Controlled release and ocular absorption of tilisolol utilizing ophthalmic insert-incorporated lipophilic prodrugs

To control ocular drug delivery, the O-butyryl ester prodrug of tilisolol (BUTL) and the O-palmitoyl ester prodrug of tilisolol (PalTL) were incorporated into an ophthalmic insert. The released TL from BUTL inserts and PalTL inserts in pH 7.4 phosphate-buffered saline until 5 h were approximately 25% and 3% of that from TL inserts, respectively. In addition, BUTL was also released from BUTL inserts. However, PalTL was not released from the PalTL insert. The release of drugs from TL inserts and BUTL inserts was little affected by the addition of bovine serum albumin (BSA) in pH 7.4 phosphate-buffered saline. In contrast, the release of drugs from PalTL inserts were enhanced by the addition of BSA. After application of TL, BUTL, and PalTL inserts to the rabbit eye, the aqueous humor concentration of TL was prolonged compared with TL instillation, and the plasma concentration of TL was much lower than that of TL instillation. The ratios of the area under the TL concentration-time curve (AUC) in the aqueous humor to AUC in the plasma (AUC(aqueous)/AUC(plasma)) after application of BUTL until 8 h were 3.1-fold and 3.8-fold higher than those of the TL insert and PalTL insert, respectively.

STM images apparently corresponding to a stable structure: considerable fluctuation of a phase boundary of the Si(111)-(square root of (3) x square root of (3))-Ag surface

We study scanning tunneling microscopy (STM) images near a phase boundary of the Si(111)- (square root of (3) x square root of (3))-Ag surface by using Monte Carlo simulations based on results of first-principles calculations. The boundary is found to fluctuate from snapshot to snapshot, and the feature of the simulated STM images differs distinctly from the observed one with a straightly extending honeycomb pattern of bright spots. Remarkably, statistical averages of the simulated images reproduce the observed feature. This study gives a warning of our tendency to relate STM images revealing clear arrangement of bright spots with some stable structure.

Effect of instillation method on the absorption of phenolsulphonphthalein as a model drug from the liver and small intestinal serosal surface in rats

We have examined the effect of the instillation method on the absorption of a drug from the liver and the small intestinal serosal surface in rats. We performed continuous microinstillation via an infusion pump and bolus instillation via a syringe, using phenolsulphonphthalein (phenol red) as the model drug. After continuous microinstillation of phenolsulphonphthalein 2.35 mg in 235 microL for 5 min on the liver and small intestinal serosal surface in rats, the AUC (area under the curve) of the plasma concentration profile up to 60 min was significantly higher compared with bolus instillation. A similar trend was observed after continuous microinstillation of phenolsulphonphthalein 2.35 mg in 117.5 microL for 2.5 min. The calculated absorption rate constants (Ka) after continuous microinstillation of phenolsulphonphthalein based on a two-compartment model with first-order absorption were higher than those after bolus instillation on the liver and small intestinal serosal surface at either instillation concentration. Moreover, Ka was increased after continuous microinstillation of 2.35 mg in 117.5 microL at either instillation site. Instillation of phenolsulphonphthalein on the liver surface resulted in a 1.2- to 2.3-fold higher Ka compared with the small intestinal serosal surface. This tendency was marked after continuous microinstillation of 2.35 mg in 117.5 microL. In conclusion, absorption could be enhanced by instilling a small amount of drug solution on the liver surface gradually and continuously, suggesting a promising approach for instillation site-selective drug delivery in the peritoneal cavity.

Effect of clonazepam treatment on antipsychotic drug-induced Meige syndrome and changes in plasma levels of GABA, HVA, and MHPG during treatment

We demonstrated the effect of clonazepam (2 mg/day) on Meige syndrome in two schizophrenic patients under continuous treatment with antipsychotic drugs, and changes in the plasma levels of gamma-aminobutyric acid (GABA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) in these cases. The plasma levels of HVA and MHPG during treatment with clonazepam were decreased in the responder, while not changed in the non-responder to clonazepam. A difference between the responder and the non-responder was not found in the plasma GABA levels. These results suggest that hyperactivities of the central dopaminergic and noradrenergic neurones are involved in the pathophysiology of Meige syndrome.

