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Biochemical reactions in cells serve as the endogenous source of heat, maintaining a constant body temperature. This process requires proper control; otherwise, serious consequences can arise due to the unwanted but unavoidable responses of biological systems to heat. This review aims to present a range of responses to heat in biological systems across various spatial scales. We begin by examining the impaired thermogenesis of malignant hyperthermia in model mice and skeletal muscle cells, demonstrating that the progression of this disease is caused by a positive feedback loop between thermally driven Ca2+ signaling and thermogenesis at the subcellular scale. After we explore thermally driven force generation in both muscle and non-muscle cells, we illustrate how in vitro assays using purified proteins can reveal the heat-responsive properties of proteins and protein assemblies. Building on these experimental findings, we propose the concept of 'trans-scale thermal signaling'. [ABSTRACT FROM AUTHOR]

Aim: In recent years, the Kuchi‐kara Taberu (KT) index has been used as a new tool for the evaluation of dysphagia; however, its predictive ability remains unknown. This study was conducted to examine the validity of oral intake recovery prediction using the KT index in patients with aspiration pneumonia. Methods: The subjects were older inpatients admitted to an acute‐care hospital for the treatment of aspiration pneumonia. A logistic regression analysis was conducted to clarify factors significantly associated with oral intake recovery. In addition, cut‐off values of the predictors were calculated using a receiver operating characteristic curve analysis with the area under the curve (P < 0.05). Results: A total of 124 patients (mean age 84.3 ± 7.9 years old, 70 males, 54 females) were enrolled in this study and divided into two groups at discharge: the oral intake group (62.1%) and the non‐oral intake group (37.9%). The significant predictors of the recovery of oral intake were the pre‐treatment period, treatment period, and the total score of the KT index; the respective odds ratios were 1.082 (95% confidence interval [CI] 1.013–1.156), 1.018 (1.003–1.033) and 0.850 (0.780–0.927), and the respective areas under the curve were 0.407 (95% CI 0.300–0.515), 0.304 (0.208–0.399), and 0.732 (0.640–0.824). The cut‐off value of the total score of the KT index was 30. The model showed 85.7% sensitivity and 57.4% specificity. Conclusion: The KT index is suggested to be a valid variable for predicting whether or not a patient with aspiration pneumonia can recover their oral intake ability during acute‐care hospitalization. Geriatr Gerontol Int 2023; 23: 221–226. [ABSTRACT FROM AUTHOR]

Functionalized diamond nanocrystals persistently expand their use for sensing and labeling in a biological context. The surface of such crystals modified chemically adds additional modality to such applications. In this Perspective, we discuss mainly applications in nanothermometry but begin with a brief general introduction of fluorescent nanodiamonds. Then we consider temperature at the sub-cellular environment, explain the working principle of fluorescent nanodiamonds as temperature probes, and demonstrate their biological applications from the literature. The application of nanohybrids (such as heater-thermometer hybrids built within a single nanoparticle) in biological cells will be covered with more details. We summarize recent results of intracellular measurements to estimate that 0.1 nJ of heat released in a cellular hot spot of 1-μm radius can produce a 1-K temperature rise lasting for about 50 μs and repeatable approximately every 2 ms. Our view on the reason for limitations in biological applications of nanodiamonds concludes the review. [ABSTRACT FROM AUTHOR]

The article presents the discussion on intracellular process being a fundamental origin of rising body temperature above the ambient value. Topics include fundamental understanding of the intracellular heat transfer requiring the advance modeling of molecular dynamics; and polymer (polydopamine or PDA) absorbing a fraction of such light and converting it into heat which being released into the media surrounding the particle.

The interaction between actin filaments and myosin molecular motors is a power source of a variety of cellular functions including cell division, cell motility, and muscular contraction. In vitro motility assay examines actin filaments interacting with myosin molecules that are adhered to a substrate (e.g., glass surface). This assay has been the standard method of studying the molecular mechanisms of contraction under an optical microscope. While the force generation has been measured through an optically trapped bead to which an actin filament is attached, a force vector vertical to the glass surface has been largely ignored with the in vitro motility assay. The vertical vector is created by the gap (distance) between the trapped bead and the glass surface. In this report, we propose a method to estimate the angle between the actin filament and the glass surface by optically determining the gap size. This determination requires a motorized stage in a standard epi-fluorescence microscope equipped with optical tweezers. This facile method is applied to force measurements using both pure actin filaments, and thin filaments reconstituted from actin, tropomyosin and troponin. We find that the angle-corrected force per unit filament length in the active condition (pCa = 5.0) decreases as the angle between the filament and the glass surface increases; i.e. as the force in the vertical direction increases. At the same time, we demonstrate that the force on reconstituted thin filaments is approximately 1.5 times larger than that on pure actin filaments. The range of angles we tested was between 11° and 36° with the estimated measurement error less than 6°. These results suggest the ability of cytoplasmic tropomyosin isoforms maintaining actomyosin active force to stabilize cytoskeletal architecture. [ABSTRACT FROM AUTHOR]

