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  • superconducting magnets  (46)
  • bioavailability  (28)
  • Springer  (74)
  • American Physical Society
  • 1980-1984  (74)
  • 1950-1954
  • 1925-1929
  • 1983  (74)
  • 1926
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  • Springer  (74)
  • American Physical Society
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  • 1980-1984  (74)
  • 1950-1954
  • 1925-1929
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  • 1
    Electronic Resource
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    Springer
    European journal of nutrition 22 (1983), S. 185-194 
    ISSN: 1436-6215
    Keywords: sugar substitutes ; D-glucose ; bioavailability ; D-glucitol (D-sorbitol) ; D-mannitol ; Palatinit® ; D-glucosyl-α(1→1)-D-mannitol ; D-glucosyl-α(1→6)-D-glucitol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Zur Vertiefung des Verständnisses vom Stoffwechsel des Zuckeraustauschstoffes Palatinit® wurden seine zwei Bestandteile D-Glucosyl-α(1→1)-D-mannit und D-Glucosyl-α(1→6)-D-glucit [D-Glucosyl-α(1→6)-D-sorbit] nach dem Verfahren von Karimzadegan et al. auf ihre Glucose-Bioverfügbarkeit an ketotischen Ratten untersucht. Bei Umwandlungsraten in Glucose von 6 bzw. 20 % für Mannit und Glucit (Sorbit) sowie von 39 bzw. 42% für Glucosylmannit und Glucosylglucit erhält demnach der metabolische Glucose-Pool nicht das volle Glucose-Äquivalent aus diesen Verbindungen. Von dem Anteil an präformierter Glucose in den Glucosylhexiten — theoretisches Maximum 50 % — sind nur 36 % aus Glucosylmannit bzw. 32 % aus Glucosylglucit bioverfügbar. Die im Vergleich zur Theorie verminderte Bioverfügbarkeit von Glucose aus Palatinit® wird auf partiellen mikrobiellen Abbau in unteren Darmabschnitten zurückgeführt. Die an Ratten erhaltenen Ergebnisse werden auch für alle anderen Spezies gelten, welche in Caecum und/oder Colon Kohlenhydrate vergären. Die Unterschiede zwischen D-Glucosyl-α(1→1)-D-mannit und D-Glucosyl-α(1→6)-D-glucit werden durch unterschiedliche Verzögerung der Glucoseresorption im Dünndarm, wo auch D-Glucit angreift, bedingt. Die Ermittlung der Glucose-Bioverfügbarkeit gewährt weitgehende Einblicke in das Schicksal von Kohlenhydraten einschließlich der Symbiose zwischen Säugetier und Mikroorganismen im Dickdarm. Da ein ziemlich vollständiger Überblick über die metabolischen Konsequenzen nach ihrer Zufuhr erhalten wird, sollte das Verfahren zur Messung der Bioverfügbarkeit von Glucose daher bei Abschätzungen der Lebensmittelsicherheit anderer Zuckeraustauschstoffe ebenfalls angewandt werden.
    Notes: Summary For the sake of metabolic insight into the fate of the sugar substitute Palatinit®, its two components D-glucosyl-α(1→1)-D-mannitol and D-glucosyl-α(1→6)-D-glucitol [D-glucosyl-α-(1→6)-D-sorbitol] were assayed for glucose bioavailability by the procedure of Karimzadegan et al. using ketotic rats. With conversion rates into glucose of 6 and 20 %, respectively, for free mannitol and glucitol (sorbitol), 39 % for glucosylmannitol and 42 % for glucosylglucitol, the metabolic glucose pool of the rat does not receive the full carbohydrate complement of these compounds. The preformed glucose moiety of the glucosylhexitols is bioavailable by 36 and 32 %, respectively, from glucosylmannitol and glucosylglucitol, with 50 % as theoretical maximum. Less than theoretical bioavailability of glucose from Palatinit® is ascribed to microbial attack in the hindgut. The data on rats are held valid also for other species demonstrating carbohydrate fermentation in the caecum and/or colon. Differences between D-glucosyl-α(1→1)-D-mannitol and D-glucosyl-α(1→6)-D-glucitol are caused by a differential delay of glucose absorption in the small intestine, also exerted by D-glucitol. The deep metabolic insight offered by the glucose bioavailability assay into the fate of carbohydrates includes the mammal-microbial symbiosis in the large bowel. Since a rather complete survey of the metabolic consequences after their intake can be obtained, the assay system should be generally applied in assessments of food safety also of other sugar substitutes.
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  • 2
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 123-141 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si riesamina la strumentalizzazione adatta all’acquisizione di segnali biomagnetici. Si studiano separatamente i componenti di base del magnetometro, cioè gli SQUID, i trasformatori di flusso e i dewar. Si discutono i possibili miglioramenti alla strumentazione attuale e alle apparecchiature complete comprendenti scudi ferromagnetici o di correnti a vortice e si valuta la loro efficenza.
    Notes: Summary The instrumentation suitable for the acquisition of biomagnetic signals is reviewed. The basic magnetometer components,i.e. SQUIDs, flux transformers and dewars, are studied separately. Possible improvements to the present instrumentation as well as complete set-ups including ferromagnetic or eddy current shields are discussed and their efficiency evaluated.
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  • 3
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 142-152 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si sviluppa un formalismo per la descrizione vettoriale e tensoriale di una procedura di bilanciamento e si sottolinea un metodo di bilanciamento di campo e di primo gradiente. Si discutono l’apparecchiatura sperimentale e le misurazioni del vettore di modo comune del primo gradienteC G 1.
    Notes: Summary A formalism for the vector and tensor description of a balancing procedure is developed and a first-gradient and field-balancing method is outlined. The experimental apparatus and measurements of the first-gradient common-mode vector,C G 1, are discussed.
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  • 4
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 175-183 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto In questo lavoro si tratta il problema dell’ottimizzazione di sistemi di sensori gradiometrici metrici superconduttori di secondo ordine che sono stati progettati per la misurazione di campi magnetici deboli disomogenei in un ambiente disturbato magneticamente. Si considerano le condizioni di massimo rapporto segnale-rumore dell’uscita del quantomagnetometro superconduttote (SQM). Si analizza l’influenza dei parametri misurati della sorgente del segnale, del rumore di una sorgente di disturbo esterna e di quello proprio del magnetometro sulla selezione della lunghezza di base del gradiometro.
    Notes: Summary In this paper we deal with an optimization problem of the second-order superconducting gradiometric sensor systems that have been designed for measurement of the weak inhomogeneous magnetic fields in a magnetically disturbed environment. The conditions of maximum signalto-noise ratio of the output of superconducting quantum magnetometers (SQM) are considered. The influence of measured signal source parameters, of an outside disturbing source and of the own noise of the magnetometer on the gradiometer base length selection is analysed.
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  • 5
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 356-367 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Sono state esaminate l’idealità e la sensibilità di parecchi conduttori magnetocardiografici vettoriali usando un modello inomogeneo fisico del tronco. Si è trovato che la componente antero-posterioreX vettore magnetico del cuore è la piú facile da scoprire. Si suggeriscono conduttori ideali per le altre due componenti. Comunque questi hanno una sensibilità inferiore. Le differenze rispetto ai risultati di precedenti ricercatori sono state spiegate con le differenze tra i modelli.
    Notes: Summary The ideality and sensitivity of several vector magnetocardiographic leads were tested by using an inhomogeneous, physical torso model. The postero-anterior component of the heart’s magnetic vector was found easiest to detect. New, more ideal leads for the other two components are suggested. However, these have lower sensitivity. The differences from the results of former investigators can be explained by the differences of the models.
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  • 6
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 203-213 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si è studiato lo spettro del rumore di un gradiometro superconduttore a derivata secon da in un agglomerato urbano. I dati sono stati ottenuti dal gradiometro con tre accelerometri ortogonali e un magnetometro a flussometro elettronico triassiale attaccato al dewar. Questi dati sono stati analizzati usando tecniche di elaborazione dei segnali, soprattutto un cancellatore adattativo di rumori, per ridurre i rumori nei dati del gradiometro. I risultati mostrano qui che il rumore dell’esterno e/o il rumore del movimento del dewar possono essere ridotti di 40 dB in potenza di rumore. Si è anche mostrato che, nel caso di basso rapporto segnale-rumore (S/N∼1), può essere estratta un’onda sunusoidale di 10 Hz. Questa tecnica non solo promette riduzione dei rumori, ma ha anche lo scopo d’identificare i segnali di rumore che potrebbero essere veramente considerati parte del responso evocato. L’analisi dei dati che contengono i responsi evocati è ora in corso.
    Notes: Summary The noise spectrum of a superconducting second-derivative gradiometer has been investigated in an urban environment. Data have been acquired from the gradiometer with three orthogonal accelerometers and a triaxial fluxgate magnetometer attached to the dewar. These data have been analyzed by using signal processing techniques, primarily an adaptive noise canceller, to reduce noise in the gradiometer data. Results shown here indicate that the environmental noise and/or the dewar motion noise can be reduced as much as 40 dB in noise power. It is also shown, in the case of poor signal-to-noise ratio (S/N∼1), that a 10 Hz sine wave can be extracted. This technique not only shows promise for noise reduction, but also aids in the identification of noise signals which might be misconstrued as part of the evoked response. Analysis of data containing evoked response is now underway.
