Biomedical subjects

L Yuan

Publications and source records attributed to L Yuan.

At least 181 records · Page 10Linked to original sources

PubMed1995

[Perinatal colonization of group B streptococcus: a study in 600 cases in Beijing Tiantan Hospital].

An epidemiologic study of perinatal colonization of group B streptococcus (GBS) was carried out. Six hundred mother-infant pairs were studied at Beijing Tiantan Hospital. Maternal carriage rate of GBS was 8% with a neonatal colonization rate of 6.7%. Overall perinatal carriage rate was 13%. Women with perinatal colonization showed prone to have more premature and low birth weight babies. We did not find that perinatal colonization was associated with prolonged rupture of membranes and IUGR in our study group. Serotypical study showed that most frequent GBS type isolated from the carriers was III, followed by I a. Antibiotic sensitivity study showed that more than half of the GBS strains were resistant to the antibiotics a severe problem which might have caused by abuse in this country.

Female↗

PubMed1995

MTS1/p16/CDKN2 lesions in primary glioblastoma multiforme.

The multiple tumor suppressor 1 (MTS1) gene encoding the p16 inhibitor of cyclin-dependent kinase 4 is deleted or mutated in a wide variety of human tumor cell lines, but the importance of this gene as a tumor suppressor in vivo appears to be highly dependent on tumor type. Because MTS1/p16/CDKN2 and the homologous MTS2/p15 gene map to a region of chromosome 9p21, which is frequently deleted in malignant gliomas, we searched for lesions of these genes in primary biopsies of glioblastoma multiforme (GBM). Our analysis confirms a sizable frequency of homozygous deletion of MTS1/p16/CDKN2 (9/27 cases) and also reveals a low but detectable frequency of intragenic DNA lesions (one point mutation in exon 2 leading to premature termination) among GBMs that retain one or both copies of the gene. No mutations were found in exon 2 of MTS2/p15 (12 cases examined), and one GBM showed a DNA deletion breakpoint in the 30 kb between MTS1/p16/CDKN2 and MTS2/p15 resulting in deletion of MTS1/p16/CDKN2 with retention of MTS2/p15. In contrast to the high-grade tumors, none of 12 low-grade gliomas showed MTS1/p16/CDKN2 deletions. These data support a role for MTS1/p16/CDKN2 as a tumor suppressor gene in the in vivo evolution of GBMs. Given that two tumors with hemizygous MTS1/p16/CDKN2 deletions and loss of heterozygosity for chromosome 9p21 did not contain detectable intragenic mutations, there may be one or more additional relevant 9p21 tumor suppressor genes.

Base Sequence↗

PubMed1995

[Prediction of retinoblastoma: linkage analysis of families with hereditary retinoblastoma by using polymorphic sites within the Rb gene].

Retinoblastoma (Rb) is one of the most common intraocular tumors in childhood. 40% of the cases are hereditary in nature. 10% are due to the transmission of a germline mutation from an affected parent, and 30% are due to new germ cell mutation. In the hereditary form, the mutation is inherited via a germ cell; therefore, the mutant gene is present in all somatic cells. The segregations of four polymorphic sites within the Rb gene were analyzed in six families with hereditary retinoblastoma. Two families were informed with probe p123M1.8, three were informed with probe p68RS2.0 and one was informed with PCR amplification of XbaI site; all six families were informed with PCR amplification of intragenic VNTR site RB1.20. Our results showed that linkage analysis of families with hereditary retinoblastoma by using intrageneic polymorphic sites could be applied to detect carriers and for prenatal diagnosis in families with hereditary retinoblastoma.

Base Sequence↗

PubMed1995

[Effect of RU486 on metabolism of glycosaminoglycans in the cultured calf trabecular meshwork cells].

