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Biomedical subjects

C H Yao

Publications and source records attributed to C H Yao.

18 recordsLinked to original sources
PubMed1992

Stroke in China (Sino-MONICA-Beijing study) 1984-1986.

We present here the results of the Sino-MONICA-Beijing stroke study based on 700,000 Beijing residents in 1984-1986. To compare incidence rates for stroke with other communities and countries, we adopted the criteria of the WHO Collaborative Study of 17 centers which used the same definition and methodology as was used in this study. Over the 3-year period of the study, 2,593 stroke events were registered in the 25- to 74-year age-group. The incidence rate for all strokes was 189.5/100,000 and the incidence rate for first strokes was 133.6/100,000. Men had a significantly higher incidence rate than women (all strokes 219.7/100,000 for male vs. 160.5/100,000 for female, OR = 1.32, 99% limits 1.19-1.46; first strokes 151.6/100,000 for male vs. 116.4/100,000 for female, OR = 1.25, 99% limits 1.11-1.42). In comparison with other studies, age-adjusted incidence rate of stroke in Beijing was higher than in other countries, especially for hemorrhagic stroke. The proportion of hemorrhagic stroke related to other types of stroke was also higher in Beijing. Further analysis of the cases confirmed by computerized tomography also supported this finding. Unlike the incidence rates, the 4-week case fatality rate for women, 39.5%, was higher than for men, 32.8%. This finding was confirmed by a multiple logistic analysis controlling for age (p less than 0.001) and for previous stroke (p less than 0.001). The adjusted sex difference is also significant (OR = 1.37, p less than 0.001). In addition, results showed that men had a higher hospitalization rate than women. More women than men were treated at home, possibly indicating better medical care for men.

Adult↗
PubMed1991

Anthropometric predictors of coronary heart disease and total mortality: findings from the US Railroad Study.

Prospective data from the US Railroad Study were used to investigate the relations of several anthropometric variables to coronary heart disease and all-cause mortality in males initially free of cardiovascular disease. Middle-aged men were examined in 1957-1960 and followed until 1977 or death. Anthropometric indicators of total body fat (body mass index and the sum of the subscapular and triceps skinfolds) and central body fat (the ratios chest circumference/biacromial (shoulder) diameter, and chest circumference/standing height) were significantly and directly associated with age-adjusted coronary heart disease mortality. When systolic blood pressure, serum cholesterol, cigarette smoking, and vital capacity were also taken into account, the ratio chest circumference/biacromial diameter remained significantly associated with coronary heart disease mortality. Total, central, and peripheral body fat had a "U"-shaped relation with all-cause mortality. Measures of the ratio of central to peripheral body fat were inconsistently related to mortality. These results indicate that certain anthropometric measurements, especially those that may indicate central adiposity, are positively related to the development of fatal coronary heart disease and quadratically related to all-causes death rates.

Adult↗
PubMed1991

Transformation of Tetrahymena to cycloheximide resistance with a ribosomal protein gene through sequence replacement.

A method for transforming Tetrahymena has been established earlier, but its application has been limited because of the lack of selectable markers other than the rRNA-encoding DNA (rDNA). Mutations in the yeast ribosomal protein L29 gene (CYH2) are known that confer cycloheximide resistance. We have cloned and sequenced the homologue of this gene from both a wild-type and a cycloheximide-resistant (ChxA) strain of Tetrahymena. Surprisingly, a comparison shows that the ChxA mutation is not present in the CYH2 homologue. We therefore created the yeast mutations in the Tetrahymena gene by site-directed mutagenesis and used them to transform Tetrahymena either with or without linking to an rDNA vector. All clones transformed by the rDNA vector also became resistant to cycloheximide when the rDNA contained the engineered mutant genes. Without the rDNA vector, the mutant genes transform approximately 1% of injected cells to become resistant to cycloheximide. DNA analysis indicates that transformation occurs by replacement of the host sequence and not by random integration of the injected sequence. The replacement occurs to some but not all copies of this gene in the polyploid macronuclear genome. Thus, transformation in Tetrahymena occurs by specific sequence replacement, and the injected mutant genes can serve as dominant selectable transformation markers in this organism.

Amino Acid Sequence↗
PubMed1991

A mutation in the large subunit ribosomal RNA gene of Tetrahymena confers anisomycin resistance and cold sensitivity.

Anisomycin, an antibiotic that specifically inhibits the peptidyl transfer function of eukaryotic ribosomes, has been used to select resistant mutants in Tetrahymena thermophila. A mutation conferring anisomycin resistance (an-r) has been localized to a 1.2-kb fragment of the large subunit ribosomal RNA (rRNA) gene by transformation via microinjection. A single base pair change was detected within this region. Nine independently isolated an-r mutants had the same base pair change. T. thermophila strains that are homozygous for this mutation are cold sensitive, unable to mate and grossly abnormal in cell morphology.

Animals↗
PubMed1990

The controlling sequence for site-specific chromosome breakage in Tetrahymena.

Site-specific chromosome breakage occurs in many ciliated protozoa during nuclear differentiation. We have determined the cis-acting sequence that controls this process in Tetrahymena thermophila. The Tetrahymena ribosomal RNA gene is bounded by two breakage sites. Injection of this gene into developing macronuclei leads to breakage at these sites. Deletion analysis has localized the sequences essential for breakage to a 28 bp region that includes a 15 bp sequence (Cbs) known to be present in other breakage sites. Insertions of Cbs allow breakage to occur at new sites, which is accompanied by elimination of surrounding DNAs and formation of telomeric sequences, as it is at natural sites. Thus, Cbs is the necessary and sufficient sequence signal for chromosome breakage in Tetrahymena.

