Ultrastructure of the gut epithelium in Acheta domesticus after long-term exposure to nanodiamonds supplied with food

Autophagic activity in the midgut cells of three arachnids responds selectively to different modes of overwintering in caves

Autophagy is a highly conserved metabolic process that regulates cellular homeostasis and energy supply by degrading dysfunctional and excess cell constituents and reserve materials into products that are reused in metabolic and biosynthetic pathways. Macroautophagy is the best studied form of autophagy in invertebrates. Starvation is a common stress factor triggering autophagy in overwintering animals. In arachnids, the midgut diverticula cells perform many vital metabolic functions and are therefore critically involved in the response to starvation. Here we studied macroautophagy in three species which apply different modes for overwintering in caves: the harvestmen Gyas annulatus in diapause, Amilenus aurantiacus with ongoing ontogenesis under fasting conditions, and the spider Meta menardi, which feeds opportunistically even in winter. The main goal was to find eventual qualitative and quantitative differences in autophagic processes by inspecting TEM micrographs. In all three species, the rates of midgut epithelial cells with autophagic structures gradually increased during overwintering, but were significantly lower in G. annulatus in the middle and at the end of overwintering than in the other two species, owing to metabolic activity having been more suppressed. Decomposition of mitochondria and glycogen took place in autophagic structures in all three species. Moreover, spherite disintegration in A. aurantiacus and a special form of lipid disintegration through "lipid bubbly structures" in M. menardi indicate the crucial involvment of selective autophagy, while no specific autophagy was observed in G. annulatus. We conclude that autophagic activities support overwintering in different ways in the species studied.

Concentration-dependent disturbances of digestive functions in house cricket (Insecta: Orthoptera) exposed to GO-AgNP composite

This study investigates the effects of graphene oxide (GO) and silver nanoparticle (AgNP) composite (GO-AgNP) on the digestive physiology and gut ultrastructure of Acheta domesticus (house cricket) during extended exposure. Various concentrations of GO-AgNP were tested to assess their impact on food consumption, assimilation, cell status (Dead Cells and ROS + cells), gut enzyme activity, and structural damage to gut cells. Concentration and exposure time had significant effects on oxidative stress, enzyme activity, and gut cell structure. The applied composite reduced cumulative food consumption and assimilation efficiency. Enzyme assays showed that lower concentrations enhanced carbohydrate-degrading enzyme activity, while higher concentrations inhibited protease activity. Histological analysis revealed structural damage to gut epithelial cells and signs of autophagy or necrosis at higher concentrations. These results suggest that GO and AgNPs contribute to oxidative stress, cell cycle disruption, and apoptosis, with AgNPs having a potentially stronger effect than GO. The disturbed enzyme activity may result from conformational changes caused by nanoparticle agglomeration. These findings underline potential risks associated with the environmental or agricultural use of GO-AgNP composites.

Investigation of potential cytotoxicity of a water-soluble, red-fluorescent [70]fullerene nanomaterial in Drosophila melanogaster

Fullerenes (C60, C70) as carbon nanomaterials can enter the environment through natural processes and anthropogenic activities, while synthetic fullerenes are commonly used in medicine in targeted therapies in association with antibodies, or anticancer and antimicrobial drugs. As the nanoparticles, they can pass through cell membranes and organelles and accumulate in the entire cytoplasm. The red-fluorescent, water-soluble [70]fullerene derivative C70-OMe-ser, which produces reactive oxygen species upon illumination with an appropriate wavelength, passed into the cytoplasm of the middle region in the Drosophila melanogaster digestive system. To determine whether [70]fullerene nanomaterials that produce fluorescence after entering the cell cytoplasm will hurt its homeostasis, it is necessary to investigate the activation of degenerative and possibly regenerative processes. In vivo, studies on the model species D. melanogaster may help to elucidate whether the water-soluble [70]fullerene derivative that produces fluorescence can still be considered among the most promising nanomaterials. The experiment involved feeding insects ad libitum with yeast paste supplemented with 40 µg of fullerenes/mL for 1 week and 1 month. Thus, adult females and males of D. melanogaster were divided into control (CWM, CWF, CMM, and CMF) and experimental groups (FWM, FWF, FMM, and FMF). The quantitative and qualitative analysis enabled the presentation of the effects of the water-soluble [70]fullerene derivatives on cell proliferation and degeneration. Our study presented that [70]fullerene derivative showed a cytoprotective effect and activated cell proliferation. Therefore, we could conclude that analyzed carbon nanomaterials seemed to be safe for the cells into which they have penetrated.

