Biomedical subjects

T S Larsen

Publications and source records attributed to T S Larsen.

At least 37 records · Page 2Linked to original sources

PubMed1997

Pyruvate reverses fatty-acid-induced depression of ventricular function and calcium overload after hypothermia in guinea pig hearts.

OBJECTIVE: High levels of free fatty acids have been shown to impair mechanical recovery and calcium homeostasis of isolated rat hearts following hypothermic perfusion. The objective of the present study was to investigate whether inhibition of fatty acid oxidation through activation of pyruvate dehydrogenase by millimolar concentrations of pyruvate could influence functional recovery and Ca2+ homeostasis after a hypothermic insult. METHODS: Ventricular function and myocardial calcium ([Ca]total) were measured in 3 different groups of Langendorff-perfused guinea pig hearts exposed to 40 min hypothermic (15 degrees C) perfusion, followed by 30 min rewarming at 37 degrees C. The hearts were perfused with either 11.1 mM glucose (G), glucose and 1.2 mM palmitate (GP), or glucose, palmitate and 5 mM pyruvate (GPP) as energy substrates. RESULTS: All groups showed marked elevations in [Ca]total during hypothermia (from 0.6-0.7 mumol.g dry wt-1 to 9.3-12.2 mumol.g dry wt-1 at 40 min hypothermia, P < 0.05), associated with a pronounced increase in left ventricular end-diastolic pressure (LVEDP from 0-2 to 50-60 mmHg). Following rewarming, GP-perfused hearts showed significantly lower recovery of mechanical function compared to both G- and GPP-perfused hearts (% recovery of left ventricular developed pressure: 27 +/- 8 vs. 62 +/- 3 and 62 +/- 8%, respectively, P < 0.05). The reduced mechanical recovery of GP-perfused hearts was associated with elevated [Ca]total. In separate experiments we found that addition of 1.2 mM palmitate reduced glucose oxidation ([14C]glucose) from 1.77 +/- 0.28 mumol.min-1.g dry wt-1 (G-perfused hearts) to 0.15 +/- 0.04 mumol.min-1.g dry wt-1 (GP-perfused hearts, P < 0.05), implying that fatty acids had become the major substrate for oxidative phosphorylation. Fatty acid oxidation was, however, less pronounced after further addition of 5 mM pyruvate. Thus, palmitate oxidation ([3H]palmitate) was more than 40% lower in GPP-perfused than in GP-perfused hearts (0.83 +/- 0.22 vs. 1.41 +/- 0.12 mumol.min-1.g dry wt-1, P < 0.05). CONCLUSIONS: The present results demonstrate impaired ventricular function and calcium homeostasis after hypothermia in guinea pig hearts perfused with fatty acids in addition to glucose, as compared to hearts perfused with glucose alone. Furthermore, we show that these unfavourable effects of fatty acids can be overcome by an exogenous supply of pyruvate.

Animals↗

PubMed1997

Voltage-sensitive dye recordings of electrophysiological activation in a Langendorff-perfused mouse heart.

The pattern of electrophysiological activation of adult mouse ventricles was measured with the use of voltage-sensitive dye methods. Di-4-ANEPPS was used to monitor membrane potential as small changes in fluorescence, which were detected by a state of the art, cooled, charged coupled device camera/image intensifier system. The extremely rapid conduction velocity, coupled with the small size of this preparation, necessitated taking these measurements at room temperature (22 to 23 degrees C). Initial experiments demonstrate that ventricular activation can be identified and its conduction pattern can be monitored reproducibly and with high resolution for extended time periods (10 to 20 mins) during spontaneous activity.

Animals↗

PubMed1996

Myocardial substrate oxidation during warm continuous blood cardioplegia.

