Temporal sequence of changes in electrophysiological properties of oculomotor motoneurons during postnatal development

The temporal sequence of changes in electrophysiological properties during postnatal development in different neuronal populations has been the subject of previous studies. Those studies demonstrated major physiological modifications with age, and postnatal periods in which such changes are more pronounced. Until now, no similar systematic study has been performed in motoneurons of the oculomotor nucleus. This work has two main aims: first, to determine whether the physiological changes in oculomotor nucleus motoneurons follow a similar time course for different parameters; and second, to compare the temporal sequence with that in other neuronal populations. We recorded the electrophysiological properties of 134 identified oculomotor nucleus motoneurons from 1 to 40 days postnatal in brain slices of rats. The resting membrane potential did not significantly change with postnatal development, and it had a mean value of -61.8 mV. The input resistance and time constant diminished from 82.9-53.1 M omega and from 9.4-4.9 ms respectively with age. These decrements occurred drastically in a short time after birth (1-5 days postnatally). The motoneurons' rheobase gradually decayed from 0.29-0.11 nA along postnatal development. From birth until postnatal day 15 and postnatal day 20 respectively, the action potential shortened from 2.3-1.2 ms, and the medium afterhyperpolarization from 184.8-94.4 ms. The firing gain and the maximum discharge increased with age. The former rose continuously, while the increase in maximum discharge was most pronounced between postnatal day 16 and postnatal day 20. We conclude that the developmental sequence was not similar for all electrophysiological properties, and was unique for each neuronal population.

No primary association of MICA polymorphism with systemic lupus erythematosus

OBJECTIVE

To replicate the described association between MHC class I chain-related A (MICA) gene polymorphism and susceptibility to systemic lupus erythematosus (SLE).

METHODS

MICA transmembrane microsatellite polymorphism was genotyped using a polymerase chain reaction (PCR)-based method. Genotyping of HLA-B* and DRB1* was performed using PCR and detection with a reverse sequence-specific oligonucleotide (SSO) probe system. Combined data for these three loci (HLA-B*, DRB1* and MICA) were obtained from a total of 333 patients and 361 healthy controls.

RESULTS

Significant association with B*08 [P < 10(-7), odds ratio (OR) 3.17, 95% confidence interval (CI) 2.02-5.00], DRB1*0301 (P < 10(-7), OR 2.07, 95% CI 1.59-2.68) and MICA5.1 (P = 0.01, OR 1.23, 95% CI 1.04-1.46) was observed. The combinations DRB1*0301-MICA5.1-B8 and HLA-DRB1*0301-B*08-positive and MICA5-1-negative were more frequent among SLE patients (11.4 vs 3.3% in healthy controls, P = 3.9 x 10(-5), OR 3.76, 95% CI 1.85-7.73, and 6.9 vs 1.7%, P = 0.0007, OR 4.32, 95% CI 1.68-13.10, respectively). Additionally, individuals who were HLA-DRB1*0301-B*08-negative and MICA5-1-positive were less frequent among patients (22.2 vs 31.3% in healthy controls, P = 0.007, OR 0.63, 95% CI 0.44-0.89) and the magnitude of the OR was similar to that obtained in individuals negative for all the three factors (OR 0.69, 95% CI 050-0.94). Further analysis performed to detect independent association strongly suggested that the association between MICA5.1 and SLE is secondary to the linkage disequilibrium of this allele with B*08.

CONCLUSIONS

Our results do not support an independent association of MICA gene polymorphism with susceptibility to SLE.

Downstream regulatory element antagonist modulator regulates Ca2+ homeostasis and viability in cerebellar neurons

