Mortality Pattern of Poecilus cupreus Beetles after Repeated Topical Exposure to Insecticide─Stochastic Death or Individual Tolerance?

The mortality of organisms exposed to toxicants has been attributed to either stochastic processes or individual tolerance (IT), leading to the stochastic death (SD) and IT models. While the IT model follows the principles of natural selection, the relevance of the SD model has been debated. To clarify why the idea of stochastic mortality has found its way into ecotoxicology, we investigated the mortality of Poecilus cupreus (Linnaeus, 1758) beetles from pesticide-treated oilseed rape (OSR) fields and unsprayed meadows, subjected to repeated insecticide treatments. We analyzed the mortality with the Kaplan-Meier estimator and general unified threshold model for survival (GUTS), which integrates SD and IT assumptions. The beetles were exposed three times, ca. monthly, to the same dose of Proteus 110 OD insecticide containing thiacloprid and deltamethrin, commonly used in the OSR fields. Kaplan-Meier analysis showed that the mortality of beetles from meadows was much higher after the first treatment than after the next two, indicating the IT model. Beetles from the OSR displayed approximately constant mortality after the first and second treatments, consistent with the SD model. GUTS analysis did not conclusively identify the better model, with the IT being marginally better for beetles from meadows and the SD better for beetles from OSR fields.

Late diagnosis of HIV infection in Warsaw: Estimating the scale of the problem and demographic trends.

BACKGROUND: Late diagnosis of a significant number of people with HIV remains a problem. This study analysed 1711 patients from the Hospital for Infectious Diseases in Warsaw who were diagnosed with HIV infection in 2008-2010 and 2016-2018. METHODS: Patients with late diagnosis and advanced disease were distinguished on the basis of the consensus definition. In statistical analysis, non-parametric tests were used to compare the groups: the χ2 test for categorized data and the Mann-Whitney U test for the comparison of continuous variables. RESULTS: There were no statistically significant differences in the percentage of patients with early diagnosis, late diagnosis, advanced disease and patients with an indicator disease between the two analysed periods in the Warsaw centre. A much higher percentage of men than women was found. The dominant route of acquisition among newly diagnosed patients and among late presenters in both periods were men who have sex with men (MSM). The highest percentage of patients with late diagnosis was among heterosexual men and the lowest was among MSM in both periods. CONCLUSIONS: The results of the analysis of patients from the Warsaw centre confirmed that late diagnosis of HIV infection continues to be a problem, with no improvement seen over the analysed periods, although the scale of the problem is smaller than in national and European statistics. MSM and heterosexual men appear to be key groups in need of intensified testing.

Is the definition of late diagnosis correct?

BACKGROUND: The study analysed 1711 patients of the Hospital for Infectious Diseases in Warsaw diagnosed with HIV infection in 2008-2010 and 2016-2018. Research was conducted examining the changes in CD4 cell counts before starting antiretroviral (ARV) treatment in order to find people who were misclassified as late-diagnosed. METHODS: Patients with late diagnosis were distinguished on the basis of the consensus definition. The Mann-Whitney U-test was used to analyse the change in CD4 cell counts before starting ARV treatment. RESULTS: In the years 2008-2010, the CD4 count was remeasured before starting ARV treatment in 90 late-diagnosed patients. The median change in the CD4 count was 22 cells/µL. In 49 of these, the number of CD4 cells spontaneously increased before the start of treatment. We can suspect that these patients were misclassified as late-diagnosed. CONCLUSIONS: The consensus definition of late diagnosis often leads to overestimation of the number of late-diagnosed patients. The crucial problem is a transient decline in the CD4 lymphocyte count in the acute phase of HIV infection. A potential solution is to introduce serum HIV viral load measurement into the definition.

Effects of agricultural landscape structure and canola coverage on biochemical and physiological traits of the ground beetle Poecilus cupreus.

