Pflügers Archiv

Subcutaneous and perirenal adipose tissue blood flows (ATBF) were measured by the133Xe washout method before, during and after 4 h exercise on a bicycle ergometer. The load corresponded to about 50% of $$\dot V_{{\text{O}}_{\text{2}} }$$ max (i.e. about 1.7l/min). Subcutaneous and perirenal ATBF increased at an average to 3–400 and 700% of their initial control values respectively. In six of nine measuring sites ATBF remained increased in the hour following work. During work plasma glycerol concentrations increased 8 fold. The core temperature increased 0.9°C, skin temperature did not change significantly. During passive elevation of body temperature (core temperature +1.5°C; skin temperature +3°C) neither subcutaneous ATBF nor plasma glycerol concentrations changed significantly. It is concluded that the increase in subcutaneous ATBF during exercise is not a reaction to increased body temperature.

 The effect of nitric oxide (NO) donors on high-voltage-activated Ca2+ channels in insulin-secreting RINm5F cells was investigated using the patch-clamp technique in the whole-cell configuration. Sodium nitroprusside (SNP, 2–400 µM) induced a dose-dependent reduction in Ba2+ currents with maximal inhibition of 58%. The IC50 for SNP was 45 µM. A different NO donor, (±)S-nitroso-N-acetylpenicillamine (SNAP, 500 µM), also produced a 50% decrease in current amplitude. When 200 µM SNP was administered together with the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidozoline-1-oxyl-3-oxide (carboxy-PTIO, 300 µM), the Ba2+ current inhibition was lowered to 7%. Administration of 500 µM 8-bromoguanosine 3′:5′-cyclic monophosphate sodium salt (8-Br-cGMP) mimicked the effects of SNP, causing a comparable decrease (56%) in peak-current amplitude. When soluble guanylyl cyclase was blocked by 10 µM 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ), the inhibitory effect of 200 µM SNP was reduced from 39% to 15%. The SNP-induced current decrease was 36% of controls after the blockade of L-type Ca2+ channels and 30% in the presence of 2.5 µM ω-conotoxin-MVIIC. These data indicate that NO inhibits both L-type and P/Q-type Ca2+ channels in RINm5F cells, probably by an increase in the intracellular levels of cGMP. NO may then significantly influence the Ca2+-dependent release of hormones from secretory cells as well as that of neurotransmitters from nerve terminals.

Mitogenic factors are known to stimulate the Na+/H+-exchanger (NHE), leading to cytosolic alkalinization and/or cell swelling. Conversely, a hallmark of apoptosis is cell shrinkage and CD95-induced apoptosis has been reported to be paralleled by cytosolic acidification. To assess whether the CD95-receptor regulates NHE activity in Jurkat T-lymphocytes, we performed conventional BCECF fluorescence measurements and SNARF flow cytometric analysis (FACS). The recoveries from acidifications following application of butyrate or a NH3 pulse were both abolished by a specific NHE-inhibitor, HOE694, indicating that they fully depend on NHE activity. Thus they were taken as a measure of NHE activity. CD95-receptor stimulation caused a cytosolic acidification and blunted the recovery from acidification following application of butyrate or a NH3 pulse. Moreover, the NHE-dependent alkalinization following osmotic cell shrinkage was almost abolished by CD95-receptor stimulation. As apparent from the effect of osmotic cell shrinkage, inhibition of the NHE by CD95-receptor stimulation was absent in Lck56-deficient J-CaM1.6 cells and restored by retransfection of J-CaM1.6-cells with Lck56. CD95-receptor stimulation led within 4 h to a decrease of cellular ATP which could contribute to NHE inhibition. Treatment of Jurkat cells with the NHE inhibitor HOE694 accelerated CD95-induced DNA fragmentation. In conclusion, CD95-receptor stimulation inhibits NHE activity through a mechanism that depends directly or indirectly on the activation of the Src-like kinase Lck56. This effect contributes to CD95-induced cytosolic acidification, DNA fragmentation and cell shrinkage.

