S100a0 (αα) Protein Is Present in Neurons of the Central and Peripheral Nervous System

The cellular distribution of S100 subunits in human brain and peripheral nerves was studied by means of an immunohistochemical technique using antibodies specific to the alpha subunit or the beta subunit of S100 protein. The results indicate that the distribution of the alpha subunit and the beta subunit is different among cell types in the nervous tissue, and that neurons in the brain and peripheral nerves contain only the alpha subunit, or S100a0 protein. The subunit distribution also appears to be different at an intracellular level, where the immunoreaction products for the alpha subunit show granular arrangement whereas those for the beta subunit are found diffusely in the cytoplasm.     

Mathematical modelling of dynamics and control in metabolic networks. II. Simple dimeric enzymes

The dynamics of enzyme cooperativity are examined by studying a homotropic dimeric enzyme with identical reaction sites, both of which follow irreversible Michaelis-Menten kinetics. The problem is approached via scaling and linearization of the governing mass action kinetic equations. Homotropic interaction between the two sites are found to depend on three dimensionless groups, two for the substrate binding step and one for the chemical transformation. The interaction between the two reaction sites is shown capable of producing dynamic behavior qualitatively different from that of a simple Michaelis-Menten system; when the two sites interact to increase enzymatic activity over that of two independent monomeric enzymes (positive cooperativity) damped oscillatory behavior is possible, and for negative cooperativity in the chemical transformation step a multiplicity of steady states can occur, with one state unstable and leading to runaway behavior. Linear analysis gives significant insight into system dynamics, and their parametric sensitivity, and a way to identify regions of the parameter space where the approximate quasi-stationary and quasi-equilibrium analyses are appropriate.     

Interstrand duplexes in Friend erythroleukemia nuclear RNA. The interaction of non-polyadenylated nuclear RNA with polyadenylated nuclear RNA and with small nuclear RNAs

Intermolecular duplexes among large nuclear RNAs, and between small nuclear RNA and heterogeneous nuclear RNA, were studied after isolation by a procedure that yielded protein-free RNA without the use of phenol or high salt. The bulk of the pulse-labeled RNA had a sedimentation coefficient greater than 45 S. After heating in 50% (v/v) formamide, it sedimented between the 18 S and 28 S regions of the sucrose gradient. Proof of the existence of interstrand duplexes prior to deproteinization was obtained by the introduction of interstrand cross-links using 4'-aminomethyl-4,5',8-trimethylpsoralen and u.v. irradiation. Thermal denaturation did not reduce the sedimentation coefficient of pulse-labeled RNA obtained from nuclei treated with this reagent and u.v. irradiated. Interstrand duplexes were observed among the non-polyadenylated RNA species as well as between polyadenylated and non-polyadenylated RNAs. beta-Globin mRNA but not beta-globin pre-mRNA also contained interstrand duplex regions. In this study, we were able to identify two distinct classes of polyadenylated nuclear RNA, which were differentiated with respect to whether or not they were associated with other RNA molecules. The first class was composed of poly(A)+ molecules that were free of interactions with other RNAs. beta-Globin pre-mRNA belongs to this class. The second class included poly(A)+ molecules that contained interstrand duplexes. beta-Globin mRNA is involved in this kind of interaction. In addition, hybrids between small nuclear RNAs and heterogeneous nuclear RNA were isolated. These hybrids were formed with all the U-rich species, 4.5 S, 4.5 SI and a novel species designated W. Approximately equal numbers of hybrids were formed by species U1a, U1b, U2, U6 and W; however, species U4 and U5 were significantly under-represented. Most of these hybrids were found to be associated stably with non-polyadenylated RNA. These observations demonstrated for the first time that small nuclear RNA-heterogeneous nuclear RNA hybrids can be isolated without crosslinking, and that proteins are not necessary to stabilize the complexes. However, not all molecules of a given small nuclear RNA species are involved in the formation of these hybrids. The distribution of a given small nuclear RNA species between the free and bound state does not reflect the stability of the complex in vitro but rather the abundance of complementary sequences in the heterogeneous nuclear RNA.(ABSTRACT TRUNCATED AT 400 WORDS)     

Interaction of coupled nonlinear oscillators having different intrinsic resting levels

The interaction among coupled oscillators is governed by oscillator properties (intrinsic frequency and amplitude) and coupling mechanisms. This study considers another oscillator property, the intrinsic resting level, and evaluates its role in governing oscillator interactions. The results of computer experiments on a chain of either three or five bidirectionally coupled nonlinear oscillators, suggest that an intrinsic resting level gradient, if present, is one of the factors governing the interaction between coupled oscillators. If there is no intrinsic frequency gradient, then an intrinsic resting level gradient is sufficient to produce many features of interaction among coupled oscillators. If both intrinsic frequency and intrinsic resting level gradients are present, then both of them determine the manner in which the coupled oscillators interact with each other.     

