[Vibration as a risk of mastitis during milking]

INTRODUCTION

Mastitis is one of the most important factor diseases in dairy cattle worldwide. Milking technique represents one of the factors involved in the development of mastitis. The purpose of this study was to investigate the influence of vibrations during milking on the rate of clinical and subclinical mastitis. For this purpose, milking measurements, tank milk analyses and survey forms (general farm data, assessment of milking work and milking hygiene, teat condition, feeding, farm problems, animal behavior) were assessed in 8 Swiss dairy farms. The results show a correlation between present vibrations at the output of the milk meter and increasing bulk milk somatic cell count. Further, a tendency was shown for vibrations at the input of the milk meter to influence bulk milk somatic cell count. Also, a tendency regarding vibrations at the outlet of the milk meter and acute phase protein milk amyloid A was evident. In conclusion, the results suggest that vibration during milking might have a negative effect on udder health. However, further research with a larger number of dairies is needed to make a more generally valid statement.

On the force between "rafts"

"Rafts" in the plasma membrane are nanoscopic domains rich in sphingolipids and cholesterol. Groups of them are thought to provide stable platforms for various proteins. How several rafts can form a larger stable platform has yet to be made clear. Here, we show that in the microemulsion theory of rafts, in which they, and the sea in which they float, are characterized by a naturally occurring length, rafts separated by a sea larger than this length will attract one another, thus making the sea smaller. Similarly, if rafts are separated by a sea that is smaller than the characteristic size, they will repel one another thus allowing the sea to increase in size. Such an elastic force can clearly stabilize a platform of many rafts.

Lipid redistribution in the highly curved footprint of Piezo1

We investigate the effects on the distribution of lipids in the plasma membrane that are caused by the insertion of a protein, Piezo1, that significantly distorts the membrane toward the cytosol. From coarse-grained molecular dynamics simulations, we find that the major effects occur in the outer, extracellular, leaflet. The mol fraction of cholesterol increases significantly in the curved region of the membrane close to Piezo1, while those of phosphatidylcholine and of sphingomyelin decrease. In the inner leaflet, mol fractions of cholesterol and of phosphatidylethanolamine decrease slightly as the protein is approached, while that of phosphatidylserine increases slightly. The mol fraction of phosphatidylcholine decreases markedly as the protein is approached. Most of these results are understood in the context of a theoretical model that utilizes two elements; (i) a coupling between the leaflets' actual curvatures and their compositionally-dependent spontaneous curvatures and, (ii) the dependence of the spontaneous curvatures not only on the mol fractions of the phospholipids, but also on the effect that cholesterol has on the spontaneous curvatures of the phospholipids.

“A sorrow shared …”: a qualitative content analysis of what couples with recurrent miscarriages expect from one another and their families and friends

STUDY QUESTION

When couples have to face recurrent pregnancy loss (RPL), what are the partners’ wishes and needs and what is their perception of helpful and unhelpful factors with regard to their own, their partners’ and their families’ and friends’ ways of dealing with the problem?

SUMMARY ANSWER

Women and men with repeated miscarriages want open communication about their losses, but expect a sensitive and empathetic attitude from others, not pity or trivialization.

WHAT IS KNOWN ALREADY

RPL not only causes the women affected and their partners considerable emotional distress; it also has an impact on the couples’ relationships and the way they relate to their families and friends. Studies suggest that women have a greater need than their male partners to talk about their losses and that these differences may lead to dissatisfaction and cause relational tension. In addition, men often assume a ‘mainstay’ role, supporting their partners and displaying fortitude in the face of distress. As yet, however, little research has been conducted so far on the question of what the members of couples with RPL expect from one another and from their families and friends.

STUDY DESIGN, SIZE, DURATION

The study sample consisted of 147 couples and 17 women with at least 2 miscarriages attending the special unit for RPL at the University Women’s Hospital in Heidelberg (Germany) for the first time between September 2018 and October 2020 (response rate: 82.7%). The patients were asked to participate in this combined qualitative and questionnaire study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In order to explore the wishes and needs of those affected in more detail, the free text responses obtained were examined in this study by using qualitative content analysis. Categories and subcategories were created inductively to summarize and systematize content.

MAIN RESULTS AND THE ROLE OF CHANCE

Patients affected by RPL want their partners and their families and friends to deal with the topic openly and empathically. In the partnership itself, acceptance of individual grieving modes and sharing a common goal are important factors. Men, in particular, want their partners to be optimistic in facing up to the situation. Regarding communication with family and friends, it transpired that ‘good advice’, playing the matter down, inquiries about family planning, pity and special treatment are explicitly not appreciated.

