Hydrological and hydrochemical behavior of a riparian zone in a high-order flatland stream

Hydrological and hydrochemical processes occurring within riparian zones in temperate mid-latitudes flatland areas have significant implications for water management by controlling nutrient transfer between the watershed and the stream system. The riparian zone in a high-order flatland stream located within a 7063-km² agricultural watershed in Argentina was investigated to study its hydrological connectivity to upland zones, interactions with the stream, and their implications for groundwater hydrochemistry. The analysis was based on 9-year-long time series of groundwater/stream water levels collected along a 220-m-long transect comprising six piezometers, a river stage sensor, and hydrochemical information from 37 groundwater/stream water sampling campaigns. Samples were analyzed for electrical conductivity (EC), Cl^-, SO₄⁺², (Ca⁺² + Mg⁺²), pH, and redox potential (ORP). Data were interpreted using descriptive statistics, statistical tests, groundwater flux calculations, and identification of hydrological patterns and associated hydrochemical responses. The system was hydrologically controlled by shallow groundwater. Three representative landscape hydrological patterns were identified: disconnected, incipient-weakly connected, and fully connected. Groundwater hydrochemistry was closely linked to hydrological connectivity, which played an important role in the mobilization and fluxes of solutes. Overall, groundwater EC, Cl^-, SO₄⁺², and (Ca⁺² + Mg⁺²) concentrations decreased from upland to lowland. For full connectivity, Cl^- concentrations reduced 33%, while SO₄⁺² reduced 42%, demonstrating the system's buffering capacity. This investigation constitutes the first attempt to formulate the riparian zone functioning in this agricultural region and has contributed to the understanding on the complex interactions between hydrologic regimes of large flatland-high-order streams and shallow groundwater systems in fine-texture sediments.

Efficacy and safety results of depatuxizumab mafodotin (ABT-414) in patients with advanced solid tumors likely to overexpress epidermal growth factor receptor

BACKGROUND

Epidermal growth factor receptor (EGFR) alterations are associated with multiple cancers. Current EGFR-directed therapies have led to increased efficacy but are associated with specific side effects. The antibody-drug conjugate depatuxizumab mafodotin (depatux-m) targets EGFR with a monoclonal antibody linked to a cytotoxin, and is highly tumor-specific.

METHODS

This phase 1/2 study evaluated the safety, pharmacokinetics, and efficacy of depatux-m in patients who had advanced solid tumors with known wild-type EGFR overexpression, amplification, or mutated EGFR variant III. A 3 + 3 dose escalation was used, and 2 dosing schedules were evaluated. Depatux-m also was manufactured under an alternate process to reduce the drug load and improve the safety profile, and it was tested at the maximum tolerated dose (MTD). In another cohort, prolonged infusion time of depatux-m was evaluated; and a cohort with confirmed EGFR amplification also was evaluated at the MTD.

RESULTS

Fifty-six patients were treated. The MTD and the recommended phase 2 dose for depatux-m was 3.0 mg/kg. Common adverse events (AEs) were blurred vision (48%) and fatigue (41%). A majority of patients (66%) experienced 1 or more ocular AEs. Grade 3 or 4 AEs were observed in 43% of patients. One patient with EGFR-amplified, triple-negative breast cancer had a partial response. Stable disease was observed in 23% of patients. Pharmacokinetics revealed that depatux-m exposures were approximately dose-proportional.

CONCLUSIONS

Depatux-m resulted in infrequent nonocular AEs but increased ocular AEs. Patient follow-up confirmed that ocular AEs were reversible. Lowering the drug-antibody ratio did not decrease the number of ocular AEs. A partial response in 1 patient with EGFR-amplified disease provides the opportunity to study depatux-m in diseases with a high incidence of EGFR amplification. Cancer 2018;124:2174-83. © 2018 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Proton pump inhibitors decrease eotaxin-3/CCL26 expression in patients with chronic rhinosinusitis with nasal polyps: Possible role of the nongastric H,K-ATPase

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) is often characterized by tissue eosinophilia that is associated with poor prognosis. Recent findings that proton pump inhibitors (PPIs) directly modulate the expression of eotaxin-3, an eosinophil chemoattractant, in patients with eosinophilic diseases suggest therapeutic potential for PPIs in those with CRSwNP.

