1,037 research outputs found
Synthetic approaches towards novel indole alkaloids
This thesis describes several synthetic approaches to some
novel indole alkaloids. The Introduction (Chapter One) outlines the
need for continuous discovery of new antibiotics in todays
environment. The family of Kinamycin antibiotics is described
along with their biosynthesis and the evidence of the novel
biosynthetic precursor known as Pre-Kinamycin.
Chapter Two (2.1) deals with a retrosynthetic analysis
leading to a study of Tandem Directed Ortho-Metallation reactions
and a proposed synthesis of Pre-Kinamycin. Section 2.2 describes
the study of stable analogues of indole-2,3-quinodimethane and the
Dials–Alder reactions thereof. Also Dials-Alder reactions of
pyrano[3,4-b]indol-3-ones with benzyne and the subsequent
manipulation of the carbazole-based products are detailed. Section
2.3 outlines the study of the Friedel–Crafts acylation reaction with
respect to the indole nucleus and the application of such a reaction
to the synthesis of the Pre-Kinamycin skeleton. Investigations into
acid mediated cyclisations to form quinones and the use of Weinreb
amides as acylating agents are also described.
Chapter Three (3.1) examines the problems of iron overload
diseases (haemochromatosis) and the efforts to produce effective
iron chelators. Section 3.2 describes the discovery of four novel
indole alkaloids known as Uvarindoles and their possible
consideration as iron chelators. Section 3.3 examines two
retrosynthetic analyses towards Uvarindole B and the investigation
into the synthesis thereof, involving similar methodology as that
developed in section 2.3.
Chapter Four describes the relevant experimental details for
the intermediates described in sections 2.1 through 3.3 and the
respective spectroscopic data obtained.
Chapter Five gives the references for all the relevant work
quoted in above sections
Alpha/beta and gamma interferons are induced by infection with noncytopathic bovine viral diarrhea virus in vivo
In contrast to the results of previous in vitro studies, experimental infection of calves with noncytopathic bovine viral diarrhea virus (ncpBVDV) was found to induce strong alpha/beta and gamma interferon responses in gnotobiotic animals. These responses were associated with depressed levels of transforming growth factor β (TGF-β) in serum. The results of this study indicate that the immunosuppression caused by ncpBVDV is not associated with low interferon responses or elevated levels of TGF-β
High resolution spectroscopy of Pluto's atmosphere: detection of the 2.3 m CH bands and evidence for carbon monoxide
The goal is to determine the composition of Pluto's atmosphere and to
constrain the nature of surface-atmosphere interactions.
We perform high--resolution spectroscopic observations in the 2.33--2.36
m range, using CRIRES at the VLT.
We obtain (i) the first detection of gaseous methane in this spectral range,
through lines of the + and + bands (ii) strong
evidence (6- confidence) for gaseous CO in Pluto. For an isothermal
atmosphere at 90 K, the CH and CO column densities are 0.75 and 0.07 cm-am,
within factors of 2 and 3, respectively. Using a physically--based thermal
structure model of Pluto's atmosphere also satisfying constraints from stellar
occultations, we infer CH and CO mixing ratios q=
0.6% (consistent with results from the 1.66 m range) and
q = 0.5. The CO atmospheric abundance is
consistent with its surface abundance. As for Triton, it is probably controlled
by a thin, CO-rich, detailed balancing layer resulting from seasonal transport
and/or atmospheric escape.Comment: Astronomy and Astrophysics Letters, in pres
A quantitative approach for measuring the reservoir of latent HIV-1 proviruses.