Biomonitoring of Heavy Metal Toxicity in Freshwater Canals in Egypt Using Creeping Water Bugs (Ilyocoris cimicoides): Oxidative Stress, Histopathological, and Ultrastructural Investigations

The abundance of metal pollutants in freshwater habitats poses serious threats to the survival and biodiversity of aquatic organisms and human beings. This study intends for the first time to assess the pernicious influences of heavy metals in Al Marioteya canal freshwater in Egypt, compared to Al Mansoureya canal as a reference site utilizing the creeping water bug (Ilyocoris cimicoides) as an ecotoxicological model. The elemental analysis of the water showed a significantly higher incidence of heavy metals, including cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni), and lead (Pb), in addition to the calcium (Ca) element than the World Health Organization's (WHO) permitted levels. The Ca element was measured in the water samples to determine whether exposure to heavy metals-induced oxidative stress engendered Ca deregulation in the midgut tissues of the creeping water bug. Remarkably, increased levels of these heavy metals were linked to an increase in chemical oxygen demand (COD) at the polluted site. Notably, the accumulation of these heavy metals in the midgut tissues resulted in a substantial reduction in antioxidant parameters, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and ascorbate peroxidase (APOX), along with a marked rise in malondialdehyde (MDA), cytochrome P450, and protein carbonyl levels. These results clearly indicate a noticeable disturbance in the antioxidant defense system due to uncontrollable reactive oxygen species (ROS). Notably, the results demonstrated that oxidative stress caused disturbances in Ca levels in the midgut tissue of I. cimicoides from polluted sites. Furthermore, the comet and flow cytometry analyses showed considerable proliferations of comet cells and apoptotic cells in midgut tissues, respectively, exhibiting prominent correlations, with pathophysiological deregulation. Interestingly, histopathological and ultrastructural examinations exposed noticeable anomalies in the midgut, Malpighian tubules, and ovarioles of I. cimicoides, emphasizing our findings. Overall, our findings emphasize the potential use of I. cimicoides as a bioindicator of heavy metal pollution in freshwater to improve sustainable water management in Egypt.

Nanoparticles-mediated entomotoxicology: lessons from biologica

Nanotechnology has grown in importance in medicine, manufacturing, and consumer products. Nanoparticles (NPs) are also widely used in the field of insect pest management, where they show a variety of toxicological effects on insects. As a result, the primary goal of this review is to compile and evaluate available information on effects of NPs on insects, by use of a timely, bibliometric analysis. We also discussed the manufacturing capacity of NPs from insect tissues and the toxic effects of NPs on insects. To do so, we searched the Web of Science database for literature from 1995 to 2023 and ran bibliometric analyses with CiteSpace© and Bibliometrix©. The analyses covered 614 journals and identified 1763 relevant documents. We found that accumulation of NPs was one of the top trending topics. China, India, and USA had the most published papers. The most overall reported models of insects were those of Aedes aegypti (yellow fever mosquito), Culex quinquefasciatus (southern house mosquito), Bombyx mori (silk moth), and Anopheles stephensi (Asian malaria mosquito). The application and methods of fabrication of NPs using insect tissues, as well as the mechanism of toxicity of NPs on insects, were also reported. A uniform legal framework is required to allow nanotechnology to fully realize its potential while minimizing harm to living organisms and reducing the release of toxic metalloid nanoparticles into the environment.

