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Biomedical subjects

H Gregersen

Publications and source records attributed to H Gregersen.

142 records · Page 8Linked to original sources
PubMed1989

[Factors of significance for short or prolonged duration of physiotherapeutic treatment from private practicing physiotherapists].

The aim of the study was to determine factors of importance for the duration of treatment of physiotherapy patients. A material of 363 patients answered questions about personal and social data and their disease. The following was related to prolonged treatment (greater than 47 days): 1) young, unmarried students. There was twice as many boys as girls. 2) Patients with psychosomatic disease. The ratio between men and women was 1, and the main symptom was headache. 3) Patients with generalized disease. This study did not reveal whether prolonged treatment is due to an ineffective treatment or whether other factors are of importance. However, we doubt the effect of physiotherapy in patients with psychosomatic disease.

Adolescent↗
PubMed1989

The effect of a new selective alpha 2-adrenoreceptor antagonist, idazoxan, and the agonist, clonidine, on fasting antroduodenal motility in healthy volunteers.

Studies were carried out on 16 healthy male volunteers to investigate whether intravenous administration of the alpha 2-adrenoreceptor antagonist, idazoxan, could affect fasting antroduodenal motility with and without administration of the agonist, clonidine. Contractile activity was recorded using an oral tube with perfused side holes positioned in the stomach and duodenum. Clonidine decreased antral contractile activity, an effect that idazoxan did not restore. Idazoxan alone did not affect antral motility. In the duodenum, clonidine decreased the number of contractions significantly and idazoxan restored them. Idazoxan alone did not increase duodenal motility but clonidine induced phase-III activity within the first 15 min after administration. The observations indicate that regulation of antroduodenal motility is influenced by alpha 2-adrenoreceptor drugs. Idazoxan may have potential as a motility restoring drug, for example, in postoperative ileus.

Adolescent↗
PubMed1989

Spontaneous anorectal pressure activity. Evidence of internal anal sphincter contractions in response to rectal pressure waves.

To characterize spontaneous anorectal pressure activity and a possible relation between the activity in the rectum and the anal canal, 11 healthy female volunteers were investigated. Resting activities were obtained during 1-h recordings with a multi-channel perfused catheter measuring the pressure 1, 2, 3, 7, and 8 cm from the anal verge. In five subjects sequences of rhythmic rectal pressure waves with amplitudes exceeding the maximal anal resting pressure coincided with a similar internal anal sphincter activity, preventing rectal pressure from exceeding the anal pressure at any point. The mean frequency was 5 x min-1 (range, 3-6 x min-1). This may well be a reflex mechanism by which the internal anal sphincter prevents incontinence in the resting state. Low-frequency pressure waves, not previously described, were detected in four women. These pressure waves were attributed to the internal anal sphincter and were named ultra-slow waves type II. The mean frequency and amplitude were 0.16 x min-1 (range, 0.15-0.17 x min-1) and 24 cm H2O (range, 11-41 cm H2O), respectively. The function of these pressure waves is unknown.

Adult↗
PubMed1989

Computer analysis of manometric recordings. A study of overnight rectal activity in normal children.

To read and analyze manometric tracings from selected biological systems, a computer program was produced using low cost personal computer hardware. The program contains facilities for automatic scoring of contractions, intercontractile intervals (modality) and frequency analysis. This report concerns analysis of two overnight rectal motility recordings in 11 normal teenagers. After A/D conversion of data the developed software offers a set of options i.e. automatized scoring of contraction, detection of intervals between contractions and analytical tools such as histographic presentation of data, and presentation in the time domain. The A/D conversion time and computer analysis time for an 8 hour recording was 15 and 13 minutes, respectively. The analysis of frequency distribution overnight showed for the material as a whole 63% of no activity, 33% of 0-2 contractions x min-1 and 4% of more than 2 contractions x min-1. Modality analysis showed a peak between 15 and 25 seconds. Approximately 30% of the tracings showed accumulated intervals, which were multiples of the peak. No significant correlation was found between the first and second night of observation regarding the number of contractions and maximum frequency overnight. Significant correlation was found for the number of periods with high frequency activity between the two nights (p less than 0.05). Long-term pressure activity can be analyzed using the presented computer-aided method, providing a rapid and objective measurement of classical parameters and access to more in-depth analysis. This actual study of normal overnight rectal activity showed a large inter- and intra-individual variation.

Adolescent↗
PubMed1988

The four-electrode impedance technique: a method for investigation of compliance in luminal organs.

