Biomedical subjects

Z Yuan

Publications and source records attributed to Z Yuan.

At least 109 records · Page 6Linked to original sources

PubMed1999

Enantiometric separation of amino acids by copper (II)-L-arginine ligand exchange capillary zone electrophoresis.

A novel method for the separation of amino acid enantiomers by ligand exchange capillary zone electrophoresis (CZE) using a chiral Cu(II)-L-arginine ligand was developed in this paper. The effects of the buffer concentration, pH, the molar ratio of L-arginine to Cu(II), and the total concentrations of Cu(II) and L-arginine on the migration times and resolutions of chiral amino acids were investigated. The optimum experimental conditions were 40 mmol/L of NH4OAc, pH 7.0, the 2:1 concentration ratio of L-arginine to Cu(II), 1 mmol/L CuSO4 x 5H2O and 2 mmol/L L-arginine. Using the proposed method, six different dansyl-amino acids were separated successfully with the resolution ranging from 1.1 to 2.3 in less than 15 min.

Amino Acids↗

PubMed1999

Determination of dissociation constants of amino acids by capillary zone electrophoresis.

A method is proposed for the determination of dissociation constants of amino acids by capillary zone electrophoresis. According to the dissociation equilibrium of amino acids and the basic theory of electrophoresis, the nonlinear relationship between the pH value of the buffer and the effective electrophoretic mobilities of the analyte was obtained. The dissociation constants can be calculated from the pH values and the corresponding effective electrophoretic mobilities using the program written in C++. The dissociation constants, pKa1 and pKa2, of 11 kinds of amino acids were determined successfully by the proposed method. The determined dissociation constants were compared with values in the literature; the differences between them are in the range of -0.03 to 0.06. No significant differences were observed between the determined dissociation constants and the corresponding literature values.

Amino Acids↗

PubMed1999

Pericardial fluid absorption into lymphatic vessels in sheep.

We estimated the volumetric lymphatic clearance rate of pericardial fluid in sheep. In the first group of studies, 125I-human serum albumin (HSA) was injected into the pericardial cavity and after 4 h, various lymph nodes and tissues were excised and counted for radioactivity. Several lymphatic drainage pathways existed defined by elevated 125I-HSA in the middle and caudal mediastinal, intercostal, and the cardiac nodes located near the root of the aorta. In a second group of experiments, the plasma recovery of intrapericardially administered tracer was compared in sheep with intact lymphatics and in animals in which thoracic duct lymph was diverted and other relevant lymphatics ligated. The 4-h plasma recoveries were reduced significantly from an average of 12.2 +/- 3. 4% injected dose in the lymph-intact group to 3.0 +/- 1.1% injected dose in the diverted/ligated group (an inhibition of approximately 75%). In order to estimate the volumetric clearance of pericardial fluid through lymphatics in conscious sheep, 125I-HSA was administered into the pericardial cavity to serve as the lymph flow marker. 131I-HSA was injected intravenously to permit calculation of plasma tracer loss and tracer recirculation into lymphatics. From mass balance equations, total pericardial clearance into lymphatics averaged 1.50 +/- 0.43 ml/h or approximately 1.13 ml/h if one was to assume that the average 25% recovered plasma tracer in lymph diverted/ligated animals was due to nonlymphatic transport. In conclusion, mediastinal lymphatic pathways remove a volume equivalent to the pericardial volume (8.1 +/- 1.1 ml) every 5.4 to 7. 2 h.

Absorption↗

PubMed1999

The sensitivity of Medicare claims data for case ascertainment of six common cancers.

BACKGROUND: Although Medicare claims data have been used to identify cases of cancer in older Americans, there are few data about their relative sensitivity. OBJECTIVES: To investigate the sensitivity of diagnostic and procedural coding for case ascertainment of breast, colorectal, endometrial, lung, pancreatic, and prostate cancer. SUBJECTS: Three hundred and eighty nine thousand and two hundred and thirty-six patients diagnosed with cancer between 1984 and 1993 resided in one of nine Surveillance Epidemiology and End Results (SEER) areas. MEASURES: The sensitivity of inpatient and Part B diagnostic and cancer-specific procedural codes for case finding were compared with SEER. RESULTS: The sensitivity of inpatient and inpatient plus Part B claims for the corresponding cancer diagnosis was 77.4% and 91.2%, respectively. The sensitivity of inpatient claims alone was highest for colorectal (86.1%) and endometrial (84.1%) cancer and lowest for prostate cancer (63.6%). However, when Part B claims were included, the sensitivity for diagnosis of breast cancer was greater than for other cancers (93.6%). Inpatient claim sensitivity was highest for earlier years of the study, and, because of more complete data and longer follow up, the highest sensitivity of combined inpatient and Part B claims was achieved in the late 1980s or early 1990s. CONCLUSIONS: Medicare claims provide reasonably high sensitivity for the detection of cancer in the elderly, especially if inpatient and Part B claims are combined. Because the study did not measure other dimensions of accuracy, such as specificity and predictive value, the potential costs of including false positive cases need to be assessed.

