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Biomedical subjects

X H Zhou

Publications and source records attributed to X H Zhou.

At least 19 recordsLinked to original sources
PubMed1996

Transjugular intrahepatic portosystemic shunt procedure: efficacy of 10-mm versus 12-mm Wallstents.

PURPOSE: To compare results of transjugular intrahepatic portosystemic shunt (TIPS) placement with 10- and 12-mm Wallstents. MATERIALS AND METHODS: Forty-six TIPS procedures in 47 patients were retrospectively reviewed. Wallstents that were 10 mm in diameter were used in 23 patients, and those that were 12 mm in diameter were used in 23 patients. Immediate results were compared, which included initial portosystemic gradient and Doppler measurements of blood flow velocity through the shunt at 1 day. Long-term patency and velocities were also assessed. RESULTS: TIPS were successfully created in 46 of 47 patients (98%). In one patient in the 10-mm group, the portal vein could not be accessed. When compared with TIPS in the 10-mm group, TIPS placed in the 12-mm group required dilation to larger diameters (mean, 11.1 vs 9.2 mm; P < .0001) to achieve an identical target gradient of 10 mm Hg and exhibited lower 1-day velocities (mean, 1.3 m/sec vs 1.7 m/sec; P < .03). The 1-day occlusion rate was 17% (four of 23 patients) in the 12-mm group versus 0% in the 10-mm group (P < .02). Patient survival was statistically significantly less in the 12-mm group (P < .03). CONCLUSION: Twelve-millimeter Wallstents yield statistically significantly poorer short- and long-term results in TIPS procedures. This is most likely due to the decreased radial strength of the larger stent, which is 50% less than that of the 10-mm stent.

Adolescent↗
PubMed1996

Pulmonary emboli from pulse-spray and mechanical thrombolysis: evaluation with an animal dialysis-graft model.

PURPOSE: To compare pulmonary emboli resulting from pulse-spray pharmacomechanical thrombolysis (PSPMT) and mechanical thrombolysis performed to declot dialysis-access grafts. MATERIALS AND METHODS: Polytetrafluoroethylene arteriovenous shunts were created in eight dogs and were deliberately clotted at monthly intervals. Animals were randomly assigned to treatment with pulse-spray urokinase thrombolysis or a low-speed rotational percutaneous thrombolytic device. Perfusion imaging, pulmonary-artery pressure measurements, and pulmonary arteriography were performed before and after each procedure. RESULTS: A total of 22 procedures were performed (11 PSPMT and 11 mechanical thrombolysis). Declotting was successful in all procedures, with 100% 30-day patency. Segmental defects were seen on perfusion images after 10 (91%) of 11 PSPMT procedures and two (18%) of 11 mechanical thrombolysis procedures (P < .002). Transient increases in pulmonary-artery pressure occurred in the PSPMT group. Complete resolution of emboli and return to baseline pressures were seen in all cases, even after multiple (up to four) procedures in the same animal. There was no histologic evidence of pulmonary infarction in either group. CONCLUSION: The percutaneous thrombolytic device is effective for declotting dialysis grafts in dogs and results in statistically significantly fewer pulmonary emboli compared with PSPMT.

Animals↗
PubMed1995

Binding characterization of the iron transport receptor from the outer membrane of Escherichia coli (FepA): differentiation between FepA and FecA.

The dissociation constants for the binding of ferric enterobactin with FepA and FecA are quantitated with displacement experiments. It is found that Kd for FepA is 12 times lower than the one for FecA. This indicates that FepA is an high-affinity receptor while FecA binds ferric enterobactin with a lower affinity. Monoclonal antibodies specific for binding epitopes of FepA inhibit the binding of ferric enterobactin with purified FepA. These same antibodies do not inhibit the binding of ferric enterobactin with purified FecA. This indicates that the binding epitopes in FecA and FepA are different.

Bacterial Outer Membrane Proteins↗
PubMed1995

Pancreatic adenocarcinoma: CT versus MR imaging in the evaluation of resectability--report of the Radiology Diagnostic Oncology Group.

