Body mass index as a risk factor for increased serum lactate during craniotomy

BACKGROUND

An increase in serum lactate can occur in patients undergoing craniotomy. We hypothesized that prolonged craniotomy for brain tumor resection leads to inadequate tissue perfusion as demonstrated by increased level of lactate. This study attempts to determine the mechanism and identify any modifiable risk factors. METHODS. Prospective, observational study of 18 patients undergoing craniotomy for brain tumor resection. The primary outcome was that peak serum lactate would correlate with length of surgery. Secondary outcomes included lactate at 3, 6 and 9 hours, creatine kinase (CK) and myoglobinuria overtime. These values were correlated with expected risk factors for lactatemia including length of surgery, Body Mass Index (BMI), hypotension, hemoglobin and mannitol therapy. RESULTS. Serum lactate consistently increased in the first 3 hours in all patients (2.21±1.22 mmol/L) with a peak increase at 9 hours (3.73±1.62 mmol/L) (P<0.05 for both). The peak serum lactate did not correlate with length of surgery (P=0.799). However, the change in lactate over 3 hours (Δ3hrLactate) did correlate with BMI (P=0.010). Serum CK was increased at 12 hours (P<0.05) and reached a peak level greater than 1000 U/L in 8 of 18 patients. Six of these patients experienced myoglobinuria. No other parameters correlated with increased lactate.

CONCLUSION

We observed a consistent and early increase in serum lactate in patients undergoing craniotomy, which correlated with BMI, but not length of surgery. Associated increases in CK and myoglobinuria support the hypothesis that elevated BMI contributed to muscle ischemia and tissue breakdown during craniotomy. Future studies are required to establish the overall clinical significance and mechanism of hyperlactatemia during neurosurgery.

P4-01-04: Effects of CYP2D6 Phenotype and Drug Adherence on Tamoxifen Metabolite Levels

Background

Although the activity of cytochrome P450 2D6 (CYP2D6), the enzyme responsible for conversion of tamoxifen (TAM) to its most important active metabolite endoxifen, varies significantly with genotype. Routine genotype testing in patients on TAM has recently been discouraged. Conflicting results in publications regarding the prognostic utility of this test remain unexplained. Confounding factors could be lack of predicted correlation between CYP2D6 genotype and TAM active metabolites, or variability of patient compliance

Methods: Consecutive breast cancer patients on TAM were asked to enroll in a study to examine the relationship between CYP 2D6 phenotype, patient-reported treatment adherence, and TAM metabolites levels. Patients were genotyped for CYP2D6 polymorphisms using long-range PCR allele-specific amplification and single-nucleotide primer extension assay. From the genotypes, four phenotype groups were defined: Ultra rapid Metabolizer (UM), Extensive Metabolizer (EM), Intermediate Metabolizer (IM) and Poor Metabolizer (PM). Plasma was collected after at least 6 weeks of TAM (20 mg daily). The parent drug TAM, as well as 4-hydroxy N-desmethyl tamoxifen (endoxifen), 4 hydroxy tamoxifen (4OHtam) and N-desmethyl-tamoxifen (NDtam), were determined by Liquid Chromatography tandem mass-spectrometry (LC-MS/MS). Patients also completed a questionnaire about ethinicity, side effects, concurrent medications and tamoxifen adherence. Correlation between metabolite/TAM ratio and phenotype was tested by Spearman correlation test. Relationship between metabolite levels and adherence was tested by Wilcoxon rank sum test. Chi square test was used to compare proportions.

Results: Of the 100 patients enrolled there were 62 Caucasians, 25 Asians, 4 Africans and 6 Unknown. We found a strong correlation between ratio of endoxifen/TAM and phenotype (p &lt;.0001) (Table 1) Over a 2 week period 68 never missed a TAM dose, 25 missed 1–2 times, 2 missed 3–5 times and 2 &gt; 5times (2 missing data). In EM group we found significantly lower levels of TAM (p &lt;.0001), NDtam (p=.008), 4OHtam (p=.003) in less adherent patients. A trend to decreased levels was also shown for endoxifen (p=.081). No associations were found between adherence or phenotype activity and side effects.

