Evaluation of risk factors and biomarkers related to arterial and venous thrombotic events in idiopathic inflammatory myopathies.

Objectives: This study aimed to assess the contribution of traditional/disease-related risk factors and biomarkers linked to arterial and venous thrombotic events (TEs) in patients with idiopathic inflammatory myopathies (IIMs).Method: The occurrence of arterial and/or venous TEs at the time of or after IIM diagnosis was retrospectively evaluated in a cohort of 253 patients with IIMs, resulting in a final population of 246 IIM patients, 51 with reported TE (cases) and 195 without a history of TE (comparators). Information on disease characteristics and traditional risk factors for arterial and venous TE (essential hypertension, diabetes, dyslipidaemia, smoking, malignancy) was retrieved. Serum levels of anti-phospholipid antibodies (aPLs) and adhesion molecules were analysed at the time of IIM diagnosis and at the time of the TE in cases.Results: One in five IIM patients (21%) had experienced a TE, arterial TE in 22 and venous TE in 29 patients, with a peak prevalence within 5 years after diagnosis. Among traditional/disease-related risk factors, only older age was associated with both arterial and venous TEs, after adjusting for other covariates. Low serum levels of e-selectin were associated with higher odds of developing a TE, without specific association with either arterial or venous TEs. Only 6% of IIM patients had aPLs, with no significant difference between cases and comparators.Conclusions: An increased risk of both venous and arterial TEs should be considered in IIM patients, particularly close to diagnosis and in elderly people. Low serum levels of e-selectin may predict TE in IIM patients, but the underlying biological mechanism is not known.

Risk of bacteremia in patients presenting with shaking chills and vomiting - a prospective cohort study.

Chills and vomiting have traditionally been associated with severe bacterial infections and bacteremia. However, few modern studies have in a prospective way evaluated the association of these signs with bacteremia, which is the aim of this prospective, multicenter study. Patients presenting to the emergency department with at least one affected vital sign (increased respiratory rate, increased heart rate, altered mental status, decreased blood pressure or decreased oxygen saturation) were included. A total of 479 patients were prospectively enrolled. Blood cultures were obtained from 197 patients. Of the 32 patients with a positive blood culture 11 patients (34%) had experienced shaking chills compared with 23 (14%) of the 165 patients with a negative blood culture, P = 0.009. A logistic regression was fitted to show the estimated odds ratio (OR) for a positive blood culture according to shaking chills. In a univariate model shaking chills had an OR of 3.23 (95% CI 1.35-7.52) and in a multivariate model the OR was 5.9 (95% CI 2.05-17.17) for those without prior antibiotics adjusted for age, sex, and prior antibiotics. The presence of vomiting was also addressed, but neither a univariate nor a multivariate logistic regression showed any association between vomiting and bacteremia. In conclusion, among patients at the emergency department with at least one affected vital sign, shaking chills but not vomiting were associated with bacteremia.

Concomitant Ro/SSA and La/SSB antibodies are biomarkers for the risk of venous thromboembolism and cerebral infarction in primary Sjögren's syndrome.

BACKGROUND: To assess the risk of incident cardiovascular disease in patients with primary Sjögren's syndrome, overall and stratified by Ro/SSA and La/SSB autoantibody status. METHODS: A cohort of patients with primary Sjögren's syndrome in Sweden (n = 960) and matched controls from the general population (n = 9035) were included, and data extracted from the National Patient Register to identify events of myocardial infarction, cerebral infarction and venous thromboembolism. Hazard ratios were estimated using cox proportional hazard regressions. RESULTS: During a median follow-up of 9.5 years, the overall hazard ratio (HR) was 1.6 (95% CI 1.2-2.1) for myocardial infarction, 1.2 (95% CI 0.9-1.7) for cerebral infarction and 2.1 (95% CI 1.6-2.9) for venous thromboembolism. Patients positive for both Ro/SSA and La/SSB autoantibodies had a substantially higher risk of cerebral infarction (HR 1.7, 95% CI 1.0-2.9) and venous thromboembolism (HR 3.1, 95% CI 1.9-4.8) than the general population. These risks were not significantly increased in Ro/SSA- and La/SSB-negative patients. Among autoantibody-positive patients, the highest HR of cerebral infarction was seen after ≥10 years disease duration (HR 2.8, 95% CI 1.4-5.4), while the HR for venous thromboembolism was highest 0-5 years after disease diagnosis (HR 4.7, 95% CI 2.3-9.3) and remained high throughout disease duration. CONCLUSIONS: Primary Sjögren's syndrome is associated with a markedly increased risk of cardiovascular disease and the presence of Ro/SSA and La/SSB autoantibodies identify the subgroup of patients carrying the highest risk. These findings suggest that monitoring and prevention of cardiovascular disease in this patient group should be considered.

