Linkage analysis of chromosome 17 markers in British and South African families with neurofibromatosis type 1

Nine markers from the pericentromeric region of chromosome 17 were typed in 16 British and five South African families with neurofibromatosis type 1 (NF1). The markers--p17H8, pHHH202, and EW204--were linked to NF1 at recombination fractions less than 1%. No evidence of locus heterogeneity was detected. Inspection of recombinant events in families informative for several markers suggests that the NF1 gene is located between the markers EW301 (cen-p11.2) and EW206 (cen-q12) and possibly distal to pHHH202 (q11.2-q12).     

The major type-1 protein phosphatase catalytic subunits are the same gene products in rabbit skeletal muscle and rabbit liver

The catalytic subunit of protein phosphatase-1 (PP1) isolated from rabbit liver had the same electrophoretic mobility as, and yielded peptide maps identical to those of the 33 kDa form of rabbit skeletal muscle PP1. The predicted amino-acid sequences of PP1 obtained from three rabbit liver cDNA clones were identical to that of PP1 alpha from rabbit skeletal muscle. These findings suggest that the distinctive substrate specificities and regulatory properties of hepatic and skeletal muscle type-1 protein phosphatases are not conferred by the catalytic subunits themselves, but by regulatory subunits that are complexed to the catalytic subunits in vivo.     

The effect of vanadate on glucose transport and metabolism in rat small intestine

The effect of sodium orthovanadate on the absorption, transmural transport and metabolism of glucose was studied by perfusion of isolated loops of rat jejunum in vitro. The presence of 1 mM vanadate in the serosal medium diminished absorption from 539 +/- 19 (n = 12) to 246 +/- 19 (P less than 0.001) mumol/h per g dry weight and transmural transport from 333 +/- 17 to 14 +/- 19 (P less than 0.001) mumol/h per g dry weight, whereas glucose utilisation was unaffected. The rate of release of lactate into the serosal medium was also diminished from 168 +/- 14 to 75 +/- 5 mumol/h per g dry weight (P less than 0.001). The observed rates were linear with respect to time and vanadate was effective within 5 min. In contrast, the rate of release of lactate into the luminal perfusate was strongly enhanced. Moreover, the progress curve showed a positive transient with an apparent lag time of 18.0 +/- 0.3 min, during which the rate increased to a value 9.2-times that of the control. Under the final steady-state conditions, the ratio of mucosal to serosal lactate production was 5.2 +/- 0.2 compared with 0.25 +/- 0.06 for the control, so that the effect of vanadate was to reverse the vectorial disposition of lactate. The concentration dependence of the effect of vanadate on absorption and metabolism was similar to that observed for the inhibition by vanadate of Na+/K+-ATPase activity in mucosal homogenates. The results are discussed in terms of the dissipation of transmembrane Na+ gradients as a result of the inhibition of the Na+/K+-ATPase.     

Expression of 9E3 mRNA is associated with mitogenicity, phosphorylation, and morphological alteration in chicken embryo fibroblasts.

Transformation of chicken embryo fibroblasts (CEF) with viruses encoding src, ros, yes, and fps as well as ras, mos, middle T, erbA and erbB, myc, and crk stimulated 9E3 mRNA expression. Treatment of CEF with agents that modulate cell shape or attachment to the substratum caused an increase in 9E3 mRNA without an increase in tyrosine phosphorylation. 9E3 mRNA was also increased in CEF in response to several agents which modulate phosphorylation, including phorbol myristic acetate, vanadate, and okadaic acid, which suggests that the rapid induction of 9E3 mRNA expression in CEF by the src protein occurs downstream of morphological or phosphorylation events.     

Medicago truncatula,a model plant for studying the molecular genetics of theRhizobium-legume symbiosis

Medicago truncatula has all the characteristics required for a concerted analysis of nitrogen-fixing symbiosis withRhizobium using the tools of molecular biology, cellular biology and genetics.M. truncatula is a diploid and autogamous plant has a relatively small genome, and preliminary molecular analysis suggests that allelic heterozygosity is minimal compared with the cross-fertilising tetraploid alfalfa (Medicago sativa). TheM. truncatula cultivar Jemalong is nodulated by theRhizobium meliloti strain 2011, which has already served to define many of the bacterial genes involved in symbiosis with alfalfa. A genotype of Jemalong has been identified which can be regenerated after transformation byAgrobacterium, thus allowing the analysis ofin-vitro-modified genes in an homologous transgenic system. Finally, by virtue of the diploid, self-fertilising and genetically homogeneous character ofM. truncatula, it should be relatively straightforward to screen for recessive mutations in symbiotic genes, to carry out genetic analysis, and to construct an RFLP map for this plant.     

