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Biomedical subjects

X Ma

Publications and source records attributed to X Ma.

At least 145 records · Page 8Linked to original sources
PubMed2000

Health outcomes of elementary school students in New Brunswick. The education perspective.

With data from the New Brunswick School Climate Study (N = 6,883 students from 147 schools), this study examined individual differences in and school effects on health outcomes of students. Results of hierarchical linear modeling showed that females reported experiencing more physical health problems, eating less healthy food, and doing fewer exercises than males. Students of high socioeconomic status (SES) reported eating more healthy food and doing more exercises than students of low SES. Native students reported experiencing more physical health problems and eating less healthy food than nonnative students. Students of single parents reported eating more healthy food and exercising more than students of both parents. Schools showed effects on health outcomes over and above the effects of students. Students in schools with high SES and positive disciplinary climate reported fewer physical and mental health problems. Students in large schools reported less healthy food intake and fewer physical exercises.

Child↗
PubMed2000

[The application of polymerase chain reaction-single strain conformation polymorphism in the pedigree analysis of familial hypercholerolemia patients].

OBJECTIVE: To discuss the value of polymerase chain reaction-single strand conformation polymorphism(PCR-SSCP) in the pedigree analysis of familial hypercholesterolemia(FH) patients. METHODS: For 4 patients with FH detected by PCR-SSCP and DNA sequence analysis (1 homozygote has point mutation in exon 7, 1 heterozygote in exon 14, and 2 heterozygotes in 3' part of exon 4 ), members of each pedigree, altogether 23 individuals, were analysed using PCR-SSCP. RESULTS: Every member of the 4 pedigrees was examined genetically. Besides the 4 probands, another 1 homozygote and 8 heterozygotes were found. CONCLUSION: The PCR-SSCP method can be used in the pedigree analysis of FH probands. The early diagnosis of siblings and relatives can help to provide genetic consultation and direction so as to pay attention to development of hypercholesterolemia.

Adolescent↗
PubMed2000

Increased platelet-activating factor receptor gene expression by corneal epithelial wound healing.

PURPOSE: Platelet activating factor (PAF) is a potent inflammatory mediator the synthesis of which increases in the cornea after injury. The effects of PAF are mediated by receptors (PAF-R), which are present in target cells. This study was undertaken to investigate the effects of wound healing, PAF, and growth factors on modulating PAF-R mRNA levels in corneal epithelial cells. METHODS: Cultures of rabbit corneal epithelial (RCE), rabbit limbal epithelial (RLE), rabbit corneal fibroblast (RCF), and rabbit corneal endothelial (RCEn) cells, as well as rabbit corneal keratocytes (RCKs) were used. For the in vivo wound-healing experiments, a 7-mm central corneal deepithelialization was performed in anesthetized rabbits. For the in vitro experiments, wounded rabbit corneas were maintained in organ culture. Corneas were stimulated with 120 nM PAF or preincubated with PAF antagonists, cyclohexamide (CHX) or actinomycin D (AcD) before adding PAF. RCE cells were stimulated with transforming growth factor (TGF)-beta1, -beta2, and, -beta3, basic fibroblast growth factor (bFGF), keratinocyte growth factor (KGF); and hepatocyte growth factor (HGF). Total RNA was isolated and PAF-R expression evaluated by reverse transcription-polymerase chain reaction (RT-PCR), Northern blot analysis, and quantitative RT-PCR. RESULTS: PAF-R mRNA was expressed in RCE, RLE, and RCEn cells and RCKs, but not in RCFs. After epithelial injury, PAF-R expression increased from 2.5 to 4 times, both in vitro and in vivo. Addition of cPAF further stimulated PAF-R gene expression in epithelium, which was abolished by PAF antagonists. Quantitative RT-PCR revealed that PAF stimulated PAF-R mRNA threefold after injury. The induction of PAF-R by its agonist required previous injury and was inhibited by AcD but not by CHX. Treatment of RCE cells with TGF-beta1, -beta2, or -beta3, HGF, and KGF increased mRNA in PAF-R; however, bFGF had no effect. CONCLUSIONS: Corneal injury produces changes in PAF-R mRNA expression. Whereas stroma fibroblastic cells lost the PAF-R gene expression found in keratocytes, corneal epithelial injury upregulated PAF-R mRNA. These results suggest that activation of selective growth factors and increases in PAF synthesis after injury stimulate PAF-R gene transcription and constitute important feedback mechanisms needed to maintain the inflammatory process and regulate epithelial wound healing.

