Biomedical subjects

Z Zhao

Publications and source records attributed to Z Zhao.

At least 271 records · Page 15Linked to original sources

PubMed1996

An assessment of the risks of syphilis and HIV infection among a sample of not-in-treatment drug users in Houston, Texas.

The research presented in this paper details the results of an assessment of the risk factors associated with having a positive syphilis or HIV serology. The study was conducted using a sample of not-in-treatment drug users volunteering to participate in an HIV risk reduction intervention. The sample was composed of individuals who had injected drugs within 30 days or smoked crack cocaine 48 hours prior to participation in the study. Study participants were approximately 75% male and 66% African-American. All participants provided a blood sample to be tested for HIV and syphilis. Analysis of risk was conducted using univariate and multivariate statistical methods. Multivariate analysis of blood results showed that women, African-Americans, and those having a positive blood test for HIV were at higher odds of having a positive syphilis test. Analysis also showed that being a gay or bisexual male, having a history of drug injection, having less than a high-school education, having a history of trading sex for money, being African-American, and having a positive blood test for syphilis significantly increased the odds of a positive HIV test. Implications for HIV and STD prevention are discussed.

Adult↗

PubMed1996

Dose-response effects of dietary fiber on NMU-induced mammary tumorigenesis, estrogen levels and estrogen excretion in female rats.

The dose-related effects of the fiber-rich isolate, soft white wheat bran (SWWB), and the pure fiber, cellulose, on N-nitrosomethylurea (NMU)-induced mammary tumorigenesis was assessed in F344 female rats. SWWB (45% total dietary fiber, TDF) was added to the AIN-76A high-fat diet at 9, 12, 15 and 18%; cellulose (98% TDF) was added to the same diet at 4.5, 6, 7.5 and 9%, to give equivalent amounts of TDF. The experimental diets were fed 3 days post-NMU and continued for a period of 25 weeks, at which time the experiment was terminated and tumors enumerated. It was found that significant inhibition of mammary carcinoma occurred only at 9% SWWB, non-significant inhibition occurred at 12% SWWB, and no inhibition was seen at higher doses. Cellulose-fed animals exhibited consistently higher tumor yields regardless of dose. The difference in tumor yields between the 9% SWWB group and the remaining seven groups was attributable to an increased incidence in tumors characterized histologically as intraductal proliferation and ductal carcinoma in situ in the latter. Analysis of blood, urine and fecal estrogens was conducted to test whether dietary fiber exerted its tumor-inhibiting effect by altering the enterohepatic recycling of estrogens. Although SWWB, in general, lowered urinary estrogen excretion, increased fecal estrogen excretion and lowered blood estrogens, there was no consistent correlation between the amount of SWWB consumed, estrogen status and tumor yields. These results suggest that (i) wheat bran fiber at 9%, or minor constituents associated with it, contain anti-promoting properties that cellulose lacks; (ii) SWWB appears to exert its effects by suppressing the clonal expansion phase of mammary carcinogenesis; (iii) there is an upper limit (12-15% w/w) to the protective effects of SWWB; and (iv) the effects of SWWB on mammary tumorigenesis may not be attributed to alterations in the enterohepatic recycling of estrogens.

Animals↗

PubMed1996

N-(4-hydroxyphenyl)-retinamide increases lecithin:retinol acyltransferase activity in rat liver.