Aged↗

PubMed1999

The utility of Medicare claims data for measuring cancer stage.

BACKGROUND: The validity of using claims data for measuring tumor stage, one of the most important determinants of choice of therapy and long-term survival, is unknown. OBJECTIVES: To determine the relative accuracy of both inpatient and hospital Outpatient Medicare claims for measuring the stage of disease of six commonly diagnosed cancers. RESEARCH DESIGN: Analysis of a database linking Surveillance, Epidemiology, and End Results (SEER) registry data and Medicare claims in patients aged 65 years with cancer. SUBJECTS: Three hundred twenty thousand, six hundred and thirty seven cases of invasive breast, colorectal, endometrial, lung, pancreatic, and prostate cancers diagnosed between 1984 and 1993. MEASURES: Using SEER files as the "gold standard," concordance with Medicare claims, as well as sensitivity and positive predictive value of coding for each stage was measured. RESULTS: Although Medicare data correctly categorized local, regional, and distant stage tumors in 97%, 33%, and 65%, respectively, the data substantially overestimated the proportion of localized tumors and underestimated the rate of regional stage disease. The highest concordance was observed for breast and colorectal cancer. However, the sensitivity and positive predictive values were never simultaneously 80% within one stage of a specific cancer. The accuracy of coding for stage in Outpatient files was inferior to inpatient data. CONCLUSIONS: With few exceptions, Medicare claims have limited utility as a measure of cancer stage. If tumor registry data are not available, investigators should consider the trade offs in sensitivity and predictive value when considering a study that will use claims data.

Aged↗

PubMed1999

Parathyroid hormone and mechanical usage have a synergistic effect in rat tibial diaphyseal cortical bone.

Previous reports showed that bone mass and architecture only partially recovered by remobilization (RM) after immobilization (IM)-induced osteopenia, and that parathyroid hormone (PTH) had an anabolic effect on the skeleton. The aim of this study was to determine whether low doses of PTH could restore IM-induced cortical bone loss and whether a combination of PTH plus loading (RM) treatment would be more effective than the PTH in unloaded (IM) limbs. One hundred and sixty 6-month-old rats were divided into aging and IM groups. The right hindlimb of the rat was immobilized by elastic bandage for 18 weeks, and then groups of rats were either kept IM or RM and treated with 30 microgram or 80 microgram of hPTH(1-38)/kg/day for 2, 10, and 20 weeks. Fluorescent-labeled, undecalcified cross-sections of right tibial shafts were studied. We found that RM for 20 weeks after 18 weeks of IM only partially recovered IM-induced muscle weight loss and PTH had no effect on muscle weight in either IM or RM limbs; that RM for 20 weeks after 18 weeks of IM partially restored some minimal cortical width by stimulating periosteal and endocortical bone formation and decreasing endocortical resorption; that PTH treatment of IM limbs completely restored IM-induced cortical bone loss and added extra bone by stimulating bone formation indices on all bone surfaces and depressing bone resorption on endocortical surface; that PTH treatment of RM limbs produced similar anabolic effects as in IM limbs with 30 microgram/kg/day dose but the 80 microgram/kg/day dose-treated limbs had a higher periosteal bone formation rate, which created a larger cross-sectional area, more cortical bone area, and a thicker cortex than the same dose treated IM limbs; and that PTH 80 microgram/kg/day treatment produced more anabolic effect than the 30 microgram/kg/day in both IM and RM limbs. We concluded that reloading the hindlimb by RM after long-term IM could not recover the cortical bone mass. PTH at employed doses was able to completely restore IM-induced cortical bone loss, and this effect was independent of mechanical stimulation. However, when PTH was combined with mechanical loading (RM), a synergistic anabolic effect on periosteal bone formation occurred which increased the cross sectional area that can increase bone strength.

Aging↗

PubMed1999

[The investigation of natural antibody level to Haemophilus influenzae type b polysaccharide in China].

