COVID-19 Vaccine Acceptance Among Latino/a Immigrants: The Role of Collective Responsibility and Confidence

Research on COVID-19 vaccine hesitancy has been sparse among Latino/a immigrants, a population at high risk for infection. This exploratory study examines rates of vaccine acceptance and its association with psychological antecedents of vaccination among Latino/a immigrants. A cross-sectional telephone survey on perceptions of COVID-19 was administered between October 2020 to February 2021 in South Florida to 200 adult Latino/a immigrants. Descriptive statistics, bivariate analysis, and logistic regression were employed to determine the influence of independent variables on vaccine acceptance. Most participants indicated a willingness to get vaccinated. Participants with higher confidence (aOR = 10.2, 95% CI: 4.8-21.8) and collective responsibility scores were (aOR = 3.1, 95%CI:1.3-6.9) more likely to report vaccine acceptance than those with lower scores. No other psychological antecedents or demographic variables were significantly associated with vaccine acceptance. Study results provide insights into motivating factors for vaccination that can inform culturally tailored education campaigns to increase vaccine acceptability in this population.

Global COVID-19 lockdown highlights humans as both threats and custodians of the environment

The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence. However, negative effects of lockdown on conservation also emerged, as confinement resulted in some park officials being unable to perform conservation, restoration and enforcement tasks, resulting in local increases in illegal activities such as hunting. Overall, there is a complex mixture of positive and negative effects of the pandemic lockdown on nature, all of which have the potential to lead to cascading responses which in turn impact wildlife and nature conservation. While the net effect of the lockdown will need to be assessed over years as data becomes available and persistent effects emerge, immediate responses were detected across the world. Thus, initial qualitative and quantitative data arising from this serendipitous global quasi-experimental perturbation highlights the dual role that humans play in threatening and protecting species and ecosystems. Pathways to favorably tilt this delicate balance include reducing impacts and increasing conservation effectiveness.

Link between packing morphology and the distribution of contact forces and stresses in packings of highly nonconvex particles

An external load on a particle packing is distributed internally through a heterogeneous network of particle contacts. This contact force distribution determines the stability of the particle packing and the resulting structure. Here, we investigate the homogeneity of the contact force distribution in packings of highly nonconvex particles both in two-dimensional (2D) and three-dimensional (3D) packings. A recently developed discrete element method is used to model packings of nonconvex particles of varying sphericity. Our results establish that in 3D packings the distribution of the contact forces in the normal direction becomes increasingly heterogeneous with decreasing particle sphericity. However, in 2D packings the contact force distribution is independent of particle sphericity, indicating that results obtained in 2D packings cannot be extrapolated readily to 3D packings. Radial distribution functions show that the crystallinity in 3D packings decreases with decreasing particle sphericity. We link the decreasing homogeneity of the contact force distributions to the decreasing crystallinity of 3D packings. These findings are complementary to the previously observed link between the heterogeneity of the contact force distribution and a decreasing packing crystallinity due to an increasing polydispersity of spherical particles.

Exposure to bisphenol A differentially impacts neurodevelopment and behavior in Drosophila melanogaster from distinct genetic backgrounds

Bisphenol A (BPA) is a ubiquitous environmental chemical that has been linked to behavioral differences in children and shown to impact critical neurodevelopmental processes in animal models. Though data is emerging, we still have an incomplete picture of how BPA disrupts neurodevelopment; in particular, how its impacts may vary across different genetic backgrounds. Given the genetic tractability of Drosophila melanogaster, they present a valuable model to address this question. Fruit flies are increasingly being used for assessment of neurotoxicants because of their relatively simple brain structure and variety of measurable behaviors. Here we investigated the neurodevelopmental impacts of BPA across two genetic strains of Drosophila-w¹¹¹⁸ (control) and the Fragile X Syndrome (FXS) model-by examining both behavioral and neuronal phenotypes. We show that BPA induces hyperactivity in larvae, increases repetitive grooming behavior in adults, reduces courtship behavior, impairs axon guidance in the mushroom body, and disrupts neural stem cell development in the w¹¹¹⁸ genetic strain. Remarkably, for every behavioral and neuronal phenotype examined, the impact of BPA in FXS flies was either insignificant or contrasted with the phenotypes observed in the w¹¹¹⁸ strain. This data indicates that the neurodevelopmental impacts of BPA can vary widely depending on genetic background and suggests BPA may elicit a gene-environment interaction with Drosophila fragile X mental retardation 1 (dFmr1)-the ortholog of human FMR1, which causes Fragile X Syndrome and is associated with autism spectrum disorder.

Impact of prenatal diagnosis of fetus-in-fetu

Fetus in fetu (FIF) is an extremely rare condition (1/500,000 live births) in which a fetiform structure is incorporated into the body of its twin. FIF can be a diagnostic dilemma due to its similarity to a teratoma, but identification of FIF is important for subsequent medical and surgical management. We compare two cases of fetal masses diagnosed on prenatal imaging that were later identified as FIF through further radiological, surgical, and pathologic evaluation. We use these cases to illustrate key pre- and postnatal features of FIF and highlight the benefits of prenatal detection and follow-up for postnatal management.

The experience of mothers caring for a child with a brain tumour

BACKGROUND

Brain tumours are the second most common form of childhood cancer, accounting for over 20% of all cases in European children. Understanding the impact of diagnosis and treatment of a brain tumour on the family is an essential pre-requisite to identifying ways to provide effective support.

AIM

(1) To explore the impact of having a child with a brain tumour on the main caregiver in the family; (2) to describe mothers' experiences of coping with their child's illness, including personal barriers and strengths; and (3) to identify causes of stress and sources of support to inform improvements in care delivery.

