An Autopsy Case of Dextromethorphan Poisoning.

A woman in her 30s who was being treated for a mental illness with several psychotropic drugs was admitted to the hospital after being found in a state of unconsciousness and respiratory arrest at home. She was pronounced dead 12 hours after she was discovered. Her autopsy revealed symmetrical hemorrhagic necrosis in the putamen on both sides of her cerebrum. Although many drugs were detected in her blood, all of those other than dextromethorphan (DXM) were within or below the therapeutic range. Her blood DXM was 1.73 µg/ml at admission and 1.61 µg/ml at autopsy, which were within the toxic range or coma-to-death range. The cause of death was diagnosed as DXM poisoning. DXM can cause hallucinations and euphoria if taken in excess, but since it is available as an over-the-counter drug at general pharmacies, an increasing number of young people are overdosing on it, mistakenly believing it to be a safe drug with few side effects. We believe that further social measures against DXM are necessary in Japan, such as disseminating correct knowledge in society and regulating over-the-counter sales.

rno-miR-203a-3p and Mex3B contribute to cell survival of iliopsoas muscle via the Socs3-Casp3 axis under severe hypothermia in rats.

Forensic diagnosis of fatal hypothermia is considered difficult because no specific findings, such as molecular markers, have been identified. Therefore, determining the molecular mechanism in hypothermia and identifying novel molecular markers to assist in diagnosing fatal hypothermia are important. This study aimed to investigate microRNA (miRNA) and mRNA expression in iliopsoas muscle, which plays a role in homeostasis in mammals, to resolve the molecular mechanism in hypothermia. We generated rat models of mild, moderate, and severe hypothermia, then performed body temperature-dependent miRNA and mRNA expression analysis of the iliopsoas muscle using microarray and next-generation sequencing. Analysis showed that rno-miR-203a-3p expression was lower with decreasing body temperature, while Socs3 expression was significantly increased only by severe hypothermia. Luciferase reporter assays suggested that Socs3 expression is regulated by rno-miR-203a-3p. Socs3 and Mex3B small interfering RNA-mediated knockdown showed that suppressing Mex3B could induce the activation of Socs3, followed by a change in caspase 3/7 activity and adenosine triphosphate levels in iliopsoas muscle cells. These findings indicate that rno-miR-203a-3p and Mex3B are deactivated by a decrease in body temperature, whereby it contributes to suppressing apoptosis by accelerating Socs3. Accordingly, the rno-miR-203a-3p-Socs3-Casp3 or Mex3B-Socs3-Casp3 axis may be the part of the biological defense response to maintain homeostasis under extreme hypothermia.

A case of sudden cardiac death due to mitochondrial disease.

A 25-year-old, emaciated man without medical treatment was found to have died suddenly at home by his mother. At autopsy, there were no injuries to his body, but significant circulatory insufficiency was observed. Electron microscopy revealed abnormal mitochondria in cells of the cardiac conduction system. The conduction system was filled with mitochondrial size abnormalities and mitochondrial cristae abnormalities. No notable abnormal findings were observed in other organs. Genetic examination of the blood revealed the mitochondrial pathogenetic variant m.3243A>G. Epileptic seizures, diabetic ketoacidosis, and hyperosmolar hyperglycemic state were unlikely to be the cause of sudden death. The cause of death was diagnosed as arrhythmia possibly induced by the failure of the cardiac conduction system due to mitochondrial disease. This is a rare case of sudden death caused by an accumulation of abnormal mitochondria in the cardiac conduction system.

Assessment of Triage DOA®, Status DS10, and DRIVEN-FLOW® M8-Z on-site drug screening kits for postmortem urine.

Based on the screening results of mass analyses using gas chromatography- mass spectrometry (GC-MS) and liquid chromatograph-tandem mass spectrometry (LC-MS/MS), we assessed the performance of Status DS10 (Status) and DRIVEN-FLOW® M8-Z (DF8), and compared the results with those of Triage DOA® (Triage) using 356 autopsy urine samples within one month of death. The sensitivity to benzodiazepines was 0.52 in Triage, 0.59 in Status, and 0.58 in DF8 with few false-positive cases. Triage detected triazolo-derivatives more easily than DF8. DF8 detected diazepam and nitro-benzodiazepines more easily than Status and Triage, with Status performing better than Triage. However, lorazepam detection with Status was difficult. There were 11 false-positive cases for amphetamines in Triage and 12 for Status-AMP at more than one week after death, but there were no false-positive in Status-MET and DF8. Tricyclic antidepressant (TCA) was detected in five cases by mass analysis, while there were 6 false-positive cases in Triage and 10 in both Status and DF8. In the TCA false-positive cases, tricyclic psychotics such as quetiapine, chlorpromazine, and carbamazepine existed. There were 23 true-positive and 6 false-positive cases for zolpidem in DF8 without false-negative cases. The accuracy of Status and DF8 for barbiturates or opiates was almost 1, but Triage was 0.98. There were no samples containing cocaine, THC, phencyclidine, or methadone. Based on the above, we conclude that Status and DF8 are comparable or slightly better than Triage, with fewer false-positive and fewer false-negative cases, except for TCA.

