The worm Adult Activity Test (wAAT): A de novo mathematical model for detecting acute chemical effects in Caenorhabditis elegans

We have adapted a semiautomated method for tracking Caenorhabditis elegans spontaneous locomotor activity into a quantifiable assay by developing a sophisticated method for analyzing the time course of measured activity. The 16-h worm Adult Activity Test (wAAT) can be used to measure C. elegans activity levels for efficient screening for pharmacological and toxicity-induced effects. As with any apical endpoint assay, the wAAT is mode of action agnostic, allowing for detection of effects from a broad spectrum of response pathways. With caffeine as a model mild stimulant, the wAAT showed transient hyperactivity followed by reversion to baseline. Mercury chloride (HgCl2 ) produced an early dose-response hyperactivity phase followed by pronounced hypoactivity, a behavior pattern we have termed a toxicant "escape response." Methylmercury chloride (meHgCl) produced a similar pattern to HgCl2 , but at much lower concentrations, a weaker hyperactivity response, and more pronounced hypoactivity. Sodium arsenite (NaAsO2 ) and dimethylarsinic acid (DMA) induced hypoactivity at high concentrations. Acute toxicity, as measured by hypoactivity in C. elegans adults, was ranked: meHgCl > HgCl2  > NaAsO2  = DMA. Caffeine was not toxic with the wAAT at tested concentrations. Methods for conducting the wAAT are described, along with instructions for preparing C. elegans Habitation Medium, a liquid nutrient medium that allows for developmental timing equivalent to that found with C. elegans grown on agar with OP50 Escherichia coli feeder cultures. A de novo mathematical parametric model for adult C. elegans activity and the application of this model in ranking exposure toxicity are presented.

Assessment of the Effects of Organic vs. Inorganic Arsenic and Mercury in Caenorhabditis elegans

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Similar developmental delays and oxidative stress with 20x DMA relative to NaAsO2.

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Dissimilar gene expression and locomotion with organic vs. inorganic mercury.

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Dissimilar unfolded protein responses for organic vs. inorganic arsenic and mercury.

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Across phyla, methylation has opposite effects on arsenic vs. mercury toxicity.

Exposures to mercury and arsenic are known to pose significant threats to human health. Effects specific to organic vs. inorganic forms of these toxic elements are less understood however, especially for organic dimethylarsinic acid (DMA), which has recently been detected in pups of rodent dams orally exposed to inorganic sodium (meta)arsenite (NaAsO2). Caenorhabditis elegans is a small animal alternative toxicity model. To fill data gaps on the effects of DMA relative to NaAsO2, C. elegans were exposed to these two compounds alongside more thoroughly researched inorganic mercury chloride (HgCl2) and organic methylmercury chloride (meHgCl). For timing of developmental milestone acquisition in C. elegans, meHgCl was 2 to 4-fold more toxic than HgCl2, and NaAsO2 was 20-fold more toxic than DMA, ranking the four compounds meHgCl > HgCl2 > NaAsO2 ≫ DMA for developmental toxicity. Methylmercury induced significant decreases in population locomotor activity levels in developing C. elegans. DMA was also associated with developmental hypoactivity, but at >100-fold higher concentrations than meHgCl. Transcriptional alterations in native genes were observed in wild type C. elegans adults exposed to concentrations equitoxic for developmental delay in juveniles. Both forms of arsenic induced genes involved in immune defense and oxidative stress response, while the two mercury species induced proportionally more genes involved in transcriptional regulation. A transgenic bioreporter for activation of conserved proteosome specific unfolded protein response was strongly activated by NaAsO2, but not DMA at tested concentrations. HgCl2 and meHgCl had opposite effects on a bioreporter for unfolded protein response in the endoplasmic reticulum. Presented experiments indicating low toxicity for DMA in C. elegans are consistent with human epidemiologic data correlating higher arsenic methylation capacity with resistance to arsenic toxicity. This work contributes to the understanding of the accuracy and fit-for-use categories for C. elegans toxicity screening and its usefulness to prioritize compounds of concern for further testing.

