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Biomedical subjects

R W Armstrong

Publications and source records attributed to R W Armstrong.

At least 19 recordsLinked to original sources
PubMed2001

Prescription of methylphenidate to children and youth, 1990-1996.

BACKGROUND: There are concerns about the frequency and appropriateness of psychostimulant drug prescription to children. In order to identify unusual or unexpected patterns of use or prescribing, we reviewed prescription of methylphenidate (Ritalin) to children and adolescents aged 19 years or less in British Columbia between 1990 and 1996. METHODS: We obtained information about patients, physicians and prescriptions from British Columbia's Triplicate Prescription Program database for controlled drugs. Prescription data were available for the period Jan. 1, 1990, to Dec. 31, 1996. Linkage with the BC Linked Health Dataset provided additional demographic and health information. RESULTS: In 1990, 1715 children received at least 1 prescription for methylphenidate (1.9 per 1000 children). By 1996, the number had increased to 10,881 children (11.0 per 1000). Because some children were prescribed methylphenidate in more than 1 year, we also calculated the frequency with which the drug was prescribed to children who had never received it before. This rate increased from 1.0 per 1000 children in 1990 to 4.7 per 1000 in 1995; the rate fell in 1996 to 3.5 per 1000. The number of children receiving methylphenidate varied across health regions of the province, from 12.0 to 35.4 per 1000. Use also varied by socioeconomic status quintile: in the 2 lowest (least privileged) quintiles, 21.6 per 1000 children received methylphenidate, compared with 18.4 per 1000 in the 3 highest quintiles (relative risk 1.2, 95% confidence interval 1.1-1.2). Pediatricians and psychiatrists wrote 23% and 21% of all prescriptions respectively. General practitioners accounted for 56% of all prescriptions and 41% of initial methylphenidate prescriptions. A claim for prior specialist consultation was found in 30% of such cases. Many of the children who received more than 10 prescriptions had seen 4 or more physicians. The average daily dosage prescribed differed little among general practitioners, pediatricians and psychiatrists, unlike the mean interval between successive prescriptions: 89.9 (standard deviation [SD] 68.2), 99.8 (SD 64.1) and 75.9 (SD 70.2) days respectively. Persistence with therapy was more likely when a psychiatrist provided the initial prescription, or with involvement of more than one specialty. INTERPRETATION: Many trends and practices in the prescription of methylphenidate to children in British Columbia are consistent with other settings and accepted standards. Some aspects warrant closer investigation, including regional and socio-economic discrepancies in the distribution of patients, the relative involvement of primary and specialist care providers, continuity of care issues and time intervals between prescriptions.

Adolescent↗
PubMed2001

Aerosol particle and organic vapor concentrations at industrial work sites in Malaysia.

The objective of this study was to establish baseline data about air pollutants potentially related to nasopharyngeal carcinoma (NPC) in the Federal Territory and Selangor, Malaysia. During 1991-1993, ambient air quality was monitored at 42 work sites representing ten industrial sectors: adhesive manufacturing, foundries, latex processing, metalworking, plywood/veneer milling, ricemilling, rubber tire manufacturing, sawmilling, shoemaking, and textile related industries. At each work site, aerosol particle size distributions and concentrations of formaldehyde, benzene, toluene, isopropyl alcohol, and furfural were measured. Mean aerosol particle concentrations ranged from 61 micrograms/m3 in foundries to 5,578 micrograms/m3 in ricemills, with five industries (adhesives, metalworking, ricemilling, sawmilling, and shoemaking) exceeding the US EPA 24-hr ambient air standard for PM-10. Formaldehyde concentrations exceeded the threshold limit value (TLV) in adhesives factories. Other vapours and elements measured were well below TLVs.

Aerosols↗
PubMed2000

Nasopharyngeal carcinoma in Malaysian Chinese: occupational exposures to particles, formaldehyde and heat.

