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Biomedical subjects

R S Chari

Publications and source records attributed to R S Chari.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1995

Induction of apoptosis in liver tumors by the monoterpene perillyl alcohol.

The monoterpenes d-limonene and perillyl alcohol (POH) inhibit the growth of mammary tumors. In this investigation we tested whether POH is also effective in reducing liver tumor growth. Diethylnitrosamine was used to induce liver tumors in male Fischer 344 rats. Two weeks after diethylnitrosamine exposure was discontinued, the animals were divided into POH-treated and untreated groups. The mean liver tumor weight for the POH-treated rats after 19 weeks of POH treatment was 10-fold less than that for the untreated animals. POH did not influence tumor cell proliferation but increased the apoptotic index approximately 10-fold. The mRNA levels for the mannose 6-phosphate/insulin-like growth factor II receptor and the transforming growth factor beta type I, II, and III receptors were also significantly increased in the liver tumors from the POH-treated animals when compared to the corresponding receptor mRNA levels in the normal tissue surrounding the tumors and in the tumors of untreated animals. These results demonstrate that POH does not promote the formation of liver tumors, but rather inhibits their growth by enhancing tumor cell loss through apoptosis.

Animals↗
PubMed1995

Pregnancies complicated by HELLP syndrome (hemolysis, elevated liver enzymes, and low platelets): subsequent pregnancy outcome and long-term prognosis.

OBJECTIVE: Our purpose was to describe subsequent pregnancy outcome and long-term maternal prognosis in women with HELLP syndrome (hemolysis, elevated liver enzymes, and low platelets) during the index pregnancy. STUDY DESIGN: This is a descriptive and analytic study of women with HELLP syndrome admitted to E.H. Crump Women's Hospital between August 1977 and July 1992. HELLP syndrome was defined by previously published laboratory criteria. Only patients who were delivered > 2 years ago were included (median 4 years, range 2 to 14 years). Data on these patients were obtained from our obstetric clinics, local physicians, local health departments, and hospital records. RESULTS: Adequate follow-up data were available on 341 patients. One hundred fifty-two women subsequently became pregnant. One hundred thirty-nine normotensive women had 192 subsequent pregnancies. Complications included preeclampsia (19%), preterm delivery (21%), intrauterine growth restriction (12%), abruptio placentae (2%), perinatal death (4%), and HELLP syndrome (3%). Seven of the 113 women with at least 5 years' follow-up (6.2%) had chronic hypertension, and 98 received oral contraceptive pills without complications. Thirteen women with preexisting chronic hypertension had 20 subsequent pregnancies. These women had a higher rate of preeclampsia (75%), preterm delivery (80%), intrauterine growth restriction (45%), abruptio placentae (20%), and perinatal death (40%) but a low rate of recurrent HELLP syndrome (5%). CONCLUSIONS: Women with HELLP syndrome have an increased risk of obstetric complications in future pregnancies but a low risk for recurrent HELLP syndrome. Oral contraceptive pills should not be contraindicated in normotensive women.

Adult↗
PubMed1995

Daily antenatal testing in women with severe preeclampsia.

OBJECTIVE: Our purpose was to determine whether daily antenatal testing in the expectant management of severe preeclampsia remote from term prevents stillbirth or neonatal compromise at birth. STUDY DESIGN: We reviewed the medical records of 68 women with severe preeclampsia remote from term who underwent expectant management with daily fetal testing until delivery. On admission each patient had reassuring nonstress testing (absence of persistent severe variable or late decelerations), biophysical profile (> or = 6), and amniotic fluid volume (> or = 2 cm maximal vertical pocket before 32 weeks or amniotic fluid index > or = 5 after 32 weeks). RESULTS: There were no stillbirths. Twenty-one patients (31%) had nonreassuring testing necessitating delivery. Two neonatal deaths occurred as a result of complications of prematurity. There were no statistical differences in the cord arterial pH (p = 0.93) or in the 1- and 5-minute Apgar scores (p = 0.18 and p = 0.88, respectively) between those with normal and abnormal antenatal testing. CONCLUSIONS: Because optimizing neonatal outcome is the only reason to prolong pregnancy in women with severe preeclampsia, confirmation of fetal well-being is mandatory. Because neither stillbirths nor fetal compromise at birth occurred in patients undergoing daily antenatal testing, we recommend daily testing in patients with severe preeclampsia managed expectantly.

Adolescent↗
PubMed1995

Down-regulation of transforming growth factor beta receptor type I, II, and III during liver regeneration.