The C. elegans model in toxicity testing

Caenorhabditis elegans is a small nematode that can be maintained at low cost and handled using standard in vitro techniques. Unlike toxicity testing using cell cultures, C. elegans toxicity assays provide data from a whole animal with intact and metabolically active digestive, reproductive, endocrine, sensory and neuromuscular systems. Toxicity ranking screens in C. elegans have repeatedly been shown to be as predictive of rat LD50 ranking as mouse LD50 ranking. Additionally, many instances of conservation of mode of toxic action have been noted between C. elegans and mammals. These consistent correlations make the case for inclusion of C. elegans assays in early safety testing and as one component in tiered or integrated toxicity testing strategies, but do not indicate that nematodes alone can replace data from mammals for hazard evaluation. As with cell cultures, good C. elegans culture practice (GCeCP) is essential for reliable results. This article reviews C. elegans use in various toxicity assays, the C. elegans model's strengths and limitations for use in predictive toxicology, and GCeCP. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. Journal of Applied Toxicology published by John Wiley & Sons Ltd.

Bioactivity of nanosilver in Caenorhabditis elegans: Effects of size, coat, and shape

The in vivo toxicity to eukaryotes of nanosilver (AgNP) spheres and plates in two sizes each was assessed using the simple model organism Caenorhabditis elegans. For each shape, smaller AgNP size correlated with higher toxicity, as indicated by reduced larval growth. Smaller size also correlated with significant increases in silver uptake for silver nanospheres. Citrate coated silver spheres of 20 nm diameter induced an innate immune response that increased or held steady over 24 h, while regulation of genes involved in metal metabolism peaked at 4 h and subsequently decreased. For AgNP spheres, coating altered bioactivity, with a toxicity ranking of polyethylene glycol (PEG) > polyvinylpyrrolidone (PVP) ≅ branched polyethyleneimine (BPEI) > citrate, but silver uptake ranking of PEG > PVP > citrate > BPEI. Our findings in C. elegans correlate well with findings in rodents for AgNP size vs. uptake and toxicity, as well as for induction of immune effectors, while using methods that are faster and far less expensive, supporting the use of C. elegans as an alternative model for early toxicity screening.

Nanosilver suppresses growth and induces oxidative damage to DNA in Caenorhabditis elegans

Studies on the effects of nanomaterial exposure in mammals are limited, and new methods for rapid risk assessment of nanomaterials are urgently required. The utility of Caenorhabditis elegans cultured in axenic liquid media was evaluated as an alternative in vivo model for the purpose of screening nanomaterials for toxic effects. Spherical silver nanoparticles of 10 nm diameter (10nmAg) were used as a test material, and ionic silver from silver acetate as a positive control. Silver uptake and localization, larval growth, morphology and DNA damage were utilized as endpoints for toxicity evaluation. Confocal reflection analysis indicated that 10nmAg localized to the lumen and tissues of the digestive tract of C. elegans. 10nmAg at 10 µg ml(-1) reduced the growth of C. elegans larvae, and induced oxidative damage to DNA as measured by 8-OH guanine levels. Consistent with previously published studies using mammalian models, ionic silver suppressed growth in C. elegans larvae to a greater extent than 10nmAg. Our data suggest that medium-throughput growth screening and DNA damage analysis along with morphology assessments in C. elegans could together provide powerful tools for rapid toxicity screening of nanomaterials.

Toxicity ranking of heavy metals with screening method using adult Caenorhabditis elegans and propidium iodide replicates toxicity ranking in rat

The utility of any model system for toxicity screening depends on the level of correlation between test responses and toxic reactions in humans. Assays in Caenorhabditis elegans can be fast and inexpensive, however few studies have been done comparing toxic responses in this easily cultured nematode with data on mammalian toxicity. Here we report that a screening assay for acute toxicity, using adult C. elegans grown in axenic liquid culture, replicated LD50 toxicity ranking in rat for five metals. This assay utilized the COPAS Biosort and propidium iodide (PI) as a fluorescent indicator of morbidity and mortality after 30-h exposures. We found that chronic toxicity assays of 2-week treatment duration, followed by analysis of PI induced red fluorescence levels, produced less consistent results than the acute assays. However, other chronic toxicity endpoints were compound and concentration specific, including changes in vulval and gonadal morphology, intestinal thickness and integrity, and the presence of retained internal eggs in post-reproductive animals. Some of these endpoints reflect similar findings in mammals, indicating that measurements of morbidity and mortality in conjunction with morphology analyses in C. elegans may have the potential to predict mammalian toxic responses.

