Biomedical subjects

Y Pang

Publications and source records attributed to Y Pang.

At least 37 records · Page 2Linked to original sources

PubMed2001

Functional dynamics in the active site of the ribonuclease binase.

Binase, a member of a family of microbial guanyl-specific ribonucleases, catalyzes the endonucleotic cleavage of single-stranded RNA. It shares 82% amino acid identity with the well-studied protein barnase. We used NMR spectroscopy to study the millisecond dynamics of this small enzyme, using several methods including the measurement of residual dipolar couplings in solution. Our data show that the active site of binase is flanked by loops that are flexible at the 300-micros time scale. One of the catalytic residues, His-101, is located on such a flexible loop. In contrast, the other catalytic residue, Glu-72, is located on a beta-sheet, and is static. The residues Phe-55, part of the guanine base recognition site, and Tyr-102, stabilizing the base, are the most dynamic. Our findings suggest that binase possesses an active site that has a well-defined bottom, but which has sides that are flexible to facilitate substrate access/egress, and to deliver one of the catalytic residues. The motion in these loops does not change on complexation with the inhibitor d(CGAG) and compares well with the maximum k(cat) (1,500 s(-1)) of these ribonucleases. This observation indicates that the NMR-measured loop motions reflect the opening necessary for product release, which is apparently rate limiting for the overall turnover.

Endoribonucleases↗

PubMed2001

Genomic structure and promoter characterization of an imprinted tumor suppressor gene ARHI.

We have recently identified a maternally imprinted tumor suppressor gene, ARHI (aplysia ras homolog I), the expression of which is lost in ovarian and breast cancers. We have now characterized the genomic structure of the gene including its promoter and the methylation status of its upstream CpG islands. The ARHI gene spans approximately 8 kb containing two exons and one intron. Exon 1 contains 81 non-translated nucleotides, connected to exon 2 with a 3.2-kb intron. The entire protein-coding region is located within exon 2 and encodes a 229-residue small GTP-binding protein belonging to the Ras superfamily. Genomic structure analysis has identified three potential CpG islands. Two of them (CpG island I and II) are located within the promoter and adjacent exon 1 of the ARHI gene. Aberrant methylation of these CpG islands has been detected in breast cancer cells but not in normal epithelial cells, supporting the possibility that appropriate methylation status of the CpG islands in the promoter region may play a role in the downregulation of ARHI gene expression. A TATA box is found 27 bp upstream of the transcription start site associated with several putative transcription factor binding sites. Transient transfection with nested deletion constructs of the 2-kb ARHI promoter regions fused to a luciferase reporter indicated a 121-bp sequence upstream of the transcription initiation site is required for basal promoter activity. Interestingly, this is the region where lower promoter activity has been observed in cancer cells than in normal cells.

Amino Acid Sequence↗

PubMed2001

Chronic ischemia preferentially causes white matter injury in the neonatal rat brain.

Chronic ischemic brain injuries were studied in 7- and 14-day-old rat pups, which were subjected to bilateral carotid artery occlusion (BCAO) on postnatal day 1. BCAO preferentially injured white matter in the corpus callosum, subcortex and internal capsule areas while largely spared cortical neurons. White matter rarefaction in the corpus callosum was observed in 12 out of the 17 BCAO rat brains and significantly enlarged lateral ventricles were found in five out of seven P14 BCAO rat brains. These white matter changes were similar to injuries found in newborn infants with periventricular leukomalacia (PVL). White matter injuries in the 7-day-old BCAO rat brain were accompanied with increased activation of microglia/macrophages, as indicated by ED1 and OX42 positive immunostaining. Immature oligodendrocytes in the 7-day-old BCAO rat brain, as indicated by O4+/O1+ staining, were much fewer than in the sham-operated rat brain. Immunostaining for myelin basic protein (MBP) at the fimbria hippocampus and the internal capsule areas in the 7-day-old BACO rat brain was also much less than in the control rat brain. Consistent with the immunostaining data, MBP mRNA expression in the 7-day-old, but not in the 14-day-old, BCAO rat brain was significantly less than in the control rat brain. The overall results suggest that pre-oligodendrocytes and immature oligodendrocytes might be major targets for chronic ischemic insults and activated microglia/macrophages are possibly involved in the process of white matter injury.

Animals↗

PubMed2001

Cloning and expression of the binary toxin gene from Bacillus sphaericus IAB872 in a crystal-minus Bacillus thuringiensis subsp. israelensis.