The Role of Brain Methamidophos in Acephate Poisoning in Mice.

We gave mice a 540 mg/kg dose of LD50 acephate, followed by an assessment of acephate, methamidophos (MP), and choline esterase (ChE) activity for up to 4 hours (hr) in order to investigate the time course of acephate intoxication. At 1 hr, the blood acephate and MP levels were 428 ± 90 µg/ml (mean ± SEM) and 4.2 ± 0.4 µg/ ml, respectively. The liver acephate levels were similar to those in the blood, but the liver MP levels were approximately 3.5 times that of the blood at 1 hr. The brain MP level tended to be higher than the blood MP at 1 hr. These levels decreased gradually over 4 hr, but the brain acephate and MP levels surpassed the blood levels significantly at 4 hr, and after 2 hr, respectively. Serum, liver, cerebrum, cerebellum, and brainstem cholinesterase activity (ChE) were inhibited at 1 hr, and remained inhibited in all but the cerebellum until the end of the experiment. The obtained data were applied to previously reported autopsy cases of acephate intake. Experimental data suggest that brain MP is involved in acute acephate-induced poisoning, even after a reduction in blood acephate. In autopsy cases with suspected acephate poisoning, the MP level in the brain should be considered in addition to the ChE activity to diagnose the cause of death.

Autopsy case of fatal hypoglycemia following ingestion of a therapeutic dose of tramadol.

An 86-year-old female was found unconscious the day after taking a prescribed tablet containing a combination of tramadol and acetaminophen. At admission to the hospital, marked hypoglycemia (blood glucose: 4 mg/dL) was confirmed, but serum insulin and C-peptide were within the normal range, which suggested that neither endogenous hyperinsulinemia nor exogenous insulin administration was responsible for the hypoglycemia. Despite resuscitation efforts, the woman subsequently died. At autopsy, there was renal disorder, but any pathological abnormalities that could have caused hypoglycemia were not observed. Blood tramadol and acetaminophen were in the therapeutic range. We speculate that the cause of fatal hypoglycemia was tramadol intake at the therapeutic dose. Older age and renal insufficiency are factors that could have potentially caused the fatal hypoglycemia in this case despite tramadol having been taken at a therapeutic dose. This is the first case report of fatal hypoglycemia following ingestion of a therapeutic dose of tramadol.

Butane detection after long-term treatment of burns in two autopsy cases.

A man and a woman were rescued from a room that had exploded. Many empty cassette gas cylinders were found in the room. The man and woman were hospitalized immediately for the treatment of burns. The woman died 6 days later, and the man died 31 days later without regaining consciousness. Carbonization and hardening of the frontal facial skin and parts of the left and right fingers were observed on the man's body. In both cases, systemic burns had led to progressive systemic edema and markedly suppressed circulation. Analytical samples for butanes obtained from their bodies at autopsy were stored at -20 °C for 14 and 25 days, respectively, before analysis. Normal butane and isobutane were quantified in the brain and subcutaneous adipose tissue of the woman. Only the isobutane was quantified in the adipose tissue of the man. The evidence suggests that the man lit a cigarette while breathing gas and the entire room exploded. Our results also suggest that butane can be detected in the adipose tissue of autopsy cases long after inhalation even under the present storage conditions, and isobutane may remain in adipose tissue longer than n-butane.

Efficacy of DRIVEN-FLOW® M7-II, a new on-site drug screening kit in postmortem urine compared with Triage DOA®.

