Inter- and intra-measurer error in the measurement of Reimers' hip migration percentage

Reimers' hip migration percentage is commonly used to document the extent of subluxation of the hip in children with spasticity. In this study, two measurers, with six months paediatric orthopaedic experience, measured the migration percentage on 44 pelvic radiographs of children with cerebral palsy, aged between two and eight years. Unknown to the measurers, each radiograph was duplicated, giving 22 non-identical radiographs (44 hips) which were measured twice at time 0 and twice six weeks later. The intra-measurer, intra-sessional absolute differences between the first and second measurements ranged from 0% to 23%, with median values of 2.5% to 3.6%. The intra-sessional median absolute differences were not statistically different between the two measurers and measuring sessions (p = 0.42, Kruskal-Wallis test). The inter-sessional absolute differences for measurements made by the same measurers ranged from 0% to 18% with a median absolute difference of 1.7% to 3.2%. Overall, only 5% of the intra-measurer measurement differences, within and between sessions, were above 13%. Repeated measurements by one measurer over time must, therefore, vary by more than 13% in order to be 95% confident of a true change. The inter-measurer error was higher with median absolute differences between the two measurers' measurements of the same hip of 3.25% to 5% (0% to 26%) and a 95th upper confidence interval of 21% to 23%. Averaging the four separate measurements over the two sessions reduced the inter-measurer error to a median absolute difference of 2.8%, but did not improve the 95th upper confidence interval, which measured 22.4%. Such inter-measurer errors may be clinically unacceptable.

Protein stability and dynamics modulation: the case of human frataxin

Frataxin (FXN) is an α/β protein that plays an essential role in iron homeostasis. Apparently, the function of human FXN (hFXN) depends on the cooperative formation of crucial interactions between helix α1, helix α2, and the C-terminal region (CTR) of the protein. In this work we quantitatively explore these relationships using a purified recombinant fragment hFXN90-195. This variant shows the hydrodynamic behavior expected for a monomeric globular domain. Circular dichroism, fluorescence, and NMR spectroscopies show that hFXN90-195 presents native-like secondary and tertiary structure. However, chemical and temperature induced denaturation show that CTR truncation significantly destabilizes the overall hFXN fold. Accordingly, limited proteolysis experiments suggest that the native-state dynamics of hFXN90-195 and hFXN90-210 are indeed different, being the former form much more sensitive to the protease at specific sites. The overall folding dynamics of hFXN fold was further explored with structure-based protein folding simulations. These suggest that the native ensemble of hFXN can be decomposed in at least two substates, one with consolidation of the CTR and the other without consolidation of the CTR. Explicit-solvent all atom simulations identify some of the proteolytic target sites as flexible regions of the protein. We propose that the local unfolding of CTR may be a critical step for the global unfolding of hFXN, and that modulation of the CTR interactions may strongly affect hFXN physiological function.

The alteration of the C-terminal region of human frataxin distorts its structural dynamics and function

Friedreich's ataxia (FRDA) is linked to a deficiency of frataxin (FXN), a mitochondrial protein involved in iron-sulfur cluster synthesis. FXN is a small protein with an α/β fold followed by the C-terminal region (CTR) with a nonperiodic structure that packs against the protein core. In the present study, we explored the impact of the alteration of the CTR on the stability and dynamics of FXN. We analyzed several pathological and rationally designed CTR mutants using complementary spectroscopic and biophysical approaches. The pathological mutation L198R yields a global destabilization of the structure correlating with a significant and highly localized alteration of dynamics, mainly involving residues that are in contact with L198 in wild-type FXN. Variant FXN 90-195, which is closely related to the FRDA-associated mutant FXN 81-193, conserves a globular shape with a native-like structure. However, the truncation of the CTR results in an extreme alteration of global stability and protein dynamics over a vast range of timescales and encompassing regions far from the CTR, as shown by proton-water exchange rates and (15) N-relaxation measurements. Increased sensitivity to proteolysis, observed in vitro for both mutants, suggests a faster degradation rate in vivo, whereas the enhanced tendency to aggregate exhibited by the truncated variant may account for the loss of functional FXN, with both phenomena providing an explanation as to why the alteration of the CTR causes FRDA. These results contribute to understanding how stability and activity are linked to protein motions and they might be useful for the design of target-specific ligands to control local protein motions for stability enhancement.

