Can stroke volume variation be an alternative to central venous pressure in patients undergoing kidney transplantation?

BACKGROUND: Stroke volume variation (SVV) is known to be a simple and less invasive hemodynamic parameter for evaluating fluid responsiveness and preload status. Central venous pressure (CVP) has been targeted to achieve an adequate level for improving the graft perfusion and long-term graft function in kidney transplantation (KT) recipients, despite the various potential complications. The aim of this study was to investigate whether SVV could substitute for CVP in guiding intravascular volume management during KT. METHODS: This retrospective study evaluated 635 patients who underwent KT because of end-stage renal disease. Hemodynamic variables including CVP and SVV were obtained before skin incision (T1), 5 minutes after iliac vein clamping (T2), and 10 minutes after renal graft reperfusion (T3). The ability of SVV to predict CVP level was investigated with receiver operating characteristic (ROC) curve analysis. RESULTS: CVPs were 6.0 ± 2.6, 8.6 ± 2.7, and 9.3 ± 2.5 mm Hg, and SVVs were 6.9 ± 3.0, 5.0 ± 2.1, and 4.3 ± 2.1% at T1, T2, and T3, respectively. ROC analysis showed that the discriminative power of SVV was fairly good with an area under the ROC curve of 0.70 (95% confidence interval, 0.67-0.72) for a CVP of 8 mm Hg, and that an optimal cutoff value of SVV was 6% as an alternative to CVP of 8 mm Hg during KT. CONCLUSIONS: SVV may replace CVP in the volume management of patients who have undergone KT. Our results suggest that SVV can guide volume management to improve graft perfusion at critical time points during KT.

Prediction of fluid responsiveness using dynamic preload indices in patients undergoing robot-assisted surgery with pneumoperitoneum in the Trendelenburg position.

We investigated the abilities of pulse pressure variation (PPV) and stroke volume variation (SVV) to predict fluid responsiveness during robot-assisted laparoscopic prostatectomy, requiring pneumoperitoneum and the Trendelenburg position. In 42 patients without cardiopulmonary disease, PPV and SVV were measured before and after administration of 500 ml colloid under pneumoperitoneum combined with the steep Trendelenburg position (35°). Fluid responsiveness was defined as a ≥15% increase in stroke volume after the fluid loading measured using transoesophageal echocardiography. Of the 42 included patients, 22 were responders and 20 were non-responders. A PPV of ≥9.5% identified responders with a sensitivity of 77.3% and a specificity of 90.0%, and a SVV of ≥9.5% also identified responders with a sensitivity of 77.3% and a specificity of 75.0%. The area under receiver operating characteristic curves for PPV and SVV were 0.87 (P <0.001) and 0.81 (P=0.001), respectively. The findings suggest that both PPV and SVV could be useful predictors of fluid responsiveness in patients without cardiopulmonary disease undergoing robotic laparoscopic surgery with pneumoperitoneum in the Trendelenberg position.

Positive end-expiratory pressure aggravates left ventricular diastolic relaxation further in patients with pre-existing relaxation abnormality.

BACKGROUND: Positive end-expiratory pressure (PEEP) has been known to adversely influence cardiac output. Even though left ventricular (LV) diastolic function significantly contributes to LV performance, the effects of PEEP on LV diastolic function remains controversial. We, therefore, aimed to examine the effects of PEEP on LV diastolic function by use of pulsed wave Doppler tissue imaging in patients with pre-existing LV relaxation abnormality. METHODS: Seventeen patients with peak early diastolic velocity of lateral mitral annulus (E') <8.5 cm s(-1) among patients who underwent coronary artery bypass graft surgery were evaluated. Echocardiographic and haemodynamic variables were measured with 0, 5, and 10 cmH2O of PEEP. E' and deceleration time (DT) of peak early transmitral filling velocity (E) were used as echocardiographic indicators of LV diastolic function. RESULTS: Mean arterial blood pressure decreased during 10 cmH2O PEEP, compared with that during 0 cmH2O PEEP. E' showed a gradual and significant decrease with an incremental increase in PEEP (6.9 ± 0.9, 5.8 ± 0.9, and 5.2 ± 1.2 cm s(-1) during 0, 5, and 10 cmH2O PEEP, respectively), and DT of E was prolonged during 10 cmH2O PEEP, compared with that during 0 cmH2O PEEP. CONCLUSIONS: Increasing PEEP led to a progressive decline in LV relaxation in patients with pre-existing LV relaxation abnormality.

