A genomic screen of autism: evidence for a multilocus etiology

We have conducted a genome screen of autism, by linkage analysis in an initial set of 90 multiplex sibships, with parents, containing 97 independent affected sib pairs (ASPs), with follow-up in 49 additional multiplex sibships, containing 50 ASPs. In total, 519 markers were genotyped, including 362 for the initial screen, and an additional 157 were genotyped in the follow-up. As a control, we also included in the analysis unaffected sibs, which provided 51 discordant sib pairs (DSPs) for the initial screen and 29 for the follow-up. In the initial phase of the work, we observed increased identity by descent (IBD) in the ASPs (sharing of 51.6%) compared with the DSPs (sharing of 50.8%). The excess sharing in the ASPs could not be attributed to the effect of a small number of loci but, rather, was due to the modest increase in the entire distribution of IBD. These results are most compatible with a model specifying a large number of loci (perhaps >/=15) and are less compatible with models specifying </=10 loci. The largest LOD score obtained in the initial scan was for a marker on chromosome 1p; this region also showed positive sharing in the replication family set, giving a maximum multipoint LOD score of 2.15 for both sets combined. Thus, there may exist a gene of moderate effect in this region. We had only modestly positive or negative linkage evidence in candidate regions identified in other studies. Our results suggest that positional cloning of susceptibility loci by linkage analysis may be a formidable task and that other approaches may be necessary.

Selective trafficking of KNOTTED1 homeodomain protein and its mRNA through plasmodesmata

Plasmodesmata are intercellular organelles in plants that establish cytoplasmic continuity between neighboring cells. Microinjection studies showed that plasmodesmata facilitate the cell-to-cell transport of a plant-encoded transcription factor, KNOTTED1 (KN1). KN1 can also mediate the selective plasmodesmal trafficking of kn1 sense RNA. The emerging picture of plant development suggests that cell fate is determined at least in part by supracellular controls responding to cellular position as well as lineage. One of the mechanisms that enables the necessary intercellular communication appears to involve transfer of informational molecules (proteins and RNA) through plasmodesmata.

Bcl10 is a positive regulator of antigen receptor-induced activation of NF-kappaB and neural tube closure

Bcl10, a CARD-containing protein identified from the t(1;14)(p22;q32) breakpoint in MALT lymphomas, has been shown to induce apoptosis and activate NF-kappaB in vitro. We show that one-third of bcl10-/- embryos developed exencephaly, leading to embryonic lethality. Surprisingly, bcl10-/- cells retained susceptibility to various apoptotic stimuli in vivo and in vitro. However, surviving bcl10-/- mice were severely immunodeficient and bcl10-/- lymphocytes are defective in antigen receptor or PMA/Ionomycin-induced activation. Early tyrosine phosphorylation, MAPK and AP-1 activation, and Ca2+ signaling were normal in mutant lymphocytes, but antigen receptor-induced NF-kappaB activation was absent. Thus, Bcl10 functions as a positive regulator of lymphocyte proliferation that specifically connects antigen receptor signaling in B and T cells to NF-kappaB activation.

Neurotransmitters as early signals for central nervous system development

During brain ontogenesis, the temporal and spatial generation of the different types of neuronal and glial cells from precursors occurs as a sequence of successive progenitor stages whose proliferation, survival and cell-fate choice are controlled by environmental and cellular regulatory molecules. Neurotransmitters belong to the chemical microenvironment of neural cells, even at the earliest stages of brain development. It is now established that specific neurotransmitter receptors are present on progenitor cells of the developing central nervous system and could play, during neural development, a role that has remained unsuspected until recently. The present review focuses on the occurrence of neurotransmitters and their corresponding ligand-gated ion channel receptors in immature cells, including neural stem cells of specific embryonic and neonatal brain regions. We summarize in vitro and in vivo data arguing that neurotransmitters could regulate morphogenetic events such as proliferation, growth, migration, differentiation and survival of neural precursor cells. The understanding of neurotransmitter function during early neural maturation could lead to the development of pharmacological tools aimed at improving adult brain repair strategies.