Human Frataxin Folds Via an Intermediate State. Role of the C-Terminal Region

The aim of this study is to investigate the folding reaction of human frataxin, whose deficiency causes the neurodegenerative disease Friedreich's Ataxia (FRDA). The characterization of different conformational states would provide knowledge about how frataxin can be stabilized without altering its functionality. Wild-type human frataxin and a set of mutants, including two highly destabilized FRDA-associated variants were studied by urea-induced folding/unfolding in a rapid mixing device and followed by circular dichroism. The analysis clearly indicates the existence of an intermediate state (I) in the folding route with significant secondary structure content but relatively low compactness, compared with the native ensemble. However, at high NaCl concentrations I-state gains substantial compaction, and the unfolding barrier is strongly affected, revealing the importance of electrostatics in the folding mechanism. The role of the C-terminal region (CTR), the key determinant of frataxin stability, was also studied. Simulations consistently with experiments revealed that this stretch is essentially unstructured, in the most compact transition state ensemble (TSE2). The complete truncation of the CTR drastically destabilizes the native state without altering TSE2. Results presented here shed light on the folding mechanism of frataxin, opening the possibility of mutating it to generate hyperstable variants without altering their folding kinetics.

Frataxin from Psychromonas ingrahamii as a model to study stability modulation within the CyaY protein family

Adaptation of life to low temperatures influences both protein stability and flexibility. Thus, proteins from psychrophilic organisms are excellent models to study relations between these properties. Here we focused on frataxin from Psychromonas ingrahamii (pFXN), an extreme psychrophilic sea ice bacterium that can grow at temperatures as low as -12°C. This α/β protein is highly conserved and plays a key role in iron homeostasis as an iron chaperone. In contrast to other frataxin homologs, chemical and temperature unfolding experiments showed that the thermodynamic stability of pFXN is strongly modulated by pHs: ranging from 5.5±0.9 (pH6.0) to 0.9±0.3kcalmol(-1) (pH8.0). This protein was crystallized and its X-ray structure solved at 1.45Å. Comparison of B-factor profiles between Escherichia coli and P. ingrahamii frataxin variants (51% of identity) suggests that, although both proteins share the same structural features, their flexibility distribution is different. Molecular dynamics simulations showed that protonation of His44 or His67 in pFXN lowers the mobility of regions encompassing residues 20-30 and the C-terminal end, probably through favorable electrostatic interactions with residues Asp27, Glu42 and Glu99. Since the C-terminal end of the protein is critical for the stabilization of the frataxin fold, the predictions presented may be reporting on the microscopic origin of the decrease in global stability produced near neutral pH in the psychrophilic variant. We propose that suboptimal electrostatic interactions may have been an evolutionary strategy for the adaptation of frataxin flexibility and function to cold environments.

Neuroblastoma chemotherapy can be augmented by immunotargeting O-acetyl-GD2 tumor-associated ganglioside

Despite recent advances in high-risk neuroblastoma therapy, the prognosis for patients remains poor. In addition, many patients suffer from complications related to available therapies that are highly detrimental to their quality of life. New treatment modalities are, thus, urgently needed to further improve the efficacy and reduce the toxicity of existing therapies. Since antibodies specific for O-acetyl GD2 ganglioside display pro-apoptotic activity against neuroblastoma cells, we hypothesized that combination of immunotherapy could enhance tumor efficacy of neuroblastoma chemotherapy. We demonstrate here that combination of anti-O-acetyl GD2 monoclonal antibody 8B6 with topotecan synergistically inhibited neuroblastoma cell proliferation, as shown by the combination index values. Mechanistically, we evidence that mAb 8B6 induced plasma cell membrane lesions, consistent with oncosis. Neuroblastoma tumour cells treated with mAb 8B6 indeed showed an increased uptake of topotecan by the tumor cells and a more profound tumor cell death evidenced by increased caspase-3 activation. We also found that the combination with topotecan plus monoclonal antibody 8B6 showed a more potent anti-tumor efficacy in vivo than either agent alone. Importantly, we used low-doses of topotecan with no noticeable side effect. Our data suggest that chemo-immunotherapy combinations may improve the clinical efficacy and safety profile of current chemotherapeutic modalities of neuroblastoma.