Animals↗
PubMed2000

Detection of TT virus sequences in children with liver disease of unknown etiology.

DNA sequences of TT virus (TTV) in 55 serum samples taken from 20 children with liver disease of unknown etiology (16 with acute liver disease, 2 with fulminant hepatitis, and 2 with chronic liver disease) and from 35 healthy children as controls were examined by using the hemi-nested polymerase chain reaction (PCR). The PCR was carried out using the established primers (NG059, NG061, NG063) to amplify TTV DNA sequences. The sequences were detected in 6 of the 20 patients (30.0%) with liver disease and in 5 of the 35 healthy children (14.2%) by direct gel analysis. There was no significant difference between the prevalence of liver disease patients and controls. However, both patients with fulminant hepatitis and both patients with chronic hepatitis had TTV DNA sequences. Four of the six TTV isolates from liver disease patients were genotype 1a, whereas only one of the five TTV isolates from controls was genotype 1a. Although the study population was small, it is possible that genotype 1a of TTV might be more pathogenic than other genotypes in children.

Adolescent↗
PubMed2000

Proinflammatory response and IL-12 expression in HIV-1 infection.

HIV-1 infection elicits a broad range of host responses, many of which interfere with the regulatory pathways of gene expression of interleukin-12 (IL-12), a heterodimeric cytokine essential for cell-mediated immunity against microbial infection. The inhibition of IL-12 production by accessory cells after HIV-1 infection has been identified as a potential factor responsible for impaired innate and Th1 cell-mediated responses observed in AIDS patients. The mechanism by which HIV-1 infection suppresses IL-12 gene expression is largely uncharacterized. Here we review all pathways identified that could potentially mediate HIV-induced impairment of IL-12 gene expression, such as IL-10, transforming growth factor beta, interferon-alpha/beta, tumor necrosis factor alpha, Fc receptors, complement regulatory proteins, and receptors. Also discussed is the decreased CD40 ligand induction in CD4 T cells during HIV infection, which may have a strong impact on T cell-dependent IL-12 production that is critical for the establishment and maintenance of a Th1 response.

Animals↗
PubMed2000

Chondrocyte allografts for repair of full-thickness defects in the condylar articular cartilage of rabbits.

PURPOSE: This study investigated the feasibility of repairing defects of the condylar articular cartilage by chondrocyte allotransplantation. MATERIAL AND METHODS: A full-thickness defect (2 mm diameter) was made in the condylar articular cartilage of 6-month-old rabbits with a No. 701 dental fissure bur that penetrated both the articular cartilage and the subchondral bone, and entered the marrow cavity. Sixty-four animals were divided into 5 groups. In the cell transplantation group (20 rabbits), the defect was filled with a collagen membrane embedded with chondrocytes of neonate rabbits cultured in vitro for 1 week. In control group 1 (18 rabbits), the defect was left untreated. In control group 2 (18 rabbits), the defect was filled with a collagen membrane without chondrocytes. In sham-operation control group (6 rabbits), the condyle surface was exposed but left unchanged. Two rabbits were added as a normal control group. Mandibular movement was not restricted postoperatively. The macroscopic and microscopic features of the condyles were observed at 1, 2, 4, 8, 12, and 20 weeks following surgery. RESULTS: The defects in the condylar articular cartilage were repaired with cartilage tissue after cell transplantation. CONCLUSION: A defect in the condylar articular cartilage can be repaired with articular cartilage-like tissue by allotransplantation of chondrocytes.

Animals↗
PubMed2000

[Biomicrocapsule membrane for cell and tissue transplantation].

