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Biomedical subjects

B Simon

Publications and source records attributed to B Simon.

At least 37 records · Page 2Linked to original sources

Management of nonfunctioning islet cell carcinomas.

Tumors arising from the pancreatic islet cells are rare and represent a heterogeneous group of benign or malignant lesions. Most tumors present with well characterized syndromes, whereas others appear to be nonfunctioning. The clinical features of 11 men and 7 women with nonfunctioning islet cell carcinomas operated on between 1983 and 1998 were reviewed. The median patient age was 53.5 years (range 26-74 years). The most frequent presenting symptoms were abdominal pain (13 patients), weight loss (7 patients), and obstructive jaundice (4 patients). Gut hormone profiles were normal in all patients. Abdominal sonography and computed tomography localized the tumor in 17 patients, and correct prediction of an endocrine tumor was achieved in 12 patients. Six of seven patients showed a hypervascular tumor upon angiography, and seven of eight patients preoperatively had positive somatostatin receptor scintigraphy. At operation, regional or distant metastases were present in 15 (83%) and 6 (33%) patients, respectively. Eleven patients underwent potentially curative resections, and the remaining seven patients were managed palliatively by resection (four patients) or bypass procedures (three patients). Three patients had up to three more resection for metastases. Eight patients received postoperative octreotide, interferon alpha therapy, or both. The overall cumulative 5- and 10-year survival rates were 65.4% and 49.1%, respectively. Of the 11 patients who underwent curative resection, 10 were alive after a median follow-up of 63 months (range 7-180 months), but only 5 are free from disease. Although surgical cure is rare in nonfunctioning islet cell carcinomas, significant long-term palliation can be achieved in a large proportion of patients with an aggressive surgical approach and, when indicated, additional medical therapy.

Adult↗

Luteinizing hormone response to controlled-release deslorelin in estradiol benzoate primed ovariectomized gilts.

Development of a controlled release formulation of gonadotropin releasing hormone that would stimulate a LH surge capable of reducing the time span of ovulations would greatly benefit reproductive management because a single timed insemination could be used. A dose-response study was conducted to determine if Deslorelin, a potent gonadotropin releasing hormone analogue, delivered via the SABER system, a biodegradable controlled release system, would stimulate an ovulatory-like LH surge in the pig. Twenty ovariectomized gilts, approximately 200 d old and 100 kg body weight (BW), received estradiol benzoate (15 microg/kg BW im) and 48 h later, the gilts were given deslorelin at 0, 12.5, 25.0, 50.0 or 100.0 microg im (n = 4 each treatment group). Compared to controls, mean blood deslorelin concentrations were still elevated at 30 h after deslorelin. Mean deslorelin magnitude, area under the curve and duration were sequentially greater (P<0.05) in a dose-dependent sequence. Compared to controls, serum LH concentrations were elevated (P<0.05) for 6 to 12 h after deslorelin. A dose-response relationship was absent for all parameters of LH secretion. Magnitude of the serum LH response was greatest (P<0.05) in the 12.5 microg and 50.0 microg groups, whereas area under the curve was lower (P<0.05) after 25.0 microg of deslorelin than after 12.5, 50.0 and 100.0 microg, which were not different from each other. Thus, no more than 12.5 microg of deslorelin is necessary to obtain maximum LH release in the model studied and doses less than 12.5 microg may also be effective.

Animals↗

Functional, biochemical and molecular biological evidence for a possible beta(3)-adrenoceptor in human near-term myometrium.

