A General Design Strategy Enabling the Synthesis of Hydrolysis-Resistant, Water-Stable Titanium(IV) Complexes.

Despite its prevalence in the environment, the chemistry of the Ti4+ ion has long been relegated to organic solutions or hydrolyzed TiO2 polymorphs. A knowledge gap in stabilizing molecular Ti4+ species in aqueous environments has prevented the use of this ion for various applications such as radioimaging, design of water-compatible metal-organic frameworks (MOFs), and aqueous-phase catalysis applications. Herein, we show a thorough thermodynamic screening of bidentate chelators with Ti4+ in aqueous solution, as well as computational and structural analyses of key compounds. In addition, the hexadentate analogues of catechol (benzene-1,2-diol) and deferiprone (3-hydroxy-1,2-dimethyl-4(1H)-pyridone), TREN-CAM and THPMe respectively, were assessed for chelation of the 45 Ti isotope (t1/2 =3.08 h, ß+ =85 %, Eß+ =439 keV) towards positron emission tomography (PET) imaging applications. Both were found to have excellent capacity for kit-formulation, and [45 Ti]Ti-TREN-CAM was found to have remarkable stability in vivo.

45Ti targeted tracers for PET imaging of PSMA.

PURPOSE: Positron Emission Tomography is an important molecular imaging technique for detection and diagnoses of various disease states. This work aims to develop novel titanium-45 (t½ = 3.08 h) PET tracers using Prostate Specific Membrane Antigen (PSMA) targeting vectors for imaging of prostate cancer as proof of concept for this relatively unexplored isotope. PROCEDURES: Titanium-45 was produced on the University of Alabama at Birmingham (UAB) TR24 cyclotron using proton bombardments on natural scandium foils and separated using procedures described previously [1]. After purification, Titanium-45 was used to radiolabel two PSMA-targeting molecules; DFO-DUPA and LDFC-DUPA. Radiochemical yields were determined via radio-high purity liquid chromatography (radioHPLC). The radiolabeled compounds were tested both in vitro and in vivo using PSMA+ cell lines (LNCaP and 22Rv1) and PSMA- cell lines (PC3). RESULTS: Titanium-45 was produced and purified in yields suitable for research studies. Radiochemical yields of up to 98 ± 1% were achieved with DFO-DUPA and 92 ± 7% with LDFC-DUPA. PSMA specific targeting was observed in vitro in PSMA positive cells (LNCaP (0.6% ± 0.05%) and confirmed by blocking (0.15% ± 0.04%) (P < 0.0001)), compared to uptake in the PSMA negative cells (PC3 (0.07% ± 0.008%)) and confirmed by blocking (0.07% ± 0.01%) (P = 0.5253). In vivo studies demonstrated statistically significant uptake in LNCaP tumors (2.3% ± 0.3% ID/g) compared to PC3 tumor uptake (0.1% ± 0.07%). CONCLUSIONS: This work shows that titanium-45 can be used to radiolabel PSMA targeting compounds with high radiochemical yields. These radiolabeled compounds remain intact in serum for at least two half-lives of titanium-45, showing that these compounds would be appropriate for implementation in the clinical setting. This study shows the feasibility of using titanium-45 as positron emitting radiometal for use in imaging PSMA+ prostate cancer, and illustrates that further research is in this area is warranted.

Characterization of subunit interactions in the hetero-oligomeric retinoid oxidoreductase complex.

