Umbilical cord mesenchymal stromal cells transplantation delays the onset of hyperglycemia in the RIP-B7.1 mouse model of experimental autoimmune diabetes through multiple immunosuppressive and anti-inflammatory responses

Type 1 diabetes mellitus (T1DM) is an autoimmune disorder specifically targeting pancreatic islet beta cells. Despite many efforts focused on identifying new therapies able to counteract this autoimmune attack and/or stimulate beta cells regeneration, TD1M remains without effective clinical treatments providing no clear advantages over the conventional treatment with insulin. We previously postulated that both the inflammatory and immune responses and beta cell survival/regeneration must be simultaneously targeted to blunt the progression of disease. Umbilical cord-derived mesenchymal stromal cells (UC-MSC) exhibit anti-inflammatory, trophic, immunomodulatory and regenerative properties and have shown some beneficial yet controversial effects in clinical trials for T1DM. In order to clarify conflicting results, we herein dissected the cellular and molecular events derived from UC-MSC intraperitoneal administration (i.p.) in the RIP-B7.1 mouse model of experimental autoimmune diabetes. Intraperitoneal (i.p.) transplantation of heterologous mouse UC-MSC delayed the onset of diabetes in RIP-B7.1 mice. Importantly, UC-MSC i. p. transplantation led to a strong peritoneal recruitment of myeloid-derived suppressor cells (MDSC) followed by multiple T-, B- and myeloid cells immunosuppressive responses in peritoneal fluid cells, spleen, pancreatic lymph nodes and the pancreas, which displayed significantly reduced insulitis and pancreatic infiltration of T and B Cells and pro-inflammatory macrophages. Altogether, these results suggest that UC-MSC i. p. transplantation can block or delay the development of hyperglycemia through suppression of inflammation and the immune attack.

Preclinical Evaluation of the Safety and Immunological Action of Allogeneic ADSC-Collagen Scaffolds in the Treatment of Chronic Ischemic Cardiomyopathy

The use of allogeneic adipose-derived mesenchymal stromal cells (alloADSCs) represents an attractive approach for treating myocardial infarction (MI). Furthermore, adding a natural support improves alloADSCs engraftment and survival in heart tissues, leading to a greater therapeutic effect. We aimed to examine the safety and immunological reaction induced by epicardial implantation of a clinical-grade collagen scaffold (CS) seeded with alloADSCs for its future application in humans. Thus, cellularized scaffolds were myocardially or subcutaneously implanted in immunosuppressed rodent models. The toxicological parameters were not significantly altered, and tumor formation was not found over the short or long term. Furthermore, biodistribution analyses in the infarcted immunocompetent rats displayed cell engraftment in the myocardium but no migration to other organs. The immunogenicity of alloADSC-CS was also evaluated in a preclinical porcine model of chronic MI; no significant humoral or cellular alloreactive responses were found. Moreover, CS cellularized with human ADSCs cocultured with human allogeneic immune cells produced no alloreactive response. Interestingly, alloADSC-CS significantly inhibited lymphocyte responses, confirming its immunomodulatory action. Thus, alloADSC-CS is likely safe and does not elicit any alloreactive immunological response in the host. Moreover, it exerts an immunomodulatory action, which supports its translation to a clinical setting.

Endobronchial autologous bone marrow-mesenchymal stromal cells in idiopathic pulmonary fibrosis: a phase I trial

Rationale

Idiopathic pulmonary fibrosis (IPF) has a dismal prognosis. Mesenchymal stromal cells (MSCs) have shown benefit in other inflammatory diseases.

Objectives

To evaluate the safety and feasibility of endobronchial administration of bone marrow autologous MSCs (BM-MSC) in patients with mild-to-moderate IPF.

Methods

A phase I multicentre clinical trial (ClinicalTrials.gov NCT01919827) with a single endobronchial administration of autologous adult BM-MSCs in patients diagnosed with mild-to-moderate IPF. In a first escalating-dose phase, three patients were included sequentially in three dose cohorts (10×10⁶, 50×10⁶ and 100×10⁶ cells). In a second phase, nine patients received the highest tolerated dose. Follow-up with pulmonary function testing, 6-min walk test and St George's Respiratory Questionnaire was done at 1, 2, 3, 6 and 12 months, and with computed tomography at 3, 6 and 12 months.

Results

21 bone marrow samples were obtained from 17 patients. Three patients were excluded from treatment due to chromosome aberrations detected in MSCs after culture, and one patient died before treatment. Finally, 13 patients received the BM-MSC infusion. No treatment-related severe adverse events were observed during follow-up. Compared to baseline, the mean forced vital capacity showed an initial decline of 8.1% at 3 months. The number of patients without functional progression was six (46%) at 3 months and three (23%) at 12 months.

Conclusions

The endobronchial infusion of BM-MSCs did not cause immediate serious adverse events in IPF patients, but a relevant proportion of patients suffered clinical and/or functional progression. Genomic instability of BM-MSCs during culture found in three patients may be troublesome for the use of autologous MSCs in IPF patients.

Endobronchial autologous mesenchymal stromal cells (MSCs) did not cause direct serious adverse events in IPF patients. However, significant progression was seen in seven out of 13 patients. Genomic instability of autologous MSCs may limit use in IPF.https://bit.ly/39akv7z

Corrigendum: Cost-Effective, Safe, and Personalized Cell Therapy for Critical Limb Ischemia in Type 2 Diabetes Mellitus

[This corrects the article DOI: 10.3389/fimmu.2019.01151.].

Cost-Effective, Safe, and Personalized Cell Therapy for Critical Limb Ischemia in Type 2 Diabetes Mellitus

Cell therapy is a progressively growing field that is rapidly moving from preclinical model development to clinical application. Outcomes obtained from clinical trials reveal the therapeutic potential of stem cell-based therapy to deal with unmet medical treatment needs for several disorders with no therapeutic options. Among adult stem cells, mesenchymal stem cells (MSCs) are the leading cell type used in advanced therapies for the treatment of autoimmune, inflammatory and vascular diseases. To date, the safety and feasibility of autologous MSC-based therapy has been established; however, their indiscriminate use has resulted in mixed outcomes in preclinical and clinical studies. While MSCs derived from diverse tissues share common properties depending on the type of clinical application, they markedly differ within clinical trials in terms of efficacy, resulting in many unanswered questions regarding the application of MSCs. Additionally, our experience in clinical trials related to critical limb ischemia pathology (CLI) shows that the therapeutic efficacy of these cells in different animal models has only been partially reproduced in humans through clinical trials. Therefore, it is crucial to develop new research to identify pitfalls, to optimize procedures and to clarify the repair mechanisms used by these cells, as well as to be able to offer a next generation of stem cell that can be routinely used in a cost-effective and safe manner in stem cell-based therapies targeting CLI.

