Quinacrine Treatment Research Articles

Continuous Quinacrine Treatment Results in the Formation of Drug-Resistant Prions

Quinacrine is a potent antiprion compound in cell culture models of prion disease but has failed to show efficacy in animal bioassays and human clinical trials. Previous studies demonstrated that quinacrine inefficiently penetrates the blood-brain barrier (BBB), which could contribute to its lack of efficacy in vivo. As quinacrine is known to be a substrate for P-glycoprotein multi-drug resistance (MDR) transporters, we circumvented its poor BBB permeability by utilizing MDR0/0 mice that are deficient in mdr1a and mdr1b genes. Mice treated with 40 mg/kg/day of quinacrine accumulated up to 100 µM of quinacrine in their brains without acute toxicity. PrPSc levels in the brains of prion-inoculated MDR0/0 mice diminished upon the initiation of quinacrine treatment. However, this reduction was transient and PrPSc levels recovered despite the continuous administration of quinacrine. Treatment with quinacrine did not prolong the survival times of prion-inoculated, wild-type or MDR0/0 mice compared to untreated mice. A similar phenomenon was observed in cultured differentiated prion-infected neuroblastoma cells: PrPSc levels initially decreased after quinacrine treatment then rapidly recovered after 3 d of continuous treatment. Biochemical characterization of PrPSc that persisted in the brains of quinacrine-treated mice had a lower conformational stability and different immunoaffinities compared to that found in the brains of untreated controls. These physical properties were not maintained upon passage in MDR0/0 mice. From these data, we propose that quinacrine eliminates a specific subset of PrPSc conformers, resulting in the survival of drug-resistant prion conformations. Transient accumulation of this drug-resistant prion population provides a possible explanation for the lack of in vivo efficacy of quinacrine and other antiprion drugs.

Gene expression profile of quinacrine‐cured prion‐infected mouse neuronal cells

Prion diseases are transmissible fatal neurodegenerative diseases of humans and animals, characterised by the presence of an abnormal isoform (scrapie prion protein; PrP(Sc)) of the endogenous cellular prion protein (PrP(C)). The pathological mechanisms at the basis of prion diseases remain elusive, although the accumulation of PrP(Sc) has been linked to neurodegeneration. Different genomic approaches have been applied to carry out large-scale expression analysis in prion-infected brains and cell lines, in order to define factors potentially involved in pathogenesis. However, the general lack of overlap between the genes found in these studies prompted us to carry an analysis of gene expression using an alternative approach. Specifically, in order to avoid the complexities of shifting gene expression in a heterogeneous cell population, we used a single clone of GT1 cells that was de novo infected with mouse prion-infected brain homogenate and then treated with quinacrine to clear PrP(Sc). By comparing the gene expression profiles of about 15 000 genes in quinacrine-cured and not cured prion-infected GT1 cells, we investigated the influence of the presence or the absence of PrP(Sc). By real-time PCR, we confirmed that the gene encoding for laminin was down-regulated as a consequence of the elimination of PrP(Sc) by the quinacrine treatment. Thus, we speculate that this protein could be a specific candidate for further analysis of its role in prion infection and pathogenesis.

Quinacrine inhibits the epidermal dendritic cell migration initiating T cell‐mediated skin inflammation

Quinacrine (QC) is an anti-inflammatory drug that has been used for the treatment of malaria and rheumatoid diseases. The mechanism(s) underlying the anti-inflammatory activity of QC remains poorly understood. We recently reported the QC-mediated inhibition of the NF-kappaB pathway using an in vitro model. To test this potential mechanism in vivo, we used the contact hypersensitivity response (CHS) to chemical allergen sensitization and challenge in mice as a model of skin inflammation. The results indicated that QC treatment inhibited NF-kappaB activation in the skin during allergen sensitization. This inhibition was reflected by decreased mRNA expression and protein production of the NF-kappaB-dependent cytokines TNF-alpha and IL-1beta and the chemokine CCL21 in the skin. The decreases in these cytokines resulted in reduced migration of allergen-presenting dendritic cells from the skin into skin-draining lymph nodes and markedly decreased activation of effector CD8+ T cells for the CHS response to allergen challenge (inhibitory concentration 50% or IC50 was 55 mg/kg). These findings reveal a previously unrecognized mechanism of QC-mediated inhibition of inflammation.

