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PubMed1985

Important associations among EEG-dynamics, event-related potentials, short-term memory and learning.

Averaged and single sweep auditory event-related potentials (ERPs) were analysed in the time and frequency domain to demonstrate a dynamic, functional relationship between prestimulus EEG activity and poststimulus ERP changes. Evidence is presented of prestimulus "preparation changes" which were elicited by the presentation of regular, frequent target tones. The development of preparation changes was associated with prestimulus EEG synchronisation, frequency selective phase alignment at the point of stimulation and a greater predictability of the poststimulus response to target and nontarget tones. Time varying responses to target and nontarget tones are described for different experimental conditions and related to preparation rhythms. The mechanisms and possible neural correlates of the endogenous P300 change are discussed. The findings from this study and other relevant investigations have been used to formulate hypotheses about the relationships among preparation changes, ERPs and short-term memory, habituation and learning.

Adult↗
PubMed1994

Supertransients and suppressed chaos in the diffusively coupled logistic lattice.

Pattern selection at medium and high nonlinearity is investigated. While in the former the transient time levels off for large system sizes, in the latter it diverges exponentially giving rise to supertransients. In both cases, the final attractors are quite stable with as a consequence that even at high nonlinearity an attractor can easily be reached by means of a parameter sweep.

Journal Article↗
PubMedDate not supplied

Determination of magnesium in foods by single-sweep polarography.

In KOH, the Mg(II)-bromopyrogallol red (BPR) complex produced a very sensitive polarographic wave at -1.30 V. The wave height was linear with the concentration of Mg(II) in the range of 0.05 to 2 microg/mL. The detection limit was 0.01 microg/mL. The electrochemical behavior of Mg(II)-BPR was studied by electrochemical and spectrophotometric methods. Experiments proved that the polarographic wave of Mg(II)-BPR was due to the reduction of BPR in the Mg(II)-BPR complex. The method, which was sensitive, selective, and simple to perform, was used to determine magnesium in foods, and the results were consistent with those obtained by atomic absorption spectroscopy.

Chemistry Techniques, Analytical↗
PubMed2004

L-type calcium channel gating is modulated by bradykinin with a PKC-dependent mechanism in NG108-15 cells.

Bradykinin (BK) excites dorsal root ganglion cells, leading to the sensation of pain. The actions of BK are thought to be mediated by heterotrimeric G protein-regulated pathways. Indeed there is strong evidence that in different cell types BK is involved in phosphoinositide breakdown following activation of G(q/11). In the present study we show that the Ca(2+) current flowing through L-type voltage-gated Ca(2+) channels in NG108-15 cells (differentiated in vitro to acquire a neuronal phenotype), measured using the whole-cell patch clamp configuration, is reversibly inhibited by BK in a voltage-independent fashion, suggesting a cascade process where a second messenger system is involved. This inhibitory action of BK is mimicked by the application of 1,2-oleoyl-acetyl glycerol (OAG), an analog of diacylglycerol that activates PKC. Interestingly, OAG occluded the effects of BK and both effects were blocked by selective PKC inhibitors. The down modulation of single L-type Ca(2+) channels by BK and OAG was also investigated in cell-attached patches. Our results indicate that the inhibitory action of BK involves activation of PKC and mainly shows up in a significant reduction of the probability of channel opening, caused by an increase and clustering of null sweeps in response to BK.

Animals↗
PubMed2004

An adaptive neuro-fuzzy method (ANFIS) for estimating single-trial movement-related potentials.

