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Biomedical subjects

H Olkkonen

Publications and source records attributed to H Olkkonen.

At least 19 recordsLinked to original sources
PubMed2001

Pamidronate increases trabecular bone mineral density in immobilization osteopenia in male rats.

BACKGROUND AND AIMS: Osteopenia is a common consequence of immobilization. We investigated the effects of pamidronate on immobilized bone in male rats. MATERIAL AND METHODS: Eighty male Wistar rats (5 months old) were divided in five groups (control (C); pamidronate at 0.5 mg/kg per dose (Pam0.5); immobilization (N); pamidronate at 0.05 mg/kg per dose + immobilization (N + Pam0.05); and pamidronate at 0.5 mg/kg per dose + immobilization (N + Pam0.5). The rats were immobilized on their right side by sciatic neurectomy. Pamidronate was given subcutaneously three times a week for three weeks. Trabecular bone mineral density (TBMD) of the upper femur, ultimate failure load of the femoral diaphysis, ash weight of femur, calcium content of femoral ash, and ash weight corrected with bone volume (AWcc [g/cm3]) were determined. Histomorphometry of proximal tibiae was performed by a semiautomatic method. RESULTS: TBMD was higher on both sides in Pam0.5 and N + Pam0.5 groups than in C or N groups. Ultimate failure load was not altered significantly with treatment. AWcc of the immobilized femur was lower (p < 0.001) than in the contralateral limb in N, N + Pam0.05 and N + Pam0.5 groups. Both resorption and formation parameters were suppressed by pamidronate. CONCLUSION: Pamidronate treatment seemed to increase trabecular bone density, although it was not effective in maintaining the AWcc of the operated extremity. Pamidronate did not seem to affect the ultimate failure load of cortical bone.

Animals↗
PubMed2001

Alendronate influences bending force of femoral diaphysis after orchidectomy in rats.

BACKGROUND AND AIMS: We examined the effect of alendronate on bone following orchidectomy-induced osteoporosis. MATERIAL AND METHODS: Eighty male rats were used. Group I (C) served as the untreated control. In group II (ALN), alendronate was administered subcutaneously (18 microg/kg). In group III (ORC), rats were castrated only. In group IV (ORC+ALN), administration of alendronate (18 microg/kg) was started immediately after castration, and in group V (ORC + ALN-21) medication was started 21 days after castration. Alendronate was given twice a week for eight weeks in the treatment groups. Bone mineral density (BMD) of the proximal femur, ultimate bending forces of femoral diaphyses, ash weights of femurs (AWcc) and the calcium content (Ca) of femoral ash were determined. Histomorphometric analysis was performed on trabecular bone of proximal tibiae. RESULTS: BMD of the proximal femur was significantly decreased by orchidectomy compared with C and ALN. However, no statistical difference was observed between alendronate-treated groups (ORC + ALN and ORC + ALN-21) and the ORC group. Histologically, alendronate reduced the trabecular bone turnover. Ultimate bending force increased significantly in the ORC+ALN-21 group compared with group C, and had a good correlation with the cortical width of tibia (r = 0.53, p < 0.001). Ash weight per bone volume (AWcc) was lowest in the ORC group, whilst alendronate maintained AWcc after orchidectomy. CONCLUSION: Alendronate increased the ultimate bending force of the femoral diaphysis after orchidectomy. On the other hand, ALN treatment was not able to maintain the BMD of the proximal femur at the pre-orchidectomy level. Our results suggest that the remodelling and modelling of bone may influence the response to ALN treatment.

Alendronate↗
PubMed2000

Effects of the histamine H(1) receptor blocker, pyrilamine, on spontaneous locomotor activity of rats with long-term portacaval anastomosis.

