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Biomedical subjects

Z Guo

Publications and source records attributed to Z Guo.

At least 91 records · Page 5Linked to original sources
PubMed2001

Dissociation of sulfur hexafluoride tracer gas in the presence of an indoor combustion source.

As an odorless, nontoxic, and inert compound, sulfur hexafluoride (SF6) is one of the most widely used tracer gases in indoor air quality studies in both controlled and uncontrolled environments. This compound may be subject to reactions with water vapor under elevated temperature to form acidic inorganic compounds such as HF and H2SO4. Thus, in the presence of unvented combustion sources such as kerosene heaters, natural gas heaters, gas log fireplaces, candles, and lamps, the SF6 dissociation may interfere with measurements of the emissions from these sources. Tests were conducted in a research house with a vent-free natural gas heater to investigate these potential interferences. It was observed that the heater operation caused about a 5% reduction of SF6 concentration, which can be an error source for the ventilation rate measurement and consequently the estimated pollutant emission rates. Further analysis indicates that this error can be much greater than the observed 5% under certain test conditions because it is a function of the ventilation flow rate. Reducing the tracer gas concentration has no effect on this error. A simple theoretical model is proposed to estimate the magnitude of this error. The second type of interference comes from the primary and secondary products of the SF6 dissociation, mainly H2SO4, SO2, HF, and fine particulate matter (PM). In the presence of approximately 5 ppm SF6, the total airborne concentrations of these species increased by a factor of 4-10. The tests were performed at relatively high SF6 concentrations, which is necessary to determine the interferences quantitatively. The second type of interference can be significantly reduced if the SF6 concentration is kept at a low ppb level.

Air Movements↗
PubMed2001

A virtual instrument for acquisition and analysis of the phonocardiogram and its internet-based application.

The objective of this study is to develop a phonocardiogram (PCG) acquisition and analysis instrument using virtual instrumentation technology and investigate its Internet-based application. The PCG instrument was developed using a Pentium 200 computer, a data acquisition board, and a two-channel custom designed bio-signal preamplifier. LabVIEW was used to create the instrument's front panels. Spectral and joint time-frequency analyses were implemented into the instrument. This instrument can be used to display the PCG and to analyze the individual heart sound and murmur for the detection of heart valve diseases. Using a test-bed, the PCG data acquisition and analysis were performed remotely over the Internet. Through the main PCG panel, an operator can control the acquisition and analysis of PCG signals. In the remote test, real-time transmission of the PCG signal over the Internet was possible. Remote operators were able to view smoothly scrolling PCG waveforms and could control all the acquisition parameters and perform spectral and time-frequency analyses on the acquired heart sound. This study demonstrated that a LabVIEW-based medical virtual instrument provides a low-cost and flexible solution for data acquisition and analysis of PCG. It also showed that the current Internet supports the transmission of real-time PCG signals. Compared with other telemedicine systems, this application transfers not only the medical data, but also the virtual instrument and its signal processing capability through the Internet.

Heart Valve Diseases↗
PubMed2001

Different worlds, different tasks for health promotion: comparisons of health risk profiles in Chinese and Finnish rural people.

The aim of this study was to compare cardiovascular risk factors of working-aged people in Chinese and Finnish rural villages. The surveys were carried out in 1989 in Tianjin, China, and in Kuopio, Finland. Altogether, 897 Chinese inhabitants and 795 Finnish subjects participated in the surveys. Health behaviours were recorded, and height, weight, blood pressure, heart rate and serum lipids were measured. Generally Finns had a significantly higher mean body-mass index, systolic and diastolic blood pressures, and serum total cholesterol, low-density lipoprotein cholesterol, and total cholesterol/high-density lipoprotein ratio than the Chinese. However, no difference was seen between Chinese and Finnish women in diastolic blood pressure and serum triglycerides. Lower high-density lipoprotein cholesterol levels were observed in Finnish men than in Chinese men, whereas a higher mean level was shown in Finnish women than in Chinese women. There were significantly higher mean heart rates and prevalence of smoking in Chinese than in Finnish populations. More people who were overweight, obese and hypertensive were found in the Finnish than in the Chinese populations. Most of the Finns had two or more cardiovascular risk factors compared with the Chinese, the majority of whom were in the group with less than two risk factors. In conclusion, the risk profiles are clearly somewhat different in these two countries. A major task for the Chinese health policy and health care system is to decrease smoking and to prevent obesity and hypertension. In Finland, the biggest task seems to be the reduction of weight and lipid abnormalities, and the prevention of hypertension.

