High-speed random access laser tuning

We have developed a technique for laser tuning at rates of 100 kHz or more using a pair of acousto-optic modulators. In addition to all-electronic wavelength control, the same modulators also can provide electronically variable Q-switching, cavity length and power stabilization, chirp and linewidth control, and variable output coupling, all at rates far beyond what is possible with conventional mechanically tuned components. Tuning rates of 70 kHz have been demonstrated on a radio-frequency-pumped CO2 laser, with random access to over 50 laser lines spanning a 17% range in wavelength and with wavelength discrimination better than 1 part in 1000. A compact tuner and Q-switch has been deployed in a 5-10-kHz pulsed lidar system. The modulators each operate at a fixed Bragg angle, with the acoustic frequency determining the selected wavelength. This arrangement doubles the wavelength resolution without introducing an undesirable frequency shift.

Effectiveness of primary and secondary enforced seat belt laws

OBJECTIVE

The objective of this study was to determine the relative efficacy of primary and secondary enforced motor vehicle occupant restraint laws on the outcomes of restraint use, crash-related mortality, and crash-related injuries.

SEARCH STRATEGY

We used the Cochrane Collaboration search strategy to search the following electronic databases: MEDLINE, EMBASE, National Technical Information Service (NTIS), Psyc-INFO, ERIC, Nursing and Allied Health (CINAHL), Transportation Research Information Service (TRIS), and EI Compendex. The reference lists from each potentially eligible study were checked, and knowledgeable people in the field were contacted, for additional leads to published reports.

SELECTION CRITERIA

Studies had to include a comparison of primary enforcement law to no law, secondary enforcement law to no law, or a primary to a secondary law. Any study design was acceptable. Acceptable outcome measures included observed restraint use, and counts or rates of deaths or serious injuries.

DATA COLLECTION

Data were collected using a standard abstract reporting from. Relative differences in outcomes and absolute differences were calculated when possible.

MAIN RESULTS

We identified 48 studies for the review. When places or time periods with primary enforcement laws were compared to those without such laws, the relative prevalence of seat belt use ranged from 1.5 to 4.5; the prevalence differences ranged from 10 to 50 per 100 observed drivers. Secondary laws had smaller effects. Two studies evaluated a change in law from secondary to primary enforcement; this was associated with an increase in belt use 6 months later of 5.3 per 100 observed drivers in Louisiana and 18 per 100 drivers in California. Primary enforcement laws were associated with a relative risk of death in MV crashes of .54 to .97. The reduction in mortality associated with secondary enforcement laws was much more modest, with relative risks estimates of .81 to 1.025. Primary enforcement laws were associated with a relative risk of severe injuries of .20 to .89; the association of secondary enforcement laws with severe injuries was smaller.

CONCLUSIONS

Our review of existing studies suggests that primary enforcement laws are likely to be more effective than secondary laws. However, few studies are of good quality, and quantitative estimates of the relative effect of primary compared with secondary laws are limited.

Systematic reviews of strategies to prevent motor vehicle injuries

BACKGROUND

Information on which strategies have been shown to be effective, which are ineffective, and which strategies have been inadequately evaluated is important for both public policy and future research.

OBJECTIVE

To provide systematic reviews of the literature on important strategies to prevent motor vehicle injuries.

METHODS

The Injury Control Research Centers (ICRCs) funded by the Centers for Disease Control and Prevention identified 9 important motor vehicle injury prevention strategies. A systematic review of the literature in 9 different computerized databases was conducted to identify relevant controlled trials. These were critically reviewed and summarized.

RESULTS

A total of 54,078 citations were reviewed; 1,111 met initial screening criteria. The reports for these citations were obtained and critically reviewed by the ICRCs. Standard criteria for inclusion of articles in the review and for evaluating the methodological quality of the articles were applied. Few randomized controlled trials were found; most controlled studies were either comparisons over time and/or across different populations. Nevertheless, these studies were able to be summarized to provide meaningful conclusions about the effectiveness of various interventions to decrease morbidity and mortality from motor vehicle crashes.

CONCLUSIONS

A large body of literature on motor vehicle injury interventions exists. The summary of this literature will provide useful information to direct policy and future research efforts.

Does the face protect the brain? A case-control study of traumatic brain injury and facial fractures

BACKGROUND

The relationship between facial fractures and traumatic brain injury is controversial. Some studies show an increased risk of brain injury with the presence of facial fractures while others claim that facial fractures protect against brain injury.

