PubMed Health⌕ Search

Biomedical subjects

J Yao

Publications and source records attributed to J Yao.

At least 19 recordsLinked to original sources
PubMed2003

The RAD30 cancer susceptibility gene.

The human skin cancer-prone disease xeroderma pigmentosum variant (XPV) results from a mutation in RAD30, which encodes the novel lesion bypass DNA polymerase eta. XPV cells are characterized by delayed completion of DNA replication and increased mutagenesis following UV irradiation. In cell-free extracts of XPV lymphoblasts, functional DNA polymerase eta is required for the complete replication of a double-stranded plasmid containing either a single (6-4) photoproduct or a cyclobutane pyrimidine dime(CPD), the major mutagenic UV-induced lesion. In cultured XPV cells, replication arrest activates downstream signalling pathways, leading to hyperphosphorylation of the 34-kDa subunit of the trimeric single-stranded DNA-binding protein, RPA (replication protein A). Many of the RAD30 mutations identified in XPV cells result in truncation and inactivation of DNA polymerase eta. To examine whether polymorphisms in the RAD30 gene that result in altered polymerase eta function, rather than enzyme inactivation, might contribute to individual susceptibility to skin cancer, methods to screen for sequence changes in the RAD30 gene in human genomic DNAhave been developed.

Animals↗
PubMed2001

Functional relationship between subfornical organ cholinergic stimulation and cellular activation in the hypothalamus and AV3V region.

The subfornical organ (SFO) has been suggested to be important for water intake and secretion of vasopressin (AVP). However, the role of the SFO cholinergic mechanism in the control of body fluid regulation is not clear. This study determined the effects of local cholinergic stimulation in the SFO produced by administration of physostigmine on drinking and cellular excitation in the anterior third ventricle (AV3V) region and in the supraoptic and paraventricular nuclei (SON and PVN). The results showed that injection of physostigmine into the SFO induced water intake and c-fos expression in the AV3V area as well as in the AVP containing neurons in the hypothalamus. Pretreatment of the SFO with mecamylamine, a nicotinic receptor antagonist, had no effect on physostigmine induced behavioral and c-fos responses. The muscarinic receptor blocker atropine, however, abolished both drinking and cellular activation after injection of physostigmine into the SFO. Immunostaining experiments demonstrated positive acetyltransferase (ChAT) in the SFO. Intensive ChAT immunoreactivity was located in the cholinergic fibers in the SFO. Together, the results indicate that SFO cholinergic mechanisms are important in co-operation with the AV3V and hypothalamic neurons in the control of thirst and AVP-mediated body fluid homeostasis.

Acetylcholine↗
PubMed2001

Multiple signaling pathways involved in activation of matrix metalloproteinase-9 (MMP-9) by heregulin-beta1 in human breast cancer cells.

Matrix metalloproteinase-9 (MMP-9) plays important roles in tumor invasion and angiogenesis. Secretion of MMP-9 has been reported in various cancer types including lung cancer, colon cancer, and breast cancer. In our investigation of MMP-9 regulation by growth factors, MMP-9 was activated by heregulin-beta1 as shown by zymography in both SKBr3 and MCF-7 breast cancer cell lines. Increase in MMP-9 activity was due to increased MMP-9 protein and mRNA levels, which mainly results from transcriptional upregulation of MMP-9 by heregulin-beta1. Heregulin-beta1 activates multiple signaling pathways in breast cancer cells, including Erk, p38 kinase, PKC, and PI3-K pathways. We examined the pathways involved in heregulin-beta1-mediated MMP-9 activation using chemical inhibitors that specifically inhibit each of these heregulin-beta1-activated pathways. The PKC inhibitor RO318220 and p38 kinase inhibitor SB203580 completely blocked heregulin-beta1-mediated activation of MMP-9. MEK-1 inhibitor PD098059 partially blocked MMP-9 activation, whereas PI3-K inhibitor wortmannin had no effect on heregulin-beta1-mediated MMP-9 activation. Therefore, at least three signaling pathways are involved in the activation of MMP-9 by heregulin-beta1. Since MMP-9 is tightly associated with invasion/metastasis and angiogenesis, our studies suggest that blocking heregulin-beta1-mediated activation of MMP-9 by inhibiting the related signaling pathways may provide new strategies for inhibition of cancer metastasis and angiogenesis.

