An immortalized in vitro model of the blood-brain barrier: glutathione levels and sensitivity to oxidative stress.
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Animals↗
Biomedical subjects
R D Hurst
Publications and source records attributed to R D Hurst.
Nitric oxide-induced blood-brain barrier dysfunction is not mediated by inhibition of mitochondrial respiratory chain activity and/or energy depletion.
Tumor necrosis factor-alpha (TNF-alpha) has been implicated in the breakdown of blood-brain barrier (BBB) function which can occur during various inflammatory conditions. Recent evidence suggests a role for the free radical nitric oxide (NO) in the process of cytokine-induced barrier dysfunction. The mitochondrial enzyme cytochrome oxidase is inhibited by NO, and hence, using a coculture model of the BBB, we have investigated whether TNF-alpha alters barrier function by a NO-mediated mechanism and, if so, whether it is related to a reduction of endothelial cell respiration and ATP synthesis. TNF-alpha mediated a marked reduction in model BBB integrity that was partially prevented by inhibition of NO synthase activity. Additionally, exposure of BBB cultures to authentic gaseous NO also resulted in a progressive decline in barrier integrity. Authentic NO inhibited endothelial cell respiration in a reversible manner. Mitochondrial respiratory chain inhibitors induced significant reductions in endothelial cell respiratory rate and ATP levels, but did not mimic the action of NO on barrier function. We conclude that NO is partially responsible for the detrimental effect of TNF-alpha on BBB function. The mechanism of NO-induced barrier dysfunction does not involve an inhibition of endothelial mitochondrial electron transport chain and reduced energy resources.
Animals↗
Prospective study of the features, indications, and surgical treatment in 513 consecutive patients affected by Crohn's disease.
BACKGROUND: The aim of this prospective study was to elucidate the features, indications, and surgical treatment in patients affected by complications of Crohn's disease. METHODS: Between January 1985 and July 1996, 513 consecutive patients (248 male, 265 female; mean age, 38 years) were operated on for 542 occurrences of Crohn's disease. Data were collected prospectively. RESULTS: Indications for abdominal surgery were often multiple but included failure of medical management (n = 220), obstruction (n = 94), intestinal fistula (n = 68), mass (n = 56), abdominal abscess (n = 33), hemorrhage (n = 7), and peritonitis (n = 9). Four hundred sixty-four abdominal procedures were performed, necessitating 425 intestinal resections and 97 stricture plasties. The use of stricture plasty was more common in the second half of the study (16.0% versus 7.3%, second half versus first half; p < 0.01). Perioperative complications occurred in 75 of the 464 abdominal operations (16%). There were no deaths. One hundred thirty patients (25%) required operation for perineal complications of Crohn's disease. The presence of Crohn's disease in the rectal mucosa was associated with a higher risk for permanent stomas in patients requiring operation for treatment of perianal Crohn's disease (67% versus 11%; p < 0.001). CONCLUSIONS: Patterns of surgical treatment in Crohn's disease are changing, with more emphasis on nonresectional options. The presence of rectal involvement significantly increases the need for a permanent stoma in patients with perianal Crohn's disease.
Adolescent↗
Prospective study of the incidence, timing and treatment of pouchitis in 104 consecutive patients after restorative proctocolectomy.
