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Biomedical subjects

S Zhao

Publications and source records attributed to S Zhao.

At least 109 records · Page 6Linked to original sources
PubMed2001

Trans-dentinal stimulation of tertiary dentinogenesis.

Trans-dentinal stimulation of tertiary dentinogenesis has long been recognized, and has traditionally been ascribed to diffusion of irritant substances arising during injury and restorative treatment. Identification of bio-active components, especially growth factors including TGF-beta s, sequestered within dentin matrix provides a new explanation for cellular signaling during tertiary dentinogenesis. Both isolated dentin matrix components and pure growth factors (TGF-beta s) have been shown to signal cellular events leading to reactionary and reparative tertiary dentinogenesis. Release of these bio-active components from dentin matrix may arise during carious attack and other injury to the tissue, and also during subsequent surgical intervention and restoration of the tooth. Both cavity-conditioning agents and leaching from restorative materials may contribute to release of these components. Distance of diffusion, as determined by cavity residual dentin thickness, and other restorative parameters may influence the signaling process after release of these components. Careful consideration of the interplay between tissue injury and surgical and restorative material factors is required for optimum exploitation of the exquisite regenerative capacity of dentin-pulp for more biological approaches to clinical treatment of dental disease.

Animals↗
PubMed2001

Evidence that relaxin inhibits apoptosis in the cervix and the vagina during the second half of pregnancy in the rat.

The growth of the cervix and vagina that occurs during the second half of rat pregnancy is accompanied by an increase in both epithelial and stromal cells. Neither the mechanism(s) that regulates this accumulation of cells nor its hormonal control is known. To test the hypothesis that the rate of apoptosis declines during the second half of pregnancy, cervices and vaginas were collected on days 5, 10, 15, 18, and 21 of pregnancy. Terminal deoxynucleotidyl transferase-mediated deoxyuridine 5'-triphosphate nick end-labeling was used to detect apoptotic cells. The rate of apoptosis declined (P < 0.05) in epithelial and stromal cells in both the cervix and vagina during the second half of pregnancy, when blood levels of relaxin are increasing. To test the hypothesis that relaxin inhibits apoptosis, cervices and vaginas were collected 6, 12, 24, 48, and 72 h after the neutralization of endogenous relaxin, on days 19-21 of pregnancy, with a monoclonal antibody for rat relaxin. Both the terminal deoxynucleotidyl transferase-mediated deoxyuridine 5'-triphosphate nick end-labeling method and electron microscopy were used to detect apoptotic cells. Withdrawal of relaxin caused an increase in the rate of apoptosis in both the cervix and the vagina (P < 0.05). It is concluded that the rate of apoptosis declines in the cervix and the vagina during the second half of rat pregnancy, and that relaxin likely contributes to this process.

Animals↗
PubMed2001

PGE(2) is essential for gap junction-mediated intercellular communication between osteocyte-like MLO-Y4 cells in response to mechanical strain.

We have observed, in our previous studies, that fluid flow increases gap junction-mediated intercellular coupling and the expression of a gap junction protein, connexin 43, in osteocyte-like MLO-Y4 cells. Interestingly, this stimulation is further enhanced during the poststress period, indicating that a released factor(s) is likely to be involved. Here, we report that the conditioned medium obtained from the fluid flow-treated MLO-Y4 cells increased the number of functional gap junctions and connexin 43 protein. These changes are similar to those observed in MLO-Y4 cells directly exposed to fluid flow. Fluid flow was found to induce PGE(2) release and increase cyclooxygenase 2 expression. Treatment of the cells with PGE(2) had the same effect as fluid flow, suggesting that PGE(2) could be responsible for these autocrine effects. When PGE(2) was depleted from the fluid flow-conditioned medium, the stimulatory effect on gap junctions was partially, but significantly, decreased. Addition of the cyclooxygenase inhibitor, indomethacin, partially blocked the stimulatory effects of mechanical strain on gap junctions. Taken together, these studies suggest that the stimulatory effect of fluid flow on gap junctions is mediated, in part, by the release of PGE(2). Hence, PGE(2) is an essential mediator between mechanical strain and gap junctions in osteocyte-like cells.

