Biomedical subjects

Z Wang

Publications and source records attributed to Z Wang.

At least 343 records · Page 19Linked to original sources

PubMed2001

Tissue-engineered bone repair of sheep cranial defects with autologous bone marrow stromal cells.

Cranial bone defect remains a major challenge to craniofacial surgeons because of limited availability of autologous bone graft to repair the defects and the donor site defects secondary to tissue harvesting. In contrast, tissue-engineering technique can generate a large bone tissue using small amount of autologous cells and therefore avoid these problems. Bone Marrow Stromal Cells (MSCs) have the potential of multi-lineage (including osteogenic) differentiation. The objective of this study was to investigate the potential of using autologous MSCs to repair cranial bone defects by a tissue-engineering approach. Autologous MSCs were isolated from eight adult sheep respectively and were in vitro expanded and induced to become osteogenic cells. Bilateral full-thickness defects (20 mm in diameter) of parietal bones were created in animals and the bone defects were either repaired with the bone implants constituted with MSCs and calcium alginate at the experimental side (n = 8) or treated with calcium alginate only without MSCs (n = 4) or left unrepaired (n = 4) at the control side. New bone tissues were observed either grossly or histologically at the defects of experimental group as early as 6 weeks post-repairing, but not in control groups. The engineered bone tissue became more mature at 18 weeks post-repairing. Three-dimensional computerized tomography (CT) scan revealed an almost complete repair of the defect of experimental group at 18 weeks. This study may provide insight for future clinical repair of cranial defect.

Alginates↗

PubMed2001

Prolongation of corneal allograft survival using cyclosporine in a polylactide-co-glycolide polymer.

PURPOSE: To test for prolongation of corneal transplant survival with cyclosporine in a polymer placed in the anterior chamber of corneal allograft recipients. METHODS: Wistar inbred rats with vascularized corneas were recipients of corneal allografts from Sprague-Dawley donor rats. Grafted rats were randomized into six groups: untreated control animals, cyclosporine-polymer anterior chamber recipients, cyclosporine-polymer subconjunctival recipients, cyclosporine-olive oil drop recipients, polymer-only anterior chamber recipients, and autografted Wistar rats. Grafts were examined by slit lamp every 3 days and the clinical condition scored. The cyclosporine concentration in the aqueous humor was assayed at 1, 2, and 4 weeks. At 2 and 4 weeks after transplantation, the eyes were collected for histopathologic evaluation of the grafts. RESULTS: The median survival time of untreated corneal allografts was 8.2 +/- 1.48 days for grafts treated with topical cyclosporine, 8.5 +/- 1.50 days for polymer-only anterior chamber implants, 10.6 +/- 1.90 days for 1% cyclosporine drops, 11.4 +/- 2.50 days for grafts given subconjunctival cyclosporine-polymer, 17 +/- 3.05 days for grafts given cyclosporine-polymer implants in the anterior chamber, and more than 3 months in autografted rats. There was a statistically significant difference ( p < 0.05) between the survival time of the allografts in the animals treated with the cyclosporine-polymer in the anterior chamber compared with the other groups of graft recipients. Significantly higher concentrations of cyclosporine were found in the eyes given an anterior chamber implant of cyclosporine-polymer than in the other treatment groups or the untreated rats. The cyclosporine-polymer implants placed in the anterior chamber induced a transient inflammatory response in transplanted eyes. CONCLUSIONS: Cyclosporine-polymer placed in the anterior chamber significantly prolongs corneal allograft survival in a high-risk corneal graft rejection. This intraocular delivery system may be a valuable adjunct for the suppression of immune graft rejection in high-risk recipients of corneal transplants.

Animals↗

PubMed2001

Reduction of cardiac norepinephrine improves postischemic heart function in stroke-prone spontaneously hypertensive rats.

