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  • Polymer and Materials Science  (29)
  • gallbladder motility  (4)
  • Conductivity  (2)
  • 1
    ISSN: 1432-2013
    Schlagwort(e): Key words Arteries ; Conductivity ; Conductance method ; Double indicator dilution method ; Shear rate ; Intravascular ultrasound
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract A double indicator dilution technique for determining the mean cross-sectional area (CSA) of a blood vessel in vivo is presented. Analogous to the thermodilution method, dilution of hypertonic saline was measured by an electrical conductance technique. Because the change in conductance rather than absolute conductance was used to calculate CSA, pulsatile changes in shear rate of blood and conductance of surrounding tissues had no effect on the data. To calculate CSA from an ion mass balance, cardiac output was needed and estimated from the thermodilution curve using the same “cold” (hypertonic) saline injection. The mean CSA, obtained from this double indicator dilution method (CSAGD), was compared with the CSA obtained from the intravascular ultrasound method (IVUS) in 44 paired observations in six piglets. The regression line is close to the line of identity (CSAGD = −1.83 + 1.06⋅CSAIVUS, r = 0.96). The difference between both CSAs was independent of the diameter of the vessel, on average −0.99 mm2± 2.64 mm2 (mean CSAGD = 46.84 ± 8.21 mm2, mean CSAIVUS = 47.82 ± 9.08 mm2) and not significant. The results show that the double indicator dilution method is a reliable technique for estimating the CSA of blood vessels in vivo.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1573-9686
    Schlagwort(e): Conductivity ; Erythrocytes ; Ultrasound ; Shear stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract A modified conductance method to determine the cross-sectional areas (CSAs) of arteries in piglets was evaluated in vivo. The method utilized a conductance catheter having four electrodes. Between the outer electrodes an alternating current was applied and between the inner electrodes the induced voltage difference was measured and converted into a conductance. CSA was determined from measured conductance minus parallel conductance, which is the conductance of the tissues surrounding the vessel times the length between the measuring electrodes of the conductance catheter divided by the conductivity of blood. The parallel conductance was determined by injecting hypertonic saline to change blood conductivity. The conductivity of blood was calculated from temperature and hematocrit and corrected for maximal deformation and changes in orientation of the erythrocytes under shear stress conditions. The equations to calculate the conductivity of blood were obtained from in vitro experiments. In vivo average aortic CSAs, determined with the conductance method CSA (G) in five piglets, were compared to those determined with the intravascular ultrasound method CSA(IVUS). The regression equation between both values was CSA (G) =−0.09+1.00·CSA(IVUS) r=0.97, n=53. The mean difference between the values was −0.29% · 5.57% (2 standard deviations). We conclude that the modified conductance method is a reliable technique to estimate the average cross-sectional areas of the aorta in piglets. © 1999 Biomedical Engineering Society. PAC99: 8780-y, 8437+q, 8719Nn
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Digestive diseases and sciences 41 (1996), S. 2404-2408 
    ISSN: 1573-2568
    Schlagwort(e): orlistat ; tetrahydrolipstatin ; lipase inhibitor ; gallbladder motility ; cholecystokinin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Orlistat (tetrahydrolipstatin) is a potent inhibitor of gastric and pancreatic lipase activity causing a diminution of free fatty acids in the intestinal lumen. The release of cholecystokinin (CCK) critically depends on the presence of free fatty acids in the small intestine. Postprandial CCK release and gallbladder contraction might be decreased by orlistat, potentially resulting in an increased risk of gallstone formation. In this double-blind, placebo-controlled, six-way crossover study, six healthy volunteers ingested in a randomized order three isocaloric test meals (250 ml) of identical osmolality with either orlistat (200 mg) or placebo: (a) a pure-fat meal (25 g triglycerides), (b) a mixed meal containing fat (8 g; 29% of caloric content), protein (10 g; 17%), and dextrose (32 g; 54%), and (c) a fat-free meal containing albumin (25 g; 46%) and dextrose (32 g; 54%). Gallbladder volumes were determined by ultrasonography, and plasma CCK, pancreatic polypeptide and gastrin levels by RIA. Gallbladder contraction (AUC, % × 90 min; difference of means ± 95% CI) in subjects receiving orlistat or placebo did not significantly differ after intake of the pure-fat meal (443 ± 1174), the mixed meal (313 ± 1170), or the fat-free-meal (−760 ± 1180). The release of CCK (AUC; pM × 90 min; difference of means ± 95% CI) was not different between orlistat and placebo after ingestion of the pure-fat meal (−18 ± 64), the mixed meal (−45 ± 62), and the fat-free meal (27 ± 63). Likewise, the release of pancreatic polypeptide and gastrin was similar after intake of the meals with either orlistat or placebo. A single dose of orlistat did not reduce gallbladder motility after ingestion of meals with differing fat contents. The safety of long-term treatment with orlistat with respect to gallstone formation remains to be determined.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1573-2568
