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R S Chari

Publications and source records attributed to R S Chari.

At least 19 recordsLinked to original sources
PubMed2001

Protective effects of ischemic preconditioning on the cold-preserved liver are tyrosine kinase dependent.

BACKGROUND: Little data exist regarding the use of ischemic preconditioning before sustained hepatic cold storage. We hypothesized that ischemic preconditioning protects hepatic grafts via a tyrosine kinase-dependent pathway. METHODS: Six porcine livers underwent routine harvest (control). Five other livers underwent 15 min of in situ ischemia followed by 15 min of reflow before harvest (ischemic preconditioning). Another five livers were pretreated with a tyrosine kinase inhibitor (genistein) before preconditioning. Upon reperfusion and after 2 hours of cold storage, graft function, graft circulatory impairment, and markers of cellular damage were analyzed. Tissue cytoplasmic extracts were analyzed for tyrosine phosphorylation with Western blot. Significance was determined with t tests. RESULTS: Ischemic-preconditioned grafts demonstrated enhanced bile production, augmented responses to a bile acid challenge, and elevated O2 consumption (P<0.05) compared to controls. Also, preconditioned grafts demonstrated improved hepatic tissue blood flow and decreased hepatic vascular resistance (P<0.005) compared to controls. Endothelial cell preservation (factor VIII immunostain) was improved in preconditioned graft biopsies compared to controls. With genistein pretreatment, all observed improvements returned to control levels. Analysis of cytoplasmic extracts demonstrated an increase in tyrosine phosphorylation before cold ischemia in preconditioned grafts only, but not in control or genistein-pretreated grafts. CONCLUSIONS: The data indicate that ischemic preconditioning protects the liver from sustained cold ischemia and that tyrosine kinases are involved in preconditioning responses.

Alanine Transaminase↗
PubMed2001

Protein kinase C inhibition abrogates hepatic ischemic preconditioning responses.

INTRODUCTION: A transient period of warm ischemia prior to a longer ischemic episode (ischemic preconditioning) protects the hepatic graft from cold ischemia. The mechanism for this protection is unknown, as is the role of protein kinase C in ischemic preconditioning responses. METHODS: Livers from 40 kg Yorkshire pigs were harvested and subjected to 2 h of cold ischemia (n = 6) (control). Another group of harvested livers was pretreated with a 15-min ischemic period followed by 15 min of in situ perfusion with (n = 5) or without (n = 5) a protein kinase C inhibitor, chelerythrine. Following cold ischemia, all grafts were reperfused on a perfusion circuit and the following variables evaluated: (1) hepatic graft function, (2) graft circulatory impairment, (3) hepatocellular damage, and (4) endothelial cell damage. Protein kinase C levels were also evaluated by Western blot in the cytoplasm of all grafts. RESULTS AND DISCUSSION: Ischemic preconditioned grafts demonstrate improved graft function, reduced graft circulatory impairment, and reduced endothelial cell damage as compared to cold ischemia controls. When preconditioned grafts were pretreated with chelerythrine, graft function, graft circulatory impairment, and endothelial cell damage were no different than cold ischemia controls. Ischemic preconditioned grafts demonstrated decreased levels of protein kinase C prior to cold ischemia. There was no change in protein kinase C levels in cold ischemia controls or chelerythrine-pretreated grafts prior to cold ischemia. These data indicate that modulation of protein kinase C is essential for ischemic preconditioning responses in the cold preserved hepatic graft.

Alkaloids↗
PubMed2001

Activator protein 1 activation following hypoosmotic stress in HepG2 cells is actin cytoskeleton dependent.

