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L Neufeld

Publications and source records attributed to L Neufeld.

6 recordsLinked to original sources
PubMed2001

Carbon monoxide as a tracer for assessing exposures to particulate matter in wood and gas cookstove households of highland Guatemala.

Kitchen-area 22-h gravimetric PM2.5 and passive diffusion stain-tube carbon monoxide (CO) concentrations were measured in homes with open fire and improved wood cookstoves in two studies. In the first study (Guat-2), which also studied homes with gas cookstoves, three samples were collected per stove condition from each of three test houses. In the second study (Guat-3), one sample was collected per house from 15 open fire and 25 improved-stove houses. CO personal samples were also taken for mother and child in both studies. Spearman correlation coefficients (R) between kitchen-area CO and PM2.5 levels in homes using open fires or impoved wood cookstoves were high ranging from 0.92 (Guat-2) to 0.94 (Guat-3), as were those between the personal samples for mother and child ranging from 0.85 (Guat-3) to 0.96 (Guat-2). In general, the correlations were lower for less-polluted conditions. The study found that CO is a good proxy for PM2.5 in homes using open fires or planchas (improved wood cookstove with chimney) but not under gas stove use conditions. It also determined that mother personal CO is a good proxy for child's (under 2 years of age) personal CO and that area CO measurements are not strongly representative of personal CO measurements. These results generally support the use of Draeger CO passive diffusion tubes as a proxy for PM2.5 in such cases where a single type of emission source is the predominant source for CO and PM2.5.

Air Pollution, Indoor↗
PubMed1998

Indoor biofuel air pollution and respiratory health: the role of confounding factors among women in highland Guatemala.

BACKGROUND: A number of studies have reported associations between indoor biofuel air pollution in developing countries and chronic obstructive lung disease (COLD) in adults and acute lower respiratory infection (ALRI) in children. Most of these studies have used indirect measures of exposure and generally dealt inadequately with confounding. More reliable, quantified information about this presumed effect is an important pre-requisite for prevention, not least because of the technical, economic and cultural barriers to achieving substantial exposure reductions in the world's poorest households, where ambient pollution levels are typically between ten and a hundred times higher than recommended standards. This study was carried out as part of a programme of research designed to inform the development of intervention studies capable of providing quantified estimates of health benefits. METHODS: The association between respiratory symptoms and the use of open fires and chimney woodstoves ('planchas'), and the distribution of confounding factors, were examined in a cross-sectional study of 340 women aged 15-45 years, living in a poor rural area in the western highlands of Guatemala. RESULTS: The prevalence of reported cough and phlegm was significantly higher for three of six symptom measures among women using open fires. Although this finding is consistent with a number of other studies, none has systematically examined the extent to which strong associations with confounding variables in these settings limit the ability of observational studies to define the effect of indoor air pollution adequately. Very strong associations (P < 0.0001) were found between the type of fire and a number of household and socioeconomic factors including the arrangement of rooms, floor type, and possession of a radio and television. The spouse's economic activity type was also significantly associated (P < 0.05). Thus, while 82% of open fire users had dirt floors and only 18% cement or tile floors, the situation was reversed for plancha users, only 16% of whom had dirt floors. CONCLUSIONS: Confounding presents a substantial problem for observational studies of indoor air pollution and health, although there is a reasonable case for believing that the observed association is causal. Intervention studies are required for stronger evidence of this association, and more importantly, to determine the size of health benefit achievable through feasible exposure reductions.

Adolescent↗
PubMed1998

Intrauterine growth retardation, body size, body composition and physical performance in adolescence.

Studies about effects of IUGR on growth in childhood as well as on body size, body composition and physical performance in adolescence and adulthood are reviewed. The review is based on 12 studies that distinguished IUGR from other types of low birthweight and compared outcomes of IUGR cases with those of non-IUGR controls. This information is complemented by results of a follow-up study of IUGR cases and controls carried out in Guatemalan adolescents and young adults. In Guatemala as well as in other countries, IUGR newborns showed partial catch-up growth during the first one or two years of life, and then maintained their achieved place in the growth distribution. Guatemalan IUGR cases were shorter, lighter and weaker than non-IUGR controls as adolescents and young adults. The differences in adult body size observed in Guatemala between cases and controls are similar to those found in more affluent countries (i.e. about 5 cm in height and 5 kg in weight).

Adolescent↗
PubMed1985

Polymerized liposomes as stable oxygen-carriers.

We have produced a surrogate erythrocyte ('hemosomes') by encapsulating human hemoglobin in polymerized vesicles composed of diacetylenic phospholipids plus or minus cholesterol. Hemoglobin (in the presence or absence of allosteric effectors) was encapsulated by a freeze-thaw method in large, unilamellar vesicles composed of monomeric lipids. Entrapment was demonstrated by molecular-sieve chromatography. Brief irradiation with ultraviolet light produced polymeric hemosomes with polymerization kinetics and conversions similar to liposomes in the absence of protein. Photo-induced oxidation of the heme was eliminated or severely limited by a combination of prior ligation with CO and the maintenance of high intravesicular hemoglobin concentrations (5-10 mM internal hemoglobin). The inclusion of allosteric effectors within polymerized hemosomes facilitated near-quantitative conversion to the oxy-HbA form. Gas permeability of monomeric and polymeric hemosomes was demonstrated by spectroscopic methods. Reversible spectral shifts, corresponding to oxygenation-deoxygenation, were obtained after brief evacuation and exposure to oxygen or nitrogen. The gas permeability of polymerized hemosomes appears sufficient for the vesicles to act as oxygen carriers in vivo, a notion that is strengthened by their apparent hemocompatibility.

Blood Substitutes↗
PubMed1975

Determination of dicumarol metabolites in bile of rats.

After intravenous administration of dicumarol-14C to rats, the bile excreted over the next 24 hr contained from 32 to 46% of the administered radioactivity. At least three primary metabolites and a small amount of unchanged dicumarol were present in the bile. Over 91% of the primary metabolites was converted to dicumarol and 7-hydroxydicumarol by hydrolysis with beta-glucuronidase. Some primary metabolites were hydrolyzed simply by acidification to pH 3 or by treatment under the acidic conditions utilized in the enzymatic hydrolysis. The three primary metabolites contain carboxylic acid groups, as indicated by their electrophoretic mobility-pH profiles, and some are simple glucuronides of dicumarol and 7-hydroxydicumarol. The possibility that others are derivatives of these compounds in which a coumarin lactone ring is opened cannot be ruled out. When the metabolites released by either acidification or enzymatic hydrolysis were chromatographed in n-butanol-3 M ammonia, artifacts were produced, presumably as a result of decomposition of 7-hydroxydicumarol. The question is raised whether a previously reported metabolite (B055) is an artifact.

Animals↗