Novel interventions to reduce oxidative-stress related brain injury in neonatal asphyxia

Perinatal asphyxia-induced brain injury may present as hypoxic-ischemic encephalopathy in the neonatal period, and disability including cerebral palsy in the long term. The brain injury is secondary to both the hypoxic-ischemic event and the reoxygenation-reperfusion following resuscitation. Early events in the cascade of brain injury can be classified as either inflammation or oxidative stress through the generation of free radicals. The objective of this paper is to present efforts that have been made to limit the oxidative stress associated with hypoxic-ischemic encephalopathy. In the acute phase of ischemia/hypoxia and reperfusion/reoxygenation, the outcomes of asphyxiated infants can be improved by optimizing the initial delivery room stabilization. Interventions include limiting oxygen exposure, and shortening the time to return of spontaneous circulation through improved methods for supporting hemodynamics and ventilation. Allopurinol, melatonin, noble gases such as xenon and argon, and magnesium administration also target the acute injury phase. Therapeutic hypothermia, N-acetylcysteine2-iminobiotin, remote ischemic postconditioning, cannabinoids and doxycycline target the subacute phase. Erythropoietin, mesenchymal stem cells, topiramate and memantine could potentially limit injury in the repair phase after asphyxia. To limit the injurious biochemical processes during the different stages of brain injury, determination of the stage of injury in any particular infant remains essential. Currently, therapeutic hypothermia is the only established treatment in the subacute phase of asphyxia-induced brain injury. The effects and side effects of oxidative stress reducing/limiting medications may however be difficult to predict in infants during therapeutic hypothermia. Future neuroprotection in asphyxiated infants may indeed include a combination of therapies. Challenges include timing, dosing and administration route for each neuroprotectant.

Tidal volume delivery during continuous chest compressions and sustained inflation

OBJECTIVE

To determine the distending pressure needed to achieve sufficient tidal volume (V_T) delivery during continuous chest compressions (CC) superimposed by sustained inflation (SI) (CC+SI).

DESIGN

Randomised animal/manikin trial.

SETTING

University laboratory.

SUBJECTS

Cadaver piglets/manikin.

INTERVENTIONS

SI distending pressures of 5, 10, 15, 20, 25 and 30 cm H₂O were delivered in random order during CC+SI for 2 min each.

MAIN OUTCOME MEASURES

V_T, gas flow and airway pressure. Spearman's r for distending pressure and V_T.

RESULTS

Distending pressure and V_T correlated in cadaver piglets (r=0.83, p<0.001), manikin (r=0.98, p<0.001) and combined data (r=0.49, p<0.001). V_T was delivered during chest recoil during CC in both models. In cadaver piglets, a distending pressure ∼25 cm H₂O was needed to achieve an adequate V_T.

CONCLUSIONS

Chest recoil generates V_T depending on an adequate distending pressure. This has previously been demonstrated in adult animals. A pressure of ∼25 cm H₂O is needed to achieve an adequate V_T delivery.

The Effects of High Frequency Oscillatory Ventilation (HFOV) with Volume Guarantee (VG) on Left Ventricular Function, Systemic and Regional Oxygenation, and Ventilation When Compared to HFOV and Conventional Mechanical Ventilation (CMV) in A Newborn Piglet Model of Respiratory Distress Syndrome (RDS)

BACKGROUND: RDS due to surfactant deficiency is commonly seen in preterm infants. These infants often require ventilatory support such as CMV and HFOV. HFOV with VG (HFOV+VG) is an alternative mode that delivers a set tidal volume. There is limited data on either HFOV mode regarding the effects on left ventricular (LV) function, systemic and regional oxygenation, and ventilation.

OBJECTIVES: We primarily compared the effects of CMV with VG, HFOV, and HFOV+VG on cardiac index (CI). Secondary parameters included heart rate (HR), mean arterial pressure (MAP), LV ejection fraction (EF), stroke volume (SV), dP/dt max, LV end-systolic volume and pressure (ESV, ESP), end-diastolic volume and pressure (EDV, EDP), and measures of oxygenation and ventilation. Oxygenation parameters included cerebral and renal near-infrared spectroscopy (NIRS), partial pressure of arterial oxygen (PaO2), and carotid artery flow index (CAFI). Ventilation parameters included partial pressure of arterial carbon dioxide (PaCO2) and minute ventilation (MV).

DESIGN/METHODS: Piglets (1.4-2.4 kg; 1-3 days old) were acutely anesthetized and instrumented with the placement of a right femoral arterial catheter for blood gas analysis, NIRS probes (Invos®), Transonic® flow probe on right common carotid artery, and Millar® catheter in the LV. Warm saline lung lavage was performed to achieve an AaDO2 of 300-450 mmHg to simulate moderate to severe RDS. Piglets were then block-randomized to CMV, HFOV or HFOV+VG for 4 hours using a Fabian HFO ventilator (Acutronic Medical Systems AG, Switzerland)(n=8 per group). Sham-operated piglets without RDS were monitored for the same duration under CMV (n=6). Two-way repeated measures ANOVA was used to analyze the data between modes or time points.

RESULTS: Piglets developed moderately severe RDS with comparable AaDO2 and Paw along with stable hemodynamic parameters. Both HFOV and HFOV+VG groups had similar PaCO2 whereas the CMV group had elevated PaCO2 when compared to that of the Sham (p&lt;0.01). Switching to HFOV resulted in a higher MV than its baseline. HFOV+VG but not HFOV or CMV groups had lower regional oxygenation and CAFI than its respective normoxic baseline (all p&lt;0.01). HFOV and HFOV+VG had higher CI, EF, and SV than CMV at 4 hours of recovery (p&lt;0.05) with similar HR, MAP, dP/dt max, ESV, ESP, EDV and EDP.

CONCLUSION: In our piglet model of RDS, HFOV shows benefits to LV function and ventilation when compared to CMV. HFOV+VG does not show benefits compared to HFOV.

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Management of hypotension in preterm infants (The HIP Trial): a randomised controlled trial of hypotension management in extremely low gestational age newborns

BACKGROUND

Extremely preterm babies (delivered at <28 completed weeks of gestation) are frequently diagnosed with hypotension and treated with inotropic and pressor drugs in the immediate postnatal period. Dopamine is the most commonly used first-line drug. Babies who are treated for hypotension more frequently sustain brain injury, have long-term disability or die compared to those who are not. Despite the widespread use of drugs to treat hypotension in such infants, evidence for efficacy is lacking, and the effect of these agents on long-term outcomes is unknown.

