Dynamic Changes in Circulating Methylated Markers in Response to Antitumor Therapy of Rectal Cancer.

BACKGROUND: Rectal cancer (RC) occupies a leading position in the structure of oncological morbidity and mortality. Aberrant methylation of tumor-suppressor genes and hypomethylation of retrotransposons were shown to be detectable in cell-free DNA, circulating in the blood (cfDNA) of cancer patients, indicating the possibility to use them as diagnostic and prognosis markers. PURPOSE: Evaluation of the changes in the methylation level of LINE-1 elements and SEPTIN9 and IKZF1 genes in the cell-surface-bound cfDNA (csb-cfDNA) from the blood of RC patients after antitumor therapy at a long-term follow-up. METHODS: Blood samples were obtained from RC patients (n = 25) before treatment, after preoperative chemotherapy (3 courses according to the XELOX scheme), 10-15 days after surgery, and every 3 months during 12 months of dynamic observation. The methylation level of LINE-1, SEPTIN9, and IKZF1 in the csb-cfDNA was evaluated by quantitative methyl-specific PCR. RESULTS: The LINE-1 methylation level in the csb-cfDNA increased 1.6 times in RC patients after chemotherapy and 3 times after tumor resection versus methylation level before therapy. The SEPTIN9 gene methylation level in the csb-cfDNA decreased by 1.7 times in RC patients after chemotherapy and by 2.3 times after tumor resection compared with the values before the treatment. The IKZF1 gene methylation level decreased by 2 times in RC patients after combined therapy. Notably, all patients with relapses (n = 5) showed an increase in methylation level for the SEPTIN9 and IKZF1 genes and a decrease of methylation level for the LINE-1 elements by 2 times or more in comparison with the level 10-15 days after surgery. There were no changes in the circulating SEPTIN9, IKZF1, and LINE-1 methylation levels during the 12-month follow-up period after the combined therapy of RC patients (n = 20) without relapses. CONCLUSION: The results indicate that SEPTIN9, IKZF1, and LINE-1 methylation levels in the csb-cfDNA are potential markers of the effectiveness of antitumor therapy and early detection of relapse in RC patients.

Validation of a plasmonic-based serology biosensor for veterinary diagnosis of COVID-19 in domestic animals.

The coronavirus disease 2019 (COVID-19) pandemic recently demonstrated the devastating impact on public health, economy, and social development of zoonotic infectious diseases, whereby viruses jump from animals to infect humans. Due to this potential of viruses to cross the species barrier, the surveillance of infectious pathogens circulation in domestic and close-to-human animals is indispensable, as they could be potential reservoirs. Optical biosensors, mainly those based on Surface Plasmon Resonance (SPR), have widely demonstrated its ability for providing direct, label-free, and quantitative bioanalysis with excellent sensitivity and reliability. This biosensor technology can provide a powerful tool to the veterinary field, potentially being helpful for the monitoring of the infection spread. We have implemented a multi-target COVID-19 serology plasmonic biosensor for the rapid testing and screening of common European domestic animals. The multi-target serological biosensor assay enables the detection of total SARS-CoV-2 antibodies (IgG + IgM) generated towards both S and N viral antigens. The analysis is performed in less than 15 min with a low-volume serum sample (<20 µL, 1:10 dilution), reaching a limit of detection of 49.6 ng mL-1. A complete validation has been carried out with hamster, dog, and cat sera samples (N = 75, including 37 COVID-19-positive and 38 negative samples). The biosensor exhibits an excellent diagnostic sensitivity (100 %) and good specificity (71.4 %) for future application in veterinary settings. Furthermore, the biosensor technology is integrated into a compact, portable, and user-friendly device, well-suited for point-of-care testing. This study positions our plasmonic biosensor as an alternative and reliable diagnostic tool for COVID-19 serology in animal samples, expanding the applicability of plasmonic technologies for decentralized analysis in veterinary healthcare and animal research.

Increased 90-Day Mortality and Morbidity Among Patients Recovering From Elective Primary Arthroplasty During the COVID-19 Pandemic in New York City.

