Lack of Drosophila cytoskeletal tropomyosin affects head morphogenesis and the accumulation of oskar mRNA required for germ cell formation

Drosophila encodes five muscle and one cytoskeletal isoform of the actin-binding protein tropomyosin. We have identified a lack-of-function mutation in the cytoskeletal isoform (cTmII). Zygotic mutant embryos show a defect in head morphogenesis, while embryos lacking maternal cTmII are defective in germ cell formation but otherwise give rise to viable adults. oskar mRNA, which is required for both germ cell formation and abdominal segmentation, fails to accumulate at the posterior pole in these embryos. nanos mRNA, however, which is required exclusively for abdominal segmentation, is localized at wild-type levels. These results indicate that head morphogenesis and the accumulation of high levels of oskar mRNA necessary for germ cell formation require tropomyosin-dependent cytoskeleton.     

Relative paucity of genes causing inviability in hybrids between Drosophila melanogaster and D. simulans

Using deficiencies from Drosophila melanogaster, we looked for genomic regions in the sister species D. simulans that could cause lethality when hemizygous on a hybrid genetic background. Such genotypes allow hemizygous genes from one species to interact with heterozygous genes from other species and may correspond to the kinds of genotypes causing Haldane's rule, the observation that if only one gender is sterile or inviable in species hybrids, it is nearly always the heterogametic sex. A survey of roughly 50% of the D. simulans genome (114 chromosome regions) revealed only four regions causing hybrid lethality and five causing severe reductions in hybrid viability. However, the viability of all of these genotypes was at least partially restored by rearing hybrids at lower temperature or using different genetic backgrounds from D. simulans. We therefore detected no D. simulans chromosome regions causing unconditional hybrid lethality, although several regions were shown to be deleterious under most tested temperatures and genetic backgrounds. The relative paucity of "inviability genes" supports the idea, suggested by work on other species, that hybrid inviability between closely related species might be caused by interactions among relatively few genes, while hybrid sterility may involve many more loci.     

The effect of growth and joint formation on bristle pattern in D. melanogaster

Dependence of bristle pattern on size and joint formation was studied for male first leg tarsi of fj (four jointed) and d (dachs) mutants in homozygotes and in mosaics resulting from X-ray induced mitotic recombination. Homozygotes have four tarsal segments, lacking a third tarsal joint in most cases. The two proximal segments are shortened, the first by one-third, and altered in bristle pattern, whereas the distal two segments are little affected. Expressivity of fj is high, and of d is low, for the extent and frequency of joint failure. The longer the second segment, the more complete the third joint and the greater the bristle number. Only the jointed side of the segment approximates two segments in its bristle pattern. Mosaic studies show that joint failure occurs autonomously in fj, or in the majority of d clones, and that joint formation by heterozygous clones is autonomous except in the border area contacting a fj or d spot lacking a joint, in which are a joint failure occurs. Bristle pattern in this jointless heterozygous area switches to that of a single segment. Localized non-autonomy also occurs in the t-rows of heterozygous tissue contacting a fj or d spot. Both mutant genes are interpreted as reducing longitudinal growth of the proximal tarsi, with joint failure as a consequence, and with alterations of bristle pattern resulting directly from size reduction, or indirectly through joint failure.     

The gene fl(2)d is needed for the sex-specific splicing of transformer pre-mRNA but not for double-sex pre-mRNA in Drosophila melanogaster

In Drosophila melanogaster, regulation of the sex determination genes throughout development occurs by sex-specific splicing of their products. The first gene is Sex-lethal(Sxl). The downstream target of Sxl is the gene transformer (tra): the Sxl protein controls the female-specific splicing of the Tra pre-mRNA. The downstream target of the gene tra is the gene double-sex (dsx): the Tra protein of females, controls the female-specific splicing of the Dsx pre-mRNA. We have identified a gene, female-lethal-2-d fl(2) d, whose function is required for the female-specific splicing of Sxl pre-mRNA. In this report we analyze whether the gene fl(2)d is also required for the sex-specific splicing of both Tra and Dsx pre-mRNAs. We found that the Sxl protein is not sufficient for the female-specific splicing of Tra pre-mRNA, the fl(2)d function also being necessary. This gene, however, is not required for the female-specific splicing of Dsx pre-mRNA.     

