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PubMed2004

Distribution and acute stressor-induced activation of corticotrophin-releasing hormone neurones in the central nervous system of Xenopus laevis.

In mammals, corticotrophin-releasing hormone (CRH) and related peptides are known to play essential roles in the regulation of neuroendocrine, autonomic and behavioural responses to physical and emotional stress. In nonmammalian species, CRH-like peptides are hypothesized to play similar neuroendocrine and neurocrine roles. However, there is relatively little detailed information on the distribution of CRH neurones in the central nervous system (CNS) of nonmammalian vertebrates, and there are currently no comparative data on stress-induced changes in CRH neuronal physiology. We used a specific, affinity-purified antibody raised against synthetic Xenopus laevis CRH to map the distribution of CRH in the CNS of juvenile South African clawed frogs. We then analysed stress-induced changes in CRH immunoreactivity (CRH-ir) throughout the CNS. We found that CRH-positive cell bodies and fibres are widely distributed throughout the brain and rostral spinal cord of juvenile X. laevis. Strong CRH-immunoreactivity (ir) was found in cell bodies and fibres in the anterior preoptic area (POA, an area homologous to the mammalian paraventricular nucleus) and the external zone of the median eminence. Specific CRH-ir cell bodies and fibres were also identified in the septum, pallium and striatum in the telencephalon; the amygdala, bed nucleus of the stria terminalis and various hypothalamic and thalamic nuclei in the diencephalon; the tectum, torus semicircularis and tegmental nuclei of the mesencephalon; the cerebellum and locus coeruleus in the rhombencephalon; and the ventral horn of the rostral spinal cord. To determine if exposure to an acute physical stressor alters CRH neuronal physiology, we exposed juvenile frogs to shaking/handling and conducted morphometric analysis. Plasma corticosterone was significantly elevated by 30 min after exposure to the stressor and continued to increase up to 6 h. Morphometric analysis of CRH-ir after 4 h of stress showed a significant increase in CRH-ir in parvocellular neurones of the anterior preoptic area, the medial amygdala and the bed nucleus of the stria terminalis, but not in other brain regions. The stress-induced increase in CRH-ir in the POA was associated with increased Fos-like immunoreactivity (Fos-LI), and confocal microscopy showed that CRH-ir colocalized with Fos-LI in a subset of Fos-LI-positive neurones. Our results support the view that the basic pattern of CNS CRH expression arose early in vertebrate evolution and lend further support to earlier studies suggesting that amphibians may be a transitional species for descending CRH-ergic pathways. Furthermore, CRH neurones in the frog brain exhibit changes in response to a physical stressor that parallel those seen in mammals, and thus are likely to play an active role in mediating neuroendocrine, behavioural and autonomic stress responses.

Acute Disease↗
PubMed1978

Evolution of vasopressin levels in the hypothalamo-posthypophysial system of the rat during rehydration following water deprivation. Correlation with ultrastructural aspects in the posterior lobe.

Evolution of the (arginine)-vasopressin (AVP) content of the supraoptic (SON), paraventricular (PVN) and suprachiasmatic nuclei (SchN) and of the posterior lobe of the hypophysis (PLH) has been studied in rats at successive stages of rehydration after 4 days deprivation of drinking water. Particular attention has been focussed on short periods of rehydration. Evolution of the AVP content of the hypothalamo-posthypophysial system (HHS), the blood serum AVP concentration and osmolalities of serum and urine were compared. Variations of the AVP content in the different hypothalamo-hypophysial structures, are parallel. A marked depletion of AVP is observed after 2 and 4 days of dehydration. The AVP content of the PLH and of the hypothalamic nuclei shows two dramatic and short increases 15 min and 3 h after the onset of rehydration; these results are discussed in relation to the known physiological regulation mechanism of the HHS. In the PLH depleted by dehydration, reloading with neurosecretory granules (NSG) begins to be noticeable only after 24 h of rehydration, so that it does not seem to account for elevations of the AVP content occurring earlier. These could be related to a marked increase of the smooth endoplasmic reticulum (SER) network taking place in axons and nerve endings before the NSG reloading.