BACKGROUND: Although long-chain fatty acids are a major energy substrate utilized by the myocardium, changes in the substrate balance toward a predominating fatty acid utilization could jeopardize the myocardium during cardiac operative procedures. METHODS: In the present study myocardial substrate utilization was examined during warm continuous blood cardioplegia (4 hours, 37 degrees C), using pigs undergoing cardiopulmonary bypass. Hearts were perfused antegradely in a closed extracorporeal circuit in which cardioplegic donor blood (hematocrit, 22%) containing 14C-glucose and 3H-oleate was delivered to the heart. Arterial and coronary sinus blood samples were taken at intervals for determination of plasma concentrations of energy substrates, as well as glucose and oleate oxidation rates (14CO2 and 3HOH production). RESULTS: The concentration of fatty acids in the cardioplegic perfusate did not change significantly during the cardiac arrest period. The mean concentration of glucose showed a 30% decline (not significant), whereas the lactate concentration increased from a starting value of 3.12 +/- 0.27 to 6.31 +/- 0.72 mmol/L at the end (mean +/- standard error of the mean; n = 8; p < 0.05). Only fatty acid levels showed a significant (positive) arterial-coronary sinus difference. Myocardial oxidation of oleate varied between 302 +/- 71 and 650 +/- 66 nmol.min-1.heart-1, whereas the range of variation for glucose oxidation was 144 +/- 64 to 355 +/- 107 nmol.min-1.heart-1. However, the changes in fatty acid levels and glucose oxidation rates during the cardiac arrest period were not statistically significant. We calculated that overall glucose oxidation accounted for less than 5% of the total aerobic energy production. CONCLUSIONS: The present results demonstrate overreliance on fatty acids as a source of energy during warm continuous blood cardioplegia, consistent with a condition of myocardial insulin resistance.

Adenosine Triphosphate↗

PubMed1996

Normotherm continuous blood cardioplegia for 4 hours in an in vivo pig model.

Warm, continuous blood cardioplegia should theoretically maintain cardiac arrest for hours without ischaemic or hypothermic injury. In the absence of in vivo studies of myocardial metabolism and ultrastructural and/or functional preservation during and after more than 2 hours of cardiac arrest and after weaning from bypass, we devised a porcine model with a closed extracorporeal circuit for the heart alone. Normothermic blood cardioplegia was administered antegrade and recirculated for 2 or 4 hours, each in seven pigs. After aortic declamping all were successfully weaned from bypass and reperfused for 1 hour. Thereafter we found no significant intergroup difference in haemodynamic characteristics (average fall in mean arterial pressure 31.7 +/- 3.2% and 26.9 +/- 2.6%) or blood analyses. After 5 and 60 minutes of cardiac arrest there was minimal lactate production (5.7 +/- 10.7 and 0.5 +/- 10.5 nmol/l, respectively), whereas in the remainder of the arrest period there was lactate uptake, indicating aerobic heart metabolism. Our setup avoids systemic hyperkalaemia, gives good cardiac protection with no deterioration between 2 and 4 hours and is well suited for studies on the quiescent, blood-perfused oxygenated heart.

Animals↗

PubMed1996

Changes in blood flow distribution and capillary function after deep hypothermia in rat.

The present experiments were carried out in the rat to investigate the peripheral vascular function prior to the development of posthypothermic circulatory collapse. In the first study, mean arterial blood pressure, heart rate, cardiac output, regional blood flow, and plasma volume of hypothermic (4 h, 15-13 degrees C) and rewarmed rats were compared with normothermic controls. In response to hypothermia, arterial blood pressure, heart rate, and cardiac output declined markedly. After rewarming, arterial blood pressure and heart rate recovered fully, whereas cardiac output was only 33 +/- 7% of the control value (p < 0.025). Tissue blood flow was markedly depressed during hypothermia (p < 0.025), except for the abdominal skin. After rewarming, blood flow in skeletal muscle returned to within control levels, whereas blood flow in internal organs remained low (p < 0.025 vs. control). Posthypothermic plasma volume was 77 +/- 3% of control (p < 0.05). In the second study, the transcapillary colloid osmotic pressure gradient (COPp-COPi) was calculated following measurement of colloid osmotic pressure in plasma (COPp) and interstitium (COPi) in prehypothermic, hypothermic, and posthypothermic rats. The posthypothermic value of COPp-COPi was 76 +/- 4% of the prehypothermic value (p < 0.05). In conclusion this study demonstrates that the reduced cardiac output in rewarmed rats is associated with an altered regional blood flow distribution compared with that of normal rats. Capillary integrity also seemed perturbed. Thus, changes in both control and function of the peripheral vasculature are important mechanisms in the development of a posthypothermic circulatory collapse.

