'Non-standard' panoramic programmes and the unusual artefacts they produce.

Dental panoramic radiographs (DPTs) are commonly taken in dental practice in the UK with the number estimated to be 2.7 million per annum. They are used to diagnose caries, periodontal disease, trauma, pathology in the jaws, supernumerary teeth and for orthodontic assessment. Panoramic radiographs are not simple projections but involve a moving X-ray source and detector plate. Ideally only the objects in the focal trough are displayed. This is achieved with a tomographic movement and one or more centre(s) of rotation. One advantage of digital radiography is hardware and software changes to optimise the image. This has led to increasingly complex manufacturer specific digital panoramic programmes. Panoramic radiographs suffer from ghost artefacts which can limit the effectiveness and make interpretation difficult. Conversely 'conventional dental imaging' such as intraoral bitewings do not suffer the same problems. There are also now several 'non-standard' panoramic programmes which aim to optimise the image for different clinical scenarios. These include 'improved interproximality', 'improved orthogonality' and 'panoramic bitewing mode'.This technical report shows that these 'non-standard' panoramic programmes can produce potentially confusing ghost artefacts, of which the practitioner may not be aware.

Exploring the spectroscopic differences of Caki-2 cells progressing through the cell cycle while proliferating in vitro.

FTIR micro-spectral images of Caki-2 cells cytospun onto calcium fluoride (CaF2) slides were used to build a computational model in order to discriminate between the biochemical events of the continuous cell cycle during proliferation. Multivariate analysis and machine learning techniques such as PCA, PLSR and SVMs were used to highlight the chemical differences among the cell cycle phases and also to point out the need for removing the distortion of the spectra due to the morphology of the cells. Results showed cell cycle dependant scattering profiles that enabled the training of a SVM in order to recognise, with a relative high accuracy, each cell cycle phase purely with the scattering curve removed from the FTIR data after being subject to the RMieS-EMSC algorithm.

Highlighting a need to distinguish cell cycle signatures from cellular responses to chemotherapeutics in SR-FTIR spectroscopy.

Previous research has seen difficulties in establishing clear discrimination by principal component analysis (PCA) between drug-treated cells analysed by single point SR-FTIR spectroscopy, relative to multisampling cell monolayers by conventional FTIR. It is suggested that the issue arises due to signal mixing between cellular-response signatures and cell cycle phase contributions in individual cells. Consequently, chemometric distinction of cell spectra treated with multiple drugs is difficult even with supervised methods. In an effort to separate cell cycle chemistry from cellular response chemistry in the spectra, renal carcinoma cells were stained with propidium iodide and fluorescent-activated cell sorted (FACS) after exposure to a number of chemotherapeutic compounds; 5-fluorouracil (5FU) and a set of novel gold-based experimental compounds. The cell spectra were analysed separately by PCA in G(1), S or G(2)/M phase. The mode of action of established drug 5FU, known to disrupt S phase, was confirmed by FACS analysis. The chemical signature of 5FU-treated cells discriminated against both the control and gold-compound (KF0101)-treated cell spectra, suggesting a different mode of action due to a difference in cellular response.

Stochastic models for systems of interacting ion channels.

We consider a variety of Markov based models for systems of ion channels exhibiting dependence between channels. It is shown how many useful properties which may be calculated for an aggregated single-channel model, or a system of independent channels, can be extended to various types of interacting channel systems. Key structure and results from the theory of aggregated Markov processes are summarized in a convenient matrix form. These are then applied to the superposition of independent and dependent channels, including a patch of channels in a random environment, and a system of channels with spatial interactions. Calculations based on the resultant matrix expressions and intensity arguments can be implemented straightforwardly in a matrix-oriented package such as Matlab. The role of reversibility is also studied. A number of examples illustrate the strengths of the methods and enable numerical comparisons between the different types of systems.

Stochastic and deterministic models for SIS epidemics among a population partitioned into households.

Models for the spread of an SIS epidemic among a population consisting of m households, each containing n individuals, are considered and their behaviour is analysed under the practically relevant situation when m is large and n small. A threshold parameter R* is determined. For the stochastic model it is shown that the epidemic has a non-zero probability of taking off if and only if R* > 1, and the extension to unequal household sizes is also considered. For the deterministic model, with households of size 2, it is shown that if R* < or = 1 then the epidemic dies out, whilst if R* > 1 the epidemic settles down to an endemic equilibrium. The usual basic reproductive ratio R0 does not provide a good indicator for the behaviour of these household epidemic models unless the household size n is large.

