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J Nygren

Publications and source records attributed to J Nygren.

54 records · Page 3Linked to original sources
PubMed1997

Site of insulin resistance after surgery: the contribution of hypocaloric nutrition and bed rest.

1. Insulin resistance after surgery has been shown to be related to several important derangements in protein and fat metabolism. However, mechanisms of impaired glucose tolerance after surgery remain ill-defined. 2. Insulin sensitivity and glucose kinetics (6,6(2)H2-glucose) were studied in seven patients before and after elective surgery (surgery group), by two step-hyperinsulinaemic (0.3 and 0.8 munits kg-1 min-1), normoglycaemic (4.5 mmol/l) clamps. Six healthy subjects were studied, using the same protocol, before and after a similar period of bed rest and hypocaloric nutrition (fast/bed rest group) to delineate the effects of surgery per se. 3. Basal endogenous glucose production and whole-body glucose disposal was higher after surgery (P < 0.001), whereas no change was found after fast/bed rest. During glucose clamps, the glucose infusion rates required to maintain normoglycaemia and whole-body glucose disposal decreased (P < 0.001) after surgery, while endogenous glucose production increased (P < 0.001). In the control subjects, levels of endogenous glucose production remained unchanged after fast/bed rest. In contrast, glucose infusion rates and whole-body glucose disposal during glucose clamps also decreased after fast/bed rest (P < 0.01). However, the relative decrease in both these parameters was greater after surgery compared with after fast/bed rest (P < 0.01). 4. After surgery, energy expenditure and fat oxidation increased (P < 0.001), whereas glucose oxidation decreased (P < 0.05). No significant change was found in glucose utilization postoperatively. After fast/bed rest, no change was found in energy expenditure. However, fat oxidation increased (P < 0.01), whereas glucose oxidation and glucose utilization decreased (P < 0.05). 5. In conclusion, impaired glucose tolerance develops after surgery as a result of decreased insulin-stimulated whole-body glucose disposal as well as increased endogenous glucose release. Despite the increase in endogenous glucose production, the reduction in endogenous glucose production with each elevation of insulin was unaffected by surgery. Perioperative bed rest and/or hypocaloric nutrition contribute to the decrease in insulin-stimulated whole-body glucose disposal in the post-operative state, whereas these factors have no effects on endogenous glucose production.

Adult↗
PubMed1997

The oxygen effect in permeabilized and histone-depleted cells: an enhanced OER for DNA double-strand breaks, compared to single-strand breaks, is abolished by soluble scavengers.

The oxygen enhancement ratios (OER) in mammalian cells for DNA single- and double-strand breaks (ssb and dsb) are similar, usually 2-3. This seems to contradict the hypothesis that dsb are formed by multiple lesions, since one would then expect a quadratic OER for dsb compared to ssb. A higher OER for dsb than for ssb was however found in permeabilized cells (OERdsb = 7.7; OERssb = 4.3) and histone-depleted cells (OERdsb = 20; OERssb = 2.3), in the presence of an SH-compound, mercaptoethylamine. This higher OER could be counteracted by addition of the OH-radical scavenger DMSO. The OERdsb/OERssb ratio thus increases when the indirect effects increase. The repair of directly induced DNA lesions by hydrogen donation seems to be less efficient than the repair of indirectly induced lesions. It is suggested that differences in the fraction of unrepairable breaks differs for ssb and dsb and that this is the reason for the non-quadratic OERdsb compared to OERssb found in cells. In the absence of SH-compounds, there was no oxygen effect for ssb in permeabilized and histone-depleted cells. In contrast to this, a small oxygen effect was observed for dsb in permeabilized cells and this effect increased after histone depletion, reaching a value of OER = 1.8. This oxygen effect seems to be linked to generation of dsb by single OH radicals.

Cell Line↗
PubMed1996

The comet assay: mechanisms and technical considerations.

The comet assay is frequently used to measure DNA damage in individual cells. In order to better understand the mechanisms behind the technique, we have studied the behaviour of DNA under different electrophoresis conditions in mammalian cells exposed to gamma radiation. The comet tails obtained after neutral electrophoresis seem to consist of DNA loops which are attached to structures in the nucleus, since the DNA cannot move in the second direction after two-dimensional electrophoresis. When the DNA is labelled by a short pulse, microautoradiography reveals that all label appear in the head of the comets when neutral electrophoresis is applied. After chase incubation, the label moves out into the tails. This gives further support to the view that the DNA loops are fixed to some structure in the nucleus where also the DNA synthesis takes place. Under alkaline electrophoresis conditions, however, the entire comet tails move in the new electrophoresis direction. Thus, it appears that the alkaline comet tails consist of free DNA fragments. Further, the effects of alkaline concentration and sodium chloride during unwinding and electrophoresis are discussed. Throughout the study, a protocol for drying and fixation of the comets has been used.

