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PubMed1985

Primary structure of papain-solubilized human histocompatibility antigen HLA-B27.

The complete amino acid sequence of papain-solubilized HLA-B27, an antigen that presents a very strong association to the development of ankylosing spondylitis, has been determined. The overall sequence homology with the cross-reactive allelic products HLA-B7 and HLA-B40 (Bw60) is 93% and 92%, respectively. Half of the differences between HLA-B27 and -B7 are located in segments 63-83 and 113-116. Most of the known HLA class I antigens are different in these segments, and it is suggested that the corresponding residues may be involved in the alloantigenic determinants of HLA-B27. A free cysteine residue is present at position 67, and it is at least partially exposed to solvent. In addition, other differences are found in various areas of the two N-terminal domains. The comparison with available HLA class I sequences allows an evaluation of their contribution to the antigenic polymorphism of these molecules. The relevance of these data is discussed in connection with the mapping of functional sites of HLA class I antigens and with the association between HLA-B27 and ankylosing spondylitis.

Amino Acid Sequence↗
PubMed2006

Analysis of lanthanide-induced NMR shifts of the Ce@C82 anion.

The mapping of bond connectivity in the carbon cage of [Ce@C82]- and full assignment of the NMR lines were successfully achieved by means of 2D INADEQUATE NMR measurement. Paramagnetic NMR analysis shows that the Ce atom in [Ce@C82]- is located at an off-centered position adjacent to a hexagonal ring along the C2 axis of the C2v-C82 cage.

Journal Article↗
PubMed2000

A comparison of folding techniques in the chemical synthesis of the epidermal growth factor-like domain in neu differentiation factor alpha/beta.

The 52-residue alpha/beta chimera of the epidermal growth factor-like domain in neu differentiation factor (NDFealpha/beta) has been synthesized and folded to form a three disulfide bridge (Cys182-Cys196, Cys190-Cys210, Cys212-Cys221) containing peptide. We investigated two general strategies for the formation of the intramolecular disulfide bridges including, the single-step approach, which used fully deprotected and reduced peptide, and a sequential approach that relied on orthogonal cysteine protection in which specific pairs are excluded from the first oxidation step. Because there are 15 possible disulfide bridge arrangements in a peptide with six cysteines, the one-step approach may not always provide the desired disulfide pairing. Here, we compare the single-step approach with a systematic evaluation of the sequential approach. We employed the acetamidomethyl group to protect each pair of cysteines involved in disulfide bridges, i.e. Cys182 to Cys196, Cys190 to Cys210 and Cys212 to Cys221. This reduced the number of possible disulfide patterns from 15 to three in the first folding step. We compared the efficiencies of folding for each protected pair using RP-HPLC, mapped the disulfide connectivity of the predominant product and then formed the final disulfide from the partially folded intermediate via 12 oxidation. Only the peptide having the Cys182-Cys196 pair blocked with acetamidomethyl forms the desired disulfide isomer (Cys190-Cys210/Cys212-Cys221) as a single homogeneous product. By optimizing both approaches, as well as other steps in the synthesis, we can now rapidly provide large-scale syntheses of NDFealpha/beta and other novel EGF-like peptides.

Amino Acid Sequence↗
PubMed2001

Identifying regulatory networks by combinatorial analysis of promoter elements.

Several computational methods based on microarray data are currently used to study genome-wide transcriptional regulation. Few studies, however, address the combinatorial nature of transcription, a well-established phenomenon in eukaryotes. Here we describe a new approach using microarray data to uncover novel functional motif combinations in the promoters of Saccharomyces cerevisiae. In addition to identifying novel motif combinations that affect expression patterns during the cell cycle, sporulation and various stress responses, we observed regulatory cross-talk among several of these processes. We have also generated motif-association maps that provide a global view of transcription networks. The maps are highly connected, suggesting that a small number of transcription factors are responsible for a complex set of expression patterns in diverse conditions. This approach may be useful for modeling transcriptional regulatory networks in more complex eukaryotes.

Cell Cycle↗
PubMed1988

Consequences for medical education of problem-solving in science and medicine.