Application of reaction-diffusion models to cell patterning in Xenopus retina. Initiation of patterns and their biological stability

We have examined the behavior of two reaction-diffusion models, originally proposed by Gierer & Meinhardt (1972) and by Kauffman, Shymko & Trabert (1978), for biological pattern formation. Calculations are presented for pattern formation on a disc (approximating the geometry of a number of embryonic anlagen including the frog eye rudiment), emphasizing the sensitivity of patterns to changes in initial conditions and to perturbations in the geometry of the morphogen-producing space. Analysis of the linearized equations from the models enabled us to select appropriate parameters and disc size for pattern growth. A computer-implemented finite element method was used to solve the non-linear model equations reiteratively. For the Gierer-Meinhardt model, initial activation (varying in size over two orders of magnitude) of one point on the disc's edge was sufficient to generate the primary gradient. Various parts of the disc were removed (remaining only as diffusible space) from the morphogen-producing cycle to investigate the effects of cells dropping out of the cycle due to cell death or malfunction (single point removed) or differentiation (center removed), as occur in the Xenopus eye rudiment. The resulting patterns had the same general shape and amplitude as normal gradients. Nor did a two-fold increase in disc size affect the pattern-generating ability of the model. Disc fragments bearing their primary gradient patterns were fused (with gradients in opposite directions, but each parallel to the fusion line). The resulting patterns generated by the model showed many similarities to results of "compound eye" experiments in Xenopus. Similar patterns were obtained with the model of Kauffman's group (1978), but we found less stability of the pattern subject to simulations of central differentiation. However, removal of a single point from the morphogen cycle (cell death) did not result in any change. The sensitivity of the Kauffman et al. model to shape perturbations is not surprising since the model was originally designed to use shape and increasing size during growth to generate a sequence of transient patterns. However, the Gierer-Meinhardt model is remarkably stable even when subjected to a wide range of perturbations in the diffusible space, thus allowing it to cope with normal biological variability, and offering an exciting range of possibilities for reaction-diffusion models as mechanisms underlying the spatial patterns of tissue structures.     

Antigenic determinants distinctive of Methanospirillum hungatei and Methanogenium cariaci identified by monoclonal antibodies

Monoclonal antibodies were prepared against two species of Methanomicrobiaceae. Antibody 1A is specific for Methanospirillum hungatei strain JF1 and the determinant it recognizes is expressed on the surface of JF1 cells, where it is exposed and accessible to antibody. The determinant is found in a polypeptide (MW<12,000) in the sheath that covers the bacterial cell; it is not present in Methanospirillum hungatei strain GP1; and it is not expressed on the surface of whole cells of the other 24 methanogenic bacteria tested. It is therefore a marker of strain JF1, consequently, antibody 1A is potentially useful for tracking JF1 and fragments thereof in a variety of samples. Antibody 7A is specific for Methanogenium cariaci JR1c. It did not react with any other methanogen tested, not even with Mg. marisnigri or Ms. hungatei JF1, although these cross-react with Mg. cariaci if tested with polyclonal antisera. Therefore antibody 7A recognizes specifically a marker of Mg. cariaci JR1c.Abbreviations SIA slide immunoenzymatic assay - SDS-PAGE sodium dodecylsulfate polyacrylamide gel electrophoresis     

The nature of the stable noncovalent dimers of band 3 protein from erythrocyte membranes in solutions of Triton X-100

Stable noncovalent dimers of band 3 protein from human erythrocyte membranes, in which state the protein is thought to exist after solubilization by the nonionic detergent Triton X-100, do not occur when purified batches of the detergent are used. Instead, the protein is in a monomer/dimer/tetramer association equilibrium. The stable dimers do appear, however, when the detergent has been 'aged'. They thus seem to be artifacts.     

Proton magnetic resonance studies of 7 Fe ferredoxins: Lower potential of the [4 Fe–4 S] redox center than the [3 Fe–3 S] cluster

Two types of iron-sulfur clusters, [3 Fe–3 S] and [4 Fe–4 S], were identified by ¹H-NMR in ferredoxins from Thermus thermophilus, Mycobacterium smegmatis and Pseudomonas ovalis. The [4 Fe–4 S] clusters always showed the redox couples which had potentials lower than that of the [3 Fe–3 S] clusters.     

Synthesis of S100 Protein on Free and Membrane-Bound Polysomes of the Rabbit Brain

Abstract: Free and membrane-bound polysomes were isolated from the cerebral hemispheres and cerebellum of the young adult rabbit. The two polysomal populations were translated in an mRNA-dependent cell-free system derived from rabbit reticulocytes. Analysis of the [³⁵S]methionine-labeled translation products on two-dimensional polyacrylamide gels indicated an efficient separation of the two classes of brain polysomes. The relative synthesis of S100 protein by free and membrane- bound polysomes was determined by direct immuno-precipitation of the cell-free translation products in the presence of detergents to reduce nonspecific trapping. Synthesis of S100 protein was found to be twofold greater on membrane-bound polysomes compared with free polysomes isolated from either the cerebral hemispheres or the cerebellum. In addition, the proportion of poly- (A+)mRNA coding for SlOO protein was also twofold greater in membrane-bound polysomes compared with free polysomes isolated from the cerebral hemispheres. These results indicate that the cytoplasmic S100 protein is synthesized predominantly on membrane-bound polysomes in the rabbit brain. We suggest that the nascent S100 polypeptide chain translation complex is attached to the rough endoplasmic reticulum by an ionic interaction involving a sequence of 13 basic amino acids in S100 protein.     

Specific interaction of proteins with 5 S RNA and tRNA in the 42 S storage particle of Xenopus oocytes

During early oogenesis in amphibia, most of the 5 S RNA and tRNA is stored in a ribonucleoprotein particle that sediments at 42 S. In Xenopus laevis the 42 S particle contains two major proteins: of M_r 48 000 (P48) and 43 000 (P43). It is shown that heterogeneity in composition of the 42 S particle reflects a changing situation whereby initially, both 5 S RNA and tRNA are complexed with P48 (1 molecule 5 S RNA: 1 molecule P48; 2 or 3 molecules tRNA: 1 molecule P48), but later, tRNA becomes increasingly associated with P43 (in a 1:1 ratio) although 5 S RNA remains complexed with a cleavage product of P48. These changes relate to the eventual utilization of the excess 5 S RNA and tRNA in ribosome assembly and protein synthesis.