Biomedical subjects

N Zhao

Publications and source records attributed to N Zhao.

At least 19 recordsLinked to original sources

PubMed2001

Conservative front tracking and level set algorithms.

Hyperbolic conservation laws are foundational for many branches of continuum physics. Discontinuities in the solutions of these partial differential equations are widely recognized as a primary difficulty for numerical simulation, especially for thermal and shear discontinuities and fluid-fluid internal boundaries. We propose numerical algorithms that will (i) track these discontinuities as sharp internal boundaries, (ii) fully conserve the conserved quantities at a discrete level, even at the discontinuities, and (iii) display one order of numerical accuracy higher globally (at the discontinuity) than algorithms in common use. A significant improvement in simulation capabilities is anticipated through use of the proposed algorithms.

Journal Article↗

PubMed2001

Crystallization and preliminary X-ray crystallographic analysis of native and selenomethionyl recombinant tabtoxin-resistance protein complexed with acetyl-coenzyme A.

Tabtoxin-resistance protein (TTR), an acetyltransferase from Pseudomonas syringae pv. tabaci, was overexpressed in Eschericha coli M15 and the TTR fusion protein complexed with acetyl-coenzyme A (AcCoA) was purified and crystallized. Diffraction data were collected to 3.0 A resolution in-house and the crystal was found to belong to space group P2(1), with unit-cell parameters a = 47.6, b = 66.6, c = 53.5 A, beta = 104.3 degrees. Furthermore, a selenomethionine (SeMet) TTR fusion protein derivative was overexpressed in the same expression system and its complex with AcCoA was purified in a reductive environment. The SeMet TTR derivative crystallized in two forms: the first was identical to that observed for native crystals and the second belonged to space group C2, with unit-cell parameters a = 101.7, b = 45.6, c = 84.2 A, beta = 105.8 degrees. Data from the P2(1) crystal form were collected in-house to 2.3 A resolution. Subsequently, three different wavelength data sets of the C2 crystal form to 1.55 A resolution were collected at the Advanced Photon Source at Argonne National Laboratory.

Acetyl Coenzyme A↗

PubMed2001

Electrocardiographic changes during postnatal development in conscious swine with cardiac autonomic imbalance.

Using a conscious swine model, we studied the effects of different patterns of cardiac autonomic denervation on alterations of R-R and Q T intervals for 8 postnatal weeks. Newborn pigs were assigned randomly to four different groups: sham-operated controls (C), stellate ganglion ablation (SGX), either left (LSGX) or right (RSGX), and the right cardiac vagus nerve (RCVX) transection. The ECGs were recorded by telemetry while animals rested quietly or were judged behaviorally to be asleep. Analyses of the ECG included measurements of R-R and Q-T intervals, as well as corrected Q-T intervals (QTc). Poincaré plots were used to display age-related differences in R-R and Q-T intervals. For stellectomized animals, significantly prolonged R-R intervals were first observed at post-surgical week 3 in the RSGX group and at week 5 in the LSGX group. Significantly prolonged QTc was found only in the RSGX group. In the RCVX group, shortened QTc and R-R intervals were noted at 6 and 7 weeks after denervation. Furthermore, three of six RSGX animals (50%) and one of four RCVX animals (25%) exhibited marked pauses in sinus rhythm that were unrelated to changes in heart rate or to sinus arrhythmia. These results in conscious animals support our hypothesis that abnormal autonomic innervation of the heart during maturation, e.g., withdrawal of vagal cardiac modulation or asymmetry of sympathetic innervation, impairs cardiac electrical stability.

Aging↗

PubMed2001

Changes of absorption spectra during heat-induced denaturation of Photosystem II core antenna complexes CP43 and CP47: revealing the binding states of chlorophyll molecules in these two complexes.

The Photosystem II (PSII) core antenna complexes, CP43 and CP47, were prepared from spinach (Spinacia oleracea L.). The absorption spectra in the red region at room temperature were recorded for the PSII core antenna samples after increased temperature treatment (up to 80 degrees C). Derivative and difference spectra revealed the existence of two groups of chlorophyll a (Chl a) molecules in both CP43 and CP47. The one with the absorption peak in the shorter wavelength region was designated as CP43-669 and CP47-669, while the other with the absorption peak in the longer wavelength region was designated as CP43-682 and CP47-680. The results of the thermal treatment experiment demonstrated that CP43-669 and CP47-669 may exist as monomers of Chl a and that their binding sites on the polypeptides are insensitive to thermal treatment, whereas CP43-682 and CP47-680 may exist as dimers or multimers of Chl a and their binding regions in the polypeptide chains are more sensitive to heat treatment. The excitation energy transfer mechanism between these two different groups of Chl a molecules is also analyzed.