Survival, growth and digestive functions after exposure to nanodiamonds - Transgenerational effects beyond contact time in house cricket strains

The long-term exposure effects of nanodiamonds (NDs), spanning an organism's entire lifespan and continuing for subsequent generation, remain understudied. Most research has focused on evaluating their biological impacts on cell lines and selected organisms, typically over short exposure durations lasting hours or days. The study aimed to assess growth, mortality, and digestive functions in wild (H) and long-lived (D) strains of Acheta domesticus (Insecta: Orthoptera) after two-generational exposure to NDs in concentrations of 0.2 or 2 mg kg-1 of food, followed by their elimination in the third generation. NDs induced subtle stimulating effect that depended on the strain and generation. In the first generation, more such responses occurred in the H than in the D strain. In the first generation of H strain insects, contact with NDs increased survival, stimulated the growth of young larvae, and the activity of most digestive enzymes in mature adults. The same doses and exposure time did not cause similar effects in the D strain. In the first generation of D strain insects, survival and growth were unaffected by NDs, whereas, in the second generation, significant stimulation of those parameters was visible. Selection towards longevity appears to support higher resistance of the insects to exposure to additional stressor, at least in the first generation. The cessation of ND exposure in the third generation caused potentially harmful changes, which included, e.g., decreased survival probability in H strain insects, slowed growth of both strains, as well as changes in heterochromatin density and distribution in nuclei of the gut cells in both strains. Such a reaction may suggest the involvement of epigenetic inheritance mechanisms, which may become inadequate after the stress factor is removed.

Effect of paracetamol on the storage cells of Hypsibius exemplaris—ultrastructural analysis

Tardigrades in their natural environment are exposed to various environmental toxicants, including non-steroidal anti-inflammatory drugs (NSAIDs) or antipyretics such as paracetamol. This drug can enter the animal’s body through the body wall or the digestive system with food and can affect the biology of organisms. In this paper, we report for the first time the effects of paracetamol on tardigrade storage cells. We analyzed the effects of short-term (7 days) and long-term (28 days) exposure of Hypsibius exemplaris storage cells to three paracetamol concentrations (0.2 µgxL−1, 230 µgxL−1, 1 mgxL−1). Our results showed that increasing paracetamol concentration and incubation time increases the number of damaged mitochondria in storage cells, and autophagy is activated and intensified. Moreover, the relocation of some organelles and cell deformation may indicate cytoskeleton damage.

Hazards related to the presence of cadmium in food - Studies on the European soil centipede, Lithobius forficatus

The soil is an environment rich in numerous potentially toxic substances/elements when present at elevated concentrations. They can be transported through the successive levels of the trophic chain. Animals living in a contaminated environment or eating contaminated food can accumulate potentially toxic elements in their bodies. One of the potentially toxic metals is cadmium, which accumulates significantly in soils. The aim of our research was to evaluate the changes caused by cadmium supplied with the food administered to invertebrates living in uncontaminated soil. The results were compared with those obtained for animals raised in contaminated soil, where cadmium entered the body via the epidermis. As the material for studies, we chose a common European soil centipede, Lithobius forficatus. Adult specimens were divided into the following experimental groups: C - control animals, Cd12 and Cd45 - animals fed with Chironomus larvae maintained in water containing 80 mg/l CdCl₂, for 12 and 45 days, respectively. The material was analyzed using qualitative and quantitative analysis (transmission electron microscopy, confocal microscopy, flow cytometry, atomic absorption spectrometry). Eventually, we can conclude that the digestive system is an effective barrier against the effects of toxic metals on the entire organism, but among the gonads, ovaries are more protected than testes, however, this protection is not sufficient. Accumulation of spherites and mitochondrial alterations are probably involved in survival mechanisms of tissues after Cd intoxication.

