1*0201 haplotype (Pc<0.02) is associated with protection from both grade II and III severe fibrosis. There was no association between HLA-B DNA haplotypes and the disease. These findings indicate that the HLA-class II molecules play a role in preventing or promoting fibrotic liver change after deposition with Schistosome eggs. Moreover, a tendency was observed within the HLA class II genes for the HLA-DR-DQ alleles to be associated with protection against early changes in liver fibrosis, whereas HLA-DP alleles were associated with protection from the late phase of fibrosis or severe hepatosplenic schistosomiasis.

Alleles↗
PubMed1999

Determination of equilibrium constant of alkylbenzenes binding to bovine serum albumin by solid phase microextraction.

Solid phase microextraction (SPME) coupled with GC has been applied to study the binding properties between bovine serum albumin (BSA) and volatile organic compounds such as benzene, toluene, ethylbenzene, propylbenzene and butylbenzene. Their protein-ligand equilibrium constants have been determined. The measurement of free and bound ligand concentrations in the aqueous solution was based on the equilibrium among the analyte in the fiber coating (Cf), headspace (Ch) and aqueous solution (Cs). The work demonstrated that SPME is a simple and effective method in the study of protein binding to measure the freely dissolved analyte concentration as well as the equilibrium constant. The theoretical aspect of the SPME applied to the equilibrium constant measurement in two-phase (liquid sample-fiber coating) and three-phase (liquid sample-headspace-fiber coating) systems has been thoroughly discussed. The results demonstrated that the interpretation of the calibration data is crucial to the determination of freely dissolved analyte concentration and the equilibrium constant especially when the sample volume is small. The error in the experimental system is discussed. It is demonstrated in this study that for the three-phase system the amount of the analyte partitioned in the headspace could be ignored only in certain circumstances, where the Henry's law constant and the ratio between headspace volume and sample volume are sufficiently small.

Animals↗
PubMed1999

The Arabidopsis dwarf1 mutant is defective in the conversion of 24-methylenecholesterol to campesterol in brassinosteroid biosynthesis.

Since the isolation and characterization of dwarf1-1 (dwf1-1) from a T-DNA insertion mutant population, phenotypically similar mutants, including deetiolated2 (det2), constitutive photomorphogenesis and dwarfism (cpd), brassinosteroid insensitive1 (bri1), and dwf4, have been reported to be defective in either the biosynthesis or the perception of brassinosteroids. We present further characterization of dwf1-1 and additional dwf1 alleles. Feeding tests with brassinosteroid-biosynthetic intermediates revealed that dwf1 can be rescued by 22alpha-hydroxycampesterol and downstream intermediates in the brassinosteroid pathway. Analysis of the endogenous levels of brassinosteroid intermediates showed that 24-methylenecholesterol in dwf1 accumulates to 12 times the level of the wild type, whereas the level of campesterol is greatly diminished, indicating that the defective step is in C-24 reduction. Furthermore, the deduced amino acid sequence of DWF1 shows significant similarity to a flavin adenine dinucleotide-binding domain conserved in various oxidoreductases, suggesting an enzymatic role for DWF1. In support of this, 7 of 10 dwf1 mutations directly affected the flavin adenine dinucleotide-binding domain. Our molecular characterization of dwf1 alleles, together with our biochemical data, suggest that the biosynthetic defect in dwf1 results in reduced synthesis of bioactive brassinosteroids, causing dwarfism.

Alleles↗
PubMed1999

Brassinosteroid-insensitive dwarf mutants of Arabidopsis accumulate brassinosteroids.

Seven dwarf mutants resembling brassinosteroid (BR)-biosynthetic dwarfs were isolated that did not respond significantly to the application of exogenous BRs. Genetic and molecular analyses revealed that these were novel alleles of BRI1 (Brassinosteroid-Insensitive 1), which encodes a receptor kinase that may act as a receptor for BRs or be involved in downstream signaling. The results of morphological and molecular analyses indicated that these represent a range of alleles from weak to null. The endogenous BRs were examined from 5-week-old plants of a null allele (bri1-4) and two weak alleles (bri1-5 and bri1-6). Previous analysis of endogenous BRs in several BR-biosynthetic dwarf mutants revealed that active BRs are deficient in these mutants. However, bri1-4 plants accumulated very high levels of brassinolide, castasterone, and typhasterol (57-, 128-, and 33-fold higher, respectively, than those of wild-type plants). Weaker alleles (bri1-5 and bri1-6) also accumulated considerable levels of brassinolide, castasterone, and typhasterol, but less than the null allele (bri1-4). The levels of 6-deoxoBRs in bri1 mutants were comparable to that of wild type. The accumulation of biologically active BRs may result from the inability to utilize these active BRs, the inability to regulate BR biosynthesis in bri1 mutants, or both. Therefore, BRI1 is required for the homeostasis of endogenous BR levels.