OBJECTIVE

To examine the association between facial fractures and traumatic brain injuries.

DESIGN

Case-control study.

SETTING

Subjects were recruited from the emergency departments of 7 hospitals in the Seattle, Wash, area.

PATIENTS

Three thousand eight hundred forty-nine injured bicyclists and 5 scene deaths were identified from March 1, 1992, to August 31, 1994, with complete data available on 3388 bicyclists.

INTERVENTIONS

None.

RESULTS

The study group was composed of 1602 cases with injuries to the head, face, or brain and 1540 control subjects. There were 203 bicyclists with traumatic brain injuries, of whom 62 had an identifiable intracranial injury and 141 suffered a concussion. A total of 81 patients sustained facial fractures. The odds ratio for the risk of intracranial injury associated with facial fractures after adjustment for significant confounders was 9.9 (95% confidence interval, 5.1-19.3). The effect was less strong but still present when all traumatic brain injuries including concussions were considered (odds ratio, 2; 95% confidence interval, 1.1-3.7). No association was found for concussion only.

CONCLUSIONS

This study demonstrates no evidence that facial fractures help prevent traumatic brain injury. Data indicate that facial fractures are markers for increased risk of brain injury.

Prevention of bicycle-related injuries: helmets, education, and legislation

Efforts to reduce the toll of bicycle-related head injuries illustrate how the basic public health principles of surveillance, epidemiologic study, intervention, and evaluation can have a substantial impact on an injury problem, using a variety of injury-prevention strategies. Head injuries are the leading cause of serious morbidity and mortality from bicycle crashes. Helmets have been shown to reduce bicycle-related head injuries for cyclists of all ages involved in all types of crashes including those with motor vehicles. Helmet use has been promoted using educational campaigns, helmet subsidies, and legislation. Careful evaluation of these strategies has shown that these interventions increase helmet use and decrease the incidence of bicycle injuries. The model developed for the prevention of bicycle injuries is widely applicable to other injury problems.

Cytokine-induced nitric oxide formation in normal but not in neoplastic murine lung epithelial cell lines

Cytomix, a mixture of interferon-gamma, tumor necrosis factor-alpha, and interleukin-1beta, induces nitric oxide (NO) production in lung epithelial cell lines. It is not known whether neoplastic transformation alters a cell's ability to form NO in response to cytokines. The present study investigated NO formation in two murine lines of immortalized "normal" (nontumorigenic) lung epithelial cells of alveolar type II origin, E10 and C10, and their sibling spontaneous transformants, E9 and A5. Nontumorigenic cells elaborated much more NO after cytomix exposure than did their tumorigenic counterparts. NO production was prevented by inhibiting protein synthesis and NO synthase and attenuated by dexamethasone. Northern and Western blot analyses of inducible NO synthase (iNOS) demonstrated cytomix-induced induction of iNOS only in nontumorigenic cells. The deficiency in NO production in tumorigenic cells was not associated with reduced iNOS mRNA stability or with differences in cytomix-induced nuclear factor-kappaB activation. Although cytomix caused a greater production of NO in E10 cells than in E9 cells, the same treatment induced equivalent proliferation in both cell lines. These results indicate a specific deficiency in cytokine-induced NO synthesis in transformed murine lung epithelial cells relative to their normal progenitor cells and provide a model for investigating iNOS regulation.

Synthesis and structure-activity relationships of potent and orally active 5-HT4 receptor antagonists: indazole and benzimidazolone derivatives

A series of indole-3-carboxamides, indazole-3-carboxamides, and benzimidazolone-3-carboxamides was synthesized and evaluated for antagonist affinity at the 5-HT4 receptor in the rat esophagus. The endo-3-tropanamine derivatives in the indazole and benzimidazolone series possessed greater 5-HT4 receptor affinity than the corresponding indole analogues. 5-HT4 receptor antagonist affinity was further increased by alkylation at N-1 of the aromatic heterocycle. In a series of 1-isopropylindazole-3-carboxamides, replacement of the bicyclic tropane ring system with the monocyclic piperidine ring system or an acyclic aminoalkylene chain led to potent 5-HT4 receptor antagonists. In particular, those systems in which the basic amine was substituted with groups capable of forming hydrogen bonds showed increased 5-HT4 receptor antagonist activity. While some of these compounds displayed high affinity for other neurotransmitter receptors (in particular, 5-HT3, alpha1, and 5-HT2A receptors), as the conformational flexibility of the amine moiety increased, the selectivity for the 5-HT4 receptor also increased. From this series of compounds, we identified LY353433 (1-(1-methylethyl)-N-[2-[4-[(tricyclo[3.3.1.1(3, 7)]dec-1-ylcarbonyl)amino]-1-piperidinyl]ethyl]-1H-indazole-3- carboxamide) as a potent and selective 5-HT4 receptor antagonist with clinically suitable pharmacodynamics.