OBJECTIVE: To determine the incidence timing and effectiveness of treatment of symptomatic pouchitis following restorative proctocolectomy with ileal J-pouch anal anastomosis. DESIGN: A cohort analytical study. SETTING: University hospitals, a tertiary referral center; all subjects entered into the study followed up for a minimum of 12 months (mean follow-up, 40 months). PATIENTS: One hundred four consecutive patients undergoing restorative proctocolectomy with ileal J-pouch anal anastomosis for either ulcerative colitis (n = 97) or familial adenomatous polyposis (n = 7) between June 1986 and December 1994. INTERVENTIONS: Patients with symptomatic pouchitis were treated with either oral metronidazole or ciprofloxacin. OUTCOMES: Diagnosis of pouchitis was determined by clinical symptoms and confirmed with endoscopy. Response to oral antibodies was determined by resolution of symptoms. RESULTS: Fifty-two patients (50%) experience at lest 1 episode of pouchitis. The first episode of pouchitis occurred within the first 12 months after restoration of intestinal continuity in 56% of the cases. In 2 patients it occurred after 30 months. Response to antibiotic treatment was 96%. Two thirds of patients had multiple episodes. Chronic pouchitis occurred in 6 patients, necessitating pouch removal in 2. CONCLUSIONS: The incidence of pouchitis after ileal J-pouch anal anastomosis is approximately 50% with two thirds of these patients having multiple episodes. Chronic pouchitis occurs in a minority of patients. In chronic pouchitis, the risk of pouch loss is substantial.
Adenomatous Polyposis Coli↗
Properties of an immortalised vascular endothelial/glioma cell co-culture model of the blood-brain barrier.
In an effort to obtain a useful in vitro model possessing some of the properties of the blood-brain barrier, we have investigated the properties and interactions of immortalized cell lines. Immortalised human umbilical vein endothelial cells (HUVEC-304), in co-culture with rat C6 glioma cells in a two-chambered assembly, form tight junctional complexes, and develop a permeability barrier having a high transcellular electrical resistance. The endothelial cells generate a barrier with greatest integrity in the presence of glioma cells, or in the presence of glioma cell conditioned medium. Under these conditions, the endothelial cells also display pronounced structural changes which do not occur in the absence of glioma cells. Morphological alterations include a flattening of cell shape from a cuboidal-type to a squamous-type of appearance, and a re-organization of F-actin microfilaments. The integrity of the barrier can be reversibly disrupted by osmotic shock or by tumor necrosis factor-alpha (TNF-alpha). We interpret these observations to indicate that co-cultures of immortalized vascular endothelial and C6 glioma cells provide a model for the investigation of cell-cell interactions required for the generation of a barrier having several properties of the blood-brain barrier.
Animals↗
Nitric oxide-induced perturbations in a cell culture model of the blood-brain barrier.
The actions of an intracellular nitric oxide generator compound on the properties of a co-culture model of the blood-brain barrier are described. Addition of the iron-sulphur cluster nitrosyl Roussin's black salt (RBS, heptanitrosyl-tri-mu3-thioxotetraferrate (1-)) resulted in a rapid and dose-dependent (50-250 microM) decline in the electrical resistance displayed by co-cultures of vascular endothelial cells and C6 glioma cells. The breach in barrier integrity elicited by RBS (250 microM) could be prevented by either haemoglobin (100 microM), methylene blue (200 microM), or by photon-induced inactivation of RBS. In contrast, the nitric oxide synthase inhibitor nitro-L-arginine methyl ester (250 microM) caused no inhibition in the decline in resistance of RBS-exposed cultures. Addition of 8-bromo-guanosine-cyclic monophosphate (500 microM) did not mimic the actions of RBS. Exposure to intense light of co-cultures manifesting a high transcellular electrical resistance resulted in a reduction in tissue resistance which could be prevented by the presence of haemoglobin (100 microM). We conclude that nitric oxide liberated from RBS results in a reversible diminution in the integrity of the endothelial cell barrier in the co-culture system, and we suggest that light-sensitive endogenous nitric oxide generator compounds may be present in intact cells. Possible roles of nitric oxide in blood-brain-barrier function are considered.
Animals↗
Investigations into the action of a novel nitric oxide donor on cellular respiration.
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Animals↗
Investigations into the mechanism of action of a novel nitric oxide generator on cellular respiration.