The hetero-oligomeric retinoid oxidoreductase complex (ROC) catalyzes the interconversion of all-trans-retinol and all-trans-retinaldehyde to maintain the steady-state output of retinaldehyde, the precursor of all-trans-retinoic acid that regulates the transcription of numerous genes. The interconversion is catalyzed by two distinct components of the ROC: the NAD(H)-dependent retinol dehydrogenase 10 (RDH10) and the NADP(H)-dependent dehydrogenase reductase 3 (DHRS3). The binding between RDH10 and DHRS3 subunits in the ROC results in mutual activation of the subunits. The molecular basis for their activation is currently unknown. Here, we applied site-directed mutagenesis to investigate the roles of amino acid residues previously implied in subunit interactions in other SDRs to obtain the first insight into the subunit interactions in the ROC. The results of these studies suggest that the cofactor binding to RDH10 subunit is critical for the activation of DHRS3 subunit and vice versa. The C-terminal residues 317-331 of RDH10 are critical for the activity of RDH10 homo-oligomers but not for the binding to DHRS3. The C-terminal residues 291-295 are required for DHRS3 subunit activity of the ROC. The highly conserved C-terminal cysteines appear to be involved in inter-subunit communications, affecting the affinity of the cofactor binding site in RDH10 homo-oligomers as well as in the ROC. Modeling of the ROC quaternary structure based on other known structures of SDRs suggests that its integral membrane-associated subunits may be inserted in adjacent membranes of the endoplasmic reticulum (ER), making the formation and function of the ROC dependent on the dynamic nature of the tubular ER network.

Optimized methods for production and purification of Titanium-45.

Titanium-45 (t1/2 = 3.08 h) is a radiometal with excellent nuclear characteristics, including a high positron branching ratio (85%) and low average positron energy (0.439 MeV), for the development of PET imaging agents. 45Ti was produced via the 45Sc(p,n)45Ti reaction on the University of Alabama at Birmingham TR24 cyclotron in GBq quantities. Optimized separation methods were developed and preliminary radiochemistry studies were also carried out. This work shows 45Ti is a promising radiometal for future studies.

The Cu(II) Reductase RclA Protects Escherichia coli against the Combination of Hypochlorous Acid and Intracellular Copper.

Enterobacteria, including Escherichia coli, bloom to high levels in the gut during inflammation and strongly contribute to the pathology of inflammatory bowel diseases. To survive in the inflamed gut, E. coli must tolerate high levels of antimicrobial compounds produced by the immune system, including toxic metals like copper and reactive chlorine oxidants such as hypochlorous acid (HOCl). Here, we show that extracellular copper is a potent detoxifier of HOCl and that the widely conserved bacterial HOCl resistance enzyme RclA, which catalyzes the reduction of copper(II) to copper(I), specifically protects E. coli against damage caused by the combination of HOCl and intracellular copper. E. coli lacking RclA was highly sensitive to HOCl when grown in the presence of copper and was defective in colonizing an animal host. Our results indicate that there is unexpected complexity in the interactions between antimicrobial toxins produced by innate immune cells and that bacterial copper status is a key determinant of HOCl resistance and suggest an important and previously unsuspected role for copper redox reactions during inflammation.IMPORTANCE During infection and inflammation, the innate immune system uses antimicrobial compounds to control bacterial populations. These include toxic metals, like copper, and reactive oxidants, including hypochlorous acid (HOCl). We have now found that RclA, a copper(II) reductase strongly induced by HOCl in proinflammatory Escherichia coli and found in many bacteria inhabiting epithelial surfaces, is required for bacteria to resist killing by the combination of intracellular copper and HOCl and plays an important role in colonization of an animal host. This finding indicates that copper redox chemistry plays a critical and previously underappreciated role in bacterial interactions with the innate immune system.

Production and Use of the First-Row Transition Metal PET Radionuclides 43,44Sc, 52Mn, and 45Ti.

With the increasing focus on a more personalized approach to medicine using imaging techniques to select patients for targeted treatment or theranostic strategies, interest in the development of new radionuclides is expanding. Through the development of production and radiochemistry techniques, several new radiometals are being added to the toolbox of the nuclear imaging community. 43,44g,mSc, 52gMn, and 45Ti are all emerging transition metal radionuclides and will be discussed in this short review. Each of these nuclides has unique imaging characteristics and shows promise for the development of new molecular imaging agents.