Epilepsy treatment in sub-Saharan Africa: closing the gap.

According to World Health Organization (WHO), the prevalence of epilepsy is highest in low- and lower middle-income countries, which include over eighty percent of the countries of sub-Saharan Africa, where the majority of people with epilepsy are not receiving appropriate care. In sub-Saharan Africa, shortages of trained health workers, limited diagnostic equipment, inadequate anti-epileptic drug supplies, cultural beliefs, and social stigma contribute to the large treatment gap for epilepsy. The number of people with epilepsy, particularly children, will continue to rise as a result of projected epidemiologic and demographic changes. This paper examines the state of epilepsy care and treatment in sub-Saharan Africa and discusses priorities and approaches to scale up access to medications and services for people with epilepsy.

Different expression patterns of Phactr family members in normal and injured mouse brain.

Phosphatase and actin regulators (Phactrs) are a novel family of proteins expressed in the brain, and they exhibit both strong modulatory activity of protein phosphatase 1 and actin-binding activity. Phactrs are comprised of four family members (Phactr1-4), but their detailed expression patterns during embryonic and postnatal development are not well understood. We found that these family members exhibit different spatiotemporal mRNA expression patterns. Phactr4 mRNA was found in neural stem cells in the developing and adult brains, whereas Phactr1 and 3 appeared to be expressed in post-mitotic neurons. Following traumatic brain injury which promotes neurogenesis in the neurogenic region and gliogenesis in the injury penumbra, the mRNA expression of phactr2 and 4 was progressively increased in the injury penumbra, and phactr4 mRNA and protein induction was observed in reactive astrocytes. These differential expression patterns of phactrs imply specific functions for each protein during development, and the importance of Phactr4 in the reactive gliosis following brain injury.

A modification of the trans-oesophageal echocardiography protocol can reduce post-operative dysphagia following cardiac surgery.

Use of intra-operative trans-oesophageal echocardiography (TEE) is an independent risk factor for post-operative dysphagia. This study investigated whether modifying the TEE probe-placement protocol could reduce the incidence of post-operative dysphagia. In group I (n = 100), the TEE probe was inserted after anaesthetic induction and remained in place until the completion of surgery. In group II (n = 100), the TEE probe was inserted after anaesthetic induction, the heart was examined, then the probe was removed. The probe was inserted again before weaning from cardiopulmonary bypass and then immediately removed after examination. The incidence of dysphagia was significantly higher in group I than in group II patients (51.1% versus 28.6%). Multivariate regression analysis showed that the length of time that the TEE probe was in the oesophagus was an independent predictor of dysphagia. Modification of the TEE protocol in this way can reduce the incidence of post-operative dysphagia in cardiac surgery patients.

A retrospective case-control study of intraoperative cardiac dysfunction in elderly patients (≥60 years) undergoing live donor liver transplantation.

