Erythrocyte deformation in simulated weightless human and rabbits

Effect and mechanism of simulated weightlessness (SWL) in humans and rabbits erythrocyte deformation were studied. Erythrocyte deformation and membrane fluidity in humans and rabbits, and erythrocyte morphology and hemorreology indices in control and HDT rabbits were measured. The results were a decrease in erythrocyte deformation and membrane fluidity in humans and rabbits during SWL, a significant increase in abnormal erythrocyte, blood viscosity, hematocrit, fibrinogen, and red blood cell aggregation index in HDT rabbits. These results show that the changes in erythrocyte shape, increase of erythrocyte internal viscosity and changes in erythrocyte visco-elasticity may be causing the decrease of erythrocyte deformation in SWL humans and rabbits.

Glutamate dehydrogenase activity profiles for type strains of ruminal Prevotella spp

The glutamate dehydrogenase (GDH) activities for the type strains of Prevotella ruminicola (strain 23), Prevotella brevis (strain GA33), and Prevotella bryantii (strain B(1)4) were assessed by a combination of enzyme assays and analysis of migration patterns of GDH proteins following nondenaturing polyacrylamide gel electrophoresis. Unlike results with most other prokaryotes, but similar to results with other members of the family Bacteroidaceae, NADPH-utilizing specific activity was greatest in all species following ammonia-limited growth. Similar also to previous findings with P. bryantii, the NAD(P)H-utilizing GDH activity of P. ruminicola can be attributed to a single protein. However, P. brevis produces an additional GDH protein(s) in response to growth with peptides. These results conclusively demonstrate that all type strains of the ruminal Prevotella sp. grouping possess GDH activity.

Mapping of Stat3 serine phosphorylation to a single residue (727) and evidence that serine phosphorylation has no influence on DNA binding of Stat1 and Stat3

During their polypeptide ligand-induced activation Stats (signaltransducers andactivators oftranscription) 1 and 3 acquire, in addition to an obligatory tyrosine phosphorylation, phosphorylation on serine which boosts their transactivating potential [Wen, Z., Zhong, Z. and Darnell, J. E. Jr. (1995) Cell 82, 241-250]. By examining phosphopeptide maps of wild-type and mutant protein we show here that the Stat3 serine phosphorylation, like the Stat1 serine phosphorylation, occurs on a single residue, serine 727. Neither the DNA binding of Stat1 nor Stat3 is demonstrably affected by the presence or absence of the serine phosphorylation. Thus the earlier demonstration that transcription is enhanced by the presence of the serine 727 residue likely occurs after DNA binding. These findings do not agree with earlier claims of excess serine to tyrosine phosphorylation in activated Stats 1 and 3 or to claims of more stable DNA binding of serine phosphorylated Stat dimers.

STAT signaling is active during early mammalian development

Cytokine activation of gene expression can be mediated through signal transducer and activator of transcription (STAT) signaling pathways resulting in expression of target genes. Because many cytokines have important regulatory roles during early development, we wanted to ascertain whether STAT signaling was also active at this time and could therefore have important roles in mediating developmental processes. We have found that Stat1 and Stat3 mRNAs are present in both maternal and extraembryonic tissues during early postimplantation stages of murine development. Furthermore, analyses of STAT activity in E4.5-E9.5 decidual swellings by electrophoretic mobility shift assay demonstrated that Stat3 protein was active during this early developmental period. The identification of activated Stat3 demonstrates that STAT signaling functions during early postimplantation development in the mouse are likely to be important during early embryogenesis.

