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Biomedical subjects

W G Parsons

Publications and source records attributed to W G Parsons.

14 recordsLinked to original sources
PubMed1998

Endoscopic pancreatic sphincterotomy: indications, outcome, and a safe stentless technique.

BACKGROUND: Endoscopic pancreatic sphincterotomy is less widely practiced than biliary sphincterotomy, in part because of the lack of firm data regarding its indications and safety. In addition, recent reports of ductal and parenchymal changes occurring after pancreatic stenting raise concerns about the standard practice of stent placement at the time of pancreatic sphincterotomy. We report our experience with pancreatic sphincterotomy and describe the use of a technique involving overnight nasopancreatic drainage rather than stenting. METHODS: We reviewed the records of the 164 pancreatic sphincterotomies performed on 160 patients at our institution between January 1, 1991, and October 1, 1996, comparing procedures done with overnight nasopancreatic catheter placement with those done with stenting or no drainage. We also examined the long-term clinical outcome of patients after pancreatic sphincterotomy. RESULTS: Of the 164 sphincterotomies, 98 were done with overnight nasopancreatic drainage, 50 with stent placement, and 16 with no drainage. Complications (all pancreatitis) were significantly more frequent in the group with no drainage (12.5%) as compared with those with drainage (0.7%); p < 0.003. Nasopancreatic drainage was as safe as stent placement, with no complications after 98 procedures. Pancreatic sphincterotomy was effective when used as primary therapy, with 64% of patients so treated experiencing complete and long-lasting resolution of symptoms after the procedure. CONCLUSIONS: Pancreatic sphincterotomy is safe and effective, although pancreatic drainage is required to reduce the incidence of pancreatitis. Overnight nasopancreatic drainage is the method of choice, as it carries as low a complication rate as stent placement, but without the need for a repeat procedure, and presumably without the risk of ductal and parenchymal damage.

Case-Control Studies↗
PubMed1998

Endoscopic management of pseudocysts of the pancreas.

Endoscopic pseudocyst management should not be regarded as an exercise in applied technology. Rather, it is of vital importance for the clinician to be thoroughly aware of the many considerations in patient selection and to understand the available treatment alternatives prior to undertaking such a venture. Despite these considerations, it is our opinion that endoscopic pseudocyst management at present is the method of choice in the majority of patients requiring drainage of symptomatic pseudocysts.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1989

Release of markedly increased quantities of prostaglandin D2 in vivo in humans following the administration of nicotinic acid.

Nicotinic acid (niacin) is a B vitamin which is also a potent hypolipidemic agent. However, intense flushing occurs following ingestion of pharmacologic doses of niacin which greatly limits its usefulness in treating hyperlipidemias. Previous studies have demonstrated that niacin-induced flushing can be substantially attenuated by pre-treatment with cyclooxygenase inhibitors, suggesting that the vasodilation is mediated by a prostaglandin. However, the prostaglandin that presumably mediates the flush has not been conclusively determined. In this study we report the finding that ingestion of niacin evokes the release of markedly increased quantities of PGD2 in vivo in humans. PGD2 release was assessed by quantification of the PGD2 metabolite, 9 alpha, 11 beta-PGF2, in plasma by gas chromatography mass spectrometry. Following ingestion of 500 mg of niacin in three normal volunteers, intense flushing occurred and plasma levels of 9 alpha, 11 beta-PGF2 were found to increase dramatically by 800, 430, and 535-fold. Levels of 9 alpha, 11 beta-PGF2 reached a maximum between 12 and 45 min. after ingesting niacin and subsequently declined to near normal levels by 2-4 hours. Levels of 9 alpha, 11 beta-PGF2 in plasma correlated with the intensity and duration of flushing that occurred in the 3 volunteers. Release of PGD2 was not accompanied by a release of histamine which was assessed by quantification of plasma levels of the histamine metabolite, N tau-methylhistamine. This suggests that the origin of the PGD2 release is not the mast cell. Only a modest increase (approximately 2-fold) in the urinary excretion of the prostacyclin metabolite, 2,3-dinor-6-keto-PGF1 alpha, occurred following ingestion of niacin and no increase in the excretion of the major urinary metabolite of PGE2 was found. These results indicate that the major vasodilatory PG released following ingestion of niacin is PGD2. The fact that markedly increased quantities of PGD2 are released suggests that PGD2 is the mediator of niacin-induced vasodilation in humans.

