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Biomedical subjects

B Armstrong

Publications and source records attributed to B Armstrong.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Health of women living near oil wells and oil production stations in the Amazon region of Ecuador].

OBJECTIVE: Investigate the environmental conditions in and the state of health of women who live in rural communities surrounded by oil wells and oil production stations in the Amazon region of Ecuador. METHOD: We used a comparative cross-sectional design, classifying exposure according to the location of the communities with respect to the oil wells and production stations. Water samples from the local rivers were analyzed to determine total petroleum hydrocarbons, and a structured questionnaire was used with the head of each family in the study. The study was performed in rural communities in northeastern Ecuador from November 1998 through April 1999. The study included 9 communities in the exposed area (368 participants) and 14 communities in the unexposed area (291 participants). RESULTS: The rivers of the exposed communities showed contamination levels much above the limits acceptable for human use. Statistically significant differences between the exposed communities and the unexposed communities were found for the prevalence of skin fungi for the two weeks prior to the study (odds ratio (OR) = 1.37; 95% confidence interval (CI) = 1.01-1.86) as well as for nasal irritation (OR = 2.18, 95% CI = 1.64-2.91) and for throat irritation (OR = 1.68, 95% CI = 1.02-2.75) in the preceding 12 months. Also associated with exposure in the two preceding weeks were fatigue and the category of "other symptoms"; similarly associated with exposure in the preceding 12 months were headaches, eye irritation, earaches, diarrhea, and gastritis. CONCLUSIONS: The symptoms found among the participants in the exposed communities match the toxicity symptoms caused by oil. There is an urgent need to establish an adequate environmental control and remediation program in order to prevent unnecessary and unacceptable health hazards for these populations.

Adolescent↗
PubMed2000

Suspension arrays for high throughput, multiplexed single nucleotide polymorphism genotyping.

BACKGROUND: Genetic diversity can help explain disease susceptibility and differential drug response. The most common type of variant is the single nucleotide polymorphism (SNP). We present a low-cost, high throughput assay for SNP genotyping. METHODS: The assay uses oligonucleotide probes covalently attached to fluorescently encoded microspheres. These probes are hybridized directly to fluorescently labeled polymerase chain reaction (PCR) products and the results are analyzed in a standard flow cytometer. RESULTS: The genotypes determined with our assay are in good agreement with those determined by TaqMan. The range of G/C content for oligonucleotide probes was 23.5-65% in the 17 bases surrounding the SNP. Further optimization of probe length and target concentration is shown to dramatically enhance the assay performance for certain SNPs. Using microspheres which have unique fluorescent signatures, we performed a 32-plex assay where we simultaneously determined the genotypes of eight different polymorphic genes. CONCLUSIONS: We demonstrate, for the first time, the feasibility of multiplexed genotyping with suspension arrays using direct hybridization analyses. Our approach enables probes to be removed from or added to an array, enhancing flexibility over conventional chips. The ability to multiplex both the PCR preparation and the hybridization should enhance the throughput, cost, and speed of the assay.

Artifacts↗
PubMed2000

Mercury exposure in Montrealers who eat St. Lawrence River sportfish.

We assessed levels and determinants of mercury biomarkers among residents of Montreal and surroundings who eat sportfish from the nearby St. Lawrence River. Participants were selected from 1118 adult fishers responding to a 1996 screening questionnaire; the study sample (n=132) overrepresented respondents expected to have the greatest and the least exposure to mercury. Tissue mercury concentrations were associated with sportfish consumption: among participants who ate sportfish at least once weekly, hair geometric mean (GM)=0.82+/-2.54 microg/g and blood mercury GM=3.03+/-2.43 microg/L, compared to hair GM=0.38+/-2.28 microg/g and blood mercury GM=1.44+/-2.23 microg/L for those who ate sportfish less than once weekly. While these levels are somewhat higher than those shown for other Greater Lakes and St. Lawrence River fishers, only one participant surpassed the Canadian recommended population mercury limit of 6 microg/g for hair and 20 microg/L for blood. Consumption of several sportfish species independently explained much of the variation in measured blood mercury; the predatory species pike was the most important in multivariable regression. Coincident consumption of waterfowl, fishing during the longer summer/fall rather than the brief winter season, and fishers' age were independently associated with blood mercury. Serum selenium related neither to the level of fish consumption nor to the participants' blood mercury.