OBJECTIVE

We assessed the effect of type 2 mediators, particularly IL-13 and eotaxin-3, on tissue eosinophilia and disease severity in patients with chronic rhinosinusitis (CRS). Further investigation focused on PPI suppression of eotaxin-3 expression in vivo and in vitro, with exploration of underlying mechanisms.

METHODS

Type 2 mediator levels in nasal tissues and secretions were measured by using a multiplex immunoassay. Eotaxin-3 and other chemokines expressed in IL-13-stimulated human sinonasal epithelial cells (HNECs) and BEAS-2B cells with or without PPIs were assessed by using ELISA, Western blotting, real-time PCR, and intracellular pH imaging.

RESULTS

Nasal tissues and secretions from patients with CRSwNP had increased IL-13, eotaxin-2, and eotaxin-3 levels, and these were positively correlated with tissue eosinophil cationic protein levels and radiographic scores in patients with CRS (P < .05). IL-13 stimulation of HNECs and BEAS-2B cells dominantly induced eotaxin-3 expression, which was significantly inhibited by PPIs (P < .05). Patients with CRS taking PPIs also showed lower in vivo eotaxin-3 levels compared with those without PPIs (P < .05). Using intracellular pH imaging and altering extracellular K⁺, we found that IL-13 enhanced H⁺,K⁺-exchange, which was blocked by PPIs and the mechanistically unrelated H,K-ATPase inhibitor, SCH-28080. Furthermore, knockdown of ATP12A (gene for the nongastric H,K-ATPase) significantly attenuated IL-13-induced eotaxin-3 expression in HNECs. PPIs also had effects on accelerating IL-13-induced eotaxin-3 mRNA decay.

CONCLUSION

Our results demonstrated that PPIs reduce IL-13-induced eotaxin-3 expression by airway epithelial cells. Furthermore, mechanistic studies suggest that the nongastric H,K-ATPase is necessary for IL-13-mediated epithelial responses, and its inhibitors, including PPIs, might be of therapeutic value in patients with CRSwNP by reducing epithelial production of eotaxin-3.

Investigating nitrate dynamics in a fine-textured soil affected by feedlot effluents

Feedlots concentrate large volumes of manure and effluents that contain high concentrations of nitrate, among other constituents. If not managed properly, pen surfaces run-off and lagoons overflows may spread those effluents to surrounding land, infiltrating into the soil. Soil nitrate mobilization and distribution are of great concern due to its potential migration towards groundwater resources. This work aimed at evaluating the migration of nitrate originated on feedlots effluents in a fine-textured soil under field conditions. Soil water constituents were measured during a three-year period at three distinct locations adjacent to feedlot retention lagoons representing different degrees of exposure to water flow and manure accumulation. A simple statistical analysis was undertaken to identify patterns of observed nitrate and chloride concentrations and electrical conductivity and their differences with depth. HYDRUS-1D was used to simulate water flow and solute transport of Cl^-, NO₄⁺N, NO₃^-N and electrical conductivity to complement field data interpretation. Results indicated that patterns of NO₃^-N concentrations were not only notoriously different from electrical conductivity and Cl^- but also ranges and distribution with depth differed among locations. A combination of dilution, transport, reactions such as nitrification/denitrification and vegetation water and solute uptake took place at each plots denoting the complexity of soil-solution behavior under extreme polluting conditions. Simulations using the concept of single porosity-mobile/immobile water (SP-MIM) managed structural controls and correctly simulated ^-all species concentrations under field data constrains. The opposite was true for the other two locations experiencing near-saturation conditions, absence of vegetation and frequent manure accumulation and runoff from feedlot lagoons. Although the results are site specific, findings are relevant to advance the understanding of NO₃^-N dynamics resulting from FL operations under heavy soils.

Cytokines in Chronic Rhinosinusitis. Role in Eosinophilia and Aspirin-exacerbated Respiratory Disease

RATIONALE

The mechanisms that underlie the pathogenesis of chronic rhinosinusitis without nasal polyps (CRSsNP), chronic rhinosinusitis with nasal polyps (CRSwNP), and aspirin-exacerbated respiratory disease (AERD) are not clear.

