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D J Kyle

Publications and source records attributed to D J Kyle.

At least 55 records · Page 3Linked to original sources
PubMed1993

Additive effects of a bradykinin antagonist, NPC 17761, and a leumedin, NPC 15669, on survival in animal models of sepsis.

The effects of coadministration of NPC 17761 (D-Arg-Arg-Pro-Hyp-Gly-Phe-Ser-D-Hype (transthiophenyl)-Oic-Arg), a potent bradykinin antagonist, and NPC 15669 (N-[9H-(2,7-dimethylfluoren-9-yl-methoxy)carbonyl]-L-leucine), a leukocyte recruitment inhibitor, were examined in rodent models of experimental shock. In mice, ED50 doses of NPC 17761 (0.12 mg/kg) and NPC 15669 (4 mg/kg), administered together, increased survival (83%) and inhibited leukopenia (60% at 4 h) in response to a lethal dose of endotoxin. In rats, independent administration of NPC 15669 (10 mg/kg, i.v. bolus) or NPC 17761 (0.1 mg/kg/h, 4 h) did not significantly increase survival (36 +/- 4 and 46 +/- 9 h, respectively) versus controls (27 +/- 1 h). However, co-treatment essentially "cured" (survival > 1 week) all septic animals, suggesting synergistic effects of the two agents.

Amino Acid Sequence↗
PubMed1993

Detection of [U-13C]eicosapentaenoic acid in rat liver lipids using 13C nuclear magnetic resonance spectroscopy.

Fatty acid carbons are well-resolved in 13C nuclear magnetic resonance (NMR) spectra of lipid extracts, but application of this methodology to the metabolism of 13C-labelled fatty acids has not yet been reported. In the present study, 13C NMR was used to monitor the presence of 98% [U-13C]eicosapentaenoic acid (EPA) in liver and carcass lipids 24 h after it had been injected into the stomach of a rat. Natural abundance 13C NMR spectra of liver total fatty acid extracts were obtained from four control rats for comparison. At 24 h post-injection, quantitative high resolution 13C NMR showed 13C enrichment in liver fatty acid extracts was present mainly at olefinic and at the n-1 to n-4 carbons, but 13C signal intensities for C-1 to C-4 of [U-13C]EPA were markedly reduced or absent. Small 13C resonances, possibly indicative of some 13C incorporation into docosahexaenoic acid and saturated or monounsaturated fatty acids, were present in spectra of liver fatty acids. Liver and carcass fatty acid composition was similar in both the controls and the EPA-injected rat, suggesting little accumulation of the injected [U-13C]EPA after 24 h. We conclude that the carbon-specific data provided by 13C NMR of lipid extracts may be useful in monitoring the fate of individual carbons during tracer studies using 13C-labelled fatty acids.

Animals↗
PubMed1992

Probing the bradykinin receptor: mapping the geometric topography using ethers of hydroxyproline in novel peptides.

Five decapeptides were prepared, each having the generic primary sequence D-Arg0-Arg1-Pro2-Hyp3-Gly4-Thi5-Ser6-X7 -Y8-Arg9. A C-terminal beta-turn was anticipated when X was an alkyl ether of D-4-hydroxyproline in either the cis or trans geometric state and Y was either a Tic or Oic residue. Whereas cis ethers have only very weak receptor affinities, the trans ethers are significantly more potent in binding to guinea pig smooth muscle having Ki values as low as 0.16 nM. Notably, these peptides do not contain a D-aromatic amino acid at position 7 of the primary sequence.

Amino Acid Sequence↗
PubMed1992

Recent developments in the understanding of bradykinin receptors.

The dramatic activities of bradykinin and related peptides as mediators of pain, inflammation and hypotension have been intensely studied for several decades. More recently, the involvement of bradykinin in regulation of ion transport by epithelia, hormone release from endocrine organs, energy metabolism, tissue growth, and leukocyte activation have become topics of study. Kininogen precursors, synthetic kallikreins, and degradative kininases have been characterized in detail with regard to catalytic mechanisms, physical structure and gene regulation; however, the actual receptors for bradykinin are still only poorly understood. This situation is caused by the lack of availability of potent, specific receptor antagonists. However, specific bradykinin receptor antagonists became available in 1985, and several very potent classes of agents are now available; also, the first bradykinin receptor has been cloned.

Amino Acid Sequence↗
PubMed1992

Endogenous allantoin excretion in response to changes in protein supply in sheep.