Intra-articular injection of two different doses of autologous bone marrow mesenchymal stem cells versus hyaluronic acid in the treatment of knee osteoarthritis: long-term follow up of a multicenter randomized controlled clinical trial (phase I/II)

Background

Mesenchymal stromal cells (MSCs) are a promising option to treat knee osteoarthritis (OA). Their safety and usefulness have been reported in several short-term clinical trials but less information is available on the long-term effects of MSC in patients with osteoarthritis. We have evaluated patients included in our previous randomized clinical trial (CMM-ART, NCT02123368) to determine their long-term clinical effect.

Materials

A phase I/II multicenter randomized clinical trial with active control was conducted between 2012 and 2014. Thirty patients diagnosed with knee OA were randomly assigned to Control group, intraarticularly administered hyaluronic acid alone, or to two treatment groups, hyaluronic acid together with 10 × 10⁶ or 100 × 10⁶ cultured autologous bone marrow-derived MSCs (BM-MSCs), and followed up for 12 months. After a follow up of 4 years adverse effects and clinical evolution, assessed using VAS and WOMAC scorings are reported.

Results

No adverse effects were reported after BM-MSCs administration or during the follow-up. BM-MSCs-administered patients improved according to VAS, median value (IQR) for Control, Low-dose and High-dose groups changed from 5 (3, 7), 7 (5, 8) and 6 (4, 8) to 7 (6, 7), 2 (2, 5) and 3 (3, 4), respectively at the end of follow up (Low-dose vs Control group, p = 0.01; High-dose vs Control group, p = 0.004). Patients receiving BM-MSCs also improved clinically according to WOMAC. Control group showed an increase median value of 4 points (− 11;10) while Low-dose and High-dose groups exhibited values of − 18 (− 28;− 9) and − 10 (− 21;− 3) points, respectively (Low-dose vs Control group p = 0.043). No clinical differences between the BM-MSCs receiving groups were found.

Conclusions

Single intraarticular injection of in vitro expanded autologous BM-MSCs is a safe and feasible procedure that results in long-term clinical and functional improvement of knee OA.

A phase II trial of autologous dendritic cell vaccination and radiochemotherapy following fluorescence-guided surgery in newly diagnosed glioblastoma patients

Background

Prognosis of patients with glioblastoma multiforme (GBM) remains dismal, with median overall survival (OS) of about 15 months. It is therefore crucial to search alternative strategies that improve these results obtained with conventional treatments. In this context, immunotherapy seems to be a promising therapeutic option. We hypothesized that the addition of tumor lysate-pulsed autologous dendritic cells (DCs) vaccination to maximal safe resection followed by radiotherapy and concomitant and adjuvant temozolomide could improve patients’ survival.

Methods

We conducted a phase-II clinical trial of autologous DCs vaccination in patients with newly diagnosed patients GBM who were candidates to complete or near complete resection. Candidates were finally included if residual tumor volume was lower than 1 cc on postoperative radiological examination. Autologous DCs were generated from peripheral blood monocytes and pulsed with autologous whole tumor lysate. The vaccination calendar started before radiotherapy and was continued during adjuvant chemotherapy. Progression free survival (PFS) and OS were analyzed with the Kaplan–Meier method. Immune response were assessed in blood samples obtained before each vaccines.

Results

Thirty-two consecutive patients were screened, one of which was a screening failure due to insufficient resection. Median age was 61 years (range 42–70). Karnofsky performance score (KPS) was 90–100 in 29%, 80 in 35.5% and 60–70 in 35.5% of cases. MGMT (O⁶-methylguanine-DNA-methyltransferase) promoter was methylated in 45.2% of patients. No severe adverse effects related to immunotherapy were registered. Median PFS was 12.7 months (CI 95% 7–16) and median OS was 23.4 months (95% CI 16–33.1). Increase in post-vaccination tumor specific immune response after vaccines (proliferation or cytokine production) was detected in 11/27 evaluated patients. No correlation between immune response and survival was found.

Conclusions

Our results suggest that the addition of tumor lysate-pulsed autologous DCs vaccination to tumor resection and combined radio-chemotherapy is feasible and safe. A multicenter randomized clinical trial is warranted to evaluate the potential survival benefit of this therapeutic approach.

Trial registration This phase-II trial was registered as EudraCT: 2009-009879-35 and ClinicalTrials.gov Identifier: NCT01006044 retrospectively registered

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1202-z) contains supplementary material, which is available to authorized users.

Dendritic cell vaccination in glioblastoma after fluorescence-guided resection

AIM: To assess whether the addition of a customized, active immunotherapy to standard of care including fluorescence-guided surgery, may provide hints of an improved survival for patients with poor-prognosis, incurable glioblastoma multiform.

METHODS: Preliminary to our ongoing, phase-II clinical trial, we conducted a small pilot study enrolling five consecutive patients with resectable glioblastoma. In terms of Recursive Partitioning Analysis, four patients were class V and one was class IV. In all five cases, fluorescence-guided surgery was employed, followed by rapid steroid discontinuation. Patients were then treated with a combination of standard radio-chemotherapy with temozolomide and tumor lysate-pulsed, mature dendritic cell-based vaccinations.

RESULTS: Though all five patients ultimately progressed, with any further treatment left to the sole decision of the treating oncologist, active immunotherapy was very well tolerated and induced specific immune responses in all three patients for whom enough material was available for such an assessment. Median progression-free survival was 16.1 mo. Even more important, median and mean overall survival were 27 mo and 26 mo, respectively. Three patients have died with an overall survival of 9 mo, 27 mo and 27.4 mo, while the other two are still alive at 32 mo and 36 mo, the former receiving treatment with bevacizumab, while the latter has now been off therapy for 12 mo. Four of five patients were alive at two years.

CONCLUSION: Active immunotherapy with tumor lysate-pulsed, autologous dendritic cells is feasible, safe, well tolerated and biologically efficacious. A phase-II study is ongoing to possibly improve further on our very encouraging clinical results.

