Synthesis, characterization, EXAFS investigation and antibacterial activities of new ruthenium(III) complexes containing tetradentate Schiff base

A series of new hexa-coordinated ruthenium(III) complexes of the type [Ru(X)(2-atmp-ba)(EPh3)] (where H2-2-atmp-ba=N,N'-bis(2-aminothiophenol)benzoylacetone; X=Cl or Br; E=P or As) have been prepared by reacting [RuX3(EPh3)3] (where X=Cl or Br; E=P or As) with tetradentate Schiff base ligand (H2-2-atmp-ba) in 1:1 molar ratio. The complexes have been characterized by elemental analyses, Infra red, electronic, electron paramagnetic resonance spectroscopy and cyclic voltammetry. In order to confirm the coordination and structure of the complexes extended X-ray absorption fine structure spectroscopy (EXAFS) studies have been carried out. Based on the above data, an octahedral structure has been confirmed for the complexes. The new complexes were also screened for their antibacterial properties.

Magnetic resonance imaging, Down's syndrome and Alzheimer's disease: research and clinical implications

BACKGROUND

The diagnosis of Alzheimer's disease (AD) remains at times difficult to make using available neuropsychological measures. Neuro-imaging is a relatively new form of detecting the changes associated with dementia. The present study investigated the role of magnetic resonance imaging (MRI) in diagnosing AD in adults with Down's syndrome (DS).

METHODS

Subjects with DS and Alzheimer-type dementia were matched to non-demented controls with DS. Magnetic resonance imaging findings (i.e. volumetric and two-dimensional scans) were compared between the two groups in order to show a relationship between the changes of AD and structural MRI abnormalities.

RESULTS

Specific structural abnormalities which are seen in non-intellectually disabled subjects with dementia are also found in individuals with both DS and AD. However, such findings cannot be used to diagnose clinical AD with good accuracy in adults with DS. A number of practical issues of patient compliance and over-sedation are demonstrated by the findings.

CONCLUSIONS

Magnetic resonance imaging has an important but limited role to play in the management of AD in the population with DS. If intravenous sedation is used, medical support is essential to prevent a serious mishap.

Inverse Marcus Gunn phenomenon

Inverse Marcus-Gunn phenomenon is very rare. It is usually acquired. We report a young male patient presenting with congenital ptosis and inverse Marcus-Gunn phenomenon.

CD80 expression is induced on activated B cells following stimulation by CD86

We examined the effects of CD86 ligation on surface densities of CD80 on activated B cells. For this, splenic B cells where CD86 levels had been enhanced upon anti-immunoglobulin M (IgM) treatment were employed. Incubation of such CD86-expressing B cells with anti-CD86 monoclonal antibody (MoAb) resulted in a marked upregulation in cell surface levels of CD80. Such an enhancement in surface levels was also accompanied by a marked increase in CD80 mRNA, suggesting that the effects of CD86-triggering are exerted at the level of CD80 message. Furthermore, coculture of CD86-upregulated B cells with CD28-expressing fibroblasts also led to the enhancement of CD80 levels, which was not obtained upon incubation with cells expressing cytotoxic T-lymphocyte-associated molecule (CTLA)-4-Ig. Finally, we also demonstrate that CD86-induced CD80 is fully competent to function as a costimulatory molecule, as revealed by its ability to enhance cytokine secretion by allogeneic T cells. Thus, these results reveal the existence of another pathway that regulates the expression of CD80, at least on activated B cells, which could have important implications in directing the course of an immune response.

The physiological environment in cancer vascularization, invasion and metastasis

One of the most lethal aspects of cancer arises from its ability to invade and metastasize. Determining the factors that promote cancer cell invasion and metastasis is therefore critically important in treating this disease. The tumour physiological environment is uniquely different from normal tissue, and exhibits hypoxia, acidic extracellular pH and high levels of lactate. This environment, dictated largely by abnormal tumour vasculature and metabolism, in turn also promotes angiogenesis. The physiological environment, tumour metabolism, angiogenesis and vascularization are therefore inextricably linked. We have developed and applied non-invasive magnetic resonance (MR) imaging (I) and spectroscopy (S) techniques to understand the role of vascular, physiological and metabolic properties in cancer invasion and metastasis. These MR studies are performed with human breast and prostate cancer cells maintained in culture or grown as solid tumours in immune-suppressed mice. We have detected significant differences in vascular, physiological and metabolic characteristics of metastatic and non-metastatic human breast and prostate cancer models with MRI and MRS. Using a combined MRI/MRS approach we are currently acquiring metabolic, extracellular pH and vascular images from the same localized regions within a solid tumour to further understand the dynamics between these parameters and their role in cancer invasion and metastasis.