LIMITATIONS, REASONS FOR CAUTION

The sample was a convenience sample, so self-selection effects cannot be excluded. In addition, the level of education in the sample was above average. Accordingly, the sample cannot be regarded as representative. The results of the content analysis are based on the respondents’ written answers to open-ended questions in the questionnaire. Unlike qualitative interview studies, further questioning was not possible in the case of ambiguities or to request more details.

WIDER IMPLICATIONS OF THE FINDINGS

Frank and sincere communication about miscarriages and about one’s own emotions and needs should be promoted both in the partnership and among family members and friends in order to strengthen the potential of social support as a resource. Open communication about the different needs of both partners is necessary to create mutual understanding. The results show the importance not only of empathy and consideration for the couples concerned but also their desire not to be pitied. Striking a fine balance between fellow-feeling and pity may also lead to tension, and this potential dilemma should be addressed in psychosocial counselling. Overall, the study contributes to a better understanding of what couples want from their families and friends when they are attempting to come to terms with RPL and highlights potential challenges in the interaction between affected couples and their families and friends.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was received for this study. None of the authors declared any conflicts of interest.

TRIAL REGISTRATION NUMBER

DRKS00014965.

A Theoretical Basis for Nanodomains

We review the current theories of nanodomain, or "raft," formation. We emphasize that the idea that they are co-exisiting Lo and Ld phases is fraught with difficulties, as is the closely related idea that they are due to critical fluctuations. We then review an alternate theory that the plasma membrane is a two-dimensional microemulsion, and that the mechanism that drives to zero the line tension between Lo and Ld phases is the coupling of height and composition fluctuations. The theory yields rafts of SM and cholesterol in the outer leaf and POPS and POPC in the inner leaf. The "sea" between rafts consists of POPC in the outer leaf and POPE and cholesterol in the inner leaf. The characteristic size of the domain structures is tens of nanometers.

P-490 Recurrent pregnancy loss acts as a posttraumatic stress event in both women and men

Study question

What are the psychological impacts of recurrent pregnancy loss (RPL) on men and women and their interdependencies?

Summary answer

Women show higher psychological risks than men, except for lack of social support. Avoidance behaviour of men correlates with higher posttraumatic stress of their partner.

What is known already

About 1-3% of all couples trying to conceive are affected by RPL. The loss of the unborn child can be the most traumatic experience in a woman’s life and is associated with significant psychological distress besides the instant grief. RPL can also be stressful for the partner, even though being at a lower risk for psychiatric morbidities. The man’s gender role expects him to support and not to show weakness which may result in a suppression of his feelings and a disenfranchised grief.

Study design, size, duration

Cross-sectional study. All women and men referred to the special unit for RPL between March 2019 and October 2020 were asked to participate voluntarily with a total sample size of 105 couples and 17 women. Exclusion criteria were less than two pregnancy losses, inadequate knowledge of the German language and incomplete data.

Participants/materials, setting, methods

Couples were invited to fill out a questionnaire package estimating their psychological risks (e.g. posttraumatic stress disorder, anxiety, depression, perceived social support) and coping strategies with established instruments. Clinical history was obtained from medical records. Couple data were analysed with the Actor Partner Interdependence Model, taking the couple as the unit of analysis.

Main results and the role of chance

The response rate was 82.3%. The following psychological risks were measured among women versus men: posttraumatic stress disorder (PTSD): 13.7% versus 3.9% (p = 0.017); anxiety: 50.4% versus 17.3% (p < 0.001), depression: 48.1% versus 14.4% (p < 0.001), lack of social support: 32.5% versus 32.7% (N.S.). A risk in at least one category showed 68.9% of women versus 44.8% of men (p < 0.001), with those at higher risk indicating a lower satisfaction with their partnership (p < 0.001) and higher impairment of their sexual life (p < 0.001). Neither total number of pregnancy losses nor time gap since last pregnancy loss showed relevant correlations with psychological risks. For women, number of curettages, controlled for the number of pregnancy losses, correlates with the severity of posttraumatic stress (p < 0.05). Higher levels of anxiety, depression and a lack of social support in women correlated positively with posttraumatic stress in their partners. The coping strategy “trivialization and wishful thinking” as well as the subscale “avoidance” of the Impact-of-Event-Scale (self-report questionnaire measuring posttraumatic stress) of men was correlated with more severe posttraumatic stress in their female partners (both p < 0.05).

