Climate change will accelerate the high-end risk of compound drought and heatwave events.

Compound drought and heatwave (CDHW) events have garnered increased attention due to their significant impacts on agriculture, energy, water resources, and ecosystems. We quantify the projected future shifts in CDHW characteristics (such as frequency, duration, and severity) due to continued anthropogenic warming relative to the baseline recent observed period (1982 to 2019). We combine weekly drought and heatwave information for 26 climate divisions across the globe, employing historical and projected model output from eight Coupled Model Intercomparison Project 6 GCMs and three Shared Socioeconomic Pathways. Statistically significant trends are revealed in the CDHW characteristics for both recent observed and model simulated future period (2020 to 2099). East Africa, North Australia, East North America, Central Asia, Central Europe, and Southeastern South America show the greatest increase in frequency through the late 21st century. The Southern Hemisphere displays a greater projected increase in CDHW occurrence, while the Northern Hemisphere displays a greater increase in CDHW severity. Regional warmings play a significant role in CDHW changes in most regions. These findings have implications for minimizing the impacts of extreme events and developing adaptation and mitigation policies to cope with increased risk on water, energy, and food sectors in critical geographical regions.

Clinical and immunohematological characterization of autoimmune hemolytic anemia in children.

Autoimmune Hemolytic Anemia (AIHA) in childhood is uncommon and estimated to be three per million annually under 18 years of age. Detailed immunohematological and clinical characterizations are essential for correct diagnosis of the disease and its management. In this study we described AIHA in children with regards to patient demography, underlying etiology, disease classification, antibody characterization, clinical features, degree of in vivo hemolysis and transfusion management. The prospective observational study was conducted over a period of 6 years and included 29 children with newly diagnosed AIHA. Patient details were obtained from the hospital information system and patient treatment file. The median age of the children was 12 years with a female preponderance. Secondary AIHA was observed in 62.1% patients. The mean hemoglobin and reticulocyte were 7.1 gm/dL and 8.8 percentages respectively. The median polyspecific direct antiglobulin test (DAT) grading was 3+. Red cell bound multiple autoantibodies were found in 27.6% children. Free serum autoantibodies were present in 62.1% patients. Twenty six of the 42 units transfused were "best match" or "least incompatible". Follow-up of 21 children showed clinical and laboratory improvement with DAT still positive at the end of 9 months. AIHA in childhood requires advanced and efficient clinical, immunohematological and transfusion support. Detailed characterization of AIHA is important, as they determine degree of in vivo hemolysis, disease severity, serological incompatibility and necessity of blood transfusion. Although blood transfusion in AIHA is a challenge but it should not be withheld in critically ill patients.

Immunohematological evaluation of red cell alloimmunization and statistical assessment of various adsorption techniques in warm autoimmune hemolytic anemia.

Adsorption techniques are widely applied to detect underlying masked alloantibodies in warm autoimmune hemolytic anemia (WAIHA). We established various adsorption techniques with an aim to detect alloimmunization in WAIHA This study conducted over a period of nine years included 298 patients of WAIHA. Complete immunohematological evaluation was performed on these 298 samples following departmental protocols. Clinical and laboratory details of patients were obtained from patient files. Various adsorption methods were performed and statistically evaluated in the study. Out of 479 cases of autoimmune hemolytic anemia, WAIHA comprised of 62.2 % (N = 298). A total of 139 (46.6 %) serum samples revealed autoantibodies. Adsorption study was performed in 101 (72.7 %) indicated samples and 24 (23.8 %) of these showed 26 alloantibodies. Among the patients subjected to adsorption study hemolytic marker were significantly deranged in the alloimmunization group (p < 0.01). Polyethylene glycol (PEG) adsorption was the quickest (52.2-54.6 min) of all adsorption techniques with minimum (1.3-1.5) numbers of adsorptions needing for complete removal of serum antibodies. The LISS-papain (LP) technique was found to be more sensitive and specific compared to the other two techniques. The agreement between PEG adsorption and LP adsorption was found to be 'perfect' (96.4 %) with a Cohen's kappa (k) value of 0.9. We conclude that identification of alloantibody specificities underlying a warm autoantibody is critical for a safe and effective transfusion. All WAIHA patients with history of blood transfusion, pregnancy or both should be subjected to adsorption study. Selection of a suitable adsorption technique depends on multiple important factors.

