Buffer Response Research Articles

Hypoxia and oxidative stress: The role of the anaerobic gut, the hepatic arterial buffer response and other defence mechanisms of the liver

Hypoxia and oxidative stress: The role of the anaerobic gut, the hepatic arterial buffer response and other defence mechanisms of the liver

Mechanical properties of a STF capsule filled flexible polyurethane composite foam

In this study, a shear thickening fluid (STF) capsule/polyurethane composite foam (STF-CPCF) was prepared and the mechanical properties were studied. The shear thickening performance of STF capsule and the excellent buffering performance of polyurethane foam are responsible for the improvement of the mechanical properties of the composite. The mechanical properties of STF-CPCF were discussed with the respect of microstructure (pore size, cavity density, etc.) for compression and dynamic impact test. The results show that PU65/30 has the maximum compression energy. PU75 under 20 J energy impact shows better buffering response, and the PU75/30 shows the best among various mass fraction of PU75. This research can be referred to the future application process of polyurethane foam, and this composite material can be applied to the field of protection.

The Influence of Superlattice Structure on the Dynamic Buffer Response of AlInN/GaN-on-Si HEMTs

In this work, we investigate the dynamic buffer response of AlInN/GaN high electron mobility transistors (HEMTs) grown on silicon substrates. Significant improvements in vertical breakdown voltage, reduced buffer conduction and charge trapping effect are observed on the samples with a superlattice layer (SL) in the buffer. The dynamic response of the buffer layer largely depends on the composition, thickness and position of the SL in the stress-mitigating buffer. The vertical breakdown voltage increases consistently with decreasing edge-type dislocations when the density of screw-type dislocations is low. Negative back-gating measurements show the lowest buffer current hysteresis in the sample with the lowest edge-type dislocation density, indicating least charge trapping in the sample. Four terminal positive back-gating measurements in the on-state, further confirm the observed trend. Based on the experimental observations, we propose that the total density of threading dislocations, (acts as vertical leakage path) and the acceptor like edge-type dislocations should be accounted along with the electron injection from the silicon substrate to the buffer. Therefore, resulting in higher vertical breakdown voltage by alleviating serious dynamic buffer response in GaN-based HEMTs.

Glucose triggers strong taxon-specific responses in microbial growth and activity: insights from DNA and RNA qSIP.

Growth of soil microorganisms is often described as carbon limited, and adding labile carbon to soil often results in a transient and large increase in respiration. In contrast, soil microbial biomass changes little, suggesting that growth and respiration are decoupled in response to a carbon pulse. Alternatively, measuring bulk responses of the entire community (total respiration and biomass) could mask ecologically important variation among taxa in response to the added carbon. Here, we assessed taxon-specific variation in cellular growth (measured as DNA synthesis) and metabolic activity (measured as rRNA synthesis) following glucose addition to soil using quantitative stable isotope probing with H218 O. We found that glucose addition altered rates of DNA and rRNA synthesis, but the effects were strongly taxon specific: glucose stimulated growth and rRNA transcription for some taxa, and suppressed these for others. These contrasting taxon-specific responses could explain the small and transient changes in total soil microbial biomass. Responses to glucose were not well predicted by a priori assignments of taxa into copiotrophic or oligotrophic categories. Across all taxa, rates of DNA and rRNA synthesis changed in parallel, indicating that growth and activity were coupled, and the degree of coupling was unaffected by glucose addition. This pattern argues against the idea that labile carbon addition causes a large reduction in metabolic growth efficiency; rather, the large pulse of respiration observed with labile substrate addition is more likely to be the result of rapid turnover of microbial biomass, possibly due to trophic interactions. Our results support a strong connection between rRNA synthesis and bacterial growth, and indicate that taxon-specific responses among soil bacteria can buffer responses at the scale of the whole community.

Computational simulations for the hepatic arterial buffer response after liver graft transplantation from an adult to a child

Live donor liver transplantation (LDLT) is an important surgical technique for treating children with end-stage liver diseases. Surgical complications may occur, e.g., due to thrombosis formed in hepatic arteries (HAs) or portal veins (PVs). From the hepatic circulation point of view, a hepatic arterial buffer response (HABR) mechanism, where the HA flow counteracts the changes in the PV flow, could play a role in graft dysfunction, yet this intricate mechanism has not been elucidated in LDLT procedures. In this short communication we simulate the HABR which may occur in an adult-to-child LDLT, where the left lateral lobe of an adult donor is transplanted to a child. Using an electrical analog model we show that the HABR could be triggered in both portal hyper-perfusion and venous obstruction scenarios, and this may be associated with arterial and/or venous thrombosis in the liver graft as reported in clinical studies. In conclusion, HABR could be important in adult-to-child LDLT and it should be considered in pre-surgical planning.