Bacillus sphaericus IAB872 has high toxicity against susceptible Culex spp. and medium larvicidal activity against binary toxin-resistant Culex spp. Sequence analysis revealed that the sequence of the binary toxin gene from IAB872 was totally identical to that of the reference strain 2362. The recombinant plasmids were introduced into an acrystalliferous B. thuringiensis strain 4Q7, and the resulting transformants produced parasporal inclusion composed of 51 kDa and 42 kDa proteins during sporulation. SDS-PAGE and Western blot further confirmed that B. thuringiensis transformants were able to express the binary toxin in a high level. Toxicity bioassays showed that they performed high toxicity to susceptible Culex spp. larvae, but no toxicity to resistant Culex larvae. It was, therefore, suggested that other unknown toxins perhaps existed in the wild strain IAB872 except the binary toxin. Their modes of action might be different from that of binary toxin, and they were possibly responsible for the activity of the wild strain IAB872 against resistant mosquito larvae.

Animals↗

PubMed2001

Highly toxic and broad-spectrum insecticidal Bacillus thuringiensis engineered by using the transposon Tn917 and protoplast fusion.

The chromosome of the Bacillus thuringiensis strain S184 that was toxic against the third instar larvae of Spodoptera litura with the LC(50) of 9.74 microg/ml was successfully integrated into two genes of cyt1Aa and cry11Aa using the transposon Tn917, yielding the primary engineered strain TnX. The strain TnX was highly toxic to the third instar larvae of Culex pipiens fatigans with the LC(50) of 5.12 ng/ml which was 1.82-fold higher than that of B. thuringiensis subsp. israelensis, but lowly toxic to lepidopterous larvae. By the protoplast fusion of the strain TnX and the strain S184-Tet(r) (resistance to tetracycline), the target engineered strain TnY was obtained. Against the third instar larvae of S. litura, the strain TnY LC(50) was of 4.68 micro g/ml and increased by 2.08-fold in comparison with the parent strain S184. Against the third instar larvae of C. pipiens fatigans, the strain TnY LC(50) was of 103.20 ng/ml. The two target genes of cyt1Aa and cry11Aa integrated into the chromosome were extremely stable and had little possibility of a second transposition. It was unclear whether some factors existing in the parent strain, S184, contributed to the high toxicity of the strains TnX and TnY.

Animals↗

PubMed2001

Compositional changes of cottonseed hull substrate during P. ostreatus growth and the effects on the feeding value of the spent substrate.

The dry matter and composition of cottonseed hull substrate for P. ostreatus cultivation were tested at different growth stages. As protein, cellulose, hemicellulose and lignin were used by P. ostreatus, the compositional profiles of the substrate were changed greatly, but their rates of change varied at different growing stages. The increase of protein content and the reduction of lignocellulose content contributed to the increase in the dry matter digestibility of the spent substrate, making it possibly acceptable as a potential ruminant feed. This could provide an alternative to environmentally sound use of P. ostreatus spent substrate.

Animal Feed↗

PubMed2001

Semi-volatile species in PM2.5: comparison of integrated and continuous samplers for PM2.5 research or monitoring.

Fine particles in urban atmospheres contain substantial quantities of semi-volatile material [e.g., NH4NO3 and semi-volatile organic compounds (SVOCs)] that are lost from particles during collection on a filter. Several diffusion denuder samplers have been developed for the determination of both NO3- and organic semi-volatile fine particulate components. The combination of technology used in the BOSS diffusion denuder sampler and the Harvard particle concentrator has resulted in the Particle Concentrator-Brigham Young University Organic Sampling System (PC-BOSS) for the 24-hr (or less) integrated collection of PM2.5, including NH4NO3 and semi-volatile organic material. Modification of the BOSS sampler allows for the weekly determination of these same species. Combination of BOSS denuder and tapered element oscillating microbalance (TEOM) monitor technology has resulted in the real-time ambient mass sampler (RAMS) for the continuous measurement of PM2.5, including the semi-volatile components. Comparison of the results obtained with the BOSS and with each of the newly developed modifications of the BOSS indicates that the modified versions can be used for the continuous, daily, or weekly monitoring of PM2.5, including semi-volatile species, as appropriate to the design of each sampler.

Air Pollutants↗

PubMed2001

A longitudinal investigation of aggregate oral intake of copper.

