Beta R2 Research Articles

Digitalis purpurea P5βR2, encoding steroid 5β‐reductase, is a novel defense‐related gene involved in cardenolide biosynthesis

The stereospecific 5 beta-reduction of progesterone is a required step for cardiac glycoside biosynthesis in foxglove plants. Recently, we have isolated the gene P5 beta R, and here we investigate the function and regulation of P5 beta R2, a new progesterone 5 beta-reductase gene from Digitalis purpurea. P5 beta R2 cDNA was isolated from a D. purpurea cDNA library and further characterized at the biochemical, structural and physiological levels. Like P5 beta R, P5 beta R2 catalyzes the 5 beta-reduction of the Delta(4) double bond of several steroids and is present in all plant organs. Under stress conditions or on treatment with chemical elicitors, P5 beta R expression does not vary, whereas P5 beta R2 is highly responsive. P5 beta R2 expression is regulated by ethylene and hydrogen peroxide. The correlation between P5 beta R2 expression and cardenolide formation demonstrates the key role of this gene in cardenolide biosynthesis, and therefore in the chemical defense of foxglove plants.

Expression of transforming growth factor beta isoforms and their receptors in malignant fibrous histiocytoma of soft tissues.

Transforming growth factor beta (TGF-beta) is a multifunctional growth factor that variably affects proliferation, differentiation, and extracellular matrix formation. Little information is currently available on the TGF-beta expression in malignant fibrous histiocytoma (MFH). The aims of the present study were to investigate the expression of TGF-beta isoforms and their receptors in human MFH specimens. The expression of TGF isoforms, and TGF-beta receptors (TGF-beta R1 and -beta R2) were immunohistochemically evaluated in 43 paraffin-embedded MFH specimens. Furthermore, the correlation of the TGF-beta and receptor expression with tumor proliferative activity assessed by MIB-1 indices was analyzed. Positive immunoreactivity for TGF-beta1, -beta2, and -beta 3 was identified in tumor cells of 42, 40, and 38 of the 43 MFHs, respectively. In each TGF-beta isoform immunostaining, the specimens were divided into two groups based on the number of positive tumor cells: those with low (<25%) and those with high (>==25%) immunoreactivity. There were no statistically significant differences in the MIB-1 indices between the two groups. Positive immunoreactivity for TGF-beta R1 and -beta R2 was identified in tumor cells of 36 and 24 of the MFHs, respectively. The specimens were divided into two groups based on their receptor expression patterns: those with both TGF-beta R1- and -beta R2-positive immunoreactivity (n = 23), and those with both or either TGF-beta R1- and -beta R2-negative immunoreactivity (n = 20). The MIB-1 indices in the both-TGF-beta R1- and -beta R2-positive group were significantly higher than those in the other group (P = 0.0102). There was no significant difference in pulmonary metastasis ratios between the two groups. These findings strongly suggest an association of the TGF-beta ligand/receptor system with a significantly higher MIB-1 index in human MFHs. Investigation of the TGF-beta R1 and -beta R2 coexpression might be useful in predicting tumor behavior of MFHs.

Acoustic scattering by inhomogeneous spheres

Acoustic scattering problems are considered when the material parameters (density rho and speed of sound c) are spherically symmetric functions of position. Explicit separated solutions are derived (i) when rho(r) = exp(beta r) and c(-2) is a linear function of r(-1), and (ii) when rho(r) = exp(-beta r2) and c(-2) is a linear function of r2. In both cases, the radial parts of the solutions are given in terms of Coulomb wave functions or Whittaker functions; these are well-studied special functions, closely related to confluent hypergeometric functions. Two problems are discussed in detail: scattering by an inhomogeneous sphere embedded in a homogeneous fluid, and scattering by a homogeneous sphere with a concentric inhomogeneous coating.

