Active Congeners Research Articles

Bombesin-related peptides induce calcium mobilization in a subset of human small cell lung cancer cell lines.

To examine the biochemical basis for growth factor-induced responses in human lung cancer cells, we used the quin2 technique to study the effect of the amphibian peptide bombesin and its congeners including mammalian gastrin-releasing peptide (GRP) on the intracellular free calcium level [Ca2+]i in small cell lung cancer cell lines. In five of eleven cell lines tested, Tyr4-bombesin or GRP elicited a rapid and transient increase in [Ca2+]i. The response was seen with as little as 1 nM ligand, was not affected by membrane depolarization, and derived in part from internal calcium stores. Desensitization to a second addition of active bombesin congeners occurs subsequent to initial addition of Tyr4-bombesin. Structure-activity analysis showed the carboxyl-terminal octapeptide was the active portion of the peptide. Analogs in which the carboxyl terminus was oxidized or deamidated were inactive. Ranatensin, litorin, alytesin, and GRP, but not physalaemin, were as active as Tyr4-bombesin. A monoclonal antibody to the carboxyl terminus of bombesin selectively blocked the increased [Ca2+]i elicited by Tyr4-bombesin. These studies suggest that bombesin congeners can act on some small cell lung cancer cell lines by a pathway utilizing increased [Ca2+]i.

A quantum-chemical and experimental study of the hallucinogen (±)-1-(2,5-dimethoxy-4-nitrophenyl)-2-aminopropane (DON)

The electronic structure of 1-(2,5-dimethoxy-4-nitrophenyl)-2-aminopropane (DON) was calculated at the CNDO/2 level, and the racemic compound was synthesized and found to be hallucinogenic at doses of 4 mg. DON differs from its similarly active congeners in that a hydrophilic nitro group replaces lipophilic substituents at C-4 of the benzene ring. The implications for the mechanism of serotonin receptor binding of these drugs are discussed.

Reproductive effects of four phthalic acid esters in the mouse

These studies compared the reproductive toxicity of four phthalates by a continuous breeding protocol. Mice were given diets with diethyl phthalate (DEP) (0.0, 0.25, 1.25, or 2.5%), di- n-butyl phthalate (DBP) (0.0, 0.03, 0.3, or 1.0%), di- n-hexyl phthalate (DHP) (0.0, 0.3, 0.6, or 1.2%), or di(2-ethylhexyl) phthalate (DEHP) (0.0, 0.01, or 0.3%). Both male and female CD-1 mice were dosed for 7 days prior to and during a 98-day cohabitation period. Reproductive function was evaluated during the cohabitation period by measuring the numbers of litters per pair and of live pups per litter, pup weight, and offspring survival. There was no apparent effect on reproductive function in the animals exposed to DEP, despite significant effects on body weight gain and liver weight. DBP exposure resulted in a reduction in the numbers of litters per pair and of live pups per litter and in the proportion of pups born alive at the 1.0% amount, but not at lower dose levels. A crossover mating trial demonstrated that female mice, but not males, were affected by DBP, as shown by significant decreases in the percentage of fertile pairs, the number of live pups per litter, the proportion of pups born alive, and live pup weight. DHP in the diet resulted in dose-related adverse effects on the numbers of litters per pair and of live pups per litter and proportion of pups born alive at 0.3, 0.6, and 1.2% DHP in the diet. A crossover mating study demonstrated that both sexes were affected. DEHP (at 0.1 and 0.3%) caused dose-dependent decreases in fertility and in the number and the proportion of pups born alive. A crossover mating trial showed that both sexes were affected by exposure to DEHP. These data demonstrate the ability of the continuous breeding protocol to discriminate the qualitative and quantitative reproductive effects of the more and less active congeners as well as the large differences in reproductive toxicity attributable to subtle changes in the alkyl substitution of phthalate esters.

Method for the determination of three toxic non-ortho chlorine substituted coplanar PCBs in environmental samples at part-per-trillion levels.

