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Biomedical subjects

Y Guo

Publications and source records attributed to Y Guo.

At least 541 records · Page 30Linked to original sources
PubMed1995

Immunoenzymatic methods applied to the search for bioactive taxoids from Taxus baccata.

Polyclonal antibodies raised against 2'-succinyltaxol-bovine serum albumin (BSA) conjugate were used for the immunodetection of bioactive taxoids in chromatographic fractions of the stem bark extract of Taxus baccata. In addition to taxol, cephalomannine, and baccatin III, two taxoids were isolated and their structures were elucidated as 4 alpha,7 beta-diacetoxy-2 alpha,9 alpha-dibenzoxy-5 beta,20-epoxy-10 beta, 13 alpha, 15-trihydroxy-11(15-->1)-abeo-tax-11-ene[5] and taxol C [6] using spectroscopic methods.

Animals↗
PubMed1995

Two new taxoids from the stem bark of Taxus baccata.

Two new taxoids, 13-deoxo-13 alpha-acetyloxy-7 beta,9 alpha-diacetyl-1,2-dideoxytaxine B[1] and 7 beta-xylosyl-10-deacetyltaxol D [7], were isolated from the stem bark of Taxus baccata cv. stricta. Their structures were elucidated using spectroscopic methods and their bioactivity was evaluated using an in vitro microtubule assembly assay.

Animals↗
PubMed1995

Gene-targeted B-deficient mice reveal a critical role for B cells in the CD4 T cell response.

The role of B cells in promoting T cell responses is still controversial. In this study, we use JHD mice which have a targeted mutation in the JH gene and are thus rendered deficient in B cells to address this issue. We show here that immunization of JHD mice with soluble antigen fails to prime CD4 T cells, for either clonal expansion or delivery of immunological help for antibody responses. This lack of CD4 T cell priming in JHD mice corresponds to a 3- to 9-fold lower co-stimulatory activity of antigen-presenting cells (APC) from the JHD mice, as measured by anti-CD3-induced proliferative responses of CD4 T cells. This in turn is due to a defect of APC from JHD mice in response to T cell-mediated induction of co-stimulatory activity. As the development of macrophages and dendritic cells is unaffected in the JHD mice, our results demonstrate that B cells play a critical role in CD4 T cell priming, possibly by delivering a critical co-stimulatory activity for clonal expansion of CD4 T cells.

Animals↗
PubMed1995

Seroepidemiological and molecular evidence for the presence of two H3N8 equine influenza viruses in China in 1993-94.

In May 1993, a severe epidemic of respiratory disease began in horses in Inner Mongolia and spread throughout horses in China. The disease affected mules and donkeys as well as horses but did not spread to other species, including humans. The severity of the disease raised the question of whether the outbreak might have been caused by the new avian-like influenza viruses detected in horses in China in 1989 or by current variants ofA/equine/Miami/1/63 (H3N8) (equine-2) or by a reassortant between these viruses. Antigenic and sequence analysis established that all gene segments of the influenza virus causing the epidemic were of recent equine-2 origin and that the virus was not a reassortant. Serological analysis of post-infection horse sera provided evidence for the continued circulation of the A/Equine/Jilin/1/89 (Eq/Jilin) (H3N8) avian-like viruses in horses in Heilongjiang province with original antigenic sin-like responses. It is noteworthy that prior infection with the avian-like Eq/Jilin strain did not afford cross-protection against a current equine-2 strain. Serological evidence for the continued circulation of the avian-like H3N8 influenza virus in horses indicates that this virus has probably established itself in horses in Asia.

Animals↗
PubMed1995

Inhibitory action of metabolites of Pseudomonas aeruginosa against gram-negative bacteria.

