Semaphorin 3A elicits stage-dependent collapse, turning, and branching in Xenopus retinal growth cones.

The semaphorin receptor, neuropilin-1 (NP-1), was first identified in Xenopus as the A5 antigen and is expressed abundantly in developing retinal ganglion cells (RGCs). Here we show that growth cones acquire responsiveness to semaphorin 3A (Sema 3A) with age and that the onset of responsiveness correlates with the appearance of NP-1 immunoreactivity. Growth cones from "old" (stage 35/36) retinal explants collapse rapidly (5-10 min) in response to Sema 3A and turn away from a gradient of Sema 3A, whereas "young" growth cones (stage 24) are insensitive to Sema 3A. Moreover, transfection of full-length NP-1 into young neurons confers premature Sema 3A sensitivity. When young neurons are aged in culture they develop Sema 3A sensitivity in parallel with those in vivo, suggesting that an intrinsic mechanism of NP-1 regulation mediates this age-dependent change. Sema 3A-induced collapse is transient, and after recovery approximately 30% of growth cones extend new branches within 1 hr, implicating Sema 3A as a branching factor. Pharmacological inhibitors were used to investigate whether these three Sema 3A-induced behaviors (collapse, turning, and branching) use distinct second messenger signaling pathways. All three behaviors were found to be mediated via cGMP. In situ hybridization shows that Sema 3A is expressed in the tectum and at the anterior boundary of the optic tract where axons bend caudally, suggesting that Sema 3A/NP-1 interactions play a role in guiding axons in the optic tract and in stimulating terminal branching in the tectum.

Chemotropic responses of retinal growth cones mediated by rapid local protein synthesis and degradation.

Growth cones contain mRNAs, translation machinery, and, as we report here, protein degradation machinery. We show that isolated retinal growth cones immediately lose their ability to turn in a chemotropic gradient of netrin-1 or Sema3A when translation is inhibited. Translation inhibition also prevents Sema3A-induced collapse, while LPA-induced collapse is not affected. Inhibition of proteasome function blocks responses to netrin-1 and LPA but does not affect Sema3A responses. We further demonstrate in isolated growth cones that netrin-1 and Sema3A activate translation initiation factors and stimulate a marked rise in protein synthesis within minutes, while netrin-1 and LPA elicit similar rises in ubiquitin-protein conjugates. These results suggest that guidance molecules steer axon growth by triggering rapid local changes in protein levels in growth cones.

Health hazards in the meatpacking industry.

Workers in the meatpacking industry face many health risks. Musculoskeletal disorders, including both acute injuries and repetitive strain injuries, are the most commonly reported problem in these workers. Other health hazards include infectious diseases, skin and respiratory disorders, and problems caused by environmental stressors such as cold, heat, noise, chemical exposures, explosions, fires, and work stress. Several studies are reviewed to show strengths and weaknesses of the purported association between work in the meatpacking industry and the development of cancer. Workplace programs designed to decrease health risks in this industry and governmental initiatives and legislation are discussed.

Cost-effectiveness of the influenza vaccine in a healthy, working-age population.

To determine if the influenza vaccine can reduce absenteeism and the cost of Influenza-Like Illness (ILI) in healthy adults in the workplace, a prospective, non-randomized, non-placebo control trial was done in six North Carolina textile plants. One hundred thirty-one vaccinated employees were compared with 131 age- and gender-matched non-vaccines from different plants. Twenty-six (20%) of the vaccinated and 64 (49%) of the unvaccinated group had ILI (P = 0.0000008). Fifteen (11%) of the vaccinated and 31 (24%) of the unvaccinated employees missed work because of ILI (P = 0.01). There were 43 lost workdays in vaccinated and 93 in unvaccinated employees (P = 0.00004). The "cost per saved lost workday" was $22.36, for a company savings of $2.58 per dollar invested in the vaccination program. We concluded that the influenza vaccine can give significant reductions in incidence, absenteeism, and cost associated with ILJ in the workplace.

