Scanning calorimetry measurements of the energy parameters of a plasmochemical polymer oxidation reaction

The contributions of heat fluxes of different nature to the total heat flux from a weakly ionized oxygen plasma of a low-pressure (20–120 Pa) RF discharge onto the calorimeter surface, on which a chemical reaction between atomic oxygen and a polymer proceeds, are distinguished. The activation energy (ΔE≈0.37 eV), the reaction heat (H≈27 kJ/g), and the rate constant for heat release in a surface plasmochemical reaction are determined.     

Dipole Theory of Heat Production and Absorption in Nerve Axon

Exact formulas are derived for the energy change of a dipole system with two energy states (or bands) in a changing field in two cases: (a) no dipole flip-flop and (b) dipole flip-flop caused by stimulation. Based on these formulas, the positive and negative heats are calculated. The results are in good agreement with experiment in case b but are 60-180% larger in case a. Furthermore, the theory shows that the negative heat cannot be less than the positive heat in case a but can be either way in case b, the latter result being found prevalent in experiment. It is concluded that nerve excitation is most likely to involve dipole flip-flop at the membrane surface. The theory is consistent in the interpretations and correlations of the electrical, optical, and thermal effects observed in nerve axon.     

A need to provide explanations for observed biological effects of radiofrequency exposure

Abstract

Although there is scientific consensus that radiofrequency (RF) exposure at high intensity can cause thermal effects, including well-established adverse health effects, there is still considerable controversy on whether low-intensity RF exposure can cause biological effects, especially adverse health effects. The objective of this paper is to describe several reported “non-thermal” effects that were later shown to be due to a weak thermal effect or an experimental artifact by properly conducted and thorough follow-on scientific research. First, the multiple factors that can cause different RF energy absorption in biological tissues are reviewed and second, several examples of experimental artifacts in published papers are described to demonstrate the importance of paying attention to dosimetry and temperature control. For example, isolated nerve response studies show that when temperature of the RF-exposed tissues is controlled, effects disappeared. During RF exposure, conductive electrodes routinely used in physiological studies have been shown to cause field intensification at the tips or contacts of the electrodes with biological tissue; thus, the RF exposure at the site of measurement could be much higher than the incident field. In some in vitro studies, a lack of temperature uniformity in RF-exposed cell cultures and rate of heating explain changes originally reported to be due to low-level RF exposure. In other studies, detailed dosimetry studies have identified artifacts that explain the reasons why so-called “non-thermal” effects were mistakenly reported. Researchers should look for explanations for their own findings, and not expect others to figure out what was the reason for their observed effects.     

A Novel Cascade Classifier for Automatic Microcalcification Detection

In this paper, we present a novel cascaded classification framework for automatic detection of individual and clusters of microcalcifications (μC). Our framework comprises three classification stages: i) a random forest (RF) classifier for simple features capturing the second order local structure of individual μCs, where non-μC pixels in the target mammogram are efficiently eliminated; ii) a more complex discriminative restricted Boltzmann machine (DRBM) classifier for μC candidates determined in the RF stage, which automatically learns the detailed morphology of μC appearances for improved discriminative power; and iii) a detector to detect clusters of μCs from the individual μC detection results, using two different criteria. From the two-stage RF-DRBM classifier, we are able to distinguish μCs using explicitly computed features, as well as learn implicit features that are able to further discriminate between confusing cases. Experimental evaluation is conducted on the original Mammographic Image Analysis Society (MIAS) and mini-MIAS databases, as well as our own Seoul National University Bundang Hospital digital mammographic database. It is shown that the proposed method outperforms comparable methods in terms of receiver operating characteristic (ROC) and precision-recall curves for detection of individual μCs and free-response receiver operating characteristic (FROC) curve for detection of clustered μCs.     