BACKGROUND: During 1990-1992, 282 Chinese residents of Selangor and the Federal Territory, Malaysia with histologically confirmed nasopharyngeal carcinoma (NPC) were interviewed about occupational history, diet, alcohol consumption, and tobacco use, as were an equal number of Malaysian Chinese population controls, pair-matched to cases by age and sex. METHODS: Exposures to 20 kinds of workplace substances, solar and industrial heat, and cigarette smoke, were analysed by univariate and multivariate methods. RESULTS: Nasopharyngeal carcinoma was associated with occupational exposures to construction, metal and wood dusts; motor fuel and oil; paints and varnishes; certain other chemicals; industrial heat; solar heat from outdoor occupations; certain smokes; cigarette smoking; and childhood exposure to parental smoking. After adjustment for risk from diet and cigarette smoke, only wood dust (OR = 2.36; 95% CI : 1.33- 4.19), and industrial heat (OR = 2.21; 95% CI : 1.12-4.33) remained clearly associated. Wood dust remained statistically significant after further adjustment for social class. No significant crude or adjusted association was found between NPC and formaldehyde (adjusted OR = 0.71; 95% CI : 0.34-1.43). CONCLUSIONS: This study supports previous findings that some occupational inhalants are risk factors for NPC. The statistical effect of wood dust remained substantial after adjustment for diet, cigarette smoke, and social class. Intense industrial heat emerged as a previously unreported risk factor, statistically significant even after adjustment for diet and cigarette smoke. No association was found between NPC and formaldehyde.

Adult↗
PubMed2000

Social impact of nasopharyngeal carcinoma on Chinese households in Selangor, Malaysia.

AIM OF STUDY: With a five-year survival rate of 20% in 1970 and 40-45% in 1990, and highest incidence and mortality in early and middle adult years, nasopharyngeal carcinoma (NPC) may have a severe social impact on families and households. The aim of this study was to measure the social impact of NPC in the Chinese population of Selangor, Malaysia. METHOD: Cases were pooled from three epidemiological case-control studies conducted in 1973-74, 1980, and 1990-92 for a total of 442. They lived in households with a grand total of 2,598 persons. Interviewers collected data on household composition: number of residents; each resident's age, sex, occupation, and relationship to the head of the household; and position of the NPC case in the household. RESULTS: Ninety-four percent of cases supported 93% of household members in some way. Most cases were employed as income earners or homemakers and 80% had a key role as head of household and/or parent of dependent children. CONCLUSION: The illness and death caused by NPC had a major social impact on immediate families and on extended family and non-kin households as well.

Adolescent↗
PubMed1999

Potential for chlorate interference in ion chromatographic determination of total nitrogen in natural waters following alkaline persulfate digestion.

Determination of total nitrogen in aqueous samples after thermal potassium peroxydisulfate (persulfate) digestion is a commonly used alternative to the tedious Kjeldahl procedure. When ion chromatography is used to quantify the nitrate formed during digestion, there is a potential for interference from a chlorate peak if the digested sample initially contained chloride in concentrations close to or greater than the concentration of nitrogen. It was determined that this interference can be avoided either by using chromatographic conditions which cleanly resolve the nitrate and chlorate peaks (e.g., the Dionex AG9-HG column) or by using digestion reagent concentrations chosen to maintain a high pH throughout the digestion. The second alternative is not a viable option for investigators using a single digestion for both total nitrogen (TN) and total phosphorus (TP) analysis.

Chlorates↗
PubMed1999

Cryptococcal meningitis in the immunocompromised host: intracranial hypertension and other complications.

Cryptococcosis as a complication of the immunocompromised host has dramatically increased in frequency since the start of the AIDS epidemic. This trend has heightened awareness of the complications of cryptococcal meningitis; of these, intracranial hypertension is common, severe, and life-threatening, as exemplified by three cases in our institutions presented here in detail. An aggressive approach to management of this complication has not been the standard of care, but neurosurgical interventional studies combined with physiologic observations suggest early intervention may reduce the devastating morbidity and mortality.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Nasopharyngeal carcinoma in Malaysian Chinese: salted fish and other dietary exposures.

We interviewed 282 histologically confirmed cases of nasopharyngeal carcinoma (NPC) in Chinese residents of Selangor and the Federal Territory, Malaysia, and an equal number of Chinese age-, sex-, and length-of-residence-matched controls sampled from the general population. Consumption of 55 dietary items during childhood, and 5 years pre-diagnosis of NPC, was analyzed by univariate and multivariate methods. Four salted preserved foods (fish, leafy vegetables, egg and root), fresh pork/beef organ meats and beer and liquor consumption exhibited strong positive associations, and 4 vegetable/fruit combinations strong negative associations with NPC. Factor analysis and multivariable modeling using estimated factor scores strongly supported separate effects on NPC of vegetables/fruits, salted preserved foods, pork/beef organ meats and beer/liquor consumption. Multivariable modeling associated NPC most clearly with high consumption of salted fish, salted eggs, pork/beef liver and beer and low consumption of Chinese flowering cabbage, oranges/tangerines and shrimp. A strong residual association of social class with NPC remained after adjustment for diet, which is consistent with a substantial role for non-dietary environmental factors.