OBJECTIVE: Investigation of natural antibody level to Haemophilus influenzae type b polysaccharide in China. METHODS: 1,596 sera samples from cord (55 sera), infants (1,383 sera), children (66 sera), adult (52 sera) and elderly (40 sera) were collected from different provinces and the natural antibody level to PRP was measured with a standardized radio immunoassay 125I-labeled PRP. RESULTS: Antibody level of infants under 5 year olds in different provinces was different. Levels of infants from Gansu, Guizhou, Jiangxi province were lower (< or = 0.07 microgram/ml) than from Shanhai, Guangxi and Heilognjiang. Comparison of antibody levels with different age groups showed that infants aged 6 months to 5 years having the lowest antibody level (< 0.15 microgram/ml). The level increased rapidly during 6-10 years of age (> or = 1.0 microgram/ml). The levels of adults and elderly were about 1-1.5 micrograms/ml. CONCLUSION: General immunity against Hib disease were low in Chinese population. Children aged 6 months to 5 years old with lowest natural antibody level to PRP were the population under high risk.

Adolescent↗

PubMed1999

Interstitial brachytherapy using iridium-192 for malignant brain tumors: clinical results.

OBJECTIVE: To determine the effects and toxicity of interstitial brachytherapy using iridium-192 on brain malignant gliomas. METHODS: Between January 1992 and January 1995, 56 patients with anaplastic astrocytoma and glioblastoma multiforme were treated with stereotactic brachytherapy using temporary high-activity iridium-192 sources. RESULTS: The median survival for patients receiving brachytherapy was 28 months. The survival rates at 1, 2, 3 years were 92.8%, 83.9% and 71.4% respectively. CONCLUSIONS: Brachytherapy may improve the control of local tumor and prolong the survival, when used in deep malignant brain gliomas, by temporary implanted high doses of iridium-192 sources.

Adult↗

PubMed1999

SSA/Ro antigen expressed on membrane of UVB-induced apoptotic keratinocytes is pathogenic but not detectable in supernatant of cell culture.

OBJECTIVES: To better understand the potential effect of ultraviolet light on the photosensitivity of patients with lupus erythematosus (LE), to elucidate the mechanisms of SSA/Ro antibody formation after UV exposure, and to investigate the role of this autoantibody in the pathogenesis of skin lesions. METHODS: Primary human keratinocytes were cultured in Medium-154. After ultraviolet-B light (UVB) irradiation, the keratinocytes were treated with affinity-purified anti-SSA/Ro sera and stained with FITC-labeled goat-anti-human IgG and propidium iodide (PI), followed by enzyme digestion with RNase, RNase-free DNase or RNase plus DNase. As target cells, the irradiated keratinocytes were incubated with affinity-purified anti-SSA/Ro sera, with or without fresh human sera as complement. The supernatants of irradiated keratinocytes were analyzed with ELISA method for SSA/Ro antigens. RESULTS: UVB irradiation induced apoptotic blebs on the cell surface. The blebs were composed of ribonucleoproteins and contained SSA/Ro antigens. SSA/Ro antigens expressed on UVB irradiated keratinocytes bound to affinity-purified anti-SSA/Ro sera, leading to complement-dependent cytotoxicity. However, no SSA/Ro antigens were detected in the supernatants. CONCLUSIONS: SSA/Ro, a ribonucleoprotein antigen expressed on UVB irradiated keratinocytes, may be recognized and presented to immune cells by a direct cell-cell contact other than be eliminated into the circulation.

Apoptosis↗

PubMed1999

[Effects of short veno-venous hemofiltration on severe acute pancreatitis].

OBJECTIVE: To estimate the effects of therapy of short veno-venous hemofiltration (SVVH, 4hr) on severe acute pancreatitis (SAP). METHODS: Twenty patients were divided randomly into hemofiltration group (HF, 10 pts) and non-hemofiltration group (NHF, 10 pts). The local, systemic manifestations were compared between two groups; and the concentration of serum pro-inflammatory cytokines (TNFalpha, IL-1beta, IL-6, IL-8, sIL-2R) and anti-inflammatory cytokines (IL-2, IL-10) were determined at different observation points. RESULTS: In the HF and NHF group, the duration for disappearance of abdominal pain and tenderness, and amelioration for abdominal distension was (8.5 +/- 6.3) d vs. (90.0 +/- 49.0) d and (16.9 +/- 5.2) d vs. (63.4 +/- 36.0) d. CT scores at the 14th day and APACHE II scores at the 10th day was (5.6 +/- 1.3) vs. (7.7 +/- 0.8) and (4.5 +/- 1.5) vs. (7.4 +/- 2.1). The average hospital stay and cost of therapy were (33.0 +/- 20.7) d vs. (56.4 +/- 16.0) d and (53,200 +/- 16,000) vs. (89,100 +/- 25,000) RMB (P < 0.05). The concentration of 5 serum pro-inflammatory cytokines at each observation points after hemofiltration was decreased significantly (P < 0.05) in the HF group. But the concentration of the two serum anti-inflammatory cytokines was increased significantly (P < 0.05) as compared with that of the NHF group. CONCLUSIONS: Through SVVH, the imbalance of pro-inflammatory and anti-inflammatory cytokines has been corrected at early stage; thus, the severity of the disease is ameliorated significantly and the efficacy of therapy is increased.

