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PubMed1993

Relationship between circulating vitamin D3 metabolites and prolactin or growth hormone levels in rat.

Previous studies (Haug & Gautvik 1985) have demonstrated specific receptors for 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in a clonal (GH3) strain of rat pituitary tumour cells. It was discovered that 1,25(OH)2D3 affected the production of prolactin and growth hormone in these cells in a calcium dependent manner. These findings were the basis for a hypothesis that vitamin D3 could be involved in the regulation of pituitary hormones in vivo. To further investigate this contention, female rats were given subcutaneous injections of 1,25(OH)2D3, 25-hydroxyvitamin D3 (25(OH)D3) or 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) three times a week for up to 12 weeks. Blood samples were withdrawn after 28, 56 and 84 days of treatment and analysed for vitamin D3 metabolites, prolactin and growth hormone, and serum ionized (free) and total calcium (Ca). Between treatment group comparisons of serum prolactin and growth hormone levels did not show significant vitamin D3 induced alterations. However, correlation matrix analyses on all variables revealed that serum level of growth hormone was significantly (P < 0.05) and inversely related to corresponding total Ca. Prolactin, on the other hand, may be subject to a complex regulation by 1,25(OH)2D3 and free Ca2+.

24,25-Dihydroxyvitamin D 3↗

PubMed2005

Fitting the factor analysis model in lI norm.

The well-known problem of fitting the exploratory factor analysis model is reconsidered where the usual least squares goodness-of-fit function is replaced by a more resistant discrepancy measure, based on a smooth approximation of the lI norm. Fitting the factor analysis model to the sample correlation matrix is a complex matrix optimization problem which requires the structure preservation of the unknown parameters (e.g. positive definiteness). The projected gradient approach is a natural way of solving such data matching problems as especially designed to follow the geometry of the model parameters. Two reparameterizations of the factor analysis model are considered. The approach leads to globally convergent procedures for simultaneous estimation of the factor analysis matrix parameters. Numerical examples illustrate the algorithms and factor analysis solutions.

Algorithms↗

PubMed1998

Dichotic pitches as illusions of binaural unmasking. I. Huggins' pitch and the "binaural edge pitch".

The two most salient dichotic pitches, the Huggins pitch (HP) and the binaural edge pitch (BEP), are produced by applying interaural phase transitions of 360 and 180 degrees, respectively, to a broadband noise. This paper examines accounts of these pitches, concentrating on a "central activity pattern" (CAP) model and a "modified equalization-cancellation" (mE-C) model. The CAP model proposes that a dichotic pitch is heard at frequency f when an individual across-frequency scan in an interaural cross-correlation matrix contains a sharp peak at f. The mE-C model proposes that a dichotic pitch is heard when a plot of interaural decorrelation against frequency contains a peak at f. The predictions of the models diverge for the BEP at very narrow transition bandwidths: the mE-C model predicts that salience is sustained, while the CAP model predicts that salience declines and that the dominant percept is of the in-phase segment of the noise. Experiment 1 showed that the salience of the BEP was sustained at the narrowest bandwidths that could be generated (0.5% of the transition frequency). Experiment 2 confirmed that the pitch of a BEP produced by a 0.5% transition bandwidth was close to the frequency of the transition band. Experiment 3 showed that pairs of simultaneous narrow 180-degree transitions, whose frequencies corresponded to vowel formants, were perceived as the intended vowels. Moreover, the same vowels were perceived whether the in-phase portion of the noise lay between the two transition frequencies or on either side of them. In contrast, different patterns of identification responses were made to diotic band-pass and band-stop noises whose cutoff frequencies corresponded to the same formants. Thus, the vowel-identification responses made to the dichotic stimuli were not based on hearing the in-phase portions of the noise as formants. These results are not predicted by the CAP model but are consistent with the mE-C model. It is argued that the mE-C model provides a more coherent and parsimonious account of many aspects of the HP and the BEP than do alternative models.

Dichotic Listening Tests↗

PubMed1998

Dichotic pitches as illusions of binaural unmasking. II. The Fourcin pitch and the dichotic repetition pitch.