Breast Neoplasms↗
PubMed2001

Methamphetamine induces AP-1 and NF-kappaB binding and transactivation in human brain endothelial cells.

Cellular and molecular mechanisms of methamphetamine (METH)-induced neurotoxicity may involve alterations of cellular redox status and induction of inflammatory genes in endothelial cells. To study these hypotheses, molecular signaling pathways of METH-induced inflammatory responses via activation of redox-sensitive transcription factors were investigated in human brain microvascular endothelial cells (HBMEC). A dose-dependent depletion of total glutathione levels was detected in HBMEC exposed to METH. In addition, electrophoretic mobility shift assay (EMSA) showed significant increases in DNA binding activities of redox-responsive transcription factors, AP-1 and NF-kappaB, in HBMEC treated with METH. METH-mediated AP-1 or NF-kappaB activation was accompanied by induction of transactivation of AP-1 or NF-kappaB, as measured by dual luciferase assay using specific reporter plasmids. Because NF-kappaB and AP-1 are known to regulate expression of inflammatory genes, expression of the gene encoding for tumor necrosis factor-alpha (TNF-alpha) was also studied in METH-treated HBMEC. A dose-dependent overexpression of the TNF-alpha gene was observed in HBMEC treated with METH. The importance of AP-1 and NF-kappaB in METH-induced TNF-alpha gene was confirmed in functional promoter studies using constructs of the TNF-alpha promoter with mutated AP-1 or NF-kappaB sites. These results indicate that METH-induced disturbances in cellular redox status and activation of AP-1 and NF-kappaB can play critical roles in the signaling pathways leading to upregulation of inflammatory genes in human brain endothelial cells.

Amphetamine-Related Disorders↗
PubMed2001

Mdm2 mutant defective in binding p300 promotes ubiquitination but not degradation of p53: evidence for the role of p300 in integrating ubiquitination and proteolysis.

Turnover of the p53 tumor suppressor protein is mediated by Mdm2 through the ubiquitin proteolysis pathway. p300, a co-activator for p53, also participates in this process by complexing with Mdm2. We now report that the mutant Mdm2, defective in p53 binding, does not promote p53 ubiquitination and degradation in vivo or inhibit p53 transcriptional activation. By contrast, the mutant Mdm2, defective in p300 binding, still retains its activity to promote p53 ubiquitination and to inhibit p53 transcriptional activation but fails in promoting p53 degradation. We also show that both wild-type Mdm2 and the mutant Mdm2, defective in p300 binding, can promote the ubiquitination of cancer-derived p53 mutants, but only wild-type Mdm2 can cause their degradation. Furthermore, adenoviral oncoprotein, 12S.E.1A, but not its deletion mutant that lacks p300 binding, was shown to decrease in vivo ubiquitination of mutant p53. Taken together, these results provide genetic evidence that p300 plays a pivotal role in the regulation of Mdm2-mediated p53 turnover by integrating the cellular ubiquitination and proteolytic processes.

Adenovirus E1A Proteins↗
PubMed2001

NMR structural and dynamic characterization of the acid-unfolded state of apomyoglobin provides insights into the early events in protein folding.

