Comparison of three methods detection of slime production by Staphylococcus aureus and Staphylococcus epidermidis

In this article, slime production of Staphylococcus aureus and Staphylococcus epidermidis strains from infective skin lesions was evaluated by three different methods: Congo red agar method (CRA), Christensen tube method (CT) and spectrophotometric method (SC). All strains by CT method interpreted as negative (dark-claret or red colonies of the surface). 12 (37.5%) strains of S. aureus, 16 (50.0%) strains of S. epidermidis produced slime as shown by CT method, 6 (18.7%) strains of S. aureus, 8 (25,0%) strains of S. epidermidis by SC method. They also found a correlation of slime production by CT and SC method (p > 0.05).     

Intérêt de l’interprétation collégiale de l’échographie cervicale,de la scintigraphie 99mTc-MIBI et de la TEP-TDM à la 18-Fluorocholine dans l’hyperparathyroïdie primaire : expérience du service de médecine nucléaire de l’hôpital Cochin

ObjectivesThis study aims to assess performances of preoperative conventional imaging (99mTc-MIBI scintigraphy, cervical Ultrasonography) and 18F-fluorocholine PET/CT (FCH PET/CT) exams in the detection of hyperfunctioning parathyroid gland(s) in patients operated from primary hyperparathyroidism (pHPT).MethodsBefore surgery, 51 consecutive patients with biochemically confirmed pHPT had successively cervical ultrasonography (cUS), 99mTc-MIBI scintigraphy and FCH PET/CT, all performed in the same Nuclear Medicine Department. 99mTc-MIBI scintigraphy were performed immediatly after cUS and interpreted by same operators. FCH PET/CT exam were interpreted independently by two nuclear medicine physicians. An additional interpretation session integrating the three imaging modalities read in consensus as a combined imaging set was performed.ResultsAt surgery, 69 lesions were removed: 32 parathyroid adenoma and 37 parathyroid hyperplasia. 70% of patients had single-gland disease and 30% had multiglandular disease at histopathology analysis. In the patient-based analysis, sensitivity and accuracy in the detection of single gland disease) for FCH PET/CT, cUS and for 99mTc-MIBI scintigraphy were 86% [0.71–0.94] and 86% [0.70–0.95], 69% [0.52–0.81] and 69% [0.51–0.83], 40% [0.26–0.56] and 40% [0.24–0.58], respectively. Sensitivity and accuracy of the combined imaging set for the detection of single gland disease were 94% [0.81–0.99] and 94% [0.81–0.99].ConclusionOur results suggest that cUS/99mTc-MIBI scintigraphy and FCH PET/CT interpreted during a comprehensive session could be the ideal practice to precisely localize parathyroid lesion(s) in patients with pHPT before surgery.     

Orogastric vaccination of guinea pigs with Helicobacter pylori sonicate and a high dose of cholera toxin lowers the burden of infection

Guinea pigs were vaccinated orogastrically with Helicobacter pylori cell sonicate (CS) and 10 microg or 100 microg cholera toxin (CT) or CT only. Nai;ve animals were used as a control. In both experiments, vaccination primed the local IgG and IgA response, irrespective of the CT dose. After challenge, only the group of animals immunised with CS and 100 microg CT had a significantly lower number of H. pylori in the antral region of the stomach, but vaccination did not prevent H. pylori infection. This protective effect was not associated with a switch in IgG subclass, which remained predominantly IgG2. The levels of specific antibodies in serum and the gastric mucosa which were similar to naive unprotected animals. In conclusion, the ability of mucosal adjuvants such as CT to induce a protective immune response may be host dependent and findings in the Helicobacter-mouse model should be interpreted with caution.     

Ontogenic Studies of Antigen Binding Cells in the Dual Thymus Glands of the South American Rodent, Octodon degus

Octodon degus (the degu) has two anatomically separate thymusglands, a cervical thymus (CT) and a mediastinal thymus (MT).Antigen binding cells taken from the two thymic components offetal and neonatal degus were enumerated by incubation withbeta-galactosidase (Gz) as antigen, followed by incubation with5-bromo-4-chloro-3-indolylbeta- D- galactoside (BIG). Gz cleavageof BIG on the surfaces of Gz antigen binding cells (ABC's) producesan indoxan catalytic product which stains the cell blue. Histochemicallytained cells are interpreted as antigen binding cells with antigenreceptors specific for Gz. The frequencies of ABC's in neonatalCT and MT were approximately 0.1% and 0.01%. Cortisone treatmentincreased the frequency of Gz ABC's, whereas Gz immunizationresulted in a rapid elimination of Gz ABC's. Cortisone treatmentdelayed the loss of Gz ABC's in neonatal degus treated withboth cortisone and Gz. Both fetal and neonatal degus may haveno detectable Gz ABC's in either CT, or MT, or both. The dataare interpreted with respect to current hypotheses for maturationof immunological repertoire, and pluripotentiality versus unipotentialityof antigen sensitive cells. The cervical and mediastinal thymiccomponents of the degu may serve as independent sites for thedevelopment of immunocompetent thymocytes.     

