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Biomedical subjects

C S Chiang

Publications and source records attributed to C S Chiang.

At least 55 records · Page 3Linked to original sources
PubMed1994

Detection of specific antibody to mycobacterial antigen 60 in tuberculous pleural effusion.

BACKGROUND: With the development of the enzyme-linked immunosorbent assay (ELISA) method, serodiagnosis of tuberculosis has been studied by many investigators. Only a few studies have been performed in pleural fluid. This study was designed to evaluate the IgG antibody levels to mycobacterial antigen 60 (Ag60) in pleural fluid, and evaluate its role in the diagnosis of tuberculous pleurisy. METHODS: Eighteen patients with tuberculous pleural effusions and 18 patients with malignant pleural effusions were studied. The levels of IgG antibodies to Ag60 in pleural fluids were measured by ELISA method. RESULTS: The mean titers of IgG against Ag60 in pleural fluids of tuberculous patients (508.3 +/- 382.7 EU) were significantly higher than those of the mean value of the malignant group (131.2 +/- 83.2 EU). In the TB pleurisy group, patients with positive M. tuberculosis cultures from pleural fluids had significantly higher titers than those with negative cultures (796.5 +/- 394.7 vs 277.8 +/- 150.2 EU); patients with impaired immune function had significantly lower titers than those without (138.4 +/- 28.9 vs 650.6 +/- 358.1 EU). Using 250 EU as a cutoff value for a positive test, the sensitivity was 72.2% and the specificity, 94.4%. CONCLUSIONS: ELISA method using Ag60 is a rapid test with an acceptable sensitivity and excellent specificity for differentiation between tuberculous and malignant pleural effusion.

Adolescent↗
PubMed1993

DNA polymerase delta from embryos of Drosophila melanogaster.

We have purified a DNA polymerase activity from 0- to 2-hr embryos of Drosophila melanogaster to near homogeneity. The purified enzyme consists of a single 120-kDa polypeptide, which contains polymerase and 3'-->5' exonuclease activities. Exonuclease activity is inhibited by deoxynucleoside triphosphates, suggesting that the polymerase and exonuclease activities are coupled. The polymerase is more active with poly(dA-dT) than with activated DNA or poly(dA)/oligo(dT) as template. It shows a low degree of processivity with poly(dA)/oligo(dT). The polymerase is sensitive to aphidicolin and carbonyldiphosphonate but resistant to N2-[p-(n-butyl)phenyl]-2-deoxyguanosine triphosphate, 2-[p-(n-butyl)anilino]-2-deoxyadenosine triphosphate, and dideoxythymidine triphosphate. The 120-kDa polypeptide can be distinguished from the large subunit of Drosophila DNA polymerase alpha on the basis of the peptides generated by partial cleavage with N-chlorosuccinimide and by its failure to react with a monoclonal antibody directed against the large subunit of DNA polymerase alpha. The DNA polymerase is inhibited by 200 mM NaCl and is unable to use poly(rA)/oligo(dT) as a template, thus differentiating it from DNA polymerase gamma. On the basis of these properties, we propose that the DNA polymerase that we have purified from 0- to 2-hr Drosophila melanogaster embryos is DNA polymerase delta.

Animals↗
PubMed1993

Late effects of radiation on the lumbar spinal cord of guinea pigs: re-treatment tolerance.

PURPOSE: Using a guinea pig model of lumbar myelopathy, various factors affecting the tolerance of spinal cord to irradiation were assessed: (a) extent of initial injury (b) time interval between priming and test doses (c) animal age at the time of initial radiation treatment. METHODS AND MATERIALS: A 3 cm section of lumbar spinal cord of guinea pigs was irradiated with fractionated doses of 4.5 Gy gamma rays given as 9 fractions per week. Guinea pigs were primed with 9 x 4.5 Gy in 7 days which is 60% of the ED50 for a continuous course of treatment. After 28 or 40 weeks, animals were retreated with 6-14 fractions of 4.5 Gy. Animals were observed for 2 years following the priming dose and both the incidence and latency of myelopathy recorded. RESULTS: Young adult guinea pigs (8 wk old) showed both a decreased radiation tolerance and latency compared to old individuals (40 wk old). At 28 or 40 wk after 9 x 4.5 Gy, only about 8% of the initial injury was remembered in young adult guinea pigs. CONCLUSION: The amount of residual injury was dependent on the initial damage as a proportion of the tolerance dose. The spinal cord shows a greater capacity for long-term recovery than generally appreciated and re-treatment doses clinically prescribed may be lower than necessary.

