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Biomedical subjects

S C Zhang

Publications and source records attributed to S C Zhang.

At least 19 recordsLinked to original sources
PubMed2005

Toxicity and protective efficiency of cryoprotectants to flounder (Paralichthys olivaceus) embryos.

With the purpose of finding an ideal cryoprotectant or combination of cryoprotectants in a suitable concentration for flounder (Paralichthys olivaceus) embryo cryopreservation, we tested the toxicities, at culture temperature (16 degrees C), of five most commonly used cryoprotectants-dimethyl sulfoxide (Me2SO), glycerol, methanol (MeOH), 1,2-propylene glycol (PG) and ethylene glycol (EG). In addition, cryoprotective efficiency to flounder embryos of individual and combined cryoprotectants were tested at -15 degrees C for 60 min. Five different concentrations of each of the five cryoprotectants and 20 different combinations of these cryoprotectants were tested for their protective efficiency. The results showed that the toxicity to flounder embryos of the five cryoprotectants are in the following sequence: PG < MeOH < Me2SO < glycerol < EG (P < 0.05); whereas the protective efficiency of each cryoprotectant, at -15 degrees C for a period of 60 min, are in the following sequence: PG > Me2SO approximately MeOH approximately glycerol > EG (greater symbols mean P < 0.05, and approximate symbols mean P > 0.05). Methanol combined with any one of the other cryoprotectants gave the best protection, while ethylene glycol combined with any one of the other cryoprotectants gave the poorest protection at -15 degrees C. Toxicity effect was concentration dependent with the lowest concentration being the least toxic for all five cryoprotectants at 16 degrees C. For PG, MeOH and glycerol, 20% solutions gave the best protection at -15 degrees C; whereas a 15% solution of Me2SO, and a 10% solution of EG, gave the best protection at -15 degrees C.

Animals↗
PubMed2005

The influence of pH on hydrolysis and acidogenesis of kitchen wastes in two-phase anaerobic digestion.

Batch and semi-continuous experiments were carried out to determine the effect of pH on hydrolysis and acidogenesis of kitchen wastes in the two-phase anaerobic digestion. The results of the batch experiment showed pH adjustment could improve both hydrolysis and acidogenesis rates of kitchen wastes. Compared with pH at 5, 9 and 11, pH 7 provided an optimum working condition for anaerobic digestion of kitchen wastes. At pH 7, about 86% of the total organic carbon (TOC) and 82% of chemical oxygen demand (COD) were solubilized and the maximum volatile fatty acid (VFA) concentration of 36 g l(-1) was achieved on the fourth day. The total VFA yield was 0.27 g (g total solid (TS))(-1), which almost doubled the yield without pH adjustment (0.15 g (g TS)(-1). The acidified products with lower concentration of lactic acid were more favorable to the subsequent methanogenesis. At pH 7, most of the protein was degraded into ammonia nitrogen (NH4(+)-N), resulting in additional buffer of acidified liquid. According to this, a novel method of pH adjustment applying NH4(+)-N buffer was established. The semi-continuous experiment indicated that adjusting pH to 7 in the acidogenic stage in the two-phase anaerobic digestion process would increase both TS loading rate (16g l(-1) d(-1)) and recovery of biological energy (520 ml methane (CH4) (g TS)(-1)).

Bacteria, Anaerobic↗
PubMed2005

The use of an herbal formula by hospital care workers during the severe acute respiratory syndrome epidemic in Hong Kong to prevent severe acute respiratory syndrome transmission, relieve influenza-related symptoms, and improve quality of life: a prospective cohort study.

OBJECTIVES: To investigate the efficacy of an herbal formula in the prevention of severe acute respiratory syndrome (SARS) transmission among health care workers. The secondary objectives are to investigate quality of life (QOL) and symptomology changes among supplement users, and to evaluate the safety of this formula. DESIGN: Controlled clinical trial. SETTINGS: Hong Kong during epidemic of SARS. SUBJECTS: Two cohorts of health care workers from 11 hospitals in Hong Kong, 1 using an herbal supplement for a 2-week period (n = 1063) and a control cohort comprising all other health care workers who did not receive the supplement (n = 36,111) were compared prospectively. INTERVENTIONS: Taking an herbal supplement for a 2-week period. OUTCOME MEASURES: SARS attack rates and changes in quality of life and influenza-like symptoms were also examined at three timepoints among herbal supplement users. RESULTS: None of the health care workers who used the supplement subsequently contracted SARS compared to 0.4% of the health care workers who did not use the supplement (p = 0.014). Improvements in influenza-like symptoms and quality of life measurements were also observed among herbal supplement users. Less than 2% reported minor adverse events. CONCLUSION: The results of this pilot study suggest that there is a good potential of using Traditional Chinese Medicine (TCM) supplements to prevent the spread of SARS.

