Biomedical subjects

H Bektas

Publications and source records attributed to H Bektas.

At least 19 recordsLinked to original sources

PubMed2005

Growth, phenotype, and function of human intestinal mast cells are tightly regulated by transforming growth factor beta1.

BACKGROUND AND AIMS: Transforming growth factor beta1 (TGF-beta1) is expressed in the healthy human intestine and controls mucosal immune responses and inflammation by regulating the function of lymphocytes, macrophages, dendritic cells, and eosinophils. Here, we asked whether human intestinal mast cells (MC) might also be subject to immunoregulation by TGF-beta1. METHODS: MC were isolated from the intestinal mucosa, purified, and cultured in vitro in the presence of stem cell factor (SCF) with or without TGF-beta1. Growth characteristics, phenotype, and immunological mediator release of MC were analysed by reverse transcription-polymerase chain reaction, flow cytometry, immunocytochemistry, western blot, and different immunoassays, respectively. RESULTS: TGF-beta1 dose dependently (ED50 approximately = 0.1 ng/ml) inhibited SCF dependent growth of human intestinal MC by both enhancing apoptosis and decreasing proliferation. In parallel, TGF-beta1 increased the percentage of connective tissue-type MC expressing tryptase and chymase while downregulating expression of the receptors for IgE and SCF. Furthermore, TGF-beta1 dramatically changed the profile of mediators released by MC following IgE receptor crosslinking. Release of histamine, cysteinyl-leukotrienes, and tumour necrosis factor alpha was strongly reduced whereas prostaglandin D2 generation and cyclooxygenase 1 and 2 expression were upregulated by TGF-beta1. CONCLUSIONS: Our data indicate that TGF-beta1 acts as a novel potent inhibitor and modulator of human intestinal MC effector functions. The change in MC mediator release profile and protease expression induced by TGF-beta1 might be of relevance for the control of MC associated disorders of the intestine such as allergic reactions, Crohn's disease, irritable bowel syndrome, and parasitic infection.

Apoptosis↗

PubMed2004

Substance P and other neuropeptides do not induce mediator release in isolated human intestinal mast cells.

Neuropeptides such as substance P (SP) and related peptides are supposed to act as mast cell agonists, and thus as mediators of neuroimmune interactions. The data supporting this hypothesis were obtained mostly from rodent experiments. Here, we studied for the first time the effect of SP and other peptides on mediator release in human intestinal mast cells, either unpurified or enriched to 85-99% purity. We found that SP at 0.1-100 micromol L(-1), or other peptides including neurokinin A and B, calcitonin gene-related peptide, vasoactive intestinal peptide and serotonin at 1 micromol L(-1) do not induce release of mediators such as histamine, sulphidoleukotrienes, and tumour necrosis factor alpha. The peptides also failed to cause mediator release in mast cells isolated from inflamed tissue derived from Crohn's disease. Using reverse transcriptase-polymerase chain reaction, flow cytometry and immunohistochemistry, we could show that human intestinal mast cells do not express the tachykinin receptors NK-1, NK-2, or NK-3 under basal conditions. However, upon stimulation by immunoglobulin E (IgE) receptor-crosslinking, which induces an extensive mediator release reaction, a subpopulation of mast cells clearly expressed NK-1, the SP receptor. In conclusion, our data show that SP and other neuropeptides do not act as secretagogues in human intestinal mast cells that have not been pre-activated by IgE receptor-crosslinking.

Cells, Cultured↗

PubMed2003

Time frame of pancreas allograft rejection: an immunogenetic analysis in MHC-disparate, presensitized inbred rat strains.

