Determining the probability of pesticide exposures among migrant farmworkers: results from a feasibility study.

BACKGROUND: Migrant and seasonal farmworkers are exposed to pesticides through their work with crops and livestock. Because workers are usually unaware of the pesticides applied, specific pesticide exposures cannot be determined by interviews. We conducted a study to determine the feasibility of identifying probable pesticide exposures based on work histories. METHODS: The study included 162 farm workers in seven states. Interviewers obtained a lifetime work history including the crops, tasks, months, and locations worked. We investigated the availability of survey data on pesticide use for crops and livestock in the seven pilot states. Probabilities of use for pesticide types (herbicides, insecticides, fungicides, etc.) and specific chemicals were calculated from the available data for two farm workers. The work histories were chosen to illustrate how the quality of the pesticide use information varied across crops, states, and years. RESULTS: For most vegetable and fruit crops there were regional pesticide use data in the late 1970s, no data in the 1980s, and state-specific data every other year in the 1990s. Annual use surveys for cotton and potatoes began in the late 1980s. For a few crops, including asparagus, broccoli, lettuce, strawberries, plums, and Christmas trees, there were no federal data or data from the seven states before the 1990s. CONCLUSIONS: We conclude that identifying probable pesticide exposures is feasible in some locations. However, the lack of pesticide use data before the 1990s for many crops will limit the quality of historic exposure assessment for most workers.

A pilot study to rate determinants of exposure from videotaped work activities of farmers' use of pesticides.

Industrial hygienists often observe workers to determine who should be measured based on a predicted exposure level. Such evaluations are usually based on real-time observation, yet surprisingly little research has been conducted on what determinants of exposure industrial hygienists use to rank workers and whether the ranking is accurate. Accuracy of the ranking may also be affected by the observation process, which is limited when conditions in the workers' immediate environment are rapidly changing. An alternative to real-time observation is videotaping workers and evaluating the tapes at a later date. A pilot study was conducted using previously collected data to determine if workers could be ranked by exposure level utilizing a scoring system to rate videotaped work practices. Six farmers had been videotaped and their dermal exposures measured as they applied insecticide to hogs. In this study, scores were developed to rate the farmers' working conditions by exposure level. Two types of determinants were used to describe exposure: touching and work practices. Touching included the number of times parts of the body had contact with surfaces possibly contaminated with insecticide. Work practices included the types of clothing and protective equipment worn as well as specific practices used by the farmer (e.g., application method). Two raters conducted independent assessments of the videotape using the same criteria. One rater reviewed the tape twice. Agreement between the raters for the "touching" score was weak (intra-class coefficient (ICC) = 0.28), but there was excellent agreement between the two raters (ICC = 0.92) for overall quality of work practices. As expected, a greater number of touches was moderately correlated with an increase in total exposure (rs = 0.60) and there was a weak inverse relationship between protective work practices and the exposure under the clothing (rs = -0.26). All other relationships with exposure level were contrary to what was expected. Since videotapes provide the industrial hygienist with a record of work events and can capture details that might otherwise be missed or not considered they may play a useful role in exposure assessment, especially if carefully developed procedures are followed to overcome the limitations found by this pilot study.

The effect of diclofenac (voltarol) and pethidine on ureteric peristalsis and the isotope renogram.

Diclofenac (a non-steroidal anti-inflammatory drug) and pethidine (a synthetic opiate) are the two analgesics most commonly used to relieve the pain of ureteric colic. Fast frame renography is a non-invasive means of imaging ureteric peristalsis and renal drainage. The aim of this study was to determine the effects of each of these drugs on the drainage pattern of the upper tracts. Twelve normal male volunteers were studied. All underwent a standard fast frame renogram using 75 MBq of technetium-99m-mercaptoacetyltriglycine, and were then administered either 100 mg pethidine or 75 mg diclofenac by intramuscular injection. Fast frame renography was then repeated. Peristalsis was determined from the condensed image of each ureter and the renogram curves were analysed to obtain standard parameters and deconvolution analysis. Diclofenac caused a profound disruption to both ureteric peristalsis and the renogram curve. This effect was not seen after the administration of pethidine. Deconvolution analysis suggests the effects of diclofenac are mediated via a direct effect on drainage rather than by any alteration of blood flow to the kidney. This study suggests that pethidine is the analgesic of choice prior to renography and that inferences about alterations of drainage in the presence of diclofenac should be interpreted with care.

