Structural and functional organization of a developing brain and formation of cognitive functions in child ontogeny

Results of multidisciplinary studies, including neuromorphological, neurophysiological, neuropsychological, and psychphysiological studies, are reviewed. They allow the brain mechanisms of cognition formation and development during maturation to be identified. The role of regulatory (modulatory) brain systems in forming the cognitive function in the child is demonstrated. Data on considerable changes in the brain systems responsible for the development of cognitive functions in children between the ages of five to six and seven to eight years are presented. At this age, the morphological and functional maturations of the frontal cortical areas and their descending connections with other cerebral structures increase the efficiencies of arbitrary selective attention, learning the activity program, inhibition of spontaneous responses, and regulation and organization of activity, i.e., the functions that are important for successful schooling.     

Form and functional morphology of Raetellops pulchella (Bivalvia: Mactridae): an example of convergent evolution with anomalodesmatans

Abstract. The bivalve Raetellops pulchella is a highly specialized, deposit-feeding member of the Mactridae. Studies of its form and function provide an example of how the bivalve body plan can be modified to facilitate the exploitation of mud as a food resource, and help in understanding how this lifestyle has evolved. Adaptations to this lifestyle include an overall reduction in ctenidial size and loss of the descending lamellae of both outer demibranchs. This reduction is associated with the enlargement of the labial palps to process inhaled sediment. In the mantle cavity, a waste canal below the posterior mantle flaps facilitates pseudofeces removal. The midgut is long and capacious, presumably to cope with the large amounts of ingested organic material. In addition, individuals of R. pulchella have unusually thin, brittle, and rostrate shells, with narrow siphonal gapes. They possess a shell buttress in each valve extending from the hinge plate to above the posterior adductor muscle. This buttress functions to prevent the brittle shell valves from fracturing when adduction occurs. A buttress is also seen in some representatives of the Anomalodesmata; in particular, the situation in R. pulchella is most like that seen in individuals of the similarly deposit-feeding species Offadesma angasi (Anomalodesmata: Periplomatidae). I interpret the similar shell form of these deposit-feeding clams as an example of convergent evolution.     

Variation in Capsella (shepherd's purse): an example of intraspecific functional diversity

The extent of functional trait diversity is quantified for 157 different Capsella bursa-pastoris (L.) medic (shepherd's purse) accessions. These individuals encompass replicate progeny generated from seed of 53 different Capsella 'maternal lines' that were isolated at random as they emerged from soil cores (used to estimate baseline seed bank numbers and weed diversity) at 34 different arable sites across the United Kingdom. The replicate progeny were subject to ex situ characterisation for traits determining life history and architecture. Seven leaf-type classes were identified and representative parents of each leaf type were distinguishable using four different simple sequence repeat markers. Life-history traits were only loosely associated with leaf shape, and cluster analysis grouped the accessions into three broad types: small plants that flowered early with intermediate reproductive output; large plants, with intermediate time to flowering and a high reproductive output; late-flowering plants, of intermediate size and low reproductive output. The most common leaf-type variants (83% of accessions) demonstrated a short time to flowering (ca. 70 days), while rarer variants included those that flowered after 140 days, accumulated more nitrogen and produced less seed: possibly representing advantageous and disadvantageous traits (respectively), in modern arable rotations. A wide trait variation was therefore found in Capsella bursa-pastoris despite decades of agricultural intensification, the range of time-to-flowering for C. bursa-pastoris being as broad the mean flowering times of the commoner annual and winter annual arable species. We propose the use of traits, rather than species, as the accounting unit to quantify functional biodiversity in arable systems.     