Endogenous allantoin derives from the breakdown of tissue nucleic acids. This study examined the effect of changes in protein supply on endogenous allantoin excretion by sheep. The animals were nourished by infusions of volatile fatty acids into the rumen and casein into the abomasum, thus avoiding ruminal microbial fermentation (i.e., no supply of exogenous nucleic acids). While a constant energy supply was maintained, the protein supply was altered in one of two ways: 1) changed from 0 to 3000 mg casein-N/kg metabolic weight (W0.75) per day in progressive steps; or 2) completely removed from an initial constant level [500 mg N/(kg W0.75.d)]. With the first alteration, endogenous allantoin excretion was not directly affected by the daily N input or N retention, but was linearly correlated with the cumulative N retention. With the second alteration, allantoin excretion increased (35-145%) on the first day after removal of the protein supply and then fell to a level equivalent to, or lower than, that before protein removal. The results suggest that the changes in endogenous allantoin excretion may reflect remodeling of the metabolic state of the animal during periods when protein supply fluctuates.

Allantoin↗
PubMed1991

Mass receptor screening for new drugs.

Mass receptor screening is capable of identifying drug candidates in large compound libraries. Our laboratory has developed a mass screening technology by standardizing assay protocols that can be transferred from receptor to receptor. The entire operation, from disbursement of compounds to data analysis, is computerized to handle vast numbers of experimental results. The success of this method depends upon strict definitions of compound activity, with rapid elimination of compounds that do not fulfill all criteria. Finally, we approach automation with caution. While certain items, such as automatic harvesters, are essential for high-throughput screening, much time can be spent optimizing gadgets instead of gathering data.

Computers↗
PubMed1991

D-Arg[Hyp3-Thi5-D-Tic7-Tic8]-bradykinin, a potent antagonist of smooth muscle BK2 receptors and BK3 receptors.

D-Arg[Hyp3-Thi5-D-Tic7-Tic8]-bradykinin (NPC 16731) inhibited bradykinin (BK) binding and BK-induced contraction in guinea-pig ileum, being markedly more potent than D-Phe7-BK analogues as a BK2 receptor antagonist. In isolated trachea NPC 16731, unlike other BK2 antagonists, inhibited BK binding and BK-induced contraction, and 45Ca2+ efflux in tracheal smooth muscle cells. That NPC 16731 potently inhibits BK effects in trachea provides further evidence for the existence of the airway BK3 receptor.

Amino Acid Sequence↗
PubMed1991

Renal clearance of plasma allantoin in sheep.

The recovery in urine of an intrajugular infusion of physiological amounts of allantoin was measured in four sheep nourished by an intragastric infusion of volatile fatty acids and casein (to eliminate rumen fermentation). The recovery was 72% (S.E.M. 7) and the remainder was presumed to have been lost by diffusion into the gut and degradation by gut microflora. Measured in two sheep, allantoin was removed from the blood at a fractional rate of 0.30 h-1, and excreted in urine at 0.23 h-1. Calculation based on creatinine excretion showed glomerular filtration rate and tubular reabsorption of allantoin to be unchanged by the intravenous infusion. Maximal tubular reabsorption at 1.28 mmol day-1 was saturated by the load of endogenous allantoin alone. In a second experiment with seven normally fed sheep (28-50 kg live weight, all given 1 kg feed), urinary excretion and plasma concentration of allantoin were linearly related. However, the errors were such that plasma allantoin concentration would be of little value as a predictor of urinary excretion. There was a nearly twofold range in allantoin excretion (the larger animals excreting less), which implied that the supply of microbial biomass to the host animal per unit of feed ingested could be profoundly affected by feeding level.

Allantoin↗
PubMed1990

Mechanism of photoinhibition in vivo. A reversible light-induced conformational change of reaction center II is related to an irreversible modification of the D1 protein.

