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Biomedical subjects

L Ren

Publications and source records attributed to L Ren.

At least 19 recordsLinked to original sources
PubMed2006

Proprioceptive guidance of saccades in eye-hand coordination.

The saccade generator updates memorized target representations for saccades during eye and head movements. Here, we tested if proprioceptive feedback from the arm can also update handheld object locations for saccades, and what intrinsic coordinate system(s) is used in this transformation. We measured radial saccades beginning from a central light-emitting diode to 16 target locations arranged peripherally in eight directions and two eccentricities on a horizontal plane in front of subjects. Target locations were either indicated 1) by a visual flash, 2) by the subject actively moving the handheld central target to a peripheral location, 3) by the experimenter passively moving the subject's hand, or 4) through a combination of the above proprioceptive and visual stimuli. Saccade direction was relatively accurate, but subjects showed task-dependent systematic overshoots and variable errors in radial amplitude. Visually guided saccades showed the smallest overshoot, followed by saccades guided by both vision and proprioception, whereas proprioceptively guided saccades showed the largest overshoot. In most tasks, the overall distribution of saccade endpoints was shifted and expanded in a gaze- or head-centered cardinal coordinate system. However, the active proprioception task produced a tilted pattern of errors, apparently weighted toward a limb-centered coordinate system. This suggests the saccade generator receives an efference copy of the arm movement command but fails to compensate for the arm's inertia-related directional anisotropy. Thus the saccade system is able to transform hand-centered somatosensory signals into oculomotor coordinates and combine somatosensory signals with visual inputs, but it seems to have a poorly calibrated internal model of limb properties.

Adult↗
PubMed2005

Regression techniques for the prediction of lower limb kinematics.

This work presents a novel and extensive investigation of mathematical regression techniques, for the prediction of laboratory-type kinematic measurements during human gait, from wearable measurement devices, such as gyroscopes and accelerometers. Specifically, we examine the hypothesis of predicting the segmental angles of the legs (left and right foot, shank and thighs), from rotational foot velocities and translational foot accelerations. This first investigation is based on kinematic data emulated from motion-capture laboratory equipment. We employ eight established regression algorithms with different properties, ranging from linear methods and neural networks with polynomial support and expanded nonlinearities, to radial basis functions, nearest neighbors and kernel density methods. Data from five gait cycles of eight subjects are used to perform both inter-subject and intra-subject assessments of the prediction capabilities of each algorithm, using cross-validation resampling methods. Regarding the algorithmic suitability to gait prediction, results strongly indicate that nonparametric methods, such as nearest neighbors and kernel density based, are particularly advantageous. Numerical results show high average prediction accuracy (rho = 0.98/0.99, RMS = 5.63 degrees/2.30 degrees, MAD = 4.43 degrees/1.52 degrees for inter/intra-subject testing). The presented work provides a promising and motivating investigation on the feasibility of cost-effective wearable devices used to acquire large volumes of data that are currently collected only from complex laboratory environments.

Adult↗
PubMed2004

Murine bone marrow cells cultured ex vivo in the presence of multiple cytokine combinations lose radioprotective and long-term engraftment potential.

