Substrate Selection Criteria in Regulated Intramembrane Proteolysis

Alzheimer's disease is the most common form of dementia encountered in an aging population. Characteristic amyloid deposits of Aβ peptides in the brain are generated through cleavage of amyloid precursor protein (APP) by γ-secretase, an intramembrane protease. Cryo-EM structures of substrate γ-secretase complexes revealed details of the process, but how substrates are recognized and enter the catalytic site is still largely ignored. γ-Secretase cleaves a diverse range of substrate sequences without a common consensus sequence, but strikingly, single point mutations within the transmembrane domain (TMD) of specific substrates may greatly affect cleavage efficiencies. Previously, conformational flexibility was hypothesized to be the main criterion for substrate selection. Here we review the 3D structure and dynamics of several γ-secretase substrate TMDs and compare them with mutants shown to affect the cleavage efficiency. In addition, we present structural and dynamic data on ITGB1, a known nonsubstrate of γ-secretase. A comparison of biophysical details between these TMDs and changes generated by introducing crucial mutations allowed us to unravel common principles that differ between substrates and nonsubstrates. We identified three motifs in the investigated substrates: a highly flexible transmembrane domain, a destabilization of the cleavage region, and a basic signature at the end of the transmembrane helix. None of these appears to be exclusive. While conformational flexibility on its own may increase cleavage efficiency in well-known substrates like APP or Notch1, our data suggest that the three motifs seem to be rather variably combined to determine whether a transmembrane helix is efficiently recognized as a γ-secretase substrate.

A conceptual framework to develop a patient-reported experience questionnaire on the cystic fibrosis journey in France: the ExPaParM collaborative study

BACKGROUND

The objective of the study was to elaborate a conceptual framework related to the domains of patient experience along the cystic fibrosis (CF) journey from the patients and parents of children with CF to inform the design of a patient-reported experience questionnaire.

METHOD

A collaborative research group including patients and parents with clinicians and academic researchers was set up. They identified the situations along the CF care pathway from diagnosis to paediatric care, transition to adult care and adult follow-up, transfer to transplant centres and follow-up after transplantation. Participants were recruited by CF centres in metropolitan France and overseas departments. Semi-structured interviews were conducted, transcribed verbatim and subjected to an inductive analysis conducted in duos of researchers/co-researchers using NVivo®. The conceptual framework was discussed with the research group and presented to the CF centres during two video conferences. The protocol obtained a favourable opinion from the Ethics Evaluation Committee of INSERM (IRB00003888-no. 20-700).

RESULTS

The analysis led to a conceptual framework composed of domains of the CF journey, each divided into several items. 1. CF care: Management of care by the CF centre team; in-hospital care; quality of care in the community; therapeutic education and self-management support; at-home care; new therapies and research; procreation; 2. Transplant care: management of transplant and CF care; coordination with other specialties; education and self-management support; at-home care; procreation; new therapies and research; 3. Turning points along the journey: diagnosis of CF, transition to adult care, transfer to transplantation; 4. Social life with CF: housing, employment and education, social relations, social welfare and family finances. The number of patients included and the diversity of situations made it possible to achieve a sufficient richness and saturation of codes by domain to develop patient experience questionnaires.

CONCLUSION

This conceptual framework, resulting from the participants' experience, will inform the design of a patient-reported experience tool, whose construct will be tested during the next phase of the ExPaParM project to assess its fidelity, intelligibility, and ability to report patient experience of the CF journey.

