There has been a recent increase in our understanding in the isolation, culture, and differentiation of mesenchymal stem cells (MSCs). Concomitantly, the availability of MSCs has increased, with ...cells now commercially available, including human MSCs from adipose tissue and bone marrow. Despite an increased understanding of MSC biology and an increase in their availability, standardization of techniques for adipogenic differentiation of MSCs is lacking. The following review will explore the variability in adipogenic differentiation in vitro, specifically in 3T3-L1 and primary MSCs derived from both adipose tissue and bone marrow. A review of alternative methods of adipogenic induction is also presented, including the use of specific peroxisome proliferator-activated receptor-gamma agonists as well as bone morphogenetic proteins. Finally, we define a standard, commonly used adipogenic differentiation medium in the hopes that this will be adopted for the future standardization of laboratory techniques--however, we also highlight the essentially arbitrary nature of this decision. With the current, rapid pace of electronic publications, it becomes imperative for standardization of such basic techniques so that interlaboratory results may be easily compared and interpreted.
Nearly every enzyme undergoes a significant change in structure after binding it's substrate. Experimental and theoretical analyses of the role of changes in HIV reverse transcriptase structure in ...selecting a correct substrate are presented. Atomically detailed simulations using the Milestoning method predict a rate and free energy profile of the conformational change commensurate with experimental data. A large conformational change occurring on a millisecond timescale locks the correct nucleotide at the active site but promotes release of a mismatched nucleotide. The positions along the reaction coordinate that decide the yield of the reaction are not determined by the chemical step. Rather, the initial steps of weak substrate binding and protein conformational transition significantly enrich the yield of a reaction with a correct substrate, whereas the same steps diminish the reaction probability of an incorrect substrate.
► Kinetics and atomic simulations quantitatively explain nucleotide binding to HIV-RT ► Reaction path, free energy, and kinetics of HIV-RT transition are computed ► Simulations show that specificity is based on induced fit ► Specificity is determined by the rate of conformation change not only chemical step
Transcatheter aortic valve replacement (TAVR) has emerged as an alternative to surgical aortic valve replacement (SAVR), but unbiased data regarding evolution of the treatment of patients with aortic ...stenosis at the nationwide level are scarce.
This study sought to evaluate the number of aortic valve replacements (AVRs) performed in France, changes over time, and the effect of the adoption of TAVR.
Based on a French administrative hospital-discharge database, the study collected all consecutive AVRs performed in France between 2007 and 2015.
A total of 131,251 interventions were performed: 109,317 (83%) SAVR and 21,934 (17%) TAVR. AVR linearly increased (from 10,892 to 18,704; p for trend <0.0001) mainly due to a marked increase in TAVR (from 244 to 6,722; p for trend = 0.0004), whereas SAVR remained stable (from 10,892 to 11,982; p for trend = 0.18). Parallel to a decrease in the Charlson index (p for trend <0.05), SAVR and TAVR in-hospital mortality rates significantly declined (both p for trend <0.01). The number of TAVRs significantly increased in all age categories (<75, 75 to 79, 80 to 84, and ≥85 years of age; all p for trend = 0.003), but reached or even exceeded SAVR in the 2 oldest categories. Although mortality rates declined for both isolated SAVR and TAVR, it became similar or slightly lower for TAVR than for isolated SAVR in 2015 in the 3 oldest age categories even if it did not reach statistical significance (p = 0.66, p = 0.47, and p = 0.06, respectively).
The number of AVRs markedly increased in France between 2007 and 2015 due to the wide adoption of TAVR, which represented one-third of all AVRs in 2015. Patients’ profile improved, suggesting that patients are referred earlier, and in-hospital mortality declined in all AVR subsets. Despite a worse clinical profile, the immediate outcome of TAVR compared favorably to isolated SAVR in patients >75 years of age. The results may have major implications for clinical practice and policymakers.
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Abstract Background We examined the effect of primary surgeon (PS) and teaching assistant (TA) seniority on operative time and outcomes for residents performing laparoscopic cholecystectomy (LC). ...Methods This was a retrospective analysis of urgent LC at a county teaching hospital. Relevant data included postgraduate year (PGY) of the PS and TA and markers of disease severity. Primary outcome was operative time. Secondary outcomes were conversion to open cholecystectomy and complications. Results There were 1,202 LCs; 415 included an intraoperative cholangiogram. On multivariable analysis, every PGY increase of PS decreased operative time by 3.2 minutes ( P = .02). For every PGY increase of TA, operative time decreased 10.8 minutes ( P < .001). Acute or gangrenous pathology increased conversion to open surgery ( P < .001). Seniority of PS and TA was not associated with increases in conversion or complication rates. Conclusions Residents' operative time improves as experience with LC increases. These improvements become more profound after adjusting for the seniority of the TA.
