Biomedical subjects

Yifeng Zhou

Publications and source records attributed to Yifeng Zhou.

34 records · Page 2Linked to original sources

PubMed2005

[Study on the original plants and macroscopic characters of Radix Paeoniae].

OBJECTIVE: For the identification of botanical origin and macroscopic characters of Radix Paeoniae. METHODS: Different types of original plant and crude of Radix Paeoniae samples were collected from 10 main producing areas. RESULTS: By taxonomical and morphological researches, Paeonia lactiflora and P. lactiflora var. trichocarpa could be identified. CONCLUSION: The root of P. lactiflora is cylindrical, pale white to reddish brown in surface color, with longitudinal furrows, flat borken section, with radial rows in xylem elements, sour taste. While the root of the variety can be differ from its irregular-cylindrical shape, brownish surface, floury transverse section and sweet taste.

Flowers↗

PubMed2004

Highly enantioselective phenylacetylene additions to ketones catalyzed by (S)-BINOL-Ti complex.

The readily available and inexpensive (S)-BINOL ligand in combination with Ti(O(i)Pr)(4) is an effective chiral catalyst for the catalytic asymmetric addition of alkynylzinc to unactivated simple ketones. Good to excellent enantioselectivities were achieved. No previous case has been reported successfully using BINOL to catalyze the addition of phenylacetylene to unactivated ketones, and thus the utility of BINOL in asymmetric catalysis is expanded.

Acetylene↗

PubMed2004

Functional haplotypes in the promoter of matrix metalloproteinase-2 predict risk of the occurrence and metastasis of esophageal cancer.

Matrix metalloproteinase-2 (MMP-2) plays important roles in cancer development and aggression. Our previous studies revealed a strong association between the MMP-2 -1306C/T polymorphism and risk of several cancers. A novel -735C/T polymorphism in MMP-2 promoter has been identified but the function is undefined. This study examined our hypothesis that these two polymorphisms might have functional relevance and impact on risk of esophageal squamous cell carcinoma in the context of haplotype. Genotypes and haplotypes were analyzed in 527 cases and 777 controls and odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression. The function of the polymorphisms was examined by electrophoretic mobility shift assays, luciferase gene expression assays, and reverse transcriptase-PCR analyses. It was found that the -735C-->T transition disrupts an Sp1 site and displays a lower promoter activity. The C(-1306)-C(-735) haplotype had 7-fold increased luciferase expression and 3.7-fold increased MMP-2 mRNA levels in esophageal tissues compared with the T(-1306)-T(-735) haplotype. A case-control analysis revealed a 1.52-fold (95% CI = 1.17-1.96) or 1.30-fold (95% CI = 1.04-1.63) excess risk of developing esophageal squamous cell carcinoma for the -1306CC or -735CC genotype carriers compared with noncarriers, respectively. A greater association was observed between elevated risk of developing esophageal squamous cell carcinoma and C(-1306) or C(-735) allele containing haplotypes, with the risk being highest for the C(-1306)-C(-735) haplotype compared with the T(-1306)-T(-735) haplotype (OR = 6.53; 95% CI = 2.78-15.33). The C(-1306)-C(-735) haplotype was also associated with increased risk for distant metastasis of esophageal squamous cell carcinoma (OR = 3.34; 95% CI = 1.16-9.63). These findings suggest that the C(-1306)-C(-735) haplotype in the MMP-2 promoter contributes to risk of the occurrence and metastasis of esophageal squamous cell carcinoma by increasing expression of MMP-2.

Alleles↗

PubMed2004

Age-related effects of bilateral frontal eye fields lesions on rapid eye movements during REM sleep in rhesus monkeys.

Rapid eye movement (REM) is one of the most characteristic features of REM sleep, but the mechanisms underlying its regulation remain unclear. The present study aims to investigate whether the frontal eye field (FEF) is involved in the regulation of the rapid eye movements during REM sleep. To address this question, we ablated the FEF in four rhesus monkeys and observed the effects of the lesions on sleep architecture. After lesions, two adult monkeys did not show any lesion effect. However, in the other two adolescent monkeys, both the total duration and percentage of the rapid eye movements during REM sleep were decreased moderately. The result suggests that the relation between the FEF and the regulation of the rapid eye movements during REM sleep may be affected by age factor, also indicating that both the functions of the FEF and the mechanisms underlying the control of rapid eye movements during REM sleep might not be the same throughout the whole life span of an animal.

