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J L Watkins

Publications and source records attributed to J L Watkins.

At least 19 recordsLinked to original sources
PubMed1998

The human homologue of Saccharomyces cerevisiae Gle1p is required for poly(A)+ RNA export.

The mechanism of mRNA export is a complex issue central to cellular physiology. We characterized previously yeast Gle1p, a protein with a leucine-rich (LR) nuclear export sequence (NES) that is essential for poly(A)+ RNA export in Saccharomyces cerevisiae. To characterize elements of the vertebrate mRNA export pathway, we identified a human homologue of yeast Gle1p and analyzed its function in mammalian cells. hGLE1 encodes a predicted 75-kDa polypeptide with high sequence homology to yeast Gle1p, but hGle1p does not contain a sequence motif matching any of the previously characterized NESs. hGLE1 can complement a yeast gle1 temperature-sensitive export mutant only if a LR-NES is inserted into it. To determine whether hGle1p played a role in nuclear export, anti-hGle1p antibodies were microinjected into HeLa cells. In situ hybridization of injected cells showed that poly(A)+ RNA export was inhibited. In contrast, there was no effect on the nuclear import of a glucocorticoid receptor reporter. We conclude that hGle1p functions in poly(A)+ RNA export, and that human cells facilitate such export with a factor similar to yeast but without a recognizable LR-NES. With hGle1p localized at the nuclear pore complexes, hGle1p is positioned to act at a terminal step in the export of mature RNA messages to the cytoplasm.

Amino Acid Sequence↗
PubMed1997

Defining the essential functional regions of the nucleoporin Nup145p.

Studies of the essential nucleoporin Nup145p have shown that its depletion is coincident with a block in RNA export and that deletion of its amino-terminal domain results in clustering of nuclear pore complexes. To further define the functional domains of Nup145p, we have characterized a panel of nup145 mutants. Deletions from both the amino terminus and the carboxy terminus resulted in temperature sensitive mutants that accumulated polyadenylated RNA in the nucleus at the non-permissive temperature. In addition, these mutants also displayed constitutive clustering of nuclear pore complexes in localized patches of the nuclear envelope. These results suggested that an internal region of Nup145p consisting of amino acids 593-893 is essential for function. Accordingly, when this region was deleted, growth was not supported at any temperature, whereas the region alone was able to complement a null mutation when expressed on a high copy plasmid. Previous studies have suggested that Nup145p is cleaved into two polypeptides of approximately 65 and 80 kDa. Interestingly, our experiments suggest that cleavage occurs in vivo. However, a small internal deletion of 17 amino acid residues that abolished cleavage had no effect on cell growth. Therefore, cleavage is not necessary for Nup145p function. When a sequence harboring the Nup145p cleavage site required for Nup145p cleavage was inserted in a chimeric protein, it was not sufficient for mediating cleavage. Cleavage likely requires a second region from amino acid residues 247-524 in addition to the cleavage site.

Fungal Proteins↗
PubMed1996

Assessment of technical competence during ERCP training.

BACKGROUND: Successful performance of diagnostic and therapeutic ERCP requires skillful manipulation of the duodenoscope and accessories. The evaluation process for assessing competency is still in evolution. Recommendations for the number of examinations has ranged from 35 to 200, made without the benefit of prospective data. METHODS: Pancreatic and common bile duct cannulation rates were prospectively recorded for 21 trainees and 9 proctors over 6 years in a large university-based training program. Trainee success rates were compared to those of the proctor and learning curves were constructed. RESULTS: Trainees performed 641 examinations over 6 years. Each did an average of 31 examinations (range, 10 to 96). For both pancreatic duct and common bile duct cannulation, there was a rapid linear rise of the success curve extending up to the fortieth procedure. Pancreatic duct cannulation rates exceeded those of the common bile duct. CONCLUSIONS: This is the first prospective evaluation of acquisition of skills in ERCP. Although the rapid rise of the learning curve ends at the fortieth examination, the 85% level of selective cannulation is not reached for the pancreas duct until the seventieth procedure and is not reached for the common bile duct even at 100 procedures. These data suggest a threshold of at least 100 procedures.

Biliary Tract Diseases↗
PubMed1996

GLE2, a Saccharomyces cerevisiae homologue of the Schizosaccharomyces pombe export factor RAE1, is required for nuclear pore complex structure and function.