All elective procedures were stopped in March 2020 because of the coronavirus disease 2019 (COVID-19) pandemic. We report the 90-day mortality and complications of patients who underwent primary arthroplasty before the stopping of elective procedures at a single academic medical center. A retrospective cohort study was conducted including patients who underwent elective primary arthroplasty between December 2019 and mid-March 2020. Their 90-day postoperative mortality and medical complications were statistically compared with those of a historical cohort from the same operative period in 2019. The 2020 and 2019 cohorts included 372 and 410 patients, respectively. Except for the prevalence of diabetes, there was no significant difference between the two cohorts regarding baseline characteristics or preoperative health. The 2020 cohort had statistically significant higher rates of pneumonia (2.7% vs 0.7%; P=.03), readmission (9.1% vs 5.4%; P=.04), pulmonary embolism (1.6% vs 0.2%; P=.04), and 90-day mortality (1.1% vs 0%; P=.04). The 2020 cohort also had a trend for increased rates of deep venous thrombosis (1.1% vs 0.7%; P=.7) and cardiac complications (1.9% vs 0.5%; P=.07) and no change in emergency department visits (14.0% vs 11.7%; P=.3). There were 7 confirmed cases of COVID-19 in the 2020 cohort and 1 death. This study demonstrates that patients who underwent primary arthroplasty procedures at our institution close to the time of the first wave of the COVID-19 pandemic experienced a statistically significant increase in mortality, pneumonia, pulmonary embolism, and readmission compared with a historical cohort. As elective procedures have resumed during the ongoing pandemic, providers and patients should be aware of these increased risks. [Orthopedics. 202x;4x(x):xx-xx.].

Predictive Value of CT Biomarkers in Lung Transplantation Survival: Preliminary Investigation in a Diverse, Underserved, Urban Population.

INTRODUCTION: Survival following lung transplant is low. With limited donor lung availability, predicting post-transplant survival is key. We investigated the predictive value of pre-transplant CT biomarkers on survival. METHODS: In this single-center retrospective cohort study of adults in a diverse, underserved, urban lung transplant program (11/8/2017-5/20/2022), chest CTs were analyzed using TeraRecon to assess musculature, fat, and bone. Erector spinae and pectoralis muscle area and attenuation were analyzed. Sarcopenia thresholds were 34.3 (women) and 38.5 (men) Hounsfield Units (HU). Visceral and subcutaneous fat area and HU, and vertebral body HU were measured. Demographics and pre-transplant metrics were recorded. Survival analyses included Kaplan-Meier and Cox proportional hazard. RESULTS: The study cohort comprised 131 patients, 50 women, mean age 60.82 (SD 10.15) years, and mean follow-up 1.78 (SD 1.23) years. Twenty-nine percent were White. Mortality was 32.1%. Kaplan-Meier curves did not follow the proportional hazard assumption for sex, so analysis was stratified. Pre-transplant EMR metrics did not predict survival. Women without sarcopenia at erector spinae or pectoralis had 100% survival (p = 0.007). Sarcopenia did not predict survival in men and muscle area did not predict survival in either sex. Men with higher visceral fat area and HU had decreased survival (p = 0.02). Higher vertebral body density predicted improved survival in men (p = 0.026) and women (p = 0.045). CONCLUSION: Pre-transplantation CT biomarkers had predictive value in lung transplant survival and varied by sex. The absence of sarcopenia in women, lower visceral fat attenuation and area in men, and higher vertebral body density in both sexes predicted survival in our diverse, urban population.

Genomic and Transcriptomic Research in the Discovery and Application of Colorectal Cancer Circulating Markers.

Colorectal cancer (CRC) is the most frequently occurring malignancy in the world. However, the mortality from CRC can be reduced through early diagnostics, selection of the most effective treatment, observation of the therapy success, and the earliest possible diagnosis of recurrences. A comprehensive analysis of genetic and epigenetic factors contributing to the CRC development is needed to refine diagnostic, therapeutic, and preventive strategies and to ensure appropriate decision making in managing specific CRC cases. The liquid biopsy approach utilizing circulating markers has demonstrated its good performance as a tool to detect the changes in the molecular pathways associated with various cancers. In this review, we attempted to brief the main tendencies in the development of circulating DNA and RNA-based markers in CRC such as cancer-associated DNA mutations, DNA methylation changes, and non-coding RNA expression shifts. Attention is devoted to the existing circulating nucleic acid-based CRC markers, the possibility of their application in clinical practice today, and their future improvement. Approaches to the discovery and verification of new markers are described, and the existing problems and potential solutions for them are highlighted.

Angiogenesis regulators S100A4, SPARC and SPP1 correlate with macrophage infiltration and are prognostic biomarkers in colon and rectal cancers.

