Deep Learning and Multimodal Artificial Intelligence in Orthopaedic Surgery

This review article focuses on the applications of deep learning with neural networks and multimodal neural networks in the orthopaedic domain. By providing practical examples of how artificial intelligence (AI) is being applied successfully in orthopaedic surgery, particularly in the realm of imaging data sets and the integration of clinical data, this study aims to provide orthopaedic surgeons with the necessary tools to not only evaluate existing literature but also to consider AI's potential in their own clinical or research pursuits. We first review standard deep neural networks which can analyze numerical clinical variables, then describe convolutional neural networks which can analyze image data, and then introduce multimodal AI models which analyze various types of different data. Then, we contrast these deep learning techniques with related but more limited techniques such as radiomics, describe how to interpret deep learning studies, and how to initiate such studies at your institution. Ultimately, by empowering orthopaedic surgeons with the knowledge and know-how of deep learning, this review aspires to facilitate the translation of research into clinical practice, thereby enhancing the efficacy and precision of real-world orthopaedic care for patients.

Lifetime cost-effectiveness analysis osseointegrated transfemoral versus socket prosthesis using Markov modelling

Aims

Prior cost-effectiveness analyses on osseointegrated prosthesis for transfemoral unilateral amputees have analyzed outcomes in non-USA countries using generic quality of life instruments, which may not be appropriate when evaluating disease-specific quality of life. These prior analyses have also focused only on patients who had failed a socket-based prosthesis. The aim of the current study is to use a disease-specific quality of life instrument, which can more accurately reflect a patient's quality of life with this condition in order to evaluate cost-effectiveness, examining both treatment-naïve and socket refractory patients.

Methods

Lifetime Markov models were developed evaluating active healthy middle-aged male amputees. Costs of the prostheses, associated complications, use/non-use, and annual costs of arthroplasty parts and service for both a socket and osseointegrated (OPRA) prosthesis were included. Effectiveness was evaluated using the questionnaire for persons with a transfemoral amputation (Q-TFA) until death. All costs and Q-TFA were discounted at 3% annually. Sensitivity analyses on those cost variables which affected a change in treatment (OPRA to socket, or socket to OPRA) were evaluated to determine threshold values. Incremental cost-effectiveness ratios (ICERs) were calculated.

Results

For treatment-naïve patients, the lifetime ICER for OPRA was $279/quality-adjusted life-year (QALY). For treatment-refractory patients the ICER was $273/QALY. In sensitivity analysis, the variable thresholds that would affect a change in the course of treatment based on cost (from socket to OPRA), included the following for the treatment-naïve group: yearly replacement components for socket > $8,511; cost yearly replacement parts OPRA < $1,758; and for treatment-refractory group: yearly replacement component for socket of > $12,467.

Conclusion

The use of the OPRA prosthesis in physically active transfemoral amputees should be considered as a cost-effective alternative in both treatment-naïve and treatment-refractory socket prosthesis patients. Disease-specific quality of life assessments such as Q-TFA are more sensitive when evaluating cost-effectiveness.

Venous malformation may be a feature of EXT1-related hereditary multiple exostoses: A report of two unrelated probands

Hereditary multiple exostoses (HME), also known as hereditary multiple osteochondroma (HMO), is an autosomal dominant disorder caused by pathogenic variants in exostosin-1 or -2 (EXT1 or EXT2). It is characterized by the formation of multiple benign growing osteochondromas (exostoses) that most commonly affect the long bones; however, it may also occur throughout the body. Although many of these lesions are clinically asymptomatic, some can lead to chronic pain and skeletal deformities and interfere with adjacent neurovascular structures. Here, we report two unrelated probands that presented with a clinical and molecular diagnosis of HME with venous malformation, a clinical feature not previously reported in individuals with HME.

