Decision Regret Following the Choice of Surgery or Active Surveillance for Small, Low-Risk Papillary Thyroid Cancer: A Prospective Cohort Study.

Background: It is important to understand cancer survivors' perceptions about their treatment decisions and quality of life. Methods: We performed a prospective observational cohort study of Canadian patients with small (<2 cm) low-risk papillary thyroid cancer (PTC) who were offered the choice of active surveillance (AS) or surgery (Clinicaltrials.gov NCT03271892). Participants completed a questionnaire one year after their treatment decision. The primary intention-to-treat analysis compared the mean decision regret scale total score between patients who chose AS or surgery. A secondary analysis examined one-year decision regret score according to treatment status. Secondary outcomes included quality of life, mood, fear of disease progression, and body image perception. We adjusted for age, sex, and follow-up duration in linear regression analyses. Results: The overall questionnaire response rate was 95.5% (191/200). The initial treatment choices of respondents were AS 79.1% (151/191) and surgery 20.9% (40/191). The mean age was 53 years (standard deviation [SD] 15 years) and 77% (147/191) were females. In the AS group, 7.3% (11/151) of patients crossed over to definitive treatment (two for disease progression) before the time of questionnaire completion. The mean level of decision regret did not differ significantly between patients who chose AS (mean 22.4, SD 13.9) or surgery (mean 20.9, SD 12.2) in crude (p = 0.730) or adjusted (p = 0.29) analyses. However, the adjusted level of decision regret was significantly higher in patients who initially chose AS and crossed over to surgery (beta coefficient 10.1 [confidence interval; CI 1.3-18.9], p = 0.02), compared with those remaining under AS. In secondary adjusted analyses, respondents who chose surgery reported that symptoms related to their cancer or its treatment interfered with life to a greater extent than those who chose AS (p = 0.02), but there were no significant group differences in the levels of depression, anxiety, fear of disease progression, or overall body image perception. Conclusions: In this study of patients with small, low-risk PTC, the mean level of decision regret pertaining to the initial disease management choice was relatively low after one year and it did not differ significantly for respondents who chose AS or surgery.

Gender Differences in Fears Related to Low-Risk Papillary Thyroid Cancer and Its Treatment.

Importance: Fear is commonly experienced by individuals newly diagnosed with papillary thyroid cancer (PTC). Objective: To explore the association between gender and fears of low-risk PTC disease progression, as well as its potential surgical treatment. Design, Setting, and Participants: This single-center prospective cohort study was conducted at a tertiary care referral hospital in Toronto, Canada, and enrolled patients with untreated small low risk PTC (<2 cm in maximal diameter) that was confined to the thyroid. All patients had a surgical consultation. Study participants were enrolled between May 2016 and February 2021. Data analysis was performed from December 16, 2022, to May 8, 2023. Exposures: Gender was self-reported by patients with low-risk PTC who were offered the choice of thyroidectomy or active surveillance. Baseline data were collected prior to the patient deciding on disease management. Main Outcomes and Measures: Baseline patient questionnaires included the Fear of Progression-Short Form and Surgical Fear (referring to thyroidectomy) questionnaires. The fears of women and men were compared after adjustment for age. Decision-related variables, including Decision Self-Efficacy, and the ultimate treatment decisions were also compared between genders. Results: The study included 153 women (mean [SD] age, 50.7 [15.0] years) and 47 men (mean [SD] age, 56.3 [13.8] years). There were no significant differences in primary tumor size, marital status, education, parental status, or employment status between the women and men. After adjustment for age, there was no significant difference observed in the level of fear of disease progression between men and women. However, women reported greater surgical fear compared with men. There was no meaningful difference observed between women and men with respect to decision self-efficacy or the ultimate treatment choice. Conclusions and Relevance: In this cohort study of patients with low-risk PTC, women reported a higher level of surgical fear but not fear of the disease compared with men (after adjustment for age). Women and men were similarly confident and satisfied with their disease management choice. Furthermore, the decisions of women and men were generally not significantly different. The context of gender may contribute to the emotional experience of being diagnosed with thyroid cancer and its treatment perception.

A Quantitative Analysis Examining Patients' Choice of Active Surveillance or Surgery for Managing Low-Risk Papillary Thyroid Cancer.