The intensifications in the agricultural landscape and the application of pesticides can cause adverse effects on the fitness of organisms in that landscape. Here, we investigated whether habitats with different agricultural pressures influenced acetylcholinesterase (AChE) activity - a biomarker for exposure to pesticides, respiration rate, and resistance to starvation in the ground beetle Poecilus cupreus. Two differently structured landscapes were selected for the study, one dominated by small (S) and another by large (L) fields. Within each landscape three habitat types were selected: in the S landscape, these were habitats with medium (M), small (S) and no canola (meadow, 0) coverage (i.e., SM, SS, S0), and in the L landscape habitats with large (L), medium (M) and no canola (meadow, 0) coverage (i.e., LL, LM, L0), representing different levels of agricultural pressure. The activity of AChE was the highest in beetles from canola-free habitats (S0 and L0), being significantly higher than in beetles from the SM and SS habitats. The mean respiration rate corrected for body mass was also the highest in S0 and L0 beetles, with significant differences between populations from L0 vs. SS and from S0 vs. SS. Only beetles from S0, SS, L0, and LM were numerous enough to assess the resistance to starvation. Individuals from the LM habitat showed better survival compared to the canola-free habitat in the same landscape (L0), whereas in S landscape the SS beetles survived worse than those from S0, suggesting that characteristics of L landscape may lead to developing mechanisms of starvation resistance of P. cupreus in response to agricultural pressure.

Physiological and biochemical response of the solitary bee Osmia bicornis exposed to three insecticide-based agrochemicals.

The physiological and biochemical stress induced by pesticides need to be addressed in economically and ecologically important non-Apis solitary bees, particularly at lower than field-applied concentrations. Thus, the aim of the present study was to analyse the physiological and biochemical changes in female adult Osmia bicornis bees upon continuous oral exposure to three insecticide-based agrochemicals - i.e. Dursban 480 EC (active ingredient - a.i. chlorpyrifos), Sherpa 100 EC (a.i. cypermethrin), and Mospilan 20 SP (a.i. acetamiprid), in a toxicokinetic manner (feeding with either insecticide-contaminated food or uncontaminated food (controls) for 8 d in the contamination phase followed by 8 d of decontamination (i.e. feeding with uncontaminated food)). All three tested agrochemicals altered the energetic budget of bees by the deprivation of energy derived from lipids and carbohydrates (but not proteins) and/or a decrease in respiration based metabolic rate (energy consumption) compared to the controls. The activities of acetylcholinesterase and glutathione-S-transferase enzymes were not altered by insecticides at tested concentrations. These results show that chronic exposure to at least some pesticides even at relatively low concentrations may cause severe physiological disruptions that could potentially be damaging for the solitary bees.

Risk factors for complicated course and recurrence of Clostridioides Difficile infections during COVID-19 pandemic.

INTRODUCTION: The primary symptom of Clostridioides difficile infection (CDI) is diarrhea of varying severity. Both malnutrition and clinical nutrition increase the risk for contracting Clostridioides difficile (C. difficile) infection and the likelihood of relapses. Moreover, the risk for recurrence is higher if there is infection with a hypervirulent strain (NAP1/BI/027). Hypoalbuminemia predisposes to a severe course of the disease and morbidity. MATERIAL AND METHODS: Analysis was carried out of the data regarding patients hospitalized at the Regional Hospital for Infectious Diseases in Warsaw from 01 January 2020 to 31 December 2021 who were diagnosed with C. difficile infection. A severe course of infection was diagnosed when a blood test showed a leukocyte count greater than or equal to 15,000/µl and/or a creatinine concentration >1.5 mg/dl (>132.6 mmol/l). RESULTS: Clostridioides difficile infection was the reason for 185 hospitalizations (involving 108 women and 77 men), of 167 patients aged from 22 to 93 years old. There were 68 (37%) cases of recurrent infection. Seventy-five (41%) infections met the study's criteria for severe CDI, and 12 (7%) patients died. Out of the total number of hospitalizations, 41 (22%) were due SARS-CoV-2 co-infection. PCR tests detecting binary toxin revealed 34 (18%) positive results. Infection with a hypervirulent strain was an independent risk factor for the recurrence of diarrhea which had C. difficile etiology. Overall, during an episode of diarrhea, one antibacterial drug was used in 139 cases (75%), two in 27 (15%), three in 14 (8%) situations, and four - twice (1%). Among these, drugs not recommended for the treatment of CDI were used in 21 (11%) cases. The number of antibacterial drugs administered during an episode of diarrhea was an independent risk factor for the death of the infected person. Clinical nutrition was applied during 19 hospitalizations (10%), out of which 12 (63%) cases showed a severe course of C. difficile infection, while four patients (21%) died. Using clinical nutrition methods was an independent risk factor for a severe course of the disease and patient death. CONCLUSIONS: Clinical nutrition and the number of antibiotics used during an episode of diarrhea are independent risk factors for the death of a patient with CDI. Infection with a hypervirulent strain increases the risk for relapse.

