Design, synthesis and evaluation of racemic 1-(4-hydroxyphenyl)-2-[3-(substituted phenoxy)-2-hydroxy-1-propyl]amino-1-propanol hydrochlorides as novel uterine relaxants

Novel 1-(4-hydroxyphenyl)-2-[3-(substituted phenoxy)-2-hydroxy-1-propyl]amino-1-propanol hydrochlorides were designed based on the pharmacophore for potent uterine relaxant activity and by utilizing the principles of structural hybridization. The designed molecules were synthesized as racemates by a novel route and were evaluated for uterine relaxant activity in vitro on isolated rat uterus and in vivo in pregnant rats. Their cAMP-releasing potential was studied using rat uterus tissue homogenates by the cAMP [(3)H] assay, and cardiac stimulant potential was evaluated on isolated guinea pig right atrium. All compounds exhibited potent uterine relaxant activity in vitro and produced a significant delay in the onset of labour in pregnant rats; their cAMP-releasing potential was slightly less, while their cardiac stimulant potential was insignificant as compared to isoxsuprine hydrochloride.     

Cyclic adenosine 3'5'-monophosphate and the relaxant action of relaxin in the rat uterus in vivo.

The relationship between relaxant actions of relaxin in the uterus and changes in uterine cAMP concentrations was assessed in anaesthetized bilaterally ovariectomized nonpregnant rats. Relaxin i.v. bolus (5 micrograms kg-1) did not change cAMP concentrations but inhibited uterine contractions with rapid onset. Uterine contractions were significantly reduced by 30-70% for 60 min. Relaxin (50 micrograms kg-1) produced a short-lived (up to 5 min) and small (up to 3.2-fold) increase in cAMP concentrations plus a marked (90%) and prolonged inhibition of uterine contractions (70-90% over 60 min). Salbutamol (an agonist at beta 2-adrenoceptors, 100 and 500 micrograms kg-1) produced a similar degree and time course of inhibition of uterine contractions to that of relaxin but a more marked (19-fold) increase in cAMP concentrations. Glibenclamide, a blocker of ATP-sensitive potassium channels, which has been shown to antagonize relaxin as a uterine relaxant, did not prevent the relaxin-induced rise in cAMP concentrations. It is suggested that the uterine relaxant action of relaxin may not result from an increase in uterine cAMP concentrations.     

Hypothyroid state reduces calcium channel function in 18-day pregnant rat uterus

Hypothyroidism significantly reduced the mean amplitude and increased the mean frequency of spontaneous rhythmic contractions in 18 day pregnant rat uterus. Nifedipine (10(-12)-10(-9) M) and diltiazem (10(-10)-10(-6) M) caused concentration related inhibition of the myogenic responses of the uterine strips obtained from both pregnant and hypothyroid state. However, nifedipine was less potent (IC50:2.11 x 10(-11) M) in pregnant hypothyroid state as compared to pregnant control (IC50: 3.1 x 10(-12) M). Similarly, diltiazem was less potent (IC50: 3.72 x 10(-9) M) in inhibiting the uterine spontaneous contractions in hypothyroid than in pregnant rat uterus (IC50:5.37 x 10(-10) M). A similar decrease in the sensitivity to nifedipine and diltiazem for reversal of K+ (100 mM)-induced tonic contraction and K(+)-stimulated 45Ca2+ influx was observed with these calcium channel antagonists in uterus obtained from hypothyroid pregnant rats compared to the controls. Nifedipine-sensitive influx of 45Ca(2+)-stimulated either by K+ (100 mM) or by Bay K8644 (1,4-dihydro-2,6-methyl-5-nitro-4-[2'-(trifluromethyl)phenyl]-3-pyridine carboxylic acid methyl ester) (10(-9) M) was significantly less in uterine strips from hypothyroid rats compared to controls. The results suggest that the inhibition of uterine rhythmic contractions may be attributable to a reduction in rat myometrial Ca2+ channel function in the hypothyroid state.     