A probe for measurement of related values of cross-sectional area (CA) and pressure has been developed to record characteristics of the walls in luminal organs. The aim of this study was to test the probe in vitro. CA was measured in the range 0.17 to 7.07 cm2 by means of the field gradient principle. Pressure was measured in the range 0 to 20 kPa (150 mmHg) by external transducers. After calibration both the pressure and the CA measuring system did measure the parameters adequately. The CA measuring system was dependent on the temperature and electrolyte concentration of the fluid, but was not affected by the size and form outside the excitation electrodes. The upper frequency limits for recordings of CA and pressure were 15.7 and 0.44 Hz, respectively. These in vitro results indicate that the tube assembly has characteristics sufficient for simultaneous measurement of CA and pressure in sphincter regions. These two variables can be used to describe mechanical wall properties such as compliance, hysteresis and creep.

Animals↗
PubMed1988

Changes in oesophageal wall biomechanics after portal vein banding and variceal sclerotherapy measured by a new technique. An experimental study in rabbits.

The biomechanical properties of the oesophageal wall were investigated in a rabbit model using a four electrode impedance technique. A specially designed probe with the electrodes inside a low pressure expandable insulating latex balloon was introduced in the oesophagus. Stepwise inflation and deflation was done for analysis of oesophageal compliance and hysteresis. The rabbits were allocated to three groups: a control group, one with oesophageal varices and one with varices which were treated by sclerotherapy. The oesophageal varices were induced by portal banding five months before the investigation. A uniform pattern of changes in the biomechanical properties of the oesophageal wall was seen in the group with oesophageal varices when compared with controls. The compliance was significantly decreased, and the hysteresis was lessened. Endoscopic sclerotherapy changed the wall properties to a pattern not distinguishable from normal. Thus, in vivo investigation of the biomechanical wall properties showed a significant loss of distensibility of the oesophagus with varices and restorement of the wall distensibility when the varices were treated with endoscopic sclerotherapy.

Animals↗
PubMed1988

The relation between antral contractile activity and the duodenal component of the migrating motility complex.

The aim of the study was to investigate the relationship between antral and duodenal fasting motor activity in 19 healthy volunteers using a perfused tube assembly with side-holes placed in the distal antrum, second part of the duodenum and in the duodenum near the ligament of Treitz. Registrations were performed until the end of the second duodenal phase III. Eighty-two per cent of the duodenal phases III were preceded by antral activity. The duration of duodenal phase III showed a positive correlation to the preceding number of antral contractions (p less than 0.001) as well as to antral phase III (p less than 0.05), but no correlation to the duration of antral phase III was found. The duration of the migrating motility complex (MMC) showed a positive correlation to the duration of duodenal phase III (p less than 0.05), but no correlation to the preceding number of antral contractions were found. It may be concluded that the level of duodenal activity is very dependent on the preceding antral activity.

Adult↗
PubMed1988

The effects of glucagon and glucagon-(1-21)-peptide on antroduodenal motility in healthy volunteers.

Since it has been argued that the spasmolytic effect of glucagon is related to the first 21 N-terminal amino acid residues, and not to the complete molecule, we have compared the effects of glucagon-(1-21)-peptide (G-(1-21) and glucagon on human antroduodenal motility. Glucagon and G-(1-21) were given as bolus injections to 30 healthy volunteers equally allocated into five groups. Each subject received two doses; one was placebo, 0.25, 0.5, 1.0 or 2.0 mg of glucagon, the other was an equimolar doses of G-(1-21) (placebo, 0.175, 0.35, 0.70 or 1.4 mg of G-1-21). The first injection was given during phase II of a migrating motility complex (MMC), and the next during the following phase II. Contractile activity was recorded using an oral tube with one sidehole positioned in the antrum and two in the duodenum. We confirmed that glucagon decreases the number of contractions in the antrum and duodenum and that normal phase II activity was restored within 20-40 minutes proportionally to the amount of the drug given. G-(1-21) did not change antroduodenal motility nor did it affect the phase II pattern in any of the groups. Neither were any side effects encountered. G-(1-21) does not seem to be an alternative to glucagon and other spasmolytic drugs for obtaining relaxation of the antroduodenal area.

Adult↗
PubMed1988

Long term reproducibility of urodynamic investigations in healthy fertile females.