Does age pay off? Effects of three-generational experiments of nanodiamond exposure and withdrawal in wild and longevity-selected model animals

Nanodiamonds (NDs) are considered a material with low toxicity. However, no studies describe the effects of ND withdrawal after multigenerational exposure. The aim was to evaluate ND exposure (in the 1st and 2nd generations) effects at low concentrations (0.2 or 2 mg kg^-1) and withdrawal (in the 3rd generation) in the wild (H) and longevity-selected (D) model insect Acheta domesticus. We measured selected oxidative stress parameters, immunity, types of cell death, and DNA damage. Most of the results obtained in the 1st generation, e.g., catalase (CAT), total antioxidant capacity (TAC), heat shock proteins (HSP70), defensins, or apoptosis level, confirmed no significant toxicity of low doses of NDs. Interestingly, strain-specific differences were observed. D-strain crickets reduced autophagy, the number of ROS+ cells, and DNA damage. The effect can be a symptom of mobilization of the organism and stimulation of physiological defense mechanisms in long-living organisms. The 2nd-generation D-strain insects fed ND-spiked food at higher concentrations manifested a reduction in CAT, TAC, early apoptosis, and DNA damage, together with an increase in HSP70 and defensins. ROS+ cells and cells with reduced membrane potential and autophagy did not differ significantly from the control. H-strain insects revealed a higher number of ROS+ cells and cells with reduced membrane potential, decreased CAT activity, and early apoptosis. Elimination of NDs from the diet in the 3rd generation did not cause full recovery of the measured parameters. We noticed an increase in the concentration of HSP70 and defensins (H-strain) and a decrease in apoptosis (D-strain). However, the most visible increase was a significant increase in DNA damage, especially in H-strain individuals. The results suggest prolonged adverse effects of NDs on cellular functions, reaching beyond "contact time" with these particles. Unintentional and/or uncontrolled ND pollution of the environment poses a new challenge for all organisms inhabiting it, particularly during multigenerational exposure.

Biochemical and histological alterations induced by nickel oxide nanoparticles in the ground beetle Blaps polychresta (Forskl, 1775) (Coleoptera: Tenebrionidae)

The present study evaluates the effect of nickel oxide nanoparticles on some biochemical parameters and midgut tissues in the ground beetle Blaps polychresta as an indicator organism for nanotoxicity. Serial doses of the NiO-NPs colloid (0.01, 0.02, 0.03, 0.04, 0.05, and 0.06 mg/g) were prepared for injecting into the adult beetles. Insect survival was reported daily for 30 days, and the sublethal dose of 0.02 mg/g NiO-NPs was selected for the tested parameters. After the treatment, nickel was detected in the midgut tissues by X-ray microanalysis. The treated group demonstrated a significant increase in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities when compared to the untreated group. However, the treated group demonstrated a significant decrease in ascorbate peroxidase (APOX) activity when compared to the untreated group. Histological and ultrastructural changes in the midgut tissues of treated and untreated beetles were also observed. The current findings provide a precedent for describing the physiological and histological changes caused by NiO-NPs in the ground beetle B. polychresta.

Do nanoparticles cause hormesis? Early physiological compensatory response in house crickets to a dietary admixture of GO, Ag, and GOAg composite

This study aimed to identify the physiological responses of house cricket females following short-term exposure to relatively low dietary doses of graphene oxide (GO, 20 μg · g^-1 food), silver (Ag, 400 μg · g^-1 food) nanoparticles (NPs), or graphene oxide‑silver nanoparticle composite (GO-AgNPs, 20: 400 μg · g^-1 food). Energy intake and distribution were measured on the third, sixth, and tenth day. A semi-quantitative API®ZYM assay of digestive enzyme fingerprints was performed on the third and tenth day of continuous treatment. Physicochemical properties of the NPs were obtained by combining SEM, EDX spectrometry, AFM, and DLS techniques. The obtained results showed decreased energy consumption, particularly assimilation as an early response to dietary NPs followed by compensatory changes in feeding activity leading to the same consumption and assimilation throughout the experimental period (10 days). The increased activities of digestive enzymes in NP-treated females compared to the control on the third day of the experiment suggest the onset of compensatory reactions of the day. Moreover, the insects treated with GO-AgNP composite retained more body water, suggesting increased uptake. The observed changes in the measured physiological parameters after exposure to NPs are discussed in light of hormesis.

