Mechanical activation of TWIK-related potassium channel by nanoscopic movement and rapid second messenger signaling

Rapid conversion of force into a biological signal enables living cells to respond to mechanical forces in their environment. The force is believed to initially affect the plasma membrane and then alter the behavior of membrane proteins. Phospholipase D2 (PLD2) is a mechanosensitive enzyme that is regulated by a structured membrane-lipid site comprised of cholesterol and saturated ganglioside (GM1). Here we show stretch activation of TWIK-related K+ channel (TREK-1) is mechanically evoked by PLD2 and spatial patterning involving ordered GM1 and 4,5-bisphosphate (PIP2) clusters in mammalian cells. First, mechanical force deforms the ordered lipids, which disrupts the interaction of PLD2 with the GM1 lipids and allows a complex of TREK-1 and PLD2 to associate with PIP2 clusters. The association with PIP2 activates the enzyme, which produces the second messenger phosphatidic acid (PA) that gates the channel. Co-expression of catalytically inactive PLD2 inhibits TREK-1 stretch currents in a biological membrane. Cellular uptake of cholesterol inhibits TREK-1 currents in culture and depletion of cholesterol from astrocytes releases TREK-1 from GM1 lipids in mouse brain. Depletion of the PLD2 ortholog in flies results in hypersensitivity to mechanical force. We conclude PLD2 mechanosensitivity combines with TREK-1 ion permeability to elicit a mechanically evoked response.

Effects of entropy in real-world noise on speech perception in listeners with normal hearing and hearing lossa)

Hearing aids show more benefit in traditional laboratory speech-in-noise tests than in real-world noisy environments. Real-world noise comprises a large range of acoustic properties that vary randomly and rapidly between and within environments, making quantifying real-world noise and using it in experiments and clinical tests challenging. One approach is to use acoustic features and statistics to quantify acoustic properties of real-world noise and control for them or measure their relationship to listening performance. In this study, the complexity of real-world noise from different environments was quantified using entropy in both the time- and frequency-domains. A distribution of noise segments from low to high entropy were extracted. Using a trial-by-trial design, listeners with normal hearing and hearing loss (in aided and unaided conditions) repeated back sentences embedded in these noise segments. Entropy significantly affected speech perception, with a larger effect of entropy in the time-domain than the frequency-domain, a larger effect for listeners with normal hearing than for listeners with hearing loss, and a larger effect for listeners with hearing loss in the aided than unaided condition. Speech perception also differed between most environment types. Combining entropy with the environment type improved predictions of speech perception above the environment type alone.

Auditory Environments and Hearing Aid Feature Activation Among Younger and Older Listeners in an Urban and Rural Area

OBJECTIVES

The purpose of this study was to investigate differences in auditory environments and hearing aid feature activation between younger listeners with normal hearing and older listeners with hearing loss in an urban and rural location. We hypothesized that (1) urban dwellers and younger listeners would encounter more diverse and demanding auditory environments than rural dwellers and older listeners, respectively; (2) the advanced hearing aid features (noise reduction and directional microphone) of urban dwellers and younger listeners would be activated more frequently than rural dwellers and older listeners, respectively.

DESIGN

The design of this study was cross-sectional with repeated measures. A total of 12 older adults with hearing loss (OHL-U) and 11 younger adults with normal hearing (YNH-U) were recruited from an urban area (Berkeley, California) and 13 older adults with hearing loss (OHL-R) and 10 YNH-U were recruited from a rural area (Iowa City, Iowa). Participants wore hearing aids that recorded data about their listening environments and completed ecological momentary assessments for 1 week.

RESULTS

The YNH-U group experienced higher sound pressure levels and hearing aid features were activated more frequently than in the OHL groups. The OHL-R group experienced significantly less diverse sound pressure levels than the YNH-U group. The YNH-R group had sound levels between the YNH-U group and the OHL groups but without significant differences from any other group. The YNH groups showed a greater likelihood of hearing aid feature activation than the OHL-R group.

