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Biomedical subjects

R McConnell

Publications and source records attributed to R McConnell.

16 recordsLinked to original sources
PubMed1992

Hazards of closed pesticide mixing and loading systems: the paradox of protective technology in the Third World.

In studies in developing countries, closed systems for mechanically mixing and loading hazardous pesticides have been shown to reduce exposure to workers. To evaluate the efficacy of closed systems in preventing worker exposure in the developing world, a cross sectional study was conducted at rural crop dusting airports in the cotton growing region of Nicaragua. Worker exposure was evaluated by measuring the activity of erythrocyte cholinesterase in the field with a new design battery operated colorimeter. The 10 mixer loaders at four airstrips with closed systems were compared with the 16 mixer loaders at four airstrips where pesticides were hand poured. Paradoxically, cholinesterase activity was 1.1 IU/ml blood (95% Cl 0.49-1.8) lower (inhibited) among workers in airstrips with closed systems than among workers hand pouring insecticides, after adjusting for weight of organophosphates sprayed in the past 14 days, and for prior training in safe use of pesticides. Mixer loaders with prior training had cholinesterase activity 0.83 IU (95% Cl 0.30-1.4) higher than untrained workers, and the weight of organophosphates sprayed was also a statistically significant predictor in the model. Unfortunately, management viewed the closed systems primarily as a production tool, rather than as a way to protect workers. Airstrips with closed systems were able to apply an average of 3250 lb organophosphates per worker in the 14 days before the survey compared with 849 lb per worker in airstrips without closed systems. Only three of 10 mixer-loaders at airstrips with closed systems had received formal training in safer use of pesticides. Because of shortage of personnel and transport, it was difficult for the responsible government agencies to train workers adequately and to enforce pesticide health and safety standards at multiple dispersed worksites.

Cholinesterase Inhibitors↗
PubMed1992

Monitoring organophosphate insecticide-exposed workers for cholinesterase depression. New technology for office or field use.

A serious limitation to the diagnosis of mild organophosphate poisoning and to the preventive screening of organophosphate-exposed workers has been the large interindividual variability in erythrocyte cholinesterase. This makes it necessary to obtain a pre-exposure baseline measurement of enzyme activity as a basis for evaluating subsequent declines. To evaluate a new battery-operated colorimetric erythrocyte cholinesterase kit, 23 workers at a Mexican pesticide formulation plant were examined. All workers had normal cholinesterase, and exposed and unexposed workers were found to have similar mean cholinesterase levels. Although erythrocyte cholinesterase was found to have a coefficient of variation of 12% (similar to that reported in previous studies), hemoglobin-adjusted erythrocyte cholinesterase had a markedly reduced coefficient of variation (7.4%). The 90% confidence interval (24.9-31.7 IU/g hemoglobin) resulted in a lower normal limit that is 78% of the upper limit. Even if a pre-exposure baseline were high normal but unknown at the time of examination, the supervising clinician can be confident that any person with a normal result will be no less than 78% of baseline. The kit is moderately priced, easy to use in the field setting, and the low variability to the assay should allow improvement in diagnosis, screening, and in the epidemiologic evaluation of exposure.

Adult↗
PubMed1991

Chronic central nervous system effects of acute organophosphate pesticide intoxication. The Pesticide Health Effects Study Group.

Acute organophosphate pesticide poisonings cause substantial morbidity and mortality world wide; however, whether organophosphates cause chronic neurological sequelae has not been established. To see whether single episodes of acute unintentional organophosphate intoxication lead to chronic neuropsychological dysfunction, we carried out a retrospective study of agricultural workers in Nicaragua who had been admitted to hospital between July 1, 1986, and July 31, 1988, for occupationally related organophosphate intoxication. This "poisoned" group (36 men) was tested on average about two years after the episode of pesticide poisoning and compared with a matched control group. The poisoned group did much worse than the control group on all neuropsychological subtests, with significantly worse performance on five of six subtests of a World Health Organisation neuropsychological test battery and on 3 of 6 additional tests that assessed verbal and visual attention, visual memory, visuomotor speed, sequencing and problem solving, and motor steadiness and dexterity. Differences in neuropsychological performance could not be explained by other factors. The findings of a persistent decrease in neuropsychological performance among individuals with previous intoxication emphasise the importance of prevention of even single episodes of organophosphate poisoning.

Acute Disease↗
PubMed1991

Respiratory disease in a textile factory in Nicaragua.