1094 A Study of the Characteristics of Hepatic Blood Flow Ex Vivo Using a Cardio-Emulation Arterial Pump Perfusion System

INTRODUCTION: The CAVESWave® organ perfusion system provides cardio-emulated systolic and diastolic pressure waves to the hepatic artery HA, as well as variable pressure to the portal vein PV, replicating in vivo hepatic perfusion conditions. This allows a unique opportunity to study the interaction between HA and PV flow patterns in the autoregulation of hepatic venous HV outflow. The conditions exclude artefacts generated from cardiac pulsations. METHODS: Ten freshly procured porcine livers were perfused on the CAVESWave® system for four hours. At the two-hour midpoint, the temperature of the perfusate was increased from 15°C to 30°C and the flow variation associated with the temperature change documented. Flow rates in the HA, PV and HV were captured using flow sensors in the perfusion circuit. The distribution of perfusate was documented using Infra-red thermography (IRT), which measured surface liver temperature to a depth of 3 mm. RESULTS: Both IRT and the flow sensor measurements demonstrated stable, steady-state values after target perfusate temperatures were reached. Pulsatile waves reflecting cardio-emulated systolic and diastolic pressure waves were present in both HA (Figure 1) and PV (Figure 2). The only possible source of pulsations in the PV was transmission from the HA. Pulsatile waves were significantly attenuated or absent in the HV (Figure 3). The flow at 150 C in the HA (630.1 + 239.9; ml/min M + SD) was significantly greater than in the PV (316.2 + 90; P < 0.004). As expected, flow in the HV (904 + 292.8) approximated the sum of HA and PV flow. Increasing the temperature of the perfusate to 300 C significantly increased flow in all three circuits: HA (761.5 + 220; P < 0.014); PV flow (375.0 + 139.1; P < 0.007) and HV (1016.1 + 302.4; P < 0.007). The flow in the HA increased by 116.75 + 140.9 ml/min; the increase was 56.7 + 80.3 in the PV and 111.8 + 100.8 in the HV. The time for this change was significantly shorter for HA (18.9 + 13.5 mins) than for PV (26.4 + 18.1; P < 0.05). The significance of the delay in the PV flow is unclear. It likely reflects greater capacitance within the venous circuit. PV flow was inversely correlated with HA flow at all temperatures, correlation coefficient, -0.26. This suggests compensation or buffering between the arterial and venous circuits. CONCLUSION: Autoregulation of flow in response to temperature change is maintained in the ex vivo perfused liver. The inverse correlation between HA and PV flow, suggests a Hepatic Artery Buffering Response, HABR in this model.

Portal hyperperfusion after major liver resection and associated sinusoidal damage is a therapeutic target to protect the remnant liver.

Extended liver resection results in loss of a large fraction of the hepatic vascular bed, thereby causing abrupt alterations in perfusion of the remnant liver. Mechanisms of hemodynamic adaptation and associated changes in oxygen metabolism after liver resection and the effect of mechanical portal blood flow reduction were assessed. A pig model (n = 16) of extended partial hepatectomy was established that included continuous observation for 24 h under general anesthesia. Pigs were randomly separated into two groups, one with a portal flow reduction of 70% compared with preoperative values, and the other as a control (n = 8, each). In controls, portal flow [mean (SD)] increased from 74 (8) mL·min-1·100 g-1 preoperatively to 240 (48) mL·min-1·100 g-1 at 6 h after resection (P < 0.001). Hepatic arterial buffer response was abolished after resection. Oxygen uptake per unit liver mass increased from 4.0 (1.1) mL·min-1·100 g-1 preoperatively to 7.7 (1.7) mL·min-1·100 g-1 8 h after resection (P = 0.004). Despite this increase in relative oxygen uptake, total hepatic oxygen consumption (V̇o2) was not maintained, and markers of hypoxia and anaerobic metabolism were significantly increased in hepatocytes after resection. Reduced postoperative portal flow was associated with significantly decreased levels of aspartate aminotransferase and bilirubin and increased hepatic clearance of indocyanine green. In conclusion, major liver resection was associated with persistent portal hyperperfusion, loss of the hepatic arterial buffer response, decreased total hepatic V̇o2 and with increased anaerobic metabolism. Portal flow modulation by partial portal vein occlusion attenuated liver injury after extended liver resection.NEW & NOTEWORTHY Because of continuous monitoring, the experiments allow precise observation of the influence of liver resection on systemic and local abdominal hemodynamic alterations and oxygen metabolism. Major liver resection is associated with significant and persistent portal hyperperfusion and loss of hepatic arterial buffer response. The correlation of portal hyperperfusion and parameters of liver injury and dysfunction offers a novel therapeutic option to attenuate liver injury after extended liver resection.