The Reduction of Serum B‐Lymphocyte Activating Factor levels following Quinacrine Add‐On Therapy in Systemic Lupus Erythematosus

B-Lymphocyte-activating factor (BAFF/BLyS) is a survival factor for B cells, belonging to the tumor necrosis ligand super family. Serum BAFF levels have been found to be elevated in patients with systemic lupus erythematosus (SLE). Neutralization of BAFF activity was suggested as an additional therapeutic approach in SLE. To determine the effect of add-on Quinacrine (Qn) treatment on serum BAFF levels and the effect of this treatment on SLE disease activity index (SLEDAI), antidsDNA and anticardiolipin (aCL) antibody levels, we treated 29 stable SLE patients, who were maintained on prednisolone and hydroxychloroquine and in some on azathioprine (AZT), with additional Qn (100 mg/d) with an aim to further reduce disease activity. SLEDAI, antidsDNA, aCL antibodies and serum BAFF levels were assessed before and 3 months after the addition of Qn. Three months following Qn initiation, a reduction in SLEDAI was noticed in 19/29 patients (mean 8.8 +/- 2.3 to 3.3 +/- 1.5, P = 0.009), followed by reduction or discontinuation of prednisolone in all patients and the discontinuation of AZT in five patients. Serum BAFF levels were significantly reduced in 8/12 patients (mean 6.3 +/- 0.5 to 3.0 +/- 0.56 ng/ml P = 0.0001). This reduction was found in correlation with a decrease in aCL titres. However, the decrease in SLEDAI scores and antidsDNA antibody titres was unrelated to the decrease in serum BAFF or aCL levels. We conclude that the addition of Qn to previous therapeutic regimens in active SLE is beneficial and seems to reduce SLEDAI scores, serum BAFF and aCL levels and therefore should be considered in many of our SLE patients before aggressive treatments are given.

Compassionate use of quinacrine in Creutzfeldt–Jakob disease fails to show significant effects

Quinacrine has been reported as an antiprion agent and proposed as an immediately applicable treatment for Creutzfeldt-Jakob disease (CJD). The authors report the results of an open compassionate procedure to which 32 CJD patients had access. In some genotypic subgroups, a slight but nonsignificant increase in survival was observed, likely due to biased inclusion of long-term surviving patients. There was no pathologic evidence of a beneficial effect of quinacrine treatment.

Scrapie-infected GT1-1 cells show impaired function of voltage-gated N-type calcium channels (Ca v 2.2) which is ameliorated by quinacrine treatment

Prions are transmissible pathogens that cause neurodegenerative diseases, although the mechanisms behind the nervous system dysfunctions are unclear. To study the effects of a prion infection on voltage-gated calcium channels, scrapie-infected gonadotropin-releasing hormone neuronal cells (ScGT1-1) in culture were depolarized by KCl and calcium responses recorded. Lower calcium responses were observed in infected compared to uninfected cells. This effect was still observed when L-type calcium channels were blocked by nimodipine. After inhibition of N-type calcium channels with ω-conotoxin GVIA, there was no difference in calcium responses. The calcium responses after nimodipine treatment became progressively lower during infection, but there was no major loss of the cellular prion protein (PrP C) or marked increase in accumulation of the abnormal prion protein (PrP Sc) in the cultures. These results indicate that scrapie infection causes a dysfunction of voltage-gated N-type calcium channels, which is exacerbated slowly over time. Quinacrine treatment cleared PrP Sc and restored calcium responses in the ScGT1-1 cultures.

