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Biomedical subjects

T Ojala

Publications and source records attributed to T Ojala.

14 recordsLinked to original sources
PubMed2000

Antimicrobial activity of some coumarin containing herbal plants growing in Finland.

Antimicrobial screening against selected Gram-positive and Gram-negative bacteria, yeasts, mold, as well as plant pathogenic fungi, with emphasis on method optimization was carried out on methanol extracts prepared from seven plants grown in Finland. Sensitivity to the extracts was found to vary considerably among the micro-organisms, the extract from Petroselinum crispum and Ruta graveolens showing the highest toxicity against Rhizoctonia solani. The growth of Heterobasidium annosum was inhibited, whereas that of Phytophtora (cactorum) was promoted by all the extracts. The antibacterial and antifungal activities of six natural coumarin compounds were weak, except for the inhibitory effect against Fusarium culmorum.

Anti-Bacterial Agents↗
PubMed1999

A bioassay using Artemia salina for detecting phototoxicity of plant coumarins.

Artemia salina (brine shrimp) has been successfully used for toxicity testing, and a screening test for phototoxicity has been developed based on this method. The ability of the method to test the phototoxic potential of seven known compounds was investigated. Athamantin (an angular furanocoumarin) and umbelliferone (a simple coumarin) showed no phototoxicity, while linear furanocoumarins exhibited phototoxic activity in the following order: psoralen > bergapten > peucedanin > xanthotoxin. The applicability of this method was also tested in screening the phototoxicity of plant material. Six plants from Apiaceae [Aegopodium podagraria L., Anethum graveolens L., Angelica archangelica L., Levisticum officinalis Koch, Petroselinum crispum (P. Mill) A. W. Hill., and Peucedanum palustre (L.) Moench] and one from Rutaceae (Ruta graveolens L.) were selected, all of them known to contain furanocoumarins. Extracts from leaves collected at different times during the growth period were used in the screening. Our results were in accordance with the furanocoumarin content of these plants and with the results of other phototoxicity tests. The Artemia salina method proved to be rapid, simple and inexpensive, and is therefore ideal in the initial biological screening of large numbers of samples for simultaneous detection of both toxicity and phototoxicity.

Animals↗
PubMed1989

Transport properties of a cation exchange membrane with sodium and potassium as counterions.

The measured transport properties for the cation exchange membrane Ionics 61AZL389 in the Na+ + K+ mixed counterion states are presented. The transport numbers of counterions and of water as well as the specific conductivity of the membrane showed approximately linear behaviour as a function of ionic fraction in the membrane. It is therefore concluded that it is possible to estimate the transport numbers of counterions from known selectivity coefficients and concentrations in the external solution. The transport number of water and the specific conductivity of the membrane can also be evaluated reasonably accurately using data for membranes in pure homoionic states. The separation ratio was found to be constant over a wide range of concentration ratios under the hydrodynamic conditions used experimentally.

Chemical Phenomena↗
PubMed1986

Apparatus for simulating extraction forces.

The extraction forces can be stimulated using a mean value indicator, extraction forceps and a phantom skull. The rocking and twisting moments occurring during "extraction" can be measured with strain gauges. Before beginning practical work on patients, dental students carried out simulated extractions of various teeth. The moments were significantly lower than forces needed for real extractions. When using the simulator, the students must be supervised by a teacher able to demonstrate the correct grips of forceps handles and the correct style in extraction.

Education, Dental↗
PubMed1981

The visual analog scale in multiple-dose evaluations of analgesics.

A double-blind, randomized trial was carried out in patients suffering from pain after removal of an impacted lower wisdom tooth. The analgesic effects of a codeine preparation (Staralgin), a dextropropoxyphene preparation (Doleron novum), and paracetamol were compared in a multiple-dose study of 94 patients. The assessments of pain were made hourly on a visual analog scale, and the evaluation was carried out according to a method which takes into account both duration of effect and number of tablets taken. The most pronounced pain reduction and the highest proportion of pain-free patients were reached with the dextropropoxyphene preparation. The reported side effects were few and equally distributed among the treatment groups. The method of evaluation is discussed, and it was noted that the pain score at tablet intake might be of significant importance in comparison of analgesics.

