Re-evaluating the Need for Routine Maximal Aerobic Capacity Testing within Fighter Pilots.

INTRODUCTION: There is a current belief in aviation suggesting that aerobic training may reduce G-tolerance due to potential negative impacts on arterial pressure response. Studies indicate that increasing maximal aerobic capacity (V˙o2 max) through aerobic training does not hinder G-tolerance. Moreover, sustained centrifuge training programs revealed no instances where excessive aerobic exercise compromised a trainee's ability to complete target profiles. The purpose of this review article is to examine the current research in the hope of establishing the need for routine V˙o2-max testing in air force pilot protocols.METHODS: A systematic search of electronic databases including Google Scholar, PubMed, the Aerospace Medical Association, and Military Medicine was conducted. Keywords related to "human performance," "Air Force fighter pilots," "aerobic function," and "maximal aerobic capacity" were used in various combinations. Articles addressing exercise physiology, G-tolerance, physical training, and fighter pilot maneuvers related to human performance were considered. No primary data collection involving human subjects was conducted; therefore, ethical approval was not required.RESULTS: The V˙o2-max test provides essential information regarding a pilot's ability to handle increased Gz-load. It assists in predicting G-induced loss of consciousness by assessing anti-G straining maneuver performance and heart rate variables during increased G-load.DISCUSSION: V˙o2-max testing guides tailored exercise plans, optimizes cardiovascular health, and disproves the notion that aerobic training hampers G-tolerance. Its inclusion in air force protocols could boost readiness, reduce health risks, and refine training for fighter pilots' safety and performance. This evidence-backed approach supports integrating V˙o2-max testing for insights into fitness, risks, and tailored exercise.Zeigler Z, Acevedo AM. Re-evaluating the need for routine maximal aerobic capacity testing within fighter pilots. Aerosp Med Hum Perform. 2024; 95(5):273-277.

A quantitative comparison of urine centrifugation and filtration for the isolation and analysis of urinary nucleic acid biomarkers.

Urine is a rich source of nucleic acid biomarkers including cell-free DNA (cfDNA) and RNA for monitoring the health of kidney allografts. In this study, we aimed to evaluate whether urine filtration can serve as an alternative to the commonly used method of centrifugation to collect urinary fluid and cell pellets for isolating cfDNA and cellular messenger RNA (mRNA). We collected urine specimens from kidney allograft recipients and obtained the urine supernatant and cell pellet from each specimen using both filtration and centrifugation for paired analyses. We performed DNA sequencing to characterize the origin and properties of cfDNA, as well as quantitative PCR of mRNAs extracted from cell fractions. Our results showed that the biophysical properties of cfDNA, the microbial DNA content, and the tissues of origin of cfDNA were comparable between samples processed using filtration and centrifugation method. Similarly, mRNA quality and quantity obtained using both methods met our criteria for downstream application and the Ct values for each mRNA were comparable between the two techniques.The Ct values demonstrated a high degree of correlation. These findings suggest that urine filtration is a viable alternative to urine centrifugation for isolation of nucleic acid biomarkers from urine specimens.

Characterization and pharmacokinetics of cinnamon and star anise compound essential oil pellets prepared via centrifugal granulation technology.

Cinnamon and star anise essential oils are extracted from natural plants and provide a theoretical basis for the development and clinical application of compound essential oil pellets. However, cinnamon oil and star anise oil have the characteristics of a pungent taste, extreme volatility, poor palatability, and unstable physical and chemical properties, which limit their clinical use in veterinary medicine. In this study, the inhibitory effects of cinnamon oil and star anise oil on Escherichia coli and Salmonella were measured. Compound essential oil pellets were successfully prepared by centrifugal granulation technology. Subsequently, the in vitro dissolution of the pellets and their pharmacokinetics in pigs were investigated. The results showd that, cinnamon and star anise oils showed synergistic or additive inhibitiory effects on Escherichia coli and Salmonella. The oil pellets had enteric characteristics in vitro and high dissolution in vitro. The pharmacokinetic results showed that the pharmacokinetic parameters Cmax and AUC were directly correlated with the dosage and showed linear pharmacokinetic characteristics, which provided a theoretical basis for the development and clinical application of compound essential oil pellets.

