Guidelines for using animal models in blast injury research.

Blast injury is a very complex phenomenon and frequently results in multiple injuries. One method to investigate the consequences of blast injuries is with the use of living systems (animal models). The use of animals allows the examination and evaluation of injury mechanisms in a more controlled manner, allowing variables such as primary or secondary blast injury for example, to be isolated and manipulated as required. To ensure a degree of standardisation across the blast research community a set of guidelines which helps researchers navigate challenges of modelling blast injuries in animals is required. This paper describes the guidelines for Using Animal Models in Blast Injury Research developed by the NATO Health Factors and Medicine (HFM) Research Task Group 234.

Guidelines for conducting epidemiological studies of blast injury.

Blast injuries are often caused by more than one mechanism, do not occur in isolation, and typically elicit a secondary multi-system response. Research efforts often do not separate blast injuries caused by blast waves from those caused by blunt force trauma and other mechanisms. 15 experts from nine different NATO nations developed in the HFM Research Task Group (RTG; HFM-234 (RTG)) 'Environmental Toxicology of Blast Exposures: Injury Metrics, Modelling, Methods and Standards' Guidelines for Conducting Epidemiological Studies of Blast Injury. This paper describes these guidelines, which are intended to provide blast injury researchers and clinicians with a basic set of recommendations for blast injury epidemiological study design and data collection that need to be considered and described when conducting prospective longitudinal studies of blast injury.

Comparison of selected skin decontaminant products and regimens against VX in domestic swine.

An anesthetized domestic swine model was used to compare the efficacy and cross-contamination potential of selected skin decontaminant products and regimens against the chemical warfare agent, VX. Animals topically exposed to 2x, 3x or 5x LD(50) VX showed typical signs of organophosphate nerve agent poisoning, including miosis, salivation, mastication, dysrhythmias, and respiratory distress prior to death. Animals were exposed to 5x LD(50) VX and then decontaminated 45 min later with the reactive skin decontamination lotion (RSDL), Fuller's earth (FE), 0.5% hypochlorite, or soapy water. Survival was 100% when the reactive skin decontamination lotion or FE was utilized, although 50% of Fuller's earth-decontaminated animals exhibited serious signs of VX poisoning. Decontamination of VX-treated animals with 0.5% hypochlorite was less effective but also increased survival. Soapy water was ineffective in preventing lethality. Blood cholinesterase levels were not predictive of clinical outcome in decontaminated animals. The potential of "decontaminated" VX in open wounds to cause poisoning was assessed by vigorously mixing 5x LD(50) VX with the test decontaminants for 5 min and then placing the mixture onto a full-thickness skin wound. Soapy water was ineffective in preventing lethality. Although treatment with dry Fuller's earth prevented death and all signs of organophosphate poisoning, a significant proportion of treated animals decontaminated with Fuller's earth in aqueous suspension exhibited serious signs of organophosphate poisoning, suggesting that live agent may be desorbed from Fuller's earth when it is exposed to a liquid environment. Animals treated with reactive skin decontamination lotion or 0.5% hypochlorite-VX mixtures showed no signs of organophosphate poisoning during the 6- h test period.

Evidence for the lack of base-change and small-deletion mutation induction by trichloroethylene in lacZ transgenic mice.

Trichloroethylene (TCE) is a widely used industrial solvent employed mainly for degreasing and cold-cleaning metal parts. It is also used for dry cleaning, and in the production of a number of chemical products. It has been shown to induce liver and lung tumors in rodents, and have a variety of positive and negative results using in vitro and in vivo mutagenicity tests. In order to assist in the interpretation of the mechanism of carcinogenicity, TCE was tested for the ability to induce gene mutations and small deletions using the lacZ transgenic mouse model (MutaMouse). Male and female animals were exposed by inhalation to 0, 203, 1153, and 3141 ppm TCE, 6 h per day for 12 days. 14 and 60 days following the last exposure, animals were sacrificed and the mutation frequency in bone marrow, kidney, spleen, liver, lung, and testicular germ cells determined. The results of this study indicate that TCE did not induce base-change or small-deletion mutations as detected in this assay in any of the tissues examined. Environ. Mol. Mutagen. 34: 190-194, 1999. Published 1999 Wiley-Liss, Inc.

Ventilatory responses in awake guinea pigs exposed to acid aerosols.

