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1.
Front Immunol ; 15: 1328175, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39229270

RESUMO

Introduction: Pediatric patients with unexplained bone marrow failure (BMF) are often categorized as aplastic anemia (AA). Based on the accepted hypothesis of an auto-immune mechanism underlying AA, immune suppressive therapy (IST) might be effective. However, due to the lack of diagnostic tools to identify immune AA and prognostic markers to predict IST response together with the unequaled curative potential of hematopoietic stem cell transplantation (HSCT), most pediatric severe AA patients are momentarily treated by HSCT if available. Although several studies indicate oligoclonal T-cells with cytotoxic activities towards the hematopoietic stem cells, increasing evidence points towards defective inhibitory mechanisms failing to inhibit auto-reactive T-cells. Methods: We aimed to investigate the role of NK- and B-cells in seven pediatric AA patients through a comprehensive analysis of paired bone marrow and peripheral blood samples with spectral flow cytometry in comparison to healthy age-matched bone marrow donors. Results: We observed a reduced absolute number of NK-cells in peripheral blood of AA patients with a skewed distribution towards CD56bright NK-cells in a subgroup of patients. The enriched CD56bright NK-cells had a lower expression of CD45RA and TIGIT and a higher expression of CD16, compared to healthy donors. Functional analysis revealed no differences in degranulation. However, IFN-γ production and perforin expression of NK-cells were reduced in the CD56bright-enriched patient group. The diminished NK-cell function in this subgroup might underly the auto-immunity. Importantly, NK-function of AA patients with reduced CD56bright NK-cells was comparable to healthy donors. Also, B-cell counts were lower in AA patients. Subset analysis revealed a trend towards reduction of transitional B-cells in both absolute and relative numbers compared to healthy controls. As these cells were previously hypothesized as regulatory cells in AA, decreased numbers might be involved in defective inhibition of auto-reactive T-cells. Interestingly, even in patients with normal distribution of precursor B-cells, the transitional compartment was reduced, indicating partial differentiation failure from immature to transitional B-cells or a selective loss. Discussion: Our findings provide a base for future studies to unravel the role of transitional B-cells and CD56bright NK-cells in larger cohorts of pediatric AA patients as diagnostic markers for immune AA and targets for therapeutic interventions.


Assuntos
Anemia Aplástica , Linfócitos B , Imunofenotipagem , Células Matadoras Naturais , Humanos , Células Matadoras Naturais/imunologia , Anemia Aplástica/imunologia , Anemia Aplástica/terapia , Criança , Masculino , Feminino , Linfócitos B/imunologia , Adolescente , Pré-Escolar , Citometria de Fluxo
2.
Clin Neuropsychol ; : 1-23, 2024 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-39256914

RESUMO

Objective: Investigate three new computer tests of visual abilities relative to traditional paper-and-pencil (P&P) tests on groups with and without cerebral neurological impairment (CNI, Non-CNI) based on MRI and EEG criteria. The new tests employ an intuitive interface with audio instructions, touch responses, non-response prompts, and videography of test behavior. The Presidents Test was designed as an achievement-related measure of visual knowledge; the Railroad Test - visual perception and delayed recognition; and the Swamp Test - visual attention. Attitudes toward testing were assessed with an original Testing Experience Questionnaire (TEQ). Method: Of the 129 participants, 84 were women, 73 identified as non-White, average age 45.5 and education 14.3 years. Procedures included the new computer tests and a selection of standard neuropsychological measures including performance validity tests (PVT). Participants who failed two or three PVTs or had missing PVT data were excluded from main analyses, resulting in N = 115. Results: The new computer tests demonstrated adequate reliability. Correlations and factor analyses confirmed the computer tests as functioning in accordance with design. The Presidents Test was associated with academic achievement. The Railroad and Swamp Tests were linked to visual perception and visual attention. Correlations between computer total test duration time and traditional speed of processing tasks were modest. Computer and traditional tests demonstrated similar discriminability between CNI and Non-CNI groups. TEQ indicated positive attitudes toward testing in general, and computer testing in particular. Conclusions: The new computer tests evaluated in this study were found to be reliable, functioned to assess the designed cognitive domains, and discriminated between CNI and Non-CNI participants similarly to the traditional neuropsychological measures. Attitudes toward computer testing were favorable.

