Pneumocystis carinii polyamine catabolism.

DL-alpha-Difluoromethylornithine (DFMO) causes polyamines of the AIDS-associated opportunistic pathogen Pneumocystis carinii to diminish 15 times more rapidly than mammalian host cells. The proposed mechanism was that, unlike mammalian cells, P. carinii is unable to regulate polyamine catabolism when synthesis is blocked. To test this, the responses of the polyamine catabolic enzymes spermidine/spermine acetyltransferase (SSAT) and polyamine oxidase (PAO) were determined using a new high-performance liquid chromatography assay to measure the products of these enzymes. The specific activities in untreated Pneumocystis carinii were 1.78 +/- 0.5 pmol min(-1) mg protein(-1) for SSAT, similar to mammalian cells, and 6.42 +/- 0.8 pmol min(-1) mg protein(-1) for PAO, 19% of that of mammalian cells. DFMO treatment for 12 h caused reductions of only 11 and 4% in SSAT and PAO, respectively, despite polyamine reductions of 94, 96, and 90% for putrescine, spermidine, and spermine, respectively. The P. carinii SSAT K(m) value of 25 microM spermidine is 20% of that of mammalian cells, and the PAO K(m) value of 14 nM N(1)-acetylspermidine is 0.01% of that of mammalian cells. Acetylated polyamines continue to be lost from P. carinii even when exposed to DFMO. Collectively, these results support the hypothesis that P. carinii is unable to regulate polyamine catabolism.     

Acetylation of spermidine in polyamine catabolism

Treatment with thioacetamide (150 mg/kg)_ was used to enhance polyamine metabolism in rat liver. The increased uptake and catabolism of [¹⁴C]spermine and the changes of putrescine, spermidine and spermine concentrations indicated enhanced polyamine turnover rates. The increase of hepatic putrescine concentration was accompanied by an increase of monoacetylputrescine and N¹-monoacetylspermidine concentration. In control animals, the latter compound was below detection levels. Thioacetamide treatment also enhanced putrescine excretion, which again was concomitant with an increased excretion of N¹-acetylspermidine.The close time-dependent correlation between induced putrescine formation and enhanced formation of N¹-acetylsperimidine at a time when liver spermidine and spermine concentrations are not changed, favors the notion that acetylation is an essential step in polyamine degradation and elimination. The increase of polyamine oxidase and decrease of acetylpolyamine deacetylase activities in the liver of thioacetamide-treated rats is in line with an increased polyamine turnover, but these enzymes. although essential, are not rate-limiting in the catabolic reactions.     

The state of the art

Graphical representation of molecular and cellular features is a key form of communication in structural biology in which abstract symbols of an economical and visually appropriate kind, pseudo-color coding, and dynamic animations all play their parts. Accordingly, it should not be surprising that many structural biologists--like traditional biologists before them--are talented artists who also express themselves on "non-scientific" topics. This article illustrates the approaches of and pictures by several practicing scientist-artists-mainly, in this sampling, electron microscopists.     

Genetic manipulation of polyamine catabolism in rodents

Activation of polyamine catabolism through the overexpression of spermidine/spermine N1-acetyltransferase (SSAT) in transgenic rodents does not only lead to distorted tissue polyamine homeostasis, manifested as striking accumulation of putrescine, appearance N1-acetylspermidine and reduction of tissue spermidine and/or spermine pools, but likewise creates striking phenotypic changes. The latter include loss of hair, lipoatrophy and female infertility. Forced expression of SSAT modulates skin, prostate and intestinal carcinogenesis, induces acute pancreatitis and blocks early liver regeneration. Although many of these features are directly attributable to altered tissue polyamine pools, some of them are more likely related to the greatly accelerated flux of the polyamines caused by activated catabolism and compensatorily enhanced biosynthesis.     

The activation of hepatic and muscle polyamine catabolism improves glucose homeostasis

The mitochondrial biogenesis and energy expenditure regulator, PGC-1α, has been previously reported to be induced in the white adipose tissue (WAT) and liver of mice overexpressing spermidine/spermine N (1)-acetyltransferase (SSAT). The activation of PGC-1α in these mouse lines leads to increased number of mitochondria, improved glucose homeostasis, reduced WAT mass and elevated basal metabolic rate. The constant activation of polyamine catabolism produces a futile cycle that greatly reduces the ATP pools and induces 5'-AMP-activated protein kinase (AMPK), which in turn activates PGC-1α in WAT. In this study, we have investigated the effects of activated polyamine catabolism on the glucose and energy metabolisms when targeted to specific tissues. For that we used a mouse line overexpressing SSAT under the endogenous SSAT promoter, an inducible SSAT overexpressing mouse model using the metallothionein I promoter (MT-SSAT), and a mouse model with WAT-specific SSAT overexpression (aP2-SSAT). The results demonstrated that WAT-specific SSAT overexpression was sufficient to increase the number of mitochondria, reduce WAT mass and protect the mice from high-fat diet-induced obesity. However, the improvement in the glucose homeostasis is achieved only when polyamine catabolism is enhanced at the same time in the liver and skeletal muscle. Our results suggest that the tissue-specific targeting of activated polyamine catabolism may reveal new possibilities for the development of drugs boosting mitochondrial metabolism and eventually for treatment of obesity and type 2 diabetes.     