The Na+/Ca2+ exchangers NCX1, NCX2, and NCX3 are vital for the control of cellular Ca2+ homeostasis. Here, we show that a doublet of downstream regulatory element sites in the promoter of the NCX3 gene mediates transcriptional repression of NCX3 by the Ca2+-modulated transcriptional repressor downstream regulatory element antagonist modulator (DREAM). Overexpression of a DREAM EF-hand mutant insensitive to Ca2+ (EFmDREAM) in hippocampus and cerebellum of transgenic mice significantly reduced NCX3 mRNA and protein levels without modifying NCX1 and NCX2 expression. Cerebellar granules from EFmDREAM transgenic mice showed increased levels of cytosolic Ca2+ and were more vulnerable to increased Ca2+ influx after partial opening of voltage-gated plasma membrane Ca2+ channels induced by increasing K+ in the culture medium but survived better in the conditions of reduced Ca2+ influx prevailing in low extracellular K+. Overexpression of NCX3 in EFmDREAM transgenic granules using a lentiviral vector restored the normal survival response to high K+ observed in wild-type granules. Thus, the downregulation of the regulator of Ca2+ homeostasis NCX3 by Ca2+-regulated DREAM is a striking example of the autoregulatory property of the Ca2+ signal in neurons.

Eye movements evoked by electrical microstimulation of the mesencephalic reticular formation in goldfish

Anatomical studies in goldfish show that the tectofugal axons provide a large number of boutons within the mesencephalic reticular formation. Electrical stimulation, reversible inactivation and cell recording in the primate central mesencephalic reticular formation have suggested that it participates in the control of rapid eye movements (saccades). Moreover, the role of this tecto-recipient area in the generation of saccadic eye movements in fish is unknown. In this study we show that the electrical microstimulation of the mesencephalic reticular formation of goldfish evoked short latency saccadic eye movements in any direction (contraversive or ipsiversive, upward or downward). Movements of the eyes were usually disjunctive. Based on the location of the sites from which eye movements were evoked and the preferred saccade direction, eye movements were divided into different groups: pure vertical saccades were mainly elicited from the rostral mesencephalic reticular formation, while oblique and pure horizontal were largely evoked from middle and caudal mesencephalic reticular formation zones. The direction and amplitude of pure vertical and horizontal saccades were unaffected by initial eye position. However the amplitude, but not the direction of most oblique saccades was systematically modified by initial eye position. At the same time, the amplitude of elicited saccades did not vary in any consistent manner along either the anteroposterior, dorsoventral or mediolateral axes (i.e. there was no topographic organization of the mesencephalic reticular formation with respect to amplitude). In addition to these groups of movements, we found convergent and goal-directed saccades evoked primarily from the anterior and posterior mesencephalic reticular formation, respectively. Finally, the metric and kinetic characteristics of saccades could be manipulated by changes in the stimulation parameters. We conclude that the mesencephalic reticular formation in goldfish shares physiological functions that correspond closely with those found in mammals.

Study of the role of functional variants of SLC22A4, RUNX1 and SUMO4 in systemic lupus erythematosus

BACKGROUND

Functional polymorphisms of the solute carrier family 22, member 4 (SLC22A4), runt related transcription factor 1 (RUNX1) and small ubiquitin-like modifier 4 (SUMO4) genes have been shown to be associated with several autoimmune diseases.

OBJECTIVE

To test the possible role of these variants in susceptibility to or severity of systemic lupus erythematosus (SLE), on the basis that common genetic bases are shared by autoimmune disorders.

METHODS

597 SLE patients and 987 healthy controls of white Spanish origin were studied. Two additional cohorts of 228 SLE patients from Sweden and 122 SLE patients from Colombia were included. A case-control association study was carried out with six single nucleotide polymorphisms (SNP) spanning the SLC22A4 gene, one SNP in RUNX1 gene, and one additional SNP in SUM04 gene.

RESULTS

No significant differences were observed between SLE patients and healthy controls when comparing the distribution of the genotypes or alleles of any of the SLC22A4, RUNX1, or SUMO4 polymorphisms tested. Significant differences were found in the distribution of the SUMO4 genotypes and alleles among SLE patients with and without nephritis, but after multiple testing correction, the significance of the association was lost. The association of SUMO4 with nephritis could not be verified in two independent SLE cohorts from Sweden and Colombia.

CONCLUSIONS

These results suggest that the SLC22A4, RUNX1, and SUMO4 polymorphisms analysed do not play a role in the susceptibility to or severity of SLE.

