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D Armstrong

Publications and source records attributed to D Armstrong.

At least 181 records · Page 10Linked to original sources

Imprinted expression of the murine Angelman syndrome gene, Ube3a, in hippocampal and Purkinje neurons.

Angelman syndrome (AS) is a human genetic disorder characterized by mental retardation, seizures, inappropriate laughter, abnormal galt, tremor and ataxia. There is strong genetic evidence that the disorder is associated with a maternally expressed, imprinted gene mapping to chromosome 15q11-13. Affected patients demonstrate varied molecular abnormalities, including large maternal deletions, uniparental paternal disomy (UPD). Imprinting mutations and loss of function mutations of E6-associated-protein (E6-AP) ubiquitin-protein ligase (UBE3A). All of these abnormalities are associated with loss of maternal expression of UBE3A. Although mutations in UBE3A cause AS, indicating that maternal-specific expression of UBE3A is essential for a normal phenotype, evidence for maternal-specific expression of UBE3A has been lacking. Using mice with partial paternal UPD encompassing Ube3a to differentiate maternal and paternal expression, we found by in situ hybridization that expression of Ube3a in Purkinje cells, hippocampal neurons and mitral cells of the olfactory bulb in UPD mice was markedly reduced compared to non-UPD littermates. In contrast, expression of Ube3a in other regions of the brain was only moderately or not at all reduced in UPD mice. The major phenotypic features of AS correlate with the loss of maternal-specific expression of Ube3a in hippocampus and cerebellum as revealed in the mouse model.

Angelman Syndrome↗

Maternal opiate use: pregnancy outcome in patients managed by a multidisciplinary approach.

The outcome of 39 pregnancies in 35 pregnant opiate users is reported. These women were managed by a multidisciplinary team resulting in 36 live births, one stillbirth. one spontaneous miscarriage and one induced abortion. The majority of patients were stabilised on methadone before the third trimester. The women were characterised by a high prevalence of previous obstetric and medical problems, 43.6% of the women were single and 87.2% unemployed The mean (SD) gestational age was 38.2 +/- 2.3 weeks, mean (SD) birth weight was 2980 +/- 543 g. There were eight cases of preterm deliveries, all occurred beyond 32 weeks' gestation. One preterm and two term babies had a birth weight below the 10th centile. Thirty-two (86.5%) women had a normal vaginal delivery, seven (10.8%) had caesarean section and one (2.7%) had forceps delivery. Comprehensive antenatal care in conjunction with methadone maintenance appears to result in a pregnancy outcome comparable with a general obstetric population.

Journal Article↗

1997 guidelines for the use of antimicrobial agents in neutropenic patients with unexplained fever. Infectious Diseases Society of America.

This is the first in a series of practice guidelines commissioned by the Infectious Diseases Society of America through its Practice Guidelines Committee. The purpose of these guidelines is to provide assistance to clinicians when making decisions on treating the conditions specified in each guideline. The targeted providers are internists, pediatricians, and family practitioners. The targeted patients and setting for the fever and neutropenia guideline are hospitalized individuals with neutropenia secondary to cancer chemotherapy. Panel members represented experts in adult and pediatric infectious diseases and oncology. The guidelines are evidence-based. A standard ranking system was used for the strength of the recommendations and the quality of the evidence cited in the literature reviewed. The document has been subjected to external review by peer reviewers as well as by the Practice Guidelines Committee and was approved by the IDSA Council. An executive summary, algorithms, and tables highlight the major recommendations. The guideline will be listed on the IDSA home page at http://www.idsociety.org.

Adult↗

Predominant localization of the LIS family of gene products to Cajal-Retzius cells and ventricular neuroepithelium in the developing human cortex.

Mutations that perturb neuronal migration provide important biological clues that can lead to an understanding of the role of specific cells and molecules in the formation of the cortex. The human neuronal migration disorder, Miller-Dieker Lissencephaly, results from a hemideletion of LIS-1, which encodes a subunit of a brain platelet-activating factor acetylhydrolase. The cellular localization of the LIS-1 gene product in human fetal brain and its normal role in neuronal migration have yet to be determined. LIS-1 belongs to a family of genes that have identical coding sequences (LIS-1 [chromosome 17] and LIS-2 [chromosome 2]). In the brain, LIS-1 is the more abundant gene as determined by Northern blot analysis. Using antibodies raised against 2 epitopes of the LIS-1/LIS-2 protein sequence, we have localized the LIS family of gene products in the developing human brain to the Cajal-Retzius cells, some subplate neurons, thalamic neurons, the ventricular neuroepithelium, and at later gestational ages, to the ependyma. Therefore, LIS-1 bears some resemblance to reelin, the gene product involved in the cortical mouse mutant reeler, in that Cajal-Retzius cells demonstrate immunolocalization. However, unlike reelin, LIS proteins are expressed not only in the Cajal Retzius cells, but also in the ventricular neuroepithelium, suggesting a potential role for this structure in neuronal migration.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

Efficacy of prophylactic aerosol amphotericin B lipid complex in a rat model of pulmonary aspergillosis.

