ABSTRACT
BACKGROUND: Balint groups use case-based discussions to explore, reflect on, and enhance the clinician-patient relationship. They facilitate the development of empathy and reflective practice and reduce burnout. This study aimed to explore how the benefits of a traditional Balint group format can be accessed and optimised for medical students during a one-year pilot programme. METHODS: Eight medical student Balint groups ran for six weeks during 2022-2023, with 90 students participating. Themes were identified from student feedback using qualitative content analysis. Group leaders kept reflective session notes and used these alongside student feedback to undertake a strengths, weaknesses, opportunities, and threats analysis. RESULTS: Strengths of the programme were emotional containment, learning to reflect, and community identity. Weaknesses were themed as strange situations, dragging along, and facilitator as an object. Opportunities were identified in expanding the scope and sharpening focus. Psychological defences and the engagement dilemma threatened the future success of the Balint group programme. DISCUSSION: Medical student Balint groups provide a unique space to combine learning and emotional support with personal, professional and community development. However, the traditional Balint group format may need adapting to be widely accessible to undergraduate learners. Sustainably integrating Balint groups into the medical school curriculum requires ongoing engagement work at both an individual and organisational level.
Subject(s)
Students, Medical , Humans , Students, Medical/psychology , Emotions , Learning , Curriculum , EmpathyABSTRACT
Hypodermic needles are sometimes reused in animal research settings to preserve the viability of and to conserve limited quantities of injected material. However, the reuse of needles is strongly discouraged in human medicine to prevent inju- ries and the spread of infectious disease. No official guidelines prohibit needle reuse in veterinary medicine, although the practice may be discouraged. We hypothesized that reused needles would be significantly more blunt than unused needles and that reuse for additional injections would cause more animal stress. To test these ideas, we evaluated mice that were injected subcutaneously in the flank or mammary fat pad to generate cell line xenograft and mouse allograft models. Needles were reused up to 20 times, based on an IACUC-approved protocol. A subset of reused needles was digitally imaged to determine needle dullness based on the area of deformation from the secondary bevel angle; this parameter was not different between new needles and needles that had been reused 20 times. In addition, the number of times a needle was reused was not significantly related to audible mouse vocalization during injection. Finally, nest building scores for mice that were injected with a needle used 0 through 5 times were similar to those of mice injected with a needle had been used 16 through 20 times. Among the 37 reused needles that were tested, 4 were positive for bacterial growth; the only organisms cultured were Staphylococcus spp. Contrary to our hypothesis, reusing needles for subcutaneous injections did not increase animal stress based on analysis of vocalization or nest building.
Subject(s)
Needles , Vocalization, Animal , Humans , Animals , Mice , Photomicrography , Injections, SubcutaneousABSTRACT
Feline piroplasmids include the genera Babesia spp., Cytauxzoon spp., and Theileria spp. In Brazil, there are few reports regarding these hemoprotozoans; however, clinicopathological and molecular data are scarce. This study aimed to characterize the clinical relevance of these parasites through hematological, biochemical, and molecular approaches. For this purpose, 166 cats from Brasilia, Federal District, Midwestern Brazil, were screened using a quantitative polymerase chain reaction (qPCR) for piroplasmids based on the LSU4 mitochondrial gene, which resulted in an overall prevalence of 36/166 (21.7%). Twelve of 166 samples (7.2%) were positive for C. felis, while 19/166 (11.4%) were positive for Babesia vogeli. No samples tested positive for Theileria spp. Babesia vogeli and Cytauxzoon spp. LSU4 sequences showed identities of 97-100% and 99.3%, respectively, to US isolates. The hematological and biochemical findings did not differ significantly between the cats that tested positive and negative for piroplasmids. Although the lack of abnormalities in clinical and laboratory parameters does not eliminate the possibility that these cats were sick and recovered, it may suggest that the Brazilian strain of Cytauxzoon spp. is not as pathogenic as that from the USA, despite the high molecular identity with North American isolates.
