Evidence for a major gene (RP10) for autosomal dominant retinitis pigmentosa on chromosome 7q: linkage mapping in a second,unrelated family

Retinitis pigmentosa is a genetically heterogeneous form of retinal degeneration, which has X-linked, autosomal recessive and autosomal dominant forms. The disease genes in families with autosomal dominant retinitis pigmentosa (adRP) have been linked to six loci, on 3q, 6p, 7p, 7q, 8q and 19q. In a large American family with late-onset adRP, microsatellite markers were used to test for linkage to the loci on 3q, 6p, 7p, 7q and 8q. Linkage was found to 7q using the marker D7S480. Additional microsatellite markers from 7q were then tested. In total, five markers, D7S480, D7S514, D7S633, D7S650 and D7S677, show statistically significant evidence for link-age in this family, with a maximum two-point lod score of 5.3 at 0% recombination from D7S514. These results confirm an earlier report of linkage to an adRP locus (RP10) in an unrelated family of Spanish origin and indicate that RP10 may be a significant gene for inherited retinal degeneration. In addition, we used recently reported microsatellite markers from 7q to refine the linkage map of the RP10 locus.     

Synthesis and DNA binding properties of an amidine-linked and phenyl-containing analogue of distamycin A

The synthesis of a novel amidine-linked analogue 1 of the phenyl-containing congener 2 of distamycin A and its DNA binding properties are described. The amidine group in 1 improves its water solubility while retaining the minor groove and AT sequence binding selectively.A phenyl-containing and amidine-linked analogue 1 of distamycin A has improved water solubility while retaining the minor groove and AT sequence binding selectivity to DNA.     

Temporal relationships betweenZea mays,ostrinia nubilalis (Lep.: Pyralidae) and endophyticBeauveria bassiana

The entomopathogenic fungus,Beauveria bassiana (Balsamo) Vuillemin, was applied to whorl-stage (V7) corn,Zea mays L., by foliar application of a granular formulation of corn grits containing conidia or by injection of a conidial suspension. All plants were infested with European corn borer larvae,Ostrinia nubilalis (Hübner), at the V7 (whorl), V12 (late-whorl), or V17 (pretassel) stage of plant development. Plants infested at whorl and late-whorl stages had significantly more European corn borer tunneling than did plants infested at the pretassel stage. The percentage of plants colonized byB. bassiana did not differ significantly among the whorl, late-whorl, and pretassel stages. As the plants matured,B. bassiana was isolated from different plant areas, with the pith more frequently colonized than the leaf collars. Foliar application ofB. bassiana provided immediate suppression ofO. nubilalis in those plants infested at whorl stage. The reduced efficacy ofB. bassiana at the intermediate plant stages relative to efficacy at harvest is discussed. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

The structural elements of hirudin which bind to the fibrinogen recognition site of thrombin are exclusively located within its acidic C-terminal tail

Six lysyl residues of human thrombin (LysB21, LysB52, LysB65, LysB106, LysB107 and LysB154) have been previously shown to participate in the binding site of hirudin, a thrombin-specific inhibitor [(1989) J. Biol. Chem. 264, 7141-7146]. In this report, we attempted to delineate the region of hirudin which binds to these basic amino acids of thrombin. Using the N-terminal core domains (r-Hir1-43 and r-Hir1-52) derived from recombinant hirudins and synthetic C-terminal peptides (Hir40-65 and Hir52-65)--all fragments form complexes with thrombin--we are able to demonstrate that the structural elements of hirudin which account for the shielding of these 6 lysyl residues are exclusively located within the acidic C-terminal region. Since hirudin C-terminal peptides were shown to bind to a non-catalytic site of thrombin and inhibit its interaction with fibrinogen [(1987) FEBS Lett. 211, 10-16], our data consequently imply that these 6 lysyl residues are constituents of the fibrinogen recognition site of thrombin.     

Receptor-activated single channels in intact human platelets.

