A system for investigating oesophageal photoplethysmographic signals in anaesthetised patients

The monitoring of arterial blood oxygen saturation in patients with compromised peripheral perfusion is often difficult, because conventional non-invasive techniques such as pulse oximetry (SpO2) can fail. Poor peripheral circulation commonly occurs after major surgery including cardiopulmonary bypass. The difficulties in these clinical situations might be overcome if the sensor were to monitor a better perfused central part of the body such as the oesophagus. A new oesophageal photoplethysmographic (PPG) probe and an isolated processing system have been developed to investigate the pulsatile signals of anaesthetised adult patients undergoing routine surgery. Measurements were made in the middle third of the oesophagus, 25 cm to 30 cm from the upper incisors. The AC PPG signals are sampled by a data acquisition system connected to a laptop computer. The signals recorded correspond to infrared and red AC PPGs from the middle third oesophagus and the finger. Preliminary results from 20 patients show that good quality AC PPG signals can be measured in the human oesophagus. The ratio of the oesophageal to finger AC PPG amplitudes was calculated for the infrared and red wavelengths for each patient. The mean (+/- standard deviation) of this ratio was 2.9 +/- 2.1 (n = 19) for the infrared wavelength and 3.1 +/- 2.4 (n = 16) for the red wavelength. The red and infrared wavelengths used are appropriate for pulse oximetry and this investigation indicates that the mid-oesophagus may be a suitable site for the reliable monitoring of SpO2 in patients with poor peripheral perfusion.

Effect of dietary inducer dimethylfumarate on glutathione in cultured human retinal pigment epithelial cells

PURPOSE

To determine the effect of dimethylfumarate (DMF), an inducer of glutathione (GSH)-dependent detoxification, on intracellular GSH levels in cultured human retinal pigment epithelium (hRPE) cells, its mechanism of action, and its effect on hRPE cells subjected to oxidative injury.

METHODS

Established hRPE cell lines were treated with DMF and assayed by high-pressure liquid chromatography for intracellular and extracellular GSH levels. Quantification of gamma-glutamylcysteine synthetase (GLCL) was determined through northern and western blot analyses, and activity was measured. Effects of pretreatment with DMF on GSH redox status of hRPE cells was determined. Sensitivity of hRPE cells to oxidative stress was determined using tert-butylhydroperoxide as the oxidative agent.

RESULTS

Dimethylfumarate caused a transient decrease followed by a significant increase in intracellular GSH. Glutathione increased maximally at 24 hours with 100 to 200 microM DMF. The initial decrease could be accounted for by the formation of a DMF-GSH conjugate. Dimethylfumarate treatment increased the steady state mRNA expression of the regulatory subunit of GLCL, but no increase was seen for the catalytic subunit. However, protein levels were increased for both, and the catalytic activity of GLCL was also increased. Whereas the initial decrease in GSH made hRPE cells more susceptible to oxidative damage, pretreatment with DMF under conditions that increased intracellular GSH protected hRPE cells against oxidative damage.

CONCLUSIONS

These results suggest a means by which the antioxidant capability of hRPE may be augmented without direct antioxidant supplementation. Specifically, a dietary compound that conjugates with GSH can induce GSH synthesis, increase GSH concentration, and improve protection by GSH-dependent detoxification pathways in hRPE. However, the early depletion of GSH before stimulated synthesis necessitates caution in prevention strategies using dietary inducers.

Mitochondrial redox signaling during apoptosis

The regulatory role of cellular redox state during apoptosis is still controversial. Early redox signaling can transduce divergent upstream signals to mitochondria and initiate apoptosis. On the other hand, release of mitochondrial cytochrome c triggers generation of reactive oxygen species (ROS) and renders apoptotic cells much more oxidized. Although the sequential caspase activation does not have apparent redox-sensitive components, redox signaling provides a separate pathway that is parallel with the caspase cascade. The function of the apoptosis-associated redox change is uncertain. It could provide positive feedback mechanisms, such as activating mitochondrial permeability transition and apoptosis signaling kinase (ASK-1). Since apoptotic cells are designated to be quickly eliminated, the dramatic cellular oxidation could be involved in the final degradation of apoptotic bodies and even the termination of the proteolytic activity after phagocytosis.

