Effects of a dye laser with correlations between additive and multiplicative noise: Transient properties.
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Journal Article↗
Biomedical subjects
C Li
Publications and source records attributed to C Li.
Excited-state nonlinear absorption in multi-energy-level molecular systems.
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Journal Article↗
Frequency dependence of electrorheological fluids in an ac electric field.
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Journal Article↗
Detection of ECG characteristic points using wavelet transforms.
An algorithm based on wavelet transforms (WT's) has been developed for detecting ECG characteristic points. With the multiscale feature of WT's, the QRS complex can be distinguished from high P or T waves, noise, baseline drift, and artifacts. The relation between the characteristic points of ECG signal and those of modulus maximum pairs of its WT's is illustrated. By using this method, the detection rate of QRS complexes is above 99.8% for the MIT/BIH database and the P and T waves can also be detected, even with serious baseline drift and noise.
Algorithms↗
Staphylococcus aureus induces platelet aggregation via a fibrinogen-dependent mechanism which is independent of principal platelet glycoprotein IIb/IIIa fibrinogen-binding domains.
Platelet aggregation by bacteria is felt to play an important role in the pathogenesis of infective endocarditis. However, the mechanisms involved in bacterium-induced platelet aggregation are not well-defined. In the present study, we examined the mechanisms by which Staphylococcus aureus causes rabbit platelet aggregation in vitro. In normal plasma, the kinetics of S. aureus-induced platelet aggregation were rapid and biphasic. The onset and magnitude of aggregation phase 1 varied with the bacterium-platelet ratio, with maximal aggregation observed at a ratio of 5:1. The onset of aggregation phase 2 was delayed in the presence of apyrase (an ADP hydrolase), suggesting that this later aggregation phase may be triggered by secreted ADP. The onset of aggregation phase 2 was delayed in the presence of prostaglandin I2-treated platelets, and this phase was absent when paraformaldehyde-fixed platelets were used, implicating platelet activation in this process. Platelet aggregation phase 2 was dependent on S. aureus viability and an intact bacterial cell wall, and it was mitigated by antibody directed against staphylococcal clumping factor (a fibrinogen-binding protein) and by the cyclooxygenase inhibitor indomethacin. Similarly, aggregation phase 2 was either delayed or absent in three distinct transposon-induced S. aureus mutants with reduced capacities to bind fibrinogen in vitro. In addition, a synthetic pentadecapeptide, corresponding to the staphylococcal binding domain in the C terminus of the fibrinogen delta-chain, blocked aggregation phase 2. However, phase 2 of aggregation was not inhibited by two synthetic peptides (alone or in combination) analogous to the two principal fibrinogen-binding domains on the platelet glycoprotein (GP) IIb/IIIa integrin receptor: (i) a recognition site on the IIIa molecule for the Arg-Gly-Asp (RGD) sequence of the fibrinogen alpha-chain and (ii) a recognition site on the IIb molecule for a dodecapeptide sequence of the fibrinogen delta-chain. This differs from ADP-induced platelet aggregation, which relies on an intact platelet GP IIb/IIIa receptor with an accessible RGD sequence and dodecapeptide recognition site for fibrinogen. Furthermore, a monoclonal antibody directed against the RGD recognition site on rabbit platelet GP IIb/IIIa receptors failed to inhibit rabbit platelet aggregation by S. aureus. Collectively, these data suggest that S. aureus-induced platelet aggregation requires bacterial binding to fibrinogen but is not principally dependent upon the two major fibrinogen-binding domains on the platelet GP IIb/IIIa integrin receptor, the RGD and dodecapeptide recognition sites.
Adenosine Triphosphate↗
Mechanics of bacterial macrofiber initiation.
The twisting and writhing during growth of single-cell filaments of Bacillus subtilis which lead to macrofiber formation was studied in both left- and right-handed forms of strains FJ7 and RHX. Filament bending, touching, and loop formation (folding), followed by winding up into a double-strand fiber, were documented. Subsequent folds that produced multistrandedness were also examined. The rate of loop rotation during winding up was measured for 26 loops from 16 clones. In most cases, the first loop formed turned at a lower rate than those produced by the following cycles of folding. The sequence of folding topologies differed in FJ7 and RHX strains and in left- versus right-handed structures. Right-handed FJ7 routinely gave rise to four-stranded helices at the second fold, whereas left-handed FJ7 and both left-handed and right-handed forms of RHX made structures with predominantly two double-stranded helical regions. Left-handed RHX structures frequently produced second folds within the initial loop itself, resulting in T- or Y-shaped fibers. Sixteen cases in which the initial touch of a filament to itself produced a loop that snapped open before it could wind up into a double-strand fiber were found. The snap motions were used to obtain estimates of the forces generated by helical growth of single filaments and to investigate theoretical models involving the material properties of cell filaments. In general, the mechanical behavior of growing single-cell filaments and fibers consisting of two-, three-, or four-strand helices was similar to that described for larger, mature, multifilament macrofibers. The behavior of multicellular macrofibers can be understood, therefore, in terms of individual cell growth.