A method has been devised combining alkali digestion, carbon chromatography and high-resolution gas chromatography for the determination of 3,3',4,4'-tetra, 3,3',4,4',5-penta, and 3,3',4,4',5,5'-hexachlorobiphenyl, the biologically active congeners of PCBs and approximate isostereomers of 2,3,7,8-TCDD. This method permits determinations of parts-per-trillion levels of these toxic residues in biological samples. Interference both from biogenic and from xenobiotic substances was reduced to extremely low levels. Using this method, 13.5 ng of 3,3'4,4'-tetrachlorobiphenyl/g, 0.89 ng of 3,3'4,4',5-pentachlorobiphenyl/g and 0.64 ng of 3,3',4,4'5,5'-hexachlorobiphenyl/g were detected on wet weight basis in the blubber of a finless porpoise. To our knowledge this is the first report on the three toxic non-ortho chlorine substituted PCB residues detected in a higher mammal in the wilderness.

Modulation of hepatic 2,3,7,8-TCDD cytosolic receptor levels by PCBs and organochlorine pollutants

Administration of several persistent PCB congeners to male Wistar rats demonstrated a structure-dependent elevation of hepatic cytosolic 2,3,7,8-TCDD receptor levels. 2,2′,4,4′5,5′-Hexachlorobiphenyl and several related compounds which exhibit low affinity for the receptor protein increased receptor levels to over 300% compared to the control animals. Aroclor 1254 and 2,3,3′,4,4′,5′-hexachlorobiphenyl both bind with moderate affinity to the receptor protein (10 uM) and effect some elevation of receptor levels. In contrast, 3,3′,4,4′,5-pentachlorobiphenyl, a toxic PCB with high in vitro binding affinity (10 uM) does not alter hepatic receptor levels. Time course studies, demonstrated that 2,2′,4,4′,5,5′-hexachlorobiphenyl elevated hepatic cytosolic receptor levels for at least 14 days with the maximum elevation occurring 7 days after initial exposure to this PCB congener. In contrast, dose and time-response studies with hexachlorobenzene, several DDT analogs and heptachlor expoxide gave variable results with respect to hepatic 2,3,7,8-TCDD receptor modulation. For the PCBs, it was apparent that the most active congeners exhibited low affinity for the receptor and were phenobarbitone (PB)-like inducers of microsomal monooxygenases. Although all the organochlorine insecticides which were tested also were PB-type monooxygenase enzyme inducers only the DDT analogs modulated hepatic receptor levels.

Phencyclidine in low doses selectively blocks a presynaptic voltage-regulated potassium channel in rat brain.

Phencylidine (PCP) is a major drug of abuse in the United States. It produces a toxic confusional psychosis in man. We show here that nanomolar to micromolar concentrations of PCP and behaviorally active congeners selectively block voltage-regulated noninactivating (or very slowly inactivating) presynaptic K channels in the brain. The rank order of potency for blockage of these K channels parallels both the relative ability of these agents to produce characteristic behavioral deficits in rats and their ability to displace [3H]PCP from its high-affinity binding sites in brain. In view of the enhanced voltage-gated Ca influx that would be expected to accompany blockage of presynaptic K channels, this mechanism could explain the excessive neurotransmitter release that is characteristic of PCP intoxication.

Effects of structure on binding to the 2,3,7,8-TCDD receptor protein and AHH induction--halogenated biphenyls.

The quantitative structure-activity relationships (QSARs) for polychlorinated biphenyl (PCB) congeners have been determined by comparing the EC50 values for three in vitro test systems, namely, aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD) induction in rat hepatoma H-4-II-E cells and competitive binding avidities to the rat cytosolic receptor protein (using 2,3,7,8-tetrachlorodibenzo-p-dioxin as a radioligand). For several PCB congeners that are in vivo inducers of rat hepatic microsomal AHH, there was a linear correlation between the -log EC50 values for receptor and the -log EC50 values for AHH (or EROD) induction; moreover, a comparable linear relationship was observed between the -log EC50 values for AHH and EROD induction. Previous in vivo studies have shown that the most active PCB congeners 3,3',4,4'-tetra-, 3,4,4',5-tetra-, 3,3',4,4',5-penta-, and 3,3',4,4',5,5'-hexachlorobiphenyl, cause many of the biologic and toxic effects reported for the highly toxic halogenated aryl hydrocarbon, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Moreover, the monoortho-substituted homologs of the four coplanar PCBs also elicit comparable in vivo biologic and toxic responses. It was evident from the QSARs for PCBs that there was an excellent correspondence between the in vivo and in vitro potencies of the individual PCB congeners. The effects of substituents on both receptor binding and AHH/EROD induction was determined for a series of 4'-substituted (X)-2,3,4,5-tetrachlorobiphenyls (where X = H, Cl, Br, I, OH, OCH3, NO2, COCH3, F, CF3, CH3, C2H5, i-C3H7, n-C4H9 and t-C4H9). Not unexpectedly, there was a linear relationship between the -log EC50 values for AHH and EROD induction, and these results confirm that both enzymatic oxidations are catalyzed by the same cytochrome P-450 isozyme(s). The effects of substituent structure on receptor binding for 12 substituents was subjected to multiple regression analysis which correlates the relative binding affinities of the compounds with the physical chemical characteristics of the substituents. The analysis gave the following equation: log (1/EC50) = 1.53 sigma + 1.47 pi + 1.09 HB + 4.08 for n = 12, s = 0.18, r = 0.978; where n is the number of substituents, s is the standard deviation, r is the correlation coefficient, and sigma = electronegativity, pi = hydrophobicity (log P) and HB = hydrogen bonding capacity for the substituent groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Structure and alpha-adrenergic activity of pyrazinimidazolines