BACKGROUND: The age range of patients accepted for the orthotopic liver transplantation (OLT) has widened. Concerns have arisen, therefore, about the ability of the hearts of elderly patients to manage these stressful conditions. The aim of this study was to investigate the preoperative echocardiographic findings and the intraoperative cardiac dysfunction among elderly cirrhotic recipients undergoing live donor OLT. METHODS: In this retrospective case-control study we evaluated clinical data, echocardiography, and intraoperative right-sided heart hemodynamic measurements from 2007 and 2009 among 56 recipients aged at least 60 years who were matched for gender and the severity of cirrhosis. Intraoperative cardiac dysfunction was defined as a decreased left ventricular stroke work index despite an increase in right ventricular end diastolic volume index (RVEDVI) or pulmonary artery occlusion pressure (PAOP). We compared measurements at predetermined times during the anhepatic and neohepatic periods with those at baseline. RESULTS: Older recipients (mean, 63 years; range, 60-69) showed significantly reduced early diastolic annular velocity (E'), early maximal ventricular filling velocity (E)/late filling velocity (A) ratio, and increased A on echocardiography versus younger recipients (mean 48 years; range, 31-56). We observed negative correlation between age and E' (r = -0.44; P < .001) and a positive correlation between age and E/E' (r = 0.31; P < .01). The incidence of intraoperative cardiac dysfunction did not differ between case and control groups with an increase of RVEDVI (11.4% vs 10.6%) or PAOP (27.2% vs 25.0%) during the anhepatic and neohepatic periods. A higher proportion of older recipients needed inotropic agents during OLT (60.7% vs 39.3%; P = .04). CONCLUSIONS: OLT patients of ar least 60 years of age may not show a greater incidence of cardiac dysfunction during OLT versus younger ones, although older recipients showed reduced diastolic function and more frequently required inotropic support.

Preoperative echocardiographic indices associated with elevated brain natriuretic peptide in liver transplant recipients.

BACKGROUND: Cardiac dysfunction may be present in patients with liver cirrhosis. Brain natriuretic peptide (BNP) concentration is a widely used biomarker for heart failure. We evaluated whether elevated BNP reflects cardiac dysfunction, as assessed by preoperative echocardiography, in liver transplant recipients. METHODS: We assessed 122 liver transplant recipients (94 males, 28 females; age, 50 ± 8 years). All underwent preoperative echocardiography, including measurements of heart chamber size, mass, ejection fraction, systolic pressure gradient between right ventricle and right atrium (PGsys [RV - RA]), mitral inflow velocities including early (E) and late (A) transmitral flow velocities, E/A, and deceleration time of E. Tissue Doppler imaging (TDI) was also performed to evaluate systolic (S'), early diastolic (E'), and late diastolic (A') myocardial velocities, E'/A', EAS index: E'/(A' × S'), and E/E'. Univariate and multivariate logistic regression analyses were performed to determine echocardiographic indices for predicting BNP ≥ 100 pg/mL. RESULTS: Of 122 recipients, 87 (71%) had BNP < 100 pg/mL (median, 32.0 pg/mL; interquartile range [IQR], 18.0-50.0), and 35 (29%) had BNP ≥ 100 pg/mL (median, 163.0 pg/mL; IQR, 136.0-479.0). Univariate analysis showed that E (P < .001), PGsys (RV-RA) (P < .001), and E/E' (P = .038) were significantly associated with BNP ≥ 100 pg/mL. Multivariate analysis showed that PGsys (RV - RA) was the only independent predictor of BNP ≥ 100 pg/mL (odds ratio, 1.171; 95% confidence interval, 1.091-1.258; P < .001). CONCLUSION: PGsys (RV - RA) is an echocardiographic index independently associated with BNP ≥ 100 pg/mL, suggesting that elevated BNP in patients with end-stage liver disease may reflect increased pulmonary arterial pressure, rather than systolic and diastolic dysfunction assessed by TDI.

Impact of intravenous lidocaine on myocardial injury after off-pump coronary artery surgery.

