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H Gregersen

Publications and source records attributed to H Gregersen.

99 records · Page 6Linked to original sources
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↗