Thermal models for microwave hazards and their role in standards development

We consider the thermal response of the body to radiofrequency (RF) energy, with emphasis on partial-body exposure, to assess potential thermal hazards. The thermal analysis is based on Pennes' bioheat equation. In this model, the thermal response is governed by two time constants. One (τ₁) pertains to heat convection by blood flow and is (for physiologically normal perfusion rates) on the order of 3 min. The second (τ₂) characterizes heat conduction, and varies as the square of a distance that characterizes the spatial extent of the heating. We examine three idealized cases. The first is a region of tissue with an insulated surface, subject to irradiation with an exponentially decreasing SAR, which models a large surface area of tissue exposed to microwaves. The second is a region of tissue in contact with a hemispherical electrode that passes current into it, which models exposure from contact with a conductor. The third is a region of tissue with an insulated surface, subject to heating from a dipole located close to it. In all three cases, we estimate the maximum steady-state temperature increase as a function of the relevant electrical and thermal parameters and the thresholds for thermal hazard. We conclude that thermal models are a potentially fruitful but underutilized means of analyzing thermal hazards from RF fields. A quantitative analysis of such hazards enables the development of data-based uncertainty factors, which can replace arbitrary “safety factors” in developing exposure limits. Finally, we comment on the need to marry quantitative modeling of data and risk assessment, and to incorporate contemporary approaches to risk assessment into RF standards development. Bioelectromagnetics 20:52–63, 1999. © 1999 Wiley-Liss, Inc.     

Gambogic acid and gambogenic acid induce a thiol-dependent heat shock response and disrupt the interaction between HSP90 and HSF1 or HSF2

Cancer cells rely on heat shock proteins (HSPs) for growth and survival. Especially HSP90 has multiple client proteins and plays a critical role in malignant transformation, and therefore different types of HSP90 inhibitors are being developed. The bioactive natural compound gambogic acid (GB) is a prenylated xanthone with antitumor activity, and it has been proposed to function as an HSP90 inhibitor. However, there are contradicting reports whether GB induces a heat shock response (HSR), which is cytoprotective for cancer cells and therefore a potentially problematic feature for an anticancer drug. In this study, we show that GB and a structurally related compound, called gambogenic acid (GBA), induce a robust HSR, in a thiol-dependent manner. Using heat shock factor 1 (HSF1) or HSF2 knockout cells, we show that the GB or GBA-induced HSR is HSF1-dependent. Intriguingly, using closed form ATP-bound HSP90 mutants that can be co-precipitated with HSF1, a known facilitator of cancer, we show that also endogenous HSF2 co-precipitates with HSP90. GB and GBA treatment disrupt the interaction between HSP90 and HSF1 and HSP90 and HSF2. Our study implies that these compounds should be used cautiously if developed for cancer therapies, since GB and its derivative GBA are strong inducers of the HSR, in multiple cell types, by involving the dissociation of a HSP90-HSF1/HSF2 complex.     

Targeting the EGFR/PCNA Signaling Suppresses Tumor Growth of Triple-Negative Breast Cancer Cells with Cell-Penetrating PCNA Peptides

Tyrosine 211 (Y211) phosphorylation of proliferation cell nuclear antigen (PCNA) coincides with pronounced cancer cell proliferation and correlates with poor survival of breast cancer patients. In epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI)-resistant cells, both nuclear EGFR (nEGFR) expression and PCNA Y211 phosphorylation are increased. Moreover, the resistance to EGFR TKI is a major clinical problem in treating EGFR-overexpressing triple-negative breast cancer (TNBC). Thus, effective treatment to combat resistance is urgently needed. Here, we show that treatment of cell-penetrating PCNA peptide (CPPP) inhibits growth and induces apoptosis of human TNBC cells. The Y211F CPPP specifically targets EGFR and competes directly for PCNA tyrosine Y211 phosphorylation and prevents nEGFR from binding PCNA in vivo; it also suppresses tumor growth by sensitizing EGFR TKI resistant cells, which have enhanced nEGFR function and abrogated classical EGFR membrane signaling. Furthermore, we identify an active motif of CPPP, RFLNFF (RF6 CPPP), which is necessary and sufficient to inhibit TKI-resistant TNBC cell growth of orthotopic implanted tumor in mice. Finally, the activity of its synthetic retro-inverted derivative, D-RF6 CPPP, on an equimolar basis, is more potent than RF6 CPPP. Our study reveals a drug candidate with translational potential for the future development of safe and effective therapeutic for EGFR TKI resistance in TNBC.     

