Punishment: the interactive effects of delay and intensity of shock

A discrete-trial punishment procedure, with rats, was used to examine how delay-of-shock intervals of 0 to 28 sec and shock intensity interact to decrease the frequency and increase the latency of a positively reinforced response. For delay-of-shock intervals of 0, 7, 14, and 28 sec, there was a range of shock intensities, for some subjects, over which the punishing effect of shock was an increasing, monotonic function of shock intensity. For other subjects this transition was abrupt. Functions relating response frequency and latency measures to shock intensity were displaced toward higher values on the shock intensity axis with an increase in delay-of-shock interval. The effects of "gradual" and "abrupt" introduction to "severe" shock, as well as re-exposure to previously used shock intensities, were examined under both the immediate and delay-of-shock conditions. With delay-of-shock intervals of 7, 14, or 28 sec, shock intensities of approximately 0.50 milliamperes or greater were necessary to decrease substantially the number and increase the latency of the lever-pressing response. For the immediate punishment group this intensity was approximately 0.20 ma. These facts were related to Annau and Kamin's (1961) conditioned emotional response experiment in which a shock intensity of 0.49 ma or greater was required to suppress the rate of a positively reinforced response.

Schedule-induced mirror responding in the pigeon

Two pigeons that were previously exposed to a multiple schedule of reinforcement in the presence of a stuffed and a live pigeon, and two of three naive pigeons, responded on a mirror during exposure to multiple fixed-ratio, fixed-ratio schedules of reinforcement for key pecking. Both the topography and temporal pattern of mirror responding were comparable to schedule-induced "attack" on live and stuffed targets. Rate of target responding was reduced when either the mirror was covered with paper or when the multiple schedule was removed. A reversal in the relationship between reinforcement schedules and discriminative stimuli demonstrated that mirror responding was controlled by the stimulus correlated with the higher fixed-ratio schedule. With one component of the multiple schedule held constant at fixed ratio 25 and the ratio requirement of the other component varying from 25 to 150, there was an inverted U-shaped relationship between rate of mirror responding and fixed-ratio schedule in the varied component. As in Flory's study (1969b) there was an inverted U-shaped relationship between target responding and inter-food intervals. The combined results of these studies suggest that the relationship between rate of target responding and reinforcement schedules is controlled primarily by the inter-food intervals resulting from the schedules.

DRL escape: effects of minimum duration and intensity of electric shock

Three dogs were exposed to a DRL-escape procedure that required them to endure a minimum duration of electric shock without responding in order for a response to terminate that shock. When this minimum duration increased from 0 to either 2.25 or 7.00 sec, response latencies increased proportionately. With the minimum duration held constant at 2.25 sec, a gradual increase in shock intensity to 5.0 ma had no systematic effect upon latencies. Even under the highest shock intensity, 5.0 ma, latency and interresponse-time distributions were unimodal with very few latencies and interresponse times less than the minimum duration. Three additional dogs were exposed to an escape procedure in which every response was immediately reinforced. For these subjects, the same increase in shock intensity to 5.0 ma was accompanied by a decrease in latencies. The precise temporal spacing of responses obtained with the DRL-escape procedure may in part be due to the fact that every response latency and interresponse time that did not meet the minimum duration was not only extinguished but was also punished.

Pictorial target control of schedule-induced attack in White Carneaux pigeons

Three pigeons with a history of attacking a mirror target, and two of six pigeons with no prior exposure to targets, attacked a colored photograph of a conspecific during exposure to intermittent schedules of reinforcement for key pecking. Rate of attack on the photograph decreased when the reinforcement schedule was removed. The topography, temporal pattern, and locus of attack on the picture were comparable to schedule-induced attack on live, stuffed, and mirror targets. When silhouette, outline, and plain paper targets were used, schedule-induced attack was more sensitive to a change in target characteristics with a concurrent target-preference procedure than with an analogous successive-testing procedure. The combined results of the two testing procedures indicated that an "upright" white-on-black silhouette of a pigeon with or without an eye was more effective in controlling attack than was a comparable "inverted" silhouette, an outline of a pigeon, or a piece of colored paper.

Conditional discrimination performance by pigeons on a response-independent procedure

Pigeons were trained on a differential autoshaping procedure in which both components of two-stimulus sequences predicted delivery or nondelivery of food. All birds acquired the conditional discrimination. When the subjects were exposed to an extinction procedure, the stimuli maintained conditional control as long as the birds continued to peck the key. When a delay interval was imposed between the two components of a stimulus sequence using a titration procedure, the stimuli maintained conditional control up to delay values of 7 to 10 sec. These data are consistent with the view that the controlling stimuli in conditional discrimination situations are compounds of stimulus elements.

The role of intermittent food in the induction of attack in pigeons

The present experiments evaluated whether transitions in reinforcer probability are necessary to induce attack in pigeons. In Experiment I, three of six pigeons exposed to response-contingent constant-probability food schedules and a photograph of a conspecific as a target exhibited sustained postreinforcement attack on the target. The postreinforcement pattern of attack developed over the course of the experiment and was accompanied by a reduction in the rate of postreinforcement key pecking and an increase in the postreinforcement pause in key pecking. These effects on key pecking resulted in unprogrammed variations in the probability of reinforcement which may have been responsible for the induction of attack. In Experiment II, the attack-inducing properties of a constant-probability response-independent food schedule were compared to a periodic food schedule matched for overall rate of food delivery and to a no-food condition. In addition to attack, the spatial location of the subjects was monitored during each interfood interval. The periodic and aperiodic food schedules generated very different patterns of spatial location. Postfood attack was induced by both food schedules, although the constant-probability schedule induced attack in fewer birds. The no-food condition was not effective in inducing attack in any birds. These experiments indicate that intermittent food schedules without reductions in reinforcer probability are sufficient to induce attack in some pigeons, although not as effective as schedules with transitions in reinforcer probability.

R-Plasmid Transfer to and from Escherichia coli Strains Isolated from Human Fecal Samples

Strains of Escherichia coli recently isolated from human feces were examined for the frequency with which they accept an R factor (R1) from a derepressed fi strain of E. coli K-12 and transfer it to fecal and laboratory strains. Colicins produced by some of the isolates rapidly killed the other half of the mating pair; therefore, conjugation was conducted by a membrane filtration procedure whereby this effect was minimized. The majority of fecal E. coli isolates accepted the R factor at lower frequencies than K-12 F, varying from 10 per donor cell to undetectable levels. The frequencies with which certain fecal recipients received the R-plasmid were increased when its R transconjugant was either cured of the R1-plasmid and remated with the fi strain or backcrossed into the parental strain. The former suggests the loss of an incompatibility plasmid, and the latter suggests the modification of the R1-plasmid deoxyribonucleic acid (DNA). In general, the fecal RE. coli transconjugants were less effective donors for K-12 F and heterologous fecal strains than was the fi K-12 strain, whereas the single strain of Citrobacter freundii examined was generally more competent. Passage of the R1-plasmid to strains of salmonellae reached mating frequencies of 10 per donor cell when the recipient was a Salmonella typhi previously cured of its resident R-plasmid. However, two recently isolated strains of Salmonella accepted the R1-plasmid from E. coli K-12 R or the RE. coli transconjugants at frequencies of 5 x 10 or less.

