Multiple neurological effects associated with exposure to organophosphorus pesticides in man.

This article reviews available data regarding the possible association of organophosphorus (OP) pesticides with neurological disorders such as dementia, attention deficit hyperactivity disorder, neurodevelopment, autism, cognitive development, Parkinson's disease and chronic organophosphate-induced neuropsychiatric disorder. These effects mainly develop after repeated (chronic) human exposure to low doses of OP. In addition, three well defined neurotoxic effects in humans caused by single doses of OP compounds are discussed. Those effects are the cholinergic syndrome, the intermediate syndrome and organophosphate-induced delayed polyneuropathy. Usually, the poisoning can be avoided by an improved administrative control, limited access to OP pesticides, efficient measures of personal protection and education of OP pesticide applicators and medical staff.

Effects of memantine and its metabolite Mrz 2/373 on soman-induced inhibition of acetylcholinesterase in vitro.

Memantine is the non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist, used in the treatment of Alzheimer's disease. It is also known that memantine pretreatment assured protection of skeletal muscles from poisoning with nerve agents and an interaction between memantine and AChE was proposed. In the study presented we examined interactions of memantine and its main metabolite (1-amino-3-hydroxymethyl-5-methyl adamantine, Mrz 2/373) with AChE in vitro as well as their effect on kinetics of the soman-induced AChE inhibition and aging. The results have shown that memantine and Mrz 2/373 exerted concentration-dependent inhibition of AChE, with Mrz 2/373 being a more potent inhibitor than the parent compound. Addition of soman 7.5 nmol/l induced gradual AChE inhibition that became almost complete after 20 min. Memantine (0.1, 0.5 and 1 mmol/l) and Mrz 2/373 (0.1, 0.5 and 1 mmol/l) concentration-dependently slowed down the AChE inhibition. After 30 min of incubation of AChE with soman, 5 min of aging and 20 min of reactivation by asoxime (HI-6 dichloride), AChE activity was 8.1% in control medium, 30.7% and 41.9% after addition of 1 and 10 mmol/l memantine, and 16.1% after addition of 1 mmol/l Mrz 2/373. It was concluded that it is possible that memantine and Mrz 2/373 can prevent AChE from inhibition by soman, which could, along with known memantine's neuroprotective activity, explain its potent antidotal effect in soman poisoning. The potential effect on aging of the soman-AChE complex warrants further studies.

Prophylactic potential of memantine against soman poisoning in rats.

BACKGROUND: Carbamates physostigmine and pyridostigmine have been used as a pretreatment against poisoning with nerve agents in order to reversibly inhibit and thus protect from irreversible inhibition a portion of acetylcholinesterase (AChE) in brain and respiratory muscles that is crucial for survival. Memantine, an adamantine derivative, has emerged as a promising alternative to carbamates, since it prevented the fasciculations and skeletal muscle necrosis induced by carbamates and organophosphates, including nerve agents. AIM: This experimental study was undertaken in order to investigate and compare the protective and behavioural effects of memantine and standard carbamates physostigmine and pyridostigmine in rats poisoned with soman and treated with atropine, oxime HI-6 and diazepam. Another goal was to elucidate the mechanisms of the antidotal effect of memantine and its potential synergism with standard antidotes against nerve agents. MATERIALS AND METHODS: Male Wistar rats were used throughout the experiments. In dose-finding experiments memantine was administered at dose interval 0-72 mg/kg sc 60 min before sc injection of soman. In time-finding experiments memantine was injected 18 mg/kg sc 0-1440 min before soman. Standard treatment antidotes - atropine 10 mg/kg, HI-6 50 mg/kg and diazepam 2.5 mg/kg - were administered im within 15 s post-exposure. Soman 0.75 LD50 was used to study its inhibitions of neuromuscular transmission on the phrenic nerve-diaphragm preparation in situ and of tissue AChE activity. Behavioural effects of the prophylactic antidotes were investigated by means of the rotarod test. Based on these data therapeutic index and therapeutic width was calculated for all three prophylactic agents. RESULTS: Memantine pretreatment (18 mg/kg sc) produced in rats poisoned with soman significantly better protective ratios (PRs) than the two carbamates - 1.25 when administered alone and 2.3 when combined with atropine pretreatment and 6.33 and 7.23 with atropine/HI-6 and atropine/HI-6/diazepam post-exposure therapy, respectively. The highest PR of 10.11 obtained in Atr/HI-6-treated rats was achieved after pretreatment with memantine 36 mg/kg. This additional protection lasted for 8 h. All three prophylactic regimens antagonised the soman-induced neuromuscular blockade, but the effect of memantine was fastest. Pretreatment with memantine assured higher AChE activity in brain and diaphragm than in unpretreated rats (46% vs 28% and 68% vs. 38%, respectively). All three prophylactic regimens affected the rotarod performance in rats, but the effect of memantine was relatively strongest. Memantine and pyridostigmine had lowest and highest therapeutic index and therapeutic width, respectively. CONCLUSIONS: Although memantine assures better and longer-lasting protection against soman poisoning in rats than the two carbamates, its small therapeutic index and narrow therapeutic width seriously limit its potential as a pretreatment agent. Despite its behavioural effects, memantine seems to be beneficial antidote when administered after soman, along with atropine/HI-6/diazepam therapy. Mechanism of the antidotal effect of memantine against soman poisoning appears to be a combination of AChE-protecting and NMDA receptor-blocking action.

