In vitro toxicity in long-term cell culture of MR contrast agents targeted to cartilage evaluation.

OBJECTIVE: Contrast-enhanced magnetic resonance (MR) imaging methods have been proposed for non-invasive evaluation of osteoarthritis (OA). We measured cell toxicities of cartilage-targeted low-generation dendrimer-linked nitroxide MR contrast agents and gadopentetate dimeglumine (Gd-DTPA) on cultured chondrocytes. DESIGN: A long-term Swarm rat chondrosarcoma chondrocyte-like cell line was exposed for 48-h to different salts (citrate, maleate, tartrate) and concentrations of generation one or two diaminobutyl-linked nitroxides (DAB4-DLN or DAB8-DLN), Gd-DTPA, or staurosporine (positive control). Impact on microscopic cell appearance, MTT spectrophotometric assays of metabolic activity, and quantitative PicoGreen assays of DNA content (cell proliferation) were measured and compared to untreated cultures. RESULTS: Chondrocyte cultures treated with up to 7.5 mM Gd-DTPA for 48-h had no statistical differences in DNA content or MTT reaction compared to untreated cultures. At all doses, DAB4-DLN citrate treated cultures had results similar to untreated and Gd-DTPA-treated cultures. At doses >1 mM, DAB4-DLN citrate treated cultures showed statistically greater DNA and MTT reaction than maleate and tartrate DAB4-DLN salts. Cultures exposed to 5 mM or 7.5 mM DAB8-DLN citrate exhibited rounded cells, poor cell proliferation, and barely detectable MTT reaction. Treatment with 0.1 µM staurosporine caused chondrocyte death. CONCLUSION: Long-term exposure, greater than clinically expected, to either DAB4-DLN citrate or Gd-DTPA had no detectable toxicity with results equivalent to untreated cultures. DAB4-DLN citrate was more biocompatible than either the maleate or tartrate salts. Cells exposed for 48-h to 5 mM or 7.5 mM DAB8-DLN salts demonstrated significant cell toxicity. Further evaluation of DAB8-DLN with clinically appropriate exposure times is required to determine the maximum useful concentration.

Role of oxygen radicals in 12-O-tetradecanoylphorbol-13-acetate-induced squamous differentiation of cultured normal human bronchial epithelial cells.

The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) inhibits growth and induces terminal squamous differentiation of normal human bronchial cells when added to the culture media [J. C. Willey, A. J. Saladino, C. Ozanne, J. F. Lechner, and C. C. Harris, Carcinogenesis (lond.), 5: 209-215, 1984]. We have investigated the possibility of oxygen free radicals being involved as intermediates in this process. Electron paramagnetic resonance measurements using the spin-trapping agent 5,5-dimethyl-1-pyrroline-1-oxide failed to detect oxygen free radicals in bronchial epithelial cells exposed to TPA, although oxy radicals were detected in bronchial epithelial cells after a nontoxic exposure to menadione, and in human neutrophils after exposure to TPA. Addition to the culture media of free radical scavenger, i.e., reduced glutathione, N-acetylcysteine, D-alpha-tocopherol, copper (II) (3,5-diisopropylsalicyclic acid)2, or the combination of superoxide dismutase and catalase did not affect the dose-dependent growth inhibition of TPA on the bronchial epithelial cells. Moreover, exposure of the bronchial epithelial cells to TPA did not result in increased DNA single strand breaks measured by alkaline elution, as would be expected with a free radical mediated mechanism. Thus, our results argue against the importance of oxygen free radicals in the inhibition of growth and the induction of squamous differentiation by TPA in normal human bronchial epithelial cells.

Role of paraquat in the uncoupling of nitric oxide synthase.

Nitric oxide synthase (NOS) oxidizes L-arginine to NO(&z.ccirf;) and L-citrulline. Recent studies have shown that this enzyme can also generate O(2)(&z.ccirf;-) during its enzymatic cycling. Herein, we used spin trapping and electron paramagnetic resonance (EPR) spectroscopy to investigate the impact paraquat has on the transport of electrons through purified neuronal NOS (NOS I). In a concentration-dependent manner, ranging from 10-100 microM of paraquat, paraquat free radical was observed under anaerobic conditions. This demonstrates that NOS shunts electrons to paraquat, thereby uncoupling this enzyme. This resulted in enhanced production of O(2)(&z.ccirf;-) at the expense of NO(&z.ccirf;). Experiments demonstrated that the reductase domain is the site of paraquat-mediated uncoupling of NOS.

