Structure-activity relationship studies of hemicholinium (HC-3) congeners

In a continuing investigation of structural requirements for hemicholinium-like activity (inhibition of neuromuscular transmission due to inhibition of uptake of choline into nerve terminals), some additional molecular modifications of hemicholinium ("HC-3"; structure 1) were made. The target compounds were prepared by standard one- or two-step sequences. Noncyclic acetal moieties in general permitted retention of pharmacological activity, as did concomitant replacement of the central biphenyl "spacer" by other bulky cyclic groupings and replacement of the oxazinium rings by piperidine or 4-methylpiperidine. However, these modifications generally produced compounds of a lower potency. Replacement of the biphenyl moiety of HC-3 with polyakylene chains permitted retention of a considerable degree of activity. In these target compounds, the two quaternary nitrogens can exist the same distance apart (approximately 14 A) as in the hemicholinium molecule. The ditertiary amino congener of a pharmacologically active bis-quaternary oxazinium compound was almost completely inactive. To date, only one tertiary amine has been found which displays a significant degree of hemicholinium-like activity.

IgA:IgM and IgA:IgA hybrid hybridomas secrete heteropolymeric immunoglobulins that are polyvalent and bispecific

Polyvalent bispecific antibodies were secreted by hybrid hybridoma cells when both parental clones expressed a naturally polymerizing immunoglobulin. Hybrid hybridomas made from IgA lambda 2 anti-trinitrophenyl (TNP) and IgA kappa anti-phosphocholine (PC) parental cells secreted polymeric IgA antibodies that bound both TNP and PC. Some of the TNP binding was dissociated from the PC binding under conditions of mild reduction and alkylation suggesting that the bispecific polymeric IgA contained disulfide-linked parental monomers as well as bispecific hybrid monomers. Hybrid hybridomas constructed from IgA lambda 2 anti-TNP and IgM kappa anti-ox erythrocyte parental cells secreted bispecific, polymeric immunoglobulin that contained mu-, alpha-, kappa-, and lambda 2-chains. The mu and kappa-chains dissociated from the alpha- and lambda 2-chains under conditions of mild reduction and alkylation, indicating that both parental monomers had been incorporated into the same polymeric immunoglobulin to form a heteropolymeric antibody molecule. Heterologous pairing of alpha and mu heavy chains in monomers was not detected. Hybrid hybridomas constructed from IgA lambda 2 and IgG3 lambda 2 or IgA lambda 2 and IgG1 kappa parents co-secreted both parental immunoglobulins, but the antibodies secreted by these clones did not form heteropolymers or exhibit heterologous heavy chain pairing. These findings establish that polyvalent, bispecific, polymeric immunoglobulin molecules can be produced by hybrid hybridomas when both parents express a naturally polymerizing class of heavy chain but not when only one parent does. Hybrid hybridomas that produce heteropolymeric immunoglobulins are sources of high avidity bispecific antibodies that may find a number of basic and practical applications. The hybridoma cells that produce these antibodies may provide useful tools for investigating the in situ determinants of immunoglobulin chain association and the regulation of antibody assembly and secretion.

IgA:IgM and IgA:IgA hybrid hybridomas secrete heteropolymeric immunoglobulins that are polyvalent and bispecific

Polyvalent bispecific antibodies were secreted by hybrid hybridoma cells when both parental clones expressed a naturally polymerizing immunoglobulin. Hybrid hybridomas made from IgA lambda 2 anti-trinitrophenyl (TNP) and IgA kappa anti-phosphocholine (PC) parental cells secreted polymeric IgA antibodies that bound both TNP and PC. Some of the TNP binding was dissociated from the PC binding under conditions of mild reduction and alkylation suggesting that the bispecific polymeric IgA contained disulfide-linked parental monomers as well as bispecific hybrid monomers. Hybrid hybridomas constructed from IgA lambda 2 anti-TNP and IgM kappa anti-ox erythrocyte parental cells secreted bispecific, polymeric immunoglobulin that contained mu-, alpha-, kappa-, and lambda 2-chains. The mu and kappa-chains dissociated from the alpha- and lambda 2-chains under conditions of mild reduction and alkylation, indicating that both parental monomers had been incorporated into the same polymeric immunoglobulin to form a heteropolymeric antibody molecule. Heterologous pairing of alpha and mu heavy chains in monomers was not detected. Hybrid hybridomas constructed from IgA lambda 2 and IgG3 lambda 2 or IgA lambda 2 and IgG1 kappa parents co-secreted both parental immunoglobulins, but the antibodies secreted by these clones did not form heteropolymers or exhibit heterologous heavy chain pairing. These findings establish that polyvalent, bispecific, polymeric immunoglobulin molecules can be produced by hybrid hybridomas when both parents express a naturally polymerizing class of heavy chain but not when only one parent does. Hybrid hybridomas that produce heteropolymeric immunoglobulins are sources of high avidity bispecific antibodies that may find a number of basic and practical applications. The hybridoma cells that produce these antibodies may provide useful tools for investigating the in situ determinants of immunoglobulin chain association and the regulation of antibody assembly and secretion.

