Memory alloreactive cytotoxic T cells do not require costimulation for activation in vitro

We have studied the costimulation requirements for the generation of cytotoxic T (Tc) cells in an in vitro recall response to alloantigens. Firstly, we demonstrate that recombinant vaccinia viruses encoding class I MHC can stimulate primary in vivo responses and prime for secondary in vitro responses specific for the immunizing alloantigen. The secondary in vitro response comprises both naive and memory components that are distinguishable kinetically. Naive alloreactive Tc cell precursors are dependent upon the presence of CD80 on the in vitro stimulating population for activation and generation of effector function, as described previously. However, Tc cells from animals primed in vivo with vaccinia virus (VV) encoding allo-MHC do not require CD28-CD80 interactions to respond to the alloantigen presented in vitro. This finding provides further evidence that memory Tc cells have less stringent activation requirements in vitro than naive cells. From limiting dilution analysis of the relative contribution of naive and memory Tc cell precursors in 'primary' responses, to MHC class I alloantigen, memory alloreactive Tc cell precursors, possibly primed by cross-reactive environmental antigens, contribute approximately one-fifth of the precursors. Memory responses exhibit similar precursor frequencies as primary responses. Thus, we conclude that memory is largely a result of qualitative rather than quantitative changes in Tc cell precursors.     

Stimulation of "stress-regulated" mitogen-activated protein kinases (stress-activated protein kinases/c-Jun N-terminal kinases and p38-mitogen-activated protein kinases) in perfused rat hearts by oxidative and other stresses

"Stress-regulated" mitogen-activated protein kinases (SR-MAPKs) comprise the stress-activated protein kinases (SAPKs)/c-Jun N-terminal kinases (JNKs) and the p38-MAPKs. In the perfused heart, ischemia/reperfusion activates SR-MAPKs. Although the agent(s) directly responsible is unclear, reactive oxygen species are generated during ischemia/reperfusion. We have assessed the ability of oxidative stress (as exemplified by H2O2) to activate SR-MAPKs in the perfused heart and compared it with the effect of ischemia/reperfusion. H2O2 activated both SAPKs/JNKs and p38-MAPK. Maximal activation by H2O2 in both cases was observed at 0.5 mM. Whereas activation of p38-MAPK by H2O2 was comparable to that of ischemia and ischemia/reperfusion, activation of the SAPKs/JNKs was less than that of ischemia/reperfusion. As with ischemia/reperfusion, there was minimal activation of the ERK MAPK subfamily by H2O2. MAPK-activated protein kinase 2 (MAPKAPK2), a downstream substrate of p38-MAPKs, was activated by H2O2 to a similar extent as with ischemia or ischemia/reperfusion. In all instances, activation of MAPKAPK2 in perfused hearts was inhibited by SB203580, an inhibitor of p38-MAPKs. Perfusion of hearts at high aortic pressure (20 kilopascals) also activated the SR-MAPKs and MAPKAPK2. Free radical trapping agents (dimethyl sulfoxide and N-t-butyl-alpha-phenyl nitrone) inhibited the activation of SR-MAPKs and MAPKAPK2 by ischemia/reperfusion. These data are consistent with a role for reactive oxygen species in the activation of SR-MAPKs during ischemia/reperfusion.     

Cooperatively breeding cottontop tamarins (Saguinus oedipus) do not donate rewards to their long-term mates.

This study tested the hypothesis that cooperative breeding facilitates the emergence of prosocial behavior by presenting cottontop tamarins (Saguinus oedipus) with the option to provide food rewards to pair-bonded mates. In Experiment 1, tamarins could provide rewards to mates at no additional cost while obtaining rewards for themselves. Contrary to the hypothesis, tamarins did not demonstrate a preference to donate rewards, behaving similar to chimpanzees in previous studies. In Experiment 2, the authors eliminated rewards for the donor for a stricter test of prosocial behavior, while reducing separation distress and food preoccupation. Again, the authors found no evidence for a donation preference. Furthermore, tamarins were significantly less likely to deliver rewards to mates when the mate displayed interest in the reward. The results of this study contrast with those recently reported for cooperatively breeding common marmosets, and indicate that prosocial preferences in a food donation task do not emerge in all cooperative breeders. In previous studies, cottontop tamarins have cooperated and reciprocated to obtain food rewards; the current findings sharpen understanding of the boundaries of cottontop tamarins’ food-provisioning behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pokeweed antiviral protein (PAP) mutations which permit E.coli growth do not eliminate catalytic activity towards prokaryotic ribosomes