The trabecular meshwork from newborn bovine eyes was used for cell culture and subculture to the third passage. Then the concentrations of RU486, a corticosteroid antagonist, in the medium were made to be 50, 100 and 200 micrograms/ml and 3H-glycosamine was introduced as the radioactive precursor. After extraction and purification, an aliquot of glycosaminoglycans (GAGs) was used for cellulose acetate electrophoresis, sequential degradation by different enzymes and radioactivity determination by scintillation counting to determine the total amount of GAGs and the amounts of constituents, such as hyaluronic acid (HA), etc. In the control group, the total amount of GAGs was 980 DPM/micrograms cell prot (disintegration per minute/micrograms cell protein) and HA accounted for 17.8%, while in the medium of 50 micrograms/ml and 100 micrograms/ml RU486, HA was increased to 50.1% and 46.1%, respectively. In the medium of 200 micrograms/ml RU486, the total amount of GAGs was decreased to 695 DPM/micrograms cell prot. The results were consistent with the theory of pharmacology and pharmacodynamics. It is possible that the corticosteroid antagonist can be used to reverse the pathogenesis of primary open-angle glaucoma.

Animals↗

PubMed1994

The relationship between class I binding affinity and immunogenicity of potential cytotoxic T cell epitopes.

The relationship between binding affinity for HLA class I molecules and immunogenicity of discrete peptide epitopes has been analyzed in two different experimental approaches. In the first approach, the immunogenicity of potential epitopes ranging in MHC binding affinity over a 10,000-fold range was analyzed in HLA-A*0201 transgenic mice. In the second approach, the antigenicity of approximately 100 different hepatitis B virus (HBV)-derived potential epitopes, all carrying A*0201 binding motifs, was assessed by using PBL of acute hepatitis patients. In both cases, it was found that an affinity threshold of approximately 500 nM (preferably 50 nM or less) apparently determines the capacity of a peptide epitope to elicit a CTL response. These data correlate well with class I binding affinity measurements of either naturally processed peptides or previously described T cell epitopes. Taken together, these data have important implications for the selection of epitopes for peptide-based vaccines, and also formally demonstrate the crucial role of determinant selection in the shaping of T cell responses. Because in most (but not all) cases, high affinity peptides seem to be immunogenic, our data also suggest that holes in the functional T cell repertoire, if they exist, may be relatively rare.

Amino Acid Sequence↗

PubMed1994

Measles outbreak in 31 schools: risk factors for vaccine failure and evaluation of a selective revaccination strategy.

OBJECTIVE: To examine the risk factors for measles vaccine failure and to evaluate the effectiveness of a selective revaccination strategy during a measles outbreak. DESIGN: Matched case-control study. SETTING: Thirty-one schools in Mississauga, Ont. SUBJECTS: Eighty-seven previously vaccinated school-aged children with measles that met the Advisory Committee on Epidemiology's clinical case definition for measles. Two previously vaccinated control subjects were randomly selected for each case subject from the same homeroom class. INTERVENTIONS: All susceptible contacts were vaccinated, and contacts who had been vaccinated before Jan. 1, 1980, were revaccinated. When two or more cases occurred in a school all children vaccinated before 1980 were revaccinated. MAIN OUTCOME MEASURES: Risk of measles associated with age at vaccination, time since vaccination, vaccination before 1980 and revaccination. RESULTS: Subjects vaccinated before 12 months of age were at greater risk of measles than those vaccinated later (adjusted odds ratio [OR] 7.7, 95% confidence interval [CI] 1.6 to 38.3; p = 0.01). Those vaccinated between 12 and 14 months of age were at no greater risk than those vaccinated at 15 months or over. Subjects vaccinated before 1980 were at greater risk than those vaccinated after 1980 (adjusted OR 14.5, 95% CI 1.5 to 135.6). Time since vaccination was not a risk factor. Revaccination was effective in reducing the risk of measles in both subjects vaccinated before 1980 and those vaccinated after 1980 (adjusted OR reduced to 0.6 [95% CI 0.1 to 5.3] and 0.3 [95% CI 0.13 to 2.6] respectively). However, only 18 cases were estimated to have been prevented by this strategy. CONCLUSIONS: Adherence to routine measles vaccination for all eligible children is important in ensuring appropriate coverage with a single dose. The selective revaccination strategy's high labour intensiveness and low measles prevention rate during the outbreak bring into question the effectiveness of such a strategy.

Adolescent↗

PubMed1994

Use of selective agonists and antagonists to characterize tachykinin receptors mediating airway responsiveness in anaesthetized guinea-pigs.

