Differences in pigment-containing organelles between color forms of the red-backed salamander,Plethodon cinereus

Summary Chromatophores of two color forms of the salamander, Plethodon cinereus were studied by electron microscopy. Erythrophores found in the red-backed form possess pterinosomes, some with regions of high electron density. In addition, a few melanosome-like organelles are present. On the other hand, the lead-backed form displays no visible erythrophores but instead melanophores with melanosomes being the most prevalent organelle and a few pterinosomes. The possibility that this represents a kind of hybrid chromatophore with intermediate stages in melanosome-pterinosome interconversion is discussed.This study was supported in part by GB-8347 from the National Science Foundation.Contribution No. 255, Department of Biology, Wayne State University.     

Protein oxidation,UVA and human DNA repair

Solar UVB is carcinogenic. Nucleotide excision repair (NER) counteracts the carcinogenicity of UVB by excising potentially mutagenic UVB-induced DNA lesions. Despite this capacity for DNA repair, non-melanoma skin cancers and apparently normal sun-exposed skin contain huge numbers of mutations that are mostly attributable to unrepaired UVB-induced DNA lesions. UVA is about 20-times more abundant than UVB in incident sunlight. It does cause some DNA damage but this does not fully account for its biological impact. The effects of solar UVA are mediated by its interactions with cellular photosensitizers that generate reactive oxygen species (ROS) and induce oxidative stress. The proteome is a significant target for damage by UVA-induced ROS. In cultured human cells, UVA-induced oxidation of DNA repair proteins inhibits DNA repair. This article addresses the possible role of oxidative stress and protein oxidation in determining DNA repair efficiency – with particular reference to NER and skin cancer risk.     

New insight into phase behavior and permeability of skin lipid models based on sphingosine and phytosphingosine ceramides

The intercellular lipid matrix of the stratum corneum (SC), which consist mainly of ceramides (CERs), free fatty acids and cholesterol, is fundamental to the skin barrier function. These lipids assemble into two lamellar phases, known as the long and short periodicity phases (LPP and SPP respectively). The LPP is unique in the SC and is considered important for the skin barrier function. Alterations in CER composition, as well as impaired skin barrier function, are commonly observed in diseased skin, yet the understanding of this relationship remains insufficient. In this study, we have investigated the influence of non-hydroxy and α-hydroxy sphingosine-based CERs and their phytosphingosine counterparts on the permeability and lipid organization of model membranes, which were adjusted in composition to enhance formation of the LPP. The permeability was compared by diffusion studies using ethyl-p-aminobenzoate as a model drug, and the lipid organization was characterized by X-ray diffraction and infrared spectroscopy. Both the sphingosine- and phytosphingosine-based CER models formed the LPP, while the latter exhibited a longer LPP repeat distance. The ethyl-p-aminobenzoate flux across the sphingosine-based CER models was higher when compared to the phytosphingosine counterparts, contrary to the fact that the α-hydroxy phytosphingosine-based CER model had the lowest chain packing density. The unanticipated low permeability of the α-hydroxy phytosphingosine-based model is probably associated with a stronger headgroup hydrogen bonding network. Our findings indicate that the increased level of sphingosine-based CERs at the expense of phytosphingosine-based CERs, as observed in the diseased skin, may contribute to the barrier function impairment.     

Organization of DNA damage,excision repair,and mutagenesis in chromatin: A genomic perspective

Genomic DNA is constantly assaulted by both endogenous and exogenous damaging agents. The resulting DNA damage, if left unrepaired, can interfere with DNA replication and be converted into mutations. Genomic DNA is packaged into a highly compact yet dynamic chromatin structure, in order to fit into the limited space available in the nucleus of eukaryotic cells. This hierarchical chromatin organization serves as both the target of DNA damaging agents and the context for DNA repair enzymes. Biochemical studies have suggested that both the formation and repair of DNA damage are significantly modulated by chromatin. Our understanding of the impact of chromatin on damage and repair has been significantly enhanced by recent studies. We focus on the nucleosome, the primary building block of chromatin, and discuss how the intrinsic structural properties of nucleosomes, and their associated epigenetic modifications, affect damage formation and DNA repair, as well as subsequent mutagenesis in cancer.     