Age Factors↗
PubMed1993

Myelin-associated changes in mouse brain following irradiation.

The goals of this study were to quantify myelin-associated changes in the brain following single doses of radiation and to determine their relationship to the dose limits that this tissue can tolerate. Mice developed a transient loss of balance 1 month after 60 Gy doses 250 kVp X-rays to the brain and 3-4 months after 30-45 Gy radiation, but not after lower doses. The symptoms were transient and lasted approximately 1 month. The ED50/300 for radiation-induced brain death, which occurred large between 200 and 240 days, was 32.4 Gy (29.1, 35.5 Gy, 95% confidence limit of mean). At the time that animals developed neurological symptoms, 3-4 months after irradiation with doses of 30-45 Gy, biochemical assays of myelin-associated proteins showed decreases in 2',3'-cyclic nucleotide phosphohydrolase (CNPase) and myelin basic protein (MBP) levels that were not seen with lower radiation doses. By 120-180 days, further dose-dependent decreases in both CNPase and MBP levels were found after 20-45 Gy irradiation that preceded and correlated with death. The correlation of the decrease in CNPase and MBP levels with the incidence of transient neurological malfunction and animal death, together with histological evidence, suggests that demyelination is responsible for these phenomena.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1993

Radiation-induced astrocytic and microglial responses in mouse brain.

The aim of this study was to investigate the responses of astrocytes and microglia to whole brain irradiation. Levels of glial fibrillary acidic protein (GFAP), which is a marker for astrocytes, were measured by ELISA in irradiated brains taken at varying time points after irradiation. GFAP levels were increased between 120 and 180 days after single doses of 20-45 Gy radiation, but not after lower doses (2 or 8 Gy). The increases in GFAP levels were confirmed by Western blot analysis and immunohistochemical staining which showed that the number of GFAP-positive astrocytes was increased, as was their staining intensity. Coincidently with the increase in astrocyte staining, there was an increase in the number and the intensity of microglial cell staining for Mac I antigen. Autoradiography of brain tissue following in vivo administration of [3H]thymidine showed an increased number of labelled cells during the same time period. The radiation-induced astrocytic and microglial responses that follows brain irradiation is indicative of reactive gliosis and inflammation occurring during the latent period up to the onset of late radiation-induced injury. This gliosis increases with radiation dose. The possibility that gliosis may participate in modifying postirradiation injury in the brain is discussed.

Animals↗
PubMed1993

Apical malignancies diagnosed by ultrasound-guided fine needle aspiration biopsy.

Sixteen patients with apical malignancies, including 12 with Pancoast tumors and four with metastatic apical pleural masses, underwent chest ultrasound (US) examinations and direct percutaneous fine needle aspiration biopsy (FNAB). Of those, 15 patients were proven to have malignancies by FNAB and the remaining patient (only revealing necrosis by FNAB) was also proven to have a Pancoast tumor after surgical intervention. Percutaneous FNAB was performed through the supraclavicular approach (n = 10) or through the upper back (n = 6). The sonographic appearances of the apical malignancies were homogeneous hypoechoic (n = 8), homogeneous isoechoic (n = 3) or heterogeneous (n = 5). No complications occurred after the FNAB. Our limited experience showed that a convex probe was convenient and useful in the detection of apical malignancies. Apical malignancies, diagnosed previously by percutaneous needle aspiration under fluoroscopy or surgical intervention, can be easily diagnosed by percutaneous FNAB, especially when the FNAB is performed using the supraclavicular approach.

Aged↗
PubMed1992

Alteration in myelin-associated proteins following spinal cord irradiation in guinea pigs.