Does peroxynitrite generate hydroxyl radical?

Nitric oxide reacts with superoxide at a diffusion controlled rate to form peroxynitrite. Some studies have indicated that peroxynitrite underwent homolytic cleavage to give the highly toxic hydroxyl radical, while others have suggested that the decomposition of peroxynitrite did not generate hydroxyl radical. Because of this controversy, the fate of peroxynitrite decomposition was investigated using electron spin resonance (EPR) spectroscopy in combination with spin trapping technique. Utilizing 4-pyridyl 1-oxide N-tert-butylnitrone (4-POBN)/ethanol as a spin trapping system, we found that peroxynitrite, at physiological pH in either the absence or the presence of chelated iron, will produce hydroxyl radical. Further quantification experiments indicated that the yield of hydroxyl radical formation was only about 1-4%. Since the concentration of hydroxyl radical produced is so low, the cytotoxicity mediated by peroxynitrite might not be due to the formation of this free radical.

Detection of free radicals as a consequence of rat intestinal cellular drug metabolism.

Because the intestine is the first pass organ for orally administered drugs and because some of these drugs are known to undergo oxidative metabolism leading to the formation of free radicals, we investigated the potential for this to occur in cell suspensions of rat enterocytes. As part of our study, the effect of intracellularly produced superoxide on cellular metabolism was investigated. The drugs chosen were the quinone, menadione and the aromatic nitro-containing compound, nitrazepam. On incubation of both drugs with isolated enterocytes and the spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), rapid appearance of an electron paramagnetic resonance (EPR) spectrum was recorded which was characteristic of hydroxyl radicals being spin trapped by DMPO giving 2,2-dimethyl-5-hydroxy-1-pyrrolidenyloxyl (DMPO-OH). Experiments were conducted which determined that the EPR spectrum of DMPO-OH resulted from the initial spin trapping of superoxide by DMPO to yield the corresponding nitroxide, 2,2-dimethyl-5-hydroxyl-1-pyrrolidenyloxyl (DMPO-OOH). Bioreduction of DMPO-OOH by glutathione peroxidase led to the rapid formation of DMPO-OH. We believe this enzymic pathway accounted for the EPR spectrum noted in incubations with either drug in the presence of the spin trap, DMPO. The incubation of enterocytes with both drugs did not mediate release of 51Cr nor lactate dehydrogenase. However, production of 14CO2 from [14C]glucose was severely inhibited (4-5-fold) in the presence of both drugs, while the incorporation of [14C]leucine into trichloroacetic acid precipitable protein was antagonized by menadione only. We conclude that superoxide can be demonstrated to arise as the result of enterocyte metabolism of menadione or nitrazepam. The consequence of oxidative metabolism of these drugs results in cellular dysfunction.

Intracellular spin-trapping of oxygen-centered radicals generated by human neutrophils.

Phagocytosing neutrophils secrete superoxide into a vacuole generally inaccessible for direct study. However, the spin-trapping agent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) enters the cytoplasm of several cell types where it can report free radical species including superoxide and hydroxyl radical. In the present study we employed a variety of experimental conditions to eliminate extracellular ESR signals and/or free radicals generated by stimulated neutrophils so that DMPO adducts reported events inside the cell. We identified a concentration of poly(ethylene glycol)-modified superoxide dismutase that permitted measurement of intracellular superoxide as determined by several criteria. It seems likely that poly(ethylene glycol)-modified superoxide dismutase is too large to enter the neutrophil phagosome. Under these conditions no hydroxyl radical was detected, as would be predicted from earlier studies with spin-trapping. Use of poly(ethylene glycol)-modified superoxide dismutase should allow on-line measurement of phagosomal events, thereby improving our understanding of microbicidal and inflammatory processes.

Binding of myeloperoxidase to bacteria: effect on hydroxyl radical formation and susceptibility to oxidant-mediated killing.

