Factors influencing the regional haemodynamic responses to methanandamide and anandamide in conscious rats

Background and purpose:

In vitro evidence suggests that metabolism of anandamide by cyclooxygenase-2 (COX-2) may be more important when the primary metabolic pathway [i.e. fatty acid amide hydrolase (FAAH)] is inhibited. Thus, the first aim of the present study was to assess the effects of COX-2 and/or FAAH inhibition, on the cardiovascular actions of anandamide. The second aim was to compare the effects of anandamide with those of the metabolically stable analogue (i.e. methanandamide) and investigate mechanisms involved in responses to the latter in conscious rats.

Experimental approach:

Rats were chronically instrumented for recording blood pressure, heart rate and renal, mesenteric and hindquarters vascular conductances in the freely moving state.

Key results:

Inhibition of FAAH with URB597 (cyclohexycarbamic acid 3′-carbamoyl-biphenyl-3-yl-ester) augmented the haemodynamic actions of anandamide, but there was no effect of COX-2 inhibition with parecoxib, either in the absence or the presence of URB597. Methanandamide caused CB₁ receptor-mediated renal and mesenteric vasoconstriction and evoked β₂-adrenoceptor-mediated hindquarters vasodilatation.

Conclusions and implications:

No evidence for an involvement of COX-2 in the systemic cardiovascular actions of anandamide could be demonstrated. Vasoconstrictor actions of methanandamide were shown to involve CB₁ receptors, whereas no involvement of CB₁ receptors in such actions of anandamide has been shown. However, β₂-adrenoceptor-mediated hindquarters vasodilatation, independent of CB₁ receptors, observed here with methanandamide, has previously been seen with anandamide and differs from previous results with other synthetic cannabinoids for which the response was CB₁ receptor-dependent. Thus, mechanisms underlying the cardiovascular actions of endocannabinoids and synthetic analogues appear to be agonist-specific.     

Comparison of inhibitors of superoxide generation in vascular smooth muscle cells

Background and purpose:

We compared the dose-dependent reductions in cellular superoxide anion (O₂⁻) by catalytic agents: superoxide dismutase (SOD), polyethylene glycol (PEG)-SOD and the nitroxide 4-hydroxy-2,2,6,6,-tetramethylpiperidine-1-oxyl (tempol) with uncharacterized antioxidants: 5,10,15,20-tetrakis (4-sulphonatophenyl) porphyrinate iron (III)(Fe-TTPS), (-)-cis-3,3′,4′,5,7-pentahydroxyflavane (2R,3R)-2-(3,4-dihydroxyphenyl)-3,4-dihydro-1(2H)-benzopyran-3,5,7-triol (-epicatechin), 2-phenyl-1,2-benzisoselenazol-3(2H)-one (ebselen) and N-acetyl-L-cysteine (NAC) with the spin trap nitroblue tetrazolium (NBT) and with the vitamins or their analogues: ascorbate, α-tocopherol and 6-hydroxy-2,5,7,8-tetramethylkroman-2-carboxy acid (trolox).

Experimental approach:

O₂⁻ was generated in primary cultures of angiotensin II-stimulated preglomerular vascular smooth muscle cells from spontaneously hypertensive rats and detected by lucigenin-enhanced chemiluminescence.

Key results:

SOD, PEG-SOD, NAC and tempol produced a similar maximum inhibition of O₂⁻ of 80–90%. -Epicatechin, NBT, ebselen and Fe-TTPS were significantly (P < 0.0125) less effective (50–70%), whereas trolox, α-tocopherol and ascorbate had little action even over 24 h of incubation (<31%). Effectiveness in disrupted and intact cells was similar for the permeable agents, PEG-SOD and tempol, but was enhanced for SOD. Generation of O₂⁻ was increased by NAC and NBT at low concentrations but reduced at high concentrations.

Conclusions and implications:

Maximum effectiveness against cellular production of O₂⁻ requires cell membrane permeability and catalytic action as exemplified by PEG-SOD or tempol. NAC and NBT have biphasic effects on O₂⁻ production. Vitamins C and E or analogues have low efficacy.     

Acute morphological sequelae of photodynamic therapy with 5-aminolevulinic acid in the C6 spheroid model

Objective Aminolevulinic acid (ALA)-mediated photodynamic therapy (PDT) may represent a treatment option for malignant brain tumors. We used a three-dimensional cell culture system, the C6 glioma spheroid model, to study acute effects of PDT and how they might be influenced by treatment conditions. Methods Spheroids were incubated for 4 h in 100 μg/ml ALA in 5% CO₂ in room air or 95% O₂ with subsequent irradiation using a diode laser (λ = 635 nm, 40 mW/cm², total fluence 25 J/cm²). Control groups were “laser only”, “ALA only”, and “no drug no light”. Annexin V-FITC, a marker used for detection of apoptosis, propidium iodide (PI), a marker for necrotic cells and H 33342, a chromatin stain, were used for morphological characterization of PDT effects by confocal laser scanning and fluorescence microscopy. Hematoxylin–eosin staining and TdT-FragEL (TUNEL) assay were used on cryosections. Growth kinetics were followed for 8 days after PDT. Results PDT after incubation in 5% CO₂ provided incomplete cell death and growth delay in spheroids of >350 μm diameter. However, complete cell death and growth arrest occurred in smaller spheroids (<350 μm). Incubation in 95% O₂ with subsequent PDT resulted in complete cell death and growth arrest regardless of spheroid size. In incompletely damaged spheroids viable cells were restricted to spheroid centers. The rate of cell death in all control groups was negligible. Cell death was accompanied by annexin/PI costaining, but there was also evidence for annexin V-FITC staining without PI uptake. Conclusions PDT of experimental glioma results in rapid and significant cell death that could be verified as acute necrosis immediately after irradiation. This effect depended on O₂ concentration and spheroid size.     

高压氧综合治疗糖尿病足的临床疗效观察

糖尿病足(diabetic foot,DF)是常见的糖尿病慢性合并症之一,也是导致糖尿病人截肢致残的主要原因.近年来,糖尿病患病率逐年增高,使糖尿病足的患病率也呈逐年上升的趋势.     

Sumatriptan blocks spreading depression in isolated chick retina

Spreading depression is a neurohumoral phenomenon that has been related to the pathophysiology of migraine. The recently introduced 5HT_1D agonist anti-migraine compound sumatriptan blocks neurogenic extravasation and induces cerebral vasoconstriction, but the actual mechanism of action against migraine remains obscure. Retinal spreading depression (RSD) velocity has been measured in isolated chick retinas in the presence of 0.05-2.00:nM sumatriptan. This drug reversibly blocks RSD in a concentration-dependent manner. Since the preparation is blood-vessel free, this effect must be related to the nervous tissue.     

Cause of signal loss in MR images of old hemorrhagic lesions

Old hemorrhagic lesions in the brain are characteristically surrounded by a band of hemosiderin-containing tissue. This region is typically of low signal intensity on long-echo-time (TE) radio-frequency (RF) spin-echo magnetic resonance (MR) images and on gradient-echo MR images. To determine the cause of signal loss in this band, the authors measured the signal that arises from imaging such a region with use of an RF spin-echo technique with a 180 degrees pulse incrementally displaced from TE/2. The incremental loss of signal was small. Using an agar phantom containing iron particles, the authors also showed that signal loss results primarily from diffusion in magnetic gradients. They conclude that most signal loss in the dark band surrounding areas of late-stage hemorrhage arises from diffusion in areas of magnetic inhomogeneity.