Alleles↗
PubMed1999

Familial density of alcoholism and onset of adolescent drinking.

OBJECTIVE: Utilizing a longitudinal prospective design, the purpose of this study was to: (1) assess the age of onset to begin drinking in relation to family history of alcoholism using survival analysis, and (2) examine the importance of selected risk factors in predicting outcome, using a Cox proportional hazards model analysis. METHOD: Fifty-two children and adolescents at low risk for developing alcoholism and 73 children and adolescents from high-risk families were studied. Subjects, spanning the ages of 7 to 18, were evaluated annually (268 total evaluations), providing 2.1 waves of longitudinal data concerning age of onset along with a number of predictors (positive familial loading of alcoholism, extraversion, and manifest anxiety scores). RESULTS: High-risk children showed a significantly earlier age of onset to begin drinking. The Cox proportional hazards analysis revealed that the onset could be predicted by a positive familial loading of alcoholism and extraversion. Further analyses revealed that extraversion was a mediator of the familial density effect. CONCLUSIONS: Age of onset to begin drinking has been shown in general population studies to predict the likelihood of developing alcohol/abuse/dependence problems. Further follow-up will determine if these high-risk children develop alcohol abuse/dependence at higher rates than control children. Further follow-up would also establish links between early childhood predictors, such as having an extraverted temperament and development of alcohol problems.

Adolescent↗
PubMed1999

Sexual dimorphism of the human spinal cord in the aging process.

There have been few morphometric studies on age-related changes in the human spinal cord. The purpose of the present study was to determine the existence of sexual dimorphism of the spinal cord between males and females during the aging process. Spinal cords were removed from cadaver specimens, 26 males and 22 females for anatomic practice, the age at death ranged from 41 to 97 years for males (average, 71.5 years) and from 59 to 92 years for females (average, 76.6 years). Spinal cord segments were embedded in celloidin after secondary fixation and dehydration. Sections were stained with the Luxol fast blue-periodic acid-Schiff-hematoxylin and Klüver-Barrera methods. Morphometric analysis was performed with an electronic optical planimeter and a computer. Each section was enlarged 13.5 times to take a picture. The areas of the transverse section white matter and gray matter of the spinal cord at segments C5 and L3 were measured. Although there was no correlation between the total transverse area of the spinal cord and age either in males or females, we noticed that the area of the gray matter decreased faster in males than in females; while the area of the white matter decreased faster in females than in males. The area ratio of the white matter to the whole segment area of the spinal cord (W/T) at level C5 is larger in males than that in females. Our results suggest that there could be a difference between males and females in changes in the white and gray matters of the spinal cord due to aging.

Adult↗
PubMed1999

The mental health status of women in the Navy and Marine Corps: preliminary findings from the Perceptions of Wellness and Readiness Assessment.

The 1995 Perceptions of Wellness and Readiness Assessment was designed to provide baseline health and risk-factor information on the physical and mental health status of women in the U.S. Navy and Marine Corps and to make comparisons both within military subpopulations and with civilian populations. A population-based, multi-stage, cluster sample of 782 active duty Navy and Marine Corps women and men were administered a structured computerized telephone interview to make Diagnostic and Statistical Manual-III-R psychiatric diagnoses. Estimates were 40 and 21% for overall lifetime and 1-year prevalence of psychiatric disorders, respectively. Women had about five times the risk of experiencing post-traumatic stress disorder than men and about twice the risk of a major depressive episode. Of all personnel meeting diagnostic criteria for an active mental disorder, only 19% sought mental health care in the last year. Women generally sought treatment more readily than men.

