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Biomedical subjects

I E Karl

Publications and source records attributed to I E Karl.

At least 37 records · Page 2Linked to original sources
PubMed1999

Inducible nitric oxide synthase (iNOS) gene deficiency increases the mortality of sepsis in mice.

BACKGROUND: Nitric oxide (NO) produced by the inducible isoform of NO synthase (iNOS or NOS2) has been implicated in the hypotension, organ failure, and death that complicate sepsis. To avoid the confounding effects and limitations of iNOS inhibitors, we used iNOS gene "knockout" mice to examine the effect of inducible NO production in a model of polymicrobial abdominal sepsis treated with antibiotics. We hypothesized that iNOS gene deficiency would significantly alter outcome. METHODS: C57BL6 wild-type (control) and congenic iNOS knockout mice were studied concurrently. Under halothane anesthesia, the ceca were ligated with 4-0 silk suture and punctured twice with a 26-gauge needle (cecal ligation and puncture, CLP). Survival was followed for 7 days, after which necropsies were performed in surviving animals. In an accompanying study examining the acute effects of sepsis, organ injury at 18 hours after CLP as determined by histology and the degree of cell death by apoptosis were examined with the use of hematoxylin and eosin (H&E) and TUNEL staining and two-channel fluorescence-activated cell sorter (FACS) analysis. RESULTS: Sham laparotomy produced no lethality in either knockout (n = 3) or wild-type (n = 3) animals. Compared with survival in controls (n = 20), survival after CLP in iNOS knockout mice (n = 21) was significantly decreased (P < .01 at 2 days, P = .080 at 7 days, Mantel-Haenszel log-rank test). CLP-induced apoptotic cell death was significantly less in the thymus of iNOS knockout mice compared with wild-type mice. CONCLUSIONS: We conclude that iNOS gene function provides a survival benefit in septic mice and is associated with increased sepsis-induced thymocyte apoptosis. To our knowledge, this is the first survival study examining the effect of iNOS gene deficiency in a clinically relevant model of sepsis.

Animals↗
PubMed1998

Nitric oxide inhibits stress-induced endothelial cell apoptosis.

OBJECTIVES: To determine a mechanism by which nitric oxide alters induction of stress-induced endothelial cell apoptosis in vitro. Apoptosis is a form of cellular suicide that has been implicated in the pathogenesis of multiple organ dysfunction syndrome. DESIGN: Prospective, controlled trial. SETTING: Research laboratory of a large, academic medical center. SUBJECTS: Cultured primary porcine aortic endothelial cells. INTERVENTIONS: Cells were treated with a range of doses of agents that either spontaneously generate nitric oxide (S-nitroso-N-acetyl-D,L-penicillamine [SNAP] or (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1- ium-1,2-diolate [DETA-NO]) or block nitric oxide production (Nomega-methyl-L-arginine [L-NMA]). The ability of these agents to alter the rate of cell death by apoptosis (induced by the sequence stimuli lipopolysaccharide [LPS] followed by sodium arsenite) was measured. Mechanistic studies included examining the ability of: a) nitric oxide "donors" to alter nuclear factor kappa B (NF-kappaB) DNA binding activity and the level of IkappaBalpha accumulation; and b) a stable cyclic guanosine monophosphate (cGMP) analog (8-bromo-cGMP) to mimic the effect of nitric oxide donors. MEASUREMENTS AND MAIN RESULTS: The sequence LPS/sodium arsenite increased the rate of endothelial cell apoptosis (47.4%, p< .05 vs. control), as measured by fluorescent-activated cell scanning using annexin V/propidium iodide staining. DETA-NO generated nitric oxide (as indicated by an increase in the concentration of the stable end-products of nitric oxide metabolism) and decreased the rate of endothelial cell apoptosis (20.6% at a dose of 2 mM, p=.0001 vs. control). DETA-NO also decreased NF-kappaB DNA binding activity and the apparent accumulation of its endogenous inhibitor, IkappaBalpha. The 8-bromo-cGMP did not mimic the effects of nitric oxide donors (DETA-NO) on apoptosis. CONCLUSIONS: These data suggest that exogenous nitric oxide can block stress-induced endothelial cell apoptosis in vitro. The mechanistic studies are consistent with our hypothesis that inhibitors of NF-kappaB DNA binding activity are associated with protection against apoptosis-inducing stimuli. The results do not support a role for cGMP in mediating the protective effect of DETA-NO in our model.