Es wird eine Apparatur beschrieben, die eine präzise und in weiten Grenzen variable Reizung der Netzhaut mit bewegten visuellen Mustern erlaubt. Sie ist nach dem Perimeter-Prinzip aufgebaut. Die bewegten Reizmuster werden mit Hilfe eines Motors und Zehnganggetriebes durch ein homogen ausgeleuchtetes Reizfeld am Pol einer Halbkugel bewegt. Ein Auge des Versuchstieres befindet sich im Mittelpunkt dieser Halbkugel. Durch eine Rahmenkonstruktion, die um eine vertikale und horizontale Achse durch den Mittelpunkt der Hemisphäre gedreht werden kann, ist das Reizmuster so verstellbar, daß jeder Punkt in der oberen Hälfte des Gesichtsfeldes des Frosches erreichbar ist.

Dem Eintritt der Galvanonarkose bei absteigend mit Gleichstrom — unter Wasser oder in Luft — durchströmten Fröschen geht ein Exzitationsstadium mit allgemeinenklonisch-tonischen Krämpfen voraus. Dieses Exzitationsstadium kann durch Stromverstärkung geschwächt oder ganz unterdrückt werden und tritt in kurz aufeinander folgenden Durchströmungen (5 bis 10 Min. Pause) mit immer geringer werdender Stärke auf, um schließlich überhaupt fort zu bleiben; die eigentliche, lähmende Wirkung des absteigenden Stromes, die Galvanonarkose, ist jedoch auch in vielen aufeinander folgenden Durchströmungen unverändert zu erhalten und tritt auch immer bei der gleichen Schwellenstromstärke ein. Die vorliegende Untersuchung ergab, daß die Krämpfe des Exzitationsstadiums mit den Krämpfen während eineraufsteigenden Durchströmung („galvanischer Krampf“) nicht gleichgesetzt werden können, da die letzteren reintonischer Art sind. Es zeigte sich weiter, daß Enthirnung von Fröschen — thermischer Querschnitt mittels Kurzwellen-Wärmebändern im Bereich des Zwischenhirnes — das Auftreten des Exzitationsstadiums verhindert oder doch ganz beträchtlich hemmt; das Exzitationsstadium muß daher auf einer erregenden Wirkung des absteigenden Stromes in den übergeordneten Zentren beruhen. Da der galvanische Krampf im aufsteigenden Strom dagegen auch bei enthirnten Tieren auszulösen ist, zeigt sich damit neuerlich ein grundstzlicher Unterschied in der Wirkung des absteigenden und aufsteigenden Stromes im Zentralnervensystem. Ähnlich wie Enthirnung wirken auf das Exzitationsstadium auch kleine Dosen von Stoffen, welche die zentrale Erregbarkeit dämpfen oder lähmen.

Malignant hyperthermia (MH) is associated with abnormal regulation of intracellular calcium in skeletal muscle fibers. Cyclic adenosine diphosphate-ribose (cADPR) is an endogenous metabolite of β-NAD+ that induces Ca2+ release from intracellular stores in many tissues. Microinjection of cADPR (0.5 or 1 µM) increased the intracellular resting Ca2+ concentration ([Ca2+]i) in intact swine skeletal muscle in a dose-dependent manner. However, the increase in [Ca2+]i was greater in malignant-hyperthermia-susceptible (MHS) fibers than in non-susceptible (MHN) fibers. Incubation of muscle fibers in low external Ca2+ solution or in the presence of L-type Ca2+ channel entry blockers, or intracellular microinjection of heparin or ruthenium red did not modify the effect of cADPR on [Ca2+]i. Dantrolene (50 µM), a known inhibitor of intracellular Ca2+ release, decreased resting [Ca2+]i and prevented the cADPR-induced increase in [Ca2+]i. These results provide evidence: (1) for the existence of Ca2+ release mechanisms occurring via non-ryanodine or inositol 1,4,5-trisphosphate (InsP 3) receptor mechanisms; (2) that MHS skeletal muscles exhibit a higher responsiveness to cADP-ribose-induced release of Ca2+ and (3) that the ability of dantrolene to block cADP-ribose-induced release of Ca2+ could be related to its pharmacologic effect on resting [Ca2+]i.