Increase of adenosine content in cerebral cortex of the cat during bicuculline-induced seizure

In order to elucidate whether adenosine may be involved in the increase in cerebral blood flow (CBF) during functional hyperemia, cortical tissue levels of adenosine, inosine and hypoxanthine were measured in the cat following bicuculline (3 mg/kg)-induced seizure. In addition, the subcellular distribution of 5-nucleotidase in the cortex was determined by histochemical techniques. Experiments were performed on anaesthetized and immobilized cats and tissue samples to be analyzed for the different purine compounds were obtained by freezing through the trepanized and non-trepanized skull. Control values for adenosine, inosine and hypoxanthine on the trepanized side were 1.31, 1.12 and 3.79 nmoles/g, respectively. The cortical content of adenosine increased to 3.85 nmoles/g, 15 s after beginning of seizure activity and remained elevated for 20 min. Inosine and hypoxanthine also increased, exhibiting highest values after 20 min. Values for adenosine and lactate were found to be generally higher when analysis was performed from tissue frozen through the intact skull bone. In all experiments the adenosine content correlated with lactate levels. From measurements of plasma concentrations of adenosine and inosine in the sinus sagittalis superior it is concluded that seizure is also accompanied by an enhanced release of adenosine from the brain. Localization of 5-nucleotidase by electron-microscopic cytochemistry revealed that this enzyme is associated almost exclusively with plasma membranes of glial cell membranes including perivascular astrocytes. Thus high concentration of adenosine can be expected to accumulate locally in the brain cortex. In view of the well known increase in CBF during onset of seizure and the time course of adenosine formation, our findings support the view that adenosine may be involved in the initial phase of seizure-induced functional hyperemia of the brain.A preliminary report of this investigation was presented at the 49th Meeting of the German Physiological Society at Göttingen (Pflügers Archiv 373: 74, 1978) and at the first conference of the studygroup for neurochemistry (Hoppe-Seyler's Z. Physiol. Chemie 359: 461–462, 1978)     

Cardiac and regional haemodynamic effects of histamine N-methyltransferase inhibitor metoprine in haemorrhage-shocked rats

Objective and design:The increase in central histamine concentrations after inhibition of histamine N-methyltransferase (HNMT) activity is associated with the reversal of critical haemorrhagic hypotension, therefore the present study examines cardiac and regional haemodynamic effects of HNMT inhibitor metoprine in haemorrhage-shocked rats. Material:Cardiovascular parameters were measured in 72 and central histamine concentrations in 12 male Wistar rats anaesthetised with ketamine/xylazine. Treatment:Metoprine (5, 15 mg/kg) was administered intraperitoneally to normotensive and critically-hypotensive rats with mean arterial pressure (MAP) 20-25 mmHg. Haemorrhage-shocked rats were pre-treated intracerebroventricularly with histamine H₃ receptor agonist R(–)--methylhistamine (10 g) or saline. Methods:MAP, heart rate (HR) and cardiac and regional haemodynamics were monitored within 2 h after treatment, or to death if it occurred earlier. Histamine concentrations were measured using enzyme immunoassay. ANOVA followed by Neuman-Keules test, and Fishers exact test were used to compare the results. Results:Bleeding resulted in an extreme decrease in cardiac index (CI), an increase in total peripheral resistance index (TPRI) and the death of control animals within 30 min. Metoprine induced increases in MAP and HR which were significantly higher in hypotensive than in normotensive animals. The resuscitating effect of metoprine (15 mg/kg) was associated with a rise in CI, a decrease in TPRI, and a 100% survival at 2 h. TPRI changes resulted from decreased renal, hindquarters and mesenteric vascular resistance. R(–)--methylhistamine inhibited metoprine-induced increases in endogenous histamine concentrations in the cerebral cortex (0.89 ± 0.12 vs. 1.25 ± 0.29 nmol/g of wet tissue; P < 0.05), hypothalamus (4.37 ± 0.42 vs. 5.74 ± 0.47 nmol/g of wet tissue; P < 0.01) and medulla oblongata (0.39 ± 0.07 vs. 0.65 ± 0.28 nmol/g of wet tissue; P < 0.05), diminished haemodynamic effects and decreased the survival rate at 2 h to 33% (P < 0.05 vs. the saline-pre-treated group). Conclusions:The results support the hypothesis that histaminergic system activation leads to mobilisation of compensatory mechanisms in haemorrhagic hypotension.Received 24 November 2003; returned for revision 13 January 2004; accepted by A. Falus 3 February 2004     