Animals↗
PubMed2000

Selective neurotoxic effects of nicotine on axons in fasciculus retroflexus further support evidence that this a weak link in brain across multiple drugs of abuse.

When administered continuously for several days at relatively low plasma levels, a variety of drugs of abuse with strong dopaminergic actions induce degeneration in axons traveling from the lateral habenula through the sheath of fasciculus retroflexus to midbrain monoaminergic nuclei. With some of these drugs, such as cocaine, this is virtually the only degeneration induced in brain. Nicotine given continuously also selectively induces degeneration in fasciculus retroflexus, but in the other half of the tract: the cholinergic axons running from medial habenula in the core of the tract to the interpeduncular nucleus. Fasciculus retroflexus appears to be a weak link in brain for diverse drugs of abuse when administered incessantly for several days. Alterations in this tract would be predicted to be especially important for the genesis of the symptomatology which develops during drug binges, residual effects of such binges, and the processes underlying relapse.

Amphetamines↗
PubMed2000

Second primary neoplasms following non-Hodgkin's lymphoma in New South Wales, Australia.

The incidence of non-Hodgkin's lymphoma (NHL) has been increasing rapidly over the last three decades. The reasons for this trend are not known although increasing exposure to sunlight has been postulated. We used data from the New South Wales Central Cancer Registry to analyse second primary neoplasms following NHL diagnosed between 1972 and 1995, to identify possible common causal agents. A total of 12,452 patients contributed 54,308 person-years of follow-up during which time there were 705 second primary neoplasms compared to 592.99 expected (standardized incidence ratio (SIR = 1.19, 95% confidence interval (CI) 1.10-1.28). There were excesses of melanomas of skin (SIR = 2.38, 95% CI 1.92-2.91), lip cancer (SIR = 2.74, 95% CI 1.59-4.38), tongue cancer (SIR = 2.53, 95% CI 1.09-4.99) and bladder cancer (SIR = 1.64, 95% CI 1.19-2.21). There was also over a threefold excess in soft tissue sarcomas (SIR = 3.61, 95% CI 1.80-6.45) and in thyroid cancer (SIR = 3.42, 95% CI 1.56-6.49). The SIR for myeloid leukaemia was 0.78 (95% CI 0.28-1.69). The increases in melanoma of the skin and cancer of the lip and tongue among patients with NHL strongly suggest sunlight exposure as a shared causal agent. The increase in soft tissue sarcomas might be due to shared effects of exposure to chemicals such as phenoxy acid herbicides. The increases in bladder and thyroid cancers are likely to be explained by effects of treatment for NHL. We did not find a chemotherapy related increased risk of myeloid leukaemia among NHL patients.

Adult↗
PubMed2000

Immune biomarkers in relation to exposure to particulate matter: a cross-sectional survey in 17 cities of Central Europe.

Human population data on air pollution and its effects on the immune system are scarce. A survey was conducted within the framework of the Central European Study of Air Quality and Respiratory Health (CESAR) to measure a panel of immune biomarkers in children of Bulgaria, Czech Republic, Hungary, Poland, Romania, and Slovakia. Seventeen cities were chosen to represent a wide range of exposure to outdoor air pollution. In each, ambient particulate matter of less than 10 microns diameter and less than 2.5 microns diameter (PM10 and PM2.5) were measured with a Harvard impactor. Blood was collected from 366 school children aged 9 to 11 yr between 11 April and 10 May 1996. The percentage of B, total T, CD4+, CD8+, and natural killer (NK) lymphocytes was determined by flow cytometry (Becton Dickinson); total immunoglobulins of class G, M, A and E (IgG, IgM, IgA, and IgE) were measured in serum using nephelometry (Behring). Associations between PM and each log-transformed biomarker concentration were studied by linear regression, in a two-stage model. The yearly average concentrations varied from 41 to 96 micrograms/m3 for PM10 across the 17 study areas, from 29 to 67 micrograms/m3 for PM2.5, and from 12 to 38 micrograms/m3 for PM10-2.5 (coarse). Number of B, CD4+, CD8+, and NK lymphocytes increased with increasing concentration of PM, having adjusted for age, gender, parental smoking, laboratory of analysis, and recent respiratory illness. Differences in lymphocyte number were larger and statistically significant for exposure to PM2.5. Similar results were found when we examined the association between PM and lymphocyte number separately for each laboratory. Total IgG was increased with increasing concentration of PM, significantly in the case of PM2.5. When we repeated the analyses with two other statistical approaches the results did not differ from those reported here. The effect of coarse PM on lymphocyte numbers appears small in comparison to PM2.5. One possible interpretation of our findings is that long-term exposure to airborne particulates leads to inflammation of the airways and activation of the cellular and humoral immune system.