Background: It is important to understand patient preferences on managing low-risk papillary thyroid cancer (PTC). Methods: We prospectively followed patients with low-risk PTC <2 cm in maximal diameter, who were offered the choice of thyroidectomy or active surveillance (AS) at the University Health Network (UHN), in Toronto, Canada. The primary outcome was the frequency of AS choice (percentage with confidence interval [CI]). Univariate and multivariable analyses were performed to identify predictors of the choice of AS. Results: We enrolled 200 patients of median age 51 years (interquartile range 42-62). The primary tumor measured >1 cm in 55.5% (111/200) of participants. The AS was chosen by 77.5% [71.2-82.7%, 155/200] of participants. In a backwards conditional regression model, the clinical and demographic factors independently associated with choosing AS included: older age (compared with referent group <40 years)-age 40-64 years-odds ratio (OR) 2.78 [CI, 1.23-6.30, p = 0.014], age ≥65 years-OR 8.43 [2.13-33.37, p = 0.002], and education level of high school or lower-OR 4.41 [1.25-15.53, p = 0.021]; AS was inversely associated with the patient's surgeon of record being affiliated with the study hospital-OR 0.29 [0.11-0.76, p = 0.012]. In a separate backwards conditional logistic regression model examining associations with psychological characteristics, AS choice was independently associated with a fear of needing to take thyroid hormones after thyroidectomy-OR 1.24 [1.11-1.39, p < 0.001], but inversely associated with fear of PTC progression-OR 0.94 [0.90-0.98, p = 0.006] and an active coping mechanism ("doing something")-OR 0.43 [0.28-0.66, p < 0.001]. Conclusions: Approximately three-quarters of our participants chose AS over surgery. The factors associated with choosing AS included older age, lower education level, and having a surgeon outside the study institution. Patients' fears about either their PTC progressing or taking thyroid hormone replacement as well as the level of active coping style were associated with the decision. Our results inform the understanding of patients' decisions on managing low-risk PTC. Registration: Clinicaltrials.gov NCT03271892.

Spatially displaced excitation contributes to the encoding of interrupted motion by a retinal direction-selective circuit.

Spatially distributed excitation and inhibition collectively shape a visual neuron's receptive field (RF) properties. In the direction-selective circuit of the mammalian retina, the role of strong null-direction inhibition of On-Off direction-selective ganglion cells (On-Off DSGCs) on their direction selectivity is well-studied. However, how excitatory inputs influence the On-Off DSGC's visual response is underexplored. Here, we report that On-Off DSGCs have a spatially displaced glutamatergic receptive field along their horizontal preferred-null motion axes. This displaced receptive field contributes to DSGC null-direction spiking during interrupted motion trajectories. Theoretical analyses indicate that population responses during interrupted motion may help populations of On-Off DSGCs signal the spatial location of moving objects in complex, naturalistic visual environments. Our study highlights that the direction-selective circuit exploits separate sets of mechanisms under different stimulus conditions, and these mechanisms may help encode multiple visual features.

Development of cognitive screening test for the severely hearing impaired: Hearing-impaired MoCA.

OBJECTIVES: To develop a version of the Montreal Cognitive Assessment (MoCA) to be administered to the severely hearing impaired (HI-MoCA), and to assess its performance in two groups of cognitively intact adults over the age of 60. STUDY TYPE: Test development followed by prospective subject recruitment. METHODS: The MoCA was converted into a timed PowerPoint (Microsoft Corp., Redmond, WA) presentation, and verbal instructions were converted into visual instructions. Two groups of subjects over the age of 60 were recruited. All subjects passed screening questionnaires to eliminate those with undiagnosed mild cognitive impairment. The first group had normal hearing (group 1). The second group was severely hearing impaired (group 2). Group 1 received either the MoCA or HI-MoCA test (T1). Six months later (T2), subjects were administered the test (MoCA or HI-MoCA) they had not received previously to determine equivalency. Group 2 received the HI-MoCA at T1 and again at T2 to determine test-retest reliability. RESULTS: One hundred and three subjects were recruited into group 1, with a score of 26.66 (HI-MoCA) versus 27.14 (MoCA). This was significant (P < 0.05), but scoring uses whole numerals and the 0.48 difference was found not clinically significant using post hoc sensitivity analyses. Forty-nine subjects were recruited into group 2. They scored 26.18 and 26.49 (HI-MoCA at T1 and T2). No significance was noted (P > 0.05), with a test-retest coefficient of 0.66. CONCLUSION: The HI-MoCA is easy to administer and reliable for screening cognitive impairment in the severely hearing impaired. No conversion factor is required in our prospectively tested cohort of cognitively intact subjects. LEVEL OF EVIDENCE: 1b. Laryngoscope, 127:S4-S11, 2017.