Differential Extraction with Purification via Organic/Microcon® and Promega DNA IQ™ Methods

The differential extraction method allows for the separation of sperm cell DNA from non-sperm cell DNA by incorporating two separate lysis steps. This is crucial in forensic casework, as sexual assault samples frequently deal with a mixture of seminal fluid and other body fluids. After performing a differential lysis, DNA extraction can be completed through a variety of methods. In addition to the differential lysis, two methods will be described in this chapter for DNA purification: Organic (Phenol)/Microcon® purification and purification with the Promega DNA IQ™ System.

Modeling time from bone metastasis to death in a racially diverse cohort of military health care beneficiaries

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Background: Development of prostate cancer (PCa) metastasis, while uncommonly observed in US men, typically occurs to bone and ultimately leads to disease-specific death. The goal of this study was to estimate OS in a racially diverse cohort of military health care beneficiaries diagnosed with metastatic PCa to bone, to enhance understanding of factors such as patient race and receipt of palliative treatment, that potentially affect OS in advanced PCa patients. Methods: A retrospective cohort study was conducted, examining men consented to participate in the CPDR multi-center national database who underwent biopsy for suspicion of prostate cancer between 1989-2017 and subsequently diagnosed with bone metastasis, confirmed by bone scan, bone biopsy and/or MRI. Multivariable Cox proportional hazards (PH) analysis was used to model OS as a function of race and palliative treatment, controlling for clinical covariates. Hazard ratios (HR) and 95% Confidence intervals (CI) are reported. Results: Among 17,356 patients diagnosed with prostate cancer (PCa) between 1989 and 2017, 869 (5.0%) developed bone metastasis. Median patient age was 67 years; median follow-up time following diagnosis with bone metastasis was 2.4 years. Over one-fifth of patients (22.5%) self-reported as African American. Only 11.5% of all patients with metastasis received palliative treatment (radiation (RT) only, RT+ hormone therapy (HT), RT+HT, or RT+HT+chemotherapy). While race did not predict OS, receipt of palliative treatment was strongly predictive of better OS (p<0.0005). Conclusions: Patient race did not predict OS among those with distant metastatic PCa but receipt of palliative care and slower PSADT were critical factors in lengthening OS. This work is being extended to examine the combinations and sequencing of palliative care on OS, to provide improved patient-tailored prediction tools for men with advanced prostate cancer. [Table: see text]

The Effect of Surgical Technique and Spacer Texture on Bone Regeneration: A Caprine Study Using the Masquelet Technique

BACKGROUND

The Masquelet-induced-membrane technique is a commonly used method for treating segmental bone defects. However, there are no established clinical standards for management of the induced membrane before grafting.

QUESTIONS/PURPOSES

Two clinically based theories were tested in a chronic caprine tibial defect model: (1) a textured spacer that increases the induced-membrane surface area will increase bone regeneration; and (2) surgical scraping to remove a thin tissue layer of the inner induced-membrane surface will enhance bone formation.

METHODS

Thirty-two skeletally mature female goats were assigned to four groups: smooth spacer with or without membrane scraping and textured spacer with or without membrane scraping. During an initial surgical procedure (unilateral, left tibia), a defect was created excising bone (5 cm), periosteum (9 cm), and muscle (10 g). Segments initially were stabilized with an intramedullary rod and an antibiotic-impregnated polymethylmethacrylate spacer with a smooth or textured surface. Four weeks later, the spacer was removed and the induced-membrane was either scraped or left intact before bone grafting. Bone formation was assessed using micro-CT (total bone volume in 2.5-cm central defect region) as the primary outcome; radiographs and histologic analysis as secondary outcomes, with the reviewer blinded to the treatment groups of the samples being assessed 12 weeks after grafting. All statistical tests were performed using a linear mixed effects model approach.