Age Factors↗

PubMed2004

Functional Phe31Ile polymorphism in Aurora A and risk of breast carcinoma.

Aurora-A/BTAK/STK15, involved in regulating centrosomes and chromosome segregation, is overexpressed in human breast carcinoma and other cancers. The Phe31-->Ile polymorphism in Aurora A alters the kinase function, with the Ile31 variant being preferentially amplified and associated with degree of aneuploidy in human tumors. We have previously shown that the Phe31Ile polymorphism is associated with the occurrence and advanced disease status of esophageal cancer. This case-control study examined the contribution of this polymorphism to susceptibility to development and progression of breast cancer. Aurora A genotypes were determined in 520 patients with breast carcinoma, 191 patients with benign breast diseases (BBD) and 520 controls. It was found that the Aurora A Ile/Ile genotype was significantly associated with increased risk of breast carcinoma occurrence [odds ratio (OR) 1.66; 95% confidence interval (95% CI) 1.29-2.12] compared with the Phe/Phe or Phe/Ile genotype. The increased risk for BBD and breast carcinoma related to the Ile/Ile genotype was more pronounced in younger subjects. Moreover, we found that patients carrying the Ile/Ile genotype tended to have ER-carcinomas (OR 2.56; 95% CI 1.24-5.26). No significant association was observed between the polymorphism and metastasis and disease stage of the cancer. These findings suggest that the Phe31Ile polymorphism in Aurora A may be a genetic modifier for developing breast carcinoma.

Adult↗

PubMed2004

Short-term depression of synaptic transmission from rat lateral geniculate nucleus to primary visual cortex in vivo.

Two forms of short-term synaptic plasticity, paired-pulse depression (PPD) and frequency depression, were prominent in the adult rat geniculo-cortical visual pathway in vivo. Iontophoresis of GABAa receptor antagonist (bicuculline methiodide) or GABAb receptor antagonist (2-hydroxy-saclofen) in the primary visual cortex significantly reduced the short-term synaptic depression. When NMDA or AMPA/kainate receptors were blocked, no obvious change of synaptic depression was observed. Application of high [Ca(2+)] enhanced the short-term synaptic depression. Our results suggest that the presynaptic Ca(2+)-dependent neurotransmitter depletion and postsynaptic GABAergic inhibition may be crucial for short-term synaptic depression in the geniculo-cortical pathway.

Animals↗

PubMed2003

A functional polymorphism in the SULT1A1 gene (G638A) is associated with risk of lung cancer in relation to tobacco smoking.

Sulfotransferase 1A1, an important member of sulfotransferase superfamily, is involved in the biotransformation of many compounds including tobacco carcinogens. A single nucleotide polymorphism (G638A) in the sulfotransferase 1A1 (SULT1A1) gene causes Arg213His amino acid change and consequently results in significantly reduced enzyme activity and thermostability. We thus hypothesized that the variant SULT1A1 allele may protect against the risk of lung cancer related to tobacco smoking. To examine this hypothesis, we analyzed 805 patients with lung cancer and 809 controls for this polymorphism in a hospital-based, case-control study. We observed that, compared with the GG genotype, the variant SULT1A1 genotype (638GA or AA) was associated with a significantly increased risk for overall lung cancer [odds ratio (OR) 1.85; 95% confidence interval (CI) 1.44-2.37]. Stratification analysis showed that the increased risk of lung cancer related to the variant SULT1A1 genotypes was more pronounced in younger subjects and limited to smokers but not non-smokers [OR 2.28 (95% CI 1.66-3.13) versus OR 1.35 (95% CI 0.91-1.99); P for homogeneity = 0.000]. Furthermore, the risk of lung cancer for the variant genotypes was increased consistently with cumulative smoking dose, with the ORs being 1.66 (95% CI, 0.75-3.68), 2.28 (95% CI, 1.47-3.54) and 3.35 (95% CI, 1.71-6.57) for those who smoked <15 pack-years, 15-36 pack-years and >36 pack-years, respectively (P for trend = 0.000). When analysis was stratified by histological subtypes of lung cancer, consistent results were observed for all three major types of the cancer, i.e. squamous cell carcinoma, adenocarcinoma and other types. Our results, which are against the original hypothesis, demonstrate that the variant SULT1A1 638A allele is associated with susceptibility to lung cancer in relation to tobacco smoking.

