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L Søndergaard

Publications and source records attributed to L Søndergaard.

At least 37 records · Page 2Linked to original sources
PubMed1994

Functional MRI of CO2 induced increase in cerebral perfusion.

The sensitivity of MR gradient echo imaging towards CO2 induced changes in cerebral blood flow was investigated in 10 normal subjects. The subjects were inhaling 5% and 7% CO2 and the experiments were carried out at 1.5 T (n = 6) and 2.0 T (n = 5), allowing a comparison of field strengths. Additional experiments were carried out using a higher spatial resolution. The largest signal increases were noted in areas corresponding to larger vessels, but significant changes were also conspicuous in deeper cortical and central grey matter. The changes appeared linearly related to the arterial CO2 tension, within the range of PaCO2 studied. In white matter, the changes were not statistically significant.

Administration, Inhalation↗
PubMed1994

Magnetic-resonance velocity mapping of the central circulation.

In magnetic-resonance (MR) velocity mapping there exists a linear relationship between the velocity and signal in each element of a tomographic image. The technique can be used for quantitative measurements of linear velocities (m s-1) and flow rates (1 min-1). By using cinematographic images the flow profile during the cardiac cycle can be determined. This allows quantification of forward flow, regurgitant volume and regurgitant fraction in cases of heart-valve insufficiency. In valvular stenosis the transvalvular pressure gradient and valve area can be determined. Magnetic-resonance velocity mapping may also provide information about diastolic function of left ventricular function. Together with other MR imaging techniques, velocity mapping gives an accurate assessment of the severity of aortic dissection. Recent studies indicate that MR velocity mapping provides quantification of renal blood flow, and that MR imaging may be used even for coronary angiography and measurements of coronary blood flow. Therefore MR velocity mapping has the potential to become an important clinical tool for examination of the cardiovascular system providing high accuracy and quantitative measurements.

Blood Circulation↗
PubMed1994

Epidemiology of sprains in the lateral ankle and foot.

The epidemiology of sprains in the lateral ankle and foot was investigated in a prospective study at the casualty ward at Hillerød County Hospital. During one year, 766 patients were registered. The overall sprain incidence was 7/1000 person-years. The incidence was highest for young males. After the age of 40 years, the incidence was higher for women than for men. Most sprains were sustained during sport, but, with increasing age, other activities became dominant. Sixty-one percent of the lesions were located around the lateral ankle, and 24% were located on the lateral midfoot.

Adolescent↗
PubMed1994

[Magnetic resonance imaging of the cardiovascular system].

Magnetic resonance (MR) is a noninvasive technique to obtain tomographic images in any desired plane of the body. MR offers possibilities not only for morphologic imaging, but also for various physiological measurements, e.g. investigation of blood flow and angiography. This paper summarizes the possibilities of the technique in evaluation of congenital and acquired cardiovascular diseases. The conclusion is that MR may become an important clinical tool for examination of the cardiovascular system providing high accuracy and quantitative measurements.

Angiography↗
PubMed1993

Cis-regulatory sequences leading to female-specific expression of yolk protein genes 1 and 2 in the fat body of Drosophila melanogaster.

The three yolk protein genes (yp) of Drosophila melanogaster are transcribed in a sex- and tissue-limited fashion. We have searched for cis-regulatory sequences in regions flanking yp1 and yp2 to identify the elements that confer female-specific expression in the fat body. One such 127 bp element has previously been identified in this region. We show here the existence of two additional regions which confer female fat body-specific expression on an Adh reporter gene and on the native yp2 gene, respectively. This suggests some redundancy in the regulation of expression of the yp genes. Computer searches for putative binding sites for the DSX protein, which regulates sex-specific expression of the yp genes, revealed several such sites in our constructs. However, the significance of these is unclear since many such sites also occur in genes which one would not expect to be regulated in a sex-specific manner (e.g. Adh, Actin 5C). We suggest that DSX acts in concert with other proteins to mediate sex- and tissue-specific expression of the yp genes.

Alcohol Dehydrogenase↗
PubMed1993

The dominant mutation Suppressor of black indicates that de novo pyrimidine biosynthesis is involved in the Drosophila tan pigmentation pathway.