HYPOTHESIS

In extremely preterm babies, restricting the use of dopamine when mean blood pressure (BP) values fall below a nominal threshold and using clinical criteria to determine escalation of support ('restricted' approach) will result in improved neonatal and longer-term developmental outcomes. RESEARCH PLAN: In an international multi-centre randomised trial, 830 infants born at <28 weeks of gestation, and within 72 h of birth, will be allocated to 1 of 2 alternative treatment options (dopamine vs. restricted approach) to determine the better strategy for the management of BP, using a conventional threshold to commence treatment. The first co-primary outcome of survival without brain injury will be determined at 36 weeks' postmenstrual age and the second co-primary outcome (survival without neurodevelopmental disability) will be assessed at 2 years of age, corrected for prematurity.

DISCUSSION

It is essential that appropriately designed trials be performed to define the most appropriate management strategies for managing low BP in extremely preterm babies.

Novel mRNA isoforms and mutations of uridine monophosphate synthetase and 5-fluorouracil resistance in colorectal cancer

The drug fluorouracil (5-FU) is a widely used antimetabolite chemotherapy in the treatment of colorectal cancer. The gene uridine monophosphate synthetase (UMPS) is thought to be primarily responsible for conversion of 5-FU to active anticancer metabolites in tumor cells. Mutation or aberrant expression of UMPS may contribute to 5-FU resistance during treatment. We undertook a characterization of UMPS mRNA isoform expression and sequence variation in 5-FU-resistant cell lines and drug-naive or -exposed primary and metastatic tumors. We observed reciprocal differential expression of two UMPS isoforms in a colorectal cancer cell line with acquired 5-FU resistance relative to the 5-FU-sensitive cell line from which it was derived. A novel isoform arising as a consequence of exon skipping was increased in abundance in resistant cells. The underlying mechanism responsible for this shift in isoform expression was determined to be a heterozygous splice site mutation acquired in the resistant cell line. We developed sequencing and expression assays to specifically detect alternative UMPS isoforms and used these to determine that UMPS was recurrently disrupted by mutations and aberrant splicing in additional 5-FU-resistant colorectal cancer cell lines and colorectal tumors. The observed mutations, aberrant splicing and downregulation of UMPS represent novel mechanisms for acquired 5-FU resistance in colorectal cancer.

Differential hemodynamic effects of levosimendan in a porcine model of neonatal hypoxia-reoxygenation

BACKGROUND

Neonatal asphyxia can be complicated by myocardial dysfunction with secondary alterations in pulmonary and regional hemodynamics. Levosimendan is a calcium-sensitizing inotrope that may support cardiac output, but little is known regarding its differential hemodynamic effects in asphyxiated neonates.

METHODS

Mixed breed piglets (1-4 days old, weight 1.6-2.3 kg) were acutely instrumented. Normocapnic alveolar hypoxia (10-15% oxygen) was induced for 2 h, followed by reoxygenation with 100% (1 h) and then 21% oxygen (3 h). At 2 h of reoxygenation, after volume loading (Ringer's lactate 10 ml/kg), either levosimendan (0.1 or 0.2 μg/kg/min) or D(5)W (placebo) was infused for 2 h in a blinded, block-randomized fashion (n = 7-8/group). The systemic, pulmonary and regional (carotid, superior mesenteric and renal) hemodynamics were compared.

RESULTS

At 0.1 and 0.2 μg/kg/min, levosimendan significantly increased cardiac output (121 and 123% of pretreatment, respectively) and heart rate, and decreased systemic vascular resistance without causing hypotension. Pulmonary arterial pressure and estimated pulmonary vascular resistance were significantly increased from pretreatment baseline in 0.1 but not 0.2 μg/kg/min levosimendan. Levosimendan infusion had no effects on regional hemodynamics. Myocardial efficiency but not oxygen consumption increased with 0.1 μg/kg/min levosimendan without significant effects on plasma troponin and myocardial lactate levels.

CONCLUSIONS

In newborn piglets following hypoxia-reoxygenation injury, levosimendan improves cardiac output but has no marked effects in carotid, superior mesenteric and renal perfusion. It appears that various doses of levosimendan increase the cardiac output through different mechanisms. Further investigations are needed to examine the effectiveness of levosimendan as a cardiovascular supportive therapy either alone or in conjunction with other inotropes in asphyxiated neonates.

Id-1 induces cell invasiveness in immortalized epithelial cells by regulating cadherin switching and Rho GTPases

Epithelial-mesenchymal transition (EMT), characterized by cadherin switching, contributes to cancer metastasis. Our recent study showed that Id-1 (inhibitor of differentiation-1) promotes metastasis in esophageal cancer cells, but whether the invasive and metastatic dynamics can be induced early in the carcinogenesis process is still unclear. Immortalization is regarded as the initial stage in the malignant transformation of normal cells. In this study, we investigated the role and mechanisms of Id-1 in inducing EMT and cell invasiveness in immortalized esophageal epithelial cells. We found that immortalized epithelial cells expressed higher endogenous levels of Id-1 compared with normal cells. Ectopic Id-1 expression inhibited the differentiation of immortalized esophageal epithelial cells and promoted cadherin switching, which was accompanied by increased adhesiveness to extracellular matrix, cell motility, migratory potential and matrix metalloproteinase-dependent invasiveness. GTPase activity assays showed that over-expression or short-hairpin RNA knockdown of Id-1 led to corresponding changes in Rac1 activity, whereas RhoA activity was significantly decreased with Id-1 depletion. Inhibitors targeting Rac1, RhoA, and Rho kinase suppressed the invasiveness of Id-1-expressing NE2-hTERT cells. Knockdown of N-cadherin in Id-1-over-expressing cells inhibited cell invasiveness and down-regulated RhoA activity. These data suggest that the Id-1-induced invasive potential may be regulated through the N-cadherin-RhoA axis and Rac1 activation.

Application of BAX system, Tecra Unique Salmonella test, and a conventional culture method for the detection of Salmonella in ready-to-eat and raw foods

AIMS

To compare the BAX system, the Tecra Unique Salmonella test, and a conventional culture method for the detection of Salmonella in various foods.