N-(4-Hydroxyphenyl)-retinamide (4-HPR; Fenretinide) is a synthetic retinoid which is undergoing investigation as a cancer chemopreventive agent. However, 4-HPR alters vitamin A kinetics and reduces the concentration of plasma retinol. We have conducted studies to examine the effects of 4-HPR on the activity of the enzyme lecithin:retinol acyltransferase (LRAT). This enzyme is implicated in the absorption and storage of vitamin A and is regulated, in liver, by vitamin A nutritional status. To determine whether 4-HPR, like retinoic acid, is able to induce liver LRAT activity, vitamin A-deficient rats having negligible liver LRAT activity were treated with single doses of 4-HPR (0.02-2.5 mg) and liver homogenates were assayed for LRAT activity using 3H-retinol bound to the cellular-retinol binding protein, CRBP, as substrate. Treatment with 4-HPR resulted in a dose- and time-dependent increase in liver LRAT activity which reached a maximum at 24 h. The activity of LRAT assayed in vitro and of hepatic 3H-retinyl ester content determined after an in vivo pulse of 3H-retinol were highly correlated (r = 0.802, P < 0.0002). When vitamin A-sufficient rats were fed a 4-HPR-supplemented diet for 30 d, LRAT activity differed significantly from control values in the liver (P < 0.0001) but not the small intestines. Changes in hepatic retinol metabolism which favor the esterification of vitamin A may be related to the mechanism by which 4-HPR alters vitamin A kinetics in vivo.

Acyltransferases↗

PubMed1996

Pathogenesis of corneal infection: binding of Pseudomonas aeruginosa to specific phospholipids.

Clinical isolates of Pseudomonas aeruginosa were examined for binding interactions with phospholipids of corneal epithelium. Thin-layer chromatography (TLC) of lipids extracted from corneal epithelia followed by staining with an ammonium molybdate spray reagent revealed three phospholipid components, PL1, PL2, and PL3. The chromatographic mobility of PL1 was similar to that of the phospholipid standards phosphatidylinositol (PI) and phosphatidylserine (PS), which were not well resolved from one other; PL2 and PL3 comigrated with the standards phosphatidylcholine and phosphatidylethanolamine, respectively. By use of a TLC-bacterial overlay procedure, 35S-labeled P. aeruginosa organisms were shown to bind to PL1 but not to PL2 or PL3. P. aeruginosa binding to PL1 was concentration dependent. Alkaline methanolysis abolished the binding. PL1 was separated into two components, PL1-I and PL1-S, by chromatography on borate-treated TLC plates. Both PL1-I and PL1-S contained binding sites for P. aeruginosa. Mass spectral analysis identified PL1-I and PL1-S as PI and PS, respectively. Radiolabeled P. aeruginosa organisms were subsequently shown to bind to commercially available bovine PI and PS and synthetic dipalmitoyl-PS but not to other phospholipid standards, including bovine SM and PC or synthetic dioleoyl- and distearoyl-PC. A control Escherichia coli strain did not bind to either PS or PI. Tetramethylurea, a disrupter of hydrophobic associations, did not influence the binding of P. aeruginosa to PS or PI. P. aeruginosa bound to the monolayers of corneal epithelial cells. P. aeruginosa binding to the monolayer cultures as well as to rabbit corneas pretreated with exogenous PS and PI was significantly higher than that to those preincubated with PC or medium alone. The data suggest that phospholipids PS and PI present in mucus or on the cell surface may function as P. aeruginosa receptors and contribute to selective bacterium-host interactions responsible for initial colonization.

Animals↗

PubMed1996

Reaction of ferrate (VI)/ferrate (V) with hydrogen peroxide and superoxide anion--a stopped-flow and premix pulse radiolysis study.

The reduction of ferrate(VI) to ferrate(V) by superoxide ions was studied over the pH range 2.6-13.0 using the premix pulse radiolysis technique. The pH dependence indicates that only the unstable protonated forms of ferrate, H2FeO4 (pKa3.5) and HFeO4- (pKa7.3) are reactive, k(HFeO4(-) + O2) = (1.7 +/- 0.2) x 10(7) M-1 s-1. The stable ferrate ion, FeO4(2-), showed no significant reactivity towards either hydrogen peroxide or superoxide anion. The rate constants for the spontaneous dimerization and decomposition of the protonated ferrates, e.g. k(HFeO4(-) + HFe04) approximately 250 M-1s-1, are orders of magnitude slower than their corresponding reduction reduction by superoxide indicating an outer-sphere mode of electron transfer for the latter process. In contrast the ferrate(VI) species H3FeO4+ (pKa = 1.6 +/- 0.2), H2FeO4, and HFeO4- oxidize hydrogen peroxide, e.g. k(HFeO4(-) + H2O2) = 170 M-1 s-1), at rates which correspond closely to their dimerization rates suggesting an inner-sphere controlled mechanism.

