Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 156 (1999), S. 487-501 
    ISSN: 1420-9136
    Keywords: Key Words: Geomagnetic data, stochastic and chaotic systems, Higuchi method.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —We use advanced methods to extract quantitative time dynamics from geomagnetic signals. In particular we analyse daily geomagnetic time series measured at three stations in Norway. The dynamics of geomagnetic measurements has been investigated using autoregressive models. The procedure is based on two forecasting approaches: the global autoregressive approximation and the local autoregressive approximation. The first technique views the data as a realisation of a linear stochastic process, whereas the second considers them as a realisation of a deterministic process, supposedly non-linear. The comparison of the predictive skill of the two techniques is a strong test to discriminate between low-dimensional chaos and stochastic dynamics. Our findings suggest that the physical system governing the phenomena is characterised by a stochastic dynamics, and the process could be described by numerous degrees of freedom. We also investigated the kind of stochasticity of the geomagnetic signals, analysing the power spectrum density. We identify a power law P(ƒ)∝ƒ-α, with the scaling exponent α which is a typical fingerprint of irregular processes. In this analysis we use the Higuchi method, which presents an interesting relationship between the fractal dimension D and the spectral power law scaling index α.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-0738
    Keywords: Key words Lectins ; Macrophages ; Axonal degeneration ; 2 ; 5-Hexanedione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The lectin binding pattern of both Schwann cells and macrophages has been studied during axonal degeneration induced in the rat sciatic nerve by chronic administration of 2,5-hexanedione (0.8 ml/kg per day i.p. for 20 days). In particular, the present study aimed to establish a possible relationship between macrophage activation and expression of lectin binding sites. To identify and distinguish between Schwann cells and macrophages, electron microscopy was combined with the lectin staining method. On 2,5-hexanedione injury, a drastic disorganization of both axon and myelin sheath occurred and nerve fibers were replaced by a chain of ovoids. Besides the well-established concept that Schwann cells and macrophages cooperate in the removal of the myelin debris during axonal degeneration, evidence is presented that expression of binding sites to lectins is closely related to macrophage activation. macrophages occasionally present in control nerves were labelled only by Con A and sialidase-peanut sequence; in 2,5-hexanedione degeneration monocytes, prephagocytes (macrophages with minute bubbles) and phagocytes (macrophages with large bubbles) were labelled also by peanut, wheat germ and BSA I-B4; moreover, phagocytes were labelled by soybean as well, thus showing a clearly differentiation-dependent binding pattern. Since changes in lectin binding pattern may reflect changes in complex carbohydrate structures, the results show that the expression of certain glycoproteins may be closely related to activation of macrophages in response to toxic injuries.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-0738
    Keywords: Key words Capsaicin ; Capsazepine ; Ruthenium red ; Cytotoxicity ; Vero cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Capsaicin is a natural product of Capsicum peppers, excitatory effects of which have been shown to be mediated by the recently cloned vanilloid receptor 1 (VR1). Since previous studies have shown that capsaicin inhibits protein synthesis, experiments were performed to investigate whether this effect is mediated by VR1 receptor on cultured monkey kidney cells (Vero cells). The capsaicin uptake was assessed in cellular homogenate and in medium by high-performance liquid chromatography (HPLC) separation and quantification on C18 reverse-phase column and fluorescence detection. Toxic effects were assessed by incorporation of [3H]L-leucine into cellular proteins in the presence of capsazepine, the VR1 vanilloid receptor antagonist and Ruthenium red or tyrosine or calcium. Capsazepine (1 to 256 μM) did not modify the uptake rate of capsaicin for incubation times up to 24 h and did not antagonize capsaicin-induced protein synthesis inhibition. It rather inhibited protein synthesis per se from 100 to 256 μM. Ruthenium red which blocks mitochondrial calcium uptake, inhibited protein synthesis and did not antagonise or increase synergistically the effects of capsaicin. Interestingly in a medium deprived of calcium and supplemented by calcium chloride (10–50 μM) the protein synthesis inhibition induced by capsaicin is antagonised somehow. There was no prevention of capsaicin diffusion into the cells. Tyrosine, which seems to be the best preventive agent of capsaicin inhibitory effects, prevents its metabolism but not its diffusion. Capsaicin might enter cells by diffusion and interfere with protein synthesis machinery by competition with tyrosine which in turn prevents the metabolism of capsaicin. The results of the present study suggest that cell responses to capsaicin may be transduced through at least two molecular pathways, one involving VR1, since the receptor antagonist capsazepine fails to prevent the inhibitory effect of capsaicin in Vero cells of renal origin.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 0392-6737
