Understanding the public health impacts of farm vehicle public road crashes in North Carolina.

Discussions with groups of North Carolina farmers identified farm vehicle public road safety as their primary occupational health and safety concern. Findings of a mail survey of North Carolina growers participating in a North Carolina Department of Labor migrant housing inspection program indicated that over 97% of them felt less safe on North Carolina public roads now (1999) than five years prior (1995), and over 79% currently (1999) felt unsafe transporting farm vehicles on North Carolina public roads. Using both primary and secondary data, we explore the context of farm vehicle public road crashes, identify contributing individual and environmental risk factors, and estimate the public health cost. Recommendations and suggestions for future farm vehicle public road safety research and interventions are proposed.

The downside of adolescent employment: hazards and injuries among working teens in North Carolina.

Occupational injuries are major adverse outcomes of teen employment in the United States. Using data from a survey of teens employed in three different retail trade settings (food service, grocery, and other retail) in the state of North Carolina, we examine how experience, gender, work setting, and the pace of work are associated with hazard exposures and injury experiences. Multivariate analyses show that, after controlling for individual and job-level variables, perceived work-pace pressure and hazard exposure are positively associated with variation in the types of injury experiences. We emphasize the need to include characteristics of the workplace and the labor process when assessing the adverse consequences of work on adolescent well-being.

Improving safety for teens working in the retail trade sector: opportunities and obstacles.

BACKGROUND: Using both quantitative and qualitative data, this study examined teen workers' perceptions about their work environments and the ways in which teens believe workplaces can be made safer. METHODS: We conducted telephone interviews (n = 117) and six focus groups (n = 49) with two separate samples of North Carolina teens who worked in the retail trade sector. RESULTS: Survey findings indicate one-fifth of teens used equipment they thought dangerous; nearly 40% always or often felt rushed at work; and about half received training on how to avoid injury. Teens in the focus groups expressed concerns about workplace physical hazards, the threat of assault, being rushed, and having little power in the work environment. They also indicated that their workplace safety training was ineffective and that child labor laws were unnecessary. CONCLUSIONS: In order to be effective, interventions targeted at working teens need to address the organization of work and adolescent-manager interaction patterns.

Teens at work: a statewide study of jobs, hazards, and injuries.

PURPOSE: Occupational injury is an ongoing and serious threat to American youth. However, little is known about the environments in which youth work or the hazards to which they are exposed. The purpose of this study was to document the patterns of work, exposures to hazardous equipment and situations, and work-related injury experiences of adolescents. METHODS: We identified a statewide targeted sample of North Carolina households with teens age 14-17 years and interviewed those who had ever worked for pay or worked on a farm. RESULTS: Five hundred sixty-two teens from 700 eligible households reported that they had worked non-farm jobs for pay. One-third were paid for work before age 14 years; two-thirds had held more than one paid job. Place of employment was most often someone's home, a retail store, or a restaurant. Common jobs were lawn care worker, cashier, and dishwasher. Common hazards to which teens were exposed included ladders or scaffolding; forklifts, tractors or riding mowers; and working around loud noises. Over half were injured at least once while working a paid job, most often from being cut or burned. CONCLUSIONS: Work among youth is common. Teens hold a variety of jobs, mostly in the retail trade and the service sector, exposing them to hazardous equipment and situations. Injuries at work are frequent and some are serious. This study supports the need to include an occupational history and work-related safety counseling in clinical encounters with adolescents.

Farm work is dangerous for teens: agricultural hazards and injuries among North Carolina teens.

Children who work in agriculture suffer more than 23,000 injuries and 300 fatalities on American farms every year. Using survey data collected from a random sample of working teens (ages 14 to 17) in North Carolina, the authors analyze the farm-based hazard exposure and injury experiences of teens who work on farms. The group of farmworking teens (N = 141) is 72 percent male, has a mean age of 16.6 years, and is, on average, in the 10th grade. The data show that teens working on farms in North Carolina are exposed to significant safety hazards throughout their farmworking careers. A majority of the respondents in this group of farmworkers reported exposure to tractors, large animals, all-terrain vehicles, farm trucks, and rotary mowers, and more than one-third reported exposure to pesticides and tobacco harvesters. Common reported injuries include insect stings, cuts, burns, and falls. The researchers find that gender, age, and farmwork experiences are related to variations in types of hazards to which teens are exposed and in the types of injuries they suffer. These variables also are related to the overall complexity of the teens' farmwork experiences and the burden of injury endured by teens.

