Biomedical subjects

L Yuan

Publications and source records attributed to L Yuan.

At least 55 records · Page 3Linked to original sources

PubMed2001

Short-term immunoglobulin A B-cell memory resides in intestinal lymphoid tissues but not in bone marrow of gnotobiotic pigs inoculated with Wa human rotavirus.

Immunological memory is important for protecting the host from reinfection. To investigate the development and sites of residence of intestinal memory B cells, and their role in protective immunity to reinfection with an enteric virus, we assessed the association between memory B cell and antibody-secreting cell (ASC) responses and protection using a gnotobiotic pig model for human rotavirus (HRV) infection and diarrhoea. The isotypes, quantities and tissue distribution of rotavirus-specific memory B cells and ASC were evaluated prechallenge (28 and 83 postinoculation days [PID]) and postchallenge (7 postchallenge days [PCD]), using enzyme-linked immunospot (ELISPOT) assay, in gnotobiotic pigs inoculated once with virulent or three times with attenuated HRV and challenged at PID 28 with the corresponding virulent HRV. Complete protection against HRV shedding and diarrhoea was associated with significantly higher numbers of immunoglobulin A (IgA) and immunoglobulin G (IgG) memory B cells and ASC in the ileum of virulent HRV-inoculated pigs at challenge. In contrast, pigs inoculated with attenuated HRV had lower numbers of IgA and IgG memory B cells and ASC in intestinal lymphoid tissues, but higher numbers in the spleen. The bone marrow had the lowest mean numbers of IgA and IgG memory B cells and ASC prechallenge in both groups of HRV-inoculated pigs. Therefore, bone marrow was not a site for IgA and IgG rotavirus-specific antibody production or for memory B cells after inoculation with live rotavirus, from 28 PID up to at least 83 PID. The effect of in vitro antigen dose was examined and it was determined to play an important role in the development of ASC from memory B cells for the different tissues examined.

Animals↗

PubMed2001

Is equity being sacrificed? Willingness and ability to pay for schistosomiasis control in China.

Decentralization of the health care system in China has led to an increasing need for income generation at all operational levels, both for curative services and for public health programmes. In general, people have accepted the costs of curative services, although the impact of charges on health-seeking behaviour has yet to be assessed. Public health programmes present particular problems in terms of revenue generation, however, because of the less direct impact of these activities on individual health and well-being. In this paper, we report the results of a cross-sectional study of willingness and ability to pay for schistosomiasis control. Questionnaires were administered to household heads of six representative villages in the Dongting Lake Region of Hunan Province, China. A total of 628 valid questionnaires were analyzed. The yearly mean household expenditure on schistosomiasis diagnosis and treatment was RMB 59.50 +/- 146.04 Yuan (US$1 = 8 RMB Yuan), accounting for 0.94% of the total yearly household income. Most household heads (514, 82%) thought schistosomiasis was the greatest health threat in their communities, but only 30.9% of them were willing to pay for screening, diagnosis and treatment of the infection. On the other hand, 72.3% of the respondents were willing to undertake volunteer work for control.

Adult↗

PubMed2001

Antibody-secreting cell responses to rotavirus proteins in gnotobiotic pigs inoculated with attenuated or virulent human rotavirus.

Because of their similarities to infants in mucosal immune responses and their susceptibility to human rotavirus (HRV) diarrhea, gnotobiotic pigs provide a useful model for rotaviral disease. In this study, we performed quantitative enzyme-linked immunospot (ELISPOT) assays to measure local and systemic isotype-specific antibody-secreting cell (ASC) responses to individual structural (VP4, VP6, and VP7) and nonstructural (NSP3 and NSP4) proteins of Wa HRV. The Spodoptera frugiperda cells expressing each recombinant baculovirus HRV protein were formalin fixed and used as antigen for ELISPOT assays. Neonatal gnotobiotic pigs were orally inoculated once with virulent Wa (WaV) or three times with attenuated Wa (WaA) HRV or mock inoculated (Mock) and then were challenged with virulent Wa (WaV/PC) 28 days after the first inoculation. The ASCs from intestinal and systemic lymphoid tissues of pigs from each group were quantitated by ELISPOT assay at the day of challenge, at postinoculation day 28 (WaV, WaA, and Mock) or at postchallenge day (PCD) 7 (WaV+WaV/PC, WaA+WaV/PC, and Mock+WaV/PC). In all virus-inoculated pigs, regardless of the inoculum, lymphoid tissue, or isotype, VP6 induced the highest numbers of ASCs, followed by VP4; ASCs specific for VP7, NSP3, and NSP4 were less numerous. At challenge, total HRV- and HRV protein-specific immunoglobulin A (IgA) and IgG ASCs in intestinal lymphoid tissues were significantly greater in WaV- than in WaA-inoculated pigs, and WaV pigs were fully protected against diarrhea postchallenge, whereas the WaA pigs were partially protected. At PCD 7, there were no significant differences in ASC numbers for any HRV proteins between the WaV+WaV/PC and WaA+WaV/PC groups.

