Dishevelled controls apical docking and planar polarization of basal bodies in ciliated epithelial cells

The planar cell polarity (PCP) signaling system governs many aspects of polarized cell behavior. Here, we use an in vivo model of vertebrate mucociliary epithelial development to show that Dishevelled (Dvl) is essential for the apical positioning of basal bodies. We find that Dvl and Inturned mediate the activation of the Rho GTPase specifically at basal bodies, and that these three proteins together mediate the docking of basal bodies to the apical plasma membrane. Moreover, we find that this docking involves a Dvl-dependent association of basal bodies with membrane-bound vesicles and the vesicle-trafficking protein, Sec8. Once docked, basal bodies again require Dvl and Rho for the planar polarization that underlies directional beating of cilia. These results demonstrate previously undescribed functions for PCP signaling components and suggest that a common signaling apparatus governs both apical docking and planar polarization of basal bodies.

Ciliogenesis defects in embryos lacking inturned or fuzzy function are associated with failure of planar cell polarity and Hedgehog signaling

The vertebrate planar cell polarity (PCP) pathway has previously been found to control polarized cell behaviors rather than cell fate. We report here that disruption of Xenopus laevis orthologs of the Drosophila melanogaster PCP effectors inturned (in) or fuzzy (fy) affected not only PCP-dependent convergent extension but also elicited embryonic phenotypes consistent with defective Hedgehog signaling. These defects in Hedgehog signaling resulted from a broad requirement for Inturned and Fuzzy in ciliogenesis. We show that these proteins govern apical actin assembly and thus control the orientation, but not assembly, of ciliary microtubules. Finally, accumulation of Dishevelled and Inturned near the basal apparatus of cilia suggests that these proteins function in a common pathway with core PCP components to regulate ciliogenesis. Together, these data highlight the interrelationships between cell polarity, cellular morphogenesis, signal transduction and cell fate specification.

Planar cell polarity acts through septins to control collective cell movement and ciliogenesis

The planar cell polarity (PCP) signaling pathway governs collective cell movements during vertebrate embryogenesis, and certain PCP proteins are also implicated in the assembly of cilia. The septins are cytoskeletal proteins controlling behaviors such as cell division and migration. Here, we identified control of septin localization by the PCP protein Fritz as a crucial control point for both collective cell movement and ciliogenesis in Xenopus embryos. We also linked mutations in human Fritz to Bardet-Biedl and Meckel-Gruber syndromes, a notable link given that other genes mutated in these syndromes also influence collective cell movement and ciliogenesis. These findings shed light on the mechanisms by which fundamental cellular machinery, such as the cytoskeleton, is regulated during embryonic development and human disease.

The ciliopathy-associated CPLANE proteins direct basal body recruitment of intraflagellar transport machinery

Cilia use microtubule-based intraflagellar transport (IFT) to organize intercellular signaling. Ciliopathies are a spectrum of human diseases resulting from defects in cilia structure or function. The mechanisms regulating the assembly of ciliary multiprotein complexes and the transport of these complexes to the base of cilia remain largely unknown. Combining proteomics, in vivo imaging and genetic analysis of proteins linked to planar cell polarity (Inturned, Fuzzy and Wdpcp), we identified and characterized a new genetic module, which we term CPLANE (ciliogenesis and planar polarity effector), and an extensive associated protein network. CPLANE proteins physically and functionally interact with the poorly understood ciliopathy-associated protein Jbts17 at basal bodies, where they act to recruit a specific subset of IFT-A proteins. In the absence of CPLANE, defective IFT-A particles enter the axoneme and IFT-B trafficking is severely perturbed. Accordingly, mutation of CPLANE genes elicits specific ciliopathy phenotypes in mouse models and is associated with ciliopathies in human patients.

Validation of international consensus guidelines for the resection of branch duct-type intraductal papillary mucinous neoplasms

Background

Classifications of intraductal papillary mucinous neoplasm (IPMN) remain ambiguous, especially for the mixed type. Factors predicting malignancy remain unclear. The aim of this study was to evaluate the usefulness of factors predicting malignancy in the new international consensus guidelines for resection of branch duct-type (BD)-IPMN and to compare them with those in the previous version.

Methods

A prospectively collected database of patients with biopsy-proven BD-IPMN was analysed to compare factors between the first and second consensus guidelines, particularly as predictors of malignancy.