Global Implications of Local Unfolding Phenomena, Probed by Cysteine Reactivity in Human Frataxin

Local events that affect specific regions of proteins are of utmost relevance for stability and function. The aim of this study is to quantitatively assess the importance of locally-focused dynamics by means of a simple chemical modification procedure. Taking human Frataxin as a working model, we investigated local fluctuations of the C-terminal region (the last 16 residues of the protein) by means of three L → C replacement mutants: L98C, L200C and L203C. The conformation and thermodynamic stability of each variant was assessed. All the variants exhibited native features and high stabilities: 9.1 (wild type), 8.1 (L198C), 7.0 (L200C) and 10.0 kcal mol^-1 (L203C). In addition, kinetic rates of Cys chemical modification by DTNB and DTDPy were measured, conformational dynamics data were extracted and free energy for the local unfolding of the C-terminal region was estimated. The analysis of these results indicates that the conformation of the C-terminal region fluctuates with partial independence from global unfolding events. Additionally, numerical fittings of the kinetic model of the process suggest that the local transition occurs in the seconds to minutes timescale. In fact, standard free energy differences for local unfolding were found to be significantly lower than those of the global unfolding reaction, showing that chemical modification results may not be explained in terms of the global unfolding reaction alone. These results provide unequivocal experimental evidence of local phenomena with global effects and contribute to understanding how global and local stability are linked to protein dynamics.

The interaction of Na+, K+, and phosphate with the gastric H,K-ATPase. Kinetics of E1-E2 conformational changes assessed by eosin fluorescence measurements

H,K-ATPase and Na,K-ATPase show the highest degree of sequence similarity among all other members of the P-type ATPases family. To explore their common features in terms of ligand binding, we evaluated conformational transitions due to the binding of Na⁺, K⁺ and Pi in the H,K-ATPase, and compared the results with those obtained for the Na,K-ATPase. This work shows that eosin fluorescence time courses provide a reasonably precise method to study the kinetics of the E1-E2 conformational changes in the H,K-ATPase. We found that, although Na⁺ shifts the equilibrium toward the E1 conformation and seems to compete with H⁺ in ATPase activity assays, it was neither possible to isolate a Na⁺-occluded state, nor to reveal an influx of Na⁺ related to H,K-ATPase activity. The high rate of the E2K → E1 transition found for the H,K-ATPase, which is not compatible with the presence of a K⁺-occluded form, agrees with the negligible level of occluded Rb⁺ (used as a K⁺ congener) found in the absence of added ligands. The use of vanadate and fluorinated metals to induce E2P-like states increased the level of occluded Rb⁺ and suggests that-during dephosphorylation-the probability of K⁺ to remain occluded increases from the E2P-ground to the E2P-product state. From kinetic experiments we found an unexpected increase in the values of k_obs for E2P formation with [Pi]; consequently, to obey the Albers-Post model, the binding of Pi to the E2 state cannot be a rapid-equilibrium reaction.

The radical soft-tissue mobilization (Kelly repair) for bladder exstrophy

The radical soft-tissue mobilization (RSTM) technique has been proposed as an alternative for staged reconstruction of bladder exstrophy. In this video, we demonstrate the successive steps of this technique.

METHODS

A newborn male with classic bladder exstrophy underwent bladder closure without pelvic osteotomies at birth; he then underwent RSTM at 1 year of age.

TECHNIQUE

Mobilization: The RSTM involved simultaneous intra-pelvic and perineal dissection, aiming at full mobilization of potential urethral sphincter striated structures, levatores ani muscles, pudendal pedicles and corpora cavernosa from their attachment on the pubic bones. From the perineal approach, a periosteum incision was performed on the antero-medial aspect of the pubic bones, and the periosteum was peeled from the ischio-pubic ramus, lifting the corpora from the bone and providing control on the pudendal pedicles. The attachments of all striated muscular structures on the lower aspects of the posterior corpora (transverse perinei, bulbo-spongiosus, ischio-cavernosus muscles) were released to allow adequate re-approximation around the reconstructed urethra. Reconstruction: After ureteric reimplantation, a funnel-shaped cervicoplasty was performed and continued by urethroplasty over an 8-Fr catheter. The muscular structures mobilized from the corpora and the bones were wrapped around the neo-urethra, which was transposed ventrally in the scrotal position, creating a temporary hypospadiac urethrostomy. After abdominal wall closure, the corpora were then de-rotated, and secured to the neo-symphisis with non-absorbable sutures, and the penile skin shaft was reconstructed.

