Electronic structure of warm dense copper studied by ultrafast x-ray absorption spectroscopy

We use time-resolved x-ray absorption spectroscopy to investigate the unoccupied electronic density of states of warm dense copper that is produced isochorically through the absorption of an ultrafast optical pulse. The temperature of the superheated electron-hole plasma, which ranges from 4000 to 10 000 K, was determined by comparing the measured x-ray absorption spectrum with a simulation. The electronic structure of warm dense copper is adequately described with the high temperature electronic density of state calculated by the density functional theory. The dynamics of the electron temperature is consistent with a two-temperature model, while a temperature-dependent electron-phonon coupling parameter is necessary.

Decay of cystalline order and equilibration during the solid-to-plasma transition induced by 20-fs microfocused 92-eV free-electron-laser pulses

We have studied a solid-to-plasma transition by irradiating Al foils with the FLASH free electron laser at intensities up to 10(16)  W/cm(2). Intense XUV self-emission shows spectral features that are consistent with emission from regions of high density, which go beyond single inner-shell photoionization of solids. Characteristic features of intrashell transitions allowed us to identify Auger heating of the electrons in the conduction band occurring immediately after the absorption of the XUV laser energy as the dominant mechanism. A simple model of a multicharge state inverse Auger effect is proposed to explain the target emission when the conduction band at solid density becomes more atomiclike as energy is transferred from the electrons to the ions. This allows one to determine, independent of plasma simulations, the electron temperature and density just after the decay of crystalline order and to characterize the early time evolution.

Multipurpose modular experimental station for the DiProI beamline of Fermi@Elettra free electron laser

We present a compact modular apparatus with a flexible design that will be operated at the DiProI beamline of the Fermi@Elettra free electron laser (FEL) for performing static and time-resolved coherent diffraction imaging experiments, taking advantage of the full coherence and variable polarization of the short seeded FEL pulses. The apparatus has been assembled and the potential of the experimental setup is demonstrated by commissioning tests with coherent synchrotron radiation. This multipurpose experimental station will be open to general users after installation at the Fermi@Elettra free electron laser in 2011.

Saturated ablation in metal hydrides and acceleration of protons and deuterons to keV energies with a soft-x-ray laser

Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 10(17) W/cm(2) were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 10(16) W/cm(2). This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities.

Impaired interhemispheric inhibition in writer's cramp

OBJECTIVES

Reduced cortical inhibition is a feature of focal hand dystonia and this likely contributes to excessive muscle contractions. Inhibition from the opposite hemisphere, known as interhemispheric inhibition (IHI), was studied bidirectionally in 7 right-handed patients with writer's cramp (WC) and age-matched healthy controls in a cross-sectional physiologic study.

METHODS

IHI was measured with paired transcranial magnetic stimulation with the conditioning stimulus applied to the motor cortex and the test stimulus applied to the contralateral motor cortex. Surface EMG was measured in right and left first dorsal interosseous muscles during rest, and while holding a pen between the thumb and index finger at 20% maximum voluntary contraction with the right dystonia-affected hand. The time course and magnitude of IHI was studied at interstimulus intervals of 6, 8, 10, 12, 30, 40, and 50 msec between the conditioning stimulus and test stimulus.

RESULTS

In WC at rest, IHI was significantly reduced in the dystonia-affected right hand (IHI from right to left motor cortex) at both short (SIHI, 10-12 msec) and long (LIHI, 30-40 msec) intervals compared to the unaffected hand. Compared to controls, SIHI and LIHI were reduced in the dystonia-affected hand only. There was no difference in IHI between controls and WC during the task of holding a pen.

CONCLUSIONS

In WC, both SIHI and LIHI are reduced in the dystonia-affected hand compared to the unaffected hand and to healthy controls. Impaired IHI may contribute to excessive muscle contraction in WC.

Electronic structure of an XUV photogenerated solid-density aluminum plasma

By use of high intensity XUV radiation from the FLASH free-electron laser at DESY, we have created highly excited exotic states of matter in solid-density aluminum samples. The XUV intensity is sufficiently high to excite an inner-shell electron from a large fraction of the atoms in the focal region. We show that soft-x-ray emission spectroscopy measurements reveal the electronic temperature and density of this highly excited system immediately after the excitation pulse, with detailed calculations of the electronic structure, based on finite-temperature density functional theory, in good agreement with the experimental results.

Synchrotron radiation analysis of possible correlations between metal status in human cementum and periodontal disease

Periodontitis is a serious disease that affects up to 50% of an adult population. It is a chronic condition involving inflammation of the periodontal ligament and associated tissues leading to eventual tooth loss. Some evidence suggests that trace metals, especially zinc and copper, may be involved in the onset and severity of periodontitis. Thus we have used synchrotron X-ray fluorescence imaging on cross sections of diseased and healthy teeth using a microbeam to explore the distribution of trace metals in cementum and adhering plaque. The comparison between diseased and healthy teeth indicates that there are elevated levels of zinc, copper and nickel in diseased teeth as opposed to healthy teeth. This preliminary correlation between elevated levels of trace metals in the cementum and plaque of diseased teeth suggests that metals may play a role in the progress of periodontitis.

Soft x-ray free electron laser microfocus for exploring matter under extreme conditions

We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: lambda = 13.5 nm, pulse length 15 fs, pulse energy 10-40 microJ, 5 Hz) using a fine polished off-axis parabola having a focal length of 270 mm and coated with a Mo/Si multilayer with an initial reflectivity of 67% at 13.5 nm. The OAP was mounted and aligned with a picomotor controlled six-axis gimbal. Beam imprints on poly(methyl methacrylate) - PMMA were used to measure focus and the focused beam was used to create isochoric heating of various slab targets. Results show the focal spot has a diameter of < or =1 microm. Observations were correlated with simulations of best focus to provide further relevant information.