Efficacy of antidotes and their combinations in the treatment of acute carbamate poisoning in rats.

BACKGROUND: Physostigmine and its analogues neostigmine, pyridostigmine and rivastigmine are carbamates nowadays used in many indications, including antidotal effects against antimuscarinic poisonings, reversal of competitive neuromuscular block, myasthenia gravis, Alzheimer's disease and prophylaxis against nerve agent intoxications. Use of these medicinal carbamates, but also of carbamate insecticides, created need for research into the potential and mechanisms of action of several antidotes against carbamate poisonings, including anticholinergics and oximes. AIM: The goal of this experimental study was to ascertain the life-preserving potential of anticholinergics atropine, hexamethonium and d-tubocurarine, oxime HI-6 and their combinations in rats poisoned with physostigmine or pyridostigmine. MATERIALS AND METHODS: Experiments were performed in Wistar rats. Carbamates were injected subcutaneously (sc) and antidotes intramuscularly (im). Median lethal dose (LD50) in animals treated with antidotes were compared to the ones in saline-treated rats and protective ratios (PRs) were calculated. Atropine (5, 10 and 20 mg/kg), hexamethonium (5, 10 and 20 mg/kg), d-tubocurarine (0.005, 0.010 and 0.020 mg/kg) and oxime HI-6 (25, 50 and 100 mg/kg) were used as monotherapies and in dual combinations, where atropine was the obligatory antidote. Biochemical experiments consisted in measuring of the cholinesterase activities in brain, whole blood and diaphragm in rats 5, 15, 30, 60, 120 and 240 min after poisoning with 0.8 LD50 of physostigmine or pyridostigmine. RESULTS: All the tested antidotes assured some degree of protection against the two carbamates. Atropine and hexamethonium produced better protection in physostigmine-poisoned rats, while d-tubocurarine and HI-6 were more efficacious in pyridostigmine-intoxicated animals. Oxime HI-6 50 mg/kg reactivated acetylcholinesterase (AChE) in brain inhibited by physostigmine and in diaphragm inhibited by pyridostigmine. CONCLUSIONS: Mechanism of physostigmine-induced lethal effect is predominantly central and it involves inhibition of brain AChE, while pyridostigmine produces the same effect exclusively outside the central nervous system, by inhibiting AChE in the respiratory muscles. As a consequence, increasing doses of atropine and their combination with hexamethonium assure excellent protection against physostigmine toxicity, while the best protection against pyridostigmine is provided by a strictly peripherally acting antinicotinic d-tubocurarine and bispyridinium oxime HI-6. The oxime acts as antidote against physostigmine and pyridostigmine poisoning by reactivating AChE in the brain and diaphragm, respectively.

Neurotoxic effects of organophosphorus pesticides and possible association with neurodegenerative diseases in man: A review.