Animals↗
PubMed2006

Genetic Parallel Programming: design and implementation.

This paper presents a novel Genetic Parallel Programming (GPP) paradigm for evolving parallel programs running on a Multi-Arithmetic-Logic-Unit (Multi-ALU) Processor (MAP). The MAP is a Multiple Instruction-streams, Multiple Data-streams (MIMD), general-purpose register machine that can be implemented on modern Very Large-Scale Integrated Circuits (VLSIs) in order to evaluate genetic programs at high speed. For human programmers, writing parallel programs is more difficult than writing sequential programs. However, experimental results show that GPP evolves parallel programs with less computational effort than that of their sequential counterparts. It creates a new approach to evolving a feasible problem solution in parallel program form and then serializes it into a sequential program if required. The effectiveness and efficiency of GPP are investigated using a suite of 14 well-studied benchmark problems. Experimental results show that GPP speeds up evolution substantially.

Algorithms↗
PubMed2003

Ethical issues raised by genetic testing with oligonucleotide microarrays.

Because genes and alterations within them determine the identity, characteristics, and inheritance of every individual, the application of genetic science to humans has long been surrounded by apprehension, controversy, and real or perceived potential for abuse. Crude eugenics practices of the past now find a theoretical rebirth and transformation through the use of modern molecular genetic technologies for mutation detection, predictive and prenatal diagnosis, and, ultimately, gene replacement. The advent of oligonucleotide microarray analysis, in which hundreds or thousands of genes and mutations can be tested in parallel, offers tremendous promise for more accurate, sensitive, and efficient genetic testing. At the same time, however, this powerful technology dramatically increases the number and scope of ethical concerns accompanying each individual test request. This article considers the evolution and implications of these concerns, from the initial ordering of a microarray test by the physician to such issues as informed consent, privacy, confidentiality, clinical utility, discrimination, stigmatization, ethnic and population impact, and reimbursement.

Confidentiality↗
PubMed1978

Pathology of experimental spinal cord trauma. I. The necrotic lesion as a function of vascular injury.

Adult Sprague Dawley rats were subjected to spinal cord trauma at the lower thoracic-lumbar levels utilizing a weight dropping technique onto the surgically exposed dorsal surface. The experimental conditions of trauma consistently produced severe paraplegia without spontaneous movement of the hindlimbs, a sensory level, and neurogenic bladder dysfunction. Changes in blood vessels and the development of tissue necrosis were studied in a posttrauma time sequence by light and electron microscopy. Fibrinoid necrosis and disruption of major arteries as well as veins were observed immediately after impact, antedating the evolution of parenchymal necrosis. A fusiform zone of spinal cord necrosis, involving the complete cross-sectional area beneath the site of impact, evolved over a period of 8 to 24 hours, being initially complete in the gray matter by 4 hours and thereafter in the white matter. Ultrastructural observations revealed that the evolution of necrotic cellular constituents was piecemeal. Except for the occurrence of intracellular calcification and heterophagocytosis in the traumatized tissue, the electron microscopic features of cellular necrosis were comparable to those of postmortem spinal cord autolysis, studied in parallel. The observations are consistent with trauma producing ischemic necrosis, resulting from major blood vessel disruption occurring at the moment of impact.

Animals↗
PubMed1994

Evolution of marsupial and other vertebrate thyroxine-binding plasma proteins.