Helical stability of the GnTV transmembrane domain impacts on SPPL3 dependent cleavage

Signal-Peptide Peptidase Like-3 (SPPL3) is an intramembrane cleaving aspartyl protease that causes secretion of extracellular domains from type-II transmembrane proteins. Numerous Golgi-localized glycosidases and glucosyltransferases have been identified as physiological SPPL3 substrates. By SPPL3 dependent processing, glycan-transferring enzymes are deactivated inside the cell, as their active site-containing domain is cleaved and secreted. Thus, SPPL3 impacts on glycan patterns of many cellular and secreted proteins and can regulate protein glycosylation. However, the characteristics that make a substrate a favourable candidate for SPPL3-dependent cleavage remain unknown. To gain insights into substrate requirements, we investigated the function of a GxxxG motif located in the transmembrane domain of N-acetylglucosaminyltransferase V (GnTV), a well-known SPPL3 substrate. SPPL3-dependent secretion of the substrate's ectodomain was affected by mutations disrupting the GxxxG motif. Using deuterium/hydrogen exchange and NMR spectroscopy, we studied the effect of these mutations on the helix flexibility of the GnTV transmembrane domain and observed that increased flexibility facilitates SPPL3-dependent shedding and vice versa. This study provides first insights into the characteristics of SPPL3 substrates, combining molecular biology, biochemistry, and biophysical techniques and its results will provide the basis for better understanding the characteristics of SPPL3 substrates with implications for the substrates of other intramembrane proteases.

Cleavage of mitochondrial homeostasis regulator PGAM5 by the intramembrane protease PARL is governed by transmembrane helix dynamics and oligomeric state

The intramembrane protease PARL acts as a crucial mitochondrial safeguard by cleaving the mitophagy regulators PINK1 and PGAM5. Depending on the stress level, PGAM5 can either stimulate cell survival or cell death. In contrast to PINK1, which is constantly cleaved in healthy mitochondria and only active when the inner mitochondrial membrane is depolarized, PGAM5 processing is inversely regulated. However, determinants of PGAM5 that indicate it as a conditional substrate for PARL have not been rigorously investigated, and it is unclear how uncoupling the mitochondrial membrane potential affects its processing compared to that of PINK1. Here, we show that several polar transmembrane residues in PGAM5 distant from the cleavage site serve as determinants for its PARL-catalyzed cleavage. Our NMR analysis indicates that a short N-terminal amphipathic helix, followed by a kink and a C-terminal transmembrane helix harboring the scissile peptide bond are key for a productive interaction with PARL. Furthermore, we also show that PGAM5 is stably inserted into the inner mitochondrial membrane until uncoupling the membrane potential triggers its disassembly into monomers, which are then cleaved by PARL. In conclusion, we propose a model in which PGAM5 is slowly processed by PARL-catalyzed cleavage that is influenced by multiple hierarchical substrate features, including a membrane potential–dependent oligomeric switch.

Collaborative research protocol to define patient-reported experience measures of the cystic fibrosis care pathway in France: the ExPaParM study

Introduction

In France, the cystic fibrosis (CF) care pathway is coordinated by multidisciplinary teams from specialised CF centres or transplant centres. It includes the care provided at home or out of hospital, risk prevention in daily life and adjustments to social life, which together contribute to the person’s quality of life. Patient experience is used to describe and evaluate the care and life of patients living with the disease.

Objectives

Our collaborative research aims to identify the most significant areas and criteria that characterise the CF pathway. It will lead to the development of a questionnaire to collect patients' experience, which can be administered to all patients or parents of children registered and followed in the centres. The article describes the protocol developed in partnership with patients and parents of children living with the disease.

Method

A multidisciplinary research group brings together researchers, patients, parents of children with CF and health care professionals. The patient partnership is involved in the 4 phases of the protocol: (1) setting up the study, recruiting patient and parent co-researchers, training them in qualitative research methods, defining the situations and profiles of patients in the study population, elaborating the protocol; (2) selecting the study sites, recruiting participants, carrying out semi-structured interviews, analysing verbatims using the grounded theory approach; (3) co-elaborating Patient-Reported Experience Measures (PREM) questionnaires adapted to the 4 types of participants: parents, adolescents, non-transplanted adults and transplanted adults; (4) validating the construct with participants and professionals from the study centres.

Results

The protocol obtained a favourable opinion from the Ethics Evaluation Committee of INSERM (IRB00003888—no. 20-700). Training was provided to the 5 patients and 2 parent co-researchers to enable them to participate effectively in the research. Eleven centres participated in the recruitment of participants in mainland France and Reunion Island. Eighty hours of interviews were conducted.