Bacillus subtilis↗
The transcriptional repressor even-skipped interacts directly with TATA-binding protein.
The Drosophila homeodomain protein Even-skipped (Eve) has previously been shown to function as a sequence-specific transcriptional repressor, and in vitro and in vivo experiments have shown that the protein can actively block basal transcription. However, the mechanism of repression is not known. Here, we present evidence establishing a direct interaction between Eve and the TATA-binding protein (TBP). Using cotransfection assays with minimal basal promoters whose activity can be enhanced by coexpression of TBP, we found that Eve could efficiently block, or squelch, this enhancement. Squelching did not require Eve DNA-binding sites on the reporter plasmids but was dependent on the presence of the Eve repression domain. Further support for an in vivo interaction between the Eve repression domain and TBP was derived from a two-hybrid-type assay with transfected cells. Evidence that Eve and TBP interact directly was provided by in vitro binding assays, which revealed a specific protein-protein interaction that required an intact Eve repression domain and the conserved C terminus of TBP. The Eve homeodomain was also required for these associations, suggesting that it may function in protein-protein interactions. We also show that a previously characterized artificial repression region behaves in a manner similar to that of the Eve repression domain, including its ability to squelch TBP-enhanced expression in vivo and to bind TBP specifically in vitro. Our results suggest a model for transcriptional repression that involves an interaction between Eve and TBP.
Amino Acid Sequence↗
High prevalence of Helicobacter pylori in saliva demonstrated by a novel PCR assay.
AIMS: To investigate the prevalence of Helicobacter pylori in the saliva of patients infected with this bacterium. METHODS: A novel polymerase chain reaction (PCR) assay was developed to detect H pylori in saliva and gastric biopsy specimens from patients undergoing endoscopy. RESULTS: Our PCR assay amplified a 417 base pair fragment of DNA from all 21 DNAs derived from H pylori clinical isolates but did not amplify DNA from 23 non-H pylori strains. Sixty three frozen gastric biopsy and 56 saliva specimens were tested. H pylori specific DNA was detected by PCR in all 39 culture positive biopsy specimens and was also identified from another seven biopsy specimens which were negative by culture but positive by histology. H pylori specific DNA was identified by PCR in saliva specimens from 30 (75%) of 40 patients with H pylori infection demonstrated by culture or histological examination, or both, and in three patients without H pylori infection in the stomach. CONCLUSION: The results indicate that the oral cavity harbours H pylori and may be the source of infection and transmission.
Base Sequence↗
Development of F-18-labeled fluoroerythronitroimidazole as a PET agent for imaging tumor hypoxia.
PURPOSE: To develop a hydrophilic ligand to image tumor hypoxia at positron emission tomography (PET). MATERIALS AND METHODS: Biodistribution of fluorine-18-labeled fluoroerythronitroimidazole (FETNIM) and F-18-labeled fluoromisonidazole (FMISO) was determined at PET and autoradiography in three mammary-tumor-bearing rats. The partition coefficient of FETNIM, FMISO, and misonidazole was determined. RESULTS: Biodistribution of F-18-labeled FETNIM at 1, 2, and 4 hours showed tumor-to-blood ratios of 2.29 +/- 0.599, 2.41 +/- 0.567 and 8.02 +/- 2.420, respectively, and tumor-to-muscle ratios of 0.66 +/- 0.267, 2.11 +/- 0.347, and 5.92 +/- 2.240, respectively. The tumor-to-blood count density ratio with F-18-labeled FETNIM at 4 hours after injection was significantly higher than with F-18-labeled FMISO. Autoradiographs indicated that both agents could help differentiate hypoxic versus necrotic region in the tumor. CONCLUSION: F-18-labeled FETNIM can help detect tumor hypoxia and is easier to prepare, less costly, and more hydrophilic than F-18-labeled FMISO.
Animals↗
Inhibitory effects of anti-prolactin receptor antibodies on prolactin binding in brain and prolactin-induced feeding behavior in ring doves.