METHOD

Participants were drawn from a group of caregivers enrolled in a longitudinal study of outcome following diagnosis of a childhood brain tumour. Six caregivers took part, two from each of the high-, medium- and low-impact groups based on their Impact on Families Scale scores. Semi-structured interviews were used, with questions covering: (1) impact of the diagnosis on main caregiver and family; (2) personal barriers and strengths; and (3) causes of stress and sources of support. Interviews were transcribed verbatim and coded manually into five themes, which comprised 19 subthemes.

FINDINGS

Coping methods and provision of help and support were major preoccupations for main caregivers from all impact groups. Caregivers in the high-impact group reported less conflict. High- and medium-impact group caregivers had experienced less 'hindrance and heartache', than those with low impact scores, suggesting that the stress associated with diagnosis and treatment of the tumour may have increased cohesion and acceptance within these families.

CONCLUSION

Families of children diagnosed with a brain tumour experience considerable negative impact and may perceive themselves as struggling to cope. Provision of help and support, within and outside the extended family, including from health, education and other services, is perceived as helpful.

Visual failure without headache in idiopathic intracranial hypertension

AIM

To determine the differences in outcome in a group of children with idiopathic intracranial hypertension (IIH) who do not present with headaches.

METHODS

Differences in epidemiological and aetiological factors, clinical presentation, and visual outcome were investigated in children with a diagnosis of IIH presenting with and without headaches to the Paediatric Neurology and Paediatric Ophthalmology Services at Guy's & St Thomas' Hospitals NHS Trust between 1997 and 2002.

RESULTS

Compared to the 29 children with headaches, the 12 children in the non-headache group were younger (7.3 v 9.5 years), presented with more neurological signs (33% v 10%), and were more likely to present with severe visual failure (33% v 4%), with a tenfold increased risk of an enlarged blind spot or field defects (50% v 5%). Permanent visual failure affected a third of all children in the non-headache group, but was rare in children presenting with headaches (33% v 3%), with one patient registered blind and two severely visually impaired.

CONCLUSION

The management of IIH is difficult in the absence of headache. Visual surveillance is vital. These children were treated with an aggressive management programme to reduce cerebrospinal fluid pressure by repeated lumbar puncture, medication, and early surgical intervention if required. Non-invasive monitoring techniques might contribute to a better understanding of the natural history of IIH, improved management, and visual outcome.

Combustion products of 1,3-butadiene are cytotoxic and genotoxic to human bronchial epithelial cells

Adverse health effects of airborne toxicants, especially small respirable particles and their associated adsorbed chemicals, are of growing concern to health professionals, governmental agencies, and the general public. Areas rich in petrochemical processing facilities (e.g., eastern Texas and southern California) chronically have poor air quality. Atmospheric releases of products of incomplete combustion (e.g., soot) from these facilities are not subject to rigorous regulatory enforcement. Although soot can include respirable particles and carcinogens, the toxicologic and epidemiologic consequences of exposure to environmentally relevant complex soots have not been well investigated. Here we continue our physico-chemical analysis of butadiene soot and report effects of exposure to this soot on putative targets, normal human bronchial epithelial (NHBE) cells. We examined organic extracts of butadiene soot by gas chromatography-mass spectrometry (GC-MS), probe distillation MS, and liquid chromatography (LC)-MS-MS. Hundreds of aromatic hydrocarbons and polycyclic aromatic hydrocarbons with molecular mass as high as 1,000 atomic mass units were detected, including known and suspected human carcinogens (e.g., benzo(a)pyrene). Butadiene soot particles also had strong, solid-state free-radical character in electron spin resonance analysis. Spin-trapping studies indicated that fresh butadiene soot in a buffered aqueous solution containing dimethylsulfoxide (DMSO) oxidized the DMSO, leading to CH(3)* radical formation. Butadiene soot DMSO extract (BSDE)-exposed NHBE cells displayed extranuclear fluorescence within 4 hr of exposure. BSDE was cytotoxic to > 20% of the cells at 72 hr. Morphologic alterations, including cell swelling and membrane blebbing, were apparent within 24 hr of exposure. These alterations are characteristic of oncosis, an ischemia-induced form of cell death. BSDE treatment also produced significant genotoxicity, as indicated by binucleated cell formation. The combination of moderate cytotoxicity and genotoxicity, as occurred here, can be pro-carcinogenic.

1,N(2)-propanodeoxyguanosine adduct formation in aortic DNA following inhalation of acrolein

Recent reports indicate that many of the cytotoxic and health-threatening components of environmental tobacco smoke (ETS) reside in the vapor phase of the smoke. We have reported previously that inhalation of 1,3-butadiene, a prominent vapor phase component of ETS, accelerates arteriosclerotic plaque development in cockerels. In this study we asked whether inhaled acrolein, a reactive aldehyde that is also a prominent vapor-phase component of ETS, damages artery-wall DNA and accelerates plaque development. Cockerels inhaled 0, 1, or 10 ppm acrolein mixed with HEPA-filtered air for 6 hr. Half were killed immediately (day 1 group) for detection of the stable, premutagenic 1,N(2)-propanodeoxyguanosine acrolein adduct (AdG3) in aortic DNA via a (32)P-postlabeling/HPLC method, and half were killed after 10 days (day 10 group) for indirect assessment of adduct repair. In the day 1 group, acrolein-DNA adducts were 5 times higher in the 1 and 10 ppm groups than in HEPA-filtered air controls. However, in the day 10 group, adduct levels in the 1 and 10 ppm acrolein groups were reduced to the control adduct level. For the plaque studies, cockerels inhaled 1 ppm acrolein (6 hr/day, 8 weeks), mixed with the same HEPA-filtered air inhaled by controls. Plaque development was measured blind by computerized morphometry. Unlike butadiene inhalation, acrolein inhalation did not accelerate plaque development. Thus, even though repeated exposure to acrolein alone has no effect on plaque size under the exposure conditions described here, a single, brief inhalation exposure to acrolein elicits repairable DNA damage to the artery wall. These results suggest that frequent exposure to ETS may lead to persistent artery-wall DNA damage and thus provide sites on which other ETS plaque accelerants can act.