Binding of radioactive thyroxine to proteins in the plasma of vertebrates was studied by electrophoresis followed by autoradiography. Albumin was found to be a thyroxine carrier in the blood of all studied fish, amphibians, reptiles, monotremes, marsupials, eutherians (placental mammals), and birds. Thyroxine binding to transthyretin was detected in the blood of eutherians, diprotodont marsupials, and birds, but not in blood from fish, toads, reptiles, monotremes, and Australian polyprotodont marsupials. Globulins binding thyroxine were only observed in the plasma of some mammals. Apparently, albumin is the phylogenetically oldest thyroxine carrier in vertebrate blood. Transthyretin gene expression in the liver developed in parallel, and independently, in the evolutionary lineages leading to eutherians, to diprotodont marsupials, and to birds. In contrast, high transthyretin mRNA levels, strong synthesis, and secretion of transthyretin in choroid plexus from reptiles and birds indicate that transthyretin gene expression in the choroid plexus evolved much earlier than in the liver, probably at the stage of the stem reptiles. NH2-terminal sequence analysis suggests a change of transthyretin pre-mRNA splicing during evolution.

Amino Acid Sequence↗
PubMed1970

Inhibition of oxygen evolution in chloroplasts isolated from leaves with low water potentials.

Chloroplasts were isolated from pea and sunflower leaves having various water potentials. Oxygen evolution by the chloroplasts was measured under identical conditions for all treatments with saturating light and with dichloroindophenol as oxidant. Evolution was inhibited when leaf water potentials were below -12 bars in pea and -8 bars in sunflower and the inhibition was proportional to leaf water potential below these limits. Inhibition was more severe in sunflower than in pea chloroplasts. In sunflower, it could be detected after 5 minutes of leaf desiccation, and, up to 1 hour, the effect was independent of the duration of low leaf water potential.In high light, the reduction in activity of sunflower chloroplasts paralleled the reduction in CO(2) fixation by intact sunflower plants having low leaf water potentials. Stomatal apertures and transpiration rates were also reduced under these conditions and were probably limiting. In low light, intact sunflowers required more light per unit of CO(2) fixed when leaf water potentials were low than when they were high. This increased light requirement in the intact system was of a magnitude which could be predicted from the reduced oxygen evolution by the isolated chloroplasts. It was concluded that moderately low leaf water potential affects photosynthesis in at least two ways: first, through an inhibition of oxygen evolution by chloroplasts and, second, by closure of stomata in intact leaves.

Journal Article↗
PubMed1988

cDNA sequence encoding the 16-kDa proteolipid of chromaffin granules implies gene duplication in the evolution of H+-ATPases.

Vacuolar H+-ATPases function in generating protonmotive force across the membranes of organelles connected with the vacuolar system of eukaryotic cells. This family of H+-ATPases is distinct from the two other families of H+-ATPases, the plasma membrane-type and the eubacterial-type. One of the subunits of the vacuolar H+-ATPase binds N,N'-dicyclohexylcarbodiimide (DCCD) and has been implicated in the proton-conducting activity of these enzymes. We have cloned and sequenced the gene encoding the DCCD-binding protein (proteolipid) of the H+-ATPase of bovine chromaffin granules. The gene encodes a highly hydrophobic protein of 15,849 Da. Hydropathy plots revealed four transmembrane segments, one of which contains a glutamic residue that is the likely candidate for the DCCD binding site. Sequence homology with the vacuolar proteolipid and with the proteolipids of eubacterial-type H+-ATPases was detected. The proteolipids from Escherichia coli, spinach chloroplasts, and yeast mitochondria matched better to the NH2-terminal part of the vacuolar protein. The proteolipids of bovine mitochondria and Neurospora mitochondria matched better to the COOH-terminal end of the vacuolar proteolipid. These findings suggest that the proteolipids of the vacuolar H+-ATPases were evolved in parallel with the eubacterial proteolipid, from a common ancestral gene that underwent gene duplication.

Amino Acid Sequence↗
PubMed1983

Co-evolution of a filamentous bacteriophage and its defective interfering particles.

