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Biomedical subjects

S Zhang

Publications and source records attributed to S Zhang.

At least 73 records · Page 4Linked to original sources
PubMed2004

Investigating implicit knowledge in ontologies with application to the anatomical domain.

Knowledge in biomedical ontologies can be explicitly represented (often by means of semantic relations), but may also be implicit, i.e., embedded in the concept names and inferable from various combinations of semantic relations. This paper investigates implicit knowledge in two ontologies of anatomy: the Foundational Model of Anatomy and GALEN. The methods consist of extracting the knowledge explicitly represented, acquiring the implicit knowledge through augmentation and inference techniques, and identifying the origin of each semantic relation. The number of relations (12 million in FMA and 4.6 million in GALEN), broken down by source, is presented. Major findings include: each technique provides specific relations; and many relations can be generated by more than one technique. The application of these findings to ontology auditing, validation, and maintenance is discussed, as well as the application to ontology integration.

Artificial Intelligence↗
PubMed2003

Formation mechanism of H2Ti3O7 nanotubes.

Formation mechanism of H2Ti3O7 nanotubes by single-step reaction of crystalline TiO2 and NaOH has been investigated via transmission electron microscopy examinations of series specimens with different reaction times and extensive ab initio calculations. It was found that the growth mechanism includes several steps. Crystalline TiO2 reacts with NaOH, forming a highly disordered phase, which recrystallized into some H2Ti3O7 thin plates. H-deficiency on the top surface leads to an asymmetrical environment for the surface Ti3O2-7 layer. The calculations of the surface tension, elastic strain energy, interlayer coupling energy, and Coulomb force indicated that the asymmetrical environment is the principal driving force of the cleavage of the single sheets of H2Ti3O7 from the plates and the formation of the multiwall spiral nanotubes.

Journal Article↗
PubMed2003

Histopathological differences of myotonic dystrophy type 1 (DM1) and PROMM/DM2.

Muscle biopsy findings in DM2 have been reported to be similar to those in DM1. The authors used myosin heavy chain immunohistochemistry and enzyme histochemistry for fiber type differentiation on muscle biopsies. Their results show that DM2 patients display a subpopulation of type 2 nuclear clump and other very small fibers and, hence, preferential type 2 fiber atrophy in contrast to type 1 fiber atrophy in DM1 patients.

Adult↗
PubMed2003

Search for variations of fundamental constants using atomic fountain clocks.

Over five years, we have compared the hyperfine frequencies of 133Cs and 87Rb atoms in their electronic ground state using several laser-cooled 133Cs and 87Rb atomic fountains with an accuracy of approximately 10(-15). These measurements set a stringent upper bound to a possible fractional time variation of the ratio between the two frequencies: d/dt ln([(nu(Rb))/(nu(Cs))]=(0.2+/-7.0)x 10(-16) yr(-1) (1sigma uncertainty). The same limit applies to a possible variation of the quantity (mu(Rb)/mu(Cs))alpha(-0.44), which involves the ratio of nuclear magnetic moments and the fine structure constant.

Journal Article↗
PubMed2003

Matrix metalloproteinases are not involved in early brain edema formation after cardiac arrest in rats.

INTRODUCTION: Resuscitation from cardiac arrest (CA) often results in a poor neurological outcome possibly due to an incomplete understanding of the pathophysiology of brain injury following CA-induced global cerebral ischemia. Brain edema is an important manifestation after CA and is associated with significant morbidity and mortality. The matrix metalloproteinases (MMPs) contribute to brain edema formation following focal cerebral ischemia. The objective of this study was to investigate the role of an MMP inhibitor, GM6001, in CA-elicited brain edema. METHODS: Eighteen rats were subjected to normothermic (37.5 +/- 0.5 degrees C) CA induced by eight minutes of asphyxiation and assigned to a CA-control group (CA), an alcohol-placebo group (CA + ETOH), or a GM6001-treated group (CA + GM6001). GM6001 in 100% alcohol or a vehicle was given i.v. before CA to achieve a whole blood concentration of 10 microM. Animals were resuscitated with CPR, ventilation and epinephrine. Brain edema was determined by brain wet-to-dry weight ratio at one hour after resuscitation. FINDINGS: Brain wet-to-dry weight ratio was 4.86 +/- 0.09 in CA, 4.76 +/- 0.12 in CA + ETOH (p = 0.30 vs. CA), and 4.72 +/- 0.03 in CA + GM6001 (p = 0.17 vs. CA and 0.42 vs. CA + ETOH). INTERPRETATION: MMPs are not involved in brain edema formation one hour following CA.