Pidotimod: the state of art

Despite the use of antibiotics and vaccines, the frequency of respiratory tract infections is still high and these infections interest a wide range of patients, from children to aged people, including in particular these extreme categories because of the deficiency of their immune system, due to immaturity in the former case and to “immunosenescence” in the latter. For that reason immunostimulant drugs are getting more important to prevent and to attenuate infections. Pidotimod (3-L-pyroglutamyl-L-thiazolidine-4carboxylic acid) is a synthetic dipeptide with immunomodulatory properties. We reviewed studies conducted on different categories of patients, with particular attention on children and senile patients suffering from recurrent respiratory tract infections, associated, or not, with asthma or COPD. The outcomes considered are both clinical and laboratory parameters. The common end-point of these studies is that Pidotimod has an immunomodulatory activity which is able both to improve the clinical conditions of patients and to enhance and stimulate their immunity cells (lymphocytes but not only) functions acting on adaptive and innate immunity. Pidotimod is also able to increase the concentration of salivary IgA directed against bacteria; furthermore, it can modulate airway epithelial cells functions up-regulating the expression of toll-like receptors and acting on adhesion molecules. According to studies conducted on patients with atopic asthma, it seems that Pidotimod could affect T-lymphocytes balance with a possible addictional anti-allergic activity. Furthermore, it has been demonstrated an improvement of FEV1 and PEF in asthmatic patients treated with Pidotimod. Main clinical outcomes are the reduction of the number of infectious episodes, lesser severity of signs and symptoms and, consequently, a reduction in use of antibiotics and symptomatic drugs, less working and school days lost, less mortality and morbidity. The studies considered give positive results, confirming Pidotimod’s efficacy. Furthermore, many studies show a good safety profile of the drug, without recording serious adverse events and mutagenic potential, and a very low incidence of side effects. Pidotimod is also a more safe solution in patients subjected to vaccination, if compared to lyophilized polibacterial, which can’t be administered for thirty days before vaccination.     

The Schistosoma gene discovery program: state of the art

Schistosoma are dioecious digenetic trematodes carrying a large (270 Mb) genome. Gaining knowledge about the genome of these parasites is of importance for the understanding of their biology, mechanisms of drug resistance and antigenic variation that determine escape from the host's immune system. This review will provide an update on the Schistosoma Gene Discovery Program, which is part of the Schistosoma Genome Project created in 1992. One of the main objectives of this program is the discovery and characterisation of new genes of Schistosoma mansoni and Schistosoma japonicum in an attempt to search for new targets for drugs and vaccine development. The success of the Schistosoma Gene Discovery Program is demonstrated by the number of catalogued genes, that now reaches 15 to 20% of the full gene complement of its genome.     

Enzyme stabilization: state of the art

Enzyme stabilization is one of the most important fields in basic and applied enzymology. In basic enzymology, it is of particular relevance to understand enzyme stabilization principles first elucidating how and why the enzymes lose their biological activity and then deriving structure-stability relationships existing in enzymatic molecules. In applied enzymology, the most significant goal is to achieve useful compounds by biocatalysis. Enzymes are good catalysts in terms of high catalytic and specific activity with ability to function under mild conditions. However, they are not always ideal catalysts for practical applications because they are generally unstable and they inactivate rapidly through several mechanisms. In order to enhance enzyme stability, many strategies have been pursued in recent years. The present article is an attempt to provide detailed information about these strategies.     

Artificial insemination: the state of the art

The history of research into artificial insemination (AI) is over two centuries old and its commercial application now spans 75 years. It is appropriate to reflect on the contribution of this powerful method of gene dispersal. AI remains as one of the most important assisted reproductive technologies. The three cornerstones for its application are: it is simple, economical and successful. The importance of AI will be challenged in the next few decades. The remarkable progress made in other assisted reproductive technologies does have the potential to rapidly generate offspring. The challenge for any of these reproductive technologies to attain widespread use is to match AI in being simple, economical and successful. This review aims at capturing the salient advances in AI, the comparisons with natural mating and other reproductive technologies, and, whether the future of AI will be challenged. It predicts what the new horizon looks like and the role that AI will play in the overall reproductive technologies landscape.     

The WWWH of remote homolog detection: the state of the art

The detection of remote homolog pairs of proteins using computational methods is a pivotal problem in structural bioinformatics, aiming to compute protein folds on the basis of information in the database of known structures. In the last 25 years, several methods have been developed to tackle this problem, based on different approaches including sequence-sequence alignments and/or structure comparison. In this article, we will briefly discuss When, Why, Where and How (WWWH) to perform remote homology search, reviewing some of the most widely adopted computational approaches. The specific aim is highlighting the basic criteria implemented by different research groups and commenting on the status of the art as well as on still-open questions.     

Phytosterol oxidation products: state of the art

This editorial gives an overview of the current status of the research on the phytosterol oxidation products. The most relevant studies on their in vivo origin, biological effects and analysis in foodstuffs and biological samples are critically reviewed, in order to give concluding remarks on and to establish the future research needs in this field.