Environmental exposures to Florida red tides: Effects on emergency room respiratory diagnoses admissions

Human exposure to Florida red tides formed by Karenia brevis, occurs from eating contaminated shellfish and inhaling aerosolized brevetoxins. Recent studies have documented acute symptom changes and pulmonary function responses after inhalation of the toxic aerosols, particularly among asthmatics. These findings suggest that there are increases in medical care facility visits for respiratory complaints and for exacerbations of underlying respiratory diseases associated with the occurrence of Florida red tides.This study examined whether the presence of a Florida red tide affected the rates of admission with a respiratory diagnosis to a hospital emergency room in Sarasota, FL. The rate of respiratory diagnoses admissions were compared for a 3-month time period when there was an onshore red tide in 2001 (red tide period) and during the same 3-month period in 2002 when no red tide bloom occurred (non-red tide period). There was no significant increase in the total number of respiratory admissions between the two time periods. However, there was a 19% increase in the rate of pneumonia cases diagnosed during the red tide period compared with the non-red tide period. We categorized home residence zip codes as coastal (within 1.6 km from the shore) or inland (>1.6 km from shore). Compared with the non-red tide period, the coastal residents had a significantly higher (54%) rate of respiratory diagnoses admissions than during the red tide period. We then divided the diagnoses into subcategories (i.e. pneumonia, bronchitis, asthma, and upper airway disease). When compared with the non-red tide period, the coastal zip codes had increases in the rates of admission of each of the subcategories during the red tide period (i.e. 31, 56, 44, and 64%, respectively). This increase was not observed seen in the inland zip codes.These results suggest that the healthcare community has a significant burden from patients, particularly those who live along the coast, needing emergency medical care for both acute and potentially chronic respiratory illnesses during red tide blooms.

Epidemiology of recreational exposure to freshwater cyanobacteria--an international prospective cohort study

BACKGROUND

Case studies and anecdotal reports have documented a range of acute illnesses associated with exposure to cyanobacteria and their toxins in recreational waters. The epidemiological data to date are limited; we sought to improve on the design of some previously conducted studies in order to facilitate revision and refinement of guidelines for exposure to cyanobacteria in recreational waters.

METHODS

A prospective cohort study was conducted to investigate the incidence of acute symptoms in individuals exposed, through recreational activities, to low (cell surface area < 2.4 mm2/mL), medium (2.4-12.0 mm2/mL) and high (> 12.0 mm2/mL) levels of cyanobacteria in lakes and rivers in southeast Queensland, the central coast area of New South Wales, and northeast and central Florida. Multivariable logistic regression analyses were employed; models adjusted for region, age, smoking, prior history of asthma, hay fever or skin disease (eczema or dermatitis) and clustering by household.

RESULTS

Of individuals approached, 3,595 met the eligibility criteria, 3,193 (89%) agreed to participate and 1,331 (37%) completed both the questionnaire and follow-up interview. Respiratory symptoms were 2.1 (95%CI: 1.1-4.0) times more likely to be reported by subjects exposed to high levels of cyanobacteria than by those exposed to low levels. Similarly, when grouping all reported symptoms, individuals exposed to high levels of cyanobacteria were 1.7 (95%CI: 1.0-2.8) times more likely to report symptoms than their low-level cyanobacteria-exposed counterparts.

CONCLUSION

A significant increase in reporting of minor self-limiting symptoms, particularly respiratory symptoms, was associated with exposure to higher levels of cyanobacteria of mixed genera. We suggest that exposure to cyanobacteria based on total cell surface area above 12 mm2/mL could result in increased incidence of symptoms. The potential for severe, life-threatening cyanobacteria-related illness is likely to be greater in recreational waters that have significant levels of cyanobacterial toxins, so future epidemiological investigations should be directed towards recreational exposure to cyanotoxins.

