L-arginine treatment alters the kinetics of nitric oxide and superoxide release and reduces ischemia/reperfusion injury in skeletal muscle

BACKGROUND

Constitutive nitric oxide synthase (cNOS) may produce species involved in ischemia/reperfusion (I/R) injury: NO in the presence of sufficient L-arginine and superoxide at the diminished local L-arginine concentration accompanying I/R.

METHODS AND RESULTS

During hindlimb I/R (2.5 hours/2 hours), in vivo NO was continuously monitored (porphyrinic sensor), and L-arginine (chromatography), superoxide (chemiluminescence), and I/R injury were measured intermittently. Normal rabbits were compared with those infused with L-arginine 4 mg x kg(-1) x min(-1) for 1 hour. In both groups, approximately 6 minutes into ischemia, a rapid increase of NO from its basal level of 50+/-17 to 115+/-7 nmol/L, P<.005 (microvessels), was observed. In animals not treated with L-arginine, NO dropped below basal to undetectable levels (<1 nmol/L) during reperfusion. In animals treated with L-arginine, the decrease of NO was slower, such that substantial amounts accumulated during reperfusion (25 nmol/L). Decreased NO during I/R was accompanied by increased superoxide, which during reperfusion reached 50 nmol/L without or 23 nmol/L with L-arginine treatment. Calcium-dependent cNOS was a major source of superoxide release (inhibited 70% by L-NMMA and 25% by L-NAME) during I/R.

CONCLUSIONS

L-Arginine treatment decreased superoxide generation by cNOS while increasing NO accumulation, leading to protection from constriction (microvessel area, 17.77+/-0.95 versus 11.66+/-2.21 microm2 untreated, P<.0005) and reduction of edema after reperfusion (interfiber area, 16.56+/-2.13% versus 27.68+/-7.70% untreated, P<.005).

Epinephrine does not impair utilization of exogenous amino acids in humans

The effect of epinephrine on leucine and phenylalanine kinetics was measured by using the stable isotope amino acid tracers L-[1-(13)C]leucine and L-[phenyl-2H5]-phenylalanine in the postabsorptive state and during the intravenous administration of a standard amino acid solution with respect to the amino acid load. Infusion of epinephrine (plasma concentration: approximately 3600 pmol/L) decreased leucine and phenylalanine and increased ketoisocaproate plasma concentrations and increased the metabolic clearance rate of leucine and phenylalanine. Epinephrine neither influenced leucine or phenylalanine flux nor leucine oxidation or leucine net balance. Hyperaminoacidemia from amino acid infusion reduced endogenous leucine release and stimulated leucine oxidation and nonoxidative disposal of leucine, resulting in a dose-dependent increase in leucine net balance. Epinephrine did not influence any changes in amino acid kinetics during parenteral amino acid administration. Therefore, we conclude that epinephrine had no catabolic effects on amino acid metabolism and no negative effect on the utilization of a parenterally offered amino acid solution in healthy humans.

Improvement of cardiac output and liver blood flow and reduction of pulmonary vascular resistance by intravenous infusion of L-arginine during the early reperfusion period in pig liver transplantation

BACKGROUND

The release of liver arginase after orthotopic liver transplantation (OLT) causes a deficiency of L-arginine and nitrite in the plasma. This deficiency is possibly related to pulmonary hypertension and reduced hepatic blood flow, which are commonly observed in the immediate reperfusion period. The aim of this study was to evaluate the impact of L-arginine supplementation on metabolic and hemodynamic parameters during liver reperfusion after OLT in pigs.

METHODS

Thirteen pig OLTs (control group, n=6; arginine group, n=7) were performed by a standard technique. Cold ischemic time was 20 hr. L-Arginine was infused at a dosage of 500 mg/kg body weight into the donor pigs (30 min before liver explantation) and also into the recipients (over a period of 3 hr from the beginning of the reperfusion period). At the end of the experimental study, the pigs were killed with an overdose of potassium.

