Mapping the effect of drugs on ACE2 as a novel target site for COVID-19 therapy

Angiotensin converting enzyme 2 (ACE2) has potentially conflicting roles in health and disease. COVID-19 coronavirus binds to human cells via ACE2 receptor, which is expressed on almost all body organs. Boosting the ACE2 receptor levels on heart and lung cells may provide more cellular enter to virus thereby worsening the infection. Therefore, among the drug targets, ACE2 is suggested as a vital target of COVID-19 therapy. This hypothesis is based on the protective role of the drugs acting on ACE2. Therefore, this review discusses the impact and challenges of using ACE2 as a target in the current therapy of COVID-19.

Ophthalmic artery chemosurgery for retinoblastoma: an initial 3-year experience from two major institutes in Egypt

Background

Intra-arterial chemotherapy has shown promising results and improved the prognosis of retinoblastoma in the developed countries. Here, we aim to report our initial experience, in Egypt, in the treatment of all stages of naïve retinoblastoma with ophthalmic artery chemosurgery (OAC), using melphalan.

Results

The technique was successful in 23 out of 26 eyes. Overall, a total of 63 treatment sessions were performed. Ophthalmic artery catheterization was performed in 59 treatment sessions, whereas middle meningeal artery catheterization was performed in 4 treatment sessions. Adequate tumor control was achieved in 95.6%. Progression has developed in one eye after the third OAC session. The mean follow-up period was 18.5 months. Recurrence of the main tumor as well as vitreous and subretinal seeds was reported in one eye after 19-month duration. A globe salvage rate of 91.3% was attained. No metastasis was recorded, and all patients were alive within the stated follow-up period.

Conclusion

A high globe salvage rate along with metastasis free survival and mild complications were achieved. Therefore, our initial experience with OAC in primary retinoblastoma proved to be safe and effective.

Cocaine Hepatotoxicity and Its Potentiation by Lipopolysaccharide: Treatment and Gender Effects

This study was conducted to investigate the effect of a 7-day treatment as well as the influence of gender on cocaine hepatotoxicity (CH). Lipopolysaccharide (LPS) potentiation of CH was also investigated. Male and female CF-1 mice were orally administered 20 mg/kg body weight cocaine hydrochloride once daily for 7 days. Four hours after the last cocaine administration, the mice were administered 12 × 106 EU LPS (or equal volume of sterile saline) intraperitoneally. Plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were evaluated as indices of liver injury. Blood and liver glutathione (GSH), glutathione reductase (GRx), and catalase (CAT) activities were also determined to investigate the oxidation stress induced by the treatment. Plasma ALT and AST concentrations were elevated in all males receiving cocaine alone or cocaine + LPS. Furthermore, blood GSH and CAT were decreased and GRx activity was elevated in the same males. Histological analysis revealed a high degree of focal necrosis in the male cocaine group, and severe necrosis in the male cocaine + LPS group. Unlike males, females showed no effect of either cocaine alone or cocaine + LPS treatments. These results indicate that gender plays a significant role in CH and its potentiation by LPS and lengthening the administration by two treatments increased the severity of cocaine + LPS hepatotoxicity dramatically in male mice.

Influence of Gender on Cocaine Hepatotoxicity in CF-1 Mice

Gender is known to play a role in the bioavailability, metabolism, and lethality of many toxic substances. This study was conducted to investigate the influence of gender on cocaine hepatotoxicity (CH) and lipopolysaccharide (LPS) potentiation of CH. Male and female CF-1 mice were orally administered 20 mg/kg body weight cocaine hydrochloride once daily for 7 days. Four hours after the last cocaine administration, the mice were administered 12 × 106 EU LPS (or equal volume of sterile saline) intraperitoneally. Plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were evaluated as indices of liver injury. Blood and liver glutathione (GSH), glutathione reductase (GRx), and catalase (CAT) activities were also determined to investigate the extent of oxidative stress induced by the treatments. Serum ALT and AST concentrations were elevated in all males receiving cocaine alone or cocaine + LPS. Furthermore, blood GSH and CAT were decreased and GRx activity was elevated in these same animals. Histological analysis revealed a high degree of hepatic focal necrosis in the male cocaine group, and severe hemorrhagic necrosis in the male cocaine + LPS group. Unlike males, females showed no damage resulting from cocaine or cocaine + LPS exposure, whereas testosterone-supplemented ovariectomized females displayed histological and biochemical profiles statistically similar to males. The results demonstrate that the extent of CH or LPS-potentiated CH is influenced by gender and sex hormones, particularly testosterone.

Effect of Ketamine on Cocaine-Induced Immunotoxicity in Rats

The abuse of cocaine (COC) with ketamine (KET) is currently popular among young drug abusers and has been associated with increased risk of human immunodeficiency virus (HIV) infection. The effect of subacute exposure to COC and KET alone and in combination on the immune system was assessed in adult male Sprague-Dawley (SD) rats. To simulate the route and mode of human exposure, rats were treated with COC alone (5 mg/kg, IV), KET alone (100 mg/kg, PO) or KET followed immediately by COC (same doses and routes of administration) once-a-day for 7 consecutive days. Rats were sacrified 30 minutes following the last treatment. Total circulating leukocyte and lymphocyte counts were decreased with relative neutrophilia, whereas immunoglobulin M (Ig M) antibody response to sheep erythrocytes (SRBCs) was increased in animals treated with COC. Moreover, treatment with COC alone increased serum interleukin-10 (IL-10) concentration; however, it did not affect serum interferon gamma (INF-γ) concentration. Spleen histology showed hyperplasia of white pulp whereas thymus gland demonstrated mild cortical degeneration. On the other hand, KET treatment did not produce any significant change of any of these parameters. However, when coadministered with COC, significant reduction of bodyweight, spleen/bodyweight, and thymus/bodyweight ratios with degeneration of splenic white pulp and thymic cortex occurred. Moreover, the primary immunoglobulin response to SRBC and serum IL-10 concentration were decreased without significant change in serum IFN-γ or circulating leukocytic counts. COC caused a significant increase in serum corticosterone concentration that KET effectively prevented. On the other hand, a significant increase in plasma and tissue concentrations of norcocaine (NC) resulted following KET and COC administration in combination. Daily SKF-525A pretreatment at a dose of 30 mg/kg, IP, for 7 days 1 hour prior to KET and COC in combination effectively reversed the effects of this combination on body weight, organ/bodyweight ratios, histopathology, and serum Ig M and IL-10 concentrations without affecting leukocytic counts. On the other hand, SKF-525A pretreatment did not change the immunomodulatory effects of COC compared to non-pretreated animals. The results suggest that COC-induced immunomodulation most likely occurred through neuroendocrinal mechanisms. On the other hand, enhanced oxidative metabolism of COC in the presence of KET-induced immunosuppression.

Hepatitis C virus genotype distribution in Egyptian diabetic patients: a preliminary study

BACKGROUND AND STUDY AIMS

There is controversy regarding whether a specific hepatitis C virus (HCV) genotype is associated with diabetes mellitus. This study aimed to investigate HCV genotype distribution in diabetics and its relation to some clinical and laboratory variables in HCV-positive diabetic versus non-diabetic Egyptians in East Delta.

PATIENTS AND METHODS

The study included 100 HCV-positive patients of which 66 were diabetic in addition to 35 healthy adults as a control group. Clinical assessment, laboratory measurements of plasma glucose, insulin, C-peptide, C-reactive protein (CRP), tumour necrosis factor-α (TNF-α) and liver functions (alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyltransferase (GGT)) as well as HCV genotype determination were done, and AST/platelet ratio index (APRI) and Homoeostasis Model of Assessment-Insulin Resistance (HOMA-IR) were calculated.

RESULTS

The main results were the presence of HCV genotype 3, in 31.8% of the diabetic group and in 26.5% of the non-diabetic group, while the remainder of cases had genotype 4, the predominant genotype in Egypt. This is the first report of the presence of HCV genotype 3 in about 30% of an Egyptian cohort. However, there was no significant difference in genotype distribution between both groups. Further, there were significantly higher values of HOMA-IR, insulin and C-peptide in HCV-positive groups in comparison to the control group, while TNF-α was significantly higher in the HCV-positive diabetic group. However, there were no significant differences between both genotypes regarding these parameters.

