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Biomedical subjects

J Guo

Publications and source records attributed to J Guo.

At least 397 records · Page 22Linked to original sources
PubMed1995

[Double embolization of bronchial artery to control massive hemoptysis].

Bronchial arteriography and double embolization is to block the peripheral bronches of the bronchial artery with micro-gelatin particles and then the trunk of the artery with sponge gelatin. The blood flow from the artery trunk and from the rich arterial bronches which forms B-P bypass is blocked. By this way the embolization is more complete. Clinical observation of 93 cases shows that the success rate reached 91% which indicate that the massive hemoptysis could stopped by this method.

Adult↗
PubMed1995

Biosensor based on chemiluminescence for serum uric acid determination.

A biosensor based on luminol chemiluminescent reaction and immobilized uricase column for serum uric acid determination has been developed. The response time by the sensor for various concentrations of serum uric acid was 47 sec with a 17-microliters sample volume at 40 samples per hr. The linear range of standard curve was from 1 mg/dL up to 20 mg/dL of serum uric acid. The imprecision within a day was 3.22% to 4.36%. The day-to-day imprecision was 6.18% to 7.80%. The recovery rate by the method was 93% to 109%. Compared with the standard colorimetric method employed, the enzymatic kit revealed that the linear regression and correlation coefficient were Y = 0.4 + 0.938x and r = 0.9909, respectively. The immobilized uricase column retained 94% of its original activity even after over 2000 runs for five and half months of continual usage.

Biosensing Techniques↗
PubMed1995

[Risk factors on hyperglycemia in newborn infants].

OBJECTIVE: To investigate high risk factors of neonatal hyperglycemia. METHODS: According to the gestational age, postnatal age, weight, hypoxia, infection, 336 hospitalized newborns receiving continuous intravenous infusion of glucose controlled by pump were divided into the study and control groups respectively, the incidences of hyperglycemia between two groups were analysed statistically. RESULTS: The results showed that the high risk factors of neonatal hyperglycemia were gestational age ( < 37 week), postnatal age ( < 72h), weight ( < 2 500g), hypoxia and (or) infection. CONCLUSIONS: In neonates with one or more high risk factors of hyperglycemia, strict control of infusion speed; treatment of original diseases and frequent monitoring of blood glucose should be noted.

Glucose↗
PubMed1995

[The visual evoked potentials of non-amblyopic eyes in children with amblyopia].

We investigated the characteristics of visual evoked potentials (VEPs) of the eyes with normal visual acuity in 84 children of whom 20 were normal, 28 of anisometropic amblyopia, 8 of anisometropic amblyopia already cured, 8 pairs of monozygotic and 6 pairs of dizygotic twins with amblyopia. The results showed that although the fellow eye of an amblyopic eye or the cured amblyopic eye had normal visual acuity, the VEPs presented abnormal, the marked abnormality being the prolongation of the latency of P100 peak. No significant difference was found in VEPs between the eye with normal visual acuity and the eye with amblyopia in the monozygotic twins with the same genetic background (P > 0.05). This study demonstrated that possibly the clinical examinations of visual acuity and VEPs reflect different visual information processes, and the "normal" eyes of amblyopes are not normal.

Amblyopia↗
PubMed1994

Clinical biochemical and pathologic correlations in Bietti's crystalline dystrophy.

We examined three affected members of a Chinese-American family with Bietti's crystalline retinopathy. The clinical characteristics of a 24-year-old proband are contrasted to the clinical findings of her grandmother, for whom we have 26 years of follow-up data. Lymphocytes and fibroblasts from a skin biopsy of the grandmother contained crystalline lysosomal material, which supports the diagnosis. Biochemical studies of the crystalline lysosomal material failed to identify the stored compounds but did not show them to be cholesterol or cholesterol ester. Finally, histopathologic studies performed for this condition demonstrated advanced panchorioretinal atrophy, with crystals and complex lipid inclusions seen in choroidal fibroblasts.

Adult↗
PubMed1994

Abnormal class I assembly and peptide presentation in the nonobese diabetic mouse.

