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Biomedical subjects

A Korhonen

Publications and source records attributed to A Korhonen.

At least 19 recordsLinked to original sources
PubMed2001

Altered phospholipid-apoB-100 interactions and generation of extra membrane material in proteolysis-induced fusion of LDL particles.

Lipid droplets and membrane material are produced in the extracellular matrix of the arterial intima during atherogenesis. Both in vitro and in vivo experimentation suggests that fusion of modified LDL particles leads to formation of such lipid droplets. Here we applied proton NMR spectroscopy to probe surface phospholipids phosphatidylcholine (PC) and sphingomyelin (SM) of LDL particles during proteolytic degradation of apolipoprotein B-100 (apoB-100). Initiation of apoB-100 degradation was accompanied by the abruptly increased intensity of the choline -N(CH(3))(3) resonance of PC molecules, indicating disruption of their interactions with apoB-100. However, subsequent particle fusion was accompanied by a steady decrease in the intensity of the choline resonances of both PC and SM. Electron microscopy of the proteolyzed LDL revealed irregularly shaped multilamellar membranes attached to aggregates of fused particles. This suggests formation of membrane material with low hydration, in which some of the atomic motions are hindered. Characterization of the behavior of the surface lipids of LDL particles during apoB-100 degradation and other types of LDL modification will aid in understanding molecular mechanisms leading to fusion and generation of multilamellar membrane material in the arterial intima during atherogenesis.

Apolipoproteins B↗
PubMed1998

Remodeling of HDL by phospholipid transfer protein: demonstration of particle fusion by 1H NMR spectroscopy.

There is evidence that phospholipid transfer protein (PLTP) can increase reverse cholesterol transport by inducing favorable subclass distribution in the high density lipoprotein (HDL) fraction. This includes generation of initial cholesterol acceptor particles, pre beta-HDL, and of enlarged particles that are rapidly cleared from the circulation. However, partly because of methodological difficulties, the mechanisms behind the PLTP-mediated interconversion of HDL particles are not fully understood. In this communication, we describe the use of a novel methodology, based on 1H NMR spectroscopy, to study the PLTP-induced size changes in the HDL particles. In accordance with native gradient gel electrophoresis, the 1H NMR data revealed a gradual production of enlarged HDL particles in the HDL3+ PLTP mixtures. In addition, according to a physical model for lipoprotein particles, relating the frequency shifts observable with NMR to the size of the lipoprotein particles, the NMR data demonstrated that PLTP-mediated HDL remodeling involves fusion of the HDL particles.

Biological Transport, Active↗
PubMed1998

Accumulation of strontium and fluoride in approximal dental plaque and changes in plaque microflora after rinsing with chlorhexidine-fluoride-strontium solution.

OBJECTIVES: To find out if strontium is incorporated into plaque and enamel in vivo during a 2-week rinsing period with a chlorhexidine-fluoride-strontium solution and to determine the effects of the rinsing on the numbers of mutans streptococci and lactobacilli in plaque. SUBJECTS AND METHODS: A total of 18 adult participants rinsed their mouths twice a day for 2 weeks, first with a placebo solution and subsequently, separated by a 1-week interval without rinsing, with a chlorhexidine gluconate (0.05%)-sodium fluoride (0.04%)-strontium (100 ppm as SrCl2) rinsing solution (CXFSr) for another 2 weeks. RESULTS: After the CXFSr rinsing period the strontium and fluoride contents (microgram g-1 plaque dry weight; mean +/- sr) of approximal plaque were 32.5 +/- 4.7 and 72.8 +/- 9.0, compared with the respective contents of 8.4 +/- 1.2 and 42.0 +/- 4.8 after placebo rinsing (P = 0.0001 for both comparisons). The strontium content remained elevated for 6 weeks. The median proportion of mutans streptococci of approximal plaque of the total viable count of bacteria was 1% after placebo rinsing but decreased to 0.2% after CXFSr rinsing. The proportion of mutans streptococci remained low at 3 weeks (P = 0.018 vs placebo) but had reached the placebo level at 6 weeks. Rinsing with CXFSr solution did not reduce lactobacilli in plaque. The strontium or fluoride contents of the enamel surfaces subjected to tooth brushing did not significantly change. CONCLUSIONS: Strontium and fluoride accumulated in dental plaque during a 2-week CXFSr rinsing period and the proportion of mutans streptococci in approximal plaque was reduced at least for 3 weeks after completion of the rinsing.

