Regional mRNA expression of key gluconeogenic enzymes in the liver of dairy cows

Liver tissue was collected from eight random dairy cows at a slaughterhouse to test if gene expression of pyruvate carboxylase (PC), mitochondrial phosphoenolpyruvate carboxykinase (PEPCKm) and cytosolic phosphoenolpyruvate carboxykinase (PEPCKc) is different at different locations in the liver. Obtained liver samples were analysed for mRNA expression levels of PC, PEPCKc and PEPCKm and subjected to the MIXED procedure of SAS to test for the sampled locations with cow liver as repeated subject. Additionally, the general linear model procedure (GLM) for analysis of variance was applied to test for significant differences for mRNA abundance of PEPCKm, PEPCKc and bPC between the livers. In conclusion, this study demonstrated that mRNA abundance of PC, PEPCKc and PEPCKm is not different between locations in the liver but may differ between individual cows.

Age-modulated association between prefrontal NAA and the BDNF gene

Brain-derived neurotrophic factor (BDNF) has been implicated in the pathophysiology of psychiatric and neurological disorders and in the mechanisms of antidepressant pharmacotherapy. Psychiatric and neurological conditions have also been associated with reduced brain levels of N-acetyl-aspartate (NAA), which has been used as a putative marker of neural integrity. However, few studies have explored the relationship between BDNF polymorphisms and NAA levels directly. Here, we present data from a single-voxel proton magnetic resonance spectroscopy study of 64 individuals and explore the relationship between BDNF polymorphisms and prefrontal NAA level. Our results indicate an association between a single nucleotide polymorphism (SNP) within BDNF, known as rs1519480, and reduced NAA level (p = 0.023). NAA levels were further predicted by age and Asian ancestry. There was a significant rs1519480 × age interaction on NAA level (p = 0.031). Specifically, the effect of rs1519480 on NAA level became significant at age ⩾34.17 yr. NAA level decreased with advancing age for genotype TT (p = 0.001) but not for genotype CT (p = 0.82) or CC (p = 0.34). Additional in silico analysis of 142 post-mortem brain samples revealed an association between the same SNP and reduced BDNF mRNA expression in the prefrontal cortex. The rs1519480 SNP influences BDNF mRNA expression and has an impact on prefrontal NAA level over time. This genetic mechanism may contribute to inter-individual variation in cognitive performance seen during normal ageing, as well as contributing to the risk for developing psychiatric and neurological conditions.

Cholesteryl ester accumulation and accelerated cholesterol absorption in intestine-specific hormone sensitive lipase-null mice

Hormone sensitive lipase (HSL) regulates the hydrolysis of acylglycerols and cholesteryl esters (CE) in various cells and organs, including enterocytes of the small intestine. The physiological role of this enzyme in enterocytes, however, stayed elusive. In the present study we generated mice lacking HSL exclusively in the small intestine (HSLiKO) to investigate the impact of HSL deficiency on intestinal lipid metabolism and the consequences on whole body lipid homeostasis. Chow diet-fed HSLiKO mice showed unchanged plasma lipid concentrations. In addition, feeding with high fat/high cholesterol (HF/HC) diet led to unaltered triglyceride but increased plasma cholesterol concentrations and CE accumulation in the small intestine. The same effect was observed after an acute cholesterol load. Gavaging of radioactively labeled cholesterol resulted in increased abundance of radioactivity in plasma, liver and small intestine of HSLiKO mice 4h post-gavaging. However, cholesterol absorption determined by the fecal dual-isotope ratio method revealed no significant difference, suggesting that HSLiKO mice take up the same amount of cholesterol but in an accelerated manner. mRNA expression levels of genes involved in intestinal cholesterol transport and esterification were unchanged but we observed downregulation of HMG-CoA reductase and synthase and consequently less intestinal cholesterol biosynthesis. Taken together our study demonstrates that the lack of intestinal HSL leads to CE accumulation in the small intestine, accelerated cholesterol absorption and decreased cholesterol biosynthesis, indicating that HSL plays an important role in intestinal cholesterol homeostasis.