Adult↗
PubMed2005

Using herbal medicine as a means of prevention experience during the SARS crisis.

At the peak of the SARS epidemic in Hong Kong, hospital workers were under high risks of contraction of the infection. Herbal preparations had been used historically in China to treat influenza-like diseases. During the SARS outbreak, herbal preparations had been used jointly with standard modern treatment in China. As a means to protect the at-risk hospital workers, an innovative herbal formula was created and consumed by 3160 of them in two weeks. During the two weeks, symptoms and adverse effects were close monitored; 37 of them had their serum checked for immunological responses. The results showed that none of the herb consumers contracted the infection, compared to 0.4% among the non-consumers. Adverse effects had been infrequent and mild. There were hardly any influenza-like symptoms and the quality of life improved. In the group who volunteered to have their immunological state checked, significant boosting effects were found. It was concluded that there might be a good indication for using suitable herbal preparations as a means of preventing influenza-like infection. The mode of preventive effect could be treatment of the infection at its very early stage instead of producing a period of higher immunological ability, as in the case of vaccination.

Adult↗
PubMed2004

Production of interspecies chimeras by transplanting rosy barb (Puntius conchonius) embryonic cells to zebrafish (Danio rerio) embryos.

Establishment of a cell-mediated gene transfer system has potential as a new breeding technique for commercially valuable fishes. As an important step toward developing an inter-species chimera, cells from blastula-stage embryos of rosy barb (Puntius conchonius) were transplanted into zebrafish (Danio rerio) blastula-stage embryos to observe the development of the recipient. From the total of 473 transplants obtained only a fraction of 13 chimeras appeared perfectly normal after one month. Over two in normal 13 chimeras showed some characters from the donor cells with scarce pigmentation. This is the first successful inter-species study on zebrafish by using blastula cell transplants from rosy barb both belonging to the same family cyprinidae.

Animals↗
PubMed2003

Cryopreservation of flounder (Paralichthys olivaceus) sperm with a practical methodology.

A simple and convenient protocol for the cryopreservation of the flounder (Paralichthys olivaceus) sperm was established for "on the spot" cryopreservation of large quantities of semen. The use of three cryoprotectants, dimethyl sulphoxide (DMSO), glycerol (Gly) and methanol was tested in the method. The percentage of motile sperm present in semen after it had been frozen and thawed in the presence of DMSO, Gly or methanol was 60.5+/-3.6, 79.17+/-4.5 and 13.25+/-4.7%, respectively. The fertilization rates of this sperm were 67.06+/-15.1, 76.20+/-10.0 and 44.93+/-22.6%, while the hatching rates of eggs fertilized with this sperm were 37.40+/-8.3, 48.18+/-25.7 and 23.35+/-10.8%, respectively. It was found that Gly and DMSO were better cryoprotectants than methanol, with Gly giving the best overall results. Under scanning electron microscopy, it could be seen that while the majority of the frozen-thawed sperm remained morphologically normal, some exhibited lost or dilated mitochondria, swollen mid-pieces, broken tails, or damaged cell membrane, which probably caused the decrease in motility and fertility of the frozen-thawed sperm.

Animals↗
PubMed2002

Phase diagram and dynamics of the projected SO(5) symmetric model of high- T(c) superconductivity.

We present numerical studies of a quantum "projected" SO(5) model which aims at a unifying description of antiferromagnetism and superconductivity in the high- T(c) cuprates, while properly taking into account the Mott insulating gap. Our numerical results, obtained by the quantum Monte Carlo technique of stochastic series expansion, show that this model can give a realistic description of the global phase diagram of the high- T(c) superconductors and accounts for many of their physical properties. Moreover, we address the question of asymptotic restoring of the SO(5) symmetry at the critical point.

Journal Article↗
PubMed2002

Subcellular targeting domains of Abutilon mosaic geminivirus movement protein BC1.

Abutilon mosaic geminivirus (AbMV) encodes two movement proteins, BV1 and BC1, which mediate the intra- and intercellular transport of viral DNA in plants cooperatively. It has been shown previously that singly expressed BC1, fused to green fluorescent protein (GFP), accumulates preferentially either at the cell periphery or around the nucleus in separate plant cells. To define the BC1 domains responsible for understanding the subcellular sorting, deletion mutants were fused to GFP and expressed transiently in epidermal cells of non-host (Allium cepa) as well as of host (Nicotiana benthamiana) plants with basically the same results in both species. BC1-mediated intracellular sorting was dependent on two protein domains, an "anchor domain" (amino acids 117 to 180) which is necessary and sufficient to fix GFP:BC1 at the cell periphery and the nuclear environment, and a "pilot domain" (amino acids 1 to 49) in the absence of which the fusion proteins were found at both sites in the same cell simultaneously.

