Determination of tryptophan and several of its metabolites in physiological samples by reversed-phase liquid chromatography with electrochemical detection

A new method for the concurrent assay of three tryptophan metabolites at the picomole level is described. The method has been developed for blood, urine, cerebrospinal fluid, and tissue samples such as whole brain, brain parts, and endocrine glands. Tryptophan itself, serotonin, and 5-hydroxyindoleacetic acid are isolated initially on extraction columns, eluted with a suitable solvent, and injected onto a liquid chromatograph with an amperometric detector. This general approach may be applicable to a variety of other tryptophan metabolites and should be useful in both research and clinical investigations.     

Cooxidation of benzidine by horseradish peroxidase and subsequent formation of possible thioether conjugates of benzidine

The human bladder carcinogen BENZIDINE was found to be converted by horseradish peroxidase and H₂O₂ to an intermediate which reacts with thiol-containing nucleophiles to give rise to a pattern of products which are identical to those produced by reaction of the two electron oxidation product of benzidine, 4,4′-biphenoquinonediimine, under identical conditions at physiological pH. The properties of the major reaction product are dependent on the identity of the thiol employed and are consistent with those expected for a ring-(S)-thioether conjugate of benzidine. These results may be indicative of a previously unrecognized minor pathway of benzidine metabolism.     

Domestic water versus imported virtual blue water for agricultural production: A comparison based on energy consumption and related greenhouse gas emissions

The supply of water, food, and energy in our global economy is highly interlinked. Virtual blue water embedded into internationally traded food crops has therefore been extensively researched in recent years. This study focuses on the often neglected energy needed to supply this blue irrigation water. It provides a globally applicable and spatially explicit approach to the watershed level for water source specific quantification of energy consumption and related greenhouse gas (GHG) emissions of irrigation water supply. The approach is applied to Israel's total domestic and imported food crop supply of 105 crops by additionally including import-related transportation energy and emissions. Total energy use and related emissions of domestic crop production were much lower (551 GWh/422 kt CO₂-equivalents [CO₂e]) than those embedded into crop imports (1639 GWh/649 kt CO₂e). Domestic energy and emissions were mainly attributable to the irrigation water supply with artificial water sources (treated domestic wastewater and desalinated water, 84%). Transport accounted for 79% and 66% of virtually imported energy and emissions, respectively. Despite transport, specific GHG emissions (CO₂e per ton of crop) were significantly lower for several crops (e.g., olives, almonds, chickpeas) compared to domestic production. This could be attributed to the high share of energy-intensive artificial water supply in combination with higher irrigation water demands in Israel. In the course of an increasing demand for artificial water supply in arid and semi-arid regions, our findings point to the importance of including “energy for water” into comparative environmental assessment of crop supply to support decision-making related to the water–energy–food nexus.     

DETERMINATION OF CATECHOLAMINES IN RAT BRAIN PARTS BY REVERSE-PHASE ION-PAIR LIQUID CHROMATOGRAPHY

Abstract— A method for the separation and determination of γ-aminobutyrylcholine (GABACh) from trichloracetic acid treated brain extracts has been developed. It consists of the separation of the extracts on Dowex 1 × 8 columns, precipitation of the quaternary ammonium bases and their separation by paper chromatography. Using this technique it was found that electrical stimulation for 30 s of one brachial plexus in the cat resulted in 4.6 fold increase in GABACh concentration in the stimulated (contralateral) cerebral cortex as compared to the non-stimulated (ipsilateral) cortex. This change in GABACh concentration was not reversed within 5 s of cessation of the stimulus. The results are discussed in relation to the possible physiological role of GABACh: (a) as a neurotransmitter; (b) as a substance participating in the inactivation process of GABA. The possible connection of GABACh to the metabolism of GABA and acetylcholine is discussed.     

Structural requirements of diacylglycerols for binding and activating phospholipid-dependent, Ca++-sensitive protein kinase

Phospholipid-dependent, Ca++-sensitive protein kinase (protein kinase C) is activated by phorbol esters and diacylglycerols. A series of diacylglycerols was synthesized with different substituents at positions 1 and 2 in order to expand known structure-activity relationships for these compounds with respect to binding and activating purified protein kinase C. Compounds were synthesized with saturated and unsaturated long chain fatty acyl groups at position 1 and acetyl, butyryl, or hexanoyl groups at position 2. Binding to protein kinase C correlated well with in-vitro activation of the enzyme. These diacylglycerols activated protein kinase C in an intact cellular system causing the phosphorylation of pp60c-src. This indicates that the length of the fatty acyl group at C2 is critical and that the existence of unsaturation in the fatty acyl group at C1 is not essential.     

Abnormal levels of urinary catecholamines in dystrophic mice and hamsters.

Twenty-four-hour urine was collected from normal and dystrophic mice and hamsters for catecholamine determinations. A new method of analysis was used whereby 3,4-dihydroxyphenylalanine (DOPA), dopamine (DA), norepinephrine (NE), and epinephrine (E) were measured simultaneously. The procedure is based on a combination of liquid-solid extraction, cation exchange chromatography, and controlled potential electrochemistry. The results of these experiments indicated that while DA levels were similar in both normal and pathological animal urine, DOPA levels decreased slightly in the dystrophic mouse but not the hamster, and NE and E levels in dystrophic groups were two and four times greater than normal in both species. The data supports the concept of biochemical alterations in tissue other than muscle. While not necessarily supportive to catecholamine abnormality as the primary cause of muscular dystrophy, the present data cast doubt that this disease is a primary muscle disease.