Biomedical subjects
Publications and source records attributed to A Marshall.
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OBJECTIVE: A chirp is a brief signal within which the frequency content changes rapidly. Spectrographic chirps are found in signals produced from many biological and physical phenomena. In radar and sonar engineering, signals with chirps are used to localize direction and range to the signal source. Although characteristic frequency changes during epileptic seizures have long been observed, the correlation with chirps and chirp technology seems never to have been made. METHODS: We analyzed 19404 s (1870 s of which were from 43 seizures) of intracranially (subdural and depth electrode) recorded digital EEG from 6 patients for the presence of spectral chirps. Matched filters were constructed from methods in routine use in non-medical signal processing applications. RESULTS: We found that chirps are very sensitive detectors of seizures (83%), and highly specific as markers (no false positive detections). The feasibility of using spectral chirps as matched filters was demonstrated. CONCLUSIONS: Chirps are highly specific and sensitive spectrographic signatures of epileptic seizure activity. In addition, chirps may serve as templates for matched filter design to detect seizures, and as such, can demonstrate localization and propagation of seizures from an epileptic focus.
Effects on mosquito breeding, acidity, and fish presence were assessed after installation of a small tidal leakage port into an acidic drain's tidal exclusion flap gate. Before gate modification the drain water had pH values as low as 2.7. These water conditions were toxic to fish and continually held mosquito larvae. At 4 wk after gate modification, water pH had risen to 6.0, at least 3 fish species inhabited the drain, and mosquito larval numbers had been reduced by 99.98%.
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AIM: Epididymal proteins are known to play an important role in the maturation of spermatozoa. We ought to determine if there are regional differences in androgen-dependent epididymal proteins. METHODS: A group of adult rats was castrated and epididymides were removed three days following castration. The epididymides were dissected into caput, corpus and cauda segments, homogenized, and proteins were fractionated by anion exchange HPLC. Proteins in selected fractions were resolved by SDS-PAGE and visualized by silver staining. RESULTS: It was observed that the levels of multiple proteins drastically reduced in the various regions of epididymis of the orchiectomized rats. CONCLUSION: The epididymal proteins appear to be useful markers to study androgenic action in the epididymis.
Nontemplated (N) nucleotide additions contribute significantly to the junctional diversity of all Ag receptor chains in adult mice except Ig light (L) chains, primarily because terminal deoxynucleotidyl transferase (TdT) expression is turned off at the time of their rearrangement in pre-B cells. However, because some Ig L chain gene rearrangements are detectable earlier during B cell ontogeny when TdT expression is thought to be maximal, we have examined the junctional processing of kappa- and lambda-chain genes of CD45(B220)+CD43+ pro-B cells from mu MT mice. We found that both kappa and lambda coding junctions formed in these B cell precursors were extensively diversified with N-region additions. Together, these findings demonstrate that Ig L chain genes are equally accessible to TdT in pro-B cells as Ig heavy chain genes. Surprisingly, however, the two L chain isotypes differed in the pattern of N addition, which was more prevalent at the lambda-chain locus. We observed the same diversity pattern in pre-B cells from TdT-transgenic mice. These results suggest that some aspects of TdT processing could be influenced by factors intrinsic to the sequence of Ig genes and/or the process of V(D)J recombination itself.
RNA encoding the rat serotonin 5-HT2C receptor undergoes editing whereby one to four adenosines are converted to inosines. This conversion can change up to three codons out of a stretch of five in the second intracellular loop of the receptor. RNA editing of the rat 5-HT2C receptor that changes all three codons was shown previously to alter intracellular signaling by 5-HT without changing its receptor-binding affinity. We analyzed 5-HT2C receptor editing in human brain and hypothalamic RNA samples and confirmed that all four adenosine editing sites observed in rat were also present in human samples. Additionally, we identified a novel editing site in the middle edited codon that extends the repertoire of 5-HT2C receptors by six additional protein isoforms. We observed that editing reduces both the binding affinity and functional potency of agonists for recombinant human 5-HT2C receptor isoforms. This effect on binding affinity was proportional to the agonist's intrinsic activity, with full agonists most affected, and antagonists showing no effect. These data suggest that RNA editing may alter coupling energetics within the ternary complex, thereby altering agonist binding affinities, G protein coupling, and functional responses. RNA editing may thus provide a novel mechanism for regulating 5-HT synaptic signaling and plasticity.
CPAP therapy helps improve oxygenation in patients who are awake and able to maintain a good respiratory drive. In many cases this means that intubation and ventilation can be avoided. The main goals of CPAP are to minimise alveolar collapse, improve compliance, decrease work of breathing and improve ventilation/perfusion matching. These effects work together to improve arterial oxygenation. A clear, concise and straightforward discussion of CPAP is difficult to find in the existing literature. As CPAP has developed into a common therapy for patients with respiratory failure, it is essential that nurses using this therapy are familiar with the equipment and the physiological effects it produces. Assessment and management of the patient receiving CPAP therapy are also important. This paper will address the physiological principles of CPAP therapy so that nurses working with critically ill patients receiving CPAP therapy understand the system and are accurate and astute in their respiratory assessment, in order to provide optimum care.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.