The aim of this study was to investigate the pathological and cellular basis for radiation-induced myelopathy in guinea pigs by monitoring biochemical alterations in levels of myelin basic protein and 2',3'-cyclic nucleotide phosphohydrolase. Guinea pigs were irradiated to the lumbar region with various doses of neutrons or cobalt gamma irradiation. The ED50s for paralysis were 17.2 Gy and 67.5 Gy for neutron and cobalt irradiation, respectively, and was histologically associated with demyelination. In spinal cords taken from animals at the onset of paralysis myelin basic protein levels were decreased in direct relationship to the radiation dose. The lowest doses to cause paralysis led to a 25% decrease in MBP levels. In a separate experiment, alterations in MBP were measured in the spinal cords over the time period leading up to paralysis. Surprisingly, decreases in MBP were found immediately after the end of the 4 week irradiation period. These early changes in MBP were not markedly dose dependent and occurred with nonparalyzing doses. Dose-dependent decreases were found only just before the onset of paralysis. CNPase activity measured in the same specimens showed changes that were essentially similar to those for MBP. In the CSF, MBP levels were essentially constant until onset of paralysis. This study showed that demyelination, as assessed by the levels of the myelin-associated proteins MBP and CNPase, can occur soon after spinal cord irradiation but that profound dose-dependent changes are seen only immediately preceding the onset of paralysis. Although increases in MBP in the CSF were associated with the onset of radiation-induced myelopathy, its assay is unlikely to predict this complication of irradiation.

2',3'-Cyclic Nucleotide 3'-Phosphodiesterase↗
PubMed1991

Radiation enhances tumor necrosis factor alpha production by murine brain cells.

Astrocytes and microglial cells cultured from murine brain were stimulated to produce tumor necrosis factor alpha (TNF) by exposure to lipopolysaccharide (LPS). TNF alpha production began within 2 h with maximum production between 4 and 8 h after stimulation. Clinically relevant low (2 Gy), but not high (8 Gy), doses of radiation significantly increased TNF production by astrocytes and microglial cells in response to LPS. The radiation effect was even more marked with multiple 2 Gy doses. TNF is cytotoxic for oligodendrocytes and for certain tumor cells. It increases vascular permeability and enhances immune responses as well as having other biological effects. It is conceivable that production of TNF by astrocytes and microglial cells during clinical radiation therapy might influence the responses of tumor and/or normal CNS tissues.

Animals↗
PubMed1991

Role of DnaA protein during replication of plasmid pBR322 in Escherichia coli.

The in vivo role of the Escherichia coli protein DnaA in the replication of plasmid pBR322 was investigated, using a plasmid derivative carrying an inducible dnaA+ gene. In LB medium without inducer, the replication of this plasmid, like that of pBR322, was inhibited by heat inactivation of chromosomal DnaA46 protein so that plasmid accumulation ceased 1 to 2 h after the temperature shift. This inhibition did not occur when the plasmid dnaA+ gene was expressed in the presence of the inducer isopropyl-1-thio-beta-D-galactopyranoside (IPTG). Inhibition was also not observed in glycerol minimal medium or in the presence of low concentrations of rifampicin or chloramphenicol. Deletion of the DnaA binding site and the primosome assembly sites (pas, rri) downstream of the replication origin did not affect the plasmid copy number during exponential growth at 30 degrees C, or after inactivation of DnaA by a shift to 42 degrees C in a dnaA46 host, or after oversupply of DnaA, indicating that these sites are not involved in a rate-limiting step for replication in vivo. The accumulation of the replication inhibitor, RNAI, was independent of DnaA activity, ruling out the possibility that DnaA acts as a repressor of RNAI synthesis, as has been suggested in the literature. Changes in the rate of plasmid replication in response to changes in DnaA activity (in LB medium) could be resolved into an early, rom-dependent, and a late, rom-independent component. Rom- plasmids show only the late effect. After heat inactivation of DnaC, plasmid replication ceased immediately.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Proteins↗
PubMed1991

Maintenance of pBR322-derived plasmids without functional RNAI.

