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Tissue regeneration requires not only the replacement of lost cells and tissues, but also the recreation of morphologies and patterns. Skin pigment pattern is a relatively simple system that can allow researchers to uncover the underlying mechanisms of pattern formation. To gain insight into how pigment patterns form, undergraduate students in the senior level course Developmental Biology designed an experiment that assayed pigment patterns in original and regenerated caudal fins of wild-type, striped, and mutant, spotted zebrafish. A majority of the WT fins regenerated with a similar striped pattern. In contrast, the pattern of spots even in the original fins of the mutants varied among individual fish. Similarly, the majority of the spots in the mutants did not regenerate with the same morphology, size, or spacing as the original fins. This was true even when only a small amount of fin was removed, leaving most of the fin to potentially reseed the pattern in the regenerating tissue. This suggests that the mechanism that creates the wild-type, striped pattern persists to recreate the pattern during regeneration. The mechanism that creates the spots in the mutants, however, must include an unknown element that introduces variability.

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This study describes a comparison of worker exposure to total and inhalable dust, inorganic As, and borates using two types of particulate sampling assemblies as part of a comprehensive industrial hygiene evaluation in a borate mining and processing facility. Employees were segmented into similar exposure groups (SEG) based on work location within the facility, job classification, and type of chemical agent. Approximately 10% of the employees from each SEG wore two personal sampling devices simultaneously for the purpose of collecting total and inhalable particulate fractions using a closed face, 37-mm mixed cellulose ester matched-weight filters (MMW), and Institute of Occupational Medicine (IOM) sampling assembly. Sample results indicated that the IOM concentrations were consistently higher than the corresponding MMW concentrations for all three agents. An analysis was performed to investigate a relationship between MMW and IOM. The data revealed correlation coefficient values of 0.72, 0.82, and 0.84 for total dust (n = 197), inorganic As (n = 137), and borates (n = 194), respectively. These positive correlation coefficients indicate that the IOM and MMW measurements are consistent with each other, and can be used for predicting exposure levels. The total dust and borate large mean ratios should be considered in developing inhalable fraction-based regulatory standards.

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Two generations of Sprague-Dawley rats were each exposed to vapors generated by countercurrent distillation (50 degrees C) at 0, 0.5, 2.5, and 5.0 mg/liter, for 6 hr/day, 5 days/week, for 124-126 days prior to mating. After mating, exposure was continuous except for the last day of gestation through lactation for F0 dams, and the last day of gestation through Day 6 of lactation for F1 dams. F1 pups were not exposed during lactation; F2 pups were exposed via nursing only. Body weights were recorded weekly before mating; organ and body weights were recorded on Days 1, 13, and 30 of gestation and on Days 1, 4, and 21 of lactation. Histopathology, reproductive performance, and certain sperm parameters were evaluated. The test material significantly (p less than 0.05) depressed body weights of F0 males and brain and lung weights of F1 weanling males at 5.0 mg/liter. Testicular weights of F1 weanling males were depressed at the 0.5 and 5.0 mg/liter concentrations. While a dose-related decrease in sperm count and sperm ATP levels and an increase in ATP/sperm ratios were observed in F0 males at 2.5 and 5.0 mg/liter, there was no adverse effect on overall reproductive performance.

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Isolated hypoglossal (XIIth cranial nerve) neurapraxia is a rare clinical presentation. We present a case of an isolated hypoglossal neurapraxia following exposure to +7.2 Gz in a human centrifuge. Although a variety of cervical spine injuries have been reported as a result of G exposure in an aircraft, no cranial nerve injuries have been reported. A review of the literature of isolated hypoglossal neurapraxia is presented with discussion of the probable cause of this nerve injury.

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Vascular headaches may occur in up to 20% of the population aged 17-40. One subgroup, exertional headaches, has many specific and nonspecific clinical presentations. Knowing the background events preceding the headache and the exact circumstances of the headache can help make a specific diagnosis. Three cases are presented to illustrate the diversity of triggers and their effect on aeromedical decision-making. The headaches are presented within the recently revised nomenclature for head and facial pain by the Headache Classification Committee of the International Headache Society.