Leukemia inhibitory factor induces nociceptin mRNA in cultured rat cortical neurons

The effects of leukemia inhibitory factor (LIF) on the expression of neurotransmitter synthetase and neuropeptide mRNAs in cultured rat cortical neurons were examined by reverse transcription-polymerase chain reaction. Nociceptin mRNA expression was increased by treatment with 20 or 80 ng/ml LIF for 24 h, but choline acetyl transferase, glutamic acid decarboxylase, enkephalin, dynorphin, substance P, somatostatin and galanin mRNA expression were not altered by LIF. These observations indicated a specific effect of LIF on nociceptin gene regulation in cultured cortical neurons.

Novel polymorphism in the 5'-upstream region of the human 5-HT6 receptor gene and schizophrenia

The localization of 5-hydroxytryptamine6 (5-HT6) receptor in the limbic and cortical regions, and the high affinity of atypical antipsychotic drugs such as clozapine for the receptor, suggest the possible involvement of the receptor in the pathogenesis of schizophrenia. In this study, we searched systematically for polymorphisms in the 5'-upstream region of the human 5-HT6 receptor gene. We identified a trinucleotide repeat polymorphism, (GCC)2/3, at a nucleotide position between -1093 and -1085 bp upstream from the translation start site. Subsequent case-control association study did not demonstrate significant differences of genotype and allele frequency between 206 controls and 246 patients with schizophrenia. Our results suggest that the 5-HT6 receptor gene polymorphism does not confer increased susceptibility to schizophrenia.

Inhibition of adenylylcyclase activity in mouse cerebellum membranes upon hydrolysis of triacylglycerols by triacylglycerol lipase, but not phospholipids by phospholipase A(2)

We previously showed that arachidonic acid and related unsaturated free fatty acids (U-FFAs) inhibit the activity of adenylylcyclase in brain membranes of mice. The level of U-FFAs elevates when the hydrolysis of triacylglycerols (TAGs) and phospholipids is promoted. In this study, we examined whether activation of triacylglycerol lipase (TAG lipase) and phospholipase A(2) (PLA(2)) results in the inhibition of adenylylcyclase activity in cerebellum membranes of mice. Incubation of Intralipos with TAG lipase in the presence of membranes mainly released oleic acid and linoleic acid and caused > or =95% inhibition of adenylylcyclase activity. In contrast, PLA(2), though releasing substantial amounts of U-FFAs, increased the enzymatic activity. To account for this difference, we examined how by-products formed in U-FFA release by TAG lipase and PLA(2) operated on the arachidonic acid-induced inhibition. Lysophosphatidylcholne and some other lysophospholipids, produced by PLA(2), enhanced the adenylylcyclase activity and attenuated the inhibitory effect of arachidonic acid. On the other hand, no such effects were found with by-products of TAG lipase-mediated lipolysis. Rather, monoacylglycerols having U-FFAs, possibly formed by TAG lipase, potentiated the arachidonic acid-induced inhibition of adenylylcyclase. Bovine serum albumin, added into the mixture for the pretreatment of membranes with TAG lipase, prevented the inhibition of adenylylcyclase. These results indicate that by-products formed in U-FFA release have a crucial role for the U-FFA's action on adenylylcyclase and that U-FFAs released from TAG are an inhibitor of adenylylcyclase. It may be that albumin in plasma, and thus FFA-binding proteins within cells, are of importance in protecting adenylylcyclase upon U-FFA release.

Sustained ocular delivery of tilisolol to rabbits after topical administration or intravitreal injection of lipophilic prodrug incorporated in liposomes

To improve the retention time of tilisolol in the precorneal area or vitreous body, we prepared liposomes incorporating the O-palmitoyl prodrug of tilisolol. O-Palmitoyl tilisolol was completely incorporated in the liposomes. After topical administration of O-palmitoyl tilisolol liposomes to the rabbit eye, O-palmitoyl tilisolol rapidly disappeared from the tear fluid. The inclusion of 2% carmellose sodium slightly prolonged the retention of O-palmitoyl tilisolol in the tear fluid. After intravitreal injection of O-palmitoyl tilisolol liposomes, there was a relatively prolonged retention of O-palmitoyl tilisolol in the vitreous body. At 24 and 48 h after intravitreal injection of O-palmitoyl tilisolol liposomes, the tilisolol concentration in the vitreous body was significantly higher compared with the concentration after intravitreal injection of tilisolol liposomes.

[Side effects and its countermeasures of antidepressant]

We reviewed the side effects of antidepressants. Tricyclic antidepressants(TCAs) are associated with a higher frequency of adverse events than those of SSRIs and SNRIs, particularly with respect to anticholinergic-like effects(dry mouth, constipation, and blurred vision), delirium, and cardiovascular adverse events. On the other hand, SSRIs have some special side effects that include nausea, sexual dysfunction, and extrapyramidal symptoms. With regard to milnacipran, a member of the SNRI family, dysuria occurs at a higher frequency than with TCAs or SSRIs. When side effects occur, clinicians give patients symptomatic treatment or substitute the drugs that cause the adverse effects with other antidepressants that have different pharmacological effects.

