Intrathecal catheters after dural puncture--some unanswered questions.
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Analgesia, Epidural↗
Biomedical subjects
A Patwardhan
Publications and source records attributed to A Patwardhan.
Topical ciprofloxacin can delay recovery from viral ocular surface infection.
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Adenoviridae Infections↗
Dynamic cardiorespiratory interaction during head-up tilt-mediated presyncope.
In 28 healthy adults, we compared the dynamic interaction between respiration and cerebral autoregulation in 2 groups of subjects: those who did and did not develop presyncopal symptoms during 70 degrees passive head-up tilt (HUT), i.e., nonpresyncopal (23 subjects) and presyncopal (5 subjects). Airflow, CO2, cerebral blood flow velocity (CBF), ECG, and blood pressure (BP) were recorded. To determine whether influences of mean BP (MBP) and systolic SP (SBP) on CBF were altered in presyncopal subjects, coherencies and transfer functions between these variables and mean and peak CBF (CBFm and CBFp) were estimated. To determine the influence of end-tidal CO2 (ETco2) on CBF, the relative CO2 reactivity (%change in CBFm per mmHg change in ETco2) was calculated. We found that in presyncopal subjects before symptoms during HUT, coherence between SBP and CBFp was higher (P=0.02) and gains of transfer functions between BP (MBP and SBP) and CBFm were larger (MBP, P=0.01; SBP, P=0.01) in the respiratory frequency region. In the last 3 min before presyncope, presyncopals had a reduced relative CO2 reactivity (P=0.005), likely a consequence of the larger decrease in ETco2. We hypothesize that the CO2-mediated increase in resistance attenuates autoregulation such that the relationship between systemic and cerebral hemodynamics is enhanced. Our results suggest that an altered cardiorespiratory interaction involving cerebral hemodynamics may contribute in the cascade of events during tilt that culminate in unexplained syncope.
Adult↗
Preparation and electrochemical behavior of gramicidin-bipolar lipid monolayer membranes supported on gold electrodes.
Gramicidin-containing synthetic bolalipid membranes comprised of 2,2'-di-O-decyl-3,3'-O-1,20-eicosanyl-bis-rac-glycero-1,1'-diphosphocholine (C20BAS) have been synthesized and supported on gold electrodes. Supported membranes were prepared by first depositing a partial bolalipid layer on the electrode using a thioctic acid-modified bolalipid (1'-O-omega-thioctamidetetraethylene glycol-2,2'-di-O-decyl-3,3'-di-O-1,20-eicosanyl-bis-rac-glycero-1-phosphate, SSC20BAS) as an anchoring group, followed by a vesicle fusion step using either pure C20BAS or gramicidin-containing C20BAS (C20BAS-GA) vesicles. The latter configuration was designed to immobilize single, continuously-on channels of gramicidin in the C20BAS membrane. Vesicle deposition to form supported bolalipid monolayer membranes was monitored by impedance spectroscopy and cyclic voltammetry. Impedances were observed to increase with vesicle deposition time. Pretreatment of the impedance electrode with SSC20BAS accelerated the supported monolayer membrane deposition rate. Impedances decreased in a gramicidin concentration-dependent manner when gramicidin was incorporated into the C20BAS membrane. These supported bolalipid membranes are also surprisingly inert to organic solvent exposure (CH(3)CH(2)OH;CH(2)Cl(2)), suggesting that they may serve as robust host matrices for integral membrane protein-based sensors.
Biosensing Techniques↗
Mass photokeratitis following exposure to unprotected ultraviolet light.
We report a cluster of patients developing photokeratitis as a result of exposure to unprotected UV-B light source. The incident occurred at a cattle livestock market auction where the light source protective covers of mercury vapour lamps were damaged because of vandalism. The incident was investigated by the District Council as a public health and safety issue. This report stresses the hazards of ultraviolet lamps routinely used in public places and the need for proper maintenance of these light sources.
Cluster Analysis↗
Attenuation of frontal asymmetry in pediatric posttraumatic stress disorder.
