Search PubMed⌕ Search

Biomedical subjects

Z Yu

Publications and source records attributed to Z Yu.

At least 289 records · Page 16Linked to original sources
PubMed1995

An evaluation of numerical integration algorithms for the estimation of the area under the curve (AUC) in pharmacokinetic studies.

Six numerical integration algorithms based on linear and log trapezoidal methods as well as four cubic-spline methods were proposed for estimation of area under the curve (AUC). These six different algorithms were implemented using IMSL/IDL command language and evaluated using data simulated under five different dosing conditions and two different sampling conditions. Comparisons between AUC estimations using these six different algorithms and the theoretical results were made in terms of both overall AUC values and the superimposability of the concentration-time profiles. In well designed studies with ample data points, the algorithm based on IMSL/IDL function CSSHAPE with concavity preservation gave the best performance. In contrast, when the frequency of blood collection was limited, the algorithm based on the log trapezoidal rule proved to be stable with reasonable accuracy, and is recommended as the practical method for numerical interpolation and integration in pharmacokinetic studies. Algorithms based on the combination of the log trapezoidal rule and cubic-spline methods using IMSL/IDL function CSSHAPE can be developed to enhance overall performance.

Algorithms↗
PubMed1995

Antiviral action of interferon-beta on Newcastle disease virus: selectivity to the hemagglutinin-neuraminidase gene expression.

Interferon-beta (IFN-beta) strongly inhibited the expression of the hemagglutinin-neuraminidase (HN) gene of Newcastle disease virus (NDV), a paramyxovirus, in HeLa cells under the conditions where it did not affect the expression of the four upstream genes encoding the nucleocapsid protein, phosphoprotein, membrane protein and fusion protein. Even the downstream gene, encoding the large protein as well as the genome replication, appeared to be less susceptible to IFN-beta than the HN gene. This selective action of IFN-beta did not appear to be attributable to its well characterized antiviral mechanisms such as acceleration of RNA decay and translation inhibition. No similar down-regulation of a particular gene expression was found with another paramyxovirus, Sendai virus, or with a rhabdovirus, vesicular stomatitis virus, or seems to have been reported previously with any negative-strand RNA viruses. This new effect of IFN-beta thus suggests gene expression mechanism unique to NDV and may further lead to the discovery of a novel biochemical effect of IFN-beta.

Animals↗
PubMed1995

Adhesion of denture tooth porcelain to heat-polymerized denture resin.

Use of porcelain denture teeth may be desirable in many clinical situations, including implant-supported prostheses. However, lack of space because of frameworks often precludes the use of conventional retention by diatorics and pins. Adhesion of porcelain denture teeth to denture resin could also stiffen and possibly strengthen dentures and decrease stain ingress between porcelain teeth and resin denture bases. Unlike previous studies that investigated the bond between conventional feldspathic metal-ceramic porcelain and bis-GMA based composite resin, this study investigated adhesion of denture tooth porcelain to polymethyl methacrylate (PMMA). High-energy air abrasion, hydrofluoric acid etching, and the use of a general purpose bonding agent resulted in an improved bond strength of heat-cured denture PMMA bonded to denture tooth porcelain. Silane coating did not improve bond strengths, and conventional air abrasion was no more effective than polishing with 600-grit silicon carbide. Storage in water and artificial aging substantially decreased bond strengths. The strongest bond strengths were achieved by a high-energy-abrasion + etching + multi-purpose bonding-agent treatment, but a simpler etching + multiple-purpose bonding-agent treatment also produced reliable results. A laboratory technique was suggested. The role of surface treatment in the mechanism of adhesion was examined with scanning electron microscopy. High-energy abrasion produced a slightly more detailed initial topography than conventional air abrasion, but after etching, the high-energy topography became much more detailed. Surface topography alone did not account for all differences found.

Analysis of Variance↗
PubMed1995

In vivo marginal adaptation of cast crowns luted with different cements.

Large marginal crown discrepancies are deleterious. Although previous studies have examined casting seating in vitro, few have evaluated the effects of different luting cements on in vivo seating. Hence this in vivo study compared marginal discrepancies created by different cements on cast crowns. Tooth preparations were completed according to acceptable procedures on previously intact human molars that were severely periodontally compromised and scheduled for extraction. Castings were made by conventional techniques. The castings were randomly assigned to the following luting agents: zinc phosphate cement, resin-modified glass-ionomer cement, and the same resin-modified glass-ionomer cement with a dentinal bonding agent. After 6 months the teeth were carefully extracted, embedded, and sectioned, and vertical and horizontal discrepancies were measured. Analysis of variance revealed that all cements resulted in similar discrepancies. Vertical discrepancies were considerably greater than horizontal discrepancies, and the distributions of marginal discrepancies were skewed towards upper ranges.

Analysis of Variance↗
PubMed1995

Induction of protective immunity against herpes simplex virus with DNA encoding the immediate early protein ICP 27.