Who's got the power? Gender differences in partners' perceptions of influence during marital problem-solving discussions.

Previous research on marital communication indicates that women have more influence in marital problem solving because they raise the issues and shape the discussion. Other studies suggest that men have the power in marital problem solving. This study re-examines power and influence from the partners' point of view. Twenty-seven couples-18 with a first child under 2, and 9 undecided about having children-were videotaped while working on a self-selected problem concerning their division of family labor. Data sources included: (a) transcribed audiotaped accounts given by each partner while viewing a videotape of their problem-solving discussion; (b) self-report questionnaires; and (c) ratings by a research team of the concordance between spouses' accounts. Husbands and wives were perceived as having a primary influence on different aspects of the discussion. Women tended to raise the issues and draw men out in the early phase of the discussion, while men controlled the content and emotional depth of the later discussion phases, and largely determined the outcome. The women's accounts emphasized that their influence in the early phase was often illusory: their behavior was shaped primarily by the effort to choose strategies that would avoid upsetting their husbands. In terms of overall satisfaction with marriage, wives had greater tolerance than their husbands for conflict in the area of division of domestic labor, but less tolerance for their husbands' domination of the discussion process. Women's marital satisfaction was higher when there was concordance between spouses in their accounts of their problem-solving discussion. This research highlights the importance of eliciting spouses' own perceptions and definitions in understanding the impact of gender-linked power differences in martial communication.

Vesicouterine fistula after cesarean section. A case report.

A 27-year-old woman, gravida 3, para 2002, underwent repeat cesarean section and inadvertent cystotomy, with subsequent development of a vesicouterine fistula. The fistula did not resolve with prolonged bladder catheterization and required total abdominal hysterectomy with resection of the fistula tract and primary closure for definitive treatment.

The shape of the size distribution of an epidemic in a finite population.

Qualitative changes in the shape of the distribution of the final size of the susceptible-->infected-->removed (S-I-R) epidemic are used by Nåsell to define a threshold concept for the stochastic S-I-R epidemic. Numerical evaluations indicate that this threshold depends on the population size N according to the formula R0 approximately 1 + p/N1/3 for large N, where R0 is the basic reproduction ratio for the model. We derive an approximation of the final size distribution that supports this numerical result.

A new ureteral anastomotic device: the Unilink system. A pilot study using the porcine model.

OBJECTIVE: Ureteral injury is a complication of gynecologic surgery in approximately 1% of all cases. The anatomic site of the injury determines the type of operative repair. When an end-to-end ureteral anastomosis is required, interrupted sutures are usually used. A prospective, randomized animal study was performed to determine the efficacy of a new microvascular anastomotic device, the Unilink system, in repairing transected ureters. STUDY DESIGN: Nineteen pigs underwent randomized anastomosis with the Unilink system on one side and traditional anastomosis with suture on the contralateral side. A postoperative intravenous pyelogram was performed immediately and 2 weeks later, before the anastomotic site at a second laparotomy was harvested. Patency rates for each type of anastomosis were compared microscopically, and the degree of hydronephrosis was compared grossly and radiographically. RESULTS AND CONCLUSION: The anastomotic repair with the Unilink system did not significantly differ structurally or functionally from traditional suture repair.

Ion channel gating and time interval omission: statistical inference for a two-state Markov model.

Statistical inference is considered for a two-state Markov model of a single ion channel, when time interval omission is incorporated. A simple method of obtaining confidence sets for the mean open and closed sojourn times for the underlying single channel, based on the method-of-moments estimators, is presented. Time interval omission induces non-identifiability, in that the method-of-moments usually leads to two distinct estimates of the mean open and closed sojourn times, one corresponding to the true values and the other being an artefact of time interval omission. A new method of overcoming such non-identifiability on the basis of one single channel record is described. The methodology is illustrated by a numerical example.

Model properties underlying non-identifiability in single channel inference.