The possible existence of a beta(3)-adrenoceptor (beta(3)-AR) in human near-term myometrium was investigated by in vitro functional and biochemical studies and analysis of mRNA expression. SR 59119A and SR 59104A and CGP 12177 (two selective agonists and a partial agonist, respectively, of the beta(3)-AR), salbutamol and terbutaline (beta(2)-AR agonists) each produced a concentration-dependent relaxation of the myometrial spontaneous contractions. There were no differences in pD(2) values for the relaxing potencies of terbutaline, salbutamol, CGP 12177 and SR 59119A. The rank order for their relaxing efficacies was SR 59119A>SR 59104A>terbutaline approximately salbutamol approximately CGP 12177 (E(max)=52+/-7%, 42+/-12% and approximately 30% respectively). Propranolol, a beta(1)- and beta(2)-AR antagonist, and ICI 118551, a beta(2)-AR antagonist (both at 0.1 microM), did not affect the SR 59119A-induced relaxation whereas SR 59230A, a selective beta(3)-AR antagonist (1 microM), significantly reduced the maximal relaxing effect of SR 59119A. SR 59119A and salbutamol induced a significant increase in cyclic AMP levels that was antagonized by SR 59230A but not by propranolol for SR 59119A, and by propranolol but not by SR 59230A for salbutamol. The beta(3)-AR mRNA was positively expressed in myometrium preparations in a reverse transcription polymerase chain assay. The results presented provide the first evidence for the existence of the beta(3)-AR subtype in human near-term myometrium and suggest that the effects of SR 59119A might be mediated through an increase in cyclic AMP level.

Adrenergic beta-Agonists↗

Initial potency of lansoprazole and omeprazole tablets on pentagastrin-stimulated gastric acid secretion-a placebo-controlled study in healthy volunteers.

BACKGROUND: The new tablet formulation of omeprazole (Losec MUPS), is thought to have a stronger acid inhibition than the previously marketed capsules. METHODS: The effects of the proton pump inhibitors lansoprazole and omeprazole tablets on pentagastrin-stimulated acid secretion were compared in Helicobacter pylori-negative healthy male volunteers (n=12). The study was placebo-controlled, crossover matched and double-blind for lansoprazole (Agopton) and placebo, and single-blind for omeprazole tablets. Gastric acid response to sub-maximal pentagastrin-stimulation (0.6 microg. h/kg b.w.) was determined from 12.5 to 14.5 h after the first and second dose of the test drugs. RESULTS: Lansoprazole 15 mg and 30 mg as well as omeprazole 20 mg tablets caused a marked decrease in gastric acid secretion, showing equipotency for 15 mg lansoprazole and 20 mg omeprazole tablets. Their efficacy, however, was lower than 30 mg lansoprazole. In addition, the inter-individual variation after omeprazole tablets was higher than following lansoprazole. Neither 7.5 mg lansoprazole nor 10 mg omeprazole tablets were clearly different from placebo on the first 2 days. The drugs were well-tolerated. No clinically relevant influence was found on either laboratory screen or cardiovascular parameters. CONCLUSION: Lansoprazole 15-30 mg shows a stronger acid inhibition and a lower inter-individual variability than the new omeprazole 20 mg tablets on days 1 and 2 of dosing.

2-Pyridinylmethylsulfinylbenzimidazoles↗

Cytochrome P-450 2E1 activity and oxidative stress in alcoholic patients.

As cytochrome P-450 2E1 (CYP2E1) induction was related to oxidative stress in experimental models, the aim of this study was to investigate the relationship between CYP2E1 activity and markers of oxidative stress in 40 alcoholic patients entering a rehabilitation programme. Plasma oxidized proteins, lipid peroxides (LPO) and antibodies against hydroxyethyl radical (HER) or malondialdehyde (MDA) adducts were assessed as markers of the production of free radicals, whereas vitamin E levels were evaluated as a marker of the antioxidant defence. CYP2E1 activity was determined by using the 6-hydroxychlorzoxazone:chlorzoxazone blood metabolic ratio, 2 h after drug intake. This ratio was increased by 4-fold in alcoholics, compared to non-alcoholic patients, and was correlated with daily intake of ethanol, carbohydrate-deficient transferrin, and blood alcohol level at the time of admission to hospital. Plasma levels of LPO and oxidized proteins were slightly increased (20%) in alcoholic patients when compared with the control group, whereas those of vitamin E were found to be slightly decreased (by 18%). Antibodies against HER or MDA adducts showed a very significant increase. However, when alcoholic patients were divided into two groups according to low or high CYP2E1 induction, no significant difference was observed in the variation of these parameters, except for anti-HER adducts antibodies. Therefore, our study confirms the main involvement of CYP2E1 in HER production. By contrast, CYP2E1 does not appear to be the main factor responsible for the oxidative stress occurring during human chronic alcoholism. Free radicals from other sources may therefore contribute significantly to the generation of this oxidative stress.

