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Biomedical subjects

A M Davis

Publications and source records attributed to A M Davis.

At least 109 records · Page 6Linked to original sources
PubMed1996

Torsade de pointes, acquired complete heart block and inappropriately long QT in childhood.

After spontaneously acquiring complete heart block, two children presented with torsade de pointes as a result of inappropriate prolongation of the QT interval. Although both remain well following pacemaker insertion, their cases illustrate the importance of QT interval assessment in patients with atrioventricular block, and demonstrate that syncopal episodes, and possibly sudden death, in children with acquired heart block can be due to bradycardia-induced ventricular tachyarrhythmias, rather than extreme bradycardia per se.

Child, Preschool↗
PubMed1995

Partitioning of ionizing molecules between aqueous buffers and phospholipid vesicles.

The distribution of four ionizing molecules between small unilamellar vesicles of dimyristoylphosphatidylcholine (DMPC) and aqueous buffers has been studied as a function of pH using an ultrafiltration method. The results show that pH-distribution behavior observed in the standard 1-octanol-water system does not always apply in model membrane systems, since the charged form of some molecules are able to partition into a phospholipid bilayer. It was further shown that the partitioning of these charged species into the bilayer is not as a consequence of ion pairing. The results clarify reports suggesting that protonated amines have a surprisingly high membrane affinity, and the implications of these findings for drug design are discussed.

Amlodipine↗
PubMed1995

Ligand binding kinetics of IL-2 and IL-15 to heteromers formed by extracellular domains of the three IL-2 receptor subunits.

Studies on the binding of IL-2 to its receptor (IL-2R) have generally been limited to receptors expressed on cell surfaces. This has hampered detailed kinetic and mechanistic studies at the molecular level. We have prepared the soluble extracellular domains of all three receptor subunits (called alpha, beta and gamma) by recombinant techniques and have used these to perform detailed kinetic studies of their binding properties using the technique of surface plasmon resonance. We describe a novel approach whereby the receptors are assembled on an antibody surface, being held by an epitope engineered into the C-terminus of each of these domains. Thus the receptors are oriented naturally leading to homogeneous ligand binding kinetics. We have characterized the interactions of the heteromeric complexes of these subunits with mouse and human IL-2 and their analogs, as well as the recently discovered cytokine, IL-15. We have also studied the extracellular domains of the mouse receptor subunits for the first time and have used these as well as mouse-human hybrid receptors to probe the mechanism of assembly of these complexes. We show that no additional proteins are required to reproduce the properties of these complexes in vitro. In addition, kinetic studies with site-specific analogs of IL-2 and the mouse-human receptor hybrids clearly indicate that the extracellular domains of alpha and beta can together readily bind ligand with kinetic properties distinct from those of the constituent subunits. In contrast, a complex containing ligand and the extracellular domains of beta and gamma was comparatively difficult to assemble and required prolonged exposure to IL-2. Our method enabled us to calculate the stoichiometry of these complexes and to determine that anchoring these subunits is necessary to efficiently drive complex formation. The kinetic and equilibrium differences between the mouse and human receptor complexes, and between IL-2 and IL-15 binding to these receptors clarify the roles of the alpha and gamma subunits in the differential response of cells to different cytokines that may be present simultaneously in the environment.

Amino Acid Sequence↗
PubMed1995

Improving asthma documentation in a paediatric emergency department.