PURPOSE: To compare findings with computed tomography (CT) and magnetic resonance (MR) imaging in pancreatic adenocarcinoma and to determine optimal pulse sequences for MR imaging. MATERIALS AND METHODS: CT scans and MR images were compared of 189 adult patients with known or suspected adenocarcinoma of the pancreas. Levels of confidence were correlated with surgical and pathologic results. RESULTS: The accuracy of CT was 0.73 and of MR imaging was 0.70. The negative predictive value of CT was 0.28 and of MR imaging was 0.23. The positive predictive value of CT was 0.89 and of MR imaging was 0.88. Gradient-echo and T1-weighted spin-echo sequences ranked equally in evaluation of vascular invasion, T1-weighted spin-echo sequences were preferred for assessing lymphadenopathy, and T2-weighted spin-echo sequences were preferred for detecting hepatic metastases. CONCLUSIONS: Cross-sectional imaging modalities are useful in the identification of unresectable pancreatic carcinoma. CT is recommended for initial imaging assessment.

Adenocarcinoma↗
PubMed1994

Effect of verification bias on positive and negative predictive values.

The pairing of sensitivity and specificity expresses the efficacy of a test, and positive and negative predictive values measure the accuracy of a diagnostic test when applied to a particular patient. To calculate these measures, one has to know the true disease status of each patient. In practice, however, some patients may not be selected for verification of disease status. It has been shown that the estimated sensitivity and specificity may be biased if one includes in the study sample only the patients with verified disease statuses. This paper concerns the properties of the estimators of positive and negative predictive values using only patients with verified disease statuses. First, I show that these estimators are unbiased and provide consistent estimators for the variances of these estimators under the assumption that the probability of selecting a patient for a disease verification procedure does not depend directly on the true disease status of the patient. Then, I use the ML method to study the sensitivity of the naive estimators to the departure from the conditional independence assumption.

Bias↗
PubMed1994

Stability and in vitro absorption of captopril, enalapril and lisinopril across the rat intestine.

In vitro absorption of three angiotensin converting enzyme (ACE) inhibitors, captopril, enalapril and lisinopril, and their stabilities in aqueous buffer as well as their resistance to intestinal and dermal tissue homogenates were investigated. The results demonstrate that the spontaneous oxidation of captopril, enalapril and lisinopril followed first-order degradation kinetics in McIlvaine's citrate-phosphate buffer. The degradation rates for enalapril and lisinopril were much slower than that for captopril. With the former two ACE inhibitors, the first-order rate constants of breakdown in the presence of dermal homogenate were not significantly different from the control values. Intestinal homogenate increased the decomposition of both of these inhibitors when compared to the enzyme-free control systems. On the other hand, the first-order rates of disappearance of captopril in the presence of both dermal and intestinal homogenates were lower than in the enzyme-free system. The extent of reduction was proportional to the amount of homogenate added. This suggests that tissue homogenates prevent the oxidation of captopril to its disulphide dimer. Transport experiments show that the amounts of ACE inhibitors transferred from solution on the mucosal side increased linearly with incubation time over the 2 hr of study. The rates of transfer from the mucosal side to the serosal side had the following rank order: captopril > enalapril > lisinopril roughly in the ratio 1:1.13:1.27. Addition of harmaline caused a significant reduction in the transfer rate of captopril compared to the control system, which strongly suggests that captopril is transported by a sodium-dependent carrier-mediated process across intestinal tissue.

Animals↗
PubMed1994

LHRH test in the assessment of puberty in normal children.

We compared the performance of a sensitive immunoradiometric assay for luteinizing hormone (LH) with a standard radioimmunoassay and assessed the utility of a single LH determination after a standard dose of LH-releasing hormone (LHRH) in distinguishing pubertal from prepubertal state. Nocturnal integrated LH concentration and LH response to a standard LHRH test were assessed in 56 normal children aged 6-17 years. For each assay we examined sensitivities at fixed specificities and areas under the receiver-operator characteristic curves. The results show that: (1) the immunoradiometric assay exhibits better test performance; (2) a single blood sample 30, 45, or 60 min after LHRH administration is as useful to distinguish pubertal from prepubertal state in normal children as the peak LH estimated by multiple blood sampling, and (3) a single cutoff level for IRMA LH can be applied to these time points.

