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D J Kyle

Publications and source records attributed to D J Kyle.

At least 19 recordsLinked to original sources
PubMed1998

Oral anti-inflammatory action of NPC 18884, a novel bradykinin B2 receptor antagonist.

This study describes the anti-inflammatory actions of NPC 18884, a non-peptide bradykinin B2 receptor antagonist in bradykinin and carrageenan-induced inflammation in the mouse model of pleurisy. The selectivity of NPC 18884 was assessed in the pleurisy caused by histamine, substance P and des-Arg9-bradykinin. NPC 18884 given intraperitoneally or orally inhibited bradykinin-induced leukocytes influx (ID50 value of 63 nmol/kg and 141 nmol/kg, respectively). The NPC 18884 also inhibited the exudation induced by bradykinin (P < 0.05). NPC 18884 given either intraperitoneally or orally caused dose-dependent inhibition of the exudation and total and differential cell content caused by intrapleural injection of carrageenan (1%, assessed 4 h after), with mean ID50, values of 132 and 295 nmol/kg, respectively. The NPC 18884 actions installs rapidly (0.5 h), lasted for up to 4 h and were selective for the bradykinin B2 receptors; at similar doses it had no significant effect against the inflammatory responses induced by des-Arg9-bradykinin, histamine or substance P. These results indicate that the novel non-peptide bradykinin B2 receptor antagonist, NPC 18884, exhibited selective intraperitoneal and oral anti-inflammatory properties when assessed in the inflammatory reaction induced by bradykinin and carrageenan in the mice model of pleurisy.

Administration, Oral↗
PubMed1998

Determination of 15N isotopic enrichment and concentrations of allantoin and uric acid in urine by gas chromatography/mass spectrometry.

A method for the determination of 15N enrichment and concentration of allantoin and uric acid simultaneously in urine using gas chromatography/mass spectrometry (GC/MS) is described. The urine samples contained [1,3-15N2] uric acid and its oxidation product allantoin. The uric acid and allantoin were isolated using an AG1-X8 (Cl-form) anion-exchange column and heated with a mixture containing 1:1 dimethylformamide and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA). The tert-butyldimethylsilyl (TBDMS) derivatives of allantoin and uric acid formed were injected into a gas chromatograph interfaced with a mass spectrometer operated under electron impact ionization conditions. Isotope ratio measurements were made from the abundance of the M-57 ions at m/z 398, 399 and 400 for allantoin and at m/z 567 and 569 for uric acid. 15N2 allantoin (99 at.%) was produced from [1,3-15N2] uric acid by treatment with uricase and used as a standard. Quantitation of allantoin and uric acid was based on isotopic dilution by spiking the urine sample with known quantities of 99 at.% [15N] uric acid and allantoin internal standards. The observed isotope ratio measurements from the prepared standards matched the theoretical values. Coefficients of variation in measurements of isotope ratio and concentration were 0.2 and 0.5%, respectively. The method was applied in a study to measure the urinary recovery of [1,3-15N2] uric acid continuously infused for 8-10 h into the blood of four sheep each on two occasions. Within 24 h, 65.9 +/- 9.1% of the tracer was excreted in the urine unchanged. Little was converted into allantoin (approximately 7% of the dose). The total recovery (5 days) of the infused tracer averaged 69.5 +/- 7.6% as uric acid and 76.8 +/- 9.3% as the sum of uric acid and allantoin. Uricase activities in plasma, liver and kidney of sheep were also measured using [1,3-15N2] uric acid as a substrate. Uricase activity was estimated to be 0.6 mU g-1 wet tissue in the liver and there appeared to be none in plasma and kidney. The low uricase activities in sheep tissues appeared to explain the limited conversion of the intravenously administered [15N] uric acid to allantoin but did not explain the large quantities of allantoin excreted in urine (8.96 +/- 0.86 and 1.36 +/- 0.25 mmol d-1 for allantoin and uric acid, respectively). The GC/MS method for the determination of 15N enrichment and concentration of allantoin and uric acid in urine is accurate and precise and provides a useful tool for studies on uric acid and allantoin metabolism.

Allantoin↗
PubMed1997

Stable expression of the human kinin B1 receptor in Chinese hamster ovary cells. Characterization of ligand binding and effector pathways.