Introduction: Increasing evidence suggests that it is necessary to find effective and robust clinically validated prognostic biomarkers that can identify "high-risk" colorectal cancer (CRC) patients. Currently, available prognostic factors largely include clinical-pathological parameters and focus on the cancer stage at the time of diagnosis. Among cells of tumor microenvironment (TME) only Immunoscore classifier based on T lymphocytes showed high predictive value. Methods: In the present study, we performed the complex analysis of mRNA and protein expression of crucial regulators of tumor angiogenesis and tumor progression, expressed by tumor-associated macrophages (TAMs): S100A4, SPP1 and SPARC. Colon and rectal cancer patients were investigated independently and in a combined cohort (CRC). For mRNA expression, we analyzed RNA sequencing data obtained from TCGA (N=417) and GEO (N=92) cohorts of colorectal cancer patients. For protein expression, we performed IHC digital quantification of tumor tissues obtained from 197 patients with CRC treated in the Department of abdominal oncology in Clinics of Tomsk NRMC. Results: High S100A4 mRNA expression accurately predicted poor survival for patients with CRC independently of cancer type. SPARC mRNA level was independent prognostic factors for survival in colon but not in rectal cancer. SPP1 mRNA level had significant predictive value for survival in both rectal and colon cancers. Analysis of human CRC tissues revealed that S100A4, SPP1 and SPARC are expressed by stromal compartments, in particular by TAMs, and have a strong correlation with macrophage infiltration. Finally, our results indicate that chemotherapy-based treatment can change the predictive direction of S100A4 for rectal cancer patients. We found that S100A4 stromal levels were higher in patients with better response to neoadjuvant chemotherapy/chemoradiotherapy, and S100A4 mRNA levels predicted better DFS among non-responders. Discussion: These findings can help improve the prognosis of patients with CRC based on S100A4, SPP1 and SPARC expression levels.

Monocyte programming by cancer therapy.

Monocytes in peripheral blood circulation are the precursor of essential cells that control tumor progression, that include tumor-associated macrophages (TAMs), dendritic cells (DCs) and myeloid-derive suppressor cells (MDSC). Monocytes-derived cells orchestrate immune reactions in tumor microenvironment that control disease outcome and efficiency of cancer therapy. Four major types of anti-cancer therapy, surgery, radiotherapy, chemotherapy, and most recent immunotherapy, affect tumor-associated macrophage (TAM) polarization and functions. TAMs can also decrease the efficiency of therapy in a tumor-specific way. Monocytes is a major source of TAMs, and are recruited to tumor mass from the blood circulation. However, the mechanisms of monocyte programming in circulation by different therapeutic onsets are only emerging. In our review, we present the state-of-the art about the effects of anti-cancer therapy on monocyte progenitors and their dedifferentiation, on the content of monocyte subpopulations and their transcriptional programs in the circulation, on their recruitment into tumor mass and their potential to give origin for TAMs in tumor-specific microenvironment. We have also summarized very limited available knowledge about genetics that can affect monocyte interaction with cancer therapy, and highlighted the perspectives for the therapeutic targeting of circulating monocytes in cancer patients. We summarized the knowledge about the mediators that affect monocytes fate in all four types of therapies, and we highlighted the perspectives for targeting monocytes to develop combined and minimally invasive anti-cancer therapeutic approaches.

PFKFB3 overexpression in monocytes of patients with colon but not rectal cancer programs pro-tumor macrophages and is indicative for higher risk of tumor relapse.

Introduction: Circulating monocytes are main source for tumor-associated macrophages (TAMs) that control tumor growth, angiogenesis, metastasis and therapy resistance. We raised the questions how monocyte programming is affected by growing tumors localized in colon and rectal sections, and how treatment onsets affect monocyte programming in the circulation. Methods: Patients with rectal cancer and colon cancer were enrolled in the study. Peripheral blood monocytes were characterized by phenotypic analysis using flow cytometry, by transcriptomic analysis using RNA sequencing and by gene expression analysis using real-time RT-PCR. Phenotypic analysis was performed with IF/confocal microscopy. Spatial transcriptomic analysis was applied using GeoMX DSP-NGS. Results: In patients with rectal cancer, increased amount of CCR2+ monocytes was indicative for the absence of both lymphatic and hematogenous metastasis. In contrast, in patients with colon cancer CD163+ monocytes were indicative for LN metastasis. NGS analysis identified tumor-specific transcriptional programming of monocytes in all CRC patients compared to healthy individuals. The key transcriptional difference between monocytes of patients with colon and rectal cancer was increased expression of PFKFB3, activator of glycolysis that is currently considered as therapy target for major solid cancers. PFKFB3-expressing monocyte-derived macrophages massively infiltrated tumor in colon. Nanostring technology identified correlation of PFKFB3 with amount and tumor-promoting properties of TAMs in colon but not in rectal cancer. PFKFB3 was indicative for tumor relapse specifically in colon cancer. Discussion: Our findings provide essential argument towards CRC definition to cover two clinically distinct cancers - colon cancer and rectal cancer, that differentially interact with innate immunity.

