High-valent iron complexes with tetraamido macrocyclic ligands: structures, Mössbauer spectroscopy, and DFT calculations

Iron complexes of tetraamido macrocyclic ligands (TAML) are unique synthetic oxidation catalysts. In general, the central Fe(III) ion (S=3/2) is surrounded by four, almost planar, deprotonated amide-N sigma-donors although the full suite with new generation systems includes some substitution of amides with related donor functionalities. Oxidation under different conditions affords a variety of high-valent forms of iron-TAMLs. This review provides a summary and discussion of structural and spectroscopic features of complexes oxidized by one equivalent above the ferric state. These comprise Fe(IV)-TAML high spin (S=2) and intermediate spin (S=1) systems, wherein the oxidation equivalent can be taken from the metal (Fe(IV)) or the ligand (TAML radical-cation Fe(III)), and coupled spin (S=0) systems of mu-oxoiron(IV) dimers. The discussion is principally based on data obtained by X-ray crystallography, M?ssbauer spectroscopy, and density functional theory calculations.     

Differentiation and speciation in mountain streams: a case study in the caddisfly Rhyacophila aquitanica (Trichoptera)

Few studies have analysed the biogeography of mountain aquatic organisms, although this habitat provides stable conditions in which many species survived Pleistocene climatic oscillations, usually in the geographical vicinity of their present distribution ranges. The mountain caddisfly Rhyacophila aquitanica was selected as a model organism for this habitat type. Morphological measurements of genitalia and external characters of male individuals were obtained from almost the entire range of distribution of the species. Morphometric results were analysed by cluster analysis and multivariate statistics. Important differences were discovered among three population groups of R. aquitanica inhabiting different European mountain ranges: (i) mountain ranges north‐west of the Alps (Massif Central, Vosges, Schwarzwald and Fribourg); (ii) the southern Alps (Lombardia and Carinthia); and (iii) the western part of the southern Carpathians. This divergence suggests a long‐term isolation among these groups, which presumably took place long before the last Pleistocene glaciation, with no secondary contact among these populations. The differentiation centres of the southern Alps and Carpathian groups may have been mostly homotopic to their actual ranges, whereas the western group must have been distributed in the areas west or north‐west of the Alps with secondary expansions and disjunctions.     

Telocytes and stem cells in limbus and uvea of mouse eye

The potential of stem cell (SC) therapies for eye diseases is well‐recognized. However, the results remain only encouraging as little is known about the mechanisms responsible for eye renewal, regeneration and/or repair. Therefore, it is critical to gain knowledge about the specific tissue environment (niches) where the stem/progenitor cells reside in eye. A new type of interstitial cell–telocyte (TC) ( www.telocytes.com ) was recently identified by electron microscopy (EM). TCs have very long (tens of micrometres) and thin (below 200 nm) prolongations named telopodes (Tp) that form heterocellular networks in which SCs are embedded. We found TCs by EM and electron tomography in sclera, limbus and uvea of the mouse eye. Furthermore, EM showed that SCs were present in the anterior layer of the iris and limbus. Adhaerens and gap junctions were found to connect TCs within a network in uvea and sclera. Nanocontacts (electron‐dense structures) were observed between TCs and other cells: SCs, melanocytes, nerve endings and macrophages. These intercellular ‘feet’ bridged the intercellular clefts (about 10 nm wide). Moreover, exosomes (extracellular vesicles with a diameter up to 100 nm) were delivered by TCs to other cells of the iris stroma. The ultrastructural nanocontacts of TCs with SCs and the TCs paracrine influence via exosomes in the epithelial and stromal SC niches suggest an important participation of TCs in eye regeneration.     