Effect of Medialization Thyroplasty on Glottic Airway Anatomy: Cadaver Model.

OBJECTIVES: The purpose of this study was to investigate the change in airway dimensions after medialization thyroplasty (MT) using a cadaveric model. Helical computerized tomography (CT) was performed before and after placement of a silastic block in human larynges to investigate the effect on airway anatomy at the level of the glottis. Tissue density (TD) of the medialized vocal fold (VF) was documented to understand the effect on tissue displacement. STUDY DESIGN: This is a cadaveric study. METHODS: Thirteen human cadaveric larynges underwent fine-cut CT scan before and after MT was performed using carved blocks in two sizes (small block and large block [LB]). Clientstream software was used to measure laryngeal dimensions: intraglottic volume (IGV), cross-sectional area (CSA), posterior-glottic diameter (PGD), VF density (in Hounsfield units [HUs]), and anterior-posterior diameter (APD). Eight sequential axial sections 0.625 mm cuts) at the level of the true VFs were analyzed. RESULTS: There was a significant decrease between the three conditions for IGV (P < 0.0001) and CSA (P < 0.0001). TD of the VF was increased after MT as indicated by HU increase (P = 0.0003). APD was not significantly changed. PGD was significantly different between the no block to LB placement (P = 0.0012). CONCLUSIONS: MT significantly changes the IGV and CSA at the level of the glottis. Density in the true VF was significantly increased. These findings have important implications for understanding volumetric effects of MT.

Engraftment and lineage potential of adult hematopoietic stem and progenitor cells is compromised following short-term culture in the presence of an aryl hydrocarbon receptor antagonist.

Hematopoietic stem cell gene therapy for HIV/AIDS is a promising alternative to lifelong antiretroviral therapy. One of the limitations of this approach is the number and quality of stem cells available for transplant following in vitro manipulations associated with stem cell isolation and genetic modification. The development of methods to increase the number of autologous, gene-modified stem cells available for transplantation would overcome this barrier. Hematopoietic stem and progenitor cells (HSPC) from adult growth factor-mobilized peripheral blood were cultured in the presence of an aryl hydrocarbon receptor antagonist (AhRA) previously shown to expand HSPC from umbilical cord blood. Qualitative and quantitative assessment of the hematopoietic potential of minimally cultured (MC-HSPC) or expanded HSPC (Exp-HSPC) was performed using an immunodeficient mouse model of transplantation. Our results demonstrate robust, multilineage engraftment of both MC-HSPC and Exp-HSPC although estimates of expansion based on stem cell phenotype were not supported by a corresponding increase in in vivo engrafting units. Bone marrow of animals transplanted with either MC-HSPC or Exp-HSPC contained secondary engrafting cells verifying the presence of primitive stem cells in both populations. However, the frequency of in vivo engrafting units among the more primitive CD34+/CD90+ HSPC population was significantly lower in Exp-HSPC compared with MC-HSPC. Exp-HSPC also produced fewer lymphoid progeny and more myeloid progeny than MC-HSPC. These results reveal that in vitro culture of adult HSPC in AhRA maintains but does not increase the number of in vivo engrafting cells and that HSPC expanded in vitro contain defects in lymphopoiesis as assessed in this model system. Further investigation is required before implementation of this approach in the clinical setting.

Optimized lentiviral vectors for HIV gene therapy: multiplexed expression of small RNAs and inclusion of MGMT(P140K) drug resistance gene.

Gene therapy with hematopoietic stem and progenitor cells is a promising approach to engineering immunity to human immunodeficiency virus (HIV) that may lead to a functional cure for acquired immunodeficiency syndrome (AIDS). In support of this approach, we created lentiviral vectors with an engineered polycistronic platform derived from the endogenous MCM7 gene to express a diverse set of small antiviral RNAs and a drug resistance MGMT(P140K) marker. Multiple strategies for simultaneous expression of up to five RNA transgenes were tested. The placement and orientation of each transgene and its promoter were important determinants for optimal gene expression. Antiviral RNA expression from the MCM7 platform with a U1 promoter was sufficient to provide protection from R5-tropic HIV in macrophages and resulted in reduced hematopoietic toxicity compared with constructs expressing RNA from independent RNA polymerase III promoters. The addition of an HIV entry inhibitor and nucleolar TAR RNA decoy did not enhance antiviral potency over constructs that targeted only viral RNA transcripts. We also demonstrated selective enrichment of gene-modified cells in vivo using a humanized mouse model. The use of these less toxic, potent anti-HIV vectors expressing a drug selection marker is likely to enhance the in vivo efficacy of our stem cell gene therapy approach in treating HIV/AIDS.

