Fibrous histiocytoma of tendon sheath of the hand.

The hand is not uncommonly afflicted by Fibrous histiocytoma/Giant Cell tumour of tendon sheath, an enigmatic and loosely-defined clinical entity only occasionally entering into the literature. The 26 cases in this clinico-pathologic review were obtained by a computerised search of histological files at the Dept. of Pathology, UCHG. Twice as many of these were female, more often in their fourth decade of life. The condition has a propensity for the long digits, more often the volar aspect and roughly evenly distibuted over each of the joints. Resection of these neoplasia is tedious due to it's propensity to grow between local anatomical structures contributing to a high recurrence rate. Interestingly it rarely figures in guesses at pre-operative diagnosis although the second commonest cause of a benign superficial hand mass after ganglion. We suggest that if this condition is suspected, referral to a specialist hand surgeon in the first instance is wise.

The role of N-methyl-D-aspartate receptors in the generation of short-term potentiation in the rat hippocampus.

The effects of stimulus intensity and the N-methyl-D-aspartate (NMDA) antagonist 2-amino-5-phosphonovalerate (AP5) were studied on the induction of short-term potentiation (STP) and long-term potentiation (LTP) in CA1 of the rat hippocampal slice. A tetanus of very weak intensity stimuli produced STP, and also LTP providing the stimuli were applied in the form of a series of high frequency trains rather than one continuous train. Increasing the intensity of the stimuli to just threshold for spike initiation produced larger amplitude STP and LTP. AP5 strongly inhibited the STP as well as the LTP produced by a series of high frequency trains, indicating a large component of this STP was generated by activation of NMDA receptors. A further residual component of STP in AP5, which was associated with a decrease in paired pulse facilitation, is probably generated by a presynaptic increase in the probability of transmitter release.

The effects of external calcium on long-term potentiation in the rat hippocampal slice.

Extracellular excitatory postsynaptic potentials (EPSPs) were recorded from the stratum radiatum of CA1 of the rat hippocampal slice. The effect of altering the external Ca concentration was studied on the amplitude of the low frequency evoked EPSP preceding and following the production of long-term potentiation (LTP). The double logarithmic plot of the relationship between the EPSP amplitude and external Ca had a maximum slope of 2.1, implying Ca cooperativity in transmitter release. The production of LTP did not alter the slope. The amplitude of LTP was found to be highly dependent on the external Ca concentration, with LTP increasing from a 5% increase in the EPSP amplitude in 0.8 mM Ca, to a 65% increase in the EPSP amplitude in 2.0 mM Ca.

Enhancement of long-term potentiation by the calcium channel agonist Bayer K8644 in CA1 of the rat hippocampus in vitro.

The effect of the Ca agonist BAY K8644 was studied on long-term potentiation (LTP) of extracellular excitatory postsynaptic potentials in the stratum radiatum of CA1 of the hippocampus in vitro. LTP was evoked by brief trains of high-frequency stimulation applied to the stratum radiatum of CA1. 0.5% Ethanol, the vehicle used to dissolve BAY K8644, reduced LTP from 43% to 15%. An amount of 15 microM BAY K8644, in 0.5% ethanol, enhanced LTP from 13% in the ethanol control to 57%. The Ca channel antagonist verapamil did not alter control LTP, but did inhibit the potentiating action of BAY K8644 on LTP. It is postulated that the enhancement of LTP by BAY K8644 may occur through enhancement of Ca influx through voltage-dependent Ca channels.