Biomedical subjects

M Juhola

Publications and source records attributed to M Juhola.

At least 37 records · Page 2Linked to original sources

PubMed2001

Expression of cyclooxygenase-2 in dysplasia of the stomach and in intestinal-type gastric adenocarcinoma.

PURPOSE: Cyclooxygenase (Cox) is the key enzyme in conversion of arachidonic acid to prostanoids. Two Cox genes have been cloned, and expression of Cox-2 mRNA and protein has been shown to be elevated in several human malignancies and in animal models of carcinogenesis. The purpose of this study was to investigate Cox-2 protein expression in human gastric dysplasias and adenocarcinomas. EXPERIMENTAL DESIGN: Performance of several Cox-2 antibodies was evaluated, after which Cox-2 protein expression was studied in 67 gastric cancer specimens and in eight definitive dysplasias by using immunohistochemistry. RESULTS: Cox-2 positivity was detected in 58% (25/43) of the intestinal-type (well-differentiated) tumors and 6% (1/18) of diffuse-type (poorly differentiated) tumors. Consistent with these data, we detected higher expression of Cox-2 mRNA, protein, and enzymatic activity in well-differentiated gastric cancer cell lines (MKN-28 and MKN-74) when compared with poorly differentiated cell lines (HSC-39 and KATO III). Cox-2 immunoreactivity was localized to the carcinoma cells, but the stroma of the tumors was negative. However, strong Cox-2 positivity was consistently detected in stromal cells at sites of erosions and ulcerations. Furthermore, four of nine (44%) definitive dysplasias of the stomach that showed no evidence of invasion were positive for Cox-2. CONCLUSIONS: Cox-2 is expressed by the neoplastic cells in the intestinal-type gastric adenocarcinoma and by precarcinogenic (dysplastic) lesions leading to this disease.

Adenocarcinoma↗

PubMed2001

On classification capability of neural networks: a case study with otoneurological data.

We investigated the capability of multilayer perceptron neural networks and Kohonen neural networks to recognize difficult otoneurological diseases from each other. We found that they are efficient methods, but the distribution of a learning set should be rather uniform. Also it is important that the number of learning cases is sufficient. If the two mentioned conditions are satisfied, these neural networks are similarly efficient as some other machine learning methods. The conditions are known in the theory of neural networks [1,2], but not often taken seriously in practice. Both networks functioned as well, excluding the case with several input variables, where the Kohonen neural networks surpassed the perceptron.

Algorithms↗

PubMed2001

Neural network and wavelet recognition of facial electromyographic signals.

The present aim was to explore the possibilities of using neural networks for recognizing significant changes in electrical activity of human facial muscles. We used multilayer perceptron neural networks to recognize bursts of electromyographic signals recorded with bipolar surface electrodes from two subject's facial muscles. Wavelets were applied for the detection of high frequency components of electromyographic signals. Coefficients of wavelets were used as an input to a neural network in order to differentiate bursts from the signals. The results showed that the recognition of bursts was very successful resulting to 84-97 percent total accuracies. The results were very encouraging and suggest further that the measurement of facial muscle activity may be a potentially useful computer input signal, for example, for affective computing which can be seen as a future versatile interaction between the computer and the user.

Electromyography↗

PubMed2001

Towards virtual reality stimulation in force platform posturography.

We developed a stimulation technique on the basis of virtual reality methods for balance investigation performed in balance laboratories of otorhinolaryngological clinics and institutes of occupational health. Such a stimulation technique is greatly progressive in the sense that by creating virtual moving views and "virtual worlds" inside which the subject is located it is possible to make effective stimuli that would be very difficult or even impossible to set in any real environment. We tested our system on healthy subjects and found out that this kind of virtual reality stimulation system is very useful for balance analysis.

Adult↗

PubMed2001

On approximate string matching of unique oligonucleotides.

The current research considers the approximate string matching search for important subsequences from DNA sequences, which is essential for numerous bioinformatics computation tasks. We tested several approximate string matching algorithms and furthermore developed one for DNA data. Run times of the algorithms are important, since the amount of data is very large.

Algorithms↗

PubMed2001

Postural control as assessed with virtual reality.

We studied the use of virtual reality technology as a stimulus in balance examinations. A pilot study was made using a small group of healthy subjects to investigate the effect of alcohol and virtual reality stimulus on the subjects' balance. The tests showed that blood alcohol concentration accounted for almost 50% of the increased lateral body sway velocity. The new stimulus technique based on virtual reality technology seems to be effective and flexible for postural investigations.