Adult↗
PubMed2001

N-(8-Quinolyl)pyridine-2-carboxamide.

The title compound, C15H11N3O, is basically planar except that the pyridine ring is slightly titled, the dihedral angle between the pyridyl and quinolyl rings being 3.55 (5) degrees. The crystal grows in two directions and the crystal packing is stabilized by pi-pi stacking interactions.

Crystallography, X-Ray↗
PubMed2001

Transcriptional regulation of the two sterol esterification genes in the yeast Saccharomyces cerevisiae.

Saccharomyces cerevisiae transcribes two genes, ARE1 and ARE2, that contribute disproportionately to the esterification of sterols. Are2p is the major enzyme isoform in a wild-type cell growing aerobically. This likely results from a combination of differential transcription initiation and transcript stability. By using ARE1 and ARE2 promoter fusions to lacZ reporters, we demonstrated that transcriptional initiation from the ARE1 promoter is significantly reduced compared to that from the ARE2 promoter. Furthermore, the half-life of the ARE2 mRNA is approximately 12 times as long as that of the ARE1 transcript. We present evidence that the primary role of the minor sterol esterification isoform encoded by ARE1 is to esterify sterol intermediates, whereas the role of the ARE2 enzyme is to esterify ergosterol, the end product of the pathway. Accordingly, the ARE1 promoter is upregulated in strains that accumulate ergosterol precursors. Furthermore, ARE1 and ARE2 are oppositely regulated by heme. Under heme-deficient growth conditions, ARE1 was upregulated fivefold while ARE2 was down-regulated. ARE2 requires the HAP1 transcription factor for optimal expression, and both ARE genes are derepressed in a rox1 (repressor of oxygen) mutant genetic background. We further report that the ARE genes are not subject to end product inhibition; neither ARE1 nor ARE2 transcription is altered in an are mutant background, nor does overexpression of either ARE gene alter the response of the ARE-lacZ reporter constructs. Our observations are consistent with an important physiological role for Are1p during anaerobic growth when heme is limiting and sterol precursors may accumulate. Conversely, Are2p is optimally required during aerobiosis when ergosterol is plentiful.

Acyltransferases↗
PubMed2001

Knockout mice heterozygous for Sod2 show alterations in cardiac mitochondrial function and apoptosis.

Heart mitochondria from heterozygous (Sod2(-/+)) knockout mice have a 50% reduction in manganese superoxide dismutase (MnSOD) activity. The decrease in MnSOD activity was associated with increased mitochondrial oxidative damage as demonstrated by a decrease in the activities of iron sulfhydryl proteins sensitive to oxygen stress (aconitase and reduced nicotinamide adenine dinucleotide-oxidoreductase). Mitochondrial function was altered in the Sod2(-/+) mice, as shown by decreased respiration by complex I and an increase in the sensitivity of the permeability transition to induction by calcium and t-butylhydroperoxide. The increased induction of the permeability transition in heart mitochondria from Sod2(-/+.)mice was associated with increased release of cytochrome c and an increase in DNA fragmentation. Cardiomyocytes isolated from neonatal Sod2(-/+) and Sod2(-/-) mice were more sensitive to cell death than cardiomyocytes from Sod2(+/+) mice after t-butylhydroperoxide treatment, and this increased sensitivity was prevented by inhibiting the permeability transition with cyclosporin A. These experiments demonstrate that MnSOD may play an important role in the induction of the mitochondrial pathway of apoptosis in the heart, and this appears to occur primarily through the permeability transition.

