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At least 919 records · Page 51Linked to original sources

PubMed2005

Brachial plexus injuries in the adult. nerve transfers: the Siriraj Hospital experience.

A strategy that uses the selective combination of neurotizations can yield a moderate degree of shoulder and elbow control. Even though some wrist and finger movement can occasionally be achieved by the current methods of neurotization,the results in terms of restoration of useful hand function are still far from satisfactory. The use of intraplexal and contralateral plexal neurotization combined with free-functioning muscle transfer and the better understanding of central-peripheral function integration may provide more purposeful hand function in the future.

Adult↗

PubMed2003

Evolution of trypsinogen activation peptides.

The activation peptide of mammalian trypsinogens contains a highly conserved tetra-aspartate sequence (D19-D20-D21-D22) preceding the K23-I24 scissile peptide bond, which is hydrolyzed as the first step in the activation process. Here, we examined the evolution and function of trypsinogen activation peptides through integrating functional characterization of disease-associated mutations with comparative genomic analysis. Activation properties of three chronic pancreatitis-associated activation peptide mutants (the novel D19A and the previously reported D22G and K23R) were simultaneously analyzed, for the first time, in the context of recombinant human cationic trypsinogen. A dramatic increase in autoactivation of cationic trypsinogen was observed in all three mutants, with D22G and K23R exhibiting the most marked increases. The physiological activator enteropeptidase activated the D19A mutant normally, activated the D22G mutant very poorly, and stimulated activation of the K23R mutant. The biochemical and structural data, taken together with a comprehensive sequence comparison, indicates that the tetra-aspartate sequence in mammalian trypsinogen activation peptides has evolved not only for optimal enteropeptidase recognition in the duodenum but also for efficient inhibition of trypsinogen autoactivation within the pancreas. Moreover, the use of lysine instead of arginine at the P1 position of activation peptides also has an advantageous effect against trypsinogen autoactivation. Finally, fixed substitutions in the key residues of the trypsinogen activation peptide may suggest the evolution of new functions unrelated to digestion, as found in the group III trypsinogens of cold-adapted fishes.

Amino Acid Sequence↗

PubMed1986

In vitro transcription of a human hsp 70 heat shock gene by extracts prepared from heat-shocked and non-heat-shocked human cells.

A cDNA clone homologous to HeLa cell mRNA encoding the 70 kDa human heat shock protein (hsp 70) was used to isolate a recombinant phage containing an entire human hsp 70 gene. Sequence analysis of the 5' and 3' flanking regions revealed the structural integrity of the regulatory elements. The functional integrity of this hsp 70 gene was substantiated by in vitro transcription studies with nuclear extracts. Specific run-off transcripts, synthesized by RNA polymerase II, were obtained with extracts prepared from heat-shocked cells. Extracts from non-heat-shocked cells were found inactive in hsp 70 gene transcription. However, 5' deletion mutants lacking the heat shock element (HSE) were transcribed by both heat shock and nonheat shock HeLa extracts.

Adenoviruses, Human↗

PubMed2002

Coherent structures in a turbulent environment.

A systematic method is proposed for the determination of the statistical properties of a field consisting of a coherent structure interacting with turbulent linear waves. The explicit expression of the generating functional of the correlations is obtained, performing the functional integration on a neighborhood in the function space around the soliton. The results show that the non-Gaussian fluctuations observed in the plasma edge can be explained by the intermittent formation of nonlinear coherent structures.

Journal Article↗

PubMed1983

Relationship between the amplitudes of the b wave and the a wave as a useful index for evaluating the electroretinogram.