The effects of newly synthetized pyrazinimidazolines on the contraction of isolated rat tail artery and on the chronotropic action of rat atria as well as the effects on blood pressure in anaesthetized rats were determined. The structure-activity relationships were studied, including standard imidazoline drugs. Starting from practically inactive derivatives the step-by-step structural modifications have been made resulting in markedly active chemical congeners, which were designed, synthetized and tested pharmacologically.

PCBs: structure-function relationships and mechanism of action.

Numerous reports have illustrated the versatility of polychlorinated biphenyls (PCBs) and related halogenated aromatics as inducers of drug-metabolizing enzymes and the activity of individual compounds are remarkably dependent on structure. The most active PCB congeners, 3,4,4',5-tetra-, 3,3',4,4'-tetra-, 3,3',4,4',5-penta- and 3,3',4,4',5,5'-hexachlorobiphenyl, are substituted at both para and at two or more meta positions. The four coplanar PCBs resembled 3-methylcholanthrene (3-MC) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in their mode of induction of the hepatic drug-metabolizing enzymes. These compounds induced rat hepatic microsomal benzo(a)pyrene hydroxylase (aryl hydrocarbon hydroxylase, AHH) and cytochromes P-450a, P-450c and P-450d. 3,4,4',5-Tetrachlorobiphenyl, the least active coplanar PCB, also induced dimethylaminoantipyrine N-demethylase and cytochromes P-450b+e and resembled Aroclor 1254 as an inducer of the mixed-function oxidase system. Like Aroclor 1254, all the mono-ortho- and at least eight di-ortho-chloro analogs of the coplanar PCBs exhibited a "mixed-type" induction pattern and induced microsomal AHH, dimethylaminoantipyrine NM-demethylase and cytochromes P-450a-P-450e. Quantitative structure-activity relationships (QSARs) within this series of PCBs were determined by comparing their AHH induction potencies (EC50) in rat hepatoma H-4-II-E cells and their binding affinities (ED50) for the 2,3,7,8-TCDD cytosolic receptor protein. The results showed that there was an excellent correlation between AHH induction potencies and receptor binding avidities of these compounds and the order of activity was coplanar PCBs (3,3',4,4' -tetra-, 3,3',4,4',5-penta- and 3,3',4,4',5,5'-hexachlorobiphenyls) greater than 3,4,4',5-tetrachlorobiphenyl approximately mono-ortho coplanar PCBs greater than di-ortho coplanar PCBs. It was also apparent that the relative toxicities of this group of PCBs paralleled their biological potencies. The coplanar and mono-ortho coplanar PCBs also exhibit differential effects in the inbred C57BL/6J and DBA/2J mice. These compounds induce AHH and cause thymic atrophy in the former "responsive" mice whereas at comparable or higher doses none of these effects are observed in the nonresponsive DBD/2J mice. Since the responsiveness of these two mice strains is due to the presence of the Ah receptor protein in the C57BL/6J mice and its relatively low concentration in the DBA/2J mice, the results for the PCB cogeners support the proposed receptor-mediated mechanism of action.