Web- vs. telehealth-based delivery of cognitive behavioral therapy for insomnia: a randomized controlled trial.

OBJECTIVES: The purpose of our study was to evaluate and compare two methods of service delivery (web-based and telehealth-based) for chronic insomnia with regard to patient preference, clinical effectiveness, and patient satisfaction. METHODS: Our study was a randomized controlled trial with manualized telehealth- and web-based delivery conditions (nonblinded). The sample comprised 73 adults with chronic insomnia. Participants received web-based delivery from their homes or telehealth-based delivery from a nearby clinic. Both interventions consisted of identical psychoeducation, sleep hygiene and stimulus control instruction, sleep restriction treatment, relaxation training, cognitive therapy, mindfulness meditation, and medication-tapering assistance. RESULTS: Using a linear mixed model analysis, results showed that both delivery methods produced equivalent changes in insomnia severity, with large effect sizes. Attendance patterns favored telehealth, whereas homework adherence and preference data favored web-based delivery. CONCLUSIONS: Web- and telehealth-based delivery are both helpful in treating chronic insomnia in rural-dwelling adults.

Regional differences regarding risk of developing rheumatoid arthritis in Stockholm County, Sweden: results from the Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA) study.

OBJECTIVES: Rheumatoid arthritis (RA) is a complex disease that is associated with genetic and environmental factors. We have investigated geospatial variation in the risk of developing RA within Stockholm County, Sweden, with respect to established environmental risk factors for RA, as well as serologically defined subgroups of RA. METHOD: Information regarding geographical location for 1432 cases and 2529 controls from the Epidemiological Investigation of Rheumatoid Arthritis (EIRA) study, living in Stockholm County at RA symptom onset, or matched date for controls, was used to estimate geospatial variation in risk. We used generalized additive models (GAMs) to create a risk surface, calculate odds ratios (ORs), and adjust for potential confounding by smoking, education level, and RA within family. We performed a stratified analysis based on the presence/absence of anti-citrullinated peptide antibodies (ACPA). RESULTS: We found significant spatial variation in the odds of developing RA in Stockholm County. After adjustment for smoking, education level, and family history of RA, this geospatial variation remained. The stratified analysis showed areas with higher ORs for ACPA-positive RA and ACPA-negative RA, after adjusting for smoking, education level, and having a family history of RA. Living in the city of Stockholm was associated with decreased risk of RA. CONCLUSIONS: The risk of developing RA in Stockholm County is not distributed evenly and there are areas of increased risk that could not be explained by known factors. Further investigations of local exposures or social factors are warranted.

The characterisation and risk factors of ischaemic heart disease in patients with coeliac disease.

