Inhibition of indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase by β-carboline and indole derivatives

β-Carboline derivatives inhibited both indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase activities from various sources. Among them, norharman is most potent for both enzymes from mammalian sources. Kinetic studies revealed that norharman is uncompetitive (K_i = 0.12 mm) with l-tryptophan for rabbit intestinal indoleamine 2,3-dioxygenase, and linearly competitive (K_i = 0.29 mm) with l-tryptophan for mouse liver tryptophan 2,3-dioxygenase. In addition, some β-carbolines selectively inhibited one enzyme or the other. Pseudomonad tryptophan 2,3-dioxygenase was inhibited by a different spectrum of β-carbolines. Such a selective inhibition by the structure of substrate analogs is more evident by the use of indole derivatives. Indole-3-acetamide, indole-3-acetonitrile and indole-3-acrylic acid exhibited a potent inhibition for mammalian tryptophan 2,3-dioxygenase, while they moderately inhibited the pseudomonad enzyme. However, they showed no inhibition for indoleamine 2,3-dioxygenase. These results suggest the difference of the structures of the active sites among these enzymes from various sources.     

Serum thyroglobulin concentration in normal pregnancy

We measured the levels of serum thyroglobulin (Tg) in 52 pregnant females at various stages and compared them with those of 15 age-matched nonpregnant females. Serum Tg was measured by a solid-phase immunoradiometric assay. In pregnant females, mean serum Tg levels at the first, second, early third, and late third trimesters were 8.4 (range; 1.3-18.0), 9.2 (1.7-25.6), 10.1 (1.8-22.8), and 12.1 ng/ml (5.3-25.2), respectively. The statistical comparison was made after logarithmic transformation of the data. The mean value only at the late third trimester was significantly higher than that of controls (mean; 6.0 ng/ml, range; 1.5-23.6), but each value was within the normal range. Although serum Tg levels have been reported to be high at the end of pregnancy, our results indicate that the Tg levels in females could be clinically interpreted without regard to the coexistence of pregnancy.     

Anomalous permeabilities of the egg cell membrane of a starfish in K(+)-Tl(+) mixtures

The electrical properties of “inward” rectifying egg cell membranes of the starfish mediastera aequalis have been studied in the presence of K(+)-Tl(+) mixtures. When the ratio of the external concentrations of these ions is changed while their sum is kept constant, both the conductance and the zero-current membrane potential go through a minimum, showing clear discrepancies from theoretical results based on conventional electrodiffusion models (E.g., Goldman’s equation). By contrast, when the ration of the two concentrations is fixed and their sum varied, the potential follows an ideal Nernst slope, consistent with Goldman’s equation. The membrane conductance which, according to previous studies on similar membranes, is to be viewed as a function of the displacement of the membrane potential from its resting value δV, shows marked differences between the cases in which K(+) or Tl(+) are the predominant ions: when K(+) is the predominant permeant ion in solution, the addition of small amounts of Tl(+) inhibits the current, while corresponding blocking effects of K(+) on the current are not observed when Tl(+) is the predominant permeant ion. Also, the time course of the conductance during voltage clamp is different in the two cases, being much faster in Tl(+) than in K(+) solution for comparable values of δV. Most of the above features are accounted for by a model in which it is assumed that the ionic channels have external binding sites for cations and that their permeability properties depend on the species of the cation bound (K(+)or Tl(+) in the present experiments).     

Loperamide in rat intestines: A unique disposition

When everted sacs of rat duodenum, jejunum and ileum were incubated with [¹⁴C]loperamide in vitro, unchanged drug and its metabolites were found not only in tissues but also in media of the mucosal side with virtually no radioactivity in media of the serosal side. The amounts of metabolites found in media of the mucosal side were comparable to or larger than those in tissues. Di-desmethyl loperamide was more predominant in the media as compared with mono-demethylated one than in the tissues. Therefore, a portion of loperamide absorbed in intestines can be metabolized there and directly secreted back into lumen. Oral loperamide thus undergoes a unique disposition, likely constituting one of mechanisms for its distinct dissociation of central and antidiarrheal activities.     

IgE-mediated 14C-serotonin release from rat mast cells modulated by morphine and endorphins

The formaldehyde method was used to examine the interaction of PGE₁ with morphine, β-endorphin and Met-enkephalin on rat mast cells by their effects on IgE-mediated ¹⁴C-serotonin release. PGE₁ (2×10^?8?2×10^?5 M) caused a dose-related inhibition of the mediator release 1 min after an antigen challenge, and morphine (3×10^?7?3×10^?5 M) reversed this PGE₁ effect dose-dependently and stereospecifically; naloxone (2×10^?4 M) antagonized this action of morphine. β-Endorphin (3×10^?7?10^?5 M) and Met-enkephalin (3×10^?6?10^?4 M) mimicked this morphine action dose-dependently and were antagonized by naloxone (2×10^?4 M). These results suggest that morphine and endorphins modulate immunological mediator release from rat mast cells through opioid receptors.     