This study reports experiments designed to evaluate the dose and temporal effects of an atmospheric pollutant, sulfuric acid (H2SO4) aerosol, on the dynamic components of the respiratory cycle. Ventilation was measured in a whole-body barometric plethysmograph in unanesthetized, unrestrained animals following a 4-h exposure to H2SO4 aerosol at 14.1, 20.1, or 43.3 mg/m3. Lung injury was assessed by histopathology and bronchoalveolar lavage (BAL). Aerosol exposure with H2SO4 caused marked alterations in both the magnitude and composition of the ventilatory response, which were both dose and time dependent. At the highest concentration tested, there was a significant increase in tidal volume (deltaVt) and a decrease in breathing frequency (f) immediately after exposure. Analysis of BAL fluid at this time showed increased inflammatory cells and protein in the acid exposed animals, and histology showed hyaline membranes and acute inflammatory cells in the proximal acinar region. By 24 h postexposure, f significantly increased whereas deltaVt decreased. This pattern of breathing was interspersed with short periods of apnea. The onset of rapid, shallow breathing was associated with histological evidence of diffuse pulmonary edema. By contrast, the immediate postexposure period at the lowest concentration of H2SO4 aerosol was characterized by a significant increase in f and little or no effect on deltaVt. These effects diminished with time, and at 24 h postexposure ventilatory parameters were indistinguishable from baseline values. An apparent crossover between the effects associated with the high and low exposure concentrations was seen at the intermediate exposure concentration; however, closer inspection of these findings on an animal-by-animal basis revealed two populations of animals with respiratory characteristics of either the high-exposure or low-exposure groups. The data suggest that the guinea pig exhibits complex interactions between dose and time to response that are consistent with the activation of neural reflexes. The indirect plethysmographic method provides a simple means to assess these responses in a model system that avoids the use of anesthetics, surgery, and restraint.

Dental health in Icelandic urban children aged 11 and 12 years.

A total of 1370 children were examined for caries, gingivitis, periodontal pocketing, calculus and loss of marginal alveolar bone. The mean DFT and DFS scores were 6.2 and 8.7 for 11-yr-old children and 8.2 and 12.1 for 12-yr-olds. The average number of initial caries lesions was 12.4 among 11-yr-olds and 15.7 among 12-yr-olds. The proximal and smooth surfaces accounted for 37% of the total DFS score in the 11-yr-old children and 43% in the 12-yr-olds. The median DFS score for the 11-yr-old boys and girls was 7, while for the 12-yr-old boys it was 9 and for the girls 11. Only 1.8% of the children were free from caries. The occurrence of gingivitis, expressed by GBI, was 20 in both age groups. 8% of the children showed no advanced gingival inflammation, while less than 1% had bleeding gingivitis at all examined surfaces. Supragingival calculus was found in 10% of the children. Neither periodontal pocketing nor loss of marginal alveolar bone was observed.

Mutans streptococci, lactobacilli and caries prevalence in 11- and 12-year-old Icelandic children.

Since the caries prevalence has not declined in Iceland as it has in other European countries, it was of interest to study the presence of cariogenic bacteria in Icelandic children. The prevalence of salivary mutans streptococci and lactobacilli was examined in 217 11- and 12-yr-old Icelandic children and was related to their caries prevalence. In 2% of the children mutans streptococci were not found whereas 31% and 35% of the 11-yr-olds and 12-yr-olds respectively carried more than 10(6) CFU per ml saliva. Lactobacilli were not detected in 8% of the children whereas 28% of the 11-yr-olds and 23% of the 12-yr-olds had more than 10(5) CFU per ml saliva. The mean caries prevalence (DFS), initial caries included, for 11-yr-olds was 21.6 and for 12-yr-olds 28.8. Both mutans streptococci and lactobacilli were significantly correlated to each other as well as to caries prevalence. An increased number of these microorganisms, especially the mutans streptococci, were associated with an increased DFS. Children with high salivary counts of mutans streptococci and lactobacilli showed four times higher DFS than children with low numbers. The magnitude of salivary cariogenic bacteria as well as caries prevalence was found to resemble the situation in Sweden 10 yr ago. S. mutans (serotype c/e/f) was carried by all mutans streptococci positive children. S. sobrinus (serotype d/g) was found in 60 children (30.2%). Children with both S. mutans and S. sobrinus had significantly higher salivary counts of mutans streptococci and lactobacilli as well as caries prevalence than children with only S. mutans.

Relationships between free smooth surface and proximal caries in the young permanent dentition.