Keratinocyte growth factor enhances glutathione redox state in rat intestinal mucosa during nutritional repletion

Malnutrition decreases tissue levels of glutathione (GSH), a major endogenous antioxidant that detoxifies reactive oxygen species and promotes cell growth. This study determined the effects of the gut trophic peptide keratinocyte growth factor (KGF) on intestinal mucosal GSH concentrations and redox state in malnourished rats. Adult rats were food-deprived for 3 d, then consumed food ad libitum or 25% of ad libitum intake for 3 d with daily intraperitoneal administration of saline or KGF (5 mg.kg-1.d-1). Mucosal GSH and glutathione disulfide (GSSG) concentrations, crypt depth and total mucosal height were measured in the jejunum, ileum and colon. In the 25% of ad libitum-refed, saline-treated group, mucosal GSH was lower in all gut tissues (42% in jejunum, 38% in ileum, and 57% in colon), and the GSH/GSSG ratio was lower in the jejunum and ileum compared to that in the ad libitum-refed controls. KGF treatment with ad libitum refeeding increased GSH/GSSG in the jejunum, ileum and colon. Furthermore, in 25% of ad libitum refeeding, KGF normalized jejunal, ileal and colonic mucosal GSH content and significantly increased the mucosal GSH/GSSG ratio relative to rats treated with saline. Increased crypt depth and total mucosal height induced by KGF and feeding could be explained in part by increased mucosal GSH content. KGF treatment improved gut mucosal glutathione redox state in malnourished, refed rats. These data provide evidence that gut trophic hormones and food intake may independently support gut mucosal glutathione antioxidant capacity during nutritional repletion.

Health status of a recently discovered population of feral swine in Kansas

Twenty feral hogs (Sus scrofa) from a newly discovered population on Fort Riley Army Base (Kansas, USA) were shot and examined from November 1993 through February 1994 to assess the health of the population. The hogs were generally healthy, although serologic evidence indicated that some individuals had been exposed to parvovirus, enterovirus, and swine influenza. We found no indications of brucellosis, pseudorabies, or porcine respiratory and reproductive syndrome. Lung worms (Metastrongylus spp.), round worms (Ascaris suum), and whipworms (Trichuris suis) were found in nine, four and two of the hogs, respectively. Seven hogs had infestations of lice (Haematopinus suis). Fence-line contacts were documented between four wild boars and domestic sows, and in three cases wild boars entered pens containing domestic sows. We recommend that hogs be examined periodically from this and other wild populations to monitor health status since new animals may enter populations through deliberate translocation, escape from shooting preserves or domestic swine producers, or dispersal from other feral populations.

Presence of a pre-apoptotic complex of pro-caspase-3, Hsp60 and Hsp10 in the mitochondrial fraction of jurkat cells

Activation of pro-caspase-3 is a central event in the execution phase of apoptosis and appears to serve as the convergence point of different apoptotic signaling pathways. Recently, mitochondria were found to play a central role in apoptosis through release of cytochrome c and activation of caspases. Moreover, a sub-population of pro-caspase-3 has been found to be localized to this organelle. In the present study, we demonstrate that pro-caspase-3 is present in the mitochondrial fraction of Jurkat T cells in a complex with the chaperone proteins Hsp60 and Hsp10. Induction of apoptosis with staurosporine led to the activation of mitochondrial pro-caspase-3 and its dissociation from the Hsps which were released from mitochondria. The release of Hsps occurred simultaneously with the release of other mitochondrial intermembrane space proteins including cytochrome c and adenylate kinase, prior to a loss of mitochondrial transmembrane potential. In in vitro systems, recombinant Hsp60 and Hsp10 accelerated the activation of pro-caspase-3 by cytochrome c and dATP in an ATP-dependent manner, consistent with their function as chaperones. This finding suggests that the release of mitochondrial Hsps may also accelerate caspase activation in the cytoplasm of intact cells.

