Vie di ossidazione della frazione extramitocondriale dei coenzimi piridinici: I. - Sull'Efficienza In Vivo del sistema ascorbato/deidroascorbato

Abstract

OXIDATION PATHWAYS OF EXTRAMITOCHONDRIAL PIRIDINE COENZYMES. I. - ON THE « IN VIVO » EFFICIENCY OF THE ASCORBATE-DEYHDROASCORBATE SYSTEM. — An evaluation of the efficiency in vivo of the AA-DHA couple as an electron carrier system has been attempted, by measuring after short time of anaerobiosis the rate of the increase of AA and of the dicrease of DHA in etiolated pea internode segments and in potato tuber disks. The changes of reduced glutathione (GSH) contents as induced by anaerobiosis or by the addition of DHA to the incubation medium were also followed.

In the pea segments anaerobiosis induced a significant increase of AA and a corresponding decrease of DHA. These changes were almost completed after 10 minutes from starting anaerobiosis. The value (extrapolated to 0 time) of the initial rate of DHA desappearance under anaerobiosis was taken as representing the rate of DHA reduction to AA « in vivo », under aerobic conditions. As this rate — in a steady state situation — corresponds to that of the inverse process of oxidation of AA to DHA, this value should give and indication on the « in vivo » efficiency of the AA-DHA system as an electron carrier in respiration. As some AA was probably reoxidized to DHA in the very short period required to kill the tissue, the value of the AA DHA turnover thus calculated is probably somewhat lower than the real one.

According to the present work, the oxidative turnover of the AA-DHA system would results of 0,7 micromoles/g. fr. weght/h. for the pea internode tissues and of 0,9 micromoles/g. fr. weght^?h for the potato tuber (aged disks). These values would account for 5% of total oxygen uptake, in the former, and for 3% in the latter material.

The very high AA/DHA ratio usually prevailing in living cells suggests that the contents in DHA (and thus the activity of the AA oxidizing systems) is a limiting factor for the efficiency of the AA-DHA system as an electron carrier. This view is supported also by experiments in which DHA (at pH 5) was fed to pea internode segments and to potato tuber disks : as the presence of DHA into the medium induced — under anaerobiotic conditions — a rapid increase of the level of AA in both types of materials. In aerobiosis uptake and reduction of DHA to AA was evident in the potato tuber tissue, while it appeared very scarce in the pea internodes. As an interpretation of this behaviour it is suggested that, in aerobiosis, the very active and probably surface localized ascorbic acid oxidase of the pea tissue re-oxidises the AA formed from reduction of the DHA fed; an accumulation of DHA into the cells would follow, and this excess of DHA would inhibit the enzyme GSH-DHA reductase. This enzyme, in fact, appears, from « in vitro » experiments, to be strongly inhibited by DHA when the DHA/GSH ratio becomes higher than 1. On the other hand, the same hypothesis is also supported by the finding that the addition of DHA to the medium induces a significant drop in the GSH level (probably due to its oxidation to GSSG) only under those conditions in which DHA is absorbed and reduced to AA; that is, in the pea internodes, under anaerobiosis, and in the potato disks, under both anaerobiosis and aerobiosis. These results are also taken as confirming the indication from the enzymatic data that GSH is acting, in vivo as a reducing agent for DHA. The results of this investigation are thus interpred as showing that a comparatively small, but by no means negligeable fraction of respiration is mediated, in higher plant tissues such as those of the pea stem and the potato tuber, by and electron transfer system including glutathione and the ascorbate-dehydroascorbate couple. The efficiency of this system in the materials investigated appears to account for 3–5% of the total 0₂ uptake (minimum value). As enzyme systems transferring electrons from TPNH to ox. glutathione are widely distributed and generally very active in higher plant tissues, it is suggested that the sequence TPNH-GSH-AA/DHA - O₂ is probably of considerable importance in mediating the reoxidation of extramitochondrial trophosphoridine nucleotide and thus in permitting the operation of the TPN requiring pentose phosphate pathway of respiration.     