Using a mouse zosteriform model that mimics human herpes simplex virus (HSV) infection in several aspects, the effectiveness of plasmid DNA encoding the immediate early protein ICP 27 was evaluated as a vaccine. Animals were immunized intramuscularly twice with DNA, then either challenged with virus or killed, and the nature of the immune response induced was measured. After intramuscular injection with plasmid DNA encoding ICP 27 (pc-ICP 27), solid protection was evident in 70-80% of mice and the lesions were delayed in the remaining animals. Immune splenocytes obtained from pc-ICP 27 immune mice showed HSV-specific lymphoproliferation, MHC-class I restricted cytotoxic T-lymphocyte (CTL) activity, and type 1 cytokine production. These animals also exhibited delayed-type hypersensitivity (DTH) reactions. Adoptive transfer studies conducted on syngeneic nude mice revealed that those recipients of immune CD4+ T cells, but not CD8+ T cells, were protected from subsequent HSV-1 (strain 17) challenge. Thus pc-ICP 27 DNA immunization protected the mice principally by CD4+ T cells and it is likely that these cells were Th-1 type because only type 1 cytokines were detectable after in vitro antigen stimulation. Our results indicate the potential value of DNA encoding nonstructural viral proteins as vaccines against HSV.

Animals↗
PubMed1995

Influence of hemodialysis membranes on gene expression and plasma levels of interleukin-1 beta.

Plasma levels of interleukin-1 beta (IL-1 beta) were measured in 10 normal subjects, in 11 nondialyzed end-stage renal failure (ESRD) patients, and in 22 hemodialysis (HD) patients. Of the HD patients, 7 were dialyzed with Cuprophan (CU), 7 with polymethylmethacrylate (PMMA), and 8 with polysulphone (PS) dialyzers. In normal controls, nondialyzed ESRD patients, and HD equipped with CU, PAMM, and PS dialyzers, plasma levels of IL-1 beta were 10.73 +/- 5.24 pg/ml, 9.97 +/- 3.61 pg/ml, 13.17 +/- 4.04 pg/ml, 15.16 +/- 6.16 pg/ml, and 13.96 +/- 5.47 pg/ml, respectively. There were no statistically significant differences among the groups (p > or = 0.05). In contrast, the gene expression of IL-1 beta for peripheral blood mononuclear cells (PBMC) by in situ hybridization showed differences among the groups. The gene for IL-1 beta for PBMC appears in HD equipped with different membranes, but not in cases of nondialyzed uremic patients and normal subjects. With computer imaging analysis, we carried out quantitative analysis of cells in in situ hybridization with an area of positive spots to an area of total cells. In HD with CU, PMMA, and PS, the results were 10.64 +/- 1.07, 3.34 +/- 0.74, and 3.27 +/- 0.64%, respectively. The levels of IL-1 beta gene expression in CU were higher than that in PMMA or PS. There were statistically significant differences (p < or = 0.001) between CU and PMMA or PS and no significant difference between the PMMA and PS (p > or = 0.05). We suggest measuring the gene expression of cytokines for PBMC and which may be better than measuring cytokine levels only for investigating the blood compatibility of dialyzers, which may help in understanding chronic complications of the dialysis procedure.

Adult↗
PubMed1995

Effect of dynamic loading methods on cement film thickness in vitro.

PURPOSE: Reduced cement flm thicknesses can improve crown seating and decrease marginal discrepancies. Improved marginal adaptation has the potential to reduce plaque accumulation, periodontal disease, and cement dissolution. Studies have indicated that dynamic seating methods can reduce seating discrepancies associated with zinc phosphate and resin cements. However, other types of cements and other dynamic techniques have not yet been studied or compared, nor has the mechanism for improved seating been fully explained. Therefore, the purpose of this study was to investigate the effect of a variety of loading methods on the film thicknesses of current types of crown and fixed partial denture cements compressed between glass plates. MATERIALS AND METHODS: This study investigated the effect of three dynamic loading methods on film thickness of six representative fixed prosthodontic cements. These included zinc phosphate, resin-modified glass ionomer, encapsulated glass ionomer, adhesive composite resin, composite resin, and polycarboxylate. The method was derived from American Dental Association specifications for cement film thickness. In control groups, the cements were placed between two glass glass plates and statically loaded with a 15-kg weight. The test groups were initially similarly loaded, and then for 30 seconds further subjected to simulated repeated patient opening and closing, vibrations from an electromallet, or an ultrasonic device. RESULTS: Mean film thicknesses ranged from 7.4 micrometers for polycarboxylate / ultrasound up to 40.3 micrometers for composite resin / static. Two-way analysis of variance revealed that the effects of material type and cementation method and their interaction all significantly affected film thickness (P < .0001). Multiple range analysis showed that dynamic methods were generally superior to static loading and that the ultrasonic method was the best overall. CONCLUSIONS: The different dynamic loading methods all significantly decreased cement film thicknesses between glass plates. The ultrasonic method was the most effective. The type of cement used also influenced film thickness. Composite resins were more affected than other materials.

Analysis of Variance↗
PubMed1995

[Treatment and prognosis of stage II testicular seminoma].

