Effects of probiotic and synbiotic supplementation on ponderal and linear growth in severely malnourished young infants in a randomized clinical trial

Severe acute malnutrition (SAM) is a major global public health problem. We aimed to assess the effects of probiotic and synbiotic supplementation on rate of weight gain and change in length in young SAM infants. This study was substudy of a single-blind randomized clinical trial (NCT0366657). During nutritional rehabilitation, 67 <6 months old SAM infants were enrolled and randomized to receive either probiotic (Bifidobacterium. infantis EVC001) or synbiotic (B. infantis EVC001 + Lacto-N-neotetraose [LNnT]) or placebo (Lactose) for four weeks and were followed for four more weeks after supplementation. In multivariable linear regression model, the mean rate of weight gain in the probiotic arm compared to placebo was higher by 2.03 unit (P < 0.001), and 1.13 unit (P = 0.030) in the synbiotic arm. In linear mixed-effects model, mean WAZ was higher by 0.57 unit (P = 0.018) in probiotic arm compared to placebo. Although not statistically significant, delta length for age z score (LAZ) trended to be higher among children in probiotc (β = 0.25) and synbiotic (β = 0.26) arms compared to placebo in multivariable linear regression model. Our study describes that young SAM infants had a higher rate of weight gain when supplemented with probiotic alone, compared to their counterparts with either synbiotic or placebo.

Antibiotic exposure among young infants suffering from diarrhoea in Bangladesh

AIMS

Appropriate rehydration has always been significant in treating diarrhoeal diseases in children. Irrational antibiotic use among diarrhoeal children has remained a major public health concern. Information regarding antibiotic use in young infants suffering from diarrhoea is very limited and a unique aspect of research. We aimed to investigate the prevalence of antibiotic use in the community among 2-6 months infants with diarrhoeal illnesses and having different nutritional status.

METHODS

We investigated a total of 5279 infants aged 2-6 months at Dhaka hospital, International Centre for Diarrhoeal Disease Research, Bangladesh, between September 2018 and June 2019. Among them, 257 infants were suffering from severe acute malnutrition (SAM). History of taking antibiotics was ascertained by direct observation of a prescription by a physician, the bottle of antibiotic or asking the caregiver about the name of antibiotic or its price that is very close to the usual market price of an antibiotic.

RESULTS

Overall, 52% of infants received antibiotics before hospital admission. Non-SAM infants had higher odds of receiving antibiotics (adjusted odds ratio [aOR] = 1.52, 95% confidence interval: 1.18, 1.97, P value = 0.003) compared to infants with SAM and use of antibiotics increased with age (aOR = 1.11, 95% confidence interval: 1.06, 1.17, P value<0.001). Commonly used antibiotics were azithromycin (13.3%), ciprofloxacin (7.7%), erythromycin (7.7%) and metronidazole (2.6%). The proportion of receiving ciprofloxacin was significantly lower in infants with SAM compared to their non-SAM counterparts (2.7% vs. 7.97%, P value = 0.004).

CONCLUSIONS

The study underscores the excessive use of antibiotics among diarrhoeal infants, which is already a major public health concern in low- and middle-income countries.

0001 Activation of Nociceptin/Orphanin-FQ Peptide (NOP) Receptors Produces an Increase in Non-REM Sleep in Rats and Constitutes a Novel and Attractive Target for the Treatment of Insomnia

Introduction

Treatments for insomnia have targeted GABA, histamine, serotonin, melatonin and orexin receptors. The nociceptin/orphanin-FQ peptide (NOP) receptor is widely expressed in the nervous system. High doses of NOP agonists administered systemically or locally into the CNS can result in sedation, however, the utility of targeting this receptor to treat insomnia has not been fully described.

Methods

V117957 is a recently described investigational oral, potent and selective NOP receptor partial agonist. We determined the brain Kp in whole brain and multiple sub-regions (50mg/kg) and receptor occupancy in the hypothalamus (30, 300mg/kg) via in vivo displacement using [3H]-NOP-1A. EEG/EMG were determined in rats chronically implanted with electrodes (cortex and dorsal neck muscle) and recorded via telemetry following dosing (3, 30, 300mg/kg); sleep stage was determined from visual analysis of EEG level. Sleep parameters were also assessed in NOP receptor knock-out rats (300mg/kg). The side-effect profile for V117957 was determined by functional observation battery, whole-body plethysmography, Morris water maze (MWM) (up to 600mg/kg) and conditioned place preference (CPP) assay (up to 300mg/kg).