The desire to improve engraftment following transplantation of limited numbers of hematopoietic stem cells (HSC) has spurred the investigation of ex vivo stem cell expansion techniques. While surrogate outcomes, such as an increase in SCID-repopulating cells, suggest successful stem cell expansion in some studies, it is not clear that such assays predict outcomes using a more clinically relevant approach (e.g., myeloablation). We have addressed this by testing three cytokine combinations for their ability to increase the radioprotective and long-term marrow reconstitution capacity of hematopoietic cells cultured ex vivo. Low numbers of light-density (LD) mouse bone marrow (BM) cells or their expanded product were injected into lethally irradiated (9 Gy) congenic recipients. Survival rates and percent donor engraftment were compared at 2, 5, and 7 months post-transplant. The three cytokine combinations used were: (i) kit-ligand (L), thrombopoietin (Tpo), Flt-3 L; (ii) cytokines in (i) plus interleukin-11 (IL-11); (iii) cytokines in (ii) plus IL-3. At 7 months post-transplant, LD cell doses of 10(4), 2-2.5 x 10(4), and 0.5-1.0 x 10(5) gave predictable survivals of 20-30%, 40-70%, and 100%, respectively. Mean percent donor engraftments were 54.9% (SEM 36%), 55.7% (SEM 36%), and 76.3% (SEM 21%), respectively. When cells expanded for 3 or 5-7 days with the various cytokine combinations were transplanted into different groups of mice, survival rates and percent donor engraftment were almost uniformly poorer than results obtained with unmanipulated cells, and cells expanded for 5-7 days led to poorer outcomes than cells expanded for 3 days. Overall, ex vivo expansion of LD BM cells with the cytokine combinations chosen failed to improve transplant outcomes in this model.

Animals↗
PubMed2004

Localization of sex steroid receptors in human skin.

Sex steroid hormones are involved in regulation of skin development and functions as well as in some skin pathological events. To determine the sites of action of estrogens, androgens and progestins, studies have been performed during the recent years to accurately localize receptors for each steroid hormone in human skin. Androgen receptors (AR) have been localized in most keratinocytes in epidermis. In the dermis, AR was detected in about 10% of fibroblasts. In sebaceous glands, AR was observed in both basal cells and sebocytes. In hair follicles, AR expression was restricted to dermal papillar cells. In eccrine sweat glands, only few secretory cells were observed to express AR. Estrogen receptor (ER) alpha was poorly expressing, being restricted to sebocytes. In contrast, ERbeta was found to be highly expressed in the epidermis, sebaceous glands (basal cells and sebocytes) and eccrine sweat glands. In the hair follicle, ERbeta is widely expressed with strong nuclear staining in dermal papilla cells, inner sheath cells, matrix cells and outer sheath cells including the buldge region. Progesterone receptors (PR) staining was found in nuclei of some keratinocytes and in nuclei of basal cells and sebocytes in sebaceous glands. PR nuclear staining was also observed in dermal papilla cells of hair follicles and in eccrine sweat glands. This information on the differential localization of sex steroid receptors in human skin should be of great help for future investigation on the specific role of each steroid on skin and its appendages.

Epidermis↗
PubMed2004

Localization of 17beta-hydroxysteroid dehydrogenase type 1 mRNA in mouse tissues.

The enzyme 17beta-hydroxysteroid dehydrogenase (17beta-HSD) type 1 catalyzes the conversion of estrone (E1) into 17beta estradiol (E2). To gain information about the cellular localization of 17beta-HSD mRNA type 1 expression, we performed in situ hybridization using a 35S-labeled cRNA probe in several tissues of adult mice of both sexes. In the ovary, high expression was found in granulosa cells of growing follicles. No specific labeling could be observed in corpora lutea or interstitial cells. In the pituitary gland of animals of both sexes, 17beta-HSD type 1 mRNA was expressed in the intermediate lobe melanotrophs while no specific signal could be detected in the anterior or posterior lobes of the pituitary. In the prostate, 17beta-HSD type 1 mRNA was exclusively found in the epithelial cells. In both male and female mouse dorsal skin, a specific hybridization signal was seen in the sebaceous glands while the epidermis, stroma, hair follicles and sweat glands were unlabeled. In the testis, a hybridization signal was detected in germ cells of the seminiferous tubules, Leydig cells being unlabeled. The present data indicate that E2 can be formed through the action of 17beta-HSD type 1 in specific cells of the gonads and peripheral tissues. In the testes and peripheral tissues, the action of E2 is probably limited to the cells involved in its formation in an intracrine fashion.

17-Hydroxysteroid Dehydrogenases↗
PubMed2003

Direct measurement of the photoelectric response time of bacteriorhodopsin via electro-optic sampling.

