Metabolism of serotonin to N-acetylserotonin, melatonin, and 5-methoxytryptamine in hamster skin culture

Biotransformation of [3H]serotonin by cultured hamster skin to 3H-metabolites corresponding to N-acetylserotonin (NAS), melatonin, and 5-methoxytryptamine (5-MT) was demonstrated. This process was time-dependent, with the highest production of radioactive NAS and melatonin metabolites after 3 and 5 h of incubation followed by a decrease in the rate of metabolite release into the media. Conversely, the formation of radioactive metabolite corresponding to 5-MT increased gradually during skin culture, reaching the highest level after 24 h of incubation. The production of 3H-metabolites, corresponding to NAS, melatonin, and 5-MT, was stimulated by forskolin with a maximum effect of forskolin at 10 microM concentration. The gas chromatographic/mass spectroscopy analysis of the fraction eluting at the retention time of NAS standard material showed that it contained NAS, further confirming production and release of NAS into the media by hamster skin. Therefore, we conclude that mammalian skin can acetylate serotonin to NAS and postulate that the NAS is further metabolized by the skin to form melatonin which is subsequently transformed to 5-MT.     

Adverse health effects of PM10 particles: involvement of iron in generation of hydroxyl radical

OBJECTIVES: Environmental particles < 10 microns average aerodynamic diameter (PM10) are associated with mortality, exacerbation of airways diseases, and decrement in lung function. It is hypothesised that PM10 particles, along with other pathogenic particles, generate free radicals at their surface in reactions involving iron, and that this is a factor in the pathogenicity of PM10 particles. Identification of free radical activity in PM10 and examination of the content and role of iron in this process was undertaken. METHODS: Free radical activity was detected with a supercoiled plasmid, phi X174 RF1 DNA, and measured as scission of the supercoiled DNA (mediated by free radicals) by scanning laser densitometry. The role of the hydroxyl radical was confirmed by the use of the specific scavenger mannitol, and the role of iron investigated with the iron chelator desferrioxamine-B (DSF-B). Iron released from PM10 particles at pH 7.2 and pH 4.6 (to mimic conditions on the lung surface and in macrophage phagolysosomes, respectively) was assessed spectrophotometrically with the Fe++ chelator ferrozine and the Fe+ + + chelator DSF-B. RESULTS: PM10 particles showed significant free radical activity by their ability to degrade supercoiled DNA. A substantial part of this activity was due to the generation of hydroxyl radicals, as shown by partial protection with mannitol. Similarly, DSF-B also conferred protection against the damage caused to plasmid DNA indicating the role of iron in generation of hydroxyl radicals. Negligible Fe++ was released at either pH 7.2 or pH 4.6 by contrast with Fe+ + +, which was released in substantial quantities at both pHs, although twice as much was released at pH 4.6. CONCLUSIONS: PM10 particles generate the hydroxyl radical, a highly deleterious free radical, in aqueous solution. This occurs by an iron dependent process and hydroxyl radicals could play a part in the pathogenicity of PM10 particles. Iron release was greatest at the pH of the lysosome (pH 4.6) indicating that iron may be mobilised inside macrophages after phagocytosis, leading to oxidative stress in the macrophages.     

Mechanical properties of uranium

The paper describes the results of mechanical tests on uranium at room temperature and at elevated temperatures. Data are given on the hardness of uranium in the temperature range 20–600 C, flow pressure on extrusion in the ^– and ^– phase ranges, tensile properties and impact strength at temperatures of the ^–, ^–, and ^– phases. The anisotropic behavior of the individual grains of coarsegrained uranium during mechanical tests has been elucidated. It is shown that the existence of allotropic transformations and the difference in the crystal structure of the modifications of uranium influence its mechanical properties to a marked degree. It is also shown that the mechanical properties depend upon the carbon content of the uranium.     

Induction of melanogenesis during the various melanoma growth phases and the role of tyrosinase, lysosome-associated membrane proteins, and p90 calnexin in the melanogenesis cascade

Melanin biosynthesis (melanogenesis) is a metabolic pathway exclusively expressed by melanocytes and melanoma cells, and is often altered and/or markedly elevated in the latter cells. The changes in melanogenesis may be responsible for some of the clinical and histopathological features unique to melanoma. Melanogenesis may also contribute to the malignant transformation of melanoma precursors (i.e., atypical moles [or dysplastic nevi]) to melanoma as seen in patients with the familial atypical multiple-mole-melanoma (FAMMM) syndrome. However, it does not appear to affect the multi-step growth phases of melanoma cells from radial to vertical and lastly metastatic growth phases. Within the melanosomal compartment, eu- and pheomelanin pigments are synthesized. Both tyrosinase and lysosome-associated membrane protein (LAMP) gene products play important roles in this process. A coordinated interaction between these two gene family products is required for melanogenesis to occur properly. p90 calnexin is a new melanosome-associated molecule that is presumed to function as a melanogenesis chaperone by controlling the assembly and folding of glycoprotein intermediates of tyrosinase and LAMP gene families.