V1 mechanisms and some figure-ground and border effects.

V1 neurons have been observed to respond more strongly to figure than background regions. Within a figure region, the responses are usually stronger near figure boundaries (the border effect), than further inside the boundaries. Sometimes the medial axes of the figures (e.g., the vertical midline of a vertical figure strip) induce secondary, intermediate, response peaks (the medial axis effect). Related is the physiologically elusive "cross-orientation facilitation", the observation that a cell's response to a grating patch can be facilitated by an orthogonally oriented grating in the surround. Higher center feedbacks have been suggested to cause these figure-ground effects. It has been shown, using a V1 model, that the causes could be intra-cortical interactions within V1 that serve pre-attentive visual segmentation, particularly, object boundary detection. Furthermore, whereas the border effect is robust, the figure-ground effects in the interior of a figure, in particular, the medial axis effect, are by-products of the border effect and are predicted to diminish to zero for larger figures. This model prediction (of the figure size dependence) was subsequently confirmed physiologically, and supported by findings that the response modulations by texture surround do not depend on feedbacks from V2. In addition, the model explains the "cross-orientation facilitation" as caused by a dis-inhibition, to the cell responding to the center of the central grating, by the background grating. Furthermore, the elusiveness of this phenomena was accounted for by the insight that it depends critically on the size of the figure grating. The model is applied to understand some figure-ground effects and segmentation in psychophysics: in particular, that contrast discrimination threshold is lower within and at the center of a closed contour than that in the background, and that a very briefly presented vernier target can perceptually shine through a subsequently presented large grating centered at the same location.     

Transgenic and knockout rodents: Novel insights into mechanisms of body weight regulation

Transgenic animals that over- or underexpress a protein of interest have been used to study obesity development, prevention, and susceptibility to diet-induced obesity such as a high-fat diet. Several transgenic models are resistant to diet-induced obesity including those that overexpress the insulin-sensitive glucose transporter, GLUT4, in adipose tissue only. In this animal there is increased adipose tissue mass but the animal maintains its insulin sensitivity. The overexpression of lipoprotein lipase (LPL) in skeletal muscle and the elimination of a protein kinase A subunit both resulted in lean and obesity resistant animals. By directing the production of the diphtheria toxin A chain to adipose tissue only the resulting animals not only had less adipose tissue mass but were resistant to MSG-induced obesity. Conversely, transgenic models with decreased brown adipose tissue or its function have all resulted in obese animals, highlighting the importance of thermoregulation in body weight maintenance. The use of transgenic technology in the field of obesity has emphasized the regional differences among fat pads as well as the dissimilarity between genders in fuel metabolism. Several transgenic models have separated obesity from insulin resistance allowing the importance of each state to be studied individually. Results using transgenic animals have re-emphasized that obesity is a polygenic disease.     

Exchange of serine residues 263 and 266 reduces the function of mouse gap junction protein connexin31 and exhibits a dominant-negative effect on the wild-type protein in HeLa cells

To characterize the role of Cx31 phosphorylation, serine residues 263 and 266 (Cx31Delta263,266) or 266 (Cx31Delta266) alone were exchanged for amino acids that cannot be phosphorylated. HeLa cells, which were stably transfected with wild type and the two different mutant Cx31-cDNA constructs, were analyzed for expression, phosphorylation, localization, formation of functional gap junction channels, and degradation of mutant Cx31 protein. Both mutant proteins showed similar reduced phosphorylation levels compared to Cx31 wild type, indicating a pivotal role of serine residue 266 for Cx31 phosphorylation. None of these mutations did interfere with correct intracellular trafficking of gap junction proteins. Pulse chase experiments with the different transfectants revealed an increased turnover of both mutated Cx31 proteins. They showed decreased intercellular communication as shown by dye transfer to neighboring cells and measurement of total conductance (mutant Cx31Delta263,266). Mutated Cx31 protein (Cx31Delta263,266) diminished the function of the Cx31 wild-type protein dependent on the amount of the mutated protein, indicating a dominant-negative effect of the mutated protein in HeLa cells.     