The efficacy of DRIVEN-FLOW® M7-II(DFM7II) for seven drug groups was compared with Triage DOA® (Triage) using 340 autopsy urine samples taken from bodies within 1 month of death based on mass screening analysis of GC/MS and LC-MS/MS. The sensitivity to benzodiazepines was 0.56 in Triage and 0.53 in DFM7II with few false positives, and their accuracy was 0.88. Triage detected triazolo diazepine derivatives more easily than DFM7II. DFM7II detected diazepam and nitro benzodiazepines more easily than Triage. There were nine amphetamine false-positive cases of more than 10 days after death in Triage, but these were absent in DFM7II during this period. The accuracy of amphetamines for Triage was 0.96 and for DFM7II was 1. Tricyclic antidepressant (TCA) was detected in five cases by mass analysis, while there were four false-positive cases using Triage and eight cases using DFM7II. In the TCA false-positive cases of both kits, tricyclic psychotics such as chlorpromazine, carbamazepine, and quetiapine were included as well as the drug poisoning cases. There were no samples containing cocaine or THC. The accuracy of DFM7II for opiate and barbiturates was 1, but those of Triage was less than 1. Based on the above, DFM7II is a more accurate kit with fewer false-positives for target drug groups, other than TCA, than Triage.

Lethal physiological effects of carbon dioxide exposure at high concentration in rats.

The acute toxicity of high concentrations of carbon dioxide (CO2) was investigated in anesthetized rats using physiological parameters. At an oxygen concentration of 21%, the survival time decreased in a concentration-dependent manner from ≥7.3 h at 20% CO2 to 1.0 h at 50% CO2. The animals were divided into groups that were exposed to 40% CO2 and 21% O2 balanced with nitrogen (CO2 group), 40% CO2 and 12.6% O2 (CO2-Hypoxia group), 0% CO2 and 12.6% O2 (Hypoxia group), and 0% CO2 and 21% O2 (Control group) for 3 h. In the CO2 group, mean blood pressure (MBP) increased temporarily in the first 60 min followed by a gradual decrease, while breathing rate (BR) decreased immediately up to 3 h and the concentration of serum indicators reflecting organ damage increased. Most of these effects progressed in the CO2-Hypoxia group. The Hypoxia group showed a contrasting response to the CO2 groups in MBP and BR, and a slight partial increase in the serum indicators. Histological changes were not observed in any primary organs of any group, except for eosinophilic or necrosis of pyramidal cells in the hippocampal CA1 region of the CO2 group. These results indicate that high concentrations of CO2 inhalation are toxic, likely due to BR suppression, and that hypoxia produced under a high CO2 environment, while showing little effect on its own, enhances the toxic effects of CO2.

[An Autopsy Case of Death After Deep Sedation of Thiopental].

The victim was a morbidly obese and bull-necked woman in her twenties. She had the disorders, due to Down's syndrome, including severe mental retardation, advanced hearing loss, congenital cataract surgery, and amblyopia at postoperative glaucoma. She was deeply sedated for rest with an intravenous drip infusion of 350 mg of thiopental (TP) for 5 minutes during an intraocular pressure examination with secondary glaucoma at a hospital. The examination was finished within 10 minutes after the TP injection, but her respiratory condition deteriorated rapidly when the doctor left the patient. Although immediate artificial respiration was carried out, she was declared dead about 20 hours after the examination. Medical malpractice was suspected for her death. At autopsy, no fatal disease or injury was observed in the victim. The serum TP level was 0.80 µg /ml. TP is an ultra-short-acting intravenous anesthetic, and usually only the smallest amount should be administered by frequent additions after pre-anesthesia administration while maintaining contact with patients. Although contact with patients with a disability can be difficult, it was diagnosed that the death was caused by both respiratory arrest due to a single dose of TP and delay in resuscitation due to the absence of a doctor.

[A Forensic Autopsy Case in which Sulpiride and Estazolam Were Detected in an Adipoceratous Cadaver by LC-MS/MS].

We had a forensic autopsy case in which drugs were detected in a cadaver that had been stored in a cold and wet condition for 5 years. The skin of the cadaver was hard, and the color was partly whitish or dark brown. Though the cadaver had transformed into adipocere in the wet and cold condition, QuEChERS extraction and LC-MS/MS revealed the presence of sulpiride and estazolam in the femoral muscle and bone marrow. The concentrations of sulpiride and estazolam in the femoral muscle were 10.6 ng/g and 39.9 ng/g, respectively. The result of a drug screening test led not only to the cause of death but also to the personal identification of the cadaver. The individual had a history of drug taking, which had been stored in his medical records at the hospital for a long time. The fact of taking sulpiride and estazolam at the same time was characteristic, and it was useful in identifying the cadaver in this case. The progress in analytical technology has made possible the detection of particle drugs from old or adipoceratous cadavers, but there have been no reports of particle drugs being detected in a cadaver that had been dead for 5 years and had transformed to adipocere, as in our present case. The analytical results by LC-MS/MS were certainly important for the diagnosis of the cause of death, and, moreover, they were useful for the purpose of personal identification.