OBJECTIVES

To first evaluate the inflammatory profiles of CRSsNP and CRSwNP tissues and then to investigate whether clinical differences observed between CRSwNP and AERD are in part secondary to differences in inflammatory mediator expression within nasal polyp (NP) tissues.

METHODS

Expression levels of numerous inflammatory mediators were determined by quantitative real-time polymerase chain reaction, ELISA, and multiplex immunoassay.

MEASUREMENTS AND MAIN RESULTS

CRSwNP NP had increased levels of type 2 mediators, including IL-5 (P < 0.001), IL-13 (P < 0.001), eotaxin-2 (P < 0.001), and monocyte chemoattractant protein (MCP)-4 (P < 0.01), compared with sinonasal tissue from subjects with CRSsNP and control subjects. Expression of IFN-γ messenger RNA or protein was low and not different among the chronic rhinosinusitis subtypes examined. Compared with CRSwNP, AERD NP had elevated protein levels of eosinophil cationic protein (ECP) (P < 0.001), granulocyte-macrophage colony-stimulating factor (GM-CSF) (P < 0.01), and MCP-1 (P = 0.01), as well as decreased gene expression of tissue plasminogen activator (tPA) (P = 0.02). Despite the higher eosinophilia in AERD, there was no associated increase in type 2 mediator protein levels observed.

CONCLUSIONS

CRSwNP was characterized by a predominant type 2 inflammatory environment, whereas CRSsNP did not reflect a classic type 1 milieu, as has been suggested previously. AERD can be distinguished from CRSwNP by elevated ECP levels, but this enhanced eosinophilia is not associated with elevations in traditional type 2 inflammatory mediators associated with eosinophil proliferation and recruitment. However, other factors, including GM-CSF, MCP-1, and tPA, may be important contributors to AERD pathogenesis.

Water and chloride transport in a fine-textured soil in a feedlot pen

Cattle feeding in feedlot pens produces large amounts of manure and animal urine. Manure solutions resulting from surface runoff are composed of numerous chemical constituents whose leaching causes salinization of the soil profile. There is a relatively large number of studies on preferential flow characterization and modeling in clayed soils. However, research on water flow and solute transport derived from cattle feeding operations in fine-textured soils under naturally occurring precipitation events is less frequent. A field monitoring and modeling investigation was conducted at two plots on a fine-textured soil near a feedlot pen in Argentina to assess the potential of solute leaching into the soil profile. Soil pressure head and chloride concentration of the soil solution were used in combination with HYDRUS-1D numerical model to simulate water flow and chloride transport resorting to the concept of mobile/immobile-MIM water for solute transport. Pressure head sensors located at different depths registered a rapid response to precipitation suggesting the occurrence of preferential flow-paths for infiltrating water. Cracks and small fissures were documented at the field site where the % silt and % clay combined is around 94%. Chloride content increased with depth for various soil pressure head conditions, although a dilution process was observed as precipitation increased. The MIM approach improved numerical results at one of the tested sites where the development of cracks and macropores is likely, obtaining a more dynamic response in comparison with the advection-dispersion equation.

Antibody deficiency in chronic rhinosinusitis: epidemiology and burden of illness

BACKGROUND

A subset of patients with chronic rhinosinusitis (CRS) has refractory disease. The risk factors for refractory CRS include atopy, a disrupted mucociliary transport system, medical conditions affecting the sinonasal tract mucosa, and immunodeficiency.

METHODS

We review four primary immunodeficiencies reported in individuals with CRS: common variable immune deficiency (CVID), selective IgA deficiency, IgG subclass deficiency, and specific antibody deficiency. We also review treatment options for individuals with both CRS and a concomitant immune defect.

RESULTS

There is a high prevalence of CRS in individuals with CVID and selective IgA deficiency. While many reports describe IgG subclass deficiency in individuals with CRS, the clinical relevance of this is unclear. Specific antibody deficiency may play a more significant role in the pathogenesis of refractory CRS.

CONCLUSION

Screening for a primary immunodeficiency should be part of the diagnostic workup of refractory CRS, as its identification may allow for more effective long-term therapeutic options.