RESULTS

Micro-CT analysis showed greater bone formation in defects with scraped induced membrane (mean, 3034.5 mm³; median, 1928.0 mm³; quartile [Q]1-Q3, 273.3-2921.1 mm³) compared with defects with intact induced membrane (mean, 1709.5 mm³; median, 473.8 mm³; Q1-Q3, 132.2-1272.3 mm³; p = 0.034). There was no difference in bone formation between textured spacers (mean, 2405.5 mm³; median, 772.7 mm³; Q1-Q3, 195.9-2743.8 mm³) and smooth spacers (mean, 2473.2 mm³; median, 1143.6 mm³; Q1-Q3, 230.2-451.1 mm³; p = 0.917).

CONCLUSIONS

Scraping the induced-membrane surface to remove the innermost layer of the induced-membrane increased bone regeneration. A textured spacer that increased the induced-membrane surface area had no effect on bone regeneration.

CLINICAL RELEVANCE

Scraping the induced membrane during the second stage of the Masquelet technique may be a rapid and simple means of improving healing of segmental bone defects, which needs to be confirmed clinically.

Caspase-2: an orphan enzyme out of the shadows

Caspase-2 has been embodied as an initiator or executioner protease in diverse apoptotic scenarios. However, accumulating evidence is challenging this view, pertaining to its true role. The enzyme's catalytic activity is currently implicated in various functions required for correct cell proliferation, such as counteracting genomic instability, as well as suppressing tumorigenesis. Here, apart from summarizing the latest observations in caspase-2-related research, we make an attempt to reconcile these findings and discuss their implications for future directions.

Can a Bayesian Belief Network Be Used to Estimate 1-year Survival in Patients With Bone Sarcomas?

BACKGROUND

Extremity sarcoma has a preponderance to present late with advanced stage at diagnosis. It is important to know why these patients die early from sarcoma and to predict those at high risk. Currently we have mid- to long-term outcome data on which to counsel patients and support treatment decisions, but in contrast to other cancer groups, very little on short-term mortality. Bayesian belief network modeling has been used to develop decision-support tools in various oncologic diagnoses, but to our knowledge, this approach has not been applied to patients with extremity sarcoma.

QUESTIONS/PURPOSES

We sought to (1) determine whether a Bayesian belief network could be used to estimate the likelihood of 1-year mortality using receiver operator characteristic analysis; (2) describe the hierarchal relationships between prognostic and outcome variables; and (3) determine whether the model was suitable for clinical use using decision curve analysis.

METHODS

We considered all patients treated for primary bone sarcoma between 1970 and 2012, and excluded secondary metastasis, presentation with local recurrence, and benign tumors. The institution's database yielded 3499 patients, of which six (0.2%) were excluded. Data extracted for analysis focused on patient demographics (age, sex), tumor characteristics at diagnosis (size, metastasis, pathologic fracture), survival, and cause of death. A Bayesian belief network generated conditional probabilities of variables and survival outcome at 1 year. A lift analysis determined the hierarchal relationship of variables. Internal validation of 699 test patients (20% dataset) determined model accuracy. Decision curve analysis was performed comparing net benefit (capped at 85.5%) for all threshold probabilities (survival output from model).

RESULTS

We successfully generated a Bayesian belief network with five first-degree associates and describe their conditional relationship with survival after the diagnosis of primary bone sarcoma. On internal validation, the resultant model showed good predictive accuracy (area under the curve [AUC] = 0.767; 95% CI, 0.72-0.83). The factors that predict the outcome of interest, 1-year mortality, in order of relative importance are synchronous metastasis (6.4), patient's age (3), tumor size (2.1), histologic grade (1.8), and presentation with a pathologic fracture (1). Patient's sex, tumor location, and inadvertent excision were second-degree associates and not directly related to the outcome of interest. Decision curve analysis shows that clinicians can accurately base treatment decisions on the 1-year model rather than assuming all patients, or no patients, will survive greater than 1 year. For threshold probabilities less than approximately 0.5, the model is no better or no worse than assuming all patients will survive.