Animals↗
PubMed1996

DNA double- and single-strand breaks induced by accelerated He2+ and N6+ ions in human cells: relative biological effectiveness is dependent on the relative contribution of the direct and indirect effects.

Double (dsb) and single-(ssb) strand breaks induced by accelerated He2+ ions (LET from 10 to 220 keV/micron with > 70% in the range of 35-55 keV/micron, mean LET about 40 keV/micron) and N6+ ions (LET 125 keV/micron) have been determined in three DNA substrates derived from human cells in culture. He ions were 50% more efficient than N ions to induce dsb in intact cells. In the presence of a high concentration of an OH-radical scavenger, dimethylsulphoxide (DMSO), the dsb were reduced by a factor of 4.5 after He ions but only a factor of 1.4 after N ions, i.e. N ions were about a factor of three more efficient in a substrate where direct hits in the DNA dominated. With gamma rays DMSO gives a reduction by a factor of 3.6. In nucleoids, where the histones were removed by salt treatment, dsb induction increased 22, 18 and 12 times for gamma rays, He ions and N ions respectively. Under these conditions dsb is about 1.5-fold higher after He compared with N ions. Total number of breaks, ssb and dsb, were determined for intact cells. Compared with gamma-rays the breaks were reduced by a factor of 4 after He ions and a factor of 14 after N ions, i.e. ssb and dsb seem to be in the same range after nitrogen ions. Although our measurements do not allow an absolute determination of relative biological effectiveness (RBE) for He and N ions induced dsb, we can show that the RBE for N ions increases by a factor of 2.5 if OH radicals are removed, and decreases by a factor of 2 if most of the protection against OH radicals is removed, altogether a variation of a factor of 5. RBE for He ions, on the other hand, is almost independent of irradiation conditions.

Cells, Cultured↗
PubMed1996

The metabolic response to cholecystectomy: insulin resistance after open compared with laparoscopic operation.

OBJECTIVE: To study the changes in insulin sensitivity and plasma concentrations of interleukin-6 (IL-6) after open compared with laparoscopic cholecystectomy. DESIGN: Prospective open study. SETTING: University hospital, Sweden. SUBJECTS: 12 otherwise healthy patients undergoing either open (n = 6) or laparoscopic (n = 6) cholecystectomy. MAIN OUTCOME MEASURE: Relative insulin sensitivity (compared with preoperative) on the day after operation. Changes in IL-6 concentrations postoperatively. RESULTS: The mean (SEM) relative reduction in insulin sensitivity was significantly smaller after laparoscopic (18 (5)%) compared with the open operation, (58 (4)%) (p < 0.01). There was a significant increase in plasma concentrations of IL-6 postoperatively, but there was no difference between the groups. CONCLUSION: Insulin sensitivity is less affected 24 hours after laparoscopic than after open cholecystectomy, which in this study was not accompanied by a simultaneous difference in the IL-6 response. The small postoperative reduction of insulin sensitivity may be a contributing factor to the clinical benefit of improved wellbeing observed after laparoscopic surgery.

Adult↗
PubMed1995

Chromatin structure and radiation-induced DNA strand breaks in human cells: soluble scavengers and DNA-bound proteins offer a better protection against single- than double-strand breaks.

In the present investigation we have studied the formation of DNA double-strand breaks (dsbs) in different chromatin substrates and made a comparison with our previous results on radiation-induced single-strand breaks (ssb). Removal of soluble scavengers increased the number of ssbs by a factor of 2, but increased dsbs only 1.2 times. Decondensation of the chromatin increased ssbs and dsbs to the same extent, by a factor of 3-4. Removal of DNA-bound proteins gave an additional increase in ssbs and dsbs by a factor of 14 and 5 respectively. The increase in both ssbs and dsbs was caused by OH radicals. The differential effect on ssbs and dsbs can be explained by assuming that dsbs are formed mainly by multiple hits from clusters of ionizations close to the DNA. When the DNA-bound proteins are removed, more distant radicals can reach the DNA, which favours ssb formation. Under those conditions dsbs also induced by single OH radicals become important. DNA-bound proteins protect DNA only to a limited extent by acting as scavengers of OH radicals. The largest part of the protection depends on the fact that DNA in the chromatin is made up of large, compact aggregates, where the distance between separate aggregates exceeds the effective range of the OH radicals and the amount of water inside the aggregates is too small to give a maximal contribution of OH radicals compared with when DNA is more evenly distributed in a given volume.