BACKGROUND: Volumetric imaging research has shown abnormal brain morphology in adults with posttraumatic stress disorder (PTSD) when compared with matched control subjects. In this article, we present brain imaging findings from a study of children with PTSD symptoms. METHODS: Twenty-four children between the ages of 7 and 14 with a history of trauma and PTSD symptoms were assessed with the Clinician-Administered PTSD Scale for Children and Adolescents (CAPS-CA). The sample underwent magnetic resonance imaging in a 1.5 T scanner. Brain images were analyzed by raters blind to diagnostic status using well-standardized methods, and images were compared with age- and gender-matched healthy control subjects. RESULTS: The clinical group demonstrated attenuation of frontal lobe asymmetry and smaller total brain and cerebral volumes when compared with the control group. There were no statistically significant differences in hippocampal volume between clinical and control subjects. CONCLUSIONS: Frontal lobe abnormalities may occur as a result of PTSD in children or, alternatively, be a risk factor for the development of the syndrome in this age group. The implications of the findings and their consistency with previous research are discussed.
Adolescent↗
Correlation between defibrillation shock outcome and coherence in electrocardiograms.
Cycle periods in ECG during VF are correlated with periods of reentrant activation. The ECGs recorded from different locations on the thorax were contributed to from electrical activations within the heart in approximately inverse proportion of their distance from the recording sites. Similarity in cycle periods between ECGs recorded from two locations, therefore, can be used as an index of spatiotemporal similarity in the rate of activation. In the present study coherence was used, which is a mathematical function that measures the degree of similarity that two signals exhibit at specific cycle periods, to test if spatiotemporal similarity in cycle periods between pairs of orthogonal ECGs was correlated with defibrillation shock outcome. The authors estimated time-varying coherence from orthogonal ECGs during 10 seconds of electrically induced VF, which was terminated with a defibrillation shock with a 50% probability of successful outcome. Defibrillation shocks were delivered between a coil electrode placed at the right ventricular apex and a subdermal patch electrode. Time-varying coherencies between pairs of ECGs were estimated using an adaptive least mean square algorithm. Time-coherence surfaces were integrated within a frequency region centered at the dominant frequency. Data were collected from ten dogs during 206 (48%) successful and 221 (52%) unsuccessful trials. The results showed that coherencies between the sagittal-transverse pair were 10%-15% higher (P < 0.05) for successful than unsuccessful trials. The correlation between coherence and defibrillation outcome suggests that more defibrillation shocks occurred when the degree of spatial similarity in the rate of activations was higher terminated VF, than those that occurred at other times. These results are consistent with a hypothesis, recently proposed by others, that more uniform activation within regions of the heart that receive low potential gradients during shock may increase the probability of successful defibrillation.
Animals↗
The simultaneous recurrent neural network for addressing the scaling problem in static optimization.
A trainable recurrent neural network, Simultaneous Recurrent Neural network, is proposed to address the scaling problem faced by neural network algorithms in static optimization. The proposed algorithm derives its computational power to address the scaling problem through its ability to "learn" compared to existing recurrent neural algorithms, which are not trainable. Recurrent backpropagation algorithm is employed to train the recurrent, relaxation-based neural network in order to associate fixed points of the network dynamics with locally optimal solutions of the static optimization problems. Performance of the algorithm is tested on the NP-hard Traveling Salesman Problem in the range of 100 to 600 cities. Simulation results indicate that the proposed algorithm is able to consistently locate high-quality solutions for all problem sizes tested. In other words, the proposed algorithm scales demonstrably well with the problem size with respect to quality of solutions and at the expense of increased computational cost for large problem sizes.
Algorithms↗
Novel feedback based stimulation protocol shows hysteresis in cardiac action potential duration restitution.