Peptide inhibitors against herpes simplex virus infections

Herpes simplex virus (HSV) is a significant human pathogen causing mucocutaneous lesions primarily in the oral or genital mucosa. Although acyclovir (ACV) and related nucleoside analogs provide successful treatment, HSV remains highly prevalent worldwide and is a major cofactor for the spread of human immunodeficiency virus. Encephalitis, meningitis, and blinding keratitis are among the most severe diseases caused by HSV. ACV resistance poses an important problem for immunocompromised patients and highlights the need for new safe and effective agents; therefore, the development of novel strategies to eradicate HSV is a global public health priority. Despite the continued global epidemic of HSV and extensive research, there have been few major breakthroughs in the treatment or prevention of the virus since the introduction of ACV in the 1980s. A therapeutic strategy at the moment not fully addressed is the use of small peptide molecules. These can be either modeled on viral proteins or derived from antimicrobial peptides. Any peptide that interrupts protein–protein or viral protein–host cell membrane interactions is potentially a novel antiviral drug and may be a useful tool for elucidating the mechanisms of viral entry. This review summarizes current knowledge and strategies in the development of synthetic and natural peptides to inhibit HSV infectivity. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Ubiquinol and a Coenzyme Q Reducing System Protect Platelet Mitochondrial Function of Transfusional Buffy Coats from Oxidative Stress

The conditions under which Coenzyme Q (CoQ) may protect platelet mitochondrial function of transfusional buffy coats from aging and from induced oxidative stress were investigated. The Pasteur effect, i.e. the enhancement of lactate production after inhibition of mitochondrial respiratory chain, was exploited as a marker of mitochondrial function as it allows to calculate the ratio of mitochondrial ATP to glycolytic ATP. Reduced CoQ 10 improves platelet mitochondrial function of transfusional buffy coats and protects the cells from induced oxidative stress. Oxidized CoQ is usually less effective, despite the presence, shown for the first time in this study, of quinone reductase activities in the platelet plasma membranes. The addition of a CoQ reducing system to platelets is effective in enhancing the protection of platelet mitochondrial function from the oxidative stress. The results support on one hand a possibility of protection of mitochondrial function in aging by exogenous CoQ intake, on the other a possible application in protection of transfusional buffy coats from storage conditions and oxidative deterioration.     

Secondo Contributo Alla Conoscenza Dello Sviluppo Embriologico del Genere Centaurea L. (Asteraceae). Centaurea Horrida Bad

Summary

The Author has studied the embryological development of Centaurea horrida Bad., pure pliocenic endemisms of Sardinia and has established that:

1°) the cromosomic number of the species is: 2n = 18.

2°) the genesis of microspores is of simultaneous type;

3°) The archesporium is constituted of one cell only seldom accompanied by a basal cell;

4°) the development of the female gamethophyte is of normal type;

5°) even showing cases of degenerated antipodal cells, the species has a marked tendency to the polyantipody, sometimes also characterized by a strong hypertrophy of its cells;

6°) in the species the contemporary germination of some megaspores in the same ovule is enough frequent;

7°) there are also some cases of coesistence of some gamethophytes in their different stages of development;

8°) the phenomenon of «multiple oospheres» and of «multiple synergidae» may happen;

9°) in some ovules, near the egg-apparatus, cells of two or four nuclei may be found.

For these last ascertainments (8° and 9°) the Author makes the hypothesis that it may be probably an anomalous prolification of micropylar nuclei, or asynchronous development, for delayed germination of some micropylar megaspores producing primary stages of gamethophyte.

Moreover the Author has the opportunity to bring into evidence:

10°) a case of ovular teratology represented by the extraovular development of an adult gamethophyte very similar to those previously found by the Author himself in Petasites fragrans;

11°) frequent cases of regretion of female sexuality, founding that about the 10% of the flowers examined were functionally male. The Author has fronted the possibility of the existence, in Asteraceae, also of the type of inflorescence where «flowers are all tubulated: the marginal ones neuter, the others or hermaphrodite or hermaphrodite and male».     

Towards a gene expression biomarker set for human biological age

We have previously described a statistical model capable of distinguishing young (age <65 years) from old (age ≥75 years) individuals. Here we studied the performance of a modified model in three populations and determined whether individuals predicted to be biologically younger than their chronological age had biochemical and functional measures consistent with a younger biological age. Those with ‘younger’ gene expression patterns demonstrated higher muscle strength and serum albumin, and lower interleukin‐6 and blood urea concentrations relative to ‘biologically older’ individuals (odds ratios 2.09, 1.64, 0.74, 0.74; P = 2.4 × 10^?2, 3.5 × 10^?4, 1.8 × 10^?2, 1.5 × 10^?2, respectively). We conclude that our expression signature of age is robust across three populations and may have utility for estimation of biological age.