Cells, Cultured↗
PubMed1995

Preoperative gastric emptying. Effects of anxiety and oral carbohydrate administration.

BACKGROUND: Overnight fasting is routine before elective surgery. This may not be the optimal way to prepare for surgical stress, however, because intravenous carbohydrate supplementation instead of fasting has recently been shown to reduce postoperative insulin resistance. In the current study, gastric emptying of a carbohydrate-rich drink was investigated before elective surgery and in a control situation. METHODS: Twelve patients scheduled for elective surgery were randomly given 400 mL of either a carbohydrate-rich drink (285 mOsm/kg, 12.0% carbohydrates, n = 6) or water 4 hours before being anesthetized. Gastric emptying was measured (gamma camera, 99Tcm). Each patient repeated the protocol postoperatively as a control. All values were presented as the mean +/- SEM by means of a nonparametric statistical evaluation. RESULTS: Despite the increased anxiety experienced by patients before surgery (p < 0.005), gastric emptying did not differ between the experimental and control situations. Initially, water emptied more rapidly than carbohydrate. However, after 90 minutes, the stomach was emptied regardless of the solution administered (3.2 +/- 1.1% [mean +/- SEM] remaining in the stomach in the carbohydrate group versus 2.3 +/- 1.2% remaining in the stomach in the water group). CONCLUSIONS: Preoperative anxiety does not prolong gastric emptying. The stomach had been emptied 90 minutes after ingestion of both the carbohydrate-rick drink and water, thereby indicating the possibility of allowing an intake of iso-osmolar carbohydrate-rich fluids before surgery.

Adult↗
PubMed1995

Disturbed anabolic hormonal patterns in burned patients: the relation to glucagon.

OBJECTIVE: Complex changes in the anabolic regulators of metabolism occur after major injury. We have studied the time course for IGF-I and IGFBP-1 after burn injury and their relations to circulating levels of other anabolic and catabolic hormones. The hormonal patterns during the onset of sepsis were also investigated. PATIENTS: Eight patients (age 36 (6) years, mean (SEM)) with major burn injury (burn area 42 (6) %) were studied. The first 2 days since the burn were used for rehydration therapy (rehydration period), after which a complete total parenteral nutrition (TPN) period was initiated. Seven positive blood cultures, during the study period. Six of the eight survived. MEASUREMENTS: The hormonal changes determined in the morning during the first 7 days after the burn and from day 22 to 24 were investigated. The superimposed effects of sepsis were studied by normalizing all data to the day of positive blood cultures and clinical onset of sepsis. RESULTS: On admission, plasma levels of glucagon, IGFBP-1 and GH were elevated while levels of IGF-I were low. During the first week after the burn, morning levels of glucagon and insulin increased while levels of GH and IGF-I decreased. GH levels were still elevated compared to healthy subjects. Despite the increase in insulin levels, IGFBP-1 remained elevated. Three weeks after the burn injury, IGF-I levels were increased but still markedly below normal, while IGFBP-1 levels remained unchanged. Persistent elevations of insulin levels were combined with reductions in glucagon levels. Admission levels of IGFBP-1 correlated to nitrogen loss (negative nitrogen balance) during the first 24 hours after the burn (r = 0.84, P < 0.05). A correlation between negative nitrogen balance and glucagon levels was found during early catabolic period in the rehydration period (i.e. days 2-3, r = 0.84, P < 0.01). The relative change in IGFBP-1 levels in the rehydration period correlated to changes in glucagon levels (days 2-3 vs admission, r = 0.85, P < 0.05). The insulin/glucagon molar ratio correlated to the IGF-I/IGFBP-1 ratio during both the rehydration period (days 2-3, r = 0.77, P < 0.05) and the third week after the burn (r = 0.77, P < 0.05). During the most catabolic phase in the first week after the burn (TPN period) there was an inverse relation between IGF-I and IGFBP-I and glucagon (r = 0.83, P < 0.05). During the less catabolic third week after the burn, an inverse correlation was found between IGF-I and glucagon (r = -0.83, P < 0.05). Sepsis, superimposed upon the burn trauma, was associated with transient elevations in IGFBP-1 and reductions in insulin despite elevated levels of glucose and a further 50% increase in nitrogen losses. CONCLUSIONS: The present findings show that marked changes is important anabolic regulating factors occur after major burn injury. Uncoupling of the GH-IGF-I axis, and the attenuation of the inhibitory effects of insulin on IGFBP-1, both contribute to the reduction in IGF-I levels and bioavailability, factors which may play an important role in post injury metabolism. Furthermore, these data suggest that the catabolic hormones (catecholamines, cortisol and glucagon), primarily glucagon seem to be involved in the modulation of IGF-I and IGFBP-1 levels following burn injury.