Short diastolic intervals (DI) produce short action potential durations (APD) due to restitution. Slope of restitution is hypothesized to be critical in initiation of VF. Importance of restitution in mechanisms of VF is recently debated, primarily because of a lack of consistent characterization of restitution. Currently used protocols, standard and dynamic, include pacing at constant S1-S1 intervals for a number of stimuli followed by an S2 or not. In these, DI are a function of both APD (memory effect) and pacing interval (DI = pacing interval--APD). Therefore, restitution functions obtained after variable number of S1 or variable S1-S1 intervals are different. We developed a novel feedback based protocol that permits selection of DI independent of pacing interval and APD. From the instant when transmembrane voltage drops below 90% of repolarization voltage, a stimulus is delivered after predetermined DI. We used DI that oscillated between 0 and 60 msec with periods ranging from 15 sec to 500 msec to quantify effects of short and long term memory on restitution. We used a Luo-Rudy dynamic model of cellular activation. Resulting restitution functions clearly showed multi-modal behavior and hysteresis. When DI increased following a period of decreasing intervals, the APD were shorter than when DI decreased following increasing intervals. Thus, same DI produce different APDs depending on past activation history. Such variation in APD may play a role in increased incidence of VF that is reported after large oscillations in heart rate, i.e. when episodes of bradycardia follow a tachycardic episode.
Action Potentials↗
Healing of partial flap necrosis in ankle disarticulation amputation by débridement and continued weight-bearing.
Five patients with partial tissue loss of the weight-bearing surface of the heel pad following ankle disarticulation were treated with residual-limb debridement and continued end-weight-bearing using a total-contact cast. The patients, ranging in age from 53 to 76 years, had insulin-requiring diabetes and insensate heel pads and were low-demand, limited-activity, community walkers before amputation surgery. Each underwent amputation surgery as a consequence of peripheral vascular disease. All patients progressed to complete wound healing over 3 to 6 months and were able to return to their previous ambulatory level using a prosthesis. At a minimum 2-year follow-up, no patient experienced further residual-limb complications. Partial loss of the weight-bearing heel pad in ankle disarticulation amputation does not preclude successful return to independent ambulation using a standard ankle disarticulation prosthesis. Weight-bearing ambulation need not be avoided during healing.
Aged↗
Brain imaging in neurogenetic conditions: realizing the potential of behavioral neurogenetics research.
Behavioral neurogenetics research is a new method of scientific inquiry that focuses on investigation of neurodevelopmental dysfunction associated with specific genetic conditions. This research method provides a powerful tool for scientific inquiry into human gene-brain-behavior linkages that complements more traditional research approaches. In particular, the use of specific genetic conditions as models of common behavioral and cognitive disorders occurring in the general population can reveal insights into neurodevelopmental pathways that might otherwise be obscured or diluted when investigating more heterogeneous, behaviorally defined subject groups. In this paper, we review five genetic conditions that commonly give rise to identifiable neurodevelopmental and neuropsychiatric disability in children: fragile X syndrome, velo-cardio-facial syndrome, Williams syndrome, Turner syndrome, and Klinefelter syndrome. While emphasis is placed on describing the brain morphology associated with these conditions as revealed by neuroimaging studies, we also include information pertaining to molecular genetic, postmortem, and neurobehavioral investigations to illustrate how behavioral neurogenetics research can contribute to an improved understanding of brain disorders in childhood.
Diagnostic Imaging↗
Single-particle electron cryo-microscopy: towards atomic resolution.
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Animals↗
Frequency modulation within electrocardiograms during ventricular fibrillation.
