Distribution of chlorpromazine and imipramine in adipose and other tissues of rats

Adipose tissue kinetics of chlorpromazine and imipramine, two drugs which are more lipophilic than thiopental, were studied in the rat. After single i.v. doses, the time-course of drug distribution was followed in adipose and various other tissues, until their concentrations in adipose tissues declined. Under these conditions the two drugs behaved almost identically. Among the tissues analyzed, the lowest concentrations were found in adipose tissue, with the exception of plasma. At its maximum concentration after about 30 minutes, total adipose tissue contained only 3 % of the dose of administered drugs. Adipose/plasma and adipose/lung concentration ratios were 2–5 and 0.05, respectively.After maximum tolerated oral doses of imipramine for 3 weeks, similar steady state concentration ratios (plasma:adipose:brain:lung 1:3:12:96) were observed. In adipose tissue the imipramine/desmethylimipramine ratio was about 1, and the desmethylimipramine steady state levels did not increase with time. Literature data indicate that many basic lipophilic drugs are not stored in adipose tissue. This is now clearly shown for chlorpromazine and imipramine, even under extreme, subchronic conditions in the case of imipramine.     

Behavioral economics of drug self-administration. I. Functional equivalence of response requirement and drug dose

Response requirement and dose of drug per administration are two separate factors that have been demonstrated to control drug self-administration. Recent developments in behavioral economics have shown that these two factors are in fact functionally equivalent for nondrug reinforcers, as indicated by a unit-price analysis. In this review, the unit-price notion was tested for drugs as reinforcers via a re-analysis of ten drug self-administration studies. The results of the re-analysis indicated that response requirement and reinforcer magnitude, the constituents of unit price, have functionally equivalent effects on drug consumption and that a positively decelerating demand curve is produced as unit price increases. This suggests that the behavioral-economic notion of unit price is a more parsimonious explanation of the effects of response requirement and dose in drug self-administration studies, in that it integrates and describes what was previously considered to be two distinct operations.     

Variation in heat shock proteins within tropical and desert species of poeciliid fishes

The 70-kilodalton heat shock protein (hsp70) family of molecular chaperones, which contains both stress-inducible and normally abundant constitutive members, is highly conserved across distantly related taxa. Analysis of this protein family in individuals from an outbred population of tropical topminnows, Poeciliopsis gracilis, showed that while constitutive hsp70 family members showed no variation in protein isoforms, inducibly synthesized hsp70 was polymorphic. Several species of Poeciliopsis adapted to desert environments exhibited lower levels of inducible hsp70 polymorphism than the tropical species, but constitutive forms were identical to those in P. gracilis, as they were in the confamilial species Gambusia affinis. These differences suggest that inducible and constitutive members of this family are under different evolutionary constraints and may indicate differences in their function within the cell. Also, northern desert species of Poeciliopsis synthesize a subset of the inducible hsp70 isoforms seen in tropical species. This distribution supports the theory that ancestral tropical fish migrated northward and colonized desert streams; the subsequent decrease in variation of inducible hsp70 may have been due to genetic drift or a consequence of adaptation to the desert environment. Higher levels of variability were found when the 30- kilodalton heat shock protein (hsp30) family was analyzed within different strains of two desert species of Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In both cases the distribution of hsp30 isoform diversity was similar to that seen previously with allozyme polymorphisms.      

Regression of line-10 hepatocellular carcinomas following treatment with water-soluble,microbial extracts combined with trehalose or arabinose mycolates

Summary Intratumor injections of the aqueous phase of phenol-water extracts of Re mutant Salmonella typhimurium (Re glycolipid) in combination with trehalose dimycolate at dose levels of 150 to 15 g were consistently and highly effective (65–93%) in producing regression of line-10 tumors in strain-2 guinea pigs. We observed that the rate of regression was more rapid than that seen after treatment with cell walls from Mycobacterium bovis strain Bacillus of Calmette and Guèrin (BCG). Arabinose mycolate could be substituted for trehalose dimycolate in the Re glycolipid-mycolate mixture without appreciably compromising antitumor activity, providing that the level of arabinose mycolate was not reduced below 15 g. In addition to the Re glycolipid preparation, similarly prepared aqueous extracts from Mycobacterium bovis strain BCG and strain AN5 in combination with trehalose dimycolate also possessed tumor-regressive activity. The activity of these last extracts was reduced when the arabinose mycolate was substituted for the trehalose dimycolate. The aqueous extract of a rickettsia, Coxiella burnetii, in combination with either trehalose dimycolate or arabinose mycolate was also active (50 and 80% tumor regression rates, respectively). Intracutaneous administration of Re glycolipid or aqueous extracts from BCG in combination with trehalose or arabinose mycolates did not produce life-threatening, clinical signs of toxicity in young mice. If additional toxicity studies demonstrate that adverse side effects can be satisfactorily controlled, these watersoluble extracts may prove beneficial in the treatment of spontaneous tumors of humans and other animals.     