Adult↗
PubMed1988

Transformation of prostaglandin D2 to isomeric prostaglandin F2 compounds by human eosinophils. A potential mast cell-eosinophil interaction.

PGD2 undergoes extensive isomerization in vivo followed by metabolism by 11-ketoreductase to yield a family of biologically active isomeric PGF2 compounds, including 9, alpha 11 beta-PGF2. Because immunologically activated human mast cells produce substantial quantities of PGD2 and eosinophils accumulate around mast cells at sites of immediate hypersensitivity reactions, the ability of eosinophils to metabolize PGD2 was investigated. Purified human circulating eosinophils from four different donors transformed PGD2 to 9, alpha 11 beta-PGF2 and 12-epi-9 alpha, 11 beta-PGF2 in a time- and concentration-dependent manner. The formation of these compounds increased rapidly during the first 30 min of incubation of eosinophils with PGD2 and tended to plateau at approximately 2 h. Detection and quantification of the formation of 9 beta,11 beta-PGF2 and its 12-epi isomer was accomplished by a negative ion chemical ionization gas chromatography/mass spectrometry assay. On one occasion, eosinophils from one donor also transformed PGD2 to two additional isomeric PGF2 compounds, the stereochemical structures of which were not identified. The ability of eosinophils to produce PGD2 was then investigated. After stimulation with 2 microM A23187, the major cyclooxygenase product formed was thromboxane B2 (2247 pg/10(6) eosinophils) whereas only small quantities of PGD2 were produced (50 pg/10(6) eosinophils). Inasmuch as PGF2 compounds can exert biologic actions that differ from those of PGD2, this ability of eosinophils to transform PGD2 to PGF2 compounds could alter the local biologic effects of PGD2 released from adjacent mast cells and thus may represent a physiologically relevant mast cell-eosinophil interaction.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Inhibition of post-translational modification and surface expression of a melanoma-associated chondroitin sulfate proteoglycan by diethylcarbamazine or ammonium chloride.

Cultured human melanoma M21 cells were treated with diethylcarbamazine (DEC), an inhibitor of proteoglycan biosynthesis in rat chondrosarcoma cells, to examine the assembly and transport of a chondroitin sulfate proteoglycan to the plasma membrane. Pretreatment of melanoma cells at 37 degrees C for 15 min with increasing doses of DEC followed by a 60-min pulse with [35S]sulfate in the presence of DEC resulted in a dose-related inhibition of incorporation of [35S]sulfate into macromolecules. In cells incubated for 75 min with both 1 mM beta-D-xyloside and 15 mM DEC, synthesis and secretion of beta-D-xyloside-bound 35S-glycosaminoglycans were inhibited by more than 80% as compared to cells treated with beta-D-xyloside alone; this inhibition was reversible. As assessed by [3H]serine incorporation into protein, overall protein synthesis was not substantially inhibited by DEC treatment. Detergent lysates from [35S]methionine-labeled melanoma cells were incubated with a monoclonal antibody (9.2.27) that specifically recognizes the peptide core of the melanoma proteoglycan. As assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the immunoprecipitate, a 240,000 Mr endoglycosidase H (Endo-H)-sensitive intermediate was the only form of the proteoglycan present inside the cells when the cultures were treated for 60-120 min with 10-15 mM DEC. When the melanoma cells were incubated for 10 min with 15 mM DEC and 100 mu Ci/ml of [35S]methionine, washed, and then chased for 15 min to 4 h in radioactive-free medium, the 240,000 Mr Endo-H-sensitive intermediate was slowly converted to a 250,000 Endo-H-resistant intermediate but not to a mature proteoglycan molecule that possessed chondroitin sulfate glycosaminoglycans. SDS-PAGE analysis of cell surface immunoprecipitates revealed that only a small amount of the 250,000 Mr intermediate was transported to the plasma membrane within 5 h of incubation in the presence of DEC. Proteoglycan synthesis was also inhibited when the melanoma cells were incubated for 60-120 min with ammonium chloride, but unlike DEC-treated cells the majority of the synthesized peptide core was converted to a 245,000 Mr Endo-H-resistant intermediate that was detected on the cell surface. Light and electron microscopic analysis of DEC-treated melanoma cells revealed large vacuoles and a distended Golgi and endoplasmic reticulum. Ammonium chloride-treated cells contained fewer vacuoles than DEC-treated cells but more vacuoles than normal cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Ammonium Chloride↗
PubMed1986

The identification of a plasma membrane 3,3',5-triiodo-L-thyronine binding protein on the cultured Swarm rat chondrosarcoma chondrocyte and the lack of its up-regulation by insulin in vitro.