Results

Of 350 patients with BD-IPMN, sensitivity (0·724) and balanced accuracy (0·751) of the second guidelines were superior to those (0·639 and 0·730) in the first version at the expense of slightly reduced specificity (0·779 versus 0·822 for the first version) by random forest models. Multiple logistic regression analysis showed that main pancreatic duct dilatation greater than 5 mm (hazard ratio (HR) 4·54, 95 per cent confidence interval 2·45 to 8·41; P < 0·001), mural nodules (HR 6·27, 3·27 to 12·01; P < 0·001) and carbohydrate antigen 19–9 level above 37 units/ml (HR 4·03, 1·83 to 8·90; P = 0·001) were independent predictors of BD-IPMN malignancy.

Conclusion

The new consensus guidelines provide better sensitivity, performance of factors predicting malignancy, and balanced accuracy in the diagnosis of BD-IPMN malignancy. Size alone was limited in predicting malignancy. Variability in clinical significance of the individual factors associated with a risk of malignancy indicates the need for a tailored approach in the management of patients with BD-IPMN.

Role of the cervical lymphatics in the Th2-type hierarchy of CNS immune regulation

CNS immune regulation is intimately dependent on the dynamics of cerebral extracellular fluid circulation. Animal models indicate that following the introduction of antigen into the CNS, normal circulation of interstitial and cerebrospinal fluids provides the opportunity for (a) delivery of CNS-derived antigen to lymphoid organs, as well as, (b) retention of immunologically significant amounts of antigen within the CNS. Thus, even in the absence of disease, CNS-derived antigen can induce antigen-specific activation of naive lymphocytes in lymphoid organs and specific reactivation of lymphoblasts that have migrated into the CNS. The initial peripheral immune response to CNS-derived antigen is induced in cervical lymph nodes and is characterized by a strong antibody response, no delayed-type hypersensitivity, and only priming for cytotoxic T-cell responses. This Th-2 type hierarchy of immune regulation is reinforced within the antigen-stimulated CNS where specific B lymphoblasts are permitted to develop their effector function but cell-mediated immunity is inhibited. Developing a paradigm for CNS immune regulation is important in understanding how CNS disorders in humans are induced, perpetuated, and may be manipulated.

Phospholipase C-delta1 is activated by capacitative calcium entry that follows phospholipase C-beta activation upon bradykinin stimulation

To characterize the regulatory mechanism of phospholipase C-delta1 (PLC-delta1) in the bradykinin (BK) receptor-mediated signaling pathway, we used a clone of PC12 cells, which stably overexpress PLC-delta1 (PC12-D1). Stimulation with BK induced a significantly higher Ca(2+) elevation and inositol 1,4,5-trisphosphate (IP(3)) production with a much lower half-maximal effective concentration (EC(50)) of BK in PC12-D1 cells than in wild type (PC12-W) or vector-transfected (PC12-V) cells. However, BK-induced intracellular Ca(2+) release and IP(3) generation was similar between PC12-V and PC12-D1 cells in the absence of extracellular Ca(2+), suggesting that the availability of extracellular Ca(2+) is essential to the activation of PLC-delta1. When PC12-D1 cells were treated with agents that induce Ca(2+) influx, more IP(3) was produced, suggesting that the Ca(2+) entry induces IP(3) production in PC12-D1 cells. Furthermore, the additional IP(3) production after BK-induced capacitative calcium entry was detected in PC12-D1 cells, suggesting that PLC-delta1 is mainly activated by capacitative calcium entry. When cells were stimulated with BK in the presence of extracellular Ca(2+), [(3)H]norepinephrine secretion was much greater from PC12-D1 cells than from PC12-V cells. Our results suggest that PLC-delta1 is activated by capacitative calcium entry following the activation of PLC-beta, additively inducing IP(3) production and Ca(2+) rise in BK-stimulated PC12 cells.

