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Oversampling data acquisition to improve resolution of digitized signals.

The ability to capture analog signals in a digital format suitable for subsequent storage, processing and analysis by a computer has revolutionized many scientific fields, including biomechanics. In the process of going from the analog signal to its digital representation, it is essential to maintain as much of the original signal content as possible. There is always a loss of information associated with the conversion from analog to digital, independently of how it is actually performed. The only possibility to reduce the loss of information is to increase the number of states or the resolution of the digital signal. The method presented here, based on the same theory used in oversampling analog to digital converters, is applicable to digital signals acquired using any converter. In most situations this method provides a feasible and inexpensive technique to significantly improve the amplitude resolution of the analog to digital conversion. This can be of fundamental importance when the information of interest is small in amplitude compared to the overall signal, or when subsequent ill-conditioned operations, like the computation of the derivatives of the signal, are to be performed.

Analog-Digital Conversion↗

Automation for continuous analysis on microchip electrophoresis using flow-through sampling.

Automation of electrophoretic microchips for sequential analysis of different samples is demonstrated. This system used an autosampler, which was on-line connected to the microchip and the whole process including sample loading and injection, analysis and data acquisition as well as washing were all automated. Rhodamin B at different concentrations was first loaded into a hydrodynamic flow stream by an autosampler, delivered to the microchip, and then sequentially injected into the electrophoretic microchannel for analysis and detection. Automation was achieved by running two independent programs, one for sample loading by an autosampler and the other one for electrophoretic injection by voltage switching, on the same computer. Using this sampling chip, each loaded volume (0.2-1 microL) can be injected for dozens of electrophoretic analyses (1-10 nL for each injection). The variances caused by the external connections, which did not affect the electrophoretic analysis but would cause band broadening of the loaded sample in the hydrodynamic flow stream, were theoretically deduced. Results indicate that the dead volume (approximately 300 nL) due to the connection fitting on the chip could lead to dilution of the loaded sample by a factor of one when 0.2 microL of sample was loaded. Such a design allows sequential analysis of a series of samples while the running buffer is continuously pumped into the connection capillary as well as microchannels for washing between two loaded samples to minimize cross contamination without human intervention. Using this sampling chip, the required sample amount and handling time can be greatly reduced compared to the manual method.

Automation↗

Development of an on-line control system for the cultivation of animal cells in a hollow-fiber reactor using flowing injection analysis and a visual programming language.

A system for the independent control of ammonia and glutamine in a hollow-fiber reactor has been developed. On-line analysis of the two chemical species was performed using FIA. A custom-made program has been written to fully automate the FIA, to perform measurements, calibrations and data acquisition, and to activate two peristaltic feed pumps. Diagnostic tests were also automatically performed in order to identify, and in some cases eliminate, erroneous measurements and calibrations due to instrument failures. For this purpose, a visual programming language (LabVIEW) has been chosen. Ammonia concentration was controlled by varying the medium supply rate to the hollow-fiber reactor which was shown to behave like an ideal-stirred tank reactor. The glutamine concentration was controlled through the intermittent activation of a pump delivering a concentrated solution of this species to the reactor. This control system was tested with a culture of hybridoma cells at three different ammonia and one glutamine set-points. The hollow-fiber reactor was successfully operated automatically for more than 1200 h with ammonia and glutamine concentrations accurately controlled at non-limiting levels. The visual programming environment was found to be reliable and highly suitable for the development of custom programs for bioprocess control.

Animals↗

Comparison of ResMed AutoSet (version 3.03) with polysomnography in the diagnosis of the sleep apnoea/hypopnoea syndrome.

