Linear Breit-Wheeler process driven by compact lasers

We report a proposal to observe the two-photon Breit-Wheeler process in plasma driven by compact lasers. A high-charge electron bunch can be generated from laser plasma wakefield acceleration when a tightly focused laser pulse propagates in a subcritical density plasma. The electron bunch scatters with the laser pulse coming from the opposite direction and resulting in the emission of high brilliance x-ray pulses. In a three-dimensional particle-in-cell simulation with a laser pulse of ∼10 J, one could produce an x-ray pulse with a photon number higher than 3×10^{11} and brilliance above 1.6×10^{23} photons/s/mm^{2}/mrad^{2}/0.1%BW at 1 MeV. The x-ray pulses collide in the plasma and create more than 1.1×10^{5} electron-positron pairs per shot. It is also found that the positrons can be accelerated transversely by a transverse electric field generated in the plasma, which enables the safe detection in the direction away from the laser pulses. This proposal enables the observation of the linear Breit-Wheeler process in a compact device with a single shot.

[Best evidence summary of prevention strategies for pressure injury in adult hospitalized burn patients]

Objective: To summarize the best evidence of prevention strategies for pressure injury in adult hospitalized burn patients. Methods: A bibliometric approach was used. Systematic searches were carried out to retrieve the published evidence of prevention strategies for pressure injury in adult hospitalized burn patients in the official websites of relevant academic organizations such as International Society for Burn injury, American Burn Association, and Japanese Dermatology Association, National Pressure Injury Advisory Panel, European Pressure Injury Advisory Panel, Pan Pacific Pressure Injury Alliance International Guidelines Website, foreign language databases such as UpToDate, BMJ Best Practice, MedSci, Joanna Briggs Institute Evidence-Based Practice Database, Cochrane Library, Web of Science, Embase, and PubMed, and Chinese databases such as China Biology Medicine disc, China National Knowledge Infrastructure, Wanfang Database, and China Clinical Guidelines Library. The literature types include clinical decision-making, evidence summary, guidelines, systematic review, and expert consensus. The search time was till February 21st, 2023. Two researchers independently screened the literature and evaluated the quality, and other researchers extracted and graded the evidence according to the topic. Results: A total of 10 papers were included, including 6 evidence summaries, 3 guidelines, and 1 expert consensus, all with high literature quality. After extracting evidence and classifying, 27 pieces of best evidences were summarized from three aspects, including prevention training and supervision, risk assessment, and prevention measures of pressure injury. Conclusions: A total of 27 pieces of best evidences of prevention strategies for pressure injury in adult hospitalized burn patients were summarized from 3 aspects. Medical workers can follow the best evidence and give personalized prevention strategies according to the specific condition of adult hospitalized burn patients to reduce the incidence of pressure injury.

High efficiency and collimated terahertz pulse from ultra-short intense laser and cone target

We propose a new, to the best of our knowledge, method to radiate a high-efficiency and collimated terahertz (THz) pulse from a relativistic femtosecond laser and cone target. Particle-in-cell simulations demonstrate that a THz source of 40 mJ, pointing at an angle of ∼20 ^∘, can be generated from a laser pulse of 1.9 J by using a cone target whose open angle is 10 ^∘. The peak power of the THz pulse is 10¹¹ W. This method, which manipulates the divergence angle and the energy conversion efficiency of the THz source, should promote THz science into the extra strong region with a compact laser system.

Effects of the circadian rhythm on milk composition in dairy cows: Does day milk differ from night milk?

Metabolism in most organisms can show variations between the day and night. These variations may also affect the composition of products derived from livestock. The aim of the present study was to investigate the difference in composition between the day milk and night milk of dairy cows. Ten multiparous Holstein cows (milk yield = 25.2 ± 5.00 kg/d) were randomly selected during mid lactation. Milk samples were collected at 0500 h ("night milk") and 1500 h ("day milk") and analyzed to determine their composition. Mid-infrared spectroscopy was used to analyze macronutrient content of milk. Metabolomics and lipidomics were used to detect and analyze small molecules and fatty acids, respectively. An automatic biochemical analyzer and ELISA kits were used to determine biochemical indicators, as well as antioxidant and immune parameters in the milk. Though milk fat, protein, lactose, and total milk solids were not different between day milk and night milk, small molecules, metabolites and lipids, and hormones and cytokines differed between day milk and night milk. Regarding biochemical and immune-related indicators, the concentrations of malondialdehyde, HSP70, and HSP90 in night milk were lower than that in day milk. However, interferon-γ levels were higher in night milk. Additionally, night milk was naturally rich in melatonin. Lipidomics analyses showed that the levels of some lipids in night milk were higher than those in day milk. Metabolomics analyses identified 36 different metabolites between day milk and night milk. Higher concentrations of N-acetyl-d-glucosamine, cis-aconitate, and d-sorbitol were observed in day milk. However, the other 33 metabolites analyzed, including carbohydrates, lipids, AA, and aromatic compounds, showed lower concentrations in day milk than in night milk. The present findings show that the composition of night milk differs considerably from that of day milk. Notable changes in the circadian rhythm also altered milk composition. These results provide evidence to support the strategic use and classification of day milk and night milk.

