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Biomedical subjects

M Zhou

Publications and source records attributed to M Zhou.

359 records · Page 20Linked to original sources
PubMed1989

Dual role of fibronectin in hematopoietic differentiation.

The adhesive glycoprotein fibronectin provides anchorage for fibroblasts and hematopoietic progenitor cells in vitro. Fibronectin also demonstrates growth factor activity for fibroblasts; however, there is no available information regarding its role as a hematopoietic growth factor. To distinguish growth factor activity of fibronectin from its anchorage activity for hematopoietic progenitors, we assessed the ability of purified human plasma fibronectin to promote human bone marrow erythroid, granulocyte-macrophage (GM) and mixed granulocyte-erythroid-macrophage-megakaryocyte (GEMM) colony formation in liquid suspension, methylcellulose, and fibrin clots under serum-free conditions. Addition of fibronectin to methylcellulose cultures, or to cultures formed in fibrin clots, using fibrinogen depleted of fibronectin by preadsorption over gelatin-Sepharose and clotted with thrombin, resulted in up to a twofold enhancement of proliferation of erythroid burst-forming units (BFU-E), erythroid colony-forming units (CFU-E), and CFU-GEMM. This effect was concentration-dependent up to a fibronectin supplement of 100 micrograms/mL. By contrast, CFU-GM proliferation was not affected by the addition of fibronectin to the cultures. Fibronectin-adherent marrow cells overlaid with liquid medium formed both early and late-appearing erythroid colonies, whereas similarly cultured plastic-adherent marrow cells did not. Erythroid colony formation was observed in cultures of fibronectin-adherent marrow cells overlaid with methylcellulose but not in cultures of plastic-adherent marrow cells under the same conditions. Finally, the erythroid growth-promoting activity of fibronectin was inhibited by arginyl-glycyl-aspartyl-serine (RGDS), a tetrapeptide that competitively blocks the interaction of fibronectin with its receptor. We conclude that fibronectin plays a dual role in hematopoiesis: providing (a) anchorage for erythroid and primitive progenitors, and (b) as a proliferative stimulus for these hematopoietic cells. Both activities may be mediated by the cell adhesion domain of the molecule.

Adult↗
PubMedDate not supplied

HPLC method for the determination of paeoniflorin in Paeonia Lactiflare Pall and its preparations.

An HPLC method was described for the determination of Paeoniflorin in Paeonia Lactiflare Pall and its set prescription preparations, Paeoniflorin was separated on an ODS column with a mobile phase of methanol-tetrahydrofuran-water (17:3:80, v/v/v) and detected at 230 nm. The result was calculated by external standard method. The recovery of Paeoniflorin in Paeonia Lactiflare Pall is 96.2% with relative standard deviation of 0.76%.

Benzoates↗
PubMedDate not supplied

NMR T2 distributions and two phase flow simulations from x-ray micro-tomography images of sandstones.

The distribution of fluids in the pore space of a series of sandstones is calculated as a function of capillary pressure using a two phase flow simulation model. The pore space is represented by a system of channels and nodes which are derived from x-ray micro-tomography images of sandstones. The sandstones studied varied in permeability from approximately 40 to 3,000 mD. The simulation results illustrate the significance of the pore level by-pass phenomena in controlling the location of fluids within the pore structure. The implications of these results on the interpretation of NMR T(2) distributions to determine the irreducible water saturation are discussed.

Computer Simulation↗
PubMedDate not supplied

Internal magnetic gradient fields in glass bead packs from numerical simulations and constant time diffusion spin echo measurements.

Internal magnetic field gradients in water saturated glass bead packs were studied by numerical simulations and a constant time spin echo (CTSE) experiment. The CTSE is comprised of two spin echo refocusing periods where each of the two evolution periods, tau1 and tau2, is varied so that the total evolution, 2(tau1 + tau2), is held constant. The experiment is similar to that introduced by Norwood and Quilter and allows the effects of dephasing due to diffusion in a magnetic field gradient to be separated from other relaxation mechanisms. In our experiments, the magnetic susceptibility difference between the pore fluid and glass beads creates the internal field gradient. CTSE measurements were performed at 7 T (300 MHz 1H) for water saturated in 50 microm diameter glass bead pack. We find that the internal gradients in the center of the pore bodies, where free diffusion applies, is in the range of 10 to 100 G/cm. This fluid volume accounts for < or =10% of the total pore volume. From direct numerical simulations of the internal magnetic field based on a first principles calculation, we find that the major fraction, >90%, of the pore volume has internal gradients of order 500 to 5,000 G/cm. Signals from water in these large gradients is not observed in our CTSE measurements.

Glass↗
PubMedDate not supplied

125I labelling of human serum albumin and fibrinogen and a study of protein adsorption properties on the surface of titanium oxide film.