OBJECTIVE: To improve documentation for children presenting to the Emergency Department (ED) of The Children's Hospital with acute asthma. METHODOLOGY: In phase I, the documentation process was analysed using a standard total quality management (TQM) approach to identify specific problems leading to poor documentation. Fifty-two medical records of children presenting over a 3 week period were reviewed for nursing and medical documentation. A set of minimum criteria, consistent with the Paediatric Asthma Management Plan, were established for documentation by both medical and nursing staff. Following dissemination and education, compliance with documentation was evaluated and compared to an asthma survey performed in the ED in 1991. In phase II, a specific proforma for medical assessment was developed and 80 medical records of children presenting over a 3 week period were reviewed. Fifty-two (65%) with completed proformas were evaluated. The outcome measure was the documentation rate for minimum criteria established by TQM process. RESULTS: In phase I, nursing compliance with documentation ranged from 46% for signs of respiratory distress to 83% for a past history of asthma and 100% for pulse rate. Doctors were similarly poor at documenting essential elements such as severity (31%), palpable pulsus paradoxus (29%), the child's usual doctor (46%) and follow-up arrangements (21-56%). In phase II, the documentation of the severity of acute asthma (42%) and of the child's usual doctor (42%) remained poor but there were statistically significant improvements in documentation of interval medications, palpable pulsus paradoxus, respiratory rate, pre-treatment oximetry, education, follow-up arrangements and communication letters. CONCLUSION: The process of TQM has proved valuable in improving some aspects of documentation of children presenting to ED with acute asthma. It remains to be shown whether improved documentation will result in improved outcome.

Asthma↗
PubMed1995

Advancing clinical privileges for nutrition support practitioners: the dietitian as a model.

The specialty of nutrition relies heavily on trained practitioners to assess patient nutritional status, define nutritional goals, and recommend therapeutic strategies to achieve those goals. To facilitate the timely delivery of nutrition care, the dietitians at the University of Massachusetts Medical Center expanded clinical privileges. With the support of the Nutrition Department, the multidisciplinary Nutrition Support Service, and the Nutrition Advisory Committee, dietitians write orders for diets, oral and parenteral nutrient supplementation; and custom mix parenteral nutrition solutions, tube feedings, transitional feedings, balance studies, blood glucose monitoring, and home care orders (parenteral and enteral). Dietitians also order laboratory tests such as chemistries, indirect calorimetry, and bone densitometry. Clinical privileges are a permanent part of each dietitian's appointment to the Health Professional Staff and are granted by the Chancellor/Dean of the Medical University.

Dietetics↗
PubMed1995

The effect of intramedullary cement on intercalary allograft reconstruction of bone defects after tumour resection: a pilot study.

OBJECTIVE: A pilot study to evaluate the surgical and functional results of resection and reconstruction of diaphyseal bone tumours with cemented and uncemented intercalary allografts. DESIGN: A retrospective case series. SETTING: A quaternary care unit within a teaching hospital. PATIENTS: Twenty-two patients with diaphyseal bone tumours treated between 1988 and 1992, with mean follow-up of 38 months (range from 20 to 70 months). INTERVENTIONS: Diagnostic biopsy in all patients. Preoperative and postoperative chemotherapy in patients with high-grade sarcoma. En-bloc excision of all tumours. Reconstruction of the defect with cemented (15 patients) or uncemented (7 patients) intercalary allografts. MAIN OUTCOME MEASURES: Nonunion at one or both osteosynthesis sites, death from systemic disease, amputation. RESULTS: Six of the 22 patients died of systemic disease with the graft intact, and 3 subsequently had amputation for either local recurrence (2 patients) or failure of free tissue transfer (1 patient), leaving 13 patients alive with the allograft in situ at an average of 36 months (range from 24 to 64 months). There were no revision procedures to remove or replace the original allograft. Five patients had nonunion at one or more osteosynthesis sites on plain radiographs 9 months after resection. Four patients with nonunion were in the cemented group of 13 patients available for assessment at 9 months, and 1 was in the uncemented group of 5 patients available for assessment at 9 months. There were two graft fractures, both in the uncemented group. CONCLUSION: The results of this pilot study offer guarded support for the use of pressurized cement in allografts prior to reconstruction of intercalary defects.

Adolescent↗
PubMed1994

The use of the GRID program in the 3-D QSAR analysis of a series of calcium-channel agonists.

