Structure-aided design of inhibitors of Mycobacterium tuberculosis thimydilate kinase

SUMMARY The aim of this work was the search for selective inhibitors of M. tuberculosis thymidine monophosphate kinase (TMPKmt) as leads for the development of new anti-tuberculosis agents. Based on the X-ray structure of TMPKmt, it was decided to establish a preliminary structure-activity relationship by synthesising a series of nucleosides and nucleotides modified at the 2’-, 3’- and 5-positions of the dTMP-scaffold. These analogues were tested for their affinities for TMPKmt. From this, a 2'-chlorine and a 2'-fluorine substituent emerged as the most promising modifications of the dTMP scaffold. Furthermore, the affinities of a series nucleosides and their corresponding nucleotides were compared. The deletion of the phosphate moiety typically resulted in a modest, in many cases negligible affinity loss. In view of the drug delivery problems of phosphorylated compounds, nucleosides seemed more useful leads for further drug design. The goal of the synthesis of a series 3'-C-branched-chain nucleosides and nucleotides (3'-CH2N3, 3'-CH2NH2, 3'-CH2F, 3'-CH2OH) was to occupy a cavity in the enzyme near the 3'-position. Biological results and modeling confirmed this hypothesis. 3'-Azidomethyl- 3'-deoxy-thymidine (4.9), combining a low Ki-value (40 mM) with a high selectivity index for the tuberculosis enzyme (Ki TMPKh/ Ki TMPKmt = 26) emerged as the most promising lead for further optimisation. Attempts were made to combine these favourable 3'-substitution patterns with 2'-halogen substituents (6.9-6.14). However, introduction of the 2'-halogen led to a drastic decrease in affinity compared to the corresponding 2'-deoxy-nucleosides. Probably, the 2'-halogens compete with the 3'-substituents for the same binding pocket. Furthermore, it was tried to supersede the good affinities of the 3'-C-branched-chain nucleosides, by further exploration of the enzyme cavity near the 3'-position with alternative nitrogen-containing substituents. However, attempted simultaneous reduction of the 6'-azido function and the 2'-hydroxyl of compound 19 (chapter 6) failed. Instead three peculiar nucleoside analogues (6.10, 6.11 and 6.12) were isolated that were tested for their affinities for TMPKmt and TMPKh. Dinucleoside 6.12 unexpectedly showed a high affinity (Ki = 37 mM) and selectivity for the tuberculosis enzyme, indicating an exceptional flexibility of TMPKmt towards the orientation of the sugar ring. Also the bicyclic nucleosides 6.10 and 6.11 showed excellent affinities. With its Ki-value of 3.5 mM (exceeding the affinity of the natural substrate) and its selectivity index of 200, 6.10 represents the highest affinity and most selective inhibitor of TMPKmt found so far. The favourable affinities and selectivities of these three inhibitors will form the basis for further drug design, considerably increasing the variety of nucleoside analogues that may be envisaged for future synthesis. Based on the encouraging affinity of anhydro-hexitol nucleotide 7.1, the effects of sixmembered sugar rings for the affinity for TMPKmt were further explored through the synthesis of 1-[2,4-dideoxy-4-C-hydroxymethyl-a-L-lyxopyranosyl]thymine (7.4). This nucleoside indeed showed the predicted equatorial orientation of the thymine ring (4C1). Affinity results were however disappointing. In conclusion, this work yielded some high affinity and selective inhibitors for TMPKmt that open interesting perspectives in the search for new anti-tuberculosis agents. Based on their high selectivity indices, especially dinucleoside 6.12 and bicyclic nucleosides 6.10 and 6.11 will be used as the starting point for the search of inhibitors with an optimal fitting in the active pocket of TMPKmt

Broadband luminescence in defect-engineered electrochemically produced porous Si/ZnO nanostructures

The fabrication, by an all electrochemical process, of porous Si/ZnO nanostructures with engineered structural defects, leading to strong and broadband deep level emission from ZnO, is presented. Such nanostructures are fabricated by a combination of metal-assisted chemical etching of Si and direct current electrodeposition of ZnO. It makes the whole fabrication process low-cost, compatible with Complementary Metal-Oxide Semiconductor technology, scalable and easily industrialised. The photoluminescence spectra of the porous Si/ZnO nanostructures reveal a correlation between the lineshape, as well as the strength of the emission, with the morphology of the underlying porous Si, that control the induced defects in the ZnO. Appropriate fabrication conditions of the porous Si lead to exceptionally bright Gaussian-type emission that covers almost the entire visible spectrum, indicating that porous Si/ZnO nanostructures could be a cornerstone material towards white-light-emitting devices

Intense violet–blue emission and paramagnetism of nanocrystalline Gd3+ doped ZnO ceramics

Nanocrystalline Zn1-xGdxO (x = 0, 0.02, 0.04, 0.06, and 0.08) ceramics were synthesized by ball milling and subsequent solid-state reaction. The transmission electron microscopy (TEM) micrograph of as synthesized samples revealed the formation of crystallites with an average diameter of 60 nm, and the selected area electron diffraction (SAED) pattern confirmed the formation of wurtzite structure. A red shift in the band gap was observed with increasing Gd3+ concentration. The photoluminescence of nanocrystalline Gd3+ doped ZnO exhibited a strong violet–blue emission. Concentration dependence of the emission intensity of Gd3+ in ZnO was studied, and the critical concentration was found to be 4 mol% of Gd3+. The Gd3+ doped ZnO exhibited paramagnetic behavior at room temperature, and the magnetic moment increased with Gd3+ concentration

CD28null CD4 T-cell expansions in autoimmune disease suggest a link with cytomegalovirus infection