To delineate ligand binding and functional characteristics of the human B1 kinin receptor, a stable clone of Chinese hamster ovary cells expressing a single class of binding sites for [3H]des-Arg10-lysylbradykinin with a Kd of 0.3 nM and a Bmax of 38 fmol/mg protein ( approximately 40,000 receptors/cell) was isolated. Studies with peptide analogs showed that a lysine residue at position 1 (based on the lysylbradykinin sequence) of ligands was essential for high affinity binding to the human B1 receptor. In marked contrast to cloned Chinese hamster ovary cells expressing the human kinin B2 receptor, which internalized approximately 80% of the ligand within 5 min upon exposure to 2 nM [3H]bradykinin, exposure of cells expressing the B1 receptor to 1 nM [3H]des-Arg10-lysylbradykinin resulted in minimal ligand internalization. Stimulation of the B1 receptor led to inositol phosphate generation and transient increases in intracellular calcium, confirming coupling to phospholipase C, while immunoprecipitation of photoaffinity-labeled G-proteins from membranes indicated specific coupling of the receptor to Galphaq/11 and Galphai1,2. The B1, unlike the B2, receptor does not desensitize (as demonstrated by continuous phosphoinositide hydrolysis), enhancing the potential role of this receptor during inflammatory events.

Animals↗
PubMed1997

The effects of acute and chronic protein depletion and accretion on plasma concentrations of insulin-like growth factor-1, fibronectin and total protein for ruminants nourished by intragastric infusion of nutrients.

The relationships of N input or protein status and the concentrations of serum insulin-like growth factor-1 (IGF-1), plasma fibronectin (FN) and total protein (TP) were examined in three experiments with steers and sheep nourished by intragastric infusion of nutrients. In Expt 1, three steers (340 kg live weight) were infused with three levels of volatile fatty acids (0, 300 and 600 kJ/kg metabolic weight (W0.75) per d) and six levels of casein (0, 200, 400, 650, 1500 and 2500 mg N/kg W0.75 per d). Each N treatment was imposed for 5 d. In Expts 2 and 3, five groups of sheep (about 35 kg live weight) were infused with casein at 500 mg N/kg W0.75 per d for 2 weeks followed by 1500, 500 or 50 mg N/kg W0.75 per d in Expt 2, and in Expt 3, with 100 mg N/kg W0.75 per d for 6 weeks or 10 mg N/kg W0.75 per d for 4 weeks. Non-protein energy was maintained constant at 500 kJ/kg W0.75 per d throughout. Daily N balance and total body N content at the end were measured, and protein status was defined as a percentage of cumulative N accretion or depletion in relation to the total body N content at maintenance. It was found that IGF-1 and FN responded rapidly and substantially to altered N input, and that when daily N input was maintained constantly at sub-maintenance, their continuous declines were related closely to progressive protein depletion in the sheep. Plasma TP concentration was independent of N input when N input was altered acutely in the steers, but declined significantly and gradually with severe, chronic body protein depletion in the sheep. Plasma content of TP in the sheep however reduced acutely with a reduction in N input. Plasma volume fell substantially over the first 2 weeks of protein depletion, compensating for the declines in TP content and maintaining TP concentration plateau. The possible implications of the changes in TP concentration and content (concentration x volume) to body protein loss in sheep are discussed.

Animal Nutritional Physiological Phenomena↗
PubMed1996

Antioedematogenic and antinociceptive actions of NPC 18521, a novel bradykinin B2 receptor antagonist.

