Search PubMed⌕ Search

Biomedical subjects

R Cotter

Publications and source records attributed to R Cotter.

35 records · Page 2Linked to original sources
PubMed1985

Comparison of the elimination of 10 and 20% TRAVAMULSION lipid emulsion from the blood of beagle dogs.

Metabolic utilization of fat emulsions containing 20% lipid and 10% lipid were compared using beagles. The key parameter measured was elimination of the lipid from the bloodstream, which serves as an indication of the emulsion's availability for metabolism. Nonlinear kinetic analysis was used in this determination. Blood concentrations of free fatty acids, phospholipid, and cholesterol were also measured as additional ways of determining emulsion metabolism. The 10 and 20% emulsions appeared to be equivalent in elimination of the caloric substrate triglyceride from the blood stream. Results also showed an adaptation to emulsion infusion over time at both dosages administered (3 and 6 g/kg of body weight). This was indicated by increased elimination capacity and stabilization of each lipid class measured. However, blood concentrations of phospholipid and cholesterol indicate that the 20% emulsion provides a lesser lipid load for the amount of calories administered when compared to an emulsion containing 10% lipid.

Animals↗
PubMed1983

N-acetylaspartylglutamate: an endogenous peptide with high affinity for a brain "glutamate" receptor.

A brain peptide with high affinity (420 nM) and marked specificity for brain receptor sites labeled with L-[3H]glutamate has been identified. Amino acid analysis and mass spectroscopy indicate that the peptide is N-acetylaspartylglutamate. The peptide exhibits potent convulsant properties when injected into the rat hippocampus, similar to those produced by the glutamate receptor agonist, quisqualic acid. These findings raise the question whether endogenous brain peptides enriched in acidic amino acids may serve as excitatory neurotransmitters.

Animals↗
PubMed1979

Dissociation of the intrinsic factor--vitamin B12 complex by bile: contributing factor to B12 malabsorption in pancreatic insufficiency.

Human bile incubated with vitamin B12 bound to intrinsic factor in human gastric juice will effectively dissociate this complex, and the vitamin will transfer to non-intrinsic factor unsaturated binding protein(s) contained in bile. Preincubation of the bile with pancreatic enzymes, particularly trypsin, and pepsin, decreases this effect of bile on the intrinsic factor--vitamin B12 complex by digesting the unsaturated binder(s) in the bile. These studies help explain why there is malabsorption of tracer amounts of vitamin B12 in some patients with pancreatic insufficiency, and why this abnormality is correctable by the administration of pancreatic extract.

Bile↗
PubMed1978

Formation of transcobalamin II--vitamin B12 complex by guinea-pig ileal mucosa in organ culture after in vivo incubation with intrinsic factor--vitamin B12.

The in vivo incubation of intrinsic factor--[57Co]vitamin B12 in an ileal loop of a guinea-pig followed by in vitro culturing of segments of the ileum for 180 min has been used to study the transepithelial transport of vitamin B12. Analysis of the solubilized supernate of mucosa following the in vivo phase demonstrated that 44% of the [57Co]vitamin B12 was bound to intrinsic factor (IF), 26% was free, and 16% was bound to transcobalamin II (TCII). Following culture, similar analysis demonstrated that 18% of the vitamin was now bound to IF, 49% was free, and 35% ws bound to TCII. In the culture medium, 54% of the [57Co]vitamin B12 was free and 37% was bound to TCII. The formation of TCII-[57Co]vitamin B12 did not occur if homogenized mucosa was incubated with free[57Co]vitamin B12, but it did form in cultures of ileal segments from animals given an excess of unlabelled vitamin to saturate all circulating TCH, and in the medium containing puromycin. Indirect immunofluorescence using chicken anti-TCII demonstrated that TCII was associated with the mucosal cells of both the ileum and jejunum. These studies demonstrate that following transepithelial flux of vitamin B12 through the ileal mucosa, the vitamin becomes coupled to TCII. This coupling requires a structurally intact mucosa and the source of the TCII appears to be the ileal mucosal cell rather than unsaturated TCII circulating in the blood.

Animals↗
PubMed1978

High pressure liquid chromatographic determination of major organic acids in cranberry juice.