Imaging of angiogenesis in metastatic breast cancer by positron emission tomography (PET) using [18F]AH11585, an [18F]- labeled alphaVbeta3 (αvβ3) peptide

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Background: In vivo imaging of avβ3 expression in tumors and tumor endothelial cells may be a useful biomarker of angiogenesis. [18F]AH11585 is a novel peptide containing an Arginine-Glycine-Aspartic Acid (RGD) motif that binds to avβ3 with high affinity designed for use in PET studies. Methods: 7 patients with metastatic breast cancer (aged 37–68 years) received intravenous injections of [18F]AH11585 and were scanned dynamically by PET over 61.5 mins. Radioactivity concentrations, derived from regions of interest placed on tumour and normal tissues, were analysed mathematically to determine the net irreversible uptake (Ki), fractional retention (FRT) and standardized uptake at 56.5min (SUV) of the radiotracer. Computed tomography (CT) was performed within 4 weeks of the scan. Results: Tumor lesions were clearly visible on PET images in 6/7 patients. In one patient with a palpable supraclavicular lymph node not visible on CT, we were unsure if a hyperintense region visible by PET was tumor. In total 18/19 tumor lesions were identified on both PET and corresponding CT images. Tumors in areas of low background were hyperintense (lung, bone, breast) whereas those in areas of high background were hypointense regions (liver). Tumors with central necrosis showed high uptake of [18F]AH11585 around the periphery only. Mathematical analysis demonstrated irreversible retention of [18F]AH11585 in tumors. [18F]AH11585-PET discriminated between non-liver lesions (n=10) and normal tissues: Ki (p=0.002), FRT (p=0.0039), SUV (p=0.002). Corresponding comparisons for liver lesions (n=8) were significant for FRT (p=0.0078) and SUV (p=0.0078) only. Conclusions: [18F]AH11585 PET is a promisng method for in vivo imaging of avβ3 integrin expression in metastatic breast cancer.

No significant financial relationships to disclose.

KIT oncoprotein interactions in gastrointestinal stromal tumors: therapeutic relevance

Most gastrointestinal stromal tumors (GISTs) express oncogenic and constitutively active forms of the KIT or platelet-derived growth factor receptor alpha (PDGFRA) receptor tyrosine kinase proteins, and these kinase oncoproteins serve as targets for effective therapies. Given that mutant KIT oncoproteins serve crucial transforming roles in GISTs, we evaluated interactions with the KIT oncoproteins and determined signaling pathways that are dependent on KIT oncogenic activation in GISTs. Tyrosine-phosphorylated KIT oncoproteins interacted with PDGFRA, PDGFRB, phosphatidylinositol 3-kinase (PI3-K) and PKCtheta in GIST cells, and these interactions were abolished by KIT inhibition with imatinib or PKC412 or KIT RNAi. Notably, tyrosine-phosphorylated PDGFRA was prominent in frozen GIST tumors expressing KIT oncoproteins, suggesting that KIT-mediated PDGFRA phosphorylation is an efficient and biologically consequential mechanism in GISTs. Activated signaling intermediates were identified by immunoaffinity purification of tyrosine-phosphorylated proteins in GIST cells before and after treatment with KIT inhibitors, and these analyses show that GRB2, SHC, CBL and MAPK activation are largely KIT dependent in GISTs, whereas PI3-K, STAT1 and STAT3 activation are partially KIT dependent. In addition, we found that phosphorylation of several tyrosine kinase proteins - including JAK1 and EPHA4 - did not depend on KIT activation. Likewise, paxillin activation was independent of the KIT oncogenic signal. These studies identify signaling pathways that can provide both KIT-dependent and KIT-independent therapeutic synergies in GIST, and thereby highlight clinical strategies that might consolidate GIST therapeutic response to KIT/PDGFRA inhibition.

The multikinase inhibitor midostaurin (PKC412A) lacks activity in metastatic melanoma: a phase IIA clinical and biologic study

Midostaurin (PKC412A), N-benzoyl-staurosporine, potently inhibits protein kinase C alpha (PKCalpha), VEGFR2, KIT, PDGFR and FLT3 tyrosine kinases. In mice, midostaurin slows growth and delays lung metastasis of melanoma cell lines. We aimed to test midostaurin's safety, efficacy and biologic activity in a Phase IIA clinical trial in patients with metastatic melanoma. Seventeen patients with advanced metastatic melanoma received midostaurin 75 mg p.o. t.i.d., unless toxicity or disease progression supervened. Patient safety was assessed weekly, and tumour response was assessed clinically or by CT. Tumour biopsies and plasma samples obtained at entry and after 4 weeks were analysed for midostaurin concentration, PKC activity and multidrug resistance. No tumour responses were seen. Two (12%) patients had stable disease for 50 and 85 days, with minor response in one. The median overall survival was 43 days. Seven (41%) discontinued treatment with potential toxicity, including nausea, vomiting, diarrhoea and/or fatigue. One patient had >50% reduction in PKC activity. Tumour biopsies showed two PKC isoforms relatively insensitive to midostaurin, out of three patients tested. No modulation of multidrug resistance was demonstrated. At this dose schedule, midostaurin did not show clinical or biologic activity against metastatic melanoma. This negative trial reinforces the importance of correlating biologic and clinical responses in early clinical trials of targeted therapies.

Specific phospholipids enhance the activity of beta-lactam antibiotics against Pseudomonas aeruginosa

Pseudomonas aeruginosa PAO1 became considerably more sensitive to the action of ampicillin when grown in the presence of certain phospholipids. Only phospholipids capable of forming lipid bilayers or micelles proved to be capable of enhancing ampicillin activity. Of the phospholipids tested, 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphate, also called monopalmitoylphosphatidic acid (MPPA), was the best enhancer. In the absence of MPPA, the MIC and MBC of ampicillin for P. aeruginosa PAO1 were 1 and 2 g/L, respectively. In the presence of MPPA, the MIC and MBC were 20 and 40 mg/L, respectively. MPPA was shown to enhance ampicillin activity by binding both Ca(2+) and Mg(2+), suggesting that the mechanism of enhancement is similar to that previously reported for Ca(2+) and Mg(2+) chelators. Surprisingly, MPPA by itself slowed the growth of four mucoid multiply antibiotic-resistant strains of P. aeruginosa recently isolated from the sputum of cystic fibrosis patients, and enhanced their sensitivity to piperacillin. It also increased the sensitivity of two ceftazidime-resistant P. aeruginosa cystic fibrosis strains to ceftazidime.

A functional cra gene is required for Salmonella enterica serovar typhimurium virulence in BALB/c mice

A minitransposon mutant of Salmonella enterica serovar Typhimurium SR-11, SR-11 Fad(-), is unable to utilize gluconeogenic substrates as carbon sources and is avirulent and immunogenic when administered perorally to BALB/c mice (M. J. Utley et al., FEMS Microbiol. Lett., 163:129-134, 1998). Here, evidence is presented that the mutation in SR-11 Fad(-) that renders the strain avirulent is in the cra gene, which encodes the Cra protein, a regulator of central carbon metabolism.

rpoS gene function is a disadvantage for Escherichia coli BJ4 during competitive colonization of the mouse large intestine

The ability of Escherichia coli to survive stress during growth in different environments is, in large part, dependent on rpoS and the genes that comprise the rpoS regulon. E. coli BJ4 and an isogenic BJ4 rpoS mutant were used to examine the influence of the rpoS gene on E. coli colonization of the streptomycin-treated mouse large intestine. Colonization experiments in which the wild-type E. coli BJ4 and its rpoS mutant were fed individually as well as simultaneously to mice suggested that E. coli BJ4 does not face prolonged periods of nutrient starvation in the mouse large intestine and that the rpoS regulon is not expressed during long-term colonization after adaptation of the bacteria to the gut environment.