Structure and function of Parkin E3 ubiquitin ligase reveals aspects of RING and HECT ligases

Parkin is a RING-between-RING E3 ligase that functions in the covalent attachment of ubiquitin to specific substrates, and mutations in Parkin are linked to Parkinson’s disease, cancer and mycobacterial infection. The RING-between-RING family of E3 ligases are suggested to function with a canonical RING domain and a catalytic cysteine residue usually restricted to HECT E3 ligases, thus termed ‘RING/HECT hybrid’ enzymes. Here we present the 1.58 Å structure of Parkin-R0RBR, revealing the fold architecture for the four RING domains, and several unpredicted interfaces. Examination of the Parkin active site suggests a catalytic network consisting of C431 and H433. In cells, mutation of C431 eliminates Parkin-catalysed degradation of mitochondria, and capture of an ubiquitin oxyester confirms C431 as Parkin’s cellular active site. Our data confirm that Parkin is a RING/HECT hybrid, and provide the first crystal structure of an RING-between-RING E3 ligase at atomic resolution, providing insight into this disease-related protein.

The Parkinson’s disease-associated protein Parkin regulates the fate of damaged mitochondria by ubiquitinating mitochondrial substrates. Riley et al. present the crystal structure of the Parkin-R0RBR domain, providing new insight into the catalytic mechanism of the enzyme.

The anti-epileptic drug levetiracetam reverses the inhibition by negative allosteric modulators of neuronal GABA- and glycine-gated currents

1. In this study in vitro and in vivo approaches were combined in order to investigate if the anti-epileptic mechanism(s) of action of levetiracetam (LEV; Keppra) may involve modulation of inhibitory neurotransmission. 2. GABA- and glycine-gated currents were studied in vitro using whole-cell patch-clamp techniques applied on cultured cerebellar granule, hippocampal and spinal neurons. Protection against clonic convulsions was assessed in vivo in sound-susceptible mice. The effect of LEV was compared with reference anti-epileptic drugs (AEDs): carbamazepine, phenytoin, valproate, clonazepam, phenobarbital and ethosuximide. 3. LEV contrasted the reference AEDs by an absence of any direct effect on glycine-gated currents. At high concentrations, beyond therapeutic relevance, it induced a small reduction in the peak amplitude and a prolongation of the decay phase of GABA-gated currents. A similar action on GABA-elicited currents was observed with the reference AEDs, except ethosuximide. 4. These minor direct effects contrasted with a potent ability of LEV (EC(50)=1 - 10 microM) to reverse the inhibitory effects of the negative allosteric modulators zinc and beta-carbolines on both GABA(A) and glycine receptor-mediated responses. 5. Clonazepam, phenobarbital and valproate showed a similar ability to reverse the inhibition of beta-carbolines on GABA-gated currents. Blockade of zinc inhibition of GABA responses was observed with clonazepam and ethosuximide. Phenytoin was the only AED together with LEV that inhibited the antagonism of zinc on glycine-gated currents and only clonazepam and phenobarbital inhibited the action of DMCM. 6. LEV (17 mg kg(-1)) produced a potent suppression of sound-induced clonic convulsions in mice. This protective effect was significantly abolished by co-administration of the beta-carboline FG 7142, from a dose of 5 mg kg(-1). In contrast, the benzodiazepine receptor antagonist flumazenil (up to 10 mg kg(-1)) was without any effect on the protection afforded by LEV. 7. The results of the present study suggest that a novel ability to oppose the action of negative modulators on the two main inhibitory ionotropic receptors may be of relevance for the anti-epileptic mechanism(s) of action of LEV.

Microbial genome analyses: comparative transport capabilities in eighteen prokaryotes

Here, we present a comprehensive analysis of solute transport systems encoded within the completely sequenced genomes of 18 prokaryotic organisms. These organisms include four Gram-positive bacteria, seven Gram-negative bacteria, two spirochetes, one cyanobacterium and four archaea. Membrane proteins are analyzed in terms of putative membrane topology, and the recognized transport systems are classified into 76 families, including four families of channel proteins, four families of primary carriers, 54 families of secondary carriers, six families of group translocators, and eight unclassified families. These families are analyzed in terms of the paralogous and orthologous relationships of their protein members, the substrate specificities of their constituent transporters and their distributions in each of the 18 organisms studied. The families vary from large superfamilies with hundreds of represented members, to small families with only one or a few members. The mode of transport generally correlates with the primary mechanism of energy generation, and the numbers of secondary transporters relative to primary transporters are roughly proportional to the total numbers of primary H(+) and Na(+) pumps in the cell. The phosphotransferase system is less prevalent in the analyzed bacteria than previously thought (only six of 14 bacteria transport sugars via this system) and is completely lacking in archaea and eukaryotes. Escherichia coli is shown to be exceptionally broad in its transport capabilities and therefore, at a membrane transport level, does not appear representative of the bacteria thus far sequenced. Archaea and spirochetes exhibit fewer proteins with multiple transmembrane segments and fewer net transporters than most bacteria. These results provide insight into the relevance of transport to the overall physiology of prokaryotes.