CONCLUSIONS

Demographics affect auditory environments and the activation of hearing aid features. Younger urban dwellers have the most diverse or demanding auditory environments and hearing aid feature activation, and older, rural dwellers with hearing loss have the least diverse or demanding auditory environments and hearing aid feature activation. Future studies of real-world auditory environments and audiology intervention effectiveness should consider location in recruitment and interpretation of results.

Auditory environment diversity quantified using entropy from real-world hearing aid data

Introduction

Using data collected from hearing aid users' own hearing aids could improve the customization of hearing aid processing for different users based on the auditory environments they encounter in daily life. Prior studies characterizing hearing aid users' auditory environments have focused on mean sound pressure levels and proportions of environments based on classifications. In this study, we extend these approaches by introducing entropy to quantify the diversity of auditory environments hearing aid users encounter.

Materials and Methods

Participants from 4 groups (younger listeners with normal hearing and older listeners with hearing loss from an urban or rural area) wore research hearing aids and completed ecological momentary assessments on a smartphone for 1 week. The smartphone was programmed to sample the processing state (input sound pressure level and environment classification) of the hearing aids every 10 min and deliver an ecological momentary assessment every 40 min. Entropy values for sound pressure levels, environment classifications, and ecological momentary assessment responses were calculated for each participant to quantify the diversity of auditory environments encountered over the course of the week. Entropy values between groups were compared. Group differences in entropy were compared to prior work reporting differences in mean sound pressure levels and proportions of environment classifications. Group differences in entropy measured objectively from the hearing aid data were also compared to differences in entropy measured from the self-report ecological momentary assessment data.

Results

Auditory environment diversity, quantified using entropy from the hearing aid data, was significantly higher for younger listeners than older listeners. Entropy measured using ecological momentary assessment was also significantly higher for younger listeners than older listeners.

Discussion

Using entropy, we show that younger listeners experience a greater diversity of auditory environments than older listeners. Alignment of group entropy differences with differences in sound pressure levels and hearing aid feature activation previously reported, along with alignment with ecological momentary response entropy, suggests that entropy is a valid and useful metric. We conclude that entropy is a simple and intuitive way to measure auditory environment diversity using hearing aid data.

Personalizing over-the-counter hearing aids using pairwise comparisons

Over-the-counter hearing aids enable more affordable and accessible hearing health care by shifting the burden of configuring the device from trained audiologists to end-users. A critical challenge is to provide users with an easy-to-use method for personalizing the many parameters which control sound amplification based on their preferences. This paper presents a novel approach to fitting hearing aids that provides a higher degree of personalization than existing methods by using user feedback more efficiently. Our approach divides the fitting problem into two parts. First, we discretize an initial 24-dimensional space of possible configurations into a small number of presets. Presets are constructed to ensure that they can meet the hearing needs of a large fraction of Americans with mild-to-moderate hearing loss. Then, an online agent learns the best preset by asking a sequence of pairwise comparisons. This learning problem is an instance of the multi-armed bandit problem. We performed a 35-user study to understand the factors that affect user preferences and evaluate the efficacy of multi-armed bandit algorithms. Most notably, we identified a new relationship between a user's preference and presets: a user's preference can be represented as one or more preference points in the initial configuration space with stronger preferences expressed for nearby presets (as measured by the Euclidean distance). Based on this observation, we have developed a Two-Phase Personalizing algorithm that significantly reduces the number of comparisons required to identify a user's preferred preset. Simulation results indicate that the proposed algorithm can find the best configuration with a median of 25 comparisons, reducing by half the comparisons required by the best baseline. These results indicate that it is feasible to configure over-the-counter hearing aids using a small number of pairwise comparisons without the help of professionals.

Computing Generalized Matrix Inverse on Spiking Neural Substrate

Emerging neural hardware substrates, such as IBM's TrueNorth Neurosynaptic System, can provide an appealing platform for deploying numerical algorithms. For example, a recurrent Hopfield neural network can be used to find the Moore-Penrose generalized inverse of a matrix, thus enabling a broad class of linear optimizations to be solved efficiently, at low energy cost. However, deploying numerical algorithms on hardware platforms that severely limit the range and precision of representation for numeric quantities can be quite challenging. This paper discusses these challenges and proposes a rigorous mathematical framework for reasoning about range and precision on such substrates. The paper derives techniques for normalizing inputs and properly quantizing synaptic weights originating from arbitrary systems of linear equations, so that solvers for those systems can be implemented in a provably correct manner on hardware-constrained neural substrates. The analytical model is empirically validated on the IBM TrueNorth platform, and results show that the guarantees provided by the framework for range and precision hold under experimental conditions. Experiments with optical flow demonstrate the energy benefits of deploying a reduced-precision and energy-efficient generalized matrix inverse engine on the IBM TrueNorth platform, reflecting 10× to 100× improvement over FPGA and ARM core baselines.