Periods of reentrant activation and effective refractory periods are correlated with dominant frequency or reciprocal of cycle periods during ventricular fibrillation (VF). In the present study, we used an analysis technique based on Wigner transforms to quantify time-varying dominant frequencies in electrocardiograms (ECGs) during VF. We estimated dominant frequencies within orthogonal ECGs recorded in 10 dogs during trials of 10 s of VF and in 9 dogs during trials of 30 s of VF. In four additional dogs, we compared dominant frequencies during 10 s of VF before and after administration of amiodarone. Our results showed the following. 1) There was substantial frequency variation or modulation within the ECGs during 10 and 30 s of VF, the average variation being +/-15% from the mean frequency. Amiodarone decreased mean frequencies (P < 0.05) as expected; however, amiodarone also decreased the variation in frequencies (P < 0.05). 2) During 30 s of VF, the dominant frequencies increased continuously from 7.3 to 8.1 Hz (P < 0.05). The increase in frequency was almost linear with a rate of 0.022 Hz/s (r(2) = 0.93, P < 0.0005). 3) Modulation of frequencies during the first and the last one-half of 30 s of VF was not different. Average (in time) mean frequencies and modulation of frequencies were similar in all three ECGs. 4) Although the averages were similar, during any VF episode, dominant frequencies in ECGs recorded from different locations on the body surface were similar to each other at some times and markedly different from each other at other times. We conclude that during VF, 1) frequencies in ECGs vary considerably and continuously, and amiodarone decreases this variation; 2) mean frequencies increase linearly during first 30 s; 3) the variability in frequency does not change during 30 s; and 4) at any given time, the frequencies within spatially different body surface ECGs can be either similar or markedly different.
Amiodarone↗
The Escherichia coli large ribosomal subunit at 7.5 A resolution.
BACKGROUND: In recent years, the three-dimensional structure of the ribosome has been visualised in different functional states by single-particle cryo-electron microscopy (cryo-EM) at 13-25 A resolution. Even more recently, X-ray crystallography has achieved resolution levels better than 10 A for the ribosomal structures of thermophilic and halophilic organisms. We present here the 7.5 A solution structure of the 50S large subunit of the Escherichia coli ribosome, as determined by cryo-EM and angular reconstitution. RESULTS: The reconstruction reveals a host of new details including the long alpha helix connecting the N- and C-terminal domains of the L9 protein, which is found wrapped like a collar around the base of the L1 stalk. A second L7/L12 dimer is now visible below the classical L7/L12 'stalk', thus revealing the position of the entire L8 complex. Extensive conformational changes occur in the 50S subunit upon 30S binding; for example, the L9 protein moves by some 50 A. Various rRNA stem-loops are found to be involved in subunit binding: helix h38, located in the A-site finger; h69, on the rim of the peptidyl transferase centre cleft; and h34, in the principal interface protrusion. CONCLUSIONS: Single-particle cryo-EM is rapidly evolving towards the resolution levels required for the direct atomic interpretation of the structure of the ribosome. Structural details such as the minor and major grooves in rRNA double helices and alpha helices of the ribosomal proteins can already be visualised directly in cryo-EM reconstructions of ribosomes frozen in different functional states.
Bacterial Proteins↗
Automated Talairach atlas-based parcellation and measurement of cerebral lobes in children.
This study applied a Talairach-based automated parcellation method, originally proposed for adults, to the measurement of lobar brain regions in pediatric study groups. Manual measures of lobar brain regions in a sample of 15 healthy boys, girls and adults were used initially to revise the original Talairach-based grid to increase its applicability to pediatric brains. The applicability of the revised Talairach grid was then tested on an independent sample of five girls with Rett syndrome. As Tables 3 and 4 in the text demonstrate, sensitivity, specificity and positive predictive values either remained unchanged or increased as a result of revising the sectors to fit the brains of children. High levels of sensitivity and specificity were achieved for all revised Talairach-based calculations in relation to the manual measures. Both positive predictive values and intraclass correlations between volumetric measures produced by the revised automated and manual methods varied with the relative size of the brain region. Values were relatively low for smaller structures such as the brainstem and subcortical region, and high for lobar regions. These results suggest that the automated Talairach atlas-based parcellation method can produce sensitive and specific volumetric measures of lobar brain regions in both normal children and children with brain disorders. Accordingly, the method holds much promise for facilitating quantitative pediatric neuroimaging research.
Adult↗
Increased occurrence of IgE+ and FcepsilonRI+ cells in adenoids from atopic children.
