Biomedical subjects

Y Yang

Publications and source records attributed to Y Yang.

At least 1,081 records · Page 60Linked to original sources

PubMed1996

The effects of nerve growth factor on newborn rat dorsal root ganglion neurons in vitro: a scanning electron microscopic observation.

The effects of nerve growth factor (NGF) on the three-dimensional structure of newborn rat dorsal root ganglion (DRG) neurons, in vitro, were examined by scanning electron microscopy. Throughout the culture in both NGF treated and control groups, two types of structures of the surface were recognized, smooth surfaced and rough surfaced neurons. Growth cones and varicosities of the processes were observed after 12 hours of culture in NGF-treated groups, in contrast they were observed after 24 hours in control groups. The size and number of growth cone and varicosity was greater in NGF-treated groups than in control groups. NGF elongated the processes of DRG neurons after 24 hours of culture. NGF also significantly increased the number of surviving neurons after 48-72 hours of culture. Rough surfaced neurons were more sensitive than smooth surfaced neurons to NGF in enhancing survival. These results suggest that NGF may induce maturation of DRG neurons through elongation of its processes and the formation of growth cones and varicosities. Furthermore, the perikaryal projections of DRG neurons may be related to neuron survival after NGF treatment.

Animals↗

PubMed1996

An in vivo method for testing hemocompatibility of materials used in prosthetic heart valves.

BACKGROUND AND AIMS OF THE STUDY: An in vivo method for testing hemocompatibility of materials used in mechanical heart valves was developed. METHODS: Discs of test materials were glued to specially designed plastic (Delrin) buttons and implanted into the superior and inferior venae cavae of sheep through a right thoracotomy. The button and disc had such configuration that the blood flow was minimally disturbed. Up to four different materials could be tested simultaneously in each animal: two in superior vena cava and two in inferior vena cava. The materials and their respective implantation sites were changed between different animals according to the Latin square principle. Ten animals were used. Three materials currently used in mechanical heart valve prostheses-titanium, cobalt-chromium alloy (Haynes 25) and pyrolytic carbon (Pyrolite)--together with a surface modified (methylated) titanium were evaluated. No heparin was given during the experiment. After two hours of testing the discs were explanted and evaluated for hemocompatibility. The thrombus area on each disc was measured with photography and planimetry. Platelet and leukocyte adhesion on the surfaces were quantitatively assessed by scanning electron microscopy (SEM). The results showed that there were significant differences in thrombus formation (p = 0.001) and leukocyte adhesion (p = 0.002) between the materials tested. There was no difference between implantation sites but significant differences between individual animals (p < 0.05). CONCLUSION: The results indicate that the method can be used to evaluate early hemocompatibility of biomaterials.

Adhesiveness↗

PubMed1996

In vivo comparison of hemocompatibility of materials used in mechanical heart valves.

BACKGROUND AND AIMS OF THE STUDY: Most studies of mechanical heart valve prostheses in recent years have focused on the hydrodynamic and clinical performance of different valve designs. Little attention has been paid to the hemocompatibility (thrombogenicity) of materials used in the prostheses. METHODS: In the present study, three materials currently used in mechanical heart valves, titanium, cobalt-chromium alloy (Haynes 25) and pyrolytic carbon (Pyrolite), together with a surface-modified (methylated) titanium, were evaluated and compared for their hemocompatibility in a sheep model. The test materials in the form of discs were glued to plastic buttons and implanted into the intrathoracic venae cavae of anesthetized sheep. Four different materials were tested simultaneously in each animal: two in the superior and two in the inferior vena cava. Eight animals were used. After two hours of exposure to flowing blood, the discs were explanted and evaluated for their hemocompatibility using close-up photography and scanning electron microscopy (SEM). Thrombus formation and blood cell adhesion were studied quantitatively. RESULTS: The results showed that there was significantly more thrombus on pyrolytic carbon and methylated titanium than on titanium and cobalt-chromium (p < 0.05). More leukocytes adhered on pyrolytic carbon and cobalt-chromium than on titanium and methylated titanium (p < 0.05). CONCLUSION: The results indicate that titanium and cobalt-chromium under the present condition were more hemocompatible than pyrolytic carbon. The clinical significance of the finding remains to be investigated.

Adhesiveness↗

PubMed1996

Effect of low-concentration CO2 on stereoacuity and energy expenditure.