Primary cultures of Swarm rat chondrosarcoma chondrocytes were examined for the presence of T3 plasma membrane binding proteins and their possible regulation by insulin. Incubation of this tumor cell with [125I]T3 at 4 C yielded saturable and reversible binding of the radioligand. As assessed by LIGAND computer analysis, the binding data in one experiment revealed two classes of [125I]T3 binding sites with association constants of 2.2 X 10(9) M-1 and 4.8 X 10(6) M-1, and binding capacities of 4.9 X 10(3) and 1.9 X 10(6) sites per cell, respectively. Whole cells and a preparation enriched for plasma membrane were affinity labeled with N-bromoacetyl-[125I]T3 (N-BrAc-[125I] T3), and the molecular weights of the radiolabeled proteins were analyzed both by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by Sephadex G-200 gel filtration chromatography. One major chondrosarcoma protein of 55,000 mol wt and two minor proteins of 47,000 and 33,000 mol wt bound N-BrAc-[125I]T3, suggesting that the mol wt of the T3 binding protein was 55,000. As assessed by isoelectric focusing, the 55,000 mol wt protein had an isoelectric point of 5.1. The radiolabeled 55,000 mol wt chondrosarcoma protein was immunoprecipitated with anti-T3 and anti-GH3 plasma membrane T3 antisera. The high degree of homology between this chondrocyte N-BrAc-[125I]T3 binding protein and the protein on rat GH3 cells was demonstrated by a comparison of the peptide maps of Staphylococcus aureus V8 protease and elastase digested radiolabeled binding protein. Although culture of the chondrocytes in medium containing insulin resulted in an approximate 400% increase in plasma membrane [125I]insulin binding, no significant increase in [125I]T3 binding was observed. Thus, expression of the T3 plasma membrane binding protein was similar to that observed previously for the insulin-like growth factor-II receptor on these chondrosarcoma chondrocytes in not being influenced by the concentration of insulin in the culture medium.

Affinity Labels↗
PubMed1985

Novel inhibition of proteoglycan synthesis and exocytosis by diethylcarbamazine in the Swarm rat chondrocyte.

Pretreatment of cultured chondrosarcoma chondrocytes at 37 degrees C for 15 min with 15 mM diethylcarbamazine (DEC) followed by a 60-min pulse with [35S] sulfate in the presence of DEC resulted in an approximate 40% inhibition of synthesis and a 75% inhibition of secretion of 35S-proteoglycan. The inhibition was dose-related and was not due to a decrease in protein synthesis. Chondrocytes exposed for 75 min to 15 mM DEC, washed, incubated for 17 h in DEC-free medium, and then pulsed with [35S]sulfate showed no inhibition in the rate of synthesis of proteoglycan or in the per cent of radiolabeled proteoglycans exocytosed into the culture medium, indicating full reversibility of the inhibitory effect. When chondrocytes were incubated for 75 min with both 1 mM beta-D-xyloside and 15 mM DEC, secretion of beta-D-xyloside-bound 35S-glycosaminoglycan was inhibited by more than 70% despite an approximate 3-fold increase in intracellular 35S-macromolecules, as compared to cells exposed to beta-D-xyloside alone. Upon removal of DEC, the block in the secretion of beta-D-xyloside-bound 35S-glycosaminoglycans was reversed, although there was a 15-30-min lag in the initiation of exocytosis. Light and electron microscopic examination of chondrocytes after 75 min of incubation with 15 mM DEC revealed large vacuoles, a distended Golgi apparatus, and a distended endoplasmic reticulum which contained electron dense material. Upon removal of DEC, the vacuoles disappeared and distended organelles returned to their normal appearance between 15 and 30 min, coincident with the start of exocytosis of 35S-proteoglycan and beta-D-xyloside-bound 35S-glycosaminoglycan. These biochemical and morphological studies indicate that DEC treatment of chondrosarcoma chondrocytes alters the transport of molecules from the endoplasmic reticulum to the Golgi and the transport of molecules from the Golgi to the cell surface.

Animals↗