Replicability of SF-36 summary scores by the SF-12 in stroke patients

BACKGROUND AND PURPOSE

The replicability of the physical and mental component summary scores of the Short Form (SF)-36 has been established using the SF-12 in selected patient populations but has yet to be assessed in stroke patients. If the summary scores of the SF-12 are highly correlated with those of the SF-36, the benefits of using a shorter health-status measure may be realized without substantial loss of information or precision. Both self-reported and proxy assessments were evaluated for replicability.

METHODS

Intraclass correlation coefficients (ICCs) and linear regression were used to assess the ability of the SF-12 physical component summary (PCS-12) scores to predict PCS-36 scores and the SF-12 mental component summary (MCS-12) scores to predict MCS-36 scores. Multivariate regression was used to explore the relationship between SF-12 and SF-36 scores.

RESULTS

The MCS-12 and PCS-12 scores were strongly correlated with the corresponding SF-36 summary scores for surveys completed by proxy or self-report (ICCs ranged from 0.954 to 0.973). Regression analysis of the proxy assessments indicated that patient age was an important effect modifier in the relationship between MCS-12 and MCS-36 scores.

CONCLUSIONS

The SF-12 reproduced SF-36 summary scores without substantial loss of information in stroke patients. Accordingly, the SF-12 can be used at the summary score level as a substitute for the SF-36 in stroke survivors capable of self-report. However, the mental health summary scores of proxy assessments are influenced by patient age, thereby limiting the replicability of the SF-36 by the SF-12 under these conditions.

The diffusion of an evidence-based disease guidance system for managing stroke

This paper describes the diffusion of an evidence-based stroke guidance system (SGS) in a field setting through participatory research. SGS enables physicians to review relevant evidence-based literature, from which patient orders are generated for managing cerebrovascular accident. The paper focuses on the question 'what are the barriers and enablers to adopting SOS?' The research site consisted of eight hospitals within two health regions in Alberta, with 47 physicians as the intended users. The data sources consisted of surveys, education sessions, design feedback, field observations, and usage logs. Preliminary results revealed an initial slow rate of adoption that gradually improved with the influence of clinical champions, more effective communication, sustained education, round-the-clock support and continued system refinement. These initial findings suggest that models of technological diffusion can help us better understand the complexities of changing physician practice behaviors.

Low serum thiol levels predict shorter times-to-death among HIV-infected injecting drug users

OBJECTIVES

To investigate whether serum thiol levels are altered by HIV disease, and whether low serum thiols predict time to death among HIV-infected injecting drug users (IDU).

DESIGN

A cross-sectional study of serum thiol levels among 13 HIV-seronegative IDU, 116 HIV-seropositive IDU, and 17 HIV-seropositive IDU with a history of AIDS, and a cohort study of the 133 HIV-infected IDU who took part in the cross-sectional study.

METHODS

Subjects were recruited from a methadone-maintenance treatment program during 1990-1991. Total serum thiols were determined spectrophotometrically at enrolment; low serum thiols were defined as those with an absorbance at 412 nm < or = 0.46. Deaths through 31 December 1993 were determined from the National Death Index (NDI). Twenty-six HIV-seropositive subjects died during follow up; death certificates, which were obtained for 23 subjects, indicated AIDS or HIV infection for 20. Product-limit estimation was used to calculate survival. Multivariate analyses employed Cox proportional-hazards regression.

RESULTS

Analysis of cross-sectional data showed that serum thiols did not differ significantly among HIV-free subjects, HIV-infected subjects, and HIV-infected subjects with a history of AIDS. Cohort analysis, adjusted for age, revealed that persons with those with high serum thiols (relative hazard = 2.83; 95% confidence interval (CI), 1.15, 6.97); a significant interaction between low serum thiols and a history of AIDS was associated with a relative hazard of 5.65 (95% CI, 1.22-2.61).

CONCLUSIONS

Among HIV-infected persons, low serum thiols, especially in concert with a history of AIDS, predict mortality risk. These findings support the hypothesis that oxidative stress is critical to the pathogenesis of HIV infection.

Expression of the alpha 7 subunit of the nicotinic acetylcholine receptor in normal and myasthenic human thymuses

The nicotinic acetylcholine receptor (AChR) is a transmembrane glycoprotein composed of five homologous subunits. Different isoforms of the AChR alpha subunit exist (alpha 1 to alpha 9). Of them, alpha 1 is expressed in muscle, alpha 2 to alpha 9 in neuronal cells. Muscle AChR is the target autoantigen in the autoimmune disease myasthenia gravis (MG). The thymus is implicated in MG pathogenesis, and the anti-AChR autoimmune response may start in this tissue, that expresses the muscle-type alpha 1 subunit as well as other muscle AChR subunits. The thymus also expresses the "neuronal" alpha 3 and alpha 5 subunits. By using polymerase chain reaction and other molecular techniques, we demonstrate here expression of the AChR alpha 7 subunit transcript in thymuses from both myasthenic patients and normal subjects. The alpha 7 subunit can form homo-oligomeric functional AChR complexes that, like muscle AChR, bind alpha-bungarotoxin. The demonstration of expression of the alpha 7 subunit in the thymus suggests that alpha-bungarotoxin binding, functional AChRs of the neuronal type are normally present in the thymus.