BACKGROUND: Studies have shown an increased risk of ischaemic heart disease (IHD) in patients with coeliac disease (CD), despite the patients' lack of traditional IHD risk factors. AIM: To characterise IHD according to CD status. METHODS: Data on duodenal or jejunal biopsies were collected in 2006-2008 from all 28 pathology departments in Sweden and were used to define CD (equal to villous atrophy; Marsh stage 3). We used the Swedish cardiac care register SWEDEHEART to identify IHD and to obtain data on clinical status and risk factors at time of first myocardial infarction for this case-only comparison. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). CD patients were compared with general population reference individuals. RESULTS: We identified 1075 CD patients and 4142 reference individuals with subsequent IHD. CD patients with myocardial infarction had lower body mass index (P < 0.001) and cholesterol values (P < 0.001) and were less likely to be active smokers (OR = 0.74; 95% CI = 0.56-0.98) than reference individuals with myocardial infarction. CD patients had less extensive coronary artery disease at angiography (any stenosis: OR = 0.80; 95% CI = 0.66-0.97; three-vessel disease: OR = 0.73; 95% CI = 0.57-0.94); but there was no difference in the proportions of CD patients with positive biochemical markers of myocardial infarction (CD: 92.2% vs. reference individuals: 91.5%, P = 0.766). CONCLUSION: Despite evidence of an increased risk of IHD and higher cardiovascular mortality, patients with coeliac disease with IHD have a more favourable cardiac risk profile compared with IHD in reference individuals.

Alcohol prevention in Swedish occupational health care.

BACKGROUND: Occupational health care (OHC) was part of the Swedish Risk Drinking Project, a government-supported continuing professional education (CPE) endeavour for health professionals, 2004-10. AIMS: To investigate OHC professionals' perceived knowledge concerning patient counselling on alcohol, perceived efficiency in achieving patient changes, use of questionnaires and biomarkers, amount and content of their alcohol-related CPE, their reasons for participating in this CPE and improvements experienced in addressing alcohol issues in the last 3 years. METHODS: Baseline 2005 and follow-up 2008 data were collected by means of anonymous questionnaires to all physicians and nurses in OHC. RESULTS: Response rates ranged from 53 to 80%. The share of nurses and physicians who had taken part in ≥ 3 days training on risk drinking issues rose from 10 to 59% and from 7 to 59%, respectively. The OHC professionals' perceived knowledge and efficiency concerning lifestyle counselling improved from 2005 to 2008, considerably more so for alcohol than the other lifestyle issues. The most competent nurses and physicians were more likely to have participated in training lasting ≥ 3 days. The most competent nurses and physicians had become better at initiating conversations about alcohol and at informing, providing advice and discussing alcohol with their clients. CONCLUSIONS: There were major improvements in the OHC professionals' perceived knowledge concerning alcohol counselling and efficiency in influencing patients' alcohol habits after participation in a comprehensive CPE project. Overall, the nurses achieved more improvements than the physicians.

Rapid increase in myocardial infarction risk following diagnosis of rheumatoid arthritis amongst patients diagnosed between 1995 and 2006.

UNLABELLED: The risk of ischaemic heart disease (IHD), and in particular myocardial infarction (MI), is increased amongst patients with established rheumatoid arthritis (RA). Few studies have included contemporary patients with RA. We recently reported that the risk of IHD is not elevated before the onset of RA symptoms. However, when, in relation to RA diagnosis, the risk is increased is unknown. OBJECTIVE: To assess the risk of MI and other IHD events amongst patients diagnosed with RA during the last decade and within 18 months following RA symptom onset, compared to the general population, by time since RA diagnosis, year of RA diagnosis and by rheumatoid factor (RF) status. METHODS AND PATIENTS: A Swedish inception cohort of RA (n = 7469) diagnosed between 1995 and 2006 and a matched general population comparator cohort (n = 37,024), was identified and linked to national registers of morbidity and mortality from IHD. Relative risks (RRs) of MI and other IHD events were estimated using Cox regression. RESULTS: During follow-up, 233 patients with RA and 701 controls developed a first MI, corresponding to an overall RR of MI of 1.6 (95% confidence interval 1.4, 1.9). Increased risks of MI were already detected within 1-4 years following RA diagnosis, as well as in patients diagnosed with RA during the last 5 years, in RF-negative patients and for transmural as well as nontransmural MIs. CONCLUSIONS: MI risk increases rapidly following RA diagnosis, suggesting the importance of additional mechanisms other than atherosclerosis. The elevated short-term risk is present amongst patients diagnosed in recent years, underscoring the importance of MI prevention from the time of RA diagnosis.

