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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 60 (1982), S. 1240-1244 
    ISSN: 1432-1440
    Keywords: Sodium homeoostasis ; Conscious dogs ; Sperrphänomen ; Atrial natriuresis ; Renin-angiotensin-aldosterone system ; Angiotensin II ; Natriumkontrolle ; Wache Hunde ; Sperrphänomen ; Atriale Natriurese ; Renin-Angiotensin-Aldosteron-System ; Angiotensin II
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An chronisch instrumentierten weiblichen Beaglehunden wurden unter standardisierten Umweltund Ernährungsbedingungen Untersuchungen zum Studium der Kontrollprozesse des Natriumhaushaltes durchgeführt. Die nach experimenteller Erhöhung des Druckes im linken Vorhof (reversible Mitralstenose) auftretende Natriurese (atriale Natriurese, AN) eignet sich als Test zur Prüfung anderer in der Kontrolle des Natriums wirksamer Mechanismen. Die Ergebnisse erlauben folgende Schlußfolgerungen: 1. Die im linken Vorhof perzipierte Expansion des Extrazellulärraumes besitzt keine unersetzbare Funktion für die Natriumhomöostase (Volumenkontrolle). 2. Natriumkontrollmechanismen reagieren sehr empfindlich auf Änderungen des Gesamtkörpernatriums (TBS). Eine geringfügige Verminderung des TBS hemmt oder ‚sperrt‘ natriumeliminierende Prozesse wie z.B. eine ‚Kochsalzdiurese‘, eine osmotische Diurese oder die atriale Natriurese (Sperrphänomen). 3. Es ist wahrscheinlich, daß ein spezieller natriuretischer Faktor existiert. 4. Das Renin-Angiotensin-Aldosteron-System scheint u.a. mit seiner Komponente Angiotensin II wesentlich für die Natriumretention zu sein. Der Gesamtkörpernatriumbestand wird von zahlreichen ‚redundanten‘ Prozessen kontrolliert. Zur Zeit sind quantitative Angaben über einzelne Mechanismen nicht möglich. Die Gesamtkontrolle für das Natrium scheint unter allen Bedingungen eine optimale Strategie für das ‚Überleben‘ oder den ‚Komfort‘ zu entwickeln, was beinhaltet, daß sich der ‚Stellenwert‘ einzelner Mechanismen ändern kann.
    Notes: Summary Chronically instrumented female beagles were maintained in standardized environmental and dietary conditions allowing careful examination of the mechanisms governing sodium homeostasis. The experimental increase in left atrial pressure (obtained by a reversible mitral stenosis) is accompanied by an increase in sodium excretion (atrial natriuresis, AN). AN served as an experimental manoeuvre from which the mechanisms governing sodium homeostasis could be elucidated. The results allow the following conclusions: (1) The ‘signals’ arising from distension of the left atrium (e.g. expansion of the extracellular fluid volume) appear not to be a necessary prerequisite for the maintenance of sodium homeostasis. (2) The control mechanisms seem to be very sensitive to changes in total body sodium (TBS). A small reduction in TBS abolishes sodium eliminating processes e.g. saline diuresis, osmotic diuresis, AN. (3) It is probable that a natriuretic factor exists for sodium elimination. In summary, total body sodium appears to be controlled by a series of ‘redundant’ mechanisms which guarantee an appropriate strategy for the comfort and ultimate survival of the organism. At the moment it is impossible to quantitate the contributions made by the various mechanisms in the control of sodium metabolism.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Langenbeck's archives of surgery 335 (1974), S. 83-93 
    ISSN: 1435-2451
    Keywords: Artificial heart ; Documentation ; Chronological ; Automatic ; Digital Computer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es wird ein System beschrieben, mit dem bei komplizierten und lang andauernden Tierversuchen die Versuchsprotokollierung erleichtert wird. Die automatisch gemessenen und die gesondert erfaßten Meßdaten werden dabei in digitaler Form oder im Klartext ausgedruckt und in chronologischer Form geordnet.
