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Biomedical subjects

S Yang

Publications and source records attributed to S Yang.

At least 595 records · Page 33Linked to original sources
PubMed1992

Regulatory mode of the pac gene expression.

1.65kb HindIII-BgIII DNA fragment containing pac operator was cloned from plasmid pPA4 to pBR322 at HindIII-BamHI sites, the resultant plasmid pPA41 was transformed into E. coli D816 carrying an intact pac operon on its chromosome, then the effect of operator titration was estimated. It was found that the penicillin acylase activity in E. coli D816 (pPA41) cells was higher than that of in E. coli D816 cells. The operators on high copy number plasmid pPA41 competed for the regulatory proteins with the single copy operator on the chromosomal pac operon, thus the expression of the pac gene was enhanced, because the free regulatory proteins were decreased by operator titration. The results of RNA-DNA hybridization showed that the cellular pac mRNA concentration was parallel to the penicillin acylase activity, and the pac mRNA in E. coli D816 (pPA41) cells was much higher than that of in E. coli D816 cells. These results indicated that the expression of pac gene was negatively controlled at transcriptional level.

Biotechnology↗
PubMed1992

Cloning of par region and the effect of par region on the stability of pUC9.

The par region of pSC101 was cloned into pUC9, and pEC302 was obtained. The stability of pEC302 and pUC9 in E. coli HB101 was tested on M9 medium to determine the effect of par region on the stability of plasmid. After 40 generations, pUC9 was almost completely lost, while pEC302 was 100% maintained in host cells.

Biotechnology↗
PubMed1992

Location and trans-action of the pac regulatory gene.

The study on the localization of the pac gene indicated that the regulatory and structural genes were located in a 3.5 kb HindIII-EcoRI fragment. In this paper we report that a series of deletion derivatives of plasmid pPA6 was constructed and the effect of deletions on the pac expression was determined. The results suggested that the pac regulatory gene was located in the SphI-PvuII fragment within the pac structural gene. Then the SphI-PvuII fragment was cloned to the plasmid pTZ18U at the SphI-SmaI sites and the resultant plasmid pPA57 was transformed into the penicillin acylase producing strain E. coli D816 to observe the effect of SphI-PvuII fragment on the chromosomal pac expression. The results demonstrated that the regulatory gene within the SphI-PvuII fragment regulated the pac expression in trans. Computer analysis indicated that there were two ORFs in the SphI-PvuII fragment as possible candidates coding for the regulatory protein. The study on precise localization of the pac regulatory gene is in progress.

Amino Acid Sequence↗
PubMed1992

[Refractive error and amblyopia in children].

The refractive status of 3,099 children was analyzed. The result showed that the incidence and degree of hyperopia decreased gradually and those of myopia increased along with the growing up of children in ametropia. In binocular refractive amblyopia, high and medium hyperopia and myopia in severe and medium amblyopia were significantly more than those in mild amblyopia. In monocular refractive amblyopia, high and medium hyperopia and high myopia in the amblyopic eyes were more than those in the nonamblyopic eyes. The refractive status of binocular esotropic amblyopia had no significant difference in various ages and degrees of amblyopia. There was also no significant difference between the refractive status of the amblyopic and nonamblyopic eyes in monocular esotropic amblyopia. It was considered that refractive amblyopia was closely related to high ametropia and the deviation of the eye might be the main cause of strabismic amblyopia.

Adolescent↗
PubMed1992

[Measuring the threshold of stereopsis for 111 children with amblyopia].

The threshold of stereopsis was measured by static stereopter for 111 children with amblyopia aged from 4 to 13 years. They were divided into three groups: 38 cases ranging in age from 4 to 5 years, 43 cases 6 to 7 and 30 cases 8 to 13. Fifty six cases were unilateral and 55 bilateral amblyopia. The average threshold of stereopsis was 149.64 second angle for the 4-5 group, 66.69 for the 6-7 and 48.48 for the 8-13. The average threshold for unilateral amblyopia was 65.3, in which mild type was 38.6 and under moderate type was 88.84, whereas the average threshold for bilateral cases was 115.81, in which mild type was 44.09 and under moderate type was 175.44. The distribution of stereopsis for different age groups, the threshold of stereopsis influenced by different types of amblyopia and the comparison of amblyopia between bilateral and unilateral are also discussed.