Magnetic field assisted centrifugal acceleration thin-layer chromatography: An approach to investigate the magnetic field effects on separation parameters including retention factor difference, selectivity factor, and resolution.

The effect of internal and external magnetic fields on the separation of antifungal drugs by centrifugal acceleration thin-layer chromatography was reported for the first time. External and internal magnetic fields were applied using neodymium magnets and CoFe2O4@SiO2 ferromagnetic nanoparticles. Separation of ketoconazole and clotrimazole was performed using a mobile phase consisting of n-hexane, ethyl acetate, ethanol, and ammonia (2.0:2.0:0.5:0.2, v/v). The influence of the magnetic field on the entire chromatographic system led to changes in the properties of the stationary and mobile phases and the analytes affecting the retention factor, shape, and width of the separated rings. The extent of this impact depended on the structure of the analyte and the type and intensity of the magnetic field. In the presence of the external magnetic field, there were more significant changes in the chromatographic parameters of the drugs, especially the width of the separated rings, and ketoconazole was more affected than clotrimazole. The changes are conceivably due to the effect of the magnetic field on the analyte distribution between the stationary and mobile phases, which is also caused by the possibility of the magnetic field affecting the viscosity, surface tension, and surface free energy between the stationary and mobile phases.

Developing centrifugal force real-time digital PCR for detecting extremely low DNA concentration.

Digital PCR (dPCR) is a technique for absolute quantification of nucleic acid molecules. To develop a dPCR technique that enables more accurate nucleic acid detection and quantification, we established a novel dPCR apparatus known as centrifugal force real-time dPCR (crdPCR). This system is efficient than other systems with only 2.14% liquid loss by dispensing samples using centrifugal force. Moreover, we applied a technique for analyzing the real-time graph of the each micro-wells and distinguishing true/false positives using artificial intelligence to mitigate the rain, a persistent issue with dPCR. The limits of detection and quantification were 1.38 and 4.19 copies/µL, respectively, showing a two-fold higher sensitivity than that of other comparable devices. With the integration of this new technology, crdPCR will significantly contribute to research on next-generation PCR targeting absolute micro-analysis.

Transient Performance Analysis of Centrifugal Left Ventricular Assist Devices Coupled With Windkessel Model: Large Eddy Simulations Study on Continuous and Pulsatile Flow Operation.

Computational fluid dynamics (CFD) simulations are widely used to develop and analyze blood-contacting medical devices such as left ventricular assist devices (LVADs). This work presents an analysis of the transient behavior of two centrifugal LVADs with different designs: HeartWare VAD and HeartMate3. A scale-resolving methodology is followed through Large Eddy Simulations, which allows for the visualization of turbulent structures. The three-dimensional (3D) LVAD models are coupled to a zero-dimensional (0D) 2-element Windkessel model, which accounts for the vascular resistance and compliance of the arterial system downstream of the device. Furthermore, both continuous- and pulsatile-flow operation modes are analyzed. For the pulsatile conditions, the artificial pulse of HeartMate3 is imposed, leading to a larger variation of performance variables in HeartWare VAD than in HeartMate3. Moreover, CFD results of pulsatile-flow simulations are compared to those obtained by accessing the quasi-steady maps of the pumps. The quasi-steady approach is a predictive tool used to provide a preliminary approximation of the pulsatile evolution of flow rate, pressure head, and power, by only imposing a speed pulse and vascular parameters. This preliminary quasi-steady solution can be useful for deciding the characteristics of the pulsatile speed law before running a transient CFD simulation, as the former entails a significant reduction in computational cost in comparison to the latter.

Separation of ochratoxins by centrifugal partition chromatography.

The present research work was dedicated to developing an efficient method based on liquid-liquid chromatography (centrifugal partition chromatography, CPC) applicable to routine purifications of ochratoxins (OT) from the liquid culture of the strain A. albertensis SZMC 2107. The crude extract contained numerous components in addition to OTA (90.1 %,) and OTB (1.1 %,) according to HPLC examinations. For the separation of OTs by CPC, several tertiary systems based on acetonitrile, acetone, and short-chain alcohols were examined to find the most applicable biphasic system. The hexane/i-propanol/water 35:15:50 system supplemented with 0.1 % acetic acid was found to be the most efficient for use in CPC separation. Using liquid-liquid instrumental separation, the two OTs, namely OTA (2.23 mg) and OTB (0.031 mg), were successfully isolated with 96.3 % and-72.8 % purity, respectively, from 1 L ferment broth. The identities and purities of the purified components were confirmed and the performance parameters of each separation step and the whole procedure were determined. The developed method could be used effectively to purify OTs for analytical or toxicological applications.