Nickel oxide nanoparticles induce genotoxicity and cellular alterations in the ground beetle Blaps polycresta (Coleoptera: Tenebrionidae)

Nickel nanoparticles (Ni-NPs) have advantageous applications in the industry; however, little is known of their adverse effects on biological tissues. In the present study, the ground beetle Blaps polycresta was employed as a sensitive indicator for nickel oxide nanoparticles (NiO-NPs) toxicity. Adult male beetles were injected with six dose levels of NiO-NPs (0.01, 0.02, 0.03, 0.04, 0.05, and 0.06 mg/g body weight). Mortality was reported daily over 30 days under laboratory conditions to establish an LD₅₀. Nickel was detected in the testicular tissues of the beetles using X-ray analysis and transmission electronic microscopy. Beetles treated with the sublethal dose of 0.02 mg/g were selected to observe molecular, cellular, and subcellular changes. Gene transcripts of HSP70, HSP90, and MT1 were found to be increased >2.5-, 1.5-, and 2-fold, respectively, in the treated group compared with the controls. Decreased gene expression of AcPC01, AcPC02, and AcPC04 (≤1.5-, ≤2-, and < 2.5-fold, respectively, vs. controls) also were reported in the treated group. Under light microscopy, various structural changes were observed in the testicular tissues of the treated beetles. Ultrastructure observations using scanning and transmission electron microscopy showed severe damage to the subcellular organelles as well as deformities of the heads and flagella of the spermatozoa. Therefore, the present study postulated the impact of NiO-NPs in an ecological model.

The Structure-Properties-Cytotoxicity Interplay: A Crucial Pathway to Determining Graphene Oxide Biocompatibility

Interest in graphene oxide nature and potential applications (especially nanocarriers) has resulted in numerous studies, but the results do not lead to clear conclusions. In this paper, graphene oxide is obtained by multiple synthesis methods and generally characterized. The mechanism of GO interaction with the organism is hard to summarize due to its high chemical activity and variability during the synthesis process and in biological buffers' environments. When assessing the biocompatibility of GO, it is necessary to take into account many factors derived from nanoparticles (structure, morphology, chemical composition) and the organism (species, defense mechanisms, adaptation). This research aims to determine and compare the in vivo toxicity potential of GO samples from various manufacturers. Each GO sample is analyzed in two concentrations and applied with food. The physiological reactions of an easy model Acheta domesticus (cell viability, apoptosis, oxidative defense, DNA damage) during ten-day lasting exposure were observed. This study emphasizes the variability of the GO nature and complements the biocompatibility aspect, especially in the context of various GO-based experimental models. Changes in the cell biomarkers are discussed in light of detailed physicochemical analysis.

Vitellogenin expression, DNA damage, health status of cells and catalase activity in Acheta domesticus selected according to their longevity after graphene oxide treatment

The increased use of graphene oxide (GO) raises worrisome questions regarding its possible threat to various ecosystems. Invertebrates represent valuable organisms for environmental studies. The lifespan can influence the ability to cope with toxins, especially those that act via oxidative stress. Two strains of Acheta domesticus, which are selected for longevity, were tested. The main aim was to investigate how GO, when administrated in food, affects: the condition of cells, DNA stability, ROS generation and the reproduction potential (the Vitellogenin (Vg) protein expression). The "recovery effect" - after removing GO from the diet for 15 days - was also measured. The results revealed different responses to GO in the wild (H) and long-living (D) strains. The D strain had a higher catalase activity compared to the H strain on the 25th day of the imago stage. Removing GO from the food resulted in a decrease in the catalase activity to the level of the control. On the 5th day of the imago stage, the H strain had a higher cell mortality than the D strain in the GO-intoxicated groups. There was more DNA damage in the H strain compared to the long-living strain. A remedial effect was seen after the GO was removed from the diet. The total Vg protein expression was higher in the H strain and lower in the D strain. The results indicated a GO concentration-dependent outcome. In both strains, removing the GO from the food led to a high Vg expression. The Vg expression after GO treatment, particularly translation and post-translational processing, should be studied in detail in the future. The D strain of crickets had more specialized mechanisms for maintaining homeostasis than the H strain. Organisms can fight off negative effects of GO, especially when they have systems that are well developed against oxidative stress.