Cross-sectional relationships between free smooth surface and proximal caries were assessed in 3 age groups, comprising 252 subjects aged 12 yr, 301 aged 15-16 yr and 102 aged 18-19 yr. Caries diagnosis was clinically on white spot and radiographically on enamel lesion level. Fair correlation between buccal-lingual and proximal caries observed among 12-yr-olds (r=0.47) declined in the older subjects (r=0.24). While statistically significant the variability in proximal caries, explained by buccal-lingual lesions, was low (range 6-22%). Sensitivity and specificity for buccal-lingual lesions as an indicator for proximal caries in the same tooth ranged from 0.37-0.44 and 0.84-0.91, respectively, with associated Pv+ and Pv- ranging from 0.41-0.44 and 0.84-0.91, respectively. Sensitivity and specificity for buccal-lingual caries in identifying subjects with proximal caries ranged from 0.33-0.44 and 0.67-0.98, respectively. Pv+ ranged from 0.94-0.99 and Pv- from 0.06-0.35. ROC curve analysis yielded A(z)-values of about 0.76 in the two younger age groups and 0.57 in the oldest. The results imply that information obtained from visual examination should be applied with caution when inferences about current caries status on proximal surfaces are made from the presence of buccal-lingual caries.

Dental behavior management problems in Swedish children.

4505 Swedish children aged 4-11 yr were surveyed regarding dental behavior management problems (BMP) and dental health. Dental charts were retrieved from clinics in the Public Dental Service in Göteborg, and data were then compiled regarding BMP, action against BMP, caries, fillings, use of local anesthetics, and number of missed appointments. Behavior management problems were found in 10.5% of the children, and were more common in the younger children, among children who missed appointments, and in children who received restorative treatment without local anesthetics. The BMP children had more carious and fewer filled surfaces. In 43.4% of the cases with BMP the strategy chosen was postponement of dental treatment or no measure taken.

Caries experience in Icelandic 12-year-old urban children between 1984 and 1991.

In order to evaluate trends in caries experience, a 20% random sample of 12-yr-old residents of Reykjavik, Iceland (252 children) was examined clinically and radiographically in 1991 under conditions consistent with those of the survey conducted in 1984. In addition to caries data, frequency of toothbrushing and use of fluoride dentifrice were recorded. The mean DFT and DFS were 3.0 and 4.1, respectively. The decrease in caries experience reached 60% with an annual fall in DFS of nearly 10%. During the 7-yr period between examinations the decline in DFT and DFS scores averaged 5.2 and 8, respectively, the annual reduction amounting to 0.7 DF teeth or 1.1 DF surfaces per child. The ratio of approximal/occlusal caries and the proportion of approximal caries were similar in both surveys. Fourteen percent of the children were free from manifest caries in 1991, but only 2% in 1984. Polarization between low and high prevalence individuals had intensified. Ninety-five percent of the children brushed their teeth regularly and 97% reported using a fluoride dentifrice.

Mutans streptococci, lactobacilli and caries experience in 12-year-old Icelandic urban children, 1984 and 1991.

In order to evaluate changes in salivary counts of cariogenic bacteria and relate these to trends in caries experience, stimulated saliva was collected from a 20% random sample of 12-yr-old residents of Reykjavik, Iceland (252 children) in 1991 under conditions consistent with those of a survey conducted in 1984. The mean and median counts of salivary mutans streptococci and lactobacilli remained similar in the two studies. However, the frequency distribution at lower levels of mutans streptococci differed significantly between 1991 and 1984, e.g. in the present study 25.8% of the children had < 10(5) compared with 13.8% in the study 1984. The mean caries prevalence in the permanent dentition (DFStot) was 11.0, which is significantly lower than in 1984 (mean DFStot 28.8). A significant difference in caries prevalence was found at various levels of salivary mutans streptococci. Strep. mutans (serotype c/e/f) was carried by all mutans streptococci-positive children, save one child, who carried only Strep. sobrinus. The proportion of 12-yr-olds who carried Strep. sobrinus had decreased significantly to 15.7% from 34.0% in 1984. Significantly more children with Strep. sobrinus showed high levels of total mutans streptococci than children with only Strep. mutans. As the case was in 1984 significantly more Strep. sobrinus carriers had a high level of salivary lactobacilli as well as higher caries prevalence than the children who did not carry this species.

Caries experience in Latvian nursery school children.