Development of myelinated nerve fibers in the sixth cranial nerve of the rat: a quantitative electron microscope study

Myelination was studied quantitatively in the sixth cranial nerves of rats by counting and measuring all myelinated fibers during the first three postnatal weeks. In transverse semithin and thin sections cut serially at a well-defined anatomical site in the midsphenoid region, only a few axons (mean 12) were myelinated at birth. On days 2, 4, and 8, counts of myelinated fibers were respectively 5 times (mean 57), 20 times (mean 230), and 24 times (mean 273) the number seen at birth. During the second postnatal week, the number of myelinated fibers remained constant, whereas growth of axons and their myelin sheaths continued. By 15 days these fibers were large and relatively uniform in size; they had compact, circular myelin sheaths. During the third postnatal week, myelination of previously unmyelinated, smaller axons began. The number of myelinated fibers increased again and the size distribution of myelinated fibers became bimodal. Axon diameters, fiber diameters, and myelin sheath dimensions for all fibers were calculated from measurements made on electron micrographs. The transverse length of the myelin membrane increased exponentially with time. The growth increased rapidly during the formation of the first 20 spiral layers and remained relatively constant during the subsequent enlargement of the compact sheath. The association of axon diameter and myelin sheath thickness was poor at young ages, but it improved progressively with maturation of the sheath. The results show that myelination begins around axons that have a wide range of diameters. Also, the first axons to be myelinated become the large myelinated fibers of the sixth nerve. The small myelinated fibers originate from axons that do not become myelinated until the third postnatal week. Myelination, though differing in onset by 2 weeks, appeared to be similar in both populations as judged by similarity of sheath morphology and growth rates. It is of interest that at the level studied, the sixth nerve also contains a fascicle of unmyelinated cranial sympathetic fibers.

R-goitrin- and BHA-induced modulation of aflatoxin B1 binding to DNA and biliary excretion of thiol conjugates in rats

Previous studies have shown that dietary R-goitrin is a potent inducer of hepatic glutathione S-transferase (GST) and epoxide hydrolase activities but has no effect on components of the mixed function oxidase system (ethoxycoumarin O-deethylase and cytochrome P-450). In the present work effects of dietary R-goitrin (200 p.p.m.) or butylated hydroxyanisole (BHA) (7500 p.p.m.) on GST activity, binding of aflatoxin B1 (AFB1) to DNA, in vivo, and biliary excretion of thiol conjugates of AFB1 in rats were studied. Increases of GST activities (1.9- and 2.1-fold) were accompanied by reductions in AFB1-DNA binding (43% and 85%) and increases (1.7- and 2.2-fold) in biliary excretion of AFB1-thiol conjugates in R-goitrin and BHA groups, respectively. Microsomal aflatoxin 8,9-epoxidase activities were not increased in either treatment group. The role of GST induction in the carcinogenesis of AFB1 and the anticarcinogenic potential of R-goitrin are discussed.

Effect of misoprostol, an antiulcer prostaglandin, on serum gastrin in patients with duodenal ulcer

Serum gastrin has been reported to increase after therapy with some agents effective in the treatment of duodenal ulcer (DU). Misoprostol, a prostaglandin E1 analog, is effective in the treatment of DU, with healing rates similar to those achieved with vigorous antacid therapy or H2-receptor antagonists. Misoprostol reduces gastric acid secretion and also possesses cytoprotective properties. This multicenter study examined serum gastrin levels before and after treatment of DU patients with misoprostol. Sera for gastrin measurement were obtained from DU patients after an 8-hr fast, and 15 and 30 min after a standard mixed meal. DU patients were studied before and after two to four weeks of treatment with placebo or misoprostol: in one study, misoprostol 100 micrograms qid (without antacid) was compared with placebo; in the other study, misoprostol at 50- or 200-micrograms qid dosages (with limited antacid, Amphojel up to 54 meq/day) was compared with placebo. In addition, the serum gastrin values obtained in healthy subjects were compared with those from DU patients. Fasting and postprandial serum gastrin concentrations were essentially similar for DU patients and healthy subjects. There were no significant differences, either in fasting serum gastrin or in integrated gastrin responses, in DU patients after treatment with placebo or misoprostol at 100 micrograms (P = 0.32), 50 micrograms, or 200 micrograms doses (P = 0.85). It is concluded that misoprostol, when administered four times daily for two to four weeks at dosages required for the acceleration of DU healing, does not affect serum gastrin levels.