RESULTS

At the 12-month follow-up, the boy was asymptomatic, still in nappies, with non-dilated upper-tracts on renal ultrasound, and dryness intervals of 90 min.

CONCLUSION

Radical soft-tissue mobilization allows a tension-free bladder-neck reconstruction, and may favour development of physiological continence mechanisms independent of the inevitable pubic symphisis re-enlargement. Creation of temporary hypospadias is most often needed to maximize penile length. This technically demanding procedure requires thorough knowledge of detailed anatomy of the bladder exstrophy pelvis, as demonstrated in this video.

[Appendicovesicostomy (Mitrofanoff procedure) in children: Long-term follow-up and specific complications]

OBJECTIVE

In children, intermittent catheterization by appendicovesicostomy according to Mitrofanoff is an interesting alternative to the urethral approach. Objective of the study was to evaluate the rate of appendicovesicostomy's specific complications.

METHOD

From 1997 to 2017, data on children treated and followed for an appendicovesicostomy in an academic institution were collected retrospectively. Rates of surgical complications specifically encountered on appendicovesicostomy, time of onset, frequency, and necessity of surgical reinterventions have been reported.

RESULTS

Thirty-four patients were operated on and followed for a median of 6.2 years [0.3-24]. Fifty percent had a complication, occurring after a median of 8 months [2-90], and 38% required at least one surgical revision. If complication occurred, adjustment of medical treatment and intermittent catheterization was effective in 12% of patients, endoscopic or over-fascial surgery was necessary in 17% of cases, and under-fascial revision in 21% of cases. Median time to complication was 4 months [1-90] after creation or revision of appendicovesicostomy. Thirty-height percent of difficult channel catheterization were reported, of which 46% were over or under-fascial stenosis. Inaugural urinary incontinence was 18%, and only 9% if using the appendix. At the end, 97% of appendicovesicostomy were continent.

CONCLUSIONS

Appendicovesicostomy is a high risk of complications and postoperative revisions surgery, in order to have a functional continent channel.

LEVEL OF EVIDENCE

4.

[Incidence and evolution of thrombotic images within the internal jugular vein following Swan-Ganz catheter insertion in cardiac surgery]

OBJECTIVES

Insertion of Swan-Ganz catheter for a few days may be necessary in cardiac surgery. This study was aimed at determining the incidence and the evolution of thrombotic images within the internal jugular vein as well as assessing their association with the presence of a prolonged fever at postoperative day 7 in the lack of any documented infection.

MATERIAL AND METHODS

All the patients undergoing cardiac surgery had a two-dimensional ultrasonography of internal jugular veins preoperatively, at discharge (day 7) and at postoperative day 90 if thrombotic images were seen at day 7.

RESULTS

Sleeve-like and compact thrombotic images have been observed in site of venipuncture in 52 patients (70.3%). None had any residual thrombotic image 90 days after the operation. No clinical thromboembolic migration has been observed. There was no statistical association between the presence of a thrombotic image at the ultrasonography and the duration of catheterization. Moreover, there was no association between the anticoagulation before, during and after the surgery and the presence of a thrombotic image. We found a non-significant association between fever at day 7 and the presence of a thrombotic image within the internal jugular vein.

CONCLUSION

Thrombotic images in the internal jugular vein after catheterization are frequent and disappear at day 90. The limited sample size of this study does not provide strong evidence of the role of jugular thrombi in the prolongation of fever after cardiac surgery.

MPharm students’ response to pharmacy staff shortages during lockdown

Introduction

During the first lockdown period of the COVID-19 pandemic, pharmacy students, particularly those with previous experience, were encouraged to help address staff shortages in pharmacy practice (1).

Aim

This study investigated the response of pharmacy students at Keele University to the request for help to address staff shortages in practice during lockdown.

Methods

An online survey using Google Forms was developed based on addressing the aim of the study and a working knowledge of pharmacy practice. The survey was piloted on academic pharmacists, and after minor amendments, was disseminated to all students in years 2, 3 and 4 of the MPharm course, along with a participant information sheet. Questions regarding consent were incorporated into the Google Form. The survey consisted of a range of question types: tick-box, Likert scale, multiple-choice and free text. A reminder email was sent out to increase response rate. The data were analysed using descriptive and inferential statistics, using Microsoft Excel and SPSS version 24.0.