Serial passage of bacteriophage f1 at high multiplicities of infection results in the appearance of defective deletion mutants (miniphage) that harbor a tandem reiteration of regions of the f1 genome near the origin of DNA replication. These miniphage interfere with the growth of wild-type f1, and cause a sharp decrease of the viable phage titer. Upon further passage, however, the titer increases again. Viable phage variants (maxiphage) appear which harbor the same tandem reiteration of DNA as the miniphage. The maxiphage are more resistant than the wild type to interference by the miniphage. In the absence of miniphage the maxiphage grow at the same rate as the wild type. The structure of the DNA reiteration gradually changes during further passage. Miniphage and maxiphage follow, in parallel, a similar course of changes in the pattern of reiteration. In miniphage the reiterations change while the deletions are conserved. Serial passage of maxiphage quickly yields miniphage, which harbor a reiteration identical to that of the parental maxiphage. Both reiteration and deletion are relevant to the mechanism of interference by miniphage. Thus serial passage of the filamentous phage affords an experimental system to study evolution of a DNA genome in test tubes. Possible mechanisms of the interference by miniphage are discussed.

Base Sequence↗
PubMed2003

Development of a multipopulation parallel genetic algorithm for structure solution from powder diffraction data.

Previously, the genetic algorithm (GA) approach for direct-space crystal structure solution from powder diffraction data has been applied successfully in the structure determination of a range of organic molecular materials. In this article, we present a further development of our approach, namely a multipopulation parallel GA (PGA), which is shown to give rise to increased speed, efficiency, and reliability of structure solution calculations, as well as providing new opportunities for further optimizing our GA methodology. The multipopulation PGA is based on the independent evolution of different subpopulations, with occasional interaction (e.g., transfer of structures) allowed to occur between the different subpopulations. Different strategies for carrying out this interpopulation communication are considered in this article, and comparisons are made to the conventional single-population GA. The increased power offered by the PGA approach creates the opportunity for structure determination of molecular crystals of increasing complexity.

Journal Article↗
PubMed2004

The consistent phylogenetic signal in genome trees revealed by reducing the impact of noise.

Phylogenetic trees based on gene repertoires are remarkably similar to the current consensus of life history. Yet it has been argued that shared gene content is unreliable for phylogenetic reconstruction because of convergence in gene content due to horizontal gene transfer and parallel gene loss. Here we test this argument, by filtering out as noise those orthologous groups that have an inconsistent phylogenetic distribution, using two independent methods. The resulting phylogenies do indeed contain small but significant improvements. More importantly, we find that the majority of orthologous groups contain some phylogenetic signal and that the resulting phylogeny is the only detectable signal present in the gene distribution across genomes. Horizontal gene transfer or parallel gene loss does not cause systematic biases in the gene content tree.

Computational Biology↗
PubMed1975

The relationship between histones F 2al and F 2a2 and the ancestral histone A peptide. Further evidence for the common origin of histones F 2al, F 2a2 and F 3.

The relationship between histones F 2al and F 2a2 becomes much more apparent if the alignment is not made between the total sequences but between the ancestral A peptide, reconstructed earlier for histone F 2al (IV) and F 2a2. 46.5% of the latter's sequence can thus be clearly connected with F 2al through this ancestral dodecapeptide. A parallel development of histones F 2al, F 2a2 and F 3 from the A peptide is proposed.

Amino Acid Sequence↗
PubMed2004

Developmental sculpting of social phenotype and plasticity.

Early developmental variables engender behavioral and neural variation, especially in species in which embryonic environment determines gonadal sex. In the leopard gecko, Eublepharis macularius, the incubation temperature of the egg (IncT) determines gonadal sex. Moreover, IncT affects the sexual differentiation of the individual and, consequently, within-sex variation. Individuals hatched from eggs incubated at an IncT that produces predominantly males are more masculinized than same-sex counterparts from IncTs that produce predominantly females. Here we review how gonadal sex and IncT interact to affect behavioral, endocrinological, and neural phenotype in the leopard gecko and influence phenotypic plasticity following hormone administration or social experience. We discuss the hormonal dependence of sex- and IncT-dependent behavioral and neural morphological and metabolic differences and highlight the parallels between IncT effects in geckos and intrauterine position effects in rodents. We argue that the leopard gecko is an important model of how the process of sex determination can affect sexual differentiation and of selection forces underlying the evolution of sex ratios.

