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PubMedDate not supplied

[Transport dependence of leaf evolution in dicots].

The diversity of tissue and cell organization in the leaves of dicots is explained as the mutual effect of light and water fluxes distribution. Equally with certain data about the role of light distribution, the same influence of water flux distribution on the leaf structure is recognized. Dorsiventral leaves of woody plants have an adequate to structure dorsiventral ring of water circulation. Rising flux from the xylem allocates via leaf apoplast with intermediate accumulation in upper epiderma. Descending flux starts and returns to bundle moving from cell to cell along the symplast (ER) of spongy parenchyma, bundle sheath and terminal complexes of the phloem. Isolateral leaves of herbs have a concentric pathway of solute circulation corresponding to the structure. Xylem flux allocates via symplast with water and nitrogen accumulation in paraveinal parenchyma. Water returns to phloem by transit via the apoplast in parallels with phloem exudate formation. Structural features correlated with the model of water circulation in the leaf are described. Numerous lines of leaf evolution well-known for dicots collect to two main topics which are typical for woody and herbaceous forms of dicots. The mechanisms of cell and tissue differentiation under the control of transport fluxes are discussed with special attention to ontogenetic and phylogenetic trends.

Biological Evolution↗
PubMed2004

Micro parallel liquid chromatography: enabling technology for discovery analytical chemistry.

Since the introduction of combinatorial chemistry, compound libraries have undergone a significant increase in size and diversity. The ensuing expansion and diversification of compound libraries have resulted in increased demand for analytical throughput. Following the evolution of new technologies for generating lead compounds and targets and the desire to increase research and development productivity, analytical chemistry is now gaining attention as a bottleneck that would benefit from advances in instrumentation for increased analytical throughput. The commercial introduction of the Veloce trade mark micro parallel liquid chromatography system from Nanostream offers discovery analytical chemists the capability to analyze 24 samples in parallel with as little as 0.5 microl of sample. The system offers a scalable analytical approach to address bottlenecks in historically underserved areas, such as compound library purity screening, as well as higher value-added applications, such as log P determination and aqueous solubility assessment. This article describes the Veloce system and presents representative data from several discovery analytical applications.

Chemistry Techniques, Analytical↗
PubMed2005

Human Lsg1 defines a family of essential GTPases that correlates with the evolution of compartmentalization.

BACKGROUND: Compartmentalization is a key feature of eukaryotic cells, but its evolution remains poorly understood. GTPases are the oldest enzymes that use nucleotides as substrates and they participate in a wide range of cellular processes. Therefore, they are ideal tools for comparative genomic studies aimed at understanding how aspects of biological complexity such as cellular compartmentalization evolved. RESULTS: We describe the identification and characterization of a unique family of circularly permuted GTPases represented by the human orthologue of yeast Lsg1p. We placed the members of this family in the phylogenetic context of the YlqF Related GTPase (YRG) family, which are present in Eukarya, Bacteria and Archea and include the stem cell regulator Nucleostemin. To extend the computational analysis, we showed that hLsg1 is an essential GTPase predominantly located in the endoplasmic reticulum and, in some cells, in Cajal bodies in the nucleus. Comparison of localization and siRNA datasets suggests that all members of the family are essential GTPases that have increased in number as the compartmentalization of the eukaryotic cell and the ribosome biogenesis pathway have evolved. CONCLUSION: We propose a scenario, consistent with our data, for the evolution of this family: cytoplasmic components were first acquired, followed by nuclear components, and finally the mitochondrial and chloroplast elements were derived from different bacterial species, in parallel with the formation of the nucleolus and the specialization of nuclear components.

Cell Nucleus↗
PubMed2003

Single eubacterial origin of eukaryotic sulfide:quinone oxidoreductase, a mitochondrial enzyme conserved from the early evolution of eukaryotes during anoxic and sulfidic times.