Animals↗
PubMed2003

Executive dysfunction and avoidant personality trait in myotonic dystrophy type 1 (DM-1) and in proximal myotonic myopathy (PROMM/DM-2).

A previous study in proximal myotonic myopathy (PROMM/DM-2) and myotonic dystrophy type 1 (DM-1) using brain positron emission tomography demonstrated a reduced cerebral blood flow in the frontal and temporal regions associated with cognitive impairment. The objective was to investigate further cognitive and behavioural aspects in a new series of patients with DM-1 and PROMM/DM-2. Nineteen patients with genetically determined PROMM/DM-2 and 21 patients with moderately severe DM-1 underwent neuropsychological testing and neuropsychiatric interviews. DM-1 and PROMM/DM-2 patients had significantly lower scores on tests of frontal lobe function compared to controls. Neuropsychiatric interviews demonstrated an avoidant trait personality disorder in both patient groups. Brain single photon emission computed tomography showed frontal and parieto-occipital hypoperfusion. The results suggest that there is a specific cognitive and behavioural profile in PROMM/DM-2 and in DM-1, and that this profile is associated with hypoperfusion in frontal and parieto-occipital regions of the brain.

Adult↗
PubMed2003

Polymorphisms of the TAP1 and TAP2 genes in human alveolar echinococcosis.

We postulated that TAP genes may influence the susceptibility of some individuals to Echinococcus multilocularis infection. Six coding region variants (codons 333 and 637 in TAP1, and 379, 565, 651 and 665 in TAP2) were typed in 94 patients and 100 controls. Thr/Thr homozygosity at TAP2/665 was more prevalent in patients than in controls [64% vs. 45%, respectively; odds ratio (OR) = 2.1 (95% confidence interval (CI) 1.1; 2.7)] and Thr/Ala heterozygozity was less prevalent (32% vs. 50%, respectively) (P = 0.014). Of the 38 patients with progressive lesions, 76% were Thr/Thr, as compared with 55% of patients without progressive lesions and 45% of controls (P = 0.058 and 0.02, respectively), independent of HLA status. To determine whether this association is functionally relevant, functional analyses and/or confirmation in distinct populations of patients with alveolar echinococcosis would be required.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

Extra small virus-like particles (XSV) and nodavirus associated with whitish muscle disease in the giant freshwater prawn, Macrobrachium rosenbergii.

A disease of Macrobrachium rosenbergii, the giant freshwater prawn, farmed in China was recently recorded in Zhejiang, Jiangsu, Shanghai, Guangxi and Guangdong provinces. The clinical sign of the disease, which develops in post-larvae (PL), is a whitish appearance of the muscles, particularly noticeable in the abdomen. Mortalities may reach 100% in some hatcheries. Investigations by transmission electron microscopy after negative staining of diseased PL homogenates showed the presence of two types of viral particles: one, unenveloped, icosahedral in shape, 26-27 nm in diameter, the second, much smaller, about 14-16 nm in diameter, designated extra small virus particle (XSV). The large virus has a genome with two pieces of ssRNA (RNA-1 and RNA-2), of 3 and 1.2 kb, respectively. Hybridization tests confirmed that this large virus is closely related to M. rosenbergii nodavirus (MrNV) which was isolated from diseased prawns in a hatchery in the French West Indies. Its very small size and hypothesized biochemical and biological characteristics suggest XSV is a new type of crustacean virus. As XSV has always been found associated with the larger virus (nodavirus) and is located in muscle and connective cells of diseased animals, it could be an autonomous virus, a helper-type virus or a satellite-like virus.