BACKGROUND: To examine the influence of atopy on the different cell populations in adenoids, we investigated the presence of IgE+ cells, cells expressing the high-affinity receptor for IgE (Fc(epsilon)RI), and various other cell populations in adenoid tissue, in atopic and nonatopic children with otitis media with effusion (OME) or adenoid hyperplasia (AH). METHODS: Cryostat sections of adenoids from 14 atopic and 16 nonatopic children suffering from long-lasting OME (n=15) or obstructive AH (n=15) were investigated with immunohistochemical markers for T-cell subsets, mast cells, eosinophils, plasma cells, CD25, CD1a, IgE, and Fc(epsilon)RI. RESULTS: Sensitization to allergens was correlated to an increase of IgE+ cells in the epithelium (P<0.01), the extrafollicular area (P<0.0001), and the follicles (P<0.001) of the adenoids and an increase of Fc(epsilon)RI+ cells in the extrafollicular area (P<0.01). A minority of the IgE+ cells were plasma cells. No significant differences in cells stained for IgE, Fc(epsilon)RI, or the other markers were observed between patients with OME and AH. CONCLUSIONS: Atopy is associated with increased numbers of IgE+ and Fc(epsilon)RI+ cells in adenoids irrespective of whether the child has OME or AH.
Adenoids↗
Animal models of spinal cord contusion injuries.
BACKGROUND AND PURPOSE: Traumatic spinal cord injury causes initial mechanical disruption of tissue, leading to a complex secondary sequence of pathophysiologic changes and neurologic impairment. These sequelae depend on the impact force delivered to the spinal cord at the time of injury. Successful clinical evaluation of the efficacy of any therapeutic regimen depends on the reliability and reproducibility of an experimental animal model. We describe a trauma device and the biomechanical parameters required to induce severe or moderate spinal cord contusion injury in cats and rats. METHODS: Recovery after injury was determined by behavioral, electrophysiologic, and histologic evaluations. RESULTS: Behavioral and electrophysiologic tests after injury clearly identified the experimental groups. A stable severe paraplegic state (defined as 6 months for cats and 8 weeks for rats), without evidence of behavioral or electrophysiologic recovery, was induced by a 65-Newton (N) load for cats and a 35-N load for rats. Moderate spinal cord contusion injury, from which cats and rats partially recovered after approximately 3 months and 4 weeks, respectively, was induced by a 45- and 25-N load, respectively. CONCLUSION: Use of these injury conditions provides reliable animal models for studies designed to evaluate potential therapeutic regimens for spinal cord injury.
Animals↗
The natural history of the cervical foramen in symptomatic and asymptomatic individuals aged 20-60 years as measured by magnetic resonance imaging. A descriptive approach.
STUDY DESIGN: This study was intended to identify normal degenerative morphologic evolution in the bony foramen in asymptomatic subjects by decade in comparison with symptomatic subjects of like decades. OBJECTIVES: To determine normal degenerative changes in the cervical spine caused by the aging process that predispose a person to foraminal stenosis and radiculopathy. SUMMARY OF BACKGROUND DATA: Cervical radiculopathy is a common problem caused by degenerative changes as people age. The characteristics of the foramen that result in stenosis are not known. METHODS: Five to six symptomatic and asymptomatic people in each decade volunteered for magnetic resonance imaging. Lordosis, disc heights, and ratio of spinal cord diameter to spinal canal diameter were measured at C4-C5, C5-C6, and C6-C7 from sagittal magnetic resonance images. Foraminal heights, widths, and areas were measured at the isthmus of the same foramen from oblique images. RESULTS: Foraminal heights, widths, and areas were larger in asymptomatic patients than in symptomatic patients. Morphologic analysis showed that inferior facet hypertrophy tended to decrease the width of the foramen in aging people. Disc heights, lordosis, and ratio of spinal cord diameter to spinal canal diameter showed no significant differences. CONCLUSIONS: Foraminal height affects overall foraminal area but tends to change little with age. Width also affects overall area and not only decreases in older people but also significantly affects the available area for the exiting nerve root.
Adult↗