Adenocarcinoma↗

PubMed2003

Generating high gray-level resolution monochrome displays with conventional computer graphics cards and color monitors.

Display systems based on conventional computer graphics cards are capable of generating images with about 8-bit luminance resolution. However, most vision experiments require more than 12 bits of luminance resolution. Pelli and Zhang [Spatial Vis. 10 (1997) 443] described a video attenuator for generating high luminance resolution displays on a monochrome monitor, or for driving just the green gun of a color monitor. Here we show how to achieve a white display by adding video amplifiers to duplicate the monochrome signal to drive all three guns of any color monitor. Because of the lack of the availability of high quality monochrome monitors, our method provides an inexpensive way to achieve high-resolution monochromatic displays using conventional, easy-to-get equipment. We describe the design principles, test results, and a few additional functionalities.

Algorithms↗

PubMed2003

Substantial reduction in risk of breast cancer associated with genetic polymorphisms in the promoters of the matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-2 genes.

The matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) have been shown to play important roles in multiple ways in all stages of cancer initiation and development. Single nucleotide polymorphisms identified in the promoters of MMP2 (-1306C-->T) and TIMP2 (-418G-->C) abolish the Sp1-binding site and thus may down-regulate expression of the genes. This case-control study examined the contribution of these functional polymorphisms to susceptibility to development and metastasis of breast cancer. MMP2 genotypes were determined by PCR-based denaturing high performance liquid chromatography analysis and TIMP2 genotypes identified by a PCR-RFLP method in 462 breast cancer patients and 509 frequency matched control women. We found that the variant MMP2 genotype (-1306CT or TT) was associated with substantially reduced risk of breast cancer [odds ratio (OR), 0.46; 95% confidence interval (95% CI), 0.34-0.63], compared with the CC genotype. For TIMP2, a moderately reduced risk of the cancer (OR, 0.76; 95% CI, 0.58-0.99) was also associated with the variant allele (-418GC or CC), compared with the GG common allele. Furthermore, it seemed that the polymorphisms in the two genes had some additive effect and the reduced risk related to the polymorphisms appeared to be more pronounced in younger subjects. However, no significant associations were observed between the polymorphisms in the two genes and tumor stage and metastasis of the cancer at the time of diagnosis. These findings suggest that the presence of the variant allele in the promoter of MMP2 or TIMP2 may be a protective factor for the development of breast cancer.

Adult↗

PubMed2003

Non-dominant eye responses in the dorsal lateral geniculate nucleus of the cat: an intracellular study.

