Glutathione Response after UVA Irradiation in Mitotic and Postmitotic Human Skin Fibroblasts and Keratinocytes

Abstract— Since Hayflick's pioneering work in the early sixties, human diploid fibroblasts have become a widely accepted in vitro model system. Recently, Bayreuther and co-workers extended this experimental approach showing that fibroblasts in culture resemble, in their design, the hemopoietic stem-cell differentiation system. They found that the chemical agent mitomycin C accelerates the differentiation pathway from mitotic to postmitotic fibroblasts. We measured the response of endogenous glutathione levels after UVA irradiation (320-400 nm) in mitotic and mitomycin C-induced postmitotic human skin fibroblasts and foreskin-derived keratinocytes. The initial levels in mitotic foreskin derived human fibroblasts were 14.4 nmol glutathione per mg protein, whereas a 30% higher value was obtained in matching foreskin-derived keratinocytes. Similiar elevated levels of this important intracellular free radical scavenging system were found in fibroblasts of a donor suffering from xeroderma pigmentosum. Furthermore, three to four times higher levels of glutathione in mitomycin C-treated mitotic fibroblasts have been determined. In mitotic skin fibroblasts, UVA irradiation resulted in a depletion of glutathione up to 90% following a fluence of 1.0 MJ/m²UVA radiation. Higher initial glutathione levels were found in keratinocytes and mitomycin C-treated skin fibroblasts. In these fibroblasts a 70% depletion was detected and a much lower depletion (10-20%) was seen in some keratinocyte cell lines following fluences up to 1.0 MJ/m². The depletion in skin fibroblasts was retained after 24 h following a fluence of 0.75 MJ/m²UVA light. In view of the fact that glutathione has been shown to be involved in a variety of metabolic processes and plays a role in cellular protection against UVA radiation, our results imply that the fibroblast differentiation system is a very useful tool to unravel the complex mechanism of UVA-induced oxidative stress.     

Bilden sich aus Pentafulven und Cyclopentadien [6+4]-Cycloaddukte??

Does [6+4] Cycloaddition between Pentafulvene and Cyclopentadiene Take Place? Reaction of a 1:1 mixture of cyclopentadiene (CPD) and pentafulvene ( 1a ) at 20° gives a complex mixture. The low-molecular-weight part mainly consists of pure and mixed dimers (ca. 73 %) besides corresponding trimers (ca. 20%) and some corresponding oligomers according to GC/MS investigations (Fig. 1). The 3 predominant ‘mixed dimers’ between CPD and 1a have been separated, and structures 4 – 6 (Scheme 3) are assigned according to 400- and 600-MHz ¹H-NMR investigations. These results show that HOMO(CPD)-LUMO(fulvene) interactions are important in pentafulvene cycloadditions. Dimer 6 results from [6+4] cycloaddition followed by [1,5]-H shifts.     

Aesculaxanthin,a New Carotenoid Isolated from Pollens of Aesculus hippocastanum

From the pollens of Aesculus hippocastanum, a new apocarotenoid was isolated as the main carotenoid and, based on the spectroscopic data, identified as (all-E,3R)-3-hydroxy-6′-apo-β-caroten-6′-al ( 4 , aesculaxanthin). In addition, (all-E)-lutein ( 3 ) and (all-E)-β-citraurin ( 5 ) were isolated. Furthermore, 6 (aesculaxanthol) was prepared by reduction of 4 with NaBH₄ and tentatively identified as natural carotenoid.     

The crystal structure of macrosalhine bromide

The chemically elucidated structure of Macrosalhine, an alkaloid of Alstonia macrophylla Wall., has been confirmed by X-ray analysis, the remaining relative stereochemical questions having been at the same time resolved.     

The canted ferrimagnetic structure of Nd5Ge4 by neutron diffraction

The chemical and magnetic structures of the intermetallic compound Nd₅Ge₄ were determined from neutron diffraction powder data. In contrast to the isomorphous heavy rare-earth compounds, Nd₅Ge₄ orders with a canted ferrimagnetic arrangement below T_c = 52 K. The ordered Nd moments are 2.6, 3.1 and 2.4 μ_B for the three sites respectively. The magnetic space group is Pnm'a' and the plane of easy magnetization (010).     

DETERMINATION OF CYTOSINE-CYTOSINE PHOTODIMERS IN THE DNA OF CLOUDMAN S91 MELANOMA CELLS USING HIGH PRESSURE LIQUID CHROMATOGRAPHY

Abstract
I measured the induction of cytosine-cytosine dimer (C-C) densities after UV-C (< 290 nm) and UV-B irradiation (290–320 nm) in the 2'-deoxy-[³H]cytidine labeled DNA of Cloudman S91 mouse melanoma cells using a new, sensitive high pressure liquid chromatography procedure. UV-B exposure resulted in 0.000034% C-C/J m^-2 of the total cytosine radioactivity which is 10 times less than the rate during UV-C irradiation. Previous work with these melanoma cells showed a 4-fold lower rate of induction of thymine-containing pyrimidine dimers by UV-B than UV-C light (Niggli Photochem. Photobiol . 52 , 519–524, 1990). Based on these results, the calculated ratios for the pyrimidine dimer subspecies showed no significant difference following UV-C and UV-B exposure. However, UV-C and UV-B light induce 10–20 times more thymine-containing pyrimidine dimers than C-C in the DNA of S91 cells.     

Measurement of the lifetime and quenching rate of metastable 2S muonic helium ions

The lifetime of the 2S state in (μ^?4He)⁺ ions has been measured at He-gas pressures between 50 Torr and 6 atm (T=300 K). We observed both X-rays from the two-photon 2S→1S transitions as well as delayed K_α X-rays associated with radiative quenching. The quenching rate is strongly pressure dependent; it is predominantly a quadratic function of pressure with a measured three-body rate coefficient k=(5.9±0.8)×10^?32cm⁶/s. At 6 atm, we find τ_2S<250 ns because of the absence of two-photon transitions.     

The antiferromagnetic structures of TbCu2Ge2 and HoCu2Ge2 by neutron diffraction

The magnetic structures of TbCu₂Ge₂ and HoCu₂Ge₂ were studied by neutron diffraction. At 293 K the chemical structure is tetragonal body centered, space group I 4/mmm. The magnetic cell at 4.2 K is four times larger than the chemical one with a wave vector $\text{k =}\text{1}\text{2}\text{0}\text{1}\text{2}$. The magnetic space group is triclinic P_a$\text{1}$(Sh₂⁷) for both compounds. The moment values and directions are μ_Tb = 8.48(6) [μ_B] along [110] tetr. and μ_HO = 6.5(1)[μ_B] making an angle of 81.4(°) with c and 80(°) with a₁. The structure consists of ferromagnetic (101) layers stacked antiferromagnetically.