Discussion

The PREM questionnaires to be elaborated will have to undergo psychometric validation before being used by the actors of the CF network to assess the impact on the care pathways of quality approaches or new therapies available in cystic fibrosis.

Trial Registration Registry: IRB00003888 – no. 20-700. Issue date: 06/09/2020.

Large-Scale Recombinant Production of the SARS-CoV-2 Proteome for High-Throughput and Structural Biology Applications

The highly infectious disease COVID-19 caused by the Betacoronavirus SARS-CoV-2 poses a severe threat to humanity and demands the redirection of scientific efforts and criteria to organized research projects. The international COVID19-NMR consortium seeks to provide such new approaches by gathering scientific expertise worldwide. In particular, making available viral proteins and RNAs will pave the way to understanding the SARS-CoV-2 molecular components in detail. The research in COVID19-NMR and the resources provided through the consortium are fully disclosed to accelerate access and exploitation. NMR investigations of the viral molecular components are designated to provide the essential basis for further work, including macromolecular interaction studies and high-throughput drug screening. Here, we present the extensive catalog of a holistic SARS-CoV-2 protein preparation approach based on the consortium's collective efforts. We provide protocols for the large-scale production of more than 80% of all SARS-CoV-2 proteins or essential parts of them. Several of the proteins were produced in more than one laboratory, demonstrating the high interoperability between NMR groups worldwide. For the majority of proteins, we can produce isotope-labeled samples of HSQC-grade. Together with several NMR chemical shift assignments made publicly available on covid19-nmr.com, we here provide highly valuable resources for the production of SARS-CoV-2 proteins in isotope-labeled form.

Altered Hinge Conformations in APP Transmembrane Helix Mutants May Affect Enzyme-Substrate Interactions of γ-Secretase

Cleavage of substrates by γ-secretase is an inherently slow process where substrate-enzyme affinities cannot be broken down into specific sequence requirements in contrast to soluble proteases. Nevertheless, despite its apparent sequence tolerance single point mutations in amyloid precursor protein can severely affect cleavage efficiencies and change product line preferences. We have determined by NMR spectroscopy the structures of the transmembrane domain of amyloid precursor protein in TFE/water and compared it to that of four mutants: two FAD mutants, V44M and I45T, and the two diglycine hinge mutants, G38L and G38P. In accordance with previous publications, the transmembrane domain is composed of two helical segments connected by the diglycine hinge. Mutations alter kink angles and structural flexibility. Furthermore, to our surprise, we observe different, but specific mutual orientations of N- and C-terminal helical segments in the four mutants compared to the wildtype. We speculate that the observed orientations for G38L, G38P, V44M, and I45T lead to unfavorable interactions with γ-secretase exosites during substrate movement to the enzyme's active site in presenilin and/or for the accommodation into the substrate-binding cavity of presenilin.

0738 Advance Taper of Antidepressants Prior to Multiple Sleep Latency Testing Increases the Number of Sleep-Onset Rapid Eye Movement Periods and Reduces Mean Sleep Latency

Introduction

Patients presenting with excessive sleepiness are frequently on antidepressant medication(s). While practice parameters recommend discontinuation of antidepressants prior to multiple sleep latency testing (MSLT), data examining the impact of tapering these medications on MSLT results are limited.

Methods

Adult patients who underwent MSLT at Mayo Clinic Rochester, Minnesota, between 2014-2018 were included. Clinical and demographic characteristics, medications, including use of rapid eye movement suppressing antidepressants (REMS-AD) at assessment and during testing, actigraphy and polysomnography data were manually abstracted. The difference in number of sleep-onset rapid eye movement periods (SOREMS), proportion with ≥2 SOREMS and mean sleep latency (MSL) in patients who were on REMS-AD and discontinued prior to testing versus those who remained on REMS-AD were examined. At our center, all antidepressants are discontinued 2 weeks prior to MSLT wherever feasible; fluoxetine is stopped 4 weeks prior. Regression analyses accounting for demographic, clinical and other medication-related confounders were performed.