BACKGROUND: Low-concentration CO2 commonly exists in our living environment in such locations as airplanes and cars. Its effect on visual performance and energy metabolism (through O2 uptake) has not been well studied, although several studies have shown that high-level CO2 (6-10%) significantly impaired visual performance. HYPOTHESIS: We felt that breathing CO2 might also interfere with the energy expenditure pathway, partly due to the reduced O2 fraction. Thus, we studied the effect of low-concentration CO2 (2.5%) on human visual stereoacuity and energy expenditure. METHODS: Computer-controlled Random Dot Stereograms and psychometric function were used for stereoacuity tests. A whole-room indirect calorimeter allowed for the accurate measurement of energy expenditure, and also served as a good testing environment. RESULTS: Of 10 subjects tested, 8 had a slight increase in resting energy expenditure after exposure to 2.5% CO2. The increase ranged from 0.4-6.1% (p = 0.087, paired t-test). In stereoacuity tests, the psychometric function curves of all three subjects tested shifted to the right when breathing 2.5% CO2 and returned to baseline 2 h after breathing fresh air. Stereoacuity value, which is the reciprocal of stereoscopic threshold, was significantly lower (p < 0.01, 2-tailed z score test) after CO2 exposure for all subjects tested. CONCLUSION: We conclude that CO2 levels as low as 2.5% can cause temporary reduction in human stereoacuity, and also cause a persistent but small increase in energy expenditure.

Adult↗

PubMed1996

An evaluation of statistical approaches to MEDLINE indexing.

Whether or not high accuracy classification methods can be scaled to large applications is crucial for the ultimate usefulness of such methods in text categorization. This paper applies two statistical learning algorithms, the Linear Least Squares Fit (LLSF) mapping and a Nearest Neighbor classifier named ExpNet, to a large collection of MEDLINE documents. With the use of suitable dimensionality reduction techniques and efficient algorithms, both LLSF and ExpNet successfully scaled to this very large problem with a result significantly outperforming word-matching and other automatic learning methods applied to the same corpus.

Abstracting and Indexing↗

PubMed1996

[Study of chromosome painting for one rare carrier with complex translocation].

This paper reports that one rare male carrier with complex translocation, being married for eight years, made his wife consecutive seven times abortions, stillbirth and teratogenesis of early death. Using human chromosome 7 and 8-specific probe pools constructed with the technique of chromosome microdissection and PCR, we carried out chromosome painting research of the patients, and identified the karyotype was: 46, XY, -7, -8, -9, +der (7)t(7; 9) (q2200; p24), +der(8)inv ins(8; 7) (q2100; q31.2q2200), +der (9)t(9; 7) (p24; q31.2).ish der(7)t(7; 9) (wcp7+), der(8)inv ins(8; 7)(wcp7+, wcp8+), der(9)t(9; 7) (wcp7+). The technique of chromosome painting provided us an effective technique of molecular cytogenetics for the study of chromosomal abnormalities. The formation mechanism of the complex translocation of the carrier is discussed.

Adult↗

PubMed1996

Carotenoid analysis of several dark-green leafy vegetables associated with a lower risk of cancers.

We have examined the carotenoid contents of several dark green vegetables found to be associated with a lower risk of various epithelial cancers in our epidemiological study and animal study. Samples of these vegetables were quantitatively examined by high-performance liquid chromatography (HPLC) on a C-18 reversed-phase column for individual carotenoid content. Pure reference compounds (alpha-carotene, beta-carotent, lycopene, canthaxanthin, and lutein) and internal standard (beta-Apo-8'-carotenal) were employed to quantify xanthophylls and carotenes in these vegetables. The results indicated that fresh, dark-green, leafy vegetables were high in beta-carotene (0.94-9.36 mg/100 g) and oxygenated carotenoids or xanthophylls, primarily lutein (0.94-7.39 mg/100 g), whereas lycopene and alpha-carotene were not prominent and canthaxanthin was non existent in these vegetables. These analyses suggest that consumption of carotenoids such as lutein in addition to beta-carotene may be associated with a lower risk of cancers.

Carotenoids↗

PubMed1996

Effect of repetitive bleeding on NADH-cytochrome b5 methemoglobin reductase activity and molybdenum content in erythrocytes in rats.

Reticulocytosis in rats was induced by repetitive bleeding. Both in the vitro and the in vivo studies showed that the detected reductive speed of methemoglobin of the bleeding group was faster than that of the control group at all time intervals. At the same time, the NADH-cytochrome b5 methemoglobin reductase activity and the molybdenum content in erythrocytes of the bleeding group were significantly increased. Regressional analysis showed that there was a significantly positive correlation between the enzyme activity and the molybdenum content. It is proposed that molybdenum might be required for the enzyme activity.