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  • 7
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 153-165 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si stabiliscono princípi per il progetto di sistemi di spire che generano campi magnetici distanti che diminuiscono secondo una potenza inversa alta della distanza. Secondo un principio di reciprocità queste disposizioni, quando usate come sensori in magnetometri ad induzione e SQUID, hanno una sensibilità intrinsecamento bassa per sorgenti distanti del campo magnetico.
    Notes: Summary Principles are established for the design of coil arrays which generate distant magnetic fields diminishing as a high inverse power of the distance. By a principle of reciprocity these arrays, when used as sensors in induction and SQUID magnetometers, have an inherently low sensitivity to distant sources of magnetic field.
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  • 8
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 166-174 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si è costruito un magnetometro SQUID differenziale a 3 canali per la misurazione simultanea delle 3 componenti ortogonali del campo magnetico nella stessa posizione. Si descrive la struttura dell’apparecchio e si mostrano i dati MCG misurati. Si discutono gli effetti d’interferenza tra i canali.
    Notes: Summary We have constructed a three-channel differential SQUID magnetometer for the simultaneous measurement of the three orthogonal components of the magnetic field in the same location. The structure of the device is described and MCG data measured are shown. Interference effects between the channels are discussed.
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  • 9
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 184-194 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si è costruito espressamente un sistema SQUID in un ospedale di Parigi, che permette indagini neuromagnetiche attinenti con applicazioni cliniche. Un gradiometro simmetrico di second’ordine lavora entro uno schermo per corrente parassite. Ciò è designato ad ottimizzare il costo e l’efficienza del sistema. Le sue prestazioni sono state sperimentate con dati da pazienti e da soggetti normali.
    Notes: Summary A SQUID system was specially built in a Parisian hospital, allowing neuromagnetic investigations dealing with clinical applications. A second-order symmetrical gradiometer works inside an eddy current shield. This was designed for optimizing the cost and the efficiency of the system. Its performances were tested with data from patients and normal subjects.
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  • 10
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 224-230 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si descrive la strumentazione per le applicazioni biomagnetiche. Le piccole dimensioni e la leggerezza del gradiometro SQUID permettono il facile trasporto e posizionamento dello strumento, rendendo cosí possibile le misurazioni biomagnetiche in una qualsiasi locazione in cui non ci siano rumori. L’apparecchio è provvisto di un alimentatore a batteria e, se riempito con 60 cm3 di elio liquido, funzionerà initerrottamente per 6 ore. L’apparecchio è adatto per la magnetocardiografia.
    Notes: Summary The instrumentation for biomagnetic applications is described. The small size and weight of the SQUID gradiometer permit easy transport and positioning of the instrument, thus making biomagnetic measurements possible in any noise-free location. The equipment is provided with a battery power supply, and, when filled with 60 cm3 of liquid helium, will operate continuously for 6 h. The device is suitable for magnetocardiography.
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  • 11
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 301-310 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si confrontano i magnetocardiogrammi misurati in un caso di infarto miocardico anterolaterale con i corrispondenti magnetocardiogrammi simulati. I cambiamenti piú notevoli nell’MCG misurato si sono osservati nelle parti superiori e inferiori del torace come previsto dalla simulazione.
    Notes: Summary The MCGs measured in a case of an anterolateral myocardial infarction were compared with the corresponding simulated MCGs. The most distinctive changes in the measured MCGs were observed in the upper and lower parts of the thorax as predicted by the simulation.
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  • 12
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 558-566 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto La conduttività elettrica delle lesioni cerebrali varia con situazioni patologiche come l’edema e la calcificazione. È stato studiato mediante una simulazione con il computer l’effetto delle disomogeneità dei tessuti delle lesioni cerebrali sulle distribuzioni spaziali dei potenziali elettrici e dei campi magnetici sulla superficie del capo.
    Notes: Summary The electrical conductivity of brain lesions varies with pathological situations such as edema and calcification. The effect of the tissue inhomogeneities of brain lesions on spatial distributions of electrical potentials and magnetic fields over the surface of the head was studied by means of a computer simulation.
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  • 13
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si è sviluppato un metodo magnetico per misurazioni dirette non invasive del ferro di immagazzinamento epatico umano con uno suscettometro SQUID. Le determinazioni magneticain vivo e chimicain vitro del ferro epatico non eme sono strettamente correlate. Le misurazioni magnetiche dei depositi di ferro sono utili, dal punto di vista clinico, nella diagnosi dei disordini nel metabolismo del ferro.
    Notes: Summary A magnetic method for direct noninvasive measurements of human hepatic storage iron with a SQUID susceptometer has been developed.In vivo magnetic andin vitro chemical determinations of liver nonheme iron are closely correlated. Magnetic measurements of iron stores are clinically useful in the diagnosis of disorders of iron metabolism.
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  • 14
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 594-607 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Il problema inverso nella misurazione magnetical del polmone è stato studiato con un metodo che usa le ipotetiche distribuzioni del pulviscolo magnetico. Si sono fatte le minimizzazioni non vincolate e vincolate di una funzione obiettiva. Le simulazioni e l’analisi hanno mostrato l’efficacia del metodo.
    Notes: Summary The inverse problem in the magnetic measurement of the lung was studied with a method using hypothetical distributions of magnetic dust. Both unconstrained and constrained minimizations of an objective function were performed. Simulations and analysis showed the efficacy of the method.
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  • 15
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 582-593 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Questo lavoro descrive un nuovo suscettometro SQUID a doppio canale coadiuvato da computer destinato a raggiungere stime accuratein vivo delle concentrazioni di accumulo di ferro nei tessuti. Si discutono le considerazioni pratiche dello schema, la funzionalità sperimentale al rumore e la risoluzione clinica anticipata del nuovo sistema.
    Notes: Summary This paper describes a new computer-enhanced dual-channel SQUID susceptometer designed to achieve accuratein vivo estimates of tissue storage iron concentrations. We discuss the practical design considerations, instrumental noise performance and anticipated clinical resolution of the new system.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 608-616 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si è trovato che la velocità di decadimento del campo residuo ottenuto tramite magnetizzazione delle particelle ferromagnetiche trattenute nei polmoni dei saldatori è associato a fattori come la quantità di polvere trattenuta, il curriculum lavorativo e la consuetudine di fumare. Una velocità di decadimento piú rapida appare correlata con un piú rapido smaltimento delle particelle di fumo di saldatura nei fumatori.
    Notes: Summary It was found that the rate of decay of the remanent field obtained through magnetization of ferrimagnetic particles retained in the lungs of are welders is associated with factors such as amount of dust retained, occupational history and smoking habits. A faster decay rate was found to correlate with a faster clearance of welding fume particles in smokers
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 617-623 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Particelle ferromagnetiche immesse per via intratracheale nei polmoni sono fagocitate da macrofagi alveolari. Dopo che queste particelle sono state magnetizzate dal campo esterno, esse producono un campo residuo che decade rapidamente a causa del disallineamento delle particelle dovuto al movimento citoplasmatico (rilassamento). I cambiamenti nel valore di rilassamento nel tempo successivo all’immissione potrebbero essere connessi alla mobilità citoplasmatica.
    Notes: Summary Ferrimagnetic particles instilled intratracheally into the lungs are phagocytized by alveolar macrophages. After these particles are magnetized by an external field, they produce a remanent field which decays rapidly due to particle misalignment from cytoplasmic motion (relaxation). Changes in relaxation rate with time following instillation might be related to cytoplasmic motility.
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  • 18
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 624-641 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto La pletismografia a suscettività magnetica (MSPG) è un nuovo metodo proposto per controllare i cambiamenti del volume cardiaco. Si riesaminano il principio di misurazione e i lavori recenti di altri ricercatori. Si studia l’effetto del movimento legato al cuore della cassa toracica anteriore sul segnale MSPG.I risultati suggeriscono che il movimento del confine cassa toracica-aria può contribuire in modo significativo (∼75%) al segnale MSPG quando è registrato vicino al cuore.
    Notes: Summary Magnetic-susceptibility plethysmography (MSPG) is a new method proposed for monitoring cardiac-volume changes. The measurement principle and recent work by other investigators are reviewed. The effect of the cardiac-related motion of the anterior chest wall on the MSPG signal is studied. The results suggest that the motion of the chest-wall-air boundary may contribute significantly (∼75%) to the MSPG signal when recorded near the heart.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 642-649 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto È stata esaminata la forma d’onda d’impulso per il magnetomiogramma (MMG) dell’arto inferiore destro umano. Le durate tipiche degl’impulsi sono di circa (10÷20) ms. La variazione spaziale del MMG suggerisce un’origine nei muscoli anteriori della tibia.
    Notes: Summary The pulse wave form for the magnetomyogram (MMG) of the human right leg was examined. The typical pulse durations are about (10÷20) ms. The spatial variation of the MMG suggests a source in the anterior muscles.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 650-659 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Le ricerche sul campo magnetico intorno alla gamba umana con l’uso di un magnetometro SQUID producono risultati consistenti e riproducibili che possono essere rappresentati mediamente due linee di corrente, orientate inversamente, parallele all’asse della gamba. I campi sono condizionati dall’attività muscolare, che decade col tempo di rilassamento della gamba.
    Notes: Summary Investigations of the magnetic field around the human leg using a SQUID magnetometer yield consistent, reproducible results which can be modelled by 2 oppositely oriented line currents parallel to the leg axis. The fields are affected by muscle activity, decaying with the time of relaxation of the leg.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 195-202 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si mostra che miglioramenti sostanziali possono essere ottenuti nelle proprietà di schermatura di una stanza schermata da corrente parassite coprendo l’accesso con lamine conduttrici. I risultati suggeriscono che non è necessario installare una porta conduttrice e mostrano che è il caso di coprire una piccola parte della porta in modo permanente.
