In motile cilia, a mechanoregulatory network is responsible for converting the action of thousands of dynein motors bound to doublet microtubules into a single propulsive waveform. Here, we use two complementary cryo-EM strategies to determine structures of the major mechanoregulators that bind ciliary doublet microtubules in Chlamydomonas reinhardtii . We determine structures of isolated radial spoke RS1, and the microtubule-bound RS1, RS2, and the nexin-dynein regulatory complex. From these structures, we identify and build atomic models for 30 proteins including 23 radial-spoke subunits. We reveal how mechanoregulatory complexes dock to doublet microtubules with regular 96-nm periodicity and communicate with one another. Additionally, we observe a direct and dynamically coupled association between RS2 and the dynein motor IDA c , providing a molecular basis for the control of motor activity by mechanical signals. These structures advance our understanding of the role of mechanoregulation in defining the ciliary waveform.

Purpose COVID-19 greatly affected millions and affected the way we practice with heightened posture in the way we treat surgical patients. Surgical consensus guidelines are recommending caution in the use of laparoscopy for the theoretical possibility of viral transmission from aerosolization of tissue and peritoneal fluid during surgery. However, there has yet to be proof of COVID-19 being present in peritoneal fluid, justifying the consensus statements. We aim to assess the presence of COVID-19 in peritoneal fluid. Methods We performed a laparoscopic appendicectomy for a COVID-19-infected patient with acute appendicitis. Peritoneal fluid and peritoneal washings were collected and sent for COVID-19 PCR. Results The peritoneal fluid sample collected on entry and at the end of the operation was negative for COVID-19 on PCR. The patient had an uneventful recovery from surgery.

Background With increasing global life expectancy, the number of major surgeries performed on aged adults invariably increases. This study aimed to examine the effectiveness of a structured prehabilitative program for aged colorectal cancer patients in improving short‐term surgical outcomes. Methods A prospective philanthropically sponsored Programme for Enhanced Elderly Recovery at Sengkang General Hospital (PEERS) was initiated in February 2017 for patients ≥70‐years‐old who were due to undergo elective colectomies. These patients were put through a 2‐ to 4‐week‐long program before surgery, which included geriatric assessment, nutrition supplementation, and resistance training. They were compared with patients from a similar age group before PEERS was introduced (non‐PEERS). Results Fifty‐eight patients, with a median age of 78.5 (70–93) years, were recruited from a single institution to undergo PEERS. Baseline characteristics between the groups were similar. There was no significant improvement of anthropometric and functional characteristics before and after PEERS. Duration of hospitalization was shorter in the PEERS group (9 vs 11 days, P = 0.01). Both groups had similar 30‐days’ morbidity rates (8.6% vs 17.4%, P = 0.26). The PEERS group had significant improvement in their median EuroQol‐5 Dimension score (0.70 presurgery to 0.80 6‐months’ postsurgery, P = 0.01). After multivariate analysis, the average duration of hospitalization in the PEERS group was 6.8 days shorter (P = 0.018; CI, 1.2–12.4) after adjusting for modality of surgery and complications. This represented a cost saving of USD$11,838.80. Conclusion A standardized prehabilitation program for aged adults reduced the duration of hospitalization, improved the quality of life after surgery, and reduced costs.

No abstract

No abstract

Surgery for octogenarians with colorectal cancers is associated with significant morbidity and mortality rates which are associated with advanced age, emergency surgery, and Charlson Comorbidity Index >3. Long-term survival is dependent on the stage of the malignancy and the presence of severe perioperative complications.

Here we report the discovery of a bacterial DNA-segregating actinlike protein (BtParM) from Bacillus thuringiensis, which forms novel antiparallel, two-stranded, supercoiled, nonpolar helical filaments, as determined by electron microscopy. The BtParM filament features of supercoiling and forming antiparallel double-strands are unique within the actin fold superfamily, and entirely different to the straight, double-stranded, polar helical filaments of all other known ParMs and of eukaryotic F-actin. The BtParM polymers show dynamic assembly and subsequent disassembly in the presence of ATP. BtParR, the DNA-BtParM linking protein, stimulated ATP hydrolysis/phosphate release by BtParM and paired two supercoiled BtParM filaments to form a cylinder, comprised of four strands with inner and outer diameters of 57 Å and 145 Å, respectively. Thus, in this prokaryote, the actin fold has evolved to produce a filament system with comparable features to the eukaryotic chromosomesegregating microtubule.D uring bacterial cell division, equal distribution of replicated plasmids to the two daughter cells ensures their stable inheritance. Type II plasmid segregation systems consist of an actin-like protein (ParM) capable of nucleotide-dependent filament formation and a centrosome-like DNA region (parC), which are linked by an adaptor protein ParR. The model ParCMR system is that of the Escherichia coli R1 plasmid (1). ParM-R1 forms actin-like double-helical straight polar filaments (2), which are paired into randomly oriented bundles. The antiparallel pairing of at least two filaments is required to push apart two R1-ParR/parC complexes (3). All other ParMs, which have been experimentally verified to segregate DNA, including AlfA from Bacillus subtilis (4) and ParM-pSK41 from Staphylococcus aureus (5), have also been shown by electron microscopy to form polar, double-stranded straight filaments with diameters between 80 and 90 Å, similar to eukaryotic F-actin (6).Actins and microtubules have gained dedicated functions during evolution that vary between eukaryotes and prokaryotes. During cell division, the contractile ring in prokaryotes depends on the microtubule-like protein FtsZ, whereas this task relies on actin in eukaryotes. In contrast, DNA segregation in eukaryotes is orchestrated by microtubules, whereas in prokaryotes plasmid DNA segregation depends largely on the actin-like proteins ParMs, although Walker-type ATPase ParA (type I) systems (7) and microtubule-like TubZ (type III) systems have also been found (8). Therefore, a long-standing question has been whether a functional equivalent of the microtubule-like DNA segregating architecture, a hollow cylinder, can be found in bacteria.Using X-ray crystallography, electron microscopy and biochemical assays, we have identified and characterized a novel DNA partitioning ParCMR system from Bacillus thuringiensis (Bt) encoded on the plasmid pBMB67 (9). The filament-forming motor protein, BtParM, proved to be entirely different from all previously studied ParMs; in contrast t...

Mesenteric embolization was found to be safe and effective in treating LGIB (100% technical success, no post-embolization ischaemia), with 65.4% of cases not requiring further intervention. Low platelet count prior to embolization appears to be associated with clinical failure.