Urinary metabolites and antioxidant products of exogenous melatonin in the mouse

Exogenous melatonin is widely used for sleep disorders and has potential value in neuroprotection, cardioprotection and as an antioxidant. Here, a novel method is described for the determination of melatonin and six metabolites in mouse urine by use of LC-MS/MS and GC-MS. LC-MS/MS is used for the measurement of melatonin, N1-acetyl-5-methoxykynuramine (AMK), N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) and 6-hydroxymelatonin (6-HMEL), while GC/MS is used for the determination of N-[2-(5-methoxy-2-oxo-2,3-dihydro-1H-indol-3-yl)-ethyl]-acetamide (2-OMEL) and cyclic 3-hydroxymelatonin (3-HMEL) with detection limits on column of 0.02-0.5 pmol, depending on the metabolite. Following oral administration of melatonin to mice, a 0-24 hr urine collection revealed the presence of melatonin (0.2% dose), 6-HMEL (37.1%) and NAS (3.1%) comprising >90% of the total metabolites; AMK and AFMK were also detected at 0.01% each; 2-OMEL was found at 2.2% of the dose, which is >100 times more than the AMK/AFMK pathway, and comprises >5% of the melatonin-related material detected in mouse urine. 3-HMEL was largely found as a sulfate conjugate. These studies establish sensitive assays for determination of six melatonin metabolites in mouse urine and confirm the potential for antioxidant activity of melatonin through the identification in vivo of AMK and AFMK, ring-opened metabolites with a high capacity for scavenging reactive oxygen species.

Statin therapy induces ultrastructural damage in skeletal muscle in patients without myalgia

Muscle pain and weakness are frequent complaints in patients receiving 3-hydroxymethylglutaryl coenzymeA (HMG CoA) reductase inhibitors (statins). Many patients with myalgia have creatine kinase levels that are either normal or only marginally elevated, and no obvious structural defects have been reported in patients with myalgia only. To investigate further the mechanism that mediates statin-induced skeletal muscle damage, skeletal muscle biopsies from statin-treated and non-statin-treated patients were examined using both electron microscopy and biochemical approaches. The present paper reports clear evidence of skeletal muscle damage in statin-treated patients, despite their being asymptomatic. Though the degree of overall damage is slight, it has a characteristic pattern that includes breakdown of the T-tubular system and subsarcolemmal rupture. These characteristic structural abnormalities observed in the statin-treated patients were reproduced by extraction of cholesterol from skeletal muscle fibres in vitro. These findings support the hypothesis that statin-induced cholesterol lowering per se contributes to myocyte damage and suggest further that it is the specific lipid/protein organization of the skeletal muscle cell itself that renders it particularly vulnerable.

Effects of colostrum feeding and glucocorticoid administration on insulin-dependent glucose metabolism in neonatal calves

Colostrum feeding and glucocorticoid administration affect glucose metabolism and insulin release in calves. We have tested the hypothesis that dexamethasone as well as colostrum feeding influence insulin-dependent glucose metabolism in neonatal calves using the euglycemic-hyperinsulinemic clamp technique. Newborn calves were fed either colostrum or a milk-based formula (n=14 per group) and in each feeding group, half of the calves were treated with dexamethasone (30 microg/[kg body weight per day]). Preprandial blood samples were taken on days 1, 2, and 4. On day 5, insulin was infused for 3h and plasma glucose concentrations were kept at 5 mmol/L+/-10%. Clamps were combined with [(13)C]-bicarbonate and [6,6-(2)H]-glucose infusions for 5.5h (i.e., from -150 to 180 min, relative to insulin infusion) to determine glucose turnover, glucose appearance rate (Ra), endogenous glucose production (eGP), and gluconeogenesis before and at the end of the clamp. After the clamp liver biopsies were taken to measure mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC). Dexamethasone increased plasma glucose, insulin, and glucagon concentrations in the pre-clamp period thus necessitating a reduction in the rate of glucose infusion to maintain euglycemia during the clamp. Glucose turnover and Ra increased during the clamp and were lower at the end of the clamp in dexamethasone-treated calves. Dexamethasone treatment did not affect basal gluconeogenesis or eGP. At the end of the clamp, dexamethasone reduced eGP and PC mRNA levels, whereas mitochondrial PEPCK mRNA levels increased. In conclusion, insulin increased glucose turnover and dexamethasone impaired insulin-dependent glucose metabolism, and this was independent of different feeding.

