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Biomedical subjects

A Roda

Publications and source records attributed to A Roda.

At least 37 records · Page 2Linked to original sources
PubMed2000

Competition in liver transport between chenodeoxycholic acid and ursodeoxycholic acid as a mechanism for ursodeoxycholic acid and its amidates' protection of liver damage induced by chenodeoxycholic acid.

BACKGROUND: Ursodeoxycholic acid has been widely used as a therapeutic agent in cholesterol gallstones and liver disease patients, but its mechanism of action is still under investigation. AIMS: The protective effect of ursodeoxycholic acid, both free, taurine and glycine conjugated, against hepatotoxic bile acids such as chenodeoxycholic acid and its taurine amidate was studied in bile fistula rats and compared with the cholic and taurocholic acid effect. METHODS: Tauroursodeoxycholic acid, glycine ursodeoxycholic acid, ursodeoxycholic acid, taurocholic acid and cholic acid were infused iv over 1 hour (8 micromol/min/kg) together with an equimolar dose of either taurochenodeoxycholic acid or chenodeoxycholc acid. Bile flow, total and individual bile acid and biliary lactate dehydrogenase and alkaline phosphatase enzymes were measured. RESULTS: Taurochenodeoxycholic acid and chenodeoxycholc acid caused cholestasis and liver damage associated with a decreased bile flow, total and individual bile acids secretion accompanied by a biliary leakage of lactate dehydrogenase and alkaline phosphatase enzymes. Tauroursodeoxycholic acid, glycine ursodeoxycholic acid, ursodeoxycholic acid and taurocholic acid, on the contrary, were choleretic, inducing an opposite effect on biliary parameters. Simultaneous infusion of taurochenodeoxycholic acid and the protective bile acid resulted in a functional and morphological improvement of the above parameters in the following order: glycine ursodeoxycholic acid > tauroursodeoxycholic acid > ursodeoxycholic acid followed by taurocholic acid; cholic acid was ineffective. CONCLUSIONS: The results show the protective effect of glycine ursodeoxycholic acid, ursodeoxycholic acid and tauroursodeoxycholic acid. This may be due to a facilitated transport of the toxic bile acid into bile; conjugation with taurine is less effective than glycine. Finally, the better protective effect of ursodeoxycholic acid and its amidates with respect to cholic acid and its taurine conjugated form seems to be related to their different lipophilicity and micellar forming capacity.

Alkaline Phosphatase↗
PubMed2000

Protein microdeposition using a conventional ink-jet printer.

Many recent bioanalytical systems based on immunologic and hybridization reactions in a mono- or bidimensional microarray format require technology that can produce arrays of spots containing biospecific molecules. Some microarray deposition instruments are commercially available, and other devices have been described in recent papers. We describe a system obtained by adapting a commercial ink-jet printer and used to produce mono- and bidimensional arrays of spots containing horseradish peroxidase on cellulose paper. In a few minutes, it was possible to obtain bidimensional arrays containing several thousands of spots with a diameter as low as 0.2 mm, with each of which requiring only a few nanoliters of the enzyme deposition solution. The quantity of enzyme in each spot was evaluated with a chemiluminescent reaction and a charge-coupled device-based, low-light imaging luminograph. The chemiluminescence measurements revealed that the reproducibility of the enzyme deposition was satisfactory for analytical purposes, with the variation coefficients being lower than 10% in almost all cases.

Horseradish Peroxidase↗
PubMed2000

Mechanism for the prevention of cholestasis involving cytochrome P4503A overexpression.