OBJECTIVE: To Provide a simple and safe way in protecting living cells from immune rejection for transplantation therapies. METHODS: Enclose cells in Alginate-poly-l-lysine (APA) biomicrocapsules which have to be satisfied the following requirements: 1. biocompatibility, 2. strength, 3. permeability. RESULTS: The transplanted cells survived and had prominence therapy function in experimental animals. CONCLUSIONS: Biomicrocapsules are feasible tools for cells immune-transplantation.

Animals↗
PubMed2000

[A comparative study on nutrient accumulation and distribution of different generations of Chinese fir plantations].

The nutrient accumulations and distribution of different generation of Chinese fir plantations in central production areas of China were studied through the investigation of plantation with different generation(first, second and third), ages (5, 10, 15, 20 years old) and sites(site index 14, 16 and 18). The nutrient accumulations and distribution of Chinese fir plantations were greatly influenced by the number of planting generation. Nutrient accumulation and utilization efficiency in tree layer of Chinese fir plantations declined with the increasing planting generation number, with the first generation > the second > the third; while the nutrient accumulation of understory vegetation was increased with the increasing of planting generation number. Compared with the first generation plantations, nutrient accumulation of tree layer of the second and the third generations decreased by 17.56% and 36.24% respectively, and the third generation platation decreased by 22.65% than the second generation. Meanwhile, successive planting resulted in a decreasing nutrient utilization efficiency of Chinese fir plantation, and an increasing nutrient necessary for dry matter production per unit, which is disadvantageous to the maintaining of soil fertility, but beneficial to the nutrient accumulation of understory vegetation.

Abies↗
PubMed2000

The effects of glucose, insulin and oxidized low density lipoprotein on apoptosis in vascular endothelial cells.

OBJECTIVE: To study the effects of high concentrations of glucose, insulin and oxidized low density lipoprotein (ox-LDL) on apoptosis in cultured bovine aortic endothelial cells (ECs). METHODS: For qualitative determination of EC apoptosis, acridine orange (AO)/ethidium bromide (EB) staining and DNA agarose gels electrophoresis were used. Cellular DNA fragmentation ELISA measured apoptosis by quantitating the fragmentation of 5-bromo-2'-deoxyuridine-labeled DNA. RESULTS: High concentrations of glucose (20 mmol/L, 40 mmol/L), insulin (3000 microU/ml) and ox-LDL (50 micrograms/ml, 100 micrograms/ml) induced concentration- and time-dependent apoptosis in ECs. They had a synergetic effect on EC apoptosis. The combined effect of high concentration of glucose, insulin and ox-LDL was greater than any two of them; the effect of two was greater than one alone. Low concentration of insulin (30 microU/ml) decreased apoptosis in ECs induced by high concentrations of glucose (40 mmol/L), but no similar effect occurred with ox-LDL (100 micrograms/ml). CONCLUSION: High ambient glucose, insulin and ox-LDL can induce excessive apoptosis in cultured ECs, and low ambient insulin can prevent EC apoptosis. Excessive EC apoptosis induced by the separate or synergetic effect of hyperglycemia, hyperinsulinemia and hyperlipidemia may be one of the reasons for loss of endothelial integrity, dysfunction of the vascular endothelium and increased plasma membrane permeability, which are all involved in the development of diabetic macrovascular complications.

Animals↗
PubMed2000

[The repairment of the condylar cartilage defect by transplantation of chondrocytes embedded in the collagen membrane].

OBJECTIVE: To study the effect of repairing the defect on the condylar articular cartilage by chondrocyte transplantation. METHODS: A full-thickness defect was made in the condylar articular cartilage of the adult rabbit. The isolated condylar chondrocytes of the rabbits cultured in vitro for one week were embedded in the collagen membrane, and then transplanted into the defect. RESULTS: The defects of the condylar articular cartilage were repaired with cartilage tissue. CONCLUSIONS: The defect of the condylar articular cartilage could be repaired with articular cartilage-like tissue by transplantation of the condylar chondrocytes.

Animals↗
PubMed2000

[A quick way in isolation and amplification of mandibular condylar cartilage cell in vitro].

