Hassan El-Fawal | Albany College of Pharmacy and Health Sciences (original) (raw)

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Papers by Hassan El-Fawal

Research paper thumbnail of Organophosphate neuropathy due to methamidophos: biochemical and neurophysiological markers

Archives of Toxicology, 1999

Neuropathy target esterase (NTE), the putative target enzyme for organophosphate induced delayed ... more Neuropathy target esterase (NTE), the putative target enzyme for organophosphate induced delayed polyneuropathy (OPIDP), can be measured in lymphocytes but has rarely been assessed in acute human poisoning. Serum autoantibodies to nervous system proteins develop in hens poisoned with neuropathic insecticides and also have not been studied after human poisoning. Serial lymphocyte NTE (LNTE) was measured in a 16-year-old boy after acute poisoning with methamidophos for evaluation as a predictor of subsequent neuropathy. The profiles of serum autoantibodies to neurofilament triplet proteins, myelin basic protein, and glial fibrillary acidic protein were measured in order to characterize changes occurring as a result of OPIDP. Clinical neuropathy characterized by steppage gate and profound lower extremity weakness, decreased grip and pinch strength, and decreased ulnar and absent tibial compound muscle action potentials developed 2 weeks following poisoning. Sensory examination and nerve conduction studies were normal. On day 3 following poisoning LNTE was depressed (77% compared with subsequent baseline enzyme activity). Marked increases in serum immunoglobulin G (IgG) autoantibodies to glial fibrillary acidic protein and to neurofilament 200 were observed after the development of OPIDP. We conclude that inhibition of lymphocyte NTE is predictive of subsequent OPIDP. Serum autoantibody titers to nervous system proteins may be useful markers of neuropathy.

Research paper thumbnail of Glial fibrillary acidic protein (GFAP) indicates in vivo exposure to environmental contaminants: PCBs in the Atlantic tomcod

Annals of The New York Academy of Sciences, 1993

Research paper thumbnail of Glial Fibrillary Acidic Protein (GFAP) Indicates in Vivo Exposure to Environmental Contaminants: PCBs in the Atlantic Tomcod

Annals of The New York Academy of Sciences, 1993

Research paper thumbnail of Ozone-Induced Alteration in β-Adrenergic Pharmacological Modulation of Pulmonary Macrophages

Toxicology and Applied Pharmacology, 1996

of b-adrenergic receptors on pulmonary macrophages results Ozone-Induced Alteration in b-Adrenerg... more of b-adrenergic receptors on pulmonary macrophages results Ozone-Induced Alteration in b-Adrenergic Pharmacological in a down-regulation of immune function and changes in the Modulation of Pulmonary Macrophages. MCGOVERN, T. J., ELstate of cell activation (Nijkamp and Henricks, 1990).

Research paper thumbnail of Nonspecific bronchial responsiveness assessed in vitro following acute inhalation exposure to ozone and ozone/sulfuric acid mixtures

Experimental Lung Research, 1995

Air pollution may play some role in the recent increase in severity and prevalence of asthma, but... more Air pollution may play some role in the recent increase in severity and prevalence of asthma, but the specific chemical components with the ambient pollutant mix that may be responsible have not been delineated. Since ambient exposures involve mixtures, it is essential to examine airway responses to realistic pollutant mixtures. This study examined the ability of single (3-h) inhalation exposures to ozone and to mixtures of ozone plus sulfuric acid to induce nonspecific airway hyperresponsiveness in healthy rabbits. Airway responsiveness was assessed using an in vitro assay involving administration of increasing doses of acetylcholine to bronchial rings obtained from animals exposed to 0.1-0.6 ppm ozone or to mixtures of ozone and 50-125 micrograms/m3 sulfuric acid aerosol; results were compared to those reported previously for sulfuric acid alone. Bronchial hyperresponsiveness to ozone was noted following exposure at all concentrations, but the combination of pollutants results in antagonism. The results support the potential for ozone to induce airway hyperresponsiveness in healthy animals and suggest that interaction with sulfuric acid may reduce the effectiveness of both pollutants.

Research paper thumbnail of Pulmonary Effects of Repeated Episodic Exposures to Nitric Acid Vapor Alone and in Combination with Ozone

Inhalation Toxicology, 1994

Abstract Inhaled acids are associated with adverse health effects, a conclusion based largely on ... more Abstract Inhaled acids are associated with adverse health effects, a conclusion based largely on studies with particulate-associated acid sulfates. The acidic component of ambient air in some regions, such as California, contains nitric acid (HNO3) vapor, but ...