Results

A total of 502 patients (age=38.18±15.90 years; 67% female) underwent MSLT; 178 (35%) were on REMS-AD at the time of assessment. REMS-AD were discontinued prior to testing in 121/178 (70%) patients. Patients tapered off REMS-AD were more likely to have ≥2 SOREMS (OR-12.20; 95%CI=1.60-92.94) compared to patients who remained on REMS-AD at the time of the MSLT. They also had shorter MSL (8.77±0.46 vs 10.21±0.28; p>0.009) and higher odds of having ≥2 SOREMS (OR=2.22; 95%CI=1.23-3.98) compared to patients not on REMS-AD at initial assessment. These differences persisted after regression analyses accounting for confounders.

Conclusion

Patients who taper off REMS-AD prior to MSLT are more likely to demonstrate ≥2SOREMs and have a shorter MSL. Pending further prospective investigations, clinicians should preferably withdraw REMs-AD before an MSLT. If this is not done, the test interpretation should include a statement regarding the potential effect of the drugs on the results.

Support

None

0787 Autonomic Dysfunction and Phenoconversion in Idiopathic/Isolated REM Sleep Behavior Disorder

Introduction

REM-sleep behavior disorder (RBD) is a common finding among patients with synucleinopathies. We aimed to determine the degree of autonomic dysfunction in patients presenting with idiopathic RBD (iRBD), and the predictive value of autonomic dysfunction for phenoconversion to a defined neurodegenerative disease.

Methods

We searched our electronic medical record for patients diagnosed with iRBD who also underwent standardized autonomic function testing within 6 months of iRBD diagnosis, and who had clinical follow-up of at least 3 years following iRBD diagnosis. Patients who received a diagnosis of phenoconversion within 3 months of autonomic testing were excluded. The composite autonomic severity score (CASS) was derived and compared between phenoconverters and non-converters using chi-square and Wilcoxon rank-sum tests.

Results

We identified 18 patients who fulfilled in- and exclusion criteria. Average age at autonomic testing was 67 ± 6.6 years. Twelve (67%) patients phenoconverted during the follow-up period; 6 developed PD, the other 6 DLB. Fifteen (83%) patients had at least mild autonomic dysfunction. There were no significant differences between overall converters and non-converters in total CASS or CASS subscores. However, iRBD patients who developed DLB had significantly higher total and cardiovagal CASS scores compared with those who developed PD (p <0.05), and a trend for higher adrenergic CASS scores compared to those who developed PD and those who did not phenoconvert (p=0.08 for each).

Conclusion

Autonomic dysfunction was seen in 83% of iRBD patients, and more severe baseline cardiovagal and adrenergic autonomic dysfunction in iRBD was associated with phenoconversion to DLB but not PD. Prospective studies are needed to confirm the value of autonomic testing for predicting phenoconversion and disease phenotype in iRBD.

Support

 

Modulating Hinge Flexibility in the APP Transmembrane Domain Alters γ-Secretase Cleavage

Intramembrane cleavage of the β-amyloid precursor protein C99 substrate by γ-secretase is implicated in Alzheimer's disease pathogenesis. Biophysical data have suggested that the N-terminal part of the C99 transmembrane domain (TMD) is separated from the C-terminal cleavage domain by a di-glycine hinge. Because the flexibility of this hinge might be critical for γ-secretase cleavage, we mutated one of the glycine residues, G38, to a helix-stabilizing leucine and to a helix-distorting proline. Both mutants impaired γ-secretase cleavage and also altered its cleavage specificity. Circular dichroism, NMR, and backbone amide hydrogen/deuterium exchange measurements as well as molecular dynamics simulations showed that the mutations distinctly altered the intrinsic structural and dynamical properties of the substrate TMD. Although helix destabilization and/or unfolding was not observed at the initial ε-cleavage sites of C99, subtle changes in hinge flexibility were identified that substantially affected helix bending and twisting motions in the entire TMD. These resulted in altered orientation of the distal cleavage domain relative to the N-terminal TMD part. Our data suggest that both enhancing and reducing local helix flexibility of the di-glycine hinge may decrease the occurrence of enzyme-substrate complex conformations required for normal catalysis and that hinge mobility can thus be conducive for productive substrate-enzyme interactions.