The novel pseudopeptide bradykinin B2 receptor antagonist containing the 1,3,8-triazaspiro[4,5]decan-4-one ring system, NPC 18521 (D-Arg-Arg-[1,3-phenyl,8-triazaspiro[4,5]-decane-4-one-3-acetyl]-S er-D -tetrahydroisoquinolinyl-octahydroindolinyl-Arg) (10 and 30 nmol/kg, i.p.), given 30 min prior, produced significant and long-lasting inhibition of rat paw oedema induced by bradykinin (3 nmol/paw) and carrageenan (300 micrograms/paw), without affecting the oedema induced by the selective bradykinin B1 receptor agonist, des-Arg9-bradykinin, in rats pretreated with Escherichia coli endotoxin. In contrast, when injected locally into the rat or mouse hindpaw, NPC 18521 (1-100 nmol) elicited dose-related oedema formation. This effect was almost completely blocked by cyproheptadine (20 mg/kg, i.p.) or by compound 48/80 (12 micrograms/paw), but was unaffected by Hoe 140 (D-Arg-[Hyp5,Thi5,Tic7,Oic8]bradykinin). NPC 18521 (0.3-10 nmol/kg, i.p.) produced significant inhibition of acetic acid, acetylcholine and kaolin- but not zymosan-induced abdominal constrictions in mice. The calculated mean ID50 values for these effects were 0.84, 0.46 and 0.55 nmol/kg, respectively. The antinociceptive action of NPC 18521 (3 nmol/kg, i.p.) had a rapid onset (15 min) and lasted for up to 120 min. Given topically (0.01-0.3 nmol), NPC 18521 produced significant attenuation of both the early and the late phase of the formalin-induced licking, as well as formalin-induced oedema formation. In addition, NPC 18521 given both systemically or topically, produced significant inhibition of the neurogenic nociception caused by topical injection of capsaicin. Given topically in the rat paw, NPC 18521 (10 nmol) caused marked hyperalgesia, an effect which was completely prevented by cyproheptadine (20 mg/kg, i.p.), but was unaffected by Hoe 140 (3 nmol/kg, i.p.). Given intraperitoneally, 30 min prior, NPC 18521 (3-30 nmol/kg) like Hoe 140 (1-10 nmol/kg) prevented, in a dose-dependent manner, bradykinin (3 nmol/paw)-induced hyperalgesia with mean ID50 values of 13.16 and 1.36 nmol/kg, respectively. Thus, the novel pseudopeptide bradykinin B2 receptor antagonist, NPC 18521, has an effect with rapid onset, and produces potent and relatively long-lasting antioedematogenic and antinociceptive properties. However, in contrast to Hoe 140, given locally into the hindpaw, NPC 18521 elicited marked oedema formation and hyperalgesia, an effect which seems to be secondary to mast cell degranulation and histamine and/or serotonin release. Finally, the anti-bradykinin actions of NPC 18521 are quite selective towards the bradykinin B2 receptor-mediated responses.

Animals↗
PubMed1996

The N terminus of bradykinin when bound to the human bradykinin B2 receptor is adjacent to extracellular Cys20 and Cys277 in the receptor.

Chemical cross-linking combined with site-directed mutagenesis was used to evaluate the role of extracellular cysteines and their positions relative to the binding site for the agonist bradykinin (BK) in the human BK B2 receptor. All extracellular cysteines, Cys20, Cys103, Cys184, and Cys277, in the receptor were mutated to serines, and single and double mutants were transfected into COS-7 cells. The Ser20 and Ser277 single mutants and the Ser20/Ser277 double mutant bound [3H]BK and the antagonist [3H]NPC17731 with pharmacological profiles identical to the wild-type B2 receptor. In contrast, the Ser103 and Ser184 single mutants were unable to bind either of the two radioligands. However, these mutants were still expressed as determined by immunoblotting with anti-B2 receptor antibodies. Previous studies on the bovine B2 receptor showed that bifunctional reagents, which are reactive to amines at one end and to free sulfhydryls in the opposite end, cross-link the N terminus of receptor-bound BK to a sulfhydryl in the receptor (Herzig, M. C. S., and Leeb-Lundberg, L. M. F. (1995) J. Biol. Chem. 270, 20591-20598). Here, we show that m-maleimidobenzoyl-N-hydroxysuccinimide ester and 1,5-difluoro-2, 4-dinitrobenzene cross-linked BK to the wild-type human B2 receptor and the Ser20 and Ser277 single mutant receptors, whereas these reagents were unable to cross-link BK to the Ser20/Ser277 double mutant. These results show that Cys103 and Cys184 are both required for expression of high affinity agonist and antagonist binding sites in the human B2 receptor, while Cys20 and Cys277 are not required. Furthermore, the results provide direct biochemical evidence that the N terminus of BK, when bound to the B2 receptor, is adjacent to Cys277 in extracellular domain 4 and Cys20 in extracellular domain 1 of the receptor.

Animals↗
PubMed1996

Synthesis and characterization of pseudopeptide bradykinin B2 receptor antagonists containing the 1,3,8-triazaspiro[4.5]decan-4-one ring system.