The Neanderthal face is not cold adapted

Many morphological features of the Pleistocene fossil hominin Homo neanderthalensis, including the reputed large size of its paranasal sinuses, have been interpreted as adaptations to extreme cold, as some Neanderthals lived in Europe during glacial periods. This interpretation of sinus evolution rests on two assumptions: that increased craniofacial pneumatization is an adaptation to lower ambient temperatures, and that Neanderthals have relatively large sinuses. Analysis of humans, other primates, and rodents, however, suggests that the first assumption is suspect; at least the maxillary sinus undergoes a significant reduction in volume in extreme cold, in both wild and laboratory conditions. The second assumption, that Neanderthal sinuses are large, extensive, or even ‘hyperpneumatized,’ has held sway since the first specimen was described and has been interpreted as the causal explanation for some of the distinctive aspects of Neanderthal facial form, but has never been evaluated with respect to scaling. To test the latter assumption, previously published measurements from two-dimensional (2D) X-rays and new three-dimensional (3D) data from computed tomography (CT) of Neanderthals and temperate-climate European Homo sapiens are regressed against cranial size to determine the relative size of their sinuses. The 2D data reveal a degree of craniofacial pneumatization in Neanderthals that is both commensurate with the size of the cranium and comparable in scale with that seen in temperate climate H. sapiens. The 3D analysis of CT data from a smaller sample supports this conclusion. These results suggest that the distinctive Neanderthal face cannot be interpreted as a direct result of increased pneumatization, nor is it likely to be an adaptation to resist cold stress; an alternative explanation is thus required.     

Exploring avenues for best use of cytotechnologists in non‐gynaecological cytology: Double screening or independent sign‐out

Objective

Cytotechnologist (CT) screening workload has been decreasing due to the falling number of Papanicolaou tests. This continuing trend has prompted exploration of ways to best employ the CT skillset. One potential way of more effective use is by having two CTs double screen non‐gynaecological (NGC) cases to assess whether this improves screening quality and concordance with pathologists. Another is evaluating the CT's performance on low‐complexity negative NGC cases for a potential independent CT sign‐out without pathologist review.

Methods

In total, 1119 NGC cases were reviewed; 577 screened by two CTs and 542 screened by one CT. All cases were signed out by a pathologist and all CT interpretations were compared to the pathologist final diagnoses. The disagreements were classified based on degree of discrepancy. The extra workload by adding the second screener was assessed.

Results

The agreement rate between the CT's screening interpretation and pathologist's interpretation did not improve by adding a second CT compared to a single screener (91.5% vs 92.9%, respectively). CT to pathologist concordance was very high on low complexity NGC cases (voided urine, fluid, sputum) whether screened and interpreted as negative by one CT (97.3%) or two CTs (99.3%).

Conclusion

Double screening of NGC cases by two cytotechnologists prior to pathologist sign‐out does not improve screening quality and is not cost‐effective. The high concordance between the CTs and pathologists in this limited group of low complexity negative cases suggests that such cases could be signed out independently by cytotechnologists.     

18F-fluoro-deoxy-glucose focal uptake in very small pulmonary nodules: fact or artifact? Case reports