Models of ion channel kinetics subserve inferential methods applied to patch clamp data. For Markov models the density function of a sojourn time in a class of states is a mixture of exponentials. Determination of kinetic parameters from density functions may be complicated by non-uniqueness of solutions. This non-identifiability is investigated analytically for a class of two states, assuming detailed balance; relations between model properties, observable density parameters, and non-uniqueness are presented. The results are further developed in terms of similarity transform methods. Additional information provided by joint distributions is discussed. An example is given where identifiability of a model can be demonstrated explicitly. Attention is drawn to instances where the number of components in a density function may be misleading when used to infer the number of underlying states.

Single ion channel models incorporating aggregation and time interval omission.

We present a general theoretical framework, incorporating both aggregation of states into classes and time interval omission, for stochastic modeling of the dynamic aspects of single channel behavior. Our semi-Markov models subsume the standard continuous-time Markov models, diffusion models and fractal models. In particular our models allow for quite general distributions of state sojourn times and arbitrary correlations between successive sojourn times. Another key feature is the invariance of our framework with respect to time interval omission: that is, properties of the aggregated process incorporating time interval omission can be derived directly from corresponding properties of the process without it. Even in the special case when the underlying process is Markov, this leads to considerable clarification of the effects of time interval omission. Among the properties considered are equilibrium behavior, sojourn time distributions and their moments, and auto-correlation and cross-correlation functions. The theory is motivated by ion channel mechanisms drawn from the literature, and illustrated by numerical examples based on these.

Development of late congenital hip dysplasia: significance of ultrasound screening.

Ultrasound for detecting congenital hip dysplasia was performed in 5970 infants, 2121 of whom were reinvestigated. Of those reinvestigated 726 belonged to the screened group not at risk examined as newborns, 70 were infants at risk first investigated as newborns and 363 were infants at risk first examined after the newborn period; the remainder were infants not at risk first investigated after the newborn period. Pathological findings were obtained in 7.7% of the entire group, in 3.9% of children at no risk, and in 5% of patients at risk. Deterioration of Graf's classification of types was seen in 3.2%. 13 children, 3 of the screened group and 10 of the nonscreened group developed hip dysplasia. None of them would have been missed since they were borderline type IIA on at least one side, which warranted mandatory follow-up.

Development of thyroid gland volume during the first 3 months of life in breast-fed versus iodine-supplemented and iodine-free formula-fed infants.

The spontaneous development of thyroid gland volume (TGV) during the first 3 months of life was studied in entirely breast-fed infants (n = 21) and compared to those fed an iodine-supplemented formula (n = 19), an iodine-free formula (n = 5), or partially breast-fed in addition to an iodine-free (n = 4) or an iodine-supplemented formula (n = 16). The TGV of the infants and their mothers was determined sonographically in addition to their urinary iodine concentrations 5-7 days postpartum and 3 months later. In ten additional lactating mothers the breast milk concentrations of thyroid hormones and iodine were determined. It was shown that at 3 months of age an infant consuming about 1000 ml breast milk per day receives about 2 micrograms thyroid hormones and 55 micrograms iodine per day. At the end of their first week of life the infants showed a TGV between 0.28 and 1.5 ml (median 0.61 ml) and a urinary iodine concentration between 0.03 and 16.3 micrograms/dl (median 3.0 micrograms/dl). At 3 months of age the TGV of the breast-fed infants had decreased by a median of 0.24 ml (= -34%; median of percentage changes) whereas those fed a formula without iodine had increased by a median of 0.26 ml (= +50%; median of percentage changes). Those receiving an iodine-supplemented formula showed a TGV reduction of 0.14 ml (= +2%; median of percentage changes). The TGV development of the partially breast-fed infants lay between those being exclusively breast or formula fed.(ABSTRACT TRUNCATED AT 250 WORDS)

Stochastic models for ion channels: introduction and bibliography.

This paper provides an introduction to and overview of the use of stochastic models and statistical analysis in the study of ion channels in cell membranes. An extensive bibliography is included.

Poisson sampling-based inference for single ion channel data with time interval omission.

Patch-clamp recording allows investigations of the gating kinetics of single ion channels. Statistical analysis of kinetic data can enhance our understanding of channel gating at a molecular level. Experimental channel records suffer from time interval omission, i.e. failure to detect brief channel openings and closings. It is important to incorporate this phenomenon into statistical analyses of ion channel data. When time interval omission is ignored, the method of maximum likelihood can usually be used to estimate gating parameters from a single channel record. However, it is far more difficult to apply this method when time interval omission is incorporated. We present an alternative approach to parameter estimation based on Poisson sampling. A simulated homogeneous Poisson process is superimposed onto the channel record and inference is based on the numbers of points in successive open and closed sojourns, rather than on the sojourn times themselves. We describe the method for the two-state Markov model C<-->O, although it is applicable to more general models. Computer-simulated data are used to demonstrate the efficacy of the method. Modifications of the method are discussed briefly.

