Advances in experimental medicine and biology最新文献

The aim of the study was to evaluate changes in eye movement conjugation in healthy volunteers in response to transcranial photobiomodulation (tPBM).

Materials and methods: 54 healthy volunteers (23 men, 31 women; median age was 23.5 years) were included in this retrospective, non-randomized study. Eye tracking (ET) was performed using the iPad app EyeTracker with a sampling rate of 20 Hz before and after 10 min tPBM (810 nm). The tracker calculated angular velocities in the vertical and horizontal planes (AV; vertical and horizontal). Data are shown as a median [interquartile range]. Pearson's correlation coefficients were used to assess agreement between computed variables. This coefficient value was designated as the vergence reactivity index (VRx), which reflects the eye movement conjugation. The differences were determined using the Wilcoxon T-criterion. The level of significance was p < 0.05.

Results: Vertical and horizontal VRx after tPBM were significantly higher than before the procedure: 0.878 [0.843; 0.902] vs. 0.783 [0.702; 0.829], p < 0.001, respectively and 0.875 [0.834; 0.912] vs. 0.927 [0.921; 0.93], p < 0.001, respectively.

Conclusion: Transcranial PBM causes a significant increase in vertical and horizontal vergence indices, which indicates an improvement in eye movement conjugation in healthy volunteers.

The focus of this overview is on the use of EPR oximetry in biological systems with an emphasis on soluble probes. EPR oximetry measures oxygen concentrations based on changes in electron spin relaxation of probes such as trityl and nitroxide radicals. The experimental relaxation rates depend on the inherent relaxation of the probe, the effects of probe-probe collisions, and the relaxation enhancement caused by collisions of the probe with O₂. To extract the oxygen concentration requires an understanding of all three contributions. The inherent relaxation rates of the probe depend on the rates of tumbling and on microwave frequency. The effects of probe-probe collisions depend on concentration, and for charged trityl radicals depend on ionic strength of the solution. The interactions of O₂ with nitroxide and trityl radicals can be described in terms of exchange interactions and the dynamics of collisions in solution. The spatial volume elements that can typically be observed in EPR imaging experiments are large enough that the volume could contain a range of concentrations of radicals and of O₂, which may result in distributions of linewidths and relaxation times that need to be considered in analyzing data. When using EPR oximetry in living systems, it is also necessary to consider whether the oxygen concentration is changing on the timescale of the experiment.

Assessment of oxygen saturation for biological tissues is crucial in many medical applications. A non-contact oxygenation measurement is important in clinical scenarios, for example, emergency situations and imaging-guided surgery, because non-contact measurement will speed up the measurement preparation by eliminating the need for cleaning skin and sensor for hygrine and placement of sensor. Near-infrared spectroscopy stands out as a key technology for probing tissue oxygenation. Non-contact measurement requires precise estimation of the distance between the tissue and the probe. However, high precision light detection and ranging in the near-infrared region is challenging to achieve when targeting biological tissues due to the strong light scattering. This challenge limits the design of non-contact instruments for oxygenation assessment.

Aim: The aim is to utilize time-of-flight (ToF) sensors to accurately determine both oxygenation (optical properties (OP), i.e., absorption and scattering coefficients) of biological tissues and the distance to these tissues.

Methods: Model-based direct ToF (DToF) models were built with a focus on highly scattering objects. A simulation study was performed to determine the OPs and distances. Two simulation tests were performed for a scattering object placed at 30 cm and 62 cm away. To demonstrate that the ToF measurements are sensitive to the OPs of the scattering object, we placed a tissue-mimicking phantom at 62 cm from the measurement plane, formed by a pulsed laser coupled to a collimator and a pinhole, while a single photon avalanche camera next to the emission point captures the ToF signals at four different wavelengths.

Results: In both cases, the retrieved OPs and distances were very close to the reference parameters with <0.5% average error, showing the accuracy of the optimization process. The multi-spectral ToF measurements confirmed the simulation.