Inositol phosphates in receptor-mediated cell signaling: metabolic origins and interrelationships

We have investigated the metabolic interrelationships of the major inositol phosphates in vasopressin-stimulated WRK 1 mammary tumor cells which were labeled to equilibrium with [14C]inositol and briefly, just prior to stimulation, with [3H]inositol. A comparison of the 3H/14C ratios of these compounds with those of the cellular inositol lipids suggests that most of the known inositol mono-, bis-, tris-, and tetrakis-phosphates are derived from precursors with turnover rates similar to those of these lipids. However, Ins(3,4,5,6)P4 (which is the major inositol tetrakisphosphate to accumulate in stimulated WRK 1 cells), Ins(1,3,4,5,6)P5, and InsP6 had 3H/14C ratios of 0 in this experiment, indicating that they must have a different metabolic origin.     

Synthesis of myo-inositol 1,3,4,5,6-pentakisphosphate from inositol phosphates generated by receptor activation.

myo-[3H]Inositol 1,3,4,5,6-pentakisphosphate can be made from myo-[3H]inositol 1,4,5-trisphosphate in a rat brain homogenate or soluble fraction. Although D-myo-inositol 3,4,5,6-tetrakisphosphate can be phosphorylated by a soluble rat brain enzyme to give myo-inositol 1,3,4,5,6-pentakisphosphate, it is not an intermediate in the pathway from myo-inositol 1,4,5-trisphosphate. The intermediates in the above pathway are myo-inositol 1,3,4,5-tetrakisphosphate, myo-inositol 1,3,4-trisphosphate and myo-inositol 1,3,4,6-tetrakisphosphate [Shears, Parry, Tang, Irvine, Michell & Kirk (1987) Biochem. J. 246, 139-147; Balla, Guillemette, Baukal & Catt (1987) J. Biol. Chem. 262, 9952-9955], and it is catalysed by soluble kinase activities of similar anion-exchange mobility and Mr value. Compounds with chromatographic and chemical properties consistent with the structures myo-inositol 1,3,4,5-tetrakisphosphate, myo-inositol 1,3,4,6-tetrakisphosphate and myo-inositol 3,4,5,6-tetrakisphosphate are present in avian erythrocytes, human 1321 N1 astrocytoma cells and primary-cultured murine bone-marrow-derived macrophages. The amounts of these inositol tetrakisphosphates rise upon muscarinic cholinergic stimulation of the astrocytoma cells or stimulation of macrophages with platelet-activating factor.     

An epizootic of Mycoplasma ovipneumoniae infection in captive Dall's sheep (Ovis dalli dalli)

In late spring of 1986, 10 of 23 Dall's sheep (Ovis dalli dalli) at the Metropolitan Toronto Zoo were moved to a new exhibit, where all developed severe respiratory signs refractory to anthelmintic and antibiotic therapy. In July, two animals died with chronic active bronch-pneumonia, and a third was euthanized because of pneumonia several months later. Bacteria were not isolated from the lungs of the first, steptococci and Pasteurella hemolytica were isolated from the other two, respectively; Mycoplasma ovipneumoniae was isolated from both. Pulmonary lesions in all three sheep were consistent with Mycoplasma sp. infection. Nasal swabs of the remaining animals yielded no consistent bacterial isolates; however, four of eight sheep were positive for M. ovipneumoniae. Viral cultures yielded an as yet unidentified herpesvirus. Sheep in the original and new herds had no serologic titers to parainfluenza-3, equine viral rhinopneumonitis, or infectious bovine rhinotracheitis, and had variable titers against bovine respiratory syncytial virus. No titers against M. ovipneumoniae were present in 13 sheep still in the original exhibit, but titers varied from 1:32 to 1:256 in eight pneumonic sheep. Sera taken from three sheep before or early in the outbreak were all negative for antibody to M. ovipneumoniae. Two of the affected Dall's sheep had been in contact with domestic sheep in the winter of 1985-1986, and M. ovipneumoniae was subsequently cultured from the domestic flock. Exposure to a new pathogen, and environmental and social stress in a new exhibit may have resulted in this severe disease in Dall's sheep.