Estimation of growth rates of Escherichia coli BJ4 in streptomycin-treated and previously germfree mice by in situ rRNA hybridization

The growth physiology of Escherichia coli during colonization of the intestinal tract was studied with four animal models: the streptomycin-treated mouse carrying a reduced microflora, the monoassociated mouse with no other microflora than the introduced strain, the conventionalized streptomycin-treated mouse, and the conventionalized monoassociated mouse harboring a full microflora. A 23S rRNA fluorescent oligonucleotide probe was used for hybridization to whole E. coli cells fixed directly after being taken from the animals, and the respective growth rates of E. coli BJ4 in the four animal models were estimated by correlating the cellular concentrations of ribosomes with the growth rate of the strain. The growth rates thus estimated from the ribosomal content of E. coli BJ4 in vivo did not differ in the streptomycin-treated and the monoassociated mice. After conventionalization there was a slight decrease of the bacterial growth rates in both animal models.

A Salmonella typhimurium mutant unable to utilize fatty acids and citrate is avirulent and immunogenic in mice

Salmonella typhimurium SR-11 is extremely virulent at a dose as low as 10(5) colony forming units (cfu) when administered perorally to BALB/c mice. Utilizing mini-transposon mutagenesis, a mutant of S. typhimurium SR-11 was isolated that was unable to utilize oleate and citrate as carbon sources. This mutant, designated S. typhimurium SR-11 Fad- (Fatty acid), was found to utilize sugars under cya/crp control as sole carbon sources, suggesting that the mutation is not in either of these genes. In addition, SR-11 Fad- utilized pyruvate and succinate, but was unable to utilize either acetate or isocitrate as sole carbon source. In contrast to SR-11, SR-11 Fad- was found to be avirulent, i.e. BALB/c mice were completely healthy after oral infection with 10(9) S. typhimurium SR-11 Fad- cells. Moreover, 21 days after SR-11 Fad- infection, BALB/c mice were found to be protected against an oral challenge with 10(9) cells of S. typhimurium SR-11.

The leuX-encoded tRNA5(Leu) but not the pathogenicity islands I and II influence the survival of the uropathogenic Escherichia coli strain 536 in CD-1 mouse bladder mucus in the stationary phase

The uropathogenic Escherichia coli strain 536 carries two pathogenicity islands, each of which is associated with either of the tRNA genes selC or leuX, respectively. Growth competition in CD-1 mouse mucus between the wild-type strain E. coli 536, its leuX mutant 536 delta 102 and its mutant 536R3, lacking both pathogenicity islands but expressing a functional tRNA5(Leu), revealed a major impact of leuX on E. coli survival in bladder mucus. The impaired survival in CD-1 mouse mucus observed upon deletion of the leuX gene was abolished after complementation with the leuX gene. The survival of bacteria in bladder mucus was not influenced by the presence of pathogenicity islands I and II.

Targeted suppression of cytokine production in monocytes but not in T lymphocytes by a tetravalent guanylhydrazone (CNI-1493)

Image analysis was used to study the cytokine-inhibitory effect of the nitric oxide inhibitor tetravalent guanylhydrazone (CNI-1493) in individual immunocytochemically stained human peripheral blood mononuclear cells (PBMC). CNI-1493 inhibited lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-alpha, interleukin (IL)-1alpha, IL-1beta, IL-6, and IL-8 production whether or not LPS stimulation was enhanced by interferon (IFN)-gamma priming. Addition of TNF-alpha to CNI-1493-exposed LPS-stimulated cells partially restored the incidence of IL-1alpha-, IL-1beta-, and IL-8-producing cells. TNF-alpha production induced by costimulation by ligation of CD3 and CD28 was inhibited by CNI-1493 in monocytes but not in T lymphocytes. The prevalence of IL-2-, IFN-gamma-, and TNF-beta-producing T cells was not reduced by CNI-1493. Phorbol ester and ionomycin activation also resulted in a CNI-1493 -induced inhibition of TNF-alpha in monocytes but resistant production of TNF-alpha, IL-2, and IFN-gamma by T cells. Thus, CNI-1493 preferentially inhibited synthesis of proinflammatory cytokines in monocytes.

Recombinant tissue plasminogen activator restores perfusion in meningococcal purpura fulminans

OBJECTIVE

To investigate whether an infusion of recombinant tissue plasminogen activator would dissolve microvascular thromboses and improve organ perfusion in a patient with fulminant meningococcemia.

DESIGN

Descriptive case report.

SETTING

Fifteen-bed pediatric intensive care unit (ICU) in a university hospital.

PATIENT

A 4-month-old male with fulminant meningococcemia, refractory shock, and multiple organ failure.

INTERVENTIONS

In addition to standard aggressive ICU care, the patient received a recombinant tissue plasminogen activator infusion at a total dose of 1.25 mg/kg over 4 hrs.

MEASUREMENTS AND MAIN RESULTS

Heart rate, arterial blood pressure, urine output, and base deficit (as a reflection of severity of metabolic acidosis) were recorded immediately before the recombinant tissue plasminogen activator infusion and 4 hrs later, after completion of the recombinant tissue plasminogen activator infusion. The amount of exogenous vasopressor and inotropic support required to maintain the patient's hemodynamic status before and after recombinant tissue plasminogen activator infusion were also compared. Subjective observations regarding the patient's peripheral perfusion status were also noted. The patient showed a dramatic improvement in hemodynamics, urine output, and metabolic acidosis, as well as a perceived increase in skin perfusion after recombinant tissue plasminogen activator infusion.

CONCLUSIONS

In this patient, recombinant tissue plasminogen activator infusion resulted in improved organ perfusion and cardiac performance. Selective use of recombinant tissue plasminogen activator in the treatment of fulminant meningococcemia merits further investigation.

Spermine inhibits proinflammatory cytokine synthesis in human mononuclear cells: a counterregulatory mechanism that restrains the immune response

The local production of proinflammatory cytokines mediates the host response to inflammation, infection, and injury, whereas an overexpression of these mediators can injure or kill the host. Recently, we identified a class of multivalent guanylhydrazone compounds that are effective inhibitors of proinflammatory cytokine synthesis in monocytes/macrophages. The structure of one such cationic molecule suggested a molecular mimicry with spermine, a ubiquitous endogenous biogenic amine that increases significantly at sites of inflammation and infection. Here, we addressed the hypothesis that spermine might counterregulate the innate immune response by downregulating the synthesis of potentially injurious cytokines. When spermine was added to cultures of human peripheral blood mononuclear cells stimulated with lipopolysaccharide (LPS), it effectively inhibited the synthesis of the proinflammatory cytokines tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-6, MIP-1alpha, and MIP-1beta. The inhibition of cytokine synthesis was specific and reversible, with significant inhibition of TNF synthesis occurring even when spermine was added after LPS. The mechanism of spermine-mediated cytokine suppression was posttranscriptional and independent of polyamine oxidase activity. Local administration of spermine in vivo protected mice against the development of acute footpad inflammation induced by carrageenan. These results identify a distinct molecular counterregulatory role for spermine in downregulating the monocyte proinflammatory cytokine response.

The critical role of p38 MAP kinase in T cell HIV-1 replication

BACKGROUND

Replication of HIV-1 in human T lymphocytes requires the activation of host cellular proteins. This study identifies p38 mitogen-activated protein kinase (MAPK) as one such kinase necessary for HIV-1 replication in T cells.

MATERIALS AND METHODS

Primary human T lymphocytes were infected with the LAI strain of HIV-1 and Jurkat cells were infected with the RF strain of HIV-1. HIV replication was measured by reverse transcriptase activity. Cellular expression of endogenous p38 MAPK protein was analyzed using immunoprecipitation. Blockade of p38 MAPK expression was achieved using antisense oligonucleotides to p38 MAPK and the guanylhydrazone compound CNI-1493, an inhibitor of p38 MAPK activation.