Subject(s)
Babesia , Babesiosis , Cat Diseases , Felis , Piroplasmida , Theileria , Animals , Babesiosis/epidemiology , Babesiosis/parasitology , Brazil/epidemiology , Cat Diseases/epidemiology , Cats , Piroplasmida/genetics , Theileria/geneticsABSTRACT
To provide insights for how to deal with pandemic mortality risk, this article introduces a mortality model that depicts the relevant pandemic effects on pricing mortality-linked securities, using a threshold jump approach. That is, to capture pandemic mortality dynamics across countries, we consider mortality jumps related to the pandemic shock and to a specific country shock. Pandemic jump occurs only when a pandemic event causes significant deaths worldwide, such as 1918 Spanish flu or COVID-19. Then the proposed pandemic mortality model can be adjusted according to country-specific mortality experiences. We further analyze the effect of pandemic mortality risk on pricing a mortality-linked bond. Using the first Swiss Re mortality bond as an example, a further derivation obtains the closed-form solution for the fixed-coupon mortality-linked bond in the pandemic mortality framework. Finally, this study details the impacts of pandemic mortality risk numerically by fitting the model to the United States, England and Wales, France, Italy, and Switzerland and calculating the fair spread of the mortality-linked bond.
ABSTRACT
Skeletal muscle possesses remarkable regenerative ability because of the resident muscle stem cells (MuSCs). A prominent feature of quiescent MuSCs is a high content of heterochromatin. However, little is known about the mechanisms by which heterochromatin is maintained in MuSCs. By comparing gene-expression profiles from quiescent and activated MuSCs, we found that the mammalian Hairless (Hr) gene is expressed in quiescent MuSCs and rapidly down-regulated upon MuSC activation. Using a mouse model in which Hr can be specifically ablated in MuSCs, we demonstrate that Hr expression is critical for MuSC function and muscle regeneration. In MuSCs, loss of Hr results in reduced trimethylated Histone 3 Lysine 9 (H3K9me3) levels, reduced heterochromatin, increased susceptibility to genotoxic stress, and the accumulation of DNA damage. Deletion of Hr leads to an acceleration of the age-related decline in MuSC numbers. We have also demonstrated that despite the fact that Hr is homologous to a family of histone demethylases and binds to di- and trimethylated H3K9, the expression of Hr does not lead to H3K9 demethylation. In contrast, we show that the expression of Hr leads to the inhibition of the H3K9 demethylase Jmjd1a and an increase in H3K9 methylation. Taking these data together, our study has established that Hr is a H3K9 demethylase antagonist specifically expressed in quiescent MuSCs.
Subject(s)
Gene Silencing , Heterochromatin , Histone Demethylases/antagonists & inhibitors , Muscle, Skeletal/physiology , Stem Cells/physiology , Transcription Factors/metabolism , Animals , Histones/genetics , Histones/metabolism , Methylation , Mice , Mice, Hairless , Muscle, Skeletal/cytology , Stem Cells/cytology , Transcription Factors/geneticsABSTRACT
αvß8 integrin, a key activator of transforming growth factor ß (TGF-ß), inhibits anti-tumor immunity. We show that a potent blocking monoclonal antibody against αvß8 (ADWA-11) causes growth suppression or complete regression in syngeneic models of squamous cell carcinoma, mammary cancer, colon cancer, and prostate cancer, especially when combined with other immunomodulators or radiotherapy. αvß8 is expressed at the highest levels in CD4+CD25+ T cells in tumors, and specific deletion of ß8 from T cells is as effective as ADWA-11 in suppressing tumor growth. ADWA-11 increases expression of a suite of genes in tumor-infiltrating CD8+ T cells normally inhibited by TGF-ß and involved in tumor cell killing, including granzyme B and interferon-γ. The in vitro cytotoxic effect of tumor CD8 T cells is inhibited by CD4+CD25+ cells, and this suppressive effect is blocked by ADWA-11. These findings solidify αvß8 integrin as a promising target for cancer immunotherapy.