A review of nitrates in drinking water: maternal exposure and adverse reproductive and developmental outcomes

In this review we present an update on maternal exposure to nitrates in drinking water in relation to possible adverse reproductive and developmental effects, and also discuss nitrates in drinking water in the United States. The current standard for nitrates in drinking water is based on retrospective studies and approximates a level that protects infants from methemoglobinemia, but no safety factor is built into the standard. The current standard applies only to public water systems. Drinking water source was related to nitrate exposure (i.e., private systems water was more likely than community system water to have nitrate levels above the maximum contaminant limit). Animal studies have found adverse reproductive effects resulting from higher doses of nitrate or nitrite. The epidemiologic evidence of a direct exposure-response relationship between drinking water nitrate level and adverse reproductive effect is still not clear. However, some reports have suggested an association between exposure to nitrates in drinking water and spontaneous abortions, intrauterine growth restriction, and various birth defects. Uncertainties in epidemiologic studies include the lack of individual exposure assessment that would rule out confounding of the exposure with some other cause. Nitrates may be just one of the contaminants in drinking water contributing to adverse outcomes. We conclude that the current literature does not provide sufficient evidence of a causal relationship between exposure to nitrates in drinking water and adverse reproductive effects. Future studies incorporating individual exposure assessment about users of private wells--the population most at risk--should be considered.

Cochlear function in mice following inhalation of brevetoxin-3

Brevetoxin-3 was shown previously to adversely affect central auditory function in goldfish. The present study evaluated the effects of exposure to this agent on cochlear function in mice using the 2f(1)-f(2) distortion-product otoacoustic emission (DPOAE). Towards this end, inbred CBA/CaJ mice were exposed to a relatively high concentration of brevetoxin-3 (approximately=400 microg/m(3)) by nose-only inhalation for a 2-h period. Further, a subset of these mice received a second exposure a day later that lasted for an additional 4 h. Mice exposed only once for 2 h did not exhibit any notable cochlear effects. Similarly, mice exposed two times, for a cumulative dose of 6 h, exhibited essentially no change in DPOAE levels.

Overview of aerosolized Florida red tide toxins: exposures and effects

Florida red tide is caused by Karenia brevis, a dinoflagellate that periodically blooms, releasing its potent neurotoxin, brevetoxin, into the surrounding waters and air along the coast of the Gulf of Mexico. Exposure to Florida red tide toxins has been associated with adverse human health effects and massive fish and marine mammal deaths. The articles in this mini-monograph describe the ongoing interdisciplinary and interagency research program that characterizes the exposures and health effects of aerosolized Florida red tide toxins (brevetoxins). The interdisciplinary research program uses animal models and laboratory studies to develop hypotheses and apply these findings to in situ human exposures. Our ultimate goal is to develop appropriate prevention measures and medical interventions to mitigate or prevent adverse health effects from exposure to complex mixtures of aerosolized red tide toxins.

Characterization of marine aerosol for assessment of human exposure to brevetoxins

Red tides in the Gulf of Mexico are commonly formed by the fish-killing dinoflagellate Karenia brevis, which produces nine potent polyether brevetoxins (PbTxs). Brevetoxins can be transferred from water to air in wind-powered white-capped waves. Inhalation exposure to marine aerosol containing brevetoxins causes respiratory symptoms. We describe detailed characterization of aerosols during an epidemiologic study of occupational exposure to Florida red tide aerosol in terms of its concentration, toxin profile, and particle size distribution. This information is essential in understanding its source, assessing exposure to people, and estimating dose of inhaled aerosols. Environmental sampling confirmed the presence of brevetoxins in water and air during a red tide exposure period (September 2001) and lack of significant toxin levels in the water and air during an unexposed period (May 2002). Water samples collected during a red tide bloom in 2001 showed moderate-to-high concentrations of K. brevis cells and PbTxs. The daily mean PbTx concentration in water samples ranged from 8 to 28 microg/L from 7 to 11 September 2001; the daily mean PbTx concentration in air samples ranged from 1.3 to 27 ng/m(3). The daily aerosol concentration on the beach can be related to PbTx concentration in water, wind speed, and wind direction. Personal samples confirmed human exposure to red tide aerosols. The particle size distribution showed a mean aerodynamic diameter in the size range of 6-12 microm, with deposits mainly in the upper airways. The deposition pattern correlated with the observed increase of upper airway symptoms in healthy lifeguards during the exposure periods.