A series of pseudopeptides containing alkyl-, cycloalkyl-, aryl-, and aralkyl-substituted 1,3,8-triazaspiro[4.5]decan-4-one-3-acetic acids as amino acid surrogates to replace the Pro2-Pro3-Gly4-Phe5 section of the peptide bradykinin B2 receptor antagonist [Pro3, Phe5]HOE 140 (D-Arg0-Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-D-Tic7+ ++-Oic8-Arg9) were prepared. These psuedopeptides were examined in vitro for their B2 receptor affinities as well as for their ability to block bradykinin mediated actions in vivo. Two compounds in particular, NPC 18521 (I) and NPC 18688 (V) were quite potent in these latter assays, indicating that a significant portion of this prototypical second generation decapeptide antagonist can be replaced with a more compact nonpeptide molecule.

Amino Acid Sequence↗
PubMed1996

Accuracy and reliability of the scaling-relaxation method for loop closure: an evaluation based on extensive and multiple copy conformational samplings.

The accuracy and reliability of the recently proposed scaling-relaxation method for loop closure were examined by using extensive conformational sampling. For each of the eight heptapeptides chosen to represent a variety of protein conformations, 1,000-2,000 conformations were sampled. Each segment contained 14 rotatable backbone dihedral angles. The average root mean square deviations (RMSDs) between the predicted and the native conformations were 0.7 angstrom for the backbone and 1.2 angstroms for the side chain atoms. These predictions were substantially more accurate than the previous predictions (1.1 angstroms for the backbone and 2.2 angstroms for the side chain atoms) of the same eight protein segments based on limited conformational sampling (100 conformations for each segment). Large prediction errors mostly occurred at polar and surface side chains that are unlikely to have any meaningful conformation. Moreover, the reliability of seven of the eight predictions was demonstrated with their energy-RMSD and stability-RMSD correlations of the low-energy conformations, where the conformational stability was estimated by using the multiple copy simultaneous sampling method.

Amino Acid Sequence↗
PubMed1996

Preclinical evaluation of single-cell oils that are highly enriched with arachidonic acid and docosahexaenoic acid.

Arachidonic acid (ARA) and docosahexaenoic acid (DHA) are important in human brain and retina development, and there is growing evidence showing the importance of these fatty acids in infant nutrition. Triglyceride oils, highly enriched in ARA (ARASCO) and DHA (DHASCO), were evaluated using very high dose acute (20 g/kg) and 4-wk subchronic gavage feedings in weanling Sprague-Dawley rats. The combination of these oils, Formulaid, was also tested in the 4-wk subchronic study, ARASCO, DHASCO and Formulaid were found to have a no-observable-adverse-effect level of more than 2.5 g/ kg/day, 1.25 g/kg/day and 3.75 g/kg/day, respectively. This represents a 50-fold safety margin over the intended use of Formulaid in infant formula. Survival, clinical signs, body weight gain, food consumption, haematology, clinical chemistry and histopathological evaluations failed to show any significant differences in animals administered ARASCO, DHASCO or Formulaid compared with that in control animals administered equal amounts of high oleic sunflower oil. The bioavailability of ARASCO, DHASCO and Formulaid was verified by increases in DHA and ARA levels in heart and liver tissues in these animals. Because these oils are enriched in only a single bioactive fatty acid, and they have been shown to be safe, they may offer a new source of these fatty acids in speciality foods such as infant formula.

Administration, Oral↗
PubMed1996

Urinary and plasma purine derivatives in fed and fasted llamas (Lama glama and L. guanacoe).

The changes in urinary and plasma purine derivatives in response to fasting and level of feeding in llamas were examines. In one experiment, four llamas were gradually deprived of feed within 3 days and then fasted for 6 days. Daily urinary excretion of purine derivatives decreased with feed intake and leveled on the last 3 days of fasting at 177 +/- 26 mumol/kg W0.75. Allantoin and uric acid comprised 71% and 15% of total purine derivatives, respectively, in both fed and fasted states, but hypoxanthine plus xanthine increased from 9% to 36%. Plasma concentration of allantoin declined with feed intake reduction, but those of uric acid (217 mumol/l) and hypoxanthine plus xanthine (27 mumol/l) remained relatively unchanged. Concentration of uric acid was higher than that of allantoin, probably due to a high reabsorption of uric acid in renal tubules, which was measured as over 90%. In a second experiment, the four llamas were fed at 860 and 1740 g dry matter/d in a crossover design. Urinary total purine derivatives excretion responded to feed intake (10.4 vs 14.4 mmol/d), although the observed differences did not reach significance. Compared with some ruminant species, it appears that the llama resembles sheep regarding the magnitude of urinary purine derivatives excretion but is unique in maintaining a high concentration of uric acid in plasma, which could be part of the llama's adaptation to their environment.