Adult↗
PubMed1999

[Screening for mitochondrial 1555(G) mutation in patients with aminoglycoside antibiotic-induced deafness].

OBJECTIVE: To identify the incidence of the 1555(G) mutation in pedigrees and sporadic patients with aminoglycoside antibiotic- induced deafness so as, to privide the theoretical evidence for establishing the method of diagnosis of this disease. METHODS: Blood samples were obtained from two pedigrees and seven sporadic patients with aminoglycoside antibiotic-induced deafness, and five mothers of the sporadic patients. DNA was extracted from the isolated leukocytes. The mitochondrial DNA fragments were amplified by PCR; 1555(G) mutation was detected by Alw26 I restriction endonuclease digestion. RESULTS: Fourteen individuals from two pedigrees carried homoplasmic 1555(G) mutation. Seven sporadic patients and the five mothers did not have 1555(G) mutation. CONCLUSION: The incidence of the 1555(G) mutation in pedigrees with aminoglycoside antibiotic-induced deafness is fairly high, while in sporadic patients is low. Screening for mitochondrial 1555(G) mutation is of potential value to clinical use.

Adolescent↗
PubMed1999

[Evaluation on the quality of life among cardiac carcinoma cases--fifteen years after surgical treatment].

OBJECTIVE: To investigate factors affecting the quality of life among long-term survivors after resection of cardiac carcinoma. METHODS: Follow-up study on the quality of life among 68 cases with carcinoma of the cardia who survived over 15 years postoperatively in our hospital, was conducted between January 1996 and June 1998. RESULTS: Results showed that 88.2% of the patients had a high sense of well-being, 86.8% of them were able to eat ordinary food, 64.7% of them could carry on regular work as well as physical labor. 89.7% of the patients were satisfied with their quality of life and 77.9% of them felt excellent. CONCLUSION: The postoperative mental status and the occurrence of long-term complications in digestive tract played an important roles in affecting the quality of life.

Aged↗
PubMed1999

[Analysis of patients survived over ten years after resection of gastric cardia carcinoma].

OBJECTIVE: To investigate factors affecting long-term survival in patients with resected gastric cardia cancer. METHODS: Survival was analyzed retrospectively in 584 patients with gastric cardia carcinoma who received tumor resection from 1964 through 1982. RESULTS: The 10-year survival rate was 17.1%. The major factors influencing survival were clinical staging, degree of differentiation, gross tumor type and size (P < 0.05) and status of lymph node metatasis (P < 0.01). Residual tumor at resection edge and tumor thrombi did not significantly affect survival, nor did sex/age, and course of the disease. CONCLUSION: Early detection, early diagnosis and early surgical resection are the key to improve 10-year survival of patients with resected cancer of the gastric cardia. Why residual tumor left at the resection edge and the presence of tumor thrombi do not influence survival needs to be further studied.

Adult↗
PubMed1999

[Establishment of a stochastic model for variation in fecal Schistosoma japonicum egg count and estimation of its parameters].

OBJECTIVE: To establish a stochastic model suitable for interpreting the variation in fecal Schistosoma japonicum egg count, and to estimate its parameters and to describe it. METHODS: Total variation in fecal egg count with a stochastic model can be divided into two kinds of sources, (1) inter-individual variation, and (2) intra-individual variation. Parameters in the model were estimated with the data collected in actual fecal egg count. RESULTS: Parameters M and r differed and k kept nearly the same in various age groups. The best cut-off point of r and M for age-splitting was at eight and 12 years, respectively. Parameter k was assumed the same in different age groups in the model E, and r differed in the groups of 2 - 7 years and 8 years of age, and M differed in the groups of 2 - 11 years and 12 years of age, with a minimum value of Akaike information criterion (AIC). CONCLUSION: Age may be an important factor contributing to the estimations of parameters M and r, and the model E was the best one.

Adolescent↗
PubMed1999

[Determination of stilbene in radix Polygoni multiflori by HPLC and its stability study].

