Remotely Delivered Cardiac Rehabilitation Exercise for Coronary Heart Disease: Nonrandomized Feasibility Study

BACKGROUND

Exercise-based cardiac rehabilitation (CR) is recommended for coronary heart disease (CHD). However, poor uptake of and poor adherence to CR exercise programs have been reported globally. Delivering CR exercise classes remotely may remove some of the barriers associated with traditional hospital- or center-based CR.

OBJECTIVE

We have developed a bespoke platform, Eastern Corridor Medical Engineering Centre-Cardiac Rehabilitation (ECME-CR), to support remotely delivered CR exercise. This pilot trial sought to test the ECME-CR platform and examine the efficacy and feasibility of a remote CR exercise program compared to a traditional center-based program.

METHODS

In all, 21 participants with CHD were recruited and assigned to either the intervention or control group. Both groups performed the same 8-week exercise program. Participants in the intervention group took part in web-based exercise classes and used the ECME-CR platform during the intervention period, whereas participants in the control group attended in-person classes. Outcomes were assessed at baseline and following the 8-week intervention period. The primary outcome measure was exercise capacity, assessed using a 6-minute walk test (6MWT). Secondary outcomes included measurement of grip strength, self-reported quality of life, heart rate, blood pressure, and body composition. A series of mixed between-within subjects ANOVA were conducted to examine the mean differences in study outcomes between and within groups. Participant adherence to the exercise program was also analyzed.

RESULTS

In all, 8 participants (male: n=5; age: mean 69.7, SD 7.2 years; height: mean 163.9, SD 5.4 cm; weight: mean 81.6, SD 14.1 kg) in the intervention group and 9 participants (male: n=9; age: mean 69.8, SD 8.2 years; height: mean 173.8, SD 5.2 cm; weight: mean 94.4, SD 18.0 kg) in the control group completed the exercise program. Although improvements in 6MWT distance were observed from baseline to follow-up in both the intervention (mean 490.1, SD 80.2 m to mean 504.5, SD 93.7 m) and control (mean 510.2, SD 48.3 m to mean 520.6, SD 49.4 m) group, no significant interaction effect (F_1,14=.026; P=.87) nor effect for time (F_1,14=2.51; P=.14) were observed. No significant effects emerged for any of the other secondary end points (all P>.0275). Adherence to the exercise program was high in both the intervention (14.25/16, 89.1%) and control (14.33/16, 89.6%) group. No adverse events or safety issues were reported in either group during the study.

CONCLUSIONS

This pilot trial did not show evidence of significant positive effect for either the remotely delivered or center-based program. The 6MWT may not have been sufficiently sensitive to identify a change in this cohort of participants with stable CHD. This trial does provide evidence that remote CR exercise, supported with digital self-monitoring, is feasible and may be considered for individuals less likely to participate in traditional center-based programs.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR2-10.2196/31855.

Efficacy of a Digital Acceptance and Commitment Therapy Intervention for the Improvement of Self-management Behaviors and Psychological Flexibility in Adults With Cardiac Disease: Protocol for a Single Case Experimental Design

BACKGROUND

Research indicates that the management of distress levels in those with cardiac disease is not only important for improving quality of life and functioning but also critical for condition management; adherence to treatment; and, ultimately, disease prognosis and progression. Acceptance and commitment therapy (ACT) has consistently demonstrated positive long-term outcomes across a wide array of conditions, including chronic illness. However, most empirical investigations conducted to date have also involved in-person therapy, which can be difficult to access, particularly for those dealing with the demands of chronic disease.

OBJECTIVE

The objective of our research is to evaluate a digital ACT intervention for improving self-management behaviors and distress levels in those with cardiac conditions.

METHODS

The digital ACT intervention will be delivered via a digital health self-management platform over 6 sessions. This will involve a randomized, multiple baseline, single case experimental design with approximately 3 to 15 adults with cardiac disease. The independent variable for each participant will be the pre-post intervention phase. The dependent variables will be a daily self-report measure of psychological flexibility as well as objective measures of condition self-management (eg, blood pressure readings) and engagement with the app (eg, completing guided mindfulness). One-to-one qualitative interviews will also be conducted to further examine participants' experiences with using the intervention and what factors contribute to or impede successful outcomes.

RESULTS

Participant recruitment and data collection began in October 2021, and it is projected that the study findings will be available for dissemination by spring 2022.

CONCLUSIONS

The findings will be discussed in terms of how a digital ACT intervention can best meet the needs of cardiac patients.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/33783.

Investigating the needs and concerns of older adults with multimorbidity and their healthcare professionals for conceivable digital psychotherapeutic interventions

Multimorbidity, defined as the concurrent experience of more than one chronic health condition in an individual, affects ∼65% of people over 65 and 85% of those over 85 years old with 30% of those also experiencing mental health concerns. This can lead to reduced quality of life and functioning as well as poorer outcomes in terms of condition management, adherence to treatment, and ultimately disease prognosis and progression. Digital health interventions offer a viable means of condition self-management, as well as psychological support, particularly for those who may have difficulty accessing in-person services. To best meet the needs of older adults with multimorbidity, deeper insights are needed into their specific concerns and issues around condition management, particularly with regard to distress in relation to managing one's condition. The present study aimed to explore this using one-to-one qualitative interviews and focus groups with people with chronic health conditions and healthcare professionals. Participants were 11 older adults with multimorbidity (4 males; mean age: M = 72.7 years) and 14 healthcare professionals including five clinical nurse specialists, four pharmacists, two general practitioners, one occupational therapist, one speech and language therapist and one dietician. Thematic analysis was used to identify key themes, which included: patient feelings of anxiety or worry leading to an unwillingness to access essential information; the various mental health challenges faced by those with multimorbidity; the importance of personal values in providing motivation; and the importance of social support. Findings are discussed in relation to the potential development of transdiagnostically applicable digital interventions for the management of distress in those with multimorbidity.

Quantifying Steps During a Timed Up and Go Test Using a Wearable Sensor System: A Laboratory-Based Validation Study in Healthy Young and Older Volunteers

Mobility is an important factor in maintaining health and independence in an aging population. Facilitating community-dwelling older adults to independently identify signs of functional decline could help reduce disability and frailty development. Step-count from a body-worn sensor system was compared with a criterion measure in healthy young (n = 10) and healthy older adults (n = 10) during a Timed Up and Go test under different conditions. Spearman's rank correlation coefficient indicated strong agreement between the sensor-obtained step-count and that of the criterion measure in both age groups, in all mobility tests. A body-worn sensor system can provide objective, quantitative measures of step-count over short distances in older adults. Future research will examine if step-count alone can be used to identify functional decline and risk of frailty.Clinical Relevance-This demonstrates the correlation between step-count derived from a wearable sensor and a criterion measure over a short distance in older adults.