Apomyoglobin forms a denatured state under low-salt conditions at pH 2.3. The conformational propensities and polypeptide backbone dynamics of this state have been characterized by NMR. Nearly complete backbone and some side chain resonance assignments have been obtained, using a triple-resonance assignment strategy tailored to low protein concentration (0.2 mM) and poor chemical shift dispersion. An estimate of the population and location of residual secondary structure has been made by examining deviations of (13)C(alpha), (13)CO, and (1)H(alpha) chemical shifts from random coil values, scalar (3)J(HN,H)(alpha) coupling constants and (1)H-(1)H NOEs. Chemical shifts constitute a highly reliable indicator of secondary structural preferences, provided the appropriate random coil chemical shift references are used, but in the case of acid-unfolded apomyoglobin, (3)J(HN,H)(alpha) coupling constants are poor diagnostics of secondary structure formation. Substantial populations of helical structure, in dynamic equilibrium with unfolded states, are formed in regions corresponding to the A and H helices of the folded protein. In addition, the deviation of the chemical shifts from random coil values indicates the presence of helical structure encompassing the D helix and extending into the first turn of the E helix. The polypeptide backbone dynamics of acid-unfolded apomyoglobin have been investigated using reduced spectral density function analysis of (15)N relaxation data. The spectral density J(omega(N)) is particularly sensitive to variations in backbone fluctuations on the picosecond to nanosecond time scale. The central region of the polypeptide spanning the C-terminal half of the E helix, the EF turn, and the F helix behaves as a free-flight random coil chain, but there is evidence from J(omega(N)) of restricted motions on the picosecond to nanosecond time scale in the A and H helix regions where there is a propensity to populate helical secondary structure in the acid-unfolded state. Backbone fluctuations are also restricted in parts of the B and G helices due to formation of local hydrophobic clusters. Regions of restricted backbone flexibility are generally associated with large buried surface area. A significant increase in J(0) is observed for the NH resonances of some residues located in the A and G helices of the folded protein and is associated with fluctuations on a microsecond to millisecond time scale that probably arise from transient contacts between these distant regions of the polypeptide chain. Our results indicate that the equilibrium unfolded state of apomyoglobin formed at pH 2.3 is an excellent model for the events that are expected to occur in the earliest stages of protein folding, providing insights into the regions of the polypeptide that spontaneously undergo local hydrophobic collapse and sample nativelike secondary structure.

Acetic Acid↗
PubMed2001

Parthenocarpic apple fruit production conferred by transposon insertion mutations in a MADS-box transcription factor.

Fruit development in higher plants normally requires pollination and fertilization to stimulate cell division of specific floral tissues. In some cases, parthenocarpic fruit development proceeds without either pollination or fertilization. Parthenocarpic fruit without seed has higher commercial value than seeded fruit. Several apple (Malus domestica) mutants (Rae Ime, Spencer Seedless and Wellington Bloomless) are known to produce only apetalous flowers that readily go on to develop into parthenocarpic fruit. Through genetics, a single recessive gene has been identified to control this trait in apple. Flower phenotypes of these apple mutants are strikingly similar to those of the Arabidopsis mutant pistillata (pi), which produces flowers where petals are transformed to sepals and stamens to carpels. In this study, we have cloned the apple PI homolog (MdPI) that shows 64% amino acid sequence identity and closely conserved intron positions and mRNA expression patterns to the Arabidopsis PI. We have identified that in the apetalous mutants MdPI has been mutated by a retrotransposon insertion in intron 4 in the case of Rae Ime and in intron 6 in the case of Spencer Seedless and Wellington Bloomless. The insertion apparently abolishes the normal expression of the MdPI gene. We conclude that the loss of function mutation in the MdPI MADS-box transcription factor confers parthenocarpic fruit development in these apple varieties and demonstrates another function for the MADS- box gene family. The knowledge generated here could be used to produce parthenocarpic fruit cultivars through genetic engineering.

Amino Acid Sequence↗
PubMed2001

A single (6-4) photoproduct inhibits plasmid DNA replication in xeroderma pigmentosum variant cell extracts.