Structural and cohesive properties of a C60 monolayer

We have explored the cohesive property of a monolayer of C (60) molecules (ML- C (60)) by means of total energy calculations with the density-functional theory. The total energy curve calculated for ML- C (60), which is obtained as a function of the lattice constant, has two minima and shows a hysteresis in the compression-tension stroke. These two minima in energy correspond to the different structural phases of ML- C (60): one is a monomer phase and the other is a polymer one. The energy band gap within the framework of the local density approximation varies from 1 eV (semiconducting phase) to 0 eV (metallic phase) with external pressure and without structural transition from the monomer phase to the polymer one.

The analyses of 17beta-hydroxysteroid dehydrogenase isozymes in human endometrial hyperplasia and carcinoma

Intratumoral metabolism and synthesis of estrogens are considered to play very important roles in the pathogenesis and development of human endometrial adenocarcinoma. The 17beta-hydroxysteroid dehydrogenase (17beta-HSD) isozymes catalyze the interconversion of estradiol (E2) and estrone and thereby serve to modulate the tissue levels of bioactive E2. To elucidate the possible involvement of this enzyme in human endometrial carcinoma, we first examined the expression of 17beta-HSD type 1 and type 2 in 20 normal cycling human endometria, 36 endometrial hyperplasia, and 46 endometrial endometrioid adenocarcinoma using immunohistochemistry, and we then studied immunoreactivity of 17beta-HSD type 2 using immunoblotting analyses, the activity of 17beta-HSD type 1 and type 2 using thin-layer chromatography and their expression using RT-PCR in endometrial endometrioid adenocarcinoma. We correlated these findings with various clinicopathological parameters to examine the biological significance of 17beta-HSDs in human endometrial disorders. 17beta-HSD type 2 immunoreactivity in normal endometrium was present in all cases of secretory phase (n = 14), but not in any endometrial mucosa of proliferative phase (n = 6). In addition, 17beta-HSD type 2 immunoreactivity was detected in 27 of 36 (75%) endometrial hyperplasia and 17 of 46 (37%) carcinoma cases. 17beta-HSD type 1 immunoreactivity was not detected in all the cases examined. In both endometrial hyperplasia and carcinoma cases there were significant positive correlations between 17beta-HSD type 2 and progesterone receptor labeling index (LI). In carcinoma cases, a significant inverse correlation was detected between 17beta-HSD type 2 immunoreactivity and age. In addition, 17beta-HSD type 2 immunoreactivity was also correlated with 17beta-HSD type 2 enzymatic activity, and semiquantitative analyses of 17beta-HSD type 2 messenger RNA. No significant correlations were detected between 17beta-HSD type 2 and estrogen receptor LI, Ki67 LI, amount of aromatase messenger RNA or histological grade. These data indicated that the expression of 17beta-HSD type 2 in hyperplastic and/or neoplastic endometrium may represent altered cellular features through hyperplastic and neoplastic transformation. However, 17beta-HSD type 2 may also play some protective and/or suppressive roles toward unopposed estrogenic effects through inactivating E2 in situ, especially in premenopausal patients.

Aldose reductase inhibition ameliorates pupillary light reflex and F-wave latency in patients with mild diabetic neuropathy

OBJECTIVE

The present study was conducted to investigate the effect of an aldose reductase inhibitor, epalrestat, on autonomic and somatic neuropathy at an early stage in type 2 diabetic patients by assessing the pupillary light reflex and minimum latency of the F-wave.

RESEARCH DESIGN AND METHODS

A total of 30 diabetic patients with subclinical or mild diabetic neuropathy were randomly allocated to a control group (n = 15) and epalrestat (150 mg/day) group (n = 15). After 24 weeks, the pupillary light reflex test, cardiovascular autonomic function tests, and nerve conduction study were performed.

RESULTS

The beneficial effect of epalrestat on the pupillary light reflex was observed in the minimum diameter after light stimuli (P = 0.044), constriction ratio (P = 0.014), and maximum velocity of constriction (P = 0.008). Among cardiovascular autonomic nerve functions, the ratio of the longest expiratory R-R interval to the shortest inspiratory R-R interval during deep breathing was significantly improved by epalrestat (P = 0.037). Minimum latencies of F-wave of median and tibial motor nerves were significantly shortened by epalrestat (P = 0.002 and P = 0.001, respectively); however, no significant effects were observed in motor or sensory nerve conduction velocity.