Accuracy of Wrist-Worn Photoplethysmography Devices at Measuring Heart Rate in the Laboratory and During Free-Living Activities

This study compared heart rate (HR) measurements taken from two wrist-worn devices; the Empatica E4 and the Apple Watch Series 5, to that taken from a Polar H10 chest strap. Ten healthy adult volunteers took part in a laboratory validation study and performed a treadmill exercise protocol. A single-subject validity study was also conducted to evaluate the accuracy of continuous HR measurements obtained during free-living activities. The participant wore both wrist devices, as well as the Polar H10 for 12-hours, as she continued her habitual daily activities. The key findings of the laboratory study were that the Apple Watch was accurate at assessing HR compared to the Polar H10 with Mean Absolute Percentage Error (MAPE) values < 5% during treadmill exercise. The accuracy of the E4 however was generally poor with MAPE values > 15%. Findings from the single-subject validity study indicate that the Apple Watch produces accurate measurements of HR, whereas the E4 device overestimated HR, except for during the more strenuous activities undertaken where HR was underestimated.Clinical Relevance- The Apple Watch has acceptable accuracy in measuring HR during treadmill exercise and during free-living activities in healthy adult volunteers.

Delivering Cardiac Rehabilitation Exercise Virtually Using a Digital Health Platform (ECME-CR): Protocol for a Pilot Trial

BACKGROUND

Exercise-based cardiac rehabilitation is recognized as a core component of cardiovascular disease management and has been shown to reduce all-cause and cardiovascular mortality and reduce the risk of hospital readmission following a cardiac event. However, despite this, the uptake of and long-term adherence to cardiac rehabilitation exercise is poor. Delivering cardiac rehabilitation exercise virtually (ie, allowing patients to participate from their own homes) may be an alternative approach that could enhance uptake and increase adherence.

OBJECTIVE

The aim of this study is to assess the feasibility of delivering a virtual cardiac rehabilitation exercise program supported by the Eastern Corridor Medical Engineering - Cardiac Rehabilitation (ECME-CR) platform.

METHODS

A convenience sample (n=20) of participants eligible to participate in community-based cardiac rehabilitation exercise will be recruited. Participants will be randomized to one of two study groups. Both study groups will perform the same exercise program, consisting of twice-weekly sessions of 60 minutes each, over an 8-week intervention period. Participants in the intervention group will partake in virtually delivered cardiac rehabilitation exercise classes in their own home. The virtual exercise classes will be delivered to participants using a videoconferencing platform. Participants in the control group will attend the research center for their cardiac rehabilitation exercise classes. Intervention group participants will receive the ECME-CR digital health platform for monitoring during the class and during the intervention period. Outcomes will be assessed at baseline and following the 8-week intervention period. The primary outcome will be exercise capacity as assessed using the 6-minute walk test. Other outcome measures will include heart rate, blood pressure, weight, percentage body fat, muscle strength, and self-reported quality of life. Semistructured interviews will also be conducted with a subset of participants to explore their experiences of using the digital platform.

RESULTS

Participant recruitment and data collection will begin in July 2021, and it is anticipated that the study results will be available for dissemination in spring 2022.

CONCLUSIONS

This pilot trial will inform the design of a randomized controlled trial that will assess the clinical effectiveness of the ECME-CR digital health platform.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/31855.

Can Ultrasound Performed in Prolonged Second Stage of Labor Predict the Difficulty and Success Rates of Operative Vaginal Delivery?

OBJECTIVE

To evaluate different sonographic methods for the prediction of the difficulty and the success of operative vaginal delivery (OPD).

MATERIALS AND METHODS

A prospective study was performed on 45 term singleton uncomplicated pregnancies with prolonged 2nd stage of delivery with cephalic presentation. Measurements of the fetal head, relations between the fetal head and maternal pelvic parameters during rest and during maternal pushing were taken using translabial ultrasound.

RESULTS

29 cases of OPD were successful and 4 cases failed ending in cesarean section. The passage of the biparietal diameter (BPD) of the infrapubic line (IPL) was statistically correlated with the success of OPD. Head station, passage of the BPD of the IPL, percentage of head after the IPL, circumference of head after IPL were all correlated with the difficulty of OPD. When the distance between the widest diameter of the head and the IPL is < 1.2 cm, there is a 90 % probability of success of OPD. When that distance is > 3.3 cm, there is 90 % probability of cesarean section. When the percentage of head beyond the IPL was > 54 %, there was 90 % probability of successful OPD.

DISCUSSION

Translabial ultrasound is useful in the prediction of the difficulty and the success of OPD. The higher the extent of head that passed the IPL, the less difficult the OPD and the greater the success rate of the OPD.

Three-dimensional digital reconstruction of human placental villus architecture in normal and complicated pregnancies

OBJECTIVE

This study aimed to examine the use of digital technology in the three-dimensional reconstruction of human placentas.

STUDY DESIGN

Placentas obtained at term elective caesarean section were sampled, formalin-fixed and embedded in paraffin. Two hundred 5 μm consecutive sections were cut from each specimen and the resultant slides stained with haematoxylin and eosin. Slides were then scanned and the digitised images reconstructed using customised software.

RESULTS

Three-dimensional reconstructions were successfully achieved in placentas from normal pregnancies and those complicated by pre-eclampsia, growth restriction, and gestational diabetes. Marked morphological differences were readily identifiable, most clearly in the stem villus architecture.

CONCLUSION

This method is an emerging research tool for examining placental histoarchitecture at high resolution and gaining clinically relevant insight into the placental pathology allied to pregnancy complications such as PET, IUGR and GD.

Differential gene expression profiles of two excitable rat cell lines after over-expression of WT- and C121W-β1 sodium channel subunits

Voltage-dependent sodium channels are membrane proteins essential for cell excitability. They are composed by a pore-forming α-subunit, encoded in mammals by up to nine different genes, and four different ancillary β-subunits. The expression pattern of the α subunit isoforms confers the distinctive functional and pharmacological properties to different excitable tissues. β-Subunits are important modulators of channel function and expression. Mutation C121W of the β1-subunit causes an autosomal dominant epileptic syndrome without cardiac symptoms. In neuroectoderm GH3 and cardiac H9C2 cells, the over-expression of β1 subunit augments α subunit mRNA and protein levels as well as sodium current density. Interestingly, the introduction of the epileptogenic C121W-β1 subunit produces additional changes in the α-subunit expression pattern of H9C2 cells, leaving unaltered the sodium channel isoform composition of GH3 cells. The challenge of the present work was to identify those genes that were differentially expressed in response to WT- or C121W-β1 subunit over-expression in the two rat cell lines under analysis. Hence, we analyzed the total mRNA extracted from control-untransfected and from WT- and C121W-β1-transfected GH3 and H9C2 cells by DNA-microarray. We found that, in agreement with their different embryonal origin, the over-expression of WT- and C121W-β1 subunits modifies the expression of different gene sets in GH3 and H9C2 cells. Focusing on the effects of the C121W mutation, we found that it causes the modification of 214 genes, most of them were down-regulated (202) in GH3 cells; on the contrary, it determined the up-regulation of only five genes in H9C2 cells. Interestingly, most genes modified by the C121W β1 subunit are involved in pivotal processes of the cell such as cellular communication and protein expression. Our results confirm the important role of the sodium channel β1 subunit in the control of NaCh gene expression, and highlight once more the tissue-specific effect of the C121W mutation.