Adult↗
PubMed1998

Detection of low density lipoprotein particle fusion by proton nuclear magnetic resonance spectroscopy.

Recent evidence suggests that fusion of low density lipoprotein (LDL) particles is a key process in the initial accumulation of lipid in the arterial intima. In order to gain a better understanding of this early event in the development of atherosclerosis, it would thus be necessary to characterize the process of LDL fusion in detail. Such studies, however, pose severe methodological difficulties, such as differentiation of particle fusion from aggregation. In this paper we describe the use of novel methodology, based on 1H NMR spectroscopy, to study lipoprotein particle fusion. To test the methodology, we chose proteolytic fusion of LDL particles, an in vitro model that has been well characterized in our laboratory. The spectroscopic data suggested that proteolysis of LDL with alpha-chymotrypsin induced slow initiation of fusion, which was followed by particle fusion at an increased rate. Moreover, 1H NMR spectroscopic data on different kinds of LDL interactions, for example, when LDL formed aggregates with antibodies against human apolipoprotein B-100, were obtained and compared with the electron microscopic characteristics of these preparations. An important finding was that limited aggregation of LDL particles did not disturb the 1H NMR spectroscopic parameters used for the detection of particle fusion and preserved the physico-chemical information on the particles. The 1H NMR methodology developed is sensitive to and specific for low density lipoprotein (LDL) fusion and may also allow for studies of the fate of LDL particles in other in vitro preparations that mimic the arterial interactions in vivo.

Arteries↗
PubMed1997

Assessment of cholesteryl ester transfer protein function in lipoprotein mixtures by 1H NMR spectroscopy.

Studies of cholesteryl ester transfer protein (CETP) function in lipoprotein mixtures pose many difficulties by conventional biochemical methods. For instance, studies on the effects of CETP on the composition of apolipoprotein B containing lipoproteins (very low and low density lipoproteins) in lipoprotein mixtures are tedious due to repeated ultracentrifugational isolations and have thus rarely been performed. Here we present a new 1H NMR spectroscopy technique to assess the CETP function in lipoprotein mixtures. This technique does not require repeated physical isolations of the lipoprotein particles but uses mathematical separation of the fractions on the basis of biochemical prior knowledge based lineshape fitting analysis of specific lipid resonances in the 1H NMR spectra. The lipoproteins are separated according to their size related chemical shift which allows for distinct quantification between very low and low density lipoproteins, the two major apolipoprotein B containing fractions. The methodological basis of the technique is discussed here together with a demonstration that this kind of approach allows dynamic follow up of the lipid transfer reactions in complex lipoprotein and CETP mixtures. The results revealed a consistent behaviour which corroborated the recent findings suggesting that the neutral lipid mass transfer among lipoproteins is not an equimolar heteroexchange.

Apolipoproteins↗
PubMed1997

Identification of Bacteroides forsythus in subgingival dental plaque with the aid of a rapid PCR method.

Bacteroides forysthus has been shown to be prevalent among patients with periodontitis. Conventional microbiological methods used to identify this bacterium, however, are laborious and time-consuming and are therefore not well-suited for screening purposes. We have developed a polymerase chain-reaction (PCR) method which is rapid, specific, and simple to perform and does not require other sample pre-treatment except a brief centrifugation. This method was applied to the detection of B. forsythus in subgingival plaque of 58 periodontitis patients. When compared with the results of conventional culturing, the PCR method always confirmed the culture-positive results, while none of the PCR negative samples was shown to be culture-positive. The PCR method appeared to give more than double the number of samples positive for B. forsythus than culturing (89.7% vs. 37.9%). The analysis requires less than 4 hrs to perform, and is specific only to B. forsythus and sensitive enough to detect fewer than 5 bacteria.

Adult↗
PubMed1997

Effects of dietary fluoride and magnesium supplements on cyclic adenosine monophosphate (cAMP), calcium and magnesium levels in aorta of genetically hypercholesterolaemic RICO rats.