Tachykinins are potent bronchoconstrictors. Here we have used novel highly selective agonists and antagonists to characterize tachykinin receptors mediating bronchoconstriction and hypotension in anaesthetized, paralysed guinea-pigs. Total lung resistance (RL) and dynamic lung compliance (Cdyn) were measured using an on-line, breath-by-breath method to analyse lung mechanics. The effects of iv injections of neuropeptide gamma (NP gamma), [Sar9,Met(O2)11]-SP (Sar-SP) (NK-1 agonist), [Lys5,MeLeu9,Nle10]-NKA(4-10) (Lys-NKA) (NK-2 agonist) and senktide (NK-3 agonist) were compared, before and after iv injection of the NK-1 antagonist CP 96345 or the NK-2 antagonists MDL 29913 and SR 48968. NP gamma, Sar-SP and Lys-NKA, but not senktide, increased RL and decreased Cdyn, accompanied by a fall in blood pressure (BP). The potency for increase of RL was Lys-NKA > NP gamma congruent to Sar-SP, for reduction of Cdyn was Lys-NKA = Sar-SP > NP gamma, and for fall in BP was Sar-SP > NP gamma >> Lys-NKA. CP 96345 (50 nmol/kg & 200 nmol/kg) significantly antagonized the changes in RL, Cdyn and BP induced by Sar-SP, and the fall in BP (but not changes in lung mechanics) in response to NP gamma, but did not alter any responses to Lys-NKA. In contrast, MDL 29913 (200 nmol/kg & 10 mumol/kg) weakly and SR 48968 (100 nmol/kg) potently inhibited the effects on RL and Cdyn induced by Lys-NKA and NP gamma. Our results show that both NK-1 and NK-2 receptors are represented in guinea-pig airways. MDL 29913 is a weak NK-2 antagonist in guinea-pig airways compared to SR 48968. In addition, NK-1 but not NK-2 receptors appear to be important in mediating the hypotensive response to these tachykinins. In spite of its ability to cause a fall in BP via NK-1 receptors, NP gamma exerted its effects on RL and Cdyn solely via NK-2 receptors.

Amino Acid Sequence↗

PubMed1994

Anatomic basis of venous drainage in donor flaps.

The venous architecture in donor flaps was observed in 17 fresh cadavers by injection of latex or ink into the vessels or by making corrosion-cast specimens. The pattern of the veins resembles that of the arteries, with the difference that there is another set of venous trunks which do not accompany the arteries. Because these trunks are of larger caliber, they are the main drainage route for flaps. There are three types of drainage based on the anatomical architecture: 1) the superficial trunk is the main drainage path; 2) the deep trunk is the main path; 3) both superficial and deep veins are involved. These morphological considerations are the basis for selection of veins for anastomosis in microsurgery. The axial veins in temporal, frontal and facial flaps on the dorsum of the hand and the foot usually loosely accompany the axial arteries. The characteristics of these vascular pedicules should be studied in transplant operation.

Adult↗

PubMed1994

Enhancement of in vitro prostaglandin E2 production by mouse fibrosarcoma cells after co-culture with various anti-tumour effector cells.

We have previously reported that an increase in the production of immunosuppressive prostaglandin E2 by a QR tumour (QR-32) is accompanied by progressive growth of the tumour in syngeneic C57BL/6 mice. In order to determine what kinds of cell and factor(s) enable QR-32 cells to promote PGE2 production, we investigated the amounts of PGE2 in the supernatant of QR-32 cells by co-culturing them with various anti-tumour effector cells. Significantly high levels of PGE2 production were observed when the QR-32 cells were co-cultured with lymphokine-activated killer (LAK) cells, natural killer (NK) cells, polymorphonuclear (PMN) leucocytes and streptococcal preparation (OK432)-activated or resident peritoneal macrophages (activated and resident macrophages). On the other hand, PGE2 production was not increased when QR-32 cells were co-cultured with cytotoxic T lymphocytes (CTLs) specific to QR-32 cells. The high levels of PGE2 production were partially or totally inhibited by the presence of radical scavengers such as superoxide dismutase (SOD), catalase and mannitol, although the cytotoxicity of LAK cells was not. We also exposed QR-32 cells to human recombinant cytokines and the growth factors which are produced when anti-tumour effector cells come in contact with tumour cells. Significant PGE2 production by QR-32 cells was observed when the cells were treated with interferon alpha (IFN-alpha), tumour necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta) (all P < 0.001). These results suggest that oxygen radicals produced by anti-tumour effector cells and inflammatory cytokines provoke QR-32 cells to produce large amounts of immunosuppressive PGE2.