The predictions of three models are compared with respect to existing experimental data on the perception of the Fourcin pitch (FP) and the dichotic repetition pitch (DRP). Each model generates a central spectrum (CS), which is examined for peaks at frequencies consistent with the perceived pitches. A modified equalization-cancellation (mE-C) model of binaural unmasking [Culling and Summerfield, J. Acoust. Soc. Am. 98, 785-797 (1995)] generates a CS which reflects the degree of interaural decorrelation present in each frequency channel. This model accounts for the perceived frequencies of FPs, but produces no output for DRP stimuli. A restricted equalization-cancellation (rE-C) model [Bilsen and Goldstein, J. Acoust. Soc. Am. 55, 292-296 (1974)] sums the time-varying excitation in corresponding frequency channels, without equalization, to form a CS. A central activity pattern (CAP) model [Raatgever and Bilsen, J. Acoust. Soc. Am. 80, 429-441 (1986)] generates a CS by scanning an interaural cross-correlation matrix across frequency. The rE-C and CAP models yield inaccurate predictions of the perceived frequencies of FPs, but predict the occurrence of the DRP and its correct pitch. The complementary predictions of the mE-C model compared to the rE-C and CAP models, together with the evidence that the FP is clearly audible for the majority of listeners, while the DRP is faintly heard by a minority of listeners, suggest that the mE-C model provides the best available account of the FP, and that the DRP is produced by a separate mechanism.

Dichotic Listening Tests↗

PubMed2002

Differential actions of antiparkinson agents at multiple classes of monoaminergic receptor. I. A multivariate analysis of the binding profiles of 14 drugs at 21 native and cloned human receptor subtypes.

Because little comparative information is available concerning receptor profiles of antiparkinson drugs, affinities of 14 agents were determined at diverse receptors implicated in the etiology and/or treatment of Parkinson's disease: human (h)D(1), hD(2S), hD(2L), hD(3), hD(4), and hD(5) receptors; human 5-hydroxytryptamine (5-HT)(1A), h5-HT(1B), h5-HT(1D), h5-HT(2A), h5-HT(2B), and h5-HT(2C) receptors; halpha(1A)-, halpha(1B)-, halpha(1D)-, halpha(2A)-, halpha(2B)-, halpha(2C)-, rat alpha(2D)-, hbeta(1)-, and hbeta(2)-adrenoceptors (ARs); and native histamine(1) receptors. A correlation matrix (294 pK(i) values) demonstrated substantial "covariance". Correspondingly, principal components analysis revealed that axis 1, which accounted for 76% variance, was associated with the majority of receptor types: drugs displaying overall high versus modest affinities migrated at opposite extremities. Axis 2 (7% of variance) differentiated drugs with high affinity for hD(4) and H(1) receptors versus halpha(1)-AR subtypes. Five percent of variance was attributable to axis 3, which distinguished drugs with marked affinity for hbeta(1)- and hbeta(2)-ARs versus hD(5) and 5-HT(2A) receptors. Hierarchical (cluster) analysis of global homology generated a dendrogram differentiating two major groups possessing low versus high affinity, respectively, for multiple serotonergic and hD(5) receptors. Within the first group, quinpirole, quinerolane, ropinirole, and pramipexole interacted principally with hD(2), hD(3), and hD(4) receptors, whereas piribedil and talipexole recognized dopaminergic receptors and halpha(2)-ARs. Within the second group, lisuride and terguride manifested high affinities for all sites, with roxindole/bromocriptine, cabergoline/pergolide, and 6,7-dihydroxy-N,N-dimethyl-2-ammotetralin (TL99)/apomorphine comprising three additional subclusters of closely related ligands. In conclusion, an innovative multivariate analysis revealed marked heterogeneity in binding profiles of antiparkinson agents. Actions at sites other than hD(2) receptors likely participate in their (contrasting) functional profiles.

Animals↗

PubMed1993

Thermal Inactivation of Aeromonas hydrophila As Affected by Sodium Chloride and Ascorbic Acid.