In order to detect the surface concentration of proteins adsorbed on a solid surface for selecting blood compatible materials, a gentle iodination reagent, Iodogen, was used to label human serum albumin and fibrinogen, and has been applied to the study of protein adsorption properties on a plate of titanium oxide film. The yields of the labelled albumin and fibrinogen are 69.7% and 49.6%. The results of adsorption show that [125I]HSA and [125I]HFG are efficacious at the surface concentration detection and can be used to investigate the protein adsorption properties of a solid material.

Adsorption↗
PubMedDate not supplied

Polymorphisms in glutathione S-transferases in French vinyl chloride workers.

The authors have recently demonstrated a significant gene-environment interaction between vinyl chloride exposure and polymorphisms in the DNA repair protein XRCC1 on the occurrence of mutant p53 biomarkers of vinyl chloride-induced genetic damage. The aim of this study was to examine the polymorphisms in the glutathione S-transferases (GSTs) as potential modifiers of this relationship, since these enzymes may be involved in the phase II metabolism of the reactive intermediates of vinyl chloride. A cohort of 211 French vinyl chloride workers was genotyped for common polymorphisms in GSTM1, GSTT1 and GSTP1. Although no independent, statistically significant effect of these polymorphisms on the occurrence of the mutant p53 biomarker was found, the null GSTM1 and null GSTT1 polymorphisms were found to interact with the XRCC 1 polymorphism to increase the occurrence of the biomarker such that, for example, workers with at least one variant XRCC1 allele who were null for both GSTM1 and GSTT1 had a significant odds ratio for the biomarker (OR =8.4, 95% CI = 1.3 54.0) compared with workers who were wild-type for all alleles, controlling for potential confounders including cumulative vinyl chloride exposure.

Adult↗
PubMedDate not supplied

Stable patterns of allelic diversity at the Merozoite surface protein-1 locus of Plasmodium falciparum in clinical isolates from southern Vietnam.

The extent of allelic diversity at the Merozoite Surface Protein-1 locus of Plasmodium falciparum (PfMSP-1) was examined in isolates collected from symptomatic patients living in a mesoendemic area in southern Vietnam. The variable blocks 2, 4 and 10 were typed by polymerase chain reaction and 24 PfMSP-1 gene types were defined as unique combinations of allelic types detected in each variable block. Nineteen PfMSP-1 gene types were identified and 182 parasite populations were fully typed among 102 isolates. Forty-eight (47%) patients harbored more than one typed parasite population, and one patient had at least eight genetically distinct subpopulations. As previously shown in the same endemic area, recombination between blocks 4 and 10 was significantly less frequent than expected from random assortment of allelic types. The distribution of PfMSP-1 gene types, however, did not differ significantly from that observed in isolates collected in the same area 17-24 mo before the present study. Furthermore, the prevalence of the most common gene types and the average number of different gene types harbored by the same host did not decrease with age. This argues against the prominence of frequency-dependent immune selection of PfMSP-1 polymorphisms in this parasite population.

Adolescent↗
PubMedDate not supplied

Incidence and clinical significance of CDKN2/MTS1/P16ink4A and MTS2/P15ink4B gene deletions in childhood acute lymphoblastic leukemia.

We have examined the incidence and clinical significance of deletions of two candidate tumor suppressor genes, CDKN2/MTS1/p16ink4A and MTS2/p15ink4B, in pediatric acute lymphoblastic leukemia (ALL). Gene deletion was evaluated in leukemic bone marrow (BM) cells obtained at diagnosis from 105 pediatric ALL patients: 83 with B-cell precursor (BCP-ALL) ALL and 22 with T-ALL. CDKN2/p16 deletion was seen in 23 of the 83 (28%) BCP-ALL and 15 of the 22 (68%) T-ALL cases. A virtually identical pattern of MTS2/p15 deletion was detected in these patients: p15 was deleted in 37 of 38 cases with p16 deletion, and p15 was not deleted in any p16-positive specimens. P16/p15 deletions were significantly related to poor prognosis factors including age under 1 year (P < 0.001), initial white cell counts greater than 50 x 10(9) per liter (P < .001), and T cell phenotype P < .005). Analysis of all 105 patients revealed that the 5-year disease-free survival rate was 68% for patients without p16/p15 deletions and 35% for those with p16/p15 deletions (P < .005). The association between gene deletion at initial diagnosis and unfavorable outcome suggests that loss of these genes is clinically significant and indicates a need for prospective studies of p16/p15 deletion in pediatric ALL patients.

Adolescent↗
PubMedDate not supplied

Cryopreservation of kiwi shoot tips.