ABSTRACT: BACKGROUND: F-fluoro-deoxy-glucose (18F-FDG) positron emission tomography integrated/combined with computed tomography (PET-CT) provides the best diagnostic results in the metabolic characterization of undetermined solid pulmonary nodules. The diagnostic performance of 18F-FDG is similar for nodules measuring at least 1 cm and for larger masses, but few data exist for nodules smaller than 1 cm. CASE PRESENTATION: We report five cases of oncologic patients showing focal lung 18F-FDG uptake on PET-CT in nodules smaller than 1 cm. We also discuss the most common causes of 18F-FDG false-positive and false-negative results in the pulmonary parenchyma. In patient 1, contrast-enhanced CT performed 10 days before PET-CT did not show any abnormality in the site of uptake; in patient 2, high-resolution CT performed 1 month after PET showed a bronchiole filled with dense material interpreted as a mucoid impaction; in patient 3, contrast-enhanced CT performed 15 days before PET-CT did not identify any nodules; in patients 4 and 5, contrast-enhanced CT revealed a nodule smaller than 1 cm which could not be characterized. The 18F-FDG uptake at follow-up confirmed the malignant nature of pulmonary nodules smaller than 1 cm which were undetectable, misinterpreted, not recognized or undetermined at contrast-enhanced CT. CONCLUSION: In all five oncologic patients, 18F-FDG was able to metabolically characterize as malignant those nodules smaller than 1 cm, underlining that: 18F-FDG uptake is not only a function of tumor size but it is strongly related to the tumor biology; functional alterations may precede morphologic abnormalities. In the oncologic population, especially in higher-risk patients, PET can be performed even when the nodules are smaller than 1 cm, because it might give an earlier characterization and, sometimes, could guide in the identification of alterations missed on CT.     

Elimination of biological and physical artifacts in abdomen and brain computed tomography procedures using filtering techniques

IntroductionMedical images are usually affected by biological and physical artifacts or noise, which reduces image quality and hence poses difficulties in visual analysis, interpretation and thus requires higher doses and increased radiographs repetition rate.ObjectivesThis study aims at assessing image quality during CT abdomen and brain examinations using filtering techniques as well as estimating the radiogenic risk associated with CT abdomen and brain examinations.Materials and MethodsThe data were collected from the Radiology Department at Royal Care International (RCI) Hospital, Khartoum, Sudan. The study included 100 abdominal CT images and 100 brain CT images selected from adult patients. Filters applied are namely: Mean filter, Gaussian filter, Median filter and Minimum filter. In this study, image quality after denoising is measured based on the Mean Squared Error (MSE), Peak Signal-to-Noise Ratio (PSNR), and the Structural Similarity Index Metric (SSIM).ResultsThe results show that the images quality parameters become higher after applications of filters. Median filter showed improved image quality as interpreted by the measured parameters: PSNR and SSIM, and it is thus considered as a better filter for removing the noise from all other applied filters.DiscussionThe noise removed by the different filters applied to the CT images resulted in enhancing high quality images thereby effectively revealing the important details of the images without increasing the patients’ risks from higher doses.ConclusionsFiltering and image reconstruction techniques not only reduce the dose and thus the radiation risks, but also enhances high quality imaging which allows better diagnosis.     

Thyroid C cells of middle-aged rats treated with estradiol or calcium

 The structure and function of C cells of middle-aged female rats (14-months old) treated with estradiol dipropionate (EDP), calcium (Ca) or a combination of EDP+Ca were studied. A stereological method was used to determine the volume of calcitonin (CT)-immunoreactive C cells and their nuclei, and the relative volume density and mean number of the C cells per section were calculated. Serum levels of CT, osteocalcin, parathyroid hormone (PTH), and β-estradiol were also measured. A significant decrease in body weight of the rats treated with EDP or EDP+Ca was observed. These treatments led to a significant decrease in cellular and nuclear volumes, relative volume density, and mean number of C cells per section, in comparison with the corresponding controls. A reduction of the serum level of CT, PTH, and osteocalcin was also recorded in EDP- and EDP+Ca-treated animals. No statistically significant differences between Ca- and vehicle-injected rats, with regard to all morphometric C cell parameters and biochemical values determined, were seen. However, a conspicuous degranulation of the C cells and decreased immunoreactivity for CT in the Ca-receiving group, which could be interpreted as the signs of increased activity of these cells, were noticed. This effect of Ca was also observed in rats injected with EDP and Ca in combination, when the inhibitory effect of EDP on C cell function was less noticeable than in the group treated with EDP alone. Accepted: 29 July 1997     

Viability and rate of development at different temperatures in Drosophila: a comparison of constant and alternating thermal regimes