    Notes: Summary A system is described, which eases the registration of datas in complex and longer lasting animal experiments. The datas are partially measured automatically, partially evaluated elsewise and are printed in digital form and ordered chronologically.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-2451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 18 Schafen mit einem durchschnittlichen Gewicht von 59 kg erfolgte ein intrathorakaler Totalersatz des Herzens durch eine zweikammerige, pneumatisch angetriebene Blutpumpe. Die Tiere wurden mit Thiobarbiturat narkotisiert und dann tracheotomiert. Der Thorax wurde durch eine mediane Sternotomie geöffnet und die Tiere an eine Herz-Lungenmaschine angeschlossen. Es mußte eine absolut blut- und luftdichte Verbindung zwischen dem zarten und leicht zerreißlichen Vorhofsgewebe und den relativ starren Vorhofsansätzen des Kunststoffherzens hergestellt werden. Beim operativen Vorgehen, etwa wie bei der homologen Herztransplantation, ergaben sich Schwierigkeiten bei der Naht des stets kurzen und zerreißlichen Vorhofseptums. Deshalb wurde zunächst das Vorhofseptum durch gedoppelte Perikardlappen verstärkt. Am besten bewährte sich schließlich eine Methode, bei der das Herz oberhalb des Klappenringes abgetrennt wurde und bei der folgenden fortlaufenden Naht zum Anschluß an die Teflonansatzstutzen des künstlichen Herzens das feste Material des Klappenringes mitgefaßt werden konnte. Zum Anschluß an Aorta und Pulmonalis dienten Steckverbindungen in Form von kurzen Rohren, in welche die Ausflußklappen eingebaut waren. Fortlaufend registriert wurden die Drucke in beiden Vorhöfen, in einer System arterie und in der Pulmonalis, sowie der Fluß durch die Pulmonalarterie. In regel mäßigen Abständen erfolgten Blutgasanalysen, die Zählung der corpusculären Bestandteile des Blutes, der Elektrolyte, sowie der Konzentrationen von Lactat, Pyruvat und LDH. Das Plasmahämoglobin und die Werte von Lactat und Pyruvat stiegen unterschiedlich stark an. Die Thrombocyten und Leukocyten fielen z. T. erheblich ab. Die meisten Tiere überlebten nur 2–5 Std. Bei einem Schaf gelang eine gute Substitution des Herzens durch diese Pumpe für 11 Std.
    Notes: Summary Intra-thoracic total replacement of the heart by double-chambered pneumatically driven blood pumps was carried out in 18 sheep with an average bodyweight of 59 kg. The animals were narcotized with thioarbiturate and then tracheotomized. The thorax was opened by median sternotomy and the animal joined to a heart-lung-machine. An absolutely blood- and air-tight connection between the delicate and easily ruptured atrial tissue and the relatively rigid atrial connections of synthetic material of the artificial heart, has to be established. During the operation difficulties arise—in the same way as in the case of homologous heart transplants with the suture of the short and easily ruptured atrial septum. Therefore the atrial septum is first reinforced with double pericardial flaps. In the end we found that the best method consisted of detaching the heart above the valve ring and using a continuous suture to join the Teflon connections of the artificial heart to the firm structure of the valvular ring. Plug-like connections in the shape of short tubes containing the valves were used for joining the aorta and the pulmonalis to the heart. The pressure in both atria, in one systemic artery and in the pulmonalis, as well as the blood-flow through the pulmonary artery were continuously recorded. Blood-gas analysis, blood and electrolyte counts, lactic acid, pyruvic acid and LDH determinations were carried out at regular intervals. The plasma haemoglobin and the lactic acid and pyruvic acid levels increased at different rates. Thrombocytes and leukocytes decreased in number, at times quite markedly. Most animals survived for only 2–5 hours. In one sheep a good substitution of the heart with this pump succeeded for 11 hours.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2013
    Keywords: Left atrial distension ; Intrarenal blood flow ; Microspheres ; Conscious dogs ; Muscle blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Measurements were made with radioactive microspheres of the distribution of renal blood flow in conscious dogs during left atrial distension. Urine volume, sodium excretion, mean arterial blood pressure and heart rate increased during the 60 min period of left atrial distension (increase in left atrial pressure by about 1.0 kPa). Total renal blood flow and cardiac output (electromagnetic flowmeters) did not change. The perfusion rates of four renal zones did not change. Striated muscle blood flow (M. psoas) fell markedly. — Stimulation of left atrial receptors in conscious dogs is followed by an increase in renal and skeletal muscle resistance. The diuresis and natriuresis during left atrial distension is not accompanied by a detectable redistribution of renal cortical blood flow.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 407 (1986), S. 382-387 