Evolution of the mitochondrial ATPase 6 gene in Drosophila: unusually high level of polymorphism in D. melanogaster

We have determined 1990 bp mitochondrial DNA sequence which extends from 3' end of the cytochrome oxidase subunit I (COI) gene to 5' end of the COIII gene from two sibling species of Drosophila, D. simulans and D. mauritiana. Analyses of the sequences and part of the NADH dehydrogenase subunit 2 gene and the COI gene together with those from D. melanogaster and D. yakuba revealed that amino-acid substitution rate of the ATPase 6 gene seems to be higher in some strains of D. melanogaster than in the other species. High level of amino-acid polymorphism in this gene was observed in D. melanogaster. Synonymous substitution rate is relatively constant in all the genes examined, suggesting that mutation rate is not higher in the ATPase 6 gene of D. melanogaster. The amino-acid substitutions found specifically in D. melanogaster are at the sites which are not conserved among mammals, yeast and E. coli. These sites of the ATPase 6 gene might lose the selective constraint in D. melanogaster, and the amino-acid substitutions can be explained by neutral mutations and random genetic drift.     

Loss of dopamine D2 receptors in Alzheimer''s disease with parkinsonism but not Parkinson''s or Alzheimer''s disease

Qualitative analyses of midfoot stabilization in triple arthrodeses utilizing bone staple versus 4.5-mm cannulated cancellous screw fixation, with and without washers, were performed in fresh cadaveric specimens. Twenty-two trials (11 matched-pair feet) were used for direct comparison. Stiffness, defined as force/displacement, was determined at each talonavicular and calcaneocuboid joint. Ultimate load failure points of each specimen were also calculated. Trial results showed no statistically significant difference in stiffness or ultimate failure between these two forms of midfoot fixation for triple arthrodeses.     

The glutamine-rich domain of the Drosophila GAGA factor is necessary for amyloid fibre formation in vitro, but not for chromatin remodelling

The Drosophila GAGA factor binds specifically to the sequence GAGAG, and synergises with nucleosome remodelling factor to remodel chromatin in vitro. It consists of an N-terminal domain (POZ/BTB) which mediates protein-protein interactions, a central region which contains the DNA-binding domain, and a C-terminal glutamine-rich region. It is shown that the glutamine-rich region is responsible for the formation of fibres in vitro which, on the basis of their tinctorial properties and CD spectra, may be classified as amyloid fibres. A large structural change, probably resulting in beta-sheet structure, is observed upon fibre formation. Mutants containing the central region, either alone or together with the glutamine-rich region, are largely lacking in secondary structure but they bind specifically to the cognate DNA and are able to remodel chromatin in vitro. Consequently, neither the N-terminal domain nor the C-terminal glutamine-rich regions of the GAGA factor are necessary for chromatin remodelling in vitro.     

Impairments in negative patterning, but not simple discrimination learning, in rats with 192 IgG-saporin lesions of the nucleus basalis magnocellularis.

Rats with 192 IgG-saporin lesions of the nucleus basalis magnocellularis (NBM) and sham-operated rats were trained in either a simple discrimination paradigm assessing simple association learning or a negative patterning paradigm assessing configural association learning. In the simple discrimination task, rats were reinforced for responding to a light but were not reinforced for responding to a tone. In the negative patterning discrimination task, rats were reinforced for responding to either a light or a tone presented alone but were not reinforced for responding to both stimuli presented simultaneously. Simple discrimination learning was not affected, whereas acquisition of negative patterning was impaired by NBM lesions. Impaired configural association learning may reflect a loss in the ability of rats with NBM lesions to attend to multiple sensory stimuli or to cope with conflicting response strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Single dissociation findings of ADHD deficits in vigilance but not anterior or posterior attention systems.

Following a distributed network model of visuospatial attention, the authors used an A-X version of the Continuous Performance Test and a covert orienting paradigm to examine the vigilance, anterior, and posterior attention systems. Compared with control participants without attention-deficit/hyperactivity disorder (ADHD), children with the predominantly inattentive (ADHD-I) and combined (ADHD-C) subtypes had lower sensitivity (d') to detect targets from nontargets. Children with ADHD-C, but not ADHD-I, additionally had a highly activated response style (lnβ). Performance for both subtypes decreased to a greater extent over time in a manner consistent with problems in sustained attention. Together, these results suggest the presence of vigilance system deficits in participants with both ADHD subtypes. However, consistent with previous meta-analytic work, there was no evidence for anterior or posterior system orienting dysfunctions in either subtype. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Survey of malathion resistance and avermectin susceptibility in field populations of Drosophila melanogaster (Diptera: Drosophilidae) and D. simulans