Adult↗
PubMed1998

Design, synthesis, and evaluation of the multidrug resistance-reversing activity of D-glucose mimetics of hapalosin.

When five substituents of hapalosin were placed on D-glucose, molecular modeling revealed that the substituents on mimetics 2 and 3 occupy similar spatial positions as the corresponding substituents on hapalosin. Mimetic 3 and all the glucopyranoside intermediates generated in its synthesis were assessed for their ability to reverse multidrug resistance (MDR) mediated by P-glycoprotein (P-gp) or the multidrug resistance-associated protein (MRP). None of the sugar compounds were as effective as hapalosin in inhibiting P-gp in cytotoxicity and drug accumulation assays using MCF-7/ADR cells. By contrast, four D-glucose compounds exhibited similar efficacy as hapalosin in antagonizing MRP in cytotoxicity assays with HL-60/ADR cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

A model for binding of structurally diverse natural product inhibitors of protein phosphatases PP1 and PP2A.

Protein phosphatases play significant roles in signal transduction pathways pertaining to cell proliferation, gene expression, and neurotransmission. Serine/threonine phosphatases PP1 and PP2A, which are closely related in primary structure (approximately 50%), are inhibited by a structurally diverse group of natural toxins. As part of our study toward understanding the mechanism of inhibition displayed by these toxins, we have developed research in two directions: (1) The standardization of an assay to be used in acquisition of the structure--activity relationship of inhibition data is reported. This nonradioactive assay affords detection levels of molecular phosphate released from a phosphorylated hexapeptide in subnanomolar quantities. The comparison of our IC50 values of these inhibitors against corresponding literature data provided validation for our method. (2) Computational analysis provided a global model for binding of these inhibitors to PP1. The natural toxins were shown to possess remarkably similar three-dimensional motifs upon superimposition and van der Waals minimization within the PP1 active site.

Antifungal Agents↗
PubMed1997

A randomized clinical trial to compare selective posterior rhizotomy plus physiotherapy with physiotherapy alone in children with spastic diplegic cerebral palsy.

A randomized controlled single-blind trial was performed to compare lumbo-sacral selective posterior rhizotomy (SPR) followed by intensive physiotherapy, with intensive physiotherapy alone in improving motor function in children with spastic diplegic cerebral palsy. Fifteen patients were randomly assigned to each treatment modality. Patients in the SPR group had rhizotomy within 1 month, followed by intensive outpatient physiotherapy for 9 months. Patients assigned to physiotherapy alone had identical intensive physiotherapy. There was a statistically significant and clinically important difference in improvement in motor function in favor of the SPR group, with a mean increase in total Gross Motor Function Measure (GMFM) score of 11.3% at 9 months for the SPR group compared with 5.2% for the physiotherapy-only group (P = 0.007). Significant improvements in spasticity (P < 0.001) and range of movement (P < 0.001) were noted in the SPR group compared to the physiotherapy-only group. The results indicate that the improvement in motor function after SPR is more than can be explained by the associated intensive physiotherapy.

Cerebral Palsy↗
PubMed1997

Human immunodeficiency virus type 1 Vpr interacts with HHR23A, a cellular protein implicated in nucleotide excision DNA repair.

The human immunodeficiency virus type 1 (HIV-1) vpr gene is an evolutionarily conserved gene among the primate lentiviruses HIV-1, HIV-2, and simian immunodeficiency viruses. One of the unique functions attributed to the vpr gene product is the arrest of cells in the G2 phase of the cell cycle. Here we demonstrate that Vpr interacts physically with HHR23A, one member of an evolutionarily conserved gene family involved in nucleotide excision repair. Interaction of Vpr with HHR23A was initially identified through a yeast two-hybrid screen and was confirmed by the demonstration of direct binding between bacterially expressed recombinant and transiently expressed or chemically synthesized protein products. Visualization of HHR23A and Vpr by indirect immunofluorescence and confocal microscopy indicates that the two proteins colocalize at or about the nuclear membrane. We also map the Vpr-binding domain in HHR23A to a C-terminal 45-amino-acid region of the protein previously shown to have homology to members of the ubiquitination pathway. Overexpression of HHR23A and a truncated derivative which includes the Vpr-binding domain results in a partial alleviation of the G2 arrest induced by Vpr, suggesting that the interaction between Vpr and HHR23A is critical for cell cycle arrest induced by Vpr. These results provide further support for the hypothesis that Vpr interferes with the normal function of a protein or proteins involved in the DNA repair process and, thus, in the transmission of signals that allow cells to transit from the G2 to the M phase of the cell cycle.