Hydrogen Peroxide↗

PubMed1996

Gangliosides of migrating and nonmigrating corneal epithelium in organ and cell culture.

PURPOSE: To identify major gangliosides - the sialated glycolipids - of corneal epithelium; to determine which specific gangliosides, if any, are synthesized in a higher amount or are downregulated during corneal epithelial cell migration; and to determine what role, if any, they play in the modulation of corneal epithelial cell proliferation. METHODS: [3H]-galactose-labeled and unlabeled glycolipids of migrating and nonmigrating rabbit corneal epithelium in cell and/or in organ culture were chromatographed on DEAE Sephadex to isolate gangliosides. The gangliosides eluted from the ion-exchange column were further characterized by thin-layer chromatography (TLC), glycosidase digestions, and TLC-immunostain analysis. A [3H]-thymidine incorporation assay was used to determine the effect of exogenous gangliosides on corneal epithelium cell proliferation. RESULTS: Upon TLC of the acidic fraction eluted from the DEAE column, only two radiolabeled glycolipids (GL1 and GL2), migrating as a doublet, were detected. Regardless of whether the epithelia were prepared by cell culture or organ culture, both GL1 and GL2 were present in a significantly higher amount in migrating compared to nonmigrating epithelia. Further characterization of GL1 and GL2 identified them as gangliosides known as GM3. TLC-immunostain analysis, as well as orcinol staining of thin-layer chromatograms of gangliosides of unlabeled cells, revealed that GM3 also accumulates in a higher amount in migrating compared to nonmigrating epithelial cell cultures. Exogenous addition of GM3, but not various other gangliosides, inhibited corneal epithelial cell proliferation in a dose-dependent manner. CONCLUSIONS: GM3 is the major ganglioside present in corneal epithelium, and its levels are elevated during corneal epithelial cell migration. It is suggested that the ganglioside plays a role in events that modulate corneal epithelial cell proliferation.

Animals↗

PubMed1996

In vitro and in vivo biotransformation of 6,7-dimethyl-2,4-di-1-pyrrolidinyl-7H-pyrrolo[2,3-D]pyrimidine (U-89843) in the rat.

The biotransformation of 6,7-dimethyl-2,4-di-1-pyrrolidinyl-7H-pyrrolo[2,3-d]pyrimidine (U-89843) has been studied in rat both in vitro and in vivo. Major metabolites observed by HPLC analysis of rat plasma, liver cytosol, and microsomal incubations were characterized by UV, LC/MS, and comparison with synthetic standards. The structures of the metabolites were shown to be the C-6 hydroxymethyl (U-97924), C-6 formyl (U-97865), and C-6 carboxyl analogs of U-89843. In the male rat, formation of U-97924 is mediated by cytochrome P4502C11. Kinetic analysis of U-97924 formation indicated that it was a high-affinity/high-capacity process (KM = 4.2 +/- 0.5 microM; Vmax = 21.2 +/- 0.8 nmol/mg/min). Formation of U-97865 via enzymatic oxidation from the primary metabolite U-97924 was catalyzed by both the microsomal subcellular fraction in a NADPH-dependent process (presumably via cytochrome P450) and in cytosol by NAD(+)-dependent alcohol dehydrogenase. Upon incubation with cytosolic fractions, U-97865 was found to undergo NAD(+)-dependent oxidation, mediated by aldehyde dehydrogenase, to the corresponding carboxylic acid. Although significant levels of U-89843, U-97924, and U-97865 were observed in vivo in rat plasma, only a minor amount of the carboxylic acid together with larger amounts of unidentified polar metabolites were excreted in urine and feces.

Administration, Oral↗

PubMed1996

Effects of benzodiazepines on potassium-induced increase in free cytosolic calcium concentration in astrocytes: interactions with nifedipine and the peripheral-type benzodiazepine antagonist PK 11195.