Limitations, reasons for caution

The data show only correlations between the measured variables, as cross-sectional studies are not suitable to analyse causal relationships. The sample was obtained in a special unit for RPL at a university hospital, so the findings may not be generalizable to all couples with RPL.

Wider implications of the findings

Screening psychological risks in couples with RPL may be reasonable considering the high risks in both sexes and the extent of PTSD diagnoses in women, their interdependencies and the potential risk of chronification. Professionals should encourage affected couples to support each other and provide targeted information on mental health services.

Trial registration number

DRKS 00014965

P–490 Recurrent pregnancy loss acts as a posttraumatic stress event in both women and men

Study question

What are the psychological impacts of recurrent pregnancy loss (RPL) on men and women and their interdependencies?

Summary answer

Women show higher psychological risks than men, except for lack of social support. Avoidance behaviour of men correlates with higher posttraumatic stress of their partner.

What is known already

About 1–3% of all couples trying to conceive are affected by RPL. The loss of the unborn child can be the most traumatic experience in a woman’s life and is associated with significant psychological distress besides the instant grief. RPL can also be stressful for the partner, even though being at a lower risk for psychiatric morbidities. The man’s gender role expects him to support and not to show weakness which may result in a suppression of his feelings and a disenfranchised grief.

Study design, size, duration

Cross-sectional study. All women and men referred to the special unit for RPL between March 2019 and October 2020 were asked to participate voluntarily with a total sample size of 105 couples and 17 women. Exclusion criteria were less than two pregnancy losses, inadequate knowledge of the German language and incomplete data.

Participants/materials, setting, methods

Couples were invited to fill out a questionnaire package estimating their psychological risks (e.g. posttraumatic stress disorder, anxiety, depression, perceived social support) and coping strategies with established instruments. Clinical history was obtained from medical records. Couple data were analysed with the Actor Partner Interdependence Model, taking the couple as the unit of analysis.

Main results and the role of chance

The response rate was 82.3%. The following psychological risks were measured among women versus men: posttraumatic stress disorder (PTSD): 13.7% versus 3.9% (p = 0.017); anxiety: 50.4% versus 17.3% (p < 0.001), depression: 48.1% versus 14.4% (p < 0.001), lack of social support: 32.5% versus 32.7% (N.S.). A risk in at least one category showed 68.9% of women versus 44.8% of men (p < 0.001), with those at higher risk indicating a lower satisfaction with their partnership (p < 0.001) and higher impairment of their sexual life (p < 0.001). Neither total number of pregnancy losses nor time gap since last pregnancy loss showed relevant correlations with psychological risks. For women, number of curettages, controlled for the number of pregnancy losses, correlates with the severity of posttraumatic stress (p < 0.05). Higher levels of anxiety, depression and a lack of social support in women correlated positively with posttraumatic stress in their partners. The coping strategy “trivialization and wishful thinking” as well as the subscale “avoidance” of the Impact-of-Event-Scale (self-report questionnaire measuring posttraumatic stress) of men was correlated with more severe posttraumatic stress in their female partners (both p < 0.05).

Limitations, reasons for caution

The data show only correlations between the measured variables, as cross-sectional studies are not suitable to analyse causal relationships. The sample was obtained in a special unit for RPL at a university hospital, so the findings may not be generalizable to all couples with RPL.

Wider implications of the findings: Screening psychological risks in couples with RPL may be reasonable considering the high risks in both sexes and the extent of PTSD diagnoses in women, their interdependencies and the potential risk of chronification. Professionals should encourage affected couples to support each other and provide targeted information on mental health services.

Trial registration number

DRKS 00014965

Model Plasma Membrane Exhibits a Microemulsion in Both Leaves Providing a Foundation for "Rafts"

