Retinyl substituted-benzyl ethers. Inhibition of mammary carcinogenesis by retinyl 3,4,5-trimethoxybenzyl ether (RTMBE).

Recently, we reported that retinyl 2-propynyl ether (RPE) inhibits MNU-induced mammary cancer in rats and is less toxic than RME and retinyl acetate. The preparation and biological investigations of retinyl ethers have now been extended to retinyl substituted-benzyl ethers, some of which bind to cellular retinol-binding protein. In long-term (160-180 days) experiments, retinyl 3,4,5-trimethoxybenzyl ether (RTMBE) has been shown to be active against MNU-induced mammary cancer in Sprague-Dawley rats. In effectiveness, RTMBE is comparable, at least, to retinyl acetate; but, unlike retinyl acetate, RTMBE is comparatively non-toxic to rats and mice, is not converted enzymatically to retinol, and does not cause significant increases in retinyl palmitate concentrations in the liver. RTMBE reaches high concentrations in mammary tissue. Two of the four RTMBE congeners that were evaluated in 90 day studies were moderately effective in inhibiting mammary carcinogenesis.

Retinyl ethers as cancer chemopreventive agents. Suppression of mammary cancer.

It had been demonstrated previously that retinyl methyl ether (RME) can suppress carcinogen-induced mammary cancers in vivo. It had also been shown that RME is demethylated enzymatically to retinol and produces the toxic effects of retinol; however, a rationale was developed for further investigations of retinyl ethers and was the basis for the synthesis and biological evaluations of new retinyl ethers for the chemoprevention of mammary cancer, reported herein. Two of the new retinyl ethers, retinyl 3-methyl-2-butenyl ether (RMBE) and retinyl 2-propynyl ether (RPE), were evaluated for the suppression of mammary cancers in vivo. RMBE, RPE, RME, the 2,3,6-trimethyl-4-methoxyphenyl analogue of RME, and retinyl acetate (a positive control) were incorporated individually into the feed of rats that had been injected with N-methyl-N-nitrosourea to induce mammary cancers. Ninety-day tests of these compounds for suppression of mammary cancer showed that RPE has significant cancer chemopreventive activity, comparable to that of retinyl acetate in simultaneous tests. RMBE demonstrated borderline activity. Both RPE and RMBE were less toxic than retinyl acetate or RME and, in contrast to the other retinoids, did not cause accumulation of large amounts of retinyl palmitate in the liver. Further investigations of RPE showed that it accumulated in mammary tissue after a single oral dose was administered to female rats, reached maximum concentrations within 24 h, and was still present at 75-80% of maximum concentrations after 72 h. In ethanol at 25 degrees C, RPE slowly underwent intramolecular cyclization; small amounts of the cyclized product also appeared in mammary tissue of rats dosed with RPE. During the mammary cancer bioassay, however, RPE was essentially stable in the feed. Some of the new retinyl ethers, as well as RME, bind to cellular retinol-binding protein.

A nursing survey to determine the characteristics of medication administration through enteral feeding catheters.

A statewide survey was designed to develop a better understanding of the current practices and problems encountered with medication administration through enteral feeding catheters (EFCs). The sample of 223 registered nurses and licensed practical nurses estimated that a median of 10% of patients received medications through an EFC. EFC obstruction was estimated to have occurred a median of 1.5 times per week, with 50% of obstructions estimated to be due to medication administration. Nine of 14 specific medications reported as "most frequently contributing to" feeding catheter obstruction available in liquid form, yet tablets were crushed and given. When nurses perceived the pharmacy department as helping them insure that liquid dosage form was used, there was greater use of liquid forms, less use of crushed forms, and less medication-associated catheter obstruction. In this sample, the majority of nurses did not follow consistently the few recommendations available.

Drug-induced thrombocytosis.

Thrombocytosis is generally defined as platelet counts greater than 400,000/mm3. Thrombocytosis can be either primary or secondary. Adrenalin was one of the first drugs noticed to cause platelet elevations, probably due to demargination of platelets in the pulmonary vasculature. Vinca alkaloids have the most convincing data to show that they can induce thrombocytosis through their thrombocyte-stimulating properties. Miconazole has been implicated in causing thrombocytosis and has a documented case validated by drug rechallenge. Iron, predictably, can cause a transient thrombocytosis. The beta-lactam antibiotic data are very difficult to interpret due to the possibility of an acute-phase reaction in an infected patient being the cause of the thrombocytosis.

Effect of sulfonates on the esterase activity of carboxypeptidase A.