Adult↗

Effects of pulsed electromagnetic fields on bone healing in a rabbit tibial osteotomy model.

OBJECTIVE: The purpose of this study was to determine the effect of pulsed electromagnetic field (PEMF) exposure on healing tibial osteotomies in New Zealand White rabbits. DESIGN: One-millimeter Gigli saw osteotomies were stabilized by external fixation. One day after surgery, rabbits were randomly assigned to receive either no exposure (sham control) or thirty minutes or sixty minutes per day of low-frequency, low-amplitude PEMF. Radiographs were obtained weekly throughout the study. Rabbits were euthanized at fourteen, twenty-one, or twenty-eight days, and tibiae underwent either destructive torsional testing or histologic analysis. To determine the baseline torsional strength and stiffness of rabbit tibiae, eleven normal intact tibiae were tested to failure. RESULTS: Sixty-minute PEMF-treated osteotomies had significantly higher torsional strength than did sham controls at fourteen and twenty-one days postoperatively. Thirty-minute PEMF-treated osteotomies were significantly stronger than sham controls only after twenty-one days. Normal intact torsional strength was achieved by fourteen days in the sixty-minute PEMF group, by twenty-one days in the thirty-minute PEMF group, and by twenty-eight days in the sham controls. Maximum fracture callus area correlated with the time to reach normal torsional strength. CONCLUSION: In this animal model, low-frequency, low-amplitude PEMF significantly accelerated callus formation and osteotomy healing in a dose-dependent manner.

Animals↗

Low frequency of p16(INK4a) alterations in insulinomas.

BACKGROUND/AIMS: The molecular mechanisms contributing to the tumorigenesis of insulinomas are poorly understood. Disruption of the cell cycle due to inactivation of the p16(INK4a) tumor-suppressor gene was identified in a variety of human tumors, including gastrinomas and nonfunctioning endocrine pancreatic carcinomas. In this study the role of p16(INK4a) in the tumorigenesis of insulinomas was evaluated. METHODS: Seventeen insulinomas (14 benign, 3 malignant) were analyzed for genetic alterations in the p16(INK4a) tumor-suppressor gene by SSCP, PCR-based deletion and methylation-specific assays. p16 expression was determined by immunohistochemistry. RESULTS: One malignant insulinoma showed a homozygous deletion of p16(INK4a) and another two benign insulinomas revealed aberrant methylation of the p16(INK4a) promoter region. All three tumors lacked p16 expression according to immunohistochemistry. None of the insulinomas carried intragenic p16(INK4a) mutations. In total, 17% of insulinomas had p16(INK4a) alterations. CONCLUSIONS: The p16(INK4a) tumor-suppressor gene contributes to tumorigenesis in only a small subset of insulinomas.

Cell Cycle↗

Treatment of neuroendocrine GEP tumours with somatostatin analogues: a review.

BACKGROUND: Somatostatin and its long-acting analogues are effective in symptom control in patients with functionally active neuroendocrine GEP tumours. Several in vitro and in vivo reports suggest that they are also able to control tumour growth. METHODS: Critical review of published data on the effect of long-acting somatostatin analogues on symptom and growth control in patients with metastatic neuroendocrine GEP tumours. RESULTS: With the exception of insulinoma and gastrinoma, octreotide acetate and other long-acting somatostatin formulations are currently the therapeutic principle of first choice to control hormone-mediated symptoms. The consequences of gastric acid hypersecretion in patients with Zollinger-Ellison syndrome are best controlled by proton pump inhibitors. Available data on growth control indicate that stabilization of tumour growth seems to be the most beneficial antiproliferative effect occurring in up to 50% of patients. This effect is limited. However, it is unknown which tumour entity responds best to long- acting somatostatin analogues. CONCLUSION: Additional studies in patients with known spontaneous tumour growth and avoiding a mix-up of different entities of neuroendocrine malignancies are necessary to identify subpopulations of neuroendocrine tumours which respond to long-acting somatostatin analogues in terms of longer lasting growth inhibition.