Animals↗

PubMed1994

The cytoplasmic domain mediates localization of furin to the trans-Golgi network en route to the endosomal/lysosomal system.

To investigate the mechanisms of membrane protein localization to the Golgi complex, we have examined the intracellular trafficking of epitope-tagged forms of the mammalian endopeptidase, furin, in stably transformed rat basophilic leukemia cells. Our studies show that furin is predominantly localized to the trans-Golgi network (TGN) at steady state, with smaller amounts present in intracellular vesicles. Biochemical and morphological analyses reveal that furin is progressively delivered to a lysosomal compartment, where it is degraded. Analyses of furin deletion mutants and chimeric proteins show that the cytoplasmic domain is both necessary and sufficient for localization to the TGN in various cell types. Interestingly, deletion of most of the cytoplasmic domain of furin results in a molecule that is predominantly localized to intracellular vesicles, some of which display characteristics of lysosomes. To a lesser extent, the cytoplasmically deleted molecule is also localized to the plasma membrane. These observations suggest the existence of an additional determinant for targeting to the endosomal/lysosomal system within the lumenal and/or transmembrane domains of furin. Thus, the overall pattern of trafficking and steady state localization of furin are determined by targeting information contained within more than one region of the molecule.

Amino Acid Sequence↗

PubMed1994

[Effects of interferon on infant with CMV hepatitis].

Fifty-seven patients with CMV hepatitis, who were within 3 months of age, were treated with interferon from August 1992 to April 1993. They were randomized to be assigned to two groups. There were 30 patients in the therapeutic group, who were given daily interferon 1,000,000 u intramuscularly for 10 days and 27 patients in the control group, who were put on daily vitamin C and inosine therapy intravenously for 10 days. The results showed that there was a significant difference in the aspects of jaundice disappearance, liver and serum SGPT recovery time between the two groups. In the therapeutic group, the average alleviating time of jaundice, hepatomegaly and serum SGPT level after treatment with interferon were 15.26, 29.89 and 14.26 days ahead of those in the control group, respectively. The cure rate at one month and two months after treatment was 43.0% and 90.0% in the therapeutic group, respectively; 18.5% and 48.0% in the control group, respectively.

Cytomegalovirus Infections↗

PubMed1994

Use of transesophageal echocardiography for evaluation of resectability of lung cancer.

BACKGROUND: When patients with lung cancer are to undergo surgical resection, chest x-ray and computed tomography (CT) are widely used for evaluation of staging and of the resectability of the lesion. Unfortunately, the above methods cannot always provide sufficient information about resectability and some patients undergo unnecessary operations. Transesophageal echocardiography (TEE) has opened a new window for viewing cardiac structure and function. By TEE, one can also image the surrounding tissues and great vessels under continuous monitoring. MATERIALS AND METHODS: We pre-operatively applied the awake TEE method in twenty whose chest CT showed suspected invasion of the heart by the tumor. RESULTS: Our experience showed the following: (1) TEE can clearly identify whether lung cancer has invaded the heart and/or great vessels and therefore avoiding unnecessary operation; (2) Two patients had tumor seen abutting epicardium and/or aorta without invasion (under continuous imaging). Two patients had tumor compressing the right and left atrium with intact but not invading pericardium, and underwent successful surgical resection. CONCLUSION: We concluded that it is useful to apply TEE preoperatively in evaluating the resectability of the lung cancer especially when a chest CT shows suspicion of local invasion of the heart and great vessels; thus unnecessary thoracotomy can be avoided.

Adult↗

PubMed1994

The effect of single bolus dose of esmolol for controlling the tachycardia and hypertension during laryngoscopy and tracheal intubation.