The present methods for the assessment of the electroretinogram (ERG) make the exchange of data between laboratories difficult owing to differences in photostimulation and recording techniques. In this study it is suggested that in addition to present techniques the b wave to a wave relationship may be a useful index for evaluating the ERG. The ERG responses evoked by relatively bright flashes are recorded in the dark-adapted state. A plot of the b wave amplitude as a function of the a wave amplitude describes the functional integrity of the retina. A normally functioning retina should elicit an ERG response that fits the normal curve regardless of the apparatus used for ERG recording. The only constraint is the use of full-field illumination. This method is based on physiological considerations regarding the origin of the ERG components. Such a method will facilitate data exchange between centres and can also be used for clinical assessment of the retina.

Dark Adaptation↗

PubMed1984

Postural and oculomotor signs in labyrinthine-defective subjects.

Bilabyrinthless subjects, i.e. subjects clinically devoid of labyrinthine responses, show a greater than normal decrease in postural stability following eye closure. Because changes in head position, which affect posture in healthy subjects, do not do so in bilabyrinthless patients, static afferent information from healthy neck receptors does not contribute to postural stabilization. Somatosensory nystagmus and dynamic cervico-ocular responses are equally greater in bilabyrinthless than normal subjects, which indicates that both categories of eye movements are mediated by the same mechanism. Optokinetic nystagmus is slightly diminished in bilabyrinthless patients and optokinetic after-nystagmus was mostly absent. In terms of the Raphan-Cohen model our findings confirm that destruction of the labyrinthine function abolishes the vestibulo-ocular integrator function.

Ear, Inner↗

PubMed1981

Outcome of the in vitro studies on drug absorption employing the isolated rat small intestine.

The in vitro methods for studying the intestinal absorption of drugs involving the use of the isolated rat small intestine are reviewed in order to provide indications on their actual usefulness and limitations. The most significant works dealing with the structural integrity of the intestinal mucosa, the functional integrity of the isolated intestine, the factors influencing passive transport such as pH, sugars, ions, physiological and synthetic surface-active agents, and complexation, are reviewed.

Animals↗

PubMed1995

An object-oriented model for the integration of knowledge-based systems.

This paper discusses functional integration, data integration, and knowledge integration as basic problems concerning the integration of knowledge-based systems into a hospital information system. A system model for an integrated knowledge-based system is introduced. Object-oriented models for the systems meta-database, patient database, and knowledge-base are presented. It is expected that the reader is familiar with the basic concepts of the object-oriented approach.

Artificial Intelligence↗

PubMed1983

Right cerebral hemispheric function: behavioral correlates.

Studies of cerebral asymmetry generally support verbal-analytic functions on the left hemisphere and nonverbal, integrative functions on the right. The hypothesis of this investigation was that right hemisphere functions have greater significance for adaptive behaviors, i.e., verbal-analytic abilities are not specifically related to environmental adjustment or coping skills. Right hemispherically strong children were compared with normal controls along six behavioral parameters. The results supported environmental awareness and adaptive skills as related more to the right hemisphere than the left. It is suggested that self-monitoring of behavior and possibly affective integration appear to be more related to the processing of spatial, sequential information on the right hemisphere than verbal-analytic functions on the left.

Adolescent↗

PubMedDate not supplied

Connectivity and complexity: the relationship between neuroanatomy and brain dynamics.

Nervous systems facing complex environments have to balance two seemingly opposing requirements. First, there is a need quickly and reliably to extract important features from sensory inputs. This is accomplished by functionally segregated (specialized) sets of neurons, e.g. those found in different cortical areas. Second, there is a need to generate coherent perceptual and cognitive states allowing an organism to respond to objects and events, which represent conjunctions of numerous individual features. This need is accomplished by functional integration of the activity of specialized neurons through their dynamic interactions. These interactions produce patterns of temporal correlations or functional connectivity involving distributed neuronal populations, both within and across cortical areas. Empirical and computational studies suggest that changes in functional connectivity may underlie specific perceptual and cognitive states and involve the integration of information across specialized areas of the brain. The interplay between functional segregation and integration can be quantitatively captured using concepts from statistical information theory, in particular by defining a measure of neural complexity. Complexity measures the extent to which a pattern of functional connectivity produced by units or areas within a neural system combines the dual requirements of functional segregation and integration. We find that specific neuroanatomical motifs are uniquely associated with high levels of complexity and that such motifs are embedded in the pattern of long-range cortico-cortical pathways linking segregated areas of the mammalian cerebral cortex. Our theoretical findings offer new insight into the intricate relationship between connectivity and complexity in the nervous system.