The use of GRID in the 3-D QSAR analysis of a series of calcium-channel agonists is described. Partial least-squares analysis of GRID maps showing the interaction energy between an alkyl hydroxyl probe and a series of agonists in 3-D space generated a predictive quantitative model of the variation of biological activity. The macroscopic descriptors CLOGP and CMR were included in the analysis, and the importance of appropriate block scaling is highlighted. The discussion highlights the interpretation of the resulting regression maps, and the steric, electrostatic, lipophilic, and hydrogen-bonding preferences of the calcium-channel receptor are identified.

Animals↗
PubMed1994

Prognostic factors in osteosarcoma: a critical review.

PURPOSE: The purpose of this critical appraisal was to determine the prognostic factors that influence survival in patients with nonmetastatic, high-grade osteosarcoma of the extremities. DESIGN: A computerized literature search of reports published from January 1973 to March 1992 was conducted to determine those eligible for inclusion in the review. Reports were reviewed blindly by two of the authors; inclusion and scoring were determined according to preestablished criteria. RESULTS: Eight reports were included in the appraisal. The prognostic variables evaluated were age, sex, anatomic tumor location, tumor size, and tumor necrosis. Tumor size and necrosis following preoperative chemotherapy were significant prognostic variables in relation to survival in univariate analysis. However, only tumor necrosis maintained its significance in multivariate modeling. CONCLUSION: The most important prognostic variable for patients with osteosarcoma of the extremity was tumor necrosis evident following preoperative chemotherapy. There is no consensus as to any prognostic variable that might be used to stratify patients before the onset of therapy.

Age Factors↗
PubMed1994

Diagnosis and management of sacral bone tumours.

OBJECTIVE: To evaluate the efficacy of current treatment in patients with sacral bone tumours. DESIGN: Retrospective case series. SETTING: A quaternary care unit within a teaching hospital. PATIENTS: Twenty-nine patients with sacral tumours referred to the unit between 1983 and 1991. Follow-up was a minimum of 18 months. INTERVENTIONS: Diagnostic biopsy in all patients. Plain radiography, ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI) and bone scanning. Sacral resection in patients with malignant or aggressive primary bone tumours. MAIN OUTCOME MEASURES: The accuracy of biopsy and local and systemic recurrence of the disease. RESULTS: Symptoms were present for a mean of 12 months to the time of presentation. Low-back pain was present in 28 of 29 patients. Radicular pain and sacral nerve dysfunction were found more often in patients with malignant tumours. Only three patients had altered bowel habits. On rectal examination a mass was palpable in 61% of patients. The sacral abnormality was demonstrated by plain radiography in 6 of 9 cases, by ultrasonography in 2 of 7 cases, by bone scanning in all of 17 cases, by CT in 24 of 25 cases and by MRI in 17 of 18 cases. Fine-needle aspiration biopsy provided the correct diagnosis in only one of four patients. Transrectal biopsy resulted in tethering of the rectum to the tumour in two patients. Core needle biopsy gave an accurate diagnosis in eight of nine patients. Open biopsy was repeated to obtain adequate tissue in 3 of 19 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Neoplasms↗
PubMed1994

Foreign-body abscesses presenting as soft-tissue tumours: two case reports.

Foreign bodies in the extremities often present as bony extensions of soft-tissue masses. Wooden foreign bodies can be detected by computed tomography and magnetic resonance imaging, but these studies are often nonspecific and cannot detect small bodies. As illustrated by two cases reported in this paper, these masses are difficult to distinguish from primary soft-tissue sarcomas when the history and imaging findings suggestive of a foreign-body reaction are absent.

Abscess↗
PubMed1993

Spontaneous pneumothorax in paediatric patients.

