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  Background & Objectives: Formation of myelin depends on maturation and development of the axonal cytoskeleton andmitochondria. Collagen gel can specifically play role in the regulation and development of axonal cytoskeleton.

  Methods: This research is an experimental study in which forty eight male rats (200-250g) were used. After axotomy, 1 cm segment of the sciatic nerve in rats was removed, and the gap was then bridged by one of the four following methods: polyvinylidene fluoride or PVDF + Collagen gel, Autograft, sham and control. Sciatic nerve was studied by electron microscope by the end of the 4^th week and the 12^th week.

  Results: By the end of the 4^th week after the regeneration the number of unmyelinated axons in autograft and Collagen Gel was not significant, by the end of the 12^th week, the number of unmyelinated axons in autograft group was superior to that of nerve growth factor group (P<0.01). After 12 weeks of regeneration, microtubular density values of normal and autograft groups were not statistically different. The cristae of axonal mitochondria in experimental groups are orientate parallel with its long dimension.

  Conclusion: The results of study indicated that because of its positive effect on the growth and development of microtubules and mitochodria, collagen Gel combination with PVDF can be used to repair peripheral nerve injuries.

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Background & objectives: Tea is a hyperaccumulator of fluoride and chronic fluoride intake is associated with multiple negative health outcomes. In this study, six brands of commercially available black and green tea were selected and the fluoride level in tea infusions tested using an ion-selective electrode method.
Methods: In this experimental study, the fluoride contents were determined using  ion-selective electrode (Mettler Toledo, USA) in four types of black tea and two types of green tea at different brewing time (3,5,15,30,60 and 120 min). The amount of tea fluoride at any time was investigated by repeated measure ANOVA and two-way ANOVA.
Results: Repeated measure ANOVA analysis showed that fluoride release for green and black tea increased as increased brewing time (p<0.05). Based on the two-way ANOVA and Bonferroni test results, the mean of fluoride concentrations was high in B black tea in all brewing time. E green tea, D black tea, F green tea, A and C black tea released less fluoride respectively p≤0.05.
Conclusion: The results of this study showed that the fluoride content of black and green tea in different companies was different. In regard to the impact of the cultivation site and the plant characteristics which the tea is made, companies should include enough information about their product to inform consumers. The amount of fluoride in the all examined tea increases after 3 and 120 min of brewing.