Visual orienting response in goldfish: a multidisciplinary study

The neural basis underlying the orienting response has been thoroughly studied in frontal-eyed mammals. However, in non-mammalian species, including fish, it remains almost unknown. Therefore, we studied the contribution of the optic tectum and the mesencephalic reticular formation to the performance of the orienting response in goldfish, using behavioural, physiological, and anatomical tracer techniques. The appearance of a visual stimulus (a pellet of food) in the environment of a goldfish evoked a turn of the body to reorient the line of sight. Left-tectal lobe ablation abolished the orienting turn response towards the contralateral hemifield. Electrical microstimulation of the optic tectum suggested the presence of a motor map, which is in correspondence with the overlying visual representation, as previously reported in other vertebrates. The tracer biotin-dextran amine was injected into different functionally identified tectal zones. The results showed that rostral and caudal poles of the mesencephalic reticular formation receive outflow mainly from the rostral and caudal tectal poles, respectively. This suggests that the tectal wiring with downstream structures is site-dependent. Furthermore, the electrical activation of rostral and caudal mesencephalic reticular formation revealed a different contribution to vertical and horizontal orienting eye movements. We conclude that the basic neural system coding the orienting response appears early in phylogenesis, although some specific characteristics are selected by adaptive pressure.

Interleukin 12 (IL12B), interleukin 12 receptor (IL12RB1) and interleukin 23 (IL23A) gene polymorphism in systemic lupus erythematosus

OBJECTIVE

The aim of this study was to assess the possible association between the interleukin-12B (IL12B) and interleukin-12 receptor beta 1 (IL12RB1) gene polymorphisms with systemic lupus erythematosus (SLE). In addition, we have undertaken a systematic search for genetic variants of interleukin 23 (IL23A).

METHODS

The study was conducted on 559 SLE patients and 603 ethnically matched healthy controls. Genotyping of the IL12B [IL12Bpro and IL12B 3' untranslated region (UTR)] and IL12RB1 (641A-->G, 1094T-->C and 1132G-->C) polymorphisms was performed with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and PCR-fluorescent methods, whereas IL23A genetic variants were realized with direct sequencing.

RESULTS

No statistically significant differences in the distribution of the IL12B and the IL12RB1 genotypes and alleles were observed when comparing SLE patients and control subjects. Additionally, no differences in the genotype and allele distribution were found when SLE patients were stratified according to the presence or absence of lupus nephritis. Despite an extensive analysis in 30 individuals, variations located in the exons and in the 5' and 3' UTR regions of IL23A gene were not found in any case.

CONCLUSIONS

These results suggest that polymorphisms located in IL12B, IL12RB1 and IL23A genes may not play a relevant role in the susceptibility or severity of SLE in the Spanish population.

The BDNF gene: exemplifying complexity in Ca2+ -dependent gene expression

Over the last 20 years, great effort has been made to decipher the molecular mechanisms used by cells to transform a cytosolic Ca2+ signal into specific, finely-controlled changes in gene expression. Several previous reviews addressed the variety of regulatory mechanisms that participate in Ca2+ -dependent gene expression in neurons (Carafoli et al., 2001; Mellstrom and Naranjo 2001; West et al., 2001). Nevertheless, recent discoveries have revealed new players and new interactions that tune this process. In this review, we will use the four promoters that regulate the expression of the brain-derived neurotrophic factor (BDNF) gene as a magnificent scenario in which these mechanisms intermingle to show the complexity of Ca2+ -dependent gene expression.

Aromatic metabolism versus carbon availability: the regulatory network that controls catabolism of less-preferred carbon sources in Escherichia coli

The current knowledge on the genetics and biochemistry of the catabolism of aromatic compounds in Escherichia coli settles the basis to consider these pathways as a model system to study the complex molecular mechanisms that control the expression of the genes involved in the metabolism of less-preferred carbon sources in this paradigmatic organism. Two different levels of regulation are reviewed: (i) the specific regulatory mechanisms that drive the expression of the catabolic genes when the cognate inducer, i.e., the substrate of the pathway or an intermediate metabolite, is available, and (ii) the global or superimposed regulation that adjust the expression of the catabolic clusters to the general physiological status of the cell.