BACKGROUND: Following hypoosmotic stress-induced cell volume change, the actin cytoskeleton reorganizes itself. The role of this reorganization in the activation of the phosphatidylinositol 3-OH-kinase/protein kinase B/activator protein 1 (PI-3-K/PKB/AP-1) proliferative signaling cascade is unknown. Focal adhesion kinase (FAK) participates in the cytoskeleton-based activation of PI-3-K. We hypothesized that hypoosmotic stress-induced activation of PKB and AP-1 in HepG2 cells is dependent on an intact actin cytoskeleton and subsequent FAK phosphorylation. METHODS: HepG2 cells were incubated for 1 h with or without 20 microM cytochalasin D, an actin disrupter, and were then exposed for up to 30 min to hypoosmotic medium (200 mOsm/L) to induce swelling. Tumor necrosis factor alpha (1.4 nM) and medium alone served as positive and negative controls, respectively. Western blots measured cytoplasmic phosphorylated or total FAK and PKB. EMSAs measured nuclear AP-1. All experiments were performed in triplicate. RESULTS: Exposure to hypoosmotic stress resulted in activation of the following signaling messengers in a sequential fashion: (1) phosphorylation of FAK occurred by 2 min, (2) phosphorylation of PKB occurred by 10 min, (3) nuclear translocation of AP-1 occurred by 30 min. All three signaling events were abolished when these cells were pretreated with cytochalasin D. CONCLUSION: Actin reorganization following hypoosmotic stress is essential for the FAK-mediated activation of the PI-3-K/PKB/AP-1 proliferative cascade. These data delineate a possible mechanism by which the cell swelling-induced cytoskeletal changes can initiate proliferative signal transduction in human liver cancer.

Actins↗
PubMed2000

Hypoosmotic stress activates p38, ERK 1 and 2, and SAPK/JNK in rat hepatocytes.

BACKGROUND: Following hepatocyte injury, changes in the perihepatocyte milieu modulate cell volume and influence growth. Hypoosmotic stress activates nuclear factor-kappa B (NF-kappaB), a transcription factor believed to prime cell cycle progression in hepatocytes. In this study, we investigate the role of mitogen-activated protein kinases (MAPKs) in the activation of NF-kappaB. MATERIALS AND METHODS: Quiescent primary hepatocytes were exposed to hypoosmotic serum-free William's E (WE) medium (200 mOsm/liter), with or without a 1-h pretreatment with either PD 98059 (15 microM) or SB 202190 (3 microM). Parallel experiments were conducted using hepatocyte growth factor (HGF) at 0.1 mg/ml and normoosmotic WE medium as positive and negative controls, respectively (n = 3). Relative densitometries of Western blots measured phosphorylated cytoplasmic p38, ERK 1 and 2, and SAPK/JNK. Electromobility shift assays examined nuclear NF-kappaB activation. RESULTS: (i) Hypoosmolar WE medium phosphorylated p38, ERK 1 and 2, and SAPK/JNK by 5 min. (ii) Hypoosmolar WE medium activated NF-kappaB at 60 min. (iii) HGF phosphorylated all three MAPKs and activated NF-kappaB with profiles similar to those of hypoosmotic stress. (iv) Both PD 98059 and SB 202190 abrogated the activation of NF-kappaB in HGF-stimulated cells but not in hypoosmotically stressed cells. CONCLUSION: (i) Both hypoosmotic cell swelling and HGF phosphorylate p38, ERK 1 and 2, and SAPK/JNK, and (ii) HGF, but not hypoosmotic stress, activates NF-kappaB via p38 and ERK 1 and 2 phosphorylation. These data suggest that cell swelling activates NF-kappaB through a pathway separate from that of growth factors.

Animals↗
PubMed2000

Bile acids in xenogeneic ex-vivo liver perfusion: function of xenoperfused livers and compatibility with human bile salts and porcine livers.

BACKGROUND: In recent years, hepatic support systems using xenogeneic cells have been developed to support patients in fulminant hepatic failure. The extent to which xenogeneic hepatocytes metabolize and excrete human organic anions is unclear. In these studies we examined the ability of the ex vivo porcine liver to clear human bile acids during extracorporeal liver perfusion (ELP). METHODS: Four patients with fulminant hepatic failure underwent extracorporeal liver perfusion with 9 porcine livers. The venovenous circuit was designed as previously described (NEJM,1994,331:234) as were the immunologic features (Transplantation 1994,58:1162). Bile from the porcine liver and serum samples were collected hourly during perfusion. Three bile acids (glycocholic, glycodeoxycholic, taurodeoxycholic acid) were selected as markers for human bile and three (glycohyocholic, glycohyodeoxycholic, and glyco-3alpha-hydroxy-6-oxo-5beta-cholanoic acid) for markers of pig bile. Bile acids from both serum and bile were processed and analyzed through high performance liquid chromatography. The Students' t test was used for statistical analysis. RESULTS: The mean duration of perfusions was 4.1+/-1.5 hr. The mean total bile acid clearance from serum (243+/-44 micromol/h) was similar to the total bile acid biliary excretion (286+/-84 micromol/hr, P = 0.06). After 1 hr of perfusion, bile samples demonstrated a predominance of pig bile salts (65%). After 3 hr of perfusion, human bile acids made up 85% of total biliary bile acids. Pig bile acids appeared in patients' sera after 1 hr of perfusion, and after 3 hr, 35% of serum bile salts were pig-specific. CONCLUSIONS: Porcine livers perfused with human blood can clear the serum of potentially toxic human bile acids and excrete them into bile. Simultaneously, the percentage of pig-specific bile acids in patient serum increases during xenogeneic perfusion for unknown reasons. The relative hepatic uptake of bile acid from serum is similar to bile acid excretion in bile. Further development of systems using porcine livers or hepatocytes is warranted.

