Intramolecular homolytic substitution in selenoxides and selenones

G3(MP2)-RAD calculations provide activation energies for intramolecular homolytic substitution in the 4-(alkylselenoxo)butyl and 4-(alkylselendioxo)butyl radicals ranging from 21–39 kJ mol−1, and 143–170 kJ mol−1 for the selenoxide and selenone, respectively. Arrhenius data translate into rate constants for ring-closure of 1.5×105−2.5×108 s−1 (80°) for the selenoxides, and 5.4×10−14−5.1×10−11 s−1 (80°) for the corresponding selenones. NBO analyses show alkyl radicals are electrophilic during homolytic substitution at selenoxide selenium. The dominant orbital interaction in the transition state is worth 2413 kJ mol−1 and involves the SOMO and the lone-pair of electrons on selenium. The corresponding selenones are calculated to ring-close through transition states in which alkyl radicals are nucleophilic, but involve weak (SOMO--> σ* and SOMO--> π*) interactions. Consequently, this chemistry is not viable for selenones because of the lack of lone-pairs of electrons on the chalcogen

7-Selenabicyclo2.2.1heptane

Thermolysis of a benzene solution of N-4-(p-(methoxybenzyl)seleno) cyclohexanoyl-N,S-dimethyldithiocarbonate affords the hitherto unknown 7-selenabicyclo2.2.1heptane in 48% conversion and in 20% yield after chromatography. G3(MP2)-RAD calculations predict a rate constant of 5 X 104 s-1 at 80 °C (3.8 X 106 s -1 at 200 °C) for the intramolecular homolytic substitution process involved in this cyclization

Mikroskopische Untersuchung der Pferdezähne und ihrer Umgebung – Teil 1: Allgemeines und Histologie der Schneidezähne

In Ergänzung zu den bildgebenden Verfahren soll die vorliegende Arbeit Bilder zur Histologie der Zähne des Pferdes samt ihrer Umgebung vermitteln. Teil 1 der Arbeit umfasst die Methodik und die Histologie der Schneidezähne, Teil 2 befasst sich mit der Histologie der Backenzähne. Aus den Gebissen von 3 Pferden verschiedenen Alters wurden nach der Fixation ganze Zähne oder Teile der Gebisse ohne Entkalkung in Methyl-Methacrylat (MMA) eingebettet. Daraus wurden um 500 μm dicke Hartschnitte bis zu einer Grösse von 60 × 110 mm hergestellt und vorwiegend nach Giemsa gefärbt. Die Oberflächen der Schnitte ergaben sowohl Übersichtsbilder als auch Details der Zahnsubstanzen und der sie bildenden Zellen mitsamt ihrer Umgebung in hoher Auflösung. Die Bilddokumentation umfasst eingehend das 5-jährige Pferd, da bei dieser Altersgruppe über lange Zeit wenig Veränderungen vorkommen. In Längs- und Querschnitten werden die Pulpahöhle, die Zahnsubstanzen und die Schmelzbecher, (Kunden) bis ins Detail gezeigt. An den unentkalkten Präparaten blieb insbesondere der Schmelz vollständig erhalten. In der Umgebung der Zähne sind im ca. 500 μm starken Periodontium neben den gegen apikal gerichteten Fasern vor allem zirkulär um den Zahn verlaufende Faserbündel vorhanden. Der Kieferknochen enthält viel lockere Spongiosa, in der die inneren, an das Periodontium angrenzenden Lamellen, mit einer Stärke bei nur 200 μm sehr dünn sind. Beim 2-jährigen Pferd sieht man im Längsschnitt durch den 1. Schneidezahn des Oberkiefers im Ersatzzahn (I1, 101) die Bildung der Zahnsubstanzen sowie den Schmelzbecher in seiner Entstehung. Außerdem erkennt man an den Wurzeln des Milchzahnes Zeichen des aktiven Abbaus der Zahnsubstanzen. An den Schneidezähnen des 13-jährigen Pferdes fallen im Unterkiefer die starke Schrägstellung der Schneidezähne auf sowie die gegen apikal größeren Zwischenräume zwischen den Zähnen. Die durch das Periodontium und die lockere Struktur der Kieferknochen weiten Zwischenräume sind mit dafür verantwortlich, dass es mit zunehmendem Alter oft zu einer Auflockerung zwischen den Schneidezähnen bis zu deren Ausfall kommen kann. Die Bilddokumentation der Pferdezähne samt ihrer Umgebung möchte für Diagnostik und Therapie Kenntnisse zur Struktur der Gewebe an den verschiedenen Lokalisationen der Gebisse vermitteln

Relativistic Wavepackets in Classically Chaotic Quantum Cosmological Billiards

Close to a spacelike singularity, pure gravity and supergravity in four to eleven spacetime dimensions admit a cosmological billiard description based on hyperbolic Kac-Moody groups. We investigate the quantum cosmological billiards of relativistic wavepackets towards the singularity, employing flat and hyperbolic space descriptions for the quantum billiards. We find that the strongly chaotic classical billiard motion of four-dimensional pure gravity corresponds to a spreading wavepacket subject to successive redshifts and tending to zero as the singularity is approached. We discuss the possible implications of these results in the context of singularity resolution and compare them with those of known semiclassical approaches. As an aside, we obtain exact solutions for the one-dimensional relativistic quantum billiards with moving walls.Comment: 18 pages, 10 figure