This study aims to recover transient, trial-varying evoked potentials (EPs), in particular the movement-related potentials (MRPs), embedded within the background cerebral activity at very low signal-to-noise ratios (SNRs). A new adaptive neuro-fuzzy technique will attempt to estimate movement-related potentials within multi-channel EEG recordings, enabling this method to completely adapt to each input sweep without system training procedures. We assume that one of the sensors is corrupted by noise deriving from other sensors via an unknown function that will be estimated. We will approach this problem by: (1) spatially decorrelating the sensors in the preprocessing phase, (2) choosing the most informative of the filtered channels that will permit the best MRP estimation (input-selection phase) and (3) training the neuro-fuzzy model to fit the noise over the chosen sensor and therefore estimating the buried MRP. We tested this framework with simulations to validate the analytical results before applying them to the real biological data. Whenever it is applied to biological data, this method improves the SNR by more than 12 dB, even to very low SNRs. The processing method proposed here is likely to complement other estimation techniques and can be useful to process, enhance and analyse single-trial MRPs.

Adult↗
PubMed1990

Effects of chronic treatment with haloperidol and bromocriptine on the processing of beta-endorphin to gamma- and alpha-endorphin in discrete regions of the rat pituitary gland and brain.

beta-Endorphin is the putative precursor molecule of gamma- and alpha-endorphin. To investigate whether long-term changes in the activity of cells producing beta-endorphin are paralleled by alterations in the enzymatic processing of beta-endorphin, the effects of chronic treatment of rats with dopamine (DA) receptor ligands were examined on the content of immunoreactivity of beta-, gamma- and alpha-endorphin of dissected regions of the pituitary gland and the brain. Treatment with the DA receptor antagonist, haloperidol, resulted in a significant increase in the concentration of immunoreactivity for beta-, gamma-, and alpha-endorphin in the neurointermediate lobe, and of beta-endorphin in the anterior lobe of the pituitary gland. Levels of immunoreactivity of alpha-melanotropin and beta-endorphin in plasma were elevated, but those of corticosterone were decreased. This indicates that, in the intermediate lobe, both the biosynthetic and the secretory activity of cells producing beta-endorphin had increased, whereas in the anterior lobe, the secretory activity of beta-endorphin cells had decreased. No effects were observed on the ratios beta-endorphin/gamma-endorphin and beta-endorphin/alpha-endorphin in the intermediate lobe. In the anterior lobe however, the ratio beta-endorphin/alpha-endorphin had significantly increased. The effects of chronic treatment with the DA receptor agonist, bromocriptine, on levels of hormones in pituitary and plasma were opposite to those induced by haloperidol. In the brain, treatment with haloperidol selectively increased the content of immunoreactivity for beta-, gamma- and alpha-endorphin of the hypothalamus and the hippocampus and did not affect levels of peptides in the other regions of the brain studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

A method for analytically generating three-dimensional isocomfort workspace based on perceived discomfort.

The purpose of this study was to develop a new method for analytically generating three-dimensional isocomfort workspace for the upper extremities using the robot kinematics. Subjective perceived discomfort scores in varying postures for manipulating four types of controls were used. Fifteen healthy male subjects participated in the experiment. The subjects were asked to hold the given postures manipulating controls for 60 s in the seated position, and to rate their perceived discomfort during the following rest of 60 s using the magnitude estimation. Postures of the upper extremities set by shoulder and elbow motions, types of controls, and left right hand were selected as experimental variables, in which the L32 orthogonal array was adopted. The results showed that shoulder flexion and adduction-abduction, elbow flexion, and types of controls significantly affected perceived discomfort for postures operating controls, but hand used for operating controls did not. Depending upon the types of controls, four regression models predicting perceived discomfort were presented. Using the models, a sweeping algorithm to generate three-dimensional isocomfort workspace was developed, in which the robot kinematics was employed to describe the translational relationships between the upper arm and the lower arm/hand. It is expected that the isocomfort workspace can be used as a valuable design guideline when ergonomically designing three-dimensional workplaces.

Adult↗
PubMed2001

Vascular endothelial growth factor in ovarian cyst fluid.

