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Biomedical subjects

S Zhou

Publications and source records attributed to S Zhou.

At least 253 records · Page 14Linked to original sources
PubMed1999

Fresh amniotic membrane transplantation for conjunctival surface reconstruction.

PURPOSE: To determine whether fresh human amniotic membrane can be used to reconstruct the conjunctival detect created during symblepharon lysis. METHODS: Forty-two eyes of 39 consecutive patients with eye burns and Stevens-Johnson syndrome were randomized to accept fresh or preserved human amniotic membrane transplantation (AMT) during the period of severe scarring. Impression cytology was performed in 12 eyes with normal tear secretion which received fresh AMT. RESULTS: During a mean follow-up of 11 months (range, 6 to 18 months), thirty-five patients (37 eyes) showed successful ocular surface reconstruction and resolution of motility restriction while four patients (2 eyes with fresh AMT, 3 eye with preserved AMT) with minimal recurrence of symblepharon. There was no significant difference statistically between two groups (Chi-square test). Amniotic epithelial cells can survive about three months after being transplanted onto ocular surfaces with normal tear secretion. CONCLUSION: Both fresh and preserved human amniotic membrane can be considered an ideal alternative substrate for conjunctival surface reconstruction during removal of severe symblepharon.

Adolescent↗
PubMed1999

[The expression and distribution of ciliary neurotrophic factor in laryngeal nerve regeneration].

OBJECTIVE: To explore the expression and distribution of ciliary neurotrophic factor(CNTF) mRNA and its protein in laryngeal nerve regeneration. METHODS: The recurrent laryngeal nerves were sectioned and then sutured in twelve dogs. Both proximal and distal stumps of sutured region were sectioned on different postoperative days and the sections were separately used for CNTF immunohistochemistry and CNTF mRNA in situ hybridization. The area and intensity of reactive product were measured by computer image processing system. RESULTS: Strongly reactive product of CNTF mRNA and its protein deposited in myelin-related Schwann cells in normal laryngeal nerves. At week 2 following neurorrhaphy, there was very little hybridization signal and detectable CNTF immunoreactivity in distal stump and no regenerated nerve fibbers were found. At week 3, reactive product of CNTF mRNA and its protein was detected in thin Schwann cell processes ensheathing regenerated axons, while reactive product was not found in the proliferating Schwann cells which didn't ensheathe axons. CNTF immunoreactivity was also detected in the regenerated nerve axons. After long survival times, hybridization signal and the CNTF immunoreactivity in Schwamm cells became more widespread, and the area and intensity of reactive product significantly increased, but even at the longest survival time, they were still significantly less than those in intact nerve. The same change of CNTF mRNA and its protein was observed in a short segment proximal to the sutured region. CONCLUSION: CNTF expression could depend on Schwann cell-axon regeneration. The level of CNTF expression stands in striking contrast to the up-regulation of nerve growth factor in peripheral nerve degeneration and regeneration. These suggest that the exogenous CNTF might provide a supportive environment for axonal regeneration.

Animals↗
PubMed1999

[The 1. 54 microm laser and upconversion luminescence of YELPP noncrystalline induced by 969 nm LD laser].

In this paper, the absorption of Er3+, Yb3+ penta-phosphate noncrystalline (YELPP) was measured and the basic spectral parameters were calculated. Adopting the longitudinal-pump method with a domestic diode laser (LD), we achieved CW 1.5 microm chipped laser in China for the first time. The power of 1.5 microm laser was quite stable. The target of 1.5 microm laser reached the international level of early 1990s' in this field. In addition, the up-conversion luminescence was measured under the condition that 1.5 microm laser was either oscillating or not. The relationship between 1.5 microm chipped laser and up-conversion luminescence was analyzed initially.

English Abstract↗
PubMed1999

[Microbeam nuclear reaction analysis and its application to individual fluid inclusions].

The principles and analytical technique of nuclear analysis of scanning microprobe (micro-NRA) was introduced. It is a useful tool for nondestructive light elements analysis which can not be detected by micro-PIXE. Using 19F (p, alphagamma)16O reaction at 872 keV resonance energy, the fluorine concentration in trapped fluid inclusions of mantle derived olived-evidence from Cenozoic basaltic rocks in Eastern-China was determined.