Evaluation of quinacrine treatment for prion diseases.

Based on in vitro observations in scrapie-infected neuroblastoma cells, quinacrine has recently been proposed as a treatment for Creutzfeldt-Jakob disease (CJD), including a new variant CJD which is linked to contamination of food by the bovine spongiform encephalopathy (BSE) agent. The present study investigated possible mechanisms of action of quinacrine on prions. The ability of quinacrine to interact with and to reduce the protease resistance of PrP peptide aggregates and PrPres of human and animal origin were analyzed, together with its ability to inhibit the in vitro conversion of the normal prion protein (PrPc) to the abnormal form (PrPres). Furthermore, the efficiencies of quinacrine and chlorpromazine, another tricyclic compound, were examined in different in vitro models and in an experimental murine model of BSE. Quinacrine efficiently hampered de novo generation of fibrillogenic prion protein and PrPres accumulation in ScN2a cells. However, it was unable to affect the protease resistance of preexisting PrP fibrils and PrPres from brain homogenates, and a "curing" effect was obtained in ScGT1 cells only after lengthy treatment. In vivo, no detectable effect was observed in the animal model used, consistent with other recent studies and preliminary observations in humans. Despite its ability to cross the blood-brain barrier, the use of quinacrine for the treatment of CJD is questionable, at least as a monotherapy. The multistep experimental approach employed here could be used to test new therapeutic regimes before their use in human trials.

Progesterone regulates IL12 expression in pregnancy lymphocytes by inhibiting phospholipase A2.

Progesterone-induced blocking factor (PIBF) is one of the pathways that mediate the immunological effects of progesterone. PIBF inhibits natural killer (NK) cytotoxic activity. Recently we showed that neutralization of PIBF results in an increased interleukin (IL)-12 expression, which is corrected by cyclooxygenase inhibitors. As exogenous arachidonic acid (AA) voids the NK blocking effect of PIBF, it is likely that PIBF acts before the level of the cyclooxygenase enzyme. Therefore in this study we investigated the effect of PIBF neutralizing antibody and simultaneous phospholipase A2 inhibitor quinacrine (Q) treatment on IL-12 production. Pregnancy lymphocytes were treated with anti-PIBF antibody or lipopolysaccharide (LPS) as a positive control, in the presence or absence of Q. IL-12 expression by PBMC was detected by immunocytochemistry. Neutralization of PIBF as well as LPS treatment resulted in an increased IL-12 expression, which was corrected by simultaneous Q treatment. Pre-treatment of lymphocytes with progesterone prevented the stimulating effect of LPS on IL-12 production. Progesterone binding of the lymphocytes is followed by the release of PIBF that inhibits AA release. The subsequent block of prostaglandin synthesis reduces IL-12 production and results in a lowered cytotoxic NK activity, which may contribute to a normal pregnancy outcome.

Quinacrine increases endothelial nitric oxide release: role of superoxide anion

The effect of acute quinacrine treatment on agonist-induced nitric oxide (NO) release was investigated in cultured human endothelial cells using electrochemical monitoring of the in situ NO concentration. Quinacrine dose-dependently increased NO release with an apparent EC 50 of 0.2 μM and a maximal effect at 1 μM. Quinacrine did not modify the dependence of NO release on extracellular l-arginine. Acceleration or deceleration of O 2 − dismutation, which altered NO release in control cells, did not modify it in quinacrine-treated cells. Quinacrine did not modify NO amperometric signal or reaction with O 2 − produced by xanthine oxidation. In the presence of quinacrine, agonist-induced NO release became Mg 2+-independent and could not be attributed to an inhibition of phospholipase A 2 activity. Quinacrine made NO release insensitive to Cu 2+ chelation. The present study demonstrates that acute treatment by low quinacrine concentrations increases endothelial NO release, possibly through an inhibition of O 2 − production.