Presence of a pre-apoptotic complex of pro-caspase-3, Hsp60 and Hsp10 in the mitochondrial fraction of jurkat cells

Activation of pro-caspase-3 is a central event in the execution phase of apoptosis and appears to serve as the convergence point of different apoptotic signaling pathways. Recently, mitochondria were found to play a central role in apoptosis through release of cytochrome c and activation of caspases. Moreover, a sub-population of pro-caspase-3 has been found to be localized to this organelle. In the present study, we demonstrate that pro-caspase-3 is present in the mitochondrial fraction of Jurkat T cells in a complex with the chaperone proteins Hsp60 and Hsp10. Induction of apoptosis with staurosporine led to the activation of mitochondrial pro-caspase-3 and its dissociation from the Hsps which were released from mitochondria. The release of Hsps occurred simultaneously with the release of other mitochondrial intermembrane space proteins including cytochrome c and adenylate kinase, prior to a loss of mitochondrial transmembrane potential. In in vitro systems, recombinant Hsp60 and Hsp10 accelerated the activation of pro-caspase-3 by cytochrome c and dATP in an ATP-dependent manner, consistent with their function as chaperones. This finding suggests that the release of mitochondrial Hsps may also accelerate caspase activation in the cytoplasm of intact cells.

Oxidant-induced apoptosis in cultured human retinal pigment epithelial cells

PURPOSE

To determine the mechanism of oxidant-induced cell death in cultured human retinal pigment epithelium (hRPE).

METHODS

Cultured hRPE cells were treated with different concentrations of a chemical oxidant, t-butylhydroperoxide (tBH), for different periods of time. Apoptosis was determined with terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) and flow cytometry. Mitochondrial membrane potential (mtdelta psi) was measured by rhodamine 123 staining and subsequent flow cytometry. Release of mitochondrial cytochrome c (cyt c) and cleavage of procaspase 3 and caspase substrates were determined by western blot analysis.

RESULTS

t-Butylhydroperoxide caused time- and dose-dependent activation of apoptosis in hRPE, indicated by characteristic morphologic changes; TUNEL-positive labeling; phosphatidylserine (PS) exposure; and procaspase 3, poly(ADP-ribose)polymerase, lamin, and tubulin cleavage. An early decrease of mtdelta psi was observed before caspase activation, together with the release of mitochondrial cyt c.

CONCLUSIONS

Results indicate that tBH can induce apoptosis in hRPE, probably by triggering the mitochondrial permeability transition, which results in swelling and release of mitochondrial intermembrane proteins.

Evaluating dispensing error detection rates in a hospital pharmacy

OBJECTIVES

The filling of unit dose orders and checking for filling errors are two essential distributive responsibilities of a hospital pharmacy. Previous studies have shown that nonpharmacists, usually technicians, are capable of assuming these distributive tasks traditionally performed by hospital pharmacists. The study tested whether nonpharmacists, in this case licensed practical nurses/medication nurses, were as competent as pharmacists in checking for errors in unit dose cassettes prepared for hospital patients.

METHODS

A university teaching hospital was used for the study. Artificial errors (n = 812) were introduced into the drug distribution system during a 4-month period in 1995. Included in the study were seven staff pharmacists and nine medication nurses (licensed practical nurses) involved in the decentralized drug distribution system. The primary measure was the ratio of errors detected to the number of artificial errors introduced into the system. This primary measure is different from those used in prior studies that do not separate dispensing errors and checking errors.

RESULTS

Overall, pharmacists were significantly more accurate in detecting errors (87.7% vs. 82.1%). In one category of serious errors, that of wrong strength, the difference between pharmacists and licensed practical nurses was even greater (93.3% vs. 83.3%).

CONCLUSIONS

This study's results do not support conclusions of prior studies that nonpharmacists can match the error detection accuracy of pharmacists. It demonstrates the importance of considering the types of errors under examination and of using appropriate measures of error checkers when drawing conclusions on relative competence.

