Library

feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
  • 1
    ISSN: 1432-1041
    Keywords: noradrenaline ; desipramine ; plasma DOPEG ; sympathetic tone ; orthostatic stress ; bicycle exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Antecubital venous blood was sampled at rest and during orthostasis or supine bicycle exercise. The plasma was analyzed for noradrenaline and 3,4-dihydroxyphenylethyleneglycol (DOPEG) by HPLC. Orthostasis resulted in increases in plasma concentrations of both noradrenaline and DOPEG. The magnitude of changes in both was dependent on the degree of orthostasis. In conditions of supine rest, sitting, and standing the plot of the geometric mean values of plasma DOPEG (ordinate) against those of plasma noradrenaline was linear, had a slope of about unity, and intersected the ordinate at a finite value of plasma DOPEG. After administration of desipramine (to block uptake1), plasma concentrations of DOPEG fell both at rest and during orthostasis. Moreover, desipramine abolished the plasma DOPEG response to orthostasis without affecting the plasma noradrenaline response. Hence, changes in plasma DOPEG brought about by changes in sympathetic tone are presynaptic in origin. The plasma concentration of DOPEG observed in the presence of desipramine was virtually identical with the ordinate intercept of the regression line relating plasma DOPEG to plasma noradrenaline in the absence of desipramine. This pool of plasma DOPEG (which amounted to about 75% of that observed at supine rest in the absence of desipramine) probably stems from intraneuronal noradrenaline leaking out of the storage vesicles of peripheral sympathetic neurones and may in part also be derived from the central nervous system. Supine bicycle exercise failed to increase plasma DOPEG. This may be due to the separation of the sampling site from the site of noradrenaline release (i.e. the exercising limbs) by organs involved in DOPEG extraction. The failure of plasma DOPEG to rise under these conditions may also be a consequence of increased blood flow in the exercising limbs, resulting in a marked decrease in the proportion of the released noradrenaline being recaptured by the sympathetic nerve endings.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A variety of BeMgZnSe–ZnSe- as well as BeTe-based quantum-well structures has been fabri- cated and investigated. BeTe buffer layers improve the growth start on GaAs substrates drasti- cally compared to ZnSe/GaAs. The valence-band offset between BeTe and ZnSe has been determined to be 0.9 eV (type II). Due to the high-lying valence band of BeTe, a BeTe–ZnSe pseudograding can be used for an efficient electrical contact between p-ZnSe and p-GaAs. BeMgZnSe quaternary thin-film structures have reproducibly been grown with high struc- tural quality, and rocking curve widths below 20 arcsec could be reached. Quantum-well structures show a high photoluminescence intensity even at room temperature. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International archives of occupational and environmental health 30 (1972), S. 161-172 
    ISSN: 1432-1246
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In Experimenten an Kaninchen, die ein CO-Luftgemisch mit 1000 ppm CO unter normalem und erhöhtem Druck einatmeten, wird der Kohlenoxid- und Sauerstoffpartialdruck im Gewebe untersucht (Pneumoperitoneum als Gewebemodell). Der O2-Partialdruck im Gewebe der Tiere ist bei der CO-Vergiftung auch unter überdruck erniedrigt, jedoch steigt er mit zunehmendem O2-Partialdruck in der Einatmungsluft an. Dieser Anstieg des O2-Partialdruckes im Gewebe wird durch die grö\ere physikalisch im Plasma gelöste und transportierte O2-Menge bedingt. Der CO-Partialdruck im Gewebe liegt im Gleichgewichtszustand unter normalem und erhöhtem Druck erheblich niedriger als in der Einatmungsluft; er sinkt sogar mit steigendem Druck in der umgebenden AtmosphÄre eindeutig ab. Bei einer CO-Konzentration von 1000 ppm betrÄgt der alveolare CO-Partialdruck unter 1 ata 0.708 mm Hg, unter 3 ata 2,23 mm Hg und unter 4 ata 2,99 mm Hg. Die im Gleichgewicht im Gewebe gemessenen CO-Partialdrucke liegen unter 1 ata bei 0,418 mm Hg, unter 3 ata bei 0,371 mm Hg und unter 4 ata bei 0,351 mm Hg. Dieser Befund beruht auf der Konkurrenz zwischen Sauerstoff und Kohlenoxid um den Receptor HÄmoglobin im Blut und lÄ\t sich durch Berechnung nach dem Massenwirkungsgesetz bestÄtigen. Bei Betrachtung des O2-Partialdruckes und CO-Partialdruckes im Gewebe lÄ\t sich also zeigen, da\ die ToxicitÄt gleicher CO-Konzentrationen in einem CO-Luftgemisch unter erhöhtem Druck nicht als höher, sondern als niedriger anzusehen ist.