CONCLUSION

Although this study reveals for the first time the presence of HCV genotype 3 in a significant percentage of a group of Egyptian patients, where the majority were diabetic, the association between diabetes and certain HCV genotypes could not be confirmed on the basis of our findings. Hence, taking into consideration the impact of such a finding on the treatment decisions of those patients, further studies are warranted to explore these findings to a greater extent.

Gender differences in cocaine pharmacokinetics in CF-1 mice

Hepatocellular damage is thought to occur as a result of cytochrome P450-mediated oxidation of cocaine to norcocaine (NC), a precursor of the hepatotoxic nitrosonium ion. However, this damage occurs only in male mice, with females exhibiting minimal biochemical and histological signs of hepatocellular stress. The objective of this study was to determine the plasma time course and tissue disposition of cocaine and its metabolites to further investigate the role that metabolism may play in the gender difference observed. Male and female CF-1 mice were orally administered 20mg/kg cocaine hydrochloride once daily for 7 days. Blood samples were withdrawn at various time points post-injection and analyzed for cocaine and its metabolites benzoylecgonine (BE), norcocaine, ecgonine methyl ester (EME), and ecgonine (E). In addition, tissue concentrations of cocaine and its metabolites were determined in liver, heart, brain, and kidney tissue. The results demonstrated that the plasma elimination half-life of cocaine is nearly three times longer in males versus females. Non-hepatotoxic hydrolysis metabolites BE, EME, and E were higher in female tissues while norcocaine was detected in tissues of male animals only. This study revealed that differences in cocaine pharmacokinetics and the resultant differences in the biodisposition of cocaine and its metabolites in tissues contribute to the mechanism of gender difference seen in cocaine hepatotoxicity.

Plasma butyrylcholinesterase activity protects against cocaine hepatotoxicity in female mice

Oral cocaine administration results in hepatic necrosis, increased plasma transaminase concentration, and decreased antioxidative capability, which is potentiated by lipopolysaccharide (LPS) in male CF-1 mice. Females administered the same treatment regimen display none of the hepatotoxic effects seen in their male counterparts. This study was conducted to further dissect the mechanism responsible for this gender difference in cocaine hepatotoxicity (CH) and lipopolysaccharide potentiation of CH. Male and female CF-1 mice were orally administered 20 mg/kg cocaine hydrochloride once daily for 7 days. Four hours after the last cocaine administration the mice were administered 12 x 10(6) EU LPS intraperitoneally. The activity of plasma esterase (butyrylcholinesterase), the enzyme responsible for the major pathway of cocaine metabolism to nonhepatotoxic metabolites, was measured. Aminotransferase release and histological analysis were used to determine hepatotoxicity. The concentration of the hepatotoxic precursor norcocaine was measured in the plasma and liver. Regardless of treatment, males were shown to have only 30% of the plasma esterase activity displayed by females. In addition, administration of testosterone to ovariectomized females resulted in a 70% reduction in plasma esterase activity when compared with surgically unaltered females. Moreover, hepatic norcocaine was not detected in the plasma or liver of surgically unaltered female animals, while it was present in males and testosterone-supplemented ovariectomized females. These results indicate that plasma esterase activity is heavily influenced by sex hormones, predominantly testosterone, in CF-1 mice. Suppression of plasma esterase by testosterone correlates with decreased norcocaine production and is therefore responsible, in part, for the increased CH seen following oral administration with and without LPS exposure in male CF-1 mice.

Endotoxin potentiates cocaine-mediated hepatotoxicity by nitric oxide and reactive oxygen species

Exposure to small, noninjurious doses of the inflammagen, bacterial endotoxin (lipopolysaccharide, LPS) augments the toxicity of certain hepatotoxicants, including cocaine. The mechanism of this interaction has not been clearly elucidated, but it seems that aspects of the inflammatory response initiated by exposure to LPS may be responsible. In particular, this study examined the role of Kupffer cells and the modulating effects of nitric oxide (NO) and reactive oxygen species (ROS) on the LPS potentiation of cocaine-mediated hepatotoxicity (CMH). Mice were administered oral cocaine hydrochloride for 5 consecutive days at a dose of 20 mg/kg with and without 12 x 10(6) EU LPS/kg given intraperitoneally (IP) 4 hours after the last cocaine injection. Pretreatment regimens consisted of administration of 300 mg/kg, IP, of aminoguanidine (AM) or 1,3-dimethylthiourea (DMU) at 1 hour or 15 minutes, respectively, before each cocaine administration. In another group, mice were pretreated with saline using the same cocaine and LPS treatment protocol, but received a single pretreatment of 7 mg gadolinium chloride (GdCl(3))/kg intravenously (IV), or sterile saline 24 hours prior to the LPS administration. The GdCl(3) (Kupffer cell inhibitor) pretreatment inhibited the LPS potentiation of CMH, but did not reverse the effects of cocaine alone. On the other hand, AM (NO synthase inhibitor), decreased the synthesis of NO as observed by the decrease in the plasma nitrate/nitrite level and completely reversed the hepatotoxic effects of cocaine and LPS alone and in combination. Moreover, DMU (hydroxyl free radical scavenger) ameliorated the effects of cocaine and significantly reduced the hepatotoxicity observed with the cocaine and LPS administration. These data suggest that cocaine sensitizes the liver and subsequent activation of Kupffer cells by LPS leads to the formation of increased levels of NO, which can promote oxidant stress and thus provide an environment favoring the generation of more reactive species such as the hydroxyl free radical.

Immunomodulation by cocaine and ketamine in postnatal rats

The abuse of cocaine (COC) in combination with ketamine (KET) among pregnant women was shown to be high. Transplacental exposure is not the only route by which a newborn may be exposed to these agents, but they can also distribute into breast milk. Chronic COC exposure is associated with immunological modulation in human and animal models. The effect of sub-chronic exposure to COC and KET alone and in combination on the developing immune system was assessed in neonatal male Sprague-Dawley (SD) rats. To simulate the route of exposure during lactation, newborn male rats were treated orally with saline, COC alone (20 mg/kg), KET alone (50 mg/kg), or KET (50 mg/kg) followed 15 min later by COC (20 mg/kg) from days 1 to 21 of life. Pups were sacrificed 30 min following the last treatment. Total circulating leukocyte and lymphocyte counts were decreased with relative neutrophilia, while spleen/body weight ratio and IgM antibody response to sheep red blood cells (SRBCs) were increased in animals treated with COC. Moreover, treatment with COC alone increased serum interleukin 10 (IL-10) concentration; however, it did not affect serum interferon gamma (IFN-gamma) concentration. On the other hand, KET treatment did not produce any significant change of any of these parameters. However, when co-administered with COC, the immunomodulatory effects of COC were prevented. COC caused a significant increase in serum corticosterone concentration that KET effectively prevented. Lack of significant change of plasma and tissue concentrations of norcocaine (NC) suggested no role for COC metabolism in COC-induced immunomodulation. However, the results of this study indicate that COC-induced immunomodulatory reactions and their prevention by KET most likely occurred through neuroendocrinal mechanisms.

Effect of a chemical mixture on dermal penetration of arsenic and nickel in male pig in vitro

The effect of a chemical mixture on the dermal penetration of arsenic or nickel was assessed by applying arsenic-73 or nickel-63 alone or with the chemical mixture to dermatomed male pig skin samples in flow-through diffusion cells. The chemical mixture consisted of chloroform, phenanthrene, and toluene for arsenic penetration studies and phenol, toluene, and trichloroethylene (TCE) for nickel studies. These are predominant chemicals found at hazardous waste sites. Arsenic and nickel bind to skin after dermal exposure. Total penetration of arsenic and nickel in the chemical mixture were significantly increased by 33% and 20% compared to arsenic and nickel alone, respectively. While more radioactivity penetrated skin with chemical treatment than metal alone, significantly less radioactivity was loosely adsorbed to skin and could be easily washed off from the skin surface with soap and water. The results of this study indicate that the potential health risk from dermal exposure to arsenic or nickel is enhanced if other chemicals are present.