In patients with the sleep apnoea/hypopnoea syndrome (SAHS), accurate and timely diagnostic evaluation and initiation of effective treatment is important. Therefore, an increasing number of limited sleep studies are now performed nowadays diagnosing the SAHS in typical patients. It was the aim of the present study to evaluate the diagnostic accuracy of one such system, the updated ResMed Sullivan AutoSet, against polysomnography. Sixty seven patients underwent full overnight polysomnography and simultaneous data acquisition with the AutoSet. Up to now, the AutoSet was designed for apnoea detection only. The new AutoSet, with software version 3.03, detects apnoeas if ventilation drops to <25%, and apnoeas+hypopnoeas if ventilation drops to <50%, compared with the recent average (100 s), using two independent detectors. A two page report with graphically displayed information on oximetry, snoring and breathing parameters, and an apnoea+hypopnoea index (AHI) and an apnoea index (AI) are provided at the end of each study night. There was a correlation between the AHI assessed by the AutoSet (AHI-AutoSet) and by polysomnography (AHI-PSG; r=0.95). The mean difference between the AHI-AutoSet minus the AHI-PSG was 4.2 (SD 7.2) respiratory events x h(-1) (p<0.001). The AutoSet identified patients with an AHI-PSG >20 events x h(-1) (a level of respiratory disturbance that would warrant consideration for treatment in most centres for sleep disorders), with a sensitivity of 97% and a specificity of 77%. The AutoSet was superior to oximetry alone. As event counting was similar between the two methods, the AHI-AutoSet may provide a reasonable indicator of the respiratory disturbance at night, especially when taking the patients graphic study report into consideration. In conjunction with full clinical information on the patients under investigation, the AutoSet might become a useful device in diagnosing the sleep apnoea/hypopnoea syndrome.

Body Mass Index↗

Acquisition of a touching style.

A qualitative study investigated dental student perceptions of learning to use touch in dental treatment. A focus group design was used to allow volunteer participants (students, general dentistry residents, and dental faculty; n = 41) to discuss issues related to this question. Each focus group was audiotaped for accuracy and transcribed by an independent person. Data gathered were textually and thematically analyzed around the specific questions asked. The data indicated that learning to touch dental patients was often trial and error and uncomfortable for these students. Further, the data suggested that a fine line exists preventing students from asking for assistance and faculty in offering assistance.

Adult↗

Direct tumorigenic conversion of human gallbladder carcinoma cells by v-src but not by activated c-H-ras oncogene.

The roles of activated ras and src oncogene products in the acquisition of fully neoplastic phenotype by human gallbladder adenocarcinoma cells were investigated by co-transfecting non-tumorigenic HAG-I human gallbladder carcinoma cells with the pSV2neo plasmid and a plasmid carrying either activated c-H-ras or v-src oncogene. G418-resistant clones were isolated and assessed for the acquisition of anchorage-independent growth potential. Neither the 10 established clones transfected with pSV2neo alone nor the 17 clones transfected with activated c-H-ras, including 4 clones expressing the mutated p21H-ras protein, could form colonies in soft agar. By contrast, out of 10 clones transfected with v-src, 2 formed colonies in soft agar and produced tumors in athymic nude mice, the resulting progressive neoplasms being poorly differentiated adenocarcinomas. These tumorigenic clones were shown to have v-src DNA and mRNA levels with p60v-src protein, but there were no significant chromosomal alterations following tumorigenic conversion. Moreover, herbimycin A, a selective src-kinase inhibitor, markedly reduced clonogenic growth of these cells in soft agar rather than monolayer growth, suggesting that anchorage-independent growth of the v-src-transformed HAG-I cells might be driven directly by p60v-src kinase activity. Taken together, our data suggest that the fully neoplastic conversion of HAG-I cells depends on src-related tyrosine-kinase activity, but not solely on the function mediated by activated ras, thus providing evidence of an src-related signaling pathway for the acquisition of tumorigenic potential by human gallbladder adenocarcinoma cells.

Adenocarcinoma↗

FAIR true-FISP perfusion imaging of the kidneys.

