Effect of Freezing Process on the Microstructure of Gelatin Methacryloyl Hydrogels

Gelatin methacryloyl (GelMA) hydrogels have aroused considerable interests in the field of tissue engineering due to tunable physical properties and cell response parameters. A number of works have studied the impact of GelMA concentration, photo-initiator concentration, methacrylic anhydride (MA) concentration, cooling rate and temperature gradient on GelMA hydrogel generation, but little attention has been paid to the effect of the freezing temperatures and freezing time of GelMA prepolymer solution during preparation. In this study, GelMA hydrogels were synthesized with different freezing temperatures and time. It was found that the lower freezing temperatures and longer freezing time caused smaller pore sizes that realized higher cell viability and proliferation of MC3T3-E1 cells. The results showed that tunable microstructure of GelMA could be achieved by regulating the freezing conditions of GelMA, which provided a broad prospect for the applications of GelMA hydrogels in tissue engineering.

Metabolic reprogramming mediates hippocampal microglial M1 polarization in response to surgical trauma causing perioperative neurocognitive disorders

Background Microglial polarization toward pro-inflammatory M1 phenotype are major contributors to the development of perioperative neurocognitive disorders (PNDs). Metabolic reprogramming plays an important role in regulating microglial polarization. We therefore hypothesized that surgical trauma can activate microglial M1 polarization by metabolic reprogramming to induce hippocampal neuroinflammation and subsequent postoperative cognitive impairment. Methods We used aged mice to establish a model of PNDs, and investigated whether surgical trauma induced metabolic reprograming in hippocampus using PET/CT and GC/TOF–MS based metabolomic analysis. We then determined the effect of the glycolytic inhibitor 2-deoxy-d-glucose (2-DG) on hippocampal microglial M1 polarization, neuroinflammation, and cognitive function at 3 d after surgery. Results We found that surgery group had less context-related freezing time than either control or anesthesia group (P < 0.05) without significant difference in tone-related freezing time (P > 0.05). The level of Iba-1 fluorescence intensity in hippocampus were significantly increased in surgery group than that in control group (P < 0.05) accompanied by activated morphological changes of microglia and increased expression of iNOS/CD86 (M1 marker) in enriched microglia from hippocampus (P < 0.05). PET/CT and metabolomics analysis indicated that surgical trauma provoked the metabolic reprogramming from oxidative phosphorylation to glycolysis in hippocampus. Inhibition of glycolysis by 2-DG significantly alleviated the surgical trauma induced increase of M1 (CD86+CD206−) phenotype in enriched microglia from hippocampus and up-regulation of pro-inflammatory mediators (IL-1β and IL-6) expression in hippocampus. Furthermore, glycolytic inhibition by 2-DG ameliorated the hippocampus dependent cognitive deficit caused by surgical trauma. Conclusions Metabolic reprogramming is crucial for regulating hippocampal microglial M1 polarization and neuroinflammation in PNDs. Manipulating microglial metabolism might provide a valuable therapeutic strategy for treating PNDs.

Optimize Initial Freezing Time of Transbronchial Cryobiopsy for the Diagnosis of Interstitial Lung Disease: A Prospective Randomized Parallel Group Study

<b><i>Background:</i></b> Transbronchial cryobiopsy (TBCB) is increasingly being identified as a potential alternative for the diagnosis of interstitial lung disease (ILD). The specimen size of TBCB is positively related to the freezing time. However, the proper initial freezing time for the clinical application of TBCB in ILD remains unknown. <b><i>Methods:</i></b> A prospective randomized parallel group study was employed to investigate ILD patients with unclear diagnosis, who were admitted to the First Affiliated Hospital of Guangzhou Medical University from May 2019 to October 2020 and required TBCB. All patients were randomly divided into 4 groups according to the different freezing times of TBCB: 3 s, 4 s, 5 s, and 6 s groups. All operations were performed under intravenous anesthesia with endotracheal intubation, 60–65 bar pressure of freezing gas source, and 1.9-mm cryoprobe. Compare differences among groups in specimen size, complications, pathological diagnosis efficiency, and multidisciplinary discussion (MDD) diagnostic efficiency. <b><i>Results:</i></b> A total of 100 patients were recruited and randomly assigned into 4 groups (<i>n</i> = 25 each group). The specimen sizes of TBCB in ILD were positively correlated with the freezing time (<i>r</i> = 0.639, <i>p</i> &#x3c; 0.05). None of the patients experienced Grade 3 severe bleeding. Pneumothorax occurred in 1 patient in the 4 s, 5 s, and 6 s groups, respectively. The diagnostic yield of MDD in the 3 s, 4 s, 5 s, and 6 s groups were 64%, 88%, 88%, and 96%, respectively (<i>p</i> &#x3c; 0.05), but showing no significant differences among 4 s, 5 s, and 6 s groups. <b><i>Conclusions:</i></b> The specimen size and diagnostic efficiency of TBCB in ILD increased with a longer freezing time. When the freezing gas pressure is 60–65 bar, we recommended 4 s as the initial freezing time of TBCB, and this time is associated with high diagnostic efficiency and low incidence of complications.