3.
bioRxiv ; 2024 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-39253442

RESUMO

Polyamines are abundant and evolutionarily conserved metabolites that are essential for life. Dietary polyamine supplementation extends life-span and health-span. Dysregulation of polyamine homeostasis is linked to Parkinson's disease and cancer, driving interest in therapeutically targeting this pathway. However, measuring cellular polyamine levels, which vary across cell types and states, remains challenging. We introduce a first-in-class genetically encoded polyamine reporter for real-time measurement of polyamine concentrations in single living cells. This reporter utilizes the polyamine-responsive ribosomal frameshift motif from the OAZ1 gene. We demonstrate broad applicability of this approach and reveal dynamic changes in polyamine levels in response to genetic and pharmacological perturbations. Using this reporter, we conducted a genome-wide CRISPR screen and uncovered an unexpected link between mitochondrial respiration and polyamine import, which are both risk factors for genetic Parkinson's disease. By offering a new lens to examine polyamine biology, this reporter may advance our understanding of these ubiquitous metabolites and accelerate therapy development.

4.
Biochem Biophys Res Commun ; 733: 150655, 2024 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-39244846

RESUMO

Astrocytes are subtypes of glial cells involved in metabolic, structural, homeostatic, and neuroprotective processes that help neurons maintain viability. Insulin-like growth factors IGF-1 and IGF-2 are known to have neuroprotective effects on neurons and glial cells through interaction with specific receptors. IGF forms a complex with IGF-binding proteins (IGFBP) in nervous tissue and is released from the complex via IGFBP proteolysis by specific proteases. It has been reported that IGFBP-2, 5 and 6 are cleaved by specific proteases in the central nervous system (CNS), followed by IGF release; however, it was unknown whether IGFBP-4 was exposed to a particular proteolysis in nervous tissue. Using neurons and astrocytes derived from human induced pluripotent stem cell lines (hiPSC), as well as rat brain-sourced primary neuron-glia cultures, we demonstrated that IGFBP-4 is specifically cleaved in nervous tissue by the Pregnancy Associated Plasma Protein A (PAPP-A) protease and that this cleavage is IGF-dependent. Our results indicate that astrocyte rather than neuron PAPP-A cleaves IGFBP-4 in nervous tissue suggesting that this may be one of the fundamental mechanisms for IGF interchange between these two types of cells.

5.
Arthroplast Today ; 29: 101422, 2024 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-39224754

RESUMO

Background: Two-stage exchange arthroplasty remains the gold standard for treating chronic hip periprosthetic joint infections. However, controversy remains regarding the optimal spacer type, particularly among patients with increased dislocation risk. This study reports on the outcomes of articulating hip spacers utilizing a single constrained-liner design. Methods: All patients who underwent treatment for hip periprosthetic joint infection at a single institution were screened. Patients were included if they received an articulating spacer utilizing a constrained liner of a single manufacturer design. Indications for constrained liner, demographic variables, and surgical variables were recorded. Patients were assessed for dislocation and component loosening prior to the second stage or at the final follow-up if the second stage was not undertaken. Comparative analysis was performed. Results: Overall, 26 constrained liners were utilized in 25 patients. Indications for constrained liner included history of dislocation (n = 14), massive proximal femoral bone loss (n = 14), greater trochanteric deficiency (n = 12), and absent abductors (n = 7). Many patients had more than one indication. In total, 9 hips (34.6%) underwent a second stage at an average of 7.4 months, while 17 hips never underwent a second stage with an average follow-up of 27.6 months. One patient experienced failure of their constrained liner prior to the second stage due to pelvic discontinuity and massive acetabular bone loss. Conclusions: Utilization of a constrained liner as an articulating spacer is a viable option for patients at high risk of instability. Meticulous cement technique, appropriate component position, and implant selection are crucial in achieving successful outcomes.