Cycle helmets and the prevention of injuries. Recommendations for competitive sport

The scientific evidence that bicycle helmets protect against head, brain and facial injuries has been well established by 5 well designed case-control studies. Additional evidence of helmet effectiveness has been provided from time series studies in Australia and the US. Bicycle helmets of all types that meet various national and international standards provide substantial protection for cyclists of all ages who are involved in a bicycle crash. This protection extends to crashes from a variety of causes (such as falls and collisions with fixed and moving objects) and includes crashes involving motor vehicles. Helmet use reduces the risk of head injury by 85%, brain injury by 88% and severe brain injury by at least 75%. Helmets should be worn by all riders whether the cyclist is a recreational rider or a serious competitor engaged in training or race competition. The International Cycling Federation (ICF) should make the use of helmets compulsory in all sanctioned races.

Comparative toxicity of eugenol and its quinone methide metabolite in cultured liver cells using kinetic fluorescence bioassays

Comparative kinetic analyses of the mechanisms of toxicity of the alkylphenol eugenol and its putative toxic metabolite (quinone methide, EQM) were carried out in cultured rat liver cells (Clone 9, ATCC) using a variety of vital fluorescence bioassays with a Meridian Ultima laser cytometer. Parameters monitored included intracellular GSH and calcium levels ([Ca2+]i), mitochondrial and plasma membrane potentials (MMP and PMP), intracellular pH, reactive oxygen species (ROS) generation, and gap junction-mediated intercellular communication (GJIC). Cells were exposed to various concentrations of test compounds (1 to 1000 microM) and all parameters monitored directly after addition at 15 s intervals for at least 10 min. Eugenol depleted intracellular GSH, inhibited GJIC and generation of ROS, and had a modest effect on MMP at concentrations of 10 to 100 microM. At high concentrations (1000 microM), eugenol also affected [Ca2+]i, PMP, and pH. Effects of EQM were seen at lower concentrations (1 to 10 microM). The earliest and most potent effects of either eugenol or EQM were seen on GSH levels and GJIC. Coadministration of glutathione ethyl ester enhanced intracellular GSH levels by almost 100% and completely protected cells from cell death caused by eugenol and EQM. These results suggest that eugenol mediates its hepatotoxic effects primarily through depletion of cytoprotective thiols and interference in thiol-dependent processes such as GJIC. Furthermore, our results support the hypothesis that the toxic effects of eugenol are mediated through its quinone methide metabolite.

A training program to improve domestic violence identification and management in primary care: preliminary results

Domestic violence as encountered in day-to-day practice is greatly underidentified. It is estimated that only 3% of cases are presently being identified, and practitioners are uncertain of what to do if a case is discovered. In this paper, a training program to improve identification and management of domestic violence (DV) in primary care and the providers' responses to the program are described. A multimodal training program was undertaken to demonstrate and practice the incorporation of didactic content into practice for the health care teams. Two medical centers from a large staff-model HMO were chosen at random from five volunteering for training. The entire adult health care medical center teams, including physicians, physician assistants, RNs, LPNs, medical assistants, and receptionists, were the recipients of the training. Assessment of provider valuation of the components of the training program was performed by administering a standardized 5-point Likert-scaled questionnaire 9 months after the training. This time interval was chosen because we were interested in lasting program effects. Core didactic content, such as the epidemiology of DV, identification and management of victims and batterers, and legal issues, was highly rated. Delivery of the content through role-playing, start-stop videos and presentations by former victims received lesser but solid support. Follow-up assessment 9 months post training demonstrates solid support for many components of the program: highest for specific information content areas, but strong for techniques and processes. The training program appears to be a promising method to improve provider skills in DV management.