    Schlagwort(e): acromegaly ; octreotide ; somatostatin ; gallbladder motility ; cholecystokinin ; pancreatic polypeptide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The increased risk of gallstone formation in acromegalics treated with the somatostatin analog octreotide has been related to an impaired gallbladder emptying. To determine the duration of these inhibitory effects, meal-stimulated gallbladder motility, plasma cholecystokinin (CCK), and pancreatic polypeptide (PP) were measured in five acromegalics treated for 6–32 months with 200–300 μg octreotide daily. Meal tests were performed 45 min, 8 hr and two weeks after the last 100-μg subcutaneous dose. Results were compared with those in normal subjects. Integrated postprandial gallbladder contraction (−125±194 cm3/120 min) and integrated PP secretion (−0.1±0.2 nmol/liter/120 min) were completely suppressed in the 45-min study, but significantly improved (P〈0.05) when measured 8 hr (1376±322 cm3/120 min and 3.0±1.0 nmol/liter/120 min) and two weeks (1437±263 cm3/120 min and 10.6±1.6 nmol/liter/120 min) after the last dose of octreotide. The integrated gallbladder contraction in acromegalics at 8 hr was comparable to that at two weeks and to that in normal subjects, but the integrated PP response at 8 hr was significantly smaller (P〈0.05 vs two weeks and vs normals). Integrated plasma CCK secretion at 45 min (0.13±0.06 nmol/liter/120 min) was not statistically significantly different from the response at 8 hr (0.15±0.02 nmol/liter/120 min) and from that in normal subjects, but it was significantly increased at two weeks after cessation of octreotide (P〈0.05 vs 45 min and 8 hr). In conclusion, during long-term octreotide treatment in acromegalics, initial abolishment of postprandial gallbladder emptying is completely reverted to normal values 8 hr after the last subcutaneous dose. No major differences in postprandial plasma CCK at 45 min and at 8 hr were observed when compared with normal subjects, whereas plasma PP responses were diminished.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1573-2568
    Schlagwort(e): hyperglycemia ; amino acids ; parenteral nutrition ; gallbladder motility ; cholecystokinin ; pancreatic polypeptide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The present study was undertaken to investigate the effect of acute hyperglycemia on the gallbladder contraction induced by intravenous administration of high doses of amino acids (Vamin 18, 250 mg protein/kg/hr). Six healthy volunteers were studied in random order on two occasions during normoglycemia and hyperglycemia with blood glucose levels stabilized at 15 mmol/liter. Gallbladder volumes, measured with ultrasonography, were studied for 60 min before and for 120 min during intravenous infusion of amino acids (IVAA). Administration of IVAA resulted in a significant reduction (P〈0.05) in gallbladder volume from 32±5 cm3 to 17±2 cm3 during normolgycemia. During hyperglycemia no significant changes in gallbladder volume were observed in response to IVAA. No significant changes in plasma CCK concentration, the major hormonal stimulus for gallbladder contraction, occurred in response to IVAA. During hyperglycemia, pancreatic polypeptide (PP) secretion, as an indirect measure of vagal cholinergic tone, in response to IVAA was significantly (P〈0.05) reduced compared to normoglycemia. It is concluded that: (1) administration of high doses of IVAA results in significant gallbladder contraction, (2) high doses of IVAA do not stimulate CCK secretion, (3) acute hyperglycemia inhibits IVAA-induced gallbladder contraction, and (4) acute hyperglycemia inhibits basal and stimulated plasma PP secretion, suggesting impaired vagal-cholinergic tone during hyperglycemia.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1573-2568
    Schlagwort(e): plasma cholecystokinin ; cerulein ; gallbladder motility ; cholescintigraphy ; gallstones
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Impaired gallbladder emptying is one of the various factors suggested to be involved in the pathogenesis of gallstones. The present study was undertaken to determine whether gallbladder emptying, endogenous cholecystokinin (CCK) secretion, or their interrelation is altered in patients with gallstones. After intraduodenal administration of 60 ml corn oil, plasma CCK concentration was measured by a sensitive and specific radioimmunoassay and gallbladder emptying by cholescintigraphy. Patients with gallstones (N=20) produced significantly less endogenous CCK (105±17 pmol/liter 60 min; P 〈0.001) than control subjects (191±11 pmol/liter 60 min, N=20); gallbladder emptying in the patients was significantly decreased at 5, 10, 40, 45, and 50 min but the reduction in gallbladder emptying did not reach statistical significance at 60 min (patients 44±8%, control subjects 60±4%). In addition, the gallbladder responsiveness to intravenous infusion of the synthetic CCK analog cerulein was investigated. Based on the results of gallbladder emptying in response to endogenous and exogenous CCK, four subgroups of gallstone patients were identified: (1) a group (N=7) with normal gallbladder sensitivity to CCK, (2) a group (N=6) with significantly increased gallbladder sensitivity to CCK, (3) a group (N=6) with impaired gallbladder emptying after corn oil due to a significantly reduced endogenous CCK secretion but with normal gallbladder sensitivity to CCK, and (4) one patient whose gallbladder was unresponsive to CCK and was found to have chronic cholecystitis at surgery.