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Biomedical subjects

Z Liu

Publications and source records attributed to Z Liu.

At least 91 records · Page 5Linked to original sources
PubMed2004

Micturition-related neuronal firing in the periaqueductal gray area in cats.

The midbrain periaqueductal gray (PAG) is the area promoting emotional motor responses, reproductive behaviors and analgesia. Recent studies suggest that neurons in the PAG may be crucial for regulating the micturition reflex in both experimental animals and humans. We examined single neuronal activities in the PAG and the adjacent area in response to isovolumetric spontaneous micturition reflexes in 20 supracollicular decerebrated cats. In total, 84 neurons were recorded in the PAG that were related to urinary storage/micturition cycles. Of the neurons recorded, the most common were tonic storage neurons (43%), followed by tonic micturition neurons (29%), phasic storage neurons (15%) and phasic micturition neurons (13%). In addition to the tonic/phasic as well as storage/micturition classification, the neurons showed diverse discharge patterns: augmenting, constant and decrementing, with the constant discharge pattern being most common. Of the 16 neurons located within the PAG that had similar discharge patterns to those just ventral to the PAG, the micturition neurons were distributed in a broader area, whereas the storage neurons seemed to be concentrated in the middle part of the PAG (P0-1, Horsley-Clarke coordinate). High-frequency stimulation (HFS; 0.2-ms duration, 100 Hz) applied in the PAG elicited inhibition of the micturition reflex. Effective amplitude of the electrical stimulation for evoking inhibitory responses was less than 50 microA. In conclusion, the results of the present study showed that HFS of the PAG inhibited the micturition reflex and there were micturition-related neuronal firings in the PAG in cats, suggesting that the PAG is involved in neural control of micturition.

Action Potentials↗
PubMed2004

Synthesis and evaluation of a thymidine analog for positron emission tomography study of tumor DNA proliferation in vivo.

This study describes the synthesis, radiolabelling and biological evaluation of 5-(2,4-difluoro-5-[18F]fluoromethyl-phenyl)-2-hydroxymethyl-tetrahydrofuran-3-ol, 13. Radiolabelling was achieved by reaction of the tosylate 3 with K[18F] in the presence of Kryptofix 222. Good stability in saline and serum solutions at physiological temperatures in vitro was observed. A cell incorporation study of 13 using SW1222 tumor cells showed a linear uptake, unfortunately, in vivo studies indicated that 13 was undergoing defluorination. Rapid defluorination of the radiotracer was confirmed by an in vitro stability study in blood plasma. Finally, a comparison between the DNA uptake of 13 and tritiated thymidine was performed in vitro to asses the potential utility of more stable analogs. These studies showed that 13 and its analogs are unsuitable as potential tracers to image DNA proliferation and highlighted the difficulty in predicting the in vivo stability of novel radiotracers.

Animals↗
PubMed2004

Identification of multiple genetic loci that regulate adenovirus gene therapy.

A key aspect of the immune response to adenovirus (Ad) gene therapy is the generation of a cytotoxic T-cell (CTL) response. To better understand the genetic network underlying these events, 20 strains of C57BL/6 x DBA/2 (BXD) recombinant inbred (RI) mice were administered with AdLacZ and analyzed at days 7, 21, 30, and 50 for liver beta-galactosidase (LacZ) expression and CTL response. Sera levels of interferon gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) were analyzed at different times after AdLacZ. There was a distinct strain-dependent expression of LacZ, which was strongly correlated with the CTL response. Among the five BXD RI strains that exhibited significantly prolonged LacZ expression, four also exhibited a marked defect in the production of Ad-specific CTL. There was a strong correlation between the sera levels of IFN-gamma, TNF-alpha, and IL-6, but cytokine responses were not significantly correlated with LacZ expression or the CTL response. Quantitative trait loci regulating LacZ on day 30 were found on chromosome (Chr) 19 (33 cM) and Chr 15 (42.8 cM). Cytotoxicity mapped to Chr 7 (41.0 and 57.4-65.2 cM), Chr 15 (61.7 cM), and Chr X (27.8 cM). IFN-gamma production mapped to Chr 18 (22, 27, and 32 cM) and Chr 11 (64.0 cM). TNF-alpha and IL-6 production mapped to Chr 6 (91.5 cM) Chr 9 (42.0 cM) and Chr 8 (52 and 73.0 cM). These results indicate that different strains of mice exhibit different pathways for effective clearance of AdLacZ depending on genetic polymorphisms and interactions at multiple genetic loci.