Simultaneous determination of adenosine, S-adenosylhomocysteine and S-adenosylmethionine in biological samples using solid-phase extraction and high-performance liquid chromatography

A sensitive and rapid method for measuring simultaneously adenosine, S-adenosylhomocysteine and S-adenosylmethionine in renal tissue, and for the analysis of adenosine and S-adenosylhomocysteine concentrations in the urine is presented. Separation and quantification of the nucleosides are performed following solid-phase extraction by reversed-phase ion-pair high-performance liquid chromatography with a binary gradient system. N6-Methyladenosine is used as the internal standard. This method is characterized by an absolute recovery of over 90% of the nucleosides plus the following limits of quantification: 0.25-1.0 nmol/g wet weight for renal tissue and 0.25-0.5 microM for urine. The relative recovery (corrected for internal standard) of the three nucleosides ranges between 98.1 +/- 2.6% and 102.5 +/- 4.0% for renal tissue and urine, respectively (mean +/- S.D., n = 3). Since the adenosine content in kidney tissue increases instantly after the onset of ischemia, a stop freezing technique is mandatory to observe the tissue levels of the nucleosides under normoxic conditions. The resulting tissue contents of adenosine, S-adenosylhomocysteine and S-adenosylmethionine in normoxic rat kidney are 5.64 +/- 2.2, 0.67 +/- 0.18 and 46.2 +/- 1.9 nmol/g wet weight, respectively (mean +/- S.D., n = 6). Urine concentrations of adenosine and S-adenosylhomocysteine of man and rat are in the low microM range and are negatively correlated with urine flow-rate.     

Involvement of endogenous adenosine in ischaemic preconditioning in swine

Adenosine release and the subsequent activation of adenosine receptors are involved in ischaemic preconditioning in dogs and rabbits. In the present study, we investigated whether adenosine also mediates ischaemic preconditioning in swine. Swine were used since, due to the lack of an innate collateral circulation, infarct development in this species most closely resembles that observed in humans. In 36 enflurane-anaesthetized swine the impact of increased adenosine breakdown with exogenous porcine adenosine deaminase (5 IU/ml blood/min) on global and regional myocardial function (sonomicrometry), subendocardial blood flow (ENDO, microspheres) and infarct size (IS, triphenyl tetrazolium chloride staining following 90 min ischaemia and 120 min reperfusion) were analysed. Low-flow ischaemia for 90 min at an ENDO of 0.09±0.04 (mean±SD) ml/min/g caused an IS of 13.2±9.7% (n=8) of the area at risk. Ischaemic preconditioning by a cycle of 10 min low-flow ischaemia followed by 15 min reperfusion prior to the 90-min ischaemic period (ENDO=0.06±0.03 ml/min/g) reduced IS to 2.6±3.0% (n=11, P<0.05). The interstitial adenosine concentration (microdialysis) increased from 1.60±0.87 nmol/ml to above 10 M during ischaemia; with intracoronary adenosine deaminase, the interstitial adenosine concentration fell from 1.65±0.23 to 0.12±0.07 nmol/ml and did not increase during ischaemia. Adenosine deaminase per se did not alter IS after 90 min ischaemia (n=7, ENDO=0.08±0.04 ml/min/g, IS=12.1±6.9%) but abolished the beneficial effect of ischaemic preconditioning (n=10, ENDO=0.06±0.03 ml/min/g, IS=8.8±5.8%). For any given ENDO, IS was significantly reduced in the ischaemic preconditioned group compared with the other three groups. Global and regional myocardial function were comparable among all groups of swine. We conclude that endogenous adenosine mediates ischaemic preconditioning also in swine.     