A deficiency in the production of beta-alanine causes the black (b) phenotype of Drosophila melanogaster. This phenotype is normalized by a semi-dominant mutant gene Su(b) shown previously to be located adjacent to or within the rudimentary (r) locus. The r gene codes for three enzyme activities involved in de novo pyrimidine biosynthesis. Pyrimidines are known to give rise to beta-alanine. However, until recently it has been unclear whether de novo pyrimidine biosynthesis is directly coupled to beta-alanine synthesis during the tanning process. In this report we show that flies carrying Su(b) can exhibit an additional phenotype, resistance to toxic pyrimidine analogs (5-fluorouracil, 6-azathymine and 6-azauracil). Our interpretation of this observation is that the pyrimidine pool is elevated in the mutant flies. However, enzyme assays indicate that r enzyme activities are not increased in Su(b) flies. Genetic mapping of the Su(b) gene now places the mutation within the r gene, possibly in the carbamyl phosphate synthetase (CPSase) domain. The kinetics of CPSase activity in crude extracts has been studied in the presence of uridine triphosphate (UTP). While CPSase from wild-type flies was strongly inhibited by the end-product, UTP, CPSase from Su(b) was inhibited to a lesser extent. We propose that diminished end-product inhibition of de novo pyrimidine biosynthesis in Su(b) flies increases available pyrimidine and consequently the beta-alanine pool. Normalization of the black phenotype results.

Animals↗
PubMed1993

Quantification of aortic regurgitation by magnetic resonance velocity mapping.

The use of magnetic resonance (MR) velocity mapping in the quantification of aortic valvular blood flow was examined in 10 patients with angiographically verified aortic regurgitation. MR velocity mapping succeeded in identifying and quantifying the regurgitation in all patients, and the regurgitant volume determined with MR velocity mapping agreed well with the grade obtained by aortic root angiography (p < 0.02). The accuracy in quantification of the aortic valvular flow rate was demonstrated by a significant correlation between the stroke volume (ml) measured by MR velocity mapping and calculated from MR imaging of the left ventricular end-diastolic and end-systolic volumes in eight patients (Y = 0.89 x X + 11, r = 0.97, p < 0.001). This finding was confirmed by a good agreement between the net cardiac output (L/min) quantified with MR velocity mapping and simultaneous 125I-indicator dilution measurement in all subjects (Y = 0.89 x X + 0.08, r = 0.82, p < 0.01). In conclusion, MR velocity mapping may be used as a noninvasive tool in the quantification of aortic regurgitation.

Adult↗
PubMed1993

Valve area and cardiac output in aortic stenosis: quantification by magnetic resonance velocity mapping.

Valve area and cardiac output were determined with magnetic resonance (MR) velocity mapping in 12 patients with aortic stenosis. Heart catheterization, Doppler echocardiography, and indicator dilution were performed for comparison. Left ventricle could be catheterized in only nine patients; in these cases, MR measured a mean valve area of 1.2 cm2 compared with 0.9 cm2 derived from catheterization data, with a mean difference of 0.2 cm2 between the 2 methods. The limits of agreement were [0.0, +0.5] cm2, less in patients with an important degree of concomitant regurgitation. In the whole material, MR measured a mean area of 1.1 cm2 compared with 1.2 cm2 derived from Doppler echocardiography data, with a mean difference of 0.1 cm2 and [-0.5, +0.6] cm2 as limits of agreement. In 11 patients the cardiac output was quantified by MR to a mean of 4.9 L/min and by indicator dilution to 5.0 L/min, with a mean difference of 0.2 L/min, and [-0.6, +0.8] L/min as limits of agreement. In addition, MR offers the major advance of simultaneous quantification of regurgitant volume in cases of concomitant regurgitation. In conclusion, because the two important prognostic determinants in aortic stenosis--the valvular area and the cardiac output--may be quantified, MR has potential to become a clinical tool in assessment of severity in aortic stenosis.

Aged↗
PubMed1993

Comparison between retrospective gating and ECG triggering in magnetic resonance velocity mapping.

ECG-triggered cinematographic studies of the cardiovascular system are hampered by several technical restrictions such as the inability to image end-diastole, ghosting, varying signal intensity, and phase contributions from eddy currents. Retrospective gating may solve these problems, but involves signal manipulation such as interpolating raw data from a time window. In this study, the performance of the two gating strategies was compared in quantitative MR velocity mapping on the abdominal aorta in eight healthy volunteers and on a pulsatile flow phantom. The results were compared to a one-dimensional velocity mapping technique and Doppler ultrasound. Finally, the consequence of decreasing the time window in the raw data interpolation used for retrospective gating was also examined. With retrospective gating, a low-pass filtering was seen, causing significantly prolonged duration and decreased amplitude of flow pulses. However, by reducing the time window retrospectively gated flow measurements were in good agreement with those that are ECG triggered. When fulfilling the demand of a narrow time window for interpolation, retrospective gating offers several advantages in MR velocity mapping.

Algorithms↗
PubMed1993

Reproducibility of cardiac volume measurements including left ventricular mass determined by MRI.