CONCLUSIONS

We showed that a Bayesian belief network can be used to predict 1-year mortality in patients presenting with a primary malignancy of bone and quantified the primary factors responsible for an increased risk of death. Synchronous metastasis, patient's age, and the size of the tumor had the largest prognostic effect. We believe models such as these can be useful as clinical decision-support tools and, when properly externally validated, provide clinicians and patients with information germane to the treatment of bone sarcomas.

CLINICAL RELEVANCE

Bone sarcomas are difficult to treat requiring multidisciplinary input to strategize management. An evidence-based survival prediction can be a powerful adjunctive to clinicians in this scenario. We believe the short-term predictions can be used to evaluate services, with 1-year mortality already being a quality indicator. Mortality predictors also can be incorporated in clinical trials, for example, to identify patients who are least likely to experience the side effects of experimental toxic chemotherapeutic agents.

HELIOS--A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopy

In this paper, we present the HELIOS (High Energy Laser Induced Overtone Source) laboratory, an in-house high-order harmonic generation facility which generates extreme ultraviolet (XUV) photon pulses in the range of 15-70 eV with monochromatized XUV pulse lengths below 35 fs. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe experiments with wavelengths ranging from 240 nm to 20,000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, first monochromatized spectra are shown with an intensity of 2 ⋅ 10(10) photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is measured to be <25 fs after monochromatization.

Heterotopic Ossification: Basic-Science Principles and Clinical Correlates

➤ Heterotopic ossification occurs most commonly after joint arthroplasty, spinal cord injury, traumatic brain injury, blast trauma, elbow and acetabular fractures, and thermal injury.➤ The conversion of progenitor cells to osteogenic precursor cells as a result of cell-mediated interactions with the local tissue environment is affected by oxygen tension, pH, availability of micronutrients, and mechanical stimuli, and leads to heterotopic ossification.➤ Radiation and certain nonsteroidal anti-inflammatory medications are important methods of prophylaxis against heterotopic ossification.➤ Well-planned surgical excision can improve patient outcomes regardless of the joint involved or the initial cause of injury.➤ Future therapeutic strategies are focused on targeted inhibition of local factors and signaling pathways that catalyze ectopic bone formation.

Regional variation in the incidence of abdominal aortic aneurysm in Sweden

BACKGROUND

The risk factor profile is similar between patients with abdominal aortic aneurysm (AAA) and coronary heart disease (CHD). CHD is more common in the north of Sweden. It is unknown whether similar regional differences in the incidence of AAA exist. The aims of this study were to investigate whether there is a regional gradient of AAA incidence, and to compare time trends and the frequency of interventions between regions.

METHODS

Swedish citizens have a 12-digit personal identification number. The Swedish Hospital Discharge Register covers inpatient care (diagnosis, admission, procedure codes, sex, date of birth, county). Population size was obtained from the central statistical bureau. Regions were south, mid and north.

RESULTS

All records for 1990-2005 were extracted and 35 418 individuals with AAA were identified (74.8 per cent men). The highest age-standardized incidence (102.7 per 100,000) was found in men in the north region. The age-adjusted incidence ratio for men in the north region compared with the south was 1.38 (95 per cent confidence interval 1.34 to 1.42). Similar differences were found in women: incidence ratio for north compared with south region 1.39 (1.07 to 1.81). The proportion treated was larger in men and varied by region: 46.9 per cent of men in the mid region compared with 43.7 per cent in the south received treatment (P < 0.001), whereas 29.8 per cent of women in the north region versus 25.4 per cent in the south had an intervention (P = 0.001). The incidence did not increase over time.

CONCLUSION

The higher incidence of AAA in the north of Sweden corresponds well with reported CHD patterns. The incidence of AAA in the population did not increase significantly over time, in contrast to the increasing intervention rates.