Adult↗
PubMed1994

Induction of DNA strand breaks by ethylene oxide in human diploid fibroblasts.

In vitro exposure of normal human diploid fibroblasts (strain VH-10) to ethylene oxide (EtO) induced DNA strand breaks in the dose range of 2.5-30 mMh of EtO. Alkaline DNA unwinding (ADU), neutral filter elution (NFE), pulsed field gel electrophoresis (PFGE), and the comet assay were used to measure DNA single (SSBs) and double strand breaks (DSBs). Different induction rates of SSBs and DSBs, depending on applied method and also on treatment conditions (cells in monolayer or in suspension were used), were found. A dose-dependent increase of DNA strand breaks was found by the ADU method in the dose range of 2.5-20 mMh of EtO when treatment was performed in monolayer and in suspension. DSBs were detected by NFE only when the cells were treated with EtO in suspension (doses 10-30 mMh). The highest induction rate of DSBs (about 4 DSBs per 100 Mbp per 1 mMh of EtO) was detected in suspension with PFGE applied. We have shown that heat-labile sites are formed by EtO. Presumably, the different DSB levels detected by PFGE and NFE result from the conversion of these sites to DSBs during cell lysis at elevated temperature in the PFGE method. The results of the comet assay confirmed that apoptotic processes are not involved in the formation of DSBs in our experimental conditions (less than 1% of apoptotic cells were observed at all doses studied). Possible mechanisms for the induction of DNA strand breaks by EtO-treatment are discussed. The capacity to repair DSBs in EtO-exposed (5-7.5 mMh) cells was studied, and it was found that a considerable part of the damage (about 50%) could be repaired during 18 hr of incubation.

Cells, Cultured↗
PubMed1992

The filter does not act as a DNA size discriminator in the neutral filter elution technique.

Various types of filters were used with the neutral filter elution technique. No significant differences in elution rate or curve shapes were found. Therefore we assume that the release of DNA fragments from the DNA gel formed by lysis of cells is the rate-determining event in elution and not the rate of migration through the filter. We suggest that the filter only serves as a support for the DNA gel.

Cells, Cultured↗
PubMed1991

DNA-bound proteins contribute much more than soluble intracellular compounds to the intrinsic protection against radiation-induced DNA strand breaks in human cells.

To assess the role of soluble intracellular compounds and DNA-bound proteins in the intrinsic protection against radiation-induced DNA strand breaks, the alkaline unwinding technique was applied to cellular, nuclear, and nucleoid monolayers. It was found that, when the soluble intracellular compounds were removed from human fibroblasts by permeabilization (nuclear monolayers) and irradiated in a phosphate buffer containing 150 mM monovalent cations (Na+ and K+) and 0.8 mM MgCl2, the frequency of radiation-induced DNA strand breaks increased twofold. Removal of both soluble intracellular compounds and DNA-bound proteins from the cells by a pretreatment with 2 M NaCl (nucleoid monolayers) resulted in a 100-fold increase in the frequency of strand-break induction by gamma radiation. Expressed as percentage of total intrinsic protection against radiation-induced DNA strand breaks, DNA-bound protein contributed 99% compared to 1% by soluble intracellular compounds. Using a different experimental approach it was found that the radioprotective capacity of soluble intracellular compounds was equivalent to about 5 mM dimethyl sulfoxide (DMSO) and DNA-bound proteins to about 70 mM DMSO. It is concluded that DNA-bound proteins play a much greater role than soluble intracellular compounds in the intrinsic protection against radiation-induced DNA strand breaks in cultured human cells.

Cells, Cultured↗
PubMedDate not supplied

Short-term hypocaloric nutrition but not bed rest decrease insulin sensitivity and IGF-I bioavailability in healthy subjects: the importance of glucagon.