Most arterial spin labeling (ASL) techniques apply echoplanar imaging (EPI) because this strategy provides relatively high SNR in short measuring times. Unfortunately, those techniques are very susceptible to static magnetic field inhomogeneities and perfusion signals from organs with fast transverse relaxation might decrease due to the exchange of water molecules in capillaries and organ tissue combined with relatively long echo times of EPI sequences. To overcome these problems a novel imaging technique, FAIR True-FISP, was developed. It combines a FAIR (flow-sensitive alternating inversion recovery) perfusion preparation and a true fast imaging with steady precession (True-FISP) data acquisition strategy. True-FISP was chosen since this sequence type does not show the mentioned disadvantages of EPI, but provides a similar SNR per measuring time. An important problem of this approach is that True-FISP sequences usually work in a steady state which is independent of a previous preparation of magnetization. For this reason a sequence structure had to be developed which keeps the advantages of True-FISP and makes the signal intensity sensitive to the FAIR preparation. Breathhold and nonbreathhold examinations of kidneys are presented and possible strategies to quantitative flow measurements are reported. It is shown that correction of spatially inhomogeneous receiver coil characteristics is easily feasible and leads to clinically valuable perfusion examinations of kidneys without application of potentially nephrotoxic contrast media.

Adult↗

Free-standing, stereotactic, microsurgical retraction technique in "key hole" intracranial procedures.

Free-standing, stereotactic, microsurgical retraction technique involves integration of a standard image-guided stereotaxis, an operating microscope and free-standing micro-retractors, data acquisition from computed tomography (CT) images, trajectory determination, and obtaining tumor configuration "in line" with the trajectory using standard CT computer program. The free-standing stereotactic micro-retractors are directed to the lesion using the stereotactic frame. The remainder of the procedure is carried out independent of the stereotactic frame. The technique allows unobstructed access to deep lesions through a "key-hole" opening with excellent visualization of the lesions, and accurate retractor placement. Independent retractor movement also allows visualization of the different corners of the wound. Experience with the first 15 consecutive procedures for stereotactic excision of deep lesions using the Patil frame is reported. Based on this preliminary experience, this technique is free of obstruction, accurate and safe.

Adolescent↗

Enhanced sensitivity for Os isotope ratios by magnetic sector ICP-MS with a capacitive decoupling Pt guard electrode.

A magnetic sector ICP-MS with enhanced sensitivity was used to measure Os isotope ratios in solutions of low Os concentration (approximately 1 ng g(-1) or less). Ratios with 192Os as the basis were determined, while the geologically useful 187Os/188Os ratio was also measured. Sample introduction was via the traditional nebuliser-spray chamber method. A capacitive decoupling Pt shield torch was developed "in-house" and was found to increase Os signals by approximately 5 x under "moderate" plasma conditions (1050 W) over that found during normal operation (1250 W). Sensitivity using the guard electrode for 192Os was approximately 250-350,000 counts s(-1) per ng g(-1) Os. For a I ng g(-1) Os solution with no guard electrode, precisions of the order of 0.2-0.3% (189Os/192Os and 190Os/192Os) to approximately 1% or greater (186Os/192Os, 187Os/192Os and 187Os/188Os) were found (values as 1 sigma for n = 10). With the guard electrode in use, ratio precisions were found to improve to 0.2 to 0.8%. The total amount of Os used in the acquisition of this data was approximately 2.5 ng per measurement per replicate. At the higher concentration of 10 ng g(-1), precisions of the order of 0.15-0.3% were measured (for all ratios), irrespective of whether the shield torch was used. Ratio accuracy was confirmed by comparison with independently obtained NTIMS data. For both Os concentrations considered, the improvement in precision offered by the guard electrode (if any) was small in comparison to calculated theoretical values based on Poisson counting statistics, suggesting noise contributions from other sources (such as the sample introduction system, plasma flicker etc). At lower Os concentrations (to 100 pg g(-1)) no appreciable loss of ratio accuracy was observed, although as expected based on counting statistics, poorer precisions of the order of 0.45-3% (1 sigma, n = 5) were noted. Re was found to have a detrimental effect on the precision of Os ratios involving 187Os, indicating that separation of Re and Os samples is a necessary pre-requisite for highly accurate and precise Os isotope ratio measurements.