BACKGROUND: The purpose of the current study was to determine vascular endothelial growth factor (VEGF) concentrations in cyst fluid from malignant, borderline, and benign ovarian tumors, and to correlate these data with preoperative serum VEGF concentrations and clinicopathologic characteristics. METHODS: One hundred seven ovarian cysts were removed and punctured for cyst fluid collection. Histologic diagnosis revealed 25 malignant, 12 borderline, and 70 benign ovarian tumors. The VEGF concentrations of all the cyst fluid specimens as well as in 37 preoperatively collected serum samples were determined by making use of a sandwich type double determinant enzyme linked immunoadsorbent assay based on a combination of 4 polyclonal antibodies. RESULTS: Statistically significantly higher VEGF concentrations were found in cyst fluid from malignant (median, 21.5 microg/L) compared with borderline (median, 3.2 microg/L; P = 0.01) or benign tumors (median, 1.3 microg/L; P < 0.0001). Preoperative serum VEGF concentrations were significantly higher in patients with malignant (median, 0.63 microg/L; range, 0.016-17.7 microg/L) compared with nonmalignant tumors (median, 0.28 microg/L; range, 0.016-0.89 microg/L; P = 0.008). A significant correlation of preoperative serum VEGF was found with VEGF cyst fluid concentrations (r = 0.38; P = 0.02). Significantly higher VEGF cyst fluid concentrations were found in serous malignant (median, 31.9 microg/L) compared with mucinous malignant tumors (median, 4.7 microg/L; P = 0.004). Not significant, though higher median VEGF cyst fluid concentrations were found in advanced International Federation of Gynecology and Obstetrics (FIGO) Stage II, III, and IV, histologic Grade 2 and 3, patients with residual tumor greater than 2 cm, with malignant cells in ascites or peritoneal washings, or with recurrent disease, as compared with FIGO Stage I, histologic grade 1, patients with less than or equal to 2-cm residual tumor, without malignant cells in ascites/peritoneal washings, or without recurrent disease, respectively. CONCLUSIONS: It has become clear from the increased study sample that ovarian tumors of different histologic etiology vary in VEGF cyst fluid concentrations, with the highest VEGF cyst fluid concentrations in malignant tumors. The prognostic significance of VEGF cyst fluid concentrations in advanced FIGO stage seems to be of limited value but may be important in the selection of high risk FIGO Stage I and borderline types. Data from this study indicate a possible role for VEGF as a serum tumor marker.

Adenocarcinoma, Mucinous↗
PubMed1993

Pulmonary alveolar macrophages in molecular epidemiology and chemoprevention of cancer.

In addition to possessing an extraordinary sweeping activity, pulmonary alveolar macrophages (PAM) are equipped with the biochemical mechanisms involved in the metabolism of carcinogens, which were found to be inducible in humans by cigarette smoke. Moreover, several defense processes were stimulated in rat PAM after in vivo administration of the anticarcinogen N-acetylcysteine (NAC). Benzo[a]pyrene diol epoxide (BPDE)-DNA adducts, as revealed by synchronous fluorescence spectrophotometry, were selectively detected in PAM of smokers and persisted up to 6 months. The amount of adducts was significantly correlated with the number of currently smoked cigarettes but not with the cigarettes smoked in a lifetime (pack-years). Nevertheless, deviations from the regression line pointed out the role of interindividual variability factors in adduct formation. Probably due to the low mitotic rate of PAM in the respiratory lumen, the frequency of micronuclei was not enhanced in smokers. However, parallel assays in rats showed that micronuclei can be enhanced after massive intratracheal administration of benzo[a]pyrene or whole-body exposure to high amounts of mainstream cigarette smoke, which also induced BPDE-DNA adducts in lung cells and other organs, including the heart. All these adverse effects were markedly inhibited by the oral administration of NAC, which provides the premise and rationale for a future study on the protective effects of oral NAC in heavy smokers.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1990

[Electroanalytical chemistry study of pilocarpine].