The benzodiazepines diazepam and midazolam at submicromolar concentrations potentiated the increase in free cytosolic calcium concentration in astrocytes in primary cultures evoked by an elevation of the extracellular potassium concentration ([K+]0), but they had little stimulatory effect at normal [K+]0 and none at maximally elevated [K+]0. Nifedipine, an inhibitor of the L-channel, counteracted both the effect of the elevated [K+]0 as such and the benzodiazepine modulation. PK 11195, an antagonist of the peripheral-type benzodiazepine receptor, counteracted the effect of the benzodiazepines, but had no effect on the increase in free cytosolic calcium evoked by the elevated [K+]0.

Animals↗

PubMed1996

Surface and edge wear of Björk-Shiley Delrin heart valve discs.

BACKGROUND AND AIMS OF THE STUDY: Wear of Björk-Shiley Delrin (BSD) heart valve discs is known to have occurred in some patients, possibly contributing to increased regurgitation. This paper specifically addresses surface and edge wear that have been observed on some discs of explanted BSD valves after implant durations up to 22.4 years. METHODS: The wear patterns have been documented using either photographic or scanning electron microscopic methods for 42 out of 73 explanted BSD valve discs. The remainder of the 73 discs were not available for analysis. RESULTS: One form of surface wear found on 18 out of 42 of the Delrin discs was the concentric wear of mild abrasive origin along the surface near the disc edge due to contact with the inlet and outlet struts. In five instances, surface anomalies were observed, primarily in the areas of high velocity blood flow. This paper also describes two Delrin discs with non-concentric edge wear patterns: (a) one which appears to be due to fatigue micro-chipping and abrasive wear of the disc of a 20 year BSD explant, which had fibrous tissue ingrowth, causing abnormal rotation of the disc during valve closure, and (b) a second one which is thought to have been caused by a cutting action of the knife-like stub of one inlet strut leg which had separated. Cross-sectional analyses of two explanted BSD discs, with full indent grooves on the inflow side, indicated that the Delrin material was primarily compressed under these wear grooves, rather than removed by abrasion. Hardness profiles indicated that the Delrin 150 microns below the surface was harder and would tend to prevent further deformation. A simple model describing the compound impact (impact with sliding) phenomenon is introduced to explain abrasive wear found on some explanted BSD discs. CONCLUSION: Based on the studies here and reports in the literature, the BSD heart valve appears to present a design which provides many years of service and, when wear occurs, it occurs in a manner that provides easily recognized clinical symptoms, which allow time for diagnosis and treatment.

Aortic Valve↗

PubMed1996

Theory of wear as related to the Björk-Shiley Delrin disc heart valve.

BACKGROUND AND AIMS OF THE STUDY: Mechanical wear is an important consideration for the Björk-Shiley Delrin (BSD) heart valve, the disc of which is periodically impacted against the inlet strut by the momentum of the blood flow during closure. Impact wear theory was used in designing experiments as well as establishing theoretical evaluation and projections of wear life. MATERIALS AND METHODS: The experimental apparatus involved a pivotal hammer device where the striking face could be varied by the inclusion of distinct spherical shapes; the sharper the radius, the higher the contact stress induced. The striking speed could be varied between one and three m/s, and the repetition rate between 2-50 Hz. Blood was simulated with an aqueous 42% glycerol solution. The same wear mechanism was induced on Delrin occluder disc specimens as the one governing the wear observed in Delrin occluder discs of some of the explanted BSD heart valves; thus two wear parameters, c and g, were established for the prediction of wear in BSD implants. The experimental runs were repeated on as many as four simultaneous specimens, for up to 7.5 x 10(7) cycles. RESULTS: The wear history was found to comprise three distinct regions, corresponding to (a) initial plastic deformations; (b) zero wear; and (c) measurable wear. The zero wear region produced very little change in the contact dimensions, and represented a fatigue threshold to the progress of a wear scar. Procedures for analytical establishment of the zero wear limit are outlined in the paper. Measurable wear was governed by the process of increasing conformance between the repetitively contacting surfaces. The differential equation of wear was then used with the physical parameters c and g previously determined experimentally. CONCLUSION: The maximum depth of the wear scar after cycling the equivalent of 20 years was predicted to be 278 microns. This value appears to represent a safe dimension for BSD heart valves.