Eosinophilia-myalgia syndrome: a long-term follow-up study.

In this case-series analysis, of 34 patients originally identified with eosinophilia-myalgia syndrome (EMS), 31 survivors were followed-up by yearly telephone interviews. We ascertained type, duration, and severity of symptoms and whether certain patient characteristics were associated with illness improvement. At a median of 3.6 years after onset, 3 patients (8.8%) had died. Two (5.9%) were well, 7 (20.6%) were improved, and 22 (64.7%) reported either no change or worsening overall condition compared to 1 year prior. Musculoskeletal and neurologic symptoms predominated. The prevalence of several symptoms, including muscle cramps, joint pain, and cognitive symptoms, increased over the course of study. Age, sex, peak eosinophil count, early prednisone use, and usual dose or duration of L-tryptophan use were not associated with significant improvement. We conclude that for the majority of patients, EMS is a chronic illness having a major impact on life-style 3.6 years after onset. The chronic, often worsening pattern of illness suggests an ongoing pathogenetic mechanism.

Clinical and epidemiological features of neurotoxic shellfish poisoning in North Carolina.

BACKGROUND: In October 1987, a red tide due to P. brevis affected the North Carolina coast for the first time. The purpose of our study was to describe the clinical and epidemiological features of neurotoxic shellfish poisoning (NSP), an illness caused by eating shellfish contaminated with the neurotoxins of P. brevis. METHODS: Active surveillance was established for cases of NSP. A descriptive study of the NSP cases was then completed. RESULTS: Forty-eight persons, who had eaten oysters at 20 meals, met the case definition. A variety of gastrointestinal tract and neurological symptoms were reported. The illnesses were generally mild and of short duration, and there were no deaths. Forty-one (85 percent) affected persons lived in five communities located within a 70-kilometer area along the coast. Cases occurred from October 27 to December 9; 27 (56 percent) of the cases occurred before the first closure of affected shellfish waters on November 2. There was a significant increase in the illness attack rate with an increase in the number of oysters eaten. CONCLUSIONS: Routine monitoring of coastal waters for P. brevis is needed to facilitate earlier recognition of red tides, closure of affected areas, and education of the public before substantial exposure to contaminated shellfish occurs.

The acoustic fields of the Wolf electrohydraulic lithotripter.

Electric sparks are used as the sources for both intra- and extracorporeal shock wave lithotripters. Upon ignition, a pressure pulse, headed by a shock, is generated that propagates as a spherically diverging wave. Simultaneously, a bubble is created that, in the case of the Wolf Model 2137.50 Electrohydraulic Lithotripter, expands to a radius of approximately 5 mm and collapses spontaneously after approximately 1 msec. Upon rebound, the bubble generates a second pressure pulse that is almost equal in amplitude and acoustic energy to the first shock wave. Measured pressures are almost entirely positive and decrease in amplitude with the reciprocal of the distance from the source. For the Wolf lithotripter at its maximum output setting, the pressure amplitude at a distance of 3 cm from the spark is typically 3 MPa.

Ciguatera fish poisoning: an outbreak associated with fish caught from North Carolina coastal waters.

Ten persons who had eaten at a seafood meal in North Carolina had gastrointestinal and neurologic symptoms suggestive of ciguatera fish poisoning. In five persons, the neurologic morbidity lasted 30 days or longer. The meal included barracuda, dolphin fish (mahimahi), and yellow-fin tuna, all of which were caught in North Carolina coastal waters. Analysis of food-specific attack rates implicated the barracuda as the probable cause of the outbreak. We believe this is the first suspected or confirmed report of ciguatera fish poisoning associated with consumption of fish harvested from mainland US coastal waters outside of Florida. Physicians treating patients with a syndrome resembling ciguatera fish poisoning should inquire about consumption of fish not only from areas where the disease is endemic but also from the southeastern US.