Pokeweed antiviral protein (PAP) has N-glycosidase activity towards both eukaryotic and prokaryotic ribosomes. This is in marked contrast with the A chains of type 2 ribosome inactivating proteins (RIPs) such as ricin and abrin, which inactivate only eukaryotic ribosomes. A recent report described spontaneous mutations in PAP that implicated specific amino acids to be involved in determining the activity of PAP towards prokaryotic ribosomes. As part of an ongoing study into RIP--ribosome interactions these mutations were specifically recreated in a PAP clone encoding the mature 262 amino acid PAP sequence. Mutants were tested for their N-glycosidase activity by analysing the integrity of eukaryotic and prokaryotic ribosomes after mutant protein expression. Mutations of F196Y and K211R, either individually or within the same clone, were active toward both classes of ribosome, indicating that these amino acid positions are not involved in differentiating ribosomal substrates. Mutation R68G led to a protein that appeared to be inactive towards prokaryotic ribosomes, but also very poorly active towards eukaryotic ribosomes. This mutation is currently under further investigation.     

Cell surface glycosaminoglycans do not serve as ligands for PECAM-1. PECAM-1 is not a heparin-binding protein

Previous studies have suggested that PECAM-1 mediates cellular interactions via both homophilic and heterophilic adhesive mechanisms. Cell surface glycoaminoglycans have been implicated as one of the heterophilic ligands for PECAM-1. To determine whether PECAM-1 is capable of interacting directly with glycosaminoglycans, we examined the adhesive properties of multiple monovalent and multivalent forms of this adhesion molecule. We found that the binding of a bivalent PECAM-1/IgG chimeric protein or multivalent PECAM-1-containing proteoliposomes to multiple different cell lines was 1) strictly dependent upon cell surface expression of PECAM-1 and 2) unaffected by the presence of excess heparin or heparan sulfate. The extracellular domain of PECAM-1 failed to interact specifically with heparin-Sepharose, 3H-labeled heparin, or a heparin-bovine serum albumin conjugate. In addition, an amino acid sequence motif inadvertently created by the juxtaposition of PECAM-1 and IgG sequences within the hinge region of certain PECAM-1/IgG chimeric constructs was found to confer glycosaminoglycan binding properties not normally present within the extracellular domain of the native molecule. Together, these data suggest that the mechanism by which heparin is able to affect PECAM-1-dependent cell-cell adhesion is indirect and occurs via inhibition of events that occur downstream from PECAM-1 engagement.     

Cholesterol synthesis inhibitors do not reduce Lp(a) levels in normocholesterolemic patients

Experimental and clinical data suggest that activation of the LDL receptors by the use of HMG CoA reductase inhibitors, in the presence of normal plasma cholesterol levels, may result in a reduction of Lp(a) concentrations. This hypothesis has been tested in an open study on seven subjects with normal cholesterolemia but marked elevations of Lp(a) levels, three of whom received pravastatin and four simvastatin at standard therapeutic doses. While the two drugs caused the expected reduction of plasma total and LDL cholesterol levels, no significant changes in Lp(a) were noted. This study contradicts a prior clinical finding and suggests that HMG CoA reductase inhibitors are unlikely to reduce plasma Lp(a) levels even in the absence of hypercholesterolemia.     

Rats (Rattus norvegicus) do not prefer salted solid food.

Conducted 3 studies to evaluate the ingestive responses of Sprague-Dawley rats to salt in foods and to determine whether prior exposure to salted foods influenced their intake. In Exp I, 16 Ss were given 1-hr access to salted and unsalted foods (e.g., potato chips, peanuts, soup) commonly consumed by humans in the salted form. In each choice situation, rats consumed more of the unsalted variety of solid food. In Exp II, the concentration of salt in a wider variety of foods was varied. 15 Ss were allowed a choice of a given salt concentration or the unsalted food. In no case was the salted solid food eaten in excess of the unsalted solid food, and in general, more of the unsalted solid food was eaten. In Exp III, 2 groups of 8 Ss were given exposure from weaning to either salted or unsalted potato chips for 3 mo. Exposure did not alter the Ss' relative intake of salted chips. When given a choice, more unsalted chips were consumed by both groups. Results indicate that sodium-replete Sprague-Dawley rats generally prefer unsalted solid foods to salted ones. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nuclear protein import is decreased by engineered mutants of nuclear transport factor 2 (NTF2) that do not bind GDP-Ran

