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Biomedical subjects

S Cheng

Publications and source records attributed to S Cheng.

At least 37 records · Page 2Linked to original sources
PubMed1991

Progress in studies on the antimutagenicity and anticarcinogenicity of green tea epicatechins.

An antioxidative fraction was extracted from green tea and the major compounds in the fraction identified as epicatechins. Experimental results showed that green tea epicatechin compounds (GTEC) inhibited the mutagenicity and/or chromosomal damage caused by different carcinogens in both bacterial and mammalian cells. In vitro, GTEC inhibited transformation of BALB/3T3 cells induced by BP, X-rays, or MCA/TPA. In vivo, green tea extract decreased the incidence of carcinoma in the forestomach and esophagus of mice induced by sarcosine and NaNO2. GTEC inhibited the development of gamma-glutamyl transpeptidase-positive foci in the livers of rats treated with diethyl nitrosamine (DEN) or DEN/phenobarbital. Our investigations indicate that the antimutagenic and anticarcinogenic mechanisms of GTBC are related to the following: increased glutathione-S-transferase activity; inhibition of edema, hyperplasia, and ODC activity induced by TPA; free radical scavenging; blocked tumor promoter-induced inhibition of intercellular communication; and enhanced cell-mediated immunity. GTEC might be useful in the prevention of some kinds of cancer and a variety of oxidation-related diseases.

Animals↗
PubMed1990

Regulation of thyroid hormone binding to its cytosolic binding protein by L-alpha-alanine.

The human cytosolic thyroid hormone binding protein (p58) was recently shown to be a monomer of pyruvate kinase, subtype PKM2, and have intrinsic pyruvate kinase activity. The present study evaluated the effect of L-alpha-alanine on the binding of 3,3',5-triiodo-L-thyronine (T3) and enzymatic activity of p58. Analysis of the competitive binding data indicated that alanine, at the physiological concentration, is a non-competitive inhibitor of T3 binding to p58. Furthermore, alanine was found to be a "mixed" inhibitor of the substrate phosphoenol pyruvate. However, binding of alanine to p58 did not block the association of p58 to form the tetrameric pyruvate kinase.

Alanine↗
PubMed1990

Mechanical efficiency of locomotion in females during different kinds of muscle action.

The mechanical efficiencies (ME) of pure positive and pure negative work as well as of stretch-shortening cycle (SSC) exercise were investigated with a special sledge apparatus. The subjects were 20 young females who performed six different types of submaximal exercise: two of pure concentric exercise (positive work), two of pure eccentric exercise (negative work) and two SSC exercises. The work intensities were determined individually, from the recordings of distance obtained during a single maximal concentric exercise. Each exercise involved 60 muscle actions lasting a total of 3 min per testing condition. The MEs of pure positive work with intensities of 30% and 60% maximum (C30 and C60 respectively) were 15.5%, SD 2.6% and 14.3%, SD 1.9%, respectively. In pure negative work, when the dropping heights were 20 cm (E20) and 80 cm (E80), MEs were 28.4%, SD 6.9% and 47.9%, SD 10.1%, respectively. In SSC-exercise, the MEs during the positive phase of the take-off were 31.3%, SD 6.3% (E20/C90) and 35.0%, SD 7.0% (E80/C69). The total MEs in SSC-exercise were 29.1%, SD 4.0% (E20/C90) and 40.1%, SD 5.2% (E80/C60 x 100). In pure negative work, the increased stretching velocity increased the value of ME. In the concentric phase of SSC-exercise, the integrated electromyographic activity (iEMG) of vastus lateralis (VL) and vastus medialis (VM) muscles were lower (P less than 0.05) than in pure concentric work, when the mechanical work was the same (C60 vs E80/C60). During pure eccentric work, iEMGs were lower in comparison to the eccentric phase of SSC-exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Neuromuscular adaptations and serum hormones in females during prolonged power training.

Training-induced adaptations in the neuromuscular and endocrine systems were investigated in seven females during prolonged power type strength training. Great (p less than 0.05) changes occurred primarily during the earlier weeks of the 16-week training especially in the time of force production (from 161 +/- 107 to 93 +/- 65 ms to produce a 500 N force) and, correspondingly, in the average forces in the earlier positions of the (absolute) force-time curve of the leg extensor muscles. These changes were accompanied by significant (p less than 0.05) increases in the neural activation of the trained muscles in the earliest positions of the IEMG-time curve. Hypertrophic changes, as judged from muscle fibre area data of both FT and ST types, were only slight (ns.) during the entire training period. No statistically significant changes occurred during the training in mean concentrations of serum testosterone, free testosterone, follicle stimulating hormone (FSH), luteinizing hormone (LH), cortisol, progesterone, estradiol (E2) or sex hormone-binding globulin (SHBG). However, the individual mean serum levels of both total and free testosterone correlated significantly (r = .81-.95, p less than 0.05-0.01) with the individual changes during the training in the time of force production and in the forces in the force-time curve of the trained muscles. The present results in female subjects indicate the important role of training-induced adaptations in the nervous system for muscular power development. In females testosterone may be of great importance for muscular power and/or strength development during prolonged training and an important indicator of the trainability of an individual.