In this article the neurotoxic disorders appearing in patients exposed to organophosphorus pesticides and known mechanisms involved are reviewed. Organophosphorus compounds cause four main neurotoxic effects in humans: the cholinergic syndrome, the intermediate syndrome, organophosphate-induced delayed polyneuropathy and chronic organophosphate-induced neuropsychiatric disorder. Compared to the cholinergic syndrome, that causes millions of cases of poisoning with fatality of more than 15% each year, other disorders involve much smaller number of patients. Possible link of exposure to organophosphorus pesticides with neurodegenerative diseases, dementia, attention deficit hyperactivity disorder and Parkinson's disease in man is also approached. This article is focused on neurotoxic disorders appearing after acute and chronic exposure to organophosphates with emphasis on molecular mechanisms, clinical presentation, pathogenesis, and possibilities for prevention/medical treatment.

Tacrolimus as a part of immunosuppressive treatment in kidney transplantation patients: sex differences.

BACKGROUND: Metabolism interaction between corticosteroids and tacrolimus (Tac) exists and can be an important factor in providing rational pharmacotherapy in kidney transplantation patients. Both Tac and corticosteroids can induce adverse metabolic effects, such as hyperglycemia, post-transplantation diabetes mellitus, and dyslipidemia. OBJECTIVE: The main goal of this study was to detect corticosteroid dose influence on Tac level within the first 6 months of immunosuppressive therapy. The secondary goal of this research was to investigate sex differences on Tac-corticosteroid interaction. We also monitored biochemical-parameter changes, which are related to immunosuppressive treatment. METHODS: This retrospective pharmacokinetic study included 30 Serbian patients after kidney transplantation. Patients received a quaternary immunosuppressive regimen including Tac, mycophenolate, mofetil, basiliximab, and corticosteroids. To compare dose-normalized level and dose of Tac in different days after transplantation, we performed the Friedman test and Wilcoxon matched-pairs signed rank sum test. Mann-Whitney test was performed to compare differences in dose of Tac, level of Tac, and dose-normalized level of Tac between male and female patient groups. We used the Friedman test to compare biological and clinical data. RESULTS: Obtained results show statistical significance between dose of Tac on day 180 post transplantation and dose on days 7, 14, 21, and 60 post transplantation. There was a statistical difference in dose-normalized level of Tac between days 7 and 21 post transplantation (P < 0.01), days 7 and 60 (P < 0.01), and between days 7 and 180 (P < 0.05). There is a statistical significance between male and female levels of Tac on day 21 after transplantation (P < 0.01). Significance also exists on day 60 after transplantation between male and female dose-normalized levels (P < 0.05). There is also a statistical difference in glucose, cholesterol, triglyceride, serum creatinine, and urea level and activity of alanine aminotransferase and alkaline phosphatase before and after operation. CONCLUSION: Our study shows that dose of corticosteroid affects Tac level in kidney transplantation patients. Tac dose and level changes showed that corticosteroid-Tac interaction has more influence on male than female patients. According to biochemical monitoring, the immunosuppressive therapy used at present is quite well tolerated.

Structure-activity relationship and efficacy of pyridinium oximes in the treatment of poisoning with organophosphorus compounds: a review of recent data.

During more than five decades, pyridinium oximes have been developed as therapeutic agents used in the medical treatment of poisoning with organophosphorus compounds. Their mechanism of action is reactivation of acetylcholinesterase (AChE) inhibited by organophosphorus agents. Organophosphorus compounds (OPC) are used as pesticides and developed as warfare nerve agents such as tabun, soman, sarin, VX and others. Exposure to even small amounts of an OPC can be fatal and death is usually caused by respiratory failure resulting from paralysis of the diaphragm and intercostal muscles, depression of the brain respiratory center, bronchospasm, and excessive bronchial secretions. The mechanism of OPC poisoning involves phosphorylation of the serine hydroxyl group at the active site of AChE leading to the inactivation of this essential enzyme, which has an important role in neurotransmission. AChE inhibition results in the accumulation of acetylcholine at cholinergic receptor sites, producing continuous stimulation of cholinergic fibers throughout the central and peripheral nervous systems. Presently, a combination of an antimuscarinic agent, e.g. atropine, AChE reactivator such as one of the standard pyridinium oximes (pralidoxime, trimedoxime, obidoxime, HI-6) and diazepam are used for the treatment of organophosphate poisoning in humans. Despite of enormous efforts devoted to synthesis and development of new pyridinium oximes as potential antidotes against poisoning with OPC, only four compounds have found their application in human medicine so far. However, they differ in their activity in poisoning with warfare nerve agents and pesticides and there is still no universal broad-spectrum oxime capable of protecting against all known OPC. In this article the latest data on structure-activity relationship of pyridinium oximes including their efficacy in treatment of poisoning with organophosphorus compounds are reviewed.

