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Biomedical subjects

C Wan

Publications and source records attributed to C Wan.

At least 37 records · Page 2Linked to original sources
PubMed2000

[Effects of electromagnetic radiation from cellular telephone handsets on symptoms of neurasthenia].

In order to study the effects of electromagnetic radiation from cellular telephone handsets on symptoms of neurasthenia, 115 and 101 persons with or without handsets were selected. The subjects were investigated by questionnaire on their general health, lifestyle, habit, mental stress, the frequency of using the handsets, living and working environment, the cases of suffered from diseases and symptoms of neurasthenia. The data were analyzed by Chi-square test and Logistic regression statistics. The results showed that the time of using handset was positively associated with depression (P < 0.05), nausea (P < 0.01) and loss of appetite(P < 0.05). The results showed that long time use of cellular telephone handset could induce the symptoms of neurasthenia.

Female↗
PubMed1999

Design of infection-resistant antibiotic-releasing polymers: I. Fabrication and formulation.

Biomaterials-related infections are often observed with prosthetic implants and in many cases result in the failure of the devices. To design a biomedically useful polymer that is intrinsically infection-resistant, we have developed a ciprofloxacin-loaded polyurethane (PU) matrix that releases antibiotic locally at the implant surface, thereby minimizing bacterial accumulation. We report here the methods of fabrication and formulation for making such antibiotic-loaded devices, as well as evidence of their bactericidal properties. Specifically, various pore-forming agents and drug loadings were examined. An optimum formulation consisting of BIOSPAN PU, poly(ethylene glycol) and ciprofloxacin offered the longest effective period of sustained release (5 days). The bactericidal efficacy of the released ciprofloxacin against Pseudomonas aeruginosa (PA) was four times that of the control PU without antibiotics. This bactericidal efficiency was due to an increase in the PA detachment from the surface. These observations suggested that the released ciprofloxacin was biologically active in preventing the bacteria from permanently adhering to the substratum, and thus decreasing the possibility of biofilm-related infection.

Anti-Infective Agents↗
PubMed1999

Femtosecond dynamics of DNA-mediated electron transfer.

Diverse biophysical and biochemical studies have sought to understand electron transfer (ET) in DNA in part because of its importance to DNA damage and its repair. However, the dynamics and mechanisms of the elementary processes of ET in this medium are not fully understood and have been heavily debated. Two fundamental issues are the distance over which charge is transported and the time-scale on which the transport through the pi-stack of the DNA base pairs may occur. With femtosecond resolution, we report direct observation in DNA of ultrafast ET, initiated by excitation of tethered ethidium (E), the intercalated electron acceptor (A); the electron donor (D) is 7-deazaguanine (Z), a modified base, placed at different, fixed distances from A. The ultrafast ET between these reactants in DNA has been observed with time constants of 5 ps and 75 ps and was found to be essentially independent of the D-A separation (10-17 A). However, the ET efficiency does depend on the D-A distance. The 5-ps decay corresponds to direct ET observed from 7-deazaguanine but not guanine to E. From measurements of orientation anisotropies, we conclude that the slower 75-ps process requires the reorientation of E before ET, similar to E/nucleotide complexes in water. These results reveal the nature of ultrafast ET and its mechanism: in DNA, ET cannot be described as in proteins simply by a phenomenological parameter, beta. Instead, the involvement of the base pairs controls the time scale and the degree of coherent transport.

Base Sequence↗
PubMed1999

Femtosecond dynamics of the DNA intercalator ethidium and electron transfer with mononucleotides in water.

Ethidium (E) is a powerful probe of DNA dynamics and DNA-mediated electron transfer (ET). Molecular dynamical processes, such as solvation and orientation, are important on the time scale of ET. Here, we report studies of the femtosecond and picosecond time-resolved dynamics of E, E with 2'deoxyguanosine triphosphate (GTP) in water, and E with 7-deaza-2'-deoxyguanosine triphosphate (ZTP) in water; E undergoes ET with ZTP but not GTP. These studies elucidate the critical role of relative orientational motions of the donor-acceptor complex on ET processes in solution. For ET from ZTP to E, such motions are in fact the rate-determining step. Our results indicate that these complexes reorient before ET. The time scale for the solvation of E in water is 1 ps, and the orientational relaxation time of E is 70 ps. The impact of orientational and solvation effects on ET between E and mononucleotides must be considered in the application of E as a probe of DNA ET.

DNA↗
PubMed1999

Randomised trial of different rates of feeding in acute diarrhoea.