Influence of immunohematological markers on severity of in vivo hemolysis in human warm autoimmune haemolytic anemia.

Autoantibody production in autoimmune haemolytic anemia (AIHA) is the result of the loss of self-immunological tolerance of the host. Here we investigated the various immunohematological markers that may influence the severity of in vivo hemolysis in warm AIHA (WAIHA). Complete direct antiglobulin test (DAT) evaluation and immunohematological characterization were performed in 247 patients of WAIHA following departmental protocols. Clinical and laboratory details of patients were obtained from patient file. The median age of WAIHA patients was 47 years with a female preponderance. Lymphoproliferative diseases were the major underlying causes of secondary WAIHA. The mean haemoglobin (Hb) and reticulocyte count (Retic) were 6.43 gm/dL and 7.58% respectively. Single autoantibody bound to red cells was investigated in 151 patients. The main IgG subclass was IgG1. Multiple autoantibodies like IgG+ C, IgG+IgA and IgG+IgA+C were found in 87 (35.2%) patients. Free autoantibodies were observed in 112 patients with a median indirect antiglobulin test (IAT) reactivity of 2+. Derangement of haematological and biochemical values was statistically significant with increase in DAT reactivity, presence of multiple autoantibodies on red cells, coating of red cells by IgG3 or multiple IgG subclass, higher DAT dilution and increasing IAT reactivity. We conclude that several important but simple immunohematological parameters may influence the degree of in vivo hemolysis in WAIHA. Since a set of common haematological and biochemical test determines the severity of in vivo hemolysis therefore a comprehensive clinical and immunohematological evaluation is advisable for a correct diagnostic and therapeutic workup of WAIHA.

Multi-walled carbon nanotubes elicit concordant changes in DNA methylation and gene expression following long-term pulmonary exposure in mice.

Pulmonary exposure to multi-walled carbon nanotubes (MWCNTs) causes inflammation and fibrosis. Our previous work has shown that industrially produced MWCNTs trigger specific changes in gene expression in the lungs of exposed animals. To elucidate whether epigenetic effects play a role for these gene expression changes, we performed whole genome bisulphite sequencing to assess DNA methylation patterns in the lungs 56 days after exposure to MWCNTs. Lung tissues were also evaluated with respect to histopathological changes and cytokine profiling of bronchoalveolar lavage (BAL) fluid was conducted using a multi-plex array. Integrated analysis of transcriptomics data and DNA methylation data revealed concordant changes in gene expression. Functional analysis showed that the muscle contraction, immune system/inflammation, and extracellular matrix pathways were the most affected pathways. Taken together, the present study revealed that MWCNTs exert epigenetic effects in the lungs of exposed animals, potentially driving the subsequent gene expression changes.

Gut melatonin: A potent candidate in the diversified journey of melatonin research.

After being discovered from the bovine pineal gland by Aaron Lerner and co-workers in the year 1958, various distinguished researchers have reported melatonin (5-methoxy-N-acetyl-tryptamine) from several extra-pineal sources, including the gastrointestinal tract (GIT). In the year 1974, Raikhlin and Kvetnoy first detected this molecule in the gastrointestinal tissue. Later, within the last 45 years, many renowned investigators found that the GIT is a rich source of melatonin, in addition to the pineal gland. In the carp gut, the estimation of Arylalkylamine-N-acetyltransferase (AANAT) mRNA/protein levels, which is the rate-determining enzyme for melatonin biosynthesis in the pineal gland, confirmed the endogenous synthesis of melatonin. The remarkable feature of the pineal gland melatonin is its rhythmic synthesis with a peak at dark-phase and lowest at light-phase in synchronization with seasonal environmental light-dark (LD) cycle. Recent studies on carp demonstrated that the melatonin concentrations and the AANAT protein intensities in different gut segments underwent significant daily fluctuations. However, compared to the melatonin rhythm in the pineal gland, the melatonin profiles in gut tissue displayed daily rhythm in parallel with the feeding cycle of the carp, irrespective of LD conditions of the environment. Notably, in carp, the temporal pattern of the gut melatoninergic system found to vary with the environmental non-photic signal(s), such as food entrainment factors (viz. availability of food, timing of food supply, number(s) of feed per day, quality of food) those act as the most dependable synchronizer(s) in daily rhythm characteristics of gut melatonin and AANAT. Thereby in this review, it appears meaningful to highlight the existing data on the mode of synthesis of melatonin in cells of the digestive tract, and most importantly, the regulation of its synthesis. Finally, in comparison with the dynamic actions of melatonin derived from the pineal gland, this review will lead to underline the role of gut-derived melatonin in a variety of physiological functions.