Subject(s)
Immunity , Immunotherapy , Integrins/metabolism , Models, Biological , Neoplasms/immunology , Neoplasms/therapy , T-Lymphocytes/immunology , Animals , Antibodies, Neoplasm/immunology , CD4-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/immunology , CTLA-4 Antigen/immunology , Cell Line, Tumor , Cell Proliferation , Gene Expression Regulation, Neoplastic , Granzymes/metabolism , Interferon-gamma/metabolism , Lymphocyte Depletion , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Mutation/genetics , Neoplasms/genetics , Neoplasms/pathology , Signal Transduction , Smad3 Protein/metabolism , Survival Analysis , T-Lymphocytes, Cytotoxic/immunology , Transforming Growth Factor beta/metabolism , Tumor Microenvironment/immunology , Tumor Necrosis Factor Receptor Superfamily, Member 9/metabolismABSTRACT
BACKGROUND: Major depressive disorder and associated mood syndromes are amongst the most common psychiatric disorders. To date, electroconvulsive therapy (ECT) is considered the most effective short-term treatment for patients with severe or treatment-resistant depression. In clinical practice, there is considerable variation in the ECT dosing schedule, with the number of sessions typically ranging from 6 to 12, with early antidepressant effects being predictive of increased positive outcomes. We describe here an unusual case of a female patient with severe depression who did not respond to ECT until the 11th session, after which she had shown a drastic improvement in her mental state. CASE PRESENTATION: A 75-year-old female presented to the old age psychiatry inpatient unit with new onset dysphoric mood, anhedonia, and severe negativity. She scored 23 on the 17-item Hamilton Rating Scale for Depression (HAM-D), and was rated 6 on Clinical Global Impression severity (CGIS) by the responsible clinician. She suffered from post-natal depression fifty years ago and was successfully treated with ECT. She was therefore initiated on a course of ECT treatment. Her condition initially deteriorated, displaying features of catatonia and psychosis, unresponsive to ECT treatment or concurrent psychotropic medications. After 11th ECT session, she started to show signs of clinical improvement and returned close to her baseline mental state after a total of 17 ECT sessions. She remained well 3 months post-treatment, scoring 4 on HAM-D, Clinical Global Improvement or change (CGI-C) rated as 1 (very much improved). The diagnosis was ICD-10 F32.3 severe depressive episode with psychotic symptoms. CONCLUSIONS: we describe here an unusual case of delayed response to electroconvulsive therapy in the treatment of severe depressive disorder. Studies have shown the number of acute ECT treatments to be highly variable, affected by a number of factors including treatment frequency, condition treated and its severity, the ECT technical parameters, as well as concurrent use of pharmacological treatment. This may call for re-consideration of the current ECT treatment guidelines, requiring more research to help stratify and standardize the treatment regime.
Subject(s)
Catatonia , Depressive Disorder, Major , Depressive Disorder, Treatment-Resistant , Electroconvulsive Therapy , Psychotic Disorders , Aged , Depressive Disorder, Major/therapy , Female , Humans , Treatment OutcomeABSTRACT
BACKGROUND: The clinical success of immune checkpoint inhibitors demonstrates that reactivation of the human immune system delivers durable responses for some patients and represents an exciting approach for cancer treatment. An important class of preclinical in vivo models for immuno-oncology is immunocompetent mice bearing mouse syngeneic tumors. To facilitate translation of preclinical studies into human, we characterized the genomic, transcriptomic, and protein expression of a panel of ten commonly used mouse tumor cell lines grown in vitro culture as well as in vivo tumors. RESULTS: Our studies identified a number of genetic and cellular phenotypic differences that distinguish commonly used mouse syngeneic models in our study from human cancers. Only a fraction of the somatic single nucleotide variants (SNVs) in these common mouse cell lines directly match SNVs in human actionable cancer genes. Some models derived from epithelial tumors have a more mesenchymal phenotype with relatively low T-lymphocyte infiltration compared to the corresponding human cancers. CT26, a colon tumor model, had the highest immunogenicity and was the model most responsive to CTLA4 inhibitor treatment, by contrast to the relatively low immunogenicity and response rate to checkpoint inhibitor therapies in human colon cancers. CONCLUSIONS: The relative immunogenicity of these ten syngeneic tumors does not resemble typical human tumors derived from the same tissue of origin. By characterizing the mouse syngeneic models and comparing with their human tumor counterparts, this study contributes to a framework that may help investigators select the model most relevant to study a particular immune-oncology mechanism, and may rationalize some of the challenges associated with translating preclinical findings to clinical studies.