Reduction of tissue concentration of cocaine in rat by ketamine

The coabuse of cocaine and ketamine occurs with high frequency. The presence of another active substance with cocaine allows for the potential of various drug-drug interactions to occur. This study investigated the tissue distribution after the administration of cocaine or ketamine alone and their combination in rat. Cocaine (5 mg/kg iv), ketamine (100 mg/kg by gavage), or ketamine followed by cocaine (same doses and routes of administration) was utilized. Tissue contents of cocaine and norcocaine were significantly lowered at 5, 15, and 30 min following ketamine administration versus cocaine alone. However, tissue contents of benzoylecgonine were significantly higher in the combination group compared to cocaine alone. On the other hand, cocaine administration did not affect the tissue disposition of ketamine. The results suggest that ketamine decreased cocaine tissue content, which may affect its pharmacological and toxicological profiles.

N-acetylcysteine pretreatment decreases cocaine and endotoxin-induced hepatotoxicity

Cocaine produces hepatotoxicity by a mechanism that remains undefined but has been linked to its oxidative metabolism. Endotoxin (lipopolysaccharide, LPS) is also a well-known cause of hepatic damage, and exposure to noninjurious doses of LPS increases the toxicity of certain hepatotoxins. Previously it was demonstrated that exposure to noninjurious doses of LPS dramatically increases cocaine-mediated hepatotoxicity (CMH). This study was conducted to investigate whether pretreatment with N-acetylcysteine (NAC), a glutathione (GSH) precursor and an antioxidant agent, inhibits LPS potentiation of CMH. For 5 consecutive days, male CF-1 mice were administered daily oral NAC (200 mg/kg) or sterile saline followed an hour later by cocaine (20 mg/kg) or sterile saline. Four hours following the last cocaine or saline treatment, the mice were administered 12 x 10(6) EU LPS/kg or sterile saline. For the cocaine alone and cocaine and LPS groups, NAC pretreatment significantly decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities with absence of necrotic hepatic lesions, indicating a reduction of liver injury. In addition, in all groups pretreated with NAC, hepatic GSH concentration was significantly increased, as were hepatic and blood glutathione peroxidase (GPx) and catalase (CAT) activities. In conclusion, the results demonstrate that NAC pretreatment exerted a protective effect against LPS potentia-tion of CMH.

Inhibition of cocaine oxidative metabolism attenuates endotoxin potentiation of cocaine mediated hepatotoxicity

The oxidative metabolism of cocaine by the microsomal monooxygenase enzymes has been postulated to be essential for cocaine mediated hepatotoxicity (CMH). Endotoxin (lipopolysaccharide, LPS), a well-known cause of hepatic damage, previously has been demonstrated to dramatically increase CMH. The mechanism of this interaction has not been clearly elucidated, but cocaine oxidative metabolism appears to sensitize hepatocytes so that subsequent exposure to small amounts of LPS can further augment CMH. This study was conducted to investigate if dimethylaminoethyl-2,2-diphenylvalerate (SKF-525A) pretreatment inhibits LPS potentiation of CMH. For 5 consecutive days, male CF-1 mice were administered daily SKF-525A (50 mg/kg) or sterile saline followed an hour later by cocaine (20 mg/kg) or sterile saline. Four hours following the last cocaine or saline treatment, the mice were administered sterile saline 12x10(6) EU LPS/kg, i.p. The mice were sacrificed 18 h later by decapitation. Pretreatment with SKF-525A reversed the hepatic injury caused by cocaine alone or cocaine and LPS treatments, as indicated by both histologic evaluation and serum alanine transaminase (ALT) and aspartate transaminase (AST) activities. In particular, SKF-525A completely reversed the effects of cocaine alone on liver and blood reduced gluthathione (GSH), glutathione peroxidase (GPx) and catalase (CAT) and hepatic glutathione reductase (GRx) activities. However, SKF-525A was ineffective against the effect of LPS alone on liver and blood GPx and CAT or on hepatic GSH and GRx, suggesting that these effects were not mediated by cytochrome P450 oxidative metabolism. The pattern of biochemical changes persisting with SKF-525A pretreatment in the LPS and cocaine group resembled those of the LPS alone group. The results suggest that cytochrome P450 oxidative metabolism of cocaine is largely responsible for CMH with potentiation by LPS achieved through a different mechanism involving oxidative stress.

Endotoxin potentiates the hepatotoxicity of cocaine in male mice

Cocaine produces hepatotoxicity by a mechanism that remains undefined but that has been linked to its oxidative metabolism. Endotoxin (lipopolysaccharide, LPS) is also a well-known cause of hepatic damage, where exposure to non-injurious doses of LPS increases the toxicity of certain hepatotoxins. This study was conducted to investigate the possible potentiation of cocaine-mediated hepatotoxicity (CMH) by LPS. Male CF-1 mice were administered oral cocaine hydrochloride for 5 consecutive days at a dose of 20 mg/kg with and without 12 x 10(6) EU LPS/kg given intraperitoneally 4 h after the last cocaine injection. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured as markers of liver injury. Blood and liver glutathione (GSH) levels were determined, as well as the activities of glutathione peroxidase (GPx) and catalase (CAT). In addition, the activity of liver glutathione reductase (GRx) was measured. The results demonstrate that endotoxin potentiated the hepatotoxicity of cocaine. Serum ALT and AST were significantly elevated with the combined cocaine and LPS treatment versus all other treatments. While cocaine alone resulted in centrilobular necrosis, the cocaine and LPS combination produced submassive necrosis. The increased hepatic GSH content and GRx activity observed with cocaine alone were not observed with the combination treatment, rendering the liver more susceptible to oxidative stress. Moreover, there was a significant decrease in the activities of hepatic GPx and CAT, particularly with the combination treatment. In conclusion, this study demonstrates that LPS potentiates the hepatotoxicity of cocaine as revealed by an array of biochemical and morphological markers.

The role of ketamine on plasma cocaine pharmacokinetics in rat

Ketamine has gained attention recently because of re-emergence of its abuse especially in combination with cocaine. When more than one drug is present simultaneously, the potential for drug--drug interaction exists, which can be pharmacokinetic, pharmacodynamic or both in nature. The objective of this study was to investigate the effect of ketamine on plasma cocaine pharmacokinetics to assess the role that the kinetic component may play in the interaction of these agents. Moreover, the effect of repetitive administration of ketamine pretreatment on the pharmacokinetics of cocaine was addressed. Male Sprague-Dawley rats were treated with cocaine alone (5 mg/kg i.v.), ketamine alone (100 mg/kg by gavage), or ketamine followed by cocaine (the same routes and doses). Blood samples were withdrawn at different time points post-injection and analyzed for determination of cocaine, its metabolites (benzoylecgonine and norcocaine) and ketamine. The results demonstrated that ketamine caused a significant decrease in cocaine's area under the curve (AUC) and elimination half-life while its total clearance was increased. The AUC of benzoylecgonine was increased by 1.5-fold after the combination compared with cocaine alone. However, cocaine did not affect ketamine's pharmacokinetic parameters. In the pretreatment study, ketamine was given orally for 3 days, followed 18 h later by a single i.v. of cocaine. Further enhancement of cocaine metabolism occurred with the appearance of norcocaine. This investigation revealed that ketamine enhances cocaine metabolism and may affect its toxicological profile.

Development and validation of a high-performance liquid chromatography method for the determination of cocaine, its metabolites and ketamine

Cocaine abuse is an extensive problem in the USA. During the past decade, ketamine abuse also has emerged as a public health concern and is now considered a controlled substance. The prevalence of the simultaneous use of cocaine and ketamine has been shown to be high. Previous research indicates that ketamine affects the enzymes that metabolize cocaine. In order to investigate this pharmacokinetic interaction, it was necessary to identify and quantitate each compound. The aim of this study is to develop a method of detecting and resolving cocaine, its metabolites and ketamine. A new precise, accurate and sensitive reversed-phase high-performance liquid chromatography method has been developed and validated. This assay employed a phosphate-buffered aqueous mobile phase (pH 6.9) with an organic component consisting of acetonitrile and methanol and a C-18 column as stationary phase at 225 nm wavelength. Minimum detection limits were 5 ng ml(-1) for cocaine and 10 ng ml(-1) for benzoylecgonine, norcocaine and ketamine. Linearity was demonstrated over a broad range of concentration in plasma, with good sensitivity for ketamine, cocaine and cocaine metabolites.