Animals↗
PubMed2003

Immobilized MICA could expand human Vdelta1 gammadelta T cells in vitro that displayed major histocompatibility complex class I chain-related A-dependent cytotoxicity to human epithelial carcinomas.

Human major histocompatibility complex class I chain-related A (MICA) is a human leucocyte antigen-related polymorphic molecule, which is expressed on many kinds of epithelial tumours and can be recognized by the Vdelta1 subset of gammadelta T cells. In the present study, monoclonal antibodies (MoAbs) were produced in mice immunized with recombinant MICA (rMICA)*008. It was found that MICA was expressed on ovarian and colonic tumour tissues and could be detected by these anti-MICA MoAbs. The immobilized rMICA could induce the proliferation of human ovarian epithelial carcinoma- or colonic carcinoma-derived gammadelta T cells of the Vdelta1 phenotype in vitro. These Vdelta1 T cells displayed a strong, broad-range cytolytic activity towards tumour cell lines positive for MICA. The efficiency of this cytolytic activity depended greatly on the level of MICA expressed on the cell surface and could be inhibited by anti-MICA MoAbs. Therefore, MICA may play an important role in immune responses against epithelial tumours and function as a stimulating factor for the growth of Vdelta1 gammadelta T cells, whereas MICA-reactive Vdelta1 gammadelta T cells might serve as a new candidate for adoptive cellular therapy of tumours.

Adult↗
PubMed2003

Qualitative semi-parametric test for genetic associations in case-control designs under structured populations.

Recently, statistical methods have been proposed using genomic markers to control for population stratification in genetic association studies. However, these methods either have unacceptable low power when population stratification becomes strong or cannot control for population stratification well under admixture population models. In this paper, we propose a semiparametric association test to detect genetic association between a candidate marker and a qualitative trait of interest in case-control designs. The performance of the test is compared to other existing methods through simulations. The results show that our method gives correct type I error rate both under discrete population models and admixture population models, and our method is robust to the extent of the population stratification. In most of the cases we considered, our method has higher power and, in some cases, substantially higher power than that of existing methods.

Case-Control Studies↗
PubMed2003

The effect of amount of crude oil on extent of its biodegradation in open water- and sandy beach-laboratory simulations.

We examined the biodegradation of varying amounts of artificially weathered Alaskan North Slope crude oil in laboratory microcosm test systems that use natural seawater and simulate spills in open water and on sandy beaches. The model bioremediation treatment consisted of periodic applications of marine bacteria, selected to degrade n-alkanes and a range of aromatic compounds, suspended in a salts solution that supplied inorganic nitrogen and phosphorous. Beach microcosms dosed with low and high oiling lost an average of 22.5% and 11.3% oil weight, respectively. Open-water microcosms dosed with high and low oiling lost 19.1% and 2.9% oil weight, respectively. Thus, the lower doses of oil were more efficiently degraded. The model bioremediation treatment also affected a greater number of selected analytical endpoints in the lower-oil-dose than higher-dose experiments and the former showed more substantial degradation of recalcitrant components. Above a certain threshold oil concentration, bioremediation did not effectively remove oil. Below this threshold the distinction between active bioremediation treatment and intrinsic biodegradation of the controls was less prominent; i.e., fewer of the oil components were statistically depleted by remediation treatment relative to controls. Furthermore, the oil-dose range over which bioremediation was realized in these systems occurred at very low oiling levels. Thus, under the environmental conditions simulated in these microcosms, the effectiveness of bioremediation peaked over a rather narrow low-dose oiling range.

Biodegradation, Environmental↗
PubMed2003

Investigations of 99mTc morpholino pretargeting in mice.