Extrinsic causes of erosion. Oral hygiene products and acidic medicines

Acidic or EDTA-containing oral hygiene products and acidic medicines have the potential to soften dental hard tissues. The low pH of oral care products increases the chemical stability of some fluoride compounds, favors the incorporation of fluoride ions in the lattice of hydroxyapatite and the precipitation of calcium fluoride on the tooth surface. This layer has some protective effect against an erosive attack. However, when the pH is too low or when no fluoride is present these protecting effects are replaced by direct softening of the tooth surface. Xerostomia or oral dryness can occur as a consequence of medication such as tranquilizers, anti-histamines, anti-emetics and anti-parkinsonian medicaments or of salivary gland dysfunction e.g. due to radiotherapy of the oral cavity and the head and neck region. Above all, these patients should be aware of the potential demineralization effects of oral hygiene products with low pH and high titratable acids. Acetyl salicylic acid taken regularly in the form of multiple chewable tablets or in the form of headache powder as well chewing hydrochloric acids tablets for treatment of stomach disorders can cause erosion. There is most probably no direct association between asthmatic drugs and erosion on the population level. Consumers, patients and health professionals should be aware of the potential of tooth damage not only by oral hygiene products and salivary substitutes but also by chewable and effervescent tablets. Additionally, it can be assumed that patients suffering from xerostomia should be aware of the potential effects of oral hygiene products with low pH and high titratable acids.

Influence of different spacers on the biological profile of a DOTA-somatostatin analogue

Radiolabeled somatostatin analogues have been successfully used for targeted radiotherapy and for imaging of somatostatin receptor (sst1-5)-positive tumors. Nevertheless, these analogues are subject to improving their tumor-to-nontarget ratio to enhance their diagnostic or therapeutic properties, preventing nephrotoxicity. In order to understand the influence of lipophilicity and charge on the pharmacokinetic profile of [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)]-somatostatin-based radioligands such as [DOTA,1-Nal3]-octreotide (DOTA-NOC), different spacers (X) based on 8-amino-3,6-dioxaoctanoic acid (PEG2), 15-amino-4,7,10,13-tetraoxapentadecanoic acid (PEG4), N-acetyl glucosamine (GlcNAc), triglycine, beta-alanine, aspartic acid, and lysine were introduced between the chelator DOTA and the peptide NOC. All DOTA-X-NOC conjugates were synthesized by Fmoc solid-phase synthesis. The partition coefficient (log D) at pH = 7.4 indicated that higher hydrophilicity than [111In-DOTA]-NOC was achieved with the introduction of the mentioned spacers, except with triglycine and beta-alanine. The high affinity of [InIII-DOTA]-NOC for human sst2 (hsst2) was preserved with the structural modifications, while an overall drop for hsst3 affinity was observed, except in the case of [InIII-DOTA]-beta-Ala-NOC. The new conjugates preserved the good affinity for hsst5, except for [InIII-DOTA]-Asn(GlcNAc)-NOC, which showed decreased affinity. A significant 1.2-fold improvement in the specific internalization rate in AR4-2J rat pancreatic tumor cells (sst2 receptor expression) at 4 h was achieved with the introduction of Asp as a spacer in the parent compound. In sst3-expressing HEK cells, the specific internalization rate at 4 h for [111In-DOTA]-NOC (13.1% +/- 0.3%) was maintained with [111In-DOTA]-beta-Ala-NOC (14.0% +/- 1.8%), but the remaining derivatives showed <2% specific internalization. Biodistribution studies were performed with Lewis rats bearing the AR4-2J rat pancreatic tumor. In comparison to [111In-DOTA]-NOC (2.96% +/- 0.48% IA/g), the specific uptake in the tumor at 4 h p.i. was significantly improved for the 111In-labeled sugar analogue (4.17% +/- 0.46% IA/g), which among all the new derivatives presented the best tumor-to-kidney ratio (1.9).