To obtain information to guide the management of children and early adolescents with apparent spontaneous pneumothorax the medical records of all patients over the age of 5 years presenting with this condition over a 25-yr period were reviewed. Twelve patients had a pneumothorax not associated with an acute episode of asthma. Six of these underwent thoracotomy at first presentation. Of the six who were initially treated conservatively five had a recurrence on the ipsilateral side. Seven patients developed a pneumothorax during an acute episode of asthma and none had a recurrence. Early intervention by either thoracotomy or some form of closed pleurodesis should be considered in paediatric patients presenting with an apparent spontaneous pneumothorax not associated with an acute episode of asthma. Pneumothorax complicating an acute episode of asthma is rare in the paediatric age group and is unlikely to recur.

Acute Disease↗
PubMed1993

Brain-heart interactions. The neurocardiology of arrhythmia and sudden cardiac death.

Neuroanatomic connections between the brain and the heart provide links that allow cardiac arrhythmias to occur in response to brain activation. Recognition and analysis of such links in the pathogenesis of malignant cardiac arrhythmia are emphasized in this review. Neurocardiac links have been shown to produce arrhythmia both experimentally and clinically; specific examples, including stroke, epilepsy, and environmental stress are presented. We hypothesize that the individual with a diseased heart has a greater likelihood of experiencing cardiac arrhythmia and sudden cardiac death when the neurocardiac axis is activated. Reviewing possible mechanisms of brain-related arrhythmias, we suggest that the nervous system directs the events leading to cardiac damage by raising catecholamine levels and potentially inducing arrhythmia.

Animals↗
PubMed1993

Transposition of the great arteries with intact ventricular septum. Arterial switch repair in patients 21 days of age or older.

Since 1985 we have performed arterial switch repair for infants with simple transposition of the great arteries (with intact or virtually intact ventricular septum) who were younger than 2 months of age. As of December 1990, a total of 118 arterial switch operations had been performed for transposition of the great arteries with intact ventricular septum. Although correction is usually performed in the first 14 days of life, 18 infants had operations at or after 21 days (range 21 to 118 days; mean 38 days). Fourteen of 18 patients had echocardiographic or catheter evidence (or both) of low left ventricular pressure at the time of operation. None of these patients had preliminary pulmonary artery banding. Mortality was 5.6% (1 of 18 patients, confidence limit 0.8% to 17%) for the older group versus 0% (0 of 100 patients; confidence limit, 0% to 1.8%) for patients less than 21 days of age. The single death occurred in a 22-day old, 1.8 kg premature baby, probably as a result of a problem with a coronary anastomosis. One patient required a left ventricular assist device for 2 days after the operation. These data suggest that with appropriate perioperative management and support, the arterial switch procedure can be safely carried out as a primary procedure for patients up to the age of 1 month and probably up to the age of 2 months.

Age Factors↗
PubMed1990

Research in physical medicine and rehabilitation X. Information resources.

Researchers in physical medicine and rehabilitation require access to information regarding possible interventions and programs, available services and technology, research (published, unpublished and in progress), statistics on incidence, prevalence and expected recovery, and funding sources. This paper provides an overview to the most readily available sources of information, including 16 abstracts and indexes, 6 sources of review articles, 9 population statistical databases and 84 journals specifically devoted to rehabilitation. Of these journals, 29 may be accessed through Medline and 32 through other sources. An additional 58 journals indexed in Medline publish more than 16 rehabilitation articles per year. The journals within Medline that publish the most rehabilitation articles are listed by topic area: geriatric rehabilitation, cardiac rehabilitation, pediatric rehabilitation, rehabilitation research, self-help devices, sports medicine and rheumatologic rehabilitation. Specific search strategies that may be used for any computer assisted search of Medline are given to locate articles in these topic areas and also the following areas: amputee rehabilitation, spinal cord injury rehabilitation, traumatic brain injury rehabilitation, cerebral palsy rehabilitation, stroke rehabilitation, decubitus care, electrodiagnosis, rehabilitation engineering, pain rehabilitation, pulmonary rehabilitation, sexual rehabilitation and urologic rehabilitation. The user friendly Grateful Med software is introduced for simplified online Medline searching. Exercises are provided for starting a journal club with the retrieved articles.

Humans↗