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Biomedical subjects

O Aziz

Publications and source records attributed to O Aziz.

At least 19 recordsLinked to original sources
PubMed2006

Meta-analysis of observational studies of ileorectal versus ileal pouch-anal anastomosis for familial adenomatous polyposis.

BACKGROUND: Surgery for familial adenomatous polyposis (FAP) aims to minimize cancer risk while providing good functional outcome. Colectomy with ileorectal anastomosis and proctocolectomy with ileal pouch-anal anastomosis both offer this, but there is no clear consensus about which is better. METHODS: This is a meta-analysis of comparative studies published between 1991 and 2003 reporting early and late postoperative adverse events, functional outcomes and quality of life. RESULTS: Twelve studies containing 1002 patients (53.4 per cent ileal pouch, 46.6 per cent ileorectal anastomosis) were identified. Bowel frequency (weighted mean difference 1.62 (95 per cent confidence interval (c.i.) 1.05 to 2.20)), night defaecation (odds ratio (OR) 6.64 (95 per cent c.i. 2.99 to 14.74)) and use of incontinence pads (OR 2.72 (95 per cent c.i. 1.02 to 7.23)) were significantly less in the ileorectal group, although faecal urgency was reduced with the ileal pouch (odds ratio 0.43 (95 per cent c.i. 0.23 to 0.80)). Reoperation within 30 days was more common after ileal pouch construction (23.4 versus 11.6 per cent; OR 2.11 (95 per cent c.i. 1.21 to 3.70)). There was no significant difference between the techniques in terms of sexual dysfunction, dietary restriction, or postoperative complications. Rectal cancer was a diagnosis only in the ileorectal group (5.5 per cent). CONCLUSION: Ileal pouch and ileorectal anastomoses have individual merits. Further research is needed to determine which most benefits patients with FAP.

Adenomatous Polyposis Coli↗
PubMed2005

Magnetic resonance colonography versus colonoscopy as a diagnostic investigation for colorectal cancer: a meta-analysis.

AIMS: Magnetic resonance colonography (MRC) is emerging as a potential complementary investigation for the diagnosis of colorectal cancer (CRC) and also for benign pathology such as diverticular disease. A meta-analysis reporting the use of MRC is yet to be performed. The aim of this study was to evaluate the diagnostic accuracy of MRC compared with the gold-standard investigation, conventional colonoscopy (CC). METHODS: A literature search was carried out to identify studies containing comparative data between MRC findings and CC findings. Quantitative meta-analysis for diagnostic tests was performed, which included the calculation of independent sensitivities, specificities, diagnostic odds ratios, the construction of summary receiver operating characteristic (SROC) curves, pooled analysis and sensitivity analysis. The study heterogeneity was evaluated by the Q-test using a random-effect model to accommodate the cluster of outcomes between individual studies. RESULTS: In all, 8 comparative studies were identified, involving 563 patients. The calculated pooled sensitivity for all lesions was 75% (95% CI: 47% to 91%), the specificity was 96% (95% CI: 86% to 98%) and the area under the ROC curve was 90% (weighted). On sensitivity analysis, MRC had a better diagnostic accuracy for CRC than for polyps, with a sensitivity of 91% (95% CI: 97% to 91%), a specificity of 98% (95% CI: 66% to 99%) and an area under the ROC curve of 92%. There was no significant heterogeneity between the studies with regard to the diagnostic accuracy of MRC for CRC. CONCLUSION: This meta-analysis suggests that MRC is an imaging technique with high discrimination for cases presenting with colorectal cancer. The exact diagnostic role of MRC needs to be clarified (e.g. suitable for an elderly person with suspected CRC). Further evaluation is necessary to refine its applicability and diagnostic accuracy in comparison with other imaging methods such as computed tomography colonography.

Adenocarcinoma↗
PubMed2005

Laparoscopic surgery for colon cancer.

Acceptance of laparoscopy for the management of oncological disease has been slow due to the increased complexity of the technique, requirement of technological advances, and fears for the oncological safety of the approach. Laparoscopic oncological surgery has a role in the management of oncological patients at all stages of disease. Good evidence exists for the laparoscopic approach being a viable option for colon cancer patients. Current large multicenter trials will report the true outcomes of laparoscopic colon cancer surgery and how it compares with open surgery. This article examines some of the parameters by which laparoscopic colectomy will be judged.

Clinical Trials as Topic↗
PubMed2003

Kinetics and regulation of a Ca2+-activated Cl- conductance in mouse renal inner medullary collecting duct cells.