Temporal patterning of apical progenitors and their daughter neurons in the developing neocortex

During corticogenesis, distinct subtypes of neurons are sequentially born from ventricular zone progenitors. How these cells are molecularly temporally patterned is poorly understood. We used single-cell RNA sequencing at high temporal resolution to trace the lineage of the molecular identities of successive generations of apical progenitors (APs) and their daughter neurons in mouse embryos. We identified a core set of evolutionarily conserved, temporally patterned genes that drive APs from internally driven to more exteroceptive states. We found that the Polycomb repressor complex 2 (PRC2) epigenetically regulates AP temporal progression. Embryonic age-dependent AP molecular states are transmitted to their progeny as successive ground states, onto which essentially conserved early postmitotic differentiation programs are applied, and are complemented by later-occurring environment-dependent signals. Thus, epigenetically regulated temporal molecular birthmarks present in progenitors act in their postmitotic progeny to seed adult neuronal diversity.

Two classes of N-methyl-D-aspartate recognition sites: differential distribution and differential regulation by glycine

The N-methyl-D-aspartate (NMDA) receptor, a subtype of excitatory amino acid receptor, mediates synaptic responses in many regions of the central nervous system. This receptor plays a critical role in the mechanisms of both synaptic plasticity and excitotoxicity. Although these receptors were generally thought to be a single homogeneous receptor population, we report observations indicating that two anatomically distinct forms of the NMDA-receptor complex exist. (i) The distribution of NMDA receptors, as labeled by the NMDA agonist L-[3H]glutamate, differs from that obtained with the radiolabeled antagonist 3H-labeled 3-[(+/-)2-carboxypiperazine-4-yl]propyl-1-phosphonic acid [( 3H]CPP). Relative to L-[3H]glutamate, [3H]CPP binding is low in the striatum and septum and high in the thalamus and inner cerebral cortex. (ii) NMDA antagonists are relatively more potent than agonists at displacing L-[3H]glutamate binding in the thalamus and cerebral cortex; agonists are relatively more potent in the striatum and cerebellum. (iii) Glycine, which potentiates NMDA-receptor responses to glutamate, causes a greater percentage increase in L-[3H]glutamate binding to NMDA receptors in the thalamus and cerebral cortex than in the striatum, septum, and cerebellum. Radiolabeled NMDA-antagonist binding, in contrast, is inhibited by glycine. Thus, as observed for gamma-aminobutyric acid type A receptors, NMDA receptors have an agonist-preferring binding-site population and an antagonist-preferring binding site population. These may represent two distinct receptors and/or two interconverting forms. It could be of significant clinical importance if these two sites differ in their response to NMDA.

Cucumber mosaic virus 3a protein potentiates cell-to-cell trafficking of CMV RNA in tobacco plants

Contrary to a previous report, electron microscopic studies on the Fny strain of cucumber mosaic virus (CMV)-infected tobacco tissues revealed that plasmodesmata were not structurally modified during CMV infection, nor were virions ever observed in plasmodesmata connecting infected cells. To further explore the basis of CMV infection, experiments were performed on the CMV 3a ORF. The 3a protein of CMV was expressed in and purified from Escherichia coli. The purified protein was labeled with fluorescein isothiocyanate (FITC) and subsequently microinjected into mesophyll cells of mature leaves of Nicotiana tabacum cv. Turkish Samsun NN. Within a brief period (as little as 1 sec), the microinjected FITC-labeled CMV 3a protein moved into neighboring cells. Co-injection of unlabeled CMV 3a protein with 9.4-kDa fluorescein-conjugated dextran (F-dextran) resulted in extensive cell-to-cell movement (diffusion) of the F-dextran, indicating that the 3a protein can interact with and dilate plasmodesmata. Furthermore, co-injection of unlabeled 3a protein with fluorescently labeled infectious CMV RNA molecules resulted in rapid and extensive cell-to-cell transport. In contrast, a mutant form of the 3a protein was unable to traffic from cell to cell, to increase the size exclusion limit of plasmodesmata, or to potentiate cell-to-cell trafficking of CMV RNA molecules. Microinjection studies performed on transgenic tobacco plants expressing the CMV 3a protein indicated that fluorescently labeled CMV RNA moved out of the target cell into the surrounding mesophyll tissue. In addition, expression of the CMV 3a protein also potentiated the cell-to-cell movement of 9.4-kDa F-dextran. Collectively, these results provide direct experimental evidence that the CMV 3a protein functions as the movement protein of CMV. These findings are consistent with the hypothesis that CMV moves from cell-to-cell in the form of a ribonucleoprotein complex.