Animals↗

PubMed1996

Transient immune blockade prevents formation of neutralizing antibody to recombinant adenovirus and allows repeated gene transfer to mouse liver.

The hepatotropic properties of human adenoviruses have been used to develop vectors for in vivo liver-directed gene therapy. Current limitations for this vector system are the associated hepatitis that develops as a result of antigen-specific cellular immune responses and the difficulty in accomplishing repeated gene transfer. This study uses mouse models to define immune responses of the recipient animal that have previously been shown to prevent successful re-administration of virus and suggests approaches for preventing the development of these blocking immune responses. Our studies are most consistent with class II MHC-dependent activation ot T helper cells and B cells to capsid proteins of the input virus leading to the production of antiviral neutralizing antibody following a primary exposure to virus; this capsid-specific antibody appears to bind to virus and prevents entry in the context of a second administration of virus. Transient ablation of CD4 function at the time of virus administration prevents the formation of neutralizing antibody thereby allowing efficient gene transfer after at least two subsequent administrations of virus. Experiments in beta(2)m(-) mice and C57BL/6 mice treated with IL-12 suggested a more selective ablation of immune function based on inhibiting the activation of the T(H2) subset of T helper cells. From these studies on immune mechanisms it is hoped that viable strategies can be developed to overcome the problem of humoral immunity that occurs after the initial genetic therapy.

Adenoviridae↗

PubMed1996

Emergency percutaneous transluminal coronary angioplasty in acute myocardial infarction complicated with cardiogenic shock.

OBJECTIVE: To approach the efficacy of emergency percutaneous transluminal coronary angioplasty (PTCA) in Chinese patients with acute myocardial infarction (MI) complicated by cardiogenic shock. METHODS: Twelve patients with cardiogenic shock treated by emergency PTCA in this institution from January 1990 to May 1994 were retrospectively reviewed. There were anterio-lateral MI in 4 cases, inferio-posterial MI in 7, anterial and inferial MI in I, of which triple vessel disease in 4 cases, double vessel disease in 6, single vessel disease in I and left main coronary artery (LM) disease in 1. PTCA was performed under assistance of IABP in 7 cases and of centrifugal pump in 1. Only infarct-related Coronary artery (IRCA) was dilated during acute phase. Direct PTCA was done in 7 cases and rescue PTCA after failure of thrombolytic therapy in 5. RESULTS: PTCA was successful in 11 (91.7%) of the 12 cases, in 1 case with failure of PTCA the IRCA was reperfused by intracoronary thrombolytic therapy. Cardiogenic shock was reverted in 7 (63.6%) of the 11 cases reperfused by PTCA, among whom 6 (54.5%) survived. Four died of irreversible shock after 3 hours-9 days and 1 case with reversed shock died of cardiac rupture after 4 days. During a period of 13-55 months follow-up, long-term survivals were obtained in 4 cases. CONCLUSIONS: Emergency PTCA can achieve a high success rate and significantly decrease the mortality rate to less than 50% in Chinese patients with acute MI complicated with cardiogenic shock. The patients tolerate the PTCA procedure very well under the assistance of intra-aortic balloon counterpulsation (IABP) even in very severe condition.

Aged↗

PubMed1996

[Laparoscopic diagnosis of tubal infertility and fallopian tube lesions].

OBJECTIVE: To analyse the diagnostic value of laparoscopy in patients with tubal infertility. METHODS: The morphological appearance of fallopian tubes and surrounding tissues of 1120 cases with proven tubal infertility were observed under laparoscopy. Hydrotubation was performed at the same time in each case. RESULTS: Tubal infertility diagnosed by laparoscopy accounted for 32.8% of infertile patients. Among them, pelvic tuberculosis occupied 63.6%, while nonspecific inflammatory disease (NSID) 36.4%. 44.8% of the tuberculosis and 62.2% of NSID group had negative findings during pelvic examination. Four types of tuberculosis lesions were demonstrated: miliary ascites (9.4%), adherent mass (35.8%), adhesion and calcification (43.1%), nodular sclerosis (11.7%). In the NSID group, simple tubal obstruction accounted for 29.9%, the remaining were mild adhesion or hydrosalphinx. Complete tubal occlusion occupied 81.2% in tuberculosis group and 70.7% in NSID cases. In the tuberculosis group the positive rate of pelvic lesion biopsy and endometrial biopsy was only 59.1% and 20.5% respectively. CONCLUSION: Laparoscopy examination is a valuable procedure for the etiological diagnosis of tubal infertility.