[The use of ultrasound in suspected giant cell arteritis - a case report]. / Wykorzystanie ultrasonografii w podejrzeniu olbrzymiokomórkowego zapalenia tetnic ­ opis przypadku.

Giant cell arteritis (GCA) is a type of large and middle arteries vasculitis that occurs in patients aged over 50 years. The typical symptoms include pain and tenderness in the temporal region, sudden vision impairment or loss and jaw claudication. If left untreated the disease may lead to permanent blindness. The diagnosis is based on the ACR criteria and the treatment of choice are glicocorticosteroids. The ultrasonography with color Doppler is characterized by high sensitivity and specificity which makes it a valuable diagnostic tool, especially in questionable cases. A CASE REPORT: 86-year-old woman, with a history of sudden left eye vision loss that occurred one month ago, reported to the hospital due to right eye vision impairment progression. The symptoms and characteristic of patient's complaints suggested GCA, however patient didn't meet the diagnostic criteria. The ultrasonography examination was used, which revealed features typical for GCA ("halo" sign and non-compressible arteries - compression sign), which contributed to the decision of the immediate treatment initiation with corticosteroids which stopped the progression of the disease and led to the slight right eye vision improvement. CONCLUSIONS: The ultrasonography examination is a useful and valuable diagnostic tool for patients with suspected GCA and its use is especially significant in the questionable cases diagnosis.

Different effects of Zn nanoparticles and ions on growth and cellular respiration in the earthworm Eisenia andrei after long-term exposure.

In this study, the effects of zinc nanoparticles (ZnO-NPs) and ions (ZnCl2) on the mortality, growth, maturation, and cellular respiration of the earthworm Eisenia andrei were assessed. Earthworms were individually exposed for 98 days, starting from the juvenile stage, to soils contaminated with either ZnO-NPs or ZnCl2 (125, 250, 500 and 1000 mg Zn kg-1 dry weight (dw)). Exposure to the highest-concentration ionic treatments (500 and 1000 mg kg-1) caused 100% mortality, while for other treatments, mortality did not exceed 15% at the end of exposure. Compared to the control treatment, both 125-1000 mg kg-1 ZnO-NPs and 125 or 250 mg kg-1 ZnCl2 stimulated earthworm growth, which might be due to a hormetic effect. ZnO-NPs and ZnCl2 caused different responses at medium Zn concentrations (250 and 500 mg kg-1): earthworms exposed to ionic treatment at 250 mg kg-1 were characterized by a significantly lower growth constant, lower cellular respiration rate, later inflection point, and higher final body weight than those exposed to ZnO-NPs treatments at the same (250 mg kg-1) or twice as high (500 mg kg-1) nominal Zn concentrations. However, differences were not observed in all examined parameters between the studied forms when the highest-concentration ZnO-NPs treatment was compared with the lowest-concentration ionic treatment, which was likely due to the same levels of available Zn concentrations in those treatments. Overall, different growth and maturation strategies accompanied by pronounced differences in cellular respiration were adopted by earthworms exposed to low and medium levels of either ZnO-NPs or ZnCl2.

Clinical Course and Outcome of Community-Acquired Bacterial Meningitis in Cancer Patients.

