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Biomedical subjects

M Almqvist

Publications and source records attributed to M Almqvist.

16 recordsLinked to original sources
PubMed2005

Development of educational image databases and e-books for medical physics training.

Medical physics education and training requires the use of extensive imaging material and specific explanations. These requirements provide an excellent background for application of e-Learning. The EU projects Consortia EMERALD and EMIT developed five volumes of such materials, now used in 65 countries. EMERALD developed e-Learning materials in three areas of medical physics (X-ray diagnostic radiology, nuclear medicine and radiotherapy). EMIT developed e-Learning materials in two further areas: ultrasound and magnetic resonance imaging. This paper describes the development of these e-Learning materials (consisting of e-books and educational image databases). The e-books include tasks helping studying of various equipment and methods. The text of these PDF e-books is hyperlinked with respective images. The e-books are used through the readers' own Internet browser. Each Image Database (IDB) includes a browser, which displays hundreds of images of equipment, block diagrams and graphs, image quality examples, artefacts, etc. Both the e-books and IDB are engraved on five separate CD-ROMs. Demo of these materials can be taken from www.emerald2.net.

Biomedical Engineering↗
PubMed2005

Confirmation of QTL on porcine chromosomes 1 and 8 influencing leukocyte numbers, haematological parameters and leukocyte function.

A genome wide search in European Wild Boar x Swedish Yorkshire (W x Y) inter-cross pigs has earlier identified quantitative trait loci (QTL) for leucocyte number and function on porcine chromosomes 1 and 8 (SSC 1 and 8). To verify the involvement of these chromosomal regions in the regulation of haematocrit (Hem) and haemoglobin (Hb) levels, leucocyte numbers and in vitro leukocyte functions (mitogen induced proliferation and IL-2 production, virus induced interferon-alpha production and neutrophil phagocytosis), animals of different genetic backgrounds were analysed. The animals comprised a back-cross sire family (n=47) of W x Y pigs and six crossbred [Y x Landrace (L)] sire families (n=191). They were genotyped for 16 genetic markers and an interval analysis was performed. On SSC1, a QTL close to S0082 on the q-arm that influenced numbers of white blood cells in L x Y pigs and numbers of band neutrophils and CD8(+) cells in W x Y pigs was identified (P<or=0.01). An additional SSC1 QTL was identified on the p-arm close to S0008 with influence on numbers of CD2(+) cells in W x Y pigs (P<or=0.05). On SSC8, a QTL influencing Hb (P<or=0.01) and Hem (P<or=0.05) levels was identified close to KIT in the W x Y pigs. For L x Y pigs, a second QTL, distal to KIT and close to S0069, on SSC8 influenced the numbers of MHCII(+) cells and mitogen induced proliferation (P<or=0.05), whilst the QTL close to KIT influenced the number of IgM(+) cells in these pigs (P<or=0.05). The results confirm the involvement of earlier identified regions of SSC1 and SSC8 on porcine immune parameters and some candidate genes were suggested.

Animals↗
PubMed2000

Characterization of air-coupled ultrasound transducers in the frequency range 40 kHz-2 mHz using light diffraction tomography.

The aim of this work was to show the applicability of light diffraction tomography on airborne ultrasound in the frequency range 40 kHz-2 MHz. Seven different air-coupled transducers were measured to show the method's performance regarding linearity, absolute pressure measurements, phase measurements, frequency response, S/N ratio and spatial resolution. A calibrated microphone and the pulse-echo method were used to evaluate the results. The absolute measurements agreed within the calibrated microphone's uncertainty range. Pulse waveforms and corresponding FFT diagrams show the method's higher bandwidth compared with the microphone. Further, the method offers non-perturbing measurements with high spatial resolution, which was especially advantageous for measurements close to the transducer surfaces. The S/N ratio was higher than or in the same range as that of the two comparison methods.

