In vitro methods to study chemically-induced hepatotoxicity: a literature review

Understanding the hepatotoxicity of drugs and chemicals is essential for progress in the pharmaceutical industry, medical science and academic research. The study of hepatotoxicity in vitro is complicated by the difficulty of maintaining hepatocytes in culture due to a lack of understanding of the humoral and matrix requirements of these cells. A variety of in vitro models of the liver have been developed, such as perfused livers, liver slices and three-dimensional perfused bioreactors, but the static cell culture is the most commonly used system. In this review we present the advantages and disadvantages of each system and their roles in the study of hepatotoxicity. We will also discuss how the various culture conditions such as medium and matrix composition affect the systems. The technological advances, which started the fields of genomics, proteomics and metabonomics are playing a very important role in uncovering novel biochemical pathways and markers of toxicity. Several of these studies have focused on hepatotoxicity, particularly on the effects of acetaminophen, carbon tetrachloride and aflatoxin B1. Finally, we will discuss the new field of systems biology, which focuses on interpreting and integrating data from all of the other fields.     

Antioxidant effect of nimodipine in young rats after pilocarpine-induced seizures

Nimodipine (ND) is a centrally active calcium antagonist that blocks the voltage-dependent L-type channels. Its antiepileptic properties have been proved in various animal models, including pilocarpine-induced seizures in adult rats. In order to investigate protective effects of the ND (10 (ND10) and 30 mg/kg (ND30), i.p.), young male rats (21-day-old) received ND injections before pilocarpine administration (400 mg/kg, s.c., pilocarpine group (P400)). The pretreatment with ND10 and ND30 prolonged the latencies of seizures and death on this seizure model. ND pretreatment in two doses decreased the levels of lipid peroxidation when compared to pilocarpine group. The P400 administration increased the striatal catalase activity. However, the administration of ND, in dose of 30 mg/kg, 30 min before pilocarpine, preserved catalase activity in normal levels. On the other hand, no change was detected in the animals treated with the dose of 10 mg/kg. Our results confirm the neuroprotective effect of ND on the seizures in young rats, suggesting that this drug acts positively on lipid peroxidation. Our observations shows that nimodipine cannot induces these effects via blockade of Ca(2+)-channel.     

Role of dopamine and glutamate receptors in cocaine-induced social effects in isolated and grouped male OF1 mice

Cocaine administration in paired male mice decreases social contacts as well as increases avoidance and flee elements. As dopamine (DA) and glutamate seem to be involved in some of cocaine's effects, an attempt was made to assess whether a range of associated receptors influenced the social impacts of this drug of abuse. The NMDA antagonist memantine (10 and 40 mg/kg); the AMPA antagonist CNQX (1 and 20 mg/kg); the DA release inhibitor CGS 10746b (2 and 8 mg/kg): the DA D1 antagonist SCH 23390 (0.05 and 0.5 mg/kg); and the DA D2/D3 antagonist raclopride (0.03 and 0.3 mg/kg) were administered prior to 25 mg/kg of cocaine and behaviour was evaluated during an encounter between an experimental and a standard opponent in a neutral cage for 10 min. Memantine reverts cocaine-induced social withdrawal and the increase in avoidance and flee, CNQX being effective only in these latter actions. On the other hand, SCH 23390 counteracts the social as well as the defensive action of cocaine, raclopride being effective only in blocking the cocaine-induced increase in avoidance and flee behaviours. In conclusion, although both neurotransmitter systems are involved in the effects of cocaine on social behaviour, NMDA and D1DA receptors seem to have an important role.     

Windows of detection of tetrazepam in urine, oral fluid, beard, and hair, with a special focus on drug-facilitated crimes