The effects of sulfonates on the carboxypeptidase A catalyzed hydrolysis of the ester substrate benzoylglycyl-L-phenyllactate were determined. The modifiers examined were benzenesulfonate, p-toluenesulfonate, 2-phenylethane-sulfonate, methanesulfonate, ethanesulfonate, propanesulfonate, butanesulfonate, pentanesulfonate, hexanesulfonate, heptanesulfonate, and 2,2-dimethyl-2-silapentane-5-sulfonate. Sulfonate activators of peptide hydrolysis were inhibitors of esterase activity. Of the sulfonates studied, 2,2-dimethyl-2-silapentane-5-sulfonate was the most effective inhibitor. 2-Phenylethanesulfonate, hexanesulfonate, heptanesulfonate, and 2,2-dimethyl-2-silapentane-5-sulfonate exhibited uncompetitive inhibition. The remaining sulfonates either did not inhibit or the inhibition was too weak to properly characterize.

N-(Retinoyl)amino acids. Synthesis and chemopreventive activity in vitro.

N-(all-trans-Retinoyl)amino acids were synthesized via all-trans-retinoyl chloride and an ester of the amino acid. The retinoyl derivatives of leucine, phenylalanine, alanine, tyrosine, and glutamic acid were prepared. The 13-cis-retinoyl derivatives of leucine, phenylalanine, alanine, and glycine were prepared similarly from 13-cis-retinoic acid. In assays of the retinoylamino acids for reversal of squamous metaplasia in hamster trachea organ cultures, these compounds were less active than retinoic acid, but the leucine, alanine, and phenylalanine derivatives were similar in activity to several retinamides that suppress bladder carcinogenesis in vivo. Two of the retinoylamino acids, as well as two simple retinamides, were shown to be moderately cytotoxic to murine leukemia and human epidermoid carcinoma cells in culture.

The sex difference in manifestations of carotid bifurcation disease.

One would think that risk factors for transient ischemic attack (TIA) and asymptomatic carotid bruit (ACB) would be similar. In our referral population and in several previously reported cohort populations, however, men outnumber women among patients with TIA. In contrast, women outnumber men among patients with ACB. We found in two independent populations that women with ACB are up to 5.7 times less likely than men to have carotid stenosis. Thus women are more prone than men to have ACB, but their bruits much less commonly reflect carotid stenosis. Women are probably predisposed to have carotid bruit even in the absence of carotid stenosis. In our referral population of ACB, this tendency among women for carotid bruit without stenosis does not seem to be related to lower hematocrit, higher prevalence of heart murmur, constitutionally smaller carotid arteries, or differences in pulse rate or body habitus.

Asymptomatic carotid bruit and stenosis. A prospective follow-up study.

We observed 70 patients with asymptomatic carotid bruits with and without stenoses for cerebral and myocardial ischemic events. Four patients developed transient ischemic attacks (TIAs) without subsequent cerebral infarctions; all of the TIAs occurred distal to vessels with greater than or equal to 50% stenoses. Three cerebral infarctions occurred, but only one was distal to a vessel with stenosis greater than or equal to 50%. Six myocardial infarctions occurred, predominantly in patients with previous myocardial infarctions, congestive heart failure, and left ventricular hypertrophy. Our results confirm previous reports that an asymptomatic carotid stenosis is more often complicated by a TIA than an unheralded cerebral infarction. Cerebral infarctions that do occur are often only marginally related to the carotid bifurcation lesion. In patients with asymptomatic carotid bruit and stenosis, myocardial infarctions occur more frequently and are more commonly the cause of death than cerebral infarctions.

Studies on synthesis and anticancer activity of selected N-(2-fluoroethyl)-N-nitrosoureas.

An activated carbamate, 2-nitrophenyl (2-fluoroethyl)nitrosocarbamate (3), was used to advantage in the synthesis of the water-soluble (2-fluoroethyl)nitrosoureas 6a--d from 2-aminoethanol, (1 alpha, 2 beta, 3 alpha)-2-amino-1,3-cyclohexanediol, cis-2-hydroxycyclohexanol, and 2-amino-2-deoxy-D-glucose. In a variation of this method, 2,4,5-trichlorophenyl (2-fluoroethyl)carbamate (4) was used to prepare the urea from which the essentially water-insoluble N-(2,6-dioxo-3-piperidinyl)-N-(2-fluoroethyl)-N-nitrosourea (6e) was derived. The anticancer activity of these nitrosoureas was determined against the murine tumors B16 melanoma and Lewis lung carcinoma and found to be significant and comparable to their chloroethyl counterparts. On the basis of results from both systems, the dihydroxycyclohexyl derivative 6b may be the most effective.

Synthesis and properties of some 13-cis- and all-trans-retinamides.

Several 13-cis-retinamides were synthesized from 13-cis-retinoic acid via either 13-cis-retinoyl chloride or 13-cis-1-retinoylimidazole. All-trans-retinoylglycine was prepared from all-trans-retinoyl chloride and ethyl glycinate. Detailed procedures were developed for the preparation of other all-trans-retinamides on a large scale for studies of the chemoprevention of cancer.