Amino Acid Sequence↗
PubMed2001

Movement proteins (BC1 and BV1) of Abutilon mosaic geminivirus are cotransported in and between cells of sink but not of source leaves as detected by green fluorescent protein tagging.

Two movement proteins (BV1 and BC1) facilitate the intra- and intercellular transport of begomoviruses in plants. In contrast to other geminiviruses the movement protein BC1 of Abutilon mosaic virus (AbMV) remained in the supernatant after centrifuging plant extracts at 20,000 g. To test whether this unusual behavior results from a distinct intracellular distribution of the protein, the BC1 gene has been fused to the gene of green fluorescent protein (GFP). The resulting plasmids were delivered into nonhost plants (Allium cepa) as well as into mature and immature cells of host plants (Nicotiana tabacum, N. benthamiana) by biolistic bombardment for transient expression in planta. BC1 directed GFP to two different cellular sites. In the majority of nonhost cells as well as in mature cells of host leaves, BC1 was mainly localized in small punctate flecks at the cell periphery or, to a lesser extent, around the nucleus. In sink leaves of host plants, GFP:BC1 additionally developed disc-like structures in the cell periphery. Cobombardment of GFP:BC1 with its cognate infectious DNA A and B did not change their subcellular distribution patterns in source leaves but led to the formation of peculiar needle-like structures in sink leaves. The nuclear shuttle protein (BV1) of AbMV accumulated mainly inside the nuclei as shown by immunohistochemical staining and GFP tagging. In sink cells of host plants it was mobilized to the plasma membrane and to the nucleus of the neighboring cell by coexpressed BC1, GFP:BC1, BC1:GFP, or after cobombardment with the cognate viral DNA. Only under these conditions were GFP:BC1 and BC1:GFP also found in the recipient cell.

Artificial Gene Fusion↗
PubMed2001

A four-dimensional generalization of the quantum Hall effect.

We construct a generalization of the quantum Hall effect, where particles move in four dimensional space under a SU(2) gauge field. This system has a macroscopic number of degenerate single particle states. At appropriate integer or fractional filling fractions the system forms an incompressible quantum liquid. Gapped elementary excitation in the bulk interior and gapless elementary excitations at the boundary are investigated.

Journal Article↗
PubMed2001

Reactive microglia in dysmyelination and demyelination.

The relationship between microglial activation and dysmyelination/demyelination was analyzed in a long-lived myelin mutant, the Long Evans shaker (les) rat, which exhibits early dysmyelination and a later loss of abnormal myelin sheaths. A microglial reaction characterized by progressive morphological transformation and increasing cell density was localized exclusively to white matter during postnatal 2-4 weeks, suggesting a microglial response to dysmyelination and oligodendroglial pathology. A further microglial reaction as marked by microglial expression of MHC II and a concomitant expression in the brain and spinal cord of mRNA for interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), and inducible nitric oxide synthase (iNOS) began around 4 weeks when the remaining myelin was lost. Ultrastructurally, activated microglia ingested numerous myelin figures, suggestive of active phagocytosis. Thus, this study indicates that microglial reaction is graded in chronic neurological disorders and suggests that MHC II expression marks a functional change of activated microglia.

Animals↗
PubMed2001

Gyrokinetic formula and experimental examination of the electron-beam misalignment effect on the efficiency of a cylindrical-cavity gyrotron oscillator.

By making use of the gyrokinetics of free-electron masers, the efficiency formula of a cylindrical-cavity gyrotron oscillator is presented, where the misalignment of the electron-beam axis to the cavity axis has been taken into account. Comparison with a recent experimental report [Int. J. Infrared and Millimeter Waves 19, 1303 (1998)] is made, which confirms the creditability of the gyrokinetic theory.

Journal Article↗
PubMed2001

Embryonic-derived glial-restricted precursor cells (GRP cells) can differentiate into astrocytes and oligodendrocytes in vivo.