pBR322-derived plasmids that lack the bla gene and 40% of the gene for the replication inhibitor, RNAI, have been constructed. Since the RNAI gene totally overlaps with the gene for the replication primer, RNAII, this primer is similarly defective and also lacks its normal promoter. The primer is presumed to by synthesized either from the counter-tet promoter (plasmid pCL59) or from an inserted lacUV5 promoter (plasmid pCL59-65). Based mainly on the observation that the plasmid Rom protein, which normally assists in the RNAI/RNAII interaction, has no effect on the replication of the RNAI/RNAII-defective plasmids, we suggest that the defective RNAI is not functional while the defective RNAII primer, although less efficient, still allows plasmid replication. The defective plasmids are fully compatible with the intact parent plasmid, indicating that they do not share a common control of replication. In the absence of antibiotics, the bacteria lose the defective plasmid, beginning after 80 generations; under the same conditions, the parent plasmid is retained even after 140 generations. During exponential growth of their host, the number of defective plasmids in a culture increases exponentially with a doubling time either smaller or greater than that of the host cell growth, depending on the growth medium and, in the case of pCL59-65, on the presence or absence of lac inducer IPTG. As a result of these differences in host cell growth and plasmid replication, the plasmids are either gradually diluted out or their copy number continually increases. This shows that, without RNAI, plasmid replication is uncoupled from the host cell growth and not, as usual, adjusted to it. It also implies that the RNAI mechanism is the only means of replication control for ColE1-type plasmids that senses and adjusts the copy number; limiting host factors cannot provide a back-up control to stabilize copy numbers.

Bacteriocin Plasmids↗
PubMed1991

Combined atelectasis of right upper and middle lobes: a clinical study of 15 cases.

Because of the independent and remote origin of the right upper and middle lobe bronchi, combined collapse of right upper and middle lobes is thought to be uncommon. We report 15 cases of combined right upper and middle lobe collapse found by plain chest radiograph in the past 8 years. Malignancies were confirmed in 13 cases. The other 2 cases with benign etiology included one case of endobronchial TB and one of pneumonia. These cases of combined bilobar collapse were possibly due to (1) the intraluminary infiltration of the primary tumor of the upper lobe to the middle lobe bronchus, (2) separated area of collapse produced by the primary tumor and its metastatic lymphadenopathy, (3) upper lobe tumor with external compression to intermediate bronchus that obstructed both the upper and middle bronchi, (4) multi-centric neoplasm, (5) tumor obstruction and sputum impaction at different bronchi, or (6) benign lesions operated at two different locations. The more frequent occurrence of bronchogenic carcinoma than that of benign lesions in our study revealed the invalidity of the "double lesion sign". Bronchoscopy or CT scan should be used to search for the etiology. If malignancy is confirmed in such condition, the prognosis is usually poor due to its advanced invasion.

Adult↗
PubMed1989

Reliable confirmation of antibodies to human immunodeficiency virus type 1 (HIV-1) with an enzyme-linked immunoassay using recombinant antigens derived from the HIV-1 gag, pol, and env genes.

An enzyme-linked immunoassay (ELISA) using six recombinant proteins corresponding to large segments of the human immunodeficiency virus type 1 (HIV-1) gag, pol, and env gene products (HIVAGEN; SmithKline Bio-Science Laboratories, Van Nuys, Calif.) was developed to confirm the presence of antibodies to HIV-1 in sera reactive in the whole-cell-derived virion screening ELISAs. Serum samples for testing were obtained from healthy seronegative blood donors and from the different categories of HIV-infected individuals (asymptomatic, acquired immunodeficiency syndrome [AIDS]-related complex, and AIDS). A positive reaction was defined as reactivity against an env and at least one other (either gag or pol) HIV-1 gene product; negative was defined as no reaction with any antigen; and indeterminate was defined as reactivity with gag or pol (or both) or with env alone. None of the 1,180 serum samples from healthy seronegative blood donors gave a positive result, and only 49 of these samples (4%) gave indeterminate results. The recombinant HIV-1 antigen ELISA panel identified seropositive individuals with a high degree of accuracy, as a positive reaction was seen with 99.3% of asymptomatic healthy seropositive individuals, 98.1% of patients with AIDS-related complex, and 90.4% of patients with AIDS. None of the 725 HIV-1-seropositive subjects had a negative test result. Reactivity with the Kp41 antigen, corresponding to an amino-terminal portion of the gp41 envelope glycoprotein, by itself demonstrated 100% sensitivity and specificity in distinguishing seronegative from seropositive sera. A subset of seronegative and seropositive samples were tested both with the recombinant HIV-1 antigen ELISA panel and by Western blot (Du Pont Co.). The recombinant HIV-1 antigen ELISA panel accurately identified more seropositive and seronegative samples and had fewer indeterminate results than did Western blot (interpreted by Du Pont criteria).