The problem-solving process used by scientists and by clinicians is compared and contrasted. The most creative step for both groups is the ability to make an association between some external stimulus or situation and concepts stored in memory. Medical education must put more emphasis on teaching that improves students' abilities to make these associations. Two teaching methods that can promote development of the necessary association skills in clinical contexts--"wait time" and "concept mapping"--are briefly reviewed. Concept mapping consists of connecting words that represent concepts with lines that represent relationships and then labeling the lines. Wait time is waiting three to five seconds between asking a group of students a question and calling on a student to answer or waiting three to five seconds before responding to the student's answer.

Association↗
PubMed2005

Uneven distribution of expressed sequence tag loci on maize pachytene chromosomes.

Examining the relationships among DNA sequence, meiotic recombination, and chromosome structure at a genome-wide scale has been difficult because only a few markers connect genetic linkage maps with physical maps. Here, we have positioned 1195 genetically mapped expressed sequence tag (EST) markers onto the 10 pachytene chromosomes of maize by using a newly developed resource, the RN-cM map. The RN-cM map charts the distribution of crossing over in the form of recombination nodules (RNs) along synaptonemal complexes (SCs, pachytene chromosomes) and allows genetic cM distances to be converted into physical micrometer distances on chromosomes. When this conversion is made, most of the EST markers used in the study are located distally on the chromosomes in euchromatin. ESTs are significantly clustered on chromosomes, even when only euchromatic chromosomal segments are considered. Gene density and recombination rate (as measured by EST and RN frequencies, respectively) are strongly correlated. However, crossover frequencies for telomeric intervals are much higher than was expected from their EST frequencies. For pachytene chromosomes, EST density is about fourfold higher in euchromatin compared with heterochromatin, while DNA density is 1.4 times higher in heterochromatin than in euchromatin. Based on DNA density values and the fraction of pachytene chromosome length that is euchromatic, we estimate that approximately 1500 Mbp of the maize genome is in euchromatin. This overview of the organization of the maize genome will be useful in examining genome and chromosome evolution in plants.

Chromosome Mapping↗
PubMed1997

A physical map of human chromosome 7: an integrated YAC contig map with average STS spacing of 79 kb.

The construction of highly integrated and annotated physical maps of human chromosomes represents a critical goal of the ongoing Human Genome Project. Our laboratory has focused on developing a physical map of human chromosome 7, a approximately 170-Mb segment of DNA that corresponds to an estimated 5% of the human genome. Using a yeast artificial chromosome (YAC)-based sequence-tagged site (STS)-content mapping strategy, 2150 chromosome 7-specific STSs have been established and mapped to a collection of YACs highly enriched for chromosome 7 DNA. The STSs correspond to sequences generated from a variety of DNA sources, with particular emphasis placed on YAC insert ends, genetic markers, and genes. The YACs include a set of relatively nonchimeric clones from a human-hamster hybrid cell line as well as clones isolated from total genomic libraries. For map integration, we have localized 260 STSs corresponding to Genethon genetic markers and 259 STSs corresponding to markers orders by radiation hybrid (RH) mapping on our YAC contigs. Analysis of the data with the program SEGMAP results in the assembly of 22 contigs that are "anchored" on the Genethon genetic map, the RH map, and/or the cytogenetic map. These 22 contigs are ordered relative to one another, are (in all but 3 cases) oriented relative to the centromere and telomeres, and contain > 98% of the mapped STSs. The largest anchored YAC contig, accounting for most of 7p, contains 634 STSs and 1260 YACs. An additional 14 contigs, accounting for approximately 1.5% of the mapped STSs, are assembled but remain unanchored on either the genetic or RH map. Therefore, these 14 "orphan" contigs are not ordered relative to other contigs. In our contig maps, adjacent STSs are connected by two or more YACs in > 95% of cases. With 2150 mapped STSs, our map provides an average STS spacing of approximately 79 kb. The physical map we report here exceeds the goal of 100-kb average STS spacing and should provide an excellent framework for systematic sequencing of the chromosome.

