Factors Associated With Increased Estimated Blood Loss and Factors Associated With Utilization of Type and Screen in Benign Gynecology: A Retrospective Chart Review.

IMPORTANCE: There is minimal literature discussing factors associated with increased estimated blood loss (EBL) or transfusion in gynecologic surgery in tertiary academic centers. OBJECTIVE: The aim of the study was to determine factors associated with transfusion and increased blood loss during gynecologic surgery. STUDY DESIGN: This retrospective cohort investigated patients undergoing benign gynecologic procedures at a tertiary medical center. We excluded women undergoing surgery for known or suspected malignancy, emergent surgery, obstetrical procedures, or cases with another surgical specialty. Patient age, body mass index, American Society of Anesthesiologists class, medical history, EBL, arterial line placement, preoperative laboratory studies, and transfusion receipt for up to 6 weeks postoperatively were extracted. The primary outcome was transfusion within 6 weeks of surgery; risk factors for high blood loss (EBL >500 mL) and transfusion were explored. RESULTS: Nine hundred seventy-five surgical procedures were included (59% vaginal, 36% laparoscopic, 4% robotic). Median EBL was 50 mL (interquartile range, 10-100 mL). Estimated blood loss increased with duration of surgery (P < 0.01). Transfusions were more likely to occur during open procedures (13%) compared with vaginal (2%), laparoscopic (2%), or robotic (3%). Arterial line placement (relative risk [RR], 11.8; 95% confidence interval [CI], 5.3-26.1) and additional intravenous placement (RR, 6.0; 95% CI, 2.6 to 13.7) were associated with transfusion. Vaginal surgery (RR, 0.13; 95% CI, 0.05 to 0.32) and urogynecologic procedures (RR, 0.1; CI, 0.01-0.7) were associated with reduced risk of needing transfusion. CONCLUSIONS: Most benign gynecologic surgical procedures have minimal blood loss. Patients undergoing surgery through minimally invasive routes or urogynecologic procedures are at further decreased risk of transfusion.

Bistability of a coupled Aurora B kinase-phosphatase system in cell division.

Aurora B kinase, a key regulator of cell division, localizes to specific cellular locations, but the regulatory mechanisms responsible for phosphorylation of substrates located remotely from kinase enrichment sites are unclear. Here, we provide evidence that this activity at a distance depends on both sites of high kinase concentration and the bistability of a coupled kinase-phosphatase system. We reconstitute this bistable behavior and hysteresis using purified components to reveal co-existence of distinct high and low Aurora B activity states, sustained by a two-component kinase autoactivation mechanism. Furthermore, we demonstrate these non-linear regimes in live cells using a FRET-based phosphorylation sensor, and provide a mechanistic theoretical model for spatial regulation of Aurora B phosphorylation. We propose that bistability of an Aurora B-phosphatase system underlies formation of spatial phosphorylation patterns, which are generated and spread from sites of kinase autoactivation, thereby regulating cell division.

Minimal model for collective kinetochore-microtubule dynamics.

Chromosome segregation during cell division depends on interactions of kinetochores with dynamic microtubules (MTs). In many eukaryotes, each kinetochore binds multiple MTs, but the collective behavior of these coupled MTs is not well understood. We present a minimal model for collective kinetochore-MT dynamics, based on in vitro measurements of individual MTs and their dependence on force and kinetochore phosphorylation by Aurora B kinase. For a system of multiple MTs connected to the same kinetochore, the force-velocity relation has a bistable regime with two possible steady-state velocities: rapid shortening or slow growth. Bistability, combined with the difference between the growing and shrinking speeds, leads to center-of-mass and breathing oscillations in bioriented sister kinetochore pairs. Kinetochore phosphorylation shifts the bistable region to higher tensions, so that only the rapidly shortening state is stable at low tension. Thus, phosphorylation leads to error correction for kinetochores that are not under tension. We challenged the model with new experiments, using chemically induced dimerization to enhance Aurora B activity at metaphase kinetochores. The model suggests that the experimentally observed disordering of the metaphase plate occurs because phosphorylation increases kinetochore speeds by biasing MTs to shrink. Our minimal model qualitatively captures certain characteristic features of kinetochore dynamics, illustrates how biochemical signals such as phosphorylation may regulate the dynamics, and provides a theoretical framework for understanding other factors that control the dynamics in vivo.

Localized light-induced protein dimerization in living cells using a photocaged dimerizer.

Regulated protein localization is critical for many cellular processes. Several techniques have been developed for experimental control over protein localization, including chemically induced and light-induced dimerization, which both provide temporal control. Light-induced dimerization offers the distinct advantage of spatial precision within subcellular length scales. A number of elegant systems have been reported that utilize natural light-sensitive proteins to induce dimerization via direct protein-protein binding interactions, but the application of these systems at cellular locations beyond the plasma membrane has been limited. Here we present a new technique to rapidly and reversibly control protein localization in living cells with subcellular spatial resolution using a cell-permeable, photoactivatable chemical inducer of dimerization. We demonstrate light-induced recruitment of a cytosolic protein to individual centromeres, kinetochores, mitochondria and centrosomes in human cells, indicating that our system is widely applicable to many cellular locations.