We consider a model lipid plasma membrane, one that describes the outer leaf as consisting of sphingomyelin, phosphatidylcholine, and cholesterol and the inner leaf of phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, and cholesterol. Their relative compositions are taken from experiment; the cholesterol freely interchanges between leaves. Fluctuations in local composition are coupled to fluctuations in the local membrane curvature, as in the Leibler-Andelman mechanism. Structure factors of components in both leaves display a peak at nonzero wavevector. This indicates that the disordered fluid membrane is characterized by structure of the corresponding wavelength. The scale is given by membrane properties: its bending modulus and its surface tension, which arises from the membrane's connections to the cytoskeleton. From measurements on the plasma membrane, this scale is on the order of 100 nm. We find that the membrane can be divided into two different kinds of domains that differ not only in their composition but also in their curvature. The first domain in the outer, exoplasmic leaf is rich in cholesterol and sphingomyelin, whereas the inner, cytoplasmic leaf is rich in phosphatidylserine and phosphatidylcholine. The second kind of domain is rich in phosphatidylcholine in the outer leaf and in cholesterol and phosphatidylethanolamine in the inner leaf. The theory provides a tenable basis for the origin of structure in the plasma membrane and an illuminating picture of the organization of lipids therein.

WEB-only treatment of ruptured and unruptured intracranial aneurysms: a retrospective analysis of 47 aneurysms

BACKGROUND

WEB (Woven EndoBridge) device is an intrasaccular flow diverter designed for endovascular treatment of intracranial aneurysms. Recent clinical trials showed good feasibility, safety, and efficacy profiles. In most of the published studies however, aneurysms treated with adjunctive devices other than WEB such as coils or stents were included which might make it difficult to reflect the real potential of this device. The purpose of this single-center study was to present the results of ruptured and unruptured aneurysms treated only with WEB device.

METHOD

Between April 2013 and July 2018, 47 (ruptured, 12; 25.5%) intracranial aneurysms treated only with WEB and a follow-up of at least 3 months were included in the study. Angiographic outcome at follow-up, peri-procedural complication rate, and rate of retreatment were recorded.

RESULTS

Of the 47 aneurysms, 12 (25.5%) were ruptured. The mean size of the aneurysms was 6.3 mm (ruptured, 5.4 mm; unruptured, 6.6 mm). Median follow-up period was 9 months. Complete occlusion was observed in 26/47 aneurysms (55.3%; ruptured, 66.6%; unruptured, 51.4%). Thirteen aneurysms (27.6%; ruptured, 16.6%; unruptured, 31.4%) showed a neck remnant. In 4/47 aneurysms (8.5%; ruptured, 8%; unruptured, 8.5%), persistent contrast enhancement inside the WEB was recorded. In 4/47 patients (8.5%; ruptured, 8%; unruptured, 8.5%), an aneurysm remnant was noted. Adequate occlusion (complete occlusion and neck remnant) was observed in 43/47 aneurysms (91.4%; ruptured, 91.6%; unruptured, 91.4%). Retreatment rate was 6.3% (ruptured, 8%; unruptured, 5.7%). Six (12.7%; ruptured, 25%; unruptured, 8.5%) thromboembolic events were recorded. Hemorrhagic complications occurred in two patients (4.2%; ruptured, 16.6%; unruptured, 0%).

CONCLUSIONS

WEB enables adequate occlusion of ruptured and unruptured intracranial aneurysms mostly without requirement of long-term antiplatelet therapy. The benefit is seen especially by the wide-necked aneurysms, but indications should be extended to include narrow-necked, smaller, and side-wall aneurysms.

Cholesterol-Dependent Bending Energy Is Important in Cholesterol Distribution of the Plasma Membrane

We consider the plasma membrane that contains a cholesterol molar fraction of 0.4 and ask how that cholesterol is distributed between the two leaves. Because of the rapid flip-flop of cholesterol between leaves, we assume that its distribution is determined by the equality of its chemical potentials in the two leaves. When we consider only the contributions of entropy and interactions to the cholesterol chemical potential in our model system, we find, not surprisingly, that the cholesterol is mostly in the outer leaf because of the strong attraction between cholesterol and sphingomyelin (SM), which is predominantly in that leaf. We find 72% there. We then include the contribution from the bending energy in each leaf that must be overcome to join the leaves in a flat bilayer. The product of bending modulus and spontaneous curvature is obtained from simulation. We find that the addition of cholesterol to the outer leaf reduces the spontaneous curvature, which is initially positive, until it passes through zero when the molar fraction of cholesterol in the outer leaf is 0.28. Additional cholesterol is driven toward the inner leaf by the sphingomyelin phosphatidylcholine mixture. This is resisted by the bending energy contribution to the inner leaf. We find, again by simulation, that the addition of cholesterol monotonically increases the magnitude of the spontaneous curvature of the inner leaf, which is negative. This increases its bending energy. We conclude that, as a result of these competing effects, the percentage of cholesterol in the outer leaf is reduced to ∼63 ± 6%.

