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K L Cox

Publications and source records attributed to K L Cox.

At least 73 records · Page 4Linked to original sources
PubMed1990

Characterization of cholecystokinin receptors on the sphincter of Oddi.

To characterize directly the ability of cholecystokinin (CCK) to interact with receptors on the sphincter of Oddi (SO), we measured binding of 125I-labeled Bolton-Hunter-labeled COOH-terminal octapeptide of cholecystokinin (125I-BH-CCK-8) to tissue sections from the guinea pig SO. Autoradiography localized binding of 125I-BH-CCK-8 over the SO smooth muscle layer. Binding was saturable, specific, dependent on time, pH, and temperature, and was reversible. Binding of 125I-BH-CCK-8 was inhibited by various CCK receptor agonists with the following potencies: CCK-8 much greater than des(SO3)CCK-8 much greater than gastrin-17-I and by various CCK receptor antagonists with the following potencies: L-364,718 greater than proglumide analogue 10 much greater than carbobenzoxy-Tyr(SO3H)-Met-Gly-Trp-Met-Asp-NH2 greater than N2,O2' dibutyryl guanosine 3',5'-cyclic monophosphate. The potencies of agonists in stimulating and of antagonists in inhibiting CCK-8-stimulated SO contractions correlated closely with their abilities to inhibit binding of 125I-BH-CCK-8. Analysis of binding of 125I-BH-CCK-8 to SO tissue sections revealed two classes of CCK binding sites: a high-affinity site [dissociation constant (Kd) 0.2 nM] and a low-affinity site (Kd 70 nM). Atropine or tetrodotoxin (TTX) caused a similar rightward shift of the CCK-8 dose-response curve for stimulation of SO contraction. Comparison of receptor occupation to CCK-8-induced contraction suggested that CCK-8 occupation of the high-affinity binding site correlated with contraction in the absence of atropine and the low-affinity CCK binding with contraction in the presence of atropine or TTX.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Determination of triacylglycerol lipase activity using carbon-13-labeled triacylglycerols and nuclear magnetic resonance spectroscopy: evidence that hepatic lipase hydrolyzes medium-chain triacylglycerols.

Triacylglycerol lipase activity was studied using glycerol [1-13C]trioctanoate mixed with postheparin rat plasma. 13C NMR spectroscopy demonstrated triacylglycerol hydrolysis into free fatty acids with no difference at the 1,3 or 2 glycerol positions. There was no inhibition by high sodium concentration, consistent with lipase of hepatic origin.

Animals↗
PubMed1989

Intravital microscopy: a new in vivo technique for visualizing and quantifying effects of regulatory peptides on choledochoduodenal junction motility.

Using intravital microscopy, we studied the in vivo effects of regulatory peptides on choledochoduodenal junction motility in guinea pigs. During basal and hormone-stimulated periods, intravital microscopy documented rhythmic, asymmetrical, "milking" contractions of the sphincter ductus choledochi (SDC) which occurred independent of sphincter ampullae (SA) contractions or were followed by SA contractions. Cholecystokinin octapeptide (CCK-8) (greater than or equal to 0.01 micrograms/kg) increased the frequency of SDC contractions and at higher doses (greater than or equal to 0.1 microgram/kg) increased the frequency of SA contractions. Pentagastrin (greater than or equal to 1.0 microgram/kg) and secretin (10 micrograms/kg) decreased the contraction frequencies of both sphincters. Biliary manometry demonstrated similar effects of these peptides on the frequency of the SDC and SA contractions, but also showed that CCK-8 (0.1 microgram/kg) increased the amplitude of SDC and SA contractions while pentagastrin (1 microgram/kg) decreased the amplitude of only SDC contractions. Tetrodotoxin and atropine did not affect hormone-induced changes in frequency, but tetrodotoxin reduced the increase in amplitude of contraction caused by CCK-8. We concluded that intravital microscopy provides a sensitive, in vivo technique to visualize and quantify the complex motility of a small structure like the choledochoduodenal junction.

Animals↗
PubMed1989

Bile flow rates and biliary motility quantitated by intravital microscopy.

Intravital microscopy was adapted to document and quantitate in vivo biliary motility and bile flow rates in guinea pigs. The movement of 10 microns diameter fluorescent beads in the bile duct was used to measure bile flow rates. Using this method, bile flow rates were comparable to those determined by measuring the volume of bile collected from the papilla, but greater (P less than 0.01) than the volume of bile collected from a bile duct cannula. During intravital microscopy, biliary contractions were only detected at the choledochoduodenal junction. While fasting, the sphincter ductus choledochi contracted at 6.0 +/- 1.0 per min and the ampulla at 1.2 +/- 0.2 per min. Postprandially, sphincter contractions had a decreased frequency and an increased duration while both duration and frequency of ampullary contractions increased. The volume of bile collected from a bile duct cannula postprandially did not change. This data suggested that the choledochoduodenal junction had a propulsive function and postprandial changes in motility were due to neurohumoral factors rather than passive response to changes in bile flow rates. Intravital microscopy proved to be a sensitive in vivo technique in which to quantitate bile flow rates and biliary motility.