Identification of novel ciliogenesis factors using a new in vivo model for mucociliary epithelial development

Mucociliary epithelia are essential for homeostasis of many organs and consist of mucus-secreting goblet cells and ciliated cells. Here, we present the ciliated epidermis of Xenopus embryos as a facile model system for in vivo molecular studies of mucociliary epithelial development. Using an in situ hybridization-based approach, we identified numerous genes expressed differentially in mucus-secreting cells or in ciliated cells. Focusing on genes expressed in ciliated cells, we have identified new candidate ciliogenesis factors, including several not present in the current ciliome. We find that TTC25-GFP is localized to the base of cilia and to ciliary axonemes, and disruption of TTC25 function disrupts ciliogenesis. Mig12-GFP localizes very strongly to the base of cilia and confocal imaging of this construct allows for simple visualization of the planar polarity of basal bodies that underlies polarized ciliary beating. Knockdown of Mig12 disrupts ciliogenesis. Finally, we show that ciliogenesis factors identified in the Xenopus epidermis are required in the midline to facilitate neural tube closure. These results provide further evidence of a requirement for cilia in neural tube morphogenesis and suggest that genes identified in the Xenopus epidermis play broad roles in ciliogenesis. The suites of genes identified here will provide a foundation for future studies, and may also contribute to our understanding of pathological changes in mucociliary epithelia that accompany diseases such as asthma.

Methylation of O(6)-methylguanine-DNA methyltransferase gene is associated significantly with K-ras mutation, lymph node invasion, tumor staging, and disease free survival in patients with gastric carcinoma

BACKGROUND

O(6)-methylguanine-DNA methyltransferase (MGMT) can remove O(6)alkylG DNA adducts. If they are not removed, then the adducts mispair with T during DNA replication, resulting in G-to-A mutation. Interrelations between MGMT gene inactivation by promoter methylation, K-ras mutation, and clinicopathologic features in patients with gastric carcinoma were studied.

METHODS

Surgically removed tumor tissues from 79 patients were analyzed with MGMT methylation by genomic DNA modification and methylation specific polymerase chain reaction analysis, K-ras mutation by mutant allele specific amplification, TNM classification according to the International Union Against Cancer system, and MGMT protein expression by immunohistochemistry.

RESULTS

MGMT-promoter methylation was found in 18 of 79 tumors. Among those 18 tumors, K-ras mutations were found in 33% and 11% of tumors at codons 12 and 13, respectively, corresponding to 20 times and 7 times greater rates of mutation compared with unmethylated tumors. MGMT methylation was associated significantly with lymph node invasion (P < 0.01), tumor stage (P < 0.03) and 5-year disease free survival (P < 0.02). MGMT protein expression was detected in intestinal metaplasia and adenocarcinoma samples, whereas no expression was detected in normal foveolar cells.

CONCLUSIONS

MGMT-promoter methylation in patients with gastric carcinoma was associated significantly with point mutations of K-ras at codons 12 and 13, lymph node invasion, tumor stage, and disease free survival. These associations indicate a significant role of MGMT methylation during gastric carcinogenesis.

The effects of GABAergic inhibition on monaural response properties of neurons in the mustache bat's inferior colliculus

The effects of GABAergic inhibition on response properties of neurons in the inferior colliculus were investigated. The experimental animals were mustache bats and responses were monitored from neurons in the hypertrophied 60 kHz isofrequency contour of the inferior colliculus. The features we report on here are: 1) the maximum discharge rates evoked by tone bursts at each unit's best frequency; 2) the forms of the rate-level functions; 3) the discharge patterns evoked by best frequency tone bursts; and 4) the changes in these response features that were observed when GABAergic inhibition was blocked with bicuculline, an antagonist specific for GABAA receptors. There were three main findings. The first is that bicuculline caused the discharge rate to increase in the majority of neurons. The maximum firing rates in more than half of the units increased by at least 100%, and in 15% of the cells the maximum spike-count increased 400% or more. Of particular interest were the 13 cells that were nearly unresponsive to any tone burst, but responded vigorously to the same stimuli after application of bicuculline. The second main finding is that the increased discharge rates were due either to a change from a phasic to a tonic discharge pattern, or to a change in overall excitability with no change in discharge pattern. The third main finding was that bicuculline changed the shape of the rate-level functions in almost half of the cells studied. The general trend was that units whose pre-drug rate-level functions were upper-threshold were most likely to be changed, followed by regular nonmonotonic and non-saturated monotonic. Units with saturated monotonic functions were the least likely to be affected by bicuculline. These results lead us to suggest that GABAergic inhibition acts on collicular cells in two principal ways. The first way is to modify the effects of the excitatory innervation and thereby shape the response features of collicular neurons. The formation of rate-level functions is but one illustration of the shaping action of GABAergic inhibition. Other features that are shaped by GABAergic inhibition include discharge patterns, thresholds, latencies and tuning curves. The second way is to provide a regulated suppression of evoked activity. We propose that the suppression is situation dependent and may act to enhance the operating range of collicular neurons in situations of particular importance to the animal, such as during periods of selective attention and perhaps in other situations as well.