Model Assisted Analysis of the Hepatic Arterial Buffer Response During Ex Vivo Porcine Liver Perfusion.

The hepatic arterial buffer response is a well-known phenomenon in hepatic circulation, describing the response of hepatic arterial resistance to changes in portal vein flow. Several vasoactive metabolites underlying its mechanism have been proposed, however, there is currently no clear consensus. The aim of this study is to investigate the hepatic arterial buffer response of porcine livers preserved in a controlled ex vivo perfusion machine. Porcine livers are perfused on an ex vivo perfusion machine and hemodynamic experiments investigating the hepatic arterial resistance response to portal vein flow and vena cava pressure variations are conducted. A simple hemodynamic model is developed to support the interpretation of the received measurements. Further, a mechanism is proposed that explains hepatic arterial resistance changes in response to vena cava pressure as myogenic and in response to portal vein flow as a combined washout and myogenic effect. A clear correlation between hepatic sinusoidal pressure levels and hepatic arterial resistance is observed where an increase of approximately 4mmHg of hepatic sinusoidal pressure level results in doubling of the hepatic arterial resistance. This relation is considered during the analysis of the portal vein flow variations resulting in a reduced isolated effect of adenosine washout on hepatic arterial resistance. With an average buffer capacity of 27% during our experiments, the hepatic arterial buffer response shows to be unimpaired in the ex vivo scenario. First, washout and myogenic effects both influence the hepatic arterial buffer response; and second, hepatic sinusoidal pressure levels strongly influence the hepatic arterial resistance. These results present new findings in hemodynamics of the liver, which are fundamental for successful ex vivo liver perfusion.

Hemodynamic aspects of the Budd–Chiari syndrome of the liver: A computational model study

Budd–Chiari syndrome (BCS) is a rare liver disease characterised by the obstruction of draining hepatic veins, and subsequent reduced blood return to the heart. Although many clinical BCS studies have been reported, few studies have quantified the associated changes that occur in the entire hepatic circulation. In this communication, we present an electrical analog model of the hepatic circulation that incorporates the Hepatic Arterial Buffer Response (HABR) mechanism in both the left and right lobes. Using this model we can simulate the hepatic flow under both normal and acute BCS conditions. The model can capture subtle features in the hepatic circulation, such as reduced total portal flow but increased arterial flow under BCS. This observation was previously reported in literature and may have clinical implications. As such, we suggest the presented model could be used for the analysis of systematic haemodynamic changes of BCS and therefore may be useful in supporting clinical interventions.

The influence of gangue particle size and gangue feeding rate on the dynamic response of suspended buffer and engineering application

The influence of gangue particle size and gangue feeding rate on the dynamic response of suspended buffer and engineering application