This laboratory is exploring the use of morpholinos (MORFs), synthetic DNA analogues, for nuclear medicine applications, including pretargeting. The anti-CEA antibody MN14 was conjugated with an 18 mer MORF and with diethylenetriaminepentaacetic acid (DTPA) for 111In labelling. In a dual label pretargeting study, tumour-bearing nude mice received different doses of (MN14-DTPA-111In+MN14-MORF) followed, at various times after i.v. injection, by 0.15 microg complementary MORF (cMORF) radiolabelled with 99mTc via MAG(3). Animals were killed 3 h thereafter and tissues were counted for both radionuclides. The 99mTc-cMORF was also administered to tumour bearing mice that, 2 days previously, had received different doses of unlabelled MN14-MORF IgG or, as control, unlabelled Sandoglobulin IgG-MORF (Sandoz-MORF). Tumour uptake was higher at all time points for the labelled antibody itself versus labelled cMORF (8-10 vs 1.3-2.3%ID/g, respectively) in part due to the rapid clearance of cMORF through the kidneys. However, target to non-target ratios were superior for pretargeting at all time points and in all tissue except blood and kidneys. By pretargeting alone, these ratios were highest in all tissues for 15 microg compared to higher MN14-MORF dosages and in all cases were superior to that of the Sandoz-MORF control. The superior target to non-target ratios for pretargeting can be partially explained through calculations based on both radiolabels: after 24 h, only 0-6% of MORF on MN14 was bound by 99mTc-cMORF in liver and spleen suggesting that the antibody is sequestered in these organs and 'invisible' to labelled MORF. Fortunately, this was not the case in tumours in which 50-60% was bound. It is concluded that pretargeting using MORFs provided encouraging results in one mouse model/anti-tumour antibody system. The advantages of pretargeting in this model were evident in the superior target to non-target ratios obtained over conventional imaging.

Animals↗
PubMed2003

The relative health related quality of life of veterans with Parkinson's disease.

OBJECTIVES: To use databases of the US Veterans Health Administration (VHA) to describe the impact of Parkinson's disease on health related quality of life (HRQoL) of veterans; to compare the HRQoL of veterans with Parkinson's disease with that of veterans reporting eight other neurological or chronic conditions; and to estimate the unique effect of Parkinson's disease on HRQoL. METHODS: Respondents to the VHA 1999 large national health survey of veteran enrollees with a diagnosis of Parkinson's disease in VHA treatment files for the fiscal years 1997-1999 were identified by merging databases. The survey incorporated the Veterans SF-36, a well validated generic measure of HRQoL and functional status. This was used to compare patient groups. Mean physical (PCS) and mental (MCS) component summary scores were calculated for Parkinson's disease and eight other diseases by multivariable regressions that adjusted for age, sex, race, education, and 15 mental and physical co-morbid conditions that were self reported in the survey. RESULTS: Of 887 775 survey respondents, 14 530 (1.64%) had a Parkinson's disease diagnosis. Controlling for sociodemographic factors and co-morbidities, veterans with Parkinson's disease had PCS and MCS below veterans with angina/coronary heart disease, arthritis, chronic low back pain, congestive heart failure, diabetes, and stroke. Veterans with spinal cord injury reported slightly lower PCS than veterans with Parkinson's disease (32.38 v 32.72; 0.03 of 1 SD). Veterans with depression reported markedly lower MCS than veterans with Parkinson's disease (35.94 v 41.48; 0.55 of 1 SD). The unique effect of having Parkinson's disease on HRQoL was to lower PCS and MCS by 4.10 and 3.42 points (0.41 and 0.34 of 1 SD), respectively. CONCLUSIONS: The analysis quantifies the negative impact of Parkinson's disease on HRQoL, after controlling for sociodemographic factors and co-morbidities. Compared with eight other chronic conditions, Parkinson's disease imposes a relatively heavy burden on US veterans in the VHA health care system.

Aged↗
PubMed2003

Stripe instability in thin films of smectic liquid-crystal polymers.