Subject(s)
CTLA-4 Antigen/genetics , Colonic Neoplasms/immunology , Genomics , Animals , CTLA-4 Antigen/antagonists & inhibitors , Cell Line, Tumor , Colonic Neoplasms/drug therapy , Colonic Neoplasms/genetics , Colonic Neoplasms/pathology , Disease Models, Animal , Gene Expression Regulation, Neoplastic/drug effects , Humans , Mice , T-Lymphocytes/immunologyABSTRACT
The COVID-19 pandemic has created an unprecedented situation demanding a rapid response to a barrage of unknown risks. Issues around infection control, resource allocation and treatment delivery have threatened the viability and accessibility of Electroconvulsive Therapy (ECT) services. Additionally, there are unquantified risks around the delivery and effect of ECT in patients who have had COVID-19. We discuss two cases where ECT was restarted in older-adults who had had symptomatic COVID-19. We consider the importance of clinical assessment, multi-speciality team involvement, and comprehensive risk assessment in making high stakes treatment decisions around ECT in patients with COVID-19. Although more research and international multi-speciality collaboration is required to develop evidence-based guidance, it is vital that we maintain equitable access to safe, effective and potentially life-saving ECT during this pandemic.
ABSTRACT
BACKGROUND AND OBJECTIVES: Cannabis use is common in people with and mood and anxiety disorders (ADs), and rates of problematic use are higher than in the general population. Given recent policy changes in favor of cannabis legalization, it is important to understand how cannabis and cannabinoids may impact people with these disorders. We aimed to assess the effects of cannabis on the onset and course of depression, bipolar disorder, ADs, and post-traumatic stress disorder (PTSD), and also to explore the therapeutic potential of cannabis and cannabinoids for these disorders. METHODS: A systematic review of the literature was completed. The PubMed® database from January 1990 to May 2018 was searched. We included longitudinal cohort studies, and also all studies using cannabis or a cannabinoid as an active intervention, regardless of the study design. RESULTS: Forty-seven studies were included: 32 reported on illness onset, nine on illness course, and six on cannabinoid therapeutics. Cohort studies varied significantly in design and quality. The literature suggests that cannabis use is linked to the onset and poorer clinical course in bipolar disorder and PTSD, but this finding is not as clear in depression and anxiety disorders (ADs). There have been few high-quality studies of cannabinoid pharmaceuticals in clinical settings. CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE: These conclusions are limited by a lack of well-controlled longitudinal studies. We suggest that future research be directed toward high-quality, prospective studies of cannabis in clinical populations with mood and ADs, in addition to controlled studies of cannabinoid constituents and pharmaceuticals in these populations. (Am J Addict 2019;00:00-00).
Subject(s)
Anxiety Disorders/drug therapy , Cannabinoids/adverse effects , Cannabinoids/therapeutic use , Medical Marijuana/adverse effects , Medical Marijuana/therapeutic use , Mood Disorders/drug therapy , Disease Progression , HumansABSTRACT
Recessive mutations in the ubiquitously expressed POLR3A and POLR3B genes are the most common cause of POLR3-related hypomyelinating leukodystrophy (POLR3-HLD), a rare childhood-onset disorder characterized by deficient cerebral myelin formation and cerebellar atrophy. POLR3A and POLR3B encode the two catalytic subunits of RNA Polymerase III (Pol III), which synthesizes numerous small non-coding RNAs. We recently reported that mice homozygous for the Polr3a mutation c.2015G > A (p.Gly672Glu) have no neurological abnormalities and thus do not recapitulate the human POLR3-HLD phenotype. To determine if other POLR3-HLD mutations can cause a leukodystrophy phenotype in mouse, we characterized mice carrying the Polr3b mutation c.308G > A (p.Arg103His). Surprisingly, homozygosity for this mutation was embryonically lethal with only wild-type and heterozygous animals detected at embryonic day 9.5. Using proteomics in a human cell line, we found that the POLR3B R103H mutation severely impairs assembly of the Pol III complex. We next generated Polr3aG672E/G672E/Polr3b+/R103Hdouble mutant mice but observed that this additional mutation was insufficient to elicit a neurological or transcriptional phenotype. Taken together with our previous study on Polr3a G672E mice, our results indicate that missense mutations in Polr3a and Polr3b can variably impair mouse development and Pol III function. Developing a proper model of POLR3-HLD is crucial to gain insights into the pathophysiological mechanisms involved in this devastating neurodegenerative disease.