Compartmentation of cardiac adenine nucleotides and formation of adenosine

Summary After prelabeling the adenine nucleotides (ATP, ADP, AMP) of isolated perfused guinea pig hearts with either¹⁴C-adenine or¹⁴C-adenosine for 35 min, labeled adenosine, inosine, hypoxanthine and cyclic 35-AMP (cAMP) were continuously released into the cardiac perfusate. Determination of the specific activities (SA) of the adenine nucleotides, cAMP, and their breakdown products (adenosine, inosine, hypoxanthine) in tissue and perfusate revealed: Under steady state conditions the SA of adenosine and cAMP in the perfusate were of the same order of magnitude and proved to be many times higher than the SA of the respective precursor adenine nucleotides. This difference was observed regardless whether adenine or adenosine was used as prelabeling substance. The SA of inosine and hypoxanthine in the perfusate were constantly lower than the SA of adenosine. Cardiac ischemia of 6 min, which resulted in a markedly increased formation of adenosine, led to a pronounced decrease in the SA of adenosine released from the heart.Our findings provide evidence that at least two different adenine nucleotide compartments of the heart serve as precursors for the formation of adenosine and cAMP, one characterized by a high, the other by a lower SA. Under normoxic conditions adenosine and cAMP released into the cardiac perfusate are derived mainly from a nucleotide fraction of high SA, which appears to be rather small. During ischemia a second compartment of much lower SA in addition contributes to the formation of adenosine.A preliminary report of part of this work appeared in Biochemistry and Pharmacology of Myocardial Hypertrophy, Hypoxia and Infarction Vol. 7 of Recent advances in studies on cardiac structure and metabolism. (P. Harris, R. J. Bing, A. Fleckenstein, eds.), pp. 171–175. München: Urban & Schwarzenberg 1976A preliminary report of part of this work appeared in Biochemistry and Pharmacology of Myocardial Hypertrophy, Hypoxia and Infarction Vol. 7 of Recent advances in studies on cardiac structure and metabolism. (P. Harris, R. J. Bing, A. Fleckenstein, eds.), pp. 171–175. München: Urban & Schwarzenberg 1976     

Release of histamine from isolated rat hearts during reperfusion is not dependent on length of ischemic insult,or contents of histamine in cardiac tissue

Release of histamine (H) by ischemia-reperfusion injury was investigated in isolated rat hearts (Langendorff model). The effect of 10, 15, 20, 25, 30, 40 and 60 min ischemia (n=10 each) on H in the coronary effluent and in cardiac tissue was studied after 4 min reperfusion. Release of creatine kinase and lactate dehydrogenase in the coronary effluent increased with time of ischemia. Tissue H increased from 95±10 ng/g rat heart (mean±SEM) before ischemia to max 148±10 ng/g after 20 min ischemia (p<0.002), and increased also after 15 (p<0.01), 25 (p<0.01), 25 (p<0.01), and 30 min (p<0.045). H in the coronary effluent increased after 15 (from 16±3 to 26±2 pmol/min,p<0.044), 30 (26±6 pmol/min,p<0.027), and 60 min ischemia (47±6 pmol/min,p<0.0044). Release of H during ischemia-reperfusion is neither dependent on the severity of the ischemic insult, nor on the level of tissue H.     

Mediation by adenosine of bradycardia in rat heart during graded global ischaemia

The role of adenosine as a mediator of the bradycardia associated with graded global ischaemia in rat heart was examined. Hearts were perfused at 37°C in the isovolumic mode with Krebs-bicarbonate medium at 12.0 ml/min/g. After equilibration, the coronary flow was reduced to 0.5, 2.5, or 5.0 ml/min/g for 20 min. Effluent was collected and assayed for adenosine and inosine by HPLC. Heart rate was measured and bipolar electrograms were obtained in severely ischaemic hearts. Basal adenosine release was 124±15 pmol/min/g. Adenosine release increased by approximately 50% in hearts perfused at 5.0 ml/min/g. In hearts perfused at 2.5 and 0.5 ml/min/g, adenosine release increased by approximately 1300 and 2300% respectively. The pattern of adenosine release at 0.5 and 2.5 ml/min/g was phasic, with adenosine release rate increasing to a maximum after about 10 min then dropping to values slightly higher than initial values. Ischaemia produced significant bradycardia and first degree AV block. Adenosine antagonism with 5 m 8-phenyltheophylline blocked up to 25% of this bradycardia and significantly reduced the conduction delay. Adenosine release rate correlated closely with that component of heart rate slowing which was inhibited by 8-phenyltheophylline. It is concluded that adenosine released during graded global ischaemia mediates up to a quarter of the associated bradycardia. The effect of adenosine is phasic. Adenosine acts primarily to depress the sinus pacemaker. First degree AV block also occurs. These effects were only apparent at coronary flow rates below 5.0 ml/min/g.     