Adaptation, Physiological↗
PubMed1990

Genetic structure and DNA sequences at junctions involved in the rearrangements of Bacillus subtilis strains carrying the trpE26 mutation.

Studies on the region upstream to ribosomal operon rrnD of Bacillus subtilis led to the characterization of two of the four chromosomal junctions involved in the rearrangements (a translocation and an inversion) of the strains carrying the trpE26 mutation. Genetic analysis, by integrative mapping, showed linkage of rrnD to cysB and hisA (both on segment A) in the trpE26-type strains. Physical analysis showed that the region upstream to rrnD is now linked to the trpE-ilvA chromosome segment as demonstrated by analyzing restriction site-polymorphism between 168 and trpE26-type strains. Similar experiments confirmed the previous genetic data on linkage in these areas in strains carrying novel rearrangements derived from the trpE26-type strains: stable merodiploids and inversions. The nucleotide sequence of the area 5' to rrnD in both types of strains (168 and trpE26), the region downstream of the citG gene and the region carrying the trpE26 mutation (made available to us by D. Henner) provided evidence for the molecular basis of the differences in structure, allowed the identification of the break points and revealed the presence of a polypurine region upstream to rrnD as seen in other systems in B. subtilis. No extensive homology was found between pairs of junctions so far sequenced. The models proposed by C. Anagnostopoulos for the role of DNA sequences of intrachromosomal homology involved in the transfer of the trpE26 mutation and the formation of novel arrangements require therefore reevaluation.

Amino Acid Sequence↗
PubMed1990

[The changes of beta-glucuronidase in rabbit model with calcium bilirubinate stone].

The aim of the present study is to determine the beta-glucuronidase changes in bile and hepatobiliary tissue of rabbit model having pigment gallstone by means of biochemical and enzymehistochemical assay methods. The result showed both of the bacterial and non-bacterial beta-glucuronidase take part in the course of pigment gallstone formation. The bacterial beta-glucuronidase level increased quickly before the formation of gallstone, then decreased with control of bacterial infection. Non-bacterial beta-glucuronidase increased slowly in pro-formation stage of gallstone, then kept high level for long period of time. The relationship between beta-glucuronidase and pigment gallstone formation is also discussed.

Animals↗
PubMed1989

In vivo vibrational wave propagation in human tibiae at different ages.

Vibrational wave propagation was tested in vivo on the tibial bone of both legs of 56 female volunteers. The impact was produced by a hammer with a force strain gauge and the response was monitored by two accelerometers. The peak amplitude of the accelerations, the velocity of the acceleration wave propagation and damping were analysed for comparison among the different age groups. The results showed significant negative correlations between age and the peak amplitude of acceleration, and the velocity of acceleration wave propagation (p less than 0.01). The damping time of the acceleration wave also had a negative correlation with age. These findings suggested that age differences were related to the differences in the mechanical properties of bone. With reduction of bone mineral density, the velocity of the vibrational wave propagation would decrease, with simultaneous increase in impedance. In addition, wave absorption would be accelerated. It is suggested that this method could be used as an indicator of bone density. The method could also be developed to provide an index to monitor the progress of osteoporosis.

Adult↗
PubMed1989

Pediatric total colonoscopy.

One hundred fifty-one total colonoscopies were performed in 105 children ranging from 1 month to 15 years of age. The cecum was reached successfully in 136 examinations without complications, generally within 30 minutes. Our major indications for total colonoscopy were abnormal findings in a contrast enema, undiagnosed rectal bleeding, and possible organic lesion causing intussusception. All procedures were performed using sedation only. The pediatric gastroscope was employed for total colonoscopy on infants less than 6 years of age; the cecum was reached successfully in 98 of 106 procedures with this instrument. Our total colonoscopy series contributed to the diagnosis of various disorders in 86 children and of normality in the 19 remaining children. The results suggest that, if performed with proper precautions and techniques, total colonoscopy is a safe and useful procedure with which to examine the entire colon of infants and children.

Adolescent↗
PubMed1989

Changes in occupational role performance after a severe burn: a retrospective study.

Ten men with severe burn injuries were interviewed to examine their perceptions of the residual impact of severe burn on performance in self-care, home management, work, and leisure occupations within the year after rehabilitation. Three patterns of occupational role performance after a burn were identified: (a) a resumption of participation in all four occupational categories; (b) a return to independence in self-care with substantive impairment in home management, work, and/or leisure roles; and (c) substantive disruption in all occupational roles. Role loss or disruption was commonly associated with reduced endurance, intolerance for standing and walking, and impaired grip strength and upper extremity skill. Suggestions for rehabilitation programming and research are made.

Activities of Daily Living↗
PubMed1988

Use of psoralen-modified oligonucleotides to trap three-stranded RecA-DNA complexes and repair of these cross-linked complexes by ABC excinuclease.