Cyclin B1 is a prognostic proliferation marker with a high reproducibility in a population-based lymph node negative breast cancer cohort.

A large proportion of women with lymph node negative breast cancer do not benefit from chemotherapy. Proliferation markers have been shown to recognize patients at high risk for recurrence. The Ki67 protein has recently been included in the St Gallen guidelines. The authors investigated the prognostic importance of cyclin B1 in node negative breast cancer and included a study of reproducibility. In a population-based case-control study, 190 women who died from breast cancer were defined as cases and 190 women alive at the time for the corresponding case's death were defined as controls. Inclusion criteria were tumor size

ADHD in adult psychiatry. Minimum rates and clinical presentation in general psychiatry outpatients.

The objective of the study was to determine the prevalence and comorbidity of persisting attention-deficit hyperactivity disorder (ADHD) in adult psychiatric outpatients. Consecutive patients, first visits excluded, at a general psychiatric outpatient clinic were offered a screening for childhood ADHD with the Wender Utah Rating Scale (WURS). One hundred and forty-one patients out of 398 (35%) completed and returned the scale. Patients above or near cut-off for ADHD (n=57) were offered an extensive clinical evaluation with psychiatric as well as neuropsychological examination. The attrition was analysed regarding age, sex and clinical diagnoses. Out of the screened sample, 40% had scores indicating possible childhood ADHD. These 57 patients were invited to the clinical part of the study, but 10 declined assessment, leaving 47 (37 women and 10 men) who were actually examined. Thirty of these (21 women and nine men) met diagnostic criteria for ADHD at the time of examination. Among the patients with ADHD, affective disorders were the most common psychiatric diagnoses. The rate of alcohol and/or substance abuse, as noted in the medical records, was also high in the ADHD group. In the WURS-screened group, 22% (30 patients assessed as part of this study and one person with ADHD previously clinically diagnosed) were shown to have persisting ADHD. Therefore, it is clearly relevant for psychiatrists working in general adult psychiatry to have ADHD in mind as a diagnostic option, either as the patient's main problem or as a functional impairment predisposing for other psychiatric disorders.

Usual drinking patterns and non-fatal injury among patients seeking emergency care.

OBJECTIVES: To explore the association between drinking patterns, irrespective of whether alcohol was consumed in the event of the injury or not, and different injury variables; and to identify settings and situations in which risky drinkers have an increased likelihood of injury. STUDY DESIGN: The study population consisted of all patients aged 18-70 years registered for an injury according to ICD-10 at a Swedish emergency department during an 18-month period. After informed consent, the injury patients were screened for drinking habits by the AUDIT-C questionnaire. The gender, age and drinking pattern of injury patients were compared with the general population. METHODS: A total of 2782 patients aged 18-70 years were registered for an injury during the study period. The number of drop-outs was 631. Drop-outs include those who did not consent to participate, were severely injured, too intoxicated or did not fill out the questionnaire satisfactory. Thus, 77.3% of the target group were included for further analysis (1944 drinkers and 207 abstainers). The patients were categorized into three drinking categories: abstainers, non-risky and risky drinkers. Risky drinkers were defined according to usual weekly consumption of 80g or more of alcohol for women and 110g or more for men and/or heavy episodic drinking (i.e. having six glasses or more one glass=12g alcohol), or both, on one occasion at least once a month, valid for both women and men. To estimate the relationship between drinking patterns and the injury variables (environment, cause of injury, activity and diagnosis), odds ratios (OR) were calculated by logistic regression. Multiple logistic regression was used in order to control for age and sex differences between the various drinking and injury categories. RESULTS: The proportion of risky drinkers was higher in the study population compared with the general population in the same area. When controlling for age and sex, risky drinkers (OR 6.4(adj) Confidence interval CI 1.9-21.2) and non-risky drinkers (OR .4.5(adj) CI 1.4-14.5) displayed an increased risk for injury compared with abstainers, in amusement locations, parks, by or on lakes or seas, especially while engaged in play, hobby or other leisure activities (risky drinkers: OR 2.8(adj) CI 1.3-5.6; non-risky drinkers: OR 2.4(adj) CI 1.2-4.6). All differences between drinking patterns in external cause of injury disappeared when age and sex were considered. During rest, meals and attending to personal hygiene, the non-risky drinkers had a lower probability of injury compared with abstainers (OR 0.3(adj) CI 0.1-0.8). Non-risky drinkers had a higher probability than abstainers of suffering luxation (dislocation) or distortion (OR 1.6(adj) CI 1.1-2.5). Nine per cent of the study population reported that they believed that their injury was related to intake of alcohol. Half of this group were non-risky drinkers (CI for the 13.7% difference was 9.7-17.6). CONCLUSIONS: Few significant associations between drinking pattern and injury remained when age and sex were controlled for.