Killing of Drosophila larvae by the fields of an electrohydraulic lithotripter.

Drosophila larvae contain small gas bodies stabilized within their respiratory system. Because these bubbles are inhibited in their capacity to expand by the surrounding tissues, it is probable that they do not respond to acoustic fields in the manner described by classical cavitation theory that assumes a spherical bubble in an infinite fluid. However, just because of this inhibited expansion, they may serve as reasonable models for the gas bodies in mammalian tissues. Approximately one half of a population of Drosophila larvae is killed by exposure to 3 to 10 double lithotripter shocks with a positive pressure of 2-3 MPa. In contrast with the predictions of classical cavitation theory, adding a negative pressure to the exposure has little influence on the killing rate or its threshold pressure. The available evidence suggests that interaction of gas bodies in tissues with pressure fields and the resultant biological effects may be qualitatively different than predicted by classical cavitation theory and that positive rather than negative pressure may be a predictor of these effects.

Computer-aided self-instruction training with hearing-impaired impulsive students.

This study explored the utility of computer-aided, self-instruction training for enhancing reflective problem-solving among impulsive hearing-impaired adolescent students. Sixteen moderate to severely hearing-impaired students were randomly assigned to either a treatment or control condition. The self-instruction treatment condition consisted of training to solve visual problems using a modified version of the LOGO computer language (REFLECT) and videotape feedback. The control condition consisted of LOGO problem-solving without self-instruction. Instruction took place over 12 weeks. On two dependent measures of impulsive problem-solving behaviors, students in the treatment condition demonstrated significantly improved problem-solving ability.

Identification of nuclear substrates of the cyclic AMP-dependent protein kinase in Dictyostelium discoideum.

A search for nuclear substrates of the cAMP-dependent protein kinase (cAMP-d PK) of Dictyostelium discoideum led to the identification of several such proteins. Identification was based initially on increased phosphorylation of the proteins in nuclear extracts catalyzed by added cAMP-d PK. One protein of Mr 38,000 was phosphorylated also in intact nuclei and in vivo; the amount of phosphoprotein or the level of phosphorylation increased during development. Both the Mr 38,000 protein and another substrate of Mr 195,000 were found in the nuclei of prespore and prestalk cells. Phosphorylation of other potential substrates of the cAMP-d PK was either prespore or prestalk cell-specific.

Wolf spider bites.

Because of their dark color and hunting habits, wolf spiders (Lycosidae) are often confused with the much more dangerous brown recluse spider (Loxosceles reclusa). Unlike the brown recluse spider, wolf spider envenomation seldom causes cutaneous necrosis or systemic symptoms. In this report, two documented cases of wolf spider bites are described and the pertinent literature reviewed.

The frequency of a Norwalk-like pattern of illness in outbreaks of acute gastroenteritis.

Records of 642 outbreaks of acute gastroenteritis were reviewed to determine the proportion of outbreaks that were clinically and epidemiologically consistent with Norwalk-like virus infection. Using as our criteria stool cultures negative for bacterial pathogens, mean (or median) duration of illness 12-60 hours, vomiting in greater than or equal to 50 per cent of cases, and, if known, mean (or median) incubation period of 24-48 hours, we found that 23 per cent of waterborne outbreaks, 4 per cent of foodborne outbreaks, and 67 per cent, 60 per cent, and 28 per cent of outbreaks in nursing homes, in summer camps, and on cruise ships, respectively, satisfied the criteria for Norwalk-like pattern. Of 54 outbreaks that satisfied the criteria for Norwalk-like pattern, 14 were investigated for virus etiology. Ten of these (71 per cent) yielded serologic evidence of Norwalk-like virus infection. Norwalk-like viruses are probably an important cause of outbreaks of acute gastroenteritis. Investigation for Norwalk virus antibody in outbreaks that are clinically and epidemiologically consistent with Norwalk-like virus infection is likely to yield diagnostically useful results.