CONCLUSIONS

These observations suggest that epalrestat may have therapeutic value at the early stage of diabetic neuropathy and that the pupillary light reflex and minimum latency of F-wave may be useful indicators of diabetic neuropathy.

Inhibition of adenylyl cyclase activity in brain membrane fractions by arachidonic acid and related unsaturated fatty acids

Pretreatment of mouse brain membranes with arachidonic acid (AA) and related unsaturated fatty acids at 30 degrees C for 10 min decreased basal activity and isoproterenol/guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S)- and forskolin-stimulated activities of adenylyl cyclase to a level less than 5% of control. The presence of the carboxyl group on the fatty acids was essential for the inhibition, because no such inhibition was found with ethyl arachidonate or AA attached to diacylglycerols and phospholipids. The AA-mediated inhibition was observed when the activity was measured in the presence of Mn2+ or forskolin and was insensitive to pertussis toxin or guanosine 5'-O-(2-thiodiphosphate) (GDPbetaS), indicating a mechanism independent of GTP-binding proteins. In addition, the fact that stimulators of the adenylyl cyclase catalytic unit, ATP, GTP gamma S and forskolin, when present during pretreatment, attenuate the inhibitory effect of AA may suggest that the catalytic unit is a target of AA. Bovine serum albumin suppressed the inhibition when present in the mixtures for pretreatment, but could not restore the adenylyl cyclase activity that had been reduced by AA, indicating an irreversible inhibition by AA. The effect of AA was found to be additive to P-site-mediated inhibition. The present study suggests the existence of another mechanism of regulation of adenylyl cyclase by unsaturated fatty acids.

Calcium concentration and pH of the periapical environment after applying calcium hydroxide into root canals in vitro

The purpose of the present study was to determine both calcium concentration and pH in the periapical region after application of 1 of 4 different calcium hydroxide preparations into experimental root canals. Fifty root canal models were divided into five groups: group 1--calcium hydroxide was mixed with distilled water at a powder/water weight ratio of 38%; group 2--calcium hydroxide was mixed with distilled water at 44%; group 3--calcium hydroxide was mixed with distilled water at 50%; group 4--calcium hydroxide powder only was used; and group 5-the control group, in which nothing was applied to the canals. All samples were immersed in distilled water maintained at 37 degrees C. Calcium concentration and pH of the distilled water were measured after 3 days, 7 days, and then at weekly intervals up to 15 wk, during which time the storage medium was renewed after each measurement. Calcium concentration and the change in pH of the distilled water were statistically quicker and greater in groups 1 to 3 (mixture groups) than group 4 (powder only) (p < 0.05). The highest calcium concentration (peak Ca2+ release) was observed after 3 days for the mixture groups, whereas that for the powder only group was found at 7 days. Peak pH change was found after 14 days for the mixture groups, whereas that for the powder only group was found at 49 days. After peaking, all groups showed a decline of the pH over time. These results suggest that the time required for optimum intracanal activity when using calcium hydroxide mixtures is at least 2 wk.

Charles Bonnet syndrome with auditory hallucinations: a diagnostic dilemma

Charles Bonnet syndrome (CBS) appears to be commoner in elderly people than was previously thought. Nonetheless, as yet, no firm diagnostic criteria have been established for CBS, leaving the need for well-defined diagnostic criteria describing this syndrome unfulfilled. Two recently proposed diagnostic criteria for CBS insist on an absence of hallucinations in modalities other than visual. However, we experienced 2 cases suffering from probable CBS who experienced auditory hallucinations. In this report, we recommend that even if CBS coexists with other hallucinations, we should not exclude CBS as a probable diagnosis when the patients recognize their hallucinations as unreal. We believe that this modification of CBS diagnostic criteria will contribute to psychiatric epidemiology by correcting the current underestimation of CBS prevalence.

