Mechanisms of the antinociceptive action of (?) Epicatechin obtained from the hydroalcoholic fraction of Combretum leprosum Mart & Eic in rodents

ABSTRACT: BACKGROUND: The mechanisms of the antinociceptive activity of () epicatechin (EPI), a compound isolated from the hydroalcoholic fraction of Combreum leprosum Mart & Eicher. METHODS: were assessed in the model of chemical nociception induced by glutamate (20 mumol/paw). To evaluate the mechanisms involved, the animals , male Swiss mice (25-30 g), received EPI (50 mg/kg p.o.) after pretreatment with naloxone (2 mg/kg s.c. opioid antagonist), glibenclamide (2 mg/kg s.c. antagonist K + channels sensitive to ATP), ketanserin (0.3 mg/kg s.c. antagonist of receptor 5-HT2A), yoimbine (0.15 mg/kg s.c. alpha2 adrenergic receptor antagonist), pindolol (1 mg/kg s.c. 5-HT1a/1b receptor antagonist), atropine (0.1 mg/kg s.c. muscarinic antagonist) and caffeine (3 mg/kg s.c. adenosine receptor antagonist), ondansetron (0.5 mg/kg s.c. for 5-HT3 receptor) and L-arginine (600 mg/kg i.p.). RESULTS: The antinociceptive effect of EPI was reversed by pretreatment with naloxone and glibenclamide, ketanserin, yoimbine, atropine and pindolol, which demonstrates the involvement of opioid receptors and potassium channels sensitive to ATP, the serotoninergic (receptor 5HT1A and 5HT2A), adrenergic (receptor alpha 2) and cholinergic (muscarinic receptor) systems in the activities that were observed. The effects of EPI, however, were not reversed by pretreatment with caffeine, L-arginine or ondansetron, which shows that there is no involvement of 5HT3 receptors or the purinergic and nitrergic systems in the antinociceptive effect of EPI. In the Open Field and Rotarod test, EPI had no significant effect, which shows that there was no central nervous system depressant or muscle relaxant effect on the results. CONCLUSIONS: This study demonstrates that the antinociceptive activity of EPI in the glutamate model involves the participation of the opioid system, serotonin, adrenergic and cholinergic.     

A student-centred,problem-based curriculum: 5 years' experience.

In 1987, the University of Sherbrooke''s school of medicine implemented a student-centred, problem-based learning (PBL) curriculum. The experience of the first 5 years is reviewed; program goals, the schedule of learning activities, the instructional format and assessment of student learning are described. The new program is more demanding of teachers and requires better faculty training in pedagogy. No new financial resources have been available. The preclinical reform has led to revision of the clerkship, where sessions on clinical reasoning are now based on the PBL philosophy. Student reactions to the program are reported. The Sherbrooke experience has demonstrated that it is both possible and feasible to shift from a traditional to a problem-based curriculum.     

Identification of a major soluble protein in mitochondria from nonphotosynthetic tissues as NAD-dependent formate dehydrogenase.

In many plant species, one of the most abundant soluble proteins (as judged by two-dimensional polyacrylamide gel electrophoresis) in mitochondria from nongreen tissues is a 40-kD polypeptide that is relatively scarce in mitochondria from photosynthetic tissues. cDNA sequences encoding this polypeptide were isolated from a lambda gt11 cDNA expression library from potato (Solanum tuberosum L.) by screening with a specific antibody raised against the 40-kD polypeptide. The cDNA sequence contains an open reading frame of 1137 nucleotides whose predicted amino acid sequence shows strong homology to an NAD-dependent formate dehydrogenase (EC 1.2.1.2) from Pseudomonas sp. 101. Comparison of the cDNA sequence with the N-terminal amino acid sequence of the mature 40-kD polypeptide suggests that the polypeptide is made as a precursor with a 23-amino acid presequence that shows characteristics typical of mitochondrial targeting signals. The identity of the polypeptide was confirmed by assaying the formate dehydrogenase activity in plant mitochondria from various tissues and by activity staining of mitochondrial proteins run on native gels combined with antibody recognition. The abundance and distribution of this protein suggest that higher plant mitochondria from various nonphotosynthetic plant tissues (tubers, storage roots, seeds, dark-grown shoots, cauliflower heads, and tissues grown in vitro) might contain a formate-producing fermentation pathway similar to those described in bacteria and algae.     

