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951.

Background  

There is an increasing interest to better understand endosymbiont capabilities in insects both from an ecological point of view and for pest control. Blochmannia floridanus provides important nutrients for its host, the ant Camponotus, while the bacterium in return is provided with a niche to proliferate. Blochmannia floridanus proteins and metabolites are difficult to study due to its endosymbiontic life style; however, its complete genome sequence became recently available.  相似文献   
952.
953.
Formamide NH2CHO chemistry provides a unitary frame into which several pieces of the origin-of-life puzzle may be adjusted. Synthetic processes were uncovered which, starting from formamide and prebiotically easily available common catalysts, yield all the necessary nucleic bases precursors, including acyclonucleosides. Formamide allows phosphorylations and trans-phosphorylations, favours the micellar aggregation of surfactants and, most importantly, determines conditions in which the formation of nucleic polymers is thermodynamically favoured. In the detected conditions, the phosphoester bonds are more stable in the polymeric than in the monomeric form, thus allowing formation and survival of informational nucleic polymers. Presented at: National Workshop on Astrobiology: Search for Life in the Solar System, Capri, Italy, 26 to 28 October, 2005.  相似文献   
954.
Since a specific inhibition of cerebral spermidine (Spd) synthase activity by alicyclic amines was preliminarily observed in vitro, we examined the in vivo inhibitory effectiveness of dicyclohexylamine (DCHA) on Spd biosynthesis in 21-day-old rat brain. For this purpose a previously reported HPLC procedure (Porta et al., 1981a) was modified to analyze the cerebral levels of DCHA at the time of polyamine determinations. The intraperitoneally injected DCHA was shown to cross the blood-brain barrier easily, reaching high levels in the cerebral tissue (approximately 750 nmol/g brain) within 1 h of its administration. The effect of the drug on the polyamine metabolism resulted in a significant depletion of Spd biosynthesis from the sixth hour after the treatment and in an earlier and prolonged increase of the putrescine (Pt) steady-state levels. Conversely, the spermine (Spm) endogenous pools remained unchanged throughout the 24-h post-DCHA period. Moreover, following the intracerebral administration of [1,4-14C]Pt, significantly lower specific radioactivity (s.r.a.) values for labeled Pt and Spd were recorded in the brains of DCHA-treated animals. Conversely, after intracerebral [14C]Spd injection, the s.r.a. of newly formed [14C]Spm remained unchanged, confirming the specificity of the DCHA effect on the Spd biosynthesis.  相似文献   
955.
The treatment of neurodegenerative diseases presents a growing need for innovation in relation to recent evidence in the field of reconstructive therapy using stem cells. Understanding the molecular mechanisms underlying neurodegenerative disorders, and the advent of methods able to induce neuronal stem cell differentiation allowed to develop innovative therapeutic approaches offering the prospect of healthy and perfectly functional cell transplants, able to replace the sick ones. Hence the importance of deepening the state of the art regarding the clinical applications of advanced cell therapy products for the regeneration of nerve tissue. Besides representing a promising area of tissue transplant surgery and a great achievement in the field of neurodegenerative disease, stem cell research presents certain critical issues that need to be carefully examined from the ethical perspective. In fact, a subject so complex and not entirely explored requires a detailed scientific and ethical evaluation aimed at avoiding improper and ineffective use, rather than incorrect indications, technical inadequacies, and incongruous expectations. In fact, the clinical usefulness of stem cells will only be certain if able to provide the patient with safe, long-term and substantially more effective strategies than any other treatment available.The present paper provides an ethical assessment of tissue regeneration through mesenchymal stem cells in neurodegenerative diseases with the aim to rule out the fundamental issues related to research and clinical translation.  相似文献   
956.
The behavioral activity of the thyrotropin-releasing hormone (TRH) analogue, L-6-ketopiperidine-2-carbonyl-leucyl-L-prolinamide (RGH 2202), has been studied in the rat. The number of errors in a radial maze test was reduced after acute intraperitoneal (IP) injection of RGH 2202 at the dose of 5 or 10 mg/kg. Grooming activity was increased with a lower dose, 1 mg/kg. Hypoxia-induced amnesia, as assessed with active and passive avoidance behavior tests, was reversed in rats treated with 5 or 10 mg/kg of the drug. The loss of learning and memory capacity shown by aged rats in the same behavioral tests was also reduced after injection of RGH 2202. In a test for sexual activity of male rats, the higher dose of the drug induced a facilitation of mounting and ejaculations, while smaller doses were ineffective. The rotorod test revealed a decreased number of falls in animals treated with 5 or 10 mg/kg of RGH 2202. In all behavioral tests, the same doses of natural thyrotropin-releasing hormone (TRH) were less effective, indicating that this analogue may be qualified as a potentially active drug in human pathologies.  相似文献   
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