    Keywords: General, theoretical and mathematical biophysics (including logic of biosystems, quantum biology and relevant aspects of thermodynamics, information theory, cybernetics and bionics)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Per studiare lo scambio d'informazioni tra sistemi biologici e l'ambiente esterno, il concetto di quantità di informazioni non è sufficiente a causa della lontananza dall'equilibrio di tali sistemi. Sono infatti necessarie ulteriori specificazioni per quel che riguarda gli effetti della recezione del messaggio, ovvero il valore dell'informazione che è quindi necessario definire di volta in volta. Noi abbiamo quindi definito il valore d'informazione di un gene e di una proteina e abbiamo analizzato un campione di circa 100 geni cercando regolarità significative nella frequenza di uso dei codoni e degli aminoacidi per individuare caratteristiche salienti di una sequenza di codoni che sia tradotta. Si è trovato che in media gli aminoacidi piú usati sono quelli con valore di informazione piú basso e che, per ciascun aminoacido, i codoni piú, usati sono quelli a piú basso valore d'informazione. Inoltre si può dire che la composizione in aminoacidi ed in codoni di una sequenza nucleotidica che sia effettivamente tradotta da un sistema biologico è tale che le mutazioni piú frequenti causano la piú piccola variazione del fenotipo. Tutto ciò mostra che le nostre definizioni di valore d'informazione per un gene e per una proteina descrivono efficacemente la trasmissione e la recezione di informazione in un organismo biologico. Esse possono essere considerate come indice dell'efficienza di un organismo ovvero delle sue capacità di minimizzare gli effetti di una mutazione del genotipo sul fenotipo.
    Abstract: Резюме При исследовании обмена информацией между биологическими системами и внешним миром концепция кояичества информации не явлется достаточной из-за удаленности таких систем от состояния равновесия. Необходимы дополнительные объяснения эффектов получения сообщения, т.е. величины информации, которую необходимо опрелятъ для каждого случая. Мы определяем величину информации для гена и белка и анализируем образец из сотни генов в поисках закономерности в частоте употребления кодонов и аминокислот для индивидуализации характеристик транслируемой последователъности кодонов. Мы получаем, что болышинство исполъзуемых аминокислот имеет, в среднем, малую величину информации, а для каждого типа аминокислот наиболее исполъзуемые кодоны имеют менъшую величину информации. Более того, мы можем сказатъ, что композиция аминокислот или кодонов для последователъности нуклеотидов в биологических системах является такой, что наиболее частые мутации вызывают наименжшее изменение в фенотипе. Все это показывает, что наше определение величины информации для гена и белка хорошо описывает передачу и прием информации в биологических организмах. Такое определение величины информации можно рассматриватъ как индекс эффективности организма, т.е. его способностж минимизировать эффекты мутации генотипа на фенотине.
    Notes: Summary For the treatment of the information exchanged by the biological system and the external world, the concept of information amount is not sufficient because of their remoteness from equilibrium states. Further explanations are, in fact, necessary about the effects of the reception of the message,i.e. its information value that is then necessary to define for each case. We have, therefore, defined the information value of a gene and of a protein and analysed a sample of about hundred genes looking for some significative regularity in the frequency of usage of codons and amino acids allowing us to individualize the salient characteristics of a translated sequence of codons. We have found that the most used amino acids have, on the average, a low information value and, for each amino acid type, the most used codons have a lower information value. Moreover, we can say that the composition in amino acids or in codons of a sequence useful for the biological systems is such that more frequent mutations cause the smaller variation in the phenotype. All that shows that our definitions well describe the system of transmission and reception of the information value in a biological organism and that they can be considered as an index of its efficiency,i.e. of its ability to minimize the effects of the mutation of the genotype on the phenotype.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 3 (1984), S. 421-435 
    ISSN: 0392-6737
    Keywords: General, theoretical and mathematical biophysics (including logic of biophysics, quantum biology and relevant aspects of thermodynamics, information theory, cybernetics and bionics)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto In questo lavoro si propone un nuovo algoritmo per predire la struttura secondaria di una proteina dall’analisi della sua sequenza aminoacidica, con il quale si è ottenuto un significativo miglioramento delle efficienze di previsione della struttura secondaria disponibili fino ad ora. Il metodo descritto tiene conto della frequenza delle coppie adiacenti di aminoacidi nelle regioni ad alpha-helix, beta sheet e random coil, in accordo con il nostro precedente risultato che in tali regioni le sequenze aminoacidiche sono autocorrelate. Le regole usate non derivano dall’analisi delle regioni di proteine con una struttura secondaria nota, ma sono invece basate esclusivamente su considerazioni statistiche. In tal modo il valore ottenuto per l’efficienza del metodo (88%) ha un’alta affidabilità, essendo corretto controllare un metodo solo sui dati non utilizzati per la sua costruzione. Per risolvere le ambiguità esistenti, inoltre, si dà qui una nuova definizione di efficienza per un metodo di previsione di strutture secondarie.