Role of myometrial constriction in the induction of wavy ribs in rat fetuses

Furosemide, a loop diuretic, was orally administered to pregnant Crj: CD (SD) rats at a dose of 300 mg/kg once on day 16 of gestation. Cartilage bone double staining of day 17 fetuses revealed a delay in ossification. Characteristic rib deformities were not seen until day 18 of gestation. Concomitant with this observation were reductions in the amount of amniotic fluid, compared to controls, on day 18 of gestation and thereafter. When isoxsuprine HCl (2 mg/kg, b.i.d.), a uterine muscle relaxant, was additionally injected ip to pregnant rats on days 17-19 of gestation, the incidence of wavy ribs was significantly (P less than or equal to .05) less than that seen after treatment with furosemide alone. These observations indicate that the myometrial constriction plays a significant role in the induction of furosemide-induced wavy ribs.     

Inhibitory effect of GnRH on isolated rat uterine muscle contractility

The effect of GnRH upon uterine contractions of both non-pregnant and pregnant rats was examined in vitro. In the non-pregnant rat uterus, GnRH inhibited in a concentration-and-time dependent manner the contractions induced by acetylcholine and oxytocin, but not those caused by bradykinin and angiotensin II. GnRH also inhibited the rhythmic contractions induced by oxytocin in uterine strips from late pregnant rats. These findings show that GnRH has a direct inhibitory effect on the rat uterine contractions, suggesting that GnRH-like substances may exert modulatory influences upon rat uterine contractility.     

Effect of bromocriptine on prostacyclin release and cyclic nucleotides on rat aortic and uterine tissues

The effect of bromocriptine mesylate on cyclic nucleotides and PGI2 release by rat aortic and uterine tissues was investigated. Treatment of rats with bromocriptine (10 mg kg-1 I.P. daily for 14 days) increased PGI2 release by the thoracic aorta from 0.67 +/- 0.02 to 1.4 +/- 0.03 ng/mg wet tissue (P less than 0.001; n = 6). This increase was antagonized by treatment with sulpiride (15 mg kg-l). Incubation of the arterial tissue with bromocriptine (50 micrograms ml-1) in vitro also stimulated PGI2 release. Mepacrine (160 micrograms ml-1) significantly decreased both basal and stimulated PGI2 release. Incubation of myometrial tissue from pregnant rats with bromocriptine (50 micrograms ml-1) in vitro significantly decreased PGI2 release from 1.25 +/- 0.07 to 0.60 +/- 0.08 ng/mg wet tissue (P less than 0.05, n = 6). It also elevated uterine cAMP from 40 +/- 2 to 64 +/- 3 pmoles/100 mg wet tissue. Both effects were antagonized by sulpiride. Bromocriptine did not affect uterine cGMP or the cyclic nucleotides in the aorta. It is concluded that the increase in aortic PGI2 was mediated via activation of dopamine D-2 receptors that stimulate phospholipase A2 enzyme. The decrease in myometrial PGI2 release may be related to the increase in uterine cAMP resulting from activation of dopamine D-1 receptors. Previous studies suggested a role for PGI2 in implantation in the rat. The results suggest that the inhibitory effect on uterine PGI2 may underlie the reported inhibition of bromocriptine on implantation. On broad basis, the decrease in uterine PGI2 together with the reported luteolytic effect of bromocriptine point to a potential role for the compound in postcoital contraception.     

Synthesis, antimicrobial, and anti-HIV-1 activity of certain 5-(1-adamantyl)-2-substituted thio-1,3,4-oxadiazoles and 5-(1-adamantyl)-3-substituted aminomethyl-1,3,4-oxadiazoline-2-thiones

The reaction of 5-(1-adamantyl)-1,3,4-oxadiazoline-2-thione 2 with iodoethane, 2-dimethylaminoethyl chloride hydrochloride or 2-piperidinoethyl chloride hydrochloride in ethanolic potassium hydroxide yielded the corresponding 5-(1-adamantyl)-2-ethyl or substituted ethylthio-1,3,4-oxadiazoles 3a-c. Interaction of 2 with formaldehyde solution and primary aromatic amines or 1-substituted piperazines, in ethanol at room temperature yielded the corresponding 5-(1-adamantyl)-3-arylaminomethyl-1,3,4-oxadiazoline-2-thiones 4a-m or 5-(1-adamantyl)-3-(4-substituted-1-piperazinylmethyl)-1,3,4-oxadiazoline-2-thiones 5a-h, respectively. All the synthesized compounds were tested for in vitro activities against certain strains of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Compounds 2, 5a, and 5e were found as the most active derivatives, particularly against the Gram-positive bacteria. In addition, the antiviral activity of compounds 2, 4a-m, and 5a-h against HIV-1 using the XTT assay was carried out. Compound 2 produced 100%, 43%, and 37% reduction of viral replication at 50, 10, and 2microg/mL concentrations, respectively.     