Adult↗

PubMed2000

Extracting VOIs from brain PET images.

A semi-automatic system for determining volumes of interest (VOI) from positron emission tomography (PET) scans of brain is described. The VOIs surface extraction is based on user selectable threshold and three-dimensional target flood-fill. Contrast to anatomical volume detection approaches, volumes are determined from functional PET images and the obtained objects are checked against anatomical images. The developed VOI program was evaluated with brain FDOPA-PET studies where the striatum was the object. The results were comparable to entirely manual method and the target extraction time is reduced to about one third of manual method.

Algorithms↗

PubMed2000

Usefulness of imputation for the analysis of incomplete otoneurologic data.

The usefulness of imputation in the treatment of missing values of an otoneurologic database for the discriminant analysis was evaluated on the basis of the agreement of imputed values and the analysis results. The data consisted of six patient groups with vertigo (N=564). There were 38 variables and 11% of the data was missing. Missing values were filled in with the means, regression and Expectation-Maximisation (EM) imputation methods and a random imputation method provided the baseline results. Means, regression and EM methods agreed on 41-42% of the imputed missing values. The level of agreement between these and the random method was 20-22%. Despite the moderate agreement between the means, regression and EM methods, the discriminant functions were similar and accurate (prediction accuracy 83-99%). The discriminant functions obtained from the randomly imputed data were also accurate having prediction accuracy 88-97%. Imputation seems to be a useful method for treating the missing data in this database. However, a lot of data was missing in otoneurologic tests, which are likely to be of less importance in the diagnosis of vertiginous patients. Consequently, the disagreement of the methods did not affect clearly the discriminant analysis, and, therefore, future research requires more complete data and advanced imputation methods.

Data Collection↗

PubMed2000

Effects of digital filtering on the parameters of impulse-like eye movements.

Influence of two filtering modes were researched with electro-oculographically recorded impulse-like eye movements. Linear finite impulse response (FIR) and non-linear hybrid median filters were explored by considering gain and latency parameters that yield the most important information in the case of these eye movements. It is stated that carefully selected lowpass filtering can securely be run without considerable changes in parameter values in order to discard noise stemming from physiological or other reasons.

Data Display↗

PubMed2000

Increased retinal image velocity after vestibular lesion.

The vestibulo-ocular reflex stabilizes gaze during head movements by producing compensatory eye movements. Retinal image velocity (RIV) is defined as the difference between the eye and head velocities. The RIV of 20 vestibular schwannoma (VS) patients and 17 healthy controls was measured with a head autorotation test. The head autorotation test had a sensitivity of 80% and a specificity of 88%. The mean RIV (degree/second) +/- 95% confidence intervals of the VS patients in the 5 frequency bands of 1 to 5 Hz was respectively 4.8 (4.2 to 5.5), 11.5 (8.6 to 14.4), 21.7 (15.5 to 27.9), 25.2 (17.1 to 33.4), and 26.1 (13.1 to 39.1). The RIV of the VS patients was asymmetrically larger on the operated side (P<0.05) in the frequency band of 1 Hz. The mean RIV was significantly (P<0.05) larger in the VS patients than in the controls in the frequency bands of 1 to 4 Hz. The vestibulo-ocular reflex is inaccurate after VS surgery; but the inaccuracy may not lead to the occurrence of any symptoms.

Adult↗

PubMed2000

Classical Barrett esophagus contrasted with Barrett-type epithelium at normal-appearing esophagogastric junction. Central Finland Endoscopy Study Group.