The long term reproducibility of uroflowmetry, urethral pressure profilometry, cystometry and pressure-flow studies was evaluated in 10 healthy fertile female volunteers over a two year period. All parameters were unchanged, except for an increase in the detrusor pressure. The volume at first sensation, the maximal cystometric capacity and the maximum flow rate, had a coefficience of variation (CV) of 24%, 15% and 21% respectively. The compliance and the opening time however showed a considerably higher CV. Several parameters showed a larger intra individual standard variation (SD) than the interindividual SD, indicating that these parameters should be interpreted with great care. Repetition of the investigations showed in this small material a reduction in the standard error of the mean (SEM). Repeating the investigation reduces the number of patients needed in a clinical trial to obtain a statistically significant change. The study showed that urodynamic investigation is a reliable tool in evaluation of patients over a period of years.

Adult↗
PubMed1986

2-Amino-5-phosphonovalerate and Co2+ selectively block depolarization and burst firing of rat hippocampal CA1 pyramidal neurones by N-methyl-D-aspartate.

Intracellular recordings from pyramidal neurones during microiontophoretic ejection of N-methyl-D-aspartate and quisqualate into the pyramidal cell layer of the CA1 region of the rat hippocampal slice showed that both amino acids caused depolarization and evoked spike activity. Whereas quisqualate evoked tetrodotoxin-sensitive spikes, those produced by N-methyl-D-aspartate consisted of bursts of tetrodotoxin-sensitive action potentials superimposed on an underlying depolarizing shift of membrane potential. Both membrane depolarization and the superimposed depolarizing shifts associated with N-methyl-D-aspartate excitation were selectively and reversibly antagonized by the D(-) isomer of 2-amino-5-phosphonovalerate and Co2+. Both amino acids caused an increase in membrane conductance when small ejection currents were used, and the depolarizing response to these compounds was prevented by current injection. However, only the increase by N-methyl-D-aspartate was blocked by 2-amino-5-phosphonovalerate and Co2+. These results provide evidence to support the suggestion that different mechanisms underlie the excitatory response to N-methyl-D-aspartate and quisqualate in CA1 pyramidal neurones.

2-Amino-5-phosphonovalerate↗
PubMed1983

The effect of fasting and time of day on the urinary excretion of chondroitin 4/6 sulphate, dermatan sulphate and four chondroitinase ABC resistant glycosaminoglycans.

The present investigation confirmed a former report of a diurnal variation with an increased urinary excretion rate of total glycosaminoglycans in the daytime [4]. Fractionation showed that this increase was solely due to three electrophoretic fractions which resisted degradation with chondroitinase ABC. Fasting in the daytime had no influence on the increased excretion of one of these fractions, whereas it prevented the increased excretion of the other two (probably both heparan sulphates). The excretion rates of chondroitin 4/6 sulphate, dermatan sulphate and a fourth chondroitinase ABC resistant glycosaminoglycan (heparan sulphate) were uninfluenced by time of day and fasting. This was contrary to the excretion of hydroxyproline which decreased during the fasting period.

Adolescent↗
PubMedDate not supplied

Mechanics of porcine coronary arteries ex vivo employing impedance planimetry: a new intravascular technique.

Our objective was to evaluate methodological aspects of impedance planimetry, a new balloon catheter-based technique, for the investigation of coronary artery mechanical wall properties. We used a four ring-electrode electrical impedance measuring system that was located inside a balloon. Two of the electrodes were used for excitation and connected to a generator producing a constant alternating current of 250 mA at 5 kHz. The other two electrodes for detection were placed midway between the excitation electrodes. The balloon was distended with electrically conducting fluid through an infusion channel. The vessel cross-sectional area (CSA) was measured according to the field gradient principle by measuring the impedance of the fluid inside the balloon. Impedance planimetry was applied in the three major branches of the coronary arteries of seven extracted porcine hearts to assess luminal CSAs in response to internal pressurization. The biomechanical wall properties were evaluated by computing the strain [(r - r0) x r0(-1), where r is the vessels inner radius computed as (CSA x pi-1)1/2 and r0 is the radius of the vessel at a minimal distension pressure], the tension [(r x dP), where dP is the transmural pressure difference], and the pressure elastic modulus (delta P x r x delta r-1). We found that in vitro testing demonstrated that impedance planimetry was accurate and reproducible. The technique has controllable sources of error. Measurements were performed with consecutively increasing pressures in the range 1-25 kPa (8-188 mmHg, 0.01-0.25 atm). The CSAs increased nonlinearly and were significantly larger in the left anterior descendent coronary artery (LAD) (1 kPa, mean 5.0 mm2; 25 kPa, mean 21.8 mm2) than in both the left circumflex (Cx) (4.5-16.0 mm2) and the right coronary artery (RCA) (2.8-15.6 mm2) (analysis of variance, P < 0.001 for both). The circumferential wall tension-strain relation showed exponential behavior. For a given strain, tension values for LAD were significantly lower than those of Cx (P < 0.01). The pressure elastic modulus-strain relation also was exponential, and values for Cx were significantly lower than values for LAD (P < 0.001) and RCA (P < 0.05). Impedance planimetry was applied to the study of coronary artery biomechanics ex vivo. The LAD had the largest CSA, and the Cx was the least compliant. Methodological aspects of an in vivo introduction of the method require additional evaluation.