PCBs: Structure-Function Relationships and Mechanism of Action

Numerous reports have illustrated the versatility of polychlorinated biphenyls (PCBs) and related halogenated aromatics as inducers of drug-metabolizing enzymes and the activity of individual compounds are remarkably dependent on structure. The most active PCB congeners, 3,4,4',5-tetra-, 3,3',4,4'-tetra-, 3,3',4,4',5-penta- and 3,3',4,4',5,5'-hexachlorobiphenyl, are substituted at both para and at two or more meta positions. The four coplanar PCBs resembled 3-methylcholanthrene (3-MC) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in their mode of induction of the hepatic drug-metabolizing enzymes. These compounds induced rat hepatic microsomal benzo(a)pyrene hydroxylase (aryl hydrocarbon hydroxylase, AHH) and cytochromes P-450a, P-450c and P-450d. 3,4,4',5-Tetrachlorobiphenyl, the least active coplanar PCB, also induced dimethylaminoantipyrine N-demethylase and cytochromes P-450b+e and resembled Aroclor 1254 as an inducer of the mixed-function oxidase system. Like Aroclor 1254, all the mono-ortho- and at least eight di-ortho-chloro analogs of the coplanar PCBs exhibited a "mixed-type" induction pattern and induced microsomal AHH, dimethylaminoantipyrine NM-demethylase and cytochromes P-450a-P-450e. Quantitative structure-activity relationships (QSARs) within this series of PCBs were determined by comparing their AHH induction potencies (EC50) in rat hepatoma H-4-II-E cells and their binding affinities (ED50) for the 2,3,7,8-TCDD cytosolic receptor protein. The results showed that there was an excellent correlation between AHH induction potencies and receptor binding avidities of these compounds and the order of activity was coplanar PCBs (3,3',4,4' -tetra-, 3,3',4,4',5-penta- and 3,3',4,4',5,5'-hexachlorobiphenyls) greater than 3,4,4',5-tetrachlorobiphenyl approximately mono-ortho coplanar PCBs greater than di-ortho coplanar PCBs. It was also apparent that the relative toxicities of this group of PCBs paralleled their biological potencies. The coplanar and mono-ortho coplanar PCBs also exhibit differential effects in the inbred C57BL/6J and DBA/2J mice. These compounds induce AHH and cause thymic atrophy in the former "responsive" mice whereas at comparable or higher doses none of these effects are observed in the nonresponsive DBD/2J mice. Since the responsiveness of these two mice strains is due to the presence of the Ah receptor protein in the C57BL/6J mice and its relatively low concentration in the DBA/2J mice, the results for the PCB cogeners support the proposed receptor-mediated mechanism of action.

Acute anthracycline cardiotoxicity. Comparative morphologic study of three analogues.

Chemotherapeutic use of anthracycline antibiotics is limited by their cardiotoxic effects. A potential solution to this problem is the development of anthracycline analogues retaining antitumor efficacy but without cardiac toxicity. An isolated perfused rabbit heart model was used to compare the nature and extent of early ultrastructural effects on the myocyte of three anthracycline analogues purported to have lesser cardiotoxicity than Adriamycin (doxorubicin). Seventeen rabbit hearts were perfused with oxygenated Krebs-Ringer bicarbonate buffer at 39 degrees C containing either Adriamycin (4 mg/L), daunomycin (10.6 mg/L), aclacinomycin (8 mg/L), or rubidazone (17.6 mg/L). For comparison, three hearts each were exposed to phosphoramide mustard (14.7 mg or 25 mg/L) or 4-hydroperoxy cyclophosphamide (24 mg or 17 mg/L), two active congeners of cyclophosphamide, an agent interacting with DNA differently than the anthracyclines and which is known to be cardiotoxic in high dose. Two hearts were exposed to dactinomycin (0.1 mg or 0.2 mg/L) which intercalates with DNA in a manner similar to the anthracyclines but which is not cardiotoxic. Ten control hearts were perfused with oxygenated buffer solution only. Light microscopic study disclosed no differences between treated and control hearts. Electron microscopic examination showed a striking and distinctive clumping of nuclear chromatin with clearing of chromatin from the nuclear membrane in all anthracycline treated hearts but in no hearts treated with 4-hydroperoxy cyclophosphamide, phosphoramide Mustard, dactinomycin, or control hearts. The nuclear effects of the four anthracycline analogues were indistinguishable. Thus, all anthracycline analogues studied produced acute nuclear alterations which were distinctive from the changes produced by other DNA interactive chemotherapeutic agents. The relationship of the distinctive anthracycline nuclear changes to the late cardiomyopathy requires further definition.