Animals↗
PubMed1998

Pyrrolidine dithiocarbamate activates the heat shock response and thereby induces apoptosis in primed endothelial cells.

Transcription factor NF-kappaB is an important regulator of the cellular response to diverse stresses. Pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-kappaB activity, was used to determine the role of this transcription factor in our model of stress-induced endothelial cell apoptosis. Porcine aortic endothelial cells were treated with an inducer of the acute phase response (LPS) followed by treatment with an inducer of the heat shock response (arsenite), a sequence that produces cell death by apoptosis. Treatment with PDTC attenuated LPS-induced NF-kappaB activity and endothelial cell death when added prior to LPS. However, PDTC unexpectedly increased cell death when given after LPS priming. This time-dependent effect of PDTC on endothelial cell death was similar to that which we had observed previously for inducers of the heat shock response. Therefore, we hypothesized that PDTC could induce the heat shock response in porcine and human endothelial cells. PDTC increased heat shock protein (HSP)-70 production and heat shock factor (HSF) activity. Thus, treatment of endothelial cells with PDTC, like other inducers of the heat shock response, increased HSP-70 levels and HSF activity and had time-dependent effects on cell death by apoptosis in primed endothelial cells. We conclude that PDTC induced the heat shock response, that induction of HSF activity may be linked with inhibition of NF-kappaB activity, and that interaction between acute phase and heat shock regulatory factors may be pivotal to determining cell fate (apoptosis).

Animals↗
PubMed1998

Reversal of hypocalcemia and decreased afterload in sepsis. Effect on myocardial systolic and diastolic function.

Sepsis is a major cause of death in intensive care units. Clinically, sepsis induces a number of physiologic and metabolic abnormalities, including decreased myocardial contractility and decreased plasma ionized calcium. There is debate about the proper therapy of hypocalcemia in sepsis because calcium administration may worsen cell function by causing intracellular Ca2+ overload. We investigated the effect of Ca2+ administration on myocardial systolic and diastolic function in an extensively utilized rat model of sepsis, i.e., the cecal ligation and puncture model (CLP). Approximately 24 h after CLP or sham surgery, rats were anesthetized and myocardial function assessed in vivo by a left ventricular Millar catheter and simultaneous two-dimensional guided M-mode echocardiography. Septic rats had a 28% decrease in peak left ventricular developed pressure, a 30% decrease in +dP/ dt, and a 23% decrease in -dP/dt (p < 0.05). Plasma ionized Ca2+ was decreased in septic compared with that in sham rats: 4.9 +/- 0.9 and 5.6 +/- 0.01 mg/dl, respectively (p < 0.05). CaCl2 improved both systolic and diastolic function and there was no evidence of adverse effects of Ca2+ even at supraphysiologic levels. Surprisingly, correction of decreased afterload in septic rats, using the pure alpha-agonist phenylephrine, caused normalization of all indices of cardiac contractility, indicating that the presumed decrease in cardiac function was due entirely to an effect of the decreased afterload to "unload" the left ventricle. We conclude that Ca2+ administration is not detrimental to cardiac function in the rat CLP model. Although the rat CLP model is widely utilized and reproduces many of the clinical hallmarks of sepsis, it does not cause intrinsic myocardial depression and, therefore, it may not be an appropriate model to investigate the clinical cardiac dysfunction that occurs in patients with sepsis.

