Linkage of X-linked retinitis pigmentosa to the hypervariable DNA marker M27β (DXS255)

Summary A hypervariable DNA marker is closely linked to one of the most severe forms of night blindness, X-linked retinitis pigmentosa (RP). Affected individuals with X-linked RP, obligate carriers, and ophthalmologically identifiable carriers of the disease were included in a linkage study. The diagnosis was established in five sibships by funduscopic and electrophysiological investigations. When the X-linked probe M27 was used, 2 recombinants out of 29 informative meioses were detected (=0.07 at a maximum lod of 4.75). The hypervariable probe detected two different alleles in 38 of 39 females tested. M27 is therefore a potentially very useful probe for carrier detection and prenatal diagnosis, as well as for addressing the question of heterogeneity of X-linked RP.     

Non-photochemical quenching of Fo in leaves is emission wavelength dependent: consequences for quenching analysis and its interpretation

The effects of light-induced non-photochemical quenching on the minimal F_o, and variable F_v, fluorescence emissions at 690 and 730 nm in leaves were determined. Non-photochemical quenching of F_o, but not F_v, was found to be dependent upon the wavelength of emission, and was greater at 690 nm than at 730 nm. For emission at 730, compared to at 690 nm, approx. 30% of F_o was not affected by non-photochemical quenching processes in leaves of C3 plants; in maize leaves this was found to be approx. 50%. The data indicate that a substantial proportion of the pigments contributing to F_o emission at 730 nm are not quenched by light-induced, non-photochemical quenching processes and that there are large differences in the pigment matrices contributing to F_o and F_v emissions at 730 nm, compared to those at 690 nm. These findings have important implications for the accurate estimation and interpretation of non-photochemical quenching of fluorescence parameters and their use in the calculation of photochemical efficiencies in leaves. Measurements of fluorescence emissions at wavelengths above 700 nm are likely to give rise to significant errors when used for determinations of photochemical and non-photochemical quenching parameters.     

Modification of excitation energy distribution to photosystem I by protein phosphorylation and cation depletion during thylakoid biogenesis in wheat

The effects of protein phosphorylation and cation depletion on the electron transport rate and fluorescence emission characteristics of photosystem I at two stages of chloroplast development in light-grown wheat leaves are examined. The light-harvesting chlorophyll a/b protein complex associated with photosystem I (LHC I) was absent from the thylakoids at the early stage of development, but that associated with photosystem II (LHC II) was present. Protein phosphorylation produced an increase in the light-limited rate of photosystem I electron transport at the early stage of development when chlorophyll b was preferentially excited, indicating that LHC I is not required for transfer of excitation energy from phosphorylated LHC II to the core complex of photosystem I. However, no enhancement of photosystem I fluorescence at 77 K was observed at this stage of development, demonstrating that a strict relationship between excitation energy density in photosystem I pigment matrices and the long-wavelength fluorescence emission from photosystem I at 77 K does not exist. Depletion of Mg²⁺ from the thylakoids produced a stimulation of photosystem I electron transport at both stages of development, but a large enhancement of the photosystem I fluorescence emission was observed only in the thylakoids containing LHC I. It is suggested that the enhancement of PS I electron transport by Mg²⁺-depletion and phosphorylation of LHC II is associated with an enhancement of fluorescence at 77 K from LHC I and not from the core complex of PS I.     

Dinuclear silver(I) complexes of 24-membered bibracchial tetraimine Schiff base macrocycles derived from 2,5-diformylthiophene

The cyclocondensation of 2,5-diformylthiophene and the amines N,N-bis-(2-aminoethyl)-2-phenylethylamine, N,N-bis-(2aminoethyl)-t-butyl-amine and N,N-bis-(2-aminoethyl)-t-butyl-amine in the presence of silver(I) salts yields homodinuclear bibracchial tetraimine Schiff base macrocyclic complexes. The structures of two such complexes are also reported. The complex Ag₂L⁴(NO₃)(PF₆) (2) crystallises in the triclinic space group , No. 2) and has unit-cell dimensions a = 12.834(6), B = 13.183(6), C = 14.588(7) Å, = 64.86(4), β = 79.77(4), γ = 69.44(3)° with Z = 2; there is a monodentate and singly bridging nitrate anion present and the Ag---Ag separation is 4.161 Å. The complex Ag₂L⁴(CH₃CN)₂(BF₄)₂·CH₃CN (9) crystallises in the triclinic space group , No. 2) and has unit-cell dimensions a = 9.297(4), B = 12.985(3), C = 21.770(5) Å, = 91.570(10), β = 92.33(3), γ = 97.92(3) ° with Z = 2; there is a strongly bonded acetonitrile molecule coordinated to each silver atom and the Ag---Ag separation is 4.920 Å.     