The NAD(P)H-dependent glutamate dehydrogenase activities of Prevotella ruminicola B(1)4 can be attributed to one enzyme (GdhA), and gdhA expression is regulated in response to the nitrogen source available for growth

Prevotella ruminicola B(1)4 possesses both NADPH- and NADH-linked glutamate dehydrogenase (GDH) activities, with the greatest specific activity being measured from ammonia-limited cultures. Relative to cells grown in the presence of 1 mM ammonium chloride, the NADPH-dependent activity was decreased approximately 10-fold when peptides were provided as a nitrogen source. Nondenaturing polyacrylamide gel electrophoresis (PAGE) was used to visualize the GDH protein(s) in cell extracts of P. ruminicola. For all growth conditions tested, only one GDH protein was detectable, and its relative abundance, as well as its reactivity with either NAD(P)+ or NAD(P)H, correlated well with the specific activities measured from whole-cell assays. Consistent with the findings from enzyme assays and PAGE activity gels, Northern (RNA) blot analysis revealed that expression of a gene encoding NAD(P)H-GDH activity was greatest in ammonia-grown cultures and that GDH activity is regulated in response to nitrogen source (ammonia versus peptides), probably at the level of transcription. A gene encoding the NAD(P)H-utilizing GDH activity (gdhA) was cloned, and its nucleotide sequence was determined and shown to contain an open reading frame of 1,332 bp which would encode a polypeptide of 48.8 kDa. The deduced amino acid sequence possesses three highly conserved motifs typical of family I GDHs, but several unique amino acid substitutions within these motifs were evident. These results are discussed within the context of ruminal nitrogen metabolism and the growth efficiency of succinate- and propionate-producing anaerobic bacteria.

Transcriptionally active Stat1 is required for the antiproliferative effects of both interferon alpha and interferon gamma

Type I (alpha, beta) and type II (gamma) interferons (IFNs) can restrict the growth of many cell types. INF-stimulated gene transcription, a key early event in IFN response, acts through the Janus kinase-signal transducers and activators of transcription pathway, in which both IFN-alpha and IFN-gamma activate the transcription factor Stat1. A cell line lacking Stat1 (U3A) was not growth-arrested by IFN-alpha or IFN-gamma, and experiments were carried out with U3A cells permanently expressing normal or various mutant forms of Stat1 protein. Only cells in which complete Stat1 activity was available (Stat1alpha) were growth-inhibited by IFN-gamma. A mutant that supports 20-30% normal transcription did not cause growth restraint. In contrast, IFN-alpha growth restraint was imposed by cells producing Stat1beta, which lacks transcriptional activation potential. This parallels earlier results showing the truncated Stat1 can function in IFN-alpha gene activation. In addition to experiments on long-term cultured cells, we also found that wild-type primary mouse embryonic fibroblasts were inhibited by IFNs, but fibroblasts from Stat1-deficient mouse embryos were not inhibited by IFNs.

Generation of Hadamard matrices for phase-code-multiplexed holographic memories

To accommodate the available spatial light modulators and to achieve the maximum possible storage capacity of a phase-code-multiplexed holographic memory, it is often necessary to generate an orthogonal phase code whose length is not a power of 2. We describe an algorithm for the generation of basic Hadamard matrices of order M = 4p (with p an odd number) and show that Hadamard matrices of order N = 4t (with t a positive integer) can be constructed by combination of the algorithms presented with the tensor-product extension method.

[The pathology of labial salivary gland in the diagnosis of Sjogren's syndrome]

To explore the sensitivity and specificity of the pathology of labial salivary gland in the diagnosis of Sjogren's syndrome (SS) and its specific pathological changes in SS, 100 labial salivary gland specimens were observed and assayed in our hospital. The results indicated that there was no significant difference in acinar atrophy, duct dilatation and lymphocytes infiltration between primary SS (1 degree SS) and secondary SS (2 degrees SS) patients. But those changes had significant difference between 1 degree SS and non-CTD patients (P < 0.01). It was also found in our study that Chisholm grade IV was achieved in 78.57% 1 degree SS specimens, 65.22% 2 degrees SS specimeus and 22.22% in non-CTD specimens, respectively. According to Chisholm standard, the sensitivity and specificity of pathology in the diagnosis of these SS patients was 78.8% and 77.1%. Our patients were still classified by using Chisholm standard. If focal lymphocytes infiltration was used as the single criterion to SS diagnosis, its specificity was not high. In the diagnosis of SS authors should consider the pathologic changes of salivary gland as well as the clinical information in order to avoid misdiagnosis.