C5 complement inhibition attenuates shock and acute lung injury in an experimental model of ruptured abdominal aortic aneurysm

BACKGROUND

Ruptured abdominal aortic aneurysm (RAAA) is associated with a systemic inflammatory response syndrome and multiple organ dysfunction. The potential role of a novel C5 complement inhibitor in attenuation of pathological complement activation and tissue injury was explored in a model of RAAA.

METHODS

Anaesthetized rats were randomized to sham (control) or shock and clamp (SC) groups. Animals in the SC group underwent 1 h of haemorrhagic shock (mean arterial pressure 50 mmHg or less), 45 min of supramesenteric aortic clamping and 2 h of reperfusion. They were randomized to receive an intravenous bolus of a functionally blocking anti-C5 monoclonal antibody (C5 inhibitor), at a dose of 20 mg/kg, or saline. Lung injury was assessed by permeability to 125I-labelled albumin, tissue myeloperoxidase (MPO) activity, and semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) for mRNAs encoding tumour necrosis factor (TNF) alpha and interleukin (IL) 6.

RESULTS

The lung permeability index was significantly increased in the SC compared with the sham group (P = 0.032); this was prevented by the C5 inhibitor (P = 0.015). Lung MPO activity was significantly increased in the SC compared with the sham group (P < 0.001), and this increase was attenuated by treatment with the C5 inhibitor (P < 0.001). Semiquantitative RT-PCR in SC group demonstrated downregulation of TNF-alpha mRNA (P = 0.050) and upregulation of IL-6 mRNA (P < 0.001), which were both prevented by the C5 inhibitor (P = 0.014 and P < 0.001 respectively).

CONCLUSION

These results indicated that C5 complement inhibition can reduce shock and acute lung injury in an experimental model of RAAA.

Adverse ventilatory strategy causes pulmonary-to-systemic translocation of endotoxin

Accumulating evidence strongly suggests that ventilatory strategy has an important impact on development of lung injury and patient outcome. Adverse ventilatory strategies have been shown to cause release of pulmonary-derived cytokines and may permit bacterial translocation from the lung to the systemic circulation. Because endotoxin is a potent and clinically important stimulant of cytokine-mediated systemic inflammatory responses that can lead to multiorgan failure, we investigated the effects of ventilatory strategy on lung-to-systemic translocation of endotoxin. We studied the effects of protective (tidal volume [VT] 5 ml. kg(-)(1), positive end-expiratory pressure [PEEP] 10 to 12.5 cm H(2)O) versus nonprotective (VT 12 ml. kg(-)(1), PEEP zero) ventilatory strategy on translocation of endotracheally instilled endotoxin. Anesthetized New Zealand White rabbits were subjected to saline lung lavage, and 32 were randomized to one of four groups: PS (protective ventilation + instilled saline); PE (protective ventilation + instilled endotoxin); NS (nonprotective ventilation + instilled saline); NE (nonprotective ventilation + instilled endotoxin), and ventilated for 3 h. Plasma endotoxin levels increased significantly in the NE group, and remained low and unchanged in the other groups. Peak levels of plasma tumor necrosis factor-alpha (TNF-alpha) were higher in NE versus other groups. Pa(O(2)) and mean arterial pressure (Pa) were lowest, and requirement for pressor and bicarbonate support greatest, in the NE group. Finally, plasma endotoxin levels were significantly greater in eventual nonsurvivors than survivors. These data provide convincing evidence for pulmonary translocation of lung-derived endotoxin. This translocation depends on ventilatory strategy, and suggests a pathophysiologic link between ventilatory strategy and outcome.

A CD18 monoclonal antibody reduces multiple organ injury in a model of ruptured abdominal aortic aneurysm

The role of CD18 antibody (anti-CD18) in remote and local injury in a model of ruptured abdominal aortic aneurysm repair was investigated. Rats were divided into sham, shock, clamp, and shock + clamp groups. Shock + clamp animals received anti-CD18 or a control monoclonal antibody. One hour of hemorrhagic shock was followed by 45 min of supramesenteric aortic clamping. Intestinal and pulmonary permeability to (125)I-labeled albumin was determined. Myeloperoxidase (MPO) activity, F(2)-isoprostane levels, and transaminases were also measured. Only shock + clamp resulted in statistically significant increases in pulmonary and intestinal permeability, which were associated with significant increases in MPO activity and F(2)-isoprostane levels. Treatment with anti-CD18 significantly decreased intestinal and pulmonary permeability in shock + clamp animals. These reductions were associated with significantly reduced intestinal and hepatic MPO activity and pulmonary F(2)-isoprostane levels and reduced alanine and aspartate aminotransferase levels; however, anti-CD18 had no effect on intestinal or hepatic F(2)-isoprostane levels or on pulmonary MPO activity. These results suggest CD18-dependent and -independent mechanisms of local and remote organ injury in this model of ruptured abdominal aortic aneurysm.