English Abstract↗
PubMed1999

[Direct upconversion sensitization luminescence of Tm(0.1) Yb (10.9) oxyfluoride vitroceramincs].

This paper studied the direct upconversion sensitization luminescence of Tm (0.1) Yb (10.9) oxyfluoride vitroceramics pumped by 966 nm diode laser for the first time. We found that there are both strong 477 nm three-photon upconversion fluorescence of 1G4 --> 3H6 transition and 799.5 nm two-photon upconversion fluorescence of 3H4 --> 3H6 transition as well as weak upconversion fluorescence of 1D2 --> 3H6, 1Dz --> 3F4,1G4 --> 3F4 and 3F3 --> 3H6 transitions at 361 nm, 449.5 nm, 647.0 nm and (679.5, 698.5 nm), respectively.

English Abstract↗
PubMed1998

An Approximate Analytic Expression for the Surface Charge Density/Surface Potential Relationship for a Spherical Colloidal Particle.

An approximate analytic expression for the surface charge density/surface potential relationship (final sigma/psi0) for a spherical colloidal particle in a solution of mixed and nonsymmetrical electrolytes is obtained by solving a nonlinear Poisson-Boltzmann equation using a linearization approximation. The approximate analytic expression is fit for the case of large kappaa(kappa = Debye-Hückel inverse parameter, a = colloidal particle radius), but for the case of small kappaa, the approximate analytic expression is applicable only when kappaa >/= 0.03, with a maximal percent relative error of 5.0, even for surface potentials up to 334 mV (25 degreesC). The approximate analytic expressions reported in the literature have a low limit of kappaa, 0.5 or even 2.0. The present approximate analytic expression has a simple structure and is characterized by the ease with which it is adapted for analysis. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Requirement for p53 and p21 to sustain G2 arrest after DNA damage.

After DNA damage, many cells appear to enter a sustained arrest in the G2 phase of the cell cycle. It is shown here that this arrest could be sustained only when p53 was present in the cell and capable of transcriptionally activating the cyclin-dependent kinase inhibitor p21. After disruption of either the p53 or the p21 gene, gamma radiated cells progressed into mitosis and exhibited a G2 DNA content only because of a failure of cytokinesis. Thus, p53 and p21 appear to be essential for maintaining the G2 checkpoint in human cells.

Apoptosis↗
PubMed1998

Identification of two distinct human SMC protein complexes involved in mitotic chromosome dynamics.

The structural maintenance of chromosomes (SMC) family member proteins previously were shown to play a critical role in mitotic chromosome condensation and segregation in yeast and Xenopus. Other family members were demonstrated to be required for DNA repair in yeast and mammals. Although several different SMC proteins were identified in different organisms, little is known about the SMC proteins in humans. Here, we report the identification of four human SMC proteins that form two distinct heterodimeric complexes in the cell, the human chromosome-associated protein (hCAP)-C and hCAP-E protein complex (hCAP-C/hCAP-E), and the human SMC1 (hSMC1) and hSMC3 protein complex (hSMC1/hSMC3). The hCAP-C/hCAP-E complex is the human ortholog of the Xenopus chromosome-associated protein (XCAP)-C/XCAP-E complex required for mitotic chromosome condensation. We found that a second complex, hSMC1/hSMC3, is required for metaphase progression in mitotic cells. Punctate vs. diffuse distribution patterns of the hCAP-C/hCAP-E and hSMC1/hSMC3 complexes in the interphase nucleus indicate independent behaviors of the two complexes during the cell cycle. These results suggest that two distinct classes of SMC protein complexes are involved in different aspects of mitotic chromosome organization in human cells.

Amino Acid Sequence↗
PubMed1998

CD38 expression on cryopreserved CD8+ T cells predicts HIV disease progression.

Previous studies have revealed that the expression of CD38 on CD8+ T cells is a strong predictor of disease progression in human immunodeficiency virus (HIV)-infected individuals. Those studies were performed using fresh patient samples over an extended trial period. After demonstrating the validity of assay results on cryopreserved cells, we performed a retrospective study using frozen cell samples to determine the predictive value of CD38 expression in patients with CD4 counts above 400 cells/microl. The CD38 expression as measured by antibody binding capacity and the CD38 median channel were shown to be associated with time to new opportunistic infection or death (both P < 0.001). These results suggest that CD38 expression on CD8+ T cells, whether fresh or frozen, provides a useful predictor of HIV disease progression.