Physical and subjective evaluation of a three-detector (TRIAD 88) SPECT system.

The three-detector TRIAD 88 is a variable cylindrical FOV whole-body SPECT system designed for both brain as well as body organ imaging. The system performance was assessed in terms of physical indices and clinical quality. Measures of low contrast resolution using contrast-detail curves, high contrast resolution using LSFs and associated frequency descriptors, display characteristics, system sensitivity, energy resolution and uniformity analysis were utilized. In addition, images of Carlson phantom, Hoffman brain phantom and clinical brain images were used to compare two collimators subjectively. Measurements and calculations were obtained for two sets of parallel hole collimators, i.e., LEUR_PAR and LEHR_PAR. Of special interest is the consistency among the three detectors. The planar and volume sensitivities for the LEUR_PAR collimator were about 58% of those of the LEHR_PAR collimator. The planar spatial resolution of the two collimators differed by about 14%. The display was characterized by a logistic model H & D curve. The planar contrast-detail curves demonstrated no statistical difference in lesion detectability between the two collimator types, however SPECT phantom and clinical images demonstrated improved performance with the LEUR_PAR collimator. Images of Hoffman single slice brain and Carlson phantoms and Tc-99m (HMPAO) brain images demonstrated excellent image quality. There was similarity in performance parameters of the three detector heads.

Memory deficits in a demented patient with probable corticobasal degeneration.

Anterograde and retrograde amnesia in a patient with probable corticobasal degeneration (pCBD) and dementia were studied in a university medical center setting. The patient with pCBD and four comparison patients of comparable global mental status (Mini-Mental State Exam) who met NINCDS-ADRDA criteria for Alzheimer's disease (AD) were included. Standard neuropsychological tests of naming, intelligence, achievement, verbal fluency, anterograde and remote verbal and visuospatial memory, and motor skill learning were given. The pCBD patient exhibited a progressive asymmetric akinetic-rigid syndrome, which was unresponsive to Sinemet. His initially mild, intellectual deficits consisted of apraxia, slowed speech, and word-finding and memory difficulties. Over a 2-year period, a dementia syndrome developed, which involved more-serious deficits in praxis and naming, as well as impairments in spelling, calculation, verbal fluency, IQ, anterograde verbal and visuospatial memory, and motor skill learning. When tested by recall methods, the pCBD patient exhibited marked deficits on several tests of remote memory; however, on recognition testing, he performed normally on the Famous Faces Test and on a test of geographical knowledge, which measures remote visuospatial memory. By contrast, the four AD patients, who showed equivalent naming difficulties, less-severe fluency deficits, and normal motor skill learning, showed severe impairments in recalling and recognizing the names of famous people from photographs. A magnetic resonance imaging (MRI) scan of the pCBD patient showed marked frontal and parietal lobe atrophy and central atrophy, with ventriculomegaly that was greater on the left side of the brain. The temporal lobes were relatively spared, and the amygdalae, hippocampi, and temporal horns were of normal size.(ABSTRACT TRUNCATED AT 250 WORDS)

Preserved cognitive skills in dementia of the Alzheimer type.

OBJECTIVE: To describe preserved cognitive skills in patients with dementia. DESIGN: Case series. SETTING: Community clinic. PATIENTS: Five patients who met National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for probable Alzheimer's disease and were claimed to retain a cognitive skill. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Standard neuropsychological tests and individualized measures of patient's skilled behaviors. For patients who remained skilled at games, performance was compared with that of normal controls in direct competition. For the patient-trombonist, raters compared premorbid and postmorbid recordings of his play. RESULTS: One patient continued to play the trombone in a Dixieland band, although he could not name well-known numbers that he played. Another continued to solve adult jigsaw puzzles. A third patient retained skill at canasta, the fourth at dominoes. The fifth patient remained a skillful contract bridge player, although he could not name the suits or articulate simple bidding rules. Four patients had impaired performance on standard anterograde and remote memory and naming tests but performed normally on pursuit rotor and letter fluency tests. Mini-Mental State Examination scores for these patients ranged from 10 to 22. One patient refused neuropsychological testing but displayed his skill. CONCLUSIONS: Together with previous studies of preserved piano playing or painting skills, our findings indicate that a broad range of complex cognitive abilities may be preserved in patients with dementia of the Alzheimer type who cannot perform simpler actions.

