Changes in activity of hepatic xenobiotic-metabolizing enzymes of tiger puffer (Takifugu rubripes) exposed to paralytic shellfish poisoning toxins

Attempts were made to examine the effect of paralytic shellfish poisoning toxins (PSP) on hepatic xenobiotic-metabolizing enzymes (XMEs) of tiger puffer (Takifugu rubripes). Two groups of nontoxic tiger fish were analyzed, and one group was fed with a PSP-containing diet (PSP group), and another with a PSP-free diet (control group). After 60 days of feeding, they were compared to each other mainly in terms of the activity of XMEs. Both groups did not differ from each other significantly in body weight gain, hepatosomatic index, and condition factor Hepatic level of cytochrome P450 was lower in PSP group than control group. NADPH-cytochrome P450 reductase, NADH-cytochrome b5 reductase, and ethoxyresorufin-O-deethylase (EROD) exhibited a reduced activity in PSP group than control group. Statistical analysis found that the activity or concentration of those enzymes correlated with the hepatic level of PSR with r2=0.497-0.611.

Localization of tetrodotoxin in the skin of a brackishwater puffer Tetraodon steindachneri on the basis of immunohistological study

A monoclonal antibody-based immunoassay for localization of tetrodotoxin (TTX) in the skin of a brackishwater puffer Tetraodon steindachneri is described in this paper. TTX was recognized in the undifferentiated basal cells and succiform cells in the skin under light microscope. Malpighian cells of the skin did not exhibit any TTX antigen. Neither gland nor enclosed gland-like apparatus possessing TTX was apparent in the skin.

A novel missense mutation in human lactate dehydrogenase B-subunit gene

Reduced activity of serum lactate dehydrogenase (LDH; EC 1.1.1.27) was found in a male medical student during practical examinations of his own blood. Serum LDH isoenzyme pattern showed reductions in activities of the isoenzymes with lower subunit A/B ratios such as LDH1 and LDH2. These findings were indicative of a partial LDH-B subunit deficiency, which was confirmed in erythrocyte hemolysates by Western blotting. Polymerase chain reaction (PCR)-based DNA sequence analysis of the LDH-B subunit gene revealed a heterozygous nucleotide change: a guanine to adenine substitution in codon 69 (GGG --> GAG) at the third exon of the LDH-B subunit gene that resulted in a glycine to glutamic acid substitution (G69E). The mutation was confirmed by PCR-restriction fragment length polymorphism (RFLP) analysis using a mismatched primer to introduce a new NcoI restriction site. The same heterozygous mutation was found in his mother but not in other family members. This mutation involves a residue belonging to alphaC helix in LDH-B subunit protein molecule that functions as an interface for other subunits.

Delayed haemolytic activity by the freshwater puffer Tetraodon sp. toxin

In order to elucidate the toxin composition of the freshwater puffer in Bangladesh, about 230 specimens of Tetraodon sp. were collected from 1997 to 1999 and extracted. After partitioning the toxins between an aqueous layer and a 1-butanol layer, the toxin in the aqueous layer was characterized as paralytic shellfish poison (PSP) (data not shown), while the toxin in the 1-butanol layer was identified as palytoxin (PTX) or PTX-like substance based on the delayed haemolytic activity which was inhibited by an anti-PTX antibody and ouabain (g-strophanthin). This is the first report on the occurrence of PTX or PTX-like substance(s) in puffer fish.

Chelonodon patoca, a highly toxic marine puffer in Japan

Toxicity of a Japanese marine puffer Chelonodon patoca ("okinawafugu") was examined by mouse assay from 1996 to 1999. Frequency of the toxic specimens was found to be 100% with high toxicity scores. Among the tissues tested, toxicity in the skin ranged from 60 to 6,700 MU/g, in the ovary from 25 to 670 MU/g, in the testis from 45 to 550 MU/g, in the muscle from 2 to 390 MU/g, and in the liver from 5 to 380 MU/g. The liver, which is known as one of the most toxic organs in Japanese marine puffer in general, showed lower toxicity in the present study. Thus, the anatomical distribution of toxicity was unique in C. patoca, in comparison with that of other Japanese puffers. C. patoca toxin was characterized as tetrodotoxin (TTX), 4-epiTTX and anhydroTTX by HPLC.