Microbiome dynamics during cast ageing in the earthworm Aporrectodea caliginosa

Earthworm casts are hotspots of microbial activity playing an important role in the nutrient cycling of soil ecosystems. Cast ageing can be considered an ecological succession, where copiotrophic bacteria are replaced by oligotrophic bacteria as the ratio labile/recalcitrant substrates decreases. Here we use next-generation sequencing to describe the bacterial communities (microbiome) of fresh casts (day 0) from the earthworm Aporrectodea caliginosa and how they change over time (7, 15, 30 and 60 days) under natural conditions. We also look for the main, transitional and day-specific core microbiomes of A. caliginosa casts and assessed whether bacterial communities in each ageing stage are clearly distinct in their composition or can be merged into metacommunities. Fresh cast microbiomes were mainly comprised of Bacteroidetes and Proteobacteria (62% of the total sequences) and, in a lesser extent, of Acidobacteria, Actinobacteria Chloroflexi, Planctomycetes and Verrucomicrobia (36% of the total sequences). These fresh casts were richer in amplicon sequence variants (ASVs) than soil microbiomes, which also had lower abundances of Bacteroidetes but higher abundances of other bacterial phyla. As expected, copiotrophic bacteria (Alphaproteobacteria but not Bacteroidetes) significantly (P < 0.0001) decreased in abundance with cast ageing, while oligotrophic bacteria (Actinobacteria, Acidobacteria and Deltaproteobacteria) increased (P < 0.03) their proportion. This also resulted in a significant (P < 0.05) decrease in alpha-diversity over the first 15 days and larger differences in beta-diversity among bacterial communities of ageing casts. Despite differences in beta-diversity, microbiomes of ageing casts were grouped into two metacommunities, one comprised of younger samples collected at days 0 and 7, and another comprised of older samples collected at days 15, 30 and 60. These two metacommunities corresponded to decreased patterns in labile C and N pools in cast ageing. We found a main core microbiome comprised of eight bacterial taxa (~5% of the total sequences). Additionally, we also found transitional and day-specific core microbiomes that were richer and compositionally different from the main core microbiome. This suggests different levels of redundancy in the cast microbiomes to buffer responses to external perturbations (e.g., weather oscillations).

Purpose of the measurement of intraoperative hepatic hemodynamics in liver transplant surgery

Liver graft function depends on different biological factors that are related to the donor, the recipient and the potential damage arising from the organ preservation technique. However, adequate hepatic artery flow and portal vein flow rates ensure a sufficient flow of oxygen and nutrients in order to ensure a suitable cellular graft function after the extreme metabolic decrease condition induced by hypothermia and the preservation solution. Liver inflow is a highly complex system due to its double irrigation system. These two systems are connected by the well-known “hepatic arterial buffer response” concept. This mechanism explains changes in hepatic arterial flow (HAF) as a compensation for changes in the portal vein flow (PVF), so that the hepatic artery adjusts total flow in relation to alterations in the portal blood flow. At the moment, the minimum HAF and PVF required for an adequate regeneration and functional recovery of the liver graft have not been yet established.

Crude oil inventories: The two faces of Janus?

In this article, we examine whether oil inventories react to oil demand and supply shocks as a buffer to the market, as a facilitation of speculative trading, or both. Unlike previous studies that discuss the role of inventories from the perspective of the relationship between inventory and price, this study derives speculative and buffer roles from the endogenous responses of inventory to demand and supply shocks. Global, US, and Cushing, Oklahoma inventories from January 2003 to June 2008 and January 2009 to May 2018 are compared from the aggregate to sub-aggregate levels. A sign-restricted structural vector autoregressive model is employed, and robustness verifications are added. Overall, while supply and demand shocks shift oil production and consumption, the buffer responses of inventories are found to be immediate for demand shocks but gradual for supply shocks, and the instantaneous speculative responses of the Cushing inventories are revealed.

04:12 PM Abstract No. 256 Splenic embolization for splenic arterial steal syndrome

Splenic arterial steal syndrome (SASS) is preferential splenic arterial flow with hepatic arterial hypo-perfusion seen on angiography without hepatic arterial anatomical abnormality. The study compares liver Doppler findings before and after splenic embolization 104 patients were treated with splenic arterial embolization (SAE) for various indications in the past seven years at our institution. After IRB approval, we identified patients with SASS as indication for SAE. Paired t-test was performed to compare the available pre and post-embolization hepatic artery peak systolic velocities (PSV), resistive indices (RI) and main portal vein velocities. 11 patients underwent proximal SAE (between the dorsal pancreatic artery and hilum with coils/plugs) for SASS. Liver Doppler findings were compared before and after SAE done to increase liver transplant hepatic arterial flow in 8/11 patients. Main portal vein velocity significantly decreased post SAE [mean 53.1 cm/s (14-98 cm/s) to 31.3 cm/s (14-54 cm/s), p<0.05]. Hepatic artery RI decreased post SAE [mean 0.74 (0.46-0.99) to 0.63 (0.34-0.88), p<0.05]. No significant difference between hepatic artery PSV (p=0.5) was observed after SAE [pre 153.5 cm/s (45-340 cm/s) to post 113.9 cm/s (48-171 cm/s)]. No splenic infarctions or abscesses were identified. Total bilirubin remained stable immediately post procedure (mean 14.4 to 13.9, p=0.4), but decreased one month post-embolization (mean 10.9 to 3.7, p=0.1). Pre-embolization albumin values remained stable immediate and 1 month post procedure. SAE is safe and effective procedure to increase hepatic arterial flow to the transplant liver with SASS. Following SAE for SASS, hepatic artery RI and main portal vein velocity are responsive to the procedure and the liver Doppler may serve as a tool to predict procedural success. Both the decrease in portal venous velocity and hepatic artery RI may support the hepatic arterial buffer response (HABR) theory as a cause or contributor to the SASS

Portal Venous Flow Alterations in Hepatic Artery Thrombosis Following Liver Transplant.