6.
bioRxiv ; 2024 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-39091787

RESUMO

Betaglycan (BG) is a transmembrane co-receptor of the transforming growth factor-ß (TGF-ß) family of signaling ligands. It is essential for embryonic development and tissue homeostasis and fertility in adults. It functions by enabling binding of the three TGF-ß isoforms to their signaling receptors and is additionally required for inhibin A (InhA) activity. Despite its requirement for the functions of TGF-ßs and InhA in vivo, structural information explaining BG ligand selectivity and its mechanism of action is lacking. Here, we determine the structure of TGF-ß bound both to BG and the signaling receptors, TGFBR1 and TGFBR2. We identify key regions responsible for ligand engagement, which has revealed novel binding interfaces that differ from those described for the closely related co-receptor of the TGF-ß family, endoglin, thus demonstrating remarkable evolutionary adaptation to enable ligand selectivity. Finally, we provide a structural explanation for the hand-off mechanism underlying TGF-ß signal potentiation.

7.
Hip Int ; : 11207000241264256, 2024 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-39114946

RESUMO

INTRODUCTION: As the volume of technology-assisted total hip arthroplasty (THA) increases, there is a need to characterise the outcomes of robotic-assisted (RA) and computer-navigated (CN) THA. The goal of this study was to assess outcomes and opioid consumption following CN-THA and RA-THA compared to conventionally-instrumented (CON) THA. METHODS: The Premier Database was queried for all patients who underwent primary, elective THA from 2015-2020. Patients were divided into 3 groups: CN, RA, or CON-THA. Yearly usage trends were assessed. Univariate and multivariate analyses were performed to assess the 90-day risk of postoperative complications. Opioid consumption was reported in morphine milligram equivalents (MME) for postoperative days (POD) 0 and 1. RESULTS: Overall, 474,707 elective THAs were identified (95.7% CON, 2.1% CN, 2.2% RA. After accounting for confounders, CN-THA patients were at decreased risk for periprosthetic joint infection (PJI) (aOR: 0.55, p < 0.001) and dislocation (aOR 0.45, p < 0.001), but increased risk for blood transfusion (aOR 1.97, <0.001) compared to CON-THA. RA-THA patients were at decreased risk of dislocation (aOR:0.66, p < 0.001) but increased risk for transfusion (aOR 1.20, p < 0.001), prosthesis breakage (aOR 3.88, p < 0.001), and periprosthetic fracture (aOR 1.72, p < 0.001). Opioid consumption for CN-THA patients was lower on POD1 and lower for RA-THA patients POD0 and 2 compared to CON-THA. DISCUSSION: CN-THA was associated with reduced rates of PJI and dislocation, but increased rates of blood transfusion while RA-THA was associated with decreased rates of dislocation, but increased rates of blood transfusion, prosthesis complications, and periprosthetic fracture compared to CON-THA. Technology-assisted THA was associated with lower postoperative opioid consumption.

8.
Immunotherapy ; : 1-12, 2024 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-39155854

RESUMO

Background: Tumor-promoting inflammation and inflammatory cytokines are linked to immune checkpoint blockade (ICB) resistance. Methods: We assessed the associations between pre-treatment Interleukin-6 (IL-6), Interleukin-8 (IL-8) levels and on-treatment changes in IL-6, IL-8 and C-reactive protein (CRP) with ICB trial end points. Results: 27 studies representing 6,719 patients were included. Low pre-treatment IL-6 levels were associated with improved objective response rate (ORR) (odds ratio (OR) = 0.31 [0.18-0.55]) and better progression-free survival (PFS) (hazard ratio (HR) = 0.59 [0.48-0.72]) and overall survival (OS) [95% confidence interval (CI)] (HR = 0.42 [0.35-0.50]). Low pre-treatment IL-8 levels were associated with improved ORR (OR = 0.47 [0.36-0.61]) and better PFS (HR = 0.65 [0.58-0.74]) and OS (HR = 0.44 [0.39-0.51]). On-treatment decline in CRP was associated with improved ORR (OR = 0.18 [0.11-0.20]), PFS (HR = 0.40 [0.31-0.91]) and OS (HR = 0.48 [0.40-0.58]). Conclusion: Peripheral blood cytokines warrant further evaluation as enrichment and pharmacodynamic biomarkers for strategies targeting tumor-promoting inflammation.