UNLABELLED: While binocularity has been established as an important characteristic of cat visual cortical neurons, neurons in the dorsal lateral geniculate nucleus (LGNd) are commonly believed to be monocular. To test whether binocularity exists at the level of the LGNd, postsynaptic potentials (PSPs) of 101 cells were intracellularly recorded in eight normal and eight monocularly deprived cats while presenting stimuli to either the dominant or non-dominant eyes. The results showed that: (1) About 92% of neurons (45 out of 49) responded to a flashing spot presented to the non-dominant eye. In contrast to the dominant eye responses, the non-dominant eye PSPs usually exhibited the same polarization tendency (hyperpolarization or depolarization) to flashing spot stimuli of light increment or decrement, and most of them were inhibitory (hyperpolarization, 35 out of 45, 78%). (2) The response field (RF) of the non-dominant eye overlapped that of the dominant eye. (3) For most binocular cells, peak-to-peak amplitudes of non-dominant eye PSPs were about half the size (46%) of those of the dominant eye. The peak latencies and half-peak latencies of non-dominant eye PSPs were significantly longer than those of the dominant eye (mean differences were 5.4 ms and 5.6 ms respectively). (4) Most of the binocular cells responded well to contrast reversing gratings presented to the non-dominant eye, and the responses were clearly spatial-frequency tuned. No null phase could be found for non-dominant eye PSPs, no matter the neuron was classified as X or Y type according to dominant eye elicited responses. Some of the cells responded well to drifting gratings presented to the non-dominant eye. (5) We also recorded 52 cells in monocularly deprived cats, and found that 49 cells (94%) showed significant responses to flashing spots presented to the non-dominant eye, a similar percentage to that found in normal cats (92%). CONCLUSION: as strongly monocular neurons, most of LGNd cells could also be driven by the non-dominant eye. The responses evoked by non-dominant eye stimulation differ greatly from those evoked by dominant eye stimulation, and remain intact even without visual experience. These observations suggest an important role of the perigeniculate nucleus in providing binocular inputs to LGNd cells.

Action Potentials↗

PubMed2003

GABA and its agonists improved visual cortical function in senescent monkeys.

Human cerebral cortical function degrades during old age. Much of this change may result from a degradation of intracortical inhibition during senescence. We used multibarreled microelectrodes to study the effects of electrophoretic application of gamma-aminobutyric acid (GABA), the GABA type a (GABAa) receptor agonist muscimol, and the GABAa receptor antagonist bicuculline, respectively, on the properties of individual V1 cells in old monkeys. Bicuculline exerted a much weaker effect on neuronal responses in old than in young animals, confirming a degradation of GABA-mediated inhibition. On the other hand, the administration of GABA and muscimol resulted in improved visual function. Many treated cells in area V1 of old animals displayed responses typical of young cells. The present results have important implications for the treatment of the sensory, motor, and cognitive declines that accompany old age.

Aging↗

PubMed2003

GABA(A) and GABA(B) receptors mediated inhibition affect the pattern adaptation of relay cells in the dorsal lateral geniculate nucleus (LGNd) of cats.

Pattern adaptation is very important for visual function, while the mechanisms that mediate pattern adaptation, especially in the dorsal lateral geniculate nucleus (LGNd), are still unclear. Iontophoresis of the antagonists and agonists of GABA receptors were employed to separately investigate the contribution of GABA(A) and GABA(B) receptors to pattern adaptation of LGNd cells. When GABA(A) receptors were blocked by bicuculline both the response amplitude of LGNd cells and the degree of adaptation increased significantly. Many neurons showing no pattern adaptation under the normal condition became adapted to a prolonged stimulus. Moreover, the proportion of cells showing adaptation doubled (from 40 to 88%). The mean adaptation index (AI, adapted response amplitude/original response amplitude) was 0.82 during bicuculline application, compared with 0.92 under the control condition. In additional, iontophoresis of baclofen, a selective GABA(B) receptor agonist, decreased the mean response amplitude to grating stimuli to 53% of normal. Nearly half of the neurons increased their adaptation index following baclofen administration and the mean AI increased from 0.89 to 1.01. Iontophoresis of GABA(B) receptor antagonist (CGP35348) could abolish this effect, though it had no significant effect on visual response amplitude and pattern adaptation itself. Iontophoresis of another GABA(B) receptor antagonist, 2-OH-saclofen, also had no significant effect on visual response amplitude and pattern adaptation. These results suggest that both GABA(A) receptors and GABA(B) receptors modulate the pattern adaptation of LGNd cells and are involved in synaptic plasticity.

Action Potentials↗

PubMed2003

Fault detection and classification in chemical processes based on neural networks with feature extraction.