Aconitate Hydratase↗
PubMed2001

Effects of long-term enalapril and losartan therapy of hypertension on cardiovascular aldosterone.

BACKGROUND: Plasma aldosterone escape is found during long-term angiotensin-converting enzyme inhibitor therapy. Evidence for aldosterone production in cardiovascular tissues raised the question of whether or not aldosterone escape occurs in these tissues. METHOD: Spontaneously hypertensive rats were treated with enalapril (20 mg/kg/day) and losartan (50 mg/kg/day) for 20 weeks; untreated spontaneously hypertensive and Wistar rats were used as positive and normal controls, respectively. Ex vivo mesenteric artery and heart perfusion, high-performance liquid chromatography, and radioimmunoassay for aldosterone were performed. RESULTS: The results showed that enalapril failed to significantly inhibit aldosterone production in mesenteric artery, myocardium and plasma. Losartan significantly inhibited aldosterone production to that of Wistar rats in the mesenteric artery, myocardium and plasma. CONCLUSION: This study provides the first evidence that long-term angiotensin-converting enzyme inhibition therapy induces aldosterone escape in hypertensive cardiovascular tissues, and angiotensin II subtype 1 receptor antagonist does not induce aldosterone escape in mesenteric artery, myocardium and plasma of spontaneously hypertensive rats.

Aldosterone↗
PubMed2001

Changes in expression of antioxidant enzymes affect cell-mediated LDL oxidation and oxidized LDL-induced apoptosis in mouse aortic cells.

Transgenic mice overexpressing Cu/Zn superoxide dismutase (hSod1Tg(+/0)) or catalase (hCatTg(+/0)) and knockout mice underexpressing manganese superoxide dismutase (Sod2(+/)(-)) or glutathione peroxidase-1 (Gpx1(-/-)) were used to study the effect of antioxidant enzymes on cell-mediated low density lipoprotein (LDL) oxidation and oxidized LDL (oxLDL)-induced apoptosis. Incubation of LDL with mouse aortic segments or smooth muscle cells (SMCs) resulted in a significant increase in LDL oxidation. However, LDL oxidation was significantly reduced when LDL was incubated with aortic segments and SMCs obtained from hSod1Tg(+/0) and hCatTg(+/0) mice compared with those obtained from wild-type mice. In contrast, LDL oxidation was significantly increased when LDL was incubated with aortic segments and SMCs obtained from Sod2(+/)(-) and Gpx1(-/-) mice. CuSO(4)-oxidized LDL increased DNA fragmentation and caspase activities in the primary cultures of mouse aortic SMCs. However, oxLDL-induced DNA fragmentation and caspase activities were reduced 50% in SMCs obtained from hSod1Tg(+/0) and hCatTg(+/0) mice compared with wild-type control mice. In contrast, oxLDL-induced DNA fragmentation and caspase activities were significantly increased in SMCs obtained from Sod2(+/)(-) and Gpx1(-/-) mice. These findings suggest that overexpression of Cu/Zn superoxide dismutase or catalase reduces cell-mediated LDL oxidation and oxLDL-induced apoptosis, whereas underexpression of manganese superoxide dismutase or glutathione peroxidase-1 increases cell-mediated LDL oxidation and oxLDL-induced apoptosis.

Animals↗
PubMed2001

Extrahepatic expression of apolipoprotein A-II in mouse tissues: possible contribution to mouse senile amyloidosis.