Neutrophils form superoxide anion (O2.-) and hydrogen peroxide (H2O2) and release myeloperoxidase (MPO) during ingestion of microbial pathogens. MPO, which adheres to some bacteria, catalyzes the formation of HOCl from H2O2, thereby enhancing H2O2/O2.- microbicidal activity. Hydroxyl radical (HO.), also is an important contributor to H2O2 and O2.- microbicidal activity. MPO decreases iron-catalyzed HO. production but also leads to HO. production through the reaction of O2.- and HOCl. We hypothesized that binding of MPO to bacteria could alter the magnitude and site of HO. production upon organism exposure to O2.-/H2O2. Incubation of MPO with Escherichia coli and Pseudomonas aeruginosa resulted in stable association of MPO with the bacteria which enhanced their susceptibility to killing by O2.-/H2O2. In the absence of MPO preincubation exposure of E. coli, but not P. aeruginosa to O2.-/H2O2, led to iron-catalyzed HO. generation. This was associated with different amounts of redox active iron in the two types of bacteria. MPO preincubation slightly decreased HO. detected with E. coli, but markedly increased HO. formation with P. aeruginosa. This likely resulted from decreased iron-catalyzed HO. production counterbalanced by increased iron-independent HO. formation. MPO preincubation did not effect bacterial killing by a system which generated only H2O2, precluding MPO-dependent HO. formation. These data are consistent with a possible role for MPO-derived HO. in the augmentation of bacterial killing by this enzyme.

Can nitric oxide be spin trapped by nitrone and nitroso compounds?

Increasing interest in the study of nitric oxide (NO.) in many facets of biological research necessitates a search for accurate techniques to directly identify the free radical. One recently employed strategy for NO. detection is the method of electron spin resonance (ESR) used in combination with nitrone and nitroso spin traps. Applying this technique to our studies with nitric oxide synthase (NOS), we found that NO. generated directly from the enzyme system could not be detected. Further investigation revealed that 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS) inhibited NO. generation by NOS at concentrations used for spin trapping. Reexamining the ability of various nitrones and DBNBS to spin trap authentic NO. dissolved in buffer, we obtained ESR spectra similar to those previously reported for the spin trap DBNBS. However, continuing our studies with 15NO. and N-hydroxylamine, we found these spectra to be artifactual. Our results emphasize the need to synthesize new spin traps, since currently available compounds are not capable of spin trapping NO. generated by NOS.

Studies of the mobility of maleimide spin labels within the erythrocyte membrane.

We have confirmed a method yielding reproducible and reliable spectrometric parameters derived from spin-labeled erythrocyte ghosts using nitroxide derivatives of maleimide compounds. The disorder parameter, W/S, was shown to vary with changes in the structure of the label, the conditions utilized for labeling such as ionic strength and erythrocyte age and the presence of drugs such as alcohol and acetaminophen. The nitroxide spectrum was also found to change with increasing and decreasing temperature in an irreversible manner. These findings should permit increased reliance to be placed on the spin-labeling technique when used to monitor changes in membrane lipid or protein assembly.

Involvement of the perferryl complex of nitric oxide synthase in the catalysis of secondary free radical formation.

Neuronal nitric oxide synthase (NOS I) has been shown to generate nitric oxide (NO*) and superoxide (O(2)* during enzymatic cycling, and the ratio of each free radical is dependent upon the concentration of L-arginine. Using spin trapping and electron paramagnetic resonance spectroscopy, we detected alpha-hydroxyethyl radical (CH(3)*CHOH), produced during the NOS I metabolism of ethanol (EtOH). The generation of CH(3)*CHOH by NOS I was found to be Ca(2+)/calmodulin dependent. Superoxide dismutase prevented CH(3)*CHOH formation in the absence of L-arginine. However, in the presence of L-arginine, the production of CH(3)*CHOH was independent of O(2)* but dependent upon the concentration of L-arginine. Formation of CH(3)*CHOH was inhibited by substituting D-arginine for L-arginine, or inclusion of the NOS inhibitors N(G)-nitro-L-arginine methyl ester, N(G)-monomethyl-L-arginine and the heme blocker, sodium cyanide. The addition of potassium hydrogen persulfate to NOS I, generating the perferryl complex (NOS-[Fe(5+)=O](3+)) in the absence of oxygen and Ca(2+)/calmodulin, and EtOH resulted in the formation of CH(3)*CHOH. NOS I was found to produce the corresponding alpha-hydroxyalkyl radical from 1-propanol and 2-propanol, but not from 2-methyl-2-propanol. Data demonstrated that the perferryl complex of NOS I in the presence of L-arginine was responsible for catalyses of these secondary reactions.