Evaluation of Transbronchial Lung Cryobiopsy Freezing Time, Biopsy Size, Histological Quality, and Incidence of Complication: A Prospective Clinical Trial

Background: Transbronchial cryobiopsy (TBCB), a novel way of obtaining a specimen of lung tissue using a flexible cryoprobe, can obtain large lung biopsies without crush artifacts. The freezing time of TBCB was empirically selected from 3 to 7 s in the previous studies. However, no consensus has yet been reached regarding the optimal freezing time used in TBCB. Objectives: The primary endpoint was biopsy size in different freezing times. The secondary endpoints included sample histological quality, diagnostic confidence, and complications in different freezing times. Methods: Patients who were suspected of DPLD requiring histopathological examination for further evaluation were enrolled in this study. Distinct biopsies were obtained by using different freezing times increased from 3 to 6 s sequentially. Samples were reviewed by 2 external expert pathologists. Results: A total of 33 patients were enrolled, and 143 transbronchial cryobiopsies were taken in this trial. An average of 4.33 samples were taken from each patient. The mean biopsy size of different freezing times from 3 to 6 s was 9.10 ± 4.37, 13.23 ± 5.83, 16.26 ± 5.67, and 18.83 ± 7.50 mm2, respectively. A strong correlation between freezing time and biopsy size was observed (r = 0.99, p < 0.01). Statistically significant difference of biopsy size was detected in the freezing time of 3 s versus 4 s (p < 0.01) and 4 s versus 5 s (p = 0.02), but not in the freezing time of 5 s versus 6 s (p = 0.10). Overall bleeding in different freezing times from 3 to 6 s was 53.33%, 67.50%, 89.47%, and 77.14%, respectively. A significantly higher overall bleeding was observed when the freezing time exceeded 4 s (RR = 1.67, p < 0.01). Pneumothorax occurred in 4 cases (12.12%). One lethal case (3.03%) was noted 25 days after TBCB. Lung parenchyma was preserved well in all cryobiopsy samples. Thirty-one (93.94%) patients’ histopathological findings were identified as sufficient to establish a CRP diagnosis. There was no statistical difference in diagnostic confidence between different freezing times. Conclusion: A longer freezing time was associated with a larger size of the biopsy sample but a higher risk of bleeding. The optimal transbronchial cryobiopsy freezing time is 3–4 s, which is easily achievable and provides an adequate biopsy size whilst creating a safety threshold from complications.

Numerical Simulation of Solar Air Heater using Paraffin Wax-Aluminum Compound as Phase Changing Material

This paper presents a theoretical investigation of solar air heater using phase change material (PCM). PCM used in present configuration is homogenous mixture of paraffin wax with Aluminium powder. The purpose of using Aluminium powder with paraffin wax is to increase the thermal conductivity. PCM mixtures are encapsulated in cylinders and are used as solar absorbers. Using MATLAB program, the effect of different parameters is studied. It has been observed that with increase in mass flow rate, air outlet temperature decreases and freezing time of cylinder decreases. However, at constant mass flow rate, with increase in cylinder radius, air temperature decreases and while freezing time increase sharply. The different parameters have to be chosen such that performance of solar air heater can be optimized.

Stress Granules Modulate SYK to Cause Tau-Associated Neurocognitive Deterioration in 5XFAD Mouse After Anesthesia and Surgery

BackgroundAlzheimer’s disease (AD) is the most common type of dementia. However, no curative therapy has been found effective to slow down the process of AD. It is reported that anesthesia and surgery will induce neurocognitive deterioration in AD, but the mechanism is not quite clear. In this study, we aim to compare the cognitive impairment between 5XFAD transgenic (Tg) mice and its littermate (LM) after isoflurane anesthesia and surgery to clarify the specific impacts of anesthesia and surgery on individuals with AD and to explore the mechanisms.MethodsWe performed abdominal surgery in cognitively impaired, 4-month-old female 5XFAD mice and LM control mice. Isoflurane anesthesia (1.4%) was induced and maintained over 2 h. Open field and fear conditioning tests were conducted on 1, 3 and 7 days after anesthesia and surgery. The total distance, velocity and freezing time were the major outcomes. P-tau (AT8), tau oligomers (T22), stress granules (SGs), the SYK tyrosine kinase and p-SYK in the hippocampus at postoperative day 1 were evaluated by Western Blot assays. The colocalization of SGs, SYK, p-SYK, and neurons in the hippocampus section was assessed using qualitative immunofluorescence.ResultsIn the open field test, no difference between the distance moved and the velocity of LM mice and 5XFAD Tg mice were found on day 1 after anesthesia and surgery. 5XFAD Tg mice exhibited reduced freezing time of fear conditioning context test on postoperative day 3, but not on day 7; the LM mice showed no changes in FCTs. Furthermore, p-tau, tau oligomers, SGs, SYK and p-SYK were evident in the hippocampus region of 5XFAD Tg mice on a postoperative day 1. In addition, SGs, SYK, p-SYK were colocalized with hippocampus neurons, as shown by immunofluorescence.ConclusionThis study demonstrates that anesthesia and surgery may induce tau-associated neurocognitive deterioration in individuals with AD. The mechanism under it may be associated with SGs and the tyrosine kinase, SYK. After anesthesia and surgery, in 5XFAD Tg mice, SGs were formed and SYK was phosphorylated, which may contribute to the phosphorylation of tau protein. This study provided hints that individuals with AD may be more vulnerable to anesthesia and surgery.