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PubMed2004

Learned birdsong and the neurobiology of human language.

Vocal learning, the substrate for human language, is a rare trait found to date in only three distantly related groups of mammals (humans, bats, and cetaceans) and three distantly related groups of birds (parrots, hummingbirds, and songbirds). Brain pathways for vocal learning have been studied in the three bird groups and in humans. Here I present a hypothesis on the relationships and evolution of brain pathways for vocal learning among birds and humans. The three vocal learning bird groups each appear to have seven similar but not identical cerebral vocal nuclei distributed into two vocal pathways, one posterior and one anterior. Humans also appear to have a posterior vocal pathway, which includes projections from the face motor cortex to brainstem vocal lower motor neurons, and an anterior vocal pathway, which includes a strip of premotor cortex, the anterior basal ganglia, and the anterior thalamus. These vocal pathways are not found in vocal non-learning birds or mammals, but are similar to brain pathways used for other types of learning. Thus, I argue that if vocal learning evolved independently among birds and humans, then it did so under strong genetic constraints of a pre-existing basic neural network of the vertebrate brain.

Animals↗
PubMed2004

Brain perfusion in children: evolution with age assessed by quantitative perfusion computed tomography.

OBJECTIVE: The objective of this study was to assess the age-related variations of brain perfusion through quantitative cerebral perfusion computed tomography (CT) results in children without brain abnormality. METHODS: Brain perfusion CT examinations were performed in 77 children, aged 7 days to 18 years. These patients were admitted at our institution for both noncontrast and contrast-enhanced cerebral CT. Only children whose conventional cerebral CT and clinical/radiologic follow-up, including additional investigations, were normal were taken into account for this study (53 of 77). RESULTS: The average regional rCBF amounts to 40 (mL/100 g per minute) for the first 6 months of life, peaks at approximately 130 (mL/100 g per minute) at approximately 2 to 4 years of age, and finally stabilizes at approximately 50 (mL/100 g per minute) at approximately 7 to 8 years of age, with a small increase of rCBF values at approximately 12 years of age. The rCBF in the gray matter averages 3 times that in the white matter, except for the first 6 months of life. The global CBF represents 10% to 20% of the global cardiac output for the first 6 months of life, peaks at approximately 55% by 2 to 4 years of age, and finally stabilizes at approximately 15% by 7 to 8 years of age. Specific age-related evolution patterns were identified in the different anatomic areas of the cerebral parenchyma, which could be related to the development of neuroanatomic structures and to the emergence of corresponding cognitive functions. CONCLUSIONS: Quantitative perfusion CT characterization of brain perfusion shows specific age variations. Brain perfusion of each cortical area evolves according to a specific time course, in close correlation with the psychomotor development.

Adolescent↗
PubMed2001

Ruminant brain ribonucleases: expression and evolution.

Molecular evolutionary analyses of mammalian ribonucleases have shown that gene duplication events giving rise to three paralogous genes occurred in ruminant ancestors. One of these genes encodes a ribonuclease identified in bovine brain. A peculiar feature of this enzyme and orthologous sequences in other ruminants are C-terminal extensions consisting of 17-27 amino acid residues. Evidence was obtained by Western blot analysis for the presence of brain-type ribonucleases in brain tissue not only of ox, but also of sheep, roe deer and chevrotain (Tragulus javanicus), a member of the earliest diverged taxon of the ruminants. The C-terminal extension of brain-type ribonuclease from giraffe deviates much in sequence from orthologues in other ruminants, due to a change of reading frame. However, the gene encodes a functional enzyme, which could be expressed in heterologous systems. The messenger RNA of bovine brain ribonuclease is not only expressed at a high level in brain tissue but also in lactating mammary gland. The enzyme was isolated and identified from this latter tissue, but was not present in bovine milk, although pancreatic ribonucleases A and B could be isolated from both sources. This suggests different ways of secretion of the two enzyme types, possibly related to structural differences. The sequence of the brain-type RNase from chevrotain suggests that the C-terminal extensions of ruminant brain-type ribonucleases originate from deletions in the ancestral DNA (including a region with stop codons), followed by insertion of a 5-8-fold repeated hexanucleotide sequence, coding for a proline-rich polypeptide.