Mitochondria occur as aerobic, facultatively anaerobic, and, in the case of hydrogenosomes, strictly anaerobic forms. This physiological diversity of mitochondrial oxygen requirement is paralleled by that of free-living alpha-proteobacteria, the group of eubacteria from which mitochondria arose, many of which are facultative anaerobes. Although ATP synthesis in mitochondria usually involves the oxidation of reduced carbon compounds, many alpha-proteobacteria and some mitochondria are known to use sulfide (H2S) as an electron donor for the respiratory chain and its associated ATP synthesis. In many eubacteria, the oxidation of sulfide involves the enzyme sulfide:quinone oxidoreductase (SQR). Nuclear-encoded homologs of SQR are found in several eukaryotic genomes. Here we show that eukaryotic SQR genes characterized to date can be traced to a single acquisition from a eubacterial donor in the common ancestor of animals and fungi. Yet, SQR is not a well-conserved protein, and our analyses suggest that the SQR gene has furthermore undergone some lateral transfer among prokaryotes during evolution, leaving the precise eubacterial lineage from which eukaryotes obtained their SQR difficult to discern with phylogenetic methods. Newer geochemical data and microfossil evidence indicate that major phases of early eukaryotic diversification occurred during a period of the Earth's history from 1 to 2 billion years before present in which the subsurface ocean waters contained almost no oxygen but contained high concentrations of sulfide, suggesting that the ability to deal with sulfide was essential for prokaryotes and eukaryotes during that time. Notwithstanding poor resolution in deep SQR phylogeny and lack of a specifically alpha-protebacterial branch for the eukaryotic enzyme on the basis of current lineage sampling, a single eubacterial origin of eukaryotic SQR and the evident need of ancient eukaryotes to deal with sulfide, a process today germane to mitochondrial quinone reduction, are compatible with the view that eukaryotic SQR was an acquisition from the mitochondrial endosymbiont.

Amino Acid Sequence↗
PubMed2005

Opisthobranchia (Mollusca, Gastropoda) - more than just slimy slugs. Shell reduction and its implications on defence and foraging.

BACKGROUND: In general shell-less slugs are considered to be slimy animals with a rather dull appearance and a pest to garden plants. But marine slugs usually are beautifully coloured animals belonging to the less-known Opisthobranchia. They are characterized by a large array of interesting biological phenomena, usually related to foraging and/or defence. In this paper our knowledge of shell reduction, correlated with the evolution of different defensive and foraging strategies is reviewed, and new results on histology of different glandular systems are included. RESULTS: Based on a phylogeny obtained by morphological and histological data, the parallel reduction of the shell within the different groups is outlined. Major food sources are given and glandular structures are described as possible defensive structures in the external epithelia, and as internal glands. CONCLUSION: According to phylogenetic analyses, the reduction of the shell correlates with the evolution of defensive strategies. Many different kinds of defence structures, like cleptocnides, mantle dermal formations (MDFs), and acid glands, are only present in shell-less slugs. In several cases, it is not clear whether the defensive devices were a prerequisite for the reduction of the shell, or reduction occurred before. Reduction of the shell and acquisition of different defensive structures had an implication on exploration of new food sources and therefore likely enhanced adaptive radiation of several groups.

Journal Article↗
PubMedDate not supplied

[The morphogenetic causes of parallelisms in the dental system of rodents].

Morphogenetic causes of the origin of true hypsodonty and transformation of bunodont teeth pattern to lophodont one in the rodent evolution are discussed. Wide distribution of these processes in different rodent groups and many other mammals can be explained by the universality of morphogenetic mechanisms of teeth development and by scantiness of their possible transformation pathways.

Animals↗
PubMed2003

Evolutionary transformations of the fetal membranes of viviparous reptiles: a case study of two lineages.

The reptilian placenta is a composite structure formed by a functional interaction between extraembryonic membranes and the maternal uterus. Study of placental structure of squamate reptiles over the past century has established that each of the multiple independent origins of placentation, which characterize the reproductive diversity of squamates, has resulted from the evolutionary transformation of these homologous structures. Because each evolutionary transformation is an independent novel relationship between maternal and embryonic tissues, the resulting placentae are not homologous, even though the individual components may be. The evolution of reptilian placentation should reveal much about evolutionary patterns and mechanisms because similar structural-functional systems have been transformed along parallel trajectories on multiple occasions. We compared extraembryonic membrane and placental development and pattern of embryonic nutrition in thamnophiine snakes and Pseudemoia lizards in the context of recent hypotheses of phylogenetic relationships. Two primary types of placentation, chorioallantoic and yolk sac, evolved in each lineage. Smooth, highly vascular regions of chorioallantoic placentation are indistinguishable homoplasies that evolved in parallel, likely to facilitate respiratory exchange. The yolk sac placenta of each lineage is specialized for histotrophic nutrient transfer, yet composition of these structures differs because of variation in the ancestral snakes and lizards. In addition, the omphalopleure that contributes to yolk sac placentation persists to later embryonic stages compared to oviparous outgroups, but the two lineages have evolved different structures that prevent replacement of the omphalopleure by the allantois. Each lineage has also evolved unique structural specializations of the chorioallantoic placenta.