Molecular electrostatic potentials from crystal diffraction: the neurotransmitter gamma-aminobutyric acid

Given the electronic charge parameters obtained from a diffraction study of the charge density distribution in a crystal, a mathematical procedure is presented for deriving the electrostatic potential. The procedure allows the mapping of electrostatic potential for a molecule or group of molecules removed from the crystal structure but with each molecule retaining the effects of polarization owing to the original crystal environment. The method is applied for the neurotransmitter gamma-aminobutyric acid. The potential for a gamma-aminobutyric acid molecule is analyzed in terms of a simple model that is suitable for rapid computations concerned with Coulombic molecular interactions. Outside the molecular envelope at 1.2 A from the atomic nuclei, the total potential is well represented by a sum of spherical atom contributions with V(r) = (q/r) + exp(-beta r2). The most important aspherical component in the potential is the dipole contribution from the hydrogen atoms. This can be represented as V(r, phi) = (0.162 cos phi)/(r2 + 0.615). Here, V is in e/A, r is the distance from each nucleus in A, q is the experimentally determined net atomic charge in electron units, and phi is the angle between r and the bond X-H. We obtain beta = 1.47, 1.66, 1.83 A-2 for C, N, and O respectively. For H, no term in beta is needed.

Entropy principle for Tokamak profiles

Experimental temperature and density profiles are consistent with the assumption that they relax towards profiles related by T(x)/T0=(n(x)/n0)gamma -1 exp( alpha (1-(n0/n(x)))) (1), gamma =5/3=adiabatic constant, alpha >or=-( gamma -1)nmin/n0 independent of x; in most cases one has nmin=0. Cases of incomplete relaxation are exceptions, e.g. certain Tokamak discharges with pellet injection in which the temperature profiles are too flat compared with the corresponding density profiles. Relation (1) follows from the entropy principle proposed. According to it, Tokamak plasmas should relax towards states described by relations T=T(n(x)), in which the total entropy of the plasma does not change when the plasma performs arbitrary internal motions slow enough not to alter the relation between T and n. The relaxation is incomplete if it is too slow to compete with influences such as very strong local heating or very large local radiation. The profiles obtained by Biskamp (1986) and Kadomtsev (1986) from an energy principle assuming the electrical conductivity given by Spitzer's law sigma =const T(x)3/2 correspond approximately to alpha =1. To get agreement with the experimental profiles considered, however, alpha values ranging from 0 to 3 are required. Tokamak equilibria are usually describable in terms of two arbitrary functions of the poloidal flux psi . For resistive plasmas with Spitzer's formula valid one can choose the temperature and density as these function. Equation (1) reduces this freedom to the free choice of one function, say T( psi ), and of a special value of the parameter alpha . Examples are presented for cylindrical plasmas with circular cross-sections. A comparison with Coppi's temperature formula ('profile consistency', see Coppi, 1980) leads in many cases to very good agreement. Combining Coppi's formula with relation (1), one obtains density and temperature profiles depending only on the two quantities alpha and beta r2, with beta being related to the plasma radius and the safety factor. Examples of a few values are shown.

Unification and higher-derivative gravity

The author considers higher-derivative theories of gravitation in which beta R2 and alpha Rmu nu Rmu nu terms are present in the Lagrangian density, in addition to the usual scalar curvature R term. The author shows that using this Lagrangian to obtain the field equations in a fibre-bundle unification of electromagnetism and general relativity leads to unacceptable modifications to Maxwell's equations even for very small alpha . Since the Kaluza-Klein unification and related fibre-bundle unifications of general relativity with a non-Abelian gauge group are major successes of the geometrical ideas behind general relativity, these results suggest that adding an Rmu nu Rmu nu term is not a profitable approach to future gravitational theories. The R3 term, on the other hand, is not ruled out by these considerations.

Analyticity of Schrodinger energy levels for confining potentials

The analyticity of the Schrodinger energy levels in the coupling constant beta for a class of confining potentials of the type V(r)=- zeta /r+ alpha r+ beta r2 has been studied by using Kato-Rellich perturbation theory for linear operators.