AIM: The pattern of rejection of vascularized pancreas allografts in presensitized recipients was studied among congeneic and recombinant rat strains in order to establish the time frame of rejection. Donors and recipients differed either in their entire MHC or in class I or class II MHC antigens. MATERIAL AND METHODS: Streptozotocin diabetic (55 mg/kg bone weight) recipients underwent an intra-abdominal heterotopic pancreas whole organ transplantation. The exocrine secretion of the pancreas was suppressed by ligation of the duct. Rejection was defined as recurrence of diabetic hyperglycemia exceeding 14 mmol/L, which was subsequently confirmed by histologic examination. The pancreas recipients were presensitized by repetitive donor-specific skin transplants performed 12, 8, and 4 weeks prior to pancreas grafting. RESULTS: The results shown accelerated rejection in all instances. Animals with incompatibility for the entire MHC showed a median rejection time in naive recipients of 12.5 days and in presensitized recipients of 8 days. Class I MHC incompatible native recipients rejected the allografts after 16.5 days (median) and presensitized recipients after 9 days (median). Concerning class II MHC incompatibility rejection appeared in naive recipients after 16 days (median) and in presensitized recipients after 7 days (median). Hyperacute rejection, however, was not observed. DISCUSSION: These results show an accelerated pattern of rejection in all instances caused by donor MHC antigens. Hyperacute rejection, however, was not observed. The effect is slightly pronounced in class II MHC incompatibility. Acceleration of rejection may be caused by stimulation of the humoral as well as the cellular pathway of the immune response. The underlying mechanisms concerning the different MHC incompatibilities, however, remain speculative.

Animals↗

PubMed2003

Ureteric reconstruction.

Although the ureter is functionally simply a tube to transport urine, ureteric surgery requires detailed anatomical knowledge and advanced surgical skills, because the ureter has a delicate blood supply. Therefore, the urological surgeon must have distinct strategies available to bridge ureteric defects of various sites and lengths. Furthermore, handling during and after surgery should be individualized to the patient's pre- and intraoperative situation. In this review, the indications for reconstruction of a specific ureteric defect, the required techniques and postoperative recommendations are discussed.

Humans↗

PubMed2003

[Surgical treatment for hilar cholangiocarcinoma (Klatskin's tumor)].

Surgical treatment of hilar bile duct carcinoma remains difficult, which is due to the inadequate possibilities in assessing tumor extent during the preoperative diagnostic procedure as well as intraoperatively. Radical resection with negative histologic margins offers the best chance for long-term survival. The decision regarding the appropriate surgical approach is challenging due to the complexity of tumor localization and neighboring vascular structures. Aggressive resection demands extended liver resection, which is associated with the risk of postoperative liver failure. However, even limited surgery such as hilar resection can be curative and leads to long-term survival in individual cases. The principles of surgical oncology have led to more aggressive procedures, including the combination of liver transplantation and multivisceral resection, and can be performed with calculable morbidity and mortality. Nevertheless, the high risk of tumor recurrence under long-term immunosuppression, the limited availability of donor organs and the excellent results of liver transplantation in non-malignant diseases do not justify this procedure at present. Neoadjuvant radiochemotherapy has failed to demonstrate major benefit. In patients with irresectable tumor or distant metastases palliative measures are aimed at restoring an unobstructed bile flow with endoscopic placement of metal stents. Palliative treatment with additional radio- or photodynamic therapy may be considered in individual cases.

Adult↗

PubMed2003

[Angiodysplasia of the colon combined with portal hypertension and recurrent gastrointestinal bleeding].

Angiodysplasia of the colon has been reported as one of the most common sources of lower gastrointestinal bleeding in the elderly whereas it is very rare in younger patients. Apart from this, portal hypertension may also have effects on the colon. There are, however, only a few reports which have investigated the colon in patients with portal hypertension. We report the case of a 16-year-old woman who presented massive bleeding from angiodysplasia of the colon assembled together with portal hypertension due to portal vein thrombosis caused presumably by neonatal umbilical cord infection. In this regard we discuss diagnosis, therapy and prognosis of this disease.

Adolescent↗

PubMed2002

[Neuroendocrine tumors of the stomach. Surgery therapy and prognosis].

Gastric carcinoid tumors are rare lesions characterized by hypergastrinemia that arise from enterochromaffin-like (ECL) cells of the stomach. A classification system distinguishing three types of gastric carcinoid tumors has been proposed: 1) tumors related to chronic atrophic gastritis, 2) tumors associated with Zollinger-Ellison syndrome, and 3) sporadic lesions. It is apparent that hypergastrinemia-associated gastric carcinoids show a rather benign biological behavior. Normo-gastrinemic sporadic lesions, on the other hand, require an aggressive surgical management. We report seven patients with gastric neuroendocrine tumors ("carcinoids"), who underwent surgical treatment in our department between 1988 and 2000. Surgical therapy included total gastrectomy with D2 lymphadenectomy in two cases with type I tumors and for one patient with type III tumor. One patient with a type II tumor was treated by distal subtotal gastrectomy and another by antrectomy. A local excision was performed on one patient with type I tumor. After a mean follow-up of 8 years, 5 of 7 patients are alive without recurrence.