OBJECTIVE: To establish a quick way in acquiring well differentiated mandibular condylar cartilage (MCC) cells with high viability in large scale. METHODS: Japan white rabbit MCC cells were harvested by enzymatic method. They were grown in a modified bioreactor culture system, which contained the cytodex-3 micro-carriers in the culture medium. Kinetic growth of MCC cells on DEAE-dextran micro-carrier was observed under phase contrast microscope and environmental scanning microscope respectively. RESULTS: MCC cells attached rapidly to the surface of micro-carriers, but their spreading was slow. A quick growth of these cells was observed when they fully spread onto the micro-carrier. The number of MCC cells increased 16.2 times compared with that of plating. CONCLUSIONS: Micro-carrier culture of MCC cells can yield a large quantity of cells within a short period of time that will be of benefit in banking MCC cells for reconstruction of impaired cartilage.

Animals↗
PubMed2000

[The study of tarnish induced by Actinobacillus actinomycetemcomitans serotype b (Aay4) on titanium and Ti-75 alloys].

OBJECTIVE: To study the tarnish induced by Aay4 on titanium and Ti-75 alloys. METHODS: Pure titanium and Ti-75 alloys were machined into size of 10 mm x 10 mm x 1 mm in tablets(30 of pure titanium; 60 of Ti-75 alloys). Thirty specimens sampled randomly from Ti-75 alloy together with 30 specimens of titanium were subjected to chemical passivation treatment. 30 specimens of the pure titanium, depassivation Ti-75 alloy and passivation Ti-75 alloy were randomly divided into three groups (blank control group, media control group and inoculated media group) respectively, every group contains 10 specimens. Under the anaerobic conditions, the surfaces of the modified GAM media were inoculated with Aay4. The labeled specimens surfaces were then aseptically placed on top of the media surface for 10 weeks with one generation time per week. The specimens were removed after 10 weeks of incubation, immersed in 0.05% glutaradehyde solution to eliminate Aay4, rinsed with distilled water. After 2 weeks, the specimens were removed and observed visually or examined by MINOLTA CR-100 color apparatus. RESULTS: Visual evaluation: Aay4 caused significant tarnish on specimens exposed to inoculated media, all the specimens surface changed into yellow color. Color apparatus evaluation: this result showed that comparing with the blank control, media control has no influence on all the specimens L*a*b* values (P > 0.05). Aay4 caused significant tarnish on specimens exposed to inoculated media, the result showed that there was significant difference between media control group and blank control group with inoculated media group on all the specimens L*a*b* values (P < 0.05). CONCLUSION: Aay4 caused significant tarnish on pure titanium, depassivation Ti-75 alloys and passivation Ti-75 alloys by naked eyes and color apparatus, according CIE1976L*a*b* color system reading, the color of titanium and Ti-75 alloys changed from the yellow-green ranges to red-yellow ranges.

Aggregatibacter actinomycetemcomitans↗
PubMed2000

[The effect of prednisolone on the regeneration of condylar cartilage of the rabbit].

OBJECTIVE: To investigate the effect of the prednisolone on the condylar cartilage regeneration. METHODS: A full-thickness defect without penetrating the subchondral compact bone was made in the condylar cartilage of the adult rabbits, and prednisolone(25 mg) was applied locally. The reparative tissue was observed histologically and histochemically. RESULTS: The compact bone in the area of the defect of the condylar cartilage showed hyperplasia, and the defect was filled with compact bone at the end of twelve weeks. CONCLUSIONS: Prednisolone is able to repair the defect of the condylar cartilage.

Animals↗
PubMed2000

[Histologic study of the temporomandibular joints after ovariectomy in rats].