RESULTS

HIV-1 infection of both primary human T lymphocytes and a T cell line rapidly activated the cellular p38 MAPK pathway, which remained activated for the duration of the culture. Addition of phosphothioated antisense oligonucleotides to p38 MAPK specifically inhibited viral replication. Blockade of p38 MAPK activation by addition of CNI-1493 also inhibited HIV-1 viral replication of primary T lymphocytes in a dose- and time-dependent manner. Stimulation of p38 MAPK activation did not occur with the addition of heat-inactivated virus, suggesting that viral internalization, and not just membrane binding, is necessary for p38 MAPK activation.

CONCLUSIONS

These results indicate that activation of the p38 MAPK cascade is critical for HIV-1 replication in primary T lymphocytes, and that blockade of this signal transduction pathway may be a novel therapeutic approach to the treatment of HIV-1 infection.

Isolation and characterization of an attenuated strain of Pseudomonas aeruginosa AC869, a 3,5-dichlorobenzoate degrader

Pseudomonas aeruginosa AC869, a 3,5-dichlorobenzoate degrader, is a mouse pathogen and has a reported 50% lethal dose (LD50) of 1.05 x 10(7) CFU when given intranasally to C3H/HeJ mice (S.E. George, M.J. Kohan, M.I. Gilmour, M.S. Taylor, H.G. Brooks, J.P. Creason, and L.D. Claxton, Appl. Environ, Microbiol. 59:3585-3591, 1993). AC869 was serotyped as O6 when grown in CD-1 mouse cecal and lung mucus but could not be assigned an O serotype when grown in Luria broth (LB). After growth in mouse cecal mucus, a less virulent mutant, AC869-11, was isolated from AC869 by using bacteriophage E79, which adsorbs to the O side chain of lipopolysaccharide (LPS). AC869-11 produced significantly less O antigen on its LPS than AC869 when grown in mouse lung and cecal mucus. The mutant also produced half the amount of exoenzyme S and 16-fold less extracellular protease than AC869 and was more sensitive than its parent to a number of antibiotics when grown either in LB or in mouse lung mucus. AC869-11 had ninefold higher LD50 than AC869 in CD-1 mice when administered intranasally. AC869-11 was found in the lungs, small intestine, cecum, and large intestine in numbers at least 100-fold below AC869, 3 h after intranasal exposure of mice to a sublethal dose of the two strains. Moreover, AC869-11 induced a decreased pulmonary inflammatory response relative to AC869. In contrast to AC869, AC869-11 did not translocate to the mesenteric lymph nodes, liver, and spleen following a sublethal dose. Despite attenuation, AC869-11 grew as well as AC869 with 3,5-dichlorobenzoate as the sole carbon and energy source. However, although AC869-11 survived in 3,5-dichlorobenzoate-contaminated soil as well as AC869 for 1 week, it failed to survive as well thereafter. These results suggest the possibility that mutations that lead to pulmonary attenuation of P. aeruginosa in mice also lead to weakness in the environment, despite such mutants maintaining the ability to degrade toxic substances under laboratory conditions.

The Escherichia coli K-12 gntP gene allows E. coli F-18 to occupy a distinct nutritional niche in the streptomycin-treated mouse large intestine

Escherichia coli F-18 is a human fecal isolate that makes type 1 fimbriae, encoded by the fim gene cluster, and is an excellent colonizer of the streptomycin-treated mouse intestine. E. coli F-18 fimA::tet, lacking type 1 fimbriae, was constructed by bacteriophage P1 transduction of the fim region of the E. coli K-12 strain ORN151, containing the tetracycline resistance gene from Tn10 inserted in the fimA gene, into E. coli F-18. E. coli F-18 fimA::tet was found to occupy a distinct niche in the streptomycin-treated mouse intestine when fed in small numbers (10(4) CFU) to mice, along with large numbers (10(10) CFU) of E. coli F-18, as defined by the ability of the E. coli F-18 fimA::tet strain to grow and colonize only 1 order of magnitude below E. coli F-18. The same effect was observed when mice already colonized with E. coli F-18 were fed small numbers of E. coli F-18 fimA::tet. Experiments which show that the E. coli K-12 gene responsible for this effect is not fim::tet but gntP, which maps immediately downstream of the fim gene cluster, are presented. gntP encodes a high-affinity gluconate permease, suggesting that the distinct niche in the mouse large intestine is defined by the presence of gluconate. The data presented here support the idea that small numbers of an ingested microorganism can colonize the intestine as long as it can utilize an available nutrient better than any of the other resident species can.

Role of lipopolysaccharide in colonization of the mouse intestine by Salmonella typhimurium studied by in situ hybridization

An avirulent, streptomycin-resistant Salmonella typhimurium strain, SL5319, and its lipopolysaccharide (LPS)-deficient mutant strain, SL5325, differ in their ability to colonize the large intestines of streptomycin-treated mice. When fed to mice independently, the strains colonize equally well, but when fed together, the LPS-deficient mutant is outcompeted by the wild-type strain during establishment in the gut (J.J. Nevola, B.A.D. Stocker, D.C. Laux, and P.S. Cohen, Infect. Immun. 50:152-159, 1985). In the present study, the spatial distribution in the intestinal mucosal layer of the two strains was visualized by specific hybridization to bacterial rRNA in histological sections of mouse colon and cecum. The first day after infection, 9.8% of the smooth SL5319 cells observed in mucus were found to be associated with the mouse epithelial cells, but three days after infection, the corresponding fraction of adhering bacteria was reduced to 2.1%. The LPS-deficient S. typhimurium strain was confined to the part of the mucosal layer closest to the colonic lumen and was not observed to adhere to the epithelium either at day 1 or 3 after infection. Quantitative determinations of the distance from the S. typhimurium cells to the epithelial wall confirmed that the average distance for the rough S. typhimurium SL5325 was much larger than for its smooth counterpart, S. typhimurium SL5319. Quantification of the hybridization signal from bacteria isolated from the cecal mucus revealed that the two strains had the same ribosome concentration, indicating that they have the same potential for growth in the intestinal environment. On the basis of these observations, we suggest that the better colonization ability of the strain carrying wild-type LPS is due to the better abilities to penetrate the intestinal mucosal layer and to subsequently bind to the epithelial cells in vivo.

Escherichia coli F-18 and E. coli K-12 eda mutants do not colonize the streptomycin-treated mouse large intestine

The Escherichia coli human fecal isolates F-18 and K-12 are excellent colonizers of the streptomycin-treated mouse intestine. E. coli F-18 and E. coli K-12 eda mutants (unable to utilize glucuronate, galacturonate, and gluconate) were constructed by insertional mutagenesis. Neither the E. coli F-18 eda nor the E. coli K-12 eda mutant was able to colonize the streptomycin-treated mouse intestine, whether they were fed to mice together with their respective parental strains or alone. Complementation of the eda mutants with pTC190 (containing a functional E. coli K-12 eda gene) completely restored the colonization ability of both eda mutants. Relative to their parental strains, the E. coli F-18 eda mutant and the E. coli K-12 eda mutant grew poorly in cecal mucus isolated from mice fed either normal mouse chow or a synthetic diet containing sucrose as the sole carbon source, yet the mutants and parental strains demonstrated identical growth rates in minimal medium with glucose as the carbon source. E. coli F-18 edd eda and E. coli K-12 edd eda double mutants colonized the streptomycin-treated intestine when fed to mice alone; however, when fed simultaneously with their respective parental strains, they were poor colonizers. Since the edd gene is involved only in gluconate metabolism via the Entner-Doudoroff pathway, these results implicate the utilization of gluconate and the Entner-Doudoroff pathway as important elements in E. coli colonization of the streptomycin-treated mouse large intestine.