Using the whole cell patch-clamp technique, a Ca2+-activated Cl- conductance (CaCC) was transiently activated by extracellular ATP (100 microM) in primary cultures of mouse inner medullary collecting duct (IMCD) cells and in the mouse IMCD-K2 cell line. ATP also transiently increased intracellular Ca2+ concentration ([Ca2+]i) from 100 nM to peak values of approximately 750 nM in mIMCD-K2 cells, with a time course similar to the ATP-induced activation and decay of the CaCC. Removal of extracellular Ca2+ had no major effect on the peak Cl- conductance or the increase in [Ca2+]i induced by ATP, suggesting that Ca2+ released from intracellular stores directly activates the CaCC. In mIMCD-K2 cells, a rectifying time- and voltage-dependent current was observed when [Ca2+]i was fixed via the patch pipette to between 100 and 500 nM. Maximal activation occurred at approximately 1 microM [Ca2+]i, with currents losing any kinetics and displaying a linear current-voltage relationship. From Ca2+-dose-response curves, an EC50 value of approximately 650 nM at -80 mV was obtained, suggesting that under physiological conditions the CaCC would be near fully activated by mucosal nucleotides. Noise analysis of whole cell currents in mIMCD-K2 cells suggests a single-channel conductance of 6-8 pS and a density of approximately 5,000 channels/cell. In conclusion, the CaCC in mouse IMCD cells is a low-conductance, nucleotide-sensitive Cl- channel, whose activity is tightly coupled to changes in [Ca2+]i over the normal physiological range.

Animals↗
PubMed2001

Regulation of an outwardly rectifying chloride conductance in renal epithelial cells by external and internal calcium.

We have used perforated patch clamp and Fura-2 microfluorescence measurements to study Ca(2+)-activated Cl- currents in cultured mouse renal inner medullary collecting duct cells (mIMCD-3). The conductance was spontaneously active under resting conditions and whole cell currents were time and voltage-independent with an outwardly rectifying current-voltage relationship. The channel blockers DIDS, niflumic acid, glybenclamide and NPPB reversibly decreased the basal currents, whereas the sulfhydryl agent, DTT produced an irreversible inhibition. Increasing or decreasing extracellular calcium produced parallel changes in the size of the basal currents. Variations in external Ca2+ were associated with corresponding changes in free cytosolic Ca2+ concentration. Increasing cytosolic Ca2+ by extracellular ATP or ionomycin, further enhanced Cl- conductance, with whole cell currents displaying identical biophysical properties to the basal currents. However, the agonist-stimulated currents were now increased by DTT exposure, but still inhibited by the other channel blockers. Using RT-PCR, three distinct mRNA transcripts belonging to the CLCA family of Ca(2+)-activated Cl- channel proteins were identified, two of which represent novel sequences. Whether different channels underlie the basal and agonist-stimulated currents in mIMCD-3 cells is unclear. Our findings establish a novel link between alterations in external and internal Ca2+ and the activity of Ca(2+)-activated Cl- transport in these cells.

Adenosine Triphosphate↗
PubMed2000

Ca2+ and cAMP-activated Cl- conductances mediate Cl- secretion in a mouse renal inner medullary collecting duct cell line.

1. The nature of Cl- conductance(s) participating in transepithelial anion secretion by renal inner medullary collecting duct (IMCD, mIMCD-K2 cell line) was investigated. 2. Extracellular ATP (100 microM) stimulated a transient increase in both whole-cell Cl- conductance and intracellular free Ca2+. In contrast, ionomycin (10-100 nM) caused a sustained increase in whole-cell Cl- conductance. Pre-loading cells with the Ca2+ buffer BAPTA abolished the ATP-dependent responses and delayed the onset of the increase observed with ionomycin. 3. The Ca2+-activated whole-cell Cl- current stimulated by ATP (peak) and ionomycin (maximal) displayed (i) a linear steady-state current-voltage relationship and (ii) time and voltage dependence with slow activation at +80 mV and slow inactivation at -80 mV. In BAPTA-loaded cells, ionomycin-elicited whole-cell currents exhibited pronounced outward rectification with time-dependent activation/inactivation. 4. Ca2+-activated and forskolin-activated Cl- conductances co-exist since ATP activation of whole-cell current occurred during a maximal stimulation by forskolin in single cell recordings. 5. In IMCD epithelial layers, ATP and ionomycin stimulated an inward short circuit current (Isc) dependent upon basal medium Na+ and Cl-/HCO3- but independent of the presence of apical bathing medium Na+ and Cl-/HCO3-. This was identical to forskolin stimulation and consistent with transepithelial anion secretion. 6. PCR amplification of reverse-transcribed mRNA using gene-specific primers demonstrated expression of both cystic fibrosis transmembrane conductance regulator (CFTR) mRNA and Ca2+-activated Cl- channel (mCLCA1) mRNA in mIMCD-K2 cells. 7. Ca2+ and forskolin-activated Cl- conductances participate in anion secretion by IMCD.