Fifty clinical isolates of Pseudomonas aeruginosa were tested for inhibition of growth of clinical isolates of Escherichia coli, Salmonella infantis, Klebsiella pneumoniae and other Gram-negative bacteria in the authors' laboratory. Pseudomonas aeruginosa was strongly active against both E. coli and Enterobacter cloacae, with 89.4% and 94.7% inhibition respectively, but weakly active against S. infantis, K. pneumoniae and Proteus mirabilis with 56.3%, 48.8% and 23.8% inhibition, respectively. The pigmented strains were found to have stronger antimicrobial activity than the unpigmented strains. Pyocyanin, the major metabolite of Pseudomonas aeruginosa, has been shown to inhibit Escherichia coli, Proteus spp. and other Gram-negative bacteria, by research with a few strains of P. aeruginosa and a single inhibited strain. However, little attempt has been made to determine the inhibitory action of many strains of P. aeruginosa against a large number of clinical isolates such as Escherichia spp., Klebsiella spp., and Salmonella spp., up to now. For this reason, in this study we examined 50 randomly selected clinical isolates of P. aeruginosa for inhibition of growth of a wide range of Gram-negative bacteria, including 30 strains of E. coli, 30 of K. pneumoniae, 30 of S. infantis, 6 of Enterobacter cloacae and 9 of Proteus mirabilis.

Antibiosis↗
PubMed1995

Human T-cell recognition of Listeria monocytogenes: recognition of listeriolysin O by TcR alpha beta + and TcR gamma delta + T cells.

The cell-mediated immune response to Listeria monocytogenes has been well characterized in the mouse. Listeriolysin O (LLO) is a major antigen in murine T-cell recognition of L. monocytogenes. In this study, we show that LLO is also recognized by human TcR alpha beta T cells and TcR gamma delta T cells. Human peripheral blood mononuclear cells (PBMC) cultured in vitro with live listeriae and then expanded with interleukin 2 were shown to respond to purified LLO. The generation of LLO-responsive T cells was dependent on the use of live bacteria during the initial in vitro challenge. LLO-induced proliferation of T cells expanded by exposure of PBMC to live listeriae was major histocompatibility complex restricted. PBMC cultured with formalin-fixed listeriae and subsequently expanded by interleukin 2 gave high proliferative responses to fixed bacteria but failed to respond to LLO. PBMC stimulated in vitro with fixed listeriae contained predominantly TcR alpha beta + T cells. In contrast, PBMC obtained from 85% of the donors studied generated high numbers of TcR gamma delta + T cells following in vitro culture with live listeriae. Using a panel of synthetic amphipathic LLO peptides, we found that LLO-specific T cells from different individuals recognized both common and unique peptides. LLO 470-508 was recognized by three of five individuals, while LLO 203-226 and LLO 107-126 were recognized by two of six individuals. A TcR gamma delta + T-cell line was established from PBMC stimulated with live listeriae and was shown to recognize LLO 470-508. Proliferative responses could be induced in this cell line by peptide-pulsed autologous PBMC but not by peptide-pulsed allogeneic PBMC. Our results establish the importance of LLO in human T-cell recognition of listeriae and show that both TcR alpha beta + T cells and TcR gamma delta + T cells recognize this antigen. Finally, since LLO 470-508 has a high degree of homology with other gram-positive bacterial toxins, the recognition of this peptide by TcR gamma delta + T cells suggests that an important role of these T cells in host defense is the recognition of bacterium-derived toxins.

Amino Acid Sequence↗
PubMed1995

HOCl effects on tracheal epithelium: conductance and permeability measurements.

It is speculated that hypochlorous acid (HOCl), produced by neutrophils, can disrupt the tracheal epithelial barrier without damage to epithelial cells. This was investigated with solute permeability (P) and electrical conductance (G) measurements on tracheae from 4-wk-old rabbits. A new system for epithelial bioelectric measurements on intact tracheae was developed and validated. Control values of G, short-circuit current, and spontaneous potential difference were 4.9 +/- 0.5 (SE) mS/cm2, 42.6 +/- 4.7 microA/cm2, and 8.9 +/- 1.0 mV (lumen negative), respectively (n = 5). Control P values for sucrose, inulin, and Dextran-20 were 5.14 +/- 0.48, 0.63 +/- 0.10, and 0.057 +/- 0.007 x 10(-7) cm/s, respectively (n = 6). Tracheae treated with HOCl had no effect; 6 mM HOCl, a concentration that could exist in infected airways, significantly increased both P and G (about two- to fourfold) without damage to epithelial cells; and 12 and 30 mM HOCl caused more than 10-fold increases for both P and G with cell disruption. Vitamin C blocked epithelial damage caused by 30 mM HOCl. Tracheae from 1-wk-old rabbits were significantly more sensitive to HOCl than those from 4-wk-old or adult rabbits. This study validated a new bioelectric measurement system and showed that HOCl has both dose- and age-dependent effects on the tracheal epithelium.

