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Biomedical subjects

T A Dickinson

Publications and source records attributed to T A Dickinson.

10 recordsLinked to original sources
PubMed1999

Convergent, self-encoded bead sensor arrays in the design of an artificial nose.

We report a new approach to designing an artificial nose based on high-density optical arrays that directly incorporate a number of structural and operational features of the olfactory system. The arrays are comprised of thousands of microsphere (bead) sensors, each belonging to a discrete class, randomly dispersed across the face of an etched optical imaging fiber. Beads are recognized and classified after array assembly by their unique, "self-encoded" response pattern to a selected vapor pulse. The high degree of redundancy built into the array parallels that found in nature and affords new opportunities for chemical-sensor signal amplification. Since each bead is independently addressable through its own light channel, it is possible to combine responses from same-type beads randomly distributed throughout the array in a manner reminiscent of the sensory-neuron convergence observed in the mammalian olfactory system. Signal-to-noise improvements of approximately n1/2 have been achieved using this method.

Artificial Organs↗
PubMed1998

An olfactory neuronal network for vapor recognition in an artificial nose.

Odorant sensitivity and discrimination in the olfactory system appear to involve extensive neural processing of the primary sensory inputs from the olfactory epithelium. To test formally the functional consequences of such processing, we implemented in an artificial chemosensing system a new analytical approach that is based directly on neural circuits of the vertebrate olfactory system. An array of fiber-optic chemosensors, constructed with response properties similar to those of olfactory sensory neurons, provide time-varying inputs to a computer simulation of the olfactory bulb (OB). The OB simulation produces spatiotemporal patterns of neuronal firing that vary with vapor type. These patterns are then recognized by a delay line neural network (DLNN). In the final output of these two processing steps, vapor identity is encoded by the spatial patterning of activity across units in the DLNN, and vapor intensity is encoded by response latency. The OB-DLNN combination thus separates identity and intensity information into two distinct codes carried by the same output units, enabling discrimination among organic vapors over a range of input signal intensities. In addition to providing a well-defined system for investigating olfactory information processing, this biologically based neuronal network performs better than standard feed-forward neural networks in discriminating vapors when small amounts of training data are used.

Animals↗
PubMed1998

Current trends in 'artificial-nose' technology.

Basic principles derived from biological olfaction, such as combining semiselective sensor arrays with pattern recognition, have been used to develop instrumentation capable of broad-band chemical detection and quantification. Commercially available instruments are useful in areas including quality control in the food, beverage and fragrance industries, environmental monitoring, chemical-purity and -mixture analysis, and medical diagnostics. Ongoing research is aimed at the development of more-advanced instruments that are smaller, cheaper, faster and more stable and reliable. These second-generation instruments are likely to find an increasing number of applications, including the on-line monitoring of fermentation and other bioprocesses.

Electronic Data Processing↗
PubMed1996

A chemical-detecting system based on a cross-reactive optical sensor array.

The vertebrate olfactory system has long been recognized for its extraordinary sensitivity and selectivity for odours. Chemical sensors have been developed recently that are based on analogous distributed sensing properties, but although an association between artificial devices and the olfactory system has been made explicit in some previous studies, none has incorporated comparable mechanisms into the mode of detection. Here we describe a multi-analyte fibre-optic sensor modelled directly on the olfactory system, in the sense that complex, time-dependent signals from an array of sensors provide a 'signature' of each analyte. In our system, polymer-immobilized dye molecules on the fibre tips give different fluorescent response patterns (including spectral shifts, intensity changes, spectral shape variations and temporal responses) on exposure to organic vapours, depending on the physical and chemical nature (for example, polarity, shape and size) of both the vapour and the polymer. We use video images of temporal responses of the multi-fibre tip as the input signals to train a neural network for vapour recognition. The system is able to identify individual vapours at different concentrations with great accuracy. 'Artificial noses' such as this should have wide potential application, most notably in environmental and medical monitoring.

Biosensing Techniques↗
PubMed1995

Mechanism of inhibition of human leucocyte elastase by beta-lactams. 3. Use of electrospray ionization mass spectrometry and two-dimensional NMR techniques to identify beta-lactam-derived E-I complexes.