CNI-1493 inhibits monocyte/macrophage tumor necrosis factor by suppression of translation efficiency

Tumor necrosis factor (TNF) mediates a wide variety of disease states including septic shock, acute and chronic inflammation, and cachexia. Recently, a multivalent guanylhydrazone (CNI-1493) developed as an inhibitor of macrophage activation was shown to suppress TNF production and protect against tissue inflammation and endotoxin lethality [Bianchi, M., Ulrich, P., Bloom, O., Meistrell, M., Zimmerman, G. A., Schmidtmayerova, H., Bukrinsky, M., Donnelley, T., Bucala, R., Sherry, B., Manogue, K. R., Tortolani, A. J., Cerami, A. & Tracey, K. J. (1995) Mol. Med. 1, 254-266, and Bianchi, M., Bloom, O., Raabe, T., Cohen, P. S., Chesney, J., Sherry, B., Schmidtmayerova, H., Zhang, X., Bukrinsky, M., Ulrich, P., Cerami, A. & Tracey, J. (1996) J. Exp. Med., in press]. We have now elucidated the mechanism by which CNI-1493 inhibits macrophage TNF synthesis and show here that it acts through suppression of TNF translation efficiency. CNI-1493 blocked neither the lipopolysaccharide (LPS)-induced increases in the expression of TNF mRNA nor the translocation of nuclear factor NF-kappa B to the nucleus in macrophages activated by 15 min of LPS stimulation, indicating that CNI-1493 does not interfere with early NF-kappa B-mediated transcriptional regulation of TNF. However, synthesis of the 26-kDa membrane form of TNF was effectively blocked by CNI-1493. Further evidence for the translational suppression of TNF is given by experiments using chloram-phenicol acetyltransferase (CAT) constructs containing elements of the TNF gene that are involved in TNF translational regulation. Both the 5' and 3' untranslated regions of the TNF gene were required to elicit maximal translational suppression by CNI-1493. Identification of the molecular target through which CNI-1493 inhibits TNF translation should provide insight into the regulation of macrophage activation and mechanisms of inflammation.

Suppression of proinflammatory cytokines in monocytes by a tetravalent guanylhydrazone

An overproduction of proinflammatory cytokines by activated macrophages/monocytes mediates the injurious sequelae of inflammation, septic shock, tissue injury, and cachexia. We recently synthesized a tetravalent guanylhydrazone compound (CNI-1493) that inhibits cytokine-inducible arginine transport and nitric oxide (NO) production in macrophages, and protects mice against lethal endotoxemia and carrageenan-induced inflammation. During these investigations we noticed that CNI-1493 effectively prevented lipopolysaccharide (LPS)-induced NO production, even when added in concentrations 10-fold less than required to competitively inhibit L-arginine uptake, suggesting that the suppressive effects of this guanylhydrazone compound might extend to other LPS-induced responses. Here, we report that CNI-1493 suppressed the LPS-stimulated production of proinflammatory cytokines (tumor necrosis factor [TNF], interleukins 1beta and 6, macrophage inflammatory proteins 1alpha and 1beta) from human peripheral blood mononuclear cells. Cytokine suppression was specific, in that CNI-1493 did not inhibit either the constitutive synthesis of transforming growth factor beta or the upregulation of major histocompatibility complex class II by interferon gamma (IFN-gamma). In contrast to the macrophage suppressive actions of dexamethasone, which are overridden in the presence of IFN-gamma, CNI-1493 retained its suppressive effects even in the presence of IFN-gamma. The mechanism of cytokine-suppressive action by CNI-1493 was independent of extracellular L-arginine content and NO production and is not restricted to induction by LPS. As a selective inhibitor of macrophage activation that prevents TNF production, this tetravalent guanylhydrazone could be useful in the development of cytokine-suppressive agents for the treatment of diseases mediated by overproduction of cytokines.

Growth of Escherichia coli K88 in piglet ileal mucus: protein expression as an indicator of type of metabolism

The physiological and molecular responses of enterotoxigenic Escherichia coli K88 strain Bd 1107/7508 during growth in piglet ileal mucus and lipids extracted from mucus were studied in terms of growth rate, protein expression, and rate of heat production. E. coli K88 multiplied at maximum speed in mucus and in lipids extracted from mucus. By two-dimensional gel electrophoresis of [35S]methionine-labelled cells, it was demonstrated that the synthesis of a subclass of 13 proteins was changed at least fourfold during exponential growth in mucus compared with growth in M9 minimal medium. Ten of these proteins were repressed, while three were induced, and one of the induced proteins was identified as heat shock protein GroEL. Furthermore, two-dimensional analysis of E. coli K88 cells grown on lipids extracted from mucus revealed a set of lipid utilization-associated proteins. None of these was induced fourfold during exponential growth in mucus. Microcalorimetric measurements (monitoring the rate of heat production) of E. coli K88 grown in mucus indicated metabolic shifts in the stationary phase, in which five of the lipid utilization-associated proteins were expressed at a higher level. An isogenic E. coli K88 fadAB mutant deficient in fatty acid degradation genes grew as well as the wild type on mucus and mucus lipids. The heat production rate curve of the mutant grown in mucus differed from that of the wild type only during the stationary phase. From these results it was concluded that protein expression is influenced when E. coli K88 is grown in piglet ileal mucus rather than in M9 minimal medium. Lipids extracted from ileal mucus can serve as a substrate for E. coli K88 but appear not to be utilized during exponential growth in mucus. Stationary-phase cells metabolize fatty acids; however, the functional purpose of this is unclear.

Induction of transforming growth factor beta 1 and its receptors during all-trans-retinoic acid (RA) treatment of RA-responsive human neuroblastoma cell lines

Recent work on a variety of normal and malignant cell lines has shown that induction and secretion of biologically active TGF-beta may occur after exposure to all-trans-retinoic acid (RA), coincident with decreased growth rate and/or differentiation. This study evaluates the expression and regulation of transforming growth factor beta (TGF-beta) and its receptors during RA-induced cell growth arrest and induction of differentiation in the RA-sensitive human neuroblastoma cell line SMS-KCNR and the RA-resistant neuroblastoma cell line SK-N-AS. RA treatment of SMS-KCNR cells results in a 40-fold increase in TGF-beta 1 mRNA after 4 days of RA, a dose-dependent increase in TGF-beta 1 secretion, an increase in types I (TBRI) and III (TBRIII) TGF-beta receptor proteins, and an increase in type II TGF-beta receptor (TBRII) mRNA coincident with RA-responsiveness of the cells. However, in the RA-resistant line SK-N-AS, TGF-beta 1 is constitutively secreted at levels that are unchanged after RA treatment, and although TBRI and TBRIII mRNA is expressed in untreated SK-N-AS cells, levels of TBRI and TBRIII protein and TBRII mRNA decrease after RA treatment. Thus, in RA-sensitive neuroblastoma cells, RA treatment may result in the induction of a negative autocrine TGF-beta 1 growth regulatory loop. These results suggest the hypothesis that: (a) induction of a TGF-beta 1 negative autocrine growth loop may be a necessary component for RA-responsiveness of neuroblastoma cells in vivo; and (b) the inability to induce or maintain this TGF-beta 1 negative autocrine growth loop may be a mechanism of RA resistance in neuroblastoma.