Cytotoxic T-lymphocyte antigen-4-CT60 polymorphism in rheumatoid arthritis

Cytotoxic T-lymphocyte antigen-4 (CTLA-4) is a functional candidate gene with susceptibility to rheumatoid arthritis (RA). The aim of this work was to investigate the possible influence of the recently described CT60A/G dimorphism of the CTLA-4 gene in the susceptibility to RA in Spanish patients. A total of 433 RA patients and 398 control subjects were included in the study. Genotyping of CTLA-4 CT60 was performed using two different methods: polymerase chain reaction restriction fragment length polymorphism system using an amplification-created restriction site and a TaqMan 5'-allelic discrimination assay. In order to validate results obtained by different methods, a quality-control exercise was performed. No significant deviation in the distribution of the alleles or genotypes of the CT60 was found when we compared RA patient and control groups. In addition, no differences in CTLA-4 CT60 genotypic distribution was found when RA patients and controls were stratified by the presence or absence of the shared epitope. In conclusion, our results do not support an association between CT60A/G polymorphism and susceptibility to RA in the Spanish population, although the contribution of other positions located within the 3' region of the CTLA-4 gene to RA susceptibility cannot be discarded.

Day-night changes in downstream regulatory element antagonist modulator/potassium channel interacting protein activity contribute to circadian gene expression in pineal gland

The molecular mechanisms controlling the oscillatory synthesis of melatonin in rat pineal gland involve the rhythmic expression of several genes including arylalkylamine N-acetyltransferase (AA-NAT), inducible cAMP early repressor (ICER), and Fos-related antigen-2 (fra-2). Here we show that the calcium sensors downstream regulatory element antagonist modulator/potassium channel interacting protein (DREAM/KChIP)-3 and KChIP-1, -2 and -4 bind to downstream regulatory element (DRE) sites located in the regulatory regions of these genes and repress basal and induced transcription from ICER, fra-2 or AA-NAT promoters. Importantly, we demonstrate that the endogenous binding activity to DRE sites shows day-night oscillations in rat pineal gland and retina but not in the cerebellum. The peak of DRE binding activity occurs during the day period of the circadian cycle, coinciding with the lowest levels of fra-2, ICER, and AA-NAT transcripts. We show that a rapid clearance of DRE binding activity during the entry in the night period is related to changes at the posttranscriptional level of DREAM/KChIP. The circadian pattern of DREAM/KChIP activity is maintained under constant darkness, indicating that an endogenous clock controls DREAM/KChIP function. Our data suggest involvement of the family of DREAM repressors in the regulation of rhythmically expressed genes engaged in circadian rhythms.

SLC11A1 promoter gene polymorphisms and fibrosis progression in chronic hepatitis C

BACKGROUND AND AIMS

The solute carrier family 11 member 1 (SLC11A1) gene (formerly Nramp1) encodes for the protein solute carrier family 11, member 1. It affects susceptibility and clinical outcome of autoimmune and infectious diseases. We investigated the possible role of the functional polymorphism located in the promoter region of SLC11A1 and tumour necrosis factor (TNF) genes in the progression of fibrosis in chronic hepatitis C.

METHODS

A total of 242 Caucasian Spanish patients with biopsy proven chronic hepatitis C and 194 healthy control subjects were genotyped for SLC11A1 and TNF promoter polymorphisms.

RESULTS

No significant differences in the distribution of frequencies among patient and control groups were observed. The SCL11A1 homozygous 2/2 genotype was rarely detected among patients showing advanced fibrosis (2/82; 2.4%) but was highly represented in those with mild fibrosis (29/160; 18.1%; odds ratio (OR) 8.85 (95% confidence interval (CI) 1.9-55.2, p(c) = 0.002). In patients carrying allele 3 of SLC11A1, the presence of -238 TNF A/G was associated with advanced fibrosis (14/26 (53.8%) v 68/216 (31.4%); OR 2.53 (95% CI 1.03-6.23); p = 0.02).

CONCLUSIONS

SLC11A1 gene promoter polymorphism could influence fibrosis progression in chronic hepatitis C in that the homozygous genotype 2/2 exerts a protective effect against cirrhosis development. Also, the combination of TNF -238 A/G and the presence of allele 3 is conducive to progression to pre-cirrhotic or cirrhotic stages of the disease.

