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Biomedical subjects

R Heikkinen

Publications and source records attributed to R Heikkinen.

16 recordsLinked to original sources
PubMed2007

The effect of oxide thickness on osteoblast attachment and survival on NiTi alloy.

NiTi alloy is used in various medical applications and the surface titanium oxide layer produced naturally or enhanced artificially has been thought to offer a protecting film against allergic and toxic effects of nickel (Ni). In this study, we investigated the effect of different oxide layer thicknesses on the survival and attachment of osteoblastic cells (ROS-17/2.8). AFM, X-ray diffraction and electrical resistance measurements were used to analyze the surface properties of oxidized NiTi samples and the effect of oxidation on material properties. The results clearly showed that straight correlation between oxide thickness and cellular well-being cannot be maid. However, the different thicknesses of oxide layer on NiTi had surprising impacts on cellular responses and also to the properties of the metal alloy.

Alloys↗
PubMed2005

The phase state of NiTi implant material affects osteoclastic attachment.

In the present work, the responses of mature osteoclasts cultured on austenite and martensite phases of NiTi shape memory implant material were studied. We used the sensitivity of osteoclasts to the underlying substrate and actin ring formation as an indicator of the adequacy of the implant surface. The results showed osteoclasts with actin ring on both NiTi phases. However, significantly more osteoclasts were present on the austenitic NiTi than on the martensitic NiTi. We also analyzed the surface free energy of the samples but found no significant difference between austenite and martensite phases. The results revealed that osteoclasts tolerated well the austenite phase of NiTi. The chemically identical martensitic NiTi was not as well tolerated by osteoclasts (e.g., indicated by diminished actin ring formation). This leads to the conclusion that certain physical properties specific to the martensitic NiTi have an adverse effect to the surviving of osteoclasts on this NiTi phase. These results confirm that mature, authentic osteoclasts can act as cell probes in experiments concerning aspects of biocompatibility of bone implant materials.

Bone and Bones↗
PubMed1998

Improved laboratory test selection and enhanced perception of test results as tools for cost-effective medicine.

Inconsistencies in the way physicians perceive and handle identical laboratory results have untoward effects on morbidity, mortality and cost of medical care. In this context, the selection of suitable tests to answer definite clinical questions, and the manner in which laboratory results are presented have great impact on the action taken by the clinician. This review addresses preferred methods to improve laboratory test selection, and examines methods that more effectively convey laboratory results to clinicians. It is anticipated that refined selection of tests, and presentation of the test results in a configuration that is easily perceived by the clinician, will facilitate interpretation of laboratory reports. Furthermore, any measures that promote the application of laboratory information in medical practice improve economics at the laboratory-clinical interface. The presently described methods to optimize test selection and interpretation are: likelihood ratios to provide estimates of the ability of a test to identify a clinical condition; consensus- and discriminant function-analysis to estimate the performance of tests in diagnosing a particular disease or condition; receiver operating characteristic (ROC) curves to assess discrimination capabilities. The methods which improve test result perception are expression of results as multiples of the upper normal limit, utilizing signal strength to provide prognostic probabilities, and presentation of results in graphic forms that display mutually interrelated functions, with a specific cluster of results being highly suggestive of a given condition. In addition, we discuss application of expert systems to provide rules based on knowledge and experience to analyze results of tests and suggest diagnosis and action, including additional tests when required. It is anticipated that judicious utilization of laboratory services by application of the reviewed methodologies will help to achieve medically justified responses at a lower cost and help to achieve a proper balance between cost of tests and their clinical usefulness.

Clinical Laboratory Techniques↗
PubMed1996

Laboratory cost management.

Laboratory cost management deals with the economical use of laboratory resources such as capital, equipment and manpower. Cost analysis is a tool for cost management, by means of which the laboratory manager can properly set priorities, choose appropriate test procedures, set personnel policies and make better investments of his resources. This article sets out some important aspects of cost analysis, such as the construction of cost curves, the factors that enter into cost analysis, the context in which cost analysis is used, and the limitations of this type of analysis.