Next-Generation Sequencing Reveals Differential Responses to Acute versus Long-Term Exposures to Graphene Oxide in Human Lung Cells.

Numerous studies have addressed the biological impact of graphene-based materials including graphene oxide (GO), yet few have focused on long-term effects. Here, RNA sequencing is utilized to unearth responses of human lung cells to GO. To this end, the BEAS-2B cell line derived from normal human bronchial epithelium is subjected to repeated, low-dose exposures of GO (1 or 5 µg mL-1 ) for 28 days or to the equivalent, cumulative amount of GO for 48 h. Then, samples are analyzed by using the NovaSeq 6000 sequencing system followed by pathway analysis and gene ontology enrichment analysis of the differentially expressed genes. Significant differences are seen between the low-dose, long-term exposures and the high-dose, short-term exposures. Hence, exposure to GO for 48 h results in mitochondrial dysfunction. In contrast, exposure to GO for 28 days is characterized by engagement of apoptosis pathways with downregulation of genes belonging to the inhibitor of apoptosis protein (IAP) family. Validation experiments confirm that long-term exposure to GO affects the apoptosis threshold in lung cells, accompanied by a loss of IAPs. These studies reveal the sensitivity of RNA-sequencing approaches and show that acute exposure to GO is not a good predictor of the long-term effects of GO.

Degradation of Single-Layer and Few-Layer Graphene by Neutrophil Myeloperoxidase.

Biodegradability of graphene is one of the fundamental parameters determining the fate of this material in vivo. Two types of aqueous dispersible graphene, corresponding to single-layer (SLG) and few-layer graphene (FLG), devoid of either chemical functionalization or stabilizing surfactants, were subjected to biodegradation by human myeloperoxidase (hMPO) mediated catalysis. Graphene biodegradation was also studied in the presence of activated, degranulating human neutrophils. The degradation of both FLG and SLG sheets was confirmed by Raman spectroscopy and electron microscopy analyses, leading to the conclusion that highly dispersed pristine graphene is not biopersistent.

Genetic Alterations in Pendrin (SLC26A4) Gene in Adult Hypothyroid Patients.

Current study was aimed to screen the SLC26A4 gene in 127 nonautoimmune and noncongenital hypothyroid patients, who were under optimal iodine nutrition and devoid of any characteristics of Pendred syndrome from eastern part of Indian population. 8 single nucleotide variants/mutations were identified in heterozygous state in 20% patient population, which include 1 novel nonsynonymous (p.C18S), 1 novel intronic (g.942C>A), 3 known nonsynonymous (p.S23X, p.V239D, and p.I455F), and 3 known intronic (g.23034G>T, g.29641C>G, and g.33893T>C) variants. Only g.23034G>T was noted also in homozygous state in 2% patient population. However, Controls exhibited only the variations g.23034G>T and p.I455F. Therefore, present study reports for the first time that the observed novel variants in pendrin gene might be linked with autoimmune negative hypothyroidism, without any characteristics of Pendred syndrome and/or congenital hypothyroidism. While, all observed known variants/mutations were reported with either Pendred syndrome and/or congenital hypothyroidism earlier, but never with nonautoimmune adult hypothyroidism solely. Thereby, the absence of any features of Pendred syndrome and/or congenital hypothyroidism in patients with observed known nonsynonymous variants/mutations may be due to either heterozygous state of each variant or differential domain specific activity of ions trafficking in the respective organ. The analysis of amino acid change at least for p.C18S, p.S23X, and p.V239D in correlation with phenotypic characteristics of respective patients might assume a possible effect on protein structure and function. Altogether, we report for the first time that genetical variations in SLC26A4 gene could play an important role in development of nonautoimmune adult hypothyroidism.