Female↗

PubMed1999

[Combined use of rhBMP2/BCB and free periosteum in repairing segmental defects in radii of rabbits].

OBJECTIVE: To study the efficacy of combined use of rhBMP2/BCBand free periosteal graft in repairing segmental bony defects. METHODS: A new grafting material (rhBMP2/BCB) was made by combining recombinant human BMP2 (rhBMP2) and an antigen-free bovine cancellous bone (BCB) as a carrier. rhBMP2/BCB was used alone in conjunction with free periosteal graft to repair a 1.5 cm defect in the radius of the rabbit. The defect-repairing capability for each of the treatment modalities was assessed radiographically, biomechanically, and by densitometry and histological studies. RESULTS: rhBMP2/BCB used alone was capable of healing the defect in large by 16 weeks, with a similar repair process and mechanism seen with RBX. Combined use of rhBMP2/BCB and free periosteal graft was superior in terms of increased amount and quality of the new bone formed at the early stage of the repair process (within 12 weeks) to rhBMP2/BCB used in isolation, with the defect basically healed by 12 weeks. CONCLUSIONS: Both methods are effective in repairing segmental bony defects, with rhBMP2/BCB used in conjunction with free periosteal graft being most preferred, considering the satisfactory osteogenesis, osteoconduction and osteoinduction.

Animals↗

PubMed1999

[Effect of calcium and cristata L extracts on bone mineral density and urinary mineral of rats].

In order to study the effect of cristata L for preventing fluoride toxicity, forty male SD rats were randomly divided into five groups. The control group(NC) was fed with staple feed stuff and tap water, the other four groups were fed with staple feed-stuff and high fluorine water. Except the high fluorine group(F), the other groups were fed with cristata L(FC), high calcium(FCa) and cristata L with high calcium(FCCa) respectively. The results showed that the serum calcium, urinary sodium, calcium, hydroxyproline(HOP) and fluorine contents of high fluorine groups were higher than that of control group; and the urinary calcium content of high calcium group was higher than that of control group. The body weight, BMC and BMD of high fluorine groups was lower than that of control group. The weight of groups FC, FCa and FCCa were significantly higher than that of group F. The BMC and BMD of group FCCa were significantly higher than that of group F. This implies that the food high in fluorine can affect the bone mineral density and urinary minerals of rats, the food supplemented with calcium can reduce the effect of high fluorine, and the food supplemented with both calcium and cristata L is better.

Animals↗

PubMed1999

[Analysis of the isomers of dihydroxybenzenes by micellar electrokinetic capillary chromatography with on-column amperometric detection at carbon-fiber microelectrode].

The effects of the concentrations of beta-cyclodextrin(CD) in electrolyte on the cyclic voltammetric properties of o-, m-, p-dihydroxybenzenes at carbon-fiber microelectrode were studied. The inclusion between o-, m-, p-dihydroxybenzenes and beta-CD was investigated based on the molecular structures and experimental results. The study showed that the order of the inclusion interaction, from strong to weak, between dihydroxybenzenes and beta-CD, was m-, o- and p-dihydroxybenzenes. The effects of the concentrations of NH4Cl, SDS and beta-CD, and the pH values of the electrophoretic buffer on the migration time of o, m, p-dihydroxybenzenes were investigated. The assay of o, m, p-dihydroxybenzenes by micellar electrokinetic capillary chromatography with on-column amperometric detection at carbon-fiber microelectrode was developed. The recovery ranged from 98% to 103%.

Carbon↗

PubMed1999

[The alternation current conductive property of blood].

The blood electro-frequency properties of normal human body were investigated in the range of 1 Hz-10 MHz. The method of testing and the equipment were examined to meet the need for the measurement of blood property. In the experiment, it was discovered that the electric conductivity of blood increased obviously with the increase of testing frequency in the rage of 100 Hz-10 KHz, but almost no change in phase was noted. This result suggests it is necessary to modify the previous work and build up a reasonable equivalent electric model of blood.