Chromosome Mapping↗
PubMed2003

Dimension change, coarse grained coding and pattern recognition in spatio-temporal nonlinear systems.

Several research programs employing spatio-temporal recurrent dynamics and changes in dimensionality have extended the dialog on neural computation and coding beyond classical frameworks such as feed forward and attractor neural networks and feature detectors. Some have emphasized spiking networks, while others emphasize oscillations and synchronization as the locus of computation and coding. In this paper, the formalism of locally connected homogeneous coupled map lattices is described. Its deployment in an extended version of the dynamical recognizer framework is described, and is compared with density coding, computational mechanics, and liquid state machine frameworks for neural computation. A population coding strategy based on coarse graining the continuous valued distribution of all sites in the lattice is developed and examined as a form of dimension reduction. Results on recognition of 3-D objects are reported. In order to better understand the dynamics supporting recognition, measures suggested by these other research programs and computational frameworks were examined. Dynamics trajectories from object recognition trials were examined for correlation with recognition rates and measures of the distance of the representation space statistics between the target objects and noise initial conditions, and the intrinsic separation between different objects in the set to be classified were performed. These results raise questions about the efficacy of density coding as an explanation for the results, and on the validity of recent criticisms that chaotic systems cannot satisfy separation requirements required for real time computation.

Artifacts↗
PubMed1999

Long-range inhibition within the zebra finch song nucleus RA can coordinate the firing of multiple projection neurons.

The zebra finch forebrain song control nucleus RA (robust nucleus of the archistriatum) generates a phasic and temporally precise neural signal that drives vocal and respiratory motoneurons during singing. RA's output during singing predicts individual notes, even though afferent drive to RA from the song nucleus HVc is more tonic, and predicts song syllables, independent of the particular notes that comprise the syllable. Therefore RA's intrinsic circuitry transforms neural activity from HVc into a highly precise premotor output. To understand how RA's intrinsic circuitry effects this transformation, we characterized RA interneurons and projection neurons using intracellular recordings in brain slices. RA interneurons fired fast action potentials with steep current-frequency relationships and had small somata with thin aspinous processes that extended throughout large portions of the nucleus; the similarity of their fine processes to those labeled with a glutamic acid decarboxylase (GAD) antibody strongly suggests that these interneurons are GABAergic. Electrical stimulation revealed that RA interneurons receive excitatory inputs from RA's afferents, the lateral magnocellular nucleus of the anterior neostriatum (LMAN) and HVc, and from local axon collaterals of RA projection neurons. To map the functional connections that RA interneurons make onto RA projection neurons, we focally uncaged glutamate, revealing long-range inhibitory connections in RA. Thus these interneurons provide fast feed-forward and feedback inhibition to RA projection neurons and could help create the phasic pattern of bursts and pauses that characterizes RA output during singing. Furthermore, selectively activating the inhibitory network phase locks the firing of otherwise unconnected pairs of projection neurons, suggesting that local inhibition could coordinate RA output during singing.

Amygdala↗
PubMed2000

Brain plasticity and stroke rehabilitation. The Willis lecture.

Neuronal connections and cortical maps are continuously remodeled by our experience. Knowledge of the potential capabilityof the brain to compensate for lesions is a prerequisite for optimal stroke rehabilitation strategies. Experimental focal cortical lesions induce changes in adjacent cortex and in the contralateral hemisphere. Neuroimaging studies in stroke patients indicate altered poststroke activation patterns, which suggest some functional reorganization. To what extent functional imaging data correspond to outcome data needs to be evaluated. Reorganization may be the principle process responsible for recovery of function after stroke, but what are the limits, and to what extent can postischemic intervention facilitate such changes? Postoperative housing of animals in an enriched environment can significantly enhance functional outcome and can also interact with other interventions, including neocortical grafting. What role will neuronal progenitor cells play in future rehabilitation-stimulated in situ or as neural replacement? And what is the future for blocking neural growth inhibitory factors? Better knowledge of postischemic molecular and neurophysiological events, and close interaction between basic and applied research, will hopefully enable us to design rehabilitation strategies based on neurobiological principles in a not-too-distant future.