Adult↗

PubMed2002

[Comparison between treatment results for gastric cancer in younger and elderly patients].

INTRODUCTION: While gastric cancer shows an increased incidence in elderly patients, the rate of younger patients affected by this disease represents up to 15 %. Younger patients are frequently diagnosed with advanced tumor stages with a poor prognosis although literature data on this issue are controversial. PATIENTS AND METHODS: 643 patients with primary gastric carcinoma were operated in our institution between March 1986 and December 2000. No neoadjuvant treatment was administered in these patients. We analysed the data of these patients retrospectively. A comparison of the results between patients younger than 40 years (n = 38, median age 37 years) and older than 70 years (n = 182, median age 75 years) was performed. RESULTS: The radical (R0-) resectability rate was rather high for both, younger (78.9 %) and elderly (76.9 %) patients. Postoperative morbidity was higher in elderly than in younger patients (32.9 % vs. 23.2 %; p < 0.05), as well as the postoperative mortality (7.7 % vs. 2.6 %; p < 0.05). Both younger and elderly patients showed advanced (II to IV) tumor stages (76.3 % vs. 73.3 %, n. s.). There was a significant difference between the rate of diffuse carcinomas in young and elderly patients (63.2 % vs. 22.5 %). The 5-years survival rate following R0-resection was significantly higher for younger patients (54.2 % vs. 32.9 %; p = 0.01), differences occurred only after the second postoperative year. CONCLUSIONS: The resectability of gastric carcinoma is not related to the patients age. Due to comorbidity, postoperative morbidity may be increased in elderly patients. Although both younger and elderly patients show advanced tumor stages, diffuse carcinomas are more frequent in younger patients. The short-term prognosis is similar for both age groups, long-term results are better for younger patients. The different life expectancy should be considered when interpreting these results.

Adult↗

PubMed2002

Results of combined gastrectomy and pancreatic resection in patients with advanced primary gastric carcinoma.

BACKGROUND/AIMS: Although the incidence of primary gastric carcinoma is decreasing, the majority of patients in Western countries are still diagnosed with advanced tumor stages. In many cases surgical therapy can be performed only by multivisceral resections including the pancreas. METHODS: Between April 1986 and April 1997, thirty-three patients with primary gastric carcinoma underwent gastric resection and segmental/total pancreatectomy at our institution (21 males, 12 females; median age 57 years). The operative and pathologic findings and clinical course in these patients were analyzed retrospectively. RESULTS: In all patients total gastrectomy with D2 lymphadenectomy was performed. In 26 patients (79%) the pancreatic tail was also resected. Other resections included the pancreatic head in 5 patients (15%) and the whole pancreas in 2 cases (6%). Radical (R0) resections were possible in 73% of all cases (n = 24). 22 patients (67%) had stage-IV disease due to liver/peritoneal metastases (n = 11) or to extensive lymph node metastases (N3, n = 11). Histology showed a predominance of the diffuse type according to Laurén (n = 16, 49%). Intraoperatively suspected tumor infiltration of the pancreas was confirmed by histology only in 39% (n = 13) of the examined resection specimens. Postoperative morbidity was 36% (n = 12) and mortality was 9% (n = 3). Five patients developed pancreatitis or peripancreatic abscess, 2 with a lethal outcome. Overall the median survival was 13 months. Following R0 resection median survival was 17 months. If the pancreas was microscopically not infiltrated, median survival was 23 months. CONCLUSION: Pancreatic invasion in patients with gastric carcinoma is often associated with positive lymph nodes and liver metastases or peritoneal carcinomatosis. Intraoperatively, true pancreas invasion is difficult to differentiate from inflammatory reactions. Postoperative morbidity and mortality are increased by pancreatic resection, mainly due to pancreatitis or peripancreatic abscess. Curative (R0) resection improves prognosis and even long-term survival can be achieved in selected individual cases. Palliative resections can be performed for local complications like bleeding or obstruction refractory to other therapies.