The aim of the study was to determine the course and outcome of bacterial meningitis (BM) in patients with cancer. We retrospectively reviewed files of patients with community-acquired BM, hospitalized in a single neuroinfection center between January 2010 and December 2017. There were 209 patients included in the analysis: 28 had cancer (9 women, 19 men; median age 76, IQR 67-80 years) and 181 were cancer-free (76 women, 105 men; median age 52, IQR 33-65 years) and constituted the control group. Cancer patients, compared with controls, were more likely to present with seizures (25% vs. 8%, p = 0.019), scored higher on the Sequential Organ Failure Assessment, and had a higher mortality rate (32% vs. 13%, p = 0.025). Further, cancer patients were less likely (64% vs. 83%, p = 0.033) to present with two or more out of four clinical manifestations of BM (pyrexia, neck stiffness, altered mental status, and headache) and had a lower white blood cell (WBC) count than non-cancer controls. In multiple regression analysis, the presence of bacterial meningitis in cancer patients was independently associated only with older age (p = 0.001) and lower WBC count (p = 0.007), while mortality was associated with lower Glasgow Coma Score (p = 0.003). In conclusion, bacterial meningitis in cancer patients is characterized by atypical symptoms and high mortality, which requires physicians' vigilance and a prompt investigation of cerebrospinal fluid in suspected cases. However, multiple regression analysis suggests that differences in clinical presentation and outcomes of bacterial meningitis between cancer and cancer-free patients may also be attributable to other factors, such as age differences.

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.

Differences and similarities in clinical manifestations of Listeria monocytogenes and Mycobacterium tuberculous meningitis.

INTRODUCTION: Tuberculous meningitis (TbM) and meningitis caused by Listeria monocytogenes (LM) require different treatment regimens and have grave prognosis if therapy is delayed. THE AIM OF THE STUDY: Comparison of clinical manifestations, laboratory features and outcome of TbM and LM. MATERIAL AND METHODS: We retrospectively analyzed records of 402 patients with community acquired bacterial meningitis (BM) who were hospitalized between January 2010 and September 2019. RESULTS: LM and TbM were diagnosed in 28 (7.0%) and 23 (5.7%) patients, respectively. Patients with TbM were more likely to present with hydrocephalus (p<0.001), scored lower on the Thwaites Index (TI) (p<0.001) and had longer duration of symptoms prior to hospitalization (p=0.001). Furthermore, TbM patients had lower concentration of c-reactive protein (CRP) (p<0.001) and lower white blood cells count (WBC) (p=0.035). When compared to BM patients with etiology other than LM and TbM (nLnTbM), TbM patients presented with lower concentration of CRP (p<0.001), and procalcitonin (PCT) (p<0.001), lower WBC (p<0.001), and lower granulocyte percentage of CSF cytosis (p<0.001), but were more likely to present with hydrocephalus (p<0.001), aphasia (p=0.003) and hemiparesis (p=0.008). In comparison with the nLnTbM group, LM patients had lower concentration of CRP (p=0.01), lower WBC (p<0.001), and lower granulocyte percentage of CSF cytosis (p<0.016). LM patients were also more likely to have concomitant cancer (p=0.008), receive immunosuppressive treatment (p<0.001) or be immunocompromised (p=0.015). CONCLUSIONS: TbM patients had less pronounced inflammation but more severe central nervous system complications compared to patients with LM and other etiologies. Furthermore, LM patients, but not TbM patients, were often immunocompromised.

Chronic alcohol abuse affects the clinical course and outcome of community-acquired bacterial meningitis.

