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Biomedical subjects

H Gregersen

Publications and source records attributed to H Gregersen.

At least 19 recordsLinked to original sources
PubMed1998

Endoscopic sclerotherapy in porcine esophagus changes luminal cross-sectional area and wall distensibility dose- and time-dependently.

The dose- and time-dependent effects of endoscopic sclerotherapy on luminal cross-sectional area and wall distensibility were studied in pigs at 5 and 12 cm proximal to the gastroesophageal junction by means of impedance planimetry. Sixteen healthy animals underwent two sessions of endoscopic sclerotherapy two weeks apart with injections of either 5 or 10 ml of 1% Polidocanol in the distal 7 cm of the esophagus each time. The animals were investigated before sclerotherapy, two weeks after each session, and finally six weeks after the last session. Six healthy animals were studied as controls. Endoscopic sclerotherapy caused luminal narrowing in the sclerosed zone followed by normalization six weeks after the last treatment (P < 0.05 in both groups). Wall distensibility decreased in the sclerosed zone after treatment with 10 ml sclerosant (P < 0.05) followed by partial normalization, while no effect was found after 5 ml sclerosant (P > 0.2). Progressive dilations were observed in the proximal esophagus in both groups and were most pronounced in the 10 ml group (P < 0.05). Wall distensibility did not change proximal to the site of sclerotherapy in either group (P > 0.1).

Animals↗
PubMed1998

Mechanical properties and collagen content differ between isolated guinea pig duodenum, jejunum, and distal ileum.

We compared the stress-strain distributions obtained from isolated segments of the guinea pig duodenum, jejunum, and distal ileum, and the relation between the elastic properties and the collagen content. The segments were immersed in Krebs-Ringer solution containing 10(-2) M MgCl2 to abolish contractile activity. Stepwise inflation of an intraluminal balloon in which the cross-sectional area (CSA) was measured provided the luminal pressure-loading stimulus. The wall thickness was measured by means of 20-MHz A-mode ultrasound. The stress-strain and the incremental elastic modulus-strain distributions were derived from the steady-state values of wall thickness, internal radius, and applied pressure. The CSA-pressure relations and the wall thickness-pressure relations were nonlinear and both differed between the segments (P < 0.01). The stress-strain distributions showed an exponential behavior that fitted well to the equation Y = a x Exp(b x X) (r2 = 0.97 +/- 0.01). The intercept with they axis (a) and the slope of the curves (b) differed between the segments (P < 0.01 and P < 0.05). The collagen contents were 3.99 +/- 0.18 microg/mg, 2.51 +/- 0.13 microg/mg, and 2.10 +/- 0.11 microg/mg in the duodenum, jejunum, and distal ileum, respectively. This difference was significant among all three locations (P > 0.05). An association was found between the collagen content and the incremental elastic modulus (stiffness) at a stress level of 70 kPa (P < 0.05).

Animals↗
PubMed1998

Luminal cross-sectional area and tension-strain relation of the porcine bile duct.

The bile duct is a distensible tube serving to transport bile from the liver and gallbladder to the duodenum. The purpose of this study was to characterize the luminal cross-sectional area (CSA) and tension-strain properties during distension of the normal isolated porcine common bile duct in vitro. An impedance planimetric system located inside a balloon was used. Eleven porcine bile ducts were examined in two locations, in the hepatic duct and in the common bile duct. The CSAs obtained in the common bile duct were significantly higher than those in the hepatic duct in the pressure range 0-8 kPa (P < 0.001). The circumferential wall tension (T)-strain (epsilon) relations for both locations fitted to the exponential equation T = a.eb. epsilon with determination coefficients of 0.97 +/- 0.01. The a and b constants were not statistically different between the two locations indicating that the elastic properties did not differ. In conclusion, the luminal CSAs were larger in the common bile duct when compared to the hepatic duct and the tension-strain relations did not differ between the two segments of the bile duct.

Animals↗
PubMed1998

A new method for combined isometric and isobaric pharmacodynamic studies on porcine coronary arteries.