    Notes: Summary We show that substantial improvements can be obtained in the shielding properties of an eddy-current-shielded room by covering the doorway with conductive plates. Results suggest that it is unnecessary to install a conductive door and show that it is worthwhile covering a small part of the doorway permanently.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 248-254 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Il magnetocardiogramma ad alta risoluzione è stato registrato mediante magnetometri superconduttori in 12 volontari sani utilizzando la camera schermata di Berlino per ridurre il livello di rumore elettromagnetico. La morfologia del trattoPR magnetico è caratterizzata dalle «rampe» in precedenza osservate, sulle quali s’inseriscono segnali. A volte la forma d’onda appare complessa.
    Notes: Summary ThePR interval of magnetocardiograms has been measured with a SQUID sensor in the Berlin magnetically shielded room. In addition to previously reported ramps with isolated superimposed signals in several cases a structured morphology has been found.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 266-279 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Sono stati osservati segnali degradanti nel segmentoPR dei magnetocardiogrammi normali registrati da 5 cani. Sono state osservate rampe maggiori dopo aver indotto con farmaci il blocco del nodo atrioventricolare di primo grado, ed è stata osservata una completa ripolarizzazione atriale a seguito d’isolate contrazioni atriali in due animali con blocco di secondo grado. Queste rampe, che variano fino a 6.7 pT in ampiezza e provengono dagli atri, possono complicare l’individuazione magnetica dell’attività di His-Purkinje.
    Notes: Summary Sloping signals were observed in thePR segment of normal magnetocardiograms recorded from five dogs. Larger ramps were observed after first-degree AV nodal blockade was induced pharmacologically, and complete atrial repolarization was observed following isolated atrial contractions in two animals with second-degree block. These ramps, ranging up to 6.7 pT in size and arising from the atria, may complicate magnetic detection of His-Purkinje activity.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 231-247 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; PACS. 85.25 ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto La motivazione fondamentale per lo studio dei fenomeni elettrofisiologici cardiaci tramite il metodo biomagnetico è dovuta al fatto che questa tecnica offre un’alta risoluzione spaziale e sembra fornire informazioni complementari rispetto alle sole registrazioni elettriche. Fino ad oggi l’interesse degli studiosi si è concentrato su due differenti fenomeni cardiaci: 1) lo studio dell’attività del sistema di conduzione atrioventricolare e 2) lo studio della depolarizzazione ventricolare anormalmente ritardata (late potentials). L’interesse clinico per lo studio non invasivo del sistema di His-Purkinje (HPS) è ben noto. Registrazioni cliniche non invasive di late potentials sono particolarmente desiderabili in quanto possono essere preziosi indicatori di rischio di morte improvvisa. In questo lavoro si presenta una rassegna sullo stato delle ricerche in entrambi i campi d’indagine.
    Notes: Summary The fundamental motivation for investigating cardiac electrophysiological phenomena by means of the biomagnetic method has been that this technique should have added spatial resolution and provided complementary information as opposed to electric recordings only. So far the interest of experimentalists has been concentrated on two different kinds of cardiac phenomena: 1) the study of the activity of the cardiac conduction system and 2) of abnormally delayed ventricular depolarization (late potentials). The clinical interest for the noninvasive investigation of the His-Purkinje system (HPS) is well known. Noninvasive clinical recording of late potentials is particularly desirable as they seem to be precious markers for risk of sudden death. A review of the state of research in both fields is presented in this paper.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 280-290 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Ein dal 1980 è iniziato uno studio sistematico dell’attività del sistema di His-Purkjnje (HPS) su soggetti normali e patologici con il metodo biomagnetico. Allo scopo di risolvere il problema di quanta parte dei segnali misurati sia attribuibile al sistema di His-Purkinje e quanta piuttosto alla ripolarizzazione atriale, è stata recentemente sviluppata una strumentazione appositamente disegnata per misure sul HPS e con una sensibilità di $$20fT/\sqrt {Hz}$$ nella banda di frequenze interessanti ((0.5÷300) Hz). Al contempo si è altresí sviluppato un nuovo modello teorico in stretta corrispondenza con le caratteristiche anatomiche del HPS che fornisce una distribuzione di campo magnetico sul torace in buon accordo qualitativo con i risultati sperimentali.
    Notes: Summary Since 1980, systematic investigations of the activity of the His-Purkinje system (HPS) by the biomagnetic method have been reported on both normal subjects and patients affected by different kinds of conduction disturbances. A first attempt to interpret the experimental results by means of a theoretical model satisfactorily accounted for the measured «ramp» patterns. Moreover, a good temporal coincidence was observed between magnetic signals and invasively recorded His bundle electrograms (HBE). An alternative explanation of the «ramp» pattern, in terms of atrial repolarization, has been recently proposed on the basis of animal experimental investigation. In order to try to solve this problem, we have carried out a twofold approach: a new second-order gradiometer, specifically designed for HPS activity investigation has been successfully set up and tested; it provides a sensitivity of $$20fT/\sqrt {Hz}$$ in the band width of interest ((0.5÷300) Hz). Second, a new model based on a closer correspondence to anatomical features of the HPS has been developed. This model provides well-defined patterns which are in quite good agreement with experimental results.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 311-323 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si registra la distribuzione sia del potenziale elettrico cardiaco sulla superficie del corpo che del campo magnetico cardiaco vicino al torace e alla schiena in momenti fissi del ciclo cardiaco. Le caratteristiche generali di entrambi i tipi di mappa sono semplici e riproducibili, inoltre ciascuno di essi fornisce informazioni differenti.
    Notes: Summary The distribution of both the cardiac electric potential on the body surface and the cardiac magnetic field near the chest and back is recorded at fixed time instants of the heart cycle. The general features of both types of maps are simple and reproducible, moreover they both reveal different information.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 324-339 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Sono stati eseguiti calcoli numerici sul campo magnetico generato dal cuore durante la depolarizzazione ventricolare. Lo scopo di questo lavoro è studiare il contributo d’inomogeneità nel conduttore di volume al campo totale e stabilire l’influenza dei gradiometri usati nelle registrazioni sperimentali.
    Notes: Summary Numerical computations were performed on the magnetic field generated by the heart during ventricular depolarization. The purpose of this study was to investigate the contribution of inhomogeneities in the volume conductor to the total field and to establish the influence of gradiometers as used in experimental recordings.
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    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
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    Description / Table of Contents: Riassunto Il magnetocardiogramma ad alta risoluzione, registrato in 22 pazienti affetti da pregresso infarto del miocardio, ha permesso di rilevare in 3 casi la presenza di segnali di ampiezza tra 0.4 e 3 pT temporalmente correlati a depolarizzazioni tardive elettriche. Si discutono de differenze tra segnali magnetici ed elettrici e il loro possibile significato fisiopatologico.
    Notes: Summary High-resolution magnetocardiograms of patients with recent myocardial infarction have been recorded. In three cases, signals have been found in theST segment that are time correlated with simultaneously recorded late electric potentials.
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    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
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    Description / Table of Contents: Riassunto Per studiare l’effetto della geometria del conduttore di volume, sono stati compiuti esperimenti usando cuori di coniglio isolati. È stato osservato un aumento del segnale magnetico con l’aumentare della dimensione del conduttore di volume. Si discutono i risultati usando un dipolo di corrente a origine fissa e un modello di sorgente di tensione per il cuore.
    Notes: Summary To study the effect of the volume conductor geometry on the MCG, experiments using isolated rabbit hearts were done. An increase of the magnetic signal when increasing the volume conductor’s size was observed. The results are discussed by using a fixed-origin current dipole and a voltage source model for the heart.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 368-378 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
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    Topics: Physics
    Description / Table of Contents: Riassunto Si presentano le prime misurazioni del campo magnetico associato col potenziale d’azione in un fascio di fibre cardiache di Purkinje isolate. Le nostre scoperte dimonstrano la fattibilità dell’uso di tecniche magnetiche per misurare le correnti assiali in un gruppo di cellule cardiache ad attività spontanea.
    Notes: Summary We present the first measurements of the magnetic field associated with the action potential in a bundle of isolated cardiac Purkinje fibers. Our findings demonstrate the feasibility of using magnetic techniques to measure the axial current in a bundle of spontaneously active cardiac cells.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 379-409 
    ISSN: 0392-6737
    Keywords: Biomagnetic (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si riesaminano le ricerche sul campo magnetico indotto compiute negli ultimi due anni. Questi studi hanno mostrato che la tecnica magnetica si puó usare 1) per rivelare aspetti complementari delle fonti di corrente comuni al potenziale indotto, 2) per identificare l’organizzazione della corteccia cerebrale e delle arce subcorticali e 3) per misurare le proprietà funzionali delle aree neurali attive le cui posizioni sono identificate.
    Notes: Summary Research in the evoked magnetic field reported in the last two years is reviewed. The studies have shown that the magnetic technique may be used 1) to reveal complementary aspects of the current sources common to evoked potential, 2) to identify the organization of the cerebral cortex and subcortical areas of the brain and 3) to measure functional properties of the active neural areas whose locations are identified.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 410-419 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Il campo magnetico corticale osservato, suscitato da uno stimolo presentato a varie eccentricità nel campo visivo, è stato interpretato come derivante da dipoli di corrente lungo la scissura longitudinale. La profondità della sorgente aumenta con l’aumento dell’eccentricità, in accordo con la classica mappatura retinotopica.