BACKGROUND: Incomplete intestinal metaplasia or specialized columnar epithelium (SCE) is the histologic hallmark of Barrett esophagus (BE), but it may also occur at a normal-appearing gastroesophageal junction without BE. We studied whether differences occur between BE patients and those with SCE at the squamocolumnar junction but without BE (abbreviated JSCE), in terms of endoscopic and histologic signs of gastroesophageal reflux disease (GERD) and Helicobacter pylori gastritis. METHODS: A total of 1059 consecutive patients referred for endoscopy in one hospital district in Finland were enrolled in the study. Biopsy specimens (at least two from each site) were obtained from the gastric antrum and the corpus of the stomach and from the esophagogastric junction and distal esophagus. RESULTS: Classical BE was detected in 25 (2%) and JSCE in 99 (9%) patients. Dysplasia in the metaplastic mucosa was observed in six BE patients but in none of the JSCE patients (P < 0.001). In multivariate analysis the independent risk factors for BE were endoscopic erosive esophagitis (odds ratio (OR), 6.08; 95% confidence interval (CI), 2.50-14.82), male sex (OR, 3.02; 95% CI, 1.20-7.65), and age (OR, 1.02 per year; 95% CI, 1.00-1.06). The independent risk factors for JSCE were endoscopic erosive esophagitis (OR, 1.88; 95% CI, 1.08-3.29) and age (OR, 1.03; 95% CI, 1.02-1.05) but not H. pylori infection (OR, 1.57; 95% CI, 0.83-2.97) or chronic gastritis (OR, 0.88; 95% CI, 0.44-1.75). In univariate analysis, however, JSCE was associated with antral-predominant atrophic gastritis (77% H. pylori-positive). Unlike in JSCE patients, male sex strongly predominated among BE patients (P = 0.01). The mean ages of BE and JSCE patients did not differ. CONCLUSIONS: Both BE and JSCE without BE increase in prevalence with age, and both associate with endoscopic erosive esophagitis but not with H. pylori gastritis. However, because of the marked sex disparity, JSCE cannot be a direct precursor of BE, and some factors other than GERD alone also play a role in the pathogenesis of BE. Compared with BE, dysplasia is a rare finding in JSCE, and endoscopic surveillance with biopsy specimens from JSCE patients without dysplasia is not recommended.

Barrett Esophagus↗

PubMed2000

Database for a hearing conservation program.

We have developed a database and an analysis program (NoiseScan) for noise-induced hearing loss (NIHL). The exposure data are based on the evaluation of the noise immission level, which includes duration, frequency content, and the use of, and the attenuation performance of, hearing protectors. The input data can handle an unlimited number of exposure periods. If the noise exposure level is not known, the program lists noise levels of comparable work places, and thus provides an estimate of exposure. Confounding medical factors that may contribute to NIHL, such as elevated serum cholesterol level, hypertension, and extensive use of pain killers, are collected. Combined exposure to agents that clearly contribute to NIHL, such as hand-arm vibration, tobacco smoking, use of aminoglycosides and exposure to solvents are also assessed. An unlimited number of audiograms can be stored, and all the data can be completed and edited following collection. The program gives the predicted hearing loss according to the ISO 1999 model based on total exposure. At present, our NoiseScan program (under continuous development in an EU research program) is suitable for the data collection of various risk factors. It can be used to determine whether the hearing loss is occupational in origin and to estimate the efficiency of hearing conservation measures. NoiseScan also predicts the development of hearing loss in individuals in 5-year periods. The goal is to improve and validate the rules by which single and combined risk factors contribute to HIHL, thus leading to more precise prediction of individual hearing loss, and for the evaluation of success of the hearing conservation programs.

Audiometry↗

PubMed2000

Gastroesophageal reflux disease: prevalence, clinical, endoscopic and histopathological findings in 1,128 consecutive patients referred for endoscopy due to dyspeptic and reflux symptoms.