BACKGROUND: To clarify the preventive effect of taurohyodeoxycholic acid on liver cholestasis induced by toxic bile acids in rats, we evaluated whether modulation of cytochrome P4503A-linked oxidases is involved in the hepatic bile acid retention and secretion mechanism. We investigated whether the safe or the toxic taurochenodeoxycholic acid, administered singly or together, affects cytochrome P450-catalyzed drug metabolism or biliary parameters. We also considered whether the inhibition of the P-glycoprotein export pump by vinblastine might be related to cytochrome P4503A overexpression. METHODS: Hydroxylation of testosterone and N-demethylation of aminopyrine were studied in subcellular rat liver preparations after intravenous infusion of hepatoprotective and toxic bile acids administered singly or together. Bile flow, calcium secretion, biliary enzymes activity, and secretion rates of the endogenous and administrated bile acids were determined. CYP3A-dependent monooxygenases were also measured in the same coinfusion model in the presence of vinblastine. RESULTS: Although wide modulation of the activities of different P450 subfamily of isoenzymes was seen, P4503A-associated monooxygenases showed similar patterns in the various situations, i.e., induction by taurohyodeoxycholic acid, reduction by taurochenodeoxycholic acid, and protection (intermediate induction) in the coinfusion experiments. This correlates well with biliary parameters demonstrating the hepatoprotective ability of taurohyodeoxycholic acid. Coadministration of bile acids and vinblastine significantly modifies CYP3A-linked activities. CONCLUSIONS: Bile acid structure seems to be linked with hepatotoxicity/hepatoprotection and P4503A modulation. Taurohyodeoxycholic acid could be therapeutic in cholestatic liver disease by inducing P4503A; we can hypothesize that an associated P-glycoprotein expression might facilitate biliary excretion of toxic taurochenodeoxycholic acid accumulated in the liver during cholestasis.

Animals↗
PubMed1999

Determination of 4-hydroxy-2-nonenal at cellular levels by means of electrospray mass spectrometry.

trans-4-Hydroxy-2-nonenal (HNE) is an end-product of lipid peroxidation in biological systems which produces a variety of powerful biological effects. A method based on electrospray mass spectrometry was developed for the determination of 4-HNE at cellular levels. Quantification was carried out by using HNE-d(11) as internal standard; the mass chromatograms were acquired in the single ion monitoring mode (SIM) on the [M + H](+) monoisotopic species for HNE and HNE-d(11). With this approach a higher precision and lower detection limit and biological sample size than those typical of the methods so far employed are achieved. Furthermore the determination of the analyte from the cell extract is directly performed without the need of any HNE derivatization. As a first application the method was used to identify and quantify HNE in human T cell leukemia extracts.

Aldehydes↗
PubMed1999

Bile acid structure and selective modulation of murine hepatic cytochrome P450-linked enzymes.

We examined the effects of the administration of different bile acids on in vivo hepatic murine cytochrome P450 (CYP) content, nicotinamide adenine dinucleotide phosphate (NADPH)-CYP-reductase, and individual mixed-function oxidases (MFOs). Neither CYP level nor reductase were appreciably affected by single intraperitoneal administration of taurodeoxycholic acid (TDCA) (12.2 or 24.4 mg x kg(-1) bw). MFO to various isoenzymes were slightly reduced 24 hours after treatment. Taurohyodeoxycholic acid (THDCA) and tauroursodeoxycholic acid (TUDCA) both induced CYP, reductase, and MFOs. CYP3A1/2-linked activity (i.e., testosterone 6beta-hydroxylase, and N-demethylation of aminopyrine) in a dose-dependent fashion was enhanced ( approximately 2-3-fold). CYP2E1- (hydroxylation of p-nitrophenol), CYP1A2-(O-demethylation of methoxyresorufin), CYP2A1/2- and CYP2B1/2-(6alpha-hydroxylase), and CYP2B9- (16alpha-hydroxylase) dependent MFOs, as well as 7alpha-, 16beta-, 2alpha-, and 2beta-hydroxylations, were all significantly induced by THDCA. Apart from alkoxyresorufin metabolism and a modest CYP2E1 increase, TUDCA behaved like THDCA. A generalized induction was also recorded after ursodeoxycholic acid (UDCA) administration. THDCA and TDCA did not show substantial differences in the N-demethylation of aminopyrine when different species (rat vs. mouse) and administration route (intraperitoneal vs. intravenous) were compared. Results on the most affected isoenzymes, CYP3A1/2 (THDCA, TUDCA, and UDCA) and CYP2E1 (UDCA), were sustained by means of Western immunoblotting. CYP3A induction was paralleled by a corresponding increase in mRNA. These data could partially explain the therapeutic mechanism of UDCA, TUDCA, and THDCA in chronic cholestatic liver disease. CYP3A induction, which is linked to P-glycoprotein (Pgp) family overexpression, may enhance hepatic metabolism, transport, and excretion of toxic endogenous lipophilic bile acids.