Four-day composite solid food and beverage duplicate plates and 1-L samples of drinking water were collected from a stratified random sample of 80 individuals as part of the National Human Exposure Assessment Survey in Maryland. The media were obtained from each participant in up to six equally spaced sampling cycles over a year and analyzed for copper by inductively coupled plasma mass spectrometry. Copper concentrations (microg/kg) and consumption rates (kg/d) of solid food, beverage and drinking water were used to derive average daily aggregate oral intake of copper (microg/d). The mean aggregate copper intake of 263 measurements obtained from 68 people was 923.2 +/- 685.6 microg/d (mean +/- SD). Intake through solid food accounted for the majority of aggregate daily intake of copper contributing 87% on average. According to results from mixed model analysis of variance procedures, the mean log-transformed average daily copper intake in each medium except beverage exhibited significant (P < 0.05) variability among sampling cycles. Between-person variability accounted for 50% of the total variance in aggregate copper intake. As measured by the coefficient of variation, distributions of copper intake consisting of one observation per individual were more variable than the distribution consisting of the long-term average intake for each person. These results suggest that estimates of the fraction of a population at risk from chronic copper deficiency or excess copper intake can be overestimated if based upon short-term measures of copper intake. In addition, these results indicate that longitudinal information is required for accurate assessment of aggregate oral intake of copper for an individual.

Administration, Oral↗

PubMed2001

Acute exposure to environmental tobacco smoke and heart rate variability.

Environmental tobacco smoke (ETS) has been associated with cardiovascular mortality. Pathophysiologic pathways leading from ETS exposure to cardiopulmonary disease are still being explored. Reduced cardiac autonomic function, as measured by heart rate variability (HRV), has been associated with cardiac vulnerability and may represent an important pathophysiologic mechanism linking ETS and risk of cardiac mortality. In this study we evaluated acute ETS exposure in a commercial airport with changes in HRV in 16 adult nonsmokers. We conducted ambulatory electrocardiographic (ECG) monitoring for 8-hr periods while participants alternated 2 hr in nonsmoking and smoking areas. Nicotine and respirable suspended particle concentrations and participants' blood oxygen saturation were also monitored. We calculated time and frequency domain measures of HRV for periods in and out of the smoking area, and we evaluated associations with ETS using comparative statistics and regression modeling. ETS exposure was negatively associated with all measures of HRV. During exposure periods, we observed an average decrement of approximately 12% in the standard deviation of all normal-to-normal heart beat intervals (an estimate of overall HRV). ETS exposures were not associated with mean heart rate or blood oxygen saturation. Altered cardiac autonomic function, assessed by decrements in HRV, is associated with acute exposure to ETS and may be part of the pathophysiologic mechanisms linking ETS exposure and increased cardiac vulnerability.

Adult↗

PubMed2001

[The pathology and DNA quantitative study of renal clear cell carcinoma in children].

OBJECTIVE: To investigate the pathological features of renal clear cell carcinoma (RCCC) in children and its relationship to the DNA content of cancer cells and DNA ploidy. METHODS: The pathologic morphology of 4 cases of RCCC in children were observed. Using image analysis instruments the quantity of tumor cell DNA was measured. RESULTS: The cytoplasm of the tumor cells were clear in all four cases. Papillary structures were present in these tumors, of which the papillary structure in two cases was over 50%, three cases had small calcified bodies with prominent bleeding and necrosis. Around tumor the glomerular and tubular of kidney always is normal the average DNA index was 1.31. They presented diploidy, high diploidy or subtetraploidy. CONCLUSIONS: The specific features of most RCCC in children are clear cytoplasm, most contain papillary structures, calcified bodies, often with bleeding and necrosis. Around tumor the glomerular and tubular of kidney is always normal. The DNA contents of cancer cells present diploidy, high diploidy or subtetraploidy.

Carcinoma, Renal Cell↗

PubMed2001

Sequence Analysis of the Bam HI-J Fragment of the Spodoptera litura Multicapsid Nucleopolyhedrovirus.

The BamHI-J fragment located at 25.8--9.9 map units of the Spodoptera litura multicapsid nucleopolyhedrovirus (SpltMNPV) genome was sequenced. The fragment contained four ORFs, one partial ORF potentially encoding C-terminal of chitinase gene and one partial homologous region (hr). The four ORFs included lef-8 gene, J domain protein gene (bjdp gene), ORF570 and ORF165. The ORF570 revealed 31% identity to the helicase-2 of Lymantria dispar MNPV. The ORF165 was unique to the SpltMNPV. The bjdp gene, reported here for the first time in baculoviruses, was one of J domain family protein genes, and the predicated amino acid sequence possessed a characteristic of J domain protein of other DnaJ proteins at its N-terminus. The lef-8 showed high identities to the homologs of reported baculovirus genomes. As a component of virus-encoded RNA polymerase, the LEF-8 of SpltMNPV had the conserved motif GIKICGIHGQKG near the C-terminal end. Analysis of the LEF-8 phylogenic tree demonstrated SpltMNPV was very closely related to SpliMNPV.