Attenuated neuroprotective effect of riboflavin under UV-B irradiation via miR-203/c-Jun signaling pathway in vivo and in vitro

Background

Riboflavin (RF) or vitamin B2 is known to have neuroprotective effects. In the present study, we report the attenuation of the neuroprotective effects of RF under UV-B irradiation. Preconditioning of UV-B irradiated riboflavin (UV-B-RF) showed attenuated neuroprotective effects compared to that of RF in SH-SY5Y neuroblostoma cell line and primary cortical neurons in vitro and a rat model of cerebral ischemia in vivo.

Results

Results indicated that RF pretreatment significantly inhibited cell death and reduced LDH secretion compared to that of the UV-B-RF pretreatment in primary cortical neuron cultures subjected to oxygen glucose deprivation in vitro and cortical brain tissue subjected to ischemic injury in vivo. Further mechanistic studies using cortical neuron cultures revealed that RF treatment induced increased miR-203 expression which in turn inhibited c-Jun expression and increased neuronal cell survival. Functional assays clearly demonstrated that the UV-B-RF preconditioning failed to sustain the increased expression of miR-203 and the decreased levels of c-Jun, mediating the neuroprotective effects of RF. UV-B irradiation attenuated the neuroprotective effects of RF through modulation of the miR-203/c-Jun signaling pathway.

Conclusion

Thus, the ability of UV-B to serve as a modulator of this neuroprotective signaling pathway warrants further studies into its role as a regulator of other cytoprotective/neuroprotective signaling pathways.     

Cleaning of inner vacuum surfaces in the Uragan-3M facility by radio-frequency discharges

A method for cleaning vacuum surfaces by a low-temperature (T _e ～ 10 eV) relatively dense (n _e ≈ 10¹² cm^?3) plasma of an RF discharge was developed and successfully applied at the Uragan-3M torsatron. The convenience of the method is that it can be implemented with the same antenna system and RF generators that are used to produce and heat the plasma in the operating mode and does not require retuning the frequencies of the antennas and RF generators. The RF discharge has a high efficiency from the standpoint of cleaning vacuum surfaces. After performing a series of cleanings by the low-temperature RF discharge plasma (about 20000 pulses), (i) the intensity of the CIII impurity line was substantially reduced, (ii) a quasi-steady operating mode with a duration of up to 50 ms, a plasma density of n _e ≈ 10¹² cm^?3, and an electron temperature of up to T _e ～ 1 keV was achieved, and (iii) mass spectrometric analysis of the residual gas in the chamber indicated a significant reduction in the impurity content.     

Heat capacity effects of water molecules and ions at a protein-DNA interface

The interaction of the TATA-box binding protein from the thermophilic and halophilic archaea Pyrococcus woesei (PwTBP) with an oligonucleotide containing a specific binding site is stable over a very broad range of temperatures and ionic strengths, and is consequently an outstanding system for characterising general features of protein-DNA thermodynamics. In common with other specific protein-DNA recognition events, the PwTBP-TATA box interaction is accompanied by a large negative change in heat capacity (ΔC_p) arising from the total change in solvation that occurs upon binding, which in this case involves a net uptake of cations. Contrary to previous hypotheses, we find no overall effect of ionic strength on this heat capacity change. We investigate the local contributions of site-specific ion and water binding to the overall change in heat capacity by means of a series of site-directed mutations of PwTBP. We find that although changes in the local ion binding capacity affect the enthalpic and entropic contributions to the free energy of the interaction, they do not affect the change in heat capacity. In contrast, we find remarkably large heat capacity effects arising from two particular symmetry-related mutations. The great magnitude of these effects is not explicable in terms of current semi-empirical models of heat capacity change. Previously reported X-ray crystal structures show that these mutated residues are at the centre of an evolutionarily conserved network of water-mediated hydrogen bonds between the protein and the DNA backbone. Consequently, we conclude that, in addition to water molecules buried in the protein-DNA interface that have been previously shown to influence heat capacity, bridging water molecules in a highly polar surface environment can also contribute substantially to negative heat capacity change on formation of a protein-DNA complex.     