Parameters associated with persistent airflow obstruction in chronic severe asthma

The significance of severe airflow obstruction in severe asthma is unclear. The current study determined whether severe airflow obstruction is related to inflammatory or structural changes in the airways. Patients with severe asthma from a tertiary referral clinic were divided into two groups according to their postbronchodilator forced expiratory volume in one second (FEV1): severe persistent airflow limitation (FEV1 <50% predicted; group S; n=37) and no obstruction (FEV1 >80% pred; group N; n=29). Smoking history, atopic status, lung function tests, exhaled NO, blood eosinophil count, quality of life scores using St George's Respiratory Questionnaire and high resolution computed tomography (HRCT) of the lungs were assessed. Patients from group S were older and had longer disease duration. There was no difference in smoking history, atopic status, hospital admissions, quality of life scores and amount of treatment with inhaled or oral corticosteroids. Exhaled NO and peripheral blood eosinophils were higher in group S (21.0 +/- 2.4 versus 12.8 +/- 2.3 ppb; 0.41 +/- 0.06 versus 0.15 +/- 0.03 x 10(9) cells x L(-1) respectively). HRCT scores for bronchial wall thickening and dilatation were higher in group S with no differences in air trapping. Peripheral blood eosinophilia and bronchial wall thickening on HRCT scan were the only parameters significantly and independently associated with persistent airflow obstruction. Patients with severe asthma and irreversible airflow obstruction had longer disease duration, a greater inflammatory process and more high resolution computed tomography airway abnormalities suggestive of airway remodelling, despite being on similar treatments and experiencing equivalent impairment in quality of life.

Antagonistic signals between BMP4 and FGF8 define the expression of Pitx1 and Pitx2 in mouse tooth-forming anlage

Members of the Pitx/RIEG family of homeodomain-containing transcription factors have been implicated in vertebrate organogenesis. In this study, we examined the expression and regulation of Pitx1 and Pitx2 during mouse tooth development. Pitx1 expression is detected in early development in a widespread pattern, in both epithelium and mesenchyme, covering the tooth-forming region in the mandible, and is then maintained in the dental epithelium from the bud stage to the late bell stage. Pitx2 expression, on the other hand, is restricted to the dental epithelium throughout odontogenesis. Interestingly, from E9.5 to E10.5, the expression domains of Pitx1 and Pitx2, in the developing mandible, overlap with that of Fgf8 but are exclusive to the zone of Bmp4 expression. Bead implantation experiments demonstrate that ectopic expression of Fgf8 can induce/maintain the expression of both Pitx1 and Pitx2 at E9.5. In contrast, Bmp4-expressing tissues and BMP4-soaked beads were able to repress Pitx1 expression in mandibular mesenchyme and Pitx2 expression in the presumptive dental epithelium, respectively. However, the effects of FGF8 and BMP4 are transient. It thus appears that the early expression patterns of Pitx1 and Pitx2 in the developing mandible are regulated by the antagonistic effects of FGF8 and BMP4 such that the Pitx1 and Pitx2 expression patterns are defined. These results indicate that the epithelial-derived signaling molecules are responsible not only for restricting specific gene expression in the dental mesenchyme, but also for defining gene expression in the dental epithelium.

Association of the multisubstrate docking protein Gab1 with the hepatocyte growth factor receptor requires a functional Grb2 binding site involving tyrosine 1356