Differential susceptibility of tracheal contraction to nonadrenergic noncholinergic relaxation

Studies of nonadrenergic noncholinergic inhibitory (NANCi) nerve-induced relaxations routinely examine relaxations in airway tissue in which tone has been established. Little is known about the ability of NANCi nerve stimulation to prevent airway smooth muscle contraction. The present study compares the capacity of NANCi nerve stimulation to prevent or reverse airway smooth muscle contraction. NANCi nerves in the trachea from ovalbumin-sensitized guinea pigs were subjected to electrical field stimulation (EFS, 10 Hz, 0.3 ms, 10 V, 35 min) initiated before or after induction of tone with antigen or histamine. In tissues precontracted with histamine or antigen, EFS elicited a rapid relaxation which peaked within the first 5 min and stabilized by 20 to 35 min. The peak relaxation was smaller in tissues precontracted with antigen, an effect that was not prevented by tissue treatment with a nitric oxide synthase inhibitor. In contrast, the stabilized level of NANCi relaxation did not differ between histamine- or antigen-contracted tissues. Activation of NANCi nerves prior to induction of tone also resulted in inhibition of the contractile actions of histamine and antigen. However, the stabilized level of tone induced by a contractile agonist added after initiation of EFS was greater than the stabilized tone caused by EFS in tissues already contracted with the same agonist. Relaxations elicited by S-nitrosoglutathione were reduced in antigen-precontracted tissues whereas vasoactive intestinal peptide-induced relaxant responses were similar in antigen- and histamine-precontracted tissues. Results of this study suggest that NANCi nerve activation is more effective at relaxing established airway smooth muscle tone than at preventing airway smooth muscle contraction. Further, the results suggest that the difference in NANCi activity in antigen-precontracted tissues cannot be ascribed solely to reductions in the nitric oxide-dependent component of the response.

Absence of tachykinin involvement in leukotriene D4 and antigen-induced contraction of guinea pig isolated bronchus

In guinea pig airways, contractions induced by leukotriene D4 or antigen are thought to be mediated primarily by an action of the agonist or of released mast cell-derived mediators directly on the airway smooth muscle cell. An indirect contractile action mediated by endogenous tachykinins also has been described for both of these stimuli. The present study evaluated the contribution of endogenous tachykinins to ovalbumin- and leukotriene D4-induced contractions in the guinea pig bronchus by modulating the concentrations of tachykinins within the tissues and by using neurokinin receptor antagonists. Acute depletion of tachykinins with capsaicin had no effect on responses elicited by either stimulus. Similarly, tetrodotoxin treatment failed to influence leukotriene D4-induced contractions. Inhibitors of neutral endopeptidase (thiorphan) and angiotensin-converting enzyme (lisinopril) enhanced neurally mediated tachykininergic responses and potentiated leukotriene D4. The latter effect persisted in the presence of tetrodotoxin or the neurokinin antagonists CP99994 and SR48968 and in tissues treated acutely with capsaicin. The potentiation was absent, however, from bronchi incubated with L-cysteine. Ovalbumin-induced contractions were unaltered by inhibition of neutral endopeptidase and angiotensin-converting enzyme. These observations suggest that tachykinins are not involved in mediation of leukotriene D4- or antigen-induced contractions of the guinea pig bronchus. The ability of protease inhibitors to potentiate leukotriene D4 but not antigen-induced responses is therefore ascribed to inhibition of bioinactivation of leukotriene D4 to leukotriene E4.

Effect of speckle on lidar pulse-pair ratio statistics

The ratio of temporally adjacent lidar pulse returns is commonly used in differential absorption lidar (DIAL) to reduce correlated noise. These pulses typically are generated at different wavelengths with the assumption that the dominant noise is common to both. This is not the case when the mean number of laser speckle integrated per pulse by the lidar receiver is small (namely, less than 10 speckles at each wavelength). In this case a large increase in the standard deviation of the ratio data results. We demonstrate this effect both theoretically and experimentally. The theoretical value for the expected standard deviation of the pulse-pair ratio data compares well with the measured values that used a dual CO(2) laser-based lidar with a hard target. Pulse averaging statistics of the pulse-pair data obey the expected varsigma(1)/ radicalN reduction in the standard deviation, varsigma(N), for N-pulse averages. We consider the ratio before average, average before ratio, and log of the ratio before average methods for noise reduction in the lidar equation. The implications of our results are discussed in the context of dual-laser versus single-laser lidar configurations.

