Biomedical subjects
Publications and source records attributed to Yan Zhang.
The title compound, C25H30NO2+.Cl-, has been synthesized, and the crystal structure shows that it is mainly stabilized through intermolecular N-H...Cl and O-H...Cl and intramolecular N-H...O hydrogen bonds. The absolute configuration of the new stereogenic center (the C atom adjacent to the N atom on the phenol side) was determined to have an R configuration.
This retrospective study consisted of 17 consecutive patients with oligodendrogliomas. We qualitatively and quantitatively assessed the diagnostic value of fluid-attenuated inversion-recovery (FLAIR) images compared with T2-weighted fast spin-echo (FSE) images for evaluating intracranial oligodendrogliomas. Qualitative evaluations of signal intensity, tumor conspicuity, definition of tumor margin, distinction between solid and cystic-like parts within tumor, and calcification were performed. Quantitative criteria comparing FLAIR to T2-weighted FSE images included tumor-to-background contrast and contrast-to-noise ratio (CNR) and tumor-to-cerebrospinal fluid (CSF) contrast and CNR. Our results demonstrate that the FLAIR sequence can replace the T2-weighted FSE sequence for evaluating oligodendrogliomas.
Selenocysteine (Sec) and pyrrolysine (Pyl) are known as the 21st and 22nd amino acids in protein. Both are encoded by codons that normally function as stop signals. Sec specification by UGA codons requires the presence of a cis-acting selenocysteine insertion sequence (SECIS) element. Similarly, it is thought that Pyl is inserted by UAG codons with the help of a putative pyrrolysine insertion sequence (PYLIS) element. Herein, we analyzed the occurrence of Pyl-utilizing organisms, Pyl-associated genes, and Pyl-containing proteins. The Pyl trait is restricted to several microbes, and only one organism has both Pyl and Sec. We found that methanogenic archaea that utilize Pyl have few genes that contain in-frame UAG codons, and many of these are followed with nearby UAA or UGA codons. In addition, unambiguous UAG stop signals could not be identified. This bias was not observed in Sec-utilizing organisms and non-Pyl-utilizing archaea, as well as with other stop codons. These observations as well as analyses of the coding potential of UAG codons, overlapping genes, and release factor sequences suggest that UAG is not a typical stop signal in Pyl-utilizing archaea. On the other hand, searches for conserved Pyl-containing proteins revealed only four protein families, including methylamine methyltransferases and transposases. Only methylamine methyltransferases matched the Pyl trait and had conserved Pyl, suggesting that this amino acid is used primarily by these enzymes. These findings are best explained by a model wherein UAG codons may have ambiguous meaning and Pyl insertion can effectively compete with translation termination for UAG codons obviating the need for a specific PYLIS structure. Thus, Sec and Pyl follow dissimilar decoding and evolutionary strategies.
Frataxin is a conserved mitochondrial protein implicated in cellular iron metabolism. Deletion of the yeast frataxin homolog (YFH1) was combined with deletions of MRS3 and MRS4, mitochondrial carrier proteins implicated in iron homeostasis. As previously reported, the Deltayfh1 mutant accumulated iron in mitochondria, whereas the triple mutant (DeltaDeltaDelta) did not. When wild-type, Deltamrs3/4, Deltayfh1, and DeltaDeltaDelta strains were incubated anaerobically, all strains were devoid of heme and protected from iron and oxygen toxicity. The cultures were then shifted to air for a short time (4-5 h) or a longer time (15 h), and the evolving mutant phenotypes were analyzed (heme-dependent growth, total heme, cytochromes, heme proteins, and iron levels). A picture emerges from these data of defective heme formation in the mutants, with a markedly more severe defect in the DeltaDeltaDelta than in the individual Deltamrs3/4 or Deltayfh1 mutants (a "synthetic" defect in the genetic sense). The defect(s) in heme formation could be traced to lack of iron. Using a real time assay of heme biosynthesis, porphyrin precursor and iron were presented to permeabilized cells, and the appearance and disappearance of fluorescent porphyrins were followed. The Mrs3/4p carriers were required for rapid iron transport into mitochondria for heme synthesis, whereas there was also evidence for an alternative slower system. A different role for Yfh1p was observed under conditions of low mitochondrial iron and aerobic growth (revealed in the DeltaDeltaDelta), acting to protect bioavailable iron within mitochondria and to facilitate its use for heme synthesis.