Structural characteristics and rheological properties of partially hydrolyzed oat β-glucan: the effects of molecular weight and hydrolysis method

Partial hydrolysates of (1→3)(1→4)-β- -glucan from oats were produced by three hydrolysis methods: acid, cellulase or lichenase. The molecular weights ranged from 31 000 to 237 000 g/mol. Six percent solutions of small molecular weight β-glucans formed elastic gels after 4 days at 4 °C whereas larger molecular weight β-glucans remained viscous liquids after 7 days. The melting temperature of the gels increased as they aged and the peak heat flow temperature, measured by differential scanning calorimetry, was 62±2 °C. Partial hydrolysates produced with cellulase, which was shown to preferentially cleave regions of the molecule with longer contiguous β-(1→4)-linked -glucopyranosyl units, tended to produce more elastic gels with stronger junction zones than partial hydrolysates produced with lichenase which cleaves the β-(1→4) glycosidic 3-o-substituted glucose links. This suggests that β-(1→3)-linked cellotriose sections of the polymer are probably the segments which form the junction zones in the gel network rather than cellulose-like segments.     

Macro shocks and micro outcomes: child nutrition during Indonesia’s crisis

A survey of households in rural Java is used to assess the nutritional impact of Indonesia's drought and financial crisis of 1997/1998. A time-age-cohort decomposition reveals significant nutritional impacts. However, child weight-for-age (WAZ) remained constant throughout the crisis, despite rapid increases in food prices and the consequent household consumption shock. The evidence is consistent with the hypothesis that within households, mothers buffered children's caloric intake, resulting in increased maternal wasting. However, reductions in the consumption of high-quality foods further resulted in increased prevalence of anemia for both mothers and children. The combined effects were particularly severe for cohorts conceived and weaned during the crisis.     

Very early and transient vegetal-plate expression of SpKrox1, a Krüppel/Krox gene from Strongylocentrotus purpuratus

All endodermal and mesenchymal cells of the sea urchin embryo descend from the vegetal plate, a thickened epithelium of approximately 50 cells arising at the early blastula stage. Cell types that derive from the vegetal plate are specified conditionally by inductive interactions with underlying micromeres, but the molecular details of vegetal-plate specification remain unresolved. In a search for regulatory proteins that have roles in vegetal-plate specification, a screen was performed to clone Krüppel/Krox-related genes from a Strongylocentrotus purpuratus embryo cDNA library. One newly identified clone, named SpKrox1, contained four zinc fingers and a leucine zipper domain. SpKrox1 expression was low in unfertilized eggs, increased severalfold to the early blastula stage and decreased between the early gastrula and pluteus stages. SpKrox1 mRNA was first seen in macromeres of 16-cell stage embryos and was restricted to cells of the developing vegetal plate thereafter. Vegetal-plate expression corresponded to a ring of cells around the blastopore and overlapped the expression patterns of other genes with potential roles in vegetal plate-specification. As the vegetal-plate cells invaginated into the blastopore, SpKrox1 expression was lost, suggesting that its role was not in endoderm differentiation per se but rather in the initial establishment of the vegetal plate.     

DEF6, a novel PH-DH-like domain protein, is an upstream activator of the Rho GTPases Rac1, Cdc42, and RhoA

In this paper, we describe the characterization of DEF6, a novel PH-DH-like protein related to SWAP-70 that functions as an upstream activator of Rho GTPases. In NIH 3T3 cells, stimulation of the PI 3-kinase signaling pathway with either H2O2 or platelet-derived growth factor (PDGF) resulted in the translocation of an overexpressed DEF6-GFP fusion protein to the cell membrane and induced the formation of filopodia and lamellipodia. In contrast to full-length DEF6, expression of the DH-like (DHL) domain as a GFP fusion protein potently induced actin polymerization, including stress fiber formation in COS-7 cells, in the absence of PI 3-kinase signaling, indicating that it was constitutively active. The GTP-loading of Cdc42 was strongly enhanced in NIH 3T3 cells expressing the DH domain while filopodia formation, membrane ruffling, and stress fiber formation could be inhibited by the co-expression of the DH domain with dominant negative mutants of either N17Rac1, N17Cdc42, or N19RhoA, respectively. This indicated that DEF6 acts upstream of the Rho GTPases resulting in the activation of the Cdc42, Rac1, and RhoA signaling pathways. In vitro, DEF6 specifically interacted with Rac1, Rac2, Cdc42, and RhoA, suggesting a direct role for DEF6 in the activation of Rho GTPases. The ability of DEF6 to both stimulate actin polymerization and bind to filamentous actin suggests a role for DEF6 in regulating cell shape, polarity, and movement.     

