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Evidence of rat tail tendon proteoglycans at emission field scanning electron microscopy
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Recovery of pre- and postsynaptic activity in frog semicircular canal after gentamicin treatment
No full textInner ear hair cells of lower vertebrates regenerate following physical or chemical insults. In the present study we aimed to define the damage and recovery of the pre and postsynaptic activity in the frog crista ampullaris after ototoxic insult with the antibiotic, gentamicin.
Frogs were treated with a single dose of gentamicin sulphate (GM-5mM) administered intraotically. The presynaptic activity was monitored by recording in isolated canal preparations the endoampullar (receptor) potential (Adc). The postsynaptic activity was monitored by recording the resting and evoked spike activity from the whole ampullar nerve and from single canal afferents.
We found that Adc was abolished 5 days after GM administration and that it progressively recovered close to control values 20 days after treatment. These resuits well fitted with the morphological damage and recovery of hair cells in the crista epithelium. Consistently with the presynaptic damage, the canal afferent activity was abolished 5 days after GM treatment, while the recovery of the background and the evoked afferent activity showed a different sequence. Background activity reappeared 7-8 days after GM treatment and in this period it was not driven by canal mechanical stimulation. In addition, background activity reached control values around 15 days post-treatment, while the evoked activity was detected 9 days after GM treatment and appeared normal close to 20 days. Intracellular recordings from single canal afferents confirmed the above mentioned results and revealed that the EPSP evoked discharge, together with the spike activity, reached normal values close to 20 days post-treatment.
The present resuits show that the frog semicircular canal rapidly and completely recovers its pre- and postsynaptic function following severe ototoxic insult and that during the recovery, the afferent activity at rest becomes functional and mature before the mechano-transduction function
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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