Biomedical subjects

L Zhou

Publications and source records attributed to L Zhou.

637 records · Page 36Linked to original sources

PubMedDate not supplied

Mutants of p53 gene presence in laryngeal carcinoma and adjacent histopathologically normal tissue.

Possible differences were analyzed between histopathological and molecular biological findings in laryngeal cancer tissue and its adjacent normal tissues. p53 gene mutations were detected in histopathologically normal tissue both within 0.5 cm of and more than 0.5 cm distant from the nearest cancerous tissue. Since the p53 mutation was common in both cancer tissue and adjacent normal tissue, the gene mutation may play an important role in laryngeal carcinogenesis. Radical excision of the tumor is defined by histopathological limits, but 'normal' tissue may nevertheless contain the gene mutation, giving rise to the danger of further cancer development. We suggest that the determination of the surgical margin should be based on a combination of histopathology and molecular biological findings.

Aged↗

PubMedDate not supplied

Effects of check size on visual cortex activation studied by functional magnetic resonance imaging.

We studied functional magnetic resonance imaging (fMRI) of visual cortex during checkerboard visual stimulation with three standard check sizes to examine whether activation in the visual cortex varied among these sizes. We acquired fMRI at 1.5 T in 8 normal subjects, each receiving the best refractive correction. Each subject underwent an experiment consisting of four conditions: black and white checkerboards with three check sizes (0.25-, 0.5-, and 1.0-degree) flickering at 8 Hz, and a black screen. SPM96 was used for a group data analysis with a random effects model after each of the subject's data was motion-corrected and spatially normalized to a standard brain. The activation in the visual cortex showed the greatest signal changes with the 0.5-degree check among the three check sizes. When standard check sizes are used to stimulate visual cortex in fMRI experiments, our results suggest that 0.5-degree checks flickering at 8 Hz produce the most vigorous activation in visual cortex.

Adult↗

PubMedDate not supplied

Herbicide retention in soil as affected by sugarcane mulch residue.

Reducing surface and subsurface losses of herbicides in the soil and thus their potential contamination of water resources is a national concern. This study evaluated the effectiveness of sugarcane (Saccharum spp.) residue (mulch cover) in reducing nonpoint-source contamination of applied herbicides from sugarcane fields. Specifically, the effect of mulch residue on herbicide retention was quantified. Two main treatments were investigated: a no-till treatment and a no-mulch treatment. The amounts of extractable atrazine [2-chloro-4-(isopropylamino)-6-ethylamino-s-triazine], metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one], and pendimethalin [N-(ethylpropyl)-3,4-dimethyl-2,6-dinitroaniline] from the mulch residue and the surface soil layer were quantified during the 1999 and 2000 growing seasons. Significant amounts of applied herbicides were intercepted by the mulch residue. Extractable concentrations were at least one order of magnitude higher for the mulch residue compared with that retained by the soil. Moreover, the presence of mulch residue on the sugarcane rows was highly beneficial in minimizing runoff losses of the herbicides applied. When the residue was not removed, a reduction in runoff-effluent concentrations, as much as 50%, for atrazine and pendimethalin was realized. Moreover, the presence of mulch residue resulted in consistently lower estimates for rates of decay or disappearance of atrazine and pendimethalin in the surface soil.

Conservation of Natural Resources↗

PubMedDate not supplied

Automation of temperature control for large-array microwave surface applicators.

An adaptive temperature control system has been developed for the microstrip antenna array applicators used for large area superficial hyperthermia. A recursive algorithm which allows rapid power updating even for large antenna arrays and accounts for coupling between neighbouring antennas has been developed, based on a first-order difference equation model. Surface temperatures from the centre of each antenna element are the primary feedback information. Also used are temperatures from additional surface probes placed within the treatment field to protect locations vulnerable to excessive temperatures. In addition, temperatures at depth are observed by mappers and utilized to restrain power to reduce treatment-related complications. Experiments on a tissue-equivalent phantom capable of dynamic differential cooling have successfully verified this temperature control system. The results with the 25 (5 x 5) antenna array have demonstrated that during dynamic water cooling changes and other experimentally simulated disturbances, the controlled temperatures converge to desired temperature patterns with a precision close to the resolution of the thermometry system (0.1 degree C).