In this study, we cloned and characterized a human gene homologous to the apoptosis-inducing factor (AIF), which is named AIF-like (AIFL). Human AIFL has 598 amino acids, with a characteristic Rieske domain and a pyridine nucleotide-disulfide oxidoreductase domain (Pyr_redox). AIFL shares 35% homology with AIF, mainly in the Pyr_redox domain. Reverse transcriptase-PCR analysis showed the expression of AIFL mRNA in all tissues tested, i.e. brain, colon, heart, kidney, liver, lung, muscle, ovary, pancreas, placenta, small intestine, and testis. We developed antibodies against human AIFL using fusion proteins as antigens. The antibodies specifically recognized the antigen and heterologously expressed AIFL proteins. The expression of AIFL proteins in human tissues was also ubiquitous, demonstrated by immunohistochemistry in tissue array slides. Subcellular fractionation and immunofluorescence staining studies revealed that AIFL is predominantly localized to the mitochondria. Similar to AIF, overexpression of AIFL induced apoptosis, as shown by increased cytoplasmic nucleosomes and subdiploid cell populations in AIFL-transfected cells. The segment 1-190 containing the Rieske domain induced apoptosis, whereas the segment containing the Pyr_redox domain did not contribute to the pro-apoptotic function. The mitochondrial membrane potential of cells transfected with AIFL was significantly more depolarized than that of the control. AIFL transfection-induced cytochrome c release and cleavage of caspase 3. Furthermore, the pan-caspase inhibitor Z-VAD-fmk inhibited AIFL induced apoptosis. In summary, AIFL induces apoptosis in a caspase-dependent manner when heterologously expressed.
OBJECTIVES: This study was designed to investigate if tissue synchronization imaging (TSI) is useful to identify regional wall delay and predict left ventricular (LV) reverse remodeling after cardiac resynchronization therapy (CRT). BACKGROUND: Echocardiographic assessment of systolic asynchrony is helpful to predict a positive response to CRT. Tissue synchronization imaging is a new imaging technique that allows quick evaluation of regional systolic delay. METHODS: Tissue synchronization imaging was performed in 56 heart failure patients at baseline and three months after CRT. Regional wall delay was identified on TSI images and the time to regional peak systolic velocity (Ts) in LV was measured by the six-basal-six-mid-segmental model. Eight TSI parameters of systolic asynchrony were computed when Ts was measured in ejection phase or also included postsystolic shortening. RESULTS: Severe lateral wall delay occurred in 17 patients, which predicted LV reverse remodeling (chi-square = 8.13, p = 0.004). Among the eight quantitative parameters of asynchrony, the predictive values were higher for parameters that measured Ts in ejection phase than in postsystolic shortening. The standard deviation of Ts of 12 LV segments in ejection phase (Ts-SD-12-ejection) was most powerful to predict reverse remodeling (r = -0.61, p < 0.001) and gain in ejection fraction (r = 0.53, p < 0.001). The area of the receiver-operating characteristic (ROC) curve was the largest for Ts-SD-12-ejection (0.90, p < 0.001), with a sensitivity of 87% and specificity of 81% at a cutoff of 34.4 ms. The combination of lateral wall delay with Ts-SD-12-ejection gave a sensitivity and specificity of 82% and 87%. CONCLUSIONS: Tissue synchronization imaging allows quick evaluation of regional wall delay, and combined with Ts-SD-12-ejection provides a reliable way of predicting reverse remodeling after CRT.
PGC-1alpha mRNA and protein are elevated in islets from multiple animal models of diabetes. Overexpression of PGC-1alpha impairs glucose-stimulated insulin secretion (GSIS). However, it is not well known which metabolic events lead to upregulation of PGC-1alpha in the beta-cells under pathophysiological condition. In present study, we have investigated effects of chronic hyperlipidemia and hyperglycemia on PGC-1alpha mRNA expression in isolated rat islets. Isolated rat islets are chronically incubated with 0, 0.2 and 0.4 mM oleic acid/palmitic acid (free fatty acids, FFA) or 5.5 and 25 mM glucose for 72 h. FFA dose-dependently increases PGC-1alpha mRNA expression level in isolated islets. FFA also increases PGC-1alpha expression in mouse beta-cell-derived beta TC3 cell line. In contrast, 25 mM glucose decreases expression level of PGC-1alpha. Inhibition of PGC-1alpha by siRNA improves FFA-induced impairment of GSIS in islets. These data suggest that hyperlipidemia and hyperglycemia regulate PGC-1alpha expression in islets differently, and elevated PGC-1alpha by FFA plays an important role in chronic hyperlipidemia-induced beta-cell dysfunction.