A series of site-specifically cross-linked, three-stranded complexes has been prepared using the RecA protein, form I (covalently closed and negatively supercoiled) pUC19 plasmid, and eight psoralen-monoadducted oligonucleotides between 30 and 107 residues in length. Complexes formed much less efficiently if linearized pUC19 was used as the duplex substrate. Quantitative analysis indicates that although RecA is able to utilize a 30-mer in its homologous pairing reaction, incorporation at 50% efficiency requires a single-stranded substrate at least 50 residues long. These three-stranded complexes have been used to study the action mechanism for cross-link repair by ABC excinuclease, and the results are consistent with the recent model of Van Houten, B., Gamper, H., Holbrook, S. R., Hearst, J. E., and Sancar, A. (1986b) Proc. Natl. Acad. Sci. U. S. A. 83, 8077-8081.

Bacterial Proteins↗
PubMed1988

Polyamine metabolism in an obligately alkalophilic Bacillus alcalophilus that grows at pH 11.0.

Bacillus alcalophilus, an obligately alkalophilic bacterium that grows at pH 11.0, has an intracellular pH of 9.5 or less. Unlike all other living organisms, polyamines (putrescine, spermidine and spermine) in B. alcalophilus, if present, will be largely unprotonated. HPLC analysis indicated that spermidine is the major polyamine in B. alcalophilus, accounting for more than 90% of total polyamines, and the level of spermidine varies during growth. Ornithine decarboxylase activity was not detectable in B. alcalophilus under all conditions examined. When [3H]arginine was added to the culture medium, the radioactivity can be recovered from polyamine pool; the distribution is 3% for putrescine, 94% for spermidine, and 3% for spermine, suggesting the presence of arginine pathway for polyamine biosynthesis. The polyamine transport system in B. alcalphilus appears to be Na+-dependent and is highly sensitive to the inhibition of gramicidin S and valinomycin.

Arginine↗
PubMed1988

Study on erythrocyte membrane fluidity by laser Raman spectroscopy.

Differences between patients with cirrhosis of liver, nephrotic syndrome, coronary heart disease and normal subjects in laser Raman spectra of erythrocyte membranes have been found. In regions of 1000-1140 cm-1 and 2840-3000 cm-1, the ratios I1130/I1080 and I2890/I2850 in patient membranes are higher than those in normal ones respectively. These results mean that erythrocyte membrane fluidity of these patients is reduced. This reduction may be attributed to the possibility that erythrocyte membrane of patients get more cholesterol from their plasma and resulted in the modification of the ratio of cholesterol/phospholipids in the membranes.

Coronary Disease↗
PubMed1988

Inbreeding effects on fertility and hatchability associated with the formation of sublines.

The deleterious effect of inbreeding on fertility and hatchability was studied in a population of Leghorns developed primarily for immunogenetics studies. The 1983 population averaged 42% inbreeding and traced back to only two sires and five dams of the 1965 base population. Up to 1975 (Period 1), the population was maintained as a single-unit closed flock, during which time inbreeding increased an average of 1.44% per year. After 1975 (Period 2), the population was split into five sublines. Inbreeding then increased at the average rate of 2.7% per year. The regression of fertility on inbreeding was -.31 +/- .04 in Period 1 and -.17 +/- .06 in Period 2. Corresponding values for hatchability of fertile eggs were +.08 +/- .05 in Period 1 and -.24 +/- .07 in Period 2. The regression of hatchability of total eggs set was -.15 +/- .04 in Period 1 and -.35 +/- .10 in Period 2. The evidence implies that both fertility and hatchability have a heritable basis. As expected, the deleterious effects of inbreeding on reproduction was more severe in Period 2, with sublining.

Animals↗
PubMed1988

Genetic analysis of immunocompetence measures in a White Leghorn chicken line.

Immunocompetence of the Iowa State University S1 White Leghorn chicken line was studied. This line was divided into eight sublines based upon erythrocyte antigen B (Ea-B) allele (B1B1 or B19B19), antibody response to glutamic acid60-alanine30-tyrosine10 (GAT) (high or low), and response to Rous sarcoma virus-induced tumors (progression or regression). Antibody responses to Pasteurella multocida (PM), Mycoplasma gallisepticum (MG), and infectious bursal disease virus vaccines were evaluated by enzyme-linked immunosorbent assay. Phagocytic activity and T cell-mediated response were measured by carbon clearance and phytohemagglutinin (PHA) injection assays, respectively. Significant haplotype (subline) differences and sire family differences were observed in all three measurements. Significant sex differences were observed in phagocytic activity and T cell-mediated responses. Haplotypes with high antibody responses to GAT had significantly higher antibody titers to PM and MG vaccines than haplotypes with low antibody responses. Significant positive correlations were observed between antibody levels to the two vaccines. A significant negative correlation was seen between phagocytic activity and T cell-mediated response of females. The data suggest that the total immunocompetence profile of an individual must be considered to select for optimum immune responsiveness.

Animals↗