Behavioral effects of a dimethylsulfonium analog of dopamine after injection into the nucleus accumbens and the striatum

We have previously synthesized a chemical analog of dopamine (DA) in which the amine group has been replaced by a permanently charged dimethylsulfonium group. In the present study, we have determined whether this compound can exert DA agonist activity in the nucleus accumbens by comparing its effects with those of DA. When DA was injected into the nucleus accumbens of rats pretreated with nialamide, a monoamine oxidase inhibitor, there was marked stimulation of locomotor activity. Similarly, after intraaccumbens injection, the sulfonium analog also produced a marked stimulation of locomotor activity, and this effect was inhibited by the DA receptor antagonist, haloperidol (0.2 mg/kg, IP). However, the sulfonium analog did not stimulate locomotor activity when rats were pretreated with saline instead of nialamide. In addition, the stimulation of locomotor activity produced by the sulfonium analog in rats pretreated with nialamide was completely inhibited by the DA synthesis inhibitor, alpha-methyl-p-tyrosine. These results suggest that the stimulation of locomotor activity by the sulfonium analog is mediated indirectly through the release of DA. The sulfonium analog was able to produce marked contralateral circling after it was injected into the striatum of rats on the side of the brain in which DA nerve terminals were previously destroyed with 6-hydroxydopamine. Similarly, the sulfonium analog produced a marked stimulation of locomotor activity after it was injected into the nucleus accumbens of rats that were previously injected into this region with 6-hydroxydopamine. These results suggest that the sulfonium analog of dopamine can exert direct as well as indirect DA agonist activity.

Effects of dietary R-goitrin on hepatic and intestinal glutathione S-transferase, microsomal epoxide hydratase and ethoxycoumarin O-deethylase activities in the rat

The influence of dietary R-goitrin on components of the xenobiotic-metabolizing system was examined in the liver and small intestine of male Sprague-Dawley rats. Given at a level of 200 ppm in the diet for 14 days, the R-goitrin caused a statistically significant (P less than 0.05) 21% increase in liver weight relative to body weight. A less pronounced, but statistically significant, 11% increase in relative liver weight resulted from the administration of R-goitrin at 40 ppm in the diet. Hepatic glutathione S-transferase (GST) activity was significantly increased 1.5- and 2-fold over the basal level at concentrations of 40 and 200 ppm R-goitrin, respectively. Hepatic microsomal epoxide hydratase (EH) activity was also significantly increased. Hepatic EH activity was 1.6- and 3.3-fold greater in the 40- and 200-ppm R-goitrin groups, respectively, than in the control group given the basal diet. R-Goitrin at 200 ppm in the diet produced significant 1.2- and 1.4-fold increases of GST and microsomal EH activities, respectively, in the mucosa of the small intestine. The administration of R-goitrin at 40 or 200 ppm in the diet had no significant effect on either hepatic or intestinal ethoxycoumarin O-deethylase activity.

Effects of commonly consumed vegetables on hepatic xenobiotic-metabolizing enzymes in the mouse

To investigate the effects of consuming a variety of common vegetables on the activities of xenobiotic-metabolizing enzymes in the mouse liver, male C57BL/6 mice were fed purified diets supplemented isocalorically with 20% freeze-dried powdered kidney bean, soya bean, alfalfa, cauliflower, mustard greens, carrot, kale, Brussels sprouts, beet, egg plant or onion or with 40% sweet potato. Hepatic ethoxycoumarin O-deethylase (ECD) activity was increased significantly (P less than or equal to 0.05) over the controls in the mice fed diets containing kidney bean (1.5-fold), alfalfa (1.6-fold), cauliflower (2.2-fold), mustard greens (1.2-fold), carrots (1.2-fold) and kale (1.3-fold). No significant increases in ECD activity were seen in the other groups. Aryl hydrocarbon hydroxylase (AHH) activity was assayed in the cauliflower and Brussels sprouts groups and was found to be unaffected by these diets. Glutathione S-transferase (GST) and epoxide hydratase (EH) activities were increased (P less than or equal to 0.05) by soya bean (1.2- and 1.6-fold respectively), Brussels sprouts (2.0- and 1.6-fold), cauliflower (1.2- and 1.6-fold), alfalfa (1.3- and 2.0-fold) and onion (1.8- and 2.3-fold). No significant increases in GST or EH activities were seen in the other groups. Of the twelve vegetables investigated, only three (sweet potato, beet and egg plant) had no statistically significant effects on any of the xenobiotic-metabolizing parameters tested. However, the beet diet caused an apparent inhibition of ECD activity (74% of control) and the sweet potato diet caused an apparent increase (1.3-fold) in GST activity, although statistical significance could not be established at P less than or equal to 0.05.