Sequential Molecular Events of Functional Trade-Offs in 5-Hydroxyisourate Hydrolase Before and After Gene Duplication Led to the Evolution of Transthyretin During Chordate Diversification.

Transthyretin (TTR), a plasma thyroid hormone distributor protein (THDP), emerged from 5-hydroxyisourate hydrolase (HIUHase), an enzyme involved in urate metabolism, by gene duplication at a stage of chordate evolution. Comparison of amino acid sequences revealed the presence of two His-rich segments in the primitive TTRs. Using several HIUHase and TTR mutants, we investigated 5-hydroxyisourate (HIU) hydrolysis activity and thyroid hormone (TH) binding activity to elucidate how a novel function as a THDP arose. Lancelet HIUHase was found to have higher enzyme activity than trout HIUHase. Two amino acid substitutions, R54E/Y119T, at the active sites of HIUHase, exerted weak [125I]-3,3',5-triiodo-L-thyronine ([125I]T3) binding activity with a concomitant loss of HIU hydrolysis activity. Addition of 3×His (3×H) to the N-terminal end weakened HIU hydrolysis activity of both lancelet and trout HIUHases, whereas it enhanced T3-binding activity of HIUHase R54E/Y119T. Trout HIUHase 3×H R54E/Y119T had higher [125I]T3-binding activity than that of lancelet HIUHase 3×H R54E/Y119T, with a Kd of 143 nM, and displayed metal dependency and no TH binding specificity. Deletion of the N-terminal His-rich segment from lamprey TTR decreased T3-binding activity, while addition of 3×H to trout TTR increased T3-binding activity, while maintaining TH binding specificity. Our results suggest that functional trade-offs of HIU hydrolysis activity with TH binding activity might have sequentially occurred before and after gene duplication, and that TH binding specificity and high-affinity sites may have been acquired later in the course of TTR evolution.

Molecular and thyroid hormone binding properties of lamprey transthyretins: The role of an N-terminal histidine-rich segment in hormone binding with high affinity.

Transthyretin (TTR) is a plasma thyroid hormone (TH) binder that emerged from an ancient hydroxyisourate hydrolase by gene duplication. To know how an ancient TTR had high affinity for THs, molecular and TH binding properties of lamprey TTRs were investigated. In adult serum, the lipoprotein LAL was a major T3 binder with low affinity. Lamprey TTRs had an N-terminal histidine-rich segment, and had two classes of binding sites for 3,3',5-triiodo-L-thyronine (T3): a high-affinity and a low-affinity site. Mutant TTRΔ3-11, lacking the N-terminal histidine-rich segment, lost the high-affinity T3 binding site. [125I]T3 binding to wild type TTR and mutant TTRΔ3-11, was differentially modulated by Zn2+. Zn2+ contents of wild type TTR were 7-10/TTR (mol/mol). Our results demonstrate that lamprey TTR is a Zn2+-dependent T3 binder. The N-terminal histidine-rich segment may be essential for neo-functionalization (i.e., high-affinity T3 binding activity) of an ancient TTR after gene duplication.

Characteristics of the brown hagfish Paramyxine atami transthyretin: Metal ion-dependent thyroid hormone binding.

Transthyretin (TTR) is a vertebrate-specific protein involved in thyroid hormone distribution in plasma, and its gene is thought to have emerged by gene duplication from the gene for the ancient TTR-related protein, 5-hydroxyisourate hydrolase, at some early stage of chordate evolution. We investigated the molecular and hormone-binding properties of the brown hagfish Paramyxine atami TTR. The amino acid sequence deduced from the cloned hagfish TTR cDNA shared 33-50% identities with those of other vertebrate TTRs but less than 24% identities with those of vertebrate and deuterostome invertebrate 5-hydroxyisourate hydrolases. Hagfish TTR, as well as lamprey and little skate TTRs, had an N-terminal histidine-rich segment, allowing purification by metal-affinity chromatography. The affinity of hagfish TTR for 3,3',5-triiodo-L-thyronine (T3) was 190 times higher than that for L-thyroxine, with a dissociation constant of 1.5-3.9nM at 4°C. The high-affinity binding sites were strongly sensitive to metal ions. Zn2+ and Cu2+ decreased the dissociation constant to one-order of magnitude, whereas a chelator, o-phenanthroline, increased it four times. The number of metal ions (mainly Zn2+ and Cu2+) was approximately 12/TTR (mol/mol). TTR was also a major T3-binding protein in adult hagfish sera and its serum concentration was approximately 8µM. These results suggest that metal ions and the acquisition of N-terminal histidine-rich segment may cooperatively contribute to the evolution toward an ancient TTR with high T3 binding activity from either 5-hydroxyisourate hydrolase after gene duplication.