Optoelectronic fuzzy associative memory with controllable attraction basin sizes

We propose and demonstrate a new fuzzy associative memory model that provides an option to control the sizes of the attraction basins in neural networks. In our optoelectronic implementation we use spatial/polarization encoding to represent the fuzzy variables. Shadow casting of the encoded patterns is employed to yield the fuzzy-absolute difference between fuzzy variables.

Distribution of the mammalian Stat gene family in mouse chromosomes

Studies of transcriptional activation by interferons and a variety of cytokines have led to the identification of a family of proteins that serve as signal transducers and activators of transcription, Stats. Here, we report that the seven mouse Stat loci map in three clusters, with each cluster located on a different mouse autosome. The data suggest that the family has arisen via a tandem duplication of the ancestral locus, followed by dispersion of the linked loci to different mouse chromosomes.

Electron-trapping materials and electron-beam-addressed electron-trapping material devices: an improved model

An improved model governing the dynamics of electron-trapping materials (ETM's) under simultaneous illumination of blue and IR light is developed. The new model takes into account previously neglected effects, such as electron-trap-density saturation and dependence of electron-trapping efficiency on the existing level of trapped-electron density. Inclusion of both effects in a model is vitally important for effective use of ETM's in optoelectronic neurocomputing with pulsating neurons. Experimental verification of the new model is given. General issues of addressing ETM's with an electron beam are also studied, and a general design equation for electron-beam-addressed ETM devices is developed. In particular, two electron-beam-addressed ETM devices that are of special interest, the field-emission microcathode ETM spatial light modulator and the ETM-based image intensifier, are presented.

Maximal activation of transcription by Stat1 and Stat3 requires both tyrosine and serine phosphorylation

Stat1 and Stat3 are latent transcriptional factors activated initially through phosphorylation on single tyrosine residues induced by cytokine and growth factor occupation of cell surface receptors. Here we show that phosphorylation on a single serine (residue 727) in each protein is also required for maximal transcriptional activity. Both cytokines and growth factors are capable of inducing the serine phosphorylation of Stat1 and Stat3. These experiments show that gene activation by Stat1 and Stat3, which obligatorily require tyrosine phosphorylation to become active, also depends for maximal activation on one or more of the many serine kinases.

STAT3 activation by cytokines utilizing gp130 and related transducers involves a secondary modification requiring an H7-sensitive kinase

Ciliary neurotrophic factor, oncostatin M, leukemia-inhibitory factor, and interleukin 6 are related cytokines that initiate signaling by homodimerizing the signal-transducing receptor component gp130 or by heterodimerizing gp130 with a gp130-related receptor component. Receptor dimerization in turn activates receptor-associated kinases of the Jak/Tyk family, resulting in the rapid tyrosine phosphorylation of several intracellular proteins, including those of two members of the signal transducers and activators of transcription (STAT) family--STAT1 and STAT3. Here we show that all cytokines that utilize gp130 sequentially induce two distinct forms of STAT3 in all responding cells examined, with the two forms apparently differing because of a time-dependent secondary serine/threonine phosphorylation involving an H7-sensitive kinase. While both STAT3 forms bind DNA and translocate to the nucleus, the striking time-dependent progression from one form to the other implies other important functional differences between the two forms. Granulocyte colony-stimulating factor, which utilizes a receptor highly related to gp130, also induces these two forms of STAT3. In contrast to a number of other cytokines and growth factors, all cytokines using gp130 and related signal transducers consistently and preferentially induce the two forms of STAT3 as compared with STAT1; this characteristic STAT activation pattern is seen regardless of which Jak/Tyk kinases are used in a particular response, consistent with the notion that the receptor components themselves are the primary determinants of which STATs are activated.