Journal Article↗

An investigation of the factors affecting development of frontal cortex self-stimulation.

Intracranial self-stimulation (ICSS) of the medial prefrontal cortex (MFC) is acquired gradually, taking 4 or more days to establish. One explanation for this finding is that the stimulation becomes more rewarding with repetition. Four experiments were conducted to test this hypotheses. In Experiment 1, the MFC ICSS frequency thresholds remained constant over the first 3 weeks of testing while the rate of lever pressing response increased. In Experiment 2, it was found that acquisition of MFC ICSS was much more rapid when a motorically simpler response (nose-poking) was employed. Similarly, Experiments 3 and 4 further demonstrated that response factors such as task complexity may ultimately determine the rate of development of frontal cortex ICSS. Overall, these data suggest that independent of the rewarding effects of MFC stimulation there are other effects that initially interfere with learning of complex operant responses.

Animals↗

Evaluation of fusion beat detection with a new ventricular automatic capture algorithm in ICDs.

This study evaluated a newly developed automatic capture verification scheme for implantable cardioverter defibrillators (ICDs) regarding discrimination of capture, fusion, and noncapture beats, with an emphasis on fusion detection. The algorithm uses evoked response detection based on a sensing vector from right ventricular shocking coil to Can. Patients undergoing ICD implant or replacement were enrolled in this study. An external system was used for pacing and data acquisition. To provoke ventricular fusion beats, VVI patients were paced close to the rate of their intrinsic rhythm and DDD patients were paced close at their intrinsic PR interval. Surface ECG and wideband filtered intracardiac electrograms were recorded for off-line analysis. Each paced beat was independently classified visually by surface ECG and by the automatic detection algorithm. The algorithm performance was then evaluated by comparing the classification results. Twenty-seven patients (22 males, 5 females; 63.8 +/- 12.5 years) were analyzed. Device and lead demographics were: 18 DDD/9 VVI; 16 dedicated bipolar, 11 integrated bipolar leads; 18 acute, 9 chronic (3.7 +/- 2.0 years) leads. In total, 2064 beats were analyzed, including 1,477 fusion beats and 587 capture beats. Fusion detection sensitivity and specificity were 99.5% and 99.0%, respectively. Seven true-fusion beats (0.5%) were classified as capture and 6 capture beats (1.0%) were identified as fusions. Capture or fusion beats were never detected as non-capture beats. It is concluded that the algorithm was effective in detecting fusion beats. It could potentially be used in ICD applications that need accurate fusion detection.

Algorithms↗

Dopamine receptors for every species: gene duplications and functional diversification in Craniates.

The neuromodulatory effects of dopamine on the central nervous system of craniates are mediated by two classes of G protein-coupled receptors (D1 and D2), each comprising several subtypes. A systematic isolation and characterization of the D1 and D2-like receptors was carried out in most of the Craniate groups. It revealed that two events of gene duplications took place during vertebrate evolution, before or simultaneously to the emergence of Gnathostomes. It led to the conservation of two-to-four paralogous receptors (subtypes), depending on the species. Additional duplication of dopamine receptor gene occurred independently in the teleost fish lineage. Duplicated genes were maintained in most of the vertebrate groups, certainly by the acquisition of a few functional characters, specific of each subtypes, as well as by discrete changes in their expression territories in the brain. The evolutionary scenario elaborated from these data suggests that receptor gene duplications were the necessary conditions for the expansion of vertebrate forebrain to occur, allowing dopamine systems to exert their fundamental role as modulator of the adaptive capabilities acquired by vertebrate species.

Animals↗

[The use of an integrable mobile full text processing systems (author's transl)].