Animals↗
PubMed2006

Computational identification of Ftz/Ftz-F1 downstream target genes.

Hox genes encode DNA binding transcription factors that regulate the body plans of metazoans by regulating the expression of downstream target 'realizator genes' that direct morphogenesis and growth. Although some Hox target genes have been identified, the code used by Hox proteins to select regulatory targets remains elusive. This failure is due, in part, to the overlapping and promiscuous DNA binding potential of different Hox proteins. The identification of cofactors that modulate Hox DNA binding specificity suggested that target site selection is specified by composite binding sites in the genome for a Hox protein plus its cofactor. Here we have made use of the fact that the DNA binding specificity of the Drosophila Hox protein Fushi Tarazu (Ftz) is modulated by interaction with its partner, the orphan nuclear receptor Ftz-F1, to carry out a computational screen for genomic targets. At least two of the first 30 potential target genes--apontic (apt) and sulfated (Sulf1)--appear to be bona fide targets of Ftz and Ftz-F1. apt is expressed in stripes within the Ftz domain, but posterior to engrailed (en) stripes, suggesting a parasegmental border-independent function of ftz. Ftz/Ftz-F1 activate Sulf1 expression in blastoderm embryos via composite binding sites. Sulf1 encodes a sulfatase thought to be involved in wingless (Wg) signaling. Thus, in addition to regulating en, Ftz and Ftz-F1 coordinately and directly regulate different components of segment polarity pathways in parallel.

Animals↗
PubMed1998

Substitution of Ala-251 of the D1 reaction centre polypeptide with a charged residue results in impaired function of photosystem II.

Ala-251 in the membrane-parallel helix in the D-E loop of the D1 polypeptide close to the Q(B) pocket of photosystem II (PS II), was mutated to aspartate (D), lysine (K), leucine (L) or serine (S) in Synechocystis 6803. O2 evolution rates (H2O-->DCBQ; 2,6-dichloro-p-benzoquinone) of A251D, A251L and A251S were lower, being 38, 16, 62 and 70%, respectively, of that of the control, and there was an even more drastic impairment of O2 evolution when measured from H2O to DMBQ (2,5-dimethyl-p-benzoquinone), demonstrating modifications in the Q(B) pocket. However, in all other mutants but A251K, the Q(B) function could sustain O2 evolution at a level high enough to support photosynthetic growth. The mutant A251S, carrying a substitution of alanine for a chemically quite similar residue serine, was less severely affected. Substitution by a positively charged residue drastically delayed chlorophyll a fluorescence relaxation in the non-photosynthetic strain A251K, implying strong impairment of Q(A)-to-Q(B) electron transfer. Delay of fluorescence relaxation was clear in A251D as well, carrying a substitution of alanine for a negatively charged residue. The effects of the substitutions of A251 demonstrate the importance of this residue of the D1 polypeptide in the conformation of the acceptor side of PS II and, accordingly, the effect on the acceptor-side function of PS II was very clear. Nevertheless, the tolerance of PS II activity to high-light-induced photoinhibition in vivo and the subsequent D1 degradation were not much impaired in any of the photosynthetic mutant strains as compared to the control.

Alanine↗
PubMed2003

LIM-domain-binding protein 1: a multifunctional cofactor that interacts with diverse proteins.

The ubiquitous nuclear adaptor protein LIM-domain-binding protein 1 (Ldb1) was originally identified as a cofactor for LIM-homeodomain and LIM-only (LMO) proteins that have fundamental roles in development. In parallel, Ldb1 has been shown to have essential functions in diverse biological processes in different organisms. The recent targeting of this gene in mice has revealed roles for Ldb1 in neural patterning and development that have been conserved throughout evolution. Furthermore, the elucidation of the three-dimensional structures of LIM-Ldb1 complexes has provided insight into the molecular basis for the ability of Ldb1 to contact diverse LIM-domain proteins. It has become evident that Ldb1 is a multi-adaptor protein that mediates interactions between different classes of transcription factors and their co-regulators and that the nature of these complexes determines cell fate and differentiation.