The hepatic vasculature is a unique system due to a dual supply that includes the hepatic artery and portal vein, which interact when the liver vascular supply is decreased. Hepatic artery buffer response, an intrinsic regulatory mechanism that compensates for blood supply, maintains increased hepatic artery flow and caliber in response to portal vein failure. Previous studies revealed that portal vein flow showed no alterations to establish adequate blood supply in response to hepatic artery occlusion. Here, we analyzed portal vein flow changes in patients with hepatic artery thrombosis after liver transplant. From December 1988 to October 2017, our center performed 580 liver transplant procedures. Those diagnosed with hepatic artery thrombosis (19 females, 24 males) by Doppler ultrasonography during postoperative week 1 were analyzed. Patients received either surgery or endovascular treatment for hepatic artery thrombosis, with patency confirmed by Doppler ultrasonography. We compared portal vein flow velocity and caliber before and after treatment using Wilcoxon signed rank and Mann Whitney U tests. Mean patient age was 18.9 ± 21.4 years. Portal vein flow velocity pretreatment (median of 70 cm/ s) was significantly higher than posttreatment (median of 52 cm/ s) in all patients (P < .001). Median flow velocity decreased significantly after treatment when subgroups were compared, including age (adult vs child), transplant type (orthotopic transplant vs living donor), and treatment (surgery vs endovascular). However, portal vein flow velocity showed a significantly higher decrease in the surgery subgroup than in the endovascular treatment subgroup (P = .018). There was no significant relationship between portal vein calibers before and after treatment (P = .36). The significant decrease in portal vein flow velocity after successful treatment of hepatic artery thrombosis may represent a compensatory flow change of the portal vein in response to diminished hepatic artery flow.

Analysis of the nonlinear dynamic response of guide rails for a suspended buffer.

Guide rails’ nonlinear dynamic response to the collision process between gangues and the suspended buffer is the basis for its intensity examination and fatigue prediction. This paper established a numerical model for simulating the dynamic response of buffer’s guide rails using Pro/E and Femap based on an analysis of the basic structural components of the suspended buffer. The effects of the gangues diameter and feeding rate on the guide rails’ dynamic response were investigated, which were mainly revealed by a tension in guide rails. Simulation results showed that the tension in guide rails rapidly increased to a peak value after the suspended buffer was impacted by gangues, followed by a periodic vibration. The peak tension, maximum and minimum tensions within the periodic vibration were exponential functions of the gangues diameter. And they depended linearly on the feeding rate. The vibration frequency of the tension in guide rails was an exponential function of the gangues diameter but did not depend on the feeding rate. Based on the backfilling workface parameters used in D.Ping coal miner’s 15601 working panel, the feeding rate of 500 t/h was selected. The diameter of the crushed gangues was selected to be 50 mm based on the strength of guide rails. Their expected service life is 54.2 years. Finally, an industrial test was performed in D.Ping coal miner’s 15601 working panel and the guide rails operated steadily. The measured vibration parameters of the tension in guide rails agree well with that of numerical predictions, which verified the reliability of the numerical model to some extent.

Acclimation temperature effects on locomotor traits in adult aquatic anurans (X. tropicalis and X. laevis) from different latitudes: possible implications for climate change.

Climate change is in part responsible for the 70% decline in amphibian species numbers worldwide. Although temperature is expected to impact whole-organism performance in ectotherms, reversible thermal acclimation has been suggested as a mechanism that may buffer responses to abrupt temperature changes. Here, we test for an effect of acclimation on locomotor performance traits (jump force and stamina) in adults of two predominantly aquatic and closely related frog species from different climatic regions, Xenopus tropicalis (tropical) and Xenopus laevis (temperate). We find significant effects of acclimation temperature on exertion capacity and for jump force in X. tropicalis but no effect of acclimation temperature on burst performance in X. laevis. Our results suggest that the two locomotor performance traits measured are differentially impacted by acclimation temperature in X. tropicalis. Our results further support the hypothesis that lower-latitude ectotherms might have greater acclimation capacity than high-latitude ones. Finally, our results highlight the importance of investigating multiple performance traits when evaluating how animals may cope with changes in temperature. Further work is required to evaluate the potential for acclimation in mitigating the negative impacts of climate change on amphibian populations.