ADP-ribosyl Cyclase↗
PubMed1998

Identification of hydrazine in commercial preparations of carnosine and its influence on carnosine's antioxidative properties.

Commercial preparations of synthetic carnosine are commonly used by researchers to investigate carnosine's biological functions and potential applications. Our studies on the interaction of synthetic carnosine and aldehydic lipid oxidation products have led to the detection and structural identification of hydrazine, a strong reducing agent. The concentrations of hydrazine in various sources of commercial carnosine were in the range of 0.01-0.20% (w/w). The levels of contaminating hydrazine in commercial carnosine were capable of interfering with the analyses of headspace aldehydes, malonaldehyde, and thiobarbituric acid-reactive substances. Since hydrazine can potentially interfere with lipid oxidation reactions and measurement of lipid oxidation products, it will be necessary to use purified carnosine to reevaluate carnosine's biological and chemical properties.

Aldehydes↗
PubMed1998

Evidence for the interaction of glutamate and NK1 receptors in the periphery.

It is known that Substance P (SP) enhances glutamate- and N-methyl-D-aspartate (NMDA)-induced activity in spinal cord dorsal horn neurons and that this enhancement is important in the generation of wind-up and central sensitization. It is now known that SP and glutamate receptors are present on sensory axons in rat glabrous skin. This raises the issue as to whether SP and glutamate interact in the periphery. Using the tail skin in rats, the present study demonstrates 1) that unmyelinated axons at the dermal-epidermal junction immunostain for antibodies directed against NMDA, non-NMDA or SP (NK1) receptors; 2) that glutamate injected into the tail skin results in dose-dependent nociceptive behaviors interpreted as mechanical hyperalgesia, mechanical allodynia and thermal hyperalgesia, which are blocked following co-injection with glutamate antagonists; 3) that peripheral injection of SP potentiates glutamate-induced nociceptive behaviors in that the co-injection of SP+glutamate results in a significantly longer duration of behavioral responses compared to the responses seen following injection of either substance alone. These data provide support for the hypothesis that primary afferent neurons might well be subject to similar mechanisms that result in wind-up or central sensitization of spinal cord neurons.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1998

Targeted deletion of Smad4 shows it is required for transforming growth factor beta and activin signaling in colorectal cancer cells.

Smad4 (DPC4) is a candidate tumor suppressor gene that has been hypothesized to be critical for transmitting signals from transforming growth factor (TGF) beta and related ligands. To directly test this hypothesis, the Smad4 gene was deleted through homologous recombination in human colorectal cancer cells. This deletion abrogated signaling from TGF-beta, as well as from the TGF-beta family member activin. These results provide unequivocal evidence that mutational inactivation of Smad4 causes TGF-beta unresponsiveness and provide a basis for understanding the physiologic role of this gene in tumorigenesis.

Activins↗
PubMed1998

A simplified system for generating recombinant adenoviruses.

Recombinant adenoviruses provide a versatile system for gene expression studies and therapeutic applications. We report herein a strategy that simplifies the generation and production of such viruses. A recombinant adenoviral plasmid is generated with a minimum of enzymatic manipulations, using homologous recombination in bacteria rather than in eukaryotic cells. After transfections of such plasmids into a mammalian packaging cell line, viral production is conveniently followed with the aid of green fluorescent protein, encoded by a gene incorporated into the viral backbone. Homogeneous viruses can be obtained from this procedure without plaque purification. This system should expedite the process of generating and testing recombinant adenoviruses for a variety of purposes.

Adenoviridae↗
PubMed1998

Transient immunosuppression allows transgene expression following readministration of adeno-associated viral vectors.