Adolescent↗
PubMed1993

Purification of outer membrane iron transport receptors from Escherichia coli by fast protein liquid chromatography: FepA and FecA.

Fast protein liquid chromatography (FPLC) with DEAE-Sepharose Fast Flow, PBE-94 and Q-Sepharose Fast Flow columns are applied to the purification of the ferric enterobactin protein receptor (FepA). The apparent single band of FepA on SDS-PAGE is isolated and purified into two proteins with very similar molecular weights. The two proteins are identified to be FepA and ferric citrate protein receptor (FecA) by N-terminus amino acid determination and a computer search with the Gene Bank file. The assay of binding activities of these proteins shows that both FepA and FecA bind ferric enterobactin, with the former having about double the activity of the latter. Competition studies shows that Fe-MECAM is competitively bound to both proteins and that ferric parabactin only slightly competes with [55Fe]ferric enterobactin. It is found that ferrichrome A has no effect on the binding of the receptor proteins with ferric enterobactin.

Amino Acid Sequence↗
PubMed1993

A novel purification of ferric citrate receptor (FecA) from Escherichia coli UT5600 and further characterization of its binding activity.

In our earlier paper, it was demonstrated that the FecA receptor protein from Escherichia coli UT5600/pBB2 (leu-, proC-, trpE-, entA-, rpsl-, delta (ompT-fepA)-/Ampr, fepA) binds with ferric enterobactin. In order to explore this further the outer membrane receptor protein, FecA, has been isolated from UT5600 (fepA-) and purified to homogeneity by DE-52-cellulose anion exchange chromatography followed by MonoPFPLC chromatofocusing. Partially purified FecA and homogeneous FecA show binding activity to [55Fe]ferric enterobactin and the binding is specific. Binding activity of FecA can be enhanced by ferric citrate. Lipopolysaccharide-free FecA as ascertained by silver staining and the endotoxin test still retains the same activity. In vivo uptake studies using different strains of E. coli suggest that FecA in E. coli plays an important role in ferrienterobactin transport.

Bacterial Outer Membrane Proteins↗
PubMed1992

Changes in lectin binding patterns of Leydig cells during fetal and postnatal development in mice.

Changes in the lectin binding of mouse Leydig cells during fetal and postnatal development were examined by light- and electron-microscopy using eight different biotinylated lectins (ConA, WGA, RCA-I, UEA-I, GS-I, PNA, SBA and GS-II). At the light-microscopic level, ConA, WGA, RCA-I, UEA-I and GS-I showed the same binding pattern in which all five lectins bound to the plasma membrane and cytoplasm of Leydig cells from the 13th day post coitum (p.c.) to the 8th postnatal week. PNA, SBA and GS-II reactions were positive in the plasma membrane and cytoplasm of Leydig cells from the 13th day p.c. to 15th day post partum (p.p.) but disappeared completely by day 20. At the electron-microscopic level, gold particles representing the GS-I or GS-II binding sites were distributed primarily along the cell surface membrane, including that of microvilli, as well as in the cytoplasm. These results indicate that certain glycoconjugates bearing D-galactose, N-acetyl-D-galactosamine, and N-acetyl-D-glucosamine residues are expressed on the cell surface and in the cytoplasm of Leydig cells during the period from the 13th day p.c. to around the 20th day p.p. The results suggest that these glycoconjugates might play some role in modulating hormone-receptor interaction in the Leydig cells before the 20th day. Furthermore, these results may indicate that sugar residues expressed on the cell surface and in the cytoplasm of Leydig cells are different from those in the fetal-neonatal and adult phases.

Animals↗
PubMed1992

A high Mr factor in human blood which confers serum resistance on gonococci: some properties and synergism with CMP-NANA.