Rupture of an abdominal aortic aneurysm causes priming of phagocytic oxidative burst

PURPOSE

The purpose of this investigation was to determine whether rupture and repair of an abdominal aortic aneurysm induced activation of phagocyte oxidant burst, reflecting a systemic inflammatory state, when compared with elective abdominal aortic aneurysm (AAA) repair.

METHODS

Blood samples were harvested from 22 patients with elective AAA and 15 patients with ruptured AAA. Phagocyte oxidant activity was measured in response to a panel of activators with luminol and lucigenin as chemiluminescent substrates. Activity of the complement pathways was measured with plasma levels of C3a des arg.

RESULTS

Elective AAA repair resulted in significant elevation in phagocyte count and oxidative activity after surgery in response to maximal dose phorbol myristate acetate (PMA) when compared with the baseline sample. In patients with ruptured AAA the oxidative activity of phagocytes was significantly increased in response to both unopsonized zymosan (899.8 +/- 192 ruptured vs 300 +/- 40 elective, p < 0.01) and maximal dose PMA (8769 +/- 2011 vs 3508 +/- 382, p < 0.01) compared with elective cases at the initial sampling. Phagocyte priming has occurred by way of two distinct pathways: receptor-mediated (unopsonized zymosan, CR3 receptor) and receptor-independent (PMA, protein kinase c).

CONCLUSIONS

Rupture of an AAA resulted in priming of the phagocyte oxidant capacity before operative repair compared with elective AAA. Phagocyte activation is a critical component of the systemic inflammatory response that may contribute to the high incidence of systemic organ dysfunction and death in this patient group.

Mechanisms of postischemic injury in skeletal muscle: intervention strategies

Reperfusion of ischemic skeletal muscle leads to adverse local and systemic effects. These detrimental effects may be attenuated by interfering with or modulating the pathophysiological processes that are set in motion during ischemia and/or reperfusion. The purpose of this paper is to review the different intervention strategies that have been employed in an attempt to elucidate the mechanisms involved in the pathogenesis of skeletal muscle ischemia-reperfusion injury. The results of these studies indicate that the postischemic injury processes that lead to cell dysfunction and death are multifactorial in nature and include oxidant generation, elaboration of proinflammatory mediators, infiltration of leukocytes, Ca2+ overload, phospholipid peroxidation and depletion, impaired nitric oxide metabolism, and reduced ATP production. Although the etiopathogenesis of skeletal muscle ischemia-reperfusion is complex, careful delineation of the mechanisms that contribute to postischemic microvascular dysfunction and muscle necrosis has progressed to the point where rational intervention strategies may be proposed and implemented as potential treatments for skeletal muscle dysfunction associated with ischemia-reperfusion.

Acute pulmonary injury in a model of ruptured abdominal aortic aneurysm

PURPOSE

The purpose of this study was to determine whether the combined insults of hemorrhagic shock and aortic clamping simulating ruptured abdominal aortic aneurysm repair had a synergistic effect on the production of pulmonary injury, indicating remote organ injury.

METHODS

Animals were randomized to one of three groups, infrarenal clamp plus 1 hour of shock, infrarenal clamp plus 2 hours of shock, and supramesenteric clamp plus 1 hour of shock. Each of these groups had four subgroups; sham, shock (mean arterial pressure of 50 mm Hg), clamp, or combined [shock plus clamp]). All animals had a laparotomy with aortic clamping in only the clamp and combined groups. Five hours after clamp removal lung permeability index and neutrophil sequestration were quantified.