Increased H-Bond Stability Relates to Altered ε-Cleavage Efficiency and Aβ Levels in the I45T Familial Alzheimer's Disease Mutant of APP

Cleavage of the amyloid precursor protein's (APP) transmembrane domain (TMD) by γ-secretase is a crucial step in the aetiology of Alzheimer's Disease (AD). Mutations in the APP TMD alter cleavage and lead to familial forms of AD (FAD). The majority of FAD mutations shift the preference of initial cleavage from ε49 to ε48, thus raising the AD-related Aβ42/Aβ40 ratio. The I45T mutation is among the few FAD mutations that do not alter ε-site preference, while it dramatically reduces the efficiency of ε-cleavage. Here, we investigate the impact of the I45T mutation on the backbone dynamics of the substrate TMD. Amide exchange experiments and molecular dynamics simulations in solvent and a lipid bilayer reveal an increased stability of amide hydrogen bonds at the ζ- and γ-cleavage sites. Stiffening of the H-bond network is caused by an additional H-bond between the T45 side chain and the TMD backbone, which alters dynamics within the cleavage domain. In particular, the increased H-bond stability inhibits an upward movement of the ε-sites in the I45T mutant. Thus, an altered presentation of ε-sites to the active site of γ-secretase as a consequence of restricted local flexibility provides a rationale for reduced ε-cleavage efficiency of the I45T mutant.

Intra-amniotic digoxin for feticide between 21 and 30 weeks of gestation: a prospective study

OBJECTIVE

Intra-amniotic injection of digoxin is a well-known method for feticide before inducing a termination of pregnancy (TOP) at 17-24 weeks of gestation. Information on its effectiveness when administered after 24 weeks of gestation is limited. This study evaluated the efficacy of intra-amniotic digoxin injection for inducing fetal demise within 18-24 hours, at 21-30 weeks of gestation, and its safety.

DESIGN

Prospective cohort study.

SETTING

Tertiary university medical centre.

POPULATION

Women at 21-30 weeks of gestation with a singleton pregnancy, admitted for TOP.

METHODS

Intra-amniotic injection of 2 mg of digoxin was performed 1 day before medical TOP. Fetal heart activity was evaluated by ultrasound for 18-24 hours after the injection. Serum digoxin level and maternal electrocardiogram (ECG) were evaluated 6, 10, and 20 hours after injection.

MAIN OUTCOME MEASURE

Frequency of successful fetal demise.

RESULTS

Fifty-nine women participated in the study. The mean gestational age was 24⁺²  weeks (range 21⁺⁰ -30⁺⁰ ), with 29 (49.2%) beyond 24⁺⁰  weeks of gestation. Fetal cardiac activity arrest was achieved in 55/59 cases (93.2%). Normal maternal ECG recordings were noted in all cases. Mean serum digoxin levels 6 and 10 hours after injection were in the therapeutic range (1.3 ± 0.7 ng/l and 1.24 ± 0.49 ng/l, respectively) and below the toxic level (2 ng/l). Extramural delivery following digoxin did not occur. There were no cases of chorioamnionitis.

CONCLUSION

Intra-amniotic digoxin for feticide at 21-30 weeks of gestation in a singleton pregnancy appears effective and safe before TOP at advanced gestational ages.

TWEETABLE ABSTRACT

This study shows that feticide by intra-amniotic digoxin injection at 21-30 weeks of gestation appears effective and safe.