Although mammalian ventricle is richly supplied with adrenergic nerves, endogenous norepinephrine is not essential to the intrinsic contractility of the normal heart. However, it is not clear whether acute changes in cardiac norepinephrine could alter heart function in genetically hypertensive rats. The purpose of this study was to examine the effect of cardiac norepinephrine reduction on basal and postischemic heart function in stroke-prone spontaneously hypertensive rats (SHRSPs) using an isolated working heart preparation. Hypertrophied hearts of SHRSPs showed higher cardiac norepinephrine content and impaired heart function at 4 months of age as compared with normal Wistar-Kyoto rats. Poor postischemic recovery of heart function observed in SHRSPs was accompanied by large amounts of coronary norepinephrine overflow. Cardiac norepinephrine reduction or depletion did not affect basal heart function in SHRSPs. Considerable reduction in cardiac norepinephrine with acute reserpine injection (5 mg/kg) in SHRSPs significantly improved postischemic recovery of cardiac output, coronary flow, and rate-pressure product. However, complete norepinephrine depletion with reserpine (10 mg/kg) was detrimental to myocardial automaticity and limited the postischemic recovery of systolic function in the hypertrophied hearts. These results suggest that acute reduction in cardiac norepinephrine may be of potential therapeutic importance to postischemic dysfunction in the hypertrophied hearts.

Animals↗

PubMed2001

Ultrastructural and functional characteristics of blast injury-induced neurotrauma.

OBJECTIVE: The present study investigates whether whole-body or local (chest) exposure to blast overpressure can induce ultrastructural, biochemical, and cognitive impairments in the brain. METHODS: Male Wistar rats were trained for an active avoidance task for 6 days. On day 6, rats that had acquired the avoidance response were subjected to whole-body blast injury (WBBI), generated by large-scale shock tube (n = 40); or local (chest) blast injury (LBI), induced by blast overpressure focused on the right middle thoracic region and generated by small-scale shock tube (n = 40) while the heads of animals were protected. At the completion of cognitive testing, rats were killed at 3 hours, 24 hours, and 5 days after injury. Ultrastructural changes in the hippocampus were analyzed electron microscopically. Parameters of oxidative stress (malondialdehyde and superoxide anion generation) and antioxidant enzyme defense (superoxide dismutase and glutathione peroxidase activity) were measured in the hippocampus to assess biochemical changes in the brain after blast. RESULTS: Ultrastructural findings in animals subjected to WBBI or LBI demonstrated swellings of neurons, glial reaction, and myelin debris in the hippocampus. All rats revealed significant deficits in performance of the active avoidance task 3 hours after injury, but deficits persisted up to day 5 after injury only in rats subjected to WBBI. Oxidative stress development and altered antioxidant enzyme defense was observed in animals in both groups. Cognitive impairment and biochemical changes in the hippocampus were significantly correlated with blast injury severity in both WBBI and LBI groups. CONCLUSION: These results confirm that exposure to blast overpressure induces ultrastructural and biochemical impairments in the brain hippocampus, with associated development of cognitive deficits.

Animals↗

PubMed2001

Pulsed-dye laser and retinoic acid delay progression of oral squamous cell carcinoma: a murine model.

OBJECTIVES/HYPOTHESIS: This study examined the role of the pulsed-dye laser (PDL) at 585 nm coupled with retinoic acid at therapeutic (5.0 mg/kg) and nontherapeutic (0.5 mg/kg) doses to delay the progression of cancer with a two-hit approach. The existing vasculature is selectively targeted by the laser, whereas retinoic acid inhibits future angiogenesis. STUDY DESIGN: Randomized, prospective study in a murine model. METHODS: Twenty-five athymic nude mice were inoculated with oral squamous cell cancers on six flank sites and randomly divided into five groups: 1) control subjects, 2) treatment with 0.5 mg/kg retinoic acid (RA 0.5), 3) treatment with 5.0 mg/kg retinoic acid (RA 5.0), 4) treatment with RA 0.5 + PDL, and 5) treatment with RA 5.0 + PDL. The PDL groups received irradiation after inoculation. The retinoic acid was administered daily. The tumors were counted and measured for 14 days. RESULTS: The control group developed visible tumors in 50% of the inoculation sites at 3 days compared with 3 days (RA 0.5) and 4 days (RA 5.0) for the retinoic acid groups and 9 days (RA 0.5 + PDL) and 10 days (RA 5.0 + PDL) for the laser treatment groups. There was no tumor growth until day 7 in the RA 5.0 + PDL group. The tumor volume was statistically different between the treatment groups. CONCLUSION: This study demonstrated the superiority of a single treatment with the PDL coupled with retinoic acid to delay the progression of cancer when compared with treatment with retinoic acid alone, thus introducing a novel strategy in cancer control.