Animals↗
PubMed1990

Cardiovascular community control programs in Beijing.

Cardiovascular community control program in Beijing started in 1969. In the past 20 years, eleven such programs had been established, covering a total population of 750,000. For those programs that have been operating for over 5-10 years, a marked drop in the mortality and morbidity rates of hypertension, stroke and acute myocardial infarction has been observed. It is proposed that this type of community control program should be further expanded in the next ten years so as to materialize the WHO goal of "Health for all by 2000".

Cerebrovascular Disorders↗
PubMed1989

Accurate processing and amplification of cloned germ line copies of ribosomal DNA injected into developing nuclei of Tetrahymena thermophila.

The ciliate Tetrahymena thermophila contains a chromosomally integrated copy of the rRNA genes (rDNA) in its germinal (micronuclear) genome. These genes are excised from the chromosome through a process involving site-specific DNA breakage, become linear palindromic molecules with added telomeres, and are greatly amplified during development of the somatic nucleus (macronucleus). In this study, we cloned a 15-kilobase segment of the germ line DNA containing these genes and injected it into developing macronuclei of T. thermophila. Up to 11% of injected cells were transformed to the paromomycin-resistant phenotype specified by the injected DNA. Transformation efficiency was dependent on the developmental stages of the injected cells and the integrity of the injected DNA but not the DNA concentration or conformation. The injected DNA was apparently processed and amplified correctly to produce rDNA molecules with the expected linear palindromic structure which carried the appropriate physical markers. Thus, the 15-kilobase DNA contained all cis-acting sequences sufficient for the DNA-processing events leading to rDNA amplification in T. thermophila.

Animals↗
PubMed1988

The Sino-MONICA-Beijing Study: report on results between 1984 and 1986.

The Beijing Heart Lung and Blood Vessel Medical Center has participated in the World Health Organisation MONICA project since 1981. Our study, named Sino-MONICA-Beijing, has been carried out in Beijing and covers a population approximately of 700,000. After a 2-year pilot study, the project started formally January 1, 1984. This paper presents the organization and methodology of the study, with emphasis on the monitoring system and on how events were found. The main results of the cardiovascular disease (CVD) event monitoring are as follows: average annual mortality from all causes, for the 3-year period of 1984-86 was 319/100,000 for men and 238/100,000 for women aged 25-64; from CVD 119/100,000 for men and 101/100,000 for women; from ischemic heart disease 29/100,000 for men and 14/100,000 for women; and from cerebrovascular disease 59/100,000 for men and 52/100,000 for women. Preliminary experience has shown that Sino-MONICA-Beijing is a well-standardized project of long-term surveillance of CVD in the communities of Beijing.

Adult↗
PubMed1987

A conserved nucleotide sequence at the sites of developmentally regulated chromosomal breakage in Tetrahymena.

Chromosomal breakage occurs at hundreds of specific sites in Tetrahymena, including the two ends of the unique ribosomal RNA genes, during the development of the somatic macronucleus. We have identified a 15-nucleotide sequence that occurs widely in the germinal micronuclear genome and is associated exclusively with chromosomal breakage sites. When copies of this sequence were cloned and analyzed, they were found in all cases to be located at or very near sites of breakage. This general rule is further supported by the observation that in a different site in which a single nucleotide substitution is found within this sequence, no chromosomal breakage occurs. The complete sequence structure of one of the breakage junctions has also been determined in both the germinal DNA and the two somatic DNA termini. This structure reveals that the 15-nucleotide conserved sequence is located within a 54-nucleotide region that is removed following chromosomal breakage.

Animals↗
PubMed1987

[Telangiectatic osteosarcoma--a case report].

Telangiectatic osteosarcoma, being a subtype of osteosarcoma, is rare. In this paper, one case is reported. The patient, a sixteen year old man, was admitted into our hospital in 1983 because of swelling and pain in the left knee for 3 months. On physical examination, a mass, 7 x 5 x 5 cm in size, was found in the distal end of the left thigh. A misdiagnosis of hemangioma of the bone was made by puncture biopsy before operation. After three months, the disease progressed and amputation had to be performed. The pathological diagnosis of telangiectatic osteosarcoma was established after operation. Finally, clinical and roentgenographic manifestations, histological and ultrastructural findings, biologic behavior, diagnosis and differential diagnosis are discussed. In particular, the differentiation from aneurysmal bony cyst and hemangioma of the bone is emphasized.

Adolescent↗
PubMed1985

Gene amplification in Tetrahymena thermophila: formation of extrachromosomal palindromic genes coding for rRNA.

Tetrahymena thermophila contains in the macronucleus multiple copies of extrachromosomal palindromic genes coding for rRNA (rDNA) which are generated from a single chromosomal copy during development. In this study we isolated the chromosomal copy of rDNA and determined the structure and developmental fate of the sequence surrounding its 5' junction. The result indicates that specific chromosomal breakage occurs at or near the 5' junction of rDNA during development. The breakage event is associated with DNA elimination and telomeric sequence addition. Similar results were also found previously for the 3' junction of this gene. These results could explain how the extrachromosomal rDNA is first generated. Near both junctions of the chromosomal rDNA, a pair of 20-nucleotide repeats was found. These sequences might serve as signals for site-specific breakage. In addition, we found a pair of perfect inverted repeats at the 5' junction of this gene. The repeats are 42 nucleotides long and are separated by 28 nucleotides. The existence of this structure provides a simple explanation for the formation of the palindromic rDNA.

Base Sequence↗