Allantoin↗
PubMed1996

Computational screening of combinatorial libraries.

We first review existing computational methods with an intrinsic combinatorial feature, then describe a new computational method for screening combinatorial libraries using a recently developed multicopy sampling technique. The new method differs from the existing ones in that it can be used to screen simultaneously an entire library of molecules, instead of the individual molecules in a library. As an example, we have applied the method to study site-directed amino acid substitutions in a protein. After two rounds of library screening, we identified the energetically most stable substitutions along with their optimal conformations from all natural amino acids. In principle, the method is generally applicable to study ligand-host systems.

Amino Acids↗
PubMed1996

Urinary excretion of purine derivatives and tissue xanthine oxidase (EC 1.2.3.2) activity in buffaloes (Bubalis bubalis) with special reference to differences between buffaloes and Bos taurus cattle.

The urinary excretion of purine derivatives (PD) was measured in six buffaloes (Bubalis bubalis) during fasting and in fourteen buffaloes given four restricted levels of roughage (2.5-4.8 kg DM/d). Only allantoin and uric acid, not xanthine and hypoxanthine, were present in the urine, the pattern of excretion being similar to that in cattle. The fasting PD excretion amounted to 0.20 (SD 0.06) mmol/kg metabolic weight (W)0.75 per d, and the rate of PD excretion as a linear function of feed intake was 5.2 mmol/kg digestible organic matter intake. Both values were considerably lower than the values for cattle reported in the literature. Creatinine excretion values were 0.33 (SD 0.06) and 0.44 (SD 0.09) mmol/kg (W)0.75 per d determined in fasting and feeding periods respectively. Fasting N excretion was 257 (SD 49) mg N/kg (W)0.75 per d. Both creatinine and fasting N excretions were also lower than in cattle. The activities of xanthine oxidase (EC 1.2.3.2) in plasma, liver and intestinal mucosa were determined in buffaloes, cattle and sheep. Xanthine oxidase activities in buffaloes were 24.5 (SD 2.7) unit/l plasma and 0.44 (SD 0.02) and 0.31 (SD 0.10) unit/g fresh tissue in liver and intestinal mucosa respectively. These activities were higher than those in cattle and sheep. Xanthine oxidase was practically absent from plasma and intestine of sheep. It is suggested that the differences in PD excretion between buffaloes and cattle were probably due to the smaller proportion of plasma PD that was disposed of in the urine of buffaloes.

Allantoin↗
PubMed1996

Antinociceptive profile of the pseudopeptide B2 bradykinin receptor antagonist NPC 18688 in mice.

