Biomedical subjects

J A Ehrenfried

Publications and source records attributed to J A Ehrenfried.

10 recordsLinked to original sources

PubMed1999

Biliary tract cancer.

Recent advances in the molecular and cellular biology, diagnosis, and treatment of biliary tract cancer are reviewed. Several studies have delineated the molecular and cellular biology of cholangiocarcinoma and gallbladder carcinoma. Hepatocyte growth factor seems to be mitogenic to gallbladder carcinoma, and its inhibition may have a therapeutic role in this disease. Evidence against an adenoma-carcinoma pathway in gallbladder mucosa is presented. Helical computed tomography may improve staging accuracy in biliary tract disease and plays a definite role in diagnosis of and treatment planning in gallbladder polyps. Complete surgical resection continues to provide the best long-term prognosis, and surgical drainage is most beneficial in cholangiocarcinoma. Controversy continues about the effects of laparoscopic procedures and abdominal wall tumor recurrence.

Journal Article↗

PubMed1997

Cell cycle-mediated regulation of hepatic regeneration.

BACKGROUND: Hepatic regeneration after partial hepatectomy (PH) is characterized by a synchronous induction of normally quiescent hepatocytes to reenter the cell cycle, leading to a complete restoration of hepatic mass. Cell cycle progression requires activation of cyclin-dependent kinases (Cdks) that are regulated by cyclins and Cdk inhibitors. METHODS: Protein expression of the cyclins (D-type and E), Cdks (Cdk2 and 4), and Cdk inhibitors (p21 and p27) was measured by Western blot after SHAM operation or PH in F344 rats. In addition, Cdk2-associated kinase activity was measured. RESULTS: Rapid induction of D-type and E cyclins, as well as their catalytic partners, Cdk2 and Cdk4, occurred after PH in rats. Complexes containing cyclin E and Cdk2 assembled in the regenerating liver, leading to increased Cdk2-associated kinase activity. The regenerating liver returned to preresection weight by day 7, at which time the Cdk2 activity also returned to SHAM levels. Biphasic induction of the Cdk inhibitor p21 was observed; the first peak occurred as early as 6 hours after PH, with a subsequent peak in expression occurring at 24 to 72 hours after PH. CONCLUSIONS: Taken together, these data support the concept that cyclins, Cdks, and Cdk inhibitors regulate cell cycle progression in the regenerating liver. In addition, the induction of p21 at two time points suggests that this protein may regulate both early proliferation and subsequent inhibition of hepatocyte regeneration.

Animals↗

PubMed1996

Caloric restriction increases the expression of heat shock protein in the gut.

OBJECTIVE: The authors determined whether caloric restriction (CR) either acutely or chronically, alters heat shock protein 70 (hsp70) gene expression in the gut. SUMMARY BACKGROUND DATA: Caloric restriction prolongs the life span and delays age-related disease (e.g., cancer) in mammals; the mechanisms responsible for these effects are not known. Heat shock proteins are a group of stress-responsive genes of which the most prominent member is hsp70. METHODS: In the first experiment, adult (4-month-old) rats (n = 3/group) were killed after a 48-hour fast or 6 and 24 hours after refeeding. In addition, three rats (controls) were killed without fasting or refeeding. The stomach was removed and RNA was extracted for hsp70 gene expression. In the second experiment, aged (22- to 26-month-old) rats were fed ad libitum (AL) or a CR diet (60% caloric intake of AL diet). Rats were killed, the stomach and duodenum were removed, and RNA was extracted for determination of hsp70 gene expression. RESULTS: In the first experiment, hsp70 mRNA levels were increased approximately threefold in the stomach of rats fasted for 48 hours; levels decreased to control values by 6 and 24 hours after refeeding. In the second experiment, hsp70 mRNA levels were increased significantly in both the stomach and duodenum of aged CR rats compared with AL controls. CONCLUSIONS: The authors have demonstrated that hsp70 mRNA levels are increased in the proximal gut of young and old rats, either acutely (with fasting) or with CR. Increased expression of the cytoprotective hsp70 gene in the gut may provide a possible cellular mechanism for the beneficial effects noted with CR.

Aging↗

PubMed1995

Glutamine-mediated regulation of heat shock protein expression in intestinal cells.

BACKGROUND: Glutamine is crucial in the growth and protection of intestinal mucosa; the molecular mechanisms for these effects are not known. Heat shock proteins (hsp) are stress-responsive genes that protect cells from various injuries. The purpose of this study was to determine whether glutamine alters hsp expression in intestinal cells after injury. METHODS: IEC-6 (rat intestinal crypt) cells were grown to 80% confluence, rinsed free of medium and serum, and then grown in medium containing various concentrations of L-glutamine (0.5 to 8.0 mmol/L) for 24 hours. Cells were then exposed to heat shock (43 degrees C for 1 hour) and RNA and protein were extracted at 0, 2, 8, and 24 hours after heat shock. Northern hybridizations were performed using an hsp 70 complementary DNA. Western blots were performed by using antibodies specific to the inducible and constitutive forms of hsp70. RESULTS: Northern blot analysis demonstrated a fourfold stimulation of hsp70 messenger RNA 2 hours after heat shock in IEC-6 cells supplemented with 8.0 mmol/L glutamine compared with 0.5 and 1.0 mmol/L glutamine. In addition, inducible Hsp70 protein levels were increased threefold in IEC-6 cells given glutamine (8.0 mmol/L) at 24 hours after heat shock. CONCLUSIONS: Glutamine augments hsp70 messenger RNA and protein expression in gut-derived IEC-6 cells after injury. Our findings demonstrate a novel mechanism for the enhanced cytoprotection of gut mucosa conferred by administration of glutamine and suggest that supplemental glutamine may be required after injury to enhance expression of stress-responsive genes in the gut.