We report "cell-attached" patch clamp studies of intact human platelets which show receptor-activated single channels. Inclusion of ADP in the patch pipette, but not in the bath, resulted in the appearance of inward currents indicative of single channels tightly coupled to the ADP receptors. The channels had a slope conductance of 11 picosiemens at the resting potential. Removal of 1 mM Ca2+ or replacement of chloride by gluconate in the pipette filling solution had little effect on the slope conductance at the resting potential or on the estimated reversed potential. With isotonic BaCl2 in the pipette, ADP evoked single channel currents with a slope conductance of 10 picosiemens. Thus these channels appear to be permeable to monovalent and divalent cations and selective for cations over anions. Addition of 5 mM Ni2+ (which blocks ADP-evoked rapid calcium entry in fura-2-loaded platelets) to the pipette solution blocked ADP-evoked channel activity. These channels may therefore provide an important mechanism for ADP to activate human platelets within a small fraction of a second.     

The major polypeptide (MIP) of lens fiber junctions and its synthesis in cultured differentiating lens epithelial cells

Lens and liver contain many gap junctions, which for a long time have been considered to be very similar. Recent results, however, point to differences on morphological and biochemical levels, especially when the liver gap junction polypeptide (26,000 Daltons) is compared with the main intrinsic polypeptide (MIP) from lens junctions. The lens fiber specific MIP, which represents a marker molecule for lens cell differentiation could be detected by indirect immunofluorescence as well as by immunodiffusion in lens epithelial cells, which differentiated in vitro under distinct culture conditions. The fine structure of these differentiated cells is presented.Based on material presented at the Symposium Intercellular Communication Stuttgart, September 16–17, 1982     

Calcium-dependent slow potassium conductance in rat skeletal myotubes

A prolonged hyperpolarizing afterpotential (amplitude 5–20 mV, half decay time about 400 msec at 25°C) follows the action potential in myotubes and myosacs cultured from rat skeletal muscle. This slow hyperpolarizing afterpotential (hap) is mediated by an increase in membrane K conductance, because its reversal potential follows the Nernst potential for K and is not affected by other ions. The conductance increase measured during the hap (up to four times the resting input conductance) correctly predicts the time course of the slow hap. The slow hap is Ca dependent. Its amplitude decreases when bath [Ca] is lowered, and both amplitude and duration increase when bath [Ca] is raised. The slow hap is blocked by intracellular injection of the calcium chelator, EGTA. It is inhibited by solutions containing 2–4 mM manganese or 1–5 mM barium, but is not blocked by 5–20 mM tetraethylammonium. Myotubes bathed in zero [Na], high [Ca] solutions show calcium action potentials, which are inhibited by 2–10 mM manganese, nickel or cobalt. Myotubes bathed in isotonic Ca salts (or in 2 mM Ca plus 5 mM caffeine) show long-lasting (up to 10 sec) spontaneous hyperpolarizations accompanied by prolonged contractions. These hyperpolarizations are associated with a large increase in input conductance, and they reverse in sign near the K equilibrium potential. They appear to reflect activation of the Ca-sensitive K conductance by Ca released from intracellular stores. The observation that spontaneous hyperpolarizations usually occur with no prior depolarization argues that at least a portion of the slow, Ca-sensitive K conductance system can be activated by internal Ca alone, with no requirement for plasma membrane depolarization. Cultured myotubes also have a faster K conductance system, which is inhibited by 5–20 mM tetraethylammonium or 1–5 mM barium, and is not dependent on Ca for its activation.     

Monitoring yeast spindles in the fluorescence microscope

Formation of the complete spindles during the budding process of Saccharomyces uvarum was investigated by fluorescence microscopy of protoplasted cells. Protoplasts were treated with anti-tubulin antibodies and DAPI, a fluorescent dye staining DNA. Thus, both chromatin and spindles could be visualized. Duplication as well as formation of separated spindle pole bodies during the different stages of budding are documented, demonstrating the occurrence and behaviour of microtubules during yeast cell cycle.