THE [14C]DEOXYGLUCOSE METHOD FOR THE MEASUREMENT OF LOCAL CEREBRAL GLUCOSE UTILIZATION: THEORY,PROCEDURE, AND NORMAL VALUES IN THE CONSCIOUS AND ANESTHETIZED ALBINO RAT1

Abstract— A method has been developed for the simultaneous measurement of the rates of glucose consumption in the various structural and functional components of the brain in vivo. The method can be applied to most laboratory animals in the conscious state. It is based on the use of 2-deoxy-D-[¹⁴C]glucose ([¹⁴C]DG) as a tracer for the exchange of glucose between plasma and brain and its phosphorylation by hexokinase in the tissues. [¹⁴C]DG is used because the label in its product, [¹⁴C]deoxyglucose-6-phosphate, is essentially trapped in the tissue over the time course of the measurement. A model has been designed based on the assumptions of a steady state for glucose consumption, a first order equilibration of the free [¹⁴C]DG pool in the tissue with the plasma level, and relative rates of phosphorylation of [¹⁴C]DG and glucose determined by their relative concentrations in the precursor pools and their respective kinetic constants for the hexokinase reaction. An operational equation based on this model has been derived in terms of determinable variables. A pulse of [¹⁴C]DG is administered intravenously and the arterial plasma [¹⁴C]DG and glucose concentrations monitored for a preset time between 30 and 45min. At the prescribed time, the head is removed and frozen in liquid N₂-chilled Freon XII, and the brain sectioned for autoradiography. Local tissue concentrations of [¹⁴C]DG are determined by quantitative autoradiography. Local cerebral glucose consumption is calculated by the equation on the basis of these measured values. The method has been applied to normal albino rats in the conscious state and under thiopental anesthesia. The results demonstrate that the local rates of glucose consumption in the brain fall into two distinct distributions, one for gray matter and the other for white matter. In the conscious rat the values in the gray matter vary widely from structure to structure (54-197 μmol/100 g/min) with the highest values in structures related to auditory function, e.g. medial geniculate body, superior olive, inferior colliculus, and auditory cortex. The values in white matter are more uniform (i.e. 33–40 μmo1/100 g/min) at levels approximately one-fourth to one-half those of gray matter. Heterogeneous rates of glucose consumption are frequently seen within specific structures, often revealing a pattern of cytoarchitecture. Thiopental anesthesia markedly depresses the rates of glucose utilization throughout the brain, particularly in gray matter, and metabolic rate throughout gray matter becomes more uniform at a lower level.     

Stable carbon isotope ratios of lipid biomarkers of sulfate-reducing bacteria

We examined the potential use of natural-abundance stable carbon isotope ratios of lipids for determining substrate usage by sulfate-reducing bacteria (SRB). Four SRB were grown under autotrophic, mixotrophic, or heterotrophic growth conditions, and the delta13C values of their individual fatty acids (FA) were determined. The FA were usually 13C depleted in relation to biomass, with Deltadelta13C(FA - biomass) of -4 to -17 per thousand; the greatest depletion occurred during heterotrophic growth. The exception was Desulfotomaculum acetoxidans, for which substrate limitation resulted in biomass and FA becoming isotopically heavier than the acetate substrate. The delta13C values of FA in Desulfotomaculum acetoxidans varied with the position of the double bond in the monounsaturated C16 and C18 FA, with FA becoming progressively more 13C depleted as the double bond approached the methyl end. Mixotrophic growth of Desulfovibrio desulfuricans resulted in little depletion of the i17:1 biomarker relative to biomass or acetate, whereas growth with lactate resulted in a higher proportion of i17:1 with a greater depletion in 13C. The relative abundances of 10Me16:0 in Desulfobacter hydrogenophilus and Desulfobacterium autotrophicum were not affected by growth conditions, yet the Deltadelta13C(FA - substrate) values of 10Me16:0 were considerably greater during autotrophic growth. These experiments indicate that FA delta13C values can be useful for interpreting carbon utilization by SRB in natural environments.     

Detection of an arbuscular mycorrhizal fungus in roots of different plant species with the PCR.

PCR was used with the primer pair VANS1-NS21 to detect the arbuscular mycorrhizal fungus Glomus intraradices (commercial inoculum source) on roots of lettuce, zinnia, leek, pepper, and endive plants. The appropriate amplification product was obtained directly from roots without DNA extraction and purification.