The essentiality of B chain in stabilizing the structure of the A chain in beta 1-bungarotoxin from Bungarus multicinctus venom

The dynamic of Trp residue in beta 1-bungarotoxin (beta 1-Bgt), the A chain of beta 1-Bgt and phospholipase A2 (PLA2) was assessed by fluorescence measurement. Acrylamide quenching studies showed that the exposure degree of the Trp in PLA2 is higher than the Trp in beta 1-Bgt. The Trp of beta 1-Bgt had a higher accessibility for iodide, reflecting that the basic nature of the B chain might exert an attractive electrostatic force for iodide and increase the susceptibility of Trp in the A chain to iodide. Removal of the B chain of beta 1-Bgt did not significantly affect the exposure degree of Trp in the A chain. Alternatively, the polarity of the environment around the Trp and the hydrophobic character of ANS and substrate binding sites in the separated A chain changed. Measurement of Trp fluorescence with increasing temperature showed that the stability of structure of beta 1-Bgt was higher than those of the separated A chain and PLA2. These results suggest that the B chain might interact with the A chain and stabilize the conformation of the A chain in beta 1-Bgt.

Localization of acyl coenzyme A:cholesterol acyltransferase gene to human chromosome 1q25

Acyl coenzyme A:cholesterol acyltransferase (ACAT) is an intracellular enzyme that catalyzes the formation of cholesterol esters from cholesterol and long-chain fatty acyl-coenzyme A. It is believed that ACAT plays a key role in lipoprotein metabolism and atherogenesis. Recently our laboratory succeeded in molecular cloning and functional expression of human macrophage ACAT cDNA. We have now mapped the ACAT gene to chromosome 1, band q25 by using fluorescence in situ hybridization to metaphase chromosomes, and by Southern blotting analysis of human--hamster somatic cell hybrid panels.

Building components contributors of the sick building syndrome

The sick building syndrome has been widely discussed from epidemiological perspectives. Although there is considerable difference in opinion regarding the concrete and objective evidence to support a distinct sick building syndrome and/or building-related illness, much data indicates that numerous variables within buildings can potentially influence human health. In this paper, we discuss in detail not only the potential and unique infectious diseases caused by Legionella, Pontiac fever, Q fever, and influenza, but also the data implicating noninfectious etiologies of sick building syndrome and building-related illnesses. In addition, the role of psychological factors, mass hysteria, and indoor pollution is discussed with respect to the nature of associations between exposure and symptoms. Finally, comparisons are made in different building construction types of old versus new buildings to highlight changes in modern construction that may have led to a putative increase in work-related symptomatology.

BCL-6 and the molecular pathogenesis of B-cell lymphoma

The results presented identify the first genetic lesion associated with DLCL, the most clinically relevant form of NHL. Although no proof yet exists of a role for these lesions in DLCL pathogenesis, the feature of the BCL-6 gene product, its specific pattern of expression in B cells, and the clustering of lesions disrupting its regulatory domain strongly suggest that deregulation of BCL-6 expression may contribute to DLCL development. A more precise definition of the role of BCL-6 in normal and neoplastic B-cell development is the goal of ongoing study of transgenic mice engineered either to express BCL-6 under heterologous promoters or lacking BCL-6 function due to targeted deletions. In addition to contributing to the understanding of DLCL pathogenesis, the identification of BCL-6 lesions may have relevant clinical implications. DLCL represent a heterogeneous group of neoplasms which are treated homogeneously despite the fact that only 50% of patients experience long-term disease-free survival (Schneider et al. 1990). The fact that BCL-6 rearrangements identify biologically and clinically distinct subsets of DLCL suggests that these lesions may be useful as markers in selection of differential therapeutic strategies based on different risk groups. Furthermore, the BCL-6 rearrangements can be used to identify and monitor the malignant clone with sensitive PCR-based techniques. Since clinical remission has been observed in a significant fraction of DLCL cases, these markers may serve as critical tools for sensitive monitoring of minimal residual disease and early diagnosis of relapse (Gribben et al. 1993).