Animals↗
PubMed2001

Hyaluronan-associated adhesive cues control fiber segregation in the hippocampus.

In various brain regions, particularly in the hippocampus, afferent fiber projections terminate in specific layers. Little is known about the molecular cues governing this laminar specificity. To this end we have recently shown that the innervation pattern of entorhinal fibers to the hippocampus is mimicked by the lamina-specific adhesion of entorhinal cells on living hippocampal slices, suggesting a role of adhesion molecules in the positioning of entorhinal fibers. Here, we have analyzed the role of extracellular matrix components in mediating this lamina-specific adhesion. We show that hyaluronidase treatment of hippocampal slices abolishes lamina-specific adhesion as well as layer-specific growth of entorhinal fibers to the dentate outer molecular layer in organotypic slice cultures. We conclude that hyaluronan-associated molecules play a crucial role in the formation of the lamina-specific entorhinal projection to the hippocampus.

Animals↗
PubMed2001

Patterning the optic neuroepithelium by FGF signaling and Ras activation.

During vertebrate embryogenesis, the neuroectoderm differentiates into neural tissues and also into non-neural tissues such as the choroid plexus in the brain and the retinal pigment epithelium in the eye. The molecular mechanisms that pattern neural and non-neural tissues within the neuroectoderm remain unknown. We report that FGF9 is normally expressed in the distal region of the optic vesicle that is destined to become the neural retina, suggesting a role in neural patterning in the optic neuroepithelium. Ectopic expression of FGF9 in the proximal region of the optic vesicle extends neural differentiation into the presumptive retinal pigment epithelium, resulting in a duplicate neural retina in transgenic mice. Ectopic expression of constitutively active Ras is also sufficient to convert the retinal pigment epithelium to neural retina, suggesting that Ras-mediated signaling may be involved in neural differentiation in the immature optic vesicle. The original and the duplicate neural retinae differentiate and laminate with mirror-image polarity in the absence of an RPE, suggesting that the program of neuronal differentiation in the retina is autonomously regulated. In mouse embryos lacking FGF9, the retinal pigment epithelium extends into the presumptive neural retina, indicating a role of FGF9 in defining the boundary of the neural retina.

Animals↗
PubMed2001

Expression of functional gap junctions and regulation by fluid flow in osteocyte-like MLO-Y4 cells.

Osteocytes are thought to be mechanosensory cells that respond to mechanical stress by sending signals to other bone cells to initiate bone remodeling. An osteocyte-like cell line MLO-Y4 provides a model system to examine whether gap junctions participate in the regulation of osteocyte function and signaling by mechanical stress. In this study, we show that MLO-Y4 cells are coupled and that gap junction channels mediate this coupling. Biochemical analyses show that connexin 43 (Cx43) is a major gap junction protein expressed in MLO-Y4 cells and approximately 5% of Cx43 protein is phosphorylated. MLO-Y4 cells were exposed to mechanical stress using a parallel plate flow chamber to model bone fluid flow shear stress. Fluid flow increased significantly the length of the dendritic processes, a morphological characteristic of osteocytes. A redistribution of the gap junction protein, Cx43 also was observed from a location circling the nucleus to punctate spots in the cytoplasm and in the dendritic processes. "Scrape-loading" dye transfer analyses showed that fluid flow increased intercellular coupling and increased the number of cells coupled immediately after fluid flow treatment, in direct proportion to shear stress magnitude. Although intercellular coupling continued to increase, stimulation of Cx43 protein expression during the poststress period was found to be biphasic. Cx43 protein was elevated 30 minutes after application of stress but decreased at 24 h poststress. Pulsating fluid flow had a similar stimulatory effect as steady fluid flow on gap junctions. However, this stimulatory effect in osteocyte-like cells was not observed in osteoblast-like 2T3 cells. Together, these results show that fluid flow has stimulatory effects on osteocyte-like MLO-Y4 cells with early effects on cellular morphology, opening of gap junctions, and redistribution of Cx43 protein and delayed effects on Cx43 protein expression. The high expression of Cx43 and its location in the cytoplasm also suggest that Cx43 may have unknown functions in addition to forming gap junctions. These studies indicate that gap junctions may serve as channels for signals generated by osteocytes in response to mechanical loading.