1. The principal aim of the present study was to explore the isometric and isobaric capacity of a new intravascular technique, impedance planimetry, in basic pharmacodynamic investigations on porcine isolated epicardial coronary arteries. 2. The balloon-based catheter technique provides simultaneous measurements of luminal cross-sectional area and pressure. Sources of errors that may influence the accuracy of measurements were evaluated in detail. 3. Under isometric conditions, the stretch ratio-tension diagram showed typical developments of resting and active tensions of the smooth muscle when exposed to alternating maximal K+ depolarization and mechanical stretching. The mean (+/- SEM) maximum active tension was 28.43 +/- 1.72 mN/mm, which was reached at a stretch ratio of 1.26 +/- 0.02, corresponding to a resting tension of 10.50 +/- 0.53 mN/mm (n = 7). The concentration-response relationship to K+ at optimal basal tension was characterized by a mean (+/- SEM) pD2 value of 1.67 +/- 0.01 (n = 7). 4. Under isobaric conditions in the pressure range 40-140 mmHg, the method allowed the investigation of active vascular responses to partial K+ depolarization. The maximal active response to 25 mmol/L K+ was found at the transmural pressure of 60 mmHg (n = 7). To obtain full K+ concentration-response curves, a basal tension corresponding to a transmural pressure of 120 mmHg was required. The mean (+/- SEM) pD2 value for the concentration-response relationship to K+ was 1.53 +/- 0.01 (n = 10). 5. The vascular sensitivities to cumulatively added K+ and various agonists, such as acetylcholine, 5-hydroxytryptamine and noradrenaline, obtained from the same vessel segment at the same initial conditions corresponding to 120 mmHg were significantly higher with the isometric than with the isobaric approach. 6. The results of the present study suggest that impedance planimetry could be a useful tool in pharmacological and physiological investigations of medium-sized arteries, both under isometric and isobaric conditions.

Acetylcholine↗
PubMed1998

The risk of bacteremia in patients with monoclonal gammopathy of undetermined significance.

We estimated the risk of bacteremia in patients with monoclonal gammopathy of undetermined significance (MGUS) compared with the general population; 1237 cases of MGUS were identified by linking information on detected monoclonal components in the North Jutland County with the Danish Cancer Registry. We evaluated the risk of bacteremia in the MGUS cohort during the 13-yr period from 1981 to 1993 by linkage to the Bacteremia Registry in the County. Follow-up for the occurrence of bacteremia started 30 d after detection of the M-component and continued until malignant transformation, death or until 31 December 1993, whichever came first. The expected numbers of bacteremia was based upon county, age, sex and period-specific incidence rates. The median follow-up period was 3.8 yr. Forty episodes of bacteremia occurred during 5500 person-years versus 18 expected. The crude standardized incidence ratio of bacteremia was 2.2 (95% confidence interval, 1.6-3.0). There was no distinct pattern of bacterial etiology in the MGUS cohort. Although we found an association between MGUS and risk of bacteremia, the overall risk is small and this finding hardly affects the clinical handling of MGUS patients.

Aged↗
PubMed1998

Relation between zero-stress state and branching order of porcine left coronary arterial tree.

The left common coronary arterial trees of eight pig hearts were dissected. The zero-stress state (the state of the organ when the external loads are removed) of the coronary arteries was determined by first cutting the arteries into short, ring-shaped segments perpendicular to the longitudinal axis of the blood vessel and then making a radial cut. This procedure caused the ring to open into a sector whose opening angle (theta), internal and external lengths (circumferences), and wall thickness were measured. Morphometric and theta data were organized in the framework of a diameter-defined Strahler system. We investigated 4 rings from the left common coronary artery (LCCA), 185 from the left anterior descending artery (LAD) and its branches, and 159 from the left circumflex artery (LCX) and its branches. The inner circumferences of the rings ranged over six orders for the LAD arterial tree and five orders for the LCX arterial tree, corresponding to a diameter range of about one order of magnitude for both arteries. theta demonstrates viscoelastic behavior and was measured 30 min after cutting. Our results show that the inner and outer circumference and the wall thickness increase as geometric sequences with the order number. theta is found to decrease linearly toward the smaller orders with a slope of 7.3 degrees/order in the range of the six largest orders. Strain calculations showed that the inner part of the arterial wall is in compression, whereas the outer part of the wall is in tension in the no-load (zero transmural pressure) state. This study provides basic data on the zero-stress state that are necessary for understanding the mechanics of the coronary artery.