The first example of the use of a reporter affinity label (NNA) that contains a fluorogenic naphthalene dialdehyde moiety to identify neighboring lysine and cysteine residues at a recognition site is described. The opioid receptors have served as the proof-of-concept because they contain multiple lysine and cysteine residues. The kinetics of isoindole formation resulting from covalent binding of NNA to wild-type and mutant opioid receptors were followed in cultured cells using flow cytometry. The finding that NNA bound to mutant mu opioid receptors (K233R and C235S) without producing specific fluorescence enhancement suggested that covalent bonding occurred at these positions to produce an isoindole fluorophore in the wild-type mu receptor. The similar kinetics of fluorophore formation for wild-type mu, delta, and kappa opioid receptors suggest that these conserved residues are the cross-linking sites in all three types of opioid receptors. The combined utilization of a reporter affinity label and site-directed mutagenesis offers a more expeditious method of identifying cross-linking at a recognition site when compared to classical procedures.
Written informed consent was obtained prior to all human studies after the institutional review board approved the protocol. A continuous arterial spin-labeling technique with an amplitude-modulated control was implemented by using a single coil at 3.0 T. Adiabatic inversion efficiency at 3.0 T, comparable to that at 1.5 T, was achieved by reducing the amplitude of radiofrequency pulses and gradient strengths appropriately. The amplitude-modulated control provided a good match for the magnetization transfer effect of labeling pulses, allowing multisection perfusion magnetic resonance imaging of the whole brain. Comparison of multisection continuous and pulsed arterial spin-labeling methods at 3.0 T showed a 33% improvement in signal-to-noise ratio by using the former approach.
Temporal lobe epilepsy (TLE) is the most common form of epilepsy, affecting approximately 1-2% of the population. Seizure events resulting from TLE are characterized by aberrant hippocampal mossy fiber sprouting and plastic responses that affect brain function. Seizure susceptibility is modulated by the enzyme tissue plasminogen activator (tPA), the normal physiological role of which includes promotion of synaptic reorganization in the mossy fiber pathway by initiating a proteolytic cascade that cleaves extracellular matrix components and influences neurite extension. tPA is concentrated at and selectively secreted from growth cones during excitatory events. However, the mechanisms underlying tPA release during seizure-induced synaptogenesis are not well understood. We examine here potential roles for the signaling enzyme phospholipase D1 (PLD1), which promotes regulated exocytosis in non-CNS cell types, and which we previously demonstrated increases in expression in hippocampal neurons during seizure-induced mossy fiber sprouting. We now show that overexpression of wild-type PLD1 in cultured neurons promotes tPA release and tPA-dependent neurite extension, whereas overexpression of an inactive PLD1 allele or pharmacological inhibition of PLD1 inhibits tPA release. Similarly, viral delivery of wild-type PLD1 into the hippocampus facilitates tPA secretion and mossy fiber sprouting in a seizure-inducing model, whereas the inactive PLD1 allele inhibits tPA release and elicits blunted and abnormal mossy fiber extension similar to that observed for tPA-/- mice. Together, these findings secretion and thus mossy fiber extension in the setting of elevated suggest that PLD1 functions endogenously to regulate tPA-/- neuronal stimulation, such as that seen in TLE.
Fescues (Festuca sp.) are major cool-season forage and turf grass species around the world. Heat stress is one of the limiting factors in the production of fescues as forage in the southern Great Plains of the US. Heat responsive gene transcripts were cloned by using suppression subtractive hybridization between a heat-tolerant and a heat-sensitive fescue genotype subjected to a slowly increased temperature mimicking the natural conditions. The temperature in the growth chamber containing the plants was gradually increased from 24 degrees C to 44 degrees C over a period of 2 weeks. Three subtractions were conducted between samples of the two genotypes collected after 12 h of exposure to 39, 42, and 44 degrees C. A total of 2495 ESTs were generated, of which 1800 clustered into 434 contigs and 656 were singlets. The putative functions of ESTs were predicted by BLASTX. Nearly 30% of the contigs and 39% of the singlets had no similarity to GenBank sequences. Differentially expressed genes selected by subtractions were classified into 10 broad categories according to their putative functions generated by BLAST analysis. Under heat-stress conditions, cell maintenance, chloroplast associated and photosynthesis-, protein synthesis-, signalling-, and transcription factor-related genes had higher expression levels in the heat-tolerant genotype. Genes related to metabolism and stress had higher expression in the heat-sensitive genotype. The expression of 17 selected gene transcripts were examined by RT-PCR using plant tissues of the two genotypes grown under heat stress and under optimal temperature conditions (24 degrees C) for fescue. Results from RT-PCR confirmed the differential expressions of these transcripts. The differential expressions of at least 11 of these genes were attributable to heat stress rather than to differences in the genetic backgrounds of the genotypes.