RESULTS

In the control group, liver revascularization increased plasma arginase concentrations (+615%) and reduced plasma levels of L-arginine (-87%), nitrite (-82%), and nitrate (-53%). Infusion of L-arginine increased plasma levels of L-arginine from 94+/-21 micromol/L to 1674+/-252 micromol/L (P<0.001), L-ornithine from 46+/-8 micromol/L to 2215+/-465 micromol/L (P<0.001), and L-citrulline from 58+/-8 micromol/L to 116+/-34 micromol/L (P<0.001), but had no effect on plasma levels of nitrite and nitrate. Administration of L-arginine in the donor pigs did not produce any systemic or organ-specific hemodynamic alterations. Infusion of L-arginine into the recipient pigs improved cardiac performance (increase in heart rate [+61%, P=0.017] and cardiac index [+53%, P=0.005], reduction in pulmonary capillary wedge pressure [-54%, P=0.014]). Moreover L-arginine infusion increased oxygen consumption (+65%, P=0.003), reduced pulmonary vascular resistance index (P=0.001), stimulated portal venous blood flow (P=0.014), and elevated body temperature during the reperfusion period (P=0.007).

CONCLUSIONS

From these data, we conclude that the infusion of L-arginine during OLT improves the hemodynamic performance of the heart, lung, and liver.

Does reoperation for abdominal sepsis enhance the inflammatory host response?

OBJECTIVE

To determine the effect of reoperation for severe abdominal sepsis on the course of proinflammatory mediators and hemodynamic factors.

DESIGN

Inception cohort.

SETTING

A university hospital and a secondary care hospital.

PATIENTS AND METHODS

Fifteen patients suffering from severe peritonitis due to intestinal perforation or infected necrotizing pancreatitis were studied following 19 subsequent operations. Plasma samples were obtained immediately before and after reoperation, as well as at 1, 3, 6, 12, and 24 hours after operation to determine endotoxin, tumor necrosis factor alpha, and interleukin-6 levels. Clinical factors and therapeutic support were recorded at the corresponding times.

MAIN OUTCOME MEASURES

Postoperative hemodynamic instability as defined by changes of the mean arterial pressure, pulmonary capillary wedge pressure, and vasopressor support. Courses of proinflammatory mediators were correlated to the hemodynamic findings.

RESULTS

Mean arterial pressure decreased from 94 mm Hg postoperatively to 80 mm Hg at 3 hours (P = .006) and 81 mm Hg at 6 hours postoperatively (P = .005). Pulmonary capillary wedge pressure dropped from 14 mm Hg postoperatively to 12 mm Hg at 1 hour (P = .05). Vasopressor support significantly increased from 1 to 6 hours postoperatively (P = .02). Neither endotoxin nor tumor necrosis factor alpha levels showed significant changes in the postoperative course. Interleukin-6 levels continously increased from 586 pg/mL preoperatively to 910 pg/mL at 1 hour (P = .02) and 931 pg/mL at 3 hours postoperatively (P = .04). Overall interleukin-6 levels (R = -0.38, P = .003) and especially early postoperative interleukin-6 levels inversely correlated with postoperative mean arterial pressure.

CONCLUSIONS

Reoperation for abdominal sepsis frequently causes substantial hypotension, and is, thus, potentially harmful to the patient. Reoperative trauma may induce an early postoperative increase in interleukin-6 levels. Because this increase occurs before the development of hypotension, a relationship between the kinetics of this cytokine and the observed hemodynamic instability may be present.

Effects of 1 alpha,25-dihydroxyvitamin D3 and cytokines on the expression of MHC antigens, complement receptors and other antigens on human blood monocytes and U937 cells: role in cell differentiation, activation and phagocytosis