Animals↗

PubMed2001

Protective immunity and antibody-secreting cell responses elicited by combined oral attenuated Wa human rotavirus and intranasal Wa 2/6-VLPs with mutant Escherichia coli heat-labile toxin in gnotobiotic pigs.

Two combined rotavirus vaccination regimens were evaluated in a gnotobiotic pig model of rotavirus infection and disease and were compared to previously tested rotavirus vaccination regimens. The first (AttHRV/VLP2x) involved oral inoculation with one dose of attenuated (Att) Wa human rotavirus (HRV), followed by two intranasal (i.n.) doses of a rotavirus-like particle (2/6-VLPs) vaccine derived from Wa (VP6) and bovine RF (VP2) rotavirus strains. The 2/6-VLPs were coadministered with a mutant Escherichia coli heat-labile toxin, LT-R192G (mLT) adjuvant. For the second regimen (VLP2x/AttHRV), two i.n. doses of 2/6-VLPs+mLT were given, followed by one oral dose of attenuated Wa HRV. To compare the protective efficacy and immune responses induced by the combined vaccine regimens with individual rotavirus vaccine regimens, we included in the experiments the following vaccine groups: one oral dose of attenuated Wa HRV (AttHRV1x and Mock2x/AttHRV, respectively), three oral doses of attenuated Wa HRV (AttHRV3x), three i.n. doses of 2/6-VLPs plus mLT (VLP3x), three i.n. doses of purified double-layered inactivated Wa HRV plus mLT (InactHRV3x), mLT alone, and mock-inoculated pigs. The isotype, magnitude, and tissue distribution of antibody-secreting cells (ASCs) in the intestinal and systemic lymphoid tissues were evaluated using an enzyme-linked immunospot assay. The AttHRV/VLP2x regimen stimulated the highest mean numbers of intestinal immunoglobulin A (IgA) ASCs prechallenge among all vaccine groups. This regimen induced partial protection against virus shedding (58%) and diarrhea (44%) upon challenge of pigs with virulent Wa HRV. The reverse VLP2x/AttHRV regimen was less efficacious than the AttHRV/VLP2x regimen in inducing IgA ASC responses and protection against diarrhea (25% protection rate) but was more efficacious than VLP3x or InactHRV3x (no protection). In conclusion, the AttHRV/VLP2x vaccination regimen stimulated the strongest B-cell responses in the intestinal mucosal immune system at challenge and conferred a moderately high protection rate against rotavirus disease, indicating that priming of the mucosal inductive site at the portal of natural infection with a replicating vaccine, followed by boosting with a nonreplicating vaccine at a second mucosal inductive site, may be a highly effective approach to stimulate the mucosal immune system and induce protective immunity against various mucosal pathogens.

Adjuvants, Immunologic↗

PubMed2001

A meiotic chromosomal core consisting of cohesin complex proteins recruits DNA recombination proteins and promotes synapsis in the absence of an axial element in mammalian meiotic cells.

The behavior of meiotic chromosomes differs in several respects from that of their mitotic counterparts, resulting in the generation of genetically distinct haploid cells. This has been attributed in part to a meiosis-specific chromatin-associated protein structure, the synaptonemal complex. This complex consist of two parallel axial elements, each one associated with a pair of sister chromatids, and a transverse filament located between the synapsed homologous chromosomes. Recently, a different protein structure, the cohesin complex, was shown to be associated with meiotic chromosomes and to be required for chromosome segregation. To explore the functions of the two different protein structures, the synaptonemal complex and the cohesin complex, in mammalian male meiotic cells, we have analyzed how absence of the axial element affects early meiotic chromosome behavior. We find that the synaptonemal complex protein 3 (SCP3) is a main determinant of axial-element assembly and is required for attachment of this structure to meiotic chromosomes, whereas SCP2 helps shape the in vivo structure of the axial element. We also show that formation of a cohesin-containing chromosomal core in meiotic nuclei does not require SCP3 or SCP2. Our results also suggest that the cohesin core recruits recombination proteins and promotes synapsis between homologous chromosomes in the absence of an axial element. A model for early meiotic chromosome pairing and synapsis is proposed.

