Spatially multiplexed single-molecule translocations through a nanopore at controlled speeds

In current nanopore-based label-free single-molecule sensing technologies, stochastic processes influence the selection of translocating molecule, translocation rate and translocation velocity. As a result, single-molecule translocations are challenging to control both spatially and temporally. Here we present a method using a glass nanopore mounted on a three-dimensional nanopositioner to spatially select molecules, deterministically tethered on a glass surface, for controlled translocations. By controlling the distance between the nanopore and glass surface, we can actively select the region of interest on the molecule and scan it a controlled number of times and at a controlled velocity. Decreasing the velocity and averaging thousands of consecutive readings of the same molecule increases the signal-to-noise ratio by two orders of magnitude compared with free translocations. We demonstrate the method's versatility by assessing DNA-protein complexes, DNA rulers and DNA gaps, achieving down to single-nucleotide gap detection.

Lgr4 and Lgr5 drive the formation of long actin-rich cytoneme-like membrane protrusions

Embryonic development and adult tissue homeostasis require precise information exchange between cells and their microenvironment to coordinate cell behavior. A specialized class of ultra-long actin-rich filopodia, termed cytonemes, provides one mechanism for this spatiotemporal regulation of extracellular cues. We provide here a mechanism whereby the stem-cell marker Lgr5, and its family member Lgr4, promote the formation of cytonemes. Lgr4- and Lgr5-induced cytonemes exceed lengths of 80 µm, are generated through stabilization of nascent filopodia from an underlying lamellipodial-like network and functionally provide a pipeline for the transit of signaling effectors. As proof-of-principle, we demonstrate that Lgr5-induced cytonemes act as conduits for cell signaling by demonstrating that the actin motor and filopodial cargo carrier protein myosin X (Myo10) and the G-protein-coupled receptor (GPCR) signaling effector β-arrestin-2 (Arrb2) transit into cytonemes. This work delineates a biological function for Lgr4 and Lgr5 and provides the rationale to fully investigate Lgr4 and Lgr5 function and cytonemes in mammalian stem cell and cancer stem cell behavior.

Dopamine D2 receptor relies upon PPM/PP2C protein phosphatases to dephosphorylate huntingtin protein

Striatal dopamine D2 receptor (D2R) relies upon G protein- and β-arrestin-dependent signaling pathways to convey its action on motor control and behavior. Considering that D2R activation inhibits Akt in the striatum and that huntingtin physiological functions are affected by Akt phosphorylation, we sought to investigate whether D2R-mediated signaling could regulate huntingtin phosphorylation. We demonstrate that D2R activation decreases huntingtin phosphorylation on its Akt site. This dephosphorylation event depends upon the Gαi-dependent engagement of specific members of the protein phosphatase metallo-dependent (PPM/PP2C) family and is independent of β-arrestin 2. These observations identify the PPM/PP2C family as a mediator of G protein-coupled receptor signaling and thereby suggest a novel mechanism of dopaminergic signaling.

Expression of Npc1 in glial cells corrects sterility in Npc1(-/-) mice

Niemann-Pick type C1 (NPC) disease is an autosomal recessive neurodegenerative disorder. One feature of the mouse model of NPC1 is it's infertility. We have made transgenic mice which express the Npc1 protein exclusively in fibrillary astrocytes, using the glial fibrillary acidic protein (GFAP) promoter. This selective expression of Npc1 corrects sterility in GFAP-Npc1(-/-), Npc1(-/-) mice. Counts of acidophils in the pituitary of GFAP-Npc1E, Npc1(-/-) mice, as compared Npc1(-/-) mice, and measurements of dopamine D2 receptor (DRD2) mRNA in the pituitary, suggest mechanisms for fertility enhancement. We conclude that the correction of sterility in GFAP-Npc1E, Npc1(-/-) mice is a result of restoring hypothalamic control of the pituitary.

A beta-arrestin 2 signaling complex mediates lithium action on behavior

Besides their role in desensitization, beta-arrestin 1 and 2 promote the formation of signaling complexes allowing G protein-coupled receptors (GPCR) to signal independently from G proteins. Here we show that lithium, a pharmacological agent used for the management of psychiatric disorders such as bipolar disorder, schizophrenia, and depression, regulates Akt/glycogen synthase kinase 3 (GSK3) signaling and related behaviors in mice by disrupting a signaling complex composed of Akt, beta-arrestin 2, and protein phosphatase 2A. When administered to beta-arrestin 2 knockout mice, lithium fails to affect Akt/GSK3 signaling and induce behavioral changes associated with GSK3 inhibition as it does in normal animals. These results point toward a pharmacological approach to modulating GPCR function that affects the formation of beta-arrestin-mediated signaling complexes.

Structure and content of the Entamoeba histolytica genome

The intestinal parasite Entamoeba histolytica is one of the first protists for which a draft genome sequence has been published. Although the genome is still incomplete, it is unlikely that many genes are missing from the list of those already identified. In this chapter we summarise the features of the genome as they are currently understood and provide previously unpublished analyses of many of the genes.

Discrepancies between self-report and objective measures for stimulant drug use in HIV: cognitive, medication adherence and psychological correlates

While it has long been recognized that self-reported drug use may be at variance with objectively obtained evidence such as urine toxicology assays, few studies have explored the behavioral correlates of such discrepancies. Here we compared self-reported and objective measures of stimulant drug use for 162 HIV infected individuals and identified a sub-group with discrepancies between data obtained via the two methods. Results showed poorer neurocognitive performance (attention, learning/memory) and lower medication adherence rates for the discrepant group as compared to those who either acknowledged their drug use or accurately denied recent stimulant use. Using the Millon Clinical Multiaxial Inventory-III, it was also found that those in the discrepant group were more hesitant to reveal psychopathology. Comparisons of self-reported and objectively measured medication adherence data are also discussed.