A mobile full text processing system is reported which is independent of a computer, yet can be completely integrated into a data processing system and is purely a storage and retrieval system for data files and data banks which, with relatively little activity ratio of the individual items of information stored, still have an unusually large, widely ramified indexing depth. Acquisition of material, storage and retrieval of information are so simplified in favor of the user, that they can be carried out without specially qualified data processing personnel, but by normal office staff and one's own colleagues after a simple short instruction. The favorable cost makes the system an alternative worth considering in many cases, because fully automatic documentation or system concepts which need digital storage of large quantities of text demand so much intellectual expense and electronic storage capacity, that they are already prohibitive on grounds of cost alone.

Costs and Cost Analysis↗

Evaluation of differential magnification during brain SPECT acquisition.

OBJECTIVE: We developed a modification of the acquisition zoom technique, referred to as differential magnification (DM), to improve the pixel resolution with fanbeam collimators. This study evaluated the effects of DM on brain SPECT image quality. METHODS: SPECT imaging was performed using a triple-head camera with and without DM for a line source in air, Jaszczak and Hoffman phantoms, and 15 clinical patients having regional cerebral blood-flow scans with 99mTc ECD. Full width at half maximum (FWHM) and contrast ratios were measured on the line source and Jaszczak phantom data, respectively. Visual image evaluation was performed by 2 independent, blinded observers for the Hoffman brain phantom images and clinical patient studies. RESULTS: FWHM improved on the fanned axis (transverse plane) by 0.05 mm (P < 0.001), and the unfanned axis (longitudinal plane) by 0.66 mm (P < 10(-6)), when DM was used. The mean improvement of contrast ratios for the spheres on the Jaszczak phantom with DM was 11.4% (P < 0.004). The images with DM were rated superior to those without, for the Hoffman brain phantom and the clinical patients. CONCLUSION: This study has demonstrated that SPECT acquisition with fanbeam collimators and DM significantly improves both FWHM and image contrast, resulting in superior image quality. DM techniques may be useful in improving clinical brain SPECT images.

Adult↗

Suppression of the transformed phenotype and induction of differentiation-like characteristics in cultured ovarian tumor cells by chronic treatment with progesterone.

Epidemiological evidence suggests that elevated levels of the pregnancy hormone progesterone might play a role in the reduced risk of women to develop ovarian cancer. In vitro studies have supported this hypothesis by demonstrating negative effects of this hormone on the growth and proliferation of cultured ovarian carcinoma cells. However, little is known about the underlying molecular processes and how progesterone might decrease the risk for ovarian tumors. Therefore, we investigated the effects of chronic hormone treatment on the cell-cycle and transformed phenotype of ovarian carcinoma cell lines in vitro. We found that long-term treatment of these cells with progesterone caused a concomitant reduction of cyclin-dependent kinase (CDK) activity. In parallel, these cells lost their transformed phenotype as indicated by the acquisition of contact inhibition and the loss of anchorage-independence, as well as the reduced expression of tumor markers such as heat shock protein (HSP) 72 and carcinoma antigen (CA) 125. In addition, progesterone-treated cells exhibited characteristics that resembled a more differentiated phenotype. Taken together, our data indicated that progesterone was able to suppress the transformed phenotype of ovarian tumor cells. This observation could serve to explain progesterone's alleged protective effect in ovarian carcinogenesis.

Blotting, Western↗

Simultaneous measurement of DeltaR2 and DeltaR2* in cat brain during hypoxia and hypercapnia.