A high relative molecular mass (M(r)) component which confers serum resistance on gonococci has been purified about 300-fold from a dialysed sonicate of human blood cells. Serum resistance conferred by the high M(r) factor (RIF), like that induced by cytidine-5' monophospho-N acetyl neuraminic acid (CMP-NANA), decreased when gonococci were incubated with neuraminidase. Also, the resistance-inducing activities of both high M(r) RIF and CMP-NANA were inhibited by CMP and inactivated at pH 4.0. These activities were not additive but synergistic. Neuraminidase decreased the activity of high M(r) RIF but not CMP-NANA. In tests with 14C CMP-NANA and gonococcal lipopolysaccharide, no sialyltransferase activity was detected, even in highly active samples of high M(r) RIF under conditions in which low activities of rat liver sialyltransferase were readily detected. Conversely, rat liver sialyltransferase was neither active in the RIF assay nor able to enhance the RIF activity of CMP-NANA. Nevertheless, high M(r) RIF greatly enhanced the sialyltransferase activity of a gonococcal extract; this enhancement suggests an explanation for the synergism between CMP-NANA and high M(r) RIF in inducing serum resistance in gonococci.

Blood Cells↗
PubMed1991

Lipophilic polylysines mediate efficient DNA transfection in mammalian cells.

Low molecular weight (Mr approximately 3000) poly(L-lysine) (PLL) conjugated to N-glutarylphosphatidylethanolamine is an effective carrier to promote DNA-mediated transfection in cultured mammalian cells. The conjugates, named 'lipopolylysines', contained an average of two phospholipid groups per molecule of PLL. Similar conjugates of the non-degradable poly(D-lysine) also had a similar transfection activity, indicating that the degradation of the carrier is not required for the activity. Unconjugated polylysines had little activity. The transfection activity of the lipopolylysine has been optimized with respect to the DNA concentration, DNA/carrier ratio, incubation time and the presence of serum in the incubation medium. The binding of lipopolylysine with DNA was measured by the degree of retardation of DNA in agarose gel electrophoresis. It was found that at the optimal DNA/lipopolylysine ratio for transfection, all DNA were found in large complexes which did not enter the gel. The transfection activity of the lipopolylysine, under optimal conditions, was approximately 3-fold higher than that of lipofectin, a widely used commercial reagent. Moreover, lipopolylysine mediated transfection even in the presence of 10% calf serum; whereas the lipofectin lost about 70% of its activity under the same condition. However, unlike lipofectin the transfection activity of the lipopolylysine depended on scraping the treated cells. Furthermore, lipopolylysine only transfected attached monolayer cells, and not suspension cells.

Animals↗
PubMed1991

Prolongation of repolarization time by electric field stimulation with monophasic and biphasic shocks in open-chest dogs.

Recent studies suggest that 1) electrically induced fibrillation and defibrillation involve prolongation of refractoriness by the shock in addition to stimulation and 2) biphasic waveforms are more efficient for defibrillation than are comparable monophasic waveforms. The purpose of this study was to compare prolongation of action potential duration at 50% repolarization by monophasic and biphasic shocks during paced rhythm. A floating glass microelectrode was used to record intracellularly from the anterior right ventricular epicardium in seven open-chest dogs. After 10 S1 beats paced at an interval of 350 msec, 5-msec and 2.5-msec monophasic shocks and biphasic shocks, with each phase of 2.5 msec, were given via mesh electrodes on either side of the microelectrode. The shock strength was adjusted so that the shock field, measured from eight extracellular electrodes encircling the microelectrode, was about 5 V/cm. Monophasic and biphasic S2 shocks were given starting with an S1-S2 interval of 120 msec, which was increased in 5-msec steps until an action potential was produced by the S2 shock. Both monophasic and biphasic 5 V/cm shock fields caused significant prolongation of action potential duration. The prolongation of action potential duration increased as the S1-S2 interval increased. This prolongation occurred at shorter S1-S2 intervals for 5-msec monophasic shocks than for biphasic shocks.

Action Potentials↗
PubMed1991

Balloon dilation treatment of phimosis in boys. Report of 512 cases.