Medical therapy as the primary modality for the management of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a prevalent disease with many potential interventions including medical and surgical treatments. Because CRS is a chronic condition it is essential that therapy limits exacerbations. The purpose of this article is to show that literature supports the implementation of aggressive medical management as the mainstay of therapy for CRS. Scientific literature on the use of intranasal and systemic corticosteroids, antibiotics, nasal saline lavages, and unique therapies for individuals with CRS (both with and without nasal polyps) are reviewed. In addition, literature comparing outcomes of medical therapy versus surgical therapy are reviewed. There is ample evidence of the beneficial effects of intranasal corticosteroids (INCSs) in CRS. The literature also favors the use of systemic corticosteroids in acute exacerbations of disease in patients with nasal polyps. Although antibiotics are commonly used for acute sinusitis, there is also evidence of their potential value in CRS. The literature indicates that saline lavages show benefit in the treatment of CRS. In addition, there are promising new biological therapies on the horizon with mepoluzimab and omalizumab. At least one study comparing medical therapy versus surgical therapy for CRS found no advantage for either modality. Treatment of CRS with aggressive medical management can potentially postpone the need for surgical intervention. Clinicians should use INCSs and nasal saline lavages as maintenance therapy. Systemic corticosteroids and antibiotics should be used for acute exacerbations, especially in individuals with nasal polyps.

Protective effects of low and high doses of cyclosporin A against reoxygenation injury in isolated rat cardiomyocytes are associated with differential effects on mitochondrial calcium levels

In this study we aimed to determine the concentration range of cyclosporin A (CsA) which was effective in protecting against reoxygenation injury in isolated cardiomyocytes, and its effects on intramitochondrial free calcium levels ([Ca2+]m). We also determined whether a high [CsA] had any deleterious effect on normal myocyte function. Isolated adult rat ventricular myocytes were placed in a chamber on the stage of a fluorescence microscope for induction of hypoxia. [Ca2+]m was determined from indo-1/am loaded cells where the cytosolic fluorescence signal had been quenched by superfusion with Mn2+. Cell length was measured using an edge-tracking device. Upon induction of hypoxia, control cells underwent rigor-contracture in 37 +/- 1 min (n = 99) (T1); CsA had no effect on T1. The percentage of control cells which recovered upon reoxygenation depended on the time spent in rigor (T2). With a T2 of 21-30 min, only 36% of control cells recovered compared with 90% and 78% of cells treated with 0.2 microM and 1 microM CsA respectively. After 40 min in rigor, [Ca2+]m was 280 +/- 60 nM in control-recovered cells (50% of cells) and 543 +/- 172 nM and 153 +/- 26 nM in cells treated with 0.2 and 1 microM CsA, respectively (all CsA treated cells recovered). In normoxic studies, CsA had no effect on cell contractility or [Ca2+]m upon rapid pacing, even in presence of an elevated external [Ca2+]. In conclusion, both low and high [CsA] protected against reoxygenation injury to cardiomyocytes despite having opposing effects on [Ca2+]m, suggesting more than one mechanism of action. CsA had no effect on either cell contractility or [Ca2+]m in normoxic cells.

Inducible nitric oxide synthase protection against coxsackievirus pancreatitis

Coxsackievirus infection causes myocarditis and pancreatitis in humans. In certain strains of mice, Coxsackievirus causes a severe pancreatitis. We explored the role of NO in the host immune response to viral pancreatitis. Coxsackievirus replicates to higher titers in mice lacking NO synthase 2 (NOS2) than in wild-type mice, with particularly high viral titers and viral RNA levels in the pancreas. Mice lacking NOS have a severe, necrotizing pancreatitis, with elevated pancreatic enzymes in the blood and necrotic acinar cells. Lack of NOS2 leads to a rapid increase in the mortality of infected mice. Thus, NOS2 is a critical component in the immune response to Coxsackievirus infection.