METHODS AND RESULTS

Ready-to-eat and raw foods were inoculated with Salmonella serotype Typhimurium, Salmonella serotype Enteritidis, Salmonella serotype Typhi, or Salmonella serotype Derby. Incubated pre-enrichment cultures were examined using the BAX system, the Tecra Unique Salmonella test, and a conventional culture method. Salmonella could be detected in all ready-to-eat food samples inoculated with S. Typhimurium, S. Enteritidis, or S. Derby, with any of the three test methods. However, false negatives were obtained with the Tecra test and the culture method when samples with higher background flora were inoculated with S. Typhi. Sensitivity test results suggested the two rapid tests performed as well as the culture method in the detection of 10(1) CFU of S. Typhimurium in 25-g cooked or raw food.

CONCLUSIONS

The BAX system and the Tecra Unique Salmonella test demonstrated results comparable with those of the culture method in the detection of Salmonella serotypes used except S. Typhi.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first evaluation of the BAX system, the Tecra Unique Salmonella test, and a culture method in the detection of Salmonella in a variety of western and oriental foods.

Evaluation of two real-time polymerase chain reaction pathogen detection kits for Salmonella spp. in food

AIMS

To evaluate the LightCycler Salmonella Detection Kit and the TaqMan Salmonella Gold Detection and Quantitation Kit for the real-time PCR detection of Salmonella in various food samples.

METHODS AND RESULTS

Ready-to-eat foods and raw food samples were artificially contaminated with Salmonella serotypes. In the specificity test, bacterial DNA extracted from sample pre-enrichment culture was analysed with the detection kits performed respectively on the LightCycler Instrument or the ABI Prism 7000 Sequence Detection System. No false-positive or false-negative results were obtained, although the LightCycler system generated invalid PCR results on two occasions. In the sensitivity test using the LightCycler system, Salmonella could be detected in pre-enrichment cultures of 25-g samples inoculated with as low as 1.5 x 10(3) CFU (depending on food type), and false-negative results were obtained for samples with low inoculum levels.

CONCLUSIONS

Two commercial kits for real-time PCR detection of Salmonella were evaluated.

SIGNIFICANCE AND IMPACT OF THE STUDY

Evaluation using more food types and matrices, and foods that contain low number of Salmonella or high number of other competing bacteria, is needed before adopting the real-time PCR technique for routine food tests.

Inhaled nitric oxide inhibits the release of matrix metalloproteinase-2, but not platelet activation, during extracorporeal membrane oxygenation in adult rabbits

BACKGROUND/PURPOSE

In neonates receiving extracorporeal membrane oxygenation (ECMO), platelet activation and dysfunction occur with the release of matrix metalloproteinase (MMP)-2, which stimulates platelet aggregation. Because inhaled nitric oxide (NO) reduces pulmonary hypertension and inhibits platelet aggregation, the authors examined the effects of inhaled NO on platelet activation induced by ECMO.

METHODS

Ten adult white New Zealand rabbits were instrumented for ECMO and assigned randomly to receive either inhaled NO at 40 ppm or 30% oxygen for 1 hour before ECMO and continued for 4 hours after starting ECMO. Platelet counts, collagen-induced platelet aggregation ex vivo, plasma MMP-2, and MMP-9 activities were measured.

RESULTS

(1) ECMO caused thrombocytopenia, decreased platelet aggregation, and increased plasma MMP-2 and MMP-9 activities in controls. (2) Inhaled NO inhibited platelet aggregation before ECMO but did not affect the ECMO-induced thrombocytopenia and platelet activation. (3) Inhaled NO significantly abolished the ECMO-induced increase in plasma MMP-2 but not MMP-9 activities.

CONCLUSIONS

Although inhaled NO did not inhibit the platelet activation during ECMO in adult rabbits, it attenuated the increase in plasma MMP-2 activity that may be important for neonates treated with ECMO.

Mycobacterium diversity and pyrene mineralization in petroleum-contaminated soils

Degradative strains of fast-growing Mycobacterium spp. are commonly isolated from polycyclic aromatic hydrocarbon (PAH)-contaminated soils. Little is known, however, about the ecology and diversity of indigenous populations of these fast-growing mycobacteria in contaminated environments. In the present study 16S rRNA genes were PCR amplified using Mycobacterium-specific primers and separated by temperature gradient gel electrophoresis (TGGE), and prominent bands were sequenced to compare the indigenous Mycobacterium community structures in four pairs of soil samples taken from heavily contaminated and less contaminated areas at four different sites. Overall, TGGE profiles obtained from heavily contaminated soils were less diverse than those from less contaminated soils. This decrease in diversity may be due to toxicity, since significantly fewer Mycobacterium phylotypes were detected in soils determined to be toxic by the Microtox assay than in nontoxic soils. Sequencing and phylogenetic analysis of prominent TGGE bands indicated that novel strains dominated the soil Mycobacterium community. Mineralization studies using [(14)C]pyrene added to four petroleum-contaminated soils, with and without the addition of the known pyrene degrader Mycobacterium sp. strain RJGII-135, indicated that inoculation increased the level of degradation in three of the four soils. Mineralization results obtained from a sterilized soil inoculated with strain RJGII-135 suggested that competition with indigenous microorganisms may be a significant factor affecting biodegradation of PAHs. Pyrene-amended soils, with and without inoculation with strain RJGII-135, experienced both increases and decreases in the population sizes of the inoculated strain and indigenous Mycobacterium populations during incubation.

Differential expression of matrix metalloproteinases and the tissue inhibitor in human milk

There are differences in the temporal expression of MMP-2 and TIMP-4 in human milk from Day 1 to 30 postpartum in healthy mothers of term pregnancies: (i) MMP-2 activity peaked at Day 1 (colostrum) then exponentially decreased afterwards; and (ii) The expression of TIMP-4 was maximal at Day 7 and persisted thereafter. From our preliminary findings, the differential expression of MMP and the tissue inhibitor in human milk may be related to the protective action of human milk.

Effects of a continuous epinephrine infusion on regional blood flow in awake newborn piglets

OBJECTIVE

To determine the effects of a continuous epinephrine infusion on renal and mesenteric blood flow in both healthy newborn piglets and animals subjected to hemorrhagic shock.

METHODS

Superior mesenteric artery (SMA) and left renal artery ultrasonic flow probes were implanted into 16 1- to 3-day-old piglets. Two days later, the effects of epinephrine on SMA and renal blood flow, mean arterial pressure (MAP) and central venous pressure were measured in conscious, non-sedated normovolemic piglets. Epinephrine doses of 0.2, 0.4, 0.8, 1.6 and 3.2 microg/kg.min were used in random order. Piglets were subsequently hemorrhaged (20 ml/kg) to mild hypotension and again received epinephrine infusion in the same doses.