Occupational exposure to aerosolized brevetoxins during Florida red tide events: effects on a healthy worker population

Karenia brevis (formerly Gymnodinium breve) is a marine dinoflagellate responsible for red tides that form in the Gulf of Mexico. K. brevis produces brevetoxins, the potent toxins that cause neurotoxic shellfish poisoning. There is also limited information describing human health effects from environmental exposures to brevetoxins. Our objective was to examine the impact of inhaling aerosolized brevetoxins during red tide events on self-reported symptoms and pulmonary function. We recruited a group of 28 healthy lifeguards who are occupationally exposed to red tide toxins during their daily work-related activities. They performed spirometry tests and reported symptoms before and after their 8-hr shifts during a time when there was no red tide (unexposed period) and again when there was a red tide (exposed period). We also examined how mild exercise affected the reported symptoms and spirometry tests during unexposed and exposed periods with a subgroup of the same lifeguards. Environmental sampling (K. brevis cell concentrations in seawater and brevetoxin concentrations in seawater and air) was used to confirm unexposed/exposed status. Compared with unexposed periods, the group of lifeguards reported more upper respiratory symptoms during the exposed periods. We did not observe any impact of exposure to aerosolized brevetoxins, with or without mild exercise, on pulmonary function.

Initial evaluation of the effects of aerosolized Florida red tide toxins (brevetoxins) in persons with asthma

Florida red tides annually occur in the Gulf of Mexico, resulting from blooms of the marine dinoflagellate Karenia brevis. K. brevis produces highly potent natural polyether toxins, known as brevetoxins, that activate voltage-sensitive sodium channels. In experimental animals, brevetoxins cause significant bronchoconstriction. A study of persons who visited the beach recreationally found a significant increase in self-reported respiratory symptoms after exposure to aerosolized Florida red tides. Anecdotal reports indicate that persons with underlying respiratory diseases may be particularly susceptible to adverse health effects from these aerosolized toxins. Fifty-nine persons with physician-diagnosed asthma were evaluated for 1 hr before and after going to the beach on days with and without Florida red tide. Study participants were evaluated with a brief symptom questionnaire, nose and throat swabs, and spirometry approved by the National Institute for Occupational Safety and Health. Environmental monitoring, water and air sampling (i.e., K. brevis, brevetoxins, and particulate size distribution), and personal monitoring (for toxins) were performed. Brevetoxin concentrations were measured by liquid chromatography mass spectrometry, high-performance liquid chromatography, and a newly developed brevetoxin enzyme-linked immunosorbent assay. Participants were significantly more likely to report respiratory symptoms after Florida red tide exposure. Participants demonstrated small but statistically significant decreases in forced expiratory volume in 1 sec, forced expiratory flow between 25 and 75%, and peak expiratory flow after exposure, particularly those regularly using asthma medications. Similar evaluation during nonexposure periods did not significantly differ. This is the first study to show objectively measurable adverse health effects from exposure to aerosolized Florida red tide toxins in persons with asthma. Future studies will examine the possible chronic effects of these toxins among persons with asthma and other chronic respiratory impairment.

An Epidemiologic Approach to the Study of Aerosolized Florida Red Tides

Very little has been published in the scientific literature on the human health effects of Florida red tide, either as human clinical case reports or formal epidemiologic studies. In addition to the health effects associated with the ingestion of contaminated shellfish, there have been multiple anecdotal reports of respiratory irritation and possible immunologic effects associated with the inhalation of aerosolized Florida red tide. To investigate the human health effects from environmental exposure to red tide toxins, we have formed an interdisciplinary team of scientists. We have created a network of public and environmental health workers who periodically report local conditions as a red tide develops. In addition, we have access to environmental monitoring data as well as data from a surveillance program supported through the Florida Poison Information Network. When a red tide moves onshore where people might be exposed, the team rapidly assembles at the site to collect environmental samples and epidemiologic data. To assess the more long-term effects from environmental exposure to red tide toxins, we are conducting epidemiologic studies involving occupational and sensitive populations who live in areas that are regularly impacted by red tides. Other scientists are evaluating the acute and chronic respiratory effects of red tides and brevetoxins in both rat and sheep models as well as refinement of toxin measurement methodology. These models are being used to refine and validate the biomarkers of brevetoxins exposure as well as explore the pathophysiology of health effects from brevetoxins respiratory exposure. Bolstered by the additional research in rat and sheep models, this interdisciplinary scientific team is exploring the acute and chronic exposures and health effects of aerosolized Florida red tides in animal models and various human populations. In the future, this research can be applied to the understanding of exposure and effects of other aerosolized natural toxins such as cyanobacterial toxins.