Subject(s)
Embryo Loss/enzymology , Hereditary Central Nervous System Demyelinating Diseases/genetics , Mutation/genetics , RNA Polymerase III/genetics , Animals , Base Sequence , Embryo Loss/genetics , Gene Expression Regulation, Enzymologic , Gene Knock-In Techniques , HEK293 Cells , Hereditary Central Nervous System Demyelinating Diseases/physiopathology , Homozygote , Humans , Mice, Inbred C57BL , Mice, Mutant Strains , Motor Activity , Myelin Sheath/metabolism , RNA Polymerase III/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolismABSTRACT
Recessive mutations in the ubiquitously expressed POLR3A gene cause one of the most frequent forms of childhood-onset hypomyelinating leukodystrophy (HLD): POLR3-HLD. POLR3A encodes the largest subunit of RNA Polymerase III (Pol III), which is responsible for the transcription of transfer RNAs (tRNAs) and a large array of other small non-coding RNAs. In order to study the central nervous system pathophysiology of the disease, we introduced the French Canadian founder Polr3a mutation c.2015G > A (p.G672E) in mice, generating homozygous knock-in (KI/KI) as well as compound heterozygous mice for one Polr3a KI and one null allele (KI/KO). Both KI/KI and KI/KO mice are viable and are able to reproduce. To establish if they manifest a motor phenotype, WT, KI/KI and KI/KO mice were submitted to a battery of behavioral tests over one year. The KI/KI and KI/KO mice have overall normal balance, muscle strength and general locomotion. Cerebral and cerebellar Luxol Fast Blue staining and measurement of levels of myelin proteins showed no significant differences between the three groups, suggesting that myelination is not overtly impaired in Polr3a KI/KI and KI/KO mice. Finally, expression levels of several Pol III transcripts in the brain showed no statistically significant differences. We conclude that the first transgenic mice with a leukodystrophy-causing Polr3a mutation do not recapitulate the childhood-onset HLD observed in the majority of human patients with POLR3A mutations, and provide essential information to guide selection of Polr3a mutations for developing future mouse models of the disease.
Subject(s)
Hereditary Central Nervous System Demyelinating Diseases/genetics , Mutation/genetics , Myelin Sheath/metabolism , RNA Polymerase III/genetics , Animals , Cerebellum/pathology , Cerebellum/physiopathology , Gene Knock-In Techniques , Hereditary Central Nervous System Demyelinating Diseases/physiopathology , Homozygote , Humans , Mice, Inbred C57BL , Mice, Knockout , Motor Activity , Purkinje Cells/metabolism , Purkinje Cells/pathology , RNA Polymerase III/metabolism , Transcription, GeneticABSTRACT
Hereditary cerebellar ataxias and hereditary spastic paraplegias are clinically and genetically heterogeneous and often overlapping neurological disorders. Mutations in SPG7 cause the autosomal recessive spastic paraplegia type 7 (SPG7), but recent studies indicate that they are also one of the most common causes of recessive cerebellar ataxia. In Quebec, a significant number of patients affected with cerebellar ataxia and spasticity remain without a molecular diagnosis. We performed whole-exome sequencing in three French Canadian (FC) patients affected with spastic ataxia and uncovered compound heterozygous variants in SPG7 in all three. Sanger sequencing of SPG7 exons and exon/intron boundaries was used to screen additional patients. In total, we identified recessive variants in SPG7 in 22 FC patients belonging to 12 families (38.7% of the families screened), including two novel variants. The p.(Ala510Val) variant was the most common in our cohort. Cerebellar features, including ataxia, were more pronounced than spasticity in this cohort. These results strongly suggest that variants affecting the function of SPG7 are the fourth most common form of recessive ataxia in FC patients. Thus, we propose that SPG7 mutations explain a significant proportion of FC spastic ataxia cases and that this gene should be considered in unresolved patients.