RESULTS

Doses of epinephrine less than 3.2 microg/kg.min had no significant effects on renal or mesenteric arterial flow. At 3.2 microg/kg.min of epinephrine during normovolemia, there was a significant decrease in SMA blood flow (34% [SD 42], p < 0.05) and increase in SMA vascular resistance (147% [SD 114], p < 0.05). Similar results were shown during hypovolemia, SMA flow decreased by 32% (SD 33), and SMA vascular resistance increased by 220.3% (SD 177). At 3.2 microg/kg.min renal artery flow decreased by 43% (SD 21) during normovolemia and a similar decrease occurred during hypovolemia, 37% (SD 31). Renal vascular resistance increased by about 200% at this dose (normovolemia 211% [SD 185], hypovolemia 186% [SD 150], p < 0.01). Low-to-moderate dose epinephrine caused no significant change in SMA or renal blood flow. During hypovolemia low dose epinephrine infusion was associated with a trend to increased SMA blood flow.

CONCLUSION

Low-dose epinephrine does not cause vasoconstriction in the renal or mesenteric circulations during normovolemia or hypovolemia. High doses of epinephrine above 1.6 microg/kg.min may cause renal or mesenteric ischemia, in either the normovolemic or hypovolemic neonate.

Quantification of recirculation by thermodilution during venovenous extracorporeal membrane oxygenation

PURPOSE

The aim of this study was to determine whether recirculation could be quantified by a thermodilution technique during venovenous (VV) extracorporeal membrane oxygenation (ECMO) in a rabbit model.

METHODS

Five New Zealand white rabbits, mean weight, 4.5 (range, 3.7 to 5.7) kg, were anesthetized, instrumented, cannulated with a double-lumen catheter, and placed on VV ECMO. Serial injections of ice-cold saline were performed at the arterial arm of the circuit, and the resultant temperature change at various pump flows was measured at the venous arm of the circuit using a thermistor-tipped catheter and a cardiac output computer. Results were compared with the respective 100% recirculation measured with all the circuit flow passing through the bridge.

RESULTS

Using linear regression, recirculation percentage could be calculated as: 19 + 0.1 x pump flow (R2 = 0.81, P < .005). Recirculation correlated positively with pump flow. Variability between results at each flow was less than 10%.

CONCLUSIONS

Recirculation can be quantified during VV ECMO by measuring the change in temperature in the venous arm using a cardiac output computer after injection of a known quantity of ice-cold saline in the arterial side of the circuit. The effect of interventions to reduce recirculation can be assessed conveniently and reliably.

Glutathione protects against myocardial ischemia-reperfusion injury by detoxifying peroxynitrite

Peroxynitrite (ONOO(-)) formation during acute reperfusion of the ischemic heart contributes to the poor recovery of mechanical function. As glutathione (GSH) detoxifies ONOO(-), we studied whether it could protect isolated rat hearts subjected to exogenous ONOO(-)or to ischemia-reperfusion. We showed that GSH (300 microm, n=5) abolished the detrimental effect of ONOO(-)(80 microm, n=5) on mechanical function of aerobically perfused hearts. Hearts were subjected to 25 min aerobic perfusion, 20 min global, no-flow ischemia and 30 min reperfusion. GSH (3-300 microm, n=7-12) or saline vehicle (control, n=22) were infused for 10 min prior to ischemia and throughout reperfusion. During reperfusion, GSH caused a concentration-dependent improvement in the recovery of mechanical function, which was not associated with significant changes in the intracellular concentration of GSH. The concentration of dityrosine (a marker of ONOO(-) formation) in the coronary effluent during reperfusion was significantly reduced in GSH-treated hearts. The concentration of myocardial cGMP was significantly elevated by GSH during ischemia and early reperfusion. GSH improves the recovery of myocardial mechanical function after ischemia-reperfusion, an effect which may be related to the detoxification of ONOO(-)by GSH and the stimulation of soluble guanylate cyclase.

The mechanisms of platelet dysfunction during extracorporeal membrane oxygenation in critically ill neonates

OBJECTIVE

Although bleeding associated with thrombocytopenia often complicates extracorporeal membrane oxygenation (ECMO), the mechanisms of platelet dysfunction during ECMO remain poorly understood. We investigated the role of matrix metalloproteinase (MMP)-2, which recently has been shown to mediate a novel pathway of platelet aggregation, in the platelet dysfunction induced by ECMO.

DESIGN

Prospective longitudinal case study.

SETTING

Level III neonatal intensive care unit.

PATIENTS

Ten neonates treated with ECMO.

INTERVENTION

ECMO procedure.

MEASUREMENTS

Platelet counts and collagen-induced platelet aggregation ex vivo; plasma markers of platelet (soluble P-selectin) and endothelial (soluble E-selectin and total nitrite/nitrate) activation; plasma MMP-2 and MMP-9 activities; and concentrations of tissue inhibitors of MMPs.

MAIN RESULTS

During ECMO, time-dependent platelet activation, as evidenced by thrombocytopenia, decreased platelet aggregation, and increased plasma soluble P-selectin concentrations were found in the absence of endothelial activation, as shown by normal plasma concentrations of soluble E-selectin and nitric oxide metabolites (nitrite/nitrate). There was a time-dependent increase in plasma MMP-2 but not MMP-9 activity; tissue inhibitors of MMPs were not detected. Plasma soluble P-selectin concentrations significantly correlated with simultaneous plasma MMP-2 (r2 = .37, p < .0001) but not with MMP-9 activities. Platelet dysfunction persisted despite repeated platelet transfusions to maintain platelet counts >100 x 10(9)/L.

CONCLUSIONS

ECMO resulted in the activation of platelets but not endothelial cells. During ECMO, platelet dysfunction persisted despite platelet transfusions. MMP-2 may play a role in the development of platelet dysfunction caused by ECMO.

Matrix metalloproteinase-2 contributes to ischemia-reperfusion injury in the heart

BACKGROUND

Matrix metalloproteinases (MMPs) contribute to collagen degradation and remodeling of the extracellular matrix after myocardial infarction; however, their role in myocardial dysfunction immediately after ischemia and reperfusion is unknown.