Environmentally Induced Epigenetic Plasticity in Development: Epigenetic Toxicity and Epigenetic Adaptation.

Epigenetic processes represent important mechanisms underlying developmental plasticity in response to environmental exposures. The current review discusses three classes of environmentally-induced epigenetic changes reflecting two aspects of that plasticity, toxicity effects as well as adaptation in the process of development. Due to innate resilience, epigenetic changes caused by environmental exposures may not always lead impairments but may allow the organisms to achieve positive developmental outcomes through appropriate adaptation and a buffering response. Thus, some epigenetic adaptive responses to an immediate stimulus or exposure early in life would be expected to have a survival advantage but these same responses may also result in adverse developmental outcomes as they persists into later life stage. Although accumulating literature has identified environmentally induced epigenetic changes and linked them to health outcomes, we currently face challenges in the interpretation of the functional impact of their epigenetic plasticity. Current environmental epigenetic research suggest that epigenetic processes may serve as a mechanism for resilience, and that they can be considered in terms of their impact on toxicity as a negative outcome, but also on adaptation for improved survival or health. This review encourages epigenetic environmental studies to move deeper inside into the functional meaning of epigenetic plasticity in the development.

MRI assessment of altered dynamic changes in liver haemodynamics following a meal challenge in compensated cirrhosis

BackgroundThe aim was to use magnetic resonance imaging (MRI) to dynamically assess postprandial changes in hepatic and collateral blood flow, liver perfusion and oxygenation in healthy participants and patients with liver disease with compensated cirrhosis (CC).MethodsWe evaluated blood flow in the portal vein, hepatic artery and azygos vein (using phase-contrast MRI), liver perfusion (using arterial spin labelling) and blood oxygenation (using transverse relaxation time [T2*] mapping). Measures were collected at baseline and at 6–7-min intervals from 20 to 65 min following a test meal (440 mL, 660 kcal) in 10 healthy participants and 10 patients with CC.ResultsIn healthy participants, we observed a significant postprandial increase in portal vein flow from baseline (+ 137 ± 26% (mean ± standard deviation), p < 0.001) coupled with a reduction in hepatic artery flow from baseline (− 30 ± 18%, p = 0.008), reflecting the hepatic artery buffer response. In patients with CC, a lower but still significant increase in portal vein flow (67 ± 50%, p = 0.014) was observed, without a clear hepatic artery buffer response. Healthy participants showed a significant increase in postprandial liver perfusion (138 ± 75%, p < 0.001), not observed in patients with CC. There was no change in liver T2* for either group.ConclusionsPostprandial changes in liver perfusion, oxygenation and hepatic and collateral circulation can be measured noninvasively using MRI. Differences between healthy participants and patients with CC were shown, which may help stratify liver cirrhosis in patients.

Liver hypertrophy: Underlying mechanisms and promoting procedures before major hepatectomy

Various procedures can promote hypertrophy of the future liver remnant (FLR) before major hepatectomy to prevent postoperative liver failure. The pathophysiological situation following portal vein embolization (PVE), hepatic artery ligation/embolization or hepatectomy remains unclear. On one hand, the main mechanisms of hepatic regeneration appear to be driven by hepatic hypoxia (involving the hepatic arterial buffer response), an increased portal blood flow inducing shear stress and the involvement of several mediators (inflammatory cytokines, vasoregulators, growth factors, eicosanoids and several hormones). On the other hand, several factors are associated with impaired liver regeneration, such as biliary obstruction, malnutrition, diabetes mellitus, male gender, age, ethanol and viral infection. All these mechanisms may explain the varying degrees of hypertrophy observed following a surgical or radiological procedure promoting hypertrophy the FLR. Radiological procedures include left and right portal vein embolization (extended or not to segment 4), sequential PVE and hepatic vein embolization (HVE), and more recently combined PVE and HVE. Surgical procedures include associated liver partition and portal vein ligation for staged hepatectomy, and more recently the combined portal embolization and arterial ligation procedure. This review aimed to clarify the pathophysiology of liver regeneration; it also describes radiological or surgical procedures employed to improve liver regeneration in terms of volumetric changes, the feasibility of the second step and the benefits and drawbacks of each procedure.