Animals↗

PubMed1995

Phospholipid degradation in hypoxic/reoxygenated cardiomyocytes in response to phospholipase C from Bacillus cereus.

In the present study, we investigated possible mechanisms behind exogenous phospholipase C-induced glycerol production in irreversibly damaged myocytes. Rat ventricular myocytes were preincubated for 60 min in substrate-free Krebs-Henseleit bicarbonate buffer equilibrated with 95% N2-5% CO2 (37 degrees C, pH = 7.4), resulting in exhaustion of cellular high energy phosphates and loss of rod-shaped morphology. At the end of the preincubation period, the incubation vials were divided into two groups; one receiving 10 mU/ml phospholipase C (PC-PLC), whereas the other received an equivalent volume of buffer (control incubations). Incubation was then continued for another 60 min under 95% air-5% CO2 atmosphere. Samples for measurement of metabolite levels were taken immediately after cell isolation, at the end of the preincubation period and at the end of the normoxic incubation period. During the 60 min incubation period following reoxygenation, glycerol output was markedly higher from PC-PLC treated than from control myocytes. However, the elevated glycerol output from these cells was not accompanied by a simultaneous rise in glycerol-3-phosphate, nor was it inhibited by inclusion of pyruvate in the incubation buffer. On the other hand, glycerol output from PC-PLC treated myocytes was effectively inhibited by a diacylglycerol lipase inhibitor (U-57908, The Upjohn Company). Analysis of cellular lipids revealed a 22% reduction of phospholipid in PC-PLC treated myocytes (P < 0.02), while the content of triacylglycerol, diacylglycerol and unesterified fatty acids increased by 76, 261 and 103%, respectively (P < 0.02). No significant changes were observed for these parameters in control myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1994

Effects of fatty acids on myocardial calcium control during hypothermic perfusion.

Although hypothermia is regarded as providing protection of the myocardium during cardiac operations, rapid cooling of the myocardium in the nonarrested state may have detrimental effects on the function of the myocardial cell membrane as a permeability barrier. We therefore measured total cellular calcium in isolated working rat hearts, receiving either glucose (11.1 mmol/L) or glucose plus palmitate (1.2 mmol/L), before, during, and after a 40-minute hypothermic arrest (10 degrees C, Langendorff perfusion). In both groups a rise in total cellular calcium, measured by 45Ca2+ technique, was observed during hypothermia, followed by a decline on rewarming. However, the rise in total cellular calcium during hypothermia was significantly (p < 0.05) higher in hearts perfused with palmitate (from 1.0 +/- 0.2 to 3.5 +/- 0.2 nmol/mg dry weight) compared with that in glucose-perfused hearts (from 1.1 +/- 0.13 to 2.6 +/- 0.2 nmol/mg dry weight). Palmitate-perfused, but not glucose-perfused, hearts showed arrhythmias and delayed pressure development 1 to 2 minutes after rewarming. In addition cardiac output of these hearts was significantly lower (p < 0.025) than that of glucose-perfused hearts 5 to 10 minutes after rewarming. These data show that hypothermia per se causes a net calcium uptake in isolated rat hearts and that this effect is aggravated by high concentrations of fatty acids. Thus the impaired recovery of myocardial function in palmitate-perfused hearts can possibly be related to a distorted calcium handling.

Adenosine Triphosphate↗

PubMed1993

Measurements of leukotrienes in human plasma by solid phase extraction and high performance liquid chromatography.

Leukotrienes (LTs) are biologically active compounds derived from lipoxygenase catalyzed metabolism of arachidonic acid in mammalian tissues. The present report describes a simple method for extraction and isolation of dihydroxy-LTs; LTB4, LTB5 and the peptido-LTs; LTC4, LTD4 and LTE4 from human plasma, using a pretreatment cartridge which utilizes both hydrophobic and ion-exchange interactions. 5 ml acidified plasma or acetate buffer containing commercially available LT standards were passed through the cartridges under suction, and the absorbed LTs were subsequently eluted in a stepwise manner with acetate buffer containing increasing amounts of methanol. The eluted LTs were analyzed by reversed-phase high performance liquid chromatography (HPLC) on octadecylsilyl (ODS)-silica, using a Waters HPLC unit. Both with plasma and acetate buffer the present methodology resulted in good separation of the LTs with a total run-time of less than 32 min. Recovery of dihydroxy-LTs was approximately 80% (range 73-82%) both when the standards were dissolved in plasma and in acetate buffer. Recovery of the peptido-LTs was, however somewhat lower (47-50%). It should be noted that the present method has the advantage that exposure to chemicals of high toxicity is avoided.

