UV-exposure,endogenous DNA damage,and DNA replication errors shape the spectra of genome changes in human skin

Human skin is continuously exposed to environmental DNA damage leading to the accumulation of somatic mutations over the lifetime of an individual. Mutagenesis in human skin cells can be also caused by endogenous DNA damage and by DNA replication errors. The contributions of these processes to the somatic mutation load in the skin of healthy humans has so far not been accurately assessed because the low numbers of mutations from current sequencing methodologies preclude the distinction between sequencing errors and true somatic genome changes. In this work, we sequenced genomes of single cell-derived clonal lineages obtained from primary skin cells of a large cohort of healthy individuals across a wide range of ages. We report here the range of mutation load and a comprehensive view of the various somatic genome changes that accumulate in skin cells. We demonstrate that UV-induced base substitutions, insertions and deletions are prominent even in sun-shielded skin. In addition, we detect accumulation of mutations due to spontaneous deamination of methylated cytosines as well as insertions and deletions characteristic of DNA replication errors in these cells. The endogenously induced somatic mutations and indels also demonstrate a linear increase with age, while UV-induced mutation load is age-independent. Finally, we show that DNA replication stalling at common fragile sites are potent sources of gross chromosomal rearrangements in human cells. Thus, somatic mutations in skin of healthy individuals reflect the interplay of environmental and endogenous factors in facilitating genome instability and carcinogenesis.     

SEM analysis of dental enamel morphological structures on the basis of their replicas in patients with systemic calcium deficiency

The aim of the present study is to examine microscopically the surface of dental enamel by using a scanning electron microscope (SEM), using their replicas formed in female patients with diagnosed periodontal diseases and systemic calcium deficiency. Replicas of dental enamel surfaces in patients referred for treatment of periodontal diseases were subjected to microscopic analysis. The replicas, after coating with platinum-palladium alloy, were examined under the scanning electron microscope at magnifications of 15–5000 x. Densitometric examinations of spine (L₂ - L₄ segment) revealed bone mineral density BMD T-score lower than −2.5 in 5 patients, in the range of −1.5 to −2.5 in 10 patients, and higher than −1.5 in the remaining patients. Non-homogenous images of surfaces in the form of light and dark areas were observed. Light areas corresponded to damaged surfaces of dental tissues. Patients with higher systemic calcium deficiency had areas lighter in color. More of these areas were found in patients with higher systemic calcium deficiency. It can be assumed that the calcium deficit is likely to appear in the selected dental tissues, particularly in the dental enamel.     

Middle Jurassic (Bathonian) encrusted oncoids from the Polish Jura,southern Poland

Oncoids from two localities (Ogrodzieniec and Blanowice) of the Polish Jura, southern Poland, have been investigated with respect to their genesis and paleoecology. These oncoids occur within Middle Jurassic (Bathonian) deposits. Those from Ogrodzieniec are large, elliptical, and embedded within a presumably condensed carbonate bed. Those from Blanowice, on the contrary, are significantly smaller, irregular to box-like in shape, and occur within the ore-bearing clays. The oncoids from both localities consist of a distinct carbonate core and laminated cortex that is significantly thicker and better preserved in the Ogrodzieniec oncoids. SEM and optical microscopic investigation of the oncoid cortices revealed the presence of carbonate and silicate layers with web-like structures similar to those occurring in recent cyanobacterial microbialites. Thus, the oncoid cortices investigated may have formed in a photic zone environment with the aid of coccoid and filamentous cyanobacteria. Oxic conditions prevailed during oncoid cortex formation within the siliciclastic setting, which is manifested by low total organic carbon content, high pristane/phytane (Pr/Ph) ratio, and significant predomination of the C₃₁ homohopanes. On the cortices’ surfaces, as well as between particular laminae, various encrusting organisms have been found. The encrusters, dominated by serpulids and bryozoans, are cryptic species that inhabited the undersides and recesses of the oncoids. Their presence on both the upper and lower surfaces of the oncoids indicates that the oncoids were episodically overturned on the seafloor. The much better developed cortex lamination and much higher diversity and abundance of encrusters in the Ogrodzieniec oncoids may point to better trophic conditions prevailing in a shallower marine environment characterized by transparent waters, as opposed to a deeper siliciclastic environment with less transparent waters and probably worse trophic conditions prevailing during formation of the Blanowice oncoids.     