N-terminal tyrosine modulation of the endocytic adaptor function of the beta-arrestins

The highly homologous beta-arrestin1 and -2 adaptor proteins play important roles in the function of G protein-coupled receptors. Either beta-arrestin variant can function as a molecular chaperone for clathrin-mediated receptor internalization. This role depends primarily upon two distinct, contiguous C-terminal beta-arrestin motifs recognizing clathrin and the beta-adaptin subunit of AP2. However, a molecular basis is lacking to explain the different endocytic efficacies of the two beta-arrestin isoforms and the observation that beta-arrestin N-terminal substitution mutants can act as dominant negative inhibitors of receptor endocytosis. Despite the near identity of the beta-arrestins throughout their N termini, sequence variability is present at a small number of residues and includes tyrosine to phenylalanine substitutions. Here we show that corresponding N-terminal (Y/F)VTL sequences in beta-arrestin1 and -2 differentially regulate mu-adaptin binding. Our results indicate that the beta-arrestin1 Tyr-54 lessens the interaction with mu-adaptin and moreover is a Src phosphorylation site. A gain of endocytic function is obtained with the beta-arrestin1 Y54F substitution, which improves both the beta-arrestin1 interaction with mu-adaptin and the ability to enhance beta2-adrenergic receptor internalization. These data indicate that beta-arrestin2 utilizes mu-adaptin as an endocytic partner, and that the inability of beta-arrestin1 to sustain a similar degree of interaction with mu-adaptin may result from coordination of Tyr-54 by neighboring residues or its modification by Src kinase. Additionally, these naturally occurring variations in beta-arrestins may also differentially regulate the composition of the signaling complexes organized on the receptor.

Signaling through the phosphatidylinositol 3-kinase regulates mechanotaxis induced by local low magnetic forces in Entamoeba histolytica

In micro-organisms, as well as in metazoan cells, cellular polarization and directed migration are finely regulated by external stimuli, including mechanical stresses. The mechanisms sustaining the transduction of such external stresses into intracellular biochemical signals remain mainly unknown. Using an external magnetic tip, we generated a magnetic field gradient that allows migration analysis of cells submitted to local low-intensity magnetic forces (50 pN). We applied our system to the amoeba Entamoeba histolytica. Indeed, motility and chemotaxis are key activities that allow this parasite to invade and destroy the human tissues during amoebiasis. The magnetic force was applied either inside the cytoplasm or externally at the rear pole of the amoeba. We observed that the application of an intracellular force did not affect cell polarization and migration, whereas the application of the force at the rear pole of the cell induced a persistent polarization and strongly directional motion, almost directly opposed to the magnetic force. This phenomenon was completely abolished when phosphatidylinositol 3-kinase activity was inhibited by wortmanin. This result demonstrated that the applied mechanical stimulus was transduced and amplified into an intracellular biochemical signal, a process that allows such low-intensity force to strongly modify the migration behavior of the cell.

A rat homologue of CED-6 is expressed in neurons and interacts with clathrin

We isolated from a brain library a cDNA encoding an isoform of rat CED-6 that has not been previously described. This transcript results from alternative splicing of the ced-6 gene present on chromosome 9. We expressed this isoform as his-tagged protein in E. coli and used the purified protein to raise antibodies to investigate the expression of CED-6 in rat brain. Immunoblot analysis showed the presence of CED-6 as a doublet of approximately 34 and 33 kDa in cortex, hippocampus and cerebellum, indicating that the protein was present in different regions of the brain. Subcellular fractionation experiments showed that CED-6 immunoreactivity did not concentrate in GFAP-containing glial vesicles, whereas it showed a distribution similar to the synaptotagmin in synaptosomes-enriched fractions, suggesting that CED-6 is present in neurons. CED-6 immunoreactivity was also investigated using immunohistochemistry analysis and it was found in several brain regions, being particularly strong in the cell body of some groups of neurons such as Purkinje cell layer of cerebellum, and pyramidal cells of the hippocampal formation and also in epithelial cells from the choroid plexus. Importantly, CED-6 immunoreactivity colocalized with a neuronal marker but not with a glial marker. Considering that several PTB-containing proteins bind clathrin, we investigated whether rat CED-6 would also have this property. Yeast two-hybrid and GST pull-down analysis indicated that ratCED-6 interacts with clathrin and in cultured cells we detected colocalization between CED-6 and clathrin-coated vesicles. The present findings suggest that CED-6 may have a role in endocytic trafficking or signaling in neurons.

G protein-coupled receptor kinase 2 and beta-arrestins are recruited to FSH receptor in stimulated rat primary Sertoli cells

FSH-receptor (FSH-R) signaling is regulated by agonist-induced desensitization and internalization. It has been shown, in a variety of overexpression systems, that G protein-coupled receptor kinases (GRKs) phosphorylate the activated FSH-R, promote beta-arrestin recruitment and ultimately lead to internalization. The accuracy of this mechanism has not yet been demonstrated in cells expressing these different molecules at physiological levels. Using sucrose gradient fractionation, we show that FSH induces the recruitment of the endogenous GRK 2 and beta-arrestin 1/2 from the cytoplasm to the plasma membrane of rat primary Sertoli cells. As assessed by ligand binding, the FSH-R was found expressed in the fractions where GRK 2 and beta-arrestins were recruited upon FSH treatment. In addition, the endogenous beta-arrestin 1 was found dephosphorylated in an agonist-dependent manner. Finally, a significant FSH-binding activity was co-immunoprecipitated with the endogenous beta-arrestins from agonist-stimulated but not from untreated Sertoli cell extracts. This FSH-R interaction with beta-arrestins was sustained for up to 30 min. In conclusion, our data strongly suggest that the GRK/beta-arrestin machinery plays a physiologically relevant role in the regulation of the FSH signaling.

Predicting historical dust and wood dust exposure in sawmills: model development and validation

Nonspecific dust measurements are used as a surrogate for wood dust exposure in sawmills. However, the wood dust component of dust has been found to vary by job and work area. Thus, the use of nonspecific dust exposure levels in epidemiologic studies may introduce exposure misclassification when assessing wood-related health effects. To improve exposure assessment in a retrospective cohort of 28,000 sawmill workers, we developed and evaluated the validity of two empirical models of exposure: one for nonspecific dust and one for wood dust. The dust model was constructed using 1,395 dust measurements collected in 13 sawmills for research or regulatory purposes from 1981 to 1997. Inter-sampler conversion factors were used to obtain inhalable dust equivalents if necessary. The wood dust model was constructed after applying adjustment factors to subtract nonwood components of the dust from the original measurements. The validity of the two models was tested against measurements (n = 213) from a technologically similar mill that was not part of the cohort study. The proportions of variability explained by the dust and wood dust models were 35% and 54%, respectively. When tested against the validation mill, the biases in the dust model were -33% for outdoor jobs and 2% for indoor jobs. The biases in the wood dust model were 2% for outdoor jobs and -3% for indoor jobs. Strong correlations were observed between the predicted and observed geometric means of jobs (0.79 and 0.70 for the dust model and wood dust model, respectively). Testing the validity of predictive models examines the generalizability of the models. The low overall bias, especially in the wood-specific model, increases our confidence in the use of these models for all sawmills to assess both nonspecific particulate and wood-related health effects in the historical cohort study.