To identify and characterize novel factors required for nuclear transport, a genetic screen was conducted in the yeast Saccharomyces cerevisiae. Mutations that were lethal in combination with a null allele of the gene encoding the nucleoporin Nup100p were isolated using a colony-sectoring assay. Three complementation groups of gle (for GLFG lethal) mutants were identified. In this report, the characterization of GLE2 is detailed. GLE2 encodes a 40.5-kDa polypeptide with striking similarity to that of Schizosaccharomyces pombe RAE1. In indirect immunofluorescence and nuclear pore complex fractionation experiments, Gle2p was associated with nuclear pore complexes. Mutated alleles of GLE2 displayed blockage of polyadenylated RNA export; however, nuclear protein import was not apparently diminished. Immunofluorescence and thin-section electron microscopic analysis revealed that the nuclear pore complex and nuclear envelope structure was grossly perturbed in gle2 mutants. Because the clusters of herniated pore complexes appeared subsequent to the export block, the structural perturbations were likely indirect consequences of the export phenotype. Interestingly, a two-hybrid interaction was detected between Gle2p and Srp1p, the nuclear localization signal receptor, as well as Rip1p, a nuclear export signal-interacting protein. We propose that Gle2p has a novel role in mediating nuclear transport.

Amino Acid Sequence↗
PubMed1996

Comparison of rigid and flexible esophagoscopy in the diagnosis of esophageal disease: diagnostic accuracy, complications, and cost.

Rigid esophagoscopy has been used by otolaryngologists for evaluation of the esophagus for over 100 years. Few studies have examined the diagnostic accuracy of rigid esophagoscopy in patients with carcinoma of the head and neck. The goal of our study was to compare the diagnostic accuracy, complication rate, and costs of rigid esophagoscopy and flexible fiber-optic endoscopy in the evaluation of the esophagus in patients with head and neck carcinoma. We retrospectively reviewed the records of 195 patients with head and neck carcinoma who underwent both rigid esophagoscopy and flexible fiber-optic endoscopy within a 6-month period. We discovered 10 cases with discordant findings, of which 5 (50%) were esophageal carcinoma. The estimated cost was less for flexible endoscopy. No complications were reported in either procedure. Our study suggests that flexible fiber-optic endoscopy should replace rigid esophagoscopy in the evaluation of the esophagus in patients with head and neck carcinoma.

Cost-Benefit Analysis↗
PubMed1996

Mucinous ductal ectasia in an octogenarian: successful treatment with the Whipple procedure.

Mucinous ductal ectasia is a recently defined neoplasm of the pancreas characterized by excessive mucin production. The natural history of this entity is unknown, and only two cases in people over the age of 80 yr have appeared in the literature. In this report, we review the literature on mucinous ductal ectasia and present the first report of an octogenarian who was successfully treated by the Whipple procedure.

Aged↗
PubMed1995

Endoscopic retrograde cholangiopancreatography and stent placement via gastrostomy: technical aspects and clinical application.

Significant advances in the field of enteral nutrition (1), combined with technical advances in percutaneous access, have increased the indications for, and safety of, enteral alimentation (2). A mature gastrostomy stoma not only provides access to the gastrointestinal lumen for nutrition, but in selected cases, provides access for the diagnostic and therapeutic endoscopist. In 1971, Wiendl first reported diagnostic fiberoptic stomal endoscopy (3). This has since been followed by reports of diagnostic endoscopic retrograde cholangiopancreatography (ERCP) (4), and more recently, the first case of therapeutic ERCP by Gray et al. (5). We report here on the second case of therapeutic ERCP in a patient with metastatic squamous-cell carcinoma of the head and neck, with liver metastasis. We discuss the technical aspects, indications, and future of therapeutic stomal endoscopy.

Carcinoma, Squamous Cell↗
PubMed1995

The GLFG repetitive region of the nucleoporin Nup116p interacts with Kap95p, an essential yeast nuclear import factor.

Nup116p is a member of a family of five yeast nuclear pore complex (NPC) proteins that share an amino terminal region of repetitive tetrapeptide "GLFG" motifs. Previous experiments characterized the unique morphological perturbations that occur in a nup116 null mutant: temperature-sensitive formation of nuclear envelope seals over the cytoplasmic face of the NPC (Wente, S. R., and G. Blobel. 1993. J. Cell Biol. 123:275-284). Three approaches have been taken to dissect the structural basis for Nup116p's role in NPC function. First, deletion mutagenesis analysis of NUP116 revealed that the GLFG region was required for NPC function. This was not true for the other four yeast GLFG family members (Nup49p, Nup57p, Nup100p, and Nup145p). Moreover, deletion of either half of Nup116p's GLFG repeats or replacement of Nup116p's GLFG region with either Nup100p's GLFG region or Nsp1p's FXFG repetitive region abolishes the function of Nup116p. At a semipermissive growth temperature, the cells lacking Nup116p's GLFG region displayed a diminished capacity for nuclear import. Second, overexpression of Nup116p's GLFG region severely inhibited cell growth, rapidly blocked polyadenylated-RNA export, and fragmented the nucleolus. Although it inhibited nuclear export, the overexpressed GLFG region appeared predominantly localized in the cytoplasm and NPC/nuclear envelope structure was not perturbed in thin section electron micrographs. Finally, using biochemical and two-hybrid analysis, an interaction was characterized between Nup116p's GLFG region and Kap95p, an essential yeast homologue of the vertebrate nuclear import factor p97/Imp90/karopherin beta. These data show that Nup116p's GLFG region has an essential role in mediating nuclear transport.

