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Biomedical subjects

J S Liu

Publications and source records attributed to J S Liu.

At least 19 recordsLinked to original sources
PubMed2006

Diffractive optical elements for beam shaping of monochromatic spatially incoherent light.

Fresnel-type diffractive optical elements (DOEs) for general beam shaping of monochromatic, spatially incoherent light are demonstrated. Direct and indirect methods, i.e., adding a lens' phase to the designed Fraunhofer-type DOEs, are used for the design. The indirect method can reduce the calculation time by approximately half without loss of design accuracy. Two different design examples are shown. For one design the direct method gives a maximum sidelobe intensity of 5.0% of the maximum intensity in the signal window. For the second design the indirect method gives 23.0% of this value. The generated patterns can maintain their basic shapes over a long distance. The elements have been fabricated by directly using gray-scale commercial slides as masks. Experimental results are in close agreement with numerical predictions.

Journal Article↗
PubMed2006

Effects of cysteamine on growth performance, digestive enzyme activities, and metabolic hormones in broilers.

A total of 600 avian male broilers at the age of 1 d were used to investigate the effects of cysteamine (CSH) on growth performance, digestive enzyme activities, and concentrations of serum hormones. The broilers received the same basal diets, with CSH added at 0 (control), 60, 90, 120, or 150 mg/kg. The feeding program consisted of a starter diet until 21 d and a grower diet until 42 d. The broilers with addition of CSH at 60 or 90 mg/kg had significantly higher growth rates during d 1 to 21 or d 21 to 42 compared with the control, respectively. However, adding 150 mg of CSH/kg significantly suppressed the growth of broilers. Adding 60 mg of CSH/kg significantly increased the activities of protease, amylase, and lipase in the pancreas and small intestinal contents during d 1 to 21, and the activities of protease and amylase in the small intestinal contents during d 21 to 42. Adding 90 mg of CSH/kg significantly increased the activities of lipase during d 1 to 21 and protease, amylase, and lipase during d 21 to 42 in small intestines. The activities of digestive enzymes during the whole period were suppressed by adding 150 mg of CSH/kg. The concentration of serum thyroxine was higher in the CSH-added birds during the whole period, whereas serum triiodothyronine was higher only during d 1 to 21 compared with the control. These findings indicate that low doses of dietary CSH may improve the growth performance and the activities of the digestive enzyme, but high doses of CSH appear to be detrimental to growth and digestion.

Aging↗
PubMed2005

Incoherent subharmonic light scattering in isotropic media.

Incoherent subharmonic light scattering in isotropic media is a new kind of nonlinear light scattering, which involves single input photon and multiple output photons of equal frequency. We investigate theoretically the dependence of the subharmonic scattering intensity on the hyperpolarizability of molecules and the incident intensity using nonlinear optics theory similar to that used for Hyper-Rayleigh scattering and degenerate optical parametric oscillators. It is derived that the subharmonic scattering intensities grow exponentially or superexponentially with the hyperpolarizability of molecules and the incident intensity.

Light↗
PubMed2005

Episodic pain syndrome restricted cheiro-oral region associated with pontine lesion.

Other than from the thalamus and sensory cortex, episodic pain is an extremely rare neurological manifestation in the central compartment. This study reports a middle-aged man who experienced an acute onset of episodic oscillatory burning pain restricted to the cheiro-oral region, who was found to have a singular infarct at the left tegmental pons. A close relationship between his pain attack and an elevation of arterial blood pressure was clearly observed. Blood adenohypophyseal hormones and electroencephalogram did not reveal an abnormality in the ictus. Neuroimaging and clinical studies did not support involvement of the thalamus, periaqueductal gray matter, hypothalamus or regional structure. Therefore, episodic pain may be an isolated manifestation with a pontine lesion. A relapsing expansion of focal cerebral oedema with fluid retention may have corresponded to the oscillation of his sensory deficit. This accumulating, devastating calamity by a repetitive and paroxysmal offense after a blood-brain barrier breakdown should be cautiously reviewed.

Acute Disease↗
PubMed2003

The validity of eye blink rate in Chinese adults for the diagnosis of Parkinson's disease.

We evaluated the eye blink rate (EBR) in healthy Chinese adults and Parkinson's disease (PD) patients. In healthy subjects, the EBR declined with age, was lower in women than men younger than 50 years of age, and did not differ from male PD patients older than 60 years or female PD patients older than 50 years. Accordingly, EBR is not a good indicator for bradykinesia in Chinese individual older than 50 years that is prevalent for PD onset also.

Adult↗
PubMed2002

A perturbation of antithrombin-III and protein C coupling associates with an increase of anti-beta2-glycoprotein I antibody in non-antiphospholipid antibody syndrome cerebral ischemia.