Short-term exposure to sublethal tebuconazole induces physiological impairment in male zebrafish (Danio rerio)

The aim of the present study was to assess the physiological response of male zebrafish Danio rerio to the fungicide tebuconazole and recovery in fungicide-free water. Acute toxicity tests were carried out and the median lethal concentration (LC(50)) from 24 to 96 h was calculated. The fish were exposed to a sublethal fungicide concentration of 230 microg/L for 7 or 14 days and allowed to recover for 7 or 14 more days, respectively. Whole-body levels of vitellogenins, triglycerides, cholesterol, glucose, lactate and proteins as well as the activities gamma-glutamil transpeptidase (gamma-GT), alanin aminotransferase (AlAT), alkaline phosphatase (AP) and lactate dehydrogenase (LDH) were assayed; corpulence factor (k) was also calculated. Fish exhibited significant increase of vitellogenins (Vtg), which continued to increase after 14 days of recovery. Levels of glucose, lactate, cholesterol and triglycerides increased after 7 and 14 days of exposure. Finally, cholesterol and glucose recovered after 14 days of recovery whereas triglycerides and lactate continued to be elevated. Proteins and k remained unaltered the entire experiments. AAT, AlAT and AP enhanced during exposure and did not recover at the end (except AlAT). A longer recovery period should be necessary to re-establish fish physiology. These results alert about the multiple disruptive physiological actions that tebuconazole may have on fish.

Effects of propanil on the European eel Anguilla anguilla and post-exposure recovery using selected biomarkers as effect criteria

The aim of this study was to assess the physiological response of Anguilla anguilla to propanil and the degree of recovery after being moved to clean water. Preliminary acute toxicity test was carried out in the laboratory and the median lethal concentration (LC50) at 96 h was calculated as 31.33 mg/L (29.60-33.59 mg/L). NOEC and LOEC values (at 96 h) were also calculated as 20 and 25mg/L, respectively. The fish were exposed to 0.63 and 3.16 mg/L of propanil for 72 h and allowed to recover for 144 h. Total proteins (TPs), gamma-glutamil transpeptidase (gamma-GT), alanin aminotransferase (AlAT), alkaline phosphatase (AP), lactate dehydrogenase (LDH) and water content (WC) were assayed in muscle and liver tissues, liver somatic index (LSI) was also determined. Liver TPs and gamma-GT activity decreased after propanil exposure while AlAT and LDH increased. Muscular AP, AlAT and proteins decreased in intoxicated eels while LDH and gamma-GT activities increased. WC increased in both tissues after herbicide exposure as well as LSI. These results revealed that propanil affects the intermediary metabolism of A. anguilla and that the assayed enzymes can be used as good biomarkers of herbicide contamination. However a longer recovery period should be necessary to re-establish eel physiology. The parameters measured in the present study can be used as herbicide toxicity indicators and are recommended for environmental monitoring assessments.

Disturbances in energy metabolism of Daphnia magna after exposure to tebuconazole

This study was conducted to investigate the change of some biochemical parameters in the aquatic invertebrate Daphnia magna following exposure to the fungicide tebuconazole and to determine the most sensitive biomarker among the ones tested in this species. Four biochemical biomarkers (protein, glycogen, lipids and caloric content) were correlated with feeding behaviour studies of D. magna after fungicide exposure. Juveniles of D. magna were exposed to four sublethal concentrations of tebuconazole (0.41, 0.52, 0.71 and 1.14 mgL(-1)) for 5d. Daphnid samples were taken from each test and control group at 24, 48, 72, 96 and 120 h after the start of the experiment. Tebuconazole EC(50) values were calculated on D. magna in our laboratory as 56.83 and 40.10 mgL(-1) at 24 and 48 h, respectively. Results showed that daphnid energy content decreased as tebuconazole concentration increased, especially after 96-120 h of exposure to 0.52 mgL(-1) and higher fungicide concentrations. The data suggest that tebuconazole is moderately toxic to D. magna but also that it seriously impairs the metabolic functions, resulting in alterations in biochemical constituents. In the D. magna feeding study, algae feeding rates were inhibited after fungicide exposure. Such findings indicate the importance of feeding studies in laboratory toxicity test as well as their relationship with others studies. The results emphasize the importance of considering different kind of biomarkers to identify and evaluate the biological effect of a fungicide in the aquatic environment. Although the biochemical biomarkers used resulted good indicators of tebuconazole toxicity, feeding rates in D. magna decreased after only 5h exposure to the fungicide resulting in the most sensitive parameter of daphnid fungicide exposure.

[Fetoscopic tracheal occlusion for the treatment of severe congenital diaphragmatic hernia: preliminary results]

OBJECTIVES

To evaluate survival and lung growth in fetuses with severe congenital diaphragmatic hernia (CDH) treated with fetoscopic tracheal occlusion (FETO) compared with control fetuses and to analyze possible complications of the anesthetic techniques used.

PATIENTS AND METHODS

This prospective study was performed on fetuses with CDH. FETO was undertaken before the 29th week of gestation on fetuses with a lung-to-head ratio (LHR) less than 1. FETO was not performed on fetuses with an LHR between 1.0 and 1.5 or those with an LHR less than 1 where consent was not given. Lung growth was monitored by means of LHR. FETO was performed under fetal intramuscular anesthesia and maternal epidural anesthesia and sedation with remifentanil.

RESULTS

Seventeen fetuses were included in the study. FETO was performed on 11 fetuses and was effective in 9. The median percentage difference between LHR at diagnosis and prior to FETO was 1.15% (P=.183); between diagnosis and before removing the balloon, the difference was 130.5% (P=.003); and between diagnosis and before delivery, 90.18% (P=.003). In the control group (n=6), the median percentage difference between LHR at diagnosis and before delivery was 49.25% (P=.028). No significant hemodynamic or respiratory changes occurred in either mother or fetus during fetoscopy. All the fetuses in the control group died; 45.5% of those in the FETO group survived.

CONCLUSIONS

The use of FETO in cases of CDH appears to increase survival and lung growth. Fetal anesthesia in association with maternal epidural anesthesia and sedation makes it possible to place and remove the endotracheal balloon via fetoscopy with acceptable maternal comfort and without notable complications.

