Biomedical subjects

Yu-Yang Li

Publications and source records attributed to Yu-Yang Li.

27 records · Page 2Linked to original sources

PubMed1998

Cloning of DNA Fragments Possessing Promoter Function from Kluyveromyces cicerisporus.

Using three yeast promoter-probe plasmids pSK-kan401, pSK-kan1105, pSK-kan1238 with different reading frames, eight DNA fragments possessing high efficient promoter function have been cloned from K. cicerisporus. Their 3'-DNA sequences have been analyzed. The relative strength of their promoter function was studied by comparing their ability to promote the expression of the reporter gene APHI with that of glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH) promoter in K. lactis. The results showed that the insertion fragments in pSK-kan401-41 and pSK-kan1105-51 have stronger promoter function and they are also functional in K. cicerisporus Y179.

Journal Article↗

PubMed1998

Cloning of GAP Gene from K. fragilis.

The K. fragilis CBS 397 gene library was screened with a GAP probe, which was designed according to the homology with S. cerevisiae, K. lactis, K. marxianus GAP gene. One positive clone pG1 containing GAP1 gene was isolated and confirmed by Southern hybridization. The GAP1 gene was partially sequenced. By using a fragment of the clone as a probe, another positive clone pG2 was acquired and also confirmed by Southern hybridization. The GAP2 gene from pG2 was completely sequenced. The upstream sequences of both genes were shown to have promoter activity. The fragment of pG1 could hybridize with three chromosomes of K. fragilis.

Journal Article↗

PubMed1997

The Mutation of mRNA Translation Initiation Region Influences Gene Translation.

In order to investigate the relationship between the structure of the mRNA translation initiation region (TIR) and gene expression, We mutated multiple sites of the 5' end of IFN-alpha8 and GM-CSF genes by site-directed mutagenesis without changing their amino acid sequences. SDS-PAGE showed that the protein products of mutated genes increased greatly in recombinant clones, as compared with their native genes. RNA dot blot revealed that the difference of their corresponding amount of mRNA transcribed between the native and the mutated genes was negligible. These results imply that the elevated expressions are attributed mainly to increased translation level. The prediction of mRNA secondary structure suggests that the delta G of TIR may have close relations to the expression level.

Journal Article↗

PubMed1997

Cloning of the K. fragilis PDI Gene.

The K. fragilis CBS 397 gene library was screened by the PDI probe, which was designed according to the homology with the S. cerevisiae PDI gene. One positive clone was found and confirmed. In order to learn its physical map,Southern hybridization was done on this positive clone. The K. fragilis PDI gene was found to locate in chromosome V genome. Its sequence was also made partly known by DNA sequencing. From the method of the turbidimetric assay of insulin disulfide reduction, we have also demonstrated that the cloned PDI gene can exhibit PDI activity.

Journal Article↗

PubMed1996

Cloning of the LAC4 Promoter from K. lactis and Studies on the Function of its UASII.

The -661 - +21 bp region of the LAC4 gene form K. lactis CBS141 was obtained by PCR technique and fused with the lacZ gene from E. coli to construct and expression vector YFD 114. It was then transformed into K. lactis Y167. The function of the cloned LAC4 promoter was tested by induction with galactose, lactose, sorbitol or IPTG. The results revealed that galactose had higher inducing effect than lactose while sorbitol and IPTG had no inducing effect. The insertion of chemically synthesized LAC4 UASII at just the upstream of the cloned LAC4 promoter could increase its basic and induced expression level. The extents of increase were different with the orientation and the copy number of the inserted UASII.

Journal Article↗

PubMed1996

The Construction and Application of the Multi-copy Integration Vector in K. lactis.

The vector pIRK was constructed by using a 2.2 kb EcoRI fragment of rDNA from Kluyveromyces lactis for targeted homologous recombination, with the URA3 gene from Saccharomyces cerevisiae acting as a selection marker. By the examination of the copy number, stability and chromosomal location of the vector in K. lactis transformants the results demonstrated that: (1) of the different transformants, the average copy number of the plasmid pIRK was 120 per cell; (2) after 50 generations of growth in rich medium, the vector displayed high stability. (3) all integration events occurred in the chromosome IV where genomic rDNA located. Using this vector, the LAC4 gene cloned from K. fragilis was expressed. The yield of beta-galactosidase related directly to the vector's copy number. The highest activity of beta-galactosidase produced by transformants was 8.6 times higher than that produced by the wild type strain of K. fragilis under the same conditions.

Journal Article↗

PubMedDate not supplied

Age-related modifications of circadian rhythm of serum leptin in healthy men.