Butadiene inhalation accelerates arteriosclerotic plaque development in cockerels

1,3-Butadiene (BD), a gas widely used in the rubber industry, is also present in automotive exhaust and in the vapor phase of environmental tobacco smoke (ETS; approximately 400 micrograms/cigarette). The threshold limit value (TLV) for BD which was 10 ppm, has now been reduced to 2 ppm. Extensive investigations of workers have identified very few statistically significant increases in BD-associated cancer mortality. However, two studies have reported increased BD-associated mortality from arteriosclerotic heart disease in black workers in the BD rubber industry. The cockerel is a sensitive animal model for studying effects of environmental agents on arteriosclerosis development. Previous studies showed that inhaled environmental levels of ETS significantly accelerate arteriosclerosis. Surprisingly, the carcinogen-rich tar fraction of ETS was ineffective. The elevated risk of death from arteriosclerotic heart disease in black BD workers and the high BD level in the vapor phase of ETS, raised the question of whether BD would accelerate arteriosclerosis in cockerels. Here, cockerels breathed either 20 ppm BD or filtered air (6 h/day, 80 days). Blinded measurements showed no differences between groups in plaque frequency or location. However, plaque sizes were significantly larger in BD-treated cockerels than in controls--results nearly identical to those reported earlier for ETS-exposed vs. air-exposed cockerels. This indicates that BD may contribute to the atherogenicity of ETS and provides experimental support for the recent reduction in the TLV for BD.

The tar fraction of cigarette smoke does not promote arteriosclerotic plaque development

In addition to being the single greatest known environmental cause of cancer, cigarette smoke (CS) is also a major contributor to heart disease. We reported previously that 1) inhalation of either mainstream or sidestream CS promotes aortic arteriosclerotic plaque development; 2) 1,3 butadiene, a vapor-phase component of CS, promotes plaque development at 20 ppm, which at the time was only 2 times higher than the threshold limit value; and 3) individual tar fraction carcinogens in CS, including polynuclear aromatic hydrocarbons (PAHs) and nitrosamines, either do not promote plaque development or do so only at high concentrations. These results suggested that the tar fraction is not the primary source of plaque-promoting agents in CS. We asked whether repeated exposure to the tar fraction of CS, collected in a cold trap (TAR), promotes plaque development in an avian model of arteriosclerosis. Acetone extracts of mainstream CS tar from burning, unfiltered reference cigarettes were solubilized in dimethyl sulfoxide (DMSO) and injected weekly into cockerels for 16 weeks (25 mg/kg/week). Positive controls were injected weekly with the synthetic PAH carcinogen, 7,12 dimethylbenz(a)anthracene (DMBA) dissolved in DMSO and negative controls were injected with DMSO. Plaque location and prevalence did not differ from group to group. Morphometric analysis of plaque cross-sectional areas showed that plaque sizes, which are log-normally distributed, were significantly larger in the DMBA cockerels compared to both the TAR and DMSO groups. There were no significant differences in plaque size between DMSO and TAR cockerels. The results reported here, combined with other recent findings, support the conclusion that the primary arteriosclerotic plaque-promoting components of CS are in the vapor phase.

1,3 Butadiene, a vapor phase component of environmental tobacco smoke, accelerates arteriosclerotic plaque development

BACKGROUND

Our recent results support predictions from epidemiology studies that thousands of excess heart disease-related deaths result yearly in the United States from involuntary exposure to environmental tobacco smoke (ETS). Limited exposures of cockerels to ETS significantly accelerate arteriosclerosis. Despite little direct in vivo support, tar fraction rather than vapor phase compounds are considered largely responsible for the plaque-promoting effects of cigarette smoke. Here, we evaluate the effects of two ETS components on plaque development: the vapor phase component, 1,3 butadiene, and the tar component, the tobacco-specific N-nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). At relatively high doses, injected NNK is carcinogenic in rodents. Epidemiology studies have identified increased mortality from arteriosclerotic heart disease among black men working in the butadiene rubber industry. Neither butadiene nor NNK has been tested experimentally for a possible role in plaque development.

METHODS AND RESULTS

Cockerels inhaled butadiene (20 ppm; 16 weeks) or were injected biweekly with NNK (10 mg/kg, 16 weeks). Control cockerels were exposed to filtered air or were injected with the NNK solvent dimethylsulfoxide. Plaque incidence, prevalence, location, and size were determined double-blind. NNK had no significant effect on any of these measurements. In contrast, butadiene elicited a statistically significant increase in plaque size comparable to that seen after steady-state exposure to ETS from 5 cigarettes.

CONCLUSION

(1) This study represents the first time that a single cigarette smoke component has been demonstrated to accelerate arteriosclerosis, at a dose that is environmentally relevant. (2) The plaque-promoting components of ETS may reside in the vapor phase. (3) The cockerel model should be valuable in understanding the mechanism underlying the reported increases in heart disease deaths among black workers in the butadiene rubber industry.

Identification of a variant collagen alpha 3 (VI) in early-stage avian arteriosclerotic plaques

A 170 kD protein, prominent in soluble extracts of rooster arteriosclerotic plaques, has been partially characterized. The protein was eluted from a size exclusion column in a broad molecular weight fraction > 100 kD. Concanavalin A and a murine polyclonal antibody raised against the isolated 170 kD protein reacted with the protein on Western blots. The 170 kD protein had an isoelectric point of approximately 5.4 and was digested by collagenase treatment. Amino acid analysis of a 70 kD fragment of the protein closely resembled that for chick collagen alpha 3 (VI). A 13 amino acid sequence within this 70 kD fragment had 69% identity and 85% homology to chicken collagen alpha 3 (VI). Soluble protein extracts from cultured plaque smooth muscle cells (SMC), and from healthy artery SMC, contained low levels of the protein. These cellular extracts also reacted with the polyclonal antibody described above. Although the protein lacks absolute amino acid sequence identity with collagen alpha 3 (VI) it shares with it many biochemical features, suggesting that the 170 kD protein is a variant species of chick collagen alpha 3 (VI).