Animals↗

PubMed1995

Heat shock proteins are differentially expressed in human gastrointestinal cancers.

The heat shock proteins (Hsp) are stress-responsive genes present in all species; increases of Hsp can confer chemotherapeutic resistance to certain cancers. The purpose of this study was to determine Hsp expression in human gastric, pancreatic and colon cancers. Gastric (n = 3), pancreatic (n = 6) and colon (n = 8) cancers were extracted for RNA and protein, and Northern and Western blots performed. We found that hsp70 and hsp27 mRNA levels were differentially expressed in the gastrointestinal cancers; mRNA expression closely correlated with protein levels suggesting regulation at the level of transcription. In addition, Hsp90 and BiP proteins were constitutively expressed in the gastrointestinal cancers. We conclude that the Hsp are differentially expressed in human gastric, pancreatic and colon cancers; these increases in Hsp occur constitutively and are not the result of physiological or environmental stresses. Increases of Hsp expression in cancer cells may enhance resistance and account for the altered sensitivity of certain gastrointestinal cancers to chemotherapeutic agents.

Gastrointestinal Neoplasms↗

PubMed1995

Increases in nup475 and c-jun are early molecular events that precede the adaptive hyperplastic response after small bowel resection.

OBJECTIVE: The authors determined whether increases of nup475 and c-jun gene expression occur after small bowel resection and whether these changes are specific to the gut. SUMMARY BACKGROUND DATA: Massive small bowel resection (SBR) is characterized by adaptive proliferation of the remaining gut mucosa; the molecular signals responsible for this adaptive hyperplasia are unknown. Increases in the "immediate-early genes" nup475 and c-jun are noted in some proliferating tissues; however, alterations in the expression of these genes have not been described in the gut after SBR. METHODS: Rats underwent either a 70% proximal SBR or intestinal transection with reanastomosis (SHAM) and were then killed over a time course (0.5, 2, and 24 hours). The ileum, duodenum, colon, and kidneys were removed and RNA was extracted for Northern hybridization. RESULTS: The authors found that steady-state mRNA levels of both nup475 and c-jun were increased 81% and 62%, respectively, in the ileal remnant at 2 hours in rats after SBR compared with the SHAM group. In addition, nup475 was increased 101% in the duodenum at 24 hours and 31% in the colon at 0.5 hours in rats after SBR. In contrast, neither gene was increased in the kidney. CONCLUSIONS: Increases in steady-state levels of nup475 and c-jun are limited to the gut after SBR, and the timing and magnitude of these changes differ, depending on the gut segment. Finally, the rapid and nutrient-independent increases of nup475 and c-jun suggest an important role for these genes as early molecular signals that participate in the adaptive hyperplasia occurring in the gut remnant after SBR.

Adaptation, Physiological↗

PubMed1994

Expression of the neurotensin gene in fetal human liver and fibrolamellar carcinoma.

OBJECTIVE: This study determined whether the neurotensin gene (NT/N) is expressed in the normal adult liver and focal nodular hyperplasia (FNH) and confirmed NT/N expression in fibrolamellar carcinoma; whether NT/N or the neurotensin receptor is expressed in the fetal liver; and whether hepatic resection leads to expression of NT/N. SUMMARY BACKGROUND DATA: Neurotensin (NT), a gut tridecapeptide localized in the gastrointestinal tract of the adult to the small bowel, is an important hormone-regulating gut motility, secretion, and mucosal growth. Expression of the NT/N gene has been identified in fibrolamellar carcinomas, but NT/N is not known to be expressed in the normal liver. METHODS: Sensitive ribonuclease (RNase) protection assays were used to determine whether NT/N is expressed in fibrolamellar carcinoma, FNH, or healthy fetal and adult livers. The authors also determined whether the receptor for NT was present in the fetal liver and whether liver resection and subsequent regeneration could lead to re-expression of NT/N in the rat. RESULTS: Neurotensin is expressed in fibrolamellar carcinoma and in the fetal human liver, but not in the adult liver or the samples of FNH. In addition, the authors were not able to detect expression of the NT receptor in the fetal liver and did not identify NT/N gene activation in the regenerating liver of the rat. CONCLUSIONS: The NT/N gene will be a useful molecular marker to differentiate fibrolamellar carcinoma from other liver tumors. The finding of NT/N expression in the fetal liver suggests a stem cell descendant that is common to both the liver and gut. The absence of NT/N expression in the regenerating liver suggests that NT does not play a role in this rapid growth process.