In vitro hepatotoxicity of alachlor and its by-products

During water treatment, potentially hazardous chemical by-products may be formed. Alachlor (2-chloro-N-(2, 6-diethylphenyl)-N-(methoxymethyl) acetamide) is a widely used pre-emergence herbicide. The present study investigated the toxicity of alachlor and its disinfection by-products on freshly isolated rat hepatocytes. Hepatocytes were harvested by a collagenase perfusion technique and were exposed to different concentrations of alachlor and its by-products for up to 2 h. Cell viability, the leakage of aspartate transaminase (AST) and alanine transaminase (ALT) and glutathione (GSH) depletion were determined throughout the incubation period. The cell viability of the hepatocytes exposed to 100 microg ml(-1) alachlor was decreased by 20% compared with the control after 60 min of incubation. At the same concentration of alachlor the leakage of ALT and AST was increased by 56% and 45%, respectively. Cell viability of the hepatocytes was decreased upon exposure to 2-chloro-N-(3-chloro-2,6-diethylphenyl)-N-(methoxymethyl) acetamide (CCDMA) and 2-chloro-N-(3-chloro-2,6-diethylphenyl) acetamide (CCDA)--the by-products of alachlor and chlorine--after 60 min of exposure. At 100 microg ml(-1) CCDMA the AST leakage was increased significantly (73%) after 30 min of incubation. The reaction mixture of alachlor (100 microg ml(-1)) and chlorine dioxide (1 ppm) caused significant increases in cell loss and ALT and AST levels by 22%, 40% and 34%, respectively, as early as 15 min incubation. Alachlor (100 and 200 microg ml(-1)) caused significant decreases in GSH contents (62%) in isolated hepatocytes. The reaction mixture of alachlor and chlorine dioxide led to significant glutathione depletion (44%) after 60 min of incubation. The by-products of alachlor and chlorine--CCDMA and CCDA--depleted GSH almost completely (93%). This investigation suggested that the by-products formed from the reaction of alachlor and chlorine decreased GSH and increased the leakage of liver enzymes, especially AST.

Oral cocaine produces dose-related hepatotoxicity in male mice

Cocaine remains a widely abused substance. While most addicts take cocaine intranasally, a considerable number abuse cocaine by mouth. It has been assumed that after oral exposure cocaine is hydrolyzed in the stomach rendering it ineffective. This study investigated the effect of orally administered cocaine on liver function and integrity as well as its effect on liver and blood antioxidative enzymes. Male CF-1 mice were orally administered either 0, 5, 10 or 20 mg cocaine/kg body weight and sacrificed 24 h after the last treatment. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured as markers of liver injury. Blood and liver glutathione (GSH) levels were determined as well as the activities of glutathione peroxidase (GPx) and catalase (CAT). In addition, the activity of liver glutathione reductase (GRx) was also measured. The results demonstrated that oral cocaine caused hepatotoxicity in a dose dependent manner. Serum ALT and AST were elevated while blood GSH concentration decreased in all cocaine treated animals. In addition, there was a significant dose dependent decrease in the activities of GPx and CAT in blood and liver of cocaine treated animals. However, hepatic GSH content and GRx activity manifested a significant increase, particularly in the group, which received 20 mg/kg cocaine. This study is the first to demonstrate that cocaine-induced hepatotoxicity results following the oral route of administration.

Oral bioaccessibility of trivalent and hexavalent chromium in soil by simulated gastric fluid

Chromium is found in soil from natural sources and anthropogenic activities. The ingestion of soil contaminated with chromium especially by children can have toxic consequences. Therefore, it is important to quantify the oral bioaccessibility of chromium in chromium in contaminated soil. In this study, chromium-51 as chromic (III) chloride and sodium chromate (VI), was mixed with an Atsion sandy soil and a Keyport clay soil and stored for 4 mo at either 21-25 degrees C or 2-4 degrees C. Utilizing simulated gastric conditions, the oral bioaccessibility of chromium in soil was determined. When the effects of soil on the bioaccessibility of chromium were compared, the data revealed the the bioaccessibility of chromium (III) from the clay soil was significantly lower than from the sandy at 21-25 degrees C. However, at 2-4 degrees C, more chromium (III) was extracted by synthetic gastric fluid from the clay soil than from the sandy soil. Temperature was also a factor as evidenced by the higher bioaccessibility of chromium (IV) in the sandy soil at 2-4 degrees C and of both chromium species in the clay soil at the same temperature. Reduction of the soluble chromium (VI) chemical to the nonsoluble chromium (III) compound in the acidic soils by naturally occurring organic matter in soil would explain the lower bioaccessibilty of chromium (VI) at 21-25 degrees C. At 2-4 degrees C, the data indicate that the rate of chromium (VI) reduction to chromium (III) was slowed. Although the results of this study are limited to one low concentration of chromium (III) and chromium (VI) and indicate that the bioaccessibility of chromium in soil can range between 18% and 72%, the data also suggest that there may be a potential health hazard from oral exposure to chromium in heavily contaminated sites. Therefore, more extensive research should be conducted to determine if thes findings can be extended to environmentally relevant concentrations.

The role of enzyme induction and inhibition on cypermethrin hepatotoxicity

Cypermethrin at different concentrations (100, 200, 400 and 800 ng ml(-1)) was incubated with a primary culture of rat hepatocytes. Cypermethrin was cytotoxic to rat hepatocytes at concentrations of 200 ng ml(-1)or greater. Toxicity was measured by a decrease in cell viability and leakage of ALT and AST enzymes into the culture medium. The role of cytochrome P450 in the hepatotoxicity of cypermethrin insecticide was investigated in fresh hepatocytes isolated either from phenobarbital pretreated rats or control rats and coincubated with SKF525A. Pretreatment with phenobarbital strongly protected the hepatocytes against the cypermethrin induced loss of cell viability percentage and increased enzyme leakage percentage. Coincubation of the hepatocytes with SKF525A, a well-known cytochrome P450 inhibitor, substantially potentiated the effect of cypermethrin on cell viability and enzyme leakage. These results suggest that the cytocidal hepatotoxicity of cypermethrin in primary hepatocyte culture depends on its parent compound and phenobarbital, as a cytochrome P450 inducer, could be of therapeutic value.

Geographic information systems as a tool for control program management for schistosomiasis in Egypt

During a 4-year study a geographic information system (GIS) risk model was constructed for predicting the relative risk of schistosomiasis in Kafr El-Sheikh governorate, Egypt. A 1-year 1990-1991 time series on diurnal temperature difference (dT) prepared from the advanced very high resolution radiometer (AVHRR) sensor on the NOAA-11 satellite was used to develop a regional risk model for the Nile delta based on thermal-hydrological domains. A May 15, 1990 Landsat TM scene (path 177, Row 38) was used to develop a local 'village-scale' environmental risk model based on higher resolution satellite sensor data (30 m picture element size at earth surface). Four of ten classes derived from a tasseled cap (Tcap) transformation of the Landsat TM scene were shown to be significantly related to a 5-year Schistosoma mansoni prevalence database from the Ministry of Health. A risk model was developed based on dT and the proportional area of the four Tcap classes in 5 km(2) buffer zones centered on rural health unit (RHU) reporting units. Available historical data on S. mansoni and its snail host Biomphalaria alexandrina, as well as recent field collected data were gathered and incorporated as separate themes. Model validation was done using data collected on snail population bionomics-infection rates, water quality, underground water table and cercariometry at 13 hydrologically representative sites. The role of soil type, water table and water quality was studied at 79 of 154 rural health unit sites. The model permitted retrieval of relevant data by RHU point location. For the first time in Egypt, the Kafr El-Sheikh GIS schistosoma prediction model can support MOH efforts to make more accurate control program decisions based on environmental predilection sites of endemic Schistosomiasis mansoni.