A reverse phase high pressure liquid chromatographic method is presented for the simultaneous separation and determination of quinic, malic, and citric acids in single strength, undiluted cranberry juice. After a 1 : 10 dilution and cleanup through a disposable column, major organic acids in cranberry juice are separated on a Bondapak/C18 column and quantitated by using a differential refractometer. Twenty-seven samples of different single strength cranberry juice were analyzed using this method; the mean content of quinic, malic, and citric acids were 1.32 (std dev. 0.150), 0.92 (std dev. 0.079), and 1.08% (std dev. 0.111), respectively. Mean percent recoveries of each acid were quinic 95.4 (std dev. 6.8), malic 96.6 (std dev. 5.8), and citric 94.0% (std dev. 4.8).

Acids↗
PubMed1977

Purification of the intestinal receptor for intrinsic factor by affinity chromatography.

The intestinal receptor for the intrinsic factor vitamin B-12 complex has been solubilized and then purified from the guinea pig ileum using a double structured affinity resin comprised of intrinsic factor coupled to vitamin B-12 which, in turn, was covalently linked to Sepharose 4B. The receptor purified approximately 57 000-fold from the crude homogenate, appears to be a homogenous protein which may be composed of two subunits which separated when the preparation was subjected to polyacrylamide disc gel electrophoresis. Ethylenediaminetetraacetic acid induced dissociation of the complex between the purified receptor and intrinsic factor-B-12 could not be reversed by the addition of excess Ca2+, unlike the effect of EDTA with semipurified receptor or crude ileal homogenates. Calcium reversed the EDTA effect only after the mixture was subjected to extensive dialysis suggesting that the chelating agent interacts directly with the receptor protein. Intrinsic factor-vitamin B-12 competively inhibited the binding of intrinsic factor-[57Co] vitamin B-12 to the purified receptor whereas vitamin B-12 free intrinsic factor did not, even at a 100-fold greater concentration.

Animals↗
PubMed1977

The sub-structure of nucleosomes.

A model for the sub-structure of the core particle of the nucleosome in chromatin, based on results from neutron and x-ray scattering and other physico-chemical observations, is presented. Two disc-shaped heterotypic tetramers of histones, opposed face-to-face, form the core protein. Each tetramer is enclasped by an annulus of DNA and the two annuli are joined by a linker piece. The mode of self assembly of core particles in solution is derived as are the changes in conformation of the core particle which occur on transcription and chromosome replication.

Animals↗
PubMed1976

Solubilization, partial purification and radioassay for the intrinsic factor receptor from the ileal mucosa.

A macromolecule which binds intrinsic factor saturated with vitamin B12 has been solubilized from the guinea-pig ileum by homogenization followed by mechanical disruption without organic solvents or detergents. This intrinsic factor 'receptor' was further purified by precipitation with 30% saturated ammonium sulphate, centrifugation at 105000 g, and filtration through Sephadex G-200. Failure to precipitate the receptor following centrifugation at 105000 g for 3 h and filtration of the receptor with the included volumes through Sepharose 4B and 6B was evidence that it was solubilized. The purification of the receptor was monitored by a radiometric assay where the intrinsic factor-[57Co]vitamin-B12 complex coupled to the solubilized receptor precipitated at 15% sodium sulphate while intrinsic factor-[57Co]B12 alone remained soluble at this salt concentration. This radioassay also permitted the in vitro study of the interaction of the solubilized receptor and intrinsic factor saturated with [57Co]B12. The receptor did not bind intrinsic factor-[57Co]B12 below pH 5 while binding was observed to pH 9.0. Binding was equivalent at 37 degrees C and 25 degrees C, but was markedly reduced at 4 degrees C and 56 degrees C and was destroyed at 100 degrees C. The receptor resisted 60 min of digestion by trypsin, chymotrypsin, pronase and subtilisin. After 180 min digestion, pronase and subtilisin inactivated 90% and 41% of the receptor respectively, whereas trypsin and chymotrypsin inactivated only 21% and 23%. Trisodium EDTA inhibited the binding of intrinsic factor-[57Co]B12 to the receptor and this inhibition could be reversed by the addition of excess Ca2+. Mg2+ and Mn2+ were less effective than Ca2+ for the activity of the receptor. Kinetic analysis of the reaction indicated a maximum velocity of 0.083 nmole IF bound B12/min with a Km of 1.36 x 10(-10) M. The solubilized receptor had a greater affinity for intrinsic factor bound to vitamin B12 than for intrinsic factor free of vitamin B12. The solubilization of this intrinsic factor receptor without chemicals suggests that it is not an integral component of the microvillus membranes hydrophobically bonded to the lipid matrix, but rather a peripheral protein weakly associated with the membrane by non-covalent interaction.