The transport mechanism of metallothionein is different from that of classical NLS-bearing protein

A nuclear localization signal (NLS) has been detected in several nuclear proteins. Classical NLS-mediated nuclear pore targeting is performed by using the cytosolic factors, importin alpha and importin beta, whereas nuclear translocation requires the small GTPase, Ran. In the present study, we demonstrated that nuclear localization of metallothionein (MT) differs from that of classical NLS-mediated substrates. In digitonin-permeabilized BALB/c3T3 cells, biotinylated MT was localized in the nucleus in the presence of ATP and erythrocyte cytosol in the same manner as for SV40 large T NLS-conjugated allophycocyanin (APC-NLS). Under ATP-free conditions, nuclear rim-binding was observed in both transport substrates. Rim-binding of labeled MT was competitively inhibited by the addition of an excess amount of unlabeled MT. Different elution profiles were observed for the localization-promoting activities of MT in the cytosol compared to those of APC-NLS. Furthermore, nuclear localization of MT was determined to be a wheat germ agglutinin-insensitive, GTPgammaS-sensitive, and anti-Ran antibody-sensitive process. Green fluorescent protein-metallothionein (GFP-MT) fusion protein was also localized in the nucleus in the stable transformant of CHL-IU cells. These results strongly suggest that the targeting by MT of the nuclear pore is mediated by cytosolic factor(s) other than importins and that MT requires Ran for its nuclear localization.

Detection of anaphylactic reaction in the percutaneously sensitized mouse using the AW method

Anaphylactic reactions of mice sensitized percutaneously with 2,4-dinitrofluorobenzene (DNFB) were investigated by the AW method assay, which is a mouse anaphylactic model using the abdominal wall as the site for induction with either 2,4-dinitrophenyl (DNP)-human serum albumin or anti-mouse IgE antibody and then estimation of the response. DNP-specific and IgE-dependent anaphylactic reaction after contact sensitization with DNFB could be induced and detected by the abdominal wall (AW) method assay in both groups with and without previous ear challenge with DNFB. Thus, the anaphylactic reaction in the group of twice-contact with 0.5% DNFB was observed on the 9th day from the sensitization (5th day from the ear challenge), and the reaction in the group of a single contact with 0.5% DNFB was observed 10 d after sensitization. The DNP-specific anaphylactic reaction was observed earlier than the 10th day with higher doses of DNFB. As for the mice of the former twice-contact group, the first and second characteristic ear swelling responses appeared within 1-6 h and 2 d of the ear challenge, respectively, and small swelling was observed 7 d after the challenge. It is suggested that Th1 and Th2 cells are activated at the almost same time, in other words, the preparation for both cell-mediated and humoral immunity could be accomplished to function, in vivo by a single percutaneous sensitization with DNFB.

Suppression and enhancement of the Freund's incomplete adjuvant-induced writhing reaction by sodium ascorbate in mice

We noticed that an intraperitoneal injection of Freund's incomplete adjuvant (FIA) into mice could stimulate the induction of a writhing reaction. The FIA emulsion-induced writhing reaction was found to be remarkably inhibited by preadministration of oral indomethacin, a non-steroidal anti-inflammatory and analgesic drug. The induction of the writhing reaction was also inhibited by intravenous preadministration of sodium ascorbate (SAs) in saline. In the experiments where SAs was added to FIA, it was demonstrated that SAs had dual activity of suppression and enhancement. At lower concentrations SAs functioned as a suppressor of the writhing reaction, while at concentrations higher than about 1 mg/50 microl/mouse it acted as an enhancer of the reaction. Furthermore, this writhing reaction induced by FIA+SAs emulsion was also inhibited by preadministraion of SAs itself as well as indomethacin. These results suggested that the mechanism of the writhing reaction induced by FIA was concerned with the production of prostaglandins (PGs), and SAs might be involved in regulation of the writhing reaction. In this paper, we propose a mouse writhing model induced by FIA or FIA+SAs emulsion as a novel pain model useful for assessment of analgesic and anti-inflammatory agents.