Characterization of apoptosis induced by transforming growth factor beta 1 in human hepatoma cells

Apoptotic cell death plays a major role in the regulation of cell growth and this process may be activated by different agents through various pathways. The present study aimed to elucidated the mechanism of apoptosis caused by transforming growth factor beta 1 (TGF-beta 1) in human hepatoma cells. Several biological parameters which were reported to be crucial in the induction of programmed cell death in other experimental systems were measured. We found that TGF-beta 1-induced cell death is independent of cytosolic calcium and protein kinase C. Insulin and tumor promotor can rescue hepatoma cells from apoptosis, but the effect is time-dependent. Our results highlight that different apoptotic signal transduction pathways exist in different cell types. Apoptosis induced by TGF-beta 1 provides a good model for the understanding of cell death and the development of new anti-cancer drugs. Apoptotic cell death (apoptosis or programmed cell death) in normal tissue is a biological phenomenon that maintains hemostasis of systems of the body under physiological conditions. The features of apoptosis include condensation of chromatin, blebbing of the cell surface, transient increase in buoyant density and fragmentation of chromatin by a specific endonuclease.

Brequinar sodium, mycophenolic acid, and cyclosporin A inhibit different stages of IL-4- or IL-13-induced human IgG4 and IgE production in vitro

We investigated the effect of cyclosporin A (CsA), mycophenolic acid (MPA), and brequinar sodium (BQ) on human IgG4 and IgE synthesis induced by IL-4 or IL-13. BQ inhibited IL-4 and IL-13-induced IgG4 and IgE synthesis in cultures of peripheral blood mononuclear cells (PBMC) or highly purified B cells costimulated by anti-CD40 mAbs in a dose-dependent fashion. CsA and MPA had either suppressive or enhancing effects depending on the concentrations tested. Interestingly, BQ inhibited IgG4 and IgE synthesis at concentrations of 10(-6)-10(-8) M, which did not affect T or B cell proliferation, indicating that the inhibitory effects of BQ on Ig production were not directly related to inhibition of T or B cell proliferation. In contrast, the inhibitory effects of MPA on Ig production were directly associated with inhibitory effects on T and B cell proliferation. CsA blocked T and B cell proliferation at the same concentration (10(-7) M) which enhanced IgG4 and IgE synthesis, indicating that reduction in T or B cell proliferation correlated with enhanced IgE production. CsA also inhibited CD40 ligand expression and IL-2, IL-4, IL-5, IFN-gamma, and GM-CSF production by activated CD4+ T cell clones, whereas MPA and BQ were ineffective, indicating that these compounds do not inhibit early events in T cell activation. Collectively, our data indicate that BQ, MPA, and CsA block different stages of the IgG4 and IgE production process. In addition, we observed that CsA and MPA, in contrast to BQ, at lower concentrations can also have potentiating effects on the production of these Ig isotypes.

Plasma PTH and PTH-rP levels and clodronate therapy in cancer patients with hypercalcemia

To investigate the roles of parathyroid hormone (PTH) and parathyroid hormone-related peptide (PTH-rP) in hypercalcemic patients with various malignancies, we measured the plasma levels of intact PTH and intact PTH-rP in five hypercalcemic patients with hematologic malignancies and 29 hypercalcemic patients with solid cancers. Ten eucalcemic cancer patients with either hepatocellular carcinoma or squamous cancer of the lung served as controls. The results showed a suppressed PTH level in all of the 34 hypercalcemic cancer patients. The PTH-rP levels were within normal limits (< 2.5 pg/mL) for all of the eucalcemic cancer controls, all of the five hematologic cancer patients with hypercalcemia, and only two out of the 29 hypercalcemic patients with solid cancers. The PTH-rP level was elevated in nearly all (27/29) hypercalcemic patients with or without bony metastasis. There was a good correlation between the corrected total serum calcium level and the natural log of PTH-rP level in 39 patients (10 eucalcemic and 29 hypercalcemic) with solid cancers (r = 0.75, p < 0.001). These results suggest that PTH-rP plays an important role in the hypercalcemia of patients with solid cancers, but this was not the case in our patients with hematologic malignancies. True ectopic secretion of PTH is unlikely in most of these patients. The mean serum total calcium levels of 17 hypercalcemic patients (13 solid cancers, four hematologic malignancies) dropped significantly after the third day of treatment with a new-generation bisphosphonate-clodronate product. This treatment consisted of 300 mg daily intravenous infusion for seven days, followed by oral administration (800 mg, bid) for the following three weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of functional involvement of tryptophan residues in phospholipase A2 from Naja naja atra (Taiwan cobra) snake venom