Role of sympathetic and parasympathetic mechanisms in formation of secondary cardiac rhythms in rats ontogenesis

In progeny of Wistar rats aged from birth to 3 week, there was studied participation of sympathetic and parasympathetic mechanisms in regulation of cardiac rhythm and its rhythmic oscillations (secondary cardiac rhythms), whose spectral composition was analyzed using rapid Fourier transformation. Consequences, which changed in the process of development, of blockade of -adrenoreceptors by propranolol, of -adrenoreceptors by phentolamine, and of muscarinic cholinoreceptors by atropine as well as of chronic desympathization by guanethidine (isobarine). It was found that due to heterochronia in establishment of functions of sympathetic and parasympathetic nervous systems, reactions to blockade of adreno- and cholinoreceptors for the first 3 weeks of postnatal ontogenesis changed not only quantitatively, but also qualitatively. Blockade of adrenoreceptors in newborn animals leads to an increase of power of the rhythm oscillations in all low-frequency diapasons. The baroreflex function of parasympathetic innervation is well expressed as early as in newborns. Tonic function with respect to frequency of heart rate and power of oscillations in the high-frequency diapason becomes evident only by the 3-week age.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 1, 2005, pp. 69–75.Original Russian Text Copyright © 2005 by Bursian, Sizonov, Semenova, Kulaev, Timofeeva, Polyakova, Dmitrieva.     

Role of functional blocks in the evolution of exotrophy in vertebrates (as exemplified by fish and mammals)

The review reports the data on the presence in fish and mammals of the identical elementary or universal functional blocks (FBs)—molecules and supramolecular complexes providing exotrophic processes, with a special focus on those involved in the regulation of feeding behavior, digestion and transport of nutrients. When describing FBs implementing symbiotic digestion and induced autolysis, the data on the bacterial and mammalian enzymes have been analyzed. It is assumed that the structural and functional similarity of FBs in different organisms, which maintains the existence of trophic networks, is based on the need to perform similar functions and hence to develop similar mechanisms of FB adaptation in organisms phylogenetically distant from each other (bacteria, invertebrates, fish and mammals).     

Pattern and process in the evolution of insect-plant associations: Yponomeuta as an example

Phylogenetic studies are increasing our understanding of the evolution of associations between phytophagous insects and their host plants. Sequential evolution, i.e. the shift of insect herbivores onto pre-existing plant species, appears to be much more common than coevolution, where reciprocal selection between interacting insects and plants is thought to induce chemical diversification and resistance in plants and food specialization in insects.Extreme host specificity is common in phytophagous insects and future studies are likely to reveal even more specialization. Hypotheses that assume that food specialists have selective advantages over generalists do not seem to provide a general explanation for the ubiquity of specialist insect herbivores. Specialists are probably committed to remain so, because they have little evolutionary opportunity to reverse the process due to genetically determined constraints on the evolution of their physiology or nervous system. The same constraints might result in phylogenetic conservatism, i.e. the frequent association of related insect herbivores with related plants. Current phylogenetic evidence, however, indicates that there is no intrinsic direction to the evolution of specialization.Historical aspects of insect-host plant associations will be illustrated with the small ermine moth genus Yponomeuta. Small ermine moths show an ancestral host association with the family Celastraceae. The genus seems to be committed to specialization per se rather than to a particular group of plants. Whatever host shift they have made in their evolutionary past (onto Rosaceae, Crassulaceae, and Salicaceae), they remain monophagous. The oligophagous Y. padellus is the only exception. This species might comprise a mosaic of genetically divergent host-associated populations.     

Catalytic promiscuity in Pseudomonas aeruginosa arylsulfatase as an example of chemistry-driven protein evolution

In recent years, it has become increasingly clear that many enzymes are catalytically "promiscuous". This can provide a springboard for protein evolution, allowing enzymes to acquire novel functionality without compromising their native activities. We present here a detailed study of Pseudomonas aeruginosa arylsulfatase (PAS), which catalyzes the hydrolysis of a number of chemically distinct substrates, with proficiencies comparable to that towards its native reaction. We demonstrate that the main driving force for the promiscuity is the ability to exploit the electrostatic preorganization of the active site for the native substrate, providing an example of chemistry-driven protein evolution.     