Carbocyclic analogues of 5-fluorouracil nucleosides.

The carbocyclic analogues of 5-fluoro-2'-deoxyuridine (5-FdUrd, 1), 5-fluorouridine, and 5-fluoro-3 alpha-deoxyuridine were prepared by fluorination of the uracil nucleoside analogues with elemental fluorine. The 5-FdUrd analogue (C-5-F-2'-dUrd, 6) was enzymatically phosphorylated to the analogue of 5-FdUrd 5'-phosphate and inhibited the incorporation of 2'-deoxyuridine into DNA of murine colon 26 tumor cells and L-1210 cells in culture. Biochemical studies also indicated that C-5-F-2'-Urd (6) was a less potent inhibitor of DNA synthesis in tumor cells than was 5-FdUrd (1). C-5-F-2'-dUrd was cytotoxic (ED50 = 2.5 mcg/mL) to L-1210 cells in culture; the other two analogues were less cytotoxic. C-5-F-2'-dUrd was inactive--or, at best, borderline active--in tests against P-388 leukemia in vivo.

Synthesis of analogues of N-(2-chloroethyl)-N'-(trans-4-methylcyclohexyl)-N-nitrosourea for evaluation as anticancer agents.

The superior activity of N-(2-chloroethyl)-N'-(trans-4-methylcyclohexyl)-N-nitrosourea (MeCCNU) against advanced murine Lewis lung carcinoma in comparisons with the cis form and other nitrosoureas prompted the synthesis of a number of MeCCNU analogues, including several cis-trans pairs. The methyl group was replaced by a variety of substituents (CO2H, CH2CO2H, CO2Me, CH2OAc, CH2Cl, OMe); the trans-3-methylcyclohexyl, cis-2-methyl-1,3-dithian-5-yl, cis- and trans-2-methyl-1,3-dithian-5-yl-tetraoxide, and 1-methylhexyl (open-chain) analogues were also prepared. Preliminary tests against murine leukemia L1210 revealed therapeutic indices (ED50/LD10) ranging from 0.26 to 0.79; all but three analogues effected 50% cure rates at nontoxic doses, the open-chain analogue being one of the least active. In terms of therapeutic index, diequatorial (trans-4) isomers were, with one exception, as active as or, in four of the eight examples, somewhat more active than the corresponding axial-equatorial (cis-4) isomers. In this series, four of the five 2-fluoroethyl analogues prepared were clearly inferior to the corresponding 2-chloroethyl analogues.

Synthesis of N-10-methyl-4-thiofolic acid and related compounds.

Compound 21 (N10-methyl-4-thiofolic acid) and related compounds were prepared as potential inhibitors of the cofactor forms of tetrahydrofolate. The preparation of 2-acetylamino-4-(benzylthio)-6-chloro-5-nitropyrimidine (4) provided an intermediate that was allowed to react with methyl p-[(3-aminoacetonyl)methylamino]benzoate oxime (16). The oxime function of the resulting 6-substituted aminopyrimidine 6 was hydrolyzed to give the corresponding acetonylaminopyrimidine 7, which on reductive cyclization gave methyl p-[[[2-amino-4-(benzylthio)-7,8-dihydro-6-pteridinyl]methyl]methylamino]benzoate (9). This dihydropteridine was oxidized with potassium permanganate, and the product was treated successively with sodium hydrosulfide to replace the benzylthio group and with aqueous sodium hydroxide to hydrolyze the ester function to give p-[[(2-amino-3,4-dihydro-4-thioxo-6-pteridinyl)methyl]methylamino]benzoic acid (N10-methyl-4-thiopteroic acid, 12). Another route to 12 involved the interaction of 2,5-diamino-4,6-dichloropyrimidine (15) with 16 to give methyl p-[[(2-amino-4-chloro-7,8-dihydro-6-pteridinyl)methyl]methylamino]benzoate (13). Displacement of the chloro group of 13 with sodium hydrosulfide followed by the simultaneous air oxidation of the dihydropteridine ring and saponification of the ester group gave 12. After protection of the 2-amino and 4-thioxo moieties of 12, the resulting intermediate benzoic acid was coupled with diethyl L-glutamate. The product of this reaction was deblocked to give 21. Methylation of 21 gave the corresponding 4-(methylthio) derivative 22, which on reaction with hydrazine gave the 4-hydrazino analog 23 of methotrexate. Reduction of 12 and 21 with sodium hydrosulfite gave the dihydropteridines 24 and 25, respectively. The title compound was an excellent inhibitor of the growth of Streptococcus faecium ATCC 8043. However, this and related compounds were ineffective inhibitors of dihydrofolic reductase and showed no significant activity in either the KB cell culture screen or against L1210 leukemia cells in mice.