Nitric oxide may regulate cellular respiration by competition with oxygen at mitochondrial cytochrome oxidase. Using an astrocyte-derived cell line, we have compared the mechanism of action of the nitric oxide-generating compound Roussin's black salt with that of sodium nitroprusside on cellular oxygen consumption. Intense light exposure induced the release of large quantities of nitric oxide from both of the donor compounds. However, in room light only Roussin's black salt generated low levels of the radical. Simultaneous measurement of oxygen consumption and of nitric oxide production demonstrated that sodium nitroprusside only had inhibitory actions when exposed to intense light (nitric oxide release), whereas Roussin's black salt had inhibitory actions in room light. Extracellular haemoglobin did not prevent the inhibition of respiration rate induced by Roussin's black salt even though stimulation of nitric oxide release on light exposure was markedly reduced. Preincubation of cells with Roussin's black salt and subsequent measurement of levels of light-liberated nitric oxide demonstrated that the compound was rapidly internalised. The uptake of sodium nitroprusside was minimal. These data suggest that, in contrast to sodium nitroprusside, the cellular internalisation of Roussin's black salt allows site-directed nitric oxide release and very effective inhibition of cellular respiration.
Animals↗
Octreotide inhibition of serotonin-induced ileal chloride secretion.
Octreotide (SMS, synthetic miniature somatostatin) effectively alleviates the secretory diarrhea of the malignant carcinoid syndrome. Although SMS inhibits tumor release of serotonin (5HT) and other bioactive agents, it also inhibits the diarrhea in patients who continue to exhibit elevated serum levels of 5HT. This observation suggest that SMS may directly inhibit mediator-stimulated intestinal ion secretion at the mucosal level. To test this hypothesis, intestinal ion secretion was studied in rabbit ileal mucosa mounted in Ussing chambers. Maximal changes in short circuit current (delta Isc) were observed as an indicator of mucosal ion secretion. The application of pathophysiologic concentrations of 5HT (10(-5) M) to the mucosal preps resulted in a delta Isc of 52 +/- 6 microA/cm2. This 5HT-stimulated delta Isc was significantly inhibited by serosal furosemide (10(-3) M) or use of a chloride-depleted medium, indicating that 5HT stimulates electrogenic chloride secretion in the rabbit ileum. Pretreatment with a therapeutic concentration of SMS (10(-8) M) resulted in a significant inhibition of 5HT-stimulated electrogenic Cl- secretion (9 +/- 1 microA/cm2) (P < 0.005). This inhibitory effect of SMS was not seen in tissue pretreated with pertussis toxin. The results of these experiments demonstrate that octreotide inhibits 5HT-stimulated electrogenic chloride secretion at the mucosal level. Additionally this inhibitory effect of octreotide is likely mediated by activation of the inhibitory subunit of membrane-bound GTP-binding regulatory proteins. These results thus provide experimental evidence in support of the ability of SMS to ameliorate the carcinoid diarrhea by a direct effect on stimulated mucosal ion secretion.
Animals↗
Prospective analysis of perioperative morbidity in one hundred consecutive colectomies for ulcerative colitis.
BACKGROUND: This study was undertaken to evaluate prospectively the indications for surgical treatment and perioperative morbidity for patients with idiopathic ulcerative colitis (UC). METHODS: Between January 1985 and August 1994, 145 patients were referred to the senior author (F.M.) for treatment of UC. Data were prospectively collected. One hundred patients have completed all stages of their surgical treatment and have been followed up for at least 1 year. These 100 patients form the basis of this study. RESULTS: Thirty patients underwent a proctocolectomy with end-ileostomy in one (25) or two (5) stages. Seventy patients underwent a restorative proctocolectomy with ileal J-pouch anal anastomosis in either one (2), two (37), or three stages (31). In total 100 patients underwent 204 procedures. Failure of medical treatment was by far the most common indication. The initial colectomy was performed electively in 61 patients and urgently in the remaining 39. The rate of perioperative complications for elective and urgent colectomy was 26% and 44%, respectively (p < 0.05). CONCLUSIONS: The overall perioperative morbidity rate remains high and almost doubles for urgent cases. Reducing the need for urgent procedures by earlier elective colectomy may allow for a reduction in perioperative morbidity.