METHODS AND RESULTS

We measured the release of MMPs into the coronary effluent of isolated, perfused rat hearts during aerobic perfusion and reperfusion after ischemia. Aerobically perfused control hearts expressed pro-MMP-2 and MMP-2, as well as an unidentified 75-kDa gelatinase. These enzymes were also detected in the coronary effluent. After 20 minutes of global no-flow ischemia, there was a marked increase in pro-MMP-2 in the coronary effluent that peaked within the first minute of reperfusion. The release of pro-MMP-2 into the coronary effluent during reperfusion was enhanced with increasing duration of ischemia and correlated negatively with the recovery of mechanical function during reperfusion (r(2)=0.99). MMP-2 antibody (1.5 to 15 microg/mL) and the inhibitors of MMPs doxycycline (10 to 100 micromol/L) and o-phenanthroline (3 to 100 micromol/L) improved whereas MMP-2 worsened the recovery of mechanical function during reperfusion.

CONCLUSIONS

These results show that acute release of MMP-2 during reperfusion after ischemia contributes to cardiac mechanical dysfunction. The inhibition of MMPs may be a novel pharmacological strategy for the treatment of ischemia-reperfusion injury.

The hemodynamic effects of inhaled nitric oxide and endogenous nitric oxide synthesis blockade in newborn piglets during infusion of heat-killed group B streptococci

OBJECTIVE

To determine the effects of therapy with inhaled nitric oxide (NO) gas and partial or complete blockade of endogenous NO synthesis with N(omega)nitro-L-arginine (L-NA) on the hemodynamic responses to group B streptococci infusion in newborn piglets.

DESIGN

Randomized, acute intervention study.

SETTING

Animal research laboratory.

SUBJECTS

Twenty-five anesthetized piglets younger than 3 days of age divided into five groups.

INTERVENTIONS

Heat-killed group B streptococci (GBS) were infused systemically until a 50% increase in pulmonary artery pressure (PAP) was obtained, and the infusion was continued for another 2 hrs. The five groups were designed as follows: group 1, sepsis control: continuous GBS infusion, with two brief trials (10 mins) of inhaled NO given after the initial development of pulmonary hypertension and again 2 hrs later; group 2, continuous inhaled NO: NO was given at 40 ppm for 2 hrs during GBS infusion; group 3, high-dose L-NA pretreatment: 10 mg/kg L-NA bolus followed by 1 mg/kg/min before, and continuing throughout, GBS infusion; group 4, high-dose L-NA: same dose as in group 3, but given after the start of the GBS infusion with continuous inhaled NO at 40 ppm; and group 5, low-dose L-NA: 3 mg/kg bolus given after start of GBS infusion with continuous inhaled NO at 40 ppm.

MEASUREMENTS AND MAIN RESULTS

The sepsis controls, group 1, had an increase in PAP, which took 15-45 mins to develop, from a mean of 3.4 (SD 0.7) to 5.9 (1.9) kPa (p < .05), at which time the cardiac index had decreased from 169 (28) to 146 (46) mL/kg/min (p < .05). Brief inhaled NO during the early phase decreased PAP to normal. Two hours later, PAP had increased to 6.1 (0.2) kPa and cardiac index had decreased to 88 (31) mL/kg/min. Inhaled NO after 2 hrs decreased PAP to 3.2 (0.5) kPa and increased cardiac index to 106 (44) ml/kg/min (p < .05). Continuous inhaled NO (group 2) ameliorated the deterioration in cardiac index, which at 2 hrs was 140 (30) mL/kg/min (significantly greater than in the sepsis controls) (p < .05). The L-NA-pretreated animals (group 3) had a greater increase in PAP and pulmonary vascular resistance index when GBS infusion was started. PAP increased from 3.0 (0.7) to 7.3 (1.5) kPa within 15 mins, and cardiac index simultaneously decreased to 68 (20) mL/kg/min. Cardiac index subsequently rapidly deteriorated to 48 (21) mL/kg/min, and only one of five animals survived for 2 hrs. Group 4 animals also developed a rapid deterioration in cardiac output, and only two of five survived for 2 hrs. Group 5 animals had results indistinguishable from group 2 animals.

CONCLUSION

Pulmonary hypertension and shock resulting from GBS infusion in newborn piglets are much worse if endogenous NO production is completely inhibited. Continuous inhaled NO with or without low-dose L-NA inhibits the decrease in cardiac output.

Recognition of protein substrates by protein-disulfide isomerase. A sequence of the b' domain responds to substrate binding

Refolding of partially folded mitochondrial malate dehydrogenase (mMDH) is assisted by protein-disulfide isomerase (PDI). The addition of a 20-fold molar excess of PDI over denatured protein (0. 1 microM) accelerates the recovery of catalytic activity. PDI fluorescence measurements show that 1 mol of PDI binds 1 mol of denatured mMDH when their concentrations approach 1 microM. The binding of PDI, derivatized with the fluorescence probe iodoacetamide fluorescein, to partially folded mMDH is characterized by a dissociation constant of 0.2 microM. It is shown that the fluorescence probe is covalently attached to a SH residue located in the b' domain. Based on the fluorescence measurements of native and derivatized PDI, it is suggested that recognition of the unfolded substrate involves conformational changes propagated to several domains of PDI.

Tonometry to estimate intestinal perfusion in newborn piglets

AIM

To determine the correlation between gastric intramucosal pH and superior mesenteric artery (SMA) flow in newborn piglets.

METHODS

Fourteen newborn piglets were randomly assigned to either a control or to an epinephrine group which received 0,1,2,4,0 microg/kg/min of epinephrine for 60 minutes, each dose. Gastric tonometry was performed, SMA flow was measured, and intramucosal pH and the ratio of tonometer pCO(2) over arterial pCO(2) (rCO(2)) were calculated.

RESULTS

Intramucosal pH decreased over time in both groups, but tended to be lower in the epinephrine group. With increasing dose of epinephrine, SMA flow decreased; this in turn increased rCO(2) (p = 0.04) with a tendency to decrease intramucosal pH (p = 0.06).

CONCLUSIONS

Gastric tonometry may be useful in human neonates to evaluate gut ischaemia.