Animals↗

PubMed2001

Ultraviolet B-induced melanoma in Monodelphis domestica occurs in the absence of alterations in the structure or expression of the p53 gene.

Monodelphis domestica, a South American opossum, has been established as a mammalian model for sporadic ultraviolet radiation (UVR)-induced melanoma. Using this model system, we investigated the role of changes in the p53 gene in the development of cutaneous melanocyte-derived lesions. Cutaneous melanocytic hyperplasias, benign melanomas and metastatic primary melanomas, plus affected lymph nodes and visceral organs, were screened for mutations in the Monodelphis p53 gene by single-strand conformation polymorphism analysis and direct sequencing. With the exception of a silent point mutation found in a single benign melanocytic hyperplasia sample, no p53 mutations were detected. Furthermore, a relative quantitative reverse transcriptase-polymerase chain reaction approach was used to analyse p53 gene expression at different stages of primary melanoma progression and revealed no substantial changes in p53 mRNA levels. These results suggest that, as in humans, UVR-induced melanoma in the Monodelphis model is initiated and progresses on the basis of predominantly p53-independent molecular pathways.

Animals↗

PubMed2001

Intra-hepatic expression of scavenger receptor and CD14 and their relationship with local inflammatory responses in endotoxemia in mice.

Our objective was to investigate the expression of scavenger receptor (SR) and CD14 in the liver and their relationship with local anti-inflammatory and proinflammatory responses in endotoxemia in order to uncover the mechanism for the liver to turn into effector organ from defense one at the level of cell receptors in sepsis. Mouse models of endotoxemia of different severity were reproduced by injection of different doses of lipopolysaccharide (LPS) via tail vein. Expression of SR and CD14 in the liver was assayed by immunohistochemistry and was then analyzed with an image analysis system. The levels of TNFalpha, IL-6, IL-4, and IL-10 in liver tissue were determined with ELISA. Expression of SR in the liver in the high-dose group was markedly decreased 1 h after injection of LPS, and also in low- and medium-dose groups at 3 h. The expression of SR in the liver in the three groups was shown to be progressively decreased with the time prolonged. There was significant difference in average optical density (OD) values of SR among the three groups. The expression of CD14 in the liver in the three groups was shown to be significantly increased 1 h after injection of LPS, and much more with the time prolonged. But there was no significant difference in OD values of CD14 among the three groups. The contents of intrahepatic proinflammatory mediators TNFalpha and IL-6 and anti-inflammatory mediators IL-4 and IL-10 were successively significantly increased after injection of LPS. The release of anti-inflammatory mediators was shown to be later than that of proinflammatory mediators. Correlation analysis indicated that there was negative correlation between expression of SR and CD14, and that changes of TNFalpha, IL-6, IL-4, and IL-10 levels in liver tissues were correlated significantly positively with OD values of CD14 and negatively with OD values of SR. Expression of SR in the liver was shown to be progressively decreased, and that of CD14 increased in endotoxemia, which was closely related to the uncontrolled inflammatory response in liver. This might be an important mechanism for the liver to turn into effector organ from defense one in sepsis.

Animals↗

PubMed2001

Pulmonary function in long-term asbestos workers in China.