IgE-mediated activation of human heartin vitro

We used human cardiac tissue from the right atrial appendages of patients undergoing corrective heart surgery to study content andde novo synthesis of mediators in the human heart. Human heart tissue contained 1.7±0.1 g/g wet weight of histamine (mean±S.E.M.) and spontaneously produced 6-keto-PGF₁ (38.4 ng/g wet weight/min), PGF₂ (1.9 ng/g wet weight/min), PGE (1.7 ng/g wet weight/min) and thromboxane B₂ (T×B₂) (1.7 ng/g wet weight/min). Spontaneous release of PGD₂, leukotriene C₄ and histamine was negligible. Rabbit anti-human IgE (1–10 g/ml) dose-dependently induced the release of histmaine (5 to 15% of the total histamine content) and of PGD₂ (5 to 100 ng/g of wet tissue). The effect of anti-IgE was dose-related and reached a maximum after 30–45 min of incubation. A significant linear correlation (r_s=0.90; p<0.001) was found betweende novo synthesis of PGD₂ and the secretion of histamine induced by anti-IgE challenge of human heart. These results support the concept that PGI₂ is the main, but not the sole, product of arachidonic acid metabolism synthesized by human heartin vitro. Additionally, anti-IgE challenge of human heartin vitro induces the release of histamine and PGD₂. The local concentrations of these mediators appear high enough to play some role in the modulation of several cardiac functionsin vivo.Supported in part by grants from the C.N.R. (83.00430.04 and 84.01756.04), Ministero Sanità and M.P.I. (Rome, Italy).     

Activity of histamine metabolizing and catabolizing enzymes during reperfusion of isolated,globally ischemic rat hearts

Myocardial ischemia-reperfusion injury increases both tissue levels and release of histamine. To study the possible effects of ischemia-reperfusion on histamine metabolism tissue activities of histidine decarboxylase (HDC), histamine N-methyl transferase (HNMT) and diamine oxidase (DAO) were investigated in isolated rat hearts subjected to either 20 min global ischemia and 40 min reperfusion (n=10) or control perfusion (n=8). Histamine in the coronary effluent increased from 21±4 nmol/min (mean ± SEM) before ischemia to 55±5 and 50±7 nmol/min after 4 and 10 min reperfusion (p<0.004 and p<0.004). Tissue HDC activity did not change during observation in any group. HNMT activity was unchanged in controls, but increased from 0.37±0.04 to 0.84±0.18 and 0.96±0.22 pmol methlylhistamine/mg protein hour after 4 and 10 min reperfusion (p<0.008 and p<0.01). DAO decreased similarily in controls and ischemic-reperfused hearts during observation. In conclusion, the previously observed increase of tissue histamine during reperfusion cannot be explained by increased histamine synthesis or decreased histamine catabolism.accepted by W. Lorenz     

Fetal sheep temperatures in utero during cooling and application of triiodothyronine,norepinephrine, propranolol and suxamethonium

Fetal sheep (n=13) were chronically instrumented to measure temperatures in the maternal femoral artery (MAT), the amniotic fluid (AFT), the fetal brown adipose tissue (BFT) and the fetal arterial blood (DAT). Cooling loops were inserted into the amniotic cavity. In 4 fetuses osmotic minipumps delivering triiodothyronine (T3) were implanted subcutaneously. One to seven days after surgery the following results were obtained: 1) During control DAT was 0.59±0.2°C (SD), BFT 0.60±0.24°C and AFT 0.38±0.31°C higher than MAT. T3 levels in treated fetuses were 3.4±1.5 g/l. 2) Infusion of norepinephrine (NE) (5.2±0.9 g/min per kg fetal body weight) with phentolamine tolamine (26.1±4.3 g/min per kg) into a fetal vein did not change temperatures. 3) During cooling (–53±15 W) MAT decreased 0.45±0.3°C, DAT 1.9±0.39°C, BFT 1.61±0.52°C and AFT 4.2±1.8°C. 4) The amniotic fluid was cooled until steady state temperatures were achieved. Then propranolol (26.1±4.3 g/min per kg) or suxamethonium (3±1 mg/kg) were introduced into the fetal vein. No consistent and significant changes of temperatures could be detected. It is concluded that 1) lowering the fetal core temperature by 1.6–1.9°C and its ambient temperature (AFT) by 4.2°C does not induce shivering or non-shivering thermogenesis suppressible by pharmacologic agents, 2) thermogenesis in fetal brown adipose tissue cannot be induced by NE (with or without supplemention of T3). In utero the fetal sheep does not respond to cold stress with an increase of heat production.Supported by Deutsche Forschungsgemeinschaft Schr 165/8-1     