[Two cases of congenital airway obstruction managed with ex utero intrapartum treatment procedures: anesthetic implications]

An ex utero intrapartum treatment (EXIT) procedure provides sufficient time to gain control of the potentially obstructed fetal upper airway while uterine placental circulation is maintained during cesarean section. We report 2 cases in which fetal congenital upper airway obstruction was managed without complications during EXIT procedures. We also discuss general considerations concerning the obstetric patient and the performance of intramuscular fetal anesthesia. Before the hysterotomy, sevoflurane at 1.5 minimum alveolar concentration was administered to assure sufficient uterine relaxation during EXIT. The 2 parturients remained hemodynamically stable during the procedure and uterine and placental perfusion was adequate. Nasotracheal intubation was possible in 1 fetus after a cervical mass was dissected. In the other, a tracheostomy was created. After the umbilical cord was clamped, the concentration of sevoflurane anesthetic gas was reduced and oxytocin and methylergometrine were administered to induce adequate uterine contractions within a few minutes. Both neonates survived the EXIT procedure with no complications.

NALP1 is a transcriptional target for cAMP-response-element-binding protein (CREB) in myeloid leukaemia cells

NALP1 (also called DEFCAP, NAC, CARD7) has been shown to play a central role in the activation of inflammatory caspases and processing of pro-IL1b (pro-interleukin-1b). Previous studies showed that NALP1 is highly expressed in peripheral blood mononuclear cells. In the present study, we report that expression of NALP1 is absent from CD34+ haematopoietic blast cells, and its levels are upregulated upon differentiation of CD34+ cells into granulocytes and to a lesser extent into monocytes. In peripheral blood cells, the highest levels of NALP1 were observed in CD3+ (T-lymphocytes), CD15+ (granulocytes) and CD14+ (monocytes) cell populations. Notably, the expression of NALP1 was significantly increased in the bone marrow blast cell population of some patients with acute leukaemia, but not among tissue samples from thyroid and renal cancer. A search for consensus sites within the NALP1 promoter revealed a sequence for CREB (cAMP-response-element-binding protein) that was required for transcriptional activity. Moreover, treatment of TF1 myeloid leukaemia cells with protein kinase C and protein kinase A activators induced CREB phosphorylation and upregulated the mRNA and protein levels of NALP1. Conversely, ectopic expression of a dominant negative form of CREB in TF1 cells blocked the transcriptional activity of the NALP1 promoter and significantly reduced the expression of NALP1. Thus NALP1 is transcriptionally regulated by CREB in myeloid cells, a mechanism that may contribute to modulate the response of these cells to pro-inflammatory stimuli.

Acute, chronic and sublethal effects of the herbicide propanil on Daphnia magna

Acute and chronic toxicity tests with propanil were conducted on Daphnia magna. The 24 and 48 h LC50 were 43.74 and 5.01 mg/l respectively. Chronic toxicity tests were carried out using sublethal propanil concentrations (0.07, 0.10, 0.21 and 0.55 mg/l) during 21 days. The effect of propanil on survival, reproduction and growth of D. magna organisms was monitored. The parameters used to evaluate herbicide effect on reproduction were: mean total young ones per female, mean brood size, time to first reproduction, mean number broods per female and intrinsic rate of natural increase (r). Survival and growth (body length) were also determined after 21 days of exposure to the herbicide. Reproduction was significantly reduced when propanil concentration increased in the medium. The intrinsic rate of natural increase (r) decreased with increasing concentrations of propanil especially in those animals exposed to 0.55 mg/l. However, growth as well as survival of the exposed organisms only decreased in daphnids exposed to the highest propanil concentration tested. The maximum acceptable toxicant concentration (MATC) was calculated for D. magna exposed to the herbicide using as parameter of evaluation the intrinsic rate of natural increase (r). The interpolation of these results gave MATC values of 0.08 mg/l herbicide. We have derived the EC50 values for some selected parameters on D. magna exposed to propanil. EC50 values indicated that reproductive parameters were very sensitive of the effect of propanil on daphnids. Finally, the daphnids were exposed to the same sublethal herbicide concentrations as in the chronic study and the effect of the toxicant on filtration and ingestion rates was determined. Feeding rates of D. magna declined with increasing propanil concentrations. The effective propanil concentrations at which feeding rates were reduced to 50% of that in controls (EC50) were also calculated.

Effects of fluctuations on electrical properties of gap-junction connected cells in the turtle retina

Electrical properties of gap-junction connected cells (input voltage and length constant) are shown to depend strongly on fluctuations in membrane and contact conductances. This opens new possibilities and incorporates a further difficulty to the analysis of electrophysiological data, since four, instead of two, parameters (the average values and the magnitude of fluctuations of the two conductances) have to be used in fitting the experimental data. The discussion is illustrated by investigating the effects of dopamine on signal spreading in horizontal cells of turtle retina, assuming a linear cell arrangement. It is shown that while a standard fitting with the average values of the two conductances leads to the conclusion that both are equally affected by dopamine, including fluctuations allows fitting the data by varying just the average contact conductance plus the magnitude of fluctuations.

Loss of a novel tumor suppressor gene locus at chromosome 8p is associated with leukemic mantle cell lymphoma

Patients with mantle cell lymphoma (MCL) may present with either nodal or leukemic disease. The molecular determinants underlying this different biologic behavior are not known. This study compared the pattern of genetic abnormalities in patients with nodal and leukemic phases of MCL using comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH) for specific gene loci. Although both leukemic and nodal MCL showed similar genomic patterns of losses (involving 6q, 11q22-q23, 13q14, and 17p13) and gains (affecting 3q and 8q), genomic loss of chromosome 8p occurred more frequently in patients with leukemic disease (79% versus 11%, P <.001). Subsequent CGH analysis confirmed the genomic loss of 8p21-p23 in 6 of 8 MCL cell lines. Interestingly, MYC gene amplification was restricted to cases with 8p deletion. These data indicate the presence of a novel tumor suppressor gene locus on 8p, whose deletion may be associated with leukemic dissemination and poor prognosis in patients with MCL.

On the validity of the two-cells model in the analysis of passive electrical properties of gap-junction connected cells

It is a rather extended practice to derive electrophysiological data (membrane and contact conductances) from experimental data for gap-junction tissues assuming that electrical connections are reduced to cell pairs. It is here shown that, if the length constant is sufficiently large, the mentioned procedure can lead to qualitatively incorrect results.