Hepatocyte growth factor/scatter factor is a multifunctional factor that induces mitogenesis, motility, invasion, and branching tubulogenesis of several epithelial and endothelial cell lines in culture. The receptor for hepatocyte growth factor has been identified as the Met-tyrosine kinase. Upon stimulation with hepatocyte growth factor, the Met beta subunit becomes highly phosphorylated on tyrosine residues, one of which, tyrosine 1356 within the carboxyl terminus, is crucial for dissociation, motility, and branching tubule formation in Madin-Darby canine kidney epithelial cells. Tyrosine 1356 forms a multisubstrate binding site for the Grb2 and Shc adaptor proteins, the p85 subunit of phosphatidylinositol 3'-kinase, phospholipase Cgamma, and a phosphatase, SHP2. To investigate additional signaling molecules that are activated by the Met receptor, we have identified hepatocyte growth factor-induced phosphoproteins in tubular epithelial cells. We have established that proteins of 100-130 kDa are highly phosphorylated following stimulation of epithelial cells and that one of these is the Grb2-associated binding protein Gab1, a possible insulin receptor substrate-1-like signal transducer. We show that Gab1 is the major substrate for the Met kinase in vitro and in vivo. Association of Gab1 with Met requires a functional Grb2 binding site involving tyrosine 1356 and to a lesser extent tyrosine 1349. Met receptor mutants that fail to induce branching tubulogenesis are impaired in their ability to interact with Gab1, suggesting that Gab1 may play a role in these processes.

Clinical-histological associations in gastroparesis: results from the Gastroparesis Clinical Research Consortium

BACKGROUND

Cellular changes associated with diabetic (DG) and idiopathic gastroparesis (IG) have recently been described from patients enrolled in the Gastroparesis Clinical Research Consortium. The association of these cellular changes with gastroparesis symptoms and gastric emptying is unknown. The aim of this study was to relate cellular changes to symptoms and gastric emptying in patients with gastroparesis.

METHODS

Earlier, using full thickness gastric body biopsies from 20 DG, 20 IG, and 20 matched controls, we found decreased interstitial cells of Cajal (ICC) and enteric nerves and an increase in immune cells in both DG and IG. Here, demographic, symptoms [gastroparesis cardinal symptom index score (GCSI)], and gastric emptying were related to cellular alterations using Pearson's correlation coefficients.

KEY RESULTS

Interstitial cells of Cajal counts inversely correlated with 4 h gastric retention in DG but not in IG (r = -0.6, P = 0.008, DG, r = 0.2, P = 0.4, IG). There was also a significant correlation between loss of ICC and enteric nerves in DG but not in IG (r = 0.5, P = 0.03 for DG, r = 0.3, P = 0.16, IG). Idiopathic gastroparesis with a myenteric immune infiltrate scored higher on the average GCSI (3.6 ± 0.7 vs 2.7 ± 0.9, P = 0.05) and nausea score (3.8 ± 0.9 vs 2.6 ± 1.0, P = 0.02) as compared to those without an infiltrate.

CONCLUSIONS & INFERENCES

In DG, loss of ICC is associated with delayed gastric emptying. Interstitial cells of Cajal or enteric nerve loss did not correlate with symptom severity. Overall clinical severity and nausea in IG is associated with a myenteric immune infiltrate. Thus, full thickness gastric biopsies can help define specific cellular abnormalities in gastroparesis, some of which are associated with physiological and clinical characteristics of gastroparesis.

Vitamin D induces innate antibacterial responses in human trophoblasts via an intracrine pathway

The active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)(2)D), is a potent inducer of the antimicrobial protein cathelicidin, CAMP (LL37). In macrophages this response is dependent on intracrine synthesis of 1,25(OH)(2)D from precursor 25-hydroxyvitamin D (25OHD), catalyzed by the enzyme 25-hydroxyvitamin D-1alpha-hydroxylase (CYP27B1). In view of the fact that trophoblastic cells also express abundant CYP27B1, we postulated a similar intracrine pathway for induction of CAMP in the placenta. Analysis of placenta explants, primary cultures of human trophoblast, and the 3A trophoblastic cell line treated with 1,25(OH)(2)D (1-100 nM) revealed dose-dependent induction of CAMP similar to that observed with primary cultures of human macrophages. Also consistent with macrophages, induction of trophoblastic CAMP was enhanced via intracrine conversion of 25OHD to 1,25(OH)(2)D. However, in contrast to macrophages, induction of CAMP by vitamin D in trophoblasts was not enhanced by costimulation with Toll-like receptor ligands, such as lipopolysaccharide. Despite this, exposure to vitamin D metabolites significantly enhanced antibacterial responses in trophoblastic cells: 3A cells infected with Escherichia coli showed decreased numbers of bacterial colony-forming units compared with vehicle-treated controls when treated with 25OHD (49.6% +/- 10.9%) or 1,25(OH)(2)D (45.4% +/- 9.2%), both P < 0.001. Treatment with 25OHD (1-100 nM) or 1,25(OH)(2)D (0.1-10 nM) also protected 3A cells against cell death following infection with E. coli (13.6%-26.9% and 22.3%-40.2% protection, respectively). These observations indicate that 1,25(OH)(2)D can function as an intracrine regulator of CAMP in trophoblasts, and may thus provide a novel mechanism for activation of innate immune responses in the placenta.