Apolipoprotein A-II (apoA-II), an apolipoprotein in serum high-density lipoprotein, is a precursor of mouse senile amyloid fibrils. The liver has been considered to be the primary site of synthesis. However, we performed nonradioactive in situ hybridization analysis in tissue sections from young and old amyloidogenic (R1.P1-Apoa2C) and amyloid-resistant (SAMR1) mice and revealed that other tissues in addition to the liver synthesize apoA-II. We found a strong hybridization signal in the basal cells of the squamous epithelium and the chief cells of the fundic gland in the stomach, the crypt cells and a small portion of the absorptive epithelial cells in the small intestine, the basal cells of the tongue mucosa, and the basal cells of the epidermis and hair follicles in the skin in both mouse strains. Expression of apoA-II mRNA in those tissues was also examined by RT-PCR analysis. Immunolocalization of apoA-II protein also indicated the cellular localization of apoA-II. ApoA-II transcription was not observed in the heart. Amyloid deposition was observed around the cells expressing apoA-II mRNA in the old R1.P1-Apoa2C mice. These results demonstrate that the apoA-II mRNA is transcribed and translated in various extrahepatic tissues and suggest a possible contribution of apoA-II synthesized in these tissues to amyloid deposition.

Aging↗
PubMed2001

Dietary restriction stimulates BDNF production in the brain and thereby protects neurons against excitotoxic injury.

Dietary restriction (DR) increases the lifespan of rodents and increases their resistance to several different age-related diseases including cancer and diabetes. Beneficial effects of DR on brain plasticity and neuronal vulnerability to injury have recently been reported, but the underlying mechanisms are unknown. We report that levels of brain-derived neurotrophic factor (BDNF) are significantly increased in the hippocampus, cerebral cortex, and striatum of rats maintained on a DR regimen compared to animals fed ad libitum (AL). Seizure-induced damage to hippocampal neurons was significantly reduced in rats maintained on DR, and this beneficial effect was attenuated by intraventricular administration of a BDNF-blocking antibody. These findings provide the first evidence that diet can effect expression of a neurotrophic factor, demonstrate that BDNF signaling plays a central role in the neuroprotective effect of DR, and proffer DR as an approach for reducing neuronal damage in neurodegenerative disorders.

Actins↗
PubMed2001

Flow-injection electrogenerated chemiluminescence determination of isoniazid using luminol.

Based on a new electrogenerated chemiluminescence (ECL) analytical idea, this paper explains a sensitive and selective flow-injection ECL method using luminol for the determination of isoniazid, based on the sensitizing effect of isoniazid for the weak ECL emission of electrochemically oxidized luminol. Under the optimum experimental conditions, the relative ECL intensity was linear with isoniazid concentration in the range of 4.0 x 10(-8) mol/L to 8.0 x 10(-6) mol/L and with a detecting limit of 2.8 x 10(-8) mol/L.

Animals↗
PubMed2001

Multicolor fluorescent differential display.

Differential display and DNA microarray have emerged as the two most popular methods for gene expression profiling. Here, we developed a multicolor fluorescent differential display (FDD) method that combines the virtues of both differential display in signal amplification and DNA microarray in signal analysis. As in DNA microarray, RNA samples being compared can be labeled with either a red or green fluorescent dye and displayed in a single lane, allowing convenient scoring and quantification of the differentially expressed messages. In addition, the multicolor FDD has a built-in signal proofreading capability that is achieved by labeling each RNA sample from a comparative study with both red and green fluorescent dyes followed by their reciprocal mixings in color. Thus, the multicolor FDD provides a platform upon which a sensitive and accurate gene expression profiling by differential display can be automated and digitally analyzed. It is envisioned that cDNAs generated by the multicolor FDD may also be used directly as probes for DNA microarray, allowing an integration of the two most widely used technologies for comprehensive analysis of gene expression.

Animals↗
PubMed2001

Sampling the intramyocellular triglycerides from skeletal muscle.