Unravelling the ZnO-NPs mechanistic pathway: Cellular changes and altered morphology in the gastrointestinal tract of the earthworm Eisenia andrei

A major uptake route of nanoparticles (NPs) occurs via the gastrointestinal (GI) tract. When GI tract cells are exposed, NPs cytotoxic effects are observed that subsequently adversely affect the GI tract morphology and have consequences for the whole organism. The aim of this study was to understand the mechanism of effects caused by ZnO-NPs compared to Zn ions on the earthworm Eisenia andrei. The following aspects of individually exposed earthworms were investigated: 1) qualitative structural alterations in the gut epithelium and chloragogen cells of the GI tract, 2) quantitative changes within chloragogen tissues after 48 h of exposure (using morphometric analysis), and 3) the ADP/ATP ratio in homogenized tissue of the whole organism after 21 days of exposure to contaminated soil (contamination phase) followed by 14 days of elimination in clean soil (decontamination phase) to identify possible recovery. Both ZnO-NPs and Zn ions adversely affect the gut epithelium and chloragogen tissue of earthworms after 48 h of exposure to contaminated soil. Morphometric measurements revealed that the proportions of debris vesicles in the chloragocytes were significantly lower in worms exposed to ZnO-NPs than in worms exposed to Zn ions. Moreover, numerous spherite granules were observed in the chloragocytes of ionic Zn-treated worms, but not the ZnO-NPs-treated worms, suggesting differential regulation of these Zn forms. The Zn cytotoxic effect was not reflected in ADP/ATP ratio measurements. Our study provides new insights into nano-specific effects that are distinctive from ion regulation inside the GI tract and furthers our understanding of the relationship between effects at the cellular and whole-body levels.

MoS2 nanoparticles induce behavioral alteration and oxidative stress mediated cellular toxicity in the social insect Oecophylla smaragdina (Asian weaver ant)

The study evaluates molybdenum disulfide (MoS₂) nanoparticles (NPs) induced oxidative stress during cellular toxicity in an invertebrate in vivo system, the weaver ant. The lethal concentration was checked and LC₅₀ was obtained as 50 µg/mL. Feeding assay and the photoluminescence activity confirmed the ingestion of MoS₂ NPs by the organism. Behavioral assays showed altered grooming behavior in the MoS₂ NP fed ants. A drastic decrease in the hemocyte count in the MoS₂ NP fed ants revealed the anti-proliferative role of MoS₂. This was further confirmed by 5-bromo-2'-deoxyuridine (BrdU) labeling assay. MoS₂ NPs induced apoptotic activity was also observed in the hemocytes by acridine orange/ethidium bromide (AO/EB) staining. The level of oxidative stress during cellular toxicity was observed. An increased reactive oxygen species (ROS) level was observed in the MoS₂ NP fed ants when compared to the control group. The increased activity of superoxide dismutase (SOD) and the lipid peroxidation (LPO) product were observed. While, the activities of catalase (CAT) and glutathione-s-transferase (GST) and the glutathione content (GSH) were decreased by MoS₂ NPs. The transcript levels of SODs, CAT and GST were up regulated in the treated group. Our results suggest that MoS₂ NPs induced oxidative stress mediates the cellular toxicity in the foragers of the weaver ant.