Prolonged use of pancuronium bromide and sensorineural hearing loss in childhood survivors of congenital diaphragmatic hernia

Sensorineural hearing loss (SNHL) is a significant neurologic morbidity in survivors of neonatal congenital diaphragmatic hernia (CDH), with a reported incidence of up to 60%. In a historical cohort study of 37 neonates with CDH, we investigated the use of pancuronium bromide (PB) and common ototoxic drugs during the neonatal period and their relationship to SNHL in childhood survivors. Survivors with SNHL (n = 23) had significantly higher cumulative dose of PB administered during the neonatal illness than survivors without SNHL (n = 14). The cumulative dose and duration of PB use significantly correlated (r = 0.66-0.81) and independently predicted (adjusted r (2) = 0.42-0.64) the greatest intensity (in decibels) and the widest band (lowest frequency in hertz) loss of SNHL. No differences were identified between survivors with and without SNHL regarding demographic and neonatal characteristics (including oxygenation and ventilation variables and the cumulative dose and duration of therapy with aminoglycosides, vancomycin, and furosemide), although survivors with SNHL had received a modestly higher cumulative dose of ethacrynic acid than survivors without SNHL. Although we show that prolonged administration of PB during the neonatal period is associated with SNHL in childhood survivors of CDH, further multicenter studies are required to investigate the possible etiologies of SNHL in this high-risk population.

The hemodynamic effects of dobutamine infusion in the chronically instrumented newborn piglet

OBJECTIVE

To determine the systemic, pulmonary, mesenteric, and renal hemodynamic effects of short and prolonged infusions of dobutamine.

DESIGN

Prospective randomized unblinded study.

SETTING

University research laboratory.

SUBJECTS

Thirteen newborn (1-3 days old) piglets.

INTERVENTIONS

Piglets were instrumented and studied 48 hrs later. Fifteen-minute infusions of dobutamine at 5, 10, 20 and 50 microg/ kg x min were randomly given with 15-min rests between the doses. After a 1-hr hiatus, a dose of 10 microg/kg x min was continuously administered for 2 hrs.

MEASUREMENTS AND MAIN RESULTS

Systemic and pulmonary arterial pressures, cardiac index (thermodilution), and superior mesenteric and renal artery flows were measured. Vascular resistance values were calculated.

MAIN RESULTS

Fifteen-minute infusions: Dobutamine dose-dependently increased cardiac index with tachycardia but not stroke volume (from 187 +/- 43 to 238 +/- 51 mL/kg x min at baseline and 50 microg/ kg x min, respectively, p < .05; values expressed as mean +/- SD). Systemic, but not pulmonary, vascular resistance decreased, resulting in a significant decrease in systemic to pulmonary arterial pressure ratio (from 3.8 +/- 0.8 at baseline to 3.2 +/- 1.0 at 50 microg/ kg x min). Superior mesenteric and renal flows were not affected. Two-hour infusion at 10 microg/kg x min: Cardiac index progressively increased from 173 +/- 34 to 240 +/- 58 mL/kg x min at baseline and 120 mins, respectively, (p < .05). The initial tachycardia was transient, and stroke volume was significantly increased at 60 mins and thereafter. Although systemic and pulmonary vascular resistance values fell simultaneously, systemic to pulmonary arterial pressure ratio decreased significantly to 3.4 +/- 0.9 at 120 mins from 3.9 +/- 0.7 at baseline. Superior mesenteric and renal artery flows increased significantly with vasodilation after 60 mins.

CONCLUSIONS

Short infusions of dobutamine dose-dependently increase cardiac output due to tachycardia, without significant effect on mesenteric and renal blood flows. Prolonged infusion of dobutamine at 10 microg/kg x min progressively increases cardiac output and stroke volume with transient tachycardia, and increases mesenteric and renal blood flows. Caution is required in the treatment of critically ill neonates with dobutamine, which could also reduce systemic to pulmonary arterial pressure ratio.

Refolding of thioredoxin reductase assisted by groEL and PDI

Thioredoxin reductase was unfolded in 2 M guanidine hydrochloride as revealed by fluorescence and CD spectroscopy. Spontaneous refolding of denatured species resulted in low recovery of 10% catalytic activity after 4 h incubation at 25 degrees C. Addition of groEL or protein disulfide isomerase to the renaturation buffer accelerated the rate of recovery of catalytic activity to a level of 35 and 15%, respectively. Fluorescence spectroscopy has been used to investigate the interaction of groEL and protein disulfide isomerase with denatured thioredoxin reductase tagged with a fluorescent probe. The fluorescence emitted by the denatured protein was quenched upon binding to either groEL or protein disulfide isomerase. It is suggested that encapsulation of the protein substrate by the chaperone plays an important role in the process of folding by facilitating the formation of correctly folded species.

Early childhood neurodevelopment in very low birth weight infants with predischarge apnea

Apnea commonly occurs in preterm infants and may persist beyond term. We prospectively investigated the relationship between apnea that persisted beyond 35 weeks post-conceptional age and subsequent neurodevelopment in early childhood. Between January, 1990-November, 1993, we performed predischarge respiratory recordings, using 24-hr, 4-channel pneumography, at 35 weeks or more of postconceptional age in 164 infants (birth weight, <1,250 g; gestational age, < or = 32 weeks), who subsequently underwent multidisciplinary neurodevelopmental assessment at 15-64 (median 24) months of adjusted age. The duration of initial artificial ventilation for respiratory distress syndrome and the grade of intraventricular hemorrhage were independent predictors of neurodevelopmental outcome. Mean oximetry desaturation and frequency of predischarge apnea correlated with mental and motor developmental scores. Mean oximetry desaturation during apnea was an independent predictor for motor score in the total population, and for both mental and motor scores in 50 infants with grade 3 or 4 intraventricular hemorrhage, but not in 114 infants without grade 3 or 4 intraventricular hemorrhage. Despite its limited predictability for early childhood neurodevelopment, predischarge respiratory recordings may be useful in predicting subsequent neurodevelopment of high-risk preterm infants, especially those with severe intraventricular hemorrhage.