Completeness and accuracy of International Classification of Disease (ICD) external cause of injury codes in emergency department electronic data

The accuracy of external cause of injury codes (E codes) for work-related and non-work-related injuries in Massachusetts emergency department data were evaluated. Medical records were reviewed and coded by a nosologist with expertise in E coding for a stratified random sample of 1000 probable work-related (PWR) and 250 probable non-work-related (PNWR) cases. Cause of injury E codes were present for 98% of reviewed cases and accurate for 65% of PWR cases and 57% of PNWR cases. Place of occurrence E codes were present in less than 30% of cases. Broad cause of injury categories were accurate for about 85% of cases. Non-specific categories (not elsewhere classified, not specified) accounted for 34% of broad category misclassifications. Among specified causes, machinery injuries were misclassified most often (39/60, 65%), predominantly as cut/pierce or struck by/against. E codes reliably identify the broad mechanism of injury, but inaccuracies and incompleteness suggest areas for training of hospital admissions staff, providers, and coders.

Characteristics of work related asthma: results from a population based survey

OBJECTIVES

Many risk factors for asthma have been investigated, one of which is the workplace. Work related asthma is a frequently reported occupational respiratory disease yet the characteristics which distinguish it from non-work related asthma are not well understood. The purpose of this study was to examine differences between work related and non-work related asthma with respect to healthcare use and asthma control characteristics.

METHODS

Data from the Massachusetts Behavioral Risk Factor Surveillance System for 2001 and 2002 were used for this analysis. Work related status of asthma was determined by self-report of ever having been told by a physician that asthma was work related. Healthcare measures evaluated were emergency room visits and physician visits for worsening asthma and for routine care. Characteristics of asthma control evaluated were frequency of asthma symptoms, asthma attacks, difficulty sleeping, and asthma medication usage in the last 30 days and limited activity in the past 12 months.

RESULTS

The prevalence of lifetime and current asthma in Massachusetts were 13.0% and 9.2%, respectively. Approximately 6.0% (95% CI 4.8 to 7.3) of lifetime and 6.2% (95% CI 4.7 to 7.8) of current asthma cases were work related. In the past 12 months, individuals with work related current asthma were 4.8 times (95% CI 2.0 to 11.6) as likely to report having an asthma attack, 4.8 times (95% CI 1.8 to 13.1) as likely to visit the emergency room at least once, and 2.5 times (95% CI 1.1 to 6.0) as likely to visit the doctor at least once for worsening asthma compared to individuals with non-work related asthma.

CONCLUSIONS

Work related asthma is associated with increased frequency of asthma attacks and use of healthcare services. A better understanding of factors that contribute to differences in healthcare use and asthma control is needed to improve prevention and control strategies for individuals suffering from the disease.

mVps24p functions in EGF receptor sorting/trafficking from the early endosome

Yeast Vps24p (vacuolar protein sorting) is part of a protein complex suggested to function in sorting/trafficking during endocytosis. We have characterized a mammalian homolog of the yeast protein, mVps24p, and examined its role in epidermal growth factor receptor trafficking. Endogenous mVps24p was distributed in both cytosol and in puncta and partially colocalized with markers for the trans-Golgi network. Adventitious expression of hrs or a mVps4p mutant deficient in ATPase activity caused a redistribution of both mVps24p and the M6PR to the resultant clustered/enlarged early endosomes. Expression of an mVps24p N-terminal fragment, that interacts with phosphatidylinositol 3,5-bisphosphate but not with mVps4p, produces enlarged early endosomes. More importantly, the mVps24p N-terminal fragment resulted in not only enhanced recycling, but also decreased degradation of the EGF receptor. These findings are consistent with a model in which mVps24p has a role in trafficking from the early endosome.

An examination of the spatial working memory deficit following neurotoxic medial dorsal thalamic lesions in rats

The present study examined the performance of rats with neurotoxic lesions centred in the thalamic nucleus medialis dorsalis on standard and modified versions of the eight arm radial maze test. In Experiment 1, the thalamic lesions produced a borderline deficit in acquisition of the standard task, but subsequently had no effect when a delay was interposed after the first four arms had been entered. The same lesions had no effect on T-maze alternation, but they did impair radial-arm maze performance when intramaze and extramaze cues were set against each other. In Experiment 2, lesions of the dorsomedial thalamus impaired acquisition of the standard radial-arm maze task, but combining the results from Experiments 1 and 2 showed that this acquisition deficit was confined to those animals in which bilateral damage extended into the adjacent anterior thalamic nuclei. In addition, lesions of the dorsomedial thalamus disrupted radial-arm maze performance when the task was modified to compare working memory and reference memory and increased activity and exploration. These changes were not associated with anterior thalamic damage. Finally, the thalamic lesions did not affect performance on a test of spontaneous object recognition. It is concluded that lesions of medialis dorsalis do not disrupt spatial memory but do affect other processes that can interact with task performance. These include a failure of extramaze cues to overshadow intramaze cues, a change in activity and exploration levels and deficits in with-holding spatial responses.