A beta-arrestin binding determinant common to the second intracellular loops of rhodopsin family G protein-coupled receptors

beta-Arrestins have been shown to inhibit competitively G protein-dependent signaling and to mediate endocytosis for many of the hundreds of nonvisual rhodopsin family G protein-coupled receptors (GPCR). An open question of fundamental importance concerning the regulation of signal transduction of several hundred rhodopsin-like GPCRs is how these receptors of limited sequence homology, when considered in toto, can all recruit and activate the two highly conserved beta-arrestin proteins as part of their signaling/desensitization process. Although the serine and threonine residues that form GPCR kinase phosphorylation sites are common beta-arrestin-associated receptor determinants regulating receptor desensitization and internalization, the agonist-activated conformation of a GPCR probably reveals the most fundamental determinant mediating the GPCR and arrestin interaction. Here we identified a beta-arrestin binding determinant common to the rhodopsin family GPCRs formed from the proximal 10 residues of the second intracellular loop. We demonstrated by both gain and loss of function studies for the serotonin 2C, beta2-adrenergic, alpha2a)adrenergic, and neuropeptide Y type 2 receptors that the highly conserved amino acids, proline and alanine, naturally occurring in rhodopsin family receptors six residues distal to the highly conserved second loop DRY motif regulate beta-arrestin binding and beta-arrestin-mediated internalization. In particular, as demonstrated for the beta2 AR, this occurs independently of changes in GPCR kinase phosphorylation. These results suggest that a GPCR conformation directed by the second intracellular loop, likely using the loop itself as a binding patch, may function as a switch for transitioning beta-arrestin from its inactive form to its active receptor-binding state.

An Akt/beta-arrestin 2/PP2A signaling complex mediates dopaminergic neurotransmission and behavior

Dopamine plays an important role in the etiology of schizophrenia, and D2 class dopamine receptors are the best-established target of antipsychotic drugs. Here we show that D2 class-receptor-mediated Akt regulation involves the formation of signaling complexes containing beta-arrestin 2, PP2A, and Akt. beta-arrestin 2 deficiency in mice results in reduction of dopamine-dependent behaviors, loss of Akt regulation by dopamine in the striatum, and disruption of the dopamine-dependent interaction of Akt with its negative regulator, protein phosphatase 2A. Importantly, canonical cAMP-mediated dopamine-receptor signaling is not inhibited in the absence of beta-arrestin 2. These results demonstrate that, apart from its classical function in receptor desensitization, beta-arrestin 2 also acts as a signaling intermediate through a kinase/phosphatase scaffold. Furthermore, this function of beta-arrestin 2 is important for the expression of dopamine-associated behaviors, thus implicating beta-arrestin 2 as a positive mediator of dopaminergic synaptic transmission and a potential pharmacological target for dopamine-related psychiatric disorders.

DNA microarray allows molecular profiling of rheumatoid arthritis and identification of pathophysiological targets

This study was undertaken to evaluate the possibility to obtain a molecular signature of rheumatoid arthritis (RA) comparatively osteoarthritis (OA), and to lay the bases to develop new diagnostic tools and identify new targets. Microarray technology was used for such an analysis. The gene expression profiles of synovial tissues from patients with confirmed RA, and patients with OA were established and compared. A set of 63 genes was selected, based, more specifically, on their overexpression or underexpression in RA samples compared to OA. Results for six of these genes have been verified by quantitative PCR using both samples identical to those used in the microarray experiments and entirely separate samples. Expression profile of the 48 known genes allowed the correct classification of additional RA and OA patients. Furthermore, the distinct expression of three of the selected genes was also studied by quantitative RT-PCR in cultured synovial cells. Detailed analysis of the expression profile of the selected genes provided evidence for dysregulated biological pathways, pointed out to chromosomal location and revealed novel genes potentially involved in RA. It is proposed that such an approach allows valuable diagnosis/prognostics tools in RA to be established and potential targets for combating the disease to be identified.

A mechanistic overview on male infertility and germ cell cancers

The testis is devoted to two important tasks: haploid cell production and sexual steroid synthesis. A number of highly sophisticated and unique strategies operate during spermatogenesis, a process crucial for reproduction, heredity and evolution. It is particularly important to decipher the underlying molecular mechanisms whose function can be perverted in pathological situations, such as infertility and testicular cancers, which represent an increasing biomedical issue today. This review summarises the currently available data concerning some key molecular components that are altered or potentially involved in male infertility and testicular tumors, with the aim of defining some common "hot spots". We particularly focused on genetically engineered in vivo models in which testicular functions are altered and we pinpointed to the potential involvement of the targeted genes in testicular pathologies. Those molecular mechanisms peculiar to the male gonad can be envisioned as a basis for the design of novel drugs potentially dedicated to testicular dysfunction.

Cost effectiveness of a latrine revision programme in Kabul, Afghanistan

INTRODUCTION

We assessed a household latrine revision intervention implemented in Kabul, Afghanistan for evidence of a reduction in diarrhoeal disease.

METHODS

A case-control design involving 1238 cases and 625 controls was used. Logistic regression modelling was performed both for children < 5 years and < or = 11 years, and the parameter estimates were later used with results from a stratified cluster sample survey. This survey used a verbal autopsy methodology to enable an estimation of the number of deaths averted over a 1-year period. A cost-effectiveness analysis using direct and indirect costs for the intervention was then conducted and the results compared with primary health care interventions identified from a Medline search.

FINDINGS

Conditional logistic regression showed that patients were less likely than controls to live in households with revised latrines (odds ratio (OR) 0.57, 95% confidence interval (CI) = 0.42-0.77 for children < 5 years, and OR 0.53, 95% = CI 0.41-0.67 for children < or = 11 years). The results from the survey of cause-specific mortality by verbal autopsy enabled estimation of the number of deaths averted over a 1-year period due to the intervention; these estimations were 235 (95% CI = 109-360) for children < 5 years and 285 (95% CI = 180-397) for children < or = 11 years. Estimates of cost effectiveness ranged from approximately US dollars 1800 to US dollars 4100 per death averted depending on age and payer perspective.