Five hundred and twelve boys, aged from 5 months to 12 years, with phimosis were treated by application of a specially designed balloon catheter (patented). 1% dicaine topical anesthesia was used. 3-6 months follow-up showed that all the patients were cured. The procedure is simple, safe and much less traumatizing than the conventional circumcision. The mechanisms of balloon dilation, the age-specificity and the anesthesia were discussed.

Age Factors↗
PubMed1989

Purification and N-terminal partial sequence of anti-epilepsy peptide from venom of the scorpion Buthus martensii Karsch.

An anti-epilepsy peptide (AEP) was isolated and purified from venom of the scorpion Buthus martensii Karsch. The purification procedure included CM-Sephadex C-50 chromatography, gel filtration on Sephadex G-50 and DEAE-Sephadex A-50 chromatography. Its homogeneity was demonstrated by pH 4.3 polyacrylamide-disc-gel electrophoresis, focusing electrophoresis and SDS/polyacrylamide-disc-gel electrophoresis. The Mr of this peptide, calculated from measurements in SDS/15%-polyacrylamide-disc-gel and SDS/20%-polyacrylamide-disc-gel electrophoresis, is 8300. The isoelectric point is 8.52 by pH 8-9.5-range isoelectric focusing. No haemorrhagic or toxic activities were found. No toxicity was found even after the dose reached 28 mg/kg. The pharmacological tests showed that the AEP had no effect on heart rate, blood pressure or electrocardiogram, but strongly inhibited epilepsy induced by coriaria lactone and cephaloridine. The fluorescence spectrum showed that the peptide has a strong emission peak at 337 nm. Amino acid analysis suggested that the AEP is composed of 66 residues from 18 amino acids and has an Mr of 8290. The sequence of the first 50 N-terminal residues is as follows: Asp-Gly-Tyr-Ile-Arg-Gly-Ser-Asp-Asn-Cys-Lys-Val-Ser-Cys-Leu-Leu-Gly-Asn- Glu-Gly - Cys-Asn-Lys-Glu-Cys-Arg-Ala-Tyr-Gly-Ala-Ser-Tyr-Gly-Tyr-Cys-Trp-Thr-Val- Lys-Leu - Ala-Gln-Asp-Cys-Glu-Gly-Leu-Pro-Asp-Thr-.

Amino Acid Sequence↗
PubMed1989

Detection of early breast cancer: an overview and future prospects.

Detection and treatment of breast cancer at an early stage is the only method with proven potential for lowering the death rate from this disease. Detection of early breast cancer is promoted by the American Cancer Society, American College of Radiology, and Canadian Association of Radiologists by encouraging the regular use of three types of screening: breast self-examination, clinical breast examination, and mammography. When all factors are considered, it has been convincingly demonstrated that the potential benefits of mammography far outweigh the minimal, clinically undetected radiation risk incurred by the examination. New technologies, such as computed tomography, magnetic resonance imaging, transillumination diaphanography, ultrasound, thermography, and digital subtraction angiography might offer a wide selection for patient examination. However, none of these procedures, in its present form, is expected to replace mammography as the first-line imaging technique for the detection and diagnosis of benign and malignant breast lesions. Breast cancer is detected now, in most cases, via casual or informed breast self-examination. This first-line of detection is not sufficient, since most tumors may metastasize before they reach a palpable size. Mammography generally shows up tumors no smaller than 1-cm diameter, which in many cases have already metastasized. The more advanced imaging modalities in their current forms suffer from a number of drawbacks that give them a lower overall detection rate than mammography. Understandably, improving breast imaging modalities is a great challenge to diagnostic radiology. The purpose of this article is to provide a comprehensive overview of the detection of early breast cancer. It briefly discusses the understanding of breast cancer, its incidence, and the mortality and survival of patients with breast cancer, as well as screening programs for breast cancer. We review the developments in mammography and other breast imaging modalities over the last several years. Prospects for digital mammography, digital image enhancement, and three-dimensional digital subtraction mammography, which may someday supplant film mammography, are also discussed.

Angiography↗