A common and recurrent 13-bp deletion in the autoimmune regulator gene in British kindreds with autoimmune polyendocrinopathy type 1.

Autoimmune polyendocrinopathy type 1 (APS1) is an autosomal recessive disorder characterized by autoimmune hypoparathyroidism, autoimmune adrenocortical failure, and mucocutaneous candidiasis. Recently, an autoimmune regulator gene (AIRE-1), which is located on chromosome 21q22.3, has been identified, and mutations in European kindreds with APS1 have been described. We used SSCP analysis and direct DNA sequencing to screen the entire 1,635-bp coding region of AIRE-1 in 12 British families with APS1. A 13-bp deletion (964del13) was found to account for 17 of the 24 possible mutant AIRE-1 alleles, in our kindreds. This mutation was found to occur de novo in one affected subject. A common haplotype spanning the AIRE-1 locus was found in chromosomes that carried the 964del13 mutation, suggesting a founder effect in our population. One of 576 normal subjects was also a heterozygous carrier of the 964del13 mutation. Six other point mutations were found in AIRE-1, including two 1-bp deletions, three missense mutations (R15L, L28P, and Y90C), and a nonsense mutation (R257*). The high frequency of the 964del13 allele and the clustering of the other AIRE-1 mutations may allow rapid molecular screening for APS1 in British kindreds. Furthermore, the prevalence of the 964del13 AIRE-1 mutation may have implications in the pathogenesis of the more common autoimmune endocrinopathies in our population.     

Splicing Defects in the COL3A1 Gene: Marked Preference for 5′ (Donor) Splice-Site Mutations in Patients with Exon-Skipping Mutations and Ehlers-Danlos Syndrome Type IV

Ehlers-Danlos syndrome (EDS) type IV results from mutations in the COL3A1 gene, which encodes the constituent chains of type III procollagen. We have identified, in 33 unrelated individuals or families with EDS type IV, mutations that affect splicing, of which 30 are point mutations at splice junctions and 3 are small deletions that remove splice-junction sequences and partial exon sequences. Except for one point mutation at a donor site, which leads to partial intron inclusion, and a single base-pair substitution at an acceptor site, which gives rise to inclusion of the complete upstream intron into the mature mRNA, all mutations result in deletion of a single exon as the only splice alteration. Of the exon-skipping mutations that are due to single base substitutions, which we have identified in 28 separate individuals, only two affect the splice-acceptor site. The underrepresentation of splice acceptor-site mutations suggests that the favored consequence of 3' mutations is the use of an alternative acceptor site that creates a null allele with a premature-termination codon. The phenotypes of those mutations may differ, with respect to either their severity or their symptomatic range, from the usual presentation of EDS type IV and thus have been excluded from analysis.     

Distribution and palaeoecology of freshwater algae and stromatolites: III, some new forms from the Carboniferous, Permian and Triassic of France and Spain

New collections allow us to describe some new algae forming: a) centimetric, unorganized, masses (Toutinella bifurcata from the Middle Triassic of Provence); b) large, decimetric masses (Zarramanella menorica from the ‘Buntsandstein’ of Minorca, Balearic Islands) and c) interesting, plurispecific biocenosis, laminated and silicified, from the French Massif Central: Lower Stephanian of Saint-Étienne basin (with Hankerpella minima, Baltzerella stephaniense, Ponsinella undulata) and Lower Autunian of Bourbon-l'Archambault basin (Hanskerpella pustulata, Baltzerella stephaniense, Ponsinella multifrons, Sarfatigirella intricata). Other forms are badly preserved, one is possibly a Broutinella sp. and another may be a coccoid form of cyanobacteria or chlorophyceae. Silicified biocenoses macroscopically occur in the form of regular laminations, exhibiting vertical, planar joints (1–2 cm wide) and horizontal, planar joints, 5 mm to 3 cm thick, with various sedimentary infillings. These facies represent early and late silicifications of biological felts (mats), probably previously partly calcified and affected by desiccation cracks partly infilled before the silicification. There is no evidence for an early silicification of living filaments and trichomes. The silicification also affects other types of sediments (petites, sandstones, conglomerates, breccias) associated with the algal formations. Macroscopically, these laminated formations do not show domes or hemispheres; on the other hand, these features clearly appear under the microscope, and these formations are true stromatolites. The basins of Saint-Étienne and Bourbon-l'Archambault contain volcanic rocks; the siliceous series, very localized in the basins, represent an impregnation of various primary materials by silica of hydrothermal origin. The present study is voluntarily limited to the palaeontological and palaeoecological appearances; algal laminations formed in ephemeral pools and small lakes, under very particular conditions, ‘hydrothermal’ sensu lato, are still to be stated more precisely.