CONCLUSION

These estimates are conservative because only 1 year of effectiveness is considered, yet they compare favourably with a review of other paediatric interventions. These results are important because funding for sanitation interventions is often limited by the belief that the interventions are not cost-effective.

RNA Editing Induces Variation in Desensitization and Trafficking of 5-Hydroxytryptamine 2c Receptor Isoforms

The 5-hydroxytryptamine2c receptor (5-HT2cR) is subjected to RNA editing, in the second intracellular loop, generating 14 different isoforms in human brain. This post-transcriptional event markedly alters the signaling properties of the receptor by reducing its ability to couple to G-proteins. Although the non-edited form of the receptor is essentially fully constitutively active, edited forms show lesser degrees of constitutive activity. We have used two extensively edited receptor isoforms, VGV and VSV, and the non-edited INI isoform to investigate how variations in constitutive receptor activity affect the trafficking and the interaction of these isoforms with components of the desensitization machinery in HEK 293 cells. We found that cell surface expression of the 5-HT2cR decreased in parallel with increased constitutive activity of the isoforms. The subcellular distribution of the various isoforms was dependent of their ability to interact with betaarrestin2, which correlated with the constitutive activity level of each isoform. We observed that the agonist-independent interaction of betaarrestin2 with constitutively active 5-HT2cR isoforms was reversed by inverse agonist treatments promoting receptor redistribution to the cell surface. Overexpression of a G-protein-coupled receptor kinase (GRK2) was able to stabilize the interaction of betaarrestin2 with constitutively active 5-HT2cR isoforms even in the presence of inverse agonists. Taken together, our observations indicate that the constitutively active 5-HT2cR isoforms are spontaneously internalized in an agonist-independent manner. This endocytosis process is mediated by a GRK/betaarrestin-dependent mechanism and is directly correlated with the constitutive activity status of the RNA edited receptor variants. Thus the ultimate physiological output of constitutively active receptors may be determined not only by their agonist-independent activity but also by their interactions with GRKs and betaarrestin.

Rapid automated simultaneous screening of (G1691A) Factor V, (G20210A) prothrombin, and (C677T) methylenetetrahydrofolate reductase variants by multiplex PCR using fluorescence scanning technology

The Factor V Leiden mutation (G1691A), and mutations in the prothrombin (G20210A) and 5,10-methylenetetrahydrofolate reductase (C677T) genes are common hereditary risk factors associated with venous thrombosis. The aim of this study was to develop an automated, PCR-based genotyping assay for rapid simultaneous screening of these three mutations. We adapted multiplex PCR, using primer modifications to introduce cleavage sites for restriction endonucleases into the fragments bearing each of the mutations. The three mutations were analyzed in a single tube by fluorescence scanning. An internal digestion control was introduced to prevent false-negative results due to incomplete digestion or a total lack of digestion. DNA fragment analysis was carried out using an automated capillary electrophoresis instrument (ABI310). This reliable, efficient, easy-to-use assay can be applied to specimens from large clinical trials and epidemiological surveys.

The prevalence of Parkinson's disease in British Columbia, Canada, estimated by using drug tracer methodology

OBJECTIVE

To estimate the prevalence of Parkinson's disease (PD) in British Columbia utilizing the prescription database of the College of Pharmacists.

METHODS

Patients receiving anti-parkinsonian drug (anti-PD) prescriptions between 1996 and 1998 were stratified by year, age, gender, drug use category, and geographic location. The numbers of patients on levodopa alone, or levodopa and/or other anti-PD drugs were adjusted using published data which gave estimates of the proportion of undiagnosed patients with PD, the proportion of those treated for parkinsonism with definite PD, the proportion of patients with PD not being treated with anti-PD medications, and the proportion of patients treated with anti-PD medications who have PD. Use of the anti-PD drug bromocriptine for other purposes in women under 50 years of age was also considered.

RESULTS

The estimated prevalences of PD based on all anti-PD medications used were 109, 121, and 125 per 100,000 population in 1996, 1997, and 1998, respectively. Estimated prevalences of PD based on levodopa use were 126, 134, and 144, respectively. The prevalence in both prescription groups increased with age. The male to female ratio of prevalence ranged from 1.16 to 1.21.

CONCLUSIONS

Using a large, accurate database, it is possible to estimate the prevalence of PD in a large population, though the assumptions built into the estimate remain to be validated in the subject population.

Cellular adhesion of primary Sertoli cells affects responsiveness of the extracellular signal-regulated kinases 1 and 2 to follicle-stimulating hormone but not to epidermal growth factor

The cellular adhesion status and the exposure to soluble growth factors both contribute to mitogen-activated protein (MAP) kinase activation. To date, however, whether mitogens acting through G-protein-coupled receptors (GPCRs) need cell adhesion to activate MAP kinases/extracellular signal-regulated kinases (ERK) 1, 2 has been poorly investigated. We addressed this point in primary cultures of Sertoli cells experimentally maintained in suspension, considering that follicle-stimulating hormone (FSH) activates ERK1, 2 in attached Sertoli cells by acting through a GPCR. We found that FSH actively repressed ERK1, 2, in a cAMP-dependent but cAMP-dependent protein kinase (PKA)-independent manner, and this inhibition required the activity of a tyrosine phosphatase. In comparison, in the absence of anchorage, ERK1, 2 were still activated by epidermal growth factor, in a PKA-dependent manner. Altogether, these data suggest that sensitivity of the MAP kinase response toward cell adhesion may depend, at least in part, on the class of receptor, GPCR or receptor with tyrosine kinase activity, by which it is triggered.

G protein-coupled receptor kinases and beta arrestins are relocalized and attenuate cyclic 3',5'-adenosine monophosphate response to follicle-stimulating hormone in rat primary Sertoli cells

The FSH receptor (FSH-R) is a member of the rhodopsin-like subfamily of G protein-coupled receptors that undergoes homologous desensitization upon agonist stimulation. In immortalized cell lines overexpressing the FSH-R, G protein-coupled receptor kinases (GRKs) and beta-arrestins are involved in the phosphorylation, uncoupling, and internalization of this receptor. In an effort to appreciate the physiological relevance of GRK/beta-arrestin actions in natural FSH-R-bearing cells, we used primary rat Sertoli cells as a model. GRK2, -3, -5, -6a, and -6b and beta-arrestins 1 and 2 were expressed in primary rat Sertoli cells. Overexpression of these different GRKs and beta-arrestins in primary rat Sertoli cells significantly attenuated the FSH-induced cAMP response, and FSH rapidly triggered a relocalization of endogenously expressed GRK2, -3, -5, and -6 and beta-arrestins 1 and 2 from the cytosol to the membranes. These results highlight the relationship existing between the GRK/beta-arrestin regulatory system and the FSH-R signaling machinery in a physiological model.

