Environmental effects on cellular photosensitization: correlation of phototoxicity mechanism with transient absorption spectroscopy measurements

The presence of actin in eukaryotic nuclei and chromosomes, and especially in higher plant nuclei and chromosomes, has not been well established. We detected actin in meristematic cells of Allium cepa with indirect immunofluorescence technique and observed bright fluorescence in the intact nuclei and chromosomes, indicating that actin is present in the nuclei and chromosomes of the higher plant. We labeled sections of the meristematic cells of A. cepa with immunogold technique, gold particles were found over the whole nuclei and a number of gold particles were concentrated in condensed chromatin and nucleoli, confirming the results of the immunofluoresence observations. We treated the nuclei and chromosomes of A. cepa with DNase I and 2M NaCl and obtained DNA- and histone-depleted nuclei and chromosomes. Indirect immunofluorescence tests showed that the DNA- and histone-depleted nuclei and chromosomes reacted positively with the anti-actin antibodies. These results demonstrate that actin exists not only in intact nuclei and chromosomes, but also in DNA- and histone-depleted nuclei and chromosomes of the plant. In addition, our immuno-fluorescence tests indicate that tropomyosin is present in the nuclei and chromosomes of A. cepa.     

The language of outcomes

Outcomes are a topic of great interest. Their potential is considerable as a mechanism to evaluate quality, improve effectiveness, and link practice to professional accountability. Greater clarity and precision in the use of outcomes terminology will allow this potential to be realized. This article identifies the current confusion in outcomes terminology, begins an outcomes lexicon, and issues a call to action for further clarification in the language of outcomes.     

Gabapentin: pharmacokinetics, efficacy, and safety

Gabapentin is a new antiepileptic drug (AED) with an attractive pharmacokinetic profile. It is absorbed by an active and saturable transport system, and has a high volume of distribution. Gabapentin is not bound to plasma proteins, does not induce hepatic enzymes and is not metabolized. At steady state, it has a half-life of 6-8 h, and is eliminated unchanged by renal route with a plasma clearance proportional to the creatinine clearance. It is devoid of significant drug-drug interactions when administered with the established AEDs or with oral contraceptives. Gabapentin used as an add-on AED significantly reduced the frequency of partial seizures and secondarily generalized tonic-clonic seizures in three large double-blind, placebo-controlled, parallel-group clinical trails. It is well tolerated, with transient somnolence and dizziness being the most frequent adverse effects. Although the mechanism of action of gabapentin is not fully established, there is strong evidence to suggest a novel mechanism of action. Gabapentin is a unique and promising drug that could improve the quality of life of patients with epilepsy and is a welcome addition to the armamentarium of currently available AEDs for the treatment of patients with seizures of partial onset.     

Superoxide: a two-edged sword

Superoxide (O2-) is the compound obtained when oxygen is reduced by one electron. For a molecule with an unpaired electron, O2- is surprisingly inert, its chief reaction being a dismutation in which it reacts with itself to form H2O2 and oxygen. The involvement of O2- in biological systems was first revealed by the discovery in 1969 of superoxide dismutase, an enzyme that catalyzes the dismutation of O2-. Since then it has been found that biological systems produce a bewildering variety of reactive oxidants, all but a few arising ultimately from O2-. These oxidants include O2- itself, H2O2 and alkyl peroxides, hydroxyl radical and other reactive oxidizing radicals, oxidized halogens and halamines, singlet oxygen, and peroxynitrite. These various oxidants are able to damage molecules in their environment, and are therefore very dangerous. They are thought to participate in the pathogenesis of a number of common diseases, including among others malignancy, by their ability to mutate the genome, and atherosclerosis, by their capacity for oxidizing lipoproteins. Their properties are put to good use, however, in host defense, where they serve as microbicidal and parasiticidal agents, and in biological signalling, where their liberation in small quantities results in redox-mediated changes in the functions of enzymes and other proteins.