Organization of fusicoccin receptor in higher plant plasma membrane: relationship between affinity and molecular mass

Higher plant plasma membranes carry receptors of different affinity for the phytotoxin fusicoccin. Reception of fusicoccin involves proteins belonging to the highly conserved 14-3-3 family, but the complete structure of the fusicoccin receptor (FCR) is unknown. Using radiation inactivation analysis, we estimated the molecular masses of low-affinity and high-affinity FCR at 63 +/- 7 and 130 +/- 15 kD, respectively. The dose dependences of receptor inactivation indicate that microsomal specimens contain "silent" FCRs of 420 +/- 90 kD in amounts commensurate with that of the active FCRs. Both low- and high-affinity FCRs are inactivated by hydrolytic enzymes from the outer surface of the plasma membrane, and impairment of protoplast integrity causes an irreversible transition of the low-affinity binding site into the high-affinity one. A scheme is proposed for the organization of different types of FCR in the plasma membrane, implying that the membrane affinity for fusicoccin reflects the interaction between proteins in the FCR complex.     

Genetic determinants of dengue type 4 virus neurovirulence for mice.

Mouse-adapted dengue type 4 virus (DEN4) strain H241 is highly neurovirulent for mice, whereas its non-mouse-adapted parent is rarely neurovirulent. The genetic basis for the neurovirulence of the mouse-adapted mutant was studied by comparing intratypic chimeric viruses that contained the three structural protein genes from the parental virus or the neurovirulent mutant in the background sequence of nonneurovirulent DEN4 strain 814669. The chimera that contained the three structural protein genes from mouse neurovirulent DEN4 strain H241 proved to be highly neurovirulent in mice, whereas the chimera that contained the corresponding genes from its non-mouse-adapted parent was not neurovirulent. This finding indicates that most of the genetic loci for the neurovirulence of the DEN4 mutant lie within the structural protein genes. A comparison of the amino acid sequences of the parent and its mouse neurovirulent mutant proteins revealed that there were only five amino acid differences in the structural protein region, and three of these were located in the envelope (E) glycoprotein. Analysis of chimeras which contained one or two of the variant amino acids of the mutant E sequence substituting for the corresponding sequence of the parental virus identified two of these amino acid changes as important determinants of mouse neurovirulence. First, the single substitution of Ile for Thr-155 which ablated one of the two conserved glycosylation sites in parental E yielded a virus that was almost as neurovirulent as the mouse-adapted mutant. Thus, the loss of an E glycosylation site appears to play a role in DEN4 neurovirulence. Second, the substitution of Leu for Phe-401 also yielded a neurovirulent virus, but it was less neurovirulent than the glycosylation mutant. These findings indicate that at least two of the genetic loci responsible for DEN4 mouse neurovirulence map within the structural protein genes.     

Romanowsky staining,the Romanowsky effect and thoughts on the question of scientific priority

I give an historical account and analysis of the scientific priority of the discovery of the polychrome staining of microscopic biological preparations provided by mixtures of eosin plus methylene blue and its derivatives, especially azure B. I maintain that both the formal priority for the discovery of the polychrome staining phenomenon and credit for initiating the development of a technique of polychrome staining properly belong to D. L. Romanowsky. His scientific work demonstrated the possibility of using a simple technique to stain hematological preparations selectively to give good contrast, high resolution and the ability to identify malaria parasites. Romanowsky’s approach constituted the starting point for the development of a family of polychrome stains for microscopic investigation of hematological preparations by a number of his contemporaries.     

Energetic aspects of CO oxidation in desulfovibrio desulfuricans

In cell suspension of Desulfovibrio desulfuricans B-1388, oxidation of CO as the only energy source is associated with reduction of SO42-. After a 2-h incubation of cells in 8% CO, 81% of the gas is converted. Oxidation of 1 mole CO results in formation of 0.23 mole H2S. Intracellular ATP content increases from 2.5 (control) to 8.3 nmoles/mg (during CO conversion). Dinitrophenol inhibits sulfate reduction and CO oxidation. CO dehydrogenase was detected in cytoplasmic and membrane cell fractions (59 and 34%, respectively).     

Feedback equilibrium control during human standing

Equilibrium maintenance during standing in humans was investigated with a 3-joint (ankle, knee and hip) sagittal model of body movement. The experimental paradigm consisted of sudden perturbations of humans in quiet stance by backward displacements of the support platform. Data analysis was performed using eigenvectors of motion equation. The results supported three conclusions. First, independent feedback control of movements along eigenvectors (eigenmovements) can adequately describe human postural responses to stance perturbations. This conclusion is consistent with previous observations (Alexandrov et al., 2001b) that these same eigenmovements are also independently controlled in a feed-forward manner during voluntary upper-trunk bending. Second, independent feedback control of each eigenmovement is sufficient to provide its stability. Third, the feedback loop in each eigenmovement can be modeled as a linear visco-elastic spring with delay. Visco-elastic parameters and time-delay values result from the combined contribution of passive visco-elastic mechanisms and sensory systems of different modalities     

Spatiotemporal patterns of macrophage migration inhibitory factor (Mif) expression in the mouse placenta

Background  

Macrophage migration inhibitory factor (MIF) has special pro-inflammatory roles, affecting the functions of macrophages and lymphocytes and counter-regulating the effects of glucocorticoids on the immune response. The conspicuous expression of MIF during human implantation and early embryonic development also suggests this factor acts in reproductive functions. The overall goal of this study was to evaluate Mif expression by trophoblast and embryo placental cells during mouse pregnancy.     

Insertion of short hepatitis virus A amino acid sequences into poliovirus antigenic determinants results in viable progeny

In an infectious poliovirus cDNA construct, the determinant encoding antigenic epitope N-Ag1 (in a loop located between two beta-strands in poly-peptide VP1) was altered by site-directed mutagenesis, to be partially similar with the determinants for presumptive epitopes in polypeptides VP1 or VP3 of hepatitis A virus (HAV). The modified constructs proved to be infectious. However, another construct, in which the same locus encoded a 'nonsense' and a relatively hydrophobic amino acid sequence, exhibited no infectivity. These data showed the feasibility of the insertion of foreign sequences in a specific antigenically active locus of the poliovirus icosahedron, and suggest some limitations with respect to the sequences to be 'transplanted'.