Two-year experience with ureteral stones: extracorporeal shockwave lithotripsy v ureteroscopic manipulation

Extracorporeal shockwave lithotripsy (SWL) and ureteroscopic manipulation became the standard treatments for ureteral stones in recent years. There still exists significant debate as to the most appropriate treatment modality for ureteral stones. During a period of 2 years, from January 1994 to December 1995, 651 patients with ureteral stones were treated, and 589 patients were retrospectively reviewed, excluding 62 patients with incomplete follow-up. Four hundred forty-two patients were treated with SWL using the MPL 9000 with ultrasonic guidance and 115 patients with ureteroscopic manipulations using 7.9F to 11.5F rigid and semirigid ureteroscopes. In SWL treatments, the overall stone-free rate was 74.7% with one session. The stone-free rate was significantly affected by the size of stones, being 83.6% when the stone was <1.0 cm and 42.1% when the stone was >1.0 cm. The stone-free rate after a second SWL session was 84.4% and was 90.3% after a third session. The stone-free rates according to the site of the stone were 72.4 (proximal), 70.0 (mid), and 80.2% (distal) after a single session. In ureteroscopic manipulation, an overall stone-free rate of 87.8% was obtained regardless of the size of the stones. The success rates according to the location of stones were 75.0 (proximal), 94.6 (mid), and 86.4% (distal). Open ureterolithotomy was performed in 32 patients, with a 100% success rate. In our study, the size of the stones was the most important factor influencing the success rate of SWL treatment. We consider ureteroscopic manipulation as the first-line treatment modality when the stone is >1.0 cm, especially if it is in the distal ureter. Proper selection of patients for in situ SWL or ureteroscopy would improve the results of initial treatment.

Subcellular Localization and Signaling Properties of Dishevelled in Developing Vertebrate Embryos

The Dishevelled protein mediates several diverse biological processes. Intriguingly, within the same tissues where Xenopus Dishevelled (Xdsh) controls cell fate via canonical Wnt signaling, it also controls cell polarity via the vertebrate planar cell polarity (PCP) cascade [1, 2, 3, 4, 5, 6, 7, 8 and 9]. The relationship between subcellular localization of Dishevelled and its signaling activities remains unclear; conflicting results have been reported depending upon the organism and cell types examined [8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20]. We have approached this issue by developing new reagents to sequester wild-type Dishevelled protein either at the cell membrane or away from the cell membrane. Removal of Dishevelled from the cell membrane disrupts convergent extension by preventing Rho/Rac activation and mediolateral cell polarization. By manipulating the subcellular localization of K-->M (dsh1), we show that this mutation inhibits Dishevelled activation of Rac, regardless of its subcellular localization. These data demonstrate that membrane localization of Dishevelled is a prerequisite for vertebrate PCP signaling. However, both membrane-targeted and cytoplasm-targeted Dishevelled can potently activate canonical Wnt signaling, suggesting that local concentration of Dishevelled protein, but not its spatial localization, is central to canonical Wnt signaling. These results suggest that in vertebrate embryos, subcellular localization is insufficient to account for the pathway specificity of Dishevelled in the canonical Wnt versus PCP signaling cascades.

Isotropic quantum scattering and unconventional superconductivity

Superconductivity without phonons has been proposed for strongly correlated electron materials that are tuned close to a zero-temperature magnetic instability of itinerant charge carriers. Near this boundary, quantum fluctuations of magnetic degrees of freedom assume the role of phonons in conventional superconductors, creating an attractive interaction that 'glues' electrons into superconducting pairs. Here we show that superconductivity can arise from a very different spectrum of fluctuations associated with a local (or Kondo-breakdown) quantum critical point that is revealed in isotropic scattering of charge carriers and a sublinear, temperature-dependent electrical resistivity. At this critical point, accessed by applying pressure to the strongly correlated, local-moment antiferromagnet CeRhIn(5), magnetic and charge fluctuations coexist and produce electronic scattering that is maximal at the optimal pressure for superconductivity. This previously unanticipated source of pairing glue opens possibilities for understanding and discovering new unconventional forms of superconductivity.