    Notes: Summary The observed cortical magnetic field evoked by a stimulus presented at various eccentricities in the visual field was interpreted as arising from current dipoles along the longitudinal fissure. The depth of the source increased as the eccentricity was increased, in agreement with the classical retinotopic map.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 420-428 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si esamiano i componenti elettrici e magnetici della risposta stimolata visiva del cervello, con picchi a 120 e 180 ms dopo lo stimolo. I risultati mostrano che entrambi i componenti magnetici sono localizzati nella corteccia occipitale superficiale tangenziale al cuoio capelluto. La distribuzione diM120 suggerisce che i generatori dei componenti elettrici e magnetici sono correlati, ma il campo magnetico elettrico registrato è una modificazione elaborata di quello prodotto dalla sorgente.
    Notes: Summary Corresponding electrical and magnetic components of the brain’s visual evoked response peaking at 120 and 180 ms poststimulus are examined. Results show that both magnetic components are localized in the superficial occipital cortex tangential to the scalp. The distribution ofM120 suggests that the generators for the electrical and magnetic components are related, but the electrical field recorded is an elaborate modification of that produced by the source.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 429-437 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Campi magnetici indotti dalla sensibilità somatica sono stati confrontati con i corrispondenti potenziali elettrici sul cuoio capelluto allo scopo di studiare le loro sorgenti neurali. Le mappature delle risposte magnetiche hanno mostrato attività a livello delle cortecce di sensibilità somatica primarie e secondarie. Ulteriori sorgenti oltre a queste aree sembrano essere coinvolte nella generazione dei potenziali del cuoio capelluto a vertice somatosensoriali.
    Notes: Summary Somatosensory evoked magnetic fields were compared with corresponding electric scalp potentials in order to study their neural sources. Mappings of the magnetic responses showed activity at the primary and secondary somatosensory cortices. Additional sources besides these areas seem to be involved in the generation of the somatosensory vertex scalp potentials.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 438-459 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto In questo lavoro si presentano alcuni tentativi di considerazioni modello, basati sul concetto di dipolo di corrente equivalente per tener conto delle risposte sonore stimolate osservate, con lo scopo di tentare un confronto delle variazioni in ampiezza e latenza con calcoli basati sul modello di nervo altamente semplificato di Rall. Si presenta un’analisi fenomenologica dei dati sperimentali sul campo magnetico sonoro tardo evocato dalla corteccia uditiva umana. Qui si pone l’accento sulle relazioni tra le proprietà del segnale (per esempio, ampiezza e latenza) e tra le proprietà del segnale e le proprietà dello stimolo (per esempio, ampiezza/latenza e frequenza in discesa relativa Δf/f per uno stimolo con frequenza in discesa) piuttosto che su problemi correlati con la posizione del dipolo di corrente equivalente, per esempio l’organizzazione tonotopica discussa da Elberlinget al. e Romaniet al. Si presentano alcuni risultati di un calcolo numerico basato su un modello a cavo lineare e li si confronta con i risultati sperimentali.
    Notes: Summary In this paper we present some tentative model considerations, based on the concept of an equivalent current dipole to account for observed auditory evoked responses, with the aim of attempting a comparison of variations in amplitude and latency with calculations based on Rall’s greatly simplified nerve model. A phenomenological analysis of experimental data on the late, auditory evoked magnetic field from the human auditory cortex is presented. The emphasis is here placed on relations between signal properties (e.g. amplitude and latency) and between signal properties and stimulus properties (e.g. amplitude/latency and relative frequency glide Δf/f for a frequency glide stimulus) rather than on questions related to the location of the equivalent current dipole,e.g. the tonotopic organization discussed by Elberlinget al. and by Romaniet al.. Some results of a numerical calculation based on a linear-cable model are presented and compared with experimental results.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 471-483 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Le sorgenti di risposte uditive magnetiche ed electtriche stimolate sono state formate con dipoli a corrente multipli. L’attività a livello delle cortecce uditive, 2.6 cm al di sotto della calotta cranica, spiega la distribuzione di campo osservata $$\overline {N100m}$$ . Un’ulteriore sorgente di corrente vicino al vertice è necessaria per spiegare le corrispondenti distribuzioni di potenziale. La posizione delle sorgenti di corrente di $$\overline {N100m}$$ non ha mostrato alcuna dipendenza sistematica dalla frequenza tonale.
    Notes: Summary The sources of auditory evoked electric and magnetic responses were modelled with multiple current dipoles. The activity at the auditory cortices, 2.6 cm beneath the skull, explains the observed $$\overline {N100m}$$ field distribution. An additional current source near the vertex is needed to explain the corresponding potential distributions. The locations of the current sources of $$\overline {N100m}$$ did not show any systematic dependence on the tonal frequency.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 460-470 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Sono stati registrati campi magnetici uditivi indotti (AEF) e potenziali uditivi indotti EEG (AEP) dalle regioni corticali uditive destra e sinistra di 12 soggetti normali adulti. Il sensore magnetico era un gradiometro SQUID a forma di otto con una linea di base di 4 cm orientato in modo da essere massimamente sensibile a un dipolo di corrente orientato perpendicolarmente alla fissure di Sylvio. Gli stimoli erano impulsi sonori di 1 kHz, lunghi 100 ms con un intervallo modale tra stimoli di 700 ms emessi a livelli di pressione sonora di 40, 60, 80 e 100 dB. Si è trovato che l’ampiezza AEF è correlata all’intensità dello stimolo in modo quadratico, l’ampiezza AEP in modo, lineare. Gli AEF erano di ampiezza maggiore in risposta alla stimolazione contralaterale che in risposta alla stimolazione ipsilaterale. Gli AEP non presentano questa relazione. In un secondo esperimento gli AEF e AEP dell’emisfero destro in risposta al tono di stimolazione nell’orecchio controlaterale in questi 12 soggetti sono stati combinati con dati simili precedenti su 24 soggetti, ottenendo cosí un totale di 36 soggetti, per esaminare la comparabilità della forma dell’onadaP50 di AEP e dell’analogaP50 di AEF. Si è trovato che la latenza dellaP50 decrese in funzione dell’intensità crescente dello stimolo sia per AEF che per AEP, e che la latenza diP50 è decisamente inferiore nelle registrazioni magnetiche rispetto alle registrazioni del potenziale.
    Notes: Summary Auditory evoked magnetic fields (AEFs) and EEG auditory evoked potentials (AEPs) were recorded from left and right auditory cortical regions of 12 normal adult subjects. The magnetic sensor was a figure-eight SQUID gradiometer with a 4 cm baseline oriented so as to be maximally sensitive to a current dipole oriented normal to the Sylvian fissure. Stimuli were 100 ms long 1 kHz tone pips with a modal interstimulus interval of 700 ms delivered at sound pressure levels of 40, 60, 80 and 100 dB. AEF amplitude was found to be related to stimulus intensity in a quadratic fashion, AEP amplitude in a linear fashion. AEFs were of larger amplitude in response to contralateral as compared to ipsilateral stimulation. AEPs did not exhibit such a relationship. In a second experiment right-hemisphere AEFs and AEPs in response to contralateral ear tone stimulation in these 12 subjects were combined with similar previous data from 24 subjects, providing a total of 36 subjects, to examine the comparability of the AEPP50 wave form and the AEFP50 analog. The latency of theP50 was found to decrease as a function of increasing stimulus intensity for both AEFs and AEPs, and theP50 latency was consistently shorter in magnetic compared to potential recordings.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 484-494 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
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    Topics: Physics
    Description / Table of Contents: Riassunto I movimenti volontari degli arti sono preceduti da spostamenti MEG che cominciano già 1.2s prima del movimento. Questi spostamenti invertono la polarità sull’area di rappresentazione della corteccia motoria dell’arto in questione.
    Notes: Summary Voluntary limb movements are preceded by MEG shifts beginning even as early as 1.2 s before the movement. These shifts reverse polarity above the cortical motor representation area of the limb concerned.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 495-504 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Sono stati registrati i campi magnetici del cervello che precedono i movimenti autonomi delle dita della mano, del piede e della dita del piede stesso, i movimenti delle dita della mano e del piede causati da uno stimolo e la parola. Sono stati trovati lenti spostamenti dei campi magnetici con morfologia simile ai coincidenti potenziali elettrici, ma con distribuzioni molto diverse. Si discutono le deduzioni ottenute dai dati sulla localizzazione dei generatori cerebrali.
    Notes: Summary Magnetic fields of the brain were recorded preceding selfinitiated finger, foot, toe movements, stimulus-triggered finger and toe movements, and speech. Slow magnetic-field shifts were found with morphology similar to coincident electrical potentials, but with very different distributions. Inferences from the data about localization of cerebral generators were discussed.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 505-511 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
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    Topics: Physics
    Description / Table of Contents: Riassunto Si è studiato il campo magnetico prodotto dal cervello prendendo in considerazione una varietà di eventi rari. Si riporta il carattere temporale della risposta a un raro stimolo uditivo. Il campo magnetico appare offrire un’utile nuova sonda dell’attività endogena nel cervello umano.