Animals↗

PubMed2001

Plasticity of endothelial cells during arterial-venous differentiation in the avian embryo.

Remodeling of the primary vascular system of the embryo into arteries and veins has long been thought to depend largely on the influence of hemodynamic forces. This view was recently challenged by the discovery of several molecules specifically expressed by arterial or venous endothelial cells. We here analysed the expression of neuropilin-1 and TIE2, two transmembrane receptors known to play a role in vascular development. In birds, neuropilin-1 was expressed by arterial endothelium and wall cells, but absent from veins. TIE2 was strongly expressed in embryonic veins, but only weakly transcribed in most arteries. To examine whether endothelial cells are committed to an arterial or venous fate once they express these specific receptors, we constructed quail-chick chimeras. The dorsal aorta, carotid artery and the cardinal and jugular veins were isolated together with the vessel wall from quail embryos between embryonic day 2 to 15 and grafted into the coelom of chick hosts. Until embryonic day 7, all grafts yielded endothelial cells that colonized both host arteries and veins. After embryonic day 7, endothelial plasticity was progressively lost and from embryonic day 11 grafts of arteries yielded endothelial cells that colonized only chick arteries and rarely reached the host veins, while grafts of jugular veins colonized mainly host veins. When isolated from the vessel wall, quail aortic endothelial cells from embryonic day 11 embryos were able to colonize both host arteries and veins. Our results show that despite the expression of arterial or venous markers the endothelium remains plastic with regard to arterial-venous differentiation until late in embryonic development and point to a role for the vessel wall in endothelial plasticity and vessel identity.

Animals↗

PubMed2001

[Molecular analysis of polymorphisms for B-LII beta(beta 1 exon) locus in some Chinese native chicken].

Molecular genetic polymorphisms were studied for MHC-B-LII beta(beta 1 exon) locus in ten breeds of chicken by PCR-RFLPs. Thirty-seven genotypes were detected in these chicken. In the 305 bp fragment derived from MHC-B-LII beta(beta 1 exon) locus digested with Hha I, EcoRV, HaeIII, Xba I, there were significant difference with the frequencies of genotype and combined genotype among individuals or breeds. Statistical results showed Hardy-Weinberg equilibrium in polymorphic sites were inconsistent among various breeds. Sequencing results suggested there are more polymorphism at the level of amino acid than at that of nucleotide. Furthermore, as antigen binding site, the highly polymorphisms of beta 1 exon sequence was a reflection to the antigen diversity of immune systems. Moreover, it was implied that there was highly association between genetic polymorphisms of beta 1 exon and reproduction performance in chicken.

Animals↗

PubMed2001

[Effects of conjugated linoleic acid on the metastasis of mouse melanoma B16-MB].

In order to explore the effects of conjugated linoleic acid on tumor metastasis, the proliferation, gap junction intercellular communication (GJIC), adhesion to extracellular matrix, and metastasis cascades of tumor cells were imitated in cell culture. The results showed that 100 and 200 mumol/L conjugated linoleic acid could inhibit the proliferation and the adhesion of tumor cells to extracellular matrix, and could recover its gap junction intercellulor communication.

Animals↗

PubMed2001

Nasal carriage of Streptococcus pneumoniae among children in Beijing.