Chemical Phenomena↗

PubMed1993

Substrate preference of isolated perfused rat hearts during hypothermia and rewarming.

Fatty acid and glucose oxidation rates were measured in isolated rat hearts undergoing hypothermia and rewarming. The hearts were perfused in the Langendorff mode with Krebs-Henseleit bicarbonate buffer containing 11.1 mM glucose plus 0.6 mM albumin-bound oleic acid as energy substrates. The hearts were stabilized at 37 degrees C and thereafter cooled progressively to 15 degrees C over a period of 60 min. The hearts were kept at this temperature for 10 min and then rewarmed to 37 degrees C during the next 30 min. Control hearts were perfused at 37 degrees C throughout the whole perfusion period. Trace amounts of [14C]glucose or [14C]oleic acid were included in the perfusate, and the rate of substrate oxidation was determined on the basis of the radioactive CO2 production. In normothermic hearts steady state oxidation rates of glucose and oleate were found to be 0.17 +/- 0.01 and 0.51 +/- 0.07 mumol min-1 g-1 dry wt, respectively (mean +/- SEM). In response to hypothermia (15 degrees C) glucose oxidation was reduced by 76% (from 0.17 +/- 0.01 to 0.04 +/- 0.01 mumol min-1 g-1 dry wt) and oleate oxidation by 47% (from 0.51 +/- 0.07 to 0.27 +/- 0.02 mumol min-1 g-1 dry wt). Upon rewarming glucose and fatty acid oxidation rates returned to essentially the same values (0.12 +/- 0.02 and 0.45 +/- 0.04 mumol min-1 g-1 dry wt) as those observed under steady state normothermic conditions. The molar ratio between glucose and fatty acid oxidation was, however, significantly (P < 0.05) lower in hypothermic than in normothermic hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1992

Myocardial cell vulnerability to exogenous phospholipase attack.

Myocardial cell vulnerability to phospholipase C (PC-PLC) attack was investigated in three different preparations of rat myocardial cells: triacylglycerol (TG)-loaded, hypothermic/rewarmed and energy depleted myocytes. The attack by PC-PLC was evaluated as PC-PLC induced glycerol output due to the combined action of phospholipase C and intracellular lipases. PC-PLC induced glycerol output was significantly higher (p < 0.05) in all three myocyte preparations, compared to their respective controls. Cell morphology (% rod shaped myocytes) of TG-loaded or hypothermic/rewarmed myocytes was not different from their controls, whereas energy depleted myocytes almost exclusively were rounded up, due to hypercontraction of the myofilaments. Hypothermic/rewarmed and energy depleted myocytes showed a significantly higher release of lactate dehydrogenase (LDH), compared to their controls although the difference was much more pronounced in the latter. Finally, the cellular contents of ATP were maintained both in TG-loaded and hypothermic rewarmed myocytes, while energy depleted myocytes contained only about 25% of the normal ATP level. These results demonstrate that attack from exogenously added phospholipases can occur, not only in seriously damaged cardiac myocytes, but in myocytes with a more subtle damage as well.

Adenosine Triphosphate↗

PubMed1992

Triacylglycerol metabolism in hypoxic, glucose-deprived rat cardiomyocytes.