The relationship of pulmonary function to exposure to asbestos and radiographic abnormalities has been controversial, especially when smoking is present as a confounder. The aim of the study was to provide further understanding on the radiographic-physiologic associations in nonsmoking and smoking asbestos workers. Radiographic asbestosis, pleural lesion, and pulmonary function were studied in 269 Chinese asbestos workers, with average exposure years of 23 for male workers and 18 for female workers. Their functional data were compared with those of 274 controls without exposure to dust. Although most of the male workers were smokers, none of the female workers smoked. In comparison with controls, asbestos workers had significantly lower lung volume and diffusing capacity, irrespective of gender. Female workers and smoking male workers had lower measurements of forced expiratory volume in 1 second and instantaneous forced expiratory flow at 50% and 25% of forced vital capacity. After adjustment for relevant covariates, asbestos exposure, asbestosis, and pleural abnormalities were associated with decreased parameters of pulmonary function, including lung volume, diffusing capacity, and airway flow. These data indicate that asbestos-related functional defects manifested by lung restriction and mild airway obstruction correlate with exposure to asbestos and with parenchymal and pleural abnormalities, independent of smoking.

Adult↗

PubMed2001

Urinary calcium as a biomarker of renal dysfunction in a general population exposed to cadmium.

Urinary beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase have been recommended as sensitive indicators of renal dysfunction induced by cadmium. However, an increase in urinary calcium in early renal damage induced by cadmium has been reported both in humans and in animal experiments. To investigate the feasibility of using urinary calcium as a biomarker of renal dysfunction induced by cadmium, two areas were selected in this study, namely, a polluted area with a 3.71 mg/kg cadmium concentration in rice and a control area with a 0.07 mg/kg cadmium concentration. The total number of participants was 499, made up of 252 in the control group and 247 from the cadmium-polluted area. Urinary cadmium, urinary calcium, and zinc concentrations were measured by atomic absorption spectrometry, and beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase in urine were analyzed. The levels of urinary cadmium and urinary calcium in persons from the exposed area were significantly higher (P < 0.05) than those in the control area for both men and women, but there was no significant difference regarding urinary zinc between the two areas. A significant dose-response relationship between the prevalence of hypercalciuria and the excretion of urinary cadmium was observed, and a significantly increased prevalence of calciuria was found when excretion of urinary cadmium exceeded 2 micrograms/g creatinine. The findings were similar to those for excess urinary secretion of beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase. Because cadmium can affect Ca2+ uptake by tubular cells, with decreased renal Ca2+ reabsorption, calciuria may reflect tubular cell damage caused by cadmium. It was concluded that cadmium exposure can result in increased excretion of urinary calcium in a general population and that there is a significant dose-response relationship. Urinary calcium can therefore be used as a biomarker of renal dysfunction induced by cadmium.

Acetylglucosaminidase↗

PubMed2001

Natrialba hulunbeirensis sp. nov. and Natrialba chahannaoensis sp. nov., novel haloalkaliphilic archaea from soda lakes in Inner Mongolia Autonomous Region, China.

Two haloalkaliphilic archaeal strains, X21T and C112T, were isolated from soda lakes in Inner Mongolia Autonomous Region, China. Their morphology, physiology, biochemical features, polar lipid composition and 16S rRNA genes were characterized in order to elucidate their taxonomy. According to these data, strains X21T and C112T belong to the genus Natrialba, although there are clear differences with respect to their physiology and polar lipid composition between the two strains and the type species, Natrialba asiatica. On the basis of low DNA-DNA hybridizations, these two strains should be considered as new species of genus Natrialba. The names Natrialba hulunbeirensis sp. nov. (type strain X21T = AS 1.1986T = JCM 10989T) and Natrialba chahannaoensis sp. nov. (type strain C112T = AS 1.1977T = JCM 10990T) are proposed.

Base Composition↗

PubMed2001

An efficient method for high-fidelity BAC/PAC retrofitting with a selectable marker for mammalian cell transfection.

