HIV-1 Vpu protein forms stable oligomers in aqueous solution via its transmembrane domain self-association.

We report our findings on the assembly of the HIV-1 protein Vpu into soluble oligomers. Vpu is a key HIV-1 protein. It has been considered exclusively a single-pass membrane protein. Previous observations show that this protein forms stable oligomers in aqueous solution, but details about these oligomers still remain obscure. This is an interesting and rather unique observation, as the number of proteins transitioning between soluble and membrane embedded states is limited. In this study we made use of protein engineering, size exclusion chromatography, cryoEM and electron paramagnetic resonance (EPR) spectroscopy to better elucidate the nature of the soluble oligomers. We found that Vpu oligomerizes via its N-terminal transmembrane domain (TM). CryoEM suggests that the oligomeric state most likely is a hexamer/heptamer equilibrium. Both cryoEM and EPR suggest that, within the oligomer, the distal C-terminal region of Vpu is highly flexible. Our observations are consistent with both the concept of specific interactions among TM helices or the core of the oligomers being stabilized by hydrophobic forces. While this study does not resolve all of the questions about Vpu oligomers or their functional role in HIV-1 it provides new fundamental information about the size and nature of the oligomeric interactions.

Combined preauricular, retroauricular bilobed flap for earlobe reconstruction.

The earlobe is an important anatomical structure that has a significant role in aesthesis. An absent ear lobule may be congenital or acquired due to the result of trauma, infection or malignancy. Its surgical repair places a challenge due to the difficulty of obtaining a natural-appearing and durable outcome. Many procedures have been described for reconstruction including the Gavello and Zenteno Alanis techniques. We have described a new method which is single staged, easy to perform and aesthetically acceptable.

Self-organized and directed branching results in optimal coverage in developing dermal lymphatic networks.

Branching morphogenesis is a ubiquitous process that gives rise to high exchange surfaces in the vasculature and epithelial organs. Lymphatic capillaries form branched networks, which play a key role in the circulation of tissue fluid and immune cells. Although mouse models and correlative patient data indicate that the lymphatic capillary density directly correlates with functional output, i.e., tissue fluid drainage and trafficking efficiency of dendritic cells, the mechanisms ensuring efficient tissue coverage remain poorly understood. Here, we use the mouse ear pinna lymphatic vessel network as a model system and combine lineage-tracing, genetic perturbations, whole-organ reconstructions and theoretical modeling to show that the dermal lymphatic capillaries tile space in an optimal, space-filling manner. This coverage is achieved by two complementary mechanisms: initial tissue invasion provides a non-optimal global scaffold via self-organized branching morphogenesis, while VEGF-C dependent side-branching from existing capillaries rapidly optimizes local coverage by directionally targeting low-density regions. With these two ingredients, we show that a minimal biophysical model can reproduce quantitatively whole-network reconstructions, across development and perturbations. Our results show that lymphatic capillary networks can exploit local self-organizing mechanisms to achieve tissue-scale optimization.

Structural basis for the allosteric modulation of rhodopsin by nanobody binding to its extracellular domain.

Rhodopsin is a prototypical G protein-coupled receptor (GPCR) critical for vertebrate vision. Research on GPCR signaling states has been facilitated using llama-derived nanobodies (Nbs), some of which bind to the intracellular surface to allosterically modulate the receptor. Extracellularly binding allosteric nanobodies have also been investigated, but the structural basis for their activity has not been resolved to date. Here, we report a library of Nbs that bind to the extracellular surface of rhodopsin and allosterically modulate the thermodynamics of its activation process. Crystal structures of Nb2 in complex with native rhodopsin reveal a mechanism of allosteric modulation involving extracellular loop 2 and native glycans. Nb2 binding suppresses Schiff base deprotonation and hydrolysis and prevents intracellular outward movement of helices five and six - a universal activation event for GPCRs. Nb2 also mitigates protein misfolding in a disease-associated mutant rhodopsin. Our data show the power of nanobodies to modulate the photoactivation of rhodopsin and potentially serve as therapeutic agents for disease-associated rhodopsin misfolding.

A mechanistic reinterpretation of fast inactivation in voltage-gated Na+ channels.