Role of Three-Dimensional Rotational Angiography in the Treatment of Spinal Dural Arteriovenous Fistulas

Spinal dural arteriovenous fistulas (AVFs), being the most commonly encountered spinal vascular malformations, result in considerable morbidity with progressive spinal cord symptoms. A selective spinal digital subtraction angiography (DSA) is needed to confirm the diagnosis, to better evaluate the fine vascular structures and to plan therapy. With the introduction of three-dimensional rotational angiography (3D-RA), the information available for the treating physician has vastly increased. In the following article, we present a case series of four patients, in which the advantages of 3D-RA over the conventional biplane projections could be observed clearly.

The Effect of Solutes on the Temperature of Miscibility Transitions in Multicomponent Membranes

We address questions posed by experiments that show small-chain alcohols reduce the miscibility transition temperature when added to giant plasma membrane vesicles (GPMVs), but increase that temperature when added to giant unilamellar vesicles. In giant unilamellar vesicles the change in temperature displays a definite minimum, between decanol and tetradecanol, as a function of alcohol chain length; in GPMVs there is no such minimum. To emphasize the competition between internal entropies of the components and the interactions between them, we model the system as consisting of three different linear polymers. Two of them are the constituents of a liquid, one that can undergo a miscibility transition. To this liquid is added the third polymer component, which represents the short-chain alcohol. We show that, within Flory-Huggins theory, the addition of alcohol causes an increase or decrease of the miscibility transition temperature depending upon the competition of two effects. The first is the dilution of the interactions between the two components of the liquid caused by the introduction of the alcohol. This tends to lower the transition temperature. The second effect is the preferential partitioning of the alcohol into one phase of the liquid or the other. This tends to raise the transition temperature irrespective of which phase the alcohol prefers. This second effect is the smallest, and the decrease in transition temperature the largest, when the alcohol partitions equally between the two phases. Such equal partitioning occurs when the effect of the entropic excluded volume interactions (which cause the alcohol to prefer one phase) just balances the effect of the direct interactions, which cause it to prefer the other. These results allow us to make several predictions, and to propose an explanation for the different behavior of the transition temperature in GPMVs and giant unilamellar vesicles that results from the addition of alcohols.

Evaluation of the RumiWatchSystem for measuring grazing behaviour of cows

Feeding behaviour is an important parameter of animal performance, health and welfare, as well as reflecting levels and quality of feed available. Previously, sensors were only used for measuring animal feeding behaviour in indoor housing systems. However, sensors such as the RumiWatchSystem can also monitor such behaviour continuously in pasture-based environments. Therefore, the aim of this study was to validate the RumiWatchSystem to record cow activity and feeding behaviour in a pasture-based system. The RumiWatchSystem was evaluated against visual observation across two different experiments. The time duration per hour at grazing, rumination, walking, standing and lying recorded by the RumiWatchSystem was compared to the visual observation data in Experiment 1. Concordance Correlation Coefficient (CCC) values of CCC=0.96 for grazing, CCC=0.99 for rumination, CCC=1.00 for standing and lying and CCC=0.92 for walking were obtained. The number of grazing and rumination bouts within one hour were also analysed resulting in Cohen's Kappa (κ)=0.62 and κ=0.86 for grazing and rumination bouts, respectively. Experiment 2 focused on the validation of grazing bites and rumination chews. The accordance between visual observation and automated measurement by the RumiWatchSystem was high with CCC=0.78 and CCC=0.94 for grazing bites and rumination chews, respectively. These results indicate that the RumiWatchSystem is a reliable sensor technology for observing cow activity and feeding behaviour in a pasture based milk production system, and may be used for research purposes in a grazing environment.

Shift in membrane miscibility transition temperature upon addition of short-chain alcohols

I consider the effect of a small concentration of a molecule, such as a short-chain alcohol, on the miscibility transition temperature of a giant plasma membrane vesicle. For concentrations sufficiently small such that the system can be treated as a dilute solution, the change in transition temperature is known to depend upon the extent of the molecule's partition into the coexisting liquid-disordered and liquid-ordered phases. Preferential partitioning into the former decreases the miscibility temperature, while preferential partitioning into the latter causes an increase. The analysis, combined with calculated values of the partition coefficient of saturated chains, illuminates the results of recent experiments on the change in miscibility transition temperatures with changing alcohol chain length, and makes several testable predictions.