Increased cytotoxicity of N6-(delta 2-isopentenyl)adenosine in combination with pentostatin against L-1210 leukemia cells

Pentostatin (I), a tight-binding inhibitor of adenosine deaminase, was evaluated in combination with the partially effective antitumor nucleoside N6-(delta 2-isopentenyl)adenosine (II) for cytotoxic activity against cultured L-1210 lymphocytic mouse leukemia cells. Although I alone (less than or equal to 10 micrograms/ml) was ineffective, it significantly potentiated and prolonged the cytotoxic and cytostatic activities of II. The combination of I (2-10 micrograms/ml) with II (25 micrograms/ml) resulted in inhibition of cellular proliferation (80-96%) within 24 hr with maintenance at that level for an extended period of time due to the continued ability of I to prevent the facile deamination of the allylic side chain of II. This type of adjuvant chemoprotection has potential use for other labile oncologic agents.

Enhancement of the antitumor activity of N6-(delta 2-isopentenyl)adenosine against cultured L-1210 leukemia cells by pentostatin using a polymeric delivery system

The adenosine deaminase inhibitor pentostatin (I), recently shown to be effective in the treatment of several types of acute and chronic human leukemias, was impregnated in a silicone polymer monolithic disk device for release in vitro in the presence of the antitumor nucleoside N6-(delta 2-isopentenyl)adenosine (II) against mouse L-1210 lymphocytic leukemia cells. Although I is ineffective alone against L-1210 cells, controlled release from the polymeric delivery matrix potentiates the antiproliferative effects of II during the midlog phase of growth (48 hr). Cytotoxicity is prolonged, leading to total cell death during the stationary phase of growth (96 hr). The present study suggests that polymeric delivery systems be used for controlled release of oncologic agents, alone or in combination with inhibitors, especially where liability is a concern.

Proteoglycans synthesized by smooth muscle cells derived from monkey (Macaca nemestrina) aorta

Smooth muscle cells derived from monkey aorta were cultured in medium with [35S]sulfate and [3H]glucosamine as labeling precursors. Proteoglycans in the medium and in 4 M guanidine HCl extracts of the cell layer were purified by DEAE-Sephacel and molecular sieve chromatography. Both preparations contained a predominant, large chondroitin sulfate proteoglycan (Kav = 0.30 on Sepharose CL-2B) with glycosaminoglycan chains of Mr approximately 43,000 average containing a ratio of 6-sulfate to 4-sulfate of approximately 2. Approximately 7 and 27% of the 3H label in this proteoglycan were present in N-linked and O-linked oligosaccharides, respectively. Reaggregation experiments indicated that a large proportion of these proteoglycans can form link protein-stabilized aggregates. The medium fraction also contained a smaller dermatan sulfate proteoglycan (Kav = 0.67 on Sepharose CL-2B) with glycosaminoglycan chains of Mr approximately 43,000 containing a ratio of 6-sulfate to 4-sulfate of about 0.5. This proteoglycan contained approximately the same percentage of N-linked oligosaccharides as the chondroitin sulfate proteoglycan, but few or no O-linked oligosaccharides. A smaller dermatan sulfate proteoglycan with a single chain was present only in the cell layer. Additionally, small amounts of heparan sulfate proteoglycans were synthesized by the cells.

Antineoplastic effects of N6-(delta 2-isopentenyl)adenosine against L-1210 mouse lymphocytic leukemic cells using a polymeric delivery system

N6-(delta 2-Isopentenyl)adenosine (I), a nucleoside previously shown to be cytotoxic against several types of tumor cells, was impregnated in silicone polymer monolithic disc devices for release in vitro against lymphocytic mouse leukemia cells. Plotting the cumulative amount of N6-(delta 2-isopentenyl)adenosine released per unit area of the device versus the square root of time revealed a linear relationship. However, the higher loading dose tended to rapidly release any drug deposited on the polymer surface. The optimum loading dose of the device for the most effective antileukemic activity in 24 hr was calculated based on a plot of the release rate versus the square root of an initial loading dose. The silicone polymer--I delivery system enabled a sustained and controllable release of additional agent. It was thus possible to achieve virtually total inhibition of leukemia cell replication using the polymeric delivery system. Increased concentrations of I, without the use of the polymeric system, resulted in maximum 24 hr inhibition of only approximately 81%, followed by a decline in overall antileukemic activity. It is possible to achieve a more predictable release rate of N6-(delta 2-isopentenyl)adenosine and corresponding antileukemic activity using a polymeric delivery system against L-1210 mouse leukemic cells in vitro. The relative data indicate the ED50 concentrations to be considerably less using the polymeric delivery system.