Phospholipase A2 (PLA2) from Naja naja atra snake venom was subjected to Trp modification with 2-nitrophenylsulfenyl chloride (NPS-Cl), and six derivatives were separated by HPLC. The results of amino-acid analysis and sequence determination revealed that Trp-18, Trp-19 and Trp-61 were modified by NPS-Cl. The order of accessibilities of the three Trp residues for NPS-Cl was Trp-18 > Trp-19 > Trp-61. Sulfenylation of Trp-18 caused a 92% drop in enzymatic activity. Modification of Trp-19 and Trp-61 resulted in a decrease in enzymatic activity of PLA2 by 45.5% and 51%, respectively. The enzyme modified on both Trp-18 and Trp-19 or on both Trp-18 and Trp-61 retained little PLA2 activity. It is evident that Trp-18 plays a more crucial function in PLA2 than Trp-19 and Trp-61. Sulfenylation did not significantly affect the secondary structure of the enzyme molecule as revealed by the CD spectra, and Ca2+ binding and antigenicity of sulfenylated PLA2 was unaffected. These observations, together with the fact that Trp-18 is involved in the substrate binding of PLA2, suggest that incorporation of a bulky NPS group on Trp-18 might give rise to a direct distortion of the interaction between substrate and the enzyme molecule. Alternatively, modification of Trp-19 and Trp-61 might indirectly affect the interfacial binding of PLA2 with its substrate.

Molecular cloning and functional expression of human acyl-coenzyme A:cholesterol acyltransferase cDNA in mutant Chinese hamster ovary cells

Accumulation of cholesterol esters as cytoplasmic lipid droplets within macrophages and smooth muscle cells is a characteristic feature of early lesions of atherosclerotic plaque. Intracellularly, an essential element in forming cholesterol ester from cholesterol is the enzyme acyl-coenzyme A:cholesterol acyltransferase (ACAT). ACAT is a membrane protein located in the endoplasmic reticulum. The ACAT protein has never been purified to homogeneity, and no antibodies directed against ACAT have been reported. The gene(s) encoding this enzyme had not been isolated. This laboratory had previously reported the isolation of Chinese hamster ovary cells expressing human ACAT activity. From DNAs of these cells, we have cloned a 1.2-kb exonic human genomic DNA. This led to the eventual cloning of a 4-kb cDNA clone (K1) from a human macrophage cDNA library. Transfection of K1 in ACAT-deficient mutant Chinese hamster ovary cells complemented the mutant defect and resulted in the expression of human ACAT activity. K1 contained an open reading frame of 1650 bp encoding an integral membrane protein of 550 amino acids. Protein homology analysis showed that the predicted K1 protein shared homologous peptide sequences with other enzymes involved in the catalysis of acyl adenylate formation followed by acyl thioester formation and acyl transfer. These results indicate that K1 encodes a structural gene for ACAT. The cDNA reported here should facilitate future molecular studies on ACAT.

Pentoxifylline inhibits the proliferation and glycosaminoglycan synthesis of cultured fibroblasts derived from patients with Graves' ophthalmopathy and pretibial myxoedema

Excessive amounts of glycosaminoglycans accumulate in the extraocular muscles of patients with Graves' ophthalmopathy and in the affected skin of patients with pretibial myxoedema. It is widely accepted that fibroblasts are the sources of glycosaminoglycan synthesis. Pentoxifylline, an analogue of the methylxanthine theobromine, inhibits the proliferation and certain biosynthetic activities of fibroblasts derived from normal human skin and from skin of patients with some fibrotic disorders. Our objective was to determine whether pentoxifylline has similar effects on fibroblasts derived from patients with Graves' ophthalmopathy and pretibial myxoedema and could serve as a candidate for the treatment of these manifestations. Fibroblasts from the extraocular muscles of two patients with Graves' ophthalmopathy and normal extraocular muscles of two subjects with strabismus, as well as the affected skin of two patients with pretibial myxoedema were cultured in vitro in the presence and absence of pentoxifylline to assay its effect on the proliferation of fibroblasts and their production of glycosaminoglycans. In subconfluent fibroblast cultures, pentoxifylline treatment caused a dose-dependent inhibition of serum-driven fibroblast proliferation. In confluent fibroblast cultures both in the presence and absence of serum, exposure to pentoxifylline similarly resulted in a dose-dependent inhibition of glycosaminoglycan synthesis for all these different kinds of fibroblasts. These findings may form the rationale for a clinical trial using pentoxifylline for the treatment of Graves' ophthalmopathy and pretibial myxoedema.