Conclusion: We developed a model-based DToF approach for precise oxygenation measurement at a distance. This method holds great potential for non-contact oxygenation measurements, offering valuable insights for various clinical scenarios.

Oximetry is used to quantify the presence of oxygen in human blood within soft tissues of the human body. Among multiple implementations of this technology, pulsatile oxygen saturation (SpO₂) is a core medical technology and is being rapidly adopted in consumer health. However, despite its long history of clinical use, recent findings indicate that the accuracy of pulse oximetry may be affected by various factors and biases. For example, the COVID-19 pandemic showed that pulse oximeters exhibited flaws in accuracy due to the skin pigmentation of patients with darker skin. Thus, the future of this technology, particularly in consumer health devices, needs to be built on foundations that account for such biases. This chapter reviews the principles of pulse oximetry, sources of its artifacts, calibration methods, and the factors that may cause inaccuracy in pulse oximeters, particularly pertinent to two-wavelength pulse oximetry. Drawing upon recent research and clinical insights, we review the multifaceted nature of pulse oximetry biases, including motion artifacts, skin pigmentation, body mass index, environmental variables, device calibration, and nail polish, among others.

Temperature directly shapes insect physiology and has a preponderant effect on life history traits. Winter conditions in temperate and polar regions are especially challenging for insects. Extremely low temperatures can indeed compromise insect survival by promoting freezing of body fluids, but mild cold temperatures above 0 °C (i.e., chilling) can also lead to complex and severe physiological dysregulations. Among physiological damages due to freezing and chilling, insect lipids are one of the primary targets. As low temperatures tend to rigidify phospholipid bilayers, membrane functions are compromised in the cold. Lipid rigidification due to cold also decreases the accessibility of fat stores for metabolic enzymes, and therefore their availability for basal metabolism. These deleterious effects, combined with low food availability in winter, result in substantial nutritional challenges for overwintering insects. Consequently, lipid modifications such as homeoviscous adaptation of cell membranes, fluidity maintenance of fat reserves, cuticular lipid accumulation, and production of antifreeze glycolipids are essential components of the physiological response to cold stress. The aim of the present chapter is to present the physiological challenges caused by low temperatures, the lipid modifications linked with cold tolerance in insects, and the molecular regulation of lipid metabolism during cold exposure.

According to the World Health Organization vector-borne diseases account for more than 17% of all infectious diseases, causing more than 700,000 deaths annually. Vectors are organisms that are able to transmit infectious pathogens between humans, or from animals to humans. Many of these vectors are hematophagous insects, which ingest the pathogen from an infected host during a blood meal, and later transmit it into a new host. Malaria, dengue, African trypanosomiasis, yellow fever, leishmaniasis, Chagas disease, and many others are examples of diseases transmitted by insects.Both the diet and the infection with pathogens trigger changes in many metabolic pathways, including lipid metabolism, compared to other insects. Blood contains mostly proteins and is very poor in lipids and carbohydrates. Thus, hematophagous insects attempt to efficiently digest and absorb diet lipids and also rely on a large de novo lipid biosynthesis based on utilization of proteins and carbohydrates as carbon source. Blood meal triggers essential physiological processes as molting, excretion, and oogenesis; therefore, lipid metabolism and utilization of lipid storage should be finely synchronized and regulated regarding that, in order to provide the necessary energy source for these events. Also, pathogens have evolved mechanisms to hijack essential lipids from the insect host by interfering in the biosynthesis, catabolism, and transport of lipids, which pose challenges to reproduction, survival, fitness, and other insect traits.In this chapter, we have tried to collect and highlight the current knowledge and recent discoveries on the metabolism of lipids in insect vectors of diseases related to the hematophagous diet and pathogen infection.