Head progression distance in prolonged second stage of labor: relationship with mode of delivery and fetal head station

OBJECTIVE

To evaluate the clinical significance of fetal head progression distance (HPD), measured by transperineal ultrasound, during prolonged second stage of labor.

METHODS

In this prospective study, a single operator, who was blinded to the results of the digital examination, assessed using transperineal ultrasound women at ≥ 37 weeks of gestation with failure to progress in the second stage of labor. Patients had an empty urinary bladder and the examination was performed during maternal pushing. HPD was defined as the length of the line perpendicular to the infrapubic line that would connect it to the lowest part of the fetal bony skull. We analyzed associations between HPD and digital examination of fetal head station, fetomaternal characteristics, mode of delivery and perinatal outcome.

RESULTS

Sixty-five patients in prolonged second stage of labor participated in the study. The overall mean HPD was 6.50 (± 1.35; 95% CI, 6.16-6.83) cm. No correlation was found between HPD and head position or mode of delivery, but HPD was positively correlated with fetal head station and neonatal head circumference measured after delivery. Logistic regression and receiver-operating characteristics curve analysis demonstrated no significant predictive value of HPD with respect to mode of delivery.

CONCLUSION

Although HPD in prolonged second stage of labor could not predict mode of delivery, it may have a role as an ancillary tool for fetal head station assessment.

Pubic arch angle in prolonged second stage of labor: clinical significance

OBJECTIVE

To evaluate the clinical significance of the pubic arch angle (PAA) measured by transperineal ultrasound during prolonged second stage of labor.

METHODS

We evaluated prospectively 62 women ≥ 37 weeks of gestation with failure to progress in the second stage of labor. Transperineal ultrasound (transverse plane) was used to measure the pubic arch angle. Correlations with fetomaternal characteristics, mode of delivery and perinatal outcome were evaluated.

RESULTS

The mean PAA was 101.1° (± 13.1°; range, 80°-135°). We found a negative correlation with maternal age. Patients with an occipitotransverse fetal position had a significantly smaller angle compared with those with occipitoanterior positions (94.3° ± 5.5° vs. 103.2° ± 14.8°, P < 0.05), as did those with operative deliveries compared with those with spontaneous vaginal delivery (97.1° ± 11.5° vs. 110.1° ± 14.0°, P < 0.05). The prediction of operative delivery in prolonged second stage of labor by receiver-operating characteristics curve using PAA alone yielded an area under the curve of 0.75. The predicted probability for operative delivery increased as PAA decreased, with an odds ratio of 0.933 for each decrease in angle of 1°.

CONCLUSION

Our study suggests a correlation between the PAA and mode of delivery in prolonged second stage of labor. This may be used as an adjunctive parameter when considering delivery mode.

Binding site of activators of the cystic fibrosis transmembrane conductance regulator in the nucleotide binding domains

The use of substances that could activate the defective chloride channels of the mutant cystic fibrosis transmembrane conductance regulator (CFTR) has been suggested as possible therapy for cystic fibrosis. Using epithelia formed by cells stably transfected with wildtype or mutant (G551D, G1349D) CFTR, we estimated the apparent dissociation constant, K(D), of a series of CFTR activators by measuring the increase in the apical membrane current. Modification of apparent K(D) of CFTR activators by mutations of the nucleotide-binding domains (NBDs) suggests that the binding site might be in these regions. The human NBD structure was predicted by homology with murine NBD1. An NBD1-NBD2 complex was constructed by overlying monomers to a bacterial ABC transporter NBD dimer in the "head-to-tail" conformation. Binding sites for CFTR activators were predicted by molecular docking. Comparison of theoretical binding free energy estimated in the model to free energy estimated from the apparent dissociation constants, K(D), resulted in a remarkably good correlation coefficient for one of the putative binding sites, located in the interface between NBD1 and NBD2.

Leptin reverses the inhibitory effect of caloric restriction on longitudinal growth

Caloric imbalance, particularly in critical periods of growth and development, is often the underlying cause of growth abnormalities. Serum levels of leptin are elevated in obesity and are low in malnutrition and malabsorption. The aim of the present study was to determine whether leptin integrates energy levels and growth in vivo, as shown previously in our ex vivo experiments, even in the presence of caloric restriction. In the first part of the study, mice were divided into three groups. Two groups were fed ad libitum and received leptin or vehicle only, and the third group was pair-fed with the group injected with leptin to dissociate leptin's effect on growth from its effect on food consumption. Mice given leptin had a significantly greater tibial length than untreated pair-fed animals and a similar tibial length as control mice fed ad libitum despite their lower weight. In addition, leptin significantly increased the overall size of the epiphyseal growth plate by 11%. On immunohistochemistry and in situ hybridization studies, leptin stimulated both the proliferation and differentiation of tibial growth plate chondrocytes without affecting the overall organization of the plate. There was also a marked increase in the expression and level of IGF-IR. In the second part of the study, two groups of mice were fed only 60% of their normal chow; one was injected with leptin, and the other was injected with vehicle alone. Caloric deprivation by itself reduced serum levels of IGF-I by 70% and the length of the tibia by 5%. Leptin treatment corrected the fasting-induced growth deficiency, but further reduced the level of serum IGF-I. These results indicate that leptin stimulates growth even in the presence of caloric restriction independently of peripheral IGF-I.

Leptin: obesity, diabetes and other peripheral effects--a review

There is an increasing epidemic of obesity in the Western and developing world that has not spared children and, hence, is of great concern. Obesity presents numerous physiological and psychosocial problems for the child. Childhood obesity not only increases the risk of obesity in adulthood, it is associated with type 2 diabetes mellitus; is the leading cause of pediatric hypertension; increases the risk of coronary heart disease; and increases stress on the weight-bearing joints. Social and psychological problems are also significant consequences of obesity in children, with lowering of self-esteem and its effects on relationships with peers. Obesity is clearly associated with increased levels of the recently discovered hormone, leptin. Leptin, secreted from adipocytes, is involved in the regulation of food intake, energy expenditure, and energy balance in humans. This review focuses on the hormone, leptin, in an effort to document some of its many local and systemic effects on the body and, specifically, its potential role in obesity-induced diabetes.