Populations belonging to the sibling species Drosophila melanogaster and D. simulans were collected in Southwestern France and Southern Spain, and investigated under constant (CT) and alternating (AT) temperature regimes. Development under CT was possible between 11 and 32 degrees C and egg-to-adult viability curves were almost 'rectangular', with a sharp decrease below 14 and above 29 degrees C. Rate of development followed a complex non-linear curve. A model described the curve as an exponential below a critical temperature (T(C)), and above T(C) as the difference between this function and another exponential which is assumed to show deleterious effects of heat. Developmental rates under two daily 12-h phases with various mid-temperatures and thermal amplitudes were compared to expected rates calculated from the above model. Acceleration effects were observed at four AT (in increasing order: 12-30, 9-21, 11-21, 16-26 degrees C); retardation occurred at three other ones (in increasing order, 7-21, 5-15, 7-29 degrees C). When expressed by the ratio observed/expected, the effects could be predicted using a multiple regression, as a positive function of the thermal amplitude and a negative one of the mid-temperature. Viability under AT was analysed considering an equivalent developmental temperature (EDT), that is the CT which would produce the same rate or development. Very low viabilities occurred under broad amplitude regimes, but the deleterious effects of some extreme temperatures, that would be lethal under CT, could be recovered by daily return to a moderate temperature. The two species exhibited slight but significant differences in their characteristic temperatures: developmental zero, critical temperature, temperature of maximum rate, upper developmental limit. All data may be interpreted by considering that D. simulans compared to D. melanogaster is more tolerant to cold but less tolerant to heat.     

Charge-transfer photochemistry under high pressure: Reductive elimination from trans-diazidotetracyanoplatinate(IV)

The quantum yield for the reductive elimination of azide from trans-Pt(CN)₄(N₃)₂²⁻ to yield P-(CN)₄²⁻ and molecular nitrogen in aqueous solution was studied as a function of pressure up to 200 MPa. The resulting volume of activation of 8.1 ± 0.4 cm³ mol⁻¹ is interpreted as evidence for the formation of a caged radical species via simultaneous scission of both PtN₃ bonds in the CT excited state. Similar measurements in ethanol result in a volume of activation of 14.3 ± 0.9 cm³ mol⁻¹. An additional deactivation route for the CT excited state is suggested to account for this result.     

Hidden termite coprolites revealed by Synchrotron microtomography inside Eocene–Oligocene filled wood-borings from the Malzieu Basin,Lozère,southern France

Fragments of filled wood-borings were recently discovered from the Eocene–Oligocene Conglomerate and Sandstone Formation of the Malzieu Basin (Lozère, southern France). Propagation phase-contrast X-ray synchrotron microtomography (PPC-SRμCT) was used to characterize their hidden inner structures. Virtual 2D sections and 3D reconstructions show that the inner microstructures of borings display a mudstone–wackestone siliceous matrix including tiny coprolites. The hexagonal cross-section of these coprolites is characteristic of termite faecal pellets. Morphology and dimensions of the coprolites share strong similarities with those of extant Kalotermitidae (drywood termites). The depositional environment is interpreted as a fluvial valley in which the lenticular sandstone and conglomerate lenses correspond to channels. This discovery complements the record of Palaeogene termites which remain poor in France and throughout the world.     

Effect of dioxane on the structure and hydration-dehydration of alpha-chymotrypsin as measured by FTIR spectroscopy

A new experimental approach based on FTIR spectroscopic measurements was proposed to study simultaneously the adsorption/desorption of water and organic solvent on solid enzyme and corresponding changes in the enzyme secondary structure in the water activity range from 0 to 1.0 at 25 degrees C. The effect of dioxane on the hydration/dehydration and structure of bovine pancreatic alpha-chymotrypsin (CT) was characterized by means of this approach. Dioxane sorption exhibits pronounced hysteresis. No sorbed dioxane was observed at low water activities (a(w)<0.5) during hydration. At a(w) about 0.5, a sharp increase in the amount of sorbed dioxane was observed. Dioxane sorption isotherm obtained during dehydration resembles a smooth curve. In this case, CT binds about 150 mol dioxane/mol enzyme at the lowest water activities. Three different effects of dioxane on the water binding by the initially dried CT were observed. At a(w)<0.5, water adsorption is similar in the presence and absence of dioxane. It was concluded that the presence of dioxane has little effect on the interaction between enzyme and tightly bound water at low a(w). At a(w)>0.5, dioxane increases the amount of water bound by CT during hydration. This behavior was interpreted as a dioxane-assisted effect on water binding. Upon dehydration at low water activities, dioxane decreases the water content at a given a(w). This behavior suggests that the suppression in the uptake of water during dehydration may be due to a competition for water-binding sites on chymotrypsin by dioxane. Changes in the secondary structure of CT were determined from infrared spectra by analyzing the structure of amide I band. Dioxane induced a strong band at 1628 cm(-1) that was assigned to the intermolecular beta-sheet aggregation. Changes in the intensity of the 1628 cm(-1) band agree well with changes in the dioxane sorption by CT. An explanation of the dioxane effect on the CT hydration and structure was provided on the basis of hypothesis on water-assisted disruption of polar contacts in the solid enzyme. The reported results demonstrate that the hydration and structure of alpha-chymotrypsin depend markedly on how enzyme has been hydrated - whether in the presence or in the absence of organic solvent. A qualitative model was proposed to classify the effect of hydration history on the enzyme activity-a(w) profiles.     