RFX2 is broadly required for ciliogenesis during vertebrate development

In Caenorhabditis elegans, the RFX (Daf19) transcription factor is a major regulator of ciliogenesis, controlling the expression of the many essential genes required for making cilia. In vertebrates, however, seven RFX genes have been identified. Bioinformatic analysis suggests that Rfx2 is among the closest homologues of Daf19. We therefore hypothesize that Rfx2 broadly controls ciliogenesis during vertebrate development. Indeed, here we show that Rfx2 in Xenopus is expressed preferentially in ciliated tissues, including neural tube, gastrocoel roof plate, epidermal multi-ciliated cells, otic vesicles, and kidneys. Knockdown of Rfx2 results in cilia-defective embryonic phenotypes and fewer or truncated cilia are observed in Rfx2 morphants. These results indicate that Rfx2 is broadly required for ciliogenesis in vertebrates. Furthermore, we show that Rfx2 is essential for expression of several ciliogenic genes, including TTC25, which we show here is required for ciliogenesis, HH signaling, and left-right patterning.

Glycine and GABA influence binaural processing in the inferior colliculus of the mustache bat

1. The mammalian inferior colliculus contains large populations of binaural cells that are excited by stimulation of the contralateral ear and are inhibited by stimulation of the ipsilateral ear, and are called excitatory/inhibitory (EI) cells. Neurons with EI properties are initially created in the lateral superior olive (LSO), which, in turn, sends strong bilateral projections to the inferior colliculus. The questions that we address in this report are 1) whether the inhibition evoked by stimulation of the ipsilateral ear occurs at the inferior colliculus or whether it occurs in a lower nucleus, presumably the LSO; and 2) if the ipsilaterally evoked inhibition occurs at the inferior colliculus, is the inhibition a consequence of glycinergic innervation or is it a consequence of GABAergic innervation. To study these questions, we recorded from 61 EI neurons in the inferior colliculus of the mustache bat before and during the iontophoretic application of the glycine receptor antagonist, strychnine. We also tested the effects of the gamma-aminobutyric acid-A (GABAA) receptor antagonist, bicuculline, on 38 of the 61 neurons that were tested with strychnine. The main finding is that glycinergic or GABAergic inhibition, or both, contribute to the ipsilaterally evoked inhibition in approximately 50% of the EI neurons in the inferior colliculus. 2. Strychnine and bicuculline had different effects on the magnitude of the spike counts evoked by stimulation of the contralateral (excitatory) ear. On average, strychnine caused the maximum spike count evoked by contralateral stimulation to increase by only 23%. The relatively small effects of strychnine on response magnitude are in marked contrast to the effects of bicuculline, which usually caused much larger increases in spike counts. For example, although strychnine caused spike counts to more than double in approximately 25% of the collicular neurons, bicuculline caused a doubling of the spike count in approximately 60% of the cells. 3. The inhibitory influences of ipsilateral stimulation were evaluated by driving the neurons with a fixed intensity at the contralateral ear and then documenting the reductions in spike counts due to the presentation of progressively higher intensities at the ipsilateral ear. In 64% of the neurons sampled, blocking glycinergic inhibition with strychnine had little or no effect on the ipsilaterally evoked inhibition. These cells remained as strongly inhibited during the application of strychnine as they did before its application. In addition, the ipsilateral intensity that produced complete or nearly complete spike suppression in the predrug condition was also unchanged by strychnine. 4. In 36% of the neurons, strychnine markedly reduced the degree of ipsilaterally evoked spike suppression. In five of these neurons, there was a complete elimination of the ipsilateral inhibition: these neurons were transformed from strongly inhibited EI neurons into monaural neurons. 5. The influence of both strychnine and bicuculline was tested sequentially in 38 neurons. In about one-half of these cells, (53%, 20/38) the ipsilaterally evoked inhibition was unaffected by either drug. In 10 other units (26%), both drugs substantially reduced or eliminated the ipsilaterally evoked inhibition. In most of these cells, both bicuculline and strychnine reduced the ipsilaterally evoked inhibition to a similar degree. In the remaining eight cells studied with both drugs (21%), the ipsilaterally evoked inhibition was reduced or eliminated by one of the drugs, but not by both. 6. These results show that both glycinergic and GABAergic projections influence the ipsilaterally evoked inhibition in about one-half of the EI neurons in the inferior colliculus. The glycinergic inhibition elicited by ipsilateral stimulation is most likely due to projections from the ipsilateral lateral superior olive, whereas the GABAergic inhibition evoked by ipsilateral stimulation is most likely caused b