Acetaminophen↗
PubMed1980

Rocking moments in extraction of teeth in the lower jaw.

The purpose of this study was to observe, by means of strain gauges attached to forcep handles, the rocking moments needed during the extraction of lower jaw teeth. Great variation was found between the values for rocking moments and their acting times in different tooth groups. There were also great individual differences in the attachment of teeth. The mean value of the highest lingual rocking moments (2.80 J) was recorded during the extraction of first and second molars, and the highest labial moments (4.78J) during the extraction of canines. The mean value of the total rocking moments was highest during the extraction of canines (1.98 J) and lowest (1.19 J) during the extraction of premolars. The mean value of total rocking moments for incisors and canines was significantly lower (P less than 0.01) and for molars almost significantly lower (P less than 0.05) for the group aged 40 and over when compared to corresponding values for the group under 40 years of age. The lowest mean value of all extraction times was observed for incisors in all age groups.

Adult↗
PubMed1980

The importance of alveolar bone loss, width of periodontal space, visibility of lamina dura and divergence of roots on the rocking moments in extraction of teeth in the lower jaw.

The purpose of this study was to investigate the effect of the alveolar bone loss, with width of the periodontal space, the visibility of the lamina dura and the divergence of the roots on the rocking moments that were measured by means of strain gauges and on their acting times. Of the factors studied, alveolar bone loss had the greatest effect on the moments. The extraction time shortened when alveolar bone loss increased. When the periodontal space widened, the moments used decreased. The extraction time was significantly lengthened when the roots were diverged.

Adult↗
PubMed1980

Rocking and twisting moments in extraction of teeth in the upper jaw.

The purpose of this study was to investigate with the strain gauge method the rocking moments needed during the extraction of upper jaw teeth. In addition to the buccal and palatinal rocking moments, the twisting moment was also measured. The highest mean value of both the average and highest buccal and palatinal movements was measured during the extraction of canines. The mean value of the average buccal moments for the first and second molars was significantly higher than for premolars, but the mean value of the average palatinal moments was significantly lower for the first and second molars than for incisors and almost significantly lower than for premolars. The longest extraction times were used during the extraction of molars and canines. There was no difference in the magnitude of the moments for the upper and lower jaw canines. The extraction of the upper jaw incisors required significantly more rocking moment than the extraction of the lower jaw incisors. There was no difference between the upper and lower jaws in the mean values of the total rocking moments for premolars. The mean values of the total and highest rocking moments for molars in the lower jaw were significantly higher than the corresponding values in the upper jaw. The difference was due to the different bone structures of the upper and lower jaw and to different roots of molars in the upper and lower jaw. The extraction times for the canines and molars were significantly higher in the upper jaw than in the lower jaw.

Adult↗
PubMedDate not supplied

Accurate segmentation of the breast region from digitized mammograms.

The segmentation of a digital mammogram into the breast region and the background is a necessary prerequisite in computer-assisted diagnosis of mammograms. By the exclusion of the background region, the accuracy of the analysis is increased and the running-time is decreased. The algorithm which segments the breast region from the background should be fully automated and give correct results for all kinds of digitized mammograms, including low-quality images. In this paper we present such an algorithm based on histogram thresholding, morphological filtering and contour modeling. Quantitative test results indicate that the computed boundary follows the estimated boundary accurately.

Algorithms↗
PubMedDate not supplied

A comparison of lossless compression methods for medical images.

In this work, lossless grayscale image compression methods are compared on a medical image database. The database contains 10 different types of images with bit rates varying from 8 to 16 bits per pixel. The total number of test images was about 3000, originating from 125 different patient studies. Methods used for compressing the images include seven methods designed for grayscale images and 18 ordinary general-purpose compression programs. Furthermore, four compressed image file formats were used. The results show that the compression ratios strongly depend on the type of the image. The best methods turned out to be TMW, CALIC and JPEG-LS. The analysis step in TMW is very time-consuming. CALIC gives high compression ratios in a reasonable time, whereas JPEG-LS is nearly as effective and very fast.

Computer Graphics↗