Incorporation of [3H] uridine into the ribonucleic acid of rat uterus during pseudopregnancy and in the presence of I.C.I. 46474 [trans-1-(p-β-dimethylaminoethoxyphenyl)-1,2-diphenylbut-1 -ene]

1. The incorporation of [(3)H]uridine into RNA of rat uterine tissue has been measured during pseudopregnancy and in rats receiving different doses of an anti-implantation compound [trans-1-(p-beta-dimethylaminoethoxyphenyl)-1,2-diphenylbut- 1-ene, I.C.I. 46474]. 2. In the uterus of the pseudopregnant rat uridine incorporation into RNA increased markedly on day 3 of pseudopregnancy, remained high until day 5 and decreased sharply by day 6, rising again by day 9. 3. This pattern of change was similar to, but not identical with, that previously found in the pregnant rat. 4. Rats receiving I.C.I. 46474 at a dose concentration below that preventing implantation showed a pattern of RNA synthesis similar to that found in untreated control rats. 5. Rats treated with doses of I.C.I. 46474 sufficient to inhibit implantation revealed a totally different pattern of incorporation of [(3)H]uridine into uterine RNA. 6. The results are discussed in terms of previous findings with the normally pregnant rat. It is concluded that the increasing uterine RNA synthesis found on day 3 in the pregnant rat is an important requirement for the occurrence of the subsequent implantation.     

Role of capsaicin-sensitive nerve fibers in uterine contractility in the rat

The possible participation of capsaicin-sensitive sensory nerves in the modulation of neurogenic contractions was studied in nonpregnant and term pregnant rat uteri. Neurogenic contractions were elicited by electric field stimulation (40 V, 1-70 Hz, 0.6 msec) in intact uteri and uteri that were previously exposed to capsaicin in vitro. In capsaicin pretreated preparations obtained both from nonpregnant and term pregnant rats, a dose-dependent increase in the amplitude of uterine contractions was detected. Prior systemic treatment of the rats with capsaicin (130 mg/kg, s.c.) abolished the effect of in vitro capsaicin administration on the amplitude of neurogenic contractions. Use of a specific antagonist of calcitonin gene-related peptide revealed that depletion of this peptide, which normally elicits uterine smooth muscle relaxation, may be responsible for the increased responsiveness of the uterus to low-frequency stimulation. Experiments on the localization of calcitonin gene-related peptide in uterine tissue specimens exposed to capsaicin revealed dose-dependent depletion of calcitonin-gene related peptide-immunoreactive nerves innervating blood vessels and the myometrium. The findings indicate that capsaicin-sensitive afferent nerves, by the release of sensory neuropeptides, significantly contribute to the modulation of uterine contractility both in nonpregnant and term pregnant rats. It is suggested that uterine sensory nerve activation may be part of a trigger mechanism leading to preterm contractions evoked by, for example, inflammation.     

Beta 2-agonist treatment enhances uterine oxytocin receptor mRNA expression in pregnant rats

The objective of this study was to disclose an interaction between Beta(2)-adrenergic (Beta(2)-ARs) and oxytocin (OT) receptors (OTRs) in the late-pregnant rat uterus. We investigated the level of uterine OTR mRNA expression after the administration of Beta(2)-AR agonists fenoterol and hexoprenaline to rats from day 18 to 22 of pregnancy, and also tested the effect of fenoterol on uterine explants. Hexoprenaline induced a maximum 24% increase of OTR mRNA. Fenoterol in vivo elicited a maximum 125% increase of OTR mRNA, in vitro produced a maximum fourfold increase in OTR mRNA. In fenoterol-treated rats the maximal contractility increasing effect of OT on isolated uterine rings was significantly higher than in intact term pregnant rats, but the EC50 values were not statistically different. It was concluded that the enhanced expression of OTR mRNA induced by Beta(2)-agonists in the late-pregnant rat uterus may be a possible drawback to effective therapy of preterm uterine contractions with Beta(2)-agonists.     