Lipidomics, a specialized branch of metabolomics, investigates the diversity and functionality of lipids in biological systems. Lipids serve crucial roles in energy storage, membrane composition, and environmental acclimation in insects, underpinning processes such as development and stress responses. Advances in analytical technologies, such as liquid chromatography-mass spectrometry (LC-MS), have enabled precise identification and quantification of lipid species, providing unprecedented insights into lipid metabolism and dynamics. Key lipid classes, including triacylglycerols and phospholipids, exhibit structural and functional versatility, adapting to environmental pressures through mechanisms like homeoviscous adaptation. These dynamic lipid responses are essential for maintaining cellular and cuticular integrity and functionality under stress. By exploring lipid diversity and adaptations, lipidomics offers valuable perspectives on insect physiology, survival strategies, and evolutionary ecology. This chapter summarizes methods used to study insect lipidomes and highlights comparative lipidomic studies that have advanced our understanding of insect biology.

Assisted reproductive technologies (ARTs) have been investigated and applied for species conservation for more than 50 years. These gamete- and embryo-based technologies require access to reproductively active males and females, which can be challenging in conservation breeding programs for threatened and endangered species. The advancements in stem cell technologies over the past 10 years, specifically the induction of pluripotent stem cells from adult somatic cells and related stem cell-based "ex vivo genesis" systems, have been remarkable. Knowledge gained from laboratory animals and humans has laid the foundation for the application of stem cell technologies in wildlife species, which prompted an increase in living cell biobanks around the world, and a recent emergence of biotech companies promising technology-based solutions for the restoration of currently threatened and resurrection of extinct species. While studies have shown the potential for stem cells in the ART arsenal, there are significant challenges that must be overcome, beginning with the low efficiency and genetic instability that are hindering the transition from research to application. This review highlights the key stem cell technologies in reproductive medicine with a focus on applications for species conservation.

Blood flow modifies oxygen availability and biomechanical forces within the vasculature of the embryo as the hematopoietic system develops. The aorta-gonad-mesonephros (AGM) envelops the largest artery in the body and is a critical site for the emergence of hematopoietic stem cells (HSCs). Herein, I discuss the role of hypoxia-inducible factors (HIFs) and force as determinants of metabolism and fate determination. To address the effects of blood flow on hematopoietic development, I employ mouse embryo models and biomimetic culture. Real-time cell metabolic analyses show that oxygen consumption rates (OCR) and extracellular acidification rates (ECAR) are altered by flow in cultures of AGM cells. Additionally, mitochondrial permeability transition pore (mPTP) activity assays indicate that mPTP opening is regulated as precursors commit to a hematopoietic fate. Moreover, transcriptome data suggest that expression of Ppif, the gene that encodes the mPTP regulator Cyclophilin D, may be downregulated by fluid force. Together, these data implicate blood flow in regulation of metabolic activity in the AGM region, influencing bioenergetics and serving as a cue for HSC emergence. The broader significance of this research lies in its potential to accurately recapitulate the hematopoietic niche in vitro for study of blood disorders and improvement of cellular therapies.

The field of structural biology has undergone a remarkable transformation over the past decade, fueled by cutting-edge advancements in X-ray crystallography and cryo-electron microscopy (cryo-EM). Central to both approaches is the critical step of sample preparation, which includes heterologous expression of membrane proteins in host systems and extraction from the membrane environment using suitable membrane mimetics. In crystallography, enhanced techniques, such as lipidic cubic phase (LCP) crystallization and serial femtosecond crystallography (SFX), have pushed the boundaries of structure determination to microcrystals and conformationally labile targets. In cryo-EM, technical advancements across many levels have fueled the "resolution revolution," enabling cryo-EM to reach near-atomic resolution and driving single-particle analysis of increasingly small, dynamic, and heterogeneous macromolecular assemblies. Emerging modalities further extend our capability to tackle previously inaccessible questions. Cryo-electron tomography (cryo-ET) is extracting structural insights from native cellular environments, and micro-electron diffraction (MicroED) has opened new frontiers for nanoscale structural studies from submicron crystals at unprecedented resolution. Collectively, these advances have improved our ability to study the structure of challenging targets, with profound implications for structure-based drug discovery, and an evolving paradigm shift toward dynamic visualization of biomolecular processes, signaling the dawn of a new era in structural biology.