The effect of calcitriol/1 alpha,25-dihydroxyvitamin D3, alone and in combination with cytokines, on the expression of various antigens (Ag) on human peripheral blood monocytes and U937 cells was studied by flow cytometry. Both constitutive and interferon-gamma (IFN-gamma), interleukin-4 (IL-4), IL-6 and tumour necrosis factor-alpha (TNF-alpha)-induced human leucocyte antigen (HLA)-DR, HLA-DP and HLA-DQ Ag expression on monocytes was significantly down-regulated by calcitriol, IL-10 and transforming growth factor-beta (TGF-beta). The effects of calcitriol were concentration dependent and reached maximal inhibitory levels after 3-5 days. Modulation of HLA-DR by calcitriol and IFN-gamma at the protein level correlated with the amount of mRNA specific for the HLA-DR alpha-chain, as judged by Northern blot analysis. The basal as well as IL-4, IL-6, IFN-gamma, TNF-alpha and TGF-beta-driven levels of HLA-ABC Ag were significantly diminished by calcitriol. On U937 cells calcitriol markedly induced CD11a and CD11b expression and weakly up-regulated CD11c whereas on monocytes, constitutive CD11a, CD11b and CD11c expression was significantly down-regulated by calcitriol. The expression of CD14 Ag was strongly induced on U937 cells but only modestly on monocytes. Both the basal level of CD71 and IL-4, IFN-gamma or TNF-alpha-driven expression was diminished on calcitriol-treated U937 cells. In addition, calcitriol suppressed the expression of CD71 Ag on monocytes. The ability of monocytes to phagocytize opsonized Escherichia coli was diminished by calcitriol. Our results demonstrate that calcitriol, alone or in combination with cytokines, modulates expression of MHC, CD11b, CD11c, CD14 and CD71 Ag on both monocytes and U937 cells, and impairs the phagocytic property of monocytes.

Genetic correlates of in vivo viral resistance to indinavir, a human immunodeficiency virus type 1 protease inhibitor

Indinavir (IDV) (also called CRIXIVAN, MK-639, or L-735,524) is a potent and selective inhibitor of the human immunodeficiency virus type 1 (HIV-1) protease. During early clinical trials, in which patients initiated therapy with suboptimal dosages of IDV, we monitored the emergence of viral resistance to the inhibitor by genotypic and phenotypic characterization of primary HIV-1 isolates. Development of resistance coincided with variable patterns of multiple substitutions among at least 11 protease amino acid residues. No single substitution was present in all resistant isolates, indicating that resistance evolves through multiple genetic pathways. Despite this complexity, all of 29 resistant isolates tested exhibited alteration of residues M-46 (to I or L) and/or V-82 (to A, F, or T), suggesting that screening of these residues may be useful in predicting the emergence of resistance. We also extended our previous finding that IDV-resistant viral variants exhibit various patterns of cross-resistance to a diverse panel of HIV-1 protease inhibitors. Finally, we noted an association between the number of protease amino acid substitutions and the observed level of IDV resistance. No single substitution or pair of substitutions tested gave rise to measurable viral resistance to IDV. The evolution of this resistance was found to be cumulative, indicating the need for ongoing viral replication in this process. These observations strongly suggest that therapy should be initiated with the most efficacious regimen available, both to suppress viral spread and to inhibit the replication that is required for the evolution of resistance.

Effects of bisaramil on coronary-occlusion-reperfusion injury and free-radical-induced reactions

The aim of this study was to determine whether bisaramil-an antiarrhythmic compound under clinical investigation-influences the reperfusion-induced arrhythmias and biochemical parameters characterizing occlusion-reperfusion-induced free-radical reactions. The left descending coronary artery (LAD) was occluded for 60 min in anaesthetized dogs followed by one hour of reperfusion. Blood samples were taken at different times of the occlusion and reperfusion for the determination of plasma concentration of malondialdehyde (MDA), reduced (GSH) and oxidized glutathione (GSSG); furthermore of the activity of catalase and superoxide dismutase (SOD). Free-radical generating capacity of polymorph neutrophil granulocytes (PMN) was also measured. At the end of the experiments heart tissue samples were excised from the injured areas and from the intact part of the left ventricular muscle. In tissues samples the concentrations of MDA and GSH and the activity of SOD were determined. Bisaramil was given as an i.v. bolus injection at a dose of 2 mg kg-1 several minutes prior to the end of LAD-occlusion; then the administration was repeated in the 30th minute of reperfusion. In the control group (10 dogs) ventricular fibrillation (VF) occurred in seven cases which resulted in death in three. In the bisaramil-treated group, however. VF was seen in three cases and no death was recorded. Bisaramil inhibited the elevation of the plasma concentration of MDA and GSSG during the reperfusion and abolished the decrease in the plasma concentration of GSH during the occlusion and reperfusion. The activity of SOD and catalase in plasma was much better preserved in the bisaramil-treated group then in the controls. Bisaramil significantly inhibited the increase of the superoxide-radical generating capacity of PMNs during the reperfusion. The data obtained from myocardial tissue samples supported the cardioprotective effect of bisaramil. The biochemical investigation of ischemic-reperfused myocardium showed that bisaramil promoted preservation of SOD-activity and of tissue glutathione. Results of this study clearly showed that bisaramil has a significant effect on ischemiareperfusion injury. Besides its inhibitory effects on ischaemia-reperfusion induced arrhythmias it has a special benefit in influencing free-radical mediated damage leading to better preservation of membranes and to limitations of irreversible cell injuries.