Résumé

Des récoltes nouvelles permettent de décrire quelques algues nouvelles formant des amas centimétriques non organisés (Toutinella bifurcata du Trias moyen de Provence), de grosses masses décimétriques (Zarmmanella menorica du Buntsandstein de Minorque) et d'intéressantes biocrenoses plurispécifiques laminées et silicifiées du Massif central français: Stephanien inférieur de Saint-Étienne (à Hankerpella minima, Baltzerella stephaniense, Ponsinella undulata), Autunien inférieur du bassin de Bourbon-l'Archambault (Hanskerpella pustulata, Baltzerella stephaniense, Ponxinella multifrons, Sarfatigirella intricata). D'autres formes sont mal conservées, l'une serait attribuables à une ? Broutinella sp. et une autre à une coccoide (cyanobactéries ou chlorophycées). Les biocœnoses silicificées se présentent macroscopiquement sous forme de laminations régulières, accidentées de fentes planes verticales (1–2 cm de largeur) et de fentes planes horizontales (5 mm–3 cm de hauteur), à remplissages sédimentaires variés. Ces faciès correspondent à des silicifications précoces et tardives de feutres biologiques probablement en grande partie calcifiés précocement et affectés de fentes de dessiccation partiellement remplies avant la silicification. Aucun indice de silicification de filaments et de trichomes du vivant des organismes n'a pu être observé. La silicification affecte aussi d'autres sédiments (pélites, grès, conglomérats, brèches), associés aux anciennes formations algaires. Macrospiquement, ces formations laminées ne montrent pas de dômes ni d'hémisphères; en revanche ces structures apparaissent parfaitement au microscope, et ce sont de véritables stromatolites. Les bassins de Saint-Étienne el de Bourbon-l'Archambault contiennent des formations volcaniques; les formations siliceuses, qui sont très localisées dans les bassins, correspondent certainement à une imprégnation par de la silice d'origine hydrothermale de sédiments variés. La présente étude se limite volontairement à l'aspect paléontologique et paléoécologique; les laminations algaires se sont formées dans des bassins ou de petits lacs éphémères, dans des conditions très particulières, hydrothermales sensu lato, encore à préciser.     

A carbon monoxide irreducible form of cytochrome c oxidase and other unusual properties of the “monomeric” shark enzyme

Contrary to previous reports, the functional and spectral properties of “monomeric” shark cytochrome c oxidases are not entirely similar to those of the “dimeric” beef enzyme. Most significantly, unlike the behavior of beef oxidase, the fully oxidized shark enzyme is not reducible by carbon monoxide. Also, preparations of the shark enzyme, isolated at pH 7.8-8.0, lead to more than 60% of the sample always being obtained in a resting form, whereas similarly prepared beef oxidase is very often obtained, both by ourselves and others, exclusively in the pulsed form. Although the electronic absorption, magnetic circular dichroism and electron paramagnetic resonance (EPR) spectra of cytochrome c oxidase obtained from several shark species are similar to those of the beef enzyme, there are some significant differences. In particular, the Soret maximum is at 422 nm in the case of the fully oxidized resting shark oxidases at physiological pH and not 418 nm as commonly found for the beef enzyme. Moreover, the resting shark oxidases do not necessarily exhibit a “g = 12” signal in their EPR spectra. The turnover numbers of recent preparations of the shark enzyme are higher than previously reported and, interestingly, do not differ within experimental uncertainty from those documented for several beef isoenzymes assayed under comparable conditions.     

