Tyrosine Hydroxylase Activity in Rat Brain Synaptosomes: Direct Measurement Using High Performance Liquid Chromatography

Abstract: By use of high performance liquid chromatography with electrochemical detection to measure dopamine production, tyrosine hydroxylase (EC 1.14.16.2) activity has been measured in rat brain synaptosomes from striatum and forebrain. Normal specific activities three- to fivefold higher than previously reported in the literature for radiochemical methods of assay were found. It is suggested that synaptosomes contain a significant amount of endogenous substrate for tyrosine hydroxylase, which causes dilution of the added labelled tyrosine and hence underestimation of the activity of this enzyme when radiochemical methods are used.     

A Rapid and Simple Method for the Determination of Picogram Levels of 3-Methoxytyramine in Brain Tissue Using Liquid Chromatography with Electrochemical Detection

Abstract: A rapid and simple technique using solvent extraction, ion-pairing extraction, and high pressure liquid chromatography with electrochemical detection has been developed for the determination of 3-methoxytyramine in striata of rats killed by microwave irradiation. The method is specific and reproducible (coefficient of variation among replications, ±4%); recovery of authentic 3-methoxytyramine added to the samples is 45–50%. 3-Methoxytyramine levels found with this technique in rat striata were 15 ± 1.7 ng/g. The method has a sensitivity of about 0.2 pmol per brain sample. Monoamine oxidase inhibition with pargyline increased 3-methoxytyramine levels in rat striata, while catechol- O -methyltransferase inhibition with 3',4'-dihydroxy-2 methylpropiophenone completely depleted 3-methoxytyramine. The effects of nomifensine, quipazine, caroxazone, piribedil, and D-amphetamine were also examined. The 3-methoxytyramine concentrations in the brains of animals killed by decapitation or by microwave irradiation were compared.     

The fine structure of a microplate-microtubule array,microfilaments and polyhedral body associated microtubules in several species of Anabaena

A microplate-microtubule array was observed in Anabaena sp. (B-378). This structure consists of an arched plate, about 8 nm thick, and various microtubules, 12 nm in diameter and 50 nm long, arranged in rows. The microtubules project at right angles from one side of the plate into the cytoplasm or towards the plasma membrane. Up to twelve microplate-microtubule arrays were observed in a single section of a cell.Microfilaments, about 2.8 nm in diameter and of undetermined length, were observed in four isolates of Anabaena. The microfilaments were always found in bundles, which varied in size, up to 0.63 m across and 0.91 long.Microtubules, 10 nm in diameter and about 150 nm in length, were observed associated with one facet of polyhedral bodies in 8 out of 20 isolates of Anabaena. The microtubules occurred in groups of up to 20 or more, and were always oriented with the long axis parallel to a facet of a polyhedral body. In cross section, the microtubules had an electron transparent lumen 5 nm wide and a wall 2.5 nm thick.These structures are compared to previously deseribed microtubules and microfilaments.     

The effect of different media and culture techniques on plating efficiency of strawberry mesophyll cells in culture

Mesophyll cells of strawberry were isolated mechanically by a hand homogenizer, One g healthy, fully-expanded leaves yielded 10⁷ cells. The agar culture method was the only culture technique found suitable to obtain any quantitative data.     

Luminometric measurement of population activity of genetically modified Pseudomonas fluorescens in the soil

Genetically modified cells of Pseudomonas fluorescens, chromosomally marked with genes for bioluminescence, were inoculated into sterile soil microcosms. During incubation for 90 days, viable cell concentration did not change significantly but light output, measured by luminometry, decreased, indicating reduced metabolic activity due to lack of substrates. Amendment with nutrients resulted in parallel increases in both luminescence and dehydrogenase activity. Luminometry therefore enables rapid monitoring of the activity of populations of luminescence-marked microbial inocula in the soil, with greater sensitivity and selectivity than traditional techniques.     

Off‐host aggregation in the non‐fed,female brown dog tick,Rhipicephalus sanguineus (Latreille), is induced by tick excreta and enhanced by low relative humidity

We report that Rhipicephalus sanguineus (Ixodida: Ixodidae) faeces and its main component, guanine, act as assembly pheromones in short‐range Petri plate bioassays. Arrestment activity in response to guanine was lower than that in response to natural excreta, indicating the presence of other active ingredients in natural excreta. The selective removal of appendages was used to establish the important roles played by the palps and the front pair of legs in the detection of the pheromone. Reaction to chemically pure guanine at varying concentrations occurred without a dose response; thus only the presence of guanine, not a critical amount, is required to induce assembly. Higher speed and intensity of clustering occurred at 33% relative humidity (RH). We conclude that female adults of R. sanguineus are more prone to assemble under dry conditions that match the arid microhabitats preferred by this species and that this tendency allows this tick to reside in human dwellings and dog kennels that maintain standards of comfort at 30–50% RH. Cleaning or removing tick excreta‐covered surfaces on which ticks aggregate from within and around human dwellings may prove useful as a means of interfering with the establishment of off‐host clusters of R. sanguineus.