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Biomedical subjects

M R Douglas

Publications and source records attributed to M R Douglas.

16 recordsLinked to original sources
PubMed2002

X-ray absorption spectroscopy measurements of thin foil heating by Z-pinch radiation.

Absorption spectroscopy measurements of the time-dependent heating of thin foils exposed to intense z-pinch radiation sources are presented. These measurements and their analysis provide valuable benchmarks for, and insights into, the radiative heating of matter by x-ray sources. Z-pinch radiation sources with peak powers of up to 160 TW radiatively heated thin plastic-tamped aluminum foils to temperatures approximately 60 eV. The foils were located in open slots at the boundary of z-pinch hohlraums surrounding the pinch. Time-resolved Kalpha satellite absorption spectroscopy was used to measure the evolution of the Al ionization distribution, using a geometry in which the pinch served as the backlighter. The time-dependent pinch radius and x-ray power were monitored using framing camera, x-ray diode array, and bolometer measurements. A three-dimensional view factor code, within which one-dimensional (1D) radiation-hydrodynamics calculations were performed for each surface element in the view factor grid, was used to compute the incident and reemitted radiation flux distribution throughout the hohlraum and across the foil surface. Simulated absorption spectra were then generated by postprocessing radiation-hydrodynamics results for the foil heating using a 1D collisional-radiative code. Our simulated results were found to be in good general agreement with experimental x-ray spectra, indicating that the spectral measurements are consistent with independent measurements of the pinch power. We also discuss the sensitivity of our results to the spectrum of the radiation field incident on the foil, and the role of nonlocal thermodynamic equilibrium atomic kinetics in affecting the spectra.

Journal Article↗
PubMed2002

Optimal wire-number range for high x-ray power in long-implosion-time aluminum Z pinches.

Experiments performed on the 8-MA Saturn accelerator to investigate the effects of interwire gap spacing on long-implosion-time Z pinches have resulted in the observation of a regime of optimal wire number. The experiments varied the wire number of 40 and 32 mm diam arrays, resulting in interwire gaps from 3.9 to 0.36 mm, with fixed mass and length. aluminum K-shell powers up to 3.4 TW were measured, with long, slow rising, lower power x-ray pulses for interwire gaps greater than 2.2 mm and less than 0.7 mm, and short, fast rising, higher power pulses for interwire gaps in the range 0.7-2.2 mm.

Journal Article↗
PubMed2002

Upregulated survivin expression in activated T lymphocytes correlates with disease activity in multiple sclerosis.

Programmed cell death (apoptosis) is critical for the normal development and homeostasis of the immune system. There is emerging evidence that failure of apoptosis to eliminate potentially pathogenic, autoreactive T lymphocytes may be involved in the pathogenesis of multiple sclerosis (MS). This failure is related to multiple abnormalities of apoptosis-regulatory molecules that involve survivin, a recently described cell cycle-regulated anti-apoptosis protein. In this study, we investigated the relationship between survivin expression in peripheral T lymphocytes and clinical features of MS. We detected a significant over-expression of survivin in mitogen stimulated T lymphocytes from patients with active MS when compared with corresponding expression in patients with stable MS or those with inflammatory and non-inflammatory neurologic disorders. This over-expression of survivin in patients with active MS correlated with cellular resistance to apoptosis and with features of disease activity, such as disease duration and the number of enhanced lesions on cranial magnetic resonance imaging. There was no correlation between cellular survivin levels and the expression of other apoptosis-inhibitory proteins, such as Bcl-2 and Fas-associated death domain-like interleukin-1beta-converting enzyme inhibitory protein (FLIP). Our findings indicate that cellular over-expression of the novel anti-apoptosis protein survivin is a feature of clinically active MS.

Age of Onset↗
PubMed2001

Cost effectiveness analysis of a smoke alarm giveaway program in Oklahoma City, Oklahoma.

OBJECTIVE: To estimate the cost effectiveness of the Lifesavers Residential Fire and Injury Prevention Program (LRFIPP), a smoke alarm giveaway program. SETTING: In 1990, the LRFIPP distributed over 10,000 smoke alarms in an area of Oklahoma City at high risk for residential fire injuries. The program also included fire prevention education and battery replacement components. METHODS: A cost effectiveness analysis was conducted from the societal and health care systems perspectives. The study compared program costs with the total costs of medical treatment and productivity losses averted over a five year period. Fatal and non-fatal residential fire related injuries prevented were estimated from surveillance data. Medical costs were obtained from chart reviews of patients with fire related injuries that occurred during the pre-intervention period. RESULTS: During the five years post-intervention, it is estimated that the LRFIPP prevented 20 fatal and 24 non-fatal injuries. From the societal perspective, the total discounted cost of the program was $531,000. Total discounted net savings exceeded $15 million. From the health care system perspective, the total discounted net savings were almost $1 million and would have a net saving even if program effectiveness was reduced by 64%. CONCLUSIONS: The program was effective in reducing fatal and non-fatal residential fire related injuries and was cost saving. Similar programs in other high risk areas would be good investments even if program effectiveness was lower than that achieved by the LRFIPP.