Adrenergic alpha-Agonists↗
PubMed1998

Stress-induced fractal rearrangement of the endothelial cell cytoskeleton causes apoptosis.

BACKGROUND: Apoptosis, a mechanism of cell death prominent in critical illnesses including disseminated inflammation and multiorgan dysfunction syndrome, is characterized by morphologic changes including cell shrinkage, condensation of organelles, blebbing, and chromatin fragmentation. These phenomena suggest substantial changes in cytoskeletal structure. We hypothesized that stress-induced apoptosis in endothelial cells is, in part, a consequence of a critical cytoskeletal rearrangement. METHODS: Porcine aortic endothelial cells in culture, surrogates for the microvasculature in vivo, were exposed sequentially to Escherichia coli endotoxin (25 micrograms/mL; 18 hours) to induce the inflammatory response and then to sodium arsenite (160 mumol/L; 120 minutes) to induce the heat-shock response, a well-characterized model of stress-induced apoptosis. Laser confocal micrographs of fluorescein isothio-cyanate-labeled phalloidin-stained cells were analyzed to calculate the border fractal dimension of the cytoskeleton. Other cells were exposed to cytochalasin D, a fungal metabolite, which interferes with polymerization of actin from its globular to its filamentous form, and similarly were analyzed with respect to fractal dimension, viability (neutral red assay), and manner of death (annexin V fluorescence-activated cell scanning analysis). RESULTS: Induction of the inflammatory or heat-shock responses caused subtle and distinct rearrangement of the actin cytoskeleton. When these stimuli were applied in sequence, a synergistic interaction led to profound cytoskeletal collapse. Reversal of the sequence did not induce the cytoskeletal disruption. Cytochalasin D alone induced a dose-dependent cytoskeletal collapse indistinguishable from that caused by the acute phase-heat shock sequence that caused cell death by apoptosis. The effect of lower doses of Cytochalasin D could be potentiated by subsequent induction of the heat-shock response. CONCLUSIONS: Sequential stresses that mimic pathophysiologic "two-hit" stimuli induce a characteristic fractal rearrangement of the actin cytoskeleton. Because cytochalasin D-induced rearrangement of this cytoskeleton produced apoptosis indistinguishable from the stress-induced apoptosis, we conclude that the cytoskeletal rearrangement is likely a critical event in the pathway to apoptosis. This disruption of intracellular interconnections mirrors endotoxin-induced disruption in signals among organs and supports the mechanistic hypothesis that multiorgan dysfunction syndrome generally reflects disruption of signals and connections at several levels of biologic organization.

Actins↗
PubMed1997

Endothelial cell apoptosis is accelerated by inorganic iron and heat via an oxygen radical dependent mechanism.

BACKGROUND: Iron participates in diverse pathologic processes by way of the Fenton reaction, which catalyzes the formation of reactive oxygen species (ROS). To test the hypothesis that this reaction accelerates apoptosis, we used human umbilical vein endothelial cells (HUVECs) as surrogates for the microvasculature in vivo. METHODS: HUVECs were loaded with Fe [III](ferric chloride and ferric ammonium citrate) with 8-hydroxyquinoline as carrier and were then challenged with two stimuli of the heat shock response, authentic heat or sodium arsenite. Iron dependence was tested with two chelators, membrane-impermeable deferoxamine and membrane-permeable o-phenanthroline. The role of ROS was assessed with superoxide dismutase, catalase, and the reporter compound dichlorofluorescein diacetate. The mechanism of cell death was assessed with three complementary techniques, Annexin V/propidium iodide labeling, the TUNEL stain, and electron microscopy. RESULTS: Iron-loaded HUVECs executed apoptosis after a heat shock stimulus. Iron-catalyzed formation of ROS appeared to be a critical mechanism, because both chelation of iron and enzymatic detoxification of ROS attenuated this apoptosis. CONCLUSIONS: Inorganic iron, in concert with chemical and physical inducers of the heat shock response, may trigger apoptosis. The accumulation of iron in injured tissue may thereby predispose to accelerated apoptosis and account, in part, for poor wound healing and organ failure.