Effect of quinacrine treatment on the activity of acid hydrolases (phosphatase, N-acetyl-beta-glucosaminidase, glucosidase, galactosidase and esterase) in Tetrahymena.

The effect of phospholipase A2 (PLA2) inhibitor, quinacrine, on the activity of hydrolytic enzymes in Tetrahymena pyriformis homogenate, was investigated. The activity of all of the enzymes studied (acid phosphatase, N-acetyl-beta-glusosaminidase, glucosidase, galactosidase and esterase) was significantly reduced in the presence of quinacrine. Since there are no data on the inhibitory effect of PLA2 and PLA2 influenced metabolic pathways to the hydrolytic enzymes, the direct effect of quinacrine on the hydrolytic enzymes (of Tetrahymena) can be supposed. This is supported by the fact that the other PLA2 inhibitor, 4-bromophenacyl bromide, did not influence phosphatase activity.

Enhancing effects of quinacrine on development of hepatopancreatic lesions in N-nitrosobis(2-oxopropyl)amine-initiated hamsters.

The modifying effects of quinacrine administration during the post‐initiation phase of carcinogenesis were investigated in hamsters treated with N‐nitrosobis(2‐oxopropyl)amine (BOP). Female Syrian hamsters were given three weekly s.c. injections of BOP at a dose of 10 mg/kg and then 300 or 100 ppm quinacrine in their diet for 37 weeks. Additional groups of animals received the BOP injection alone, or only the 300 ppm quinacrine treatment as BOP‐negative controls. At week 40 of the experiment, all surviving animals were killed and development of proliferative lesions was assessed histopathologically. The multiplicity of pancreatic adenocarcinomas and dysplastic lesions per hamster was significantly higher (P<0.01 and P<0.05) in the BOP/Q100 group (1.92 and 1.78) than in the BOP‐alone group (1.07 and 0.79). The incidence of hepatocellular adenomas plus carcinomas was also significantly elevated (P<0.05) in the BOP/Q300 and BOP/Q100 groups. In contrast, the multiplicity of lung adenomas plus adenocarcinomas was significantly decreased (P<0.05) by the Q300 treatment. Neither the incidence nor the multiplicity of renal cell tumors (adenomas and carcinomas) or nephroblastomas significantly differed between the BOP‐treated groups. Electron microscopic examination revealed an abundance of myeloid lamellar bodies filling the cytoplasm of hepatocytes and pancreatic ductular and acinar cells, and epithelial cells of the gallbladder in the quinacrine‐treated animals, the degree being dose‐dependent. Our results indicate that quinacrine enhances pancreatic and hepatic carcinogenesis in hamsters induced by BOP.

Effect of quinacrine, a phospholipase A2 inhibitor on stress and chemically induced gastroduodenal ulcers.

Quinacrine, a phospholipase A2 inhibitor, has been studied for its ability to inhibit gastric secretion and to protect the gastric and duodenal mucosa against chemically and stress-induced ulcers. Acid secretion studies were undertaken in pylorus-ligated rats with and without quinacrine treatment. Experimental gastric lesions were induced by water-immersion restraint stress, indomethacin and 80% ethanol in rats; whereas duodenal ulcers were produced by treatment of rats with cysteamine. The level of nonprotein sulfhydryl compounds and gastric wall mucus were also measured in the glandular stomach of the rats following ethanol-induced gastric lesions. The results of this study demonstrate that quinacrine produces a dose-dependent inhibition of gastric acid secretion in rats. Pretreatment with quinacrine significantly attenuated the formation of stress-, indomethacin- and ethanol-induced gastric lesions. Quinacrine also protected intestinal mucosa against cysteamine-induced duodenal ulcers. The antiulcer activity of quinacrine was associated with appreciable inhibition of ethanol-induced depletion of nonprotein sulfhydryls and gastric wall mucus. These findings point towards the mediation of sulfhydryls in quinacrine-induced gastrointestinal cytoprotection. In conclusion, this study demonstrates that quinacrine possesses significant antiulcer and cytoprotective activity against various experimentally induced gastroduodenal lesions. Although the mechanism of action of quinacrine requires further evaluation, the experimental observations derived from this study may have future clinical relevance and therefore deserve to be investigated thoroughly.