Blotting, Western↗
PubMed2001

Classification of osteoporosis based on bone mineral densities.

In this article we examine the role of bone mineral density (BMD) in the diagnosis of osteoporosis. Using information from 7671 women in the Study of Osteoporotic Fractures (SOF) with BMD measurements at the proximal femur, lumbar spine, forearm, and calcaneus, we examine three models with differing criteria for the diagnosis of osteoporosis. Model 1 is based on the World Health Organization (WHO) criteria using a T score of -2.5 relative to the manufacturers' young normative data aged 20-29 years, with modifications using information from the Third National Health and Nutrition Examination Survey (NHANES). Model 2 uses a T score of -1 relative to women aged 65 years at the baseline of the SOF population. Model 3 classifies women as osteoporotic if their estimated osteoporotic fracture risk (spine and/or hip) based on age and BMD is above 14.6%. We compare the agreement in osteoporosis classification according to the different BMD measurements for the three models. We also consider whether reporting additional BMD parameters at the femur or forearm improves risk assessment for osteoporotic fractures. We observe that using the WHO criteria with the manufacturers' normative data results in very inconsistent diagnoses. Only 25% of subjects are consistently diagnosed by all of the eight BMD variables. Such inconsistency is reduced by using a common elderly normative population as in model 2, in which case 50% of the subjects are consistently diagnosed as osteoporotic by all of the eight diagnostic methods. Risk-based diagnostic criteria as in model 3 improve consistency substantially to 68%. Combining the results of BMD assessments at more than one region of interest (ROI) from a single scan significantly increases prediction of hip and/or spine fracture risk and elevates the relative risk with increasing number of low BMD subregions. We conclude that standardization of normative data, perhaps referenced to an older population, may be necessary when applying T scores as diagnostic criteria in patient management. A risk-based osteoporosis classification does not depend on the manufacturers' reference data and may be more consistent and efficient for patient diagnosis.

Adult↗
PubMed2001

Number of phase levels in a two-dimensional separable Talbot array illuminator.

The number of phase levels in a Talbot array illuminator (TAIL) is an important factor for estimation of practical fabrication complexity and cost. We show that the number of phase levels in a two-dimensional TAIL (2D-TAIL) has a simple relation to the prime number. When the output array is alternatively pi phase modulated, there are similar simple relations. These simple relations should be highly interesting for practical use. An experiment with the 2D-TAIL based on the joint-Talbot effect is given as well.

Journal Article↗
PubMed2001

[Review of filtering algorithms for medical ultrasonic images].

Several kinds of filters for medical ultrasonic images, such as multidimensional filter, adaptive weighted filter (for example, adaptive weighted median filter), adaptive window selecting filter (for example, homogeneous region growing mean filter and adaptive speckle suppression filter) and two-step filter, are introduced. The existing problems and the progress trend are also discussed. Some application instances for medical ultrasonic images of the filters discussed and the performance of the filters presented are based on the present authors' practice.

Algorithms↗
PubMed2001

[Auto-detection of contour in echocardiographic images based on active contour model].

Contour detection is one of the most difficult problems in the multi-dimensional reconstruction of echocardiographic images. A method based on active contour model is presented in the present paper to solve this problem. First, according to the characteristic of the ultrasonic medical images, an adaptive weighted median filter is used to suppress speckle noise and an adaptive threshold value is selected to get binary image. Then, mathematical morphological treatment is utilized to get the initial contour. At last, active contour model is employed to revise the initial contour and get the accurate final contour. Experiments with real and interpolated ultrasonic images are presented. The results show the effectiveness of this method. This method has practical use in the multi-dimensional reconstruction of ultrasonic medical images.