Carbon nanotubes promote neuron differentiation from human embryonic stem cells

Human embryonic stem cells (hESCs) hold great promise for regenerative medicine and transplantation therapy due to their self-renewal and pluripotent properties. We report that 2D thin film scaffolds composed of biocompatible polymer grafted carbon nanotubes (CNTs), can selectively differentiate human embryonic stem cells into neuron cells while maintaining excellent cell viability. According to fluorescence image analysis, neuron differentiation efficiency of poly(acrylic acid) grafted CNT thin films is significant greater than that on poly(acrylic acid) thin films. When compared with the conventional poly-L-ornithine surfaces, a standard substratum commonly used for neuron culture, this new type thin film scaffold shows enhanced neuron differentiation. No noticeable cytotoxic effect difference has been detected between these two surfaces. The surface analysis and cell adhesion study have suggested that CNT-based surfaces can enhance protein adsorption and cell attachment. This finding indicates that CNT-based materials are excellent candidates for hESCs' neuron differentiation.

X-ray diffuse scattering measurements of nucleation dynamics at femtosecond resolution

Femtosecond time-resolved small and wide angle x-ray diffuse scattering techniques are applied to investigate the ultrafast nucleation processes that occur during the ablation process in semiconducting materials. Following intense optical excitation, a transient liquid state of high compressibility characterized by large-amplitude density fluctuations is observed and the buildup of these fluctuations is measured in real time. Small-angle scattering measurements reveal snapshots of the spontaneous nucleation of nanoscale voids within a metastable liquid and support theoretical predictions of the ablation process.

The effects of multifocal refractive lenses on occipital extension and forward head posture during a visual task

The purpose of this study was to determine if a change in forward head posture and occipital extension occurred in participants who wore multifocal lenses vs. those persons with non-multifocal lenses while performing an 8-min visual reading task on a visual display unit (VDU). Forty-two healthy human participants were recruited for this study. Thirty-three participants completed the study. Fourteen participants wore multifocal lenses and 19 wore frames with non-multifocal lenses. To evaluate the degree of change of forward head posture and occipital extension digital photographs of cervical posture were taken at four different time intervals: prior to performing the reading task and at 3, 5 and 8 min during the reading task. The digital photographs were analysed utilizing a computer program. Two one-way ANOVA were utilized to determine the degree of change of forward head posture and occipital extension between groups. A significant difference was identified between groups for changes in degrees of forward head posture while performing a visual reading task on a VDU. However, no significant difference between groups was found for occipital extension while performing the same task. Multifocal wearers exhibit greater degrees of change in forward head posture and occipital extension than non-multifocal wearers. These postural changes may place them at a greater risk for musculoskeletal disorders and headaches.

The relationship between skin temperature and neuronal characteristics in the median, ulnar and radial nerves of non-impaired individuals

The purpose of this study was to evaluate the relationship between the nerve conduction characteristics in the median, ulnar and radial nerves and presenting skin temperature in non-impaired individuals as they were subjected to electrophysiological testing. Previous researchers artificially manipulated the skin temperature and demonstrated that there was a positive relationship between temperature and nerve conduction velocity and a negative correlation between distal latency and evoked motor action potential (EMAP). The sample population was 50 non-impaired individuals derived from a venue in the New York City and Long Island region. The independent variable was skin temperature. The dependent variables were: motor nerve conduction velocity, motor distal latency, EMAP of median and ulnar nerves, sensory distal latency and sensory nerve action potential (SNAP) of median, ulnar and radial nerves. The data were analyzed using descriptive statistics, the Bonferroni correction factor and correlation statistics. The study showed significant correlation in median motor distal latency, ulnar motor distal latency, ulnar sensory distal latency, median sensory amplitude, and ulnar sensory amplitude. The NCV, the distal latency and the amplitude of the median, ulnar and radial nerves were similar in values to other researchers' normal values.

Comparison of the distributions of bromine, lead, and zinc in tooth and bone from an ancient Peruvian burial site by X-ray fluorescence

Synchrotron micro X-ray fluorescence was used to study the distribution of selected trace elements (Zn, Pb, and Br) in tooth and bone samples obtained from an individual from a pre-Columbian archaeological site (Cabur) located on the north coast of Peru. The results show that Zn, Pb, and Br are present in both the teeth and bone samples and that the Zn and Pb seem to be confined to similar regions (cementum and periostium), while Br shows a novel distribution with enrichment close to the Haversian canals and (or) in regions that appear to be Ca deficient.Key words: teeth, bone, metals, XRF, Br, Zn, and Pb.

Immunotoxicity assessment for the novel Spleen tyrosine kinase inhibitor R406

Spleen tyrosine kinase (Syk) is a novel pharmaceutical target for treatment of allergic, autoimmune, and neoplastic disorders. Previous studies have indicated that Syk signaling plays critical roles in regulating the lymphohematopoietic system. These observations prompted us to investigate whether inhibition of Syk would promote immunotoxicity. In a series of studies, rats were treated orally with R406, at dose levels up to and including 100 mg/kg/day (or its prodrug R788 at dose levels up to and including 100 mg/kg/day, reduced to 50 mg/kg/day for females as MTD was exceeded), a potent Syk inhibitor, twice daily for 28 days. In addition to standard toxicological assessments, immunophenotyping by flow cytometric analysis, and a study of humoral immune response measuring anti-KLH IgM and IgG levels, were undertaken. Other immunotoxicity studies included three host resistance models in female Balb/c mice to further ascertain effects of R406 on innate and acquired immunity. Following R406 treatment, expected immunomodulating effects (e.g., decreased thymic and spleen weight, hypocellularity of bone marrow, and reduced lymphocyte counts, including T and B cells) were observed in the rat studies. These changes essentially resolved during a 14-day treatment-free recovery period. A KLH challenge in rats demonstrated no adverse effects on IgG or IgM response. R788/406, administered orally at dose levels up to and including 80 mg/kg/day for 28 days, did not affect bacterial or viral clearance in the Listeria, Streptococcal, or Influenza host resistance mouse models, respectively. This correlated with previous in vitro macrophage and neutrophil function assays (assessing migration, phagocytosis, oxidative burst and microbicidal activity), which revealed that R406 did not adversely affect macrophage or neutrophil function in innate immune responses. Collectively, these results demonstrate that R406 has minimal functional immunotoxicity notwithstanding its lymphocytopenic effect, suggesting that inhibition of Syk might not lead to unacceptable mechanism-based adverse effects.