Two-dimensional nanostripes are formed in thin films of side-chain liquid-crystalline polymer films when the material enters the smectic phase. The structure is investigated using transmission electron microscopy. Electron diffraction patterns show that the chain molecules are mostly aligned in the film plane and the average molecular director is parallel to the direction of the stripes. We discuss factors affecting the stripe amplitude and periodicity, such as the film thickness and the temperature of annealing in the nematic phase, and suggest a possible mechanism for their formation. We propose that an equilibrium instability occurs due to a competition between the layer-aligning effect of the substrate and the planar director alignment, forcing smectic layers perpendicular to the film surface. The stripes decorate the overall patterns of nematic director in the polymer film and provide a means of high-resolution imaging for observation of textures and disclinations.

Journal Article↗
PubMed2003

Fertility in male sheep: modulators of the acute effects of nutrition on the reproductive axis of male sheep.

Animals adjust the time of year that they reproduce through their ability to perceive and respond to critical aspects of their environment, such as photoperiod, nutrition or the socio-sexual milieu, and their genotype determines the degree of response to each stimulus. Ultimately, information from environmental cues filters through to the GnRH neurones in the brain which are the primary regulator of fertility. Each of these cues has been studied in isolation and the mechanisms by which they affect GnRH secretion are now better, if not fully, understood. In the field, the brain centres that control GnRH must integrate information from all cues at any given time before 'formulating a reproductive decision'. In this review, the effect of this integration is illustrated by showing how the acute GnRH response to a nutritional signal can be modulated by genotype, photoperiod and social cues, to the point of being completely blocked under some circumstances. Candidate pathways that may mediate these modulatory effects at both the whole body and brain have been proposed, although none of these pathways are confirmed and some have not yet been studied. As a guide for further research, we propose a working model that integrates the inputs and explains the interactions between them.

Animal Nutritional Physiological Phenomena↗
PubMed2002

Expression of green fluorescent protein and its inheritance in transgenic oat plants generated from shoot meristematic cultures.

The expression of green fluorescent protein (GFP) and its inheritance were studied in transgenic oat ( Avena sativa L.) plants transformed with a synthetic green fluorescent protein gene [sgfp(S65T)] driven by a rice actin promoter. In vitro shoot meristematic cultures (SMCs) induced from shoot apices of germinating mature seeds of a commercial oat cultivar, Garry, were used as a transformation target. Proliferating SMCs were bombarded with a mixture of plasmids containing the sgfp(S65T) gene and one of three selectable marker genes, phosphinothricin acetyltransferase (bar), hygromycin phosphotransferase (hpt) and neomycin phosphotransferase (nptII). Cultures were selected with bialaphos, hygromycin B and geneticin (G418), respectively, to identify transgenic tissues. From 289 individual explants bombarded with the sgfp(S65T) gene and one of the three selectable marker genes, 23 independent transgenic events were obtained, giving a 8.0% transformation frequency. All 23 transgenic events were regenerable, and 64% produced fertile plants. Strong GFP expression driven by the rice actin promoter was observed in a variety of tissues of the T(0) plants and their progeny in 13 out of 23 independent transgenic lines. Stable GFP expression was observed in T(2) progeny from five independent GFP-expressing lines tested, and homozygous plants from two lines were obtained. Transgene silencing was observed in T(0) plants and their progeny of some transgenic lines.

Avena↗
PubMed2002

The structure of trititanate nanotubes.

A comprehensive chemical and structural analysis is made of a new type of trititanate nanotube, which is synthesized via the reaction of TiO(2) particles with NaOH aqueous solution. It is found that the trititanate nanotubes are multi-walled scroll nanotubes with an inter-shell spacing of about 0.78 nm and an average diameter of about 9 nm. An atomic model of the nanotube is derived based on information from powder X-ray diffraction, selective-area electron diffraction, high-resolution electron microscopy and structure simulations. A model nanotube may be constructed by wrapping a (100) sheet of H(2)Ti(3)O(7) along [001] with the tube axis parallel to [010].

Journal Article↗