The use of DNA array technology in studies of ocular viral pathogenesis

DNA arrays can be used to simultaneously analyze the expression of hundreds of genes and permit systematic approaches to biological discovery with a potentially profound impact on genomics, pharmacogenomics, and proteomics. Microarrays have been used to study host-pathogen interactions, and recently this technology has been applied to investigate host-virus interactions. DNA arrays are used to monitor host alterations in several virus-induced cancers and upon infection with wild-type or modified viruses, or viral gene products. Alternatively, viral chips are used to characterize the transcriptional program of pathogenic viruses and in antiviral drug screening and drug resistance. With an aim to extend the use of this technology to ocular research, and specifically to study changes in host cell transcription in ocular adenovirus infection, we used a commercial array to compare adenovirus-infected human corneal cells to mock-infected cells. Of the 1176 genes analyzed, 72 genes associated with cell cycle regulation, apoptosis, oncogenesis, transcription, signaling, and inflammation were differentially regulated. In this review we summarize the use of DNA arrays in the study of viral infections and suggest potential uses of the technology in ocular viral pathogenesis research.

A secretion signal is present in the Collybia velutipes oxalate decarboxylase gene

The oxalate decarboxylase (OXDC) gene from Collybia velutipes is overexpressed as an active form in Schizosaccharomyces pombe. The recombinant enzyme shows similar pH optima and stability, while substrate kinetic analysis shows a ninefold decrease in K(m) value with respect to native OXDC. Most of the expressed protein was present in periplasm and remained firmly bound to cell-wall materials. However, 20% of enzyme expressed was secreted out into the medium suggesting the presence of a secretion signal (C. velutipes) in the oxalate decarboxylase gene. This secretion signal is associated with the N-terminal of OXDC as is evident by secretion of nonsecretory genes AmA1 and beta-galactosidase. An expression vector using this signal is constructed for expression and secretion of heterologous proteins in S. pombe.

Signal thresholds and modular synergy during expression of costimulatory molecules in B lymphocytes

We analyzed intracellular pathways modulating surface densities of CD80 and CD86 in B cells activated through ligation of the Ag receptor, and the adhesion molecule CD54. Whereas B cell Ag receptor (BCR) cross-linking alone stimulated increased expression of CD86, up-regulation of CD80 required dual stimulation with anti-IgM and anti-CD54. The principal downstream component contributed by BCR signaling, toward both CD80 and CD86 induction, was the elevated concentration of free cytoplasmic Ca(2+), recruited by way of capacitative influx. This alone was sufficient to generate an increase in CD86 levels. However, CD80 enhancement required the concerted action of both intracellular Ca(2+) concentration and CD54-initiated pathways. The nexus between anti-IgM and anti-CD54 stimulation, in the context of CD80 regulation, was identified to involve a self-propagating process of sequential synergy. The first step involved amplified accumulation of intracellular cAMP, as a result of cross-talk between BCR-mobilized Ca(2+) and CD54-derived signals. This then facilitated a second synergistic interaction between Ca(2+) and cAMP, culminating in CD80 expression. Our findings of distinct signal transducer requirements, with the added consequences of cross-talk, offers an explanation for variable modulation of costimulatory molecule expression in response to diverse physiological stimuli. Importantly, these results also reveal how concentration threshold barriers for recruitment of individual second messengers can be overcome by constructive convergence of signaling modules.

A T cell receptor transgenic model of severe, spontaneous organ-specific autoimmunity

The development of mouse models of human organ-specific autoimmune diseases has been hampered by the need to immunize mice with autoantigens in potent adjuvants. Even autoantigen-specific T cell receptor transgenic models of autoimmunity have proven to be complex as the transgenic mice frequently fail to develop disease spontaneously. We have isolated a CD4(+) T cell clone (TxA23)that recognizes the gastric parietal cell antigen, H/K ATPase alpha-chain(630-641), from a mouse with autoimmune gastritis that developed after thymectomy on day 3 of life. The T cell receptor alpha and beta genes from this clone were used to generate A23 transgenic mice. All A23 transgenic animals spontaneously developed severe autoimmune gastritis, and evidence of disease was detected as early as day 10 of life. Gastritis could be transferred to immunocompromised mice with a limited number of transgenic thymocytes (10(3)), but as many as 10(7) induced only mild disease in wild-type animals. Due to the complete penetrance of spontaneous disease, identity of the auto-antigen, susceptibility to immunoregulation, and close relation to autoimmune gastritis in man, A23 transgenic mice represent a unique CD4(+) T cell-mediated disease model for understanding the multiple factors regulating organ-specific autoimmunity.