The photovoltaic signal associated with the primary photochemical event in an oriented bacteriorhodopsin film is measured by directly probing the electric field in the bacteriorhodopsin film using an ultrafast electro-optic sampling technique. The inherent response time is limited only by the laser pulse width of 500 fs, and permits a measurement of the photovoltage with a bandwidth of better than 350 GHz. All previous published studies have been carried out with bandwidths of 50 GHz or lower. We observe a charge buildup with an exponential formation time of 1.68 +/- 0.05 ps and an initial decay time of 31.7 ps. Deconvolution with a 500-fs Gaussian excitation pulse reduces the exponential formation time to 1.61 +/- 0.04 ps. The photovoltaic signal continues to rise for 4.5 ps after excitation, and the voltage profile corresponds well with the population dynamics of the K state. The origin of the fast photovoltage is assigned to the partial isomerization of the chromophore and the coupled motion of the Arg-82 residue during the primary event.

Bacteriorhodopsins↗
PubMed2003

Sex-related expression of 20alpha-hydroxysteroid dehydrogenase mRNA in the adult mouse.

The enzyme 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) catalyzes the conversion of progesterone into its inactive form, 20alpha-hydroxyprogesterone. To gain information about the exact sites of 20alpha-HSD mRNA expression, we performed in situ hybridization using a (35)S-labeled cRNA probe in tissues of adult mice of both sexes. 20alpha-HSD mRNA was expressed in both male and female gonads. In the ovary, high expression was found in luteal cells of corpora lutea, while much lower expression could be detected in granulosa cells of growing follicles. In the testis, a specific hybridization signal was detected only in Leydig cells. In the female reproductive tract, 20alpha-HSD mRNA was found in the epithelial cells of the uterine cervix. In the adrenal cortex, only the zona reticularis exhibited specific radiolabeling, the expression being very high in the female and very low in the male. In the skin, specific labeling was restricted to sebaceous glands, the hybridization signal being much higher in the female than in the male. In the liver, 20alpha-HSD mRNA was found in hepatocytes, with a higher degree of expression in the female. In the kidney, specific labeling was observed in the epithelial cells of distal convoluted tubules, the signal being also much more striking in the female than in the male. In non-reproductive tissues, it clearly appears that the expression of 20alpha-HSD mRNA is higher in the female than in the male, suggesting that 20alpha-HSD may play an important role in reducing the intracellular concentration of progesterone originating from the circulation at a much higher level in the female.

20-Hydroxysteroid Dehydrogenases↗
PubMed2002

Treatment of antibiotics wastewater utilizing successive hydrolysis, denitrification and nitrification.

A process consisting of anaerobic hydrolysis, denitrification, and oxidation/nitrification was proposed for simultaneous removal of carbon and nitrogen from terramycin crystallizing mother solution (TCMS), and its performance was investigated by treating diluted TCMS in a lab-scale continuous flow column system. Direct denitrification-nitrification of diluted TCMS produced a significant residual of nitrate and nitrite, which disappeared 44 days after startup of anaerobic hydrolysis column. The electron donors available to denitrification were increased by 6 times after diluted TCMS was treated in the hydrolysis column under an HRT of 2.5 h or longer. The reaction rates of organics decomposition, nitrification, and denitrification were also significantly increased due to reduction of terramycin and decomposition of complicated molecules to small molecules during anaerobic hydrolysis. The specific denitrification rate and nitrification rate increased from 0.033 d(-1) and 0.01 d(-1) to 0.045 d(-1) and 0.021 d(-1) respectively after diluted TCMS (dilution ratio: 1:4) was hydrolyzed in anaerobic hydrolysis column at a hydraulic retention time (HRT) of 4 h.

Anti-Bacterial Agents↗
PubMed2001

Molecular mechanism of spectral tuning in sensory rhodopsin II.