Inhibitory effects of thyrotropin-releasing hormone on neuronal activity in the nucleus accumbens

The effects of thyrotropin-releasing hormone (TRH) were examined on neuronal activity in the nucleus accumbens, receiving an input from the parafascicular nucleus of the thalamus or the hippocampus, in chloral hydrate-anesthetized rats, using a microiontophoretic technique. The spikes produced by stimulation of the parafascicular nucleus were predominantly and dose-dependently inhibited during iontophoretic application of TRH. When the effects of TRH and dopamine were tested on the same neurons of the nucleus accumbens, inhibition of the generation of spikes by both drugs was observed in most neurons. In contrast, spikes elicited by stimulation of the hippocampus in most neurons of the nucleus accumbens were not affected by TRH or dopamine. Both TRH- and dopamine-induced inhibition of the spikes induced by stimulation of the parafascicular nucleus was antagonized by simultaneous application of haloperidol. In animals treated with reserpine, inhibition of the generation of spikes upon stimulation of the parafascicular nucleus did not occur in any neurons in the nucleus accumbens during application of TRH, whereas the dopamine-induced inhibition was still observed. These results suggest that inhibitory effects of TRH on the neurons of the nucleus accumbens receiving an input from the parafascicular nucleus are mediated by dopamine released from the dopaminergic nerve terminals located in the nucleus accumbens.

Effects of diphenhydramine iontophoretically applied onto neurons in the medial and lateral vestibular nuclei

Electrophysiological studies were carried out to elucidate the effects of diphenhydramine, an antihistamine (H1-receptor blocking) drug, on neuron activities in the medial vestibular nucleus (MVN) and lateral vestibular nucleus (LVN) of cats using a microiontophoretic method. According to the firing pattern and latency of the first spike with vestibular nerve stimulation, neurons in the MVN and LVN were classified into two groups: monosynaptic and polysynaptic neurons. In the MVN, the spike generation of polysynaptic neurons was dose-dependently inhibited with the iontophoretic application of diphenhydramine up to 200 nA, and that of the monosynaptic neurons was also suppressed by the maximum dose of 200 nA. In contrast to the MVN neurons, the spike generation of LVN monosynaptic neurons remained unaffected with diphenhydramine up to 200 nA, although an inhibition of the LVN polysynaptic neurons was obtained with 200 nA of the drug. These results suggest that small doses of diphenhydramine more selectively interfere with synaptic transmission in the MVN neuron than that in the LVN neuron.

Vestibular efferent fibers to ampulla of anterior, lateral and posterior semicircular canals in cats

Origins of vestibular efferent fibers to ampulla of semicircular canals in cats were examined using retrograde transport of horseradish peroxidase. The anterior canal was innervated from bilateral parvocellular reticular nucleus (PCRN), contralateral gigantocellular reticular nucleus and ipsilateral lateral reticular nucleus (LRN); the lateral canal, from ipsilateral PCRN and LRN as well as ipsilateral lateral vestibular nucleus; and the posterior canal, from bilateral PCRN and ipsilateral medial and lateral vestibular nuclei.

Internuclear fiber connections of vestibular nuclear complex. A horseradish peroxidase study

Internuclear fiber connections among the superior (SVN), lateral (LVN), medial (MVN) and descending (DVN) vestibular nuclei were examined in cats using retrograde transport of horseradish peroxidase (HRP). HRP was microiontophoretically applied in the respective vestibular nucleus at doses of 300-500 nA for 5-10 min, and with the treatment the HRP injection site was limited to 0.2-0.5 mm in diameter within the nucleus. Major commissural connections were found between the bilateral SVN and between the bilateral DVN. Minor commissural connections were observed from MVN to SVN, LVN and MVN, from DVN to LVN, and from LVN to the contralateral LVN. In the ipsilateral vestibular nuclei, fiber connections were found from LVN to SVN, from MVN to SVN, LVN and DVN, and from DVN to SVN and LVN.