Transfer function measurement and analysis for a magnetic resonance imager.

The transfer function characteristics of a 1.5T imager have been determined. An edge response function (ERF) was obtained from a water/Plexiglas interface at various pixel widths ranging from 0.312 to 1.0 mm. An SE pulse sequence was used with a 5-mm transaxial slice. The ERF was smoothed, differentiated, and Fourier transformed to obtain MTF curves. The LSF was analyzed for skewness and kurtosis. The area under the MTF amplitude curves and the equivalent bandpass were calculated. All ERFs, LSFs, and MTFs were well behaved. The resulting LSF was Gaussian. All calculated MTFs had cutoff frequencies slightly less than the theoretical Nyquist limit. The MTF calculated from the theoretical Gaussian LSF is slightly superior to that calculated from experimental data and provides an upper limit to the MTF. Spatial resolution in our MR imager is dominated by the pixel size via the Nyquist sampling theorem. System performance is slightly less than theoretically predicted, possibly due to image processing algorithms during the reconstruction process.

Transient white matter changes on MR images in children undergoing chemotherapy for acute lymphocytic leukemia: correlation with neuropsychologic deficiencies.

The cranial magnetic resonance (MR) images of 25 children with acute lymphocytic leukemia (ALL) who were undergoing chemotherapy were retrospectively studied to determine the frequency of white matter changes and to analyze the significance of these observed changes in predicting subsequent neuropsychologic deficiencies. MR images showed transient white matter abnormalities in 17 of the 25 patients during consolidation therapy. Twelve of 20 children showed neuropsychologic deficits. There was no correlation between white matter changes and neuropsychologic deficits. In the subgroup of children under age 5 years at the time of diagnosis, 10 of 11 showed neuropsychologic deficits, and eight of 11 had white matter changes. Children under age 5 who undergo chemotherapy for ALL are at high risk to develop neuropsychologic deficiencies. Age at diagnosis is a reliable predictor of subsequent neuropsychologic deficits.

John Caffey award. MR imaging determination of the location of the normal conus medullaris throughout childhood.

This retrospective study was designed to determine the location of the conus medullaris in normal children by reviewing a series of MR images of the lumbar spine. The study group consisted of 184 children ranging in age from newborn to 20 years who had a normal conus level as reported by the radiologist of record. The range of conus levels for the entire group of normal children was T12 to L3. The range for the 0-2-year-old group was T12 to L2-L3 with an average of L1-L2. The range of conus levels for the 19-20-year-old group was L1 to L2 with an average of L1-L2. We conclude that the conus medullaris does not ascend throughout childhood as stated by previous authors but attains the adult level sometime during the first few months of life. A conus level at L2-L3 or above should be considered normal at any age. A conus level at L3 is indeterminate, since it is possible for a normal or a tethered conus to be located at this level.

Bootstrap sensitometry for nuclear medicine.

A full radioscintigraphic monitor/film system sensitometric curve has been obtained utilizing a bootstrap technique in which individual characteristic curve segments, obtained from stepwedge-graded exposures, are tied together at the point of overlap. Curve segments were first smoothed by employing the linearized form of the logistic distribution function. This function allows calculation of gradient-exposure and gradient-density relations for the full characteristic curve.

MRI in infants and children with spinal dysraphism.

Magnetic resonance imaging (MRI) of the spine was used in 37 infants and children to assess the potential of this new technology to evaluate suspected lumbosacral dysraphic myelodysplasia. Eighteen of these patients had correlative metrizamide myelotomography and metrizamide computed tomography (CT). MRI using a spin-echo pulse sequence with short repetition times (TR) and echo delay times (TE) affords optimal delineation of normal and abnormal spinal cord morphology in the lumbosacral region. Coronal projections usually provide an adequate demonstration of the normal conus medullaris for screening purposes; however, multiplanar acquisitions are necessary for more complete delineation of the dysraphic myelopathy. The sensitivity of MRI compares favorably with metrizamide tomography and CT, although these procedures provide somewhat better specificity. These results suggest that MRI is a reliable, noninvasive procedure to screen patients for lumbosacral dysraphism.