Centrifugo-Pneumatic Reciprocating Flowing Coupled with a Spatial Confinement Strategy for an Ultrafast Multiplexed Immunoassay.

Immunoassays serve as powerful diagnostic tools for early disease screening, process monitoring, and precision treatment. However, the current methods are limited by high costs, prolonged processing times (>2 h), and operational complexities that hinder their widespread application in point-of-care testing. Here, we propose a novel centrifugo-pneumatic reciprocating flowing coupled with spatial confinement strategy, termed PRCM, for ultrafast multiplexed immunoassay of pathogens on a centrifugal microfluidic platform. Each chip consists of four replicated units; each unit allows simultaneous detection of three targets, thereby facilitating high-throughput parallel analysis of multiple targets. The PRCM platform enables sequential execution of critical steps such as solution mixing, reaction, and drainage by coordinating inherent parameters, including motor rotation speed, rotation direction, and acceleration/deceleration. By integrating centrifugal-mediated pneumatic reciprocating flow with spatial confinement strategies, we significantly reduce the duration of immune binding from 30 to 5 min, enabling completion of the entire testing process within 20 min. As proof of concept, we conducted a simultaneous comparative test on- and off-the-microfluidics using 12 negative and positive clinical samples. The outcomes yielded 100% accuracy in detecting the presence or absence of the SARS-CoV-2 virus, thus highlighting the potential of our PRCM system for multiplexed point-of-care immunoassays.

Automated sample preparation for electrospray ionization mass spectrometry based on CLOCK-controlled autonomous centrifugal microfluidics.

We report a centrifugal microfluidic device that automatically performs sample preparation under steady-state rotation for clinical applications using mass spectrometry. The autonomous microfluidic device was designed for the control of liquid operation on centrifugal hydrokinetics (CLOCK) paradigm. The reported device was highly stable, with less than 7% variation with respect to the time of each unit operation (sample extraction, mixing, and supernatant extraction) in the preparation process. An agitation mechanism with bubbling was used to mix the sample and organic solvent in this device. We confirmed that the device effectively removed the protein aggregates from the sample, and the performance was comparable to those of conventional manual sample preparation procedures that use high-speed centrifugation. In addition, probe electrospray ionization mass spectrometry (PESI-MS) was performed to compare the device-treated and manually treated samples. The obtained PESI-MS spectra were analyzed by partial least squares discriminant analysis, and the preparation capability of the device was found to be equivalent to that of the conventional method.

Examination of ejaculate fructose levels on male infertility patients at various times and centrifugation using semiautomatic method.

OBJECTIVE: Various factors, such as obstructive azoospermia, cause infertility in men. Biochemical examination of ejaculate, especially measurement of fructose, can be an additional investigation that can be used for this diagnosis in reproductive health. Examination of fructose is carried out after routine ejaculate analysis, resulting in prolonging the examination time so that it will affect the measurement of fructose level in the ejaculate and the accuracy of the diagnosis. This study aims to determine the best timing and procedure for measurement of fructose using a semiautomatic method. METHODS: This research is an analytic observational study conducted at Dr. Soetomo General Hospital, Surabaya. A total of 13 ejaculate samples from infertile male patients who met the inclusion criteria were evaluated. Each ejaculate was divided into eight aliquots that were examined for fructose using a semiautomated method after different intervals of time and centrifugation modalities. RESULTS: This study showed a significant difference in fructose levels when aliquots were centrifuged and examined immediately or after different interval of time (p=0.036). In addition, aliquots left standing for more than 60 minutes (p=0.012) and 120 minutes (p<0.001) before centrifugation, showed significantly lower levels compared to aliquots that were centrifuged and then immediately examined. CONCLUSIONS: We suggest that measuring fructose immediately after centrifugation is more reliable than measuring fructose left standing before or after centrifugation. Leaving the ejaculate standing will reduce the fructose level so that it does not resemble its real level.