Measuring a substance called C-reactive protein (CRP) in the blood can help predict if cancer treatments that boost the immune system, like immune checkpoint blockers (ICB), will work. CRP levels are increased when there is inflammation in the body, helping cancer cells grow. IL-6 and IL-8 are related blood markers that are more specific to cancer cells and may improve our ability to predict if ICB will effectivity destroy cancer cells. Our study found that having lower levels of IL-6 and IL-8 before treatment and low levels of CRP during treatment might mean patients live longer and respond better to ICB treatments. Measuring IL-6 and IL-8 before treatment and CRP during treatment could help improve how doctors use ICB to treat cancer by managing inflammation that helps cancer grow.

9.
medRxiv ; 2024 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-39132485

RESUMO

Vancomycin-resistant Enterococcus faecium (VREfm) is a prevalent healthcare-acquired pathogen. Gastrointestinal colonization can lead to difficult-to-treat bloodstream infections with high mortality rates. Prior studies have investigated VREfm population structure within healthcare centers. However, little is known about how and why hospital-adapted VREfm populations change over time. We sequenced 710 healthcare-associated VREfm clinical isolates from 2017-2022 from a large tertiary care center as part of the Enhanced Detection System for Healthcare-Associated Transmission (EDS-HAT) program. Although the VREfm population in our center was polyclonal, 46% of isolates formed genetically related clusters, suggesting a high transmission rate. We compared our collection to 15,631 publicly available VREfm genomes spanning 20 years. Our findings describe a drastic shift in lineage replacement within nosocomial VREfm populations at both the local and global level. Functional and genomic analysis revealed, antimicrobial peptide, bacteriocin T8 may be a driving feature of strain emergence and persistence in the hospital setting.

10.
BMJ Case Rep ; 17(8)2024 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-39097322

RESUMO

Chronic skin defects in the head, face and neck pose challenges for closure, especially after multiple surgeries or radiation therapy. We report the case of a woman in her 70s with a chronic occipital wound following squamous cell carcinoma resections, resulting in exposed skull bone. Despite various options, we successfully treated the 4 cm x 5 cm wound with a Kerecis fish skin graft (FSG), observing significant improvement within a week. The FSG promoted granulation tissue formation, enabling subsequent full-thickness skin grafting from the patient's groin. Complete wound closure was achieved within 2 weeks, indicating FSG's efficacy in complex wound management. Our experience highlights FSG's potential as a valuable tool in wound healing and reconstruction, particularly in challenging cases involving the head and neck.


Assuntos
Carcinoma de Células Escamosas , Transplante de Pele , Cicatrização , Humanos , Feminino , Transplante de Pele/métodos , Carcinoma de Células Escamosas/cirurgia , Idoso , Animais , Peixes , Neoplasias de Cabeça e Pescoço/cirurgia , Neoplasias Cutâneas/cirurgia , Resultado do Tratamento , Doença Crônica , Osso Occipital/cirurgia
11.
Sci Adv ; 10(35): eadq6073, 2024 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-39213356

RESUMO

In this work, we demonstrate the first pulsed electron paramagnetic resonance (EPR) experiments performed under magic angle spinning (MAS) at high magnetic field. Unlike nuclear magnetic resonance (NMR) and dynamic nuclear polarization (DNP), commonly performed at high magnetic fields and under MAS to maximize sensitivity and resolution, EPR is usually measured at low magnetic fields and, with the exception of the Spiess group work in the late 1990s, never under MAS, due to great instrumentational challenges. This hampers the investigation of DNP mechanisms, in which electron spin dynamics play a central role, because no experimental data about the latter under DNP-characteristic conditions are available. We hereby present our dedicated, homebuilt MAS-EPR probehead and show the pulsed MAS-EPR spectra of P1 center diamond defect recorded at 7 tesla. Our results reveal unique effects of MAS on EPR line shape, intensity, and signal dephasing. Time-domain simulations reproduce the observed changes in the line shapes and the trends in the signal intensity.