Feedback control of unstable periodic orbits in equivariant Hopf bifurcation problems

Symmetry-breaking Hopf bifurcation problems arise naturally in studies of pattern formation. These equivariant Hopf bifurcations may generically result in multiple solution branches bifurcating simultaneously from a fully symmetric equilibrium state. The equivariant Hopf bifurcation theorem classifies these solution branches in terms of their symmetries, which may involve a combination of spatial transformations and temporal shifts. In this paper, we exploit these spatio-temporal symmetries to design non-invasive feedback controls to select and stabilize a targeted solution branch, in the event that it bifurcates unstably. The approach is an extension of the Pyragas delayed feedback method, as it was developed for the generic subcritical Hopf bifurcation problem. Restrictions on the types of groups where the proposed method works are given. After addition of the appropriately optimized feedback term, we are able to compute the stability of the targeted solution using standard bifurcation theory, and give an account of the parameter regimes in which stabilization is possible. We conclude by demonstrating our results with a numerical example involving symmetrically coupled identical nonlinear oscillators.

Three-wave interactions and spatiotemporal chaos

Three-wave interactions form the basis of our understanding of many pattern-forming systems because they encapsulate the most basic nonlinear interactions. In problems with two comparable length scales, it is possible for two waves of the shorter wavelength to interact with one wave of the longer, as well as for two waves of the longer wavelength to interact with one wave of the shorter. Consideration of both types of three-wave interactions can generically explain the presence of complex patterns and spatiotemporal chaos. Two length scales arise naturally in the Faraday wave experiment, and our results enable some previously unexplained experimental observations of spatiotemporal chaos to be interpreted in a new light. Our predictions are illustrated with numerical simulations of a model partial differential equation.

Amplification in the auditory periphery: the effect of coupling tuning mechanisms

A mathematical model describing the coupling between two independent amplification mechanisms in auditory hair cells is proposed and analyzed. Hair cells are cells in the inner ear responsible for translating sound-induced mechanical stimuli into an electrical signal that can then be recorded by the auditory nerve. In nonmammals, two separate mechanisms have been postulated to contribute to the amplification and tuning properties of the hair cells. Models of each of these mechanisms have been shown to be poised near a Hopf bifurcation. Through a weakly nonlinear analysis that assumes weak periodic forcing, weak damping, and weak coupling, the physiologically based models of the two mechanisms are reduced to a system of two coupled amplitude equations describing the resonant response. The predictions that follow from an analysis of the reduced equations, as well as performance benefits due to the coupling of the two mechanisms, are discussed and compared with published experimental auditory nerve data.

Quasipatterns in parametrically forced systems

We examine two mechanisms that have been put forward to explain the selection of quasipatterns in single- and multifrequency forced Faraday wave experiments. Both mechanisms can be used to generate stable quasipatterns in a parametrically forced partial differential equation that shares some characteristics of the Faraday wave experiment. One mechanism, which is robust and works with single-frequency forcing, does not select a specific quasipattern: we find, for two different forcing strengths, 12-fold and 14-fold quasipatterns. The second mechanism, which requires more delicate tuning, can be used to select particular angles between wavevectors in the quasipattern.

The treatment of restless legs syndrome and periodic limb movement disorder. An American Academy of Sleep Medicine Review

A task force consisting of six authors reviewed the published literature on the therapy of the restless legs syndrome or periodic limb movements in sleep available in indices through April, 1998. They selected the 45 articles for detailed review which presented original investigations of therapeutic impact on the restless legs syndrome (RLS) or periodic limb movements (PLM) and which met minimal standards. These articles dealt with a range of pharmacological and other treatment modalities, although most dealt with medications and almost half of those concentrated on dopaminergic agents, especially levodopa in various formulations. Almost half of the articles reviewed used controlled methodologies, most commonly cross-over methodologies with randomized allocation of subjects. Multi-center studies with large numbers of subjects and long-term controlled studies were not found. Information was extracted from the articles and study design, clinical definition, evaluative measures, side effects, and outcomes were tabulated in 6 evidence tables and summarized in the accompanying text. This literature was evaluated for the nature of the studies performed and its coverage of potential therapies. The review concludes with comments on possible future directions for therapeutic investigation based on the current state of the literature.

