DIAGNOSTIC ROLE OF DIFFUSION-WEIGHTED IMAGE OF THE LIVER WITH MAGNETIC RESONANCE IMAGING IN PREDICTING ABSTINENCE DISORDERS IN PATIENTS WITH ALCOHOLIC LIVER DISEASE

Objective. To assess the diagnostic role of diffusion-weighted images of the liver with magnetic resonance imaging in predicting abstinence disorders in patients with alcoholic liver disease. Methods. A total of 122 patients with ALD aged 48±5.4 years were examined. The survey algorithm we used included: performing liver DWI with MRI (n=122) with b-value values of 100/600/1000, ultrasound of abdominal organs with clinical elastography – 97 (80%) patients. Trepan liver biopsy was chosen as a reference method (n=64). Results. The patients were monitored for 2.5 years. The terms of follow-up were selected individually, depending on the results of clinical and laboratory research methods. A high correlation was established (r=0.879), when comparing clinical elastography and quantitative indicators of DWI of the liver, at admission and during dynamic observation of patients, also at the middle level, the data obtained correlated with the results of trephine biopsy of the liver (r=0.721). After 3 months, 6 (15%) of 40 patients showed normalization of biochemical blood test parameters with no diffusion restriction according to the results of DWI of the liver. Based on the results obtained, a high correlation was noted between changes in the biochemical blood test and MRI data in the DWI mode. After 9 months of follow-up, according to DWI data, 34 patients showed persistence of cytolysis syndrome and limited diffusion on DWI of the liver. After collecting an additional history and clarifying the details of the lifestyle of the patients' relatives, it was found that these patients continued to consume alcoholic beverages against the background of the received treatment, which was manifested by the presence of diffusion restriction on MRI in the DWI mode, which was a magnetic resonance sign of the presence of inflammatory processes in the structure of the parenchyma liver. After 12 months, positive dynamics – the absence of diffusion restriction according to the results of DWI of the liver was noted in 34 patients, which indicates the effectiveness of using the qualitative characteristics of DWI of the liver to assess the violation of the abstinence regimen (AUROC=0.906 (95% CI 0.872-0.916)). But in 16 (13%) patients from this group, changes in the biochemical blood test were noted, but no diffusion limitation was noted according to the DWI of the liver. Patients (n=16) underwent a correction of the received treatment – after 1 month there was a positive trend. There was a correlation of quantitative parameters of DWI of the liver with clinical forms of ALD, regardless of the presence or absence of diffusion restriction (r=0.936). Next, we assessed the prognostic and diagnostic significance of the developed criteria for DWI of the liver for patients with ALD on admission. The results of the study indicated the effectiveness of using the diagnostic and prognostic model of MRI in the DWI mode for patients with ALD on admission and in dynamic observation. Conclusions. 1. A high correlation was found between the quantitative parameters of DWI of the liver and clinical elastography (r=0.879) at admission and follow-up. Average correlation relationship of DWI of the liver with the results of trephine biopsy of the liver in patients with ALD on admission and follow-up (r=0.721). There was a high correlation between the results of DWI of the liver on MRI with the data of clinical and laboratory parameters in dynamic observation of patients with ALD: no diffusion limitation – positive (r=0.887); yes – negative (r=0.887). The high prognostic and diagnostic value of DWI of the liver in assessing the violation of the abstinence regimen in patients with ALD was established (AUROC=0.906 (95% CI 0.872-0.916)). Prognostic and diagnostic criteria for liver DWI on MRI in patients with ALD at admission: qualitative characteristic – AUROC=0.846 (95% CI 0.811-0.862), quantitative characteristic – AUROC=0.909 (95% CI 0.879-0.912); with dynamic observation: qualitative characteristic – AUROC=0.949 (95% CI 0.907-0.965), quantitative characteristic – AUROC=0.917 (95% CI 0.876-0.932).

Long-Term Stability of Nitrifying Granules in a Membrane Bioreactor without Hydraulic Selection Pressure

To understand the long-term stability of nitrifying granules in a membrane bioreactor (GMBR), a membrane module was submerged in an airlift reactor to eliminate the hydraulic selection pressure that was believed to be the driving force of aerobic granulation. The long-term monitoring results showed that the structure of nitrifying granules could remain stable for 305 days in the GMBR without hydraulic selection pressure; however, the majority of the granule structure was actually inactive due to mass diffusion limitation. As a consequence, active biomass free of mass diffusion limitation only inhabited the top 60–80 µm layer of the nitrifying granules. There was a dynamic equilibrium between bioflocs and membrane, i.e., 25% of bioflocs attached on the membrane surface within the last nine days of the backwash cycle in synchronization with the emergence of a peak of soluble extracellular polymeric substances (sEPS), with a concentration of around 47 mg L−1. Backwash can eventually detach and return these bioflocs to the bulk solution. However, the rate of membrane fouling did not change with and without the biofloc attachment. In a certain sense, the GMBR investigated in this study functioned in a similar fashion as an integrated fixed-film activated sludge membrane bioreactor and thus defeated the original purpose of GMBR development. The mass diffusion problem and sEPS production should be key areas of focus in future GMBR research.