Animals↗
PubMed1988

Identification of serotonin from rabbit upper stomach as a stimulant of in vitro gallbladder contraction.

Using an in vitro rabbit gallbladder bioassay, the distribution and identification of bioactive substances in rabbit gastrointestinal tract were investigated. Comparison of the bioactivities of tissue extracts before and after cholecystokinin was removed by affinity chromatography demonstrated that the distributions of cholecystokinin and non-cholecystokinin substances were different. While cholecystokinin bioactivity per g of tissue was highest in the duodenum, non-cholecystokinin bioactivity was greatest in the upper stomach. The biochemical properties of the non-cholecystokinin substance in the upper stomach could not be distinguished from those of serotonin. These included molecular weights of 176, identical ultraviolet spectra, similar nuclear magnetic resonance spectra, and co-chromatography in HPLC. By weight, serotonin had 1/6th of the bioactivity of cholecystokinin octapeptide. We conclude that the principal gallbladder-contracting substance in rabbit upper stomach is serotonin.

Animals↗
PubMed1988

The noninvasive determination of linoleic acid content of human adipose tissue by natural abundance carbon-13 nuclear magnetic resonance.

A new method to assess noninvasively the proportionate storage of poly- and mono-unsaturated fatty acids in human adipose tissue is described. The method is based on in vivo natural abundance 13C NMR at 1.9 T using a TMR 32/200. Data were acquired with a concentric coil system placed below subcutaneous adipose tissue of the calf or the lower arm. Continuous single-frequency decoupling was used to optimize the signal in the spectral region of interest and minimize potential heating effects. Only adipose triglycerides contributed significantly to the resonance intensities. Typical linewidths for the in vivo 13C resonances were 10-14 Hz resulting in excellent resolution in the region of the unsaturated carbons. Signal-to-noise ratios for the resonance at 128.4 ppm (due to carbon atoms of polyunsaturated fatty acids) were typically 50-90 in 8 min using 0.25s repetition time. The relative storage of polyunsaturated fatty acids was determined by comparing the peak intensity at 128.4 ppm with the intensities of the peaks due to the carbonyl, the glycerol, or the main methyl carbons. High-resolution in vitro NMR of adipose biopsies and various mixtures of triglycerides studied with the in vivo NMR protocols provided further evidence that the described in vivo NMR methods allowed precise information on the relative storage of linoleic acid, the main constituent of the pool of polyunsaturated fatty acids. Conventional gas chromatography was performed on adipose biopsies of two volunteers and resulted in close agreement with the in vivo NMR methods. The average polyunsaturated fatty acid concentration in adipose tissue in seven healthy volunteers was 19.83 mol% +/- 1.74 (SD) as determined by in vivo NMR, consistent with conventional studies based on gas chromatography of biopsied material. Preliminary data on three cystic fibrosis patients showed a decreased polyunsaturated fatty acid concentration of 13.12 mol% +/- 2.73 (SD). The high accuracy of this method and its noninvasive character should be especially valuable in clinical research and diagnosis as repetitive adipose biopsies can be avoided.

Adipose Tissue↗
PubMed1988

Adipose tissue abnormalities in cystic fibrosis: noninvasive determination of mono- and polyunsaturated fatty acids by carbon-13 topical magnetic resonance spectroscopy.

Natural abundance in vivo carbon-13 topical magnetic resonance (TMR) spectroscopy was used to assess human adipose tissue stores of essential (polyunsaturated) fatty acids. TMR spectra were obtained from 17 normal volunteers and nine cystic fibrosis patients using an Oxford TMR-32 with a surface coil that sampled tissue less than 1 cm below the surface of an extremity. Spectra were taken of lower leg adipose tissue. Polyunsaturated fatty acid content was determined by comparing peak heights of the polyunsaturated peak (internal unsaturated carbons, 128 ppm) to C-1 carboxyl groups (173 ppm). Monounsaturated fatty acid content was determined by subtracting the polyunsaturated peak from the peak observed for all unsaturated carbons (external unsaturated carbon, 130 ppm) and dividing this ratio by the carboxyl peak. In vivo TMR of normal volunteers resulted in observed polyunsaturated fatty acid content of 17.8 +/- 2.1% and a monounsaturated content of 44.8 +/- 3.8%. The polyunsaturated and monounsaturated fatty acid content of adipose tissue from the cystic fibrosis patients was 15.0 +/- 2.0% (p less than 0.005 versus normal volunteers) and 47.8 +/- 6.5% (NS), respectively. One cystic fibrosis patient without fat malabsorption had decreased adipose polyunsaturates, whereas another patient on high calorie gastrostomy feeds had normal levels. Carbon-13 TMR spectroscopy is a sensitive, noninvasive technique for determining essential fatty acid status in subcutaneous adipose tissue of patients with cystic fibrosis.