Dynamic population epidemic models.

Most multipopulation epidemic models are of the contact distribution type, in which the locations of successive contacts are chosen independently from appropriate contact distributions. This paper is concerned with an alternative class of models, termed dynamic population epidemic models, in which infectives move among the populations and can infect only within their current population. Both the stochastic and deterministic versions of such models are considered. Their threshold behavior is analyzed in some depth, as are their final outcomes. Velocities of spread of infection are considered when the populations have a spatial structure. A criterion for finding the equivalent contact distribution epidemic for any given dynamic population epidemic is provided, enabling comparisons to be made for the velocities and final outcomes displayed by the two classes of models. The relationship between deterministic and stochastic epidemic models is also discussed briefly.

Detection of Norwalk-like virus and specific antibody by immune-electron microscopy with colloidal gold immune complexes.

Direct electron-microscopy (DEM), immune electron microscopy (IEM) and four different procedures of immune electron microscopy with colloidal gold immune complexes were evaluated for the detection of Norwalk-like virus and specific antibody. A solid-phase immune electron microscopy with colloidal gold immune complexes-triple layer method (SPIEMGIC-TLM) is developed for screening patients' specimens for the detection of Norwalk-like virus and its specific antibody. The method demonstrates low non-specific background labelling and is simple, sensitive and easy to perform. A quadruple layer method (SPIEMGIC-QLM), which is a modification of the triple layer method, has been established by adding a cross-linking anti-IgG layer to amplify the reaction and to provide a more sensitive test which is suitable for screening monoclonal antibodies prepared against 32-34-nm Norwalk-like virus isolated in our laboratory.

[Atypical pathogen spectrum in community-acquired infections of the lower respiratory tract in childhood]. / Atypisches Erregerspektrum bei ausserhalb der Klinik erworbenen Infektionen der tiefen Atemwege im Kindesalter.

Over a period of 14 months, we obtained nasal and throat swabs for virological examinations from patients, admitted to hospital with suspected pneumonia. Fifty-five cases of perihilar bronchitis and 103 cases of pneumonia were diagnosed based on radiological criteria. In 36% (n = 57) of the children, a pathogen could be determined by antigen ELISA. We found the following spectrum: Respiratory syncytial virus: 42%; Influenza A: 8%; Influenza B: 10%; Parainfluenza 1: 3%; Parainfluenza 2: 10%; Parainfluenza 3: 2%; Chlamydia: 17%; and Mycoplasma pneumoniae (serology only): 7%. In a control group of 59 healthy children, only one child showed a pathogen. In the past, viruses and Chlamydia have been underestimated as causes of lower respiratory tract infections. Antigen determination by ELISA has proved to be a reliable and rapid method for their detection.

Single-channel data and missed events: analysis of a two-state Markov model.

Patch-clamp recording permits investigation of the gating kinetics of single ion channels. Careful statistical analysis of kinetic data can yield clues as to the molecular events underlying channel gating. However, it is important that such analysis should take full account of the limitations that arise from the finite time resolution of patch-clamp recording techniques. Single-ion-channel data are generally interpreted in terms of Markov process models of channel gating mechanisms. Experimental channel records suffer from time interval omission, i.e. failure to detect brief channel openings and closings. This leads to an identifiability problem when analysing single-channel data, i.e. different gating mechanisms provide equally convincing descriptions of the same experimental data. We consider a two-state Markov model of receptor-channel gating in which the channel opening rate is proportional to the agonist concentration, C in equilibrium with OA. By using computer-simulated data, the approximate likelihood of the data is maximized to yield parameter estimates for the model. At a single agonist concentration there is an identifiability problem in that two pairs of parameter estimates are obtained. The 'true' parameter estimates cannot be distinguished from the 'false' ones. By considering data corresponding to a range of agonist concentrations one may identify the 'true' parameter estimates as those that do not change as the agonist concentration is increased. Alternatively, one may identify the 'true' parameter estimates directly by maximizing a global likelihood, the latter being obtained by simultaneous consideration of data obtained at several different agonist concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)