Implications of False Negative and False Positive Diagnosis in Lymph Node Staging of NSCLC by Means of 18F-FDG PET/CT

Background

Integrated ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) is widely performed in hilar and mediastinal lymph node (HMLN) staging of non-small cell lung cancer (NSCLC). However, the diagnostic efficiency of PET/CT remains controversial. This retrospective study is to evaluate the accuracy of PET/CT and the characteristics of false negatives and false positives to improve specificity and sensitivity.

Methods

219 NSCLC patients with systematic lymph node dissection or sampling underwent preoperative PET/CT scan. Nodal uptake with a maximum standardized uptake value (SUVmax) >2.5 was interpreted as PET/CT positive. The results of PET/CT were compared with the histopathological findings. The receiver operating characteristic (ROC) curve was generated to determine the diagnostic efficiency of PET/CT. Univariate and multivariate analysis were conducted to detect risk factors of false negatives and false positives.

Results

The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of PET/ CT in detecting HMLN metastases were 74.2% (49/66), 73.2% (112/153), 54.4% (49/90), 86.8% (112/129), and 73.5% (161/219). The ROC curve had an area under curve (AUC) of 0.791 (95% CI 0.723-0.860). The incidence of false negative HMLN metastases was 13.2% (17 of 129 patients). Factors that are significantly associated with false negatives are: concurrent lung disease or diabetes (p<0.001), non-adenocarcinoma (p<0.001), and SUVmax of primary tumor >4.0 (p=0.009). Postoperatively, 45.5% (41/90) patients were confirmed as false positive cases. The univariate analysis indicated age > 65 years old (p=0.009), well differentiation (p=0.002), and SUVmax of primary tumor ≦4.0 (p=0.007) as risk factors for false positive uptake.

Conclusion

The SUVmax of HMLN is a predictor of malignancy. Lymph node staging using PET/CT is far from equal to pathological staging account of some risk factors. This study may provide some aids to pre-therapy evaluation and decision-making.     

Functional inference of the methylenetetrahydrofolate reductase 677 C > T and 1298A > C polymorphisms from a large-scale epidemiological study

Two functional single nucleotide polymorphisms, 677C > T and 1298A > C have been described for the methylenetetrahydrofolate (MTHFR) gene. Both are associated with reduced enzyme activity in vitro. For the 677T, but not the 1298C allele, significantly lower serum folate and higher plasma total homocysteine (tHcy) have been reported. We genotyped 10,034 middle-aged (50–64 years old) subjects and measured serum folate and tHcy. Within strata of 677 genotypes, 1,298 genotypes had significantly different serum folate and tHcy (P ≤ 0.03 for all comparisons). Each additional 1298C allele reduced mean serum folate and increased mean tHcy, by (on average) 4.5 and 3.0%, respectively. In comparison, within strata of 1,298 genotypes, the increase from no, to one 677T-allele reduced serum folate and increased tHcy by, 7.1 and 6.3%, respectively. Lowest serum folate and highest tHcy level was found for the 677TT/1298AA genotype. The difference in tHcy was significantly larger at low folate than at high folate when genotypes 677TT/1298AA and 677CT/1298AA, 677CT/1298AC and 677CC/1298AC, and genotypes 677CT/1298AC and 677CT/1298AA were compared. We interpreted these data in the context of a model of the MTHFR enzyme that describes the enzyme as a dimer that mainly exist in six different configurations. The model reconciled the observed phenotypic effects of the 677/1,298 combination genotypes with previous in vitro measurements, and identified enzyme configurations that are sensitive to low folate levels. In conclusion, this report demonstrates functional inference of the MTHFR 677 C > T and 1,298 A > C polymorphisms from a large-scale epidemiological study.     