Work patterns and occupational hazard exposures of North Carolina adolescents in 4-H clubs.

OBJECTIVES: This study documents sex differences in work patterns, injuries, and hazard exposures among adolescents in homes, farms, and other work sites. METHODS: 14 to 17 year old 4-H club members were asked to complete self administered questionnaires regarding their lifetime experience of work, hazard exposure, and injuries. RESULTS: Of 323 respondents, more than two thirds had ever worked paid jobs. Fifty seven per cent were injured during non-farm work and hazards were part of the non-farm work environment for 54% of the respondents. Males were more likely to work in hazardous conditions, including operating heavy equipment on farms or construction sites. Almost three quarters of the teens who worked on farms reported being injured there and 100% were exposed to at least one farm hazard. CONCLUSIONS: Adolescents perform jobs at homes, farms, or other work sites where they are exposed to numerous safety hazards. Prevention efforts should target specific hazards youths are exposed to rather than the general work site.

Purification and identification of dTDP-oleandrose, the precursor of the oleandrose units of the avermectins.

The nucleotide sugar precursor of the oleandrose units of the avermectins has been purified from a mutant of Streptomyces avermitilis, which does not synthesize any avermectins but which converts avermectin aglycones to their respective disaccharides. This precursor has been identified as dTDP-oleandrose. The purification was achieved by anion exchange and reverse phase high performance liquid chromatography. The purified nucleotide sugar had an absorption spectra characteristic of thymidine, released dTMP when treated with phosphodiesterase, and possessed an NMR spectrum in which three resonances characteristic of oleandrose were seen in addition to the thymidine signals. The enzyme, avermectin aglycone dTDP-oleandrose glycosyltransferase, which catalyzes the stepwise addition of oleandrose to the avermectin aglycones, has been demonstrated in cell-free extracts and (NH4)2SO4 fractions of cell-free extracts of S. avermitilis. The enzyme is specific for dTDP-oleandrose as the glycosyl donor but utilizes all avermectin aglycones as glycosyl acceptors. The stoichiometry between dTDP-oleandrose consumed in the reaction and oleandrose units transferred to the avermectin mono- and disaccharide was found to be 1:1.

The farm crisis: an analysis of social psychological distress among North Carolina farm operators.

Using data from a statewide survey of North Carolina farm operators collected during a period of economic and ecological crisis, the relationships between perceived social psychological distress, social support, and demographic, farm structure, and socioeconomic characteristics were analyzed. Younger operators showed higher distress levels, and age and social support interact so that social support lowered distress levels more for younger than for older operators. Results also showed that total family income has a curvilinear relationship with perceived distress: low and high income farm operators manifest higher levels of distress than middle income operators. By identifying the farm operators that show the highest levels of distress, the results have implications for policy intervention and farm crisis support programs.

Methylation of demethylavermectins.

Demethylavermectins, which lack methyl groups on the oleandrose moiety, were fed to wild-type "Streptomyces avermitilis," which produces the normal avermectin components, and the bioconversion products were identified. The oleandrose units of the demethylavermectins were not methylated by the wild-type strain, but the C-5 of the macrolide ring was methylated. This demonstrates that methylation of the oleandrose units is not a terminal step in avermectin biosynthesis and that it occurs before attachment of the sugars to the macrolide ring. Avermectin biosynthesis thus differs from that of tylosin and erythromycin, in which methylation of the hexose moieties is a terminal reaction.

"Streptomyces avermitilis" mutants defective in methylation of avermectins.

"Streptomyces avermitilis" mutants defective in the methylation of the avermectins have been isolated and characterized. Four mutant strains, CR-1, CR-2, CR-3, and CR-4, were unable to methylate the oxygen at C5 of the macrolide moiety and produced essentially only the avermectin B components. These four strains lack avermectin B2 O-methyltransferase (B2OMT) activity. Two mutant strains were unable to methylate the oleandrose moiety at the oxygens at C3' and C3'' and produced essentially only demethylavermectin components. One of these mutants, strain CR-5 (derived from wild-type "S. avermitilis"), produced demethylavermectin A and B components and possessed normal B2OMT levels. The other mutant, strain CR-6 (derived from strain CR-1, which lacks B2OMT activity), produced only demethylavermectin B components. Reaction of 3"-O-demethylavermectin B2a and S-adenosylmethionine with either cell extracts or purified B2OMT resulted in the methylation of the oxygen at C5 of the macrolide moiety and yielded only 3''-O-demethylavermectin A2a as the product. These experiments indicate that different enzymes are required for methylation of the macrolide (the oxygen at C5) and the oleandrose (oxygen at C3) and that methylation of the oleandrose occurs before attachment to the macrolide ring.