Effects of benfluorex-vitamin C supplementation on cutaneous capillaries of diabetic rats

The ultrastructural changes on capillaries of the dermis in diabetic and benfluorex-vitamin C treated diabetic rats have been investigated. Three groups of 21 Wistar albino rats were used in the examination: control, diabetes, and benfluorex-vitamin C treated diabetic rats. Diabetes was induced by injection of streptozotocin. The streptozotocin-induced group was treated for 21 days with vitamin C and benfluorex, of which antidiabetic and antihyperlipidemic effects were experimentally proved. Samples taken from the skin of rats' legs were examined under transmission electron microscopy. Swollen endothelial cells, narrowed capillary lumens, a thickened basement membrane, and fusion of mitochondrial cristae in the capillaries of diabetic rat dermis were seen. In the benfluorex-vitamin C treated group, contrary to the diabetic group, neither signs of degeneration in endothelial cells nor a significant difference with the control group with regard to capillary structure were observed. Amelioration in capillaries appears to be due to benfluorex and vitamin C treatment in diabetes.     

Thermal sensitivity mapping - warmth and cold detection thresholds of the human torso

Skin as the largest organ of the human body accomplishes many important functions, including thermoregulation. In this context, investigating cold (CDT) and warmth detection thresholds (WDT) constitutes an important research branch, and investigating thermal thresholds has a significant impact on the clothing and fabric textile industry. In this regard, not only the extremities, but also torso regions are of high relevance. However, only few examinations have conducted detailed mapping studies of the human torso. Additionally, some of these studies show certain methodological limitations. Furthermore, the issue of whether cutaneous thermal sensitivity is gender-dependent is still controversial. Therefore, the present study investigated the cutaneous thermal sensitivity (CDT, WDT) of 42 male and female young and healthy subjects. Measurements were taken at 11 anatomical regions. We found that gender plays an important role when investigating thermal thresholds: Females tended to be more sensitive than males. We also found considerable differences between the tested regions, even within the anterior torso, for example. We identified locations which were constantly sensitive (lower back), while others were consistently insensitive (e.g. scapula). We also detected greater data variability for males compared to females, and for WDT compared to CDT. Furthermore, mainly for WDT, we found a proximal-to-distal increase of thermal torso and upper arm sensitivity. In line with previous investigations, our subjects were more sensitive to cold than to warmth. The findings of this study have important implications. First, our data may complement basic research, e.g. in terms of reference data of body regional maps. Second, our data provides important insights that could be leveraged in the textile industry, and also used to optimize current broadly applicable test methods and tools, like thermal manikins and thermophysiological models.     

Skin color comparisons among ethnic groups of college men

Reflectance readings of skin color were taken on the medial aspect of the left upper arm. The subjects were United States college men between ages 18 and 27 years attending the University of South Carolina. Using the DSL 99 Reflectance Spectrophotometer, readings were obtained under controlled conditions at five settings (601, 603, 605, 607, 609). Ethnic groups studied included young men of 1) Northwest European White ancestry, 2) West African Black ancestry, and 3) Afro-Black/Amerind ancestry. Means and variability statistics serve to describe the skin color distributions. Means were near 12 and 32 for filters 601 and 609 on men of West African Black ancestry, with corresponding means near 36 and 64 on men of Northwest European White ancestry. There was no overlapping of comparable frequency distributions from these two ethnic groups. Significance tests at P = .01 allowed acceptance of the hypothesis that skin color on the medial arm surface was darker for young men of Afro-Black ancestry than for those of 75% Afro-Black ancestry and 25% Amerind ancestry. Means from original data were compared with means from earlier studies on black and white males in Africa, America, and Europe.     

Influence of collagen denaturation on the chemorheological properties of skin,assessed by differential scanning calorimetry and hydrothermal isometric tension measurement

The curves obtained for skin samples of different ages and species by hydrothermal isometric tension (‘HIT’) measurement are compared to those obtained by differential scanning calorimetry (DSC) under the same thermal conditions (for a rise in temperature at a rate of 1.0°C/min). Collagen denaturation, observed by DSC, directly affects the kinetics of the tension variations in the first part of the ‘HIT’ curves, including the early peak due to the presence and destruction of the heat-labile cross-links in the collagen network. The presence of cross-links is in term shown to delay collagen denaturation to an extent which depends in part on their heat-stability. The final part of the ‘HIT’ curves reflecting the effects of heat in the stable polymeric collagen network is no longer affected by collagen denaturation. Thus, both ‘HIT’ and DSC are useful methods to evaluate collagen reticulation in connective tissues.