Animals↗

PubMed2005

Motor control in the human spinal cord.

Features of the human spinal cord motor control are described using two spinal cord injury models: (i) the spinal cord completely separated from brain motor structures by accidental injury; (ii) the spinal cord receiving reduced and altered supraspinal input due to an incomplete lesion. Systematic studies using surface electrode polyelectromyography were carried out to assess skeletal muscle reflex responses to single and repetitve stimulation in a large number of subjects. In complete spinal cord injured subjects the functional integrity of three different neuronal circuits below the lesion level is demonstrated: first, simple mono- and oligosynaptic reflex arcs and polysynaptic pathways; second, propriospinal interneuron system with their cell in the gray matter and the axons in the white matter of the spinal cord conducting activity between different spinal cord segments; and third, internuncial gray matter neurons with short axons and dense neuron contact within the spinal gray matter. All of these three systems participate continuously in the generation of spinal cord reflex output activating muscles. The integration of these systems and their relative degree of excitation and set-up produces characteristic functions of motor control. In incomplete spinal cord injured patients, the implementation of brain motor control depends on the profile of residual brain descending input and its integration with the functional neuronal circuits below the lesion. Locomotor patterns result from the establishment of a new structural relationship between brain and spinal cord. The functions of this new structural relationship are expressed as an alternative, but characteristic and consistent neurocontrol. The more we know about how the brain governs spinal cord networks, the better we can describe human motor control. On the other hand such knowledge is essential for the restoration of residual functions and for the construction of new cord circuitry to expand the functions of the injured spinal cord.

Electric Stimulation↗

PubMed1999

[The quantitative assessment of functional disorders of the hand and upper limb].

Methods have been developed for calculation of quantitative indicators of the hand and upper limb function, which rely on measurement of sensitivity of fingers, the pick-objects-up test (a modified Moberg test), measurement of active and passive movements of joints, hand grips. The following quantitative indicators are computable from formulae: sensitivity, motor function of joints, grips/grasps, coordination of movements. Based on the above four indicators is computation of the integral function of the hand and upper extremity. Computation procedure for quantitative determinants of the upper limb function has been approved of in 156 patients with sequelae of injuries. For a comparative analysis an assessment was performed in these patients of the nerve function by the scoring scale M0-M5, S0-S5, and of the tendon function by the methodology of the American Association of surgeons of the hand and as recommended by Strickland J. W. (1989). The proposed methodology significantly reflects the principal determinants of the function, secures quantitative data on different aspects and integral determinants of the function of the hand and upper extremity.

Amputation, Traumatic↗

PubMed2002

Evaluation of renal glomerular and tubular functional and structural integrity in neonates.

BACKGROUND: Renal cells are not fully differentiated at birth, representing a major risk in preterm infants. We evaluated glomerular and tubular functional integrity as well as structural integrity of renal tubules among healthy full-term and preterm infants as well as diseased preterm infants. METHODS: A total of 50 newborns (10 healthy full-term, 10 healthy preterm, and 30 diseased preterm, at 38.9 +/- 1.10, 34.2 +/- 0.92, and 32 +/- 2.47 weeks gestational age, respectively) were included in the present study. Glomerular function was assessed by measuring urinary levels of both microalbumin and immunoglobulin G as well as serum creatinine levels, whereas the proximal tubular function was investigated by measuring the urinary levels of both alpha1-microglobulin and beta2-microglobulin as well as retinol-binding protein. Also, distal tubular reabsorption capacity was investigated by assessing fractional excretion of sodium. Moreover, the structural integrity of renal proximal tubules was studied by measuring the urinary activities of both the brush-border membrane enzyme leucine-aminopeptidase (LAP) and the lysosomal enzyme N-acetyl-beta-D-glucosaminidase. The preceding investigations were done on both the first and third days of life of all 50 newborns. RESULTS: Glomerular and tubular function and structure was relatively impaired at birth among both healthy and diseased preterm as well as healthy full-term neonates and improved rapidly thereafter. The diseased preterm neonates showed worse renal function and structure with minimal improvement regardless of the underlying sickness. CONCLUSION: Renal insufficiency and renal immaturity could be evaluated using enzymuria and low- and high-molecular-weight proteinuria as noninvasive methods.

