Induction of heme oxygenase and inhibition of delta-aminolevulinic acid synthetase of rat liver by thioacetamide and thioacetamide-S-oxide

Thioacetamide and one of its metabolite, thioacetamide-S-oxide, were shown to increase heme oxygenase and to inhibit delta-aminolevulinic acid (ALA) synthetase when administered in vivo to male rats. Concomitant with the increase of heme oxygenase and the decrease of ALA synthetase, concentration of cytochrome P-450 and drug metabolizing enzyme activities were decreased by in vivo administration of thioacetamide and thioacetamide-S-oxide to rats. The results of these studies indicate that thioacetamide and thioacetamide-S-oxide are not only inhibitor of ALA synthetase, but also inducer of heme oxygenase in rats. Further, thioacetamide-S-oxide is generally more effective than thioacetamide with respect to the effects on cytochrome P-450, ALA synthetase and heme oxygenase.

Placental transfer and distribution of 241Am in the rat

The placental transfer and distribution of 241Am in the feto-placental system were studied in pregnant rats. Rats were injected intravenously with 241Am citrate at 15 or 18 days of gestation. Groups injected at 15 days of gestation were sacrificed 2, 24, 48, or 120 hr after injection, and the group injected at 18 days was sacrificed 24 hr after. The radioactivities of 241Am in fetus, fetal membrane, and placenta were determined, and its distribution in the feto-placental system was investigated by high-speed autoradiography using a silver-activated zinc sulfide-coated membrane as an intensifying screen. The deposition of 241Am in feto-placental units increased with the number of days of gestation. Results of autoradiography revealed that major deposition sites of 241Am in the fetus are the skeleton and liver. Heavy deposition of 241Am in the yolk sac splanchnopleure and its existence in the exocoelom strongly suggest that the yolk sac placenta plays an important role in the placental transfer of this nuclide.

[Evaluation of Hancock mitral valve by M-mode echocardiography. Clinical significance of the timing of closing and opening of the valve]

The valve function of a Hancock xenograft in the mitral position was evaluated by M-mode echocardiograms guided by the two-dimensional echocardiogram. From M-mode echocardiograms, the intervals from the second heart sound to mitral valve opening (II-MVo) and from the Q wave to mitral valve closure (Q-MVc) were measured in 24 patients with a Hancock xenograft, 16 with mitral stenosis (MS) and 20 normal controls. Twenty-four patients with a Hancock xenograft were divided into four groups according to the echocardiographic pattern of the xenograft. Fourteen with normal echocardiograms (I: N.P.), five with delayed opening of cusps from 20 to 90 msec (II: D.O.), three with a coarse fluttering of cusps in diastole (III: D.F.), and two with an obstructed prosthesis (IV: O.P.). The valve function of groups II and III was clinically normal. This suggests that a coarse fluttering of cusps and delayed opening of cusps do not always indicate malfunction of the Hancock xenograft. M-mode echocardiograms of group IV showed an increased thickening of cusps, multiple dense echoes between valve stents and a lack of a clear E point. The beat-to-beat variations of Q-MVc and II-MVo intervals showed no significant differences among patients with the Hancock xenograft, MS and normal controls. A small time-dependent variation of Q-MVc and II-MVo intervals observed in patients with the Hancock xenograft did not seem to interfere the reliable reproducibility of these intervals. In group I, II-MVo interval was 104 +/- 8 msec (mean +/- S.E.), which was significantly longer than that of normal controls (54.5 +/- 2.5 msec) (p less than 0.005). In groups II and III, II-MVo interval was almost equal to that of group I, but in two of group IV, this interval was 20 and 30 msec, respectively which was markedly shortened. Q-MVc intervals did not show significant differences among groups I, II, III and IV. There were significant differences in Q-MVc interval among patients with MS and the Hancock xenograft and normal controls. II-MVo interval of group I was inversely correlated with mean diastolic posterior wall velocity (MDPWV), stroke index (SI) and delta ejection time (ET), but significantly correlated with delta preejection period (PEP) and PEP/ET. However, there was no significant relationship between II-MVo interval and pulmonary capillary wedge pressure. This suggested that prolonged II-MVo interval reflects postoperative left ventricular dysfunction. In conclusion, to evaluate the function of a Hancock xenograft, echocardiograms of valve cusps and measurement of II-MVo interval have useful clinical significance.

The effects of CCl4 on the accumulation of mercury in rat tissues after methylmercury injection

Rats were administered a dose of 10 mg of CH3HgCl/kg by single s.c. injection. They were subsequently treated with 0.5 ml of CCl4/kg by three i.p. injections at 48-h intervals. The treatment with CCl4 resulted in the rise of total mercury level in brain, although the increase of mercury level was transitory and the difference between with and without CCl4 treatment gradually diminished. In addition, the mercury levels in other tissues involving liver, kidney, and muscle were increased by the treatment with CCl4. These results suggest that a hepatic damage by CCl4 is responsible for the duration of mercury accumulation in brain and other tissues after the single injection of methylmercury.

Distribution and accumulation of [2,3-14C]acrylonitrile in rat after single injection

The distribution and accumulation of acrylonitrile after the single i.p. injection of [2,3-14C]acrylonitrile were examined by whole-body autoradiography and by the determination of 14C radioactivities in several tissues and subcellular fractions after a whole-body perfusion. 14C Radioactivity was seen strongly in blood, particularly in red blood cells, and in several tissues including lung, liver, and kidney. Longer retention of radioactivity in brain and muscle was observed. At the subcellular level a relatively high specific radioactivity was seen in cytosol fractions of the brain, liver, and kidney.