Air↗
PubMed1999

High resolution light diffraction tomography: nearfield measurements of 10 MHz continuous wave ultrasound

Light diffraction tomography is an ultrasound measurement method that offers possibilities to make high spatial resolution measurements. The aim of this study was to investigate the spatial resolution of light diffraction tomography by characterizing the complex pressure and phase patterns 0.5-1 mm from the surface of a 5 mm diameter 10 MHz ultrasound transducer. Three different transducers were measured with a detection width of 5 microm, sample distances of 20-40 microm and 50-100 projections/180 degrees. They were excited with a 10 Vpp CW-signal. To verify the results the optical measurements were compared with 75 microm diameter hydrophone measurements and with theoretical calculations. The light diffraction tomography results show very good agreement with the hydrophone measurements and pressure peaks separated 160 microm were resolved. Comparison with the theoretical calculation shows that small distortions, caused by defects in the matching layer or in the piezo-electric disc, disturb the symmetric ring-pattern characteristic of an ideal piston source.

Journal Article↗
PubMed1997

Ultrasound Doppler vector tomography measurements of directional blood flow.

An experimental system has been developed to verify the possibility of detecting flow activity using a technique called ultrasound Doppler vector tomography. A tomography algorithm is used to reconstruct blood flow vector fields using data from computer-controlled ultrasound continuous-wave Doppler scanning equipment. The result is a picture in which the brightness variations represent the reconstructed values of the curl of the velocity field (inverted delta x v). Continuous ultrasound is transmitted into a region with flow activity and the Doppler-shifted signals are received. To obtain measurement data suited for fan beam tomography, the scanning is performed in a plane from points encircling the region. Reconstructions have been achieved using measurement data from two different flow phantoms. A comparison between the experimental results and simulations shows good conformity.

Blood Circulation↗
PubMed1994

cDNA cloning and expression of inducible nitric oxide synthase from rat vascular smooth muscle cells.

Nitric oxide (NO) is an important signal molecule. In blood vessels, nitric oxide produced by the endothelium modulates vascular tone by inducing cGMP formation in smooth muscle cells. The latter cell type does not express NO synthase normally but expression is induced by the cytokines, interferon-gamma, tumor necrosis factor, and interleukin-1. We have constructed a cDNA library from cytokine-stimulated rat aortic smooth muscle cells and isolated a cDNA clone that contains the full-length sequence of inducible NO synthase. It is 4119 bp and confers NO synthesizing activity when transfected into COS-7 cells. The nucleotide sequence is 92% identical with inducible NO synthase of murine macrophages and contains a 497 bp untranslated 3' sequence with five conserved A(U)nA motifs that may be important in the regulation of mRNA turnover. This is supported by the short half-life (2.6 h) of smooth muscle NO synthase mRNA, which contrasts with brain and endothelial NO synthase.

Amino Acid Oxidoreductases↗
PubMed1992

Measurement of height loss during whole body vibrations.

An experimental, in vivo study was performed to measure height changes in subjects exposed to whole body vibrations while seated. Twelve women, with an average age of 22 years, were exposed to sinusoidal vibrations for 5 mins. The vibration frequency was 5 Hz, and the acceleration was 0.1 g Rms. The height loss stemming from vibration exposure was compared with that experienced while sitting without being subjected to vibrations. The height losses that always occurred from the two exposures were corrected for the effect of posture change. The height loss from vibration was significantly greater than when no vibration was present. Height loss due to posture change was responsible for approximately 50% of the total height loss. From this study it was concluded that whole body vibrations cause increased height loss.

Adult↗
PubMed1989

Theophylline disturbs sleep mainly in caffeine-sensitive persons.