To find out whether the changes in the brain histaminergic system are involved in the pathophysiology of portal-systemic encephalopathy, we examined the effects of histamine H(1) receptor blockade on spontaneous locomotor activity, feeding, and circadian rhythmicity in rats with portacaval anastomosis (PCA). Pyrilamine, an H(1) receptor blocker (15 mg/kg/day), was delivered with osmotic minipumps. Spontaneous locomotor activity was recorded for 72 hours in the open-field with an electromagnetic detector. Food intake was monitored twice daily at the end of the light (7 PM) and the dark (7 AM) phases for 3 days. Histamine H(1) receptor density in the suprachiasmatic nucleus (SCN) was examined with receptor autoradiography, employing [(3)H]pyrilamine. PCA surgery led to decreased movement time and velocity and flattened amplitude of the circadian rhythms of locomotion and feeding. In sham-operated rats, pyrilamine significantly decreased the movement time and velocity, as well as the total food consumption and completely abolished the circadian rhythmicity of locomotion. In contrast, pyrilamine increased the movement time and velocity in PCA-operated rats, particularly in the dark phase, and improved the precision of the circadian rhythms of locomotion and feeding. Histamine H(1) receptor density was not altered by PCA surgery, whereas pyrilamine treatment led to the complete blockade of H(1) receptors in both sham- and PCA-operated rats. We suggest that histaminergic imbalance has contributed to the generation and maintenance of the decreased spontaneous locomotor activity and altered circadian rhythmicity following PCA surgery in the rat, probably via an H(1) receptor-mediated mechanism.

Animals↗
PubMed1999

Gain optimized cosine transform domain LMS algorithm for adaptive filtering of EEG.

The most common adaptive filtering method is based on the least mean square (LMS) algorithm, which updates the filter coefficients by a gradient based method. The convergence properties of the LMS algorithm can be improved by updating the filter coefficients in the frequency domain. This work presents a new LMS algorithm, which updates the filter coefficients in the cosine transform domain. Instead of a constant gain factor in the coefficient updating the present method uses a time-varying optimized gain factor. This yields a considerably improved convergence performance. The algorithm was applied to the EEG activity analysis of freely behaving rats.

Algorithms↗
PubMed1998

The fasciculus retroflexus controls the integrity of REM sleep by supporting the generation of hippocampal theta rhythm and rapid eye movements in rats.

The fasciculus retroflexus (FR) fiber bundle comprises the intense cholinergic projection from the medial division of the habenula nucleus (Hbn) of the epithalamus to the interpeduncular nucleus (IPN) of the limbic midbrain. Due to the widespread connections of the Hbn and IPN, it could be surmised that the FR is integrated in the processings of various subsystems that are known to be involved in the sleep-wake mechanisms; relevant sites include the limbic forebrain and midbrain areas and more caudal pontine structures. Consequently, the present study addressed the significance of the FR in the spontaneous sleep-wake stage-associated variations of the different activity patterns of frontal cortex and hippocampal electroencephalograms (EEGs), the electrooculogram, and body movements, in freely behaving rats that had been subjected to either bilateral electrolytic lesioning of the FR or control operations. The evolution of different state combinations was assessed by the combinatory analysis of different activity stages appearing on the 6-h records. As compared to the control-operated group, the FR lesioning substantially reduced the time spent in rapid eye movement (REM) sleep by 79%, moderately decreased the duration of the intermediate state of sleep by 29%, and quiet waking state by 44%, but had virtually no effects on the durations of different types of non-REM sleep (i.e., drowsiness that which involved quiet sleep or slow-wave sleep containing delta and spindle state components) or on the times of active waking behavior that corresponded to the body movements. Quantitative decomposition analyses revealed marked variations in the frontal cortex and hippocampal activity as well as REM during the course of the extracted sleep-wake stages described and there were also some group differences. Of those individual features that were used to determine different sleep-wake stages, the overall hippocampal theta time (41% decrease) and single REM frequency (71% reduction during the REM sleep) were most affected. In contrast, the various properties of desynchronization/synchronization patterns of frontal cortex EEGs were consistently hardly influenced by the FR lesioning. Therefore, the present data suggest the involvement of the FR in the REM sleep processes by establishing prominent associations with the limbic and REM control mechanisms that involve the hippocampus and plausibly pontine ocular activity networks.

Animals↗
PubMed1996

Histaminergic modulation of neocortical spindling and slow-wave activity in freely behaving rats.

