Citations

AbstractTherapeutic endoscopy (TE) has provided a new means for treating peptic ulcer disease, prompting a reevaluation of surgery's role. The aim of this study was to determine if surgical therapy of bleeding duodenal ulcers has changed since the advent of TE. This retrospective review involved consecutive time periods during which TE was (1985–1990) and was not (1980–1984) widely available. Exclusion criteria were prior gastric surgery, nonpeptic conditions, and untreated ulcers. Inclusion standards were met by 252 patients (180 men, 72 women) whose mean age was 67 years. Patients were grouped by the initial therapeutic intervention. Groups were similar in age, medical condition (mean APACHE II score 16), and morbidity. Seventy‐five patients had surgery alone during 1980–1984 and 38 during 1985–1990. TE was initially performed on 134 patients during 1985–1990. Bleeding (n=30) and perforation (n=1) prompted emergent operation in 23% of cases following TE. Thus 69 (38+31) patients underwent surgery between 1985 and 1990. Preprocedure transfusions averaged 4.1 units in the endoscopic group and 8.2 units in the operative groups (p<0.0001). Disagreement existed between the endoscopic and surgical descriptions of ulcer location in 53% of cases. Emergent surgery was required in 45% of hemodynamically unstable patients versus 14% of stable patients who initially underwent TE (p<0.0001). Sixty‐one percent of incompletely visualized TE‐treated lesions required operation, and 18% of well visualized ulcers underwent operation (p<0.0001). Hospital mortality was similar (8% versus 16%) in the endoscopic and operated groups (p=0.7). Mean follow‐up was 540 days. The number of operations performed for bleeding duodenal ulcer did not change significantly during the TE era, and a significant subset (23%) of endoscopically treated patients required surgical therapy. TE failure was portended by hemodynamic instability or incomplete endoscopic visualization.

Objective. Inherited long QT syndrome (LQTS) may present with syncope, seizures, and/or sudden death as a result of ventricular tachyarrhythmias. Identification of family members who are at risk because they harbor the genetic substrate for LQTS is critical. Presently, such identification relies on the 12-lead electrocardiogram (ECG). The purpose of this study was to evaluate the efficacy of the automated ECG as a screening tool for LQTS. Method. Molecular testing of a proband and 22 additional family members for the KVLQT1 mutation and symptomatic status facilitated the classification of each family member into the following patient groups: noncarriers (13), asymptomatic carriers (5), and symptomatic carriers (5). Each individual had a standard 12-lead ECG from which the computer and manual (lead II) corrected QT interval were determined. In addition, we determined the accuracy of the computer ECG diagnostic interpretation for each patient group. Results. With the use of a corrected QT interval of ≥460 ms as a diagnostic cutoff, the positive and negative predictive values for identifying at-risk individuals were 100%. Despite this, the computer-generated ECG diagnostic interpretation erroneously classified 6 of 23 family members. Moreover, half of the family members, proved to have the ion channel defect, received the diagnostic interpretation “normal ECG.” Conclusion. Reliance on the computer-generated ECG diagnostic interpretation alone will fail to identify many at-risk family members. It is suggested that all first-degree relatives of an identified LQTS proband have a 12-lead ECG that is reviewed independently by a physician who is familiar with LQTS in an effort to improve screening for this potentially lethal syndrome.electrocardiogram, long QT syndrome, QT interval, sudden death.

The function of Type 1, classic cadherins depends on their association with the actin cytoskeleton, a connection mediated by α- and β-catenin. The phosphorylation state of β-catenin is crucial for its association with cadherin and thus the association of cadherin with the cytoskeleton. We now show that the phosphorylation of β-catenin is regulated by the combined activities of the tyrosine kinase Fer and the tyrosine phosphatase PTP1B. Fer phosphorylates PTP1B at tyrosine 152, regulating its binding to cadherin and the continuous dephosphorylation of β-catenin at tyrosine 654. Fer interacts with cadherin indirectly, through p120ctn. We have mapped the interaction domains of Fer and p120ctn and peptides corresponding to these sequences release Fer from p120ctn in vitro and in live cells, resulting in loss of cadherin-associated PTP1B, an increase in the pool of tyrosine phosphorylated β-catenin and loss of cadherin adhesion function. The effect of the peptides is lost when a β-catenin mutant with a substitution at tyrosine 654 is introduced into cells. Thus, Fer phosphorylates PTP1B at tyrosine 152 enabling it to bind to the cytoplasmic domain of cadherin, where it maintains β-catenin in a dephosphorylated state. Cultured fibroblasts from mouse embryos targeted with a kinase-inactivating ferD743R mutation have lost cadherin-associated PTP1B and β-catenin, as well as localization of cadherin and β-catenin in areas of cell-cell contacts. Expression of wild-type Fer or culture in epidermal growth factor restores the cadherin complex and localization at cell-cell contacts.