Accident Prevention↗
PubMed2001

Holarctic phylogeography of Arctic charr (Salvelinus alpinus L.) inferred from mitochondrial DNA sequences.

This study evaluated mitochondrial DNA (mtDNA) sequence variation in a 552-bp fragment of the control region of Arctic charr (Salvelinus alpinus) by analyzing 159 individuals from 83 populations throughout the entire range of the complex. A total of 89 (16.1%) nucleotide positions were polymorphic, and these defined 63 haplotypes. Phylogenetic analyses supported the monophyly of the complex and assigned the observed haplotypes to five geographic regions that may be associated with different glacial refugia. Most notably, a formerly defined major evolutionary lineage (S. a. erythrinus) ranging from North America across the Arctic archipelago to the Eurasian continent has now been partitioned into the Arctic group and the newly identified Siberian group. The Beringian group, formed entirely by specimens assigned to S. malma (Dolly Varden), encompassed the area formerly assigned to S. a. taranetzi. The latter, due to a unique haplotype, became the basal member of the Arctic group. Overall, the S. alpinus complex reflects divergent evolutionary groups coupled with shallow intergroup differentiation, also indicated by an analysis of molecular variance that attributed 73.7% (P < 0.001) of the total genetic variance among groups. Time estimates, based on sequence divergence, suggest a separation of the major phylogeographic groups during early to mid-Pleistocene. In contrast, colonization of most of today's range started relatively recently, most likely late Pleistocene during the last retreat of ice sheets some 10,000-20,000 years ago. This time scale obviously is too shallow for detecting significant variation on a smaller scale using mtDNA markers. However, other studies using nuclear microsatellite DNA variation strongly suggested ongoing evolution within groups by revealing strong population-genetic substructuring and restricted gene flow among populations. Thus, Arctic charr could serve as a model organism to investigate the linkage between historical and contemporary components of phylogeographic structuring in fish, and, with a global perspective of the distribution of genetic variation as a framework, meaningful comparisons of charr studies at a smaller geographic scale will now be possible.

Animals↗
PubMed2001

Child abuse and neglect: a public health perspective.

Child abuse and neglect prevention are now poised at the threshold of the public health arena just as the prevention of communicable diseases and unintentional injuries once stood. The principles of public health combined with epidemiology helped eradicate smallpox. The expertise of many disciplines and the three-pronged (primary, secondary, and tertiary) prevention approach have moved the concept of unintentional injuries from "accidents will happen" to predictable and, therefore, preventable. Child abuse and neglect are now seen as epidemic in society. Through surveillance, intervention, prevention, and policy changes, the rate of child abuse and neglect can be significantly impacted in the same way that rates of unintentional injuries and communicable diseases have been reduced.

Child↗
PubMed2000

Predictors of systolic augmentation from left ventricular preexcitation in patients with dilated cardiomyopathy and intraventricular conduction delay.

BACKGROUND: VDD pacing can enhance systolic function in patients with dilated cardiomyopathy and discoordinate contraction; however, identification of patients likely to benefit is unclear. We tested predictors of systolic responsiveness on the basis of global parameters as well as directly assessed mechanical dyssynchrony. METHODS AND RESULTS: Twenty-two DCM patients with conduction delay were studied by cardiac catheterization with a dual-sensor micromanometer to measure LV and aortic pressures during sinus rhythm and LV free-wall pacing. Pacing enhanced isovolumetric (dP/dt(max)) and ejection-phase (pulse pressure, PP) systolic function by 35+/-21% and 16.4+/-11%, respectively, and these changes correlated directly (r=0.7, P=0.001). %DeltadP/dt(max) was weakly predicted by baseline QRS (r=0.6, P<0.02), more strongly by baseline dP/dt(max) (r=0.7, P=0.001), and best by bidiscriminate analysis combining baseline dP/dt(max) < or =700 mm Hg/s and QRS > or =155 ms to predict %DeltadP/dt(max) > or =25% and %DeltaPP > or =10% (P<0.0005, chi(2)), with no false-positives. Benefit could not be predicted by %DeltaQRS. To test whether basal mechanical dyssynchrony predicted responsiveness to LV pacing, circumferential strains were determined at approximately 80 sites throughout the LV by tagged MRI in 8 DCM patients and 7 additional control subjects. Strain variance at time of maximal shortening indexed dyssynchrony, averaging 28.0+/-7.1% in normal subjects versus 201.4+/-84.3% in DCM patients (P=0.001). Mechanical dyssynchrony also correlated directly with %DeltadP/dt(max) (r=0.85, P=0.008). Conclusions-These results show that although mechanical dyssynchrony is a key predictor for pacing efficacy in DCM patients with conduction delay, combining information about QRS and basal dP/dt(max) provides an excellent tool to identify maximal responders.