Adult↗

PubMed1996

Phacoemulsification and posterior chamber intraocular lens implantation.

OBJECTIVE: The study was designed to evaluate the therapeutic effects of phacoemulsification and PMMA posterior chamber intraocular lens implantation. METHODS: The surgery was performed on 74 eyes of 67 patients with senile, complicated and congenital cataracts. RESULTS: Post-operatively, the visual acuities with spherical correction or without correction were 0.5 or better in 80.5% at one week and with correction, in 97.6% at three months. The mean astigmatism was 1.90 +/- 1.15 D at one week and 0.93 +/- 0.55 D at three months which were respectively less than that in the control group with a 10-12 mm large incision (P < 0.001), but almost the same as that in the control group with a small incision and manual nucleus division technique (P > 0.05). The main complications were iris bite in 6 eyes, capsular rupture in 2 eyes and aseptic hypopyon in one eye. The selection of cases, surgical techniques and management of intraoperative complications were discussed. CONCLUSION: These results suggest that phacoemulsification be applied extensively. However, that it has more complications and risk must be emphasized for a beginner.

Adult↗

PubMed1996

[Accommodation in pseudophakic eyes with monofocal posterior chamber intraocular lens].

OBJECTIVE: To study the accommodative problem of pseudophakic eyes with commonly implanted monofocal posterior chamber intraocular lens (PC-IOL). METHODS: Slataper's method, dynamic retinoscopy and pattern-visual evoked potentials were used to measure the accommodative power in 120 pseudophakic eyes (101 patients) with monofocal PC-IOL. RESULTS: The mean accommodative power was 2.15 +/- 0.76 D. Stepwise regression analyses revealed that the apparent accommodation is positively correlated with the corrected distant vision and the distantly corrected near vision, respectively. CONCLUSION: The apparent accommodation of pseudophakic eyes does exist, but it is a false one. The result of accommodative power measured by dynamic retinoscopy is the most objective and precise. The central visual efficiency and the applicable range of accommodation in pseudophakic eyes with low myopia (-1.00 D) are better than that in emmetropic pseudophakic eyes.

Accommodation, Ocular↗

PubMed1996

Acute bacterial meningitis in children in Hefei, China 1990-1992.

OBJECTIVE: To obtain etiologic and epidemiologic information about bacterial meningitis, especially the H influenza type B (Hib), from a medium-sized city, Hefei, China. METHODS: Data were collected prospectively over 3 years, from 1990 to 1992 by a well-organized group including 13 hospitals. All children with a clinical diagnosis of acute bacterial meningitis were enrolled and the specimens were taken for the etiologic studies. CSF and blood were tested by standard bacteriologic technique. CSF, blood and concentrated urine were tested directly for detection of antigen by countercurrent immuno-electrophoresis (CIE). Data were analyzed by epidemiologic methods. RESULTS: Bacterial culture and CSF Gram's staining were positive only in 13.3% and 11.7%, respectively. Bacterial antigen detection was positive in up to 90% by CIE which was more sensitive than bacterial culture (chi 2 = 67.7, P < 0.005). The annual incidence of acute bacterial meningitis in the city is calculated as 9.3 cases/100,000 children from 1 month to 15 years of age and 19.2 cases/100,000 children from 1 month to 5 years of age. Hib meningitis accounted for 51.7%, N. meningitis (Nm) for 38.3%, and S. pneumoniae (Sp) for 8.3%. There was no significant seasonal variation. Of the patients, 76.7% were children under 5 years of age, and 51.7% under 1 year of age. The case fatality rate was 11.7% for all bacterial meningitis, 9.7% for Hib, 17.4% for Nm and 20% for Sp. A total of 22.6% of survivors suffered from neurological or psychological problems. CONCLUSIONS: Using antigen detection combined with bacterial culture, we could make an etiologic diagnosis in up to 90% of the patients in this group. Hib, Nm and Sp were the predominant pathogens, which was similar to the findings in other countries. Hib was the most common cause of bacterial meningitis, but the incidence was much lower than in most parts of the world.

Child↗

PubMed1996

[Experimental studies on the quality control of xiaoluo pills].

