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Background: Palliative care addresses a range of needs, from symptom management to providing support to patients with hepatocellular cancer (HCC) and their families throughout the illness. However, research on palliative care in HCC remains limited, particularly during the COVID-19 pandemic. This study investigates the healthcare utilization associated with palliative care referral among patients with HCC. Methods: This is a retrospective cross-sectional analysis conducted using the National Inpatient Sample (NIS) database from 2019 to 2021 among patients with HCC age ≥18 years. Results: Among the 35,220 hospitalizations with HCC as the principal diagnosis, 18.7% received inpatient palliative care referrals. Factors associated with increased palliative care referrals included age ≥65 years, Midwest region, Charlson Comorbidity Index (CCI) score ≥3, and end-of-life care, as reflected by discharge resulting in death. No racial or insurance disparities were observed. Palliative care consultations were associated with lower total hospital costs ($20,573 vs $26,035, <0.0001). A higher prevalence of "do-not-resuscitate" status was also found among patients with palliative care referrals. Conclusion: The study provides an understanding of palliative care utilization across pre-pandemic and pandemic periods. Factors such as advanced age, hospital region, and underlying comorbidities influenced the likelihood of referral, with no discernible racial or insurance disparities identified. Palliative care involvement has also been shown to provide cost-effective supportive care with lower hospital costs. These findings provide invaluable guidance for optimizing the integration of palliative care alongside HCC management.
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Formation and retrieval of remote contextual memory depends on cortical engram neurons that are defined during learning. Manipulation of astrocytic Gq and Gi associated G-protein coupled receptor (GPCR) signaling has been shown to affect memory processing, but little is known about the role of cortical astrocytic Gs-GPCR signaling in remote memory acquisition and the functioning of cortical engram neurons. We assessed this by chemogenetic manipulation of astrocytes in the medial prefrontal cortex (mPFC) of male mice, during either encoding or consolidation of a contextual fear memory, while simultaneously labeling cortical engram neurons. We found that stimulation of astrocytic Gs signaling during memory encoding and consolidation did not alter remote memory expression. In line with this, the size of the mPFC engram population and the recall-induced reactivation of these neurons was unaffected. Hence, our data indicate that activation of Gs-GPCR signaling in cortical astrocytes is not sufficient to alter memory performance and functioning of cortical engram neurons.
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Astrócitos , Medo , Neurônios , Córtex Pré-Frontal , Transdução de Sinais , Animais , Astrócitos/metabolismo , Masculino , Córtex Pré-Frontal/metabolismo , Córtex Pré-Frontal/fisiologia , Transdução de Sinais/fisiologia , Neurônios/metabolismo , Neurônios/fisiologia , Medo/fisiologia , Camundongos Endogâmicos C57BL , Subunidades alfa Gs de Proteínas de Ligação ao GTP/metabolismo , Camundongos , Memória/fisiologia , Memória de Longo Prazo/fisiologiaRESUMO
An animal's body size impacts many aspects of its structure and function (Y); insights that only become apparent when viewed over several orders of magnitude of body mass (M) and expressed allometrically in the form of power law equations (Y=aMb). The resulting relationships are apparent clusters of similar exponents (b) revealing emergent 'patterns of design' that shed light on the universal principles of structure and function. Basic physical principles of surface area, volume and heat exchange apply to all objects, including animals, and many consequences must be attributed to these fundamental properties. Starting with Galileo's description of the shapes of bones in the 16th century and extending to 19th century explanations of heat production and loss by Sarrus and Rameaux, allometric patterns have provided numerous biological insights. Here, we examine several of these insights and explore how the selective pressures and scaling may differ when comparing animals in a vegetative (basal) state and those utilizing their maximum metabolic capacities. It seems that the selective pressures under those two conditions differ. We caution that allometric patterns invite explanations that lack supporting data or may be dismissed because there is hesitation among biologists to make comparisons lacking phylogenetic support. We argue that emergent allometric patterns have inherent value and continue to be the fodder for many fruitful hypotheses.
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Metabolismo Basal , Termogênese , Animais , Filogenia , Tamanho Corporal , Especificidade da EspécieRESUMO
Ibrutinib is an oral, first-line, targeted therapy for chronic lymphocytic leukemia (CLL). Commonly reported adverse events are diarrhea, fatigue, and musculoskeletal pain, but rarely it has been associated with visual disturbances. Here, we present a rare case of spontaneous hyphema in a 60-year-old patient with a known diagnosis of CLL on ibrutinib treatment.