Amino Acid Sequence↗
PubMed1997

Human immunodeficiency virus type 1 vpr gene induces phenotypic effects similar to those of the DNA alkylating agent, nitrogen mustard.

The product of the human immunodeficiency virus type 1 (HIV-1) vpr gene induces cell cycle arrest in the G2 phase of the cell cycle and is characterized by an accumulation of the hyperphosphorylated form of cdc2 kinase. This phenotype is similar to the effect of DNA-damaging agents, which can also cause cells to arrest at G2. We previously reported that Vpr mimicked some of the effects of a DNA alkylating agent known as nitrogen mustard (HN2). Here we extend these earlier observations by further comparing the activation state of cdc2 kinase, the kinetics of G2 arrest, and the ability to reverse the arrest with chemical compounds known as methylxanthines. Infection of cells synchronized in the G1 phase of the cell cycle with a pseudotyped HIV-1 resulted in arrest at G2 within 12 h postinfection, before the first mitosis. Similar to that induced by HN2, Vpr-induced arrest led to a decrease in cdc2 kinase activity. Vpr-mediated G2 arrest was alleviated by methylxanthines at concentrations similar to those needed to reverse the G2 arrest induced by HN2, and cells proceeded apparently normally through at least one complete cell cycle. These results are consistent with the hypothesis that Vpr induces G2 arrest through pathways that are similar to those utilized by DNA-damaging agents.

Alkylating Agents↗
PubMed1997

Intrathecally administered baclofen for treatment of children with spasticity of cerebral origin.

Management of severe spasticity in children is often a difficult problem. Orally administered medications generally offer limited benefits. This study examines the value of intrathecally administered baclofen in the treatment of 19 children with severe spasticity of cerebral origin: eight of whom sustained brain injury associated with trauma, near drowning, or cardiac arrest; 10 with cerebral palsy (spastic quadriplegia); and one child with Leigh's disease. At the time of entry into the study, patients ranged from 4 to 19 years of age, and all were completely dependent on caretakers for activities of daily living. Children who responded positively to a trial dose of intrathecal baclofen underwent insertion of a drug delivery system for continuous infusion. This was followed by a double-blind trial of baclofen or placebo and follow-up review at 3 and 6 months, and yearly thereafter. Seven children did not undergo pump implantation because of excess sedation or poor response. The 12 remaining children have been followed for a period of 1 to 5 years. Favorable responses were present in all 12 children as determined by the Ashworth Scale, with the greatest benefit being reduction of lower limb tone. Except in the case of one child who had reduction in lower limb tone that resulted in difficulty with transfers, the caretakers all reported significant benefits from intrathecal baclofen, with improvement in muscle tone, behavior, sitting, and general ease of care being most commonly noted. Central side effects were seen in some children who received continuous intrathecal baclofen infusion and included hypotension (two patients), bradycardia (two), apnea or respiratory depression (two), and sedation (one). During a total of 568 months of pump operation there were 10 mechanical complications, including two related to pump or side port failure and eight related to catheter kinks, extrusions, or dislodgment. Pump pocket effusion occurred in five children and a cerebrospinal fluid fistula was seen in one child. Local infection occurred in three children and meningitis in two children. The results demonstrate the potential value of continuous intrathecal baclofen infusion for treatment of severe spasticity of cerebral origin. However, this treatment can result in significant complications and more experience is required before the long-term benefits can be determined.

Adolescent↗
PubMed1996

Trends in incidence rates of adenocarcinoma of the oesophagus and gastric cardia in New Zealand, 1978-1992.

