Search PubMed⌕ Search

Biomedical subjects

Y Cao

Publications and source records attributed to Y Cao.

At least 415 records · Page 23Linked to original sources
PubMed1995

A new monoclonal antibody (A78-G/A7) to the Thomsen-Friedenreich pan-tumor antigen.

A new monoclonal antibody to the Thomsen-Friedenreich (TF) antigen (or, more precisely, epitope; Gal beta 1-3GalNAc-) has been developed that is specific for both anomeric forms of this disaccharide (TF alpha and TF beta, including related structures on glycolipids), and not assay restricted. We demonstrate that this avid antibody (A78-G/A7) is well suited for immunohistochemistry on paraffin-embedded and cryosectioned tissues, immunoblotting, ELISA techniques, and hemagglutination. Immunohistochemistry on paraffin sections does not require proteolytic or microwave pretreatment. The binding characteristics of this antibody are largely independent of variations in pH (6.0-8.2) and temperature (4-37 degrees C). Immunoblotting with KG-1 (human acute myelogenous leukemia) cells revealed a series of TF-active glycoproteins with a main band at about 155 kDa. Immunoprecipitation was performed using a new technique applicable to IgM-type antibodies.

Animals↗
PubMed1995

The mechanism of recA polA lethality: suppression by RecA-independent recombination repair activated by the lexA(Def) mutation in Escherichia coli.

The mechanism of recA polA lethality in Escherichia coli has been studied. Complementation tests have indicated that both the 5'-->3' exonuclease and the polymerization activities of DNA polymerase I are essential for viability in the absence of RecA protein, whereas the viability and DNA replication of DNA polymerase I-defective cells depend on the recombinase activity of RecA. An alkaline sucrose gradient sedimentation analysis has indicated that RecA has only a minor role in Okazaki fragment processing. Double-strand break repair is proposed for the major role of RecA in the absence of DNA polymerase I. The lexA(Def)::Tn5 mutation has previously been shown to suppress the temperature-sensitive growth of recA200(Ts) polA25::spc mutants. The lexA(Def) mutation can alleviate impaired DNA synthesis in the recA200(Ts) polA25::spc mutant cells at the restrictive temperature. recF+ is essential for this suppression pathway. recJ and recQ mutations have minor but significant adverse effects on the suppression. The recA200(Ts) allele in the recA200(Ts) polA25::spc lexA(Def) mutant can be replaced by delta recA, indicating that the lexA(Def)-induced suppression is RecA independent. lexA(Def) reduces the sensitivity of delta recA polA25::spc cells to UV damage by approximately 10(4)-fold. lexA(Def) also restores P1 transduction proficiency to the delta recA polA25::spc mutant to a level that is 7.3% of the recA+ wild type. These results suggest that lexA(Def) activates a RecA-independent, RecF-dependent recombination repair pathway that suppresses the defect in DNA replication in recA polA double mutants.

Bacterial Proteins↗
PubMed1995

Multiple genes, tissue specificity, and expression-dependent modulationcontribute to the functional diversity of potassium channels in Arabidopsis thaliana.

K+ channels play diverse roles in mediating K+ transport and in modulating the membrane potential in higher plant cells during growth and development. Some of the diversity in K+ channel functions may arise from the regulated expression of multiple genes encoding different K+ channel polypeptides. Here we report the isolation of a novel Arabidopsis thaliana cDNA (AKT2) that is highly homologous to the two previously identified K+ channel genes, KAT1 and AKT1. This cDNA mapped to the center of chromosome 4 by restriction fragment length polymorphism analysis and was highly expressed in leaves, whereas AKT1 was mainly expressed in roots. In addition, we show that diversity in K+ channel function may be attributable to differences in expression levels. Increasing KAT1 expression in Xenopus oocytes by polyadenylation of the KAT1 mRNA increased the current amplitude and led to higher levels of KAT1 protein, as assayed in western blots. The increase in KAT1 expression in oocytes produced shifts in the threshold potential for activation to more positive membrane potentials and decreased half-activation times. These results suggest that different levels of expression and tissue-specific expression of different K+ channel isoforms can contribute to the functional diversity of plant K+ channels. The identification of a highly expressed, leaf-specific K+ channel homolog in plants should allow further molecular characterization of K+ channel functions for physiological K+ transport processes in leaves.

Amino Acid Sequence↗
PubMed1995

In pursuit of the "holy grail": recombinant allergens and peptides as catalysts for the allergen-specific immunotherapy.