Algorithms↗
PubMed2001

FDG uptake and glucose transporter subtype expressions in experimental tumor and inflammation models.

UNLABELLED: Although FDG uptake is closely related to the expression of the glucose transporter (GLUT) in malignant tumors, such a relationship has not been fully investigated in inflammatory lesions. The aim of our study was to determine the expression of GLUT subtypes in experimental inflammatory lesions and to compare the results with those in malignant tumors in relation to FDG accumulation. METHODS: Rats were inoculated with a suspension of Staphylococcus aureus or allogenic hepatoma cells (KDH-8) into the left calf muscle. Five days after S. aureus inoculation (n = 9) and 14 d after KDH-8 inoculation (n = 11), [(14)C]FDG was injected intravenously and its accumulation in the infectious and tumor tissues was determined as the percentage activity of the injected dose per gram of tissue (%ID/g). The expression of glucose transporters (GLUT-1 to GLUT-5) was investigated by immunostaining the infectious tissues (n = 6) and the tumor tissues (n = 6). Immunohistochemical grading was assessed semiquantitatively by 5 observers. RESULTS: The [(14)C]FDG uptake was significantly higher in the tumor lesion than in the inflammatory lesion (2.04 +/- 0.38 %ID/g vs. 0.72 +/- 0.15 %ID/g; P < 0.0001). The tumor and inflammatory tissues highly expressed GLUT-1 and GLUT-3. The GLUT-1 expression level was significantly higher in the tumor tissue than in the inflammatory tissue (P < 0.05). CONCLUSION: The results based on our models showed a high FDG uptake and high GLUT-1 expression level not only in the tumor lesion but also in the inflammatory lesion. The higher GLUT-1 expression level in the tumor lesion may partially explain the higher FDG accumulation in the tumor than in the inflammatory lesion.

Animals↗
PubMed2001

Propranolol increases phosphatidic acid level via activation of phospholipase D.

AIM: To investigate the propranolol-induced phospholipase D (PLD) activity, its contribution to the increase in the level of phosphatidic acid, and the role of protein kinase C (PKC) in this event. METHODS: A combination of [3H]-myristate labeling, transphosphatidylation reaction, lipid extraction, and thin layer chromatography was used to measure the PLD activity. PKC inhibitors and prolonged phorbol-12-myristate-13-acetate (PMA) treatment were used to study the involvement of PKC in propranolol-induced PLD activation. Immunoblotting was used to detect the intracellular levels of PKC. RESULTS: Treatment of A-549 cells with propranolol in the presence of butanol, resulted in the rapid activation of PLD. Propranolol induced the formation of phosphatidylbutanol (PBut), a unique product of PLD, at the expense of phosphatidic acid (PA) formation. Pretreatment of cells with PKC inhibitors Ro-31-8220, staurosporine, and rottlerin increased the propranolol-induced PLD. Down-regulation of PKC by prolonged treatment of cells with PMA also potentiated the propranolol-induced PLD activity. CONCLUSION: Propranolol induces rapid activation of PLD activity, which results in the increase in intracellular level of PA. The data also indicate that propranolol-induced PLD activity could be negatively regulated by PKC.

Enzyme Activation↗
PubMed2001

Activation of NF-kappa B in bronchial epithelial cells from children with asthma.

OBJECTIVES: To determine whether nuclear factor-kappa B (NF-kappa B) is activated in epithelial cells from children with asthma and to understand the role of NF-kappa B in airway inflammation in asthma. METHODS: Bronchial mucosa specimens were obtained from 9 children with asthma and 6 control subjects. NF-kappa B expression in epithelial cells were detected by immunohistochemical examination, and NF-kappa B-DNA binding was measured by electrophoretic mobility shift assay (EMSA). RESULTS: Nuclear expression of NF-kappa B in epithelial cells was observed in the 9 asthmatic children. NF-kappa B-DNA binding was found in 4 asthmatic children (EMSA was performed in 6 asthmatic children). In contrast, both nuclear expression and NF-kappa B-DNA binding were absent in the 6 control subjects. CONCLUSION: These results indicated that NF-kappa B is activated in epithelial cells from asthmatic children and the NF-kappa B activation may be the basis for the increased expression of many inflammatory genes and for airway inflammation in asthma.