Presentation of self-antigens by major histocompatibility complex (MHC) class I molecules requires the function of the MHC class II-linked genes Tap-1 and Tap-2. Evidence suggests that interruption of self-peptide presentation results in reduced cell surface expression of MHC class I molecules and the interruption correlates with progression to diabetic autoimmunity in nonobese diabetic (NOD) mice and humans. NOD mice possess a rare Tap-1 allele (Tap-1b); this is associated with reduced Tap-1 mRNA abundance in lymphocytes from diabetes-prone females and decreased conformationally correct class I molecules on the cell surface. In this study, we demonstrate that, similar to lymphoma cell lines with mutations in Tap-1 or Tap-2, the reduced expression of class I molecules on the surface of lymphocytes from diabetes-prone female NOD mice was normalized by incubation at low temperatures or by exposure to class I allele-specific peptides. As would be expected for cells that express surface class I molecules not associated with peptide, female NOD lymphocytes were resistant to lysis by class I-restricted, peptide-specific cytotoxic T lymphocytes. Furthermore, the rate of class I exit from the endoplasmic reticulum of lymphocytes from female NOD mice was delayed as demonstrated by delayed glycosylation. Male NOD mice, which are not prone to diabetes, lacked these functional defects in class I assembly and had near-normal levels of Tap-1 mRNA and exhibited normal density of class I epitopes that were peptide filled. These results are consistent with the possibility that the rare Tap-1b allele is associated with a quantitative defect in Tap-1 expression that influences disease course.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Crystal structure of a catalytic antibody with a serine protease active site.

The three-dimensional structure of an unusually active hydrolytic antibody with a phosphonate transition state analog (hapten) bound to the active site has been solved to 2.5 A resolution. The antibody (17E8) catalyzes the hydrolysis of norleucine and methionine phenyl esters and is selective for amino acid esters that have the natural alpha-carbon L configuration. A plot of the pH-dependence of the antibody-catalyzed reaction is bell-shaped with an activity maximum at pH 9.5; experiments on mechanism lend support to the formation of a covalent acyl-antibody intermediate. The structural and kinetic data are complementary and support a hydrolytic mechanism for the antibody that is remarkably similar to that of the serine proteases. The antibody active site contains a Ser-His dyad structure proximal to the phosphorous atom of the bound hapten that resembles two of the three components of the Ser-His-Asp catalytic triad of serine proteases. The antibody active site also contains a Lys residue to stabilize oxyanion formation, and a hydrophobic binding pocket for specific substrate recognition of norleucine and methionine side chains. The structure identifies active site residues that mediate catalysis and suggests specific mutations that may improve the catalytic efficiency of the antibody. This high resolution structure of a catalytic antibody-hapten complex shows that antibodies can converge on active site structures that have arisen through natural enzyme evolution.

Amino Acid Sequence↗
PubMed1994

Pathogenesis of posttransfusion viral hepatitis in children with beta-thalassemia.

The pathogenesis of posttransfusion hepatitis was determined in 14 children with beta-thalassemia. All had blood samples obtained in 1980 or 1981, were vaccinated against hepatitis B virus in 1983 and had another serum sample collected in 1989. Seven children had detectable antibodies against hepatitis C virus before vaccination, and all were positive in 1989. With specific solid-phase enzyme immunoassays, all children had antibodies against hepatitis B virus, X and polymerase antigens in 1981, and six had one or both antibodies in 1989. Hepatitis B virus infection was confirmed by means of polymerase chain reaction, which demonstrated virus DNA in 13 of the 14 children. The amplification products spanning the X/precore region were smaller than expected, suggesting mutations in this region. Cloning and sequencing of these products revealed deletions spanning part or all of the X gene. The results show that these children were infected with hepatitis B virus even without other markers in serum, that hepatitis B persists years after vaccination and that such infections are associated with the presence of X deletion mutants. Coinfection with hepatitis B and C viruses, the former containing a new class of variants, is common in children with beta-thalassemia.

Adolescent↗
PubMed1994

Occurrence of multiple JC virus variants with distinctive regulatory sequences in the brain of a single patient with progressive multifocal leukoencephalopathy.

We established 99 JC virus (JCV) DNA clones directly from the brain of a single patient with progressive multifocal leukoencephalopathy (PML). Based upon restriction patterns, the cloned viral DNAs were classified into two major groups (NY-1A and -1B) containing 53 and 35 clones, respectively, and several minor groups containing one or a few clones. The regulatory sequences of representative clones were compared with the archetypal regulatory sequence, which has been detected in JCV DNAs cloned from the urine of healthy and nonimmunosuppressed individuals. The regulatory sequence of NY-1B had the two structural features common to most PML-type regulatory regions, duplication and deletion of specific segments in the archetypal sequence, while that of NY-1A contained a small deletion and an insertion of a 29-bp sequence originating from the early region of the JCV genome. A regulatory region similar to that of NY-1A has never been detected in JCV isolates obtained thus far.

AIDS-Related Opportunistic Infections↗
PubMed1994

Study of natural diamonds by dynamic nuclear polarization-enhanced 13C nuclear magnetic resonance spectroscopy.