Detection of toluene in a body buried for years with a fatal cardiac contusion.

This report aimed to present the postmortem finding of toluene in a homicide victim buried under the ground for six years. The bones of the skull and limbs were exposed, and the remainder of the subcutaneous tissues, brain and heart had formed into adipocere. There were numerous fractures in the skull and the anterior side of the ribs. A cardiac contusion extending into the cavity of the right ventricle was also observed. No other obvious injuries were identified on the body. The concentration of toluene in the bone marrow within the head of the humerus was 58.4 µg/g. The cause of death was suspected as heart rupture, possibly from a forceful impact or compression of the anterior chest under toluene intoxication. This report presents a rare case where toluene intake by a human was disclosed by autopsy even after several years of death.

[A Forensic Autopsy Case Applied for Asbestos-Related Disease].

We had a forensic autopsy case that required additive pathological examination for the asbestos-related lung disease compensatory application afterwards. A man in his sixties with a history of occupational asbestos inhalation who had neither visited a hospital nor received a physical examination received forensic autopsy because of his death from unknown cause. An inmate said, "He developed cough and dyspnea, and died in the progression of the symptoms." The autopsy revealed widespread pleural plaques on both sides of the parietal pleura and multiple tumors in both sides of the lungs. The cause of death was diagnosed as lung cancer. Additional pathological examination was asked by his family to certify that he had suffered from asbestos-related lung disease in order to apply to the Asbestos-related Damage Relief Law. The Japanese criteria of the compensation law of asbestos-related lung cancer is the detection of more than 5,000 asbestos bodies per gram of dry lung tissue, while his number of asbestos bodies was 4,860. Asbestos bodies were reported to be accumulated in the distal lung parenchyma with no pathological changes. The present lung samples were collected from proximal section around the tumor, which might have made the number of asbestos bodies less than the criteria. Both the number of patients suffering from asbestos-related lung disease and the number of forensic autopsy cases have increased in Japan. Collecting lung samples from the appropriate lung section is essential and should be noted when the lung cancer is suspected at forensic autopsy in order to apply for asbestos-related lung disease compensation.

Exposure to 3,3',5-triiodothyronine affects histone and RNA polymerase II modifications, but not DNA methylation status, in the regulatory region of the Xenopus laevis thyroid hormone receptor ßΑ gene.

Thyroid hormones (THs) play a critical role in amphibian metamorphosis, during which the TH receptor (TR) gene, thrb, is upregulated in a tissue-specific manner. The Xenopus laevis thrb gene has 3 TH response elements (TREs) in the 5' flanking regulatory region and 1 TRE in the exon b region, around which CpG sites are highly distributed. To clarify whether exposure to 3,3',5-triiodothyronine (T3) affects histone and RNA polymerase II (RNAPII) modifications and the level of DNA methylation in the 5' regulatory region, we conducted reverse transcription-quantitative polymerase chain reaction, bisulfite sequencing and chromatin immunoprecipitation assay using X. laevis cultured cells and premetamorphic tadpoles treated with or without 2 nM T3. Exposure to T3 increased the amount of the thrb transcript, in parallel with enhanced histone H4 acetylation and RNAPII recruitment, and probably phosphorylation of RNAPII at serine 5, in the 5' regulatory and exon b regions. However, the 5' regulatory region remained hypermethylated even with exposure to T3, and there was no significant difference in the methylation status between DNAs from T3-untreated and -treated cultured cells or tadpole tissues. Our results demonstrate that exposure to T3 induced euchromatin-associated epigenetic marks by enhancing histone acetylation and RNAPII recruitment, but not by decreasing the level of DNA methylation, in the 5' regulatory region of the X. laevis thrb gene.