Biocompatible Materials↗

PubMed1996

[Cleft palate repair with a combined method of mucosal flap pushback of the hard palate].

From January of 1992, we applied a combined method to repair cleft palate in 20 patients and received satisfactory results. The method is characterized by pushing back the mucosal flap of the hard palate, a Z-plasty on the nasal mucosa, repositioning the levator muscle to lengthen the palate, circumferential pharyng oplasty using denervated extensor hallucis brevis muscle, without making relaxing incisions and elevating the mucoperiosteal flap, avoiding interference to the greater and lesser palatine vessels and nerves, without relaxing palatal aponeurosis. The advantages of this method are preserving the normal anatomy and function of the palate and nasopharyngeal cavity, improving the function of velopharyngeal closure and minimizing secondary deformities.

Adolescent↗

PubMed1996

[Establishment of an effective way for separating and culturing tumor infiltrating lymphocytes].

The key to preparing TILs for clinical application is to enhance its capacity of proliferation and cytotoxicity. For this purpose we have made a study of methodology and established an effective way consisting of 3 processes to separate and culture TILs. It included: (1) mechanical splitting; (2) digesting with 0.05% collagenase I and 0.003% DNAase I mixture in room temperature for 6 hrs and 18hrs in cool, and (3) centrifuging with 75% and 100% Ficoll non-continuous grade density. The separated TILs were suspended in conditional culture medium for proliferation. Most of them reached the amount of 10(9) at the end of culture, which was essential for clinical therapy. Their NK and LAK activities were 56.3 +/- 11.7% and 48.6% +/- 10.6% respectively, in which the CD6+ T cells played an important role. The results suggest this a perfect way for separating and culturing TILs.

Cell Culture Techniques↗

PubMed1996

[Specific binding of human bone morphogenetic protein (2A) with mouse osteoblastic cells].

Human bone morphogenetic protein 2A (hBMP2A) cDNA terminal S67 nucleotides were cloned and expressed in a phage display vector pCSM21. Human BMP2A C-terminal peptide displayed on the surface of the phage can bind specifically to the surface of mouse osteoblastic cell (MC3T3) membrane. ELISA assay showed a positive signal of the binding by using antibody against M13 phage gene 8 protein. After labeling with 3HTdR, the counts of the binding groups were 3 to 10 times higher than the control groups. It suggests that the surface of MC3T3 cells exist the receptor for hBMP2A.

Animals↗

PubMed1996

[Improved MTT colorimetric assay for NKC activity].

The established improved 3-(4,5-dimethyl thiazoly)2,5-diphenyl-tetrazolium bromide (MTT) colorimetric assay for measuring the amount and function of living cell by the authors has the characteristics of simplicity, dependability and good repeatability within 3-12 hours. We have used this improved MTT colorimetric assay in measuring natural kill cell (NKC) activity of human peripheral blood. The results show that when the activities of effector cell (EC) and target cell (TC) are > or = 95%, and the density of EC is > or = 3 x 10(2)/well and that of TC > or = 1.6 x 10(2)/well, the number of living cell is positively correlated with the OD570nm volume of purple formazan metabolite of MTT solution (re = 0.94, ri = 0.97, P < 0.001). When the ratio of EC/TC is 40:1, the NKC activity of peripheral blood of health adults is equal to that report by Zhang Chongjie et al. By this MTT colorimetric assay, the NKC activity of peripheral blood of 10 leukemic patients has been detected. The mean +/- s of NKC activity is 34.86 +/- 7.80%, which is postively correlated with the result (35.16 +/- 8.40%) of the inhibition of 3H-TdR incorporation assay performed at the same time (r = 0.876, P < 0.001). MTT colormetric assay for NKC activity avoids getting in touch with isotope. It is a convenient and valuable method.