Junctional communication of pancreatic beta cells contributes to the control of insulin secretion and glucose tolerance

Proper insulin secretion requires the coordinated functioning of the numerous beta cells that form pancreatic islets. This coordination depends on a network of communication mechanisms whereby beta cells interact with extracellular signals and adjacent cells via connexin channels. To assess whether connexin-dependent communication plays a role in vivo, we have developed transgenic mice in which connexin 32 (Cx32), one of the vertebrate connexins found in the pancreas, is expressed in beta cells. We show that the altered beta-cell coupling that results from this expression causes reduced insulin secretion in response to physiologically relevant concentrations of glucose and abnormal tolerance to the sugar. These alterations were observed in spite of normal numbers of islets, increased insulin content, and preserved secretory response to glucose by individual beta cells. Moreover, glucose-stimulated islets showed improved electrical synchronization of these cells and increased cytosolic levels of Ca(2+). The results show that connexins contribute to the control of beta cells in vivo and that their excess is detrimental for insulin secretion.

Physiological perturbations in several generations of Daphnia magna straus exposed to diazinon

Daphnia magna was exposed to sublethal diazinon concentrations (0.05, 0.1, 0.5, 0.75, and 1.0 ng/L) for 21 days. The algae Nannochloris oculata (5x10(5) cells/mL) was used to feed the daphnids. Chronic toxicity tests were carried out using neonates of F(1) (first brood) and F(1) (third brood) offspring generations from parentals (F(0)) preexposed to the organophosphate. The effect of diazinon on survival, reproduction, and growth was monitored for the selected daphnid generations. The parameters used to evaluate pesticide effect on reproduction were mean total young per female, mean brood size, time to first reproduction, mean number broods per female, and intrinsic rate of natural increase (r). Survival and growth (body length) were also determined after 21 days of exposure to the pesticide. Reproduction as well as survival was significantly reduced when diazinon concentration increased in the medium. This effect was greater in F(1) (first) and F(1) (third) offspring compared to the parental generation (F(0)) daphnids. The intrinsic rate of natural increase (r) decreased with increasing concentrations of diazinon, especially in those animals from the first and third brood. However, the growth of the exposed organisms decreased in the same order of magnitude in all generations tested. The maximum acceptable toxicant concentration (MATC) was calculated for F(0), F(1) (first), and F(1) (third) generations of D. magna exposed to the pesticide using as parameter of evaluation the intrinsic rate of natural increase (r). The interpolation of these results gave MATC values of 0.62 and 0.07 ng/L pesticide for F(0)-F(1) (first) generations and F(1) (third) generation, respectively. Therefore, F(1) (third) generation seems to be more sensitive to diazinon than generations F(0) and F(1) (first). The EC(50) values have been derived for some selected parameters on the generations of D. magna exposed to diazinon. EC(50) values decreased in F(1) (first) and F(1) (third) generations compared to the parental generation F(0). Expanding the reproduction tests to several generations revealed important information on chronic toxicity that could add to an increased cost-effectiveness in the protection of aquatic environments.

Effects of tetradifon on Daphnia magna during chronic exposure and alterations in the toxicity to generations pre-exposed to the pesticide

Daphnia magna was exposed to some nominal sublethal tetradifon concentrations (0.10, 0.18, 0.22 and 0.44 mg/l) during 21 days. Chronic toxicity tests were carried out using neonates of F(1) first brood (F(1)-1st) and F(1) third brood (F(1)-3rd) offspring generations from parentals (F(0)) pre-exposed to the pesticide. The effect of tetradifon on survival, reproduction and growth was monitored for the selected daphnid generations. The parameters used to evaluate pesticide effect on reproduction were: mean total young per female, mean brood size, time to first reproduction, mean number broods per female and intrinsic rate of natural increase (r). Survival and growth (body length) were also determined after 21 days of exposure to the pesticide. Reproduction was significantly reduced when tetradifon concentration increased in the medium. This effect was higher in F(1)-1st and F(1)-3rd offsprings compared to the parental generation (F(0)) daphnids. The intrinsic rate of natural increase (r) decreased with increasing concentrations of tetradifon especially in those animals from F(1)-3rd. However, the growth of the exposed organisms decreased in the same order of magnitud in all the generations tested. Survival was not affected after exposure to the selected tetradifon concentrations. The maximum acceptable toxicant concentration (MATC) was calculated for F(0), F(1)-1st and F(1)-3rd generations exposed to the pesticide using as parameter of evaluation the intrinsic rate of natural increase (r). The interpolation of these results gave MATC values of 0.13 mg/l pesticide for F(0) and F(1). The EC50 values have been derived for some selected parameters on D. magna exposed to tetradifon. EC50 values decreased in F(1)-1st and F(1)-3rd generations compared to the parental generation F(0), these results mean that less amount of toxicant would be necessary to reduce the selected parameters to 50% in the first and third broods of D. magna. Expanding the reproduction tests to several broods of a parental generation revealed important information on chronic toxicity that could be used in the protection of aquatic environment.

Engineering pancreatic islets

Pancreatic islets are neuroendocrine organs that control blood glucose homeostasis. The precise interplay of a heterogeneous group of cell populations (beta, alpha, delta and PP cells) results in the fine-tuned release of counterbalanced hormones (insulin, glucagon, somatostatin and pancreatic polypeptide respectively). Under the premises of detailed knowledge of the physiological basis underlying this behaviour, two lines of investigation might be inferred: generating computational and operational models to explain and predict this behaviour and engineering islet cells to reconstruct pancreatic endocrine function. Whilst the former is being fuelled by new computational strategies, giving biophysicists the possibility of modelling a system in which new "emergent" properties appear, the latter is benefiting from the useful tools and strategic knowledge achieved by molecular, cell and developmental biologists. This includes using tumour cell lines, engineering islet cell precursors, knowledge of the mechanisms of differentiation, regeneration and growth and, finally, therapeutic cloning of human tissues. Gaining deep physiological understanding of the basis governing these processes is instrumental for engineering new pancreatic islets.

Role of architecture in determining passive electrical properties in gap junction-connected cells

The electrical properties of gap junction-connected cells were analysed in terms of their architectural organization. Two major architectural categories were considered: trees and rings. Trees are described by means of Bethe lattices (lattices with no rings) with arbitrary co-ordination and rings by two-dimensional periodic lattices with fourfold (square) or sixfold (triangular) co-ordination. The Bethe lattice is solved analytically by the transfer constant method, which allows the introduction of several physiologically relevant effects in a very simple manner. The experimental data for the length constant and the input resistance were fitted by varying the coupling and membrane resistances for various morphologies. The large variations in the length constant observed experimentally in two systems (turtle retina horizontal cells with and without dopamine and pancreatic beta-cells in the active and silent phases) could not be explained by means of the Bethe lattice, indicating that the cell arrangements form rings. Subsequent analysis by means of a linear chain and the square and triangular lattices showed the crucial relevance of architecture in deriving the electrical characteristics of gap junction-connected cells from experimental data.