The ERK-dependent signalling is stage-specifically modulated by FSH, during primary Sertoli cell maturation

Primary cultures of Sertoli cells provide an interesting model to study how signalling pathways induced by a single hormone in a single cell type evolve, depending on the developmental stage. In vivo, follicle-stimulating hormone (FSH) induces proliferation of Sertoli cells in neonate and controls the subsequent differentiation of the entire population. Molecular mechanisms underlying Sertoli cell pleiotropic responses to FSH have long been investigated. But to date, only cAMP-dependent kinase (PKA) activation has been reported to account for most FSH biological activities in male. Here, we demonstrate that FSH activates the ERK MAP kinase pathway following dual coupling of the FSH-R both to Gs and to Gi heterotrimeric proteins, in a PKA- and also Src-dependent manner. This activation is required for FSH-induced proliferation of Sertoli cells isolated 5 days after birth. Consistently, we show that the ERK-mediated FSH mitogenic effect triggers upregulation of cyclin D1. In sharp contrast, at 19 days after birth, as cells proceed through their differentiation program, the ERK pathway is dramatically inhibited by FSH treatment. Taken together, these results show that FSH can exert opposite effects on the ERK signalling cascade during the maturation process of Sertoli cells. Thus, signalling modules triggered by the FSH-R evolve dynamically throughout development of FSH natural target cells.

Kinase-inactive G-protein-coupled receptor kinases are able to attenuate follicle-stimulating hormone-induced signaling

Homologous desensitization of G-protein-coupled receptors (GPCR) is thought to occur in several steps: binding of G-protein-coupled receptor kinases (GRKs) to receptors, receptor phosphorylation, kinase dissociation, and finally binding of beta-arrestin to phosphorylated receptors and functional uncoupling of the associated Galpha protein. It has recently been reported that GRKs can inhibit Galphaq-mediated signaling in the absence of phosphorylation of some GPCRs. Whether or not comparable phosphorylation-independent effects are also possible with Galphas-coupled receptors remains unclear. In the present study, using the tightly Galphas-coupled FSR receptor (FSH-R) as a model, we observed inhibition of the cAMP-dependent signaling pathway using kinase-inactive mutants of GRK2, 5, and 6. These negative effects occur upstream of adenylyl cyclase activation and are likely independent of GRK interaction with G protein alpha or beta/gamma subunits. Moreover, we demonstrated that, when overexpressed in Cos 7 cells, mutated GRK2 associates with the FSH activated FSH-R. We hypothesize that phosphorylation-independent dampening of the FSH-R-associated signaling could be attributable to physical association between GRKs and the receptor, subsequently inhibiting G protein activation.

Downsizing and industrial restructuring in related to changes in psychosocial conditions of work in British Columbia sawmills

OBJECTIVES

This paper investigates changes in the psychosocial and physical work conditions of the sawmill industry in British Columbia, Canada, over the past 35 years.

METHODS

Shifts in work conditions were examined within the context of historical changes in sawmill labor demography and job taxonomy as the industry was both downsized and restructured, largely in response to an economic recession in the early 1980s.

RESULTS AND CONCLUSIONS

Downsizing eliminated approximately 60% of the work force and 1/4 of sawmill job titles. Although all the job categories in restructured sawmills showed increased levels of control, the gradient in control across job categories was steeper in 1997 than in 1965; this change may have important health implications particularly for the unskilled workers in the restructured mills.

Uncoupling of proopiomelanocortin (POMC) fragments is related to self-injury

Proopiomelanocortin (POMC) contains several interesting, behaviorally active peptides. Release patterns of these fragments have been related to bizarre episodes of self-injurious behavior (SIB) among autistic individuals. Moreover, elevation in beta-endorphin (betaE) but not ACTH levels was associated with a positive response to an acutely administered, centrally acting opioid blocker among autistic individuals exhibiting SIB. In the present study, POMC fragments were measured in 12 self-injurious patients before and after long term (3 month) treatment with an opiate blocker naltrexone (NTX). POMC fragments were sampled from blood collected at the beginning of the baseline and placebo-controlled treatment phases of the study. Results indicated that the co-release (coupling) of POMC fragments were stable over time and the profile of POMC fragments in plasma predicted the effectiveness of a CNS acting drug in autistic subjects who self-injure.

Hepatocellular carcinoma cell lines from diethylnitrosamine phenobarbital-treated rats. Characterization and sensitivity to endothall, a protein serine/threonine phosphatase-2A inhibitor

Primary hepatocellular carcinoma (HCC) is probably one of the most common fatal forms of liver cancer. We have established permanent cell lines from diethylnitrosamine/phenobarbital induced primary rat liver carcinomas to study new anticancer therapies. The rat hepatocellular carcinoma cell lines (HR-2, HR-3, and HR-4) have been maintained in culture for over 3 years. They form tumors when transplanted sc or im into young syngeneic rats. Immunocytology (alpha-fetoprotein, albumin), biochemical (gamma-glutamyl transferase), and histochemical (glycogen) marker studies and electron microscopy (biliary canaliculi) showed unique, stable differentiation patterns in these tumor lines. They overproduced the c-met protooncogene product and formed colonies spontaneously in semisolid culture with high cloning efficiency (HR-2: 50%-80%, HR-3: 35%-50% and HR-4: 50%-65%). The sensitivity of these cell lines to inhibitors of protein ser/thr phosphatase-2A (PP2A), a key enzyme in the control of G1/S and G2/M cell cycle phase transitions in eukaryotes, was studied in vitro. The specific, weak inhibitor of PP2A, endothall, caused dose- and time-dependent cytostasis specifically in G2/M. The cells died later by apoptosis, which was confirmed by cytology (annexin V-FITC labeling, propidium iodide painting of apoptotic bodies) and by fluorescent activated cell sorter (FACS) DNA measurements. The HR-2, HR-3, HR-4, and Zajdela hepatocellular carcinomas were most sensitive to endothall (IC50 of 1.7, 1.2, 0.9, and 1.7 microg/mL), whereas newborn rat hepatocytes growing exponentially in primary culture (IC50 = 6.2 microg/mL), rat DHD/K12 colon carcinoma cells (IC50 = 3.6 microg/mL), or human HT-29 colon carcinoma cells (IC50 = 4.9 microg/mL) were less sensitive. Thus, endothall inhibits preferentially HCC growth and these new rat hepatocellular carcinoma lines may be useful for further biochemical and pharmacological studies on PP2A inhibitors, and for testing new forms of treatment of hepatic cell carcinomas.

