Y E Karakullukçu

Publications of Y E Karakullukçu

• Movement-related cortical potentials: their relationship to the laterality, complexity and learning of a movement.

  Authors: T Demiralp, S Karamürsel, Y E Karakullukçu, N Gökhan

  The International journal of neuroscience. 04/1990; 51(1-2):153-62.

  Movement-related cortical potentials (MRCPs) to self-paced unilateral movements of different laterality, complexity and practice level were recorded from 14 healthy subjects using the EMG onset asMovement-related cortical potentials (MRCPs) to self-paced unilateral movements of different laterality, complexity and practice level were recorded from 14 healthy subjects using the EMG onset as the trigger. The amplitudes at certain time points and slopes of linear regression lines fitted to 3 main shifts have been evaluated. In the early phase of MRCP the potential and slope values were symmetrically distributed around the midline maximum, which indicates that this part of MRCP can not originate from the primary motor area, which is in a contralateral relation with the movement, but from secondary motor areas (SMA and premotor areas). The changes in the voltage levels and slopes of this phase due to the changes in laterality, complexity and practice level of the movement show the relation of this activity with the abstract characteristics of the movement. The decrease of voltages and slope values in the later phases of MRCP in the complex task, which is replaced by higher voltages and slopes after a certain learning period was evaluated as a result of inhibition of associative movements via reafferent feedback signals occurring often in the first stages of learning period.

• Changes in cyclic nucleotides during the calcium paradox in the isolated rat heart.

  Authors: Y E Karakullukçu, T Ozçelik, N Gökhan

  Pflügers Archiv : European journal of physiology. 01/1988; 410(6):657-63.

  Reperfusion of hearts with a Ca2+-containing medium after a perfusion period in Ca2+-free medium results in irreversible cell damage (calcium paradox). In this investigation we have studied coronaryReperfusion of hearts with a Ca2+-containing medium after a perfusion period in Ca2+-free medium results in irreversible cell damage (calcium paradox). In this investigation we have studied coronary flow and cyclic AMP and cyclic GMP levels after several periods of Ca2+-free perfusion in isolated rat hearts. We also investigated the effects of papaverine (Pap), noradrenaline (NA), acetylcholine (ACh) and absence of inorganic phosphate during Ca2+-free perfusion on coronary flow (CF) and cyclic nucleotide levels. Inability of the heart to recover contractile activity with development of contracture during the reperfusion period was accepted as indicative of the calcium paradox. Ca2+-free perfusion alone and NA and absence of inorganic phosphate during the Ca2+-free perfusion period increased CF, whereas Pap and ACh decreased it. However, only Ca2+-free perfusion and NA elevated cyclic AMP. On the other hand, Pap and ACh increased cyclic GMP (with a transient rise of cyclic AMP in Pap infusion), and absence of inorganic phosphate decreased both cyclic AMP and cyclic GMP. Pap, ACh and absence of phosphate prevented the calcium paradox. Our study suggests that increased cyclic AMP during the Ca2+-free perfusion may contribute, with the other factors, to the occurrence of the calcium paradox.