Population dynamics in Daphnia magna as modified by chronic tetradifon stress

Two Daphnia magna offsprings (animals from the first and third brood) whose parentals (F0-generation) were exposed during 21 days to different tetradifon (4-chlorophenyl 2,4,5-trichlophenyl sulfone) concentrations, were transferred to a pesticide free medium during 21 days (recovery period). The algae Nannochloris oculata (5 x 10(5) cells/mL) was used as food. In this recovery study, survival, growth and reproduction (mean total young per female, mean brood size, onset of reproduction and mean number broods per female) were assessed as individual parameters and the intrinsic rate of natural increase (r) as population parameter, for F1 generation (1st and 3rd broods). Reproduction was still reduced in F1 (1st and 3rd broods) generation daphnids from parentals (F0) exposed to 0.18 mg/L tetradifon and higher concentrations even after 21 days in clean water. However, survival was not significantly different (p > 0.05) in those F1 offsprings from parentals pre-exposed to the acaricide. Growth was still reduced in F1 daphnids from parentals pre-exposed to 0.10-0.44 mg/L tetradifon. The intrinsic rate of natural increase (r) was still affected in F1 generation daphnids, specially in those from the third brood. Therefore, F1 generation D. magna offsprings from a parental generation (F0) previously exposed to the acaricide tetradifon were not able to recuperate completely when a recovery period of 21 days was allowed.

Assessment of the toxicity of a pesticide with a two-generation reproduction test using Daphnia magna

Daphnia magna (F0 generation) were exposed during 21 days to different diazinon concentrations. Offspring (animals from the first and third brood: F1 (1st) and F1 (3rd), respectively) were transferred to a free pesticide medium during a 21-day recovery period. The algae Nannochloris oculata (5x10(5) cells/ml) were used as food. In this recovery study, survival, growth and reproduction (mean total young per female, mean brood size, onset of reproduction and mean number broods per female) were assessed as individual parameters, and the intrinsic rate of natural increase (r) as population parameter for F1 (1st and 3rd broods) daphnids. Reproduction as well as survival was still reduced in F1 (1st) generation daphnids from parentals (F0) exposed to the highest diazinon concentration. However, F1 (1st) and F1 (3rd) individuals from parentals exposed to pesticide concentrations below 0.5 ng/l were able to restore reproduction and survival when a recovery period of 21 days was allowed.

Mechanisms of glucose hypersensitivity in beta-cells from normoglycemic, partially pancreatectomized mice

Increased beta-cell sensitivity to glucose precedes the loss of glucose-induced insulin secretion in diabetic animals. Changes at the level of beta-cell glucose sensor have been described in these situations, but it is not clear whether they fully account for the increased insulin secretion. Using a euglycemic-normolipidemic 60% pancreatectomized (60%-Px) mouse model, we have studied the ionic mechanisms responsible for increased beta-cell glucose sensitivity. Two weeks after Px (Px14 group), Px mice maintained normoglycemia with a reduced beta-cell mass (0.88 +/- 0.18 mg) compared with control mice (1.41 +/- 0.21 mg). At this stage, the dose-response curve for glucose-induced insulin release showed a significant displacement to the left (P < 0.001). Islets from the Px14 group showed oscillatory electrical activity and cytosolic Ca2+ ([Ca2+]i) oscillations in response to glucose concentrations of 5.6 mmol/l compared with islets from the control group at 11.1 mmol/l. All the above changes were fully reversible both in vitro (after 48-h culture of islets from the Px14 group) and in vivo (after regeneration of beta-cell mass in islets studied 60 days after Px). No significant differences in the input resistance and ATP inhibition of ATP-sensitive K+ (K(ATP)) channels were found between beta-cells from the Px14 and control groups. The dose-response curve for glucose-induced MTT (C,N-diphenyl-N''-4,5-dimethyl thiazol 2 yl tetrazolium bromide) reduction showed a significant displacement to the left in islets from the Px14 group (P < 0.001). These results indicate that increased glucose sensitivity in terms of insulin secretion and Ca2+ signaling was not due to intrinsic modifications of K(ATP) channel properties, and suggest that the changes are most likely to be found in the glucose metabolism.

Daphnia magna feeding behavior after exposure to tetradifon and recovery from intoxication

The feeding behavior of the cladocera Daphnia magna subjected to a short-term exposure to the acaricide tetradifon (4-chlorophenyl 2,4, 5-trichlorophenyl sulfone) was studied. The experiments were performed using the unicellular algae Nannochloris oculata at a density of 5x10(5) cells/ml as food for the organisms. In a first experiment, three generations (F0, F1, and F3) of the daphnids were exposed to sublethal levels of tetradifon (0.1, 0.18, 0.22, and 0.44 mg/l) and the effect of the toxicant on filtration and ingestion rates was determined. Rates of filtration and ingestion of D. magna declined in the three generations studied with increasing toxicant concentrations; however, toxicant effect was greater in daphnids from generations F1 and F3 than in those from the parental generation F0. A second experiment was conducted in order to evaluate whether animals of a first (1) or third (F3) generation coming from parental daphnids (F0) previously exposed to those pesticide concentrations exhibited any alteration in feeding behavior when transferred to clean water (recovery period). The results indicated that the feeding rates of D. magna generations F1 and F3 were still affected during the recovery period but to a less degree. The effective tetradifon concentrations D. magna at which feeding rates were reduced to 50% that of controls (EC(50)) were also calculated.