Parametrically excited surface waves: two-frequency forcing, normal form symmetries, and pattern selection

Motivated by experimental observations of exotic free surface standing wave patterns in the two-frequency Faraday experiment, we investigate the role of normal form symmetries in the associated pattern-selection problem. With forcing frequency components in ratio m/n, where m and n are coprime integers that are not both odd, there is the possibility that both harmonic waves and subharmonic waves may lose stability simultaneously, each with a different wave number. We focus on this situation and compare the case where the harmonic waves have a longer wavelength than the subharmonic waves with the case where the harmonic waves have a shorter wavelength. We show that in the former case a normal form transformation can be used to remove all quadratic terms from the amplitude equations governing the relevant resonant triad interactions. Thus the role of resonant triads in the pattern-selection problem is greatly diminished in this situation. We verify our general bifurcation theoretic results within the example of one-dimensional surface wave solutions of the Zhang-Viñals model [J. Fluid Mech. 341, 225 (1997)] of the two-frequency Faraday problem. In one-dimension, a 1:2 spatial resonance takes the place of a resonant triad in our investigation. We find that when the bifurcating modes are in this spatial resonance, it dramatically effects the bifurcation to subharmonic waves in the case that the forcing frequencies are in ratio 1/2; this is consistent with the results of Zhang and Viñals. In sharp contrast, we find that when the forcing frequencies are in a ratio 2/3, the bifurcation to (sub)harmonic waves is insensitive to the presence of another spatially resonant bifurcating mode. This is consistent with the results of our general analysis.

A highly stable and selective biosensor using modified nicotinic acetylcholine receptor (nAChR)

Methods for developing stable, sensitive and selective bilayer lipid membrane (BLM)-based biosensors are discussed. Stable BLMs were formed over micromachined polyimide apertures. Selective sensors were made by incorporating nicotinic acetylcholine receptors (nAChRs) modified with bispecific antibodies (BsAbs). When two BsAbs, attached to one nAChR, encounter antigen (Ag), channels are blocked. Sensitivity to single Ag molecules would be possible by monitoring closure of individual nAChRs.

Menstrual cycle and work schedule: effects on women's sexuality

Sexual interest and coital frequency reportedly fluctuate according to phases of the menstrual cycle, but attention has not been paid to factors such as wishes or fears regarding pregnancy or to the daily schedule of work vs. leisure time. With a view to simultaneous evaluation of the effects both of hormonal and social factors on sexual interest and activity, a group of women rated their level of sexual interest and frequency of coitus. Some variation in sexual interest and in the incidence of coitus during different menstrual phases was found. The incidence of coitus, however, was also affected by the work schedule with time off as a positive determinant. Present results are compared with those from a similar study of hysterectomized women in which the work schedule but not hormonal fluctuations of the ovarian cycle, influenced the likelihood of coitus.

Oxytocin, somatostatin, insulin and gastrin concentrations vis-à-vis late pregnancy, breastfeeding and oral contraceptives

Oxytocin concentrations increased during pregnancy and during medication with low-dose oral contraceptives (o.c.). Postprandial somatostatin concentrations were lower during medication with o.c. Insulin concentrations were elevated during pregnancy with the same tendency during medication with o.c. Gastrin levels were unaffected during the peripartal period and during medication with o.c. Women who were breastfeeders at 3 months after delivery had higher concentrations of oxytocin and lower somatostatin concentrations post-prandially during pregnancy and fasting at 3 months after delivery compared with non-breastfeeders at 3 months after delivery. Metabolic and behavioral implications are discussed.

Temporary peripartal impairment in memory and attention and its possible relation to oxytocin concentration

The aim of the present study was to investigate peripartal performance on cognitive tests and its possible relationship with plasma oxytocin concentrations. Twenty women (cases) were tested on five experimental occasions, the first toward the end of pregnancy and the last 12 months postpartum. On each experimental occasion performance on cognitive tests of memory and attention was recorded and oxytocin concentrations were simultaneously assayed in plasma-samples. Twenty non-pregnant women (controls) were investigated at similar intervals. Cases were found to have improved their performance on some cognitive tests significantly more than controls when results at 6 and 12 months after delivery were compared with those from the end of pregnancy and up to three months after partus. This observation strongly suggests impairment in cognitive performance during the peripartal period. Cases had significantly higher oxytocin concentrations than controls in plasma samples up to three months post partum. No correlation was, however, found between cognitive test results and levels of oxytocin concentration.