The results of a study of two types of natural-diamond crystals by dynamic nuclear polarization (DNP)-enhanced high-resolution solid-state 13C nuclear magnetic resonance (NMR) are reported. The home-built DNP magic-angle spinning (MAS) 13C NMR spectrometer operates at 54 GHz for electrons and 20.2 MHz for carbons. The power of the microwave source was about 30 W and the highest DNP enhancement factor came near to 10(3). It was shown that in the MAS spectra the 13C NMR linewidths of the Ib-type diamond were broader than those of IaB3-type diamond. From the hyperfine structure of the DNP enhancement as a function of frequency, four kinds of nitrogen-centred and one kind of carbon-centred free radicals could be identified in the Ib-type diamond. The hyperfine structures of the DNP enhancement curve that originated from the anisotropic hyperfine interaction between electron and nuclei could be partially averaged out by MAS. The 13C polarization time of DNP was rather long, i.e. 1500 s, and the spin-lattice relaxation time (without microwave irradiation) was about 300 s, which was somewhat shorter than anticipated. Discussions on these experimental results have been made in this report.

Diamond↗
PubMed1994

Cytosylglucuronic acid synthase (cytosine: UDP-glucuronosyltransferase) from Streptomyces griseochromogenes, the first prokaryotic UDP-glucuronosyltransferase.

Cytosylglucuronic acid synthase (cytosine: UDP-glucuronosyltransferase), the first prokaryotic UDP-GT and a key enzyme in the biosynthesis of the antibiotic blasticidin S, was purified 870-fold. It has optimum activity at a pH of 8.4 to 8.6, Kms of 6.0 (UDP-glucuronic acid) and 243 (cytosine) microM, and a maximum rate of metabolism of 14.6 mumol/min/mg. The apparent M(r) is 43,000. Activity was slightly enhanced by Mg2+ or Ca2+ but was not inhibited by EDTA. Activity was strongly inhibited by UDP. Cytosylglucuronic acid differs from eukaryotic UDP-glucuronosyltransferases in being a soluble protein with no apparent phospholipid requirement.

Chromatography, Affinity↗
PubMed1994

Transmission of the human polyomavirus JC virus occurs both within the family and outside the family.

JC polyomavirus (JCV) is a ubiquitous symbiote in the human population, infecting children asymptomatically and then persisting in renal tissue. We reevaluated the urinary excretion of JCV in subjects in various age groups using PCR. The detection rate for urinary JCV DNA was 9 to 17% until the age of 20 years; this rate increased dramatically to about 46% at the ages of 20 to 29 years and then increased gradually with age. Therefore, it appears that in most people excretion of JCV begins at the age of 20 to 29 years, which is earlier than suggested previously. Next, we studied the way in which JCV is spread in the human population. We selected eight Japanese families in which both parents and children excreted JCV in their urine. Their JCV subtypes were determined by PCR amplification of a JCV DNA fragment; this was followed by restriction enzyme analysis. JCV species in all JCV-positive family members were classified into either of the two subtypes, subtypes CY and MY, which are prevalent in the Japanese population. The following features of JCV subtype distribution were seen in the families: (i) both subtypes were detected in children of five of the eight families, and (ii) of 21 children who excreted JCV, 14 children excreted the same subtypes excreted by their mothers or fathers, while the remainder (7 children) excreted subtypes different from those excreted by their parents. These features suggest that JCV is transmitted both within the family and outside the family. The data also indicate that vertical transmission is not common in the spread of JCV.

Adolescent↗
PubMed1994

Capsid assembly and involved function analysis of twelve core protein mutants of duck hepatitis B virus.

The roles of different regions of the duck hepatitis B virus (DHBV) core protein on viral capsid assembly and related functions were examined. Twelve deletion and insertion mutations which covered 80% of the DHBV C open reading frame were constructed and expressed in Escherichia coli. The N-terminal region (amino acids 3 to 66) of DHBV core protein was important for its tertiary structure and function in E. coli. The expressed core mutants without this region apparently inhibited E. coli growth. The results of transmission electron microscopy of E. coli thin sections, capsid agarose gel, and sucrose gradient sedimentation demonstrated that a few DHBV core mutants with insertion in the N terminus and deletion in the C terminus retained the ability to form core-like particles in E. coli. However, other mutations in most of N-terminal and central regions strongly inhibited the self-assembly ability of DHBV core protein in E. coli. In addition, the mutant with a C-terminal region deletion (amino acids 181 to 228) lost most of the nucleic acid-binding activity of the DHBV core protein.

Amino Acid Sequence↗