Predictors of condom use in sexually active adolescents

Unprotected sexual intercourse places a substantial number of adolescents at risk for sexually transmitted disease (STD) and human immunodeficiency virus (HIV) infection. While the most effective means of preventing STD/HIV infection among sexually active adolescents is consistent condom use, little is known about the factors that influence their consistent use among adolescents. This study of adolescents (n = 1049, mean age = 16.2 years) found that of the 266 teens who recently became sexually active, only 29% reported using condoms consistently. Consistent condom use was more frequent in males, those with little history of risk behavior and those with stronger intentions to use condoms in the future. Fear and anxiety of HIV, attitudes about risks other than HIV, and other safe behavior intentions were not significantly related to consistent condom use. Although intentions and recent behavior were significantly related, a different group of factors was found to predict intention to use condoms (e.g., perception of condom use by friends, general impulsive attitudes). Identifying and understanding the factors that influence adolescent sexual behavior and intentions is important for developing maximally effective HIV education/prevention programs.

Enhanced performance of PbS-sensitized solar cells via controlled successive ionic-layer adsorption and reaction

The performance of PbS-sensitized solar cells is significantly improved by controlling successive ionic layer adsorption and reaction.

Induction of growth inhibition of 293 cells by downregulation of the cyclin E and cyclin-dependent kinase 4 proteins due to overexpression of TIS21

We earlier reported that TIS21 mRNA expression was markedly decreased in A549 and NCIH69 human lung cancer cells and in thymic carcinoma tissues obtained from transgenic mice containing simian virus 40 large T antigen (J Cancer Res Clin Oncol 121:279-284, 1995). To determine how TIS21 inhibits growth, we made 293 cells that constitutively expressed TIS21 protein. The constitutive TIS21 expresser lines C9 and C11 grew to a lower saturation density than did those in the vector-transfected clones (V7 and V10) and antisense-transfected clones (AS1 and AS4), and the size of the C9 and C11 cells increased significantly after transfection with TIS21 cDNA. The serum-stimulated cell cycle was analyzed by fluorescence-activated cell sorting after double thymidine treatment; V10 progressed normally through the cell division cycle, but C9 and C11 cells accumulated continuously in G1 phase until 36 h after treatment. On the other hand, the progression of cells that had already entered to S or G2/M phase was not inhibited. When cell-cycle regulatory proteins were measured, C9 and C11 cells showed significantly reduced synthesis of cyclin E and cyclin-dependent kinase (cdk) 4 as well as a decrease in cyclin E-associated cdk activity. These observations led us to conclude that TIS21 overexpression in G1 phase decreased the amounts of cyclin E and cdk4, thereby decreasing the activity of cdks at the G1-S transition.

Latency as a function of intensity in auditory neurons: influences of central processing

The response latencies of sensory neurons typically shorten with increases in stimulus intensity. In the central auditory system this phenomenon should have a significant impact on a number of auditory functions that depend critically on an integration of precisely timed neural inputs. Evidence from previous studies suggests that the auditory system not only copes with the potential problems associated with intensity-dependent latency change, but that it also modifies latency change to shape the response properties of many cells for specific functions. This observation suggests that intensity-dependent latency change may undergo functional transformations along the auditory neuraxis. The goal of our study was to explore these transformations by making a direct, quantitative comparison of intensity-dependent latency change among a number of auditory centers from the lower brainstem to the thalamus. We found two main ways in which intensity-dependent latency change transformed along the neuraxis: (1) the range of latency change increased substantially and (2) one particular type of latency change, which has been suggested to be associated with sensitivity to temporally segregated stimulus components, occurred only at the highest centers tested, the midbrain and thalamus. Additional testing in the midbrain (inferior colliculus) indicated that inhibitory inputs are involved in shaping latency change. Our findings demonstrate that the central auditory system modifies intensity-dependent latency changes. We suggest that these changes may be functionally incorporated, actively enhanced, or modified to suit specific functions of the auditory system.