We have isolated and characterized a unique glial-restricted precursor cell (GRP) from the embryonic spinal cord. Clonal analysis demonstrated that these cells are able to generate oligodendrocytes and two distinct type of astrocytes (type 1 and type 2) when exposed to appropriate signals in vitro. We now show that many aspects of these cells are retained in vivo. GRP cells are restricted to the glial lineage in vivo as they seem to be unable to generate neuronal phenotypes in an in vivo neurogenic environment. GRP cells survive and migrate in the neonatal and adult brain. Transplanted GRP cells differentiate into myelin-forming oligodendrocytes in a myelin-deficient background and also generate immature oligodendrocytes in the normal neonatal brain. In addition, GRP cells also consistently generated glial fibrillary protein-expressing cells in the neonatal and adult brain, a property not consistently expressed by other glial precursor cells like the O-2A/OPC cells. We suggest that the lineage restriction of GRP cells and their ability to generate both oligodendrocytes and astrocytes in vivo together with their embryonic character that allows for extensive in vitro expansion of the population makes the cell useful for clinical application.

Animals↗
PubMed2001

In vitro differentiation of transplantable neural precursors from human embryonic stem cells.

The remarkable developmental potential and replicative capacity of human embryonic stem (ES) cells promise an almost unlimited supply of specific cell types for transplantation therapies. Here we describe the in vitro differentiation, enrichment, and transplantation of neural precursor cells from human ES cells. Upon aggregation to embryoid bodies, differentiating ES cells formed large numbers of neural tube-like structures in the presence of fibroblast growth factor 2 (FGF-2). Neural precursors within these formations were isolated by selective enzymatic digestion and further purified on the basis of differential adhesion. Following withdrawal of FGF-2, they differentiated into neurons, astrocytes, and oligodendrocytes. After transplantation into the neonatal mouse brain, human ES cell-derived neural precursors were incorporated into a variety of brain regions, where they differentiated into both neurons and astrocytes. No teratoma formation was observed in the transplant recipients. These results depict human ES cells as a source of transplantable neural precursors for possible nervous system repair.

Animals↗
PubMed2001

Magnetodendrimers allow endosomal magnetic labeling and in vivo tracking of stem cells.

Magnetic resonance (MR) tracking of magnetically labeled stem and progenitor cells is an emerging technology, leading to an urgent need for magnetic probes that can make cells highly magnetic during their normal expansion in culture. We have developed magnetodendrimers as a versatile class of magnetic tags that can efficiently label mammalian cells, including human neural stem cells (NSCs) and mesenchymal stem cells (MSCs), through a nonspecific membrane adsorption process with subsequent intracellular (non-nuclear) localization in endosomes. The superparamagnetic iron oxide nanocomposites have been optimized to exhibit superior magnetic properties and to induce sufficient MR cell contrast at incubated doses as low as 1 microg iron/ml culture medium. When containing between 9 and 14 pg iron/cell, labeled cells exhibit an ex vivo nuclear magnetic resonance (NMR) relaxation rate (1/T2) as high as 24-39 s-1/mM iron. Labeled cells are unaffected in their viability and proliferating capacity, and labeled human NSCs differentiate normally into neurons. Furthermore, we show here that NSC-derived (and LacZ-transfected), magnetically labeled oligodendroglial progenitors can be readily detected in vivo at least as long as six weeks after transplantation, with an excellent correlation between the obtained MR contrast and staining for beta-galactosidase expression. The availability of magnetodendrimers opens up the possibility of MR tracking of a wide variety of (stem) cell transplants.

3T3 Cells↗
PubMed2000

Tracing human oligodendroglial development in vitro.

Human neural precursor cell cultures (neurospheres) were established from fetal brain tissues of 15-20 gestation weeks and propagated for over a year in the presence of epidermal growth factor, basic fibroblast growth factor and leukemia inhibitory factor. Neurospheres were differentiated without the presence of above growth factors to follow the development of oligodendroglia. Oligodendroglial progenitors, identified by their bipolar morphology and expression of platelet-derived growth factor receptor-alpha (PDGFRalpha), emerged from spheres as early as 1 DIV; O4+ cells with bipolar to multipolar processes were observed at 3 DIV whereas O1+ multiprocess-bearing oligodendroglia did not appear until 5-7 DIV. They further differentiated to myelin basic protein-expressing oligodendrocytes after 2-3 weeks in culture. Thus, human oligodendroglial maturation in vitro follows the same pathway as rat cells but takes twice as long as their rodent counterparts. Bromodeoxyuridine incorporation indicated that PDGFRalpha-expressing cells but not O4+ oligodendroglia proliferated. More oligodendroglial progenitors incorporated BrdU and more O4+ cells survived when they were in contact with neurons and astrocytes than when they developed beyond the astrocyte layer. In addition, oligodendroglia on astrocytes had a complex process branching whereas those growing beyond astrocyte layer often formed membrane sheaths. Thus the survival, proliferation and maturation of oligodendroglia are influenced by other cell types.

Brain↗