The outcome of very low birth weight neonates (</=1500 g) rescued by inhaled nitric oxide: neurodevelopment in early childhood

Although inhaled nitric oxide (INO) improves oxygenation in critically ill neonates, the neurodevelopmental outcome of premature neonates with severe hypoxemic respiratory failure treated with INO has not been reported. Mortality and prospective neurodevelopmental assessment in early childhood were studied in a cohort of 24 very low birth weight neonates (</=1500 g) consecutively admitted from 1993 to 1997 and rescued with INO because of severe hypoxemic respiratory failure (oxygenation index 28 to 52) unresponsive to aggressive conventional treatment. Significant improvements in arterial oxygen tension and oxygenation index with lower inspired oxygen concentration and less ventilator support after initiating INO were observed (P <.05, analysis of variance). Despite the dramatic improvement in systemic oxygenation, the mortality rate was high (14 of 24, 58%). Only 6 of 23 had normal cranial ultrasonographies. At 13 to 40 (22 +/- 10) months of adjusted age, 10 survivors had Bayley Scales mental and psychomotor developmental indexes of 81 +/- 21 and 64 +/- 22, respectively. Of the 10 children, 5 (50%) were disabled, 2 (20%) were developmentally delayed, and 3 (30%) had normal development. In view of the poor outcome in very low-birth-weight neonates rescued by INO, randomized controlled trials are required to examine the role of INO in premature neonates. Before, during, and after INO therapy, cranial ultrasonography is recommended.

High prevalence of sensorineural hearing loss among survivors of neonatal congenital diaphragmatic hernia. Western Canadian ECMO Follow-up Group

OBJECTIVE

This study aimed to determine the prevalence of sensorineural hearing loss (SNHL) in 2-5-year-old survivors with neonatal respiratory failure due to congenital diaphragmatic hernia (CDH) with or without the need for extracorporeal membrane oxygenation (ECMO).

STUDY DESIGN

The study design was a prospective, multicenter, longitudinal outcome study of consecutively surviving neonates admitted to a single tertiary intensive care unit.

SETTING

The study was conducted at four audiologic departments affiliated with tertiary-level intensive care follow-up programs.

PATIENTS

Thirty-seven surviving children receiving neonatal intensive care from February 1989 through January 1995 for neonatal respiratory failure due to CDH were studied. Excluded were 15 children with early death and I child lost to follow-up.

INTERVENTION

The initial treatment depended on the severity of neonatal respiratory failure: ECMO-treated (n=31, 20 survivors) (death before ECMO initiation, 2) and non-ECMO treated (n=20, 17 survivors, another survivor lost to follow-up).

MAIN OUTCOME MEASURE

Early childhood audiologic test results were measured.

RESULTS

Sensorineural hearing loss was found in almost 60% of subjects: ECMO-treated, 12 (60%) of 20; non-ECMO-treated, 10 (59%) of 17. Of the 22 children with SNHL, 16 had mild- to-moderate low-frequency sloping to moderate-to-severe high-frequency loss. Of the remaining, six had severe-to-profound loss at 500 Hz and above. Seventeen children had normal responses to sound as newborns or in infancy. Five children were not tested. Documented progression was found in nine children. Twenty children currently are using amplification, and 2 have had cochlear implantation.

CONCLUSIONS

Of children with CDH in this area presenting early with severe neonatal respiratory failure, SNHL developed in 60% by 2-5 years of life. Ongoing monitoring of the hearing status of children with CDH is imperative.

Comparative study of mortality and morbidity in premature infants (birth weight, < 1,250 g) with candidemia or candidal meningitis

Little information is available on long-term neurodevelopment of premature neonates with invasive candidal infections. We retrospectively studied the outcomes for 25 premature neonates (birth weight, < 1,250 g) with candidemia or candidal meningitis (cases) and compared them with 25 neonates matched for birth weight (+/- 100 g) and gestational age (+/- 1 week) (controls). Durations of antibiotic therapy, artificial ventilation, invasive catheterizations, and hyperalimentation were longer for cases than for controls. Cases had a higher final grade of intraventricular hemorrhage than did controls (median: 3.0 vs. 2.5, respectively; P < .05). Forty-four percent (11 of 25) of cases and 16% (4 of 25) of controls died (P > .05), and 29% (4 of 14) of surviving cases and 14% (3 of 21) of controls were disabled (P > .05). More cases had combined mortality and neurodevelopmental disabilities than did controls (60% vs. 28%, respectively; P < .05). Use of invasive therapies should be minimized for premature neonates at risk for invasive candidal infection that is associated with adverse outcomes.

Temporal effects of prolonged hypoxaemia and reoxygenation on systemic, pulmonary and mesenteric perfusions in newborn piglets

OBJECTIVE

Temporal effects of prolonged hypoxaemia and reoxygenation, on the systemic pulmonary and mesenteric circulations in newborn piglets, were investigated.

METHODS

Two groups [control (n = 5), hypoxaemic (n = 7)] of 1-3 day old anaesthetised piglets were instrumented with ultrasound flow probes placed to measure cardiac, hepatic arterial flow and portal venous flow indices, and catheters inserted for measurements of systemic and pulmonary arterial pressures. Hypoxaemia with arterial oxygen saturation 40-50% was maintained for 3 h, followed by reoxygenation with 100% inspired oxygen.

RESULTS

Cardiac index was transiently elevated at 30-60 min of hypoxaemia (23% increase from baseline 158 +/- 39 ml/kg/min), along with increases in stroke volume but not heart rate. A significant decrease in systemic vascular resistance after 30 min of hypoxaemia was followed by hypotension at 180 min of hypoxaemia. Progressive pulmonary hypertension with significant vasoconstriction was found after 30 min of hypoxaemia. The hypoxaemic mesenteric vasoconstriction was transient with a 37% decrease in portal venous flow index at 15 min of hypoxaemia (29 +/- 12 vs. 46 +/- 18 ml/kg/min of baseline, p < 0.05). The hepatic arterial to total hepatic oxygen delivery ratio increased significantly during hypoxaemia. In contrast to the significant increase in systemic oxygen extraction throughout hypoxaemia, elevation in mesenteric oxygen extraction decreased after 30 min of hypoxaemia associated with modest decreases in oxygen consumption. Following reoxygenation, the pulmonary hypertension was partially reversed. Cardiac index decreased further (130 +/- 39 ml/kg/min) with reduced stroke volume, persistent systemic hypotension and decreased systemic oxygen delivery.

CONCLUSIONS

We demonstrated differential temporal changes in systemic, pulmonary and mesenteric circulatory responses during prolonged hypoxaemia. Cautions need to be taken upon reoxygenation because the neonates are at risk of developing myocardial stunning, persistent pulmonary hypertension and necrotising enterocolitis.