Ca2+distribution is spatially and temporally non-uniform inside cells due to cellular compartmentalization. However, Ca2+sensing with small organic dyes, such as fura-2 and fluo-4, has been practically applied at a single cell level where the averaged signal from freely diffusing dye molecules is acquired. In this study, we aimed to target azide-functionalized fura-2 (N3-fura-2) to a specific site of subcellular compartments to realize focal Ca2+sensing. Using scAVD (single-chain avidin)–biotin interaction and a copper-free click reaction system, we linked N3-fura-2 to specifically-targeted scAVD protein fused with a red fluorescent protein mCherry, so that Ca2+sensors conjugated with four N3-fura-2 dyes with dibenzocyclooctyne (DBCO)-PEG4-biotin as a linker were generated at subcellular compartments in living cells. In cytoplasm, N3-fura-2 showed a prolonged retention period after binding to scAVD. Furthermore, the reacted N3-fura-2 was retained inside cells even after free dyes were washed out by methanol fixation. When scAVD was overexpressed on endoplasmic reticulum (ER) membranes, N3-fura-2 was accumulated on ER membranes. Upon histamine stimulation, which increases cytosolic Ca2+concentration, ER-localized N3-fura-2 successfully sensed the Ca2+level changes at the cytosolic side of ER membrane. Our study demonstrated specific targeting of N3-fura-2 to subcellular compartments and the ability of sensing focal Ca2+level changes with the specifically targeted Ca2+sensors. [ABSTRACT FROM PUBLISHER]

We describe organelle thermometry using an endoplasmic reticulum-targeting small molecule dye and cytosolic mCherry, whose fluorescence lifetimes reduce with increasing temperature and can be monitored by fluorescence lifetime imaging microscopy. The results show that heat production in single myotubes is highly localized and is coupled to a Ca2+ burst. [ABSTRACT FROM AUTHOR]

We propose an instant micro-thermography method using a fluorescent-nanoparticle thermosensor capable of reporting temperature as the fluorescence intensity ratio of the temperature-sensitive dye to the reference. We demonstrate “temperature mapping” inside a fruit fly larva that was orally dosed with nanoparticle thermosensors. [ABSTRACT FROM AUTHOR]

Intracellular thermometry at the microscopic level is currently a hot topic. Herein we describe a small molecule fluorescent thermometer targeting mitochondria (Mito thermo yellow). Mito thermo yellow successfully demonstrates the ability to monitor the intracellular temperature gradient, generated by exogenous heating, in various cells. [ABSTRACT FROM AUTHOR]

This paper proposes a remarkably facile staining protocol to visually investigate dynamic physiological events in insect tissues. We attempted to monitor Ca2+ dynamics during contraction of electrically stimulated living muscle. Advances in circuit miniaturization and insect neuromuscular physiology have enabled the hybridization of living insects and man-made electronic components, such as microcomputers, the result of which has been often referred as a Living Machine, Biohybrid, or Cyborg Insect. In order for Cyborg Insects to be of practical use, electrical stimulation parameters need to be optimized to induce desired muscle response (motor action) and minimize the damage in the muscle due to the electrical stimuli. Staining tissues and organs as well as measuring the dynamics of chemicals of interest in muscle should be conducted to quantitatively and systematically evaluate the effect of various stimulation parameters on the muscle response. However, existing staining processes require invasive surgery and/or arduous procedures using genetically encoded sensors. In this study, we developed a non-invasive and remarkably facile method for staining, in which chemical indicators can be orally administered (oral dosing). A chemical Ca2+ indicator was orally introduced into an insect of interest via food containing the chemical indicator and the indicator diffused from the insect digestion system to the target muscle tissue. We found that there was a positive relationship between the fluorescence intensity of the indicator and the frequency of electrical stimulation which indicates the orally dosed indicator successfully monitored Ca2+ dynamics in the muscle tissue. This oral dosing method has a potential to globally stain tissues including neurons, and investigating various physiological events in insects. [ABSTRACT FROM AUTHOR]

A triblock copolymer, poly(styrene-b-2-vinyl pyridine- b-ethylene oxide) (PS-b-P2VP-b-PEO) was used as a soft template to synthesize large-sized mesoporous phosphosilicate thin films. The kinetically frozen PS core stabilizes the micelles. The strong interaction of the inorganic precursors with the P2VP shell enables the fabrication of highly robust walls of phosphosilicate and the PEO helps orderly packing of the micelles during solvent evaporation. The molar ratio of phosphoric acid and tetraethyl orthosilicate is crucial to achieve the final mesostructure. The insertion of phosphorus species into the siloxane network is studied by 29Si and 31P MAS NMR spectra. The mesoporous phosphosilicate films exhibit steady cell adhesion properties and show great promise as excellent materials in bone-growth engineering applications. [ABSTRACT FROM AUTHOR]