OBJECTIVE: To compare the effect of different feeding frequencies on the speed of recovery from diarrhoea. METHODS: A randomised, non-blinded trial provided 0.452 MJ/kg/day as either 6 or 12 feeds of cows' milk each day to 262 hospitalised male infants aged 3-12 months with acute diarrhoea. Stool frequency, stool weight, body weight, and diarrhoea complications were monitored until recovery or for 14 days. RESULTS: A proportional hazards regression model controlling for age, diarrhoea aetiology, and severity of dehydration on admission revealed that the frequently fed group had a significantly shorter duration of diarrhoea (hazards ratio, 1.29; 95% confidence interval, 1.002 to 1.653). Frequently fed infants had a significantly greater weight gain and significantly lower faecal frequency and faecal weight. CONCLUSIONS: Breast feeding remains the preferred method of feeding infants with acute diarrhoea, but feeding cows' milk to adequately nourished infants with acute diarrhoea is safe and is more rapidly effective if provided in frequent feeds with low energy loads.

Acute Disease↗
PubMed1999

[Markov process method in analyzing longitudinal quality of life data].

OBJECTIVE: To present a method to analyze longitudinal quality of life data and discuss some relevant questions. METHOD: Based on the theories of Markov process, the Markov method was presented and used to analyze the change of quality of life status for 212 cases being detoxificated drug addicts and their influence factors. RESULTS: The intensity coefficients of status transient for 1-->2 and 2-->3 for occupation were 0.7912 and 0.6797 respectively; the coefficients for status 1-->2 for the detoxification time was 0.5663 and that for 2-->3 for the detoxification method was 0.2765. CONCLUSIONS: The Markov method is good to analyze longitudinal quality of life data for it can analyze both the transient probabilities between any two status of quality of life and their influence factors. The results showed that the occupation of drug addicts, the detoxification time and method can affect the change of quality of life.

Humans↗
PubMed1999

[Quality of life as a time-dependent covariable in cox regression analysis and its application].

OBJECTIVE: To present a statistical method for combined evaluation of the quality of life and survival time and to study some issues in its application. METHODS: Based on Cox regression model, quality of life was used as a time-dependent covariable in analysis of the influence factors for the effectiveness of detoxification in 212 drug addicts. RESULTS: The influence factors entered the regression equation were ways of detoxification for drug abusers, marital status, mode of drug abuse, frequency of detoxification, maternal educational level, maternal occupation, family atmosphere and help and encourage from their relatives and friends, with their hazard ratios of 0.673, 1.315, 1.319, 0.867, 1.120, 1.318, 0.724 and 1.150, respectively. CONCLUSION: Combined statistical analysis of quality of life and survival time was a better method for the evaluation of the effectiveness of detoxification and its influence factors, which depended mainly on their mother's qualification, family atmosphere, mode and length of drug abuse, etc.

Humans↗
PubMed1999

[Modification of the surface of prosthetic valve material by LGDP for protection against microbial adhesion].

This study aimed at the surface modification of prosthetic valve materials by means of cold glow discharge plasma. Orthogonal design was adopted to select the optimal scheme by the experiments of the singular factor, such as output power, gas flow rate, treatment time etc. The PEG-200 was introducted to the surface. Grafting a layer of heparin onto the surface; coating a layer of PEG-like onto the surface first, and then the grafting heparin. Comparing the adhesive amounts of staphylococcus epidermidis (SE), the adhesive curves for Dacron, which was treated by the above methods; the last one is the best.

Bacterial Adhesion↗
PubMed1999

[The development and clinical application of a multipurpose neuroendoscope].

The multipurpose rigid neuroendoscope MGE-4 has been developed with the application of the self-focussing lens technology. We have been using it to examine and treat 10 neurosurgical patients who suffered from tumours, hydrocephalus, intracerebral haematomas of head injury and hypertensive cerebral haemorrhage. The short-term effect was satisfactory and there was no operative complications. It is considered that Model MGE-4 with the accessories can be used safely for the brain functional subcortical lesion or the deep-seated cystic lesions and haematomas.

Adult↗
PubMed1998

Unexpected frameshifts from gene to expressed protein in a phage-displayed peptide library.

A library of long peptides displayed on the pIII protein of filamentous phage was used in biopanning experiments against several protein targets. We find that a large percentage of phage clones that bind specifically to a target contain peptide-encoding genes that do not have an ORF. Instead, the reading frame is either interrupted by one or more nonsuppressed stop codons, or a post-transcriptional frameshift is needed to account for the expression of the minor phage coat protein pIII. The percentage of frameshifted clones varies depending on the target. It can be as high as 90% for clones specific for soluble forms of certain cytokine receptors. Conversely, biopanning against four mAbs did not yield any frameshifted clones. Our studies focused on one clone that binds specifically to rat growth hormone binding protein (GHBP) yet does not have an ORF. A secondary peptide library containing random mutations of this sequence was constructed and panned against GHBP to optimize and correct the reading frame. In the last round (round two) of panning with this library, none of the phage clones that bound to GHBP had an ORF. However, careful analysis of these clones allowed us to design a synthetic peptide capable of binding to GHBP. The results of this study indicate that ORFs are not required to obtain gene expression of the minor coat protein of filamentous phage and suggest that some ORF- clones may have a selective advantage over the clones having ORFs.