Neurotoxic lesions of the dorsomedial thalamus impair the acquisition but not the performance of delayed matching to place by rats: a deficit in shifting response rules

This study examined the acquisition of a T-maze matching to place task by rats with neurotoxic lesions of the thalamic nucleus medialis dorsalis. This test of spatial working memory also entails learning a task rule that is contrary to the animals' innate preference. The rats next performed the same matching task over different retention delays. Finally, they were trained on a reversal of the task rule, i.e., to nonmatch to place. Although the lesions produced a clear acquisition impairment on the matching task, there was no evidence of a loss of working memory. A series of control tasks found no appreciable effect on a conditioned cue preference task or on open field activity. The pattern of results shows that medialis dorsalis lesions lead to a selective increase in perseverative behavior that can retard task acquisition. This perseverative deficit closely resembles that observed after prefrontal damage in rats, strongly indicating dysfunction in a common system.

Evolution of post and core systems

Post and core systems have evolved dramatically over the past few years. Some procedures based on the use of resin-composite systems seem destined for failure in the long term. New glass ionomer based systems, employing resin hybrid materials should give rise to fewer complications and prove simpler to use. Nevertheless, intelligent case selection and the application of sound basic design principles are required to make the best use of any system.

The effects of selective lesions within the anterior thalamic nuclei on spatial memory in the rat

Groups of rats received cytotoxic lesions centred in either the anterior thalamic nucleus (AM), the anterior ventral and anterior dorsal thalamic nuclei (AV/AD), or all three nuclei combined (ANT.T). These lesions were made by injecting N-methyl-D-aspartate acid (NMDA). These rats, and a group of surgical controls (SHAM), were trained on a rewarded forced-alternation task in a T-maze. While the selective AM and AV/AD lesions produced an initial acquisition impairment, only the animals with combined lesions (ANT.T) showed a persistent deficit throughout the 16 acquisition sessions. Subsequent testing with a cross-maze confirmed that the SHAM, AV/AD, and AM groups were able to use allocentric cues, while the ANT.T group were impaired. In contrast none of the three anterior groups were impaired on a subsequent egocentric discrimination and reversal task run in the same apparatus. A final test using the eight arm radial-maze, revealed marked deficits in the ANT.T group as well as milder deficits in the AV/AD group. The results from these experiments help to confirm the importance of the anterior thalamic nuclei for allocentric tasks, but suggest that no region is pre-eminently important. The findings also help to account for other studies which have reported that anterior thalamic lesions have seemingly mild effects on tests of spatial memory.

A comparison of the effects of anterior thalamic, mamillary body and fornix lesions on reinforced spatial alternation

The effects of cytotoxic lesions in either the anterior thalamic nuclei or the mamillary bodies were compared with those of fornix lesions on a test of spatial working memory. All three lesions impaired acquisition of a forced alternation task in a T-maze, but the disruptive effects of the mamillary body lesions were significantly less than those following either fornix or anterior thalamic damage. When the alternation task was changed, so as to increase proactive interference, the impairment associated with mamillary body damage became more evident and was now equal in severity to that in the animals with anterior thalamic lesions. The fornix lesion group were the most impaired. In contrast, all three groups performed normally on a test of object recognition. The results add weight to the view that hippocampal--anterior thalamic connections are critical for normal spatial memory and that the relative contribution of the mamillary bodies is task dependent.

The effects of lesions to the fornix and dorsomedial thalamus on concurrent discrimination learning by rats

Rats with lesions in either the fornix or the thalamic nucleus medialis dorsalis were unimpaired on the acquisition of two object discrimination tasks. The same animals were then tested on a concurrent learning task in which various object discriminations were presented at different rates during the same session. This arrangement was primarily designed to minimise any response bias effects. Animals were able to acquire the various concurrent tasks, even when only one trial per day was given for a particular discrimination. It was found that fornix lesions had little or no effect and only produced a mild impairment when the rate of stimulus presentation resembled that used in typical concurrent tasks. Lesions of medialis dorsalis produced a more general, but again mild, deficit. In a final task, the animals were trained to discriminate between two stimuli composed of common elements arranged in different spatial combinations. Fornix lesions impaired acquisition of this spatial configural discrimination, while lesions of medialis dorsalis had a variable effect. The results indicate that fornix lesions can spare concurrent discrimination learning, and that any deficits may be related to interference effects associated with common elements in the stimuli. Lesions in medialis dorsalis appear to affect the initial learning of reward-based performance rules.