RESULTS

Lung permeability index (6.60 +/- 0.63, p < 0.05 vs all other groups) and neutrophil sequestration (3.72 +/- 0.45 vs sham and clamp, p < 0.05) were significantly increased when shock and supramesenteric clamp were combined. After 1 or 2 hours of shock and infrarenal clamping, no increase in lung permeability index was noted, although neutrophil sequestration was increased in the 2-hour shock group.

CONCLUSIONS

These results demonstrate the additive effect of shock and supramesenteric clamping, which initiated a cascade of injurious events that resulted in a rapid pulmonary injury. The high mortality rate related to remote organ failure in ruptured abdominal aortic aneurysm may be related to the synergy of these two injurious processes.

Phospholipid peroxidation deacylation and remodeling in postischemic skeletal muscle

Reperfusion of ischemic skeletal muscle is associated with white blood cell (WBC) sequestration and hydroperoxy-conjugated diene (HCF) formation, a marker of free radical-mediated phospholipid peroxidation. The purpose of this study was to define the kinetics of phospholipid fatty acyl peroxidation, deacylation, and remodeling in postischemic skeletal muscle during prolonged reperfusion in vivo, and to determine whether reperfusion with WBC and plasma-depleted blood would attenuate postischemic phospholipid peroxidation and myocyte necrosis. The isolated, paired, canine gracilis muscle model was used. After 5 h of ischemia, muscles underwent unaltered reperfusion or initial reperfusion with WBC-deficient blood cells resuspended in hydroxyethyl starch, followed by return to normal circulation (modified reperfusion). The concentration of native fatty acids and HCDs of linoleic acid extracted from muscle phospholipids was quantified by gas chromatography and positively identified by mass spectrometry. Ischemia and reperfusion resulted in phospholipid deacylation and a selective increase in phospholipid stearic acid content, but had no effect on total phospholipid phosphorus. Modified reperfusion decreased 1) early HCD formation (54%) and 2) postischemic skeletal muscle necrosis (49%). These data suggest that reperfusion results in phospholipid deacylation and remodeling, and that the initial oxidant stress during reperfusion may be a significant determinant of ultimate muscle necrosis.

Decreased leukocyte adhesion with anti-CD18 monoclonal antibodies is mediated by receptor internalization

BACKGROUND

Adhesion of polymorphonuclear leukocytes (PMNs) to endothelial cells is mediated partially by CD11/CD18 integrins. The purpose of this study was to define (1) the response of PMNs to anti-CD18 monoclonal antibody binding, and (2) the mechanism responsible for anti-CD18 monoclonal antibody-mediated decreases in PMN adhesion to endothelial cells.

METHODS

Canine PMN O2- production, myeloperoxidase, and lysozyme release in response to the anti-CD18 monoclonal antibody IB4 were measured by standard assays. To examine endocytosis of CD18 receptors, PMNs incubated with IB4 and a fluorescein isothiocyanate secondary antibody were analyzed by flow cytometry.

RESULTS

Treatment of PMNs with IB4 did not stimulate O2- production or degranulation but decreased adhesion of 51Cr-labeled PMNs to ex vivo canine aorta. Incubation of PMNs at 25 degrees C resulted in a decrease in fluorescence intensity that was not affected by NaN3 or vanadate but was blocked by NaF, 4 degrees C, and bafilomycin, which prevents endosomal acidification. Treatment with an antifluorescein antibody decreased the fluorescence intensity in NaF and 4 degrees C, but not in bafilomycin-treated neutrophils.

CONCLUSIONS

IB4 decreases PMN-endothelial cell adhesion but does not stimulate neutrophil oxidative metabolism or degranulation. These data suggest that reduced adhesion may be the result of internalization of the CD18/IB4 complex. Anti-CD18 monoclonal antibodies may be useful in preventing PMN adhesion without the potentially deleterious effects of cell activation.