Previous observations have suggested that low intakes of fluoride prevent pathological calcifications of internal organs, including the aortic wall, in experimental animals, fed a basically low magnesium diet. Our group found recently that fluoride has some potentially preventive effect against atherosclerotic serum lipid profiles in genetically hypercholesterolaemic rats. To study whether the apparently positive potential of fluoride against atherosclerosis is also reflected in aortic tissue, through its well known activation of adenylate cyclase, the aortic cAMP content of the rats used in our recent study was determined. Out of a total of 56 male RICO rats, mean weight 160 g, the control group C was fed an adequate diet, with 44% sucrose, a magnesium content of 883 p.p.m. and with 0.5% cholesterol. Group D had the same diet as group C except that the magnesium content was reduced to 200 p.p.m. Group E had the same diet as group D but with the fluoride content elevated from 1.9 to 12 p.p.m. Group G had the same diet as group E but with the magnesium content elevated from 200 to 300 p.p.m. After a feeding period of 6 weeks, the aortas of the animals were removed, cleaned and kept at -70 degrees C until analysed. The mean cAMP content of the aortas, measured by radioimmunoassay, in groups C, D E and G was 439, 546, 681, and 1394 mumol mg-1 protein, respectively. In group G only, the cAMP content was significantly higher than that of the other groups (p < 0.001). The mean calcium and magnesium contents of the aortas of different groups did not significantly differ from each other. Thus in RICO rats, fed a high-sugar low-magnesium diet with cholesterol, supplementation of the diet with a small amount of fluoride elevates the cAMP content of the aorta, provided that the intake of Mg is not very low.

Animals↗
PubMed1997

[The Oulu University Hospital has developed day case surgery for children].

After several changes the children's day surgery was moved to new premises--to the day case surgery unit. Due to these changes there was an excellent opportunity to question the former care practices and to "turn over a new leaf" in the new premises. Care is implemented according to primary nursing. The primary nurse cares for the patient/ the family from hospitalization to discharge. Individuality, family-centerdness, safety and comprehensiveness are emphasized. The personnel and the patients are satisfied with the changes in care practices.

Ambulatory Surgical Procedures↗
PubMed1995

Development of a rapid PCR method for identification of Helicobacter pylori in dental plaque and gastric biopsy specimens.

A rapid and simple polymerase chain reaction (PCR) method was developed to detect Helicobacter pylori in gastric biopsy specimens and dental plaque samples. The primers were targeted to the 16S rRNA sequence of Helicobacter pylori strain ATCC 43504. The system was found to have a theoretical detection level of 0.5 to 5 Helicobacter pylori cells in a 5 microliters sample of dental plaque. In the absence of plaque, the detection level was even better: theoretically, 0.05 to 0.5 Helicobacter pylori cells were detected in water suspension. However, this appeared to be due to the presence of free bacterial DNA in the culture used for the sensitivity determination. Thus, the actual sensitivity of the system was found to be fewer than five Helicobacter pylori cells, irrespective of the type of sample used. The method was then used to analyse 29 dental plaque and gastric biopsy specimens collected from patients with a history of recurrent peptic ulcer disease. Fourteen stomach specimens were positive for Helicobacter pylori when tested with the PCR method, while the respective figures with culture, histological examination and the urease test were 11, 12 and 9. No positive dental plaque samples were observed.

Adult↗
PubMed1995

Inhibitory effect on S. mutans by fluoride-treated conventional and resin-reinforced glass ionomer cements.

The aim of the present study was to study the effect of fluoride gel treatment on fluoride release and inhibition of acid production of Streptococcus mutans by different glass ionomer cements. Test slabs of four glass ionomer materials were fitted into the bottom of a test tube. A layer of S. mutans cells was centrifuged onto the test slabs, and the specimens were incubated for 4 h in 1.7% sucrose solution. Incubations were made using fresh, aged (29 d), aged and F-treated (1.25% F-gel), and aged, F-treated and aged samples (n = 15 per group). After each incubation, pH and F contents of the fluid phase were determined. The freshly mixed glass ionomer samples released large amounts of fluoride, and the pH fall in the fluid phase was significantly inhibited. For aged samples, the fluoride release decreased strongly and no inhibitory effect on acid production by S. mutans was seen. After application of fluoride gel, fluoride release and inhibitory effect were significantly higher than initially for all glass ionomer cements. In conclusion, all glass ionomer cements were able to take up fluoride and subsequently release it, which resulted in reestablishment of their antibacterial effect. The patterns of fluoride release and antibacterial action were virtually the same for conventional and resin-reinforced glass ionomer cements.