Animals↗
PubMed1998

Third generation oral contraceptives and heritable thrombophilia as risk factors of non-fatal venous thromboembolism.

Third generation oral contraceptives (OCs) are apparently stronger risk factors for venous thromboembolism (VTE) than other OCs, however, the increased risk may be due to confounding by indication related to differences in prescription behaviour. We estimated the risk of VTE associated with use of OCs with and without the presence of Factor V Leiden mutation, protein C-, protein S- or antithrombin deficiency. Sixty-seven cases with VTE were compared with 134 controls. The risk of VTE in the presence of thrombophilia was of the same magnitude for third generation OC users as for users of other OCs; OR: 52.5 (95% CI: 3.7-738.1) and OR: 63.3 (95% CI: 6.2-648.4), respectively. It is unlikely that confounding by indication entirely explains the risk of VTE associated with third generation OCs since the combined effect exceeds what could be explained if this source of error was the only determinant of the association.

Adult↗
PubMed1997

[Renal insufficiency in myelomatosis. Prognostic factors and survival].

Clinical features, occurrence and reversibility of renal failure, response to treatment and survival duration in 190 multiple myeloma patients were reviewed in a retrospective study based on hospital records. Renal failure was present in 27% of the patients and constituted an important prognostic factor. Reversibility of renal failure occurred in 52% of the patients and was more frequent in those with low serum creatinine, hypercalcaemia, high erythrocyte sedimentation rate and high level of IgA. Response to chemotherapy resulted in a prolonged survival, whereas recovery of renal function did not significantly affect survival.

Adult↗
PubMed1997

Dimensions and mechanical properties of porcine aortic segments determined by combined impedance planimetry and high-frequency ultrasound.

The aim of the study is to devise a method for direct measurements of pressure, cross-sectional area (CSA) and wall thickness of a vessel when pressurised. Segments of porcine descending thoracic aorta from 22 and 35 kg pigs (in groups 1 and 2, respectively) and of abdominal aorta from 35 kg pigs are studied in vitro. Impedance planimetry provides measurements of the luminal pressure and CSA of the aorta. The wall thickness is measured simultaneously by means of 20 MHz A-mode ultrasound. The pressure, CSA and wall thickness are registered at different pressure at steady state. At maximum pressure, the CSAs are 107 +/- 10, 215 +/- 19 and 257 +/- 17 mm2 in the abdominal, group 1 and 2 segments, respectively. There is a difference between the abdominal group and groups 1 and 2 (p < 0.05), but not between group 1 and 2 segments (p > 0.2). At maximum pressure, the wall thickness is 0.52 +/- 0.04, 0.79 +/- 0.07 and 1.07 +/- 0.02 mm, in the abdominal group 1 and 2 segments, respectively (p < 0.05). The circumferential stress-strain relationship accorded well with stress = a x exp(b x strain). The stress-strain curve of the abdominal aortas is shifted to the left, indicating an increase (p < 0.05).

Animals↗
PubMed1997

Static elastic wall properties of the abdominal porcine aorta in vitro and in vivo.

OBJECTIVES: To characterise possible differences in vascular mechanics between in vitro and in vivo settings. DESIGN: Experimental animal study. MATERIAL: Segments of abdominal aorta from five 30kg pigs were studied in vitro and five porcine abdominal aortas were investigated in vivo. METHODS: Vessel luminal cross-sectional area (CSA) was assessed in vitro and in vivo by measuring the electrical impedance of fluid inside a distensible balloon mounted on a catheter. Wall thickness was measured in vitro by means of 20 MHz A-mode ultrasound. The obtained values in vitro were used to calculate wall thickness in vivo. RESULTS: The CSAs were larger in vitro than in vivo (p < 0.05). All segments showed stress-strain relations that accorded well with the exponential equation: Stress = a.exp(b. Strain). The y-axis intercepts (a) and the slope of the curves (b) were different in vitro and in vivo (p < 0.05). Differences were found between the aorta in vivo and in vitro regarding the circumferential stress-strain relations, i.e. the stiffest abdominal aorta was found in vivo. CONCLUSIONS: The differences in dimensions and wall stiffness may be attributed to the tethering to the surrounding tissues in vivo. Impedance planimetry combined with high frequency ultrasound is an accurate way of measuring segmental vascular elasticity in vivo.

