Concetta Corsaro

In vitro scavenger activity of some flavonoids and melanins against O2−dot

The scavenger activity against O2-. of some flavonoids and melanins (synthetic melanins and melanins isolated from animal tissues, vegetable seeds, and mushroom spores) has been studied by ESR spectrometry. All these substances, except flavon and flavanone, diminish the signal of O2-. generated in vitro by a system containing H2O2 and acetone in an alkaline medium. It is shown that the presence of hydroxyl groups in the B ring of flavonoids is essential for their scavenger activity. Moreover, the presence of a hydroxyl at C-3 enhances the scavenger ability of flavonoids. Generally, aglycons are more active than their glycosides. It seems plausible that the antioxidant property of these substances comes from their scavenger activity against O2-(.). It is also pointed out that the scavenger activity shown by melanins, is strictly correlated with their nature of stable free radical.

Eumelanins as free radicals trap and superoxide dismutase activities in Amphibia

Abstract 1. 1. Electron paramagnetic resonance (EPR) studies concerning the interaction between purified melanins and superoxide anion are reported; in addition the superoxide dismutase activities in the liver and brain of frog and rat were measured. Liver melanins considerably inhibit the EPR signal ascribed to superoxide anion. 2. 2. The rat and frog brain show similar values of Cu, Zn SOD and Mn SOD. On the contrary, in frog liver, the specific activity of Cu, Zn SOD was significantly lower when compared to rat; no Mn SOD activity has been found in the frog liver.

Characterisation of Kupffer cells in some Amphibia

A study on the Kupffer cells (KCs) of Amphibia was undertaken in order to compare these cells with those of endothermic animals. Liver tissue and isolated and cultured KCs were studied by light microscopy and by transmission and scanning electron microscopy. We have shown that amphibian KCs can be divided into 2 principal types: ‘small’ and ‘large’. Both cell types possess the distinctive KC morphology. They show nonspecific esterase activity, weak endogenous peroxidase activity in the nuclear envelope and in the rough endoplasmic reticulum, and the ability to engulf naturally present cell debris or experimentally administered zymosan or latex particles. The principal difference between the small and the large cells consists in the substantial quantity of inclusion bodies that exist only in the latter. We conclude that amphibian KCs, apart from their ability to build melanosomes and synthesise melanins, are very similar to mammalian KCs.

The extracutaneous pigmentary system: evidence for the melanosynthesis in Amphibia and Reptilia liver

Abstract 1. 1. In vitro incorporations of [ 14 C] l -tyrosine and [ 14 C] l -DOPA into purified melanin, extracted from frog and turtle liver after incubation of surviving tissue and purified melanosomes were measured. 2. 2. The results show an incorporation of labelled precursors in melanin both in incubating tissue slices and incubating isolated melanosomes and that the radioactivity detected in purified melanin was not due to an adsorption or binding phenomenon of labelled tyrosine. 3. 3. We conclude that melanins occurring in the pigment cells of Amphibia and Reptilia liver originate from the melanosynthetic activity of Kupffer cells and that these pigment cells are to be considered as belonging to the extracutaneous pigmentary system.

Genomic localization of the human gene encoding Dr1, a negative modulator of transcription of class II and class III genes

Dr1 is a nuclear protein of 19 kDa that exists in the nucleoplasm as a homotetramer. By binding to TBP (the DNA-binding subunit of TFIID, and also a subunit of SL1 and TFIIIB), the protein blocks class II and class III preinitiation complex assembly, thus repressing the activity of the corresponding promoters. Since transcription of class I genes is unaffected by Dr1. it has been proposed that the protein may coordinate the expression of class I, class II and class III genes. By somatic cell genetics and fluorescence in situ hybridization, we have localized the gene (DR1), present in the genome of higher eukaryotes as a single copy, to human chromosome region 1p21-->p13. The nucleotide sequence conservation of the coding segment of the gene, as determined by Noahs ark blot analysis, and its ubiquitous transcription suggest that Dr1 has an important biological role, which could be related to the negative control of cell proliferation.

ATPASE ACTIVITY OF MELANOSOMES IN LIVER PIGMENT CELLS OF RANA ESCULENTA L.

Luminometric methods show that melanosomes in liver pigment cells of Rana esculenta L. have endogenous ATP and ATPase activity. The Km value of ATPase is 0.42 x 10(-8) mol/l at pH 7.0. Inhibition of ATPase by antimycin and by ouabain is not effective. In the presence of an excess of ADP and Pi, ATP synthesis was observed.