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Biomedical subjects

D Tuscano

Publications and source records attributed to D Tuscano.

At least 19 recordsLinked to original sources
PubMed2002

A3 adenosine receptors in human astrocytoma cells: agonist-mediated desensitization, internalization, and down-regulation.

A(3) adenosine receptor activation has been previously demonstrated to result in both neuroprotective and neurodegenerative effects, depending upon specific pathophysiological conditions. This dual effect may depend on receptor regulation mechanisms that are able to change receptor availability and/or function. In the present study, we investigated desensitization, internalization, and down-regulation of native A(3) adenosine receptors in human astrocytoma cells after exposure to the agonist 2-chloro-N6-(3-iodobenzyl)-N-methyl-5'-carbamoyladenosine (Cl-IBMECA). Cl-IBMECA induced a concentration-dependent inhibition of adenylyl cyclase activity with an EC(50) value of 2.9 +/- 0.1 nM. The effect was suggested to be mediated by A(3) adenosine receptor subtype by the use of selective adenosine receptor antagonists. Cell treatment with pertussis toxin abolished Cl-IBMECA-mediated inhibition of adenylyl cyclase activity, evidencing an A(3) receptor coupling to inhibitory G protein. Short-term exposure to the agonist Cl-IBMECA (100 nM) caused rapid receptor desensitization, within 15 min. Agonist-induced desensitization was accompanied by receptor internalization: A(3) adenosine receptor internalized with rapid kinetics, within 30 min, after cell exposure to 100 nM Cl-IBMECA. The localization of A(3) adenosine receptors on the plasma membrane and in intracellular compartments was directly revealed by immunogold electron microscopy. After desensitization, the removal of agonist led to the restoration of A(3) adenosine receptor functioning through receptor recycling to the cell surface within 120 min. Prolonged agonist exposure (1-24 h) resulted in a marked down-regulation of A(3) adenosine receptors that reached 21.9 +/- 2.88% of control value after 24 h. After down-regulation, the recovery of receptor functioning was slow (24 h) and associated with the restoration of receptor levels close to control values. In conclusion, our results demonstrated that A(3) receptors, in astrocytoma cells, are regulated after short- and long-term agonist exposure.

Adenylyl Cyclases↗
PubMed2001

7-Nitrobenzofurazan (NBD) derivatives of 5'-N-ethylcarboxamidoadenosine (NECA) as new fluorescent probes for human A(3) adenosine receptors.

New fluorescent ligands for adenosine receptors (ARs), obtained by the insertion, in the N(6) position of NECA, of NBD-moieties with linear alkyl spacers of increasing length, proved to possess a high affinity and selectivity for the A(3) subtype expressed in CHO cells. In fluorescence microscopy assays, compound 2d, the most active and selective for human A(3)-AR, permitted visualization and localization of this human receptor subtype, showing its potential suitability for internalization and trafficking studies in living cells.

Adenosine-5'-(N-ethylcarboxamide)↗
PubMed2000

Agonist-induced internalization and recycling of the human A(3) adenosine receptors: role in receptor desensitization and resensitization.

A(3) adenosine receptors have been proposed to play an important role in the pathophysiology of cerebral ischemia with a regimen-dependent nature of the therapeutic effects probably related to receptor desensitization and down-regulation. Here we studied the agonist-induced internalization of human A(3) adenosine receptors in transfected Chinese hamster ovary cells, and then we evaluated the relationship between internalization and signal desensitization and resensitization. Binding of N(6)-(4-amino-3-[(125)I]iodobenzyl)adenosine-5'-N-methyluronamide to membranes from Chinese hamster ovary cells stably transfected with the human A(3) adenosine receptor showed a profile typical of these receptors in other cell lines (K:(D) = 1.3+/-0.08 nM; B(max) = 400+/-28 fmol/mg of proteins). The iodinated agonist, bound at 4 degrees C to whole transfected cells, was internalized by increasing the temperature to 37 degrees C with a rate constant of 0.04+/-0.034 min(-1). Agonist-induced internalization of A(3) adenosine receptors was directly demonstrated by immunogold electron microscopy, which revealed the localization of these receptors in plasma membranes and intracellular vesicles. Moreover, short-term exposure of these cells to the agonist caused rapid desensitization as tested in adenylyl cyclase assays. Subsequent removal of the agonist led to restoration of the receptor function and recycling of the receptors to the cell surface. The rate constant of receptor recycling was 0.02+/-0.0017 min(-1). Blockade of internalization and recycling demonstrated that internalization did not affect signal desensitization, whereas recycling of internalized receptors was implicated in the signal resensitization.

Adenosine↗
PubMed1996

Double synchronous occluding tumors of the large bowel: a report of three cases.

The development of acute large bowel obstruction secondary to colorectal cancer is very common and, while right hemicolectomy with a primary anastomosis is the accepted procedure for right-sided obstructing tumors, the different strategies performed for left-sided tumors, including staged procedures, Hartmann's procedure, and resection with anastomosis, remain a subject of controversy. We present herein the case reports of three patients who developed two synchronous occlusive tumors of the large bowel. Complete exploration of the entire colon is highly recommended to assess the most feasible therapeutic option in such cases, as the second occlusive tumor, often hidden within the bowel segments, can cause failure of limited resection or intestinal decompression.

Acute Disease↗
PubMed1994

[Surgical treatment of 4th-stage hemorrhoids: the role of anatomical techniques].

Surgical options for fourth-degree hemorrhoids are still matter of debate. The high incidence of the disease encouraged research and brought to technical improvements able to achieve a painless, reliable, harmless and well tolerated surgical treatment. The Authors report a retrospective study of 193 patients who underwent surgery for fourth-degree hemorrhoids. In these cases the Authors advise anatomic techniques using local anaesthesia with i.v. administration of sedatives, thus allowing a 24-hour hospitalization.