BACKGROUND: Increasing incidence rates for adenocarcinomas of the oesophagus and gastric cardia have been reported from the United States, Denmark, United Kingdom, Switzerland, and Sweden. This paper reports on the incidence of adenocarcinomas of the oesophagus and gastric cardia in New Zealand in the Maori (Polynesian), and non-Maori (predominantly European) populations. METHODS: Incidence data from the National Cancer Registry for 1978 through 1992 were used to compute age-adjusted rates by sex, ethnic group, anatomic subsite, morphology, 14 area health districts, and for three periods: 1978-1982, 1983-1987 and 1988-1992. Statistical tests for significance of trends and differences in frequencies were employed. RESULTS: Incidence rates for adenocarcinoma of the oesophagus are increasing in non-Maori men and women, but at a lesser rate than that reported for the US. The rate of 2.3 per 100000 population (1988-1992) for non-Maori men is similar to the rate for US white men of 2.5 (1988-1990). Rates for adenocarcinoma of the gastric cardia in non-Maori men declined from 2.5 in 1983-1987 to 1.9 in 1988-1992, and were stable at 0.4 in non-Maori women. However, rates for cases with unspecified anatomic subsite fluctuated over the 15-year period and probably caused a deflation in rates in the most recent 5-year period. CONCLUSIONS: The incidence patterns of adenocarcinomas of the oesophagus and gastric cardia in New Zealand should be monitored over the next decade for confirmation of the trends observed here. There is need to review the quality of the data in the New Zealand registry.

Adenocarcinoma↗
PubMed1994

Septic arthritis after arthroscopy: the contributing roles of intraarticular steroids and environmental factors.

During a 9-month period at a small surgical center, seven cases of postarthroscopic septic arthritis occurred after 352 arthroscopic procedures, for an infection rate of 2.0%. Electrocardiographic cables contaminated with Pseudomonas aeruginosa from an unsterile cleaning solution probably led to two shoulder infections. Five other infections (one definite Staphylococcus aureus and three definite and one possible coagulase-negative staphylococci) were attributed to inadequate arthroscope disinfection. In the initial phase of the outbreak, use of intraoperative intraarticular corticosteroids correlated with the occurrence of infection.

Adrenal Cortex Hormones↗
PubMed1994

Parent-professional agreement on diagnosis and recommendations for children with developmental disorders.

Twenty-eight children with developmental disorders underwent an interdisciplinary assessment for diagnosis and recommendations about management. Following this assessment, the degree of agreement on diagnosis and recommendations between parents and the team was determined. There was substantial agreement for diagnosis of clearly identifiable conditions such as genetic disorders, autism, and mental retardation but less agreement for milder disorders such as learning disabilities, attention deficit disorder, and emotional disorders. Agreement on management varied, being higher for speech therapy and psychosocial interventions but lower for use of stimulant medication and diet. The parents identified additional diagnostic labels in their child and mentioned more recommendations than the clinicians prescribed. The results suggest the need for careful attention to parent perceptions following interdisciplinary assessment.

British Columbia↗
PubMed1994

The adequacy of prenatal care and incidence of low birthweight among the poor in Washington State and British Columbia.

OBJECTIVES: The purpose of this study was to examine differences in adequacy of prenatal care and incidence of low birthweight between low-income women with Medicaid in Washington State and low-income women with Canadian provincial health insurance in British Columbia. METHODS: A population-based cross-sectional study was done by using linked birth certificates and claims data. RESULTS: Overall, the adjusted odds ratio for inadequate prenatal care in Washington (comparing women with Medicaid with those with private insurance) was 3.2. However, the risk varied by time of Medicaid enrollment relative to pregnancy (2.0, 1.0, 2.7, 6.3; for women who enrolled prior to pregnancy, during the first trimester, during the second trimester, or during the third trimester, respectively). In British Columbia, the adjusted odds ratio for inadequate care (comparing women receiving a health premium subsidy with those receiving no subsidy) was 1.5 for women receiving a 100% subsidy and 1.2 for women receiving a 95% subsidy. The risk for low birthweight followed a similar trend in both regions, but there was no association with enrollment period in Washington. CONCLUSIONS: Overall, the risk for inadequate prenatal care among poor women was much greater in Washington than in British Columbia. Most of the difference was due to Washington women's delayed enrollment in Medicaid. In both regions, the poor were at similar risk for low birthweight relative to their more affluent counterparts.

Adult↗