BACKGROUND AND AIMS: Gastroesophageal reflux disease (GERD) reportedly has increased in prevalence while Helicobacter pylori infection and peptic ulcer disease have been on the decrease. The aim of the present study was to examine the prevalence of GERD as well as the clinical, endoscopic and histologic variables that associate with GERD in patients referred for endoscopy. PATIENTS AND METHODS: The study population was drawn from 1,562 consecutive patients referred for endoscopy. The exclusion criteria were previous H. pylori eradication, gastric surgery, anemia and weight loss. Thus 1,128 patients were enrolled in the present study. RESULTS: Of the 1,128 patients, 199 (18%) were referred for endoscopy due to heartburn and/or regurgitation. GERD, defined as chronic (>6 months) heartburn and/or regurgitation with or without erosive esophagitis, Barrett's esophagus, esophageal ulcer or stricture, was detected in 248 (22%) patients. Of the 248 GERD patients, 81 (33%) had endoscopy-negative GERD, but of those aged <50 years (n = 67), 57 (85%) were endoscopy-negative. The overall incidence of GERD was 307 per 100,000 population/year and that of endoscopy-positive GERD 207/100,000/year. The positive and negative predictive values of heartburn and regurgitation for endoscopy-positive GERD were 0.37 (95% CI 0.31-0.44) and 0.90 (95% CI 0.88-0.92), respectively. Independent risk factors for GERD were male sex (OR 1.9, 95% CI 1.3-2.7), previous medication for upper gastrointestinal symptoms (OR 2.7, 95% CI 1.7-4.1), the use of nonsteroidal anti-inflammatory drugs (NSAIDs; OR 2.0, 95% CI 1.3-3. 0), histologic esophagitis (OR 2.2, 95% CI 1.5-3.2) and incomplete intestinal metaplasia at the gastroesophageal junction (OR 1.7, 95% CI 1.0-3.1). Chronic gastritis was protective against GERD (OR 0.7, 95% CI 0.5-0.9). No association was observed between GERD and H. pylori infection. The risk of patients aged <50 years (n = 407) of having major lesion (Barrett's esophagus, esophageal stricture, peptic ulcer, esophageal/gastric carcinoma) was significantly lower than that of patients aged >50 years (n = 721; OR 0.5, 95% CI 0.3-0. 9, p = 0.01). CONCLUSIONS: The correlation between reflux symptoms and endoscopy-positive GERD is poor and most GERD patients aged <50 years have endoscopy-negative GERD. The use of NSAIDs is a risk factor for GERD, whereas chronic gastritis, but not H. pylori infection, may protect against GERD. Incomplete intestinal metaplasia at the gastroesophageal junction is associated with GERD.

Adenocarcinoma↗

PubMed2000

Production of diagnostic rules from a neurotologic database with decision trees.

A decision tree is an artificial intelligence program that is adaptive and is closely related to a neural network, but can handle missing or nondecisive data in decision-making. Data on patients with Meniere's disease, vestibular schwannoma, traumatic vertigo, sudden deafness, benign paroxysmal positional vertigo, and vestibular neuritis were retrieved from the database of the otoneurologic expert system ONE for the development and testing of the accuracy of decision trees in the diagnostic workup. Decision trees were constructed separately for each disease. The accuracies of the best decision trees were 94%, 95%, 99%, 99%, 100%, and 100% for the respective diseases. The most important questions concerned the presence of vertigo, hearing loss, and tinnitus; duration of vertigo; frequency of vertigo attacks; severity of rotational vertigo; onset and type of hearing loss; and occurrence of head injury in relation to the timing of onset of vertigo. Meniere's disease was the most difficult to classify correctly. The validity and structure of the decision trees are easily comprehended and can be used outside the expert system.

Databases, Factual↗

PubMed2000

Lossless compression of emission tomography images.

An adaptive lossless compression method using predictive coding with the Rice codes is proposed for low resolution three-dimensional biomedical images. The method is evaluated with the brain positron emission tomography (PET) images. The results are considerably better than with static arithmetic coding.

Algorithms↗

PubMed2000

Lossy compression of auditory brainstem response signals.

Compression of digital signals is frequently utilised in numerous applications like music and speech signals. So far compression of biomedical signals has concentrated almost purely on electrocardiography. We recently opened compression studies on biomedical signals concerning otological measurements performed in accord with hearing and balance problems of humans. In this paper we shall present results for auditory brainstem response signals gained with traditional and modern compression methods as well as one of ours.

Brain Stem↗

PubMed2000

Neural network prediction of polyproline type II secondary structures.

This study considers detection of polyproline type II secondary structures from protein sequences. This difficult problem was handled with multilayer perceptron neural networks, which were found to be useful for such bioinformatics studies. Polyproline II secondary structures have not previously been tried to be predicted from sequences.

Humans↗

PubMed2000

Nearest neighbour classification with heterogeneous proximity functions.

Heterogeneous proximity functions are similarity or distance functions which process data differently according to the scale of attributes. We compared two Minkowskian distance functions with three heterogeneous proximity functions to test whether these functions were better in data sets with attributes of mixed type. Significant differences in nearest neighbour classification accuracy were found in 11 of all the 21 data sets. City-block and Euclidean distance functions outperformed Gower's similarity function and Heterogeneous Euclidean-Overlap Metric, while Heterogeneous Value Difference Metric (HVDM) was better than the other functions. HVDM classified mixed data best, because it treats nominal attributes more carefully than the other functions.

Artificial Intelligence↗