The aim of the study was to determine the effect of chronic alcohol abuse on the course and outcome of bacterial meningitis (BM). We analyzed records of patients with BM who were hospitalized between January 2010 and December 2017 in the largest neuroinfection center in Poland. Out of 340 analyzed patients, 45 (13.2%) were alcoholics. Compared with non-alcoholics, alcoholics were more likely to present with seizures (p < 0.001), scored higher on the Sequential Organ Failure Assessment (SOFA) (p = 0.002) and lower on the Glasgow Coma Scale (GCS) (p < 0.001), and had worse outcome as measured by the Glasgow Outcome Score (GOS) (p < 0.001). Furthermore, alcoholics were less likely to complain of headache (p < 0.001) and nausea/vomiting (p = 0.005) and had lower concentration of glucose in cerebrospinal fluid (CSF) (p = 0.025). In the multiple logistic regression analysis, alcoholism was associated with lower GCS (p = 0.036), presence of seizures (p = 0.041), male gender (p = 0.042), and absence of nausea/vomiting (p = 0.040). Furthermore, alcoholism (p = 0.031), lower GCS score (p = 0.001), and higher blood urea concentration (p = 0.018) were independently associated with worse outcome measured by GOS. Compared with non-alcoholics, chronic alcohol abusers are more likely to present with seizures, altered mental status, and higher SOFA score and have an increased risk of unfavorable outcome. In multivariate analysis, seizures and low GCS were independently associated with alcoholism, while alcoholism was independently associated with worse outcome.

Effects of Cadmium Bioavailability in Food on Its Distribution in Different Tissues in the Ground Beetle Pterostichus oblongopunctatus.

In most laboratory studies with oral exposure of terrestrial invertebrates to metals an artificial food, which is easy to handle, is used. The bioavailability of metals from this artificial food may, however, be much higher than from more field relevant food sources. Such differences may affect toxicokinetic processes in different tissues. To test the effect of bioavailability of Cd in food on Cd toxicokinetics and internal distribution in terrestrial invertebrates, we performed the experiment using the ground beetle Pterostichus oblongopunctatus exposed to Cd via food differing in their soluble Cd pool. We showed that in carabids Cd accumulation and elimination pattern in different tissues is not governed by the metal availability in food.

Non-AIDS defining bacterial infections in patients with HIV infection

OBJECTIVES: The use of effective combinated antiretroviral therapy has significantly improved the prognosis of patients with HIV infection. Although current antiretroviral regimens are very effective in inhibiting viral replication, its elimination is not a viable goal of treatment. Despite cART, non­AIDS-defining bacterial infections are still a serious problem. The spectrum of these infections, and in particular the proportion of particular bacterial pathogens, is not sufficiently described in the scientific literature. METHODS: In the study, HIV-infected patients followed at the HIV Out-Patient Clinic in Warsaw were registered in the clinic from 1 January 2007 to 31 July 2016. Survival analysis included 558 patients who met the study criteria. RESULTS: Among 251 (44.9%) of those with positive culture, the most common bacterial pathogen was Staphylococcus aureus (33%) and Escherichia coli (11.1%). The most common bacteria in the upper respiratory tract was Staphylococcus aureus (26.6%). In urine cultures the most common bacteria was Escherichia coli (9.5%). Staphylococcus aureus (2.3%) and Staphylococcus epidermidis (2.3%) were the most common bacterial cultures in the wound. In skin cultures the most common bacteria was Staphylococcus aureus (3.9%). The highest number of positive cultures was obtained from the upper respiratory tract -166 (66.1%). CONCLUSION: Non­AIDS-defining bacterial infections are a common clinical problem in HIV-infected patients despite the introduction of antiretroviral therapy and the pathogens that cause these infections are a very diverse group.

Usefulness of SOFA score and artesunate - based treatment in severe malaria ­ a single center study