The estrogenic activity of the Chinese herb kudzu root was investigated by a recombinant yeast screening assay (YES). Isoflavones are the main components in the plant, of which puerarin is the most abundant one. The kudzu root extract was separated into four fractions according to the polarity. The crude extract and its sub-fractions, except the water fraction, showed clear estrogenic activity and the potencies were in the range of 10(-3) to 10(-1)g/l. The ligand potency was used to compare the estrogenic activity of these fractions. The crude extract and its sub-fractions were further analyzed by high performance liquid chromatography (HPLC) to correlate the activity and the active components. Bioassay and chemical analysis showed that theoretical estrogenic activity expressed as equivalent 17beta-estradiol concentration or the cumulative effects are comparable to that experimentally determined by YES. The results showed that the high content of isoflavones as well as the high estrogenic activity could make kudzu root extract an interesting candidate for hormone replacement therapy.
BACKGROUND: SARS coronavirus has been identified as the cause of severe acute respiratory syndrome (SARS). Few tests allow confirmation or exclusion of SARS within the first few days of infection. A gene chip is a useful tool for the study of microbial infections mainly for its capability of performing multi-target analysis in a single test. OBJECTIVES: Investigate the possibility of early detection of SARS virus from clinical samples using the gene chip-based method. STUDY DESIGN: We purified RNA from SARS-CoV obtained from routinely collected peripheral blood and sputum samples of 34 patients who had been identified as probable SARS patients by following the interim U.S. case definition. Four segments of the SARS-CoV were amplified using reverse transcription-nested PCR and the products examined using the 70-mer gene chips for SARS-CoV detection. RESULTS: A blind-test of both peripheral blood and sputum specimens lead to the positive detection of SARS-CoV in 31 out of 34 patients. SARS-CoV was not found in peripheral blood or sputum specimens from three patients. Two of the 34 patients were only 3 days post-onset of symptoms and were subsequently confirmed to be SARS positive. Our results indicate that the gene chip-based molecular test is specific for SARS-CoV and allows early detection of patients with SARS with detection rate about 8% higher than the single PCR test when the sputum sample is available.
OBJECTIVE: To analyze the characteristics, treatment, and natural course during two years of the patients with acute coronary ischemic syndrome (ACS) without ST elevation in China as a part of the international multicentre registry of acute ischemic syndrome, Organization to Assess Strategies for Ischemic Syndromes (OASIS). METHODS: 2294 patients with ACS without ST elevation, including unstable angina pectoris and non-Q-wave myocardial infarction, aged 63 +/- 8, 62.3% being males, were registered and observed for 2 years based on informed consent in the northwest, north, and northeast China. The specific clinical protocols for patients were decided by the attending physicians without outside intervention. The patients' clinical characteristics, treatments, major events in hospital, and natural course of disease during the period of two years were recorded by filling in Case Report Forms offered by Canadian Cardiovascular Collaboration. RESULTS: 89.8% of the patients showed abnormal ECG. The most probable clinical diagnosis on admission was unstable angina in 88.5% of the patients and non-Q-wave myocardial infarction in the other 11.5%. 56.2% of the patients had past history of coronary artery disease, and nearly half of them had myocardial infarction. 57.4%, 18.3%, 47.6%, and 7.1% of them had the prior history of hypertension, diabetes, cigarette smoking and stroke respectively. During hospitalization, anti-platelet therapy and nitrate were used in 94.5% and 96.6% of the cases respectively, and 67.5%, 57.4%, and 59.1%t of them took beta-blockers, calcium antagonists and angiotensin-converting enzyme inhibitor (ACEI) respectively simultaneously. The medication rate dropped by 20.2% approximately 50.2% after discharge from hospital. During the two-year follow up the therapeutic rates of anti-platelets, nitrates, beta-blockers, calcium antagonists, and ACEI were 73.8%, 69.4%, 43.9%, 35.8%, and 31.6% respectively. During the 2 years 43.1%, 23.1%, and 8.2% of the patients underwent coronary angiography, percutaneous coronary intervention (PCI), and coronary artery bypass graft surgery (CABG) respectively. The two-year total mortality was 8.0%. The most common causes of death were severe arrhythmias or sudden death with an incidence of 4.3%. The major events were refractory angina, heart failure, new MI, stroke, and major bleeding with incidence rates of 29.4%, 15.4%, 7.9%, 4.8%, and 0.3%, respectively. CONCLUSION: Most patients with acute ischemic syndrome without ST elevation in China are diagnosed as unstable angina. The patients with acute ischemic syndrome are diagnosed as unstable angina mostly in China. More than half of the patients are treated with anti-platelets, nitrates, beta-blockers, calcium antagonists, and ACEI during hospitalization. The medication rate gradually decreases after discharge. The two-year mortality is 8.0%. The most common causes of death include severe arrhythmias and sudden death.