Amino Acid Sequence↗
PubMed1995

Lateralization of predator-evasion response in a teleost fish (Girardinus falcatus).

Evidence of lateral asymmetries in the direction of turning during escape behaviour in a species of poeciliid fish, Girardinus falcatus, is reported. When repeatedly faced with a simulated predator (in five successive sessions, spaced 7 days apart), immature Girardinus falcatus exhibited a significant population bias to turn right on the first session and a progressive bias to turn left in subsequent sessions. Mature Girardinus were then tested to check whether the shift in the direction of turn with repeated sessions depended on maturation or habituation. It was found that adult Girardinus showed a slight population bias to turn right in the first session and a strong subsequent bias to turn left after repeated sessions. The implications of these findings to our current understanding of the evolution of brain lateralization are discussed.

Animals↗
PubMedDate not supplied

[2 types of generalization in the evolution of the visual brain].

It has been shown that mechanism of generalization with respect to the size (shift of differentiation of the size from objects of one form to other forms) is located in dogs within the suprasylvian convolution, in cats--within the median part of the lateral suprasylvian region. After removal of these parts of the brain, other visual functions including the invariant description of the image, remain unaffected. The latter is disturbed after extirpation of the field 21; however, the shift with respect to the size does not undergo any significant changes. Therefore, two types of visual generalization, i.e. phylogenetically less ancient generalization of the detected properties and evolutionary more ancient subject generalization (invariant image), are located in different parts of the visual brain.

Animals↗
PubMed2005

Development of the central nervous system in the larvacean Oikopleura dioica and the evolution of the chordate brain.

In non-vertebrate chordates, central nervous system (CNS) development has been studied in only two taxa, the Cephalochordata and a single Class (Ascidiacea) of the morphologically diverse Urochordata. To understand development and molecular regionalization of the brain in a different deeply diverging chordate clade, we isolated and determined the expression patterns of orthologs of vertebrate CNS markers (otxa, otxb, otxc, pax6, pax2/5/8a, pax2/5/8b, engrailed, and hox1) in Oikopleura dioica (Subphylum Urochordata, Class Larvacea). The three Oikopleura otx genes are expressed similarly to vertebrate Otx paralogs, demonstrating that trans-homologs converged on similar evolutionary outcomes by independent neo- or subfunctionalization processes during the evolution of the two taxa. This work revealed that the Oikopleura CNS possesses homologs of the vertebrate forebrain, hindbrain, and spinal cord, but not the midbrain. Comparing larvacean gene expression patterns to published results in ascidians disclosed important developmental differences and similarities that suggest mechanisms of development likely present in their last common ancestor. In contrast to ascidians, the lack of a radical reorganization of the CNS as larvaceans become adults allows us to relate embryonic gene expression patterns to three subdivisions of the adult anterior brain. Our study of the Oikopleura brain provides new insights into chordate CNS evolution: first, the absence of midbrain is a urochordate synapomorphy and not a peculiarity of ascidians, perhaps resulting from their drastic CNS metamorphosis; second, there is no convincing evidence for a homolog of a midbrain-hindbrain boundary (MHB) organizer in urochordates; and third, the expression pattern of "MHB-genes" in the urochordate hindbrain suggests that they function in the development of specific neurons rather than in an MHB organizer.

Animals↗
PubMed1985

Electron microscopic study of central axons degeneration in traumatic human brain edema.

Cortical axonal degeneration was studied in seven cortical biopsies taken from patients with traumatic brain injuries. After one day of evolution of brain injury, myelinated axons underwent axonal swelling, myelin sheath vacuolization and distortion, rupture of axolemma and phagocytosis of myelin ovoids by neuroglial cells. After 8 days, the brain trauma induced an increased number of neurofilaments and augmented volume of oligodendroglial ad-axonal cytoplasm. Fifteen days after brain lesion, varicose fiber swelling and retraction of axoplasm were found with disappearance of axoplasmic organelles. After 21 days, the dark type of degeneration was observed in two cases. At this time, hypertrophic oligodendrocytes invaded the myelin sheath and phagocyted the axoplasmic content. After a long evolution time (2 years) the complete sequence of degeneration events could be followed from the initial axoplasmic changes to the advanced degeneration with phagocytosis by neuroglial and invading cells.