Quinacrine attenuates cyclosporine-induced nephrotoxicity in rats.

The biochemical mechanism underlying cyclosporine (CsA)* induced nephrotoxicity is far from clear. Increased generation of oxygen derived free radicals (ODFR) and enhanced activity of phospholipase A2 (PLA2) have been observed in experimental animals following treatment with CsA. Several recent reports have shown that quinacrine, besides being a potent inhibitor of PLA2, suppresses the generation of ODFR. The present study was designed to investigate the effect of quinacrine on CsA induced nephrotoxicity in rats. Male Wistar rats (weighing 280-300 g) were randomized into eight groups of eight animals each. Group 1 (control) received appropriate vehicles only, whereas the rats in groups 2, 3, 4, and 5 received subcutaneous injection of CsA (17.5 mg/kg dissolved in olive oil) daily for 8 weeks. The animals in groups 3, 4, and 5 were also given intraperitoneal injections of quinacrine in three different doses of 2.5 mg/kg, 5 mg/kg, and 10 mg/kg body weight, respectively, in addition to CsA. The animals in groups 6, 7, and 8 received intraperitoneal injection of quinacrine alone at doses of 2.5 mg/kg, 5 mg/kg, and 10 mg/kg respectively for eight weeks. After 8 weeks, animals were sacrificed under light ether anesthesia and blood and kidney samples were collected for various biochemical and histological studies. The biochemical parameters included blood urea nitrogen (BUN), serum creatinine (Scr), potassium, and sodium. The blood was also analyzed for the level of CsA. The kidney samples were analyzed for malondialdehyde (MDA), glutathione, and vitamin E (VE). Kidney sections were prepared for histopathological studies using hematoxylin-eosin staining. There was an increase in BUN, Scr, and potassium levels and decrease in sodium levels in cyclosporine alone treated group, suggesting a significant nephrotoxicity. Quinacrine treatment significantly protected animals against CsA induced biochemical changes. Our studies on free radical indices showed that quinacrine treatment protected animals against cyclosporine induced increase in MDA and depletion of glutathione and VE. The beneficial effect of quinacrine against CsA induced nephrotoxicity was also confirmed by histological studies.

Role of microtubule organization in centrosome migration and mitotic spindle formation in PtK1 cells

Quinacrine, an acridine derivative, has previously been shown to disrupt lateral associations between non-kinetochore microtubules (nkMTs) of opposite polarity in PtK1 metaphase spindles such that the balance of spindle forces is significantly altered. We extended the analysis of the spatial relationship of spindle microtubules (MTs) in this study by using quinacrine to compare ATP-dependent requirements for early prometaphase centrosome separation and spindle formation. The route used for centrosome migration can take a variety of pathways in PtK1 cells, depending on the location of the centrosomes at the time of nuclear envelope breakdown. Following quinacrine treatment centrosome separation decresased by 1.9 to 14.0 μm depending on the pathway utilized. However, birefringence of the centrosomal region increased approximately 50% after quinacrine treatment. Quinacrine-treated mid-prometaphase cells, where chromosome attachment to MTs had occurred, showed a decrease in spindle length of approximately 6.0 μm with only a slight increase in astral birefringence. Computer-generated reconstructions of quinacrine-treated prometaphase cells were used to confirm changes in MT reorganization. Early-prometaphase cells showed more astral MTs (aMTs) of varied length while mid-prometaphase cells showed only a few short aMTs. Late prometaphase cells again showed a large number of aMTs. Our results suggest that: (1) quinacrine treatment affects centrosome separation, (2) recruitment of nkMTs by kinetochores is quinacrine-sensitive, and (3) development of the prometaphase spindle is dependent on quinacrine-sensitive lateral interactions between nkMTs of opposite polarity. These data also suggest that lateral interactions between MTs formed during prometaphase are necessary for centrosome separation and normal spindle formation but not necessarily chromosome motion.