12.
Front Sports Act Living ; 6: 1420220, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39086855

RESUMO

This study aimed to assess youth-to-senior transition rates, quantify the magnitude of relative age effect (RAEs), and evaluate how RAEs affect these transitions in 9,527 men's national football players of England, France, Germany, Italy, and Spain. Regardless of national team, only -15%, 25%, and 40% of U17, U19, and U21 players successfully transitioned to the senior team, respectively, whilst -14%-24% progressed to senior level without being selected during youth. Data suggested a skewed birthdate distribution favouring relatively older players at U17, U19, and U21 levels across all countries, whereas RAEs were also present in England, Italy, and Spain at senior level. Youth-to-senior transition rates were modulated by birthdate at U17 and U19, whereby Q4 players were -2 and 1.5 times more likely to successfully transition at senior level than Q1 players, respectively. Selection at youth international level does not guarantee selection at senior level, but does make it more likely. Moreover, relatively younger athletes are disadvantaged in youth categories, although are more likely to transition to senior level once they have entered the pathway.

13.
ACS Org Inorg Au ; 4(4): 424-431, 2024 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-39132014

RESUMO

Parallel Minisci reactions of nonfluorinated and gem-difluorinated C4-C7 cycloalkyl building blocks (trifluoroborates and carboxylic acids) with a series of electron-deficient heterocycles were studied. A comparison of the reaction's outcome revealed better product yields in the case of carboxylic acids as the radical precursors in most cases, albeit these reagents were used with three-fold excess under optimized conditions. The nature of the heterocyclic core was found to be important for successful incorporation of the cycloalkyl fragment. The impact of the CF2 moiety on the oxidation potential of fluorinated cycloalkyl trifluoroborates and the reaction outcome, in general, was also evaluated.

14.
Semin Ophthalmol ; : 1-5, 2024 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-39149972

RESUMO

PURPOSE: The objective of this study was to evaluate the relationship between research activity and National Institutes of Health (NIH) funding status of the United States (US) academic ophthalmologists. METHODS: A retrospective cross-sectional analysis of bibliometric data was conducted. The NIH Research Portfolio Online Reporting Tools Expenditures and Reports (rePORTER) website was utilized to identify ophthalmology departments in the US that received NIH funding. Affiliated faculty from these institutions were then identified using NIH rePORTER and institutional websites. H-index was calculated using the Scopus database, and the NIH iCite tool was used to determine the Relative Citation Ratio (RCR). The h-index and w-RCR quantified research productivity, while m-RCR measured research impact. RESULTS: Data on 2688 faculty members from 66 departments we re identified, of which 21% were NIH-funded. Faculty members who received NIH-funding had significantly greater research productivity and impact as measured by h-index (32.5 vs 16.6; p < .001), m-RCR (2.2 vs 1.6; p < .001), and w-RCR (147.2 vs 70.1; p < .001) than their non-funded peers. When stratified by academic rank, NIH-funded faculty still had significantly higher h-index (16.1 vs 7.9; p < .001), m-RCR (2.2 vs 1.4; p < .001), and w-RCR (63.2 vs 61.8; p < .001) than non-funded peers. A similar trend was observed among non-tenured faculty members. CONCLUSION: NIH funding is associated with higher research productivity and impact among US academic ophthalmologists as measured by h-index and RCR, which suggests that NIH funding may be a critical factor in enhancing scholarly contributions of ophthalmologists.  These findings underscore the importance of continued investment in NIH funding to foster high-impact research within the field of ophthalmology.