BACKGROUND: After partial hepatectomy (PH), it has been shown that hepatocytes are resistant to the mitoinhibitory effects of transforming growth factor beta (TGF-beta). Three types of TGF-beta receptors have been characterized in mammals. MATERIALS AND METHODS: In this study, changes in the protein and mRNA expression of TGF-beta types I, II, and III receptors relative to DNA synthesis were studied as a function of time after PH in the rat. RESULTS: There was a significant decrease in the protein and mRNA for all three receptor subtypes immediately after PH. All three receptors reached a nadir at 24 hours after PH, which correlated to the time of peak DNA synthesis. The type II receptor recovered to preoperative levels by 120 hours after PH, whereas the types I and III receptors remained at 60% of prehepatectomy levels. Sham-operated rats did not experience a significant drop in receptor protein or mRNA levels. CONCLUSIONS: This decrease in TGF-beta type II receptor expression may account for the reduction in the sensitivity of hepatocytes to TGF-beta after PH. Furthermore, the TGF-beta receptors appear to represent a class of immediate-early genes that are negatively, rather than positively, regulated after PH.

Animals↗
PubMed1995

Preoperative radiation and chemotherapy in the treatment of adenocarcinoma of the rectum.

OBJECTIVE: In this study, the impact of preoperative chemotherapy and radiation on the histopathology of a subgroup of patients with rectal adenocarcinoma was examined. As well, survival, disease-free survival and pelvic recurrence rates were examined, and compared with a concurrent control group. SUMMARY BACKGROUND DATA: The optimal treatment of large rectal carcinomas remains controversial; current therapy usually involves abdominoperineal resection plus postoperative chemoradiation; the combination can be associated with significant postoperative morbidity. In spite of these measures, local recurrences and distant metastases continue as serious problems. METHODS: Fluorouracil, cisplatin, and 4500 cGy were administered preoperatively over a 5-week period, before definitive surgical resection in 43 patients. In this group of patients, all 43 had biopsy-proven lesions > 3 cm (median diameter), involving the entire rectal wall (as determined by sigmoidoscopy and computed tomography scan), with no evidence of extrapelvic disease. The patients ranged from 31 to 81 years of age (median 61 years), with a male:female ratio of 3:1. A concurrent control group consisting of 56 patients (median: 62 years, male:female ration of 3:2) with T2 and T3 lesions was used to compare survival, disease-free survival, and pelvic recurrence rates. RESULTS: The preoperative chemoradiation therapy was well tolerated, with no major complications. All patients underwent repeat sigmoidoscopy before surgery; none of the lesions progressed while patients underwent therapy, and 22 (51%) were determined to have complete clinical response. At the time of resection, 21 patients (49%) had gross disease, 9 (22%) patients had only residual microscopic disease, and 11 (27%) had sterile specimens. Of the 30 patients with evidence of residual disease, 4 had positive lymph nodes. In follow-up, 39 of the 43 remain alive (median follow-up = 25 months), and only 1 of the 11 patients with complete histologic response developed recurrent disease. Six of the 32 patients with residual disease (2 with positive nodes) have developed metastatic disease in follow-up (median time to diagnosis 10 months, range 3-15 months). Three of these patients with metastases have died (median survival after diagnosis of metastases = 36 months). Local recurrence was seen in only 2 of 43 patients (< 5%). Cox-Mantel analysis of Kaplan-Meier distributions demonstrated increased survival (p = 0.017), increased disease-free survival (p = 0.046), and decreased pelvic recurrence (p = 0.031) for protocol versus control patients. CONCLUSIONS: This therapeutic regimen has provided enhanced local control and decreased metastases. Furthermore, the marked degree of tumor downstaging, as seen by a 27% incidence of sterile pathologic specimens and a low rate of positive lymph nodes in this group with initially advanced lesions, strongly suggest that less radical surgery and sphincter preservation may be used with increasing frequency.

Adenocarcinoma↗
PubMed1995

Transforming growth factor-beta receptors and mannose 6-phosphate/insulin-like growth factor-II receptor expression in human hepatocellular carcinoma.