Sixty-five patients with stage II testicular seminoma treated from 1960 through 1990 were reviewed. According to Royal Marsden Hospital staging, there were 11 stage IIA, 13 stage IIB, and 41 stage IIC. Thirty Patients were treated with combination of radiotherapy and chemotherapy, 11 chemotherapy alone, 24 rediotherapy alone. The overall 5-year survival rate was 75.6%, with 100% for stage IIA, 92.3% for stage IIB and 62.9% for stage IIC. The differences were statistically significant. In stage IIC patients, there was no significant difference between those tumors > 10cm and < 10cm in diameter. Of the 41 IIC cases, 4 were treated with chemotherapy, 15 were treated with whole abdominal rediation, 22 with paraaortic and ipsilateral pelvic radiation. The 5-year survival rate was 91.7% and 51.2%, respectively. These differences was statistically significant. We recommand that stage IIC disease should be treated primarily with whole abdominal radiation. Regardless of the stage of the disease, prophylactic mediastinal irradiation did not influence the survival nor the relapse rate and may therefore be omitted.

Adult↗
PubMed1995

[Relationship between elevated plasma endothelin-1 level and renal function in patients with diabetic nephropathy].

Plasma endothelin-1 (ET-1) level was measured with radioimmunoassay in 33 normal subjects and 92 patients with different stages of diabetic nephropathy, consisting of 35 cases of diabetes mellitus with normal urinary albumin excretion (DM), 22 cases of incipient diabetic nephropathy (IDN), 22 cases of overt diabetic nephropathy (ODN), 8 cases with azotemia (DNa) and 5 cases with uremia (DNu). The results showed that plasma ET-1 levels in DNa and DNu groups (30.24 +/- 1.93 ng/L and 36.38 +/- 3.62 ng/L respectively) were significantly higher than those in other groups (P < 0.05); ET-1 level in ODN group (20.50 +/- 0.93 ng/L) was significantly higher than those in DM and IDN groups (P < 0.001); ET-1 level in IDN group was also significantly higher than that in DM group (17.79 +/- 0.74 vs. 15.06 +/- 0.63 ng/L, P < 0.01); All the above values were significantly higher than that in normal subjects (7.08 +/- 0.22 ng/L) (P < 0.001). There was significant positive correlation between ET-1 level and HbA1c, systolic pressure, diastolic pressure, blood urea nitrogen, serum creatine, uAER and a significant negative correlation between ET-1 level and glomerular filtration rate. It is shown that progressive elevation of plasma ET-1 level is closely related with different stages of renal function impairment, suggesting strongly the role of ET-1 in the development and progression of diabetic nephropathy.

Diabetic Nephropathies↗
PubMed1995

[Relative changes between calcium content and number of atrial specific granules induced by water and salt loading].

Rats prepared by either deprivation of water intake for 5 d or drinking 2% NaCl solution for 4 d were sacrificed for dissection of auricle, and making ultrathin sections. The numerical density (Nv) of atrial specific granules (ASG) were counted by using electron microscopic morphometry, and Ca concentration in ASG and in terminal cisterna of sarcoplasmic reticulum (TSR) was determined by using electron microscopic X-ray microanalysis. In the drinking 2% NaCl solution group, the Nv of ASG decreased from 6.02 +/- 2.30 to 2.96 +/- 1.62/microns 3 (P < 0.01) and all companied by a decrease of Ca concentration from 64 +/- 16 to 38 +/- 21 mmol/kg (P < 0.01), while the secretion of atrial natriuretic peptide (ANP) showed some increase. Water deprivation induced all the contrary results. However, the Ca concentration in TSR was not affected by water-salt loading. It is suggested that when the atrial cardiocytes were stimulated by salt loading, Ca in ASG was released into cytosol and thus promoted fusion of ASG membrane with sarcolemma which resulted in release of ANP. Therefore, it is considered that ASG as an intracellular Ca store participates in the stimulus-secretion coupling of ANP through the release of Ca ions.

Animals↗
PubMed1995

[Removal of petrous bone cholesteatoma and obliteration with adipose tissue].

Three cases of petrous bone cholesteatoma removed through translabyrinthine-cochlear approach with the surgical defect obliterated by using adipose tissue covered with superficial temporalis fasia flap were reported. The average follow-up period was two years without any sign of recurrence. The etiology, diagnosis and methods of surgical treatment were discussed.

Adipose Tissue↗
PubMed1995

[Clinical study of laryngeal and laryngopharyngeal cancers with ultra-weak chemiluminescence analysis].

Ultra-weak luminescence of serum in 30 normal persons and 40 patients (12 laryngeal cancers, 18 laryngopharyngeal cancers, and 10 benign tumour patients) was studied using SHG-1 type photobiological photometer. The results showed that the intensity in malignant tumour group was higher than that of the benign group, which in turn was higher than that of the normal group with significant statistical differences (P < 0.05). The study implied that ultra-weak luminescence test is of value in diagnosis of laryngeal and laryngopharyngeal cancers.

Adult↗