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Biomedical subjects

C Wan

Publications and source records attributed to C Wan.

49 records · Page 3Linked to original sources
PubMed1994

Reorientations in the bacteriorhodopsin photocycle.

Reversible photoinduced reorientations of bacteriorhodopsin have been detected in suspensions of the purple membrane of Halobacterium salinarium. The anisotropy in bacteriorhodopsin during the nanosecond through millisecond stages of the photocycle was measured by time-resolved linear dichroism and transient absorption measurements. From these measurements the anisotropies of the K, L, M, and O intermediates were determined and related to the chromophore orientation with respect to the initially selected orientation. The anisotropies of the K and L states are 0.38 +/- 0.01 and 0.35 +/- 0.01, respectively. Further anisotropy decay after formation of the M intermediate in about 0.5 ms is evidence of orientational motion at this stage in the photocycle. A constant anisotropy with a value of 0.39 +/- 0.02 in the O intermediate demonstrates a recovery of the initial protein orientation with the formation of the O state. These results demonstrate that reorientations in BR are photoinduced and reversible. Similar measurements for L and M were carried out for purple membrane in polyacrylamide gels, where the anisotropies in the L and M states are 0.38 +/- 0.014 and 0.36 +/- 0.01, respectively. These results show that reorientations also occur in BR immobilized in gels. Anisotropy decay in the M state after formation of the M intermediate was not detected in the gels, in contrast to the M intermediate in suspensions. Orientational changes are observed for BR in purple membrane suspensions in the K state, during the K-->L step, in the M state possibly related to an M1-->M2 transition, and in the O state, where an almost complete return to the original orientation occurs.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗
PubMed1994

Comparison of personality traits of only and sibling school children in Beijing.

The number of only children in China has increased rapidly since the late 1970s, when the Chinese government advocated the "one-child-per-family" policy. This increase has caused much public concern about the healthy growth of the young generation. In this study the behavioral traits of Chinese, urban, only children were investigated. The participants were 444 children with siblings and 473 only children from Grades 1, 3, and 5 in Beijing primary schools. An inventory consisting of 27 items covering three behavioral traits was developed. The children were rated on the inventory by the principal teacher of the class. Factor analysis revealed three main factors: achievement motivation, interpersonal skills, and attitude toward manual labor. The only children exceeded the sibling children on achievement motivation. No differences were found between only children and sibling children on interpersonal skills and attitude toward manual labor. Gender differences were evident; girls consistently received higher ratings on achievement motivation and interpersonal skills. The possible underlying reasons for these differences are discussed.

Achievement↗
PubMed1994

[Studies on the detection of Legionella pneumophila by the application of polymerase chain reaction (PCR)].

DNA fragment of Legionella pneumophila, the PCR was performed with a pair of artificial synthesized primer. Results of agarose electrophoresis and EB staining showed that there was a 870 bp band shared by serogroups 1-14 of L.pneumophila. The sensitivity of PCR in detecting Legionella from water was 350cfu/ml, however, the specific DNA probe labeled with 32P was .43cfu/ml by blot hybridization. The positive rate of tissue specimens from infected guinea-pigs with Legionella pneumophila was 83.3% by PCR detection, and only 26.6% by bacteriological culture method. An outbeak caused by Lp10 was verified by PCR. The result showed that the PCR could detect the infection of Legionella rapidly, specifically and sensitively.

Animals↗
PubMed1993

Thermal biofeedback as an effective substitute for sympatholytic medication in moderate hypertension: a failure to replicate.

Thirty-three moderate hypertensives were converted to a 2-drug regimen of metoprolol and diuretic and BPs stabilized at a well-controlled level. They then completed one of three conditions over an 8-week interval: (I) 16 sessions of TBF (hand and foot warming); (II) 16 sessions of frontal EMG-BF; (III) regular home monitoring of BP. Attempts were then made to withdraw the patients from the sympatholytic medication. Those successfully withdrawn were followed up for one year. There were no significant advantages for TBF over the other two conditions in the short term or with long-term follow-up. Only 27% of treated patients (including Condition III failures who were remedicated and treated with TBF) were successfully off of the sympatholytic at a one-year follow-up. The generally poor results on clinical outcome were confirmed by clinic BPs, home BPs by patients, and 24-hour ambulatory BPs.

Biofeedback, Psychology↗
PubMed1993

Light-induced reorientation in the purple membrane.

Reorientation of bacteriorhodopsin in the native purple membrane was studied by time-resolved linear dichroism spectroscopy (TRLD) over the millisecond time regime. The time responses observed in TRLD are distinctly different from the isotropic transient absorption (TA) at wavelengths in the range 550-590 nm, where the bacteriorhodopsin ground state absorbs. In contrast, the TA and TRLD responses have nearly identical time dependence at 410 and 690 nm, where the intermediates M and O, respectively, principally contribute. These results demonstrate ground-state bacteriorhodopsin reorientation triggered by the photocycle. The TRLD and TA data are analyzed to test models for reorientational motion. Rotational diffusion of ground-state bacteriorhodopsin cannot account for the details of the data. Rather, the results are shown to be consistent with a reversible reorientation of "spectator" (nonexcited) members of the bacteriorhodopsin trimer in the purple membrane in response to the photocycling member of the trimer. This response may be associated with cooperativity in the trimer.