Afferent connectivity to different functional zones of the optic tectum in goldfish

This work studies the afferent connectivity to different functionally identified tectal zones in goldfish. The sources of afferents contributed to different degrees to the functionally defined zones. The dorsocentral area of the telencephalon was connected mainly with the ipsilateral anteromedial tectal zone. At diencephalic levels, neurons were found in three different regions: preoptic, thalamic, and pretectal. Preoptic structures (suprachiasmatic and preoptic nuclei) projected mainly to the anteromedial tectal zone, whereas thalamic (ventral and dorsal) and pretectal (central, superficial, and posterior commissure) nuclei projected to all divisions of the tectum. In the mesencephalon, the mesencephalic reticular formation, torus longitudinalis, torus semicircularis, and nucleus isthmi were, in the anteroposterior axis, topographically connected with the tectum. In addition, neurons in the contralateral tectum projected to the injected zones in a symmetrical point-to-point correspondence. At rhombencephalic levels, the superior reticular formation was connected to all studied tectal zones, whereas medial and inferior reticular formations were connected with medial and posterior tectal zones. The present results support a different quantitative afferent connectivity to each tectal zone, possibly based on the sensorimotor transformations that the optic tectum carries out to generate orienting responses.

A dual lethal system to enhance containment of recombinant micro-organisms

Active containment systems based on the controlled expression of a lethal gene are designed to increase containment of recombinant micro-organisms used for environmental applications. A major drawback in containment is the existence of mutations that generate surviving cells that cease to respond to the toxic effect of the lethal function. In this work the authors have developed for the first time a strategy to reduce the problem of mutations and increase the efficiency of containment based on the combination of two lethal functions acting on different cellular targets of major concern in containment, DNA and RNA, and whose expression is under control of different regulatory signals. To engineer the dual gene containment circuit, two toxin–antitoxin pairs, i.e. the colicin E3–immunity E3 and theEcoRI restriction–modification systems, were combined. The genes encoding the immunity E3 and theEcoRI methyltransferase proteins (antitoxins) were stably inserted into the chromosome of the host cell, whereas the broad-host-range lethal genes encoding the colicin E3 RNase and theEcoRI restriction endonuclease (toxins) were flanking the contained trait in a plasmid. This dual lethal cassette decreased gene transfer frequencies, through killing of the recipient cells, by eight orders of magnitude, which provides experimental evidence that the anticipated containment level due to the combination of single containment systems is generally achieved. Survivors that escaped killing were analysed and the mutational events involved were characterized.

Connectivity of the goldfish optic tectum with the mesencephalic and rhombencephalic reticular formation

The optic tectum of goldfish, as in other vertebrates, plays a major role in the generation of orienting movements, including eye saccades. To perform these movements, the optic tectum sends a motor command through the mesencephalic and rhombencephalic reticular formation, to the extraocular motoneurons. Furthermore, the tectal command is adjusted by a feedback signal arising from the reticular targets. Since the features of the motor command change with respect to the tectal site, the present work was devoted to determining, quantitatively, the particular reciprocal connectivity between the reticular regions and tectal sites having different motor properties. With this aim, the bidirectional tracer, biotin dextran amine, was injected into anteromedial tectal sites, where eye movements with small horizontal and large vertical components were evoked, or into posteromedial tectal sites, where eye movements with large horizontal and small vertical components were evoked. Labeled boutons and somas were then located and counted in the reticular formation. Both were more numerous in the mesencephalon than in the rhombencephalon, and ipsilaterally than contralaterally, with respect to the injection site. Furthermore, the somas showed a tendency to be located in the area containing the most dense labeling of synaptic endings. In addition, labeled boutons were often observed in close association with retrogradely stained neurons, suggesting the presence of a tectoreticular feedback circuit. Following the injection in the anteromedial tectum, most of the boutons and labeled neurons were found in the reticular formation rostral to the oculomotor nucleus. Conversely, following the injection in the posteromedial tectum, most of the boutons and neurons were also located in the caudal mesencephalic reticular formation. Finally, boutons and neurons were found in the rhombencephalic reticular formation surrounding the abducens nucleus. They were more numerous following the injection in the posteromedial tectum. These results demonstrate characteristic patterns of reciprocal connectivity between physiologically different tectal sites and the mesencephalic and rhombencephalic reticular formation. These patterns are discussed in the framework of the neural substratum that underlies the codification of orienting movements in goldfish.