Risk factors for local recurrence after breast-conserving surgery.

BACKGROUND: It is not clear whether risk factors for local recurrence after breast-conserving surgery differ in women having surgery for in situ or invasive cancer. Furthermore, the Nottingham Prognostic Index (NPI) and Nottingham Histological Grade (NHG) have been little studied as determinants of local recurrence risk. METHOD: In a case-control study (491 cases and 1098 controls) nested within a cohort of 7502 women who had surgery for in situ or invasive cancer of the breast, patient characteristics, tumour characteristics and treatment-related variables were evaluated as risk factors for local recurrence. RESULTS: Multivariate conditional logistic regression analyses showed that age below 40 years, tumour multicentricity and an unclear or unknown surgical margin were significant risk factors for local recurrence. Radiotherapy to the breast and adjuvant hormone therapy were protective. Cancer in situ was not associated with a higher risk of local recurrence than invasive cancer (odds ratio 1.0, 95 per cent confidence interval 0.8 to 1.3). NHG and NPI were not helpful in determining risk of local recurrence. CONCLUSION: Margin status, age, tumour multicentricity, and use of radiotherapy and adjuvant hormone therapy were important determinants of risk of local recurrence. With the exception of surgical margin, variables related to the quality of surgical management did not predict risk of local recurrence.

Local recurrence in the breast after conservative surgery--a study of prognosis and prognostic factors in 391 women.

In a population-based cohort of 6613 women with invasive breast cancer, who had breast-conserving surgery between 1981 and 1990, 391 recurrences in the operated breast were identified. The main aim of this study was to examine the prognosis and prognostic factors in different subgroups of local recurrences, characterised by the time to recurrence, location of recurrence and previously given radiotherapy. The median follow-up for women who had a local recurrence was 7.9 years. The life-table estimates for breast cancer-specific survival in women with local recurrences were 84.5% (standard error (S.E.) 1.8) at 5 years and 70.9% (S.E. 2.7) at 10 years. The risk of breast cancer death was highest among women who had an early (

Consequences of axillary recurrence after conservative breast surgery.

BACKGROUND: The aim was to study the incidence, time course and prognosis of patients who developed axillary recurrence after breast-conserving surgery, and to evaluate possible risk factors for axillary recurrence and prognostic factors after axillary recurrence. METHODS: In a population-based cohort of 6613 women with invasive breast cancer who had breast-conserving surgery between 1981 and 1990, 92 recurrences in the ipsilateral axilla were identified. Risk factors for axillary recurrence were studied in a case-control study nested in the cohort, and late survival was documented in the women with axillary recurrence. RESULTS: The overall risk of axillary recurrence was 1.0 per cent at 5 years and 1.7 per cent at 10 years. The risk of axillary recurrence increased with tumour size (P = 0.033) and was highest in younger women (odds ratio (OR) 3.9 for women aged less than 40 years compared with those aged 50-59 years). Radiotherapy to the breast reduced the risk of axillary recurrence (OR 0.1 (95 per cent confidence interval 0.1 to 0.4)). The breast cancer-specific survival rate after axillary recurrence, as measured from primary treatment, was 78.0 per cent at 5 years and 52.3 per cent at 10 years. Tumour size and node status had a statistically significant effect on death from breast cancer. CONCLUSION: Axillary recurrence is rare, although more common in younger women with large tumours. Radiotherapy to the breast was protective. Tumour size and node status were the most important prognostic factors in women with axillary recurrence.