Generic physical mechanisms of morphogenesis and pattern formation as determinants in the evolution of multicellular organization

Early embryos of metazoan species are subject to the same set of physical forces and interactions as any small parcels of semi-solid material, living or nonliving. It is proposed that such “generic” properties of embryonic tissues have played a major role in the evolution of biological form and pattern by providing an array of morphological templates, during the early stages of metazoan phylogeny, upon which natural selection could act. The generic physical mechanisms considered include sedimentation, diffusion, and reaction-diffusion coupling, all of which can give rise to chemical nonuniformities (including periodic patterns) in eggs and small multicellular aggregates, and differential adhesion, which can lead to the formation of boundaries of non-mixing between adjacent cell populations. Generic mechanisms that produce chemical patterns, acting in concern with the capacity of cells to modulate their adhesivity (presumed to be a primitive, defining property of metazoa), could lead to multilayered gastrulae of various types, segmental organization, and many of the other distinguishing characteristics of extant and extinct metazoan body plans. Similar generic mechanisms, acting on small tissue primordia during and subsequent to the establishment of the major body plans, could have given rise to the forms of organs, such as the vertebrate limbs. Generic physical processes acting on a single system of cells and cell products can often produce a widely divergent set of morphological phenotypes, and these are proposed to be the raw material of the evolution of form. The establishment of any ecologically successful form by these mechanisms will be followed, under this hypothesis, by a period of genetic evolution, in which the recruitment of gene products to produce the “generically templated” morphologies by redundant pathways would be favoured by intense selection, leading to extensive genetic change with little impact on the fossil record. In this view, the stabilizing and reinforcing functions of natural selection are more important than its ability to effect incremental change in morphology. Aspects of evolution which are problematic from the standard neo-Darwinian viewpoint, or not considered within that framework, but which follow in a straightforward fashion from the view presented here, include the beginnings of an understanding of why organisms have the structure and appearance they’ do, why homoplasy (the recurrent evolution of certain forms) is so prevalent, why evolution has the tempo and mode it does (“punctuated equilibrium”), and why a “rapid” burst of morphological evolution occurred so soon after the origin of the metazoa.     

Changes in functional glutamate receptors on a postsynaptic neuron accompany formation and maturation of an identified synapse

N-Methyl-D-aspartate (NMDA)-type glutamate receptors play important roles at developing synapses and in activity-dependent synaptic plasticity. Recent studies in Aplysia suggest that NMDA-like receptors may contribute to some forms of plasticity of sensorimotor synapses accompanying associative learning. We examined at various times after plating neurons in culture the contribution of NMDA- and alpha-amino-3 hydroxy-5 methyl-4 isoxazole proprionic acid (AMPA)-like glutamate receptors to responses evoked in motor cell L7 either by action potentials in sensory neurons (SNs) or by focal applications of glutamate. We found that (D,L)-2-amino-5-phosphopentoic acid-sensitive receptors contributed significantly to postsynaptic responses in 1-day cultures but contributed little in the same cultures on day 4. By contrast, postsynaptic responses on day 4 increased significantly in amplitude by the addition of functional 6-cyano-7 nitroquinoxaline-2,3-dione- or 1-(4-aminophenyl)-4-methyl-7,8-methylendioxy-5H-2,3-benzodiazepine hydrochloride-sensitive receptors. Receptors with NMDA-like properties are detected on day 1 only at sites on L7 apposed to SN varicosities, and are not detected on L7 cultured alone. The results indicate that changes in expression and distribution of functional receptors on L7 accompany the formation and maturation of SN synapses. Signals from the SN appear to trigger expression and clustering of functional NMDA-like receptors at sites contacted by presynaptic structures capable of transmitter release. With time, functional AMPA-like receptors are added to these sites enhancing synaptic efficacy. The results are consistent with the idea that the expression and sequential clustering of NMDA- and AMPA-type receptors may be essential for the formation and maturation of central synapses.     

Food bodies in Cissus verticillata (Vitaceae): ontogenesis, structure and functional aspects

Background and Aims

The distinction between pearl bodies (or pearl glands) and food bodies (FBs) is not clear; neither is our understanding of what these structures really represent. The present work examined the ontogenesis, structure, ultrastructure and histochemical aspects of the protuberances in Cissus verticillata, which have been described since the beginning of the 19th century as pearl glands or pearl bodies, in order to establish a relationship between their structure and function.

Methods

Segments of stems and leaves in different stages of development were collected and fixed for study under light microscopy as well as electron transmission and scanning microscopy. Samples of FBs were subjected to chemical analysis using thin-layer chromatography.

