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L C Wu

Publications and source records attributed to L C Wu.

At least 55 records · Page 3Linked to original sources
PubMed1995

Use of fluorine-18 fluorodeoxyglucose positron emission tomography in the detection of thymoma: a preliminary report.

Thymomas are lacking in malignant cytological features. Their staging is defined by the invasiveness of the tumour. This study aimed to analyse the uptake patterns of fluorine-18 fluorodeoxyglucose (FDG) in thymomas of different stages. FDG positron emission tomography (PET) scan was performed in 12 patients suspected of having thymoma and in nine controls. Qualitative visual interpretation was used to detect the foci with FDG uptake higher than that of normal mediastinum. Tumour/lung ratio (TLR) was calculated from the counts of ROIs over the mass and over comparable normal lung tissue in thymoma patients. Mediastinum/lung ratio (MLR) was calculated from the counts of ROIs over the anterior mediastinum and lung in controls. The PET scan patterns of distribution of foci with FDG uptake and TLRs were correlated with the computed tomography (CT) or magnetic resonance imaging (MRI) findings, and staging of the thymomas. Thymectomy was performed in ten patients and thoracoscopy was done in two patients. The results revealed ten thymomas (two stage I tumours, two stage II, four stage III and two stage IV, according to the Masaoka classification), and two cases of thymic hyperplasia associated with myasthenia gravis. Myasthenia gravis was also noted in four thymoma patients. FDG studies showed (a) diffuse uptake in the widened anterior mediastinum in patients with thymic hyperplasia, (b) confined focal FDG uptake in the non-invasive or less invasive, stage I and II thymomas, and (c) multiple discrete foci of FDG uptake in the mediastinum and thoracic structures in stage III and IV advanced invasive thymomas. The thymomas had the highest TLRs, followed by the TLRs of thymic hyperplasia and the MLRs of control subjects (P <0.005). No significant difference was found between thymomas in different stages or between thymomas with and thymomas without myasthenia gravis. In comparison with CT and/or MRI, FDG-PET detected more lesions in patients with invasive thymomas and downgraded the staging of thymoma in four patients. Our preliminary results suggest that FDG-PET is useful in the assessment of the invasiveness of thymomas, and may have the potential to differentiate thymomas from thymic hyperplasia.

Adult↗
PubMed1995

Bipartite structure of the alpha-lactalbumin molten globule.

Molten globules are thought to be general intermediates in protein folding. Apparently conflicting studies have failed to clarify whether one of the best characterized molten globules, that of alpha-lactalbumin, resembles an expanded native-like protein or a nonspecific collapsed polypeptide. Here we show that the molten globule properties of alpha-lactalbumin are largely confined to one of its two domains. The alpha-helical domain forms a helical structure with a native-like tertiary fold, while the beta-sheet domain is largely unstructured. Molten globules thus possess a native-like backbone topology, but this topology does not necessarily encompass the entire polypeptide chain. Our studies indicate that molten globules provide an approximate solution to, and considerable simplification of the protein folding problem.

Amino Acid Sequence↗
PubMed1995

Three distinct genotypes within Candida parapsilosis from clinical sources.

Three genetically distinct groups of Candida parapsilosis were detected among clinical isolates. These were distinguishable on the basis of isoenzyme profiles and DNA sequences of internally transcribed spacer (ITS) sequences flanking the 5.8S RNA gene. In an investigation of 45 strains, including 32 clinical isolates from Texas, C. parapsilosis group I composed the majority of the common clinical isolates. The type strain of C. parapsilosis was a member of this group. The 10 group II isolates were indistinguishable from group I strains when tested with the API 20C kit. The two group III isolates differed from those in groups I and II by being D-xylitol positive by the API 20C kit; however, isolates in all groups assimilated D-xylitol from broth. Isoenzyme profiles excluded the close relationship of any of these groups to Lodderomyces elongisporus, which is a teleomorphic yeast that has a physiological profile similar to that of C. parapsilosis. Although there were insignificant differences in the ITS2 rDNA sequences, comparisons of the ITS1 sequences revealed several differences. A sequence analysis of ITS1 in which missing bases were counted as mismatches showed the following similarities: group I versus group II, 87.7%; group I versus group III, 82.1%; group II versus group III, 84.5%. Also, the activity of secreted proteinase showed differences among the three groups, with many group I isolates having moderate to high activity. The degree of susceptibility to antifungal agents, amphotericin B, ketoconazole, and 5-fluorocytosine, could not be used to determine an isolate's group.