Inducible Nitric Oxide Synthase Protection Against Coxsackievirus Pancreatitis

Coxsackievirus infection causes myocarditis and pancreatitis in humans. In certain strains of mice, Coxsackievirus causes a severe pancreatitis. We explored the role of NO in the host immune response to viral pancreatitis. Coxsackievirus replicates to higher titers in mice lacking NO synthase 2 (NOS2) than in wild-type mice, with particularly high viral titers and viral RNA levels in the pancreas. Mice lacking NOS have a severe, necrotizing pancreatitis, with elevated pancreatic enzymes in the blood and necrotic acinar cells. Lack of NOS2 leads to a rapid increase in the mortality of infected mice. Thus, NOS2 is a critical component in the immune response to Coxsackievirus infection.

Thalidomide analogue CC1069 inhibits development of rat adjuvant arthritis

The cytokine tumour necrosis factor-alpha (TNF-alpha) has been implicated in the aetiology of rheumatoid arthritis in humans as well as of experimental arthritis in rodents. Thalidomide, and to a greater extent the new thalidomide analogue CC1069, inhibit monocyte TNF-alpha production both in vitro and in vivo. The aim of the present study is to establish whether these drugs block production of TNF-alpha as well as IL-2 by rat leucocytes and whether this inhibition affects the development of rat adjuvant arthritis (AA). Cultured splenocytes were stimulated with either lipopolysaccharide (LPS) or concanavalin A (Con A) in the presence of thalidomide, CC1069, or solvent, and the production of TNF-alpha and IL-2 were compared. Next, adjuvant was injected into the base of the tail of rats without or with daily intraperitoneal injections with 100-200 mg/kg per day thalidomide or 50-200 mg/kg per day CC1069. Disease activity, including ankle swelling, hind limb radiographic and histological changes, weight gain, and ankle joint cytokine mRNA levels, were monitored. CC1069, but not the parent drug thalidomide, inhibited in vitro production of TNF-alpha and IL-2 by stimulated splenocytes in a dose-dependent manner. In vivo, a dose-dependent suppression of AA disease activity occurred in the CC1069-treated animals. In contrast, thalidomide-treated rats experienced comparable arthritis severity to placebo-treated animals. There was also a reduction in TNF-alpha and IL-2 mRNA levels in the ankle joints of CC1069-treated rats compared with thalidomide- and placebo-treated arthritic rats. Early initiation of CC1069 treatment suppressed AA inflammation more efficiently than delayed treatment. We conclude that thalidomide, which did not suppress TNF-alpha or IL-2 production in vitro by Lewis rat cells, did not suppress development of rat AA. However, the development of rat AA can be blocked by the thalidomide analogue CC1069, which is an efficient inhibitor of TNF-alpha production and IL-2 in vitro.

Differential cytokine modulation and T cell activation by two distinct classes of thalidomide analogues that are potent inhibitors of TNF-alpha

TNF-alpha mediates both protective and detrimental manifestations of the host immune response. Our previous work has shown thalidomide to be a relatively selective inhibitor of TNF-alpha production in vivo and in vitro. Additionally, we have recently reported that thalidomide exerts a costimulatory effect on T cell responses. To develop thalidomide analogues with increased anti-TNF-alpha activity and reduced or absent toxicities, novel TNF-alpha inhibitors were designed and synthesized. When a selected group of these compounds was examined for their immunomodulatory activities, different patterns of cytokine modulation were revealed. The tested compounds segregated into two distinct classes: one class of compounds, shown to be potent phosphodiesterase 4 inhibitors, inhibited TNF-alpha production, increased IL-10 production by LPS-induced PBMC, and had little effect on T cell activation; the other class of compounds, similar to thalidomide, were not phosphodiesterase 4 inhibitors and markedly stimulated T cell proliferation and IL-2 and IFN-gamma production. These compounds inhibited TNF-alpha, IL-1beta, and IL-6 and greatly increased IL-10 production by LPS-induced PBMC. Similar to thalidomide, the effect of these agents on IL-12 production was dichotomous; IL-12 was inhibited when PBMC were stimulated with LPS but increased when cells were stimulated by cross-linking the TCR. The latter effect was associated with increased T cell CD40 ligand expression. The distinct immunomodulatory activities of these classes of thalidomide analogues may potentially allow them to be used in the clinic for the treatment of different immunopathological disorders.