Histaminergic H3 receptor antagonists stimulate neuronal histamine release and could consequently have a number of physiological effects in the brain. The effects of H3 receptor blockade, induced by systemically administered thioperamide, were assessed on the frontal cortex electroencephalographic (EEG) properties in freely behaving rats. The relationship of EEG activity variables to endogenous brain histaminergic markers was also examined, both in controls and in portocaval anastomosis (PCA)-operated rats (which show increased levels of brain histamine and t-methylhistamine). Thioperamide reduced the incidence of thalamus-regulated EEG spindles, while it slightly increased their amplitude. It furthermore reduced the spectral power of low-frequency (1.5-5Hz) EEG, which effect was equally distributed over the spindle and non-spindle EEG states. These EEG effects were accompanied by increased motor activity of the animals. Both the low-frequency EEG activity and spindle incidence correlated inversely with the histamine level of the brain (hypothalamus and cerebellum excluded) while t-methylhistamine level correlated with the degree of thioperamide-induced reduction of slow-wave EEG activity. The present results provide evidence for the involvement of endogenous brain histamine level, histamine release (as assessed by t-methylhistamine level) and H3 receptors in the histaminergic regulation of neocortical synchronization patterns assumed to be linked to arousal control.

Animals↗
PubMed1995

Running discrete Fourier transform for time--frequency analysis of biomedical signals.

The present work introduces a running discrete Fourier transform (RDFT) for time-frequency analysis (TFA) of nonstationary short-term signals. The RDFT algorithm adapts a window function, which has adjustable time-frequency characteristics. A generalized weighting filter was proposed, which maps the time-dependent signal into the time-frequency plane. As an example the weighting filters were deduced for exponential, gamma and binomial window sequences. Application of the RDFT algorithm to the analysis of biomedical signals is discussed.

Algorithms↗
PubMed1994

Clodronate prevents immobilization osteopenia in rats.

We investigated the effect of clodronate on immobilization osteopenia (IO) induced by sciatic neurectomy in rats. 100 Wistar female rats were divided into 5 groups of 20 animals each: 1) sham-operated, control group, 2) IO+saline control group, 3) IO+clodronate 3 mg/kg/day, 4) IO+clodronate 10 mg/kg/day, and 5) IO+clodronate 30 mg/kg/day. Clodronate was administered subcutaneously beginning on the day after nerve sectioning. After 7 weeks, the animals were killed and both tibiae were removed. Bone mineral density, ash weight and calcium, phosphorus and magnesium contents of the ash of the tibiae were analyzed. The weight of the rats did not differ between the groups during the experiment. The ash weight of the tibiae decreased by 6.6 percent and the mineral density decreased by 5.1 percent after neurectomy. Clodronate reduced IO in a dose-dependent manner and the highest dose neutralized the effect of neurectomy. The calcium content of the ash decreased after neurectomy as compared to the sham-operated group, and clodronate increased it to the sham-operated level. The bone Ca/P ratio remained normal.

Animals↗
PubMed1992

Running discrete cosine transform.

The discrete cosine transform (DCT) has become an important tool in digital signal processing because its performance is close to the optimal Karhunen-Loeve transform. In this work the running discrete cosine transform (RDCT) is introduced. Using the properties of the discrete Fourier transform kernel W = exp (-2 pi j/N), a fast recursive algorithm was developed for real-time computation of the RDCT coefficients. For N-point RDCT the present algorithm needs only 2N real multiplications. The hardware implementations of the RDCT algorithm and applications in real-time data processing are discussed.

Algorithms↗
PubMed1987

Microcomputer-aided measurement of puff parameters during smoking of low- and medium-tar cigarettes.

A portable microcomputer-assisted flow transducer was developed for analysing puff parameters during smoking of low- and medium-tar cigarettes. Smoke flow was determined by measuring pressure difference between two sites within an orifice flowmeter. According to the Bernoulli equation, the pressure difference is proportional to the square of flow. For calibration of the method, various sizes of air volumes were puffed through the flowmeter by a piston syringe. The calibration curve, which consisted of the flow as a function of the square root of pressure difference, was linear (r = 0.98). The automatic microcomputer analysis consists of the following variables: mean flow and mean volume of inhaled smoke gas, puff duration, time interval between two puffs, number of puffs and total volume inhaled. Eight volunteers smoked 10 low- and 10 medium-tar cigarettes during the cross-over experiments. The investigation indicated that the total inhalation volume of smokers in the case of low-tar cigarettes is twice as large as in the case of medium-tar cigarettes.

Humans↗
PubMed1986

Microcomputer assisted measurement of inhalation parameters during smoking.