Removal of the hippocampus and transection of the fornix produce comparable deficits on delayed non-matching to position by rats

Rats with radiofrequency lesions of the fimbria/fornix or with extensive aspiration lesions of the hippocampal region (the hippocampus proper, dentate gyrus, and subicular complex) were tested on their performance of a delayed non-matching to position task which had been learnt before surgery. On a given trial, one of two sample levers was presented in a random manner. Following a response on this lever and a subsequent delay, both levers were presented and reward was now contingent on a response on the lever that was not used as the sample. Both lesions produced equivalent performance deficits on this test of spatial working memory, the pattern of these deficits being consistent with a mnemonic impairment. The lack of difference between these two groups on a variety of performance measures indicates that hippocampal connections passing through the fornix are not only necessary for this test, but that non-fornical hippocampal connections appear unable on their own to maintain accurate responding.

Ovarian follicular response of mares to GnRH agonist (leuprolide acetate) treatment after pituitary suppression

Follicular growth and ovulation were monitored in 18 horse mares during a control cycle and during a cycle in which the mares received a GnRH agonist, leuprolide acetate (LA; 200 or 400 mug), twice daily until ovulation. Prior to both of these cycles, follicular growth was suppressed using a 10-day estrogen-progesterone treatment regimen, with prostaglandin F-2alpha (10 mg) administered on Day 10. Four of the mares treated with LA remained anovulatory for at least 3 weeks after the end of treatment and were excluded from statistical analysis. The dosage of LA did not affect response. Treatment with LA significantly (P=0.0375) increased the percentage of large follicles per ovulation (i.e., follicles greater than 30 mm in diameter on the day on which the largest follicle reached 35 mm) and also increased (P=0.0539) the diameter of the second largest follicle. However LA did not significantly alter the number of ovulations. Mean daily concentrations of luteinizing hormone (LH) were not significantly different during treatment and control cycles. The LH in blood samples collected repeatedly on Day 19 after the start of estrogen-progesterone treatment did not show a difference in frequency or amplitude of pulses between treatment and control cycles. Mares were artificially inseminated during estrus and the embryos were recovered. Fewer embryos were recovered per ovulation from mares after treatment with LA (26%) than during the control cycle (64%). Results indicate that treatment with LA either suppressed follicular activity or induced multiple follicular growth.

Medial dorsal thalamic lesions and working memory in the rat

Pigmented rats of the DA strain with either radiofrequency or ibotenic acid lesions of the thalamic nucleus medialis dorsalis were postoperatively given nonspatial and spatial tests of working memory. In the nonspatial task, delayed nonmatching-to-sample, rats with both types of thalamic lesions showed acquisition impairments. The subgroup of rats with nucleus medialis dorsalis lesions that were able to reach the acquisition criterion did, however, perform normally when the retention interval was extended to 60 s. In the spatial task, delayed forced-alternation, rats were tested with differing retention intervals and with both spaced and massed trials. Damage to nucleus medialis dorsalis had no effect on acquisition or on spaced trials, but a slight deficit was found in the animals with radiofrequency lesions under the massed trial condition. Much clearer deficits were, however, present in those animals in which the lesion extended appreciably into the anterior thalamic nuclei. The findings indicate that while cellular damage to nucleus medialis dorsalis may disrupt learning, some impairments in tests of spatial working memory attributed to this nucleus may reflect damage to the adjacent anterior thalamic nuclei.

The effects of mammillary body and combined amygdalar-fornix lesions on tests of delayed non-matching-to-sample in the rat

A series of experiments compared the effects of mammillary body lesions with those of combined damage to the amygdala and fornix on 2 tests of working memory, both of which used the delayed non-matching-to-sample rule. This comparison was based on evidence of the involvement of these regions in anterograde amnesic syndromes. The mammillary body lesions had no effect on the acquisition or subsequent performance of a non-spatial recognition task and had only a mild effect on the acquisition of a spatial forced-alternation task. Although the animals with combined amygdalar plus fornix lesions were able to master the non-spatial recognition task they were impaired when the levels of proactive interference were increased. The same animals were also severely impaired on the forced-choice alternation task. The overall pattern of results is seen as mirroring those found in primates and points to an underlying similarity in the mnemonic roles of these limbic regions.

