Biomedical subjects

P W Day

Publications and source records attributed to P W Day.

15 recordsLinked to original sources

PubMed1999

Selective regulation of Galpha(q/11) by an RGS domain in the G protein-coupled receptor kinase, GRK2.

G protein-coupled receptor kinases (GRKs) are well characterized regulators of G protein-coupled receptors, whereas regulators of G protein signaling (RGS) proteins directly control the activity of G protein alpha subunits. Interestingly, a recent report (Siderovski, D. P., Hessel, A., Chung, S., Mak, T. W., and Tyers, M. (1996) Curr. Biol. 6, 211-212) identified a region within the N terminus of GRKs that contained homology to RGS domains. Given that RGS domains demonstrate AlF(4)(-)-dependent binding to G protein alpha subunits, we tested the ability of G proteins from a crude bovine brain extract to bind to GRK affinity columns in the absence or presence of AlF(4)(-). This revealed the specific ability of bovine brain Galpha(q/11) to bind to both GRK2 and GRK3 in an AlF(4)(-)-dependent manner. In contrast, Galpha(s), Galpha(i), and Galpha(12/13) did not bind to GRK2 or GRK3 despite their presence in the extract. Additional studies revealed that bovine brain Galpha(q/11) could also bind to an N-terminal construct of GRK2, while no binding of Galpha(q/11), Galpha(s), Galpha(i), or Galpha(12/13) to comparable constructs of GRK5 or GRK6 was observed. Experiments using purified Galpha(q) revealed significant binding of both Galpha(q) GDP/AlF(4)(-) and Galpha(q)(GTPgammaS), but not Galpha(q)(GDP), to GRK2. Activation-dependent binding was also observed in both COS-1 and HEK293 cells as GRK2 significantly co-immunoprecipitated constitutively active Galpha(q)(R183C) but not wild type Galpha(q). In vitro analysis revealed that GRK2 possesses weak GAP activity toward Galpha(q) that is dependent on the presence of a G protein-coupled receptor. However, GRK2 effectively inhibited Galpha(q)-mediated activation of phospholipase C-beta both in vitro and in cells, possibly through sequestration of activated Galpha(q). These data suggest that a subfamily of the GRKs may be bifunctional regulators of G protein-coupled receptor signaling operating directly on both receptors and G proteins.

Aluminum Compounds↗

PubMed1996

An experimental teaching model for laparoscopic choledochojejunostomy.

For advanced laparoscopic procedures, team collaboration and good suturing skills are only two of many requirements to achieve success. Teaching opportunities are mandatory to allow general surgeons to become acquainted with advanced procedures and to gain confidence in new laparoscopic procedures. In this teaching model presented herein, the technical difficulties and operative steps of a laparoscopic choledochojejunostomy and drainage via Roux-en-Y-loop are outlined as performed on eight pigs weighing about 35 kg each (range, 31.2-41.2) with nondistended common bile ducts (5.6 mm; range, 4.2-6.3). Functionality of the bypass was assessed by a weekly monitoring of bilirubin levels and a contrast material injection into the gallbladder after a 4-month follow-up with measurements of the common bile duct (9.8 mm; range, 7.2-15.2) and the diameter of the choledochojejunostomy (5.0 mm; range, 3.6-6.2) at necropsy. This model provides outstanding conditions for teaching laparoscopic suture techniques to be applied in advanced laparoscopy and demonstrates the feasibility of laparoscopic choledochojejunostomy within a reasonable operation time (122 min; range, 105-155).

Animals↗

PubMed1994

Analysis of radiolabeled CHO cell-derived rHuGM-CSF pharmacokinetics and biodistribution in rhesus monkeys following intravenous and subcutaneous injection.

The purpose of these studies was to examine the biodistribution and pharmacokinetics of radiolabeled human CHO cell-derived rHuGM-CSF in normal Rhesus monkeys (Macaca mulatta) following intravenous (i.v.) and subcutaneous (s.c.) injection. A dual radioisotope tracer technique was utilized to monitor the behavior of rHuGM-CSF in vivo. Recombinant HuGM-CSF was radiolabeled with I-123 (a 13.2 h half-life, 140 KeV pure gamma emitting radionuclide detected using gamma scintigraphic imaging) using a mild chloramine T reaction. A separate preparation of rHuGM-CSF radiolabeled with S-35 methionine by bioincorporation in tissue culture was mixed with the I-123-labeled protein, permitting comparison of data obtained from the two radiolabels. Two dose levels of rHuGM-CSF were used for i.v. bolus (15 and 300 micrograms/kg) and s.c. (10 and 100 micrograms/kg) studies. The results of these studies demonstrated that the co-administered I-123 rHuGM-CSF and S-35 rHuGM-CSF followed similar blood elimination kinetics after i.v. or s.c. injection. Following i.v. bolus injection, rHuGM-CSF was found to rapidly distribute to all central body cavity high blood flow organs, followed by rapid uptake in the kidneys and elimination in the urine. There were no differences in the pharmacokinetic values obtained for I-123- and S-35-labeled rHuGM-CSF nor for the two dose levels examined. Following, s.c. injection, I-123- and S-35-labeled rHuGM-CSF were found to reach maximal plasma levels after approximately 16 h. The primary route of elimination was the urine. Monkeys previously exposed to rHuGM-CSF were found to have circulating antibodies to rHuGM-CSF. Studies in these animals revealed a significantly altered distribution and clearance of radiolabeled rHuGM-CSF, with the majority of the injected activity being cleared by the liver.