Microscopic and physico-chemical methods have been used in the qualitative study of Xiaoluo Pills. The contents of peimine, peiminine and calcium carbonate in these pills have been determined. The proposed method can be used to control the quality of Xiaoluo Pills.

Antitussive Agents↗

PubMed1996

[The PCR amplification, cloning, sequencing, expression in E. coli of gene encoding endoflagella subunit protein (fla B) from Leptospira interrogans serovar lai].

A pair of oligonucleotide primers were designed by ourselves to amplify the endoflagella gene of L. interrogans serovar lai. A fragment about 840 bp was generated with PCR and inserted into plasmid pUC8 after the fragment and pUC8 were digested respectively with Bam HI and Pst I. A recombinant plasmid (designated as pLF1) was obtained. SDS-PAGE analysis indicated that a 33 kd was expressed in E. coli JM103 harboring pLF1 and the expression level of the protein was 11% of total bacterial soluble proteins. Western blot analysis showed that the protein band could be recognized by the antiserum against the endoflagella (Axiall filament) of Leptospira interrogans serovar lai. Nucleotide seguence data showed an open reading frame encoding 282 aminoacids residues, corresponding to a protein of molecular weight 33.6 kd. The G + C content of endoflagella subunit protein gene was 48 mol%. Therefore, the G + C content of the leptospiral fla B Gene is significantly higher than the reported 39 mol% G + C content of leptospiral genome of L.interrogans serovar lai but similar to the G + C of the Treponema pallidum genome. Comparison of the deduced endoflagellar subunit protein (fla B) amino acid sequence with flagellins from other bacteria revealed a high level of identity with the Treponema pallidum fla B proteins. Immunization/protection experiment was performed on the model of BALB/c mice and showed that the survival rate in the group JM103-pLF1 was higher than that in the group JM103-pUC8, but statistically the difference between them was significant (P < 0.05) and pLF1 did not induce significant levels of agglutinating antibodies against L.interrogans serovar lai.

Amino Acid Sequence↗

PubMed1996

Left ventricular diastolic dysfunction in patients with angina decubitus.

OBJECTIVE: To investigate the relationship between left ventricular diastolic dysfunction and episodes of angina decubitus. METHODS: The study population consisted of three groups, groups I (20 controls) had no cardiovascular diseases. Group II (20 patients) had coronary artery disease (CAD) without angina decubitus. Group III (24 cases with ejection fraction (EF) > 45%) were selected from 26 patients with angina decubitus. RESULTS: Left ventriculography (LVG) showed that left ventricular (LV) first 1/3 filling fraction (1/3FF) was significantly reduced in groups III as compared with groups II and I (P < 0.01). Left ventricular end-diastolic pressure (LVEDP) significantly increased in patients with angina decubitus after LVG as compared with that before LVG (P < 0.01). However, there were no statistically differences in LVEDP, before and after LVG in both groups II and I. CONCLUSIONS: Patients with angina decubitus have abnormalities of LV diastolic filling and decrease in LV compliance.

Adult↗

PubMed1996

[Treatment of uterine leiomyoma by two different doses of mifepristone].

OBJECTIVE: To study the response of uterine leiomyoma to two different daily dosages of mifepristone. METHODS: Prospective nonrandomized clinical trial on women with symptomatic uterine leiomyoma was conducted. Twenty-eight patients were treated with 10mg of mifepristone daily and fifteen patients with 20mg daily for 12 weeks, beginning on day 1 to 3 of the menstrual cycle. Volume changes of leiomyoma and uterus were measured with ultrasonography before treatment (as baseline) and monthly during the course of therapy. Blood samples for hemoglobin, liver and renal function were obtained monthly. RESULTS: Ovarian acyclicity was induced in both groups of patients given different daily doses of mifepristone and dysmenorrhea and low abdominal pain disappeared. All symptoms and signs of anemia were resolved. The average hemoglobin level elevated 14-16g/L monthly. After 12 weeks of mifepristone treatment, the leiomyoma volume decreased to 41.4% of baseline in the 10mg daily dose group and 43.0% in the 20mg daily dose group. There was no significant difference between the two treatment groups; the side effects were similar. CONCLUSION: Mifepristone of 10mg daily is considered to be a more ideal dosage for treatment. Mifepristone therapy is indicated in larger fibroids, and/or as preoperative medication for severely anemic patients and in perimenopausal patients with symptomatic fibroids.

Adult↗