Effect of mobile ions on the electric field needed to orient charged diblock copolymer thin films

We examine the behavior of lamellar phases of charged/neutral diblock copolymer thin films containing mobile ions in the presence of an external electric field. We employ self-consistent field theory and focus on the aligning effect of the electric field on the lamellae. Of particular interest are the effects of the mobile ions on the critical field, the value required to reorient the lamellae from the parallel configuration favored by the surface interaction to the perpendicular orientation favored by the field. We find that the critical field depends strongly on whether the neutral or charged species is favored by the substrates. In the case in which the neutral species is favored, the addition of charges decreases the critical electric field significantly. The effect is greater when the mobile ions are confined to the charged lamellae. In contrast, when the charged species is favored by the substrate, the addition of mobile ions stabilizes the parallel configuration and thus results in an increase in the critical electric field. The presence of ions in the system introduces a new mixed phase in addition to those reported previously.

How cholesterol could be drawn to the cytoplasmic leaf of the plasma membrane by phosphatidylethanolamine

In the mammalian plasma membrane, cholesterol can translocate rapidly between the exoplasmic and cytoplasmic leaves, so that its distribution between them should be given by the equality of its chemical potential in the leaves. Due to its favorable interaction with sphingomyelin, which is almost entirely in the outer leaf, one expects the great majority of cholesterol to be there also. Experimental results do not support this, implying that there is some mechanism attracting cholesterol to the inner leaf. We hypothesize that it is drawn there to reduce the bending free energy of the membrane caused by the presence of PE (phosphatidylethanolamine). It does this in two ways: first by simply diluting the amount of PE in the inner leaf, and second by ordering the tails of the PE to reduce its spontaneous curvature. Incorporating this mechanism into a model free energy for the bilayer, we find that between 50 and 60% of the total cholesterol should be in the inner leaf of human erythrocytes.

Improving ergonomics in milking parlors: empirical findings for optimal working heights in five milking parlor types

Milking postures have shifted from seated milking in tethered stalls to milking in a standing position in parlors. However, the musculoskeletal workload of dairy farmers remains high. Previous studies have shown that different working heights affect ergonomics, but they could not objectively evaluate and quantify the workload. The aim of the present study was to assess the effect of working height in different milking parlor types on the milker's workload during the task of attaching milking clusters. Computer-assisted recording and long-term analysis of movements were used to record positions of joints and body regions while performing certain tasks in terms of angular degrees of joints (ADJ) according to the neutral zero method. The 5th, 50th, and 95th percentiles described the distribution of angular degree values measured for each joint. The ADJ were evaluated according to international standards and other scientific literature on the issue to assess the muscular load. The workload was compared between 5 parlor types (auto tandem, herringbone 30°, herringbone 50°, parallel, and rotary) on 15 farms with 2 subjects per parlor and 1 milking period per subject. The working height was defined as a coefficient based on the milker's body height, the floor level, and the cow's udder height. The data recorded during the attachment task were analyzed using generalized linear mixed-effects models taking into account the hierarchical experimental design. The results indicated that the interaction of the cow's udder height, the milker's body height, and the parlor type had a larger effect on ergonomics than each parameter had independently. The interaction was significant in at least 1 of the 3 percentiles in 28 out of 31 ADJ. The postural differences between parlor types, however, were minor. A milking health formula was created to calculate the ideal depth of pit by considering the parlor type, the milker's height, and the mean herd udder height. This formula can be used to develop individual recommendations for future parlor construction.

Model of a raft in both leaves of an asymmetric lipid bilayer

We present a theory of inhomogeneities in the plasma membrane, or rafts, that can exist in both leaves of the plasma membrane. We note that although neither of the major phospholipid components of the outer leaf, sphingomyelin (SM) nor phosphatidylcholine (PC), evinces a tendency to form phases characterized by nonzero curvature, one of the major components of the inner leaf, phosphatidylethanolamine (PE), displays a strong tendency to do so whereas the other, phosphatidylserine (PS), does not. Therefore, we posit that the concentration difference of PS and PE couples to height fluctuations of the plasma membrane bilayer. This brings about a microemulsion in the inner leaf. Coupling of the concentration difference between PS and PE in the inner leaf and SM and PC in the outer leaf propagates the microemulsion to that leaf as well. The characteristic size of the inhomogeneities is equal to the square-root of the ratio of the bending modulus of the bilayer to its surface tension, a size which is ~100 nm for the plasma membrane. If the coupling between leaves were to be provided by the interchange of cholesterol, then our model raft would consist of SM and cholesterol in the outer leaf and PS and cholesterol in the inner leaf floating in a sea of PC and PE in both leaves.