Allantois↗
PubMedDate not supplied

[Evolutionary physiological analysis of body reactions to oxygen exposure under increase pressure].

In experiments on adult animals (rabbit, cat, dog), it has been found that changes during the initial stages of the effect of high oxygen pressure include: stabilization of the main rhythm of the EEG, inhibition of spindle-like activity and onset (or the increase) of interhemispheral asymmetry of the electrocorticogram, the increase of the amplitude of positive wave of primary response and slow negative wave of the evoked potential of the brain cortex, as well as the increase in the threshold level of inhibition of respiration in response to electrical stimulation of the cranial end of the vagal nerve and the increase in the stability of respiration and cardiac activity. These changes are similar to those which take place in the course of progressive evolution of functions of the central nervous system, respiratory and cardio-vascular systems in onto- and phylogenesis. On the basis of this parallelism, it is concluded that the initial (pre-toxic) effect of hyperoxia results in the increase of the activity of evolutionary younger functional systems of the brain. During the continuous effect of hyperoxia, oxygen intoxication of the organism takes place, which include particularly dissolution phenomena in the activity of the brain. These phenomena are most evident during the development of pre-seizure and seizure periods.

Animals↗
PubMed2005

Perisylvian language networks of the human brain.

Early anatomically based models of language consisted of an arcuate tract connecting Broca's speech and Wernicke's comprehension centers; a lesion of the tract resulted in conduction aphasia. However, the heterogeneous clinical presentations of conduction aphasia suggest a greater complexity of perisylvian anatomical connections than allowed for in the classical anatomical model. This article re-explores perisylvian language connectivity using in vivo diffusion tensor magnetic resonance imaging tractography. Diffusion tensor magnetic resonance imaging data from 11 right-handed healthy male subjects were averaged, and the arcuate fasciculus of the left hemisphere reconstructed from this data using an interactive dissection technique. Beyond the classical arcuate pathway connecting Broca's and Wernicke's areas directly, we show a previously undescribed, indirect pathway passing through inferior parietal cortex. The indirect pathway runs parallel and lateral to the classical arcuate fasciculus and is composed of an anterior segment connecting Broca's territory with the inferior parietal lobe and a posterior segment connecting the inferior parietal lobe to Wernicke's territory. This model of two parallel pathways helps explain the diverse clinical presentations of conduction aphasia. The anatomical findings are also relevant to the evolution of language, provide a framework for Lichtheim's symptom-based neurological model of aphasia, and constrain, anatomically, contemporary connectionist accounts of language.

Adult↗
PubMed1991

Abnormal skin temperature and abnormal sympathetic vasomotor innervation in an experimental painful peripheral neuropathy.

A chronic constriction injury to the sciatic nerve of the rat produces a neuropathic pain syndrome that has many of the symptoms that are seen in humans with painful peripheral neuropathy. In particular, both the clinical and experimental conditions are accompanied by an abnormality of cutaneous temperature regulation in the painful area. A time course study was made of this phenomenon in the experimental model. In normal rats, there is little or no difference between the temperature of the two hind paws (plantar skin). After nerve injury, however, approximately 75% of the rats (N = 30) had abnormally large (greater than +/- 0.9 degrees C) temperature differences (delta T) between the affected and sham-operated sides. The abnormal delta Ts could be either positive or negative, i.e., the affected side could be hotter or colder than normal. For individual cases, the temperature abnormality was highly variable over time periods of hours to days; abnormally hot skin could switch to being abnormally cold, and vice versa, and small delta Ts in the normal range could switch between abnormal extremes. Despite this individual variability, the average delta T of the group as a whole displayed a clear evolution over the course of the 30-day observation period: abnormally hot initially and progressing to abnormally cold. A parallel time course study was made of the status of the sympathetic vasoconstrictor innervation to the affected hind paw (plantar artery and vein). As demonstrated with a histofluorescence method that visualizes catecholamines, there was a gradual loss of norepinephrine (NE)-containing sympathetic efferents on the nerve-injured side. The decrease was first noted on postoperative day 5 (PO5), was very marked by PO10-PO14, and progressed to a complete or nearly complete loss by PO30. There was a concomitant decrease in staining for two other substances found in vasoconstrictor efferents, dopamine-beta-hydroxylase (DBH) and neuropeptide Y (NPY). The NE-containing innervation of the contralateral (sham-operated) plantar vessels appeared to be normal at all times. Lastly, in order to determine whether there was any relation between the temperature abnormality and the status of the sympathetic perivascular plexus, additional rats were sacrificed immediately after skin temperature measurement and the hind paw vessels were stained for NE. The vasculature of some abnormally cold paws had no detectable NE. Some rats that did not appear to have a temperature abnormality also had no detectable NE on the affected hind paw's vasculature. The vasculature of some abnormally hot paws had normal NE.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2004

Horizontal gene transfer and archaeal origin of deoxyhypusine synthase homologous genes in bacteria.