Detection of phagocyte-derived free radicals with spin trapping techniques: effect of temperature and cellular metabolism.

Human neutrophils activated with either particulate or soluble stimuli generate oxygen-centered free radicals which are detected by spin trapping in conjunction with electron spin resonance (ESR) spectroscopy. We investigated the effect of temperature on ESR spectra resulting from stimulation of human neutrophils with phorbol myristate acetate (PMA) or opsonized zymosan in the presence of the spin trap, 5,5-dimethyl-1-pyrroline 1-oxide (DMPO). At 20 degrees C with either stimuli, neutrophil superoxide production was manifested predominantly as the superoxide spin-trapped adduct, 5,5-dimethyl-5-hydroperoxy-1-pyrrolidinyloxy (DMPO-OOH). In contrast, at 37 degrees C, the hydroxyl spin-trapped adduct, 2,2-dimethyl-5-hydroxy-1-pyrrolidinyloxy (DMPO-OH) was dominant. No evidence of hydroxyl radical (defined as the methyl spin-trapped adduct, 2,2,5-trimethyl-1-pyrrolidinyloxy, DMPO-CH3) was observed, suggesting that elevated temperatures increased the rate of DMPO-OOH conversion to DMPO-OH. In addition, the elevated temperature activated a neutrophil reductase which accelerated the rate of DMPO-OH reduction to its corresponding hydroxylamine, 2,2-dimethyl-5-hydroxy-1-hydroxypyrrolidine. This bioreduction was dependent upon the presence of both superoxide and a phagocyte-derived factor (possibly a thiol) released into the surrounding media.

Diffusion of singlet oxygen into human bronchial epithelial cells.

The respiratory epithelium undergoes morphological and functional changes following exposure to single oxygen. However, mechanisms by which singlet oxygen causes cellular injury are unclear. The present experiments were designed to investigate the possibility that singlet oxygen, a highly reactive species, diffuses into respiratory epithelial cells. Of the various methods for detection of singlet oxygen, the electron spin resonance (ESR) spectrometric technique was judged to be most compatible and sensitive for use with cell suspensions. ESR spectrometry was used to monitor the singlet oxygen-mediated conversion of 2-(9,10-dimethoxyanthracenyl)-tert-butylhydroxylamine, (I), to 2-(9,10-dimethoxyanthracenyl)-tert-butylnitroxide, (II), and its corresponding endoperoxide, (III), in human bronchial epithelial cells treated with extracellularly generated singlet oxygen. In a second series of experiments, bronchial epithelial cells labeled with (I) were treated with singlet oxygen in the presence of 1,4-diazabicyclo[2.2.2]octane, a singlet oxygen quenching agent. The addition of this quenching agent eliminated the ESR spectrum corresponding with (II) and (III). This result is consistent with the quenching of singlet oxygen by 1.4-diazabicyclo[2.2.2]octane. Collectively, our results indicate that extracellularly generated singlet oxygen diffuses into human bronchial epithelial cells and that this process is a potentially important step in the cytotoxic action of singlet oxygen to the respiratory epithelium.

Electron paramagnetic resonance studies of membrane proteins in hepatic microsomes.

Hepatic microsomal membranes, prepared under various conditions that yield either 'intact' or 'disrupted' microsomal vesicles, have been labeled via the sulfhydryl groups of intrinsic membrane proteins using nitroxide analogs of N-ethylmaleimide. Electron paramagnetic resonance spectra revealed the presence of two dominant classes of bound label corresponding to differing degrees of immobilization, the ratio of which were quantitated using a parameter designated the 'W/S' ratio. For latent microsomes, the value of this parameter was determined to be 0.65 +/- 0.02 and was influenced by factors such as label/protein ratio, incubation period, nitroxide structure, temperature and pH. The W/S ratio was also sensitive to the degree of membrane integrity as revealed by the latency of mannose 6-phosphate activity of glucose-6-phosphohydrolase. In addition, membrane disruption resulted in a corresponding decrease in the order parameter for nitroxide-labeled fatty acids intercalated within the lipid bilayer. The W/S ratio was observed to be dependent upon the method of microsome preparation yielding values of 1.02 +/- 0.02 for 'hypertonically disrupted' vesicles and 1.28 +/- 0.02 for 'mechanically disrupted' vesicles. Microsomal marker enzymes such as cytochrome P-450 and FAD-containing monooxygenase retained significant levels of functionality following nitroxide incorporation.