Antifungal Agents↗
PubMed1995

Pulmonary endothelial nitric oxide synthase gene expression is decreased in a rat model of congenital diaphragmatic hernia.

Nitric oxide (NO) produced by the enzyme nitric oxide synthase (NOS) is critically involved in the cardiopulmonary transition from fetal to neonatal life. In congenital diaphragmatic hernia (CDH) this transition often does not occur normally, resulting in persistent pulmonary hypertension of the newborn (PPHN). We sought to determine if pulmonary NOS expression is altered in a rat model of CDH induced by maternal ingestion of the herbicide 2,4-dichlorophenyl-p-nitrophenyl ether (Nitrofen) on day 9 of gestation (term = 22 days). Sixty-three percent of Nitrofen-exposed fetuses developed CDH. Endothelial NOS (eNOS) and neuronal NOS (nNOS) protein expression were assessed in ipsilateral CDH lungs and in control lungs (Nitrofen-treated, no hernia) at 20 d gestation using immunoblot analyses. eNOS and nNOS have been immunohistochemically localized to rat pulmonary endothelium and bronchiolar epithelium, respectively, and we have previously demonstrated that their expression normally increases during late gestation to be maximal near term. eNOS protein expression was decreased in CDH versus control lung (58 +/- 6 versus 100 +/- 6% of control, n = 5). In contrast, nNOS protein abundance was similar. Factor VIII-associated antigen expression was comparable in CDH and control lung, indicating that the change in eNOS is not related to differences in endothelial cell density. eNOS mRNA abundance was evaluated in semiquantitative reverse transcription-polymerase chain reaction assays. Paralleling the decline in eNOS protein expression, eNOS mRNA was decreased in CDH versus control lung (22 +/- 8 versus 100 +/- 31% of control, n = 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

99Tcm-HMPAO and 99Tcm-DTPA radioaerosol clearance measurements in idiopathic pulmonary fibrosis.

The clearance rate of an inhaled aerosol of a lipophilic complex, 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO), was compared with that of a hydrophilic complex, 99Tcm-diethylenetriamine pentaacetate (99Tcm-DTPA), in nine normal subjects and in eight patients with idiopathic pulmonary fibrosis (IPF). Data were acquired as follows. The subjects were placed supine with their back against the scintillation camera and breathed aerosol for 2 min; pulmonary radioactivity was then monitored for 30 min. A time-activity curve (TAC) was generated from the region of interest (ROI) over the periphery of each lung field and a computer program was then used to calculate percentage clearance per minute (k) in each lung. The mean (+/- S.E.M.) rate of clearance of 99Tcm-DTPA (k = 1.31 +/- 0.13% min-1) was not significantly different from that of 99Tcm-HMPAO (k = 1.32 +/- 0.27% min-1, P > 0.025) in the normal subjects. However, 99Tcm-DTPA clearance was 1.91 +/- 0.27% min-1 and 99Tcm-HMPAO clearance 0.78 +/- 0.17% min-1 in eight patients with IPF (P < 0.001, 99Tcm-DTPA vs 99Tcm-HMPAO). By regression analysis using a multiplicative model, both values correlated fairly [r = -0.71, y = exp (0.08-0.85 ln chi); P < 0.005], with a change in clearance rate in the opposite direction in all eight patients. The results of our study demonstrate that the pulmonary clearance of 99Tcm-HMPAO is different from that of 99Tcm-DTPA in IPF.

Aerosols↗
PubMed1995

[Effects of Shenmai injection on immune function in stomach cancer patients after chemotherapy].

Sixty-three cases with stomach cancer were randomized and observed, the results showed that the count of T lymphocytes in chemotherapy combined with Shenmai injection (SMI) group increased, while in control group it decreased, the difference was significant (P < 0.05). The results also indicated that the count of OKT4 cells and the ratio of OKT4/OKT8 decreased after chemotherapy, but in SMI group both parameters increased in advence which were higher in the 4th week after chemotherapy than that before chemotherapy. However, the count of OKT1 cells and the ratio of OKT4/OKT8 were still in low level. Serum interleukin-2 receptor (sIL-2R) level also decreased (P < 0.05), while activities of natural killer cell (NK) and lymphokine activated killer cell (LAK) level increased (P < 0.05) in SMI group. Although the sIL-2R level had no change, both NK and LAK level decreased in control group. In addition, the difference of IgA, IgM, IgG level were not significant between these two groups. This suggested that SMI might improve human immune function to facilitate the chemotherapy of patients with stomach cancer.