This presentation reviews recent progress in knowledge of (i) molecular biology and immunology of allergens and (ii) the methods for the modulation of allergen-specific immune response, with special emphasis on our grass pollen allergens, particularly Pao p IX AL, used as a model. The last few years have seen tremendous progress in molecular characterization of allergens, leading to synthesis of a number of recombinant allergens. Furthermore, studies of the structure-activity relationship of allergens have led to the delineation of the epitopes of these allergens and of widespread cross-reactivities among diverse allergens. In view of the requirement for extensive pre-clinical studies, the application of the recombinant allergens and epitopes in the clinical realm has just begun. Studies in murine systems suggest that these allergens and/or their epitopic peptides downregulate allergen-specific immune responses de novo. The potential and drawbacks of the recombinant allergens and peptides for improving the existing immunotherapeutic approaches and for developing new approaches to specific immunotherapy are discussed.

Allergens↗
PubMed1995

Primary isolates of human immunodeficiency virus type 1 are relatively resistant to neutralization by monoclonal antibodies to gp120, and their neutralization is not predicted by studies with monomeric gp120.

A panel of anti-gp120 human monoclonal antibodies (HuMAbs), CD4-IgG, and sera from people infected with human immunodeficiency virus type 1 (HIV-1) was tested for neutralization of nine primary HIV-1 isolates, one molecularly cloned primary strain (JR-CSF), and two strains (IIIB and MN) adapted for growth in transformed T-cell lines. All the viruses were grown in mitogen-stimulated peripheral blood mononuclear cells and were tested for their ability to infect these cells in the presence and absence of the reagents mentioned above. In general, the primary isolates were relatively resistant to neutralization by the MAbs tested, compared with the T-cell line-adapted strains. However, one HuMAb, IgG1b12, was able to neutralize most of the primary isolates at concentrations of < or = 1 microgram/ml. Usually, the inability of a HuMAb to neutralize a primary isolate was not due merely to the absence of the antibody epitope from the virus; the majority of the HuMAbs bound with high affinity to monomeric gp120 molecules derived from various strains but neutralized the viruses inefficiently. We infer therefore that the mechanism of resistance of primary isolates to most neutralizing antibodies is complex, and we suggest that it involves an inaccessibility of antibody binding sites in the context of the native glycoprotein complex on the virion. Such a mechanism would parallel that which was previously postulated for soluble CD4 resistance. We conclude that studies of HIV-1 neutralization that rely on strains adapted to growth in transformed T-cell lines yield the misleading impression that HIV-1 is readily neutralized. The more relevant primary HIV-1 isolates are relatively resistant to neutralization, although these isolates can be potently neutralized by a subset of human polyclonal or monoclonal antibodies.

Amino Acid Sequence↗
PubMed1995

Genetic analysis of human immunodeficiency virus type 1 strains from patients in Cyprus: identification of a new subtype designated subtype I.

DNA sequences encoding the C2 to V3 region of envelope glycoprotein gp120 of human immunodeficiency virus type 1 (HIV-1) were amplified by PCR from uncultured peripheral blood mononuclear cells obtained from 24 of 25 HIV-1-seropositive patients from Cyprus. By using a heteroduplex mobility assay (HMA), all amplified products were studied genetically and compared with 16 previously characterized HIV-1 strains belonging to subtypes A through F. HMA results revealed that HIV-1 gp120 sequences from 15 of our patients were of subtype B of HIV-1, whereas one isolate was of subtype C. However, gp120 sequences from eight patients had no obvious similarities to the known subtypes as defined by HMA. DNA sequencing and phylogenetic analyses of molecular clones confirmed the HMA results and placed the eight undefined HIV-1 isolates into three distinct genetic clusters. On the basis of branch topology and lengths of the phylogenetic tree, we conclude that one group consisting of three clones from two patients represents a new HIV-1 env subtype, which we have termed subtype I. The remaining two sequence clusters, consisting of five sequences from four patients and two sequences from two other patients, are distally related to subtypes A and F. These data demonstrate the extensive heterogeneity of HIV-1 in Cyprus, including the presence of new subtype.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Inhibition of cytoplasmic and organellar protein synthesis in Toxoplasma gondii. Implications for the target of macrolide antibiotics.