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Fast-spiking interneurons (FSINs) provide fast inhibition that synchronizes neuronal activity and is critical for cognitive function. Fast synchronization frequencies are evolutionary conserved in the expanded human neocortex despite larger neuron-to-neuron distances that challenge fast input-output transfer functions of FSINs. Here, we test in human neurons from neurosurgery tissue, which mechanistic specializations of human FSINs explain their fast-signaling properties in human cortex. With morphological reconstructions, multipatch recordings, and biophysical modeling, we find that despite threefold longer dendritic path, human FSINs maintain fast inhibition between connected pyramidal neurons through several mechanisms: stronger synapse strength of excitatory inputs, larger dendrite diameter with reduced complexity, faster AP initiation, and faster and larger inhibitory output, while Na+ current activation/inactivation properties are similar. These adaptations underlie short input-output delays in fast inhibition of human pyramidal neurons through FSINs, explaining how cortical synchronization frequencies are conserved despite expanded and sparse network topology of human cortex.
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Neocórtex , Neurônios , Humanos , Potenciais de Ação/fisiologia , Neurônios/fisiologia , Células Piramidais/fisiologia , Interneurônios/fisiologiaRESUMO
Human cortex transcriptomic studies have revealed a hierarchical organization of γ-aminobutyric acid-producing (GABAergic) neurons from subclasses to a high diversity of more granular types. Rapid GABAergic neuron viral genetic labeling plus Patch-seq (patch-clamp electrophysiology plus single-cell RNA sequencing) sampling in human brain slices was used to reliably target and analyze GABAergic neuron subclasses and individual transcriptomic types. This characterization elucidated transitions between PVALB and SST subclasses, revealed morphological heterogeneity within an abundant transcriptomic type, identified multiple spatially distinct types of the primate-specialized double bouquet cells (DBCs), and shed light on cellular differences between homologous mouse and human neocortical GABAergic neuron types. These results highlight the importance of multimodal phenotypic characterization for refinement of emerging transcriptomic cell type taxonomies and for understanding conserved and specialized cellular properties of human brain cell types.
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Neurônios GABAérgicos , Interneurônios , Neocórtex , Animais , Humanos , Camundongos , Fenômenos Eletrofisiológicos , Neurônios GABAérgicos/metabolismo , Ácido gama-Aminobutírico/metabolismo , Interneurônios/metabolismo , Neocórtex/citologia , Neocórtex/metabolismo , Técnicas de Patch-ClampRESUMO
BACKGROUND AND OBJECTIVES: The 9-valent human papillomavirus (9vHPV) vaccine Phase III immunogenicity study in 9- to 15-year-old boys and girls was extended to assess immunogenicity and effectiveness through 10 years after the last vaccine dose (NCT00943722). METHODS: Boys (n = 301) and girls (n = 971) who received three 9vHPV vaccine doses in the base study (day 1, months 2 and 6) enrolled in the extension. Serum was collected through month 126 for antibody assessments by competitive Luminex immunoassay and immunoglobulin G-Luminex immunoassay. For effectiveness analysis starting at age 16 years, genital swabs were collected (to assess HPV DNA by polymerase chain reaction) and external genital examinations conducted every 6 months. Primary analyses were conducted in per-protocol populations. RESULTS: Geometric mean antibody titers peaked around month 7, decreased sharply between months 7 and 12, then gradually through month 126. Seropositivity rates remained ≥81% by competitive Luminex immunoassay and ≥95% by immunoglobin G-Luminex immunoassay at month 126 for each 9vHPV vaccine type. After up to 11.0 (median 10.0) years of follow-up postdose 3, there were no cases of HPV6/11/16/18/31/33/45/52/58-related high-grade intraepithelial neoplasia or condyloma in males or females. Incidence rates of HPV6/11/16/18/31/33/45/52/58-related 6-month persistent infection in males and females were low (54.6 and 52.4 per 10000 person-years, respectively) and within ranges expected in vaccinated cohorts, based on previous human papillomavirus vaccine efficacy trials. CONCLUSIONS: The 9vHPV vaccine demonstrated sustained immunogenicity and effectiveness through â¼10 years post 3 doses of 9vHPV vaccination of boys and girls aged 9 to 15 years.