Adipose Tissue↗
PubMed1987

Highly transformable mutants of Streptomyces fradiae defective in several restriction systems.

Streptomyces fradiae JS85 is a mutant defective in tylosin production and an efficient recipient for conjugal transfer of tylosin genes. JS85 was mutagenized with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and derivatives defective in restriction were isolated by sequential selection for increased transformability by several plasmid DNAs. From the number of mutation and selection cycles required to eliminate most restriction, it was estimated that wild type S. fradiae expressed at least five restriction systems. From the patterns of restriction enzyme digestion of chromosomal DNA observed in the series of mutants that became progressively less restricting, it was suggested that wild type S. fradiae normally expresses modification (and presumably restriction) systems similar or analogous to PstI, XhoI, ScaI and EcoRI. The least restricting mutant of S. fradiae was readily transformable by many plasmids, including a bifunctional cosmid vector containing a large insert of Streptomyces DNA.

Bacteriophages↗
PubMed1987

Effects of growth and maturation on biliary structures of guinea pigs.

The biliary system and major duodenal papilla of male guinea pigs were examined in vivo using intravital microscopy. Study of the photomicrographs and videotape recordings indicated that biliary organs changed with age and growth of the guinea pigs. Physiological data including the frequency of sphincteric contractions were recorded and efforts were made to correlate these data with changes in structure thought to be due to maturation. The volume of smooth muscle in the bile duct sphincter (measured using histological sections) increased with age as did surface area of the mucosa. The bile duct was separate from the pancreatic duct in each of 28 guinea pigs. Study of the guinea pig extrahepatic biliary system (EBS) allowed the isolated examination of effects of maturation on bile duct capacity. The anatomical reason for this is that the ampulla of the bile duct emptied into the duodenum (independently of the pancreatic duct) at the major duodenal papilla. The duct of the pancreas entered the duodenum distally (caudally) to the major duodenal papilla on the minor duodenal papilla. The separation of biliary and pancreatic ducts simplified the making of casts of the EBS. It is important to consider this feature in selection of a model for studies of bile duct function in living animals. Three anatomical techniques were selected to focus from differing perspectives on growth-related changes that occurred among the EBS of neonatal, juvenile and adult animals. These techniques were: The capacity (volume) of bile contained within the EBS was determined using plastic casts of the system.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Biliary motility: postnatal changes in guinea pigs.

Intravital microscopy, a new in vivo technique, documented age-dependent changes in choledochoduodenal junction motility in male guinea pigs. In the guinea pig, the choledochoduodenal junction served as a pump that actively emptied its luminal contents into the duodenum. In the neonates (less than or equal to 1 wk old), this choledochoduodenal junction pump was not fully developed. Unlike the older guinea pigs, some neonates had an incompetent sphincter ductus choledochi (SDC) allowing retrograde flow of bile during ampullary contractions. While fasting, neonates had decreased frequency of SDC (1.2 +/- 0.4 contractions/min) and ampullary (0.1 +/- 0.1 contractions/min) contractions as compared to juveniles (4-6 wk old) (SDC = 6.4 +/- 1.0; ampulla = 1.2 +/- 0.2 contractions/min) and adults (greater than 1 yr old) (SDC = 6.7 +/- 1.6; 0.8 +/- 0.2 contractions/min). Following a meal (Ensure), unlike older guinea pigs, the neonate did not have a significant increased duration and decreased frequency of SDC contractions. Altered neonatal SDC motility correlated with an incompletely developed SDC including decreased muscle mass and mucosal thickness. By 4 wk of age, choledochoduodenal junction motility was similar to that of the adult. These developmental alterations in junctional motility and structure may affect the flow of bile into the duodenum contributing to physiologic cholestasis and decreased intraduodenal bile acids seen in neonates.

Animals↗
PubMed1987

Orthotopic liver transplantation in patients with cystic fibrosis.

An 11-year-old boy who had cystic fibrosis underwent an orthotopic liver transplantation. His immediate postoperative course was not unusually complicated when compared with other liver transplant recipients. Transplantation did not correct abnormalities in the sweat test or the respiratory disease. Cholestasis due to obstruction of the recipient duct with tenacious bile was cleared by instilling N-acetylcysteine into the duct. On the 48th day after the transplantation, he died of an intraventricular and intracerebral hemorrhage caused by an Aspergillus brain abscess. We conclude that certain patients with cystic fibrosis may be appropriate candidates for liver transplantation, but their pre- and post-operative management may need to differ from other liver transplant recipients.