Amino Acid Sequence↗
PubMed1998

[Progress in the controlled release systems of hirudin].

Hirudin is very effective in treating and preventing cardiovascular disorders. In this review several polymeric controlled release systems of hirudin are introduced. The advantages of the local delivery for restenosis and the feasibility of endovascular drug-containing pharmaceutic stents for local therapy of cardiovascular thrombosis are discussed.

Coronary Thrombosis↗
PubMed1998

[A novel high quality specific antithrombotic drug--hirudin].

Hirudin is the most potent specific inhibitor of thrombin, which is currently undergoing clinical trials as a novel antithrombotic drug. In this paper, the composition and structure, the pharmacological and pharmacokinetic characteristics, the anticoagulant and antithrombotic activity and function, the methods of isolation, recombination and syntheses were reviewed.

Fibrinolytic Agents↗
PubMed1997

Vascular delay in skeletal muscle: a model for microcirculatory studies.

Dynamic myoplasty is a relatively new use for muscle flaps and has led us to revisit the mechanisms of vascular delay as a means of optimizing blood supply to muscle flaps. Despite the well-documented effectiveness of vascular delay in skin flaps, vascular delay in muscle flaps has not been widely reported. Regardless of the many mechanisms postulated in the literature as contributors to the delay effect in skin, the one element common to all these hypotheses is the importance placed on changes in the microcirculation. Based on this factor, in the present study we developed and validated an animal model in which delay-induced microvascular changes could be measured in skeletal muscle flaps. We used the hairless mouse latissimus dorsi muscle flap because its vascular distribution is similar to that of humans and its thin structure will enable us in future studies to directly view and measure its microvasculature using videomicroscopy. In 12 animals, we found that delay significantly (p < 0.01) reduced necrosis of the distal part of the muscle from 57 +/- 9 percent in nondelayed flaps (n = 7) to 22 +/- 3 percent in delayed (n = 5) flaps. In these studies, we also determined that the hairless mouse latissimus dorsi muscle flap will serve as an excellent model for defining microvascular changes throughout delay.

Animals↗
PubMed1997

The effect of pioglitazone on hepatic glucose uptake measured with indirect and direct methods in alloxan-induced diabetic dogs.

Pioglitazone, a thiazolidinedione derivative, ameliorates hyperglycemia by augmenting peripheral glucose disposal and suppressing hepatic glucose production in diabetic animals. However, the effect of this agent on hepatic glucose uptake has not been explored. To determine this, experiments were conducted in alloxan-induced diabetic dogs with (pioglitazone group, n = 7) or without (control group, n = 5) a 10-day oral treatment with pioglitazone (1 mg x kg(-1) x day(-1)). A euglycemic-hyperinsulinemic (insulin infusion rate 25.2 pmol x kg(-1) x min(-1)) clamp was maintained by adjusting the peripheral glucose infusion rate (GIR). After a 60-min basal period (period I), portal glucose infusion (Pinf, 33.3 micromol x kg(-1) x min(-1)) was administered for 120 min (period II). This was followed by a 60-min recovery period (period III). Arterial insulin levels were kept stable in the supraphysiological range throughout the experiment (1,623 +/- 52, pioglitazone group; 1,712 +/- 52 pmol/l, C group). There was no significant difference in whole-body glucose utilization determined by [3-3H]glucose between the pioglitazone and C groups in period I (68.4 +/- 2.8 vs. 70.1 +/- 2.8 micromol x kg(-1) x min(-1), respectively) and period III (81.2 +/- 5.0 vs. 74.5 +/- 3.3 micromol x kg(-1) x min(-1), respectively). Net hepatic glucose uptake (NHGU) determined by arteriovenous difference method was approximately zero in the basal period (-0.7 +/- 1.1, pioglitazone group; 0.1 +/- 1.2 micromol x kg(-1) x min(-1), C group). In period II, hepatic glucose uptake, determined by the changes in GIR, was significantly higher in the pioglitazone group (6.5 +/- 0.6 micromol x kg(-1) x min(-1)) than in the C group (-0.4 +/- 0.6 micromol x kg(-1) x min(-1), P < 0.001). This observation was also confirmed by NHGU during portal glucose infusion (6.9 +/- 1.4 vs. 2.1 +/- 1.8 micromol x kg(-1) x min(-1), pioglitazone vs. C, respectively; P < 0.025). We conclude that pioglitazone treatment enhances hepatic glucose uptake during portal glucose loading in alloxan-induced diabetic dogs. However, in hyperinsulinemic conditions, pioglitazone does not enhance the already high peripheral glucose uptake.

