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PubMed1986

[The 3-dimensional voice field].

Extension of the voice field (voice profile) by a third variable which characterizes the phonation has various advantages as well as drawbacks. Since the voice field evaluates the laryngeal function, the use of aerodynamic variables improve the representation of the laryngeal efficiency in the voice field. On the other hand, the measurement of these variables complicates the method. When voice quality measures (presence of singing formant, sharpness) are used as the third dimension, the limits of the voice field are unique references for the measures. However, the voice quality at the physiologic limits is not representative of the voice as produced in singing or speaking. Measures which characterize the "hoarseness" of the voice yield important results with respect to the perturbation of the voice production (jitter, shimmer, additive noise). The perturbation measures evaluate the laryngeal function at defined points in the frequency--intensity area. However, in forte phonation, the natural perturbation is reduced, in piano phonation, the perturbation is increased, and the results cannot be interpreted in relation to the perturbation magnitude within the voice field. Besides, the measurement of perturbation requires digital signal processing. If EMG data are used for the voice field, as it is shown for the M. vocalis, the voice field reveals interesting relationships between acoustic and physiologic features. For instance, in the piano phonation, the EMG signal power is constant on a low level. In the forte phonation, in the chest register, the EMG signal power shows a medium level and a high level in the head register. In the falsetto, however, the EMG signal power is low.(ABSTRACT TRUNCATED AT 250 WORDS)

Electromyography↗
PubMedDate not supplied

Activation and inhibition of Na/K-ATPase by filipin-cholesterol complexation. A correlative biochemical and ultrastructural study on the microsomal and purified enzyme of the avian salt gland.

The Na/K-ATPase-rich microsomal fraction and purified Na/K-ATPase membranes of the salt-stressed avian salt gland were studied at defined filipin/cholesterol molar ratios (F/C) using enzyme assay and electron microscopy including negative staining, thin sectioning and freeze fracturing. Comparative examinations of detergent-treated microsomal fractions and the use of electron microscopic tracers revealed that F/C up to 2 activated latent Na/K-ATPase in sealed right-side-out vesicles by increasing membrane permeability without disrupting the vesicular membrane. Therefore, filipin offers an alternative to the detergents for the activation of latent vectorial membrane enzymes and a possible tool to examine their subcellular localization and sidedness in the membrane. The same F/C had no stimulatory effect on the microsomal anion-ATPase suggesting that the 2 ATPases are not located in the same membrane. Increasing F/C applied to the unfixed Na/K-ATPase membranes caused an increase in the number of structural F-C-complexes and a progressive lateral displacement of the enzyme particles which finally led to a separation of the areal distribution of these structures at F/C = 10. Such displacements did not occur in unfixed microsomes and were prevented by glutaraldehyde fixation of the purified membranes. F/C exceeding 2 progressively and temperature-dependently inhibited the Na/K-ATPase in its membrane-bound states, whereas the solubilized enzyme was rather insensitive. The structural and biochemical data suggest that inhibition results from the perturbation of the lipidic microenvironment of the enzyme caused by filipin-cholesterol complexation.

Animals↗
PubMed1981

[Application of flow cytometric analysis to brain tumor chemotherapy. Report 1: Changes of cell kinetics induced by anticancer drugs (author's transl)].

It has been reported that flow cytometric analysis offers good indicators to select drugs for chemotherapy of malignant neoplasms, however, there are still few reports to try to apply these data to clinical treatment. For this purpose perturbation of cell cycle traverse which induced by several anticancer drugs was studied to determined the fundamental factors to indicate the sensitivity of each drugs. Results were: 1) Drugs showed high efficiency of accumulation of cells in SG2M phase even in low concentration; MMC, AD, CQ. 2) Drugs showed high efficiency of accumulation of cells in SG2M from low concentration high concentration; Vincristine. 3) Drugs which showed accumulation of SG2M in high concentration; ACNU, BCNU. 9L rat glioma cells treated with BCNU showed high efficiency of accumulation of cells in SG2M phase. In this cell line cytocidal effect was high. However, C6 cells which showed low accumulation in SG2M even by treatment with high concentration of BCNU revealed quite resistant to anticancer drugs from nitrosourea derivatives (ACNU, BCNU). Cytocidal effect of MMC and ACNU on C6 glioma cells was studied by colony forming efficiency assay using multicell spheroids treated with these drugs and it was discussed the correlation between percent of accumulated cells and cytocidal effect of each drug.