The electrochemical behaviour of pilocarpine was investigated by differential pulse polarography and cyclic voltammetry. The optimum conditions for the determination of pilocarpine were as follows: The electrolyte was 0.4 mol/L HAc-NaAc(pH 4.0) buffer solution, Zn (II) 1.0 x 10(-3) mol/L; initial potential -0.80 V (vs Ag-AgCl), final potential -1.30 V (vs Ag-AgCl), and voltage sweep rate 5 mV/s. A fair reproducibility in the above procedure and a good relationship between peak current and pilocarpine concentration (4.0 x 10(-6)-4.0 x 10(-5) mol/L) were achieved. The detection limit was 8.0 x 10(-7) mol/L. This paper also reports that the application of cyclic voltammetry to study electrode process behavior has been established. The PVC membrane ion-selective electrode for pilocarpine also was studied. It is based on the use of tetraphenylborate pilocarpine ion pair complex as the active material. The PVC membrane electrode showed Nernstian response over the pilocarpine concentration range from 1.0 x 10(-2) to 3.0 x 10(-5) mol/L, with a slope of 36 mV/decade, the detection limit being 3.0 x 10(-6) mol/L. The electrode gave fast response and good reproducibility. This method provides a rapid and simple way to the determination of pilocarpine in pharmaceutical preparations.

Electrodes↗
PubMed1999

Selectivity of finasteride as an in vivo inhibitor of 5alpha-reductase isozyme enzymatic activity in the human prostate.

The type II 5alpha-reductase inhibitor finasteride is used in the treatment of benign prostatic hyperplasia (BPH), reducing local production of the growth promoting androgen dihydrotestosterone (DHT). The effect of prolonged treatment with this time-dependent irreversible inhibitor on the recently described prostatic type I 5alpha-reductase, however, is not clear. Therefore, we assessed the effects of 5 mg. finasteride per day for 6 months on prostatic 5alpha-reductase isozymes, and prostatic tissue composition and androgen content of patients suffering from BPH. In prostatic tissue from these patients, the type II enzymatic activity is inhibited 100-fold compared with tissues obtained from placebo treated patients. The type II immunoreactivity is up regulated 2-fold. The type I isozyme is inhibited 3-fold and potentially still contributes to DHT production. In conclusion, finasteride is a selective type II inhibitor in vivo. Further research is warranted to assess the possibly distinct roles of the 5alpha-reductase isozymes in the normal prostate, in BPH, and during finasteride treatment.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1995

Post-stroke autonomic nervous system function: palmar sympathetic skin responses thirty or more days after cerebrovascular accident.

We studied sympathetic nervous system (SNS) function after cerebrovascular accident (CVA) by measuring hypothenar sympathetic skin responses (SSR) to normal or hemiplegic arm electrical stimulation. We anticipated SNS function after CVA to be asymmetric and selected null hypotheses of bilaterally symmetric SSR latencies and amplitudes irrespective of side of stimulation and/or recording. Thirteen patients between ages 44 and 77 years (median 59) were tested between 1 and 72 months (median 15) after CVA. Hypothenar recording and dorsal reference surface electrodes were used. Amplifier bandwidth was set from 0.5 to 100 Hz. Gain was adjusted to allow adequate recognition of the waveforms. Sweep speed was set to 500ms/div. Stimulus width was set to 0.2 ms and intensity was increased stepwise from 10mA initially until optimum responses were obtained. Nonparametric statistics were used to analyze the data. SSRs were present in all patients on both the normal and the hemiplegic sides irrespective of the side of stimulation. Median SSR latency recorded homolaterally to the stimulus site was found to be 80ms shorter than median SSR latency recorded heterolaterally. Median SSR latency in left hemiplegics was found to be 16% longer than in right hemiplegics. Otherwise, neither side of hemiplegia, side of stimulation, side of recording nor any paired combination thereof were found to be significant. Our finding of bilaterally obtainable SSRs after CVA diverges from that of Uncini and colleagues but presumably only reflects the difference in poststroke chronology between the respective samples.

