The origin of quantal size variation: vesicular glutamate concentration plays a significant role

Fusion of a single vesicle induces a quantal response, which is critical in determining synaptic strength. Quantal size varies at most synapses. Its underlying mechanisms are not well understood. Here, we examined five sources of variation: vesicular glutamate concentration ([Glu]v), vesicle volume, ultrafast fusion pore closure, the postsynaptic receptor, and the location between release and the postsynaptic receptor cluster at glutamatergic, calyx of Held synapses. By averaging 2.66 million fusion events from 459 synapses, we resolved the capacitance jump evoked by single vesicle fusion. This capacitance jump, an indicator of vesicle volume, was independent of the amplitude of the miniature EPSC (mEPSC) recorded simultaneously at the same synapses. Thus, vesicle volume is not the main source of mEPSC variation. The capacitance jump was not followed by submillisecond endocytosis, excluding ultrafast endocytosis as a source of variation. Larger mEPSCs were increased to a lesser extent by presynaptic glutamate dialysis, and reduced to a lesser extent by gamma-DGG (gamma-D-glutamylglycine), a competitive AMPA receptor blocker, suggesting that a higher glutamate concentration in the synaptic cleft contributes to the large size of mEPSCs. Larger mEPSCs were not accompanied by briefer rise times, inconsistent with the prediction by, and thus arguing against, the scenario that larger mEPSCs are caused by a shorter distance between the release site and the postsynaptic receptor cluster. In summary, the different amplitudes of mEPSCs were mainly attributable to release of vesicles having similar volumes, but different glutamate amounts, suggesting that [Glu]v is a main source of quantal size variation.

Radiation safety survey on a flattening filter-free medical accelerator

Dose rates at several locations outside a treatment room were measured for 6 and 18 MV photon beams from a Varian Clinac 21EX accelerator operated with and without a flattening filter. Also, dose rates in the treatment room due to activation were measured at 18 MV. An analysis of the measured data is presented. The results suggest that substantial reduction in doses outside the treatment room and lower activation can be achieved with a flattening-filter free accelerator.

The evidence base of complementary and alternative therapies in depression

BACKGROUND

Depression is one of the leading indications for using Complementary and Alternative Medicine (CAM). This paper reviews the evidence of efficacy of different types of CAM in depression with the aim of identifying the highest level of evidence.

METHODS

We conducted literature searches restricted to the English language for studies on CAM as monotherapy in depression. All papers were reviewed by two researchers and the evidence was ranked according to a widely referenced hierarchy of evidence.

RESULTS

19 papers formed the final review. We found Grade 1 evidence on the use of St. John's wort, Tryptophan/5-Hydroxytryptophan, S-adenosyl methionine, Folate, Inositol, Acupuncture and Exercise in Depressive disorders, none of which was conclusively positive. We found RCTs at the Grade 2 level on the use of Saffron (Herbal medicine), Complex Homoeopathy and Relaxation training in Depressive disorders, all of which showed inconclusive results. Other RCTs yielded unequivocally negative results. Studies below this level yielded inconclusive or negative results.

LIMITATIONS

Searches were restricted to the English language. Our list of CAM approaches may not have been comprehensive. We excluded studies on the use of CAM as an adjunctive treatment and this review aimed to identify only the highest level of evidence.

CONCLUSIONS

None of the CAM studies show evidence of efficacy in depression according to the hierarchy of evidence. The RCT model and the principles underlying many types of CAM are dissonant, making its application in the evaluation of those types of CAM difficult. The hierarchy of evidence we used has limited utility in grading trials of CAM.

Structural, spectral, linear and nonlinear optical properties of new nonlinear optical L-histidinium trichloroacetate crystals

Single crystals of a new histidinium salt: L-histidinium trichloroacetate {abbreviated as LHTCA; [(C(3)N(2)H(4))CH(2)CH(NH(3))(CO(2))](+)CCl(3)COO(-)} were grown by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in a non-centrosymmetric space group P2(1) of monoclinic system with cell parameters a=5.4505(18) A, b=25.769(8) A, c=9.210(2) A and beta=99.98(2) degrees. The vibrational structure of the compound confirms the presence of various functional groups in the molecule. The UV-vis-NIR spectrum shows a good transparency in the whole of the region from ultraviolet to near IR. The Kurtz powder SHG measurement confirms the frequency doubling of the crystal. Thermal behaviour of the crystals has been investigated by DSC analysis. These preliminary results suggest that LHTCA crystal can act as a potential and promising candidate for frequency doubling applications even from the near UV region to the near IR.