A combination of NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS) was used to probe the identity of beta-lactam-derived complexes with serine proteases. The carbon and proton NMR chemical shifts of the human leucocyte elastase (HLE)-inhibitor complex derived from [4-13C]-L-680,833, [S-(R*,S*)]-4-[(1-(((1-(4- methylphenyl)butyl)amino)carbonyl)-3,3-diethyl-2-oxo-4- azetidinyl)oxy]benzeneacetic acid, were consistent with an sp3 hybridized carbon. The ESI-MS spectrum of the L-680,833-derived HLE-I complex indicated an increase of 333 Da over the mass of the free enzyme. The data are consistent with acylation of the active site serine, loss of p-hydroxybenzeneacetic acid, and formation of a carbinolamine at the carbon deriving from C-4 of the lactam ring. The complexes produced from HLE and the diastereomers of L-680,833 display identical masses. Since the 4R-isomers produce more stable complexes [Green et al. (1995) Biochemistry 34, 14331-14343], these data suggest that these complexes differ in their stereochemistry or conformation. The structural model of the HLE-I complexes derived from the diastereomers predicts that the hydroxyl of the carbinolamine derives from a structurally observed water molecule yielding S-stereochemistry in all cases. In this model, the 4S- and 4R-diastereomers produce complexes that differ by the location of the side chain of a phenylalanine residue. The mass of HLE was increased by that of L-684,481, (R)-1-(((1-(4-methylphenyl)butyl)amino)carbonyl)-3,3-diethyl-2-azetidino ne, which lacks a leaving group at C-4 in the complex derived from this compound. L-691,886, [S-(R*,S*)]-4-[(1-(((1-(4-ethoxyphenyl)butyl)amino)carbonyl)- 3,3-diethyl-4-oxo-2-azetidinyl)-oxy]benzeneacetic acid, produces two complexes of different mass that reactivate with different rates. The mass of the less stable complex is consistent with the acyl-enzyme of 2,2-ethyl-3-oxopropanoic acid while the mass of the more stable complex is analogous to the carbinolamine observed during L-680,833 inactivation. Porcine pancreatic elastase (PPE) produces a complex with a mass consistent with replacement of the C-4 leaving group by water to produce a carbinolamine from L-684,248, [S-(R*,S*)]-4-[(1-(((1-(4-methylphenyl)butyl)amino)carbonyl)-3,3-dimethy l - 2-oxo-4-azetidinyl)oxy]benzoic acid. The C-4 diastereomer, L-684,249, produces two PPE-I complexes with different masses. One of these complexes has a mass identical to the mass of the complex derived from L-684,248 while the mass of the other complex indicates the presence of the entire inhibitor molecule.(ABSTRACT TRUNCATED AT 400 WORDS)

Humans↗
PubMed1994

A comparison of the benefits of roller pump versus constrained vortex pump in adult open-heart operations utilizing outcomes research.

The purpose of this study was to compare roller pump and centrifugal pump technologies in routine adult open-heart operations to demonstrate the usefulness of applying a proven method of uniform risk stratification (outcomes research). Objective and readily available preoperative patient data was collected retrospectively on 102 non-randomized and consecutive adult open-heart operations. Group 1 consisted of 51 adult open-heart operations utilizing a roller pump for arterial blood perfusion. Group 2 consisted of 51 adult open-heart procedures utilizing a constrained vortex pump for arterial blood perfusion. A comparison between the frequency of occurrence of 53 different preoperative risk factors in the roller pump group and the centrifugal pump group found no statistically significant differences (p < 0.05). Outcome data for the roller pump and centrifugal pump groups included such data comparisons as intensive care unit length of stay (LOS), post operative LOS, total LOS, total patient charge, reimbursement, morbidity, and mortality, which revealed no statistically significant differences (p < 0.05). Further comparison studies of roller pumps versus centrifugal pumps for arterial blood perfusion should incorporate this kind of comprehensive data comparison and analysis to reasonably assure that both pump groups are very similar before outcomes research is performed.

Cardiopulmonary Bypass↗
PubMed1993

How to do it: utilizing risk stratification to evaluate outcomes in adult open-heart operations.

The purpose of this study is to demonstrate that by using a proven method of stratifying open-heart operations into levels of predicted mortality, hospitals can closely monitor trends of their open-heart programs and possibly improve the health planning decisions for their institution. A proven method of uniform risk stratification utilizing objective and readily available preoperative patient data was implemented at our institution for a 12 month period (September 1, 1991 through August 31, 1992). A total of 367 patients were included in this study. The patients were categorized into four risk ranges (0 to 4% good risk, 5 to 9% fair risk, 10 to 14% poor risk, and greater than or equal to 15% high risk) indicating a predictive percent probability of operative mortality. The number of patients categorized as either 0 to 4% good risk, 5 to 9% fair risk, 10 to 14% poor risk, and greater than or equal to 15% high risk were 46, 74, 84 and 163, respectively. The patient's average post-operative length of stay in each risk category was 7.6 days, 8.2 days, 10 days, and 12 days, respectively. The patient's average total hospital charges in each risk category were $48,241, $53,531, $60,416 and $75,555, respectively. This information has helped our hospital administration make relevant and objective decisions concerning our open-heart program. Uniform risk stratification (outcomes research) should be incorporated into all adult open-heart surgery programs because it is simple, inexpensive, and can evaluate the outcomes and cost of open-heart surgery.

Cardiopulmonary Bypass↗
PubMed1992

Peptides presented to the immune system by the murine class II major histocompatibility complex molecule I-Ad.

Between 650 and 2000 different peptides are associated with the major histocompatibility complex class II molecule I-Ad. Sequences for nine of these were obtained by a combination of automated Edman degradation and tandem mass spectrometry. All of the peptides are derived from secretory or integral membrane proteins that are synthesized by the antigen-presenting cell itself. Peptides were 16 to 18 residues long, had ragged NH2-and COOH-termini, and contained a six-residue binding motif that was variably placed within the peptide chain. Binding data on truncated peptides suggest that the peptide binding groove on class II molecules can be open at both ends.

Amino Acid Sequence↗
PubMed1981

Benign (solitary) ulcer of the rectum -- another cause for rectal stricture.

Benign rectal ulcer syndrome is an uncommon cause of lower gastrointestinal bleeding. Patients may present with mild, often recurrent, rectal bleeding frequently ascribed to hemorrhoids. Barium enema may be normal during the early, nonulcerative phase of proctitis. Single (or multiple) ulcers with or without rectal stricture are the hallmarks of the radiographic diagnosis. Radiologic demonstration of the ulcer(s) is not required, however, for the diagnosis. Benign rectal ulcer should be included in the differential diagnosis of benign-appearing rectal strictures.

Adult↗