Novel PD-1 inhibitor prolgolimab: expanding non-resectable/metastatic melanoma therapy choice.

BACKGROUND: Prolgolimab is an IgG1 anti-PD-1 (programmed cell death protein 1) monoclonal antibody containing the Fc-silencing 'LALA' mutation. We assessed the efficacy and safety of two dosing regimens of prolgolimab in patients with advanced melanoma in a multicenter open-label parallel-arm phase II trial (MIRACULUM). We present the final analysis after 1 year of follow-up and additional efficacy results from 2 years of follow-up. METHODS: Patients with advanced cutaneous or non-cutaneous melanoma, including stable brain metastasis, without autoimmune disease and who underwent no prior targeted therapy, anti-PD-(L)1 or anti-CTLA-4 (cytotoxic T-lymphocyte-associated protein 4) therapy were randomly assigned (1:1) to receive prolgolimab in 2 dosing regimens, 1 mg/kg every 2 weeks (arm 1) or 3 mg/kg every 3 weeks (arm 2), until disease progression or intolerable toxicity. Randomisation was stratified based on performance status (Eastern Cooperative Oncology Group 0 or 1), lactate dehydrogenase levels (elevated or normal) and prior systemic therapy (naive or previously treated). The primary outcome was the objective response rate, assessed as per immune-related Response Evaluation Criteria in Solid Tumours by independent central review. The hypothesis that each dosing regimen of prolgolimab has an overall response rate >28% was tested independently for each study arm comprising all patients who received at least one dose of prolgolimab. Exploratory assessment of efficacy, including subgroup analysis, at 2 years of follow-up was not specified in the protocol. This study is registered withClinicalTrials.gov(NCT03269565). RESULTS: Between August 2017 and March 2018, 126 patients with advanced melanoma were enrolled. At main 1-year data cut-off, the median follow-up was 13.8 and 14.5 months in arm 1 and 2, respectively. An objective response was observed in 38.1% of patients (arm 1) and in 28.6% (arm 2). Grade III-IV treatment-related adverse events occurred in 12.7% and 3.2% of patients in arm 1 and 2, respectively. For exploratory efficacy analysis, the median follow-up was 25.4 and 25.7 months in arm 1 and 2, respectively. The 2-year progression-free survival was 33.3% in arm 1 and 30.2% in arm 2, and the 2-year overall survival was 57.1% and 46.0%, respectively. CONCLUSIONS: The MIRACULUM study met its primary end-point in both the study arms. Prolgolimab showed significant antitumour activity and a manageable safety profile in patients with advanced melanoma.

"Cyclopropanation of Cyclopropanes": GaCl3-Mediated Ionic Cyclopropanation of Donor-Acceptor Cyclopropanes with Diazo Esters as a Route to Tetrasubstituted Activated Cyclopropanes.

A new ionic cyclopropanation process involving the addition of diazo esters to donor-acceptor cyclopropanes (DAC) activated by GaCl3 has been developed. The reactions occur via 1,2-zwitterionic gallium complexes with elimination of nitrogen in all cases to give 1,1,2,3-tetrasubstituted cyclopropanes as the main products. Also, a number of related processes with the formation of various polysubstituted cyclopropanes, alkenes, and cyclobutanes, including products of multiple diazo ester addition, have been developed. Obtained by the developed method tetrasubstituted cyclopropanes are activated cyclopropanes such as DAC and can be used for further synthesis in this capacity. Their new reaction with benzaldehyde promoted by TiCl4 and involving one of the additional functional groups has been demonstrated, which leads to five-membered lactones. The mechanisms of the occurring processes, as well as the structures and stereochemistry of a rich range of products formed, are discussed in detail.

Features of Postnatal Hippocampal Development in a Rat Model of Sporadic Alzheimer's Disease.