Transcriptional profiling shows that Gcn4p is a master regulator of gene expression during amino acid starvation in yeast

Starvation for amino acids induces Gcn4p, a transcriptional activator of amino acid biosynthetic genes in Saccharomyces cerevisiae. In an effort to identify all genes regulated by Gcn4p during amino acid starvation, we performed cDNA microarray analysis. Data from 21 pairs of hybridization experiments using two different strains derived from S288c revealed that more than 1,000 genes were induced, and a similar number were repressed, by a factor of 2 or more in response to histidine starvation imposed by 3-aminotriazole (3AT). Profiling of a gcn4Delta strain and a constitutively induced mutant showed that Gcn4p is required for the full induction by 3AT of at least 539 genes, termed Gcn4p targets. Genes in every amino acid biosynthetic pathway except cysteine and genes encoding amino acid precursors, vitamin biosynthetic enzymes, peroxisomal components, mitochondrial carrier proteins, and autophagy proteins were all identified as Gcn4p targets. Unexpectedly, genes involved in amino acid biosynthesis represent only a quarter of the Gcn4p target genes. Gcn4p also activates genes involved in glycogen homeostasis, and mutant analysis showed that Gcn4p suppresses glycogen levels in amino acid-starved cells. Numerous genes encoding protein kinases and transcription factors were identified as targets, suggesting that Gcn4p is a master regulator of gene expression. Interestingly, expression profiles for 3AT and the alkylating agent methyl methanesulfonate (MMS) overlapped extensively, and MMS induced GCN4 translation. Thus, the broad transcriptional response evoked by Gcn4p is produced by diverse stress conditions. Finally, profiling of a gcn4Delta mutant uncovered an alternative induction pathway operating at many Gcn4p target genes in histidine-starved cells.

Transcriptional profiling shows that Gcn4p is a master regulator of gene expression during amino acid starvation in yeast

Starvation for amino acids induces Gcn4p, a transcriptional activator of amino acid biosynthetic genes in Saccharomyces cerevisiae. In an effort to identify all genes regulated by Gcn4p during amino acid starvation, we performed cDNA microarray analysis. Data from 21 pairs of hybridization experiments using two different strains derived from S288c revealed that more than 1,000 genes were induced, and a similar number were repressed, by a factor of 2 or more in response to histidine starvation imposed by 3-aminotriazole (3AT). Profiling of a gcn4Delta strain and a constitutively induced mutant showed that Gcn4p is required for the full induction by 3AT of at least 539 genes, termed Gcn4p targets. Genes in every amino acid biosynthetic pathway except cysteine and genes encoding amino acid precursors, vitamin biosynthetic enzymes, peroxisomal components, mitochondrial carrier proteins, and autophagy proteins were all identified as Gcn4p targets. Unexpectedly, genes involved in amino acid biosynthesis represent only a quarter of the Gcn4p target genes. Gcn4p also activates genes involved in glycogen homeostasis, and mutant analysis showed that Gcn4p suppresses glycogen levels in amino acid-starved cells. Numerous genes encoding protein kinases and transcription factors were identified as targets, suggesting that Gcn4p is a master regulator of gene expression. Interestingly, expression profiles for 3AT and the alkylating agent methyl methanesulfonate (MMS) overlapped extensively, and MMS induced GCN4 translation. Thus, the broad transcriptional response evoked by Gcn4p is produced by diverse stress conditions. Finally, profiling of a gcn4Delta mutant uncovered an alternative induction pathway operating at many Gcn4p target genes in histidine-starved cells.

Structural basis of MHC class I recognition by natural killer cell receptors

Natural killer (NK)-cell function is regulated by NK receptors that recognize MHC class I (MHC-I) molecules on target cells. Two structurally distinct families of NK receptors have been identified, the immunoglobulin-like family (killer cell immunoglobulin-like receptors (KIRs), leukocyte immunoglobulin-like receptors (LIRs)) and the C-type lectin-like family (Ly49, CD94/NKG2A, NKG2D, CD69). Recently, the three-dimensional structures of several NK receptors were determined, in free form or bound to MHC-I. These include those of unbound KIRs, NKG2D, CD69, LIR-1 and the CD94 subunit of the CD94/NKG2A heterodimer. Together, these structures define the basic molecular architecture of both the immunoglobulin-like and C-type lectin-like families of NK receptors. In addition, crystal structures have been reported for the complex between Ly49A and H-2Dd, and for KIR2DL2 bound to HLA-Cw3. The complex structures provide a framework for understanding MHC-I recognition by NK receptors from both families and reveal striking differences in the nature of this recognition, despite the receptors' functional similarity.