Autophagy and Apoptosis in the Midgut Epithelium of Millipedes

The process of autophagy has been detected in the midgut epithelium of four millipede species: Julus scandinavius, Polyxenus lagurus, Archispirostreptus gigas, and Telodeinopus aoutii. It has been examined using transmission electron microscopy (TEM), which enabled differentiation of cells in the midgut epithelium, and some histochemical methods (light microscope and fluorescence microscope). While autophagy appeared in the cytoplasm of digestive, secretory, and regenerative cells in J. scandinavius and A. gigas, in the two other species, T. aoutii and P. lagurus, it was only detected in the digestive cells. Both types of macroautophagy, the selective and nonselective processes, are described using TEM. Phagophore formation appeared as the first step of autophagy. After its blind ends fusion, the autophagosomes were formed. The autophagosomes fused with lysosomes and were transformed into autolysosomes. As the final step of autophagy, the residual bodies were detected. Autophagic structures can be removed from the midgut epithelium via, e.g., atypical exocytosis. Additionally, in P. lagurus and J. scandinavius, it was observed as the neutralization of pathogens such as Rickettsia-like microorganisms. Autophagy and apoptosis ca be analyzed using TEM, while specific histochemical methods may confirm it.

Chronic toxicity of nanodiamonds can disturb development and reproduction of Acheta domesticus L

The use of nanodiamonds in numerous materials designed for industry and medicine is growing rapidly. Consequently health and environmental risks associated with the exposure of humans and other biota to nanodiamonds-based materials are of the utmost importance. Scarcity of toxicological data for these particles led us to examine the potentially deleterious effects of nanodiamonds in model insect species, Acheta domesticus (Orthoptera) chronically exposed to ND in its diet. Organism-level end-point indices (lifespan, body weight, consumption, caloric value of faeces, reproduction) revealed adverse changes in the treated crickets in comparison with the control. Preliminary studies of oxidative stress level in the offspring of ND-treated crickets suggest toxicity of these particles limited to the exposed individuals. EPR analysis showing increase of radical signal in the faeces of ND-fed crickets led us to propose novel mechanism of nanodiamonds toxicity that is discussed in the light of literature data.

CAPSULE

Development and reproduction of Acheta domesticus can be disturbed by the chronic exposure to nanodiamonds.

Fine structure of the midgut epithelium in the millipede Telodeinopus aoutii (Myriapoda, Diplopoda) with special emphasis on epithelial regeneration

The midgut of millipedes is composed of a simple epithelium that rests on a basal lamina, which is surrounded by visceral muscles and hepatic cells. As the material for our studies, we chose Telodeinopus aoutii (Demange, 1971) (Kenyan millipede) (Diplopoda, Spirostreptida), which lives in the rain forests of Central Africa. This commonly reared species is easy to obtain from local breeders and easy to culture in the laboratory. During our studies, we used transmission and scanning electron microscopes and light and fluorescent microscopes. The midgut epithelium of the species examined here shares similarities to the structure of the millipedes analyzed to date. The midgut epithelium is composed of three types of cells-digestive, secretory, and regenerative cells. Evidence of three types of secretion have been observed in the midgut epithelium: merocrine, apocrine, and microapocrine secretion. The regenerative cells of the midgut epithelium in millipedes fulfill the role of midgut stem cells because of their main functions: self-renewal (the ability to divide mitotically and to maintain in an undifferentiated state) and potency (ability to differentiate into digestive cells). We also confirmed that spot desmosomes are common intercellular junctions between the regenerative and digestive cells in millipedes.

Ultrastructure of the larval midgut of Bittacus planus (Mecoptera: Bittacidae) and Neopanorpa longiprocessa (Mecoptera: Panorpidae)

Bittacidae and Panorpidae are the two largest families in Mecoptera. The larvae of Bittacidae are different from those of Panorpidae in external morphology and habits, and have an interesting habit of spraying the body surface with soil through the anus. However, it remains unknown to date whether the larval midguts are different in structure between the two families. Here the ultrastructure of the larval midguts of the hangingfly Bittacus planus Cheng and the scorpionfly Neopanorpa longiprocessa Hua & Chou were compared using light, scanning, and transmission electron microscopy. The midguts of both species are simple tubes of single layered epithelia with digestive and regenerative cells but without diverticula. The basal plasma membrane of epithelial cells exhibits infolding in B. planus, but is closely apposed to its basal lamina in N. longiprocessa. Lymph spaces are present between adjacent epithelial cells in B. planus, but are absent in N. longiprocessa. The regenerative cells are scattered among the digestive cells in B. planus, but are aggregated in N. longiprocessa. The longitudinal muscle bands are compact in B. planus, but are sparse in N. longiprocessa. The compact longitudinal muscle bands are likely associated with their soil-spraying habit in Bittacidae.