Results

V117957 displayed limited distribution into the CNS but achieved a high level of receptor occupancy (75% at 30mg/kg). Administration of V117957 produced dose-dependent and statistically significant increases in non-REM sleep with a minimally efficacious dose of 30mg/kg; a coincident dose-dependent and statistically significant decrease in wakefulness and a non-dose-dependent effect on REM sleep occurred. These changes were not seen in knock-out animals demonstrating effects are via NOP receptors. At doses higher than those that increased non-REM sleep, V117957 had no effects in a functional observational battery, did not affect escape latency in MWM or produce CPP; additionally, V117957 did not affect respiratory parameters.

Conclusion

We conclude that activation of NOP receptors decreases wakefulness and increases non-REM sleep in rats with an improved preclinical profile compared to historical profiles of current treatments and, therefore, may represent a novel and attractive target for the treatment of insomnia.

Support

Funded by Shionogi and Imbrium Therapeutics, a subsidiary of Purdue Pharma L.P.

Certification of Total Arsenic in Blood and Urine Standard Reference Materials by Radiochemical Neutron Activation Analysis and Inductively Coupled Plasma - Mass Spectrometry

A newly developed procedure for determination of arsenic by radiochemical neutron activation analysis (RNAA) was used to measure arsenic at four levels in SRM 955c Toxic Elements in Caprine Blood and at two levels in SRM 2668 Toxic Elements in Frozen Human Urine for the purpose of providing mass concentration values for certification. Samples were freeze-dried prior to analysis followed by neutron irradiation for 3 h at a fluence rate of 1×1014cm-2s-1. After sample dissolution in perchloric and nitric acids, arsenic was separated from the matrix by extraction into zinc diethyldithiocarbamate in chloroform, and 76As quantified by gamma-ray spectroscopy. Differences in chemical yield and counting geometry between samples and standards were monitored by measuring the count rate of a 77As tracer added before sample dissolution. RNAA results were combined with inductively coupled plasma - mass spectrometry (ICP-MS) values from NIST and collaborating laboratories to provide certified values of (10.81 ± 0.54) μg/kg and (213.1 ± 0.73) μg/kg for SRM 2668 Levels I and II, and certified values of (21.66 ± 0.73) μg/kg, (52.7 ± 1.1) μg/kg, and (78.8 ± 4.9) μg/kg for SRM 955c Levels 2, 3, and 4 respectively. Because of discrepancies between values obtained by different methods for SRM 955c Level 1, an information value of < 5 μg/kg was assigned for this material.

Membrane protein damage and repair: Selective loss of a quinone-protein function in chloroplast membranes

A loss of electron transport capacity in chloroplast membranes was induced by high-light intensities (photoinhibition). The primary site of inhibition was at the reducing side of photosystem II (PSII) with little damage to the oxidizing side or to the reaction center core of PSII. Addition of herbicides (atrazine or diuron) partially protected the membrane from photoinhibition; these compounds displace the bound plastoquinone (designated as Q(B)), which functions as the secondary electron acceptor on the reducing side of PSII. Loss of function of the 32-kilodalton Q(B) apoprotein was demonstrated by a loss of binding sites for [(14)C]atrazine. We suggest that quinone anions, which may interact with molecular oxygen to produce an oxygen radical, selectively damage the apoprotein of the secondary acceptor of PSII, thus rendering it inactive and thereby blocking photosynthetic electron flow under conditions of high photon flux densities.

Plasma phosphatidylcholine docosahexaenoic acid content and risk of dementia and Alzheimer disease: the Framingham Heart Study

BACKGROUND

Docosahexaenoic acid (DHA) is an abundant fatty acid in the brain. In the diet, DHA is found mostly in fatty fish. The content of DHA has been shown to be decreased in the brain and plasma of patients with dementia.

OBJECTIVE

To determine whether plasma phosphatidylcholine (PC) DHA content is associated with the risk of developing dementia.

DESIGN, SETTING, AND PARTICIPANTS

A prospective follow-up study in 899 men and women who were free of dementia at baseline, had a median age of 76.0 years, and were followed up for a mean of 9.1 years for the development of all-cause dementia and Alzheimer disease.