OBJECTIVE: The authors examined the expression of transforming growth factor-beta receptor (TGF-beta r) types I and II and the mannose 6-phosphate/insulin-like growth factor-II receptor (M6-P/IGF-IIr) in human hepatocellular carcinoma (HCC). SUMMARY BACKGROUND DATA: Transforming growth factor-beta (TGF-beta) is part of a superfamily of peptide-signaling molecules that play an important role in modulating cell growth. It is secreted as a latent complex and therefore, must be activated to elicit a biological response. Bioactivation of the TGF-beta complex is facilitated by binding to the M6-P/IGF-IIr. Once activated, TGF-beta exerts its effects by binding to specific cell membrane TGF-beta receptors. The loss of responsiveness of hepatocytes to TGF-beta has been implicated in hepatocarcinogenesis and could result from a loss in the expression of either the TGF-beta receptors or the M6-P/IGF-IIr. METHODS: Human hepatocellular carcinomas and surrounding normal tissue were collected from operating room samples and snap-frozen in liquid nitrogen (n = 13). Tissues from two tumors were fixed in Omni-fix for sectioning and immunohistochemistry staining for the M6-P/IGF-IIr and TGF-beta 1. RNA was extracted from both normal and malignant liver tissue and analyzed using an RNase protection assay. SDS-PAGE of purified membrane hybridized with 125I-TGF-beta 1 and 125I-IGF-II was used to determine the TGF-beta type I (TGF-betarI) and type II (TGF-beta rII) receptors and M6-P/IGF-IIr protein levels, respectively. Gels were quantitated by phosphorimager, and a paired t test was used for statistical analysis. RESULTS: In HCC, a 60% (p < 0.01) and 49% (p < 0.02) reduction in the mRNA levels for T beta rI and T beta rII, respectively, relative to the receptor levels in surrounding normal liver, was shown. A similar decrease in the receptor protein levels also was observed. The M6-P/IGF-IIr mRNA and protein levels were reduced in 7 of 11 hepatocellular carcinomas. Immunohistochemical staining demonstrated an absence of intracellular TGF-beta 1 and reduced M6-P/IGF-IIr in the hepatocellular carcinoma cells. CONCLUSIONS: These results demonstrate that human HCCs have a significantly reduced expression of both the TGF-beta rI- and TGF-beta rII-signaling receptors for TGF-beta. This may provide a selective growth advantage to the HCC by allowing them to escape the mito-inhibitory effects of activated TGF-beta. Furthermore, in the subset of HCC in which the expression of the M6-P/IGF-IIr is downregulated, the bioactivation of TGF-beta also may be impaired.

Adult↗
PubMed1994

Mechanisms of injury in porcine livers perfused with blood of patients with fulminant hepatic failure.

Hyperacute rejection of renal and cardiac xenografts is initiated by the reaction of recipient natural antibodies and complement with endothelial cell antigens of the donor organ. The liver is thought to be less susceptible to this form of rejection; however, the mechanisms underlying its decreased susceptibility are not known. We investigated the organ injury occurring in porcine livers perfused with blood from 4 human subjects with fulminant hepatic failure. Nine porcine livers were perfused via an extracorporeal circuit in order to provide temporary metabolic support. Each porcine liver exhibited metabolic function, and the duration of xenoperfusion ranged from 2 to 5 hr. Histologic examination of the xenoperfused livers revealed focal hepatocellular necrosis, prominent infiltration of neutrophils, and, in 7 of 9 cases, periportal and centrilobular hemorrhage and thrombosis. Immunopathology demonstrated minimal or no human IgM and IgG along the small vessels and sinusoidal surfaces. Trace deposits of human IgM were observed along the luminal surfaces of large blood vessels in most cases. Trace deposits of C3 were noted in 2 of 9 livers; however, C4, iC3b, C5b, properdin, and the membrane attack complex were not detected. Human anti-porcine natural antibody titers decreased less than expected during the perfusions. Serum CH50, C3, and C4 levels were low before each procedure and decreased slightly with perfusion. One patient perfused 2 porcine livers and a human liver. The human liver had focal hepatocellular necrosis, trace deposits of IgM, no deposits of complement, and an infiltrate consisting of neutrophils; however, the neutrophil influx was less than that observed in the xenoperfused livers. To further evaluate the effects of alloperfusion, venovenous bypass was established in 2 pigs and the extracorporeal circuit was utilized to perfuse 2 porcine livers. The alloperfused porcine livers had focal hepatocellular necrosis and a minimal infiltrate of neutrophils. There were no deposits of porcine IgM, IgG, or complement components. In conclusion, although the porcine livers perfused by human blood sustained structural damage, the time course, the absence of immune deposits, and the findings of similar, albeit less severe, lesions in the alloperfused livers suggest that the pathogenesis of tissue injury in the xenoperfused livers differs from that of hyperacute rejection and may be related to the action of recipient neutrophils.

Adult↗
PubMed1994

Transforming growth factor-beta receptors type I, II and III in phenobarbital-promoted rat liver tumors.