A novel function for the MAP kinase SMA-5 in intestinal tube stability

In vivo evidence links SMA-5 to the maintenance of the apical domain in the Caenorhabditis elegans intestine. sma-5 mutations induce morphological and biochemical changes of the intermediate filament system, demonstrating the close relationship between posttranslational modification and structural integrity of the evolutionarily conserved intestinal cytoskeleton.

Intermediate filaments are major cytoskeletal components whose assembly into complex networks and isotype-specific functions are still largely unknown. Caenorhabditis elegans provides an excellent model system to study intermediate filament organization and function in vivo. Its intestinal intermediate filaments localize exclusively to the endotube, a circumferential sheet just below the actin-based terminal web. A genetic screen for defects in the organization of intermediate filaments identified a mutation in the catalytic domain of the MAP kinase 7 orthologue sma-5(kc1). In sma-5(kc1) mutants, pockets of lumen penetrate the cytoplasm of the intestinal cells. These membrane hernias increase over time without affecting epithelial integrity and polarity. A more pronounced phenotype was observed in the deletion allele sma-5(n678) and in intestine-specific sma-5(RNAi). Besides reduced body length, an increased time of development, reduced brood size, and reduced life span were observed in the mutants, indicating compromised food uptake. Ultrastructural analyses revealed that the luminal pockets include the subapical cytoskeleton and coincide with local thinning and gaps in the endotube that are often enlarged in other regions. Increased intermediate filament phosphorylation was detected by two-dimensional immunoblotting, suggesting that loss of SMA-5 function leads to reduced intestinal tube stability due to altered intermediate filament network phosphorylation.

Chromosome-wide mechanisms to decouple gene expression from gene dose during sex-chromosome evolution

Changes in chromosome number impair fitness by disrupting the balance of gene expression. Here we analyze mechanisms to compensate for changes in gene dose that accompanied the evolution of sex chromosomes from autosomes. Using single-copy transgenes integrated throughout the Caenorhabditis elegans genome, we show that expression of all X-linked transgenes is balanced between XX hermaphrodites and XO males. However, proximity of a dosage compensation complex (DCC) binding site (rex site) is neither necessary to repress X-linked transgenes nor sufficient to repress transgenes on autosomes. Thus, X is broadly permissive for dosage compensation, and the DCC acts via a chromosome-wide mechanism to balance transcription between sexes. In contrast, no analogous X-chromosome-wide mechanism balances transcription between X and autosomes: expression of compensated hermaphrodite X-linked transgenes is half that of autosomal transgenes. Furthermore, our results argue against an X-chromosome dosage compensation model contingent upon rex-directed positioning of X relative to the nuclear periphery.

DOI:http://dx.doi.org/10.7554/eLife.17365.001

DNA inside cells is packaged into structures called chromosomes, each of which contains numerous genes. Many organisms, including humans, have two copies of most chromosomes in their cells. If the process of cell division goes awry, cells can end up with too many or too few copies of their chromosomes, which can cause serious illnesses.

Sex chromosomes pose a conundrum for cells. In humans, females have two copies of the X chromosome, whereas males only have one. This means that males have half the copy number (dose) of genes on the X chromosome. Human cells correct this imbalance by suppressing the activity, or expression, of most of the genes on one of the X chromosomes in females.

“Dosage compensation” also occurs in the roundworm species Caenorhabditis elegans, because male worms have one X chromosome whilst hermaphrodites have two. The dosage compensation mechanism in roundworms differs from that in humans. It involves turning down the expression of both hermaphrodite X chromosomes by half. The process is enacted by a dosage compensation complex that binds to specific sites along both hermaphrodite X chromosomes.