Effects of increasing times of incomplete cerebral ischemia upon the energy state and lipid peroxidation in the rat

 Different times of incomplete cerebral ischemia (2, 4, 6, 8, 10 and 30 min) were induced by bilateral common carotid artery occlusion in anesthetized rats to evaluate the time course of changes in lipid peroxidation and energy metabolism. Analysis of malondialdehyde (used to assess the levels of lipid peroxidation), ascorbic acid, oxypurines, nucleosides, nicotinic coenzymes and high-energy phosphates, was carried out by high-performance liquid chromatography on neutralized perchloric acid extract of brain tissue. Under the present experimental conditions, malondialdehyde, nicotinic coenzymes and ATP catabolites (oxypurines and nucleosides) were affected by increasing times of ischemia, with respect to control sham-operated rats. In particular, the concentration of malondialdehyde, undetectable in control brains, increased from 1.26 nmol/g wet weight after 2 min of carotid clamping to 13.42 nmol/g wet weight at the end of 30 min of incomplete cerebral ischemia. The presence of oxidative stress was further supported by ascorbic acid depletion, which was particularly significant after 10 and 30 min of incomplete ischemia. Carotid clamping provoked an imbalance between energy production and consumption that was evidenced by a reduction in ATP and GTP concentrations and an increase in ATP degradation products such as AMP, oxypurines and nucleosides. A decrement in the sum of adenine nucleotides and the energy charge potential indicated a progressive malfunctioning of energy-producing metabolic cycles. A possible contribution to such a severe change in energy state might be related to depletion of NAD and NADP, particularly noticeable after the longest incomplete brain ischemia times, that should have provoked a consequent lessening of oxido-reductive reactions. Bilateral carotid clamping causes a significant reduction in brain oxygen and substrate supply that results in inhibition of energy metabolism and triggering of oxygen-radical-induced lipid peroxidation. Received: 22 July 1996 / Accepted: 17 January 1997     

Temperature and the energy cost of oscillatory work in teleost fast muscle fibres

Bundles of 20–30 fast muscle fibres were isolated from the abdominal myotomes of the short-horned sculpin (Myoxocephalus scorpius L.). The energy cost of contraction was measured during oscillatory work at 4 °C and 15 °C following treatment with iodoacetate and nitrogen gas to block glycolysis and aerobic metabolism. Isolated fibres were subjected to sinusoidal length changes about in situ resting length and stimulated at a selected phase in the strain cycle. Preliminary experiments with untreated preparations established the strain amplitude and stimulation parameters required to maximize work output over a range of cycle frequencies at 4 °C and 15 °C. Following oscillatory work, treated preparations were rapidly frozen, freeze-dried and the concentrations of phosphocreatine (PCr), creatine, adenosine 5-triphosphate (ATP), adenosine 5- di- and mono-phosphate and inosine 5-monophosphate measured by high performance liquid chromatography. The concentration of PCr declined in proportion to the total work done for up to 64 cycles without a significant change in ATP. Maximum power output was produced at a cycle frequency of 5 Hz at 4 °C (14–18 W/kg) and 17 Hz at 15 °C (23–27 W/kg). The rate of utilization of PCr per cycle was independent of temperature. However, since work per cycle was higher at 4 °C (2.7–3.7 mJ/g wet weight) than 15 °C (1.2–1.6 mJ/g wet weight), the energetic cost of contraction decreased with increasing temperature.     