Large-scale analysis of the Alu Ya5 and Yb8 subfamilies and their contribution to human genomic diversity

We have utilized computational biology to screen GenBank for the presence of recently integrated Ya5 and Yb8 Alu family members. Our analysis identified 2640 Ya5 Alu family members and 1852 Yb8 Alu family members from the draft sequence of the human genome. We selected a set of 475 of these elements for detailed analyses. Analysis of the DNA sequences from the individual Alu elements revealed a low level of random mutations within both subfamilies consistent with the recent origin of these elements within the human genome. Polymerase chain reaction assays were used to determine the phylogenetic distribution and human genomic variation associated with each Alu repeat. Over 99 % of the Ya5 and Yb8 Alu family members were restricted to the human genome and absent from orthologous positions within the genomes of several non-human primates, confirming the recent origin of these Alu subfamilies in the human genome. Approximately 1 % of the analyzed Ya5 and Yb8 Alu family members had integrated into previously undefined repeated regions of the human genome. Analysis of mosaic Yb8 elements suggests gene conversion played an important role in generating sequence diversity among these elements. Of the 475 evaluated elements, a total of 106 of the Ya5 and Yb8 Alu family members were polymorphic for insertion presence/absence within the genomes of a diverse array of human populations. The newly identified Alu insertion polymorphisms will be useful tools for the study of human genomic diversity.

I.V. busulfan in pediatrics: a novel dosing to improve safety/efficacy for hematopoietic progenitor cell transplantation recipients

A retrospective population pharmacokinetic (PPK) analysis was performed in 24 pediatric patients (PEDS) (0.45-16.7 years old) receiving i.v. busulfan/cyclophosphamide (i.v. Bu/Cy 4) regimen prior to allogeneic hematopoietic stem cell transplantation. I.V. Bu doses were given as a 2-hour infusion every 6 h over 4 days. Initial dosing of i.v. Bu was 1 mg/kg for children < or =4 years old and 0.8 mg/kg for patients >4 years old. Bu plasma concentrations at doses 1, 9 and 13 were analyzed through a multivariate NONMEM analysis. A close log-linear relationship between body weight (BW) and i.v. Bu clearance was demonstrated with no further age-dependency or gender effect. The interpatient coefficient of variation (CV) in Bu clearance significantly decreased from 56% (covariate-free model) to 19% (BW covariate model) and reproducible i.v. Bu exposure between doses was illustrated (intraindividual CV=9%). Based on the PPK model, a novel Bu dosing regimen (ie: doses in mg/kg adjusted to discrete weight categories) for a better AUC targeting was developed by simulation on 1000 patients. Age-based dosing was demonstrated not to be clinically relevant with i.v. Bu. Use of the new BW-based dosing appears to be more appropriate for the PEDS.

Outbreak of nosocomial urinary tract infections due to Pseudomonas aeruginosa in a paediatric surgical unit associated with tap-water contamination

An outbreak of 14 cases of urinary tract infections by Pseudomonas aeruginosa, including six symptomatic infections, occurred from September to November 1994 in a paediatric surgical unit. During the outbreak, urine samples from patients and multiple samples from the environment of patients were tested for the presence of P. aeruginosa. Bacterial isolates were studied by pulsed-field gel electrophoresis. Genotypic analysis showed that most of the isolates from children were different. Multiple P. aeruginosa isolates were also found in the tap water, as the only putative source of contamination. Two of these isolates were identified in two infected patients, indicating possible direct contamination of patients via tap water and this was related to the distal colonization of faucets. Bacteria were eradicated from tap water by replacement of taps. The cluster of cases of P. aeruginosa urinary infection was, therefore, related to multiple contaminations through tap water. These results illustrate an unexpected risk of nosocomial infection and emphasizes the importance of checking tap water to prevent bacterial contamination through handwashing in contaminated water.