Apoproteins↗

PubMed2001

Transcript map and comparative analysis of the 1.5-Mb commonly deleted segment of human 5q31 in malignant myeloid diseases with a del(5q).

Loss of a whole chromosome 5, or a del(5q), are recurring abnormalities in malignant myeloid diseases. In previous studies, we defined a commonly deleted segment (CDS) of 1.5 Mb between D5S479 and D5S500 in patients with a del(5q), and we established a P1 artificial chromosome-based contig encompassing this interval. To identify candidate tumor suppressor genes (TSGs), we developed a transcript map of the CDS. The map contains 18 genes and 12 expressed sequence tags/UniGenes. Among the 18 genes are 10 genes that were previously cloned and 8 novel genes. The newly identified genes include CDC23, which encodes a component of the anaphase-promoting complex; RAB6KIFL, which encodes a kinesin-like protein involved in organelle transport; and KLHL3, which encodes a human homologue of the Drosophila ring canal protein, kelch. We determined the intron/exon organization of 14 genes and eliminated each gene as a classical TSG by mutation analysis. In addition, we established a single-nucleotide polymorphism map as well as a map of the mouse genome that is syntenic to the CDS of human 5q31. The development of a transcription map will facilitate the molecular cloning of a myeloid leukemia suppressor gene on 5q.

Acute Disease↗

PubMed2001

Pyrolytic characteristics of microalgae as renewable energy source determined by thermogravimetric analysis.

Two kinds of autotrophic microalgae, Spirulina platensis (SP) and Chlorella protothecoides (CP) were pyrolyzed at the heating rates of 15, 40, 60 and 80 degrees C/min up to 800 degrees C in a thermogravimetric analyzer to investigate their pyrolytic characteristics. Three stages (dehydration, devolatilization and solid decomposition) appeared in the pyrolysis process. SP and CP mainly devolatilized at 190-560 degrees C and 150-540 degrees C, respectively. A total volatile yield of about 71% was achieved from each microalga. As the heating rate increased, a lateral shift to higher temperatures was observed in their thermograms, and the instantaneous maximum and average reaction rates in the devolatilization stage were increased while the activation energy was decreased. The value of activation energy for CP pyrolysis was 4.22-5.25 x 10(4), lower than that of SP (7.62-9.70 x 10(4)), and the char in final residue of CP was 14.00-15.14%, less than that of SP by 2-3%. This indicated that CP is preferable for pyrolysis over SP. The experimental results may provide useful data for the design of pyrolytic processing systems using planktonic microalgae as feedstock.

Bioelectric Energy Sources↗

PubMed2001

Coronary artery disease in patients with chest pain who have low-risk clinical characteristics and negative cardiac troponin I.

Patients who have low-risk clinical features and negative cardiac troponin levels may be suitable for early discharge after a brief period of observation in the emergency department (ED). Little is known about the prevalence and severity of coronary artery disease in such patients, although this has implications for follow-up. Subjects included 570 patients who were at < or =7% risk of acute myocardial infarction (AMI), remained clinically stable (defined as the absence of new ischemic changes on their electrocardiograph, signs or symptoms of heart failure, the development of a cardiac arrhythmia or hypotension requiring either inotropes or volume repletion) and had cardiac troponin I (cTnI) levels <0.2 microgl(-1) during the initial 12 hours of hospitalization. Clinical features were documented and those undergoing stress tests and/or coronary angiograms had these graded by 2 independent observers. Overall, 190 (33.3%) of this population, who might be considered suitable for early discharge, had objective evidence of coronary artery disease. Patients with chest pain who are at low risk of AMI, remain clinically stable and have negative cTnI over the initial 12 hours of observation are a heterogeneous population, some of who have threatening coronary disease. This does not preclude early discharge from the ED but emphasizes the need for careful assessment and follow-up.

Aged↗

PubMed2001

Soluble intercellular adhesion molecule-1 as a predictor of early adverse events in patients with chest pain compatible with myocardial ischemia.