Screening by genomic linkage studies and mutation analysis of hereditary adenomatous polyposis coli: usefulness for clinical practice

A heterogeneous group of patients suffering from adenomatous polyposis coli (APC) were evaluated by clinical and genetic investigations for the first time in Austria. The patients belonged to eight unrelated APC families. In six families several family members were affected with APC, and linkage analysis with highly informative markers was used to estimate the risk of single individuals in these families to develop APC. All index patients were also tested for the most frequent mutation in the APC gene (mutation cluster region, exon 15). Clinical investigations included ophthalmologic tests for congenital hypertrophy of retinal pigment epithelium and colonoscopy. According to DNA analysis, 5 of 19 at-risk individuals had to be considered to be at high risk of having inherited the disease. Four of them underwent proctocolectomy, one patient at risk is under colonoscopic surveillance. The predictive value of indirect genotype analyses reached 83.3%; direct mutation analyses allowed risk estimation in 50% of cases. Ophthalmologic investigation was informative in 75% of the families. Direct and indirect genotyping using a panel of highly polymorphic, closely linked microsatellite markers is a valuable, rapid, reliable method for establishing a presymptomatic diagnosis of APC, especially in families in which more than one affected individual is available for analysis. With regard to the onset of APC and extracolonic manifestations, the variability of APC demands clinical investigations in addition to the molecular tests for all patients and their first-degree relatives.

Vertical strabismus after cataract surgery

PURPOSE

To compare anesthesia methods with resultant strabismus patterns in patients with vertical diplopia after cataract surgery.

METHODS

The authors analyzed 28 consecutive patients with acquired vertical diplopia after cataract surgery to identify the strabismus pattern. The method of anesthesia administration was available in 21 patients. Three orbital dissections with simulated retrobulbar blocks were performed on cadavers to ascertain the possibility of injuring the vertical rectus muscles at the time of injection.

RESULTS

Fifty percent of the involved muscles were overactive, 39 percent were restricted, and 11 percent were paretic. Eleven patients received retrobulbar, and ten received peribulbar anesthesia. The inferior rectus in 17 patients and the superior rectus muscle in 11 were involved. The odds of damaging the inferior rectus, as opposed to the superior rectus muscle, with peribulbar anesthesia was 4.8 times higher than with retrobulbar blocks. Cadaveric dissections showed the likelihood of direct needle injury to either vertical recti with retrobulbar blocks.

CONCLUSIONS

In this patient population, permanent vertical strabismus after cataract surgery results more often from overacting or restricted muscles than from primary muscle paresis. Both the superior and inferior recti can be injured with retrobulbar anesthesia, but peribulbar injections affect the inferior rectus muscle more frequently.

[Ultra-high dosage streptokinase lysis in dysfunction of a St. Jude aortic prosthesis]

HISTORY AND CLINICAL FINDINGS

A 64-year-old man was hospitalised because of progressively worsening dyspnoea over the preceding few months. Three years previously he had undergone aortic valve replacement (St. Jude Medical bileaflet valve) for severe aortic stenosis and some regurgitation. He was much improved postoperatively and one year after the operation echocardiography demonstrated a well functioning prosthetic valve and a transvalvar pressure gradient (by Doppler echocardiography) of 28 mm Hg. On admission the patient reported to have stopped phenprocoumon 9 months before admission. The patient was in cardiac failure, grade III (NYHA classification). On auscultation there was a 4/6 crescendo-decrescendo systolic murmur and a 2/6 early diastolic decrescendo murmur maximal over the second right ICS.