Animals↗
PubMed1999

Chemiluminescence Western blot assay for the detection of immunity against parvovirus B19 VP1 and VP2 linear epitopes using a videocamera based luminograph.

A chemiluminescent Western blot (WB) assay was developed to detect the immune status against linear epitopes of parvovirus B19 structural proteins VP1 and VP2. The chemiluminescent WB assay combined the sensitivity of chemiluminescent substrates and the objective evaluation of the luminescent signal obtained with a new system which consists of a videocamera-based, high-performance, low light level imaging luminograph connected to a personal computer for image analysis. The potential for diagnostic purposes was evaluated using reference serum samples and 75 clinical samples from patients with different clinical conditions and laboratory evaluations regarding B19 infection. The chemiluminescent Western blot assay provided reproducible results, an objective evaluation of the results and a semi-quantitative analysis of the presence of antibodies against VP1 and VP2 in human sera. The chemiluminescent Western blot assay proved more sensitive than the classic colourimetric Western blot assay.

Adolescent↗
PubMed1999

Sluggish small bowel motility is involved in determining increased biliary deoxycholic acid in cholesterol gallstone patients.

OBJECTIVE: Our aim was to establish whether small intestine transit time is defective in subjects with cholesterol gallstones. METHODS: We enrolled 10 patients (eight women, two men; mean age, 48.7 yr; mean body mass index [BMI], 22.4 Kg/m2) with recently diagnosed cholelithiasis, with no liver pathology, who were not taking any drugs, and 11 comparable healthy volunteers (eight women, three men; mean age, 46.2 yr; mean BMI, 22.7 Kg/m2), who served as controls. All subjects underwent orocecal (by starch breath test technique and serum assays of salazopyrin), oroileal (by serum assays of tauroursodeoxycholic acid), and duodenoileal (by serum assays of taurocholic acid) transit times; cholesterol saturation index; and bile acid composition and gallbladder motility studies (by ultrasound). For serum assays, blood samples were collected over a period of 7 h. Gallbladder motility and orocecal transit time were evaluated simultaneously. RESULTS: All four means of assessing transit time gave longer times in cholesterol gallstone patients than in controls: orocecal transit time (salazopyrin) = 366 +/- 13 vs 258 +/- 16 min, p < 0.0005; orocecal transit time (starch breath test) = 415 +/- 139 vs 290 +/- 15 min, p < 0.01; duodenoileal transit time: 272 +/- 23 vs 205 +/- 23 min, p < 0.03; and oroileal transit time: 308 +/- 18 vs 230 +/- 19 min, p < 0.009. Cholesterol gallstone patients showed an increase in percent molar biliary deoxycholic acid (30% +/- 4.5% vs 16% +/- 1.3%, p < 0.02) and a decrease in percent molar cholic acid 32% +/- 2.2% vs 40% +/- 1.3%, p < 0.03) and chenodeoxycholic acid (34% +/- 3% vs 41% +/- 1.8%, p < 0.03), compared with controls; patients also had greater percent molar biliary cholesterol. A linear relationship (r2 = 0.6324, p = 0.0012) between biliary deoxycholic acid and small bowel transit time was found. Residual gallbladder volumes were larger in cholesterol gallstone patients (11.38 +/- 1.27 vs 7.55 +/- 0.39 ml, p < 0.04), whereas basal gallbladder volumes, although higher, did not reach statistical significance (24.25 +/- 2.41 vs 19.98 +/- 1.63 ml; p = ns). CONCLUSIONS: This study confirms that patients with cholesterol gallstones have delayed small bowel transit, defective gallbladder motor function, and increased biliary deoxycholic acid. Delayed small bowel transit may contribute to supersaturation of bile with cholesterol by increasing deoxycholic acid production.