Mild hypercapnia improves brain tissue oxygen tension but not diffusion limitation in asphyxial cardiac arrest: an experimental study in pigs

Background We sought to evaluate the effect of mild hypercapnia on brain tissue oxygen tension (Pbto2) and diffusion limitation (impaired ability of oxygen extraction) in a porcine post asphyxial cardiac arrest model. Methods In 16 Bama pigs, asphyxial cardiac arrest was induced by endotracheal tube clamping and remained untreated for another 4 min. After return of spontaneous circulation (ROSC), animals were randomly assigned to mild hypercapnia (end-tidal carbon dioxide (EtCO2): 45 ~ 50 mmHg) and normocapnia (EtCO2: 35 ~ 40 mmHg) groups for 12 h. Intracranial pressure (ICP), Pbto2, and brain tissue temperature were invasively measured by multimodality monitors. Blood gas analysis, neuron specific enolase (NSE), and S100β were tested at baseline, ROSC 1 h, 6 h, and 12 h. Generalized mixed model with a compound symmetry covariance matrix was used to compare the time-variables of the two groups. Results Twelve (75%) pigs had ROSC and 11 pigs survived for the study period, with 6 pigs in mild hypercapnia group and 5 in the normocapnia group. The mean EtCO2 in the mild hypercapnia was significantly higher than normocapnia group (48 vs 38 mmHg, p < 0.001). Compared with normocapnia, mild hypercapnia group had higher Pbto2 (p < 0.001), slightly higher mean arterial pressure (p = 0.012) and ICP (p = 0.009). There were no differences in cerebral perfusion pressure (p = 0.106), gradient of partial pressure of jugular venous bulb oxygen (Pjvo2) and Pbto2 (p = 0.262), difference of partial pressure of jugular venous CO2 and arterial CO2 (p = 0.546), cardiac output (p = 0.712), NSE (p = 0.822), and S100β (p = 0.759) between the two groups. Conclusions Short term mild hypercapnia post-resuscitation could improve Pbto2. However, no corresponding improvements in the gradient of Pjvo2 to Pbto2 and biomarkers of neurological recovery were observed in the porcine asphyxial cardiac arrest model.

Evidence that non-pathogenic microorganisms drive sea star wasting disease through boundary layer oxygen diffusion limitation

ABSTRACTSea star wasting disease describes a condition affecting asteroids that resulted in significant Northeastern Pacific population decline following a mass mortality event in 2013. The etiology of sea star wasting is unresolved. We hypothesized that asteroid wasting is a sequela of microbial organic matter remineralization near respiratory surfaces which leads to boundary layer oxygen diffusion limitation (BLODL). Wasting lesions were induced in Pisaster ochraceus by enrichment with a variety of organic matter (OM) sources and by experimentally reduced oxygen conditions. Microbial assemblages inhabiting tissues and at the asteroid-water interface bore signatures of copiotroph proliferation before wasting onset, followed by the proliferation of putatively facultative and strictly anaerobic taxa. These results together illustrate that suboxic conditions at the animal-water interface may be established by heterotrophic bacterial activity in response to organic matter loading. Wasting susceptibility was significantly and positively correlated with rugosity, a key determinant of boundary layer thickness. At a semi-continuously monitored field site (Langley Harbor), wasting predictably occurred at annual peak or decline in phytoplankton biomass over 5 years, suggesting that primary production-derived OM may contribute to BLODL. Finally, wasting individuals from 2013 – 2014 bore stable isotopic signatures reflecting anaerobic processes which suggests that this phenomenon may have affected asteroids during mass mortality. The impacts of BLODL may be more pronounced under higher temperatures due to lower O2 solubility, in more rugose asteroid species due to restricted hydrodynamic flow, and in larger specimens due to their lower surface area to volume ratios which affects diffusive respiratory potential. Moreover, our results demonstrate that marine invertebrate disease may result from heterotrophic microbial activity that occurs adjacent to respiratory tissues, which raises important questions about the etiology of marine diseases in other benthic taxa.