A stable latent reservoir for HIV-1 in resting CD4+ T cells is the principal barrier to a cure1-3. Curative strategies that target the reservoir are being tested4,5 and require accurate, scalable reservoir assays. The reservoir was defined with quantitative viral outgrowth assays for cells that release infectious virus after one round of T cell activation1. However, these quantitative outgrowth assays and newer assays for cells that produce viral RNA after activation6 may underestimate the reservoir size because one round of activation does not induce all proviruses7. Many studies rely on simple assays based on polymerase chain reaction to detect proviral DNA regardless of transcriptional status, but the clinical relevance of these assays is unclear, as the vast majority of proviruses are defective7-9. Here we describe a more accurate method of measuring the HIV-1 reservoir that separately quantifies intact and defective proviruses. We show that the dynamics of cells that carry intact and defective proviruses are different in vitro and in vivo. These findings have implications for targeting the intact proviruses that are a barrier to curing HIV infection
Motivational Interviewing Counseling to Increase Endocrine Therapy Adherence in Diverse Patients
Background: Oral endocrine therapy (ET) is an inexpensive and effective therapy for hormone receptor-positive (HR+) breast cancer that prevents recurrence but relies upon long-term adherence for up to ten years. More than 80% of breast cancer patients have an HR+ phenotype and are candidates for ET, but approximately half discontinue or become non-adherent by five years. ET underuse is more prevalent in Black and young (18 years old, English speaking, and with stage I–III HR+ breast cancer. Participants were recruited across a large academic medical center and four community sites. Feasibility and acceptability were assessed by measures of participant recruitment, retention, session participation, and patient-reported satisfaction. ET adherence at 12 months was assessed by self-report and medication event monitoring system (MEMS) caps using a continuous measure of the proportion of days covered (PDC) as well as a dichotomous measure of the optimal adherence, defined as >80% PDC. Results: Forty-two women initiated the intervention, of whom thirty-five participants (83%) completed outcome assessments at 12 months, including thirteen Black and twenty-two non-Black participants. The average participant age was 54.8 years (range: 25–73). Overall, 97% completed at least three MI sessions and 83% completed at least four sessions. Participant retention and satisfaction were high, particularly among Black women. Self-reported adherence at 12 months was 88% overall (100% in Black women and 81% in non-Black women). The majority of women also achieved 80% of days adherent using MEMS caps, with a greater adherence in Black women. Conclusions: This study demonstrates the feasibility, acceptability, and early promise of the effectiveness of an MI counseling-based intervention to promote ET adherence and prevent breast cancer recurrence in diverse populations
Canonical Quantization of (2+1)-Dimensional Gravity
We consider the quantum dynamics of both open and closed two- dimensional
universes with ``wormholes'' and particles. The wave function is given as a sum
of freely propagating amplitudes, emitted from a network of mapping class
images of the initial state. Interference between these amplitudes gives
non-trivial scattering effects, formally analogous to the optical diffraction
by a multidimensional grating; the ``bright lines'' correspond to the most
probable geometries.Comment: 22 pages, Mexico preprint ICN-UNAM-93-1
Modifying the m6A brain methylome by ALKBH5-mediated demethylation: a new contender for synaptic tagging
Synaptic plasticity processes, which underlie learning and memory formation, require RNA to be translated local to synapses. The synaptic tagging hypothesis has previously been proposed to explain how mRNAs are available at specific activated synapses. However how RNA is regulated, and which transcripts are silenced or processed as part of the tagging process is still unknown. Modification of RNA by N6-methyladenosine (m6A/m) influences the cellular fate of mRNA. Here, by advanced microscopy, we showed that m6A demethylation by the eraser protein ALKBH5 occurs at active synaptic ribosomes and at synapses during short term plasticity. We demonstrated that at activated glutamatergic post-synaptic sites, both the YTHDF1 and YTHDF3 reader and the ALKBH5 eraser proteins increase in co-localisation to m6A-modified RNAs; but only the readers showed high co-localisation to modified RNAs