Environmental public health surveillance: possible estuary-associated syndrome

Public health surveillance involves the collection, analysis, and dissemination of data for use in public health practice. A surveillance system includes the capacity to collect and analyze data as well as the ability to disseminate the data to public health agencies that can undertake effective prevention and control activities. An emerging issue in environmental public health surveillance involves human exposure to the toxins produced by microorganisms present in oceans and estuaries. One of these organisms is Pfiesteria piscicida Steidinger & Burkholder, a dinoflagellate found in estuaries along the Atlantic and gulf coasts of the United States. There have been reports of both human illness associated with occupational exposures to concentrated laboratory cultures of P. piscicida and massive fill kills associated with the presence of the organism in rivers and estuaries. These reports, and anecdotal reports from people who worked on rivers where the organism has been found, generated concern that environmental exposures to P. piscicida, similar organisms, or perhaps a toxin or toxins produced by the organism(s), could cause adverse human health effects. To begin to evaluate the public health burden associated with P. piscicida, investigators from the National Center for Environmental Health at Centers for Disease Control and Prevention and health agencies from states along the Atlantic coast collaborated to develop a passive surveillance system for collecting, classifying, and tracking public inquiries about the organism. Specifically, the group developed exposure and symptom criteria and developed data collection and reporting capabilities to capture the human health parameters collectively referred to as possible estuary-associated syndrome (PEAS). The surveillance system was implemented in six states (Delaware, Florida, Maryland, North Carolina, South Carolina, Virginia) beginning in June 1998. From 1 June 1998 through 30 June 2001, the six state health agencies participating in the PEAS surveillance system received 3,859 calls: 3,768 callers requested information and 91 callers reported symptoms. Five individuals have been identified as meeting PEAS criteria.

Pet dogs as sentinels for environmental contamination

The presence of environmental contaminants in air, water and food may pose significant health risks to the exposed human population. However, problems associated with assessing chronic exposure to low doses of environmental chemicals, multiple exposure routes, diseases with long latency periods, and non-specific health outcomes make it difficult to conduct the appropriate human epidemiologic studies. It may be useful to complement human epidemiology with animal studies. Animals monitored or evaluated in situ for the appropriate suite of endpoints can provide information about both exposure levels and potential adverse health effects. Animals have served as sentinel indicators for health effects associated with a number of environmental exposures, including pesticides and asbestos. Pet dogs may be particularly valuable sentinels because they share the human environment. In addition, dogs respond to many toxic insults in ways analogous to humans, they have physiologically compressed life spans, and they are free from some important lifestyle risk factors for disease. An example of how pet dogs may be used as sentinels for potential human health hazards involves a study of the genotoxic effects resulting from exposure to a mixture of chemicals from nearby Superfund sites. We conducted a cross-sectional study of exposed dogs (living in the community with the Superfund sites) and controls (living in a nearby community). The pet owners completed a questionnaire, and we collected a blood sample from each dog. The blood samples were analyzed for standard clinical parameters and assays for possible genotoxic effects (peripheral blood lymphocyte micronucleus frequency and lymphocyte subtyping). Pet dogs living near the Superfund sites had a higher micronucleus frequency than control animals, suggesting that the dogs may have been exposed to environmental contaminants from these sites.

Assessing the acute gastrointestinal effects of ingesting naturally occurring, high levels of sulfate in drinking water

Concerns regarding the health effects from sulfate in drinking water have been raised because of reports that diarrhea may be associated with ingesting water that contains high levels of sulfate. Of particular concern are groups in the general population (i.e., infants and transients) that may be at greater risk from the laxative effects of sulfate when they switch abruptly to drinking water with high sulfate concentrations. There have been a number of studies of the effects of sulfate in the drinking water of domestic animals (cattle, swine, and poultry), and most report minimal adverse effects from exposure to fairly high levels of sulfate. Anecdotal reports and case studies suggest that people suffer gastrointestinal effects when exposed to drinking water containing high levels of sulfate. However, there have been few experimental studies of the effects of sulfate on adults, and only two epidemiologic studies designed to assess the effects of high levels of sulfate on infants, and it is not yet possible to accurately determine the concentration of sulfate in drinking water that will produce adverse human health effects.