Cadmium-binding proteins in human organs

Cadmium-binding proteins (CdBPs) in the cytosol fractions from several organs of man orally exposed to cadmium (Cd) were examined by gel chromatography. In kidney and liver most of the cadmium (76-87%) in the cytosols was bound to metallothionein, and hepatic metallothionein contained zinc also at a similar level. The pancreas cytosol also contained a metallothionein-like CdBP, although its content was only one-tenth of the hepatic one. In the thyroid gland a prominent CdBP, eluting later than that of metallothionein, was observed; this CdBP was not detectable in normal dogs, pigs, and oxen. No CdBPs were observed in other organs including heart, muscle, genital organs, aorta, and bone. These results suggest that CdBPs participate in accumulation and distribution of cadmium in man, since organs containing CdBP such as kidney, liver, pancreas, and thyroid gland show a tendency to accumulate high levels of cadmium.

Electrocatalytic four-electron reduction of oxygen at the cytochrome c3-adsorbed electrode

The electrocatalytic activity of cytochrome c3 for the reduction of molecular oxygen was characterized from the studies of the adsorption of cytochrome c3 and the co-adsorption of cytochrome cs with cytochrome c on the mercury electrode by the a.c. polarographic technique. The adsorption of cytochrome c3 on the mercury electrode is irreversible and is diffusion-controlled. The maximum amount of cytochrome c3 absorbed was 0.92 . 10(-11) mol . cm-2 at -0.90 V. The amount of cytochrome c3 in the mixed adsorbed layer with cytochrome c was determined from the differential capacitance measurement. It was shown that the fractional coverage of cytochrome c3 can be estimated from its bulk concentration and the diffusion coefficient (1.05 . 10(-6) cm2 . s-1). Cytochrome c3 catalyzes the electrochemical reduction of molecular oxygen from the two-electron pathways via hydrogen peroxide to the four-electron pathway at the mercury electrode in neutral phosphate buffer solution. The catalytic activity varies with the bulk concentration of cytochrome c3. The highest catalytic activity for the oxygen reduction (no hydrogen peroxide formation) is attained when one-half of the mercury electrode surface is covered by cytochrome c3. The addition of cytochrome c or bovine serum albumin to the cytochrome c3 solution inhibits the catalytic activity of cytochrome c3. The reversible polarographic behavior of cytochrome c3 through the mixed adsorbed layer of cytochrome c3 and cytochrome c was also investigated.

Effects of methylmercury on zinc-thionein levels of rat liver

The induction of metallothionein synthesis by administration of methylmercury chloride as studied. A repetitive sc dose of methylmercury chloride to rats in amounts of 10 mg/kg/day for 3 days produced profound hypozincemia and 3-fold increase in hepatic zinc bound to metallothionein by the initial 24 h. The incorporation of 35S-cysteine into hepatic metallothionein was about 4 times larger for rats treated with methylmercury, which was comparable with it for rats treated with cadmium, than for control rats. These results suggest the induction of de novo synthesis of metallothionein by administration of methylmercury, although methylmercury was found to be unable to bind to produced metallothionein both in vivo and in vitro. A stress produced by methylmercury administration appears to be involved in the induction of hepatic zinc-thionein by methylmercury, through its mechanism is not clear.

Automated determination of red cell methaemoglobin reductase activity by a continuous-flow system for screening hereditary methaemoglobinaemia

A flow diagram for the automated determination of ferricyanide reductase activity in red blood cells was prepared in the modules from AutoAnalyzer AA I (Technicon Instruments Inc). Ferricyanide reductase assay can be substituted for assay of cytochrome b5 reductase (EC 1.6.2.2), which plays a major role in reducing methaemoglobin in erythrocytes, and is defective specifically in the erythrocytes of patients with hereditary methaemoglobinaemia. The effective sampling rate of the analysis is 30/h, and less than 0.05 ml of whole blood is required. Interference of haemoglobin with absorption by potassium ferricyanide at 420 nm is effectively exculded by dialysis. This automated method was compared with the accepted diaphorase method, and it distinguished clearly the ferricyanide reductase activity of cord bloods from that of adult bloods. The activity of the blood from a patient with hereditary methaemoglobinaemia was only residual. It is suggested that the method is useful as a mass screening test for hereditary methaemoglobinaemia.

Micro-determination of total phthalate esters in biological samples by gas-liquid chromatography

A method was investigated in which all of the phthalate esters in biological samples were determined as phthalic acid by gas-liquid chromatography. The method is based on the separation of phthalate esters from the sample with n-hexane, saponification of the esters with an alkaline ethanolic solution to give phthalic acid, purification of the acid by extraction with diethyl ether and column chromatography using silica gel, and conversion of the acid into bis(2,2,2-trifluoroethyl) phthalate with a 2,2,2-trifluoroethanol solution containing boron trifluoride. The derivative obtained is highly sensitive to an electron-capture detector, giving a sensitivity of 0.1 pg. Biological samples fortified with di(2-ethylhexyl) phthalate at levels of 5-100 ppb were analyzed, with recoveries of 70-100%.