Adult↗

PubMed1999

[Cloning and expression of the binary toxin genes of Bacillus sphaericus C3-41 in a crystal minus B. thuringiensis subsp. israelensis].

Bacillus sphearicus C3-41, belonging to serotype H5a5b, is ahighly toxic strain isolated from a mosquito-breeding site in China. It has been shown that it had a higher toxicity against Culex spp. than the reference strain 2362 at the laboratory and field conditions. Using synthetic oligonucleotides designed on the basis of the binary toxin gene sequence of 2362, a 1.1 kb DNA fragment was produced and the genetic library was prepared from a HindIII digest of total DNA from C3-41. One colony containing the 3.5 kb HindIII fragment was selected for further studies. Sequence analysis revealed that this 3.5 kb Hind DNA fragment was composed of 3479 nucleic acids and the sequence of the binary toxin gene of C3-41 is completely identical to that of strain 2362. The toxin genes have been transferred into a nontoxic crystal-minus strain of Bacillus thuringiensis subsp. israelensis. The recombinant strains could express the binary toxin of B. sphaericus as crystaline structures during their sporulation. The expression products of the recombinants have a highly toxicity to susceptible Culex pipiens subsp. quinquefasciatus and no toxicity to resistant larvae(Culex pipiens subsp. pipiens) from France.

Animals↗

PubMed1999

[Location of the binary toxin gene of Bacillus sphaeriucs and some biological characteristics of its asprogenous mutants].

Location of the binary toxin gene of Bs C3-41 and some biological characteristics of its asporogenous mutants which obtained by DES treatment were studied in this paper. Mutant C4, L5 with blocked at the stage II of sporulation course were not possessed of any crystalline inclusion, but the binary toxin proteins were detected in their cells by SDS-PAGE analysis. Another mutant G5 which blocked at the stage III of sporulation course formed parasporal crystal in the cells, and its toxicity to larvae of Culex quinquefasciatus was about 50 times higher than those of mutant C4 and L5. The result of curing plasmid and Southern blot analysis confirm the binary toxin gene of Bs C3-41, Bs 1691 and Bs-10 locate on the chromosome.

Animals↗

PubMed1998

Exploring structure-activity relationships around the phosphomannose isomerase inhibitor AF14049 via combinatorial synthesis.

Phosphomannose Isomerase (PMI) has been shown by genetic methods to be an essential enzyme in fungal cell wall biosynthesis. The PMI inhibitor AF14049 was discovered as an unanticipated side product from high-throughput library screening against the enzyme from C, albicans. Solid-phase synthetic methods were developed and a series of libraries and discrete analogs synthesized to explore SAR around AF14049.

Amides↗

PubMed1998

Use of Medicare claims data to measure county-level variations in the incidence of colorectal carcinoma.

BACKGROUND: Population-based cancer registries that can be used to compare cancer incidence and mortality across regions of the U.S. are currently lacking. The authors conducted this study to validate Medicare claims as a measure of county-level colorectal carcinoma incidence among older Americans. Variations found among counties are described in this article. METHODS: A total of 183,174 hospitalized patients age 65 years in 1991-1993 with newly diagnosed colorectal carcinoma who resided in one of 480 large counties were identified in Medicare files. The county-level truncated age, race, and gender adjusted incidence rates for the population age 65 years, the proportion of patients with a code indicating distant metastases, and the 2-year case-fatality rates were determined. Corresponding rates from the SEER database were compared. RESULTS: The median truncated adjusted 3-year incidence rate was 870 per 100,000 (Quartile 1-Quartile 3, 779-955), with almost twofold differences among counties even after the exclusion of outliers. The median proportion of patients with codes indicating distant metastases was 23.4% (range, 10.2-46.9%; Quartile 1-Quartile 3, 20.8-25.8), and the average 2-year case-fatality rate was 39.2% (range, 26.5-51.4%; Quartile 1-Quartile 3, 37.0-41.6). Medicare files tended to underestimate the truncated incidence rate according to SEER, but among counties the two sets of rates were closely correlated (r = 0.94, P < 0.0001). CONCLUSIONS: Medicare files are a potential alternative source of national data for the study of colorectal carcinoma incidence among the elderly at the county level. The data also suggest significant variations among counties in colorectal carcinoma incidence, stage, and mortality that could be used in public health initiatives.

Age Factors↗