The human skin cancer-prone disease xeroderma pigmentosum variant (XPV) results from a mutation in the human RAD30 gene, which encodes the lesion bypass DNA polymerase eta. XPV cells are characterized by delayed completion of DNA replication and increased mutagenesis following UV-irradiation. Using extracts of an XPV lymphoblast cell line (GM2449C) that has a truncating mutation in the RAD30 gene, we investigated the effect of a (6-4) photoproduct and a cyclobutane pyrimidine dimer (CPD), at a unique -TT- site on either the leading or lagging strand, on plasmid DNA replication. Compared to normal cell extracts, XPV cell extracts have a reduced capacity to carry out complete replication of DNA containing either a (6-4) photoproduct or a CPD on the leading strand, whereas there is little difference between the two cell extracts in replication of DNA containing a lesion on the lagging strand. Inhibition of replication in the presence of a (6-4) photoproduct is attributed to arrest of nascent DNA strand synthesis at the lesion site; in XPV cell extracts, the proportion of arrested products is increased compared to that of normal cell extracts. These results are consistent with a requirement for functional DNA polymerase eta in the replication of a double-stranded plasmid containing either a (6-4) photoproduct or a CPD, on the leading but not the lagging strand.

Base Sequence↗
PubMed2001

Expression of epithelial growth factor receptor and its two ligands, transforming growth factor-alpha and epithelial growth factor, in normal and neoplastic squamous cells in the vulva: an immunohistochemical study.

Epithelial growth factor receptor (EGFR) sends signals to the proliferation signal transduction system, receiving two ligands: epithelial growth factor (EGF) and transforming growth factor-alpha (TGF-alpha). This immunohistochemical study examined the roles of EGFR and its ligands in the proliferation of normal and neoplastic vulvar squamous cells in 25 patients with vulvar squamous cell carcinoma (VSCC), 10 patients with vulvar condyloma acuminata (VCA), 15 patients with vulvar intra-epithelial neoplasm I-II or III (VIN I-II or III), and 5 subjects with vulvar normal squamous cells (VNSC). EGFR was detected in a few basal cells in 40% of the VNSC, in highly dysplastic cells in 40% of the VIN III, in many neoplastic cells in 80% of the VCA, and in some malignant cells in 64% of the VSCC. EGF was seen in the cytoplasm in 20% of the VIN I-II, 100% of the VIN III, 100% of the VCA, and 100% of the VSCC. Diffuse TGF-alpha was weakly expressed in the cytoplasm in 100% of the VNSC, more intensely in 100% of the VIN and 100% of the VCA, and intensely in 100% of the VSCC. These findings led to the suggestion that the TGF-alpha-EGFR system maintains the growth of normal squamous cells and, in part, maintains the growth of dysplastic and neoplastic squamous cells in the vulva. EGF expression was an early sign of neoplasia. The expression of EGFR with overexpression of its two ligands contributed to the proliferation of dysplastic and neoplastic squamous cells in VIN III and VCA. EGFR expression appeared to contribute to essential neoplastic abnormalities in 64% of the VSCC.

Carcinoma in Situ↗
PubMed2001

Staging of neurofibrillary degeneration caused by human tau overexpression in a unique cellular model of human tauopathy.

The hyperphosphorylation of human tau and its aggregation into neurofibrillary tangles are central pathogenic events in familial tauopathies and Alzheimer's disease. However, the cellular consequences of neurofibrillary tangle formation in vivo have not been directly studied because cellular models of human neurofibrillary degeneration have been unavailable until recently. Incorporation of human tau into filaments in vivo and the association of filamentous tau with cytodegeneration were first demonstrated experimentally with the overexpression of human tau in identified neurons (anterior bulbar cells) in the lamprey central nervous system. In this system, filamentous tau deposits are associated with the loss of dendritic microtubules and synapses, plasma membrane degeneration, and eventually the formation of extracellular tau deposits and cell death. Here we show that human tau hyperphosphorylation in anterior bulbar cells is spatiotemporally correlated with a highly stereotyped sequence of degenerative stages closely resembling those seen in human neurofibrillary degeneration. Hyperphosphorylated tau deposits first appear in the distal dendrites and somata, together with degenerative changes that begin in distal dendrites and progress proximally over time. This sequence is independent of the tau isoform used, the presence of epitope tags and the method used to overexpress tau, and thus has important implications for the cytopathogenesis of human neurofibrillary disease.

Animals↗
PubMed2001

Assessment of myocardial perfusion by myocardial contrast echocardiography using harmonic power and the transvenous contrast agent SHU 563A in acute coronary occlusion and after reperfusion.