Clinical dysentery in hospitalized children

BACKGROUND

Clinical dysentery is a severe presentation of an enteric infection. The aim of the study was to evaluate the impact of a serious bacterial etiology in clinical dysentery in hospitalized children and determine if children at high risk can be identified on the basis of clinical or laboratory parameters.

PATIENTS AND METHODS

A prospective study design was used. The study population included 60 children admitted to our department with clinical dysentery over a 16-month period. Fresh stool specimens were collected on days 1, 2 and 3. The clinical and laboratory data of the children were analyzed.

RESULTS

Clinical dysentery accounted for 1.7% of all pediatric hospitalizations during this period. Stool cultures were positive for Shigella spp. in 18 children (30%), and Salmonella spp. in 15 children (25%), Campylobacter jejuni was identified in one patient (2%). There were no significant differences in clinical characteristics or laboratory parameters between children with positive and negative stool cultures.

CONCLUSION

40% of the children hospitalized for clinical dysentery were eligible for antibiotic treatment. Early administration of empiric antibiotic treatment is justified in children hospitalized for clinical dysentery in Israel. Clinical or laboratory parameters were unable to differentiate those with clinical dysentery at risk of serous bacterial pathogens in stool.

Bone mineral response to a 7-month randomized controlled, school-based jumping intervention in 121 prepubertal boys: associations with ethnicity and body mass index

We examined the effects of a 7-month jumping intervention (10 minutes, 3 times per week) on bone mineral gain in prepubertal Asian and white boys (10.3+/-0.6 years, 36.0+/-9.2 kg) at 14 schools randomized to control (n = 60) and intervention (n = 61) groups. Intervention and control groups had similar mean baseline and change in height, weight, lean mass and fat mass, baseline areal bone mineral density (aBMD; g/cm2), bone mineral content (BMC; g; dual-energy X-ray absorptiometry [DXA], QDR 4500W), and similar average physical activity and calcium intakes. Over 7 months, the intervention group gained more total body (TB) BMC (1.6%,p < 0.01) and proximal femur (PF) aBMD (1%, p < 0.05) than the control group after adjusting for age, baseline weight, change in height, and loaded physical activity. We also investigated the 41 Asian and 50 white boys (10.2+/-0.6 years and 31.9+/-4.4 kg) who were below the 75th percentile (19.4 kg/m2) of the cohort mean for baseline body mass index (BMI). Boys in the intervention group gained significantly more TB and lumbar spine (LS) BMC, PF aBMD, and trochanteric (TR) aBMD (+ approximately2%) than boys in the control group (adjusted for baseline weight, final Tanner stage, change in height, and loaded physical activity). Bone changes were similar between Asians and whites. Finally, we compared the boys in the control group (n = 16) and the boys in the intervention group (n = 14) whose baseline BMI fell in the highest quartile (10.5+/-0.6 years and 49.1+/-8.2 kg). Seven-month bone changes (adjusted as aforementioned) were similar in the control and intervention groups. In summary, jumping exercise augmented bone mineral accrual at several regions equally in prepubertal Asian and white boys of average or low BMI, and intervention effects on bone mineral were undetectable in high BMI prepubertal boys.

Molecular simulation of the interaction of kappa-conotoxin-PVIIA with the Shaker potassium channel pore

Molecular simulation techniques were appplied to predict the interaction of the voltage-dependent Shaker potassium channel with the channel-blocking toxin kappa-conotoxin-PVIIA (PVIIA). A structural thee-dimensional model of the extracellular vestibule of the potassium channel was constructed based on structural homologies with the bacterial potassium channel Kcsa, whose structure has been solved by X-ray crystallography. The docking of the PVIIA molecule was obtained by a geometric recognition algorithm, yielding 100 possible conformations. A series of residue-residue distance restraints, predicted from mutation-cycle experiments, were used to select a small set of a plausible channel-toxin complex models among the resulting possible conformations. The four final conformations, with similar characteristics, can explain most of the single-point mutation experiments done with this system. The models of the Shaker-PVIIA interaction predict two clusters of amino acids, critical for the binding of the toxin to the channel. The first cluster is the amino acids R2, I3, Q6 and K7 that form the plug of the toxin that interacts with the entrance to the selectivity filter of the channel. The second cluster of residues, R22, F23, N24 and K25, interacts with a channel region near to the external entrance of the pore vestibule. The consistency of the obtained models and the experimental data indicate that the Shaker-PVIIA complex model is reasonable and can be used in further biological studies such as the rational design of blocking agents of potassium channels and the mutagenesis of both toxins and potassium channels.

Skeletal muscle sodium channel is affected by an epileptogenic beta1 subunit mutation

The syndrome of generalized epilepsy with febrile seizures plus type 1 (GEFS+) has been associated to the gene SCN1B coding for the sodium channel beta1 subunit (Wallace, R. H. et al. (1998) Nature Genetics 19, 366-370). In patients, a mutation of the cysteine 121 to trpyptophane (C121W) would cause a lack of modulatory activity of the beta1 subunit on sodium channels expressed in the brain, rendering neurons hyperexcitable. We have confirmed that the normal beta1-modulation of type-IIA adult brain alpha subunits (BIIA) expressed in frog oocytes is defective in C121W. We observed that the mixture of wild-type and mutant beta1 subunits is less effective than wild-type alone, suggesting that the mutant beta1 subunit does bind the alpha subunit. However, we also observed a similar lack of modulation by C121W of the in adult skeletal muscle alpha subunit (SkM1). This finding is in contrast with the simple idea that the mutational effect observed in the oocyte expression system is the principal physiopathological correlate of GEFS+, because no skeletal muscle symptoms have been reported in GEFS+ patients. We conclude that the manifestation of the pathological phenotype is conditioned by the presence of susceptibility genes and/or that the frog oocyte expression system is inadequate for the study of the mutant beta1 subunit physiopathology.

Functional properties of sodium channels do not depend on the cytoskeleton integrity

Several observations suggest an interaction of the sodium channel alpha-subunit with the cytoskeletal structures. However, there is a wide variability in the results of experiments of heterologous expression in Xenopus oocytes and studies on mammalian cells are sometimes contradictory. In general, there has been no direct demonstration that ad hoc large perturbations of the cytoskeleton modify the intrinsic properties of the sodium channels expressed endogenously or heterologously in plasma membranes. We have studied in CHO cells transfected with the rat muscle sodium channel alpha-subunit the effects of two substances expected to produce drastic perturbations of the cytoskeletal structure: Cytochalasin-D, which depolymerizes microfilaments, and Colchicine, which inhibits the microtubules polymerization. We observed no significant differences in the voltage dependence, kinetic parameters and surface density of the expressed sodium channels after treatment of the cells with these substances. We conclude that the two known main components of the cytoskeleton do not interfere directly with the sodium channel function or with the heterologous expression of channels in the cell membrane.