Populations of Drosophila melanogaster (Meigen) and Drosophila simulans (Sturtevant) from various geographic locations in North America and elsewhere were sampled to assess the distribution of malathion resistance and avermectin tolerance. Comparisons are made to previous reports of a differential response to malathion selection in these species. Results indicate that for malathion, resistance is widespread in D. simulans but varies considerably in D. melanogaster. For avermectins, although the pattern of tolerance is similar in both species, there exists a significant amount of variation in these levels between geographic regions. We consider how these different geographic patterns of resistance distribution may shed insight on the relative roles of population structure and exposure history in affecting the spread of resistance. In addition, we consider further the use of D. melanogaster and D. simulans as a model for examining the effects of insecticide exposure on sympatric populations.     

Enhancement of excessive lever-pressing after post-training signal attenuation in rats by repeated administration of the D? antagonist SCH 23390 or the D? agonist quinpirole, but not the D? agonist SKF 38393 or the D? antagonist haloperidol.

The authors have recently shown that attenuation of an external response feedback leads to excessive lever-pressing that is not associated with attempts to collect reward, and they have suggested that this may be an analogue to "unreasonable" excessive behavior characteristic of obsessive–compulsive disorder. The present study shows that repeated administration of SCH 23390 or quinpirole, but not SKF 38393 or haloperidol, enhances this behavioral pattern. On the basis of data regarding the enduring effects of chronic treatment with dopaminergic agents, these results suggest that overstimulation of striatal D? receptors underlies enhanced response to signal attenuation. These results may link the hypothesis that obsessions and compulsions result from a deficient response feedback mechanism with findings implicating dopaminergic abnormalities in the production of obsessions and compulsions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disruption of appetite but not hunger or satiety following small lesions in the amygdala of rats.

In 5 experiments, discretely localized lesions were made in the amygdala of adult male albino Sprague Dawley rats to examine how specifically they might alter various measures of feeding behavior. Behavioral tests included spontaneous intake and body weight regulation, reactivity to saccharin and quinine solutions, conditioned taste aversion, the feeding response to food deprivation, the response to glucose gavage, and the response to dietary amino acid imbalance. Lesions in virtually all regions of the amygdala disrupted feeding behavior in some respect, but alterations in specific tasks were associated only with highly circumscribed brain damage. Body weight regulation, spontaneous food and water intake, and the responses to glucose gavage and long-term food deprivation were not altered by lesions in the amygdala. Results provide evidence that in the rat, the amygdala may play a greater role in appetite than in hunger or satiety. In particular, amygdaloid nuclei may participate in maintaining a negative bias in the reactivity to all appetitive stimuli. (64 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recombinant bovine somatotropin (rbST) administration to creep-fed beef calves increases muscle mass but does not affect satellite cell number or concentration of myosin light chain-1f mRNA

Our objective in this study was to determine the effect of recombinant bovine somatotropin (rbST) on indices of muscle development in creep-fed beef calves. Crossbred steer calves were assigned to one of two treatment groups: control (sham-injected; n = 12) or rbST-treated (.09 mg x kg(-1) x d(-1); n = 12). Calves were injected every 14 d starting at d 28 of age and were weaned at 205 d of age. Supplemental creep feed was supplied free access to all calves to compensate for an expected increased protein and energy requirement in calves given rbST. Biopsy (d 100) and slaughter (d 206) samples of semitendinosus muscle were evaluated for satellite cell, myofiber nuclei numbers, and myosin light chain (MLC-1f) mRNA quantification. Myofiber nuclei and satellite cell numbers per 100 myofibers and MLC-1f mRNA:rRNA ratios at 100 and 206 d of age were not different (P > .10) between control and rbST-treated calves. Total gain, ADG, quality grade, femur length, percentage kidney, pelvic, and heart fat, dressing percentage, plasma IGF-I, and plasma urea nitrogen concentrations did not differ (P > .10) between control and rbST-treated calves. However, rbST-treated calves had larger longissimus muscle areas (P < .03), less marbling (P < .001), higher carcass conformation scores (P < .04), greater mass of separated muscle (P < .03), more ground meat (P < .01), and heavier carcass weights (P < .05) than control calves. Thus, rbST treatment increased muscle characteristics while nuclei number and MLC-1f mRNA concentrations remained the same, implying that the additional muscle growth was in a normal fashion.     

Interactive but not direct effects of perceived racism and trait anger predict resting systolic and diastolic blood pressure in black adolescents.