System for in situ studies of atmospheric corrosion of metal films using soft x-ray spectroscopy and quartz crystal microbalance

We present a versatile chamber ("atmospheric corrosion cell") for soft x-ray absorption/emission spectroscopy of metal surfaces in a corrosive atmosphere allowing novel in situ electronic structure studies. Synchrotron x rays passing through a thin window separating the corrosion cell interior from a beamline vacuum chamber probe a metal film deposited on a quartz crystal microbalance (QCM) or on the inside of the window. We present some initial results on chloride induced corrosion of iron surfaces in humidified synthetic air. By simultaneous recording of QCM signal and soft x-ray emission from the corroding sample, correlation between mass changes and variations in spectral features is facilitated.

Resonant inelastic x-ray scattering at the oxygen K resonance of NiO: nonlocal charge transfer and double-singlet excitations

We report high-resolution polarization-dependent resonant inelastic x-ray scattering (RIXS) at the O K resonance of NiO showing a rich excitation spectrum. We perform multisite Ni6O19 cluster model calculations, revealing that solid state effects are substantial. We identify a nonlocal charge transfer excitation at 4-5 eV and double-singlet creation at 1.75 eV, both exhibiting significant scattering geometry dependence. Apart from an intense band of local charge transfer excitations (above 5 eV) also dd excitations at 1 eV are observed. Finally, we point out that O K RIXS of correlated metal oxides allows a quantitative and consistent determination of the charge transfer energy delta and the Hund coupling energy J(H).

Working memory and novel word learning in children with hearing impairment and children with specific language impairment

BACKGROUND

Working memory is considered to influence a range of linguistic skills, i.e. vocabulary acquisition, sentence comprehension and reading. Several studies have pointed to limitations of working memory in children with specific language impairment. Few studies, however, have explored the role of working memory for language deficits in children with hearing impairment.

AIMS

The first aim was to compare children with mild-to-moderate bilateral sensorineural hearing impairment, children with a preschool diagnosis of specific language impairment and children with normal language development, aged 9-12 years, for language and working memory. The special focus was on the role of working memory in learning new words for primary school age children.

METHODS & PROCEDURES

The assessment of working memory included tests of phonological short-term memory and complex working memory. Novel word learning was assessed according to the methods of. In addition, a range of language tests was used to assess language comprehension, output phonology and reading.

OUTCOMES & RESULTS

Children with hearing impairment performed significantly better than children with a preschool diagnosis of specific language impairment on tasks assessing novel word learning, complex working memory, sentence comprehension and reading accuracy. No significant correlation was found between phonological short-term memory and novel word learning in any group. The best predictor of novel word learning in children with specific language impairment and in children with hearing impairment was complex working memory. Furthermore, there was a close relationship between complex working memory and language in children with a preschool diagnosis of specific language impairment but not in children with hearing impairment.

CONCLUSIONS

Complex working memory seems to play a significant role in vocabulary acquisition in primary school age children. The interpretation is that the results support theories suggesting a weakened influence of phonological short-term memory on novel word learning in school age children.

Production of asymmetric hybrids between Arabidopsis thaliana and Brassica napus utilizing an efficient protoplast culture system