Ultrasound as an aid to diagnosis of granulosa cell tumour in the mare

The ultrasonic appearance of seven cases of granulosa cell tumour is described, and compared with an ovarian haematoma and an ovarian serous cystadenoma. The granulosa cell tumours varied from being uniformly dense to having one or several large fluid filled cysts. Some tumours resembled the haematoma or cystadenoma and also, in some aspects, normal ovarian structures such as corpora haemorrhagica or follicles in early pregnancy. There was no typical ultrasonographic appearance of the granulosa cell tumours which enabled definitive diagnosis. However, ultrasound may be a diagnostic aid when used in conjunction with the history and findings on rectal palpation.

Cervical hyperplasia with prolapse in a mare

Cervical hyperplasia with prolapse through the vulvar lips was documented in a mare. Postmortem examination indicated that the mass originated from the cervical wall. The surface of the prolapsed mass had histologic features of normal cervix. Cervical hyperplasia can be considered in a list of differential diagnoses in cases of prolapse of the internal genitalia in mares.

The future of esthetic dentistry

The materials and techniques of esthetic dentistry are provoking reconsideration of the basic principles of operative dentistry. Cavity preparations can be minimized, demands on retention are altered, and prevention can be practiced. Problems remain, particularly in bonding and sealing to dentin. The newer materials have yet to prove themselves in terms of durability, especially in regard to fracture and wear.

The effects of hippocampal lesions upon spatial and non-spatial tests of working memory

A series of experiments examined the proposal that the primary effect of hippocampal damage in rats is to disrupt working memory. Although extensive hippocampal lesions produced a severe impairment in forced-choice alternation--a test of spatial working memory--the same lesions did not impair the acquisition of a non-spatial test of working memory--delayed non-matching-to-sample. This test of object recognition required the rats to select that arm in a Y-maze which contained unfamiliar stimuli. Rats with hippocampal lesions were able to learn and perform this task at normal rates, even with retention delays of as long as 60 s. Two additional experiments helped confirm that the animals had indeed learnt a non-spatial test of working memory. The final experiment examined whether hippocampal lesions resulted in an increased sensitivity to proactive interference. It was found that repetition of test stimuli within a session, which increased interference, did attenuate recognition performance but there was no evidence that the animals with hippocampal lesions were differentially affected.

Influence of airway and airspace sizes on particle deposition in excised donkey lungs

Tests of aerosol deposition with breath holding and of lung function were performed on the excised lungs of three donkeys following regional in vivo radioaerosol deposition tests. Corrosion casts were made of the lungs to determine the dimensions of the tracheobronchial (TB) tree, and histological sections were taken to determine average alveolar airspace size. Static lung function tests, i.e., static compliance and specific compliance (Cstat and Cspec), agreed well with the predicted and reported in vivo values, as did the slope of Phase III from the single breath nitrogen washout (SBNW). Dynamic tests, i.e., dynamic compliance (Cdyn) and pulmonary resistance (Rpulm), displayed larger inter- and intra-subject variation, and showed poor agreement with reported in vivo values. Breathholding tests using 0.55 micron diameter aerosol indicated a mean respiratory airspace dimension of 0.16 mm, while the mean alveolar diameter from the lung sections was 0.19 mm. Breathholding tests with 1.18 micron aerosol indicated a mean small airway size of 0.65 mm, corresponding to the sizes of small airways on the corrosion casts. The donkeys have larger central airways but smaller peripheral airways than humans, and greater tracheobronchial deposition efficiency for 5 micron diameter particles. Tracheobronchial deposition in donkeys appears to be concentrated more distally than in humans, and may be related to the monopodal airway branching pattern in the former.

Safety aspects of mandibular lingual surgery

Mandibular lingual surgery is commonly used in periodontal practice. There are inherent risks in such surgery which are illustrated by a case report described here. This was a case in which an emergency tracheotomy was needed after a minor procedure which involved lingual tissues. The potential problems of any form of lingual surgery are discussed. Various other surgical procedures in this region are examined in order to establish some surgical principles which may be of use to periodontists.