Algorithms↗

PubMedDate not supplied

Role of opioid peptides of rat's nucleus reticularis paragigantocellularis lateralis (RPGL) in acupuncture analgesia.

The present study was to investigate the role of the RPGL and its endogenous opioid peptides in acupuncture analgesia (AA) using techniques of brain stimulation and lesion, microinjection, push-pull perfusion and radioimmunoassay (RIA). The results showed that electrical stimulation of the RPGL could increase the pain threshold and enhance the effect of AA, whereas lesion of the RPGL reduce the effect of AA. Microinjection of naloxone (5 micrograms/0.5ul/2min) into the RPGL could partially reverse the effect of AA and the reversal effect of naloxone was dose-dependent. The release of leu-enkephalin (LEK) and B-endorphin (B-EP) from the RPGL in the electrical acupuncture (EA) group was significantly higher than that in the control group (P < 0.05). There were positive correlations between the changes of release of LEK, B-EP and the increase of pain threshold. The results mentioned above imply that the RPGL plays an important role in AA. The activation of the RPGL and the endogenous opioid peptides within it produce an advantageous effect on AA.

Acupuncture Analgesia↗

PubMedDate not supplied

[Histamine as modulator of potassium currents in ventricular cells isolated from heart of guinea pig. A possible regulator effect of ventricular electric activity].

Histamine is present in cardiac tissues in considerable amount, but its physiological role is not well understood. There are two kinds of histamine receptors on the cardiac cells (H1 and H2). Whereas the H2 actions are very well studied little is known about H1 effects. It has been reported that stimulation of H1 receptors induce a shortening of the action potential as a decrease in excitability, but the ionic mechanisms responsible for these are not known. The aim of the present paper is to explore the possible ionic mechanisms related to these effects on isolated ventricular myocytes by means of voltage clamp technique. Histamine induced a shift in the current-voltage relationship of the potassium background current to the right. This shift implies an increase in outward current at the plateau level, responsible for the shortening, as well as for the decrease in excitability. This is, as far as we know, the first report in potassium background channel modulation by an endogenous substance and firmly support the hypothesis that histamine is playing a role in cardiac modulation.

Action Potentials↗

PubMedDate not supplied

Separation of cis-/trans-diastereomers and enantiomers of aminoindanol and aminoindan using capillary electrophoresis.

Aminoindanol poses an interesting separation problem because it contains two chiral centers and exists as four stereoisomers. The capillary electrophoretic separation of the cis- and the larger trans-diastereomers of aminoindanol is simply achieved by pH control of the tris buffer background electrolyte. In accordance with theory, maximum separation occurs at the pH equal to the mean value of the pKA values of the isomers. The separation of the enantiomers of both the cis- and trans-diastereomers is effected using the chiral selector alpha-cyclodextrin (alpha-CD). The cis-enantiomeric pair is better separated than the trans-pair, as reflected by the larger difference in the binding constants, K, for the cis-enantiomers with the alpha-CD, K values were measured from the change in electrophoretic mobility with selector concentration, over the temperature range 15 degrees C-35 degrees C. The associated delta H degrees and delta S degrees values were determined for the transfer of each enantiomer from the aqueous buffer phase to the alpha-CD phase. The corresponding K values and associated thermodynamic quantities were also measured for the aminoindan enantiomers, which lack the hydroxyl group of aminoindanol. The effect of chiral selector size was evaluated for the aminoindanols by measuring K and the associated values using beta-CD, which has a larger cavity than the alpha-CD. The better fit of the larger trans-isomers leads to larger K values for the trans-isomers but reduced Ks for the cis-. The gamma-CD cavity is too large to produce chiral discrimination. The low solubility of the beta-CD requires the addition of high concentrations of urea to the tris buffer. Urea has little effect on the K values of the trans-aminoindanols with alpha-CD, but leads to larger values for the cis-isomers.

Electrophoresis, Capillary↗