BACKGROUND: Harmonic power Doppler imaging is a novel technique for the assessment of myocardial perfusion by contrast echocardiography. In this study, we examined whether myocardial contrast echocardiography using harmonic power Doppler and the new transvenous contrast agent SHU 563A can identify myocardial perfusion defects during coronary occlusion and reperfusion. METHODS: To assess the potential of this technique, we occluded either the left anterior descending coronary artery or the circumflex coronary artery for 2 to 3 h followed by 1 h reperfusion in 10 dogs in an open chest model. After transvenous administration of SHU 563A, an air-filled, polymeric contrast agent, myocardial contrast echocardiography was performed in short and long axis views with triggered harmonic power Doppler imaging after coronary occlusion and reperfusion. Post-mortem triphenyl tetrazolium chloride staining was performed to verify infarction. Harmonic power Doppler and anatomic data were analyzed by independent observers. RESULTS: During coronary occlusion, harmonic power Doppler showed perfusion defects in all 10 dogs. The defect size in the short axis view at papillary muscle level ranged 4-51% (14+/-13%) and 3-43% (16+/-10%) in the long axis view (% total LV slice area). After reperfusion (1 h) and infusion of dipyridamole (0.56 mg/kg), power Doppler demonstrated perfusion defects in seven dogs: 0-20% (9+/-8%) (short axis view) and 0-48% (13+/-14%) (long axis view). Five dogs showed anatomic infarction. The anatomic infarct area was 0-18% (6+/-8%) (slices corresponding to the echocardiographic short axis images). Perfusion defect size by harmonic power Doppler correlated well with residual infarct size (r=0.82, P<0.01). CONCLUSIONS: Myocardial contrast echocardiography using harmonic power Doppler and the new contrast agent SHU 563A accurately displays perfusion defects during acute coronary occlusion and after reperfusion. The site and size of residual myocardial infarction is reliably identified on line, in color. This approach has excellent potential for clinical application.

Animals↗
PubMed2001

Effects of mulberry leaves to replace rapeseed meal on performance of sheep feeding on ammoniated rice straw diet.

This study was conducted to investigate effects of leaves of mulberry tree (Morus alba) as a protein supplement to isonitrogenously replace rapeseed meal (RSM) on performance of growing lambs offered ammoniated rice straw (ABRS) (Trial 1), and to evaluate the digestive characteristics of the ABRS supplemented with different ratios of RSM and mulberry leaves in terms of in vitro gas production (Trial 2). In Trial 1, 45 Huzhou lambs were divided into five equal groups according to their body weight and gender. Lambs in each group were kept in three pens (male, female and mixed (one male and two females)), and received one of the following dietary treatments: 100g RSM (A), 75g RSM plus 60g mulberry leaves (B), 50g RSM plus 120g mulberry leaves (C), 25g RSM plus 180g mulberry leaves (D), and 240g mulberry leaves (E). All animals were given ABRS ad libitum along with 100g ground corn per head per day. The intake of ABRS was slightly increased with the supplementary level of mulberry leaves, and hence total intake increased with the increasing level of mulberry leaves. The growth rates were higher in diets A and E than those in other treatments (P<0.05), with little difference between diets A and E, and the slowest in C. Animals of all genders showed a similar trend, though male lambs was higher in weight gain than the female. While feed efficiency was higher in diet A, concentrate consumption per kilogram of weight gain was lower when higher level of mulberry leaves was supplemented (diets D and E). Feed cost per kilogram gain was lower in diets E and A compared to other treatments. Degradation of dry matter in the rumen of sheep were higher for mulberry leaves than for RSM, but crude protein was less degraded for mulberry leaves than for RSM. The potential GP was significantly higher in diet A than those in B, C and D (P<0.05), and higher in E than in C (P<0.05) (Trial 2), indicating a negative associate effect of mulberry leaves and RSM on digestion. It is inferred that mulberry leaves may be used as a protein supplement to ammoniated straw diets to fully substitute for RSM, but these two supplements should unlikely be supplemented together to avoid the negative associate effect.