MAIN OUTCOME MEASURES

Plasma PC fatty acid levels were measured at baseline. Cox proportional regression analysis was used to assess relative risks of all-cause dementia and Alzheimer disease according to baseline plasma levels.

RESULTS

Ninety-nine new cases of dementia (including 71 of Alzheimer disease) occurred during the follow-up. After adjustment for age, sex, apolipoprotein E epsilon4 allele, plasma homocysteine concentration, and education level, subjects in the upper quartile of baseline plasma PC DHA levels, compared with subjects in the lower 3 quartiles, had a relative risk of 0.53 of developing all-cause dementia (95% confidence interval, 0.29-0.97; P=.04) and 0.61 of developing Alzheimer disease (95% confidence interval, 0.31-1.18; P=.14). Subjects in the upper quartile of plasma PC DHA levels had a mean DHA intake of 0.18 g/d and a mean fish intake of 3.0 servings per week (P<.001) in a subset of 488 participants. We found no other significant associations.

CONCLUSION

The top quartile of plasma PC DHA level was associated with a significant 47% reduction in the risk of developing all-cause dementia in the Framingham Heart Study.

Improving synthetic efficiency using the computational prediction of biological activity

A process has been developed whereby libraries of compounds for lead optimization can be synthesized and screened with greater efficiency using computational tools. In this method, analogues of a lead chemical structure are considered in the form of a virtual library. Less than 1/3 of the library is selected as a training set by clustering the compounds and choosing the centroid of each cluster. This training set is then used to generate a model using PLS regression upon the experimental values from that assay using 1D/2D descriptors. The model is applied to the remaining compounds (the test set) for which assay values are predicted and a rank ordering established. An example of this was a set of 169 PDE4 inhibitors. A predictive model was achieved using a training set of 52 compounds. When applied to the remaining 117 compounds this model allowed a rank ordering of these compounds for synthesis and testing. Selecting the top 33 compounds of the test set gives 78% of the compounds with the desired activity (hits) by synthesizing only 50% of the library, including the training set. Selecting the top 59 of the test set gives 97% of the hits from only 67% of the library. This process succeeds by avoiding two principal weaknesses of 2D descriptors: lack of interpretation and lack of extrapolation. Two principal assumptions of QSAR are shown to be unnecessary; removing descriptor redundancy does not improve fit and a predictive r2 greater than 0.5 is not necessary if rank-ordering is desired.

Variation between sheep in renal excretion of [14C]allantoin

The objectives of the present study were to investigate the recovery of [14C]allantoin in urine of sheep dosed intravenously and degradation of allantoin by rumen micro-organisms. The recovery of [14C]allantoin in the urine of eight sheep was measured during three periods in two experiments. Individual values of [14C]allantoin recovery varied from 66 to 95 % (mean value 83 (se 1.6) %). The recovery of [14C]allantoin showed no relation to the level of feed intake. There was some evidence that glomerular filtration rate was an important factor affecting the amount of urinary allantoin recovered in one experiment. Incomplete recovery of plasma [14C]allantoin in the urine indicated losses of plasma [14C]allantoin via non-renal routes. This is supported by the disappearance of 14C from rumen contents incubated in vitro with [14C]allantoin for 48 h (88 %) and the presence of 14C in saliva in vivo from sheep sampled after dosing with [14C]allantoin. However, the amount of 14C activity in the saliva was very low (equivalent to only 1.5 % of the total dose in sheep producing saliva at a rate of 15 litres/d). The proportion of renal and non-renal excretion of purine derivatives was found to be unpredictable both between and within individual animals. The factors responsible for this variability need to be identified, and existing models of excretion of purine derivatives may need to be modified accordingly to improve their accuracy of prediction. A single intravenous injection of [4,5-14C]allantoin provides a simple alternative to infusion methods used to measure the proportion of plasma allantoin excreted in the urine of sheep. Using this method it may be feasible to validate PD excretion models in other ruminant livestock.