The combined effects of sodium chloride (0, 1.0, 1.5, and 3.0%) and ascorbic acid (0, 1.0, and 2.0 mmol/liter) with mild heat (46 degrees C) on the survival of Aeromonas hydrophila were evaluated. Because of the nonlinear nature of the survivor curves obtained, several equations yielding an R (coefficient of multiple determination) of congruent with 1 were tested. The equation that most closely fit the curvature of the observed data set was a hyperbolic function. Equation coefficients were combined to obtain a so-called death value. This value (46.67% explained variance) was calculated by extracting the larger eigenvalue and the relative eigenvector from the correlation matrix of the coefficients. the effects of the experimental factors on the death value were described by a quadratic response surface model. Results revealed that the death value was not influenced by the presence of ascorbic acid. However, increased mortality resulted from the interaction between sodium chloride and ascorbic acid.

Journal Article↗

PubMed1998

Extent of antigenic diversity in the V3 region of the surface glycoprotein, gp120, of human immunodeficiency virus type 1 group M and consequences for serotyping.

Human immunodeficiency virus type 1 (HIV-1) may be studied by molecular or immunological approaches. Most analyses have been performed by genetic comparison of isolates and have led to the definition of clades or subtypes within the major (M) group of HIV-1. Five subtypes (A to E) were initially identified by comparison of genomic sequences. Four new subtypes (F to I) were identified more recently. Amino acid differences in the immunogenic V3 loop between isolates have also been studied, leading to a phenetic classification of at least 14 clusters (1 to 14) of sequences (B. T. M. Korber, K. McInnes, R. F. Smith, and G. Myers, J. Virol. 68:6730-6744, 1994). In this study, we compared the antigenicity of the V3 consensus sequences defined by phylogenetic analysis to the antigenicity of those defined by phenetic analysis. We used a recently developed subtype-specific enzyme immunoassay (SSEIA) that uses the principle of blocking with an excess of peptide in the liquid phase. Two SSEIAs were performed, the first with five V3 sequences defined by phylogenetic analysis and the second with 14 V3 sequences defined by phenetic analysis. A total of 168 HIV-1 sera taken from seropositive individuals from seven different countries or regions were studied. Experimental and statistical data, including correlation matrix and cluster analyses, demonstrated associations between the genetic subtypes and phenetically associated groups. Most of these were predicted by Korber et al. (J. Virol. 68:6730-6744, 1994) by theoretical analysis. We also found that V3 sequences can be grouped into between three and five antigenically unrelated categories. Residues that may be responsible for major antigenic differences were identified at the apex of the V3 loop, within the octapeptide xIGPGxxx, where x represents the critical positions. Our study provides evidence that there is a limited number of V3 serotypes which could be easily monitored by serological assays to study the diversity and dynamics of HIV-1 strains.

Amino Acid Sequence↗

PubMed2001

Genetic clustering of hepatitis C virus strains and severity of recurrent hepatitis after liver transplantation.

The influence of viral factors on the severity of hepatitis C virus (HCV)-related liver disease is controversial. We studied 68 liver transplant patients with recurrent hepatitis C, of whom 53 were infected by genotype 1 strains. Relationships between core sequences, serum HCV RNA levels, and fibrosis scores for each patient were analyzed in pairwise fashion 5 years after transplantation. We used Mantel's test, a matrix correlation method, to evaluate the correspondence between measured genetic distances and observed phenotypic differences. No clear relationship was found when all 68 patients were analyzed. In contrast, when the 53 patients infected by genotype 1 strains were analyzed, a strong positive relationship was found between genetic distance and differences in 5-year fibrosis scores (P = 0.001) and differences in virus load (P = 0.009). In other words, the smaller the genetic distance between two patients' viral core sequences, the smaller the difference between the two patients' fibrosis scores and viral replication levels. No relationship was found between genetic distance and differences in age, sex, or immunosuppression. In multivariate analysis, the degree of fibrosis was negatively related to the virus load (r = -0.68; P = 0.003). In the particular setting of liver transplantation, and among strains with closely related phylogenetic backgrounds (genotype 1), this study points to a correlation between the HCV genetic sequence and the variability of disease expression.

Genotype↗

PubMed2002

Thermal undulations of quasi-spherical vesicles stabilized by gravity.