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GWAS have identified numerous genes associated with human cognition but their cell type expression profiles in the human brain are unknown. These genes overlap with human accelerated regions (HARs) implicated in human brain evolution and might act on the same biological processes. Here, we investigated whether these gene sets are expressed in adult human cortical neurons, and how their expression relates to neuronal function and structure. We find that these gene sets are preferentially expressed in L3 pyramidal neurons in middle temporal gyrus (MTG). Furthermore, neurons with higher expression had larger total dendritic length (TDL) and faster action potential (AP) kinetics, properties previously linked to intelligence. We identify a subset of genes associated with TDL or AP kinetics with predominantly synaptic functions and high abundance of HARs.
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Neurônios , Células Piramidais , Adulto , Humanos , Neurônios/metabolismo , Células Piramidais/fisiologia , Cognição , Lobo Temporal , EncéfaloRESUMO
Importance: The large overlap between symptoms of acute sinusitis and viral upper respiratory tract infection suggests that certain subgroups of children being diagnosed with acute sinusitis, and subsequently treated with antibiotics, derive little benefit from antibiotic use. Objective: To assess if antibiotic therapy could be appropriately withheld in prespecified subgroups. Design, Setting, and Participants: Randomized clinical trial including 515 children aged 2 to 11 years diagnosed with acute sinusitis based on clinical criteria. The trial was conducted between February 2016 and April 2022 at primary care offices affiliated with 6 US institutions and was designed to evaluate whether symptom burden differed in subgroups defined by nasopharyngeal Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis on bacterial culture and by the presence of colored nasal discharge. Interventions: Oral amoxicillin (90 mg/kg/d) and clavulanate (6.4 mg/kg/d) (n = 254) or placebo (n = 256) for 10 days. Main Outcomes and Measures: The primary outcome was symptom burden based on daily symptom scores on a validated scale (range, 0-40) during the 10 days after diagnosis. Secondary outcomes included treatment failure, adverse events including clinically significant diarrhea, and resource use by families. Results: Most of the 510 included children were aged 2 to 5 years (64%), male (54%), White (52%), and not Hispanic (89%). The mean symptom scores were significantly lower in children in the amoxicillin and clavulanate group (9.04 [95% CI, 8.71 to 9.37]) compared with those in the placebo group (10.60 [95% CI, 10.27 to 10.93]) (between-group difference, -1.69 [95% CI, -2.07 to -1.31]). The length of time to symptom resolution was significantly lower for children in the antibiotic group (7.0 days) than in the placebo group (9.0 days) (P = .003). Children without nasopharyngeal pathogens detected did not benefit from antibiotic treatment as much as those with pathogens detected; the between-group difference in mean symptom scores was -0.88 (95% CI, -1.63 to -0.12) in those without pathogens detected compared with -1.95 (95% CI, -2.40 to -1.51) in those with pathogens detected. Efficacy did not differ significantly according to whether colored nasal discharge was present (the between-group difference was -1.62 [95% CI, -2.09 to -1.16] for colored nasal discharge vs -1.70 [95% CI, -2.38 to -1.03] for clear nasal discharge; P = .52 for the interaction between treatment group and the presence of colored nasal discharge). Conclusions: In children with acute sinusitis, antibiotic treatment had minimal benefit for those without nasopharyngeal bacterial pathogens on presentation, and its effects did not depend on the color of nasal discharge. Testing for specific bacteria on presentation may represent a strategy to reduce antibiotic use in this condition. Trial Registration: ClinicalTrials.gov Identifier: NCT02554383.
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Amoxicilina , Antibacterianos , Ácido Clavulânico , Nasofaringe , Sinusite , Criança , Humanos , Masculino , Doença Aguda , Amoxicilina/efeitos adversos , Amoxicilina/uso terapêutico , Antibacterianos/efeitos adversos , Antibacterianos/uso terapêutico , Ácido Clavulânico/efeitos adversos , Ácido Clavulânico/uso terapêutico , Resfriado Comum/diagnóstico , Sinusite/diagnóstico , Sinusite/tratamento farmacológico , Sinusite/etiologia , Sinusite/microbiologia , Feminino , Pré-Escolar , Nasofaringe/microbiologia , Streptococcus pneumoniae/isolamento & purificação , Haemophilus influenzae/isolamento & purificação , Moraxella catarrhalis/isolamento & purificaçãoRESUMO
Animals traversing different environments encounter both stable background stimuli and novel cues, which are thought to be detected by primary sensory neurons and then distinguished by downstream brain circuits. Here, we show that each of the â¼1,000 olfactory sensory neuron (OSN) subtypes in the mouse harbors a distinct transcriptome whose content is precisely determined by interactions between its odorant receptor and the environment. This transcriptional variation is systematically organized to support sensory adaptation: expression levels of more than 70 genes relevant to transforming odors into spikes continuously vary across OSN subtypes, dynamically adjust to new environments over hours, and accurately predict acute OSN-specific odor responses. The sensory periphery therefore separates salient signals from predictable background via a transcriptional rheostat whose moment-to-moment state reflects the past and constrains the future; these findings suggest a general model in which structured transcriptional variation within a cell type reflects individual experience.