Effects of omeprazole on ethanol lesions

Male Sprague-Dawley rats were used to study the effects of omeprazole on normal and ethanol damaged gastric mucosa, and to estimate plasma gastrin levels following the administration of omeprazole for 2 weeks. The dosage of omeprazole was 50 mg/kg body weight, once daily via gavage. In omeprazole treated animals, serum gastrin levels showed statistically significant increases compared with the control and ethanol treated animals. Our results indicate that omeprazole has no protective effect on ethanol-induced alterations in gastric mucosa and, in fact, appears to produce worsened lesions. In achlorohydric doses, omeprazole can induce significant gastrin levels with consequent hypertrophy and hyperplasia of enterochromaffin-like cells and somatostatin cells. It is believed that this powerful drug should be reserved for patients who are refractory to standard H(2)-receptor antagonist therapy.

In vitro penetration of soil-aged mercury through pig skin

The dermal bioavailability of mercury "aged" in soil for 3 mo was compared to that of pure mercury (without soil) and to mercury in brief contact with soil (16 h). Studies were conducted in vitro with [203Hg]mercuric chloride on dermatomed male pig skin by flow-through diffusion cell methodology. Less than 0.5% of the initial mercury dose penetrated through skin into receptor fluid after each treatment. The majority of pure mercury became covalently bound to skin. However, a short contact time with either an Atsion (sandy) or Keyport (clay) soil significantly decreased the total penetration of mercury (sum of receptor fluid and skin) by 40%. After aging, a 95% reduction in total penetration was observed for the compound relative to chemical without soil. Both soils bind mercury more strongly with time, as evidenced by larger quantities of radioactivity in soil and smaller amounts in skin decontaminate after aging than in soil for 16 h. Decreased mercury bioavailability with aging indicates lower health risk and reduced need for soil cleanup.

Teratogenic effect of ketamine and cocaine in CF-1 mice

Pregnant CF-1 mice were used to study the teratogenic effect of ketamine and cocaine, alone and in combination. The dose of ketamine was 50 mg/kg and that of cocaine was 20 mg/kg, given intravenously (tail) once daily (these doses of ketamine and cocaine are comparable to doses used by addicted humans). Treatment was started from day 6 to day 15 of gestation, and dams were sacrificed on day 18. There were significant decreases in the fetal weight and length in the combined group. Skeletal defects such as incomplete ossification of skull bones and vertebrae were observed in both the cocaine and combined group, compared with the control. An increased frequency of cerebral and abdominal hemorrhages as well as hydrocephalus and hydronephrosis was observed in the combined group. This study showed that fetal exposure to ketamine and cocaine in combination was more teratogenic than each drug alone in CF-1 mice.

Pharmacokinetics of acrylamide after oral administration in male rats

Acrylamide (AMD) is a commonly used industrial chemical. However, it produces a dying back type of peripheral neuropathy in animals and man. This study was performed to investigate the pharmacokinetics of AMD after oral administration at 50 mg/g ([1-(14)C]AMD) in male Sprague-Dawley rats. Absorption from the gastrointestinal tract was rapid and radioactivity was detected in blood 5 min post-administration. The peak plasma concentration occurred 38 min after administration and was equivalent to 47 μg/ml. The elimination pattern for plasma was fitted to a one-compartment model with 6 h half-life. However, in the blood the elimination pattern was fitted to a two-compartment model with 7.93 and 374 h for distribution and elimination phases, respectively. Tissue concentrations of radioactivity determined at 28 and 144 h post-administration differed substantially. After 28 h the highest activity was in the gastric content, followed by stomach, lung, bone marrow and skin, while after 144 h the order of total radioactivity was lung>bone marrow>esophagus. The activities in the rest of the organs in both experiments were very low. The excretion study revealed that the kidney is the major route of elimination and the majority of radioactivity in urine was excreted during the first 12 h. The feces contained approximately 10% of the administered dose after 144 h. This study indicated that AMD is rapidly absorbed from the rat's gastrointestinal tract, distributed and eliminated from the body. AMD bound but did not accumulate in the erythrocytes or the neural tissues.

Effect of alcohol and/or cocaine on blood glutathione and the ultrastructure of the liver of pregnant CF-1 mice

Alcohol and cocaine are abused by the general population as well as by pregnant women. Since alcohol and cocaine are hepatotoxic, pregnant mice were used to study the effect of alcohol and/or cocaine on alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and on liver ultrastructure. Also, blood glutathione (GSH) and GSH related enzymes such as glutathione reductase (GSH-Rx) and glutathione peroxidase (GSH-Px) were studied. The mice were treated with 0.6 g/kg ethanol twice daily via gavage and/or 20 mg/kg of cocaine hydrochloride intravenously once daily. The treatment was from day 6 to 15 of gestation and these studies were performed at day 18. Our results indicated a significant increase in AST level after treatment with ethanol alone or in combination with cocaine. The blood GSH levels decreased significantly in all the treated groups compared to the control. The activity of GSH-Px was significantly decreased only in the ethanol and cocaine combination group compared to the control. Histopathological studies indicated that co-administration of ethanol and cocaine lead to a significant potentiation in liver toxicity as indicated by increased fatty infiltration.

Ethanol does not increase the hepatotoxicity of cocaine in primary rat hepatocyte culture

Rat hepatocytes were utilized to investigate the role of cocaine metabolism and the contribution of ethylcocaine formation to cocaine-induced liver damage. Hepatocytes were prepared from rats pretreated with saline, phenobarbital or ethanol and exposed to cocaine, ethanol, or their combination. Hepatotoxicity was assessed by lactate dehydrogenase (LDH) leakage and was correlated with cocaine metabolism which was assessed quantitatively using HPLC. Only phenobarbital-pretreatment produced increases in LDH leakage from cultures exposed to cocaine. This increase in LDH release occurred simultaneous to a decrease in benzoylecognine formation and a marked increase in norcocaine generation. Exposing cultures to ethanol alone did not result in LDH leakage from hepatocytes. Furthermore, including ethanol in cultures treated with cocaine did not enhance the LDH leakage produced by cocaine alone. This study confirms quantitatively that cocaine-induced hepatotoxicity is mediated through cocaine oxidative events and is enhanced by microsomal induction produced by phenobarbital. The finding that ethylcocaine formation was maximal in the ethanol-pretreatment group where no toxicity was observed suggests that ethylcocaine is not the agent responsible for the hepatotoxicity observed in this study.

Trials for control of ixodid ticks using pheromone acaricide tick decoys

Experimental application of Hyalomma dromedarii pheromone-impregnated in cyfluthrin (pyrethroid) decoys on experimentally infested camels revealed efficacy rate of 85.33%, while the control group showed normal pattern of tick engorgement. This study proved the rapid movement of males toward decoys and some males took the mounting position with such decoys. On the other side, the same decoys (H. dromedarii) when used on naturally infested cattle with Boophilus annulatus did not even disturb the Boophilus ticks indicating that B. annulatus contain specific pheromones which should be furtherly identified.

Kinetics and rat locomotor activity following cocaine and lidocaine administration

Cocaine abuse is a widespread problem in the USA. Illicit cocaine is usually never found in pure form but is adulterated with other agents, among which are the local anesthetics such as lidocaine. Adulteration of cocaine with another active agent allows the potential for various drug-drug interactions to occur. The presence of an additional active agent in illicit cocaine samples can complicate the pharmacological and toxicological responses elicited and possibly the mode of emergency medical care thereafter. When studying drug interactions, both the kinetic and dynamic aspects of each agent must be considered. This study investigated the plasma time course and tissue distribution of cocaine and lidocaine alone and in combination following a 5 mg kg(-1) intravenous injection in rats. The plasma time course of cocaine and lidocaine in combination did not differ from that seen when each drug was alone. Tissue contents were without change when administered alone or in combination at 5, 10 and 15 min following treatment. However, rats treated with cocaine and lidocaine in combination had significantly greater locomotor activity initially than animals treated with cocaine alone. The results suggest that cocaine and lidocaine interact on a pharmacodynamic basis without a change in the drug level of each agent.