BACKGROUND: Lidocaine has been demonstrated to exert cardioprotective effects against myocardial ischaemia and reperfusion injury. We evaluated whether a continuous i.v. infusion of lidocaine reduced myocardial injury in patients undergoing off-pump coronary artery bypass graft surgery (OPCAB). METHODS: In this randomized, double-blinded trial, 99 patients received i.v. lidocaine 2% (i.e. a 1.5 mg kg(-1) bolus at induction of anaesthesia followed by a 2.0 mg kg(-1) h(-1) infusion intraoperatively) or an equal volume of saline. Serum creatine kinase-myocardial band (CK-MB) and troponin I (TnI) concentrations were measured before surgery, upon arrival in the intensive care unit, and at 6, 24, 48, and 72 h after surgery. Cardiac enzymes, other biological markers, and rate of postoperative adverse events were compared between the groups. RESULTS: The median (25-75% inter-quartile range) TnI [0.90 (0.43-1.81) vs 1.71 (0.88-3.02) ng ml(-1), P=0.027] and CK-MB [6.5 (3.9-12.3) vs 9.8 (6.0-18.6) ng ml(-1), P=0.005] concentrations 24 h after surgery were significantly lower in the lidocaine group than in the control group. Moreover, lidocaine infusion reduced the total area under the curve of TnI and CK-MB release after surgery by 42% and 27%, respectively, compared with control. CONCLUSIONS: Continuous i.v. infusion of lidocaine during surgery reduces myocardial injury in patients undergoing OPCAB.

Evaluation of the toxic effect of star fruit on serum biochemical parameters in rats.

The objective of the present study was to evaluate the toxic effect of Averrhoa carambola (star fruit) juice at different storage conditions in Sprague Dawley (SD) rats. Twenty female rats weighing 180 +/- 20 g were randomly assigned into four groups with five rats per group (n = 5). First group served as the control group, fed with distilled water (vehicle). Second, third and fourth groups were orally treated with juice of A. carambola stored for 0, 1 and 3 h respectively for 14 days. Cage-side observations were done daily after each treatment. Body weight, food consumption and water intake were recorded on day-0, day-3, day-7 and day-14. All rats were fasted overnight prior to blood collection through cardiac puncture on day-15. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), urea and creatinine in blood serum were measured. Data were analyzed using Dunnett's test. From the results obtained, there was no lethality found and LD(50) could not be determined. Increment of ALT levels (P<0.05) was reported in those rats treated with A. carambola juice stored for 3 h. On the basis of these results, we can conclude that A. carambola juice stored for 0 hand 1 h are safe to be consumed. However, juice stored for 3 h exerts toxic effect on rat liver at hepatocellular level.

Prophylactic control of post-operative nausea and vomiting using ondansetron and ramosetron after cardiac surgery.

BACKGROUND: The aim of this study was to evaluate the efficacy of ondansetron and ramosetron in the reduction of post-operative nausea and vomiting (PONV) associated with patient-controlled analgesia (PCA) after cardiac surgery. METHODS: A total of 320 patients scheduled for elective cardiac surgery were enrolled. Patients were randomly assigned to one of four treatment regimens (n=80 in each group): no prophylactic antiemetics (group P); intravenous (i.v.) ondansetron 4 mg at the end of surgery and 12 mg added to PCA (group O); i.v. ramosetron 0.3 mg at the end of surgery and no antiemetics added to PCA (group R1); and i.v. ramosetron 0.3 mg at the end of surgery and 0.6 mg added to PCA (group R2). RESULTS: The incidence of PONV during the 48-h post-operative period was lower in groups O (46%), R1 (54%), and R2 (35%) compared with group P (71%, P<0.001). The incidence and severity of nausea were lower in groups O, R1, and R2 than in group P during the 24-h post-operative period, whereas the incidence and severity of nausea during 24-48 h after surgery were lower in groups O and R2, but not in group R1, than in group P. Compared with group P (53%), the frequency of rescue antiemetic usage was significantly lower in groups O (34%) and R2 (29%), but not in group R1 (43%). CONCLUSION: The addition of either ondansetron or ramosetron to PCA can reduce the incidence of PONV during 48 h after cardiac surgery.

Torsades de pointes triggered by severe diastolic hypotension with low hematocrit in the neohepatic stage of liver transplantation: a case report.