Synthesis and tumoricidal activity of water soluble porphyrinyl-thymidines and related porphyrins

The new cobalt(II)meso-5,10-di(N-methyl-4-pyridinium)-15,20-di(p-phenylene-5′-O-thymidine)porphyrin suppressed the growth of human malignant melanoma cells (M21-HPB) by 95 percent when applied as 2.5 x 10⁻⁵ M solution in tris for 3 days without exposure to light. It was the most effective of the investigated porphyrinyl-nucleosides.     

Temporary Changes in the dc ElectricalConductivity of MX (3-Chloro-4(Dichloromethyl)-5-Hydroxy-2(5H)-Furanone) Treated Collagen

The influence of MX(3-Chloro-4(Dichloromethyl)-5-Hydroxy-2(5H)- Furanone), a stronglymutagenic compound, on the temperature dependence of the dcelectrical conductivity of collagen as a function of time was studied.Collagen was immersed in MX solution, next dried and pressed intotablets. The MX concentration was measured by HPLC analysis.The reduction of MX concentration to 10% of the initial value wasobserved in the presence of collagen in the solution, whereas in thecontrol solution concentration of MX decreased to 70% of the initialvalue. Measurements of electrical conductivity were performed for thetemperature range 295–453K and activation energies for the chargeconduction process were calculated. Within the temperature range295–340K, the presence of MX decreased electrical conductivity ofcollagen. Calculated activation energies were typical for dry proteins.Within the temperature range 295–320K activation energy decreasedwith time, probably due to the stronger interactions in thecollagen-water-MX system. For temperatures between 320–410 and430–450K the activation energy was not time dependent and theapplication of MX did not change the structure of the collagenmacromolecule. The temporary changes occurring at the lowertemperatures being due solely to changes in the collagen-waterinteractions.     

Effects of heavy central metal on the ground and excited states of chlorophyll

Chlorophylls, owing to their adjustable π-electron system and intense, well-separated electronic transitions, can serve as convenient intrinsic spectroscopic probes of ligand–metal center interactions. They are also interesting for their photosensitizing properties. In order to examine the heavy-atom effects on the chlorophyll triplet state, a key intermediate in chlorophyll–photosensitized reactions, the synthesis of a novel Pt(II)-substituted chlorophyll a was carried out, and the effects of the substitution on steady-state and transient photophysical properties of chlorophyll were studied by absorption and fluorescence spectroscopies, and by laser flash photolysis. The presence of highly electronegative platinum as the central ion increases the energies of the chlorophyll main absorption transitions. As laser flash photolysis experiments show, in air-equilibrated solutions, chlorophyll triplets are efficiently quenched by molecular oxygen. Interestingly, this quenching by oxygen is more effective with metal-containing pigments, in spite of the increased spin–orbit coupling, introduced with the central metals. This points to occurrence of nonspecific interactions of molecular oxygen with metallochlorophylls. The differences in the effects exerted on the pigment triplet by the central metal become distinct after the removal of oxygen. The lifetime of a Pt-chlorophyll triplet remains very short, in the range of only a few microseconds, unlike in the free-base and Mg- and Zn-substituted chlorophylls. Such drastic shortening of the triplet lifetime can be attributed to a large heavy-atom effect, implying that strong interactions must occur between the central Pt(II) ion and the chlorophyll macrocycle, which lead to a more efficient spin–orbit coupling in Pt-chlorophyll than in Pt-porphyrins.Electronic Supplementary Material Supplementary material is available for this article at .