Adenoviridae↗
PubMed2004

Further evidence for paternal inheritance of mitochondrial DNA in the sheep (Ovis aries).

The mitochondrial DNA of 172 sheep from 48 families were typed by using PCR-RFLP, direct amplification of the repeated sequence domain and sequencing analysis. The mitochondrial DNA from three lambs in two half-sib families were found to show paternal inheritance. Our findings provide direct evidence of paternal inheritance of mitochondria DNA in sheep. A total of 12 highly polymorphic microsatellite markers, which mapped on different chromosomes, were employed to type the sheep population to confirm family relationships. Possible mechanisms of paternal inheritance are discussed.

Animals↗
PubMed2004

Baseline Na-Li countertransport and risk of hypertension in children: a 10-year prospective study in Hanzhong children.

Sodium-lithium countertransport (Na-Li CT) is associated with blood pressure (BP) and in many cross-sectional investigations and some longitudinal studies, essential hypertension has been proposed as a biochemical marker or predictor of hypertension risk in adults. The present study investigated prospectively whether baseline Na-Li CT rate was an index of increased risk of future development of hypertension in children. At baseline visit in 1987 of the Hanzhong Children Hypertension Study comprising 4000 school children aged 5-6 years old, 310 samples were randomly selected for measurement of baseline Na-Li CT rate; we made a 10-year follow-up of them in the same season in 1997. This cohort of children is the sample for analysis in the present report. Baseline Na-Li CT rate was positively correlated to systolic BP (SBP) both in baseline and follow-up (baseline, gamma=0.21, P<0.05; follow-up, gamma=0.32, P<0.01), and positively correlated to diastolic BP (DBP) (gamma=0.20, P<0.05) and body mass index (gamma=0.18, P<0.05) in follow-up examination. Longitudinal analysis of 10-year BP evolution, children in higher baseline Na-Li CT (ie, >260 micromoll RBC/h) had greater BP change than children in lower baseline Na-Li CT (ie, </=260 mumol/l RBC/h) (SBP, 15.8+/-12.9 vs 19.3+/-13.1, DBP 8.8+/-11.2 and 11.3+/-10.6, P<0.05). Multiple logistic regression analysis showed that children in the higher Na-Li CT (>260 mumol/l RBC/h) were associated with approximately 1.5 times greater risk of high BP) in comparison to placement in lower Na-Li CT (</=260 mumol/l RBC/h). Elevated baeline RBC Na-Li countertransport could be a risk predictor predisposing to the development of hypertension in children.

Antiporters↗
PubMed2004

Estimation of bioavailability of DL-methionine hydroxy analogue relative to DL-methionine in layers with exponential and slope-ratio models.

An experiment was conducted using molted hens to estimate the bioavailability of DL-methionine hydroxy analogue-free acid (MHA-FA) relative to DL-methionine (DLM). In this experiment, 5 supplemental levels (0.012, 0.024, 0.036, 0.048, and 0.060%) of DLM or equimolar concentrations of MHA-FA were added to a basal diet containing 14.97% protein and 0.27% methionine. The low protein diet was used to increase the sensitivity of laying hens to methionine deficiency. Feed consumption, egg production, egg mass, and egg weight increased (P < 0.05), and feed conversion decreased (P < 0.05) when DLM or MHA-FA was added to the basal diet for some supplemental methionine levels. There was no difference (P > 0.05) in feed consumption between hens fed DLM and hens fed MHA-FA. Regression analysis showed that the bioavailability of MHA-FA relative to DLM on a molar basis was 88.7% (egg production), 88.0% (egg mass), and 84.6% (egg weight) with the exponential model, and was 89.7% (egg production), 89.6% (egg mass), and 86.8% (egg weight) with the slope-ratio model. The average bioavailability of MHA-FA relative to DLM was 88% on a molar basis.

Animal Feed↗
PubMed2004

Identification of mariner elements from house flies (Musca domestica) and German cockroaches (Blattella germanica).