Research paper thumbnail of Calpain Activity in Organophosphorus-induced Delayed Neuropathy (OPIDN): Effects of a Phenylalkylamine Calcium Channel Blocker

Annals of The New York Academy of Sciences, 1993

Calpains (calcium-activated neutral proteases) are cysteine proteases which have been identified ... more Calpains (calcium-activated neutral proteases) are cysteine proteases which have been identified in numerous cell types.' Two isozyrnes of calpain have been identified and designated calpain I and calpain 11, according to their requirement for either pM or mM concentration of calcium, respectively, for activation.? However, chicken tissues apparently contain only calpain II.3 Studies of both the central and peripheral nervous system indicate that proteases, including calpains, may precipitate the breakdown of cytoskeletal elements in Wallerian degeneration,' Alzheimers Disease4 and excitotoxicity.' This role of calpains in the pathophysiology of the nervous system is likely a consequence of increases in free cytosolic c a k i~m .~. '

Research paper thumbnail of Use of the Biventer Cervicis Nerve-Muscle Preparation to Detect Early Changes following Exposure to Organophosphates Inducing Delayed Neuropathy

Toxicological Sciences, 1990

Indices of organophosphorus (OP)-induced delayed neuropathy (OPIDN) in the hen model have traditi... more Indices of organophosphorus (OP)-induced delayed neuropathy (OPIDN) in the hen model have traditionally been restricted to the early inhibition of neuropathy target esterase (NTE) and ataxia with associated pathological changes in hind limb peripheral nerve which occur more than 7 days after OP exposure. The biventer cervicis nerve-muscle preparation was used to evaluate OPIDN in adult hens at various time periods after treatment with either the protoxicant tri-o-tolyl phosphate (TOTP), 360 mg/kg po, or the active congener phenyl saligenin phosphate (PSP), 2.5 mg/kg im. NTE activity was 21 and 48% of control for TOTP and PSP, respectively, 4 days after administration. Clinical signs were notable by 10 days and progressed in severity to paralysis by 21 days. Partial clinical recovery was evident at 37 days. Denervation hypersensitivity of biventer cervicis muscle to acetylcholine (ACh) was evident as early as 4 days following TOTP or PSP treatment. The sensitivity to ACh was greatest 21 days after OP administration, with partial recovery at 37 days. Strength-duration curves (SDC) of preparations from OP-treated hens showed an increase in excitability thresholds and elevated rheobase with shorter chronaxie than did preparations from controls as early as 4 days following treatment with either compound. SDC at 37 days indicated partial reinnervation. Peripheral nerve myelinated fiber degeneration and regeneration consistent with these physiological changes was seen on histopathological examination. This study suggests that the biventer cervicis nerve-muscle preparation may prove useful for detection of functional and morphological changes that occur during the interval between NTE inhibition and appearance of clinical deficits.

Research paper thumbnail of Organophosphate neuropathy due to methamidophos: biochemical and neurophysiological markers

Archives of Toxicology, 1999

Neuropathy target esterase (NTE), the putative target enzyme for organophosphate induced delayed ... more Neuropathy target esterase (NTE), the putative target enzyme for organophosphate induced delayed polyneuropathy (OPIDP), can be measured in lymphocytes but has rarely been assessed in acute human poisoning. Serum autoantibodies to nervous system proteins develop in hens poisoned with neuropathic insecticides and also have not been studied after human poisoning. Serial lymphocyte NTE (LNTE) was measured in a 16-year-old boy after acute poisoning with methamidophos for evaluation as a predictor of subsequent neuropathy. The profiles of serum autoantibodies to neurofilament triplet proteins, myelin basic protein, and glial fibrillary acidic protein were measured in order to characterize changes occurring as a result of OPIDP. Clinical neuropathy characterized by steppage gate and profound lower extremity weakness, decreased grip and pinch strength, and decreased ulnar and absent tibial compound muscle action potentials developed 2 weeks following poisoning. Sensory examination and nerve conduction studies were normal. On day 3 following poisoning LNTE was depressed (77% compared with subsequent baseline enzyme activity). Marked increases in serum immunoglobulin G (IgG) autoantibodies to glial fibrillary acidic protein and to neurofilament 200 were observed after the development of OPIDP. We conclude that inhibition of lymphocyte NTE is predictive of subsequent OPIDP. Serum autoantibody titers to nervous system proteins may be useful markers of neuropathy.

Research paper thumbnail of Glial fibrillary acidic protein (GFAP) indicates in vivo exposure to environmental contaminants: PCBs in the Atlantic tomcod

Annals of The New York Academy of Sciences, 1993

Research paper thumbnail of Glial Fibrillary Acidic Protein (GFAP) Indicates in Vivo Exposure to Environmental Contaminants: PCBs in the Atlantic Tomcod

Annals of The New York Academy of Sciences, 1993

Research paper thumbnail of Ozone-Induced Alteration in β-Adrenergic Pharmacological Modulation of Pulmonary Macrophages

Toxicology and Applied Pharmacology, 1996

of b-adrenergic receptors on pulmonary macrophages results Ozone-Induced Alteration in b-Adrenerg... more of b-adrenergic receptors on pulmonary macrophages results Ozone-Induced Alteration in b-Adrenergic Pharmacological in a down-regulation of immune function and changes in the Modulation of Pulmonary Macrophages. MCGOVERN, T. J., ELstate of cell activation (Nijkamp and Henricks, 1990).