Animals↗
PubMed1995

Intracellular signaling events during positive and negative selection of CD4+CD8+ thymocytes in vitro.

We have used in vitro models of thymocyte positive and negative selection in conjunction with selective inhibitors of the TCR-mediated signaling cascade to investigate the intracellular signaling events that mediate these processes. We report that Ro 31.8425, a potent and selective inhibitor of protein kinase C, which blocks the activation of mature T cells in a dose-dependent fashion, has no effect on either positive or negative selection of CD4+8+ thymocytes. In contrast, cyclosporin A fails to prevent negative selection, but inhibits positive selection through a direct effect on developing thymocytes, rather than through the perturbation of stromal cell support. Thus, our data suggest that positive and negative selection may operate via distinct intracellular signaling pathways.

Animals↗
PubMed1995

Cell wall synthesis specific cytocidal effect of Hansenula mrakii toxin-1 on Saccharomyces cerevisiae.

HM-1 toxin produced by Hansenula mrakii kills sensitive Saccharomyces cerevisiae. We found that the budding cells and the cells that responded to mating factor were sensitive to HM-1 toxin. These findings indicate that the target sites of HM-1 toxin are developing buds and conjugating tubes. The in vitro activity of beta-1,3-glucan synthase solubilized and partially purified from S. cerevisiae membranes was inhibited by HM-1 toxin at a concentration (around 50 nM, 0.5 micrograms/ml) that coincided well with its minimum inhibitory concentration for the growth of yeast cells. These data indicate that the HM-1 toxin perturbs the synthesis of yeast cell walls by inhibiting the glucan synthesis occurring at a budding site or a conjugating tube, which results in cell lysis.

Cell Cycle↗
PubMed2001

The adaptor protein shc is involved in the negative regulation of NK cell-mediated cytotoxicity.

The activation of protein tyrosine kinase(s) (PTK) is a critical event required for the development of NK cell-mediated cytotoxicity. Here we demonstrate that the adaptor protein shc undergoes tyrosine phosphorylation during the generation of antibody-dependent cellular cytotoxicity (ADCC) and natural killing. In addition, we report that, upon direct or antibody-dependent target cell interaction, shc coprecipitates with the Src homology 2 (SH2)-containing inositol phosphatase, SHIP. To gain information on the functional role of shc in NK cytotoxicity, we overexpressed wild-type or dominant negative shc constructs in the human NKL cell line. Our findings show a consistent shc-mediated down-regulation of ADCC and natural killing. Such functional effect correlates with a perturbation of the phosphoinositide (PI) metabolism by means of a shc-mediated negative regulation of inositol 1,4,5 triphosphate (IP3) generation and intracellular calcium flux upon CD16 ligation. Furthermore, our data show that dominant-negative shc-mediated perturbation of shc/SHIP interaction leads to inhibition of ligand-dependent SHIP recruitment to CD16 zeta chain. We suggest that shc plays a role of negative adaptor by modulating SHIP recruitment to activation receptors involved in the generation of NK cytotoxic function.

Adaptor Proteins, Signal Transducing↗
PubMed2004

ElNemo: a normal mode web server for protein movement analysis and the generation of templates for molecular replacement.

Normal mode analysis (NMA) is a powerful tool for predicting the possible movements of a given macromolecule. It has been shown recently that half of the known protein movements can be modelled by using at most two low-frequency normal modes. Applications of NMA cover wide areas of structural biology, such as the study of protein conformational changes upon ligand binding, membrane channel opening and closure, potential movements of the ribosome, and viral capsid maturation. Another, newly emerging field of NMA is related to protein structure determination by X-ray crystallography, where normal mode perturbed models are used as templates for diffraction data phasing through molecular replacement (MR). Here we present ElNémo, a web interface to the Elastic Network Model that provides a fast and simple tool to compute, visualize and analyse low-frequency normal modes of large macro-molecules and to generate a large number of different starting models for use in MR. Due to the 'rotation-translation-block' (RTB) approximation implemented in ElNémo, there is virtually no upper limit to the size of the proteins that can be treated. Upon input of a protein structure in Protein Data Bank (PDB) format, ElNémo computes its 100 lowest-frequency modes and produces a comprehensive set of descriptive parameters and visualizations, such as the degree of collectivity of movement, residue mean square displacements, distance fluctuation maps, and the correlation between observed and normal-mode-derived atomic displacement parameters (B-factors). Any number of normal mode perturbed models for MR can be generated for download. If two conformations of the same (or a homologous) protein are available, ElNémo identifies the normal modes that contribute most to the corresponding protein movement. The web server can be freely accessed at http://igs-server.cnrs-mrs.fr/elnemo/index.html.