Radiolysis of NaCl at high and low temperatures: development of size distribution of bubbles and colloids

New experimental results are presented on low temperature irradiation (18 °C) of rock-salt samples which had been exposed to initial doses up to 320 GRad at 100 °C. Differential scanning calorimetry (DSC) shows that the latent heat of melting (LHM) of sodium colloids decreases during subsequent low-temperature irradiation, whereas the stored energy (SE) increases slowly, indicating that the process of radiolysis continues. The decrease of the LHM is due to dissolution of large colloids, because the intensities of the melting peaks decrease during the second stage irradiation at low temperature. The model is formulated to describe the nucleation kinetics and the evolution of the size distribution of chlorine precipitates and sodium colloids in NaCl under high dose irradiation. It is shown that the mechanism of dissolution of large Na colloids during low temperature irradiation can be related to melting of sodium colloids.

Newly defined ATP-binding cassette subfamily B member 5 positive dermal mesenchymal stem cells promote healing of chronic iron-overload wounds via secretion of interleukin-1 receptor antagonist

In this study, we report the beneficial effects of a newly identified dermal cell subpopulation expressing the ATP‐binding cassette subfamily B member 5 (ABCB5) for the therapy of nonhealing wounds. Local administration of dermal ABCB5+‐derived mesenchymal stem cells (MSCs) attenuated macrophage‐dominated inflammation and thereby accelerated healing of full‐thickness excisional wounds in the iron‐overload mouse model mimicking the nonhealing state of human venous leg ulcers. The observed beneficial effects were due to interleukin‐1 receptor antagonist (IL‐1RA) secreted by ABCB5+‐derived MSCs, which dampened inflammation and shifted the prevalence of unrestrained proinflammatory M1 macrophages toward repair promoting anti‐inflammatory M2 macrophages at the wound site. The beneficial anti‐inflammatory effect of IL‐1RA released from ABCB5+‐derived MSCs on human wound macrophages was conserved in humanized NOD‐scid IL2rγ null mice. In conclusion, human dermal ABCB5+ cells represent a novel, easily accessible, and marker‐enriched source of MSCs, which holds substantial promise to successfully treat chronic nonhealing wounds in humans

INS-1 Cells Undergoing Caspase-Dependent Apoptosis Enhance the Regenerative Capacity of Neighboring Cells

Our results suggest that apoptosing INS-1 cells shed microparticles that may stimulate PSP/reg induction in neighboring cells, a mechanism that may facilitate the recovery of β-cell mass in HNF1A-MODY

Caerulein-induced acute pancreatitis in mice that constitutively overexpress Reg/PAP genes

BACKGROUND: The cystic fibrosis (CF) mouse pancreas has constitutively elevated expression of the Reg/PAP cell stress genes (60-fold greater Reg3α, and 10-fold greater PAP/Reg3β and Reg3γ). These genes are suggested to be involved in protection or recovery from pancreatic injury. METHODS: To test this idea the supramaximal caerulein model was used to induce acute pancreatitis in wild type and CF mice. Serum amylase, pancreatic water content (as a measure of edema), pancreatic myeloperoxidase activity, and Reg/PAP expression were quantified. RESULTS: In both wild type and CF mice caerulein induced similar elevations in serum amylase (maximal at 12 h), pancreatic edema (maximal at 7 h), and pancreatic myeloperoxidase activity (MPO, a marker of neutrophil infiltration; maximal at 7 h). By immunohistochemistry, Reg3α was strongly expressed in the untreated CF pancreas but not in wild type. During pancreatitis, Reg3α was intensely expressed in foci of inflamed tissue in both wild type and CF. CONCLUSION: These data demonstrate that the severity of caerulein-induced pancreatitis is not ameliorated in the CF mouse even though the Reg/PAP stress genes are already highly upregulated. While Reg/PAP may be protective they may also have a negative effect during pancreatitis due to their anti-apoptotic activity, which has been shown to increase the severity of pancreatitis

TET family dioxygenases and DNA demethylation in stem cells and cancers

The methylation of cytosine and subsequent oxidation constitutes a fundamental epigenetic modification in mammalian genomes, and its abnormalities are intimately coupled to various pathogenic processes including cancer development. Enzymes of the Ten-eleven translocation (TET) family catalyze the stepwise oxidation of 5-methylcytosine in DNA to 5-hydroxymethylcytosine and further oxidation products. These oxidized 5-methylcytosine derivatives represent intermediates in the reversal of cytosine methylation, and also serve as stable epigenetic modifications that exert distinctive regulatory roles. It is becoming increasingly obvious that TET proteins and their catalytic products are key regulators of embryonic development, stem cell functions and lineage specification. Over the past several years, the function of TET proteins as a barrier between normal and malignant states has been extensively investigated. Dysregulation of TET protein expression or function is commonly observed in a wide range of cancers. Notably, TET loss-of-function is causally related to the onset and progression of hematologic malignancy in vivo. In this review, we focus on recent advances in the mechanistic understanding of DNA methylation-demethylation dynamics, and their potential regulatory functions in cellular differentiation and oncogenic transformation