Tachycardia and hypertension usually accompany laryngoscopy and tracheal intubation. This response is undesirable, especially in patients with cardiovascular or intracranial diseases. Esmolol is a cardioselective, ultrashort-acting beta adrenergic blocking agent with a very short half-life. The efficacy of bolus dose of esmolol in blunting hemodynamic responses during laryngoscopy and tracheal intubation was evaluated. 45 patients (15 in each group) of ASA physical status I and II scheduled for elective non-cardiac surgery were included in this randomized, placebo-controlled study. At time zero, the study preparation (placebo, 100 or 200 mg of esmolol) was administered intravenously, followed by thiopentone 5 mg/kg and succinylcholine 1.5 mg/kg for induction. Tracheal intubation was performed 2 minutes after time zero. Anesthesia was maintained with 50% nitrous oxide and 1.0 MAC halothane in oxygen, and vecuronium 0.08 mg/kg. Heart rate (HR) and systolic blood pressure (SBP) were recorded every minute for 10 minutes. To compare with the placebo group, there was a significant decrease in either HR or SBP in 200 mg group in the 8 minutes course after intubation (p < 0.05). There was a significant decrease in HR in the 100 mg group at the 3rd, 4th, and 5th minutes when compared with the placebo group (p < 0.05). The differences in SBP between the 100 mg group and placebo group were significant at the 3rd and 4th minutes (p < 0.05). Both bolus dosages of esmolol could effectively attenuate the tachycardia and hypertension produced by laryngoscopy and tracheal intubation. Furthermore, esmolol 200 mg presented a better hemodynamic stability than esmolol 100 mg during induction of anesthesia.

Adrenergic beta-Antagonists↗

PubMed1993

Regulation of T cell receptor expression in immature CD4+CD8+ thymocytes by p56lck tyrosine kinase: basis for differential signaling by CD4 and CD8 in immature thymocytes expressing both coreceptor molecules.

Signals transduced through the T cell antigen receptor (TCR) are modulated by the src family tyrosine kinase p56lck (lck), which associates in mature T cells with the coreceptor molecules CD4 and CD8. Here we describe a novel function of lck in immature CD4+CD8+ thymocytes, that of regulating TCR expression. Activation of lck in immature CD4+CD8+ thymocytes by intrathymic engagement of CD4 maintains low TCR expression by causing most TCR components to be retained and degraded within the endoplasmic reticulum. Importantly, activation of lck in immature CD4+CD8+ thymocytes results from engagement of surface CD4 molecules, but not surface CD8 molecules, despite the nearly fourfold greater surface expression of CD8 than CD4. The competence of CD4 to activate lck in CD4+CD8+ thymocytes relates to the fact that a relatively large fraction of surface CD4 molecules (25-50%) are associated with intracellular lck molecules, whereas only 2% of surface CD8 molecules are associated with lck. The amount of lck associated with CD4 in CD4+CD8+ thymocytes is diminished by chronic CD4 engagement in the thymus, as activated lck molecules subsequently dissociate from CD4. Indeed, the amount of lck associated with CD4 in CD4+CD8+ thymocytes is markedly increased in major histocompatibility complex (MHC) class II- mice that lack the intrathymic ligand for CD4 and in which surface CD4 molecules are consequently not engaged. Thus, the present study demonstrates that (a) activation of lck in CD4+CD8+ thymocytes regulates distribution and expression of TCR components; (b) unlike CD4 molecules, CD8 molecules on CD4+CD8+ thymocytes cannot efficiently activate lck despite their significantly greater surface expression; and (c) the amount of lck associated with CD4 in the CD4+CD8+ thymocytes is inversely related to the extent of CD4 engagement by MHC class II molecules in the thymus.

Animals↗

PubMed1993

Comparing the human and schistosomal hypoxanthine-guanine phosphoribosyltransferases by circular dichroism.

The hypoxanthine-guanine phosphoribosyltransferases (HGPRTases) of human and the parasitic trematode, Schistosoma mansoni, are of biomedical importance. The conformations of these two enzymes were studied by circular dichroism (CD). The schistosomal HGPRTase is estimated to contain 27% alpha-helix and 30% beta-structure. This result is consistent with what is predicted from a tertiary model (Craig, S.P., Cohen, F.E., Yuan, L., McKerrow, J.H. and Wang, C.C. (1991) in Molecular & Immunological Aspects of Parasitism (Wang, C.C., ed.), pp. 122-138, Am. Assoc. Adv. Sci., Washington DC, USA), which proposes that the enzyme is an alpha/beta barrel protein. The human enzyme is estimated to contain 21% alpha-helix and 53% beta-form. The two enzymes are different in their thermostability. The human enzyme remains active after being heated to 85 degrees C for 15 min, while the schistosomal enzyme only retains its activity at temperature below 65 degrees C. The transition temperature (T1/2) of the schistosomal HGPRTase was determined by CD measurement to be 57.5 degrees C. One of the enzyme substrates, phosphoribose pyrophosphate (PRPP), stabilizes the HGPRTases by preventing the human enzyme from unfolding at 85 degrees C and partially protecting the schistosomal enzyme from unfolding at 65 degrees C. It is suggested that the amino-acid substitutions in the human enzyme improve the spatial structure and stability of its alpha-helices, which may lead to an enhanced thermostability.