Adolescent↗
PubMed2006

Expression and evolution of the mammalian brain gene Ttyh1.

Homologues of the Drosophila melanogaster tweety (tty) gene are present in mammals and Caenorhabditis elegans. The encoded proteins have five predicted membrane-spanning regions and recent findings suggest that some family members may be chloride channels. Phylogenetic analysis of the tty family including novel members from slime mould Entamoeba and plants has revealed the occurrence of independent gene duplication events in different lineages. expressed sequence tag data indicate that expression of the mammalian Ttyh1 gene is restricted mainly to neural tissue and is up-regulated in astrocytoma, glioma and several other cancers. In this study, mammalian expression vectors were used to investigate the subcellular localization and the effect of over-expression of Ttyh1 in human epithelial kidney cells. The results confirm that Ttyh1 is a membrane protein and show that it is deposited on the substratum along the migration paths of motile cells above the alpha5beta1-integrin complex. The ectopic expression of Ttyh1 also induced long filopodia, which were branched and dynamic in both stationary and migratory cells. The filopodia contained F-actin and occurred at the ends of microtubules which were polarized towards the membrane. Upon contact with nearby cells some filopodia stabilized and filled with F-actin, whereas Ttyh1 was highly concentrated at the cell-cell interface. Ttyh1 N- and C-terminal antipeptide antibodies detected Ttyh1 along the axons of neurones in primary rat hippocampal cell cultures, and in situ in whole rat brain slices around the hippocampus and occasionally between cells. These data suggest a role for Ttyh1 in process formation, cell adhesion and possibly as a transmembrane receptor.

Actins↗
PubMed2004

A mosaic pattern characterizes the evolution of the avian brain.

Diversity in vertebrate brain size and composition is thought to arise from either developmental constraints that cause coordinated changes between brain regions or a mosaic model, whereby changes in individual brain regions are independent of changes in other brain regions. These two mechanisms were tested in birds using multiple regression analyses. Across 13 orders, significant correlations were present between some brain regions, but not all. Most of the correlated changes reflect the connectivity between different brain components, such that regions with the most interconnections are correlated with one another but not other brain regions. Whether mosaic changes are characteristic of brain regions or systems in birds, however, to our knowledge, remains to be investigated.

Animals↗
PubMed1984

Brain traits through phylogeny: evolution of neural characters.

We have previously derived a hypothetical tree of the lines of mammalian descent, based upon a comprehensive numerical taxonomic cross-analysis of primitive and derived states of 15 brain traits in 38 representative species. In this communication we use this tree to describe the probable sequence of changes that have taken place in phylogenetic history. 2 characters proved to be multiply convergent, occurring in parallel in several disparate lines of descent. The remaining 9 characters each appeared in ancestors of one or another of the lineages and characterize related progeny.

Animals↗
PubMed2004

Sequence comparison of human and mouse genes reveals a homologous block structure in the promoter regions.

Comparative sequence analysis was carried out for the regions adjacent to experimentally validated transcriptional start sites (TSSs), using 3324 pairs of human and mouse genes. We aligned the upstream putative promoter sequences over the 1-kb proximal regions and found that the sequence conservation could not be further extended at, on average, 510 bp upstream positions of the TSSs. This discontinuous manner of the sequence conservation revealed a "block" structure in about one-third of the putative promoter regions. Consistently, we also observed that G+C content and CpG frequency were significantly different inside and outside the blocks. Within the blocks, the sequence identity was uniformly 65% regardless of their length. About 90% of the previously characterized transcription factor binding sites were located within those blocks. In 46% of the blocks, the 5' ends were bounded by interspersed repetitive elements, some of which may have nucleated the genomic rearrangements. The length of the blocks was shortest in the promoters of genes encoding transcription factors and of genes whose expression patterns are brain specific, which suggests that the evolutional diversifications in the transcriptional modulations should be the most marked in these populations of genes.

Animals↗