Immunochemical visualization and identification of rat liver proteins adducted by 2,6-di-tert-butyl-4-methylphenol (BHT)

Several alkylphenols (e.g., 2,6-di-tert-butyl-4-methylphenol, BHT) form reactive quinone methide intermediates (e.g., 2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone, BHT-QM) upon oxidation by cellular enzymes. In order to pursue the role of protein alkylation in alkylphenol toxicity, we used an immunochemical approach to identify protein targets alkylated by BHT. Synthetic BHT-N-acetylcysteine (BHT-NAC) was coupled to keyhole limpet hemocyanin and used as an antigen from which polyclonal antibodies were raised in New Zealand white rabbits. Rabbit serum contained an antibody which was highly specific for BHT-NAC, as determined by competitive ELISA. The BHT antibody was used as a probe to look for the presence of BHT-protein adducts in in vitro incubations with rat liver microsomes or tissue slices and also in vivo in liver tissue from male Sprague-Dawley rats exposed to BHT. Western blotting of protein gels revealed BHT-dependent protein alkylation over a wide molecular weight range. Prominent recurrent bands were observed at approximately 34.5, 52, 64.5, 74, and 97 kDa. Detection of adducts was inhibited in microsomal incubations by cytochrome P450 inhibitors, deuterated BHT, and the omission of NADPH. Similar protein alkylation patterns were observed in rat liver microsomes exposed to synthetically prepared BHT-QM as in the enzyme-mediated incubations. In rats gavaged with up to 1000 mg/kg BHT, the amount of protein alkylation observed was maximal at 24 h postdosing and was dose-dependent. Two alkylated proteins were isolated and identified by N-terminal sequencing: a mitochondrial beta-oxidation enzyme, enoyl-CoA hydratase, and a plasma membrane/cytoskeletal linker protein from the ezrin/moesin/radixin family.

Damage to bicycle helmets involved with crashes

The objective was to evaluate the relationship between helmet damage and head injuries in helmeted bicyclists in a sub-study of a large case-control study of bicycle injuries and helmet effectiveness. The setting consisted of seven hospital emergency departments in Seattle, WA. Hospitalized patients and medical examiners cases were included. The participants in the study were helmeted bicyclists who suffered a head injury or who damaged or hit their helmet in a crash. The Snell Memorial Foundation laboratory evaluated the helmets, blinded to crash circumstance and injury diagnosis. Damage was scored on a five-point scale (0 = none to 4 = destroyed). The damage location for each helmet was coded into regions (six longitudinal and three latitudinal) and mapped onto a three-dimensional CAD (computer-aided design) model of a helmet. The same procedure was also followed for injury location, which was mapped onto a three-dimensional ISO (International Organization for Standardization) headform for visualization of head-injury distribution. 785 helmeted subjects met the criteria for inclusion in the sub-study, and 527 helmets were purchased and evaluated (67%). 316 (60%) of the helmets had no or minimal damage, and 209 (39.7%) had significant damage (score 2, 3 or 4). Helmet types were 49.7% hard shell, 34.2% thin shell and 16.1% no shell. The risk of head and brain injury increased if the helmet was destroyed: OR = 5.3 (95% CI 2.9, 9.9) and OR = 11.2 (95% CI 3.5, 37.9), respectively. A high proportion of helmet impacts were along the front edge of the helmet, with a preponderance of head injuries in the same region. The large number of impacts to the front rim of the helmet, combined with the substantial number of riders with injuries to the forehead, indicate that some helmets, because of poor fit or wearing style, expose the forehead to injury. In addition, the data indicate that for a small proportion of injuries, the energy to the helmet may exceed design limits.

Epidemiology of bicycle injuries and risk factors for serious injury

OBJECTIVE

To determine the risk factors for serious injury to bicyclists, aside from helmet use.

DESIGN

Prospective case-control study.

SETTING

Seven Seattle area hospital emergency departments and two county medical examiner's offices.

PATIENTS

Individuals treated in the emergency department or dying from bicycle related injuries.

MEASUREMENTS

Information collected from injured bicyclists or their parents by questionnaire on circumstances of the crash; abstract of medical records for injury data. Serious injury defined as an injury severity score > 8.

ANALYSIS

Odd ratios computed using the maximum likelihood method, and adjusted using unconditional logistic regression.