Expression of stem cell factor and c-kit in human neuroblastoma. The Children's Cancer Group

During development, mice with mutations of stem cell factor (SCF) or its receptor c-kit exhibit defects in melanogenesis, as well as hematopoiesis and gonadogenesis. Because melanocytes derive from neural crest cells, the role of SCF and c-kit was investigated in the neural crest-derived childhood tumor neuroblastoma. Using reverse transcription-polymerase chain reaction analysis, simultaneous expression of steady-state mRNA for the SCF ligand and its receptor c-kit was found in 14 of 14 (100%) human neuroblastoma cell lines and clones and in 8 of 18 (45%) human neuroblastoma tumor samples. Functional blockade of c-kit receptors in the cell lines SK-N-BE(2) and SH-SY5Y using the mouse monoclonal anti-c-kit antibody SR-1 resulted in a significant decrease in cellular growth rate when measured by either 3H-thymidine incorporation or clonogenicity. In addition, higher levels of c-kit mRNA expression were associated with parental neuroblastoma cell lines and subclones with a neuronal (N) differentiation phenotype, whereas lower levels of c-kit mRNA were associated with neuroblastoma cell line subclones having a schwannian/glial/melanocytic pattern of differentiation. However, the differentiation phenotype of neuroblastoma cell lines was not directly altered when c-kit expression was blocked using the SR-1 antibody. In summary, these data indicate that c-kit receptor expression may play a significant role in the growth regulation of the two neuroblastoma cell lines examined and suggest that c-kit may also play a similar role in neuroblastoma growth regulation in vivo. Simultaneous expression of SCF and c-kit mRNA in both neuroblastoma cell lines and tumors implies that c-kit may act as part of an autocrine growth loop in conjunction with endogenous production of SCF in this disease.

Role of leuX in Escherichia coli colonization of the streptomycin-treated mouse large intestine

Escherichia coli F-18, a normal human fecal isolate, is an excellent colonizer of the streptomycin-treated mouse large intestine. E. coli F-18 Col-, a derivative of E. coli F-18 that no longer makes the E. coli F-18 colicin, colonizes the mouse large intestine as well as E. coli F-18 when fed alone, but is eliminated when fed together with E. coli F-18. Recently, a random bank of E. coli F-18 DNA was transformed into E. coli F-18 Col-, the resultant population was fed to streptomycin-treated mice, and the intestine was used to select the best colonizer. In this fashion, a 6.5 kb E. coli F-18 DNA fragment was isolated. This fragment was shown to enhance E. coli F-18 Col- mouse large intestinal colonizing ability and survival during stationary phase in intestinal mucus in vitro, as well as stimulate the synthesis of type-1 fimbriae. Here, we present evidence that the gene responsible for the enhanced E. coli F-18 Col- colonizing ability and survival during stationary phase in vitro is leuX. This gene encodes a rare leucine tRNA specific for the UUG codon. In addition, we show that the presence of a functional leuX gene is necessary for E. coli K-12 intestinal colonization and for survival in stationary phase.

Stimulation of Escherichia coli F-18Col- type-1 fimbriae synthesis by leuX

Escherichia coli F-18, a normal human fecal isolate, is an excellent colonizer of the streptomycin-treated mouse large intestine. E. coli F-18Col-, a derivative of E. coli F-18 which no longer makes the E. coli F-18 colicin, colonizes the large intestine as well as E. coli F-18 when fed to mice alone but is eliminated when fed together with E. coli F-18. Recently we randomly cloned E. coli F-18 DNA into E. coli F-18Col- and let the mouse intestine select the best colonizer. In this way, we isolated a 6.5-kb E. coli F-18 DNA sequence that simultaneously stimulated synthesis of type 1 fimbriae and enhanced E. coli F-18Col- colonizing ability. In the present investigation we show that the gene responsible for stimulation of type 1 fimbriae synthesis appears to be leuX, which encodes a tRNA specific for the rare leucine codon UUG. Moreover, it appears that expression of leuX may be regulated by two proteins (22 kDa and 26 kDa) encoded by genes immediately adjacent to leuX.

Piglet ileal mucus contains protein and glycolipid (galactosylceramide) receptors specific for Escherichia coli K88 fimbriae

The aim of this study was to characterize the Escherichia coli K88-specific receptors in mucus from the small intestines of 35-day-old piglets with the isogenic strains E. coli K-12(pMK005) (K88+) and E. coli K-12(pMK002) (K88-). These strains differed only in that the latter one cannot produce intact K88 fimbriae because of a deletion in the gene coding for the major fimbrial subunit. Adhesion was studied by incubating 3H-labeled bacteria with crude mucus, pronase-treated whole mucus, mucus fractionated by gel filtration, delipidated mucus, or extracted lipids immobilized in microtiter wells. In addition, E. coli strains were tested for adhesion to glycolipids extracted from mucus by overlaying glycolipid chromatograms with 125I-labeled bacteria. The recently reported finding that K88 fimbriae bind to glycoproteins in mucus from the piglet small intestine was confirmed in two ways. Pronase treatment of immobilized mucus reduced adhesion by 82%, and adhesion to delipidated mucus was 14 times greater for the K88+ than for the K88- strain. E. coli K88+ adhered to several of the fractions collected after gel filtration of crude mucus, including the void volume (M(r), > 250,000). Receptor activity specific for the K88 fimbriae was demonstrated in the lipids extracted from mucus, as the neutral lipids contained six times as much receptor activity as the acidic lipid fraction. Specificity was confirmed by demonstrating that adhesion to the total lipids could be inhibited by pretreatment of the immobilized lipids with K88 fimbriae. Relative to K-12 (K88-), the K-12 (K88+) bacterial cells bound more avidly to galactosylceramide when the neutral lipids were separated on thin-layer chromatography plates. No adhesion to lipids in the acidic fraction separated on thin-layer plates was detected. Relative to adhesion of K-12 (K88-), adhesion of K-12 (K88+) to commercially available galactosylceramide immobilized in microtiter wells confirmed the results with the thin-layer plates. It can be concluded that 35-day-old piglet mucus contains both protein and glycolipid receptors specific for K88 fimbriae, the latter being galactosylceramide.

Utilization of the mouse large intestine to select an Escherichia coli F-18 DNA sequence that enhances colonizing ability and stimulates synthesis of type 1 fimbriae

Escherichia coli F-18, a normal human fecal isolate, is an excellent colonizer of the streptomycin-treated mouse large intestine. E. coli F-18 Col-, a derivative of E. coli F-18 which no longer makes the E. coli F-18 colicin, colonizes the large intestine as well as E. coli F-18 when fed to mice alone but is eliminated when fed together with E. coli F-18. Random sequences of E. coli F-18 DNA were cloned into pRLB2, a par-B-stabilized derivative of pHC79. The entire gene library was transformed into E. coli F-18 Col- and fed to streptomycin-treated mice. The mouse large intestine selected a predominant clone which contained a recombinant plasmid (pRLB7) that enhanced E. coli F-18 Col- colonizing ability 100-fold but did not stimulate colicin synthesis. Moreover, pRLB7 simultaneously improved the survival of E. coli F-18 Col- in stationary phase in vitro, utilizing nutrients derived from mouse cecal mucus, and stimulated synthesis of both type 1 fimbriae and three E. coli F-18 Col- outer membrane proteins (74, 71, and 69 kDa). The 6.5-kb E. coli F-18 DNA sequence in pRLB7 does not contain either the fim operon or pilG (hns), both known to be involved in type 1 fimbrial synthesis. The sequence encodes six proteins, all smaller than the three E. coli F-18 Col- outer membrane proteins whose synthesis it stimulates. Collectively, the results suggest that the cloned E. coli F-18 DNA sequence contains one or more regulators of E. coli F-18 Col- operons expressed in the mouse large intestine in vivo and in isolated mouse cecal mucus in vitro.