Application of the protoplast culture method developed for Brassica protoplasts to protoplasts of Arabidopsis thaliana has increased the opportunities for interspecific hybridizations involving Arabidopsis. A more-efficient and much-simpler method was established compared to the earlier-reported protocol developed for A. thaliana protoplasts in which alginate beads were utilized. Mesophyll protoplasts of A. thaliana (ecotypes 'Landsberg erecta' and 'Wassilewskija') were cultured in the modified 8p liquid medium, which had been developed for Brassica protoplasts. For comparison, protoplasts were cultured in sodium alginate beads supplied with B5 medium according to the protocol for A. thaliana. The protoplasts divided with high frequencies in the 8p medium, and calli proliferated more rapidly than in the sodium alginate beads. High frequencies of shoot differentiation and regeneration were observed in calli of both ecotypes, from about 30% in the ecotype 'Wassilewskija' to about 60% for 'Landsberg erecta'. The more-rapidly the calli developed, the higher the regeneration frequencies were. Asymmetric hybrids between A. thaliana and Brassica napus were obtained by treating the protoplasts of A. thaliana with iodoacetamide (IOA) and B. napus protoplasts with UV-irradiation before fusion with polyethylene glycol (PEG). By using the culture procedure developed for Brassica protoplasts, calli developed and plants were regenerated. Although most of the plants regenerated after cell fusion were A. thaliana-like and were judged to be escapes from IOA treatment, more than ten plants showed hybrid features of both morphological and molecular characters. Among the hybrids that have flowered so far, both male-fertile and male-sterile plants have been obtained. Back-crossings to A. thaliana are now in progress as is morphological and molecular characterization of the plants.

Redox signalling in chloroplasts and mitochondria: genomic and biochemical evidence for two-component regulatory systems in bioenergetic organelles

Redox chemistry is central to the primary functions of chloroplasts and mitochondria, that is, to energy conversion in photosynthesis and respiration. However, these bioenergetic organelles always contain very small, specialized genetic systems, relics of their bacterial origin. At huge cost, organellar genomes contain, typically, a mere 0.1% of the genetic information in a eukaryotic cell. There is evidence that chloroplast and mitochondrial genomes encode proteins whose function and biogenesis are particularly tightly governed by electron transfer. We have identified nuclear genes for 'bacterial' histidine sensor kinases and aspartate response regulators that seem to be targeted to chloroplast and mitochondrial membranes. Sequence similarities to cyanobacterial redox signalling components indicate homology and suggest conserved sensory and signalling functions. Two-component redox signalling pathways might be ancient, conserved mechanisms that permit endogenous control over the biogenesis, in situ, of bioenergetic complexes of chloroplasts and mitochondria.

Molecular recognition in thylakoid structure and function

In photosynthesis, light-harvesting chlorophyll molecules are shunted between photosystems by phosphorylation of the protein to which they are bound. An anchor for the phosphorylated chlorophyll-protein complex has now been identified in the reaction centre of chloroplast photosystem I. This finding supports the idea that molecular recognition, not membrane surface charge, governs the architecture of the chloroplast thylakoid membrane. We describe a model for the chloroplast thylakoid membrane that is consistent with recent structural data that specify the relative dimensions of intrinsic protein complexes and their dispositions within the membrane. Control of molecular recognition accommodates membrane stacking, lateral heterogeneity and regulation of light-harvesting function by means of protein phosphorylation during state transitions--adaptations that compensate for selective excitation of photosystem I or photosystem II. High-resolution structural description of membrane protein-protein interactions is now required to understand thylakoid structure and regulation of photosynthesis.

Heat stress response in pea involves interaction of mitochondrial nucleoside diphosphate kinase with a novel 86-kilodalton protein

In this work we have further characterized the first mitochondrial nucleoside diphosphate kinase (mtNDPK) isolated from plants. The mitochondrial isoform was found to be especially abundant in reproductive and young tissues. Expression of the pea (Pisum sativum L. cv Oregon sugarpod) mtNDPK was not affected by different stress conditions. However, the pea mtNDPK was found to interact with a novel 86-kD protein, which is de novo synthesized in pea leaves upon exposure to heat. Thus, we have evidence for the involvement of mtNDPK in mitochondrial heat response in pea in vivo. Studies on oligomerization revealed that mtNDPK was found in complexes of various sizes, corresponding to the sizes of e.g. hexamers, tetramers, and dimers, indicating flexibility in oligomerization. This flexibility, also found for other NDPK isoforms, has been correlated with the ability of this enzyme to interact with other proteins. We believe that the mtNDPK is involved in heat stress response in pea, possibly as a modulator of the 86-kD protein.