Air Pollutants↗
PubMed1999

Fish consumption and contaminant exposure among Montreal-area sportfishers: pilot study.

A 1995 pilot study assessed sport fish consumption and contaminant exposure among Montreal-area residents fishing the frozen St. Lawrence River. Interviews conducted among 223 ice fishers met on-site were used to create an index of estimated exposure to fish-borne contaminants. A second-stage assessment of sport fish consumption and tissue contaminant burdens included 25 interviewees at the highest level of estimated contaminant exposure (of 38, or 66% of those solicited) and 15 low-exposure fishers (of 41, or 37% of those solicited). High-level fisher-consumers reported eating 0. 92+/-0.99 sport fish meals/week during the previous 3 weeks compared to 0.38+/-0.21 (P<0.05) for the low-level group. Based on the product of consumption frequency times mass of sport fish meals consumed, high-level consumers ate a mean of 18.3 kg of sport fish annually versus 3.3 kg for the low-level consumers. Tissue contaminant assessments showed significant (P<0.05) groupwise differences: 0-1 cm hair mercury (median 0.73 microgram/g for the high versus 0.23 microgram/g for the low group), lipid-adjusted plasma PCB congeners (Aroclor 1260: median 0.77 microgram/g versus 0.47 microgram/g), and lipid-adjusted plasma DDE (median 0.35 microgram/g versus 0.26 microgram/g). No participant had a hair mercury or plasma DDE concentration above Health Canada recommendations but 2/25 high-level participants (8%) had plasma Aroclor 1260 concentrations above recommended limits. The results of this pilot study suggest that a small number of Montreal-area sportfishers consume their catch as often as three times weekly and that those consuming sport fish frequently have significantly higher tissue levels of mercury, PCBs, and DDE than do infrequent consumers. On the other hand, compared to other groups in Quebec, such as the Inuit or commercial fishers on the North Shore of the Gulf of St. Lawrence, Montreal-area sportfishers eat less fish and have lower tissue concentrations of fish-related contaminants.

Adult↗
PubMed1999

Contaminant exposure in Montrealers of Asian origin fishing the St. Lawrence River: exploratory assessment.

Fishing and fish consumption are widely practiced among members of certain ethnocultural groups. Informal assessment led us to ascribe high levels of consumption of locally caught sportfish to Montrealers of Asian origin and to hypothesize that their choices of species and fish organs differ from those of the majority group. An exploratory assessment of contaminant bioindicators reflective of St. Lawrence River fish consumption was conducted in late 1995 among nine Vietnamese and nine Bangladeshi Montreal sportfishers identified by community contacts. Vietnamese participants, six men and three women, were 27-70 (median 36) years of age and had immigrated to Canada 3-20 (median 7) years earlier. In contrast, the nine Bangladeshi males aged 28-41 (median 34) years had been in Canada for 2-13 (median 4) years. Bio-indicator concentrations among Bangladeshi and Vietnamese participants are compared to those found for majority-community Montreal-area high-level consumers recruited on the St. Lawrence River during winter 1995. All results are presented as the median and 90th percentile. Hair mercury concentrations were higher for both Vietnamese (1.2, 4.6 microgram/g) and Bangladeshis (1.1, 2.3 microgram/g) than for majority-community sportfishers (0.7, 1.9 microgram/g). Certain organochlorine levels, specifically total PCB (estimated by plasma Aroclor 1260), p,p'-DDT, p,p'-DDE, and B-BHC, were highest in the Bangladeshis compared to Vietnamese and to majority-community sportfishers. In contrast, plasma levels of other pesticides were low in all three groups, including mirex, chlordane, and cis-nonachlor. A correlation between plasma p,p'-DDT levels and recency of arrival in Canada was found for the Bangladeshis. These data suggest a distinct pattern of tissue organochlorines, which we postulate relates to exposure prior to arrival in Canada and perhaps to the ongoing consumption of foods (other than St. Lawrence River sportfish) specific to these groups.