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Neurônios Receptores Olfatórios/metabolismo , Sensação/genética , Transcrição Gênica , Animais , Encéfalo/metabolismo , Regulação da Expressão Gênica , Camundongos Endogâmicos C57BL , Camundongos Knockout , Odorantes , Bulbo Olfatório/metabolismo , Receptores Odorantes/metabolismo , Transcriptoma/genéticaRESUMO
Approximately 20% of American 9 to 18 year olds are obese, and most carry their excess adiposity, with its associated increased risk for cardiovascular disease, into adulthood. We studied cardiovascular disease risk markers changes associated with 3 healthy eating patterns (HEPs) in 96 9 to 18 year olds with a body mass index >95% in a Midwestern health system 1-year randomized trial. All HEPs were associated with similar statistically significant (P < .05 to <.001) cardiovascular disease risk marker improvements in weight, systolic and diastolic blood pressure, total cholesterol, low-density lipoprotein, and myeloperoxidase. Time required was the only identified significant (P < .001) deterrent from enrolling in study. These HEPs had characteristics common to most HEPs: encouraging whole foods, fruits and vegetables, whole grains, beans other legumes, and limiting added salt, saturated fatty acids, added sugars, red meat, processed meats, and other processed foods. Further research on initiatives to ease the time burden, and increase implementation of established healthy eating principles is needed.
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Índice de Massa Corporal , Doenças Cardiovasculares/prevenção & controle , Dieta Saudável/métodos , Obesidade Infantil/terapia , Adolescente , Criança , Comportamento Alimentar , Frutas , Humanos , Educação de Pacientes como Assunto , VerdurasRESUMO
BACKGROUND: Official recommendations differ regarding tympanostomy-tube placement for children with recurrent acute otitis media. METHODS: We randomly assigned children 6 to 35 months of age who had had at least three episodes of acute otitis media within 6 months, or at least four episodes within 12 months with at least one episode within the preceding 6 months, to either undergo tympanostomy-tube placement or receive medical management involving episodic antimicrobial treatment. The primary outcome was the mean number of episodes of acute otitis media per child-year (rate) during a 2-year period. RESULTS: In our main, intention-to-treat analysis, the rate (±SE) of episodes of acute otitis media per child-year during a 2-year period was 1.48±0.08 in the tympanostomy-tube group and 1.56±0.08 in the medical-management group (P = 0.66). Because 10% of the children in the tympanostomy-tube group did not undergo tympanostomy-tube placement and 16% of the children in the medical-management group underwent tympanostomy-tube placement at parental request, we conducted a per-protocol analysis, which gave corresponding episode rates of 1.47±0.08 and 1.72±0.11, respectively. Among secondary outcomes in the main analysis, results were mixed. Favoring tympanostomy-tube placement were the time to a first episode of acute otitis media, various episode-related clinical findings, and the percentage of children meeting specified criteria for treatment failure. Favoring medical management was children's cumulative number of days with otorrhea. Outcomes that did not show substantial differences included the frequency distribution of episodes of acute otitis media, the percentage of episodes considered to be severe, and antimicrobial resistance among respiratory isolates. Trial-related adverse events were limited to those included among the secondary outcomes of the trial. CONCLUSIONS: Among children 6 to 35 months of age with recurrent acute otitis media, the rate of episodes of acute otitis media during a 2-year period was not significantly lower with tympanostomy-tube placement than with medical management. (Funded by the National Institute on Deafness and Other Communication Disorders and others; ClinicalTrials.gov number, NCT02567825.).