Effect of isometric exercise on catecholamines in the coronary circulation

Summary Arterial and coronary sinus blood levels of catecholamines, adenosine 3, 5-cyclic monophosphate (c-AMP) and lactate were measured during isometric exercise in fourteen patients. In no patient did lactate production occur. Mean resting total catecholamine levels both arterial (0.53±0.07 ng/ml; 2.94±0.38 nmol/l) and coronary sinus (0.4±0.08 ng/ml; 2.22±0.44 nmol/l), did not change significantly on exercise. Coronary sinus c-AMP levels fell on exercise from 11.5±0.8 nmol/l (resting) to 9.9±0.8 nmol/l (exercise) (P<0.01) with an arterial-coronary sinus difference of 1.2 nmol/l (P<0.01) on exercise.Our findings suggest that isometric exercise does not normally result in excessive cardiac symphathetic activity.     

Einfluß von Prostaglandin E1 auf den Aminosäurestoffwechsel des menschlichen Skelettmuskels

Summary The influence of an intraarterial infusion of PGE₁ on the amino acid metabolism of human sceletal muscle was examined in healthy volunteers using the forearm technique. A continuous increase of perfusion from 2.9±0.1 ml/100 g × min to 5.4±1.5 after 60 min could be observed. Muscular amino acid balances were not changed after 30 min but significantly after 60 min of PGE₁ infusion. Muscular release of most of the amino acids was reduced or shifted to an uptake. The accumulated balance of the amino acids showed a significant increase from –21.9 to +33.2 nmol/ 100 g × min after 60 min. Thus the infusion of PGE₁ led to an inhibition of muscular proteolysis and/or to a stimulation of proteosynthesis. In view of the fact that kinines are released during exercise and are partially effective via prostaglandine liberation, the protein-anabolic effect of exercise might be explained by action of prostaglandins.

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Abkürzungsverzeichnis PGE₁ Prostaglandin E₁ - AVD arterio-venöse Differenz (mol/l) - A arterielle Konzentration (mol/l) - V venöse Konzentration (mol/l) - DB Durchblutung (ml/100 g × min)     

Effects of atrial natriuretic peptide on systemic and renal hemodynamics and renal excretory function in patients with chronic renal failure

Summary We examined the effects of 60 min-hANP infusion (24 ng/min/kg) on glomerular filtration rate (GFR), renal blood flow (RBF), cardiac index (CI) and blood pressure (BP) in 8 patients with chronic renal failure (CRF) with GFR ranging from 18 to 80 ml/min/1.73 m² and in 8 control (C) subjects with normal renal function. Basal plasma levels of ANP and cGMP were elevated in CRF (ANP: 60.6±9.1 vs 13.6±1.9 pmol/l,p<0.05; cGMP: 14.3±2.9 vs 6.6±1.1 pmol/ml,p<0.05). During ANP infusion, peak levels of cGMP were higher in CRF than in C (27.5±3.2 vs. 17.3±1.3 pmol/ml,p<0.05). During ANP infusion, GFR increased in CRF by 70.7±4.2% from 34.5±6.8 to 57.4±9.9 ml/min/1.73m² (p<0.001) as compared to 16.2±1.4% in C (p<0.001 vs CRF). RBF increased in CRF by 43.6±6.4% and in C by 3.1±1.2% (p<0.01). Basal urinary sodium excretion (U_NaV) was slightly lower in CRF than in C but rose to the same level in both groups during ANP infusion. In CRF, as opposed to C, U_NaV remained elevated above baseline after the end of the infusion. The effect of ANP on fractional sodium excretion (FE_Na), however, was more pronounced in C. Basal FE_Na was higher in CRF (12.8±2.5% vs 2.4±1.5% in C,p<0.001), FE_Na remained elevated at 180% over baseline in C sixty minutes after cessation of ANP infusion, while it had returned to baseline in CRF. During ANP infusion, CI increased in CRF after 30 min from 2.91±0.08 to 3.12±0.091/min/m² (p<0.001) and in C from 3.20±0.11 to 3.39±0.13 l/min/m² (p< 0.05). Mean arterial BP was higher in CRF and its decrease was greater than in C (21.1±2.7% vs 9.1±1.0%,p<0.001). In patients with CRF GFR, RPF, and CI remained significantly elevated and BP was still significantly decreased 60 min after ANP infusion. Total peripheral vascular resistance (TPR) was elevated in CRF and declined during ANP infusion in both CRF and C. The decline of TPR was sustained and more pronounced in CRF than in C. Renal vascular resistance (RVR) was high in CRF and dropped by nearly 50% during ANP infusion, whereas only a moderate decline in RVR during ANP application was observed in C. Thus, exogenous ANP had greater and prolonged effects on systemic hemodynamics and renal function in CRF than in C. They may be due to higher levels of ANP following ANP infusion and appear to be mediated by a more sustained formation of the second messenger cGMP.Abbreviations ANP atrial natriuretic peptide - CRF chronic renal failure; - GFR glomerular filtration rate - FF filtration fraction - ERPF effective renal plasma flow - ERBF effective renal blood flow - BP blood pressure - MAP mean arterial blood pressure - HR heart rate - SV stroke volume - CO cardiac output - CI cardiac index - TPR total peripheral resistance - RVR renal vascular resistance - U_NaV urinary sodium excretion - FE_Na fractional sodium excretion - PRA plasma renin activity - ECFV extracellular fluid volume - PAH paminohippuric acid Dedicated to Prof. Dr. med. F. Krück on the occasion of his 70th birthday     