    Notes: Summary We have studied the magnetic field produced by the brain when attending to a variety of rare events. The temporal character of the response to a rare auditory stimulus is reported. The magnetic field appears to offer a useful new probe of endogeneous activity in the human brain.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 538-546 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; PACS. 85.25 ; Superconducting devices ; superconducting magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Uno studio sull’attività spontanea del cervello in soggetti normali è stato eseguito con il metodo neuromagnetico. Sono stati usate 2 diverse strumentazioni per le misure magnetiche. Ambedue usavano gradiometri di second’ordine disegnati specificatamente per gli studi sul cervello: 2.9 cm di diametro, 5 cm di baseline. Uno SQUID r.f. e uno SQUID d.c. erano accoppiati ai gradiometri. I livelli di rumore misurati sono stati rispettivamente di $$40fT/\sqrt {Hz}$$ e $$25fT/\sqrt {Hz}$$ . In alcuni soggetti sono state effettuate mappe di campi magnetici generati dall’attività spontanea del cervello. Le mappe dell’ampiezza media dei segnali del ritmo α hanno mostrato 2 massimi dell’attività su 2 regioni simmetriche dello scalpo. Comunque, malgrado una generale simmetria fra gli emisferi, la complessità delle mappe misurate suggerisce una corrispondente complessità dei generatori responsabili dell’attività α.
    Notes: Summary An investigation of the spontaneous brain activity from normal subjects has been carried out by means of the neuromagnetic method. Two different systems were used for magnetic measurements. Both used 2nd-order gradiometers specifically designed for brain studies: 2.9 cm diameter, 5 cm baseline. A r.f. SQUID and a d.c. SQUID were coupled to the gradiometers. The measured noise levels are $$40fT/\sqrt {Hz}$$ and $$25fT/\sqrt {Hz}$$ , respectively. Thorough magnetic mapping of the spontaneous activity was performed on a few subjects. By mapping the average amplitude of the α-rhythm signals two maxima of activity over two symmetric regions of the scalp were clearly observed. Despite a general symmetry between hemispheres, however, the complexity of the measured maps suggests a corresponding complexity of the generators responsible for α-activity.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 214-223 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; PACS. 85.25 ; Superconducting devices ; superconducting magnets
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    Topics: Physics
    Description / Table of Contents: Riassunto Si discutono magnetometri del tipo del flussometro elettronico e di risonanza (precisione libera, pompata otticamente) che possono in qualche caso sostituire il magnetometro SQUID. Si descrivono i princípi di funzionamento, la sensibilità, l’intervallo dinamico e la risposta di frequenza. Si dà un accenno riguardo l’applicazione di questi magnetometri nelle misurazioni biomagnetiche.
    Notes: Summary Flux gate and resonance type of magnetometers (free precession, optically pumped), which can in some cases replace the SQUID magnetometer, are discussed. The principles of operation, sensitivity, dynamical range and frequency response are described. The application of these magnetometers for biomagnetic measurements is mentioned.
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 255-265 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
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    Topics: Physics
    Description / Table of Contents: Riassunto È stata sfruttata la risoluzione spaziale del sensore magnetico per fornire stime numeriche del contributo atriale ai campi magnetici registrati esattamente prima della depolarizzazione ventricolare. Si trova che il contributo è piccolo, e questo rafforza l’interpretazione originale secondo la quale questi campi derivano principalmente dal sistema di conduzione del cuore.
    Notes: Summary We have exploited the spatial resolution of the magnetic sensor to provide numerical estimates of the atrial contribution to magnetic fields recorded just prior to ventricular depolarization. The contribution is found to be small, strenghening our original interpretation that such fields originate mostly in the conduction system of the heart.
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  • 44
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 291-300 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
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    Topics: Physics
    Description / Table of Contents: Riassunto Si presentano i risultati preliminari ottenuti costruendo mediante computer mappe di distribuzione di campo magnetico sulla base di registrazioni ad alta risoluzione effettuate con magnetometro superconduttore. La procedura è stata applicata per esaminare i MCG di 16 pazienti affetti da pregresso infarto del miocardio. Sulla base di questa elaborazione è stato possibile dividere i pazienti in due classi, una delle quali contiene tutti i pazienti con depolarizzazioni tardive.
    Notes: Summary A possible clinical application of a high-resolution magnetic isofield contour mapping technique in cardiography is discussed. Preliminary results are presented in applying this technique to patients with recent myocardial infarction. The patients could be divided into two classes; one of them contains patients with electrical late potentials as a subclass.
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  • 45
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 512-516 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
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    Topics: Physics
    Description / Table of Contents: Riassunto Si presentano le prime misurazioni del campo magnetico prodotto da correnti di azione che si propagano lungo l’assone singolo di un nervo gigante. Questi dati sono stati ottenuti con un trasduttore a bobina toroidale e un amplificatore o semiconduttore a temperatura ambiente.
    Notes: Summary We present the first measurements of the magnetic field produced by action currents propagating along a single giant nerve axon. These data were obtained with a toroidal pick-up coil and a room temperature semiconductor amplifier.
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  • 46
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 517-537 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
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    Topics: Physics
    Description / Table of Contents: Riassunto Finora la magnetoencefalografia spontanea (MEG) in soggetti normali e patologici non è stata investigata a fondo. Si conoscono pochissimi contributi in questo campo. A parte il lavoro del gruppo di biomagnetismo di Roma, il solo contributo clinico finora è stato quello di Hughes e collaboratori che era abbastanza limitato nel numero e nella scelta dei soggetti studiati. La nostra esperienza condotta fin dal 1980 su un gran numero di casi (principalmente epilessie focali) mostra che il MEG può evidenziare attività significative anche se non sono presenti anormalità EEG; esso ha inoltre una risoluzione spaziale maggiore rispetto all’EEG. I foci epilettici mostrano un’area limitata di attività massima. Finora non è stata osservata nessuna evidenza sperimentale di una differente distribuzione delle ampiezze del campo sullo scalpo. La risoluzione spaziale del MEG riguarda anche la possibilità di risolvere la morfologia dei segnali EEG (per esempio onde aguzze EEG risolte in gruppi di spikes dal MEG) o di separare topograficamente le anormalità EEG mescolate e non ben localizzate (per esempio, attività delta ed epilettiche mescolate nell’EEG e discriminate nel MEG). I migliori risultati si osservano quando la localizzazione è nella corteccia esterna. Dopo una descrizione del materiale studiato, si sottolinea l’importanza dei risultati ottenuti per la prima volta in casi di epilessie focali.
    Notes: Summary So far spontaneous magnetoencephalography (MEG) in normal and pathological subjects has not been deeply investigated. Very few contributions in this field are available. Aside from the work of the Rome biomagnetic group in this field, the only clinical contribution up to now has been that of Hughes and co-workers which was rather limited in the number and in the selection of subjects investigated. Our experience, carried out since 1980 on a large number of cases—mainly focal epilepsies— shows that the MEG may evidence significant activities even if EEG abnormalities are not present and has a higher spatial resolution with respect to the EEG. Epileptic foci show a limited area of maximal activity. So far no experimental evidence of a different distribution of field amplitude over the scalp has been observed. The spatial resolution of the MEG also regards the possibility of resolving the morphology of EEG signals (for instance, EEG sharp waves resolved into groups of spikes by MEG) or topographically separate EEG abnormalities mixed up and not well localized (for instance, delta and epileptic activities mixed up in the EEG, but differently in the MEG). The best results are observed when the localization is in the outer cortex. After a description of the material studied, the importance of the results obtained for the first time in cases of focal epilepsies is outlined.
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  • 47
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    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 547-557 
    ISSN: 0392-6737
    Keywords: Biomagnetism (including magnetocardiography) ; Superconducting devices ; superconducting magnets
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    Topics: Physics
    Description / Table of Contents: Riassunto Durante l’ultimo anno gli autori hanno condotto una ricerca sistematica su un gran numero di soggetti patologici registrando simultaneamente l’EEG e il MEG. La presente versione del nostro apparato sperimentale permette di effettuare misure MEG con un solo sensore magnetico, impedendo la rilevazione simultanea di attività MEG su punti differenti della testa. Ciò ha condotto gli autori a concentrarsi sulle epilessie focali. Fin dalle prime misure il sensore magnetico ha dimostrato un notevole potere localizzante, rafforzando l’interesse per la localizzazione in casi patologici. In questo lavoro si riportano risultati che sembrano confermare la straordìnaria capacità delle misure MEG nel localizzare sorgenti di attività cerebrali patologiche in casi di epilessie focali.
    Notes: Summary During the last year the authors have been carrying out a systematic investigation on a large number of pathological subjects simultaneously recording the EEG and the MEG. The present version of our experimental apparatus allows MEG measurements with only one magnetic detector, thus preventing the detection of simultaneous MEG activities over different points of the head. This has led the authors to concentrate upon focal epilepsies. Since the first measurements a remarkable localizing power was shown by the magnetic detector, thus strengthening the interest in pathological localization. In this contribution we report results which seem to confirm the extraordinary capability of MEG measurements to localize sources of pathological brain activities in cases of focal epilepsies.
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  • 48
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    European journal of clinical pharmacology 24 (1983), S. 127-136 
    ISSN: 1432-1041
    Keywords: statistical analysis ; nonparametric statistical methods ; bioavailability ; confidence interval ; ANOVA
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary For a two-way cross-over design, which appears to be the most common experimental design in bioavailability studies, 95%-confidence limits for expected bioavailability can be obtained by classical analysis of variance (ANOVA). If symmetry of the confidence interval is desired about zero (differences) or unity (ratios) rather than about the corresponding point estimator, Westlake's modification can be used. Two nonparametric methods and their adaptations to bioavailability ratios are reviewed, one based on Wilcoxon's signed rank test (Tukey), and the other on Pitman's permutation test. The necessary assumptions and the merits of these procedures are discussed. The methods are illustrated by an example of a comparative bioavailability study. A FORTRAN program facilitating the procedures is available from the authors upon request.