Adult↗
PubMed1999

Methodological problems and the role of statistics in cluster response studies: a framework.

More and more citizens urge public health authorities to investigate reports of disease excess in their neighbourhood. These environmental concerns are legitimate and it is part of good public health practice to respond to these complaints. However, the methodological and practical problems are severe and a lot of controversy exists about the usefulness of these investigations. To clarify the possibilities and limitations in this situation, this paper proposes a typology of cluster studies. According to this framework, cluster response is distinguished from two other types of cluster studies: Cluster monitoring. screening proactively for clusters to act as an early warning system, and cluster research, scrutinizing clustering to generate and test aetiological hypotheses. To each of these three types of cluster studies corresponds a different public health context; respectively public health action, public health surveillance and public health research. Probably, part of the controversy mentioned stems from not acknowledging sufficiently the corresponding intrinsic differences in rationality and practical constraints. Cluster response is crisis management and not scientific research. In a relatively short time, an informed decision should be taken by a multidisciplinary team of experts using readily available information and knowledge. In accordance with this point of view, cluster reports should be handled stepwise and the role of statistics is to quantify a cluster exploring different points of view as an input to the decision process.

Cluster Analysis↗
PubMed1999

An audit of breast cancer pathology reporting in Australia in 1995.

To measure the quality of pathology reporting of breast cancer and establish a baseline against which future changes can be measured, we audited item completeness in breast cancer reports in Australia in 1995 before the release of specific recommendations from the Australian Cancer Network. Tumour type and size were given in reports of invasive breast cancer for 93% of women, 70% had, in addition, grade and clearance of the margins while only 28% had all recommended information. The most complete items in reports were histological type of breast cancer (99.6% of cases), tumour size (94%, 95% confidence interval (CI) 92-95) and margins of excision (87%, 95% CI 85-89). Histological grade (84%, 95% CI 82-86 of cases) and presence or absence of ductal carcinoma in situ (DCIS) (79%, 95% CI 77-81) were less complete and vessel invasion (61%, 95% CI 58-63) and changes in non-neoplastic breast tissue adjacent to the breast cancer (68%, 95% CI 66-71) the least complete. Less than half the reports of DCIS reported on tumour size (49%, 95% CI 42-57), presence or absence of necrosis (41%, 95% CI 34-49) or nuclear grade (39%, 95% CI 31-46). Around 1500 reports were identified as issued by 147 laboratories and 392 pathologists; 69% of pathologists issued fewer than two reports a month in the audit. We concluded that infrequency of reporting may have contributed to incompleteness of reporting. In addition, we found significant variation across Australian states with some indication that reporting was consistently poor in one state. The audit highlighted areas for improvement for breast cancer reporting in Australia. Research evidence suggests that multifaceted strategies are needed to assist practitioners with implementing more uniform reporting standards.

Aged↗
PubMed1999

Clinical and pathologic overlap in nonsteroidal anti-inflammatory drug-related small bowel diaphragm disease and the neuromuscular and vascular hamartoma of the small bowel.

Diaphragm disease (DD) is a radiographically subtle cause of small bowel obstruction and is part of the spectrum of diseases associated with nonsteroidal anti-inflammatory drug injury. The neuromuscular and vascular hamartoma (NMVH) is a nonepithelial hamartomatous, submucosally based proliferation of mature submucosal elements capable of causing small bowel obstruction. The authors report two patients in whom the clinical setting and gross pathology are that of DD, but the histologic characterization is identical to that described for NMVH. It is probable that in some patients the two diseases overlap so that some patients readily fit the criteria for both entities.