Crystallography, X-Ray↗
PubMed1998

Incorporation of tryptophan analogues into staphylococcal nuclease, its V66W mutant, and Delta 137-149 fragment: spectroscopic studies.

We have biosynthetically incorporated several tryptophan analogues into three forms of Staphylococcal nuclease to investigate the spectroscopic characteristics of these "intrinsic" probes and their effect on the structure of the proteins. The set of tryptophan analogues includes 5-hydroxytryptophan, 7-azatryptophan, 4-fluorotryptophan, 5-fluorotryptophan, and 6-fluorotryptophan. 5-Hydroxytryptophan and 7-azatryptophan have red-shifted absorbance spectra, and the latter has a red-shifted fluorescence, which is very sensitive to its environment (being heavily quenched in water). The fluorotryptophans can serve as 19F NMR probes, and 4-fluorotryptophan has a very low fluorescence quantum yield, thus making it a "knock-out" fluorescence analogue. The set of proteins studied includes wild-type nuclease, which has a single tryptophan site at position 140; its V66W mutant, which has a second tryptophan at position 66; and the Delta 137-149 fragment, V66W', which only has a tryptophan at position 66. The environments of positions 66 and 140 are significantly different; position 140 is near the end of the long C-terminal alpha-helix and is moderately solvent-exposed, whereas position 66 is in the beta-barrel core region of the protein and is surrounded by apolar side chains. Absorbance and 19F NMR spectra are used to estimate the extent of analogue incorporation for each protein. Steady-state and time-resolved fluorescence data are reported to characterize the emission of the analogues in these positions in the three proteins and to develop the use of the analogues as probes of protein structure and dynamics. Circular dichroism spectra are reported to show that, in all but a couple of cases, the secondary structure of the proteins containing the analogues is not significantly perturbed by the probes. Additionally, fluorescence anisotropy decay data show the variants of wild-type nuclease to have a rotational correlation time similar to that of tryptophan-containing nuclease.

Amino Acid Substitution↗
PubMed2006

Gender differences in plasma lipid response to dietary fat.

The relationship between type of dietary fat, cardiovascular disease risk, and lipid/lipoprotein profiles has been studied since the early 1900s. For the most part, observational data from international comparisons, migration studies, and prospective studies have identified a positive relationship between saturated fatty acid (SFA) intake and coronary heart disease (CHD) risk, although in the latter case these observations were attenuated and in some cases became non-significant after adjusting for other dietary factors. Data from large-scale primary and secondary intervention studies support a positive relationship between CHD and SFA. The majority of data available were derived from male subjects, and if female subjects were included, few studies assessed the effect of gender on responsiveness. Recent evidence has emerged suggesting that females respond differently to diet with respect to CHD progression. This review discusses controlled clinical intervention studies that included data for both genders and their responses to dietary fat perturbations and lipoprotein profiles. The scope was limited for the most part to reports that included identifiers in the title or abstract that indicated data for female and male subjects were reported separately, although a statistical comparison between the genders may not have been reported. Overall, whether the studies assessed the effect of the ratio of SFA to monounsaturated fatty acids (MUFA), SFA to polyunsaturated fatty acids (PUFA), MUFA to PUFA, individual SFA, or SFA to trans fatty acids, female and male subjects responded similarly, and when differences were identified there was no consistent pattern.

Cardiovascular Diseases↗
PubMed1997

Practice modifies the developing automatic postural response.