Synthesis, crystal structure and charge transfer spectra of dinuclear copper(I) complexes bearing 1,2-bis(arylimino)acenaphthene acceptor ligands

A series of dinuclear halide bridged copper(I) complexes with a central [Cu₂(μ-X)₂] diamond core (X = Cl, Br and I) and substituted bis(imino)acenaphthene (BIAN) ligands acting as strong π-acceptor subunits was prepared and characterized by elemental analysis, X-ray crystallography and various spectroscopic techniques. In the visible spectral range, the electronic spectra of these deeply colored air-stable compounds are dominated by low-lying charge transfer (CT) transitions. The corresponding broad absorption bands display a bathochromic shift and a decreasing amount of negative solvatochromism in the series X = Cl, Br and I. At the same time, the distance between the two metals becomes shorter and reaches the range of cuprophilic interactions. These systematic trends are interpreted as a decreasing amount of charge transfer character and a more pronounced delocalization between the two copper centers within in the same series.     

Different patterns of circadian oscillation in the suprachiasmatic nucleus of hamster,mouse, and rat

Although spontaneous neural firing in the mammalian suprachiasmatic nucleus is accepted to peak once during mid-subjective day, dual activity peaks have been reported in horizontal brain slices taken from hamsters. These two peaks were interpreted as new evidence for the theory of dual circadian oscillators and raised the expectation that such activity would be found in other circadian model systems. We examined hamster, mouse, and rat slices in both coronal and horizontal planes and found a second peak of activity only in hamster horizontal preparations. This raises interesting questions about the relative circadian physiology of these important experimental animals.Abbreviations CT circadian time - SCN suprachiasmatic nucleus P.W. Burgoon and P.T. Lindberg contributed equally to this work.     

Computed tomography scanning as a tool for linking the skeletal and otolith‐based fossil records of teleost fishes

Micro‐computed tomography (μCT) scanning now represents a standard tool for non‐destructive study of internal or concealed structure in fossils. Here we report on otoliths found in situ during routine μCT scanning of three‐dimensionally preserved skulls of Palaeogene and Cretaceous fishes. Comparisons are made with isolated otolith‐based taxa to attempt correlations between the body fossil and otolith fossil records. In situ otoliths previously extracted mechanically from specimens of Apogon macrolepis and Dentex laekeniensis match our μCT models. In some cases, we find a high degree of congruence between previously independent taxonomic placements for otolith and skeletal remains (Rhinocephalus, Osmeroides, Hoplopteryx). Unexpectedly, in situ otoliths of the aulopiform Apateodus match isolated otoliths of Late Cretaceous age previously interpreted as belonging to gempylids, a group of percomorph fishes that do not appear in the body fossil record until the Palaeogene. This striking example of convergence suggests constraints on otolith geometry in pelagic predators. The otoliths of Apateodus show a primitive geometry for aulopiforms and lack the derived features of Alepisauroidea, the lizardfish clade to which the genus is often attributed. In situ otoliths of Early Cretaceous fishes (Apsopelix and an unidentified taxon) are not well preserved, and we are unable to identify clear correlations with isolated otolith morphologies. We conclude that the preservation of otoliths suitable for μCT scanning appears to be intimately connected with the taphonomic history, lithological characteristics of surrounding matrix, and syn‐ and postdepositional diagenetic effects.     

The relation between external dimensions of the human mandible and cortical bone morphology as determined with the aid of CT scans

Computerized tomographs were taken of 22 mandibles, selected from an early Arab population and aged between 17 and 60 years. A specially designed holder was used to define specific locations along the mandible, namely symphysis, mid sagittal section through the corpus, midpoint of the first molar (M1), gonion and ramus. Cortical cross sectional area and principal moments of inertia were then calculated for the locations specified, to obtain estimates of the resistance of the bone to deformation. They were analyzed in relation to age, sex, side and external dimensions of the mandible. The error of measurement calculated from (i) repeated CT scans (ii) repeated measurements (iii) from comparison of CT scans with a sectioned mandible, were of the same order of magnitude. All values were greater in males than in females; they were only slightly affected by age and were unaffected by side. Mandibular length and ramus height accounted for most of the variation observed in moments of inertia. We consider that these results can best be interpreted in accordance with the hypotheses put forward by Hylander (1975, 1985) according to which the mandible acts as a third degree lever, with “wishboning” forces acting at the symphysis and parasagittal bending at the first molar. We now plan to apply this method to study the “strength” of the mandibles of past populations with different dietary adaptations.