Biosynthesis of the avermectins by Streptomyces avermitilis. Incorporation of labeled precursors.

The biosynthesis of the avermectins, a group of 16 membered macrolides with potent anthelmintic and insecticidal activity produced by Streptomyces avermitilis, was studied by supplying cultures with 14C and 13C precursors. [1-14C] and [2-14C]acetate and propionate were poor precursors of the avermectins and were instead rapidly oxidized to 14CO2. The S-methyl of methionine in contrast was incorporated extensively and equally into the three methoxyl groups of the avermectins. The carbon backbone of methionine was not a precursor of the avermectins. Feeding of [1-13C]glucose yielded avermectins labeled specifically in the C1' and C1" of the oleandrose moiety and in the aglycone moiety in carbons known to be derived from the methyl of acetate. Feeding [U-13C]glucose showed that the entire avermectin molecule is derived from glucose carbons.

Avermectin B2 O-methyltransferase activity in "Streptomyces avermitilis" mutants that produce increased amounts of the avermectins.

The level of activity of avermectin B O-methyltransferase, the enzyme which catalyzes the conversion of avermectin B components to avermectin A components, was analyzed in a series of "Streptomyces avermitilis" mutants selected for increased production of the avermectins. In all of the mutants, increased avermectin production was accompanied by increased avermectin B O-methyltransferase activity. Both the average specific activity and the maximum observed specific activity of avermectin B O-methyltransferase increased in direct proportion to avermectin production. The level of avermectin B O-methyltransferase alone did not determine the extent of conversion of avermectin B components to avermectin A components, since a constant ratio of B components to A components was maintained throughout the fermentation even though avermectin B O-methyltransferase specific activity varied three- to fivefold. These results indicate that avermectin B O-methyltransferase is not rate limiting. The correlation between avermectin B O-methyltransferase specific activity and avermectin production is compatible with the hypothesis that genes coding for successive steps in the same secondary metabolite biosynthetic pathway are coordinately regulated.

Demethylavermectins. Biosynthesis, isolation and characterization.

Streptomyces avermitilis normally produces eight avermectins. Avermectin A components contain three methoxyl groups; two on the oleandrose disaccharide and one on the aglycone moiety at C5. Avermectin B components contain methoxyl groups only on the oleandrose disaccharide. Sinefungin inhibits methylation at all three sites. Addition of sinefungin to S. avermitilis Agly-1, a mutant which produces virtually only avermectin aglycone A components, alters the fermentation and causes an accumulation of avermectin aglycone B components. Addition of sinefungin to S. avermitilis 08, a high producing strain, results in accumulation of 8 new avermectins which lack methoxyl groups on the oleandrose moieties as well as the aglycone. These new avermectins were isolated and shown to possess anthelmintic and insecticidal activity.

Dose-dependent pharmacokinetics and efficacy of MK-401 against old, and young-mature infections of Fasciola hepatica in the rat.

The dose-dependent pharmacokinetics and the efficacy of MK-401 (4-amino-6-trichloroethenyl-1,3-benzenedisulfonamide) against old and young-mature infections of Fasciola hepatica were studied in experimentally infected rats. Fractionation of the host's blood after administration of 14C-MK-401 (0.77-15.8 mg/kg) showed that MK-401 was bound predominately to erythrocytes at doses below 4 mg/kg and at higher doses was distributed equally between the red cells and the plasma. Maximum amounts of MK-401 in the blood occurred 2 to 4 hr postadministration and were a hyperbolic function of dose, increasing almost linearly with dose up to 6 mg/kg and then beginning to saturate. Drug uptake by F. hepatica occurred at all doses and increased in direct proportion to the blood level. A single oral dose of MK-401 at 5 mg/kg was found to be highly effective (89%) against older infections (39-44 wk) but was virtually ineffective (1.5%) against younger flukes (9-16 wk). After administration of 14C-MK-401 at 5 mg/kg, drug concentrations in the blood and flukes of rats harboring older infections were significantly higher than those in the blood and flukes of rats with younger infections. Virtually identical differences in the blood level of MK-401 were observed in young and in old, noninfected rats after administration of 14C-MK-401 at 5 mg/kg. The increased efficacy of MK-401 against older infections of F. hepatica in the rat may be related to the age of the host rather than the parasite.