A STAT protein domain that determines DNA sequence recognition suggests a novel DNA-binding domain

Stat1 and Stat3 are two members of the ligand-activated transcription factor family that serve the dual functions of signal transducers and activators of transcription. Whereas the two proteins select very similar (not identical) optimum binding sites from random oligonucleotides, differences in their binding affinity were readily apparent with natural STAT-binding sites. To take advantage of these different affinities, chimeric Stat1:Stat3 molecules were used to locate the amino acids that could discriminate a general binding site from a specific binding site. The amino acids between residues approximately 400 and approximately 500 of these approximately 750-amino-acid-long proteins determine the DNA-binding site specificity. Mutations within this region result in Stat proteins that are activated normally by tyrosine phosphorylation and that dimerize but have greatly reduced DNA-binding affinities.

Optoelectronic neural dendritic tree processing with electron-trapping materials

We show that under simultaneous illumination of pulsed blue light and constant IR light the dynamic responses of electron-trapping materials could be employed to implement optically controlled neural dendritic responses. The importance of neurocomputing with biology-oriented spiking neurons and the role played by dendritic trees are discussed. Computer simulations of dendritic responses in biological neuron and experimental results of electron-trapping material dynamics are presented. These results show that electron-trapping materials are well suited for implementing optically controlled dendritic responses for use in large-scale biology-oriented optoelectronic spiking neural networks.

The genomic structure of the STAT genes: multiple exons in coincident sites in Stat1 and Stat2

The genomic structure of Stat2 has been determined and compared with a large portion of the Stat1 gene. There are 24 exons in the Stat2 gene and a matching number in very similar positions in the Stat1 gene. Thus a very complicated genomic structure was presumably duplicated and has been closely maintained throughout evolution.

In vivo growth hormone treatment rapidly stimulates the tyrosine phosphorylation and activation of Stat3

The mechanisms by which GH regulates gene expression to alter growth and metabolism are unknown. We have demonstrated previously that in vivo GH treatment rapidly stimulates the tyrosine phosphorylation of multiple nuclear proteins and have identified the inducible transcription factor Stat1 (formerly Stat91) as one of the major GH-activated nuclear phosphoproteins. We now show that Stat3, a new member of the STAT (signal transducer and activator of transcription) family of transcription factors, is also phosphorylated on tyrosine residues and rapidly appears in the nucleus in response to GH. Activated Stat3 interacts with the naturally occurring c-sis-inducible element of the c-fos gene after GH treatment, as demonstrated by gel mobility shift assay, and is a component of gel-shifted bands A and B when the high affinity sis-inducible element is used as a probe. Our results suggest that multiple STAT proteins may mediate some of the pleiotropic effects of GH on gene expression.

Pulsating neuron produced by electron-trapping materials

We report our results from the study of the dynamics of electron-trapping materials (ETM's) under simultaneous illumination of pulsed blue light and constant IR light. By combining the dynamic property of ETM with the S-shaped nonlinear I-V characteristic of a programmable unijunction transistor, we produce an optoelectronic pulsating neuron. A proof-of-concept experiment successfully produces oscillations and demonstrates the great potential of using ETM's to implement dense arrays of pulsating neurons.

Epidermal growth factor and lipopolysaccharide activate Stat3 transcription factor in mouse liver

Previous studies demonstrated that the intraperitoneal injection of epidermal growth factor (EGF) into mice resulted in the appearance, within minutes, of several tyrosine-phosphorylated proteins in liver nuclei. Two of these proteins have been identified as the transcription factors p91/p84 (Stat1 alpha/1 beta) (Ruff-Jamison, S., Chen, K., and Cohen, S. (1993) Science 261, 1733-1736). We have now identified, by Western blotting and immunoprecipitation, an additional EGF-modulated transcription factor, Stat3. We find that Stat3 is tyrosine-phosphorylated and present in mouse liver nuclei following either EGF or lipopolysaccharide administration. Gel shift analyses show that Stat3 is capable of specifically binding the SIE (a DNA sequence present in the c-fos promoter). Three active SIE binding complexes (SIF A, B, and C) exist in the nucleus after the administration of EGF: one complex that contains Stat3, one that contains Stat1, and a third complex that appears to contain both proteins. Only one active SIE binding complex, containing Stat3, was detected after the administration of lipopolysaccharide.