Adenosine Triphosphate↗
PubMed1999

On-line monitoring of the intravascular volume during haemodialysis by continuous refractometry.

The control of intravascular volume (IVV) by continuous on-line measurement of protein concentration would optimise the patients' specific rate of ultrafiltration. To prove the accuracy of a refractometric device, plasma was continuously drawn by haemofiltration during 10 haemodialysis treatments of male patients. Refractometry reflects highly significant changes in the concentrations of filtrate proteins (r = 0.862, p < 0.001) and blood proteins (rtotal = 0.593, ptotal < 0.001). In vitro, the refractometric device detected a change of protein concentration of 0.041 g/L through a refraction increase of 0.1 mV. The power of discrimination was 0.067% of IVV However, in vivo, the accuracy of IVV refractometric monitoring is reduced by interference factors such as sodium (0. 141 mV/mmol/L), glucose (0.034 mV/mg/dl) and triglycerides (-0.040 mV/mg/dl). Adjustment of the refraction data using sodium and glucose electrodes and plasma filters with a cut-off below the size of chylomicrons is recommended.

Blood Proteins↗
PubMed1991

[Electrochemical measuring system for the registration of transmucosal gastrointestinal potential differences].

An electrochemical measuring system for the recording of transmucosal gastrointestinal potential differences based on silver electrodes with double-junctions and continuous-flow saline bridges is described. Under bioelectrochemical control, a probe can passed from the esophagus via the stomach into the duodenum can be accurately assigned to each of these three segments of the intestine. Measurements are demonstrated and applications discussed.

Animals↗
PubMed1988

[Mechanism of electrolyte and water transport in the first 2 minutes of hypotonic water resorption].

1.2 ml of water or 1.2-2.4 ml of 1/2-isotonic saline were injected into the duodenum of the unanaesthetized rat. Continuous measurements of conductivity and sodium concentration in whole blood, the last by means of ion-selective electrodes, and of protein and electrolyte concentration in a filtrate of portal vein blood were made. Whereas conductivity and sodium or electrolyte concentration dropped promptly and steeply, the drop of protein concentration (Cprot) was registered with a delay of 1.9 min. A quantitative comparison of the conductivity and sodium concentration curves, showing strictly synchronous courses, suggested that no hematocrit changes (these would have influenced conductivity) had taken place during the period of constancy of Cprot. In rats having thirsted for 36 h, Cprot did not fall during a period of 5-8 min in which they drank up to 5.5 ml of water, despite a great drop of electrolyte concentration. It is concluded that at the beginning of water absorption all the fluid absorbed is transported via the lymph ducts. A gradient of negative pressure from the interstitial tissues to the lymphatic system in the non-absorbing gut is proposed, an additional electrolyte secretory process being taken into consideration.

Animals↗
PubMed1987

[Osmotic equilibrium between the intestinal lumen and blood of the growing rat without increase in the fluid content of portal vein blood].

In rats weighting 230-280 g, the resistance, the protein, and the electrolyte concentration of portal vein blood were measured continuously. At constant electrolyte concentration (Cel) resistance was a true measure of hematocrit. Protein concentration (Cprot) was monitored refractometrically in a continuous stream of filtered plasma. The changes brought about by intraduodenal and intragastric injections of water were studied. For comparison, equal amounts (0.5-1% of body weight) of isotonic NaCl were instilled intraduodenally. Water led in all experiments to an immediate and steep but variable drop of Cel within a minute without an accompanying drop of Cprot. The drop of Cprot was delayed by 1.4-2.6 min. The delay was even greater when a small increase of Cprot by 65 mg/dl took place. No such delay occurred when saline was given. After this initial phase, the course of Cprot and hct curves was identical for both fluids. Using these two parameters as independent indicators of volume, similar values for blood volume increase were calculated from their final change. The result suggests that in the gut, osmotic equilibration has priority over fluid transport.

Animals↗
PubMed1985

[Effect of intestinal circulation on the osmotic balance between the intestinal lumen and blood in awake rats].

Total electrolyte concentrations in portal vein and aortic blood of unanesthetized rats were measured continuously by means of ultrafiltrate conductometry. Portal flow rate and mesenteric venous pressure (pmes) could also be measured. The last could be raised to any desired level by a specially developed portal vein clamp. Intraduodenal injections of water (0.5 or 1% BW) were given in a first series of experiments with and without sham-attacking (activating) the animal for 10 s and in a second series with and without raising pmes. Portal flow rate dropped in both cases. But whereas activation led to a decrease in the concentration changes in the v. portae and in arteriovenous differences, a rise in pmes had the opposite effect. Comparison of the total free water change in the v. portae (Mpo) with the quantity of water given (MH2O) revealed that Mpo/MH2O dropped in both series of experiments, provided that pmes was not increased by much more than 2 mm Hg (portal flow did not decrease much under normal). The differing results were explained by taking into account the specificities of blood circulation in the gut wall. The experiments have shown that even transient obstruction of gut tissue perfusion can delay dissipation of concentration imbalance between the gut and parenteral space, thus having adverse effects on the gut cells.