Temporal changes in reproductive hormones and conceptus-endometrial interactions during embryonic diapause and reactivation of the blastocyst in European roe deer (Capreolus capreolus)

The roe deer blastocyst is in diapause between August and December, after which time it expands and elongates rapidly before implantation. Blood samples were taken from 30 animals to define temporal changes in reproductively important hormones to investigate the physiological cues present at embryo reactivation. In 15 of these animals, changes in uterine and conceptus protein synthesis and secretion, and luteal progesterone release during diapause and reactivation, were assessed after culture of these tissues in vitro. Oestradiol concentrations remained low during diapause (1.07 +/- 0.4 pg ml(-1)) and expansion (1.2 +/- 0.4 pg ml(-1)) but increased by 30 times at trophoblast elongation (49.17 +/- 0.37 pg ml(-1)). Prolactin remained at basal concentrations (4.69 +/- 0.86 ng ml(-1)) and increased after implantation (12.34 +/- 2.71 ng ml(-1)). Peripheral progesterone concentrations and luteal progesterone release remained constant throughout diapause, reactivation and implantation (peripheral progesterone: 3.82 +/- 1.97 ng ml(-1); luteal progesterone: 6.72 +/- 0.81 ng mg(-1) protein). Incorporation of a radiolabel into conceptus secretory proteins increased by four times at expansion compared with diapause, whereas incorporation into endometrial secretions remained constant. At elongation, incorporation into endometrial secretions increased two times and conceptus secretions increased 32 times. Two-dimensional electrophoresis and fluorography showed that the profile of endometrial secretory proteins was constant until implantation when qualitative changes were evident. Although a role for an endocrine maternal trigger of reactivation from diapause cannot be dismissed, these data provide no supporting evidence and indicate that the conceptus itself may drive reactivation.

Temporal changes in reproductive hormones and conceptus-endometrial interactions during embryonic diapause and reactivation of the blastocyst in European roe deer (Capreolus capreolus)

The roe deer blastocyst is in diapause between August and December, after which time it expands and elongates rapidly before implantation. Blood samples were taken from 30 animals to define temporal changes in reproductively important hormones to investigate the physiological cues present at embryo reactivation. In 15 of these animals, changes in uterine and conceptus protein synthesis and secretion, and luteal progesterone release during diapause and reactivation, were assessed after culture of these tissues in vitro. Oestradiol concentrations remained low during diapause (1.07 +/- 0.4 pg ml(-1)) and expansion (1.2 +/- 0.4 pg ml(-1)) but increased by 30 times at trophoblast elongation (49.17 +/- 0.37 pg ml(-1)). Prolactin remained at basal concentrations (4.69 +/- 0.86 ng ml(-1)) and increased after implantation (12.34 +/- 2.71 ng ml(-1)). Peripheral progesterone concentrations and luteal progesterone release remained constant throughout diapause, reactivation and implantation (peripheral progesterone: 3.82 +/- 1.97 ng ml(-1); luteal progesterone: 6.72 +/- 0.81 ng mg(-1) protein). Incorporation of a radiolabel into conceptus secretory proteins increased by four times at expansion compared with diapause, whereas incorporation into endometrial secretions remained constant. At elongation, incorporation into endometrial secretions increased two times and conceptus secretions increased 32 times. Two-dimensional electrophoresis and fluorography showed that the profile of endometrial secretory proteins was constant until implantation when qualitative changes were evident. Although a role for an endocrine maternal trigger of reactivation from diapause cannot be dismissed, these data provide no supporting evidence and indicate that the conceptus itself may drive reactivation.

In vitro genotoxicity testing of ARASCO and DHASCO oils

ARASCO and DHASCO oils are microbially-derived triglycerides rich in arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids, respectively. Both oils were tested for mutagenic activity in three different in vitro mutagenesis assays. All assays were conducted with and without metabolic activation. Neither ARASCO nor DHASCO oil was mutagenic in the Ames reverse mutation assay using five different Salmonella histidine auxotroph tester strains, nor were the oils mutagenic in the mouse lymphoma TK(+/-) forward mutation assay. The oils showed no clastogenic activity in chromosomal aberration assays performed with Chinese hamster ovary cells. Based on these assays, neither ARASCO nor DHASCO oils appear to have any genotoxic potential.