Surrogate modeling of the effect of object motion on image degradation in radioscintigraphy.

Image degradation has been modeled for uniform, harmonic, parabolic and random motion using analytical functions. Parameters investigated include the modulation transfer function (MTF), the information transfer function (the square of the MTF), the optimum frequency response (peak of the MTF x k versus k curve) and the modulation index (the MTF at the optimum frequency response). The results of this modeling demonstrate that motion causes not only a major degradation in the resolution matrices investigated but also that some simulated motions cause phase shifts, a previously underappreciated phenomenon.

FORTRAN algorithms for evaluating Fourier transforms of line spread functions.

FORTRAN IV algorithms are presented for calculating the modulation transfer function, the phase transfer function, the modulation transfer function area, an information transfer function, and the optimum frequency response as well as plotting the curves for these matrices. An important feature of the programs is an editing routine.

Electron microscope studies on the effects of dimethyl sulphoxide in mammary glands of Long Evan rats during foetalogeneis.

The effects of dimethyl sulphoxide (DMSO) in mammary glands of rats during foetalogeneis was studied by means of electron microscopy. Certain morphological alterations were observed in secretory tubules and epithelial cels of mammary glands. These alterations were not evident in control tissues. Secretory tubules of DMSO-treated mammary glands showed dissociation, thickening of granular fibrous-like material and profound darkening. Morphological alterations observed in epithelial cells involved decrease and dissociation of fibrillar complexes, numerous electron-dense droplets, mitochondria with disrupted cristae, hypertrophied granular endoplasmic reticuli, vacuoles and cellular debris. Thus, the results in this study suggest that DMSO at sublethal dosages induces morphological alterations in mammary gland tissue of rats during 16.5 days of gestation.

Pharmacokinetics of pertechnetate administered after pretreatment with 400 mg of potassium perchlorate: concise communication.

The pharmacokinetic behavior of pertechnetate in normal subjects has been studied. Each received 400 mg of potassium perchlorate 30 min before pertechnetate injection. Timed blood samples were collected and counted. The time-activity curves for whole blood and plasma could both be fitted to an open two-compartment model of the form 3 comes from 1 in equilibrium with 2, where Compartment 1 refers to the vascular pool, Compartment 2 to the perivascular pool, and Compartment 3 to the urine. The pharmacokinetic state equation is given by: leads to X = -KX. Rate constants determined were: k21 = 1.47 hr-1; k12 = 3.11 hr-1; k01 = 0.137 hr-1. The rate constants were the same for the whole-blood and plasma time-activity curves.

An evaluation of the 24-hour RAIU test performed with an Anger camera and a pinhole collimator.

RAIU measurements obtained with a conventional thyroid uptake probe have been compared with those obtained with an Anger camera and a pinhole collimator. Although the field distribution for the pinhole collimator deviates markedly from the IAEA recommendations, the group data from the comparative measurements in this series were identical, with a confidence level of 99%. However, in several cases the data from differing measurement regimes for individuals varied markedly.

Thyroid imaging with iodine-125 and technetium-99m.

Eighty-eight patients referred consecutively for thyroid imaging were studied. Each patient was scanned with a 3'' rectilinear scanner using both 125I and 99mTc. The paired scans were evaluated independently by two physicians experienced in thyroid evaluation and image analysis. The images were ranked on a scale from 1 to 5 as follows: 1) 125I scan much better than the 99mTc scan, 2) ..., 3) 125I scan and 99mTc scan the same, 4) ..., 5) 99mTc scan much better than 125I scan. The scores were statistically analyzed by the sign test and transformed normal score methods. Categories analyzed were: A. Hypothyroid, B. Euthyroid, C. Hyperthroid, (A-C based upon RAIU measurements), D. Cold Nodules, E. Graves Disease, F. Hot-Nodules, G. Multinodular Nontoxic Goiter, H. Miscellaneous and I. Normal. The significance of this study is that regardless of the classification we used, in no category was the 99mTc scan considered better than the 125I scan. This finding is at variance with the observations of some others comparing 99mTc with other iodine radioisotopes. 99mTc may have some procedural advantages and does deliver a lower radidation dose to the thyroid.