Cell Survival↗
PubMed1997

Apoptosis in lymphoid and parenchymal cells during sepsis: findings in normal and T- and B-cell-deficient mice.

OBJECTIVES: To determine if apoptosis (programmed cell death) occurs systemically in lymphoid and parenchymal cells during sepsis. To examine the potential role of T and B cells in the apoptotic process using knockout mice deficient in mature T and B lymphocytes. DESIGN: Prospective, randomized, controlled trial. SETTING: Animal laboratory in a university medical setting. INTERVENTIONS: Cecal ligation and puncture (CLP) (n = 34) or sham surgery (n = 13) was performed in female ND4 mice and, 15 to 22 hrs postoperatively, thymus, lung, heart, spleen, ileum, colon, liver, kidney, brain, and muscle were obtained and examined for apoptosis. A second group of mice (Rag-1) which are totally deficient in mature T and B cells also underwent CLP (n = 14) or sham surgery (n = 14) and had examination of tissues for apoptosis. MEASUREMENTS AND MAIN RESULTS: Four methods with varying sensitivities and specificities were used to detect apoptosis, including: a) DNA agarose gel electrophoresis; b) terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL); c) electron microscopy; and d) light microscopy. In CLP mice, multiple methods demonstrated apoptosis in lymphocytes in thymus, spleen, ileum, colon, lung, and skeletal muscle. In addition to lymphocytes, parenchymal cells in ileum, colon, lung, and to a lesser extent, in skeletal muscle and kidney were apoptotic in CLP mice. There was no evidence of apoptosis by any method of detection in liver, brain, or heart. Results in Rag-1 mice which are deficient in T and B cells demonstrated extensive apoptosis in thymus, spleen, and ileum with less degrees of apoptosis in colon and lung. Both lymphoid cells and parenchymal cells were apoptotic. Rag-1 mice which underwent CLP did not die prematurely and there were no apparent observable differences in the physical response (tachypnea, piloerection, lethargy, etc), or intra-abdominal bowel inflammation/adhesions compared with CLP mice with normal T and B cells. CONCLUSIONS: Apoptosis is an important mechanism of cell death in lymphocytes and parenchymal cells in sepsis and occurs systemically in many organs. Apoptosis may be an important cause of immunologic suppression in sepsis by inducing widespread lymphocyte depletion. Alternately, apoptosis may be beneficial to host survival by down-regulating the inflammatory response which accompanies sepsis. The degree to which parenchymal cell apoptosis is contributing to multiple organ failure cannot be determined from the present study. Findings in Rag-1 mice demonstrate that mature T and B cells and their secretory products are not necessary for apoptosis to occur during sepsis and that apoptotic cell death is not restricted to T or B cells. Apoptosis may be a key regulator of the balance between the pro- and anti-inflammatory process.

Animals↗
PubMed1997

Cecal ligation and puncture (CLP) induces apoptosis in thymus, spleen, lung, and gut by an endotoxin and TNF-independent pathway.