Household exposures to drinking water disinfection by-products: whole blood trihalomethane levels

Exposure to drinking water disinfection by-products (DBPs), such as trihalomethanes (THMs), has been associated with bladder and colorectal cancer in humans. Exposure to DBPs has typically been determined by examining historical water treatment records and reconstructing study participants' water consumption histories. However, other exposure routes, such as dermal absorption and inhalation, may be important components of an individual's total exposure to drinking water DBPs. In this study, we examined individuals' exposure to THMs through drinking, showering, or bathing in tap water. Thirty-one adult volunteers showered with tap water for 10 min (n = 11), bathed for 10 min in a bathtub filled with tap water (n = 10), or drank 1 l of tap water during a 10 min time period (n = 10). Participants provided three 10 ml blood samples: one sample immediately before the exposure; one sample 10 min after the exposure ended; and one sample 30 min (for shower and tub exposure) or 1 h ( for ingestion) after the exposure ended. A sample of the water (from the tap, from the bath, or from the shower) was collected for each participant. We analyzed water samples and whole blood for THMs (bromoform, bromodichloromethane, dibromochloromethane, and chloroform) using a purge-and-trap/gas chromatography/mass spectrometry method with detection limits in the parts-per-quadrillion range. The highest levels of THMs were found in the blood samples from people who took 10 min showers, whereas the lowest levels were found in the blood samples from people who drank 1 l of water in 10 min. The results from this study indicate that household activities such as bathing and showering are important routes for human exposure to THMs.

Animals as sentinels of human health hazards of environmental chemicals

A workshop titled "Using Sentinel Species Data to Address the Potential Human Health Effects of Chemicals in the Environment," sponsored by the U.S. Army Center for Environmental Health Research, the National Center for Environmental Assessment of the EPA, and the Agency for Toxic Substances and Disease Registry, was held to consider the use of sentinel and surrogate animal species data for evaluating the potential human health effects of chemicals in the environment. The workshop took a broad view of the sentinel species concept, and included mammalian and nonmammalian species, companion animals, food animals, fish, amphibians, and other wildlife. Sentinel species data included observations of wild animals in field situations as well as experimental animal data. Workshop participants identified potential applications for sentinel species data derived from monitoring programs or serendipitous observations and explored the potential use of such information in human health hazard and risk assessments and for evaluating causes or mechanisms of effect. Although it is unlikely that sentinel species data will be used as the sole determinative factor in evaluating human health concerns, such data can be useful as for additional weight of evidence in a risk assessment, for providing early warning of situations requiring further study, or for monitoring the course of remedial activities. Attention was given to the factors impeding the application of sentinel species approaches and their acceptance in the scientific and regulatory communities. Workshop participants identified a number of critical research needs and opportunities for interagency collaboration that could help advance the use of sentinel species approaches.

Animals as sentinels of human health hazards of environmental chemicals

A workshop titled "Using Sentinel Species Data to Address the Potential Human Health Effects of Chemicals in the Environment," sponsored by the U.S. Army Center for Environmental Health Research, the National Center for Environmental Assessment of the EPA, and the Agency for Toxic Substances and Disease Registry, was held to consider the use of sentinel and surrogate animal species data for evaluating the potential human health effects of chemicals in the environment. The workshop took a broad view of the sentinel species concept, and included mammalian and nonmammalian species, companion animals, food animals, fish, amphibians, and other wildlife. Sentinel species data included observations of wild animals in field situations as well as experimental animal data. Workshop participants identified potential applications for sentinel species data derived from monitoring programs or serendipitous observations and explored the potential use of such information in human health hazard and risk assessments and for evaluating causes or mechanisms of effect. Although it is unlikely that sentinel species data will be used as the sole determinative factor in evaluating human health concerns, such data can be useful as for additional weight of evidence in a risk assessment, for providing early warning of situations requiring further study, or for monitoring the course of remedial activities. Attention was given to the factors impeding the application of sentinel species approaches and their acceptance in the scientific and regulatory communities. Workshop participants identified a number of critical research needs and opportunities for interagency collaboration that could help advance the use of sentinel species approaches.

Serum follicle-stimulating hormone and luteinizing hormone levels in women aged 35-60 in the U.S. population: the Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994)

OBJECTIVE

The objective of this study was to examine age-specific population-based values for serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels in women in the U.S. population.

DESIGN

Data were collected from a nationally representative cross-sectional health examination survey that included measurements of follicle-stimulating hormone and luteinizing hormone and information from a personal interview. A total of 3388 women aged 35 to 60 years were examined during the third National Health and Nutrition Examination Survey, 1988-1994.

RESULTS

Among U.S. women aged 35-60 years, median FSH and LH levels began to increase for women in their late 40s and reached a plateau for women in their early 50s. This study supports the previously reported association between serum FSH and age (i.e., serum FSH and LH levels increase with age) and smoking (i.e., current smoking was associated with an increased level of serum FSH). At FSH levels of > or = 15 IU/L or > or = 20 IU/L. 70 and 73% of women, respectively, were postmenopausal. Our study also found an interaction between age and oophorectomy. In addition, the present data suggest that women with only one ovary may have higher FSH levels than women with both of their ovaries.