Renal blood flow after bilateral ureteral ligation in the rat

Renal blood flow (RBF) in rat was measured by using a noncannulating electromagnetic flowmeter. In the sham control rats, anesthetized with Inactin, RBF averaged 7 ml/min/g KW when arterial blood pressure was above 110 mm Hg. Auroregulation of RBF was observed when the arterial blood pressure was in the range of 110–150 mm Hg. Glomerular filtration rate (GFR), measured by polyfructosan clearance, averaged 1.08 ml/min/g KW. In experimental rats with 24 h of bilateral ureteral ligation (BUL), RBF averaged 38% of control value. During 1/2–3 h following release of the left ureteral occlusion, RBF increased to 60% of control value. The autoregulatory ability of the damaged kidney was reduced during BUL and did not improve after releasing occlusion. During the post-obstructive period arterial blood pressure remained stable. Thus, a high total renal vascular resistance was responsible for the depressed RBF. GFR in these rats averaged only 9% of control value. The reduction in RBF alone does not explain the drastic reduction in GFR in this model of renal failure.     

Influence of seeding density and dynamic deformational loading on the developing structure/function relationships of chondrocyte-seeded agarose hydrogels

Chondrocytes cultured in agarose hydrogels develop a functional extracellular matrix. Application of dynamic strain at physiologic levels to these constructs over time can increase their mechanical properties. In this study, the effect of seeding density (20 and 60×10⁶ cells/ml) on tissue elaboration was investigated. Higher seeding densities increased tissue properties in free-swelling culture, with constructs seeded at 20 and 60×10⁶ cells/ml reaching maximum values over the 63 day culture period of aggregate modulus H _A: 43±15 kPa, Youngs modulus E _Y: 39±3 kPa, and glycosaminglycan content [GAG]: 0.96%±0.13% wet weight; and H _A: 58±12 kPa, E _Y: 60±5 kPa, and [GAG]: 1.49% ± 0.26% wet weight, respectively. It was further observed that the application of daily dynamic deformational loading to constructs seeded at 20×10⁶ cells/ml enhanced biochemical content (150%) and mechanical properties (threefold) compared to free-swelling controls by day 28. However, at a concentration of 60×10⁶ cells/ml, no difference in mechanical properties was found in loaded samples versus their free-swelling controls. Multiple regression analysis showed that the mechanical properties of the tissue constructs depend more strongly on collagen content than GAG content; a finding that is more pronounced with the application of daily dynamic deformational loading. Our findings provide evidence for initial cell seeding density and nutrient accessibility as important parameters in modulating tissue development of engineered constructs, and their ability to respond to a defined mechanical stimulus. © 2002 Biomedical Engineering Society. PAC2002: 8717-d, 8719Rr     

Glucose,insulin and lipid parameters in 10,000 m running

Summary Thirteen conditioned athletes were studied before and 5 min after running 10,000 m. This distance was run in an average of 41±4 min. All runners lost weight and accompanying this weight loss was an increase in the serum osmolality in the six runners in which it was measured. There was a significant increase in serum glucose (96±11 mg-% before run; 170±48 mg-% after run) and this increase was inversely correlated with running time. There was also a small, but significant, increase in serum insulin (15±2 U/ml before run; 19±4 U/ml after run). There was no consistent effect of running 10,000 m on serum cholesterol and triglyceride levels and on plasma lipoprotein electrophoresis patterns.     