15.
Sports Med ; 2024 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-39207610

RESUMO

A clearer understanding of, and tighter boundaries between, terms are important for researchers designing studies as well as for other sport stakeholders creating evidence-informed policies. This article considers the terms 'athlete', 'talent', and 'player' from psychological and sociocultural perspectives and in different sporting communities to highlight the importance of terminological clarity in sport research. We present considerations to clarify the use of these terms within different contexts and how the use of specific terms may affect knowledge mobilization in diverse sporting populations. A conceptual discussion is provided to help operationalize development-related terminology and its associated stages, to better reflect contemporary academic thought, and enhance practical interpretations. Importantly, we also call for greater transparency from researchers when presenting findings and encourage practitioners to clearly define key terms when working in sport. Our intention in this paper is to energize readers to consider how we use language in athlete identification and development contexts, to stimulate deeper thought and discourse around the possible implications these terms may have at any point of an individual's development in sport. Greater deliberation, identification, and acknowledgment of the drawbacks accompanying these terms will be needed before more confident assertions can be made on how researchers and practitioners could (or even should) implement certain terminology across youth sport contexts moving forward. This paper adds to a growing literature on the importance of clarity in terminology and acts as an impetus for those working in specific sports to co-design key terms used by researchers, practitioners, and policy makers.

16.
ACS Nano ; 2024 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-39172118

RESUMO

Photons do not carry sufficient momentum to induce indirect optical transitions in semiconducting materials, such as silicon, necessitating the assistance of lattice phonons to conserve momentum. Compared to direct bandgap semiconductors, this renders silicon a less attractive material for a wide variety of optoelectronic applications. In this work, we introduce an alternative strategy to fulfill the momentum-matching requirement in indirect optical transitions. We demonstrate that when confined to scales below ∼3 nm, photons acquire sufficient momentum to allow electronic transitions at the band edge of Si without the assistance of a phonon. Confined photons allow simultaneous energy and momentum conservation in two-body photon-electron scattering; in effect, converting silicon into a direct bandgap semiconductor. We show that this less-explored concept of light-matter interaction leads to a marked increase in the absorptivity of Si from the UV to the near-IR. The strategy provides opportunities for more efficient use of indirect semiconductors in photovoltaics, energy conversion, light detection, and emission.

17.
Nat Commun ; 15(1): 6355, 2024 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-39069540

RESUMO

The miniaturization of photonic technologies calls for a deliberate integration of diverse materials to enable novel functionalities in chip-scale devices. Topological photonic systems are a promising platform to couple structured light with solid-state matter excitations and establish robust forms of 1D polaritonic transport. Here, we demonstrate a mechanism to efficiently trap mid-IR structured phonon-polaritons in topological defects of a metasurface integrated with hexagonal boron nitride (hBN). These defects, created by stitching displaced domains of a Kekulé-patterned metasurface, sustain localized polaritonic modes that originate from coupling of electromagnetic fields with hBN lattice vibrations. These 0D higher-order topological modes, comprising phononic and photonic components with chiral polarization, are imaged in real- and Fourier-space. The results reveal a singular radiation leakage profile and selective excitation through spin-polarized edge waves at heterogeneous topological interfaces. This offers impactful opportunities to control light-matter waves in their dimensional hierarchy, paving the way for topological polariton shaping, ultrathin structured light sources, and thermal management at the nanoscale.

18.
Angew Chem Int Ed Engl ; : e202408568, 2024 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-39073277

RESUMO

The mimicking of natural lipid bilayers with synthetic amphiphilic systems is of great interest to researchers, as insights could lead to better understanding of the complexities of cell membranes, as well as new materials and healthcare technologies. Recapitulating natural lipid asymmetry across bilayer membranes has important implications for curvature in cell, vesicle, and organelle morphologies, but has been challenging to achieve with synthetic lipid combinations or standard amphiphilic block copolymers. In a recent article, Elizebath et al. report the synthesis of a new type of synthetic amphiphile able to dynamically induce asymmetry in an artificially bilayer membrane. The molecules were designed around an extended π-conjugated hydrophobic core with tertiary amine terminated oxyalkylene side chains. Protonation of the tertiary amines on the bilayer exterior leads to curvature induction, bilayer fission, and vesicle formation as monitored by time resolved spectroscopy techniques and microscopy. The results were further validated with density functional theory (DFT) calculations. The delicate balance between different molecular scale interactions in the supramolecular structures led to the dynamic transformation of the bilayer membranes. Insights described could be used to advance the assembly of hierarchical life-like materials.