Albumins↗

PubMed1997

Clathrin-coated vesicle formation and protein sorting: an integrated process.

Clathrin-coated vesicles were the first discovered and remain the most extensively characterized transport vesicles. They mediate endocytosis of transmembrane receptors and transport of newly synthesized lysosomal hydrolases from the trans-Golgi network to the lysosome. Cell-free assays for coat assembly, membrane binding, and coated vesicle budding have provided detailed functional and structural information about how the major coat constituents, clathrin and the adaptor protein complexes, interact with each other, with membranes, and with the sorting signals found on cargo molecules. Coat constituents not only serve to shape the budding vesicle, but also play a direct role in the packaging of cargo, suggesting that protein sorting and vesicle budding are functionally integrated. The functional interplay between the coated vesicle machinery and its cargo could ensure sorting fidelity and packaging efficiency and might enable modulation of vesicular trafficking in response to demand.

Adaptor Protein Complex alpha Subunits↗

PubMed1998

Mammalian sex determination: from gonads to brain.

In mammals, sex is determined by the Y chromosome, which encodes a testis-determining factor (TDF). This factor causes the undifferentiated embryonic gonads to develop as testes rather than ovaries. The testes subsequently produce the male sex hormones that are responsible for all male sexual characteristics. In 1990, the sex-determining gene, TDF, was identified and termed SRY in humans (Sry in mice). It encodes a protein containing a high mobility group (HMG) motif, which confers the ability to bind and to bend DNA. Genetic evidence supporting SRY as TDF came from the observation of a male phenotype in XX mice transgenic for a small genomic fragment containing Sry, and from the study of XY sex-reversed individuals who harbor de novo mutations in the SRY coding sequence. Other non-Y-linked genes involved in sex determination were subsequently found by genetic analysis of XY sex-reversed patients not explained by mutations in SRY. These genes are WT1, SF1, DAX1, and SOX9. A regulatory cascade hypothesis for mammalian sex determination, proposing that SRY represses a negative regulator of male development, was recently supported by observation of mice that expressed a DAX1 transgene and developed as XY sex-reversed females. The role of some sex-determining genes, such as DAX1 and SF1, in the development of the entire reproductive axis, a functionally integrated endocrine axis, leads to a new concept. Normal sexual development may result from the functional and developmental integration of a number of different genes that play roles in sex determination, sexual differentiation, and sexual behavior.

Amino Acid Sequence↗

PubMed2006

A structural equation model to integrate changes in functional strategies during old-field succession.

From a functional perspective, changes in abundance, and ultimately species replacement, during succession are a consequence of integrated suites of traits conferring different relative ecological advantages as the environment changes over time. Here we use structural equations to model the interspecific relationships between these integrated functional traits using 34 herbaceous species from a Mediterranean old-field succession and thus quantify the notion of a plant strategy. We measured plant traits related to plant vegetative and reproductive size, leaf functioning, reproductive phenology, seed mass, and production on 15 individuals per species monitored during one growing season. The resulting structural equation model successfully accounts for the pattern of trait covariation during the first 45 years post-abandonment using just two forcing variables: time since site abandonment and seed mass; no association between time since field abandonment and seed mass was observed over these herbaceous stages of secondary succession. All other predicted traits values are determined by these two variables and the cause-effect linkage between them. Adding pre-reproductive vegetative mass as a third forcing variable noticeably increased the predictive power of the model. Increasing the time after abandonment favors species with increasing life span and pre-reproductive biomass and decreasing specific leaf area. Allometric coefficients relating vegetative and reproductive components of plant size were in accordance with allometry theory. The model confirmed the trade-off between seed mass and seed number. Maximum plant height and seed mass were major determinants of reproductive phenology. Our results show that beyond verbal conceptualization, plant ecological strategies can be quantified and modeled.