Invasive pulmonary aspergillosis remains an important cause of morbidity and mortality among transplant recipients and patients receiving cancer chemotherapy. The lipid-associated formulation of amphotericin B (AmB), AmB lipid complex (ABLC), was evaluated for its prophylactic efficacy when it was administered as an aerosol in a rat model of pulmonary aspergillosis. Aerosol ABLC (aero-ABLC), in doses from 0.4 to 1.6 mg/kg of body weight given 2 days before infection, significantly delayed mortality compared to the mortality of rats given placebo (P < 0.001). At day 10 postinfection, 50% of rats in the 0.4-mg/kg group and 75% of rats in the 1.6-mg/kg group were alive, while all control animals had died. In a second trial aero-ABLC was more effective than an equivalent dose of aerosol AmB (aero-AmB) in prolonging survival, with 100% survival at day 14 postinfection in the ABLC group, compared to 62.5% survival in the AmB group. Mean concentrations of AmB in lungs were 3.7 times higher at day 1 (P < 0.002) and almost six times higher at day 7 (P < 0.001) after treatment with aero-ABLC than after treatment with a similar dose of aero-AmB. We conclude that aero-ABLC provided higher and more prolonged levels of the parent compound in the lungs than aero-AmB and was more effective in delaying mortality from aspergillosis in this model.

Aerosols↗

Activity of voriconazole (UK-109,496) against clinical isolates of Aspergillus species and its effectiveness in an experimental model of invasive pulmonary aspergillosis.

Voriconazole, a new azole antifungal agent, showed potent activity against clinical isolates of Aspergillus spp. in vitro. For A. fumigatus, the MIC range was < 0.03 to 0.5 microgram/ml and the MIC at which 90% of isolates are inhibited was 0.25 microgram/ml. In an experimental model of invasive pulmonary aspergillosis which mimics infection in humans, oral voriconazole at dosages of 30 mg/kg of body weight per day significantly delayed or prevented mortality.

Amphotericin B↗

Antimicrobial activities of squalamine mimics.

We investigated the antimicrobial properties of compounds with structural features that were designed to mimic those of squalamine, an antibiotic isolated from the stomach of the dogfish shark. The mimics, like squalamine, are sterol-polyamine conjugates. Unlike squalamine, the mimics were simple to prepare, at high yield, from readily available starting materials. Several squalamine mimics showed activity against gram-negative rods, gram-positive cocci including methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecium, and fungi. Some had little or no hemolytic activity. The hydrophobicity of the sterol backbone and the length and the cationic charge of the side chains appeared to be critical determinants of activity. One of the squalamine mimics, SM-7, was bactericidal against Escherichia coli, Pseudomonas aeruginosa, and S. aureus; its activity was decreased by divalent or monovalent cations and by bovine serum albumin. Subinhibitory concentrations of SM-7 markedly enhanced the antimicrobial activity of rifampin against gram-negative rods. These results suggest that the compounds may disrupt an outer membrane of gram-negative rods. Squalamine mimics are a new class of broad-spectrum antimicrobial agents. The antagonism of their activity by serum and albumin and their hemolytic properties may limit their use as systemic agents. The squalamine mimics, because of their potencies, broad spectra of antimicrobial activity, and potential for systemic toxicity, appear to be good candidates for development as topical antimicrobial agents.

Anti-Bacterial Agents↗

Lymphatic drainage of the CNS: effects of lymphatic diversion/ligation on CSF protein transport to plasma.

The plasma recovery of an intraventricularly administered protein was compared before and after lymph diversion/ligation in the same conscious sheep to determine the relative roles of arachnoid villi and lymphatics in the clearance of a cerebral spinal fluid tracer. 125I-human serum albumin was injected into both lateral ventricles, and venous blood was sampled. One day later, multiple cervical vessels and the thoracic duct were cannulated for lymph collection. Uncannulated vessels were ligated. The experiment was repeated with 131I-human serum albumin as the tracer. Before lymph diversion/ligation, the time-averaged tracer transport into the plasma was 6.4 +/- 1.0%/h, with an average 6-h plasma recovery of 38.2 +/- 5.7% (percentage of injected dose). After lymph diversion/ligation, the values dropped to 2.9 +/- 0.5%/h and 17.7 +/- 2.7%, respectively. The collected lymph contained 8.7 +/- 2.6% of the tracer. No significant differences were observed in sham-operated animals. In conclusion, extracranial lymphatic vessels in sheep transport approximately one-half of the protein tracer from the cerebral spinal fluid compartment into plasma.