Rat liver tumors initiated with N-nitrosodiethylamine (DEN) followed by promotion with phenobarbital (PB) were examined for expression of transforming growth factor-beta (TGF beta) type I, II and III receptors. RNase protection and TGF beta 1 affinity labeling assays were used to determine TGF beta receptor steady-state mRNA and protein levels, respectively. We have demonstrated that all three TGF beta receptors are expressed in both normal and malignant hepatic tissues. Long-term PB administration did not alter TGF beta receptor mRNA or protein levels in normal liver. However, type I, II and III TGF beta receptor mRNA and protein levels were decreased by approximately 50% in the DEN-initiated/PB-promoted liver tumors as compared to the receptor levels in normal liver tissue surrounding the tumors. In contrast, TGF beta receptor mRNA and protein levels were unchanged in liver tumors initiated with DEN but not PB-promoted. These data demonstrate that PB promotes the formation of a tumor phenotype that is characterized by a significantly reduced number of TGF beta type I, II and III receptors. This suggests that the down-regulation of TGF beta receptors in PB-promoted hepatic tumors may provide a selective growth advantage to the tumor cells by reducing the ability of TGF beta to inhibit their growth.

Animals↗
PubMed1994

The effect of propofol on the canine sphincter of Oddi.

To assess the effect of propofol on the canine sphincter of Oddi(SO), sphincter of Oddi manometry (SOM) was performed in fasting dogs which had undergone cholecystectomy and placement of modified Thomas duodenal cannulae. Using two water-perfused, single-lumen manometric catheters, SO and duodenal pressures were measured simultaneously. Baseline SO activity was recorded for at least one complete interdigestive cycle followed by bolus injections of propofol (Diprivan) (N = 31) from 0.1 to 4.0 mg/kg during Phase I of the Migrating Motor Complex (MMC). When propofol was administered in bolus doses < or = 0.4 mg/kg, no change in SO or duodenal motor function was seen. In doses > or = 0.5 mg/kg, SO basal pressure, amplitude, and frequency of contractions increased significantly. Increases in duodenal activity paralleled SO activity. Our results suggest that propofol in low doses may be useful for sedation during Sphincter of Oddi manometry in humans. Further studies of the effect of propofol on the human sphincter of Oddi are warranted.

Animals↗
PubMed1994

Expression of alpha 1-adrenergic receptor subtype mRNA in rat tissues and human SK-N-MC neuronal cells: implications for alpha 1-adrenergic receptor subtype classification.

At least three subtypes of alpha 1-adrenergic receptors (alpha 1ARs) have been identified using molecular techniques (alpha 1a/d, alpha 1b, and alpha 1c), whereas two subtypes of alpha 1ARs have been identified pharmacologically (alpha 1A and alpha 1B); however, controversies exist regarding how these two classification schemes relate to each other. In an attempt to clarify some of the controversies regarding classification of alpha 1AR subtypes, we have re-evaluated the distribution of mRNA for the cloned alpha 1AR subtypes (alpha 1a/d, alpha 1b, and alpha 1c) in various rat tissues thought to express alpha 1AR subtypes, as well as the human neuronal cell line SK-N-MC (a recently described model for pharmacologically defined alpha 1AAR and alpha 1BAR subtypes), using sensitive ribonuclease protection assay techniques. Total RNA extracted from various rat tissues and SK-N-MC cells was hybridized with rat and human alpha 1AR subtype-specific probes, respectively. In contrast to previously reported Northern blot analyses, alpha 1cAR mRNA is expressed in many rat tissues. Expression of alpha 1cAR mRNA is highest in those tissues that have been previously characterized by radioligand binding as expressing the classical, pharmacologically defined alpha 1AAR. Likewise, the human neuronal SK-N-MC cell line, classically thought to express pharmacological alpha 1AAR and alpha 1BAR subtypes, expresses both alpha 1a/dAR and alpha 1cAR mRNA and no alpha 1bAR mRNA. Collectively, these data suggest that the cloned alpha 1cAR subtype may represent the pharmacological alpha 1AAR, and they have important implications for merging pharmacological and molecular classifications of alpha 1AR subtypes.

Animals↗
PubMed1993

Complications of laparoscopic cholecystectomy.

Laparoscopic cholecystectomy is a safe and effective treatment of cholelithiasis in experienced hands. Mortality is rare. The Southern Surgeons Club data and several other recent large series indicate that major complications occur in less than 3% of patients. The most significant common complication is injury to the bile duct, for which the greatest risk factor is inexperience. Major biliary injury usually requires reoperations. Roux-en-Y hepaticojejunostomies, often multiple, are usually necessary for repair. The popularity of this technique continues, and further efforts should be focused on elimination of the learning curve for major biliary injury. If injuries do occur, they should be recognized early, and patients should be referred to centers experienced in their treatment.

Bile Ducts↗
PubMedDate not supplied

Impact of cell swelling on proliferative signal transduction in the liver.