A study of the adhesive capacity of Escherichia coli strain Bd 1107/7508 (K88ac) in relation to growth phase

It has previously been reported that the relative rate of synthesis of K88 fimbriae was influenced by the growth phase of Escherichia coli K88. Consequently, the effect of growth phase on the adhesive capacity of the K88 bearing cells of E. coli strain Bd 1107/7508 (K88ac) has now been investigated. The adhesion process was studied in terms of adhesion to and affinity for the immobilized piglet ileal mucus, the latter by applying Michaelis-Menten kinetics. The amount of K88 fimbriae per cell was determined by both the ELISA technique and by quantitative 1D-gel electrophoresis. The adhesion to, as well as the affinity for the mucus receptors was shown to be rather constant throughout growth. In agreement with these findings the cells collected at the different growth phases were found to be equally fimbriated. From these results it is concluded that, although the relative synthesis rate of K88 fimbriae varied during the growth cycle, the amount of K88 fimbriae expressed on the E. coli cell surface and the adhesive capacity of E. coli strain Bd 1107/7508 is largely constant throughout growth.

Escherichia coli F-18 phase locked 'on' for expression of type 1 fimbriae is a poor colonizer of the streptomycin-treated mouse large intestine

Escherichia coli F-18, a human fecal isolate, makes type 1 fimbriae in vitro and in the streptomycin-treated mouse large intestine in vivo, and is an excellent colonizer of the cecal mucus layer in the streptomycin-treated mouse large intestine. E. coli F-18(pPKL91) harbors an extra fimB gene on a parB stabilized pPBR322 plasmid and is therefore phase-locked 'on' such that all cells express type 1 fimbriae. E. coli F-18(pPR633) contains essentially the same plasmid minus the fimB gene and in L-broth about 30% of the cells express type 1 fimbriae. When fed alone to streptomycin-treated mice, E. coli F-18(pPKL91) colonized the large intestine at about 10(7) cfu/g of feces. However, when simultaneously fed with E. coli F-18(pPR633) at either high (10(10) cfu), or low doses (10(4) cfu), E. coli F-18(pPKL91) was a poor colonizer dropping to a level of between 10(2) and 10(3) cfu/g of feces. When given enough time to establish the state of colonization (10 days), E. coli F-18(pPKL91) persisted in feces in high numbers despite subsequent challenge by E. coli F-18(pPR633). Moreover, although both E. coli F-18(pPR633) and E. coli F-18(pPKL91) grew equally well in cecal mucus in vitro, E. coli F-18(pPR633) traveled through a layer of cecal mucus in vitro much faster than E. coli F-18(pPKL91). Together, the data suggest that type 1 fimbriated cells are at a disadvantage in initiating the colonization state because they have difficulty entering the mucus layer of the intestine as rapidly as non-fimbriated cells. The data also point to the possible biological significance of type 1 fimbrial phase-variation in the mouse large intestine.

Ribosomes exist in large excess over the apparent demand for protein synthesis during carbon starvation in marine Vibrio sp. strain CCUG 15956

Carbon starvation induces the development of a starvation- and stress-resistant cell state in marine Vibrio sp. strain S14 (CCUG 15956). The starved cells remain highly responsive to nutrients during prolonged starvation and exhibit instantaneous severalfold increases in the rates of protein synthesis and RNA synthesis when substrate is added. In order to elucidate the physiological basis for the survival of cells that are starved for a long time, as well as the capacity of these cells for rapid and efficient recovery, we analyzed the ribosome content of carbon-starved Vibrio sp. strain S14 cells. By using direct chemical measurements of the amounts of ribosomal particles in carbon-starved cultures, we demonstrated that ribosomes were lost relatively slowly (half life, 79 h) and that they existed in large excess over the apparent demand for protein synthesis. After 24 h of starvation the total rate of protein synthesis was 2.3% of the rate during growth, and after 3 days this rate was 0.7% of the rate during growth; the relative amounts of ribosomal particles at these times were 81 and 52%, respectively. The ribosome population consisted of 90% 70S monoribosomes, and no polyribosomes were detected in the starved cells. The 70S monoribosomes were responsible for the bulk of the protein synthesis during carbon starvation; some activity was also detected in the polyribosome size region on sucrose density gradients. We suggest that nongrowing carbon-starved Vibrio sp. strain S14 cells possess an excess protein synthesis capacity, which may be essential for their ability to immediately initiate an upshift program when substrate is added.

Phosphatidylserine found in intestinal mucus serves as a sole source of carbon and nitrogen for salmonellae and Escherichia coli

Salmonella choleraesuis (a pig pathogen), Salmonella typhimurium (a virulent strain in mice), and three strains of Escherichia coli (including a human enterohemorrhagic strain, a human urinary tract isolate, and a human fecal isolate) grew as well in vitro utilizing the lipids derived from mouse cecal mucus as the sole source of carbon and nitrogen as they did in mouse crude cecal mucus. Further analysis of the total lipid extracts of mucus dialysates showed that the acidic lipid fraction supported growth nearly as well as the total lipid fraction. Interestingly, among the many purified acidic lipids from mucus which were tested and analyzed, including several phospholipids, only phosphatidylserine was found to support the growth of all of these enteric bacteria, including Salmonella milwaukee, a human pathogen. The possible role of growth on pure phosphatidylserine in the pathogenesis of salmonellae is discussed.

Expression of Escherichia coli F-18 type 1 fimbriae in the streptomycin-treated mouse large intestine

Escherichia coli F-18, isolated from the feces of a healthy human, makes type 1 fimbriae and is an excellent colonizer of the streptomycin-treated mouse large intestine. Recently, it was shown that the inability to produce type 1 fimbriae had no effect on the ability of E. coli F-18 to colonize the streptomycin-treated mouse large intestine, suggesting the possibility that E. coli F-18 does not express type 1 fimbriae in vivo. However, we show here that E. coli F-18 does express type 1 fimbriae in mouse cecal mucus in vivo and, in fact, appears to express substantially more type 1 fimbriae in cecal mucus in vivo than in L broth in vitro.

Characterization and identification of a porcine small intestine mucus receptor for the K88ab fimbrial adhesin

The ability of Escherichia coli K-12(K88ab) to adhere to immobilized porcine small intestine mucus was examined. E. coli K-12(K88ab) but not the isogenic E. coli K-12 strain was found to adhere readily to immobilized crude mucus but not to bovine serum albumin. The adhesion of E. coli K-12(K88ab) was inhibited in a specific fashion by anti-K88 antiserum. Adhesion was also inhibited by pretreatment of receptor-containing crude mucus preparations with sodium metaperiodate or proteolytic enzymes. Removal of glycolipids from crude mucus by chloroform-methanol extraction did not affect the ability of E. coli K-12(K88ab) to bind to mucus preparations. Adsorption of crude mucus preparations with K88ab fimbriae but not type 1 fimbriae resulted in the removal of K88-specific receptors. Analysis of the pelleted fimbriae-receptor complex by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, together with gel filtration chromatography of crude mucus preparations, suggest that the K88-specific receptor present in porcine small intestine mucus is a 40- to 42-kDa glycoprotein.

Neuropeptide Y expression in the developing adrenal gland and in childhood neuroblastoma tumors

Neuropeptide Y (NPY) expression is limited to tissues of the central and peripheral nervous system. In the adrenal gland, NPY is found in a subset of cells of the adrenal medulla. Using in situ hybridization analysis, NPY mRNA expression was characterized during human fetal adrenal medullary development. We found a biphasic pattern of NPY mRNA expression during the development of the human adrenal medulla. NPY mRNA is detectable at the earliest evaluable time point (7.5 weeks of gestational age) through 18 weeks of gestational age, and is then not detectable until 8 months after birth. We also analyzed NPY mRNA expression in neuroblastoma tumors, which often arise in the adrenal medulla. Thirty-eight neuroblastoma tumors were analyzed for NPY mRNA expression using in situ hybridization. We found NPY mRNA expression in 30 of 38 tumors; 15 of 15 Stage IVS tumors from children under 1 year of age at diagnosis expressed NPY mRNA, whereas 0 of 4 Stage IV tumors from children less than 1 year of age at diagnosis expressed NPY mRNA. These data suggest that in children under 1 year of age at diagnosis, Stage IVS and Stage IV neuroblastoma may be marked by the presence or absence, respectively, of NPY mRNA expression. Moreover, since NPY is expressed for only a short period of time during embryogenesis, these tumors may arise from different neuroblast populations occurring during the course of adrenal medullary development.