OBJECTIVE: To investigate histologic changes of the temporomandibular joints (TMJ) after ovariectomy in adult rats. METHODS: Sixty-eight female SD rats aged twenty weeks were assigned to 2 groups. One group underwent bilateral ovariectomies served as experimental group. The other underwent sham ovariectomy served as control group. The rats were killed at the intervals of 1, 2, 4, 8 and 12 weeks postoperatively. Histologic observation of the TMJ was performed in a synchronous manner by using light microscopy(LM), scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The serum levels of estrogen and bone mineral density of femur were also determined. RESULTS: In the experimental group, the serum levels of estrogen were obviously decreased, and bone mineral density of femur was significantly decreased at 12 weeks postoperatively. No obvious histological changes of TMJ of rats were observed at 1 and 2 weeks after the ovariectomy, whereas thickness of the condylar cartilage was increased, with irregular shape of chondrocytes at 4 and 8 weeks postoperatively. A serial of degenerative changes in the TMJ was observed in osteoporotic rats at 12 weeks after the ovariectomy. CONCLUSIONS: Estrogen deficiency in rats may cause alterations of the TMJ, and osteoporosis may predispose to degenerative changes in the TMJ.

Animals↗
PubMed2000

[Randomized controlled trial of sequence mass screening program for colorectal cancer].

OBJECTIVE: In order to assess the effectiveness of mass screening program for colorectal cancer, a sequence mass screening program based on RPHA-FOBT and individual quantitative risk assessment model (attributive degree value, AD) was used and evaluated on its effectiveness in a randomized controlled trial. METHODS: The residents of Jiashan county aged 30 years and over were randomized to either screening or control groups in 1989. Participants in screening group were asked to fill in a questionnaire and to submit one paper slide with stool. Participants who tested positive underwent diagnostic evaluations including flexible sigmoidoscopy and colonoscopy. RESULTS: According to the cancer registry of Jiashan, after initial mass screening in 1989, the 8-year cumulative incidence per 1,000 of colorectal cancer in screening and control groups appeared to be 3.95 (95% CI 3.81 - 4.10) and 4.01 (95% CI 3.86 - 4.16) respectively. There was no significant statistical difference between two groups (P > 0.05). Nevertheless, the 8-year cumulative mortality for colorectal cancer in screening group (2.08 per 1,000; 95% CI 1.96 - 2.18) was reduced 14.7% comparing with the control group (2.44 per 1,000; 95% CI 2.33 - 2.55). In particular, the cumulative mortality of rectal cancer was significantly (31.7%) lower than that in control group. Log-rank test showed that survival rate of rectal cancer in screening group was higher than that in controls (log-rank = 9.01, P = 0.0027). CONCLUSIONS: The sequential mass-screening program which based on RPHA-FOBT and ADV might reduce the mortality for colorectal cancer in the Chinese population.

Adult↗
PubMed2000

[Relationship between human herpesvirus 6 infection and idiopathic thrombocytopenic purpura].

OBJECTIVE: To investigate the pathogenic role of human herpesvirus 6 (HHV-6) in idiopathic thrombocytopenic purpura (ITP). METHODS: HHV-6 DNA was examined by polymerase chain reaction (PCR) in bone marrow mononuclear cells (BMMNC) of 105 ITP patients. Human cytomegalovirus (HCMV) and parvovirus B(19) DNA were also examined in some cases. Platelet-associated antibodies (PAIg) were measured by competitive ELISA in 66 ITP patients. Serum IgG titer to HHV-6 was observed by indirect immunofluorescence assay in 19 ITP patients. RESULTS: (1) HHV-6 DNA positivity was 41.0% for ITP patients, significantly higher than that for control group (P < 0.05). HHV-6 DNA positivity for adult ITP patients, especially adult chronic cases was significantly higher than that for childhood patients (P < 0.025). Positivities for parvovirus B(19) and HCMV DNA were 24.1% and 9.7%, respectively. (2) HHV-6 DNA positivity for patients with abnormal level of PAIgG was significantly higher than that for patients with normal level of PAIgG (P < 0.05). (3) Patients coinfected with HHV-6 and B(19) or HCMV had more severe symptoms or poorer prognosis. CONCLUSION: HHV-6 infection might be associated with excessive PAIgG. Coinfection with HHV-6, B(19) or HCMV may cause more severe symptoms in ITP patients.

Adolescent↗