Abstract Background The urgency of laparoscopic cholecystectomy for acute cholecystitis is under debate. We hypothesized that nighttime cholecystectomy is associated with decreased length of stay. ...Methods Retrospective review of 1,140 patients at 2 large urban referral centers with acute cholecystitis who underwent daytime (7 am to 7 pm) versus nighttime (7 pm to 7 am) cholecystectomy was conducted. Results Nighttime cholecystectomy did not affect the overall length of stay (3.7 vs 3.8 days, P = .08) or complication rate (5% vs 7%, P = .5) versus daytime cholecystectomy. Nighttime cholecystectomy was associated with a higher conversion rate to open cholecystectomy (11% vs 6%, P = .008). On multivariable analysis, independent predictors of conversion to open surgery were nighttime cholecystectomy, age, and gangrenous cholecystitis ( P = .01). The only predictor of complications was gangrenous cholecystitis ( P = .02). Conclusions Nighttime cholecystectomy is associated with an increased conversion to open surgery without decrease in length of stay or complications. These findings suggest that laparoscopic cholecystectomy for acute cholecystitis should be delayed until normal working hours.
Hepatitis C virus (HCV) infection is highly efficient in the establishment of persistent infection, which leads to the development of chronic liver disease and hepatocellular carcinoma. Impaired T ...cell responses with reduced IFN-γ production have been reported to be associated with persistent HCV infection. Extracellular HCV core is a viral factor known to cause HCV-induced T cell impairment via its suppressive effect on the activation and induction of pro-inflammatory responses by antigen-presenting cells (APCs). The activation of STAT proteins has been reported to regulate the inflammatory responses and differentiation of APCs. To further characterize the molecular basis for the regulation of APC function by extracellular HCV core, we examined the ability of extracellular HCV core to activate STAT family members (STAT1, -2, -3, -5, and -6). In this study, we report the activation of STAT3 on human monocytes, macrophages, and dendritic cells following treatment with extracellular HCV core as well as treatment with a gC1qR agonistic monoclonal antibody. Importantly, HCV core-induced STAT3 activation is dependent on the activation of the PI3K/Akt pathway. In addition, the production of multifunctional cytokine IL-6 is essential for HCV core-induced STAT3 activation. These results suggest that HCV core-induced STAT3 activation plays a critical role in the alteration of inflammatory responses by APCs, leading to impaired anti-viral T cell responses during HCV infection.
Objective As vascular surgeons strive to meet the Fistula First Initiative, some authors have observed a decrease in arteriovenous fistula (AVF) maturation rates in association with an increase in ...AVF creation. In May 2012, we adopted a practice change in an attempt to maintain the same high level of AVF creation while leading to a decrease in fistula failures. Methods A retrospective study was conducted of all dialysis access procedures performed by a single vascular surgeon before (period 1; before May 1, 2012) and after (period 2; after May 1, 2012) the change in practice pattern. The adopted change included favoring the brachiocephalic location unless the patient was an ideal anatomic candidate for a radiocephalic AVF, creating a larger and standardized arteriotomy, and using a large venous footplate whenever possible. The main outcome measure was primary functional patency at 1 year. Secondary outcome measures included primary patency at 1 year, time to maturation, type of fistula created, steal syndrome, and tunneled hemodialysis catheter infections. Results Of 213 vascular access procedures performed, 191 (90%) were AVFs. There was no difference in use of AVFs between period 1 (93% AVFs) and period 2 (88% AVFs; P = .2). Use of brachiocephalic AVFs increased from 38% in period 1 to 56% in period 2 ( P = .01), with a corresponding trend toward a decrease in radiocephalic AVFs in period 2 (36% in period 1 to 27% in period 2; P = .2). Primary functional patency at 1 year was 47% in period 1 and 63% in period 2 ( P = .03). Primary patency at 1 year was 51% in period 1 and 70% in period 2 ( P = .001). Time to reach functional maturation was decreased in period 2 (median, 76 vs 82.5 days; P = .046). There was no difference in steal syndrome ( P = 1.0), and the incidence of hemodialysis catheter infections was lower in period 2 (0 vs 7 7%; P = .006). Conclusions Increasing brachiocephalic AVF creation and reducing our reliance on radiocephalic AVFs resulted in a significant increase in primary functional patency at 1 year. This was achieved while maintaining the same high percentage of fistulas, a lower rate of central catheter infections, and the same low incidence of steal syndrome.