Neither motility nor chemotaxis plays a role in the ability of Escherichia coli F-18 to colonize the streptomycin-treated mouse large intestine

Escherichia coli F-18, isolated from the feces of a healthy human in 1977, is an excellent colonizer of the streptomycin-treated mouse large intestine and displays normal motility and chemotaxis ability. A chemotaxis-defective derivative of E. coli F-18, E, coli F-18 CheA-, and a nonflagellated derivative, E. coli F-18 Fla-, were constructed. These strains were found to colonize the streptomycin-treated mouse large intestine as well as E. coli F-18 when mice were fed both E. coli F-18 and either the CheA- or Fla- derivative at high levels (10(10) CFU of each strain per mouse) or low levels (10(4) CFU of each strain per mouse). Furthermore, E. coli F-18 lost motility and chemotaxis ability when grown in colonic or cecal mucus in vitro despite retaining the ability to synthesize flagella. Thus, it appears that neither motility nor chemotaxis plays a role in the ability of E. coli F-18 to colonize because this strain becomes functionally nonmotile upon growth in the streptomycin-treated mouse large intestine.

Escherichia coli F-18 makes a streptomycin-treated mouse large intestine colonization factor when grown in nutrient broth containing glucose

Escherichia coli F-18 FimA-, a type 1 fimbria-less derivative of a normal human fecal isolate, E. coli F-18, has previously been shown to be as good a colonizer of streptomycin-treated mouse large intestine as its parent, suggesting that type 1 fimbriae are not necessary in this process. In this study it was found that when E. coli F-18 FimA- was grown standing overnight at 37 degrees C in nutrient broth, it remained uniformly suspended; however, when grown in nutrient broth containing 1% (wt/wt) D-glucose, it settled to the bottom of culture tubes. Settling was associated with the formation of clumps (microcolonies) of more than 10 cells each. The effect of glucose could be partially reversed by growing E. coli F-18 FimA- in nutrient broth containing 1% D-glucose supplemented with cyclic AMP (greater than or equal to 1 mM). A reduced-settling mutant of E. coli F-18 FimA-, E. coli F-18 FimA- Set-, selected after Tn5 mutagenesis, was found to be a poor colonizer of streptomycin-treated mouse large intestine when fed to mice simultaneously with the parent strain. These results suggest that glucose-induced settling is, at least in part, regulated in a way related to catabolite repression and that the ability of E. coli F-18 FimA- to form microcolonies plays an important role in its ability to colonize streptomycin-treated mouse large intestine.

Construction of stable cloning vectors that do not segregate from a human fecal Escherichia coli strain in the streptomycin-treated mouse large intestine

Escherichia coli F-18 Col- was previously shown to be a poor colonizer of the streptomycin-treated mouse large intestine, relative to its parent, E. coli F-18. Prior to attempting to clone genes responsible for the colonization phenotype of E. coli F-18 into E. coli F-18 Col-, a suitable cloning vector had to be found. In this investigation, we report that the commonly used cloning vectors pBR322, pHC79, and pBR329 all segregate from E. coli F-18 Col- both when grown in L broth under conditions of nonselection (i.e., in vitro) and when fed to streptomycin-treated mice (i.e., in vivo). Insertion of the cer region (which promotes resolution of replicating plasmids into monomeric forms) into pHC79 stabilized this plasmid in E. coli F-18 Col- in vitro and in vivo. In contrast, two independent cer insertions into pBR329 did not stabilize the plasmid completely in E. coli F-18 Col- in vitro, and feeding the strain to streptomycin-treated mice resulted in rapid segregation of the plasmids in vivo. Also, stability of all three plasmids in E. coli F-18 Col- in vitro was achieved by insertion of the parB region of plasmid R1, which encodes a cell-killing protein, Hok, that is active only postsegregationally. However, as with cer, complete in vitro and in vivo stabilization was achieved only in parB constructs of pBR322 and pHC79.

Human neuroblastoma tumor cell lines correspond to the arrested differentiation of chromaffin adrenal medullary neuroblasts

We have examined the hypothesis that nonhematopoietic malignancies may contain cells corresponding to those which occur during the differentiation of tissue precursors. Neuroblastoma, an embryonal tumor of the adrenal medulla, was studied because of its well described ability to differentiate both in vivo and in vitro. We examined the expression of four genes during development of the human adrenal medulla: tyrosine hydroxylase, chromagranin A, pG2, and beta-2-microglobulin. The sequential expression of these genes by adrenal neuroblasts marks successive stages during maturation of the chromaffin lineage. We also observed a population of neuroblasts during adrenal medullary development that did not express any of these four genes, suggestive of adrenal medullary cells differentiating along nonchromaffin lineage(s). We then evaluated 27 neuroblastoma cell lines for the expression of these genes and found that 24 expressed chromaffin markers, with 19 of these mimicking the pattern of gene expression found during development. Three cell lines did not express tyrosine hydroxylase, chromogranin A, or pG2, consistent with either a very undifferentiated neural crest cell or maturation along a nonchromaffin lineage. These data indicate that neuroblastoma tumor cells correspond to adrenal neuroblasts arrested during morphogenesis of the adrenal medulla and raise the possibility that malignant transformation of cells at different stages of tissue maturation may contribute to the diversity that characterizes tumors of solid tissues.

Reduced serum cholesterol with dietary change using fat-modified and oat bran supplemented diets

A low-fat, low-cholesterol diet and oat bran supplementation for treatment of hypercholesterolemia were studied for their effectiveness in lowering blood lipids and their impact on dietary intake. Seventy-one free-living men and women with hypercholesterolemia (serum cholesterol greater than 75th percentile) were randomly assigned to one of the following four groups: low-fat, low-cholesterol diet (LFLC); low-fat, low-cholesterol diet plus 50 gm/day oat bran (LFLC + OB); 50 gm/day oat bran supplemented diet (OB); or 42.5 gm/day processed oat bran (ready-to-eat cereal containing beta-glucan concentrated from oat bran) (POB). Subjects assigned to regimens OB and POB were requested to add the oat supplement without making additional changes in their diet. Serum cholesterol and high-density lipoprotein cholesterol analyses were performed at 4-week intervals, and diet records were assigned and analyzed. All groups experienced significant decreases in cholesterol from original levels (p less than .05). The average decrease in total serum cholesterol varied from 10% to 17%, with no significant differences among the four groups. High-density lipoprotein cholesterol concentrations decreased in all groups except group 4, in which there was a slight increase; however, no differences were found between groups. Energy, fat, and cholesterol intakes decreased in all groups, suggesting that displacement of higher fat foods from the diet may be one of the many mechanisms whereby oat supplements lower serum cholesterol. In addition, all groups reduced their intakes of calcium, copper, folic acid, and potassium from marginal levels at the beginning of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropeptide Y expression distinguishes malignant from benign pheochromocytoma

No reliable gross or microscopic features distinguish benign from malignant pheochromocytomas. The diagnosis of malignant pheochromocytoma is based solely on the presence of regional or distant metastases. This study evaluated the expression of neuropeptide Y messenger RNA (mRNA) in nine benign and 11 malignant pheochromocytomas and has found that neuropeptide Y mRNA was expressed in all nine benign tumors but in only four of 11 malignant tumors (P = .0084). These data suggest that the determination of neuropeptide Y expression in the evaluation of patients with pheochromocytoma may have prognostic significance.