Protein tyrosine phosphorylation in the transition to light state 2 of chloroplast thylakoids

Redox dependent protein phosphorylation in chloroplast thylakoids regulates distribution of excitation energy between the two photosystems of photosynthesis, PS I and PS II. Several thylakoid phosphoproteins are known to be phosphorylated on N-terminal threonine residues exposed to the chloroplast stroma. Phosphorylation of light harvesting complex II (LHC II) on Thr-6 is thought to account for redistribution of light energy from PS II to PS I during the transition to light state 2. Here, we present evidence that a protein tyrosine kinase activity is required for the transition to light state 2. With an immunological approach using antibodies directed specifically towards either phospho-tyrosine or phospho-threonine, we observed that LHC II became phosphorylated on both tyrosine and threonine residues. The specific protein tyrosine kinase inhibitor genistein, at concentrations causing no direct effect on threonine kinase activity, was found to prevent tyrosine phosphorylation of LHC II, the transition to light state 2, and associated threonine phosphorylation of LHC II. Possible reasons for an involvement of tyrosine phosphorylation in light state transitions are proposed and discussed.

High prevalence of Chlamydia pneumoniae DNA in peripheral blood mononuclear cells in patients with cardiovascular disease and in middle-aged blood donors

Nested polymerase chain reaction (nPCR) demonstrated the presence of Chlamydia pneumoniae-specific DNA in peripheral blood mononuclear cells (PBMC). PBMC samples were obtained from 103 consecutive patients (62 male, 41 female) aged 22-85 years (mean, 64) admitted for coronary angiography because of suspected coronary heart disease and from 52 blood donors (43 male, 9 female) aged 40-64 years (mean, 49). Of the 101 evaluable patients, 60 (59%) were identified by nPCR assay as C. pneumoniae DNA carriers; C. pneumoniae-specific microimmunofluorescence (MIF) serology confirmed exposure to the bacterium in 57 (95%) of the 60 nPCR-positive patients. Among the 52 blood donors, the nPCR assay identified 24 (46%) C. pneumoniae DNA carriers, all of whom were positive by C. pneumoniae-specific serology. Thirty-two patients (32%) and 23 blood donors (44%) were MIF antibody-positive but repeatedly nPCR-negative; Bartonella henselae- or Bartonella quintana-specific antibodies were not detected among any of these subjects. In this study, C. pneumoniae DNA was common in PBMC of patients with coronary heart disease and in middle-aged blood donors.

Periapical radiolucencies as evaluated by bisecting-angle and paralleling radiographic techniques

Two groups of patients were included in the study. The first group consisted of patients who received root canal treatment of single-rooted teeth (n = 63). The completed roof fillings were exposed to two different radiographic techniques, the paralleling and the bisecting-angle technique. The second group consisted of 1-year review radiographs of patients who had received apicectomies of single-rooted teeth (n = 105). Three observers examined the radiographic images. First, they were asked to identify teeth with a normal apical condition and those with an apical radiolucency. Thereafter pairs of radiographs were compared; cases judged as normal by all observers were excluded. The observers were now asked to ascertain whether the apical radiolucency was largest in the first image, the apical radiolucency was largest in the second picture or both radiolucencies were the same size. Both intraobserver and interobserver agreement, calculated as Cohen's kappa, was high with respect to the presence of lesions within both samples and it was at the same level for both radiographic techniques. The evaluation of the size of the lesions proved to be more inconsistent. Kappa values were in the range 0.38-0.71 for intraobserver comparisons and in the range 0.25-0.48 for interobserver comparisons. No significant difference was found between the size of lesions as recorded by the two techniques (P > 0.05). It is concluded that, when correctly adjusted the bisecting-angle technique and the paralleling technique provide similar diagnostic results.