Antineoplastic Agents↗

The double negative effect: the (almost) paradoxical role of the individual self in minority and majority members' information processing.

The authors examined the interactive influence of accessibility of the individual self and relative in-group size on group-level as opposed to individual-level information processing. In Expt 1, the authors predicted and found that, when accessibility of the individual self was low, minority members tended more towards group-level information processing than did majority members. This was not true when accessibility of the individual self was high. Contrary to the authors' hypothesis, however, the disappearance of the minority-majority effect in the high-accessibility condition did not result from a decrease in group-level information processing among minority members, but from an increase among majority members. Experiment 2 replicated this unexpected effect using two different measures of group level information processing. It also provided additional data on the dynamic interplay of the individual self and the collective self which seems to be responsible for the observed effects.

Adult↗

Pyrazinamide is not active against Mycobacterium tuberculosis residing in cultured human monocyte-derived macrophages.

SETTING: Mycobacteriology Laboratory, National Jewish Medical and Research Center, Denver, Colorado. OBJECTIVE: To evaluate the antimicrobial activity of pyrazinamide against Mycobacterium tuberculosis in cultured human monocyte-derived normal and activated macrophages. DESIGN: Monocytes separated from human blood were incubated in plastic plates for seven days to mature into macrophage monolayers. After activation with TNF-alpha or IFN-gamma or without prior treatment, the macrophages were infected with M. tuberculosis. Various concentrations of pyrazinamide (PZA), morphazinamide (MZA) or isoniazid (INH) were added the next day, and the viable counts of the intracellular bacteria were determined at days 0, 4, and 8. RESULTS: No inhibitory activity of PZA at any concentration was detected, while clear dose-dependent bacteriostatic and bactericidal activities were demonstrated by MZA and INH in the same experimental model. CONCLUSIONS: PZA has neither bacteriostatic nor bactericidal activity against M. tuberculosis persisting or multiplying in cultured monocyte-derived human macrophages, and it might be that the well-known effectiveness of this drug in tuberculosis patients is not related to its supposed activity against intracellular bacterial subpopulations.

Antitubercular Agents↗

Effect of faradic products on direct current-stimulated calvarial organ culture calcium levels.

Calcium release from mouse calvarial organ cultures was used to analyse the well-described biological effects of constant direct current (20 microA) in combination with Faradic products generated at a titanium wire cathode. Constant 20-microA direct current stimulation alone, delivered by agar salt bridges, consistently lowered the media calcium levels. Direct exposure of calvariae to a titanium cathode and its faradic products resulted in further lowering of media calcium levels and also a significant increase in the media pH. Hydrogen peroxide is a faradic product of the titanium cathode, micromolar amounts being generated by our system over 24 hr. H(2)O(2) is pro-resorptive whereas elevated pH stimulates osteoblast activity. We propose that where bone tissue is in direct contact with metal wire cathodes, the faradic products, hydrogen peroxide and hydroxyl ion, are significant factors which, in their own right, further contribute to accelerated remodelling and improved clinical outcome.

Animals↗

Ethnic susceptibility to lung cancer: differences in CYP2E1, CYP1A1 and GSTM1 genetic polymorphisms between French Caucasian and Chilean populations.