RESULTS

There were 3854 injured cyclists in the three year period; 3390 (88%) completed questionnaires were returned 51% wore helmets at the time of crash. Only 22.3% of patients had head injuries and 34% had facial injuries. Risk of serious injury was increased by collision with a motor vehicle (odds ratio (OR) = 4.6), self reported speed > 15 mph (OR = 1.2), young age (< 6 years), and age > 39 years (OR = 2.1 and 2.2 respectively, compared with adults 20-39 years). Risk for serious injury was not affected by helmet use (OR = 0.9). Risk of neck injury was increased in those struck by motor vehicles (OR = 4.0), hospitalized for any injury (OR = 2.0), and those who died (OR = 15.1), but neck injury was not affected by helmet use.

CONCLUSIONS

Prevention of serious bicycle injuries cannot be accomplished through helmet use alone, and may require separation of cyclists from motor vehicles, and delaying cycling until children are developmentally ready.

Injuries involving off-road cycling

BACKGROUND

Data on injuries due to off-road bicycling are scarce, but do indicate that injuries in this sport are frequent. We examined the pattern of injuries to off-road riders as part of a larger study of bicycle injuries and helmet use.

METHODS

We undertook a prospective study of bicycle-related injuries identified at seven emergency departments in Seattle, Washington, between March 1992 and August 1994. Hospitalized patients and medical examiners' cases were included. Detailed questionnaires and abstraction of all medical records provided information on crash and rider characteristics and injury type and severity.

RESULTS

A total of 3390 injured riders participated, representing an 88% response rate. Of all injured cyclists, 127 (3.7%) were injured riding "off road." Seventy-three percent of off-road cyclists were 20 to 39 years of age, and 86.6% were male. Helmet use was 80.3% for off-road cyclists as compared with 49.5% for other cyclists. The number of head and face injuries for the off-road cyclists was only 40% of the number incurred by other cyclists. Four percent of off-road cyclists had severe injuries (injury Severity Score > 8), and 6.3% were hospitalized, compared with 6.8% and 9.4%, respectively, of other cyclists.

CONCLUSIONS

The majority of off-road bicycling injuries are minor. Off-road cyclists are less likely to have head and face injuries than other cyclists and are more likely to wear helmets.

Bike speed measurements in a recreational population: validity of self reported speed

OBJECTIVE

Speed at the time of a bicycle crash is an important determinant of the amount of energy transmitted. Controlling for speed is thus important in the evaluation of outcomes and effectiveness of intervention strategies. This study was conducted to evaluate the accuracy of self reported speed in a population of recreational cyclists.

METHODS

Children's and adults' bicycle speeds were measured with a radar gun as they rode along a closed road at weekend recreational events. Cyclists were then stopped and asked to estimate their speed. Measured speed, cyclist's estimate of their speed, age, and sex were documented. Parents were also asked to estimate their child's speed.

RESULTS

One hundred and fifty two cyclists from 4 to 80 years of age participated. Seventy per cent were children 13 years of age or younger. The mean (SD) speed of this group was 8.9 (2.5) mph. Cyclists age 14 and older were traveling at a mean speed of 9.7 (2.87) mph. Estimated speeds were significantly higher than measured speeds for this older group, but there was no significant difference between mean measured and estimated speeds for the younger riders. There was also no significant difference between measured and estimated speed for males and females. Parents estimated their child's speed quite accurately.

CONCLUSIONS

Self reported speeds for children were in close agreement with measured speeds and, thus, are sufficiently accurate to be a useful measure of crash severity in evaluating helmet effectiveness.

Effectiveness of bicycle safety helmets in preventing head injuries. A case-control study

OBJECTIVES

To examine the protective effectiveness of bicycle helmets in 4 different age groups of bicyclists, in crashes involving motor vehicles, and by helmet type and certification standards.

RESEARCH DESIGN

Prospective case-control study

SETTING

Emergency departments (EDs) in 7 Seattle, Wash, area hospitals between March 1, 1992, and August 31, 1994.

PARTICIPANTS

Case subjects were all bicyclists treated in EDs for head injuries, all who were hospitalized, and all who died at the scene. Control subjects were bicyclists treated for nonhead injuries.