Animals↗

A reevaluation of cancer incidence near the Three Mile Island nuclear plant: the collision of evidence and assumptions.

Previous studies concluded that there was no evidence that the 1979 nuclear accident at Three Mile Island (TMI) affected cancer incidence in the surrounding area; however, there were logical and methodological problems in earlier reports that led us to reconsider data previously collected. A 10-mile area around TMI was divided into 69 study tracts, which were assigned radiation dose estimates based on radiation reading and models of atmospheric dispersion. Incident cancers from 1975 to 1985 were ascertained from hospital records and assigned to study tracts. Associations between accident doses and incidence rates of leukemia, lung cancer, and all cancer were assessed using relative dose estimates calculated by the earlier investigators. Adjustments were made for age, sex, socioeconomic characteristics, and preaccident variation in incidence. Considering a 2-year latency, the estimated percent increase per dose unit +/- standard error was 0.020 +/- 0.012 for all cancer, 0.082 +/- 0.032 for lung cancer, and 0.116 +/- 0.067 for leukemia. Adjustment for socioeconomic variables increased the estimates to 0.034 +/- 0.013, 0.103 +/- 0.035, and 0.139 +/- 0.073 for all cancer, lung cancer, and leukemia, respectively. Associations were generally larger considering a 5-year latency, but were based on smaller numbers of cases. Results support the hypothesis that radiation doses are related to increased cancer incidence around TMI. The analysis avoids medical detection bias, but suffers from inaccurate dose classification; therefore, results may underestimate the magnitude of the association between radiation and cancer incidence. These associations would not be expected, based on previous estimates of near-background levels of radiation exposure following the accident.

Dose-Response Relationship, Radiation↗

Efficacy and safety of topotecan in the treatment of advanced ovarian carcinoma.

Topotecan (Hycamtin; SmithKline Beecham Pharmaceuticals, Philadelphia, PA) has emerged as a promising new chemotherapy drug for patients with refractory and progressive stage III and IV epithelial ovarian carcinoma. A semisynthetic analog of camptothecin, topotecan exerts its antitumor effects through inhibition of the nuclear enzyme topoisomerase I. Phase I trials found antitumor activity in many topotecan dosing schedules, one of which involved the administration of topotecan daily as a 30-minute infusion for 5 consecutive days, with the cycle repeated every 21 days. With this schedule, the maximum tolerated dose was found to be 1.5 mg/m2/d. In a series of phase II investigations in platinum-resistant ovarian cancer patients, response rates have ranged from 13% to 25%. In addition, a number of patients exhibit prolonged disease stabilization, with overall rates of nonprogression ranging from 37% to 81%. Activity in paclitaxel-resistant patients is also seen, with a multicenter phase II trial showing a response rate of 13% among first-line paclitaxel failures and 14.3% among second-line failures. A phase III trial compared topotecan and paclitaxel as second-line therapies in 226 advanced ovarian cancer patients who had been previously treated with platinum-containing regimens. Preliminary data show that patients treated with topotecan evidenced a higher response rate (23% v 14%), longer response duration (32 weeks v 20 weeks), and significantly longer time to progression (23 weeks v 14 weeks; P = .002). Additional schedules are still being evaluated, with a phase II trial of prolonged infusion of relatively low-dose topotecan over 21 days demonstrating a 37% response rate in 16 patients. All phase II and III trials analyzed thus far indicate that topotecan is well tolerated with an acceptable toxicity profile, with myelosuppression as the dose-limiting toxicity. Hematologic toxicities are predictable, of short duration, and noncumulative. Mild to moderate nonhematologic toxicities are manageable. These findings demonstrate that topotecan is a viable new second-line or salvage treatment for patients with advanced ovarian cancer who are refractory or resistant to prior chemotherapy, including platinum-based agents and/or paclitaxel.

Antineoplastic Agents↗

The Second Canadian Consensus Conference on the Management of Patients with Gastroesophageal Reflux Disease.