Two challenges (intraperitoneal lipopolysaccharide (LPS) administration and cecal ligation and puncture (CLP)) and two strains of mice (LPS-normoresponder (C3H/HeN) and LPS-hyporesponder (C3H/HeJ)) were used to investigate pathways of cell injury. After intraperitoneal administration of LPS, endotoxin was absorbed into the bloodstream (HeN, 10.4 +/- 9.4 x 10(4) EU/mL; HeJ, 14.7 +/- 6.0 x 10(4) EU/mL), but as expected, only C3H/HeN mice produced serum tumor necrosis factor (TNF) (HeN, 2.5 +/- 2.0 x 10(3)pg/mL; HeJ, 87.0 +/- 38.7 pg/mL). Gel electrophoretic analysis of DNA extracted from six organs demonstrated the apoptotic "ladder" only in the thymus and only in the HeN mice. When the mice were challenged with CLP, both HeN and HeJ produced a small amount of serum TNF (HeN, 5.8 +/- 3.5 x 10(2) pg/mL; HeJ, 2.2 +/- 2.5 x 10(2) pg/mL) and both strains had very mild endotoxemia (HeN, 23.4 +/- 3.8 EU/mL; HeJ, 27.9 +/- 10.1 EU/mL). The DNA fragmentation pattern characteristic of apoptosis was observed not only in thymus but also in spleen, lung, and Peyer's patch of gut of both strains. This organ-specific pattern was more pronounced in the thymus of HeN mice; otherwise, the organ-specific patterns were similar for HeN and HeJ mice challenged by CLP but absent in those same organs when those same mice were challenged with LPS. The data suggest the existence not only of an endotoxin-driven activation for thymic apoptosis, but also of an endotoxin-independent, TNF-independent pathway activating widespread apoptosis in the murine CLP model of sepsis.

Animals↗
PubMed1997

Calcium antagonists inhibit oxidative burst and nitrite formation in lipopolysaccharide-stimulated rat peritoneal macrophages.

Activated macrophages are important cell effectors in sepsis/endotoxemia. Superoxide (SO) and nitric oxide (NO) are produced by activated macrophages and are responsible for host defense against microorganisms. Using laser scanning confocal microscopy, we investigated the role of intracellular free calcium ([Ca2+]i) on SO and NO production by rat peritoneal macrophages activated by lipopolysaccharide (LPS). Calcium influx from the extracellular space versus release of calcium from intracellular stores was determined using calcium channel blockers (diltiazem [DIL], verapamil [VER], and nicardipine [NIC]) and dantrolene (DAN), respectively. Cells incubated with LPS had a 30-50 nM increase in [Ca2+]i, (p < .05) compared with non-LPS-treated cells. When stimulated with phorbol myristate acetate, both control and LPS-treated cells sustained a comparable increase in [Ca2+]i, but [Ca2+]i, remained elevated 30 min later in LPS-treated cells. Calcium channel blockers and DAN reduced phorbol myristate acetate-stimulated SO and LPS-stimulated NO production at all concentrations tested (p < .05). Although increased extracellular calcium influx and calcium from intracellular stores are important regulators of SO and NO production in macrophages, extracellular calcium influx seems to have the predominant effect. Calcium antagonists may modulate the inflammatory response via their effects on macrophages.

Animals↗
PubMed1996

Glutamine interferes with glucocorticoid-induced expression of glutamine synthetase in skeletal muscle.

Skeletal muscle atrophy from glucocorticoids is prevented by glutamine infusion. Because the gene-encoding glutamine synthetase (GS) is glucocorticoid inducible, it represented an appropriate model for resting whether glucocorticoids and glutamine exert opposing actions on the expression of specific genes related to atrophy in muscle tissue. Rats were administered hydrocortisone 21-acetate or the dosing vehicle (carboxymethyl cellulose) and were infused with saline (Sal) or glutamine (Gln, 240 mM, 0.75 ml/h) for 7 days. Hormone treatment did not significantly lower glutamine levels in fast-twitch white or red regions of the quadriceps. Despite higher serum glutamine concentrations with amino acid infusion [1.52 +/- 0.03 (Gln) vs. 1.20 +/- 0.04 (Sal) mumol/ml], muscle glutamine concentrations were not markedly increased in these fiber types. In saline-infused animals, glucocorticoid treatment produced 200-300% increases in plantaris, fast-twitch white, and fast-twitch red muscle GS enzyme activity and mRNA. Moreover, in all muscle types studied, glutamine infusion diminished glucocorticoid effects on GS enzyme activity to 131-159% and on GS mRNA to 110-200% of the values in saline-treated controls. These data demonstrate that glutamine infusion results in inhibiting GS expression, but the absence of changes in muscle glutamine concentration suggests the interplay of additional regulators of the GS gene.