In 1993 the dental health was assessed in 631 Latvian 3--4-yr-old nursery school children. Forty-eight percent of the 3-yr-olds and 26% of the 4-yr-olds were caries free. The mean dmft for the total sample was 3.2 (2.2 and 3.8 in the 3-and 4-yr-olds, respectively). Molar caries, accounting for 66% of the total dmft score, was dominant in both age groups. Sixteen percent of the children had received restorations, 38% of which manifested recurrent caries. Recurrent caries was relatively more frequent in the younger children. Concomitant with a general increase in caries level, the polarization of the disease was less pronounced in the older children. The upper 25% of the distribution for 3- and 4-yr-olds contained 74% and 40% of the dmft, respectively. Daily toothbrushing was reported for 60% of the children. Of those, 38% used fluoride-containing dentifrice. No significant associations were found between caries experience and toothbrushing frequency, use of fluoride dentifrice or parents' education.

Inhalation toxicology of urban ambient particulate matter: acute cardiovascular effects in rats.

Wistar rats were exposed for 4 hours by nose-only inhalation to clean air, resuspended Ottawa ambient particles (EHC-93*, 48 mg/m3), the water-leached particles (EHC-93L, 49 mg/m3), diesel soot (5 mg/m3), or carbon black (5 mg/m3). Continuous data for physiologic endpoints (heart rate, blood pressure, body temperature, animal's activity) were captured by telemetry before and after exposure. Blood was sampled from jugular cannulas 1 to 3 days before exposure and at 2 and 24 hours after exposure, and by heart puncture on termination at 32 hours (histology group) or 48 hours (telemetry group) after exposure. Lung injury was assessed by 3H-thymidine autoradiography after the rats were killed. We measured endothelins (plasma ET-1, big ET-1, ET-2, ET-3) to assess the vasopressor components; nitric oxide (NO)-related metabolites (blood nitrate, nitrite, nitrosyl compounds, and plasma 3-nitrotyrosine) to assess the vasodilator components; and catecholamines (epinephrine, norepinephrine, L-DOPA, dopamine) and oxidative stressors (m- and o-tyrosine) for additional insight into possible stress components. Lung cell labeling was uniformly low in all treatment groups, which indicates an absence of acute lung injury. Inhalation of EHC-93 caused statistically significant elevations (P < 0.05) of blood pressure on day 2 after exposure, plasma ET-1 at 32 hours after exposure, and ET-3 at 2, 32, and 48 hours after exposure. In contrast, the modified EHC-93L particles, from which soluble components had been extracted, did not affect blood pressure. The EHC-93L particles caused early elevation (P < 0.05) of the plasma levels of ET-1, ET-2, and ET-3 at 2 hours after exposure, but the endothelins returned to basal levels 32 hours after exposure. Exposure to diesel soot, but not carbon black, caused an elevation (P < 0.05) of plasma ET-3 at 36 hours after exposure; blood pressure was not affected by diesel soot. Our results indicate that inhalation of the urban particles EHC-93 can affect blood levels of ET-1 and ET-3 and cause a vasopressor response in Wistar rats without causing acute lung injury. Furthermore, the potency of the particles to influence hemodynamic changes appears to be modified by removing polar organic compounds and soluble elements. Because the pathophysiologic significance of elevated endothelins has been clinically established in humans, our observations suggest a novel mechanism by which inhaled particles may cause cardiovascular effects. These findings in rats contribute to the weight of evidence in favor of a biologically plausible epidemiologic association between ambient particulate matter and cardiovascular morbidity and mortality in human populations.

Temporary tooth separation in the treatment of approximal carious lesions.

The tunnel preparation is among the techniques proposed for restoration of approximal carious lesions. The preparations minimizes the sacrifice of sound tooth structure. The diagnostic and management problems associated with the restricted access to the approximal area, however, have limited use of this treatment modality. The difficulty of ascertaining the possible loss of enamel surface integrity is overcome by temporary tooth separation, which permits direct visual and tactile examination of approximal sites. Additionally, the increased access facilitates both preparation of the cavity and placement of the restorative material.

On dental health in Icelandic children. Observations during a clinical dentifrice trial.

