Comparison of paired-pulse facilitation of AMPA and NMDA synaptic currents in the lateral amygdala

Stimulating thalamic fibers exiting from the internal capsule evokes a glutamatergic excitatory postsynaptic current (EPSC) recorded in vitro with patch electrodes in neurons of the rat lateral amygdala (LA). The purpose of this study is to compare paired-pulse facilitation (PPF), a form of short-term synaptic plasticity, of AMPA and NMDA receptor-mediated EPSCs. Analysis of PPF at this synapse is important since, in fear-conditioned animals, PPF reflects an enhanced transmitter release but the amplitude of only AMPA EPSCs is facilitated. PPF magnitude of the composite EPSC is a result of both AMPA and NMDA receptor activation; however, the characteristics of AMPA and NMDA PPF are dissimilar. Specifically, the NMDA EPSC shows greater PPF (NMDA PPF) than does the AMPA EPSC whether measuring the NMDA PPF magnitude in an AMPA antagonist/Mg(2+)-free solution or by subtracting the AMPA EPSC from the composite EPSC in normal Mg(2+). Presynaptic NMDA receptors neither influence AMPA PPF nor account for the difference between the NMDA and AMPA PPF. Another difference was that removal of inhibitory tone enhanced AMPA PPF, while it had mixed effects on NMDA PPF. Furthermore, AMPA PPF was independent of stimulus intensity and postsynaptic voltage, unlike the NMDA PPF. Another dissimilarity was that the amplitudes of pairs of AMPA EPSCs were not correlated, suggesting presynaptic mechanisms. In contrast, NMDA PPF was dependent on stimulus intensity and postsynaptic voltage and the amplitudes of paired NMDA EPSCs had a positive correlation, suggesting a postsynaptic influence. Both AMPA and NMDA PPF were influenced by GABA inhibition and this could be a factor in the magnitude disparity. These data show that AMPA and NMDA PPF have different characteristics and contribute to the composite PPF in the thalamic to lateral amygdala pathway.     

A simple and inexpensive method to routinely produce customized neck supports for patient immobilization during radiotherapy

Accurate and reproducible patient positioning is fundamental to the success of fractionated radiotherapy. Poor patient positioning could result in geographic misses. We have recently reported on an improved method of customized face mask production using laser surface scanning. In this report, we sought to identify and develop a method to routinely make customized neck supports for patients prescribed radiotherapy to the brain or head and neck regions. We identified a potentially suitable product—sealed packs containing two liquids that produce expanding polyurethane foam when mixed—and developed a method for their use. The neck supports are inexpensive and simple to produce (taking less than 5 min of radiation therapist labour). We assessed the customized neck supports in several ways. The effect on setup accuracy was assessed by comparing two consecutive cohorts of patients. Statistically significant differences favouring the customized neck supports included a reduced total displacement error (mean 3.4 vs. 2.1 mm) and a reduced left–right setup error (mean 1.8 vs. 1.1 mm). This is consistent with the greater support provided by the customized neck supports. This method could easily be undertaken by other departments.     

Laparoscopic management of the acute abdomen, appendix, and small and large bowel.

The application of laparoscopy for diagnosis and treatment of the acute abdomen, appendicitis, and in the management of small and large bowel diseases is a natural step for the general surgeon. Acute appendicitis is a common general surgical problem that can be difficult to diagnose. Laparoscopy is an excellent aid in diagnosis and laparoscopic appendectomy can be performed easily. The controversy of incidental appendectomy and recommendations for management are discussed. Small and large bowel diseases and their surgical treatment now can be managed laparoscopically thus decreasing morbidity and mortality. The uses and limitations of these techniques are discussed as well as future trends in treatment.     

Another mechanism for creating diversity in gamma-aminobutyrate type A receptors: RNA splicing directs expression of two forms of gamma 2 phosphorylation site.

Diversity of gamma-aminobutyrate type A (GABAA) receptors has recently been proposed to be achieved by assembly of receptor subtypes from a multitude of subunits (alpha 1-6, beta 1-3, gamma 1-2, and delta) encoded by different genes. Here we report a further mechanism for creating GABAA receptor diversity: alternative RNA splicing. Two forms of bovine gamma 2 subunit cDNA were isolated (gamma 2S and gamma 2L) that differed by the presence or absence of a 24-base-pair (8-amino acid) insertion in the cytoplasmic domain between the third and fourth putative membrane-spanning regions. Polymerase chain reaction from RNA demonstrated that the two forms of gamma 2 subunit are expressed in bovine, human, and rat brain. Sequencing of genomic DNA clones encoding the gamma 2 subunit demonstrated that the 24-base-pair insert is organized as a separate exon. Analysis of the sequence of the 8-amino acid insert revealed that it contains a protein kinase C consensus phosphorylation site. Expression of the large cytoplasmic loop domains of gamma 2S and gamma 2L in Escherichia coli, followed by phosphorylation of the recombinant proteins by protein kinase C, demonstrated that gamma 2L, but not gamma 2S, could be phosphorylated. Thus the two forms of gamma 2 subunit differ by the presence or absence of a protein kinase C phosphorylation site. This mechanism for creating GABAA receptor diversity may allow differential regulation of the function of receptor subtypes.