Dose-dependent enhancing effects of quinacrine on induction of preneoplastic glutathione S-transferase placental form positive liver cell foci in male F344 rats

Dose-dependent modifying effects of quinacrine on induction of preneoplastic liver cell foci were investigated in male F344 rats. Six week old animals were injected i.p. with N-nitrosodiethylamine (DEN) at a dose of 200 mg/kg, and starting 2 weeks later, rats were given quinacrine at dietary levels of 20, 100 and 500 p.p.m. for 6 weeks. Groups without either DEN or quinacrine treatment were used as controls. At week 3 following DEN administration, all animals were subjected to two-thirds partial hepatectomy, and after killing the animals at week 8, development of preneoplastic liver cell foci was investigated using the glutathione S-transferase placental form (GST-P) as a marker. The numbers and unit areas of GST-P-positive foci per cm2 were significantly increased in the DEN/quinacrine (500 p.p.m.) group as compared to DEN-alone group values. An increase in number was also evident in the 100 p.p.m. but not the 20 p.p.m. treated group, no lesions being induced by quinacrine alone (500 p.p.m.). Electron microscopic study confirmed that quinacrine dose-dependently induces lipidosis in hepatocytes, i.e. markedly myeloid lamellar cytoplasmic inclusion bodies were observed. The results thus demonstrated that quinacrine treatment enhances GST-P-positive liver cell foci development in a dose-dependent way, this effect presumably being related to the induction of lipidosis.

Selective reduction of anaphase B in quinacrine-treated PtK1 cells.

Quinacrine, an acridine derivative which competitively binds to ATP binding sites, has previously been shown to cause the reorganization of metaphase spindle microtubules (MTs) due to changes in interactions of non-kinetochore microtubules (nkMTs) of opposite polarity (Armstrong and Snyder: Cell Motil. Cytoskeleton 7:10-19, 1987). In the study presented here, mitotic PtK1 cells were treated in early anaphase with concentrations of quinacrine ranging from 2 to 12 microM to determine energy requirements for chromosome motion. The rate and extent of chromosome-to-pole movements (anaphase A) were not affected by these quinacrine treatments. The extent of anaphase B (kinetochore-kinetochore separation) was reduced with increasing concentrations of quinacrine. Five micromolar quinacrine reduced the extent of kinetochore-kinetochore separation by 20%, and addition of 12 microM quinacrine reduced the kinetochore-kinetochore separation by 40%. To determine the role of nkMTs in anaphase spindle elongation, quinacrine-treated metaphase cells were treated with hyperosmotic sucrose concentrations, and spindle elongation was measured (Snyder et al.: Eur J. Cell Biol. 39:373-379, 1985). Metaphase cells treated with 2-10 microM concentrations of quinacrine for 2-5 min reduced spindle lengths by 10-50% prior to 0.5 M sucrose treatment for 5 min. This treatment showed a significant reduction in the ability of sucrose to induce spindle elongation in cells pretreated with quinacrine. As spindle length and birefringence was reduced by quinacrine treatment, sucrose-induced elongation was concomitantly diminished. These data suggest that quinacrine-sensitive linkages are necessary for anaphase B motions. Reduction in these linkages and/or MT length in the nkMT continuum may reduce the ability of the nkMTs to hold compression at metaphase. This form of energy is thought to drive a significant proportion of normal anaphase B in PtK1 cells and sucrose-induced metaphase spindle elongation.

Quinacrine-induced changes in mitotic PtK1 spindle microtubule organization.