Adenocarcinoma↗
PubMed1994

Structure and genetics of the partially duplicated gene RP located immediately upstream of the complement C4A and the C4B genes in the HLA class III region. Molecular cloning, exon-intron structure, composite retroposon, and breakpoint of gene duplication.

The correlation of many HLA-associated autoimmune and genetic diseases with the polymorphic complement C4 genes may be attributed to the presence of disease susceptibility genes in the close proximity of C4. We have cloned and characterized a pair of partially duplicated genes, RP1 and RP2, located 611 base pairs upstream of the human C4A and C4B genes, respectively. The putative RP protein, consisting of 364 amino acid residues, is basic and highly hydrophilic. There is a bipartite nuclear localization signal at residues 114-131 and therefore RP may be a nuclear protein. Northern blot analysis suggested that RP is ubiquitously expressed. The 5' region of the RP1 gene is CpG rich, which is a characteristic of housekeeping genes. The RP1 gene contains nine exons. Located in the fourth intron is a cluster of Alu elements, and a newly defined composite retroposon SVA with a SINE, multiple copies of GC-rich VNTRs and an Alu element altogether enclosed by direct terminal repeats. Members of SVA are also present in the complement C2 gene located about 20 kilobases upstream of RP1 in the HLA and in the cytochrome CYP1A1 gene. Determination of the DNA sequences for RP2 from two different HLA haplotypes revealed identical hybrid sequences which resulted from fusion of RP with the tenascin-like Gene X and truncation of the 5' regions of both genes. Cumulative data suggest that the four tandemly arranged genes RP, complement C4, steroid 21-hydroxylase (CYP21), and Gene X altogether form a modular structure, RCCX. The number of RCCX modules varies from one to three or more in the population. Absence of the truncated genes RP2 and Gene XA have been detected in genomes with single RCCX modules. Duplication of the RCCX modules probably occurred before the speciation of great apes and humans as they contain the same breakpoint region of RP and Gene X gene duplication.

Alleles↗
PubMed1994

The V(D)J recombination signal sequence and kappa B binding protein Rc binds DNA as dimers and forms multimeric structures with its DNA ligands.

The murine DNA binding protein Rc binds to the heptamer motif of the V(D)J recombination signal sequences and to the kappa B motif of the immunoglobulin enhancer. Bacterial fusion proteins for Rc and DNA ligands of Rc form multiple protein-DNA complexes in electrophoretic mobility shift assays (EMSA). Large complexes formation is favored by an increased Rc concentration. In order to determine the architecture of these complexes, the apparent molecular weights of the protein-DNA complexes were first determined by their gel mobilities. The data suggest that Rc binds to its DNA ligands as dimers, tetramers, and multiples of tetramers. The inference that Rc binds DNA as dimers was substantiated by the formation of chimeric complexes when two electrophoretically distinguishable Rc proteins were employed in EMSA. Methylation interference experiments show that there are no contiguous protein binding sites evident in the DNA of the larger complexes. Apparently, multimerization occurs via protein-protein interactions. Such interaction was demonstrated by the formation of Rc dimers and tetramers in a chemical crosslinking experiment. Significantly, the multimerization of DNA-bound Rc could be involved in bringing the variable region gene segments together for the somatic V(D)J recombination.

Amino Acid Sequence↗
PubMed1994

Transcriptional regulation of the gene for the second component of human complement: promoter analysis.

The 5' flanking region of the human gene for the second component of complement was sequenced and analyzed functionally. RNase protection demonstrated a cluster of four initiation sites in the 5' flanking region utilized in the hepatoma cell line, HepG2. Utilization of all four initiation sites increased in response to gamma-interferon (IFN-gamma). Transient transfection analysis was used to examine cis-acting sequence motifs controlling transcription from the 5'-flanking region. We identified a 228-bp minimal promoter fragment which was able to direct basal and IFN-gamma inducible transcription from authentic initiation sites. Sequence motifs outside of this region may modulate the transcriptional regulation of the second component of complement. Although complement components are not coordinately regulated, we identified four regions of significant homology with the promoters of multiple other complement components. Three of these regions were within the minimal promoter fragment.