Gain-of-function mutation at the extracellular domain of KIT in gastrointestinal stromal tumours

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the human gastrointestinal tract. Previous studies of GISTs found gain-of-function mutations of the c-kit gene, which encodes a receptor tyrosine kinase (KIT). All the mutations were confined to exon 11, which encodes the juxtamembrane domain. By further examination of the whole coding region of c-kit complementary DNA in 35 GISTs, two were found to show the identical mutation at exon 9, which encodes the extracellular domain. The aims of the present study were to examine the frequency of the extracellular domain mutation and to determine whether the mutation is a gain-of-function type or not. Genomic DNA was extracted from paraffin-embedded tissues of 133 GISTs and exon 9 of the c-kit gene was amplified by polymerase chain reaction. Screening of the mutation was carried out by single-strand conformation polymorphism analysis and direct sequencing was done. Mutant c-kit cDNA was transfected into 293T human embryonic kidney cells and the magnitude of autophosphorylation of the mutant KIT was examined with or without the ligand of KIT, stem cell factor (SCF). In total, seven GIST cases (approximately 5%) were found with the identical mutation at exon 9. The mutant KIT exhibited constitutive autophosphorylation without SCF stimulation. The prognosis of the patients with the extracellular domain mutation was comparable to that of the patients with the juxtamembrane domain mutation.

Gain-of-function mutation at the extracellular domain of KIT in gastrointestinal stromal tumours

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the human gastrointestinal tract. Previous studies of GISTs found gain-of-function mutations of the c-kit gene, which encodes a receptor tyrosine kinase (KIT). All the mutations were confined to exon 11, which encodes the juxtamembrane domain. By further examination of the whole coding region of c-kit complementary DNA in 35 GISTs, two were found to show the identical mutation at exon 9, which encodes the extracellular domain. The aims of the present study were to examine the frequency of the extracellular domain mutation and to determine whether the mutation is a gain-of-function type or not. Genomic DNA was extracted from paraffin-embedded tissues of 133 GISTs and exon 9 of the c-kit gene was amplified by polymerase chain reaction. Screening of the mutation was carried out by single-strand conformation polymorphism analysis and direct sequencing was done. Mutant c-kit cDNA was transfected into 293T human embryonic kidney cells and the magnitude of autophosphorylation of the mutant KIT was examined with or without the ligand of KIT, stem cell factor (SCF). In total, seven GIST cases (approximately 5%) were found with the identical mutation at exon 9. The mutant KIT exhibited constitutive autophosphorylation without SCF stimulation. The prognosis of the patients with the extracellular domain mutation was comparable to that of the patients with the juxtamembrane domain mutation.

Induction of direct adducts, apurinic/apyrimidinic sites and oxidized bases in nuclear DNA of human HeLa S3 tumor cells by tetrachlorohydroquinone

DNA damage induced by tetrachlorohydroquinone (Cl(4)HQ), the quinonoid metabolite of pentachlorophenol (PCP), was investigated in human HeLa S3 tumor cells. Formation of one major and two minor DNA adducts in cells treated with Cl(4)HQ (50-300 microM) was detected by (32)P-post-labeling assay and the adducts accumulated over the course of the experiment (0.5-2 h), with total adduct levels estimated to be 3-6 per 10(8) nucleotides. These adducts did not correspond to those derived from calf thymus DNA treated with tetrachloro-1,4-benzoquinone. Results from the apurinic/apyrimidinic (AP) sites assay indicated that the number of AP sites was 2-fold greater in cells exposed to Cl(4)HQ (300 microM) than the corresponding control. Further characterization of the AP sites confirmed that Cl(4)HQ induced predominantly (75%) putrescine-excisable AP sites in HeLa S3 cells. In parallel, the concentration of 8-hydroxy-2'-deoxyguanosine (8-HO-dG) in cells treated with Cl(4)HQ for 0.5 and 2 h was increased 2- and 5-fold, respectively, compared with the control. The extent of oxidative DNA damage induced by Cl(4)HQ was approximately two orders of magnitude greater than those of direct DNA adducts. Overall, it appears that reactive oxygen species mediate the parallel formation of AP sites and 8-HO-dG in HeLa S3 cells following treatment with Cl(4)HQ and that the contribution of depurination/depyrimidination of direct DNA adducts is relatively insignificant compared with the formation of oxidized AP sites. We conclude that putrescine-excisable AP sites represent a major type of ROS-mediated oxidative DNA damage in cellular DNA induced by Cl(4)HQ and may play a role in PCP-induced clastogenicity in mammalian cells.

The influence of two concentrations of sodium hypochlorite on human blood: changes in haemolysis, pH and protein

AIM

To evaluate the in vitro effect of 2.5% and 5.0% sodium hypochlorite (NaOCl) on human blood.

METHODOLOGY

Each concentration of NaOCl was reacted with human blood for 5 min at volume ratios of 1 : 1, 1 : 6, 1 : 12, each creating changes in colour, pH and temperature. Reaction suspensions were separated by centrifugation, and absorption measurements made for separated bilirubin, Fe, and protein supernatants. Each supernatant was desalted, lyophilized, and treated by SDS polyacrylamide gel electrophoresis (SOS-PAGE).