Adeno-associated viral (AAV) vectors have much promise in gene therapy. Among the many properties that make AAV an ideal vector for gene therapy are its ability to infect both dividing and nondividing cells and the longevity of expression in tissues such as brain, skeletal muscle, and liver. However, like other viral vectors, readministration of vector is limited because of the host's immune response to viral components of the vector. Using class I, class II, and CD40 ligand (CD40L)-deficient mice, we demonstrate that neutralizing antibodies to the viral capsid proteins prevent transgene expression following readministration of rAAV vectors. Transient immunosuppression of mice by treatment with antibody to CD4 at the time of primary infection allowed transgene expression after readministration of rAAV vectors to animals. Transient immunosuppression with antibody to CD40L had only a modest effect on the efficacy of readministration. The ability to readminister virus was inversely correlated with both AAV capsid enzyme-linked immunosorbent assay titers and AAV neutralizing antibody titers. These studies demonstrate that readministration of rAAV can be accomplished by down regulating the anti-AAV immune response and suggest the use of repeated administration of rAAV as a viable form of therapy for the treatment of chronic diseases.

Animals↗
PubMed1998

Architectural DNA binding by a high-mobility-group/kinesin-like subunit in mammalian SWI/SNF-related complexes.

The SWI/SNF complex in yeast and Drosophila is thought to facilitate transcriptional activation of specific genes by antagonizing chromatin-mediated transcriptional repression. The mechanism by which it is targeted to specific genes is poorly understood and may involve direct DNA binding and/or interactions with specific or general transcription factors. We have previously purified a mammalian complex by using antibodies against BRG1, a human homologue of SWI2/SNF2. This complex is likely functionally related to the yeast SWI/SNF complex because all five subunit identified so far (referred to as BAFs, for BRG1-associated factors) are homologues of the yeast SWI/SNF subunits. However, we now describe the cloning of the 57-kDa subunit (BAF57), which is present only in higher eukaryotes but not in yeast. BAF57 is shared by all mammalian complexes and contains a high-mobility-group (HMG) domain adjacent to a kinesin-like region. Both recombinant BAF57 and the whole complex bind four-way junction (4WJ) DNA, which is thought to mimic the topology of DNA as it enters or exits the nucleosome. Surprisingly, complexes with mutations in the HMG domain of BAF57 can still bind 4WJ DNA and mediate ATP-dependent nucleosome disruption. Our work describes the first DNA binding subunit for SWI/SNF-like complexes and suggest that the mechanism by which mammalian and Drosophila SWI/SNF-like complexes interact with chromatin may involve recognition of higher-order chromatin structure by two or more DNA binding domains.

Amino Acid Sequence↗
PubMed1998

Incidence and clinical consequences of surface and polymerase gene mutations in liver transplant recipients on hepatitis B immunoglobulin.

Mutations in the "a" determinant of the surface gene have been associated with failure of hepatitis B immunoglobulin (HBIg) prophylaxis. We compared sequences from the surface and polymerase regions of hepatitis B virus (HBV) from 4 patients who failed high-dose HBIg therapy with two control groups: HBIg-treated patients who remained hepatitis B surface antigen (HBsAg)-negative (n = 4) and HBV-infected transplant recipients who never received HBIg (n = 4). Mutations within the surface and overlapping polymerase region were more common in patients failing HBIg than controls (P = .03), and mutations in the region of the "a" determinant were present only in patients failing HBIg. To examine the relationship between HBIg failure and duration of therapy, five additional treatment failures from a second transplantation center were sequenced (total with HBIg failure = 9). Mutations in the "a" determinant developed in 1 of 3 patients receiving HBIg for less than 6 months compared with 5 of 6 patients failing HBIg after 6 months of therapy (P = .23). The most frequently identified amino acid substitution was glycine to arginine at position 145 (present in 4 of 6 patients who failed HBIg after at least 6 months of treatment). A unique mutation within the YMDD motif (methionine to leucine) was present in 1 patient who failed HBIg treatment and who received a short course of ganciclovir. We conclude that the emergence of mutations in the "a" determinant accounts for some, but not all, treatment failures in patients receiving HBIg prophylaxis. Mutations in other regions of the S gene were more common in patients failing HBIg than controls, suggesting that domains other than the "a" determinant may be important.

Adult↗
PubMed1998

Animal experimental study on surgical repair of hypospadias by free peritoneal graft.

Surgical repair of hypospadias was successfully performed by using free peritoneal graft in the model of rabbit hypospadias. The results showed that free peritoneal graft used as a substitute for urathra had a high survival rate, and the canal was formed well. Our study demonstrated that peritoneum could be used for the surgical repair of hypospadias and other urethral disorders such as urethral stricture.

Animals↗