Essential arterial hypertension and polymorphism of angiotensinogen M235T gene

Several candidate genes, chosen from the renin‐ angiotensin system, were examined for their association with essential hypertension. The genes of the renin‐ angiotensin system (RAS) are good candidates for such an approach because this system is well known to be involved in the control of blood pressure. One of these candidate genes is the gene encoding for angiotensinogen (the most important gene of the RAS associated with essential hypertension in the most population, is the gene for angiotensin‐converting enzyme‐ ACE). One DNA polymorphism within exon 2‐ with threonine instead of methionine at position 235 (M235T) was found to be significantly associated with hypertension. The objective of this study is the analysis of M235T polymorphism in angiotensinogen gene in Romanian patients with essential hypertension as well as controls. We examined 38 patients with essential hypertension and 21 normotensive patients. In order to identify the M235T angioteninogen variant, we used the following methods: DNA extraction, PCR amplification and enzymatic digestion of the PCR product using Tth IIII restriction endonuclease enzyme. In the study groups, the M235T variant (Met?Thr in aminoacid position 235) was found more frequently in hypertensive patients (81,57%), than in control subjects (66,66%). We identified 52,63% M235T heterozygotes in the hypertensive group compared with 47,61% in the control group, and 28,94% T235T homozygotes in the hypertensive group compared with 19,04% in the control group. The results of our study suggest an association of the M235T polymorphism in the gene encoding angiotensinogen with essential hypertension     

In Situ Fluorescence Imaging of Myelination

We describe a novel fluorescent dye, 3-(4-aminophenyl)-2H-chromen-2-one (termed case myelin compound or CMC), that can be used for in situ fluorescent imaging of myelin in the vertebrate nervous system. When administered via intravenous injection into the tail vein, CMC selectively stained large bundles of myelinated fibers in both the central nervous system (CNS) and the peripheral nervous system (PNS). In the CNS, CMC readily entered the brain and selectively localized in myelinated regions such as the corpus callosum and cerebellum. CMC also selectively stained myelinated nerves in the PNS. The staining patterns of CMC in a hypermyelinated mouse model were consistent with immunohistochemical staining. Similar to immunohistochemical staining, CMC selectively bound to myelin sheaths present in the white matter tracts. Unlike CMC, conventional antibody staining for myelin basic protein also stained oligodendrocyte cytoplasm in the striatum as well as granule layers in the cerebellum. In vivo application of CMC was also demonstrated by fluorescence imaging of myelinated nerves in the PNS. (J Histochem Cytochem 58:611–621, 2010)     

Methane monooxygenase hydroxylase and B component interactions

The interaction of the soluble methane monooxygenase regulatory component (MMOB) and the active site-bearing hydroxylase component (MMOH) is investigated using spin and fluorescent probes. MMOB from Methylosinus trichosporium OB3b is devoid of cysteine. Consequently, site-directed mutagenesis was used to incorporate single cysteine residues, allowing specific placement of the probe molecules. Sixteen MMOB Cys mutants were prepared and labeled with the EPR spin probe 4-maleimido-2,2,6,6-tetramethyl-1-piperidinyloxy (MSL). Spectral evaluation of probe mobility and accessibility to the hydrophilic spin-relaxing agent NiEDDA showed that both properties decrease dramatically for a subset of the spin labels as the complex with MMOH forms, thereby defining the likely interaction surface on MMOB. This surface contains MMOB residue T111 thought to play a role in substrate access into the MMOH active site. The surface also contains several hydrophilic residues and is ringed by charged residues. The surface of MMOB opposite the proposed binding surface is highly charged, consistent with solvent exposure. Probes of both of the disordered N- and C-terminal regions remain highly mobile and exposed to solvent in the MMOH complex. Spin-labeling studies show that residue A62 of MMOB is located in a position where it can be used to monitor MMOH-MMOB complex formation without perturbing the process. Accordingly, steady-state kinetic assays show that it can be changed to Cys (A62C) and labeled with the fluorescent probes 6-bromoacetyl-2-dimethylaminonaphthalene (BADAN) or 5-((((2-iodoacetyl)amino)ethyl)amino)naphthalene-1-sulfonic acid (1,5-IAEDANS) without loss of the ability of MMOB to promote turnover. The BADAN fluorescence is partially quenched and red shifted as the complex with MMOH forms, allowing affinity measurements. It is shown that the high affinity of labeled MMOB (K(D) = 13.5 nM at pH 6.6, 25 degrees C) for the oxidized MMOH decreases substantially with increasing pH and increasing ionic strength but is nearly unaffected by addition of nonionic detergents. Similarly, the fluorescence anisotropy of the 1,5-IAEDANS-labeled A62C-MMOH complex is perturbed by salts but not nonionic detergents. This suggests that the MMOB-MMOH complex is stabilized by electrostatic interactions consistent with the characteristics of the proposed binding surface. Reduction of MMOH results in a 2-3 order of magnitude decrease in the affinity of the BADAN-labeled A62C-MMOB-MMOH complex, consistent with previous indications of structural change associated with reduction of the active site dinuclear iron cluster. Utilizing BADAN-labeled MMOB, the association and dissociation rate constants for the MMOB-MMOH binding reaction were determined and found to be consistent with a two-step process, possibly involving rapid association followed by a slower conformational change. The latter may be related to the regulation of substrate access into the active site of MMOH.     