Nuclear transport factor 2 (NTF2) is associated with the translocation stage of nuclear protein import and binds both to nuclear pore proteins (nucleoporins) containing phenylalanine-rich repeats and to the Ras family GTPase Ran. In this study we probed the role of the NTF2-Ran interaction in nuclear protein import using site-directed mutants of NTF2 that interfere with its interaction with GDP-Ran. The design of these mutants was based on the X-ray crystal structure of NTF2 and was concentrated on conserved residues in and around the molecule's hydrophobic cavity. The mutant NTF2 cDNAs were expressed in Escherichia coli. Purified mutant proteins retained the interaction with FxFG-repeat nucleoporins, but several mutants in the negatively charged residues that surround the NTF2 cavity or in residues in the cavity itself were unable to bind GDP-Ran in vitro. The crystal structure of the E42K mutant protein showed significant structural changes only in this side-chain, indicating that it participated directly in the interaction with GDP-Ran. In permeabilised cell nuclear protein import assays, only wild-type NTF2 and mutants that bound GDP-Ran were functional. Furthermore, when the NTF2 E42K and D92N/D94N NTF2 mutants that failed to bind GDP-Ran in vitro were substituted for the chromosomal yeast NTF2, the yeast cells became non-viable, whereas yeast substituted with wild-type human NTF2 remained viable. We conclude that interaction between NTF2 and GDP-Ran is important for efficient nuclear protein import.     

Mitogen-activated protein kinases (Erk1,2) phosphorylate Lys-Ser-Pro (KSP) repeats in neurofilament proteins NF-H and NF-M

Mammalian neurofilament proteins, particularly midsized (NF-M) and heavy (NF-H) molecular weight neurofilament proteins, are highly phosphorylated in axons. Neurofilament function depends on the state of phosphorylation of the numerous serine/threonine residues in these proteins. Most phosphorylation occurs in the lys-ser-pro (KSP) repeats in the C-terminal tail domains of NF-H and NF-M. In our previous study, cyclin-dependent kinase 5 (cdk5) was shown to phosphorylate specifically the KSPXK repeats in rat NF-H. Because 80% of the repeats are of the KSPXXXK type, it was of interest to determine which kinase phosphorylates these motifs. Using a synthetic KSPXXXK peptide to screen for a specific kinase, we fractionated rat brain extracts by column chromatography and identified extracellular signal-regulated kinase (Erk2) activated by an upstream activator, the mitogen-activated protein kinase kinase MAPKK (MEK), by Western blot analysis, sequence identification, and inhibition by a specific MEK inhibitor (PD 98059). The fraction containing Erk2, as well as bacterially expressed Erk1 and Erk2, phosphorylated all types of KSP motifs in peptides (KSPXK, KSPXXK, KSPXXXK, and KSPXXXXK) derived from NF-M and NF-H. They also phosphorylated an expressed 24 KSPXXXK repeat NF-H polypeptide, an expressed NF-H as well as dephosphorylated native rat NF-H, and NF-M proteins with accompanying decreases in their respective electrophoretic mobilities. A comparative kinetic study of Erk2 and cdk5 phosphorylation of KSPXK and KSPXXXK peptides revealed that, in contrast to cdk5, which phosphorylated only the KSPXK peptide, Erk2 could phosphorylate both. The preferred substrate for Erk2 was KSPXXXK peptide. The MEK inhibitor PD 98059 also inhibited phosphorylation of NF-H, NF-M, and microtubule-associated protein (MAP) in primary rat hippocampal cells and caused a decrease in neurite outgrowth, suggesting that Erk1,2 may play an important role in neurite growth and branching. These data suggest that neuronal Erk1 and Erk2 are capable of phosphorylating serine residues in diverse KSP repeat motifs in NF-M and NF-H.     