Colectomy↗
Glomerular mesangial cell altered contractility in high glucose is Ca2+ independent.
In diabetes, loss of renal arteriolar smooth-muscle cell contractility leads to intraglomerular hypertension. In glomeruli isolated from streptozotocin (STZ)-induced diabetic rats, the mesangial cells (smooth muscle-like) display loss of contractile responsiveness to angiotensin II. This study examines the mechanistic relationship between altered mesangial cell contractility and vasopressor hormone-stimulated Ca2+ signaling in high glucose. Glomeruli were isolated from normal or STZ-induced diabetic rats to observe ex vivo mesangial cell contractile function. Also, rat mesangial cells were cultured (10-20 passages) in normal (5.6 mmol/l) or high (10-25.6 mmol/l) glucose for 1-5 days. Reduction of glomerular volume and decreased planar surface area of cultured mesangial cells in response to vasoconstrictor stimulation over 60 min were measured by videomicroscopy and personal computer-based morphometry. Contraction of glomeruli isolated from STZ-administered rat in response to endothelin (ET)-1 (0.1 mumol/l) or the Ca2+ ionophore A23187 (5 mumol/l) was impaired significantly compared with that in normal glucose. In the presence of arginine vasopressin (AVP) (1.0 mumol/l) or ET-1 (0.1 mumol/l), mesangial cells demonstrated a dose-dependent loss of contractile response to increasing glucose concentrations (5.6-25.6 mmol/l) within 24 h of high-glucose exposure, which was sustained for 5 days. Mesangial cells in high glucose were consistently smaller in size compared with those in normal glucose. Mesangial cells were preloaded with myo-[2-3H]inositol and intracellular [3H] inositol phosphate release in response to AVP (1.0 mumol/l) was analyzed by Dowex chromatography. Comparing cells in normal (5.6 mmol/l) verus high (25.6 mmol/l) glucose, we observed no significant difference in stimulated inositol phosphate levels from 10 to 60 s.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Calcium signaling and contractile response of diabetic glomerular mesangial cells.
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Animals↗
High glucose alters actin assembly in glomerular mesangial and epithelial cells.
BACKGROUND: Glomerular mesangial and epithelial cell structure and function are maintained by cytoskeletal protein organization and function. To determine whether the diabetic milieu alters filamentous (F-) actin assembly, the spatial distributions and content of F- and monomeric (G-) actin were analyzed in rat mesangial and glomerular epithelial cells (10 to 15 passages) cultured for 5 days in high (22.4 mM) or normal (5.2 mM) glucose and in cells of whole glomeruli isolated from streptozotocin-treated diabetic or normal rats. EXPERIMENTAL DESIGN: Cells were labeled with the fluorescent probes rhodamine-phalloidin and FITC-DNase-1 specific for F- and G-actin, respectively. The average pixel intensities per cell were measured using dual channel confocal laser scanning microscopy (N = 60 cells per group). Total and G-actin were measured in mesangial cells by a spectrophotometric-based DNase-1 inhibition assay. RESULTS: In response to endothelin-1, 0.1 microM, vasopressin 1.0 microM, or angiotensin II 1.0 microM, mesangial cells cultured in normal glucose displayed partial disassembly of F-actin characterized by decreased fluorescence intensity (microfilament bundle pattern changed to network) with no change in G-actin fluorescence. In high glucose, but not mannitol (22.4 mM), partial disassembly of F-actin and loss of response to the agonists were observed. In high glucose, the F-actin content (micrograms/mg cellular protein) was reduced significantly with no change in absolute G-actin compared with normal glucose exposure. The effect of high glucose on mesangial cell actin was reversed by returning the cells to normal glucose for 2 days, stimulation with insulin 2 micrograms/ml, or with a protein kinase C inhibitor. Mesangial cells in high glucose were smaller in planar area and exhibited loss of contractile response to endothelin-1 (0.1 microM) or vasopressin (1.0 microM) measured by videomicroscopy. High glucose-induced F-actin disassembly, possibly due to activated protein kinase C, could account for smaller cell size and lack of response to vasopressor agents. Glomerular epithelial cells cultured in normal glucose demonstrated F-actin disassembly and increased G-actin fluorescence intensity in response to A23187 (5 microM) or bradykinin (10 nM). When cultured in high glucose, but not mannitol, increased epithelial G-actin fluorescence and loss of F- and G-actin response to agonists were observed. Although stimulation with insulin reversed the high glucose effect on epithelial G-actin, F-actin remained unresponsive to agonists. The cells of glomeruli isolated from the diabetic rat displayed the same increase in G-actin, no change in F-actin fluorescence, and loss of response to agonist stimulation as observed in cultured epithelial cells. CONCLUSIONS: These findings suggest that high glucose alters actin assembly in both glomerular mesangial and epithelial cells in vitro and in vivo, possibly contributing to cellular dysfunction in early diabetes.