The hinged-lid model was long accepted as the canonical model for fast inactivation in Nav channels. It predicts that the hydrophobic IFM motif acts intracellularly as the gating particle that binds and occludes the pore during fast inactivation. However, the observation in recent high-resolution structures that the bound IFM motif is located far from the pore, contradicts this preconception. Here, we provide a mechanistic reinterpretation of fast inactivation based on structural analysis and ionic/gating current measurements. We demonstrate that in Nav1.4 the final inactivation gate is comprised of two hydrophobic rings at the bottom of S6 helices. These rings function in series and close downstream of IFM binding. Reducing the volume of the sidechain in both rings leads to a partially conductive, leaky inactivated state and decreases the selectivity for Na+ ion. Altogether, we present an alternative molecular framework to describe fast inactivation.

Management of helical adhesion malformation.

Congenital auricular anomalies are common, however very few articles in the English literature address helical adhesion malformation, whereby the helix is adhered to the scapha. We describe a surgical approach to correct helical adhesion malformation which, unlike previously described methods, is simpler and results in an inconspicuous scar on the back of the ear. We illustrate our technique with an 11-year-old girl with bilateral helical adhesion malformations. Satisfactory ear shape was achieved bilaterally without complication. Meticulous dissection over the helix and exposure beyond the adhesion is of paramount importance in successfully correcting this malformation. Through a posterior auricular incision, this wide exposure and visualisation of the helix can be attained, with the added benefit of a scar hidden on the back of the ear.

A randomized vagus nerve stimulation study demonstrates that serum aldosterone levels decrease with age in women, but not in men.

In this randomized, sham-controlled study, we explored the effects of acute transcutaneous vagus nerve stimulation (tVNS) on serum aldosterone in 20 younger (21-26 years) and 19 older (40-70 years) healthy participants. Blood samples were collected on two different days before and after a 20-min application of active tVNS at the inner tragus or sham stimulation of the earlobe. Irrespective of the stimulation mode, aldosterone levels decreased from pre- to post-stimulation in both the young (active: ß = - 1.610 (- 2.855, - 0.365), p = 0.022; sham: ß = - 0.857 (- 2.102, 0.388), p = 0.257) and the old cohort (active: ß = - 1.969 (- 3.234, - 0.703), p = 0.005; sham: ß = - 1.334 (- 2.600, - 0.069), p = 0.063). Although this decline was significant during active tVNS, the difference in estimated ß-coefficients between active and sham stimulation was not statistically significant in either cohort. Nevertheless, aldosterone concentrations showed a significant interaction effect between sex and age (p = 0.001). Among all study participants, younger women (23.3 ± 1.6 years) had the highest mineralocorticoid levels (pre active: 172.1 ± 102.0 pg/ml, pre sham: 214.3 ± 82.3 pg/ml), whereas the lowest were observed in older females (59.4 ± 9.4 years) (pre active: 104.9 ± 85.8 pg/ml, pre sham: 81.1 ± 53.8 pg/ml). This post hoc analysis did not suggest that active auricular tVNS reduces serum aldosterone levels compared to sham stimulation in healthy subjects. However, serum aldosterone levels differed among subjects depending on their age and sex, irrespective of tVNS.

Partition complex structure can arise from sliding and bridging of ParB dimers.

In many bacteria, chromosome segregation requires the association of ParB to the parS-containing centromeric region to form the partition complex. However, the structure and formation of this complex have been unclear. Recently, studies have revealed that CTP binding enables ParB dimers to slide along DNA and condense the centromeric region through the formation of DNA bridges. Using semi-flexible polymer simulations, we demonstrate that these properties can explain partition complex formation. Transient ParB bridges organize DNA into globular states or hairpins and helical structures, depending on bridge lifetime, while separate simulations show that ParB sliding reproduces the multi-peaked binding profile observed in Caulobacter crescentus. Combining sliding and bridging into a unified model, we find that short-lived ParB bridges do not impede sliding and can reproduce both the binding profile and condensation of the nucleoprotein complex. Overall, our model elucidates the mechanism of partition complex formation and predicts its fine structure.

Usefulness of resorbable plate in auricular elevation in two-stage microtia reconstruction.