The role of augmented breaths (sighs) in bronchial asthma attacks

Summary In an attempt to test the hypothesis whether adenosine is involved in the regulation of coronary flow, adenosine, inosine and hypoxanthine were measured in the effluent perfusate and in the tissue of isolated guinea pig hearts under various experimental conditions. In addition, the release of¹⁴C-adenosine,¹⁴C-inosine and¹⁴C-hypoxanthine was determined after prelabeling cardiac adenine nucleotides with¹⁴C-adenine.The decrease in coronary resistance induced by hypoxic perfusion (30% and 20% in the gas phase) and during autoregulation was associated with a considerable increase in the release of adenosine, inosine and hypoxanthine. Under both conditions the concentrations of adenosine in the effluent perfusate were clearly within the coronary vasodilating range of exogenously administered adenosine. The tissue content of adenosine also increased significantly when the perfusion pressure was reduced. The release of¹⁴C-adenosine closely paralleled the changes in coronary resistance during hypoxic perfusion, autoregulation and during reactive hyperemia. The specific activity of adenosine in the effluent perfusate, however, decreased substantially upon reduction of the oxygen supply to the heart, indicating that the release of¹⁴C-adenosine does not provide an absolute measure of total adenosine release by the heart.Our data indicate that the greater part of the adaptive changes of vascular resistance during hypoxia and autoregulation can be attributed to adenosine which is formed at an enhanced rate under these conditions. However, other factors might be involved as well.A preliminary report of these studies was given at the VI. Annual Meeting of the International Study Group for Research in Cardiac Metabolism, Freiburg i. Br., September 1973 and appeared in Recent advances in studies on cardiac structure and metabolism, Vol. 7, Editors: P. Harris, R. J. Bing, and A. Fleckenstein, pp. 171–175. Urban & Schwarzenberg 1976     

Effects of a small bolus dose of ANF in healthy volunteers and in patients with volume retaining disorders

Summary Thirty-seven patients with volume-retaining disorders (liver cirrhosis with ascites,n=8; heart failure NYHA III–IV,n=12; endstage renal failure,n=17) and twelve healthy age-matched controls were given a small dose (33 g) of hANF (human atrial natriuretic factor). We tested the resulting hemodynamic and renal effects as well as the effect on plasma cyclic GMP levels and compared them with the properties of platelet ANF receptors. The ANF injection evoked an increase in cyclic GMP plasma levels of 19.3±2.2 nM in healthy controls. This increase tended to be smaller in the cirrhosis group (15.5±3.3 nM) and in the heart failure group (16.8±2.3 nM) than in the dialysis group (20.5±2.5 nM). The invasion rates of cyclic GMP were comparable in all groups, but the evasion rates increased more in the heart failure and endstage renal failure groups (27.9±7.7 min and 26.1±3.4 min, respectively) than in the cirrhosis and control groups (14.9±1.9 min and 14.2±1.9 min, respectively). Patients with endstage renal failure and congestive heart failure showed a smaller decrease in diastolic blood pressure than controls and patients with liver cirrhosis. Renal actions of ANF were diminished in cirrhosis and heart failure patients. Binding capacities of platelet ANF receptors were higher in the control group (12.2±1.5 receptors/cell) than in the patient groups (cirrhosis, 7.8±1.2; endstage renal failure, 8.0±0.9; heart insufficiency, 8.0±1.0 receptors/ cell), with no differences among the patient groups. Binding affinities were not significantly different. Correlation analysis showed that the relationship between the actions of ANF and the increases in plasma cyclic GMP levels is loose and cannot predict the hemodynamic or renal effects of exogenous ANF in a given patient. Although the behavior of plasma cyclic GMP levels fails to predict the responsiveness of the body to ANF in a given patient, it does reflect the differences between the patient groups and the control group. In contrast, we found no correlation between the properties of platelet ANF receptors and ANF action.Abbreviations ANF atrial natriuretic factor - cyclic GMP guanosine 3,5-monophosphate - NYHA New York Heart Association This work was part of the doctoral thesis of K. Gottmann This study was supported by the Deutsche Forschungsgemeinschaft (DFG Ge 399/3-2 and We 1130/1-1)