Amino Acid Sequence↗

PubMed1993

An evaluation of the effects of cytokines on intracellular oxidative production in normal neutrophils by flow cytometry.

To evaluate the effects of inflammatory cytokines on oxidative production in normal neutrophils, seven kinds of cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), interleukin-2 (IL-2), IL-6, IL-1 alpha, IL-1 beta, and interferon-beta (IFN-beta) were tested. The intracellular hydrogen peroxide (H2O2) in individual cells was determined by flow cytometry. According to the levels of intracellular H2O2 enhanced by cytokines, these seven cytokines were classified into three types: (1) prominently effective--GM-CSF; (2) moderately effective--G-CSF, IL-6, and IL-2; (3) weakly or ineffective--IFN-beta, IL-1 alpha, and IL-1 beta. Changes in cell size and cell surface structure after stimulation of those seven cytokines were simultaneously measured by flow cytometry. The most prominently effective cytokine, GM-CSF, initially caused enlargement of cell size and irregularity of the cell surface and subsequently increased H2O2 production by neutrophils. In contrast, the weakly or ineffective cytokines, like IL-1 beta, had no effects on cell size or cell surface. Our study indicates that some kinds of cytokines enhance oxidative production and cause morphological changes in neutrophils.

Cell Membrane↗

PubMed1993

Factors contributing to reinfection with schistosomiasis japonica after treatment in the lake region of China.

The prevalence of schistosomiasis due to S. japonicum is focally high in the lake regions of China, and reinfection after treatment with praziquantel is frequent. In this study, the total reinfection rate among 740 treated persons was 12.9%. Factors associated with reinfection were age and sex, water contact and the distance from homes to snail habitats. The reinfection rate was higher among men (15.0%) than among women (8.3%). The frequency of water contact is the main factor in reinfection. Among persons with more than 120 and 10-120 water-contact days, the reinfection rates were 24.0% and 16.4%, respectively. The reinfection rates among people living 0 m, 500 m and 1000 m from snail-ridden areas were 14.1%, 8.3% and 4.3%, respectively. Fishing was the most frequent reason for water-contact, followed by herding animals and playing in water; reinfection rates among those engaging in these activities were 36.4%, 16.3% and 22.9%, respectively. Reinfection is clearly a problem, and since much of it is connected with essential economic activities, the cycle of infection and reinfection is not likely to be broken until effective methods for eliminating reservoirs of infection are developed.

Adolescent↗

PubMed1993

Abuse of antibiotics in China and its potential interference in determining the etiology of pediatric bacterial diseases.

There is scant information about the etiology and epidemiology of bacterial diseases of infants and children in China because of very little success with bacterial culture. This study describes the severity of abuse of antibiotics among Chinese pediatricians and this abuse's potential interference in determining the etiology of bacterial diseases. According to a survey in Beijing Children's Hospital more than 98% of the patients in the Outpatient Department who were diagnosed with common cold were given antibiotics by physicians. More than one-third of the patients had been taking antibiotics before coming to the hospital. Using a sensitive Staphylococcus aureus assay we found that 70% of blood samples and 43% of cerebrospinal fluid samples from the patients with bacterial meningitis and pneumonia contained antibacterial activity. Bacteria were recovered significantly less often from the samples with antibacterial activity than from those who did not from which antibiotic was not recovered, both in blood (5.3% vs. 12.5%) and in cerebrospinal fluid (2.5% vs. 14.8%). This study indicates that antibiotic abuse is a severe problem in China and that judicious use of antibiotics is urgently needed.

Adolescent↗