We have described herein a 39-year-old male patient with hepatitis B virus-related cirrhosis (Child class C), showing a prolonged corrected QT interval, who developed torsades de pointes (TdP) in the neohepatic stage of liver transplantation (LT). There was no arrhythmia in the pre-anhepatic and anhepatic stages. Multiple premature ventricular complexes, ventricular tachycardia, and TdP suddenly developed at 16 minutes after graft reperfusion without any prodromal arrhythmia; they persisted for 118 seconds. Laboratory tests showed that serum potassium, calcium, and magnesium concentrations of 4.7 mmol/L, 1.05 mmol/L, and 1.85 mg/dL, respectively were within normal ranges. Likely causative factors for TdP in this patient included a prolonged corrected QT interval (553 msec), a low hematocrit (21%), and a low arterial blood pressure (systolic blood pressure, 80-90 mm Hg; diastolic blood pressure; 20-26 mm Hg) in the neohepatic stage. This case demonstrated the importance of optimal maintenance of coronary perfusion, with an adequate hematocrit level and electrolyte concentrations, to prevent the development of TdP in cirrhotic patients with a prolonged corrected QT interval during LT.

Aggravation of mitral regurgitation by calcium administration in a patient with hypertrophic cardiomyopathy during liver transplantation: a case report.

Aggravation of mitral regurgitation (MR) due to left ventricular outflow tract obstruction (LVOTO) is likely to occur during liver transplantation in cirrhotic patients with hypertrophic cardiomyopathy (HCMP). Moreover, calcium administration following severe hypocalcemia due to inadequate citrate metabolism and massive transfusion may induce MR aggravation with LVOTO in such patients. Herein we have described a cirrhotic patient with HCMP in whom MR was aggravated due to LVOTO resulting from inadvertent rapid administration of calcium during liver transplantation.

Association between central venous pressure and blood loss during hepatic resection in 984 living donors.

BACKGROUND: Although low central venous pressure (CVP) anesthesia has been used to minimize blood loss during hepatectomy, the efficacy of this technique remains controversial. We therefore assessed the association between blood loss and CVP during hepatic resection, and examined significant determinants associated with intraoperative hemorrhage during hepatectomy in living donors. METHODS: Between April 2004 and April 2008, 984 living donors who underwent a hepatic resection were assessed retrospectively. Univariate and multivariate analyses were performed to explore the relationships between intraoperative blood loss and several variables including CVP. RESULTS: The mean intraoperative blood loss was 691.3 +/- 365.5 ml. Only four donors required packed red blood cell transfusions (mean, 1.5 U). The mean duration of hepatic resection was 92.1 +/- 26.3 min. The mean, maximum, and minimum values of CVP measured during hepatectomy were 4.6 +/- 1.7, 5.3 +/- 1.8, and 4.0 +/- 1.8 mmHg, respectively, and were not significantly correlated with intraoperative blood loss. On multivariate analysis, predictors of hemorrhage were liver fatty change, gender, and body weight, but none of the mean CVP, surgeons, anesthesiologists, anesthesia duration, resected liver volume, hepatectomy type, systolic blood pressure, heart rate, or body temperature were significant. CONCLUSIONS: CVP during hepatic resection was not associated with intraoperative blood loss in living liver donors, suggesting that CVP may not be an important factor in predicting blood loss during hepatectomy in healthy subjects.

Toxicity study of Orthosiphon stamineus Benth (Misai Kucing) on Sprague Dawley rats.