Organophosphate induced delayed polyneuropathy in man: an overview.

About 80 years have passed since the first cases of organophosphate induced delayed polyneuropathy (OPIDP), as the consequence of human poisoning with certain organophosphorus compounds, were described in the literature. OPIDP is a relatively rare neurodegenerative disorder in humans characterized by loss of function, ataxia and paralysis of distal parts of sensory and motor axons in peripheral nerves and ascending and descending tracts of spinal cord appearing 2-3 weeks after exposure or later. The molecular target for OPIDP is considered to be an enzyme in the nervous system known as neuropathy target esterase (NTE). This review discusses OPIDP in man with emphasis on clinical presentation, pathogenesis, molecular mechanisms, and possibilities for prevention/therapy.

Quantitative analysis of toxic and essential elements in human hair. Clinical validity of results.

Over the last three decades, there has been an increasing awareness of environmental and occupational exposures to toxic or potentially toxic trace elements. The evolution of biological monitoring includes knowledge of kinetics of toxic and/or essential elements and adverse health effects related to their exposure. The debate whether a hair is a valid sample for biomonitoring or not is still attracting the attention of analysts, health care professionals, and environmentalists. Although researchers have found many correlations of essential elements to diseases, metabolic disorders, environmental exposures, and nutritional status, opponents of the concept of hair analysis object that hair samples are unreliable due to the influence of external factors. This review discusses validity of hair as a sample for biomonitoring of essential and toxic elements, with emphasis on pre-analytical, analytical, and post-analytical factors influencing results.

Comparison of vasorelaxant effect and tolerance profile of a novel isosorbide-5-mononitrate derivative with its stereoisomer and parent drug on rat mesenteric artery.

BACKGROUND/AIMS: 5-Ketoximeisosorbide-2-mononitrate (50-IS-2-MN) was synthesized and its pharmacological and toxicological characteristics were examined and compared with its parent drug, isosorbide-5-mononitrate (IS-5-MN, CAS 16051-77-7), and its diastereoisomer 2-ketoximeisosorbide-5-mononitrate. METHODS: Vasorelaxation was studied on phenylephrine-precontracted rat superior mesenteric artery rings in organ bath procedure. In some rings, the endothelium was mechanically removed. In vitro tolerance was induced by treating the precontracted rings with maximal concentrations of the parent drug and the ketoximes, and after washing out, the procedure was repeated for two times. Furthermore, rats were treated with a single oral dose (1000 mg/kg) of 50-IS-2-MN and 20-IS-5-MN. RESULTS: After a phenylephrine-induced contraction, 50-IS-2-MN (10(-8)-10(-4) mol/l) caused a concentration-dependent relaxation of the rat superior mesenteric artery that was strongly potentiated after the removal of the vascular endothelium. In preparations with or without endothelium, 50-IS-2-MN was a more potent relaxant than either the parent compound or its isomer. The mechanism of the relaxant effect of 50-IS-2-MN involves the activated soluble guanylyl cyclase-cyclic GMP pathway. Hydralazine (10(-5) mol/l), a strong antioxidant, ameliorated tolerance to IS-5-MN, but did not affect the absence of tolerance to either ketoxime. The minimum lethal dose in rat for 5O-IS-2-MN and 20-IS-5-MN was greater than 1000 mg/kg. CONCLUSION: These results suggest that the modification of the configuration at the ester carbon of IS-5-MN contributes to more potent and tolerance-devoid activity on the rat superior mesenteric artery.

Neurotoxic effects in patients poisoned with organophosphorus pesticides.

In this paper we review neurotoxic disorders appearing in patients poisoned with organophosphorus pesticides. These compounds cause four important neurotoxic effects in humans: the cholinergic syndrome, the intermediate syndrome, organophosphate-induced delayed polyneuropathy (OPIDP) and chronic organophosphate-induced neuropsychiatric disorder (COPIND). Compared to the cholinergic syndrome, that causes millions of cases of poisoning each year, other disorders involve much smaller numbers of patients. The review is focused on the neurotoxic effects appearing after acute and chronic exposure to organophosphates with emphasis on clinical presentation, pathogenesis, molecular mechanisms, and possibilities for prevention/therapy.