A comparison between vecuronium and atracurium in myasthenia gravis

We evaluated the effect of vecuronium bromide and atracurium besylate on the train-of-four response in the management of muscle relaxation in 20 patients with myasthenia gravis (MG) who were undergoing thymectomy. We confirmed the safe use of these two non-depolarizing muscle relaxants in MG patients. Vecuronium (0.04 mg.kg-1) demonstrated a lesser clinical duration than did atracurium (0.2 mg.kg-1) (38 +/- 19 vs 50 +/- 21 min, mean +/- s.e.mean). The recovery time for vecuronium patients was shorter than that for atracurium patients (22 +/- 18 vs 38 +/- 18 min), but the time until onset of neuromuscular blockade was longer with vecuronium (246 +/- 105 vs 107 +/- 103 s). During spontaneous recovery from neuromuscular relaxation, at T1/C of 25% and 100%, the train-of-four fade with vecuronium was significantly greater than that with atracurium (0.04 +/- 0.02, 0.16 +/- 0.03 vs 0.17 +/- 0.01, 0.83 +/- 0.03), suggesting that vecuronium had a greater prejunctional effect than did atracurium.

Chemical modification of amino groups in cardiotoxin III from Taiwan cobra Naja naja atra) venom

Cardiotoxin III (CTX III), a major cardiotoxin analogue isolated from the Taiwan cobra (Naja naja atra) venom was modified, either with trinitrobenzene sulfonate (TNBS) or 4-chloro-3,5-dinitrobenzoate (CDNB). Under the conditions of limited reagent availability, three mono-TNP derivatives modified at Lys-5, 12, or 44, and three mono-CDNP derivatives at Lys-12, 23, or 44 were isolated, respectively. The biological activities of CTX III were more or less affected after each of these reactive amino groups were modified. In particular, the hemolytic activity to human erythrocytes and cytotoxicity on NS-1 cells of CTX III decreased to 31% and 50%, respectively, when Lys-12 was trinitrophenylated. More pronounced alteration in these activities was observed as this amino group was carboxydinitrophenylated. A good correlation between the hemolytic activity and cytotoxicity was found. These results indicate that epsilon-amino group at Lys-12 is most closely related to the hemolytic and cytotoxic activities of CTX III. The antigenicity of modified derivatives still remained intact as measured by ELISA.

O2 occlusion and cyanide induced immediate relaxation and contraction of murine skeletal muscle

The acute changes of muscle tone and membrane current upon occlusion of oxygenation (O2 occlusion) were studied in vitro in mouse diaphragms. O2 occlusion immediately produced a contraction and a relaxation, respectively, in ryanodine- and high K(+)-contracted muscles while a biphasic change (an initial decrease then a late increase) of muscle tone was produced in muscles contracted with caffeine. The O2 occlusion effects were reversed after reoxygenation. CN- produced similar acute changes of muscle tone and abolished O2 occlusion effects. The O2 occlusion-induced relaxation in high K+ medium was converted into a contraction by 3,4-diaminopyridine and by low Cl- Tyrode's. O2 occlusion induced a small outward current and membrane hyperpolarization at a rate slower than the changes of muscle tone. Glybenclamide inhibited all of the changes induced by O2 occlusion. It is possible that the K+ and Cl- permeabilities of sarcoplasmic reticulum are highly sensitive to hypoxic challenge and related to the immediate changes of muscle tone after O2 occlusion.

Improvement by diazepam of neuromuscular transmission blocked by anticholinesterase agents in mouse diaphragms

Effects of diazepam on the neuromuscular transmission blocked by neostigmine were studied in isolated mouse phrenic nerve-diaphragm preparations. Diazepam, in the absence of neostigmine, had no significant effect on the neuromuscular transmission at concentrations lower than 100 microM, except to enhance muscle contractility. Single and train pulses-evoked endplate potentials (e.p.p.s) and miniature e.p.p.s (m.e.p.p.s) were also unaffected. At concentrations of 175 microM or higher, diazepam caused an axonal conduction block. However, neostigmine-induced twitch potentiation, spontaneous fasciculation and tetanic fade were antagonized by diazepam at 3.5-35 microM. Diazepam did not decrease the amplitude of neostigmine-augmented e.p.p.s and m.e.p.p.s but slightly reduced their decay time. The incidence of regenerative depolarization of endplates induced by repetitive stimulation in the presence of neostigmine, was decreased from 92% to 35% junctions and the duration shortened from 650 ms to 230 ms. The amplitude of train e.p.p.s was increased. It is suggested that diazepam reverses the muscle paralysis induced by anticholinesterase agents by inhibiting the regenerative release of acetylcholine.