Large scale recovery and characterization of stromal cell-associated primitive haemopoietic progenitor cells from filter-retained human bone marrow

Bone marrow aspirates are composed of two cellular compartments, an abundant buffy coat suspension and a minor particulate fraction. The particulate fraction is routinely removed by filtration prior to transplantation in order to reduce the risk of embolism. This study shows that the filter-retained fraction includes many multicellular complexes, previously defined as haematons. A haematon is a finely arborized stromal-web which is tightly packed with haemopoietic progenitor cells and differentiated postmitotic cells. Comparison of the pooled buffy coat and the filter-retained materials from healthy donors showed that the haematon fraction contained 8-40 x 10(6) CD34+ cells, 20-115 x 10(3) high proliferative potential colony-forming cells (HPP-CFC) and 0.49-2.67 x 10(6) granulocyte-macrophage colony-forming unit (GM-CFU) which constituted 24+/-8% (10-36; n=8) of the total GM-CFU population harvested. Similar, but more variable recoveries of GM-CFU were obtained from the haematon fractions from patients with breast cancer (21+/-13%; n=10), Hodgkin's disease (33+/-19%; n=4), non-Hodgkin's lymphoma (21+/-18; n=7), but the recovery was lower from patients with acute myelogenous leukaemia (AML) (13+/-13%; n=6). The haematon fraction was enriched in CD34+ cells (2.5-fold), long-term culture initiating cells (LTC-IC/CAFC, week 5) (3.5-fold), HPP-CFC (2.8-fold) and GM-CFU (2.3-fold) over the buffy coat. Purified CD34+ cells expanded exponentially and produced 800 to 4000-fold more nucleated cells, 300 to 3500-fold more GM-CFU and 10 to 80-fold more HPP-CFC in stroma-free suspension culture with interleukin-1 (IL-1beta), IL-3, IL-6, GM-CSF and stem cell factor (SCF), than did the starting cell input. The haematon fraction produced significantly more progenitor cells than the buffy coat in long-term liquid culture (LTC). This was due to the higher frequency of LTC-IC/CAFC and to the presence of the whole spectrum of native, stroma cell-associated CAFC in haematons. Thus, the haematon includes the most productive haematogenous compartment in human BM. This simple enrichment strategy, using filter-retained haematons, provides a rational source of BM cells for large scale experimental and/or clinical studies on haemopoietic stem cells and on critical accessory stromal cells.

Alterations of biological parameters in mice chronically exposed to low-frequency (50 Hz) electromagnetic fields

In an experimental study we measured changes in hematological, biochemical and cortisol parameters in 6-week-old Swiss mice continuously exposed to ELF generated by a transformer station and high current bus bars. Mean daily exposure of 5.0 microT was maintained for 350 days. Hematological parameters were compared to those of control mice (n=12) exposed to a field level lower than 0.1 microT. Serum biochemical parameters (sodium, potassium, chloride, calcium, magnesium, phosphorus, amylase, creatine phosphokinase, and lactate dehydrogenase) were measured after 28 days of exposure and serum cortisol after 90 and 190 days. Granulocyte/macrophage colony-forming cells (GM-CFC) were counted at the end of the 350-day exposure. On day 20, exposed animals showed a significant decrease in leukocyte, erythrocyte, lymphocyte and monocyte counts and in hemoglobin and hematocrit values, while MCV increased. On days 43 and 63 no significant difference was observed in leukocyte and erythrocyte values, as if hemopoiesis had recovered. On day 90, a significant fall in the leukocyte, polynuclear neutrophil and eosinophil counts was observed in the exposed animals. No significant difference was noted in the biochemical parameters studied. On day 190, exposed animals had neutropenia and a decrease in the cortisol value. On day 350, no significant difference in hematological parameters was noted. Individual differences in sensitivity were observed, as 8 mice in the exposed group showed a significant decrease in the leukocyte, polymorphonuclear neutrophil and GM-CFC counts, while in two mice there was a significant increase in these same values compared to those unexposed mice.

Study of human neurovegetative and hematologic effects of environmental low-frequency (50-Hz) electromagnetic fields produced by transformers

A survey of neurovegetative and hematologic disorders was conducted in a population (n = 13) exposed occupationally to environmental electromagnetic fields; the population was matched with 13 control subjects. The exposed subjects worked at least 8 h/d for 1-5 y in premises located above transformers and high-tension cables, and the subjects were submitted to low-frequency electromagnetic fields (i.e., 50 Hz) of 0.2 microT-6.6 microT. The subjects were matched with respect to socioeconomic category, sex, and age with a control population of subjects that worked in premises outside of the immediate vicinity of transformers or high-tension cables. The exposed population had a significant increase in degree of certain neurovegetative disorders (i.e., physical fatigue, psychical asthenia, lipothymia, decreased libido, melancholy, depressive tendency, and irritability). In addition, the population experienced a significant fall in total lymphocytes and CD4, CD3, and CD2 lymphocytes, as well as a rise in NK cells. Leukopenia and neutropenia were also observed in two persons permanently exposed to doses of 1.2-6.6 microT. The disorders disappeared when exposure stopped, and they reappeared on reexposure.