The irritative property of alpha-tricalcium phosphate to the rabbit skin.

The aim of this study was to assess the irritant properties of a new developed calcium phosphate ceramic, alpha-tricalcium phosphate (alpha-TCP) after single application to intact skin of the rabbit. The test substance, alpha-TCP was produced by modified hydrothermal method and prepared in two different forms, as a solid material (disc 5 x 2 mm) and paste. Both, solid material and paste of alpha-TCP were evaluated for primary skin irritation to the ISO 10993-10:2002/Amd 1:2006 Biological Evaluation of Medical Devices - Part 10. At the end of the study macroscopic examination of the skin was performed. In this model, general and local tolerances were good. Score of primary irritation (SPI) and primary irritation index (PII) of alpha-TCP for both, solid material and paste, revealed that there was no significant toxicity/irritability (PII = 0.0) as compared to the negative control (PII = 0.0). Positive control did cause significant skin irritation in acute irritation test using Draize technique in rabbit model (PII = 2.11). Based on present results, it can be concluded that the the irritation potential of the tested material is negligible. However, other procedures for preclinical safety assessments of the alpha-TCP material are needed in order to completely elucidate its toxic potential.

Medical treatment of acute poisoning with organophosphorus and carbamate pesticides.

Organophosphorus compounds (OPs) are used as pesticides and developed as warfare nerve agents such as tabun, soman, sarin, VX and others. Exposure to even small amounts of an OP can be fatal and death is usually caused by respiratory failure. The mechanism of OP poisoning involves inhibition of acetylcholinesterase (AChE) leading to inactivation of the enzyme which has an important role in neurotransmission. AChE inhibition results in the accumulation of acetylcholine at cholinergic receptor sites, producing continuous stimulation of cholinergic fibers throughout the nervous systems. During more than five decades, pyridinium oximes have been developed as therapeutic agents used in the medical treatment of poisoning with OP. They act by reactivation of AChE inhibited by OP. However, they differ in their activity in poisoning with pesticides and warfare nerve agents and there is still no universal broad-spectrum oxime capable of protecting against all known OP. In spite of enormous efforts devoted to development of new pyridinium oximes as potential antidotes against poisoning with OP only four compounds so far have found its application in human medicine. Presently, a combination of an antimuscarinic agent, e.g. atropine, AChE reactivator such as one of the recommended pyridinium oximes (pralidoxime, trimedoxime, obidoxime and HI-6) and diazepam are used for the treatment of OP poisoning in humans. In this article the available data related to medical treatment of poisoning with OP pesticides are reviewed and the current recommendations are presented.

Pyridinium oximes as cholinesterase reactivators. Structure-activity relationship and efficacy in the treatment of poisoning with organophosphorus compounds.

During more than five decades, pyridinium oximes have been developed as therapeutic agents used in the medical treatment of poisoning with organophosphorus compounds. Their mechanism of action is reactivation of acetylcholinesterase (AChE) inhibited by organophosphorus agents. Organophosphorus compounds (OPC) are used as pesticides and developed as warfare nerve agents such as tabun, soman, sarin, VX and others. Exposure to even small amounts of an OPC can be fatal and death is usually caused by respiratory failure resulting from paralysis of the diaphragm and intercostal muscles, depression of the brain respiratory center, bronchospasm, and excessive bronchial secretions. The mechanism of OPC poisoning involves phosphorylation of the serine hydroxyl group at the active site of AChE leading to the inactivation of this essential enzyme, which has an important role in neurotransmission. AChE inhibition results in the accumulation of acetylcholine at cholinergic receptor sites, producing continuous stimulation of cholinergic fibers throughout the central and peripheral nervous systems. Presently, a combination of an antimuscarinic agent, e.g. atropine, AChE reactivator such as one of the standard pyridinium oximes (pralidoxime, trimedoxime, obidoxime, HI-6) and diazepam has been used for the treatment of organophosphate poisoning in humans. Despite enormous efforts devoted to synthesis and development of new pyridinium oximes as potential antidotes against poisoning with OPC, only four compounds have found their application in human medicine so far. However, they differ in their activity in poisoning with warfare nerve agents and pesticides and there is still no universal broad-spectrum oxime capable of protecting against all known OPC. In this article, we review data on structure-activity relationship of pyridinium oximes and discuss their pharmacological and toxicological significance.