Cardiac volumes including left ventricular mass were determined by magnetic resonance imaging (MRI) in 30 patients using a contiguous multislice technique. Eleven patients were studied on two different days. Intra- as well as interobserver and interstudy variation were evaluated. For volume measurements the standard deviation of differences (SDD) was rather constant, independent of the size of the measured volume indicating lower percentual variability in measuring large volumes. Lowest variability was noticed for left ventricular myocardial mass estimates between observers as well as between studies. In 13 patients left ventricular mass was estimated by this technique as well as by a method using only one long axis and four short axis slices and by two-dimensional echocardiography. Although highly correlated, limits of agreement between the methods were too wide to accept interchangeable clinical use of the methods.

Adult↗
PubMed1992

Quantification of complex flow using MR phase imaging--a study of parameters influencing the phase/velocity relation.

In this study, we describe how motion-induced phase angle is affected by different flow models and imaging parameters when using the MR flow phase mapping technique. In a phantom with straight as well as constricted tubes, simulating healthy and stenotic vessels, nonpulsatile flow in the velocity range 0-1 m/sec was maintained. The phase/velocity relation was studied for various degrees of complex flow caused by the constriction, and regions with a breakdown in linearity were determined. Further studies in these regions were made regarding the influence of pulse sequence parameters on the phase/velocity relation. The results showed that in poststenotic areas characterized by so-called separated flow, the phase/velocity relation became nonlinear due to dephasing effects. In regions with fully developed turbulent flow in straight tubes, however, no breakdown in linearity was observed. Parameters seen to have a substantial influence on the phase/velocity relation were first- and second-order velocity encoding and voxel size. Finally, a pilot in vivo demonstration of complex flow was done using a sequence designed to be robust with respect to linearity of the phase/velocity relation. The results indicate that the MR phase mapping technique can be used to measure flow quantitatively in regions with complex flow. This opens possibilities for future clinical use of the technique in the study of areas of complex flow such as valvular heart disease.

Aortic Valve Stenosis↗
PubMed1991

Long-term follow-up of the cemented Caffinière prosthesis for trapezio-metacarpal arthroplasty.

20 patients with 22 Caffinière prostheses in the trapezio-metacarpal joint were evaluated at a median of nine years after operation. The indication was degenerative osteoarthrosis in 20 cases and rheumatoid arthritis in two cases. We found 18 of the 22 (82%) original prostheses still in place, with satisfactory pain relief and good function. Three hands had been revised due to aseptic loosening, with replacement of two cups and one total prosthesis. Two of the revised prostheses were functioning well 6 1/2 and 10 years after the revision. We conclude that function does not deteriorate within the first nine years, that late loosening is not a significant problem with this prosthesis and that, if aseptic loosening occurs, it is possible to obtain good results by replacing the loose component.

Aged↗
PubMed1991

Early mobilizing treatment for grade III ankle ligament injuries.

Eighty patients with grade III lateral ligament ruptures were treated either with total immobilization in a walking plaster cast or early mobilization in a stabilizing orthosis. The criterion for entrance was a talar tilt of more than 9 degrees and an anterior translation of more than 10 mm at stress radiography, a previously stable ankle, and a contralateral ankle showing normal stress radiographic values. Ninety-one percent of the patients were evaluated at 7 weeks, 3 months, and 1 year postinjury. While functionally treated patients reached normal mobility and resumed work and sports earlier than immobilized patients there were no differences between the treatment groups in ankle stability or symptoms during activity after 1 year. Ninety-five percent of the ankles in either group were mechanically stable after treatment. Residual symptoms were present 1 year postinjury in 13% of the functionally treated ankles and in 9% of the cast-mobilized ankles. In lateral ankle ligament ruptures causing gross mechanical instability early mobilization results in a better early functional result; however, at 1 year postinjury there was no statistically significant difference in outcome as compared to cast-immobilized ankles.

Adolescent↗
PubMed1990

[Arthrosis of the lower limb and running].

In order to assess whether running training for many years predisposes to arthrosis in the lower limbs, the hips, knees and ankle joints of 30 runners who began running training at the beginning of the nineteen fifties were examined. Three of these runners were no longer active. One of these had given up late in the nineteen seventies on account of arthroses in the upper and lower limbs i.e. changes which can scarecely be attributed to the stresses of running. The remaining 27 (90%) had run 20-40 km/week throughout 40 years. Subjective, objective and radiological data were compared with data from 27 non-active control persons who were comparable as regards age, weight/height and occupational stress with the runners. We found no differences in joint mobility, axial deviations or complaints of pain between the two groups. Radiologically, the distances between the osseous joint surfaces in the hip and ankle joints and the degrees of degeneration in the knees were assessed according to Ahlback's classification without any differences being found between the groups. Our results suggest that running training to a moderate extent for many years does not predispose to arthrosis in the lower limbs in healthy individuals.

Adult↗