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Biomedical subjects

G Chen

Publications and source records attributed to G Chen.

At least 919 records · Page 51Linked to original sources
PubMed1966

Metachromatic leucodystrophy: isolation and chemical analysis of metachromatic granules.

The abnormal, cytoplasmic metachromatic granules found in the brain of metachromatic leucodystrophy were isolated in high purity. They show metachromasia by von Hirsch-Peiffer's cresyl violet method. Electron microscopy revealed very slight contaminations by other components, such as mitochondria, myelin, and ribosomes. Chemical analysis of two separately obtained collections has shown that the molar ratio of cholesterol to galactolipids to phosphatides is 1 : 1 : 1. Most of the galactolipids are sulfatides.

Cerebrosides↗
PubMedDate not supplied

Alginate as a displacer for protein displacement chromatography.

Alginate use in displacement chromatography as a displacer has been studied. The experiments showed that untreated alginate is the basis of potential displacer for displacement chromatography, but needs to be cleaved into smaller chains. Alginate treated with ultrasound, which cleaves alginate into shorter polysaccharide chains, gave better displacement than untreated alginate, while alginate subjected to limited acid hydrolysis gave the best results in displacement chromatography. It was found that the mixture of ovalbumin and beta-lactoglobulin separated well, and several components of ovalbumin were also separated and purified when alginate hydrolysate was used as a displacer. beta-Lactoglobulins A and B, which have the same molecular weight and differ in isoelectric point by only 0.1 pH units, were displaced from Q-Sepharose by alginate hydrolysate.

Alginates↗
PubMedDate not supplied

Discrete signal processing of dynamic contrast-enhanced MR imaging: statistical validation and preliminary clinical application.

A high-resolution image-based method was developed to analyze dynamic contrast agent-enhanced magnetic resonance images quantitatively. This method determines the initial rate of contrast agent accumulation, the delayed rate of accumulation, and the maximum enhancement in each pixel. These three parameters allow characterization of the dynamic signal features. Simulated noisy test sets of dynamic enhancement curves have shown this method to yield a fast and accurate characterization of the dynamic signal. Clinical examples of both qualitative image parameter maps and quantitative statistical analysis of the parameter distributions demonstrated the quality and potential of the technique. The technique is designed to yield imaging and quantitative information on contrast agent accumulation that can be useful in detecting residual tumor and evaluating response to therapy, while requiring less than 7 minutes of imaging time and 5 minutes of processing time per study.

Adult↗
PubMedDate not supplied

Quantitative MR imaging of children with sickle cell disease: striking T1 elevation in the thalamus.

Nineteen patients with sickle cell disease (SCD) were examined with conventional MR imaging (cMRI), including T1- and T2-weighted sequences and MR angiography (MRA). qMRI mapping of T1 was also done using a precise and accurate inversion-recovery (PAIR) technique optimized and validated previously. In addition, 21 healthy African-American control subjects had the qMRI examination. Nonparametric Kruskal-Wallis analysis of variance of control subjects, of SCD patients without stroke, and of SCD patients with stroke showed that T1 increased with disease severity in the thalamus, frontal white matter, genu, and occipital white matter. T1 was significantly longer in SCD patients without stroke (n = 13) than in control subjects (n = 21) in the thalamus and frontal white matter. In addition, T1 values were significantly longer in SCD patients with stroke than in patients without stroke in the genu and frontal white matter. Abnormality of the thalamus was identified by qMRI in a substantial fraction of patients read as normal by both cMRI and MRA, suggesting that it may be possible to use T1 elevation to identify a subset of patients with SCD who are at elevated risk for stroke.

Adolescent↗
PubMedDate not supplied

A conditional bootstrap procedure for reconstruction of the incubation period of AIDS.

Data on the incubation period of AIDS patients are often fragmented and censored. parametric models have been proposed in the literature to impute the missing segment of the incubation period. The numerical results vary widely with the parametric models used. We propose a nonparametric conditional bootstrap (CB) procedure for imputation. The quality of the CB data is studied by checking the asymptotic accuracy of the CB estimators. We establish the asymptotic accuracy of the CB procedure for two basic nonparametric estimators: the empirical distribution function and a kernel-type conditional empirical distribution function. The rates of convergence of the CB approximation are obtained. The results for the kernel-type estimators hold also for the nearest-neighbor-type estimators.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Xenotransplantation of human decay accelerating factor transgenic porcine kidney to non-human primates: 4 years experience at a Canadian center.

From July 1999 to December 2002, a total of 27 baboons underwent transplantation with human decay accelerating factor (hDAF) transgenic porcine kidneys. The immunosuppressive protocol included combinations of 1 or more of the following immunosuppressive agents: cyclosporine, TPC, cyclosphophamide, methylprednisolone, GAS914 (a polymeric alpha-Gal), rabbit antithymocyte serum (RATS), and rapamycin derivative (RAD). The animals were followed up clinically with monitoring of renal function based on daily creatinine and urinary output. Histopathological examination of the tissue samples was performed after paraffin embedding. Electron microscopy was performed on occasion. All pathology was read blindly with a semiquantitative scoring method to assess the presence or absence of histological features of xenotransplant rejection. Mean survival time was 20.7 days (range, 4-75 days) with 15 animals dying of classic humoral rejection and 12 dying of complications unrelated to rejection. The most frequent complications were as follows: chronic diarrhea with malabsorption, bleeding diathesis, infections, and drug toxicity. Irrespective of the immunosuppressive regimen, a significant number of baboons (10) developed untreatable diarrhea and gastrointestinal bleeding. Samples of their gastrointestinal tracts showed evidence of varying degrees of necrotizing vasculitis with immunoglobulin (Ig)G,IgM, and fibrin deposition. The survival in pig-to-baboon kidney xenotransplantation continues to be limited by acute xenograft rejection and complications of immunosuppression. Although significantly increased survivals have been obtained, an ideal protocol has not yet been achieved. Efforts will continue in an attempt to develop a protocol with minimal complications and long-term survival beyond 90 days.

Animals↗