Effect of propofol on perception of pain in mice: mechanisms of action

The latencies of pain threshold to different subhypnotic doses (12.5, 25 and 50 mg kg-1) of propofol, an anaesthetic, administered intraperitoneally (i.p.) into male mice were measured using a hot plate method. The possible mechanism of pain control by propofol was also investigated through blocking beta-endorphin receptors and measuring serum level of beta-endorphin. Morphine (1.5 mg kg-1; i.p.) was used as a reference of reduction of pain sensation. The results showed that propofol in doses of 25 and 50 mg kg-1 significantly (P < 0.01) increased the latency of pain threshold but a lower dose (12.5 mg kg-1) failed to produce any significant change. This indicates that propofol reduced pain and this effect is dose-dependent. Propofol prevents hyperalgesia produced by prostaglandin PGE2, (0.5 mg kg-1, i.p.; P < 0.01). Pretreatment with naloxone (1.0 mg kg-1, i.p.) abolished significantly (P < 0.01) the antinociceptive action of propofol. Furthermore, serum level of beta-endorphin was increased (P < 0.01) after propofol injection particularly at the peak time of propofol action. The serum level of corticosterone was also increased (P < 0.01) at the time of beta-endorphin release. It was concluded that propofol can control pain and this action may be centrally modulated through the opioid system rather than at the level of the spinal cord.

Hepatoprotective activity of thymoquinone in isolated rat hepatocytes

Thymoquinone, the active constituent of Nigella sativa, was tested in isolated rat hepatocytes as a hepatoprotective agent against tert-butyl hydroperoxide (TBHP) toxicity. TBHP (2 mM) was used to produce oxidative injury in isolated rat hepatocytes and caused progressive depletion of intracellular glutathione (GSH), loss of cell viability as evidenced by trypan blue uptake and leakage of cytosolic enzymes, alanine transaminase (ALT) and aspartic transaminase (AST). Preincubation of hepatocytes with 1 mM of either thymoquinone or silybin, which is a known hepatoprotective agent, resulted in the protection of isolated hepatocytes against TBHP induced toxicity evidenced by decreased leakage of ALT and AST, and by decreased trypan blue uptake in comparison to TBHP treated hepatocytes. Both thymoquinone and silybin prevented TBHP induced depletion of GSH to the same extent. Although thymoquinone protected the liver enzymes leakage, the degree of protection was less than that caused by silybin.

Effect of cypermethrin on isolated male and female rat hepatocytes

Cypermethrin is a synthetic pyrethroid that belongs to a group of insecticides with low mammalian toxicity but high insecticidal activity. The present study was designed to investigate the toxicity of cypermethrin on freshly isolated hepatocytes from male and female rats. Hepatocytes were harvested by a collagenase perfusion technique and were exposed to different concentrations of cypermethrin (100, 200, 400, or 800 ng/2 x 10(6) cells) for up to 2 h. Cell viability and the leakage of aspartate transaminase (AST) and alanine transaminase (ALT) were determined throughout the incubation period. The cell viability of the hepatocytes from male and female rats exposed to 400 ng and 800 ng was significantly reduced after 60 and 30 min of incubation, respectively. With cells from female rats, viability was also reduced upon exposure to 200 ng cypermethrin for 2 h. The decrease in cell viability was dose and time dependent. The leakage of ALT and AST was significantly increased with 400 and 800 ng concentrations at 60 and 30 min, respectively. ALT leakage from female hepatocytes was significantly increased at 60 min of incubation with the 200-ng dose, whereas 2 h of incubation was required for the leakage of ALT from the cells of male rats. The present data indicate that cypermethrin has toxic effects on male and female rat hepatocytes in a dose- and time-dependent manner. The data suggest that female rat hepatocytes may be more sensitive to the toxic effects of cypermethrin than male cells.

Influence of atenolol and/or metformin on glutathione and magnesium levels in diabetic rats

Recently there has been growing interest in studying the differences between different classes of antihypertensive drugs in preventing cardiovascular events in diabetic patients. Hypomagnesemia is common in diabetes mellitus, and correlates to its chronic complications and the associated alteration of the antioxidant enzyme activity. Depletion of reduced glutathione (GSH) in the blood has been demonstrated with myocardial injuries associating hypomagnesemia. A previous study has demonstrated a beneficial effect of metformin hydrochloride (Met), an antihyperglycemic drug, on both magnesium (Mg) and GSH levels in diabetic animals. The purpose of this study was to investigate the effect of oral atenolol, metformin (50 and 60 mg kg[-1] day[-1], respectively) and their combination for 14 days on Mg and GSH levels in blood, liver and heart of diabetic male Wistar rats, as these two parameters have been shown to be altered in diabetics and linked to myocardial ischemic injuries. The results of this investigation showed a state of low levels of Mg and GSH in both blood and liver of the diabetic animals. Treatment with atenolol alone did not change these levels significantly, however administration of metformin or atenolol/metformin increased significantly the GSH levels in both liver and blood, and returned the liver Mg content back to normal values.

Development and validation of a satellites based geographic information system (GIS) model for epidemiology of Schistosoma risk assessment on snail level in Kafr El-Sheikh Governorate

The aim of the present study was to test the accuracy of Advanced Very High Resolution Radiometer (AVHRR) satellite derived temperature difference (dT) maps as a guide for the suitability of the environment for local snail hosts and Schistosoma development-transmission at the village level. The study provided field validation data from 13 villages in Kafr El Sheikh in the Nile Delta that sites present in wet zones of low dT value have more abundant snail populations than that present in the drier zones with high dT values. Results suggest that lower dT values were associated with wetter hydrologic regimes related to the level of underground water table and that this is reflected in the abundance of snail populations and Schistosoma snail infection rates at the village level. Water quality parameters on pH salinity and dissolved oxygen were not correlated with presence of Schistosoma infected snails. Results indicate that abundance of snails and S. mansoni prevalence are related to thermal-hydrology domains associated with surface water, that habitat suitability is related to depth to water table and that regional hydrology characteristics that affect snail host habitat suitability (ie. wet, moist, dry or very dry) can be evaluated using AVHRR dT maps.

Decreased cocaine- and lidocaine-induced seizure response by dextromethorphan and DNQX in rat

The present study investigated the effect of dextromethorphan and 6,7-dinitroquinoxaline-2,3-dione (DNQX) pre-treatment on the development of cocaine- and lidocaine-induced seizures. The dopaminergic action of cocaine was also studied. The NMDA antagonist dextromethorphan and the non-NMDA (AMPA/kainate) antagonist DNQX both significantly decreased the intensity of the seizure response to intravenous convulsant doses of cocaine and lidocaine individually (20 mg/kg) and in combination (5 mg/kg each). The incidence of seizures in rats receiving cocaine or lidocaine individually was significantly reduced by pre-treatment with dextromethorphan but not DNQX. Haloperidol did not have an effect on the incidence or intensity of seizures induced by cocaine or lidocaine, alone or in combination. The results suggest that local anesthetic-induced convulsive seizures are mediated by excitatory glutamate transmission through both NMDA and non-NMDA receptor systems.

Role of ethanol exposure on cocaine metabolism in rat hepatocytes

Cocaine remains a widely abused illicit substance in our society. Cocaine hepatotoxicity has been linked to cocaine metabolism. Cocaine can undergo hydrolytic inactivation via plasma and hepatic esterases or it can be N-oxidized by cytochrome P-450 and FAD-containing monooxygenases. Ethanol is frequently used in combination with cocaine. The presence of ethanol can affect the metabolism of other agents, depending on the dose and duration of exposure. In this investigation, hepatocytes isolated from male Sprague-Dawley rats were utilized to study the effect of ethanol exposure on cocaine metabolism. Hepatocytes were isolated using a two-step collagenase perfusion system. Hepatocytes (2 x 10(6) cells ml(-1)) were exposed to cocaine, ethanol or the combination of cocaine and ethanol for a 2-h period in a shaking water-bath at 30 oscillations per minute maintained at 37 degrees C. Sodium fluoride (NaF) was added to aliquots of cells which were removed from the incubation following 30, 60 and 120 min. The cells were homogenized on ice and immediately extracted for the quantification of cocaine, benzoylecognine, norcocaine and ethylcocaine by HPLC. Quantitative analysis revealed that there was a time-dependent increase in the disappearance of cocaine from hepatocytes. The rate of cocaine disappearance was not changed when ethanol was included in incubations containing cocaine. However, in the presence of ethanol there was a difference in the quantities of cocaine metabolites produced. When ethanol was included in incubations containing cocaine, the formation of norcocaine and benzoylecognine was less than that formed in hepatocytes exposed to cocaine alone. Additionally, when hepatocytes were exposed to cocaine in combination with ethanol, the formation of ethylcocaine was linear with time. This study revealed that in the presence of ethanol, cocaine qualitative metabolism is altered.