Journal Article↗

PubMed2001

[Detection of enterotoxin genes in Bacillus thuringiensis by PCR].

The presence of hemolysin HblA (hblA), enterotoxin BceT (bceT) and enterotoxin S (entS) genes from 45 strains of B. thuringiensis, 4 strains of B. cereus and B. sphaericus have been detected respectively by multiple PCR. The results showed that 95.6% B. thuringiensis strains contain the B component of hblA gene, 91.1% and 93.3% of them contain bceT and entS genes sequences respectively. The enterotoxin productions in all strains have also been analysis using two commercial immunoassay kits(TECRA and RPLA) and it has proved that most of B. thuringiensis stains and the positive B. cereus strain can produce entero toxins during their growth. However, the two hblA sequence positive stains, DBT007 was negative when tested both by RPLA and Tecra, T24 001 was negative when assayed by Tecra and positive by RPLA. One hblA sequence negative strain Dmu39 was negative when tested by RPLA but positive by Tecra. No enterotoxin and enterotoxin gene could be detected in B. thuringiensis DBT248 and the B. sphaericus strains. The results suggest that the potential risk of using B. thuringiensis, as biopesticide needs to be further evaluated.

Bacillus↗

PubMed2001

[Identification and location of the toxin protein genes in 56 Bacillus thuringiensis isolates].

Polymerase chain reaction was performed to screen Bacillus thuringiensis isolates for cryI, cryIII, and cryV genes with cryI-, cryIII-, and cryV-specific primers respectively. The results indicated that, in the 56 Bt isolates examined, 7 isolates contain cryI gene, 2 isolates contain cryIII gene, and 21 isolates contain both cryI and cryV genes. The cryV gene was located by Southern hybridization in the large plasmid of about 150 MD molecular mass.

Bacillus thuringiensis↗

PubMed2001

Pathological, ultrastructural and immunohistochemical observations of adenoma of retinal pigment epithelium.

PURPOSE: To Study the clinical, pathological, ultrastructural and immunohistchemical characters of adenoma of the retinal pigment epithelium in order to offer evidence to diagnose this tumor. METHODS: Routine paraffin slices HE stain, histochemistry PAS and VG stain, transmission electron microscopy, and immunohistochemistry for S-100 and vimentin with LSAB method were used. RESULTS: The tumor cells were oval and cuboidal in shape. Part of the tumor had a tubular arrangement. Around the sheets of tumors cells there was a large amount of uniform red stick-like substances. The above matter represented positive in PAS stain. Most of the above matter was yellow, while less of the matter showed red in VG stain. Transmission electron microscopy showed that there were tight junctions between tumor cells. Immunohistochemistry showed positive for S-100, negative for vimentin. CONCLUSIONS: The ultrastructural and immunohistochemical characters of the adenoma of retinal pigment epithelium are consistent with the retinal pigment epithelium.

Adenoma↗

PubMed2001

Role of calcineurin in angiotensin II-induced cardiac myocyte hypertrophy of rats.

OBJECTIVE: The present study investigated the role of calcineurin in angiotensin II(AngII) -induced cardiac myocyte hypertrophy of rats. METHOD: The primary cardiac myocytes were cultured under the standard conditions. The calcineurin activity in AngII-treated cardiomyocytes was tested by using PNPP; protein synethsis rate was assessed by 3H-leucine incorporation; atrial natriuretic factor(ANF) mRNA level was determined by Northern blot analysis. Cell viability was estimated by lactate dehydrogenase (LDH) levels in cultured medium and by dyed cell numbers. RESULT: After stimulation of 10, 100 and 1 000 nmol/L of AngIi, calcineurin activities in the cardiomyocytes were increased by 13%, 57% (P < 0.05) and 228% (P < 0.01) respectively, compared with control group. Cyclosporin A(CsA), a specific inhibitor of calcineurin, markedly inhibited the calcineurin activity and decreased the 3H-leucine incorporation in AngII-treated cardiomyocytes in a dose-dependent manner. It was also found that CsA slightly reduced the mRNA level of ANF gene in AngII-stimulated cardiomyocytes. CONCLUSION: During AngII-induced cardiac myocyte hypertrophy, calcineurin signal pathway is activated, and inhibition of the pathway can attenuate AngII-induced cardiac myocyte hypertrophy, which suggests that the calcineurin signal pathway may play an important role in AngII-induced myocardial hypertrophy of rats.