Comparable renal graft survival in African-American and Caucasian recipients

In past years, many pediatric transplant centers found African-American renal transplant recipients to have poor graft survival. Since 1991 anti-lymphocyte induction therapy has been routinely used for pediatric cadaveric (CAD) and living-related donor (LRD) renal allograft recipients at the University of Tennessee, Memphis. Sixteen African-American first renal allograft recipients received induction therapy: 11 CAD allografts (10 OKT3, 1 ATGAM) and five LRD (all ATGAM). Sixteen Caucasian recipients received induction therapy; 3 CAD (all OKT3), 1 living-unrelated donor (OKT3), and 12 LRD (9 ATGAM, 3 OKT3). Mean age at renal transplantation was 11.8 and 10.5 years for African-American and Caucasian recipients, respectively. Predicted graft survival (PGS) estimated by the Kaplan-Meier method for the African-American patients was 94% at both 1 and 3 years, and for Caucasian patients was 94% and 85% at 1 and 3 years, respectively. Eleven African-American CAD recipients had a PGS of 91% at 1 and 3 years. Renal allograft survival for African-American and Caucasian pediatric recipients at our center appears to be comparable. This could be due, in part, to the use of anti-lymphocyte induction therapy. However, other factors, such as improved compliance or better immunological and pharmacological monitoring, may also have contributed.

Mitochondrial control of apoptosis: the role of cytochrome c

Mitochondrial cytochrome c (cyt c) has been found to have dual functions in controlling both cellular energetic metabolism and apoptosis. Through interaction with apoptotic protease activating factors (Apaf), cyt c can initiate the activation cascade of caspases once it is released into the cytosol. The loss of a component of the mitochondrial electron transport chain also triggers the generation of superoxide. Although cyt c can be released independent of the mitochondrial permeability transition (MPT), the accompanying cellular redox change can trigger the MPT. Since another apoptotic protease, AIF, is released by MPT, the two separate pathways provide redundancy that ensures effective execution of the cell death program. Anti-apoptotic Bcl-2 family proteins function as gatekeepers to prevent the release of both cyt c and AIF. In spite of their stabilization effect on the mitochondrial outer membrane, Bcl-2 proteins may also be involved in the direct binding of Apaf molecules as regulatory elements further downstream from the mitochondrial apoptotic signals.

Glutathione measurement in human plasma. Evaluation of sample collection, storage and derivatization conditions for analysis of dansyl derivatives by HPLC

Literature values for human plasma GSH vary over 10-fold despite the use of apparently valid analytical procedures for GSH measurement. The purpose of this study was to develop a procedure to minimize error in sample collection, processing and storage that could contribute to such differences. HPLC with fluorescence detection of dansyl derivatives was used for quantification. The results show that collection of blood with a butterfly needle and syringe reduces overestimation due to limited hemolysis and that use of a preservation solution designed to inhibit autooxidation and enzymatic degradation allows quantitative recovery of both GSH and GSSG. Stability tests showed that non-derivatized samples were stable for at least 2 months at - 80 degrees while dansyl derivatives were stable in the dark at 0-4 degrees for 12 months. Results from 59 healthy individuals (20-43 years) provided a mean (+/-1 SD) GSH value of 2.09+/-1.14 micromolar.

Detection of pro-caspase-3 in cytosol and mitochondria of various tissues

Caspases are a family of cysteine proteases of critical importance in the apoptotic cell death process. They are normally present as zymogens (pro-caspases) in the cytoplasm of vertebrate and other organisms. In this study we have shown that pro-caspase-3 is localized to cytosol and mitochondria of various rat tissues (brain, heart, kidney, liver, spleen and thymus). Although the majority of pro-caspase-3 was localized in the cytosol, the amount of mitochondrial pro-caspase-3 was significant. The ratio of cytosolic and mitochondrial pools of pro-caspase-3 appeared to vary between different tissues. The higher amount of mitochondrial pro-caspase-3 was found in thymus and spleen, i.e. tissues in which spontaneous apoptosis plays an important role. Our findings provide further support for mitochondrial localization of pro-caspase-3 and the critical role of this organelle in apoptosis.