Costs and Cost Analysis↗
PubMed1991

Serum markers for breast cancer.

A considerable number of tumour markers and other laboratory tests are used for follow up and evaluation of breast cancer patients. No marker presently available is sensitive enough for early diagnosis and screening, but markers can be used to evaluate response to therapy and for early detection of a relapse. Of the markers presently available, CA 15-3 and CEA are mostly used. CA 15-3 appears to be somewhat more sensitive than CEA. When a cut-off level giving 97.5% specificity is used, the sensitivity of these assays is only about 5-25% in local disease and 50-70% in advanced disease. The combined use of these markers increase the sensitivity by 5-10%. The CA 15-3 assay measures a family of molecules called breast mucins, and several newer assays including MCA, MSA, CA 549, CA M26, CA M29 and BCM appear to measure members of the same family. The results obtained by these assays and with CA 15-3 correlate fairly well. So far none of the new assays has proven superior to CA 15-3. Of patients with advanced cancer, 20-30% are negative for the above mentioned markers. For these patients it may be worthwhile to try other markers not related with the above mentioned.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1984

Identification of the isoflavonic phytoestrogen daidzein in human urine.

The identification by gas chromatography-mass spectrometry of the isoflavonic phytoestrogen daidzein [7-hydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one] for the first time in human urine is described. The metabolism and effect on reproduction of isoflavones in animals and the possible significance of phytoestrogens in man is discussed. Preliminary results on the quantitative excretion of daidzein in female subjects consuming different diets are also reported.

Chromans↗
PubMed1983

Selective chromatographic fractionation of catechol estrogens on anion exchangers in borate form.

The borate form of anion exchangers has been investigated for its utility in the field of estrogen analysis. The borate form of a weak (DEAE-Sephadex A-25) and a strong (QAE-Sephadex A-25) anion exchanger was easily prepared by appropriate washing of the gels, without the need of time consuming immobilization techniques. Estrogens with vicinal cis-hydroxyls were strongly retained in both gels through formation of borate complexes and readily separated from estrogens not possessing such groups. Moreover, borate complex formation with the labile o-dihydroxyphenyl moiety of catechol estrogens fully protected them from decomposition during chromatography. Quantitative recovery of catechol estrogens was thereby obtained without use of antioxidants. The borate form of QAE-Sephadex A-25 was capable, in addition, of separating estrogens not possessing vicinal cis-hydroxyls from the corresponding neutral steroids.

Anion Exchange Resins↗
PubMed1983

5. Analytical methods: physiochemical assays. Use of ion exchange chromatography in steroid analysis.

Ion exchange chromatography (IXC) has been utilized in many different ways in the field of steroid analysis already for more than thirty years. Steroid conjugates can be extracted and fractionated on anion exchangers by virtue of their anionic nature, and in the same way the weakly acidic phenolic steroids are separated from the neutral ones. Anionic and cationic contaminants are removed by IXC during purification of the samples, and further, the use of lipophilic ion exchangers allow the simultaneous reversed phase chromatographic elimination of neutral lipids. Finally, certain steroids with specific functional groups can be selectively fractionated by ion exchangers converted to a suitable form. The high capacity and flexibility of IXC has made it a technique of choice in the purification of biological samples for the multicomponent analysis of steroids by GC or GC-MS during the last decade.

Chromatography, Gas↗
PubMed1982

Excretion of the lignans enterolactone and enterodiol and of equol in omnivorous and vegetarian postmenopausal women and in women with breast cancer.

Dietary studies and assays of urinary lignans in postmenopausal women showed that lignan excretion is significantly lower in urine of women with breast cancer than in normal omnivorous and vegetarian women and confirmed that there is a significant correlation between fibre intake and lignan excretion. It is suggested that the precursors of the human lignans enterolactone and enterodiol formed by the intestinal microflora are to be found in fibre-rich foods such as grains, nuts, and legumes. Excretion of equol, which has antioestrogenic properties, was similar in all groups studied and did not correlate with fibre intake, but occasional high values were found in some subjects.