Bile↗
PubMed1999

Prenatal diagnosis of parvovirus B19-induced hydrops fetalis by chemiluminescence in situ hybridization.

Parvovirus B19 can be transmitted transplacentally from the infected mother to the fetus during pregnancy, and hydrops fetalis, abortion, or stillbirth can result. In our study we explored the use of chemiluminescence in situ hybridization to detect B19 DNA on cord blood cells, amniotic fluid cells, and pleuric fluid cells from several cases of hydrops fetalis. B19 DNA was detected by using digoxigenin-labeled probes immunoenzymatically visualized with the chemiluminescent adamantil-1,2-dioxetane phenyl phosphate substrate for alkaline phosphatase. The luminescent signal emitted from the hybridized probes was detected, analyzed, and measured with a high-performance, low-light-level imaging luminograph connected to an optical microscope and to a personal computer for the quantification and localization of the chemiluminescent emission inside individual cells.

Amniotic Fluid↗
PubMed1998

Development of a chemiluminescent urease activity assay for Helicobacter pylori infection diagnosis in gastric mucosa biopsies.

A chemiluminescent urease activity assay has been developed and optimized using the chemiluminescent pH indicator phthalhydrazidylazoacetylacetone. This compound is stable at pH </= 7 and decomposes at higher pH values, emitting light in the presence of H2O2. Urease catalyzes hydrolysis of urea to form NH3 and CO2 which increase the pH of the reaction medium, thus allowing the chemiluminescent indicator to decompose and produce photons. The emitted light is proportional to the urease activity when urea is in excess. Urease tests based on colorimetric pH indicators like phenol red are commercially available and commonly used for the rapid diagnosis of Helicobacter pylori infection in gastric mucosa biopsy specimens, since this bacterium produces high amounts of urease. Such colorimetric tests often lack sensitivity, giving false-negative results. The developed chemiluminescent test proved to be at least 50-fold more sensitive than the colorimetric tests, permitting early diagnosis of infection, and it is more rapid, giving results in 1-10 min compared to 30 min. Further applications of this assay could be the in situ localization of urease activity, corresponding to the presence of H. pylori, in gastric mucosa cryosections and the development of high-throughput screening assays of antimicrobial drugs able to inactivate the bacterium.

Adult↗
PubMed1998

Separation techniques for bile salts analysis.

The analysis of bile salts in biological samples has remained a difficult task, due to the complex nature of the salts and also to their low concentration in common sample fluids such as plasma and urine. Given their importance, the development of accurate and sensitive methods of instrumental analysis has been the subject of intensive research, and recent advances have eliminated or lessened some of the difficulties. Currently available techniques are the following: thin-layer chromatography, gas chromatography, high-performance liquid chromatography, supercritical fluid chromatography, gas chromatography-mass spectrometry and capillary electrophoresis. Liquid chromatography coupled with mass spectrometry (thermospray, fast atom bombardment, electrospray and ionspray), a method undergoing continuous improvement, is also being applied to bile salts analysis. In this paper, these various techniques, which differ greatly in specificity, accuracy and simplicity, are reviewed and discussed, in terms of analytical performance, applicability to a given sample fluid, major limitations, ability to identify uncommon bile salts, including unsaturated oxo derivatives, glucuronides, sulfates, glycosides and bile alcohols.

Bile Acids and Salts↗
PubMed1998

Chemiluminescent imaging of enzyme-labeled probes using an optical microscope-videocamera luminograph.