Combinatorial RNA-based gene therapy for the treatment of HIV/AIDS.

INTRODUCTION: HIV/AIDS continues to be a worldwide health problem and viral eradication has been an elusive goal. HIV+ patients are currently treated with combination antiretroviral therapy (cART) which is not curative. For many patients, cART is inaccessible, intolerable or unaffordable. Therefore, a new class of therapeutics for HIV is required to overcome these limitations. Cell and gene therapy for HIV has been proposed as a way to provide a functional cure for HIV in the form of a virus/infection resistant immune system. AREAS COVERED: In this review, the authors describe the standard therapy for HIV/AIDS, its limitations, current areas of investigation and the potential of hematopoietic stem cells modified with anti-HIV RNAs as a means to affect a functional cure for HIV. EXPERT OPINION: Cell and gene therapy for HIV/AIDS is a promising alternative to antiviral drug therapy and may provide a functional cure. In order to show clinical benefit, multiple mechanisms of inhibition of HIV entry and lifecycle are likely to be required. Among the most promising antiviral strategies is the use of transgenic RNA molecules that provide protection from HIV infection. When these molecules are delivered as gene-modified hematopoietic stem and progenitor cells, long-term repopulation of the patient's immune system with gene-modified progeny has been observed.

Ring-opening photoreactions of 5-methylcytosine with 3-mercaptopropionic acid and other thiols.

The photoproducts from reaction of thymine with cysteine, an amino acid containing a sulfhydryl group, have been studied in detail, whereas results of less extensive studies have been reported for the uracil-cysteine system. However, products arising from corresponding reactions of cytosine and related compounds with compounds containing a sulfhydryl group have not been similarly studied. We report here the results of our study of the photoreaction of 5-methylcytosine (5MeCyt), a minor base occurring in mammalian DNA, with 3-mercaptopropionic acid (3MP), a model compound for cysteine. We found that this reaction proceeds at pH 7 to yield N-(N'-(2'-carboxyethyl)thiocarbamoyl)-3-amino-2-methylacrylamidine (Ia) as a primary photoproduct. A secondary thermal product, identified as 3-(2'-carboxyethylthio)-2-methylacrylamidine (IIa), appears if photoreacted solution is allowed to stand for appreciable times prior to workup; this latter compound is formed via an intermediate product. Heating of purified Ia at 100°C or standing at lower temperatures produces 3-amino-2-methylacrylamidine (IId); similarly, irradiation of Ia with UVB light in aqueous solution converts it into IId. Results from exploratory studies suggest that 5MeCyt similarly reacts with other thiols (2-mercaptoethanol, 2-mercaptoacetic acid) to form analogs of Ia and IIa. Other preliminary results suggest that 5-methyl-2'-deoxycytidine and 1,5-dimethylcytosine photoreact with 3MP to form compounds similar to Ia.

Congenital cholesteatoma and cochlear implantation: Implications for management.