Premenstrual syndrome in a group of hysterectomized women of reproductive age with intact ovaries

In this prospective study 13 women of reproductive age, unselected with regard to the presence of premenstrual syndrome (PMS) and hysterectomized but with intact ovaries, eight variables were rated as indicative of PMS on visual analog scales (VAS) for 35 consecutive days. Their menstrual cycles were subsequently reconstructed in relation to the luteinizing hormone (LH) surge as pin-pointed in urine samples and confirmed with progesterone in saliva. The aim of the study was to investigate PMS apart from psychological and psychosocial factors and to compare prospective and retrospective ratings of PMS. Retrospectively, 50% of the participants reported having had both somatic and mood changes typical of PMS, but only 3/13 were found to have PMS according to prospective ratings. Symptoms of PMS were absent in one woman according to retrospective ratings and in 4/13 with prospective ratings. There was no significant correlation between retrospective and prospective ratings of PMS. The results indicate that PMS does exist apart from psychological and psychosocial factors.

Elevated plasma levels of oxytocin in women taking low-dose oral contraceptives. Identification of the plasma oxytocin with high performance liquid chromatography

The aim of the present study was to investigate whether low-dose oral contraceptives affect oxytocin concentrations in plasma. Twenty women participated in an open cross-over study. Six consecutive blood samples were drawn twice, with a 4-week interval, in the luteal phase of the menstrual cycle when the women were/were not taking oral contraceptives. Plasma levels of oxytocin were analysed with a radio-immunoassay specific for oxytocin. A significant increase in oxytocin concentrations was observed following ingestion of oral contraceptives (p less than 0.02). Women with the highest oxytocin levels during a normal menstrual cycle increased their levels the most when on oral contraceptives. Analysis with high performance liquid chromatography demonstrated that immunoreactive oxytocin found in plasma, whether with or without oral contraceptives, co-eluted with synthetic oxytocin standard. An interesting possibility could be that the mental side effects and effects on glucose metabolism occurring after treatment with oral contraceptives might be related to elevated oxytocin levels, since metabolic and CNS effects of oxytocin are known.

Successful outcome of pregnancy complicated by giant myoma and severe heparin-induced osteopenia

A case of giant myoma and severe heparin-induced osteopenia during pregnancy is reported. The increased risk of osteopenia with heparin treatment during pregnancy is stressed.

The effect of oral contraceptive pills on levels of oxytocin in plasma and on cognitive functions

Millions of healthy women use combined oral contraceptives (o.c.) for decades. In spite of that, little is known about their possible effects on cognitive functions. In this open cross-over study, 20 women were examined twice at four-week intervals at a fixed period of the menstrual cycle when they were and when they were not taking o.c. They were examined with a test-battery to assess cognitive functions. Blood samples were taken before and after breakfast to assess levels of oxytocin and prolactin. A significant increase in levels of oxytocin was registered when the women were on o.c. There was no significant difference in performance on the psychometric tests when the participants were on o.c. compared to when they were without o.c.

Autosomal recessive idiopathic torsion dystonia in a kindred of mixed ancestry

A family with idiopathic torsion dystonia (dystonia musculorum deformans) was seen in a peripheral clinic in the Richtersveld in the north-western Cape. This rare inherited form of neurological disease has maximal prevalence in individuals of Ashkenazi Jewish ancestry, and there is controversy regarding the exact mode of inheritance. The kindred documented in this study was of mixed ancestry (Cape Coloured), and autosomal recessive inheritance was suggested by the finding of affected male and female siblings born to normal parents in an isolated inbred community.