Membrane heterogeneity: manifestation of a curvature-induced microemulsion

To explain the appearance of heterogeneities in the plasma membrane, I propose a hypothesis which begins with the observation that fluctuations in the membrane curvature are coupled to the difference between compositions of one leaf and the other. Because of this coupling, the most easily excited fluctuations can occur at nonzero wave numbers. When the coupling is sufficiently strong, it is well-known that it leads to microphase separation and modulated phases. I note that when the coupling is less strong, the tendency toward modulation remains manifest in a liquid phase that exhibits a transient structure of a characteristic size, that is, it is a microemulsion. The characteristic size of the fluctuating domains is estimated to be on the order of 100 nm, and experiments to verify this hypothesis are proposed.

Phase behavior of lipid bilayers under tension

Given the proposed importance of membrane tension in regulating cellular functions, we explore the effects of a finite surface tension on phase equilibrium using a molecular theory that captures the quantitative structure of the phase diagram of the tensionless DPPC/DOPC/Cholesterol lipid bilayer. We find that an increase in the surface tension decreases the temperature of the transition from liquid to gel in a pure DPPC system by ∼1.0 K/(mN/m), and decreases the liquid-disordered to liquid-ordered transition at constant chemical potentials by approximately the same amount. Our results quantitatively isolate the role of tension in comparison to other thermodynamic factors, such as pressure, in determining the phase behavior of lipid bilayers.

Hip strength assessment using handheld dynamometry is subject to intertester bias when testers are of different sex and strength

Handheld dynamometry (HHD) is a promising tool for obtaining reliable hip strength measurements in the clinical setting, but intertester reliability has been questioned, especially in situations where testers exhibit differences in upper-extremity muscle strength (male vs female). The purpose of this study was to examine the intertester reliability concerning strength assessments of hip abduction, adduction, external and internal rotation, flexion and extension using HHD, and to test whether systematic differences in test values exist between testers of different upper-extremity strength. Fifty healthy individuals (29 women), aged 25 ± 5 years were included. Two physiotherapist students (one female, one male) of different upper-extremity strength performed the measurements. The tester order and strength test order were randomized. Intraclass correlation coefficients were used to quantify reliability, and ranged from 0.82 to 0.91 for the six strength test. The female tester systematically measured lower strength values for all isometric strength tests (P < 0.05). In hip strength assessments using HHD, systematic bias exists between testers of different sex, which is likely explained by differences in upper-extremity strength. Hence, to improve intertester reliability, the dynamometer likely needs external fixation, as this will eliminate the influence of differences in upper-extremity strength between testers.

Variations of the aortic arch - a study on the most common branching patterns

BACKGROUND

Anatomical variants of the aortic arch and its branching patterns often appear as an incidental finding during routine computed tomography (CT) scanning. These variations can be of relevance when performing angiography or endovascular interventions and may cause symptoms such as dysphagia.

PURPOSE

To analyze common anatomical variations found within the arteries originating from the aortic arch in patients using contrast CT imaging techniques.

MATERIAL AND METHODS

A total of 2033 contrast CT scans were analyzed. To obtain a truly representative sample, cases were chosen from different hospital departments without previous knowledge of the patient history.

RESULTS

The total percentage of variations within the analyzed patients was 13.3%. In 8.0% a truncus bicaroticus was found. 4.2% of the patients showed a left vertebral artery originating directly from the aortic arch, mostly proximal, and in 1 case distal to the left subclavian artery. In 1.0% we found an aberrant right subclavian artery. We also found a single case of a right descending aortic arch.

CONCLUSION

Variations of the aortic arch and its branching are frequently found, mostly as an incidental finding during routine diagnostic scanning. A contrast-enhanced CT scan is a good method with which to study the aortic arch and its associated branching pattern.

Insights on raft behavior from minimal phenomenological models

We construct a simple phenomenological theory of phase separation in ternary mixtures of cholesterol and saturated and unsaturated lipids. Such separation is relevant to the formation of 'rafts' in the plasma membrane. We also show how simple cross-linking of proteins which prefer one form of lipid to the other can trigger raft-formation, the first step in a signaling pathway.