Geographic information systems and the distribution of Schistosoma mansoni in the Nile delta

New computer-based sensor technology and geographic methods have led to emerging interest in use of satellite environmental assessment tools for design of disease control programs, especially for those that are vector borne. The long-range goal of work reported here by John Malone and colleagues on behalf of this Egyptian Ministry of Health-USAID Schistosomiasis Research Project team (Box 1) is to utilize data from sensor systems on board earth-observing satellites to develop more-sensitive disease-prediction and -control models. If successful, methods developed may provide a potentially vital capability for use by disease control program managers, particularly in less-developed countries, where mapping resources are not well advanced. Longer term, broader basic questions on the interaction of environment and disease in anticipation of predicted global climate change may be addressed. These studies focused on the lower Nile river basin of Egypt. The specific objective was to link data on environmental requirements for propagation and transmission of schistosomiasis with parameters measurable from space.

Cocaine and lidocaine in combination are synergistic convulsants

The abuse of cocaine has dramatically increased in the recent decade. Cocaine obtained on the illegal market is rarely found in pure form. Most often it is adulterated with various substances, especially other local anesthetics. Lidocaine is one of the most common local anesthetics employed for adulteration of illicit cocaine. Toxicity due to the simultaneous ingestion of cocaine and lidocaine has been reported. Acute toxicity to cocaine and other local anesthetics is manifested in central nervous system aberrations, such as seizures and convulsions. This study investigated the convulsant potency of cocaine and lidocaine alone and in combination. Rats were administered intravenous injections of 5 mg/kg or 20 mg/kg of cocaine or lidocaine alone and in combination in equal proportion. Seizure activity and intensity were evaluated. The plasma concentration and brain content of each agent was also determined at the time of toxicity. The administration of 5 mg/kg of each drug alone did not yield seizure activity. However, the concomitant administration of 5 mg/kg of both cocaine and lidocaine produced a seizure response nearly equal to that produced after administration of 20 mg/kg of cocaine alone. Diazepam pre-treatment successfully antagonized the seizures induced by cocaine and lidocaine and raised the seizure threshold dose for the combination treatment by approximately four fold. The results suggest that cocaine and lidocaine interact synergistically to increase seizure activity and that the nature of this response occurs in part through a depression of inhibitory neuronal transmission.

Teratogenic effect of diphenylhydantoin and/or fluphenazine in mice

Diphenylhydantoin and fluphenazine are two drugs that act on the central nervous system. Many patients are taking these two drugs together and sometimes during pregnancy. Therefore, this study was conducted to determine the safety or the teratogenic effect of these two drugs alone or in combination. Pregnant mice were administered diphenylhydantoin at 50 mg kg-1 body wt. and/or fluphenazine at 1 mg kg-1 body wt. by gavage. The control group was administered the vehicle of diphenylhydantoin (water containing 0.6% alcohol). All pregnant animals were treated from day 6 to day 15 of gestation. The females were sacrificed on day 18. A significant reduction of fetal weight and length was found in all treatment groups when compared to the control. As regards to skeletal anomalies, it was found that the incidence of incomplete ossification of sternebrae and skull bones was significantly increased in the combination group when compared to the control group. Examination of visceral anomalies showed that dilated cerebral ventricles were observed in the fluphenazine-treated group, with the incidence of these malformations increasing significantly when diphenylhydantoin was administered in combination with fluphenazine. In summary, the administration of diphenylhydantoin and fluphenazine in combination was shown to be more teratogenic than each drug alone.

Development and validation of a high-performance liquid chromatography method for the determination of cocaine, its metabolites and lidocaine

Street cocaine varies in purity and is often adulterated with various compounds. Some of these additives, such as lidocaine, may increase the toxicity of cocaine. A new precise, accurate and sensitive reversed-phase high-performance liquid chromatography method for the determination of cocaine, its metabolites and lidocaine in plasma samples has been developed and validated. This assay employed a phosphate-buffered aqueous mobile phase (pH 6.0) with an organic component consisting of acetonitrile and methanol and a C-18 column as the stationary phase. Minimum detection limits were 1 ng ml-1 for cocaine, 2.5 ng ml-1 for ethylcocaine and 5 ng ml-1 for benzoylecgonine, norcocaine, norethylcocaine and lidocaine. Linearity was demonstrated over a broad range of concentrations in plasma, with good sensitivity for cocaine and cocaine derivatives.

Safety evaluation of benzophenone-3 after dermal administration in rats

Benzophenone-3 (BZ-3) is a category 1 (over-the-counter) product approved by the US Food and Drug Administration (FDA) for use as a sunscreen agent in medicine, cosmetics, industry, and agriculture. This is due to its ability to absorb and dissipate ultraviolet light in a harmless manner, thus protecting human skin and products from UV irradiation. This study investigated the safety of BZ-3 after repeated administration. BZ-3 in ointment base was applied at a dose of 100 mg/kg body wt. twice daily, for 4 weeks to the skin of male Sprague-Dawley rats. Body weight, organ to body weight ratios, hematological, and clinical chemistry parameters were not effected. Pathological examination revealed no significant changes between control and treated animals. No gross external abnormalities were observed. Both in vivo and in vitro blood glutathione (GSH) levels were effected by BZ-3 treatment. However, after 60 min of incubation, a reversal of this effect was observed in the treatment group as blood GSH levels approached normal levels. Furthermore, investigation of GSH-reductase and peroxidase with time indicated an increase in GSH-reductase activity at 60 and 90 min with no effect on GSH-peroxidase. Pre-treatment with phenobarbital modulated the metabolic disposition of BZ-3. There was an increase in the formation of the hydroxy metabolites but not the O-dealkylated form. This study suggests that BZ-3 is not toxic to rats when applied dermally at a dose of 100 mg/kg body wt. for 4 weeks.

Effect of metformin on glutathione and magnesium in normal and streptozotocin-induced diabetic rats

Recently there has been growing interest in magnesium deficiency and its correlation with coronary artery disease, chronic complications of diabetes mellitus and antioxidant enzyme activity. Hypomagnesemia is a common association of diabetes mellitus, and the blood glutathione (GSH) level is significantly lower in both conditions. Metformin (Met), 'an oral antihyperglycemic drug' frequently used in the management of diabetes mellitus outside the USA, has been shown to have an insulin-like action. The purpose of this study was to investigate the effect of oral administration of Met (60 mg kg(-1)) for 14 days on GSH and magnesium levels in blood, liver and heart of normal and streptozotocin-induced diabetic Wistar rats. Diabetes was induced by an i.p. injection of streptozotocin (60 mg kg(-1)). Our results showed that Met did not affect fasting serum glucose concentration in non-diabetic animals but reduced it significantly in diabetic animals. Serum and liver magnesium levels were significantly decreased in the untreated diabetic group compared with the normal group. Treatment with Met improved liver magnesium concentration in the diabetic group only. It has no effect on serum magnesium in diabetic or non-diabetic rats. Heart magnesium levels showed non-significant changes in all groups. In diabetic animals a significant decrease of GSH in both blood and liver was observed. Treatment with Met increased these levels significantly, with a similar effect on GSH levels in non-diabetic rats. There were no significant changes in heart GSH levels in any of the groups. This study demonstrates that oral Met therapy improves the altered levels of magnesium and GSH in diabetic rats.