Some biological activities of a series of 9a-homo-9,11-epoxy prostanoic acid analogues

A number of stereochemical variants at C-8, C-12 and C-15 of 9a-homo-9,11-epoxy prostaglandins (PGs) have been examined for in vivo activity on blood pressure, bronchial resistance, tracheal segment pressure, heart rate and on intestinal and uterine contractility in artificially respired anaesthetised guinea-pigs; and on blood pressure and blood platelet aggregation in rats (using the extra-corporeal filter-aorta loop technique). In vitro tests for smooth muscle activity were carried out on the isolated rat fundus strip, the guinea-pig tracheal chain and the rat uterus. The following was found: 1. In the guinea-pig, in vivo, all the homo-epoxy PGs were vasopressor and bronchoconstrictor following bolus injections of 250 micrograms i.v. The effects on heart rate, and intestinal and uterine contractility were equivocal. The configurations at the chiral centres, C-8, C-12 and C-15 play an important role in determining potency. The 15-(S)-hydroxy derivatives were the most potent in stimulating vascular and respiratory muscle. The 8-iso configuration appeared to enhance potency amongst the 15-(S)-hydroxy compounds. The 15-(R)-hydroxy configuration markedly reduced constrictor potency. The same pattern of activity was seen on rat blood pressure, in vivo. The 15-(S)-hydroxy configuration combined with the 8-iso configuration had the most potent constrictor activity, while the 15-(R)-hydroxy group negated this and even led, in the case of the natural configuration at C-8 and C-12, to vasodepression. 2. In vitro, the activity on the rat fundus and guinea-pig tracheal chain followed the same pattern. The 15-(S)-hydroxy derivatives were very much more potent than the 15-(R)-hydroxy derivatives at contracting the smooth muscle preparations. Uterine muscle appeared to be relaxed by the PGs with the natural configuration at C-8 and C-12, with the 15-(R)-hydroxy compound exhibiting greater activity. 3. Inhibition of ADP-induced rat blood platelet aggregation after "intra-arterial" administration was shown only by the derivatives with a single change in the natural configuration either at C-8 or at C-15. Additional changes either resulted in inactivity or, in the case of the 8,12-di-iso-15-(S)-hydroxy compound, even reversed the effect to aggregation. The inhibition of aggregation was long lasting with both the 8-iso-15-(S)-hydroxy derivative and the 8,12-nat-15-(R)-hydroxy derivative. In the case of the latter compound, GBR-30731, activity increased during the 30 min after administration. GBR-30731 deserves further investigation as a platelet aggregation inhibitor because of its relatively low smooth muscle stimulant (sometimes even relaxant effects) and its long lasting platelet aggregation inhibiting activity.     

Synthesis and biological evaluation of 2-trifluoromethyl/sulfonamido-5,6-diaryl substituted imidazo[2,1-b]-1,3,4-thiadiazoles: a novel class of cyclooxygenase-2 inhibitors

A series of 2-trifluoromethyl/sulfonamido-5,6-diarylsubstituted imidazo[2,1-b]-1,3,4-thiadiazole derivatives 15a-j have been synthesized by the reaction of 2-amino-5-trifluoromethyl/sulfonamido-1,3,4-thiadiazoles 14a-b and appropriately substituted alpha-bromo-1,2-(p-substituted)diaryl-1-ethanones 13a-h. Structures of these compounds were established by IR, (1)H NMR, (13)C NMR, Mass, and HRMS data. The selected compounds were evaluated for their preliminary in vitro cyclooxygenase inhibitory activity against COX-2 and COX-1enzymes using colorimetric method. The compounds tested showed selective inhibitory activity toward COX-2 (80.6-49.4%) over COX-1 (30.6-8.6), amongst them compounds 15f and 15j showed appreciable COX-2 selective inhibitory activity. These compounds also exhibited significant anti-inflammatory activity (70.09-42.32%), which is comparable to that of celecoxib in the carrageenan-induced rat paw edema method.     