Dosage compensation mechanisms that reduce X chromosome expression in females cause sex chromosomes to have lower gene expression than non-sex chromosomes. Modern sex chromosomes evolved from a pair of non-sex chromosomes, and males lost one copy of all of the genes located on those ancestral chromosomes. This evolutionary history causes both sexes to have lower gene expression from X chromosomes than the other chromosomes, raising the question of whether a mechanism exists to balance out the difference in gene expression between sex chromosomes and non-sex chromosomes.

Wheeler et al. now show that the expression of any foreign gene artificially added to the X chromosomes of C. elegans is equalized between males and hermaphrodites despite the difference in gene dose. The equalization works regardless of where on the X chromosome the new gene is added. The foreign gene does not need to be adjacent to a binding site for the dosage compensation complex. These results indicate that dosage compensation mechanisms regulate gene expression on a chromosome-wide scale.

Wheeler et al. also show that genes added to X chromosomes are expressed at half the level as the same genes added to non-sex chromosomes. These results mean that no chromosome-wide mechanism balances gene expression levels between the X chromosome and the non-sex chromosomes.

It remains unknown how C. elegans, and many other living organisms, evolved to tolerate a lower level of gene expression from the sex chromosomes. Instead of a chromosome-wide mechanism, it is likely that individual genes evolved different ways to alter their expression levels. Working out what these mechanisms are remains a challenge for further research.

DOI:http://dx.doi.org/10.7554/eLife.17365.002

The novel intestinal filament organizer IFO-1 contributes to epithelial integrity in concert with ERM-1 and DLG-1

The nematode Caenorhabditis elegans is an excellent model system in which to study in vivo organization and function of the intermediate filament (IF) system for epithelial development and function. Using a transgenic ifb-2::cfp reporter strain, a mutagenesis screen was performed to identify mutants with aberrant expression patterns of the IF protein IFB-2, which is expressed in a dense network at the subapical endotube just below the microvillar brush border of intestinal cells. Two of the isolated alleles (kc2 and kc3) were mapped to the same gene, which we refer to as ifo-1 (intestinal filament organizer). The encoded polypeptide colocalizes with IF proteins and F-actin in the intestine. The apical localization of IFO-1 does not rely on IFB-2 but is dependent on LET-413, a basolateral protein involved in apical junction assembly and maintenance of cell polarity. In mutant worms, IFB-2 and IFC-2 are mislocalized in cytoplasmic granules and accumulate in large aggregates at the C. elegans apical junction (CeAJ) in a DLG-1-dependent fashion. Electron microscopy reveals loss of the prominent endotube and disordered but still intact microvilli. Semiquantitative fluorescence microscopy revealed a significant decrease of F-actin, suggesting a general role of IFO-1 in cytoskeletal organization. Furthermore, downregulation of the cytoskeletal organizer ERM-1 and the adherens junction component DLG-1, each of which leads to F-actin reduction on its own, induces a novel synthetic phenotype in ifo-1 mutants resulting in disruption of the lumen. We conclude that IFO-1 is a multipurpose linker between different cytoskeletal components of the C. elegans intestinal terminal web and contributes to proper epithelial tube formation.

Development of corpus luteum susceptibility to an analog of prostaglandin F2α, throughout the luteal phase in llamas (Lama glama)

The aim of the present study was to evaluate the susceptibility of the corpus luteum to d-cloprostenol (synthetic analog of PGF(2α)) throughout the luteal phase in llamas. Female llamas (n=43) were induced to ovulate by GnRH injection in the presence of an ovulatory follicle and randomly assigned into one of six groups: control and treated with an injection of d-cloprostenol on Day 3, 4, 5, 6 or 8 post GnRH. Blood samples were collected to determine plasma progesterone concentrations. There was no effect of treatment on animals injected on Day 3 or 4 post-GnRH. In animals treated on Day 5, different responses were observed. No effect of treatment was recorded in 27% of the animals whereas 55% of the llamas showed a transitory decrease followed by a recovery in plasma progesterone concentrations after d-cloprostenol injection, indicative of a resurgence of the corpus luteum, extending the luteal phase a day more than in control animals. In the remaining 18% of the animals injected on Day 5, (corresponding to those exhibiting the greatest plasma progesterone concentrations at the day of injection), complete luteolysis was observed. Plasma progesterone concentrations decreased to below 1 ng ml(-1) 24 h after d-cloprostenol in llamas injected on Day 6 or 8 post-GnRH. In conclusion, the corpus luteum of llamas is completely refractory to PGF(2α) until Day 4 after induction of ovulation, being partially sensitive by Day 5 and fully responsive to PGF(2α), by Day 6 after induction of ovulation.