Adult↗

PubMed1996

[Traffic multiple trauma patient with head injuries: a study of 146 cases].

146 cases of traffic multiple trauma associated with head injuries were studied. There was a significant difference in the ratio of associated injuries in various parts of the body. The three most encountered parts were chest, shoulder and leg. Death were mainly due to severe head injury, chest injury and shock. Atypical ushing syndrome was due to severe blood loss, even intracranial hypertension existed. The blood pressure decreased rapidly after operation. Since comatous patients were unable to provide chief complaint, misdiagnosis occurred during emergency stage.

Accidents, Traffic↗

PubMed1996

[Monoclonal antibodies against transitional cell carcinoma assay tumor associated antigens in different grades bladder cancer patients].

Monoclonal antibodies (McAb) 19A211, M344 against transitional cell carcinoma (TCC) was used to assay the tumor associated antigens on paraffin-embedded tissue sections of 51 different grades bladder cancer patients with immunohistochemical stain method. The positive rates of 19A211, M344 antigens expression were 82.4% and 88.2% in 17 grade I patients 77.7% and 83.3% in 18 grade II patients, 37.5% and 37.5% in 16 grade III patients. 19A211 and M344 antigens expression in statistical analysis was as follows: 19A211, grade I/grade III, P < 0.01, grade II/grade II, P < 0.05, M344, grade I/grade III, P < 0.01, grade II/grade II, P < 0.05, showed significant differences. Combined use of McAb 19A211 and M344 assay bladder TCC tumor associated antigens, showed that the positive rates of antigen expression in grade I was 100% (17/17), in grade II was 88.8% (16/18), in grade III was 68.8% (11/16). The results indicate that McAb 19A211, M344 were fit to diagnose grade I, II bladder TCC. Using both of two McAb can increase the positive rate in finding superficial bladder TTC.

Antibodies, Monoclonal↗

PubMed1996

[Analysis of surface antigen molecule expression on serovar stains of Neisseria gonorrhoeae by flow cytometry].

In the present experiment, flow cytometry was employed for analysing expression characteristics of the antigen molecules distingushed by 10 monoclonal antibodies against Neisseria gonorrhoeae lipooligosaccharides. Stability of antigen expression and amount of epitope on the surface of N. gonorrhoeae were quantitative determined. Reactivity of the monoclonal antibodies with serovar strains of N. gonorrhoeae were evaluated.

Antibodies, Monoclonal↗

PubMed1995

Iron(II) oxidation by H chain ferritin: evidence from site-directed mutagenesis that a transient blue species is formed at the dinuclear iron center.

The iron storage molecule, ferritin, consists of an iron core surrounded by a shell of 24 protein subunits, which, in mammals, are of two types, H and L. Prior to storage of iron as a hydrous ferric oxide within the protein shell, Fe(II) is catalytically oxidized at dinuclear centers within H chains. When 48 Fe(II) atoms/molecule were added to 1 microM recombinant human H chain apoferritin (apo-HuHF), in 0.1 M Mes (pH 6.5), oxidation was 80% complete within about 0.2 s while 99% of the Fe(II) was oxidized within 10 s. A broad visible absorption band (400-800 nm, with a maximum at 650 nm) appeared during the fast phase of Fe(II) oxidation. It reached a plateau at 0.2-0.3 s and then declined while Fe(II) oxidation proceeded to completion and absorbance in the near-UV (300-400 nm) increased. The transient visible species was not observed when Tyr-34 was replaced by phenylalanine or when other conserved amino acids at the ferroxidase centers were substituted by residues which are unable to bind iron or which alter the charge balance. When a second increment of 48 iron atoms was added, 10 min after the first, the visible absorbance was absent and the rate of oxidation slower. Restoration of full oxidative activity took over 24 h. The data indicate that the fast oxidation of Fe(II) by apo-HuHF and the transient visible absorbance associated with it are due to Fe(II) oxidation at the ferroxidase centers.

Binding Sites↗