BACKGROUND: Achieving a well-reconstructed retroauricular sulcus with satisfactory projection and a sufficiently deep retroauricular sulcus is important and at the same time challenging. The selection of the support material is crucial to obtain a sustainable, deep sulcus. The costal cartilage is the conventional material of choice. However, risk of slippage of inserted cartilage and donor site morbidity exists. Resorbable plates are durable, easy to secure and can be easily modified into desired shape. The current study aimed to demonstrate the effectiveness of using a resorbable plate for auricular elevation. METHODS: Retrospective review of patients who received auricular elevation with resorbable plates from December 2020 to October 2022 was performed. Patients demographics, number of inserted plates and screws, postoperative complication were analyzed. RESULTS: Of 65 patients with microtia who underwent auricular reconstruction, resorbable plates were applied to 12 patients. Mean follow up period was 198 (range, 86-360) days. Auricular elevation was performed with one plate at cavum conchae and remnant rib cartilage at the helix in 10 patients (87)%. Two patients had resorbable plate as support material at the both sites. Regarding postoperative complications, there were no hematoma, seroma, plate exposure or plate fracture. Two patients suffered wound problems. One patient recovered only with conservative management. The other healed completely after debridement and intravenous antibiotics administration without undesired change of shape of ear. CONCLUSIONS: We suggest using resorbable plates as an ideal support material, as it can provide firm support to achieve appropriate depth of sulcus without excessive bulk.

Subtractive thinking: A novel combined application of antihelix reconstruction and outer helix reconstruction to treat mild cases of type I to II conchal microtia.

BACKGROUND: The management of mild cases of type Ⅰ to Ⅱ conchal microtia involves grafting cartilage to the affected ear to increase the cartilaginous area and transfer more skin to cover the larger cartilage. Herein, we performed a novel combined surgical procedure based on "subtractive thinking" that included antihelix reconstruction and outer helix reconstruction that was successful in patients with mild type I to II conchal microtia. METHODS: From January 2018 to September 2022, 65 patients with mild, unilateral, type I to II conchal microtia were enrolled in this study. All patients were treated with a novel method at the Plastic Surgery Hospital of Peking Union Medical College. The perimeters, widths, and lengths of the healthy and affected ears were measured both preoperatively and postoperatively. Patients' levels of satisfaction were determined based on postoperative results. RESULTS: The mean postoperative follow-up duration was 14.9 ± 2.65 months. All patients experienced no complications. Analysis revealed that our surgical method could effectively treat mild type I to II concha microtia irrespective of the auricular perimeter, width, and length (p < 0.0001). Furthermore, the patient satisfaction rate was 100%. CONCLUSION: The combined surgical procedure, which includes antihelix and outer helix reconstructions, is a viable method of reconstructing type I to II auricular concha microtia.

A reinforced framework construction technique using unilateral auricular cartilage in Asian rhinoplasty to prevent long-term nasal tip drooping.

BACKGROUND: Enhancing nasal tip projection is an important objective in Asian rhinoplasty. Nasal tip enhancement using auricular cartilage is simple and suitable for Asian patients. However, the long-term retraction problem of the auricular framework still needs to be solved for optimal results. OBJECTIVES: The authors propose a modified auricular cartilage framework construction technique that provides stronger long-term support to the nasal tip and columellar base. METHODS: Eighty-one patients underwent augmentation rhinoplasty between January 2016 and December 2019. The cymba and cavum conchae were harvested from one ear in all cases. The cymba concha was carved and folded to form a caudal septal extension graft (CSEG). The cavum concha was divided into an integrated cap/shield graft and a columella base graft. The columella base graft was diced into particles in size of 1 mm3, and inserted into the gap between CSEG, anterior nasal spine, and the medial crus to strengthen the foundation. The nasal profile was analyzed before the operation and at least 12 months after the operation. The patient satisfaction score was assessed 12 months after surgery. RESULTS: Patients were followed up for 12-36 months. The nasal tip projection from both the lateral and basal views was significantly improved. The columella-labial angle was increased from 83.15° (6.20°) to 96.50° (7.40°) (p < 0.05). The nostril tip proportion increased from 0.83 (0.14) to 1.17(0.16) (p < 0.01). A stable long-term outcome was achieved. CONCLUSIONS: With the modified framework construction technique, long-term nasal tip drooping can be prevented. This method can be a practical choice for Asian patients seeking augmentation rhinoplasty.

Firm elevation of the auricle in reconstruction of microtia with a retroauricular fascial flap wrapping two titanium plate struts.