Animals↗
PubMed1997

Impedance planimetric characterization of esophagus in systemic sclerosis patients with severe involvement of esophagus.

This study was designed to evaluate the distensibility and secondary peristalsis of the esophagus in patients suffering from systemic sclerosis with severe esophageal involvement. Balloon distension with impedance planimetric measurement of luminal cross-sectional area was done 7 and 15 cm above the lower esophageal sphincter in 13 patients and nine healthy controls. The controls were studied both with and without receiving the anticholinergic drug butylscopolamine. The cross-sectional area--pressure relations were nonlinear with the largest cross-sectional area in patients at both measuring sites when compared to controls (P < 0.001). The anticholinergic drug butylscopolamine increased the cross-sectional area in controls (P < 0.001). The cross-sectional area distensibility, defined as CSA0(-1) delta CSA delta P-1 did not differ between patients and controls. Balloon distensions elicited contractions proximal to the distension site. The amplitude and frequency of contractions at the distal distension site were significantly reduced in the patients when compared to the controls (P < 0.05). In conclusion, the distal esophagus is most severely affected in patients with systemic sclerosis with increased cross-sectional area and impaired peristalsis.

Adult↗
PubMed1997

Impaired human coronary artery distensibility by atherosclerotic lesions: a mechanical and histological investigation.

The objective of this study was to evaluate the relationship between human coronary artery distensibility and vessel wall morphology assessed by histomorphometry. Coronary artery pressure-cross-sectional area relations and distensibility were studied in excised autopsy hearts by means of a balloon-based impedance planimetric technique 2 cm from the aortic orifice of the arteries. Later the hearts were perfusion fixed at 100 mm Hg and cross-sectioned 17, 20 and 23 mm distal to the aortic orifice. The areas of lumen, intima and media were measured. Nineteen left anterior descending coronary arteries (LAD) and 15 right coronary arteries (RCA) from 25 hearts (12 women and 13 men) were investigated. The age of the subjects was 48-97 years (mean 73.8 years). Non-linear relations were found between balloon pressure and coronary cross-sectional area (according with the function y = a + bx0.5) and between balloon pressure and coronary distensibility, but there were no differences in these relations between the LAD and RCA. Subjects' age was positively correlated with wall thickness (r = 0.44, P < 0.05), intima area (r = 0.46, P < 0.01) and media area (r = 0.44, P < 0.05) of the coronary arteries. Additionally, the distensibility at low pressures was inversely correlated with arterial wall thickness (r = -0.37, P < 0.05). When focusing only on arteries with concentric atherosclerotic lesions, distensibility at low pressures was inversely correlated with arterial wall thickness (r = -0.57, P = 0.01) and intima area (r = -0.53, P < 0.05). Arteries with concentric lesions were less distensible at low pressures compared with arteries having eccentric lesions (5.4 +/- 0.8.10(-2) vs. 3.6 +/- 0.7.10(-2) kPa-1, P < 0.05) but this difference was absent at higher pressures. No difference in coronary artery distensibility was found between men and women. Age and distensibility were not correlated. These findings may have in vivo implications for complications to angioplasty procedures such as recoil and restenosis.

Aged↗
PubMed1997

Morphometry and strain distribution in guinea pig duodenum with reference to the zero-stress state.

The aim of the present study is to determine the distribution of residual circumferential strains along the duodenum in anesthetized guinea pigs. A silicone elastomer was allowed to harden in the duodenal lumen under a pressure of 0.7 kPa. The duodenum was excised with the cast and photographed. The zero-stress state was obtained by cutting rings of duodenum radially. The geometric configuration at the zero-stress state is of fundamental importance, because it is the basic state with respect to which the physical stresses and strains are defined. A basic piece of information is the way the tangent vector rotates from one end of the circumference to the other. In the duodenum at zero-stress state, the total rotation of the tangent from one tip to the other is -500 to -850 , with the lowest absolute value in the proximal duodenum. In other words, the duodenum usually turns itself inside out on changing from a loaded state to the zero-stress state. The serosal circumference, the duodenal wall thickness, and the ratio of wall thickness to mucosal circumference decreased in the distal direction. In the pressurized state, the serosal Cauchy strain was tensile and increased in the distal direction; the mucosal Cauchy strain was compressive in the proximal half of the duodenum and tensile in the distal half. The large circumferential residual strains must be taken into account in a study of physiological problems in which the stresses and strains are important, e.g., the bolus transport function.