BACKGROUND: Leptin, the product of the ob gene, is secreted by the adipocyte and is involved in the regulation of body weight, energy homeostasis and a wide spectrum of biological activities. OBJECTIVE: We studied how variations in circadian serum leptin levels change as people age. METHODS: Serum leptin levels were studied on a circadian basis in 26 men, 6 overweight (BMI >27.8) and 20 with normal weight. The normal-weight men were divided into four age groups: (A) in their 30s, (B) in their 40s, (C) in their 50s, and (D) in their 60s. Serum samples were drawn at 2-hour intervals from 8:00 to 22:00 and hourly from 22:00 to 8:00 for a total of 24 h. RESULTS: A significant circadian variation of leptin levels was found whatever the age with a peak at night and a trough around noon. The circadian leptin levels were higher in the older normal-weight groups (50s and 60s) and in the groups with a BMI >27.8. CONCLUSION: Our study demonstrates that changes in the characteristics of the circadian rhythm of serum leptin in healthy men are associated with both advancing age and increased BMI.

Adult↗

PubMedDate not supplied

Quantitative study of circadian variations of ambulatory blood pressure in Chinese healthy, hypertensive, and diabetes subjects.

Ambulatory blood pressure monitoring (ABPM) recorded abundant data of BP and heart rate (HR) variations with even more derived parameters for evaluation of BP. Using our ABP database system established recently, we studied quantitatively the data of 24-hr ABP in Chinese. First, 155 Chinese were divided into three groups: 50 healthy subjects (C) of 20 men and 30 women, aged 60.0 +/- 10.3 (SD) years; 58 hypertensive patients (H, mild or moderate hypertension) of 33 men and 25 women, aged 59.4 +/- 8.0 years; 47 diabetes patients (D, type 2 diabetes, all were normotensive and with no insulin treatment) with 28 men and 19 women, aged 61.0 +/- 8.5 years. Then 24-hr ABP was monitored by TM-2421 Monitor and data were analyzed by ABP database, cosinor method, and conventional statistics. Our results were 4-fold: 1) systolic BP (SBP), diastolic BP (DBP), HR, rate-pressure product (HR x SBP) showed circadian variations, and significant circadian rhythms were confirmed by cosinor method in all groups. MESOR (midline estimate statistic of rhythm) differed significantly among three groups (H had the highest and C had the lowest values); 2) BP means (SBP, DBP, pulse pressure [PP], and HR x SBP) and BP loads (SBP, DBP, and PP) showed significant differences among the groups (H and D had higher values than that of C); 3) there were no significant differences of BP variability (BPV) of SBP, DBP, and PP among the groups; 4) areas under curve of BP (SBP, DBP, and PP) in H were significantly higher than in C and there was no significant difference between H and D. We concluded that ABPM can offer abundant information on BP evaluation by its direct recording data and derived parameters. The computerized way of treating the large numbers of ABPM values supplies a useful tool in evaluation of BP. Our results suggest that clinically normotensive diabetes patients had some pathological alterations in their BP systems.

Adult↗

PubMedDate not supplied

Overweight influence on circadian variations of ambulatory blood pressure in Chinese adolescents.

Childhood obesity and its consequences have been the subject of intense interest in recent years. In this study we examined the influence of overweight on circadian variations of ambulatory blood pressure (ABP) in Chinese adolescents. First, 24-hr ABP monitoring was performed in 252 adolescents divided into two groups with equivalent sex, age, and body height (49 girls and 77 boys in each group): controls (normal weight) were aged 13.68 +/- 1.21 years, height 165.37 +/- 9.45 cm, body mass index (BMI) 18.82 +/- 2.3; overweights (BMI > or = 24) were aged 13.71 +/- 1.23 years, height 165.75 +/- 9.47 cm, BMI 27.70 +/- 3.1. ABP recordings were treated by ABP database system and analyzed by cosinor method and conventional statistics methods. The circadian variations of ABP in adolescent patterned as "dipper" and circadian rhythmicity of ABP variations were confirmed by cosinor analysis in most adolescents of both groups. Significant statistical differences were found for rhythm parameters: the MESOR (midline estimate statistic of rhythm), peak, trough (the maximum and minimum values derived from the composed curves, respectively), and amplitude values between control and overweight groups. Significant higher values also were seen in the overweight group for most of ABP parameters (p < .01), such as, BP means (SBP, DBP, MAP: mean arterial pressure, or PP: pulse pressure), BP variability, BP loads and rate-pressure product (HR x SBP). Our results have shown that overweight influenced significantly on ABP and parameters derived from ABP recordings in Chinese adolescents, which suggests an increasing risk of cardiovascular diseases in overweight adolescents.

Adolescent↗