Azimuthal receptive fields are shaped by GABAergic inhibition in the inferior colliculus of the mustache bat

1. In this study we examine the effects of GABAergic inhibition on the response properties and the constructed azimuthal receptive fields of 54 excitatory/inhibitory (EI) neurons tuned to 60 kHz in the inferior colliculus of the mustache bat. The constructed azimuthal receptive fields predict the spike counts that would be evoked by different intensities of 60-kHz sounds presented from each of 13 azimuthal locations in the frontal sound field. 2. Action potentials were recorded with a micropipette attached to a multibarrel glass electrode. Bicuculline, an antagonist specific for gamma-aminobutyric acid-A (GABAA) receptors, was iontophoretically applied through the multibarrel electrode. Both monaural and binaural response properties were initially recorded at a variety of interaural intensity disparities (IIDs) and absolute intensities, and the same response properties were subsequently assessed while GABAergic inhibition was blocked by bicuculline. Azimuthal receptive fields both before and during the application of bicuculline were constructed from response properties obtained with earphones after correcting for the directional properties of the ear and the IIDs generated by 60-kHz sounds presented from a variety of azimuthal locations. 3. Bicuculline had virtually no effect on either the monaural or binaural properties of 19 cells (35%). The constructed azimuthal receptive fields of these cells were also unaffected by bicuculline. Presumably the properties of these cells were formed in a lower nucleus, most likely the contralateral lateral superior olive (LSO), and were imposed on the collicular cell via the crossed projection from the LSO to the inferior colliculus, which is known to be excitatory. 4. In more than half of the neurons (65%) GABAergic inhibition influenced one or more features of the cell's response properties and thus its azimuthal receptive field. Some response properties were formed in the colliculus through GABAergic inhibition, whereas others appear to have been shaped initially in a lower nucleus and then further modified by GABAergic inhibition in the inferior colliculus. Moreover, a number of features of GABAergic inhibition that acted on inferior collicular cells were evoked by stimulation of the contralateral (excitatory) ear, whereas other features were influenced by stimulation of the ipsilateral (inhibitory) ear. 5. In 20 cells (37%) blocking GABAergic inhibition reduced or abolished the inhibition evoked by the ipsilateral ear. The receptive fields of cells in which the ipsilaterally evoked inhibition was reduced by bicuculline expanded further into the ipsilateral sound field than they did before bicuculline.(ABSTRACT TRUNCATED AT 400 WORDS)

Traumatic cervical Brown-Sequard and Brown-Sequard-plus syndromes: the spectrum of presentations and outcomes

Brown-Sequard syndrome (BSS) and Brown-Sequard-plus syndrome (BSPS) are characterised by asymmetrical paresis with hypalgesia more marked on the less paretic side. This study examined the clinical features of 38 patients (30 males and 8 females; mean age = 32 years) with traumatic cervical BSS or BSPS who underwent comprehensive inpatient rehabilitation. Twenty two injuries were caused by road traffic accidents, 8 by penetrating injuries, 5 by diving injuries, and 3 by other causes. After an average of 35 days in acute care and 79 days in rehabilitation, 37 patients had increased muscle strength, all 38 patients improved functional abilities, 29 patients walked independently, 34 had spontaneous bladder emptying, 36 were discharged home, and 14 were employed. Statistically significant increases (p less than 0.001) were made in modified Barthel index functional scores between admission and discharge. Patients with BSPS had a better prognosis than did those with 'pure' BSS. Patients with predominant upper limb weakness had more favourable outcomes than did those with predominant lower limb weakness. Few other potentially predictive demographic, injury, or neurological factors were associated with functional outcome. Patients with BSS or BSPS generally have a good prognosis for neurological and functional improvement.

Medial superior olive in the free-tailed bat: response to pure tones and amplitude-modulated tones

