Effects of restricted knee flexion and walking speed on the vertical ground reaction force during gait.

Although lower extremity immobilization, including restricted knee flexion, is commonly used in rehabilitation, the effect of angle of knee restriction and walking speed on the vertical ground reaction forces during gait is unclear. Force plate measurements were made on 36 healthy males walking at three different speeds when knee flexion was unrestricted and restricted to both 10 and 25 degrees. Analysis of variance and post hoc analyses showed significant increases in four characteristics of the vertical ground reaction force in the restricted leg and in two characteristics in the unrestricted leg during walking with restricted knee flexion. Loading rate and unloading rate for the restricted leg and peak force for both legs showed significant speed-knee flexion restriction interactions. At the fast walking speed, two significant differences were found between knee flexion restrictions of 10 and 25 degrees. The clinical implications of these findings are that restricted knee flexion during gait may significantly alter the forces applied to both lower limbs.

Radon exposure: a review of the public health risk in Anne Arundel County, Maryland.

Long-term exposure to indoor radon may lead to an increased lifetime risk of lung cancer. Because millions of U.S. residential homes may have elevated radon levels, indoor radon exposure may pose a substantial public health threat. In Anne Arundel County (Maryland), a county-wide residential radon survey indicated that 82% of all residential radon readings in the survey were below Environmental Protection Agency remediation guidelines. Of the elevated indoor measurements, however, 94.4% were distributed in the southern portion of the county. These results are consistent with data compiled by the EPA and the U.S. Geologic Survey. Continued residential radon testing should be encouraged, especially in areas with elevated readings.

Synapsin-1 is found in a microtubule-associated complex of proteins isolated from bovine brain.

We have prepared microtubules from brain tissue by stabilizing the cellular microtubules in 6.7 M glycerol buffer, instead of the usual procedure which extracts the solubilized protein and then reassembles microtubules in vitro at some later time. There are substantial differences in the microtubule associated proteins obtained by the two methods, and brain spectrin is a major component of the stabilized microtubules. We have now modified the buffer used for the isolation of stabilized microtubules to minimize their tendency to aggregate. When the stabilized microtubules were further purified by sucrose density gradient centrifugation, we were able to distinguish previously unidentified polypeptides at 49, 74 (doublet), and 100 kilodaltons (doublet). These bands maintained staining intensity in the same proportion to tubulin as in the original homogenate, whereas background proteins were diminished in staining intensity. We now report the identification of the 74-kilodalton doublet polypeptides as synapsin-1 by peptide mapping. Synapsin-1 is a protein known to bind to brain spectrin and also to microtubules, and may thus serve as a linker between these cytoskeletal components.

Lead exposure and child behavior.

OBJECTIVES: Unlike cognitive impairments associated with lead exposure, lead-associated child behavior problems have been difficult to specify, particularly in young children. METHODS: The Child Behavior Checklist (CBCL) and the Center for Epidemiologic Studies Depression Scale were used as the outcome and confounding variables, respectively, of major interest. These measures were examined with respect to blood lead levels of 201 African-American children aged 2 through 5 years. RESULTS: In comparison with the low exposed group, the high exposed group (two consecutive blood lead levels greater than or equal to 15 micrograms/dL) had a significantly higher mean CBCL Total Behavior Problem Score (TBPS) and Internalizing and Externalizing scores; when other factors, including maternal depressive symptomatology, were controlled for, regression procedures indicated a .18-point TBPS increase for each unit increase in lead and a 5.1-point higher TBPS in the high exposed group; children in this group were 2.7 times more likely to have a TBPS in the clinical range. CONCLUSIONS: Through its use of a standardized parent-report measure of behavior and its consideration of maternal morale in multiple linear and logistic regression procedures, this study provides further evidence of lead's detrimental effect on child behavior at levels typical of present-day exposure.

Preventing wading pool suction-drain injuries.

Wading pools with displaced drain covers and single drain outlets can lead to life-threatening injuries. This is a case of a Maryland child who sustained transanal suction which resulted in prolapse and avulsion of the small intestine from its blood supply. Because the injury would likely have been prevented if at least one of three safety precautions had been followed, standards for pool operation and pool design are reviewed.