Amino Acid Sequence↗
PubMed1995

Endoscopic findings and overtube-related complications associated with esophageal variceal ligation.

Esophageal variceal ligation (EVL) has emerged as a popular alternative to endoscopic sclerotherapy (ES), with equal efficacy as ES in control of active bleeding, rebleeding rate, and variceal eradication. The complication rate for EVL has been reported lower than for ES in several clinical trials. However, several unique complications inherent to EVL have been recognized. Overtube injury to the pharynx and proximal esophagus has been the most serious complication. Transient vocal cord paralysis, cricopharyngeal perforation, proximal esophageal laceration, varix rupture, and free esophageal perforation have also been reported. Direct banding-induced complications have been limited to rebleeding from banded ulcers, transient esophageal obstruction, and simple strictures. Pulmonary as well as serious systemic complications have yet to be reported. We report four complications of EVL, review the literature, and suggest strategies for the recognition, management, and prevention of EVL complications.

Adult↗
PubMed1994

The esophageal mucosal resistance: structure and function of an unique gastrointestinal epithelial barrier.

The purpose of this review is to delineate the factors that contribute to the innate epithelial resistance of the esophageal mucosa when challenged with potentially damaging intraluminal aggressive factors that are present as a result of gastroesophageal reflux. The ability of this mucosa to act as an effective barrier is dependent on the structural complexity of its 20 to 30 cell layer-thick stratified squamous epithelia, its convoluted intercellular spaces (paracellular resistance), and the cellular ion transport mechanisms that maintain intracellular homoestasis (cellular resistance). Because H+ ion is the most important damaging agent in the gastroesophageal refluxate, we have primarily focused on mechanisms that impede or prevent H+ ion entry into the mucosa ("pre-epithelial" and "mucosal factors"), cellular mechanisms that allow cells to maintain their intracellular pH in the presence of an external acid environment ("cellular factors"), mechanisms that limit continued mucosal and cellular injury ("submucosal factors") and reparative processes that come into play after damage has occurred.

Animals↗
PubMed1993

Computer programs in gastrointestinal endoscopy: issues, problems, and solutions.

For 10 years, a computerized gastrointestinal endoscopy database was promoted as necessary and desirable. At least 2 endoscopy societies, the American Society for Gastrointestinal Endoscopy (ASGE) and the World Society for Gastrointestinal Endoscopy (OMED), devoted considerable effort to develop appropriate terminology and structure. Numerous vendors and individuals developed software conforming, to various degrees, with the ASGE and OMED recommendations, and hundreds of institutions in the United States and an equal number worldwide have computerized their endoscopy paperwork. Dozens of articles and several large multicenter research efforts signal the usefulness of the database concept. Although desired, and apparently needed, endoscopy databases have not, however, caught the attention of a majority of physicians who could benefit from them--probably because of perceived difficulty with user interface. Whereas the keyboard has succeeded in virtually every other discipline, it is an enigma why there is so much anathema to this ubiquitous device among the majority of the medical community. Attempts at alternate input modalities, such as voice, resulted in several commercially available report-writers; however, the original database concept is insignificant in these current products. The international experience with this subject is reviewed with an optimistic prediction that a satisfactory doctor-computer interface will be developed, perhaps with totally new technology, and that continued interest, use, and development of an endoscopy database is justified.

Endoscopy, Gastrointestinal↗
PubMed1993

Gallstones: choosing the right therapy despite vague clinical clues.

Therapeutic decisions are quite clear-cut for asymptomatic gallstone disease and acute cholecystitis. However, the appropriate therapeutic course for older patients with chronic cholecystitis may be less obvious. Watchful waiting may be reasonable for patients with mild and infrequent symptoms. For healthy patients, cholecystectomy is recommended if symptoms are becoming more frequent and severe. Laparoscopy may reduce the complication rate and be safely performed even in those with underlying medical illness. Oral dissolution therapy can be attempted for qualifying symptomatic patients who are at poor surgical risk or who refuse surgery. Shock wave lithotripsy and contact dissolution therapy show some promise but are currently experimental.

Acute Disease↗
PubMed1993

Gastrointestinal manifestations of amyloidosis: a case of diverticular perforation.

Amyloidosis is an intriguing disorder. Its clinical presentation usually rests on the organ(s) infiltrated with the amyloid. We report a patient who presented with peritonitis secondary to a perforated large jejunal diverticulum and multiple small bowel diverticula. We believe the diverticula were a direct result of primary amyloid infiltration of the intestine in the antimesenteric location. This is the first reported case of small bowel diverticula caused by amyloidosis.

Aged↗