MAIN RESULTS

There were 3390 injured bicyclists in the study; 29% of cases and 56% of controls were helmeted. Risk of head injury in helmeted vs unhelmeted cyclists adjusted for age and motor vehicle involvement indicate a protective effect of 69% to 74% for helmets for 3 different categories of head injury: any head injury (odds ratio [OR], 0.31; 95% confidence interval [CI], 0.26-0.37), brain injury (OR, 0.35; 95% CI, 0.25-0.48), or severe brain injury (OR, 0.26; 95% CI, 0.14-0.48). Adjusted ORs for each of 4 age groups (<6 y, 6-12 y, 13-19 y, and > or = 20 years) indicate similar levels of helmet protection by age (OR range, 0.27-0.40). Helmets were equally effective in crashes involving motor vehicles (OR, 0.31; 95% CI, 0.20-0.48) and those not involving motor vehicles (OR, 0.32; 95% CI, 0.20-0.39). There was no effect modification by age or motor vehicle involvement (P=.7 and P=.3). No significant differences were found for the protective effect of hard-shell, thin-shell, or no-shell helmets (P=.5).

CONCLUSIONS

Bicycle helmets, regardless of type, provide substantial protection against head injuries for cyclists of all ages involved in crashes, including crashes involving motor vehicles.

Firearm patient education and firearm regulation: health care providers' attitudes and practices

A survey of two large HMOs was conducted to assess health care providers' attitudes and practices regarding firearm patient education, firearm patient counselling, and firearm regulation. Survey results were intended to provide background data on barriers to be addressed and opportunities to be used in developing day-to-day office practice interventions to reduce enrollees' risk of firearm injury.

Metabolism and toxicity of 4-hydroxyphenylacetone in rat liver slices: comparison with acetaminophen

Acetaminophen is oxidized by cytochrome P450 to a reactive quinone imine, N-acetyl-p-benzoquinone imine, which is thought to be responsible for its hepatotoxic effects. 4-Hydroxyphenylacetone (4-HPA) is a structural analog of acetaminophen in which the amine group is replaced by a methylene group. Following a similar metabolic pathway, 4-HPA would be oxidized to form a reactive quinone methide intermediate. We compared the metabolism and toxicity of 4-HPA and acetaminophen in liver microsomes and precision-cut liver slices from male Sprague-Dawley rats. Both 4-HPA and acetaminophen formed glutathione conjugates in microsomal incubations. 4-HPA formed diastereomeric glutathione conjugates, which is consistent with the formation of an intermediate quinone methide. The rate of conjugate formation with 4-HPA was 8.5-fold greater than that with acetaminophen. In rat liver slices a concentration of 5 mM 4-HPA killed approximately 50% of hepatocytes after 6 hr of incubation, whereas acetaminophen was not toxic at concentrations up to 50 mM. N-Acetylcysteine protected slices from 4-HPA-induced toxicity, whereas phenobarbital enhanced metabolism and toxicity. In summary, 4-HPA is more hepatotoxic than acetaminophen, and this may be the result of differences in the metabolic rate and/or the type of reactive intermediate formed.

Studies on the mechanism of hepatotoxicity of 4-methylphenol (p-cresol): effects of deuterium labeling and ring substitution

We recently observed that 4-methylphenol (p-cresol) is toxic to rat liver tissue slices. A possible mechanism involves biotransformation of 4-methylphenol to a reactive quinone methide intermediate which covalently binds to cellular macromolecules and elicits cytotoxicity. In order to obtain further evidence for this proposed mechanism, we studied the effects of deuterium-labeled 4-methylphenol (4-[alpha, alpha, alpha-d3]-methylphenol), and the presence of various ring substituents, on the metabolism and toxicity of 4-methylphenol in precision cut liver slices prepared from male Sprague-Dawley rats. Deuterium-labeled 4-methylphenol was significantly less toxic than the parent compound in rat liver slices (LC50 = 3.36 vs. 1.31 mM, respectively). In addition, the deuterium-labeled compound was metabolized to a reactive intermediate (measured as glutathione conjugate formation) at a slower rate than that of 4-methylphenol in both liver slices and liver microsomal incubations. The presence of electron withdrawing substituents (2-chloro or 2-bromo) markedly enhanced both metabolism and toxicity, with the exception of 2,6-dibromocresol, which was similar to cresol in terms of rate of metabolism and toxicity. Conversely, the presence of electron donating substituents (2-methoxy, 2-methyl or 2,6-dimethyl) diminished metabolism and toxicity. In addition, methylation of the hydroxyl group to form 4-methylanisole, greatly reduced toxicity. These results support the hypothesis that the toxicity of 4-methylphenol is dependent on the formation of a reactive quinone methide intermediate.