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Antibacterianos/uso terapêutico , Ventilação da Orelha Média , Otite Média/tratamento farmacológico , Otite Média/cirurgia , Doença Aguda , Antibacterianos/efeitos adversos , Pré-Escolar , Farmacorresistência Bacteriana , Feminino , Humanos , Lactente , Análise de Intenção de Tratamento , Estimativa de Kaplan-Meier , Masculino , Otite Média com Derrame , Qualidade de Vida , RecidivaRESUMO
BACKGROUND: Group B streptococcus (GBS) is a major cause of invasive disease in young infants. Infants born to women with sufficient pre-existing anti-GBS capsular IgG antibodies are at reduced risk of GBS disease, making maternal immunisation a potential strategy for prevention. We aimed to assess the safety and immunogenicity of a novel hexavalent (serotypes Ia, Ib, II, III, IV, and V) GBS conjugate vaccine (GBS6). METHODS: This phase 1/2, placebo-controlled, observer-blinded, dose-escalation trial, was done at four clinical research centres in the USA (Kentucky, Georgia, and two sites in Utah). Healthy, non-pregnant adults aged 18-49 years were randomly assigned using an interactive, web-based response technology system. Within each dose group (low, medium, or high), participants in sentinel cohorts were randomly assigned 2:2:1 and expanded cohort participants were randomly assigned 4:4:1 to receive GBS6 with aluminium phosphate (AlPO4), GBS6 without AlPO4, or placebo (saline control). One 0·5 mL dose of either saline placebo or 5 µg capsular polysaccharide per serotype in the low-dose group, 10 µg capsular polysaccharide per serotype in the medium-dose group, or 20 µg capsular polysaccharide per serotype in the high-dose group was administered by intramuscular injection into the deltoid muscle on day 1. The primary outcome was safety up to 6 months after vaccination, including the proportion of sentinel cohort participants with clinical laboratory abnormalities at 1 week, the proportion of all participants reporting solicited local reactions, systemic events, or use of antipyretic or pain medication within 14 days, adverse events up to 1 month, and medically attended or serious adverse events up to 6 months. The secondary outcome was GBS immunogenicity (serotype-specific IgG geometric mean concentrations at 1 month). This study is registered with ClinicalTrials.gov, NCT03170609. FINDINGS: Between June 5, 2017, and June 25, 2018, 365 participants were randomly assigned and 364 (52 in each dose group) were vaccinated and included in the safety analysis. Unsolicited adverse events were reported by 15 (29%) participants in the 5 µg with AlPO4 group, 13 (25%) in the 5 µg without AlPO4 group, 22 (42%) in the 10 µg with AlPO4 group, 12 (23%) in the 10 µg without AlPO4 group, 25 (48%) in the 20 µg with AlPO4 group, 21 (40%) in the 20 µg without AlPO4 group, and 20 (38%) in the placebo group. The most common unsolicited adverse events were in the system organ class of infections and infestations in any dose or formulation of GBS6 (ranging from six [12%] in the 10 µg without AlPO4 group to 15 [29%] in the 20 µg with AlPO4 group and placebo group). Three participants reported at least one serious adverse event during the study, one each in the 5 µg GBS6 with AlPO4 group (diabetic ketoacidosis, two events; resolved), 10 µg GBS6 with AlPO4 group (died by suicide), and 20 µg GBS6 with AlPO4 group (metrorrhagia; resolved). None of these serious adverse events were considered related to the vaccine. 11 of the 365 participants were excluded from the evaluable immunogenicity population, including one participant who did not receive the vaccine, and ten who at 1 month after vaccination were withdrawn for various reasons. GBS serotype-specific IgG geometric mean concentrations increased by 1 week after vaccination for all GBS6 groups, peaked at 2 weeks, stabilised by 1 month, and declined gradually but remained higher than placebo at 6 months. INTERPRETATION: GBS6 was well tolerated in healthy adults and elicited robust immune responses for all dose levels and formulations that persisted 6 months after vaccination. This study supports further evaluation of GBS6 in pregnant women. FUNDING: Pfizer.