INTRODUCTION: Cholesteatoma is an uncommon condition that has occasionally been associated with cochlear implantation (CI). Cases of secondary acquired cholesteatoma have been described, in which intra-operative breech of the posterior canal wall is thought to be a contributing factor. Primary acquired cholesteatoma is not typically associated with congenital sensorineural hearing loss (SNHL) or CI in children. Congenital cholesteatoma is a rarer entity yet with an incidence in the literature of 2­4% of all cholesteatomas. We present lessons learned from our experience of congenital cholesteatoma in CI candidates. METHODS: Retrospective reviews of departmental CI and cholesteatoma databases in a tertiary/quaternary pediatric center were conducted. Cases of congenital cholesteatoma were identified. The proportion of congenital cholesteatoma cases in CI candidates was compared with number of acquired cholesteatoma. Optimum management of congenital cholesteatoma in CI candidates was reviewed. RESULTS: In our pediatric CI population, 2/794 patients (0.25%) were recognized as having a congenital cholesteatoma during their evaluation for CI. No cases of primary acquired cholesteatoma were identified in this population at presentation or at follow up to 18 years. DISCUSSION: The 0.25% incidence of congenital cholesteatoma in our population of CI patients is higher than expected of this rare condition. It is surprisingly common given the absence of any cases of primary acquired cholesteatoma, which is considerably more common even in the pediatric population. Both patients likely had an inherited form of hearing loss and a genetic contribution to the presence of congenital cholesteatoma cannot be excluded. The presence of congenital cholesteatoma has implications for the algorithm currently employed for the assessment of CI. We consider that surgery should be staged to ensure complete removal of the cholesteatoma before implantation. Thus bilateral CI should be provided sequentially rather than simultaneously in the presence of unilateral cholesteatoma.

Endogenous MCM7 microRNA cluster as a novel platform to multiplex small interfering and nucleolar RNAs for combinational HIV-1 gene therapy.

Combinational therapy with small RNA inhibitory agents against multiple viral targets allows efficient inhibition of viral production by controlling gene expression at critical time points. Here we explore combinations of different classes of therapeutic anti-HIV-1 RNAs expressed from within the context of an intronic MCM7 (minichromosome maintenance complex component-7) platform that naturally harbors 3 microRNAs (miRNAs). We replaced the endogenous miRNAs with anti-HIV small RNAs, including small interfering RNAs (siRNAs) targeting HIV-1 tat and rev messages that function to induce post-transcriptional gene silencing by the RNA interference pathway, a nucleolar-localizing RNA ribozyme that targets the conserved U5 region of HIV-1 transcripts for degradation, and finally nucleolar trans-activation response (TAR) and Rev-binding element (RBE) RNA decoys designed to sequester HIV-1 Tat and Rev proteins inside the nucleolus. We demonstrate the versatility of the MCM7 platform in expressing and efficiently processing the siRNAs as miRNA mimics along with nucleolar small RNAs. Furthermore, three of the combinatorial constructs tested potently suppressed viral replication during a 1-month HIV challenge, with greater than 5-log inhibition compared with untransduced, HIV-1-infected CEM T lymphocytes. One of the most effective constructs contains an anti-HIV siRNA combined with a nucleolar-localizing U5 ribozyme and TAR decoy. This represents the first efficacious example of combining Drosha-processed siRNAs with small nucleolar ribonucleoprotein (snoRNP)-processed nucleolar RNA chimeras from a single intron platform for effective inhibition of viral replication. Moreover, we demonstrated enrichment/selection for cells expressing levels of the antiviral RNAs that provide optimal inhibition under the selective pressure of HIV. The combinations of si/snoRNAs represent a new paradigm for combinatorial RNA-based gene therapy applications.

The cyclobutane dimers of 2'-deoxyuridine, 2'-deoxycytidine, 5-methyl-2'-deoxycytidine and 5-bromo-2'-deoxyuridine.

Irradiation of DNA and RNA pyrimidine nucleosides with UV light in frozen aqueous solution or in solution with acetone often results in the formation of cyclobutane dimers (CBDs). Many of these photodimers have not been characterized. We present here the results of work designed to achieve the isolation, spectroscopic characterization and determination of the stereochemical nature of a number of little studied or previously unstudied CBDs of four 2'-deoxyribonuclesides. These nucleosides are 2'-deoxyuridine (dUrd), 2'-deoxycytidine (dCyd), 5-methyl-2'-deoxycytidine (5-MedCyd) and 5-bromo-2'-deoxyuridine (5-BrdUrd). In particular, we have isolated and characterized six dUrd CBDs, five dCyd CBDs, five 5-MedCyd CBDs and four 5-BrdUrd CBDs. Photoproducts were studied by UV spectroscopy, mass spectrometry, proton NMR spectroscopy and via chemical approaches. Also presented are results from less definitive studies of a number of (6-4) (or 5-4) photoadducts of these nucleosides. In addition, results from exploratory photochemical studies of other 2'-deoxyribonucleosides in frozen solution, as well as some mixtures of two nucleosides, are given. The latter results indicate that 5-iodo-2'-deoxyuridine (5-IdUrd), 5-bromo-2'-deoxycytidine and 5-iodo-2'-deoxycytidine each form putative CBDs and that 5-BrdUrd is capable of forming putative mixed CBDs and (6-4) and/or (5-4) adducts with thymidine (Thd); 5-IdUrd similarly forms a (6-4) (or (5-4)) adduct with Thd.