INVESTIGATIONS

Echocardiography confirmed the suspected diagnosis of dysfunction of the prosthetic valve, one leaflet being immobile, with severe outflow obstruction (peak transvalvar pressure gradient 101 mm Hg) combined with severe regurgitation. At fluoroscopy one leaflet moved normally, the other one being fixed between opening and closing positions.

TREATMENT AND COURSE

As thrombosis was the most likely cause of the prosthetic valve dysfunction, thrombolysis treatment was started. After administration of 9 mill. IU streptokinase both leaflets showed normal movement. The peak transvalvar gradient (by echocardiography) was now 40 mm Hg and there was only slight regurgitation. No complications were noted. After oral anticoagulation for 6 months the prosthetic valve was functioning normally with unchanged movement pattern of both leaflets.

CONCLUSION

Thrombolysis may be successful in thrombotic dysfunction of a prosthetic valve. If there are no contraindications, this form of treatment should be tried before reoperation is undertaken.

[Glutamine: effects on the immune system, protein balance and intestinal functions]

Glutamine is the most abundant free amino acid of the human body. In catabolic stress situations such as after operations, trauma and during sepsis the enhanced transport of glutamine to splanchnic organs and to blood cells results in an intracellular depletion of glutamine in skeletal muscle. Glutamine is an important metabolic substrate for cells cultivated under in vitro conditions and is a precursor for purines, pyrimidines and phospholipids. Increasing evidence suggests that glutamine is a crucial substrate for immunocompetent cells. Glutamine depletion in the cultivation medium decreases the mitogen-inducible proliferation of lymphocytes, possibly by arresting the cells in the G0-G1 phase of the cell cycle. Glutamine depletion in lymphocytes prevents the formation of signals necessary for late activation. In monocytes glutamine deprivation downregulates surface antigens responsible for antigen preservation and phagocytosis. Glutamine is a precursor for the synthesis of glutathionine and stimulates the formation of heat-shock proteins. Moreover, there are suggestions that glutamine plays a crucial role in osmotic regulation of cell volume and causes phosphorylation of proteins, both of which may stimulate intracellular protein synthesis. Experimental studies revealed that glutamine deficiency causes a necrotising enterocolitis and increases the mortality of animals subjected to bacterial stress. First clinical studies have demonstrated a decrease in the incidence of infections and a shortening of the hospital stay in patients after bone marrow transplantation by supplementation with glutamine. In critically ill patients parenteral glutamine reduced nitrogen loss and caused a reduction of the mortality rate. In surgical patients glutamine evoked an improvement of several immunological parameters. Moreover, glutamine exerted a trophic effect on the intestinal mucosa, decreased the intestinal permeability and thus may prevent the translocation of bacteria. In conclusion, glutamine is an important metabolic substrate of rapidly proliferating cells, influences the cellular hydration state and has multiple effects on the immune system, on intestinal function and on protein metabolism. In several disease states glutamine may consequently, become an indispensable nutrient, which should be provided exogenously during artificial nutrition.

Prediction of graft dysfunction by analysis of liver biopsies after cold storage

Failure of the hepatic allograft continues to be a serious life-threatening risk for the recipient. Because no effective method of extracorporeal support is available for these patients, early retransplantation is the only alternative that offers the potential for survival. The aim of this prospective analysis was to search for a predictor of primary non-function of hepatic allografts before reperfusion. From March to June 1993 we investigated 19 liver biopsies which were obtained during the preparation of the donor liver in the back table bath immediately before the implantation of the organ. All organs were preserved by UW solution. Biopsies were stored at -80 degrees C, the working-up process was started by dividing the biopsy into several portions for the determination of fat (petrol-ether extraction), water (weighing before thawing and after drying) and free amino acids (OPA-HPLC method). Graft function was categorized into three groups: (1) good function; (2) fair function; (3) primary non-function (PNF). In addition to known risk factors for delayed graft function such as a long stay of the donor in intensive care and a prolonged anhepatic period of the recipient, we were able to demonstrate that organs with malfunction had a higher fat and water content. Donor livers developing PNF showed a trend towards higher total and subdivided amino acids, which could be explained by the incapacity of the liver to utilize available substrates for gluconeogenesis.