A clinically applicable method for long-term salvage of postischemic skeletal muscle

The clinical significance and applicability of interventions aimed at reducing reperfusion injury in postischemic skeletal muscle remain unproven, since long-term muscle salvage has not been demonstrated by most treatment protocols that attenuate early reperfusion injury. We have shown that reperfusion of ischemic skeletal muscle results in an early and prolonged sequestration of white blood cells and activation of the alternative complement cascade. The purpose of this study was to determine if 40 minutes of reperfusion with blood depleted of white blood cells and complement proteins, followed by 2 days of normal perfusion, would reduce muscle necrosis after 5 hours of ischemia. The isolated paired canine gracilis muscle model was used. The treatment muscle was initially reperfused with arterial blood that had been spun, washed, passed through a leukocyte removal filter, and resuspended in hydroxyethyl starch (greater than 99.9% removal of white blood cells and the complement proteins factor B and C4). The contralateral control muscle was subjected to unaltered reperfusion. Blood flow (ml/min/100 gm) was measured by timed collection of gracilis venous blood. Myeloperoxidase activity (absorbance at 655 nm/min/mg tissue protein) in muscle biopsies was used to monitor white blood cell sequestration. After 48 hours of reperfusion in vivo, necrosis was quantified by nitroblue tetrazolium staining. Initial reperfusion with white blood cell and complement depleted blood significantly reduced muscle necrosis (53% +/- 3% vs 29% +/- 8%, p less than 0.0025, paired t test). Early blood flow was improved, (p = 0.0025, repeated measure-ANOVA), but subsequent white blood cell sequestration was not altered (p = 0.33, repeated measure-ANOVA). This suggests that a significant amount of white blood cell mediated injury occurs during the first 40 minutes of reperfusion. Preventing early complement activation and white blood cell mediated reperfusion injury is an intervention that is feasible during surgery and may result in clinically significant salvage of postischemic skeletal muscle.

The role of extracellular calcium in ischemia/reperfusion injury in skeletal muscle

Ischemia-reperfusion injury to skeletal muscle, following an acute arterial occlusion is a significant cause of morbidity and mortality. The purpose of this study is to examine the role of extracellular calcium in the production of cellular necrosis following a prolonged period of normothermic ischemia. Bilateral canine gracilis muscles were made ischemic for 4.5 to 5 hr. The control muscle had normal blood reperfusion (ionized Ca2+ 1.2 mM). The treated muscle was perfused for 30 min with an oxygenated solution (ionized Ca2+ 0.11 mM) containing free radical scavengers followed by normal blood perfusion. Necrosis was determined by nitroblue tetrazolium staining after 48 hr of reperfusion. Total muscle Ca2+ was measured by atomic absorption spectrometry. Pre- and postischemic muscle Ca2+ levels were similar (2.8 +/- 0.4 vs 3.2 +/- 0.8 nmole/mg protein, n = 13, P greater than 0.1). After 30 min of reperfusion the treated muscle Ca2+ was 2.4 +/- 0.4 compared to control levels of 8.6 +/- 0.8 nmole/mg protein (P less than 0.001). Total tissue calcium returned to normal at 60 min in viable muscle, but continued to accumulate in necrotic tissue. However, the delay in initial muscle Ca2+ influx was not associated with increased overall salvage of muscle 78 +/- 9% vs 77 +/- 8% necrosis, (P greater than 0.1). In conclusion we could not demonstrate a protective effect of reduced extracellular Ca2+ during early reperfusion, and it negated our previously demonstrated beneficial effects of free radical scavengers. It was shown however that the early ability to extrude intracellular calcium was associated with significant salvage of muscle tissue.

The rate and distribution of muscle blood flow after prolonged ischemia

The magnitude and distribution of muscle blood flow in the lower extremity after relief of an acute arterial occlusion may influence the extent of the resulting necrosis. The object of this study was to document the distribution of blood flow in the resting state and after prolonged periods of complete ischemia, and to assess the relationship between the degree of reactive hyperemia and subsequent necrosis. The isolated bilateral canine gracilis muscle preparation that we have previously characterized was used for microsphere studies. Total blood flow was measured by means of timed venous collections, and the distribution of flow was determined by means of a multiple microsphere injection technique. Measurements of microsphere distribution and blood flow were made before ischemia and during the initial 48 minutes of reperfusion after both 4 and 5 hours of normothermic ischemia, which resulted in 46.7% +/- 6% and 71.2% +/- 7% necrosis, respectively. The muscle was harvested and sectioned transversely into six slices approximately 1.5 cm thick, and the extent of necrosis was quantified by means of nitroblue tetrazolium staining 48 hours after reperfusion. Blood flow distribution during the early reperfusion phase was determined in each muscle slice and in both the alive and dead portions of each slice by use of the microsphere injection technique. Preischemic blood flow was distributed homogeneously throughout the muscle and was 4.5 +/- 0.8 ml/100 gm/min (mean +/- SEM, n = 8). On reperfusion total flow was 6 to 10 times higher than it was before ischemia and was distributed predominantly to the middle slices (p less than 0.05, n = 12).(ABSTRACT TRUNCATED AT 250 WORDS)