Key Results

The FBs in C. verticillata are globose and attached to the plant by a short peduncle. These structures are present along the entire stem during primary growth, and on the inflorescence axis and the abaxial face of the leaves. The FBs were observed to be of mixed origin, with the participation of both the epidermis and the underlying parenchymatic cells. The epidermis is uniseriate with a thin cuticle, and the cells have dense cytoplasm and a large nucleus. The internal parenchymatic cells have thin walls; in the young structures these cells have dense cytoplasm with a predominance of mitochondria and plastids. In the mature FBs, the parenchymatic cells accumulate oils and soluble sugars; dictyosomes and rough endoplasmic reticulum predominate in the cytoplasm; the vacuoles are ample. Removal of the FBs appears to stimulate the formation of new ones, at the same place.

Conclusions

The vegetative vigour of the plant seems to influence the number of FBs produced, with more vigorous branches having greater densities of FBs. The results allow the conclusion that the structures traditionally designated pearl glands or pearl bodies in C. verticillata constitute FBs that can recruit large numbers of ants.Key words: Ant–plant interactions, Cissus verticillata, food bodies, myrmecophily, pearl glands, pearl bodies, cell ultrastructure, Vitaceae     

Microparticle-enhanced cultivation of filamentous microorganisms: increased chloroperoxidase formation by Caldariomyces fumago as an example

Microparticle-enhanced cultivation (MPEC) was applied as a novel method for improved biomass and product formation during cultivation of filamentous microorganisms. Exemplarily, chloroperoxidase (CPO) formation by Caldariomyces fumago was analyzed in the presence and absence of microparticles of different size. Particles of approximately 500 microm in diameter had no effect on growth morphology or productivity of CPO formation by C. fumago. In contrast particles of < or =42 microm in diameter led to the dispersion of the C. fumago mycelia up to the level of single hyphae. Under these conditions the maximum specific productivity of CPO formation was enhanced about fivefold and an accumulated CPO activity in the culture supernatant of more than 1,000 U mL(-1) was achieved after 10-12 days of cultivation. In addition, the novel cultivation method also showed a positive effect on growth characteristics of other filamentous microorganisms proven by the stimulation of single hyphae/cell formation.     

Expression and function of Xenopus laevis p75(NTR) suggest evolution of developmental regulatory mechanisms

Neurotrophins signal through two different classes of receptors, members of the trk family of receptor tyrosine kinases, and p75 neurotrophin receptor (p75(NTR)), a member of the tumor necrosis factor receptor family. While neurotrophin binding to trks results in, among other things, increased cell survival, p75(NTR) has enigmatically been implicated in promoting both survival and cell death. Which of these two signals p75(NTR) imparts depends on the specific cellular context. Xenopus laevis is an excellent system in which to study p75(NTR) function in vivo because of its amenability to experimental manipulation. We therefore cloned partial cDNAs of two p75(NTR) genes from Xenopus, which we have termed p75(NTR)a and p75(NTR)b. We then cloned two different cDNAs, both of which encompass the full coding region of p75(NTR)a. Early in development both p75(NTR)a and p75(NTR)b are expressed in developing cranial ganglia and presumptive spinal sensory neurons, similar to what is observed in other species. Later, p75(NTR)a expression largely continues to parallel p75(NTR) expression in other species. However, Xenopus p75(NTR)a is additionally expressed in the neuroepithelium of the anterior telencephalon, all layers of the retina including the photoreceptor layer, and functioning axial skeletal muscle. Finally, misexpression of full length p75(NTR) and each of two truncated mutants in developing retina reveal that p75(NTR) probably signals for cell survival in this system. This result contrasts with the reported role of p75(NTR) in developing retinae of other species, and the possible implications of this difference are discussed.     

Population of hortobiontic heteropterans in urbanized territories (with Kemerovo as an example)

Hortobiontic Heteroptera in the city of Kemerovo are represented by 71 species of 50 genera and 12 families, with the dominating family Miridae. The richest assemblages as to the number of species were observed in lawns.