Unilateral multi-channel cochlear implantation results in significant improvement in quality of life.

OBJECTIVES: To investigate the effects of unilateral multi-channel cochlear implant surgery on health-related quality of life and to determine if there is an age-related impact of cochlear implantation on these effects. DESIGN: Prospective study. SETTING: Tertiary health-care center. METHODS: The Short Form-36 survey (SF-36) was administered to determine the health-related quality of life of 283 age-stratified patients before and after cochlear implant surgery. MAIN OUTCOMES: Precochlear to postcochlear implantation changes in health-related quality of life as determined by the SF-36 questionnaire. RESULTS: There were significant increases in precochlear and postcochlear implantation scores for 5 of the 8 SF-36 survey domains: vitality, physical role functioning, mental health, emotional role functioning, and social functioning. Significant differences were found between age groups in the domains of social functioning, emotion role functioning, and mental health. CONCLUSION: Cochlear implant surgery significantly improves health-related quality of life as categorically stratified by the SF-36 questionnaire. These improvements were most evident in the mental health, emotional and social functioning, and physical functioning at work questions of the survey. Cochlear implant recipients younger than 65 years perceive a greater improvement in their level of energy, mental health, and social function compared with those older than 65 years.

The (α-4) photoconjugates of 5-methylcytosine, 1,5-dimethylcytosine, 1-methylthymine and thymidine.

The pyrimidine nucleobases contained in DNA undergo a variety of photoinduced reactions in which two moieties become joined to form a product (e.g. formation of cyclobutane dimers and [6-4] adducts). Herein, we describe a new type of photoconjugation reaction that has been shown to occur for 5-methylcytosine (5-MeC), 1,5-dimethylcytosine (1,5-diMeC), 1-methylthymine and thymidine; in this reaction the 5-methyl group of one nucleobase (or nucleoside) becomes attached to the 4-position of the second moiety. For example, 5-MeC forms α-4'-(5'-methylpyrimidin-2'-one)-5-methylcytosine. The various (α-4) conjugates are produced upon irradiation of the parent compound in frozen aqueous solution at -78.5°C. The UV spectra of these compounds display a characteristic "double humped" profile, similar to that expected from overlaying the spectrum of parent nucleobase with that of a 2'-pyrimidone moiety. Preliminary results suggest that thymine and 5-methyl-2'-deoxycytidine (5-MedCyd) form analogous photoproducts. A variety of other previously unreported photoproducts are described as well for the 5-MeC, 1,5-diMeC and 5-MedCyd systems.

Opened-ring adducts of 5-methylcytosine and 1,5-dimethylcytosine with amines and water and evidence for an opened-ring hydrate of 2'-deoxycytidine.

A variety of nucleic acid components and related compounds undergo photoreaction with water to form so-called "photohydrates" (e.g. uracil forms 6-hydroxy-5,6-dihydrouracil). However, the corresponding hydrates of 5-methylcytosine (a minor nucleobase in eukaryotic DNA) and related compounds have not been characterized. We report the preparation of opened-ring forms of such products for 5-methylcytosine (m5C) and 1,5-dimethylcytosine (DMC). This was accomplished via thermal reaction of ring-opened amine adducts (e.g. N-carbamoyl-3-amino-2-methylacrylamidine (IVa) or N-(N'-methylcarbamoyl)-3-amino-2-methylacrylamidine (IVb)) produced by photo-induced reactions of m5C with ammonia or methylamine. When these adducts were treated with dilute trifluoroacetic acid, the amino group at the 3-position was replaced with a hydroxyl group; with IVa, N-carbamoyl-3-hydroxy-2-methylacrylamidine (Va) was formed, while reaction of IVb led to N-(N'-methylcarbamoyl)-3-hydroxy-2-methylacrylamidine (Vb). These compounds are ring-opened isomers of 5,6-dihydro-6-hydroxy-5-methylcytosine (Ia and IIa) and 5,6-dihydro-6-hydroxy-1,5-dimethylcytosine (Ib and IIb). Compounds Va and Vb each undergo thermal ring closure reactions to form two unstable compounds with chemical and UV spectral properties expected for Ia and IIa (or Ib and IIb). The latter compounds have been identified as minor products in UV-irradiated aqueous solutions of m5C and DMC. Evidence is also presented that the 2'-deoxycytidine photohydrates coexist with an opened-ring form, possibly similar in nature to Vb.