4-Butyrolactone↗
PubMed1982

Capillary gas chromatographic method for the analysis of lignans in human urine.

We describe a capillary column gas chromatographic (GC) method for the analysis of lignans in urine. Lignans are excreted as mono-glucuronides which are first extracted on a small reversed-phase cartridge of octadecylsilane bonded silica (Sep-Pak C18) and thereafter isolated by anion exchange chromatography on DEAE-Sephadex A-25, prepared in the acetate form. Lignan mono-glucuronides are enzymatically hydrolysed and re-extracted on a Sep-Pak C18 cartridge. Quantification is carried out by capillary column GC of the trimethylsilyl ether derivatives. The specificity of the method was checked by GC/MS and the intra-assay coefficient of variation (CV) for the two lignans, enterolactone (trans-2,3-bis(3-hydroxybenzyl)butyrolactone) and enterodiol (2.3-bis(3-hydroxybenzyl)butane-1,4-diol) varied between 5 and 8%. Some values for the excretion of these lignans by normal men and women are presented.

4-Butyrolactone↗
PubMed1982

Use of hypnosis in studies of the effect of stress on cardiovascular function and hormones.

In an attempt to separate the somatic and mental components of stress, groups of young male volunteers underwent running exercises and sauna baths, and roughly one year later had the same experiences recalled under hypnosis. In addition, experiments involving mental stress in the form of mental arithmetic were performed. A variety of physiological and biochemical parameters was measured on each occasion. Results for cardiovascular responses, renin-angiotensin-aldosterone, cortisol, testosterone, androstenedione, prolactin and growth hormone are reported. It is concluded that the mental component of combined mental and somatic stress may be separated from the somatic component by hypnotic suggestion. The response during hypnotic suggestion of the stress is usually of less but sometimes of the same magnitude as that obtained during the actual stress. Occasionally the response goes in the opposite direction during hypnotic suggestion as compared to the real situation. The individual responses vary considerably between individuals. The hormones most sensitive to mental stress are growth hormone, androstenedione, cortisol, renin and angiotensin II. In the present study, mental stress had a depressing effect, if any, on plasma prolactin. Hypnosis in itself has no effect on plasma hormones in unstressed subjects compared to the normal diurnal variations.

Adult↗
PubMed1981

Diet and urinary excretion of lignans in female subjects.

Lignans, a class of compounds having a 2,3-dibenzylbutane skeleton, have recently been identified for the first time in humans and animals and evidence indicating their formation by intestinal microflora has previously been established in rats and humans. In the present report the influence of diet on the biosynthesis of this new group of compounds was investigated by comparing the urinary excretion of the principal lignan, trans-2,3-bis-(3-hydroxybenzyl) -butyrolactone (enterolactone, HBBL), in 12 omnivoric and 14 vegetarian women. Young vegetarian women were found to excrete significantly greater amounts of enterolactone than omnivores, while old vegetarians excreted comparable amounts to the omnivore group. A statistically significant (P less than 0.01-0.001) correlation was found between the amount of fibre in the diet and the urinary enterolactone excretion.

Adult↗
PubMed1981

Reversed-phase C18 cartridge for extraction of estrogens from urine and plasma.

We describe a simple method for extraction of estrogens that is efficient over the whole polarity range of estrogen metabolites in urine and plasma. A small reversed-phase C18 cartridge (Sep-Pak C18, Waters Associates, Inc.) is used for this purpose. After application of the biological fluid, followed by an aqueous wash, estrogens are eluted in 3 mL of methanol. For urine the pH should be kept at 3 before the methanol elution. When estrogens are extracted from plasma, the steroid-protein interaction is counteracted by the presence of triethylammonium sulfate and D-norgestrel at pH 5. The recoveries of added 3H-labeled estrogens are essentially quantitative. The capacity of the column is high and estrogens can be extracted from large volumes of pregnancy urine without loss in the washing water. Because of the high flow rate (2 mL/min) and the small volume of methanol in which the estrogens are eluted, the whole procedure is convenient and rapid.

Chromatography, High Pressure Liquid↗