Animals↗
PubMed2000

NFkappaB expression during cold ischemia correlates with postreperfusion graft function.

In liver transplantation, activation of NFkappaB occurs upon reperfusion, yet few data exist regarding NFkappaB activation during cold ischemia. We hypothesized that activation of NFkappaB may initially occur during cold ischemia, prior to reperfusion, and serve as an important determinant of postreperfusion function. To test this hypothesis, serial biopsies during porcine liver harvest were obtained immediately upon laparotomy, upon completion of dissection, after 45 and 120 min of cold ischemia, and 60 and 180 min after reperfusion. Nuclear extracts were isolated for Western blot analysis of NFkappaB. Hepatic function was assessed through bile output and sorbitol dehydrogenase (SDH) activity. NFkappaB expression was maximal at 45 min of cold ischemia and decreased by 120 min. The expression at 120 min of cold ischemia correlated with markers of postreperfusion function, namely bile flow and SDH activity. During reperfusion a second distinct peak occurred at 180 min. Increased expression of NFkappaB at 180 min of reperfusion correlated directly with prior expression at 120 min during cold ischemia and with increased SDH activity. These data indicate that nuclear expression of NFkappaB demonstrate two distinct peaks of activity, one during cold ischemia and one after reperfusion. Enhanced expression of NFkappaB during cold ischemia not only correlates directly with NFkappaB expression during reperfusion, but also correlates inversely with postreperfusion graft function.

Animals↗
PubMed2000

A critical appraisal of laparoscopic staging in hepatobiliary and pancreatic malignancy.

Prognosis for patients with hepatobiliary and pancreatic cancers is dismal. Surgery is the best therapeutic option for those with tumors which have not yet metastasized. Standard radiologic tests such as computed tomography (CT) scan and trans-abdominal ultrasound are useful in identifying patients for whom an attempt at resection would be futile. Staging laparoscopy with laparoscopic ultrasound allows greater precision in identifying those for whom resection would be helpful with less morbidity than an open exploration. Metastatic disease can be identified more precisely than with radiologic tests and can be characterized by biopsy techniques. Palliative procedures are now being performed laparoscopically with low morbidity and short hospital stays. The use of laparoscopy prior to open exploration for patients with hepatobiliary and pancreatic tumors is advantageous.

Biliary Tract Neoplasms↗
PubMed1998

Domino liver transplantation for familial amyloid polyneuropathy.

Familial amyloid polyneuropathy is an autosomal dominant disorder in which the liver produces a variant prealbumin that is deposited along nerves, leading to a progressive and fatal polyneuropathy that begins in the third decade of life. Liver transplantation has been the only successful treatment to date. Apart from the production of the variant protein, there are no other abnormalities in these amyloid livers. We describe two cases in which, at the time of transplantation, the amyloid livers were subsequently used for transplantation in another patient, and we discuss the implications.

Adult↗
PubMed1998

Venovenous bypass in adult orthotopic liver transplantation: routine or selective use?