1. The purpose of this study was to investigate the topical and systemic anti-hyperalgesic effect of the newly-developed pseudopeptide B2 receptor antagonist, NPC 18688, in different models of nociception in mice. 2. Given systemically 30 min beforehand, NPC 18688 (10-300 nmol kg-1, i.p.) caused no agonist effect, but produced a dose-related and significant inhibition of abdominal constrictions caused by intraperitoneal injection of acetic acid (0.6%), acetylcholine (ACh, 4.5 mg kg-1) or kaolin (50 mg kg-1). The calculated mean ID50s and the percentages of maximal inhibitions (MI) for these effects were: 77, 34 and > 300 nmol kg-1 and 65 +/- 6, 70 +/- 5 and 40 +/- 3%, respectively. The anti-hyperalgesic effect of NPC 18688 (100 nmol kg-1, i.p.) occurred rapidly (30 min) and lasted for at least 150 min. Hoe 140 (3-30 nmol kg-1, i.p.) given 30 min beforehand also inhibited, in a graded manner, acetic acid and ACh-induced writhing, with mean ID50s and MI of 6 and 9 nmol kg-1 and 56 +/- 7 and 62 +/- 6%, respectively. 3. NPC 18688 (10-300 nmol kg-1, i.p.) caused a graded inhibition of both phases of formalin (2.5%)-induced pain, its effects being more potent in relation to the second phase of the formalin test. The calculated mean ID50s and the MI were > 300 and 60 nmol kg-1 and 20 +/- 3 and 60 +/- 5% against the first and second phases of formalin-induced nociception, respectively. NPC 18688 at the same doses also inhibited, in a dose-related manner, formalin-induced paw oedema (MI of 35 +/- 3%). 4. When injected locally in the mouse paw, NPC 18688 (2, 10 and 20 nmol/paw) had no agonist activity. However, when co-injected with formalin NPC 18688 (2-20 nmol/paw), it produced significant inhibition of both phases of formalin response, with MI of 40 +/- 3 and 33 +/- 2%, respectively. NPC 18688 at 10 nmol/paw also significantly inhibited formalin-induced paw oedema (25 +/- 2%). 5. Given intraperitoneally, NPC 18688 (30-300 nmol kg-1) determined a graded inhibition of the nociceptive response caused by intraplantar injection of capsaicin (1.6 micrograms/paw) (40 +/- 2%). However, NPC 18688 (up to 300 nmol kg-1, i.p.), given 30 min beforehand, had no significant analgesic effect when analyzed in the tail flick and in the hot plate pain models, nor did it change the performance of animals in the rota rod test. 6. The action of NPC 18688 was quite selective for the B2 receptor, and like Hoe 140, (1 to 100 nmol kg-1, i.p.) it caused graded inhibition of bradykinin (BK, 3 mol/paw)-induced increase in mouse paw volume, with mean ID50s of 61 and 6 nmol kg-1, respectively. In addition, at 100 nmol kg-1, the dose at which NPC 18688 significantly antagonized BK (3 nmol)-mediated rat paw oedema in naive animals, it had no significant effect on des-Arg9-BK (100 nmol/paw)-induced oedema in paws that had been desensitized to BK. NPC 18688 (210 nmol kg-1), like Hoe 140 (230 nmol kg-1) given s.c. 30 min beforehand, completely abolished BK (28 nmol)-induced hypotension, without affecting the fall of mean arterial blood pressure induced by i.v. injection of ACh (2 nmol kg-1). Finally, NPC 18688 (1 microM) did not affect ACh-mediated contraction in the guinea-pig ileum or toad rectus abdominii in vitro. 7. These results demonstrate that the newly-developed and selective pseudopeptide B2 receptor antagonist, NPC 18688, although less potent than the available second generation of B2 peptide BK receptor antagonists, exhibits topical and long-lasting systemic anti-hyperalgesic properties when analysed in several models of nociception in mice, making it a useful tool for investigating the participation of BK and related kinins in physiological and pathological processes. Finally, this new class of selective pseudopeptide B2 receptor antagonist may constitute a new strategy for developing the third generation of potent and long-lasting orally-active non-peptide BK antagonists, which may be useful for the management of clinical disorders involving BK and relate

Acetylcholine↗
PubMed1996

A pharmacological analysis of receptor subtypes and the mechanisms mediating the biphasic response induced by kinins in the rat stomach fundus in vitro.

Bradykinin (BK), des-Arg9-BK (DABK) and related kinins caused biphasic response (BR) in rat stomach fundus (RSF) precontracted with BaCl2. The B2 receptor antagonist HOE 140 (3-30 nM) produced parallel rightward shifts of the contractile concentration-response curve (CRC) for BK, yielding a pA(2) value of 9.07 +/- 0.27 and slope of 0.99, but caused only discrete rightward shift of the relaxant CRC for BK, leaving the BR CRC to DABK unaffected. The B1 receptor antagonist des-Arg9-NPC 17761 (10 nM to 1 microM) caused graded rightward shifts of the relaxant (but not the contractile) CRC to DABK, yielding a pA2 value of 8.35 +/- 0.05 and slope of 0.59, but had no effect on BK-induced BR. BK- and DABK- (100 nM) induced relaxation were almost suppressed by apamin (1 microM) or by nifedipine (1 nM), but were unaffected by nitric oxide synthase inhibitors, methylene blue, lipo and cyclooxygenase inhibitors, selective receptor antagonist for histamine (H1 and H2), nicotine, platelet activating factor, tachykinins (both NK1 and NK2, calcitonin gene-related peptide, vasoactive intestinal peptide and ganglion blocking agent. BK- and DABK-mediated relaxations were reduced in Ca2+ -free medium plus EGTA, although BK-mediated contraction was more resistant. Escherichia coli endotoxin treatment (10 microgram /rat), 24 hr before, potentiated DABK-induced relaxation, but not contraction, and reduced BK-mediated relaxation (P < .05). It is concluded that RSF express both B1 and B2 receptors. BK-induced contraction involves activation of B2 receptors, although DABK-induced relaxation is mediated by B1 receptors. Both B1 and B2 receptors in RSF are constitutive, but LPS treatment caused induction of B1 and down-regulation of B2 receptors. Finally, kinin-mediated relaxation in RSF are coupled to activation of Ca2+ activated K+ channels, and rely on Ca2+ influx via L-type voltage-sensitive channels.