We investigated potential targets for the activity of protein synthesis inhibitors against the protozoan parasite Toxoplasma gondii. Although nanomolar concentrations of azithromycin and clindamycin prevent replication of T. gondii in both cell culture and in vivo assays, no inhibition of protein labeling was observed in either extracellular or intracellular parasites treated with up to 100 microM drug for up to 24 h. Quantitative analysis of > 300 individual spots on two-dimensional gels revealed no proteins selectively depleted by 100 microM azithromycin. In contrast, cycloheximide inhibited protein synthesis in a dose-dependent manner. Nucleotide sequence analysis of the peptidyl transferase region from genes encoding the large subunit of the parasite's ribosomal RNA predict that the cytoplasmic ribosomes of T. gondii, like other eukaryotic ribosomes, should be resistant to macrolide antibiotics. Combining cycloheximide treatment with two-dimensional gel analysis revealed a small subset of parasite proteins likely to be synthesized on mitochondrial ribosomes. Synthesis of these proteins was inhibited by 100 microM tetracycline, but not by 100 microM azithromycin or clindamycin. Ribosomal DNA sequences believed to be derived from the T. gondii mitochondrial genome predict macrolide/lincosamide resistance. PCR amplification of total T. gondii DNA identified an additional class of prokaryotic-type ribosomal genes, similar to the plastid-like ribosomal genes of the Plasmodium falciparum. Ribosomes encoded by these genes are predicted to be sensitive to the lincosamide/macrolide class of antibiotics, and may serve as the functional target for azithromycin, clindamycin, and other protein synthesis inhibitors in Toxoplasma and related parasites.

Animals↗
PubMed1995

Isolated growth hormone deficiency: testing the little mouse hypothesis in man and exclusion of mutations within the extracellular domain of the growth hormone-releasing hormone receptor.

The phenotypic characteristics of isolated growth hormone deficiency (IGHD) type IB in humans, such as autosomal recessive inheritance, time of onset of growth retardation, diminished secretion of growth hormone (GH) and IGF-I, proportional reduction in weight and size, and delay in sexual maturation, has much in common with the phenotype of the homozygous little/little (lit/lit) mouse. Sequencing of the GH releasing hormone (GHRH) receptor in lit/lit mice has shown a single nucleotide substitution within the extracellular peptide binding domain at codon 60 that changed aspartic acid to glycine. Therefore, the GHRH receptor is a reasonable candidate gene for causing IGHD in humans. DNA from 65 unrelated healthy Caucasians of normal stature and 65 children with IGHD type IB of whom 12 did not respond to exogenous treatment with GHRH were studied. Restriction endonuclease analysis, linkage studies, and polymerase chain reaction amplification and sequencing of the whole extracellular domain including the first three membrane spanning domains of the GHRH receptor gene were performed. None of the analyses revealed any structural abnormalities in these patients with IGHD. This suggests that a lit/lit mouse equivalent is an unlikely explanation for the majority of children with IGHD. Although gross structural abnormalities in the whole gene have been ruled out in this study, mutations in the carboxyl terminus are still possible, and, therefore, the remaining part of the gene needs to be sequenced.

Animals↗
PubMed1995

Competitive complexation of trace metals with dissolved humic acid.

In this study we investigated the effects of competing trace metals and Ca2+ on Cd(II), Pb(II), and Cu(II) complexation by humic acid extracted from groundwater in Orange County, California. Two types of titration experiments were conducted, those using a single metal and those in which the humic acid had been preequilibrated with a competing metal (either a trace metal or Ca2+). The labile metal concentration in the titration was determined by differential pulse polarography (DPP). Results show the different effects of competing trace metal ions and the effect of Ca2+. Both trace metals and Ca2+ do not compete effectively with Cd(II) complexation. While no effects of Cu(II) on Pb(II) complexation were observed, the presence of Cd(II) appeared to slightly enhance the binding between Pb(II) and humic acid. The addition of Pb(II) decreased the amount of Cu(II) complexation, but Cd(II) caused a slight increase at the lower concentrations. Calcium, however, decreased the amount of complexation for all three metals. Results indicate that the metals are not necessarily competing for the same sites. Conformational changes that occur when trace metals bind to the different sites may cause this competing or enhanced effect. Since Ca(II) is introduced at two orders of magnitude higher in concentration than the trace metals, it can outcompete the trace metal for sites where electrostatic interactions dominate. The results indicate that in groundwater situations, where more than one metal is present, the effect of other metals must be considered in predicting metal speciation.

Animals↗
PubMed1995

Locating VEP equivalent dipoles in magnetic resonance images.

Pattern-reversal and diffuse flash visual evoked potentials (VEPs) were obtained from 4 normal adults. A spatiotemporal dipole model was used to determine the location of the hypothetical equivalent dipoles consistent with the scalp distribution of the VEPs. Equivalent dipoles representing ERG and VEP activity were placed within 3-D magnetic resonance images of the brain. Most of the localization error appeared to be due to inadequate sampling of the potential field in frontal and occipital areas by the 10-20 system of electrode placement. Locating electrophysiologic dipoles within magnetic resonance images of brain structure allows evaluation of dipole localization techniques.

Adult↗
PubMed1995

[The Chinese traditional treatment with "ShengYang" prescription as a post-operative auxiliary method using on the oral squamous cells carcinoma patients.].