Spin trapping of nitric oxide by ferro-chelates: kinetic and in vivo pharmacokinetic studies.

Biologically generated nitric oxide appears to play a pivotal role in the control of a diverse series of physiologic functions. Iron-chelates and low-frequency EPR spectroscopy have been used to verify in vivo production of nitric oxide. The interpretation of in vivo identification of nitric oxide localized at the site of evolution in real time is complicated by the varied kinetics of secretion. The quantitative efficiency of the spectroscopic measurement, so important in understanding the physiology of nitric oxide, remains elusive. The development of a more stable iron-chelate will help better define nitric oxide physiology. In this report, we present data comparing the commonly used ferro-di(N-methyl-D-glucamine-dithiocarbamate) (Fe2+(MGD)2) and the novel chelate ferro-di(N-(dithiocarboxy)sarcosine) (Fe2+(DTCS)2) quantifying the in vitro and in vivo stability of the corresponding spin trapped adducts, NO-Fe(MGD)2 and NO-Fe(DTCS)2. Finally, very low frequency EPR spectroscopy has been used to evaluate the pharmacokinetics of NO-Fe(MGD)2 and NO-Fe(DTCS)2 in mice in real time.

Detection of the production of oxygen-centered free radicals by human neutrophils using spin trapping techniques: a critical perspective.

Human neutrophils generate oxygen reduction products as a consequence of membrane interactions with a number of stimuli. One oxygen-centered free radical (superoxide) has been unequivocally shown to result from this "respiratory burst," and some experimental evidence for another (hydroxyl radical) has been published, although debate remains as to its significance. The role of phagocyte-derived free radicals in microbicidal and tumoricidal activity as well as tissue damage at sites of inflammation has been the focus of extensive investigation in recent years. Of the techniques available to study free radical generation in biological systems, spin trapping has emerged as a powerful tool for detection and identification of these reactive species, owing in part to its ability to measure production of free radicals inside the phagosome. However, interpretation of resulting spectra is extremely complex and filled with pitfalls and limitations. In this communication we review spin-trapping techniques and discuss the application of this system to the identification of free radicals resulting from stimulation of human neutrophils. Criteria are established which are necessary for definitive identification of superoxide and hydroxyl radical when employing this technology. In this context a critical perspective of previous studies of neutrophil-derived free radicals is offered.

Oxygen metabolism of the HL-60 cell line: comparison of the effects of monocytoid and neutrophilic differentiation.

HL-60 cells are promyelocytic leukemia cells that respond to culture conditions with differentiation into granulocytelike or macrophagelike phagocytes. O2 metabolism is critical to the microbicidal function of phagocytic cells. O2 metabolism was studied in HL-60 cells differentiated with dimethylsulfoxide (Me2SO) and 1,25(OH)2D3, with the objective of 1) determining the validity of these cells as models for human neutrophils and monocytes, respectively, and 2) determining whether these cells are capable of forming hydroxyl radical. Me2SO-treated cells had morphology consistent with human neutrophils. O2 consumption by these cells in response to phorbol myristate acetate (PMA; 100 ng/ml) or opsonized zymosan (3 mg/ml) was less than that by neutrophils, as was superoxide formation. O2 metabolism was not inhibited by KCN or antimycin A. Myeloperoxidase (MPO) activity decreased during differentiation but remained greater than that of human neutrophils. Cytochalasin B enhanced recovery of superoxide secreted in response to zymosan, implying its release from the phagosome. 1,25(OH)2D3-treated cells had morphology consistent with monocytes. O2 consumption and superoxide release were less than with Me2SO-treated cells. Unlike the case with human monocytes, O2 consumption was not inhibited by KCN or antimycin A. MPO activity was minimally reduced by differentiation. Cytochalasin B inhibited recovery of superoxide. Luminol-dependent luminescence was greater among 1,25(OH)2D3-treated cells than among Me2SO-treated cells. Free radicals were also measured with a spin trapping technique using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). Spin trapping allows direct, simultaneous detection of superoxide and hydroxyl radicals. Regardless of the mechanism of differentiation, only superoxide was formed by HL-60 cells. These results show that Me2SO-treated HL-60 cells represent an excellent model for the study of human neutrophil oxidative function. However, 1,25(OH)2D3-treated cells are quite different in their O2 metabolism from peripheral blood monocytes.