STUDY OBJECTIVE: Inflammation plays an important role in acute coronary syndromes, and some evidence indicates that patients with a more pronounced vascular inflammatory response have a poorer outcome. Soluble intercellular adhesion molecule-1 (sICAM-1) is a specific marker for vascular endothelial cell activation. The aim of this study was to investigate the prognostic value of plasma sICAM-1 levels in patients with acute chest pain compatible with myocardial ischemia. METHODS: This prospective study was conducted at 2 urban university medical centers. The study cohort consisted of 119 consecutive patients with chest pain in whom myocardial ischemia was suspected clinically at presentation. Patients with conditions that affect sICAM-1 levels were ineligible. Cardiac troponin I (cTnI), C-reactive protein, and sICAM-1 levels were assayed at presentation to the emergency department. The primary end point was the occurrence of a serious cardiac event (death, nonfatal acute myocardial infarction, coronary revascularization) in the hospital. RESULTS: Although sICAM-1 levels tended to be higher in patients with a serious cardiac event, there was no significant association. In contrast, a cTnI level greater than 0.2 ng/mL was a powerful predictor of an in-hospital serious cardiac event (odds ratio 16.3, 95% confidence interval [CI] 4.7 to 55.9; P <.0001). Soluble ICAM-1 levels of more than 260 ng/mL at presentation had a sensitivity for predicting a serious cardiac event of 63% (95% CI 46% to 81%) but a specificity of only 47% (95% CI 38% to 57%). CONCLUSION: In a heterogeneous population of patients with chest pain compatible with myocardial ischemia, elevated sICAM-1 levels are poor predictors of an individual patient suffering a serious cardiac event in the hospital.

Adult↗

PubMed2001

Partial recovery of light-independent chlorophyll biosynthesis in the chlL-deletion mutant of Synechocystis sp. PCC 6803.

A chlL-deletion mutant of Synechocystis sp. PCC 6803 designated as chlL- was unable to make significant amounts of chlorophyll in darkness. However, an apparent pseudorevertant has been generated spontaneously that can synthesize an increased amount of chlorophyll under light-activated heterotrophic growth conditions. Under these conditions, the chlorophyll content in this pseudorevertant was about 20% of that in the wild-type strain and about 4 times more than that in the original and in the recently recreated chlL-deletion mutant. This is paralleled by increased performance of dark-grown cells in terms of chlorophyll fluorescence induction and oxygen evolution rates in the pseudorevertant versus in the original mutant. PCR analysis confirmed that the chlL- -pseudorevertant mutant still lacked the chlL gene. These results imply that the light-independent chlorophyll biosynthesis pathway was partly recovered.

Bacterial Proteins↗

PubMed2001

Prediction of hyperkalemia in dogs from electrocardiographic parameters using an artificial neural network.

OBJECTIVE: To predict severe hyperkalemia from single electrocardiogram (ECG) tracings. METHODS: Ten conditioned dogs each underwent this protocol three times: Under isoflurane anesthesia, 2 mEq/kg/hr of potassium chloride was given intravenously until P-waves were absent from the ECG and ventricular rates decreased > or =20% in < or =5 minutes. Serum potassium levels (K(+)) were measured at regular intervals with concurrent digital storage of lead II of the surface ECG. A three-layer artificial neural network with four hidden nodes was trained to predict K(+) from 15 separate elements of corresponding ECG data. Data were divided into a training set and a test set. Sensitivity, specificity, and diagnostic accuracy for recognizing hyperkalemia were calculated for the test set based on a prospectively defined K(+) = 7.5. RESULTS: The model produced data for 189 events; 139 were placed in the training set and 50 in the test set. The test set had 37 potassium levels at or above 7.5 mmol/L. The neural network had a sensitivity of 89% (95% CI = 75% to 97%) and a specificity of 77% (95% CI = 46% to 95%) in recognizing these. The positive likelihood ratio was 3.87. Overall accuracy of this model was 86% (95% CI = 73% to 94%). Mean (+/-SD) difference between predicted and actual K(+) values was 0.4 +/- 2.0 (95% CI = -0.2 to 1.0). CONCLUSIONS: An artificial neural network can accurately diagnose experimental hyperkalemia using ECG parameters. Further work could potentially demonstrate its usefulness in bedside diagnosis of human subjects.