An alternative route for multistep tumorigenesis in a novel case of hereditary renal cell cancer and a t(2;3)(q35;q21) chromosome translocation.

Through allele-segregation and loss-of-heterozygosity analyses, we demonstrated loss of the translocation-derivative chromosome 3 in five independent renal cell tumors of the clear-cell type, obtained from three members of a family in which a constitutional t(2;3)(q35;q21) was encountered. In addition, analysis of the von Hippel-Lindau gene, VHL, revealed distinct insertion, deletion, and substitution mutations in four of the five tumors tested. On the basis of these results, we conclude that, in this familial case, an alternative route for renal cell carcinoma development is implied. In contrast to the first hit in the generally accepted two-hit tumor-suppressor model proposed by Knudson, the familial translocation in this case may act as a primary oncogenic event leading to (nondisjunctional) loss of the der(3) chromosome harboring the VHL tumor-suppressor gene. The risk of developing renal cell cancer may be correlated directly with the extent of somatic (kidney) mosaicism resulting from this loss.     

Comparative effects of insecticides with different mechanisms of action on Chrysoperla externa (Neuroptera: Chrysopidae): Lethal,sublethal and dose–response effects

The comprehensive knowledge that the delayed systemic and reproduction side effects can be even more deleterious than acute toxicity, has caused a shift in focus toward sublethal effects assessment on physiology and behavior of beneficial insects. In this study, we assessed the risks posed by some insecticides with different mode of action through lethal and delayed systemic sublethal effects on the pupation, adult emergence, and reproduction of the chrysopid Chrysoperla externa (Hagen, 1861; Neuroptera: Chrysopidae), an important predator in pest biological control. The maximum field recommended dose (MFRD) and twice (2×MFRD) for chlorantraniliprole, tebufenozide, and pyriproxyfen were harmless to C. externa. In contrast, all the tested chitin synthesis inhibitors (CSIs) were highly detrimental to the predator, despite of their lack of acute lethal toxicity. Therefore, the safety assumed by using IGRs toward beneficial insects is not valid for chrysopids. Dose–response data showed that although all CSIs have a similar mechanism of action, the relative extent of toxicity may differ (novaluron > lufenuron > teflubenzuron). For CSIs, the delayed systemic effects became obvious at adult emergence, where the predicted no observable effect dose (NOED) was 1/2 048 of the MFRD for novaluron (0.085 ng/insect), and 1/256 of the MFRD for both lufenuron (0.25 ng/insect) and teflubenzuron (0.6 ng/insect). Finally, this work emphasized the significance of performing toxicity risk assessments with an adequate posttreatment period to avoid underestimating the toxicities of insecticides, as the acute lethal toxicity assays may not provide accurate information regarding the long‐range effects of hazardous compounds.     

Organic and inorganic nutrient effects on growth rate–irradiance relationships in the Texas brown‐tide alga Aureoumbra lagunensis (Pelagophyceae)1

Pelagophyte species in the genera Aureococcus and Auroumbra form brown tides in coastal bays that cause food‐web disruption and extensive shading of benthic primary producers. Organic nutrients have been suggested as key factors in the origination and persistence of the East Coast (USA) brown‐tide alga Aureococcus anophagefferens Hargraves et Sieburth. To evaluate this finding for the Texas brown‐tide alga Aureoumbra lagunensis D. A. Stockw., DeYoe, Hargraves et P. W. Johnson, we grew strain TBA‐2 with dissolved inorganic nitrogen (DIN; or ) or dissolved organic nitrogen (DON; urea or glutamate) as the nitrogen (N) source under eight light intensities. Maximum growth rates decreased with N source from (1.0 div · d^?1) to (0.48 div · d^?1). Neither growth rate efficiency (α) nor I_k varied significantly between N treatments. Both inorganic phosphorus (P) and β‐glycerophosphate supported growth. Aureoumbra lagunensis can utilize at least some forms of organic N and P and can use them to persist or grow when inorganic forms become limiting. We found no evidence to support the hypothesis that organic utilization enhances or supplements growth at low light levels.     