Animals↗
PubMed1996

Alanyl-glutamine prevents muscle atrophy and glutamine synthetase induction by glucocorticoids.

The aims of this work were to establish whether glutamine infusion via alanyl-glutamine dipeptide provides effective therapy against muscle atrophy from glucorticoids and whether the glucocorticoid induction of glutamine synthetase (GS) is downregulated by dipeptide supplementation. Rats were given hydrocortisone 21-acetate or the dosing vehicle and were infused with alanine (AA) or alanyl-glutamine (AG) at the same concentrations and rates (1.15 mumol.min-1.100 g body wt-1, 0.75 ml/h) for 7 days. Compared with AA infusion in hormone-treated animals, AG infusion prevented total body and fast-twitch muscle mass losses by over 70%. Glucocorticoid treatment did not reduce muscle glutamine levels. Higher serum glutamine was found in the AG-infused (1.72 +/- 0.28 mumol/ml) compared with the AA-infused group (1.32 +/- 0.06 mumol/ml), but muscle glutamine concentrations were not elevated by AG infusion. Following glucocorticoid injections, GS enzyme activity was increased by two- to threefold in plantaris, fast-twitch white (superficial quadriceps), and fast-twitch red (deep quadriceps) muscle/fiber types of the AA group. Similarly, GS mRNA was elevated by 3.3- to 4.1-fold in these same muscles of hormone-treated, AA-infused rats. AG infusion diminished glucocorticoid effects on GS enzyme activity to 52-65% and on GS mRNA to 31-37% of the values with AA infusion. These results provide firsthand evidence of atrophy prevention from a catabolic state using glutamine in dipeptide form. Despite higher serum and muscle alanine levels with AA infusion than with AG infusion, alanine alone is not a sufficient stimulus to counteract muscle atrophy. The AG-induced muscle sparing is accompanied by diminished expression of a glucocorticoid-inducible gene in skeletal muscle. However, glutamine regulation of GS appears complex and may involve more regulators than muscle glutamine concentration alone.

Alanine↗
PubMed1996

Calcium: a regulator of the inflammatory response in endotoxemia and sepsis.

Calcium functions as a critical intracellular second messenger and regulates many cellular processes such as muscle contractility, glycogen and protein turnover, hormone secretion, and vascular smooth muscle tone which are markedly abnormal during sepsis/endotoxemia. There also is increasing recognition of the role of calcium in the production of a variety of cytokines such as tumor necrosis factor alpha and interleukin-1 beta, which are important mediators of sepsis. Our hypothesis is that disturbances in cellular calcium regulation are responsible for or contribute to many of the metabolic manifestations of sepsis/endotoxemia and may be the driving force behind the development of multiorgan failure. In this article, we focus on a) new insights into calcium's regulation of the inflammatory cascade, b) the controversy concerning whether free cytosolic calcium concentration ([Ca2+]i) is increased in the disorder, and c) the potential therapeutic uses of calcium antagonists. An important message is that there are fundamental differences in the pathophysiology of the endotoxin model versus the cecal ligation and perforation (CLP) model of sepsis. Although calcium antagonists improve survival in the endotoxin model, they increase mortality in the CLP model of sepsis. Possible reasons for the differences in the effect of the drugs in the two different models and insight into the mechanisms of cell injury in endotoxin versus sepsis are presented.

Animals↗
PubMed1995

Calcium antagonists decrease plasma and tissue concentrations of tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-1 alpha in a mouse model of endotoxin.