Determinants of the progression of aortic stenosis (AS) remained unclear. Metabolic syndrome (MetS) and diabetes are suspected to play an active role but literature is scarce and results conflicting. ...We sought to assess their impact in an ongoing prospective cohort of asymptomatic patients with at least mild AS.
We enrolled 203 patients (73±9years, 75% men) with at least 2years of follow-up. Risk-factors assessment was performed at baseline. Annual progression was calculated as (final-baseline measurements)/follow-up duration for both mean pressure gradient (MPG) and degree of aortic valve calcification (AVC) measurements.
Ninety-nine patients (49%) had MetS and 50 (25%) had diabetes (including 39 with MetS). After a mean follow-up of 3.2±1.2years, AS progression was not different between patients with and without MetS either using MPG (+3±3 vs. +4±4mmHg/year, p=0.25) or AVC (+211±231 vs. +225±222AU/year, p=0.75). Same results were obtained for patients with diabetes (3±3 vs. 4±4mmHg/year p=0.53, 187±140 vs. 229±248AU/year p=0.99). MetS had no impact on AS progression in all tested subgroups based on age, statin prescription, valve anatomy and AS severity (all p≥0.10).
In our prospective cohort of AS patients, we found no impact of MetS or diabetes on AS progression. Although MetS and diabetes should be actively treated, no impact on AS progression should be expected. Our results support the theory that if cardiovascular risk-factors may play a role at the early phase of AS disease they have no or limited influence on AS progression.
Whether a percutaneous mitral commissurotomy (PMC) should be attempted in patients with mitral stenosis (MS) and valvular calcification, especially located at the commissural level remained debated. ...We sought to evaluate the impact of the degree and location of mitral valve calcifications on PMC results.
Over a 3-year period, we enrolled 464 consecutive patients who underwent a PMC at our institution. According to the location (within the body valve leaflets' or at the commissural level) and the degree of calcification, patients were divided into three groups: 261 patients were in Group 1 (no leaflets' or commissural calcification), 141 in Group 2 (leaflets' calcification with no significant commissural calcification), and 62 in Group 3 (at least one commissure significantly calcified). Final valve area (1.83 ± 0.26, 1.71 ± 0.25, and 1.60 ± 0.24 cm(2), P < 0.00001) and the rate of complete opening of at least one commissure (92, 94, and 84%, P = 0.05) were significantly different. However, the rate of post-PMC mitral regurgitation (MR) of grade ≥ 3 (10, 10, and 8%, P = 0.90) was not different among the groups and if the rate of good immediate result, defined as valve area ≥ 1.5 cm(2) with no MR >2/4 was different among the three groups (88, 78, and 73%, P = 0.004), an overallprocedural success could be achieved in most patients with calcified commissures.
In this large contemporary series of patients with MS, a procedural success was obtained less frequently in patients with calcified commissure but a successful PMC could still be safely achieved in a large proportion of patients. Our results support the use of PMC as a first-line treatment of patients with severe MS even in the presence of significant commissural calcifications with otherwise favourable clinical characteristics.
Abstract Background The prognostic value of N-terminal fragment of pro B-type natriuretic peptide (Nt-proBNP) in aortic stenosis (AS) is still being debated. We sought to evaluate the determinants of ...Nt-proBNP in AS and its prognostic value in asymptomatic patients. Methods Patients with pure isolated at least mild degenerative AS enrolled in our prospective cohort (2006–2013) constituted our population. Clinical and biological measurements as well as echocardiographic evaluations were performed at study entry for all patients. Severe AS was defined by a valve area < 1 cm2 . Asymptomatic patients were contacted every six months and seen every year. The occurrence of AS-related events (sudden death, congestive heart failure or new onset of symptoms) within two years was recorded prospectively. Results We enrolled 809 patients. Nt-proBNP increased with AS severity ( p < 0.0001) and symptomatic status ( p < 0.0001) but there was a wide overlap between groups of AS severity or symptomatic status. Nt-proBNP was the result of complex interactions between multiple determinants, including AS severity and symptomatic status but also age ( p = 0.0008), history of coronary artery disease ( p = 0.03), rhythm ( p = 0.007) and diastolic function ( p < 0.0001). Consequently, in asymptomatic patients with moderate/severe AS, normal ejection fraction and in sinus rhythm, Nt-proBNP was associated with AS-related events in univariate analysis ( p = 0.009) but not after adjustment for AS severity ( p = 0.12). Repeated Nt-proBNP measurements at one year did not improve their predictive value ( p = 0.43). Conclusion This study highlights the limitations of Nt-proBNP in AS and raises caution regarding its use, at least as a single factor, in the decision-making process regarding asymptomatic patients with AS.
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