Age Factors↗
PubMed2001

Activity-dependent factors affecting poststroke functional outcomes.

Over the last several years, there has been increasing recognition of the potential for central nervous system (CNS) recovery after brain damage. One commonality across the recovery and brain plasticity literature is that practice induces plastic, dynamic changes in the CNS. However, more than simply repetition, it is the manipulation of specific practice variables that appears to drive these dynamic processes in the CNS. The experimental manipulations used in the studies on neuroplasticity largely derive from the concept that in the undamaged or healthy brain neuronal connections and cortical maps are continuously remodeled by experience and by the performance of specific, intensive, and complex movements used to solve motor problems and attain goals. Intervention designed to promote recovery rather than compensation after stroke would then manipulate these same practice variables that have consistently promoted behavioral recovery and neuroplasticity in laboratory settings. Three current intervention strategies that incorporate these practice variables are reviewed. Preliminary results provide evidence that manipulation of task intensity and specificity and the sensorimotor experience of the task training are the necessary ingredients for maximizing the tremendous potential for recovery in patients with stroke.

Journal Article↗
PubMed2005

[The problem of goiter. Geoecological aspects].

The study determined the leading role of such geographic and geological factor as geological formations (mineralogical composition, structure, and the degree of metamorphism), tectonics, history of geological development, relief, and paleorelief in the microelementary status of the biosphere. The study proved that thyroimmunological profile of patients with goitre and geographic-and-geological conditions of the area are closely connected. The microelementary map of Bashkortostan regions was developed.

Bashkiria↗
PubMed2006

Change management in government.

Since the days of John F. Kennedy's New Frontier, the American public's regard for the competence of public agencies and the value of the services they perform has steadily declined. During that time, innovations in management practice and thinking have mostly originated and been tested in the private sector. But recent events, such as the attacks on the World Trade Center and the engulfment of New Orleans, have demonstrated how essential it is for public agencies to be well run, too. Unfortunately, few public administrators have a background in change management, and a variety of factors-such as civil service rules, political considerations, and the limited tenures of agency heads-have combined to make true reform a rare event. These facts of public life may never go away. But some agency leaders have figured out how to court important stakeholders, rededicate staffers to an agency's true mission, undertake reform so comprehensively that resistant elements are unable to subvert it, and lay the groundwork for next steps clearly and systematically. Consultant Frank Ostroff has studied turnarounds at the federal Occupational Safety and Health Administration, the Government Accountability Office, and Special Operations Forces-the fast-response, clandestine arm of the military. From these examples and others, he has distilled five principles that underlie successful change efforts: Improve performance against agency mission; win over external and internal stakeholders; establish a road map; recognize the connections among all the organizational elements; and be a leader, not a bureaucrat. Change programs that follow these principles are more likely to survive when leadership changes hands.

Efficiency, Organizational↗
PubMed2006

Transcranial magnetic stimulation: the method and application.

Transcranial magnetic stimulation is a noninvasive method for stimulation of brain that is based on the ability of magnetic field to penetrate skull and brain meninges, subsequently inducing electric current in the brain tissues that produces neuronal depolarization and generation of action potentials. Moreover, transcranial magnetic stimulation has effects on neurochemical and synaptic processes in neurons. Due to its easy use and relatively fair side effects, nowadays, transcranial magnetic stimulation is widely used in neurosciences and medicine. The main areas of transcranial magnetic stimulation application are: 1) the investigation of cortical and spinal excitability, 2) the investigation of neuronal plasticity, 3) the investigation of neuronal connectivity, 4) functional mapping, and 5) the treatment of some neurological and psychiatric disorders. Transcranial magnetic stimulation alone or in combination with other noninvasive neuroimaging (PET--positron emission topography, MRI--magnetic resonance imaging) and neurofunctional (EEG--electroencephalography, ERP--event-related potentials, fMRI--functional magnetic resonance imaging) methods allows conducting research on brain functions. Thus, transcranial magnetic stimulation is suitable as a diagnostic tool in neurologic and neuropsychiatric brain research.