Amines↗
PubMed1995

Effect of Lactobacillus rhamnosus strain GG (ATCC 53103) on the growth of Streptococcus sobrinus in vitro.

Lactobacillus GG, a recently characterized L. rhamnosus GG strain (ATCC 53103), has been shown to exert inhibitory activity against a variety of bacterial species, including streptococci. We isolated and studied the effect of the inhibitory substance of Lactobacillus GG on some oral streptococci. The inhibitory activity of the isolated substance was weak, but some growth inhibition was observed in Streptococcus sobrinus pretreated with the substance in comparison with untreated controls. Zones of growth inhibition on agar plates were apparent only at pH values below 5, indicating that the inhibitory activity was restricted to a low pH range. Growth curve experiments showed a statistically significant inhibition between series with and without the isolated substance (P < 0.05). The ultrastructure of S. sobrinus was not affected when treated with the inhibitory substance. The Lactobacillus GG itself did not ferment sucrose. The results offer interesting perspectives for future research focusing on the protective function of normal flora and in the attempt to replace harmful bacterial species in oral microflora with less harmful ones.

Antibiosis↗
PubMed1995

Simultaneous detection of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis by a rapid PCR method.

The identification of periodontal pathogens by conventional methods is time-consuming and difficult. Therefore, a multiplex PCR method for simultaneous detection of Actinobacillus actinomycetemcomitans (A.a.) and Porphyromonas gingivalis (P.g.) was developed for rapid and easy determination of these risk-indicator bacteria in human periodontal disease. The PCR primers were designed to hybridize to various regions of 16S rRNA genes, and a hot-start technique was used to obtain maximum sensitivity and specificity. This method can detect both of these bacteria in subgingival plaque samples at concentrations as low as 5 to 50 cells per sample. The sensitivity, however, was even 10 times better when the bacteria were analyzed in a water suspension. Since the only step between sample collection and the actual analysis is a brief centrifugation of the patient sample, the detection can be readily carried out in four hours. The performance of the method was studied with 36 patient samples. The results showed that the PCR method detected A.a. (44% vs. 25%, respectively) and P.g. (56% vs. 42%, respectively) more often than the conventional culture in plaque samples. Thus, our multiplex PCR method is rapid and more effective than conventional protocols in detecting these periodontal pathogens.

Aggregatibacter actinomycetemcomitans↗
PubMed1995

Serum lipoprotein levels in genetically hypercholesterolaemic RICO rats: effects of a high-sucrose-cholesterol diet without or with altered magnesium and fluoride content.

Genetically hypercholesterolaemic RICO rats (male, 6 weeks old) were randomly distributed into 6 experimental groups. The zero-time basal group A was sacrificed at the start of the experiment while the other groups were fed for 6 weeks and then sacrificed. Group B was fed a stock diet. Control group C was fed a high-sucrose (45%) diet with 0.5% added cholesterol. In the diet of group D, only the magnesium (Mg) content was reduced from the level of group C (883 ppm) to 200 ppm. The diet of group E was the same as that of group D with the addition of 12 ppm of fluoride (F) and the diet of group G was the same as that of group E, but with its Mg content elevated from 200 ppm to 300 ppm. Analysis of aortic blood samples, taken before sacrifice, indicated significant increases in total serum cholesterol (p < 0.01), very low density lipoprotein (VLDL) (p < 0.001) and low density lipoprotein (LDL), (p < 0.001) cholesterol, and a trend to lower high density lipoprotein (HDL) cholesterol in group C, as compared to group B. Significantly lower total (p < 0.05), VLDL (p < 0.01) and LDL (p < 0.01) triglycerides were observed in group C when compared to group B. The LDL phospholipids were significantly higher in group C (p < 0.001) than in group B. When cholesterol levels in groups D, E and G were compared with group C, the VLDL cholesterol in group E and the LDL cholesterol in group G were slightly but significantly (p < 0.05) reduced, while total cholesterol and the other subfractions were unaltered. The LDL triglycerides of groups E and G were significantly smaller still than the already small fraction in group C. The VLDL triglyceride in group E was significantly lower than that of group C (35% reduction, p < 0.001), D and G (p < 0.05). Phospholipids were slightly but significantly reduced in the VLDL fraction of group E and in the LDL fraction of group G (p < 0.05 and 0.01, respectively), as compared to those of group C.