OBJECTIVES: This study sought to investigate the incremental prognostic value of non-invasive measures of early myocardial relaxation and left ventricular diastolic pressure (LVDP) in patients with impaired left ventricular (LV) systolic function. BACKGROUND: The early diastolic mitral annulus velocity (Em) reflects myocardial relaxation, and the combined ratio of the early transmitral flow velocity (E) to Em (E/Em) >15 correlates well with elevated mean LVDP. It is unknown if these new indexes will predict poorer survival in patients with LV systolic dysfunction. METHODS: Echocardiograms were prospectively obtained in 182 patients with impaired LV systolic function, defined as an LV ejection fraction <0.50. The end point was cardiac mortality. The majority of this patient sample (80%) has been reported on in a previous publication. RESULTS: After a median 48 months' follow-up, Em emerged as an independent predictor of survival (hazard ratio 0.61, 95% confidence interval 0.45 to 0.82). An Em <3 cm/s was associated with a significantly excess mortality (log-rank statistic 9.36, p = 0.002), and this measurement added incremental prognostic value to standard indexes of systolic or diastolic function, including a deceleration time <140 ms and an E/Em >15 (p = 0.038). CONCLUSIONS: Early diastolic mitral annulus velocity is a powerful predictor of cardiac mortality in patients with LV systolic impairment; Em <3 cm/s emerged as the best prognosticator in long-term follow-up, incremental to other clinical or echocardiographic variables, including the ratio E/Em.
Information about the kinetic behavior and lifespan of lymphocytes is crucial to understanding the mechanisms that regulate processes such as immunologic memory. We have used in vivo labeling of dividing cells with 6,6-(2)H(2)-glucose, combined with cell sorting and gas-chromatography-mass spectrometry for deuterium enrichment, in order to analyze the kinetics of human total, naive, or memory B lymphocytes, separated from peripheral blood using monoclonal antibodies. We show that total blood B cells of young adults divide at an average rate of 1.9% (+/-1.0%) per day and at a similar though slightly slower rate, 1.5% (+/-1.3%) per day, in the elderly. Separation of naive and memory B cells according to expression of CD27 indicates that naive peripheral blood B cells divide slowly (0.46% per day), while memory cells proliferate more rapidly (2.66% per day). These data are compatible with the view that B-cell memory may be maintained by clones of proliferating B cells.
Chicken retina contains circadian oscillators that drive rhythmic transcription of several genes expressed in photoreceptor cells. To determine if gap junctions assist in coordinating these transcript rhythms, we examined the effects of two compounds, 18alpha-glycyrrhetnic acid-3-hemisuccinate (ACO) and 18beta-glycyrrhetnic acid (18beta-GA), on photoreceptor iodopsin and arylalkylamine N-acetyltransferase (AANAT) transcript rhythms in embryonic chicken retinal explant cultures that were maintained under different lighting conditions. Both compounds, whose actions include reversibly block gap junction permeability, produced rapid and sustained reductions in iodopsin and AANAT mRNA levels, but did not alter the levels of guanylate cyclase activating protein-1 (GCAP1) mRNA, a noncircadian-regulated, photoreceptor-specific gene. The iodopsin and AANAT mRNA rhythms re-emerged in the cultured retinas within 24 h of removal of the compounds. These results show that the effects of ACO and 18beta-GA on iodopsin and AANAT mRNA levels were not due to generalized suppression of gene transcription. The dramatic reduction in the levels of iodopsin and AANAT mRNA induced by these compounds suggests a mechanism of action that directly affects the synthesis and/or degradation of these transcripts rather than the synchronization or function of the retinal oscillators that drive transcription of these genes.
A new echocardiographic technology, the timing of regional volumetric changes by 3-dimensional echocardiography, was applied to assess intraventricular mechanical synchronicity in 13 patients who had received cardiac resynchronization therapy (CRT). When biventricular pacing was withheld, left ventricular (LV) asynchrony occurred as reflected by these echocardiographic parameters, whereas LV volume increased and the ejection fraction decreased. Further studies are needed to explore whether this novel method can be used to select suitable candidates for CRT and to predict a favorable response.