BACKGROUND: The role of venovenous bypass (VVB) during orthotopic liver transplantation (OLT) remains controversial. The aims of this study were to evaluate the current role of VVB at all major centers in North America, to examine the results of OLT and complications of VVB between two periods with a strict policy for routine versus selective use of VVB, and to review the literature. STUDY DESIGN: A survey of 50 major liver transplant centers was conducted using mailed questionnaires. A retrospective chart review was performed for 547 OLT patients having transplantation during two distinct periods with a strict policy for routine versus selective use of VVB at the University of Toronto, Canada, and at Duke University Medical Center, Durham, North Carolina. The literature was reviewed with a focus on the benefits and indications for routine versus selective use of VVB. RESULTS: Thirty-eight (76%) of 50 centers responded. Sixteen (42%) of them used VVB routinely, with a reported complication rate of 10-30%. Lymphocele and hematoma were the most common complications, but patients having major vascular injury, air embolism, and death were reported. A recent change to selective use of VVB was reported in 30% of the centers (11 of 38). In the Duke-Toronto series, the complication rates were similar between the two periods, at 13.4% and 18.8%, respectively. The outcome of OLT was not influenced by the policy of routine or selective use of VVB. CONCLUSIONS: There is a trend away from the routine use of VVB during OLT. Intraoperative hemodynamic instability during the hepatectomy and a failed trial of hepatic venous occlusion were the most important criteria for using VVB. We conclude that VVB should be used selectively to avoid associated complications and to decrease operative time and costs.

Adult↗
PubMed1997

MR imaging differentiation of benign and malignant peripheral nerve sheath tumors: use of the target sign.

BACKGROUND: T2-weighted MR imaging of soft tissue tumors of neural origin may show round lesions with a central hypointensity and a hyperintense rim resembling a target. We define the "target sign" as a mass consisting of a solitary target, or a multicompartmental mass in which the largest component consists of multiple targets. OBJECTIVE: The objective of this study was to determine whether the target sign can differentiate benign neurofibromas and their malignant counterparts, malignant peripheral nerve sheath tumors. Materials and methods. Preoperative T2-weighted MR images of 23 neurofibromas or malignant peripheral nerve sheath tumors were retrospectively reviewed in 16 patients, aged 3 weeks to 20 years (median 15 years), without knowledge of the pathologic diagnosis. The presence or absence of a target sign was noted. RESULTS: The target sign was seen in all 12 neurofibromas and 1 of the 11 malignant peripheral nerve sheath tumors. Statistical analysis showed good differentiation of benign and malignant tumors using this sign (chi = 0.91). CONCLUSION: The target sign on T2-weighted MR imaging is helpful in differentiating neurofibromas from malignant peripheral nerve sheath tumors.

Adolescent↗
PubMed1996

Regeneration of a transplanted liver after right hepatic lobectomy.

Liver regeneration has been described after heterotopic liver transplantation, small-for-size orthotopic liver transplantation and reduced-size liver transplantation. In this report, we document the regenerative response of a whole liver transplant to major resection for the first time. A right hepatic lobectomy for liver ischemia was performed in a 30-year-old female after transplantation for autoimmune disease of the liver. Volumetric analysis of computed tomography (CT) scans revealed a preoperative liver volume of 1,961 mL, whereas analysis of the 6-week posthepatectomy CT scan showed a volume of 1,820 mL. Factors influencing regeneration in the setting of a liver transplant include rejection, ischemia/thrombosis, infection, or cyclosporine hepatotrophic/hepatotoxic effects. These factors, balanced with the intrinsic ability of hepatocytes to achieve a standard liver volume, determine the extent of regeneration.

Adult↗
PubMed1996

Is fetal neurologic and physical development accelerated in preeclampsia?

OBJECTIVE: Our objective was to determine whether the Ballard score, a maturity score for neonatal neuromuscular and physical development, is more advanced in preterm infants of preeclamptic women than in controls. STUDY DESIGN: A matched cohort study design was used. One hundred women with strictly defined preeclampsia (new-onset hypertension, proteinuria, and hyperuricemia) were matched for gestational age, race, and gender to 100 normotensive women with preterm delivery. All patients had an assigned antenatal gestational age based on ultrasonography before 24 weeks. The gestational age, based on antenatal ultrasonography and last menstrual period, was compared with the Ballard score given at the time of neonatal physical examination within the first 12 hours after delivery. The difference in gestational age between the Ballard score and antenatal ultrasonography (Ballard score - ultrasonography) was calculated for each patient. Results are expressed as median and range and are compared with a Student t test. RESULTS: The mean gestational age at delivery by antenatal ultrasonography in patients with severe preeclampsia was 32.06 +/- 2.74 and 32.03 +/- 2.70 weeks, respectively. The median difference between scores in patients with severe preeclampsia and normal patient were 1.3 +/- 1.8 and 1.5 +/- 1.6 weeks, respectively (p = 0.41). CONCLUSION: On the basis of criteria defined by the Ballard score, preeclampsia was not associated with accelerated fetal neurologic and physical development.