CONCLUSIONS

NHANES III provides population-based data that support previously reported associations between serum FSH level and age, smoking, and menopausal status.

Exposure to regular gasoline and ethanol oxyfuel during refueling in Alaska

Although most people are thought to receive their highest acute exposures to gasoline while refueling, relatively little is actually known about personal, nonoccupational exposures to gasoline during refueling activities. This study was designed to measure exposures associated with the use of an oxygenated fuel under cold conditions in Fairbanks, Alaska. We compared concentrations of gasoline components in the blood and in the personal breathing zone (PBZ) of people who pumped regular unleaded gasoline (referred to as regular gasoline) with concentrations in the blood of those who pumped an oxygenated fuel that was 10% ethanol (E-10). A subset of participants in a wintertime engine performance study provided blood samples before and after pumping gasoline (30 using regular gasoline and 30 using E-10). The biological and environmental samples were analyzed for selected aromatic volatile organic compounds (VOCs) found in gasoline (benzene, ethylbenzene, toluene, m-/p-xylene, and o-xylene); the biological samples were also analyzed for three chemicals not found in gasoline (1,4-dichlorobenzene, chloroform, and styrene). People in our study had significantly higher levels of gasoline components in their blood after pumping gasoline than they had before pumping gasoline. The changes in VOC levels in blood were similar whether the individuals pumped regular gasoline or the E-10 blend. The analysis of PBZ samples indicated that there were also measurable levels of gasoline components in the air during refueling. The VOC levels in PBZ air were similar for the two groups. In this study, we demonstrate that people are briefly exposed to low (ppm and sub-ppm) levels of known carcinogens and other potentially toxic compounds while pumping gasoline, regardless of the type of gasoline used.

Evidence that methanol inhalation does not induce chromosome damage in mice

Mice were exposed by inhalation to 800 or 4000 ppm methanol for 5 days, and cytogenetic effects were analyzed in blood erythrocytes, lung cells, and testicular germ cells. The results were uniformly negative; no increased frequencies of micronuclei in blood cells, of sister-chromatid exchanges, chromosome aberrations, or micronuclei in lung cells, or of synaptonemal complex damage in spermatocytes were found. From the standpoint of risk assessment, these experimental studies do not reveal any evidence of a cytogenetic hazard associated with inhalation of methanol.

Stage-specific damage to synaptonemal complexes and metaphase chromosomes induced by X rays in male mouse germ cells

Synaptonemal complexes reveal mutagen-induced effects in germ cell meiotic chromosomes. This study was aimed at characterizing relationships between damage to synaptonemal complexes and metaphase I chromosomes following radiation exposure at various stages of spermatogenesis. Male mice were irradiated with doses of 0, 2, or 4 Gy, and spermatocytes were harvested at times consistent with earlier exposures as spermatogonial stem cells, preleptotene cells (premeiotic DNA synthesis), or meiotic prophase cells. After stem-cell exposure, twice as many rearrangements were observed in synaptonemal complexes as in metaphase I chromosomes. Irradiation during premeiotic DNA synthesis resulted in dose-related increases in synaptonemal complex breakage and rearrangements (including novel forms) and in metaphase chromosomal aberrations. Following prophase exposure, various types and levels of damage to synaptonemal complexes and metaphase chromosomes were observed. Irradiation of zygotene cells led to high frequencies of chromosome multivalents in metaphase I without a correspondingly high level of damage in preceding prophase synaptonemal complexes. Thus irradiation of premeiotic and meiotic cells results in variable relationships between damage to synaptonemal complexes and metaphase chromosomes. Interpretations of these relationships are based upon what is known about both radiation clastogenesis and the structural/temporal relationships between synaptonemal complexes at prophase and chromosomes at metaphase I of meiosis.