Phobic anxiety in 11 nations. Part I: Dimensional constancy of the five-factor model

The Fear Survey Schedule-III (FSS-III) was administered to a total of 5491 students in Australia, East Germany, Great Britain, Greece, Guatemala, Hungary, Italy, Japan, Spain, Sweden, and Venezuela, and submitted to the multiple group method of confirmatory analysis (MGM) in order to determine the cross-national dimensional constancy of the five-factor model of self-assessed fears originally established in Dutch, British, and Canadian samples. The model comprises fears of bodily injury-illness-death, agoraphobic fears, social fears, fears of sexual and aggressive scenes, and harmless animals fears. Close correspondence between the factors was demonstrated across national samples. In each country, the corresponding scales were internally consistent, were intercorrelated at magnitudes comparable to those yielded in the original samples, and yielded (in 93% of the total number of 55 comparisons) sex differences in line with the usual finding (higher scores for females). In each country, the relatively largest sex differences were obtained on harmless animals fears. The organization of self-assessed fears is sufficiently similar across nations to warrant the use of the same weight matrix (scoring key) for the FSS-III in the different countries and to make cross-national comparisons feasible. This opens the way to further studies that attempt to predict (on an a priori basis) cross-national variations in fear levels with dimensions of national cultures.

The effects of telencephalic pallial lesions on spatial, temporal, and emotional learning in goldfish

In mammals, the pallial amygdala is implicated in emotional learning and memory, whereas the hippocampus is involved in spatial, contextual, or relational memory. This review presents a set of experiments aimed to study the involvement of the dorsomedial and dorsolateral telencephalon of goldfish in spatial and active avoidance learning. Results showed that (1) medial lesions impaired both acquisition and retention of conditioned avoidance response in two-way active avoidance learning experiments with stimuli overlapping (emotional factor) and with an interstimuli gap (temporal and emotional factors), and (2) the medial lesion did not affect spatial learning (spatial, contextual, or relational factors). In contrast, lateral lesions did not impair conditioned avoidance response with stimuli overlapping, but affected conditioned avoidance response with an interstimuli gap and spatial learning. These results support the presence of two differentiated memory systems in teleost fish based on discrete pallial regions: emotional (dorsomedial telencephalon) and spatial/temporal or relational (dorsolateral telencephalon). Furthermore, these functional data support the homology between the medial pallium of the teleost and the pallial amygdala of land vertebrates, and between the teleost lateral pallium and the mammalian hippocampus.

Neural substrata underlying tectal eye movement codification in goldfish

The optic tectum encodes orienting eye saccades in a spatially ordered map. To investigate whether the functional properties of each tectal site are related to a particular pattern of connectivity with downward structures in the brainstem, two sets of experiments were carried out. First, biotinylated dextran amine (BDA) was injected at different tectal sites along the anteroposterior axis. Electrical stimulation at these sites evoked saccades whose horizontal component amplitudes increased with the distance to the rostral pole. In the second experiment, BDA and fluoro-ruby (FR) were injected at different tectal sites along the mediolateral axis. Electrical stimulation here evoked saccades with different upward and downward directions, but similar horizontal component amplitudes. A major finding of the first experiment was that a topographic link of the tectum exists with the mesencephalic reticular formation, but that such a connection was absent or very attenuated for the rhombencephalic reticular formation. In the second set of experiments, the clusters of BDA and FR boutons left by the mediolateral tectal sites were separated in the rostral mesencephalon, at the level of the nucleus of the medial longitudinal fasciculus, but overlapped in the caudal mesencephalon and rhombencephalon. These data provide evidence that decodification of tectal motor commands is based, at least in part, on the connectivity of each tectal locus on downward structures with the brainstem.