Research paper thumbnail of Nonspecific bronchial responsiveness assessed in vitro following acute inhalation exposure to ozone and ozone/sulfuric acid mixtures

Experimental Lung Research, 1995

Air pollution may play some role in the recent increase in severity and prevalence of asthma, but... more Air pollution may play some role in the recent increase in severity and prevalence of asthma, but the specific chemical components with the ambient pollutant mix that may be responsible have not been delineated. Since ambient exposures involve mixtures, it is essential to examine airway responses to realistic pollutant mixtures. This study examined the ability of single (3-h) inhalation exposures to ozone and to mixtures of ozone plus sulfuric acid to induce nonspecific airway hyperresponsiveness in healthy rabbits. Airway responsiveness was assessed using an in vitro assay involving administration of increasing doses of acetylcholine to bronchial rings obtained from animals exposed to 0.1-0.6 ppm ozone or to mixtures of ozone and 50-125 micrograms/m3 sulfuric acid aerosol; results were compared to those reported previously for sulfuric acid alone. Bronchial hyperresponsiveness to ozone was noted following exposure at all concentrations, but the combination of pollutants results in antagonism. The results support the potential for ozone to induce airway hyperresponsiveness in healthy animals and suggest that interaction with sulfuric acid may reduce the effectiveness of both pollutants.

Research paper thumbnail of Pulmonary Effects of Repeated Episodic Exposures to Nitric Acid Vapor Alone and in Combination with Ozone

Inhalation Toxicology, 1994

Abstract Inhaled acids are associated with adverse health effects, a conclusion based largely on ... more Abstract Inhaled acids are associated with adverse health effects, a conclusion based largely on studies with particulate-associated acid sulfates. The acidic component of ambient air in some regions, such as California, contains nitric acid (HNO3) vapor, but ...

Research paper thumbnail of Calpain Activity in Organophosphorus-induced Delayed Neuropathy (OPIDN): Effects of a Phenylalkylamine Calcium Channel Blocker

Annals of The New York Academy of Sciences, 1993

Calpains (calcium-activated neutral proteases) are cysteine proteases which have been identified ... more Calpains (calcium-activated neutral proteases) are cysteine proteases which have been identified in numerous cell types.' Two isozyrnes of calpain have been identified and designated calpain I and calpain 11, according to their requirement for either pM or mM concentration of calcium, respectively, for activation.? However, chicken tissues apparently contain only calpain II.3 Studies of both the central and peripheral nervous system indicate that proteases, including calpains, may precipitate the breakdown of cytoskeletal elements in Wallerian degeneration,' Alzheimers Disease4 and excitotoxicity.' This role of calpains in the pathophysiology of the nervous system is likely a consequence of increases in free cytosolic c a k i~m .~. '

Research paper thumbnail of Use of the Biventer Cervicis Nerve-Muscle Preparation to Detect Early Changes following Exposure to Organophosphates Inducing Delayed Neuropathy

Toxicological Sciences, 1990

Indices of organophosphorus (OP)-induced delayed neuropathy (OPIDN) in the hen model have traditi... more Indices of organophosphorus (OP)-induced delayed neuropathy (OPIDN) in the hen model have traditionally been restricted to the early inhibition of neuropathy target esterase (NTE) and ataxia with associated pathological changes in hind limb peripheral nerve which occur more than 7 days after OP exposure. The biventer cervicis nerve-muscle preparation was used to evaluate OPIDN in adult hens at various time periods after treatment with either the protoxicant tri-o-tolyl phosphate (TOTP), 360 mg/kg po, or the active congener phenyl saligenin phosphate (PSP), 2.5 mg/kg im. NTE activity was 21 and 48% of control for TOTP and PSP, respectively, 4 days after administration. Clinical signs were notable by 10 days and progressed in severity to paralysis by 21 days. Partial clinical recovery was evident at 37 days. Denervation hypersensitivity of biventer cervicis muscle to acetylcholine (ACh) was evident as early as 4 days following TOTP or PSP treatment. The sensitivity to ACh was greatest 21 days after OP administration, with partial recovery at 37 days. Strength-duration curves (SDC) of preparations from OP-treated hens showed an increase in excitability thresholds and elevated rheobase with shorter chronaxie than did preparations from controls as early as 4 days following treatment with either compound. SDC at 37 days indicated partial reinnervation. Peripheral nerve myelinated fiber degeneration and regeneration consistent with these physiological changes was seen on histopathological examination. This study suggests that the biventer cervicis nerve-muscle preparation may prove useful for detection of functional and morphological changes that occur during the interval between NTE inhibition and appearance of clinical deficits.