Dental health and the relative caries preventive effect of different fluoride dentifrice formulations were assessed in an Icelandic child population. For a cross sectional study 1370 children, aged 11 and 12 years were examined for caries and periodontal conditions employing standardized methods. Longitudinal data were obtained from 1161 children, participating in a three-year dentifrice trial. Randomly selected subgroups were employed to study salivary levels of mutans streptococci and lactobacilli, consumption of high-sucrose products and enamel fluoride content in relation to caries experience. Relative caries preventive effect of anticalculus agents (HEBP and AHBP) and lowered fluoride concentration (250 ppm) in dentifrices were evaluated in a three-year double blind randomized clinical trial. At the baseline examination a comparatively high mean caries prevalence (DFS 9.9) was registered. Longitudinal observations showed a mean caries increment of 10.5 surfaces during a three-year period. Simultaneously an improvement of gingival health was observed. A majority of children harbored mutans streptococci (98%) and lactobacilli (92%). High numbers of either microorganism were associated with high caries prevalence. S. sobrinus carriers were more frequent among children with high numbers of CFU per ml saliva. The consumption of sugar-containing products was generally frequent. Higher caries increment was associated with consumption of sweets and bakery products during mealtimes. The fluoride content of surface enamel was comparatively low, reflecting scarce post eruptive exposure. Dentifrice, containing 250 ppm fluoride showed significantly lower caries preventive effect compared to 1000 ppm sodium fluoride and MFP formulations. Addition of anticalculus agents (biphosphonates) had no negative effect on reducing caries increment. These studies show that dental caries constitutes a major health problem among Icelandic children, where high sugar consumption and comparatively low exposure to fluoride appear to play major roles. The use of fluoride dentifrice has not been able to limit caries development.

Caries risk assessment in adolescents.

Detailed caries records and salivary microbiological tests were utilized to predict caries development in a group of 15-16-year-old Swedish adolescents. Both, caries experience and salivary microorganisms, correlated significantly with a subsequent 3-year increment of DFS. The strongest associations were recorded between the prevalence of baseline incipient lesions and the development of manifest caries (r = 0.51). Incipient lesions accounted for 27% of the 31% variability in the DFS increment explained by joined caries and salivary data. All predictors analysed showed insufficient sensitivity for identifying true caries active individuals. However, the combined sensitivity and specificity for incipient lesions and comprehensive caries record (incipient + manifest lesions) attained values allowing to predict caries development in the majority of individuals. Using precavity lesions as a sole predictor, 79-81% of the individuals were correctly classified with regard to their future caries levels. The addition of manifest caries increased the accuracy of classification to 86-89% depending on the stringency of screening and validation criteria.

Mutans streptococci, lactobacilli and caries prevalence in 15 to 16-year olds in Göteborg. Part II.

During the fall of 1987 one hundred and fifty-five 15 to 16-year-olds were examined with regard to caries prevalence, saliva secretion rate and salivary numbers of mutans streptococci and lactobacilli. In 15% of the subjects no mutans streptococci were detected, while 17.7% carried > 10(6) colony forming units (cfu) per ml saliva. The median value was 1.8 x 10(5) cfu per ml saliva. No lactobacilli were detected in 19% of the subjects and 14.3% had > 10(5) cfu per ml saliva. The mean caries prevalence was 21.0, of these 14.1 were incipient lesions. Increased numbers of mutans streptococci and lactobacilli were associated with increasing caries prevalence. Subjects with high numbers of both microorganisms showed about 4 times higher mean caries prevalence than those with low numbers. Streptococcus sobrinus carriers (15%) had both higher mean caries prevalence and a higher proportion of subjects with > 10(6) cfu mutans streptococci per ml saliva than was found in the whole group.

Dental caries in a group of 15 to 16-year-olds from Göteborg. Part I.

301 adolescents aged 15 to 16 years (158 girls and 143 boys) were examined for caries under standardized conditions during the fall and spring terms of 1987/88. Clinical examinations, performed by two calibrated examiners were supplemented with posterior bite-wing radiographs which were assessed by one of the examiners. The mean DFT and DFS scores (incipient lesions included) were 9.8 and 19.4, respectively. The mean DFS score (dentin lesions+restorations) was 6.4. On average 1.9 surfaces had frank cavities or recurrent lesions and 13 surfaces had incipient lesions. Occlusal surfaces contributed 75%, approximal 21% and bucco-linqual 4% to the manifest component of the DFS score (4.8, 1.4 and 0.2 surfaces, respectively). 3% of the incipient lesions were found occlusally, 51% approximally and 46% bucco-linqually (0.4, 6.6 and 5.9 surfaces, respectively). Only 3% of the participants were completely free from caries, whereas 9% had no dentin lesions or restorations. 15% of the subjects with the highest caries prevalence averaged 15.8 dentin lesions or restorations. A tendency towards polarization of low and high caries prevalence groups was observed. Totally 91% of the individuals had occlusal caries, 82% approximal and 76% bucco-lingual, whereas dentin lesions or restorations had 88%, 42% and 14%, respectively.