Adult↗
PubMed2000

Preferred levels of auditory danger signals.

An important issue at the design stage of the auditory danger signal for a safety system is the signal audibility under various conditions of background noise. The auditory danger signal should be clearly audible but it should not be too loud to avoid fright, startling effects, and nuisance complaints. Criteria for designing auditory danger signals are the subject of the ISO 7731 (International Organization for Standardization [ISO], 1986) international standard and the EN 457 European standard (European Committee for Standardization [CEN], 1992). It is required that the A-weighted sound pressure level of the auditory danger signal is higher in level than the background noise by 15 dB. In this paper, the results of an experiment are reported, in which listeners adjusted most preferred levels of 3 danger signals (tone, sweep, complex sound) in the presence of a noise background (pink noise and industrial noise). The measurements were done for 60-, 70-, 80-, and 90-dB A-weighted levels of noise. Results show that for 60-dB level of noise the most preferred level of the danger signal is 10 to 20 dB above the noise level. However, for 90-dB level of noise, listeners selected a level of the danger signal that was equal to the noise level. Results imply that the criterion in the existing standards is conservative as it requires the level of the danger signal to be higher than the level of noise regardless of the noise level.

Acoustics↗
PubMed2001

High tumor levels of vascular endothelial growth factor predict poor response to systemic therapy in advanced breast cancer.

Vascular endothelial growth factor (VEGF), a potent angiogenic factor, has been reported to be associated with a poor prognosis in primary breast cancer and in several other cancer types. In the present study, we have measured with ELISA the levels of VEGF in cytosolic extracts of 845 primary breast tumors of patients who developed a recurrence during follow-up. All of the patients received tamoxifen (n = 618) or cyclophosphamide, methotrexate, 5-fluorouracil (CMF) or 5-fluorouracil, Adriamycin, cyclophosphamide (FAC) chemotherapy (n = 227) as first-line systemic therapy after diagnosis of advanced disease. VEGF levels were not related to age or menopausal status but were negatively related to the cytosolic levels of estrogen receptor and progesterone receptor (P < 0.0001). In patients who relapsed within 1 year after primary surgery, tumor VEGF levels were higher than in patients who showed a longer disease-free interval (P = 0.0005). In patients with a first relapse in the viscera, VEGF levels were higher compared with those that relapsed to the bone or soft tissue (P = 0.0004). In univariate analysis for response to first-line tamoxifen therapy, patients with high or intermediate levels showed a poor rate of response, compared with patients with low tumor-VEGF levels (P = 0.0001). Similarly, in multivariate analysis for response to tamoxifen treatment, corrected for age, site of relapse, disease-free interval, and estrogen receptor and progesterone receptor status, VEGF status was an independent predictive factor (P = 0.009). In concordance, higher levels of VEGF were associated with a short progression-free survival and postrelapse overall survival (both, P < 0.0001). On first-line chemotherapy, the rate of response decreased with higher tumor levels of VEGF, both in univariate (P = 0.003) and in multivariate analysis (P = 0.004). Furthermore, higher VEGF levels were associated with a short progression-free survival (P = 0.003) and postrelapse overall survival (P = 0.001). In conclusion, the tumor VEGF level is an important independent marker that predicts a poor efficacy of both tamoxifen and chemotherapy in advanced breast cancer. Knowledge of the tumor level of VEGF might be helpful in selecting individual patients who may benefit from treatments with antiangiogenic agents combined with conventionally used drugs.

Adult↗
PubMed2004

[Visual perception of Kanji characters and complicated figures. Part 3. Visual P300 event-related potentials in patients with attention deficit/hyperactivity disorders].