Aging↗
PubMed1995

Tissue cultures of Taxus baccata as a source of 10-deacetylbaccatin III, a precursor for the hemisynthesis of taxol.

Callus cultures of Taxus baccata L. cv. stricta were induced from hypocotyl and leaf explants on Woody Plant medium (hormone-free or additionated with phytohormones). Under continuous dark condition, adventitious roots were regenerated from hypocotyl- and leaf-derived callus cultures. Antibodies raised in rabbits against 10-succinyl-10-deacetylbaccatin III were used for the detection and the semi-quantitative determination of 10-deacetylbaccatin III in Taxus cultures. The presence of 10-deacetylbaccatin III in callus extracts was confirmed by TLC, HPLC using a photodiode array detector and mass spectrometry (CI-MS). The highest equivalent content of the taxoid derivatives (7.83 mg/100 g dry wt.) was detected in an extract from leaf-derived callus.

Chromatography, High Pressure Liquid↗
PubMed1995

Differential gene expression in healing rat corneal epithelium.

PURPOSE: The authors used and validated a recently developed method, mRNA differential display, to detect and clone genes that are differentially expressed in healing compared to stationary corneal epithelium. METHODS: RNAs from unwounded and 18-hour postwound corneal epithelia were isolated and subjected to mRNA differential display analysis. The generated cDNAs were used as probes in Northern blot analysis and in situ hybridization to confirm their differential expression and to clone longer or full-length cDNAs from a healing corneal epithelial cDNA library. RESULTS: Changes in the pattern of gene expression in healing epithelium, compared with that in stationary cells, were noted. To date, 15 combinations of 5'- and 3'- primers were used with approximately 1500 mRNA species screened. Differential expression of nine mRNA species were observed. These included four known proteins. They are nonmuscle tropomyosin TM-1, cytokeratin K14, small GTP binding protein rab 11, and amyloid beta-A4 precursor-like protein-2. One is a sequence with homology to type II cytokeratin, and four represent genes with sequences that are unreported. The differential expression of five of these genes was confirmed by Northern blot analysis, in situ hybridization, or both. CONCLUSION: mRNA differential display provides a unique and powerful experimental system to study differential gene expression in wound healing and cell migration. Using this system, differential expression of nine genes was observed. Detection of genes differentially expressed in healing epithelium may prompt studies that will define the specific role of each of the proteins in wound healing.

Amino Acid Sequence↗
PubMed1995

[The cytotoxicity of malignant pleural effusion lymphocytes and LAK cells against autologous tumor cells].

In malignant pleural effusion, lymphocytes (MPEL) and autologous tumor cells (ATC) were obtained by centrifugation on discontinuous density gradients from 16 patients with malignant pleural effusion. The cytotoxicity of MPEL against ATC were compared with that of peripheral blood lymphocytes (PBL). It was demonstrated that the results for separation with 100%: 60% Ficoll-Hypaque which formed a discontinuous density gradients were the best in three sets of discontinuous density gradients. The cytotoxicity of PBL was higher than that of MPEL (P < 0.001), but the cytotoxicity and expansion of MPEL-activated by rIL2 was much higher than that of PBL-activated by rIL2 (LAK cells) (P < 0.001). This shows that local immune reaction within pleural cavity of patients with malignant pleural effusion was in the state of suppression, but the state could be improved by using rIL2. Therefore, we consider that MPEL could be the better effector cells than LAK cells in tumor adoptive immunotherapy.

Adult↗
PubMed1995

[Microthrombi in coronary heart disease].