Results

The online survey was distributed to 352 students. A total of 106 responses were collected; providing a response rate of 30.1%. Fifty-nine (55.7%) of these students did not undertake paid employment in a pharmacy during lockdown, compared to 47 (44.3%) who did. Of the 47 who did, most obtained paid employment in a community pharmacy (n=42; 89%), the rest in hospital. Seventy percent of respondents (n = 74) had undertaken work experience in a community pharmacy prior to lockdown. A number of reasons were given for choosing not to work in a pharmacy, including needing time to study for exams or living with a vulnerable family member, but the most frequent reason reported (40.7%) was that students found it difficult to find work. For those students who did work in a pharmacy during lockdown, the reported reasons varied, with the most frequent being to gain experience (n = 35; 74.5%), followed by a sense of duty to help the community (n=31; 66.0%). The time spent working ranged from 8 to 40 hours per week. The majority of students reported working in the dispensary and on the medicines counter, undertaking a wide range of activities. Final year students and those who had previously undertaken work experience in a pharmacy were statistically more likely to obtain paid employment during lockdown. Perceived advantages to working during lockdown included the opportunity to improve communication and clinical skills and apply theory to practice, as well as being able to ‘give back’ to the community. 97.9% (n= 46) reported feeling under pressure whilst working, although 72.3% (n=34) reported that they enjoyed working despite this.

Conclusion

Pharmacy students had various reasons for choosing to work in practice or not during lockdown. Those who did work reported benefiting from the experience in a number of ways. This suggests that pharmacy students with prior experience of pharmacy working, should be encouraged to offer their support in times of staff shortages if future lockdowns occur.

Reference

(1) Supporting the COVID-19 response: Joint Guidance: Facilitating deployment of pharmacy undergraduate students to support the pharmacy workforce. Health Education England, NHS Education for Scotland, Health Education and Improvement Wales, Pharmacy Schools Council, Royal Pharmaceutical Society and the British Pharmaceutical Students’ Association. 09 April 2020, pp.1–9. Available at: https://www.hee.nhs.uk/sites/default/files/documents/MPharm%20student%20deployment%20joint%20guidance%20FINAL.pdf [Accessed 14 October 2021].

Molecular basis of RNA recombination in the 3'UTR of chikungunya virus genome

Chikungunya virus (CHIKV) is a rapidly spreading re-emergent virus transmitted from mosquitoes to humans. The emergence of epidemic variants has been associated with changes in the viral genome, such as the duplication of repeated sequences in the 3' untranslated region (UTR). Indeed, blocks of repeated sequences seemingly favor RNA recombination, providing the virus with a unique ability to continuously change the 3'UTR architecture during host switching. In this work, we provide experimental data on the molecular mechanism of RNA recombination and describe specific sequence and structural elements in the viral 3'UTR that favor template switching of the viral RNA-dependent RNA polymerase on the 3'UTR. Furthermore, we found that a 3'UTR deletion mutant that exhibits markedly delayed replication in mosquito cells and impaired transmission in vivo, recombines in reference laboratory strains of mosquitoes. Altogether, our data provide novel experimental evidence indicating that RNA recombination can act as a nucleic acid repair mechanism to add repeated sequences that are associated to high viral fitness in mosquito during chikungunya virus replication.

How ligands modulate the gastric H,K-ATPase activity and its inhibition by tegoprazan

The introduction of potassium-competitive acid blockers (P-CABs) has been a major innovation in gastric H,K-ATPase inhibition and many laboratories are actively engaged in the development of novel molecules within this class. This work investigates the interaction between H,K-ATPase and tegoprazan, a representative of the P-CABs group, in terms of K+ and H+ binding, through functional and structural analyses. First, by studying the H,K-ATPase activity, we found a model to describe the non-Michaelis-Menten kinetics through a "ping-pong" mechanism that explains a stoichiometry of 1 H+, 1 K+, and 1 ATP molecule, but also considering the influence of H+ on the ionization states of the protein. A kinetic evaluation of the inhibition of tegoprazan denotes the binding to two different intermediates states with apparent Kd (μM) 0.56 ± 0.04 and 2.70 ± 0.24 at pH 7.2. Molecular dynamics simulations revealed important changes in the interactions of tegoprazan with the transmembrane residues depending on whether the site contains K+ or not. This explains the decrease in affinity as a function of K+ concentration observed in the kinetic experiments. On the other hand, the structures predict that the protonation of tegoprazan is responsible for the change in its dihedral angle. The rotation of the benzimidazole ring allows the inhibitor to be positioned further into the luminal cavity, a situation compatible with the higher inhibition affinity of H,K-ATPase measured at low pH. Results presented herein will provide a basis for the rational design of novel P-CABs ligands.