The effect of starvation and re-feeding on mitochondrial potential in the midgut of Neocaridina davidi (Crustacea, Malacostraca)

The midgut in the freshwater shrimp Neocaridina davidi (previously named N. heteropoda) (Crustacea, Malacostraca) is composed of a tube-shaped intestine and a large hepatopancreas that is formed by numerous blind-ended tubules. The precise structure and ultrastructure of these regions were presented in our previous papers, while here we focused on the ultrastructural changes that occurred in the midgut epithelial cells (D-cells in the intestine, B- and F- cells in the hepatopancreas) after long-term starvation and re-feeding. We used transmission electron microscopy, light and confocal microscopes and flow cytometry to describe all of the changes that occurred due to the stressor with special emphasis on mitochondrial alterations. A quantitative assessment of cells with depolarized mitochondria helped us to establish whether there is a relationship between starvation, re-feeding and the inactivation/activation of mitochondria. The results of our studies showed that in the freshwater shrimp N. davidi that were analyzed, long-term starvation activates the degeneration of epithelial cells at the ultrastructural level and causes an increase of cells with depolarized (non-active) mitochondria. The process of re-feeding leads to the gradual regeneration of the cytoplasm of the midgut epithelial cells; however, these changes were observed at the ultrastructural level. Additionally, re-feeding causes the regeneration of mitochondrial ultrastructure. Therefore, we can state that the increase in the number of cells with polarized mitochondria occurs slowly and does not depend on ultrastructural alterations.

Investigating the Influence of MoS2 Nanosheets on E. coli from Metabolomics Level

Molybdenum disulfide, a type of two-dimensional layered material with unique properties, has been widely used in many fields. However, an exact understanding of its toxicity remains elusive, let alone its effects on the environmental microbial community. In this study, we utilized metabolomics technology to explore the effects of different concentrations of molybdenum disulfide nanosheets on Escherichia coli for the first time. The results showed that with increasing concentration of molybdenum disulfide nanosheets, the survival rate of Escherichia coli was decreased and the release of lactic dehydrogenase was increased. At the same time, intracellular concentrations of reactive oxygen species were dramatically increased. In addition, metabolomics analysis showed that high concentrations of molybdenum disulfide nanosheets (100, 1000 μg/mL) could significantly affect the metabolic profile of Escherichia coli, including glycine, serine and threonine metabolism, protein biosynthesis, urea cycle and pyruvate metabolism. These results will be beneficial for molybdenum disulfide toxicity assessment and further applications.

Oxidative stress and genotoxic effects of diamond nanoparticles

Due to the unique and useful properties of nanodiamonds (ND), their production and use is rapidly increasing. Thus, more of these particles will be released into the environment and organisms will inevitably be exposed to them. The current knowledge about the toxicity of ND, especially in vivo toxicity, is fragmentary. In this study, the toxicity of nanodiamonds was assessed in Acheta domesticus following chronic exposure to different nominal concentrations of ND (20 and 200µgg(-1) food) administrated in food for the entire lifespan. The activity of oxidative stress enzymes (catalase, glutathione peroxidase), total antioxidant capacity, as well as the level of heat shock protein were determined. A significant increase in all of the measured parameters was observed after seven weeks of exposure in individuals exposed to higher concentrations of ND (200µgg(-1) food). In animals exposed to lower concentrations of ND (20µgg(-1) food), there were few significant changes to these parameters. Analysis of DNA damage performed after fourteen weeks using the comet assay revealed DNA instabilities in the insects, especially the ones that had been exposed to the higher doses of ND. These findings may suggest that the toxicity of ND is concentration dependent. While high doses interact in a toxic manner, trace amounts, which are more likely in the environment, might be safe for organisms. Extreme caution should be taken when handling nanodiamonds.