Orthosiphon stamineus Benth (Family: Lamiaceae) or locally known as Misai Kucing has been widely used in Malaysia for treating kidney problems, gout, and diabetes. This study aims to evaluate the possible toxic effect after following fourteen days oral administration of methanol extract of O. stamineus in female Sprague Dawley (SD) rats. Control groups were treated orally with distilled water (vehicle) while the four test groups were treated up to fourteen days with 0.5 g/kg, 1 g/kg, 3 g/kg and 5 g/kg body weight of methanol extract of O. stamineus respectively. Toxicity of the methanol extract of O. stamineus was evaluated by the incident of lethality, side-cage observation and blood serum biochemical parameters. No lethality or adverse toxic signs were seen during the experimental period. A significant decrease in several serum biochemical parameters i.e. AST and ALT and increase in liver weight was observed in young female SD rat after being fed fourteen days with methanol extract of O. stamineus. No delayed toxic effect and lethality was observed in all rats during fourteen days of recovery period. In conclusion, methanol extract of O. stamineus within these range and treatment duration would not cause any severe toxic effects and organ damages in rats.

Cloning and expression of a novel lipase gene from Bacillus sphaericus 205y.

A Bacillus sphaericus strain (205y) that produces an organic solvent-tolerant lipase was isolated in Port Dickson, Malaysia. The gene for the lipase was recovered from a genomic library and sequenced. Phylogenetic analysis was performed based on an alignment of thirteen microbial lipase sequences obtained from the NCBI database. The analysis suggested that the B. sphaericus lipase gene is a novel gene, as it is distinct from other lipase genes in Families I.4 and I.5 reported so far. Expression in Escherichia coli under the control of the lacZ promoter resulted in an eight-fold increase in enzyme activity after a 3-h induction with 1 mM IPTG. The crude enzyme thus obtained showed a slight (10%) enhancement in activity after a 30-min incubation in 25% (v/v) n-hexane at 37 degrees C, and retained 90% of its activity after a similar period in 25% (v/v) p-xylene.

Nociceptin/orphanin FQ modulation of ionic conductances in rat basal forebrain neurons.

Nociceptin/orphanin FQ (N/OFQ) is an endogenous opioid-like heptadecapeptide that plays an important role in a variety of physiological functions. N/OFQ and its receptor opioid receptor-like orphan receptor-1 are abundant in the diagonal band of Broca (DBB), a basal forebrain nucleus where the loss of cholinergic neurons is linked to memory and spatial learning deficits. In the whole animal, central injections of N/OFQ have been shown to disrupt spatial learning. In this study, we investigated the basis for these behavioral observations by examining the cellular effects of N/OFQ on chemically identified DBB neurons. Whole cell patch-clamp recordings were performed on enzymatically dissociated DBB neurons. Under voltage-clamp conditions, bath application of N/OFQ (10 pM-1 microM) resulted in a dose-dependent depression of whole cell currents. Single cell reverse transcription-polymerase chain reaction analysis identified cholinergic and fewer GABAergic cells to be N/OFQ-responsive. [Nphe(1)]nociceptin-(1-13)-NH(2) and CompB (J-113397) antagonized the N/OFQ response, but both compounds also displayed partial agonist activity. Using a combination of channel blockers we determined that the effects of N/OFQ were mediated via a suite of Ca(2+) (N- and L-type) and Ca(2+)-dependent K(+) (iberiotoxin-sensitive) conductances. In addition, biophysical analysis of voltage subtraction protocols revealed that N/OFQ reduces transient outward and the delayed rectifier K(+) currents. Because N-type and L-type Ca(2+) channels are important in the context of neurotransmitter release, our observations indicate that N/OFQ inhibition of Ca(2+)-dependent conductances in cholinergic neurons would be expected to result in depression of acetylcholine release, which may explain the behavioral actions of N/OFQ in the brain.

Magnolol attenuates peroxidative damage and improves survival of rats with sepsis.