Short communication: A decrease in diameter of milk fat globules accompanies milk fat depression induced by conjugated linoleic acid supplementation in lactating dairy cows

Milk fat is secreted from the mammary gland in the form of milk fat globules (MFG). Although milk fat depression has been studied since the beginning of the last century, the extent to which this phenomenon alters MFG synthesis is not fully understood. The aim of this study was to evaluate the effect of conjugated linoleic acid (CLA) on the size and distribution of MFG during milk fat depression in dairy cows. Twelve Holstein cows in mid lactation (145 ± 31 d in milk, 583 ± 34.6 kg of body weight, and 27.2 ± 2.4 kg of milk/d) were randomly assigned to a control diet or control plus Ca-protected CLA at 15 g/kg of dry matter for a 6-d period. The average diameter and particle size distribution of MFG were measured using a Mastersizer 3000 laser particle size analyzer (Malvern Instruments Ltd., Malvern, UK). Feeding CLA did not affect dry matter intake (16.2 ± 0.4 kg/d), milk production (28.4 ± 0.4 kg/d), milk protein, or lactose, but it decreased milk fat content (3.46 vs. 2.52%). In addition, surface area-related mean diameter of fat globules in cows fed CLA was lower compared with controls (3.02 vs. 3.45 μm). The percentage of large fat globules decreased and that of small fat globules increased in response to CLA. Overall, the data suggest that the milk fat depression induced by CLA is accompanied by a decrease in average diameter of MFG.

Phosphorylation of AKT serine/threonine kinase and abundance of milk protein synthesis gene networks in mammary tissue in response to supply of methionine in periparturient Holstein cows

The main objective was to evaluate the effect of increasing the supply of Met around parturition on abundance and phosphorylation of insulin- and mechanistic target of rapamycin complex 1 (mTORC1)-related signaling proteins along with mRNA abundance of milk protein and fat synthesis-related genes in postpartal mammary tissue. A basal control diet (control) or the basal diet plus ethyl-cellulose rumen-protected Met (0.9 g/kg of dry matter intake; Mepron, Evonik Nutrition & Care GmbH, Hanau-Wolfgang, Germany) were fed (n = 30 cows/diet) from d -28 to 60 relative to parturition. Mammary tissue and blood plasma were harvested from the same cows (n = 5/diet) in the control and Met groups at d 21 postpartum for mRNA, protein, and AA analysis. Increasing the supply of Met led to greater milk protein percentage and milk yield along with greater ratio of phosphorylated (p-)AKT to total AKT. The ratio of p-mTORC1 to total mTORC1 did not differ, but ratio of p-RPS6 to total ribosomal protein S6 (RPS6) was lower in response to Met supply. These responses were associated with greater mRNA abundance of the signaling proteins Janus kinase 2 (JAK2) and insulin receptor substrate 1 (IRS1). Greater Met supply also upregulated mRNA abundance of high-affinity cationic (SLC7A1) and sodium-coupled AA transporters (SLC38A1, SLC38A2); leucyl-tRNA (LARS), valyl-tRNA (VARS), and isoleucyl-tRNA synthetases (IARS); glucose transport solute carrier family 2 member 3 (SLC2A1); glucose transport solute carrier family 2 member 3 (SLC2A3); and casein α-s1 (CSN1S1). The mRNA abundance of components of the unfolded protein response, such as x-box binding protein 1 (XBP1) and activating transcription factor 6 (ATF6), were upregulated, and protein phosphatase 1, regulatory subunit 15A (PPP1R15A) was downregulated in response to greater Met supply. Overall, the data suggest that increased dry matter intake, greater phosphorylation status of AKT, upregulation of glucose and AA transporters, and transcripts of tRNases in response to enhanced Met supply might have compensated for a reduction in ribosome biogenesis due to a lower ratio of p-RPS6 to total RPS6. Together, these cellular responses constitute a mechanism whereby Met supply can regulate milk protein synthesis in early lactation.

Overexpression of SREBF chaperone (SCAP) enhances nuclear SREBP1 translocation to upregulate fatty acid synthase (FASN) gene expression in bovine mammary epithelial cells