Competitive protein-binding assay for somatomedins and their carrier protein (author's transl)

Rat liver explants in culture release a protein which has a molecular weight of approximately 65,000 and both an affinity and a specificity for somatomedins (SMs) similar to that of the carrier protein found in human serum. A competitive binding assay has been set up using this protein and purified NSILA-S, with a sensitivity threshold of 0.05 mu U NSILA-S. By means of gel filtration in acetic acid of the biological samples, SMs and their carrier protein are separated and the two parameters can therefore be measured within the same sample. Purified preparations of NSILA-S and SM-A, and endogenous SMs extracted from various mammalian sera and from rat liver culture medium give parallel dose-response curves. The mean SM concentrations in human serum, expressed in terms of mu U NSILA-S/ml were 199 +/- 10.8 (SE) in 9 normal adults, 19 +/- 2.7 in 18 hypopituitary patients and 255 +/- 14 in 18 acromegalics. Compared with the levels in normal subjects, acromegalic had high, and hypopituitary patients low carrier protein concentrations.     

Mutagenesis of endopolygalacturonase from Fusarium moniliforme: histidine residue 234 is critical for enzymatic and macerating activities and not for binding to polygalacturonase-inhibiting protein (PGIP)

The sequence encoding the endopolygalacturonase (PG) of Fusarium moniliforme was cloned into the E. coli/yeast shuttle vector Yepsec1 for secretion in yeast. The recombinant plasmid (pCC6) was used to transform Saccharomyces cerevisiae strain S150-2B; transformed yeast cells were able to secrete PG activity into the culture medium. The enzyme (wtY-PG) was purified, characterized, and shown to possess biochemical properties similar to those of the PG purified from F. moniliforme. The wtY-PG was able to macerate potato medullary tissue disks and was inhibited by the polygalacturonase-inhibiting protein (PGIP) purified from Phaseolus vulgaris. The sequence encoding PG in pCC6 was subjected to site-directed mutagenesis. Three residues in a region highly conserved in all the sequences known to encode PGs were separately mutated: His 234 was mutated into Lys (H 234-->K), and Ser 237 and Ser 240 into Gly (S 237-->G and S 240-->G). Each of the mutated sequences was used to transform S. cerevisiae and the mutated enzymes were purified and characterized. Replacement of His 234 with Lys abolished the enzymatic activity, confirming the biochemical evidence that a His residue is critical for enzyme activity. Replacement of either Ser 237 or Ser 240 with Gly reduced the enzymatic activity to 48% and 6%, respectively, of the wtY-PG. When applied to potato medullary tissue, F. moniliforme PG and wtY-PG caused comparable maceration, while the variant PGs exhibited a limited (S 234-->G and S 240-->G) or null (H 234-->K) macerating activity. The interaction between the variant enzymes and the P. vulgaris PGIP was investigated using a biosensor based on surface plasmon resonance (BIAlite). The three variant enzymes were still able to interact and bind to PGIP with association constants comparable to that of the wild type enzyme.     

Why some capuchin monkeys (Cebus apella) use probing tools (and others do not).

Tufted capuchins (Cebus apella) were provided with a task that facilitated the use and modification of sticks as probing tools. It was found that subjects aged 10 years or older at initial task exposure were less likely to use tools than were younger subjects. Furthermore, juveniles whose mothers died before the subjects were aged 3 years were less likely to use tools than were juveniles whose mothers survived through this period. The ability to use tools was not related to subject sex or to access to the tool site or raw tool materials. Subjects modified tools both before and during their use, and the relative percentage of tools modified increased with subject age. Thus, it appears that capuchins most readily acquire tool use before the age of 10 years and that early disruption of the mother–infant relationship has deleterious effects on the emergence of instrumental behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immunoglobulin G and F(ab')2 polyvalent antivenoms do not differ in their ability to neutralize hemorrhage, edema and myonecrosis induced by Bothrops asper (terciopelo) snake venom

The ability of whole immunoglobulin G (IgG) and F(ab')2 polyvalent (Crotalinae) antivenoms to neutralize the hemorrhagic, edema-forming and myotoxic activities of Bothrops asper venom was studied. Both antivenoms were adjusted to the same neutralizing potency against lethal and hemorrhagic activities in experiments where venom and antivenoms were incubated before injection. Thus, in these experimental conditions, differences in the neutralizing ability in experiments involving independent injection of venom and antivenoms would depend mainly on the different pharmacokinetic profiles of whole IgG and F(ab')2 antivenoms. Experiments involving local injection of venom followed by intravenous administration of antivenom at either 0, 15 or 30 min after envenomation did not reveal any significant difference between whole IgG and F(ab')2 products concerning neutralization of hemorrhage, edema and myonecrosis induced by B. asper venom. The three effects were neutralized by antivenoms only to a partial extent and neutralization decreased as the time-lapse between envenomation and antivenom administration increased. Moreover, with the exception of one time-interval, no significant differences in the neutralization of hemorrhage were observed when antivenom was administered by the intramuscular or intraperitoneal route. The results do not support the assumption that F(ab')2 antivenom is more effective than whole IgG antivenom in the neutralization of local hemorrhage, edema and myonecrosis induced by B. asper venom in mice.     