Five days serum glucose stability at room-temperature in centrifuged fast-clotting serum tubes and the comparability with glucose in heparin-plasma and plasma containing citrate-stabilizer.

Glucose measurement plays a central role in the diagnosis of gestational diabetes mellitus (GDM). Because of earlier reports of overestimation of glucose in the widely used tubes containing granulated glycolysis inhibitor, the study assessed the performance of fast-clotting serum tubes as an alternative sample for the measurement of glucose. Glucose concentration in fast-clotting serum was compared to lithium-heparin plasma placed in an ice-water slurry after sample collection and glucose stability at room-temperature was studied. Blood samples from 30 volunteers were drawn in four different types of tubes (serum separator tubes, fast-clotting serum tubes, lithium-heparin tubes and sodium fluoride, EDTA and a citrate buffer (NaF-EDTA-citrate) tubes, all from Greiner Bio-One). Lithium-heparin tubes were placed in an ice-water slurry until centrifugation in accordance with international recommendations and centrifuged within 10 min. After centrifugation, glucose was measured in all tubes (timepoint T0) and after 24, 48, 72, 96 and 120 h of storage at 20-22 °C. NaF-EDTA-citrate plasma showed significant overestimation of glucose concentration by 4.7% compared to lithium-heparin plasma; fast-clotting serum showed glucose concentrations clinically equivalent to lithium-heparin plasma. In fast-clotting serum tubes, mean bias between glucose concentration after 24, 48, 72, 96 and 120 h and T0 was less than 2.4%. All individual differences compared to T0 were less than 6.5%. The results fulfill the acceptance criteria for sample stability based on biological variation. Fast-clotting serum tubes can be an alternative for the measurement of glucose in diagnosis and management of GDM and diabetes mellitus, especially when prolonged transportation is necessary.

Isolation of Extracellular Vesicles Using Formulas to Adapt Centrifugation to Different Centrifuges.

Extracellular vesicles (EVs) are small lipid bilayer vesicles released by cells to facilitate cell-to-cell communication. To study their biological roles and functions, they need to be isolated and purified, which can be achieved through a variety of methods. Here, we describe different methods for isolating and purifying EVs, with a focus on calculating the required g-force and centrifugation time with different centrifuges and rotors. We have compiled key formulas and tested predicted parameters for EV acquisitions to provide a comprehensive guide for EV isolation.

Effect of storage and single layer centrifugation before cryopreservation on stallion sperm cryosurvival.

The objectives of this study were to evaluate the effect of a short, cooled storage before cryopreservation on sperm progressive motility (PM) and compare the effect of different centrifugation methods on post-thaw PM of stored samples. Semen was diluted in chilling extender and aliquoted in 6 protocols: i) Standard centrifugation (SC) followed by freezing; ii) Single Layer Centrifugation (SLC) followed by freezing; iii) Storage for 8 h/5 °C before SC; iv) Storage for 8 h/5 °C before SLC; v) Storage for 8 h/15 °C before SC; and vi) Storage for 8 h/15 °C before SLC. PM was assessed before centrifugation, after centrifugation, and post-thawing. Stallions were classified as "good freezers" (GF) or "bad freezers" (BF). The PM in samples immediately frozen was greater than in the stored ones (71.98 ± 14.2, 52.91 ± 17.8, 53.93 ± 18.9 for no storage, 5 ºC storage and 15 ºC storage, respectively) (P˂ 0.0001). There was an effect of storage condition (p ˂ 0.0001), centrifugation method (p ˂ 0.0001), and freezability (P=0.0016), with an interaction between them (P= 0.0004), on PM after centrifugation. Post-thaw PM was greater in samples treated by SLC than in samples processed by SC, for all storage conditions (p ˂ 0.05). All BF stallions 'showed post-thaw PM ˂ 30 % when samples were previously stored. Storage at 5 ºC or 15º C for 8 h maintains an appropriate quality in GF stallions. Applying a sperm selection technique as SLC is suggested to improve post-thaw motility, allowing GF straws to be frozen after storage, although BF semen should be prepared by SLC immediately after collection.