The initiation factor 5A (IF-5A) of archaea and eukaryotes undergoes an unusual post-translational modification consisting of the transformation of a specific conserved lysine residue into the amino acid hypusine. This occurs in a two-step reaction catalysed by the enzymes deoxyhypusine synthase (DHS) and deoxyhypusine hydroxylase. Bacteria do not have IF-5A but only a very distant homologue, the elongation factor P (EF-P). Consequently, all bacteria appeared to also lack genes with significant homology to DHS genes. However, we have carried out BLAST searches and found DHS-like genes in a number of bacterial species. The phylogenetic analysis of these sequences strongly suggests that they have been acquired from archaea by horizontal gene transfer (HGT). Our analysis also suggests, although with weaker support, that a single HGT event from archaea, followed by several HGT between bacterial species, accounts for the patchy distribution of DHS-like genes in bacteria. The activity of these genes in bacteria is enigmatic, since we have not found any evidence of interaction between this protein and the bacterial EF-P. Nevertheless, we cannot discard that it exists, since it appears that the interaction between the DHS and its natural substrate, the IF-5A, is rather weak. This is exemplified by the fact that, in archaea, the complex evolutionary history of the DHS is not paralleled by that of the IF-5A, indicating that these proteins do not follow a perfect co-evolution.

Amino Acid Sequence↗
PubMed2000

Molecular evidence of a unique lipoamide dehydrogenase in plastids: analysis of plastidic lipoamide dehydrogenase from Arabidopsis thaliana.

Lipoamide dehydrogenase is a subunit of the alpha-ketoacid dehydrogenases and the glycine decarboxylase complex in mitochondria, and the pyruvate dehydrogenase complex in plastids. We report here the unexpected finding of two plastidic isoforms of lipoamide dehydrogenase from Arabidopsis thaliana that are different from the mitochondrial form of the enzyme. The cDNA clones were confirmed by sequence alignment analysis and their location verified by chloroplast import assay. They are single copy genes that appear to be expressed in parallel in different tissues with highest level in developing siliques. Phylogenetic analysis gives further exemplary evidence for the plastidic evolution derived from cyanobacteria.

Amino Acid Sequence↗
PubMed2005

Targeted 'knockdown' of spliceosome function in mammalian cells.

The existence of two sophisticated parallel splicing machineries in multicellular organisms has raised intriguing questions--ranging from their impact on proteome expansion to the evolution of splicing and of metazoan genomes. Exploring roles for the distinct splicing systems in vivo has, however, been restricted by the lack of techniques to selectively inhibit their function in cells. In this study, we show that morpholino oligomers complementary to the branch-site recognition elements of U2 or U12 small nuclear RNA specifically suppress the function of the two splicing systems in mammalian cells. The data provide the first evidence for a role of distinct spliceosomes in pre-mRNA splicing from endogenous mammalian genes and establish a tool to define roles for the different splicing machineries in vivo.

Animals↗
PubMed2001

Effect of rigidity on the crystallization processes of short polymer melts.

Order formation in crystallization processes of the dense melts of chain molecules has been studied by the coarse-grained molecular dynamics method. For semirigid molecules, the parallel orientation and elongation of chains take place simultaneously. However, for semiflexible molecules, long induction periods are observed. Time evolution studies of local order parameters indicated that two different processes occur, which implies that a precondition exists. For flexible molecules, the structures become mostly amorphous at certain sharp threshold conditions of chain rigidity. It was determined that the rigidity of the main chains strongly influences the dynamic behavior of crystallization for dense melts, particularly in the early stage.

Journal Article↗
PubMed2003

Phonon avalanches in paramagnetic impurities with spin S=1/2.

We theoretically study the dynamics of transverse-and-longitudinal acoustic waves propagating parallel to an external magnetic field in a crystal containing ion impurities with an effective spin S=1/2. Corresponding evolution equations describing the coherent pulse evolution are derived. These equations are used to study the phonon avalanches arising due to decay of an initially unstable state of the spin systems for different geometries of interaction. It is found that the coherent dynamics of acoustic pulses propagated in one direction is described by a pair of integrable systems of evolution equations. The picosecond acoustic pulses governed by these systems are "a few-cycle" pulses. By using a modified set of equations of the inverse scattering transform, it is found that the strong interaction of three or two components of the acoustic waves with the spin system is asymptotically described by the quasi-self-similar solutions. Physical applications of the obtained results are discussed.