Asthma↗
PubMed2001

Interaction of hypertension and diabetes on impairment of endothelial function.

OBJECTIVE: To investigate whether the interaction of hypertension and diabetes aggravates endothelial dysfunction and leads to smooth muscle dysfunction. METHODS: Noninvasive methods were used to the investigated patients with type 2 diabetes mellitus (2-DM) (Group 1), patients with hypertension (Group 2) and patients with both 2-DM and hypertension (Group 3), as well as a normal control group (Group 4) by studying a brachial artery without evidence of atherosclerotic plaque formation. RESULTS: Results showed that endothelium-dependent vasodilation decreased significantly in Group 1 (5.74% +/- 3.32%, P < 0.05), Group 2 (4.14% +/- 2.93%, P < 0.01), and Group 3 (2.78% +/- 2.08%, P < 0.001) as compared to the control (9.45% +/- 3.88%). The nitroglycerin-induced vasodilation (smooth muscle function) in Group 3 was significantly decreased as compared to the control group (14.11% +/- 4.63% vs 23.53% +/- 6.77%, P < 0.001), but there were no differences in nitroglycerin-induced vasodilation between Group 1, Group 2 and Group 4. On univariate analysis, a reduced vasodilator response to nitroglycerin was associated with endothelium-dependent vasodilation (r = 0.54, P < 0.001). CONCLUSION: Our results indicate that the interaction of 2-DM and hypertension aggravates endothelial dysfunction and further impairs the smooth muscle function.

Aged↗
PubMed2001

Quantification of amino acid enantiomers in single cells by capillary electrophoresis.

An analytical method is described to quantify amino acid enantiomers in single cells. Cellular samples were derivatized with a fluorescence tagging reagent, naphthalene-2,2-dicarboxaldehyde, in a mini-volume (4 microl) prior to separation. Enantiomeric resolution was achieved by beta-cyclodextrin modified micellar electrokinetic chromatography. The separation was coupled with laser induced fluorescence detection. The method had a detection limit of 0.1 microM for aspartic acid enantiomers (1.0 microl sample solution was derivatized). Single neurons isolated from the five major ganglia of Aplysia californica were analyzed to determine the D/L enantiomeric ratios of aspartic acid, phenylalanine and leucine. D-aspartic acid was found at high levels in many neurons tested and its cellular distribution was highly heterogeneous.

Amino Acids↗
PubMed2001

[Relationship between expression of inducible nitric oxide synthase and of VEGF in oral carcinoma].

OBJECTIVE: To study the expression of inducible NOS in oral carcinoma and it's relationship with the expression of VEGF, MVD and lymphatic metastasis. METHODS: With 9 cases of normal oral mucosa as control, the expression of iNOS in 41 cases of oral carcinoma was evaluated by immunohistochemistry SP staining. Meanwhile MVD and the expression of VEGF were also detected. RESULTS: The expression rate of iNOS in 41 cases was 63.41%, and the rate between N+ group and N- group was significantly different (P < 0.01). There were significant difference of MVD (P < 0.001) and of the expression of VEGF(P < 0.05) among groups of different iNOS expression level. CONCLUSIONS: The expression of iNOS in oral carcinomas is high, and it is closely related to angiogenesis and lymphatic metastasis. The expression of iNOS probably takes part in VEGF's angiogenic effect.

Carcinoma, Squamous Cell↗
PubMed2001

[Different sampling method affects the voice assessment results for the patient with vocal polyp].

OBJECTIVE: In order to definitude the influence caused by the different sampling in voice assessment. METHOD: We comparing the results acquired by total section and subsection sampling. RESULT: The results acquired by subsection tended to normal more than those acquired by total section. CONCLUSION: Subsection sampling voice assessment might conceal the degree of the disease state of patients.

Adult↗