    Notes: Summary The partial pressures of carbon monoxide and oxygen in tissue were measured in rabbits breathing 1000 ppm CO at normal and increased pressure. A pneumoperitoneum was used as tissue model. In carbon monoxide intoxication the partial pressure of oxygen in tissue is decreased even if the animals are inhaling the mixture of CO and air at very high pressure. However, when the oxygen partial pressure in the inspired air is increased there is an increase of oxygen partial pressure in tissue. This increase is based on the greater quantity of oxygen dissolved and transported in the blood plasma. At normal or increased pressure the CO partial pressure in tissue is considerably lower than that in the inspired air, once diffusion equilibrium has been reached. The CO partial pressure in tissue falls even when pressure is increasing in ambient air. When the CO concentration of the inspired air is 1000 ppm the alveolar CO pressure is 0.708 mm Hg at 1 ata, 2.23 mm Hg at 3 ata and 2.99 mm Hg at 4 ata. The CO partial pressures measured in tissue at diffusion equilibrium are 0.418 mm Hg at 1 ata, 0.371 mm Hg at 3 ata and 0.351 mm Hg at 4 ata. This result is explained by the competition between oxygen and carbon monoxide for the receptor hemoglobin in the blood and is confirmed by calculation according to the law of mass action. Consideration of the partial pressures of oxygen and carbon monoxide in tissue shows that toxicity of a definite CO concentration in a mixture of CO and air is not higher but lower under increased pressure.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International archives of occupational and environmental health 28 (1971), S. 127-140 
    ISSN: 1432-1246
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Untersuchungen an freiwilligen Versuchspersonen unter überdruck sollten zur Klärung der Frage beitragen, ob Kohlenoxid bei Einatmung gleicher CO-Luftgemische unter erhöhtem Druck giftiger ist als unter normalem atmosphärischem Druck (1 ata). Die Versuche mit CO-Konzentrationen von 50 sowie 100 ppm bei 1 ata und 3 ata wurden in einer 8,3 m3 großen Druckkammer vorgenommen, in der die O2-, CO2- und CO-Konzentrationen während der Exposition überwacht wurden. Bei Messung der CO-Konzentration in der Alveolarluft und des COHb-Wertes im Blut zeigt sich, daß die Sättigung des Blutes mit CO — wie auch die Einstellung des Diffusionsgleichgewichtes im Organismus — bei 3 ata erheblich schneller erfolgt als unter dem Druck von 1 ata. Bei Einatmung von 100 ppm CO beträgt beispielsweise die CO-Konzentration in der Alveolarluft der unter 3 ata atmenden Probanden nach 2 Std 73 ppm, bei den unter 1 ata atmenden Probanden jedoch nur 36,7 ppm CO. Dieses Ergebnis erklärt sich aus dem erhöhten CO-Angebot bei erhöhtem CO-Partialdruck. Hervorzuheben ist der Befund, daß die COHb-Konzentration im Diffusionsgleichgewicht unter erhöhtem Druck signifikant niedriger liegt als unter normalem Druck (p〈0,001). Im Diffusionsgleichgewicht findet man beispielsweise bei Einatmung von 50 ppm CO bei 3 ata einen COHb-Wert von 4,5%, bei 1 ata dagegen von 7,25 %. Dieses Ergebnis läßt sich mit der Konkurrenzreaktion von CO und O2 um den Receptor Hämoglobin erklären, die dem Massenwirkungsgesetz unterliegt. Es besteht somit nach unseren Ergebnissen kein Grund, den MAK-Wert von 50 ppm CO bei Arbeiten unter erhöhtem atmosphärischem Druck zu senken.
    Notes: Summary On healthy volunteers we investigated whether carbon monoxide would be more toxic under increased pressure than under normal pressure, if this gas is inspired at the same concentration under both conditions. It was shown by measurements of CO concentration in alveolar air and of the CO-Hb content of blood that under 3 ata the blood is saturated faster with carbon monoxide than under normal atmospheric pressure, indicating that under increased pressure diffusion equilibrium in the organism is achivied earlier. In subjects breathing 100 ppm CO for 2 hours the CO concentration in alveolar air is 73 ppm under 3 ata and not more than 36.7 ppm at 1 ata. This result is explained by the increased CO supply under increased pressure. It must be emphasized that the CO-Hb concentration is significantly lower under increased pressure than under atmospheric pressure (p〈0.001), once diffusion equilibrium has been attained. In subjects breathing 50 ppm CO the CO-Hb concentration is only 4.5 % at 3 ata but 7.25 % at 1 ata. This result is explained by application of the law of mass action on the competition of CO and O2 for the receptor hemoglobin in the blood. It must be concluded from our experimental data that there is no reason to lower the threshold limit value of 50 ppm CO for work carried out under increased pressure.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-0738