Cytochrome c release and caspase activation in hydrogen peroxide- and tributyltin-induced apoptosis

The ability of H2O2 and tributyltin (TBT) to trigger pro-caspase activation via export of cytochrome c from mitochondria to the cytoplasm was investigated. Treatment of Jurkat T lymphocytes with H2O2 resulted in the appearance of cytochrome c in the cytosol within 2 h. This was at least 1 h before caspase activation was observed. TBT caused cytochrome c release already after 5 min, followed by caspase activation within 1 h. Measurement of mitochondrial membrane potential (delta psi(m)) showed that both H2O2 and TBT dissipated delta psi(m), but with different time courses. TBT caused a concomitant loss of delta psi(m) and release of cytochrome c, whereas cytochrome c release and caspase activation preceded any apparent delta psi(m) loss in H2O2-treated cells. Thus, our results suggest that different mechanisms are involved in triggering cytochrome c release with these apoptosis-inducing agents.

Superoxide in apoptosis. Mitochondrial generation triggered by cytochrome c loss

Activation of apoptosis is associated with generation of reactive oxygen species. The present research shows that superoxide is produced by mitochondria isolated from apoptotic cells due to a switch from the normal 4-electron reduction of O2 to a 1-electron reduction when cytochrome c is released from mitochondria. Bcl-2, a protein that protects against apoptosis and blocks cytochrome c release, prevents superoxide production when it is overexpressed. The switch in electron transfer provides a mechanism for redox signaling that is concomitant with cytochrome c-dependent activation of caspases. The block of cytochrome c release provides a mechanism for the apparent antioxidant function of Bcl-2.

Glutathione in human plasma: decline in association with aging, age-related macular degeneration, and diabetes

Blood samples were analyzed for GSH and GSH redox state in 40 age-related macular degeneration (ARMD) patients (> 60 y), 33 non-ARMD diabetic patients (> 60 years), 27 similarly aged non-ARMD and nondiabetic individuals (> 60 years), and 19 younger individuals (< 60 years) without ARMD or diabetes. Results showed a significantly lower plasma GSH in older individuals (ARMD, diabetes, and controls) than in younger individuals (p < .01). Total GSH (GSHt) obtained following treatment with dithiothreitol was significantly lower only in diabetic cases (p < .05) but also approached significance for ARMD cases (p = .089). Estimation of redox potential indicated that the plasma GSH pool is considerably more oxidized in all of the older groups. Analyses of whole blood GSH showed that GSH was significantly lower in diabetic cases compared to the other groups, but did not reveal any difference associated with age or ARMD. In contrast, GSSG in whole blood was significantly higher in the older groups compared to the younger controls. The results suggest that in studies of age-related pathologies, oxidation of GSH may be a more important parameter than a decline in pool size, while in specific pathologies such as diabetes, both oxidation and a decline in pool size may be important.

Glutathione oxidation is associated with altered microtubule function and disrupted fertilization in mature hamster oocytes

We hypothesized that depletion of glutathione (GSH) with diamide, a relatively specific GSH oxidant, may alter the meiotic spindle apparatus in mature hamster oocytes. Immunofluorescent analysis of oocytes exposed to diamide for 1.5 or 3 h revealed time- and concentration-dependent disruption of spindle morphology accompanied by chromosome clumping. In oocytes first cultured in diamide for 1.5 h and then in diamide-free medium for 1.5 or 3 h, microtubules appeared to repolymerize, but normal spindle structure was not regained. HPLC confirmed that diamide oxidized oocyte GSH under conditions identical to those associated with spindle-related abnormalities. Exposure of oocytes to 25 or 50 microM diamide before in vitro fertilization did not affect their ability to undergo fertilization. A significant proportion of the fertilized oocytes that had been exposed to 50 microM diamide before insemination exhibited abnormal multiple female pronuclei with an apparently normal male pronucleus. These observations indicate that mature hamster oocytes are susceptible to oxidative stress during the critical period that precedes fertilization and provide further evidence that GSH plays important roles in oocyte spindle function and pronucleus development.