RESULTS

Increased ratios and concentrations of NaOCl caused an increase in both pH and temperature. Protein supernatants tended to decompose on SDS-PAGE. Supernatants showed increased decolourisation with 5.0% NaOCl. Concentrations of bilirubin, Ferrum and protein in supernatants decreased with increased NaOCl concentration. NaOCl had an effect on the protein component in blood.

CONCLUSIONS

These data suggest that changes in molecular structure are due to the chemical effects of NaOCl. Protein bands tended to show low molecular weight, suggesting that haemoglobin components effect the oxidation-reduction reaction.

Increased libido in a woman treated with fluvoxamine: a case report

OBJECTIVE

The aim of this paper is to describe a case of increased libido during fluvoxamine therapy.

METHOD

Single case report.

RESULTS

The patient, a 27-year-old married Japanese woman with borderline personality disorder, developed an increased libido with the administration of fluvoxamine. The increased libido disappeared after fluvoxamine was discontinued.

CONCLUSION

The present findings suggest that fluvoxamine can cause increased libido in some patients.

Oxidative damage and direct adducts in calf thymus DNA induced by the pentachlorophenol metabolites, tetrachlorohydroquinone and tetrachloro-1,4-benzoquinone

DNA damage induced by quinoid metabolites of pentachlorophenol (PCP), i.e. tetrachloro-1,4-benzoquinone (Cl(4)BQ) and tetrachlorohydroquinone (Cl(4)HQ), was investigated in calf thymus DNA. The (32)P-post-labeling assay revealed four major and several minor adducts (3.5 adducts per 10(5) total nucleotides) that were produced in calf thymus DNA treated with Cl(4)BQ (5 mM). These DNA adducts were chemically stable even after conditions that induce thermal depurination and are unlikely to undergo depurination/depyrimidination to form apurinic/apyrimidinic (AP) sites. In addition, increases in 8-hydroxy-deoxyguanosine (8-HO-dG) (5 8-HO-dG per 10(5) nucleotides) and AP sites (0.5 AP sites per 10(5) nucleotides) were observed in Cl(4)BQ-modified calf thymus DNA. Further investigation indicated that in the presence of Cu(II) and NADPH, low concentrations of Cl(4)BQ (1 microM) induced a doubling of 8-HO-dG (10 8-HO-dG per 10(5) nucleotides) and dramatic increases in AP sites (20 AP sites per 10(5) nucleotides) and DNA single-strand breaks. The types of DNA damage induced by Cl(4)HQ plus Cu(II) were similar to those by Cl(4)BQ plus Cu(II) and NADPH, whereas catalase inhibited the formation of DNA damage. These data suggest that oxidative damage is causally involved in the formation of AP sites. Concentration-dependent increases in 8-HO-dG induced by Cl(4)HQ plus Cu(II) and Cl(4)BQ plus Cu(II) and NADPH were correlated with the formation of AP sites (r(2) = 0.977) with a ratio of 8-HO-dG to AP sites at 1:1.6. The AP site-cleavage assay confirmed that approximately 85% of the AP sites induced by Cl(4)HQ and Cu(II) were detected as 5'-cleaved AP sites. Since hydrogen peroxide alone causes similar DNA damage, these results suggest the involvement of Cu(II) and hydrogen peroxide in the induction of oxidative DNA damage by Cl(4)HQ/Cl(4)BQ. The data demonstrate that PCP quinone and hydroquinone induce direct and oxidative base modifications as well as the formation of 5'-cleaved AP sites in genomic DNA. These lesions may have important implications for PCP clastogenicity and carcinogenicity.

Catalytic creativity. The case of Linus Pauling

This article illustrates how creativity is constituted by forces beyond the innovating individual, drawing examples from the career of the eminent chemist Linus Pauling. From a systems perspective, a scientific theory or other product is creative only if the innovation gains the acceptance of a field of experts and so transforms the culture. In addition to this crucial selective function vis-à-vis the completed work, the social field can play a catalytic role, fostering productive interactions between person and domain throughout a career. Pauling's case yields examples of how variously the social field contributes to creativity, shaping the individual's standards of judgment and providing opportunities, incentives, and critical evaluation. A formidable set of strengths suited Pauling for his scientific achievements, but examination of his career qualifies the notion of a lone genius whose brilliance carries the day.