Relationship between FGF21 and UCP1 levels under time-restricted feeding and high-fat diet

Fibroblast growth factor 21 (FGF21) exhibits a circadian oscillation, and its induction is critical during fasting. When secreted by liver and skeletal muscle, FGF21 enhances thermogenic activity in brown adipose tissue (BAT) by utilizing uncoupling protein 1 (UCP1) to dissipate energy as heat. Recently, it has been reported that UCP1 is not required for FGF21-mediated reduction in body weight or improvements in glucose homeostasis. As the relationship between FGF21 and UCP1 induction in tissues other than BAT is less clear, we tested the effect of restricted feeding (RF) and high dietary fat on FGF21 circadian expression and its correlation with UCP1 expression in liver and white adipose tissue (WAT). High dietary fat disrupted Fgf21 mRNA circadian oscillation but increased its levels in WAT. RF led to increased liver FGF21 protein levels, whereas those of UCP1 decreased. In contrast, WAT FGF21 protein levels increased under high-fat diet, whereas those of UCP1 decreased under RF. In summary, FGF21 exhibits circadian oscillation, which is disrupted with increased dietary fat. The relationship between FGF21 and UCP1 levels depends on the tissue and the cellular energy status.     

Genome-wide identification and expression analysis of the 2OG-Fe(II) oxygenase gene family in upland cotton (Gossypium hirsutum L.)

The 2OG-Fe(II) oxygenase (RF) family of enzyme proteins can affect bulliform cells and cause leaf curling. However, there are few studies related to this family in cotton, and there has been no systematic analysis of RF genes. Here, we determined 25 RF genes in the complete genome sequence of upland cotton (Gossypium hirsutum L.) and 11 RF genes in the complete genome sequence of Arabidopsis thaliana. Cotton RF proteins can be divided into three categories. Whole genome/fragment and scattered replication events played an important role in the expansion of the RF gene family. qRT-PCR analysis results showed that RF genes respond to drought stress Pairwise comparison results showed that the expression of RF genes in Shi yuan 321 was higher than that in Kui 85–174. Overall, genome-wide identification approach was used to further analyze the related functions of the RF gene family, which may include the response to drought stress, in cotton.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-01065-4.     

Computational design of a CNT carrier for a high affinity bispecific anti-HER2 antibody based on trastuzumab and pertuzumab Fabs

This is a preliminary cross multidisciplinary theoretical-computational approach for the design of a drug delivery system based on immunoconjugated carbon nanotube against HER2- overexpressing cancer cells. This drug delivery system allows the release of an encapsulated cytotoxic cocktail in a controlled manner under pulsed radio frequency (RF) irradiation. Our effort is focused on the computational aided design of a high affinity bispecific anti-HER2 antibody and an opening mechanism of the carbon nanotube (CNT) based cytotoxic carrier for controlling multiple drug release. We study the main interactions between the antibody and the antigen by a computational scanning mutagenesis approach of trastuzumab and pertuzumab fragment antigen binding (Fab) structures in order to enhance their binding affinity. Then, each Fab fragments is joined by a polypeptide linker which should be stable enough to avoid the “open form” of antibody. On the other hand, we also conjugate the engineered antibody to functionalized CNTs (f-CNTs), which encapsulate the inhibitors of the HER2/PI3K/Akt/mTOR signaling pathway. We take advantage of the fact that f-CNT converts the RF radiation absorption into heat release. A pulsed laser at 13.45 MHz increments the temperature around 40 °C for triggering the nano-caps destabilization, which allows the switching of the opening mechanism of the drug carrier. Nano-caps will be a dual pH/temperature responsive in order to take advantage of lysosome characteristic (acidic pH) and heat release from the carrier. Nano-caps are functionalized with organic amide moieties, which hydrolyze quickly at an acidic pH into primary amines, and protonated amines generate repulsion interactions with other charged species, which trigger the cytotoxics release.