Structural dependence of in vitro cytotoxicity, oxidative stress and uptake mechanisms of poly(propylene imine) dendritic nanoparticles.

The in vitro cytotoxic and intracellular oxidative stress responses to exposure to poly(propylene imine) (PPI) dendritic nanoparticles of increasing generation (number of repeated branching cycles) (G0-G4) were assessed in an immortal non-cancerous human keratinocyte cell line (HaCaT). Confocal fluorescence microscopy with organelle staining was used to explore the uptake and intracellular trafficking mechanisms. A generation- and dose-dependent cytotoxic response was observed, increasing according to generation and, therefore, number of surface amino groups. A comparison of the cytotoxic response of G4 PPI and the related G4 poly(amido amine) dendrimer indicates that the PPI with the same number of surface amino groups elicits a significantly higher cytotoxic response. The trend of cytotoxicity versus dendrimer generation and, therefore, size is discontinuous in the region of G2, however, indicating a difference in uptake mechanism for higher compared to lower generations. Whereas the higher generations elicit an oxidative stress response at short exposure times, the lower generations indicate an antioxidant response. Confocal microscopy indicates that, whereas they are prominent at early exposure times for the larger PPI dendrimers, no evidence of early stage endosomes was observed for lower generations of PPI. The results are consistent with an alternative uptake mechanism of physical diffusion across the semipermeable cell membrane for the lower generation dendrimers and are discussed in terms of their implications for predictive models for nanotoxicology and design strategies for nanomedical applications.

Biological interactions of carbon-based nanomaterials: From coronation to degradation.

Carbon-based nanomaterials including carbon nanotubes, graphene oxide, fullerenes and nanodiamonds are potential candidates for various applications in medicine such as drug delivery and imaging. However, the successful translation of nanomaterials for biomedical applications is predicated on a detailed understanding of the biological interactions of these materials. Indeed, the potential impact of the so-called bio-corona of proteins, lipids, and other biomolecules on the fate of nanomaterials in the body should not be ignored. Enzymatic degradation of carbon-based nanomaterials by immune-competent cells serves as a special case of bio-corona interactions with important implications for the medical use of such nanomaterials. In the present review, we highlight emerging biomedical applications of carbon-based nanomaterials. We also discuss recent studies on nanomaterial 'coronation' and how this impacts on biodistribution and targeting along with studies on the enzymatic degradation of carbon-based nanomaterials, and the role of surface modification of nanomaterials for these biological interactions. FROM THE CLINICAL EDITOR: Advances in technology have produced many carbon-based nanomaterials. These are increasingly being investigated for the use in diagnostics and therapeutics. Nonetheless, there remains a knowledge gap in terms of the understanding of the biological interactions of these materials. In this paper, the authors provided a comprehensive review on the recent biomedical applications and the interactions of various carbon-based nanomaterials.

Primuline derivatives that mimic RNA to stimulate hepatitis C virus NS3 helicase-catalyzed ATP hydrolysis.

ATP hydrolysis fuels the ability of helicases and related proteins to translocate on nucleic acids and separate base pairs. As a consequence, nucleic acid binding stimulates the rate at which a helicase catalyzes ATP hydrolysis. In this study, we searched a library of small molecule helicase inhibitors for compounds that stimulate ATP hydrolysis catalyzed by the hepatitis C virus (HCV) NS3 helicase, which is an important antiviral drug target. Two compounds were found that stimulate HCV helicase-catalyzed ATP hydrolysis, both of which are amide derivatives synthesized from the main component of the yellow dye primuline. Both compounds possess a terminal pyridine moiety, which was critical for stimulation. Analogs lacking a terminal pyridine inhibited HCV helicase catalyzed ATP hydrolysis. Unlike other HCV helicase inhibitors, the stimulatory compounds differentiate between helicases isolated from various HCV genotypes and related viruses. The compounds only stimulated ATP hydrolysis catalyzed by NS3 purified from HCV genotype 1b. They inhibited helicases from other HCV genotypes (e.g. 1a and 2a) or related flaviviruses (e.g. Dengue virus). The stimulatory compounds interacted with HCV helicase in the absence of ATP with dissociation constants of about 2 µM. Molecular modeling and site-directed mutagenesis studies suggest that the stimulatory compounds bind in the HCV helicase RNA-binding cleft near key residues Arg-393, Glu-493, and Ser-231.