Kinetic modulation of Kv4-mediated A-current by arachidonic acid is dependent on potassium channel interacting proteins.

The Kv4 subfamily of voltage-gated potassium channels is responsible for the transient A-type potassium current that operates at subthreshold membrane potentials to control membrane excitability. Arachidonic acid was shown recently to modulate both the peak amplitude and kinetics of the hippocampal A-current. However, in Xenopus oocytes, arachidonic acid only inhibited the peak amplitude of Kv4 current without modifying its kinetics. These results suggest the existence of Kv4 auxiliary subunit(s) in native cells. We report here a K-channel interacting protein (KChIP)-dependent kinetic modulation of Kv4.2 current in Chinese hamster ovary cells and Kv4.2 and Kv4.3 currents in Xenopus oocytes by arachidonic acid at physiological concentrations. This concentration-dependent effect of arachidonic acid resembled that observed in cerebellar granule neurons and was fully reversible. Other fatty acids, including a nonhydrolyzable inhibitor of both lipooxygenase and cyclooxygenase, 5,8,11,14-eicosatetraynoic acid (ETYA), also mimicked arachidonic acid in modulating Kv4.3 and Kv4.3/KChIP1 currents. Compared with another transient potassium current formed by Kv1.1/Kvbeta1, Kv4.3/KChIP1 current was much more sensitive to arachidonic acid. Association between KChIP1 and Kv4.2 or Kv4.3 was not altered in the presence of 10 microm ETYA as measured by immunoprecipitation and association-dependent growth in yeast. Our data suggest that the KChIP proteins represent a molecular entity for the observed difference between arachidonic acid effects on A-current kinetics in heterologous cells and in native cells and are consistent with the notion that KChIP proteins modulate the subthreshold A-current in neurons.

A novel nervous system beta subunit that downregulates human large conductance calcium-dependent potassium channels.

The pore-forming alpha subunits of many ion channels are associated with auxiliary subunits that influence channel expression, targeting, and function. Several different auxiliary (beta) subunits for large conductance calcium-dependent potassium channels of the Slowpoke family have been reported, but none of these beta subunits is expressed extensively in the nervous system. We describe here the cloning and functional characterization of a novel Slowpoke beta4 auxiliary subunit in human and mouse, which exhibits only limited sequence homology with other beta subunits. This beta4 subunit coimmunoprecipitates with human and mouse Slowpoke. beta4 is expressed highly in human and monkey brain in a pattern that overlaps strikingly with Slowpoke alpha subunit, but in contrast to other Slowpoke beta subunits, it is expressed little (if at all) outside the nervous system. Also in contrast to other beta subunits, beta4 downregulates Slowpoke channel activity by shifting its activation range to more depolarized voltages and slowing its activation kinetics. beta4 may be important for the critical roles played by Slowpoke channels in the regulation of neuronal excitability and neurotransmitter release.

Compound exocytosis in voltage-clamped mouse pancreatic beta-cells revealed by carbon fibre amperometry.

Capacitance measurements of exocytosis were combined with carbon fibre amperometry for time-resolved measurements of the properties of secretion in single, insulin-secreting, mouse pancreatic beta-cells pre-loaded with the amine serotonin (5-HT). Glucose-induced electrical activity was associated with the appearance of brief and transient amperometric currents reflecting the serotonin co-released with insulin. The integrated amperometric responses resulting from voltage-clamp depolarisations were proportional to the corresponding increase in cell capacitance. Both parameters exhibited U-shaped relationships to the membrane potential with maximums around 0 mV. There was a variable latency (40-730 ms, average 230 ms) between the onset of the depolarisation and the amperometric current. During high-frequency repetitive stimulation, a progressive decrease in the exocytotic capacity ("depression") was observed. This was paralleled by a corresponding reduction of the amperometric responses. Using the carbon fibre to map the beta-cell for release sites indicated that exocytosis was confined to the part of the cell containing the highest density of secretory granules. Two types of amperometric responses were observed. In about 50% of the cells, a smooth increase was observed with no discernible discrete events. In the remaining cells, the amperometric records contained large spikes. These were ten or more times larger than that expected for the fusion of individual secretory granules. We propose that these large spikes reflect the exocytosis of multigranular complexes formed inside the beta-cell prior to exocytosis.