Effects of norcantharidin, a protein phosphatase type-2A inhibitor, on the growth of normal and malignant haemopoietic cells

Cantharidin is a natural toxin that inhibits protein phosphatase type 2A (PP2A) and has antitumour effects in man. We have studied the synthetic analogue, norcantharidin (NCTD), which has less nephrotoxic and phlogogenic side-effects, investigating the effects on the normal haemopoietic system and leukaemia cell growth. Daily intraperitoneal (i.p.) injection of NCTD induced dose and circadian time-dependent transient leucocytosis in normal mice, but did not accelerate bone marrow (BM) regeneration, or have haemopoietic offe-effects following chronic administration. NCTD stimulated the cell cycle progression of granulocyte-macrophage colony-forming cells (GM-CFC), stimulated DNA synthesis and increased the frequency of mitotic cells in short-term human BM cultures. NCTD also stimulated the production of interleukin (IL)-1 beta, colony stimulating activity (CSA) and tumour necrosis factor (TNF)-alpha. Continuous in vitro NCTD treatment, however, inhibited both DNA synthesis and GM-CFC growth. Fluorescence-activated cell sorting (FACS) analysis of DNA profiles and cytological studies in HL-60, K-562 or MRC5V2 (fibroblast) cells indicated that low doses of NCTD accelerated the G1/S phase transition, while higher doses or prolonged incubations inhibited the cell cycle at the G2/M phases or during the formation of postmitotic daughter cells. Electron microscopy revealed that NCTD impaired the neogenesis of chromatin material and nuclear membrane during the M/G1 phase transition in K-562 cells. The biphasic effect of NCTD may be due to inhibition of PP2A activity, which regulates the cell cycle, both at the restriction point and at the G2 and M phases. Our data provide new insight into the cellular and molecular actions of NCTD, and partly explain its therapeutical effects in cancer patients.

One monoclonal antibody to human thyrotropin (TSH) receptor agonist of TSH hormone stimulates the proliferation of human thyroid cells

The question of thyroid cell growth induction by monoclonal antibodies (mAbs) to human thyrotropin receptor (hTSH-R), which stimulate increases in cAMP thyroid cells, is under debate and their implication in Graves' disease (GD) is controversial. In order to address this issue, we used characterized reagents, i.e., mAbs to hTSH-R, and cloned human thyroid hybridoma cells (GEJ). Cell counting on Days 1, 2, and 3 after addition of mAb and Northern blot analysis of mRNA specific for the c-fos oncogene were used to assess the proliferation of the thyroid cells. MAbs to hTSH-R, obtained by immunization of DBA/1 mice with affinity-purified hTSH-R, were added to GEJ cells in concentrations varying from 0.66 to 660 nM. Their effects on GEJ cell growth were compared to those of human TSH, of hLH, and of control mAb. Cell counting and evaluation of GEJ c-fos transcripts showed that mAbs to hTSH-R induce significant GEJ cell growth, whereas they were ineffective on the control cell line. Among them, one mAb, 34A, exhibited an impressive activity on thyroid cell growth and induced cAMP production comparable to that induced by bovine or human TSH. Our data demonstrate the existence of immunoglobulin which stimulates thyroid growth and elevates cAMP. The higher the cAMP production, the greater the thyroid cell proliferation. Furthermore, the data suggest a possible role for agonistic anti-hTSH-R autoantibodies in the immunopathogenesis of GD.

Maintenance of stellite and tungsten carbide saw tips: respiratory health and exposure-response evaluations

OBJECTIVE

To study exposure to cobalt and chromium in saw maintenance rooms and test respiratory health among saw filers at lumber mills. Hard-metal lung disease is associated with cobalt in the manufacture of tungsten carbide tools; recently it has also been reported among tool maintenance workers. Lumber mills often use saws tipped with tungsten carbide or with a newer alloy, stellite (containing more cobalt, as well as chromium).

METHODS

A cross sectional study of 118 saw filers at eight lumber mills was carried out that included a standardised questionnaire, spirometry, personal air sampling, and examination of tasks every 10 minutes (by observation). Comparison data were from a study of bus mechanics tested with similar methods.

RESULTS AND CONCLUSION

Cobalt exposure was associated with tungsten carbide grinding but not with stellite grinding. Chromium exposure was associated mainly with stellite welding. Saw filers had a twofold increase in phlegm and wheeze (P < 0.01) and a threefold increase in cough, phlegm, and wheeze related to work (P < 0.001), but no increase in breathlessness. Stellite welding was associated with a significant increase in nasal symptoms and cough related to work and a small decrease in airflow (forced expiratory volume in one second/forced vital capacity (FEV1/FVC%), P < 0.05). Saw filers wet grinding with tungsten carbide had significant reductions in forced expiratory lung volumes (FEV1 and FVC, P < 0.05) and were significantly more likely to have FEV1 and FVC values in the abnormal range. Cobalt exposure (in wet grinding) and duration of work that involved tungsten carbide grinding were both associated with significant reductions in FEV1 and FVC. Average cobalt exposures in this study were about 5 micrograms/m3, well below the currently accepted permissible concentration, which suggests that the current workplace limit for cobalt may be too high.

Induction of autoimmunity by immunization of mice with human thyrotropin receptor

The development of autoimmunity was investigated after repeated immunizations with human thyrotropin receptor (hTSH-R) of five congenic strains of female and male mice. After each immunization, free T3 levels and antibodies to hTSH-R and to six peptides of the hTSH-R were assayed. Our results showed that H-2s and H-2q female mice developed features of autoimmunity such as antibody responses to hTSH-R and to hTSH-R peptides, transient variations in the levels of free T3 thyroid hormone, and lymphocytic infiltrations in their thyroid glands. Concerning the antibody responses to hTSH-R peptides, we found that peptide P1 (352-366) contained a major B cell epitope. Furthermore, strain-specific B cell epitope was exemplified by peptide 92 (12-30) and two male- and female-specific B cell epitopes were located in peptides 91 (32-46) and 93 (316-330), respectively. These features appeared rather related to hyperthyroidism.

Antibodies specific for human thyrotropin receptor induce MHC antigen expression in thyroid cells

Autoantibodies (AAbs) to hormone receptors are found in autoimmune diseases such as Graves' disease (GD) or myasthenia gravis. A structural link between hormone receptor and MHC genes has been documented, suggesting a possible co-regulation of MHC and hormone receptor genes. Thus, in vitro experiments were designed to search for a pathologic role for AAbs. In a model study, we investigated whether adding murine anti-human thyrotropin receptor mAbs would affect MHC gene expression in either cloned human thyroid epithelial cell or primary murine thyroid epithelial cell cultures. We found that two anti-human thyrotropin receptor monoclonal AAbs, 11E7 and 34A, induced, with an intensity comparable to that of IFN-gamma, transcription and expression of class I and class II/Ii chain proteins in human and murine thyroid epithelial cells. Two other anti-human thyrotropin receptor mAbs, 12E3 and 243-3, were ineffective. These data suggest a new role for autoantibodies in the pathology of autoimmune endocrinopathies.