Analysis of Variance↗
PubMedDate not supplied

History-dependent mechanical behavior of guinea-pig small intestine.

Measurement of pressure-volume relations is a commonly used technique to elucidate small intestinal stiffness. There is a lack of data on the relation between stiffness and history-dependent mechanical properties of the gastrointestinal tract. We aimed to distinguish between passive properties of the tissue that depend on the time-history of load (viscoelastic effects) versus those that depend on the maximum previous load (strain softening effects). Ten repeated pressure-volume relations were measured at each peak pressure level in six isolated, passive guinea-pig jejuni in vitro during balloon inflation and deflation cycles. With inflation to a new higher peak pressure (ranging from 3 to 15 mm Hg), the pressure-volume relation became less stiff, particularly in the low pressure range, without a significant change in unloaded jejunal volume. We computed the jejunal normalized volume change as a function of the integrated volume-time history and maximum volume. Analysis of covariance revealed significant dependence of the normalized volume change on the volume-time history (P < 0.001) and the maximum volume history (P < 0.001). Multiple linear regression analysis showed that approximately 90% of the history dependence could be attributed to the maximum volume. Most softening (loss of stiffness) happens in the low pressure range of the curve (0-3 mm Hg). We adopted the Johnson and Beatty strain softening theory and computed the volume amplification factor. This factor was shown to be a linear function of the normalized peak volume (r2 > 0.999). Since strain softening effects were significantly greater than viscoelastic effects, we conclude that history-dependent changes in jejunal stiffness are more likely to involve alterations to elastic rather than viscous structures in the tissue. These effects must be taken into account when performing balloon distension studies in the gastrointestinal tract for studying physiological and pathophysiological problems in which loading conditions are altered, e.g., mechanoreceptor studies in normal intestine and in acute and chronic obstruction, in order to have an accurate description of the biomechanics.

Analysis of Variance↗
PubMedDate not supplied

Biomechanical properties of porcine cerebral bridging veins with reference to the zero-stress state.

Passive mechanical and morphometric properties of porcine cerebral bridging veins were studied. Fifteen cerebral bridging veins were obtained from 7 pigs. The superior sagittal sinus, bridging veins and the meninges were excised and placed in aerated calcium-free Krebs solution. The outflow cuff segment is a narrow region at the junction of the cerebral bridging veins and superior sagittal sinus. The principal direction of collagen fibres was longitudinal in the bridging vein and circumferential in the cuff region. The diameter was smaller in the outflow cuff segment than in the cerebral bridging veins in the pressure range studied (0-23 mm Hg) whereas the thickness was highest in the outflow cuff segment (p < 0.01). The circumferential stress-strain analysis showed that the outflow cuff segment was extensible up to a strain of 0.25. At higher strains the outflow cuff segment was progressively stiffer than the cerebral bridging vein (p < 0.05). The longitudinal stress-strain relation for the cerebral bridging vein was shifted to the left compared to the outflow cuff segment (p < 0.05). When compared to the stress-strain properties in the circumferential direction, the outflow cuff segment was more extensible and the cerebral bridging vein stiffer in longitudinal direction (p < 0.05). The opening angle of the outflow cuff segment and the cerebral bridging vein was 115 +/- 4 and 120 +/- 4 (means +/- SE) without statistical difference between the two regions. In conclusion the difference in biomechanical properties between the outflow cuff segment and the cerebral bridging vein was associated to their difference in histology and fibre arrangement. This indicates that the function of the outflow cuff segment is to act as a flow-limiting resistance to the outflow from the cerebral circulation.

Adaptation, Physiological↗