Osteonecrosis: current perspectives on pathogenesis and treatment

Nontraumatic osteonecrosis results from impairment of circulation to the affected bone. The femoral head is affected most frequently. The underlying cause for the circulatory defect in osteonecrosis varies and may involve both local and systemic changes. Steroid use, alcohol consumption, pancreatitis, and lipid disorders appear to lead to bone death either by development of fat emboli in the microcirculature surrounding the affected bone or by fatty infiltration of the marrow. Decompression syndrome results from the presence of gaseous emboli in the microcirculature. In Legg-Calvé-Perthes disease other associated features are present such as short stature, suboptimal growth velocity, and/or hormonal imbalances, and it is likely that osteonecrosis may be secondary to systemic abnormalities, although specific factors have not been identified. Other frequently suggested pathogenic factors that play a role in the development of osteonecrosis include increased intraosseous pressures, the presence of cytotoxic cellular factors, intravascular coagulation, venous stasis, and the hyperviscosity syndrome. Some investigators have attempted, without success, to find a common etiology for all cases of osteonecrosis. In addition, patients have developed osteonecrosis without any known risk factors; this syndrome has been coined idiopathic avascular necrosis. In advanced stages of femoral head osteonecrosis, total hip arthroplasty appears to be the best therapeutic modality, particularly in older individuals.

Purification, sequencing and characterization of single amino acid-substituted phospholipase A2 isozymes from Trimeresurus gramineus (green habu snake) venom

Two phospholipases A2 named PLA2-III and IV were newly isolated from Trimeresurus gramineus (green habu snake) venom in addition to PLA2-I and II reported previously [ODA et al. (1991) Toxicon 29, 157; Fukagawa et al. (1992) Toxicon 30, 133]. Their isoelectric points were determined to be about 4.5. PLA2-III and IV exhibited almost unchanged lipolytic activity toward egg-yolk when compared with PLA2-I. The amino acid sequences were determined by sequencing the native proteins and the peptides produced by enzymatic (Achromobacter protease I and clostripain) and chemical (hydroxylamine) cleavages of the S-carboxamidomethylated derivative of the proteins. Both proteins consisted of 122 amino acid residues. When compared with PLA2-I, PLA2-III showed only a single amino acid substitution at the N-terminal position; namely from His to Asn. PLA2-IV also showed a single substitution from Ala to Asp at position 72. It was inferred that these amino acid substitutions between PLA2-I and PLA2-III or IV are due to the single base substitution at the corresponding codons of genes, which might be preserved independently. The unique presence of Phe at position 28, where Tyr is commonly located and assumed to be a part of the Ca(2+)-binding loop, was conserved in both PLA2-III and IV as in PLA2-I. There was no significant difference in the dissociation constants (4.3-5.2 x 10(-4) M) for Ca2+ between these PLA2S and Tyr-28-containing PLA2S. These results suggested that the p-hydroxy group of Try-28 does not play a crucial role in binding of PLA2S to Ca2+.

Transmitter-mediated local contracture of the endplate region of the focally innervated mouse diaphragm treated with anticholinesterase

1. Local contraction of the endplate region in response to nerve stimulation was studied in isolated mouse diaphragms. In normal preparations, muscle contractions involved the whole length of the muscle fibre with rise and decay times in the order of tens of ms whether evoked with a single or train of pulses. 2. When acetylcholinesterase was inhibited with neostigmine, tetanic stimulation produced a twitch-like phasic contraction and a delayed tonic contracture. A brief train of pulse (10 ms, 300 Hz) was enough to trigger a full size tonic contracture which reached an amplitude about one tenth that of control tetanus and had a duration of about 4 s. 3. Tetanic stimulation evoked a non-propagating prolonged depolarization at the endplate region lasting for about 1 s following a few muscle action potentials. 4. mu-Conotoxin, a specific inhibitor of muscle Na+ channel, selectively abolished the phasic contraction and the muscle action potentials leaving the tonic contracture and the prolonged depolarization unaffected. 5. Both the tonic contracture and the prolonged depolarization were highly sensitive to blockade by tubocurarine (IC50 0.05-0.1 microM) and vesamicol (1 microM, an inhibitor of packaging acetylcholine into synaptic vesicles), were attenuated by increasing Ca2+ concentration and were prolonged by decreasing Ca2+. 6. The results suggest that prolonged activation of endplate nicotinic receptors by endogenously released transmitter can produce substantial contractions of the endplate region when acetylcholinesterase are inhibited. The source of Ca2+ for the contraction seems to come mainly from intracellular stores.