Calcium plays an important role in the toxic effects of endotoxin, and calcium antagonists also have been shown to improve survival in animals challenged with endotoxin. Calcium may be involved in regulating cytokine production. Therefore, the protective effect of calcium-antagonists in endotoxin may be due to decreased cytokine formation and/or systemic release. In a mouse model of endotoxin, dantrolene (10 mg/kg) and azumolene (20 mg/kg), drugs that decrease calcium release from intracellular stores, or diltiazem (20 mg/kg), a calcium channel blocker, decreased plasma tumor necrosis factor-alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), and IL-1 beta (47.2, 63.2, and 62.4%, respectively, p < .05) when the animals were injected intraperitoneally with endotoxin. Dantrolene and azumolene decreased IL-1 alpha by 56.6 and 65.4%, respectively, (p < .05) and IL-1 beta by 51.7 and 69.7%, respectively (p < .05). Diltiazem had no effect on IL-1 alpha or IL-1 beta. Dantrolene decreased TNF-alpha in lung (26.1%), liver (29.4%), and spleen (35.4%) (p < .05) and IL-1 alpha in lung (30.0%) and liver (25.4%) (p < .05). The present findings indicate that calcium-antagonists may be efficacious in treating cytokine mediated inflammatory disorders.

Animals↗
PubMed1994

Dantrolene ameliorates the metabolic hallmarks of sepsis in rats and improves survival in a mouse model of endotoxemia.

Sepsis is the systemic inflammatory response resulting from serious infection and is the most common cause of death in intensive care units. Intracellular free calcium concentration ([Ca2+]i) is an important regulator of numerous cellular processes and when increased excessively may act as a potent cellular toxin. To determine if [Ca2+]i is responsible for the major metabolic changes which are hallmarks of sepsis, we examined if sodium dantrolene, a drug which decreases release of calcium from sarcoplasmic reticulum, affected the metabolic abnormalities in plasma and epitrochlearis muscles of rats made septic by cecal ligation and perforation. Dantrolene when added in vitro or when given in vivo decreases many of the metabolic hallmarks of sepsis--i.e., muscle protein breakdown approximately 30%, muscle glucose transport approximately 38%, muscle lactate formation approximately 28%, and plasma lactate approximately 29% (P < 0.05). In addition, we examined the ability of dantrolene to improve survival in a mouse model of endotoxemia. Dantrolene caused > 2-fold improvement in survival when it was administered concurrently with endotoxin (54% vs. 20% survival in dantrolene-treated and control mice, respectively (P < 0.001). Our results are consistent with the hypothesis that an increase in [Ca2+]i plays an important role in the metabolic abnormalities which occur during sepsis and that dantrolene administration may be an effective therapeutic strategy.

Animals↗
PubMed1994

Low plasma and renal tissue levels of L-arginine in rats with obstructive nephropathy.

Rats with bilateral ureteral obstruction (BUO) of 24 hours duration had significantly lower plasma levels of L-arginine than at baseline (P < 0.0001), but no significant changes occurred in sham-operated rats (SOR). In contrast, rats with bilateral nephrectomy had greater plasma levels of L-arginine four hours (P < 0.03) and 24 hours (not significant) after nephrectomy than at baseline. Total body irradiation prior to obstruction prevented the decrease in plasma levels of L-arginine in rats with BUO but had no effect on these values in SOR. Renal tissue levels of L-arginine were 20% lower in rats with BUO than in SOR. Total body irradiation prior to BUO resulted in greater renal tissue levels of L-arginine than occurred in nonirradiated rats with BUO (P < 0.002). Total body irradiation did not effect renal tissue levels of L-arginine in SOR. Excretion of reactive nitrogen intermediates in urine (URNI), indicative of L-arginine metabolism through the nitric oxide pathway, was lower in rats with BUO than in SOR (P < 0.001). Proximal tubules from rats with BUO synthesized less L-arginine than those from SOR (P < 0.02). The results indicate that: (1) decreased levels of L-arginine in plasma and renal tissue of rats with BUO correlate with leukocyte infiltration of the kidney, and (2) decreased synthesis of L-arginine occurs in proximal tubules of rats with BUO when compared to tubules from SOR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