Amino Acid Sequence↗
PubMed2002

Phylogeny of the Lake Tanganyika cichlid species flock and its relationship to the Central and East African haplochromine cichlid fish faunas.

Lake Tanganyika, the oldest of the East African Great Lakes, harbors the ecologically, morphologically, and behaviorally most complex of all assemblages of cichlid fishes, consisting of about 200 described species. The evolutionary old age of the cichlid assemblage, its extreme degree of morphological differentiation, the lack of species with intermediate morphologies, and the rapidity of lineage formation have made evolutionary reconstruction difficult. The number and origin of seeding lineages, particularly the possible contribution of riverine haplochromine cichlids to endemic lacustrine lineages, remains unclear. Our phylogenetic analyses, based on mitochondrial DNA sequences of three gene segments of 49 species (25% of all described species, up to 2,400 bp each), yield robust phylogenies that provide new insights into the Lake Tanganyika adaptive radiation as well as into the origin of the Central- and East-African haplochromine faunas. Our data suggest that eight ancient African lineages may have seeded the Tanganyikan cichlid radiation. One of these seeding lineages, probably comprising substrate spawning Lamprologus-like species, diversified into six lineages that evolved mouthbrooding during the initial stage of the radiation. All analyzed haplochromines from surrounding rivers and lakes seem to have evolved within the radiating Tanganyikan lineages. Thus, our findings contradict the current hypothesis that ancestral riverine haplochromines colonized Lake Tanganyika to give rise to at least part of its spectacular endemic cichlid species assemblage. Instead, the early phases of the Tanganyikan radiation affected Central and East African rivers and lakes. The haplochromines may have evolved in the Tanganyikan basin before the lake became a hydrologically and ecologically closed system and then secondarily colonized surrounding rivers. Apparently, therefore, the current diversity of Central and East African haplochromines represents a relatively young and polyphyletic fauna that evolved from or in parallel to lineages now endemic to Lake Tanganyika.

Africa↗
PubMed2004

Progression from frontal-parietal to mesial-temporal epilepsy after fluid percussion injury in the rat.

We recently described an in vivo model of post-traumatic epilepsy (PTE) in the rat where chronic spontaneous recurrent seizures appear following a single episode of fluid percussion injury (FPI). PTE, studied during the first 2 months post-injury, was focal and seizures originated predominantly from the frontal-parietal neocortex at or around the injury site. However, rarer bilateral seizures originating from a different and undefined focus were also observed. To shed light on the Posttraumatic Epileptogenic mechanisms and on the generation of bilateral seizures, we studied rats up to 7 months post-injury. In vivo paired epidural and depth-electrode recordings indicated that the anterior hippocampus evolves into an epileptic focus which initiates bilateral seizures. The rate of frontal-parietal seizures remained constant over time after 2 weeks post-injury, while the rate of hippocampal seizures greatly increased over time, suggesting that different mechanisms mediate neocortical and hippocampal post-traumatic epileptogenesis. Because of different temporal evolution of these foci, the epileptic syndrome was characterized by predominant frontal-parietal seizures early after injury, but by predominant mesio-temporal seizures at later time points. Pathological analysis demonstrated progressive hippocampal and temporal cortex pathology that paralleled the increase in frequency and duration of bilateral seizures. These results demonstrate that FPI-induced frontal-parietal epilepsy (FPE) progresses to mesial-temporal lobe epilepsy (MTLE) with dual pathology. These observations establish numerous similarities between FPI-induced and human PTE and further validate it as a clinically relevant model of PTE.

Animals↗