Carrier-density-dependent lattice stability in InSb

The ultrafast decay of the x-ray diffraction intensity following laser excitation of an InSb crystal has been utilized to observe carrier dependent changes in the potential energy surface. For the first time, an abrupt carrier dependent onset for potential energy surface softening and the appearance of accelerated atomic disordering for a very high average carrier density have been observed. Inertial dynamics dominate the early stages of crystal disordering for a wide range of carrier densities between the onset of crystal softening and the appearance of accelerated atomic disordering.

Ultrafast bond softening in bismuth: mapping a solid's interatomic potential with X-rays

Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid.

Synthesis and Characterization of the Nitrides of Platinum and Iridium

Transition metal nitrides are of great technological and fundamental importance because of their strength and durability and because of their useful optical, electronic, and magnetic properties. We have evaluated a recently synthesized platinum nitride (PtN) that was shown to have a large bulk modulus, and we propose a structure that is isostructural with pyrite and has the stoichiometry PtN2. We have also synthesized a recoverable nitride of iridium under nearly the same conditions of pressure and temperature as PtN2. Although it has the same stoichiometry, it exhibits much lower structural symmetry. Preliminary results suggest that the bulk modulus of this material is also very large.

Synchrotron X-ray fluorescence and trace metals in the cementum rings of human teeth

Synchrotron micro X-ray fluorescence has been used to study differences in the trace element concentration between the dentine and cementum rings of human teeth. The results show that metals such as zinc are concentrated in the cementum rings. This suggests that if the rings are deposited annually a temporal record of metal exposure may be extracted from this material.

Neuronal conduction studies of the median nerve in non-impaired humans: a comparison of accepted techniques

BACKGROUND AND PURPOSE

There are two commonly accepted techniques used for distal electro-stimulation placement when performing median motor nerve conduction studies. The purpose of this study was to compare latency using two commonly accepted sites of distal stimulation of the median nerve when performing motor nerve conduction studies on non-impaired adult humans.

PARTICIPANTS

The sample consisted of 36 non-impaired participants (15 female, 21 male) aged 20 to 40 years.

METHODS

Participants were randomly assigned to two groups and tested bilaterally for the median motor nerve. For distal stimulation of the median motor nerve, in the first group, 8 cm was measured from the center of the muscle diagonally to arrive at a point between the flexor carpi radialis and plamaris longus tendons. In the second group, 3.5 cm was measured from the distal wrist crease proximally along the median nerve for the distal stimulation of the median motor nerve. Distal latency of both techniques was obtained. Surface skin temperature of the palm was recorded throughout the procedures.

RESULTS

No significant differences were found between the 8 cm and 3.5 cm techniques at p < or = 0. 05 level.

COMMENT

Even though no differences were found between the two techniques, the 3.5-cm technique is recommended because of its consistency as an anatomical landmark reducing the potential for measurement error.

Chemically transformable configurations of mercaptohexadecanoic acid self-assembled monolayers adsorbed on Au(111)

Carboxyl-terminated self-assembled monolayers (SAMs) are commonly used in a variety of applications, with the assumption that the molecules form well-ordered monolayers. In this work, near-edge X-ray absorption fine structure measurements verify that well-ordered monolayers can be formed using acetic acid in the solvent. Disordered monolayers with unbound molecules present in the film result using only ethanol. A stark reorientation occurs upon deprotonation of the end group by rinsing in a KOH solution. This reorientation of the end group is reversible with tilted-over, hydrogen-bound carboxyl groups while the carboxylate ion end groups are upright. C(1s) photoemission shows that SAMs formed and rinsed with acetic acid in ethanol have protonated end groups, while SAMs formed without acetic acid have a large fraction of carboxylate-terminated molecules.

Tactile stimulus predictability modulates activity in a tactile-motor cortical network

Manipulating objects in the hand requires the continuous transformation of sensory input into appropriate motor behaviour. Using a novel vibrotactile device combined with fMRI, the cortical network associated with tactile sensorimotor transformations was investigated. Continuous tactile stimuli were delivered in a random or predictable pattern to the second digit on the right hand of all subjects. To better distinguish sensory and motor processes, subjects were instructed to make proportionate motor gripping responses with their left hand. A consistent cortical network of activation was revealed that included the supplementary motor, dorsal and ventral premotor, posterior parietal, primary and secondary somatosensory and primary motor cortex. Tracking the unpredictable versus predictable tactile stimulus led to greater delays in motor responses and to increased performance errors. Cortical effects due to stimulus predictability were observed in several components of the network, though it was most evident as increased cortical activation in frontal motor regions during tracking of unpredictable tactile stimuli. In contrast to the proposed hypotheses, primary and secondary somatosensory cortices contralateral to tactile input did not reveal enhanced responses during unpredictable tracking. Facilitation during unpredictable tracking was also observed in primary somatosensory cortex contralateral to motor responses, the receptive site for movement-related afference. The present study provides a novel and controlled approach to investigate the loci associated with tactile-motor processing and to measure the task-specific effect of stimulus predictability on network components.