Rapid insulinotropic effect of 17beta-estradiol via a plasma membrane receptor

Impaired insulin secretion is a hallmark in both type I and type II diabetic individuals. Whereas type I (insulin-dependent diabetes mellitus) implies ss-cell destruction, type II (non-insulin dependent diabetes mellitus), responsible for 75% of diabetic syndromes, involves diminished glucose-dependent secretion of insulin from pancreatic beta-cells. Although a clear demonstration of a direct effect of 17beta-estradiol on the pancreatic ss-cell is lacking, an in vivo insulinotropic effect has been suggested. In this report we describe the effects of 17beta-estradiol in mouse pancreatic ss-cells. 17beta-Estradiol, at physiological concentrations, closes K(ATP) channels, which are also targets for antidiabetic sulfonylureas, in a rapid and reversible manner. Furthermore, in synergy with glucose, 17beta-estradiol depolarizes the plasma membrane, eliciting electrical activity and intracellular calcium signals, which in turn enhance insulin secretion. These effects occur through a receptor located at the plasma membrane, distinct from the classic cytosolic estrogen receptor. Specific competitive binding and localization of 17beta-estradiol receptors at the plasma membrane was demonstrated using confocal reflective microscopy and immunocytochemistry. Gaining deeper knowledge of the effect induced by 17beta-estradiol may be important in order to better understand the hormonal regulation of insulin secretion and for the treatment of NIDDM. receptor.

In vivo inhibition of AChE activity in the European eel Anguilla anguilla exposed to technical grade fenitrothion

European eel (Anguilla anguilla) were exposed to sublethal fenitrothion concentrations in a continuous flow-through system for 4 days. Plasma acetylcholinesterase (AChE) activity was evaluated after 2, 8, 12, 24, 32, 48, 56, 72 and 96 h pesticide exposure. AChE activity in the plasma of the eel decreased as concentration of fenitrothion increased. Pesticide induced significant inhibitory effects on the AChE activity of A. anguilla ranging from 51% inhibition at sublethal concentration of 0.02 ppm to 57% inhibition at sublethal concentration of 0.04 ppm. Eel were exposed to both fenitrothion concentrations for 96 h and then allowed a period of recovery in pesticide-free water. Following 1 week of recovery, the AChE activity for those animals previously exposed to fenitrothion was still different from the controls. Animals transferred to clean water showed plasma AChE activities reduced in a 34 and 51% when previously exposed to 0.02 and 0.04 ppm pesticide, respectively. This is probably due because regeneration of the enzyme is mainly by the novo synthesis after exposure to organophosphates and levels need a large extent to recover.

Liver energy metabolism of Anguilla anguilla after exposure to fenitrothion

This paper deals with the effect of fenitrothion (0.04 mg/liter) on the energy metabolism of the European eel, Anguilla anguilla, and its recovery from intoxication. Various parameters such as glycogen, lactate, proteins, total lipids, and glucose in eel liver and blood were analyzed after 2, 8, 12, 24, 32, 48, 56, 72, and 96 h of fenitrothion exposure. Subsequently, the fish were allowed recovery periods of 8, 12, 24, 48, 72, 96, 144, and 192 h in clean water, and the same parameters were evaluated. Liver glycogen and lipid contents decreased significantly during the exposure, while blood glucose levels increased markedly. Liver and blood lactate values increased during pesticide exposure, while proteins were decreased in comparison to unexposed controls. Most of the metabolic disorders did not persist after less than a week of recovery in clean water. The observed effects of fenitrothion on fish metabolism are discussed in relation to a stress syndrome, and probable reasons for alterations are also discussed.

Response and recovery of brain acetylcholinesterase activity in the European eel, Anguilla anguilla, exposed to fenitrothion

European eel (Anguilla anguilla) were exposed to sublethal fenitrothion concentrations in a continuous flow-through system for 4 days. Brain acetylcholinesterase (AChE) activity was evaluated after 2, 8, 12, 24, 32, 48, 56, 72, and 96 h pesticide exposure. Results indicated that AChE activity in eel brains decreased as the concentration of fenitrothion increased. The pesticide induced significant inhibitory effects on the AchE activity of A. anguilla, ranging from > 40% inhibition at a sublethal concentration of 0.02 ppm to > 60% inhibition at a sublethal concentration of 0.04 ppm. Eel were exposed to both fenitrothion concentrations for 96 h and then allowed a period of recovery in pesticide-free water. Samples were removed at 8, 12, 24, 48, 72, 96, 144, and 192 h and eel brain AChE activity was evaluated. Following 1 week of recovery, the AChE activity of those animals previously exposed to 0.02 and 0.04 ppm fenitrothion was still different from that of the controls. So, the AChE activity of eel brains at the end of the recovery phase remained significantly depressed.

Response and recovery of acethylcholinesterase activity in the European eel Anguilla anguilla exposed to fenitrothion

European eel (Anguilla anguilla) were exposed to sublethal fenitrothion concentrations in a continuous flow-through system for 4 days. Muscle acetylcholinesterase (AChE) activity was evaluated after 2, 8, 12, 24, 32, 48, 56, 72 and 96 hours pesticide exposure. Results showed that AChE activity in eel muscle tissue decreased as concentration of fenitrothion increased. Pesticide induced significant inhibitory effects on the AChE activity of A. anguilla ranging from > 35% inhibition at sublethal concentration of 0.02 ppm to > 44% inhibition at sublethal concentration of 0.04 ppm. Eel were exposed to both fenitrothion concentrations for 96 hours and then allowed a period of recovery in pesticide-free water. Samples were taken out at 8, 12, 24, 48, 72, 96, 144 and 192 hours and eel muscle AChE activity was evaluated. Following 1 week of recovery, the AChE activity for those animals previously exposed to 0.02 and 0.04 ppm fenitrothion was still different from the controls. So, the AChE activity of eel muscle at the end of the recovery phases remained significantly depressed.

Inhibition of gill Na+,K+-ATPase activity in the eel, Anguilla anguilla, by fenitrothion

European eels (Anguilla anguilla) were exposed to sublethal fenitrothion concentrations (0.02 and 0.04 mg/liter) in a continuous flow-through system for 4 days. Gill Mg2+- and Na+,K+-ATPase activities were evaluated after 2, 8, 12, 24, 32, 48, 56, 72, and 96 h of pesticide exposure. Results indicated that ATPase activity in gill tissue decreased as concentration of fenitrothion increased. Pesticide induced significant inhibitory effects on the Na+, K+-ATPase activity of A. anguilla, ranging from >56% inhibition at a sublethal concentration of 0.02 ppm to >73% inhibition at a sublethal concentration of 0.04 ppm. Eels were exposed to both fenitrothion concentrations for 96 h and then allowed a period of recovery in pesticide-free water. Samples were removed at 8, 12, 24, 48, 72, 96, 144, and 192 h and eel gill ATPase activity was evaluated. Following 1 week of recovery, the Na+,K+-ATPase activity for those animals previously exposed to 0.04 ppm fenitrothion was still different from that of the controls.