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  • 49
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    European journal of clinical pharmacology 24 (1983), S. 791-796 
    ISSN: 1432-1041
    Keywords: furosemide ; bioavailability ; diuretic effect ; urine sodium ; urine potassium ; power of ANOVA ; tablet formulations ; urinary flow rate ; normal volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The relative bioavailability and diuretic effect of 2 commercially available tablet preparations of furosemide 40 mg was examined in 10 healthy male volunteers. A close linear relationship between the urinary excretion rate of furosemide and the rate of sodium ion excretion in urine and/or flow rate of urine was demonstrated. There were no significant differences in the urinary excretion of furosemide, sodium and potassium ions or urinary volume following the oral doses. The difference in drug content affected the urinary recovery of furosemide over 24 h but had no effect on the pharmacological response. The analytical power of ANOVA using the various parameters of the responses to furosemide was no lower than when the parameters of urinary excretion of furosemide were used.
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  • 50
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    European journal of clinical pharmacology 25 (1983), S. 237-241 
    ISSN: 1432-1041
    Keywords: triamterene ; bioavailability ; pharmacokinetics ; metabolism ; hydroxy triamterene sulphate ; urinary excretion ; i.v. administration ; first-pass-effect
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary With a new formulation, which made intravenous infusion of triamterene (TA) possible, plasma levels and urinary excretion rates of TA and its main metabolite (OH-TA-ester) were measured in a randomized, cross-over trial in 6 healthy volunteers given triamterene 10 mg i.v. and 50 mg p.o. TA and OH-TA-ester were determined by densitometric measurement of native fluorescence after thin layer chromatography. Distribution volumes of the central compartment of TA and OH-TA-ester were 1.49 l/kg and 0.11 l/kg, respectively. Terminal half-lives were 255 min for TA and 188 min for OH-TA-ester after i.v. administration. For TA total plasma clearance was 4.5 l/min and renal plasma clearance 0.22 l/kg. The formation of OH-TA-ester was very rapid and the concentration of the metabolite exceeded that of TA at all times. After i.v. administration the urinary recovery of TA and OH-TA-ester was 4.4% and 50.9%, respectively. The bioavailability of TA was 52%, corresponding to absorption of 83%. TA is partly eliminated by a first-pass-effect. The main metabolite of TA is OH-TA-ester, which is pharmacologically active.
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  • 51
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    European journal of clinical pharmacology 25 (1983), S. 449-453 
    ISSN: 1432-1041
    Keywords: canrenone ; pharmacokinetics ; plasma level ; bioavailability ; urinary excretion ; spironolactone
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Five healthy male volunteers received canrenoate-K 200 mg (Sincomen® pro injectione) by intravenous injection and one week later spironolactone 200 mg (Sincomen®-100) orally. Plasma levels and urinary excretion of unchanged canrenone were determined up to 24 h by a specific HPLC method. Following intravenous administration, the maximum plasma level of 2066±876 ng/ml was found after 29±15 min and thereafter the concentration declined with a half-life of 3.7±1.2 h. Total clearance was 4.2±1.7 ml/min·kg. After oral ingestion, the maximum concentration of 177±33 ng/ml was observed at 4.4±0.9 h. The absolute bioavailability of canrenone was 25±9%. Within 24 h, respectively 0.4 and 0.6 mg, canrenone were excreted by the kidney after intravenous and oral administration. The half-life of elimination was 4.9±1.8 h (i.v.) and 3.9±1.2 h (p.o.).
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  • 52
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    European journal of clinical pharmacology 24 (1983), S. 103-108 
    ISSN: 1432-1041
    Keywords: dexamethasone ; bioavailability ; pharmacokinetics ; ‘first-pass’ effect ; pre-systemic elimination
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and oral biovailability of dexamethasone were studied in 6 patients with neurological disease being treated with high dosages of the drug. A specific high performance liquid chromatographic assay was used to measure dexamethasone concentrations. Unlike the previously published mean figure of 0.78 for the oral bioavailability of the drug given in single doses to healthy volunteers, the mean bioavailability of dexamethasone in the patients studied was 0.53±SD 0.40. It appeared more likely that this incomplete bioavailability was due to presystemic elimination than to poor absorption. The intravenous clearance of the drug was relatively high (0.4902±SD 2291 l kg−1, approximately 65% of expected hepatic plasma flow), the oral clearance higher (2.5804±SD 3.2181 l kg−1 h−1) while the absorption rate constant (4.8729±8.4998 h−1), suggested rapid absorption after oral administration. Prior phenytoin and possibly prior dexamethasone therapy is likely to have contributed to the higher clearance values of the drug in these patients than the values reported in healthy volunteers after single dose studies.
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  • 53
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    Keywords: oxmetidine ; pharmacokinetics ; bioavailability ; plasma half-life ; clearance ; oral dose ; i.v. dose
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentration curves and urinary excretion of oxmetidine after administration of single i.v. (100 mg) and oral (200 mg) doses have been studied in 11 patients with peptic ulcer disease. The mean bioavailability of the drug was 70% (range 53–91%). After intravenous administration, the mean plasmat 1/2β was 3.0 h, the mean apparent volume of distribution 0.7 l/kg, the mean total plasma clearance 12.3 l/h and the mean plasma renal clearance was 0.7 l/h. Following intravenous and oral administration an average of 6% and 3%, respectively, of unchanged drug was found in the urine. The plasma concentration curve after oral administration in most patients exhibited two maxima, with peak concentrations appearing between 45 and 210 min after dosing.
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  • 54
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    European journal of clinical pharmacology 25 (1983), S. 689-693 
    ISSN: 1432-1041
    Keywords: amiodarone ; bioavailability ; calculation ; linear pharmacokinetics ; absorption
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Methods for estimating the bioavailability of drugs with long elimination half-lives are examined. Provided both absorption and disposition are linear a simple linear regression method is developed which can be used to calculate bioavailability in situations where only an incomplete estimate of the area under the curve (AUC) is available. The regression method and the traditional method of comparing the AUC following an oral dose to the AUC following an i.v. dose were applied to simulated data. It was found that the AUC ratio method works well as long as absorption is complete within the time over which the AUC is computed. The regression method is less precise than the AUC ratio method but is more accurate for drugs with long absorption half-lives. When applied to published data on a beta blocker the two methods produced comparable results. The bioavailability of amiodarone in three human subjects was calculated to be 0.20, 0.44 and 0.98 using the regression method with similar results from the ratio method. It is not possible to estimate the clearance of amiodarone from single dose data.
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  • 55
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    Keywords: chlorambucil ; prednimustine ; plasma concentrations ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of chlorambucil has been investigated in a cross over study after oral administration of the free drug (10 mg) and its prednisolone ester (prednimustine, 100 mg). The bioavailability of chlorambucil was about five times lower when given as prednimustine as compared to administration of the free drug. The peak plasma concentration was about twice as high and it was obtained more rapidly when the free drug was given. No intact prednimustine could be detected in plasma.
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    European journal of clinical pharmacology 24 (1983), S. 563-568 
    ISSN: 1432-1041
    Keywords: indomethacin ; multi-dose kinetics ; controlled release formulation ; capsule formulation ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of a controlled release (CR) formulation of indomethacin 75 mg (Indocid-Retard®) given once daily was compared with a conventional 25 mg indomethacin capsule (Indocid®) given 3 times daily for 7 days, to 14 healthy volunteers, using a randomized, cross-over, multiple-dose study design. The following differences in plasma indomethacin profiles after the 2 treatments were observed: average peak concentrations (Cmax) for the CR regimen were higher and the time to peak (Tmax) was significantly delayed. Trough (pre-morning dose) plasma concentrations (Cmin) on Days 2, 5, 6 and 7 were significantly lower after the CR-formulation. No statistically significant differences between preparations for area under the plasma concentration time curve (AUC0–24h) or for renal clearance were observed. Average steady-state plasma concentrations (C p ss ) on Day 7 of the multiple dose regimens averaged 0.477 and 0.427 µg/ml for the 75 mg CR once daily and the conventional 25 mg t.i.d. treatments, respectively. These results show that the bioavailability of the CR and conventional indomethacin formulations under these multiple-dose conditions was not significantly different.
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  • 57
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    European journal of clinical pharmacology 24 (1983), S. 537-542 
    ISSN: 1432-1041
    Keywords: morphine ; analgesic activity ; tablets solution ; pharmacokinetics ; bioavailability ; pain score ; dose-response relationship ; chronic pain
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The steady-state kinetics of morphine given as tablets and solution were compared in 7 cancer patients with chronic pain. There was no accumulation of morphine (20–40 mg) when repeatedly administered every 4 to 6 h. The mean steady-state concentration of morphine during the dose interval varied between 5.9 and 68.4 ng/ml (20.7–240 nmol/l), and was linearly related to the daily dose of morphine. There were no significant differences between the tablets and the solution of morphine with regard to relative oral bioavailability or peak concentration. The time-to-maximum plasma concentrations was significantly longer for the tablets. The pain score profile, assessed by a visual analogue scale during a dose interval, showed a similar pattern after the two oral formulations of morphine. No significant linear relationship between the scores and the plasma concentrations of morphine was observed.