Environmental tobacco smoke: experimental facts and societal issues

Involuntary exposure to environmental tobacco smoke (ETS) in public or in working places is considered to be a serious risk to human health. This symposium addressed several issues of toxicological interest that are associated with exposure to ETS. Epidemiologic evidence obtained in human studies suggests that "passive smoking" increases the risk of developing lung cancer in nonsmokers and favors the development of respiratory tract infections in children. Comparatively few data are available from animal studies that provide experimental support of the observations. Exposure of pregnant or neonate rats to cigarette sidestream smoke (SS) affects developmental patterns of drug metabolizing enzymes that may persist up to 90 days. In young roosters, SS accelerates the development of arteriosclerotic plaques. On the other hand, exposure of adult rats for up to 90 days induces only transient signs of damage in the nasal passages, but not in the deep lung, and this only at extremely high concentrations of ETS. So far, experimental toxicology has provided comparatively few data on the correlation between exposure to ETS and adverse health effects. yet, such data are needed, particularly since many conclusions drawn from the epidemiological studies remain open to criticism and questions.

Erythroid progenitor cells that survive benzene exposure exhibit greater resistance to the toxic benzene metabolites benzoquinone and hydroquinone

Benzene is a well known hematotoxicant which induces hematopoietic dyscrasias of varying intensities in different individuals and even in different strains of the same experimental animal species. Although there is ample evidence that diverse responses to benzene are related to differences in benzene metabolism, we have recently provided evidence implicating differences in host target cell susceptibility to these diverse responses to benzene. The present study extends our previous work and concerns strain-specific differences in marrow progenitor cells that survive benzene exposure. Two mouse strains (Swiss-Webster and C57B1/6J) which respond to benzene exposure with different intensities of bone marrow cytotoxicity were used. Bone marrow cells from benzene-exposed and untreated mice were cultured with one of five benzene metabolites: 1,4-benzoquinone (BQ), catechol (C), hydroquinone (HQ), muconic acid (MA) or phenol (P) and the abilities of these cells to produce erythroid (CFU-e) or granulocyte/macrophage colonies (GM-CFU-c) were assessed. In both strains, marrow cells isolated from benzene-exposed mice showed a higher percentage of plated CFU-e surviving culture with BQ, HQ or MA than marrow cells isolated from control mice. In contrast, both strains of benzene-exposed mice displayed decreased percentages of plated CFU-e surviving culture with catechol than cells isolated from control mice. Only one condition (the culturing of cells with HQ under GM-CFU-c forming conditions) showed any strain-specific difference in plating efficiency. In all, 20 possible combinations of benzene metabolites and cell types were examined (5 metabolites x 2 progenitor cell types x 2 strains).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhalation of steady-state sidestream smoke from one cigarette promotes arteriosclerotic plaque development

BACKGROUND

A number of epidemiologic studies have suggested that every year environmental tobacco smoke (second-hand smoke) is responsible for tens of thousands of deaths, mostly from heart disease, in the United States. Environmental tobacco smoke is composed mainly (80% to 85%) of aged and diluted sidestream smoke. The remainder is exhaled mainstream smoke. Among the thousands of compounds that have been identified in environmental tobacco smoke are a number of carcinogens, including polynuclear aromatic hydrocarbon carcinogens, such as benzo(a)pyrene. We have demonstrated previously that a number of carcinogens, including benzo(a)pyrene, promote plaque development after injection into cockerels. There have been almost no studies showing a direct stimulatory effect of environmental tobacco smoke on plaque development. Recently we demonstrated that cockerels exposed to sidestream smoke for approximately 0.4% of their projected lifespan exhibited accelerated development of arteriosclerotic plaques. In that study, cockerels in specially designed inhalation chambers were exposed to the steady-state sidestream smoke from 5 cigarettes for 6 h/d for 16 weeks. This level of exposure is high but environmentally plausible. Statistically significant increases in plaque size were demonstrated in the smoke-exposed cockerels.

METHODS AND RESULTS

In the present study, exposure levels were decreased by a factor of 5. Thirty cockerels were exposed to the steady-state sidestream smoke from 1 cigarette for 6 hours per day for 16 weeks. The smoke was mixed with filtered air. Ten control cockerels were exposed to filtered air only. Levels of smoke surrogates, including carbon monoxide and total suspended particulates, were measured three times a day. Again, there was a statistically significant increase in plaque size in the smoke-exposed cockerels. To place these studies within a context of environmental relevance, levels of carbon monoxide were measured independently over 1 to 3 hours in four bars where there was heavy smoking. Measured carbon monoxide levels were as high or higher in the bars than they were in the exposure chambers during the 1-cigarette sidestream-smoke study.

CONCLUSIONS

Experimental exposure to secondhand smoke at levels equal to or even below those routinely encountered by people in smoke-filled environments is sufficient to promote arteriosclerotic plaque development.

Inhalation of sidestream cigarette smoke accelerates development of arteriosclerotic plaques

BACKGROUND

Environmental tobacco smoke has been blamed for approximately 40,000 excess deaths from heart disease annually in the United States. As yet, no pathophysiological process that could be responsible for these deaths has been identified. Environmental tobacco smoke is composed mainly of aged and diluted sidestream smoke but also contains 15% to 20% exhaled mainstream smoke. Carcinogens, including nitrosamines and polynuclear aromatic hydrocarbons, are present in mainstream smoke and sidestream smoke. Carcinogen levels in sidestream smoke, unlike those in mainstream smoke, are not reduced in filtered cigarettes. The US Environmental Protection Agency has designated environmental tobacco smoke as a human (class A) carcinogen. In cockerels, subtumorigenic doses of polynuclear aromatic hydrocarbons carcinogens accelerate aortic arteriosclerotic plaque development.