Extinction models for cancer stem cell therapy

Cells with stem cell-like properties are now viewed as initiating and sustaining many cancers. This suggests that cancer can be cured by driving these cancer stem cells to extinction. The problem with this strategy is that ordinary stem cells are apt to be killed in the process. This paper sets bounds on the killing differential (difference between death rates of cancer stem cells and normal stem cells) that must exist for the survival of an adequate number of normal stem cells. Our main tools are birth-death Markov chains in continuous time. In this framework, we investigate the extinction times of cancer stem cells and normal stem cells. Application of extreme value theory from mathematical statistics yields an accurate asymptotic distribution and corresponding moments for both extinction times. We compare these distributions for the two cell populations as a function of the killing rates. Perhaps a more telling comparison involves the number of normal stem cells N_H at the extinction time of the cancer stem cells. Conditioning on the asymptotic time to extinction of the cancer stem cells allows us to calculate the asymptotic mean and variance of N_H. The full distribution of N_H can be retrieved by the finite Fourier transform and, in some parameter regimes, by an eigenfunction expansion. Finally, we discuss the impact of quiescence (the resting state) on stem cell dynamics. Quiescence can act as a sanctuary for cancer stem cells and imperils the proposed therapy. We approach the complication of quiescence via multitype branching process models and stochastic simulation. Improvements to the τ-leaping method of stochastic simulation make it a versatile tool in this context. We conclude that the proposed therapy must target quiescent cancer stem cells as well as actively dividing cancer stem cells. The current cancer models demonstrate the virtue of attacking the same quantitative questions from a variety of modeling, mathematical, and computational perspectives.     

Organizational requirements for multicellular autonomy: insights from a comparative case study

In this paper we explore the organizational conditions underlying the emergence of organisms at the multicellular level. More specifically, we shall propose a general theoretical scheme according to which a multicellular organism is an ensemble of cells that effectively regulates its own development through collective (meta-cellular) mechanisms of control of cell differentiation and cell division processes. This theoretical result derives from the detailed study of the ontogenetic development of three multicellular systems (Nostoc punctiforme, Volvox carteri and Strongylocentrotus purpuratus) and, in particular, of their corresponding cell-to-cell signaling networks. The case study supports our claim that a specific type of functional integration among the cells of a multicellular ensemble (namely, a regulatory control system consisting in several inter-cellular mechanisms that modulate epigenesis and whose operation gets decoupled from the intra-cellular metabolic machinery), is required for it to qualify as a proper organism. Finally, we argue why a multicellular system exhibiting this type of functionally differentiated and integrated developmental organization becomes a self-determining collective entity and, therefore, should be considered as a second-order autonomous system.     

Reliable Single Cell Array CGH for Clinical Samples

Background

Disseminated cancer cells (DCCs) and circulating tumor cells (CTCs) are extremely rare, but comprise the precursors cells of distant metastases or therapy resistant cells. The detailed molecular analysis of these cells may help to identify key events of cancer cell dissemination, metastatic colony formation and systemic therapy escape.

Methodology/Principal Findings

Using the Ampli1™ whole genome amplification (WGA) technology and high-resolution oligonucleotide aCGH microarrays we optimized conditions for the analysis of structural copy number changes. The protocol presented here enables reliable detection of numerical genomic alterations as small as 0.1 Mb in a single cell. Analysis of single cells from well-characterized cell lines and single normal cells confirmed the stringent quantitative nature of the amplification and hybridization protocol. Importantly, fixation and staining procedures used to detect DCCs showed no significant impact on the outcome of the analysis, proving the clinical usability of our method. In a proof-of-principle study we tracked the chromosomal changes of single DCCs over a full course of high-dose chemotherapy treatment by isolating and analyzing DCCs of an individual breast cancer patient at four different time points.

Conclusions/Significance

The protocol enables detailed genome analysis of DCCs and thereby assessment of the clonal evolution during the natural course of the disease and under selection pressures. The results from an exemplary patient provide evidence that DCCs surviving selective therapeutic conditions may be recruited from a pool of genomically less advanced cells, which display a stable subset of specific genomic alterations.