A chemiluminescent system has been developed for ultrasensitive, quantitative analysis as well as visualization of the spatial distribution of biomolecules such as antigens, enzymes, antibodies, DNA probes in tissue, or cells. The system consists of a low-light imaging Vidicon videocamera connected to an optical microscope, able to measure light at the single photon level and perform 3D image analysis of the subcellular distribution of the analyte. The concentration and the spatial distribution of enzymes, or enzyme-labeled biospecific reagents can be determined using appropriate chemiluminescent substrates. Analytes are also determined with coupled enzymatic reactions terminating in light emission. Oxirane acrylic beads (250-micron-diameter macroporous particles) with immobilized horseradish peroxidase have been used as a model system to optimize the experimental conditions in terms of signal intensity and spatial resolution as a function of different chemiluminescent substrates such as luminol/enhancer/H2O2 and acridancarboxylate ester/H2O2. Localization of oxirane beads immobilized acetylcholinesterase has been also used to optimize a system in which the detection and localization of the primary enzyme involves two secondary enzymes in solution, choline oxidase and horseradish peroxidase, leading to a final light emission. Immunoenzymatic reactions for the detection of viral antigens and in situ hybridization assays for the detection of viral DNAs (cytomegalovirus, herpes simplex virus) have been performed in cells using peroxidase-labeled antibodies or cDNA probes and the analytical performance of different chemiluminescent substrates for the enzyme has been evaluated. The results obtained showed the possibility to sharply image the bioprobes in single cells and peroxidase is a suitable label when luminol/H2O2 system is used in conjunction with enhancer as in the ECL and SuperSignal Ultra reagents; other substrates such as Lumigen PS-3, despite adequate detectability, showed problems of localization of the signal as a result of the relatively long half-life of the excited emitting species and its diffusion in the chemiluminescent cocktail. The system has proven to be highly sensitive, able to perform quantitative analysis, and relatively simple.

Acetylcholinesterase↗
PubMed1998

Chemiluminescent real time imaging of post-ischemic oxygen free radicals formation in livers isolated from young and old rats.

Oxygen free radicals generation is a major cause of liver injury during reperfusion. Luminescence analysis has been recently proposed to measure free radical generation by isolated cells or organs, but it allows only global tissue luminescence. Using a special Saticon videocamera with image intensifier we aimed to visualize and localize oxygen free radical generation in isolated perfused livers exposed to an oxydative stress. Livers isolated from rats aged 4 and 30 months were exposed to ischemia/reperfusion; photons emission by the organs was continuously recorded. Lucigenin was utilized as a chemiluminigenic probe to assess superoxide anion generation. In both groups, chemiluminescence was not detectable during ischemia, while it was observed after reperfusion. Photons emission started after few minutes of reperfusion, was maximal after 15-20 min and disappeared within 50-60 min. Chemiluminescence emitted by livers from younger rats however, was significantly higher when compared to chemiluminescence emitted by organs isolated from old rats (0.8 +/- 0.1 vs 0.44 +/- 0.08 photons x 10(5)/s, respectively, after 15 min; p < .01). The superimposition of chemiluminescent and live image permitted to determine the regional production rate and distribution of photons. In conclusion, the age of the rats influences significantly the amount of oxyradicals produced in the liver during post-ischemic reperfusion. The method described, allowing the visualization in real time of oxygen free radicals generation on the surface of isolated intact organs, represents a novel and potent tool for the study of oxidative stress.

Acridines↗
PubMed1998

Taurohyodeoxycholic acid protects against taurochenodeoxycholic acid-induced cholestasis in the rat.