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In anticipation of the commercialization of its shale oil retorting and upgrading process, Unocal Corp. conducted a testing program aimed at better defining potential health impacts of a shale industry. Acute toxicity studies using rats and rabbits compared the effects of naphtha, Jet-A, JP-4, diesel and "residual" distillate fractions of both petroleum derived crude oils and hydrotreated shale oil. No differences in the acute oral (greater than 5 g/kg LD50) and dermal (greater than 2 g/kg LD50) toxicities were noted between the shale and petroleum derived distillates and none of the samples were more than mildly irritating to the eyes. Shale and petroleum products caused similar degrees of mild to moderate skin irritation. None of the materials produced sensitization reactions. The LC50 after acute inhalation exposure to Jet-A, shale naphtha, (greater than 5 mg/L) and JP-4 distillate fractions of petroleum and shale oils was greater than 5 mg/L. The LC50 of petroleum naphtha (greater than 4.8 mg/L) and raw shale oil (greater than 3.95 mg/L) also indicated low toxicity. Results demonstrate that shale oil products are of low acute toxicity, mild to moderately irritating and similar to their petroleum counterparts. The results further demonstrate that hydrotreatment reduces the irritancy of raw shale oil.

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From 1958 to 1986, 27 crewmembers with suspected sleep disorders were referred to the USAF School of Aerospace Medicine. The presenting complaint in most cases was excessive daytime sleepiness (EDS). Prior to 1984, evaluations included neurologic and psychiatric testing, screening laboratory studies, and awake and asleep electroencephalography. Polysomnography and sleep latency studies were included after 1984. In the majority of cases, the etiology of the complaint could not be determined. The prevalence of EDS is estimated to be between 0.3% and 4.0% of the adult population. Major causes cited in the world literature include the sleep apnea syndromes, narcolepsy, parasomnias interrupting sleep, hypersomnia secondary to systemic or affective disorders, and essential hypersomnia. Current sleep lab techniques and human leukocyte antigen (HLA) typing are reported to make the diagnosis in up to 90% of sleep disorders. Evaluation of EDS should begin with a history emphasizing sleep habits, work schedules, daytime naps, and presence of vegetative signs. A sleep diary will allow a more accurate estimate of the quantity of nocturnal sleep. This diary may reveal poor sleep hygiene or insomnia. Polysomnography and/or multiple sleep latency determination can then be used to diagnose sleep apnea, parasomnias, and narcolepsy.

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Ten test materials derived from petroleum or hydrotreated shale oils were applied 3 times/week for up to 105 weeks to the shaved skin of 25 male and 25 female C3H/HeN mice per group. Mineral oil and benzo(a) pyrene (0.15%) were control materials. Clinical observations were recorded during the study. At death, histopathologic examination was conducted on skin, internal organs and any gross lesions. Exposures to some materials were ended midway in the study due to severe irritation. Chronic toxicity of all materials was limited to inflammatory and degenerative skin changes. Significant increases over control incidence of skin tumors (squamous cell carcinoma and fibrosarcoma) occurred with both petroleum and shale-derived naphtha (21%, 50%), Jet A (26%, 28%), JP-4 (26%, 50%), and crude oils (84%, 54%). Severely hydrotreated shale oil and petroleum and shale-derived diesel distillates were not considered tumorigenic. Results indicate that toxicity of comparable petroleum and shale-derived fractions was qualitatively similar and confirm earlier findings that hydrotreating reduces or eliminates carcinogenicity of raw shale oil.

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Three patients who presented initially with dystonia and subsequently developed typical idiopathic parkinsonism were evaluated. One patient presented with a writer's cramp, one with axial dystonia, and one with Meige syndrome. All three displayed amelioration of their dystonia with progression of their parkinsonism over a period of 2 to 15 years. Treatment with levodopa gave some relief of the parkinsonism symptoms in two patients but exacerbated or reactivated the dystonia. It is suggested that both the dystonia and the parkinsonism represent the changing clinical expression of the same disorder at different times in its evolution.

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Mercury contamination in three rarely studied areas of the hospital is discussed.

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