Animals↗

PubMed2001

Changes in R-R and Q-T intervals following cardiac vagotomy in neonatal swine.

Asymmetric innervation of the myocardium, especially a predominance of sympathetic innervation, may establish conditions whereby electrical instability could result. Using a swine animal model, we studied the effect of right cardiac vagal denervation on the variability of R-R and Q-T intervals. Newborn pigs were assigned randomly to two groups: sham-operated controls (C), or denervation of the right cardiac vagus nerve (RCVX). EKGs were recorded weekly until the two groups exhibited significant heart rate differences. Analysis of the EKG included measurements of R-R and Q-T intervals and corrected Q-T intervals (QTc). Poincaré plots were used to display age-related differences in R-R and Q-T intervals. For RCVX animals, decreased QTc and R-R intervals were noted at 6 and 7 weeks after denervation, respectively. Unexpectedly, one RCVX animal exhibited marked sudden pauses in sinus rhythm. These data indicated that reduced vagal cardiac modulation during development might alter cardiac electrical stability in conscious swine.

Age Factors↗

PubMed2001

Hot topics in adeno-associated virus as a gene transfer vector.

Adeno-associated virus (AAV) is a promising viral vector in treating many kinds of hereditary diseases. The broad host range, low level of immune response, and longevity of gene expression observed with this vector have enabled the initiation of a number of clinical trials using this gene delivery system. Another potential benefit of AAV vectors is their ability to integrate site-specifically in the presence of Rep proteins. However, this virus is not well characterized. To obtain high level, persistent expression of the foreign gene, some problems should be solved. In this article, we will describe the advances in some fields of recombinant AAV technology that overcome certain limitations of the vector as a gene delivery system, such as the transduction efficiency, the production, the package capacity, and elimination of immune responses, as well as the applications involving these recombinant vectors for the treatment of some diseases.

Dependovirus↗

PubMed2001

[The outlook of using chitosan related materials in nerve regeneration].

Chitosan is a kind of biodegradable materials with excellent biocompatibility. This article interpreted the progress and outlook of using chitosan related materials in nerve regeneration from the following points: the positive charges on chitosan, its ability to adsorb proteins, the specific adhesion of nerve cells on chitosan, and the surface roughness, aperture and surface topography of chitosan.

Biocompatible Materials↗

PubMed2001

[The relationship between cyanotoxin (microcystin, MC) in pond-ditch water and primary liver cancer in China].

OBJECTIVE: To explore the relationship between primary liver cancer (PLC) and MC in drinking pond-ditch water. METHODS: Epidemiological and ecological assays, Meta-analysis and risk assessment were used in this study. Cyanotoxin (Microcystin, MC) in the water of different sources was detected by ELISA. The F344 and HBVx transgenic mice were used to confirm the promotion effect on PLC and the synthetically carcinogenic effect of HBV, aflatoxin and MC. RESULTS: Using Meta-analysis the results of six case-control studies showed that the pooled odds ratio (OR) was 2.46 (95% CI 1.69-2.59), population attributable rick (PAR) was 30.39% (95% CI, 23.30%-37.47%), heterogeneity test P > 0.05. Eutrophication led to cyanobacterial bloom in the pond-ditch water. Cyanotoxin released from dead cyanobacteria was hepatotactic tumor promoter. In HBVx transgenic rats, hepatocellular carcinoma was induced by the joint administration of aflatoxin B1 and cyanotoxin. Epidemiological study showed that the recombined index of HBsAg, aflatoxin-albumin adducts and drinking of pond-ditch water correlated with PLC mortalities in 13 townships. CONCLUSION: Microcystin in the pond-ditch water is a hepatotactic toxin which can induce hepatitis and promote development of hepatocellular carcinoma. The combined effect of microcystin, HBV and aflatoxin may be responsible for the endemicity of PLC.

Aflatoxin B1↗

PubMed2000

cDNA cloning and genomic structure of three genes localized to human chromosome band 5q31 encoding potential nuclear proteins.