MosSCI and gateway compatible plasmid toolkit for constitutive and inducible expression of transgenes in the C. elegans germline

Here we describe a toolkit for the production of fluorescently tagged proteins in the C. elegans germline and early embryo using Mos1-mediated single copy insertion (MosSCI) transformation. We have generated promoter and 3′UTR fusions to sequences of different fluorescent proteins yielding constructs for germline expression that are compatible with MosSCI MultiSite Gateway vectors. These vectors allow tagged transgene constructs to be inserted as single copies into known sites in the C. elegans genome using MosSCI. We also show that two C. elegans heat shock promoters (Phsp-16.2 and Phsp-16.41) can be used to induce transgene expression in the germline when inserted via MosSCI transformation. This flexible set of new vectors, available to the research community in a plasmid repository, should facilitate research focused on the C. elegans germline and early embryo.

Long-Term Prognosis in an ST-Segment Elevation Myocardial Infarction Population Treated With Routine Primary Percutaneous Coronary Intervention

Background— We sought to describe the long-term prognosis after routine primary percutaneous coronary intervention (pPCI) in a contemporary consecutive population of patients with presumed ST-segment elevation myocardial infarction, compare it with similar results from the landmark DANAMI-2 trial, and to identify a possible impact of time of presentation and referral pattern.

Methods and Results— Long-term prognosis in 1019 presumed ST-segment elevation myocardial infarction patients, treated according to modern routine pPCI during the year 2004, was analyzed and compared with similar data from the DANAMI-2 trial. Furthermore, we analyzed the impact of patient presentation to the angioplasty center during “off hours” (4 pm to 8 am plus weekends and holidays) and the impact of being referred from noninvasive hospitals. At 3 years, 20.4% in the routinely treated population versus 19.6% in the DANAMI-2 trial reached the combined end point of death, reinfarction, or stroke ( P =0.68), whereas the all-cause mortality was 13.0% and 13.7%, respectively ( P =0.65). Patients admitted during off hours had the same risk of reaching the combined end point of death, reinfarction, or stroke compared with patients admitted during office hours (hazards ratio, 1.04; 95% CI, 0.8 to 1.5; P =0.81). Door-to-balloon times of less than 90 minutes were achieved in 60% among patients admitted directly to an invasive center but only in 40% among transferred patients ( P <0.001). Despite this difference, no difference in unadjusted or adjusted long-term prognosis was found between the 2 groups.

Conclusions— This study shows that ST-segment elevation myocardial infarction patients treated with contemporary routine pPCI achieve a similar long-term prognosis as patients in the landmark randomized pPCI trial (DANAMI-2). Furthermore, the long-term prognosis was the same regardless of whether the pPCI was performed during off hours or office hours. Thus, pPCI including transportation of patients from noninvasive centers can be applied successfully in a real-life population.

Induction of H2AX phosphorylation in pulmonary cells by tobacco smoke: a new assay for carcinogens