Angiotensin II↗

PubMed2001

Externalization and internalization of cardiac endothelin receptors during different phases of sepsis in rat.

OBJECTIVE: To study the redistribution of endothelin-1 (ET-1) receptors in two subcellular organelles, the sarcolemmal membrane and the light vesicle, of rat heart during the progression of sepsis. METHODS: Sepsis was induced by cecal ligation and puncture (CLP). ET1 receptor was assayed by using [125I]-ET1 binding. Marker enzyme activities, protein yield, and dry-to-wet weight ratio of cardiac membranes were measured. RESULTS: Septic rat heart exhibited two distinct phases: an initial hyperdynamic phase( 9h after CLP; early stage of sepsis) followed by a hypodynamic (18h after CLP, late stage of sepsis) phase. [125I]-ET1 binding study showed that during early stage of sepsis, the B(max) of ET1 receptors was increased by 30% in sarcolemma but decreased by 19% in light vesicles, while during late stage of sepsis, the B(max) was decreased by 24% in sarcolemma but increased by 38% in light vesicles. The total binding of sarcolemma and light vesicles was increased by 25% during early stage of sepsis but decreased by 17% during late stage of sepsis. CONCLUSIONS: These data indicated that ET1 receptors in the rat heart were externalized from light vesicles to sarcolemmal membranes during early hyperdynamic phase while internalized from surface membranes to intracellular compartment during late hypodynamic phase of sepsis.

Animals↗

PubMed2001

Intracellular redistribution of cardiac endothelin-1 receptor in rat during myocardial hypertrophy.

OBJECTIVE: In a model of rat cardiac hypertrophy, the changes in the distribution of ET-1 receptors in two subcellular fractions, the sarcolemma and the light vesicles during myocardial hypertrophy were studied. METHODS: Cardiac hypertrophy was produced by placing a constricting clip around the suprarenal abdominal aorta of rats, and ET-1 receptor was assayed with radioactive analysis method. RESULTS: It was found that plasma and ventricular ET-1 levels increased significantly on week 2 and week 4 of pressure overload. ET-1 binding studies showed that during myocardial hypertrophy, the maximum binding capacity (B(max)) was increased by 41% (P < 0.01) and 65% (P < 0.01) in sarcolemma in H-2 week and H-4 week groups, but was decreased by 24% (P < 0.01) and 21% (P < 0.01) in light vesicles. The sum of B(max) of sarcolemmal and light vesicle fractions was increased by 33% (P < 0.01) and 57% (P < 0.01) in group H-2 week and H-4 week, respectively. CONCLUSION: ET-1 receptors in rat heart were externalized from light vesicles to sarcolemma, which may contribute to the development of myocardial hypertrophy.

Animals↗

PubMed2000

Effects of lipopolysaccharide on oligodendrocyte progenitor cells are mediated by astrocytes and microglia.

Oligodendrocytes are the primary cells injured in periventricular leukomalacia (PVL), a predominant form of brain white matter lesion in preterm infants. To explore the possible linkage between white matter injury and maternal infection, purified rat O-2A progenitor (Oligodendrocyte-type 2 astrocyte progenitor) cell cultures were used as a model in studying the effects of lipopolysaccharide (LPS), an endotoxin, on survival and differentiation of oligodendrocytes and the involvement of other glial cells in the effects of LPS. O-2A progenitor cells were cultured from optic nerves of 7-day-old rat pups in a chemically defined medium (CDM). Astrocyte and microglia cell cultures were prepared from the cortex of 1-day-old rat brains in the CDM. Direct treatment of LPS (1 microg/ml) to O-2A cells had no effect on viability or differentiation of these cells. When O-2A progenitor cells were cultured in the conditioned medium obtained from either astrocyte or microglial cell cultures for 48 hr, survival rate and differentiation of O-2A cells into mature oligodendrocytes were greatly enhanced as measured by the MTT assay and immunocytochemistry. The conditioned medium obtained from astrocytes or microglia treated with LPS for 48 hr, however, failed to show such a promotional effect on viability and differentiation of O-2A cells. When 5 microg/ml LPS was used to stimulate astrocytes or microglia, the conditioned medium from these glial cell cultures caused O-2A cell injury. The overall results indicate that astrocytes and microglia may promote viability and differentiation of O-2A progenitor cells under physiological conditions, but they may also mediate cytotoxic effects of LPS on oligodendrocytes under an infectious disease biochemical environment.

Animals↗