Animals↗
PubMed1995

Synthesis of linoleate and alpha-linolenate by chain elongation in the rat.

The objective was to determine whether rats could synthesize longer chain polyunsaturates from hexadecadienoate (16:2n-6) and hexadecatrienoate (16:3n-3). Rats were gavaged with uniformly 13C-labelled hexadecadienoate or hexadecatrienoate, euthanized 24 h later, and total lipids were extracted from liver and carcass. Gas chromatography/combustion/isotope ratio mass spectrometry was used to measure 13C levels in individual liver, carcass, and whole body fatty acids. 13C Enrichment was present in desaturated and chain-elongated polyunsaturates, including linoleate, arachidonate, alpha-linolenate, and docosahexaenoate at 12-13% of the dose of tracer given. 13C Enrichment from hexadecatrienoate was highest in carcass and liver alpha-linolenate, representing 3.5 and 17.9% of the total alpha-linolenate pool, respectively. For linoleate, arachidonate, or docosahexaenoate, the contribution of 13C did not exceed 0.2% of the total body pool. Green leafy vegetables common in the human diet were shown to contain up to 1.2% of total fatty acids as hexadecadienoate and 11.6% as hexadecatrienoate. Hence, humans consuming green vegetables probably synthesize a small proportion of their total body content of linoleate and alpha-linolenate.

Animals↗
PubMed1995

Effects of long-term protein excess or deficiency on whole-body protein turnover in sheep nourished by intragastric infusion of nutrients.

The effect of long-term dietary protein excess and deficit on whole-body protein-N turnover (WBPNT) was examined in lambs nourished by intragastric infusions of nutrients. Ten sheep were given 500 mg N/kg metabolic weight (W0.75) per d from casein for 2 weeks and then either 50 (L), 500 (M) or 1500 (H) mg N/kgW0.75 per d for 6 weeks. Volatile fatty acids were infused at 500 kJ/kgW0.75 per d. Daily WBPNT was measured by continuous intravenous infusion of [1-13C]leucine 3 d before, and on days 2, 21 and 42 after the alteration in protein intake. Whole-body protein-N synthesis (WBPNS) was calculated as the difference between WBPNT and the protein-N losses as urinary NH3 and urea. Whole-body protein-N degradation (WBPND) was then estimated from WBPNS minus protein gain determined from N balance. Fractional rates of WBPNS and WBPND were calculated against fleece-free body N content. WBPNS rates at the L, M and H intakes were respectively 35.1, 41.5 and 63.7 g/d (P < 0.001) on average over the 6 weeks and WBPND rates were 39.5, 41.1 and 56.8 g/d (P < 0.001). The fractional rates of WBPNS were 5.01, 6.37 and 7.73% per d (P < 0.001) while those of WBPND were 5.64, 6.29 and 6.81% per d (P < 0.005) respectively. On days 2, 21 and 42, WBPNS rates at intake H were 54.0, 61.8 and 75.4 g/d (P = 0.03) respectively, and WBPND rates were 43.2, 56.4 and 70.9 g/d (P = 0.03); at intake L the amounts were 38.2, 34.2 and 32.8 g/d for WBPNS (P = 0.003) and for WBPND were 43.4, 38.0 and 36.9 g/d (P = 0.016) respectively. There were no significant (P > 0.05) differences in fractional rates of WBPNS and WBPND with time at either the L or H intake. We concluded that absolute protein turnover was affected both by dietary protein intake and body condition while the fractional rate of turnover was predominantly influenced by intake.

Ammonia↗