ChemInform Abstract: POTENTIAL ANTITUMOR AGENTS. 37. ORGANOPHOSPHORUS DERIVATIVES OF 9‐ANILINOACRIDINE

AbstractDas Chloracridin (I) reagiert mit den aromatischen Aminen (II) zu den 9‐Anilinoacridinen (III), die in vitro und in vivo auf Wirkung gegen L121 0‐ und P‐388‐Leukämie der Maus untersucht werden.

Potential antitumor agents. 37. Organophosphorus derivatives of 9-anilinoacridine.

A series of 9-anilinoacridine derivatives substituted in the anilino ring with a variety of phosphoramide and related substitutents has been prepared, and the antitumor activity has been evaluated both in vivo and in vitro against the L1210 or P-388 mouse leukemia systems. The DNA-binding properties were measured using the ethidium displacement method, and the structural requirements for strong binding were found to differ from those for antileukemic activity. For high biological activity a marked preference for oxygen-containing substituents on the phosphorus atom was noted, while for high DNA binding a requirement for nitrogen-containing or cyclized substituents was observed. The most active congeners, as assayed in both in vitro and in vivo systems, were comparable in activity to the clinically utilized anilinoacridine derivative N-[4'-(9-acridinylamino)-3'-methoxyphenyl]methanesulfonamide (m-AMSA, amsacrine).

Amino acids and peptides. XIX. Synthetic study of optically active carene skeleton from .ALPHA.-amino acid. Total synthesis of (+)-2-carene.

For a total synthesis of the optically active carene congeners from optically active α-amino acids, several attempts were made on intramolecular cyclization of 2-cyclohexenyl esters of α-substituted α-diazoacetic acid (III) which were derived from the corresponding amino acid esters. One of the optically active diastereoisomers (X) which was obtained by separation of 2-cyclohexenyl L-alaninate was diazotized with isoamylnitrite and then cyclized using Cu powder as a catalyst to afford the optically active lactone (XIX). XIX was then converted into the key intermediate (XXI) having the bicyclo[4, 1, 0]heptane ring system, from which (+)-2-carene was synthesized.

Activity of Congeners of Hydroxyurea Against Advanced Leukemia L1210

SummaryVarious analogs of hydroxyurea have been screened for antitumor activity against advanced mouse leukemia L1210. The results indicate that in this series of compounds the essential structural requirement is the hydroxamic acid group.

Structure-action relationship among drugs acting on connective tissues (anti-rheumatic agents).

CONVENTIONAL assays for anti-inflammatory (anti-rheumatic) drugs frequently measure the inhibition by a drug of granuloma formation, induced by sub-cutaneously implanting foreign bodies (cotton pellets, plastic sponges, agar gels, etc.) in small laboratory animals. Other in vivo assays for anti-inflammatory activity, for example, inhibition of exudate formation by formalin-blisters, indicate the relationship between the activity of a compound in suppressing tissue inflammation and as an inhibitor of de novo connective tissue formation. This latter property is readily assayed in vitro by measuring the action of a drug on induced biogenesis of cartilage in tissue cultures1 or on the biosynthesis of mucopolysaccharides in connective tissue slices2. In both these in vitro systems, anti-inflammatory corticosteroids and salicylate strongly inhibit the incorporation of inorganic sulphate-35S (35Si) into mucopolysaccharides, thus reproducing the known effect of these drugs on 35Si incorporation into connective tissue polysaccharides in vivo. Using the techniques described2, it has now been found that these particular drugs and other anti-inflammatory drugs such as phenylbutazone, chloroquine, their respective active congeners (oxyphenbutazone, sulphinpyrazone, hydroxychloroquine, etc.) and cinchophene, each inhibit the incorporation of glucose-U-14C, acetate-1-14C and 35Si into cartilage mucopolysaccharides and of 35Si into corneal mucopolysaccharides in vitro (Table 1). These drugs were active inhibitors at concentrations in the incubation medium which corresponded to the plasma levels required for therapeutic action (for example, salicylate, phenylbutazone). Sodium aurothiomalate had no significant effect, but thiomalic acid (10−3 M) and many other thiols (thiosalicylic acid, cysteamine) were potent inhibitors of polysaccharide sulphation.