Journal Article↗
PubMed1989

Stathmin is a major phosphoprotein and cyclic AMP-dependent protein kinase substrate in mouse brain neurons but not in astrocytes in culture: regulation during ontogenesis.

Stathmin is a ubiquitous soluble protein (Mr approximately 19,000; pI approximately 6.2-5.5) whose phosphorylation is associated with the intracellular mechanisms involved in the regulations of cell differentiation and functions by extracellular effectors. It is present in various tissues and cell types and has several nonphosphorylated and increasingly phosphorylated forms, and it is particularly abundant in brain. Very high concentrations of stathmin were also detected in mouse embryo striatal neurons grown in primary culture, whereas stathmin was barely detectable in astrocytes from the same source. Stathmin appeared in neurons as a major substrate for protein phosphorylation and, in particular, for the cyclic AMP (cAMP)-dependent protein kinase, because its phosphorylation was stimulated by cAMP in cell-free preparations and in intact cells by forskolin, a potent activator of adenylate cyclase. During brain ontogenesis, stathmin was first detected at embryonic day 12; its concentration increased until birth and then decreased from postnatal day 10 to adulthood. In parallel, its molecular forms shifted from the least phosphorylated to the more phosphorylated ones. This result may reflect the evolution of the activity of stathmin during development and the subsequent maturation of the brain. In conclusion, our results substantiate the likely role of stathmin as an intracellular relay of extracellular regulations, as they point out its specific importance related to neuronal functions and brain differentiation.

1-Methyl-3-isobutylxanthine↗
PubMed1985

Experimental evolution of penicillin G acylases from Escherichia coli and Proteus rettgeri.

Proteus rettgeri and Escherichia coli W were shown to express structurally different penicillin G acylases. The enzymes had similar substrate specificity but differed in molecular weight, isoelectric point, and electrophoretic mobility in polyacrylamide gels and did not antigenically cross-react. When the organisms were subjected to environmental conditions which made expression of this enzyme essential for growth, spontaneous mutants were isolated that used different amides as the only source of nitrogen. These mutants acquired the ability to use amides for growth by deregulating the penicillin G acylase and by their evolution to novel substrate specificities. The enzymes expressed by mutants isolated from each genus appeared to have evolved in parallel since each acylase attained similar new substrate specificities when the organisms were subjected to identical selection pressure.

Amidohydrolases↗
PubMed2005

[Protocol for prevention and treatment of osteoporosis in patients with cystic fibrosis].

BACKGROUND AND OBJECTIVE: Reduction of bone mineral density (BMD) is a complication of cystic fibrosis (CF) which is observed in parallel to the increment of life expectancy in these patients. The aim of this study was to analyze the evolution of BMD following the application of a protocol for the prevention and treatment of osteoporosis. PATIENTS AND METHOD: We performed a multidisciplinary prospective study in 21 adult patients with CF with a mean age of 24.3 (r: 19-44) years. We evaluated BMD results depending on the treatment schedule, and the annual relative change of BMD percentage was correlated with changes observed in respiratory function, corporal mass index (CMI), Brasfield radiologic score and Shwachman clinical score for a 3 years follow up period. Three regimens of treatment were applied: general measurements, supplementation of calcium and vitamin D, and 10 daily mg of alendronate plus calcium and vitamin D supplements. RESULTS: Basal assessment showed that 14.2% of CF patients had a marked diminution of bone mass with respect to an age and sex matched control population, with a Z score of < -2 DE in lumbar vertebral and/or total femur. Another 38% showed a lessening of Z score between -1 and -2.5 DE. We observed a progressive annual reduction of BMD in all the anatomic areas analyzed: -0.52% (1.87) in lumbar spine, -1.17% (1.91) in total femur and -2.16% (2.65) in neck femur. The hip BMD annual decrement was related to that observed in FEV1. Only patients treated with alendronate did not suffer progressive BMD lose. Treatment with a combination of calcium, vitamin D and alendronate was more efficient in hip BMD than calcium plus vitamin D alone (p < 0.05). Also, this combination was better than no treatment at hip and femoral neck levels (p < 0.05). CONCLUSIONS: Our work confirms that Spanish young adults patients with CF show low control matched BMD, and that it even worsens at follow-up. This decrement is not adequately halted with preventive treatment with supplements of calcium and vitamin D, and only patients treated with alendronate show increments of their BMD.

Adult↗