Although binding sites for prolactin (PRL) have been mapped and partially characterized in the brains of several species, there is as yet no direct evidence that the effects of intracranial PRL on brain function are receptor-mediated events. We addressed this question by testing whether antibodies generated against rat liver PRL receptors can effectively antagonize the ability of PRL to enhance feeding behavior in male ring doves (Streptopelia risoria). Both agents were administered directly to the ventromedial hypothalamic nucleus (VMN), which is an effective site of PRL action in promoting hyperphagia in this species. In the initial study, affinity-purified gamma-globulin (IgG) from the receptor antiserum preparation was tested for its ability to compete with 125I-ovine PRL for binding to receptors in rat liver, dove choroid plexus, and 6 PRL-sensitive dove brain regions using in vitro quantitative film autoradiography. Although the binding affinity of the anti-PRL receptor antibodies was at least 50 times lower in dove brain than in rat liver, a 40-50% inhibition of specifically bound 125I-ovine PRL was observed in choroid plexus and in 5 of 6 brain regions with anti-receptor IgG concentrations of 5.8 x 10(-7) M and 1.2 x 10(-6) M, using sections incubated with normal rabbit serum (NRS) IgG as a control. In a second study, anti-PRL receptor IgG or NRS IgG (2.4 micrograms) was injected unilaterally into the VMN at 45-60 min prior to VMN injection of ovine PRL (50 ng) or saline vehicle. This procedure was repeated at twice-daily intervals for 5 days. When compared to the feeding behavior of PRL-injected birds given NRS IgG, antireceptor antibody-treated animals showed a marked reduction in PRL-induced hyperphagia. The magnitude of this reduction was calculated to be approximately 50% after corrections were made for a mild hypophagia induced by the anti-receptor IgG treatment alone, as reflected in the feeding behavior of the anti-PRL receptor IgG + vehicle-treated group. These results suggest that PRL receptors in dove brain and rat liver exhibit structural similarities as well as differences and that the hyperphagia induced by intracranial injections of PRL is mediated, at least in part, by interactions with PRL receptors in the brain.
Animals↗
[Simplified enzyme-linked immunoadsorbent assays for myelin basic protein and antibodies to myelin basic protein].
Synchronous quantitative determination using simplified enzyme-linked immuno adsorbent assay has been developed for myelin basic protein (MBP) and antibodies to myelin basic protein (Anti-MBP). Antisera were prepared by immunizing rabbits with purified MBP from human white matter. Antibodies to MBP was conjugated with horseradish peroxidase (HRP) by using modified periodate oxidation method. Minimum detection amounts of MBP and Anti-MBP are 0.25 ng/ml and 0.20 ng/ml respectively. The activities of Anti-MBP-HRP conjugates are stable (stored at -30 degrees C) for at least 2 years. The detection procedure can be accomplished within 24 hours.
Animals↗
[Enzyme-linked immunoadsorbent assays for myelin basic protein and antibodies to myelin basic protein in serum and CSF of patients with diseases of the nervous system].
Simplified enzyme-linked immunoadsorbent assays (ELISA) for myelin basic protein (MBP) and antibodies to myelin basic protein (Anti-MBP) have been used to test 337 patients with diseases of the nervous system including 36 compressive diseases (CMP), 33 multiple sclerosis (MS), 34 cerebrovascular diseases (CVD), 31 inflammatory diseases of central nervous system (ID), 161 epilepsy (EP) and 42 other nervous diseases (OND). Comparison of results among various groups indicates that serum mean MBP values of CMP, MS, CVD, ID and EP groups are significantly higher than those of OND group and normal control (P < 0.01). The serum mean MBP value of 33 acute trauma patients with spine fracture and paraplegia, the majority of CMP group, is the highest compared with MS group (P < 0.05), CVD, ID and EP groups (P < 0.01). CSF mean MBP value of 15 CVD patients is markedly greater than that of OND group (P < 0.05). No statistically significant differences are found in serum MBP values between OND group and normal control, and in serum and CSF Anti-MBP values among six groups by using our method.
Autoantibodies↗
[The value of serum myelin basic protein in assessment of severity of acute closed head trauma].
Serum levels of myelin basic protein (MBP) were measured in 112 patients after acute head injury by enzyme linked immuno-absorbent assay (ELISA). Patients with cerebral concussion showed no significant change in serum MBP. Patients with cerebral contusion, extradural hematoma or intracerebral hematoma had a mean serum MBP concentration much higher than that of patients with cerebral concussion. And patients with extradural hematoma had a mean serum MBP concentration much lower than that of patients with cerebral contusion and intracerebral hematoma; the differences were significant (P < 0.05). But there was no significant difference between patients with cerebral contusion and intracerebral hematoma (P > 0.05). The amount of serum MBP was significantly correlated with the volume of extradural hematoma, intracerebral hematoma and with the extent of the cerebral contusion (P < 0.05). This study suggested that the serum MBP may reflect the type and severity of closed head injury patients.