Adult↗

PubMed2001

Early gastric cancer--excellent prognosis after curative resection in 87 patients irrespective of submucosal infiltration, lymph-node metastases or tumor size.

BACKGROUND AND AIMS: Despite a decreasing incidence of primary gastric carcinoma over the last decade, the incidence of early gastric cancer has remained unchanged. Some aspects of the surgical treatment (e.g., extent of resection, lymphadenectomy) are still controversially discussed in the literature. PATIENTS/METHODS: Between May 1986 and July 1999, 87 patients were operated upon due to primary early gastric adenocarcinoma. All patients data were analyzed retrospectively. RESULTS: Of 626 patients with primary gastric carcinoma, 87 (13.9%) had an early carcinoma (54 men, 33 women; median age 61 years). In all patients, curative (R0-) gastrectomy could be performed, total in 62 patients (71.4%) and subtotal in 25 patients (28.6%). Postoperative morbidity was 23% and mortality 4.5%. Mucosal tumors were found in 34 (39.1%) and submucosal in 53 (60.9%) patients. Multicentricity was present in eight cases (9.1%). Twelve patients (13.8%) had lymph-node metastases. The 5-year survival rate was 88.8%. The submucosal infiltration, the lymph-node infiltration, the histological type, and the tumor size had no statistically significant impact on prognosis. CONCLUSION: Radical resection of early gastric cancer cured most of the patients, irrespective of lymph-node metastases or tumor size. Multicentricity, increasing incidence of proximal cancers, and low mortality suggest that total gastrectomy may be indicated. Patients with early gastric cancer may benefit from D2-lymphadenectomy, but this has to be assessed in further randomized studies, in particular for those with small mucosal tumors.

Adenocarcinoma↗

PubMed2001

Expression and cell-specific and membrane-specific localization of NHE-3 in the human and guinea pig upper gastrointestinal tract.

Na+/H+ exchangers (NHEs) are vital transmembrane transport proteins mediating the electroneutral exchange of Na+ and H+ ions in mammalian cells. In the epithelium of the lower intestine, the isoform NHE-3 is apparently involved in Na+ absorption; however, its presence and cellular localization in the duodenum and particularly in the stomach remain largely unclear. Therefore, we studied the human and guinea pig stomach and duodenum for the expression, regional and mucosal distribution pattern, and membrane-specific localization of NHE-3. Reverse transcription/polymerase chain reaction analyses revealed strong expression of NHE-3 in the stomach and duodenum, where it was identified as a 85-kDa immunoreactive protein by Western blotting experiments. Whereas NHE-3 was localized to the basolateral membrane of surface mucous cells of the stomach, it was exclusively confined to the brush border membrane of epithelial cells in the duodenum. We conclude that the basolateral NHE-3 in the stomach protects the mucosa by secreting protons that diffuse into the mucous cells. In the duodenum, the localization of NHE-3 to the apical membrane of enterocytes suggests a resorptive function by directional Na+ transport. These findings indicate that NHE-3 may be involved in various segment-specific functions in the upper gastrointestinal tract.

Animals↗

PubMed2001

Improved prognosis following peritonectomy procedures and hyperthermic intraperitoneal chemotherapy for peritoneal carcinomatosis from appendiceal carcinoma.

AIMS: The prognosis of patients with peritoneal carcinomatosis from gastrointestinal malignancies is poor. The aim of this study was to analyse the results of multimodality treatment for peritoneal carcinomatosis of appendiceal carcinoma. PATIENTS AND METHODS: From 07/95 to 01/00, 17 patients (13 males, 4 female, median age 58 years) underwent peritonectomy procedures in combination with intraperitoneal hyperthermic chemotherapy. Surgical, pathological and survival data were analysed retrospectively. RESULTS: All patients had undergone previous surgical treatment and one patient had received chemotherapy. In all patients peritonectomy procedures, as described by Sugarbaker, were performed with the aim of achieving a macroscopically complete cytoreduction (range 2-6, median 4 procedures per patient). Following resection, open hyperthermic intraperitoneal chemotherapy with cisplatin was performed. Eleven patients had postoperative complications (predominantly "non-surgical") and two patients died postoperatively. The 4-year survival rate was 75%. Complete cytoreducion had a statistically significant positive influence on long-term survival. CONCLUSIONS: In selected patients (WHO status 0/1, minimal residual disease, no distant metastases, complete cytoreduction), the prognosis for patients with peritoneal carcinomatosis of appendiceal origin can be improved by peritonectomy procedures and hyperthermic intraperitoneal chemotherapy. Postoperative morbidity may be increased due to "non-surgical" complications.