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 4 (1993), S. 213-219 
    ISSN: 1045-4861
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The aim of this study was to investigate the bone response to three different types of titanium (Ti) alloys and hydroxyapatite (HA) coated titanium alloy by histological and histomorphometrical analysis. Therefore, implants made of these materials were inserted into the tibia of rabbits. Implantation times were 6 and 16 weeks. The histological evaluation included measurement of the amount of bone apposition and analysis of the bone reaction and interface characteristics around the implants. The results demonstrated no marked differences in bony reaction to the different implant materials. In addition, the HA coatings showed loss of thickness. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 24 (1990), S. 295-307 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: This study reports on certain aspects of wound-healing around percutaneous implants. Plasma-sprayed and dense hydroxylapatite, titanium, and carbon test implants were inserted into the tibia and the cranium of 12 rabbits. Four and 8 months after insertion, the animals were sacrificed and the implants with their surrounding tissues were processed histologically. Light- and transmission electron microscopic investigations were performed. It is found that direct and indirect boneanchoring favors the longevity of percutaneous implants. No differences in tissue reaction between the various implant materials were observed.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 511-518 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: To evaluate the effect of surface treatment and surface microtexture on cellular behavior, smooth and microtextured silicone substrata were produced. The microtextured substrata possessed parallel surface grooves with a width and spacing of 2.0 (SilD02), 5.0 (SilD05), and 10 μm (SilD10). The groove depth was approximately 0.5 μm. Subsequently, these substrata were either left untreated (NT) or treated by ultraviolet irradiation (UV), radiofrequency glow discharge treatment (RFGD), or both (UVRFGD). After characterization of the substrata, rat dermal fibroblasts (RDF) were cultured on the UV, RFGD, and UVRFGD treated surfaces for 1, 3, 5, and 7 days. Comparison between the NT and UV substrata revealed that UV treatment did not influence the contact angles and surface energies of surfaces with a similar surface topography. However, the contact angles of the RFGD and UVRFGD substrata were significantly smaller than those of the UV and NT substrata. The dimension of the surface microevents did not influence the wettability characteristics. Cell culture experiments revealed that RDF cell growth on UV-treated surfaces was lower than on the RFGD and UVRFGD substrata. SEM examination demonstrated that the parallel surface grooves on the SilD02 and SilD05 substrata were able to induce stronger cell orientation and alignment than the events on SilD10 surfaces. By combining all of our findings, the most important conclusion was that physicochemical parameters such as wettability and surface free energy influence cell growth but play no measurable role in the shape and orientation of cells on microtextured surfaces. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 1047-1054 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: This study reports on the soft-tissue response to titanium fiber mesh percutaneous implants. The implants were inserted in the backs of 15 rabbits. The surgical procedure was performed in two steps: implantation of the subcutaneous part of the implants and, after 3 months, fixation of the percutaneous part into the subcutaneous part. Two and 6 months after insertion the animals were sacrificed and the implants, with their surrounding tissues, were processed histologically. Light microscopic analysis demonstrated that only one implant showed considerable skin retraction in the percutaneous area. Around the rest of the implants no downgrowth or only a very limited epidermal downgrowth was observed. Furthermore, the fiber mesh material showed good biocompatible behavior. These results confirm the previous finding that sintered titanium fiberweb structures are effective for the stabilization of percutaneous devices located in soft tissues and can improve their performance. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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