AIDS-Related Complex↗
PubMed1989

Development of a confirmatory enzyme-linked immunosorbent assay for HIV-1 antibodies.

We subcloned six discrete protein-coding regions representing the gag (Kp24 and Kp55), env (Kp41, Kp120N, and Kp120CC), and pol (Kp66/31) gene products of the human immunodeficiency virus type 1 (HIV-1) and expressed them in Escherichia coli as fusion proteins with the first 56 residues of galactokinase. An enzyme-linked immunosorbent assay for confirming the presence of HIV-1 antibodies was developed by coating the six purified antigens on individual wells of a microtiter plate (the HIVAGEN assay). This assay yielded no false-negative results and fewer indeterminate results than the Western blot assay for 143 specimens from patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC). Analysis of 1016 specimens from seronegative donors by the HIVAGEN assay yielded no false-positive results, and the rate of indeterminate results was substantially lower than for the Western blot assay. The HIVAGEN assay is well suited for routine confirmation of the presence of HIV-1 antibodies because it is objective, quantitative, rapid, precise, and readily automatable.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Stability of pBR322-derived plasmids.

The stability of pBR322-derived plasmids was studied during growth of their Escherichia coli host in the absence of antibiotics. Plasmid pBR322, as well as its delta rom and delta bla derivatives, were lost from their host within 60 generations, but a number of delta tet derivatives were quite stable under the same conditions. An evaluation of the data indicated that primary plasmid loss due to random partitioning corresponds to the generation of a plasmid-free cell about every 10(4) divisions (probability P0; = "intrinsic" instability). Secondary loss of plasmid-carrying cells resulted from a growth advantage of the plasmid-free cells when bacteria die, perhaps due to unrepaired lethal damage in the DNA, under conditions of stationary incubation (= "apparent" instability). This cell death also occurred in the absence of plasmids but was accelerated by the presence of extra plasmid DNA in the cell and further accelerated by a functional tet gene. This was the reason for the differential apparent stabilities of delta bla and delta tet plasmids. There was no indication that an accumulation of plasmid multimers contributed to the plasmid instability, as has been suggested in the literature. The value of P0 = 10(-4) is 14 orders of magnitude greater than expected under the assumption of a random (Poisson) distribution of plasmid copy numbers in a population of cells.

Chromosome Deletion↗
PubMed1987

A linear method for determining specific activity of tracers in radioimmunoassays.

I describe a rapid and objective method for graphically determining specific activity of radioactive tracers by self-displacement. Two sets of results are plotted on the same graph: total/bound counts vs concentration of unlabeled analyte (for the standard curve results) or quantity of radioactivity (for tracer self-displacement results). Because these plots are linear, not only are the difficulties of curve fitting and the need for numerous data points avoided, but also how well the data fit the lines can be assessed by calculating the standard deviation of the slope of the lines. This method minimizes uncertainty between data points, allows easier interpolation, and often yields more precise results than do previously published procedures.

Half-Life↗
PubMed1986

Expression of hepatitis B surface antigen by yeast actin gene promoter.

The promoter sequence (from position -500 to -21) of the yeast actin gene was subcloned into the multiple cloning site of pUC12 to generate a new recombinant plasmid pYAP12. The actin gene promoter can therefore be readily excised from pYAP12 by several restriction enzymes and subsequently placed upstream of the desired protein coding sequence. Results of expression of the hepatitis B surface antigen controlled by the actin gene promoter of pYAP12 in yeast suggest it is a strong functional promoter. To our knowledge, this is the first demonstration of the potential application of the yeast actin gene promoter for expression of foreign proteins in yeast.

Actins↗
PubMed1982

cAMP radioimmunoassay without interference from calcium or EDTA.

Calcium and EDTA interfere with radioimmunoassay of cAMP or acetylated cAMP. Both interferences with the assay of acetylated cAMP can be obviated by including in the buffer 15 mmol of CaCl2 per liter, which at the same time increases the affinity of the antibody by 89%. As a result, antibody can be decreased by 65%. This method requires no prepurification (extraction or chromatography), and no correction for analytical recovery is necessary. This assay can detect 12 fmol of cAMP per tube, so only microliter quantities of plasma are needed.

Adult↗