Cloning, expression, signaling mechanisms, and membrane targeting of P2Y(11) receptors in Madin Darby canine kidney cells

The P2Y(11) receptor is hypothesized to link to both G(s) and G(q), although this proposition is based on expression and separate assays of G(s) and G(q) function in different cell types [J Biol Chem 1997;272:31969-31973]. We have cloned and characterized a canine P2Y(11)-like (cP2Y(11)) receptor from cultured Madin Darby canine kidney (MDCK-D1) cells. When cP2Y(11) receptors are expressed in canine thymocyte (CF2Th) cells that normally lack functional purinergic responses, ADP beta S stimulates phosphatidylinositol (PI) hydrolysis, Ca(2+) mobilization, and cAMP accumulation. Pharmacologic analysis indicates that the stimulation of cAMP production is direct and not a result of eicosanoid synthesis, activation of PKC, or elevation of cell Ca(2+). The rank order of potency for stimulation of PI hydrolysis by cP2Y(11) receptors (adenosine 5'-(2-O-thio) diphosphate = 2-methylthio-ADP >/= 2-methylthio-ATP >> ADP > ATP) differs from that of hP2Y(11) receptors. Microscopic examination of MDCK-D1 cells expressing carboxyl-terminal green fluorescent protein (GFP)-tagged cP2Y(11) (cP2Y(11)-GFP) receptors indicates primarily basolateral (BL) targeting. BL addition of 200 microM ADP beta S to confluent monolayers of MDCK-D1 cells produces an increase in short circuit current (I(sc)) (11.6 +/- 1.6 microA/cm(2)) whereas apical addition of agonist has no effect, confirming targeting of functional endogenous P2Y(11) receptors to the BL surface. In contrast, when either cP2Y(11) or cP2Y(11)-GFP is overexpressed in MDCK-D1 cells, the sensitivity of I(sc) to BL agonist increases by nearly 2 orders of magnitude, as if receptor density normally limited agonist potency; moreover, apical addition of ADP beta S now produces an increase in I(sc) but with low potency. The data support the BL localization of cP2Y(11) receptors and receptor coupling to changes in I(sc) in MDCK-D1 cells except in cases in which receptors are overexpressed; receptor overexpression leads to altered sensitivities and sites of coupling to physiologic responses.

P2Y receptors of MDCK cells: epithelial cell regulation by extracellular nucleotides

1. Madin-Darby canine kidney (MDCK) cells, a well- differentiated renal epithelial cell line derived from distal tubule/collecting duct, respond to extracellular nucleotides by altering ion flux and the production of arachidonic acid-derived products, in particular prostaglandin E2 (PGE2). Our work has defined the receptors and signalling events involved in such responses. 2. We have found evidence for expression of at least three P2Y receptor subtypes (P2Y1, P2Y2 and P2Y11) in MDCK-D1 cells, a subclone from parental MDCK. 3. These receptors appear to couple to increases in calcium and protein kinase C activity, probably via a Gq/G11-mediated activation of phospholipase C. 4. In addition, P2Y receptor activation can promote a prominent increase in cAMP. This includes both a P2Y2 receptor-mediated cyclo-oxygenase (COX)-dependent component and another COX-independent component mediated by other P2Y receptors. 5. We have documented that changing media in which cells are grown releases ATP and, in turn, activates P2Y receptors. Such release of ATP contributes in a major way to basal cAMP levels in these cells. 6. The data indicate that MDCK cells are a useful model to define the regulation of epithelial cells by extracellular nucleotides. Of particular note, spontaneous or stretch-induced release of ATP and subsequent activation of one or more P2Y receptors contributes to establishing the basal activity of signalling pathways.

Eye-movement recording in freely moving animals

A new method is described for precise recording of eye movements in freely moving animals using Hall-effect devices. This inexpensive system, of small size and low weight, allows the analysis of horizontal and vertical components of saccadic eye movements, optokinetic nystagmus, slow tracking movements, eye vergence, etc., in unrestrained animals. A set of Hall-effect devices mounted in the skull is used to sense variations in the position of high-power miniature magnets fixed to the eye sclera. The output of the Hall-effect devices is amplified by operational amplifiers and collected through an analog-to-digital converter to be displayed on-line in a personal computer and stored for later analysis by specific software. Some examples of simultaneous body- and eye-movement recordings obtained in freely moving goldfish in different experimental situations are presented. This method would be useful in the recording of eye and gaze movements under natural conditions and for behavioural studies in freely moving animals.