Aging is the major risk factor of the most common (∼95% of cases) sporadic Alzheimer's disease (AD). Accumulating data indicate middle age as a critical period for the relevant pathological processes, however, the question of when AD starts to develop remains open. It has been reported only recently that in the early postnatal period-when brain development is completing-preconditions for a decrease in cognitive abilities and for accelerated aging can form. Here, we hypothesized that specific features of early postnatal brain development may be considered some of the prerequisites of AD development at an advanced age. To test this hypothesis, we used OXYS rats, which are a suitable model of sporadic AD. The duration of gestation, litter size, and weight at birth were lower in OXYS rats compared to control Wistar rats. The shortened duration of gestation may result in developmental retardation. Indeed, we noted decreased locomotor activity and increased anxiety in OXYS rats already at a young age: possible signs of altered brain development. We demonstrated retardation of the peak of postnatal neurogenesis in the hippocampal dentate gyrus of OXYS rats. Delayed neuronal maturation led to alterations of mossy-fiber formation: a shortened suprapyramidal bundle and longer infrapyramidal bundle, less pronounced fasciculation of granule cells' axons, and smaller size and irregular shape of nuclei in the CA3 pyramidal layer. These changes were accompanied by altered astrocytic migration. The observed features of early development may be considered some of the risk factors of the AD-like pathology that manifests itself in OXYS rats late in life.

Scanning the Future of Medical Imaging.

The medical device industry is undergoing rapid change as innovation accelerates, new business models emerge, and artificial intelligence and the Internet of Things create disruptive possibilities in health care. On the innovation front, global annual patent applications related to medical devices have tripled in 10 years, and technology cycle times have halved in just 5 years. Connectivity has exploded-by 2021, the world will have more than three times as many smart connected devices as people-and more and more medical devices and processes contain integrated sensors. In this article, we report on recent McKinsey (McKinsey & Company, New York, New York) work to map start-ups and trends shaping the future of medical imaging. We identify technology clusters with prospects of future growth, look at some of their cutting-edge practices, and consider what the implications may be for our specialty.

Three-Component Gallium(III)-Promoted Addition of Halide Anions and Acetylenes to Donor-Acceptor Cyclopropanes.

A new strategy for the three-component addition of halide anions and acetylenes to donor-acceptor cyclopropanes (DACs) is presented. This reaction, which occurs with high E selectivity, is promoted by gallium(III) salts and based on the 1,2-zwitterionic reactivity of DACs. It opens up a new group of processes involving DACs. The reaction occurs readily with a broad range of substrates and is tolerant of various functional groups. This methodology makes it possible to assemble highly functionalized vinyl halides, which are very convenient building blocks in organic synthesis. A possible mechanism of this reaction and its stereochemical aspects are discussed in detail.

[4 + 2] Annulation of Donor-Acceptor Cyclopropanes with Acetylenes Using 1,2-Zwitterionic Reactivity.

A new process for the [4 + 2] annulation of donor-acceptor cyclopropanes with acetylenes under the effect of anhydrous GaCl3 using 1,2-zwitterion reactivity was elaborated. The reaction opens access to substituted dihydronaphthalenes, naphthalenes, and other fused carbocycles. The direction of the reaction can be efficiently controlled by temperature.

A thrombopoietin receptor antagonist is capable of depleting myelofibrosis hematopoietic stem and progenitor cells.

Recently, interactions between thrombopoietin (TPO) and its receptor, the myeloproliferative leukemia (MPL) virus oncogene, have been shown to play a role in the development and progression of myeloproliferative neoplasms including myelofibrosis (MF). These observations have led to the development of strategies to disrupt the association of TPO with its receptor as a means of targeting MF hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs). In this report, we show that although both splenic and peripheral blood MF CD34(+) cells expressed lower levels of MPL than normal CD34(+) cells, TPO promoted the proliferation of MF CD34(+) cells and HPCs in a dose-dependent fashion. Furthermore, the treatment of MF but not normal CD34(+) cells with a synthesized MPL antagonist, LCP4, decreased the number of CD34(+)Lin(-) cells and all classes of assayable HPCs (colony-forming unit-megakaryocyte [CFU-MK], CFU-granulocyte/macrophage, burst-forming unit-erythroid/CFU-erythroid, and CFU-granulocyte/erythroid/macrophage/MK) irrespective of their mutational status. In addition, LCP4 treatment resulted in the depletion of the number of MF HPCs that were JAK2V617F(+) Moreover, the degree of human cell chimerism and the proportion of malignant donor cells were significantly reduced in immunodeficient mice transplanted with MF CD34(+) cell grafts treated with LCP4. These effects of LCP4 on MF HSCs/HPCs were associated with inhibition of JAK-STAT activity, leading to the induction of apoptosis. These findings demonstrate that such specific anti-cytokine receptor antagonists represent a new class of drugs that are capable of targeting MF HSCs.