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  • 58
    ISSN: 1432-1041
    Keywords: metoprolol ; bioavailability ; young ; elderly ; metoclopramide ; probanthine ; gut motility
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of metoprolol was studied in eight healthy young and seven healthy elderly volunteers. Large interindividual differences in the bioavailability of metoprolol were observed in both groups. However, there was no significant difference in AUC, peak plasma concentration or elimination half-life between young and elderly, but time to peak concentration was significantly longer in the elderly. Pretreatment with metoclopramide had no effect on AUC but caused significant increases in peak concentration and decreases in time to peak concentration in both groups. Probanthine pretreatment (only to the young) resulted in a significant decrease in peak concentration of metoprolol and a significant increase in time to peak concentration but had no effect on the AUC. These results suggest that alterations in gastric emptying and gut motility due to ageing or other drugs have no effect on the overall availability of metoprolol to the systemic circulation but may have significant effects on the time to peak plasma concentration and peak concentration achieved after a single oral dose.
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  • 59
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    European journal of clinical pharmacology 25 (1983), S. 419-424 
    ISSN: 1432-1041
    Keywords: dihydrocodeine ; pharmacokinetics ; acid metabolites ; radioimmunoassay ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Serum concentrations of dihydrocodeine and its acid metabolites have been determined in seven human volunteers (6 male) who received the drug orally (30 mg and 60 mg) and intravenously (30 mg) on separate occasions, and in twenty-four patients (12 male) receiving 25 mg or 50 mg of the drug intravenously. The concentrations were estimated by radioimmunoassay on reconstituted extracts from serum after an extraction process which effectively separates dihydrocodeine from its polar acidic metabolites. The intravenous data show that dihydrocodeine kinetics followed a two-compartment distribution model. The concentration curves after oral administration indicated relatively rapid absorption with mean peak concentrations at 1.6h–1.8h. The mean half-lives varied between 3.3h–4.5h. From the AUC, the mean bioavailability of orally administered drug was 21% (range 12–34%). The peak levels of the acidic metabolites occurred between 1.8h–2.0h after oral administration and 2.2h–2.5h after i.v. administration, and they were significantly greater after oral administration. The low bioavailability of dihydrocodeine, together with the earlier and higher plasma levels of the acid metabolites after oral administration is suggestive of substantial first-pass metabolism.
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    European journal of clinical pharmacology 25 (1983), S. 467-473 
    ISSN: 1432-1041
    Keywords: hydralazine ; heart failure ; pharmacokinetics ; bioavailability ; metabolism ; hypertension ; dapsone ; acetylator phenotype
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of various disease states, other than hypertension, on the pharmacokinetic behaviour of hydralazine is not completely known. In the present study the pharmacokinetics of oral hydralazine has been evaluated in 7 patients with severe, chronic heart failure, using 8 compensated hypertensives as controls. The pharmacokinetics was evaluated by measuring the plasma concentrations of hydralazine (“apparent” and “real” hydralazine) and hydralazine pyruvate hydrazone, and by assessing acetylator phenotype after a small dose of dapsone. The AUC (area under the plasma concentration curve) following a single, oral 50 mg dose was significantly larger in patients with chronic heart failure NYHA Class III–IV than in patients with essential hypertension without cardiac decompensation. A decreased rate of hepatic elimination of hydralazine is suggested as a major contributory factor to this finding.
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    European journal of clinical pharmacology 25 (1983), S. 553-556 
    ISSN: 1432-1041
    Keywords: Endralazine ; pharmacokinetic ; acetylator phenotype ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Endralazine (E), a new hydralazine-like antihypertensive was given intravenously (0.05 mg/kg) to 10 normal volunteers (5 slow and 5 fast acetylators). Plasma levels were fitted to a 3 compartment model and pharmacokinetic parameters (area under curve [AUC 0 ∞ ], clearance, volume of distribution, half-lives) obtained in the usual way. Bioavailabilities of 5 and 10 mg oral doses of E were determined from the AUC 0 ∞ generated in a previous study of oral E given to the same subjects. E had high system bioavailability (73.5–99.1%) suggesting that it was almost completely absorbed without undergoing appreciable first-pass metabolism. Furthermore, dose size and acetylator phenotype did not significantly affect the bioavailability of E. This behaviour contrasts with that of hydralazine where systemic bioavailability was 〈40%, and 2 to 3 times higher in slow acetylators than in fast acetylators. It is concluded that the bioavailability of E is high and not influenced by acetylator phenotype; these properties suggest some clinical advantages for the drug.
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  • 62
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    Keywords: theophylline ; asthma ; children ; sustained-release ; diurnal ; absorption ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absolute oral bioavailability of a sustained release theophylline tablet (Nuelin-SR250), given 12 hourly was determined in 14 asthmatic children aged 5 to 13 years. In 4 of the patients, mean bioavailability of the fourth dose was 38.9±8.4% and that of the sixth dose was 67.9±25.9% (p〈0.05) in the other ten patients. This suggests steady-state had not been achieved after four doses. In the initial study with 9 patients, a significant diurnal variation in predose plasma theophylline concentrations was observed, as the mean morning predose concentrations were 2.9 fold greater than the mean evening predose concentrations (p〈0.005). Dual peak plasma concentrations occurred in 5 out of the 9 patients. The mechanism of this diurnal variation was investigated in a further 5 asthmatic children (10.8 years ±1.6). Morning and night steady-state plasma theophylline concentrations during a continuous intravenous infusion of aminophylline were not different (14.9±5.3 mg/l vs. 15.6±5.9 mg/l), demonstrating that there was no diurnal variation in the plasma clearance of theophylline. The diurnal variation in predose concentrations with Neulin-SR250 was confirmed with the morning concentrations again being 2.6 fold greater than those in the evening. However, bioavailability was not significantly different for day (09.00–21.00) and night (21.00–09.00) dosing intervals after doses 6 and 7 respectively of Nuelin-SR250. The plasma concentration versus time profiles suggested that the diurnal variation in predose concentrations was due to slower absorption of the evening dose.
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    European journal of clinical pharmacology 24 (1983), S. 509-515 
    ISSN: 1432-1041
    Keywords: cibenzoline ; pharmacokinetics ; bioavailability ; urinary excretion ; antiarrhythmic drug ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of cibenzoline (UP 339.01), a new antiarrhythmic drug, was studied after i.v. and oral administration to 5 healthy subjects. Cibenzoline levels in plasma and urine cibenzoline were measured by a GLC method. After i.v. administration, the total clearance was 826 ml · min−1. The fraction of cibenzoline excreted unchanged in the urine was 0.602 and it was correlated with the creatinine clearance. After i.v. and oral administration, the renal clearances were 499 ml · min−1 and 439 ml · min−1, and the half-lives were 4 h 01 min and 3 h 24 min, respectively. The differences were not significant. Availability by the oral route was 0.92, the maximum plasma concentration being observed at 1 h 36 min. The results were compared with those for other antiarrhythmic drugs.
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    European journal of clinical pharmacology 25 (1983), S. 281-283 
    ISSN: 1432-1041
    Keywords: dyphylline ; pharmacokinetics ; bioavailability ; drug levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of 3 oral dyphylline preparations, solution (S), regular (R) and sustained release (SR), were studied in 8 healthy subjects (mean age 25 years). A single dose of each preparation, 20 mg·kg−1, was given at one week intervals and multiple serum samples obtained over 24 h. Drug levels were measured by high performance liquid chromatography. No adverse effects were found. The dyphylline half-life for the solution was 2.16±0.18 h and for the tablet 2.59±0.56 h. The mean clearance rate for S was 13.6±1.7 h−1 and volume of distribution 43.0±3.91. Peak concentration (Cmax, µg·ml−1), time of peak (Tmax, h), area under the curve (AUC, µg·ml−1·h) and relative bioavailability (RB, %), were determined for three preparations: The data confirm the short half-life of dyphylline, demonstrate a lack of toxicity for the 20 mg·kg−1 dose and establish bioequivalence for the products studied.
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  • 65
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    European journal of clinical pharmacology 25 (1983), S. 357-359 
    ISSN: 1432-1041
    Keywords: pindolol ; bioavailability ; fluorimetric assay ; GLC-ECD assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absolute oral bioavailability of pindolol has been estimated by two analytical methods, fluorimetry and GLC-ECD. The study was carried out in six healthy subjects who received either i.v. or oral pindolol in random order. The results obtained by both methods were similar and confirm the high bioavailability (about 75%) of pindolol. The present findings are compared with previous publications and emphasize the importance of undertaking bioavailability studies in the same subjects.
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  • 66
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    European journal of clinical pharmacology 24 (1983), S. 21-30 
    ISSN: 1432-1041
    Keywords: clonidine ; bioavailability ; blood pressure ; elimination half-life ; pharmacokinetics ; plasma catecholamines ; rebound phenomenon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Using considerably improved analytical methods, the kinetics and effects of clonidine were observed in healthy volunteers over periods of time more than 3 times longer than those previously reported. The high sensitivity and small work load of the newly developed method permitted the performance of low-dose and multipledose trials. 1. The complete bioavailability of clonidine and its elimination half-life (20 to 25.5 h) remained constant after single and multiple doses. 2. Approximately 62% of a given dose was excreted unchanged in the urine, independent of the quantity administered (0.075, 0.15, 0.2, 0.25 or 0.3 mg), the drug formulation (solution, tablet, Perlonget) or of the mode of administration (i.v., p.o.; single or multiple doses). 3. As the pharmacokinetics of the drug were affected by entero-hepatic circulation, it cannot be described by a conventional, open one or two compartment model. 4. The time courses of the plasma clonidine concentration and its drug effects ran asynchronously. 5. On cessation of chronic clonidine administration, blood pressure and plasma catecholamine levels increased to pretreatment levels without exhibiting any “overshoot” reaction.