P2Y(2) receptor of MDCK cells: cloning, expression, and cell-specific signaling

Madin-Darby canine kidney (MDCK)-D1 cells, a canine renal epithelial cell line, co-express at least three different P2Y receptor subtypes: P2Y(1), P2Y(2), and P2Y(11) (24). Stimulation of P2Y receptors in these cells results in the release of arachidonic acid (AA) and metabolites and the elevation of intracellular cAMP. To define in more precise terms the signaling contributed by the MDCK-D1 P2Y(2) (cP2Y(2)) receptor, we have cloned and heterologously expressed it in CF2Th (canine thymocyte) cells, a P2Y(2)-null cell. Analysis by RT-PCR indicated that canine P2Y(2) receptors are expressed in skeletal muscle, spleen, kidney, lung, and liver. When expressed in CF2Th cells, cP2Y(2) receptors promoted phospholipase C-mediated phosphatidylinositol (PI) hydrolysis [uridine 5'-triphosphate > or = ATP > adenosine 5'-diphosphate > 2MT-ATP] and mobilization of intracellular Ca(2+). In contrast to their actions in MDCK-D1 cells, cP2Y(2) receptors did not stimulate formation of cAMP or AA release when expressed in CF2Th cells. The data indicate that cell setting plays an essential role in the ability of P2Y receptors to regulate AA release and cAMP formation. In particular, renal epithelial cells preferentially express components critical for cP2Y(2)-induced cAMP formation, including the expression of enzymes involved in the generation and metabolism of AA and receptors that respond to PGE(2).

Connectivity of the tectal zones coding for upward and downward oblique eye movements in goldfish

Deep layers of the goldfish tectum code movements in a topographically ordered motor map. This work studies the relationship between tectal sites (coding eye movements with different vertical directions) and the distributions of boutons (left by their projections), within rostral mesencephalic structures and rhombencephalic reticular formations. These regions have been involved in the generation of the vertical and horizontal components of eye movement, respectively, as suggested by the Cartesian hypothesis of de-codification of tectal signal. With this aim, discrete injections of biotinylated dextran amine (BDA) and Fluoro-Ruby (FR) were made into functionally identified tectal sites, coding oblique eye movements with similar amplitude of the horizontal component but opposite upward and downward vertical directions, and the distribution of synaptic endings was determined. The main findings of the present work were as follows: 1) within the tectal descending tract, axons were organized according to the location of injected sites within the tectum; 2) BDA and FR boutons were distributed in separate clusters within the medial longitudinal fasciculus and oculomotor nuclei, as well as in the nearby mesencephalic reticular formation; and 3) the regions containing both types of bouton overlapped moderately within the mesencephalic reticular formation at the isthmus level. Overlapping was more extended at the different levels of the rhombencephalic reticular formation, although a shift in the distribution of both types of bouton was always observed. These results suggest that, within the vertical generator, the endings were separated to contact the different neuronal population that codes the upward and downward components of movements. In contrast, in the horizontal generator, tectal endings more likely converge on the same neuronal population to code the horizontal component of movements, irrespective of whether the oblique movements were directed upward or downward.

A gene containment strategy based on a restriction-modification system

Engineering barriers to the spread of specific genes are of great interest both to increase the predictability of recombinant microorganisms used for environmental applications and to study the role of gene transfer in the adaptation of microbial communities to changing environments. We report here a new gene containment circuit based on a toxin-antidote pair that targets the cell DNA, i.e. the type II EcoRI restriction-modification system. The set-up involved linkage of the ecoRIR lethal gene encoding the EcoRI endonuclease (toxin) to the contained character in a plasmid and chromosomal insertion of the ecoRIM gene encoding the cognate EcoRI methylase (antidote) that protects the target DNA from restriction. Transfer of the contained character to a recipient cell lacking the antidote caused EcoRI-mediated chromosomal breaks, leading to cell death, thereby preventing gene spread. Using transformation and conjugation as mechanisms of DNA transfer and different environmentally relevant bacteria as recipients, we have shown that the potentially universal EcoRI-based containment system decreases gene transfer frequencies by more than four orders of magnitude. Analyses of the survivors escaping killing revealed a number of possible inactivation mechanisms.