INTRODUCTION: This study was conducted to assess the usefulness of the guidelines of treatment recommended in Malaria diagnosis and treatment guideline published by University College London Hospitals-NHS Foundation Trust on 26th June 2013, usefulness of artesunate-based therapy and usefulness of SOFA (sepsis-related organ failure assessment) score in treatment of severe malaria. Severe malaria is usually caused by Plasmodium falciparum and most of the time fulfills the criteria of sepsis which are specified in the new definition of sepsis. The other malaria species are commonly considered to be the cause of mild course of malaria, however more and more cases of severe malaria are reported in the course of tertian fever malaria caused by Plasmodium vivax and in the disease caused by Plasmodium knowlesi. MATERIALS AND METHODS: Fourteen patients with malaria were hospitalized in the Department of Adults' Infectious Diseases and in the Intensive Care Unit of the Hospital for Infectious Diseases in Warsaw between December 2013 and April 2017. All patients were treated according to Malaria diagnosis and treatment guideline UCLH. RESULTS: Thirteen patients in our study fulfilled the criteria of severe malaria. All fourteen patients presented with a SOFA score ≥2 points. Intravenous artesunate was administered to all patients in doses recommended in the UCLH guidelines. All patients presented with thrombocytopenia and elevated level of D-Dimers. The main factor influencing the dynamics of SOFA score was thrombocytopenia. All the patients fully recovered without any complications. CONCLUSIONS: The malaria treatment guidelines used in the Department for Infectious Diseases in Adults and in the Intensive Care Unit of the Hospital for Infectious Diseases in Warsaw in years 2013-2017 are effective. In assessing the severity of malaria SOFA score is useful especially as a warning of possibility of a severe course of the disease.

Toxicokinetics of zinc-oxide nanoparticles and zinc ions in the earthworm Eisenia andrei.

The toxicokinetics of zinc in the earthworm Eisenia andrei was investigated following exposure for 21 days to ionic zinc (ZnCl2) or zinc oxide nanoparticles (ZnO-NPs) in Lufa 2.2 soil, followed by 21 days elimination in clean soil. Two concentrations were tested for both ZnCl2 (250 and 500µg Zn g-1) and ZnO-NPs (500 and 1000µg Zn g-1), corresponding to EC25 and EC50 for effects on reproduction. Based on the measured internal Zn concentrations in the earthworms over time of exposure, the kinetics parameters ka - assimilation rate constant (gsoil g-1body weight day-1) and ke - elimination rate constant (day-1) were estimated using a one-compartment model for either total Zn concentrations in the soil or porewater Zn concentrations. In the ZnCl2 treatments, ka was higher for total Zn concentrations in soil, whereas in the ZnO-NP treatments, ka was higher for porewater Zn concentrations. The value of ke did not differ between the two Zn forms (ZnCl2 vs ZnO-NPs) for either EC50 or EC25 when related to total Zn concentrations in soil, but for EC50, ke related to porewater Zn concentrations was significantly higher for ZnCl2 than for ZnO-NPs. It is concluded that differences in kinetic parameters between treatments were connected with exposure concentrations rather than with the form of Zn. Zinc was efficiently regulated by the earthworms in all treatments: a 2-fold increase in exposure concentration resulted in a less than 2-fold increase in internal concentration, and after transfer to uncontaminated soil the internal Zn concentrations in the earthworms returned to ca 111µgg-1 dw in all treatments.

Effect of cadmium bioavailability in food on its compartmentalisation in carabids.

Metals assimilated by organisms are sequestered in various compartments and some forms are more stable than others. Sequestration mechanisms used by invertebrates to detoxify metals and prevent interaction with important biomolecules include metal binding to proteins and other ligands, and storage in inorganic granules. The rate and extent at which metal concentrations in different compartments respond to metal concentrations in food and food characteristics has not received much attention, despite being of great relevance. We performed an experiment on the carabid beetle Pterostichus oblongopunctatus exposed to Cd via food made of ground mealworm (Tenebrio molitor) larvae, either reared on Cd contaminated medium or artificially spiked after grinding with CdCl2 solution. Thus, in both cases we used the same type of food, differing only in the soluble Cd pool available to the predators, represented by P. oblongopunctatus. Subcellular compartmentalisation of Cd into organelles, heat-sensitive and heat-stable proteins (the first supernatant, S1 fraction), cellular debris (the second supernatant, S2 fraction) and metal-rich granules (G fraction) was checked a few times during the contamination (90 d) and decontamination (24 d) phases in a toxicokinetic experiment by using different centrifugation steps. The results showed no effect of the type of food (naturally, Cd-N, vs. artificially contaminated with Cd, Cd-A) on Cd sequestration kinetics in P. oblongopunctatus, but the amount of Cd sequestered in the S1 and G fractions were in general higher in the Cd-A than the Cd-N treatment, indicating that Cd transfer in the food web depends on the speciation of the metal in the food. The proportional distribution of Cd over different fractions was, however, similar in beetles fed both food types. Most of the accumulated Cd in the beetles existed as fraction S1 (ca. 35%), which is important for the transfer of metals to higher trophic levels in a food web.