Current understanding of the mechanisms involved in metabolic detoxification of warfare nerve agents.

This study reviews current understanding of chemical, biochemical and toxicological aspects and mechanisms of metabolism of warfare nerve agents. Among enzymes participating in metabolism of nerve agents the role of A-esterases, serum cholinesterase and carboxylesterases is discussed. This article also discusses other aspects of metabolism of the agents such as protein binding and the role of tissue depots for these compounds.

Effects of dexrazoxane and amifostine on evolution of Doxorubicin cardiomyopathy in vivo.

Doxorubicin is one of the most active drugs in oncology, with cardiotoxicity as a serious side effect of its application. The aim of this study was to investigate dexrazoxane and amifostine impact on the evolution of myocardial changes induced by doxorubicin. BalbC female mice were treated with doxorubicin only (10 mg/kg, single intravenous push), or with dexrazoxane (200 mg/kg, intraperitoneal [ip]) or amifostine (200 mg/kg, ip) 60 mins or 30 mins prior to treatment with doxorubicin, respectively. Blood sampling for determination of conventional serum-marker activity was performed 48 hrs later. The grade of histopathology changes was evaluated by light microscopy 1.5 and 3 months after treatments using the Billingham scoring method. Control groups consisted of nontreated mice. After doxorubicin-only treatment, the grade of heart tissue damage was found to increase in the period between 1.5 and 3 months. A similar but less intense progression was also detected in amifostine-pretreated animals, with significant difference among median Billingham scores between the two time points. The pretreatment with dexrazoxane suspended expansion of tissue lesions in time. Changes in serum enzyme activity revealed two correlations: the greater reduction in alpha-hydroxybutyrate dehydrogenase (alpha-HBDH) leakage is associated with a lower percentage of damaged tissue, and the creatine kinase to alpha-HBDH percent of difference ratio being greater than one is correlated with limited spreading of pathological lesions. Our results indicate that the development of doxorubicin-induced heart failure is based on a slow and persistent expansion of pathological process even long after the completion of the treatment. Dexrazoxane has proved to be successful and superior over amifostine against such an evolution of doxorubicin cardiomyopathy.

The association of exposure to cadmium through cigarette smoke with pregnancy-induced hypertension in a selenium deficient population.

Oxidative stress has been postulated as major contributor to endothelial dysfunction and pregnancy-induced hypertension. We have examined the association of exposure to cadmium through cigarette smoke with hypertension disorders during pregnancy in the selenium deficient population. Markers of lipid peroxidation and antioxidative defense were measured and correlated with cadmium blood concentration in normotensive and hypertensive pregnant smokers and nonsmokers. We have observed significantly higher blood Cd in hypertensive smokers and significant differences in all other parameters. Se concentrations were lower in smokers, both in normotensive and hypertensive group as well as values of nonenzymatic (Zn, Cu, and glutathione) and enzymatic (superoxide dismutase, glutathione peroxidase, and glutathione reductase) parameters of antioxidative defense. Results of the study indicate that exposure to cadmium through cigarette smoke in pregnant women, living in Se deficient areas is associated with significantly higher cadmium concentrations and lower levels of enzymatic and nonenzymatic antioxidants and that it can be considered as a risk factor for pregnancy-induced hypertension. Selenium supplementation should be considered for recommendation in such condition.

Current understanding of the application of pyridinium oximes as cholinesterase reactivators in treatment of organophosphate poisoning.

This paper reviews the mechanisms of interaction of organophosphorus compounds with cholinesterases and clinical signs of acute poisoning. Further, we describe the current understanding of the mechanisms of action of pyridinium oximes pralidoxime (PAM-2), trimedoxime (TMB-4), obidoxime (LüH-6, Toxogonin), HI-6 and HLö-7 which are used as cholinesterase reactivators in the treatment of poisoning with organophosphorus compounds. We also review the most important literature data related to the efficacy of these oximes in the treatment of poisoning with warfare nerve agents soman, sarin, tabun, VX and cyclosarin and organophosphorus insecticides. Finally, we discuss the criteria for selection of oximes intended for further development as antidotes in poisoning with organophosphorus compounds and auto-injectors for their application in urgent situations.