Reversible inactivation of soluble liver guanylate cyclase by disulfides

A new amino acid was isolated from the cuticle collagen of $\text{Ascaris lumbricoides}$ and characterized by ultraviolet, mass and nmr spectroscopies and chemical degradation. The results indicate that the compound is an isomer of trityrosine, having an ether linkage. The name “isotrityrosine” is proposed. Its structure suggests that it serves as a crosslink and plays a role in the organization of the collagen structure.     

Thermographic visualization of cell death in tobacco and Arabidopsis

Pending cell death was visualized by thermographic imaging in bacterio‐opsin transgenic tobacco plants. Cell death in these plants was characterized by a complex lesion phenotype. Isolated cell death lesions were preceded by a colocalized thermal effect, as previously observed at sites infected by tobacco mosaic virus (TMV) ( Chaerle et al. 1999 Nature Biotechnology 17, 813–816). However, in most cases, a coherent front of higher temperature, trailed by cell death, initiated at the leaf base and expanded over the leaf lamina. In contrast to the homogenous thermal front, cell death was first visible close to the veins, and subsequently appeared as discrete spots on the interveinal tissue, as cell death spread along the veins. Regions with visible cell death had a lower temperature because of water evaporation from damaged cells. In analogy with previous observations on the localized tobacco–TMV interaction ( Chaerle et al. 1999 ), the kinetics of thermographic and continuous gas exchange measurements indicated that stomatal closure preceded tissue collapse. Localized spontaneous cell death could also be presymptomatically visualized in the Arabidopsis lsd2 mutant.     

The stable evolutionary fixation of a bifunctional tyrosine-pathway protein in enteric bacteria

Abstract The bifunctional T-protein (chorismate mutase-T: cyclohexadienyl dehydrogenase) of l -tyrosine biosynthesis was found to be present in all genera making up the enteric bacteria. The dehydrogenase component of the T-protein was active with both prephenate and l -arogenate, showing it to be a cyclohexadienyl dehydrogenase. The dehydrogenase component, but not the mutase component, of the T-protein was feedback-inhibited by l -tyrosine. Unlike some other bifunctional proteins, the T-protein has evolved recently and is not ubiquitous. However, once the biochemical specialization of bifunctionality becomes established, the results indicate that such character states are strongly conserved through evolutionary time. Thus, bifunctional proteins can provide particularly reliable markers for small (recent origin), intermediate, and large (ancient origin) phylogenetic clusters.     

The effect of caffeine,different fixation regimes and low temperature on microtubules in the cells of higher plants

Caffeine, (1:3:7-tri-methyl-xanthine), either as a prefixation treatment or included with glutaralde-hyde as the primary fixative, destroys or disorganises the microtubules associated with the formation of secondary walls in fibres from the flowering stem of the grass Lolium temulentum L. There is no observable effect of caffeine treatment on the microtubules associated with primary wall formation in collenchyma and young fibres from L. temulentum or in root cap cells of Zea mays L. and Phaseolus vulgaris L. The microtubules associated with primary wall formation are destroyed by cold treatment but not those associated with secondary wall formation. Tannic acid included in the fixative shows the microtubules associated with secondary wall formation in fibres of L. temulentum to be composed of 13 subunits. Treatment with lanthanum hydroxide does not stain the core or the halo of the microtubules.Abbreviation PIPES Piperazine N-N- bis 2 ethanol sulphonic acid The Grassland Research Institute is financed through the Agricultural Research Council     

The structure of 180° supernumerary limbs and a hypothesis of their formation

The results of a detailed analysis of 100 supernumerary limbs generated by 180° ipsilateral rotation (on the same limb stump) of regeneration blastemas is presented. The limbs were analyzed in terms of their position of origin, frequency, cartilage structure by Victoria blue staining, and muscle structure by serial sections. Single, double, or triple supernumeraries can be produced at no unique position of origin, although the posterodorsal quadrant was preferred. Four classes of supernumerary limbs were generated by such operations—normal; double dorsal or double ventral; part normal/part mirror imaged; part normal/part inverted in approximately equal frequencies. After amputation of these supernumeraries the same muscle patterns are faithfully regenerated. A hypothesis to explain the production of these abnormal limbs is proposed based on the observed phenomenon of fusion of supernumerary blastemata, but their regenerative behaviour presents problems for current models of pattern formation. Similar results have been obtained with developing limb buds and the relation between development and regeneration is discussed.     

Identification and Distribution of Phenylacetic Acid in the Brain of the Rat

Abstract: Phenylacetic acid, the major metabolite of phenylethylamine, has been identified and quantitated in rat brain regions by capillary column high-resolution gas chromatography mass spectrometry. Its distribution is heterogeneous and correlates with that of phenylethylamine. The values obtained were (ng/g ± SEM): whole brain, 31.2 ± 2.7; caudate nucleus, 64.6 ± 6.5; hypothalamus, 60.1 ± 7.4; cerebellum, 31.3 ± 2.9; brainstem, 33.1 ± 3.3, and the "rest," 27.6 ± 3.0.     

Substrate-dependent inhibition of yeast enolase by fluoride

A possibly physiologically significant inhibition of yeast enolase by fluoride occurs in the absence of inorganic phosphate. The inhibition increases with time, is strongly dependent on fluoride concentration and requires substrate and “catalytic” Mg²⁺. The inhibition increases more slowly in the presence of product (phosphoenolpyruvate) than substrate (2-phosphoglycerate). The dependence on fluoride concentration and the spans of substrate analogue displacement titrations suggest the inhibition is produced by two moles of fluoride per active site.