Functional properties of sodium channels do not depend on the cytoskeleton integrity

Several observations suggest an interaction of the sodium channel alpha-subunit with the cytoskeletal structures. However, there is a wide variability in the results of experiments of heterologous expression in Xenopus oocytes and studies on mammalian cells are sometimes contradictory. In general, there has been no direct demonstration that ad hoc large perturbations of the cytoskeleton modify the intrinsic properties of the sodium channels expressed endogenously or heterologously in plasma membranes. We have studied in CHO cells transfected with the rat muscle sodium channel alpha-subunit the effects of two substances expected to produce drastic perturbations of the cytoskeletal structure: Cytochalasin-D, which depolymerizes microfilaments, and Colchicine, which inhibits the microtubules polymerization. We observed no significant differences in the voltage dependence, kinetic parameters and surface density of the expressed sodium channels after treatment of the cells with these substances. We conclude that the two known main components of the cytoskeleton do not interfere directly with the sodium channel function or with the heterologous expression of channels in the cell membrane.

Endogenous expression of the beta1A sodium channel subunit in HEK-293 cells

The expression of the sole alpha-subunit of muscle or brain sodium channels in frog oocytes mediates currents with a bimodal inactivation with an abnormal slow mode that is strongly depressed only by co-expression of the beta1-subunit. In contrast, in the expression of the alpha-subunit in the human embryonic kidney cell line, HEK-293, the slow mode is almost absent, suggesting an endogenous expression of the beta1-subunit. We have tested this hypothesis by reverse transcriptase-polymerase chain reaction. We found an abundant expression of mRNA encoding the beta1A splicing of the putative regulatory sodium channel subunit but no mRNA encoding the beta1-subunit in HEK cells. This finding is consistent with the idea that the endogenous beta1A-subunit is sufficient for suppressing the slowly inactivating mode of sodium currents by co-assembly with alpha-subunits, and calls attention to the reliability of effects attributed in HEK cells to alpha-beta1 co-expression.

Myopathic mutations affect differently the inactivation of the two gating modes of sodium channels

Three groups of mutations of the alpha subunit of the rat skeletal muscle sodium channel (rSkM1), homologous to mutations linked to human muscle hereditary diseases, have been studied by heterologous expression in frog oocytes: S798F, G1299E, G1299V, and G1299A, linked with potassium-aggravated myotonia (PAM); T1306M, R1441C and R1441P, linked with paramyotonia congenita (PC); T698M and M1353V, linked with the hyperkalemic periodic paralysis (HyPP). Wild-type rSkM1 channels (WT) show two gating modes, M1 and M2, which differ mainly in the process of inactivation. The naturally most representative mode M1 is tenfold faster and develops at approximately 30 mV less depolarized potentials. A common feature of myopathy-linked mutants is an increase in the mode M2 probability, P(M2), but phenotype-specific alterations of voltage-dependence and kinetics of inactivation of both modes are also observed. The coexpression of the sodium channel beta1 subunit, which has been studied for WT and for the five best expressing mutants, generally caused a threefold reduction of P(M2) without changing the properties of the individual modes. This indicates that the mutations do not affect the alpha - beta1 interaction and that the phenotypic changes in P(M2) observed for the enhanced mode M2 behavior of the sole alpha subunits, although largely depressed in the native tissue, are likely to be the most important functional modification that causes the muscle hyperexcitability observed in all patients carrying the myotonic mutations. The interpretation of the more phenotype-specific changes revealed by our study is not obvious, but it may offer clues for understanding the different clinical manifestations of the diseases associated with the various mutations.

KCNE1-like gene is deleted in AMME contiguous gene syndrome: identification and characterization of the human and mouse homologs

We describe the identification and characterization of a new gene deleted in the AMME contiguous gene syndrome. This gene is predominantly expressed in heart, skeletal muscle, spinal cord, and brain. Screening of placenta and NT2 cDNA libraries enabled us to obtain the 1.5-kb full-length transcript, which shows a 426-bp open reading frame. Since the resulting 142-amino-acid peptide has a single putative transmembrane domain and a weak but suggestive homology with KCNE1 (minK), a protein associated with the KCNQ1 potassium channel (KVLQT1), we named this new gene KCNE1-like (KCNE1L). To obtain greater insight into this new member of an apparently distinct protein family, we have identified and characterized the homologous mouse gene (Kcne1l), which encodes a peptide of 143 amino acids with 91% homology and 80% identity. The expression pattern of mouse Kcne1l in the developing embryo revealed strong signal in ganglia, in the migrating neural crest cells of cranial nerves, in the somites, and in the myoepicardial layer of the heart. The specific distribution in adult tissues, the putative channel function, and the expression pp6tern in the developing mouse embryo suggest that KCNE1L could be involved in the development of the cardiac abnormalities as well as of some neurological signs observed in patients with AMME contiguous gene syndrome.

Tonic and phasic tetrodotoxin block of sodium channels with point mutations in the outer pore region

Tonic and use-dependent block by tetrodotoxin (TTX) has been studied in cRNA-injected Xenopus oocytes expressing mutants W386Y, E945Q, D1426K, and D1717Q, of the outer-pore region of the rat brain IIA alpha-subunit of sodium channels. The various phenotypes are tonically half-blocked at TTX concentrations, IC50(t), that span a range of more than three orders of magnitude, from 4 nM in mutant D1426K to 11 microM in mutant D1717Q. When stimulated with repetitive depolarizing pulses at saturating frequencies, all channels showed a monoexponential increase in their TTX-binding affinity with time constants that span an equally wide range of values ([TTX] approximately IC50(t), from approximately 60 s for D1426K to approximately 30 ms for D1717Q) and are in most phenotypes roughly inversely proportional to IC50(t). In contrast, all phenotypes show the same approximately threefold increase in their TTX affinity under stimulation. The invariance of the free-energy difference between tonic and phasic configurations of the toxin-receptor complex, together with the extreme variability of phasic block kinetics, is fully consistent with the trapped-ion mechanism of use dependence suggested by and developed by. Using this model, we estimated for each phenotype both the second-order association rate constant, kon, and the first-order dissociation rate constant, koff, for TTX binding. Except for mutant E945Q, all phenotypes have roughly the same value of kon approximately 2 microM-1 s-1 and owe their large differences in IC50(t) to different koff values. However, a 60-fold reduction in kon is the main determinant of the low TTX sensitivity of mutant E945Q. This suggests that the carboxyl group of E945 occupies a much more external position in the pore vestibule than that of the homologous residue D1717.