Quinacrine, an acridine derivative which competitively binds to ATP binding sites, has been used to study the role of ATP requiring molecules in microtubule organization in mitotic PtK1 cells. Brief treatments of metaphase cells with concentrations of quinacrine ranging from 2 to 10 microM decreased spindle length and birefringence in a concentration-dependent manner. With either increasing quinacrine concentrations or duration of treatment, metaphase cells demonstrated a specific reorganization of spindle microtubules. Both polarization and electron microscopy showed a substantial loss of non-kinetochore spindle microtubules with an increase in astral microtubules: this was particularly evident in the region adjacent to the spindle domain. Addition of millimolar concentrations of dinitrophenol to quinacrine-containing medium did not potentiate the response of metaphase cells to quinacrine treatment. Time-lapse video analysis demonstrated that the astral microtubules are the result of reorganization of spindle microtubules. These data suggest that functional ATP binding sites are required to maintain stable interactions between microtubules and that these interactions are responsible for maintaining the bowed configuration of non-kinetochore spindle microtubules which are under compression at metaphase.

Frame-shift mutants induced by quinacrine are recognized by the mismatch repair system in Streptococcus pneumoniae.

We describe the isolation of amethopterin-resistant mutants induced by quinacrine treatment of exponentially growing cultures of Streptococcus pneumoniae. Only mutants located by recombination analysis in a few hundred base pairs were further studied. They were cloned and their DNA sequences show that most of them are +/-1-base frame-shift mutants. They are excised and repaired to a degree similar to transition mutants (low efficiency class), suggesting that the mismatches resulting from a transition or a +/-1-base mutation are similar substrates for the Hex mismatch repair system.

GENETIC STUDIES OF ACRIDINE-INDUCED MUTANTS IN STREPTOCOCCUS PNEUMONIAE

The mutagenic properties of acridines on pneumococcus are described. All seven acridines tested were mutagenic at the amiA locus conferring a resistance to 10(-5) M aminopterin. The effects of quinacrine were more specifically investigated. It was observed that: mutants can be obtained only by treatment of exponentially growing cells; a sharp maximum mutagenic effect occurs at a concentration slightly lower than the bacteriostatic value; and the amount of quinacrine required to yield the maximum mutagenic effect decreases with the pH of the medium. Moreover, the number of mutants detected after quinacrine treatment varies from locus to locus. The majority of quinacrine-induced mutants are readily reverted by quinacrine, but not by nitrosoguanidine treatment. This suggests that in pneumococcus quinacrine induces mainly frameshift mutations. A further study of the revertants obtained by quinacrine treatment of quinacrine-induced mutants strengths this interpretation: most of the revertants result from a mutation at the same site; some partial revertants exhibiting an intermediate resistance to aminopterin were found to contain two very closely linked mutated sites, each mutation conferring the maximum level of resistance to aminopterin. Thus, the majority of quinacrine-induced mutants at the amiA locus of pneumococcus consists of frameshift mutations. Nearly all of the isolated mutants induced by quinacrine as well as other acridines belong to the low efficiency class of transformation. It was concluded that the mismatch resulting from the pairing between the wild type and the frameshift-containing sequence is recognized by the excision-repair system involved in the discrimination function in a way similar to that in which it recognizes mismatched base pairs between a transition mutation and the wild-type sequence.

Staining of human metaphase chromosomes with fluorescent conjugates of polylysine

The interaction of polylysine and partially substituted dansyl, fluorescein, and quinacrine conjugates of polylysine with cytological preparations of human metaphase chromosomes has been studied by fluorescence microscopy. The fluorescence intensity along chromosomes stained with the dansyl and fluorescein conjugates exhibits little variation, suggesting that regions capable of binding these polycations are nearly evenly distributed. In contrast, the quinacrine derivatives of polylysine stain the chromosomes in a banded fluorescence pattern resembling that observed following quinacrine or quinacrine mustard treatment.