Sherine Wasfi Mikhail Abdelmissih

Raw data on exopodite beating in the first three developmental stages of the lobster Homarus gammarus were collected and analysed for key beating parameters. The analysis was computer assisted and the main procedures used are described. Beating patterns are the same in all three stages and are usually very regular although perturbations do occur (figures 1, 2). When beating stops the deceleration and subsequent re-acceleration is very rapid (figure 1) and limb movement sequences usually start posteriorly and move forwards (figures 1, 2d). Ipsilateral phase relations are generally maintained at 0.4-0.6 (figures, 3,4) and while the coupling between adjacent exopodites is usually stronger than for those further apart various deviations from this are occasionally seen (figure 5). No significant correlation between the ipsilateral phase relations of adjacent exopodites and base cycle duration was detected for any of the stages (figure 6). Contralateral phase relations undergo a constant progression (figures 7, 9) and this was found to be due to a heterodyne effect (figure 8) also described as gliding coordination. The powerstroke/returnstroke ratio for all stages was approximately 0.5 (figure 10) and no significant correlation was found with cycle duration (figure 11). The only substantial difference between the three larval stages which was noted was that of cycle duration, the cycles of stage III being shorter than those of the first two stages. The exopodite beating pattern was discussed in context with other metachronously cycling systems in arthropods and the implications of the present study discussed.

Background: It is estimated that 10% of the population suffer a single convulsive episode during their lifetime. Epilepsy is the second most common chronic neurological disorder after stroke affecting 0.5% of the population in developed countries and 1.5-2% in developing countries.
Aim: The target of this investigation was to find out the effect of phosphodiesterase-4 inhibitor (PDE4I), rolipram (Rol), on the isoniazid (INH)-induced seizures and the penty- lenetetrazole (PTZ) kindled rats, in comparison to the benzo- diazepine (BZ) agonist, diazepam (DZ).
Methods: Acute seizures were produced by intraperitoneal (i.p.) administration of INH, 250 mg/kg, either alone or 10 minutes before either i.p. 10mg/kg DZ, or i.p. 0.5mg/kg Rol. Kindling model was produced by repeated i.p. administration of 30mg/kg PTZ, every other day, for one month and every two days for another month, either alone or followed, ten minutes later, by i.p. 10mg/kg DZ or 0.5mg/kg Rol. Following drug(s) administration, seizure severity score, electroenceph- alography, biochemical measurement of gamma-aminobutyric acid (GABA), glutamate, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in brain homogenate were done.
Results: In the acute INH-induced seizures, single i.p.
0.5 mg/kg Rol effects were opposite to DZ. These included unchanged seizure severity, significantly reduced power of the fast waves (ß and a ), significantly increased brain GABA/glutamate ratio, together with no significant change in cAMP/cGMP ratio. While in kindled rats, i.p. 0.5mg/kg Rol administration on chronic basis, showed similar effects, but less than DZ, in the form of significantly improved seizure severity score, accompanied by reduced power of S wave with unchanged a and 0 waves, significantly increased GABA/ glutamate ratio, together with unchanged cAMP/cGMP ratio.
Conclusion: Based on this preclinical study, caution with the use of rolipram in case of INH-induced seizures. In contrast to this preliminary warning, rolipram might be able, on chronic basis, to aid in the management of epilepsy, though less than DZ,These changes did not correspond to cyclic nucleotides changes.