The purpose of this study was to examine effects of experience with a postural task on components of the automatic postural response including: (1) probability of activation of functionally appropriate postural muscles; (2) number of functionally appropriate postural muscles activated; and (3) onset latencies of functionally appropriate postural muscles in infants. Infants (n=15; age 36-48 weeks old) able to pull themselves into a standing position but not able to walk independently were tested using a postural task requiring the infant to stand and balance, with support, following a forward or backward movement of the support surface (platform perturbation). Infants were tested twice at 5-day intervals. One-half of the infants, the training group, were given intense platform perturbation training on the days between test sessions. Infants in the second group were also brought into the laboratory on the days between test sessions but were not exposed to platform perturbations during those days. Electromyograms of six leg and trunk muscles were recorded during test sessions to provide muscle onset latencies, probability of muscle activation data, and the number of postural muscles activated following a perturbation. Training infants demonstrated significant increases in probability of activating functionally appropriate muscles with tibialis anterior, quadriceps, and abdominal muscles activated in response to backward sway and gastrocnemius muscle in response to forward sway. The number of functionally appropriate postural muscles activated in a single trial also increased in the training group. There were no significant changes in mean postural muscle onset latencies or number of trials with antagonist muscle coactivation for either training or control groups. These findings suggest that during development selective parameters of the automatic postural response are affected by experience with the postural task.

Child Development↗
PubMed2001

Regional variations in sulfate and nitrate on annual, seasonal, and synoptic time scales.

Ambient data from Interagency Monitoring of Protected Visual Environments (IMPROVE) monitors are analyzed to evaluate the spatial structure of SO4 and NO3 aerosols in the mid-Atlantic region. Sub-weekly, seasonal, and annual data values are compared between the IMPROVE Washington, DC, site and three rural sites. Synoptic perturbations are compared between sites to quantify similarities in short-term temporal perturbations of SO4 and NO3. Based on these comparisons between the rural and urban IMPROVE monitors, the spatial structure of SO4 shows broad regional homogeneity that is recognizable from both the long-term average values and the short-term variations. NO3 data on a seasonal and annual basis show much larger spatial gradients between the urban Washington monitor and the three rural monitors than do SO4 data. Short-term NO3 perturbations at the three rural monitors also differ significantly from those at the Washington site. These dissimilarities in NO3 levels between the rural and urban IMPROVE monitors on both short-term and longer-term time scales indicate little homogeneity of NO3 aerosols in the mid-Atlantic region considered here. The volatility of NO3 aerosols and the removal rate of HNO3 via dry deposition could contribute to the spatial variability differences shown here between SO4 and NO3.

Air Pollutants↗
PubMed2006

The natural mutation by deletion of Lys9 in the thrombin A-chain affects the pKa value of catalytic residues, the overall enzyme's stability and conformational transitions linked to Na+ binding.

The catalytic competence of the natural thrombin mutant with deletion of the Lys9 residue in the A-chain (deltaK9) was found to be severely impaired, most likely due to modification of the 60-loop conformation and catalytic triad geometry, as supported by long molecular dynamics (MD) simulations in explicit water solvent. In this study, the pH dependence of the catalytic activity and binding of the low-molecular mass inhibitor N-alpha-(2-naphthylsulfonyl-glycyl)-4-amidinophenylalanine-piperidine (alpha-NAPAP) to the wild-type (WT) and deltaK9 thrombin forms were investigated, along with their overall structural stabilities and conformational properties. Two ionizable groups were found to similarly affect the activity of both thrombins. The pKa value of the first ionizable group, assigned to the catalytic His57 residue, was found to be 7.5 and 6.9 in ligand-free deltaK9 and WT thrombin, respectively. Urea-induced denaturation studies showed higher instability of the deltaK9 mutant compared with WT thrombin, and disulfide scrambling experiments proved weakening of the interchain interactions, causing faster release of the reduced A-chain in the mutant enzyme. The sodium ion binding affinity was not significantly perturbed by Lys9 deletion, although the linked increase in intrinsic fluorescence was lower in the mutant. Essential dynamics (ED) analysis highlighted different conformational properties of the two thrombins in agreement with the experimental conformational stability data. Globally, these findings enhanced our understanding of the perturbations triggered by Lys9 deletion, which reduces the overall stability of the molecule, weakens the A-B interchain interactions, and allosterically perturbs the geometry and protonation state of catalytic residues of the enzyme.

