Biosynthesis of the Securinega alkaloids. Investigations of the early and late stages of the pathway

Feeding experiments with Securinega suffruticosa have established that tyrosine is a specific precursor of the alkaloid securinine. Additional experiments show that tyrosine is incorporated into securinine with loss of the 3-pro-S hydrogen atom of the amino acid and that neither 4′-hydroxy-2-phenylethanol nor 4′-hydroxyphenylacetic acid serves as a securinine precursor. Investigation of the metabolic relationship between securinine and dihydrosecurinine has shown that the former alkaloid is the precursor of the latter.     

An initial assessment of the genotoxic impact of the Sea Empress oil spill by the measurement of DNA adduct levels in the intertidal teleost Lipophrys pholis

The Sea Empress oil spill resulted in the release of vast quantities of potentially genotoxic contaminants into the coastal environment of the county of Pembrokeshire (UK). We are at present attempting to determine the potential genotoxic impact of the incident upon the native marine species of the area. Here we describe the levels of DNA adducts in specimens of the intertidal teleost, Lipophrys pholis, exposed to extensive oil contamination as an indication of exposure to potential genotoxins. We detected elevated levels of adducts in L. pholis specimens from an area that underwent heavy oil contamination as compared to specimens from a clean reference area devoid of oil contamination. These preliminary studies indicated that the oil contamination induced DNA adducts in the L. pholis specimens, which could potentially cause genetic damage in this native marine species. Further studies are now required to assess the full extent of the genotoxic impact of the oil spill upon the Pembrokeshire area's native marine life.     

Synthesis of 21-carboxy-D-arabinitol-1-phosphate in French bean (Phaseolus vulgaris L.): a search for precursors

Discs of French bean leaves were vacuum infiltrated with solutionscontaining ¹⁴C-labelled substances. The infiltrated discs wereeither transferred immediately to darkness or first illuminatedfor 2 h and then transferred to darkness. After 6 h in darknessthe discs were extracted with buffer containing CO₂, Mg²⁺ andadditional ribulose-1, 5-bisphosphate carboxylase/oxygenase(Rubisco; EC 4.1.1.39 [EC] ). Protein in the extracts was separatedfrom substances of low molecular weight by gel filtration andcoagulated by heating to 100C. Coagulated protein was removedby centrifugation and cations in the supernatant solution wereremoved by ion exchange resin. The non-volatile anions in theresulting solutions, among which was 2¹-carboxy-D-arabinitol-1-phosphate(CA1P), were separated by HPLC. The amount of CA1P was determinedfrom the signal of a pulsed amperometric detector and its radioactivityby scintillation counting. Vacuum infiltration of [2¹–¹⁴C]2¹-carboxy-D-arabinitol (CA) resulted in 12.6% of the radioactivityin the leaf discs being in CA1P after 6 h in darkness and 21.6%when 2 h light was given before the dark treatment. Where radioactiveglucose, fructose, sucrose, hamamelose, glycerate, glycine oracetate were infiltrated, ¹⁴C in CA1P was less than 1% of thetotal present after the dark period with or without a precedingperiod of light. Incorporation of ¹⁴C from [¹⁴C] CA into CA1Pin darkness was strongly inhibited by 2,4-dinitrophenol andalso to a lesser extent by tentoxin. With both inhibitors themain effect was a decreased uptake of the substrate. Illuminationprior to darkness stimulated the incorporation of radioactivityfrom CA, glycine, glucose, sucrose, and hamamelose into CA1Pin subsequent darkness. Unlike the other substrates, which wereextensively metabolized, CA and hamamelose were converted tofew products; CA was converted almost exclusively to CA1P andCA1P was a major product of hamamelose metabolism. Key words: CA1P, Phaseolus vulgaris, precursors, synthesis     

Collagen fibril morphology in developing chick metatarsal tendon: 2. Electron microscope studies

Transverse section of embryonic chick metatarsal tendons ranging in age from 11 days to 18 days fetal were examined by electron microscopy to determine both the diameters and the lateral arrangements of the cylindrical collagen fibrils. In early developmental stages, from 11 days to 14 days fetal, sharp unimodal distributions of diameters centred near 32 or 40 nm were observed, but increasingly heterogeneous diameters were seen with increasing age. The heterogeneous diameter distributions were not uniform, but showed discrete populations of preferred diameters. The centre-to-centre distance separating the fibrils in the early developmental stages was about twice the fibril diameter and constant with age. Comparison of X-ray diffraction results with these observations indicated that the saptial relationships of the structures are preserved during the preparative procedures for electron microscopy, but that a transverse shrinkage of 25–30% had occurred relative to the wet dimension.     

The LH-RH system of the male European starling: photoperiod induces changes to a possible multifunctional peptide system

In many birds reproduction is triggered by long daylengths but, paradoxically, continued exposure to long days leads to photorefractoriness and a complete shut down of the reproductive system. As these effects are thought to be mediated through the secretion of LH-RH, immunocytochemical techniques were used to investigate changes in the LH-RH system when European starlings were exposed to different photoperiods. Starlings exposed to 11L:13D and with mature testes show strong immunostaining both of LH-RH perikarya and fibers. Photosensitive short-day (8L:16D) starlings with undeveloped testes show an almost identical distribution of strongly immunoreactive perikarya but with less dense fibre staining. However, long-day (18L:6D) photorefractory starlings with fully regressed testes, show a profound reduction in LH-RH immunostaining. Perikarya have the same distribution but show a much reduced intensity of staining and fibers had almost entirely disappeared from all regions of the brain. Preliminary observations on the ultrastructure of immunocytochemically identified LH-RH neurones are also reported.     

Coma Associated with Vincristine Therapy

Three cases of coma after vincristine therapy are described. One patient had hyponatraemia and other features of inappropriate secretion of antidiuretic hormone. The effects were temporary, and full recovery occurred in all three patients.