Delayed centrifugation weakens the in vitro biological properties of platelet-rich fibrin membranes.

OBJECTIVE: To investigate how delayed blood centrifugation affects the composition of the resultant platelet rich fibrin membrane (PRF, a concentrated growth factor preparation) and its biological effects towards gingival fibroblasts. MATERIALS AND METHODS: Blood samples were collected from 18 healthy individuals and centrifuged immediately (T-0), or after a 1-6-minute delay (T-1-6, respectively), to generate PRF. Each PRF membrane was weighed. T-0 and T-6 membranes were incubated for 48 h in cell culture medium at 37 °C to create PRF "releasates" (soluble factors released from the PRF). Human gingival fibroblasts were incubated for 48 h with or without the releasates, followed by RNA isolation and real-time polymerase chain reaction to measure expression of select genes associated with granulation tissue formation, angiogenesis and wound contraction. Additional T-0 and T-6 membranes were used for visualization of leucocyte nuclei and platelets by immunostaining. RESULTS: Immediate centrifugation (T-0) resulted in the largest membranes, T-6 membranes being on average 29% smaller. Leucocytes and platelets were significantly more abundant in T-0 than in T-6 samples. Majority of the fibroblast genes studied were consistently either upregulated or downregulated by the T-0 PRF releasates. However, centrifugation after a 6-minute delay significantly weakened the fibroblast responses. CONCLUSIONS: Delayed centrifugation resulted in smaller PRF membranes with fewer leucocytes and platelets and also significantly reduced on the expression of a set of healing-related gingival fibroblast genes. CLINICAL RELEVANCE: The higher expression of wound healing-related genes in gingival fibroblasts by the immediately-centrifuged PRF membranes may increase their biological properties in clinical use.

[Study of centrifuge conditions for preparing rabbit leukocyte-poor platelet-rich plasma by single centrifugation].

Objective: To explore the best centrifuge condition for preparing rabbit leukocyte-poor platelet-rich plasma (LP-PRP) by using single centrifugation method. Methods: Sixteen healthy New Zealand rabbits, aged 3-4 months, were utilized in the investigation. A total of 15 mL anticoagulated blood was extracted from the central ear artery of each rabbit, with a repeat of the blood collection procedure after 1 and 2 months. The obtained blood specimens were individually subjected to centrifugation at a radius of 16.7 cm and speeds of 1 200, 1 300, 1 400, and 1 500 r/min (equivalent to centrifugal forces of 269× g, 315× g, 365× g, and 420× g) for durations of 2, 3, 4, and 5 minutes, resulting in a total of 16 groups. Following centrifugation, collect plasma from each group to a distance of 1.5 mL from the separation plane. The volumes, platelet enrichment coefficient, and platelet recovery rates of LP-PRP in each group, under varying centrifugation conditions, were methodically computed and subsequently compared. Results: The volume of LP-PRP obtained under all centrifugation conditions ranged from 1.8 to 7.6 mL. At a consistent centrifugal speed, an extension of centrifugation time leaded to a significant increase in the volume of LP-PRP, accompanied by a declining trend in the platelet enrichment coefficient of LP-PRP. When centrifuged for 2 minutes, the volume of LP-PRP at speeds of 1 200 and 1 300 r/min was less than 2.0 mL, while the volume of LP-PRP obtained under other conditions was more than 2.0 mL. When centrifuged for 4 and 5 minutes, the volume of LP-PRP obtained at each speed was more than 4 mL. LP-PRP with a platelet enrichment coefficient more than 2.0 could be prepared by centrifuging at 1 200 r/min for each time group and 1 300 r/min for 2 and 3 minutes, and the highest LP-PRP platelet enrichment coefficient could be obtained by centrifugation for 2 minutes at a speed of 1 200 r/min. The platelet recovery rates of LP-PRP obtained by centrifugation at 1 200 r/min for 4 and 5 minutes, as well as centrifugation at 1 400 r/min for 5 minutes, were both greater than 60%. There was no significant difference between the groups when centrifuged at 1 200 r/min for 4 and 5 minutes ( P>0.05). Conclusion: In the process of preparing rabbit LP-PRP using a single centrifugation method, collecting 15 mL of blood and centrifuging at a radius of 16.7 cm and speed of 1 200 r/min for 4 minutes can prepare LP-PRP with a volume exceeding 2.0 mL, platelet enrichment coefficient exceeding 2.0, and platelet recovery rate exceeding 60%. This centrifugal condition can achieve the optimal LP-PRP action parameters in the shortest possible time.