Time-of-flight secondary ion mass spectrometry analysis of hair from archaeological remains

Hair from four individuals excavated from burial sites in Pacatnamu, Peru from the Moche (450-800 AD) and Lambayeque (900-1100 AD) periods was sectioned longitudinally and analysed with time-of-flight secondary ion mass spectrometry (ToF-SIMS). An attempt was made to distinguish biogenic and diagenetic contributions to the elemental concentrations in the hair samples. Significant contamination was observed to have penetrated the hair samples from the burial environment. Results from the analyses indicate that the burial environment plays an important role in the postmortem variation in elemental content of hair samples. Various elements demonstrated an ability to permeate through the hair matrix over time. In addition, NaCl and what are believed to be aluminosilicates and mineral sulphates, were observed to have accumulated on the surface of the samples. Degradation of the samples was also suspected due to the presence of molecular fragments, possibly resulting from oxidation of the keratin proteins. The results should assist in the identification of reliable elemental signals in the analysis of ancient hair samples and promote caution when considering elements that are abundant in the burial environment.

Rhenium bipyridine complexes for the recognition of glucose

Bipyridine ligands containing pendant methyl, amino, and amino-boronic acid groups were synthesized. Coordination complexes of these ligands with rhenium were prepared straightforwardly and in good yield. The fluorescence behavior of the Re complexes was studied as a function of pH and exposure to various concentrations of glucose. The methyl bipyridine complex showed no change in fluorescence with pH, the amino derivative showed a rapid decrease from low pH to neutral, and the amino-boronate derivative showed little change from pH 4 to 10. Fluorescence quenching was observed at high pH as expected on the basis of a photoinduced electron transfer (PET) signaling mechanism. This behavior can be explained on the basis of the first oxidation and reduction potentials of these complexes. Glucose testing showed a significant dependence on the solvent system used. In pure methanol, the rhenium boronate complex exhibited a 55% fluorescence intensity increase upon increasing glucose concentration from 0 to 400 mg/dL. However, in 50 vol % methanol/phosphate buffered saline, none of the complexes showed significant response in the glucose range of physiological interest.

The gain of initial somatosensory evoked potentials alters with practice of an accurate motor task

The gain of somatosensory afferent paths from the lower limb to the cerebral cortex was investigated during the acquisition of one target location during plantar flexion. Sensory gain was measured as the magnitude of somatosensory evoked potentials (SEPs) following electrical stimulation of a peripheral nerve in the lower limb, and was recorded from the scalp. We hypothesized gain attenuation of SEPs from sensory paths serving the limb segment responsible for target acquisition. SEP gain was studied as subjects plantar flexed about the anide to a target that was 15 degrees beyond the occurrence of a cutaneous stimulus (cue) to the lateral border of the foot. The "cue" was either fixed in one location or could appear at one of three positions in space. SEP gain was tested during practice and with task acquisition. Electroencephalographic (EEG) recordings were made of primary and secondary complexes of cortical SEPs from sural and tibial nerve stimulation, with 30-40 samples averaged per subject-condition. Electromyographic (EMG) records were made of soleus muscle H-reflexes and M-waves. Target acquisition was recorded as percent correct hits. The results showed significant attenuation in sural and tibial nerve primary SEPs with task acquisition when the cue was fixed or varied in movement space (P<0.05). Secondary SEPs from tibial nerve followed this pattern. Spinal H-reflexes only attenuated with movement per se. We conclude that the CNS preferentially reduces the cerebral inflow of sensory information once such a motor task has been successfully acquired.

Comparing stepping-in-place and gait ability in adults with and without hemiplegia

OBJECTIVE

To determine and compare select temporal-distance measures of stepping-in-place with gait ability in 2 age-matched groups.

DESIGN

Repeated measures, matched research design.

SETTING

Gait laboratory and hospital outpatient unit.

PARTICIPANTS

Convenience sample recruited from within the community and the outpatient unit of a local rehabilitation hospital included 30 healthy adults (age range, 58.1 +/- 10.8yr) and 30 age-matched adults with hemiplegia (age range, 58.6 +/- 10.3yr), secondary to a cerebrovascular accident.

INTERVENTIONS

Subjects were videotaped in the sagittal plane performing stepping-in-place and while walking. Select temporal-distance measures obtained by manual calculations from the video recordings were determined for 3 20-second trials of each activity.

MAIN OUTCOME MEASURES

Single limb support duration (SLSD) of the lower extremities (LEs) and step frequency during stepping-in-place and during gait.

RESULTS

A significant difference was found between the step frequency of each activity for the adults with hemiplegia (p <.05), but not for the healthy adults. A significant difference was also found between SLSD of the same LE across activities for each group (p <.05). SLSD of each LE during each individual activity, stepping-in-place, or gait, was not significantly different for the healthy adults, indicating LE symmetry; but it was significantly different for the adults with hemiplegia (p <.05), indicating LE asymmetry.

CONCLUSIONS

Stepping-in-place incorporates reciprocal, rhythmic LE movement patterns similar to gait. And, although SLSD of the LEs was different between the activities in both groups, each group showed similar LE movement patterns during each individual activity. In addition, step frequency was consistent between the activities for the healthy adults. These results seem to indicate that the reciprocal, rhythmic LE movement patterns, which are invoked during gait, may also be invoked during stepping-in-place. However, further research is needed to enhance the data related to stepping-in-place and gait ability in clinical populations.

The afferent origin of the secondary somatosensory evoked potential from the lower limb in humans

The afferent origin of the secondary somatosensory evoked potential elicited from stimulation of the sural and tibial nerves was investigated as the limb was cooled. It was hypothesized that the peak of this potential is initiated from primary afferents in the A alpha group. We conclude that the peak of the secondary SEP arises from an afferent source whose diameter is of similar size to that of large diameter A alpha afferents.