Light scattering and excitation in lobster giant axon Effects of ion substitution

Changes in the light scattering signal from single giant axons of lobster were observed during the propagation of the action potential in order to correlate membrane excitability with possible structural changes reflected in the optical properties of the axolemma. Substitution of guanidine and aminoguanidine for sodium resulted in a decreased action potential amplitude to 69 and 50% of control values, respectively. The amplitude of the light signal was, however, not significantly changed by these substitutions and is, therefore, reported to be independent of the transmembrane potential and current. The venom of the scorpion Leiurus quinquestriatus caused a marked prolongation of the action potential and the light scattering signal without significantly altering their amplitudes. A two-state model of the early (sodium) activation channel is suggested, in which the light scattering signal is correlated with a possible difference in the scattering efficiency between the states of the channel.     

Identification of sequences within the murine granulocyte-macrophage colony-stimulating factor mRNA 3'-untranslated region that mediate mRNA stabilization induced by mitogen treatment of EL-4 thymoma cells

Phorbol esters (TPA) and concanavalin A (ConA) are known to induce granulocyte-macrophage colony-stimulating factor (GM-CSF) production in murine thymoma EL-4 cells by mRNA stabilization. The role of the 3'-untranslated region (3'-UTR) in GM-CSF mRNA stabilization induced by TPA and ConA in EL-4 cells was examined by transfection studies using chloramphenicol acetyltransferase (CAT) constructions. The GM-CSF 3'-UTR contains a 63-nucleotide region at its 3' end with repeating ATTTA motifs which is responsible for mRNA degradation in a variety of cell types (Shaw, G., and Kamen, R. (1986) Cell 46, 659-666). We produced constructs containing most of the GM-CSF 3'-UTR (303 nucleotides, pRSV-CATgm) or the 3'-terminal AT-rich region (116 nucleotides, pRSV-CATau) and measured CAT enzyme activity and CAT mRNA after transient transfection into EL-4 and NIH 3T3 cells. Low levels of CAT activity were seen in both cells with either plasmid compared with levels of CAT activity obtained with pRSV-CAT. TPA treatment caused an approximately 10-fold increase in CAT activity and mRNA in EL-4 cells transfected with pRSV-CATgm. No increases were seen in EL-4 cells transfected with pRSV-CATau or pRSV-CAT. No response to TPA was detected in transfected NIH 3T3 cells, indicating that the response to TPA is relatively cell-specific. There was no increase in CAT activity after ConA treatment in EL-4 or NIH 3T3 cells transfected with any of the constructs suggesting that the GM-CSF 3'-UTR lacks elements that can respond alone to ConA. Nuclear run-on and actinomycin D chase experiments in EL-4 cells showed that TPA induces CAT activity via mRNA stabilization. By linker-substitution mutagenesis we show that TPA inducibility depends on a 60-nucleotide region of the 3'-UTR whose 5' end is located 160 nucleotides upstream of the 5' end of the AU-rich region.     

Liver-specific drug targeting by coupling to bile acids.

Bile acids are selectively taken up from portal blood into the liver by specific transport systems in the hepatocyte plasma membrane. Therefore, studies were performed to evaluate the potential of bile acids as shuttles to deliver drugs specifically to the liver. The alkylating cytostatic drug chlorambucil and the fluorescent prolyl-4-hydroxylase inhibitor 4-nitrobenzo-2-oxa-1,3-diazol-beta-Ala-Phe-5-oxaproline-Gly were covalently linked via an amide bond to 7 alpha, 12 alpha,-dihydroxy-3 beta- (omega-aminoalkoxy)-5-beta-cholan-24-oic acid. The chlorambucil-bile acid conjugates S 2521, S 2539, S 2567, and S 2576 inhibited Na(+)-dependent [3H]taurocholate uptake in a concentration-dependent manner both into isolated rat hepatocytes and rabbit ileal brush border membrane vesicles, whereas the parent drug chlorambucil showed no significant inhibitory effect. The chlorambucil-bile acid conjugates were able to prevent photoaffinity labeling of bile acid binding proteins in rat hepatocytes by the photolabile [3H]7,7-azo derivative of taurocholic acid indicating their bile acid character. The chlorambucil-bile acid conjugate S 2577 was able to alkylate proteins demonstrating the drug character conserved in the hybrid-molecules. Liver perfusion experiments revealed a secretion profile of the chlorambucil-bile acid conjugate S 2576 into bile very similar to taurocholate compared to chlorambucil which is predominantly excreted by the kidney. 4-Nitrobenzo-2-oxa-1,3-diazol-beta-Ala-Phe-5-oxaproline-Gly- t-butylester (S 4404), a fluorescent peptide inhibitor of prolyl-4-hydroxylase, was not transported in intact form from portal blood into bile in contrast to its bile acid conjugate S 3744; about 25% of the peptide-bile acid conjugate S 3744 was secreted in intact form into bile within 40 min compared with less than 4% of the parent oxaprolylpeptide S 4404. In conclusion, these studies reveal that modified bile acid molecules can be used as "Trojan horses" to deliver a drug molecule specifically into the liver and the biliary system. This offers important pharmacological options for the development of liver-specific drugs.