Follow-Up Studies↗
PubMed1992

Low anterior resection versus abdominoperineal excision: a comparison of local recurrence after curative surgery for "very low" rectal cancer.

In the controversy regarding whether sphincter-saving resection (SSR) or abdominoperineal resection (APER) is more appropriate for the treatment of very low rectal cancer, local recurrence rates seem to play a fundamental role in patient outcome. In order to operate an effective patient selection, very low rectal cancer is defined herein as being located within 4.5 to 7.5 cm from the anal verge. This retrospective report investigates the incidence of local recurrence after curative surgery for very low rectal carcinoma in 24 consecutive patients treated by the same surgical team over a 15-year period using the above surgical procedures. In the APER group, the local recurrence rate was 45.5%, occurring in 5 of 11 cases; and in the SSR group 46.1%, occurring in 6 of 13 cases, with no significant difference between the two groups. Recurrence was found within one year of surgical treatment in all except one case. Despite the strict follow-up program, it was only possible to perform reoperation in two recurrent cases, both previously submitted to SSR and diagnosed by means of transanal ultrasonography and macrobiopsy. The high incidence of local recurrence in this series is explained by the advanced stage of disease in the majority of cases. Thus, as the choice between APER and SSR does not seem to affect the incidence of local recurrence, which is related more to tumor size, site, stage, and grading, preservation of the sphincters and restoration of digestive continuity should be achieved whenever technically possible.

Adenocarcinoma↗
PubMed1986

The microflora of the gastric juice after Billroth I and Billroth II partial gastrectomy.

Detailed analyses of biochemical and microbiological variables such as pH, nitrite concentration, total viable counts (TVC), nitrate reductase-positive bacterial counts (NRPBC), and identification of microorganisms were carried out on 76 fasting gastric juice samples obtained at endoscopy from 64 patients previously submitted to partial gastrectomy (22 end-to-end Billroth I, 42 Billroth II/Reichel-Polya) and from 12 normal controls. Samples from normal controls were sterile, but bacteria were detected in the juice from all the operated patients. Significantly higher mean pH values and nitrite levels (p less than 0.001) were found in partial gastrectomies than in normal controls. In relation to surgical methods, higher mean pH values (p less than 0.005), nitrite levels (p less than 0.01), TVC (p less than 0.01), and NRPBC (p less than 0.005) were observed in the juice of patients with Billroth II as compared with Billroth I gastrectomies. Anaerobic bacteria, typical of faecal flora, and particularly Escherichia coli (p less than 0.05) characterized Billroth II samples. All these data suggest that the presence of bacteria in the gastric juice of gastroresected patients can be considered a risk factor of gastric neoplasia and that the type of operation used for the reconstruction of digestive continuity may influence the magnitude of this risk.

Adult↗
PubMed1984

Portal stump pressure monitorization in the conscious rat after porta-caval shunt and total liver arterialization with the left gastric artery.

A method for portal stump pressure monitorization following arterialization is presented. Both intra and postoperative pressure determinations were performed and a significant difference between intra and postoperative values was observed. The pressure of the arterialized portal stump either using the left gastric artery or one of its branches, when compared to the free portal pressure did not reveal significant differences. According to these data, the proposed method of arterialization seems to create a "physiologic" arterialized stump pressure. This information while contributing to a better understanding of the complex hemodynamics of the arterialized liver represents essential guidelines for further studies on liver trophism and experimental portal hypertension.

Animals↗
PubMed1984

Occult gallbladder microlithiasis causing acute recurrent pancreatitis. A report of three cases.

Gallbladder microlithiasis may be a cause of acute recurrent pancreatitis. When this process cannot be detected with routine investigative procedures, a precise etiologic diagnosis cannot be formulated. In such circumstances, endoscopic collection of bile followed by microscopic examination for presence of cholesterol crystals constitutes a valid diagnostic tool. Three cases of acute recurrent pancreatitis are presented in which cholesterol crystals were found in the bile. The technique and advantages of the method are described and a useful diagnostic approach is proposed.

Acute Disease↗
PubMed1984

Role of cholesterol and calcium bilirubinate crystals in acute postoperative acalculous cholecystitis.

Acute acalculous cholecystitis is rather unusual, but it is considered an increasing entity. Particularly interesting are the post-traumatic or post-operative forms of acute acalculous cholecystitis. Ischemia of the gallbladder and biliary stasis are the most likely pathogenetic factors. A case of acute acalculous cholecystitis after total gastrectomy for cancer is presented. Particular emphasis is put on the significance of cholesterol and calcium bilirubinate crystals findings in the bile of the gallbladder. The pathogenetic role of this microscopic form of lithiasis in post-operative acalculous cholecystitis is discussed. It is concluded that all surgeons should be aware of this pathology since it is becoming much more common to be faced with elderly patients having life-threatening post-operative gallbladder complications unrelated to macroscopic lithiasis.

Acute Disease↗
PubMed1984

[Surgical risk of the Oddi sphincterotomy. Results of an international survey (25541 cases)].

Operative risks of transduodenal sphincterotomy (T.D.S.) are the principal subject of discussion between those surgeons who practice the operation and those that condemn it. An international survey of 25, 541 cases treated by 130 surgeons showed that the incidence of specific complications such as acute pancreatitis (0.6 p. 100), hemorrhage (0,65 p. 100), and early cholangitis (0,5 p. 100), and relative mortality were lower than those usually reported by surgeons attributing an excessive operative risk to the procedure. Data was also obtained indicating that certain "risk factors" due to teh surgical technique were statistically significant (X2 test) and that knowledge of these enabled complications to be avoided. Morbidity and mortality of TDS could then be reduced to the level of those common to biliary tract surgery.

Acute Disease↗