Thiols protect the inhibition of myocardial aconitase by peroxynitrite

Peroxynitrite (ONOO-) is a potent inhibitor of myocardial aconitase. Because ONOO- reacts with sulfhydryl moieties, we investigated whether thiols protect against ONOO(-)-mediated inhibition of aconitase. Aconitase activity was examined in ventricular homogenates prepared from freshly isolated rat hearts. Peroxynitrite, but not the nitric oxide donor S-nitroso-N-acetyl-d,l-penicillamine (0.03-300 microM), inhibited aconitase activity (IC50 = 47 +/- 6 microM). L-Cysteine (0.03-3 mM), glutathione (0.03-3 mM), and N-(2-mercaptoproprionyl)-glycine (MPG, 0.1-3 mM) protected against the inhibitory effect of ONOO- (100 microM) with the rank order of potency of MPG > glutathione > L-cysteine. D-Cysteine (3 mM) had a protective effect similar to L-cysteine, but L-cystine, the oxidized form of L-cysteine, offered no protection. Ferrous ammonium sulfate (1 mM) markedly enhanced the protection provided by L-cysteine, but not by glutathione or MPG. Thiols protect myocardial aconitase against inhibition by ONOO- in a manner which is sulfhydryl group dependent and not stereospecific. The protection is related to the maintenance of the redox state of the iron-sulfur cubane cluster and cysteine residues at the active site of the enzyme. Both naturally occurring thiols and thiol-based drugs may be useful to protect the heart during ischemia-reperfusion injury where there is an excessive production of ONOO-.

Nitric oxide and platelet function: implications for neonatology

Nitric oxide (NO) is a mediator that modulates vessel wall tone and hemostatic-thrombotic balance. Platelet function is regulated by NO generated from platelets, endothelial cells and leukocytes. Nitric oxide has been shown to inhibit platelet adhesion, aggregation, and stimulate disaggregation of preformed platelet aggregates. Many of the effects of NO are mediated by its stimulation of guanylate cyclase and the formation of cyclic GMP and its subsequent transduction mechanism. In vivo, NO is likely to interact with prostacyclin, metabolites of ecto-nucleotidase, and lipoxygenase to modulate platelet function in a synergistic manner. An imbalance of NO production (deficiency or overproduction) has been implicated in the pathogenesis of various vascular disorders including thrombosis, atherosclerosis, septicemia, and ischemia-reperfusion injury. It is likely that some of detrimental effects of NO are mediated through its reaction with superoxide anion to form the potent oxidant, peroxynitrite. Nitric oxide gas and NO donors are used for the pharmacological treatment of various vascular disorders. Because inhaled NO has been documented to improve systemic oxygenation and reduce the need for extracorporeal membrane oxygenation, it has been widely used in neonates with severe hypoxemia. An inhibition of platelet function, resulting in a prolonged bleeding time, has been shown in adults receiving inhaled NO. Because bleeding complications may occur in high-risk infants, it is important to evaluate the effect of inhaled NO on platelet function and its correlation with clinical consequences such as intracranial hemorrhage. For these reasons, hemostasis should be carefully monitored during the administration of inhaled NO to critically ill neonates.

Glutathione causes coronary vasodilation via a nitric oxide- and soluble guanylate cyclase-dependent mechanism

The actions of thiols on coronary vascular tone in the intact heart are unknown. Glutathione (GSH), glutathione disulfide (GSSG), and L-cysteine (10-1,000 microM each) and GSH ethyl ester (3-300 microM) were infused into isolated rat hearts perfused with Krebs buffer at a constant pressure by the Langendorff method. GSH, GSSG, and GSH ethyl ester, but not L-cysteine, caused a concentration-dependent increase in coronary flow with the following order of potency: GSH ethyl ester > GSH = GSSG. The nitric oxide synthase inhibitor NG-monomethyl-L-arginine (300 microM), prevented the increase in coronary flow with GSH and attenuated that with GSSG (300 microM each). The vasodilation with GSH or GSSG and the associated increase in myocardial guanosine 3',5'-cyclic monophosphate were abolished by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (a specific inhibitor of soluble guanylate cyclase) at 1 and 3 microM, respectively. The vasodilator action of GSH was abolished by superoxide dismutase (50 U/ml). Inhibition of GSH reductase abolished GSSG-induced vasodilation. Neither glibenclamide (1 microM) nor indomethacin (4 microM) affected the vasodilator action of GSH and GSSG. We conclude that GSH and GSSG cause coronary vasodilation that is mediated by a nitric oxide- and guanylate cyclase-dependent mechanism, possibly mediated by the reaction between GSH and peroxynitrite to form S-nitrosoglutathione, a nitric oxide donor.

The role of tyrosine phosphorylation in lipopolysaccharide- and zymosan-induced procoagulant activity and tissue factor expression in macrophages

The expression of surface procoagulants by exudative macrophages represents an important mechanism underlying local fibrin deposition at sites of extravascular inflammation. The present studies investigated the contribution of tyrosine phosphorylation to the generation of macrophage procoagulant activity (PCA) and tissue factor expression in response to proinflammatory stimuli. Both lipopolysaccharide (LPS) and zymosan rapidly stimulated tyrosine phosphorylation in elicited murine peritoneal macrophages. This effect was prevented by the tyrosine kinase inhibitors genistein and herbimycin and augmented by the addition of the phosphotyrosine phosphatase inhibitor vanadate. The vanadate-mediated rise in phosphotyrosine accumulation was abrogated by the use of diphenylene iodonium, an inhibitor of the respiratory burst oxidase, suggesting a role for peroxides of vanadate as contributors to the tyrosine phosphorylation. This notion was supported by the finding that vanadyl hydroperoxide markedly increased the accumulation of phosphotyrosine residues. To define the role of tyrosine phosphorylation in the induction of macrophage PCA by LPS, the effects of tyrosine kinase inhibition by genistein and herbimycin were investigated. Both agents inhibited the expression of macrophage PCA. Further, Northern blot analysis with the cDNA probe for murine tissue factor indicated that the inhibition occurred at the mRNA level or earlier. Since vanadate augmented phosphotyrosine accumulation, it was hypothesized that it might enhance generation of macrophage products. However, vanadate reduced induction of PCA in response to LPS. By contrast, vanadate augmented basal prostaglandin E2 (PGE2) release and stimulated PGE2 release by macrophages. Indomethacin prevented the increase in PGE2 but only partially restored normal levels of PCA. The effect of vanadate on tissue factor expression appeared to be posttranscriptional. These studies thus demonstrate, by functional Western blotting and Northern blotting techniques, that tyrosine phosphorylation plays a role in the regulation of macrophage PCA and tissue factor expression in response to proinflammatory stimuli.