Efficient cellular transformation by the Met oncoprotein requires a functional Grb2 binding site and correlates with phosphorylation of the Grb2-associated proteins, Cbl and Gab1

The Tpr-Met oncoprotein consists of the catalytic kinase domain of the hepatocyte growth factor/scatter factor receptor tyrosine kinase (Met) fused downstream from sequences encoded by the tpr gene. Tpr-Met is a member of a family of tyrosine kinase oncoproteins generated following genomic rearrangement and has constitutive kinase activity. We have previously demonstrated that a single carboxyl-terminal tyrosine residue, Tyr489, is essential for efficient transformation of Fr3T3 fibroblasts by Tpr-Met and forms a multisubstrate binding site for Grb2, phosphatidylinositol 3' kinase, phospholipase Cgamma, SHP2, and an unknown protein of 110 kDa. A mutant Tpr-Met protein that selectively fails to bind Grb2 has reduced transforming activity, implicating pathways downstream of Grb2 in Tpr-Met mediated cell transformation. We show here that the 110-kDa Tpr-Met substrate corresponds to the recently identified Grb2-associated protein, Gab1. Moreover, we show that tyrosine phosphorylation of the Cbl protooncogene product as well as Gab1 required Tyr489 and correlated with the ability of Tpr-Met to associate with Grb2 and to transform cells, providing evidence that pathways downstream of Gab1 and/or Cbl may play a role in Tpr-Met-mediated cell transformation.

Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function

Alpha-hydroxy acids are effective agents for the treatment of skin xerosis and it is known that, following treatment with lotions containing D,L-lactic acid, the stratum corneum prevents xerosis more effectively. To date, the relative efficacy of the different isomers of lactic acid has not been evaluated and the mode of action of lactic acid in improving stratum corneum resilience is not known. The objective of the present studies was to determine the effects of lactic acid isomers on keratinocyte ceramide biosynthesis, stratum corneum barrier function and the resistance of the stratum corneum to the appearance of skin xerosis. In vitro, lactic acid enhanced the production of ceramides by keratinocytes. L-Lactic acid was more effective than the D isomer (300% increase vs 100% increase). Carbon label from lactic acid was incorporated into all keratinocyte lipid species and a greater incorporation of label into ceramides was achieved with L-lactate than with D-lactate. In vivo, lactic acid increased the levels of stratum corneum ceramides. Whereas, lotions containing L-lactic acid resulted in the greatest increase (48% increase) followed by D,L-lactic acid (25% increase), D-lactic acid had no effect on stratum corneum ceramide levels. The increases in stratum corneum ceramide levels following lactic acid treatment also led to improvements in stratum corneum barrier function, measured by transepidermal water loss following a challenge to the skin with SLS and in the regression phase of a moisturization efficacy study. Significant improvements in barrier function and resistance to the appearance of skin xerosis were observed following L-lactic acid and D,L-lactic acid, but not following D-lactic acid treatment. From these results we believe that lactic acid, particularly the L isomer, stimulates ceramide biosynthesis leading to increased stratum corneum ceramide levels which results in superior lipid barrier and a more effective resistance against xerosis.

Factors related to abdominal pain in gastroparesis: contrast to patients with predominant nausea and vomiting

BACKGROUND

Factors associated with abdominal pain in gastroparesis are incompletely evaluated and comparisons of pain vs other symptoms are limited. This study related pain to clinical factors in gastroparesis and contrasted pain/discomfort- with nausea/vomiting-predominant disease.

METHODS

Clinical and scintigraphy data were compared in 393 patients from seven centers of the NIDDK Gastroparesis Clinical Research Consortium with moderate-severe (Patient Assessment of Upper Gastrointestinal Disorders Symptoms [PAGI-SYM] score ≥ 3) vs none-mild (PAGI-SYM < 3) upper abdominal pain and predominant pain/discomfort vs nausea/vomiting.

KEY RESULTS

Upper abdominal pain was moderate-severe in 261 (66%). Pain/discomfort was predominant in 81 (21%); nausea/vomiting was predominant in 172 (44%). Moderate-severe pain was more prevalent with idiopathic gastroparesis and with lack of infectious prodrome (P ≤ 0.05) and correlated with scores for nausea/vomiting, bloating, lower abdominal pain/discomfort, bowel disturbances, and opiate and antiemetic use (P < 0.05), but not gastric emptying or diabetic neuropathy or control. Gastroparesis severity, quality of life, and depression and anxiety were worse with moderate-severe pain (P ≤ 0.008). Factors associated with moderate-severe pain were similar in diabetic and idiopathic gastroparesis. Compared to predominant nausea/vomiting, predominant pain/discomfort was associated with impaired quality of life, greater opiate, and less antiemetic use (P < 0.01), but similar severity and gastric retention.