The prevention of the hepatotoxic effects produced by intravenous infusion of taurochenodeoxycholic acid (TCDCA) by coinfusion with taurohyodeoxycholic acid (THDCA) was evaluated in bile fistula rats; the hepatoprotective effects of the latter were also compared with those of tauroursodeoxycholic acid (TUDCA). Rats infused with TCDCA at a dose of 8 micromol/min/kg showed reduced bile flow and calcium secretion, as well as increased biliary release of alkaline phosphatase (AP) and lactate dehydrogenase (LDH). This was associated with a very low biliary secretion rate of TCDCA (approximately 1 micromol/min/kg). Simultaneous infusion of THDCA or TUDCA at the same dose preserved bile flow and almost totally abolished the pathological leakage of the two enzymes into bile. The effect was slightly more potent for THDCA. The maximum secretion rate of TCDCA increased to the highest value (8 micromol/min/kg) when coinfused with either of the two hepatoprotective bile acids (BA), which were efficiently and completely secreted in the bile, without metabolism. Calcium output was also restored and phospholipid (PL) secretion increased with respect to the control saline infusion. This increase was higher in the THDCA study. These data show that THDCA is highly effective in the prevention of hepatotoxicity induced by intravenous infusion of TCDCA by facilitating its biliary secretion and reducing its hepatic residence time; this was associated with selective stimulation of PL biliary secretion.

Alkaline Phosphatase↗
PubMed1998

Chemiluminescence imaging in bioanalysis.

The development, analytical performance and applications of chemiluminescence imaging as a tool for quantitative analyte localization in target biological specimens are described. The detection of acetylcholinesterase activity both in array format and on a target surface are described. A proposed application of the method is a 384 well microtiter format assay for high throughput screening of acetylcholinesterase inhibitors such as tacrine, a drug widely used in the treatment of Alzheimer's disease, and two recently developed analogues. The chemiluminescent system in conjunction with optical microscopy allowed localization of acetylcholinesterase in brain tissue sections. We also describe the chemiluminescent immunohistochemical localization of interleukin 8 in Helicobacter pylori infected gastric mucosa cryosections and an in situ hybridization assay for the detection of herpes simplex virus DNA in single cells.

Acetylcholinesterase↗
PubMed1998

Evaluation of short-term low-dose triple therapy for the eradication of Helicobacter pylori by factorial design in a randomized, double-blind, controlled study.

BACKGROUND: Studies demonstrating the efficacy of short-term low-dose triple therapies including omeprazole (O), clarithromycin (C) and a nitroimidazole (tinidazole, T) for Helicobacter pylori eradication have largely been open and uncontrolled, and have not assessed antibiotic sensitivity. Simpler regimens using the component drugs have not been evaluated. AIM: To evaluate the OCT regimen in a randomized, controlled trial, testing for pre- and post-treatment antibiotic resistance and comparing, in a factorial design, the OCT regimen with simpler combinations of its components. METHODS: One hundred and twenty-eight patients (68 males, 60 females, age 22-80 years, mean 53 years) with H. pylori gastritis were randomly assigned to one of the following four treatment groups: (C) clarithromycin 250 mg b.d.; (OC) omeprazole 20 mg o.d. + clarithromycin 250 mg b.d.; (CT) clarithromycin 250 mg b.d. + tinidazole 500 mg b.d.; (OCT) omeprazole 20 mg q.d.s. + clarithromycin 250 mg b.d. + tinidazole 500 mg b.d. The drugs were administered for 1 week. Medical interview, upper gastrointestinal endoscopy (with four antral and four corpus biopsies) and the 13C-urea breath test were carried out for all patients prior to and 4 weeks after treatment. Biopsy specimens were used for the urease test, histology, and culture and sensitivities. RESULTS: All but one patient completed treatment. Side-effects were rare and mild in all groups. The eradication rate was 93.8% in group OCT, 59.4% in group CT, 31.3% in group OC and 6.3% in group C. Pre-treatment metronidazole resistance was 12.8%, clarithromycin 1.1% and, to both antibiotics, 2.1%. In patients with pre-treatment metronidazole resistance, the eradication rate was 75% in group OCT and 33% in group CT. Post-treatment resistance to clarithromycin was induced in 28.5% of the failures in group C, but in none of group OC. Resistance to both antibiotics occurred in 22.2% of the failures in group CT and in none of group OCT. CONCLUSIONS: (i) The high efficacy of the OCT regimen is proved and each of the individual components of the regimen is essential to the result, possibly via a synergistic effect. (ii) Pre-treatment metronidazole resistance is scarcely relevant to the outcome. (iii) Acquired resistance is essentially nil if omeprazole is part of the regimen.