We have recently shown that a triacylglycerol (TG)-fatty acid cycle is operating in rat myocardial cells incubated in a hypoxic, glucose-containing incubation medium (Myrmel et al., 1991a). In the present study we investigated whether this cycle occurred in hypoxic, glucose-deprived myocytes, and whether high TG levels would increase TG-fatty acid cycling and thereby energy consumption. Myocytes with elevated contents of TG were obtained from the hearts of streptozotocin-induced diabetic rats (diabetic myocytes) and from normal rat myocytes prepared in the presence of oleic acid (TG-loaded myocytes). The TG content of diabetic and TG-loaded myocytes prior to hypoxic incubations was more than two times higher (P < 0.05) than that of their respective controls (123.8 +/- 20.6 and 125.3 +/- 12.7 vs 56.8 +/- 6.0 and 58.6 +/- 9.4 nmol/10(6) cells, mean +/- S.E., n = 7). Only diabetic and TG-loaded myocytes expressed marked reductions in TG content during glucose free incubations. There were no differences in TG-fatty acid cycling between the various myocyte groups, calculated as the difference between glycerol output and the concomitant decrease in TG (range: 36.7 +/- 8.1- 48.9 +/- 9.7 nmol TG/10(6) cells.2h). Apparently, the cycle was continuous throughout the whole incubation period despite falling ATP levels, contracture (rounding up) of myocytes, as well as cessation of glycogenolysis after about 40 min incubation. The cellular content of glycerol-3-phosphate, known to control TG-fatty acid cycling, increased continuously and to the same extent throughout the 2 h incubation period. Futile energy consumption associated with TG-fatty acid cycling, amounted to approximately 30% of total cellular energy consumption for the whole incubation period. In conclusion, hypoxic glucose deprived rat myocytes show TG-fatty-acid cycling, even after cessation of glycogenolysis. The extent of cycling, and thus the energy cost associated with it, was not influenced by the initial level of TG in the myocytes. We propose that glycerol-3-phosphate needed to fuel the TG-fatty acid cycle after exhaustion of the glycolytic supply is derived from phospholipid degradation.

Animals↗

PubMed1992

Effects of hypothermia and rewarming on phospholipase C-evoked glycerol output in rat myocardial cells.

The combined action of phosphatidylcholine preferring phospholipase C (PC-PLC) and intracellular lipases has recently been shown to cause glycerol output in energy deprived rat cardiomyocytes. In the present study we examined the effect of hypothermia and rewarming on PC-PLC evoked glycerol output in freshly isolated, calcium-tolerant myocytes. The cells were preincubated for 60 min at hypothermic (5 degrees C) or normothermic (37 degrees C) conditions in Krebs-Henseleit bicarbonate buffer (pH 7.4) supplemented with 1 mM DL-carnitine, 1% B.S.A. and 5 mM glucose. Addition of PC-PLC resulted in a significantly higher (P less than 0.05) output of glycerol in myocytes undergoing rewarming than in myocytes kept constantly at 5 degrees C or 37 degrees C. The values obtained for PC-PLC induced glycerol output (difference in glycerol output between incubations with and without PC-PLC) were 6.77 +/- 2.6 (37 degrees C), 4.54 +/- 1.7 (5 degrees C) and 22.85 +/- 5.9 (5-37 degrees C) nmol/10(6) cells.h. Rewarming in addition caused a significantly higher (P less than 0.05) leakage of lactate dehydrogenase (LDH) from the rewarmed cells as compared to cells at constant temperatures (5 degrees C or 37 degrees C). However, there was no additional effect of PC-PLC on LDH leakage. The elevated PC-PLC induced glycerol output in rewarmed myocytes was not related to a fall in the percentage of rod-shaped cells or a reduced cellular content of ATP, since no differences could be detected between the various myocyte preparations with respect to these parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1992

Glycogen consumption in hypoxic rat cardiomyocytes.

Glycogen consumption was investigated in isolated adult rat myocytes incubated for 2 h (37 degrees C) in substrate-free, hypoxic Krebs-Henseleit bicarbonate buffer. No consumption of glycogen occurred after 1 h of incubation, and the residual glycogen after 2 h was 23% despite an 89% reduction of the initial ATP content (from 27.1 +/- 1.8 to 3.1 +/- 0.5 nmol/mg dry weight, n = 12). The residual glycogen was not due to lactate inhibition of glycolytic enzymes, since myocytes incubated in the presence of 5 mM glucose maintained high energy phosphates throughout the incubation period despite a considerable lactate accumulation (1740 +/- 43 nmol/mg dry weight in glucose-supplemented vs. 138 +/- 14 nmol/mg dry weight in substrate-free incubations, n = 12). We have previously shown that the content of cyclic AMP in myocytes is not altered in response to hypoxia, thereby excluding activation of glycogen phosphorylase a. In the present study, the fall in myocyte ATP content was not followed by a rise in AMP, possibly preventing allosteric activation of glycogen phosphorylase b. However, addition of cyanide to the hypoxic incubations increased cellular AMP (initial level 2.1 +/- 0.4 nmol/mg dry weight vs. 9.8 +/- 0.7 after 30 min, n = 12) without increasing the amount of glycogen consumed, also ruling out the lack of glycogen phosphorylase b activation in the myocytes. Therefore, the glycogen rest was probably confined to the 17% of myocytes hypercontracted at the start of incubations.