Donor-Acceptor Cyclopropanes as 1,2-Dipoles in GaCl3-Mediated [4 + 2]-Annulation with Alkenes: Easy Access to the Tetralin Skeleton.

A new process for (4 + 2)-annulation of donor-acceptor cyclopropanes (DACs) with unsaturated compounds in the presence of anhydrous GaCl3 has been developed. In this process, DACs act as sources of formal 1,2- and 1,4-dipoles to give polysubstituted tetralins in high yields and with high regio- and diastereoselectivity. Alkenes with both aryl and alkyl substituents at the double bond undergo this reaction equally readily. A most likely mechanism of the reaction has been proposed. It involves preliminary generation of a key 1,2-dipolar gallium complex and its subsequent participation in annulation with an alkene.

A new type of donor-acceptor cyclopropane reactivity: the generation of formal 1,2- and 1,4-dipoles.

A new type of donor-acceptor cyclopropane reactivity has been discovered. On treatment with anhydrous GaCl3 , they react as sources of even-numbered 1,2- and 1,4-dipoles instead of the classical odd-numbered 1,3-dipoles due to migration of positive charge from the benzyl center. This type of reactivity has been demonstrated for new reactions, namely, cyclodimerizations of donor-acceptor cyclopropanes that occur as [2+2]-, [3+2]-, [4+2]-, [5+2], [4+3]-, and [5+4]-annulations. The [4+2]-annulation of 2-arylcyclopropane-1,1-dicarboxylates to give polysubstituted 2-aryltetralins has been developed in a preparative version that provides exceedingly high regio- and diastereoselectivity and high yields. The strategy for selective hetero-combination of donor-acceptor cyclopropanes was also been developed. The mechanisms of the discovered reactions involving the formation of a comparatively stable 1,2-ylide intermediate have been studied.

Potent agonists of a hematopoietic stem cell cytokine receptor, c-Mpl.

Several growth factors feature prominently in the control of hematopoiesis. Thrombopoietin, a class I hematopoietic cytokine, plays critical roles in regulating hematopoietic stem cell numbers and also stimulates the production and differentiation of megakaryocytes, the bone marrow cells that ultimately produce platelets. Thrombopoietin interacts with the c-Mpl cell-surface receptor. Recently, several peptide and small-molecule agonists and antagonists of c-Mpl have been reported. We conducted a bioinformatics and molecular modeling study aimed at understanding the agonist activities of peptides that bind to c-Mpl, and developed new potent peptide agonists with low nanomolar activity. These agonists also show very high activity in human CD34(+) primary cell cultures, and doubled the mean blood platelet counts when injected into mice.

Principal signalling complexes in haematopoiesis: structural aspects and mimetic discovery.

Blood production is a highly regulated process involving multiple inhibitory and stimulatory cytokines present in the haematopoietic stem cell niche. Small molecules mimics of these signalling molecules have substantial potential as drugs and in the development of bioreactors to generate blood products. We review the structural biology of the extracellular signalling domains of five of the most important cytokines, analyze their structure-property relationships, and summarize the progress in developing small molecule mimics using the molecular information from structural biology and mutation studies.

Effect of humic substances on toxicity of inorganic oxidizer bioluminescent monitoring.

The current study deals with the effect of humic substances (HS) on toxicity of solutions of a model inorganic oxidizer, potassium ferricyanide. Chemical reactions responsible for toxicity changes are under consideration. The bioluminescent system of coupled enzymatic reactions catalyzed by bacterial luciferase and oxidoreductase was used as a bioassay. General and oxidative toxicity of ferricyanide solutions were evaluated. Ability of HS to decrease or increase general and oxidative toxicity of the solutions was revealed. Two types of chemical processes are supposed to be responsible for detoxification by HS: ferricyanide-HS complex formation and acceleration of endogenous redox reactions in the bioluminescent assay system. Decrease of oxidative toxicity of ferricyanide solution was observed under incubation with HS at all concentrations of HS used. Conditions for general toxicity decrease were prior incubation of ferricyanide with HS and low HS concentrations (< 10⁻4g/L). Acceleration of NADH auto-oxidation under higher HS concentrations was supposed to result in a toxicity increase.