Animals↗
PubMed1994

Autonomous subdomains in protein folding.

Proteolytic dissection of native trp repressor and horse heart cytochrome c has been used to infer some of the steps in the folding pathways of the intact proteins. For both proteins, small fragments are capable of undergoing spontaneous noncovalent association to form subdomains with native-like secondary and/or tertiary structural features, suggesting that dissection/reassembly may be a general method to gain insight into the structures of folding intermediates. The importance of this approach is its simplicity and potential applicability to studying the folding pathways of a wide range of proteins. The proteases report on the structure and dynamics of the native state, circumventing the need for prior knowledge of the structures of folding intermediates. The observation that small fragments of proteins can associated noncovalently suggests that protein folding can be viewed as an intramolecular "recognition" process. The results imply that substantial information about protein structure and folding is encoded at the level of subdomains, and that chain connectivity has only a minor role in determining the fold.

Animals↗
PubMed1994

The dichotomous size variation of human complement C4 genes is mediated by a novel family of endogenous retroviruses, which also establishes species-specific genomic patterns among Old World primates.

The human complement C4 genes in the HLA exhibit an unusual, dichotomous size polymorphism and a four-gene, modular variation involving novel gene RP, complement C4, steroid 21-hydroxylase (CYP21), and tenascin-like Gene X (RCCX). The C4 gene size dichotomy is mediated by an endogenous retrovirus, HERV-K(C4). Nearly identical sequences for this retrotransposon are present precisely at the same location in the long C4 genes from the tandem RCCX Module I and Module II. Specific nucleotide substitutions between the long and short C4 genes have been identified and used for diagnosis. Southern blot analyses revealed that HERV-K(C4) is present at more than 30 locations in the human genome, exhibits variations in the population, and its analogs exist in the genomes of Old World primates with species-specific patterns. Evidence of intrachromosomal recombination between the two long terminal repeats of HERV-K(C4) is found near the huntingtin locus on chromosome 4. It is possible that members of HERV-K(C4) are involved in genetic instabilities including the RCCX modules, and in protecting the host genome from retroviral attack through an antisense strategy.

Amino Acid Sequence↗
PubMed1994

Endothelial nitric oxide synthase is expressed in cultured human bronchiolar epithelium.

Nitric oxide (NO) is an important mediator of physiologic and inflammatory processes in the lung. To better understand the role of NO in the airway, we examined constitutive NO synthase (NOS) gene expression and function in NCI-H441 human bronchiolar epithelial cells, which are believed to be of Clara cell lineage. NOS activity was detected by [3H]arginine to [3H]citrulline conversion (1,070 +/- 260 fmol/mg protein per minute); enzyme activity was inhibited 91% by EGTA, consistent with the expression of a calcium-dependent NOS isoform. Immunoblot analyses with antisera directed against neuronal, inducible, or endothelial NOS revealed expression solely of endothelial NOS protein. Immunocytochemistry for endothelial NOS revealed staining predominantly in the cell periphery, consistent with the association of this isoform with the cellular membrane. To definitively identify the NOS isoform expressed in H441 cells, NOS cDNA was obtained by degenerate PCR. Sequencing of the H441 NOS cDNA revealed 100% identity with human endothelial NOS at the amino acid level. Furthermore, the H441 NOS cDNA hybridized to a single 4.7-kb mRNA species in poly(A)+ RNA isolated from H441 cells, from rat, sheep, and pig lung, and from ovine endothelial cells, coinciding with the predicted size of 4.7 kb for endothelial NOS mRNA. Guanylyl cyclase activity in H441 cells, assessed by measuring cGMP accumulation, rose 6.6- and 5.4-fold with calcium-mediated activation of NOS by thapsigargin and A23187, respectively. These findings indicate that endothelial NOS is expressed in select bronchiolar epithelial cells, where it may have autocrine effects through activation of guanylyl cyclase. Based on these observations and the previous identification of endothelial NOS in a kidney epithelial cell line, it is postulated that endothelial NOS may be expressed in unique subsets of epithelial cells in a variety of organs, serving to modulate ion flux and/or secretory function.

Amino Acid Oxidoreductases↗
PubMed1993

Molecular cloning of a zinc finger protein which binds to the heptamer of the signal sequence for V(D)J recombination.