The outcome of heart transplant recipients following the development of end-stage renal disease: analysis of the Canadian Organ Replacement Register (CORR).

End-stage renal disease is a significant complication of heart transplantation (HTx), but our understanding of dialysis outcomes in HTx recipients remains limited. We performed a retrospective analysis looking at dialysis mortality in HTx recipients as compared to a matched dialysis cohort. We also examined outcomes with respect to kidney transplantation (KTx) in these cohorts. 2709 incident HTx recipients were captured from the Canadian Organ Replacement Register between 1981 and 2002. The incidence of dialysis after HTx was 3.9% (n = 105) and carried a greater crude mortality compared to HTx recipients not requiring dialysis (56.2% vs. 35.9%, p < 0.001). Compared to the matched dialysis cohort, survival of HTx patients on dialysis was also significantly worse (19% vs. 40%, p = 0.003). In those receiving a KTx, survival did not differ between the two cohorts; however, in those that did not receive a KTx the survival was significantly lower in the dialysis post-HTx group compared to the matched dialysis cohort (15.7% vs. 35.2%, p < 0.025). Our analysis suggests mortality on dialysis following HTx is greater than would be expected from a similar dialysis population, and KTx may abrogate some of this increased risk. Attention should be placed on preventing chronic kidney disease progression following HTx.

Nonmedical drug use among adolescent students: highlights from the 1999 Ontario Student Drug Use Survey.

BACKGROUND: During the 1990s, rates of nonmedical drug use among adolescents escalated. We assessed data from 5 cycles of the Ontario Student Drug Use Survey for overall trends in the proportion of students reporting illegal drug use between 1991 and 1999. METHODS: The survey is a repeated, cross-sectional, 2-stage cluster-design survey of students enrolled in grades 7, 9, 11 and 13. Outcome measures were prevalence of use of 17 drugs, including alcohol and tobacco, over the 12 months preceding the survey. RESULTS: The rates of drug use increased between 1993 and 1999. The 95% confidence intervals (CIs) for the differences in proportions between 1997 and 1999 indicated significant increases in the overall use of 6 drugs: alcohol (95% CIdiff 6.1, 1.9-10.3), cannabis (95% CIdiff 46.3, 0.2-8.4), glue (95% CIdiff 2.3, 1.3-3.3), other solvents (95% CIdiff 5.0, 3.1-6.3), barbiturates (95% CIdiff 1.9, 0.4-3.4) and hallucinogens such as mescaline and psilocybin (95% CIdiff 3.5, 0.8-6.9). Fewer grade 7 students in 1999 than in earlier cohorts reported using alcohol or cigarettes by age 9. INTERPRETATION: The public health implications of the findings are mixed. On the positive side, there is no evidence of increases in early onset of drug use. On the negative side, the overall proportion of students reporting illegal drug use has continued to rise.

Incorporating the AUDIT into a general population telephone survey: a methodological experiment.

This study assessed potential ordering and wording effects of the alcohol use disorders identification test (AUDIT). In total, 688 respondents were randomly assigned to one of four experimental conditions: Intact order/original wording (n=148), intact order/revised wording (n=183), split order/original wording (n=192), split order/revised wording (n=166). Changes to question order and wording had no discernable impact on the scores of the AUDIT. Our results suggest that alterations to the AUDIT can be made in order to integrate it within a larger survey without adversely affecting its measurement properties.

Prevalence of methylphenidate use among adolescents in Ontario.

Despite a growing interest in the use of methylphenidate (Ritalin) to treat attention deficit/hyperactivity disorders, prevalence data has been scarce in Canada. A probability school survey conducted in 1997 among Ontario students in grades 7, 9, 11 and 13 is used to collect data on such use. Overall, 3.4% of students (5.3% of males, 1.7% of females) used methylphenidate in the previous year. Rates and patterns are similar to those found in the United States. Future research needs to examine reasons and correlates of use, extent of medical supervision and possible non-medical use of methylphenidate.