Interleaflet coupling and domain registry in phase-separated lipid bilayers

There is clear evidence of an interleaflet coupling in model lipid/cholesterol membranes exhibiting liquid-liquid phase separation. The strength of this coupling is quantified by the mismatch free energy, γ. We calculate it using a molecular mean-field model of a phase-separated lipid/cholesterol bilayer and obtain values that increase as the concentration of saturated lipids in the coexisting phases is increased. These values lie in the range 0.01-0.03 k(B)T/nm(2). We clarify the relationship between the interleaflet coupling and the extent of interleaflet alignment of liquid domains by analyzing a statistical mechanical model of coupled fluctuating domain interfaces. The model is solved exactly using the correspondence between statistical mechanics and quantum mechanics, yielding an expression for the characteristic size of fluctuations out of domain registry. This length scale depends only weakly on the strength of the interleaflet coupling and inevitably is only of the order of nanometers, which explains the experimental result that fluctuations out of domain registry have not been observed by optical microscopy.

Aprotinin and classic wound drainage are unnecessary in total hip replacement - a prospective randomized trial

BACKGROUND

Classic wound drainage is still common in hip replacement but its benefit is doubtful. The role of systemic administration of proteinase inhibitors like aprotinin to avoid perioperative blood loss is still unclear.

PATIENTS AND METHODS

In a prospective randomized trial, the perioperative blood loss in alloplastic hip replacement under the influence of proteinase inhibitor (aprotinin, Trasylol®) using wound drainage as well as compression treatment alone were compared. 80 patients were prospectively randomized in 4 arms. Patients received either aprotinin or placebo during surgery as well as drainage or targeted external wound compression.

RESULTS

Observing the "drug therapy" aprotinin had no effect on the intra- or postoperative blood loss (p>0.05), a trend to lower postoperative hemoglobin decline was found, but without significance. Thrombosis occurred in neither the aprotinin nor in the placebo group. Two patients had a severe allergic drug reaction and were excluded from the study. Under "non drug therapy" with compression therapy and wound drainage a significant difference in blood loss was found (p<0.001). The blood loss was higher under the wound drainage. There was no influence on the infection rate. Yet we could observe increased bruising under the sole external compression treatment.

CONCLUSION

The administration of aprotinin did not achieve the desired reduction of perioperative blood loss. Hence, costs and two severe allergic drug reactions in our study represent arguments against its use in regular treatment. Furthermore, it seems that wound drainage is neglectable in hip replacement and can be substituted by a sole compression treatment.

Calculating partition coefficients of chain anchors in liquid-ordered and liquid-disordered phases

We calculate partition coefficients of various chain anchors in liquid-ordered and liquid-disordered phases utilizing a theoretical model of a bilayer membrane containing cholesterol, dipalmitoyl phosphatidylcholine, and dioleoylphosphatidylcholine. The partition coefficients are calculated as a function of chain length, degree of saturation, and temperature. Partitioning depends on the difference between the lipid environments of the coexisting phases in which the anchors are embedded. Consequently, the partition coefficient depends on the nature of the anchor, and on the relative compositions of the coexisting phases. We find that saturated anchors prefer the denser liquid-ordered phase, and that the fraction of anchors in the liquid-ordered phase increases with increasing degree of saturation of the anchors. The partition coefficient also depends upon the location of the double bonds. Anchors with double bonds closer to the middle of the chain have a greater effect on partitioning than those near the end. Doubling the number of saturated chains increases the partitioning into the liquid-ordered phase for tails that are nearly as long or longer than those comprising the bilayer. Partitioning of such chains increases with decreasing temperature, indicating that energy considerations dominate entropic ones. In contrast, partitioning of shorter chains increases with increasing temperature, indicating that entropic considerations dominate.

Stability and liquid-liquid phase separation in mixed saturated lipid bilayers

The phase stability of a fluid lipid bilayer composed of a mixture of DC(18)PC, (DSPC), and a shorter DCn(s) PC, with n(s) from 8 to 17, has been studied using a self-consistent field theory that explicitly includes molecular details and configurational properties of the lipid molecules. Phase separation between two liquid phases was found when there was a sufficient mismatch between the hydrophobic thicknesses of the two bilayers composed entirely of one component or the other. This occurs when n(s) 12, we observe that the effect of the shorter lipid is to increase the susceptibility of the system to fluctuations in the concentration. This is of interest, given that a common motif for the anchoring of proteins to the plasma membrane is via a myristoyl chain, that is, one with 14 carbons.