Genetic evidence for a complex of species within Rugopharynx australis (Mönnig, 1926) (Nematoda: Stronglyloidea) from macropodid marsupials

An electrophoretic analysis using 17 enzyme loci was carried out on specimens of the gastric nematode of macropodid marsupials, Rugopharynx australis (Mönnig, 1926), collected from Macropus eugenii (Desmarest), M. fuliginosus (Desmarest), M. giganteus Shaw, M. robustus Gould, M. rufogriseus (Desmarest), M. rufus (Desmarest), Thylogale billardierii (Desmarest) and Wallabia bicolor (Desmarest) from south-eastern Australia. The extent of fixed genetic differences between nematodes from different host species ranged from 0–53%. The two distinct morphological forms of the parasite found in M. rufogriseus differed at 50% of loci. Specimens present in M. fuliginosus and M. giganteus were indistinguishable genetically, as were nematodes from M. rufus and M. robustus. Of the two morphologically distinct congeners included in the analysis as controls, Rugopharynx epsilon (Johnston & Mawson, 1939) was genetically distinct (46–69% fixed genetic differences) from all specimens of the R. australis complex while R. rufogrisea Magzoub, 1964 was closely related to one of the two species occuring in M. rufogriseus. It was concluded that R. australis is a species complex, with a genetically distinct species present in M. eugenii, M. fuliginosus/M. giganteus, M. robustus/M. rufus, W. bicolor and T. billardierii, and two species in M. rufogriseus.     

Multiple phenotypes associated with Myc-induced transformation of chick embryo fibroblasts can be dissociated by a basic region mutation.

Chimaeric alleles were constructed to assay the biological functions of an N-terminal deletion and C-terminal mutations which were found in a naturally occurring mutant of feline vMyc, T17. The mutant alleles were assayed for their ability to transform chick embryo fibroblasts in vitro by a number of criteria, namely the ability to induce morphological transformation, an accelerated growth rate and growth in soft agar. Feline cMyc could transform the avian cells, whilst T17 vMyc could not, and the N-terminal deletion was responsible for conferring the primary transformation defect on the mutant protein. The C-terminal mutations which consist of a point mutation adjacent to the nuclear localisation signal and a point mutation/amino acid insertion within the basic region (BR) could, however, dissociate the Myc-induced parameters of transformation. This effect was a specific function of the BR mutation alone, and the mutation could be transferred into avian cMyc with comparable biological consequences. The BR mutation did not disrupt the sequence specific DNA binding activity of the protein in vivo, despite exerting a biological effect. These data suggest a novel phenotype where the mutation may affect a subset of Myc-regulated genes through altered DNA binding specificity or protein-protein interactions.     

Electro-immunoblotting characterization ofPseudo-nitzschia multiseries andP. pungens antigens recognized by antibodies directed against whole cells

Separate polyclonal antibodies have previously been developed against the domoic-acid-producingPseudonitzschia multiseries (=Pseudo-nitzschia pungens f.multiseries) and the non-toxicP. pungens (=P. pungens f.pungens). These antibodies bind to the surface of the diatoms as shown by immunofluorescence studies. Here we examine the molecular nature of the antigens by Western blotting (electro-immunoblotting) analysis. The major antigens for both polyclonal antibodies migrated as high molecular-weight diffuse bands, mostly remaining in the stacking gel, using an SDS-PAGE system. The antibodies prepared againstP. multiseries strongly labelled the high molecular-weight antigens of allP. multiseries strains tested and showed little reactivity towardsP. pungens extracts on Western blots.P. pungens antibodies strongly labelled high molecular-weightP. pungens antigens and faintly labelled a fewP. multiseries antigens. The selectivity of the antibodies for their respective species correlates with the results of the immunofluorescence experiments, suggesting that the antigens examined in this study are responsible for the selective labelling in immunofluorescence studies. The electrophoretic mobility and the antibody labelling of antigens were not altered by proteolytic digestion of cell pellets. However, disruption of carbohydrates in the pellets by treatment with periodic acid resulted in loss of the antigen. These data suggest that the major antigens of toxicP. multiseries and non-toxicP. pungens are high molecular-weight (°>100kDa) polysaccharides located on the surface of these diatoms.Author for correspondence