Feed forward neural networks are investigated here for fault diagnosis in chemical processes, especially batch processes. The use of the neural model prediction error as the residual for fault diagnosis of sensor and component is analyzed. To reduce the training time required for the neural process model, an input feature extraction process for the neural model is implemented. An additional radial basis function neural classifier is developed to isolate faults from the residual generated, and results are presented to demonstrate the satisfactory detection and isolation of faults using this approach.

Algorithms↗

PubMed2003

Differential dendritic shrinkage of alpha and beta retinal ganglion cells in cats with chronic glaucoma.

PURPOSE: To study changes in the dendritic morphology of retinal ganglion cells (RGCs) in cats with experimental chronic glaucoma. METHODS: Chronic elevation of intraocular pressure (IOP) was produced by injecting endogenous ghost red blood cells into the unilateral anterior chamber of the feline eyes for 1 month. The morphologic features of retrograde-labeled RGCs by bilateral injection of horseradish peroxidase (HRP) into layers A and Aa1 of the lateral geniculate nucleus (LGN) were examined and compared between the normal and glaucomatous eyes. Nissl staining was used for measuring the change in cell density in the retina and the LGN. RESULTS: Quantitative analysis of 720 labeled alpha and beta type RGCs showed that the cell density, body size, maximum dendritic field radius, total dendritic length, and number of branch bifurcations of dendrites decreased significantly in glaucomatous eyes compared with normal ones. The cell loss and shrinkage of dendrites in alpha type ganglion cells in the retina was more pronounced than that in beta type cells. The cell density of all kinds of cells in the retina and LGN monotonically declined with time while IOP was elevated, and cell loss was more significant in large cells than in small ones. CONCLUSION: Progressive cell loss and dendritic damage by chronic elevation of IOP in RGCs and LGN cells are more pronounced in the Y-channel (large cells) than the X-channel (small cells) in feline glaucomatous eyes. The dendritic structure changes and corresponding physiological deficits of RGCs occur before cell death and thus may provide an opportunity for clinical treatment.

Animals↗

PubMed2003

Effects of magnesium sulfate on neuron apoptosis and expression of caspase-3, bax and bcl-2 after cerebral ischemia-reperfusion injury.

OBJECTIVE: To investigate the effects of magnesium sulfate on neuron apoptosis and the expressions of caspase-3, bax and bcl-2 after cerebral ischemia-reperfusion injury. METHODS: Thirty-six gerbils were randomly divided into three groups: Sham-operation group (So, n = 12), ischemia-reperfusion group (I-R, n = 12) and magnesium sulfate group (Ms, n = 12). The neuron apoptosis was detected by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-fluorescence nick end labeling (TUNEL stain), and the protein expressions of caspase-3, bax and bcl-2 were detected by immunohistochemisty stain. RESULTS: Apoptotic neurons and the expressions of caspase-3 and bax were significantly increased in I-R and Ms groups, compared with those in So group. Apoptotic neurons and the expressions of bax and caspase-3 in Ms group were significantly less than those in I-R group. There was no significant difference in the expression of bcl-2 among three groups. CONCLUSIONS: Magnesium sulfate decreases neuron apoptosis after cerebral ischemia-reperfusion injury, which may be related with the suppressed expressions of caspase-3 and bax.

Animals↗

PubMedDate not supplied

Degradation of response modulation of visual cortical cells in cats with chronic exposure to morphine.

The primary visual cortex (V1) plays an important role in vision and visual perception. Studies in many brain regions demonstrate that opiate abuse can change excitatory and inhibitory neurotransmission. To investigate the effect of chronic morphine exposure on the response modulation of V1 simple and complex neurons, we carried out in vivo extracellular recordings in V1 of morphine- and saline-treated (control) cats. Response modulation was quantified as the ratio of first Fourier components (F1) to the mean response (F0). Compared with saline-treated cats, V1 neurons in morphine-treated cats exhibited weaker response modulation and a longer time course of response. The decrease of response modulation was caused by an increase of F0. Further, morphine re-exposure significantly improved the response properties of V1 neurons in morphine-treated cats. These results suggest that chronic morphine treatment leads to a significant degradation of response modulation of V1 neurons and a morphine dependence of primary visual cortical function.

Action Potentials↗