One of the most important issues in blood-oxygen-level-dependent (BOLD)-based brain functional magnetic resonance imaging is the understanding of the vascular structures that are responsible for the signal changes observed. The T2*-related signal changes observed during variations in susceptibility-induced magnetic field gradients are a function both of non-refocusable mechanisms, such as diffusion, and of refocusable effects such as field inhomogeneities. Conversely, T2-related signal changes are only a function of non-refocusable effects. It has been suggested that T2-weighted images could be less sensitive to blood susceptibility changes in a macrovascular environment than T2*-weighted images and could thus be more accurate in identifying the "activation" of the parenchyma rather than "draining vein" effects. In this study we use hypoxia and hypercapnia challenges in cats to provide a change in blood deoxyhemoglobin concentration (as a model for classic BOLD changes and not as a model for neuronal activation). A combined gradient echo and spin echo echo-planar-imaging (EPI) pulse sequence was used to map DeltaR2 (i.e., Delta(1/T2)) and DeltaR2* (i.e., Delta(1/T2*)) changes during the challenges. Our experiments demonstrate that: (i) the acquisition of T2-weighted EPI data does not in itself differentiate signal changes in the parenchyma from those occurring in regions around larger vessels, but that (ii) the simultaneous acquisition of T2- and T2*-weighted images could be useful in identifying microvascular regions in gray matter by analyzing the ratio DeltaR2/DeltaR2*. This value seems independent of the degree of deoxyhemoglobin concentration change, but is related to properties of the vascular environment. We suggest a possible application of the results to the study of brain function in humans.

Animals↗

Enhancement of the bulbocavernosus reflex during intraoperative neurophysiological monitoring through the use of double train stimulation: a pilot study.

OBJECTIVE: Electrophysiological bulbocavernosus reflex (BCR) testing, during surgeries in which the constituent neural components are at risk, might supplement other low sacral (S2-4) stimulation/recording techniques. However, intraoperative BCR is not always reliably implemented. We proposed to analyze BCR signals in five surgical patients monitored with the novel application of double train stimulation (DTS) to determine if the potential could be enhanced. METHODS: We prospectively planned a regime of DTS BCR with a series of intertrain delays in five monitored patients at risk for low sacral neural injury. Patients were maintained with propofol, opiate infusion, and low inhalant anesthesia without muscle relaxant. Cutaneous sensory nerves of the penis (or clitoris) were stimulated using two consecutive pulse trains (DTS). Intertrain delays were 75, 100, 125, 150, 175, 200, and 250 ms. For BCR recording, uncoated paired wires were inserted into the external anal sphincter (EAS) bilaterally. For each trial, waveform amplitude, duration, and turn count measures for the first (single train) and second (double train) response were recorded. Percent increase/decrease of the second train response compared to the first train response was calculated. RESULTS: There was at least a 30% increase in measures of amplitude, turn count, and duration of the second train response in 22/28, 22/28, and 14/28 of the total trials respectively. There was an insufficient number of independent observations to determine statistical significance. CONCLUSIONS: Intraoperative BCR is currently obtained with some difficulty using pulse train stimulation. Our preliminary evidence has identified BCR waveform enhancement using DTS and suggests that the reliability of intraoperative BCR acquisition may be further improved by the addition of this technique. Our data are insufficient to define the best intertrain interval.

Adult↗

Associative and non-associative changes in unit activity of the rat hippocampus.

Two main types of neurons of the dorsal hippocampus were recorded in chronic rats during the classical conditioning of an arousal phenomenon (neocortical EEG desynchrony). The relative importance of the associative and non-associative factors was assessed by a differentiation procedure. In naive rats, during the "acquisition" session most type-I neurons rapidly acquired an "inhibitory" response closely parallel to the EEG response. Neither of these responses showed differentiation. Some type-II neurons acquired an "excitatory" response which was independent of the EEG response and which had a significant tendency to differentiation. These data were confirmed in rats submitted to several "retention" sessions. All the type-I neurons were undifferentiated while 11 out of 41 type-II neurons were differentiated. Type-I neurons were characterized by a bursting mode of discharge. Their activity was higher during slow wave sleep (SWS) than during wakefulness (W) or paradoxical mode of discharge. Most of the differentiated type-II neurons were more active during W and/or PS than during SWS.

Acoustic Stimulation↗