Pregnancy-induced long-term uterine vascular remodeling in the rat

Despite the available research investigating uterine physiology during and immediately following pregnancy, including at the vascular and muscular levels, knowledge of the potential long-term timeline of such changes is limited. Thus, our study sought to investigate the potential long-term changes in uterine vasculature and horn length in the postpartum rat, following delivery and weaning. Female Long-Evans rats (n = 9–11 rats/group/timepoint) were divided into two groups: a pregnant group and an age-matched virgin control group. Rat weight, food consumption and vaginal impedance measurements were recorded throughout the experiment. Rats in the pregnant group were bred and pregnancy was confirmed using ultrasound imaging. The uterus and its vasculature were collected at various timepoints following weaning: 3 (week of weaning), 8–9 and 13 weeks postpartum, and at age-equivalent timepoints in the virgin group, and the diameters of the main uterine artery and vein, and lengths of the mesometrial segmental vessels (MSV) and uterine horns were recorded. The results indicated a significant difference between the previously-pregnant and virgin rats in both internal and external arterial diameters (but not arterial wall thickness), as well as the uterine horn length, 3 weeks postpartum, but not 8–9 and 13 weeks postpartum. Significant differences were observed in both venous diameter and MSV length at all timepoints measured. Placental scars were also observed in previously-pregnant rats at all timepoints measured. Our study highlights the long-term impact of pregnancy on the uterine vasculature and the necessity for consideration of such changes on subsequent pregnancies, as well as pregnancy-related vascular pathologies.     

Heme oxygenase-carbon monoxide (HO-CO) system in rat uterus: effect of sexual steroids and prostaglandins

Pregnancy maintenance is a very complex phenomenon, and the mechanisms that allow the survival of the fetus within the maternal uterus are still poorly understood. Our objectives were to analyze heme oxygenase (HO) activity and expression in the pregnant rat and to study its association with steroid hormones and prostaglandins. Uterine tissues were obtained from non-pregnant and from time-mated rats at days 5, 13, 18-22 of pregnancy and postpartum. HO activity was significantly higher at days 5 and 20 while HO-1 protein levels measured by Western blot, were significantly elevated from days 19 to 22. In ovariectomized rats, estrogen and progesterone in estrogenized animals increased HO activity and expression. Cyclooxygenase inhibitors augmented HO activity and HO-1 expression. Pre-incubation with prostaglandin F2alpha (PGF2alpha) diminished the enzymatic activity in ovariectomized rat uterus. Tin protoporphyrin IX, an HO inhibitor, significantly decreased uterine cGMP accumulation. Bilirubin decreased uterine thiobarbituric acid substances levels (an index of lipid peroxidation). These results demonstrate a uterine gestational pattern of HO activity and expression in the rat. In addition, these results suggest that uterine HO activity could regulate uterine quiescence in pregnancy via cGMP and it may contribute to the defense against oxidative stress.     

Effects of newly synthetized isoquinoline derivatives on rat uterine contractility and ROCK II activity

Protein kinases have an important role in signal transduction in the cellular system via protein phosphorylation. RhoA activated Rho-kinases have a pivotal role in the regulation of smooth muscle contraction. ROCK I and ROCK II phosphorylate myosin-phosphatase and myosin-kinase, which induces contraction in the myometrium. Several studies have investigated the affinity of isoquinoline alkaloids (HA-1077, H1152P) to Rho-kinases, and these compounds notably inhibited the Ca²⁺-independent process.We measured the efficiency of 25 original, newly synthesized isoquinoline derivatives for the Rho-kinase activity using Rho-associated kinase activity assay and determined their effects on the non-pregnant, 20-day pregnant and parturient rat myometrial contraction in vitro.The IC₅₀ values of 11 from among the 25 derivatives were significantly lower on the oxytocin-induced non-pregnant rat uterine contraction compared with Y-27632 and fasudil, although their maximal inhibitory effects were weaker than those of Y-27632 and fasudil. We measured the effects of 11 isoquinoline molecules with significant IC₅₀ values on ROCK II activity. We found two isoquinolines out of 11 compounds (218 and 852) which decreased the active ROCK II level similarly as Y-27632. Then we found that 218 and 852 relaxed the 20th-day pregnant and parturient rat uterus with greater potency as compared with fasudil.The majority of the synthesized isoquinoline derivatives have uterus relaxant effects and two of them significantly suppress the Rho-kinase mediated myosin light chain phosphorylation. Our results may suggest that the isoquinoline structure has a promising prospect for the development of new and effective inhibitors of uterine contractions in preterm birth.     