Animals↗
PubMed1996

[Acute porphyria and multiple organ failure during treatment with lamotrigine].

A 38-year-old female suffered from an acute porphyric attack, multi-organ failure and disseminated intravascular coagulation (DIC) within two weeks of starting lamotrigine, a new antiepileptic drug. The porphyric attack was characterized by excess urinary excretion of aminolevulinic acid (ALA), porphobilinogen (PBG) and coproporphyrin III, a pattern similar to that seen in hereditary coproporphyria, however the diagnostic criteria for this specific porphyria were not fulfilled. We suggest that the observed clinical picture represents a rare adverse reaction to lamotrigine.

Adult↗
PubMed1996

Unexplained chest pain: the hypersensitive, hyperreactive, and poorly compliant esophagus.

OBJECTIVE: To determine whether neuromuscular dysfunction of the esophagus causes chest pain in patients in whom no disease is found on cardiac work-up, upper gastrointestinal endoscopy, esophageal manometry, and 24-hour pH studies. DESIGN: Prospective study. SETTING: Tertiary referral center. PATIENTS: 24 consecutive patients and 12 healthy controls. MEASUREMENTS: A new technique, impedance planimetry, was used to measure the sensory, motor, and biomechanical properties of the human esophagus. The impendance planimeter, which consists of a probe with four ring electrodes, three pressure sensors, and a balloon, simultaneously measures intraluminal pressure and cross-sectional areas. This allows calculation of the biomechanical variables of the esophageal wall. RESULTS: Stepwise balloon distentions from 5 to 50 cm H2O induced a first sensation at a mean pressure (+/- SD) of 15 +/- 9 cm H2O in patients and 30 +/- 11 cm H2O in controls (P < 0.001). Moderate discomfort and pain were reported by 20 of 24 patients (83%) at 26 +/- 9 cm H2O and at 36 +/- 9 cm H2O, respectively, but by none of the controls (P < 0.001). Typical chest pain was reproduced in 20 of 24 patients (83%). In patients, the reactivity of the esophagus to balloon distention was greater (P = 0.01), the pressure elastic modulus was higher (P = 0.02), and the tension-strain association showed that the esophageal wall was less distensible (P = 0.02). Distention excited tertiary contractions and secondary peristalsis at a lower threshold of pressure (P = 0.05) and with a higher motility index in patients than in controls (P = 0.04). CONCLUSION: In patients with chest pain and normal cardiac and esophageal evaluations, impedance planimetry of the esophagus reproduces pain and is associated with a 50% lower sensory threshold for pain, a 50% lower threshold for reactive contractions, and reduced esophageal compliance.

Adult↗
PubMed1996

Systemic treatment with epidermal growth factor in the rat. Biomechanical properties of the growing small intestine.

Prolonged treatment with epidermal growth factor (EGF) in the rat provides an experimental model to growth of the gastrointestinal tract. We treated female Wistar rats for 0 (n = 15), 1 (n = 8), 2 (n = 8), and 4 (n = 8) weeks with subcutaneous EGF (i50 micrograms.kg-1.day-1). Segments were taken from locations at 10, 50 and 90% along the length of the small intestine, weighed, the wall thickness was measured and the luminal cross-sectional area and passive biomechanical properties were assessed using impedance planimetry. In addition, the wall composition was evaluated on histological sections. The weight of the total small intestine and of the three segments (measured in mg.cm-1) increased with the duration of the EGF treatment due to mucosal and muscular growth. After 1 week of treatment the wall thickness increased. After 2 weeks of treatment the cross-sectional area began to increase. The circumferential stress-strain distributions revealed translation of the curves to the right in the graphs implying reduced wall stiffness during EGF treatment. In conclusion EGF treatment for 1 to 4 weeks caused a time-dependent increase in intestinal weight. The growth was characterized by increased wall thickness, increased cross-sectional area and reduced wall stiffness.

Animals↗