| 1. |
- Degens, Hans, et al.
(författare)
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Post-operative effects on insulin resistance and specific tension of single skeletal muscle fibres
- 1999
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Ingår i: Clinical Science. - : Lippincott Williams & Wilkins. - 0143-5221 .- 1470-8736. ; 97:4, s. 449-455
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Tidskriftsartikel (refereegranskat)abstract
- Surgery and accidental trauma are associated with a transient period of insulin resistance, substrate catabolism and muscle weakness. In the present study, we evaluated the changes in the force-generating capacity of chemically skinned single muscle fibresfollowing abdominal surgery. Biopsies of the m. vastus lateralis were obtained in three patients 1 day before and 3 or 6 days after surgery. Part of the biopsy was frozen for histochemical analysis of the fibre cross-sectional area (FCSA) and myofibrillar protein content, and another part was used for single-fibre contractile measurements. All patients developed insulin resistance following surgery. The maximum velocity of unloaded shortening of single muscle fibres did not change following surgery. The FCSA did not decrease after surgery, as determined either from histochemical sections or from singlefibres measured at a fixed sarcomere length of 2.76+/-0.09 microm (mean+/-S.D.). Further, the force-generating capacity of the single fibres, measured as maximal Ca(2+)-activated force (P(0)) or as P(0) normalized to FCSA (specific tension), remained unchanged, as did the myofibrillar protein content of the muscle. In conclusion, the muscle weakness associated with post-operative insulin resistance is not related to a decreased specifictension or a loss of myofibrillar proteins. Other potential cellular mechanisms underlying post-operative weakness are discussed.
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| 2. |
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| 3. |
- Ljungqvist, Mattias, 1969
(författare)
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Fluid and Solid Particle Dynamics in Stirred Vessels
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present thesis deals with the fluid dynamics of stirred vessels and particularly those that are to be used in conjunction with solids suspensions. Stirred vessels are very common in the process industry and large amounts of energy can be saved by optimising their operation. Several types of unit operations such as chemical reaction, leaching, dissolution and crystallisation involve solids suspensions. Axial flow impellers are best suited for suspension of solids and therefore, pitched blade turbines were used in the present work. A standard type of stirred vessel with a single impeller and an industrial type of tank with two parallel impellers, were studied. The single-phase flow and the simultaneous flow of particles and liquid were investigated. Measurements were made on the single-phase flow using Laser-Doppler anemometry and on the two-phase flow using Phase-Doppler anemometry. Numerical computations were performed using the commercially available CFD-code CFX4. The two-phase calculations were done using the multi-fluid approach. Good agreement between the experiments and calculations was obtained for the fluid phase but the particle phase predictions were less satisfactory. The axial component of the slip velocity was generally slightly overestimated and the radial and tangential components severely underestimated by the computational model. The single-phase flow in a completely filled vessel equipped with a lid was investigated in detail and compared with results for a vessel lacking a lid. It was found that the influence of the lid was small and changes in the impeller discharge flow were observed only after lowering the lid to half of the vessel height. The simultaneous measurement of fluid and particle velocities revealed that generally, particles lag when the fluid is moving upwards and vice versa but also, that exceptions to this are common. The largest differences between the velocities of the two phases where found in regions with large mean velocity gradients such as the impeller discharge. For the industrial type of tank, it was found that horizontal displacement of the two impellers in opposite directions could break-up the segregated mixing zones that tended to form in the tank.
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| 4. |
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| 5. |
- Nygren, Jonas O., et al.
(författare)
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Perioperative insulin and glucose infusion maintains normal insulin sensitivity after surgery
- 1998
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Ingår i: American Journal of Physiology. - : American Physiological Society. - 0002-9513 .- 2163-5773. ; 275:1 Part 1, s. E140-E148
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Tidskriftsartikel (refereegranskat)abstract
- Elective surgery was performed after overnight fasting, a routine that may affect the metabolic response to surgery. We investigated the effects of insulin and glucose infusions before and during surgery on postoperative substrate utilization and insulin sensitivity. Seven patients were given insulin and glucose infusions 3 h before and during surgery (insulin group), and a control group of six patients underwent surgery after fasting overnight. Insulin sensitivity and glucose kinetics (D-[6,6-2H2]glucose) were measured before and immediately after surgery using a hyperinsulinemic, normoglycemic clamp. Glucose infusion rates and whole body glucose disposal decreased after surgery in the control group (-40 and -29%, respectively), whereas no significant change was found in the insulingroup (+16 and +25%). Endogenous glucose production remained unchanged in both groups. Postoperative changes in cortisol, glucagon, fat oxidation, and free fatty acids were attenuated in the insulin group (vs. control). We conclude that perioperative insulin and glucose infusions minimize the endocrine stress response and normalize postoperative insulin sensitivity and substrate utilization.