Actins↗
Isolated rat glomerular cells demonstrate L-type Ca(2+)-channel activity.
The presence of L-type calcium (Ca2+)-channels and the effects of Ca(2+)-channel antagonists on cells of rat glomeruli were investigated. Glomeruli were isolated by graded sieving and after preincubation (10 min) in zero Ca2+, the uptake of 45Ca2+ by glomerular cells was measured. Depolarization with KCl (50 mM) or the dihydropyridine agonist Bay K 8644 (10 microM) stimulated 45Ca2+ uptake by 13% and 24%, respectively, above control (100%), which was inhibited by nifedipine (Nif, 10 microM), P < 0.05, and by both S and R isomers of verapamil (Ver, 10 microM), P < 0.001. In a separate experimental preparation, isolated glomeruli were preloaded (45 min) with 45Ca2+. Following a 45 min perifusion (37 degrees C, CaCl2 1.26 mM, in the absence of 45Ca2+), both KCl (50 mM) and Bay K 8644 (10 microM) induced cellular 45Ca2+ efflux with peak values above control of 11% and 15%, respectively, (P < 0.05). Exposure to Bay K 8644 preceded by depolarization with KCl resulted in enhanced 45Ca2+ efflux identifying the presence of voltage-dependent Ca(2+)-channel activity. Cultured rat mesangial cells grown to confluence on coverslips were preloaded with Fura-2 and cytosolic Ca2+ was measured by microfluorometry. KCl (50 mM), gramicidin (2 microM) and/or Bay K 8644 (6 microM) stimulated Ca2+ influx which was inhibited by Ver (10 microM). Ver did not alter endothelin-stimulated Ca2+ signalling. We conclude that L-type Ca2+ channels are present on both rat glomerular (endothelial and/or mesangial) cells in vivo and on cultured mesangial cells, and their activation may be hormone specific.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
Use of radiolabeled somatostatin analogs in the identification and treatment of somatostatin receptor-bearing tumors.
Radiolabeled somatostatin analogs are potentially of considerable value in both the localization and treatment of somatostatin receptor-bearing tumors. Whole body 123I-labeled Tyr3-octreotide scintigraphy is capable of detecting and localizing primary tumors and metastatic disease that may not be detectable by other methods. Although it is possible that this technique may be applicable to a wide variety of neoplasms, 123I-Tyr3-octreotide scans appear particularly useful for imaging various gut neuroendocrine tumors, meningiomas, and paragangliomas. This primarily reflects the level of expression of somatostatin receptors by these lesions. In addition to whole body scintigraphy, intraoperative localization by receptor identification utilizing a hand-held gamma detector probe may prove to be an effective means of identifying spread and micrometastasis of somatostatin receptor-bearing tumors. Aside from identification and topographic localization of disease, the detection of an 123I-Tyr3-octreotide labeled tumor may be utilized as in vivo assay for the presence of somatostatin receptors. Such observations may prove useful in predicting the susceptibility of an individual tumor to octreotide therapy. Additionally, it may prove possible to deliver a therapeutic dose of radiation to receptor-bearing tumors by the administration of specific radiolabeled somatostatin analogs.