Ecology↗

PubMed2006

Experimentally tracing the key steps in the origin of life: The aromatic world.

Life is generally believed to emerge on Earth, to be at least functionally similar to life as we know it today, and to be much simpler than modern life. Although minimal life is notoriously difficult to define, a molecular system can be considered alive if it turns resources into building blocks, replicates, and evolves. Primitive life may have consisted of a compartmentalized genetic system coupled with an energy-harvesting mechanism. How prebiotic building blocks self-assemble and transform themselves into a minimal living system can be broken into two questions: (1) How can prebiotic building blocks form containers, metabolic networks, and informational polymers? (2) How can these three components cooperatively organize to form a protocell that satisfies the minimal requirements for a living system? The functional integration of these components is a difficult puzzle that requires cooperation among all the aspects of protocell assembly: starting material, reaction mechanisms, thermodynamics, and the integration of the inheritance, metabolism, and container functionalities. Protocells may have been self-assembled from components different from those used in modern biochemistry. We propose that assemblies based on aromatic hydrocarbons may have been the most abundant flexible and stable organic materials on the primitive Earth and discuss their possible integration into a minimal life form. In this paper we attempt to combine current knowledge of the composition of prebiotic organic material of extraterrestrial and terrestrial origin, and put these in the context of possible prebiotic scenarios. We also describe laboratory experiments that might help clarify the transition from nonliving to living matter using aromatic material. This paper presents an interdisciplinary approach to interface state of the art knowledge in astrochemistry, prebiotic chemistry, and artificial life research.

Hydrocarbons, Aromatic↗

PubMed2005

Immunocytochemical characterization of the incubated rat renal cortical slices.

The use of renal cortical slices in vitro and the data obtained in these studies have been subjects of controversy, largely due to uncertain viability, e.g., structural and functional integrity of the proximal and other tubules. However, detailed studies of tubule integrity have not been reported. To correlate functional and structural viability of the hand-cut rat renal cortical slices, incubated in optimally conditioned media for up to 25 h, we studied the time course of p-aminohippurate (PAH) uptake, the immunocytochemical distribution of several proteins that reside in the proximal tubule basolateral [Na/K-ATPase, organic anion transporters (OAT)1 and OAT3], or brush border [megalin, sodium-proton exchanger (NHE)3] membrane, as well as the general integrity of the tubule epithelium and its cytoskeleton (actin filaments, microtubules). PAH uptake in slices was proportional to time within 1 h of incubation and gradually declined thereafter. The immunostaining experiments indicated a fast, time-dependent loss of basolateral transporters, at a rate of OAT1 > Na/K-ATPase > OAT3. In the brush border membrane, the loss of megalin was faster than that of NHE3, and a partial redistribution of NHE3 into the basolateral domain indicated the loss of cell polarity. The loss of intracellular actin and tubulin cytoskeleton in the proximal tubule was already visible after 15 min of incubation and gradually increased with time, whereas a partial redistribution of actin to the basolateral domain indicated a compromised polarity of the cells. The data also revealed very early (after 15 min) necrotic events in the proximal tubule epithelium, with sloughing of brush border and cell debris into the tubule lumen, detachment of cells from the basal membrane, and opening and widening of the tubule lumen. We conclude that the loss of cellular structure, cytoskeleton, and cell membrane transporters in the nephron epithelium is a very early event in the incubated rat renal cortical slices.

Actins↗