Large-scale genomic sequencing projects have provided DNA sequence information for many genes, but the biological functions for most of them will only be known through functional studies. Bacterial artificial chromosomes (BACs) and P1-derived artificial chromosomes (PACs) are large genomic clones stably maintained in bacteria and are very important in functional studies through transfection because of their large size and stability. Because most BAC or PAC vectors do not have a mammalian selection marker, transfecting mammalian cells with genes cloned in BACs or PACs requires the insertion into the BAC/PAC of a mammalian selectable marker. However, currently available procedures are not satisfactory in efficiency and fidelity. We describe a very simple and efficient procedure that allows one to retrofit dozens of BACs in a day with no detectable deletions or unwanted recombination. We use a BAC/PAC retrofitting vector that, on transformation into competent BAC or PAC strains, will catalyze the specific insertion of itself into BAC/PAC vectors through in vivo cre/loxP site-specific recombination.

Animals↗

PubMed2001

Hormonal changes in the grains of rice subjected to water stress during grain filling.

Lodging-resistant rice (Oryza sativa) cultivars usually show slow grain filling when nitrogen is applied in large amounts. This study investigated the possibility that a hormonal change may mediate the effect of water deficit that enhances whole plant senescence and speeds up grain filling. Two rice cultivars showing high lodging resistance and slow grain filling were field grown and applied with either normal or high amount nitrogen (HN) at heading. Well-watered and water-stressed (WS) treatments were imposed 9 days post anthesis to maturity. Results showed that WS increased partitioning of fixed (14)CO(2) into grains, accelerated the grain filling rate but shortened the grain filling period, whereas the HN did the opposite way. Cytokinin (zeatin + zeatin riboside) and indole-3-acetic acid contents in the grains transiently increased at early filling stage and WS treatments hastened their declines at the late grain filling stage. Gibberellins (GAs; GA(1) + GA(4)) in the grains were also high at early grain filling but HN enhanced, whereas WS substantially reduced, its accumulation. Opposite to GAs, abscisic acid (ABA) in the grains was low at early grain filling but WS remarkably enhanced its accumulation. The peak values of ABA were significantly correlated with the maximum grain filling rates (r = 0.92**, P < 0.01) and the partitioning of fixed (14)C into grains (r = 0.95**, P < 0.01). Exogenously applied ABA on pot-grown HN rice showed similar results as those by WS. Results suggest that an altered hormonal balance in rice grains by water stress during grain filling, especially a decrease in GAs and an increase in ABA, enhances the remobilization of prestored carbon to the grains and accelerates the grain filling rate.

Abscisic Acid↗

PubMed2001

Blind separation of slow waves and spikes from gastrointestinal myoelectrical recordings.

Myoelectrical recordings of the gut contains slow waves (slow rhythmicity) and spikes (fast rhythmicity). While the slow wave determines the frequency and propagation of gastrointestinal contractions, spike activities are directly associated with the contractions. Traditionally, spikes are extracted from the myoelectrical recording using high-pass/bandpass filters. Due to sharp rising edge (high-frequency component) of the slow wave, the conventional method is not accurate in the separation of the slow wave and spikes, although it has been used for years. In this paper, a novel and fast blind source separation algorithm was developed. Experimental results showed that the proposed method was able to accurately extract spike activities from the myoelectrical recordings obtained in dogs and that its performance was not affected by the high-frequency components of the slow wave.

Action Potentials↗

PubMed2001

Deflection characteristics of a trapezoidal multilayer in-plane bending piezoelectric actuator.

A novel multilayer split-morph actuator has been designed and fabricated using the thick film screen-printing technology. Deflection characteristics of the split-morph actuator have been investigated by theoretical analysis and experimental measurement. The results indicate that the tip displacement is inversely proportional to the thickness of each piezoelectric layer, but is independent of the number of layers and the total thickness of the actuator. The displacement/voltage sensitivity of the trapezoidal actuator is larger than that of the rectangular design, assuming both have the same width of clamped end and the same thickness of the piezoelectric layers. The maximum displacement/voltage sensitivity of 0.157 micron/V was obtained with a split-morph actuator with 30-micron thick layers. The proposed actuator is a promising candidate for the secondary fine-tuning actuator of a dual stage head-positioning servo system in high density hard disk drives.

