Atrial natriuretic factor messenger ribonucleic acid and peptide in the human heart during ontogenic development

We have investigated the level of expression of the atrial natriuretic factor (ANF) gene in the human heart during ontogenic development by determining the concentrations of ANF messenger ribonucleic acid (ANF mRNA), of immunoreactive ANF (IR ANF) and of receptor reactive ANF (RR ANF), in myocardial samples of the various heart chambers. We found the level was high and almost identical in the left and right ventricles in utero. It gradually decreased during ontogenic development to reach the low adult levels, with a more rapid decrease in the right than in the left ventricle after birth. In the atria, ANF gene expression was high as early as the 13th week of gestation, was higher in the right than in the left atrium, and appeared little affected by ontogenic development.     

Microelectrode studies of amphotericin B on Na+ and K+ conductance in bullfrog cornea

Addition of 10(-5) M amphotericin B to the tear solution of an in vitro preparation of the frog cornea increased the transepithelial conductance, gt, and decreased the apical membrane fractional resistance, f(R0), in the presence or absence of tear Na+ and Cl-. In the presence of tear Na+ and Cl-, amphotericin B increased the short-circuit current, Isc, from 3.9 to 8.8 microA.cm-2 and changed the intracellular potential, V0, from -48.5 to -17.9 mV probably due to a higher increase in the Na+ than in the K+ conductance. In the absence of tear Na+ and Cl-, amphotericin B decreased Isc from 5.5 to about 0 microA.cm-2 due to K+ (and possibly Na+) flux from cell to tear and changed V0 from -35.4 to -63.6 mV due to the increase in conductance of both ions. Increase in the tear K+ from 4 to 79 mM (in exchange for choline), in the presence of amphotericin B and absence of tear Na+ and Cl-, decreased f(R0) from 0.09 to 0.06, increased gt from 0.23 to 0.31 mS, increased Isc from 0.63 to 7.3 microA.cm-2, and changed V0 from -65.5 to -17.3 mV due to the change in EK in the presence of a high conductance in the tear membrane. Similar effects were observed with an increase of tear Na+. Results support the concept that the Na+ conductance opened by amphotericin B in the apical membrane is greater than the K+ conductance. Previously observed transepithelial effects of the ionophore may be explained mostly on the basis of its effect on the apical membrane.     

In vitro study of transgenic tobacco expressing Arabidopsis wild type and mutant acetohydroxyacid synthase genes

Summary Genes coding for the enzyme acetohydroxyacid synthase, often referred to as acetolactate synthase (AHAS, ALS; EC 4.1.3.18), from wild type Arabidopsis thaliana and a sulfonylurea-resistant mutant line GH50 (csrl-1; Haughn et al. 1988) were introduced in Nicotiana tabacum. Both genes were expressed at high levels with the 35S promoter. The csrl-1 gene conferred high levels of resistance to chlorsulfuron whereas the wild type gene did not. As selectable markers, chimaeric AHAS genes yielded transgenic plants on chlorsulfuron but at much lower efficiencies than with a chimaeric neomycin phosphotransferase gene on kanamycin (Sanders et al. 1987). Shoot differentiation from leaf discs was delayed on chlorsulfuron by 4–6 weeks. This study indicated a role for mutant AHAS genes in the genetic manipulation of herbicide resistance in transgenic plants but as selectable markers for plant cells undergoing differentiation no advantage over other genes was perceived.     

Localization of the Miller-Dieker critical region is proximal to locus D17S34 (p144D6) in 17p13.3

A child with normal growth and development and the abnormal karyotype 46,XY,17ps, was analyzed using molecular probes localized to 17p13. The results indicated the presence of two copies of the probes YNZ22.1 (D17S5) and YNH37.3 (D17S28), previously shown to be deleted in all Miller-Dieker (MDS) patients studied. However, the patient was hemizygous for probe p144D6 (D17S34), which is absent in approximately 75% of the MDS patients. As the patient is active at 9 months of age, with no clinical signs of MDS, the results confirm that the absence of locus D17S34 does not lead to the phenotypic expression of MDS. Furthermore, this deletion should assist in defining the distal limits of this contiguous gene syndrome.     

New solution method for equations of reaction and mass transfer in biocatalyst particles

Summary For numerical solution of the reaction-mass transfer equations for immobilised biocatalysts it may be better to start integration at the particle surface and proceed inwards: calculations are targetted on the region to which practically interesting changes are often confined (because concentrations are effectively zero in the interior); and during iterative solution wrong initial estimates may be rejected after detecting anomalies early in the integration.Symbols C_b substrate concentration in bulk (mol m^–3) - c dimensionless substrate concentration (C/C_b) (-) - D_e effective diffusion coefficient (m²s^–1) - Da Damkohler number (V.r_o ²/D_e.K_s) (-) - K_s substrate concentration kinetic coefficient (mol m^–3) - k_e external mass transfer coefficient (ms^–1) - r_o bead radius (m) - Sh Sherwood number (k_e.r_o/D_e) (-) - V maximum rate per unit volume in beads (mol m^–3s^–1) - x dimensionless distance from bead centre (r/r_o) (-) - dimensionless kinetic coefficient (K_s/C_b) (-) - _o effectiveness factor (-)     

Expression of {beta}-galactoside {alpha}2,6 sialyltransferase blocks synthesis of polysialic acid in Xenopus embryos

Polysialic acid is a developmentally regulated carbohydratestructure found on neural cell adhesion molecules (NCAM). Expressionof ß-galactoside 2,6-sialyltransferase in Xenopusembryos, by injection of mRNA, prevents the polysialylationof NCAM, presumably by introducing a different type of sugarlinkage that terminates chain elongation. Abnormalities in neuraldevelopment result from this treatment, but in general the bodyplan of the injected embryos is not severely affected. The resultsprovide evidence that the mis-expression of glycosyltransferasescan be used to interfere with the normal pattern of glycosylationin whole organisms. glycosylation NCAM polysialic acid Xenopus development