离体子宫张力测定在药物生殖毒性研究中的应用

目的:建立药物生殖毒性研究中孕鼠离体子宫平滑肌张力的测定方法。方法:SD大鼠于妊娠第6~15天(GD6-15)给予受试物,在妊娠第20天(GD20)取子宫平滑肌,分别给予不同浓度缩宫素和硫酸镁溶液刺激,选择试验的最佳条件。在此基础上,测定不同剂量组孕鼠离体子宫平滑肌张力的变化情况,采用RM-6240BD多道生理信号采集处理系统分析数据,统计结果。结果:选择0.007 U/m L缩宫素、0.008 mol/m L硫酸镁为最佳刺激浓度。随着受试物剂量的增加,加入缩宫素后,各组妊娠子宫平滑肌的频率和张力均呈逐渐上升的趋势,而加入硫酸镁后,各剂量组妊娠子宫平滑肌的活动幅度、频率和张力均呈现降低的趋势,但各剂量组与溶媒对照组相比均未见明显差异(P0.05)。结论:本研究建立了孕鼠离体子宫平滑肌张力的测定方法,该方法可以更好的反映受试物对孕鼠子宫肌的毒性作用,更加全面的评价受试物的生殖毒性。     

Uterine estrogen sulfatase activity at the time of blastocyst implantation in the rat

The conversion of estrone sulfate (E1S) to estrone (E1) was measured during the in vitro incubation of the labeled sulfoconjugate with implantation sites (IS) and nonimplanted regions (NIS) of uterine horns from 6-day pregnant rats. Extensive metabolism of E1S occurred in both tissues, being noticeably less (29.31%) in IS than in NIS. Estrogen sulfatase activity present in the uterus of ovariectomized virgin rats was found to be higher than in both uterine regions of the pregnant rats. We suggest that E1S present in uterine fluids may be accessible to be metabolized into unconjugated estrogens by both intrauterine tissues of 6-day pregnant rats. This metabolism could be locally modulated in IS through the participation of the estrogen sulfatase, the activity of which is in turn controlled by the presence of free estrogens, possibly synthesized and/or secreted by the embryo, which has been shown to inhibit the sulfohydrolase activity.     

Estrogen effects on platelet-activating factor and platelet-activating factor acetylhydrolase activity in rat uterus during the late stages of pregnancy.

The platelet-activating factor (PAF) concentration of the uterus spontaneously increased during pregnancy. When 17alpha-ethynylestradiol (0.25 mg/kg) was administered subcutaneously to pregnant rats for 3 days starting on Day 17 of pregnancy, some rats delivered prematurely on Day 20. However, none of the vehicle-treated (80% dimethylsulfoxide and 20% ethanol) pregnant rats delivered prematurely. The PAF concentration of the uterus in pregnant rats treated with 17alpha-ethynylestradiol was significantly higher than in those treated with vehicle on Days 19 and 20. On the other hand, the specific activity of uterine PAF-acetylhydrolase (PAF-AH) in pregnant rats treated with 17alpha-ethynylestradiol was significantly lower than in those treated with vehicle on Days 19 and 20, and the plasma PAF-AH activity in pregnant rats treated with estrogen was also significantly lower than in treated with vehicle on Days 18, 19, and 20. These findings indicate that estrogen increases PAF concentrations in the rat uterus, and this was correlated with a decrease in PAF-AH in the uterus and plasma. The increase in PAF concentrations in the uterus may be related to premature delivery and labor caused by PAF's known effect on myometrial contraction.     

Synthesis and antimicrobial studies of novel 1-benzhydryl-piperazine sulfonamide and carboxamide derivatives

A series of novel substituted 1-benzhydryl-piperazine sulfonamide 8(a-f) and benzamides 9(a-h) were synthesized and their antimicrobial activities evaluated in vitro by paper disc diffusion and micro dilution method against standard strains of Gram-positive (Staphylococcus aureus ATCC 25953, Staphylococcus epidermis 25212, Bacillus cereus 11778, Bacillus substilis 6051) and Gram-negative (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 2853, Proteus vulgaris ATCC 2853 and Salmonella typhi ATCC 9484) bacteria. Among the synthesized new compounds 8d, 8e, 9c, 9e, 9f and 9 h showed potent antimicrobial activities compared to the standard drug streptomycin.