Adult↗
PubMed1998

13C labelled cholesteryl octanoate breath test for assessing pancreatic exocrine insufficiency.

BACKGROUND: A non-invasive test for assessment of fat digestion has been developed based on the intraluminal hydrolysis of cholesteryl-[1-13C]octanoate by pancreatic esterase. AIMS: To determine the diagnostic performance of this breath test in the assessment of exocrine pancreatic function. METHODS: The test was performed in 20 healthy controls, 22 patients with chronic pancreatic disease (CPD), four with biliopancreatic diversion (BPD), and 32 with non-pancreatic digestive diseases (NPD); results were compared with those of other tubeless tests (faecal chymotrypsin and fluorescein dilaurate test). RESULTS: Hourly recoveries of 13CO2 were significantly lower in CPD when compared with healthy controls or NPD. In patients with CPD with mild to moderate insufficiency, the curve of 13CO2 recovery was similar to that of healthy controls, while in those with severe insufficiency it was flat. In three patients with CPD with severe steatorrhoea, a repeat test after pancreatic enzyme supplementation showed a significant rise in 13CO2 recovery. The four BPD patients had low and delayed 13CO2 recovery. Only eight of the 32 patients with NPD had abnormal breath test results. There was a significant correlation between the results of the breath test and those of faecal chymotrypsin, the fluorescein dilaurate test, and faecal fat measurements. For the diagnosis of pancreatic disease using the three hour cumulative 13CO2 recovery test, the sensitivity was 68.2% and specificity 75.0%; values were similar to those of the other two tubeless pancreatic function tests. In seven healthy controls, nine patients with CPD, and nine with NPD a second breath test was performed using Na-[1-13C]octanoate and a pancreatic function index was calculated as the ratio of 13C recovery obtained in the two tests: at three hours this index was abnormal in eight patients with CPD and in three with NPD. CONCLUSION: The cholesteryl-1[1-13C]octanoate breath test can be useful for the diagnosis of fat malabsorption and exocrine pancreatic insufficiency.

Adult↗
PubMed1998

Chemiluminescence: a sensitive detection system in in situ hybridization.

Chemiluminescence is the light emission produced by a chemical reaction in which chemically excited molecules decay to the ground state. The phenomenon is utilized in various analytical techniques in which small amounts of analytes or enzymes can be detected and quantified by measurement of the light emitted by bio- or chemiluminescent reactions. Recently chemiluminescence has been proposed as a valid alternative to radioactive or colorimetric methods in in situ hybridization assays, in which target nucleic acids are localized by labeled probes inside individual cells with the preservation of cell morphology. Chemiluminescence in situ hybridization is performed using probes that are detected using enzymes with their appropriate chemiluminescent substrates. The luminescent signal from the hybrid formation is detected, analysed and measured with a high performance low light level imaging apparatus connected to an optical microscope and to a personal computer for quantitative image analysis. Generally, the instrumental system to detect positive signals after in situ hybridization operates in three steps: firstly tissue structures and cells are recorded in transmitted light then the luminescent signal is measured with an optimized photon accumulation; and then, after a computer elaboration of the luminescent signal with pseudocolors corresponding to the light intensity, an overlay of the two images on the screen provided by the transmitted light and by the luminescent signal allows the spatial distribution of the labeled probe to be localized and evaluated. The main advantages of chemiluminescence in situ hybridization are mainly the sensitivity, the quantification of the data, the objectivity of the evaluation and the digital imaging of the results. The chemiluminescence in situ hybridization assay, which can be applied to cell smears, archival frozen and paraffin embedded tissue samples, can be a useful tool for a sensitive and specific diagnosis of viral infections and for the detection and study of specific genic sequences inside the cells. The use of the chemiluminescent in situ hybridization assay is also promising for an estimation and quantification of nucleic acids present in tissue samples or cellular smears and for imaging gene expression in cells.

Animals↗