Activation of mitogen activated protein (MAP) kinases by vanadate is independent of insulin receptor autophosphorylation

Treatment of Chinese hamster ovary (CHO) cells over-expressing the human insulin receptor (CHO-HIRc) with the insulin mimetic agent, vanadate, resulted in a dose- and time-dependent tyrosine phosphorylation of two proteins with apparent molecular sizes of 42 kDa (p42) and 44 kDa (p44). However, vanadate was unable to stimulate the tyrosyl phosphorylation of the beta-subunit of the insulin receptor. By using myelin basic protein (MBP) as the substrate to measure mitogen-activated protein (MAP) kinase activity in whole cell lysates, vanadate-stimulated tyrosyl phosphorylation of p42 and p44 was associated with a dose- and time-dependent activation of MAP kinase activity. Furthermore, affinity purification of cell lysates on anti-phosphotyrosine agarose column followed by immunoblotting with a specific antibody to MAP kinases demonstrated that vanadate treatment increased the tyrosyl phosphorylation of both p44mapk and p42mapk by several folds, as compared to controls, in concert with MAP kinase activation. In addition, retardation in gel mobility further confirmed that vanadate treatment increased the phosphorylation of p44mapk and p42mapk in CHO-HIRc. A similar effect of vanadate on MAP kinase tyrosyl phosphorylation and activation was also observed in CHO cells over-expressing a protein tyrosine kinase-deficient insulin receptor (CHO-1018). These results demonstrate that the protein tyrosine kinase activity of the insulin receptor may not be required in the signaling pathways leading to the vanadate-mediated tyrosyl phosphorylation and activation of MAP kinases.     

High-level cryIVD and cytA gene expression in Bacillus thuringiensis does not require the 20-kilodalton protein, and the coexpressed gene products are synergistic in their toxicity to mosquitoes

Interactions among the 20-kDa protein gene and the cytA and cryIVD genes located in a 9.4-kb HindIII fragment were studied. A series of plasmids containing a combination of these different genes was constructed by using the Escherichia coli/Bacillus thuringiensis shuttle vector pHT3101. The plasmids were then used to transform an acrystalliferous strain, cryB, derived from B. thuringiensis subsp. kurstaki. The results from sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analyses suggest that although the 20-kDa protein is required for the efficient CytA protein production in E. coli, it is not required in B. thuringiensis. With or without the truncated 20-kDa protein gene, the CtyA and/or CryIVD proteins are produced and form parasporal inclusions in B. thuringiensis cells. However, more-efficient expression is obtained when a second protein, probably acting as a chaperonin, is present. In addition, the time course studies show that the CytA and CryIVD proteins are coordinately produced. Both the crude B. thuringiensis culture and purified inclusions from each recombinant B. thuringiensis strain are toxic to Culex quinquefasciatus larvae. The parasporal inclusions formed in B. thuringiensis cells are mosquitocidal, with CytA synergizing CryIVD toxicity.     

Extracellular signal-regulated protein kinases (ERKs) and ERK kinase (MEK) in brain: regional distribution and regulation by chronic morphine