Full-length mariner elements were isolated and sequenced from house flies (Musca domestica) and German cockroaches (Blattella germanica). The amino acid sequence of the house fly mariner element (accession number: AF373028) showed 99.5% identity with Mos1 and peach elements, whereas the German cockroach mariner element (accession number: AF355143) showed 98.8% and 99.8% identity, respectively. Sequence analysis revealed that the mariner elements in house flies and German cockroaches differed from the active Mos1 mariner element by seven and 15 nucleotides, respectively. Four essential nucleotide substitutions at positions 64, 154, 305, and 1203, which have been proposed to contribute to the loss of activity of the inactive elements, were detected in the German cockroach mariner element. In contrast, although the mariner element in house flies contained substitutions at positions 64, 154, and 305, it retained T at position 1203, identical to active mariner elements. Mariner is present in approximately eight copies in the German cockroach genome.

Amino Acid Sequence↗
PubMed2004

Involvement of interleukin 18 in Crohn's disease: evidence from in vitro analysis of human gut inflammatory cells and from experimental colitis models.

An imbalance of immunoregulatory factors and/or cells contributes to uncontrolled mucosal T cell activation and inflammation in Crohn's disease (CD). Bioactive interleukin (IL)-18 has been shown to be produced by macrophages in CD lesions. We report here that T cells freshly isolated from inflamed tissue of CD patients (and not T cells from control intestinal tissue) were responsive to IL-18. In the presence of IL-18, these T cells produced more interferon (IFN)-gamma and less IL-10. To analyse further the role of IL-18 in this disease, an acute and a chronic model of murine colitis were used. IL-18 mRNA was significantly enhanced in trinitrobenzene sulphonic acid (TNBS) induced colitis, and treatment with IL-18 binding protein (IL-18BPa), which neutralizes IL-18 bioactivity, significantly reduced the severity of colitis. However, IL-18BPa did not affect the course of chronic colitis in CD45RBhighCD4+ T cell reconstituted SCID mice. Production of IFN-gamma in lamina propria mononuclear cell cultures from IL-18BPa-treated SCID mice was decreased, but at the same time fewer lamina propria CD4+ T cells harvested from IL-18BPa-treated mice compared to non-treated mice were in apoptosis. We conclude that IL-18 clearly has a modulatory role in the inflammatory cascade of CD and experimental colitis by affecting IFN-gamma and IL-10 production, and apoptosis. In view of the divergent effects of IL-18 neutralization in the two different murine colitis models, it is unlikely that IL-18 is at the top of this cascade.

Adult↗
PubMed2004

Confocal laser scanning microscopy - an attractive tool for studying the uptake of xenobiotics into plant foliage.

The application of confocal laser scanning microscopy (CLSM) to the study of xenobiotic uptake into plant foliage is explored in this paper. Three fluorescent dyes of low molecular weight and contrasting polarities (hydrophilic, moderately lipophilic and lipophilic) were selected to represent foliage-applied pesticides. These model compounds were applied as droplets to the surfaces of various leaves and/or fruits according to the particular experiment. The transcuticular diffusion behaviour, the compartmentation into epidermal cells and the influence of a surfactant on the uptake of these fluorescent compounds were visualized by CLSM. Distinct differences in diffusion speed across the cuticle and distribution in cell compartments were found between different fluorescent compounds. The presence of a surfactant significantly accelerated the uptake of the moderately lipophilic dye into both thin- and thick-cuticled leaves. The results are discussed in relation to the current knowledge on pesticide uptake and translocation. The advantages and limitations of this technique are highlighted.

Fluorescent Dyes↗
PubMed2004

Identification of a novel HLA-DPB1 allele--DPB1*0102.

In this report, we describe the identification of a novel HLA-DPB1 allele, DPB1*0102, which was first found in a 27-year-old woman and was later detected again in another person, from the Han population of China. According to the nucleotide alignment, DPB1*0102 was the most similar to DPB1*0202, with only one nucleotide substitution from A to G at position 192 among three closely related alleles--DPB1*0202, DPB1*2401 and DPB1*0501. This substitution was a non-synonymous one, which caused a change of amino acid from E to K at codon 69 of DP beta-chain in the mature protein.

Adult↗
PubMed2004

Characterization of a novel HLA-DQB1 allele, DQB1*020102.