Brain metabolism in Alzheimer disease and vascular dementia assessed by in vivo proton magnetic resonance spectroscopy

Proton magnetic resonance spectroscopy (MRS) allows the assessment of various cerebral metabolites non-invasively in vivo. Among 1H MRS-detectable metabolites, N-acetyl-aspartate and N-acetyl-aspartyl-glutamate (tNAA), trimethylamines (TMA), creatine and creatine phosphate (tCr), inositol (Ins) and glutamate (Gla) are of particular interest, since these moieties can be assigned to specific neuronal and glial metabolic pathways, membrane constituents, and energy metabolism. In this study on 94 subjects from a memory clinic population, 1H MRS results (single voxel STEAM: TE 20 ms, TR 1500 ms) on the above metabolites were assessed for five different brain regions in probable vascular dementia (VD), probable Alzheimer's disease (AD), and age-matched healthy controls. In both VD and AD, ratios of tNAA/tCr were decreased, which may be attributed to neuronal atrophy and loss, and Ins/tCr-ratios were increased indicating either enhanced gliosis or alteration of the cerebral inositol metabolism. However, the topographical distribution of the metabolic alterations in both diseases differed, revealing a temporoparietal pattern for AD and a global, subcortically pronounced pattern for VD. Furthermore, patients suffering from vascular dementia (VD) had remarkably enhanced TMA/tCr ratios, potentially due to ongoing degradation of myelin. Thus, the metabolic alterations obtained by 1H MRS in vivo allow insights into the pathophysiology of the different dementias and may be useful for diagnostic classification.

Inflammation and NO(X)-induced nitration: assay for 3-nitrotyrosine by HPLC with electrochemical detection

The identification of 15N-labeled 3-nitrotyrosine (NTyr) by gas chromatography/mass spectroscopy in protein hydrolyzates from activated RAW 264.7 macrophages incubated with 15N-L-arginine confirms that nitric oxide synthase (NOS) is involved in the nitration of protein-bound tyrosine (Tyr). An assay is presented for NTyr that employs HPLC with tandem electrochemical and UV detection. The assay involves enzymatic hydrolysis of protein, acetylation, solvent extraction, O-deacetylation, and dithionite reduction to produce an analyte containing N-acetyl-3-aminotyrosine, an electrochemically active derivative of NTyr. We estimate the level of protein-bound NTyr in normal rat plasma to be approximately 0-1 residues per 10(6) Tyr with a detection limit of 0.5 per 10(7) Tyr when > 100 nmol of Tyr is analyzed and when precautions are taken to limit nitration artifacts. Zymosan-treated RAW 264.7 cells were shown to have an approximately 6-fold higher level of protein-bound NTyr compared with control cells and cells treated with N(G)-monomethyl-L-arginine, an inhibitor of NOS. Intraperitoneal injection of F344 rats with zymosan led to a marked elevation in protein-bound NTyr to approximately 13 residues per 10(6) Tyr, an approximately 40-fold elevation compared with plasma protein of untreated rats; cotreatment with N(G)-monomethyl-L-arginine inhibited the formation of NTyr in plasma protein from blood and peritoneal exudate by 69% and 53%, respectively. This assay offers a highly sensitive and quantitative approach for investigating the role of reactive byproducts of nitric oxide in the many pathological conditions and disease states associated with NO(X) exposure such as inflammation and smoking.

Antibiotic-dependent correlation between drug-induced killing and loss of luminescence in Streptococcus gordonii expressing luciferase

Measuring antibiotic-induced killing relies on time-consuming biological tests. The firefly luciferase gene (luc) was successfully used as a reporter gene to assess antibiotic efficacy rapidly in slow-growing Mycobacterium tuberculosis. We tested whether luc expression could also provide a rapid evaluation of bactericidal drugs in Streptococcus gordonii. The suicide vectors pFW5luc and a modified version of pJDC9 carrying a promoterless luc gene were used to construct transcriptional-fusion mutants. One mutant susceptible to penicillin-induced killing (LMI2) and three penicillin-tolerant derivatives (LMI103, LMI104, and LMI105) producing luciferase under independent streptococcal promoters were tested. The correlation between antibiotic-induced killing and luminescence was determined with mechanistically unrelated drugs. Chloramphenicol (20 times the MIC) inhibited bacterial growth. In parallel, luciferase stopped increasing and remained stable, as determined by luminescence and Western blots. Ciprofloxacin (200 times the MIC) rapidly killed 1.5 log10 CFU/ml in 2-4 hr. Luminescence decreased simultaneously by 10-fold. In contrast, penicillin (200 times the MIC) gave discordant results. Although killing was slow (< or = 0.5 log10 CFU/ml in 2 hr), luminescence dropped abruptly by 50-100-times in the same time. Inactivating penicillin with penicillinase restored luminescence, irrespective of viable counts. This was not due to altered luciferase expression or stability, suggesting some kind of post-translational modification. Luciferase shares homology with aminoacyl-tRNA synthetase and acyl-CoA ligase, which might be regulated by macromolecule synthesis and hence affected in penicillin-inhibited cells. Because of resemblance, luciferase might be down-regulated simultaneously. Luminescence cannot be universally used to predict antibiotic-induced killing. Thus, introducing reporter enzymes sharing mechanistic similarities with normal metabolic reactions might reveal other effects than those expected.