Comparison between oral and dermal bioavailability of soil-adsorbed phenanthrene in female rats

Phenathrene is a major coal tar component found in hazardous waste disposal sites. The purpose of this study was to evaluate the extent to which phenanthrene adsorption to either of 2 different soils affects the manner in which phenanthrene is subsequently handled in orally and dermally exposed adult female rats. Absorption from the gastrointestinal tract was relatively rapid for all treatments with maximum plasma concentration of radioactivity occurring within 1 h following oral administration. After dermal application, the time to reach maximum plasma concentration (12 h) was the same in all 3 phenanthrene treatment groups although sandy soil lowered the area under the plasma concentration time curve (AUC) compared to the pure and clay soil groups. Dermal exposure increased absorption half-lives 8-fold compared to oral exposure in the pure group and 15-fold in each of the soil groups. After oral or dermal treatment with phenanthrene alone or adsorbed to soil, the urine represented the primary excretion route of 14C activity. Ileum contained the highest tissue concentration of radioactivity in all oral treatment groups. However, the skin application site contained the highest concentration of radioactivity followed by ileum after dermal exposure. Phenanthrenequinone and 9,10-phenanthrene dihydrodiol were the major urinary metabolites detected in the 0-12-h urine of all treatment groups in both routes of administration. The data suggest that the oral exposure route for phenanthrene is a greater health risk than the dermal route. However, the presence of sandy or clay soil tends to delay the elimination of phenanthrene from the plasma.

Evaluation of the use of uncertainty factors in deriving RfDs for some chlorinated compounds

Risk assessment of exposure to chemicals having a toxic endpoint routinely uses the reference dose (RfD) approach based on uncertainty factors of 10. The purpose of this investigation was to evaluate whether the magnitude of the U.S. Environmental Protection Agency (EPA) 10x uncertainty factors has scientific merit when compared with data from recent human and animal experimental studies. A compilation and comparison of ratios between LOAEL/NOAEL (lowest observed adverse effect level/no observed adverse effect level) and subchronic/chronic values was made for six chlorinated compounds, namely, carbon tetrachloride, methylene chloride, pentachlorophenol, monochlorobenzene, chlorpyrifos, and 1,1-dichloroethane. Data sets demonstrated that 91.3% of the LOAEL/NOAEL ratios were < or = 6 while 87% of the ratios for the same parameter were < or = 5. Furthermore, subchronic/chronic ratios were < or = 3.5. From our investigation we concluded that automatic safety factors of 10x are not scientifically supportable and are overly conservative for the chlorinated compounds studied here.

Pharmacokinetics of benzophenone-3 after oral exposure in male rats

Benzophenone-3 (BZ-3) is one of the UV-absorbing agents that has been used in industry and medicine for more than 30 years. Millions of consumers are exposed to benzophenones on a daily basis owing to the widespread use of these compounds in many of the products on the market, such as lipsticks, hair sprays, hair dyes, shampoo and detergent bars and sunscreen lotions. This study was performed to investigate the pharmacokinetics of BZ-3 after oral administration at 100 mg kg-1 body weight in male Sprague-Dawley rats. Absorption from the gastrointestinal tract was rapid because BZ-3 was detected in blood 5 min after administration. The peak plasma concentration (Cmax) was 25.6 +/- 4.6 micrograms ml-1 and the time of occurrence (tmax) was 3.0 +/- 0.4 h. The half-life of absorption of BZ-3 was 0.71 h. The elimination pattern was biphasic with alpha and beta half-lives of elimination of 0.88 and 15.90 h, respectively. The results of this study indicate the presence of strong binding between the plasma protein and BZ-3. Tissue distribution studies at 6 h indicate that the liver contained the highest concentration of free (58.9 +/- 23.8 micrograms) and total (free+bound or conjugated) BZ-3 (2087 +/- 60.1 micrograms), followed by kidney and testes, respectively. Urine and feces analysis indicate that urine was the major route of excretion, followed by feces. Further analysis of urine samples also indicates that conjugation of BZ-3 with glucuronic acid was the major systemic elimination route for the compound.

Salicylamide reverses the aspirin-antagonistic effect of salicylic acid on rat platelet cyclooxygenase

The antagonistic effect of salicylic acid (SA), the major metabolite of aspirin, on aspirin (ASA)-induced inhibition of cyclooxygenase has been recognized in vivo and in vitro. Salicylamide is available with aspirin in some analgesic preparations. Salicylamide shares important characteristics with salicylic acid including the lack of effect on cyclooxygenase and platelet aggregation as well as a close structural resemblance. This prompted us to study the interaction of salicylamide with aspirin and/or SA on rat platelet and cyclooxygenase. Our results showed that salicylamide has, unlike SA, no blocking effect on the anticyclooxygenase effect of aspirin in vitro. Moreover, salicylamide could dose-dependently prevent the aspirin-blocking effect of SA on platelet cyclooxygenase. These results suggest that salicylamide and SA compete for a receptor on cyclooxygenase different to that of aspirin. A functional model of cyclooxygenase enzyme is proposed.

A comparative study of the kinetics and bioavailability of pure and soil-adsorbed naphthalene in dermally exposed male rats

The aim of this study was to utilize pharmacokinetic techniques to assess the bioavailability of sandy or clay soil-adsorbed naphthalene vs chemical alone following dermal treatment of male rats. Animals were exposed to 43 micrograms total of 14C-naphthalene (pure or adsorbed to one of two soils) introduced into a shallow glass cap covering a 13-cm2 area on the skin of each rat. While both soils delayed the time to reach maximum plasma concentration of radioactivity and significantly increased the half-life of plasma absorption, only sandy soil significantly decreased the peak plasma concentration of radioactivity versus the pure compound. Within 12 h after dermal application, approximately 50% of the naphthalene dose was excreted in the urine of the pure and clay soil-adsorbed groups. However, when naphthalene was adsorbed to sandy soil, the percentages of the initial dose excreted in the urine collected between 0-12 h and 12-24 h were nearly equal (33-39%). Furthermore, sandy soil adsorption shifted the secondary excretion route from expired air to feces and significantly lowered the amount of radioactivity in expired air relative to naphthalene alone. In the presence of sandy soil, a significantly larger amount of radioactivity washed off of the skin application sites. In all groups the predominant urinary metabolites determined by high performance liquid chromatography were 2,7- and 1,2-dihydroxynaphthalenes.

Soil decreases the dermal penetration of phenol in male pig in vitro

Skin is a primary route of exposure to phenol, a major chemical found in hazardous waste sites. The effect of soil adsorption on the dermal bioavailability of phenol was assessed by applying [14C]phenol alone (P) or with sandy (P-S) or clay (P-C) soil to dermatomed male pig skin samples in flow-through diffusion cells. Maximum penetration of P-S and P-C was significantly decreased by one-half and by two-thirds, respectively, compared to P. Furthermore, the penetration of phenol into receptor fluid and the amount bound to skin were significantly lower when phenol was adsorbed to either soil versus P. While less radioactivity penetrated skin with soil-adsorbed phenol treatment than P, significantly more radioactivity was loosely adsorbed to skin and could be easily washed off of the skin surface by soap and water. Only a small fraction (< 5%) of the chemical was metabolized by skin to hydroquinone and catechol in all treatment groups. The results of this study indicate that the bioavailability and thus the potential health risk from dermal exposure to phenol is reduced if the chemical is adsorbed to soil.

Evaluation of chloroform cardiotoxicity utilizing a modified isolated rat cardiac myocytes

An improved technique for the isolation of cardiac myocytes from adult rat is described. This method produced a high yield of isolated cardiomyocytes (30-35 x 10(6) cells/heart) with viability over 88%. The rod-shaped cells represented about 70% of the viable cardiac myocytes. The leakage of creatine phosphokinase (CPK) in the incubation medium from the control was about 37% at zero time. This model was used to investigate chloroform (CHCl3) cardiotoxicity by measuring dye exclusion, change the viable cardiac myocytes shape and CPK leakage. As a result of CHCl3 exposure, there was a significant decrease in Trypan blue exclusion after 30 min and during the entire time course. The percentage of rod-shaped cells decreased significantly during the whole period of the study. Also, a significant elevation in CPK leakage after treatment with 1000 ppm CHCl3 was observed. The data show that the present technique for cardiomyocytes isolation from adult rats produced high percentage of viable cells. Furthermore, the toxic effect of CHCl3 on cardiac myocytes was time dependent.