DNA double strand breaks (DSBs) are potentially carcinogenic lesions. The induction of DSBs triggers phosphorylation of histone H2AX. Phosphorylated H2AX, denoted p-H2AX, may be detected immunocytochemically and the intensity of p-H2AX immunofluorescence (IF) reveals the frequency of DSBs. Using this assay we tested whether the exposure of A549 human pulmonary adenocarcinoma cells to tobacco smoke, and normal human bronchial epithelial cells (NHBE) to tobacco smoke condensate, induces DSBs. Cellular p-H2AX IF and DAPI fluorescence of individual cells were measured by laser scanning cytometry (LSC). Exposure of A549 cells to tobacco smoke and NHBE cells to smoke condensate led to H2AX phosphorylation in both a time and dose dependent manner. The maximal rate of H2AX phosphorylation was seen during the initial 4h of cell treatment. At high doses (50 microg/ml of smoke condensate), H2AX phosphorylation continued to increase for up to 24h. No differences in the level of H2AX phosphorylation were apparent between cells in G(1) vs S vs G(2)/M phase of the cell cycle in response to treatment with smoke condensate. The data provide strong evidence that exposure of A549 cells to tobacco smoke or NHBE cells to smoke condensate rapidly induces DSBs in these cells. The present assay to detect and measure DSBs induced by tobacco products complements other mutagenicity assays and may be applied to test potential carcinogens in other products.

The C. elegans ric-3 gene is required for maturation of nicotinic acetylcholine receptors

Mutations in ric-3 (resistant to inhibitors of cholinesterase) suppress the neuronal degenerations caused by a gain of function mutation in the Caenorhabditis elegans DEG-3 acetylcholine receptor. RIC-3 is a novel protein with two transmembrane domains and extensive coiled-coil domains. It is expressed in both muscles and neurons, and the protein is concentrated within the cell bodies. We demonstrate that RIC-3 is required for the function of at least four nicotinic acetylcholine receptors. However, GABA and glutamate receptors expressed in the same cells are unaffected. In ric-3 mutants, the DEG-3 receptor accumulates in the cell body instead of in the cell processes. Moreover, co-expression of ric-3 in Xenopus laevis oocytes enhances the activity of the C.elegans DEG-3/DES-2 and of the rat alpha-7 acetylcholine receptors. Together, these data suggest that RIC-3 is specifically required for the maturation of acetylcholine receptors.

The Caenorhabditis elegans gene unc-25 encodes glutamic acid decarboxylase and is required for synaptic transmission but not synaptic development

The neurotransmitter GABA has been proposed to play a role during nervous system development. We show that the Caenorhabditis elegans gene unc-25 encodes glutamic acid decarboxylase (GAD), the GABA biosynthetic enzyme. unc-25 is expressed specifically in GABAergic neurons. Null mutations in unc-25 eliminate the UNC-25 protein or alter amino acids conserved in all known GADs, result in a complete lack of GABA, and cause defects in all GABA-mediated behaviors. In unc-25 mutants the GABAergic neurons have normal axonal trajectories and synaptic connectivity, and the size and shape of synaptic vesicles are normal. The number of synaptic vesicles at GABAergic neuromuscular junctions is slightly increased. Cholinergic ventral nerve cord neurons, which innervate the same muscles as GABAergic ventral cord neurons, have normal morphology, connectivity, and synaptic vesicles. We conclude that GAD activity and GABA are not necessary for the development or maintenance of neuromuscular junctions in C. elegans.

Sex differences in androgen-regulated cytochrome P450 aromatase mRNA in the rat brain

The conversion of testosterone to estradiol by cytochrome P450 aromatase (P450(AROM)) in the medial preoptic area is required for full expression of male sexual behavior in rats. Preoptic P450(AROM) activity is stimulated by androgens through an androgen-receptor mediated mechanism that regulates P450(AROM) gene expression. The mechanism of enzyme induction appears to be sexually dimorphic in several species leading to greater testosterone-stimulated P450(AROM) activity in males than in females. The present study was designed to determine whether the sex difference in androgen-regulated P450(AROM) activity is manifested at the levels of mRNA expression. We compared the concentrations of P450(AROM) mRNA and enzyme activity between five different treatment groups: intact males, castrated males (CX), ovariectomized females (OVX), CX males treated with dihydrotestosterone (CX+DHT), and OVX females treated with DHT (OVX+DHT). We found that unstimulated levels of P450(AROM) mRNA and enzyme activity in both the preoptic area and medial basal hypothalamus were similar in the CX and OVX groups. However, when treated with equivalent doses of DHT, the levels of P450(AROM) mRNA and enzyme activity in both brain regions were significantly higher in males than in females (i.e., CX+DHT group >OVX+DHT group). These results demonstrate that sex differences in the regulation of P450(AROM) in brain are exerted pretranslationally by androgen and suggest that gender differences in androgen responsiveness play an important role in regulating gene expression in the adult rat brain.