Cellular swelling has emerged as an important initiator of metabolic and proliferative changes in various cells. Because of the unique regenerative capacity of the adult liver, researchers have delineated key intracellular signals that are activated following mitogens, injury, and partial hepatectomy. Although hepatocellular swelling is commonly observed following these regenerative stimuli, only recently has the relationship between cell volume increase and proliferative activity been investigated; to date, the data implicating cell volume increase with hepatocyte regeneration has been mostly indirect. Hepatocyte swelling has been demonstrated in various clinical scenarios from sepsis, hepatic resection, ischemia-reperfusion injury, glucocorticoid excess, and hyperinsulinemia. Using various in vivo and in vitro models of hepatocyte swelling, particularly hypo-osmotic stress, investigators have demonstrated changes in cellular structure: (1) cell membrane stretch, (2) cytoskeletal microtubule and microfilament reorganization, and (3) alterations in cytoskeletal-membrane complexes. Similar studies have demonstrated a causal relationship between cell volume increase and intracellular signals: (1) activation of cytoplasmic signaling cascades such as MAPKs, PI-3-K, and PKC, (2) activation of proliferative transcription factors NF-kappaB, AP-1, STATs, C/EBPs, and (3) transcription of metabolic and immediate early genes of regeneration. Through mechanotransduction, or the translation of physical changes to chemical signals, cell volume is a potent effector of these signaling events. Growing evidence demonstrates a link between these physical and chemical changes in the swelling-mediated growth in the liver.

Animals↗
PubMedDate not supplied

Bosentan, an endothelin antagonist, augments hepatic graft function by reducing graft circulatory impairment following ischemia/reperfusion injury.

Endothelin is a potent hepatic vasoconstrictor. We evaluated the role of an endothelin antagonist in hepatic ischemia/reperfusion injury. Bosentan, a novel endothelin receptor antagonist, was infused directly into the portal vein prior to cold ischemia and immediately on reperfusion, in five porcine livers. Five other pigs underwent routine liver harvest and reperfusion without bosentan treatment. Hepatic vascular resistance and liver tissue blood flow, as measured by thermistor flow probes, were determined following reperfusion. Hepatocellular damage was assessed through hepatic venous levels of sorbitol dehydrogenase and lactate dehydrogenase. Endothelial cell damage was determined in sections immuno-stained for factor VIII. Graft function was determined through oxygen consumption, bile production, and response to bile acid challenge. Organs treated with bosentan demonstrated lower vascular resistance and enhanced tissue blood flow (P < 0.05) as compared to untreated organs. Portal vein inflow to hepatic tissue was significantly enhanced (4.4-fold) in the bosentan-treated organs (P < 0.05). No difference was observed in hepatocellular damage. Pathology scores for factor VIII immunohistochemical staining were 2.3-fold higher in the bosentan-treated livers as compared to untreated livers (P < 0.05). The bosentan-treated livers also demonstrated enhanced oxygen consumption, increased bile production, and augmented biliary response to a bile acid challenge (P < 0.05). These results indicate that administration of bosentan before and after ischemia/reperfusion reduces hepatic circulatory disturbances, diminishes endothelial cell damage, and augments hepatic graft function.

Animals↗
PubMedDate not supplied

Alterations in intrahepatic hemodynamics of the harvested porcine liver.

Hemodynamic properties of a donor liver, during initial reperfusion, are associated with the degree of graft preservation injury and have been proposed to correlate with subsequent markers of liver function. In the present study, hepatic hemodynamics, that is, portal venous pressure, hepatic vascular resistance, and compliance (vascular distensibility), were characterized (1) in situ before porcine livers were manipulated, (2) after these same livers were isolated and perfused within a bypass circuit, and (3) on reperfusion after 2 hours of cold ischemia. Hepatic vascular resistance was determined in each of these three states from the portal vein pressure response to differing hepatic blood flows. In addition, the response of the same livers to norepinephrine and nitroprusside was evaluated in each condition. In the in situ and isolated perfused liver, portal venous pressure increased only modestly despite doubling of hepatic flows. After cold ischemia, the pressure response to higher flows was significantly greater and much less of a reduction in hepatic vascular resistance was noted than in studies prior to cold ischemia. Unlike livers prior to cold ischemia, the pressure response to norepinephrine was attenuated following cold ischemia. The response to nitroprusside, however, remained intact reducing the portal pressure to that of in situ livers. Therefore the portal hypertension that follows cold ischemia appears to be largely provoked by the preservation injury and not by surgical manipulation or the bypass circuit. This increment in portal pressure is responsive to a nitric oxide donor.

Animals↗