Binge eating and substance use among male and female adolescents.

OBJECTIVE: This study examines the relationship between binge eating and substance use behaviors and attitudes in adolescents and explores gender differences and mental health correlates. METHOD: The data are derived from the 1997 Ontario Student Drug Use Survey of public and Catholic school students. A weighted sample of 1,031 girls and 888 boys was categorized as nonbingers, past bingers, and noncompensating or compensating binge eaters. RESULTS: Binge eaters, particularly those who compensated, were more likely to use all types of substances, particularly cannabis and drugs other than tobacco and alcohol. Binge eating was associated with more problematic and heavier substance use and with lowered self-esteem and more depression. Female bingers were more likely to report compensatory behaviors than male students but gender differences in the relationship between binge eating and substance use were few. DISCUSSION: Adolescent binge eaters who engage in compensatory behaviors may be an appropriate target group for preventive programs in high schools.

Recent findings from the Ontario Student Drug Use Survey.

BACKGROUND: Every 2 years, the Addiction Research Foundation of Ontario, a division of the Centre for Addiction and Mental Health, sponsors the Ontario Student Drug Use Survey. The results of the surveys conducted in 1995 and 1997 are presented here and compared with results from the early 1990s. METHODS: Questionnaires were completed by 3870 and 3990 Ontario public school students enrolled in grades 7, 9, 11 and 13 in 1995 and 1997 respectively. The outcome measures were prevalence of use of 20 types of drugs and other substances, including alcohol, tobacco and prescription drugs, over the previous 12 months. RESULTS: For several drugs the prevalence of use in the previous 12 months had increased from 1993 to 1995, but from 1995 to 1997 there was a significant increase for only one type (hallucinogens such as mescaline and psilocybin). The inhalation of glue declined, and the use of the other 18 types of drugs remained stable. INTERPRETATION: Recent data suggest that increases in adolescent student drug use reported earlier this decade have not continued. However, the stability in rates of drug use is not a justification for complacency in this important area of public health.

The effect of question structure on self-reports of heavy drinking: closed-ended versus open-ended questions.

OBJECTIVE: We compared open-ended versus closed-ended questions on the frequency of consuming five or more drinks in a single sitting. METHOD: From a general population survey of Ontario adults (N = 2,022, 62% male), we analyzed a subsample of 649 respondents who reported drinking five or more drinks in a single sitting at least once in the past year. Differences in agreement between the two questions and rates of missing data were evaluated. RESULTS: For the most part, the two measures were not consistent, with the closed-ended question eliciting higher rates of heavier drinking. Rates of missing data were also higher for the open-ended question. CONCLUSIONS: Open-ended question may not necessarily be more suitable than closed-ended questions for estimating the frequency of heavy alcohol use.

Enduring resurgence or statistical blip? Recent trends from the Ontario Student Drug Use Survey.

This paper describes trends in alcohol and other drug use among Ontario students between 1977 and 1995, especially those occurring between 1993 and 1995. Data are based on the Ontario Student Drug Use Survey, which to date represents 10 cross-sectional surveys conducted every two years since 1977. In each survey, approximately 4,000 students in grades 7, 9, 11 and 13 are interviewed in their classrooms. The findings show that after a decade of declining drug use, rates of use increased between 1993 and 1995. Of the 20 drugs surveyed in 1995, the use of 8 increased significantly from 1993. Increases in drug use were more common among 9th- and 11th-grades.

Is the association between drug use and delinquency weakening?

In this paper we examine period or secular changes in the association between drug use and delinquency among Ontario adolescent students between 1983 and 1991. The results show that during this period drug use and drug-selling declined significantly, whereas reported non-drug-related delinquency increased. In addition to differing secular trends in rates of drug use and delinquent behaviour, the association between the two behaviours weakened. There was a steady decline in the correlations between drug use and delinquency across time, and the typological patterning of drug use and delinquency changed significantly.