Cytogenetic evaluation of boars with a low prolificacy: two new types of chromosome translocation

Using the National Program for Sow Herd Management, two hypoprolific boars have been identified. The first one, a Large White, had produced on an average 7.2 piglets per litter in 24 litters. The second one, a Pietrain, had produced 6.11 piglets per litter in 28 litters. These animals are carrying two new chromosome translocations involving chromosomes 1 and 15 and 4 and 15, respectively. The animal production consequences of the chromosome translocations are discussed.     

Chromosome-mediated alterations of the MYC gene in human cancer

The step-wise accumulation of genetic and epigenetic alterations in cancer development includes chromosome rearrangements and viral integration-mediated genetic alterations that frequently involve proto-oncogenes. Protooncogenes deregulation lead to unlimited, self-sufficient cell growth and ultimately generates invasive and destructive tumors. C-MYC gene, the cellular homologue of the avian myelocitic leukemia virus, is implicated in a large number of human solid tumors, leukemias and lymphomas as well as in a variety of animal neoplasias. Deregulated MYC expression is a common denominator in cancer. Chromosomal rearrangements and integration of oncogenic viruses frequently target MYC locus, causing structural or functional alterations of the gene. In this article, we illustrate how genomic rearrangements and viruses integration affect MYC locus in certain human lymphomas and solid tumors.     

The connective connection: interstitial cells of Cajal (ICC) and ICC-like cells establish synapses with immunoreactive cells. Electron microscope study in situ

We present transmission electron microscope (TEM) evidence that ICC and ICC-like cells frequently establish close contacts (synapses) with several types of immunoreactive cells (IRC): lymphocytes, plasma cells, eosinophils, basophils, macrophages and mast cells. Such synapses were found in various organs: human mammary gland and myometrium, as well as rat stomach, gut, bladder and uterus. Specimens were observed by conventional TEM on ultrathin sections. Based on morphometric analyses and computer-aided 3-D reconstructions from serial sections, we propose an operational definition of ICC-IRC synapses: cell-to-cell close contacts where the two cells are separated by only approximately 15 nm, equivalent to twice the plasmalemmal thickness. Two types of such synapses were found: (i) uniform ('plain') synapses (PS). close contact extending for >200 nm, and (ii) multi-contact ('kiss and run') synapses (MS)--with multiple, focal, close-contact points alternating with regions of wider intermembrane distance. For instance, a typical PS between a rat bladder ICC-like cell and an eosinophil was 2.48 microm long and 11+/-4 nm wide. By contrast, a MS synapse in rat myometrium (between an ICC-like cell and an eosinophil) was 8.64 microm long and had 13 contact points. The synaptic cleft measured 15+/-8 nm at contact points and approximately 100 nm or more in wider areas. These synapses are different from gap junctions usually seen between ICC and between ICC and smooth muscle cells. We previously proposed that ICC-like cells might represent stromal progenitor cells, participate in juxtacrine/paracrine signaling and play a role in immune surveillance. The nanoscopic distances between the two contiguous membranes suggest a juxtacrine cell-to-cell signaling (chemical synapse), via juxtacrinins, a specific case of phenomenins. However, the (micro)vesicles found in the synaptic cleft may correspond to an exosome-based mechanism.