Animals↗
PubMed1996

Changes in binding affinity of a monoclonal antibody to a platelet binding domain of fibrinogen adsorbed to biomaterials.

Previously, we found that when fibrinogen-coated polyurethanes resided in a buffer for a period of time (the 'residence time') platelet adhesion to these materials decreased. Other changes in adsorbed fibrinogen such as decreases in polyclonal antibody binding and SDS elutability supported the conclusion that fibrinogen undergoes postadsorptive conformational changes. Subsequently we measured the binding of monoclonal antibodies to the three putative platelet binding sites on fibrinogen, using a single mid-range concentration of antibody. We found that binding of a monoclonal antibody to the platelet binding site at the C-terminus of the gamma chain of fibrinogen changed little with residence time, while binding of monoclonal antibodies to the other two putative binding sites on fibrinogen either increased with residence time (RGDF at A alpha 95-98), or first increased and then decreased with residence time (RGDS at A alpha 572-575). In the current study, we measured antibody binding affinity, Ka, by measuring antibody binding at a series of antibody concentrations. This is a more sensitive method for detecting changes in adsorbed fibrinogen than measuring antibody binding from a single antibody concentration. The Ka was determined for two antibodies, M1 (4A5), which binds to a platelet binding domain of fibrinogen (gamma 402-411) and R1 (155 B 1616), which binds to residues 87-100 of the A alpha chain (containing an RGDF site). A summary of the results for the M1 antibody are as follows. The Ka was higher for M1 binding to fibrinogen adsorbed to Immulon I than to Biomer, Biospan or poly(ethylene terephthalate), suggesting that fibrinogen adsorbed to Immulon I is more platelet adhesive than fibrinogen adsorbed to the other polymers. On Biospan, the Ka decreased from 2.8 x 10(9) to 1.0 x 10(9) M-1 after a 24 h 37 degrees C residence time, which correlated with the decrease in platelet adhesiveness of adsorbed fibrinogen observed previously under these conditions. The change in Ka was greater when adsorbed fibrinogen was kept under denaturing conditions. For example, the Ka decreased from 2.8 x 10(9) to 0.8 x 10(9) M-1 after a 1 h 70 degrees C residence time whereas it remained approximately the same, 2.9 x 10(9) M-1, after a 24 h 0 degree C residence time.

Adsorption↗
PubMed1996

[A legionella pneumophila strain serologically cross-reacting with thirteen serogroups of this species].

A bacterial strain, designated as Jin-1, was isolated from a water sample taken from the Jinyang Lake located in the suburbs of Taiyuan City, Shanxi Province. Its morphologic and tinctorial properties, nutritional requirements, growth characteristics, biochemical reactions, as well as results of DNA and peptide analysis overall met the criteria for identification of Legionella pneumophila. In serogrouping, extensive cross-reactions between Jin-1 and the type strains of L. pneumophila serogroup 1 through 14 were observed in both slide and tube agglutination tests mediated by the IgM antibodies. However, Jin-1 revealed the L. pneumophila serogroup 5 specificity in IFA, ELISA and dot-ELISA, all mediated by the IgG antibodies. Jin-1 was finally identified as a strain of L. pneumophila serogroup 5 with the more complex antigenic composition than the ATCC type strain of this serogroup. The taxonomic conclusion has been confirmed by CDC. A Legionella pneumophila strain which serologically cross-reacting with so many serogroups of this species has never been reported in the published articles. It is presumed that the cross-reacting antigen of Jin-1 belongs to the thymus-independent antigen by nature.

Antigens, Bacterial↗
PubMed1995

[The course of malaria control and present status in Zhejiang Province].

Through forty years' sustained efforts in the prevention and treatment of malaria in Zhejiang Province, the malaria incidence dropped from 76.650/000 in the Fifties to 0.910/000 in the Eighties. Three malaria epidemics emerged in 1954, 1962 and 1973, respectively, among them the epidemic in 1962 was the most serious one with 0.88 million cases reported and an incidence of 3300/000. The annual incidence of the overall counties/cities was below 10/000 after 1988. Only 172 malaria cases were found in 1992, the incidence being 0.040/000. No indigenous malaria case was found in 38 counties in 1992, accounting to 43.7% of the total malaria endemic counties. The number of imported malara cases was 3,829, amounting to 89.2% of the total number of cases. Through the spot-check of the Ministry of Public Health in 1993, it was confirmed that the criteria of basic elimination of malaria in the province was attained.

Animals↗