In order to study effects of theophylline on sleep, a randomised double-blind cross-over study with slow release theophylline vs. placebo was performed on 13 healthy male volunteers (mean age 24 years), eight of whom were considered caffeine-sensitive and five caffeine-insensitive. A sleep diary was filled in during the entire period. At the end of each 2 week study period a sleep questionnaire was filled in and a sleep recording was conducted. Seven of the eight caffeine-sensitive persons reported that their sleep was disturbed during the theophylline period, while none of the five caffeine-insensitive experienced any difference between the periods. Analysis of the sleep diaries (mean +/- SD) revealed a significant increase in sleep latency (16 +/- 11 vs 4 +/- 7 min) and decrease in sleep efficiency (95 +/- 3 vs 98 +/- 3%) among the caffeine-sensitive persons during the theophylline period compared with the placebo period, while no such difference was found among the caffeine-insensitive. We conclude that theophylline seems to disturb sleep mainly in caffeine-sensitive persons.

Caffeine↗
PubMed1989

Increased CSF opioid activity in sleep apnea syndrome. Regression after successful treatment.

The etiology of the SAS is unknown. To test whether endogenous opioids could be pathologically active in SAS, markers of opioid systems were measured in the CSF of 15 patients with SAS and in control subjects. Measured by receptor assay, the concentration of so-called fraction 1 opioid was higher in patients with SAS (3.0 +/- 1.5 pmol/ml; mean +/- SD) than in control subjects (1.1 +/- 0.5 pmol/ml) (p less than 0.01), whereas that of fraction 2 opioid was similar in the two groups. Beta-endorphin-like activity, measured by radioimmunoassay, was somewhat lower in patients with SAS (14.0 +/- 2.8 pmol/ml) than in control subjects (21.8 +/- 7.6 pmol/ml) (p less than 0.05). Six months after surgical treatment of the soft palate, new measurements were made in eight patients. Fraction 2 endorphin and beta-endorphin showed no consistent changes. A decrease in the level of fraction 1 from 4.1 +/- 1.5 pmol/ml to 2.3 +/- 1.0 pmol/ml (p less than 0.02) was noted in those six patients showing a successful clinical course. The data support the hypothesis that in SAS the opioid activity is increased.

Adult↗
PubMed1988

Uvulopalatopharyngoplasty in the sleep apnea syndrome. Predictors of results.

A prospective study of 34 consecutive patients with the sleep apnea syndrome was undertaken to evaluate the effectiveness and complications of, and predictors of, results in a conservative type of uvulopalatopharyngoplasty (UPPP). At six months, 65% of the patients had a 50% or greater reduction in the number of apneas and hypopneas per hour (responders). The responders to UPPP were less severely affected preoperatively regarding apneas and hypopneas, the mean number of which (+/- SD) were 32.7 +/- 20.8 compared with 64.6 +/- 26.0. They also had a lower body mass index before UPPP (31.3 +/- 4.1 vs 36.0 +/- 7.0 kg/m2). Preoperative computed tomography and cephalometry indicated that the nonresponders had narrower upper airways. It is concluded that UPPP is the treatment of choice for mild to moderate sleep apnea syndrome, but not for severely affected, heavily overweight patients with an increased tongue width.

Adult↗
PubMed1988

Prevalence of sleep apnea syndrome among Swedish men--an epidemiological study.

The prevalence of the sleep apnea syndrome (SAS) among Swedish men 30-69 years old was estimated by a two-stage procedure. In the first stage, 4064 questionnaires were mailed to a random sample of a defined population in the municipality of Uppsala. The response rate was almost 80%; 15.6% of the responders were habitual snorers and 5.8% complained of daytime sleepiness. From these, a group of 166 men highly suspected of having SAS was selected. Eventually, 61 of these came for all-night polysomnographic studies, and 15 of these were found to have SAS. On this basis the lower limit of the prevalence of SAS was estimated to be as high as 1.3%. The majority of subjects with the syndrome were in the age group 50-59 years.

Adult↗
PubMed1988

The prevalence of insomnia: the importance of operationally defined criteria.