Adenine Nucleotides↗

PubMed1992

Lipolytic effect of low-molecular-weight-heparin (Fragmin) and heparin/dihydroergotamine in thromboprophylactic doses during total hip replacement.

Eighteen patients admitted for implantation of a primary hip prosthesis were randomized to one of the following thromboprophylactic regimens: (1) dextran 500 ml 12 h-1 on the day of surgery and 500 ml on days 1, 3, and 5 postoperatively, (2) heparin 5000 IU and dihydroergotamine 0.5 mg 8 h-1, or (3) Fragmin (Kabi-Pharmacia, Sweden) 2500 IU 12 h-1 on the day of surgery and 5000 IU 24 h-1 throughout the observation period. Fragmin is a low molecular-weight heparin which has proven both efficient and safe as a thromboprophylactic drug. The purpose of the study was to elucidate whether Fragmin had a lower lipolytic (fatty acid-mobilizing) effect than standard heparin. The plasma level of lipoprotein lipase (LPL) was increased on the first post-operative day both in the heparin/dihydroergotamine (preoperative 217 +/- 79 microU ml-1 vs. 1289 +/- 318, n = 6, p < 0.05) and the Fragmin-groups (136 +/- 16 vs. 668 +/- 123, n = 6, p < 0.05). This increase in plasma LPL was significantly higher in the heparin/dihydroergotamine-group compared to the Fragmin-group (p < 0.05). In both groups, the enzyme activity gradually decreased during the next 2 days. The circulating level of non-esterified fatty acids increased post-operatively only in the heparin/dihydroergotamine-group. Thus, the lower lipolytic effect of Fragmin compared to standard heparin is detectable using thromboprophylactic doses during surgery in patients on a standard hospital diet. From a theoretical viewpoint, the use of Fragmin is advantageous in patients with myocardial ischaemia and patients risking respiratory distress problems due to a low circulating level of non-esterified fatty acids.

Adult↗

PubMed1991

Regulation of lipolysis in normoxic and hypoxic rat myocytes.

The mechanism involved in ischemia-induced myocardial lipolysis is still a matter of controversy. To elucidate the regulation of lipolysis at the cellular level, we incubated isolated rat myocytes in normoxic or hypoxic medium containing 11.1 mM glucose. Rates of lipolysis (glycerol output) were significantly (P less than 0.05, n = 12) higher in hypoxic than in normoxic myocytes (34.9 +/- 3.9 vs. 17.7 +/- 3.4 nmol/10(6) cells.30 min). However, there was no change in the content of cellular triacylglycerol (TG) in normoxic myocytes whereas it fell slightly (8 +/- 2 nmol/10(6) cells.30 min, P less than 0.05, n = 12) in hypoxic myocytes. On a molar basis glycerol output was significantly higher than the corresponding fall in TG (P less than 0.05, n = 12, both normoxic and hypoxic myocytes). This difference (glycerol output--TG reduction) amounted to 17.1 +/- 3.4 nmol/10(6) cells.30 min in normoxic myocytes and 27.6 +/- 5.1 nmol/10(6) cells.30 min in hypoxic myocytes (P less than 0.05, n = 12, normoxic vs. hypoxic). The hypoxia-induced rise in glycerol output was paralleled by an increased intracellular level of glycerol-3-phosphate. Both these responses were, however, dose-dependently inhibited by addition of pyruvate to the incubation medium, giving rise to a close correlation between cellular glycerol-3-phosphate and glycerol output (r = 0.75, P less than 0.05). This indicates mass action of glycerol-3-phosphate on fatty acid-TG cycling under these conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1991

Membrane phospholipid metabolism of rat myocardial cells during hypothermia and rewarming.