In mammals with good low-frequency hearing and a moderate to large interear distance, neurons in the medial superior olive (MSO) are sensitive to interaural time differences (ITDs). Most small mammals, however, do not hear low frequencies and do not experience significant ITDs, suggesting that their MSOs participate in functions other than ITD coding. In one bat species, the mustached bat, the MSO is a functionally monaural nucleus, acting as a low-pass filter for the rate of sinusoidally amplitude-modulated (SAM) stimuli. We investigated whether the more typical binaural MSO of the MExican free-tailed bat also acts as an SAM filter. We recorded from 60 MSO neurons with their best frequencies covering the entire audiogram of this bat. The majority revealed bilateral excitation and indirect evidence for inhibition (EI/EI; 55%). The remaining neurons exhibited reduced inputs, mostly lacking ipsilateral inputs (28% I/EI; 12% O/EI; 5% EI/O). Most neurons (64%) responded with a phasic discharge to pure tones; the remaining neurons exhibited an additional sustained component. For stimulation with pure tones, two thirds of the cells exhibited monotonic rate-level functions for ipsilateral, contralateral, or binaural stimulation. In contrast, nearly all neurons exhibited nonmonotonic rate-level functions when tested with SAM stimuli. Eighty-eight percent of the neurons responded with a phase-locked discharge to SAM stimuli at low modulation rates and exhibited low-pass filter characteristics in the modulation transfer function (MTF) for ipsilateral, contralateral, and binaural stimulation. The MTF for ipsilateral stimulation usually did not match that for contralateral stimulation. Introducing interaural intensity differences (IIDs) changed the MTF in unpredictable ways. We also found that responses to SAMs depended on the carrier frequency. In some neurons we measured the time course of the ipsilaterally and contralaterally evoked inhibition by presenting brief frequency-modulated sweeps at different ITDs. The duration and timing of inhibition could be related to the SAM cutoff for binaural stimulation. We conclude that the response of the MSO in the free-tailed bat is created by a complex interaction of inhibition and excitation. The different time constants of inputs create a low-pass filter for SAM stimuli. However, the MSO output is an integrated response to the temporal structure of a stimulus as well as its azimuthal position, i.e., IIDs. There are no in vivo results concerning filter characteristics in a "classical" MSO, but our data confirm an earlier speculation about this interdependence based on data accessed from a gerbil brain slice preparation.

The homeodomain transcription factor NK-4 acts as either a transcriptional activator or repressor and interacts with the p300 coactivator and the Groucho corepressor

NK-4 (tinman) encodes an NK-2 class homeodomain transcription factor that is required for development of the Drosophila dorsal mesoderm, including heart. Genetic evidence suggests its important role in mesoderm subdivision, yet the properties of NK-4 as a transcriptional regulator and the mechanism of gene transcription by NK-4 are not completely understood. Here, we describe its properties as a transcription factor and its interaction with the p300 coactivator and the Groucho corepressor. We demonstrate that NK-4 can activate or repress target genes in cultured cells, depending on functional domains that are conserved between Drosophila melanogaster and Drosophila virilis NK-4 genes. Using GAL4-NK-4 fusion constructs, we have mapped a transcriptional activation domain (amino acids 1-110) and repression domains (amino acids 111-188 and the homeodomain) and found an inhibitory function for the homeodomain in transactivation by NK-4. Furthermore, we demonstrate that NK-4-dependent transactivation is augmented by the p300 coactivator and show that NK-4 physically interacts with p300 via the activation domain. In addition, cotransfection experiments indicate that the repressor activity of NK-4 is strongly enhanced by the Groucho corepressor. Using immunoprecipitation and in vitro pull-down assays, we show that NK-4 directly interacts with the Groucho corepressor, for which the homeodomain is required. Together, our results indicate that NK-4 can act as either a transcriptional activator or repressor and provide the first evidence of NK-4 interactions with the p300 coactivator and the Groucho corepressor.

Twist-mediated activation of the NK-4 homeobox gene in the visceral mesoderm of Drosophila requires two distinct clusters of E-box regulatory elements

NK-4, also called msh2 and tinman, encodes a homeodomain transcription factor that is required for the development of the dorsal mesoderm and its derivatives in the Drosophila embryo. Genetic analyses indicate that NK-4 resides downstream of the mesodermal determinant twist, which encodes a basic helix-loop-helix-type transcription factor. However, the regulation of NK-4 by twist remains poorly understood. Using expression assays in cultured cells and transgenic flies, we show that two distinct clusters of E-box regulatory sequences, present upstream of the NK-4 gene, mediate NK-4 expression in the visceral mesoderm. These elements are conserved between the Drosophila melanogaster and Drosophila virilis NK-4 genes and serve as binding sites for Twist (E1 cluster) and NK-4 (E2 cluster) proteins. In cultured cells, Twist and NK-4 binding results in activation of NK-4 gene expression. In transgenic animals, the E1 and E2 clusters are functionally connected, and both elements are required for NK-4 activation in cells of the visceral mesoderm and also for NK-4 repression in cells of the somatic musculature. These results demonstrate that NK-4 is a direct transcriptional target for Twist and its own gene product in visceral mesodermal cells, supporting the idea that twist and NK-4 function in the subdivision of the mesoderm during Drosophila embryogenesis.