Identification and analysis of hepatitis C virus NS3 helicase inhibitors using nucleic acid binding assays.

Typical assays used to discover and analyze small molecules that inhibit the hepatitis C virus (HCV) NS3 helicase yield few hits and are often confounded by compound interference. Oligonucleotide binding assays are examined here as an alternative. After comparing fluorescence polarization (FP), homogeneous time-resolved fluorescence (HTRF®; Cisbio) and AlphaScreen® (Perkin Elmer) assays, an FP-based assay was chosen to screen Sigma's Library of Pharmacologically Active Compounds (LOPAC) for compounds that inhibit NS3-DNA complex formation. Four LOPAC compounds inhibited the FP-based assay: aurintricarboxylic acid (ATA) (IC50=1.4 µM), suramin sodium salt (IC50=3.6 µM), NF 023 hydrate (IC50=6.2 µM) and tyrphostin AG 538 (IC50=3.6 µM). All but AG 538 inhibited helicase-catalyzed strand separation, and all but NF 023 inhibited replication of subgenomic HCV replicons. A counterscreen using Escherichia coli single-stranded DNA binding protein (SSB) revealed that none of the new HCV helicase inhibitors were specific for NS3h. However, when the SSB-based assay was used to analyze derivatives of another non-specific helicase inhibitor, the main component of the dye primuline, it revealed that some primuline derivatives (e.g. PubChem CID50930730) are up to 30-fold more specific for HCV NS3h than similarly potent HCV helicase inhibitors.

First-Line Nivolumab and Relatlimab Plus Chemotherapy for Gastric or Gastroesophageal Junction Adenocarcinoma: The Phase II RELATIVITY-060 Study.

PURPOSE: Open-label phase II study (RELATIVITY-060) to investigate the efficacy and safety of first-line nivolumab, a PD-1-blocking antibody, plus relatlimab, a lymphocyte-activation gene 3 (LAG-3)-blocking antibody, plus chemotherapy in patients with previously untreated advanced gastric cancer (GC) or gastroesophageal junction cancer (GEJC). METHODS: Patients with unresectable, locally advanced or metastatic GC/GEJC were randomly assigned 1:1 to nivolumab + relatlimab (fixed-dose combination) + chemotherapy or nivolumab + chemotherapy. The primary end point was objective response rate (ORR; per RECIST v1.1 by blinded independent central review [BICR]) in patients whose tumors had LAG-3 expression ≥1%. RESULTS: Of 274 patients, 138 were randomly assigned to nivolumab + relatlimab + chemotherapy and 136 to nivolumab + chemotherapy. Median follow-up was 11.9 months. In patients with LAG-3 expression ≥1%, BICR-assessed ORR (95% CI) was 48% (38 to 59) in the nivolumab + relatlimab + chemotherapy arm and 61% (51 to 71) in the nivolumab + chemotherapy arm; median progression-free survival (95% CI) by BICR was 7.0 months (5.8 to 8.4) versus 8.3 months (6.9 to 12.1; hazard ratio [HR], 1.41 [95% CI, 0.97 to 2.05]), and median overall survival (95% CI) was 13.5 months (11.9 to 19.1) versus 16.0 months (10.9 to not estimable; HR, 1.04 [95% CI, 0.70 to 1.54]), respectively. Grade 3 or 4 treatment-related adverse events (TRAEs) occurred in 69% and 61% of all treated patients, and 42% and 36% of patients discontinued because of any-grade TRAEs in the nivolumab + relatlimab + chemotherapy and nivolumab + chemotherapy arms, respectively. CONCLUSION: RELATIVITY-060 did not meet its primary end point of improved ORR in patients with LAG-3 expression ≥1% when relatlimab was added to nivolumab + chemotherapy compared with nivolumab + chemotherapy. Further studies are needed to address whether adding anti-LAG-3 to anti-PD-1 plus chemotherapy can benefit specific GC/GEJC patient subgroups.

SUMO protease FUG1, histone reader AL3 and chromodomain protein LHP1 are integral to repeat expansion-induced gene silencing in Arabidopsis thaliana.