The classical treatment of quasi-spherical vesicle undulations has, in the present work, been reviewed and extended to systems, which are affected by a gravitational field caused by a density difference across the membrane. The effects have been studied by the use of perturbation theory leading to corrections to the mean shape and the fluctuation correlation matrix. These corrections have been included in an analytical expression for the flicker spectrum to probe how the experimentally accessible spectrum changes with gravity. The results are represented in terms of the gravitational parameter, g(0) = Delta(rho)g R(4)/kappa. The contributions from gravity are in most experimental situations small and thus negligible, but for values of g(0) above a certain limit, the perturbational corrections must be included. Expressions for the relative error on the flicker spectrum have been worked out, so that it is possible to define the regime where gravity is negligible. An upper limit of g(0) has also been identified, where the error in all modes of the flicker spectrum is significant due to distortion of the mean shape.

Journal Article↗

PubMed1996

Equilibrium and attractivity analysis for a class of hetero-associative neural memories.

Based on the natural structure of Kosko's Bidirectional Associative Memories (BAM), a high-performance, high-capacity associative neural model is proposed which is capable of simultaneous hetero-associative recall. The proposed model, Modified Bidirectional Decoding Strategy (MBDS), improves the recall rate by adding some association fascicles to Kosko's BAM. The association fascicles are sparse coding neuron structures that provide activating strengths between two neuron fields (say, field X and field Y). The sufficient conditions for a state to become an equilibrium state of the MBDS network is derived. Based on these results, we discuss the basins of attraction of the training pairs in one iteration. The upper bound of the number of error bits which can be tolerated by MBDS is also derived. Because the attractivity of a stored training pair can be increased markedly with the aid of its corresponding association fascicles, we recommend a high capacity realization of MBDS, Bidirectional Holographic Memory (BHM), so that each training pair is stored uniquely and directly in the connection weights rather than encoded in a correlation matrix. Finally, computer simulations demonstrate the attractiveness of three different realizations of MBDS to verify our results.

Association↗

PubMed2003

Morphological correlates of intrinsic electrical excitability in neurons of the deep cerebellar nuclei.

To what degree does neuronal morphology determine or correlate with intrinsic electrical properties within a particular class of neuron? This question has been examined using microelectrode recordings and subsequent neurobiotin filling and reconstruction of neurons in the deep cerebellar nuclei (DCN) of brain slices from young rats (P13-16). The neurons reconstructed from these recordings were mostly large and multipolar (17/21 cells) and were likely to represent glutamatergic projection neurons. Within this class, there was considerable variation in intrinsic electrical properties and cellular morphology. Remarkably, in a correlation matrix of 18 electrophysiological and 6 morphological measures, only one morphological characteristic was predictive of intrinsic excitability: neurons with more spines had a significantly slower basal firing rate. To address the possibility that neurons with fewer spines represented a slowly maturing subgroup, recordings and reconstructions were also made from neurons at a younger age (P6-9). While P6-9 neurons were morphologically indistinguishable from P13 to 16 neurons, they were considerably less excitable: P6-9 neurons had a lower spontaneous spiking rate, larger fast AHPs, higher resting membrane potentials, and smaller rebound depolarizations. Thus while the large projection neurons of the DCN are morphologically mature by P6-9, they continue to mature electrophysiologically through P13-16 in a way that renders them more responsive to the burst-and-pause pattern that characterizes Purkinje cell inhibitory synaptic drive.

Action Potentials↗

PubMed2001

Application of neural networks to the classification of pancreatic intraductal proliferative lesions.

The aim of the study was to test applycability of neural networks to classification of pancreatic intraductal proliferative lesions basing on nuclear features, especially chromatin texture. Material for the study was obtained from patients operated on for pancreatic cancer, chronic pancreatitis and other tumours requiring pancreatic resection. Intraductal lesions were classified as low and high grade as previously described. The image analysis system consisted of a microscope, CCD camera combined with a PC and AnalySIS v. 2.11 software. The following texture characteristics were measured: variance of grey levels, features extracted from the grey levels correlation matrix and mean values, variance and standard deviation of the energy obtained from Laws matrices. Furthermore we used moments derived invariants and basic geometric data such as surface area, the minimum and maximum diameter and shape factor. The sets of data were randomly divided into training and testing groups. The training of the network using the back-propagation algorithm, and the final classification of data was carried out with a neural network simulator SNNS v. 4.1. We studied the efficacy of networks containing from one to three hidden layers. Using the best network, containing three hidden layers, the rate of correct classification of nuclei was 73%, and the rate of misdiagnosis was 3%; in 24% the network response was ambiguous. The present findings may serve as a starting point in search for methods facilitating early diagnosis of ductal pancreatic carcinoma.