OBJECTIVE: To investigate the antimicrobial susceptibility of Streptococcus pneumoniae carried in the nose among children in Beijing and the distribution of serotypes, and to analyze the risk factors for nasal carriage of penicillin non-susceptible S. pneumoniae. METHODS: A disk diffusion test was applied to detect the antimicrobial susceptibilities of S. pneumoniae to erythromycin, trimethoprim-sulfamethoxazole, chloramphenicol and tetracycline. The E test was applied to determine the minimal inhibitory concentrations of penicillin, cefuroxime, cefotaxime, augmentin and imipenem. S. pneumoniae isolates were serotyped by the Quellung reaction. RESULTS: S. pneumoniae that was resistant to penicillin or cefuroxime was not found, but S. pneumoniae intermediate resistant to penicillin and cefuroxime accounted for 8.2% and 2.1%, respectively. All of the isolates were susceptible to cefotaxime, augmentin and imipenem. S. pneumonia that was resistant to erythromycin, trimethoprim-sulfamethoxazole and tetracycline were extremely numerous, accounting for 72%, 70% and 79%, respectively. Five serotypes (19, 6, 14, 23, 17) accounted for 54.7%, and nontypables accounted for 20.6% of all the S. pneumoniae. Previous history of otitis media was a risk factor we found for nasal carriage of penicillin non-susceptible S. pneumoniae. CONCLUSIONS: Continued surveillance of the antimicrobial susceptibilities of S. pneumoniae is necessary. A larger scale investigation is needed to identify if the 7 or 9-valent conjugate pneumococcal vaccine is appropriate for Chinese children.

Child, Preschool↗

PubMed2001

Antistress effect of oligosaccharides extracted from Morinda officinalis in mice and rats.

AIM: To explore the antistress effect of Morinda officinalis (Chinese medicine "Bajitian") oligosaccharides (MW-97) in mice. METHODS: Male mice and rats were subjected to a variety of unpredictable stressors on a daily basis over 15 d period and then the Vidiomex-V image pattern analytic system was used to observe the spontaneous motor activity. Meanwhile, regular method was used to prepare pathologic section of adrenal gland and blood cells analytic system was used to detect white blood cell (WBC) count (including relative WBC percentages) in peripheral blood. On the end, the serum level of stress hormone was detected using radioimmunoassay. RESULTS: Chronic stress resulted in diffuse hyperplasia of the adrenal cortex and atrophy of the adrenal medulla in mice, which suggested that stress-adaption failure of the adrenal gland occurred, while adrenal gland of the mice pretreated with MW-97 (100 mg/kg, ip) prior to each stressor for 15 d did not occur any pathologic changes. In addition, chronic stress also significantly reduced the WBC count and relative WBC percentages in the peripheral blood, including the percentage of lymphocytes, monocytes, neutrophils, however, MW-97 (25 and 100 mg/kg) reversed these changes and raised WBC count, along with relative WBC percentages significantly. Furthermore, the serum concentration of testosterone was decreased and corticosterone was increased significantly in chronically stressed animals. MW-97 also declined the serum level of corticosterone and raised level of testosterone. MW-97 had no effects on the spontaneous motor activity in the stressed mice. CONCLUSION: MW-97 had antistress effect against chronic stress, moreover, MW-97 had no excitatory or inhibitory effects on the CNS, which suggested that MW-97 might become a new kind of antistress agent.

Adrenal Glands↗

PubMed2001

[Effect of physical and chemical factors on Macaca Mulatta's pulp and change of the collagen in pulp].

OBJECTIVE: To investigate the change of pulp and its collagen to outside stimuli. METHODS: 51 permanent teeth from 10 adult healthy Macaca Mulatta's monkeys were chosen as experimental teeth. 39 of them were prepared Class V cavities. The teeth were divided into two groups, one was filled with zinc phosphate cement and another group with zinc oxide eugenol. A blank control group of 12 teeth was set at the same time. Just after the operation, 3 d, 7 d, 1 month and 3 months later, the animals were executed. Histologic changes were evaluated by means of HE and collagen staining method. RESULTS: Local inflammation was the major representation in the pulps of the zinc phosphate cement group from 7 d to 3 months after operation. The percentage of collagen decrease dropped sharply, and there was no inflammation cells infiltration in the pulps of zinc oxide eugenol group from 1 to 3 months after operation. By means of collagen staining method, the morphological characters, distribution and the change of pulpal collagen during a certain pathologic process were clearly represented in histologic slices. The change of collagen appeared earlier than the inflammation cells infiltration. CONCLUSIONS: Zinc phosphate cement can lead to medium inflammation of the pulp. The change of collagen appears earlier than that of WBC, which can be used as a sensitive indicator.