Aged↗
PubMed1999

High-throughput isolation of Caenorhabditis elegans deletion mutants.

The nematode Caenorhabditis elegans is the first animal whose genome is completely sequenced, providing a rich source of gene information relevant to metazoan biology and human disease. This abundant sequence information permits a broad-based gene inactivation approach in C. elegans, in which chemically mutagenized nematode populations are screened by PCR for deletion mutations in a specific targeted gene. By handling mutagenized worm growth, genomic DNA templates, PCR screens, and mutant recovery all in 96-well microtiter plates, we have scaled up this approach to isolate deletion mutations in >100 genes to date. Four chemical mutagens, including ethyl methane sulfonate, ethlynitrosourea, diepoxyoctane, and ultraviolet-activated trimethylpsoralen, induced detectable deletions at comparable frequencies. The deletions averaged approximately 1400 bp in size when using a approximately 3 kb screening window. The vast majority of detected deletions removed portions of one or more exons, likely resulting in loss of gene function. This approach requires only the knowledge of a target gene sequence and a suitable mutagen, and thus provides a scalable systematic approach to gene inactivation for any organism that can be handled in high density arrays.

Algorithms↗
PubMed1999

Involving men in reproductive health: the Young Men's Clinic.

OBJECTIVES: This report describes the population of young men who use the Young Men's Clinic in New York City, presents a profile of their reproductive behaviors, and describes the clinic's model of service delivery. METHODS: Data were gathered through a routine clinic visit form administered by clinic staff. RESULTS: The clinic sees approximately 1200 predominately Dominican young men each year for a wide range of clinical and mental health services. Two thirds of clients had ever been sexually active, three quarters had ever used birth control, and 69% had used birth control at their last sexual encounter. CONCLUSIONS: The Young Men's Clinic may serve as a model for health care delivery to adolescent and young adult males.

Adolescent↗
PubMed1998

Risk of congenital anomalies near hazardous-waste landfill sites in Europe: the EUROHAZCON study.

BACKGROUND: Waste-disposal sites are a potential hazard to health. This study is a multicentre case-control study of the risk of congenital anomalies associated with residence near hazardous-waste landfill sites in Europe. METHODS: We used data from seven regional registers of congenital anomalies in five countries. We studied 1089 livebirths, stillbirths, and terminations of pregnancy with non-chromosomal congenital anomalies and 2366 control births without malformation, whose mothers resided within 7 km of a landfill site; 21 sites were included. A zone within 3 km radius of each site was defined as the "proximate zone" of most likely exposure to teratogens. FINDINGS: Residence within 3 km of a landfill site was associated with a significantly raised risk of congenital anomaly (295 cases/511 controls living 0-3 km from sites, 794/1855 living 3-7 km from sites; combined odds ratio 1.33 [95% CI 1.11-1.59], adjusted for maternal age and socioeconomic status). There was a fairly consistent decrease in risk with distance away from the sites. A significantly raised odds ratio for residence within 3 km of a landfill site was found for neural-tube defects (odds ratio 1.86 [1.24-2.79]), malformations of the cardiac septa (1.49 [1.09-2.04]), and anomalies of great arteries and veins (1.81 [1.02-3.20]). Odds ratios of borderline significance were found for tracheo-oesophageal anomalies (2.25 [0.96-5.26]), hypospadias (1.96 [0.98-3.92]), and gastroschisis (3.19 [0.95-10.77]). There was little evidence of differences in risk between landfill sites but power to detect such differences was low. INTERPRETATION: This study shows a raised risk of congenital anomaly in babies whose mothers live close to landfill sites that handle hazardous chemical wastes, although there is a need for further investigation of whether the association of raised risk of congenital anomaly and residence near landfill sites is a causal one. Apparent differences between malformation subgroups should be interpreted cautiously.

Case-Control Studies↗