Purification, characterization and inhibition by MK-401 of Fasciola hepatica phosphoglyceromutase.

Phosphoglyceromutase (EC 2.7.5.3) of Fasciola hepatica was purified 1390-fold to homogeneity. The enzyme had a molecular weight of 120 000 and was a tetramer composed of identical 30 000 molecular weight subunits. The enzyme was 2,3-dephosphoglyceric acid dependent, possessed reactive sulfhydryl groups and was inhibited irreversibly by iodoacetamide, and N-ethylmaleimide and reversibly by p-chloromercuribenzoate and 5,5'-dithiobis(2-nitrobenzoic acid). Initial velocity studies suggest that reaction occurred via a sequential mechanism and that MK-401 was a competitive inhibitor versus both 3-phosphoglyceric acid and 2,3-diphosphoglyceric acid.

Mechanism of action of MK-401 against Fasciola hepatica: inhibition of phosphoglycerate kinase.

The effect of MK-401 (4-amino-6-trichloroethenyl 1,3-benzenedisulfonamide) on Fasciola hepatica phosphoglycerate kinase (EC 2.7.2.3) was investigated. MK-401 was a competitive inhibitor of both 3-phosphoglycerate and ATP and had a Ki of 0.29 mM. ATP, 1,3-diphosphoglycerate and MK-401 protected the Fasciola enzyme from inhibition by N-ethylmaleimide. Analogues of MK-401 with different substituents at the 6 position (R = Cl, CF3, C2 F3, C3 F7) were competitive inhibitors of both 3-phosphoglycerate and ATP and a good correlation between the Ki and in vivo activity of these analogues was observed.

Purification and characterization of phosphoglycerate kinase from Fasciola hepatica.

Phosphoglycerate kinase (EC 2.7.2.3) of Fasciola hepatica was purified 375-fold to homogeneity. The enzyme was monomeric, and had a molecular weight of 47 900 and a sedimentation coefficient of 3.0-3.5 S. The enzyme was composed of 397 amino acids and was relatively rich in sulfur amino acids containing 13 methionine and 2 cysteine residues per mole. The enzyme possessed a highly reactive essential sulfhydryl group and was inhibited irreversibly by iodoacetamide and N-ethylmaleimide and reversibly by p-chloromercuribenzoate and 5,5'-dithio-bis(2-nitrobenzoic acid). Initial velocity studies suggested that reaction occurred via a sequential mechanism. The Km values for 3-phosphoglycerate and ATP were 1.26 and 0.90 mM, respectively. ADP was a noncompetitive inhibitor with respect to both ATP and 3-phosphoglycerate.

Factors influencing rumen fermentation: effect of hydrogen on formation of propionate.

The effect of hydrogen on fermentation of lactate, pyruvate, fumarate, and succinate by resting rumen microorganisms has been investigated. Under an atmosphere of nitrogen, lactate was fermented to yield acetate as the major product (85 to 100 mole %) and propionate (0 to 17 mole %) and butyrate (0 to 3%) as secondary products. Under hydrogen, there was increased formation of both propionate and total volatile fatty acids. The amount of propionate increased 4 to 8 times and total volatile fatty acids 2.5 to 3.2 times. Propionate formation was proportional to the hydrogen concentration and reached a maximum at a partial pressure of hydrogen of .2 N/m2. With [2-carbon-14] lactate, propionate was formed via the dicarboxylic acid pathway under both nitrogen or hydrogen. Hydrogen did not affect significantly the fermentation of pyruvate or succinate. With fumarate under hydrogen, propionate and total volatile fatty acids increased 6.8 and 2 times while acetate was unchanged. The mechanism by which hydrogen exerts these effects is discussed in relation to the role of methanogenesis in the rumen.