Previous studies on the prevalence of sleep disturbances have shown that insomnia occurs in 3.2-42% of different populations. The wide reported variation in prevalence prompted a rigorous definition of insomnia to be introduced in this study. Randomly selected members of the population aged 30 to 65 years from two geographically different rural parts of central Sweden answered a sleep questionnaire. The response rates were 69.2% and 70.2%, respectively. Females significantly more often reported difficulty in falling asleep (7.1% of the women and 5.1% of the men). Among women 8.9 and among men 7.7% of individuals reported trouble with nocturnal awakenings. Using a stringently defined concept of insomnia as a disorder of initiating sleep (DIS), the prevalence rate of insomnia among women was 1.1% and among men 0.5%. Defining insomnia as a disorder of maintaining sleep (DMS), the prevalence among both women and men was 1.1%. Defining insomnia as a disorder of initiating and maintaining sleep (DIMS), the prevalence rate was 1.7% among women and 1.4% among men. This prevalence, which is lower than previously reported, demonstrate the importance of an operational definition of insomnia.

Adult↗
PubMed1987

Effects of propiomazine on the EEG sleep of normal subjects.

The effects of 25 mg propiomazine were examined in ten healthy volunteers in a sleep laboratory setting. A significant decrease in sleep latency and a corresponding decrement in subjectively assessed sleep latency was found during drug treatment. The distribution of the different sleep stages was affected to a relatively small extent. Some evidence for a suppression of REM-sleep in the early part of the treatment period was found. Based on subjective assessment, the subjects rated their sleep quality as significantly improved during treatment. Ratings of "drowsiness in the morning" were not different during baseline and drug treatment, but there was a significant decrease at withdrawal.

Adult↗
PubMed1987

Somatic diseases and sleep complaints. An epidemiological study of 3,201 Swedish men.

The prevalence of sleep complaints and somatic diseases was estimated in a random sample of 4064 Swedish men aged 30-69 years. Great difficulty initiating sleep (DIS) was experienced by 6.9% and moderate problems in DIS by 14.3%. Complaints of major difficulty maintaining sleep (DMS) were reported by 7.5% of the men and of moderate DMS by 14.9%. DMS was more frequent with increasing age. Excessive daytime sleepiness (EDS) was reported by 5.7%. Altogether 879 men were attending regular medical examinations for somatic diseases. Among the 299 hypertensive men, major complaints of DMS (13.5%), DIS (8.4%) and EDS (8.8%) were more common, but the 167 men treated with beta-blockers rather showed a proportionally somewhat lower prevalence of sleep complaints. Men with obstructive pulmonary disease (n = 113) had a higher prevalence of DMS (18.8%) and EDS (12.4%). Diabetic men (n = 74) complained also more often of DMS (21.9%), DIS (21.1%) and EDS (12.2%). Men with rheumatic disease (n = 176) and obesity (n = 221) also had increased prevalence of sleep complaints.

Adult↗
PubMed1986

The effects of chlormethiazole in EEG recorded sleep in normal elderly volunteers.

Chlormethiazole has sedative, hypnotic and anticonvulsant properties, and is used in the treatment of sleep disorders and confusion in the elderly. In this study we examined the effects of chlormethiazole on EEG recorded sleep in six normal volunteers aged 67-74 years. After baseline registration, chlormethiazole (base), 384 mg p.o. (i.e. 2 capsules), was administered during 5 nights followed by one withdrawal registration. Sleep latency decreased from 52 to 27 min during the treatment period (P less than 0.01) and increased to 57 min during withdrawal. Wakeful periods during sleep decreased from 106 to 62 min during the treatment period and increased during withdrawal to 104 min (P less than 0.001). The sleep efficiency improved slightly during chlormethiazole treatment. The distribution of the sleep stages was essentially unaffected by chlormethiazole. According to subjective assessment the subjects rated their ability to fall asleep and their sleep quality as significantly better during the drug period. Based on sleep recordings and subjective ratings, there was no evidence of rebound insomnia on withdrawal. Psychoperformance tests revealed no evidence of hangover effects.

Age Factors↗