Antibodies specific for human thyrotropin receptor induce MHC antigen expression in thyroid cells

Autoantibodies (AAbs) to hormone receptors are found in autoimmune diseases such as Graves' disease (GD) or myasthenia gravis. A structural link between hormone receptor and MHC genes has been documented, suggesting a possible co-regulation of MHC and hormone receptor genes. Thus, in vitro experiments were designed to search for a pathologic role for AAbs. In a model study, we investigated whether adding murine anti-human thyrotropin receptor mAbs would affect MHC gene expression in either cloned human thyroid epithelial cell or primary murine thyroid epithelial cell cultures. We found that two anti-human thyrotropin receptor monoclonal AAbs, 11E7 and 34A, induced, with an intensity comparable to that of IFN-gamma, transcription and expression of class I and class II/Ii chain proteins in human and murine thyroid epithelial cells. Two other anti-human thyrotropin receptor mAbs, 12E3 and 243-3, were ineffective. These data suggest a new role for autoantibodies in the pathology of autoimmune endocrinopathies.

Production of Ab2 beta, anti-idiotypic monoclonal antibodies, specific for human thyrotropin receptor

We had previously selected five monoclonal antibodies (mAb1) upon their specific binding to human thyrotropin (hTSH). These mAbs1, which are specific for two distinct epitopes of the hTSH beta-chain, also inhibit the hTSH binding to human thyroid membrane preparations. We then immunized BALB/c mice with the various mAbs1 in attempt to generate anti-idiotypic Abs (Ab2) directed to the hTSH receptor (hTSHR). Five hybridomas secreting monoclonal antibodies (mAb2) to the hTSHR were selected from one mouse immunized with the mixture of the five mAbs1. These monoclonal antibodies to the hTSHR were selected upon their ability to specifically bind to the hTSHR. Moreover, we showed that binding of mAbs2 to the individual mAbs1 used for immunization was specifically inhibited by hTSH and not by insulin or by human chorionic gonadotrophin, a highly related glycoprotein hormone. The five mAbs2 inhibited the binding of iodine-labeled hTSH to its receptor by 8 to 41%; moreover, two of them stimulated the adenylate-cyclase system of the thyroid cells. With respect to their properties, mAbs2 were classified as mAb2-beta.

Fipexide-induced fulminant hepatitis. Report of three cases with emergency liver transplantation

Fipexide belongs to a new class of cognition activators and is noted for its lack of amphetamin-like side effects. We describe three patients who developed fulminant hepatic failure less than 2 months after beginning fipexide administration. The mean interval from the onset of jaundice to the onset of encephalopathy was 8 days. Emergency liver transplantation was undertaken when factor V was 20% of normal or less and coma developed. All patients were transplanted less than 1 week after the onset of encephalopathy. Two survived and one died immediately after transplantation. Histologic examination of the livers revealed massive liver cell necrosis, predominantly centrilobular, and a moderate inflammatory infiltrate within the portal spaces. We conclude that fipexide can induce massive liver cell necrosis and fulminant liver failure. As a result of this life-threatening complication, reconsideration of the indications for this drug is warranted.

Characterization of monoclonal antibodies to the human thyrotropin receptor

We have produced four monoclonal antibodies (mAbs), 34A, 49G, 11E7, and 12E3, which bind the human TSH receptor (hTSH-R) when expressed on a human thyroid cell line (GEJ), freshly dissociated human and murine thyroid cells, or Chinese hamster ovary cells stably transfected with the hTSH-R gene. These mAbs were obtained after immunization of DBA/1 mice with affinity-purified TSH-binding sites from GEJ cells. Biochemical studies, including sodium dodecyl sulfate-polyacrylamide-gel electrophoresis, Western blot, and immunoprecipitation of solubilized GEJ cell membranes or human thyroid cells showed that most of the mAbs recognized two bands: one located at 46-48 kilodaltons and the other at 86-88 kilodaltons. Inhibition of [125I]hTSH binding to solubilized porcine membranes (TSH-receptor auto-antikörper assay) or Chinese hamster ovary cell membranes previously transfected with hTSH-R gene showed that mAb 34A recognizes the hTSH-binding site of both receptors. In contrast, mAbs 49G, 11E7, and 12E3 recognize a structure located near the hTSH-binding site. Lastly, the ability of these mAbs to stimulate murine thyroid function was investigated by measuring cAMP production and iodide accumulation. The 34A mAb, which fully competes with [125I]TSH for binding to hTSH-R, was able to induce both functions. Conversely, the 12E3 mAb, which was the least potent inhibitor of [125I]TSH binding to hTSH-R-transfected cells had no effect. A relationship was, therefore, established between the capacity of mAb to hTSH-R to inhibit [125I]hTSH binding and their ability to induce thyroid functions.

A phase I trial of 21-day continuous venous infusion of alpha-interferon at circadian rhythm modulated rate in cancer patients

The toxicity and/or the stimulation of natural killer cell activity that resulted from exposure to alpha-interferon varied according to circadian dosing time, both in mice and in human beings. Ten patients with advanced renal cell carcinoma or melanoma were treated with recombinant alpha-interferon-2b using a continuous 21-day intravenous schedule at circadian modulated rate. Patients received 15-20 MU/m2/day in an ambulatory care program. The drug was delivered via an external programmable-in-time pump. Thirty-nine courses of therapy were given (2-12 courses per patient). Severe side effects included World Health Organization grade III somnolence (one patient, 1 course) and grade III-IV neutropenia (five patients, 10 courses). Karnofsky performance status decreased by 40% in 3 patients (five courses). Two of these patients were withdrawn from the study because of toxicity. Disease was stabilized in four of the seven patients evaluable for response. Seven of the 10 patients are alive at 15 months' median follow-up. Two have continued with chronotherapy for 9+ and 13+ months, respectively. A large interpatient variability characterized the maximally tolerated dose. Two patients led their usual activities while receiving 20 MU/m2/day for three courses or more. Conversely, two patients exhibited severe side effects with 10 MU/m2/day. As compared with schedules of standard administration or continuous flat infusion, this circadian schedule of infusion allowed a large increment in total daily dose and dose intensity. A starting dose of 15 MU/m2/day was well tolerated by 8 of 10 patients and can be recommended using this circadian modulated schedule.