OBJECTIVE: To develop a HPLC method for determining stilbene in Radix Polygoni Multiflori and studying its stability. METHOD: HPLC conditions: An Econosphere C18 column, a mixture of methanol-water(30:70) as mobile phase, and UV detection at 310 nm. In addition, the stability of stilbene was studied at high temperature and in acidic solution. RESULT: The linear range of calibration curve was 2.24 x 10(-2)-1.12 x 10(-1) micrograms(n = 6) with a correlation coefficient of 0.99998, the average recovery with RSD being 99.96% +/- 1.54%. CONCLUSION: The method is sensitive, accurate and speedy. Stilbene in aqueous solution is stable, but high temperature(80 degrees C) tends to affect the stability. In acidic solution no stability can be found.

Drug Stability↗
PubMed1999

[Radiofrequency treatment of ethmoidal nerve with allergic rhinitis under nasal endoscopy].

OBJECTIVE: To study the effect of radiofrequency treatment of ethmoidal nerve on allergic rhinitis. METHOD: Eighty-eight cases of allergic rhinitis were treated with ethmoidal nerve radiofrequency under nasal endoscopy. RESULT: It showed marked effectiveness in 73 cases (83.0%), immprovement in 11 cases (12.5%) and failed in 4 cases (4.5%) in one year follow-up. The overall effective rate was 95.5%. CONCLUSION: This result indicated that it is a choice for treating allergic rhinitis to apply ethmoidal nerve radiofrequency under nasal endoscopy.

Adolescent↗
PubMed1999

[Study on family aggregation of cases of advanced schistosomiasis japonica].

AIM: To explore the family aggregation of advanced schistosomiasis japonica. METHODS: Eighty-one cases of advanced schistosomiasis(AS) and 67 cases of non-advanced schistosomiasis with history of infections in Yushan County, Jiangxi Province were chosen as proband groups and control groups respectively, then grades 1 and 2 relatives of them were investigated on AS. Family aggregation of AS was analyzed through comparing the prevalence rate between the close and distant relatives of probands and controls and fitting the observed distribution of AS cases among the population by zero-truncated Poisson distribution and zero-truncated negative binomial distribution. RESULTS: The prevalence rate was higher in the close relatives (Group I relatives) of the probands than in the distant relatives(Group II relatives) of the probands and in the controls' relatives. The observed distribution of AS was beyond the probability of the zero-truncated Poisson distribution, but consistent with the zero-truncated negative binomial distribution. CONCLUSION: Family aggregation of advanced schistosomiasis does exist.

Adult↗
PubMed1998

Inhibition of host RNA polymerase II-dependent transcription by vesicular stomatitis virus results from inactivation of TFIID.

During infection with vesicular stomatitis virus (VSV), host-cell mRNA synthesis is inhibited due to shut off of host-cell transcription. The transcriptional activity of nuclear extracts prepared from VSV-infected cells was compared to the activity of nuclear extracts from uninfected cells. An exogenous DNA template was used which contained an adenovirus major late promoter (AdMLP) but lacked upstream activating sequences, so that only basal transcription activity was assayed in these experiments. AdMLP-initiated transcription was decreased by 75% in nuclear extracts from infected cells as early as 3 h p.i. and by >90% by 6 h p.i. Mixing nuclear extracts from uninfected and VSV-infected cells revealed that the inhibition was caused by lack of an active form of a host factor involved in basal transcription rather than by the presence of an excess of inhibitory factor. To determine which transcription factors were lacking from nuclear extracts of infected cells, host transcription initiation factors isolated from uninfected cells by ion-exchange chromatography were added separately to nuclear extracts inactivated by VSV infection. A phosphocellulose column fraction from uninfected cells eluted with 0. 8 M KCl, which contained transcription factor IID (TFIID), overcame the inhibition. The corresponding fraction from infected cells had no detectable activity in a TFIID-dependent in vitro transcription assay. TATA-binding protein (TBP) is the DNA-binding subunit of TFIID and has been shown previously to substitute for TFIID in basal transcription. Purified recombinant TBP also reconstituted the transcription activity of nuclear extracts from infected cells, supporting the idea that TFIID is the target of virus-induced inhibition. Western blot analysis showed that the level of TBP in nuclear extracts or in the 0.8 M KCl column fraction was not changed by VSV infection. These results indicated that VSV infection leads to an inhibition of host transcription by inactivation of TFIID rather than reduction in the level of TFIID.

Blotting, Western↗