The place of Neandertals in the evolution of hominid patterns of growth and development

This study uses the two developmental fields of dental maturation and femoral growth to determine if the pattern of growth and development in Neandertals (archaic Homo sapiens) was intermediate between that of Homo erectus and recent modern humans. Specimens used in the analysis included Neandertals and Upper Palaeolithic early modern Homo sapiens from Europe and individuals from two recent modern human populations. Ontogenetic data for the H. erectus adolescent KNM-WT 15000 and for Gorilla gorilla were included for comparison. Previous reports have indicated that H. erectus demonstrates a pattern of ontogeny characterized by earlier and more rapid linear growth than in modern humans. Results reported here demonstrate that Upper Paleolithic early modern Homo sapiens display a growth trajectory indistinguishable from that of recent modern humans. The pattern of Neandertal ontogeny is not intermediate between the pattern displayed in H. erectus and the derived pattern seen in the modern reference samples and the early modern H. sapiens sample. The Neandertal growth trajectory is consistent with either slow linear growth or advanced dental development.

Temporal properties of attention sharing consequent to disturbed balance

The time course and extent of attentional shifts associated with compensatory balancing reactions were explored using a novel dual-task paradigm. Seated subjects performed a continuous visuomotor tracking task with the hand while the feet simultaneously balanced an inverted pendulum. The pendulum was randomly perturbed, evoking compensatory balance reactions. Changes in tracking performance were held to reflect attentional shifts. Discrete deviation in visuomotor tracking, typically a pause in tracking, began on average 235 ms after the onset of the balance reaction (TA EMG; average latency 90 ms). Such pauses lasted on average 600 ms, although additional errors in tracking lasted up to 9 s following the perturbation. The findings reveal evidence of dynamic shifts in attention associated with distinct phases of compensatory balance control. The initial phase appears to be triggered automatically, whereas later phases involve varying degrees of attentional resources.

Potential for Dispersal of Fusarium oxysporum f. sp. erythroxyli by Infested Seed

Fusarium oxysporum f. sp. erythroxyli causes a vascular wilt of the narcotic plant coca (Erythroxylum coca var. coca). To determine whether this pathogen can be transmitted by infested seed, fruit from symptomatic and asymptomatic plants was collected from different coca-growing areas in Peru and from an experimental field site in Hawaii. A total of 202 fruit from Peru and 69 fruit from Hawaii were surface-disinfested and separated into five parts: pedicel, pericarp, seed coat, endosperm, and cotyledons. After the pedicel and pericarp were removed from the seed coat, the seed was surface disinfested again. Each fruit part was plated separately. Both F. oxysporum and F. moniliforme were recovered from fruit collected in Peru. Both species were isolated from all parts of some fruit. F. oxysporum was isolated from 33% of the fruit plated and most (35%) of these isolates were obtained from the seed coat. Slightly greater numbers of isolates (57%) were recovered from asymptomatic plants than from symptomatic plants (43%). Only F. oxysporum was isolated from fruit collected in Hawaii. Most of these isolates (59%) were from the pedicels of fruit collected from symptomatic plants. Out of 91 isolates of F. oxysporum, 21 were pathogenic to coca seedlings in a bioassay. Six of these pathogenic isolates were originally from the pedicel of the fruit, eight from the pericarp, four from the seed coat, and three from the endosperm. No isolates from the cotyledons were pathogenic. Most of the pathogenic isolates (76%) were from symptomatic plants. The pathogenic isolates were characterized using random amplified polymorphic DNA analysis and vegetative compatibility groups. Based on these analyses, two different subpopulations of the forma specialis erythroxyli were found in Peru, whereas only one was present in Hawaii. These data indicate that infested seed may contribute significantly to dissemination of this pathogen because seed is collected by growers and planted fresh or fermented briefly before planting.

The effects of circumferential wrist pressure on reproduction accuracy of wrist placement in healthy young and elderly adults

BACKGROUND

The purpose of this study was to determine the effect of circumferential wrist pressure on reproduction accuracy of wrist placement in healthy young and elderly adults. A convenience sample of 20 young adults having a mean age of 22.9 years and 20 elderly adults with a mean age of 68.2 years participated in the study.

METHOD

Blindfolded subjects were asked to actively self-select a neutral wrist position (reference) and then, when signaled, to actively reproduce the previously selected position. Wrist joint reproduction accuracy was assessed under four pressure conditions: no contact, wrist contact, 10 mm Hg, and 20 mm Hg. A single axis dynamic wrist electrogoniometer measured three dependent variables: absolute, constant, and variable errors. Data were analyzed by means of multivariate analysis of variance (MANOVA) for repeated measures.

RESULTS

No significant differences in reproduction accuracy under the four pressure conditions for young or elderly adults were found.

CONCLUSIONS

Healthy young and elderly adults may utilize existing intrinsic feedback and central control mechanisms to achieve accuracy during a reproduction task. Some subjects in both age groups who entered into the study with high error scores benefited from circumferential pressure by possibly relying on peripheral mechanisms. Further studies are needed to determine the effect of circumferential pressure on subjects with poor reproduction performance.

Traumatic nerve injuries about the elbow

Although not common, nerve injuries about the elbow occur because of the proximity of the three upper extremity nerves or because of the relationship of the median, ulnar, and radial nerves to the bony and soft-tissue structures about the elbow joint. Nerve injuries at and about the elbow joint occur more frequently with fractures than with any other kind of trauma. Nerve injuries may be found with periarticular fractures, dislocations, gunshot wounds, lacerations, and other iatrogenic causes.