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| 6. |
- Nygren, Jonas, et al.
(författare)
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Preoperative oral carbohydrate administration reduces postoperative insulin resistance
- 1998
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Ingår i: Clinical Nutrition. - : Elsevier. - 0261-5614 .- 1532-1983. ; 17:2, s. 65-71
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Tidskriftsartikel (refereegranskat)abstract
- Infusions of carbohydrates before surgery reduce postoperative insulin resistance. We investigated the effects of a carbohydrate drink, given shortly before surgery, on postoperative metabolism. Method: Insulin sensitivity, glucose turnover ([6,6, 2H2]-D-glucose) and substrate utilization were measured using hyperinsulinemic normoglycemic clamps and indirect calorimetry in two matched groups of patients before and after elective colorectal surgery. The drink group (n = 7) received 800 ml of an isoosmolar carbohydrate rich beverage the evening before the operation (100 g carbohydrates), as well as another 400 ml (50 g carbohydrates) 2 h before the initiation of anesthesia. The fasted group (n = 7) was operated after an overnight fast. Results: After surgery, energy expenditure increased in both groups. Endogenous glucose production was higher after surgery and the difference was significant during low insulin infusion rates in both groups (P < 0.05). The supressibility of endogenous glucose production by the two step insulin infusion was similar pre- and postoperatively in both groups. At the high insulin infusion rate postoperatively, whole body glucose disposal was more reduced in the fasted group (-49 ± 6% vs -26 ± 8%, P < 0.05 vs drink). Furthermore, during high insulin infusion rates, glucose oxidation decreased postoperatively only in the fasted group (P < 0.05) and postoperative levels of fat oxidation were greater in the fasted group (P < 0.05 vs drink). Only minor postoperative changes in cortisol and glucagon were found and no differences were found between the treatment groups. Conclusions: Patients given a carbohydrate drink shortly before elective colorectal surgery displayed less reduced insulin sensitivity after surgery as compared to patients who were operated after an overnight fast.
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| 7. |
- Nygren, Jobas, et al.
(författare)
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Preoperative oral carbohydrates and postoperative insulin resistance
- 1999
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Ingår i: Clinical Nutrition. - : Elsevier. - 0261-5614 .- 1532-1983. ; 18:2, s. 117-120
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Tidskriftsartikel (refereegranskat)abstract
- Infusions of carbohydrates before surgery have been shown to reduce postoperative insulin resistance. Presently, we investigated the effects of a carbohydrate drink, given shortly before surgery, on postoperative insulin sensitivity. Methods: Insulin sensitivity and glucose turnover (16, 6, 2H2]-D-glucose) were measured using hyperinsulinemic, normoglycemic clamps before and after elective surgery. Sixteen patients undergoing total hip replacement were randomly assigned to preoperative oral carbohydrate administration (CHO-H, n = 8) or the same amount of a placebo drink (placebo, n = 8) before surgery. Insulin sensitivity was measured before and immediately after surgery. Patients undergoing elective colorectal surgery were studied before surgery and 24 h postoperatively (CHO-C (n = 7), and fasted (n = 7), groups). The fasted group underwent surgery after an overnight fast. In both studies, the CHO groups received 800 ml of an isoosmolar carbohydrate rich beverage the evening before the operation (100 g carbohydrates), as well as another 400 ml (50 g carbohydrates) 2 h before the initiation of anesthesia. Results: Immediately after surgery, insulin sensitivity was reduced 37% in the placebo group (P < 0.05 vs. preoperatively) while no significant change was found in the CHO-H group (-16%, p = NS). During clamps performed 24 h postoperatively, insulin sensitivity and whole-body glucose disposal was reduced in both groups, but the reduction was greater compared to that in the CHO-C group (-49 ± 6% vs. -26 ± 8%, P < 0.05 fasted vs. CHO-C). Conclusions: Patients given a carbohydrate drink shortly before elective surgery displayed less reduced insulin sensitivity after surgery as compared to patients undergoing surgery after an overnight fast.
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