We investigated the hypothesis that increased intracellular [Na + ] i in heart failure contributes to preservation of SR Ca 2+ load which may become particularly evident at slow heart rates.[Na + ] i in SBFI-loaded myocytes from rabbits with pacing-induced heart failure (PHF) was significantly higher at each frequency as compared to Sham-operated animals. Furthermore, PHF rabbits demonstrated reduced SR Ca 2+ -ATPase protein levels (À 37%, p < 0.04) but unchanged Na + /Ca 2+ exchanger protein levels. At 0.25 Hz, isometric force was similar in cardiac trabeculae from PHF rabbits as compared to control (PHF, 3.6 T 1.3; Sham, 4.4 T 0.6 mN/mm 2 ). Rapid cooling contractures (RCCs) were unchanged indicating preserved SR Ca 2+ load at this frequency. In Sham, isometric twitch force increased with rising frequencies to 29.0 T 2.8 mN/mm 2 at 3.0Hz ( p < 0.05) as compared to 0.25 Hz. RCCs showed a parallel increase by 186 T 47% ( p < 0.01). In PHF, frequency-dependent increase in force (15.8 T 4.7 mN/mm 2 at 3.0 Hz) and RCCs (increase by 70 T 40%) were significantly blunted.Thus, in PHF in rabbits SR Ca 2+ load is preserved at low frequencies despite decreased SR Ca 2+ -ATPase expression. This may result from [Na + ] i -dependent changes in Na + /Ca 2+ exchanger activity.
25Summary Cisternal cerebrospinal fluid (CSF) was tapped from anaesthetized guineapigs by an improved technique. This method allowed repeated weekly punctures of the same animal without any cellular or neurochemical changes in CSF or changes in behaviour. About 60% of the punctures produced enough CSF (30-330 J.d) with no or a sufficiently low blood contamination for neurochemical analysis. The CSF space in the spinal canal, cisterna magna and basal cisterns was demonstrated by myelography.The analysis of cerebrospinal fluid (CSF) of guineapigs for characterization of immunologic events in the brain or changes in blood-CSF barrier function is now of increasing importance since chronic relapsing experimental allergic encephalomyelitis of the strain 13 guinea pig is regarded as a model system for multiple sclerosis (Wisniewski, Lassmann, Brosman, Mehta, Lidsky & Madrid, 1982). For characterization of neurochemical similarities between diseases, analysis of CSF is necessary. For puncture of CSF different methods have been reported, as reviewed by Jones & Robinson (1981). The animals were killed after a single puncture or treated by more or less complicated surgical procedures for cannulation.None of the methods for CSF puncture reported so far (literature cited in Jones & Robinson, 1981) allow repeated punctures of the same animal over a long time interval without the use of surgical procedures.Materials and methods Strain 13 guinea pigs were obtained from Rep Instituten GO-TNO/Rejswijk, Netherlands. The anaesthetics were Ketanest (50 mg/ml ketamine, Parke Davis & Co, Pontypool, UK) and Rompun (2% xylazine, Bayer/Leverkusen, FRG). The contrast medium metrizamide (Amipaque, Schenng AG/Berlin) was diluted to 6'75/8'1 ml. 23-gauge needles with a transparent hub were from Terumo (neolus No 14).
Previously published methods of venous puncture in guinea pigs did not provide reliable venous access for more than a few minutes, and therefore surgical intervention was necessary to cannulate the femoral or external jugular vein or the vena cava. In the present report cannulation of the Vena saphena lateralis via the Vena plantaris lateralis or of the Vena saphena medialis is described by inserting a 22 gauge teflon catheter. These catheters are commercial products. The method is timesaving and inexpensive. Successful cannulation was accomplished in 34 of 35 guinea pigs. No lethal incidents occurred.
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