Radiographic simulation of a periapical lesion comparing the paralleling and the bisecting-angle techniques

Sixty apical areas of single-rooted teeth were examined in this study. A simulated periapical lesion was produced using an acrylic sphere (diameter 2.0 mm), the surface of which was covered with a thin layer of zinc cement. The sphere was placed in close contact with the apical foramen using a thin orthodontic wire inserted into the apical portion of the root canal. The correctly adjusted parallel projection depicted the simulated lesion with a very low degree of error. Overangulation of the central beam with maintenance of parallelism between tooth and film resulted in a moderate degree of magnification. When correctly adjusted, the bisecting-angle technique produced images with almost the same accuracy as the paralleling technique. Over-angulation resulted in most images showing a reduced size of the simulated lesion. Moderate under-angulation most often recorded the correct dimension of the globe. In some cases a magnified image of the sphere was produced. Generally, this was associated with a palatally curved root. The investigation thus clearly indicated that the paralleling technique provides the most reliable information about the extent of a pathological process.

A method for experimental dental radiography

An apparatus was designed for experimental dental radiography, which permitted separate adjustment of the subject, target and film. The precision of the apparatus was tested by radiographing a test subject, consisting of small steel globes embedded in a plastic plate. The subject was placed in the apparatus and exposed 30 times on dental X-ray film with different adjustments of angles and distances. All exposures were repeated after readjustment of the same form. Three linear distances between pairs of the projected steel globes were selected and measured on each radiograph. Depending on the different orientations of film, target and subject, the distances measured ranged from 9.0-11.1 mm, from 7.0-10.7 mm and from 12.7-17.3 mm, respectively. From the measurements on the radiographs the error of method was calculated to be 0.07-0.08 mm and the error of measurement to be 0.05-0.06 mm. The precision of the apparatus was thus found to be adequate for measurement of differences in small, but clinically relevant, distances.

Radiographic reproduction of endodontic "working length" comparing the paralleling and the bisecting-angle techniques

The reproduction of a metal indicator simulating a root canal instrument at the apex of a tooth was examined as a function of paralleling, modified paralleling, and bisecting-angle radiographic techniques. Radiographs exposed according to the paralleling and modified paralleling principles demonstrated good correlation between the radiographic position of the metal indicator and its position on direct inspection. The bisecting-angle technique, either correctly or incorrectly angulated, produced the least accurate results. The apical location of the metal indicator was significantly more reliable with the paralleling principle than with the bisecting-angle technique (p less than 0.05).

Size discrimination among conspecific hostplants in two pierid butterflies; Pieris napi L. and Pontia daplidice L

Females of the butterflies Pieris napi and Pontia daplidice discriminate against large hostplant individuals, usually preferring low rosettes or seedlings, when hostplants are abundant. In this paper the larval mobility between young hostplant, and differences in survival and growth rate on low versus tall conspecific hostplants were studied in these two species in Sweden. The results suggest that the largest effect of plant size is that small plants support faster growth than bigger ones. This seems to be due to differences in microclimate conditions, not an effect of different suitability as food. Thus, on the assumption that there are no systematic differences in larval death rate, which is supported by the results in this study, preference for small hostplants should be advantagous, leading to higher survival during development, and higher probability for an additional brood per year.

Interaction of ascorbate with the radioprotective effect of mercaptoethylamin. An exploratory study in mice, whole animals and cell cultures

The injection of ascrobate together with cysteamine (beta-mercaptoethylamin or MEA) was shown to cause a partial reversion of the radioprotective action of MEA in mice, and simultaneously of the suppressive action of MEA on RNA synthesis in bone marrow cells. In mouse spleen lymphocytes stimulated by concanavalin A in vitro, MEA and ascorbate exhibited a strong antagonism, neutralizing each other's inhibitory action on RNA synthesis. The latter effect failed to appear after chelation of trace metals, and it is indicated that the ability of ascorbate to counteract the effects of MEA on radiosensitivity and metabolism requires the formation of oxidized products, probably monodehydroascorbate, in agreement with previous observations on bacteria.