An outbreak of phototoxic dermatitis due to limes.

During the week beginning July 29, 1984, 12 children in a day camp in a suburb of Baltimore, Maryland, were noted to have skin eruptions consistent with phototoxic dermatitis. These eruptions were confined to the hands, wrists, and forearms, and appeared as discrete and confluent polymorphous patches and linear streaks. These eruptions were also macular, hyperpigmented, and nonpruritic. Clinical examination revealed that 97 (16%) of 622 children, seven (7%) of 104 counselors, and no adult staff members had a similar rash. Onsets of the rash ranged from July 19-August 11, with peak occurrence on July 25-27. All camp members were white. Sex did not vary significantly between those affected and not affected. The mean age (5.3 years) of affected children was significantly different from the mean age (6.9 years) of unaffected children (p less than 0.001). Attack rates for the eight camp units were highest in two units (57% and 74%, respectively) and ranged between 0-6% for the other six units. Activities involving work with hands by various camp units were investigated. Only exposure to making pomander balls (sachets) in arts and crafts class (when other activities were controlled for) was significantly associated with illness (p less than 0.03). In making pomander balls, children punctured the skin of limes (the principal component) with scissors, releasing oils known to contain photoreactive furocoumarin (psoralen) compounds. These compounds evidently coated the children's skin and, upon exposure to the sun, caused a phototoxic dermatitis. An environmental and botanical survey of the camp did not reveal other phototoxic agents with which campers may have had contact. This is one of the largest reported outbreaks of phototoxic dermatitis and the first in which a citrus fruit was implicated on a large scale.

Occupational exposure to electromagnetic fields and the occurrence of brain tumors. An analysis of possible associations.

To explore the association between occupation and the occurrence of brain tumor, an epidemiologic study was conducted using data from the death certificates of 951 adult white male Maryland residents who died of brain tumor during the period 1969 through 1982. Compared with the controls, men employed in electricity-related occupations, such as electrician, electric or electronic engineer, and utility company serviceman, were found to experience a significantly higher proportion of primary brain tumors. An increase in the odds ratio for brain tumor was found to be positively related to electromagnetic (EM) field exposure levels. Furthermore, the mean age at death was found to be significantly younger among cases in the presumed high EM-exposure group. These findings suggest that EM exposure may be associated with the pathogenesis of brain tumors, particularly in the promoting stage.

Soil lead abatement and children's blood lead levels in an urban setting.

OBJECTIVES: The effect of abating soil lead was assessed among Baltimore children. The hypothesis was that a reduction of 1000 parts per million would reduce children's blood lead levels by 0.14 to 0.29 mumol/L (3-6 micrograms/dL). METHODS: In 2 neighborhoods (study and control), 187 children completed the protocol. In the study area, contaminated soil was replaced with clean soil. RESULTS: Soil lead abatement in this study did not lower children's blood lead. CONCLUSIONS: Although it did not show an effect in this study, soil lead abatement may be useful in certain areas.

Comparative studies of glutathione reductase and lipoamide dehydrogenase.

1. Glutathione reductase and lipoamide dehydrogenase are structurally and mechanistically related flavoenzymes catalyzing various one and two electron transfer reactions between NAD(P)H and substrates with different structures. 2. The two enzymes differ in their coenzyme and functional specificities. Lipoamide dehydrogenase shows higher coenzyme preference while glutathione reductase displays greater functional specificity. 3. Binding preference of the two flavoenzymes for nicotinamide coenzymes is demonstrated by 31P-NMR spectroscopy. 4. The presence of arginines in glutathione reductase which is inactivated by phenyl glyoxal, is likely to be responsible for the NADPH-activity of glutathione reductase. 5. The substrate binding sites of the two enzymes are similar, though their functional details differ. 6. The active-site histidine of glutathione reductase functions primarily as the proton donor during catalysis. While the active-site histidine of lipoamide dehydrogenase stabilizes the thiolate anion intermediate and relays a proton in the catalytic process.