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Infecções Estreptocócicas/prevenção & controle , Vacinas Estreptocócicas/imunologia , Streptococcus agalactiae , Adolescente , Adulto , Relação Dose-Resposta Imunológica , Feminino , Humanos , Masculino , Vacinas Estreptocócicas/efeitos adversos , Vacinas Combinadas , Vacinas Conjugadas , Adulto JovemRESUMO
Granule cells (GCs) of the cerebellar input layer express high-affinity δ GABAA subunit-containing GABAA receptors (δGABAARs) that respond to ambient GABA levels and context-dependent neuromodulators like steroids. We find that GC-specific deletion of δGABAA (cerebellar [cb] δ knockout [KO]) decreases tonic inhibition, makes GCs hyperexcitable, and in turn, leads to differential activation of cb output regions as well as many cortical and subcortical brain areas involved in cognition, anxiety-like behaviors, and the stress response. Cb δ KO mice display deficits in many behaviors, but motor function is normal. Strikingly, δGABAA deletion alters maternal behavior as well as spontaneous, stress-related, and social behaviors specifically in females. Our findings establish that δGABAARs enable the cerebellum to control diverse behaviors not previously associated with the cerebellum in a sex-dependent manner. These insights may contribute to a better understanding of the mechanisms that underlie behavioral abnormalities in psychiatric and neurodevelopmental disorders that display a gender bias.
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Cerebelo/metabolismo , Deleção de Genes , Subunidades Proteicas/metabolismo , Receptores de GABA-A/metabolismo , Caracteres Sexuais , Animais , Ansiedade/patologia , Comportamento Animal , Feminino , Aprendizagem , Masculino , Comportamento Materno , Camundongos Endogâmicos C57BL , Camundongos Knockout , Atividade Motora , Especificidade de Órgãos , Estresse PsicológicoRESUMO
The low-spin structure of the semimagic ^{64}Ni nucleus has been considerably expanded: combining four experiments, several 0^{+} and 2^{+} excited states were identified below 4.5 MeV, and their properties established. The Monte Carlo shell model accounts for the results and unveils an unexpectedly complex landscape of coexisting shapes: a prolate 0^{+} excitation is located at a surprisingly high energy (3463 keV), with a collective 2^{+} state 286 keV above it, the first such observation in Ni isotopes. The evolution in excitation energy of the prolate minimum across the neutron N=40 subshell gap highlights the impact of the monopole interaction and its variation in strength with N.
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An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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The cortex organizes sensory information to enable discrimination and generalization1-4. As systematic representations of chemical odour space have not yet been described in the olfactory cortex, it remains unclear how odour relationships are encoded to place chemically distinct but similar odours, such as lemon and orange, into perceptual categories, such as citrus5-7. Here, by combining chemoinformatics and multiphoton imaging in the mouse, we show that both the piriform cortex and its sensory inputs from the olfactory bulb represent chemical odour relationships through correlated patterns of activity. However, cortical odour codes differ from those in the bulb: cortex more strongly clusters together representations for related odours, selectively rewrites pairwise odour relationships, and better matches odour perception. The bulb-to-cortex transformation depends on the associative network originating within the piriform cortex, and can be reshaped by passive odour experience. Thus, cortex actively builds a structured representation of chemical odour space that highlights odour relationships; this representation is similar across individuals but remains plastic, suggesting a means through which the olfactory system can assign related odour cues to common and yet personalized percepts.
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Odorantes/análise , Córtex Olfatório/anatomia & histologia , Córtex Olfatório/fisiologia , Condutos Olfatórios , Compostos Orgânicos/análise , Compostos Orgânicos/química , Animais , Masculino , Camundongos , Bulbo Olfatório/citologia , Bulbo Olfatório/fisiologia , Córtex Olfatório/citologia , Percepção Olfatória/fisiologia , OlfatoRESUMO
Since its belated discovery, our understanding of the giant protein titin has grown exponentially from its humble beginning as a sarcomeric scaffold to recent recognition of its critical mechanical and signaling functions in active muscle. One uniquely useful model to unravel titin's functions, muscular dystrophy with myositis (mdm), arose spontaneously in mice as a transposon-like LINE repeat insertion that results in a small deletion in the N2A region of titin. This small deletion profoundly affects hypertrophic signaling and muscle mechanics, thereby providing insights into the function of this specific region and the consequences of its dysfunction. The impact of this mutation is profound, affecting diverse aspects of the phenotype including muscle mechanics, developmental hypertrophy, and thermoregulation. In this review, we explore accumulating evidence that points to the N2A region of titin as a dynamic "switch" that is critical for both mechanical and signaling functions in skeletal muscle. Calcium-dependent binding of N2A titin to actin filaments triggers a cascade of changes in titin that affect mechanical properties such as elastic energy storage and return, as well as hypertrophic signaling. The mdm phenotype also points to the existence of as yet unidentified signaling pathways for muscle hypertrophy and thermoregulation, likely involving titin's PEVK region as well as the N2A signalosome.