Subcellular partitioning of cadmium and zinc in mealworm beetle (Tenebrio molitor) larvae exposed to metal-contaminated flour.

By studying the internal compartmentalization of metals in different subcellular fractions we are able to better understand the mechanisms of metal accumulation in organisms and the transfer of metals through trophic chains. We investigated the internal compartmentalization of cadmium (Cd) and zinc (Zn) in mealworm beetle (Tenebrio molitor) larvae by breeding them in flour contaminated with either Cd at 100, 300 and 600mgkg(-1), or Zn at 1000 and 2000mgkg(-1). We separated the cellular components of the larvae into 3 fractions: the S1 or cytosolic fraction containing organelles, heat-sensitive and heat-stable proteins, the S2 or cellular debris fraction and the G or metal-rich granule fraction. The concentration of Cd and Zn in each fraction was measured at 0, 7, 14 and 21 days of being fed the flour. The concentration of Cd in the flour affected the concentration of Cd measured in each larval subcellular fraction (p≤0.0001), while the concentration of Zn in the flour only affected the Zn concentration in the S2 and G fractions (p≤0.02). Both Cd and Zn concentrations in mealworms remained relatively constant during the exposure (days 7, 14 and 21) in all three fractions, but the Cd concentrations were much higher than those found in larvae before the exposure (day 0). The concentration of Cd in the flour, however, did not affect the percentage of Cd in the S1 fraction. The contribution of Cd in the G fraction to the total Cd amount was similar (30-40%) in all Cd treatments. The percentage of Zn in all three fractions was not affected by the concentration of Zn in the flour and the relative contributions of each subcellular fraction to the total burden of Zn remained generally constant for both control and treated larvae. In general, larvae sequestered approximately 30% of Cd and Zn in the S1 fraction, which is important for the transport of metals to higher trophic levels in a food web.

Regulation of body metal concentrations: Toxicokinetics of cadmium and zinc in crickets.

Previous studies indicated that essential and xenobiotic metals differ substantially in terms of their toxicokinetics. Whether these differences are due to different assimilation rates, different elimination rates, or both, and whether all metals are regulated in a similar manner but with different efficiency remains unclear. To compare the mechanisms responsible for the regulation of different metals, parameters for toxicokinetic models have to be tested under exposures to the identical molar concentration of those metals. In this study, the cricket Gryllus assimilis was exposed to Zn or Cd at 2.5, 10, and 40mMkg(-1) dry food. The body concentrations of the metals were not perfectly regulated by the crickets. For Zn, a clear increase in the body concentration was found only at the highest treatment; whereas at the lowest treatment, the internal concentration remained unchanged throughout the experiment. At the lowest Zn concentration, the assimilation (kA) [day(-1)] and elimination (kE) [day(-1)] rate constants were balanced (kA=0.024, kE=0.024). When increasing the Zn exposure, kA decreased to 0.018 at 10mMkg(-1) and 0.01 at 40mMkg(-1), and kE increased to 0.05 and 0.07, respectively. Therefore, the body concentration of Zn was regulated by simultaneously changing the assimilation and elimination rate. By contrast, even at the lowest treatment, a significant increase in Cd concentration was observed in the crickets. The equilibrium Cd concentration resulted almost exclusively from increasing kE from 0.17, through 0.28 to 0.61 at 2.5, 10 and 40mMkg(-1). The kA for Cd did not reveal any clear trend. Zn was more efficiently regulated by crickets than was Cd: a 16-fold increase in exposure concentration (from 2.5 to 40mM Znkg(-1)) resulted only in a twofold increase of internal concentration, whereas the identical increase in Cd exposure concentration resulted in almost a sevenfold increase in internal concentration of this metal.