The light-induced inactivation of the photochemical reaction center II (RCII) of oxygenic chloroplasts (photoinhibition) was investigated in cells and isolated thylakoids of the green alga Chlamydomonas reinhardtii. The process is resolved into a reversible conformational change followed by an irreversible modification of RCII D1 protein. The light-induced changes in vivo persisted in isolated thylakoids. The first step is characterized by (i) destabilization of the secondary acceptor semiquinone anion, Q-B, bound to the D1 protein. This is demonstrated by a reduction in the activation energy of S2,3Q-B charge recombination as measured by the thermoluminescence technique; and (ii) a rise in the intrinsic fluorescence and a decrease of the maximal fluorescence. Unoccupancy of the QB site by plastoquinone partially protected RCII against the light-induced destabilization of Q-B. The extent of charge separation (P+680Q-A) was not affected. However, the slow phase (microsecond) of P+680 dark reduction increased, and the amplitude of signal II was reduced by 20-30%, indicating that in a fraction of RCII, electron donation from Z to P+680 was impaired without losing primary photochemistry. This modification correlates with the irreversible change in D1 protein resulting in the formation of a trypsin-resistant fragment of 16 kDa detected in D1 isolated from light-exposed cells. The change in the Q-B stability could allow charge equilibration with QA and thus explain the rise in the intrinsic fluorescence level and reduction of electron flow to plastoquinone. The change in the lifetime of P+680 can account for further reduction in electron flow (photo-inhibition). The irreversible light-dependent modification of D1 may serve as the signal for its degradation and replacement by a newly synthesized molecule (turnover).

Chlamydomonas↗
PubMed1989

The effect of clenbuterol on basal protein turnover and endogenous nitrogen loss of sheep.

Seven measurements of the effect of clenbuterol on basal nitrogen excretion (UNE), and protein turnover were made in six female sheep. The sheep were sustained by the intraruminal infusion of energy as volatile fatty acids to provide maintenance, but given no protein (N-free) for 12 d (6 d control, 6 d clenbuterol). Clenbuterol reduced UNE by 20%, but only on day 2 of the 6 d subperiod. Protein flux (equivalent to degradation on N-free nutrition), measured on day 6 by the irreversible loss of leucine was significantly increased (12%) by clenbuterol. Amino-N oxidation measured by N excretion was unchanged and, therefore, protein synthesis was also increased. During the 12 d N-free period, the recovery of urinary total N (Kjeldahl) as the sum of urea, ammonia, creatinine and purine derivatives, declined from 87.7 to 74.2%. The form of this missing N was not identified. The effect of clenbuterol of increasing both degradation and synthesis is unlike that reported in the literature for animals receiving protein when, in general, synthesis is unchanged and degradation reduced. This could be due to a different effect of clenbuterol in the N-free state, or to unchanged effects on protein pools other than muscle whose relative contribution to protein metabolism is different in the N-free state.

Animals↗
PubMed1989

Pharmacological profile of NPC 12626, a novel, competitive N-methyl-D-aspartate receptor antagonist.

The novel compound 2-amino-4,5-(1,2-cyclohexyl)-7-phosphonoheptanoic acid (NPC 12626) was evaluated for activity in a variety of tests associated with receptors for excitatory amino acids. NPC 12626 failed to inhibit the specific binding of RS-[3H] amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid or [3H] kainic acid to brain membranes in vitro but displaced both agonist and antagonist binding to N-methyl-D-aspartic acid (NMDA) receptors. Like cis-(+/-)-3-(2-carboxypiperazine-4-yl)propyl-1-phosphonic acid, NPC 12626 competitively blocked NMDA-induced enhancement of [3H]-1-thienylcyclohexyl)piperidine binding. In the voltage-clamped frog oocyte expression system, NPC 12626 was a competitive inhibitor of NMDA-evoked inward current with a pA2 of 6.24. After both i.c.v. or i.p. administration, NPC 12626 was a potent anticonvulsant in the pentylenetetrazol, maximal electroshock and NMDA seizure models. Furthermore, low doses (25 mg/kg) of NPC 12626 given i.v. were effective in preventing damage to the CA1 region of hippocampus in the gerbil model of global ischemia. Unlike the noncompetitive NMDA antagonist, phencyclidine, but like cis-(+/-)-3-(2-carboxypiperazine-4-yl)propyl-1-phosphonic acid and pentobarbital, NPC 12626 only partially substituted for phencyclidine in a drug discrimination study. The results of the current study indicate that NPC 12626 is a novel, systemically active and competitive NMDA receptor antagonist.

Amino Acids↗
PubMed1987

Undernutrition in sheep. Nitrogen repletion by N-depleted sheep.