In order to evaluate visual perception, the P300 event-related potentials (ERPs) for visual oddball tasks were recorded in 11 patients with attention deficit/hyperactivity disorders (AD/HD), 12 with mental retardation (MR) and 14 age-matched healthy controls. With the aim of revealing trial-to-trial variabilities which are neglected by investigating averaged ERPs, single sweep P300s (ss-P300s) were assessed in addition to averaged P300. There were no significant differences of averaged P300 latency and amplitude between controls and AD/HD patients. AD/HD patients showed an increased variability in the amplitude of ss-P300s, while MR patient showed an increased variability in latency. These findings suggest that in AD/HD patients general attention is impaired to a larger extent than selective attention and visual perception.

Attention↗
PubMed1987

Managed care contracting: a systematic approach.

Managed care is sweeping the health care industry and has produced some special challenges for providers. Success in contracting depends on preparation. In this article, the author defines managed care and outlines who should be involved in the contracting for these services. Special attention is given to how to develop the appropriate internal support. The author contends that a provider should not embrace all contracting offers and suggests criteria for selection of the best offers. Finally, the prevailing pricing schemes are reviewed and caveats given on their interpretation and use.

Contract Services↗
PubMed1988

Tympanometry using a sweep-frequency probe tone and its clinical evaluation.

In this new tympanometric system, air pressure in the external meatus is kept constant at either -200 daPa or 0 daPa. The frequency of the probe tone is swept from 220 to 2,000 Hz (or 2,500 Hz, if necessary) in 4 s. During this frequency sweep, sound pressure in decibels and phase angle in degrees in the external meatus are sampled and the differences in sound pressure and phase angle measured at -200 and 0 daPa pressures are computed. These results are figured as a frequency-sound pressure curve and a frequency-phase angle curve. From the study on 8 fresh human cadaver temporal bones, four parameters in these curves are selected by discriminant analysis to provide diagnostic criteria: the minimum value and the 0-cross frequency of the frequency-sound pressure curve and the maximum value and its frequency of the frequency-phase angle curve. Normal parameters were determined in 50 normal ears. Evaluation of 40 patients with ossicular disorders revealed that 10 out of 12 cases of ossicular discontinuity and 5 out of 6 cases of malleus and/or incus fixation were correctly diagnosed. For stapes fixation, the diagnosis was correct in 12 out of 22 ears. This system is useful in the clinical diagnosis of ossicular disorders, producing a collection of curves and parameters that are distinctively different for the ossicular discontinuity and the ossicular fixation.

Acoustic Impedance Tests↗
PubMed2002

[Possible role of soluble erythropoietin receptors in renal anemia].

Recombinant human erythropoietin(rHuEpo) is effective for the treatment of renal anemia associated with chronic renal failure(CRF). However, we have encountered some patients with CRF who have sometimes developed a resistance to rHuEpo. This resistance can be due to iron or folate deficiency, aluminum toxicity, hyperparathyroidism, or auto-antibodies for rHuEpo. In this study, we focused on the soluble erythropoietin receptor(sEpoR), which can bind to rHuEpo. To demonstrate the possibility that the sweeping of rHuEpo by sEpoR results in resistance to rHuEpo, we performed a bioassay using the rHuEpo-dependent cell line, UT7/EPO. The results showed that recombinant mouse sEpoR(rmsEpoR) can reduce the proliferation of UT7/EPO induced by rHuEpo in a dose-dependent manner. We consider that this cell line could be a useful tool in a bioassay to detect the inhibitory factor(s) against Epo. We selected sera from three groups of patients with renal anemia associated with CRF who were receiving hemodialysis three times a week: the first was a patient group that needed a high dose of rHuEpo(7,500-9,000 unit/dialysis), the second was a patient group that needed an intermediate dose of rHuEpo (4,500 unit/dialysis), the third was a patient group that needed a low dose of rHuEpo(below 1,500 unit/dialysis). Interestingly, the proliferation of UT7/EPO determined with [3H]-thymidine incorporation was reduced by the addition of sera from the first group, but not by the addition of sera from the third group. These results suggested that serum sEpoR may play an important role in signal transduction via EpoR on erythroid progenitor in CRF patients.

Adult↗