Epigenetic gene silencing induced by expanded repeats can cause diverse phenotypes ranging from severe growth defects in plants to genetic diseases such as Friedreich's ataxia in humans. The molecular mechanisms underlying repeat expansion-induced epigenetic silencing remain largely unknown. Using a plant model with a temperature-sensitive phenotype, we have previously shown that expanded repeats can induce small RNAs, which in turn can lead to epigenetic silencing through the RNA-dependent DNA methylation pathway. Here, using a genetic suppressor screen and yeast two-hybrid assays, we identified novel components required for epigenetic silencing caused by expanded repeats. We show that FOURTH ULP GENE CLASS 1 (FUG1)-an uncharacterized SUMO protease with no known role in gene silencing-is required for epigenetic silencing caused by expanded repeats. In addition, we demonstrate that FUG1 physically interacts with ALFIN-LIKE 3 (AL3)-a histone reader that is known to bind to active histone mark H3K4me2/3. Loss of function of AL3 abolishes epigenetic silencing caused by expanded repeats. AL3 physically interacts with the chromodomain protein LIKE HETEROCHROMATIN 1 (LHP1)-known to be associated with the spread of the repressive histone mark H3K27me3 to cause repeat expansion-induced epigenetic silencing. Loss of any of these components suppresses repeat expansion-associated phenotypes coupled with an increase in IIL1 expression with the reversal of gene silencing and associated change in epigenetic marks. Our findings suggest that the FUG1-AL3-LHP1 module is essential to confer repeat expansion-associated epigenetic silencing and highlight the importance of post-translational modifiers and histone readers in epigenetic silencing.

Aurintricarboxylic acid modulates the affinity of hepatitis C virus NS3 helicase for both nucleic acid and ATP.

Aurintricarboxylic acid (ATA) is a potent inhibitor of many enzymes needed for cell and virus replication, such as polymerases, helicases, nucleases, and topoisomerases. This study examines how ATA interacts with the helicase encoded by the hepatitis C virus (HCV) and reveals that ATA interferes with both nucleic acid and ATP binding to the enzyme. We show that ATA directly binds HCV helicase to prevent the enzyme from interacting with nucleic acids and to modulate the affinity of HCV helicase for ATP, the fuel for helicase action. Amino acid substitutions in the helicase DNA binding cleft or its ATP binding site alter the ability of ATA to disrupt helicase-DNA interactions. These data, along with molecular modeling results, support the notion that an ATA polymer binds between Arg467 and Glu493 to prevent the helicase from binding either ATP or nucleic acids. We also characterize how ATA affects the kinetics of helicase-catalyzed ATP hydrolysis, and thermodynamic parameters describing the direct interaction between HCV helicase and ATA using microcalorimetry. The thermodynamics of ATA binding to HCV helicase reveal that ATA binding does not mimic nucleic acid binding in that ATA binding is driven by a smaller enthalpy change and an increase in entropy.

Melatonin: a potent candidate in the regulation of fish oocyte growth and maturation.

Recent studies on several fish species, especially carp, implicated pineal hormone melatonin (N-acetyl-5-methoxytryptamine) as a potent candidate in the regulatory mechanism of seasonal reproduction. Under natural conditions, the temporal pattern of serum melatonin varied with daily light-dark cycle and the reproductive status of the fish as well. Carefully controlled study revealed that exogenous administration of melatonin may result in stimulation or inhibition or no influences at all on the gonadal functions depending on the reproductive status of fish. Cross-talk between the melatonin and ovarian steroid has been evident from in vitro study, in which melatonin accelerated the action of 17α,20ß-dihydroxy-4-pregnen-3-one or maturation inducing hormone (MIH) on meiotic cell cycle resumption in carp oocytes by formation of maturation promoting factor (MPF) - a complex of two proteins, cyclin B and cyclin dependant kinase Cdk1. While several lines of evidence suggest melatonin effects on hypothalamo-hypophyseal-gonadal axis, localization and dynamics of a 37-kDa melatonin receptor protein in carp oocytes argued in favor of extra-hypothalamic direct action of melatonin on fish reproduction. A recent study in carp indicated that influences of an identical regimen of photoperiods in different parts of annual cycle on ovarian functions vary in relation to the profiles of serum melatonin, but not to any rhythm parameters of MT1 or MT2 receptors on the gonad or brain. The purpose of this short review is to bring together the current knowledge on the biological effects of melatonin on fish reproduction mainly focusing the recent findings on carp.