Of 180 patients with coronary heart disease (CHD) 43 (23.9%) showed in microthrombi conjunctival microcirculation. We compared the healthy subjects with the patients with microthrombi and thrombi-free as well as with the patients with microthrombi pre- and post-treatment of heparin or salvia miltiorrhizae. The formation and the number of microthrombi in the CHD patients were closely related to symptoms, ECGS, plasma TXB2, 6-kero-PGF1a and other indexes on hemodynamics. Follow-up of the patients with microthrombi revealed that their death rate was higher than that of CHD patients without microthrombi, especially in the sudden deaths. We consider that microthrombi may be regarded as an important index of the state, therapeutic efficacy, and prognosis of the CHD patients. The use of heparin may certainly be based on the condition of the microthrombi in the microcirculation of CHD patients.

Adult↗
PubMed1995

[A study on the relationship between malignant tumour mortality and environmental pollution in Beicun countryside of Datong City].

The paper reports investigations on malignant tumor mortality in Beicun countryside of Datong city, with Hua yuan tun countryside as the control group. The result showed that malignant tumor mortality (117.04/10(5)) in Beicun countryside was significantly higher than that in the control group (61.06/10(5)). The nitrate and nitrite in drinking water and five kinds of vegetables in Beicun countryside were significantly higher than those in the control group (P < 0.05 - P < 0.001). Serum Cu and Cu/Zu levels in the inhabitants of Beicun countryside were significantly higher than those in the control group (P < 0.001 and P < 0.01). The benzo (a) pyrene and airborne particulates in Beicun countryside area were higher than those in the control group area. The results showed that the malignant tumor mortality was strongly correlated with severe pollution of vegetables, drinking water and air.

Benzo(a)pyrene↗
PubMed1995

The relation of the location of haptics of posterior chamber intraocular lenses and peripheral anterior synechia.

PURPOSE: To investigate the occurrence, outcome and influencial factors of the peripheral anterior synechia (PAS) following implantation of posterior chamber intraocular lenses for finding a way to reduce the PAS. SUBJECTS: 40 eyes of 38 senile cataract patients with normal chamber angle and intraocular pressure (IOP) preoperatively were examined. METHODS: Extracapsular cataract extraction was performed under microscope with insertion of a posterior chamber lens implant vaulted anteriorly by 10 degrees. Gonioscopy and slit-lamp examination and photography of the operated eyes were performed 3 to 6 months postoperatively. RESULTS: PAS were found in 20 (50%) of the 40 eyes. Among the 20 eyes with PAS the locations of 23 haptics in 17 eyes corresponded with those of the PAS. PAS were seen more frequently with vertically sulcus-fixated haptics than with the horizontally capsular-fixated haptics, showing a significant difference (P < 0.05). 88% of the eyes with PAS had pupillary deformation, but their visual acuities and IOP were not affected. CONCLUSIONS: PAS is more likely to occur with vertically sulcus-fixated IOL. Rotating the capsular-fixated haptics to the horizontal position may reduce the incidence of PAS. Gonioscopy should be a routine follow-up examination.

Adult↗
PubMed1995

Pandysautonomia: clinicopathological. Report of 5 cases.

Five cases of pandysautonomia were reported. Pupils, salivary and sweat glands, gastrointestinal tract, urinary bladder and heart were impaired in all cases, indicating that the peripheral parts of both sympathetic and parasympathetic nervous systems were involved, especially the cholinergic post ganglionic efferent fibers. Besides, two cases showed sensory impairment of the distal parts of the extremities, slight atrophy of small hand muscles and weak or absence of deep tendon reflexes. Three cases showed elevation of CSF protein without cellular reaction. Sural nerve biopsy was performed in 3 cases. Neuropathological changes included the reduction of myelinated neurofibers, atrophy of Schwann's cells and the presence of degeneration products and myelin-like structures. One case also revealed small vasculitis among neurofascicles. It seems that the disease entity is a result of autoimmune dysfunction. The prognosis of pandysautonomia in the present group was good, four cases have some improvement during 1-4 years of follow-up study.

Adolescent↗