Characterization of a murine gene homologous to the bovine CaCC chloride channel

The bovine CaCC protein is a putative Ca2+-dependent Cl- channel of airway epithelial cells. Therefore, CaCC proteins could contribute to transepithelial Cl- transport and accordingly modify the phenotype of cystic fibrosis (CF) patients. We have identified a murine EST containing a full-length cDNA coding for a 902-amino-acid protein highly homologous to bovine CaCC. The murine gene (mCaCC) maps to chromosome 3 at the H2-H3 band and is expressed, as indicated by Northern blot analysis, in mouse skin and kidney but not in brain, heart, lung or testis. RT-PCR indicates a low expression in tracheal epithelial cells. Heterologous expression of mCaCC in Xenopus oocytes elicits membrane currents that are anion-selective and inhibited by DIDS and by niflumic acid, a blocker of the endogenous chloride current in oocytes. The identification of genes belonging to the CaCC family will help to evaluate their role as ion channels or channel regulators and their actual contribution to epithelial chloride transport.

Fast- and slow-gating modes of the sodium channel are altered by a paramyotonia congenita-linked mutation

We have studied the expression in frog oocytes of the alpha subunit of the rat skeletal muscle sodium channel mutation T1306M, homologous to the mutation T1313M of the human isoform that causes the muscular hereditary disease paramyotonia congenita. Wild-type (WT) channels show a bimodal behavior, with two gating modes characterized by inactivation time constants that differ at least by one order of magnitude and with voltage dependencies shifted by +27 mV in the slow mode (M2) relative to the fast (M1) mode. In the myopathy-linked mutant the propensity of the channel for the mode M2 is increased fourfold and the kinetics and voltage dependence of inactivation in both modes are altered. In mode M1, the onset of inactivation is faster and the recovery from inactivation is slower whereas both processes are slowed in mode M2. The half-inactivation potential of both modes is shifted by the mutation to positive potentials. Coexpression of beta subunit causes a threefold reduction of the M2 propensity of both WT and T1306M channels, with small changes in the voltage dependency and kinetic properties of inactivation. All the changes are consistent with the hyperexcitability of the muscle fibers observed in patients affected by potassium-aggrevated myotonia (PAM).

Calcium dependent shifts of Na+ channel activation correlated with the state dependence of calcium-binding to the pore

Calcium ions block the open configuration and antagonise the tonic binding of TTX to the closed state of sodium channels in very different ranges of extracellular concentration, [Ca]o. We measured the open-state block in channels expressed in Xenopus oocytes by alpha-subunits from rat brain (rBIIa) or adult rat skeletal muscle (rSkM1). Recordings of instantaneous tail-currents from cell-attached macro patches show that the binding of Ca2+ to the blocking site has a dissociation constant of about 20 mM at 0 mV and senses about 30% of the membrane potential drop, whereas the concentration of half-inhibition of TTX-binding is less than 1 mM and voltage-insensitive. Assuming that both effects involve a single binding site, a simple model predicts that the state-dependency of the dissociation constant entails positive shifts of activation and faster kinetics of deactivation at increasing [Ca]o. The shifts of activation measured for rBIIA and rSkM1 channels are comparable in size to those predicted by the model, which accounts also for the observed larger shifts of the rBIIA-mutant K226Q as a consequence of its reduced voltage-sensitivity. Shifts attributable to surface-charge screening effects seem smaller in the oocyte than in native cell-membranes. The experimental [Ca]o-dependence of deactivation kinetics is also consistent with the model and with the idea that Ca(2+)-binding changes to the same extent, but in opposite directions, the activation free-energies of both opening and closing transitions.

Interaction between dihydropyridines and phospholipid bilayers: a molecular dynamics simulation

Interaction of the calcium-channel antagonist dihydropyridines (DHPs), lacidipine and nifedipine, with a phospholipid bilayer was studied using 600 ps molecular dynamic simulations. We have constructed a double layer membrane model composed of 42 dimirystoyl-phosphatidylcholine molecules. The DHP molecules locate at about 7 A from the centre of the membrane, inducing an asymmetry in the bilayer. While lacidipine did not induce significant local perturbations as judged by the gauche-trans isomerisation rate, nifedipine significantly decreased this rate, probably by producing a local rigidity of the membrane in the vicinity of the DHP.

Inactivation defects produced by a myopathic II-S6 mutation of the muscle sodium channel

We have studied the expression in frog oocytes of the alpha-subunit of the rat skeletal muscle sodium channel mutation S798F, homologous to the mutation S804F of the human isoform, that causes potassium aggravated myotony (PAM), a muscular hereditary disease in humans. Wild type channels show a bimodal inactivation, with two gating modes that inactivate with time constants that differ at least by one order of magnitude and a steady steady-state voltage dependence of the slow mode shifted by +27 mV relative to that of the fast mode. In the myopathy-linked mutant the propensity of the channel to gate in the slow mode is significantly increased and there are alterations in the inactivation properties of both modes. The half inactivation potential of the fast mode is shifted negatively, and the inactivation kinetics of both modes are slower, with an apparent shift in their voltage dependence. The changes on the inactivation properties of the mutant channel may be related with the muscle fibre hyperexcitability observed patients affected by PAM.

Simulation of action potential damping produced by anticonvulsant drugs

Anticonvulsant drugs reduce the ability of central neurones to sustain high-frequency repetitive firing of action potentials. In recent years, it has been demonstrated that this effect is primarily due to a Na+ conductance reduction. We have simulated the electrical behaviour of a neurone, including Ca2+ and various K+ conductances. Although a reduction of Na+ conductance produces a progressive reduction until a complete suppression of the action potential bust, a smaller reduction of this conductance is necessary to produce the same effect when the delayed-rectifier K+ conductance and the Ca2+ conductance are concomitantly reduced . The results indicate that the drugs action on conductances other than Na+ is important for determining their anticonvulsant effect on neurones at therapeutic concentrations.

Use dependence of tetrodotoxin block of sodium channels: a revival of the trapped-ion mechanism

The use-dependent block of sodium channels by tetrodotoxin (TTX) has been studied in cRNA-injected Xenopus oocytes expressing the alpha-subunit of rat brain IIA channels. The kinetics of stimulus-induced extra block are consistent with an underlying relaxation process involving only three states. Cumulative extra block induced by repetitive stimulations increases with hyperpolarization, with TTX concentration, and with extracellular Ca2+ concentration. We have developed a theoretical model based on the suggestion by Salgado et al. that TTX blocks the extracellular mouth of the ion pore less tightly when the latter has its external side occupied by a cation, and that channel opening favors a tighter binding by allowing the escape of the trapped ion. The model provides an excellent fit of the data, which are consistent with Ca2+ being more efficient than Na+ in weakening TTX binding and with bound Ca2+ stabilizing the closed state of the channel, as suggested by Armstrong and Cota. Reports arguing against the trapped-ion mechanism are critically discussed.