METHODS AND RESULTS

To determine whether sidestream smoke inhalation affects arteriosclerotic plaque development, we exposed cockerels to sidestream smoke (n = 30) or to filtered air (n = 12) in inhalation chambers for 6 hours per day, 5 days a week from 6 to 22 weeks of age (0.4% of projected lifespan). Chamber levels of carbon monoxide, total suspended particulates, and nicotine were measured regularly during the exposures. The abdominal aorta from each cockerel was cut into 10 segments, and the plaque index (mean plaque cross-sectional area [mm2]/mean luminal circumference [mm] x 100) was calculated for each segment. There were no differences in plaque incidence or distribution between sidestream smoke-exposed and control cockerels; however, plaque indexes were significantly greater for sidestream smoke-exposed than control cockerels in all segments.

CONCLUSIONS

Thus, relatively brief exposures to sidestream smoke early in life are sufficient to enhance arteriosclerotic plaque development.

Determination of the atherogenic potential of inhaled carbon monoxide

The effects of chronic exposure to moderate levels of carbon monoxide upon the augmentation of arteriosclerotic plaque development were investigated in a series of in vivo studies in the cockerel (young rooster). This animal model has been well characterized, especially regarding the role of environmental agents in exacerbating early stages of plaque development. Cockerels injected with subtumorigenic doses of carcinogens exhibit markedly accelerated development of aortic arteriosclerotic plaques. Inhalation of mainstream smoke from two packs of cigarettes (100 minutes/day for 16 weeks) causes small but statistically significant increases in plaque size. As is the case with many animal models of plaque development, raised fat-proliferative plaques also appear in these animals following cholesterol feeding. Carbon monoxide is a ubiquitous pollutant in urban environments, where it is derived largely from mobile sources and cigarette smoke. Exposure to chronically elevated carbon monoxide levels has been implicated in a number of health-related problems. Whether such exposure plays a role in the development of arteriosclerosis has not been determined conclusively. In the present study, three questions were posed: 1. Will inhaled carbon monoxide at levels of 50 to 200 parts per million (ppm)* (two hours/day for 16 weeks) be sufficient to augment arteriosclerotic plaque development in cockerels, in the absence of other plaque-promoting agents? 2. Will the inhalation of 100 ppm carbon monoxide (two hours/day for 16 weeks), concomitant with the feeding of low levels (0.1%) of cholesterol, yield larger plaques than those obtained with either of these agents administered alone? 3. Will inhalation of 100 ppm carbon monoxide (two hours/day for 11 or 22 weeks), by cockerels in whom plaques have already appeared, further augment plaque development? Cockerels were exposed to carefully regulated levels of carbon monoxide in stainless-steel and Plexiglas dynamic exposure chambers. The volume percentage of plaques in the wall of the abdominal aorta of each exposed and control animal was determined by a point-counting method. Chronic inhalation of carbon monoxide at levels as high as 200 ppm did not affect augmentation of arteriosclerotic plaque development. (In separate studies involving inhalation of 200 ppm carbon monoxide, carboxyhemoglobin levels 10 minutes after exposures ended were 11% to 12%.) When administered at the same time that plaque development was being promoted by cholesterol feeding, carbon monoxide had no further effect upon plaque development.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhalation of carbon monoxide does not accelerate arteriosclerosis in cockerels

The effects of chronic exposure to moderate levels of carbon monoxide (CO) upon the augmentation of arteriosclerotic plaque development were investigated in a series of in vivo studies. Cockerels were exposed to carefully regulated CO levels in dynamic exposure chambers. The plaque volume percentage in the aortic walls of experimental and control animals was determined by point-counting. Chronic CO inhalation, at levels up to 200 ppm, did not stimulate arteriosclerotic plaque development (at 200 ppm CO, carboxyhemoglobin (COHb) levels 10 min after exposures ended were 11-12%). When administered concomitantly with cholesterol feeding, CO did not augment plaque development. When administered after either carcinogen-associated or diet-promoted plaque size increases had occurred, CO elicited no further plaque size increases. Thus, in this animal model, daily exposures to moderately high CO levels were without discernable effect upon arteriosclerotic plaque development, although high COHb levels were attained.

Evidence for strain-specific differences in benzene toxicity as a function of host target cell susceptibility

It has long been recognized that benzene exposure produces disparate toxic responses among different species or even among different strains within the same species. There is ample evidence that species- or strain-dependent differences in metabolic activity correlate with the disparate responses to benzene. However, bone marrow cells (the putative targets of benzene toxicity) may also exhibit species- or strain-dependent differences in susceptibility to the toxic effects of benzene. To investigate this hypothesis, two sets of companion experiments were performed. First, two strains of mice, Swiss Webster (SW) and C57B1/6J (C57), were exposed to 300 ppm benzene via inhalation and the effects of the exposures were determined on bone marrow cellularity and the development of bone marrow CFU-e (Colony Forming Unit-erythroid, an early red cell progenitor). Second, bone marrow cells from the same strains were exposed in vitro to five known benzene metabolites (1,4 benzoquinone, catechol, hydroquinone, muconic acid, and phenol) individually and in binary combinations. Benzene exposure, in vivo, reduced bone marrow cellularity and the development of CFU-e in both strains; however, reductions in both these endpoints were more severe in the SW strain. When bone marrow cells from the two strains were exposed in vitro to the five benzene metabolites individually, benzoquinone, hydroquinone, and catechol reduced the numbers of CFU-e in both strains in dose-dependent responses, phenol weakly reduced the numbers of the C57 CFU-e only and in a non-dose-dependent manner, and muconic acid was without effect on cells from either strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Transforming potential is detectable in arteriosclerotic plaques of young animals