19.
FEMS Microbiol Ecol ; 100(8)2024 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-39020097

RESUMO

Leaf litter microbes collectively degrade plant polysaccharides, influencing land-atmosphere carbon exchange. An open question is how substrate complexity-defined as the structure of the saccharide and the amount of external processing by extracellular enzymes-influences species interactions. We tested the hypothesis that monosaccharides (i.e. xylose) promote negative interactions through resource competition, and polysaccharides (i.e. xylan) promote neutral or positive interactions through resource partitioning or synergism among extracellular enzymes. We assembled a three-species community of leaf litter-degrading bacteria isolated from a grassland site in Southern California. In the polysaccharide xylan, pairs of species stably coexisted and grew equally in coculture and in monoculture. Conversely, in the monosaccharide xylose, competitive exclusion and negative interactions prevailed. These pairwise dynamics remained consistent in a three-species community: all three species coexisted in xylan, while only two species coexisted in xylose, with one species capable of using peptone. A mathematical model showed that in xylose these dynamics could be explained by resource competition. Instead, the model could not predict the coexistence patterns in xylan, suggesting other interactions exist during biopolymer degradation. Overall, our study shows that substrate complexity influences species interactions and patterns of coexistence in a synthetic microbial community of leaf litter degraders.


Assuntos
Bactérias , Interações Microbianas , Folhas de Planta , Poaceae , Folhas de Planta/metabolismo , Folhas de Planta/microbiologia , Bactérias/metabolismo , Ecossistema , Especificidade da Espécie , Xilanos/metabolismo , Xilose/metabolismo , Modelos Teóricos , Actinobacteria/crescimento & desenvolvimento , Actinobacteria/metabolismo , Bacteroidetes/crescimento & desenvolvimento , Bacteroidetes/metabolismo , Proteobactérias/crescimento & desenvolvimento , Proteobactérias/metabolismo , Interações Microbianas/fisiologia , Poaceae/microbiologia
20.
Phys Med ; 124: 104491, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-39079308

RESUMO

BACKGROUND: Optimization of the dose the patient receives during scanning is an important problem in modern medical X-ray computed tomography (CT). One of the basic ways to its solution is to reduce the number of views. Compressed sensing theory helped promote the development of a new class of effective reconstruction algorithms for limited data CT. These compressed-sensing-inspired (CSI) algorithms optimize the Lp (0 ≤ p ≤ 1) norm of images and can accurately reconstruct CT tomograms from a very few views. The paper presents a review of the CSI algorithms and discusses prospects for their further use in commercial low-dose CT. METHODS: Many literature references with the CSI algorithms have been were searched. To structure the material collected the author gives a classification framework within which he describes Lp regularization methods, the basic CSI algorithms that are used most often in few-view CT, and some of their derivatives. Lots of examples are provided to illustrate the use of the CSI algorithms in few-view and low-dose CT. RESULTS: A list of the CSI algorithms is compiled from the literature search. For better demonstrativeness they are summarized in a table. The inference is done that already today some of the algorithms are capable of reconstruction from 20 to 30 views with acceptable quality and dose reduction by a factor of 10. DISCUSSION: In conclusion the author discusses how soon the CSI reconstruction algorithms can be introduced in the practice of medical diagnosis and used in commercial CT scanners.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador , Doses de Radiação , Tomografia Computadorizada por Raios X , Tomografia Computadorizada por Raios X/métodos , Processamento de Imagem Assistida por Computador/métodos , Humanos , Compressão de Dados/métodos
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