    ISSN: 1432-2013
    Keywords: Conscious dogs ; Renal nerves ; Sodium balance ; Osmoregulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The ability to retain sodium was investigated in six conscious dogs before and after surgical renal denervation. 1. Dietary sodium and water intake were kept constant (2.5 mmol Na·kg−1 bw·day−1 and 91 ml water·kg−1 bw·day−1). Balance experiments were performed from 6 days before to 8 days after having produced a sodium deficit of 6.4±0.4 (intact dogs) and 5.8±0.2 (renal denervated dogs) mmol Na·kg−1 bw by means of a peritoneal dialysis (PD). Having the same sodium excretion before PD, intact and renal denervated dogs demonstrated a similar striking decrease of sodium excretion and a similar increase of plasma renin activity after PD until the amount of sodium lost had been replenished (4th day after PD). In intact and renal denervated dogs plasma sodium concentration (PNa) decreased and renal water excretion increased on the first day after PD, indicating a homeostatic response to the fall of PNa. 2. After dietary sodium restriction (from 2.5 to 0.5 mmol Na·kg−1·day−1) a similar striking decrease of renal sodium excretion occurred in intact and renal denervated dogs. It therefore is concluded that in conscious dogs the presence of the renal nerves is not essential in order to maintain body sodium homeostasis after an acute sodium loss or after dietary sodium restriction.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2013
    Keywords: Volume regulation ; Cardiac nerves ; Atrial natriuresis ; Renin-Angiotensin-system ; Conscious dogs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Conscious, chronically instrumented dogs, maintained on a high sodium intake, were used to investigate whether surgical cardiac denervation impairs the natriuresis associated with left atrial pressure increase produced in three ways: during an increase in left atrial pressure by means of a reversible mitral stenosis (protocol 1); after an i.v. saline load (1.0 ml 0.9%·saline min−1·kg−1 over 60 min) (protocol 2); after an oral saline load (14.5 mmol Na·kg−1 given with the food as an isotonic solution) (protocol 3). During a reversible mitral stenosis, in intact dogs, urine volume and sodium excretion increased markedly (from 34–145 μl·min−1·kg−1 and from 3–12 μmol·min−1·kg−1); mean arterial pressure increased by an average of 2 kPa (15 mm Hg) and heart rate by 55 b/min; plasma renin activity fell from 0.37–0.21 ng Al·ml−1·h−1. Cardiac denervation eliminated these effects of left atrial distension except for a small increase in heart rate (12 b/min). This indicates that the natriuresis and diuresis during left atrial distension resulted from stimulation of receptors located in the left atrium. In contrast, during protocol 2 and 3, the same amounts of sodium and water were excreted in the cardiac denervated dogs as compared to the intact dogs. A comparable decrease in plasma renin activity also was observed. — Apparently the presence of the cardiac nerves is not a prerequisite for maintenance of sodium and water homeostasis.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2013
    Keywords: Left atrial pressure ; Sodium excretion ; Renal perfusion pressure ; Conscious dogs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An experimental elevation of left atrial pressure (eLAP ↑) by means of a reversible mitral stenosis is accompanied with an increase in sodium excretion (UNa—) and arterial blood pressure (by about 20 mm Hg, 2.7 kPa), and by a decrease in plasma renin activity. It is well established that an increase in renal perfusion pressure (Pren) can augment UNa—. Therefore the present study was undertaken to examine whether the eLAP ↑-induced natriuresis was caused by the increased Pren. — Four female beagle dogs were kept under controlled environmental conditions. They received asodium rich diet (14.5 mmol/Na/kg/d). The dogs were chronically instrumented: purse string around the mitral annulus, catheter in the left atrium, carotid loop, pneumatic cuff above the renal arteries, pressure transducer below the renal arteries. Pren was kept constant by means of a digital servofeedback control circuit. The dogs served as their own controls (13 experiments without and 15 experiments with a controlled renal perfusion pressure were performed). After eLAP↑(+1.0 kPa), UNa— rose from 4.1±2.6 to 10.3±3.9 μmol Na/min/kg. If Pren was kept constant, the corresponding values were 4.2±2.8 and 9.3±2.9 μmol/min/kg. These data clearly indicate that the atrial natriuresis is not mediated by an augmentation of renal perfusion pressure. Therefore these results support the hypothesis that atrial natriuresis probably is due to an eLAP↑-induced suppression of the renin-angiotensin-system or other natriuretic mechanisms.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 381 (1979), S. 143-150 