A developmental safety study in rats using DHA- and ARA-rich single-cell oils

The long-chain omega-3 and omega-6 fatty acids, docosahexaenoic and arachidonic acids, are important in fetal development, but may be depleted from the mother during pregnancy as she transfers reserves to the developing fetus in utero and later to the infant through her breast milk. Pregnant women can increase their dietary intake of these nutrients to maintain adequate maternal reserves and ensure an optimal infant supply. DHASCO(R) and ARASCO(R) oils, concentrated sources of docosahexaenoic and arachidonic acids, respectively, have been tested in acute and subchronic studies without toxic effects. The present developmental toxicity study was undertaken to test for potential teratogenic activity of these oils to ensure their safe use during pregnancy. DHASCO and ARASCO oils were administered by oral gavage to pregnant rats at doses up to 1250 and 2500 mg/kg body weight/day, respectively, during the period of organogenesis. Caesarean sections and necropsies were performed on day 20 of gestation. Maternal reproductive outcomes were analyzed, and fetal external, soft and skeletal tissue were examined. Treatment with these oils did not produce overt maternal toxicity, nor did either oil result in changes in pre- or postimplantation losses, resorptions, live births or sex ratios. Neither oil caused fetal malformations. Increased frequencies of renal variations in development occurred in a non-dose-dependent manner and were not toxicologically significant. We conclude that these oils are not teratogenic at doses that represent a 100-fold safety factor over expected use levels.

A combined subchronic (90-day) toxicity and neurotoxicity study of a single-cell source of docosahexaenoic acid triglyceride (DHASCO oil)

Docosahexaenoic acid (DHA), a 22-carbon long-chain polyunsaturated fatty acid of the omega-3 family, is a major structural component of neural membranes and is a particularly important nutrient during infant development. New safe and well-defined sources of DHA are required for infant formula fortification and dietary supplementation. DHASCO oil is an algal-derived triglyceride containing 40-50% DHA. Previous studies have shown that DHASCO oil is neither mutagenic nor toxic in acute or 28-day subchronic tests. To further establish the safety of this oil, a 90-day subchronic toxicity study in rats which included haematology, clinical chemistry, pathology and ophthalmologic, neurobehavioural and neuropathological assessments, using doses of 0.5 and 1.25g/kg body weight/day was performed. There were no treatment-related adverse effects in any of the parameters measured at either dose. Based on these results, the no-adverse-effect level (NOAEL) for DHASCO oil under the conditions of this study corresponds to the highest dose level. The DHA in the DHASCO oil was bioavailable, resulting in significant elevations in the levels of this fatty acid in liver, heart and brain after 90 days of administration. In conclusion, this 90-day subchronic toxicity study provides additional evidence that DHASCO oil is a safe and bioavailable source of dietary DHA.

High-affinity binding of peptide agonists to the human B1 bradykinin receptor depends on interaction between the peptide N-terminal L-lysine and the fourth extracellular domain of the receptor

The aim of this study was to identify the location of the N terminus of peptide agonist ligands when bound to the human B1 bradykinin (BK) receptor. To reach this aim, we exploited the fact that high-affinity binding of kinin peptides to the human B1 receptor subtype requires a peptide N-terminal L-Lys, whereas high-affinity binding to the B2 receptor subtype does not require this residue. This was done by comparing the affinities of BK, a B2 receptor-selective peptide, and kallidin or Lys-BK, a less receptor-selective peptide, for chimeric proteins in which each B1 receptor domain had been substituted in the human B2 receptor and expressed in HEK293 cells. Individual substitution of transmembrane domains 1-7 (TM-I-VII) and extracellular domains 1-4 (EC-I-IV) of the B1 receptor in the B2 receptor influenced the affinities of BK and Lys-BK approximately equally. In contrast, substitution of B1 EC-IV dramatically reduced the affinity and potency of BK, whereas these parameters for Lys-BK were essentially unaltered. Substitution of either the N- or C-terminal half of B1 EC-IV in the B2 receptor only had a limited effect on the peptide binding constants, indicating the involvement of multiple residues throughout this domain. Complementary mutations of the N-terminal residue in Lys-BK revealed that both the positive charge and the proper spatial orientation of this residue were required for interaction with B1 EC-IV. Thus, the N-terminal residue of peptide agonists when bound to the human B1 receptor is positioned extracellularly and interacts with EC-IV.