Reactive oxygen species and peroxidative damage are implicated in the pathophysiology of sepsis. Magnolol is a compound extracted from the Chinese medicinal herb Magnolia officinalis and has multiple pharmacological effects, notably antioxidant functions. To determine whether magnolol can modulate the course of sepsis, survival rate and biochemical parameters were analyzed in rats with sepsis with various treatment protocols. Magnolol at doses ranging from 10(-9) g/kg to 10(-5) g/kg was administered either before or after induction of sepsis by cecal ligation and puncture. Magnolol did not modulate the course of sepsis induced by two cecal punctures. When one cecal puncture was performed, a moderately evolving type of sepsis was induced, and the survival rate of affected rats was significantly improved by pretreatment with 10(-7) g/kg magnolol. The beneficial effect was partially retained if magnolol was administered 6 hours after onset of sepsis when a higher dose (10(-5) g/kg) was used. The intensity of lipid peroxidation in plasma, liver, and lung of septic rats was also attenuated in a treatment-dependent manner. Magnolol at this dose range exerted these beneficial effects probably through its antioxidant efficacy. These significant results may suggest magnolol as a candidate agent for the treatment of sepsis.

Heat shock activates c-Src tyrosine kinases and phosphatidylinositol 3-kinase in NIH3T3 fibroblasts.

There is increasing evidence that cellular responses to stress are in part regulated by protein kinases, although specific mechanisms are not well defined. The purpose of these experiments was to investigate potential upstream signaling events activated during heat shock in NIH3T3 fibroblasts. Experiments were designed to ask whether heat shock activates p60 c-Src tyrosine kinase or phosphatidylinositol 3-kinase (PI 3-kinase). Using in vitro protein kinase activity assays, it was demonstrated that heat shock stimulates c-Src and PI 3-kinase activity in a time-dependent manner. Also, there was increased PI 3-kinase activity in anti-phosphotyrosine and anti-c-Src immunoprecipitated immunocomplexes from heated cells. Heat shock activated mitogen-activated protein kinase (MAPK) and p70 S6 kinase (S6K) in these cells. The role of PI 3-kinase in regulating heat shock activation of MAPK and p70 S6K was investigated using wortmannin, a specific pharmacological inhibitor of PI 3-kinase. The results demonstrated that wortmannin inhibited heat shock activation of p70 S6K but only partially inhibited heat activation of MAPK. A dominant negative Raf mutant inhibited activation of MAPK by heat shock but did not inhibit heat shock stimulation of p70 S6K. Genistein, a tyrosine kinase inhibitor, and suramin, a growth factor receptor inhibitor, both inhibited heat shock stimulation of MAPK activity and tyrosine phosphorylation of MAPK. Furthermore, a selective epidermal growth factor receptor (EGFR) inhibitor, tryphostin AG1478, and a dominant negative EGFR mutant also inhibited heat shock activation of MAPK. Heat shock induced EGFR phosphorylation. These results suggest that early upstream signaling events in response to heat stress may involve activation of PI 3-kinase and tyrosine kinases, such as c-Src, and a growth factor receptor, such as EGFR; activation of important downstream pathways, such as MAPK and p70 S6K, occur by divergent signaling mechanisms similar to growth factor stimulation.

Impaired cAMP-mediated gene expression and decreased cAMP response element binding protein in senescent cells.

The capacity of various growth factors to induce c-fos expression is diminished with senescence. Because adenosine 3',5'-cyclic monophosphate (cAMP)-mediated responses are also blunted with aging, we wondered whether cAMP-induced c-fos gene expression might be impaired with senescence. Using IMR fibroblasts, we found that prostaglandin E1 (PGE1) and forskolin, stimulators of cAMP accumulation in young and senescent cells, increased abundance of c-fos and junB mRNA more in young than senescent cells. The abundance of the cAMP response element binding protein (CREB), a transcription factor which enhances gene expression when phosphorylated by protein kinase A, was markedly decreased in both whole cell and nuclear extracts of senescent cells, in both Western blotting and in gel retardation assays. Also, PGE1-induced phosphorylation of CREB by protein kinase A was markedly attenuated in senescent cells. There is a marked decrement in expression of CREB with senescence, and the results suggest the possibility that the diminished expression of CREB may contribute to altered cAMP-mediated regulation of gene expression with senescence.