Animals↗

PubMed1994

Temporal-specific and spatial-specific patterns of neurotensin gene expression in the small bowel.

Expression of the neurotensin/neuromedin N (NT/N) gene is developmentally regulated in a temporal- and spatial-specific pattern in the small bowel. The purpose of our study was to determine 1) whether the temporal expression of NT/N could be altered by ectopic placement of small bowel and 2) whether the spatial-specific expression of NT/N could be altered by different diets. We found that the relative temporal pattern of NT/N expression was unchanged in rat jejunal and ileal xenografts implanted into the flanks of athymic nude mice. To determine whether the spatial-specific pattern of NT/N expression could be altered by different luminal nutrients, 28-day-old rats were randomized to receive chow or chemically defined liquid diets for 60 days at which time the jejunoileum was divided into eight equal segments, and NT/N expression was analyzed. The normal pattern of increasing levels of NT/N mRNA along the jejunum-to-ileum axis was not altered by any of the liquid diets. In contrast to NT/N, we found that expression of sucrase-isomaltase varied greatly depending on both location and type of luminal nutrients. We conclude that the strict temporal- and spatial-specific pattern of NT/N expression is not affected by either location or luminal contents, thus suggesting an intrinsic program of NT/N gene expression. Furthermore, we speculate that the NT/N gene may provide a useful endocrine paradigm to investigate the factors regulating the establishment and maintenance of certain cell lineage-specific patterns along the cephalocaudal axis of the gut.

Aging↗

PubMed1994

Characterization of functional neurotensin receptors on human lymphocytes.

BACKGROUND: Neurotensin, a tridecapeptide, regulates gut motility, secretion, and mucosal growth; an immunomodulatory role for neurotensin has been postulated but not clearly defined. The purpose of this study was to determine whether neurotensin receptors (NTR) are present on peripheral blood lymphocytes (PBLs) and to characterize binding, functional, and molecular properties. METHODS: Iodine 125 labeled-neurotensin binding was determined for both human PBLs and the T-cell lines, Molt-4 and Jurkat, by Scatchard analysis. To analyze functional capacity of the NTR, PBLs were cultured in the presence of phytohemagglutinin (1 microgram/ml) with or without neurotensin and harvested at 48 hours after an 8-hour pulse of tritiated thymidine. For molecular analyses, RNA extracted from PBLs and T-cell lines was analyzed by either Northern hybridization with a labeled NTR cDNA or ribonuclease protection with an antisense human NTR probe. RESULTS: Scatchard analyses of neurotensin binding to human PBLs and MOLT-4 showed two classes of binding sites with different affinities. Incubation of phytohemagglutinin-stimulated PBLs with neurotensin significantly enhanced proliferation. Northern hybridization showed mRNA of the authentic NTR or a receptor subtype of close homology in PBLs and the T-cell lines; ribonuclease protection analysis identified the authentic human NTR in the MOLT-4 cell line. CONCLUSIONS: Using a combination of molecular techniques and Scatchard analysis, we have demonstrated the presence of a cell surface NTR with a high affinity for neurotensin on human PBLS and the MOLT-4 cell line. The functional role of NTR has been established by enhanced proliferation with addition of neurotensin. These data provide further evidence for a link between neurotensin and the immune system and suggest that neurotensin may play an important regulatory role in gut mucosal immune responses in vivo.

Blotting, Northern↗

PubMed1991

Prostaglandin F1 alpha levels during and after neonatal extracorporeal membrane oxygenation.

Infants receiving extracorporeal membrane oxygenation therapy undergo long-term cardiopulmonary bypass, are systemically heparinized, and frequently receive platelet transfusions. Prostacyclin is a powerful inhibitor of platelet aggregation as well as a potent vasodilator. The levels of its stable metabolite prostaglandin F1 alpha increase significantly in children undergoing cardiopulmonary bypass during heart operations but decrease to preoperative levels after bypass. To determine the effect of long-term bypass on prostacyclin levels, multiple plasma samples were analyzed in 10 human neonates both during extracorporeal membrane oxygenation therapy and within 24 hours after extracorporeal membrane oxygenation. Prostaglandin F1 alpha, the stable metabolite of prostacyclin, was quantitated by radioimmunoassay in picograms per milliliter. Prostaglandin F1 alpha levels were elevated while the patients received extracorporeal membrane oxygenation therapy but decreased with duration of extracorporeal membrane oxygenation. In most infants, prostaglandin F1 alpha levels rose again during weaning from extracorporeal membrane oxygenation and remained elevated for 24 hours after extracorporeal membrane oxygenation. Extracorporeal membrane oxygenation course influenced circulating prostaglandin F1 alpha levels. Fluctuating prostaglandin F1 alpha levels are of clinical significance in the management of vasomotor tone and platelet function, common problems in the care and the prevention of hemorrhage in these critically ill infants.

Blood Platelets↗