Study of Staphylococcus aureus pathogenic genes by transfer and expression in the less virulent organism Streptococcus gordonii

Because Staphylococcus aureus strains contain multiple virulence factors, studying their pathogenic role by single-gene inactivation generated equivocal results. To circumvent this problem, we have expressed specific S. aureus genes in the less virulent organism Streptococcus gordonii and tested the recombinants for a gain of function both in vitro and in vivo. Clumping factor A (ClfA) and coagulase were investigated. Both gene products were expressed functionally and with similar kinetics during growth by streptococci and staphylococci. ClfA-positive S. gordonii was more adherent to platelet-fibrin clots mimicking cardiac vegetations in vitro and more infective in rats with experimental endocarditis (P < 0.05). Moreover, deleting clfA from clfA-positive streptococcal transformants restored both the low in vitro adherence and the low in vivo infectivity of the parent. Coagulase-positive transformants, on the other hand, were neither more adherent nor more infective than the parent. Furthermore, coagulase did not increase the pathogenicity of clfA-positive streptococci when both clfA and coa genes were simultaneously expressed in an artificial minioperon in streptococci. These results definitively attribute a role for ClfA, but not coagulase, in S. aureus endovascular infections. This gain-of-function strategy might help solve the role of individual factors in the complex the S. aureus-host relationship.

Proliferation signal inhibitor-induced decrease of vascular endothelial cadherin expression and increase of endothelial permeability in vitro are prevented by an anti-oxidant

BACKGROUND: Rapamycines, sirolimus (SRL) and everolimus (ERL), are proliferation signal inhibitors (PSIs). PSI therapy often leads to edema. We hypothesized that increased oxidative stress in response to PSIs may modulate the expression of vascular endothelial (VE)-cadherin on endothelial cells (ECs) and, subsequently, vascular permeability, which in turn may be involved in the development of edema. METHODS: Experiments were performed on human umbilical vein ECs (HUVECs). Oxidative stress was measured by dichlorofluorescein-diacetate. Expression of VE-cadherin was evaluated by immunofluorescent staining and western blot analysis. Endothelial "permeability" was assessed using a transwell model. RESULTS: SRL and ERL, at concentrations of 1, 10 and 100 nmol/liter, enhanced oxidative stress (SRL: 24 +/- 12%, 29 +/- 9%, 41 +/- 13% [p < 0.05, in all three cases]; ERL: 13 +/- 10%, 27 +/- 2%, 40 +/- 12% [p < 0.05, in the latter two cases], respectively) on HUVECs, which was inhibited by the anti-oxidant, N-acetyl-cysteine (NAC) and, to a lesser extent, by the specific inhibitor of nitric oxide synthase, N-Omega-nitro-L-arginine methylester. By the use of NAC, VE-cadherin expression remained comparable with control, according to both immunocytochemistry and western blot analysis. Permeability was significantly increased by SRL and ERL at 100 nmol/liter (29.5 +/- 6.4% and 33.8 +/- 4.2%, respectively); however, co-treatment with NAC abrogated the increased permeability. CONCLUSIONS: EC homeostasis, as indicated by VE-cadherin expression, may be damaged by SRL and ERL, but resolved by the anti-oxidant NAC.