Quantitative blot immunolabeling techniques were used to determine the concentrations of ERK1 (M(r) 44 kDa) and ERK2 (M(r) 42 kDa), the two major extracellular signal-regulated protein kinases, in different regions of rat brain. The aggregate ERK concentrations (ERK1 and ERK2) were relatively high in each of the brain regions studied, ranging from approximately 0.35 ng/microgram protein in cerebellum to approximately 1.2 ng/microgram protein in nucleus accumbens. However, differences in the regional distributions of ERK1 and ERK2 resulted in ratios of their relative abundance that differed by close to 10-fold among the regions studied. The ratios of ERK1 protein to ERK2 protein varied along a rostral-caudal gradient from a low of 0.16 in frontal cortex to a high of 1.5 in pons/medulla. In hypotonic homogenates from regions at either extreme of the gradient, ERK1 and ERK2 were both found to be predominantly (> 80%) soluble. In subcellular fractions prepared from sucrose homogenates of frontal cortex and pons/medulla, both ERK1 and ERK2 were enriched in the synaptosomal and cytosolic fractions, whereas ERK2 was also enriched in the microsomal fraction. By contrast, in subfractions containing purified nuclei, levels of ERK1 and ERK2 were about one-third of those seen in homogenates and, in subfractions enriched in mitochondria, both ERK1 and ERK2 were barely detectable. The catalytic activity of the ERKs paralleled their protein levels in all of the brain regions except the hippocampus, in which the activity and phosphotyrosine content were disproportionately high. As a possible explanation for this apparent disparity, the regional distribution of ERK kinase (MEK), which phosphorylates and activates the ERKs, was also investigated. The levels of immunoreactivity of the M(r) 45 kDa ERK kinase band differed by about threefold among the brain regions, with the highest levels being present in nucleus accumbens, hippocampus, substantia nigra, and caudate/putamen. Therefore, a higher concentration of ERK kinase immunoreactivity did not appear to account for the disproportionate levels of ERK activity and phosphotyrosine content in the hippocampus. Potential regulation of ERK and ERK kinase levels was also investigated in rats subjected to chronic morphine treatment. ERK1 and ERK2 levels were increased selectively in locus coeruleus and caudate/putamen after chronic morphine treatment, whereas ERK kinase immunoreactivity remained unchanged in all of the brain regions analyzed. In summary, the regional differences in ERK and ERK kinase expression and the region-specific regulation of ERK expression suggest that ERK-related signaling may play an important role in CNS function and its adaptive responses.     

The R1 subunit of herpes simplex virus ribonucleotide reductase is a good substrate for host cell protein kinases but is not itself a protein kinase

The N terminus of the R1 subunit of herpes simplex virus type 2 ribonucleotide reductase is believed to be a protein kinase domain mainly because the R1 protein was phosphorylated in a protein kinase assay on blot. Using Escherichia coli and adenovirus expression vectors to produce R1, we found that, whereas the reductase activity of both recombinant proteins was similar, efficient phosphorylation of R1 and casein in the presence of Mg2+ was obtained only with the R1 purified from eukaryotic cells. Phosphorylation of this R1, in solution or on blot, results mainly from the activity of casein kinase II (CKII), a co-purifying protein kinase. Labeling on blot occurs from CKII leakage off the membrane and its subsequent high affinity binding to in vivo CKII-phosphorylated R1. CKII target sites were mapped to an acidic serine-rich segment of the R1 N terminus. Improvement in purification of the R1 expressed in eukaryotic cells nearly completely abolished its phosphorylation potential. An extremely low level of phosphorylation observed in the presence of Mn2+ with the R1 produced in E. coli was probably due to an unidentified prokaryotic protein kinase. These results provide evidence that the herpes simplex virus type 2 R1 does not possess an intrinsic protein kinase activity.     

Lipopolysaccharide-induced reductions in food intake do not decrease the efficiency of lysine and threonine utilization for protein accretion in chickens

Exposure of animals to infectious agents induces immune responses that result in reductions in food consumption and weight gain. The effect of these changes on amino acid requirements and utilization remains unclear. Three assays were conducted with young chicks with Escherichia coli lipopolysaccharide (LPS) used to stimulate the immune system. An initial study was conducted to evaluate the effects of LPS on animal performance. In a daily or alternate day injection regimen for 9 d, chicks were given intraperitoneal injections of sterile saline containing 0, 100 or 400 microgram LPS. Administration of 100 or 400 microgram LPS daily, or every other day, decreased both weight gain and food consumption. In two subsequent growth assays, chicks were fed graded levels of lysine or threonine and injected with either 0 or 400 microgram LPS every other day to evaluate the effect of LPS administration on the efficiency of amino acid utilization. At the three lowest amino acid doses, whole-body protein accretion was a linear function of supplemental lysine or threonine intake, and slopes of the accretion curves were not altered by LPS administration. The dietary lysine concentration required to maximize protein accretion was unaffected by LPS, but the absolute lysine intake required to maximize chick performance was lower in LPS-injected chicks than in saline-injected chicks. These results show that LPS administration reduces weight gain, food intake, efficiency of food utilization and the absolute quantity of lysine required to maximize these criteria. However, LPS administration does not affect the efficiency of amino acid utilization, nor does it affect the concentration of dietary lysine required to maximize performance.