Animals↗

PubMed2001

[A study on the relationship between respiratory tract viruses antigen in peripheral blood mononuclear cells and their antibody from children with steroid-sensitive and simple nephrotic syndrome].

OBJECTIVE: To explore whether respiratory tract viruses infection was involved in the pathogenesis of sterioid-senstive and simple nephrotic syndrome(SSSNS). METHODS: Using APAAP and ELISA, the authors assayed the expression of respiratory tract viruses antigen in peripheral blood mononuclear cells (PBMC) and the production of viruses antibody in serum from 20 cases of children with steroid-sensitive and simple nephrotic syndrome. RESULTS: The positive rate of viruses in the active stage group of SSSNS children increased (P < 0.05), compared with that in the remission group and the healthy control group. The positive rate of virus detection in SSSNS children was closely related with the quantity of urinary protein(P < 0.05). The positive rate of virus detection in the group with urinary protein > or = 50 mg/(kg.d) was higher than that in the group with urinary protein < 50 mg/(kg.d). CONCLUSION: The onset of SSSNS may be related to the infection of respiratory tract viruses.

Antibodies, Viral↗

PubMed2001

[The preparation and study on hepatic targeting tendency of galactosyl-anti-CD3-McAb in mice].

OBJECTIVE: This study sought to reduce the recurrence rate of primary liver cacer (PLC) after hepatectomy by increasing the concentration of infiltrating lymphocytes(TILs) at the target organ. METHODS: It has been reported that galactosyl-anti-CD3-McAb has an obvious hepatic targeting tendency in vitro. On the basis of that work, the present authors conducted a study in mice. Galactosyl-anti-CD3-McAb was prepared and its carbohydrate density was measured with the phenol-sulphyric acid method, and then anti-CD3-McAb (labeled with 125I) and galactosyl-anti-CD3-McAb (labeled with 131I) were infused respectively via the peripheral vein and the radioactivity in each organ was measured. RESULTS: The carbohydrate density of galactosyl-anti-CD3-McAb in this experiment was 58.12, which effectively guaranteed the specific binding between galactosyl-anti-CD3-McAb and hepatic binding protein(HBP). It was also noticed that anti-CD3-McAb tended to aggregate in the lungs while being infused via the peripheral vein, and that galactosyl-anti-CD3-McAb had an obvious hepatic targeting tendency in vivo and it stayed in liver for quite a long period. CONCLUSIONS: Galactosyl-anti-CD3-McAb has an obvious hepatic targeting tendency in vivo while being infused through peripheral vein; this may be due to the specific binding between galactose and HBP.

Animals↗

PubMed2001

[Effects of bite force loss on the expression of IL-6 mRNA in rat periodontium].

OBJECTIVE: The aim of this study is to evaluate the expression of IL-6 mRNA in rat periodontal cells under normal bite force and without bite force, and to explain periodontal remodeling from the molecular level. METHODS: Animal models with normal bite force and without bite force were established by using Wistar rats. In situ hybridization technique was applied to detect changes of IL-6 mRNA expression in rat periodontal tissue. RESULTS: Without bite force, the expression level of IL-6 mRNA increased significantly in periodontal cells. CONCLUSION: This study initially investigates the molecular mechanism of periodontal remodeling, and suggests that the histological morphology may be closely related to the mechanical stimulation.

Animals↗

PubMed2001

[Analysis on the dermal irritation caused by imported cosmetics].

Dermal irritation tests on 902 kinds of cosmetics were conducted. The acute dermal irritation/corrosion tests for 175 samples showed no irritation in 65.1% of them, and 34.9% of them were considered as slight irritation. The chronic dermal irritation/corrosion tests for another 727 samples showed no irritation for 32.2% of them, and 67.8% of them were considered as slight irritation, most of which are lipsticks, eye shadows, fluid powder foundations and powder foundations.

Animals↗

PubMed2001

[Observation on effect of supplementary treatment by Astragalus injection in treating senile pulmonary tuberculosis patients].