Aspergillosis↗
PubMed1986

Cloning and expression of a tylosin resistance gene from a tylosin-producing strain of Streptomyces fradiae.

A gene conferring high-level resistance to tylosin in Streptomyces lividans and Streptomyces griseofuscus was cloned from a tylosin-producing strain of Streptomyces fradiae. The tylosin-resistance (Tylr) gene (tlrA) was isolated on five overlapping DNA fragments which contained a common 2.6 Kb KpnI fragment. The KpnI fragment contained all of the information required for the expression of the Tylr phenotype in S. lividans and S. griseofuscus. Southern hybridization indicated that the sequence conferring tylosin resistance was present on the same 5 kb SalI fragment in genomic DNA from S. fradiae and several tylosin-sensitive (Tyls) mutants. The cloned tlrA gene failed to restore tylosin resistance in two Tyls mutants derived by protoplast formation and regeneration, and it restored partial resistance in a Tyls mutant obtained by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) mutagenesis. The tlrA gene conferred resistance to tylosin, carbomycin, niddamycin, vernamycin-B and, to some degree, lincomycin in S. griseofuscus, but it had no effect on sensitivity to streptomycin or spectinomycin, suggesting that the cloned gene is an MLS (macrolide, lincosamide, streptogramin-B)-resistance gene. Twenty-eight kb of S. fradiae DNA surrounding the tlrA gene was isolated from a genomic library in bacteriophage lambda Charon 4. Introduction of these DNA sequence into S. fradiae mutants blocked at different steps in tylosin biosynthesis failed to restore tylosin production, suggesting that the cloned Tylr gene is not closely linked to tylosin biosynthetic genes.

Cloning, Molecular↗
PubMed1985

Orthotopic liver transplantation in a patient with Amanita poisoning.

Orthotopic liver transplantation in patients with acute toxic hepatitis has not, to our knowledge, been reported. Our recent experience with orthotopic liver transplantation in a 3-year-old girl with acute hepatic failure secondary to Amanita poisoning is described. Aspects of Amanita toxin-induced pathophysiology pertinent to orthotopic liver transplantation are discussed. The results in this case provide important implications for patients with fulminant hepatic failure secondary to other hepatotoxic agents in whom liver transplantation is considered.

Acute Kidney Injury↗
PubMed1985

Evidence of a noncholecystokinin stimulant of gallbladder contraction: comparison of fasting serum concentrations in healthy subjects and in patients with gallstones.

Some investigators have reported that patients with gallstones empty their gallbladders more rapidly than do healthy subjects. This may contribute to the formation of lithogenic bile. To date, cholecystokinin is considered the prime mediator of gallbladder contraction. Evidence exists that cholecystokinin may not be the major hormone accounting for gallbladder emptying. The purpose of this study was to demonstrate the existence of this noncholecystokinin substance in healthy persons and to compare its concentration with that in patients with cholesterol gallstones. Fasting serum levels from 15 healthy human subjects (8 women and 7 men, mean age 32 +/- 8 years) and 10 patients with cholesterol gallstones (5 women and 5 men, mean age 48 +/- 16 years) were studied. Using rabbit in vitro gallbladder bioassay and cholecystokinin-8 as standards, serum bioactivity was measured and expressed as cholecystokinin-8 equivalent bioactivity. The effectiveness of serum to contract the gallbladder was tested before and after removal of cholecystokinin from the serum. Cholecystokinin was removed from the serum samples by affinity chromatography with Sepharose 4B beads coated with cholecystokinin 5135 antibody. Gallbladder contractility from this treated serum thus reflects the action of a noncholecystokinin stimulant. The cholecystokinin-8 bioactivity equivalents in untreated samples from healthy subjects and from patients with gallstones were 2.9 +/- 0.3 and 7.6 +/- 0.7 ng/ml, respectively. The fact that bioactivity of serum persisted after removal of cholecystokinin in both groups of subjects provides evidence that a noncholecystokinin stimulant of gallbladder contraction exists. This substance is found in significantly higher concentrations in the fasting serum of patients with gallstones compared with healthy subjects. This finding may explain, at least in part, the increased gallbladder emptying rate in patients with gallstones and may account for the reduced bile salt pool size and, thus, formation of lithogenic bile.

Adult↗
PubMed1985

Surgery of anorectal anomalies.

This article discusses the disparate views regarding sphincteric anatomy, both normal and abnormal, and describes preoperative procedures for and operative approaches to resolving anorectal anomalies.

Anal Canal↗