Adenocarcinoma↗

PubMedDate not supplied

Psychometric normalization of a hyperacusis questionnaire.

Clinical hyperacusis consists of a marked intolerance to ordinary environmental sounds, while hearing thresholds are quite often normal. Hyperacusis appears to be a subjective phenomenon, which is not easily defined or quantified by objective measurements. In order to create a tool suitable to quantify and evaluate various hyperacusis symptoms, a questionnaire screening several aspects of auditory symptomatology has been constructed. Two hundred and one subjects (who were either hyperacusic or not), randomly selected from the general population, were tested. A principal component analysis performed on the correlation matrix of the 14 items of the questionnaire isolated three dimensions: attentional, social, and emotional. The three dimensions had satisfactory internal consistency reliability. The mean +/- SD total score was 15 +/- 6.7 out of 42 (maximum of hyperacusis) and a score greater than 28 seems to represent a strong auditory hypersensitivity. This new psychometric tool should further be tested on hyperacusic patients to verify its relevance in pathology and define the involvement of the three dimensions statistically obtained on the hyperacusis symptomatology.

Adolescent↗

PubMed1996

Vitamin A levels and growth hormone axis.

Vitamin A (VA) is required for normal growth and development retinoic acid may be the active metabolite through binding to nuclear receptors. Recently a correlation between nocturnal growth hormone (GH) secretion and VA was was found in short slowly growing children. We determined the 24-hour integrated concentration of GH (IC-GH), GH response to provocative stimuli, IGF-I, IGF-binding protein-3 (IGF-BP3) and GH-binding protein (GH-BP) in 34 prepubertal children (25 m/9 f) 5-10 years of age, height -2.5 to 1.5 SDS and body mass index -1.5 to 1.5 SDS for age and sex. Since folic acid, vitamin B12, IGF-I, cholesterol, triglycerides and VA carrier proteins were normal we assumed that no major nutritional deficiency existed. The correlation matrix of the variates tested were p < 0.05 for VA and IC-GH and p < 0.006 for IGF-BP3. It is suggested that VA might have a direct affect on both ICGH and IGF-BP3.

Carrier Proteins↗

PubMed2005

What can a neuron learn with spike-timing-dependent plasticity?

Spiking neurons are very flexible computational modules, which can implement with different values of their adjustable synaptic parameters an enormous variety of different transformations F from input spike trains to output spike trains. We examine in this letter the question to what extent a spiking neuron with biologically realistic models for dynamic synapses can be taught via spike-timing-dependent plasticity (STDP) to implement a given transformation F. We consider a supervised learning paradigm where during training, the output of the neuron is clamped to the target signal (teacher forcing). The well-known perceptron convergence theorem asserts the convergence of a simple supervised learning algorithm for drastically simplified neuron models (McCulloch-Pitts neurons). We show that in contrast to the perceptron convergence theorem, no theoretical guarantee can be given for the convergence of STDP with teacher forcing that holds for arbitrary input spike patterns. On the other hand, we prove that average case versions of the perceptron convergence theorem hold for STDP in the case of uncorrelated and correlated Poisson input spike trains and simple models for spiking neurons. For a wide class of cross-correlation functions of the input spike trains, the resulting necessary and sufficient condition can be formulated in terms of linear separability, analogously as the well-known condition of learnability by perceptrons. However, the linear separability criterion has to be applied here to the columns of the correlation matrix of the Poisson input. We demonstrate through extensive computer simulations that the theoretically predicted convergence of STDP with teacher forcing also holds for more realistic models for neurons, dynamic synapses, and more general input distributions. In addition, we show through computer simulations that these positive learning results hold not only for the common interpretation of STDP, where STDP changes the weights of synapses, but also for a more realistic interpretation suggested by experimental data where STDP modulates the initial release probability of dynamic synapses.

Action Potentials↗

PubMed1999

Cytokine levels correlate with a radiologic score in active pulmonary tuberculosis.