Oral antinociception and oedema inhibition produced by NPC 18884, a non-peptidic bradykinin B2 receptor antagonist

This study investigates the antinociceptive and the oedema inhibition properties of the novel non-peptide bradykinin (BK) B2 receptor antagonist, NPC 18884. Given by i.p. or p.o. routes NPC 18884 produced graded and long-lasting (at least 2.5h and 5.0h, respectively, for i.p. and p.o. administration) inhibition of acetic acid-induced abdominal constrictions in mice, with mean ID50 values of 8.3 nmol/kg and 439.9 nmol/kg. NPC 18884 also inhibited kaolin-induced abdominal constrictions (44+/-9% and 48+/-3% of inhibition, for i.p. and p.o. routes, respectively). Given by i.p. or p.o. routes NPC 18884 attenuated both phases of formalin-induced licking, as well as formalin-induced oedema formation. At similar doses NPC 18884 produced significant inhibition of capsaicin-induced nociception. NPC 18884, like HOE 140 given i.p., prevented the nociception caused by BK with mean ID50 values of 0.85 nmol/kg and 0.44 nmol/kg, respectively. Given orally NPC 18884, but not HOE 140, caused graded inhibition of BK-induced nociception (mean ID50 value of 50 nmol/kg). In rats, NPC 18884 given i.p. prevented BK and carrageenan-induced hyperalgesia (mean ID50 values of 6 nmol/kg and 13 nmol/kg), without affecting the hyperalgesia induced by des-Arg9-bradykinin (DABK) or by prostaglandin E2 (PGE2). NPC 18884 given i.p. inhibited the mouse paw oedema induced by tyrosine8-bradykinin or by carrageenan, but had no effect on DABK-induced oedema in mice pre-treated with Escherichia coli endotoxin, or that induced by PGE2. Thus, the novel non-peptide BK B2 receptor antagonist NPC 18884 produces rapid onset, potent and relatively long-lasting oral antinociceptive and oedema inhibition properties. The anti-BK actions of NPC 18884 are quite selective towards the BK B2 receptor-mediated responses.

Effect of glucose supply on fasting nitrogen excretion and effect of level and type of volatile fatty acid infusion on response to protein infusion in cattle

Two experiments were carried out on cattle nourished entirely by intragastric infusion, to determine the extent to which glucose or a glucose precursor determines the response to protein infusion in energy-undernourished animals. In order to determine the requirement for glucose in 1-year-old fasting cattle, glucose was infused at increments to supply 0, 1.5, 2.5, 3.5, 4.5, 5.5 and 6.5 g/kg metabolic body weight (W0.75) and the effects on plasma beta-hydroxybutyrate and N excretion were measured. At 5.5 g glucose/kg W0.75 plasma beta-hydroxybutyrate was reduced to a basal level of 1.65 mmol/l and fasting N excretion reduced from 529 to 280 mg N/kg W0.75. No further reduction was observed with the higher level of 6.5 g glucose/kg W0.75. In the second trial, three steers were used in a 3 x 3 Latin square design and infused with a volatile fatty acid mixture of 65, 27 and 8 mol acetic, propionic and butyric acids respectively/100 mol, either at an estimated maintenance energy level of 450 kJ/kg W0.75 and supplying a calculated glucose equivalent level of 13.0 g/kg W0.75 (M1A), or at 1.5 x maintenance supplying a glucose equivalent of 20 g/kg W0.75 (M1.5A). Another mixture infused at the maintenance energy level contained 49, 43 and 8 mol acetic, propionic and butyric acids respectively/100 mol but with a glucose equivalent of 20 g/kg W0.75 (M1P). Casein was infused at each of these energy treatments to supply 0, 200, 400, 800, 1600 and 2500 mg N/kg W0.75 daily, and N balance and blood metabolites were measured. N retention increased linearly (r 0.98) with casein infusion. The coefficients for N retention were 0.55, 0.57 and 0.64 for M1A, M1.5A and M1P respectively. The mean efficiency of N utilization was 0.58. The results suggest that provided the glucose need is met there is no relationship between energy supply and efficiency and level of protein retention. However, the results also indicate that glucose requirement in cattle may be higher than that previously observed in sheep.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

Novel pseudopeptides with high affinities for the human bradykinin B2 receptor

We recently proposed a model of bradykinin bound to the rat bradykinin B2 receptor that is constructed on the basis of structural homology modeling to the criomicroscopic structure of the seven transmembrane domains of bacteriorhodopsin, extensive conformational searches and experimental mutagenesis results. On the basis of that model, a novel third-generation pseudopeptide antagonist, NPC 18325 (D-Arg1-Arg2-[aminotridecanoyl]3-Ser4-D-Tic5-Oic6++ +-Arg7) (Ki = 440 nM, guinea pig ileum), was designed and also reported. NPC 18325 has been proposed to adopt a C-terminal beta turn separated from N-terminal positive charges by a linear 12 carbon chain spacer. Experimentally, the four amino acids making up the C-terminus have been shown by NMR to preferentially adopt a beta turn at neutral pH in aqueous solution. We now present a series of peptides, related to and including NPC 18325, that explore the relationship between the length of the carbon chain and the affinity to the human bradykinin B2 receptor. The results show that there is a structure-activity relationship (SAR) associated with the chain length and that these pseudopeptides have better affinity to the human bradykinin receptor than they have to the guinea pig ileal-derived B2 receptor. Specifically, peptide I (a 12-methylene linker) had a measured Ki of 31 nM and peptide V (a 4-methylene linker) had a Ki of 471 nM. Implications regarding conformation and hydrophobicity are also described.