Adolescent↗
PubMed1996

Postoperative incision complications after cesarean section in patients with antepartum syndrome of hemolysis, elevated liver enzymes, and low platelets (HELLP): does delayed primary closure make a difference?

OBJECTIVE: Our purpose was to evaluate wound complications between patients with antepartum HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome with primary closure versus delayed closure and Pfannenstiel versus midline skin incisions. STUDY DESIGN: Medical records of patients with antepartum HELLP syndrome undergoing cesarean section were examined for type and timing of skin closure: Pfannenstiel versus midline skin incision and primary versus delayed closure. The immediate (before hospital discharge) and late (2-week postoperative check) wound complications were analyzed with respect to timing of wound closure and type of skin incision. RESULTS: A total of 104 patients were identified; 75 had a primary skin closure and 29 had a delayed closure 48 to 72 hours postoperatively. Immediate wound complications (wound infection, hematoma), occurred in 18 (26%) patients who had primary closure versus 8 (24%) who had a delayed closure, odds ratio 1.13 (95% confidence interval 0.39 to 3.27). A late wound breakdown was seen in only 1 patient with primary closure but in none with delayed closure. There were no fascial wound dehiscences. No statistical difference in wound complication was found between midline (primary, delayed) and Pfannenstiel (primary, delayed) incisions, odds ratio 0.65 (95% confidence interval 0.23 to 1.88). CONCLUSION: In women with antepartum HELLP syndrome delivered by cesarean section the frequency of wound complications is not influenced by type of skin incision or time of skin closure (primary or delayed).

Adult↗
PubMed1996

Laparoscopic radical prostatectomy in the canine model.

The purpose of this study was to determine the feasibility of performing laparoscopic radical prostatectomy in a canine model. Laparoscopic radical prostatectomy was performed on six adult male canines. A new endoscopic needle driver was used to construct a secure vesicourethral anastomosis. Average operative time required to complete the procedure was 304 min (range 270-345 min). Dissection of the prostate gland took an average of 67 min (range 35-90 min), and construction of the vesicourethral anastomosis took 154 min (rage 80-240 min). There were no intraoperative complications and only one postoperative complication (anastomotic leak). Five of the six animals recovered uneventfully from the procedure, and their foley catheters were removed 10-14 days postoperatively after a retrograde cystourethrogram demonstrated an intact vesicourethral anastomosis. Four (80%) of the surviving animals were clinically continent within 10 days after catheter removal. Post mortem examination confirmed that the vesicourethral anastomosis was intact with no evidence of urine extravasation. These data demonstrate the feasibility of laparoscopic radical prostatectomy in a canine model, and suggest that additional work with this technique should be continued to develop its potential clinical application.

Animals↗
PubMed1996

Adenosine nucleotides in bile.

Activation of purinergic receptors by ATP stimulates Cl- efflux in biliary epithelial cells. To determine whether purinergic agonists are present under physiological conditions, we have assayed mammalian bile for nucleotides and assessed whether hepatoma and cholangiocarcinoma cell lines are capable of nucleotide release. Bile samples were collected from human, rat, and pig donors and assayed for nucleotide concentrations by luminometry. ATP, ADP, and AMP were present in bile from each species, and the average total nucleotide concentration in human bile was 5.21 +/- 0.91 microM (n = 16). In an in vitro model of HTC rat hepatoma cells or Mz-ChA-1 cholangiocarcinoma cells on a superfused column, nucleotides were present in the effluent from each cell type. Addition of alpha, beta-methyleneadenosine 5'-diphosphate (50 microM) to inhibit 5'-nucleotidase activity increased AMP concentrations two- to threefold. Exposure to forskolin (100 microM) or ionomycin (2 microM) stimulated nucleotide release from cholangiocarcinoma but not hepatoma cells. These studies indicate that adenosine nucleotides are present in bile in concentrations sufficient to activate purinergic receptors. Purinergic receptor activation by local nucleotide release might constitute an autocrine and/or paracrine mechanism for modulation of biliary secretion.

5'-Nucleotidase↗