BACKGROUND: Reconstruction of the cephaloauricular sulcus in patients with microtia in ear reconstructions remains challenging. Costal cartilage and other support materials wedge were used for ear elevation. Each material has its disadvantages. To reconstruct a stable cephaloauricular sulcus and reduce costal cartilage harvesting, we used two titanium plate struts to support the costal cartilage framework. METHODS: A titanium plate strut was designed. The angle of the strut was 60°, the arm length was 0.8 cm, and the width was 0.5 cm. The thickness was 0.6 mm. Four small pores are formed on the titanium plate. The implanted framework was separated from the underlying bed. Two titanium plate struts were fixed on the raised ear framework, tendon, and periosteum, and then wrapped with a turned-over retroauricular fascia flap. The raw surface was covered with a split-thickness skin graft, harvested from the scalp. RESULTS: From 2019 to 2022, 51 patients underwent second-stage operations. All patients were followed up for a minimum of 6 months. The auricular projection was well-maintained, and the cephaloauricular sulcus of the constructed auricle was acceptable in 50 patients. There was one infection, and the titanium plate struts were removed, which resulted in shrinking cephaloauricular angles. CONCLUSIONS: Titanium plate is effective as a supportive material to obtain the proper and firm projection of the constructed auricle. It provides a new option for patients whose costal cartilage volume is insufficient or who do not want to have the costal cartilage harvested again.

Ear reconstruction stage I: Minor modifications in sculpting the auricle support using the 7th and 8th costal cartilages.

BACKGROUND: The verisimilitude of the reconstructed auricle and its long-term stability largely depends on the framework sculpting. This study described three kinds of minor modifications based on Firmin's way of sculpting the auricle framework and reported the clinical outcomes achieved with them. METHODS: We conducted a retrospective study of congenital microtia patients undergoing detail-improved auricular reconstruction from June 2016 to June 2020. The three kinds of minor modifications included: (1) fabricating the base frame using the 7th costal cartilage, (2) fabricating the helix and the antihelix complex using the 8th costal cartilage, and (3) fabricating the helix using the combination of the 8th and 9th costal cartilage. RESULTS: Ninety-eight patients (aged 9-27 years, 62.2% male) were included. Ninety-five patients (97.0%) adopted minor modifications 1, 2, and 3 patients (3.0%) adopted minor modifications 1, 2, and 3. All patients achieved an excellent auricle appearance and a well-laid foundation for subsequent operations. During the follow-up period, 89 patients (90.8%) were satisfied with the reconstructed auricles, 6 (6.1%) complained of hypertrophic scars in the retroauricular sulcus or pigmentation in the skin graft area, and 3 (3.1%) developed surgery-related complications. CONCLUSIONS: Three minor modifications of the auricle framework sculpting can make more satisfactory use of cartilage and adjust with the flexibility of the reconstructed auricle in different situations, making it similar to the contralateral auricle, thus, improving patients' satisfaction.

Measurement of pressure discomfort threshold in auricular concha for in-ear wearables design.

In an effort to mitigate the homogenization of in-ear wearables, designers have been focusing on finding new solutions to enhance user comfort. While the concept of pressure discomfort thresholds (PDT) in humans has been applied to product design, research on the auricular concha remains scarce. In this study, we conducted an experiment to measure the PDT at six points in the auricular concha of 80 participants. Our results showed that the tragus was the most sensitive area and that gender, symmetry, and Body Mass Index (BMI)had no significant effect on PDT. Based on these findings, we generated pressure sensitivity maps of the auricular concha to aid in the optimization of in-ear wearable design.

Cartilage transposition and anchoring: A surgical technique for the reconstruction of congenital tragal malformation in children.

BACKGROUND: Because of the various types and complexity of congenital tragal malformation, tragal reconstruction is one of the most challenging objects in otoplasty. This study aimed to introduce a surgical technique of cartilage transposition and anchoring that was used to construct a cartilage framework for natural tragus reconstruction. METHODS: A retrospective study was performed for 49 patients who underwent cartilage transposition and anchoring from January 2020 to August 2022. Gender, age, malformation, complication, operation record, preoperative and postoperative photograph, score of esthetic outcomes (4 = excellent, 3 = good, 2 = fair, 1 = poor), and Vancouver Scar Assessment score were reviewed. RESULTS: Twenty-six boys and 23 girls with an average age of 35.79 ± 32.97 months underwent revision. The follow-up time was 13.87 ± 6.57 months. No complications were noted. The average score of esthetic outcomes and the Vancouver Scar Assessment score were 3.94 and 0.08 in the postoperative period, respectively. The overall effect was satisfactory. CONCLUSIONS: Postoperative results showed that cartilage transposition and anchoring were effective techniques for the reconstruction of congenital tragal malformation. The use of cartilage and fascia tissue around the tragus to fill up the depression and reconstruct the tragus were the emphases. The remolded tragus showed less scars and had the similar appearance like the natural tragus of the patient.