Anti-beta -glycoprotein I antibody (abetaGPI) has been recognized in raising the risk of cerebral ischemia in patients with antiphospholipid antibody syndrome (APS), especially by protein C (PC) axis perturbation. Although a high potential is also seen in non-APS patients, the mechanism is substantially unknown. In the present study, we examined the effect of abetaGPI on PC and antithrombin-III (AT-III) activity in non-APS patients with non-cardiac cerebral ischemia (NCCI). A total of 111 NCCI patients and 30 healthy controls were enrolled. They were free of APS manifestation, and their anticardiolipin antibody and lupus anticoagulant tests were within normal range. There were 14.4% patients found to have an abnormal increase of blood abetaGPI. The PC, AT-III, albumin, aminotransferases, creatinine, prothrombin time and activated partial thromboplastin time did not differ between our patients and controls, or patients with or without increased abetaGPI. However, a marked decrease of the PC/AT-III ratio was found in patients with increased abetaGPI. The correlation between PC and AT-III activity was highly significant in patients with an increase of abetaGPI (P = 0.001), only marginal in controls (P = 0.042), and was insignificant in patients with a normal abetaGPI (P = 0.277). The abetaGPI did not correlate to PC or AT-III activity in either patients or controls. These findings suggest that high PC/AT-III coupling may relate to NCCI in non-APS patients associated with an increase of abetaGPI. This coupling effect seems not to be caused by abetaGPI directly.

Adult↗
PubMed2001

DNA damage by the enediyne C-1027 results in the inhibition of DNA replication by loss of replication protein A function and activation of DNA-dependent protein kinase.

Treatment of cells with the enediyne C-1027 is highly efficient at inducing single- and double-strand DNA breaks. This agent is highly cytotoxic when used at picomolar levels over a period of days. For this study, C-1027 has been used at higher levels for a much shorter time period to look at early cellular responses to DNA strand breaks. Extracts from cells treated with C-1027 for as little as 2 h are deficient in SV40 DNA replication activity. Treatment with low levels of C-1027 (1-3 nM) does not result in the presence of a replication inhibitor in cell extracts, but they are deficient in replication protein A (RPA) function. Extracts from cells treated with high levels of C-1027 (10 nM) do show the presence of a trans-acting inhibitor of DNA replication. The deficiency in RPA in extracts from cells treated with low levels of C-1027 can be fully complemented by the addition of exogenous RPA, and may be due to a C-1027-induced decrease in the extractability of RPA. This decrease in the extractability of RPA correlates with the appearance of many extraction-resistant intranuclear RPA foci. The trans-acting inhibitor of DNA replication induced by treatment of cells with high levels of C-1027 (10 nM) is DNA-dependent protein kinase (DNA-PK). DNA-PK is activated by the presence of DNA fragments induced by C-1027 treatment, and can be abrogated by removal of the DNA fragments. Although it is activated by DNA damage and phosphorylates RPA, DNA-PK is not required for either RPA focalization or loss of RPA replication activity.

Aminoglycosides↗
PubMed2001

Microbial growth by a net heat up-take: a calorimetric and thermodynamic study on acetotrophic methanogenesis by Methanosarcina barkeri.

To answer the intriguing question whether or not endothermic microbial growth exists, and in particular, to verify Heijnen and van Dijken's prediction (1992), acetotrophic methanogen, Methanosarcina barkeri, has been cultivated in a highly sensitive bench-scale calorimeter (an improved Bio-RC1 reaction calorimeter) in a pH auxostat fashion. A growth yield of 0.043 C-mol C-mol(-1) has been obtained and a cell density as high as 3 g L(-1) was attained. Heat uptake during growth has indeed been quantitatively measured with calorimetry, resulting in a heat yield of +145 kJ C-mol(-1). Thermodynamics of the growth of acetotrophic methanogens was analyzed in detail. The changes in Gibbs energy, enthalpy, and entropy during growth of M. barkeri were compared with some typical aerobic and anaerobic growth processes of different microorganisms on various substrates. In the growth of M. barkeri on acetate, the retarding effect of the positive enthalpy change on the driving force of growth is overcompensated by the large positive entropy change, resulting from converting one organic molecule (acetic acid) to two gaseous products, CH(4) and CO(2). Both the enthalpy and the entropy increases are due partially to the transition of these two products into the gaseous phase. The thermodynamic role of this phase transition for the growth process is analyzed. Microbial growth characterized by enthalpy increase and correspondingly by a large increase in entropy may be called enthalpy-retarded growth.