Differential Cytokine Modulation and T Cell Activation by Two Distinct Classes of Thalidomide Analogues That Are Potent Inhibitors of TNF-α

TNF-α mediates both protective and detrimental manifestations of the host immune response. Our previous work has shown thalidomide to be a relatively selective inhibitor of TNF-α production in vivo and in vitro. Additionally, we have recently reported that thalidomide exerts a costimulatory effect on T cell responses. To develop thalidomide analogues with increased anti-TNF-α activity and reduced or absent toxicities, novel TNF-α inhibitors were designed and synthesized. When a selected group of these compounds was examined for their immunomodulatory activities, different patterns of cytokine modulation were revealed. The tested compounds segregated into two distinct classes: one class of compounds, shown to be potent phosphodiesterase 4 inhibitors, inhibited TNF-α production, increased IL-10 production by LPS-induced PBMC, and had little effect on T cell activation; the other class of compounds, similar to thalidomide, were not phosphodiesterase 4 inhibitors and markedly stimulated T cell proliferation and IL-2 and IFN-γ production. These compounds inhibited TNF-α, IL-1β, and IL-6 and greatly increased IL-10 production by LPS-induced PBMC. Similar to thalidomide, the effect of these agents on IL-12 production was dichotomous; IL-12 was inhibited when PBMC were stimulated with LPS but increased when cells were stimulated by cross-linking the TCR. The latter effect was associated with increased T cell CD40 ligand expression. The distinct immunomodulatory activities of these classes of thalidomide analogues may potentially allow them to be used in the clinic for the treatment of different immunopathological disorders.

Mitochondrial calcium transporting pathways during hypoxia and reoxygenation in single rat cardiomyocytes

OBJECTIVE

Mitochondrial [Ca2+] ([Ca2+]m) rises in parallel with cytosolic [Ca2+] ([Ca2+]c) following ATP-depletion rigor contracture induced by hypoxia in isolated cardiomyocytes. We investigated the pathways involved in the hypoxia induced changes in [Ca2+]m by using known inhibitors of mitochondrial Ca2+ transport, namely ruthenium red, an inhibitor of the Ca2+ uniporter (the normal influx route) and clonazepam, an inhibitor of Na+/Ca2+ exchange, (the normal efflux route).

METHODS

[Ca2+]m was determined from indo-1/am loaded rat myocytes where the cytosolic fluorescence signal had been quenched by superfusion with Mn2+. [Ca2+]c was measured by loading myocytes with indo-1 pentapotassium salt during the isolation procedure. Cells were placed in a specially developed chamber for induction of hypoxia and reoxygenated 40 min after rigor development.

RESULTS

50% of control cells hypercontracted upon reoxygenation; this correlated with a [Ca2+]m or [Ca2+]c higher than approximately 350 nM at the end of rigor. Clonazepam completely abolished the rigor-induced rise in [Ca2+]m but not [Ca2+]c. On reoxygenation [Ca2+]m increased over the first 5 min and remained elevated whereas [Ca2+]c fell. In the presence of ruthenium red a dramatic increase in [Ca2+]m occurred 5-10 min after rigor development (the indo-1 fluorescence signal was saturated); [Ca2+]c also increased but to a lesser extent. On reoxygenation, [Ca2+]m fell rapidly even though cells hypercontracted and [Ca2+]c remained elevated.

CONCLUSIONS

During hypoxia following rigor development Ca2+ uptake into mitochondria occurs largely via the Na+/Ca2+ exchanger rather than the Ca2+ uniporter whereas on reoxygenation the transporters resume their normal directionality.

Nitric oxide inhibition of coxsackievirus replication in vitro

Nitric oxide is a radical molecule with antibacterial, -parasitic, and -viral properties. We investigated the mechanism of NO inhibition of Coxsackievirus B3 (CVB3) replication in vitro by determining the effect of NO upon a single replicative cycle of CVB3 grown in HeLa cells. Transfection of inducible NO synthase cDNA into HeLa cells reduces the number of viral particles produced during a single cycle of growth. Similarly, a noncytotoxic concentration of the NO donor S-nitroso-amino-penicillamine reduces the number of viral particles in a dose-dependent manner. To explore the mechanisms by which NO exerts its antiviral effect, we assayed the attachment, replication, and translation steps of the CVB3 life cycle. NO does not affect the attachment of CVB3 to HeLa cells. However, NO inhibits CVB3 RNA synthesis, as shown by a [3H]uridine incorporation assay, reverse transcription-PCR, and Northern analysis. In addition, NO inhibits CVB3 protein synthesis, as shown by [35S]methionine protein labeling and Western blot analysis of infected cells. Thus, NO inhibits CVB3 replication in part by inhibiting viral RNA synthesis by an unknown mechanism.