Sensory rhodopsin II (SRII) is unique among the archaeal rhodopsins in having an absorption maximum near 500 nm, blue shifted roughly 70 nm from the other pigments. In addition, SRII displays vibronic structure in the lambda(max) absorption band, whereas the other pigments display fully broadened band maxima. The molecular origins responsible for both photophysical properties are examined here with reference to the 2.4 A crystal structure of sensory rhodopsin II (NpSRII) from Natronobacterium pharaonis. We use semiempirical molecular orbital theory (MOZYME) to optimize the chromophore within the chromophore binding site, and MNDO-PSDCI molecular orbital theory to calculate the spectroscopic properties. The entire first shell of the chromophore binding site is included in the MNDO-PSDCI SCF calculation, and full single and double configuration interaction is included for the chromophore pi-system. Through a comparison of corresponding calculations on the 1.55 A crystal structure of bacteriorhodopsin (bR), we identify the principal molecular mechanisms, and residues, responsible for the spectral blue shift in NpSRII. We conclude that the major source of the blue shift is associated with the significantly different positions of Arg-72 (Arg-82 in bR) in the two proteins. In NpSRII, this side chain has moved away from the chromophore Schiff base nitrogen and closer to the beta-ionylidene ring. This shift in position transfers this positively charged residue from a region of chromophore destabilization in bR to a region of chromophore stabilization in NpSRII, and is responsible for roughly half of the blue shift. Other important contributors include Asp-201, Thr-204, Tyr-174, Trp-76, and W402, the water molecule hydrogen bonded to the Schiff base proton. The W402 contribution, however, is a secondary effect that can be traced to the transposition of Arg-72. Indeed, secondary interactions among the residues contribute significantly to the properties of the binding site. We attribute the increased vibronic structure in NpSRII to the loss of Arg-72 dynamic inhomogeneity, and an increase in the intensity of the second excited (1)A(g)(-) -like state, which now appears as a separate feature within the lambda(max) band profile. The strongly allowed (1)B(u)(+)-like state and the higher-energy (1)A(g)(-) -like state are highly mixed in NpSRII, and the latter state borrows intensity from the former to achieve an observable oscillator strength.

Amino Acid Substitution↗
PubMed2001

Electro-Viscous Effects on Liquid Flow in Microchannels.

The presence of the electrical double layer near a solid-liquid interface results in the electro-viscous effect on pressure-driven liquid flow through microchannels. The objective of this paper is to examine the magnitude of the additional flow resistance caused by the electrokinetic effect in microchannels. Deionized ultrafiltered water, 10(-4) and 10(-2) M aqueous KCl solutions, 10(-4) M AlCl(3) solution, and 10(-4) M LiCl solution were used as the testing liquids. Carefully designed flow measurements were conducted in three silicon microchannels with a height of 14.1, 28.2, and 40.5 µm, respectively. The measured dP/dx for the pure water, the 10(-4) M KCl solution, and the 10(-4) M LiCl solution was found to be significantly higher than the prediction of the conventional laminar flow theory at the same Reynolds number. Such a high flow resistance and the resulting high apparent viscosity strongly depend on the channel's height, the ionic valence, and the concentration of the liquids. The zeta potentials for the liquid-solid systems were calculated by using the measured streaming potential data. The experimentally determined dP/dx approximately Re relationships were compared with the predictions of a theoretical electro-viscous flow model, and a good agreement was found for pure water, 10(-4) M KCl solution, and 10(-4) MAlCl(3) solution systems. The present electrokinetic flow model cannot interpret the flow characteristics of the LiCl solution. Copyright 2001 Academic Press.

Journal Article↗
PubMed2001

SwellGel: an affinity chromatography technology for high-capacity and high-throughput purification of recombinant-tagged proteins.