Effect of trifluoromethyl ketone-based elastase inhibitors on neutrophil function in vitro.

Neutrophils release elastase, which is known secondarily to cause tissue damage. However, it is rapidly inactivated by the endogenous alpha1-proteinase inhibitor (alpha1Pi). Nevertheless, under pathological conditions, alpha1i is inactivated by oxidants released from neutrophils, resulting in an excess of elastase at the site of inflammation. This elastase/alpha1Pi imbalance has been implicated as a pathogenic factor in cystic fibrosis, acute respiratory distress syndrome, and emphysema. Elastase inhibitors, which do not interfere with the microbicidal activity of neutrophils and are resistant to neutrophil-released oxidants, would undoubtedly represent an important advance in the management of neutrophil-mediated tissue injury. We report that a new family of elastase inhibitors ICI200355 and ZD0892 was found to be resistant toward superoxide, hypochlorous acid, hydrogen peroxide, hydroxyl radical, and peroxynitrite mediated degradation as well as having no effect on the formation of these oxidants by activated neutrophils. More importantly, we found that these inhibitors did not interfere with the ability of human neutrophils to phagocytose and to kill Staphylococcus aureus. In conclusion, a new potent class of elastase inhibitors, while blocking the effects of neutrophil elastase, was found not to impede various physiological functions of human neutrophils, in particular the ability of these phagocytic cells to phagocytose and kill bacteria.

A mimic of superoxide dismutase activity protects Chlorella sorokiniana against the toxicity of sulfite.

The spin-trapping agent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) has been used to demonstrate the light-dependent production of O2- by Chlorella sorokiniana. In the presence of SO3= a light-dependent production of the sulfur trioxy anion radical (SO3-.) could also be seen. A complex prepared by reacting desferrioxamine with MnO2, which catalyzes the dismutation of O2-, protected the alga against the toxicity of sulfite. The data suggest that SO2 toxicity is at least partially due to the effects of sulfoxy-free radicals generated by the oxidation of SO3= by O2-.

Do humans neutrophils form hydroxyl radical? Evaluation of an unresolved controversy.

Hydroxyl radical is a potent oxidizing agent of potential importance in human pathobiology. Since neutrophilic phagocytes make superoxide and hydrogen peroxide during phagocytosis, it has been proposed that hydroxyl radical is also formed. In this paper we review the literature which supports or refutes formation of hydroxyl radical by neutrophils and the mechanism(s) by which this radical might be formed. We conclude that there is no definitive proof for hydroxyl radical formation by neutrophils. In fact, neutrophil release of lactoferrin and myeloperoxidase appears to limit formation of this radical. Future studies are likely to determine whether superoxide released by neutrophils interacts with target substrates to allow formation of hydroxyl radical.

The role of a sleep disorder center in evaluating sleep violence.

To review the state-dependent nature of violence and present a clinically useful classification of sleep violence, this article reviews our experience with sleep-related violence, establishing a differential diagnosis, methods of evaluation, and treatment options. The study occurs in a full-service clinical sleep disorders center evaluating approximately 1000 patients annually with an active participation of 16 physicians representing seven specialties. The patients were self-, physician-, or court/social service-referred for evaluation of violent or injurious behaviors associated with the sleep period. Interventions were dependent on the final diagnosis following clinical and (usually) sleep laboratory evaluation. The main outcome measures were self-reported. During routine clinical evaluations at a multidisciplinary sleep disorder center, it has become apparent that violence is often state-dependent, occurring only during the sleep period, resulting from a number of both neurologic and psychiatric conditions (including malingering and Munchausen syndrome by proxy). In such cases, careful clinical and laboratory evaluation usually results in a specific diagnosis, with effective therapeutic recommendations. Violence may be state-dependent. It is clear that violent behaviors may arise from the sleep period, often without conscious awareness on the part of the subject. This has social, forensic, and clinical implications, and may help contribute to the understanding of violence in general.