Catalytic Domain↗
PubMed2005

Determination of kinetic and thermodynamic parameters of surface confined species through ac voltammetry and a nonstationary signal processing technique: the Hilbert transform.

Data analysis of voltammetric responses has usually been done through application of the fast Fourier transform although it is widely accepted that electrochemical signals are intrinsically nonlinear and nonstationary. In this work, we present a time-series analysis based on the Hilbert transform (HT), a nonstationary signal processing technique, as an alternative tool that can overcome many of the difficulties associated with Fourier techniques. We use the HT to study the behavior of thin-film processes when the excitation perturbation is ac voltammetry. From the analysis of simulated data, we propose simple relations that enable species-specific kinetic and thermodynamic parameters to be estimated, without prior utilization of baseline subtraction even when double layer capacitance significantly influences the current response. We also propose a method to determine whether the characteristics of the applied voltage perturbation are adequate for the accurate estimation of these parameters. The methodology developed here will be applied to previously published experimental time series data (Guo, S. X.; Zhang, J.; Elton, D. M.; Bond, A. M. Anal. Chem. 2004, 76, 166-177.) obtained with ac voltammetry to show how a number of physical parameters can be directly extracted from the processed data.

Algorithms↗
PubMed2003

Sleep-deprived mice show altered cytokine production manifest by perturbations in serum IL-1ra, TNFa, and IL-6 levels.

Serum cytokine and chemokine levels were examined in mice following 36 h of sleep deprivation, or after exposure to a known physical stressor (rotational stress). Significant changes in inflammatory cytokines/chemokines (IL-1beta, TNFalpha, IL-1ra, IL-6, and MIP-1beta, MCP-1) were observed following each manipulation, but qualitative and quantitative differences were seen. Interestingly, only physical stress was associated with measured increases in serum corticosterone levels, and with independent evidence (using in vitro immune allostimulation) for a generalized immunosuppression secondary to the experimental manipulation. Our data suggest that altered cytokine production following sleep perturbation occurs by a different mechanism from that (HPA axis) commonly attributed to stress per se.

Acebutolol↗
PubMed2006

Integrative investigation of metabolic and transcriptomic data.

BACKGROUND: New analysis methods are being developed to integrate data from transcriptome, proteome, interactome, metabolome, and other investigative approaches. At the same time, existing methods are being modified to serve the objectives of systems biology and permit the interpretation of the huge datasets currently being generated by high-throughput methods. RESULTS: Transcriptomic and metabolic data from chemostat fermentors were collected with the aim of investigating the relationship between these two data sets. The variation in transcriptome data in response to three physiological or genetic perturbations (medium composition, growth rate, and specific gene deletions) was investigated using linear modelling, and open reading-frames (ORFs) whose expression changed significantly in response to these perturbations were identified. Assuming that the metabolic profile is a function of the transcriptome profile, expression levels of the different ORFs were used to model the metabolic variables via Partial Least Squares (Projection to Latent Structures--PLS) using PLS toolbox in Matlab. CONCLUSION: The experimental design allowed the analyses to discriminate between the effects which the growth medium, dilution rate, and the deletion of specific genes had on the transcriptome and metabolite profiles. Metabolite data were modelled as a function of the transcriptome to determine their congruence. The genes that are involved in central carbon metabolism of yeast cells were found to be the ORFs with the most significant contribution to the model.

Algorithms↗
PubMed2005

Fishing perturbations and beached corals in the Cape d'Aguilar Marine Reserve, Hong Kong (2000-2002) and a summary of data obtained from January 1996 to March 2003.

Every month for four years (1996-1999) and every three months for three years thereafter (2000-2003) stranded corals were collected from Telecom Bay Beach in the Cape d'Aguilar Marine Reserve, Hong Kong. Over time, the numbers of coral pieces and heads recovered declined progressively. Exceptions to this at first occurred after the passage of tropical depressions and typhoons over Hong Kong when the numbers of coral heads rose sharply. This was particularly obvious from 1996 to 1999. During this period, however, fishing was banned in the marine reserve and in 2000 and 2001 only a few corals were beached despite the passage of a series of typhoons over Hong Kong in both years. It is argued that gill net and purse seine fishermen had stopped snagging their nets on the shallow corals of Telecom Bay and they were thus no longer being dislodged and subsequently deposited on the beach by typhoon surges and waves. In 2002, therefore, few corals were collected. This situation changed in September 2002, however, when Severe Tropical Storm Hagiput deposited numerous large living coral heads on the beach. A seabed inspection showed there to be three active ghost nets in the reserve. Natural perturbations such as, for example, coral bleaching in the El Nino year of 1997-1998 also affected community composition at Cape d'Aguilar through selective, low salinity-induced mortality.