The revolution in genomics and proteomics is having a profound impact on drug discovery. Today's protein scientist demands a faster, easier, more reliable way to purify proteins. A high capacity, high-throughput new technology has been developed in Perbio Sciences for affinity protein purification. This technology utilizes selected chromatography media that are dehydrated to form uniform aggregates. The SwellGel aggregates will instantly rehydrate upon addition of the protein sample, allowing purification and direct performance of multiple assays in a variety of formats. SwellGel technology has greater stability and is easier to handle than standard wet chromatography resins. The microplate format of this technology provides high-capacity, high-throughput features, recovering milligram quantities of protein suitable for high-throughput screening or biophysical/structural studies. Data will be presented applying SwellGel technology to recombinant 6x His-tagged protein and glutathione-S-transferase (GST) fusion protein purification.

Binding Sites↗
PubMed2001

Retaining hard-to-reach women in HIV prevention and vaccine trials: Project ACHIEVE.

Project ACHIEVE, which conducts HIV prevention research studies, maintains a women's site in the South Bronx in NewYork City. Owing to a focused retention effort at the South Bronx site, high retention rates were achieved in a vaccine preparedness study for women at high risk of HIV infection. Comparable retention rates have been achieved in HIV vaccine trials with similar cohorts of women at this site. These results suggest that concerns about retaining hard-to-reach populations should not cause these populations to be excluded from HIV vaccine and prevention trials.

AIDS Serodiagnosis↗
PubMed2001

Cytokine-induced iNOS expression in C6 glial cells: transcriptional inhibition by ethanol.

The effect of cytokines, lipopolysaccharide, and ethanol on inducible nitric-oxide synthase (iNOS) expression was studied in C6 glial cells. Maximal induced activity, measured by the accumulation of nitrite in culture medium, occurred following treatment with lipopolysaccharide and interferon-gamma. Each cytokine alone was ineffective, whereas an optimal combination of interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma was near maximal, indicating synergistic interactions. Other combinations caused submaximal activity. Ethanol is known to suppress iNOS expression in C6 cells induced by a phorbol ester plus lipopolysaccharide. The current work shows ethanol also suppresses cytokine-induced iNOS expression and reduces interleukin-1beta and tumor necrosis factor-alpha potency without affecting interferon-gamma potency. Ethanol-mediated reductions in cytokine-induced iNOS mRNA and immunoreactive protein levels suggested an effect on gene transcription. Therefore, C6 cells stably expressing 1846 and 526 base fragments of the rat iNOS gene promoter fused to a luciferase reporter gene were prepared and characterized and used to study the effect of ethanol on iNOS promoter activity. Promoter activity in stable transfected C6 cells was inhibited by ethanol exposure with a similar concentration dependence as observed for inhibition of nitrite production, indicating that iNOS inhibition by ethanol is transcriptional. Furthermore, ethanol inhibition of the 526 base fragment activity, which lacks interferon-gamma enhancement of lipopolysaccharide-induced luciferase activity, confirmed that interferon-gamma-responsive elements do not participate in acute ethanol-induced inhibition of rat iNOS gene transcription.

Blotting, Western↗
PubMed2001

[Set up brain compartment model and simplify CBF-quantification].

In order to simplify the non-invasive quantitative evaluation of cerebral blood flow (CBF), we used computer simulation and adopted the pulse function as the input function of compartment model for calculting the mean retention fraction of 99mTc-ECD in brain from the time activity curves (n = 24). We found that there is a significant correlation between R2 (the retention fraction) from the 2-compartment model and R3 from the 3 compartment model with a correlation coefficient of 0.9836. The CBF by R2 is 29.48 +/- 1.51 ml/min per 100 g, the CBF by R3 is 29.10 +/- 1.48 ml/min per 100 g, and no significant difference between them is seen (P > 0.05, n = 24). These data indicate that the simplified two-compartment model for the mechanism of the uptake of 99mTc-ECD in brain is better. And we found that, compared with the entricular function, the pulse function may be used as a more appropriate input function for the model.