Maturational difference in functional/metabolic sequelae of free radical formation on reperfusion

To detect maturational differences with ischemia/reperfusion injury on cardiac metabolism and function, isolated nonworking rabbit hearts were subjected to 30 min of 37 degrees C ischemic arrest and reperfusion. Pre- and postischemic high energy phosphate contents (ATP, ADP, AMP), conjugated diene (products of free radical mediated lipid peroxidation) production, and peak isovolumic developed pressure (PDP) were measured in newborn (3-5 days, n = 8), 2- to 3-week-old (n = 8), and adult (2-4 months, n = 8) rabbits. ATP content decreased significantly during ischemia in all three age groups but recovered significantly toward preischemic levels in the newborn and 2-week-old groups but not in adult animals. AMP was much better preserved in the two younger groups with significantly higher levels at end-ischemia. Conjugated dienes were present in newborn and adult heart in small amounts at preischemia and rose slightly by end-ischemia. Newborn hearts accumulated large amounts of dienes by 10 min of reperfusion, which were significantly greater than those adult hearts. PDP returned to 85 and 91% of control in newborn and 2-week-old hearts, respectively, and to only 66% of control in adult hearts (P less than 0.05). These data suggest that the postischemic immature heart recovers energy stores and ventricular function faster than the adult heart which can be attributed to preservation of the total adenine nucleotide pool during ischemia. This improved recovery occurs despite a greater amount of free radical-mediated lipid peroxidation with reperfusion in newborn hearts.

Free radical mediated damage in skeletal muscle

Skeletal muscle subjected to prolonged ischemia will develop significant injury, however it can withstand periods of ischemia that would be irreversible in other tissues such as brain and heart. Reperfusion injury has been measured and suggested to occur secondary to oxygen free radicals. The increases in vascular permeability and resistance following ischemia/reperfusion can be blunted using free radical scavengers. Also skeletal muscle necrosis can be reduced if these scavengers are provided in high concentration during reperfusion. Recently increases in hydroxy-conjugated dienes, a marker of lipid peroxidation, have been found in reperfused skeletal muscle, providing chemical evidence for free radical injury during reperfusion. These studies have provided some insight into ischemia/reperfusion injury in skeletal muscle, but more investigations are required to detail the mechanisms involved in this injury.

Participation of the complement system in ischemia/reperfusion injury

Reperfusion of ischemic skeletal muscle is associated with an early infiltration of WBC, a process mediated by locally generated chemotactic factors. We present evidence that selective activation of the alternative complement cascade occurs in response to skeletal muscle ischemia/reperfusion injury. Complement activation may result in the generation of peptides which are chemotactic for neutrophils, and the formation of molecular complexes which injure cell membranes.

Quantitation of postischemic skeletal muscle necrosis: histochemical and radioisotope techniques

Skeletal muscle necrosis will result from prolonged periods of ischemia. The purpose of this study was to develop a method to estimate the extent of necrosis using nitroblue tetrazolium staining and technetium scanning. The bilateral canine gracilis muscle preparation with total vascular isolation was exposed to 4 hr of complete normothermic ischemia followed by reperfusion. After 45 hr of reperfusion 99mTc pyrophosphate (PYP) was injected and 3 hr later the muscles were harvested, cut into six slices, and stained with nitroblue tetrazolium. Biopsies were taken from tetrazolium-positive and -negative areas for electron microscopy to confirm the ability of the stain to distinguish viable from necrotic muscle. Computerized planimetry of the staining pattern was used to estimate the extent of necrosis as a percentage of the total muscle. Electron microscopy confirmed the validity of nitroblue tetrazolium to discriminate between viable and necrotic skeletal muscle in this experimental model. After 4 hr of ischemia the percentage necrosis was 30.2 +/- 6.1% (mean +/- SEM, n = 12), there was no difference in the extent of necrosis in left vs right paired muscles, using tetrazolium staining or technetium PYP uptake. There was a statistically significant correlation between the percentage necrosis and the density of 99mTc PYP uptake per muscle (r = 0.83, P less than 0.001) and per slice (r = 0.94, P less than 0.001). This study demonstrates the ability of tetrazolium staining to accurately differentiate between viable and necrotic skeletal muscle and provides a reproducible method for estimating the extent of necrosis in the gracilis muscle model.