In this study, the effect of various factors, including the physiological state of mother-plants and parameters of the encapsulation-dehydration protocol (cryoprotective treatment, freezing protocol) on the regrowth of shoot tips of kiwi in vitro plantlets was studied. The optimal protocol established was the following: shoot tips were sampled on mother-plants after a one month cold-acclimation period at 5 degrees C. For preculture, which was performed at 5 degrees C, encapsulated shoot tips were transferred at 24-hour intervals on solid media with increasing sucrose concentrations, from 0.5 to 1.0M. Beads were then desiccated to 26% moisture content (fresh weight basis), prefrozen from 0 degrees C to -40 degrees C at 0.2 degrees C/min and immersed rapidly in liquid nitrogen. No differences were noted between in vitro plantlets produced from cryopreserved and control shoot tips as regards leaf color, average height, multiplication rate and peroxidase zymogram pattern. Apices of 3 kiwi accessions were frozen using the above protocol with regrowth percentages ranging between 22 and 56%.

Actinidia↗
PubMedDate not supplied

Cryopreservation of axillary buds of grape (Vitis vinifera) in vitro plantlets.

Axillary buds sampled from in vitro plants of four grape varieties could withstand cryopreservation using the encapsulation-dehydration technique. Regrowth percentages ranged between 15 and 40%. Buds were encapsulated in alginate beads containing 0.5M sucrose, precultured at 5 degrees C on media containing daily increasing sucrose concentrations from 0.1 to 1.0M, then desiccated to 21% moisture content (fresh weight basis) and frozen slowly (pre-freezing to -40 degrees C at 0.2 degrees C/min followed by immersion in liquid nitrogen). The physiological state of the in vitro mother-plants and the freezing procedure employed dramatically influenced the results. Regrowth after cryopreservation was achieved only when buds were sampled from mother-plants that had been kept without subculture for 3 to 4 months. An additional one-month period of cold-acclimation of mother-plants at 5 degrees C and a two-step freezing procedure improved growth recovery. The multiplication rate of shoots produced from cryopreserved buds was lower than that of controls during the first subcultures after thawing. However, the rooting ability of control and cryopreserved plantlets became similar from the fourth subculture onwards.

Cryopreservation↗
PubMedDate not supplied

Cryopreservation of apple dormant buds and shoot tips.

Shoot tips excised from apple (Malus domestica Borkh. cv. Golden Delicious) dormant buds immediately before freezing were successfully cryopreserved using three different methods (vitrification, encapsulation-dehydration and two-step freezing). Two-step freezing produced the highest in vitro growth recovery (83%) of cryopreserved shoot tips, followed by vitrification (60%) and encapsulation-dehydration (33%). By contrast, when dormant buds were cryopreserved using the two-step freezing technique, shoot tips excised from buds after rewarming and cultured in vitro displayed only 16% recovery.

Cryopreservation↗
PubMedDate not supplied

Determination of oxyfluorfen herbicide and oxyfluorfen amine residues in garbanzo beans by liquid chromatography.

Oxyfluorfen and oxyfluorfen amine were determined by liquid chromatography (LC) with ultraviolet (UV) and photoconductivity detection (PCD). A simple extraction procedure acceptably recovered both analytes from garbanzo beans over a wide range of fortifications (0.05 to 20 ppm) (83 +/- 4 for oxyfluorfen; 85 +/- 4 for oxyfluorfen amine). Percent recoveries decreased slightly as the fortification level decreased. Both analytes could be determined simultaneously at a concentration greater than 0.2 ppm in garbanzo beans. Detection limits were 3 ng for oxyfluorfen and 100 ng for oxyfluorfen amine using LC/UV, and 12 ng for both oxyfluorfen and oxyfluorfen amine with LC/PCD. Different knitted reaction coils and photoreactors were evaluated. Photoproduct yields and identification were determined by ion chromatography. The LC/PCD method measures oxyfluorfen and oxyfluorfen amine separately and has a shorter analysis time, while the standard method using gas chromatography measures total residues and is more sensitive.

Chromatography, Liquid↗
PubMedDate not supplied

Determination of nabam fungicide in crops by liquid chromatography with postcolumn reaction detection.

The ethylenebisdithiocarbamate (EBDC) fungicide, nabam, was determined in several crop matrixes using liquid chromatography with postcolumn reaction detection. After separation by micellar liquid chromatography, nabam (EBDC sodium salt) was acid hydrolyzed to ethylenediamine and fluorigenically labeled with o-phthalaldehyde-mercaptoethanol (OPA-MERC). Standard curves were linear from the detection limit of ca 1 ng to 1000 ng. Nabam was recovered in high yield (89 plus or minus 7.7%) over a range of concentrations (0.1 to 20 ppm) from fortified samples of papaya, lettuce, cucumber, spinach, and applesauce using a simple extraction method. Efforts to convert the more popular EBDC fungicides, maneb and mancozeb, to nabam are discussed.

Cetylpyridinium↗