Cyclische Diazastannylene. - XXVI : Funktionalisierte Cyclodisilazane aus cyclischen Diazanstannylenen

1,3-Di-tert-butyl-2,2-dihalogen-4,4-dimethylcyclodisilazane Substituent Chlor (3), Brom (4), Iod (5)) lassen sich aus dem 1,3-Di-tert-butyl-2,2-dimethyl-1,2,3,2,42-diazasilastannetidin (1) durch Umsetzung mit SiCl4, SiBr4 oder SiI4 erhalten. Je leichter das Halogen im Tertahalogenid ist, um so drastischere Reaktionsbedingungen müssen gewählt werden. Aus 4 ist durch Umsetzung mit Natriumazid auch das entsprechende Si, Si-Diazid (9) zugänglich. Alle neu synthetisierten Verbindungen 3, 4, 5 und 9 lösen sich als Monomere in Benzol

Darstellung einer molekularen, monomeren Thallium(I)-Verbindung mit einem neuen chelatisierenden Liganden

Der chelatisierende Ligand Me3COSiMe2N(CMe3)H (III) ist präparativ in ohen Ausbeuten, einfach zugänglich und wurde für die Darstellung einer Reihe on Metallderivaten eingesetzt. Mit n-Butyllithium bildet III das in Lösung und asphase Dimere [Me2Si(Me3CO)(Me3CNLi)]2 (IV). Mit Thallium(I)chlorid etzt sich IV in Diethylether unter Abspaltung von Lithiumchlorid zu monoserem, sehr reaktivem Me2Si(Me3C ) (II) um. Die Ringstruktur und hysikalischen Eigenschaften von II kann man mit Hilfe der Isoteriebeziehung ?cyclischen Diazasilastannylenen erklären. II bildet mit Methanol das Tetramer (TlOMe)4 und addiert kein Methyljodid an das Metall. Bei letzterer Umsetzung atsteht Thallium(I)jodid. Behandelt man II mit Magnesiumdichlorid in Diethylther, so entsteht neben Thallium(I)chlorid die Spiro-Verbindung [Me2Si(Me3-CO)(Me3CN)]2Mg (VI), in der das Magnesium vierfach koordiniert ist

Spektroskopischer Nachweis eines Bis(amino)silylens

The photolysis of the silicon diazide 3a in benzene solution and in an Ar matrix is described. Both irradiations cause the elimination of 3 equivalents of N2. Loss of N2 from 3a in benzene leads to the formation of the analytically investigated product or products 4 of uncertain structure. However, the matrix photolysis of 3a results in a compound which is stable up to 77 K and has been identified as the bis(amino)silylene 2 d by comparison of its IR spectra with those of the homologous Sn and Ge compond

Spektroskopischer Nachweis eines Bis(amino)silylens

The photolysis of the silicon diazide 3a in benzene solution and in an Ar matrix is described. Both irradiations cause the elimination of 3 equivalents of N2. Loss of N2 from 3a in benzene leads to the formation of the analytically investigated product or products 4 of uncertain structure. However, the matrix photolysis of 3a results in a compound which is stable up to 77 K and has been identified as the bis(amino)silylene 2 d by comparison of its IR spectra with those of the homologous Sn and Ge compond

Read-Across of 90-day Rat Oral Repeated-Dose Toxicity: A Case Study for Selected n-Alkanols

n-Alkanols provide an excellent example where a category-approach to read-across may be used to estimate the repeated-dose endpoint for a number of untested derivatives (target chemicals) using experimental data for tested derivatives (source chemicals). n-Alkanols are non-reactive and exhibit the unspecific, reversible simple anaesthesia or non-polar narcosis mode of toxic action in that the metabolic products of the parent alcohols do not contribute to the toxic endpoint evaluated. In this case study, the chemical category is limited to the readily bioavailable (C5 to C13) analogues. The toxicokinetic premise includes rapid absorption via the gastrointestinal tract, distribution in the circulatory system, and first-pass metabolism in the liver resulting in metabolism via oxidation to CO2 and with minor elimination of oxidative intermediate as glucuronides. Two analogues have experimental 90-day oral repeated-dose toxicity data which exhibit qualitative and quantitative consistency. Typical findings include decreased body weight, slightly increased liver weight which, in some cases, is accompanied by clinical chemical and haematological changes but generally without concurrent histopathological effects at the Lowest Observed Effect Level (LOEL). Chemical similarity between the analogues is readily defined by a variety of structure-related properties; data uncertainty associated with toxicokinetic and toxicodynamic similarities is low. Uncertainty associated with mechanistic relevance and completeness of the read-across is reduced by the concordance of in vivo and in vitro results, as well as high throughput and in silico methods data. As shown in detail, the 90-day oral repeated-dose toxicity No Observed Effect Level (NOEL) value of 1000 mg/kg bw/d for 1-pentanol and 1-hexanol based on LOEL of very low systemic toxicity can be read across to fill the data gaps of the untested analogues in this category with acceptable uncertainty