Adolescent↗
[Myelin basic protein level in serum of patients with chronic cor pulmonale in acute phase].
With a sensitive enzyme-linked immunoadsorbent assay that can detect as little as 0.5ng/ml of myelin basic protein (MBP), we studied serum specimens from 34 patients with chronic cor pulmonale (CP) and 33 patients with chronic bronchitis (CB) during acute attack in hospital and 30 control subjects. The results showed that the serum mean MBP level of CP patients was markedly higher than those of CB patients and controls (P < 0.01), but no statistically significant differences were found between CB patients and controls (P > 0.05). There was a positive correlation between elevated levels of serum MBP and carbon dioxide partial pressure (PaCO2). This suggested that elevated serum MBP levels may be associated with brain destruction by hypercapnia and hypoxia of CP patients.
Acute-Phase Reaction↗
[Some biochemical indexes in white rabbit's blood affected by acute high intensity microwave].
Irradiation of white rabbits by 10, 50, 100 and 200 mW/cm2 microwave respectively can cause the disorder of protein metabolism, the abnormality of blood sugar, and the change of the activity of serum alpha-hydroxybutyrate dehydrogenase, lactate dehydrogenase, glutamic oxalacetic transaminase, glutamic pyruvic transaminase, acid phosphatase ect. These changes can be used as indexes in the evaluation of the effect of acute high intensity microwave exposure. The effect on the organism mainly depends on the intensity of exposure provided the dose of microwave remains the same.
Acid Phosphatase↗
[Preconcentration of trace chromium in natural water with activated carbon and its determination by colorimetry].
The adsorption and desorption behavior of chromium was studied. Trace chromium in water could be adsorbed on activated carbon at pH 9-10, then eluted with 0.5% sulfuric acid and determined by colorimetry. The content of chromium could be concentrated by 100 times. For sample, the coefficient of variation of 8 parallel determinations was 7.7%. The proposed method has been applied to the determination of trace chromium in natural waters with the recovery of 71.4%-90.0%, and with the detection limit of 0.04 microgram/L.
Carbon↗
HIMeg-1, a cell line derived from a CML patient, is capable of monocytic and megakaryocytic differentiation.
We have characterized HIMeg-1, a subclone of the promegakaryoblastic cell line HIMeg, in terms of its capability of proliferation and differentiation when it is exposed to various agents. We observed that phorbol 12-myristate 13-acetate (PMA) arrested HIMeg-1 growth and induced expression of monocytic surface antigens CD11c and CD14, but not the megakaryocytic surface antigen CD14a. In addition, PMA treatment of HIMeg-1 led to rapid activation of mRNA expression of egr-1, a transcription factor involved in regulating differentiation of hematopoietic progenitor cells. On the other hand, treatment of HIMeg-1 with the activated peripheral blood lymphocyte-conditioned medium (PBL-CM) resulted in greatly enhanced incorporation of 3H-thymidine into newly synthesized DNA. This enhanced 3H-thymidine incorporation appears to be specific to HIMeg-1 since the same concentrations of PBL-CM had little effect on the growth of the megakaryoblastic leukemia cell line SAM-1. The PBL-CM-induced DNA synthesis in HIMeg-1 was associated with activation of CD41a and CD41b surface antigen expression and down-regulation of expression of the erythroid marker glycophorin A and the early myeloid surface antigen CD33. HIMeg-1 capable of responding differentially to PMA and PBL-CM by changing its growth rate as well as its differentiation patterns will provide an ideal model to study the underlying mechanism regulating lineage restriction of hematopoietic progenitor cells.
Antigens, CD↗
[The significance of immune island appeared in pleural and peritoneal effusion].
Macrophage surrounded by transformed or untransformed lymphocytes is called immune island. Aimming at this problem, we made a survey of 120 pleural and peritoneal effusion smears with a variety of patients and discovered that this island appeared in 52 (43.3%) cases. The positive results existed in 11 of 14 (79%) cases with tuberculosis and 29 of 60 (48%) cases with malignant diseases. The average number of island on each positive smear (2.0cm x 2.5cm) is 59.6 +/- 12.8 in the former and 39.2 +/- 18.9 in the latter. The mechanism of this phenomenon may be due to the response to foreign stimulus from pathogenic and cancer antigen.
Adolescent↗