Characterization of little skate (Leucoraja erinacea) recombinant transthyretin: Zinc-dependent 3,3',5-triiodo-l-thyronine binding.

Transthyretin (TTR) diverged from an ancestral 5-hydroxyisourate hydrolase (HIUHase) by gene duplication at some early stage of chordate evolution. To clarify how TTR had participated in the thyroid system as an extracellular thyroid hormone (TH) binding protein, TH binding properties of recombinant little skate Leucoraja erinacea TTR was investigated. At the amino acid level, skate TTR showed 37-46% identities with the other vertebrate TTRs. Because the skate TTR had a unique histidine-rich segment in the N-terminal region, it could be purified by Ni-affinity chromatography. The skate TTR was a 46-kDa homotetramer of 14.5kDa subunits, and had one order of magnitude higher affinity for 3,3',5-triiodo-l-thyronine (T3) and some halogenated phenols than for l-thyroxine. However, the skate TTR had no HIUHase activity. Ethylenediaminetetraacetic acid (EDTA) treatment inhibited [(125)I]T3 binding activity whereas the addition of Zn(2+) to the EDTA-treated TTR recovered [(125)I]T3 binding activity in a Zn(2+) concentration-dependent manner. Scatchard analysis revealed the presence of two classes of binding site for T3, with dissociation constants of 0.24 and 17nM. However, the high-affinity sites were completely abolished with 1mM EDTA, whereas the remaining low-affinity sites decreased binding capacity. The number of zinc per TTR was quantified to be 4.5-6.3. Our results suggest that skate TTR has tight Zn(2+)-binding sites, which are essential for T3 binding to at least the high-affinity sites. Zn(2+) binding to the N-terminal histidine-rich segment may play an important role in acquisition or reinforcement of TH binding ability during early evolution of TTR.

A method to determine the 5' end of the binding site of primers included in a commercially available forensic human identification kit.

Analysis for short tandem repeat (STR) loci is widely performed in forensic laboratories for human identification that utilizes commercially available kits that employ fluorescently labeled primers and capillary electrophoresis. With only a few exceptions, the sequences of the primers included in a kit are not disclosed by the kit manufacturers. Therefore, we developed a simple method to determine the 5' end of the binding site of the primers included in commercial kits. Our method requires only custom primers and human genome sequence data and routinely used equipment and consumables. One or two custom primers are added to the PCR reaction mixture containing kit primers and input human DNA prior to amplification, and PCR products are separated by capillary electrophoresis after amplification. With this method we can determine which primer of the pair is fluorescently labeled and the 5' end of the binding site of primers based on the changes in an electropherogram that are caused by the addition of the custom primer(s), and the human genome sequence data. This method is also useful for the determination of the shortest possible lengths of labeled kit primers.

Characterization of Oncorhynchus mykiss 5-hydroxyisourate hydrolase/transthyretin superfamily: evolutionary and functional analyses.

Teleosts have highly diverged genomes that resulted from whole genome duplication, which leads to an extensive diversity of paralogous genes. Transthyretin (TTR), an extracellular thyroid hormone (TH) binding protein, is thought to have evolved from an ancestral 5-hydroxyisourate hydrolase (HIUHase) by gene duplication at some stage of chordate evolution. To characterize the functions of proteins that arose from duplicated genes in teleosts, we investigated the phylogenetic relationship of teleost HIUHase and TTR aa sequences, the expression levels of Oncorhynchus mykiss HIUHase and TTR mRNA in various tissues and the biological activities of the O. mykiss re-HIUHase and re-TTR. Phylogenetic analysis of the teleost aa sequences revealed the presence of two HIUHase subfamilies, HIUHase 1 (which has an N-terminal peroxisomal targeting signal-2 [PTS2]) and HIUHase 2 (which does not have an N-terminal PTS2), and one TTR family. The tissue distributions of HIUHase 1 and TTR mRNA were similar in juvenile O. mykiss and the mRNA levels were highest in the liver. The O. mykiss re-HIUHase and re-TTR proteins were both 40-50 kDa homotetramers consisting of 14-15 kDa subunits, with 30% identity. HIUHase had 5-hydroxyisourate (5-HIU) hydrolysis activity with Zn(2+) sensitivity, whereas TTR had ligand binding activity with a preference for THs and several environmental chemicals, such as halogenated phenols. Our results suggest that O. mykiss HIUHase and TTR have diverged from a common ancestral HIHUase with no functional complementation.