Protocol to separate small and large extracellular vesicles from mouse and human cardiac tissues.

Extracellular vesicles (EVs) are secreted by cells under various conditions and can contribute to the disease progression in tissues. Here, we present a protocol to separate small and large EVs from mouse hearts and cardiac tissues collected from patients. We describe steps for utilizing enzymatic digestion for release of EVs from interstitial space followed by differential centrifugation and immunoaffinity purification. The isolated EVs can be used for various experiments to gain insight into their in vivo functions. For complete details on the use and execution of this protocol, please refer to Liang et al. (2023).1.

High-speed centrifugation rather than Lipoclear reagent can be used for removing the interference of lipemia on serological tests of infectious diseases: AIDS, hepatitis B, hepatitis C, and syphilis by chemiluminescent microparticle immunoassay.

The aim of this study was to investigate the interference of lipemia on measurement of HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc, anti-HCV, HIV Ag/Ab, and anti-TP in serum by chemiluminescent microparticle immunoassay (CMIA) and compare lipemia removing performance between high-speed centrifugation and Lipoclear reagent. Mixed native serum samples (NSs) and hyperlipemia serum samples (HLS) were prepared for the investigated parameters. The levels of these parameters in NS and HLS were determined by CMIA on an Abbott ARCHITECT i2000SR immunoassay analyzer. HBsAg, anti-HBs, and anti-TP were affected with relative bias >12.5% (acceptable limit) when the level of triacylglycerol (TG) was higher than 27.12 mmol/L in HLS. Clinically unacceptable bias were observed for HBeAg and anti-HBe in HLS with TG higher than 40.52 mmol/L. However, anti-HCV and HIV Ag/Ab were not interfered in severe lipemia with TG < 52.03 mmol/L. In addition, the Lipoclear reagent did not reduce the interference of lipemia with relative bias from -62.50% to -18.02%. The high-speed centrifugation under the optimized condition of 12 000g for 10 min successfully removed the interference of lipemia with relative bias from -5.93% to 0% for HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc, and anti-TP. To conclude, high-speed centrifugation can be used for removing the interference of lipemia to measure HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc, and anti-TP. Accordingly, a standardized sample preanalytical preparation of the patients and other screening participants as well as a specimen examination procedure for removing lipemia interference on the serological tests was recommended.

Preparation of Highly Enriched ER Membranes Using Free-Flow Electrophoresis.

Free-flow electrophoresis (FFE) is a technique for separation of proteins, peptides, organelles, and cells. With zone electrophoresis (ZE-FFE), organelles are separated according to surface charge. The ER is the only remaining major cellular compartment in Arabidopsis not to have been isolated using density centrifugation, immune-isolation, or any other method previously applied to purification of plant membranes. By using continuous-flow electrophoresis, ER vesicles of similar surface charge, which may have been fragmented during cell lysis, can be focused. A large portion of these vesicles are of sufficiently different surface charge that separation from the majority of Golgi and other contaminants is possible. Here we adapt an earlier ZE-FFE Golgi isolation protocol for the isolation of highly pure ER vesicles and for tracking the migration of peripheral ER vesicles. Isolating ER vesicles of homogeneous surface charge allows multi-omic analyses to be performed on the ER. This facilitates investigations into structure-function relationships within the ER.

Organ-Specific Microsomes from Dark-Grown Hypocotyls of Arabidopsis thaliana.

In this book chapter, we present a method for microsome isolation from the hypocotyl tissue of dark-grown Arabidopsis thaliana. Microsomes are heterogeneous, vesicle-like membranes, which are, not exclusively, derived but enriched with membranes of the endoplasmic reticulum (ER). Here, we describe the experimental setup, including sample preparation, homogenization, differential centrifugation steps, and quality control measures after microsome isolation.