Subject(s)
Intellectual Disability/genetics , Metalloendopeptidases/genetics , Muscle Spasticity/genetics , Mutation, Missense , Optic Atrophy/genetics , Spinocerebellar Ataxias/genetics , ATPases Associated with Diverse Cellular Activities , Adult , Exome , Female , Genes, Recessive , Heterozygote , Humans , Intellectual Disability/epidemiology , Intellectual Disability/pathology , Male , Middle Aged , Muscle Spasticity/epidemiology , Muscle Spasticity/pathology , Optic Atrophy/epidemiology , Optic Atrophy/pathology , Prevalence , Quebec , Spinocerebellar Ataxias/epidemiology , Spinocerebellar Ataxias/pathologyABSTRACT
In late spring of 2009 and 2010, there were reports of severe black fly (Simulium spp., shown in Fig. 1) outbreaks in various counties in Mississippi, especially those in and around the Mississippi River Delta. Complaints were of black flies attacking multiple species of backyard poultry and causing high morbidity and mortality in affected flocks. At several affected locations, black flies were readily observed swarming around and feeding on birds. A large number of these parasites were easily trapped on fly strips (Fig. 2). Multifocal to coalescing cutaneous hemorrhagic lesions, consistent with fly bites, were seen on the birds. Upon necropsy examination, a large number of black flies were also observed in the digestive tract (Fig. 3). Although black flies may cause disease directly, such as cardiopulmonary collapse and anaphylactoid reactions, detection of Leucocytozoon in blood smears (Fig. 4) of affected birds prompted further investigations of this protozoan as a cause of disease. Leucocytozoon spp. are known to be transmitted by black flies and may be associated with morbidity and mortality in birds such as poultry. From June 2009 through July 2012, the investigation included a total collection of 1068 individual blood samples, representing 371 individual premises in 89 counties/parishes across Mississippi (59), Alabama (10), Louisiana (4), and Tennessee (16). Of the 371 premises where blood samples were collected, 96 (26%) were either positive or highly suspected to be positive for Leucocytozoon spp. by blood smear analysis, and 5 (1.2%) were positive for Haemoproteus spp. by blood smear analysis. Attempts to diagnose Leucocytozoon spp. by PCR analysis and sequencing were complicated by coinfections with two closely related haemosporidians (Haemoproteus spp. and Plasmodium spp.). A novel technique involving flow cytometry was also explored. This study discusses the black fly field outbreak, the involvement of haemosporidians, molecular methods for detection of both the black flies and blood parasites, and initial attempts at flow cytometry.
Subject(s)
Haemosporida/isolation & purification , Insect Bites and Stings/epidemiology , Poultry Diseases/parasitology , Protozoan Infections, Animal/parasitology , Simuliidae , Animals , Mississippi/epidemiology , Poultry , Poultry Diseases/epidemiology , Protozoan Infections, Animal/epidemiologyABSTRACT
The knowledgebase TopFIND is an analysis platform focussed on protein termini, their origin, modification and hence their role on protein structure and function. Here, we present a major update to TopFIND, version 3, which includes a 70% increase in the underlying data to now cover a 90,696 proteins, 165,044 N-termini, 130,182 C-termini, 14,382 cleavage sites and 33,209 substrate cleavages in H. sapiens, M. musculus, A. thaliana, S. cerevisiae and E. coli. New features include the mapping of protein termini and cleavage entries across protein isoforms and significantly, the mapping of protein termini originating from alternative transcription and alternative translation start sites. Furthermore, two analysis tools for complex data analysis based on the TopFIND resource are now available online: TopFINDer, the TopFIND ExploRer, characterizes and annotates proteomics-derived N- or C-termini sets for their origin, sequence context and implications for protein structure and function. Neo-termini are also linked to associated proteases. PathFINDer identifies indirect connections between a protease and list of substrates or termini thus supporting the evaluation of complex proteolytic processes in vivo. To demonstrate the utility of the tools, a recent N-terminomics data set of inflamed murine skin has been re-analyzed. In re-capitulating the major findings originally performed manually, this validates the utility of these new resources. The point of entry for the resource is http://clipserve.clip.ubc.ca/topfind from where the graphical interface, all application programming interfaces (API) and the analysis tools are freely accessible.