Acute effects of insulin-like growth factor I on interorgan glucose and lactate flux in protein-catabolic dogs

Insulin-like growth factor-I (IGF-I) is a potent protein-anabolic hormone with a glucose-lowering effect and is therefore a possible agent for treating catabolic patients. In this study we investigated the effect of recombinant human (rh) IGF-I on the interorgan flux of glucose under hypo- and normoglycemic conditions in catabolic, anaesthetized, and catheterized dogs. We administered a primed (40 micrograms/kg) continuous (1.5 micrograms.kg-1.min-1) infusion of rhIGF-I (Kabi Biopharma, Stockholm, Sweden) for 180 min together with either a saline (0.9% NaCl) or an amino acid solution (2.2 mg AA.kg-1.min-1 solution of Vamin, Kabi Nutrition, Stockholm, Sweden). RhIGF-I administration lowered plasma glucose levels for approximately 50% of the baseline (P < 0.001) and stimulated glucose uptake from skeletal muscle about twofold (P < 0.01), but did not modify glucose balances across the gut and liver. The same effects were found when infusing rhIGF-I together with AA. A co-infusion of rhIGF-I and glucose to maintain normoglycemic conditions stimulated glucose uptake from skeletal muscle by about fivefold (P < 0.001) and glucose uptake across the gut by about 50%, but reduced the hepatic glucose liberation (-65%; P < 0.01). The rhIGF-I infusion did not alter arterial lactate levels, but stimulated lactate release from skeletal muscle (P < 0.05) and lactate uptake across the liver (P < 0.05). We conclude that rhIGF-I reduces plasma glucose levels mainly by stimulating glucose uptake across skeletal muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

[A new mode of expression for the assessment of capacities of DNA repair by flow cytometry]

Flow cytometry technic was used to study DNA synthesis of Hep G2 cells following mitomycin C and adriblastine treatments during 24 hours. DNA synthesis was expressed by 2 methods: the new expression global DNA synthesis (S+G2)/G1 that considered the cells during scheduled and unscheduled DNA syntheses of S and G2 phases and the cell cycle (Fox program) that evaluated the cells during scheduled DNA synthesis by the terms G1 = 2n, S = 2n+x and G2 = 4n which excluded unscheduled DNA synthesis. The experimental data treated with this new expression led to the determination of threshold concentrations for the two tested compounds where the DNA repair mechanisms were overloaded, leading to cell death. This term was shown to be more accurate to describe the genotoxic action of compounds. Furthermore, these threshold concentrations of DNA damages was found to be linked with significant increase of micronuclei in the micronucleus test.

Influence of glutamine on the phenotype and function of human monocytes

Reduced concentrations of glutamine (GLN) in plasma and skeletal muscle, defective host defense systems, and a diminished expression of the HLA-DR antigen on monocytes are important diagnostic parameters for late post-injury sepsis. In this in vitro study, we investigated whether blood monocyte-derived macrophage antigen expression and function from healthy donors is influenced by GLN. Lowering the GLN concentration in culture medium from 2 mmol/L to 200 mumol/L reduced the expression of HLA-DR by 40% (P < .001) on monocyte-derived macrophages, and decreased tetanus toxoid-induced antigen presentation. In addition, low GLN levels downregulated the expression of intercellular adhesion molecule-1 (ICAM-1/CD54), Fc receptor for IgG (Fc gamma RI/CD64), and complement receptors type 3 (CR3; CD11b/CD18) and type 4 (CR4; CD11c/CD18). A correlation was found between the phagocytosis of IgG-sensitized ox erythrocytes or opsonized Escherichia coli and the decreased expression of Fc gamma RI and CR3. Monocyte expression of CD14, CD71, and Fc gamma RIII/CD16 and capacity to phagocytose latex beads were not affected by altering the level of GLN. Depletion of GLN was associated with a significant reduction in cellular adenosine triphosphate (ATP), which may have influenced cell surface marker expression and phagocytosis. It remains to be seen whether these in vitro findings are of clinical significance in the treatment of sepsis.