Adult↗

PubMed2001

[Surgical therapy of cystic echinococcosis of the liver].

This study analyses the results of a surgical deroofing technique that was used for the treatment of cystic echinococcosis of the liver in our institution during the last 18 years. The deroofing technique was used on 106 of 132 patients from January 1981 to December 1998. Other operative techniques (pericystectomy, hemihepatectomy) were performed on 26 patients. In 12 cases (9%) the operative procedure was completed by interventions at the extrahepatic bile ducts. 99 patients (75%) showed one or two cysts, and the remaining 33 patients (25%) had three or more cysts in the liver. 18 (14%) patients had to be reoperated on account of complications: in 5 cases a postoperative hemorrhage, in 11 cases a bile duct leakage and in 2 cases an intraabdominal abscess had to be treated operatively. The follow-up of 74 patients (81%) revealed recurrent disease in 14 (19%) cases. Surgical deroofing of cystic echinococcosis of the liver is easy to perform and in contrast to other minor surgical interventions universally applicable. The recurrence rate and the rate of postoperative complications are comparable to other minor surgical techniques. Therefore in our view this procedure represents the therapy of choice.

Adolescent↗

PubMed2000

[Peritoneal carcinosis in appendiceal carcinoma--at what price can the prognosis be improved?].

BACKGROUND AND AIM: Many patients with appendix carcinoma develop peritoneal carcinomatosis with poor prognosis. The purpose of this study was to look for results of multimodality treatment in these patients. PATIENTS AND METHODS: Data of 13 patients (11 men, 2 women, median age 58 years) with proven peritoneal carcinomatosis from appendiceal carcinoma, operated between 07/1995 and 10/1998 were analysed retrospectively with special regard to extent of resection, postoperative morbidity and mortality, survival. RESULTS: A macroscopically complete cytoreduction could be achieved in all patients by multivisceral resection with peritonectomy. Intraoperatively, after resection, an open, hyperthermic intraperitoneal chemotherapy with Cisplatin was performed. Morbidity and 90-days-mortality were 62% and 15%, respectively. After a median follow-up of 36 months all patients survived the therapy (excepting two postoperative deaths). CONCLUSIONS: In selected patients with advanced appendix carcinoma and peritoneal carcinomatosis prognosis can be improved by peritonectomy with intraperitoneal hyperthermic chemotherapy. This results in high mortality and morbidity.

Adenocarcinoma↗

PubMed1999

Solid-pseudopapillary tumor of the pancreas--a rare and frequently misdiagnosed neoplasm.

INTRODUCTION: We describe a young woman with an unusual pancreatic tumor. FINDINGS AND DISCUSSION: Intraoperatively, a smoothly demarcated and encapsulated tumor was exposed. It was large (5 cmx4 cm) and of solid consistency, with a small stalk attached to the uncinate process. The tumor was partially surrounded by the pancreatic head. The macroscopic appearance suggested a benign tumor. Frozen sections revealed a benign pancreatic tumor, most likely of endocrine nature. Based on these findings, tumor enucleation was performed. The patient recovered rapidly from the intervention and was discharged from hospital after 2 weeks. One year after surgical treatment, the patient is without recurrence. The final diagnosis of the tumor was a solid pseudo-papillary tumor.

Adult↗

PubMed1998

Expression of proliferation associated antigens and detection of numerical chromosome aberrations in primary human liver tumours: relevance to tumour characteristics and prognosis.