This paper observed the clinic investigation.Which prove the relationship among the Chinese dialectical fur condition pulse condition,dialectical divided into types and survival time,immunity function before and after therapy,which will provide scientific basis and new train of thinking for recovery of stomatological carcinoma patient following operation.These patients according to dialectical type.were divided into type of feeble kidney and type of mixed excess and deficiency syndrome that the survive time compare with control group through treat by statistics,were P<0.05.The positive cases of immunity response of administration group were more increased than control group, the rate was 22.2%,maintenance and decrease rate were 7.5% and 14.6% compare with control group,with multiple factor computer analysis in two groups.There is some evidence that the traditional Chinese prescription of "ShengYang" treat in tumor patients with the type of feeble kidney and type of mixed excess an deficiency syndrome were remarkably regulate the immunity function and promote the action of anti tumor.For recovery therapy after tumor operation which reach a fairly action.

English Abstract↗
PubMed1995

[Effect of Chinese traditional prescription "Shen Yang" on the immune function of oral squamous cells carcinoma patients.].

This report tries to compare the immunologic function of being take the Chinese medicine "Fu-Fang Shen Yang" or placebo C which is based on randomized clinical trials after operation for 238 cases of oral squamous cancer.DNCB test is for observable index.The results as follows:DNCB position rate of 1 "Shen Yang" group is significantly increased to compare with the placebo C group,after 3m(P<0.01) 6m (P<0.001).Two groups are significantly increased after one year.This suggestion that "Fu-Fang Shen Yang" can enhance immunologic function after operation fro oral squamous cells carcinoma patients.

English Abstract↗
PubMed1995

[Post-operative radiotherapy of glioma in the cerebral hemisphere in adult--a retrospective study of 326 cases].

Three hundred twenty-six cases of adult patients with glioma in the cerebral hemisphere treated by post-operative radiotherapy at the General Hospital, Tianjin Medical University from 1976 through 1990 were reviewed. The 1-, 3-, 5- and 10-year survival rate was 76.8%, 62%, 55.7% and 42.1%, respectively in low grade gliomas and the 1-, 3-, and 5-year survival rate was 44.3%, 35% and 27.1% respectively in high grade gliomas. In this study, patients' age, performance status before radiotherapy and histopathologic type of the tumor are important factors influencing the treatment outcome. There is no correlation between radiation dose and survival rate. Since 1988, combined photon and electron beams from linear accelerator have been used with a total dose of 65-70Gy to the target area.

Adolescent↗
PubMed1995

[Effects of Chinese ginseng root and stem-leaf saponins on learning, memory and biogenic monoamines of brain in rats].

The present investigation has shown that Ginseng root saponins (ig, 50mg/kg x 7d) facilitate the learning and memory of normal male Wistar rats, while the effect of Ginseng stem-leaf saponins (ig, 50mg/kg x 7d) on antielectrconvulsive shock-induced impairment of memory consolidation in rats is more intensive than that of root saponins. Both Ginseng root and stem-leaf saponins can significantly raise the levels of biogenic monoamines in normal rat's brain.

Animals↗
PubMed1995

[The change in tissue oxygenation after severe steam inhalation injury].

Tissue oxygenation was observed in dogs inflicted with steam inhalation injury in this study. Main findings were as follows: there was significant decrease in cardiac output (CO), oxygen delivery (DO2), alveolar oxygen partial pressure (PAO2), arterial oxygen partial pressure (PaO2), mixed venous oxygen partial pressure (PVO2), arterial oxygen saturation (SaO2), mixed venous oxygen saturation (SVO2), and pH (P < 0.01), and marked increase in P(A-a)O2, oxygen extraction ratio (ERO2), and arterial carbon dioxide partial pressure (PaCO2) (P < 0.01 and P < 0.05). However there was no obvious change in oxygen consumption rate (VO2) within four hours after inhalation injury. The results indicated that the tissue hypoxia was caused directly by insufficient blood perfusion and oxygen supply as well.

Animals↗
PubMed1994

Angiostatin: a novel angiogenesis inhibitor that mediates the suppression of metastases by a Lewis lung carcinoma.

The phenomenon of inhibition of tumor growth by tumor mass has been repeatedly studied, but without elucidation of a satisfactory mechanism. In our animal model, a primary tumor inhibits its remote metastases. After tumor removal, metastases neovascularize and grow. When the primary tumor is present, metastatic growth is suppressed by a circulating angiogenesis inhibitor. Serum and urine from tumor-bearing mice, but not from controls, specifically inhibit endothelial cell proliferation. The activity copurifies with a 38 kDa plasminogen fragment that we have sequenced and named angiostatin. A corresponding fragment of human plasminogen has similar activity. Systemic administration of angiostatin, but not intact plasminogen, potently blocks neovascularization and growth of metastases. We here show that the inhibition of metastases by a primary mouse tumor is mediated, at least in part, by angiostatin.

Amino Acid Sequence↗