Absorption of Copper by Lemna as Influenced by Some Factors Which Nullify the Copper Effect on Flowering and Growth

The effect of copper on flowering and growth of Lemna paucicostata6746 and Lemna gibba G3 in a copper-containing medium is nullifiedby the addition of EDTA, ammonium ions or salicylic acid tothe medium or a decrease in its nitrate concentration. Thesefactors were examined for their effects on the absorption ofcopper by the plants. The addition of EDTA to the medium completelyinhibited the absorption of copper in both species, thus eliminatingthe copper effect. Ammonium ions also inhibited copper absorption,their effectiveness rising with their concentration. Loweringthe nitrate concentration in the medium nullified the coppereffect on flowering in L. paucicostata 6746, and the additionof salicylic acid to the medium also nullified the copper effectin L. gibba G3, both without affecting the absorption of copper. (Received June 7, 1982; Accepted August 27, 1982)     

Fixation of Dinitrogen-15 Associated with Rice Plants

Rice plants (IR26 and Latisail) obtained at near heading stage from a wetland field were transferred to water culture and exposed to ¹⁵N₂ in a gas-tight growth chamber for 7 days to measure N₂-fixing activities associated with the rice. The activities measured varied from 6.5 to 11.6 μmol of N₂ fixed per hill per day. The outer leaf sheath had about 2.5 times higher N₂-fixing activities per unit weight than the root. Slight activities were also found in the basal node and inner leaf sheath. Wrapping basal parts of the stem with aluminum foil did not decrease the activities of N₂ fixation in these parts. Thus, the outer leaf sheath as well as the root are N₂-fixing sites in rice plants. N₂ fixation found in above-ground parts is not due to photoautotrophic organisms. Less than 10% of the fixed nitrogen was translocated from the fixing sites to the leaf blades and the young panicles.     

A general characteristic of tumor mitochondria: Leakage of endogenous Mg2+ on incubation with uncoupler and resultant reduction of uncoupler-stimulated ATPase activity

Previous studies showed that stimulation of mouse mitochondrial ATPase activity of tumor cells, fetal liver, and adult brain by the uncoupler 2,4-dinitrophenol was markedly suppressed during incubation of the mitochondria with the uncoupler (J.-I. Hayashi et al., 1980, Biochem. Biophys. Res. Commun.92, 261–267). The present work showed the reason for this suppression. More than half the endogenous Mg²⁺ leaked from mitochondria of all tumor cells tested, and of fetal liver and adult brain during incubation with the uncoupler, while only about 30% of the endogenous Mg²⁺ leaked from mitochondria of other normal tissues. The effect of the uncoupler on Mg²⁺ leakage from liver mitochondria changed from the fetal to the adult type within about 30 min after birth. In hypotonic medium, normal liver mitochondria also lost more than half their total Mg²⁺ and concomitantly stimulation of their ATPase activity by uncoupler was considerably reduced. Exogenously added Mg²⁺ could reverse this reduced effect of the uncoupler on ATPase activity of mitochondria from normal tissues and tumor cells. These results show that the endogenous Mg²⁺ content of mitochondria directly affects the stimulation by uncoupler of ATPase activity of mitochondria from both normal tissues and tumor cells. Thus, mitochondria of all tumor cells tested, and of fetal liver and adult brain are leaky to Mg²⁺ during incubation with uncoupler and as a result of the leakage, the stimulatory effect of the uncoupler on their ATPase activity is greatly reduced.     

An anticomplementary agent, K-76 monocarboxylic acid: its site and mechanism of inhibition of the complement activation cascade.

A monocarboxylic acid derivative (K-76 COOH) of K-76, purified from the culture filtrate of Stachybotrys complement I nov. sp. K-76, inhibits complement (C) activity. Its inhibitory action is mainly on C5 step. It strongly inhibits the generation of EAC1,4b,2a,3b,5b from C5 and EAC1,4b,2a,3b, and accelerates the decay of EAC1,4b,2a,3b,5b. It also causes some inhibition of the reactions of the reactions of C2,C3,C6,C7 and C9 with their respective preceding intermediate cells. It has no effect on the generation of EAC1,4b from C4 and EAC1, or of EAC-8 from C8 and EAC-7, and apparently increases the generation of EAC1,4b from C1 and EAC4b probably by inhibiting transfer or turnover of C1. It does not affect the rate of decay of EAC1,4b,2a or the T max of generation of EAC1,4b,2a, and it inhibits immune adherence only at high concentration. K-76 COOH also strongly inhibits hemolysis through the alternative pathway of C activation by cobra venom factor, but it does not seem to inhibit the early steps of the alternative pathway, because it has little affect on the consumption of C3 or the conversion of beta 1C to beta 1A on treatment of C serum with zymosan. K-76 COOH probably combines with C5 molecules, forming the inactive complexes, or it causes the structural alteration of C5.