Action Potentials↗
PubMed2000

Lipari-Szabo mapping: A graphical approach to Lipari-Szabo analysis of NMR relaxation data using reduced spectral density mapping.

In this paper, we explore connections between the Lipari-Szabo formalism and reduced spectral density mapping, and show how spectral density estimates can be associated with Lipari-Szabo parameters via a simple geometric construction which we call Lipari-Szabo mapping. This relationship can be used to estimate Lipari-Szabo parameters from spectral density estimates without the need for nonlinear optimization, and to perform 'model selection' in a graphical manner. The Lipari-Szabo map also provides insight into the Lipari-Szabo model, and allows us to determine when a given set of experimental spectral densities are inconsistent with the Lipari-Szabo formalism. Practical applications of Lipari-Szabo mapping in conjunction with more traditional analysis methods are discussed.

Anisotropy↗
PubMed2004

Connective tissue growth factor induces c-fos gene activation and cell proliferation through p44/42 MAP kinase in primary rat hepatic stellate cells.

BACKGROUND/AIMS: Connective tissue growth factor (CCN2) is expressed during activation of hepatic stellate cells (HSC) and promotes HSC proliferation, adhesion, and collagen production. The aim of the study was to investigate CCN2 signaling pathways in HSC. METHODS: Primary HSC were obtained by enzymatic perfusion of rat liver. DNA synthesis was evaluated by [(3)H]thymidine incorporation. Phosphorylation of Elk-1, extracellular signal-regulated kinase (ERK1/2) and focal adhesion kinase (FAK) was evaluated by Western blot. Transcriptional factor binding activity was determined by gel mobility shift assay while c-fos promoter and CCN2 promoter activity was evaluated using luciferase reporters. c-fos mRNA expression was evaluated by Northern blot. RESULTS: CCN2 stimulated DNA synthesis and phosphorylation of FAK, Elk-1 and ERK1/2, the latter of which was blocked by heparin. The serum response element binding activity and luciferase reporter activity of the c-fos promoter, together with expression of c-fos, were enhanced by CCN2. CCN2-induced c-fos gene activation, expression and cell proliferation were blocked by inhibiting ERK1/2 with PD98059. CCN2 promoter activity was enhanced by TGF-beta1 or PDGF via a Smad7-dependent pathway. CONCLUSIONS: CCN2-stimulated HSC DNA synthesis is associated with transient induction of c-fos gene activation and expression as well as activation of the ERK1/2 signal pathway.

Animals↗
PubMed1982

Prolonged and decremental antegrade conduction properties in right anterior accessory connections: Wide QRS antidromic tachycardia of left bundle branch block pattern without Wolff-Parkinson-White configuration in sinus rhythm.

Four patients are described who had long conduction times and decremental conduction through right anterior accessory connections. None had Wolff-Parkinson-White syndrome on their ECG. Each had recurrent sustained wide QRS tachycardia due to antegrade conduction through the accessory connection. Three patients underwent epicardial mapping and successful surgical division of their accessory connection. Two of the three had a second accessory connection that was also divided surgically. Each of the three are free of tachycardia without medication. It is postulated that these accessory connections represent the remnants of anterior atrioventricular ring tissue described by Anderson.

Adult↗
PubMed2000

Induction of visual orientation modules in auditory cortex.

Modules of neurons sharing a common property are a basic organizational feature of mammalian sensory cortex. Primary visual cortex (V1) is characterized by orientation modules--groups of cells that share a preferred stimulus orientation--which are organized into a highly ordered orientation map. Here we show that in ferrets in which retinal projections are routed into the auditory pathway, visually responsive neurons in 'rewired' primary auditory cortex are also organized into orientation modules. The orientation tuning of neurons within these modules is comparable to the tuning of cells in V1 but the orientation map is less orderly. Horizontal connections in rewired cortex are more patchy and periodic than connections in normal auditory cortex, but less so than connections in V1. These data show that afferent activity has a profound influence on diverse components of cortical circuitry, including thalamocortical and local intracortical connections, which are involved in the generation of orientation tuning, and long-range horizontal connections, which are important in creating an orientation map.

Animals↗