A novel human leukocyte antigen (HLA)-DQB1 allele, DQB1*020102, was detected in a 28-year-old woman of Han ethnic in Guangzhou, China. Compared with HLA-DQB1*020101 and HLA-DQB1*0202, they differed in only one nucleotide at the position 167 (C to T) of exon 2, which was a highly conserved position. This is a synonymous mutation, which does not cause any change in the amino acid sequence of mature protein.

Base Sequence↗
PubMed2004

Structural features and hypoglycaemic activity of an exopolysaccharide produced by Sorangium cellulosum.

AIMS: To investigate the structural features and hypoglycaemic activity of an exopolysaccharide (EPS) produced by Sorangium cellulosum NUST06. METHODS AND RESULTS: The chemical structure of the EPS from S. cellulosum NUST06 was determined by gas-liquid chromatography, gas chromatography (GC), GC-mass spectrometry and nuclear magnetic resonance. The EPS was composed of a beta-D-(1-->4)-glucose backbone with alpha-D-(1-->6)-mannose side chains. The molecular weight of the EPS was approx. 2x10(5) Da. Healthy and alloxan-induced diabetic mice were used in the study. Blood glucose levels of the experimental animals during the trial period were analysed by a glucose test kit based on the glucose oxidase method. When 100 and 200 mg kg(-1) day(-1) of purified EPS was orally administered for 7 days, the serum glucose in alloxan-induced diabetic mice was reduced by 35.9 and 41.4% (P<0.01), and the serum glucose in healthy mice was reduced by 27.3 and 30.1% (P<0.05), respectively. CONCLUSIONS: The EPS produced by S. cellulosum NUST06 decreased blood glucose levels distinctly in both healthy and alloxan-induced diabetic mice. SIGNIFICANCE AND IMPACT OF THE STUDY: To elucidated the chemical structure of the EPS from S. cellulosum NUST06 and exploited the anti-diabetic potential of the EPS.

Animals↗
PubMed2004

Isolating Mortierella alpina strains of high yield of arachidonic acid.

AIMS: To develop a fast isolation method for arachidonic acid-producing fungi of high yield. METHODS AND RESULTS: Relation between the staining degree of mycelia of Mortierella alpina stained with triphenyltetrazolium chloride (TTC) and arachidonic acid content in the fungal lipids was investigated. Results showed that staining degree of mycelia stained with TTC increased when arachidonic acid content in mycelia lipids increased. This finding was used to isolate strains of high arachidonic acid yield. Arachidonic acid producing fungi were selectively isolated from soil at a low temperature of 4 degrees C and the mycelia of these isolates were stained with TTC. CONCLUSIONS: The strain M. alpina M6 that had the highest staining degree had the highest arachidonic acid content (72.3%). The yield of arachidonic acid in this strain reached 4.82 g l(-1). SIGNIFICANCE AND IMPACT OF THE STUDY: A fast and effective method to isolate strains of high arachidonic acid yield was established according to the finding that staining degree of mycelia of M. alpina was positively correlated with arachidonic acid content in mycelia lipid.

Arachidonic Acid↗
PubMed2004

Derivation and calculation of approximate reliabilities and daughter yield-deviations of a random regression test-day model for genetic evaluation of dairy cattle.

Test-day milk, fat, protein yield, and somatic cell score (SCS) were analyzed separately using data from the first 3 lactations and a random regression model. Data used in the model were from Austria, Germany, and Luxembourg and from Holstein, Red, and Jersey dairy cattle. For reliability approximation, a multiple-trait effective daughter contribution (MTEDC) method was developed under general multiple trait models, including random regression test-day models, by extending the single-trait daughter equivalents concept. The MTEDC was applied to the very large dairy population, with about 15.5 million animals. The calculation of reliabilities required less computer memory than the corresponding iteration program and a significantly lower computing time equivalent to 24 rounds of iteration. A formula for daughter-yield deviations was derived for bulls under multiple-trait models. Reliability associated with daughter-yield deviations was approximated using the MTEDC method. Both the daughter-yield deviation formula and associated reliability method were verified in a simulation study using the random regression test-day model. Correlations of lactation daughter-yield deviations with estimated breeding values calculated from a routine genetic evaluation were 0.996 for all bulls and 0.95 for young bulls having only daughters with short lactations.

Analysis of Variance↗
PubMed2003

Role of taurine supplementation to prevent exercise-induced oxidative stress in healthy young men.