Bleomycin effects on mouse meiotic chromosomes

The effects of a radiomimetic chemical, bleomycin (BLM), on meiotic chromosomes was evaluated in mice treated by intraperitoneal (i.p.) or intratesticular (i.t.) injection. Chromosome aberrations were analyzed at meiotic metaphase I, and damage to the synaptonemal complex (SC) was analyzed in meiotic prophase cells. In the metaphase aberration studies, an i.p. injection of 80 mg/kg BLM, timed to precede or coincide with pre-meiotic S phase, led to a significant increase in structural damage (P less than 0.01) in cells reaching metaphase I 12 days after treatment. However, no increases in clastogenic effects were observed at metaphase I after treatment of cells during various stages of prophase. SC analyses in pachytene cells following an i.p. or i.t. injection at S phase revealed various forms of synaptic errors and structural anomalies, including qualitative changes similar to those observed following irradiation. I.p. doses ranging from 25 to 100 mg/kg, and i.t. doses as low as 0.5 mg/kg, caused roughly 6-fold increases over control levels in the number of damaged cells. SC analyses in pachytene cells following BLM treatments 2 days earlier (at leptotene-zygotene) or 16 h earlier (at early-mid pachytene), also revealed induced structural and synaptic anomalies. Following the treatment at early-mid pachytene, there was some suggestion of interference with chiasma formation as evidenced by univalent-like configurations detected at diakinesis-metaphase. It was concluded that BLM is clastogenic for meiotic chromosomes; however, it does not reveal the strong S-independent clastogenic activity at meiosis that is characteristic of its activity at meiosis. SC analysis indicated that some damage is induced at meiotic prophase, although structurally aberrant cells are not recoverable at meiotic metaphase I. The results call forth various possible explanations for germ-line specific responses to BLM clastogenic activity.

Genotoxicity of inhibitors of DNA topoisomerases I (camptothecin) and II (m-AMSA) in vivo and in vitro

The present study was designed to determine and compare the clastogenicity of m-AMSA and camptothecin (CAMP) in vivo in mouse bone marrow and peripheral blood lymphocytes (PBLs), and in vitro in mouse lymphoma L5178Y cells. m-AMSA interferes with topoisomerase II to induce double-strand DNA breaks. CAMP interferes with topoisomerase I to induce single-strand DNA breaks. Thus, we expected the two drugs to induce different types of chromosomal aberrations (CAs). However, both drugs produced quantitatively and qualitatively similar numbers and types of aberrations under similar experimental conditions. In mouse bone marrow exposed over and 18-h period, both drugs (3 mg/kg) induced approximately 30 damaged cells, with an average of 0.4 chromatid breaks per cell (in 100 cells analyzed/mouse). In addition, both drugs induced only chromatid-type aberrations in mouse bone marrow in vivo when exposure occurred during G2. Cell cycle specificity was indicated by the absence of CAs when exposure to the drugs occurred in vivo in mouse PBLs during G0. In L5178Y cells, m-AMSA was considerably more potent for the induction of mutations and somewhat more potent for the induction of CAs than CAMP was. In contrast to the in vivo bone marrow results, the drugs induced high levels of both chromatid- and chromosome-type aberrations in vitro. The ultimate types of chromosomal damage induced by m-AMSA and CAMP result from a complex interaction of (i) cell cycle specific variations in topoisomerase enzyme levels, (ii) the abilities of these drugs to interfere with the orderly DNA breakage/reunion associated with topoisomerase activity, and (iii) the processing of the damage resulting from these interactions.

Synaptonemal complex damage as a measure of genotoxicity at meiosis

Synaptonemal complex aberrations can provide a sensitive measure of chemical-specific alterations to meiotic chromosomes. Mitomycin C, cyclophosphamide, amsacrine, ellipticine, colchicine, vinblastine sulfate, and cis-platin exposures in mice have been shown to cause various patterns of synaptonemal complex structural damage and synaptic irregularity. These effects are suggestive of abnormal homologue pairing/synapsis/recombination effects which, theoretically, could be implicated in mechanisms leading to aneuploidy and other potentially heritable chromosomal disorders.

Synaptonemal complex damage induced by clastogenic and anti-mitotic chemicals: implications for non-disjunction and aneuploidy

Mice were treated with mitomycin C, cyclophosphamide, amsacrine, colchicine, or vinblastine sulfate, and meiotic prophase cells analyzed for synaptonemal complex (SC) damage. All test agents caused synaptonemal complex breakage and synapsis irregularities, although propensities for inducing specific types of damage at S-phase or prophase stages varied among the chemicals. The data indicate that SC analysis can reveal chemical-specific alterations to meiotic homologue pairing/synapsis which have not generally been recognized, and which theoretically may be implicated in non-disjunction.

