Samples, brain

A sample (brain half) was treated exactly as if used in a calcium efflux experiment except no radioactivity or Rf power was used. Following this procedure, which required about 55 min, the tissue was placed in an oxygen electrode cell containing 1.6 mL of the medium (pH 7.8) at 37° C, and the rate of oxygen consumption was measured (7,23). 

Collection and Treatment of Brain Samples Brains were obtained form animals, which were sacrificed 3 h post oral dosing of the drug. Brains of untreated (control) animals were used in order to obtain the blank brain homogenates for calibration standard and quality control samples (control animals received the pure vehicle, 0.2 % w/v agarose gel). 

Flow injection analysis determination methods have been used in various foods such as seafood, meat, and fruit, and also in beverages (wine, cider, etc.). Also, many of these methods could be applied to other biological samples (brain tissue, plasma) in addition to food matrices. Flow injection analysis determination of BAs has been successfully correlated with traditional methods. 

By far the most important sulfide is CS2, a colourless, volatile, flammable liquid (mp — 111.6°, bp 46.25°, flash point —30°, autoignition temperature 100°, explosion limits in air 1.25 50%). Impure samples have a fetid almost nauseating stench due to organic impurities but the purified liquid has a rather pleasant ethereal smell it is very poisonous and can have disastrous effects on the nervous system and brain. CSt was formerly manufactured by direct reaction of S vapour and coke in He or steel retorts at 750 1000°C but, since the early 1950s, the preferred synthesis has been the catalysed reaction between sulfur and natural gas ... 

Human GAL1 receptor mRNA has been detected in multiple cell and tissue samples including Bowes melanoma cells, brain, gastrointestinal tract (from esophagus to rectum), heart, prostate, and testes. Rat GAL1 mRNA was detected in olfactory regions, many hypothalamic nuclei (including supraoptic nucleus),... 

Brain et al. [137] reported a tandem mass spectrometry (MS-MS) procedure by which a direct measurement from an n-pentane extract of a surfactant is possible. This procedure is excellent from the standpoint of sensitivity and simplicity of sample preparation but is not commonly applied because of the need of an MS-MS instrument. 

Methyl parathion was determined in dog and human serum using a benzene extraction procedure followed by GC/FID detection (Braeckman et al. 1980, 1983 DePotter et al. 1978). An alkali flame FID (nitrogen-phosphorus) detector increased the specificity of FID for the organophosphorus pesticides. The detection limit was in the low ppb (pg/L). In a comparison of rat blood and brain tissue samples analyzed by both GC/FPD and GC/FID, Gabica et al. (1971) found that GC/FPD provided better specificity. The minimum detectable level for both techniques was 3.0 ppb, but GC/FPD was more selective. The EPA-recommended method for analysis of low levels (<0.1 ppm) of methyl parathion in tissue, blood, and urine is GC/FPD for phosphorus (EPA 1980d). Methyl parathion is not thermally stable above 120 °C (Keith and Walters 1985). 

GC/MS has been employed by Demeter et al. (1978) to quantitatively detect low-ppb levels of a- and P-endosulfan in human serum, urine, and liver. This technique could not separate a- and P-isomers, and limited sensitivity confined its use to toxicological analysis following exposures to high levels of endosulfan. More recently, Le Bel and Williams (1986) and Williams et al. (1988) employed GC/MS to confirm qualitatively the presence of a-endosulfan in adipose tissue previously analyzed quantitatively by GC/ECD. These studies indicate that GC/MS is not as sensitive as GC/ECD. Mariani et al. (1995) have used GC in conjunction with negative ion chemical ionization mass spectrometry to determine alpha- and beta-endosulfan in plasma and brain samples with limits of detection reported to be 5 ppb in each matrix. Details of commonly used analytical methods for several types of biological media are presented in Table 6-1. 

In cases where the mode of action is the strong or irreversible inhibition of an enzyme system, the assay may measure the extent of inhibition of this enzyme. This may be accomplished by first measuring the activity of the inhibited enzyme and then making comparison with the uninhibited enzyme. This practice is followed when studying acetylcholinesterase inhibition by organophosphates (OP). Acetylcholinesterase activity is measured in a sample of tissue of brain from an animal that has been exposed to an OP. Activity is measured in the same way in tissue samples from untreated controls of the same species, sex, age, etc. Comparison is then made between the two activity measurements, and the percentage inhibition is estimated. 

Uniformly labeled C-8-D with a specific activity of 2.99 juc/mg was administered orally to pregnant females at 2 /xg/kg/day from 6-15 days of gestation. Three females were sacrificed on alternate days during days 6-20 of pregnancy. Triplicate samples of fetus, placenta, blood, brain, abdominal fat, and sartorius muscle were procured from each female. The samples were dissolved in 1 ml of Soluene (Packard Instruments) to which 15 ml of Aquasol were added. Each sample vial was counted for 30 min in a Nuclear Chicago Mark I liquid scintillation counter. 

Oral treatment of pregnant dams with 0.25 /xg (or more) /kg/day of 2,3,7,8-tetrachlorodibenzo-p-dioxin for 10 days during gestation resulted in adverse effects on rat development. No adverse effects were seen at the 0.125 ju,g/kg/day. When C-2,3,7,8-tetrachlorodibenzo-p-dioxin (2.99 fjLc/mg) was given at 2 /xg/kg/day there was activity, primarily in liver and to a lesser extent, in fat and brain. When a single oral dose of 200 /Ag/kg was administered on gestation days 16, 17, or 18 and was followed 6 hours later with tissue sampling, the label was also observed in the fetus and placenta. Placenta had approximately twice as much label as the fetus. 

Figure 8.11 Noradrenaline efflux, measured by microdialysis, in the rat frontal cortex and hypothalamus, (a) Repeated exposure to a tone, alone, has no effect on noradrenaline efflux in either brain region, (b) After repeated pairing of the tone with transfer of the rat to a brightly lit (aversive) arena, the sound of the tone alone triggers a significant ( P<0.05, cf last basal sample) increase in noradrenaline efflux in the frontal cortex, but not the hypothalamus. (Based on a figure from McQuade and Stanford 2000)...

Most of the mercury in muscle is present as MeHg. Barr (1986) reported that adult loons from a site closest to a mercury somce with 1.87 ppm Hg in fish, resulted in a muscle Hg concentration of 4.57 ppm ww and a brain Hg concentration of 1.49 ppm. Those loons had only 20% of territories successful (Barr 1986). Mallard hens receiving 0.5 ppm dietary mercury for 18 months had a muscle Hg concentration of 0.82 ppm compared with brain Hg = 0.50 ppm. Mallard hens receiving 3 ppm for the same period had 5.01 ppm in muscle and 4.57 in brain (Heinz 1976). Based on these assessments, muscle Hg concentration is more representative of brain Hg concentration and correlates better with effect than the more commonly measured fiver residue. It is also possible to sample muscle tissue nonlethally via biopsy, in... 

In studies in Alzheimer s brain, in vitro induction of lipid peroxidation by iron is more intense than in control cortical samples (Andorn et al., 1990 Subbarao et nL, 1990 McIntosh et al., 1991). The 21-aminosteroid U-74500A has been shown to effectively inhibit iron-induced lipid peroxidation in Alzheimer s brain samples (Subbarao et al., 1990). 

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