Anisotropy↗
PubMed1992

Preparation of cross-section specimens for transmission electron microscopy from alpha-Al2O3/Ni solid state bonded bicrystal interfaces.

The technique which is described combines the advantages of the techniques formerly proposed in the literature in each stage of the preparation of transmission electron microscopy (TEM) specimens including a single metal-ceramic interface. It allows easy handling of the thin foils in spite of their brittleness. Preferential thinning of the softer material in the two-phase foil is prevented, and both sides of the interface are thinned down to comparable thicknesses. The nickel-alumina bicrystal interface observed in TEM is neat and free from any reaction layer. This method is easily adaptable to other metal-ceramic systems.

Aluminum Oxide↗
PubMed1990

[A preliminary investigation of an outbreak of Legionnaires' disease caused by Legionella micdadei at a building-site in the rural area of Beijing].

During the period from December 1989 to January 1990, An outbreak of upper respiratory infection (influenza-like syndrome) took place in the workers of a building-site in a rural area of Beijing. An epidemiological investigation and bacteriological examination were carried out in this area. The results showed that it was an outbreak of Legionnaires' Disease caused by Legionella micdadei (Lm). The incidence was 26.67% (24/90). This was the first report on Lm infection in China.

Adolescent↗
PubMed1988

Insulin-like growth factor-I is an essential regulator of the differentiation of 3T3-L1 adipocytes.

Murine 3T3-L1 preadipocytes proliferate normally in medium containing fetal calf serum depleted of insulin, growth hormone, and insulin-like growth factor-I (IGF-I). However, the cells do not differentiate into adipocytes in the presence of the hormone-depleted serum. Supplementation of the growth medium with 10-20 nM IGF-I or 2 microM insulin restores the ability of 3T3-L1 cells to develop into adipocytes. The cells acquire an adipocyte morphology, accumulate triglycerides, and express a 450-fold increase in the activity of the lipogenic enzyme glycerol-3-phosphate dehydrogenase. The increase in glycerol-3-phosphate dehydrogenase activity is paralleled by the accumulation of glycerol-3-phosphate dehydrogenase mRNA and mRNA for the myelin P2-like protein aP2, another marker for fat cell development. IGF-I or insulin-stimulated adipogenesis in 3T3-L1 cells is not dependent on growth hormone. Occupancy of preadipocyte IGF-I receptors by IGF-I (or insulin) is implicated as a central step in the differentiation process. The IGF-I receptor binds insulin with a 70-fold lower affinity than IGF-I, and 30-70-fold higher levels of insulin are required to duplicate the effects of an optimal amount of IGF-I. The effects of 10-20 nM IGF-I are likely to be mediated by high affinity (KD = 5 nM) IGF-I receptors that are expressed at a density of 13,000 sites/preadipocyte. In undifferentiated cells the IGF-I receptor concentration is twice that of the insulin receptor. After adipocyte differentiation is triggered, the number and affinity of IGF-I receptors remain constant while insulin receptor number increases approximately 25-fold as developing adipocytes become responsive to insulin at the level of metabolic regulation. Thus, preadipocytes have the potential for a maximal response to IGF-I, whereas the accumulation of more than 95% of adipocyte insulin receptors and the appearance of responsiveness to insulin are consequences of differentiation. IGF-I or insulin is essential for the induction of a variety of abundant and nonabundant mRNAs characteristic of 3T3-L1 adipocytes.

Adipose Tissue↗
PubMedDate not supplied

Age, gender and circadian or circasemidian blood pressure and heart rate variation of children.

Systolic (S) and diastolic (D) blood pressure (BP) and heart rate (HR) of clinically healthy children (24 boys and 15 girls) 3 to 7 years of age were measured with a standard mercury sphygmomanometer at 3-hour intervals for 24 hours in April 1991. The children slept and/or rested from 2100 to 0700 and napped from 1230 to 1530; they had meals at 0730, 1200 and 1800. A statistically significant circadian and about 12-hour (circasemidian) component of variation is documented for SBP and DBP of boys and girls and for HR of boys. No gender difference was found for the circadian and circasemidian components. A positive correlation with age is found for the MESOR and circadian amplitude of SBP and DBP (p < 0.05); a negative correlation with age is found for the MESOR of HR (p < 0.001).

Activity Cycles↗
PubMedDate not supplied

[The role of biological clocks in formation of standards, pathology, and in therapy. 1. Chronobiological aspects of formation of blood pressure in children with positive and negative family history of relatively high blood pressure].

There are a difference in average values and in amplitudes of about-7 and monthly rhythms of infants' blood pressure with positive and negative family history to the hypertension. Chronobiological approach to these problem can reveal hypertension risk at the early stage of life.

Biological Clocks↗