OBJECTIVE: To observe the clinical therapeutic supplementary effect of Astragalus injection (ASI) as anti-tuberculosis agents in treating senile tuberculosis (ST). METHODS: Seventy-six ST patients were divided according to their hospitalization order into two groups randomly, 39 in the ASI group and 37 in the control group. The anti-tuberculosis regimen applied on all patients were HRE (S)Z for first treated patients and KHZ1321 TH for retreated patients. In the ASI group, ASI was given additionally by adding ASI 20 ml into 500 ml 5% glucose solution for intravenous dripping, once a day. The therapeutic course was 2 months. The changes of focal size, bacteria in sputum, and erythrocyte immune function (EIF) were observed before and after treatment, and the EIF obtained from 30 healthy subjects was taken for control. RESULTS: EIF in patients of both groups was lower than that in healthy subjects (P < 0.01). Rosette rate of RBC-C3b receptor in both groups was all increased after treatment, the increment was higher in the ASI group than that in the control group significantly (P < 0.01). After 2 months ASI treatment, the effective rate of focal absorption examined by X-ray was 84.6% and the negative conversion rate of bacteria in sputum was 79.4%. CONCLUSION: ASI has the effect of elevating erythrocyte immunity in senile pulmonary tuberculosis patients, it is able to enhance the therapeutic effect of treatment.

Adjuvants, Immunologic↗

PubMed2001

[Comparative studies on the fatty acids contained in four species of medicinal plants from family Euphorbiaceae and their endophytic fungi].

OBJECTIVE: The relation of four species of medicinal plants from family Euphorbiaceae and their endophytic fungi was studied to find the source of active substances for developing new pharmaceutical resources. METHOD: The main fatty acids contained in Sapium sebiferum, Euphorbia pekinensis, Euphorbia helioscopia, Bischofia polycarpam and their 28 strains of endophytic fungi were compared and analysed by GC. RESULT: The main fatty acids of the plants are: alpha-linolenic acid, palmitic acid, linolenic acid and oleic acid. Linolenic acid, palmitic acid and oleic acid are the main fatty acids of the endophytic fungi. CONCLUSION: The fatty acids could be produced by the endophytic fungi, which could be used as a factor for identification. There are great differences at the contents of alpha-linolenic acid between the plants and their endophytic fungi, which were suggested to be related with the nutrition absorption and the relationship between the endophytes and the host plant.

Euphorbia↗

PubMed2000

Hospital ventilation and risk for tuberculous infection in canadian health care workers. Canadian Collaborative Group in Nosocomial Transmission of TB.

BACKGROUND: The risk for and determinants of transmission of tuberculosis in hospitals caring for moderate numbers of patients with tuberculosis remain uncertain. OBJECTIVE: To study the association of tuberculin conversion among health care workers with ventilation of patient care areas. DESIGN: Cross-sectional observational survey. SETTING: 17 acute-care community or university hospitals. PARTICIPANTS: All personnel who worked at least 2 days per week in the respiratory and physiotherapy departments or in selected nursing units. MEASUREMENTS: Participating workers underwent tuberculin skin testing and completed self-administered questionnaires. Previous tuberculin tests and bacille Calmette-Guérin vaccinations were verified. Records of patients with tuberculosis who were hospitalized in the 3 years preceding the study were reviewed. Air exchanges per hour in patient care areas were measured by using a tracer gas technique. Multivariate proportional hazards regression was used to estimate the effect of occupational factors on documented tuberculin conversion, after adjustment for nonoccupational factors, among participants with at least one previous negative result on tuberculin skin testing. RESULTS: Tuberculin conversion was associated with ventilation of general or nonisolation patient rooms of less than 2 air exchanges per hour (adjusted hazard ratio, 3.4 [95% CI, 2.1 to 5.8]); with work in moderate- to high-risk hospitals (adjusted hazard ratio, 2.2 [CI, 1.3 to 3.5]); and with work in the nursing (adjusted hazard ratio, 4.3 [CI, 2.7 to 6.9]), respiratory therapy (adjusted hazard ratio, 6.1 [CI, 3.1 to 12.0]), and physiotherapy (adjusted hazard ratio, 3.3 [CI, 1.5 to 7.2]) departments or housekeeping (adjusted hazard ratio, 4.2 [CI, 2.3 to 7.6]). Conversion was not associated with inadequate ventilation of respiratory isolation rooms (adjusted hazard ratio, 1.0 [CI, 0.8 to 1.3]). CONCLUSION: Tuberculin conversion among health care workers was strongly associated with inadequate ventilation in general patient rooms and with type and duration of work, but not with ventilation of respiratory isolation rooms.

Canada↗