Relationship of the replication and incompatibility genes of an IncFVI haemolysin plasmid with other F-like haemolysin plasmids

The replication and incompatibility region of the IncFVI plasmid pSU502 has been isolated by in vitro DNA manipulation as part of a 12.6 kb plasmid, denominated pSU503. Plasmid pSU503 was strongly incompatible with its parental plasmid, pSU1, but was fully compatible with the haemolytic plasmids pSU316 (IncFIII/IV), pHly152 (IncI2) and pSU233 (Inc-pSU233). Furthermore, the 6.9 kb EcoRI fragment of pSU503 which carries the replication and incompatibility determinants of pSU1 did not show any detectable homology (less than 70%) with any of the haemolysin-determining plasmids with which it is compatible. Thus, homologous haemolysin determinants have become linked to apparently unrelated replicons.     

Ecdysteroids in the haemolymph and the ovaries of the firebrat Thermobia domestica (Packard) (Insecta,Thysanura): Correlations with integumental and ovarian cycles

Ecdysteroids were analysed with radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC) in females of the apterygotous insect Thermobia domestica, which ahs overlapping moulting and reproductive cycles. During each moulting cycle, a peak in the haemolymph concentration of ecdysteroids occurs at day 9 (in the 11-day standard cycle), which can be correlated with apolysis and the beginning of new cuticle deposition. The ovaries show a peak of ecdysteroids at day 5 (i.e. one day before egg-laying), which suggests that these hormones are also involved in the reproductive cycle. In both cases, HPLC analysis combined with RIA suggests that the main ecdysteroid is 20-hydroxyecdysone. This duality in the function of ecdysteroids is discussed.     

Reinvestigation of the shape and state of hydration of the skeletal myosin subfragment 1 monomer in solution

Hydrodynamic calculations lead to the conclusion that chymotryptic (or ethylenediaminetetraacetic acid) myosin S1 in solution (hydrated), at 1-5 degrees C, can be modeled as a prolate ellipsoid, with an axial ratio lying between p = 1.0 and 2.5 (major axis between 100.5 A, for p = 1.0, and 162.5 A, for p = 2.5). The degree of hydration is considerable (1.24 g/g for p = 2.5 and 2.02 g/g for p = 1.0). The dehydrated myosin head is pear-shaped under the electron microscope, and its narrowest part is located near the junction with the tail [Elliott, A., & Offer, G. (1978) J. Mol. Biol. 123, 505-519]. Mendelson & Kretzschmar [Mendelson, R. A., & Kretzschmar, K.M. (1980) Biochemistry 19, 4103-4108] have shown that the pear-shaped molecule does not predict the experimental X-ray scattering curve. Nor is this model able to predict the hydrodynamic values. The three-dimensional model for S1 used by Mendelson and Kretzschmar gives a rather good fit to the experimental X-ray scattering curve, but it does not predict the hydrodynamic values. In order to try to reconcile the three models and to fit the X-ray scattering curve and the hydrodynamic data, we suggest that, in solution, the S1 monomer has the shape of a prolate ellipsoid and that an inclusion of bound water exists at one extremity of the protein. The rest of bound water surrounds the protein. As first approximation, the dry protein and the hole are assumed to have the same shape as the hydrated molecule (prolate ellipsoid; p).(ABSTRACT TRUNCATED AT 250 WORDS)     

Transport properties of rigid, symmetrical oligomeric structures composed of prolate, ellipsoidal subunits

We have calculated translational and rotational diffusion coefficients and intrinsic viscosities of oligomeric structures composed of n identical subunits having a prolate ellipsoidal shape with axial ratio p. Results are presented for p = 1-6 for a variety of structures with n = 1-6. We compare our results with those obtained by a different modeling procedure, proposed by other workers, in which the monomeric subunit is represented as a string of touching, colinear spheres. If n and an estimate of p are known, the structure of the oligomer can be. in most cases, unambiguously determined by comparison of the experimental oligomer-to-monomer ratios of a given property with the numerical results of this work. As examples of the applicability of our results, we examine the relationship between structure and properties for neurophysin. bovine serum albumin, hemoglobin and phycocyanin.     

Lambda Ig constant region genes are translocated to chromosome 8 in Burkitt''s lymphoma with t(8;22)

By in situ hybridization of normal human chromosomes with a cloned genomic probe specific for the constant region of the lambda immunoglobulin genes, band 22q11 was preferentially labelled. In two cell lines with t(8;22) derived from Burkitt's lymphoma a strong signal was noted on the 8q+ chromosome derivative, indicating that the constant region of the lambda Ig gene cluster was translocated from chromosome 22 to chromosome 8. In addition, the signal observed on the 22q- derivative chromosome was stronger than the background in one of the two cell lines tested, but not in the other. The implications are that the break point in chromosome 22 in some cases lies within the Ig gene itself or between clusters of such genes, and that different cases have different break points.     

Geotropism and the lateral transport of auxin in the corn mutant amylomaize

Summary In coleoptiles of the amylomaize corn mutant (AM), the amyloplasts are much reduced in size in comparison with the wild type corn (WT), permitting a comparison of geotropic responsiveness as related to lateral displacement of amyloplasts and lateral transport of auxin. The amyloplasts of AM showed 30–40% lesser lateral redistribution in response to horizontal exposure in comparison with WT. With geotropic stimulation, the lateral transport of auxin in the direction of growth was 40–80% less, and the geotropic curvature by the coleoptiles was also significantly less in the mutant as compared with WT. These correlations support the hypothesis that the starch plastids serve as gravity sensors in the geotropic responses of coleoptiles.