Loss of a whole chromosome 5, or a del(5q), is a recurring abnormality in malignant myeloid diseases. By cytogenetic and molecular analyses, we delineated previously a 1- to 1.5-Mb region that is deleted in all patients with a del(5q). In our efforts to identify a myeloid tumor suppressor gene within the commonly deleted segment (CDS), we have cloned and characterized the genes encoding three putative nuclear proteins, each of which contains a bipartite nuclear localization signal (NLS). In addition, C5ORF5 contains a putative rhoGAP domain at the N-terminus, C5ORF6 has a proline-rich sequence near the N-terminus, and C5ORF7 has a zinc-finger domain that partially overlaps the NLS. All three genes are ubiquitously expressed and encode novel proteins. The C5ORF5 cDNA is 5.47 kb encoding a protein of 915 amino acids (aa) with a predicted molecular mass of approximately 105 kDa. C5ORF5 has 23 exons spanning over 27 kb. The C5ORF6 transcript is 4.1 kb encoding a protein of 392 aa with a predicted molecular mass of approximately 43 kDa. C5ORF6 has 5 exons and spans approximately 11 kb. The C5ORF7 cDNA is 6.3 kb and encodes a protein of 1417 aa with a predicted molecular mass of approximately 155 kDa. C5ORF7 has 24 exons spanning approximately 64 kb. All three genes were localized to the distal half of the CDS between D5S1983 and D5S500. We evaluated each as a candidate tumor suppressor gene by the analysis of myeloid leukemia cells from patients with -5/del(5q), but no inactivating mutations were identified.

Amino Acid Sequence↗

PubMed2000

cDNA cloning, expression pattern, genomic structure and chromosomal location of RAB6KIFL, a human kinesin-like gene.

Kinesin-like proteins are microtubule-associated motors that play important roles in intracellular transport and cell division. We report here the characterization of a new human kinesin-like protein, Rabkinesin6 (RAB6KIFL). The composite cDNA sequence is 2957bp, and encodes a protein of 890 amino acids with a predicted molecular weight of 100kDa. It has high homology (93% similarity) with the mouse kinesin-like protein, Rab6kifl, indicating that it is the human homologue of the mouse gene. RAB6KIFL has all of the structural characteristics required to function as a microtubule-associated motor. Unlike the mouse gene which is ubiquitously expressed, RAB6KIFL expression appears to be tissue specific. It is widely expressed in fetal tissues, abundantly expressed in adult thymus, bone marrow and testis, and is expressed at low levels in heart, placenta and spleen. The RAB6KIFL gene is mapped to human chromosome 5, band q31, spans approximately 8.5kb of genomic DNA, and contains 19 exons. RAB6KIFL maps within the smallest commonly deleted segment in myeloid leukemias characterized by a deletion of 5q; however, we detected no mutations of RAB6KIFL in malignant myeloid disorders with loss of 5q. The description of this human kinesin-like protein may provide a better understanding of the diversity of this large family of proteins.

Acute Disease↗

PubMed2000

Photochemistry of substituted benzyldiphenylphosphine oxides

Photochemical reactions (lambda irr = 254 nm) of substituted benzyldiphenylphosphine oxides 1a-e have been investigated in benzene and acetonitrile. alpha-Cleavage from the singlet excited state is proposed as the primary process, and products formed both before and after escape of the primary intermediates from the solvent cage result. Radicals 2 and 3 are observed by nanosecond flash photolysis following excitation of 1a at 266 nm in acetonitrile. Acetone sensitization of 1a,b fails to improve the efficiency of product formation. The quantum yields of disappearance of 1a,b are unaffected by O2, and mechanisms for product formation from 1a in the presence of oxygen are proposed.

Journal Article↗

PubMed2000

Spectroscopic study of trypsin, heat and triton X-100-induced denaturation of the chlorophyll-binding protein CP43.

Trypsin-, heat- and Triton X-100-induced denaturation of CP43, the core antenna complex of photosystem II purified from spinach, has been investigated using absorption, fluorescence and circular dichroism spectroscopy. Triton X-100 was found to bring about considerable dissolution of pigments from the protein to the monomeric state in solution and destruction of the interactions among the chlorophyll, carotene and protein. Heat induced significant unfolding of the protein secondary structure and loss of excitonic interactions of the pigments, but no apparent dissolution of the pigments from CP43. Trypsin caused structural changes in the extrinsic part of the protein but no change of the native state of the pigments. Trypsin, heat and Triton X-100 treatments increased the light sensitivity of chlorophyll in CP43 to different extents. The results suggest that the protein and beta-carotene can protect the chlorophyll from light-induced destruction in CP43.

Binding Sites↗