An evaluation of the Technicon RA-1000 random-access analyzer

We evaluated the Technicon RA-1000 analyzer, with emphasis on its potential for user-defined method development. Optical linearity and sample pipetting linearity were good. The reagent pipetting system delivered slightly less than the nominal amount, owing to the volumetric effect of added mixing bubbles. Carryover of aqueous solutions was negligible. The instrument had good adaptability for user-defined methods and performed well in method comparisons. The observed dynamic range for enzymes (0-3000 U/L) was excellent. The worklisting software performed its intended functions well, but has limitations. We believe that the RA-1000 represents a significant contribution to the practice of clinical chemistry. A sophisticated benchtop machine, it includes several innovations, along with a few problems that are peculiar to its technology.

An evaluation of the Technicon RA-1000 random-access analyzer

We evaluated the Technicon RA-1000 analyzer, with emphasis on its potential for user-defined method development. Optical linearity and sample pipetting linearity were good. The reagent pipetting system delivered slightly less than the nominal amount, owing to the volumetric effect of added mixing bubbles. Carryover of aqueous solutions was negligible. The instrument had good adaptability for user-defined methods and performed well in method comparisons. The observed dynamic range for enzymes (0-3000 U/L) was excellent. The worklisting software performed its intended functions well, but has limitations. We believe that the RA-1000 represents a significant contribution to the practice of clinical chemistry. A sophisticated benchtop machine, it includes several innovations, along with a few problems that are peculiar to its technology.

The in vivo effects of 3-deoxy-3-fluoro-D-glucose metabolism on respiration in Locusta migratoria

The basis of the toxicity of 3-deoxy-fluoro-D-glucose (3FG) in adult Locusta migratoria is examined in vivo by a radiorespirometric analysis of 14CO2 from the locust after injections of 3FG prior to injections of D-[1-14C]glucose, D-[6-14C]glucose, or [1-14C]acetate. The results indicate that 3FG metabolism irreversibly inhibits glycolysis and not the hexose monophosphate pathway or the tricarboxylic acid cycle. It is also established that during metabolism of 3FG fluoride ion is released. Evidence for the metabolism of 3FG in the whole insect as far as triosephosphate isomerase is based on 3H2O release after injections of D-[3-3H]3FG. Further support for the metabolism of 3FG to fluorinated sugar phosphates is provided by chromatographic and 19F MNR analysis of 3FG poisoned locust tissue extracts. Based on these results a biochemical mode of toxicity of 3FG in locusts is discussed.

The metabolism of 3-deoxy-3-fluoro-D-glucose by Locusta migratoria and Schistocerca gregaria

3-Deoxy-3-fluoro-D-glucose (3FG) administered by injection is toxic to adult Locusta migratoria or Schistocerca gregaria (LD50, 4.8 mg/g). temperature-programmed and isothermal gas chromatographic analysis of poisoned locust haemolymph reveals the presence of a fluorinated metabolite identified as 3-deoxy-3-fluoro-D-glucitol (3FGL). The enzymes responsible for the accumulation of this metabolite are located in the fat body of the insect and partially purified as aldose reductase (alditol: NADP+ 1-oxidoreductase, EC 1.1.1.21) and sorbitol dehydrogenase (L-iditol: NAD+ 5-oxidoreductase EC 1.1.1.14) 3FGL is shown to be both a competitive inhibitor of the NAD-linked sorbitol dehydrogenase with Ki 8¿x 10(-2) M as well as a substrate with Km 0.5 M. A kinetic rate equation is derived and verified to account for the kinetic duality of 3FGL. These results partially explain the toxic effects of 3FG and are consistent with the presence of a hitherto undetected sorbitol metabolism in locusts.