Slob, a novel protein that interacts with the Slowpoke calcium-dependent potassium channel.

Slob, a novel protein that binds to the carboxy-terminal domain of the Drosophila Slowpoke (dSlo) calcium-dependent potassium channel, was identified with a yeast two-hybrid screen. Slob and dSlo coimmunoprecipitate from Drosophila heads and heterologous host cells, suggesting that they interact in vivo. Slob also coimmunoprecipitates with the Drosophila EAG potassium channel but not with Drosophila Shaker, mouse Slowpoke, or rat Kv1.3. Confocal fluorescence microscopy demonstrates that Slob and dSlo redistribute in cotransfected cells and are colocalized in large intracellular structures. Direct application of Slob to the cytoplasmic face of detached membrane patches containing dSlo channels leads to an increase in channel activity. Slob may represent a new class of multi-functional channel-binding proteins.

Characterization of gating and peptide block of mSlo, a cloned calcium-dependent potassium channel.

The 20 amino acid Shaker inactivation peptide blocks mSlo, a cloned calcium-dependent potassium channel. Changing the charge and degree of hydrophobicity of the peptide alters its blocking kinetics. A "triple mutant" mSlo channel was constructed in which three amino acids (T256, S259, and L262), equivalent to those identified as part of the peptide's receptor site in the S4-S5 cytoplasmic loop region of the Shaker channel, were mutated simultaneously to alanines. These mutations produce only limited changes in the channel's susceptibility to block by a series of peptides of varying charge and hydrophobicity but do alter channel gating. The triple mutant channel shows a significant shift in its calcium-activation curve as compared with the wild-type channel. Analysis of the corresponding single amino acid mutations shows that mutation at position L262 causes the most dramatic change in mSlo gating. These results suggest that the three amino acids mutated in the mSlo S4-S5 loop may contribute to, but are not essential for, peptide binding. On the other hand, they do play a critical role in the channel's calcium-sensing mechanism.

A visually elicited escape response in the fly that does not use the giant fiber pathway.

A housefly elicits an escape in response to an approaching target (Holmqvist & Srinivasan, 1991). This study tests if the giant fiber pathway, which mediates a light-off escape response in a fruitfly (Wyman et al., 1985), also mediates escape to an approaching target in a housefly. Visual stimuli simulating an approaching or receding dark disk were presented to houseflies, Musca domestica, in both behavioral and physiological experiments. Freely behaving flies escaped in response to an expanding dark disk but not to a contracting dark disk. In restrained flies, the giant fiber, here called the giant descending neuron (GDN), was recorded from intracellularly and the tergotrochanteral muscle (TTM), which provides the main thrust in an escape jump, was recorded from extracellularly. During electrical stimulation of the brain, by means of stimulating electrodes inserted into the ventral part of each compound eye, a single spike in the GDN drives the TTM. However, when the TTM responds to visual stimulation that elicits an escape response in a behaving fly, the GDN shows no activity. Similarly to the behavioral results, the TTM of restrained flies showed muscle potentials in response to an expanding dark disk, but not to a contracting disk. However, freely moving flies elicit escapes more than 100 ms on average before the first TTM spike, suggesting that this type of escape does not start with a jump powered by the TTM. In conclusion, this visually evoked escape response in the housefly is not likely to be mediated by the giant fiber pathway. The findings suggest that there exist at least two pathways mediating visually evoked escape responses in flies.