    ISSN: 1432-2013
    Keywords: Volume regulation ; Atrial pressures ; Postprandial natriuresis ; Renal blood flow ; Conscious dogs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Conscious, chronically instrumented dogs (n=24; left and right atrial catheter, electromagnetic flow probe around the left renal artery, carotid loop) were used in 97 expts. to study mechanisms mediating postprandial (pp) excretion of sodium and water up to at least 180 min after food intake. The dogs were kept under standardized conditions and maintained on ahigh (14.5 mmol Na/kg b.w./day) or alow (0.5 mmol Na/kg b.w./day) sodium intake diet (HSI, LSI) which was given once daily in the morning. In HSI dogs left atrial pressure (LAP) increased from a fasting control value of 0.2 kPa (2 cm H2O) to 0.7 kPa (7 cm H2O) (120–180 min pp), right atrial pressure from 0.0 kPa (0 cm H2O) to 0.3 kPa (3 cm H2O). 25% of the sodium intake were excreted up to 180 min pp. There was a highly significant positive correlation between pp sodium excretion (U Na V) and pp LAP.U Na V was not related to pp increase in renal blood flow (RBF) and glomerular filtration rate (GFR). Fractional sodium excretion increased from a fasting control value of 0.6% to more than 4% in HSI dogs and from 3.3% to more than 7% in anadrenalectomized HSI dog. DOCA did not diminishU NA V in HSI dogs. In LSI dogs, RBF and GFR increased pp, LAP did not change pp. No substantial increase inU Na V was observed. The close correlation between ppU Na V and pp LAP in HSI dogs supports the hypothesis that intrathoracic vascular receptors are involved in the mediation of volume regulation by stimulation of still unknown natriuretic mechanisms which operate on the tubular level in the presence of high mineralocorticoid activity.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2013
    Keywords: Left atrial pressure ; Sodium excretion ; Adrenal activity ; Plasma renin activity ; Conscious dogs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An experimental increase in left atrial pressure (eLAP↗) leads to an increase in sodium excretion (UNa $$\dot V$$ ). This ‘atrial natriuresis’ is probably involved in the adjustment of sodium balance, but the mechanism is not well understood. The present studies were undertaken to examine 1. the influence of eLAP↗ on plasma renin activity (PRA) and UNa $$\dot V$$ in conscious dogs, and 2. the influence of eLAP↗ on UNa $$\dot V$$ with and without the presence of adrenal glands. Twenty-three female beagle dogs were kept under controlled environmental conditions. They had chronically implanted instruments (purse string around the mitral annulus, catheter in the left atrium, carotid loop; 5 dogs were adrenalectomized). PRA waselevated by a chronic low sodium intake (LSI). When eLAP↗ was performed (+1.0 kPa), PRA decreased by about 50% within at least 60 min. PRA was chronicallylowered by a high sodium intake (HSI). Even under HSI conditions a decrease of PRA could be demonstrated if eLAP↗ was performed (by about 50%). However both HSI and LSI dogs showed a marked increase in UNa $$\dot V$$ if eLAP↗ was performed. After the removal of the adrenals a decrease in glomerular filtration rate was observed (40% of the control values), but eLAP↗ led to a similar increase in UNa $$\dot V$$ to that found in intact dogs (Δ mean 110%). These results indicate that stretching of the left atrium leads to a reduction of tubular sodium reabsorption in a twofold manner: 1st by reduction of PRA, possibly followed by a reduction in aldosterone secretion and 2nd by activating an adrenal independent mechanism of unknown origin. This could be a direct influence of angiotensin II on the tubular reabsorption of sodium. These results are compatible with the hypothesis that reflexes out of the low pressure system are important for the adjustment of sodium balance independent of changes in mineralocorticoid activity.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2013
    Keywords: GFR measurement ; bolus technique ; conscious dogs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The renal clearance of creatinine was measured following orogastric administration in conscious dogs. Values of creatinine clearance were compared with simul taneously determined values of inulin clearance, when urine volume, glomerular filtration rate and volume status were acutely altered by a variety of experimental manoeuvres. At urine volumes greater than 20 μl. min−1 · kg−1, creatinine clearance was not significantly different from inulin clearance. At low urine volumes there was some evidence of creatinine reabsorption. It is concluded that the bolus creatinine technique provides reliable estimates of glomerular filtration rate and is particularly applicable to long-term studies in conscious dogs.
    Type of Medium: Electronic Resource
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