Animals↗
PubMedDate not supplied

Age-related changes in energy production in fresh senescence-accelerated mouse brain slices as revealed by positron autoradiography.

To investigate age-related changes in cerebral energy production, we compared senescence-accelerated prone mice (SAMP8) as an animal model of accelerated aging and senescence-accelerated resistant mice (SAMR1) as a control. Considering that the cerebral glucose metabolic rate (CMRglc) at the time of O(2) deprivation and 2,4-dinitrophenol (DNP) loading would reflect anaerobic glycolytic capacity and mitochondrial function, respectively, we investigated dynamic changes in CMRglc before and after loading with these perturbations. Fresh brain slices were incubated with [(18)F]2-fluoro-2-deoxy-D-glucose ([(18)F]FDG) in oxygenated Krebs-Ringer solution at 36 degrees C, and serial two-dimensional time-resolved images of [(18)F]FDG uptake in these slices were obtained on the imaging plates. The fractional rate constant (=k(3)*) of [(18)F]FDG proportional to the CMRglc was evaluated by applying the Gjedde-Patlak graphical method to the image data. The k(3)* value before the hypoxic perturbation in all of the brain sites analyzed was higher in SAMP8 than SAMR1 in both the 2- and 10-month-old groups. With O(2) deprivation, k(3)* values were higher without site specificity in the 2-month-old SAMP8 than in 2-month-old SAMR1, whereas in 10-month-old mice, there was no significant difference between the two groups. In contrast, with DNP loading, while no significant difference was noted between 2-month-old SAMP8 and 2-month-old SAMR1, in 10-month-old mice, the SAMP8 group showed lower values in certain regions than SAMR1 mice. These results suggest that in the brain tissue of SAMP8, a marked transient enhancement of anaerobic glycolytic capacity in the 2-month-olds and a decrease in mitochondrial function in the subsequent period occur, as a result of which glucose metabolism appears to be enhanced in both the 2- and 10-month-old groups compared to SAMR1 mice.

Age Factors↗
PubMed1998

NMR spectroscopic and enzymatic studies of DNA hairpins containing mismatches in the EcoRI recognition site.

We have correlated the structural perturbations caused by DNA mismatches with the enzymatic data of the interaction of the restriction endonuclease EcoRI with DNA. Oligonucleotides d(CGAGAATTCTCA5GAXAATTCT) (X = G, A, T) and d(CGCGAATTYGCGT4CGCXAATTCGCG) (Y = C, X = G, T and Y = A, X = T) containing single mismatches within the EcoRI recognition site were characterized by NMR spectroscopy and by their EcoRI substrate properties. UV melting and gel electrophoresis studies confirm that the oligonucleotides form hairpin structures. The presence of either a CT or a CA mismatch results in markedly lower Tm and van't Hoff enthalpies compared with the fully base paired control. NMR imino proton spectra of these hairpins demonstrate that the perturbation caused by the two mispairs or a noncanonical AT pair is localized and limited to one or two base pairs on either side of the perturbation. The DNA hairpin structures containing single mismatches, and to a lesser extent also sequences with a single noncanonical base pair, are substrates for the restriction endonuclease. In addition to the strand scission at the nonperturbed GpA phosphodiester bond some cleavage is observed at the mismatched position. The interactions of the CA and CT mismatched hairpin with the enzyme are characterized by binding constants that are only 33 and 57 times lower, respectively, than that for the canonical sequence, corresponding to 8-10 kJ x mol(-1) less favorable free binding energy. This, taken together with the NMR data, indicates that the CA and CT mismatches have only small effects on the EcoRI recognition of the DNA substrate. We conclude that two out of the three hydrogen bonds that characterize the interaction of EcoRI with the CG base pair in the canonical sequence can still be formed for either the CT or CA mismatched recognition site.

Base Pairing↗