To evaluate the protective effects of taurine supplementation on exercise-induced oxidative stress and exercise performance, eleven men aged 18-20 years were selected to participate in two identical bicycle ergometer exercises until exhaustion. Single cell gel assay (SCG assay) was used to study DNA damage in white blood cells (WBC). Pre-supplementation of taurine, a significant negative correlation was found between plasma taurine concentration before exercise and plasma thiobaribituric-acid reactive substance (TBARS) 6 hr after exercise (r = -0.642, p<0.05). WBC showed a significant increase in DNA strand breakage 6 hr and 24 hr after exercise. Seven-day taurine supplementation reduced serum TBARS before exercise ( p<0.05) and resulted in a significantly reduced DNA migration 24 hr after exercise ( p<0.01). Significant increases were also found in VO(2)max, exercise time to exhaustion and maximal workload in test with taurine supplementation ( p<0.05). After supplementation, the change in taurine concentration showed positive correlations with the changes in exercise time to exhaustion and maximal workload. The results suggest that taurine may attenuate exercise-induced DNA damage and enhance the capacity of exercise due to its cellular protective properties.

Adolescent↗
PubMed2003

Analysis of HMW glutenin subunits and their coding sequences in two diploid Aegilops species.

Considerable progress has been made in understanding the structure, function and genetic regulation of high-molecular-weight (HMW) glutenin subunits in hexaploid wheat. In contrast, less is known about these types of proteins in wheat related species. In this paper, we report the analysis of HMW glutenin subunits and their coding sequences in two diploid Aegilops species, Aegilops umbellulata (UU) and Aegilops caudata (CC). SDS-PAGE analysis demonstrated that, for each of the four Ae. umbellulata accessions, there were two HMW glutenin subunits (designated here as 1Ux and 1Uy) with electrophoretic mobilities comparable to those of the x- and y-type subunits encoded by the Glu-D1 locus, respectively. In our previous study involving multiple accessions of Ae. caudata, two HMW glutenin subunits (designated as 1Cx and 1Cy) with electrophoretic mobilities similar to those of the subunits controlled by the Glu-D1 locus were also detected. These results indicate that the U genome of Ae. umbellulata and the C genome of Ae. caudata encode HMW glutenin subunits that may be structurally similar to those specified by the D genome. The complete open reading frames (ORFs) coding for x- and y-type HMW glutenin subunits in the two diploid species were cloned and sequenced. Analysis of deduced amino acid sequences revealed that the primary structures of the x- and y-type HMW glutenin subunits of the two Aegilops species were similar to those of previously published HMW glutenin subunits. Bacterial expression of modified ORFs, in which the coding sequence for the signal peptide was removed, gave rise to proteins with electrophoretic mobilities identical to those of HMW glutenin subunits extracted from seeds, indicating that upon seed maturation the signal peptide is removed from the HMW glutenin subunit in the two species. Phylogenetic analysis showed that 1Ux and 1Cx subunits were most closely related to the 1Dx type subunit encoded by the Glu-D1 locus. The 1Uy subunit possessed a higher level of homology to the 1Dy-type subunit compared with the 1Cy subunit. In conclusion, our study suggests that the Glu-U1 locus of Ae. umbellulata and the Glu-C1 locus of Ae. caudata specify the expression of HMW glutenin subunits in a manner similar to the Glu-D1 locus. Consequently, HMW glutenin subunits from the two diploid species may have potential value in improving the processing properties of hexaploid wheat varieties.

Amino Acid Sequence↗
PubMed2003

Matrix-assisted laser desorption/ionization detection of polymerase chain reaction products by utilizing the 5'-3' exonuclease activity of Thermus aquaticus DNA polymerase.

The 5'-3' exonuclease activity of DNA polymerase was utilized in the polymerase chain reaction system to generate a specific signal concomitant with amplification. These signals were detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). This method obviates the need to perform extensive DNA purification of reaction products that is often necessary for detecting larger DNA molecules by mass spectrometry. Oligonucleotides complementary to the internal region of the amplicon are degraded by the 5'-3' exonuclease activity and the degradation products are analyzed by MALDI mass spectrometry. We refer to this assay as the Exo-taq assay or probe degradation assay. This method should be amenable to automation.

DNA↗