The somatic V(D)J recombination for the assembly of the Ig and TCR genes is mediated by the recombination signal sequences (Rss) and the V(D)J recombinase. A cDNA clone was isolated from a lambda gt11 expression library made from mouse thymocyte poly(A)+ RNA, using the Rss as a ligand. The deduced amino acid sequence of the putative protein, designated Recognition component (Rc), reveals a pair of Cys2-His2 zinc fingers followed by a Glu- and Asp-rich acidic domain. In addition, there are five copies of the Ser/Thr-Pro-X-Arg/Lys sequence, which are putative DNA binding units. The zinc finger-acidic domain structures present in Rc are also found in several enhancer binding proteins, such as those for the kappa B motif of the Ig kappa light chain enhancer or related sequences. Bacterial fusion proteins for Rc bind preferentially to the Rss heptamer and to the kappa B motif. The dual affinities of Rc for the Rss heptamer and the kappa B motif suggest a possible link between Ig transcription and somatic recombination. The formation of multiple 'gel-shifted' DNA-protein complexes for Rc and its DNA ligand suggests that these complexes tend to multimerize.

Amino Acid Sequence↗
PubMed1993

A noncovalent peptide complex as a model for an early folding intermediate of cytochrome c.

Horse heart cytochrome c is one of a small number of proteins for which the folding pathway has been elucidated in structural detail by pulsed hydrogen exchange and NMR. Those studies indicated that a partially folded intermediate with interacting N- and C-terminal helices is formed at an early stage of folding when most of the chain is still disordered. This report describes a peptide model for this early intermediate, consisting of a noncovalent complex between a heme-containing N-terminal fragment (residues 1-38) and a synthetic peptide corresponding to the C-terminal helix (residues 87-104). Far-UV circular dichroism and proton NMR indicate that the isolated peptides are largely disordered, but when combined, they form a flexible, yet tightly bound complex with enhanced helical structure. These results emphasize the importance of interactions between marginally stable elements of secondary structure in forming tertiary subdomains in protein folding.

Amino Acid Sequence↗
PubMed1993

Reduced activation of transcriptional factor AP-1 among peripheral blood T cells from elderly humans after PHA stimulation: restorative effect of phorbol diesters.

In the present study, we evaluated if aging influences the activation and characteristics of transcriptional factor AP-1 in human T cells. Using gel mobility shift assays, the activation of AP-1 was quantified in peripheral blood T cells from 11 elderly (mean 74 year) and young (mean 33 year) subjects following stimulation with PHA, PMA, or PHA plus PMA. The results showed that the activation of AP-1 was significantly reduced in PHA-stimulated T cells from the group of elderly subjects when compared to T cells from young subjects (P < 0.05). Even though PHA-stimulated T cells from 8 of the elderly subjects had pronounced impairments in the activation of AP-1, additional signals provided by costimulation with PMA frequently restored AP-1 activation to more normal levels. Other experiments demonstrated that the AP-1 complexes expressed by stimulated T cells of elderly and young subjects exhibited similar properties in gel shift assays with competing unlabeled AP-1 oligonucleotides and with blocking antibodies specific for Fos and Jun. Thus, these data suggest that the activation of AP-1 can be reduced in human T cells during aging and that these reductions may often be related to impairments in signal transduction rather than represent an absolute loss in the ability to express AP-1.

Adult↗
PubMed1993

Comparison of pulsed-field gel electrophoresis with isoenzyme profiles as a typing system for Candida tropicalis.

Candida species are important nosocomial pathogens, particularly in immunocompromised and critically ill patients. A variety of methods have been used to differentiate strains, but an optimal system has not been established. We compared methods for typing a panel of nine related isolates of Candida tropicalis from an outbreak of sternal wound infections as well as four unrelated control isolates of this species. (The genetic relationships of the nine isolates in the panel had been confirmed previously by restriction fragment analysis.) Typing was undertaken without knowledge of an isolate's origin. Karyotyping by contour-clamped homogeneous electric field (CHEF) gel electrophoresis failed to distinguish between outbreak and control isolates. However, when chromosome-sized DNA was digested with SfiI, EagI, SacII, or NaeI and the fragments were separated by CHEF electrophoresis, the outbreak isolates were readily identified. The isoenzyme profiles of the outbreak isolates were identical and were distinctly different from those of the control isolates. While both isoenzyme profiles and the modified CHEF procedure were discriminatory, the latter is recommended as a relatively convenient and reproducible technique for comparison of types of C. tropicalis.

Acid Phosphatase↗