Many investigators have reported an association between genetic polymorphisms of cytochromes P-450 CYP2E1, CYP1A1 or glutathione S-transferase Mu (GSTM1) and susceptibility to lung cancer. However, pronounced interethnic variations have been described in the frequencies of these polymorphisms, especially between Asians and Caucasians. The present study was set up to establish CYP2E1 (c1, c2 and C, D), CYP1A1 (m1, m2 and Ile, Val) and GSTM1 (null) allelic frequencies in Chileans (n = 96) who are an admixture of Native Americans and Caucasians (Spaniards). The rare allele frequencies were found to be 0.15 (c2), 0.21 (C), 0.23 (m2), 0.32 (Val) and 0.21 ('null' genotype). These values are significantly higher than those of Caucasians except for the GSTM1 'null' genotype and suggest differences in susceptibility to lung cancer between both populations.

Adult↗

Inhibition of mitochondrial ATP generation by nitric oxide switches apoptosis to necrosis.

Under pathological conditions, the mode of cell death, apoptosis or necrosis, is relevant for the subsequent fate of the tissue. Cell demise may be shaped by endogenous mediators such as nitric oxide (NO) which interfere with subroutines of the death program. Here we show that apoptosis of Jurkat cells elicited by either staurosporine (STS) or anti-CD95 antibodies in glucose-free medium is converted to necrosis by NO donors. In the presence of NO, release of mitochondrial cytochrome c was delayed and activation of execution caspases was prevented. Stimulated cells died nonetheless. The switch in the mode of cell death was due to NO-dependent failure of mitochondrial energy production. Restoration of intracellular ATP by glucose supplementation recovered the cells' ability to activate caspases and undergo apoptosis. In this system, the apoptosis/necrosis conversion promoted by NO was not mediated by cyclic guanosine monophosphate-dependent mechanisms, poly-(ADP-ribose)-polymerase (PARP) activation, or inhibition of caspases due to S-nitrosylation and glutathione depletion. In contrast, depleting intracellular ATP with rotenone, an inhibitor of mitochondrial complex I mimicked the effect of NO. The findings presented here suggest that NO can decide the shape of cell death by lowering intracellular ATP below the level required to allow the coordinated execution of apoptosis.

Adenosine Triphosphate↗

Higher frequency of DPC4/Smad4 alterations in pancreatic cancer cell lines than in primary pancreatic adenocarcinomas.

The tumor suppressor gene DPC4/Smad4 at 18q21.1 is inactive in about 50% of pancreatic carcinoma xenografts and cell lines. However, the role of DPC4 in the multistep carcinogenesis of primary pancreatic adenocarcinomas remains uncertain. Therefore, we examined 45 primary human pancreatic adenocarcinomas and 12 pancreatic cancer cell lines for DPC4 alterations by single-strand conformational variant (SSCV) analysis and a PCR-based deletion assay. DPC4 was inactivated by either homozygous deletion or point mutation in 6 of 12 cell lines (50%). None of the primary pancreatic carcinomas carried a DPC4 mutation, although 66% revealed LOH of 18q21 sequences. These findings suggest that inactivation of DPC4 occurs more frequently in tumor-derived cell lines than in primary pancreatic adenocarcinomas. In addition, another, yet unidentified, tumor suppressor gene(s) may be linked with the frequent LOH of 18q21 in primary pancreatic adenocarcinomas.

Adenocarcinoma↗

Nitric oxide inhibits execution of apoptosis at two distinct ATP-dependent steps upstream and downstream of mitochondrial cytochrome c release.

The endogenous mediator nitric oxide (NO) blocked apoptosis of Jurkat cells elicited by staurosporine, anti-CD95 or chemotherapeutics, and switched death to necrosis. The switch in the mode of cell death was dependent on the ATP loss elicited by NO. This affected two distinct steps of the apoptotic cascade. First, the release of cytochrome c from mitochondria was delayed by NO. Second, processing of procaspases-3/7 to the active proteases was prevented even after cytochrome c had been released. Thus, NO interferes with execution steps of apoptosis both upstream and downstream of cytochrome c release.

Adenosine Triphosphate↗