Adult↗
PubMed1999

Differential association of cytoplasmic signalling molecules SHP-1, SHP-2, SHIP and phospholipase C-gamma1 with PECAM-1/CD31.

Recent studies have shown that, in addition to its role as an adhesion receptor, platelet endothelial cell adhesion molecule 1/CD31 becomes phosphorylated on tyrosine residues Y663 and Y686 and associates with protein tyrosine phosphatases SHP-1 and SHP-2. In this study, we screened for additional proteins which associate with phosphorylated platelet endothelial cell adhesion molecule 1, using surface plasmon resonance. We found that, besides SHP-1 and SHP-2, platelet endothelial cell adhesion molecule 1 binds the cytoplasmic signalling proteins SHIP and PLC-gamma1 via their Src homology 2 domains. Using two phosphopeptides, NSDVQpY663TEVQV and DTETVpY686SEVRK, we demonstrate differential binding of SHP-1, SHP-2, SHIP and PLC-gamma1. All four cytoplasmic signalling proteins directly associate with cellular platelet endothelial cell adhesion molecule 1, immunoprecipitated from pervanadate-stimulated THP-1 cells. These results suggest that overlapping immunoreceptor tyrosine-based inhibition motif/immunoreceptor tyrosine-based activation motif-like motifs within platelet endothelial cell adhesion molecule 1 mediate differential interactions between the Src homology 2 containing signalling proteins SHP-1, SHP-2, SHIP and PLC-gamma1.

Amino Acid Sequence↗
PubMed1999

Estimating the proportion of homes with functioning smoke alarms: a comparison of telephone survey and household survey results.

OBJECTIVES: This study determined the proportion of homes with functioning smoke alarms in a low-income area experiencing a high rate of residential fire-related injuries. METHODS: An on-site survey of households was conducted to confirm the results of a telephone survey. RESULTS: In the telephone survey, 71% of households reported having functioning smoke alarms. In the household survey, 66% of households reported having functioning alarms; however, when the alarms were tested, the percentage dropped to 49%. CONCLUSIONS: Telephone surveys may overestimate the presence of functioning smoke alarms in some populations. Thus, the use of telephone surveys to establish baseline measures could significantly affect the evaluation of smoke-alarm giveaway programs.

Accidents, Home↗
PubMed1998

Evaluation of three smoke detector promotion programs.

CONTEXT: Seventy percent of U.S. residential fire deaths occur in homes without a working smoke detector. To help prevent residential fire deaths, many programs have distributed or installed detectors in unprotected homes. Because persons receiving a detector may not install it and because detector batteries require annual replacement, the enduring effectiveness of these programs may be questioned. OBJECTIVE: We evaluated the long-term functional status of smoke detectors distributed to high-risk households in eight areas of Minnesota, Cherokee County (North Carolina), and Oklahoma City (Oklahoma). DESIGN: Cross-sectional. SETTING: Home visits were made to check the detectors that were distributed 3 to 4 years earlier. PARTICIPANTS: Randomly selected households from the three detector promotion programs. MAIN OUT-COME MEASURE: At least one working smoke detector. RESULTS: Participation rates ranged from 72% to 82%. The percentage of evaluation households with at least one working detector ranged from 58% in Oklahoma to 73% in North Carolina. In 76% of households with nonworking detectors, the batteries were either missing or disconnected. When batteries in nonworking detectors were replaced, 83% of the detectors regained function. CONCLUSIONS: Future programs should consider distributing detectors that do not require annual battery changes or find effective ways to ensure that batteries are routinely replaced. Programs should also provide each household with the number of detectors needed to meet the most current recommended standard of the National Fire Protection Agency. The evaluation's participation rates support the practicality of unannounced home visits to evaluate home injury prevention programs in high-risk groups.

Accident Prevention↗
PubMed1998

Comparison of community based smoke detector distribution methods in an urban community.