AIMS: To assess cell proliferation and the presence of numerical chromosome aberrations involving chromosomes 1 and 8 in benign and malignant liver tumours. METHODS: Cell proliferation was studied immunohistochemically in paraffin wax embedded material from 62 primary liver tumours (20 hepatocellular carcinomas, 16 cholangiocellular carcinomas, 15 liver cell adenomas, 11 focal nodular hyperplasias), and the results were compared with histological characteristics and clinical data. Copy numbers of chromosomes 1 and 8 were assessed by interphase fluorescence in situ hybridisation (FISH) with satellite probes in fresh tumour material. RESULTS: The expression of proliferation associated antigen Ki67, using the monoclonal antibody MIB-1, and proliferating cell nuclear antigen (PCNA), using the antibody PC10, was found to be significantly higher in malignant versus benign liver tumours. Neither Ki67 nor PCNA expression were independent prognostic parameters. However, there was a tendency for a worse outcome (survival < 12 months) for patients with a high MIB-1 labelling index (> 20%) compared with patients having the same tumour stage and a low MIB-1 index. Aneusomy for chromosomes 1 and 8 was demonstrated by FISH in malignant tumours (six of seven hepatocellular carcinomas, four of five cholangiocellular carcinomas) but not in benign tumours (none of nine) or non-neoplastic liver (none of nine). CONCLUSION: Both the determination of the proliferating cell fraction and FISH analysis are useful for distinguishing hepatocellular carcinoma from liver cell adenoma or focal nodular hyperplasia; high fractions of proliferating cells are predictive of an early relapse.

Antigens, Neoplasm↗

PubMed1997

Long-term results after surgery for acute mesenteric ischemia.

BACKGROUND: Acute mesenteric ischemia is associated with high mortality rates, and little is known about the long-term prognosis of patients after initially successful surgical intervention. METHODS: Ninety patients were treated by vascular reconstruction or bowel resection, or both, between 1972 and 1993. The overall mortality was 66%. The outcomes and rehabilitational statuses of those 31 patients who were discharged from the hospital were analyzed retrospectively. Anticoagulation consisted of vitamin K antagonists in patients with venous thrombosis and arterial embolism or inhibition of thrombocyte aggregation in patients with arterial thrombosis and nonocclusive mesenteric ischemia. RESULTS: In 31 patients discharged from the hospital venous thrombosis, arterial embolism, arterial thrombosis, and nonocclusive disease occurred in 19, 5, 5, and 2 patients, respectively. The 2- and 5-year survival rates were 70% and 50% and mainly related to cardiovascular comorbidity and malignant disease. Only one patient died after a recurrent attack of arterial mesenteric thrombosis. Twenty percent of the patients suffered from chronic short bowel syndrome after extensive bowel resection, but none required permanent parenteral nutrition. CONCLUSIONS: Under appropriate anticoagulation there is a remarkably low risk of recurrent mesenteric ischemia. The impaired life expectancy of long-surviving patients is mainly due to cardiovascular comorbidity and malignancies.

Acute Disease↗

PubMed1997

Differential effect of donor-specific blood transfusions after kidney, heart, pancreas, and skin transplantation in major histocompatibility complex-incompatible rats.

BACKGROUND: Donor-specific blood transfusion prior to transplantation has been demonstrated to prolong allograft survival. This study compared the effect of donor-specific blood transfusion after kidney, heart, pancreas, and skin allotransplantation in congenic rats of reciprocal strain combinations across a major histocompatibility complex barrier. STUDY DESIGN AND METHODS: Whole donor-specific and third-party blood was administered to the prospective graft recipients 14 and 7 days before the transplantation of kidney, heart, pancreas, and skin. Rejection was defined by cessation of organ-specific function (i.e., uremia, cessation of heartbeat, and recurrence of diabetes). The survival of skin grafts was monitored visually. All allografts were histologically assessed immediately after rejection or at the end of a 100-day observation period. RESULTS: Donor-specific blood transfusion leads to permanent acceptance of all renal allografts. LEW.1U heart allografts were accepted by LEW.1A recipients, but they were rejected in the reciprocal situation. Survival of pancreas and skin allografts was not significantly prolonged. Third-party blood had no effect on allograft survival. CONCLUSION: The beneficial effect of donor-specific blood transfusion depends on both the kind of transplanted organ and the genetic incompatibility involved. The precise mechanisms responsible for the remarkable organ-specific differences remain unknown.

Animals↗