Rhabdomyosarcomas (RMS) arising at different anatomic sites have distinct clinicopathologic features that affect prognosis and outcome. RMS arising in the extremities generally have a worse prognosis. Case reports and anecdotal experience suggests the possibility that RMS of the hand or foot (RMSHF) may behave even more aggressively than RMS elsewhere in the extremities. This study describes clinicopathologic features and outcome of RMSHF. Charts and pathologic material from RMSHF cases from institutional files over a 32-year interval were reviewed. Additional cases from published reports and series over a 42-year interval were identified by a MEDLINE search. Pertinent clinicopathologic features for each case were compiled. Survival analysis and other data from these patients were compared with previously reported statistics in the literature for RMS at other anatomic sites, including elsewhere in the extremities. Six patients from the institutional files and 46 from published reports were identified. A number of adverse prognostic indicators were observed in the majority of these patients including alveolar morphology (86%) and distant metastasis at presentation (63%). Despite the aggressive nature of these tumors, the majority were smaller than 5 cm (61%). A propensity was observed for metastases to unusual sites such as breast, ovary, testis, pancreas, and kidney. The median survival was 19 months, and the 5-year survival was 27%. While these may reflect a constellation of findings related to site, it is also possible that alveolar histology is the main influence. RMSHF can present as a very small primary tumor with clinically evident or occult metastatic disease. Whether this reflects the location, the predominantly alveolar histologic type, or a molecular genetic subtype will require further analysis. Patients presenting with RMSHF should be thoroughly evaluated for occult metastases at the time of diagnosis and followed closely throughout treatment for subsequent involvement of unusual sites.

AbstractCholecystokinin (CCK) and gastrin are structurally related peptide hormones synthesized and secreted by endocrine cells in the gastric antrum, the proximal small intestine, and the central and enteric nervous systems. A broad spectrum of cells express receptors and represent physiologic targets for these peptides. The major physiologic targets for gastrin in the oxyntic gastric mucosa, including the parietal cells and select enterochromaffin cells, while CCK has a broader range of targets, with most involved in nutrient assimilation and appetite control, and the regulation of anxiety. This unit describes binding assays for the determination of receptor number, ligand affinity, and inhibition constants for both CCKA and CCKB receptors, in addition to procedures detailing the preparation of tissues from various sources.

Receptor desensitization is a key process for the protection of the cell from continuous or repeated exposure to high concentrations of an agonist. Well-established mechanisms for desensitization of guanine nucleotide-binding protein (G protein)-coupled receptors include phosphorylation, sequestration/internalization, and down-regulation. In this work, we have examined some mechanisms for desensitization of the cholecystokinin (CCK) receptor which is native to the pancreatic acinar cell, and have found the predominant mechanism to be distinct from these recognized processes. Upon fluorescent agonist occupancy of the native receptor, it becomes "insulated" from the effects of acid washing and becomes immobilized on the surface of the plasma membrane in a time- and temperature-dependent manner. This localization was assessed by ultrastructural studies using a colloidal gold conjugate of CCK, and lateral mobility of the receptor was assessed using fluorescence recovery after photobleaching. Of note, recent application of the same morphologic techniques to a CCK receptor-bearing Chinese hamster ovary cell line demonstrated prominent internalization via the clathrin-dependent endocytic pathway, as well as entry into caveolae (Roettger, B.F., R.U. Rentsch, D. Pinon, E. Holicky, E. Hadac, J.M. Larkin, and L.J. Miller, 1995, J. Cell Biol. 128: 1029-1041). These organelles are not observed to represent prominent compartments for the same receptor to traverse in the acinar cell, although fluorescent insulin is clearly internalized in these cells via receptor-mediated endocytosis. In this work, the rate of lateral mobility of the CCK receptor is observed to be similar in both cell types (1-3 x 10(-10) cm2/s), while the fate of the agonist-occupied receptor is quite distinct in each cell. This supports the unique nature of desensitization processes which occur in a cell-specific manner. A plasmalemmal site of insulation of this important receptor on the pancreatic acinar cell could be particularly effective to protect the cell from processes which might initiate pancreatitis, while providing for the rapid resensitization of this receptor to ensure appropriate pancreatic secretion to aid in nutrient assimilation for the organism.

Receptor molecules play a major role in the desensitization of agonist-stimulated cellular responses. For G protein-coupled receptors, rapid desensitization occurs via receptor phosphorylation, sequestration, and internalization, yet the cellular compartments in which these events occur and their interrelationships are unclear. In this work, we focus on the cholecystokinin (CCK) receptor, which has been well characterized with respect to phosphorylation. We have used novel fluorescent and electron-dense CCK receptor ligands and an antibody to probe receptor localization in a CCK receptor-bearing CHO cell line. In the unstimulated state, receptors were diffusely distributed over the plasmalemma. Agonist occupation stimulated endocytosis via both clathrin-dependent and independent pathways. The former was predominant, leading to endosomal and lysosomal compartments, as well as recycling to the plasmalemma. The clathrin-independent processes led to a smooth vesicular compartment adjacent to the plasmalemma resembling caveolae, which did not transport ligand deeper within the cell. Potassium depletion largely eliminated clathrin-dependent endocytosis, while not interfering with agonist-stimulated receptor movement into subplasmalemmal smooth vesicle compartments. These cellular endocytic events can be related to the established cycle of CCK receptor phosphorylation and dephosphorylation, which we have previously described (Klueppelberg, U. G., L. K. Gates, F. S. Gorelick, and L. J. Miller. 1991. J. Biol. Chem. 266:2403-2408; Lutz, M. P., D. I. Pinon, L. K. Gates, S. Shenolikar, and L. J. Miller. 1993. J. Biol. Chem. 268:12136-12142). The rapid onset and peak of receptor phosphorylation after agonist occupation correlates best with a plasmalemmal localization, while stimulated receptor phosphatase activity correlates best with receptor residence in intracellular compartments. We postulate that the smooth vesicular compartment adjacent to the plasmalemma functions for the rapid resensitization of the receptor, while the classical clathrin-mediated endocytotic pathway is key for receptor downregulation via lysosomal degradation, as well as less rapid resensitization.