In vitro positive selection and anergy induction of class II-restricted TCR transgenic thymocytes by a cortical thymic epithelial cell line

Thymic epithelial cell lines isolated from hyperplastic thymi of transgenic mice over-expressing human papilloma viral oncogenes E6 and E7 constitutively displayed a phenotype consistent with a cortical origin. Exposure to IFN-gamma induced class II MHC and ICAM-1 expression, and up-regulated expression of VCAM-1 and class I MHC molecules. CD40 expression was maximally induced by a combination of IFN-gamma and IL-1, with lower levels of induction observed with a mixture of IFN-gamma and tumor necrosis factor (TNF)-alpha or TNF-alpha alone. B7-1 or B7-2 was not expressed constitutively or in response to cytokines. These stromal cells supported the development of CD4 single-positive (SP) cells in reaggregate co-cultures with CD4+ CD8+ thymocytes from TCR transgenic mice, but did not stimulate class II MHC-restricted, moth cytochrome c (MCC)-reactive T cells in vitro. The behavior of the culture system was consistent with positive selection, i.e. increased numbers of CD4 SP cells, gain of antigen responsiveness, and requirement for epithelial class II MHC products. Some variants of these stromal cell lines required exogenous MCC peptide in the reaggregation cultures (RC) for positive selection to occur. While a low concentration of MCC peptide (0.01-0.1 microM) significantly enhanced the accumulation of CD4 SP cells, higher concentrations of peptide (1-10 microM) resulted in recovery of predominantly CD4- CD8- and CD4(low) CD8- cells. Thymocytes recovered from RC containing low, but not high concentrations of peptide responded to MCC peptide in secondary cultures with splenic antigen-presenting cells.

Physical activity before and after exercise in women with chronic fatigue syndrome

We measured physical activity after strenuous exercise in 20 women with chronic fatigue syndrome (CFS), compared to 20 sedentary healthy volunteers who exercised no more than once per week. Activity was measured for 2 weeks using a portable waist-worn vertical accelerometer. After the first week of activity monitoring, all participants returned for a maximal treadmill test, followed by continued activity monitoring for the second week. Five activity measures were derived from the data: (i) average activity; (ii) total activity; (iii) duration of waking day; (iv) duration; and (v) number of daily rests. A repeated measures ANCOVA was used to determine post-treadmill group differences accounting for pre-treadmill differences. There was a significant reduction in overall average activity after the treadmill test, with the greatest decrease on days 12 through 14. This reduction was accompanied by a significant increase in the duration of the waking day and number of daily rests. Thus, marked exertion does produce changes in activity, but later than self-report would suggest, and are apparently not so severe that CFS patients cannot compensate.

Genetic Characterization by RAPD Analysis of Isolates of Fusarium oxysporum f. sp. erythroxyli Associated with an Emerging Epidemic in Peru

ABSTRACT An epidemic of vascular wilt caused by Fusarium oxysporum f. sp. erythroxyli is currently occurring on Erythroxylum coca var. coca in the coca-growing regions of the Huallaga Valley in Peru. Random amplified polymorphic DNA (RAPD) analysis of isolates of the pathogen was undertaken to elucidate its genetic complexity, as well as to identify a specific DNA fingerprint for the pathogen. Two hundred isolates of Fusarium were collected from 10 coca-growing regions in Peru. Of these, 187 were confirmed to be F. oxysporum, and 143 of the F. oxysporum were shown to be pathogens of coca by a root-dip pathogenicity test. The pathogens could be grouped into two subpopulations based on RAPD analysis, and no polymorphism in RAPD pattern was observed among isolates of either subpopulation. Both subpopulations were present in the central Huallaga Valley, where earliest reports of the epidemic occurred. RAPD analysis could easily distinguish the isolates of F. oxysporum f. sp. erythroxyli from the nonpathogenic isolates of F. oxysporum from E. coca var. coca, indicating its utility in DNA fingerprinting.

Lameness and foot lesions in adult British dairy goats

In the first population-based study of lameness and foot lesions in adult goats in the UK, a random sample of 307 adult goats from four large commercial dairy farms was examined. The overall proportion of lame goats was 9.1 per cent (2.6 to 24.4 per cent). The abnormalities detected were horn separation (29.6 per cent), white line lesions (13.0 per cent) slippering (10.1 per cent), abscess of the sole (4.2 per cent), foreign body, and granulomatous lesions (1.0 per cent). Between 83.1 and 95.5 per cent of the goats had overgrown horn on at least one foot. The number of feet of individual goats with horn separation followed a Poisson distribution suggesting that it was associated with environmental rather than genetic or nutritional factors. Horn separation, abscess of the sole and footrot were significantly associated with lameness, but white line lesions, slippering and granulomatous lesions were not. There were differences between the farms in the prevalence of lameness and foot lesions. Routine foot trimming was associated with a lower prevalence of lameness.

Attitudes of physical therapists who possess sports specialist certification

Physical therapists contemplating sports specialist certification need research-based information to facilitate their decision-making process. The purpose of this study was to investigate the attitudes of physical therapists who have received sports specialist certification. These attitudes encompass the physical therapists' sense of fulfillment and their feelings of satisfaction or dissatisfaction with the certification process. Factors contributing to the therapist's decision to become sports specialist certified have also been investigated. Physical therapists who are sports certified specialists (N = 110) participated in this study. Questionnaires were mailed to the entire population of physical therapists who are sports certified specialists (N = 148). Frequency distributions and percentages were used on qualitative data, and mode was calculated for quantitative data. One hundred ten surveys were returned, for a response rate of 74.3%. Analysis of responses from the subject group suggests that physical therapists feel a high level of satisfaction with their decision to specialize, and that continued professional growth, development, and personal achievement are the major contributing factors in their decision to specialize. Based on these findings, physical therapists appeared to display overall satisfaction in their attitudes toward sports specialist certification. Further research may be warranted to further examine sports certified therapists' attitudes toward the specialization process.