The Second Canadian Consensus Conference on the Management of Patients with Gastroesophageal Reflux Disease (GERD) was organized by the Canadian Association of Gastroenterology to address major advances in the understanding of the pathophysiology of GERD, to review the new methods of investigation and therapy introduced since the first conference in 1992 and to examine the issue of relevant health economics. The changes that have taken place over the past four years have been sufficiently dramatic to necessitate reassessment of the recommendations made following the first conference. The second conference dealt with the investigation and treatment of uncomplicated GERD and the complex issues of esophageal and extraesophageal complications such as chest pain, Barrett's esophagus, and reflux-related pulmonary and laryngeal disorders. The role of laparoscopic surgery was also discussed. A decision tree for investigation and treatment of patients with GERD was developed. The 38 participants represented a broad spectrum of experience, location of practice and special interests. The distribution of participants conformed to the recommendations of the Canadian Medical Association guidelines for consensus documents in that there should be input from all possible interested parties. A list of the state-of-the-art lectures presented during the conference, the small group sessions, the session chairpersons and participants are appended to this document. CONCLUSIONS. UNCOMPLICATED GERD: GERD with alarm symptoms must be investigated immediately. There was no consensus about when to investigate uncomplicated GERD, ie, whether to perform endoscopy immediately or after initial therapy fails. There was controversy regarding 'step up' (H2 receptor antagonist [H2RA] or prokinetic [PK] first therapy) versus 'step down' therapy (proton pump inhibitor [PPI] first therapy). The majority decision was for short term 'step up' therapy and investigation if symptoms do not improve or recur. Maintenance therapy should be carried out with the initial therapy that was effective. H2RAs and PKs may suffice for maintenance therapy in milder GERD; however, for severe esophagitis, PPIs should be used. SURGERY: Indications for laparoscopic surgery should be the same as for conventional antireflux operations. NONCARDIAC ANGINA-LIKE CHEST PAIN: After exclusion of nonesophageal causes, the majority decided that eight weeks of therapy with a PPI should be performed, while some suggested work-up before a therapeutic test. In the absence of response or recurrence, esophagogastroduodenoscopy (EGD) and, depending on the circumstances, 24 h ambulatory pH/motility may be indicated. BARRETT'S ESOPHAGUS: Only patients who, in case of future discovery of cancer or dysplasia, are able or willing to undergo therapy should have surveillance. In the absence of dysplasia EGD should be performed every two years, and in the presence of mild dysplasia every three to six months. All agreed that for severe dysplasia, esophagectomy or poor risk patients, esophageal mucosal ablation is indicated. ESTRAESOPHAGEAL COMPLICATONS (EECs): Asthma, chronic cough and posterior laryngitis were considered EECs. Although PPIs may decrease symptoms, improvement alone is not diagnostic of the presence of EEC. Ambulatory pH studies with two pH probes or ambulatory pH/motility may be useful in establishing causation. HEALTH ECONOMICS: There are limited data for an economic comparison among the different drugs or between medical and surgical therapy.

Canada↗

Efficacy of H2 receptor antagonists in the treatment of gastroesophageal reflux disease and its symptoms.

Gastroesophageal reflux disease (GERD) is caused by prolonged esophageal mucosal exposure to acid gastric refluxate due to failure of the normal antireflux mechanisms of the lower esophageal sphincter. Gastroesophageal reflux can be controlled by suppression of acid secretion or by improvement of gastric emptying and esophageal clearance. H2 receptor antagonists are the most commonly used antisecretory drugs, and in the past 20 years have constituted the cornerstone of therapy for the treatment of reflux disease. They have been shown to be effective in the symptomatic treatment of intermittent or mild nonerosive GERD (greater than 70%). When used at the usual recommended dose, all four H2 receptor antagonists (cimetidine, ranitidine, famotidine and nizatidine) are equally effective and are found to be generally very safe; interactions with other drugs metabolized through the cytochrome p450 notwithstanding. However, their efficacy is limited in more severe forms of GERD such as erosive esophagitis (symptomatic improvement 40% to 60%, endoscopic healing 40% to 50%) in which the superior efficacy and more rapid symptomatic relief provided by proton pump inhibitors is clearly demonstrated. The availability of H2 receptor antagonists for over-the-counter use will increase their use for mild and intermittent disease but is unlikely to alter the need for more potent acid suppression in aggressive reflux disease.

Gastroesophageal Reflux↗

Recent developments in neuropathology--electron microscopy--brain pathology.

Until this meeting the observed pathology of Rett syndrome could be summarized as being a reduction of brain size, involving particularily the frontal lobes, the cauate and the midbrain, a reduced pigmentation of the substantia nigra, reduced lengths of dendrites in selected regions of the cortex, decreased neuronal size with increased neuronal packing density, reduced axonal input into the cortex, and neurochemical alterations in subplate neurons. The presentations at this session of Hand-in Hand were devoted to morphologic studies. They confirmed and further defined the selective nature of the changes in the Rett brain, cortex, and basal ganglia. They presented additional information about alterations in neuronal chemoarchitecture which support the idea that there is a developmental arrest in Rett syndrome. The degenerative changes seen in some Rett brains were not discussed. An altered morphology of the conduction system in the Rett heart was described.

Brain↗