Journal Article↗
PubMed2001

Diagnosis of acute cholecystitis: sensitivity of sonography, cholescintigraphy, and combined sonography-cholescintigraphy.

BACKGROUND: Radiographic diagnosis of acute cholecystitis can be established using ultrasonography (US), cholecystoscintigraphy (HIDA), or both. Although both modalities have been effective in diagnosing acute cholecystitis (AC), physicians from the emergency department and admitting surgeons continue to request both tests in an attempt to increase the diagnostic accuracy of AC. This article reports the institutional experience of a large tertiary care health care facility, with respect to the sensitivity of US, HIDA, and combined US and HIDA. STUDY DESIGN: We conducted a retrospective review of 132 patients diagnosed with AC who underwent laparoscopic cholecystectomy during the same hospitalization. Patients were stratified into three groups: Group 1 (Gp1, n = 50) included patients who underwent US alone, group 2 (Gp2, n = 28) included patients who underwent HIDA scan alone, and group 3 (Gp3, n = 54) included patients who underwent both US and HIDA. RESULTS: The three groups did not differ with respect to age, liver chemistry, time to operation, and hospital length of stay. The sensitivity of US, HIDA, and combined US/HIDA as diagnostic modalities for acute cholecystitis was referenced to histopathologic confirmation. Sensitivity was 24 of 50 (48%), 24 of 28 (86%), and 49 of 54 (90%) for US, HIDA, and the combination of US/HIDA, respectively. CONCLUSIONS: HIDA scan is a more sensitive test than US in diagnosing patients with AC. Based on the results of this study, we recommend that HIDA scan should be used as the first diagnostic modality in patients with suspected acute cholecystitis; US should be used to confirm the presence of gallbladder stones rather than to diagnose AC.

Acute Disease↗
PubMed2001

Construction of a generic reaction knowledge base by reaction data mining.

As synthesis by combinatorial chemistry and high throughput screening have become well-established strategies in the drug discovery process, chemists face increased challenges in managing large amounts of data and using these data to design more diverse and focused libraries. As synthesis is an intuitive and empirical process, however, the classical approaches to computer-assisted synthesis planning do not fully satisfy the needs of the synthetic chemist. We describe a novel computational technique for extracting reaction data and building a generic reaction knowledge base (GRKB) to provide chemists with useful and well-organized knowledge. The method consists of three key steps: (1) the automatic recognition of reaction centers, (2) the definition of a hierarchy of reaction patterns, and (3) the organization of the generic reaction knowledge. Significant reaction knowledge has been discovered via mining a subset of the InfoChem Reaction database. A frame system has been constructed to store and retrieve the GRKB. Applications of this GRKB to synthesis planning are illustrated.

Artificial Intelligence↗
PubMed2001

Real-time observation of hemodynamic changes in glomerular aneurysms induced by anti-Thy-1 antibody.

BACKGROUND: Blood flow in the microvasculature plays a pivotal role in determining the outcome of injury and repair in inflamed tissue. Real-time observation of the kidney microvasculature, including the glomerular capillary tufts, is extremely difficult because of the methodological limitations of currently available microscope optics. In the present study, we attempted to analyze hemodynamic events that occurred in vivo during microvascular regeneration following destruction of the glomerular capillary tuft, functionally and quantitatively by the use of a real-time confocal laser-scanning microscope (CLSM) system. METHODS: A polyethylene catheter was inserted into the carotid artery to allow blood pressure measurement. Mesangiolytic lesions producing microaneurysms were induced by the injection of anti-Thy-1.1 antibody. On days 3 and 7 after antibody injection, we examined hemodynamic changes under an intravital microscope equipped with real-time CLSM in combination with a high-speed CCD video camera. To measure vessel diameter and erythrocyte velocity, rats were injected with fluorescein isothiocyanate (FITC)-labeled dextran and FITC-labeled red blood cells (RBCs). RESULTS: On day 3 of the disease, mean arterial blood pressure was 112 +/- 5 mm Hg, which was significantly higher than that of normal rat or of rats on day 7 (93 +/- 1 and 101 +/- 9 mm Hg, respectively). Within mircroaneurysms on day 3, RBC velocity was greatly suppressed. By day 7, RBC velocity, in glomeruli with normal appearances, recovered to about half of the level seen in normal controls (430.6 +/- 284.7 microm/sec), while in narrowed glomerular tufts, it was still only 104.6 +/- 35.1 microm/sec. CONCLUSIONS: The noninvasive procedure, using CLSM in combination with a high-speed video camera, allowed us to examine hemodynamic events quantitatively and to analyze microvascular architecture three dimensionally in the kidney. It is useful for estimating hemodynamic response and vascular regeneration in vivo and may be promising for clinical application.