Reducing the capacity of a victim to react against sexual assault, coupled with a possible abrupt unconsciousness-inducing effect and ease of administration in spiked drinks, have resulted in the use of sedative agents in cases of drug-facilitated offence. Among these compounds, tetrazepam may impair an individual rapidly. The chances of detecting this substance increase if the most sensitive methods are used and if the biologic matrix that allows the longest possible detection time is available. To document the window of detection of tetrazepam, 50 mg of the drug was administered orally to 2 volunteers, and the following samples were collected: oral fluid (n = 1) over 515 minutes, urine (n = 2) over 236-240 hours, hair (n = 2) 4 weeks after exposure, and beard (n = 1) over 34 days. Tetrazepam was analyzed by LC-MS/MS (Micromass Quattro Micro) after alkalinization and extraction by dichloromethane/diethyl ether in the presence of diazepam-d5, used as internal standard. Reversed-phase separation on an XTerra MS C18 column was achieved in 12 minutes, under gradient conditions. Pseudo-molecular ions selected were m/z 289.2 and 290.2 for tetrazepam and the internal standard (IS), respectively, and the corresponding daughter ions selected were m/z 225.2 and 253.2 for tetrazepam and m/z 154.1 and 198.3 for the IS. Urine tested positive for tetrazepam over 236-240 hours (14-13 ng/mL). Oral fluid tested positive for tetrazepam over 515 minutes (2.5 ng/mL). Tetrazepam was detected in beard over 27 days (6.5 pg/mg). A single tetrazepam dose was detected in hair 4 weeks after intake (123-175 pg/mg). Tetrazepam tested positive over the studied time intervals but would be expected to be detectable for a considerably longer time. Therefore, in cases of drug-facilitated crimes in which tetrazepam is involved, hair and beard analyses can be an important complement to urine analyses to document exposure, particularly if LC-MS/MS is used.     

A case of absent right and persistent left superior vena cava: echocardiographic diagnosis

A 49-year-old man underwent transthoracic echocardiography for atypical chest pain. A dilated coronary sinus was found and venous contrast echocardiography raised the suspicion of absent right and persistent left superior vena cava. Transesophageal echocardiography showed no presence of right superior vena cava. The echocardiographic findings were confirmed by upper venous digital subtraction cavography.     

Challenges in determining how child work affects child health

Credible findings from well-crafted research studies are essential in assessing the impact of child work on children's health. Researchers, however, encounter significant challenges in defining the relevant group of workers for a study and identifying an appropriate comparison group. This article describes some of those challenges and explains how choices about study and comparison groups can lead to biased research results. When selecting study groups, researchers should be aware that the impact of work on health may depend on the type and intensity of the work, and on the context in which it occurs. They should avoid drawing conclusions about the health effects of particular work situations from studies of very heterogeneous groups of workers and should not overgeneralize from studies of more homogenous groups. When choosing comparison groups, researchers should select children whose health outcomes are likely to be comparable to the outcomes working children would experience if they did not work. In particular, researchers should attempt to find children who are similar to the workers of interest on relevant non-work characteristics, including socioeconomic status and levels of parental education. In addition, they should consider the extent to which healthier children are more likely to select into the labor force as a result of decisions by parents or employers, or due to their own greater fitness. Ideally, studies of the health effects of child work should use multiple comparison groups, including children who work in relatively safe, non-strenuous occupations.     

Equivalence of information from single versus multiple frequency bioimpedance vector analysis in hemodialysis

BACKGROUND: In suspended cells, low-frequency current only passes through extracellular fluids, while current at higher frequencies passes through extra- and intracellular fluids. Cells in soft tissues are in contact with each other, which causes tissue anisotropy, meaning that impedance changes along different cell directions, with part of low-frequency current also passing through cells. Hence, equivalent information on body impedance change is expected at all frequencies, which we proved in a dynamic condition of fluid removal with hemodialysis. METHODS: We performed whole-body impedance spectroscopy (496 frequencies from 4 to 1024 kHz, SEAC SFB3 analyzer; Brisbane, Australia) before and during fluid removal (0, 60, 120, 180 min, 2.5 kg) in 67 hemodialysis patients. With increasing current frequency, resistance (R) decreases and reactance (Xc) moves along the Cole's semicircle on the R-Xc plane. RESULTS: The Cole's semicircles progressively enlarged and moved to the right on the R-Xc plane following fluid removal (increase in both R and Xc values at any given frequency). Xc values at 5 kHz (expected values close to 0 Ohm) were 70% of the maximun Xc, indicating an intracellular current flows at low frequencies. The correlation coefficient between R at 50 kHz (standard frequency) and R at other frequencies ranged from 0.96 to 0.99, and the correlation coefficient between Xc at 50 kHz and Xc at other frequencies at any time point ranged from 0.65 to 0.99. CONCLUSION: From high Xc values at low frequency, tissue anisotropy is inferred. Intra- and extracellular current flow causes equivalence of information based on functions of R and Xc measurements made at 50 kHz versus other frequencies.