Myocyte adaptation to chronic hypoxia and development of tolerance to subsequent acute severe hypoxia

Studies in animal models and humans suggest that myocardium may adapt to chronic or intermittent prolonged episodes of reduced coronary perfusion. Stable maintenance of partial flow reduction is difficult to achieve in experimental models; thus, in vitro cellular models may be useful for establishing the mechanisms of adaptation. Since moderate hypoxia is likely to be an important component of the low-flow state, isolated adult rat cardiac myocytes were exposed to 1% O2 for 48 hours to study chronic hypoxic adaptation. Hypoxic culture did not reduce cell viability relative to normoxic controls but did enhance glucose utilization and lactate production, which is consistent with an anaerobic pattern of metabolism. Lactate production remained transiently increased after restoration of normal O2 tension. Myocyte contractility was reduced (video-edge analysis), as was the amplitude of the intracellular Ca2+ transient (indo 1 fluorescence) in hypoxic cells. Relaxation was slowed and was accompanied by a slowed decay of the Ca2+ transient. These changes were not due to alterations in the action potential. Tolerance to subsequent acute severe hypoxia occurred in cells cultured in 1% O2 and was manifested as a delay in the time to full ATP-depletion rigor contracture during severe hypoxia and enhanced morphological recovery of myocytes at reoxygenation. The latter was still seen after normalization of the data for the prolonged time to rigor, suggesting a multifactorial basis for tolerance. An intervening period of normoxic exposure before subsequent acute severe hypoxia did not result in loss of tolerance but rather increased the delay to subsequent ATP depletion rigor. Cellular glycogen was preserved during chronic hypoxic exposure and increased after the restoration of normal O2 tension. As mitochondrial cytochromes should be fully oxygenated at levels well below 1% O2, hypoxic adaptation may be mediated by a low-affinity O2-sensing process. Thus, adaptations that occur during prolonged periods of moderate hypoxia are proposed to poise the myocyte in a better position to tolerate impending episodes of severe O2 deprivation.

Inhibition of mitochondrial calcium efflux by clonazepam in intact single rat cardiomyocytes and effects on NADH production

The aims of this study were to determine: (i) whether clonazepam and CGP37157, which inhibit the Na+/Ca2+ exchanger of isolated mitochondria, could inhibit mitochondrial Ca2+ efflux in intact cells; and (ii) whether any sustained increase in mitochondrial [Ca2+] ([Ca2+]m) could alter mitochondrial NADH levels. [Ca2+]m was measured in Indo-1/AM loaded rat ventricular myocytes where the cytosolic fluorescence signal was quenched by superfusion with Mn2+. NADH levels were determined from cell autofluorescence. Upon exposure of myocytes to 50 nM norepinephrine (NE) and a stimulation rate of 3 Hz, [Ca2+]m increased from 59 +/- 3 nM to a peak of 517 +/- 115 nM (n = 8) which recovered rapidly upon return to low stimulation rate (0.2 Hz) and washout of NE. In the presence of clonazepam, the peak increase in [Ca2+]m was 937 +/- 192 nM (n = 5) which remained elevated at 652 +/- 131 nM upon removal of the stimulus. CGP37157 in some cells did give the same inhibition of mitochondrial Ca2+ efflux as clonazepam, but the effect was inconsistent since not all cells were capable of following the stimulation rate in presence of this compound. NADH levels increased upon exposure to rapid stimulation in the presence of NE alone and recovered upon return to low stimulation rates, whereas in clonazepam treated cells the recovery of NADH was prevented. We conclude that clonazepam is an effective inhibitor of mitochondrial [Ca2+] efflux in intact cells and also maintains the increase in NADH levels which occurs upon rapid stimulation of cells.