Head and neck pain review: traditional and new perspectives

A variety of conditions are frequently associated with the occurrence of head and neck pain. The purposes of this review are: to describe the characteristics of several musculoskeletal, neurological, and systemic conditions frequently cited as possible causes of head and neck pain and to suggest a new technique for treating head and neck pain. The characteristics of musculoskeletal conditions, such as muscle spasm, tendinitis, trigger points, and joint inflammation, and their relationship to head and neck pain are considered. The features and clinical implications of neurologic conditions, such as atypical facial pain, trigeminal and glossopharyngeal neuralgia, reflex sympathetic dystrophy, and neurogenic inflammation, are also described. The distinguishing characteristics of headaches, including cluster, tension, chronic daily, rebound, posttraumatic, and postlumbar puncture, are detailed. This review also addresses the contributions of systemic disorders, such as osteoarthritis, rheumatoid arthritis and the variants, and rheumatoid-related conditions, like dermatomyositis, temporal arteritis, Lyme's disease, and fibromyalgia, to head and neck pain. The results of a recent pilot study of the effectiveness of intraoral circulating ice water for resolving symptoms related to head and neck pain secondary to neurogenic inflammation are presented in this work. Ice water circulating through hollow metal tubes was placed intraorally for 15 minutes in the posterior maxillary area on 12 individuals with cervical pain and muscle spasm. In nine of these individuals, reduced cervical pain perception, upper trapezius electromyography signal reduction, and increased cervical range of motion was produced. Six out of 12 individuals had accompanying headache, which was reduced or eliminated in four cases. These findings suggest a strong trigemino-cervical relationship to neck pain and headache.

The murine homolog of human Ep-CAM, a homotypic adhesion molecule, is expressed by thymocytes and thymic epithelial cells

In this report, we demonstrate that gp40, a molecule previously shown to be expressed by thymic epithelial cell lines in vitro and by thymic epithelial cells in vivo, is the murine homolog of human Ep-CAM, a calcium-independent homotypic adhesion molecule. gp40 is also expressed at low levels by thymocytes and peripheral T cells. In the adult thymus, gp40 expression was inversely related to the state of thymocyte maturation, with the highest levels associated with CD4-CD8- and CD4+CD8+ thymocyte populations. Ultrastructural immunohistochemistry revealed gp40 localization to areas of thymocyte/epithelial contact and demonstrated that gp40 is also expressed by thymic dendritic cells. During fetal development, thymocytes at days 14-16 of gestation expressed high levels of gp40. At later stages, the observed decline in the frequency of gp40+ cells and levels of expression correlated with the emergence of alpha beta+ thymocytes by day 18 of gestation. In short-term cultures, stimulation of unfractionated adult thymocytes with concanavalin A increased gp40 expression, particularly among CD3hi and CD3int thymocyte populations. This demonstration that Ep-CAM, initially considered to be expressed primarily by epithelial cells, is also expressed by thymocytes, T cells and antigen-presenting cells, raises the possibility that Ep-CAM may contribute to adhesive interactions between thymocytes and epithelial cells or dendritic cells, either in the context of thymocyte development or peripheral T cell trafficking and function.

Expression of gp40, the murine homologue of human epithelial cell adhesion molecule (Ep-CAM), by murine dendritic cells

Dendritic cells (DC) can be distinguished from other antigen-presenting cells (APC) by their morphology, motility and ability to initiate primary responses in naive T cells. Certain cell surface proteins (e.g. major histocompatibility complex antigens, co-stimulatory/adhesion molecules and DEC205) are selectively expressed by DC, and may contribute to the potent APC activity of these leukocytes. As an outgrowth of studies of adhesion molecules expressed by epithelia and Langerhans cells (LC), we examined DC from murine epidermis and various lymphoid tissues for evidence of expression of gp40, a glycoprotein recently identified as the murine homologue of human epithelial cell adhesion molecule (Ep-CAM). gp40 was detected on freshly-obtained LC, cultured LC and LC that migrated from skin explants, as well as on keratinocytes. In skin-associated lymph nodes, gp40 was selectively expressed by some DC in T cell-dependent areas. DC-enriched preparations from skin-associated lymph nodes and spleen contained many cells that co-expressed DC markers (CD11c and DEC205) and high levels of gp40. Lower levels of gp40 were present on DC from gut-associated lymph nodes. These results demonstrate that the putative homophilic adhesion molecule gp40 is expressed by subpopulations of DC in selected tissues; we propose that gp40 expression may have functional consequences for DC.

Expression of two structurally identical viral superantigens results in thymic elimination at distinct developmental stages

Mouse mammary tumor virus proviral integrants encode superantigens. Developing thymocytes bearing TCRs with particular V beta elements encounter these endogenous viral superantigens as self molecules in the thymus and are consequently clonally eliminated. To study this mechanism of tolerance induction, we have bred B10.BR-Mtv-1 and B10.BR-Mtv-6 mice, which carry either Mtv-1 or Mtv-6 proviruses but are otherwise genetically identical. The protein products of these mouse mammary tumor virus integrants, vSAG1 and vSAG6, both interact with V beta 3+ T cells and have identical amino acid sequences. Interestingly, vSAG6 expression results in the complete deletion of V beta 3+ peripheral T cells, whereas vSAG1 expression results in only partial deletion. Flow cytometric analyses indicate that B10.BR-Mtv-6 mice delete V beta 3+ thymocytes at the immature CD4+8+ stage, whereas B10.BR-Mtv-1 mice delete only mature CD4+ or CD8+ cells. In addition, the two strains exhibit different time courses of thymic deletion: neonatal B10.BR-Mtv-6 mice eliminate V beta 3+ T cells by day 2, in contrast to B10.BR-Mtv-1 mice in which deletion does not occur until day 15. RNase protection assays demonstrate that B10.BR-Mtv-6 mice have significantly greater thymic vSAG6 mRNA expression levels than vSAG1 levels in B10.BR-Mtv-1 animals, correlating with a more complete deletion of reactive thymocytes at an earlier point in the maturational sequence.