Aneurysm↗
PubMed2001

Bulls-eye display and quantitation of myocardial perfusion defects using three-dimensional contrast echocardiography.

Three-dimensional (3-D) myocardial contrast echocardiography (MCE) is able to derive parallel cutting planes of the left ventricle (LV). However, assessment of the site and extent of myocardial perfusion abnormalities has to rely on the reader's 3-D mental reconstruction from the tomograms, and a manual approach has to be employed for quantitative analysis. The objective of this study was to explore the display and quantitative capability of a bulls-eye format from contrast 3-D MCE in the assessment of perfusion abnormalities derived from a canine model of acute myocardial infarction (MI). Three-dimensional MCE data were acquired sequentially in a rotational scanning format during triggered harmonic imaging with an intravenous contrast agent. Reconstructed short-axis views of the LV were aligned in a bulls-eye format with the apex as the inner most ring. The total LV was divided into 120 sectors. The number of sectors with lack of contrast enhancement was used to derive the percent of the LV (%LV) with perfusion defect and was compared with the extent of MI calculated from postmortem triphenyl tetrazolium chloride (TTC) staining. The perfusion defect regions shown on bulls-eye images corresponded correctly with the territories of the occluded coronary arteries. Three-dimensional MCE perfusion defect mass (19.2 +/- 6.0 %LV) correlated well with anatomic MI mass (19.3 +/- 5.6 %LV; r = 0.92, SEE = 2.3%, mean differential = 0.1 +/- 2.4%). We conclude that bulls-eye display of contrast 3-D MCE demonstrates the site and extent of perfusion abnormalities in an easily appreciable manner. It also allows fast and accurate assessment of endangered myocardium.

Animals↗
PubMed2001

UV-induced hyperphosphorylation of replication protein a depends on DNA replication and expression of ATM protein.

Exposure to DNA-damaging agents triggers signal transduction pathways that are thought to play a role in maintenance of genomic stability. A key protein in the cellular processes of nucleotide excision repair, DNA recombination, and DNA double-strand break repair is the single-stranded DNA binding protein, RPA. We showed previously that the p34 subunit of RPA becomes hyperphosphorylated as a delayed response (4-8 h) to UV radiation (10-30 J/m(2)). Here we show that UV-induced RPA-p34 hyperphosphorylation depends on expression of ATM, the product of the gene mutated in the human genetic disorder ataxia telangiectasia (A-T). UV-induced RPA-p34 hyperphosphorylation was not observed in A-T cells, but this response was restored by ATM expression. Furthermore, purified ATM kinase phosphorylates the p34 subunit of RPA complex in vitro at many of the same sites that are phosphorylated in vivo after UV radiation. Induction of this DNA damage response was also dependent on DNA replication; inhibition of DNA replication by aphidicolin prevented induction of RPA-p34 hyperphosphorylation by UV radiation. We postulate that this pathway is triggered by the accumulation of aberrant DNA replication intermediates, resulting from DNA replication fork blockage by UV photoproducts. Further, we suggest that RPA-p34 is hyperphosphorylated as a participant in the recombinational postreplication repair of these replication products. Successful resolution of these replication intermediates reduces the accumulation of chromosomal aberrations that would otherwise occur as a consequence of UV radiation.

Amino Acid Sequence↗