Accumulation of long-lasting inactivation in rat brain K(+)-channels

We studied the phenomenon of cumulative inactivation in the voltage-dependent K+ channels of the Shaker-related subfamily Kv1 cloned from rat brain and expressed in Xenopus oocytes. In Kv1.4, repetitive stimulations at intervals shorter than 20 s produce cumulative inactivation even for brief stimuli that elicit K+ currents which do not show any significant decline during the depolarising pulse. These effects are absent or greatly reduced in the clones Kv1.1, Kv1.3, Kv1.5 and Kv1.6, and in the deletion mutant Kv1.4-delta-110, characterised by lack of "fast" (N-type) inactivation. We find that the inactivation caused by a single pulse increases after the pulse while the channels deactivate, and subsides with two time constants, indicating the existence of (at least) two inactivated states: IS, with a slow recovery kinetics and IF, with faster kinetics. In the simplest kinetic scheme accounting for our observations, IF is coupled sequentially to the open state O, while IS can be reached at a fast rate both from IF and from a pre-open, activated state, A, that is in fast equilibrium with O. The accumulation of long-lasting inactivation during the repolarisation is favoured by the prolongation of the lifetime of activated states due to the presence of IF. This explains the smaller accumulation effect observed in channels lacking fast inactivation. The physiological implications of these findings suggest how different channels of the Kv1 subfamily can affect differently the firing behaviour of neurones.

Primary peritoneal serous papillary carcinoma: a study of 25 cases and comparison with stage III-IV ovarian papillary serous carcinoma

The clinical characteristics and treatment outcome of patients with primary peritoneal serous papillary carcinoma (PPSC) (n = 22) was compared with stage III-IV papillary serous ovarian carcinoma (PSOC) patients (n = 63). There were no statistically significant differences between the PPSC and PSOC patients with regard to the mean age, menopausal status, parity, ascites fluid volume, proportion of stage IV disease, and the rate of optimal debulking achieved. The median disease-free interval was 15 and 18 months; the median survival was 21 and 26 months; and the 5-year survival was 18 and 24% for the PPSC and PSOC groups, respectively. The median survival time for patients with a residual tumor > or = 2 cm was 20.5 and 24 months, and for residual tumor > or = 2 cm was 46 and 41 months, in PPSC and PSOC patients, respectively. Survival was thus better, in both groups, when residual disease at the end of the operation was < 2 cm, though this was statistically significant only for PSOC (P < 0.02). We conclude that patients with PPSC should be treated as other stage II-IV PSOC patients. Combining optimal debulking with a platinum-based chemotherapy may offer the patient the most effective treatment.

Modulation by protein kinase C activation of rat brain delayed-rectifier K+ channel expressed in Xenopus oocytes

The modulation by protein kinase C (PKC) of the RCK1 K+ channel was investigated in Xenopus oocytes by integration of two-electrode voltage clamp, site-directed mutagenesis and SDS-PAGE analysis techniques. Upon application of beta-phorbol 12-myristate 13-acetate (PMA) the current was inhibited by 50-90%. No changes in the voltage sensitivity of the channel, changes in membrane surface area or selective elimination of RCK1 protein from the plasma membrane could be detected. The inhibition was mimicked by 1-oleoyl-2-acetyl-rac-glycerol (OAG) but not by alphaPMA, and was blocked by staurosporine and calphostin C. Upon deletion of most of the N-terminus a preceding enhancement of about 40% of the current was prominent in response to PKC activation. Its physiological significance is discussed. The N-terminus deletion eliminated 50% of the inhibition. However, phosphorylation of none of the ten classical PKC phosphorylation sites on the channel molecule could account, by itself or in combination with others, for the inhibition. Thus, our results show that PKC activation can modulate the channel conductance in a bimodal fashion. The N-terminus is involved in the inhibition, however, not via its direct phosphorylation.

Prediction of polypeptide secondary structures analysing the oscillation of the hydropathy profile

The hydropathy profile of a polypeptide can reflect periodicity tightly linked, in particular, with alpha-helix and beta-strand conformations. We have developed an algorithm to detect such periodicity to predict the secondary structure of proteins. The method uses profiles constructed with the weighted average of hydropathy along the primary structure of the polypeptide and does the analysis of the variation of the profile for looking for periodic oscillations, using a variation detecting algorithm, without the definition of an empirical threshold. The independence of the method from known structures makes it particularly reliable for analysing membrane proteins.

Properties of the Kv1.1 rat brain potassium channels expressed in mammalian cells: temperature effects

We studied the temperature dependence of the currents mediated by potassium channels Kv1.1 cloned from rat brain expressed by permanent transfection in the human embryonic kidney cell line 292er. Voltage-gated outward currents, with a reversal potential near to the Nernst potential for potassium, were elicited by depolarising pulses. The currents activate fast and do not show inactivation during 50-ms test pulses. Increasing temperature decreased the amplitude of the currents, slowed the kinetics of activation and deactivation and shifted the activation curve to more negative potentials. We conclude that in Kv1.1 channels the closed states are associated with more ordered structure of the channel protein than the open state. The voltage-dependence and the kinetic properties are similar to those expressed in frog oocytes injected with cRNA coding the same Kv1.1.

Inward rectifier potassium channels in plants differ from their animal counterparts in response to voltage and channel modulators

We have investigated the electrophysiological basis of potassium inward rectification of the KAT1 gene product from Arabidopsis thaliana expressed in Xenopus oocytes and of functionally related K+ channels in the plasma membrane of guard and root cells from Vicia faba and Zea mays. The whole-cell currents passed by these channels activate, following steps to membrane potentials more negative than -100 mV, with half activation times of tens of milliseconds. This voltage dependence was unaffected by the removal of cytoplasmic magnesium. Consequently, unlike inward rectifier channels of animals, inward rectification of plant potassium channels is an intrinsic property of the channel protein itself. We also found that the activation kinetics of KAT1 were modulated by external pH. Decreasing the pH in the range 8.5 to 4.5 hastened activation and shifted the steady state activation curve by 19 mV per pH unit. This indicates that the activity of these K+ channels and the activity of the plasma membrane H(+)-ATPase may not only be coordinated by membrane potential but also by pH. The instantaneous current-voltage relationship, on the other hand, did not depend on pH, indicating that H+ do not block the channel. In addition to sensitivity towards protons, the channels showed a high affinity voltage dependent block in the presence of cesium, but were less sensitive to barium. Recordings from membrane patches of KAT1 injected oocytes in symmetric, Mg(2+)-free, 100 mM-K+, solutions allowed measurements of the current-voltage relation of single open KAT1 channels with a unitary conductance of 5 pS. We conclude that the inward rectification of the currents mediated by the KAT1 gene product, or the related endogenous channels of plant cells, results from voltage-modulated structural changes within the channel proteins. The voltage-sensing or the gating-structures appear to interact with a titratable acidic residue exposed to the extracellular medium.