    Abstract: Резюме В этой работе предлагается новый метод для предсказания вторичной структуры белков, исходя из последовательности аминокислот. Получается существенное улучшение эффективности предсказания. Предложенный метод учитывает частоту каждой пары аминокислот в альфа-спиральной области, бета-слоистой области и в области случайных спиралей, в соответствии с предыдущими результатами, согласно которым последовательности аминокислот в этих областях являются автокоррелированными. Правила метода не выводятся из анализа областей белков с известной вторичной структурой, а основываются на статистических рассмотрениях. Полученное значение эффективности (88%) имеет высокую надежность. Корректность метода проверялась не только на данных, использованных для его конструирования. Предлагается новое определение эффективности для разрешения неоднозначностей, связанных с ранее принятыми определениями.
    Notes: Summary In this paper we propose a new method to predict the secondary structure of proteins from sequence data. A satisfactory improvement of the available efficiency of prediction is obtained. The described method takes into account the frequency of each pair of amino acids in alpha-helical, beta-sheet and random coil regions according to previous results that the sequences of amino acidic residues in these regions are autocorrelated. The rules of the method are not derived from the analysis of the regions of proteins with a known secondary structure, but they are instead based on statistical considerations. In such a way the obtained value of efficiency of the method (88%) has a high reliability: in fact, it is correct to test a method only on the data not used to construct it. A new definition of efficiency of a predictive method is given to resolve the ambiguities arising from the previously accepted definitions.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Comparative Biochemistry and Physiology -- Part B: Biochemistry and 71 (1982), S. 281-283 
    ISSN: 0305-0491
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0305-0491
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical Systematics and Ecology 15 (1987), S. 635-637 
    ISSN: 0305-1978
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 67 (1996), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Because σ receptors are richly concentrated in the rat pineal gland, the present study was performed to investigate their possible role in the modulation of melatonin production. To this purpose, we assessed in vivo the effects of the σ-receptor ligands 1,3-di(2-tolyl)guanidine and (+)-N-allylnormetazocine on the rat pineal gland activity during either the daytime or the nighttime. Compared with vehicle, 1,3-di(2-tolyl)guanidine and (+)-N-allylnormetazocine potentiated the enhancement of N-acetyltransferase activity and pineal melatonin content induced by isoproterenol administration during the daytime, whereas they did not affect the diurnal basal biosynthetic activity of the gland. Conversely, at night, 1,3-di(2-tolyl)guanidine and (+)-N-allylnormetazocine enhanced significantly the physiological increases in both pineal N-acetyltransferase activity and melatonin levels. This enhancement was prevented by pretreatment with rimcazole, a specific σ-receptor antagonist. These findings suggest that, in rats, the activation of pineal σ-receptor sites does not affect the biosynthetic activity of the pineal gland during daytime, whereas it pontentiates the production of melatonin when the gland is noradrenergically stimulated either by isoproterenol administration or by the endogenously released norepinephrine at nighttime.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Archives of Gerontology and Geriatrics 5 (1986), S. 343-349 
    ISSN: 0167-4943
    Keywords: Corollospora maritima ; age pigments ; free radicals ; fungi ; heavy metals ; lipofuscin
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...