Subject(s)
Databases, Protein , Proteome , Alternative Splicing , Animals , Humans , Mice , Peptide Hydrolases/metabolism , Protein Isoforms/chemistry , Protein Processing, Post-Translational , Proteomics , SoftwareABSTRACT
We have generated large libraries of single-chain Fv antibody fragments (>10(10) transformants) containing unbiased amino acid diversity that is restricted to the central combining site of the stable, well-expressed DP47 and DPK22 germline V-genes. Library WySH2A was constructed to examine the potential for synthetic complementarity-determining region (CDR)-H3 diversity to act as the lone source of binding specificity. Library WySH2B was constructed to assess the necessity for diversification in both the H3 and L3. Both libraries provided diverse, specific antibodies, yielding a total of 243 unique hits against 7 different targets, but WySH2B produced fewer hits than WySH2A when selected in parallel. WySH2A also consistently produced hits of similar quality to WySH2B, demonstrating that the diversification of the CDR-L3 reduces library fitness. Despite the absence of deliberate bias in the library design, CDR length was strongly associated with the number of hits produced, leading to a functional loop length distribution profile that mimics the biases observed in the natural repertoire. A similar trend was also observed for the CDR-L3. After target selections, several key amino acids were enriched in the CDR-H3 (e.g., small and aromatic residues) while others were reduced (e.g., strongly charged residues) in a manner that was specific to position, preferentially occurred in CDR-H3 stem positions, and tended towards residues associated with loop stabilization. As proof of principle for the WySH2 libraries to produce viable lead candidate antibodies, 114 unique hits were produced against Delta-like ligand 4 (DLL4). Leads exhibited nanomolar binding affinities, highly specific staining of DLL4+ cells, and biochemical neutralization of DLL4-NOTCH1 interaction.
Subject(s)
Antibody Specificity , Complementarity Determining Regions/immunology , Complementarity Determining Regions/therapeutic use , Peptide Library , Single-Chain Antibodies/biosynthesis , Single-Chain Antibodies/therapeutic use , Adaptor Proteins, Signal Transducing , Animals , Antibody Specificity/genetics , Calcium-Binding Proteins , Cloning, Molecular , Complementarity Determining Regions/genetics , HEK293 Cells , Humans , Intercellular Signaling Peptides and Proteins/genetics , Intercellular Signaling Peptides and Proteins/immunology , Mice , Models, Molecular , Mutation , Receptor, Notch1/antagonists & inhibitors , Receptor, Notch1/genetics , Receptor, Notch1/immunology , Single-Chain Antibodies/geneticsABSTRACT
In the presence of rhodium(I) hydride catalysts, tertiary N-allylamines are known to isomerise into E enamines. In contrast, we have recently found that N-allylaziridines isomerise to form Z enamines. On the basis of literature data, the most likely mechanism of isomerisation would involve a rhodium hydride addition/beta-hydride elimination sequence. We show that the observed selectivity cannot be adequately explained by this pathway and is more consistent with initial CH-activation followed by rearrangement to form a five-membered cyclometallated rhodium intermediate. This intermediate subsequently undergoes reductive elimination to form a C--H bond. The resulting geometrically stable Z enamines are useful building blocks for stereoselective synthesis.
Subject(s)
Amines/chemical synthesis , Aziridines/chemistry , Rhodium/chemistry , Amines/chemistry , Catalysis , Molecular Structure , StereoisomerismABSTRACT
PURPOSE: Because resistance to paclitaxel and docetaxel is frequently observed in the clinic, new anti-microtubule agents have been sought. The aim of this study was to evaluate the efficacy and oral activity of a novel taxane (MST-997) in paclitaxel- and docetaxel-resistant tumor models in vitro and in vivo. EXPERIMENTAL DESIGN: Tubulin polymerization assays, immunohistochemistry, and cell cycle analysis was used to evaluate mechanism of action of MST-997. The effect of MST-997 on growth inhibition in a panel of paclitaxel- and docetaxel-resistant cell lines that overexpressed P-glycoprotein (MDR1) or harbored beta-tubulin mutations were assayed in vitro and in murine xenografts. RESULTS: MST-997 induced microtubule polymerization (EC50 = 0.9 micromol/L) and bundling, resulting in G2-M arrest and apoptosis. In addition, MST-997 was a potent inhibitor of paclitaxel- and docetaxel-sensitive tumor cell lines that did not have detectable P-glycoprotein (IC50 = 1.8 +/- 1.5 nmol/L). Minimal resistance (1- to 8-fold) to MST-997 was found in cell lines that either overexpressed MDR1 or harbored point mutations in beta-tubulin. Most notable, MST-997 displayed superior in vivo efficacy as a single i.v. or p.o. dose either partially or completely inhibited tumor growth in paclitaxel- and docetaxel-resistant xenografts. CONCLUSIONS: MST-997 represents a potent and orally active microtubule-stabilizing agent that has greater pharmacologic efficacy in vitro and in vivo than the currently approved taxanes. Our findings suggest that MST-997, which has entered phase I clinical trials, may have broad therapeutic value.