Synaptonemal complex damage in relation to meiotic chromosome aberrations after exposure of male mice to cyclophosphamide

The genetic implications of induced synaptonemal complex (SC) damage are not known. However, on theoretical grounds, such aberrations could be involved in mechanisms leading to potentially heritable defects. Cyclophosphamide (CP), a chemical reported to cause structural and numerical chromosomal aberrations in the mouse, was used to determine if SC damage observed in meiotic prophase is related to subsequent metaphase chromosomal aberrations. Male mice were injected i.p. with CP. In some instances, mice were also injected simultaneously with tritiated thymidine to label DNA so that cells could be tracked autoradiographically through spermatogenesis. Prophase, primary metaphase (M1), and secondary metaphase (M2) samples were sequentially harvested at appropriate times from the same individual, and nuclei were examined for aberrations. Correlation coefficients between SC and metaphase chromosome aberrations were calculated. The inclusion of tritium labeling increased the number and significance of positive correlations. Positive correlations were found between (1) dose-dependent total SC damage and damage to M1, and to a lesser extent, M2 chromosomes; (2) SC breaks/fragments and M1 chains/rings as well as isochromatid breaks/fragments; (3) SC asynapsis and M1 chromatid breaks/fragments; (4) SC multi-axial configurations and M1 chains/rings as well as isochromatid and chromatid breaks/fragments; and (5) SC multi-axial configurations and M2 hyperploidy. These correlations do not define mechanistic or causal relationships between SC and chromosomal damage. However, taken together with the observation that induced SC damage is many times greater than ensuing metaphase chromosome damage, they substantiate SC analysis as a highly sensitive indicator of potentially heritable effects of this (and presumably other) genotoxic agents.

Tumorigenesis and genotoxicity of ethyl carbamate and vinyl carbamate in rodent cells

Vinyl carbamate (VC) is a suspect metabolic intermediate in ethyl carbamate (EC) carcinogenesis. In the present studies, EC and VC were evaluated for their relative abilities to induce adenomas and sister chromatid exchanges (SCEs) in lung cells of A/J, C3HeB/FeJ, and C57BL/6J strain mice. For both end points, animals were administered a single i.p. injection of the test chemical. Percentage of mice with adenomas and number of adenomas per mouse were compared among the three strains 24 weeks following exposure to EC or VC. Although the relative order of strain sensitivity was the same for both chemicals: A/J greater than C57BL/6J greater than C3HeB/FeJ, VC was much more potent than EC. For SCE analysis of primary lung cells cultured from treated animals, EC and VC showed potency differences similar to those observed for tumorigenesis. All three mouse strains revealed significant dose-dependent increases in SCE frequency. However, there was no strain specificity for this effect. SCE persistence over time was also compared in treated A/J and C57BL/6J mice. Although EC- and VC-induced SCE frequencies declined over a 2-week observation period, again, there was no strain specificity for this effect. VC was also tested for enhancement of SA7 virus transformation of Syrian hamster embryo cells. Significant concentration-dependent increases in cell transformation frequency were observed.

Sister chromatid exchange and chromosome aberration analyses in mice after in vivo exposure to acrylonitrile, styrene, or butadiene monoxide

The use of polymers in plastic and rubber products has generated concern that monomers potentially active in biological systems may be eluted from these substances. We have evaluated two such monomers, acrylonitrile and styrene, for the induction of chromosome damage in mice. Butadiene monoxide, a presumed metabolite of a third important monomer, 1,3-butadiene, was also tested. These chemicals were administered as a single intraperitoneal injection; sister chromatid exchanges and chromosome aberrations were analyzed in bone marrow cells. Acrylonitrile and styrene were largely negative for these endpoints when tested at doses ranging to 60 mg/kg and 1,000 mg/kg, respectively. Butadiene monoxide, which previously has not been tested in a mammalian system, was determined to be a very effective inducer of sister chromatid exchanges and chromosome aberrations. Both endpoints showed a clear dose response and a greater than ten-fold increase over control levels at high doses. These studies represent an initial step in our efforts to evaluate genetic risk associated with exposure to common polymeric chemicals.

The effect of nicotine on blood pressure in the genetically hypertensive mouse

Mice genetically selected for high and low blood pressure were exposed to nicotine via a single injected dose or addition to drinking water for 52 weeks. In the acute study, the response of mice with high blood pressure was a statistically significant increase in blood pressure. In the chronic study the pattern of response to nicotine ingestion was similar for mice with high blood pressure and those with low. Both lines responded with an increase in blood pressure after 6 weeks followed by a decrease to below baseline blood pressure at 12 weeks.