Stat3 and Stat4: members of the family of signal transducers and activators of transcription

The deduced amino acid sequence of two members of the signal transducers and activators of transcription (STAT) family from the mouse are described. Comparison with the deduced protein sequence of the two previously described genes (Stat91 and Stat113), discovered because of their activation as transcription factors after interferon-induced tyrosine phosphorylation, shows several highly conserved regions, including the putative SH3 and SH2 domains. The conserved amino acid stretches likely point to conserved domains that enable these proteins to carry out the several required functions they are known and proposed to carry out. While Stat1 and Stat3 are widely expressed, Stat4 expression is restricted to testis, thymus, and spleen. Antiserum to Stat3 detects a major approximately 92-kDa protein and a minor approximately 89-kDa protein, while antiserum to Stat4 precipitates one major protein of approximately 89 kDa.

Stat3: a STAT family member activated by tyrosine phosphorylation in response to epidermal growth factor and interleukin-6

The STAT family of proteins carries out a dual function: signal transduction and activation of transcription. A new family member, Stat3, becomes activated through phosphorylation on tyrosine as a DNA binding protein in response to epidermal growth factor (EGF) and interleukin-6 (IL-6) but not interferon gamma (IFN-gamma). It is likely that this phosphoprotein forms homodimers as well as heterodimers with the first described member of the STAT family, Stat91 (renamed Stat1 alpha), which is activated by the IFNs and EGF. Differential activation of different STAT proteins in response to different ligands should help to explain specificity in nuclear signaling from the cell surface.

Dynamics of electron-trapping materials for use in optoelectronic neurocomputing

An analytical model governing the dynamics of the trapped-electron density in electron-trapping materials (ETM's) under simultaneous blue and near-IR illuminations is developed and studied in detail. Experimental results confirming the theoretical findings based on the model are presented, including a new method for experimentally determining a parameter of ETM's, β, which describes the rate of decay of electron-trap density under constant IR illumination and which is obtained by measurement of the phase shift of the ETM response to IR illumination containing a sinusoidally modulated temporal component. Issues concerning the use of ETM's as the synaptic connection weights in an optoelectronic neurocomputer are discussed; in particular, we propose a novel scheme for stabilizing the stored weight information in ETM's during readout and learning; this scheme is based on the dynamic equilibrium of the trapped-electron density established by simultaneous blue and uniform IR illuminations. It is shown thatETM's are deally suited for realizing dense, modifiable synapses that have the wide dynamic range needed in implementing large-scale programmable optoelectronic neural networks of pulsed neurons.

Binding of peptides lacking consensus anchor residue alters H-2Ld serologic recognition

CTL recognize class I MHC/peptide complexes on the surface of target cells. Crystallographic and serologic data have indicated that peptide ligands can influence the conformation of class I molecules and hence T cell recognition. How the binding of peptides with disparate sequence motifs affects the conformation of distinct regions within a class I molecule remains unknown. A series of site-directed mutants of the murine class I molecule H-2Ld was studied to address this question. These mutants were generated by in vitro mutagenesis and used to map the serologic epitopes recognized by a panel of Ld-reactive mAb. The influence of six different ligands on serologic recognition by these mAb was then examined. Of 12 mAb tested, only one, B22/249, was found to be significantly influenced by the bound peptide. Peptide discrimination by B22/249 was observed at the cell surface and in immunoprecipitates of Ld after incubation with two of the six ligands. The two peptides that caused suboptimal B22/249 recognition of Ld/peptide lack a proline at position 2, which is present in the other four peptides and has previously been defined as an anchor residue for Ld ligands. The epitope on Ld detected by mAb B22/249 includes residues 63 to 70 on the alpha 1 domain helix. Two of these residues are in pocket B, which computer modeling predicts to be in contact with the second residue of Ld-binding peptides. Therefore, these data imply that a mAb to a class I molecule can distinguish peptides with different motifs, possibly reflecting peptide-dependent conformational changes in the class I molecule.