Animals↗

PubMed1992

Long-term implantation of a new implantable programmable insulin pump in two diabetic dogs.

A positive-pressure implantable programmable pump with an integrated sideport and a detachable catheter was tested for long-term intraperitoneal insulin delivery in 2 diabetic dogs. Programming and refilling of the pump was simple and presented no problems during 28 months of pump function. During pump therapy an acceptable degree of glycemic control was maintained. No catheter occlusion occurred, and no skin erosions or infections were observed. Insulin in the pump reservoir was stable. After 9.5 months of pump function, flow progressively decreased because of insulin precipitation in the valved accumulator. Solubilization of these precipitates using 0.1 N NaOH injected in the reservoir and drained through the sideport normalized pump delivery rates. We conclude that this device is safe for long-term intraperitoneal insulin delivery. The sideport enables discrimination between different causes of pump malfunction and allows for the safe use of an alkaline solution to remove insulin precipitates, thus avoiding pump explantation.

Animals↗

PubMed1987

Five-month oral (diet) toxicity/infectivity study of Bacillus thuringiensis insecticides in sheep.

Bacillus thuringiensis insecticides (Bt) [Dipel (test substance D or Thuricide-HP (test substance T)] were administered in the diet for 5 months to castrated mixed rambouillet/merino sheep (24-34 kg at the beginning of the study) at a dose of 500 mg/kg/day (approximately 10(12) spores per day). No treatment-related effect was seen on weight gain or clinical chemistry parameters nor were significant gross clinical changes observed. Several blood and tissue samples taken just prior to the time the animals were killed or at necropsy were found to be positive for Bt when cultured. Detailed gross and microscopic pathologic examination of the sheep revealed several incidental lesions. However, the only lesion that may have been associated with the treatment was lymphocytic hyperplasia in Peyer's patches seen in the cecum of three sheep and it was not considered to be clinically significant.

Administration, Oral↗

PubMed1981

The kinetics of peritoneal insulin absorption.

This study examined the relationship between the delivery of insulin into the peritoneal space and its absorption into the peripheral circulation. Studies were performed in conscious dogs receiving somatostatin (5.0 microgram/min) to suppress endogenous insulin secretion, and intravenous glucose (50 mg/min) to prevent hypoglycemia. The biologic effectiveness of the absorbed insulin was determined by its hypoglycemic effect. The possibility of direct absorption of insulin into the portal circulation from the peritoneal space in anesthetized, portal vein-catheterized dogs was examined with radiolabeled I125 insulin. Our results suggest that absorption of insulin from the peritoneal space is volume, concentration, and time-dependent. Maximal absorption of insulin was observed at 50 min when 1.92 U of insulin in a volume of 3 ml was infused intraperitoneally over 30 min. More rapid absorption was observed at 30 min when this quantity of insulin was given in a 1-min intraperitoneal bolus, compared to 30 min of intraperitoneal infusion. Least rapid absorption of insulin followed the delivery of 1.92 U of insulin in a volume of 15 ml. Intermediate absorption of insulin was observed at 40 min when the 1.92 U was delivered in a volume of 0.6 ml. Peripheral intravenous insulin delivery of 1.92 U reached a maximal plasma concentration at 20 min, which was more than three times the concentration observed with intraperitoneal insulin. Isotopic tracer studies, in which radioiodinated insulin was placed into the peritoneal space in anesthetized dogs, demonstrated greater radioactivity in the portal vein than in the aorta throughout a 30-min observation period. These studies demonstrate that intraperitoneal administration of insulin results in absorption of insulin which is volume, concentration, and time-dependent. Thus, the peritoneal space may be an appropriate site for insulin delivery through a transcutaneous catheter.

Absorption↗

PubMed1981