Improved high-performance liquid chromatographic assay method for the enantiomers of ibuprofen

A rapid, inexpensive and sensitive high-performance liquid chromatographic method for the quantitation of ibuprofen enantiomers from a variety of biological fluids is reported. This method uses a commercially available internal standard and has significantly less interference from endogenous co-extracted solutes than do previously reported methods. The method involves the acid extraction of drug and internal standard [(±)-fenoprofen] from the biological fluid with isooctane—isopropanol (95:5) followed by evaporation and derivatization with enthylchloroformate and R-(+)-α-phenylethylamine. Excellent linearity was observed between the peak-area ratio and enantiomer concentration (r > 0.99) over a concentration range of 0.25–50 μg/ml. This method is suitable for the quantitation of ibuprofen from single-dose pharmacokinetic studies involving either rats or humans.     

Carbon Flow in Mercury Biomethylation by Desulfovibrio desulfuricans

Radiocarbon incorporation from pyruvate and serine into monomethylmercury by Desulfovibrio desulfuricans was consistent with the proposal that the methyl group originates from C-3 of serine. Immunodiagnostic assays measured 4 to 35 μg of tetrahydrofolate and 58 to 161 ng of cobalamin or a closely related cobalt porphyrin per g of cell protein in D. desulfuricans. The light-reversible inhibition of mercury methylation by propyl iodide in D. desulfuricans indicates methyl transfer by a cobalt porphyrin.     

The sensory functions of the cerebellum of the thornback ray,Platyrhinoidis triseriata

Summary Single unit spikes and evoked field potentials were recorded in different parts and depths of the corpus cerebelli and auricle of immobilized rays before and after stimulating with light, electric fields, touch, tail bending and direct shock to mechanoreceptive nerves of the lateral line.Discrete areas of the cerebellum are responsive to these modalities and the areas show limited overlap; they are all distinct from the area reported by Plassmann to be responsive to angular acceleration. The visual and tactile-proprioceptive areas are large; the electric area is small. Most units are excited only by one modality.The tail is represented only in the posterior lobe; trigeminal innervation extends from the posterior onto the anterior lobe, suggesting some topographic projection.The dynamic characteristics of the responses were examined particulary in the visual units. To a flash, units discharge up to six bursts of spikes in 500 ms. This pattern is reduced at repetition rates > 1/s; above ca. 4/s units tend to fire irregularly. Various kinds of units are found in respect to the succession of responses to short trains of flashes. Some units fire much better to objects moving in a limited visual field with a certain direction and rate.Abbreviation EP evoked potential     

Inhibition of porphobilinogen synthase by heme and an enol-ether amino acid

The enol-ether amino acid, L-2-amino-4-methoxy-$\text{trans}$-butenoic acid (AMTB) is an inhibitor of porphobilinogen synthase (PBG synthase) when added prior to the addition of the substrate δ-aminolevulinic acid. The inhibition of PBG synthase by several stereoisomers and analogues of AMTB was investigated to determine those structural features of AMTB which may be necessary for inhibition. The D-$\text{trans}$ isomer was also an inhibitor after preincubation, whereas the L-$\text{cis}$ isomer inhibited with or without preincubation. The amino acid analogues, DL-vinylglycine, DL-2-aminobutanoic acid, the reduced form of L-2-amino-4-methoxy-$\text{trans}$-3-butenoic acid, L-2-amino-4-(2-aminoethoxy)-$\text{trans}$-3-butenoic acid and its reduced congener did not inhibit PBG synthase even with preincubation. This structure activity relationship indicates that the $\text{trans}$ double bond and methoxy moiety of L-2-amino-4-methoxy-$\text{trans}$-3-butenoic acid are probably required for inhibition.Heme, when preincubated with PBG synthase, was an inactivator of the enzyme. However, when both L-2-amino-4-methoxy-$\text{trans}$-3-butenoic acid and heme were simulatneously preincubated with PBG synthase, inactivation of the enzyme was greater than with either compound separately. The possibility of multiple catalytic sites was suggested by the use of multiple inhibition kinetics in the presence of heme and L-2-amino-4-methoxy-$\text{trans}$-3-butenoic acid.     

Monoamine oxidase of rat skeletal muscle: substrate specificity and half-life

The substrate specificity of rat skeletal muscle MAO has been studied. By the use of clorgyline as a MAO A inhibitor, it is found that 5-hydroxytryptamine, tryptamine, and kynuramine are deaminated by MAO A whereas benzylamine is a substrate for both forms of MAO. Phenethylamine displays a concentration-dependent preference for the two forms of MAO. These substrate specificies of the two forms of MAO in skeletal muscle are different from those observed in liver and brain but resemble closely that seen with heart. The half-lives of MAO A and MAO B in muscle estimated by rate of recovery from pargyline inhibition are 6.9 and 6.4 days, respectively.     

Liver tissue graft rejection in murine major histocompatibility complex mutants

Liver tissue grafts between seven H-2 mutants and their parental strains have been studied. Each of these mutants was originally identified by reciprocal mutant—parental strain skin graft rejection. However, liver grafts among mutants and parental standard strains are not uniformly rejected. Liver graft rejection also fails to correlate with mutant—parental stimulation in CML and MLC. In addition, the immune reaction pattern of female mutant animals against grafts of male liver differs from the reaction pattern found in parental standard strains. Several explanations for the differences between immune response to liver and skin grafts are proposed, including different T cell subsets involved in recognition, availability of antigenic sites to immunocompetent cells, and structural differences between mutant and parental H-2 antigens. Abbreviations used in this paper: bml, 2, 3, 4,14; dml; fm2=mutants of strains C57BL/6, B10.D2 and B10.M respectively; B6=C57BL/6