To determine the extent and microanatomical distribution of extramyocellular adipocytes associated with skeletal muscle, histological, biochemical, nuclear magnetic resonance proton spectroscopic and microcomputed tomography techniques were employed to analyze skeletal muscle samples from lean and obese Sprague-Dawley rats. Significant amounts of extramyocellular adipocytes were found on the exterior surface of rat gastrocnemius, soleus, and tibialis anterior muscles. The triglyceride content of these exterior adipocytes in these muscle groups was 2- to 3-fold greater than that of the respective intramyocellular triglyceride pool (P = 0.01). Thus, the exterior adipocytes associated with skeletal muscle samples are an abundant source of extramyocellular fat potentially contaminating the intramyocellular triglyceride pool if not carefully and completely removed. On the other hand, no adipocytes were found in the interfascicular space (between muscle bundles) or the intrafascicular space (between muscle fibers) in any of the three rat muscles. The feasibility of and procedures for removing extramyocellular fat by microdissection techniques to obtain pure muscle sample were also evaluated. Complete removal of the extramyocellular adipocytes from rat skeletal muscle, using microdissection with a stereo microscope, was found to be practical and effective. It is concluded that pure muscle samples free of contamination by extramyocellular fat can be obtained, but only if microdissection techniques are utilized.

Adipocytes↗
PubMed2001

Allelic losses in OraTest-directed biopsies of patients with prior upper aerodigestive tract malignancy.

Genetic alterations at critical chromosome loci have been shown to be predictors of the progression of oral premalignancy-to-invasive cancer. We obtained a unique group of oral biopsies, initially collected during a prospective study designed to test the ability of OraTest (toluidine blue), to identify recurrent oral neoplastic lesions in patients with definite therapy for head and neck or upper aerodigestive tract (UADT) cancer. A total of 46 cases, including 13 squamous cell carcinoma (SCC), 11 carcinoma-in situ or dysplasia, and 22 morphologically normal oral biopsies, were analyzed for loss of heterozygosity (LOH) at 9p21, 3p21, and 17p13(TP53) by microsatellite analysis. LOH at one or more tested markers in at least one biopsy was detected in 76% (35 of 46) cases. All of the SCC and carcinoma-in situ cases showed LOH, and, strikingly, more than one-half (69%, 13 of 22) of morphologically normal epithelia also harbored LOH in at least one tested marker. The most frequent LOH was found on chromosome 9p21 (69%, 31 of 45). LOH was observed at 3p21, 17p13(TP53), or in multiple chromosomal arms significantly more often in SCC than in normal epithelia. In the majority of cases, two oral biopsies, one from an OraTest-staining positive area and another from a negative area adjacent to the stain, were collected. Among 25 LOH positive cases with two biopsies, identical allelic losses were confirmed between stained and nonstained biopsies in 16 cases. In the remaining nine cases with discordant LOH patterns between two biopsies, eight cases showed LOH at more genetic loci in OraTest-stained areas. Our data confirm that clonal genetic alterations, especially 9p21 deletion, are often present in the oral epithelia of patients with previous UADT malignancy and, combined with previous studies, suggest that genetic analysis will help stratify patients at risk of developing a secondary oral cancer. In addition to detecting cancer, our study suggests that OraTest can detect clinically occult lesions in the progression pathway to oral cancer.

Adult↗
PubMed2001

Identification of potential substrate-binding sites in yeast and human acyl-CoA sterol acyltransferases by mutagenesis of conserved sequences.

In mammals, the esterification of sterols by ACAT plays a critical role in eukaryotic lipid homeostasis. Using the predominant isoform of the yeast ACAT-related enzyme family, Are2p, as a model, we targeted phylogenetically conserved sequences for mutagenesis in order to identify functionally important motifs. Deletion, truncation, and missense mutations implicate a regulatory role for the amino-terminal domain of Are2p and identified two carboxyl-terminal motifs as required for catalytic activity. A serine-to-leucine mutation in the (H/Y)SF motif (residues 338-340), unique to sterol esterification enzymes, nullified the activity and stability of yeast Are2p. Similarly, a tyrosine-to-alanine change in the FYxDWWN motif of Are2p (residues 523-529) produced an enzyme with decreased activity and apparent affinity for oleoyl-CoA. Mutagenesis of the tryptophan residues in this motif completely abolished activity. In human ACAT1, mutagenesis of the corresponding motifs (residues 268-270, and 403-409, respectively) also nullified enzymatic activity. On the basis of their critical roles in enzymatic activity and their sequence conservation, we propose that these motifs mediate sterol and acyl-CoA binding by this class of enzymes.