This is the first epidemiologic study conducted in a textile mill in Nicaragua using techniques and diagnostic criteria similar to those used in the United States and England. The prevalence of byssinosis and nonspecific respiratory symptoms were studied in 194 workers in a cotton mill in Managua. Limited environmental sampling, performed using a vertical elutriator in yarn preparation and weaving areas, indicated that exposures were similar to those reported in other parts of the developing world. A modified translated version of the Medical Research Council respiratory questionnaire was administered. Pulmonary function tests were performed before and after the Monday workshift to measure across-shift change in ventilatory function. The prevalence of byssinosis was 5.9% and all the cases occurred among exposed women. Nonspecific respiratory symptoms were also more prevalent among exposed workers. After adjusting for age, gender, smoking habit, and work tenure, the exposure odds ratios for usual cough and usual phlegm were 3.3 and 2.2, respectively. The association between exposure and across-shift decrement in FEV1 was not significant. Byssinotic workers, however, had greater decrements in FEV1% than those without byssinosis: 5.5% versus 1.8%. A consistent gender effect was observed in which both exposed and unexposed women were found to have greater across-shift decrements in FEV1 than men. The gender difference existed among long-term workers as well as workers who had been employed less than 2 years. Results are related to cotton dust exposure, as has been documented elsewhere. The poorer health status of the women in this study population deserves follow-up.

Adult↗
PubMed1991

Difference between the calcium- and the phorbol ester-induced association of protein kinase C with phospholipid membrane.

1. Membrane association of protein kinase C is thought to be a prerequisite for the activation of the enzyme. 2. We studied the association of the enzyme with liposome. 3. We show here that the mechanisms for the calcium- and the phorbol ester-induced association of protein kinase C with liposome are different from each other. 4. Diacylglycerol is not crucial for the association of the enzyme with liposome.

Animals↗
PubMed1991

Neurotoxicity of 1-methoxycycloheptatriene--a Purkinje cell toxicant.

The toxicity of 1-methoxycycloheptatriene (1-MCHT), a sensory irritant, has been investigated in beagles. It was found to produce gross inco-ordination of the limbs at intravenous doses greater than 10 mg kg-1. The main histological abnormalities were in the cerebellum and consisted of Purkinje cell death and subsequent reactive gliosis. A few necrotic neurons were seen in the diencephalon, pons and medulla. Haematological abnormalities, e.g. leucocytosis with relative lymphopenia, were seen, while biochemical changes included hyperglycaemia and a rise in plasma aminotransferases. The no-effect dose for the histological and biochemical changes was the same. These abnormalities are compared with cerebellar changes observed in acrylamide and other toxic states.

Animals↗
PubMed1990

Poly(anhydride) administration in high doses in vivo: studies of biocompatibility and toxicology.

Poly(anhydrides) proposed for use as vehicles for controlled drug delivery were administered subcutaneously in Sprague-Dawley rats at two dosage levels (800 mg/kg rat and 2400 mg/kg rat) for a period of eight weeks. Biocompatibility was assessed using a number of methods. Thirty-six clinical chemistry and hematology parameters were monitored throughout the study. Blood values were statistically analyzed for any possible effects due to the implanted polymer. After 8 weeks, rats were sacrificed and complete necropsies were performed. Histological evaluations of 33 organ sites including heart, lung, liver, kidney, and brain were performed. In addition, subcutaneous implant sites were excised and examined both grossly and microscopically. Results from evaluations of blood chemistry and hematology data, organ analyses and local implant site analyses overall demonstrated that the poly(anhydride) biomaterial possessed excellent in vivo biocompatibility.

Animals↗
PubMed1990

Crop duster aviation mechanics: high risk for pesticide poisoning.

A cross-sectional medical survey was conducted among 63 Nicaraguan aviation mechanics exposed to organophosphate and other toxic pesticides. Thirty-one (49 percent) reported having been acutely poisoned on the job. Also, seven of 14 novice mechanics, with less than one year on the job, reported that they had been poisoned. Thirty-eight (61 percent) had cholinesterase levels below the lower limit of normal, including three workers with levels less than 20 percent of the lower limit of normal. Risk factors for low cholinesterase included recent hire and recent poisoning. Workers did not use protective equipment, nor were there facilities for bathing on site. As a result of this survey, the government has prohibited the mixing and loading of pesticides at this airport and requires the washing of planes prior to maintenance work; coveralls and thin, pesticide impermeable gloves are to be issued to mechanics handling pesticide-contaminated parts. Closed system mixing and loading systems have been installed at satellite airstrips.

Adolescent↗
PubMed1986

Sequence landscapes.

We describe a method for representing the structure of repeating sequences in nucleic-acids, proteins and other texts. A portion of the sequence is presented at the bottom of a CRT screen. Above the sequence is its landscape, which looks like a mountain range. Each mountain corresponds to a subsequence of the sequence. At the peak of every mountain is written the number of times that the subsequence appears. A data structure called a DAWG, which can be built in time proportional to the length of the sequence, is used to construct the landscape. For the 40 thousand bases of bacteriophage T7, the DAWG can be built in 30 seconds. The time to display any portion of the landscape is less than a second. Using sequence landscapes, one can quickly locate significant repeats.

DNA, Viral↗
PubMed1986

Hereditary monocyte esterase deficiency.

An inherited cytochemical staining abnormality of monocytes is described, affecting members of three generations of one family. alpha-Naphthyl acetate and alpha-naphthyl butyrate esterase staining reactions have been consistently negative in 95% of the monocytes of the propositus and her son and in 60-70% of the monocytes in two of four grandchildren.

Aged↗