Journal Article↗

PubMed2001

Force-frequency coefficient of symmetrical incomplete circular quartz crystal resonator.

The changes in the resonance frequencies of the thickness-shear vibration of symmetrical incomplete circular AT-cut quartz crystal resonators (QXRs), which are used as sensing elements in digital force sensors or pressure transducers, by the application of diametrical forces are discussed by considering the piezoelectric effect and the anistropic characteristics of crystal plates. Two-dimensional motion equations for predicting the frequency changes are derived from three-dimensional piezoelectricity equations, and equations deduced by Janiaud for solving the stress distribution in crystal plates are used to calculate the force-frequency coefficients of incomplete circular resonators. The results show that the piezoelectric effect of crystal plates decreases the force-frequency coefficient of the azimuth angle 0 degrees by 7% as compared with no piezoelectricity assumption. The incomplete circular shape can be applied to a larger load than the circular disc because the flat regions of the incomplete shape provide a distributed load application without the problems of stress concentration of a point force inherent to a circular disc. The incomplete shape gives an increased force sensitivity when compared with the complete disc near azimuth angle 0 degrees. The theoretical curves agree well with Ratajski's experimental results.

Journal Article↗

PubMed2001

Cutaneous neuroendocrine (Merkel cell) carcinoma occurred after resection of malignant melanoma.

An elderly man presented with a brown border nodule of the left upper lip that appeared to be clinically consistent with metastatic melanoma; he had previously undergone two surgical removals of melanoma in the right temporal region. Routine histologic examination was not sufficient for diagnosis, but Merkel cell carcinoma was diagnosed by immunohistochemical studies Neuroendocrine carcinoma of viscera was excluded. Because this case could not be differentiated from amelanotic melanoma and malignant lymphoma based on histologic appearances, immunohistochemical staining was helpful for diagnosis and differentiation.

Aged↗

PubMed2001

Social disadvantage and variation in the incidence of end-stage renal disease in Australian capital cities.

OBJECTIVE: To evaluate variation in the incidence of end-stage renal disease (ESRD) within Australian capital cities. To explore the relation between the incidence of ESRD and socioeconomic disadvantage. METHODS: We obtained data from the Australian and New Zealand Dialysis and Transplant Registry (ANZDATA) regarding 5,013 patients from capital cities who started ESRD treatment between 1 April 1993 and 31 December 1998. We used the postcode at the start of treatment to calculate the average annual incidence of ESRD for each of 51 capital city regions using 1996 Census counts based on place of usual residence. We calculated standardised incidence ratios with 95% confidence intervals for each region. The standardised incidence ratios were examined in relation to the SEIFA Index of Relative Socio-economic Disadvantage (IRSD), derived from the 1996 Census. Low IRSD values indicate more disadvantaged areas. RESULTS: There is significant variation in the standardised incidence of ESRD within capital cities. There was a significant correlation (r=-0.41, p=0.003) between the standardised incidence ratio for ESRD and the SEIFA IRSD. CONCLUSIONS AND IMPLICATIONS: Capital city areas that are more disadvantaged have a higher incidence of ESRD. Socioeconomic factors may be important determinants of the risk of developing ESRD.

Australia↗

PubMed2001

Coupled guided acoustic modes in water-filled thin-walled tubes.

Recent results [J. D. N. Cheeke et al., J. Acoust. Soc. Am. 104, 3678 (1998)] reported a 20% decrease in group velocity for flexural mode circumferential waves propagating around water-filled thin-walled stainless-steel tubes. In the present work, the full theory of such modes is developed to explain the structure modes which originates from the coupling between the water filler and stainless tube. Calculated values of the group velocity for the first two coupled modes are in excellent agreement with experiment. The results are of interest for the physics of acoustic waves in fluid-loaded structures and have potential application for liquid level detection.

Journal Article↗