This correlation study explicated the association of perceived racism and trait anger to resting blood pressure in a high school sample of 234 Blacks. Perceived racism and trait anger were assessed via self-report, and resting blood pressure was measured with a noninvasive blood pressure monitor. Hierarchical regression analyses indicated that perceived racism and trait anger were not independent predictors of systolic or diastolic blood pressure. However, these analyses revealed that the interactive effects of perceived racism and trait anger were predictive of systolic and diastolic blood pressure. Although perceived racism was not significantly related to blood pressure among those who were high in trait anger, perceived racism was inversely associated with blood pressure among those who were low in trait anger. The findings may have important longer term implications for future research examining the contribution of psychosocial factors to cardiac and vascular functioning in Blacks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Peripheral and intraamygdalar administration of the dopamine D? receptor antagonist SCH 23390 blocks fear-potentiated startle but not shock reactivity or the shock sensitization of acoustic startle.

Central dopamine (DA) activity is thought to play a role in fear motivation. The aim of the present study was to assess the involvement of DA D? receptors in emotional learning. The authors report that peripheral and intraamygdalar administration of the specific D? receptor antagonist SCH 23390 blocked the acquisition of fear-potentiated startle. Analysis of shock reactivity during footshock administration revealed that the learning impairment could not be explained by a diminution in the aversive properties of the unconditioned stimulus. Additionally, systemic and intraamygdalar injection of SCH 23390 did not alter fear expression as measured with the shock sensitization of acoustic startle. The potential contribution of mesoamygdaloid DA to the acquisition and retrieval of conditioned fear responses is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Muscimol in the deep layers of the superior colliculus/mesencephalic reticular formation blocks expression but not acquisition of fear-potentiated startle in rats.

Deposits of the retrograde tracer Fluoro-Gold into the ventrolateral nucleus reticularis pontis caudalis labeled neurons in the deep layers of the superior colliculus/mesencephalic reticular formation (deep SC/Me). To test the involvement of this area in the fear-potentiated startle effect, rats were implanted with cannulas into the deep SC/Me and trained for fear-potentiated startle after infusion of the GABAA agonist muscimol (0.1 μg/0.5 μl). Two days later, they were tested for fear-potentiated startle. Rats then received a 2nd training session without any infusions, and 2 days later they were reinfused with muscimol (0.1 μg/0.5 μl) and tested for fear-potentiated startle. Local infusion of muscimol into the deep SC/Me completely blocked the expression but not the acquisition of fear-potentiated startle. These results indicate that a synapse in the midbrain is critical for the expression of fear-potentiated startle. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Suppression of VMH-lesion-induced reactivity and aggressiveness in the rat by stimulation of lateral septum, but not medial septum or cingulate cortex.

32 male hooded rats made vicious with bilateral ventromedial hypothalamic lesions had bipolar electrodes implanted unilaterally in the lateral septum, medial septum, or cingulate cortex. Four days later, the Ss' reactivity and aggressiveness were evaluated 5 min before, during, and 5 min after stimulation at 20 muA (60 Hz, sine wave). Lateral septal stimulation suppressed reactivity and aggressiveness by almost 80% compared with pre- and poststimulation levels. Stimulation of neither the cingulate cortex nor the medial septum produced a change reliably different from that seen in unstimulated control Ss. Further tests with stimulation of the lateral septum at the 20 muA level showed that neither rewarding self-stimulation nor disruption of ongoing water drinking was produced. These results are congruent with evidence from lesion studies that the lateral septum normally acts to suppress reactivity and aggressiveness in the rat; they do not support previous suggestions that the medial septum is involved in the modulation of these behaviors. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Blockade of cocaine reinforcement in rats with the dopamine receptor blocker pimozide, but not with the noradrenergic blockers phentolamine or phenoxybenzamine.

31 male Wistar rats self-administering cocaine were treated with the dopamine receptor blocker pimozide or the noradrenergic blockers phentolamine or phenoxybenzamine. Pimozide caused a dose-related (.0625–.5 mg/kg) acceleration of responding; at the higher doses responding subsequently ceased. These effects of pimozide parallel the known effects of reward (unit dose) reduction and reward termination and thus suggest an important role for dopaminergic brain mechanisms in the mediation of cocaine reinforcement. Neither phenoxybenzamine given systemically nor phentolamine given intraventricularly had similar effects; thus no similar role for noradrenergic brain mechanisms is suggested by these experiments. (French summary) (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)