Expression of two structurally identical viral superantigens results in thymic elimination at distinct developmental stages

Mouse mammary tumor virus proviral integrants encode superantigens. Developing thymocytes bearing TCRs with particular V beta elements encounter these endogenous viral superantigens as self molecules in the thymus and are consequently clonally eliminated. To study this mechanism of tolerance induction, we have bred B10.BR-Mtv-1 and B10.BR-Mtv-6 mice, which carry either Mtv-1 or Mtv-6 proviruses but are otherwise genetically identical. The protein products of these mouse mammary tumor virus integrants, vSAG1 and vSAG6, both interact with V beta 3+ T cells and have identical amino acid sequences. Interestingly, vSAG6 expression results in the complete deletion of V beta 3+ peripheral T cells, whereas vSAG1 expression results in only partial deletion. Flow cytometric analyses indicate that B10.BR-Mtv-6 mice delete V beta 3+ thymocytes at the immature CD4+8+ stage, whereas B10.BR-Mtv-1 mice delete only mature CD4+ or CD8+ cells. In addition, the two strains exhibit different time courses of thymic deletion: neonatal B10.BR-Mtv-6 mice eliminate V beta 3+ T cells by day 2, in contrast to B10.BR-Mtv-1 mice in which deletion does not occur until day 15. RNase protection assays demonstrate that B10.BR-Mtv-6 mice have significantly greater thymic vSAG6 mRNA expression levels than vSAG1 levels in B10.BR-Mtv-1 animals, correlating with a more complete deletion of reactive thymocytes at an earlier point in the maturational sequence.

Characterization of a CD6 ligand(s) expressed on human- and murine-derived cell lines and murine lymphoid tissues

CD6, a type I cell surface glycoprotein expressed predominantly by thymocytes and mature T lymphocytes, becomes phosphorylated on tyrosine residues following T cell activation and has been implicated as an accessory molecule in T cell activation. The purpose of this study was to identify cell lines and tissues which express CD6 ligand(s), determine the requirements for CD6 binding, and biochemically characterize the putative CD6 ligand(s). Binding studies with a CD6 immunoglobulin fusion protein, CD6-Rg, allowed the identification of a number of human cell lines which express a CD6 ligand(s). The binding to these cell lines was trypsin sensitive, in part required divalent cations, was blocked by an anti-CD6 mAb, and could be downregulated by tumor necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta) and interferon-gamma (IFN-gamma). Among the cell lines tested, the human breast carcinoma-derived cell line HBL-100 expressed the highest levels of CD6 ligand(s) and was used for immunoprecipitation studies. Following metabolic labeling, CD6-Rg immunoprecipitated glycoproteins of approximately 100, approximately 90, and approximately 45 kDa from HBL-100 cells. Using CD6-Rg we were able to show that murine thymus, lymph nodes, and skin express high levels of CD6 ligand(s) and that CD6-Rg bound to a murine thymic epithelial cell line and to cultured human epidermal keratinocytes.

Information needs of the dairy industry for health and nutrition management

Current DHI records usage is demonstrated with lactation curves, peak milk production versus rolling average peak milk production, and linear score monitoring sensitivity. Suggestions for the future of DHI records include national congruity, reduction in DHI fees, increased use of electronic transfer of information, increased availability of records from all testing centers, decreased use of DHI supervisors, milk urea nitrogen testing, and tracking of metabolic diseases.

Isolation of a monocot 3-hydroxy-3-methylglutaryl coenzyme A reductase gene that is elicitor-inducible

The rice (Oryza sativa) phytoalexins, momilactones and oryzalexins, are synthesized by the isoprenoid pathway. An early step in this pathway, one that is rate-limiting in mammalian systems, is catalyzed by the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR). A gene that encodes this enzyme has been isolated from rice, and found to contain an open reading frame of 1527 bases. The encoded protein sequence of the rice HMGR appears to be conserved with respect to other HMGR proteins, and 1 or 2 membrane-spanning domains characteristic of plant HMGRs are predicted by a hydropathy plot of the amino acid sequence. The protein is truncated at its 5' end, and shows reduced sequence conservation in this region as compared to other plant sequences. The rice genome contains a small family of HMGR genes. The isolated gene, HMGR I, is expressed at low levels in both vegetative and floral organs of rice plants. It is not induced in plants by wounding, but is strongly and rapidly induced in suspension cells by a fungal cell wall elicitor from the pathogen Magnaporthe grisea, causal agent of rice blast disease. This suggests that HMGR I may be important in the induction of rice phytoalexin biosynthesis in response to pathogen attack, and therefore may play a key role as a component of the inducible defense mechanism in rice.

Medullary thymic epithelium expresses a ligand for CTLA4 in situ and in vitro

A fusion protein consisting of the extracellular domain of CTLA4 and an Ig C gamma 1 chain (CTLA4-Ig) was used to examine the distribution of the ligands for CTLA4 within the murine thymus and to characterize the nature of these ligands. Two-color immunofluorescence of thymus tissue revealed binding of the fusion protein to medullary thymic epithelial cells and dendritic cells within the corticomedullary and medullary areas of the thymus. Medullary cells binding the fusion protein also expressed MHC class II products and ICAM-1. Thymus tissue sections treated with cross-linking fixatives, such as glutaraldehyde, paraformaldehyde, or 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide no longer bound the CTLA4 fusion protein, indicating that binding was very sensitive to the tertiary structure of the tissue ligand. The ability of thymic tissue to bind the fusion protein was developmentally regulated. At day 14 of gestation, only scattered single cells were labeled. Clusters of labeled cells, which were detected by day 16 of gestation, increased in frequency with advancing gestational age. Consistent with the in situ labeling studies, CTLA4-Ig also labeled several thymic epithelial cell lines previously shown to have a medullary phenotype. Polymerase chain reaction analysis of mRNA extracted from these cells indicated they contained mRNA for B7, a known counter receptor for CTLA4 and CD28. Immunoprecipitation of 125I-labeled thymic epithelial cells with the CTLA4-Ig detected a M(r) 65,000 to 70,000 species under reducing conditions, consistent with previous studies of B7. These data suggest that the ligand for CTLA4 expressed by thymic epithelial cells in vitro is B7 and that the expression of this ligand in situ is largely restricted to the medullary compartment and is associated with epithelial cells and dendritic cells.