Adolescent↗
PubMed1992

[Chondronecrosis induced in rhesus monkeys fed with grains and water of Kaschin-Beck's disease endemic area].

Immature Rhesus monkeys were fed with grains and/or water of Kashin-Beck disease (KBD) endemic area for 6 or 18 months. Multifocal and zonal chondronecrosis and a series of secondary reactions following necrosis were found in articular cartilage and growth plate in most of the monkeys. These changes are very similar to the characteristics of human KBD. The results suggest that growing Rhesus monkey should be the susceptible animal for reproduction of chondronecrosis model of KBD and the articular cartilage of greater trochanter proximal to femur is a portion predisposing to cartilage lesions. The experiment also indicated that pathogenic factor resulting in chondronecrosis is still remaining in water and grains of endemic area, though the area is no longer actively endemic for KBD.

Animals↗
PubMed1992

[Purification and characterization of alpha-glucosidase from an extreme thermophile, Thermus thermophilus HB 8].

A highly thermostable alpha-glucosidase (E C.3.2.1.20) from an extreme thermophile, Thermus thermophilus HB 8, was purified to homogeneous by ammonium sulfate fractionation, DEAE-cellulose chromatography and preparative slab gel electrophoresis. The enzyme was purified 17 fold with 21% recovery of activity. The enzyme had a molecular weight of 67000 by SDS-PAGE. The isoelectric point was pH4.5 by IEF on PAG. The enzyme hydrolized p-nitrophenyl-alpha-glucoside (PN-PG), sucrose and maltose, but not cellobiose, melibiose and soluble starch. The km value for PNPG was 0.4mmol/L, the Vmax was 0.29 mumol.min-1.mg-1. The enzyme exhibited high thermostability. After incubation at 90 degrees C for 10 h in 50 mmol/L acetate buffer pH 5.8, the enzyme retained 90% of its original activity. The half-live (t1/2) at 95 degrees C was 108 min. The enzyme was activated by Mg2+, Mn2+, Ca2+, Ba2+ and strongly inhibited by Hg2+, Cu2+. Modification of the enzyme by EDC or DEPC led to complete loss of activity, which suggests that carboxyl group(s) and histidine residue(s) are essential for activity of alpha-glucosidase.

Thermus thermophilus↗
PubMed1991

Altered T cell subpopulations and lymphocytes expressing natural killer cell phenotypes in patients with progressive systemic sclerosis.

Scleroderma (progressive systemic sclerosis [PSS]) is known to be associated with abnormal T cell immunoregulation. In the present study, we evaluated lymphocyte phenotypes in patients with PSS and normal control subjects by flow cytometry and monoclonal antibodies for total T (CD3), T suppressor (CD8), T helper (CD4), T helper-inducer (CDw29), T suppressor-inducer (CD45R), human leukocyte antigen, DR+B (CD19), DR+T, and natural killer subsets, HNK-1 (CD57) and NKH-1 (CD56) cells. Patients with PSS compared to normal subjects had significantly lower percentages of CD3+ (p less than 0.005) and CD8+ (p less than 0.05) (similar to several patients with rheumatoid arthritis also evaluated), as well as CD45R (p less than 0.05), T+DR+ (p less than 0.05), and NKH-1 (CD56) (p less than 0.0005) cells. Patients with PSS with late-limited or generalized disease had lower percentages of CD8+, CD19, NKH-1+, and CDw29, but higher percentages of CD4+, HNK-1, and CD45R cells compared to patients with early stage disease, but these results were not statistically significant. These unique alterations in patients with PSS may prove to be useful in monitoring the stage of disease activity for therapy and further define immunologic defects.

Adult↗