The carcinogen-treated cockerel is a model for studying the early stages of arteriosclerotic plaque development. Carcinogen administration accelerates arteriosclerotic plaque development in cockerels, and transforming elements are present in DNA from advanced human plaques. In this study, we asked whether transforming elements could also be detected at early stages of plaque development in cockerels. NIH3T3 cells were transfected with DNA from plaques isolated from carcinogen-treated cockerels and from the healthy arterial wall underlying the plaques. Approximately 5 x 10(6) cells from each group were injected into nude mice. Tumors appeared in five of five mice in the plaque DNA group; no tumors appeared in mice from the healthy arterial wall group. All five plaque DNA-associated tumors hybridized to a cockerel genomic probe. Eight cockerel-specific bands were identified in EcoRI digests of first-round (primary) tumors. DNA from a primary tumor was tested in a second round of transfection. Five of five mice developed tumors after injection with these secondary transformants. All second-round tumors contained cockerel DNA, and a prominent cockerel-specific band (greater than 28 kb) was seen in EcoRI digests of all second-round tumors. In addition, a 5.2-kb band appeared prominently in one of five second-round tumors. No evidence was found for activation of the oncogenes Ha-ras, Ki-ras, src, or myc in the plaque-associated tumors. Similarly, DNA from plaque-associated tumors did not hybridize to probes for Marek disease virus, herpes simplex virus 1, or reverse transcriptase, suggesting that neither herpesviruses nor retroviruses are involved in the transforming activity of plaque DNA. These results indicate that transforming elements are a general property of arteriosclerotic plaques and are detectable in plaques of young animals.

Cultured human atherosclerotic plaque smooth muscle cells retain transforming potential and display enhanced expression of the myc protooncogene

The proliferation of vascular smooth muscle cells (SMC) is critical to atherosclerotic plaque formation. The monoclonal hypothesis proposes that the stimulus for this SMC proliferation is a mutational event. Here we describe a procedure for growing human plaque smooth muscle cells (p-SMC) in culture. We show that p-SMCs derived from two patients differ from SMC cultured from normal vascular tissue in expression of the protooncogene myc. One p-SMC strain was extensively characterized; these diploid, karyotypically normal cells have a finite life span in culture. Ultrastructural examination revealed two populations, one with classic contractile SMC appearance, the other, modulated to a synthetic state. Northern blotting showed a 2- to 6-fold and a 6- to 11-fold enhanced expression of myc by p-SMC, compared to SMC derived from healthy human aorta (HA-SMC) and saphenous vein (HV-SMC), respectively. In contrast, the p-SMC and HV-SMC expressed similar levels of message for the genes N-myc, L-myc, Ha-ras, fos, sis, myb, LDL receptor, EGF receptor, IGF I receptor, IGF II, and HMG CoA reductase. Finally, although p-SMCs are not tumorigenic, DNA isolated from these cells is positive in the transfection-nude mouse tumor assay. Myc, however, does not appear to be the transforming gene because no newly introduced human myc gene was detected in the p-SMC-associated nude mouse tumor. Thus human atherosclerotic p-SMCs possess both an activated myc gene and a transforming gene that is retained throughout many cell passages.

International Commission for Protection Against Environmental Mutagens and Carcinogens. ICPEMC Working Paper 7/1/1. Mutational events in the etiology of arteriosclerotic plaques

The arteriosclerotic plaque is the lesion most often associated with cardiovascular disease, which is the leading cause of death in North America and Western Europe. Plaques are composed of cells (mostly smooth muscle cells but also macrophages and some lymphocytes) and formed elements (cellular debris, collagen, elastin, glycosaminoglycans, lipid droplets, cholesterol crystals and sometimes calcium deposits). Proliferation of smooth muscle cells is essential to plaque formation and development. Most theories of plaque development have viewed this proliferation as a secondary event following an initiating stimulus (e.g., endothelial injury). According to this view, the proliferating smooth muscle cells are otherwise identical to the large number of non-proliferating smooth muscle cells in the artery wall. The 'monoclonal' hypothesis of plaque formation presents a fundamentally different view; namely, that the cell proliferation critical to plaque development follows the stable transformation of smooth muscle cells and that the plaques can therefore be viewed as benign smooth muscle cell tumors of the artery wall. Environmental agents, including viruses and chemicals that have been previously associated with cell transformation and tumorigenesis may therefore also contribute directly to plaque development. Data are provided from in vivo and in vitro studies in support of this proposition. Evidence is also presented that in standardized assays human and animal plaque DNAs elicit responses similar to those elicited by tumor DNAs. Thus, both plaque formation and tumorigenesis may share common mechanisms.