Design and in vitro characterization of highly sst2-selective somatostatin antagonists suitable for radiotargeting

Radiolabeled sst 2 and sst 3 antagonists are better candidates for tumor targeting than agonists with comparable binding characteristics (Ginj, M.; Zhang, H.; Waser, B.; Cescato, R.; Wild, D.; Erchegyi, J.; Rivier, J.; Mäcke, H. R.; Reubi, J. C. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 16436-16441.). Because most of the neuroendocrine tumors express sst 2, we used the known antagonists acetyl- pNO 2Phe (2)- c[ dCys (3)-Tyr (7)- dTrp (8)-Lys (9)-Thr (10)-Cys (14)]- dTyr (15)-NH 2 ( 1) (Bass, R. T.; Buckwalter, B. L.; Patel, B. P.; Pausch, M. H.; Price, L. A.; Strnad, J.; Hadcock, J. R. Mol. Pharmacol. 1996, 50, 709-715. Bass, R. T.; Buckwalter, B. L.; Patel, B. P.; Pausch, M. H.; Price, L. A.; Strnad, J.; Hadcock, J. R. Mol. Pharmacol. 1997, 51, 170; Erratum.) and H-Cpa (2)- c[ dCys (3)-Tyr (7)- dTrp (8)-Lys (9)-Thr (10)-Cys (14)]-2Nal (15)-NH 2 ( 7) (Hocart, S. J.; Jain, R.; Murphy, W. A.; Taylor, J. E.; Coy, D. H. J. Med. Chem. 1999, 42, 1863-1871.) as leads for analogues with increased sst 2 binding affinity and selectivity. Among the 32 analogues reported here, DOTA- pNO 2Phe (2)- c[ dCys (3)-Tyr (7)- dAph (8)(Cbm)-Lys (9)-Thr (10)-Cys (14)- dTyr (15)-NH 2 ( 3) and DOTA-Cpa (2)- c[ dCys (3)-Aph (7)(Hor)- dAph (8)(Cbm)-Lys (9)-Thr (10)-Cys (14)]- dTyr (15)-NH 2 ( 31) had the highest sst 2 binding affinity and selectivity. All of the analogues tested kept their sst 2 antagonistic properties (i.e., did not affect calcium release in vitro and competitively antagonized the agonistic effect of [Tyr (3)]octreotide). Moreover, in an immunofluorescence-based internalization assay, the new analogues prevented sst 2 internalization induced by the sst 2 agonist [Tyr (3)]octreotide without being active by themselves. In conclusion, several analogues (in particular 3, 31, and 32) have outstanding sst 2 binding and functional antagonistic properties and, because of their DOTA moiety, are excellent candidates for in vivo targeting of sst 2-expressing cancers.

Development of Optically Based pH Sensing Hydrogel and Controlled Nitric Oxide Release Polymer

Nitric oxide has the potential to greatly improve intravascular measurements by locally inhibiting thrombus formation and dilating blood vessels. pH, the partial pressure of oxygen, and the partial pressure of carbon dioxide are three arterial blood parameters that are of interest to clinicians in the intensive care unit that can benefit from an intravascular sensor. This work explores fabrication of absorbance and fluorescence based pH sensing chemistry, the sensing chemistries' compatibility with nitric oxide, and a controllable nitric oxide releasing polymer. The pH sensing chemistries utilized various substrates, dyes, and methods of immobilization. Absorbance sensing chemistries used sol-gels, fumed silica particles, mesoporous silicon oxide, bromocresol purple, phenol red, bromocresol green, physical entrapment, molecular interactions, and covalent linking. Covalently linking the dyes to fumed silica particles and mesoporous silicon oxide eliminated leaching in the absorbance sensing chemistries. The structures of the absorbance dyes investigated were similar and bromocresol green in a sol-gel was tested for compatibility with nitric oxide. Nitric oxide did not interfere with the use of bromocresol green in a pH sensor. Investigated fluorescence sensing chemistries utilized silica optical fibers, poly(allylamine) hydrogel, SNARF-1, molecular interactions, and covalent linking. SNARF-1 covalently linked to a modified poly(allylamine) hydrogel was tested in the presence of nitric oxide and showed no interference from the nitric oxide. Nitric oxide release was controlled through the modulation of a light source that cleaved the bond between the nitric oxide and a sulfur atom in the donor. The nitric oxide donor in this work is S-nitroso-N-acetyl-D-penicillamine which was covalently linked to a silicone rubber made from polydimethylsiloxane. It is shown that the surface flux of nitric oxide released from the polymer films can be increased and decreased by increasing and decreasing the output power of the LED light source. In summary, an optical pH sensing chemistry was developed that eliminated the chronic problem of leaching of the indicator dye and showed no reactivity to nitric oxide released, thereby facilitating the development of a functional, reliable intravascular sensor.