Hyperinsulinemic, normoglycemic clamps were performed before and after 24 h of either hypocaloric nutrition or bed rest in healthy subjects. Decreased insulin sensitivity and insulin-like growth factor-I (IGF-I) bioavalibility, as measured by the serum IGF-I/insulin-like growth factor binding protein-1 (IGFBP-1) ratio, was found after fasting, whereas no metabolic changes were found after bed rest. Glucagon seems to be a key regulator of IGFBP-1 after brief hypocaloric nutrition. Hypocaloric nutrition and immobilization may add to the catabolic response to surgery and other trauma. Presently, six healthy subjects were studied before and after a 24-h period of hypocaloric nutrition (200 kcal/24 h, fast) or immobilization (bed rest) using the hyperinsulinemic (0.8 mU.kg-1.min-1), normoglycemic (4.5 mmol/L) clamp, indirect calorimetry, and circulating levels of substrates and hormones. After fast, body weight decreased (P < 0.05), and nitrogen balance was negative (-10 +/- 1 g urea nitrogen/24 h). Basal levels of free fatty acids, glucagon, and IGFBP-1 increased (P < 0.05), whereas c-peptide levels and the IGF-I/IGFBP-1 ratio decreased (P < 0.05). However, no change was found in basal levels of IGF-1 or substrate oxidation. Furthermore, changes (%) in basal levels of glucagon after fast correlated to IGFBP-1 (r = 1.0, P < 0.05), whereas the suppressibility of IGFBP-1 by insulin was maintained at normal levels. During clamps, glucose infusion rates (GIR) decreased after fast (-43 +/- 13%, mean +/- SEM, P < 0.001). Although not significantly, clamp levels of fat oxidation tended to increase and glucose oxidation tended to decrease. Levels of IGFBP-1 during clamps were higher as compared with the control clamp (P < 0.05). No adverse metabolic changes were seen after bed rest, and no change in GIR during clamps were seen as compared with the control measurement (0 +/- 14%). After brief hypocaloric nutrition, insulin sensitivity is reduced, whereas IGF-I bioavalibility is reduced by an increase in levels of IGFBP-1. Glucagon seems to contribute to the increase in IGFBP-1 during these conditions.

Adult↗
PubMedDate not supplied

Radiation and hypothermia: changes in DNA supercoiling in human diploid fibroblasts.

The influence of hypothermia (2 degrees, 15 degrees and 28 degrees C) upon the effect of X-irradiation on chromatin from human diploid fibroblast cells (AG1518) was studied using the fluorescent halo assay. Rewinding of supercoils was inhibited in a dose-dependent manner when cells were irradiated with 4, 8 or 16 Gy. This inhibition of rewinding was reduced when cells were irradiated at subnormal temperatures compared with cells irradiated at 37 degrees C. One hour's preincubation at low temperature did not influence rewinding. When AG1518 cells were irradiated at 37 degrees C in the presence of the radical scavenger DMSO (0.5 M), the radiation-induced damage was reduced. No additional protection of DMSO in hypothermic cells (2 degrees C) was found, possibly indicating that OH-radical-mediated effects are more temperature dependent. These results are similar to those recently found for the malignant MCF-7 cell line.

Cold Temperature↗
PubMedDate not supplied

Effect of hypothermic irradiation of the growth characteristics of two human cell lines.

The effect of hypothermic irradiation on the growth characteristics of two human cell lines was investigated. Low temperature (2 degrees C) X-irradiation of MCF-7 cells (2, 3 and 4 Gy) resulted in higher surviving fractions compared to irradiation at 37 degrees C as assessed by the colony forming assay. The ratios for the surviving fraction between the two temperatures were 1.2, 1.5 and 1.7 at 2, 3 and 4 Gy, respectively. Correspondingly, the dose modifying factor was 1.23. The distribution of colony sizes (of those with more than 50 cells) was different with proportionally more small-sized colonies from cells irradiated at 2 degrees C. Colonies from diploid fibroblasts (HS27) were ill-defined and could not be counted. In conclusion, hypothermia during irradiation seems to influence the radioresponse in MCF-7 cells. The growth in multiwell plates of MCF-7 cells and human diploid fibroblasts (HS27) after irradiation with 3 and 4 Gy, respectively, at 2 degrees C or 37 degrees C was assessed by using the crystal violet growth assay. No difference between 2 degrees C or 37 degrees C irradiation was found for either of the two cell lines.

Adenocarcinoma↗