    Keywords: Acute CO Intoxication ; Venous Oxygen Pressure ; Blood Sugar Concentration ; High (Atmospheric) Pressure ; Effects of CO ; Akute Kohlenoxidvergiftung ; Venöser Sauerstoffdruck ; Blutzuckerverhalten ; Überdruck ; Spezifische Kohlenoxidwirkungen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In drei Versuchsreihen an Kaninchen werden nach 1stündiger Einwirkung hoher CO-Konzentrationen unter normalem und erhöhtem Luftdruck Blutzucker, Kohlenoxidhämoglobingehalt (COHb) und Sauerstoff-Partialdruck (pO2) in der V. jugularis gemessen. Hierzu werden analoge Versuche mit reinem Sauerstoffmangel, erzielt durch 1stündige Einwirkung von Sauerstoff-Stickstoffgemischen, in Beziehung gesetzt. Bei 2000 ppm CO in der Einatmungsluft steigt unter normalem atmosphärischen Druck im Mittel von 22 Versuchen der Blutzucker nach 1 Std um 87 % gegenüber dem Ausgangswert von 98,5 mg- % an. Der Sauerstoffdruck im venösen Blut fällt von etwa 45 Torr bereits nach 10 min auf die Hälfte ab und erreicht den Endwert von 9,5 Torr O2 schon nach 30 min. Der sich ebenfalls rasch einstellende COHb-Endwert beträgt 47,9 % im Mittel. Bei Einatmung eines Luftgemisches mit 2000 ppm CO unter einem Druck von 4 ata steigt der Blutzucker trotz annähernd gleichem COHb (43,1 % im Mittel) und etwa gleichem pCO im Gewebe nicht an. Hierbei ist von Bedeutung, daß der venöse pO2 nur auf einen Endwert von 20 Torr absinkt. Die Endwerte für pO2 und COHb sind bereits nach 10 min erreicht. Durch Inhalation eines sauerstoffarmen Stickstoff-Luftgemisches (4 bis 6 Vol- % O2 in der Einatmungsluft) läßt sich der venöse pO2-Abfall der ersten Versuchsreihe mit 2000 ppm CO in Luft unter 1 ata nachahmen. Es zeigt sich, daß pO2 auf etwa 10 Torr absinkt, während der Blutzucker um 100 % gegenüber dem Ausgangswert ansteigt. Nach diesen Untersuchungen scheint der Blutzuckeranstieg bei akuter CO-Vergiftung nicht spezifisch durch den CO-Gehalt von Blut und Geweben, sondern durch den unspezifischen Sauerstoffmangel der Gewebe — als Folge der hypoxischen Wirkung des Kohlenoxids — verursacht zu sein.
    Notes: Abstract In rabbits, exposed to high CO concentration at normal and increased atmospheric pressure for 1 h, we investigated the effects of CO intoxication of the level of blood sugar, on carboxyhemoglobin (COHb) concentration in blood and on the partial pressure of oxygen (pO2) in jugular venous blood. Analogous experiments were performed with rabbits exposed for 1 h to oxygen deficiency produced by breathing a mixture of oxygen and nitrogen. In animals exposed to 2000 ppm CO under normal atmospheric pressure the level of blood sugar increases after 1 h from 98,5 mg- % to 184 mg- % (mean value of 22 experiments). The partial pressure of oxygen in venous blood decreases within 10 min from 45 torr to about 23 torr and reaches a final value of 9,5 torr O2 after 30 min. The final value of COHb (mean value 47,5 %) is also reached within a short time. Breathing 2000 ppm CO under 4 ata the blood sugar concentration does not increase in spite of about the same CO Hb concentration (mean value 43,1 %) and similar pCO values at the same time. The venous pO2 decreases only to a final value of 20 torr. The final values of pO2 and CO Hb are reached within only 10 min. Breathing mixture of nitrogen and air (4 to 6 % O2 per volume) the venous decrease of pO2 is similar to effects described in the first series with 2000 ppm CO at 1 ata: decrease of pO2 to about 10 torr and increase of blood sugar of about 100% compared to the initial value were observed. These results support the hypothesis that the increase of blood sugar after carbon monoxide intoxication is induced by the nonspecific oxygen deficiency of the organism — caused by CO-poisoning — and is therefore not primarily specific for the CO concentration of blood and tissue.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 275 (1972), S. 277-287 
    ISSN: 1432-1912
    Keywords: Protein Binding ; Phenol Red ; Digitoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The binding of phenol red and digitoxin to bovine albumin has been measured by means of equilibration dialysis and characterized by the following parameters: binding constant K 1, number of binding sites per albumin molecule n, and free binding energy DF o. Protein binding of phenol red yields a saturation type curve with saturation at about 11.3 mmole/l. Phenylbutazon and probenecid were able to displace phenol red from albumin binding sites in concentrations which are regularly reached after therapeutic doses. With digitoxin because of its hydrophobic character plasma binding could not be measured beyond concentrations of 0.82 mmole/l. Though in principle there is no difference between phenol red and digitoxin binding (a digitoxin binding curve could be calculated also for high concentrations) no displacement effect was seen with probenecid, phenylbutazon, salicylic acid and benzbromaron up to tenfold therapeutic plasma levels. These drugs were effective, however, in the displacement of digitoxin in diluted plasma albumin solutions. This indicates that for an effective displacement multiple molar concentrations of bound and displacing drug with respect to the binding protein are necessary. Displacement from plasma protein therefore plays no role in the possible interference of drugs if one of them is applied in doses far below the molar concentration of the binding proteins.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 67 (1995), S. 1164-1165 
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 19 (1983), S. 271-280 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The finite element reduced scalar potential method of calculating magnetic fields is investigated by comparing it with a classical series method. Both methods are applied to two problems having a current band surrounding a ferromagnetic shell. The magnetic field distributions obtained by both methods are shown to be in generally good agreement.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...