Structural features of the bradykinin receptor as determined by computer simulations, mutagenesis experiments, and conformationally constrained ligands: establishing the framework for the design of new antagonists

1. In recent years, two classes of second generation bradykinin receptor antagonists have been reported. Both are of the general sequence D-Arg0-Arg1-Pro2-W3-Gly4-X5-Ser6-Y7-Z8+ ++-Arg9, where W is either Pro or Hyp, and X is an aromatic or aliphatic side chain-containing amino acid. Y and Z are unnatural amino acids, presumed to enforce a beta-turn structure. The de novo design of a non-peptide receptor antagonist (or the optimization of a lead discovered by random screening) will ultimately require knowledge about the receptor topology. In the absence of an experimentally determined structure of the bradykinin-bradykinin receptor complex, we have attempted to gain insights from other sources. 2. We have synthesized conformationally constrained ligands and completed extensive computer modeling on the bradykinin receptor. Moreover, using systematic synthetic modifications, we have explored the relative importances of selected amide bonds and side chains in second generation peptides and have made a series of C alpha- and/or N-methyl substitutions at positions four and five which led to the discovery of two new cyclic peptide antagonists. 3. Computational simulations led to a proposed model of bradykinin bound to its receptor which was found to be in good agreement with mutagenesis results. This model led ultimately to the design and synthesis of D-Arg0-Arg1-(12-aminododecanoyl)2-Ser3-D-Tic4-Oic5+ ++-Arg6. Consideration of this new lead compound, together with the extensive structure-activity relationship (SAR) which has been developed for peptide ligands and the receptor, represents a tangible framework for the design of more potent and longer-lasting antagonists of the bradykinin receptor.

Multiple copy sampling: rigid versus flexible protein

Effects of protein flexibility on multiple copy conformational sampling were systematically evaluated by studying the side-chain placement of Phe-14 in protein Zif268. The multiple copy sampling is shown to be significantly more efficient when a flexible but harmonically constrained protein is used instead of a rigid protein. A range of constraint force from 1 to 25 kcal/mol.A per atom is determined to be sufficient to prevent the protein from distortion while allowing the protein to fluctuate for enhanced sampling. The protein fluctuations are essential in smoothing the effective energy surface as shown by the opening-closing of a protein hydrophobic pocket during a multiple copy energy minimization, a phenomenon that has been previously observed only in molecular dynamics. These results provide a practical guidance for applying the multiple copy techniques to molecular modeling and computer-aided drug design.

A proposed model of bradykinin bound to the rat B2 receptor and its utility for drug design

A putative model of bradykinin bound to the rat B2 receptor was generated using a combination of homology modeling (from the known transmembrane structure of bacteriorhodopsin), energy minimization, molecular dynamics, and a two-stage conformational search as a docking simulation. Overall, the proposed bound ligand adopts a twisted "S" shape, wherein a C-terminal beta-turn is buried in the receptor just below the extracellular boundary of the cell membrane and the N-terminus is interacting with negatively charged residues in extracellular loop 3 of the receptor (most notably Asp268 and Asp286). Mutagenesis experiments describing mutations which result in both a loss of bradykinin affinity as well as those which have no effect on bradykinin affinity are in good agreement with the proposed structure. In short, the mutagenesis results and the computational simulations each point to the same region of the receptor as likely to bind bradykinin. A double mutation, predicted as being likely to have a dramatic effect on bradykinin binding affinity, was confirmed experimentally, adding some validation to the proposed complex. Moreover, a new pseudopeptide bradykinin receptor antagonist (D-Arg0-Arg1-[12-aminododecanoyl]2- Ser3-D-Tic4-Oic5-Arg6) was designed on the basis of the model, and found to have good receptor affinity. Speculation regarding other possible sites for mutagenesis are also described.