CONCLUSIONS & INFERENCES

Moderate-severe abdominal pain is prevalent in gastroparesis, impairs quality of life, and is associated with idiopathic etiology, lack of infectious prodrome, and opiate use. Pain is predominant in one fifth of gastroparetics. Predominant pain has at least as great an impact on disease severity and quality of life as predominant nausea/vomiting.

ClpE, a novel member of the HSP100 family, is involved in cell division and virulence of Listeria monocytogenes

We identified, in the facultative intracellular pathogen Listeria monocytogenes, a previously unknown Clp ATPase, unique among the HSP100 proteins because of the presence of a short N-terminal region with a potential zinc finger motif. This protein of 726 amino acids is highly homologous to ClpE of Bacillus subtilis, and is a member of a new subfamily of HSP100/Clp ATPases. The clpE gene is transcribed as a monocistronic mRNA from a typical consensus sigma A promoter. clpE is not stimulated by various stresses, but is upregulated in a clpC mutant. This is the first example of cross-regulation between Clp ATPases. By constructing a clpE mutant of L. monocytogenes, we found that ClpE is required for prolonged survival at 42 degrees C and is involved in the virulence of this pathogen. A double mutant deficient in both ClpE and ClpC was avirulent in a mouse model and completely eliminated in the liver. Electron microscopy studies did not show any morphological alterations in clpE or clpC mutants. In the clpE-clpC double mutant, however, cell division was affected, indicating that ClpE acts synergistically with ClpC in cell septation. These results show that the Clp chaperones play a crucial role in both cell division and virulence of L. monocytogenes.

Renal vein thrombosis: a 10-year review

PURPOSE

Renal vein thrombosis (RVT) is a rare cause for pediatric surgical consultation. The purpose of this study is to review the Montreal experience in the 1990s with RVT.

METHODS

A retrospective chart review was conducted from 1990 through 1999.

RESULTS

Twenty-three cases were identified by Duplex ultrasound scan. Mean length of follow-up was 42 months. Eighty-three percent (83%) of cases were diagnosed within the first month of life. In utero thrombosis was suspected in 22% and was associated with caval thrombosis and factor V Leiden. Known risk factors were present in 87%. The "diagnostic triad" of flank mass, gross hematuria, and thrombocytopenia was present in only 13% at the time of diagnosis. Long-term renal function impairment was detected in 100% of those who did not receive heparin, and in 33% of those who did receive heparin. No patient required dialysis. One patient required nephrectomy for recurrent pyelonephritis.

CONCLUSIONS

RVT occurs more commonly than anticipated. Because the "classic" triad of signs usually is absent at presentation, the presence of either a flank mass, hematuria, or thrombocytopenia in a patient with risk factors should prompt investigation for RVT. Factor V Leiden is a risk factor for in utero RVT. Anticoagulation improves renal outcome. Patients with RVT require long-term follow-up.

Prospective validation of a novel IV busulfan fixed dosing for paediatric patients to improve therapeutic AUC targeting without drug monitoring

INTRODUCTION

Oral busulfan clearance is age-dependent and children experience a wide variability in plasma exposure. BSA- or age-based dosing is used with therapeutic drug monitoring (TDM) to reduce this variability.

PURPOSE

A new intravenous (IV) dosing of busulfan (Bu) based on body weight, designed to improve AUC targeting without TDM and dose-adjustment, was prospectively evaluated.

METHOD

Bu was administered as a 2 h IV infusion every 6 h over 4 days (16 administrations). Five dose levels were defined on body weight as follows: 1.0 mg/kg for <9 kg; 1.2 mg/kg for 9 to <16 kg; 1.1 mg/kg for 16-23 kg; 0.95 mg/kg for >23-34 kg; 0.80 mg/kg for >34 kg. Bu treatment was followed by Cyclophosphamide or Melphalan prior to allogeneic or autologous transplantation in 55 children aged 0.3-17.2 years (median 5.6 years).

RESULTS

No difference in AUC values was observed between weight strata (mean +/- SD 1248 +/- 205 micromol.min), whereas a significant difference in Bu clearance was demonstrated. This new dosing enabled to achieve a mean exposure comparable to that in adults. At dose 1, 91% of patients achieved the targeted AUC range (900-1500 micromol.min) while no patients were underexposed. At doses 9 and 13, over 75% of patients remained within that target whilst most of the others were slightly above. Successful engraftment was achieved in all patients. In conclusion, from infants to adults this new dosing enabled, without TDM and dose adjustment, to successfully target a therapeutic AUC window.