A microcomputer aided, battery operated method for analysing puff parameters during smoking was developed. The equipment included a sensitive, differential pressure transducer, a portable microcomputer and a modified cigarette flowmeter. The method is based on measuring pressure differences between two points within the flowmeter. The pressure difference is linearly proportional to smoke flow according to the Poiseuille-Hagen principle. The calibration curve, the mean flow as a function of (the area of puff curve)/puff duration, showed to be linear (r = 0.99) for calculating flow and volume of smoke. In experiments with 11 male volunteers the total inhalation volume reached the range 296-678 ml, the mean puff volume 19-65 ml, the mean puffing rate 15-26 ml/s, the mean puff duration 1.3-3.5 s, the number of puffs 9-16 and the mean interval between puffs 17-25 s.

Adult↗
PubMed1986

Acute effects of dihydralazine mesylate, furosemide, and metoprolol on maternal hemodynamics in pregnancy-induced hypertension.

The intervillous blood flow and other maternal hemodynamic parameters were assessed in 40 mothers with pregnancy-induced hypertension in late pregnancy before and after hypotensive treatment. Furosemide caused a significant decrease in the intervillous blood flow, whereas the effects of dihydralazine and metoprolol were both negative and positive, that is, more individual and diverse. These changes in the intervillous blood flow did not have any correlation with the changes in other maternal hemodynamic parameters. The importance of placental hemodynamic studies in the evaluation of hypotensive drugs is stressed.

Adult↗
PubMed1985

Fast method for computing the Fourier integral transform via Simpson's numerical integration.

A new algorithm for computing the Fourier transform is described. The method is based on the calculation of the Fourier integral transform (FIT) with the aid of the numerical Simpson's integration technique. Compared to the conventional fast Fourier transform (FFT), the new SFIT algorithm, gives results which are much closer to the analytic Fourier transform for discrete signals. Especially in the calculation of the phase spectra considerable improvement is obtained. The N-point SFIT can effectively be computed by using two N/2-point FFTs.

Biomedical Engineering↗
PubMed1984

Dual diode transducer for laser Doppler skin blood velocimeter.

Two parallel, oppositely placed photo-diodes were used to measure the scattered coherent light in the laser Doppler velocimeter used for skin blood flow measurements. The dual-diode arrangement effectively rejects the noise due to mode interference in the laser cavity and 50 Hz pick-up. During clinical tests, the skin blood velocity obtained by the transducer was compared with the results yielded by the conventional single-diode device.

Biomedical Engineering↗
PubMed1982

Interaction between Li, Ni and Sr content in human cancellous bone.

Li, Sr and Ni content of human cancellous bone and their relation to elemental composition was studied in specimens obtained from 88 subjects with a normal mineral status and from 50 subjects having osteoporotic changes due to chronic immobilizing diseases. The concentrations of Ca, Mg, Cd, Co, Cu, Mn, Ni, Li, Pb, Sr and Zn were analyzed with an atomic absorption spectrophotometer and fluoride with an ion selective electrode. The data was analyzed with the linear multiple regression analysis. Ni had a statistically significant inverse relation to Li. There was a significant positive correlation between Sr and Ni contents. Chronic immobilizing diseases did not affect significantly Li, Sr and Ni contents. Also no age dependent changes of these elements were found. The mean concentration S.D. of Li was 0.23 +/- 0.14 microgram/g, of Sr 65.5 +/- 40.7 micrograms/g and Ni 1.29 +/- 0.83 micrograms/g, respectively. The strong interrelation between Li, Sr and Ni suggest that these elements should be analyzed together in studying the role of these elements in the mineralization.

Adolescent↗
PubMed1982

Caries reduction in rats through F + Mg supplementation of dietary sucrose with observations on bone mineral density and soft and hard tissue minerals.

Two control diets with different sucrose contents (44% and 22%) were given to weanling rats for 55 d. The test diets were supplemented with an F + Mg combination, 75 parts/10(6) F as NaF + 50 parts/10(6) Mg as MgO and 38 parts/10(6) F + 25 parts/10(6) Mg, respectively, i.e. using the same supplement/sucrose ratio in each test diet. The supplementation in each test diet caused the same percentage fissure caries reduction, but the absolute mean caries scores were higher in the high-sucrose groups than in the respective low-sucrose groups. Enamel solubility was reduced by the supplementation. Despite the high fluoride supplementation, no untoward effects were recorded in growth and in aortic, heart, and renal calcium contents. Bone mineral density was reduced in the low-sucrose controls and slightly reduced in the high-sucrose F + Mg supplemented rats, as compared with the high-sucrose controls.

Animals↗