Multiple copy sampling in protein loop modeling: computational efficiency and sensitivity to dihedral angle perturbations

Multiple copy sampling and the bond scaling-relaxation technique are combined to generate 3-dimensional conformations of protein loop segments. The computational efficiency and sensitivity to initial loop copy dispersion are analyzed. The multicopy loop modeling method requires approximately 20-50% of the computational time required by the single-copy method for the various protein segments tested. An analytical formula is proposed to estimate the computational gain prior to carrying out a multicopy simulation. When 7-residue loops within flexible proteins are modeled, each multicopy simulation can sample a set of loop conformations with initial dispersions up to +/- 15 degrees for backbone and +/- 30 degrees for side-chain rotatable dihedral angles. The dispersions are larger for shorter and smaller for longer and/or surface loops. The degree of convergence of loop copies during a simulation can be used to complement commonly used target functions (such as potential energy) for distinguishing between native and misfolded conformations. Furthermore, this convergence also reflects the conformational flexibility of the modeled protein segment. Application to simultaneously building all 6 hypervariable loops of an antibody is discussed.

Measurement of allantoin in urine and plasma by high-performance liquid chromatography with pre-column derivatization

A method is reported for determination of allantoin in urine and plasma based on high-performance liquid chromatography (HPLC) and pre-column derivatization. In the derivatization procedure, allantoin is converted to glyoxylic acid which forms a hydrazone with 2,4-dinitrophenylhydrazine. The hydrazone appears as syn and anti isomers at a constant ratio. These derivatives are separated by HPLC using a reversed-phase C18 column from hydrazones of other keto acids possibly present in urine and plasma and then monitored at 360 nm. All components were completely resolved in 15 min. Both the reagents and derivatization products are stable. Recovery of allantoin added to urine and plasma was 95 +/- 3.7% (n = 45) and 100 +/- 7.5% (n = 64), respectively. The lowest allantoin concentration that gave a reproducible integration was 5 mumol/l. The between-assay and within-day coefficients of variation were 2.8 and 0.6%, respectively.

NMR and computational evidence that high-affinity bradykinin receptor antagonists adopt C-terminal beta-turns

Three tetrapeptides were prepared, each corresponding to the four C-terminal amino acid residues of highly potent, second-generation bradykinin receptor antagonists. The tetrapeptides are (IA) Ser-D-Phe-Oic-Arg, (IIA) Ser-D-Tic-Oic-Arg, and (IIIA) Ser-D-Hype(trans-propyl)-Oic-Arg. Solution conformations for each were determined by incorporating interproton distance restraints, determined by 2D NMR experiments performed in water at neutral pH, into a series of distance geometry/simulated annealing model building calculations. Similarly, systematic conformational analyses were performed for each using molecular mechanics calculations. Both the NMR-derived structures, as well as the calculated structures, are shown to adopt a beta-turn as the primary conformation. Excellent agreement between the predicted structures and the NMR-derived structures is demonstrated. Aside from being the first examples of linear tetrapeptides reported to be ordered in aqueous solvent, the results presented support the hypothesis that high-affinity bradykinin receptor antagonists must adopt C-terminal beta-turn conformations.

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.

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.

Disbudding of red deer stag calves to prevent antler growth

Red deer stag calves aged five to seven months were disbudded with a standard cattle disbudding iron as a means of preventing antler growth and development. Two sizes of iron, one 2.2 cm in diameter and one 1.5 cm in diameter, were compared at disbudding in November or January. Disbudding in November and January with the 2.2 cm iron had success rates of 97 per cent and 92 per cent, respectively. Treatment with the 1.5 cm iron was less effective at both times. There was no significant difference between the liveweights of the treated groups and a non-disbudded control group at turnout in the spring or at slaughter in November when the stags were 16 months of age.

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.

A novel beta-turn mimic useful for mapping the unknown topology of peptide receptors

Ethers of cis or trans D-4-hydroxyproline (Hype), adjacent to octahydroindole-carboxylic acid (Oic), introduce a beta-turn into the backbone of peptides when positioned respectively at the i+1 and i+2 position of the turn. This is confirmed by NMR experiments performed on a model tetrapeptide in water. Synthetic alteration of the ether group allows simple probing of the steric limits and electrostatic potential of a receptor binding site, a technique applied successfully to the bradykinin receptor.

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.