Brain↗
PubMed2001

[Studies on lignocellulolytic enzymes production and biomass degradation of Pleurotus sp2 and Trametes gallica in wheat straw cultures].

Pleurotus sp2 and Trametes gallica were selected in this assay because of their high activities of lignocellulolytic enzymes and the enzyme peaks appeared at the early stage of liquid state fermentation. Solid state fermentation was also investigated for their abilities and behaviors of enzyme-production. The capabilities and characteristics of the two strains in degrading biomass were studied. When Pleurotus sp2 was incubated in wheat straw powder containing the liquid medium of low-nitrogen, no-carbon and high inorganic salt, the activities of MnP and Lac reached the peaks on the tenth day, but the activities of hemicellulases reached the peak on the 40th day. Pleurotus sp2 caused 17.6% of biomass loss. When T. gallica was incubated in wheat straw powder containing the liquid medium of hlig-nitrogen, or low-nitrogen, no-carbon and high inorganic salt, the activities of MnP reached the peaks on the tenth day, the lac and hemicelluloses on the 40th day, and the lignin peroxidases reached the peaks on the 50th day, and it caused more than 64% of biomass loss. Among them the hemicellulose was degraded by 71.96%, and the cellulose 66.21%. T. gallica was very capable of degrading lignin of wheat straw and caused 34.37% loss during 20 days, 46. 71% loss during 30 days and 70.14% loss during 60 days. It was interesting that T. gallica degraded lignin preferentially with respect to cellulose, which was very beneficial to biopulping of paper industry.

Basidiomycota↗
PubMed2001

[Study on active constituents of traditional Chinese medicine reversing multidrug resistance of tumor cells in vitro].

OBJECTIVE: To screen drugs reversing multidrug resistance of tumor cells from active constituents of traditional Chinese medicine and to study the reversal action. METHODS: The kill effects of the drugs on tumor cell lines in vitro were determined with MTT method. The Jin's formula was used to analyse the effect of drug combination. RESULTS: 5 micrograms/ml rhynchophylline, 2 micrograms/ml jatrorrhizine and 1.25 micrograms/ml indirulin could reverse multidrug resistance for vincristine on KBv200 cell line by 16.8, 5.1 and 4 fold respectively. 1.56-12.5 micrograms/ml curcumine combining with vincristine could sensitize antitumor effect both on KB and KBv200 cell lines. CONCLUSION: All rhynchophylline, jatrorrhizine and indirulin could reverse multidrug resistance for vincristine on KBv200 cell line. Curcumine combinating vincristine could sensitize antitumor effect both on kB and kBv200 cell lines.

Antineoplastic Agents, Phytogenic↗
PubMed2001

[Bioremediation of mineral oil and polycyclic aromatic hydrocarbons (PAHs) in soils with two plant species].

With alfalfa (Medicago sativa) and paddy rice as test plants, and with pollutant level, specific bacteria, fungi and organic fertilizer as control factors, the bioremediation of mineral oil and polycyclic aromatic hydrocarbons (PAHs) in soils with two plant species was conducted. The results showed that the degradation rate of mineral oil was promoted by fertilization in alfalfa soil, but not in paddy rice soil. The degradation rate of total PAHs (11 PAH listed in USEPA) was increased by fertilization both in alfalfa and in paddy rice soil, and the promotion effect of fertilizer was better in paddy rice soil than in alfalfa soil. The fertilization rate was positively related to the rhizospheric indigenous fungi and bacteria's CFU in alfalfa soil, but only to the indigenous bacteria's CFU in paddy rice soil. The fungi and bacteria's CFU in both test soils had no positive relation with the amount of specific bacteria and fungi spiked. The degradation rate of 3-ring PAHs was enhanced in both alfalfa and paddy rice soil by fertilization, and the effect was stronger in paddy rice soil than in alfalfa soil. However, fertilization had no positive effect on the degradation of 4-ring PAHs.

Bacteria↗