Immunolocalization and temporal distribution of cytokine expression during the development of vein graft intimal hyperplasia in an experimental model

AbstractPurpose: Vein graft stenosis caused by intimal hyperplasia (IH) accounts for 30% to 50% of late bypass graft failures; however, the biochemical mediators of vein graft IH have been poorly defined. We attempted to evaluate the spatial and temporal distribution of five principal cytokines (interleukin-1 beta [IL-1β], platelet-derived growth factor AA [PDGF-AA], basic fibroblast growth factor [bFGF], interferon gamma [INFγ], and tumor necrosis factor alpha [TNF-α]) during the development of IH in a rat vein graft model.Methods: Rat epigastric vein interposition grafts in the femoral artery were harvested at 6 hours, 2 days, 1 week, 2 weeks, and 4 weeks after the grafting procedure and studied with immunohistochemical and standard histologic techniques. The cytokine expression in the endothelium and media/neointima was quantified as the percentage of immunopositive cells per high-power field.Results: Maximal hyperplasia occurred 2 weeks after the grafting procedure. Peak expression of IL-1β and bFGF occurred by 2 days. PDGF-AA expression paralleled the development of IH, peaking at 2 weeks and then declining. TNF-α expression increased at 1 week and remained elevated. INFγ was seen only in control grafts.Conclusions: The coordinated early release of IL-1β and bFGF and the down-regulation of INFγ seem to trigger an inflammatory response, thereby initiating IH. The process then is propagated by the release of PDGF-AA and TNF-α, with concomitant smooth muscle cell proliferation and production of extracellular matrix. It is likely that this complex milieu of local paracrine signaling is required to generate the hyperplastic response seen in failing vein grafts. (J Vasc Surg 1996;24:463-71.

Developing Telemental Health Partnerships Between State Medical Schools and Federally Qualified Health Centers: Navigating the Regulatory Landscape and Policy Recommendations

BackgroundFederally Qualified Health Centers (FQHCs) deliver care to 26 million Americans living in underserved areas, but few offer telemental health (TMH) services. The social missions of FQHCs and publicly funded state medical schools create a compelling argument for the development of TMH partnerships. In this paper, we share our experience and recommendations from launching TMH partnerships between 12 rural FQHCs and 3 state medical schools.ExperienceThere was consensus that medical school TMH providers should practice as part of the FQHC team to promote integration, enhance quality and safety, and ensure financial sustainability. For TMH providers to practice and bill as FQHC providers, the following issues must be addressed: (1) credentialing and privileging the TMH providers at the FQHC, (2) expanding FQHC Scope of Project to include telepsychiatry, (3) remote access to medical records, (4) insurance credentialing/paneling, billing, and supplemental payments, (5) contracting with the medical school, and (6) indemnity coverage for TMH.RecommendationsWe make recommendations to both state medical schools and FQHCs about how to overcome existing barriers to TMH partnerships. We also make recommendations about changes to policy that would mitigate the impact of these barriers. Specifically, we make recommendations to the Centers for Medicare and Medicaid about insurance credentialing, facility fees, eligibility of TMH encounters for supplemental payments, and Medicare eligibility rules for TMH billing by FQHCs. We also make recommendations to the Health Resources and Services Administration about restrictions on adding telepsychiatry to the FQHCsâ Scope of Project and the eligibility of TMH providers for indemnity coverage under the Federal Tort Claims Act.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149739/1/jrh12323_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149739/2/jrh12323.pd