Sublethal effects of an organophosphate insecticide on the European eel, Anguilla anguilla

The present communication deals with the effects of fenitrothion (0.02 mg/liter) on the energy metabolism of the European eel, Anguilla anguilla, and its recovery from intoxication. Various parameters such as glycogen, lactate, proteins, and glucose levels were measured in different eel tissues after 2, 8, 12, 24, 32, 48, 56, 72, and 96 hr of fenitrothion exposure. Subsequently, the fish were allowed recovery periods of 8, 12, 24, 48, 72, 96, 144, and 192 hr in clean water, and the same parameters were evaluated. Liver glycogen content showed no significant changes during the exposure time, while blood glucose levels increased markedly. Gill, liver, and blood lactate values increased during pesticide exposure, while proteins decreased in comparison to unexposed controls. Most of the metabolic disorders did not persist after eels were allowed to recover in clean water for less than a week. The observed effects of fenitrothion on fish metabolism are discussed in relation to a stress syndrome, as are probable reasons for alterations.

Oscillation of gap junction electrical coupling in the mouse pancreatic islets of Langerhans

1. Pancreatic beta-cells oscillate synchronously when grouped in islets. Coupling seems essential to maintain this oscillatory behaviour, as isolated cells are unable to oscillate. This allows the islet to be used as a model system for studying the role of coupling in the generation of oscillatory patterns. 2. Pairs of beta-cells were intracellularly recorded in islets. beta-Cells oscillated synchronously. Propagated voltage deflections were observed as a function of glucose concentration and of the distance between the recording electrodes. Space constants were smaller in the silent than in the active phases, suggesting a higher intercellular connection in the active phases. 3. Coupling coefficients and estimated coupling conductances were larger in the active than in the silent phases. 4. Coupling coefficients and coupling conductances changed dynamically and in phase with the membrane potential oscillations, pointing to an active modulation of the gap junctions. 5. We hypothesize a role for coupling in the generation of the oscillatory events, providing different levels of permeability dependent on the state of conductance during the oscillatory phases.

Diminished fraction of blockable ATP-sensitive K+ channels in islets transplanted into diabetic mice

The reasons for the poor outcome of islet transplantation in diabetic patients are not well known; a better understanding of the pathophysiology of transplanted islets is needed. To study the mechanism coupling secretagogue stimuli with insulin release in transplanted islets, we determined the effects of glucose, tolbutamide, and carbamylcholine on the beta-cell membrane potential and cytosolic calcium concentrations ([Ca2+]i) of islets syngeneically transplanted into normal and streptozocin-induced diabetic mice. In both groups, normoglycemia was maintained after transplantation. Islets transplanted into normal recipients showed similar changes in beta-cell membrane potential and [Ca2+]i oscillations to those in control islets. In contrast, when islets were transplanted into diabetic mice, bursts of electrical activity were triggered at lower glucose concentrations (5.6 mmol/l) than in control islets (11 mmol/l), and maximal electrical activity was achieved at lower glucose concentrations (11 mmol/l) than in control islets (22 mmol/l). When membrane potential was plotted as a function of glucose concentration, the dose-response curve was shifted to the left. Compared with control islets, glucose-induced [Ca2+]i oscillations were broader in duration (22.3 +/- 0.6 s vs. 118.1 +/- 12.6 s; P < 0.01) and higher in amplitude (135 +/- 36 nmol/l vs. 352 +/- 36 nmol/l; P < 0.01). Glucose supersensitivity was attributed to a resting decrease in the fraction of blockable ATP-sensitive K+ (K+(ATP)) channels in transplanted islets that maintained normoglycemia with a limited beta-cell mass.

Physiological stress responses of Anguilla anguilla to fenitrothion

The present communication deals with the effect of fenitrothion (0.04 ppm) on the carbohydrate metabolism of the european eel Anguilla anguilla and its recovery from intoxication. Analysis of various parameters such as glycogen, lactate and glucose was made on different eel tissues after 2, 8, 12, 24, 32, 48, 56, 72 and 96 hr of fenitrothion exposure. Subsequently, the fish were allowed recovery periods of 8, 12, 24, 48, 72, 96, 144 and 192 hr in clean water, and the same parameters were evaluated. Muscle glycogen content decreased significantly during the exposure time, while blood glucose levels increased markedly. Gill, muscle and blood lactate values increased during pesticide exposure. Most of the metabolic disorders did not persist after allowing recovery in clean water during less than a week. The observed effects of fenitrothion on fish metabolism are discussed in relation to a stress syndrome and probable reasons for alterations have been exposed.

Pesticide effects on eel metabolism pesticide; levels did not decline at any time when animals were exposed to 4.1 mg/liter

Previous works on endosulfan eel toxicology in this laboratory demonstrated that 0.041 mg/liter of endosulfan was the 50% lethal concentration of 96 hr exposure. Eels of species Anguilla anguilla were exposed to two sublethal endosulfan concentrations: 8.2 micrograms/liter (1/5 LC50) and 4.1 micrograms/liter (1/10 LC50), and the experiment was done at different exposure times: 12, 24, 48, 72, and 96 hr. Muscle glycogen content decreased significantly (p < 0.05) at 24, 48, 72, and 96 hr exposure to 8.2 micrograms/liter. Muscle lactate levels in fish did not change significantly while lactate levels in eel blood increased at 12, 24, 48, 72, and 96 hr exposure to 8.2 micrograms/liter. Mean blood glucose values were elevated after exposure to both endosulfan concentrations. The results are discussed in relation to the stress effect produced by the pesticide and the related responses of the fish.

Ecotoxicological studies with the freshwater rotifer Brachionus calyciflorus. III. The effects of chemicals on the feeding behavior

The effect of short-term exposure to xenobiotics on the feeding behavior of the freshwater rotifer Brachionus calyciflorus was studied. The filtration and ingestion rates of this rotifer decreased after an exposure of 5 hr to sublethal concentrations of copper, pentachlorophenolate, 3,4-dichloroaniline, and lindane. The effective concentrations at which feeding rate was reduced to 50% of that in controls (EC50) for the respective chemicals are 0.032, 1.85, 41.2, and 8.5 mg/liter. The potential use of feeding behavior as test criterion for toxicity screening tests with aquatic invertebrates is discussed.