Animals↗
PubMed1983

Studies on intestinal absorption by single-injection technique and continuous measurement of portal vein blood electrolyte concentration and hematocrit in the alert rat.

Whole blood and ultrafiltrate conductivity in the portal vein (as a measure of hematocrit and total electrolyte concentration, Cel, respectively) and arterial pressure of alert rats were measured continuously. Single intraduodenal injections of solutions iso- and hyperosmotic to blood (0.5 or 1 per cent of body weight) produced characteristic changes which were compared with those after the application of water. Whereas H2O and isosmotic passively absorbed substances (sorbose and urea) caused a very variable Cel drop, isosmotic actively absorbed nutrients elicited individually constant but interindividually different (glucose greater than alanine++ greater than arginine) changes due to solute coupled electrolyte free water transport. This was taken as evidence of variable paracellular shunt permeability playing a role in passive, but not in active absorption. The magnitude of Cel changes was related to absorption rate, which was confirmed by behaviour with hypertonic solutions, where osmotic activity in the gut was lost the sooner, the more rapid absorption rate was. Shunt permeability was temporarily blocked by arginine. Hct changes immediately after injections indicated fluid loss from portal vein blood, which could be evaluated in the case of mannitol. The thickness of the absorptive layer, obtained from latency of Cel change after urea, delivered values not exceeding 0,51 mm for the unstirred layer. The latencies after glucose and alanine were usually not much greater than after urea. Cel rise after hypertonic solutions had the same latency as Cel drop after water. Small arterial pressure changes after nutrient solutions, mostly absent after injections of water and NaCl, indicated circulatory effects originating in the gut in association with the former.

Alanine↗
PubMed1980

Continuous and discontinuous ionography of the pancreatic juice and the parotid saliva using carrier-membrane disc-electrodes.

The methodology for continuous ionography (monitoring of electrolytic composition) of the pancreatic secretion using a multianalyser is described. The system employs special electrodes which make use of sensing elements constructed of carrier-membrane discs. The procedure has been applied successfully in investigations on animals and is presently being tested in the clinical diagnostic laboratory. The apparatus can also be used for discontinuous measurements, in which case it has the advantage of needing only extremely small quantities of fluid which can be analyzed successively for the different ions, as the electrodes are connected in series.

Calcium↗
PubMed1978

[Investigations in the streaming blood of the alert animal and man. III. Postprandial and therapeutically induced changes of electrolyte concentration and hematocrit in man during hemodialysis (author's transl)].

Arterial haematocrit and blood electrolyte concentrations are measured continuously by conductometry in three hemodialysis patients. Haematocrit elevation during meals, particularly when rich in carbohydrates, indicate fluid losses into the gut. Simultaneous biphasic responses in electrolyte concentration indicate osmotic and diffusional shifts of water and electrolytes. Similarly, blood volume and electrolyte concentration changes can be followed during and after intravenous infusion of colloid and crystalloid solutions. The quantitative aspects of such measurements are discussed.

Adult↗
PubMed1978

[Investigations on the performance of calcium selective disc-electrodes with electrically charged and neutral ligands in anaerobic serum measurements (author's transl)].

Anaerobically prepared serum samples from healthy subjects were simultaneously analysed for Ca++ in a flow-through-system of three ion selective disc-electrodes (electrochemical multimeasurementsystem). Two of the sensors contained electrically charged ligands, the third contained a neutral carrier. With neutral carriers an improvement of performance was noted in that there was a large increase in selectivity toward H+- and NH+4-ions and a distinct enhancement of reproducibility.

Anaerobiosis↗
PubMed1978

[Ammonium-selective disc-electrode with the carrier-antibiotic nonactin. A method for the continuous enzymatic, electrochemical determination of urea, I (author's transl)].

An ammonium-selective disc-electrode is described; the membrane consists of a polyvinylchloride-matrix with an active phase of nonactin in tris (2-ethylhexyl)phosphate and diphenyl ether as the ion-selective plastic. One side of the membrane is in contact with the solution to be measured and the other with the front surface of a platinum wire, which is enclosed in acrylic glass. This arrangement results in a very low drift potential.

Anti-Bacterial Agents↗