Acyltransferases↗
PubMed2001

Biological features of mesenchymal stem cells from human bone marrow.

OBJECTIVE: To study the biological characteristics of mesenchymal stem cells (MSCs) from human bone marrow. METHODS: A culture of mesenchymal stem cells was initiated from bone marrow low-density mononuclear cells separated by Percoll Centrifugation and maintained in low-glucose Dulbecco's modified Eagle's medium (DMEM) with 10% selected fetal calf serum. Cell growth pattern and its responses to cytokines were evaluated by trypan blue exclusion and MTT test, respectively. Cell cycle and surface antigenic features were analyzed by flow cytometry technique. Cytochemistry characteristics of MSCs were determined. RESULTS: Easy-handling methods to isolate and culture expand MSCs were developed in this study. MSCs were unique in their phenotypes. They were positive for CD29, CD44, CD166, and negative for CD34, CD45, HLA-DR and Ulex europaeus. Cytochemistry evaluation showed that MSCs were homogeneously positive for acid alpha-naphthl acetate esterase (ANAE), glycogen (periodic acid Schiff reaction, PAS), and negative for acid phosphatase (ACP) and the Sudan black reaction (SB). Around 5% of them were positive for alkaline phosphatase (ALP). The cells had a population doubling time of 30 hours and cell cycle analysis showed that approximately 10% of them were in S phase. MSCs grew at significantly different rates when incubated in the presence of various recombinant human cytokines, of which interferon gamma, tumor necrosis factor alpha, stem cell factor and insulin-like growth factor promoted the proliferation of MSCs dramatically, while others tested had no effects on cell growth. CONCLUSIONS: MSCs are a homogenous population of cells that have unique growth, phenotypical and cytochemical characteristics. Furthermore, the diverse responses of MSCs to different cytokines provide a clue for the selection of optimal expansion and maintenance of MSCs.

Activated-Leukocyte Cell Adhesion Molecule↗
PubMed2001

[Immunoelectron microscopic analysis of P-glycoprotein, p53, and Bcl-2 proteins expressions in lung cancer].

OBJECTIVE: To determine the ultrastructural localization of P-gp, p53 protein, and Bcl-2 protein in lung cancer cells, their relation to multidrug resistance and possible mechanisms of action. METHODS: Expression of P-gp, p53, and Bcl-2 proteins was examined in 8 NSCLC surgical specimens and 7 SCLC bronchoscopically biopsied specimens using postembedding PAG immunolabelling technique for electron microscopy. RESULTS: P-gp was detected on the cell membrane and the periphery of endoplasmic reticulum (ER). P53 protein was observed not only in the nuclei associated with heterochromatin but also in the cytosol. Bcl-2 protein immunoreactivity was associated with mitochondria and ER. P-gp, p53, and Bcl-2 were detected in 5(33%), 9(60%), and 4 (26.7%) out of the 15 samples examined, respectively. In 8 normal lung tissues, these three proteins were detected. Of 5 P-gp positive samples 4 were NSCLC, only 1 was SCLC after chemotherapy. CONCLUSION: P-gp, p53, and Bcl-2 proteins are detectable immuno-electron microscopically in lung cancer cells. No correlation in expression existed between of p53 and P-gp, nor did that between p53 and Bcl-2. The plasma membrane localization of P-gp supports its action as a transmembrane drug efflux pump. P-gp may play a role in MDR in lung cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