Immunosenescence is thought to contribute to the increase of autoimmune diseases in older people. Immunosenescence is often associated with the presence of an expanded population of CD4 T cells lacking expression of CD28 (CD28null). These highly cytotoxic CD4 T cells were isolated from disease-affected tissues in patients with rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, or other chronic inflammatory diseases and their numbers appeared to be linked to disease severity. However, we recently demonstrated that the common herpes virus, cytomegalovirus (CMV), not ageing, is the major driver of this subset of cytotoxic T cells. In this review, we discuss how CMV might potentiate and exacerbate autoimmune disease through the expansion of CD28null CD4 T cells

Microglia-astrocyte crosstalk in the amyloid plaque niche of an Alzheimer's disease mouse model, as revealed by spatial transcriptomics

The amyloid plaque niche is a pivotal hallmark of Alzheimer's disease (AD). Here, we employ two high-resolution spatial transcriptomics (ST) platforms, CosMx and Spatial Enhanced Resolution Omics-sequencing (Stereo-seq), to characterize the transcriptomic alterations, cellular compositions, and signaling perturbations in the amyloid plaque niche in an AD mouse model. We discover heterogeneity in the cellular composition of plaque niches, marked by an increase in microglial accumulation. We profile the transcriptomic alterations of glial cells in the vicinity of plaques and conclude that the microglial response to plaques is consistent across different brain regions, while the astrocytic response is more heterogeneous. Meanwhile, as the microglial density of plaque niches increases, astrocytes acquire a more neurotoxic phenotype and play a key role in inducing GABAergic signaling and decreasing glutamatergic signaling in hippocampal neurons. We thus show that the accumulation of microglia around hippocampal plaques disrupts astrocytic signaling, in turn inducing an imbalance in neuronal synaptic signaling

Cytomegalovirus infection exacerbates autoimmune mediated neuroinflammation

Tumorimmunolog

Facile Synthesis of ZnO Nanorods by Microwave Irradiation of Zinc–Hydrazine Hydrate Complex

ZnO nanorods have been successfully synthesized by a simple microwave-assisted solution phase approach. Hydrazine hydrate has been used as a mineralizer instead of sodium hydroxide. XRD and FESEM have been used to characterize the product. The FESEM images show that the diameter of the nanorods fall in the range of about 25–75 nm and length in the range of 500–1,500 nm with an aspect ratio of about 20–50. UV–VIS and photoluminescence spectra of the nanorods in solution have been taken to study their optical properties. A mechanism for microwave synthesis of the ZnO nanorods using hydrazine hydrate precursor has also been proposed

Perceived discrimination is associated with severity of positive and depression/anxiety symptoms in immigrants with psychosis: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Immigration status is a significant risk factor for psychotic disorders, and a number of studies have reported more severe positive and affective symptoms among immigrant and ethnic minority groups. We investigated if perceived discrimination was associated with the severity of these symptoms among immigrants in Norway with psychotic disorders.</p> <p>Methods</p> <p>Cross-sectional analyses of 90 immigrant patients (66% first-generation, 68% from Asia/Africa) in treatment for psychotic disorders were assessed for DSM-IV diagnoses with the Structured Clinical Interview for DSM Disorders (SCID-I, sections A-E) and for present symptom severity by The Structured Positive and Negative Syndrome Scale (SCI-PANSS). Perceived discrimination was assessed by a self-report questionnaire developed for the Immigrant Youth in Cultural Transition Study.</p> <p>Results</p> <p>Perceived discrimination correlated with positive psychotic (r = 0.264, p < 0.05) and depression/anxiety symptoms (r = 0.282, p < 0.01), but not negative, cognitive, or excitement symptoms. Perceived discrimination also functioned as a partial mediator for symptom severity in African immigrants. Multiple linear regression analyses controlling for possible confounders revealed that perceived discrimination explained approximately 10% of the variance in positive and depression/anxiety symptoms in the statistical model.</p> <p>Conclusions</p> <p>Among immigrants with psychotic disorders, visible minority status was associated with perceived discrimination and with more severe positive and depression/anxiety symptoms. These results suggest that context-specific stressful environmental factors influence specific symptom patterns and severity. This has important implications for preventive strategies and treatment of this vulnerable patient group.</p

Ethical issues relating to the banking of umbilical cord blood in Mexico

<p>Abstract</p> <p>Background</p> <p>Umbilical cord banks are a central component, as umbilical cord tissue providers, in both medical treatment and scientific research with stem cells. But, whereas the creation of umbilical cord banks is seen as successful practice, it is perceived as a risky style of play by others. This article examines and discusses the ethical, medical and legal considerations that arise from the operation of umbilical cord banks in Mexico.</p> <p>Discussion</p> <p>A number of experts have stated that the use of umbilical cord goes beyond the mere utilization of human tissues for the purpose of treatment. This tissue is also used in research studies: genetic studies, studies to evaluate the effectiveness of new antibiotics, studies to identify new proteins, etc. Meanwhile, others claim that the law and other norms for the functioning of cord banks are not consistent and are poorly defined. Some of these critics point out that the confidentiality of donor information is handled differently in different places. The fact that private cord banks offer their services as "biological insurance" in order to obtain informed consent by promising the parents that the tissue that will be stored insures the health of their child in the future raises the issue of whether the consent is freely given or given under coercion. Another consideration that must be made in relation to privately owned cord banks has to do with the ownership of the stored umbilical cord.</p> <p>Summary</p> <p>Conflicts between moral principles and economic interests (non-moral principles) cause dilemmas in the clinical practice of umbilical cord blood storage and use especially in privately owned banks. This article presents a reflection and some of the guidelines that must be followed by umbilical cord banks in order to deal with these conflicts. This reflection is based on the fundamental notions of ethics and public health and seeks to be a contribution towards the improvement of umbilical cord banks' performance.</p