Pre- and postpubertal LH and estradiol pattern in gilts subjected to intermittent inescapable electroshock

The effect of intermittent electroshock on LH and estradiol secretory pattern and on reaching puberty was studied in 24 prepubertal gilts. Twelve gilts 115-168 days of age received unpredictable and inescapable electroshocks 0-5 times daily between 8 am and 4 pm and 12 gilts served as controls. At an age of 168 +/- 0.7 days all gilts were moved, regrouped and exposed to a boar for 30 min. Observations for signs of oestrus were carried out twice daily. Indwelling jugular catheters were inserted into 8 gilts on each treatment after the initial boar contact. Blood samples were collected to determine LH profiles for 4 h every 15 min on day 2 and day 4 after the initial boar contact. The remaining 4 gilts on each treatment were catheterized one day prior to the initial boar contact and blood was collected to determine LH profiles the day before initial boar contact and day 1 and day 2 after initial boar contact for 6 h every 15 min. In addition, blood samples were collected and analyzed for LH and estradiol from all gilts daily at 8 am, 12 am and 4 pm for the first 3 days following the initial boar contact and thereafter every 4 h until the end of oestrus (diurnal samples). Samples taken daily at noon the first 5 days following initial boar contact were analyzed for cortisol. The electroshock treatment significantly increased the age at puberty (p = 0.04) and tended to decrease the mean LH concentration prior to the preovulatory LH surge (p = 0.08) and the maximal concentration of LH during the preovulatory LH surge (p = 0.07). The apparent down regulation of the plasma concentration of LH was not associated with increased activity in the hypothalamus-pituitary-adrenal axis in that the basal concentration of cortisol was not affected by treatment. This indicates that other physiological mechanisms are involved in stress-induced suppression of LH.

The GABAergic nervous system of Caenorhabditis elegans

gamma-Aminobutyric acid (GABA) is the most abundant inhibitory neurotransmitter in vertebrates and invertebrates. GABA receptors are the target of anxiolytic, antiepileptic and antispasmodic drugs, as well as of commonly used insecticides. How does a specific neurotransmitter such as GABA control animal behaviour? To answer this question, we identified all neurons that react with antisera raised against the neurotransmitter GABA in the nervous system of the nematode Caenorhabditis elegans. We determined the in vivo functions of 25 of the 26 GABAergic neurons by killing these cells with a laser microbeam in living animals and by characterizing a mutant defective in GABA expression. On the basis of the ultrastructurally defined connectivity of the C. elegans nervous system, we deduced how these GABAergic neurons act to control the body and enteric muscles necessary for different behaviours. Our findings provide evidence that GABA functions as an excitatory as well as an inhibitory neurotransmitter.

Genes required for GABA function in Caenorhabditis elegans

gamma-Aminobutyric acid (GABA) neurotransmission is widespread in vertebrate and invertebrate nervous systems. Here we use a genetic approach to identify molecules specific to GABA function. On the basis of the known in vivo roles of GABAergic neurons in controlling behaviour of the nematode Caenorhabditis elegans, we identified mutants defective in GABA-mediated behaviours. Five genes are necessary either for GABAergic neuronal differentiation or for pre- or postsynaptic GABAergic function. The gene unc-30 is required for the differentiation of a specific type of GABAergic neuron, the type-D inhibitory motor neuron. The gene unc-25 is necessary for GABA expression and probably encodes the GABA biosynthetic enzyme glutamic acid decarboxylase. The genes unc-46 and unc-47 seem to be required for normal GABA release. Finally, the gene unc-49 is apparently necessary postsynaptically for the inhibitory effect of GABA on the body muscles and might encode a protein needed for the function of a GABAA-like receptor. Some of these genes are likely to encode previously unidentified proteins required for GABA function.