Gastrointestinal Neoplasms↗
Immunoprecipitation of a pertussis toxin substrate of the G(o) family from rat islets of Langerhans.
Rat islets express a pertussis toxin sensitive G-protein involved in receptor-mediated inhibition of insulin secretion. This has been assumed previously to represent "G(i)" which couples inhibitory receptors to adenylate cyclase. Incubation of islet G-proteins with 32P-NAD and pertussis toxin resulted in the labelling of a band of molecular weight 40,000. This band was very broad and did not allow resolution of individual components. Incubation of the radiolabelled proteins with an anti-G(o) antiserum resulted in specific immunoprecipitation of a 32P-labelled band. These results demonstrate that the complement of pertussis toxin sensitive G-proteins in rat islets includes G(o).
Adenylate Cyclase Toxin↗
Management of groin hernias in patients with ascites.
The records of 18 cirrhotic patients with ascites and groin hernias (20 inguinal and one femoral) were retrospectively reviewed. Eleven patients underwent repair of their groin hernias (total of 13 repairs). Ten herniorrhaphies were performed electively, two were performed urgently because of recent difficult reduction, and one was performed emergently for incarceration without strangulation. No major and four minor postoperative complications occurred. There were no perioperative deaths or ascites leaks. Of the 13 hernias in 11 patients undergoing repair, 12 (92%) were available for follow-up. In this group, the 12 groin hernia repairs were followed for a mean of 25 months. One recurrence (8%) occurred 11 months after repair. In this same group of patients, five umbilical hernias were repaired, with three recurrences (60%). From this retrospective study, it appears that serious complications from groin hernias in cirrhotics are not common, and elective repair can usually await control of ascites. Additionally, for appropriately selected patients with ascites, elective inguinal hernia repair can be performed safely, with an acceptable rate of recurrence.
Adult↗
Diabetic rat glomerular mesangial cells display normal inositol trisphosphate and calcium release.
Since diabetes may cause cellular myo-inositol depletion, we investigated whether the observed in vitro hypocontractile response of streptozotocin (STZ)-treated rat glomeruli to angiotensin II (ANG II) is associated with an alteration in inositol trisphosphate (IP3) mobilization of intracellular Ca2+. Contraction of diabetic isolated glomeruli induced by ANG II (5 microM), measured in vitro by changes in the planar area, was reduced by 60%, compared with normal up to 60 min (P < 0.05). In cells of isolated glomeruli, preloaded with myo-[3H]inositol, production of [3H]inositol phosphates ([3H]IPs) and [3H]inositol trisphosphate ([3H]IP3) was analyzed by Dowex chromatography. ANG II (1 microM) evoked an immediate peak (5-10 s) in total [3H]IPs of 60.5 +/- 18.8% (mean +/- SE) above basal (nonstimulated state) in normal glomeruli, and 88.4 +/- 19.4% in diabetic condition [not significant (NS), n = 8]. At 60 s, the normal and diabetic total [3H]IPs responses were not significantly different from each other. The immediate (10 s) [3H]IP3 response from normal glomeruli, 8.1 +/- 7.9% above basal, was not significantly different from that of diabetic glomeruli, 15.7 +/- 7.4%. ANG II receptor-mediated rise in cytosolic Ca2+ in the cells of normal and diabetic isolated glomeruli was compared by measuring the efflux of 45Ca2+. Isolated glomeruli were preloaded with 45Ca2+. Following ANG II stimulation, peak 45Ca2+ efflux values at 1 min were 141.7 +/- 15.9% (normal) vs. 143.7 +/- 7.8% (diabetic) of baseline (100%), respectively (NS, n = 4). Thapsigargin, 2 microM, specifically prevented ANG II-stimulated and IP3-mediated 45Ca2+ efflux (73% inhibition, P < 0.001) from cells of whole glomeruli.(ABSTRACT TRUNCATED AT 250 WORDS)
Angiotensin II↗