The phospholipid bilayer of the plasma membrane plays an important role in forming a functional barrier against leakage of ions and other cell constituents. We have examined the effect of an exogenously added phospholipase C (PLC) on phospholipid degradation in isolated rat myocardial cells subjected to hypothermia (5 degrees C) and hypothermia followed by rewarming to 37 degrees C. The activity of PLC was measured as glycerol output to the incubation medium since the combined action of PLC and endogenous lipases will result in glycerol production. Addition of PLC resulted in a significantly higher output of glycerol in rewarmed myocytes than in myocytes kept constantly at 5 degrees C and 37 degrees C. Rewarmed cells also showed the highest leakage of lactate dehydrogenase (LDH), but there was no additional effect of PLC on LDH leakage. Normal levels of cellular ATP were maintained in all myocyte groups. These results show that rewarming from hypothermia may cause structural derangements in the phospholipid bilayer of the sarcolemma which in turn could favor attack by endogenous phospholipases.

Animals↗

PubMed1990

Influence of exogenous fatty acids and ketone bodies on rates of lipolysis in isolated ventricular myocytes from normal and diabetic rats.

The effect of oleate (0.3 and 1.2 mM) and the combined effect of beta-hydroxybutyrate (4 and 8 mM) and acetoacetate (1 and 2 mM) on rates of lipolysis (glycerol output) was determined with calcium-tolerant myocytes isolated from the hearts of normal rats and hearts from acutely (2-3 days; 100 mg/kg streptozotocin) diabetic rats. In addition, the effect of these exogenous substrates on rates of lipolysis was investigated in triacylglycerol (TG) loaded myocytes prepared from normal hearts by inclusion of oleate in the isolation solutions. Diabetic and TG-loaded myocytes had higher lipolytic rates than normal myocytes. In control myocytes, oleate (1.2 mM) did not affect basal lipolysis, but it reduced isoproterenol-stimulated lipolysis by 30%. In diabetic and TG-loaded myocytes, the addition of 1.2 mM oleate inhibited basal rates of lipolysis by 41 and 40%, respectively, and isoproterenol-stimulated rates of lipolysis by 43 and 53%, respectively. However, lipolytic rates measured in the presence of 1.2 mM oleate with diabetic and TG-loaded myocytes were still higher than lipolysis in normal myocytes incubated in the absence of oleate. Ketone bodies increased both basal and isoproterenol-stimulated lipolysis in normal myocytes. In diabetic myocytes, ketone bodies produced a modest stimulation of basal lipolysis but had no effect on isoproterenol-stimulated rates of lipolysis. These data indicate that mobilization of endogenous TG may play an important role in supplying energy to the heart in the diabetic state. Moreover, accumulation of endogenous TG in diabetic myocardium can only partly be explained by inhibition of lipolysis by exogenous substrates.

Animals↗

PubMed1989

[The evaluation of the marginal bone height on traditional and digitized panoramic radiographs].

The aim of the present study was to compare original and digitized panoramic radiographs (with a 512 X 512 digitization matrix) for the assessment of alveolar bone loss using intraoral radiographs as a reference. Intraoral radiographs of 2+, +5, and 6- and an orthopantomogram were obtained from each of 55 patients. Alveolar bone level was measured on the intraoral, the original panoramic, and the digitized panoramic radiographs using a Schei ruler as percentage of bone left from the cemento-enamel junction to the apex. Mean values between the separate observations of the two authors were used. A statistically significant reduction in bone level was observed when assessed by the panoramic methods compared to the intraoral radiographs (P less than 0.01 for all tooth groups). Similarly a significant reduction was observed in the digitized panoramic radiographs compared to the originals (P less than 0.05) except for the molar region. The results indicate that the 512 X 512 spatial resolution is not sufficient for the digitization of extraoral radiographs when fine-detail diagnostics are needed. It is suggested that extraoral radiographs are digitized in segments when working with this matrix.

Alveolar Process↗