during late-stage plasticity. The YTHDF1 and YTHFDF3 readers also exhibited differential roles during synaptic maturation suggesting that temporal and subcellular abundance may determine specific function. m6A-sequencing of human parahippocampus brain tissue revealed distinct white and grey matter m6A methylome profiles indicating that cellular context is a fundamental factor dictating regulated pathways. However, in both neuronal and glial cell-rich tissue, m6A effector proteins are themselves modified and m6A epitranscriptional and posttranslational modification processes coregulate protein cascades. We hypothesise that the availability m6A effector protein machinery in conjunction with RNA modification, may be important in the formation of condensed synaptic nanodomain assemblies through liquid-liquid phase separation. Our findings support that m6A demethylation by ALKBH5 is an intrinsic component of the synaptic tagging hypothesis and a molecular switch which leads to alterations in the RNA methylome, synaptic dysfunction and potentially reversible disease states
IDENTIFICATION OF RISK AREAS USING SPATIAL CLUSTERING TO IMPROVE DENGUE MONITORING IN URBAN ENVIRONMENTS
Monitoring the occurrence and spread of epidemics is essential for improving decision-making and developing better public policies in urban environments. Besides temporal aspects, it is also essential to evaluate risk areas. However, only a few works in the literature apply spatial analysis of dengue epidemics in Brazil due mainly to a lack of data availability. Additionally, few methodologies available allow for identifying risk areas considering spatial aspects. The main objective of this work was to identify spatial clusters of risk for dengue cases according to the social vulnerability of each area. This constitutes a powerful tool for effective epidemiological and urban management. This work carries out an ecological study that considered dengue cases in São Carlos-SP, Brazil, in the years 2018, 2019 and 2020. The spatial scan technique was applied to classify the risk areas, considering the relative risk (RR) with a confidence interval of 95\% (CI95\%:) and the São Paulo Social Vulnerability Index (IPVS) to characterize these areas. Three clusters were identified in 2018, with high risk relative (RR=28.86), twenty clusters were identified in 2019, with high risk relative (RR=36.26) and five clusters were identified in 2020, with high risk relative (RR=23.32). The highest risk was located in a region with high vulnerability, and the second was in a region with very low vulnerability. These results provide information that allows the targeting of specific control actions from the early detection of cases in places with greater dengue transmissibility.DOI: 10.36558/rsc.v12i3.792
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Tandem quadruplication of HMA4 in the zinc (Zn) and cadmium (Cd) hyperaccumulator noccaea caerulescens
Zinc (Zn) and cadmium (Cd) hyperaccumulation may have evolved twice in the Brassicaceae, in Arabidopsis halleri and in the Noccaea genus. Tandem gene duplication and deregulated expression of the Zn transporter, HMA4, has previously been linked to Zn/Cd hyperaccumulation in A. halleri. Here, we tested the hypothesis that tandem duplication and deregulation of HMA4 expression also occurs in Noccaea. A Noccaea caerulescens genomic library was generated, containing 36,864 fosmid pCC1FOSTM clones with insert sizes ~20–40 kbp, and screened with a PCR-generated HMA4 genomic probe. Gene copy number within the genome was estimated through DNA fingerprinting and pooled fosmid pyrosequencing. Gene copy numbers within individual clones was determined by PCR analyses with novel locus specific primers. Entire fosmids were then sequenced individually and reads equivalent to 20-fold coverage were assembled to generate complete whole contigs. Four tandem HMA4 repeats were identified in a contiguous sequence of 101,480 bp based on sequence overlap identities. These were flanked by regions syntenous with up and downstream regions of AtHMA4 in Arabidopsis thaliana. Promoter-reporter b-glucuronidase (GUS) fusion analysis of a NcHMA4 in A. thaliana revealed deregulated expression in roots and shoots, analogous to AhHMA4 promoters, but distinct from AtHMA4 expression which localised to the root vascular tissue. This remarkable consistency in tandem duplication and deregulated expression of metal transport genes between N. caerulescens and A. halleri, which last shared a common ancestor >40 mya, provides intriguing evidence that parallel evolutionary pathways may underlie Zn/Cd hyperaccumulation in Brassicaceae
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