The (5-4) and (6-4) adducts of 1-methylthymine and their Dewar valence isomers.

Previous studies of the photochemical reaction of 1-methylthymine (MeT) in frozen aqueous solution have indicated that four cyclobutane type dimers are formed. We have restudied this system and have found that, in addition to cyclobutane dimers, both a (5-4) adduct and a (6-4) adduct of MeT are formed in significant amounts. Upon standing in aqueous solution, the (5-4) adduct is susceptible to reaction to form an isomeric form of the parent adduct, possibly via ring-opening and closure reactions at C-6 of the saturated pyrimidine ring component of the adduct. Irradiation of each of these three adducts with UVB light produces a pair of Dewar-type adducts. The nine products were individually characterized by mass spectrometry, proton NMR spectroscopy and UV spectroscopy. A less comprehensive study showed that irradiation of thymidine in frozen aqueous solution produces a diastereomeric pair of (5-4) adducts, along with the previously known diastereomeric pair of (6-4) adducts.

Four children and one toy: Chinese and Canadian children faced with potential conflict over a limited resource.

Quartets of Chinese (n=125) and Canadian (n=133) 7-year-old children were observed as they played with a single attractive toy. Chinese children exhibited more assertive and general rule bids, engaged in more spontaneous giving, and reacted more positively to assertions of others whereas Canadian children more frequently referred to norms of sharing. Evidence of cultural scripts for dealing with potential conflict, that is, sharing for Canadian children and hierarchical organization for Chinese children, emerged. Passive and reticent behaviors in Chinese children and assertion and object control by Canadian children were associated with group acceptance, results suggesting the meaning of these patterns of social behavior may differ in these two countries.

Current progress and challenges in HIV gene therapy.

HIV-1 causes AIDS, a syndrome that affects millions of people globally. Existing HAART is efficient in slowing down disease progression but cannot eradicate the virus. Furthermore the severity of the side effects and the emergence of drug-resistant mutants call for better therapy. Gene therapy serves as an attractive alternative as it reconstitutes the immune system with HIV-resistant cells and could thereby provide a potential cure. The feasibility of this approach was first demonstrated with the 'Berlin patient', who was functionally cured from HIV/AIDS with undetectable HIV-1 viral load after transplantation of bone marrow harboring a naturally occurring CCR5 mutation that blocks viral entry. Here, we give an overview of the current status of HIV gene therapy and remaining challenges and obstacles.

Photoinduced ring opening reactions and subsequent thermal ring closure reactions in the thymine-ammonia system and related systems.

The photo-induced ring opening reactions of thymine (Thy) and 1-methylthymine (MeT) with ammonia and with methylamine (MA) at basic pH, and the subsequent ring closure reactions of the resulting adducts, have been studied. In the photo-induced reaction of Thy with ammonia, the dominant product is the E form of N-carbamoyl-3-amino-2-methylacrylamide (IIIa). Heating or acid treatment of aqueous IIIa results in rapid formation of Thy as final product, while allowing IIIa to stand at 4 degrees C produces Thy and two isomeric Thy hydrates, namely trans- and cis-6-hydroxy-5,6-dihydrothymine (Ia and IIa). The main products in the other reactions have analogous structures and undergo analogous ring closure reactions. Incubation of IIIa (and similar adducts) in phosphate buffer near pH 7 significantly enhances the rate of hydrate formation; other weak acid/conjugate base buffer systems also increase the rate of hydrate formation. A mechanism leading from opened ring adduct (e.g.IIIa) to hydrates (e.g.Ia and IIa) is proposed; ring closure leads initially to a dihydrothymine intermediate containing a 6-amino moiety, while further reaction with water produces the observed hydrates. The results described may be relevant to understanding the fate of cross-links generated by photo-induced reaction of thymine moieties in DNA with lysine residues in nuclear proteins (e.g. histones) when they are formed in a cellular environment. Decomposition of such cross-links, catalyzed by cellular phosphate, could lead to production of thymine hydrates attached to lysine residues contained in the protein partner and concurrent generation of an apyrimidinic site in the DNA partner.