Polyamidoamine dendrimer nanoparticle cytotoxicity, oxidative stress, caspase activation and inflammatory response: experimental observation and numerical simulation.

Mechanisms underlying the in vitro cytotoxicity of Polyamidoamine nano-dendrimers in human keratinocytes are explored. Previous studies demonstrated a systematic, dendrimer-generation-dependent cytotoxicity, oxidative stress, and genotoxicity. The emerging picture is of dendrimer endocytosis, endosomal rupture and subsequent mitochondrial attack and cell death. To understand the underlying mechanisms, the evolution of reactive oxygen species, intracellular glutathione, caspase activation, mitochondrial membrane potential decay, and inflammatory responses have been examined. Early-stage responses are associated with endosomal encapsulation, later-stage with mitochondrial attack. In all cases, the magnitude and evolution of responses depend on dendrimer generation and dose. The early-stage response is modelled using a rate equation approach, qualitatively reproducing the time, dose and generation dependences, using only two variable parameters. The dependence of the response on the nanoparticle physicochemical properties can thus be separated from internal cellular parameters, and responses can be quantified in terms of rate constants rather than commonly employed effective concentrations. FROM THE CLINICAL EDITOR: This contribution reports on the intracellular mechanism of PAMAM dendrimer cytotoxicity in human keratinocytes. In all cases, the magnitude and evolution of responses depend on dendrimer generation and dose. Experimental data were supported by numerical simulation using only two variables. It is suggested that responses can be quantified in terms of rate constants rather than effective concentrations.

Residues in the central beta-hairpin of the DNA helicase of bacteriophage T7 are important in DNA unwinding.

The ring-shaped helicase of bacteriophage T7 (gp4), the product of gene 4, has basic beta-hairpin loops lining its central core where they are postulated to be the major sites of DNA interaction. We have altered multiple residues within the beta-hairpin loop to determine their role during dTTPase-driven DNA unwinding. Residues His-465, Leu-466, and Asn-468 are essential for both DNA unwinding and DNA synthesis mediated by T7 DNA polymerase during leading-strand DNA synthesis. Gp4-K467A, gp4-K471A, and gp4-K473A form fewer hexamers than heptamers compared to wild-type helicase and alone are deficient in DNA unwinding. However, they complement for the growth of T7 bacteriophage lacking gene 4. Single-molecule studies show that these three altered helicases support rates of leading-strand DNA synthesis comparable to that observed with wild-type gp4. Gp4-K467A, devoid of unwinding activity alone, supports leading-strand synthesis in the presence of T7 DNA polymerase. We propose that DNA polymerase limits the backward movement of the helicase during unwinding as well as assisting the forward movement necessary for strand separation.

Interaction between dry and hot extremes at a global scale using a cascade modeling framework.

Climate change amplifies dry and hot extremes, yet the mechanism, extent, scope, and temporal scale of causal linkages between dry and hot extremes remain underexplored. Here using the concept of system dynamics, we investigate cross-scale interactions within dry-to-hot and hot-to-dry extreme event networks and quantify the magnitude, temporal-scale, and physical drivers of cascading effects (CEs) of drying-on-heating and vice-versa, across the globe. We find that locations exhibiting exceptionally strong CE (hotspots) for dry-to-hot and hot-to-dry extremes generally coincide. However, the CEs differ strongly in their timescale of interaction, hydroclimatic drivers, and sensitivity to changes in the soil-plant-atmosphere continuum and background aridity. The CE of drying-on-heating in the hotspot locations reaches its peak immediately driven by the compounding influence of vapor pressure deficit, potential evapotranspiration, and precipitation. In contrast, the CE of heating-on-drying peaks gradually dominated by concurrent changes in potential evapotranspiration, precipitation, and net-radiation with the effect of vapor pressure deficit being strongly controlled by ecosystem isohydricity and background aridity. Our results help improve our understanding of the causal linkages and the predictability of compound extremes and related impacts.