Acetic Acid↗
PubMed2001

The cellular response to DNA damage induced by the enediynes C-1027 and neocarzinostatin includes hyperphosphorylation and increased nuclear retention of replication protein a (RPA) and trans inhibition of DNA replication.

This study examined the cellular response to DNA damage induced by antitumor enediynes C-1027 and neocarzinostatin. Treatment of cells with either agent induced hyperphosphorylation of RPA32, the middle subunit of replication protein A, and increased nuclear retention of RPA. Nearly all of the RPA32 that was not readily extractable from the nucleus was hyperphosphorylated, compared to < or =50% of the soluble RPA. Enediyne concentrations that induced RPA32 hyperphosphorylation also decreased cell-free SV40 DNA replication competence in extracts of treated cells. This decrease did not result from damage to the DNA template, indicating trans-acting inhibition of DNA replication. Enediyne-induced RPA hyperphosphorylation was unaffected by the replication elongation inhibitor aphidicolin, suggesting that the cellular response to enediyne DNA damage was not dependent on elongation of replicating DNA. Neither recovery of replication competence nor reversal of RPA effects occurred when treated cells were further incubated in the absence of drug. C-1027 and neocarzinostatin doses that caused similar levels of DNA damage resulted in equivalent increases in RPA32 hyperphosphorylation and RPA nuclear retention and decreases in replication activity, suggesting a common response to enediyne-induced DNA damage. By contrast, DNA damage induced by C-1027 was at least 5-fold more cytotoxic than that induced by neocarzinostatin.

Aminoglycosides↗
PubMed2001

Phylogenetic footprinting of transcription factor binding sites in proteobacterial genomes.

Toward the goal of identifying complete sets of transcription factor (TF)-binding sites in the genomes of several gamma proteobacteria, and hence describing their transcription regulatory networks, we present a phylogenetic footprinting method for identifying these sites. Probable transcription regulatory sites upstream of Escherichia coli genes were identified by cross-species comparison using an extended Gibbs sampling algorithm. Close examination of a study set of 184 genes with documented transcription regulatory sites revealed that when orthologous data were available from at least two other gamma proteobacterial species, 81% of our predictions corresponded with the documented sites, and 67% corresponded when data from only one other species were available. That the remaining predictions included bona fide TF-binding sites was proven by affinity purification of a putative transcription factor (YijC) bound to such a site upstream of the fabA gene. Predicted regulatory sites for 2097 E.coli genes are available at http://www.wadsworth.org/resnres/bioinfo/.

Base Sequence↗
PubMed2001

Expression of inducible nitric oxide synthase and nitrotyrosine in multiple sclerosis lesions.

Nitric oxide generated by the inducible form of nitric oxide synthase (iNOS) may contribute to the pathogenesis of multiple sclerosis (MS). In this report, we studied postmortem tissues of MS patients for the expression of iNOS by in situ hybridization and immunocytochemistry. Immunocytochemistry for nitrotyrosine, a putative footprint for peroxynitrite formation was also performed. In acute MS lesions, intense reactivity for iNOS mRNA and protein was detected in reactive astrocytes throughout the lesion and in adjacent normal appearing white matter. Staining of macrophages, inflammatory cell infiltrates, and endothelial cells was variable from case to case, but generally detected only in acute lesions. In chronic MS lesions reactive astrocytes at the lesion edge were positive for iNOS whereas the lesion center was nonreactive. Normal appearing white matter demonstrated little reactivity, as did tissues from noninflamed control brains. Staining for nitrotyrosine was also detected in acute but not chronic MS lesions, and displayed a diffuse parenchymal, membranous, and perivascular pattern of immunoreactivity. These results support the conclusion that iNOS is induced in multiple cell types in MS lesions and that astrocyte-derived nitric oxide could be important in orchestrating inflammatory responses in MS, particularly at the blood-brain barrier.

Adult↗
PubMed2001

A reevaluation and discussion on the threshold limit for hemolysis in a turbulent shear flow.

One major factor of red blood cell damage induced by artificial heart valves is the magnitude of turbulent shear stresses in the flow field. An often-cited threshold for hemolysis is 400 N/m(2) (Sallam and Hwang, Biorheology 21 (1984) 783). This value, however, was measured with a one-component laser Doppler anemometer and was not calculated from the major principal Reynolds shear stress, therefore underestimating the threshold. This study performed flow field measurements under similar conditions, using a two-component laser Doppler anemometer and determining major principal Reynolds shear stress, to reevaluate the hemolytic threshold as 800 N/m(2) with an exposure time of 1 ms. The Kolmogorov length scales, approximately 9 microm, are capable of inflicting direct damage to the red blood cells. These results will serve as a more accurate reference in future heart valve design and testing.

