MM-22

Characteristics of an MM 22 medical microtron 21 MV photon beam.[Pubmed:3922930]

Int J Radiat Oncol Biol Phys. 1985 Jun;11(6):1221-4.

Beam quality, surface doses, depths of maximum dose, peak dose rates, beam profiles, and central axis percentage depth doses of a medical microtron's 21 MV photon beam were measured. The half-value layer of lead was 1.35 cm, the half-value layer of water was 23 cm, and the nominal acceleration potential was 17.7 MV. For a 10 X 10 cm2 field at 100 cm SSD, the maximum dose occurred at a depth of 3 g X cm-2 and the surface dose was 18% of the maximum. The highest dose rate at isocenter was approximately 800 cGy X min-1. The worst horns on beam profiles occurred at a depth of 5 cm for the 35 X 35 cm2 field where the dose rate 4 cm from the edge of the beam was 3% higher than that on the central ray. No horns were apparent for fields 25 X 25 cm2 or smaller.

Post-dural puncture headache in young orthopaedic in-patients: comparison of a 0.33 mm (29-gauge) Quincke-type with a 0.7 mm (22-gauge) Whitacre spinal needle in 200 patients.[Pubmed:1539481]

Acta Anaesthesiol Scand. 1992 Jan;36(1):58-61.

The incidence of postdural puncture headache (PDPH) following spinal anaesthesia with a 0.33 mm (29-gauge) and two types of 0.7 mm (22-gauge) Whitacre needles was investigated in 400 patients less than 40 years old. The incidence of PDPH was 2% in the 0.33 mm group, and 3.5% in the 0.7 mm group. Headache of other origin was seen in 12 patients (6%) in the 0.33 mm and in five patients (2.5%) in the 0.7 mm group. These differences were not significant. The failure rate was significantly higher in the 0.33 mm group (8.5% vs 2%) than in the 0.7 mm group (P less than 0.05). It is concluded that the 0.33 mm needle is associated with a low incidence of PDPH in young patients, but has a significantly higher failure rate than the Whitacre 0.7 mm needle, which is also a suitable choice in this age-group because of its ease of handling and the low incidence of PDPH.

Characteristics of an MM 22 medical microtron 6-MV photon beam.[Pubmed:6439997]

Med Phys. 1984 Nov-Dec;11(6):862-5.

Instrument AB Scanditronix offers a 6-MV therapeutic photon beam as an option with the 22-MeV medical microtron (MM 22). The method of acceleration, target assembly, and use of two flattening filters produce beams having several characteristics (e.g., field flatness, penetration, and intensity) that are superior to many 6-MV Linac beams. Characteristics of the microtron's 6-MV photon beams including quality, surface dose, depth of maximum dose, peak dose rates, peak scatter factors, central axis percentage depth doses, tissue maximum ratios, and beam profiles are described.

Pitfalls and solutions in assaying anandamide transport in cells.[Pubmed:20447929]

J Lipid Res. 2010 Aug;51(8):2435-44.

Nonspecific binding of anandamide to plastic exhibits many features that could be mistaken as biological processes, thereby representing an important source of conflicting data on the uptake and release of this lipophilic substance. Herein, we propose an improved method to assay anandamide transport, by using glass slides (i.e., coverslips) as physical support to grow cells. Although the results obtained using plastic do not differ significantly from those obtained using glass, the new procedure has the advantage of being faster, simpler, and more accurate. In fact, the lack of aspecific adsorption of anandamide to the glass surface yields a lower background and a higher precision and accuracy in determining transport kinetics, especially for the export process. Remarkably, the kinetic parameters of anandamide uptake obtained with the old and the new procedures may be similar or different depending on the cell type, thus demonstrating the complexity of the interference of plastic on the transport process. In addition, the novel procedure is particularly suitable for visualization and measurement of anandamide transport in intact cells by using a biotinylated derivative in confocal fluorescence microscopy.

Molecular identification of albumin and Hsp70 as cytosolic anandamide-binding proteins.[Pubmed:19481477]

Chem Biol. 2009 Jun 26;16(6):624-32.

The cellular uptake and the intracellular synthesis/degradation of anandamide are crucial steps for controlling its extracellular level and the duration of its activity. Although the biosynthesis and breakdown of anandamide are well understood, little is known about the mechanisms underlying its intracellular transport. Here, we investigated the presence of a potential carrier-mediated trafficking of anandamide within the cytosol, using a biotinylated analog as a tool to catch by affinity chromatography anandamide-interacting proteins. The identity of two of these anandamide-binding proteins, Hsp70 and serum albumin, was determined by mass spectrometry, confirmed by western blotting and confocal microscopy, and further validated through an anandamide-binding assay. These findings suggest that the trafficking of anandamide from the plasma membrane to the internal compartments of a cell occur via a nonvesicular mechanism mediated by cytosolic carriers.

Characterization of biotin-anandamide, a novel tool for the visualization of anandamide accumulation.[Pubmed:18316795]

J Lipid Res. 2008 Jun;49(6):1216-23.

Anandamide (N-arachidonoylethanolamide; AEA) acts as an endogenous agonist of both cannabinoid and vanilloid receptors. During the last two decades, its metabolic pathways and biological activity have been investigated extensively and relatively well characterized. In contrast, at present, the effective nature and mechanism of AEA transport remain controversial and still unsolved issues. Here, we report the characterization of a biotinylated analog of AEA (b-AEA) that has the same lipophilicity of the parent compound. In addition, by means of biochemical assays and fluorescence microscopy, we show that b-AEA is accumulated inside the cells in a way superimposable on that of AEA. Conversely, b-AEA does not interact or interfere with the other components of the endocannabinoid system, such as type-1 and type-2 cannabinoid receptors, vanilloid receptor, AEA synthetase (N-acylphosphatidylethanolamine-hydrolyzing phospholipase D), or AEA hydrolase (fatty acid amide hydrolase). Together, our data suggest that b-AEA could be a very useful probe for visualizing the accumulation and intracellular distribution of this endocannabinoid.

Evidence for the intracellular accumulation of anandamide in adiposomes.[Pubmed:18213445]

Cell Mol Life Sci. 2008 Mar;65(5):840-50.

Anandamide is a lipid messenger that carries out a wide variety of biological functions. It has been suggested that anandamide accumulation involves binding to a saturable cellular component. To identify the structure(s) involved in this process, we analyzed the intracellular distribution of both biotinylated and radiolabeled anandamide, providing direct evidence that lipid droplets, also known as adiposomes, constitute a dynamic reservoir for the sequestration of anandamide. In addition, confocal microscopy and biochemical studies revealed that the anandamide-hydrolase is also spatially associated with lipid droplets, and that cells with a larger adiposome compartment have an enhanced catabolism of anandamide. Overall, these findings suggest that adiposomes may have a critical role in accumulating anandamide, possibly by connecting plasma membrane to internal organelles along the metabolic route of this endocannabinoid.