Wether lambs of 29-44 kg live-weight, totally nourished by the infusion of volatile fatty acids (VFA) into the rumen and casein into the abomasum, were given five treatments in consecutive periods. The treatments were (daily amounts per kg live weight (W)0.75): (a) high-protein for 7 d (2500 mg nitrogen, 650 kJ VFA); (b) low-protein for 7-15 d (525 mg N, 650 kJ VFA); (c) N-free for 7 d (no N, 450 kJ VFA); (d) very-low-protein for 24-28 d (300 mg N, 400 kJ VFA); (e) high-protein for 40 d (2500 mg N, 650 kJ VFA). Nine lambs were subjected to treatments (a), (b) and (c) (Expt 1) and four of the lambs additionally received treatments (d) and (e) (Expt 2). In Expt 1 all nine lambs had a positive N retention on treatment (a) but abrupt change to treatment (b) resulted in substantial negative N balances initially, and a period of approximately 5 d adaptation was required before N equilibrium was re-established. Animals again exhibited negative N balances when the N-free infusion (treatment c) was introduced and during that period there was no evidence of adaptation. Basal urinary N excretion was estimated to be 356 (SE 12) mg N/kg W 0.75. In Expt 2 all four lambs were depleted of N when receiving the very-low-protein treatment (d). The progressively decreasing N losses recorded during days 1 to 12 of the treatment period were slightly greater than those recorded during days 13 to 28 but the difference between the means was not significant (P greater than 0.05). There was no evidence of an adaptation in N retention between days 13 and 28 of the treatment. As assessed during days 13 to 28 of the treatment the efficiency of utilization of infused casein N was 1.0; this compared with a value of 0.66 recorded during treatment (b) in Expt 1. Live weight loss during the period of N depletion was 101 (SE 27) g/d. When lambs were given treatment (e) during the last period of Expt 2, N repletion was rapid and complete within a few days. Ten days after the introduction of the treatment the rate of N retention was estimated to be 1019 (SE 38) mg/kg W 0.75 per d and this value declined at a rate of 9.5 (SE 1.9) mg N/kg W 0.75 per d for the following 30 d.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Biological↗
PubMed1986

Flow of nitrogen from the rumen and abomasum in cattle and sheep given protein-free nutrients by intragastric infusion.

1. Three experiments were conducted to determine the flow of nitrogen through the rumen and abomasum when cows, steers and lambs were totally nourished on volatile fatty acids infused into the rumen. 2. In two dairy cows (650-700 kg) and two large steers (370-405 kg) the daily flow of non-ammonia-N (NAN) from the rumen was 50.7 and 58 mg/kg live weight (W)0.75 respectively. 3. The flows of NAN through the rumen and abomasum in four young steers (240-315 kg) were 85.0 (SE 21.0) and 195 (SE 7.0) mg/kg W 0.75 respectively. 4. In the third experiment the effects of altering rumen pH and osmotic pressure on flow of NAN through the rumen and abomasum were investigated in lambs. While rumen pH and osmotic pressure influenced rumen volume and outflow they had no significant effect on NAN flow. The mean values for NAN outflow from the rumen and abomasum were 76 and 181 mg N/kg W 0.75 respectively. 5. Abomasal NAN flow increased with increasing abomasal pH. When osmotic pressure was greater than about 330 mosmol/l in the rumen there was a net inflow of water, while below this value there was net loss of water. 6. For all experiments the flow of N both from the rumen and abomasum was highly variable; this has to be considered if a constant value is used for endogenous N in estimating dietary N in the abomasum. 7. With N-free infusion the rumen NH3 concentration varied from 50 to 120 mg NH3-N/l. 8. The amino acid composition of rumen and abomasal N was also determined. Relative to tissue N it contained a higher proportion of cysteine.

Abomasum↗
PubMed1985

Light-dependent degradation of the Q(B)-protein in isolated pea thylakoids.

The 32 000-dalton Q(B)-protein of photosystem II (PS II) is rapidly damaged and removed from isolated pea thylakoids during incubation in the light resulting in a loss of photosynthetic electron flow through PS II. This in vitro photoinhibition is similar to that previously reported with intact Chlamydomonas cells. The damage occurs at a faster rate in vitro, however, due to the inability of isolated thylakoids to synthesize replacement Q(B)-protein. The removal of the damaged Q(B)-protein does not require any soluble components of the chloroplast stroma and is unaffected by the protease inhibitors phenyl-methylsulfonylfluoride or antipain. Unlike the effect of trypsin, no low mol. wt. membrane-bound or soluble fragments of the labelled Q(B)-protein could be identified either by autoradiography or immunologically using polyclonal antibodies specific for the Q(B)-protein. The lightinduced damage to the Q(B)-protein (indicated by a loss of Q(B) functional activity), preceded the removal of the protein from the membrane. We conclude that photodamage of the Q(B)-protein generates a conformational change which renders the protein susceptible to attack by a highly efficient, intrinsic membrane protease.

Journal Article↗