Discrimination between bacteriophage T3 and T7 promoters by the T3 and T7 RNA polymerases depends primarily upon a three base-pair region located 10 to 12 base-pairs upstream from the start site

The bacteriophage T3 and T7 RNA polymerases are closely related, yet are highly specific for their own promoter sequences. To understand the basis of this specificity, T7 promoter variant that contain substitutions of T3-specific base-pairs at one or more positions within the T7 promoter consensus sequence were synthesized and cloned. Template competition assays between variant and consensus promoters demonstrate that the primary determinants of promoter specificity are located in the region from -10 to -12, and that the base-pair at -11 is of particular importance. Changing this base-pair from G.C, which is normally present in T7 promoters, to C.G, which is found at this position in T3 promoters, prevented utilization by the T7 RNA polymerase and simultaneously enabled transcription from the variant T7 promoter by the T3 enzyme. Substitution of T7 base-pairs with T3 base-pairs at other positions where the two consensus sequences diverge affected the overall efficiency with which the variant promoter was utilized by the T7 RNA polymerase, but these changes were not sufficient to permit recognition by the T3 RNA polymerase. Switching the -11 base-pair in the T3 promoter consensus to the T7 base-pair prevented utilization by the T3 RNA polymerase, but did not allow the T3 variant promoter to be utilized by the T7 RNA polymerase. This probably reflects a greater specificity of the T7 RNA polymerase for base-pairs at other positions where the promoter sequences differ, most notably at -15. The magnitude of the effects of base substitutions in the T7 promoter on promoter strength (-11C much greater than -10C greater than -12A) correlates with the affinity of the T7 polymerase for the promoter variants, suggesting that the discrimination of the phage RNA polymerases for their promoters is mediated primarily at the level of DNA binding, rather than at the level of initiation.

The status of periodontal health and oral hygiene of Miraa (catha edulis) chewers

Two hundred and thirty one miraa chewers and 199 non miraa chewers were assessed for gingivitis, loss of attachment and oral hygiene status. The mean gingivitis score among miraa chewers was 1.6 and 1.7 among non miraa chewers (P less than 0.05). The mean facial gingivitis score among miraa chewers was 1.5 and 1.6 among non miraa chewers (P greater than 0.05). The mean distal gingivitis score among miraa chewers was 1.5 and 1.7 among non miraa chewers (P less than 0.05). The mean lingual gingivitis score among miraa chewers was lower than that of non miraa chewers (P less than 0.05). The means of loss of attachment of the teeth of miraa chewers were equal to those of non miraa chewers. Although the mean surface plaque scores of miraa chewers were generally lower than those of non miraa chewers, only the mean lingual plaque score of miraa chewers was found to be significantly lower than that of non miraa chewers (P less than 0.05). It is concluded that the oral hygiene status of miraa chewers was generally better than that of non miraa chewers and there was no evidence to show that chewing miraa is detrimental to periodontal health.

Pantethine lipomodulation: evidence for cysteamine mediation in vitro and in vivo

Recent human studies suggest rapid in vivo hydrolysis of the lipid-lowering drug, pantethine, to the vitamin pantothenic acid and the small aminothiol compound, cysteamine. To test whether the active agent is a hydrolysis product, we repeated three experimental models of pantethine's effect with pantothenate and cysteamine. In vitro experiments with human fetal fibroblasts showed equivalent modulation of cholesterol and methyl sterol synthesis by pantethine, cysteamine, or cystamine (the disulfide of cysteamine), but pantothenate had no effect. Similarly, in vivo experiments with 0.5% cholesterol-fed rabbits showed oral pantethine or equimolar cystamine significantly lowered plasma cholesterol, while pantothenate, cystine, and 2-hydroxyethyl disulfide did not. Lastly, diabetic male rats (40 mg/kg streptozotocin) fed 0.1% pantethine and lower plasma free fatty acids after 2 weeks than controls, an effect not seen with pantothenate and largely duplicated by cystamine. The efficacy of pantethine has previously been attributed to altered vitamin metabolism and increased coenzyme A concentration. Pantethine did increase CoA levels 45% in rat liver homogenates while equivalent amounts of cystamine or pantothenate did not. However, a causal relationship between CoA levels and pantethine's action as a hypolipemic agent has never been shown. At least in 3 independent experimental models, the lipomodulating effect of pantethine appears instead to be mediated by the hydrolysis product cysteamine.