Fatty acid synthase is a key enzyme for the synthesis of milk fat in the ruminant mammary gland. In nonruminants, sterol regulatory element binding protein 1 (SREBP1) is a regulator of FASN gene expression, and SREBF chaperone (SCAP) is essential for SREBP1 maturation and activity. However, the role of SCAP on the regulation of FASN gene expression in ruminants is unknown. The objective of this study was to investigate the transcriptional regulation of FASN by overexpressing SCAP in bovine mammary epithelial cells. A bovine SCAP expression vector, SREBP1 expression vector, and the promoter of FASN were cloned. The transcription factor binding sites of FASN promoter were predicted using bioinformatics analysis. After transfection with FASN promoter vectors in the immortalized bovine mammary epithelial cell line MAC-T, we co-overexpressed the SCAP + SREBP1 expression vector with pcDNA3.1 vector as control. The effect of SCAP + SREBP1 overexpression on the regulation of FASN was investigated using luciferase assay, immunofluorescence, Western blot, real-time PCR, and lipid droplet staining. We observed that co-overexpression of SCAP + SREBP1 significantly increased activity of the FASN promoter containing a sterol response element binding site. The FASN mRNA abundance and lipid droplet formation increased due to co-overexpression of SCAP + SREBP1. Compared with overexpression of SREBP1 alone, co-overexpression of SCAP + SREBP1 enhanced the nuclear translocation and nuclear SREBP1 protein abundance. Overall, as in nonruminants cells, results indicate that SCAP is essential for promoting nuclear translocation of SREBP1 and activation of FASN gene transcription, leading to lipid droplet formation in bovine mammary epithelial cells.

mRNA abundance and expression of SLC27A, ACC, SCD, FADS, LPIN, INSIG, and PPARGC1 gene isoforms in mouse mammary glands during the lactation cycle

The functions of distinct isoforms of solute carrier family 27 transporters (SLC27A1-6), acetyl-CoA carboxylase (ACACA, ACACB), stearoyl-CoA desaturase (SCD1-4), fatty acid desaturase (FADS1-3), LPIN (LPIN1-3), insulin-induced gene (INSIG1, 2), and peroxisome proliferator-activated receptor gamma coactivator1 (PPARGC1A, B) were studied in the mouse mammary gland from pregnancy to lactation. The relative mRNA abundance and percent change in real-time PCR were determined. mRNA expression of SLC27A3 and SLC27A4 was 37- and 1.4-fold more upregulated at 12 days of lactation, respectively (P < 0.01). Transcripts of SCD isoforms were the most abundant, accounting for 59% of all genes measured, and PPARGC1 isoforms were the least (0.06% of all genes measured). The mRNA abundance from ACC, FADS and LPIN accounted for 29, 9 and 2.6%, respectively. INSIG1 mRNA expression was 32-fold more upregulated (P < 0.05), while PPARGC1B was 0.18-fold downregulated at 18 days of lactation (P < 0.01). We concluded that mRNA abundance and expression of these isoforms are affected by the stage of lactation.

Selection and use of reference genes in mouse mammary glands

Obtaining quantitative data concerning gene expression is important for understanding milk synthesis in mammary glands. Quantitative real-time PCR (qRT-PCR) is an efficient tool to calculate gene expression; however, it is necessary to find valid reference genes for normalization of qRT-PCR data. We applied the geNorm software to eight commonly used reference genes to identify the most stable and optimal genes for the mouse mammary gland. Based on this analysis, HPRT, RPL and GAPDH are the most appropriate reference genes for data normalization. We tested the expression of the alpha-lactalbumin and fatty acid synthase genes using these three reference genes, both normalized and non-normalized. The normalized mRNA expression ratio was significantly different from the non-normalized ratio. We recommend the use of these three reference genes for the normalization of qRT-PCR data in gene expression studies of mouse mammary glands.

[Electron microscopic studies of the endoplasmic reticulum in whole--mount cultured human nasopharyngeal carcinoma cell line]

The endoplasmic reticulum system (ER) in whole-mount human nasopharyngeal carcinoma parent cell line (CNE-2Z) and its variants L2, H2, L4 was observed using potassium permangnate as a fixtive. In lamellapodia and labopodia, the ER was arranged as a nest structure, but it usually formed lines of straight tubules in the filopodia. The results suggested that there may be some relationship between the ER and the functional activities of pseudopodia. No significant difference of ER was found yet in morphology, structure, quantities and distribution between CNE-2Z cells and its variants.

[Studies on the gap junctional intercellular communication of human nasopharyngeal carcinoma cells and effect of RII]

To evaluate the effects of gap junctional intercellular communication (GJIC) on the growth, invasion and metastasis of tumor, human nasopharyngeal carcinoma (HNPC) parent cell line (CNE-2Z) and its variants (L2, H2, L4) with different invasive and metastatic potential were examined in vitro. Only a few intermediate junction (IJ) but no gap junction (GJ) structures were observed under EM. The parent line cells showed marked GJIC, while its variants lacked this function by SLDT technique. It was further shown that L2 cell line (variant with high invasive potential) had lower concentration of cytosolic free calcium ([Ca2+]i) compared to H2, L4 cell lines (variants with medium and low invasive potential, respectively). It reflected that some correlation may exist between [Ca2+]i level and the invasive potential of HNPC cell lines. The effect of RII on GJIC of HNPC was also investigated. After 3-7 ds of RII (0.0001 mol/L) treatment, there was no change in the number of GJs. The GJIC function of CNE-2Z weakened and then disappeared finally with prolonged RII treatment. The level of [Ca2+]i in HNPC cells apparently fell after 6h of RII treatment, and rose to original level with persistent RII treatment. Whether the fluctuating of [Ca2+]i level relates the inhibitory effect of RII treatment. Treatment on the growth and invasion needs to be further studied.