Blood Flow Velocity↗
PubMed2001

Bayesian analysis of haplotypes for linkage disequilibrium mapping.

Haplotype analysis of disease chromosomes can help identify probable historical recombination events and localize disease mutations. Most available analyses use only marginal and pairwise allele frequency information. We have developed a Bayesian framework that utilizes full haplotype information to overcome various complications such as multiple founders, unphased chromosomes, data contamination, and incomplete marker data. A stochastic model is used to describe the dependence structure among several variables characterizing the observed haplotypes, for example, the ancestral haplotypes and their ages, mutation rate, recombination events, and the location of the disease mutation. An efficient Markov chain Monte Carlo algorithm was developed for computing the estimates of the quantities of interest. The method is shown to perform well in both real data sets (cystic fibrosis data and Friedreich ataxia data) and simulated data sets. The program that implements the proposed method, BLADE, as well as the two real datasets, can be obtained from http://www.fas.harvard.edu/~junliu/TechRept/01folder/diseq_prog.tar.gz.

Bayes Theorem↗
PubMed2001

An unusual increase of blood anti-beta 2-glycoprotein-I antibody but not antiphospholipid antibody in cerebral ischemia--a case report.

An abnormal increase in anti-beta2-glycoprotein I antibodies (abeta2GPI) is capable of producing thrombosis and the vasculopathy-simulating antiphospholipid antibody (aPL). However, it is rarely described in cerebral ischemia without an association with aPL. The authors report a middle-aged man who experienced recurrent cerebral ischemia and diffuse cerebral stenosis without the apparent traditional cardiovascular risk factor. He was free of antiphospholipid/cofactor syndrome (APCS) and systemic lupus erythematosus (SLE). An increase of blood abeta2GPI was detected in serial measurements. The aPL, Venereal Disease Research Laboratory (VDRL) test, Coombs' test, and antinuclear factor were negative. Activated partial thromboplastin time was normal. This patient is a reminder to consider abeta2GPI in an unexplained recurrent cerebral thrombosis and cerebral artery stenosis even when the typical clinical manifestation or laboratory data of APCS is absent.

Antibodies, Antiphospholipid↗
PubMed2001

BioProspector: discovering conserved DNA motifs in upstream regulatory regions of co-expressed genes.

The development of genome sequencing and DNA microarray analysis of gene expression gives rise to the demand for data-mining tools. BioProspector, a C program using a Gibbs sampling strategy, examines the upstream region of genes in the same gene expression pattern group and looks for regulatory sequence motifs. BioProspector uses zero to third-order Markov background models whose parameters are either given by the user or estimated from a specified sequence file. The significance of each motif found is judged based on a motif score distribution estimated by a Monte Carlo method. In addition, BioProspector modifies the motif model used in the earlier Gibbs samplers to allow for the modeling of gapped motifs and motifs with palindromic patterns. All these modifications greatly improve the performance of the program. Although testing and development are still in progress, the program has shown preliminary success in finding the binding motifs for Saccharomyces cerevisiae RAP1, Bacillus subtilis RNA polymerase, and Escherichia coli CRP. We are currently working on combining BioProspector with a clustering program to explore gene expression networks and regulatory mechanisms.

Bacillus subtilis↗
PubMed2001

[Effects of opioids on Ca2+/calmodulin dependent protein kinase signal pathway in NG108-15 cells].

AIM: To observe the change of Ca2+/calmodulin dependent protein kinase II (CaMK II) signal pathway in opioid dependent NG108-15 cells. METHODS: NG108-15 cells were used as an in vitro model system. Competitive protein binding assay and radioimmunoassay were used to examine the intracellular cAMP accumulation. Calmodulin activity was assayed by PDE method. CaMK II activity was assayed by gamma-32 P incorporation of syntide-2. RESULTS: DPDPE long-term treatment increased calmodulin activity and CaMK II activity in both cytoplasm and nucleus of NG108-15 cells. Specific calmodulin antagonist W-7 was found to significantly inhibit the elevation of calmodulin and CaMK II activity which resulted from DPDPE long-term treatment, and CaMK II inhibitor KN-62 also inhibited elevation of CaMK II activity by DPDPE long-term treatment. When naloxone was added to NG108-15 cells which were long-term treated by DPDPE, calmodulin and CaMK II activity increased, indicating that naloxone withdrawal can increase Ca2+/CaMK II pathway activity. CONCLUSION: The results indicate that Ca2+/CaMK II pathway was involved in the mechanisms of opioids dependence when DPDPE was long-term administered to NG108-15 cells.

Analgesics, Opioid↗