The transported cations impose differences in the thermostability of the gastric H,K-ATPase. A kinetic analysis

This work analyses the thermostability of a membrane protein, the gastric H,K-ATPase, by means of a detailed kinetic characterization of its inactivation process, which showed to exhibit first-order kinetics. We observed parallel time courses for the decrease of ATPase activity, the decrease of the autophosphorylation capacity and the loss of tertiary structure at 49 °C. Higher temperatures were required to induce a significant change in secondary structure. The correspondence between the kinetics of Trp fluorescence measured at 49 °C and the decrease of the residual activity after heating at that temperature, proves the irreversibility of the inactivation process. Inactivation proceeds at different rates in E1 or E2 conformations. The K⁺-induced E2 state exhibits a lower inactivation rate; the specific effect is exerted with a K_0.5 similar to that found at 25 °C, providing a further inkling that K⁺ occlusion by the H,K-ATPase is not really favoured. Increasing [H⁺] from pH 8 to pH 7, which possibly shifts the protein to E1, produces a subtle destabilizing effect on the H,K-ATPase. We performed a prediction of potential intramolecular interactions and found that the differential stability between E1 and E2 may be mainly explained by the higher number of hydrophobic interactions in the α- and β-subunits of E2 conformation.

Technical aspects of the Koff procedure (urethral mobilization) in anterior hypospadias

INTRODUCTION

In our center the level of division of the corpus spongiosum as the determinant to classifying hypospadias. The hypospadias with a distal division is less severe and they present a little curvature.

MATERIAL AND METHODS

We present a case of distal hypospadias corrected by Koff technique and we showed our tricks for avoiding curvature.

RESULTS

In this selected case a Koff procedure are preferred because it has the main advantage of exicing the dysplastic tissues and avoiding a urethroplasty using nonurethral tissues. Late penile curvature is a source of concerns for some, but in our experience no significant curvature was found at follow up.

DISCUSSION

We believe that some tricks, showed in our video, are necessary to avoid iatrogenic curvature and to obtain a good cosmetic result.

CONCLUSIONS

Koff technique is a good technique for hypospadias with distal division of corpus spongiosum, without significant curvature at follow up.

Measurements of Na+-occluded intermediates during the catalytic cycle of the Na+/K+-ATPase provide novel insights into the mechanism of Na+ transport

The Na⁺/K⁺-ATPase is an integral plasma membrane glycoprotein of all animal cells that couples the exchange of intracellular Na⁺ for extracellular K⁺ to the hydrolysis of ATP. The asymmetric distribution of Na⁺ and K⁺ is essential for cellular life and constitutes the physical basis of a series of fundamental biological phenomena. The pumping mechanism is explained by the Albers-Post model. It involves the presence of gates alternatively exposing Na⁺/K⁺-ATPase transport sites to the intracellular and extracellular sides and includes occluded states in which both gates are simultaneously closed. Unlike for K⁺, information is lacking about Na⁺-occluded intermediates, as occluded Na⁺ was only detected in states incapable of performing a catalytic cycle, including two Na⁺-containing crystallographic structures. The current knowledge is that intracellular Na⁺ must bind to the transport sites and become occluded upon phosphorylation by ATP to be transported to the extracellular medium. Here, taking advantage of epigallocatechin-3-gallate to instantaneously stabilize native Na⁺-occluded intermediates, we isolated species with tightly bound Na⁺ in an enzyme able to perform a catalytic cycle, consistent with a genuine occluded state. We found that Na⁺ becomes spontaneously occluded in the E1 dephosphorylated form of the Na⁺/K⁺-ATPase, exhibiting positive interactions between binding sites. In fact, the addition of ATP does not produce an increase in Na⁺ occlusion as it would have been expected; on the contrary, occluded Na⁺ transiently decreases, whereas ATP lasts. These results reveal new properties of E1 intermediates of the Albers-Post model for explaining the Na⁺ transport pathway.