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  • 67
    ISSN: 1432-1041
    Keywords: theophylline ; smoking ; sustained release formulation ; dosage forms ; multidose pharmacokinetics ; bioavailability ; circadian variation in kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of theophylline following 10 days of multiple doses of a plain uncoated (640 mg, q.i.d.) and a sustained-release tablet formulation (600 mg, b.i.d.) were related to habitual smoking in 11 healthy adult male volunteers, who had previously taken part in a single-dose study of an intravenous preparation of theophylline and of the same oral dosage form. There were significant differences (p〈0.05 to 0.01) in the steady-state mean and minimum theophylline concentration and AUC between the groups (6 smokers versus 5 nonsmokers), but not between other variables. A difference (p〈0.05) in peak time was also found between the dosage forms. The mean elimination t1/2 was significantly (p〈0.05) shorter in smokers than in nonsmokers. The intersubject variability in plasma theophylline concentration observed on the final trial day in the smoking group was larger and diverged more from simulation curves generated from the mean pharmacokinetic parameters of the single-dose study of the same formulations as compared to that of the nonsmoking group. There was no significant difference between the two groups in the mean accumulation ratio and absolute bioavailability of the two dosage forms. The mean morning (7 a.m.) trough theophylline concentrations after both formulations were significantly (p〈0.05 to 0.01) greater than the evening (7 p.m.) values within the same group. The average number of reported side-effects was significantly (p〈0.001) greater during the earlier period (Days 1 to 3) than the later period of the trial. A trend was observed suggesting that the incidence of side-effects was less in smokers than in nonsmokers. The results indicate that smoking is a determinant not only of enhanced elimination of theophylline but that it also produces more variability in the plasma level, irrespective of the dosage form administered or the dosing scheme employed. There may be circadian variation in theophylline kinetics.
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  • 68
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    European journal of clinical pharmacology 24 (1983), S. 415-419 
    ISSN: 1432-1041
    Keywords: prednisolone ; bioavailability ; non-linear pharmacokinetics ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of prednisolone after oral and intravenous administration of 10 and 20 mg have been studied. Serum protein binding of prednisolone was also measured after the i.v. injections. The bioavailability after oral administration was 84.5% after 10 mg and 77.6% after 20 mg (p〉0.05). Dose dependent pharmacokinetics were found, the VDss and Clt being significantly larger (p〈0.01) after 20 mg i.v. than after 10 mg i.v. The protein binding of prednisolone in all subjects was non-linear, and is the most likely cause of the dose dependent pharmacokinetics, as there was no dose dependent variation in elimination half-time.
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  • 69
    ISSN: 1432-1041
    Keywords: ranitidine ; duodenal ulceration ; pharmacokinetics ; non-responders ; therapeutic response ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of orally administered ranitidine were studied in 17 male patients with chronic duodenal ulceration. The patients were divided into 2 groups, 10 responders and 7 nonresponders, on the basis of their endoscopic response to ranitidine treatment. The 10 responders were studied both after a single 150 mg dose (SD) and after multiple dosing (MD) with ranitidine 150 mg twice daily for 4 weeks. The area under the curve (AUC) and maximum concentration (Cmax) were significantly higher (p〈0.01 andp〈0.05, respectively) after MD than after SD, but the half-life (t1/2) and minimum concentration (Cmin) 12 h postdosing did not differ. The non-responders were studied after MD only and their pharmacokinetic characteristics were compared with those of responders. No differences between the 2 groups were found. However, 2 non-responders had particularly low plasma ranitidine levels and high acid output. Such patients may need larger doses of ranitidine for adequate suppression of gastric acid. Five patients (4 responders and 1 non-responder) received ranitidine 20 mg i.v. The drug followed a two-compartment model, with mean values for t1/2β, volume of distribution steady-state and total plasma clearance of 80 min, 701 and 680 ml/min, respectively. The oral bioavailability of ranitidine in these 5 patients showed wide variation (27–76%; mean 51%).
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  • 70
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    European journal of clinical pharmacology 24 (1983), S. 761-767 
    ISSN: 1432-1041
    Keywords: theophylline ; bioavailability ; sustained release tablet ; pharmacokinetics ; Theograd-250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of theophylline after oral administration of a new sustained release tablet Theograd®-250 mg was studied in 7 healthy volunteers, under fasting and non-fasting conditions. Whilst fasting the bioavailability was moderate at 64±22% (mean±SD), whereas in the non-fasting state the relatively high bioavailability of 90±13% was found. The drug appeared to be significantly more slowly absorbed when a tablet was taken after a meal, than when it was ingested on an empty stomach. In the former case, the peak level was reached after 6.9±1.0 h, whereas in the fasting state the maximum serum concentration occurred 4.0±1.7 h after administration of the drug. Despite the slow absorption, the peak non-fasting level of 4.4±1.4 mg·l−1 was significantly higher than the 3.1±1.0 mg·l−1 observed in the fasting state. The profiles of the serum concentration-time curves showed that the concentration remained above 75% of Cmax for 8.7±1.3 h in the fasting and 9.0±1.1 h in the non-fasting state. It was concluded that to define the optimal dosage regime for sustained release oral dosage forms of theophylline, the influence of food on absorption from these preparations should be taken into account. Based on the present results, Theograd®-250 mg tablets have predictable absorption and a high (90%) bioavailability if taken after a meal.
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  • 71
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    European journal of clinical pharmacology 25 (1983), S. 69-72 
    ISSN: 1432-1041
    Keywords: levodopa ; intestinal absorption ; small intestine ; bioavailability ; benserazide ; presystemic clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In four healthy subjects the intestinal absorption of levodopa (l-dopa) was investigated by measuring the plasma concentration of the amino acid following the administration of l-dopa at three different sites in the small intestine. In order to minimize presystemic clearance of l-dopa, the subjects were pretreated with the peripheral decarboxylase inhibitor benserazide 3×50 mg every 8 h on the previous day and 1×50 mg 2 h prior to administration of the l-dopa. L-dopa 100 mg dissolved in 0.05 N HCl and 50 mg benserazide dissolved in 0.05 N HCl were coadministered. Under these conditions no difference in tmax, cmax or AUC of l-dopa was observed between administration of the drug into the proximal or the distal part of duodenum, or into the upper part of jejunum. The results indicate that in healthy subjects, during inhibition of peripheral decarboxylase, the rate and extent of l-dopa absorption does not differ at any site in the upper small intestine.
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  • 72
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    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 561-576 
    ISSN: 1573-8744
    Keywords: methylprednisolone ; bioavailability ; pharmacokinetics ; oral and parenteral administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This study was conducted to evaluate the influence of route of administration upon the bioavailability and pharmacokinetics of methylprednisolone sodium succinate. Fourteen healthy adult male volunteers received 40 mg doses of methylprednisolone as the following treatments after an overnight fast in a 4-way crossover design: (a) as a 1 ml i.v. bolus;(b) as a 1 ml i.m. injection;(c) administered as an oral solution;and (d) as 5×8 mg oral tablets. Both the ester and free methylprednisolone were determined in plasma and urine. Study results indicate that the ester is rapidly and extensively converted to free methylprednisolone after all routes. The extent of methylprednisolone absorption was equivalent after i.v. and i.m. administration. Both orally administered treatments resulted in a lower extent of absorption attributed to a first-pass effect. Although a slightly lower extent of absorption was demonstrated following the oral administration of the methylprednisolone sodium succinate solution relative to the methylprednisolone oral tablets, this average difference of 9% would probably be of minimal therapeutic importance.
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    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 205-214 
    ISSN: 1573-8744
    Keywords: bioavailability ; clearance ; V area ; V ss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The limitations of using estimates of extent of bioavailability (F) based on the assumption that either clearance (CL) or Varea remain, constant are discussed in relation to the situation where CL changes between doses. When estimates of F assume CL to remain constant, the entent of the error is the same for all drugs where the percentage change in CL is the same. Assuming Varea to remain constant, the error in F will vary between drugs for similar percentage changes in CL and is related to the extent to which the kinetics of the disposition process deviate from a one compartment body model. A noncompartmental method is described where, provided the reference dose is given intravenously, F can be estimated based on the assumption that Vss remains constant between doses. This method is more accurate than those based on the assumption that either CL or Varea remain, constant when CL changes between doses, but is subject to error when the terminal loglinear slope of Cp vs. time better reflects the process of absorption rather than elimination.
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  • 74
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    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 529-545 
    ISSN: 1573-8744
    Keywords: bioavailability ; nitrofurantoin ; capacity-limited elimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of route of administration on the absolute bioavailability and GI tract absorption of nitrofurantoin was investigated in rabbits. The disposition of nitrofurantoin was described by a one-compartment model with simultaneous first-order and Michaelis-Menten type elimination kinetics, and bioavailability was estimated by nonlinear assessment. The plasma levels following oral administration were significantly lower than those after intravenous administration, and absolute Fvalues for oral administration were approximately 0.3. However, Fvalues following intraduodenal administration and portal vein infusion were nearly unity, and it was concluded that the reduction of bioavailability following oral administration could not be attributed to metabolism by intestinal microflora or to the hepatic first-pass effect. Thus, reduction of Fvalues following oral administration is probably due to gastric degradation of the drug. The effects of factors influencing bioavailability, such as water volume taken with the drug, change of gastric emptying rate and effect of particle size, were also investigated. Increase of volume of water administered tended to improve the bioavailability, and a particle size dependency was also observed.
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