Activation and deactivation properties of rat brain K+ channels of the Shaker-related subfamily

We studied the activation properties of members of the Shaker-related subfamily of voltage-gated K+ channels cloned from rat brain and expressed in Xenopus oocytes. We find that Kv1.1, Kv1.4, Kv1.5, and Kv1.6 have similar activation and deactivation kinetics. The k+ currents produced by step depolarisations increase with a sigmoidal time course that can be described by a delay and by the derivative of the current at the inflection point. The delay tends to zero and the logarithmic derivative seems to approach a finite value at large positive voltages, but these asymptotic values are not yet reached at +80 mV. Deactivation of the currents upon stepping to negative membrane potentials below -60 mV is fairly well described by a single exponential. The decrease of the deactivation time constant at increasingly negative voltages tends to become less steep, indicating that this parameter also has a finite limiting value, which is not yet reached, however, at -160 mV. The various clones studied have very similar voltage dependencies of activation with half-activation voltages ranging between -50 and -11 mV and maximum steepness yielding and e-fold change for voltage increments between 3.8 and 7.0 mV. The shallower activation curve of Kv1.4 is likely to be due to coupling with the fast inactivation process present in this clone.

Proline mutations on the S4 segment of rat brain sodium channel II

We have studied S4-proline mutants of the rat brain sodium channel II. In mutant A224P one proline was added on the S4 segment of repeat I, and in mutant P1313V a proline was removed from the segment S4 of the repeat II. In both mutants, the activation curve was shifted to more positive potentials, without changing the steepness of the voltage dependence. The time course of inactivation, consisting of two exponential components, was similar in the wild type and in mutant A224P. Differently, the decay of the current in mutant P1313V had only one component, with a time constant similar to that of the fast component of wild type channels. This change in kinetics was accompanied in mutant P1313V by a change in the voltage dependence of the apparent steady-state inactivation. We conclude that the addition or deletion of prolines in segment S4 does not affect significantly the activation of sodium channels, but alters their mode of inactivation.

On the structure of mitochondrial porins and its homologies with bacterial porins

By use of computer modelling, we have predicted a model of 16 transmembrane beta-strands for mitochondrial porins structure from human, Saccharomyces cerevisiae, Neurospora crassa and Dictyostelium discoideum. The proposed model takes into account biochemical and immunological data reported in the literature, as well as electrophysiological results obtained with yeast mitochondrial porins with mutations at selected amino acids. The predicted structure is very similar to that of some bacterial porins, as apparent from the homology of their hydropathic profiles.

Properties of the transient potassium currents in cerebellar granule cells

Macroscopic potassium currents were studied in cell-attached and inside-out patches from rat cerebellar granule cells. They were related with transient IA type potassium channels. Currents activated rapidly at potentials higher than -40 mV and did not inactivate completely. The magnitude of the current diminished when the membrane patches were excised. No differences in the activation and inactivation properties were found between patches in the integral cells and cell free membrane patches. A biophysical description of the currents is presented.

Outpatient endometrial sampling with the Pipelle curette

This study compares outpatient endometrial sampling using the Pipelle endometrial sampling curette with conventional dilation and curettage (D&C) in patients with abnormal uterine bleeding. Endometrial sampling with the Pipelle curette was performed in 172 and D&C in 97 women. No complications were encountered with either of these procedures. One hundred and seventy (98.8%) of the Pipelle aspirations attempted were successfully completed. Sufficient material for histological assessment was obtained in 154 (90.6%) of the women who underwent Pipelle endometrial sampling and in only 66 (68%) of those who underwent D&C (p < 0.0001). In postmenopausal women, adequate specimens were obtained in 74 of 88 (84.1%) by Pipelle and in only 22 of 48 (45.8%) by D&C. In 45 cases the histologic diagnosis of the endometrium obtained by Pipelle sampling was compared with the one of endometrium obtained by D&C or hysterectomy performed shortly thereafter. The diagnosis was identical in 43 (95.5%) cases. Endometrial sampling with the Pipelle was well tolerated causing occasionally only slight discomfort.

Cytologic examination of ovarian cyst fluid for the distinction between benign and malignant tumors

OBJECTIVE

To assess the feasibility of using cytologic examination of ovarian cyst fluid for distinguishing between benign and malignant tumors.

METHODS

Cyst fluid was aspirated at surgery in 83 women with benign and 35 women with malignant (25 invasive and ten borderline) ovarian tumors and submitted for routine cytologic examination.

RESULTS

The specificity of the cytologic examination was 100%, but the sensitivity and negative predictive value were only 26 and 76%, respectively.

CONCLUSION

The low sensitivity and negative predictive value of cytologic cyst fluid examination preclude its use for the distinction between benign and malignant ovarian tumors.

Modulation of voltage-dependent calcium channels by glutamate in rat cerebellar granule cells in culture

Voltage-dependent calcium channels of cerebellar granule cells maintained in a Ca(2+)-free depolarising solution were recorded using the cell-attached configuration of the patch-clamp technique. An increase in the maximum open probability of calcium channels and a shift in their activation curve toward more hyperpolarizing potentials were found in the presence of glutamate, a natural, excitatory amino acid. Such an increase in the activity of calcium channels was not due to ionic fluxes activated by glutamate, and was probably produced by a second messenger pathway triggered by the binding of glutamate to its receptor.

Channels in mitochondrial membranes: knowns, unknowns, and prospects for the future

Rapid diffusion of hydrophilic molecules across the outer membrane of mitochondria has been related to the presence of a protein of 29 to 37 kDa, called voltage-dependent anion channel (VDAC), able to generate large aqueous pores when integrated in planar lipid bilayers. Functional properties of VDAC from different origins appear highly conserved in artificial membranes: at low transmembrane potentials, the channel is in a highly conducting state, but a raise of the potential (both positive and negative) reduces drastically the current and changes the ionic selectivity from slightly anionic to cationic. It has thus been suggested that VDAC is not a mere molecular sieve but that it may control mitochondrial physiology by restricting the access of metabolites of different valence in response to voltage and/or by interacting with a soluble protein of the intermembrane space. The latest application of the patch clamp and tip-dip techniques, however, has indicated both a different electric behavior of the outer membrane and that other proteins may play a role in the permeation of molecules. Biochemical studies, use of site-directed mutants, and electron microscopy of two-dimensional crystal arrays of VDAC have contributed to propose a monomeric beta barrel as the structural model of the channel. An important insight into the physiology of the inner membrane of mammalian mitochondria has come from the direct observation of the membrane with the patch clamp. A slightly anionic, voltage-dependent conductance of 107 pS and one of 9.7 pS, K(+)-selective and ATP-sensitive, are the best characterized at the single channel level. Under certain conditions, however, the inner membrane can also show unselective nS peak transitions, possibly arising from a cooperative assembly of multiple substrates.