Cardiovascular effects of dynorphin A (1–13) in conscious rats and its modulation of morphine bradycardia over time

The short-term cardiovascular effects of dynorphin A (1–13), as well as its effects upon morphine bradycardia were investigated. In unanesthetized, unrestrained rats, intracerebroventricular (ICV) dynorphin A (1–13) injections (10–20 μg) produced a dose-related pressor effect, whereas intravenous (IV) dynorphin A (1–13) (1.0 mg/kg) produced a depressor effect; these responses persisted less than five min. Heart rate was not significantly altered by these doses or routes of administration. Dynorphin A (1–13) also produced behavioral effects in the unanesthetized animals, such as wet dog shakes in response to IV administration and wet dog shakes accompanied by barrel rolling in response to ICV administration. To evaluate the effects of dynorphin A (1–13) pretreatment on the bradycardic response to IV morphine, rats were pretreated with 10 μg dynorphin A (1–13) ICV four, six or eight hours prior to challenge with morphine sulfate (0.1 mg/kg IV). Four hour pretreatment with dynorphin A (1–13) (tested at 14:00 hr) resulted in a potention of morphine bradycardia, with six hours pretreatment (tested at 16:00 hr) no effect was observed, and eight hours following dynorphin A (1–13) pretreatment (tested at 18:00 hr) morphine bradycardia was attenuated. Additionally, the bradycardic response to IV morphine alone became more exaggerated as rats approached their nocturnal activity cycle. These data further establish that dynorphin A (1–13) exerts a potent, long lasting modulatory effect on morphine bradycardia and emphasize the importance of circadian variables in altering the magnitude of cardiovascular responses to opioid agonists.     

Understanding the binding interaction between phenyl boronic acid P1 and sugars: determination of association and dissociation constants using S–V plots,steady‐state spectroscopic methods and molecular docking

Continuous monitoring of glucose and sugar sensing plays a vital role in diabetes control. The drawbacks of the present enzyme‐based sugar sensors have encouraged the investigation into alternate approaches to design new sensors. The popularity of fluorescence sensors is due to their ability to bind reversibly to compounds containing diol. In this study we investigated the binding ability of phenyl boronic acid P1 for monosaccharides and disaccharides (sugars) in aqueous medium at physiological pH 7.4 using steady‐state fluorescence and absorbance. P1 fluorescence was quenched due to formation of esters with sugars. Absorbance and fluorescence measurements led to results that indicated that the sugars studied could be ordered in terms of their affinity to P1, as stated: sucrose > lactose > galactose > xylose > ribose > arabinose. In each case, the slope of modified Stern–Volmer plots was nearly 1, indicating the presence of only a single binding site in boronic acids for sugars. Docking studies were carried out using Schrodinger Maestro v.11.2 software. The binding affinity of phenyl boronic acid P1 with periplasmic protein (PDB ID 2IPM and 2IPL) was estimated using GlideScore.     

Anxiogenic effects of substance P and its 7–11 C terminal, but not the 1–7 N terminal, injected into the dorsal periaqueductal gray

The dorsal periaqueductal gray matter (DPAG) is one of the main output regions of the brainstem for the expression of defense reaction. Recent findings implicating neurokinins in the expression of fear or anxiety-like behaviors, have stimulated interest in the participation of these neuropeptides in the generation of aversive states in the dorsal periaqueductal gray matter. Analyses of traditional measures of the behavior of rats submitted to the elevated plus-maze test in this laboratory have shown that microinjections of substance P (SP) into the DPAG produce anxiogenic-like effects. The present study employs an ethological analysis of the behavior of animals in this test to investigate the involvement of substance P (SP) and its C- and N- fragments (7–11 and 1–7) in the expression of the different aspects of fear upon injection into the DPAG. To this end, rats were implanted with a cannula in the DPAG and injected one week later with 35 and 70 pmol of either substance P, or C- or N- SP fragments and tested immediately afterwards in the elevated plus-maze. The results show that SP and its C terminal fragment, produced increases in scanning, stretched attend posture, head dipping and flat–back approach, whereas the fragment N terminal produced only an increase in rearing. Therefore, the effects of SP and its C terminal fragment were associated to risk assessment behavior, whereas those of N terminal fragment were related to vertical exploratory activity. The results indicate that SP produces anxiogenic effects through activation of neural substrates of aversion in the DPAG and that this effect is probably related to its C terminal fragment.