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Biomedical subjects

H Olkkonen

Publications and source records attributed to H Olkkonen.

47 records · Page 3Linked to original sources
PubMed1976

Effect of the left lateral recumbent position compared with the supine and upright positions on placental blood flow in normal late pregnancy.

The placental blood flow was assessed by the 99mTc accumulation method in 10 normal pregnancies in the left lateral recumbent position accomplished by a 15 degree wedge and in the supine position. The postural change caused a 17% decrease in the mean placental accumulation rate, which was not statistically significant. Ten patients were moved from the left lateral recumbent position to the upright position, which caused a statistically significant 23% decrease in the mean accumulation rate. Other haemodynamic variables studied were the maternal heart rate and the systolic and diastolic blood pressures. The clinical significance of the haemodynamic changes produced by alterations in posture are briefly discussed.

Adult↗
PubMed1975

Computation of muscle blood flow by 133Xe clearance using polynomial fitting techniques.

A polynomial fitting technique suitable for small computers has been developed for calculation of the muscle blood flow function by the 133Xe clearance method. An application of the method for blood flow measurements in the lower limbs during hyperaemia is presented. The calculated maximum blood flow and peak time values were closely correlated with the manually elicited results.

Blood Volume↗
PubMed1975

A 170Tm gamma scattering technique for the determination of absolute bone density.

A new technique for the determination of absolute bone density is described. The procedure is based on the measurement of both transmitted and scattered photons emitted from a 650 mCi radioisotope source of 170Tm in a narrow beam geometry. The method takes into consideration the change in the effective Z/A as a function of bone density which is due to the changing of the elementary composition of bone when bone material is resorbed. The experimental results show that the density of homogeneous materials can be measured with a reproducibility of 2 per cent. The bone density values for the 24 bone specimens measured by the new method show a good correlation (r=0 with 94) with results obtained by application of Archimedes' principle.

Acrylates↗
PubMedDate not supplied

Effect of clodronate on fracture healing in denervated rats.

The effect of clodronate on healing of the fracture of osteopenic bone was studied in rats. A total of 165 female rats (14 +/- 1 weeks, 216 +/- 2 g) were divided into five fracture groups (n = 30), and a neurectomized group (n = 15). Osteopenia (op) was induced by right sciatic neurectomy 4 weeks before the fracture. Nonosteopenic (nop) rats were not operated. A closed prepinned diaphyseal fracture of the right femur was done by three-point bending method both to op and nop rats, and the left femur served as an unoperated control. All the fracture groups were divided into treatment (clodronate 10 mg/kg/day sc) and control (saline sc) groups, and the administration was continued throughout the study. The op rats were killed 2, 4, 8, and 12 weeks and nop rats 8 weeks after the fracture. Fracture healing was examined by x-ray and bone-bending strength. Neurectomy reduced bone strength (p < 0.01) at 4 weeks. Clodronate did not affect the bending strength of healing callus of op rats at 2, 4, 8, or 12 weeks after fracture, but reduced the strength of healing callus in nop rats (p < 0.05) at 8 weeks. Radiologic callus width increased in clodronate-treated groups both in op (8 and 12 weeks, p < 0.001) and nop rats (8 weeks, p < 0.05) when compared with saline-treated groups. Clodronate did not affect normal bone strength. In conclusion, clodronate did not affect the bending strength of op fracture nor the strength of the control bones. The remodeling of the fracture was delayed with clodronate.

Animals↗
PubMedDate not supplied

The relationship between audiogenic seizure (AGS) susceptibility and forebrain tone-responsiveness in genetically AGS-prone Wistar rats.

The present study characterized the intensity-response functions of extracellular field responsiveness of different cortical/subcortical structures of the forebrain following the free-field presentation of tone stimuli, within a population of genetically audiogenic seizure (AGS)-prone KM-Wistar rats. The neural response properties of each case were compared to its propensity to exhibit AGSs during the continuous tone stimulation (15 kHz, 90 s at max.). The amplitudes or slope components of the evoked responses and their peak latencies showed significant positive (amplitude and slope) and negative (peak latency) Bolzmann's sigmoid relationships with the onset-latency of AGS. These relationships, with areal differences in the slopes of saturation functions, applied for the three different data sets recorded simultaneously from the stratum radiatum dendritic layer of the hippocampal CA1 area, primary auditory cortex layers II-IV, and frontal cortex surface. In addition, the similar type of functions between the evoked response variables and AGS onset latency held when all the areas were considered together. These data suggest that the neural responsiveness to acoustic stimulation of the primary sensory, multimodal and association cortices of the forebrain may altogether contribute to the seizure initiation by that modality in the genetically AGS-prone rats. It has been previously shown that there exist abundant and dispersed auditory projections from these forebrain areas to the brain stem and spinal cord, structures that are generally considered to be the key predisposing factors in the generation of AGS. Hence, the types of correlation found reflect the subject-specific stage of forebrain responsiveness, being either related or unrelated to genetic AGS-specific changes, and possibly its triggering impact upon the lower brain AGS network. Accordingly, the mere comparison of forebrain response measures of these AGS-prone animals with those of the AGS-resistant ones could not reveal the result presented.

Acoustic Stimulation↗
PubMedDate not supplied

Cadmium content of human cancellous bone.

The cadmium content of human cancellous bone was related to age, sex, bone loss, physical properties, and elemental composition. Bone specimens from the anterior iliac crest were collected from 889 cadavers with a normal mineral status, and from 50 cadavers which had bone loss from chronic diseases and immobilization. The element concentrations were analyzed using atomic absorption spectrophotometry. Bone fluoride levels ere determined with the ion specific electrode, the mineral density with the gamma ray attenuation method, and the compressive strength with a strain transducer. The data were analyzed using multiple linear regression analysis. The mean cadmium content of 0.22 +/- 9.16 micrograms/g dry weight (+/- SD) in the samples did not change with age and its content was slightly greater in males than in females. Furthermore, no statistically significant relation was found in cadmium content to bone loss changes or to the calcium content of bone. The cadmium content had a high statistically significant positive correlation with the strontium and nickel content.

Adolescent↗
PubMedDate not supplied

A coherent/Compton scattering method for measurement of trabecular bone mineral density in the distal radius.

A new technique was developed for determination of the trabecular bone mineral density in the distal radius. The method is based on measurement of the intensity ratio of coherently and Compton scattered photons using a 241Am radionuclide as the radiation source and a semiconductor crystal as the detector. The bone material consisted of 28 autopsy samples from distal radii of female subjects. A good correlation was observed between bone ash content and the coherent/Compton scattering ratio. The trabecular bone mineral density correlated well with the mineral density values obtained by the gamma transmission method. The method was reproducible within 3%.

Female↗
PubMedDate not supplied

In vivo measurement of absolute tissue iodine content by fluorescence excitation.

A method based on the measurement of fluorescent and transmitted photons has been developed for the quantitative determination of stable iodine concentrations in tissues. The results are independent of the thickness of the material surrounding the measuring site. The method yields an accuracy of better than 3% for both Ge semiconductor and NaI(TI)detector arrangements.

Elementary Particles↗