Pulmonary tuberculosis is an infectious disease caused by Mycobacterium tuberculosis. This microorganism is capable of inducing a delayed hypersensitivity reaction in the lung, with subsequent expression of the disease. This reaction depends on the presence of different cytokines that exert specific functions. The aim of this study was to evaluate the presence and the concentrations of nine different modulators in bronchoalveolar lavage fluid (BALF). For this purpose, 15 patients with active pulmonary tuberculosis were enrolled at the time of diagnosis, prior to institution of antituberculous therapy. All the patients demonstrated M. tuberculosis in the sputum, and their disease extention was defined by high-resolution computed tomography (HRCT) using a score which included the presence of six findings: miliary nodules, nodules < 10 mm, consolidation, ground glass, cavity and bronchial wall thickening. This score was more sensitive than an equivalent score calculated on the basis of chest radiology. HRCT score was calculated for each area of the two lungs in order to define the more and the less affected lung for each patient. The bronchoalveolar lavage (BAL) was performed in the more affected area for each lung. The HRCT total score for each washed area ranged between 1 and 15, and showed more significant differences between the more and less affected lungs (p = 0.0004) than those obtained with the individual radiologic findings (p ranged between 0.60 and 0. 004). The BAL concentrations of the nine cytokines evaluated for the more and less affected lungs were compared: interleukin-6 (IL-6), IL-8, IL-12, tumor necrosis factor-alpha (TNF-alpha), and interferon gamma (IFN-gamma) showed significant differences (p ranged between 0. 016 and 0.0007). In addition, each cytokine concentration was correlated with the HRCT score. Significant correlations were found with IL-12, IL-6, IL-8, IL-2, and TNF-alpha. The correlations between cytokines and HRCT total score were better than those observed with the individual radiologic findings. A correlation matrix for the different cytokines evaluated one against each other, has also been added to show common behavior of these modulators. A similar analysis was also performed for the radiologic abnormalities.

Adolescent↗

PubMed2005

Microscopy and quantitative morphology of aluminum silicate nanoparticles grown on organic templates.

Biomimetic synthesis of ceramic materials is increasing in popularity because it offers many advantages. In this work, aluminum silicate nanoparticles were obtained on a self-assembled organic multilayer at near room temperature (30 < or = T < or = 50 degrees C) and at atmospheric pressure. Morphological and microanalytical characterization was carried out by means of transmission electron microscopy and subsequent image analysis. The roles of some process parameters such as template type, reactant concentration, [Al]:[Si] molar ratio, number of initiation steps (IS) of mineralization, and reaction time (rt) were assessed by comparing images, diffraction patterns, and EDX spectra. Generally, the Si-rich phase exhibited higher crystallinity, whereas the Al-rich phase was mostly amorphous. Crystal structure resulted with rt > or = 4 days for template-grown materials. Images of materials obtained at T = 50 degrees C, rt = 3 days, and 1 < or = IS < or = 4 were further analyzed by "spectrum enhancement," an algorithm based on the Fourier transform. Morphological indicators were extracted from suitably processed power spectral densities, a correlation matrix was formed, and multivariate statistics was carried out. Visual differences in nanoaggregate morphology were quantitatively translated. Materials were ranked by the spatial uniformity of nanoparticle distribution: the most uniform aggregates were those grown on templates by IS > or = 2. Univariate statistics validated the conclusion: the particles of those same materials had a narrower size distribution and sharper edges. This last property has been ascribed to crystalline structure, independently demonstrated by diffraction patterns.

Aluminum↗

PubMed2006

Validation of the Sexual Assault Symptom Scale II (SASS II) using a panel research design.

To examine the utility of a self-report scale of sexual assault trauma, 223 female victims were interviewed with the 43-item Sexual Assault Symptom Scale II (SASS II) at 1, 3, 7, 11, and 15 months postassault. Factor analyses using principal-components extraction with an oblimin rotation yielded 7 common factors with 31 items. The internal consistency was high for 4 factors and moderate for 2 factors. The multitrait-multimethod matrix, correlating the factor subscale scores of self-reported trauma and clinical assessment ratings, demonstrated both convergent and discriminant validity, indicating that the SASS II has construct validity. Correlations between the SASS II subscales and the intrusion subscale of the Impact of Events Scale also indicated the convergent and discriminant validity of the SASS II. Significant positive correlations between current and prior trauma levels further evidence the validity of the SASS.

Adolescent↗