Animals↗
PubMedDate not supplied

Nonlinear kinetic analysis of the elimination of lipid emulsion administered intravenously to dogs.

A model based on a Michaelis-Menten nonlinear kinetic approach was used to analyze the kinetics of elimination of an intravenously infused lipid emulsion in the dog. The emulsion was administered at doses of 0.3, 3, or 6 g of lipid/kg of body weight. The model was applicable to all data regardless of the kinetic order of the elimination process operating. This can be either zero (linear), mixed, or first order (exponential). Furthermore, it was also found that parameters derived with the model can be used to predict the kinetics of elimination at different dosages. However, it was also shown that elimination parameters for a single bolus dose of lipid emulsion cannot be used to predict the manner in which a continuously infused dose will be eliminated.

Animals↗
PubMedDate not supplied

Comparison of the elimination and metabolism of 10% Travamulsion and 10% Intralipid lipid emulsion in the dog.

A study was performed comparing the elimination kinetics of two soybean oil/egg phosphatide lipid emulsions (10% Travamulsion vs 10% Intralipid) from the vascular compartment of the dog. Elimination kinetics were evaluated after bolus injection and after continuous infusion studies. Evaluation of triglyceride and free fatty acid data indicates the emulsions are similar metabolic substrates. Phospholipid and cholesterol data indicate a possible difference in remnant particle removal. At the higher lipid dosages, remnant particles from Travamulsion injection were removed at a faster rate than those from Intralipid.

Animals↗
PubMedDate not supplied

Fatty acid profiles in response to soybean oil lipid emulsion infusions in essential fatty acid-deficient miniature swine.

The ability of soybean oil lipid emulsions to affect essential fatty acid deficiency (EFAD) and plasma fatty acid distribution was studied in neonatal pigs. The test animals were maintained on a fat-free diet prior to administration of lipid emulsion. Plasma and red blood cell (RBC) membrane levels of essential [linoleic (C-18:2 omega 6) and arachidonic (C-20:4 omega 6)] and nonessential [palmitic (C-16, palmitoleic (C-16:1 omega 7), stearic (C-18), and oleic (C-18:1 omega 9)] fatty acids and the triene:tetraene ratio [5,8,11-eicosatrienoic acid (C-20:3 omega 9):arachidonic acid (C-20:4 omega 6)] were monitored to ascertain the establishment of EFAD and its correction. Nonessential fatty acids were studied, as these components of lipid therapy have received little attention. Results indicate that soybean oil emulsions are effective in reversing fatty acid profiles found in EFAD, and both essential and nonessential fatty acids are under strict metabolic control.

8,11,14-Eicosatrienoic Acid↗
PubMedDate not supplied

Alternative lipids to usual omega 6 PUFAS: gamma-linolenic acid, alpha-linolenic acid, stearidonic acid, EPA, etc.

The intravenous administration of parenteral fat emulsions is widely used in total parenteral nutrition (TPN) to supply essential fatty acids and concentrated energy in a relatively small volume of isotonic solution. They contain very high amounts of linoleic acid and usually about 8% of alpha-linolenic acid calculated in the fat phase (10 or 20% of the total emulsion). Most of the time one emulsion is given as the sole source of fat, giving direct venous entry to a fatty acid composition substantially different from that encountered in a normal diet. Since the latter greatly influences the fatty acid composition of phospholipids which are critical determinants of membrane structural properties influencing a variety of membrane functions (Fig. 1) (enzyme activity, membrane transport, receptor function) and functional precursors of intracellular and intercellular mediators (diacylglycerols, prostaglandins, leukotrienes, hydroxy fatty acids), do we provide the right fatty acid at the right place and the right time for efficient cell cell interaction? In other words, given the three roles of fatty acids--energetic, structural, functional--are we using the best strategy to avoid imbalances between the three roles?

Animals↗