Ingestion of chlorinated water has no effect upon indicators of cardiovascular disease in pigeons

Cardiovascular disease (CVD) accounts for nearly half the deaths, yearly, in the United States. The arterio(athero)sclerotic plaque is the principal lesion of CVD. The White Carneau (WC) pigeon is an animal model that has been employed extensively for studying CVD. Cholesterol (CHOL) feeding aggravates atherosclerosis in WC pigeons greater than 2 years old. In 1986, two reports appeared from a single laboratory claiming a direct effect of drinking chlorinated (Cl) water upon lipid levels and plaque development in young (less than 1 year) WC pigeons. These are the only reports of such direct effects, to date. Three months' exposure to 2 ppm or 15 ppm Cl in the drinking water, resulted in increased circulating CHOL levels in young male WC pigeons fed a normocholesterolemic (NC) diet in which Ca2+ levels were reduced. In addition, at both Cl concentrations there was a significant increase in plaque size, compared to controls. Pigeons in the 2 ppm group also exhibited elevated low density lipoprotein (LDL) levels after 3 months on the NC diet. These findings, if extrapolated to man, could have considerable public health consequences, since nearly 200 million people in the United States drink Cl water. We have carried out a similar set of studies but with strikingly different results. We used the same suppliers of pigeons and feed as did the authors of the 1986 reports and followed their approach where possible. Six month-old male WC pigeons drank water with 2 ppm or 15 ppm Cl (pH 8.5) and ate a NC diet with Ca2+ reduced to 80% of normal. At both 1 and 3 months, body weight, CHOL, triglyceride and LDL levels were unaffected by drinking Cl water. There was also no effect of Cl water on plaque size after 3 months. Thus, we found no evidence that drinking chlorinated water has any effect upon circulating lipid levels or upon the development of arteriosclerotic plaques, in this animal model.

Resistance of tumor-derived DNA to restriction enzyme digestion

The major finding of this work is that there are specific restriction enzyme inhibitors present in "purified" tumor DNA which cause partial digestion patterns when tumor DNA is digested by standard procedures with any of three commonly employed restriction enzymes (HindIII, KpnI, XbaI). These aberrant patterns are not seen when DNA of cell lines derived from these tumors is digested. Thus, when working with tumor DNA these restriction enzymes should be used with caution.

Arteriosclerotic plaque development is 'promoted' by polynuclear aromatic hydrocarbons

In previous work we found that weekly injections of the polynuclear aromatic hydrocarbon (PAH) carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) induced spontaneous aortic plaques in cockerels to grow to a larger size and at a faster rate than plaques in control animals. To determine whether plaque-stimulating ability is related to carcinogenic potency or mutagenicity we have now tested a variety of agents, including PAH carcinogens, non-PAH carcinogens and weakly carcinogenic PAHs. Cockerels were injected weekly (from 4-20 weeks of age) with one of the following compounds: benzo[a]pyrene (B[a]P), benzo[e]pyrene (B[e]P), dibenz[a,h]anthracene (AH), dibenz[a,c]anthracene (AC), 3-methylcholanthrene (MCA), acetylaminofluorene (AAF), N-methyl-N,N'-nitro-nitrosoguanidine (MNNG) or anthracene (ANT). Plaques were present in the abdominal aortas of all animals. Plaque volumes were 8-14 times greater in AC-, B[a]P-, B[e]P-, MCA- and AH-treated cockerels than in controls. Plaques were slightly larger in the AAF-treated group than in control animals, and in the ANT- and MNNG-treated groups were indistinguishable in size from plaques in control animals. The largest plaque volumes were in AH-treated cockerels and were comparable in size to those elicited by DMBA treatment. The accelerated development of plaques is consistent with a 'promotional' role for these agents. There was a poor correlation between mutagenicity or carcinogenicity and plaque 'promotion', which may reflect a role for different metabolites in these processes.

Transforming gene in human atherosclerotic plaque DNA

The monoclonal hypothesis equates atherosclerotic plaques with benign smooth muscle cell tumors and proposes that plaques can arise via mutational or viral events. Here, we provide direct evidence that molecular events, heretofore associated only with tumor cells, are common to plaque cells as well. Three distinct groups of human coronary artery plaque (hCAP) DNA samples transfected into NIH 3T3 cells gave rise to transformed foci. DNA samples from a panel of normal noncancerous human tissues, including coronary artery, were negative in the assay. Southern-blotted focus DNA yielded positive signals when hybridized to the 32P-labeled nick-translated repetitive human "Alu" DNA sequence. The DNA from cloned foci was used successfully in a second round of transfection. Focus DNA hybridized to nick-translated v-Ki-ras, v-Ha-ras, or N-ras probes failed to detect human fragments of these genes. Primary focus cells from each of five clones elicited tumors after injection into nude mice (6/42). Several distinct high molecular weight (greater than 6.6 kilobases) bands were detected after BamHI-digested tumor DNA was hybridized to Alu. Preliminary characterization of these hCAP DNA-associated tumors indicates that they are similar to the fibrosarcomas that arise after injection of ras-transformed cells into nude mice. We propose that transforming genes in plaque cells behave in a manner analogous to the way in which oncogenes behave in cancer cells.

Tumor promoter-stimulated protein phosphorylation in mouse epidermis is inhibited by bromophenacyl bromide

Phosphorylation of mouse epidermal proteins by endogenous protein kinases and production of arachidonic acid are processes stimulated by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate. In mouse epidermal homogenates, each process, as well as production of diacylglycerol (the physiologic activator of protein kinase C), was inhibited by bromophenacyl bromide at concentrations equivalent to those that inhibit tumor promotion. These results lend support to the hypothesis that tumor promotion in mouse skin may be mediated by activation of protein kinase C.

Enhanced expression of a high-molecular-weight protein in arteriosclerotic plaques

We report the detection of a high-molecular-weight protein which is present in the 12,000 X g supernatant of arteriosclerotic plaques from the abdominal aortas of cockerels. The protein has a molecular weight of 160-170 kd when resolved via sodium dodecyl sulfate polyacrylamide gel electrophoresis (7.5%) in the presence of beta-mercaptoethanol. Densitometric scans of silver-stained gels indicate that the 160 kd protein is 8-10 times more prominent in plaques than in the underlying artery wall. This protein, which is present in all plaques analyzed to date, can be detected in animals as young as 8 weeks of age. This represents the first demonstration of the elaboration of a unique protein during the early stages of arteriosclerotic plaque development.