Effects of insulin on TGF-beta 1-induced cell growth inhibition in the human hepatoma cell lines

The effects of insulin on cell growth control by transforming growth factor beta 1 (TGF-beta 1) in human hepatoma cell lines were studied. TGF-beta 1 inhibited cell growth and DNA synthesis of Hep3B cells but not that of HA22T/VGH cells. The cell cycle-dependent p34cdc2 kinase activity was inhibited by TGF-beta 1 in a dose-dependent manner in Hep3B cells. In contrast, the p34cdc2 kinase activity of HA22T/VGH cells was not regulated by TGF-beta 1. When insulin (10(-7) M) was added simultaneously with TGF-beta 1, we found that the inhibitory effects of TGF-beta 1 on cell growth and DNA synthesis in Hep3B cells was completely blocked and the p34cdc2 kinase activity of Hep3B cells was recovered after insulin administration. Thus, cell growth inhibition by TGF-beta 1 in Hep3B hepatoma cells can be antagonized by insulin and their interaction may play an important role in the tumor progression stage of hepatocarcinogenesis.

Effects of epidermal growth factor on growth control and signal transduction pathways in different human hepatoma cell lines

The roles of epidermal growth factor (EGF) on cell growth control and phosphatidylinositol signal transduction pathway in human hepatoma cell lines with different differentiated states were evaluated. Ligand binding study showed that only one receptor type with similar affinity was found in all three cell lines. Under serum-free conditions, EGF (10(-8)-10(-11) M) enhanced DNA synthesis and cell proliferation of the three cell lines in a dose-dependent manner. The response of the poorly differentiated HA22T/VGH hepatoma cells was most obvious whereas much smaller effects were found in Hep3B and Chang liver cells. The metabolism of phosphoinositides also increased in HA22T/VGH cells as compared with both Hep3B and Chang liver cells under basal and EGF-treated conditions. Our data indicated that EGF had different effects on different human hepatoma cell lines and its role might be more important in poorly differentiated hepatoma cells than in well differentiated ones.

Anordiol is more potent than anordrin for terminating pregnancy when administered with RU 486

In view of the unexpected ability of anordrin to synergize with RU 486 in terminating pregnancy, it was pertinent to examine the actions of the dihydroxylated metabolite of anordrin, anordiol, alone and in combination with RU 486. Does of RU 486 (1 mg/kg/day) and anordiol (0.6 mg/kg/day) that were ineffective when given alone terminated pregnancy with complete resorption of embryos when administered together. A smaller dose of anordiol than anordrin is required to achieve this synergistic effect with RU 486. This anordrin metabolite increased uterine weight in the ovariectomized rat similar to estradiol. The estrogenicity of anordiol in the uterine weight assay was about 1/120 of that of estradiol. Anordiol does not exert antiestrogenic activity in the uterine weight assay when administered at doses that terminate pregnancy. Administration of anordiol at doses that do not terminate pregnancy resulted in a significant suppression of serum progesterone concentrations during the period of medication; these observations suggest that anordiol has an inhibitory effect on progesterone biosynthesis. When the same dose of anordiol was given concomitantly with sufficient RU 486 (e.g., 1 mg/kg/day) to terminate pregnancy, the progesterone levels were reduced to low levels throughout the experiment. These observations support the postulate that the actions of anordrin are mediated by its metabolite, anordiol. The administration of anordiol plus RU 486 results in a more dramatic change in the functional progesterone:estradiol ratio than when either agent is administered alone.

Termination of early pregnancy in the rat, rabbit, and hamster with RU 486 and anordrin

The effectiveness of oral RU 486 and anordrin given alone and in combination for terminating early pregnancy was tested in the rat, rabbit, and hamster. In the rat and rabbit, the combination of RU 486 and anordrin is more effective in terminating pregnancy than either of the two compounds used alone. A non-effective dose of RU 486 combined with a non-effective or a sub-effective dose of anordrin, or a low effective dose of RU 486 in combination with a non-effective dose of anordrin, exerted additive or synergistic effects resulting in resorption of embryos and termination of pregnancy in rats and rabbits. The serum progesterone as well as estradiol concentrations were significantly suppressed by these combinations when pregnancy was terminated. In the hamster, however, RU 486 was not effective in interrupting early pregnancy, even at a 4-fold higher dose than was effective in the rat, due to the fact that RU 486 does not bind to the progestin receptor in this species. Unexpectedly, there were also no effects of anordrin on pregnancy termination in the hamster even at high doses. It is concluded that in rat and rabbit, the synergistic action between RU 486 and anordrin not only greatly enhances efficacy in terminating pregnancy but also reduces substantially the doses required to produce this effect.