Animals↗
PubMed1994

Enamel dissolution in relation to fluoride concentrations in the fluid of dental plaque-like layers of precultured Streptococcus sobrinus.

Two experiments were conducted to find out what concentration of fluoride (F), when added as NaF to the fluid of an in vitro caries model, would be sufficient for full protection of the underlying enamel during a long (20 or 40 h) fall in 'plaque' pH. An existing caries model with bovine enamel and Streptococcus sobrinus 'plaque' was employed, while the fluid phase was initially either fully or partially saturated with tricalcium phosphate. In the model with fully saturated and more strongly buffered fluid, a 10 parts/10(6) addition of F to the fluid phase caused no inhibition of the pH fall. In the model with partially saturated and weakly buffered fluid, prevention of the pH fall increased along with increase of added F from 2 to 20 parts/10(6). In each model, the 10 parts/10(6) addition of F was associated with complete prevention of the increase of calcium (Ca) in the fluid phase. In the partially saturated, weakly buffered model, findings on the inorganic P of the fluid phase agreed with findings on Ca. The findings for microhardness of the enamel surface indicated a complete prevention of the enamel softening through the 10 parts/10(6) F additive. Enamel F content was elevated by the fermentation, and even more so when F was added with sugar to the fluid phase. The Ca content of Strep. sobrinus cells was reduced when incubated with sucrose for 40 h and, especially, with sucrose and F.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

1H NMR-based absolute quantitation of human lipoproteins and their lipid contents directly from plasma.

A new method is presented for absolute quantitation of lipid and protein contents of human lipoproteins directly from plasma. The method enables complete lipoprotein lipid profiles to be obtained in a total time of less than one hour. Absolute concentrations of triglycerides, phospholipids, total cholesterol, free cholesterol, esterified cholesterol, total proteins, and total masses can be estimated for the very low density (VLDL) and low density (LDL) lipoprotein fractions. For the high density lipoprotein (HDL) fraction all components except triglycerides can be quantitated. The method is a combination of 1H NMR spectroscopy and a sophisticated lineshape fitting analysis technique. In this paper we present the calibration of the method using 15 plasma samples followed by a double-blind test of 51 plasma samples from 43 individuals. In total, 66 plasma samples were analyzed. Comparison of the 1H NMR-based results with the data of the biochemical assays showed excellent agreement; the correlation coefficient for VLDL triglycerides was 0.98, for LDL cholesterol 0.88, and for HDL cholesterol 0.93. This method can be directly integrated to many kinds of biomedical NMR studies to offer additional biochemically important quantitative lipoprotein information, the measurement of which is usually too laborious by conventional biochemical methods and too high-priced to be adapted into the study protocols. Moreover, the method also has considerable potential to be developed for a routine clinical assay.

Adult↗
PubMed1992

Complications of nephropathia epidemica: three cases.

Haemorrhagic fever with renal syndrome (HFRS) in Scandinavia is called nephropathia epidemica (NE), and is caused by the Puumala-virus, which belongs to the Hanta-virus genus. The clinical course of NE is mostly benign, complications are uncommon, and deaths are rarely observed. We report the cases of three patients who developed serious complications in the course of NE caused by the Puumala-virus. One patient died within 24 h after admission, another developed progressive neuromuscular dysfunction (Guillain-Barré syndrome) which required auxiliary ventilation for several weeks before a slow recovery, and a third patient developed empty sella syndrome with pituitary gland insufficiency. In the first two cases the diagnosis of NE was confirmed by a rapid avidity assay for IgG antibody against Puumala-virus. In the third case the clinical course, and demonstration of NE immunity 16 years later, suggested that NE might have caused the hypopituitarism. Some patients with NE caused by the Puumala-virus may require intensive-care treatment, and the development of late complications such as empty sella syndrome and hypopituitarism should be taken into consideration.

Adult↗