OBJECTIVES: Various methods of soliciting participation for a large smoke detector giveaway program were tested to determine the most effective method of distributing smoke detectors to a high risk urban population. SETTING: The target area was a 24 square mile (62 km2) section on the south side of Oklahoma City where 16% (73,301) of the city's population resided in 16% (34,845) of the dwellings (excluding apartments). Of the 66 persons in Oklahoma City who were injured in residential fires from September 1987 to April 1990, 45% (30) were in the target area. Of the target area injuries, 47% resulted from fires started by children playing with fire (fireplay). METHODS: The number of homes without detectors was estimated by telephone survey. Four different methods of soliciting participants were used, including notifying residents by mail; placing flyers on the doors of every habitable residence; and displaying flyers at public places (grocery stores, convenience stores, restaurants, etc). Each of these methods alerted residents that free smoke detectors were available at specific fire stations. The fourth method was distributing detectors door-to-door (canvassing). RESULTS: The canvassing method resulted in significantly more smoke detectors being distributed to homes without detectors (107%) than any of the three other methods (18%) (p < 0.00001). The canvassing method distributed detectors to 31% of the total target homes, compared with 5% with the other methods (p < 0.00001). Canvassing also resulted in the lowest estimated cost per detector distributed ($1.96) (all other methods, $3.95), and in the largest number distributed per volunteer hour (5.9 v 3.1 detectors per hour by other methods). CONCLUSIONS: Distributing smoke detectors directly to homes (canvassing) was the most effective and cost efficient method to reach high risk urban residents.

Accidents, Home↗
PubMed1997

Osmotic stress activates phosphatidylinositol-3,5-bisphosphate synthesis.

Inositol phospholipids play multiple roles in cell signalling systems. Two widespread eukaryotic phosphoinositide-based signal transduction mechanisms, phosphoinositidase C-catalysed phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) hydrolysis and 3-OH kinase-catalysed PtdIns(4,5)P2 phosphorylation, make the second messengers inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) sn-1,2-diacylglycerol and PtdIns(3,4,5)P3. In addition, PtdIns(4,5)P2 and PtdIns3P have been implicated in exocytosis and membrane trafficking. We now show that when the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe are hyperosmotically stressed, they rapidly synthesize phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P2) by a process that involves activation of a PtdIns3P 5-OH kinase. This PtdIns(3,5)P2 accumulation only occurs in yeasts that have an active vps34-encoded PtdIns 3-OH kinase, showing that this latter kinase makes the PtdIns3P needed for PtdIns(3,5)P2 synthesis and indicating that PtdIns(3,5)P2 may have a role in sorting vesicular proteins. PtdIns(3,5)P2 is also present in mammalian and plant cells: in monkey Cos-7 cells, its labelling is inversely related to the external osmotic pressure. The stimulation of a PtdIns3P 5-OH kinase-catalysed synthesis of PtdIns(3,5)P2, a molecule that might be a new type of phosphoinositide 'second messenger, thus appears to be central to a widespread and previously uncharacterized regulatory pathway.

Animals↗
PubMed1997

Esophageal foreign bodies: safety and efficacy of Foley catheter extraction of coins.

OBJECTIVE: Continued controversy over the role of fluoroscopically guided Foley catheter removal of esophageal foreign bodies has limited the use of this technique despite its significant economic advantages. We reviewed our experience for the safety, efficacy, and applicability of this technique with pediatric patients who had swallowed coins. MATERIALS AND METHODS: We retrospectively reviewed 10 years of experience with pediatric patients who had undergone fluoroscopically guided Foley catheter removal of coins. All the pediatric patients with a suspected esophageal foreign body were first evaluated by plain film radiography. Foley catheter extraction was attempted when a radiopaque coin was seen and the patient lacked signs of significant esophageal edema resulting in tracheal compromise. During the 10 years covered by our review, 14 pediatric radiologists with specific training in the Foley catheter technique were involved in such removals. A separate review (of consecutive pediatric patients who had a history of or symptoms suggesting ingestion of a foreign body) focused on the percentage of these patients in which the Foley catheter technique was used. RESULTS: Of the 337 coin extractions attempted using a Foley catheter, coin extraction was successful in 322 (96%) of 337 patients. No complications were encountered. Our focused review found 422 consecutive patients who had undergone radiography to rule out foreign bodies. A radiopaque object was found in 249 (59%) of 422 patients. Of these 249 objects, 208 (84%) were ingested coins. Of 208 coins, 123 (59%) were retained in the esophagus; of these 123 coins retained in the esophagus, 116 (94%) were amenable to fluoroscopically guided Foley catheter extraction. CONCLUSION: Fluoroscopically guided Foley catheter extraction of retained coins in pediatric patients who lack evidence of significant esophageal edema causing tracheal compromise is a safe and efficacious technique. It should be considered the technique of choice for such extractions.

Catheterization↗
PubMed1994

Substance abuse and the nurse manager: ethical and legal issues.

Nurse managers have a pivotal role in intervening in situations of substance abuse among employees. This article addresses ethical and legal dimensions of chemical impairment from the perspective of the nurse manager. The value of a rehabilitative rather than a punitive approach to the chemically impaired nurse is emphasized. Ethics of care and relevant legal considerations, including the Americans With Disabilities Act, are explored through case analysis. Covenantal relationships offer a framework for examining the responsibilities of the nurse manager with respect to the community, employer, the actual or allegedly chemically impaired nurse, and one's self.

Ethics, Nursing↗